1. Hos, T.; Sror, G.; Herskowitz, M., "Autothermal reforming of methanol for on-board hydrogen production in marine vehicles", International Journal of Hydrogen Energy, (2024), 49, 1121 – 1132. The current systems for air independent propulsion systems are based on hydrogen stored in a limited number of cylinders for the continuous operation of the fuel cells in marine vehicles. Hydrogen generation by on-board steam reforming of methanol could extend the air-independent period. This study presents an autothermal reactor for the coupled endothermic (methanol steam reforming) and exothermic (oxidation) reactions in a compact reactor. A commercial Cu-based catalyst (ReforMax® M) was used. The kinetics of both reactions were evaluated over a wide range of conditions. This catalyst was found to be very stable under moderate operating conditions (500h). The combined process provides operational advantages, high energy efficiency (84.2%) and hydrogen yield (75.2%).
2. Sror, G.; Cohen, O.; Dahan, H. O.; Landau, M. V.; Herskowitz, M., “Methane conversion to syngas by chemical looping on La0.8Sr0.2FexCo1‑xO3 (x = 0, 0.25, 0.50, 0.75) perovskites with CO2 co‑feeding”, Discover Chemical Engineering,(2023), 3, 17 . Partial oxidation of methane (POM) by chemical looping with CO2 co-feeding on La0.8Sr0.2FeO3 (LSF) perovskite catalyst yielded a highly selective operation and enabled to extend the duration of reduction cycle. In this work, the conversion of methane to syngas was studied on La0.8Sr0.2Fe(x)Co(1-x)O3 (x = 0, 0.25, 0.5, 0.75) perovskites in chemical-looping mode, co-feeding CO2 and methane. The reaction was conducted at 850 °C, 15 min reduction (10% methane in N2, 0–3% CO2), and 10 min oxidation (10% O2 in N2) cycles. The perovskites activity decreased with increasing Co content, in the absence of CO2, due to intensified coke deposition on the catalyst. Addition of CO2 during the reduction step (1–3%) reduced coke accumulation. A run conducted on La0.8Sr0.2CoO3 (LSC) with continuous feeding of CO2 and periodical (on–off) methane feeding indicated that CO2 reacts with the accumulated coke in reverse-Boudouard reaction, increasing CO selectivity without affecting the methane conversion. XRD analysis of reduced Co-containing perovskites indicates a decreasing perovskite content. Metallic Co and La2O3 phases increased as the Co content in the fresh perovskite increased, increasing coke deposition. As the Co content increased, the process shifts from POM with oxygen replenishment (LSF) to cracking followed by reverse-Boudouard reaction (LSC).
3. Dahan, H. O.; Sror, G.; Landau, M. V.; Edri, E.; Herskowitz, M., ”Selective Partial Oxidation of Methane with CO2 Using Mobile Lattice Oxygens of LSF”, ACS Engineering Au, (2023), 3, 265−277. The effects of co-feeding CO2 and methane on the performance of La0.8Sr0.2FeO3 (LSF) were studied with different CO2 concentrations. The reaction was conducted in chemical looping mode at 900 °C and a weight hourly space velocity (WHSV; g methane/g catalyst/h) of 3 h–1 during 15 min reduction (10 mol % methane with 0–1.8% CO2 in nitrogen) and 10 min oxidation (10 mol % oxygen in nitrogen) cycles. Analyses of X-ray diffraction and X-ray photoelectron spectroscopy data of spent materials indicated that CO2 reacts with the oxygen vacancies on the LSF surface during methane reduction, increasing CO selectivity in POM. As the CO2 feed concentration increased to an optimal value (1.6% CO2), the CO selectivity increased to 94%. Under those conditions, the EOR (extent of reduction) of LSF, defined as the amount of oxygen depleted from the lattice, was 0.18–0.15 mmol/min·gcat. Reducing the EOR to 0.09–0.08 mmol/min·gcat (1.8% CO2) led to partial methane combustion. These results were confirmed by altering the operating conditions (WHSV = 2 and 1 h–1, T = 950 °C) and CO2 feed concentrations while extending the reduction time. Operation in an optimal EOR range (0.17–0.10 mmol/min·gcat) that enabled optimal CO selectivity (>90%) was obtained without oxidative regeneration for the 18 h reduction time.
4. Hos, T.; Herskowitz, M., “Techno-economic Analysis of Biogas Conversion to Liquid Hydrocarbon Fuels through Production of Lean-Hydrogen Syngas”, ACS Engineering Au, (2022), 2(5), 450-460 . Large-scale biogas plants are a viable source of CH4 and CO2 to be converted efficiently into high-value products. Specifically, production of liquid hydrocarbons can enhance the availability of green fuels while achieving significant CO2 reductions on site. In this study, the production of liquid hydrocarbons is simulated by dry reforming of biogas into lean-hydrogen syngas, further converted in CO hydrogenation and oligomerization reactors. The process was modeled by using CHEMCAD based on published experimental results with the projected feed composition. A high molar feed ratio of CO2/CH4 (>1.7) was set for the reformer to minimize steam requirement while avoiding carbon formation and reaching an optimal H2 to CO molar ratio (0.7). Two options were techno-economically evaluated based on a biogas plant with a capacity of 5000 N m3/h that produces between 13.8 and 15.7 million liters per year of blending stock for transportation fuels. The economics of the process depends mainly on the cost and availability of the biogas. The minimum selling price of the liquid fuels is $1.47/L and $1.37/L for options 1 (once-through conversion of syngas to liquid fuels) and 2 (recycle of tail gas from oligomerization reactor), respectively, and can be significantly reduced in case the biogas throughput is increased to >20 000 N m3/h. Recycling of the tail gas (option 2) yielded higher productivity, resulting in higher carbon yield (77.9% on the basis of methane) and energy efficiency (67.1%). The economic viability of the process can be improved by implementing CO2 tax or other incentives to reduce capital investment. It provides a potential route for efficient conversion of biogas into liquid hydrocarbons to meet the increased demand for renewable fuels as blending stock in the transportation sector while improving the sustainability of the plant.
5. Yevilevich, Y.; Vradman, L.; Zana, J.; Weinstock, I. A.; Herskowitz, M., “Investigation into La(Fe/Mn)O3 Perovskites Formation over Time during Molten Salt Synthesis” Inorganic Chemistry, (2022), 61(17), 6367-6375 . Molten salt synthesis (MSS) of complex oxides is generally investigated by characterization of the product phases with no insight into evolution of particle morphology. In this work, LaFeO3 and LaMnO3 MSS was investigated in KF-KCl and LiCl-KCl at 850 °C using a "feeding-and-sampling" procedure. By feeding the oxide reagents into a molten salt, the reaction starting point was clearly defined, while subsequent sampling of the melt provided means for tracking the phase composition along with the shape and size of product particles during MSS. Samples taken just after 1 min contained perovskite particles along with reagents and intermediates, which were consumed over time to yield a pure product within 10-30 min. The shape and size of perovskite particles sampled at different times during MSS were virtually unchanged, revealing a lack of notable growth. The observed fast MSS along with prevailing nucleation provided means to control perovskite particle size by varying the extent of reagent dissolution. Thus, increasing the salt/reagent ratio (from 10:1 to 25:1) strikingly reduced the duration required to obtain a pure product, along with decreasing the size of product particles (from 0.5-1.5 μm to 80-200 nm). Furthermore, performing MSS in KF-KCl, which exhibits greater oxide solubility compared to LiCl-KCl, resulted in a shorter duration and smaller perovskite particles (80-200 nm and 0.6-2.0 μm, respectively). This insight into perovskite formation and growth during MSS and its kinetics provides valuable guidelines for tuning MSS conditions to better control synthesis duration and particle size.
6. Dahan, H. O.; Sror, G.; Landau, M. V.; Herskowitz, M., “Chemical looping reaction of methane with oxygen from La0.8Sr0.2FeO3-δ and La0.8Sr0.2FeO3-δ -Fe2O3 systems to syngas”, Discover Chemical Engineering, (2022), 2, 3 .The reaction of methane with oxygen from La0.8Sr0.2FeO3-δ (LSF) and several LSF-Fe2O3 configurations was studied in chemical looping mode. Shell (LSF) and core (Fe2O3) (four catalysts called CS-3, CS-4, CS-5 and CS-6, over a range of coverage), LSF mixed uniformly with Fe2O3 (UM) and Fe2O3 (front) followed by LSF (PIS) were packed in a tubular reactor. The reaction was conducted at 900 °C and weight hourly space velocity (g methane/g catalyst/h) of 3 h−1 in 20 min reduction (10 mol% methane in nitrogen) and 20 min oxidation (10 mol% oxygen in nitrogen) cycles. LSF, CS, UM and PIS configurations yielded a significantly different performance (methane conversion, CO, CO2 and H2 selectivity and coke formation) measured in 10 reproducible cycles. The reaction and XRD data indicate that CO2 and steam formed by combustion of methane on Fe2O3 modify the phase composition of LSF, inhibits the initial LSF activity and improves the performance. Feeding a mixture containing 0.4 mol% CO2, 10 mol% methane in nitrogen to LSF confirms the positive effect of CO2 on the performance of LSF.
7. Hos, T.; Landau, M. V.; Herskowitz, M., “Hydrogenation of CO2 on Fe-Based Catalysts: Preferred Route to Renewable Liquid Fuels”, Industrial & Engineering Chemistry Research, (2022), 61(29), 10387-10399. Catalytichydrogenationof CO2can be conductedeither in one pot (CO2hydrogenation)or in two stages (RWGSandCO hydrogenation).Its configurationconsistsof either threereactorsin series with interimwater removal(one-potprocess)orCO2separationand recycling(two-stageprocess)to reach highCO2conversion.The two-stageprocessenablesto reach optimalH2/CO and temperaturein the hydrogenationreactorto yieldhigher productivitywhile minimizingproductionof the aqueousphase, which offset the advantagesof the one-potprocess.Thetechno-economicstudy determinedthat there is no apparentadvantagein operatingthe hydrogenationreactionin one stage atcurrent green hydrogenprices. The decisionbetweenthe two routesshould be based on catalyststabilityand selectivitytoward desiredproducts.Blending10% of liquid productfrom both processeswith fossil fuels at current prices increasesthe fuel productioncost by30%, which can be offset by higher carbon pricing or equivalentincentives.
8. Dahan, H. O.; Landau, M. V.; Vidruk Nehemya, R; Edri, E.; Herskowitz, M.; Ruan, C.; Li, F, “Core-Shell Fe2O3@La1−xSrxFeO3−δ Material for Catalytic Oxidations: Coverage of Iron Oxide Core, Oxygen Storage Capacity and Reactivity of Surface Oxygens”, Materials, (2021), 14, 7355. A series of Fe2O3@LSF (La0.8Sr0.2FeO3−δ perovskite) core-shell materials (CSM) was prepared by infiltration of LSF precursors gel containing various complexants and their mixtures to nanocrystalline aggregates of hematite followed by thermal treatment. The content of LSF phase and amount of carboxyl groups in complexant determine the percent coverage of iron oxide core with the LSF shell. The most conformal coating core-shell material was prepared with citric acid as the complexant, contained 60 wt% LSF with 98% core coverage. The morphology of the CSM was studied by HRTEM-EELS combined with SEM-FIB for particles cross-sections. The reactivity of surface oxygen species and their amounts were determined by H2-TPR, TGA-DTG, the oxidation state of surface oxygen ions by XPS. It was found that at complete core coverage with perovskite shell, the distribution of surface oxygen species according to redox reactivity in CSM resemble pure LSF, but its lattice oxygen storage capacity is 2–2.5 times higher. At partial coverage, the distribution of surface oxygen species according to redox reactivity resembles that in iron oxide.
9. Hos, T; Herskowitz, M., "Utilization of CO-rich waste gases from the steel industry for production of renewable liquid fuels", Energy Conversion and Management, (2021), 240, 114233. Waste gases generated during steelmaking are an enormous source of CO2 emissions. Rather than supply heat and power to the plant by combustion, those gases can be utilized efficiently at a low cost to produce renewable liq. fuels. It upgrades the economic value of the gases and reduce CO2 emissions. CO-rich waste gases emitted from the blast furnace or basic oxygen furnace are of particular interest since they contain a valuable reactive compd. that is simply combusted rather than converting it to green products. A novel Fe-based catalyst was used in this study to evaluate the performance of the projected syngas compns. as feed (H2/CO molar ratio of 0.7 and CO2 content above 30%vol./vol.) for the CO hydrogenation process. The C5+ selectivity of the combined CO conversion and oligomerization processes was 81%, while the CO conversion was dependent on the WHSVCO and syngas partial pressure. Three cases were techno-economically evaluated based on the integrated steel plant with a prodn. capacity of 12MM tonnes/yr. The economics of the process depends mainly on the cost, compn. and availability of the gases. Generally, the levelized cost of product is in the range of 0.38-0.78$/L, which is significantly lower than the recent market price of renewable fuels. Sensitivity anal. suggests that the price can be further decreased. The energy efficiency is in the range of 41.7%-54.6% for all cases. Environmental benefits can be improved by integrating carbon-free H2 in the process, but its price should be reduced considerably to be economically feasible.
10. Landau, M. V.; Hos, T; Vidruk Nehemya, R; Nomikos, G; Herskowitz, M.,"Eco-friendly and sustainable process for converting hydrous bioethanol to butanol", Catalysts,(2021), 11(4), 498. The purpose of the study was the development of water-resistant catalyst and catalytic processes for the conversion of hydrous ethanol to 1-butanol. Water, in hydrous ethanol, strongly inhibits conversion to 1-butanol on solid catalysts. In this study, the nonstoichiometric P-deficient hydroxyapatite contg. carbonate anions (C-HAP), Ca10-x/2(PO4)6-x(CO3)x(OH)2, displayed good performance in the Guerbet condensation of hydrated ethanol to 1-butanol, after proper stabilization of reaction conditions. Hydrous ethanol (96 wt%) was converted on C-HAP formed as extrudates with silica binder at 400°C and wt. hour space velocity (WHSV) = 0.5-1.0 h-1 to yield 21-23% 1-butanol and 73-74% selectivity. It displayed stable operation for up to 170 h on streams conducted in bench and mini-pilot rigs with catalyst loadings of 2 and 50 cm3, resp. The process simulation employed the recycling of ethanol without lab. verification to reach 68% theor. yield of 1-butanol. The techno-economic anal. demonstrated the feasibility of this process, showing that it may be profitable depending on the prices of hydrated ethanol and 1-butanol.
11. Dahan, H. O; Landau, M. V.; Herskowitz, M., "Effect of surface acidity-basicity balance in modified ZnxZryOz catalyst on its performance in the conversion of hydrous ethanol to hydrocarbons", Journal of Industrial and Engineering Chemistry, (2021), 95, 156-169 . ZnxZryOz and modified MuZnxZryOz (M = Si, W, Sc, Mg)/Zn/(W-Zr) catalysts were studied in conversion of hydrous (4 wt.% H2O) ethanol at P = 15 bar, T = 450°C and WHSV = 0.8-7.9 h-1. The basicity of the catalysts changed from 0.015 to 0.66 mmol/g and the acidity from 0.07 to 0.24 mmol/g resulting in a wide range of basicity/acidity ratio (R) of 1.3 to 7.3. Measurements of the catalysts activity, selectivity and stability indicate a strong dependency on the R-value. The yield of org. liq. C5-C11 increased from 17 wt.% to 59 wt.% while the yield of light olefins C2-C4 decreased from 60 wt.% to 14 wt.%, as R increased from 1.3 to 7.3. The content of C5-C11 iso-olefins and aroms. in org. liq. on ZnxZryOz (R = 3.9), WuZnxZryOz (R = 2.0) and MguZnxZryOz (R = 7.3) increased significantly with the residence time. ZnxZryOz was stable up to 360 h on stream, while the activity and selectivity of MguZnxZryOz and WuZnxZryOz altered after 90 h on stream due to coke deposition blocking the acid and basic sites. It was proposed a comprehensive scheme of ethanol transformations routes consistent with the measured effects of the residence time, catalysts R-value and time on stream on the products distribution.
12. Kulkarni, A. P.; Hos, T.; Landau, M. V.; Fini, D.; Giddey, S.; Herskowitz, M., "Techno-economic analysis of a sustainable process for converting CO2 and H2O to feedstock for fuels and chemicals", Sustainable Energy & Fuels, (2021), 5(2), 486-500. Environmentally friendly and economically competitive production of renewable fuels and chemicals from CO2 and H2O, harnessing renewable electricity, is a key component in the solution to climate change. Integration of highly efficient solid oxide cells (SOECs) to convert CO2 and H2O to syngas – a mixture of H2 and CO at a molar ratio of 0.7, with a high-performance process for converting syngas to liquid feedstock for fuels and chemicals is described in this arelectrolysisticle. A novel configuration of SOECs provides a low-cost solution to produce high syngas production rates at low cell degradation. Integration of natural gas in the process directly to the anode further improves the economics and energy management. In the fuel synthesis reactor, CO conversion was 82% while C5+ selectivity of the combined CO conversion and oligomerization processes was 79%. Stable operation for 4000 h was demonstrated. The overall energy efficiency was 67%. The economics of the process depends mainly on the cost of energy and the size of the plant.
13. Utsis, N.; Landau, M. V.; Erenburg, A.; Herskowitz, M., "Reverse Water Gas Shift by Chemical Looping with Iron-Substituted Hexaaluminate Catalysts", Catalysts, (2020), 10(9), 1082.The Fe-substituted Ba-hexaaluminates (BaFeHAl) are active catalysts for reverse water-gas shift (RWGS) reaction conducted in chemical looping mode. Increasing of the degree of substitution of Al3+ for Fe3+ ions in co-precipitated BaHAl from 60% (BaFeHAl) to 100% (BaFe-hexaferrite, BaFeHF), growing its surface area from 5 to 30 m2/g, and promotion with potassium increased the CO capacity in isothermal RWGS-CL runs at 350–450 °C, where the hexaaluminate/hexaferrite structure is stable. Increasing H2-reduction temperature converts BaFeHAl to a thermally stable BaFeHF modification that contains additional Ba-O-Fe bridges in its structure, reinforcing the connection between alternatively stacked spinel blocks. This material displayed the highest CO capacity of 400 µmol/g at isothermal RWGS-CL run conducted at 550 °C due to increased concentration of oxygen vacancies reflected by greater surface Fe2+/Fe3+ ratio detected by XPS. The results demonstrate direct connection between CO capacity measured in RWGS-CL experiments and calculated CO2 conversion.
14. Dahan, H. O.; Porgador, B.; Landau, M. V.; Herskowitz, M., "Conversion of hydrous bio-ethanol on ZnxZryOz catalyst to renewable liquid chemicals and additives to gasoline", Fuel Processing Technology, (2020), 198, 106246. The conversion of ethanol on the ZnxZryOz catalyst was studied over a wide range of operating conditions to determine the possibility of producing organic liquid (olefins, aromatics and oxygenates). The content of water in the feed was found to be the key parameter. At ≥60 wt% water, no organic liquid is formed. As water content decreased, the yield of organic liquid increased. Furthermore, increasing pressure increased the yield of organic liquids. Experiments conducted at increasing residence time indicated that ethanol was first converted to oxygenates then to aromatics and higher olefins (C5–C11) with propylene, ethylene, carbon dioxide and hydrogen as the main by-products. Increasing temperature at high residence time (WHSV = 0.8 h−1) decreased the yield of liquid oxygenates while increasing the yield of aromatics and higher olefins. A tentative scheme of reactions was proposed considering the special nature of the ZnxZryOz catalyst with balanced basic-acidic sites. The catalyst was stable, tested for >300 h. Tail gas containing light olefins, mainly propylene and ethylene, was converted by oligomerization on a commercial H-ZSM-5 catalyst to higher olefins (>90%) and aromatics at high conversion (>90%). The organic liquid from the two reactors can be used as feedstock for chemicals or as blending stock for gasoline.
15. Dahan, H. O.; Landau, M. V.; Herskowitz, M., " Effect of surface acidity-basicity balance in modified ZnxZryOz catalyst on its performance in the conversion of hydrous ethanol to hydrocarbons", Journal of Industrial and Engineering Chemistry, (2020). ZnxZryOz and modified MuZnxZryOz (M = Si, W, Sc, Mg)/ Zn/(W-Zr) catalysts were studied in conversion of hydrous (4 wt% H2O) ethanol at P =15 bar, T = 450 °C and WHSV = 0.8-7.9 h-1. The basicity of the catalysts changed from 0.015 to 0.66 mmol/g and the acidity from 0.07 to 0.24 mmol/g resulting in a wide range of basicity/acidity ratio (R) of 1.3 to 7.3. Measurements of the catalysts activity, selectivity and stability indicate a strong dependency on the R-value. The yield of organic liquid C5-C11 increased from 17 wt% to 59 wt% while the yield of light olefins C2-C4 decreased from 60 wt% to 14 wt%, as R increased from 1.3 to 7.3. The content of C5-C11 iso-olefins and aromatics in organic liquid on ZnxZryOz (R = 3.9), WuZnxZryOz (R = 2.0) and MguZnxZryOz (R = 7.3) increased significantly with the residence time. ZnxZryOz was stable up to 360 h on stream, while the activity and selectivity of MguZnxZryOz and WuZnxZryOz altered after 90 h on stream due to coke deposition blocking the acid and basic sites. It was proposed a comprehensive scheme of ethanol transformations routes consistent with the measured effects of the residence time, catalysts R-value and time on stream on the products distribution.
16. Elishav, O.; Shener, Y.; Beilin, V.; Shter, G.E.; Ng, B.; Mustain, W.E.; Landau, M.V.; Herskowitz, M.; Grader, G.S., "Electrospun nanofibers with surface oriented lamellar patterns and their potential applications." Nanoscale, (2020), 12(24), 12993-13000. This work shows conclusively that lamellar surface patterns can be obtained with diverse ceramic compositions during electrospinning. The lamellar structure formation is governed by the creation of an outer
shell during the thermal treatment of initially uniform cylindrical fibers, consisting of polymer and preceramic compounds. By changing the polymer to pre-ceramic ratio in the electrospinning solution, we
demonstrate for the first time a facile way to control the obtained surface structure and the orientation of
the lamellas. Furthermore, the lamellar morphology was illustrated in seven different compositions. This
report provides a new pathway to obtain unique surface patterns in metal–oxide nanofibers and demonstrates their utilization in different applications. Specifically, we demonstrate the prospect of utilizing Ni–
Al–O fibers with lamellar structures as alternative Li-ion battery anodes. In addition, we show the potential
of Fe–Al–O fibers as an effective catalyst material.
17. Elishav, O.; Shener, Y.; Beilin, V.; Landau, M. V.; Herskowitz, M.; Shter, G. E.; Grader, G. S., "Electrospun Fe–Al–O Nanobelts for Selective CO2 Hydrogenation to Light Olefins", ACS applied materials & interfaces, (2020), 12(22), 24855-24867. Ceramic nanobelt catalysts consisting of Fe−Al−O spinel modified with potassium were synthesized for CO2 hydrogenation into hydrocarbons. Nanobelts and hollow nanofibers were produced utilizing the internal heat released by oxidation of the organic component within the fibers. This extremely fast and short heating facilitated crystallization of the desired phase, while maintaining small grains and a large surface area. We investigated the effects of mat thickness, composition, and heating rate on the final morphology. A general transformation mechanism for electrospun nanofibers that correlates for the first time the mat’s thickness and the rate of oxidation during thermal treatment was proposed. The catalytic performance of carburized ceramic K/Fe−Al−O nanobelts was compared to the K/Fe−Al−O spinel powder. The electrospun catalyst showed a superior carbon dioxide conversion of 48% and a selectivity of 52% to light C2−C5 olefins, while the powder catalyst produced mainly C6 + hydrocarbons. Characterization of steady state catalytic materials by energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and N2-adsorption methods revealed that high olefin selectivity of the electrospun materials is related to a high extent of reduction of surface iron atoms because of more efficient interaction with the potassium promoter.
18. Žerjav, G.; Pintar, A.; Ferentz, M.; Landau, M.; Haimovich, A.; Goldbourt, A.; Herskowitz, M., "Effect of Surface Chemistry and Crystallographic Parameters of TiO2 Anatase Nanocrystals on Photocatalytic Degradation of Bisphenol A", Catalysts, (2019), 9(5), 447. The photocatalytic activity of a series of anatase TiO2 materials with different amounts of exposed (001) facets (i.e., 12% (TiO2-1), 38% (TiO2-3), and 63% (TiO2-3)) was tested in a batch slurry reactor towards liquid-phase bisphenol A (BPA, c0(BPA) = 10 mg/L, ccat. = 125 mg/L) degradation. Photo-electrochemical and photo-luminescence measurements revealed that with the increasing amount of exposed anatase (001) facets, the catalysts generate more electron-hole pairs and OH∙ radicals that participate in the photocatalytic mineralization of pollutants dissolved in water. In the initial stages of BPA degradation, a correlation between % exposure of (001) facets and catalytic activity was developed, which was in good agreement with the findings of the photo-electrochemical and photo-luminescence measurements. TiO2-1 and TiO2-3 solids achieved 100% BPA removal after 80 min in comparison to the TiO2-2 sample. Adsorption of BPA degradation products onto the TiO2-2 catalyst surface was found to have a detrimental effect on the photocatalytic performance in the last stage of the reaction course. Consequently, the global extent of BPA mineralization decreased with the increasing exposure of anatase (001) facets. The major contribution to the enhanced reactivity of TiO2 anatase (001) surface is the Brønsted acidity resulting from dissociative chemisorption of water on a surface as indicated by FTIR, TPD, and MAS NMR analyses.
19. Meir, R.; Vradman, L.; Zana, J.; Herskowitz, M., "Effect of salt type on the particle size of LaMn1-xFexO3 (0.1≤ x≤ 0.5) synthesized in molten chlorides", Materials Chemistry and Physics, (2019), 231, 181-187. LaMn1-xFexO3 perovskites were successfully synthesized via molten salt synthesis in NaCl-KCl and LiCl-KCl, for the first time. The effect of salt type on the size of the obtained perovskite particles was investigated using two procedures. The first, corresponding to the common “mixing” synthesis procedure, included heating the La-, Mn- and Fe-nitrates and chlorides mixture above the melting point of the chloride mixture. While the synthesis temperature (600–850 °C) and perovskite composition (0.1 ≤ x ≤ 0.5) had no significant effect on the LaMn1-xFexO3 particle size, the effect of molten salt type was dramatic. The average size of LaMn1-xFexO3 particles synthesized in LiCl-KCl was 0.7–0.8 μm, while more than twice smaller particles were obtained in NaCl-KCl. Since different salts have both different melting points as well as different chemical and physical properties, it is impossible to distinguish between the individual contributions of these characteristics to the observed size difference. In order to address this problem, a second “feeding” procedure was employed, which skips the melting event by feeding the metal nitrates into already molten salt. Particles obtained using “feeding” procedure in LiCl-KCl (∼0.5 μm) were still larger than those obtained in NaCl-KCl (∼0.3 μm). The remnant effect, attributed solely to the salt properties, is explained by the nucleation and crystal growth model, with respect to higher perovskite solubility in LiCl-KCl. The suggested “feeding” procedure renders the separate analysis of synthesis conditions (e.g. the sole effect of salt type) for the first time, and can assist in the unraveling of molten salt synthesis mechanistic aspects.
20. Ferentz, M.; Landau, M. V.; Herskowitz, M., " Relationship of crystals shape, aggregation mode and surface purity in catalytic wet peroxide oxidation of phenol in dark with titania anatase nanocrystals", Catalysis Letters, (2018), 148(11), 3524-3533. A series of TiO2 anatase materials with a thickness to width ratio of 0.22–0.62 in their primary nanocrystals, 1.03–1.27 nanocrystals aggregation ratio and 38–68% exposure of (001) facets were tested in phenol CWPO in a fixed-bed reactor in dark. Inactive oxyfluoride phase that covers the as-synthesized nanocrystals should be removed in order to get the highest catalytic activity. Catalytic activity was proportional to the value of surface area related to the exposed (001) facets at the TiO2 nanocrystals surface excluding any synergistic effects between (001) and (101) facets in catalysis. The linear regression of experimental data for studied reaction revealed that the specific catalytic activity per 1 m2 of (001) facets at the surface of TiO2 nanocrystals is at least four times higher compared with that of (101) facets. This is in agreement with theoretical predictions attributing the catalytic activity to surface titanols as active sites and formation of titanols mainly at the surface of (001) facets due to dissociative adsorption of water.
21. Utsis, Natalie; Landau, Miron V.; Erenburg, Alexander; Nehemya, Roxana Vidruk; Herskowitz, Moti. "Performance of Reverse Water Gas Shift on Coprecipitated and C-Templated BaFe-Hexaaluminate: The Effect of Fe Loading, Texture, and Promotion with K", ChemCatChem (2018), 10(17), 3795-3805. The effects of chem. compn., texture, and promotion with potassium of copptd. and carbon-templated BaFe-hexaaluminate catalysts on their performance in reverse water gas shift (RWGS) reaction were studied in a fixed-bed catalytic reactor at T=350 °C, p=20 bar, H2: CO2 of 3. The methane selectivity at these conditions did not exceed 0.1 %. It was established that the rate of RWGS is strongly affected by the catalysts iron content gradually increasing up to 45 % Fe. Decreasing the catalyst nanocrystals platelets size (diam./thickness) from 500-800/50-80 nm to 150-250/30-50 nm (SEM) by implementing the CT increased the surface area and the rates of reaction. Modeling of the redox cycle of RWGS by CO2-TPD, TP reaction and TP redn. indicated that H2 redn. is needed for regeneration of active sites Fe2+ ions assocd. with oxygen vacancies. Potassium displayed a strong promotion effect on the activity of Ba-Fe-hexaaluminates. At optimal K content of 6 wt %, the RWGS rates increased by a factor of 12-15 without changing the TOF no. This was attributed to increasing concn. of active sites due to the redn. of Fe3+ ions (XPS).
22. Samanta, A.; Landau, M. V.; Vidruk-Nehemya, R.; Herskowitz, M. "CO2 hydrogenation to higher hydrocarbons on K/Fe-Al-O spinel catalysts promoted with Si, Ti, Zr, Hf, Mn and Ce", Catalysis Science & Technology (2017), 7(18), 4048-4063. Metal oxides grafted on K/Fe-Al-O spinel precursors prepd. by co-pptn. in the presence of the surfactant CTAB displayed significant effects on the performance of the catalysts in CO2hydrogenation to hydrocarbons. Specifically, 20 wt% titania and 20 wt% zirconia increased the rates of both the reverse water gas shift reaction (RWGS) and the Fischer-Tropsch synthesis (FTS), as reflected in the increase of the CO2conversion and the decrease of CO selectivity. While 20 wt% titania increased methane and C2-C4 selectivity and decreased C5+ selectivity, 20 wt% zirconia displayed no effect on methane and increased C2-C4 and C5+ selectivity. The 5 wt% hafnia and 5 wt% manganese oxide had little effect on performance and 5 wt% ceria enhanced the selectivity to both methane and light C2-C4 and significantly decreased the selectivity to C5+. Silica inserted by grafting at the Fe-Al-O surface at 5 wt% acted as a promoter of CO2 conversion but at high loading of 15 wt% was a strong inhibitor to FTS, increased methane and CO selectivity and decreased CO2conversion. Nanoparticles of both spinel and Fe-carbide phases in contact with zirconia caused a decline in the electron d. of surface iron atoms, as reflected by the increase of the binding energy of Fe (2p) electrons by 0.7-0.8 eV as detected by XPS. This may be a result of a strong interaction of iron oxide and zirconia due to incorporation of Zr in the Fe-Al-O spinel structure and a strong interaction of near metallic iron in carbide nanocrystals in contact with ZrO2 nanoparticles that plays a role of an electron acceptor as a Lewis acid and explains the increase of CO2 conversion. The extremely low activity of the silica modified catalyst in FTS and enhanced activity in methanation are consistent with the model of selective blocking of the surface iron ions of the Fe-carbide component with grafted silica moieties and their interaction with the potassium promoter.
23. Vradman, L.; Friedland, E.; Zana, J.; Vidruk-Nehemya, R.; Herskowitz, M. "Molten salt synthesis of LaCoO3 perovskite", Journal of Materials Science (2017), 52(19), 11383-11390. LaCoO3 perovskite was successfully synthesized in molten NaCl-KCl eutectic mixt. Heating La-nitrate, Co-nitrate, and NaCl-KCl mixt. to 800° yielded large (≤5 μ) LaCoO3 cubic particles. Conversely, when La- and Co-nitrates were fed into the NaCl-KCl mixt., molten, and stabilized at 800 °C, much smaller (sub-micron) particles were obtained. These results expound the mechanistic aspects of the perovskites formation in molten salts involving nucleation and crystal growth phenomena.
24. Landau, M. V.; Meiri, N.; Utsis, N.; Vidruk Nehemya, R.; Herskowitz, M. "Conversion of CO2, CO, and H2 in CO2 Hydrogenation to Fungible Liquid Fuels on Fe-Based Catalysts", Industrial & Engineering Chemistry Research (2017), 56(45), 13334-13355. CO2 hydrogenation conducted on Fe-based catalysts consists of a wide range of reactions with CO2 and H2 reacting in the reverse water-gas shift (RWGS) to produce CO and CO and H2reacting in the Fischer-Tropsch (FT) type reactions leading to hydrocarbons and oxygenates. Methanation and Boudouard side reactions are extremely detrimental to selectivity and stability of the Fe-based catalysts. The catalytic system is very complex, posing challenging issues that require fundamental understanding of the dynamics of changes in the catalytic phases, mechanism of key reactions, and effects of catalyst compn. including key promoters. A comprehensive anal. of fundamental aspects of catalytic materials, phases, and promoters and the catalytic mechanisms are presented in this paper. It was established that the ratio of Fe(carbide)/Fe(oxide) atoms at the surface of an activated catalyst responsible for its selectivity is detd. by the environment of iron ions in oxide precursors changed by insertion of ions of other metals. Fungible liq. fuels were produced in bench scale reactors and demonstrated to be suitable as blending stock for transportation fuels. The techno-economic anal. of processes using CO2 and either water, biogas, or natural gas as feedstock was conducted. As expected, the prodn. of eco-friendly, renewable fuels based on CO2 is not competitive with fuels based on crude oil because of the high cost of prodn. of hydrogen.
25. Amoyal, Meital; Vidruk-Nehemya, Roxana; Landau, Miron V.; Herskowitz, Moti. "Effect of potassium on the active phases of Fe catalysts for carbon dioxide conversion to liquid fuels through hydrogenation", Journal of Catalysis (2017), 348, 29-39. The effect of potassium was tested with unpromoted and K-promoted Fe-Al-O oxide and Fe5C2 carbide materials, formed during CO2 hydrogenation from Fe-Al-O spinel. Each one of the tested catalysts contained a single phase (oxide or carbide). The 2 wt% potassium enhanced the reverse water gas shift reaction rate of reaction on the oxide phase tenfold compared with the unpromoted oxide. This correlated with increase of Fe2+/Fe3+ ratio (XPS) detg. oxygen vacancies as active sites for reverse water gas shift reaction. Potassium suppressed the methanation rate on the carbide catalyst by a factor of five and increased the CO FTS rate to C2+ hydrocarbons by a factor of 1.4. The EFTEM images and elemental profiles of unpromoted carbide nanocrystals measured after testing in CO hydrogenation displayed an amorphous surface layer enriched with oxygen. Potassium stabilized the surface iron atoms in reduced form. The obsd. effects of potassium on carbide phase were explained by a model implementing carbon vacancies for methanation and near-metallic iron atoms for FTS.
26. Meiri, Nora; Radus, Roman; Herskowitz, Moti. "Simulation of novel process of CO2 conversion to liquid fuels", Journal of CO2 Utilization (2017), 17, 284-289. Carbon dioxide utilization by conversion with hydrogen into liq. fuels was simulated based on the exptl. data of a novel process using CHEMCAD. A detailed kinetic model of the novel iron-based spinel catalyst that included reverse water gas shift (RWGS), Fischer-Tropsch synthesis (FTS), C5+ hydrocarbons and oxygenates, oligomerization of olefins, as well as hydrogenation of light olefins (C2-C4) was employed. The RWGS reaction rate was significantly inhibited by steam produced in the process because of the chem. equil. limitation and apparent strong adsorption. Therefore, periodical water removal is crit. in the process, which required operation in several reactors in series or in a reactor with recycle. Those system configurations were examd. and compared over a range of temps., pressures, wt. hourly space velocities and carbon dioxide with hydrogen feed ratios. The other aspect of this process which has a significant impact on performance is the oligomerization of light olefins. Both reactors-in-series and single reactor with recycle improved dramatically the productivity and the selectivity to C5+.
27. Cole, Andrew; Dinburg, Yakov; Haynes, Brian S.; He, Yaya; Herskowitz, Moti; Jazrawi, Christopher; Landau, Miron; Liang, Xiao; Magnusson, Marie; Maschmeyer, Thomas; et al, "From macroalgae to liquid fuel via waste-water remediation, hydrothermal upgrading, carbon dioxide hydrogenation and hydrotreating", Energy & Environmental Science (2016), 9(5), 1828-1840. This article showcases a proof-of-concept in the prodn. of high quality renewable biofuel from algae. Here, we introduce a path combining a no. of approaches that, when integrated as a whole, create a process that takes algae grown in waste-water through to a liq. fuel contg. fractions ready for blending with regular gasoline, jet fuel and diesel. With the overarching goal of reducing the nitrogen content invariably assocd. with whole algal biomass, we apply a no. of approaches including (i) nutrient starvation to reduce the internal nitrogen of the freshwater alga Oedogonium (ii) continuous co-solvent (10 wt% n-heptane) hydrothermal liquefaction (HTL) to produce a non-polar biocrude contg. <1 wt% N; (iii) blending the biocrude with green feed produced from the hydrogenation of CO2 to obtain <0.5 wt% N; (iv) hydrogenation and hydro-isomerization of the blend in two stages over nanodisperse silica-supported Ni2P (achieving 630 ppm N) and acidic zeolite-supported Pt catalysts resp. to produce a synthetic paraffinic mixt. (SPM) contg. 277 ppm N and 0.12% O. With the incorporation of renewable H2(which can be from gasification of polar orgs. produced in the solvent HTL, or other renewable sources) and captured CO2 the process demonstrates a new and tech. cohesive approach to the prodn. of renewable, high-quality biofuels for demanding transport applications.
28. Utsis, N.; Vidruk-Nehemya, R.; Landau, M. V.; Herskowitz, M. "Novel bifunctional catalysts based on crystalline multi-oxide matrices containing iron ions for CO2 hydrogenation to liquid fuels and chemicals", Faraday Discussions (2016), 188(Designing New Heterogeneous Catalysts), 545-563. Seven solid mono-, bi- and tri-metallic oxide matrixes where Fe(2+,3+) ions are distributed in different chem./spatial environments were synthesized and characterized by XRD, N2-adsorption and EDAX methods. After basification with potassium, all matrixes were activated by carburization or redn.-carburization under conditions selected based on the TPC/TPR spectra, tailoring the carburization extent of iron. The performances of the activated Fe-based catalysts with respect to CO2 conversion and C5+ selectivity were measured in a fixed-bed reactor under std. conditions in transient and continuous operation modes in units contg. one or three reactors in series with water sepns. between the reactors. The catalysts were characterized by XRD, N2-adsorption, HRTEM-EELS and XPS before and after steady-state operation in the reactors. It was found that the rate of CO2 conversion is not limited by thermodn. equil. but is strongly restricted by water inhibition and it depends on the nature of the Fe-oxide precursor. The ratio between the FTS and RWGS rates, which dets. the C5+ hydrocarbons productivity, is strongly affected by the nature of the Fe-oxide matrix. The catalysts derived from the Fe-Al-O spinel and Fe-Ba-hexaaluminate precursors displayed the best balance of the two functions RFTS/RRWGS = 0.77-0.78. They were followed by magnetite, CuFe-delafossite, K-ferrite, Fe-La-hexaaluminate and LaFe-perovskite with a gradual lowering of RFTS/RRWGS from 0.60 to 0.15 and a gradual decrease in the C5+ productivity. The active sites that enhance the RWGS reaction are located on the surface of the Fe-oxide phases, while the FTS and methanation reactions occur on the surface of the Fe-carbide phases.
29. Herskowitz, M., Landau, M.V., Koukouliev, S., Zarchin, R., Vidruk-Nehemya, R., Wee, Lik H. and Martens, Johan A. "Homogeneous Tubular-Flow Process for Monoolein Preparation", Journal of the American Oil Chemists' Society (2015), 92(10), 1525-1529. Esterification of fatty acids with glycerol is characterized by negligible soly. of the two liq. phases. The reactions to mono-, di- and triglycerides taking place in the fatty acid phase, are limited by chem. equil. The scope of this study is to investigate in a tubular reactor the conversion of a homogeneous mixt. of oleic acid and glycerol in tert-butanol. The liq. compn. in this study was 1 mol of oleic acid, 6 mol of glycerol and 14 mol of tert-butanol. Expts. were conducted in a tubular reactor at 35 atm over a temp. range of 200-240 °C and residence times of 0.7-17.6 h to det. the kinetics and the chem. equil. The selectivity to monoolein was >95 mol %. A reversible second order reaction fits the data well.
30. Rabaev, M., Landau, M.V., Vidruk-Nehemya, R., Koukouliev, V., Zarchin, R. and Herskowitz, M. "Conversion of vegetable oils on Pt/Al2O3/SAPO-11 diesel and jet fuels containing aromatics", Fuel (2015)161, 287-294. Vegetable oils are excellent feedstock for prodn. of diesel and jet fuels. However, catalysts and processes published in the literature do not produce drop-in fuels. One of the major problems is the selectivity and stability of the catalysts. It is vital that the hydrotreating is tested after at least 200 h on stream to measure the steady-state performance of the catalyst rather than its initial activity. The presence of aroms. is a crit. issue. This study addresses specifically the issue of aroms. related to the compn. of the vegetable oils. A novel Pt/Al2O3/SAPO-11 is used. Testing six different oils indicates that a certain level of poly-unsatn. of the fatty acids is required to produce relatively high aroms. content. This was further supported in specific tests of vegetable oils, fatty acids and C16 hydrocarbons dissolved in decane. Therefore, poly-unsatd. soybean, sunflower and camelina oils produce fuels contg. about 15 wt% aroms. while the content of aroms. in the product of palm or castor oils hydrotreating is 2 wt%. A tentative reactions sequence was suggested leading to triglycerides aromatization on the basis of measured dependency of hydrotreated oil products on the process space time, structure of arom. hydrocarbons and published chem. transformations of triglycerides. Three stage processes were proposed to produce jet fuels that meet the stds. 42-48 wt% yield of the jet fuel is reported. This is a basis for com. prodn. of drop-in diesel and jet fuel.
31. Meiri, N., Dinburg, Y., Amoyal, M., Koukouliev, V., Vidruk-Nehemya, R., Landau, M.V. and Herskowitz, M. "Novel Process and catalytic materials for converting CO2 and H2 containing mixtures to liquid fuels and chemicals", Faraday Discussions (2015), 183(Carbon Dioxide Utilisation), 197-215. Carbon dioxide and water are renewable and the most abundant feedstocks for the prodn. of chems. and fungible fuels. However, the current technologies for prodn. of hydrogen from water are not competitive. Therefore, reacting carbon dioxide with hydrogen is not economically viable in the near future. Other alternatives include natural gas, biogas or biomass for the prodn. of carbon dioxide, hydrogen and carbon monoxide mixts. that react to yield chems. and fungible fuels. The latter process requires a high performance catalyst that enhances the reverse water-gas-shift (RWGS) reaction and Fischer-Tropsch synthesis (FTS) to higher hydrocarbons combined with an optimal reactor system. Important aspects of a novel catalyst, based on a Fe spinel and three-reactor system developed for this purpose published in our recent paper and patent, were investigated in this study. Potassium was found to be a key promoter that improves the reaction rates of the RWGS and FTS and increases the selectivity of higher hydrocarbons while producing mostly olefins. It changed the texture of the catalyst, stabilized the Fe-Al-O spinel, thus preventing decompn. into Fe3O4 and Al2O3. Potassium also increased the content of Fe5C2 while shifting Fe in the oxide and carbide phases to a more reduced state. In addn., it increased the relative exposure of carbide iron on the catalysts surface, the CO2 adsorption and the adsorption strength. A detailed kinetic model of the RWGS, FTS and methanation reactions was developed for the Fe spinel catalyst based on extensive exptl. data measured over a range of operating conditions.
32. Rabaev, M, Landau M.V.,Vidruk-Nehemya, R., Goldbourt, A. and Herskowitz, M. "Improvement of hydrothermal stability of Pt/SAPO-11 catalyst in hydrodeoxygenation-isomerization-aromatization of vegetable oil", Journal of Catalysis (2015)332, 164-176.SAPO-11 component of Pt/SAPO-11-Al2O3 catalysts displays relatively low hydrothermal stability in hydrotreating of vegetable oils that produces water during the process. Application of XRD, HRTEM, NH3 TPD, TPO, H2 pulse chemisorptions and 29Si MAS NMR revealed that the reason for hydrothermal deactivation of SAPO-11 is partially reversible desilication of its framework. This results in gradual loss of acidity and catalytic activity in isomerization of normal paraffins - products of oil deoxygenation. Addn. of amine surfactant hexadecylamine to SAPO-11 crystn. gel at HDA/Al2O3 ratio of ∼0.6 strongly increases the hydrothermal stability of SAPO-11. This translates in stable operation of Pt/SAPO-11-Al2O3 catalyst in hydrotreating of soybean oil yielding >99% deoxygenation and producing liq. org. product with cloud point < -35 °C contg. 15 wt% monoaroms. The stabilizing effect of HDA is a sequence of increasing the relative content of Si(nAl(4-n)Si) tetrahedra with n = 3-4 displaying higher resistance to hydrothermal desilication.
33. Zarchin, R., Rabaev, M., Vidruk-Nehemya, R., Landau, M.V. and Herskowitz, M. "Hydroprocessing of soybean oil on nickel- phosphide supported catalysts", Fuel (2015), 139, 684-691. Ni2P /silica and Ni2P /HY were prepd. and for the first time tested in hydroprocessing of soybean oil. The content of Ni2P in each catalyst was about 25 wt %. The expts. conducted in a trickle- bed reactor operated at conditions normally used in such processes, yielded high hydrodeoxygenation (HDO) activity of both catalysts. No apparent hydrocracking activity was recorded with Ni2P /silica while Ni2P /HY displayed high hydrocracking and isomerization activity that diminished with time on stream. Characterization of the fresh and spent Ni2P /HY indicated that exposing the catalyst to water vapors generated by hydrodeoxygenation reduced the acidity of the catalyst thus reducing its hydrocracking activity. After removal of >99.5 % oxygen by HDO of soybean oiland sepn. of water vapors, the Ni2P /HY material displayed stable operation during >250 h on stream yielding up to 50 vol % of light fraction boiling out at <250 °C.
34. Yitzhaki, D.; Landau, M. V.; Berger, D.; Herskowitz, M., "Deep desulfurization of heavy atmospheric gas oil with Co-Mo-Al catalysts, effect of sulfur adsorption", Appl. Catal. A, (1995), 122(2), 99-110.Transient sulfur adsorption and reaction on partially sulfided and oxidn.-regenerated Co-Mo/Al2O3 catalysts in the hydrodesulfurization of heavy atm. gas oil (HAGO) was studied in batch and trickle-bed reactors at 360° C and 5.5 MPa. The contribution of sulfur adsorption to sulfur removal was significant in cases of 1000-1800 ppm sulfur in the feedstock. The sulfur level in the hydrotreated HAGO was decreased by 50-350 ppm due to sulfur adsorption on the catalyst for periods of 20-50 h. The principle of regeneration and adsorption in a trickle bed was demonstrated. A model that describes the transient adsorption and reaction was proposed.
35. Landau, M. V.; Herskowitz, M., "Silica-supported crystals of ZSM-5 zeolite: Effect of zeolite loading", Stud. Surf. Sci. Catal. (Catalysis by Microporous Materials), (1995), 94, 357-62. The small crystals of ZSM-5 zeolite were synthesized and stabilized inside the pores of silica gel support. Changing the synthesis conditions, six samples with zeolite loading 5-90 wt.% and a ref. 100% crystallinity zeolite, all with SiO2/Al2O3 ratio .apprx. 90 were prepd. Two stages of crystn. were identified: i) formation of small ZSM-5 zeolite crystals (0.025mm) in the supports mesopores and large zeolite crystals (4mm) on the outer surface of the silica pellets followed by ii) faster crystn. in the interior of the carriers pellet. The second stage proceeds faster giving 50-90 wt.% zeolite/SiO2, leaving empty spaces inside the pellets and fully destroying the carriers pore structure. At low (<15 wt.%) and high (>50 wt.%) loadings, zeolite crystals are partially blocked with amorphous material. The optimal zeolite loading providing good accessibility of small crystals and maximal catalytic activity is about 40 wt.%.
36. Landau, M. V.; Berger, D.; Herskowitz, M., "Hydrodesulfurization of methyl-substituted dibenzothiophenes: fundamental study of routes to deep desulfurization", J. Catal. (1996), 159(1), 236-45. Four catalysts, Co-Mo and Ni-Mo, designed to cover a wide range of activity for arom. ring hydrogenation and two catalysts, zeolite-Co-Mo, with different cracking activities were tested, in the hydrodesulfurization of dibenzothiophene (DBT) and 4,6-dimethyl-DBT (DMDBT) in a fixed-bed reactor at 360° and a hydrogen pressure of 5.4 MPa. Increasing the hydrogenation activity of the catalysts increased the mole ratio, a, of cyclohexylbenzenes to biphenyls produced from both reactants. Although a had little effect on the hydrodesulfurization (HDS) rate of DBT, the HDS rate of DMDBT increased significantly with a, approaching the same level as for DBT at a = 2. Introduction of zeolite HZSM-5 to the Co-Mo-Al catalyst increased the HDS rate of DBT at a lower value of a and decreased that of DMDBT. No cracking reactions of DBT and DMDBT were detected. A Co-Mo-Al catalyst contg. HY zeolite displayed significant cracking activity of DMDBT defined by two routes: demethylation of benzenic rings and scission of the C-C bond connecting the benzenic rings. It resulted in increasing HDS rates of DMDBT about threefold relative to the Co-Mo-Al catalyst, yielding toluene and benzene, at a ratio of about 3, as the main HDS products. About 80% of the DMDBT desulfurized with HY-Co-Mo-Al catalyst was converted through "cracking" intermediates, 90% of those intermediates being produced through the scission of the C-C bond connecting the benzenic rings.
37. Landau, M. V.; Kaliya, M. L.; Herskowitz, M. van den Oosterkamp, P. F.; Bocque, P. S. G., "Produce light olefins from paraffins by catalytic oxidation", CHEMTECH (1996), 26(2), 24-9. LPG contg. 25 wt.% butane, 25 wt.% isobutane, and 50 wt.% propane was oxidatively dehydrogenated in the presence of rare earth oxide-contg. catalysts to give light olefins.
38. Berger, D.; Landau, M. V.; Herskowitz, M.; Boger, Z., "Deep hydrodesulfurization of atmospheric gas oil. Effects of operating conditions and modeling by artificial neural network techniques", Fuel, (1996), 75(7), 907-911. Artificial neural networks (ANN) are currently being explored in various engineering fields as valuable tools for automatic model-building and knowledge acquisition. This technique was applied to model hydrodesulfurization of atm. gas oil in a mini-pilot trickle-bed reactor. Sulfur removal was measured as a function of temp., pressure and liq. hourly space velocity (LHSV) for three sulfur feed concns. The potential of a two-stage process was also tested. A set of exptl. data was used to teach a three-layer neural network. The capability of the artificial neural network to predict the performance was tested with a different set of data. The agreement between predicted and exptl. values was good. Temp., LHSV and staging of the process were detd. to be important parameters, while pressure had a little effect over the range tested in this study.
39. Landau, M. V.; Herskowitz, M.; Givoni, D.; Laichter, S.; Yitzhaki, D., "Medium-severity hydrotreating and hydrocracking of Israeli shale oil. 1. Novel catalyst systems", Fuel, (1996), 75(7), 858-866. Novel catalysts were developed for the hydrodesulfurization, hydrodenitrogenation and hydrocracking of Israeli shale oil. They were designed to operate on feedstock contg. a high level of sulfur and nitrogen. Two hydrotreating stages and one hydrocracking stage were performed in a batch reactor. High-activity catalysts with large macropores yielded 97 and 79% conversion of sulfur and nitrogen resp. in the first stage. 1H and 13C NMR and nitrogen distribution measurements among the distn. cuts showed that nitrogen remaining after the first hydrotreating stage comprised low-mol.-wt. hetero-aroms. A further redn. of the sulfur to 100-200 ppm and nitrogen to 7-30 ppm was obtained in the second stage using zeolite-contg. catalysts. The major parameters affecting the catalyst performance were tested. A moderate temp. of 380°C and pressure of 15 MPa were used in both stages. A selective dual-zeolite hydrocracking catalyst in a third stage yielded 80% of the product in the naphtha boiling range.
40. Landau, M. W.; Herskowitz, M.; Givoni, D.; Laichter, S.; Yitzhaki, D., "Medium severity hydrotreating and hydrocracking of Israeli shale oil-II. Testing of novel catalyst systems in a trickle bed reactor", Fuel, (1997), 77(1/2), 3-13. Hydrotreating Israeli shale oil at 150 atm, an LHSV of 0.5-1.5 h-1, a temp. of 340-400°C, and a hydrogen to oil ratio of 1500 NL L-1 was studied in a trickle-bed reactor pilot plant packed with two novel catalysts in series. The first catalyst was Ni-Mo supported on wide-pore alumina and the second catalyst was Co-Mo-Cr supported on combined zeolite HY-alumina carrier. The desulfurization conversion was higher than 99% over the operating conditions tested while denitrogenation conversion varied over the range 74.3-99.9%. The pseudo-first-order denitrogenation rate consts. measured at 380°C increased from 1.9 to 2.9 h-1 with increasing distn. temps. of shale oil fractions from <250°C to >380°C. The apparent activation energy decreased from 29.8 to 23.1 kcal mol-1. The effects of LHSV and temp. on the structure of shale oil components and hydrocarbons distribution was studied using 1H and 13C NMR and GC-MS methods. The yields of total liq. product, gasoline, jet and diesel fuels at 380°C and LHSV = 0.5 h-1 were 89.4, 9.3, 22.5 and 65.8 wt% of crude shale oil. The vol. yield of liq. product per crude shale oil at those conditions was 106.9%. It contained 160 ppm sulfur and 80 ppm nitrogen. The quality parameters of motor fuels produced from shale oil by hydrotreating with the two-catalyst system meets certain specifications except gasoline, which displayed low Reid vapor pressure and RON 72. A 400 h stability test at 380°C indicated no catalysts deactivation.
41. Landau, M. V.; Herskowitz, M.; Givoni, D.; Laichter, S.; Yitzhaki, D., "Medium severity hydrotreating and hydrocracking of Israeli shale oil. III. Hydrocracking of hydrotreated shale oil and its atmospheric residue for full conversion to motor fuels", Fuel, (1998), 77(14), 1589-1597. Hydrocracking of hydrotreated Israeli shale oil and its atm. residue was studied at 50 atm hydrogen pressure, LHSV 0.5-4.4 h-1, temp. 350°C and VH2 1500 NL/L in a fixed bed reactor pilot plant with two Ni-Mo-zeolite catalysts based on mono-(HY + Al2O3) and bi-zeolite (HY + H-ZSM-5 + Al2O3) supports. Desulfurization and denitrogenation and conversion of the feedstock was higher than 99.7% (sulfur content 134 ppm, nitrogen content 4.4 ppm) and it comprised 14 vol.% atm. residue boiling out at 360°C +. Hydrocracking of the whole hydrotreated shale oil yielded full conversion of atm. residue at LHSV = 2.75 h-1 with mono-zeolite catalyst (A) and at LHSV = 3.5 h-1 with bi-zeolite catalyst (B). The yield of liq. fuel at these conditions was 87.6 wt% with catalyst A vs. 82.4 wt% with catalyst B. The contents of light naphtha (< 100°C), heavy naphtha (<200 .ANG.C) and jet fuel (160-280°C) and jet fuel (160-280°C) in the liq. product were 10-15% higher with catalyst B compared with A. Hydrocracking at full residue conversion produced shifts of the hydrocarbon distributions to lighter mols. inside the hydrocarbon groups, decreased n-paraffins concns. by isomerization and splitting to C5-. Hydrocracking of the atm. residue with catalyst A yielded full conversion into 360°C-products at LHSV = 0.5 h-1. The only liq. product obtained in this case at 72.3% yield was naphtha with distn. patterns corresponding to gasoline specification. The nitrogen content in the liq. hydrocracking products at full conversion of atm. residue fraction of the shale oil was <1 ppm and the sulfur content <15 ppm.
42. Landau, M. V.; Kogan, L. O.; Herskowitz, M., "Tail-selective hydrocracking of heavy gas oil in diesel production", Stud. Surf. Sci. Catal. (Hydrotreatment and Hydrocracking of Oil Fractions), (1997), 106, 371-378. Hydrocracking of straight run heavy atm. gas oil (HAGO) was carried our in a batch high pressure autoclave and fixed-bed high pressure minipilot at 50-55 atm. and temps. 350-390°C with Ni-No-Al catalysts contg. to the Ni-Mo-AL-HY catalyst increased its activity significantly beyond corresponding increase of HY zeolite loading. It reduced the 90 and 95% b.ps. (BP) of diesel fraction by 17-30°C and pour point (PP) by about 12-20°C depending on zeolite H-ZSM-5 loading and testing conditions. The overall conversion of HAGO with the bi-zeolite catalyst was not additive yielding lower gasoline yields compared to the sum of the yields obtained with mono-zeolite catalysts. Based on GC-MS anal. of the HAGO, tail fractions those effects were attributed to increased conversion of the least reactive paraffins as a result of H-ZSM-5 zeolite addn.
43. Landau, M. V.; Kogan, S. B.; Herskowitz, M., "Dehydrogenation of methoxyisopropanol to methoxyacetone on supported bimetallic Cu-Zn catalysts", Stud. Surf. Sci. Catal. (Heterogeneous Catalysis and Fine Chemicals IV), (1997), 108, 407-414. Dehydrogenation of methoxyisopropanol on reduced Cu/Zn catalysts was studied in a fixed bed reactor at 200-300°C and atm. pressure. Al2O3 supported catalysts yielded a lower initial activity compared with SiO2 supported catalysts and displayed a lower deactivation rate. The main route for deactivation of Cu/Zn/Al2O3 was coking while that of Cu/Zn/SiO2 was the crystn. of the Cu0 phase. Oxidative regeneration of Cu/Zn/Al2O3 catalyst after 250 h on stream gave complete recovery of initial activity. Kinetic expts. yielded a Langmuir-Hinshelwood type rate equation.
44. Landau, M. V.; Kogan, S. B.; Tavor, D.; Herskowitz, M.; Koresh, J. E., "Selectivity in heterogeneous catalytic processes",Catal. Today (1997), 36(4), 497-510. The selectivity of several catalytic systems was studied. Shape selectivity of Pt on carbon fiber catalysts was demonstrated in the competitive hydrogenation of 1-hexene and cyclohexene and in the parallel dehydrogenation of cyclohexanol to cyclohexanone and phenol. Both reactions were carried out in a gas-phase fixed-bed reactor. Catalysts prepd. on carbon fibers, contg. pores with small constrictions (5 .ANG.) yielded significantly higher rates of hydrogenation of 1-hexene compared to those of cyclohexene and selectively produced cyclohexanone from cyclohexanol. Other catalysts, supported on carbon fibers with large constrictions (7 .ANG.) or activated carbon, displayed comparable rates of hydrogenation for both reactants and yielded cyclohexanone as well as phenol from cyclohexanol. Nitration of o-xylene with nitrogen dioxide was carried out in the gas phase over a series of solid acid catalysts packed in a fixed bed. Several zeolites, supported sulfuric acid, and sulfated zirconia were tested. Zeolite H-b was found to be the most active and selective catalyst for the prodn. of 4-nitro-o-xylene. A preliminary kinetic model indicated that the selectivity to 4-nitro-o-xylene increased with decreasing concn. of nitrogen dioxide. Alkylation of phenol with methanol was performed on zeolites, supported sulfuric and phosphoric acids, and sulfated zirconia packed in a fixed-bed. The ratio of o- to c-alkylation, measured at 180°C and methanol to phenol feed molar ratio of unity, ranged from 4 with the supported acids to 2 with zeolite H-b. This ratio decreased with temp. The ratio of o- to p-cresol changed from about 2 in zeolites in supported sulfuric acid and to 0.5 in phosphoric acid supported on carbon fibers.
45. Landau, M. V., "Deep hydrotreating of middle distillates from crude and shale oils", Catal. Today, (1997), 36(4), 393-429. A review with 141 refs. The potential scientific and technol. solns. to the problems that appear as a result of shifting the hydrotreating of crude oil middle distillates and shale oils from the 'normal' to the 'deep' mode are considered on the basis of the reactivities and transformation routes of the least-reactive sulfur-, nitrogen-, and oxygen-contg. compds. The efficiency of selecting the optimal feedstock, increasing the process severity, improving the catalysts activity, and using alternative catalytic routes are compared, taking into account the specific issues related to deep hydrodesulfurization/hydrodenitrogenation/hydrodeoxygenation, i.e., chem. aspects, kinetics and catalysts.
46. Landau, M. V.; Kaliya, M. L.; Gutman, A.; Kogan, L. O.; Herskowitz, M.; Van Den Oosterkamp, P. F., "Oxidative conversion of LPG to olefins with mixed oxide catalysts: surface chemistry and reactions network", Stud. Surf. Sci. Catal. (3rd World Congress on Oxidation Catalysis, 1997), (1997), 110, 315-326. The catalytic performance of 3 mixed oxide catalytic systems V-Mo-, V-Mg and RE-Li-Halogen (RLH) in LPG oxidative conversion was measured at different O/LPG ratios, temps. and WHSV. At high LPG conversions V-Mo-based catalysts yielded low olefins selectivity and high LPG combustion (CB), V-Mg - medium olefins selectivity by oxidative dehydrogenation (ODH) route and medium LPG CB selectivity, while RLH catalysts displayed high olefins selectivity by ODH and cracking (CR) routes at low CB. TP-reaction expts. and the effects of O partial pressure on catalytic performance indicated a dynamic interaction of surface O in the ODH, CB and CR routes. ESCA and TPD measurements detected three types of surface O with different nucleophilicity and bonding strength. Their distribution correlated with LPG conversion selectivities. A correlation between catalysts acidity, the surface exposed metal cations concn. and the productivity by the CR route was derived. The surface basicity was also significant in olefins productivity by the ODH and CR routes. The selectivity of LPG oxidative reactions were attributed to different intermediates formed on the surface as a result of interaction of C3-C4 paraffins with O atoms of different nucleophilicity. Both the redox balance of surface metal cations and the acidity-basicity balance are proposed to be significant.
47. Vradman, L.; Landau, M. V.; Herskowitz, M., "Deep desulfurization of diesel fuels: kinetic modeling of model compounds in trickle-bed", Catal. Today, (1999), 48(1-4), 41-48. Five catalysts with different hydrodesulfurization (HDS) and hydrogenation activity were tested in HDS of fresh crude heavy atm. gas oil (HAGO) (1.33 wt% S), two partially hydrotreated HAGO (1100 and 115 ppm S) and two model compds., dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (DMDBT), dissolved in model solvents and HAGO. Arom. compds. in the liq. decreased significantly the HDS rate of 4,6-DMDBT, esp. for catalysts with high hydrogenation activity. H2S displayed a similar inhibition effect with all catalysts. These effects were extremely pronounced in HAGO where the DBT HDS rate decreased by a factor of 10 while 4,6-DMDBT - of 20 relative to paraffinic solvent. The feasibility of using a highly active hydrogenation catalyst for deep HDS of HAGO is diminished by the strong impact of aroms.
48. Phillips, J.; Weigle, J.; Herskowitz, M.; Kogan, S., "Metal particle structure. Contrasting the influences of carbons and refractory oxides", Appl. Catal. A, (1998), 173(2), 273-287. A review with 87 refs.; an anal. of the literature suggests that there are at least three different characteristics of carbon that can be utilized to generate metal surfaces not found on refractory oxide supports. First, on graphitic carbon many metals interact very weakly, allowing bimetallic particles to form structures identical to those anticipated for bulk materials. Of particular significance is the formation of true alloys, both in the bulk and on the (catalytic) surface of the bimetallic particles. In contrast, on conventional refractory-oxide supports these same structures will not form for certain base-metal/noble-metal pairs. Instead, a preferential and strong interaction between the more 'base' metal and the support generally leads to preferential segregation of that metal to the refractory oxide interface and, concomitantly, dominance of the catalytic interface by the 'more noble' metal. As a result of these structural differences, the catalytic chem., both activity and selectivity, of some bimetallic particles supported on refractory oxides and graphitic carbons are dramatically different. Second, it is clear that it is possible to directly bond metals to unsatd. active sites on high surface-area carbon blacks, activated carbon, etc. This has been demonstrated to yield thermally stable particles of a unique structure. On refractory oxides, strong interaction generally leads to the creation of complex, ionic-bonded 'interface' phases. Third, carbon structure can be manipulated to generate shape-selective supports. This can be done with refractory oxides, but only carbon surfaces are neutral. Thus, only on carbon will reduced metal readily form. There is surprisingly little research into any of these phenomena, suggesting there are many opportunities to create unique metal surfaces using carbon as a support.
49. Landau, M. V.; Tavor, D.; Regev, O.; Kaliya, M. L.; Herskowitz, M.; Valtchev, V.; Mintova, S., "Colloidal Nanocrystals of Zeolite b Stabilized in Alumina Matrix", Chem. Mater., (1999), 11(8), 2030-2037. Characteristics of zeolite b in stable aq. colloidal soln. were measured by cryo-TEM, DLS, SAXS and after sepn. from soln. by SEM, HR-TEM. Twenty-nanometer spherical zeolite crystals were measured in equil. with flocculates. Mixing of colloidal zeolite soln. with aluminogel yielded coagulation of both materials. The mass of zeolite adsorbed by aluminogel increased with decreasing pH. After calcination, pellets of the composite material at zeolite loading below 60 wt % contained sepd. nanocrystals of 10-15-nm zeolite b stabilized in the mesopores of alumina matrix. The imbedded zeolite had high structure order and acidity. No blocking of the zeolite micropores in composite materials was detected. The activity of zeolite b nanocrystals (imbedded in alumina matrix) in cumene cracking twice that of bulk nanozeolite clusters.
50. Kogan, S.; Herskowitz, M.; Woerde, H. M.; Van den Oosterkamp, P. F., "Selective dehydrogenation of propane using an improved dehydrogenation catalyst", Kinetics Technology International B.V., Zoetermeer, Neth. Proc. - Ethylene Prod. Conf., (1998), 7, 1-6. A Pt-based catalyst was developed for selective dehydrogenation of propane to propene.
51. Landau, M. V.; Varkey, S. P.; Herskowitz, M.; Regev, O.; Pevzner, S.; Sen, T.; Luz, Z., "Wetting stability of Si-MCM-41 mesoporous material in neutral, acidic and basic aqueous solutions", Microporous Mesoporous Mater., (1999), 33(1-3), 149-163. The wetting stability of three calcined Si-MCM-41 materials synthesized at room temp. and under hydrothermal conditions with and without pH adjustment and salt addn. was studied by SAXS, SEM, HR-TEM, BET-BJH, FTIR and NMR techniques. The stability was investigated after wetting with neutral, basic and acidic aq. solns. and further recalcination. Calcined Si-MCM-41 materials synthesized at room temp. fully degraded under wetting with neutral water. Crystn. under hydrothermal conditions improved their wetting stability. pH adjustment and NaCl addn. during hydrothermal crystn. led to a further improvement. It was proposed, based on spectroscopic data, that the structure degrdn. during wetting is caused by hydration of the siloxane structure at the wetting stage followed by siloxane hydrolysis-hydroxylation of strained Si(-OSi-)4 units and their rearrangement-redehydroxylation during recalcination. This leads to intergrowth of curved hexagonal crystal rods, redn. of the surface area and pore vol. of the material forming a disordered pore structure with increased pore walls thickness. The water-stable Si-MCM-41 synthesized with pH adjustment and salt addn. was also insensitive to wetting with acidic aq. soln. However, treatment of this non-strained material with a basic soln. at pH 7.8-8.9 resulted in silica leaching and a redn. in crystallinity, the mean pore diam. and the pore vol. The rod shape and surface area remained relatively unchanged after wetting at pH 7.8.
52. Landau, M. V.; Vradman, L.; Herskowitz, M.; Yitzhaki, D., "Effects of gaseous and liquid components on rate of deep desulfurization of heavy atmospheric gas oil" Stud. Surf. Sci. Catal. (Hydrotreatment and Hydrocracking of Oil Fractions), (1999), 127, 393-396. The effects of sulfur, nitrogen, bicyclic arom., and monocyclic arom. components in a heavy atm. gas oil (390 °C final b.p. and 1.24 wt.% sulfur) and H2S and ammonia in the gas phase on the hydrodesulfurization (HDS) rate were studied. The deep hydrodesulfurization stage (Sin 1110-60 ppm) was carried out over Co-Mo-alumina and Ni-W-silica catalysts. The complete elimination of hydrogen sulfide, ammonia, polycyclic arom. and partial elimination of monocyclic arom. components prior to the deep desulfurization stage increased the overall rate of deep HDS by a factor of about six.
53. Vankelecom, I.; Wolfson, A.; Geresh, S.; Landau, M.; Gottlieb, M.e; Hershkovitz, M., "First heterogenization of Rh-MeDuPHOS by occlusion in PDMS (polydimethylsiloxane) membranes", Chem. Commun., (1999), (23), 2407-2408. The first heterogeneous system of Rh-MeDuPHOS, obtained by occlusion of the complex in a PDMS membrane, is reported and tested in the hydrogenation of methylacetoacetate (MAA).
54. Pradier, C. M.; Rodrigues, F.; Marcus, P.; Landau, M. V.; Kaliya, M. L.; Gutman, A.; Herskowitz, M., "Supported chromia catalysts for oxidation of organic compounds The state of chromia phase and catalytic performance", Appl. Catal. B, (2000), 27(2), 73-85. A series of 13 bulk transition metals oxides frequently used as components of full oxidn. catalysts was tested in air oxidn. of n-butane and ethylacetate (EA). Co3O4, Cr2O3, CuO and MnO2,displayed the best activity, about one order of magnitude higher than the others. Chromia displayed the highest CO2 productivity. The activity and CO2 selectivity of Cr2O3 catalyst deposited on mineral supports (SiO2, Al2O3, MCM-41) depended strongly on the supports nature, texture and chromia loading. XPS, EDAX, XRD, FTIR and TPR-TPO measurements displayed two forms of Cr3+-oxide on silica-supported catalysts: bulk a-Cr2O3 nanocrystals of 10-20 nm and a monolayer of chromia surface species chem. bonded to the support: -Si-O-Cr:O. The chromia nanocrystals detected by XRD displayed higher activity and selectivity in complete EA oxidn. due to higher redox mobility of chromium cations on their surface compared with grafted chromium silicate species. The optimized Cr2O3/SiO2 catalyst showed high efficiency in wet oxidn. of amino-3-phosphonopropionic acid, comparable with the best catalysts reported in the literature.
55. Herskowitz, M.; Levitsky, S.; Shreiber, I., "Attenuation of ultrasound in porous media with dispersed microbubbles", Ultrasonics, (2000), 38(1-8), 767-769. The dispersion relation for a granular bed with a small amt. of fine bubbles is formulated and analyzed. It is assumed that the grain size is much larger than the bubble's radius and that their vol. concn. is small. The study is motivated by the problem of acoustic diagnostics of fixed bed chem. reactors operating in multiphase flow regime.
56. Kogan, S. B.; Schramm, H.; Herskowitz, M., "Dehydrogenation of propane on modified Pt/q-alumina Performance in hydrogen and steam environment", Appl. Catal. A, (2001), 208(1,2), 185-191. Dehydrogenation of propane was carried out on several promoted Pt catalysts. The performance of the catalysts (activity, selectivity and coke formation) was compared in steam and hydrogen environment. Promoting Pt supported on q-alumina with Sn and K is essential for developing high-performance catalysts. The combination of optimal catalyst compn. and steam yields high activity and selectivity at low coke formation. Inferior results were measured with hydrogen as diluent. Characterization of catalysts using XPS, TEM and chemisorption methods supported the results of reaction data.
57. Wolfson, A.; Geresh, S.; Landau, M. V.; Herskowitz, M., "Enantioselective hydrogenation of methyl acetoacetate catalyzed by nickel supported on activated carbon or graphite", Appl. Catal. A, (2001), 208(1,2), 91-98. Heterogeneous enantioselective catalysts based on nickel, tartaric acid and NaBr supported on activated carbon or graphite were characterized and tested in the asym. hydrogenation of Me acetoacetate (MAA). Nickel crystallite size depended on the type of carbon support, the prepn. conditions and redn. temp. of nickel. Enantioselectivity increased significantly with increasing nickel crystallite size. High nickel loading (up to 85 wt. %) and large crystal size (<5000 A) were examd. Operating conditions such as temp., hydrogen pressure and catalyst to substrate ratio were varied over a wide range to achieve high enantiomeric excess values. Enantiomeric excess as high as 91% was obtained with nickel on graphite.
58. Landau, M. V.; Kaliya, M. L.; Herskowitz, M., "Ammoxidation of p-cresol to p-hydroxybenzonitrile High-performance boria-phosphoria supported catalysts", Appl. Catal. A, (2001), 208(1,2), 21-34. Ammoxidn. of p-cresol to p-hydroxybenzonitrile (pHBN) was studied over a large no. of catalysts, mainly oxides of Bi-Mo and B-P. Supported boria-phosphoria on silica displayed superior performance. Feed compn. and rate had a significant effect on catalyst performance. The best performance was measured at ammonia, air and nitrogen to cresol molar ratios of 10, 40, 120, resp. The best performance of fresh catalyst was 63 wt. % yield of pHBN at P:B molar ratio ranging from 5 to 8 and total oxide content on silica between 10-18 wt. %. Polymeric deposits on the catalyst generated extensive deactivation. Regeneration of catalyst in a mixt. of air-nitrogen and steam restored initial performance. Testing of various promoters indicated that 0.03 wt. % Pt improved both catalyst stability and regenerability with no effect on selectivity. Cycled operation of 12 h ammoxidn. and 12 h regeneration over 200 h onstream demonstrated that an av. yield of 55 wt. % pHBN could be maintained. A tentative mechanism was derived based on reaction and adsorption measurements: p-cresol and ammonia adsorbed on medium strength acidic sites form p-hydroxybenzylamine as intermediate product. p-Hydroxybenzylamine reacts with oxygen to produce pHBN. Two different routes for formation of polymeric coke were identified: direct condensation of p-cresol on acidic sites and ammonia-induced condensation of p-hydroxybenzaldehyde formed by p-hydroxybenzylamine oxidn.
59. Vradman, L.; Herskowitz, M.; Korin, E.; Wisniak, J., "Regeneration of Poisoned Nickel Catalyst by Supercritical CO2 Extraction", Ind. Eng. Chem. Res., (2001), 40(7), 1589-1590. Regeneration of a thiophene-poisoned Ni-supported catalyst was carried out by supercrit. CO2 extn. The catalyst activity was measured in the hydrogenation of 2-butanone to 2-butanol at 373 K and 1.7 MPa. The supercrit. extn. was tested over a range of operating conditions. Regeneration at 313 K and 41 MPa for 16 h recovered completely the catalyst activity. Other methods cited in the literature displayed a lower performance in regeneration of Ni catalysts.
60. Landau, M. V.; Vradman, L.; Herskowitz, M.; Koltypin, Y.; Gedanken, A., "Ultrasonically controlled deposition-precipitation of cobalt and molybdenum oxides in the preparation of hydrodesulfurization catalysts", J. of Catal., (2001), 201(1), 22-36. Mo and Co oxides were pptd. under ultrasonication treatment from Mo(CO)6 and Co(CO)3NO dissolved in decalin. Introduction of wide-pore Al-MCM-41 material with an av. pore diam. 8.3 nm and a surface area of 840 m2/g increased the Mo oxide pptn. rate by an order of magnitude. This is a result of an ultrasonically induced chem. interaction between metal carbonyl (oxide) and the surface silica at. layer yielding surface silicates (XPS, MAS NMR). The ultrasonication of such a slurry yields deposition-pptn. of the corresponding metal oxide, forming a close-packed monolayer at the support surface (N2 adsorption, HR-TEM, XPS, XRD). Ultrasonically controlled deposition-pptn. produced .apprx.45 wt% MoO3 loading, which is satn. of the wide-pore Al-MCM-41 surface monolayer. The high-loading Co-Mo/Al-MCM-41 catalyst prepd. by ultrasonically controlled deposition-pptn. was 1.7 times more active in hydrodesulfurization of dibenzothiophene, based on the reaction rate normalized per catalyst wt., than com. Co-Mo-Al catalyst.
61. Landau, M. V.; Dafa, E.; Kaliya, M. L.; Sen, T.; Herskowitz, M., "Mesoporous alumina catalytic material prepared by grafting wide-pore MCM-41 with an alumina multilayer", Microporous and Mesoporous Materials, (2001), 49(1-3), 65-81. An alumina multilayer grafted on the surface of MCM-41 produced a mesoporous material with the surface chem. functionality of alumina. The starting MCM-41 material (WPMCM) with a wide pore size distribution, a surface area of 858 m2/g, an av. pore diam. of 8.2 nm and a pore vol. of 1.75 cm3/g was synthesized by expanding the cetyltrimethylammonium chloride (CTAC) surfactant micelles with mesitylene at a high solubilizer/CTAC ratio of 10. Successive grafting consisting of aluminum butoxide anchoring followed by hydrolysis and calcination steps yielded a gradual increase of the aluminum content in WPMCM. Tetrahedral Al in the silica pore walls and clusters of a sep. octahedral Al alumina phase were identified. Four grafting cycles produced a material with a surface area of 542 m2/g and a mean pore diam. of 4 nm contg. 38 wt.% Al2O3 that displayed chem. surface functionality of pure alumina. The activity of this material in the alkylation of phenol with methanol was 2.3 times higher than the activity of a ref. alumina (460 m2/g). The highest activity of grafted alumina in cumene cracking and isopropanol dehydration was achieved at 21 wt.% Al2O3. Independent measurements of surface charging in aq. soln., of [Mo7O24]6- anions adsorption and of surface acidity indicated that the material grafted with alumina and the ref. alumina display similar chem. functionality.
62. Landau, M. V.; Gutman, A.; Herskowitz, M.; Shuker, R.; Bitton, Y.; Mogilyansky, D., "The role and stability of Li2O2 phase in supported LiCl catalyst in oxidative dehydrogenation of n-butane", J. of Mol. Catal. A, (2001), 176(1-2), 127-139. This study was aimed at defining the role of active phases in supported LiCl and LiCl-DyCl3 catalysts in the catalytic oxidative dehydrogenation (ODH) of n-butane. LiCl supported on silica displayed the highest activity and selectivity in n-butane ODH compared with other alkali metal halides. Addn. of DyCl3 increased the activity. TPO, XRD and Raman light scattering (RLS) data showed that LiCl and DyCl3 formed during the prepn. stage were converted to Li2O2 and DyOCl phases, resp., by calcination in air at >400°C. The results of sep. TPR expts. (O2-oxidn.-butane redn.) along with XRD, RLS and XPS data proved that butane reacts mainly with oxygen species of Li2O2 phase at ODH conditions, probably attributed to [Li+O-] pairs. The proposed functions of chlorine and dynamic oxygen in the ODH of butane are consistent with the activity, selectivity and stability of silica and magnesia-supported catalysts. High thermal stability of Li2O2 in oxidized LiCl catalyst was attributed to the formation of protective Li2O×LiCl surface layer. Deactivation of LiCl/SiO2 catalyst in n-butane ODH is caused by the formation of Li-silicates at reaction conditions while LiCl/MgO display a stable performance.
63. Jyothi, T. M.; Kaliya, M. L.; Landau, M. V., "A Lewis acid catalyst anchored on silica grafted with quaternary alkylammonium chloride moieties", Angewandte Chemie, Int. Ed., (2001), 40(15), 2881-2884. We have demonstrated a new supported Lewis acid catalyst which is resistant to leaching and shows high selectivity in the synthesis of 3-methyl-3-buten-1-ol by the Prins condensation of isobutene and formaldehyde. Formation of a complex between SnCl4, and the tetraalkylammonium chloride moiety was confirmed by NMR spectroscopy. Clearly, complexation of SnCl4 with tetraalkylammonium chloride improves the selectivity for the unsatd. alc.
64. Jyothi, T. M.; Kaliya, M. L.; Herskowitz, M.; Landau, M. V., "A comparative study of an MCM-41 anchored quaternary ammonium chloride/SnCl4 catalyst and its silica gel analogue", Chem. Commun. (2001), (11), 992-993. A novel reusable Lewis acid catalyst has been prepd. by the heterogenization of a Lewis acid/tetrapropylammonium adduct; anchoring of tin chloride on quaternary ammonium chloride functionalized MCM-41 yielded a catalyst with higher activity compared to the corresponding silica analog in terms of turnover rates and product yield in the Prins condensation of isobutene and formaldehyde to isoprenol.
65. Kogan, S. B.; Herskowitz, M., "Selective propane dehydrogenation to propylene on novel bimetallic catalysts", Catal. Commun., (2001), 2(5), 179-185. Platinum catalysts (0.1-0.2% of Pt) supported on corundum and promoted by indium and tin were prepd., characterized by XPS, XRD, TEM and chemisorption and tested in propane dehydrogenation at 500-580°C with steam and hydrogen as diluents. The characteristics of samples based on corundum were compared with catalysts of similar compn. supported on α-alumina. The catalytic performance in steam was superior by far to that in hydrogen. Coking of corundum-supported catalysts decreased by a factor of 30-60 so their stability was much higher than with α-supported catalyst. For the first time high dispersion and high activity of corundum-based dehydrogenation catalysts are reported.
66. Kaliya, M. L.; Malinovskaya, O. V.; Landau, M. V.; Herskowitz, M., "Kinetics of oxidative dehydrogenation of LPG to olefins on Dy-Li-Cl-Zr-O catalyst", Stud. Surf. Sci. Catal. (Reaction Kinetics and the Development and Operation of Catalytic Processes), (2001),133, 113-121. The kinetics of oxidative dehydrogenation of LPG, a mixt. of 50 mol% propane, 25 mol% butane and 25 mol% isobutene, on a high-performance Dy-Li-Cl-Zr-O catalyst was studied. Exptl. data measured over a range of concns. and temps. was the basis for the development of a kinetic model. Sixteen reactions that include oxidative dehydrogenation and cracking to olefins and oxidn. to carbon monoxide and carbon dioxide were included in the model. The kinetic parameters were estd. by using SIMULSOLV. Comparison of predicted and exptl. data measured in two different modes of operation yielded a good agreement.
67. Gedanken, A.; Tang, X.; Wang, Y.; Perkas, N.; Koltypin, Y.; Landau, M. V.; Vradman, L.; Herskowitz, M., "Using sonochemical methods for the preparation of mesoporous materials and for the deposition of catalysts into the mesopores'. Chemistry-A Eur. J., (2001), 7(21), 4546-4552. A review; ultrasound radiation can be used to synthesize a variety of mesporous materials. The reaction time is considerably shorter than the conventional methods. Ultrasonic waves can be further used for the insertion of amorphous nanosized catalysts into the mesopores. A detailed study demonstrates that the nanoparticles are deposited as a monolayer on the inner mesopores walls without blocking them. When the ultrasonically prepd. catalyst/mesoporous-subtrate composite is used in catalysis a high conversion into product is obtained.
68. Vradman, L.; Landau, M. V., "Structure-function relations in supported Ni-W sulfide hydrogenation catalysts", Catal. Letters, (2001), 77(1-3), 47-54. Ni-W catalysts were prepd. by impregnation of com. g-alumina and silica supports. The sulfidation, performed directly after drying at 100°C, yielded fully sulfided Ni-W species on both supports (SEM-EDAX, XPS, XRD). At optimal metals loading (.apprx.50 wt% NiO + WO3, Ni/W = 2), the sulfided catalysts had similar texture (N2 adsorption) and displayed similar activity in dibenzothiophene hydrodesulfurization (DBT HDS), while the activity of the Ni-W/SiO2 catalyst in toluene hydrogenation (HYD) was six times higher than that of Ni-W/Al2O3. This is due to the more than two times higher WS2 slabs stacking no. in Ni-W/SiO2 compared with Ni-W/Al2O3 (XRD, HR-TEM), yielding stronger adsorption of toluene (TPD).
69. Guernik, S.; Wolfson, A.; Herskowitz, M.; Greenspoon, N.; Geresh, S., "A novel system consisting of Rh-DuPHOS and ionic liquid for asymmetric hydrogenations'', Chem. Commun., (2001), (22), 2314-2315. The ionic liq. [bmim][PF6] was found to provide extra stability to the air-sensitive chiral catalyst Rh-MeDuPHOS in asym. hydrogenation of enamides.
70. Kogan, S. B.; Kaliya, M. L.; Froumin, N.; Herskowitz, M., "Selective oxidative catalytic conversion of n-butane to C2-3-olefins at moderate temperatures", DGMK Tagungsbericht, (Proceedings of the DGMK-Conference "Creating Value from Light Olefins--Production and Conversion", 2001), (2001), 219-226. The oxidative dehydrogenation of butane on Co and V deposited on alumina and silica was studied at 500-550. The highly active Co/Al2O3 catalyst yielded ethylene and propylene, while butenes were produced with the other catalysts.
71. Wolfson, A.; Janssens, S.; Vankelecom, I.; Geresh, S.; Gottlieb, M.; Herskowitz, M., "Aqueous enantioselective hydrogenation of methyl 2-acetamidoacrylate with Rh-MeDuPHOS occluded in PDMS", Chem. Commun., (2002), (4), 388-389. A new chiral heterogeneous catalytic system obtained by occlusion of the Rh-MeDuPHOS complex in a polydimethylsiloxane film was tested in the asym. hydrogenation of Me 2-acetamidoacrylate in aq. medium. E.e. values of 91.1-96.9 were achieved.
72. Wolfson, A.; Geresh, S.; Gottlieb, M.; Herskowitz, M., "Heterogenization of Rh-MeDuPHOS by occlusion in polyvinyl alcohol films", Tetrahedron: Asymmetry, (2002), 13(5), 465-468. A new recyclable chiral heterogeneous catalytic system was obtained by the occlusion of Rh-MeDuPHOS in polyvinyl alc. film. Enantiomeric excess of up to 96% was achieved in the asym. hydrogenation of Me 2-acetamidoacrylate in aq. medium.
73. Kaliya, M. L.; Kogan, S. B.; Froumin, N.; Herskowitz, M., "Novel nitrogen containing heterogeneous catalysts for oxidative dehydrogenation of light paraffins", Catal. Commun., (2002), 3(8), 327-333. Novel nitrogen contained catalyst CoNx/Al2O3 yielded high performance in the oxidative dehydrogenation of propane and n-butane. 47.6 and 37.4 wt% yield of olefins at 82% butane and 76.7% propane conversion were measured at 600 °C. Ethylene and propylene were mainly formed at >400 °C via oxidative cracking of paraffins. XRD and XPS studies of the novel catalytic system indicate an essential modification of cobalt by nitrogen.
74. Wolfson, A.; Wuyts, S.; De Vos, D. E.; Vankelecom, I. F. J.; Jacobs, P. A., "Aerobic oxidation of alcohols with ruthenium catalysts in ionic liquids", Tetrahedron Letters (2002), 43(45), 8107-8110. The aerobic oxidns. of aliph. and arom. alcs. into the corresponding aldehydes and ketones have been efficiently performed with several ruthenium catalysts in various ammonium salts under low oxygen pressure and without any co-catalyst.
75. Kaliya, M.L.; Kogan, S.B.; Froumin, N.; Herskowitz, M., "Development of Novel Hrterogeneous Catalyst for oxidation reactions: preparation and performance of CoNx catalyst in partial oxidatiopn of n-butane and toluene.", Stud. Surf. Sci. Catal., (2002), 143, 679. CoNx on alumina catalyst yielded high performances in the oxidative dehydrogenation of n-butane. 47.6 mol% yield of olefins at 82% butane conversion was reached at 600°C. Most of olefins were ethylene and propylene formed via route of oxidative cracking of n-butane. Catalyst was prepared by deposition of sodium salt of octa (4, 5-carboxy) cobalt phthalocyanine (NaCoPc) followed by calcinations in He at 700°C. Decomposition of NaCoPc in inert medium results in formation of Co-Nx structure that was stable in oxidative processes. Comparison of performances on the novel catalyst Co-O/Al2O3 and traditional metal oxides catalysts shows that the novel catalytic system is significantly more active in production of light olefins particularly at low temperatures (400-450°C). XRD and XPS studies of the novel system indicate an essential modification of the active component by nitrogen.
76. Vradman, L.; Landau, M. V.; Herskowitz. M., Ezersky, V.; Talianker, M., Nikitenko, S.; Koltypin, Y.; Gedanken. A., "High loading of short WS2 slabs inside SBA-15 nanotubes: Promotion with nickel and performance in hydrodesulfurization and hydrogenation", J. Catal., 2003, 213, 163-175. 2002. Layered nanoslabs of a WS2 phase with a well-defined hexagonal crystalline structure, average slab length of 3.6 nm and stacking number of 3.2, were inserted into the nanotubular channels of SBA-15, an ordered pure silica material (surface area of 800 m2/g, uniform mesopore diameter of 6.5 nm) at loadings up to 60 wt.%. Sonication of a slurry containing SBA-15 in a W(CO)6-sulfur-diphenylmethane solution yielded an amorphous WS2 phase inside the mesopores. By sulfidation with 1.5% dimethyldisulfide in toluene under a hydrogen flow at 593 K and 5.4 MPa, the amorphous phase was transformed into hexagonal crystalline WS2 nanoslabs [as shown by XRD, HRTEM, and selected area electron diffraction (SAED)]. The WS2 nanoslabs were distributed exclusively inside the mesopores in a uniform manner (HRTEM, quantitative microanalysis), without blocking the pores (N2-sorption), and were orientated with their edge planes toward the support surface. This study constitutes the first report of such a combination of high loading of a well-defined crystalline catalytic phase into the nanotubular channels of mesoporous silica without blocking them. The first well-resolved HRTEM images of the well-defined crystalline catalytic phase (WS2) inside the nanotubes SBA-15 are presented. A Ni component was introduced into the WS2/SBA-15 composite by impregnation from an aqueous solution of nickel acetate. It increased the catalytic activity up to Ni/W ratio of 0.4. In the hydrodesulfurization (HDS) of dibenzothiophene and the hydrogenation (HYD) of toluene, the activity of the optimized Ni W S/SBA-15 catalyst was 1.4 and 7.3 times higher, respectively, than that of a sulfided commercial Co-Mo/Al2O3. This finding illustrates the excellent potential of high loading Ni-W-S/SBA-15 catalysts for deep hydrotreatment of petroleum feedstocks.
77. Abecassis-Wolfovich, M.; Rotter, H.; Landau, M.V.; Korin, E., Erenburg, A.I.; Mogilyansky, D.; Garshtein. E., "Texture and Nanostructure of Choromia Aerogels Prepared by Urea-Assisted Homogeneous Precipitation and Low-Temperature Supercritical Drying", J. Non-Crystalline solids, 2003, 318, 95-111. Mesoporous chromia aerogels with a surface area of 484-735 m2g-1, a pore volume of 0.4-0.9 cm3 g-1 and a pore diameter of 3-9 nm were prepared by urea-assisted homogeneous precipitation from an aqueous Cr(NO3)3 solution, followed by continuous supercritical extraction with CO2 under different conditions (pressure and time) after replacement of the water with a hexane/2-butanol mixture. The texture and chemistry of the aerogels transformed by heating in air or an inert atmosphere and the structure of the nanoparticles were characterized by means of N2-adsorption isotherms, AA, HR-TEM, FTIR, a variety of thermoanalytical methods (TPD, DSC, TGA, TPO-TPR) and X‑ray diffraction in combination with structure modeling. At the CO2 extraction stage, a pressure of about 400 bars was critical for production of aerogels with surface areas > 700 m2g-1. The fresh chromia aerogels consisted of closely packed almost globular, 3- to 5-nm nanoparticles with a structure analogous to that of monoclinic α‑CrOOH, in which half of the O atoms and OH groups were replaced with coordinately bonded water molecules. After dehydration at 550-600 K, the materials retained their texture, being converted to faceted 3- to 5-nm nanoparticles, consisting of two-dimensional fragments (clusters) of a ‑CrOOH crystals built on [Cr(OH)3O3] octahedra without bonding along the Z-axis. The texture of dehydrated chromia aerogels was stable at temperatures up to 650 K in air and up to 773 K in an inert atmosphere. At higher temperatures, the material underwent a glow transition, yielding microcrystalline 50-nm particles with the well- defined structure of α-Cr2O3 and a surface area < 200 m2g-1.
78. Goldbourt, A.; Landau, M.V.; Vega, S., "Aluminum Species in Alumina Multilayer grafted inside mesoporous MCM-41 and characterized with 27Al FAM(II)-MQMAS NMR", J. Phys. Chem. B, 2002. Grafting of 4-fold alumina multilayer inside the nanotubes of wide-pore MCM-41 material by consecutive reactions with Al(O-sec-Bu)3 followed by hydrolysis-calcination (773 K) changes the surface chemical functionality of the material from silica to alumina. It leads to partial filling of MCM-41 mesopores with an amorphous alumina phase. The multi-grafting process and the structure of produced aluminum containing phases were characterized by performing FAM-II enhanced 3QMAS and 5QMAS experiments. The reference γ-alumina phase with surface area of 460 m2/g and domain diameter of 1.5-2 nm prepared from Al(O-sec-Bu)3 by sol-gel method and calcined at 773 K had a similar short range order as a commercial well-crystalline g-Al2O3 and contained a negligible amount of penta-coordinated (Pd) aluminum atoms. The relative aluminum population at the octahedral (Oh) and tetrahedral (Td) sites was 72 and 28%, respectively. In Al2O3/MCM-41 sample grafted in one step (Si/Al = 4.9) Al-species were observed in Oh and Td positions, belonging to alumina clusters inside the pores, and Td Al species that were implanted in silica walls or at their surface. It yielded about 35% of Td aluminum substituting silicon based on total aluminum content. After successive grafting (4 steps, Si/Al = 1.6) the relative population of silica substituted sites decreased (~25%) and thermally stable Pd aluminum species appeared in the spectrum. The population of Pd based on aluminum content in grafted alumina clusters was ~10% - significantly higher compared with that generally observed in transition aluminas. With about 31% Td sites in the grafted phase, and the large portion of surface sites in the confined alumina particles, the higher acidity and catalytic activity of alumina multilayer inside the pores of MCM-41 could be explained, compared with the reference alumina.
79. Vradman, L.; Landau, M.V.; Herskowitz, M., "Hydrodearomatization of petroleum feedstocks on the silica supported Ni-W-S catalyst with increased sticking number of WS2 phase", Fuel, 2002 (in press). Hydrodearomatization of petroleum feedstocks on the silica supported Ni-W-S.Ni-W catalysts supported on commercial α-alumina and silica displayed similar activity in dibenzothiophene hydrodesulfurization (DBT HDS), while the activity of the Ni-W/SiO2 catalyst in toluene hydrogenation (HYD) was 6 times higher compared with Ni-W/Al2O3. The dearomatization performance of Ni-W/SiO2 catalyst was tested over a wide range of operation conditions with naphtha and middle distillates. 90% saturation of aromatics in FCC naphtha (340 oC, LHSV of 1 h-1) and 50% in LCO (360 oC, LHSV of 1 h-1) was achieved at 5.4 MPa. In a two stage process with the same Ni-W/SiO2 and intermediate separation of hydrogen sulfide 90% saturation of aromatics in LCO was achieved at 320oC and total LHSV of 0.5 h-1. At equal conditions, Ni-W/Al2O3 catalyst yielded 1.5 - 4 times lower total aromatics saturation.
80. M.V. Landau, “Other Oxides. Transition Metal Oxides", Chapter in “Handbook of Porous Solids" Edited by F.Schüth, K.Sing and J.Weitkamp, WILEY-VCH, 2002, p. 1677-1765.
81. M. Abecassis-Wolfowich, H. Rotter, M.V. Landau, E. Korin, A. Erenburg, D. Mogylyansky and E. Garstein, “Chromia Aerogels by Urea-Assisted Homogeneous Precipitation and Low-Temperature Supercritical Drying: Materials Textutre and Structure of Nanoparticles", J. Non-Crystal Solids, 2003, 318, 95-111. Mesoporous chromia aerogels with a surface area of 484–735 m2 g−1, a pore volume of 0.4–0.9 cm3 g−1 and a pore diameter of 3–9 nm were prepared by urea-assisted homogeneous precipitation from an aqueous Cr(NO3)3 solution, followed by continuous supercritical extraction with CO2 under different conditions (pressure and time) after replacement of the water with a hexane/2-butanol mixture. The texture and chemistry of the aerogels transformed by heating in air or an inert atmosphere and the structure of the nanoparticles were characterized by means of N2-adsorption isotherms, AA, HRTEM, FTIR, a variety of thermoanalytical methods (TPD, DSC, TGA, TPO–TPK) and X-ray diffraction in combination with structure modeling. At the CO2 extraction stage, a pressure of about 400 bars was critical for production of aerogels with surface areas >700 m2 g−1. The fresh chromia aerogels consisted of closely packed almost globular, 3- to 5-nm nanoparticles with a structure analogous to that of monoclinic -CrOOH, in which half of the O atoms and OH groups were replaced with coordinately bonded water molecules. After dehydration at 550–600 K, the materials retained their texture, being converted to faceted 3- to 5-nm nanoparticles, consisting of two-dimensional fragments (clusters) of -CrOOH crystals built on [Cr(OH)3O3] octahedra without bonding along the Z-axis. The texture of dehydrated chromia aerogels was stable at temperatures up to 650 K in air and up to 773 K in an inert atmosphere. At higher temperatures, the material underwent a glow transition, yielding microcrystalline 50-nm particles with the well-defined structure of -Cr2O3 and a surface area <200 m2 g−1.
82. Vradman, L.; Landau, M. V.; Herskowitz, M., "Hydrodearomatization of petroleum fuel fractions on silica supported Ni-W sulphide with increased stacking number of the WS2 phase". Fuel (2003), 82(6), 633-639. Ni-W catalysts supported on com. g-alumina and silica displayed similar activity in dibenzothiophene hydrodesulfurization (DBT HDS), while the activity of the Ni-W/SiO2 catalyst in toluene hydrogenation (HYD) was 6 times higher compared with Ni-W/Al2O3. The dearomatization performance of Ni-W/SiO2 catalyst was tested over a wide range of operation conditions with naphtha and middle distillates. 90% Satn. of aroms. in FCC naphtha (340°, LHSV of 1 h-1) and 50% in Light cyclic oil (LCO) (360°, LHSV of 1 h-1) was achieved at 5.4 MPa. In a two stage process with the same Ni-W/SiO2 and intermediate sepn. of hydrogen sulfide 90% satn. of aroms. in LCO was achieved at 320° and total LHSV of 0.5 h-1. At equal conditions, Ni-W/Al2O3 catalyst yielded 1.5-4 times lower total aroms. satn.
83. Kogan, S. B.; Herskowitz, M., "Dehydrogenation of Neohexane to Neohexene on Platinum Polymetallic Catalysts". Industrial & Engineering Chemistry Research (2002), 41(24), 5949-5951. Selective dehydrogenation of neohexane to neohexene was carried out on platinum polymetallic catalysts at high diln. in steam to overcome severe chem. equil. limitations. The conversion at 550°, WHSV = 1 h-1, and a diln. ratio of 20 was close to equil. values of 17%. Two catalysts, Pt-Sn-K/alumina and Pt-Sn-K-Fe/alumina, yielded similar initial performances of high selectivity of 83 mol %, significantly higher than those of supported Cr catalysts. However, fast coke formation is inherent to this process. Therefore, regeneration of the catalysts is a crit. step in the process. Steam regeneration is the most practical method of regeneration if the catalyst performances can be retained for many cycles. Addn. of Fe to the Pt-Sn-K/alumina catalyst yielded excellent long-term stability in steam regeneration compared with the poor behavior of the basic Pt catalyst.
84. Shtemler, Y. M.; Shreiber, I. R.; Herskowitz, M., "Micro-level instability of bubble flows in packings". Chemical Engineering Science (2003), 58(8), 1631-1640. Bubbly liq. flow through fixed beds and its transition to dispersed-bubble flow is analyzed. The system is described as a compressible fluid filtrating through porous media. The system peculiarities the isothermal variation of perfect gas in the spherical bubbles, weak compressibility of the liq., etc. are accounted for in the state equation for bubbly liq. Dimensionless criteria were found detg. the bubbly-liq. flow in packings at the macro (bed) scale as well as criterion for its stability at the micro (pore) scale. The modeling results are compared with the exptl. data.
85. Landau M V; Titelman L; Vradman L; Wilson P, "Thermostable sulfated 2-4 nm tetragonal ZrO2 with high loading in nanotubes of SBA-15: a superior acidic catalytic material". Chemical communications (Cambridge, England) (2003 Mar 7), (5), 594-5. The high-loaded (48-60 wt.%) 2-4 nm tetragonal ZrO2 phase inserted in mesostructured silica SBA-15 by chemical solution decomposition (CSD) of Zr(n-PrO)4 and activated at 873 K displayed approximately 3 times higher capacity for surface sulfate ions and, respectively, 1.5-2.2 times higher catalytic activity per gram of SO4-ZrO2/SBA-15 composite in condensation of MeOH with t-BuOH and dehydration of isopropanol compared with the regular bulk sulfated zirconia material.
86. Vradman, L.; Peer, Y.; Mann-Kiperman, A.; Landau, M. V., "Thermal decomposition-precipitation inside the nanoreactors. High loading of W oxide nanoparticles into the nanotubes of SBA-15". Studies in Surface Science and Catalysis (2003), 146(Nanotechnology in Mesostructured Materials), 121-124. The soln. thermal decompn.-pptn. of an oxide precursor inside nanotubes (nanoreactors) of a mesoporous silica support under an atm. satd. with solvent at the oxide precursor decompn. temp. was explored for loading of W oxide nanoparticles into SBA-15 silica. The pptn. of W-ethoxide soln. in decalin yielded WO3/SBA-15 composites with the WO3 phase located exclusively inside the pores in the form of nanocrystals strongly blocking the pores. The pptn. of W(CO)6 from soln. yielded a WOx phase with a £32 wt.% spread as an amorphous monolayer on the pore walls with minor pore blockage
87. Abecassis-Wolfovich, M.; Rotter, H.; Landau, M. V.; Korin, E.; Erenburg, A. I.; Mogilyansky, D.; Garshtein, E., "Texture of chromia aerogels and structure of their nanocrystals". Studies in Surface Science and Catalysis (2003), 146(Nanotechnology in Mesostructured Materials), 247-250. Mesoporous chromia aerogels with a surface area of 484-735 m2/g, pore vol. of 0.4-0.9 cm3/g and pore diam. of 3-9 nm were prepd. by urea-assisted homogeneous pptn. from an aq. Cr(NO3)3 soln., followed by continuous supercrit. CO2 extn. The aerogels were characterized by means of N2-adsorption isotherms, AA, high-resoln. TEM, FTIR, thermoanal. methods TPD, TPO, DSC and x-ray diffraction in combination with structure modeling. For prodn. of mesoporous aerogels with surface areas >700 m2/g a CO2 pressure of .apprx.400 bar was required. The chromia aerogels consisted of 3-5 nm nanoparticles representing a monoclinic analog of a-CrOOH in which half the O atoms and OH groups were replaced with coordinately bonded water mols. After dehydration at 550-600 K, the materials retained their texture and were converted to two-dimensional fragments (clusters) of a-CrOOH crystals built on Cr(OH)3O3 octahedra without bonding along the Z-axis (N2, vacuum) or to amorphous CrO2 (air). At temps. >650 K in air and >773 K in an inert atm., the product was converted to a-Cr2O3 with 50-nm particles.
88. Vradman, L.; Landau, M. V.; Herskowitz, M.; Ezersky, V.; Talianker, M.; Nikitenko, S.; Koltypin, Y.; Gedanken, A., "High loading of short W(Mo)S2 slabs inside the nanotubes of SBA-15. Promotion with Ni(Co) and performance in hydrodesulfurization and hydrogenation". Studies in Surface Science and Catalysis (2003), 146(Nanotechnology in Mesostructured Materials), 721-724. Layered nanoslabs of a MoS2 and WS2 phases with a well-defined hexagonal cryst. structure were inserted into the nanotubular channels of SBA-15 at loadings up to 60 wt%. Sonication of a slurry contg. SBA-15 in a W(Mo)(CO)6-sulfur-diphenylmethane soln. yielded an amorphous W(Mo)S2 phase inside the mesopores that was transformed into hexagonal cryst. W(Mo)S2 nanoslabs by further sulfidation. The nanoslabs were distributed exclusively inside the mesopores in a uniform manner (HRTEM, local quant. microanal.), without blocking the pores (N2-sorption). The Ni(Co) promoters were introduced into the W(Mo)S2/SBA-15 composites by impregnation from an aq. soln. of nickel (cobalt) acetate. The activity (based on the vol. of the catalyst loaded into reactor) of the optimized Ni-W-S/SBA-15 catalyst in hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrogenation (HYD) of toluene was 1.4 and 7.3 times higher, resp., than that of a sulfided com. Co-Mo/Al2O3. The HDS activity of Co-Mo-S/SBA-15 catalyst was 1.2 times higher than that of com. catalyst. After promotion with Co, the directly introduced MoS2 slabs and MoS2 slabs prepd. by sulfidation of Mo-oxide monolayer spread over SBA-15 displayed similar HDS performance.
89. Rotter, H.; Landau, M. V.; Carrera, M.; Goldfarb, D.; Herskowitz, M., "High surface area chromia aerogel efficient catalyst and catalyst support for ethylacetate combustion". Applied Catalysis, B: Environmental (2004), 47(2), 111-126. The effect of dispersion and the ensembling mode of chromium oxide nanocrystals in bulk xerogels and aerogels on their performance, as well as the efficiency of high-surface-area chromia aerogel as catalyst support, were investigated in complete Et acetate (EA) oxidn. Two series of chromia catalysts with a structure of a-Cr2O3 (7-110 m2/g) and a-CrOOH (230-735 m2/g) were tested in EA complete oxidn. as a model reaction for VOC combustion. For a-Cr2O3, the specific activity increased 3.3 times with a decrease of the crystal diam. from .apprx.100 to 13 nm. For a-CrOOH materials, where the surface area was detd. by the different packing mode of primary nanoparticles of the same size (3-5 nm), similar specific rate consts. were measured with all the tested samples. The activity of the chromia aerogel (a-CrOOH, 630 m2/g) was four times higher than 0.5% Pt/Al2O3 and 30 times higher relative to 30% Cr2O3/SiO2. Oxidative treatment (O2) at elevated temps. converts both phases to CrO2, in case of a-Cr2O3, only in the crystal surface layer. In both reduced and oxidized states, a high concn. of surface oxygen vacancies were detected in a-Cr2O3 and a-CrOOH catalysts. A redox cycle Cr(III)[]OH .tautm. Cr(IV)[O]O, which dets. the catalysts' performance at the surface of both types of bulk chromia materials, was proposed. Promotion of high-surface-area chromia aerogel with Pt, Au, Mn, and Ce increased its activity in EA complete oxidn. by a factor of 1.25-2.7. Addn. of Pt, Mn to ceria-promoted chromia aerogel has a significant effect, yielding a high specific rate const. Promotion with Ce and Mn additives improved the efficiency of the redox cycle in Cr aerogel and increased the concn. of surface oxygen vacancies.
90. S. Ruthstein, V. Frydman, S. Kababya, M.V. Landau and D. Goldfarb, "Study of the formation of the Mesoporous Material SBA-15 by EPR Spectroscopy", J.Phys.Chem.B, 2003, 107 (8), 1739 –1748. SBA-15 is an hexagonal mesoporous material which is synthesized with nonionic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers (Pluronics, EOyPOxEOy), templates. Pore diameters in the range of 2-30 nm can be obtained with a relatively thick silica wall (up to 6 nm). This material possesses both large, uniform, and ordered channels, along with a complementary net of micropores which provides connectivity between the ordered channels through the silica. This study focuses on the investigation of the formation mechanism of SBA-15 with emphasis on the PEO interactions with the silica and the initiation of the micropores. This was achieved using in situ X-band EPR spectroscopy in combination with electron spin-echo envelope modulation (ESEEM) experiments. The paramagnetic centers were introduced as spin-labeled Pluronic L62 (EO6PO30EO6) where nitroxides replace the OH groups at the end of the polypropylene oxide (PEO) blocks (L62-NO). Initially, the acidic reaction conditions were adjusted to prevent the decomposition of the nitroxide radical, while still producing highly ordered SBA-15. Then, the locations of the nitroxides of L62-NO within the micelles of Pluronic P123 (y = 20, x = 70) and L64 (y = 13, x = 30) were determined through three-pulse ESEEM experiments on solutions prepared in D2O. In these experiments, the 2H modulation induced by D2O was compared with that of a series of small spin-probes with known hydrophilic and hydrophobic characters that were introduced into the micelles. The NO group of L62-NO was found to be close to the core-corona interface in both types of Pluronics. The temporal evolution of the EPR spectrum during the reaction showed that for SBA-15 made with P123 the most significant changes in the L62-NO spectrum occur within the first 100 min. Furthermore, X-ray diffraction measurements of dried materials showed that the hexagonal structure of SBA-15 is also created within the first 2 h. A partitioning of the L62-NO between the precursors of the mesopores and micropores of the SBA-15 structure takes place at the very early stages of the reaction, and a continuous depletion of water within the corona-core interface was observed. In the final product obtained without a thermal stage, the majority of the PEO chains are located in the micropores. The extent of the PEO chains located within the silica micropores depends on the thermal stage temperature and on the Si/P123 molar ratio. In the L64 synthesis, practically all of the NO groups of L62-NO are located within the silica network and experience a single environment.
91. Vradman, L.; Peer, Y.; Mann-Kiperman, A.; Landau, M. V., "Thermal decomposition-precipitation inside the nanoreactors. High loading of W oxide nanoparticles into the nanotubes of SBA-15". Studies in Surface Science and Catalysis (2003), 146(Nanotechnology in Mesostructured Materials), 121-124. The soln. thermal decompn.-pptn. of an oxide precursor inside nanotubes (nanoreactors) of a mesoporous silica support under an atm. satd. with solvent at the oxide precursor decompn. temp. was explored for loading of W oxide nanoparticles into SBA-15 silica. The pptn. of W-ethoxide soln. in decalin yielded WO3/SBA-15 composites with the WO3 phase located exclusively inside the pores in the form of nanocrystals strongly blocking the pores. The pptn. of W(CO)6 from soln. yielded a WOx phase with a £32 wt.% spread as an amorphous monolayer on the pore walls with minor pore blockage.
92. Brosius, R.; Habermacher, D.; Martens, J. A.; Vradman, L.; Herskowitz, M.; Capek, L.; Sobalik, Z.; Dedecek, J.; Wichterlova, B.; Tokarova, V.; Gonsiorova, O., "NO oxidation kinetics on iron zeolites: Influence of framework type and iron speciation". Topics in Catalysis (2004), 30/31(1-4), 333-339. Zeolites having MFI, FER and *BEA topol. were loaded with iron using solid state cation exchange method. The Fe:Al at. ratio was 1:4. The zeolites were characterized using nitrogen adsorption, FTIR and DR UV-Vis-NIR spectroscopy. The catalytic activity in NO oxidn. and the occurrence of NOx adsorption was detd. in a fixed-bed mini reactor using gas mixts. contg. oxygen and water in addn. to NO and NO2 and temps. of 200-350 °C. Under these reaction conditions, the NOx adsorption capacity of these iron zeolites was negligible. The kinetic data could be fitted with a LHHW rate expression assuming a surface reaction between adsorbed NO and adsorbed O2. The kinetic anal. revealed the occurrence of strong reaction inhibition by adsorbed NO2. FER and MFI zeolites were more active than *BEA type zeolite. MFI zeolite is most active but suffers most from NO2 inhibition of the reaction rate. FTIR and UV-Vis spectra suggest that isolated Fe3+ cations and binuclear Fe3+ complexes are active NO oxidn. sites. Compared to the isolated Fe3+ species, the binuclear complexes abundantly present in the MFI zeolite seem to be most sensitive to poisoning by NO2.
93. Rao, P. Madhusudhan; Wolfson, A.; Landau, M. V.; Herskowitz, M., "Efficient immobilization of 12-tungstophosphoric acid catalyst at the surface of silica support grafted with alumina". Catalysis Communications (2004), 5(6), 327-331. 12-Tungstophosphoric acid (HPW) was successfully immobilized on alumina-grafted silica-gel supports without significant structural damage. The thus prepd. catalysts were employed in representative acid catalyzed reactions which involve polar substrates and products. It was found that HPW supported on alumina-grafted silica-gel displayed higher activity compared with HPW/g-Al2O3. Moreover, in reactions that did not require strong acid sites, activities comparable to the bulk HPW were obtained.
94. Wang, Xueguang; Landau, M. V.; Rotter, H.; Vradman, L.; Wolfson, A.; Erenburg, A., "TiO2 and ZrO2 crystals in SBA-15 silica: performance of Pt/TiO2(ZrO2)/SBA-15 catalysts in ethyl acetate combustion". Journal of Catalysis (2004), 222(2), 565-571. TiO2 (40-64 wt%) and ZrO2 (48-62 wt%) were inserted in SBA-15 mesostructured silica by chem. soln. decompn. or hydrolysis of the corresponding alkoxides inside the host pores. It yielded composites with 85-94% TiO2 crystallinity (anatase) and >95% crystallinity of ZrO2 (tetragonal phase). The 4.5 nm (ZrO2) or 5.0 and 8.5 nm (TiO2) nanocrystals did not block the SBA-15 pores, and their surface was fully accessible for adsorbed nitrogen or Et acetate mols. After deposition of 0.3 wt% Pt the activity of Ti(Zr)O2/SBA-15 materials in Et acetate combustion was proportional to the surface area of the corresponding transition metal oxide nanoparticles, being a function of their loading and crystal size. The platinized composite materials displayed 1.7-3 times higher activity compared with platinum on bulk Ti(Zr)O2 oxides prepd. by the same methods and two orders of magnitude higher activity relative to Pt/SBA-15 and Pt/g-Al2O3 catalysts.
95. M. Abecassis-Wolfovich, M.; Landau, M. V.; Brenner, A.; Herskowitz, M., "Catalytic wet oxidation of phenol with Mn-Ce-based oxide catalysts: Impact of reactive adsorption on TOC removal". Industrial & Engineering Chemistry Research (2004), 43(17), 5089-5097. Catalytic wet oxidn. of phenol solns. at low temps. of 80-130 °C and space velocities of 1-100 h-1 using Mn-Ce catalysts was studied with an emphasis on the reactive adsorption mechanism and total org. carbon (TOC) removal. Eight catalysts (Mn/Ce = 6:4) were activated under different conditions and promoted with alkali metals (K, Cs) or noble metals (Pt, Ru). The compns. and phys. properties of all catalysts were measured. Preliminary runs were conducted in a batch reactor, but most expts. were carried out in a continuous-flow trickle-bed reactor. Catalysts contg. mixed Mn3O4-CeO2 phases pure and promoted with alkali metals displayed a higher activity and a higher adsorption of org. deposits on their surface. Noble metals had little effect on process performance. The adsorption capacity of the catalysts was found to be considerably higher than that reported for activated carbon. Furthermore, complete regeneration of a catalyst in three consecutive tests was demonstrated under relatively low temp. and with no loss of activity. The selectivity toward reactive adsorption was highest on Mn-Ce-Cs catalysts. Low space velocity yielded essentially complete adsorption of phenol, resulting in deposits on the catalyst surface. The conversion of phenol to water-sol. oxygenates was found to increase water toxicity. The catalytic reactive adsorption-regeneration process should become an attractive treatment method for phenol solns. and other complex waste streams.
96. Landau, M. V., Shter, G. E., Titelman, L., Gelman, V., Rotter, H., Grader, G. S., Herskowitz, M., "Alumina Foam Coated with Nanostructured Chromia Aerogel: Efficient Catalytic Material for Complete Combustion of Chlorinated VOC", Industrial & Engineering Chemistry Research, 45(22), 7462-69 (2006). Com. volatile org. compd. (VOC) combustion catalysts, including V-W-Ti-O, Mn-Al-O, and Mn-W-Al-O, that operate well below 600 K produce only dehydrochlorination of 2-chloropropane to HCl and propylene. Catalytic materials based on chromia aerogel, prepd. in this study, yielded complete combustion with about 90% selectivity to CO2 at mild conditions. -Al2O3 ceramic foam was coated with chromia aerogel consisting of 1-2 nm CrOOH nanocrystals with surface area of 670 m2/g. The layer thickness changed from 15 to 80 m corresponding to CrOOH loading of 4.5-21.5 wt % with the total surface area of 40-105 m2/g. The chromia-loaded foams were packed in a tubular reactor and tested with a mixt. of 1000 ppmv 2-chloropropane (2-CP) in air at 450-550 K and GHSV = 60 000 h-1. Ceramic foam contg. 7.7 wt % CrOOH yielded essentially complete conversion of 2-CP to mainly CO2/H2O/HCl at 550 K. Actually, those results were obtained despite apparent bypassing at high chromia loading indicated by the anal. of three catalysts tested in this study. Increasing chromia loading from 7.7 to 21.5 wt % little increased the apparent rate const. This is further reflected by the relatively low apparent activation energy of 14 kcal/mol calcd. from the measured values. The measured pressure drop was low, as expected, in general agreement with the predictions of a literature correlation developed for various foams. The results of this study demonstrate the significant potential of ceramic foams. For high-loaded catalytic systems further work is needed to create the right configuration of the foam.
97. Ben-Harush, K., Wolfson, A., Herskowitz, M., "Unexpected performance of solid alkaline metal hydroxides in liquid phase oxidation of 1-phenylethanol", Letters in Organic Chemistry 3(9), 664-667(2006). Solid alk. metal hydroxides displayed activity in alc. oxidn. in non-polar medium. Both org. mols. and mol. oxygen were employed as oxidants. The activity was in order KOH > NaOH >> LiOH.
98. Capek, L., Vradman, L., Sazama, P., Herskowitz, M., Wichterlova, B., Zukerman, R., Brosius, R., Martens, J. A., "Kinetic experiments and modeling of NO oxidation and SCR of NOx with decane over Cu- and Fe-MFI catalysts" Applied Catalysis, B: Environmental 70(1-4), 53-57(2007). A kinetic model of NO redn. to N2 by decane, developed based on exptl. data over an Fe-MFI catalyst, was applied to assess the oxidn. of NO to NO2 and redn. of NO2 to N2 by decane over a Cu-MFI catalyst. This model fit exptl. data of NO oxidn. to NO2 and NO redn. to N2 well. Remarkable differences were obsd. for Cu-MFI and Fe-MFI catalyst performance. While Fe-MFI was more active in oxidizing NO to NO2, Cu-MFI exhibited much higher activity in reducing NO by decane. The kinetic model indicated the significantly lower activity of Fe-MFI vs. Cu-MFI in transforming NOx to N2 was due to higher rate of transformation of NO2, formed in the first step by NO oxidn., back to NO instead of to N2.
99. Abecassis-Wolfovich, M., Landau, M. V., Brenner, A., Herskowitz, M., "Low-temperature combustion of 2,4,6-trichlorophenol in catalytic wet oxidation with nanocasted Mn-Ce-oxide catalyst" Journal of Catalysis 247(2), 201-213(2007). The essentially complete mineralization (>95% total org. carbon elimination) of 2,4,6-trichlorophenol by a CWO is reported at a very mild operating conditions (120, PO2 = 10 bar), with the use of a nanocasted Mn-Ce-oxide catalyst. This unique catalyst was prepd. by fabrication of a thin nanometric layer of Mn-Ce oxides inside the tubular mesopores of SBA-15 silica using internal gelation of corresponding metal chlorides. Crystn. of this oxide layer at 700, followed by removal of silica matrix, yielded a nanostructured mixed-oxide catalyst with surface area up to 316 m2/g. It demonstrated superior textural, structural, and surface oxygen properties compared with a ref. co-pptd. bulk Mn-Ce-oxide catalyst. This is a result of redn. and equalization of the crystal size of both oxide-phases Mn2O3 and CeO2 at the level of 2-3 nm, providing the full availability of their surface for reacting mols. The performance measured with the novel catalyst indicates a major improvement in the efficient application of CWO processes for complete purifn. of complex waste streams.
100. Landau, M. V., Rao, P. M., Thomas, S., Pitchon, V., Zukerman, R., Vradman, L., Herskowitz, M., "Application of Cs salt of 12-tungstophosphoric acid supported on SBA-15 mesoporous silica in NOx storage" Topics in Catalysis 42-43(1-4), 203-207 (2007). Cs salt of 12-tungstophosphoric acid (HPW) was deposited simultaneously at the external surface of the SBA-15 silica microcrystals and inside its mesoporous channels at loading of 60 wt% and Cs/W ratio in the range between 0.9 and 2, followed by impregnation of 1 wt% Pt. The performance of the Pt/CsHPW/SBA-15 composite materials was tested in the NOx storage. The optimal NOx storage capacity and efficiency were achieved at Cs/W of 1.5. The dispersion of CsHPW on SBA-15 led to a significant decrease of its crystal size (5-13 nm) compared with bulk HPW and HPW supported on titania (28-29 nm). Pt/CsHPW/SBA-15 displayed lower NOx absorption capacity but much higher absorption and desorption efficiency than the ref. Pt/HPW and Pt/HPW/TiO2 materials. Consequently, Pt/CsHPW/SBA-15 displayed a better performance in short lean (2 min)-rich (1 min) absorption-desorption cycles. The novel Pt/CsHPW/SBA-15 nanocomposites presents the basis for improved storage material for NOx removal from lean exhaust gases in highly dynamic aftertreatment technologies.
101. Rao, P. Madhusudhan, Goldberg-Oppenheimer, P., Kababya, S., Vega, S., Landau, M. V., "Proton enriched high-surface-area cesium salt of phosphotungstic heteropolyacid with enhanced catalytic activity fabricated by nanocasting strategy", Journal of Molecular Catalysis A: Chemical (2007), 275(1-2), 214-227. The elimination by HF of the silica matrix from the composites obtained by the two-step reaction deposition of CsxH3-xPW12O40 (CsHPW) salt nanocrystals with a Cs/W12 ratio equal 2.5 on SBA-15 yields materials with substantially lower Cs/W12 ratios of 1.7-2.0. The value of the Cs/W12 ratio in the nanocasts is detd. by the Cs-precursor (Cs n-propoxide or Cs-acetate) used at the first stage of materials prepn. The surface area of the CsHPW nanocasts is 41-45 times higher than their co-pptd. analogs at the same Cs/W12 ratios. We report here that implementation of the nanocasting prepn. technique yields for the first time a bulk CsHPW material that combines a high concn. of acid sites (Cs/W12 = 1.7-2.0) with a high surface area of 41-93 m2 g-1. Co-pptd. analogs at the same Cs/W12 ratios are nonporous and exhibit a surface area smaller than 5 m2 g-1. Our nanocasted CsHPW materials are stable against leaching and colloidization in polar solvents, and their catalytic performance exceeded that of bulk Cs2.5H0.5PW12O40, known as the most active among the acidic HPW salts. The catalytic activity of CsHPW nanocasts in MTBE synthesis and in the isopropanol dehydration reactions is shown to be higher by a factor of 2-3 than that of the std. Cs2.5H0.5PW12O40 material.
102. Markovich, V., Fita, I., Mogilyansky, D., Wisniewski, A., Puzniak, R., Titelman, L., Vradman, L. Herskowitz, M., and Gorodetsky, G., "Magnetic properties of nanocrystalline La1-xMnO3+δ manganites: size effects", Journal of Physics: Condensed Matter., 19(34), 346210 (2007). The magnetic properties of nanocryst. manganites La1-xMnO3+ with particle size of 20 (LMO20), 25 (LMO25), and 30 nm (LMO30), prepd. by the citrate method, were studied in the temp. range 5-320 K, magnetic field up to 90 kOe and under quasi-hydrostatic pressures up to 14.5 kbar. The studies involve sequential zero-field-cooled magnetization (M) measurements followed by magnetization measurements during cooling in the same magnetic field (H) and complementary measurements of a.c. susceptibility. Addnl. measurements of M vs. H were carried out at ambient and applied pressures. All nanoparticles exhibit a paramagnetic to ferromagnetic transition (PFT) at a Curie temp. TC > 200 K. The relative vol. of the ferromagnetic phase increases for larger particle size and approaches a value of .apprx.93% for LMO30. The real part of the a.c. susceptibility of sample LMO20 exhibits strong frequency dependence in a wide temp. range below TC, whereas for sample LMO30 only relatively weak frequency dependence was obsd. The magnetization of sample LMO30 exhibits a PFT of 2nd order; the type of transition could not be established for the smaller particles. An applied pressure enhances the TC of La1-xMnO3+ nanoparticles with a pressure coeff. of dTC/dP 1.9 K kbar-1 for LMO20 and dTC/dP 1.4 K kbar-1 for LMO25 and LMO30 samples. Peculiar magnetic memory effects obsd. for sample LMO20 are discussed.
103. Markovich, V., Fita, I., Wisniewski, A., Puzniak, R., Mogilyansky, D., Titelman, L., Vradman, L., Herskowitz, M., Gorodetsky, G., "Metastable diamagnetic response of 20 nm La1-xMnO3 particles", Physical Review B: Condensed Matter and Materials Physics (2008), 77(1), 014423/1-014423/6. The magnetic properties of compacted 20 nm La1-xMnO3 particles, prepd. by the citrate method, in pristine and metastable states have been studied. In its pristine state the studied sample displays a paramagnetic-to-ferromagnetic transition near TC 220 K, below which the relative vol. of the ferromagnetic (FM) phase at 5 K approaches a value of .apprx.24%. Magnetization and ac-susceptibility measurements exhibit a cluster-glass-like behavior characterized by a noticeable difference between zero-field-cooled and field-cooled magnetization and frequency-dependent a.c. susceptibility. Different metastable states with highly reduced FM phase and neg. ferromagnetism developed after quick coolings of the sample placed in a container filled with Si oil. The recorded temp. dependence of the neg. FM moment appears to be a normalized replica of the corresponding FM dependence. Hysteresis loops of magnetization at low temps. in both pristine and diamagnetic (DIA) states exhibit the same value of coercive field at 5 K, HC 400 Oe. The abnormal DIA state can only be erased after a few hours storage of the sample at room temp. These observations are discussed with ref. to a model in which the neg. ferromagnetism is attributed to the appearance of nondispersive orbital currents which result in a coupling between the core of the FM particles and the surrounding diamagnetic matrix formed during the quick cooling cycles.
104. Markovich, V., Fita, I., Wisniewski, A., Puzniak, R., Mogilyansky, D., Titelman, L., Vradman, L., Herskowitz, M., Gorodetsky, G., "Surface and exchange-bias effects in compacted CaMnO3-δ nanoparticles", Department of Physics, Ben-Gurion University of the Negev, Beer Sheva, Israel. Physical Review B: Condensed Matter and Materials Physics (2008), 77(5), 054410/1-054410/5. Magnetic properties of compacted 50 nm CaMnO3-δ (CMO) nanoparticles have been investigated. Measurements of ac-susceptibility exhibit upon cooling two magnetic transitions at T .apprx. 270 K accompanied by a small spontaneous magnetic moment and a para-antiferromagnetic (AFM) transition at TN .apprx. 120 K, obsd. previously in bulk CMO. Asym. magnetization hysteresis loops obsd. in applied magnetic fields H 90 kOe are attributed to an exchange coupling between the antiferromagnetic core and the ferromagnetic (FM) shell of the CMO nanoparticles. This work provides the observation of exchange bias effect in manganite nanoparticles with inverted AFM-core-FM-shell structure, as compared to the typical FM-core-AFM-shell. Effects of surface and exchange anisotropy are also discussed.
105. Levi, R., Milman, M., Landau, M. V., Brenner, A., Herskowitz, M., "Catalytic Wet Air Oxidation of Aniline with Nanocasted Mn-Ce-Oxide Catalyst", Environmental Science & Technology (2008), 42(14), 5165-5170. The catalytic wet air oxidn. of aq. soln. contg. 1000 ppm aniline was conducted in a trickle-bed reactor packed with a novel nanocasted Mn-Ce-oxide catalyst (surface area of 300 m2/g) prepd. using SBA-15 silica as a hard template. A range of liq. hourly space velocities (5-20 h-1) and temps. (110-140 C) at 10 bar of oxygen were tested. The expts. were conducted to provide the intrinsic performance of the catalysts. Complete aniline conversion, 90% TOC conversion, and 80% nitrogen mineralization were achieved at 140 C and 5 h-1. Blank expts. yielded relatively low homogeneous aniline (<35%) and negligible TOC conversions. Fast deactivation of the catalysts was experienced due to leaching caused by complexation with aniline. Acidification of the soln. with HCl (molar HCl to aniline ratio of 1.2) was necessary to avoid colloidization and leaching of the nanoparticulate catalyst components. The catalyst displayed stable performance for over 200 h on stream.
106. Fita, I., Markovich, V., Mogilyansky, D., Puzniak, R., Wisniewski, A., Titelman, L., Vradman, L., Herskowitz, M., Varyukhin, V. N., Gorodetsky, G., "Size- and pressure-controlled ferromagnetism in LaCoO3 nanoparticles", Physical Review B: Condensed Matter and Materials Physics (2008), 77(22), 224421/1-224421/9.Magnetic properties of nanocryst. LaCoO3 with particle size of 25, 30, 32, and 38 nm, prepd. by the citrate method, were investigated in temp. range 2-320 K, magnetic field up to 50 kOe, and under hydrostatic pressure up to 11 kbar. All nanoparticles exhibit weak ferromagnetism below TC85 K, in agreement with recent observation on LaCoO3 particles and tensile thin films. It was found that with decreasing particle size, i.e., with increasing the surface to vol. ratio, the unit-cell vol. increases monotonically due to the surface effect. The ferromagnetic moment increases as well, simultaneously with lattice expansion, whereas TC remains nearly unchanged. On the other hand, an applied hydrostatic pressure suppresses strongly the ferromagnetic phase leading to its full disappearance at 10 kbar, while the TC does not change visibly under pressure. It appears that the ferromagnetism in LaCoO3 nanoparticles is controlled by the unit-cell vol. This clear correlation suggests that the nature of ferromagnetic ground state of LaCoO3 is likely related to orbitally ordered Jahn-Teller active Co3+ ions with intermediate-spin (IS) state, which may persist in the expanded lattice at low temps. A robust orbital order presumed among the IS Co3+ species can explain the very stable TC obsd. for LaCoO3 samples prepd. under different conditions: single crystal powders, nanoparticles, and thin films.
107. Landau, Miron V., Herskowitz, Moti, Agnihotri, Rajeev, Kegerreis, James E., "Ultradeep Adsorption-Desulfurization of Gasoline with Ni/Al-SiO2 Material Catalytically Facilitated by Ethanol", Industrial & Engineering Chemistry Research (2008), 47(18), 6904-6916.Adsorptive desulfurization of low-sulfur (22 ppmw) gasoline on solids in a liq.-full (no hydrogen) fixed bed was conducted at 503 K. Addn. of 3 wt.% ethanol to gasoline increased significantly the adsorption rate of sulfur-contg. hydrocarbons on Ni/Al-SiO2 and its sulfur capacity, leading to <0.5 ppmw residual sulfur with a sulfur capacity of 2 wt.% (mass of sulfur per mass of sorbent). Three potential routes for improving desulfurization performance of Ni sorbent in the presence of ethanol and its decompn. products contg. CO and hydrogen were considered: (1) formation of nickel carbide (Ni3C) phase with reactivity toward S-org. compds. higher than that of metallic nickel, (2) redn. of carbon deposits in the presence of hydrogen, and (3) formation of nickel sulfide nanoparticles in the presence of H2/H2S vs adsorbed sulfur/sulfur orgs. that block the surface of metallic nickel in the absence of EtOH (hydrogen). Catalyst characterization data (N2 adsorption, XRD, EDX, HRTEM, FTIR, XPS, AES depth profile anal.) indicated that the effect of ethanol on the desulfurization performance was a result of redn. of coke deposition and changing the sulfur uptake mode from adsorption to reactive adsorption with the formation of bulk nickel sulfide phases Ni3S2 and Ni3S4. This is facilitated by hydrogen produced from the catalytic decompn. of ethanol that participates in the desulfurization of S-orgs. and in the formation of nickel sulfide phases.
108. Markovich, V., Jung, G., Fita, I., Mogilyansky, D., Wu, X., Wisniewski, A., Puzniak, R., Froumin, N., Titelman, L., Vradman, L., Herskowitz, M., Gorodetsky, G., "Magnetotransport in granular LaMnO3+δ manganite with nano-sized particles", Journal of Physics D: Applied Physics (2008), 41(18), 185001/1-185001/9. Transport and magnetic properties of compacted LaMnO3+δ manganite nanoparticles of an av. size of 18 nm have been investigated in the temp. range 5-300 K. The nanoparticles exhibit a paramagnetic-to-ferromagnetic (FM) transition at the Curie temp. TC .apprx. 246 K. However, the spontaneous magnetization disappears at a higher temp. of about 270 K. It was found that at low temps. the FM core occupies about 50% of the particle vol. The temp. dependent of the respectivity shows a metal-insulator transition and a low-temp. upturn below the resistivity min. at T .apprx. 50 K. The transport at low temps. is controlled by the charging energy and spin-dependent tunnelling through grain boundaries. It has been found that the charging energy decreases monotonically with increasing magnetic field. The low temp. I-V characteristics are well described by an indirect tunnelling model while at higher temps. both direct and resonant tunnelling dominates. The exptl. features are discussed in the framework of a granular ferromagnet model.
109. Markovich, V., Fita, I., Mogilyansky, D., Wisniewski, A., Puzniak, R., Titelman, L., Vradman, L., Herskowitz, M., Gorodetsky, G., "Effect of particle size on magnetic properties of LaMnO3+δ nanoparticles", Superlattices and Microstructures (2008), 44(4-5), 476-482. Magnetic properties of nanocryst. LaMnO3+δ manganites with particle sizes of 20 (LMO20), 25 (LMO25), and 30 nm (LMO30), prepd. by the citrate method, have been investigated. All nanoparticles exhibit paramagnetic to ferromagnetic transition (PFT) at TC > 200 K. It was found that the relative vol. of the ferromagnetic phase increases with increasing particle size and approaches a value of about 93% for LMO30. Ac susceptibility of LMO20 sample exhibits strong frequency dependence below TC, whereas for LMO30 sample only weak frequency dependence was obsd. The magnetization of LMO30 sample exhibits a PFT of second order. It was found that an applied pressure enhances TC of LaMnO3+δ particles with a pressure coeff. of dTC/dP = 1.4-1.9 K/kbar for all samples. Peculiar magnetic memory and neg. magnetization effects obsd. for LMO20 sample are discussed.
110. Zukerman, Roie, Vradman, Leonid, Titelman, Leonid, Weidenthaler, Claudia, Landau, Miron V., Herskowitz, Moti, "Effect of silica wall microporosity on the state and performance of TiO2 nanocrystals in SBA-15 matrix", Microporous and Mesoporous Materials (2008), 116(1-3), 237-245. TiO2 guest phase was incorporated by internal hydrolysis (IH) method inside SBA-15 mesostructured silica matrixes with high and low microporosity (14.2% and 4.7% of microporous pore vol., resp.). TiO2 phase was located inside the SBA-15 pores in form of small crystals with anatase structure without blocking the mesopores over wide range of loadings (8-50 wt%) (N2 sorption, HRTEM and XRD). In the highly microporous SBA-15 (SBA-15-HM), the crystn. of titania anatase phase was detected at 150C due to initiation of the crystn. process in the micropores. This is supported by the fact that the crystn. was significantly delayed and started at 350C inside the SBA-15 with low microporosity (SBA-15-LM). Therefore, it was proposed that the formation of nanocryst. titania in SBA-15 micropores initiates the nucleation stage thus enhancing the crystn. process of titania in the mesopores. Furthermore, micropores enhanced the dispersion of TiO2 phase. As a result, TiO2/SBA-15-HM adsorbed more vanadia than TiO2/SBA-15-LM. The catalytic activity in selective catalytic redn. (SCR) of NO with ammonia was proportional to the vanadia content. Thus, V2O5-TiO2/SBA-15-HM catalysts were more active than V2O5-TiO2/SBA-15-LM at all TiO2 loadings due to the higher vanadia content in TiO2/SBA-15-HM than in TiO2/SBA-15-LM. These results show that SBA-15 wall microporosity strongly affects the crystn., state and performance of the guest phase confined in mesoporous channels of silica matrix.
111. Fita, I., Mogilyansky, D., Markovich, V., Puzniak, R., Wisniewski, A., Titelman, L., Vradman, L., Herskowitz, M., Varyukhin, V. N., Gorodetsky, G., "Pressure-induced suppression of ferromagnetic phase in LaCoO3 nanoparticles", Journal of Non-Crystalline Solids (2008), 354(47-51), 5204-5206. Magnetic and structural properties of nanocryst. LaCoO3 with particle size ranging from 25-38 nm, prepd. by the citrate method, were studied. All nanoparticles exhibit ferromagnetism below TC 85 K It was found that the unit-cell vol. increases monotonically with decreasing particle size and ferromagnetic (FM) moment increases simultaneously with lattice expansion, whereas TC remains nearly unchanged. It appears that both magnetic and structural properties of LaCoO3 nanoparticles are size-dependent due to the surface effect. However, an applied pressure suppresses strongly the FM phase leading to its disappearance at .apprx.11 kbar. Remarkably, the TC does not change visibly under pressure. The data reveal that the ferromagnetism in LaCoO3 nanoparticles, likely related to the intermediate-spin (IS) Co3+ state, is simply controlled by the unit-cell vol. Within this scenario, the FM coupled IS states appear/disappear with expanding/compressing the lattice and/or Co-O bonds.
112. Vidruk, Roxana, Landau, Miron V., Herskowitz, Moti, Talianker, Michael, Frage, Nahum, Ezersky, Vladimir, Froumin, Natali, "Grain boundary control in nanocrystalline MgO as a novel means for significantly enhancing surface basicity and catalytic activity", Journal of Catalysis (2009), 263(1), 196-204. The grain boundaries in nanocryst. MgO were formed by dehydration of densified magnesium hydroxide aerogel; the configuration was regulated by controlling the contact interface between the nanocrystals in the hydroxide precursor. The MgO with high contact interface was obtained by application of chem. (multiple aerogel condensation) and phys. (pressing) densification methods. Formation of distorted zones at the grain boundaries during densification resulted in increased surface basicity of MgO by as much as 8 times for crystal domain size of 5 nm. The grain boundaries contributed coordinative unsatd. surface ions and vacancies in nanocryst. MgO, as detd. by a variety of phys. and chem. methods. The significant increase of surface basicity yielded a major enhancement of catalytic activity of densified MgO material measured in Knoevenagel condensation of benzaldehyde with malononitrile and transesterification of Ph acetate with 1-phenylethanol.
113. Landau, Miron V., Herskowitz, Moti, Hoffman, Tali, Fuks, David, Liverts, Edward, Vingurt, Dima, Froumin, Natali, "Ultradeep Hydrodesulfurization and Adsorptive Desulfurization of Diesel Fuel on Metal-Rich Nickel Phosphides", Industrial & Engineering Chemistry Research (2009), 48(11), 5239-5249. Three materials contg. Ni2P, Ni12P5, and Ni3P phases on silica gel with surface area 320 m2/g at loadings of 32-37 wt % and the crystal size of NixP phases 30, 9, and 13 nm, resp., were prepd. by a combination of impregnation and TPR methods and tested in hydrodesulfurization (HDS) and adsorptive desulfurization (ADS) of diesel fuel. There were established opposite trends in changing the DS efficiency in two processes: The HDS rate const. decreased while the ADS sulfur capacity (breakthrough at 1 ppmw) increased with increasing the Ni to P ratio in NixP from 2 to 3. The obsd. behavior was attributed to the specific features of the densities of states (DOS) obtained from the d. functional theory calcns. of total and partial DOS for Ni and P in NixP phases and revealed in XPS measurements of binding energy of Ni 2p3/2- and P 2p-electrons. This attribution was consistent with the anal. of the relative part of d-electrons of Ni participating in bonding with p-electrons of phosphorus in these phases.
114. Landau, Miron V., Vradman, Leonid, "Catalytic phases embedded in mesostructured matrices and their nanocasts: effects of spatial dimension and assembling mode on activity", Editors: Valtchev, Valentin; Mintova, Svetlana; Tsapatsis, Michael. Ordered Porous Solids (2009), 693-724. A review; insertion of catalytic phases inside the pores of mesostructured host matrixes allows simultaneous control of the catalytic phase size and assembling modes: nanoparticles ensemble, nanowires or coating layers. The surface area of the catalytic phase-mesostructured host matrix composite can exceed that of pure catalytic phase with D = 10 nm only with a nanoparticle ensemble. Removal of the mesostructured host matrix from preformed composites allows exceeding the surface area of pure 10-nm catalytic phase with all the assembling modes. The catalytic activity follows the catalytic phase surface area in cases when the specific activity of the catalytic phase is const. at that size range. This behavior alters in cases when the diminishing of the catalytic phase size and/or changing the shape significantly affect its specific activity in a selected reaction. The available information about the directing of a catalytic phase to proper assembling modes created in mesostructured host matrixes and in corresponding nanocasts and their effects on catalytic performance of catalytic phases is analyzed.
115. Zukerman, R.; Vradman, L.; Herskowitz, M.; Liverts, E.; Liverts, M.; Massner, A.; Weibel, M.; Brilhac, J. F.; Blakeman, P. G.; Peace, L. J., Modeling and simulation of a smart catalytic converter combining NOx storage, ammonia production and SCR, Chemical Engineering Journal (Amsterdam, Netherlands), Volume155, Issue1-2, pp. 419-426 (2009). Dynamic simulation of the smart catalytic converter, proposed by Daimler AG, is presented. The smart catalytic converter combines NOx storage, on-board NH3 prodn., selective catalytic redn. (SCR), and functions in a dual-mode operation, alternating between lean- and rich-burn. It relies on intrinsic dynamic operation and synchronization of all units; its development demands a reliable dynamic simulator. A platform capable of simulating the dynamic behavior of a multiple-unit after-treatment system was developed based on the COMSOL package. Predictive kinetic models were developed for the NOx storage unit which includes NH3 formation function and for the NH3-SCR unit. Using these kinetic models, a 2-unit smart catalytic converter was simulated on the developed simulator. Simulator results were validated using 2-unit exptl. data. The simulator was also used to control and optimize smart catalytic converter performance. Results showed the simulator is vital to optimize lean- and rich-burn periods to ensure stable lean/rich cycles.
116. Fuks, David; Vingurt, Dima; Landau, Miron V.; Herskowitz, Moti, Density Functional Theory Study of Sulfur Adsorption at the (001) Surface of Metal-Rich Nickel Phosphides: Effect of the Ni/P Ratio, Journal of Physical Chemistry C, Volume114, Issue31, pp. 13313-13321 (2010). A significant increase of the sulfur uptake by NixP with an increasing Ni to P ratio from 2 to 3 was reported recently in ultradeep adsorption desulfurization (ADS) of diesel fuel. It corresponded to increased NixP surface coverage, while no bulk Ni-P-S phases were identified. D. functional theory is applied in this communication to calc. the adsorption energies for S adatoms adsorbed on the surface of Ni2P, Ni12P5, and Ni3P phases. The preferable (001) surface-terminated slabs are considered to link the coverage tendency with the peculiarities of the electron d. of states at the Fermi energy. The electron charge redistribution due to the adsorption of S atoms is calcd., and the nature of bonding of S with the substrates is discussed. The combination of ab initio calcns. performed in the ground state for the considered systems with statistical thermodn. renders the possibility to obtain the coverage at the temps. beyond T = 0 K in good agreement with exptl. data. The increase of surface coverage of NixP phases with an increase in the x value is the result of fine interplay between the no. of possible sites for S adsorption and the difference in the adsorption energies for these sites.
117. Wolfson, Adi; Ben-Harush, Kfir; Herskowitz, Moti, Aerobic oxidation of benzylic alcohols with solid alkaline metal hydroxides, Kinetics and Catalysis, Volume51, Issue1, pp. 63-68, (2010). Solid alk. metal hydroxides displayed high catalytic activity and full selectivity in the aerobic oxidn. of benzylic alcs. in a nonpolar medium. The activity of the solid bases, in decreasing order of reactivity, was KOH > NaOH » LiOH. H2O, which is the only byproduct of the reaction, plays a crucial role in KOH deactivation by converting the crystal phase of KOH to KOH·H2O, as confirmed by XRD measurements.
118. Zukerman, R.; Vradman, L.; Titelman, L.; Zeiri, L.; Perkas, N.; Gedanken, A.; Landau, M. V.; Herskowitz, M., Effect of SBA-15 microporosity on the inserted TiO2 crystal size determined by Raman spectroscopy, Materials Chemistry and Physics, Volume122, Issue1, pp. 53-59 (2010). The effect of SBA-15 microporosity on the crystal size of TiO2 was investigated employing SBA-15 materials with high (SBA-15-HM) and low (SBA-15-LM) microporosities (14.2 and 4.7% of microporous vol., resp.). TiO2 phase was incorporated inside SBA-15 using internal hydrolysis method over a wide range of loadings (7-63 wt%). At all loadings, TiO2 inside SBA-15 pores was in the form of anatase nanocrystals as found in characteristic Raman spectra. The crystal size of TiO2 anatase phase was detd. by Raman spectroscopy using a correlation between Raman peak position and peak width and TiO2 crystal size. The correlation was established based on the set of unsupported TiO2 samples with the crystals size in the range 5-120 nm (BET and XRD). Using this correlation, it was found that the crystal size of TiO2 inside SBA-15 with high microporosity was lower than inside SBA-15 with low microporosity. This is a direct proof of the effect of wall microporosity on the dispersion of TiO2 inside SBA-15. Due to the higher TiO2 dispersion, TiO2/SBA-15-HM adsorbed more vanadia than TiO2/SBA-15-LM at the same TiO2 loadings. As a result, V2O5/TiO2/SBA-15-HM displayed higher activity than V2O5/TiO2/SBA-15-LM in NO SCR with ammonia.
119. Markovich, V.; Jung, G.; Fita, I.; Mogilyansky, D.; Wu, X.; Wisniewski, A.; Puzniak, R.; Titelman, L.; Vradman, L.; Herskowitz, M.; Gorodetsky, G., Magnetotransport properties of ferromagnetic LaMnO3+δ nano-sized crystals, Journal of Magnetism and Magnetic Materials, Volume322, Issue9-12, pp. 1311-1314 (2010). ansport and magnetic properties of LaMnO3+δ nanoparticles with av. size of 18 nm were studied. The ensemble of nanoparticles exhibits a paramagnetic to ferromagnetic (FM) transition at T C∼246 K, while the spontaneous magnetization disappears at T ≈ 270 K the blocking temp. lies slightly below T C. The temp. dependence of the resistivity shows a metal-insulator transition at T ≈ 192 K and low-temp. upturn at T<50 K The transport at low temps. is controlled by the charging energy and spin-dependent tunnelling through grain boundaries. The low temp. I-V characteristics are well described by indirect tunnelling model while at higher temps. both direct and resonant tunnelling dominates.
120. Markovich, V.; Jung, G.; Fita, I.; Mogilyansky, D.; Wu, X.; Wisniewski, A.; Puzniak, R.; Titelman, L.; Vradman, L.; Herskowitz, M.; Gorodetsky, G., Magnetotransport properties of ferromagnetic LaMnO3+δ nano-sized crystals, Journal of Magnetism and Magnetic Materials, Volume322, Issue9-12, pp. 1311-1314 (2010). Transport and magnetic properties of LaMnO3+δ nanoparticles with av. size of 18 nm were studied. The ensemble of nanoparticles exhibits a paramagnetic to ferromagnetic (FM) transition at T C∼246 K, while the spontaneous magnetization disappears at T ≈ 270 K the blocking temp. lies slightly below T C. The temp. dependence of the resistivity shows a metal-insulator transition at T ≈ 192 K and low-temp. upturn at T<50 K The transport at low temps. is controlled by the charging energy and spin-dependent tunnelling through grain boundaries. The low temp. I-V characteristics are well described by indirect tunnelling model while at higher temps. both direct and resonant tunnelling dominates.
121. Vidruk, Roxana; Landau, Miron V.; Herskowitz, Moti; Ezersky, Vladimir; Goldbourt, Amir, Control of surface acidity and catalytic activity of γ-Al2O3 by adjusting the nanocrystalline contact interface, Journal of Catalysis, Volume282, Issue1, pp. 215-227 (2011). Densification of 2-2.5 nm nanocrystals assemblies in the three-level hierarchical structure of γ-Al2O3 aerogel significantly increases the surface acidity, as detd. using indicator titrn., NH3-TPD, and FTIR of adsorbed pyridine. Thermal treatment at 1073 K and insertion of addnl. alumina inside the aerogel pores eliminated the slit micropores with shrinkage of nanocrystals assemblies (N2-adsorption, HRTEM, SEM) increasing the contact interface by a factor of 2. It caused a fivefold increase in alumina surface acidity and the strength of Lewis acid sites with no measurable dehydration (wt. loss, TGA). This was attributed to the formation of addnl. low-coordinated aluminum ions with higher charge in the areas with at. disorder of high-angle grain boundaries, detected by 27Al MAS NMR, HRTEM, XPS, and XRD. Densification of nanocryst. alumina aerogel yielded a higher catalytic activity in dehydration of isopropanol; it was 10-fold more active compared with com. γ-alumina on the catalyst wt. basis.
122. Sui, Zhi-Jun; Vradman, Leonid; Reizner, Ieudit; Landau, Miron V.; Herskowitz, Moti, Effect of preparation method and particle size on LaMnO3 performance in butane oxidation, Catalysis Communications, Volume12, Issue15, pp.1437-1441 (2011). LaMnO3 with different crystal domain sizes and surface areas were prepd. by citrate and sol-gel combustion methods and tested as catalysts for butane total oxidn. reaction. The catalysts were characterized by N2 physisorption, x-ray diffraction and SEM. LaMnO3 with crystal domain sizes in the range of 30-90 nm were detected by x-ray diffraction characterization when high calcination temp., at least 500° for sol-gel combustion method and 700° for citrate method, was required to prep. pure nanocryst. phase. Although LaMnO3 prepd. by these two methods had similar crystal domain sizes, BET surface areas of samples by citrate method were significantly larger than that of samples prepd. by combustion method. The difference of surface area lies in the morphol. differences between the two series of samples (SEM micrographs) generated by strong sintering of samples prepd. by combustion method. The catalytic activity of LaMnO3 in butane total oxidn. increased with increasing surface area being higher for materials prepd. by citrate method. Thus, citrate method showed significant advantages over combustion method in prepn. of perovskite catalysts.
123. Landau, M. V.; Savilov, S. V.; Ivanov, A. S.; Lunin, V. V.; Titelman, L.; Koltypin, Yu.; Gedanken, A., Corrugation of the external surface of multiwall carbon nanotubes by catalytic oxidative etching and its effect on their decoration with metal nanoparticles, Journal of Materials Science, Volume46, Issue7, pp. 2162-2172 (2011). Partial combustion of carbon constituting the walls of multiwall carbon nanotubes (MWCNTs) catalyzed by previously deposited CaCO3 nanoparticles converts parallel graphene layers in a multiwall structure to aggregates formed by nano-onions with a diam. of 5-12 nm. The areas with pos. curvature of graphene layers on the external surface of air-etched MWCNTs played the role of docking stations for nickel nanoparticles inserted by sonochem. deposition after removal of the CaCO3. The nickel nanoparticles were located exclusively at the tops of the onions. Formation of nanoscale curvature at the MWCNT support surfaces decreased the av. size of Ni nanocrystals at similar loading of 50-60% from 8 to 2 nm. Partial catalytic combustion did not change the concn. of surface carbonyl groups measured by titrn., which attributes the obsd. phenomena directly to the corrugation of the MWCNT surfaces. The catalytic tests revealed a significant increase of catalytic activity of supported Ni catalyst due to corrugating of the external surface of the MWCNT support. After oxidative etching of the MWCNTs, the rate of chloroacetophenone hydrogenation measured with a Ni-MWCNT catalyst increased by a factor of 2 without change in selectivity yielding chlorophenylethanol as the main product.
124. Landau, Miron V.; Savilov, Sergei V.; Kirikova, Marina N.; Cherkasov, Nikolai B.; Ivanov, Anton S.; Lunin, Valery V.; Koltypin, Yuri; Gedanken, Aharon, Decoration of multiwall carbon nanotubes with nickel nanoparticles: effect of deposition strategy on metal dispersion and performance in the hydrogenation of p-chloroacetophenone, Mendeleev Communications, Volume21, Issue3, Pages125-128 (2011). The sonochem. deposition of nickel nanoparticles onto the multiwall carbon nanotube aggregates leads to a uniformly distributed metal phase at high loadings and an av. nickel crystal size of 4-8 nm at a 25-50 wt% nickel content. Its application enhances the catalytic activity of Ni/multiwall carbon nanotube material in the selective hydrogenation of chloroacetophenone by factors of 2-18, as compared with that prepd. by traditional decoration methods.
125. Satishkumar, G., Landau, M.V., Buzaglo, T., Frimet, L., Ferentz, M., Vidruk, R., Wagner, F., Gal Y. and Herskowitz, M., "Fe/SiO2 heterogeneous Fenton catalyst for continuous catalytic wet peroxide oxidation prepared in situ by grafting of iron released from LaFeO3", Applied Catalysis B: Environmental, 138–139, 276-284 (2013). Functionalization of silica-gel by immobilization of iron ions at its surface was carried out through a novel method – selective extraction–deposition (SED) in acidic solution using LaFeO3 orthoferrite with perovskite structure as a solid precursor. Isolated Fe-ions produced as a result of precursors decomposition in acidic aqueous solution were trapped by silica surface silanols. The presence of iron in the only one state of isolated surface ions over 2 wt%Fe/SiO2 material at the Fe content corresponded to surface silanols concentration was confirmed using ESR, Mossbauer spectroscopy, UV Raman, FTIR and XPS techniques. Catalytic performance of 2 wt% Fe/SiO2 was examined toward catalytic wet peroxide oxidation (CWPO) of phenol in up flow fixed bed reactor at pH 4, 80 °C, LHSV 6 h−1 with 200 ppmw phenol and 1300 ppmw hydrogen peroxide in water. It was demonstrated that mixing of LaFeO3 with silica-gel gives an advanced catalytic material with high activity (TOC removal of 90%) and stability without iron leaching. This effect is due to dynamic behavior of iron that includes its SED–leaching–condensation along the catalysts layer. In this case, the LaFeO3 has a multiple function–active catalytic component, precursor of iron ions and buffer controlling the pH along the catalysts layer.
126. M.Herskowitz, M.V.Landau, Y.Reizner, D.Berger. A commercially-viable, one-step process for production of green diesel from soybean oil on Pt/SAPO-11. Fuel, 2013, 111, 157-164. The conversion of soybean oil to green diesel was carried out on Pt/SAPO-11-Al2O3 catalyst in a trickle-bed reactor. Steady-state operation was reached after about 150 h. The steady-state performance was recorded at 375–380 °C, 30 atm and LHSV = 1 h−1. The green diesel produced in this study was characterized according to ASTM procedures by a certified lab. Most of its properties were found to fit the standard of qualified diesel fuel (European standard EN-590) making it an excellent component for diesel fuel blends.
127. D. Vingurt, D. Fuks, M. V. Landau, R. Vidruk, M. Herskowitz. Grain boundaries at the surface of consolidated MgO nanocrystals and acid-base Functionality. Phys. Chem.Chem.Phys. 2013, !5(35), 14783-14796. The increase of the surface basicity-acidity of MgO material by factors of 1.8-3.0 due to consolidation of its nanocrystals was demonstrated by the indicator titration. It was shown that the parallel increase of surface acidity and basicity is attributed to the formation of grain boundaries (GB) after MgO aerogel densification. A simple model predicting the increase of surface acidity-basicity of MgO that correlates with the results of direct measurements was proposed. The model is based on the study of the fine atomic structure at GB surface areas in consolidated MgO nanocrystals in the framework of Density Functional Theory. It is found that the displacements of coordinatively unsaturated surface ions near the GB are significant at the distances ~3-4 atomic layers from the geometrical contact plane between nanocrystals. The detailed analysis of atomic positions inside GB demonstrated the coordination deficiency of surface atoms at the GB areas leading to the formation of stretched bonds and to creation of low coordinated surface ions due to splitting of coordination numbers of surface atoms belonging to GB areas. Density of states for electrons shows the existence of additional states in the band gap close to the bottom of the conduction band. The adsorption energy of CO2 molecules atop oxygen atoms exposed at surface GB areas is of the same order of magnitude as that reported for oxygen atoms at crystallographic edges and corners of MgO crystals. It provides additional options for bonding of molecules at the surface of nanocrystalline MgO increasing the adsorption capacity and catalytic activity.
128. Wee, L. H., Lescouet, T., Fritsch, J., Bonino, F., Rose, M., Sui, Z., Garrier, E., Packet, D., Bordiga, S., Kaskel, S., Herskowitz, M., Farrusseng, D. and Martens, J. A., "Synthesis of Monoglycerides by Esterification of Oleic Acid with Glycerol in Heterogeneous Catalytic Process Using Tin-Organic Framework Catalyst", Catalysis Letters, 143(4), 356-363 (2013). Selective synthesis of monoglycerides by esterification of glycerol with fatty acids is a difficult reaction because of immiscibility of reagents and the formation of di- and tri-glyceride by-products. In this work a heterogeneous catalytic process was conceived in which the reactant mixture was homogenized usingtert-butanol solvent. Candidate catalysts were screened in the reaction of oleic acid with glycerol. While under such reaction conditions zeolites were rather inactive, metal–organic frameworks and, especially, tin–organic frameworks were found promising. A tin–organic framework (Sn–EOF) was most active and achieved ≥98 % monoglyceride selectivity at 40 % conversion in catalyzing esterification of oleic acid with glycerol at a low reaction temperature of 150 °C. Leaching of tin from Sn–EOF catalyst was suppressed by limiting the amount of oleic acid in the starting mixture. Characterization of the acid sites of Sn–EOF by pyridine-chemisorption and FTIR revealed Lewis acidity to be responsible for the catalytic activity.
129. Vradman, L., Zana, J., Kirschner, A. and Herskowitz, M., " Synthesis of LaMnO3 in molten chlorides: effect of preparation conditions", Phys. Chem. Chem. Physics, 15(26), 10914-10920 (2013). LaMnO3 perovskite was successfully synthesized in molten chlorides. In order to explore the effect of the molten salt type, NaCl-KCl and LiCl-KCl eutectic mixtures were employed as a liquid medium for the perovskite formation process. The synthesis included heating the La-nitrate, Mn-nitrate and chlorides mixture to above the melting point of the corresponding chlorides. This procedure yielded a LaMnO3 phase integrated in the fused chloride matrix. Washing with water removed the salts completely, yielding pure LaMnO3 perovskite crystals. The synthesis without molten salt at 800 °C yielded several by-products in addition to the LaMnO3 phase, while with LiCl-KCl the pure perovskite phase was obtained at temperatures as low as 600 °C. Variation of temperature in the range 600-800 °C for LiCl-KCl and 700-800 °C for NaCl-KCl had no significant effect either on the morphology or on the particle size of the product. On the other hand, the effect of the molten salt type on the morphology and size of perovskite particles was remarkable. The synthesis in NaCl-KCl resulted in sub-micron LaMnO3 particles with shapes that range from truncated hexahedrons to spheres, while in LiCl-KCl mostly cubic particles of up to 2-microns were obtained. The effect of the molten salt type on LaMnO3 perovskite formation is explained based on the nucleation and crystal growth model and difference in the melting point of eutectic mixtures.
130. Wee, L. H., Lescouet, T., Ethiraj, J., Bonino, F., Vidruk, R., Garrier, E., Packet, D., Bordiga, S., Farrusseng, D Herskowitz, M. and Martens, J.A., "Hierarchical Zeolitic Imidazolate Framework-8 Catalyst for Monoglyceride Synthesis", ChemCatChem, 5(12), 3562-3566 (2013)
131. Miron V. Landau, Roxana Vidruk, and Moti Herskowitz," Sustainable Production of Green Feed from CarbonDioxide and Hydrogen",ChemCatChem 2014, 7, 785-794. Carbon dioxide hydrogenation to form hydrocarbons was conducted on two iron- based catalysts, prepd. according to procedures described in the literature, and on a new iron spinel catalyst. The CO2 conversion measured in a packed- bed reactor was limited to about 60 % because of excessive amts. of water produced in this process. Switching to a system of three packed- bed reactors in series with interim removal of water and condensed hydrocarbons increased CO2 conversion to as much as 89 %. The pure spinel catalyst displayed a significantly higher activity and selectivity than those of the other iron catalysts. This process produces a product called green feed, which is similar in compn. to the product of a high- temp., iron- based Fischer- Tropsch process from syngas. The green feed can be readily converted into renewable fuels by well- established technologies.
132. Ferentz, M., Landau, M.V., Vidruk, R. and Herskowitz, M., "Fixed- bed catalytic wet peroxide oxidation of phenol with titania and Au /titania catalysts in dark", Catalysis Today 241 (2015) 63–72. It was established that nanostructured TiO2 with crystal size in range of 4.5- 30 nm display stable operation in phenol CWPO in dark [PhOH = 200 ppmw] yielding 52- 76 % TOC conversion in afixed- bed reactor at pH = 2.5, T = 80 °C and LHSV = 3.8 h- 1. Deposition of ∼3 wt. % of Au nanoparticles increases the catalytic activity of TiO2 in CWPO of phenol defined as pseudo- first- order rate const. of substrate mineralization by a factor of 2.0- 2.8 depending on Au crystal size. Small 3- 4 nm Au nanoparticles aggregate at reaction conditions with complete deactivation of Aucomponent. Larger 7- 8 nm Au nanoparticles are stable against aggregation and deactivation. No leaching of Ti and Au was detected in runs with duration up to 300 h. The CWPO with both Auand TiO2 catalysts proceeds according to radical mechanism mostly in the part of catalysts layer where H2O2 is completely decompd. At proper operation conditions TiO2 and Au/TiO2 catalystsallow reaching >95 % mineralization of phenol and stable operation.
133. Landau, M.V., Vidruk, R., Vingurt, D, Fuks, D. and Herskowitz, M. "Grain boundaries in nanocrystalline catalytic materials as a source of surface chemical functionality", Rev. Chem. Eng., 30(4), 379-401 (2014).This review considers for the first time the effects in heterogeneous catalysis of grain boundaries (GB) created as a result of consolidation of catalytic materials nanoparticles without their sintering. Different methods proposed for quant. characterization of nanoparticles consolidation extent were considered together with theor. basis for increasing of catalytic activity at the GBsurface areas between consolidated nanocrystals of metals and metal oxides. The review systemizes the GB effects obsd. in different areas of heterogeneous catalysis implementing metallic and oxide catalysts with acidic, basic, and redox surface functionality. The review analyzed exptl. data that demonstrated the fine details of the structure of GB's. Their contribution to improving the performance of catalytic materials should be accounted for in development of novel catalysts and deeper understanding of catalysts functioning.
