Hydrocracking of vacuum gas oil in the presence of supported nickel-tungsten catalysts

The supports containing 70% Al₂O₃ and 30% β zeolite (AZ-1 and AZ-2), which differed in mixing procedures, and the Ni-W/AZ-1 and Ni-W/AZ-2 catalysts were characterized using an adsorption technique, high-resolution electron microscopy, IR spectroscopy, and X-ray photoelectron spectroscopy and tested in the hydrocracking reaction of vacuum gas oil (VGO). It was found that the supports differed in texture characteristics and surface Lewis acidity at the same composition and similar concentrations of Brønsted acid sites. The formation of Ni-W-S sulfide species on the surfaces of both of the supports occurred in different manners: multilayer Ni-W-S sulfide species were formed on AZ-1 (S _sp = 220 m²/g), whereas single-layer species were mainly formed on AZ-2 (S _sp = 380 m²/g). It was found that catalysts containing multilayer Ni-W-S sulfide species, which were characterized by a higher degree of sulfidation, provided a higher yield of diesel fuel upon the hydrocracking of VGO, whereas catalysts containing single-layer Ni-W-S sulfide species were more active in the reactions of VGO hydrodesulfurization and hydrodenitration.     

Effect of the support and the reduction temperature on the formation of metallic nickel phase in Ni/silica gel precursors of vegetable oil hydrogenation catalysts

Ni/SiO₂ materials with identical composition (SiO₂/Ni = 1.0) have been synthesized by precipitation of Ni(NO₃)₂ · 6H₂O solution with Na₂CO₃ solution on the silica gel, obtained at three different pH values. The present investigation was undertaken in an endeavor to study the effects of the silica gel support type and the reduction temperature on the formation and dispersion of the metallic nickel phase in the reduced Ni/SiO₂ precursors of the vegetable oil hydrogenation catalyst. The physicochemical characterization of the unreduced and reduced precursors has been accomplished appropriately by powder X-ray diffraction, infrared spectroscopy, temperature programmed reduction and H₂-chemisorption techniques. It can be stated that the texture peculiarities of the silica gels used as supports influence on the crystalline state and distribution of the deposited Ni-containing phases during the preparation of the precursors, on the reduction temperature of the investigated solids as well as on the bulk size and surface dispersion of the arising metallic nickel particles. It was shown that two types of Ni²⁺-species are formed during the synthesis procedure, namely basic nickel carbonate-like and Ni-phyllosilicate with different extent of presence, location and strength of interaction. The different location of these species is supposed to result in various strength of Ni-O and Ni-O-Si interaction, thus determining the overall reducibility of the precursors. It was specified that the Ni²⁺-species are strongly bonded to the surface of the silica gel obtained at neutral pH value and weakly bonded to the surface of those prepared in acidic and alkaline conditions. It was established that the precursor, derivates from the silica gel obtained at alkaline conditions, demonstrates both significant reduction of the Ni2+ ions at 430°C and finely dispersed metallic nickel particles on its surface. High dispersion of the metallic nickel might be the crucial reason for achieving of high activity in the vegetable oil hydrogenation.     

Effect of the nature of the support on the activity of palladium catalysts for oxidation of carbon monoxide

We have studied the catalytic activity of TiN_0.65, TiO₂, Al₂O₃, and palladium catalysts supported on them in the oxidation of carbon monoxide. The order in which the activities of the supported catalysts vary, Pd/Al₂O₃>Pd/TiO₂>Pd/TiN_0.65, is the reverse of the activity series for the supports. This is explained by the effect of transfer of electron density from the palladium to the substrate. Taras Shevchenko Kiev University, 64 Vladimirskaya ul., Kiev 252033, Ukraine, G. V. Kurdyumov Institute of the Physics of Metals, National Academy of Sciences of Ukraine, 36 Akademika Vernadskogo bul’var, Kiev-142 252642, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 2, pp. 118–121, March–April, 1998.     

Effect of the nature of support and Cu precursor on the activity of copper-containing catalysts in CO oxidation

We have studied the catalytic activity of supported copper-containing catalysts based on ZSM-5, Al₂O₃, and SiO₂ in oxidation of CO. We have established that the difference between the activities of systems with 1.8% copper content obtained from different precursors is determined by the different reducibilities of their active sites, the number of such sites, and the distribution of the metal ions. The fact that the activity is highest for 1.8% Cu-ZSM-5 obtained from copper acetate is due to the relatively higher number of associated Cu²⁺ cations in square planar coordination in a non-lattice oxygen environment, which have high reducibility, and the higher overall oxygen content O_ads + O_OH in the surface layer of the catalyst.     

负载的Ni催化剂上植物油脂加氢脱氧制备第二代生物柴油

在半连续反应器中,以棕榈酸甲酯为植物油脂模型化合物,进行了加氢脱氧制取高品质生物柴油燃料的研究。采用浸渍法制备了HY、SiO₂、γ-Al₂O₃及SAPO-11四种载体负载的Ni催化剂,采用XRD、NH₃-TPD、H₂-TPR、BET、SEM等技术进行催化剂表征。结果表明,Ni/SAPO-11催化剂由于SAPO-11表面呈现的弱酸和中强酸性质,在保持较高的加氢脱氧反应性的同时,抑制了裂解反应的发生,具有较好的催化性能。进一步对SAPO-11上不同的Ni负载量、反应温度、反应压力等进行了研究,发现当Ni负载量为7%,反应温度为220℃,压力为2MPa时,催化剂具有较高的催化性能,棕榈酸甲酯的转化率达到了99.8%,C_9~16烷烃的总选择性为92.71%。     

Effect of the nature of the support for copper-cerium oxide catalysts on selective oxidation of CO in hydrogen-rich mixtures

We have studied the catalytic properties of copper-cerium oxide catalysts, supported on zirconium, aluminum, titanium, and manganese oxides, in the reaction of selective oxidation of CO in hydrogen-rich mixtures. We have shown that the high activity and selectivity of catalysts supported on zirconium and aluminum oxides is connected with the presence of (in addition to divalent copper) higher amounts of copper in the (+1) oxidation state in the catalysts. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 2, pp. 119–124, March–April, 2006.     

Dependence of copper species on the nature of the support for dispersed CuO catalysts

Copper catalysts prepared by chemisorption-hydrolysis technique over silica (Cu/Si) and silica-alumina (Cu/SiAl) supports were studied to understand the role of the support on the nature and surface properties of the copper species stabilized on their surfaces. The morphological and surface properties of the copper phases have been characterized by complementary techniques, such as HRTEM, EXAFS-XANES, EPR, XPS, and FTIR. For the FTIR investigation, molecular probes (CO and NO) were also adsorbed on the surfaces to test the reactivity of the copper species. Moreover, the catalytic performances of the two catalysts have been compared in the HC-SCR reaction (NO reduction by C(2)H(4)) performed in highly oxidant conditions. The superior activity and selectivity of the supported silica-alumina catalyst with respect to that supported on silica could be related with the different nature of the copper species stabilized on the two supports, as emerged from the results obtained from the spectroscopic investigations. Small and well-dispersed CuO particles were present on silica, whereas isolated copper ions predominated on silica-alumina, likely in regions rich in alumina that made some exchangeable sites available, as indicated by FTIR spectra of adsorbed CO. The less positive global charge of copper species on Cu/SiAl than in Cu/Si has been confirmed by EPR, XPS, and EXAFS-XANES analyses.     

Oligomerization of butenes on borate-containing alumina

The effects of the chemical composition of borate-containing alumina on its physicochemical properties, catalytic activity, and selectivity in the oligomerization of butenes are reported. The preparation of catalysts containing 2.6–12.4 wt % B₂O₃ by modifying γ-alumina with orthoboric acid leads to a 9–60 m²/g decrease in the specific surface area and to a 0.02–0.14 cm³/g decrease in the pore volume relative to the same parameters of the initial support. At boron oxide contents of ≥8.8 wt %, these changes are due to the buildup of B₂O₃ on the catalyst surface. This is accompanied by a decrease in the number of surface B-OH groups, which are active sites of oligomerization. This finding correlates well with the results of catalytic measurements. The catalyst containing 4.5 wt % B₂O₃ is the most active. It was found by experimental design methods that the most favorable combination of catalytic activity (total butene conversion of 77.8–86.8%) and selectivity (butene oligomer concentration of at least 90 wt % in the liquid product) is attained at T = 150°C, P = 8.0 MPa, and a butene WHSV of 0.5–1.0 h^?1. Under these conditions, the butene conversion decreases by no more than 13% from the initial level in 14 h. The activity of the catalyst can be restored by oxidative regeneration.     

Effect of the nature of the active component and support on the activity of catalysts for the hydrolysis of sodium borohydride

The effect of the nature of an active component and a support on the rate of hydrolysis of aqueous sodium borohydride solutions was studied. It was found that the activity of supported catalysts, which were reduced in a reaction medium of sodium borohydride, decreased in the order Rh > Pt ≈ Ru ? Pd regardless of the nature of the support (γ-Al₂O₃, a Sibunit carbon material, or TiO₂). The catalysts based on TiO₂ exhibited the highest activity. As found by UV-vis diffuse reflectance spectroscopy, the composition and structure of the supported precursor of an active component depend on the nature of the support. It is likely that rhodium clusters with different reaction properties were formed on various supports under the action of a reaction medium.     

Influence of the clay and the nickel content in catalysts for vegetable oil hydrogenation

Nickel catalysts prepared using two different clays as support, natural bentonite and palygorskite, and with different nickel contents have been tested in the hydrogenation of a sunflower oil. The influence of the clays, and of the nickel-bentonite ratio on the activity, selectivity and trans-isomer formation was investigated. Previously it was establised that no diffusional limitations were controlling the rate. Bentonite with the highest nickel content was the most active and selective catalysts.     

Effect of support on activity of palladium catalysts in nitrobenzene hydrogenation

The effect of two types of catalysts on the activity of the catalytic hydrogenation of nitrobenzene was studied. Catalysts were prepared by the surface deposition of palladium hydroxide with a simultaneous reduction with formaldehyde in a basic environment and were characterised by X-ray powder diffraction, transmission electron microscopy, adsorption-desorption, and catalytic tests — hydrogenation of nitrobenzene in methanol. The influence of the supports’ (activated carbon and a mixture of activated carbon and multi-walled carbon nanotubes) surface area is discussed. Despite having a size comparable (4–5 nm) to crystallites of metallic palladium, the catalyst prepared on a mixture of activated carbon and nanotubes (Pd/C/CNT) was significantly less active than the catalyst prepared on pure activated carbon (Pd/C); the rate of this reaction was approximately 30 % lower than the initial reaction rate. This feature could be attributed to the lower specific surface area of the Pd/C/CNT (531 m² g^?1) in comparison with the Pd/C (692 m² g^?1).     

络合作用对重油加氢处理催化剂性能的影响

以Ni、W为催化剂的活性金属组分,考察在金属组分浸渍液中加入有机络合剂对催化剂性质及加氢脱硫、脱氮性能的影响。结果表明,络合剂与金属组分共浸渍更有利于金属组分的分散;提高络合剂用量,既有利于提高主活性金属组分WO₃在载体表面的分散,又能促进六配位八面体Ni物种及高加氢活性相NiWO₃的形成;焙烧温度具有调变催化剂金属组分分散性及酸性的双重作用,在适宜的焙烧温度下制得的催化剂具有较好的酸性及加氢活性,主要表现为较高的加氢脱硫及脱氮活性。     

Effect of the chemical nature of the support on the properties of platinum catalysts for the combined oxidation of CO and H2

The steady-state rate of hydrogen oxidation catalyzed by platinum on an inert support (corundum) is greater than the rate of oxidation of carbon monoxide, while the rate of hydrogen oxidation on a platinum-vanadium catalyst is less than the rate of oxidation of carbon monoxide. The conditions for the complete selective oxidation of the reaction mixture components were determined. Hydrogen is oxidized on the Pt/corundum cataljst at 273K in a non-steady-state mode, while CO is oxidized on the same catalyst at 273 K and on Pt/BaSO₄-V₂O₅ at 383–393K in a steady-state mode.Deceased.Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 31, No. 2, pp. 81–85, March–April, 1995.     

Effect of support and loading on oxidation of methane over platinum catalysts

Catalytic combustion of methane was carried out using platinum catalysts supported on low-and high-surface area alumina (denoted respectively as LSA and HSA) and platinum supported on silica. Methane conversion was the highest for platinum supported on LSA alumina, smaller for Pt/HSA alumina and the smallest for Pt/silica. However, the 3 wt.% Pt/HSA catalyst was found to show the highest selectivity.     

Effect of oxygen enrichment on CI engine behavior fueled with vegetable oil: an experimental study

Journal of Thermal Analysis and Calorimetry - The present study investigated the effect of oxygen enrichment in a CI engine on performance, emission and combustion characteristics with mahua oil...     

Effect of activated carbon support on CS_2 removal over coupling catalysts

Supported coupling catalysts for CS2 removal were prepared with different activated carbons originated from wood,coconut shell and coal as supports,and their catalytic activities for CS2 removal were tested at ambient temperature.The textural and surface properties of the activated carbons were characterized by nitrogen adsorption,temperature-programmed desorption(TPD)and Boehm titration.The activated carbon support with meso-and macropores,and oxygen-functional groups performs higher CS2 removal ability at ambient temperature.The effects of flow rate,CS2 inlet concentration,temperature and relative humidity on CS2 removal were also investigated.High efficient removal is obtained at temperature of 50-C,space velocity of 2000 h-1,inlet CS2 concentration of 500 mgS/m3 and relative humidity of 20%with the breakthrough sulfur capacity up to 4.3 gS/gCat and working sulfur capacity up to 7 gS/gCat.     

Influence of the chemical nature of the oxide support on selectivity of iron catalysts for carbon monoxide hydrogenation

The influence of the nature of the oxide support on selectivity of Fe catalysts in Fischer-Tropsch synthesis at atmospheric pressure has been studied. It was found that selectivity towards lower olefins increases with increasing basicity of the oxide support. It is suggested that this effect is due to participation of basic oxide sites in hydrogen-atom abstraction from the surface metal-alkyl complex.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 30, No. 3, pp. 152–157, May–June, 1994.The authors are grateful to V. V. Pryanikova, M. G. Petrosyan, and A. M. Puzii for assistance with individual experiments.