Showing papers by "Mohan S. Rana published in 2001"

Studies on physico-chemical characterization and catalysis on high surface area titania supported molybdenum hydrotreating catalysts

Abstract: A series of titania supported molybdenum catalysts were prepared by incipient wetness impregnation method and characterized by BET surface area, XRD, TPR, FTIR, ESCA, and low temperature oxygen chemisorption. Thiophene, cyclohexene and tetrahydrofuran were taken as model compounds for evaluating catalytic activities for hydrodesulfurization (HDS), hydrogenation (HYD), and hydrodeoxygenation (HDO) reactions, respectively. XRD results indicate that molybdenum oxide species are dispersed as a monolayer on the support up to 8 wt.% Mo and the formation of crystalline MoO 3 is observed above this loading. FTIR and TPR results showed that molybdenum oxide species were present predominantly in tetrahedral form at lower loading and polymeric octahedral forms are dominant at higher loading. Both oxygen chemisorption and rates of reaction were found to increase with increasing Mo loading up to 8 wt.% and then decrease with further increase in loading. HDS and HYD activities are more or less same but HDO activity is two times higher than HDS and HYD activities. The results are also interpreted with the help of other parameters, like dispersion, equivalent molybdenum surface area, surface coverage, crystalline size, quasi-turnover frequencies and intrinsic activities. ESCA results suggest that electron transfer is taking place from support to metal.

TiO2–ZrO2 mixed oxide as a support for hydrotreating catalyst

Abstract: Pure TiO2, ZrO2 and TiO2–ZrO2 mixed oxides are prepared by urea hydrolysis. Hydrotreating catalysts containing 12 wt% molybdenum are prepared using these oxides and characterized by BET surface area, pore volume, XRD and oxygen chemisorption. It is observed that oxides produced by the method of urea hydrolysis have higher surface area as compared to those available commercially. With increasing zirconia content in the mixed oxide, the surface area increases and a maximum value is obtained for a mixed oxide having Ti and Zr molar ratio of 65/35. XRD results indicate that mixed oxides are poorly crystalline in nature. Thiophene hydrodesulfurization, cyclohexene hydrogenation and tetrahydrofuran hydrodeoxygenation are taken as model reactions for evaluating catalytic activities. It is found that both O2 uptake and catalytic activities increase with increasing zirconia content in mixed oxide and reach maximum values for the 12 wt% Mo/TiO2–ZrO2 (65/35) catalyst. With further increases in zirconia content, O2 uptake and catalytic activities decrease and the lowest values are observed for the pure ZrO2 supported catalyst.

26-P-08-Catalytic functionalities of USY zeolite supported hydrotreating catalysts

Abstract: Publisher Summary This chapter discusses the catalytic functionalities of USY zeolite-supported hydrotreating catalysts. USY zeolites of varying silicon/aluminium (Si/Al) ratios are used as support for molybdenum (Mo), nickel molybdenum (NiMo), cobalt molybdenum (CoMo), and NiW catalysts. Both the effect of variation of Si/A1 ratio of the zeolite and Mo content on support at fixed Si/Al ratio is studied. The catalysts are examined by X-ray diffraction (XRD), oxygen chemisorptions, and temperature programmed reduction (TPR) techniques. The hydrodesulfurization and hydrogenation reaction studies indicate that these catalysts are more active than γ-A1 2 O 3 supported catalysts, and the increase in activities may be attributed to an increase in Mo dispersion and reducibility. Oxygen uptake correlates well with the catalytic activity.

26-P-17-Characterization and catalytic activities of MCM-41 supported WS2 hydrotreating catalysts

Abstract: Publisher Summary This chapter discusses the characterization and catalytic activities of MCM-41 supported WS 2 hydrotreating catalysts. WO 3 -MCM-41 catalysts are prepared with good dispersion of WO 3 . The oxygen chemisorption in the sulfided state indicate that WS 2 is also well dispersed on MCM-41 surface. Oxygen (O 2 ) chemisorption as a function of W loading indicate that maximum dispersion and maximum number of anion vacancies are obtained with 19wt% W with highest catalytic activities for hydrodesulfurization, hydrogenation, and hydrooxydation. The small crystallite size and its constancy as function of W loading coupled with low-surface coverage by WS 2 indicate that monolayer WS 2 patches are formed on the selected regions of support surface. The correlation between O 2 uptake and catalytic activity indicate that oxygen chemisorption is not specific to any of the functionalities of the overall dispersion of WS 2 . Cobalt (Co) and nickel (Ni) addition result in promotional effect for both HYD and HDS, and the three catalytic functionalities originate from different set of sites on the WS 2 and its promoted analogs.

Characterization and catalytic activity of Ni-W/SiO2-Al2O3 hydrocracking catalysts

Abstract: Hydroprocessing is used to upgrade fuel quality in the petroleum refining industry. The principal applica­ tions of hydroprocessing includes not only the con­ ventional hydrotreating to remove undesirable sul­ phur, nitrogen and oxygen compounds from petro­ leum and coal-derived oils but also for more versatile processes like hydrocracking which converts high boiling refractory petroleum fractions to low boiling value-added middle distillates like kerosene, jet fuel and gas oil. Hydrocracking involves the cleavage of C-C bonds of hydrocarbons in the presence of acid sites provided by the support of the catalyst and the hydrogenation of the cracked products on the metal sites in presence of hydrogen. The major advantage of hydrocracking over catalytic cracking (FCC) is that the former produces a wide spectrum of products of high fuel quality and stability. It appears that th e main components of heavy oi l fraction, i.e. the polycyclic aromatics, undergo hydrogenation/ring opening in the presence of a catalyst and dehydrogenation, polymeri­ zation in the absence of a catalyst. The condensation and dehydrogenation reactions lead to coke formation 1 • Cracked products give more branched paraffins than linear ones 2 • Olefins are formed as intermediates dur­ ing the conversion of saturated hydrocarbons over bifunctional catalysts in presence of H2 as in catalytic reforming, hydrocracking and hydroisomerization 1 •