Hydrogenation of toluene on Ni-Co-Mo supported zeolite catalysts

Mixed oxides of Ni, Co and Mo supported on five zeolites -ZSM-5-a, ZSM-5-b, HY-a, HY-b and Mordenite were prepared and characterized using many techniques for use as hydrotreating catalysts. In a preliminary investigation, toluene was employed as model compound to test the catalysts in hydrogenation, as a major upgrading reaction. TGA/DSC analysis showed that the impregnation of the metals slightly affected the thermal stability of the zeolites with all catalytic samples displaying good stability up to 730oC.The XRD patterns for all the catalytic samples showed that the framework of the zeolites were retained after impregnation. XRD and TPR results confirmed the presence of molybdenum trioxide on the zeolites with NiCoMo/HY-b displaying high metal-support interaction due to low reduction temperatures. The activity results showed that toluene conversion of almost 100% and selectivity to mainly methyl-cyclohexane was achieved. The catalysts activity test showed that the zeolite support textural properties particularly surface area, pore volume and pore diameter affect the performance of the catalysts. NiCoMo/HY-b displayed the best performance after the few minutes of the reaction due to its high surface area, pore volume and average pore diameter.Keywords: Hydro treating catalysts; Hydrogenation; Toluene conversion; Surface area; Pore diamete

Insight from the study of acidity and reactivity of Cr2O3 catalyst in propane dehydrogenation: a computational approach

By converting low-value commodity fuels into high-value products, like polymer precursors, chemical and other intermediates, the dehydrogenation of light paraffin (such as ethane and propane) into olefins, can add significant value to the refining processes that generate propane. In this study, the parameterised method 3 (PM3) approximation of semi empirical theory was employed to study the acidity and reactivity of chromium (III) oxide catalyst in the dehydrogenation of propane into propylene. Ammonia and pyridine were used computationally as molecular probes for the evaluation of the Lewis acidity of the catalyst sites. The propane adsorption and dissociation activation energies were also evaluated. The study showed that the chromium sites are highly acidic and reactive compared to the oxygen sites. In particular, the study showed that the chromium site is the main active site in the promotion of propane dehydrogenation into propylene, over chromium (III) oxide catalyst. Keywords: Acidity, Reactivity, Dehydrogenation, Propane, Chromium

Kinetics of Hydrodesulfurization of Dibenzothiophene on Sulfided Commercial Co-Mo/γ-Al2O3 Catalyst

Kinetics of hydrodesulfurization of dibenzothiophene (DBT) has been studied on a commercial CoMo/γ-Al2O3 catalyst at 633 - 683 K and 10 atm. A low DBT concentration typically obtained in hydrodesulfurization operations was used. Pseudo-first-order model was found to fit the experimental data for the consumption of DBT. The activation energy for the conversion of DBT was found to be 51.7 kcal/mol. Biphenyl (BP) and cyclohexylbenzene (CHB) were obtained as dominant products. For the reaction network, both parallel and parallel-sequential routes were explored. The latter was found to give a better description of the BP and CHB distributions. The ratio of BP to CHB depended on the reaction temperature. The values of activation energies of DBT hydrogenolysis to BP (EBP), DBT hydrogenation to CHB (ECHB1) and hydrogenation of BP to CHB (ECHB2) were found to be in a decreasing order of ECHB2 > EBP > ECHB1. The result suggests the presence of different catalytic sites leading to the two products on the catalysts

Catalytic Influences of Dispersed copper Complex ion on Aquathermolysis of Heavy Crude Oil

Copper based catalyst Cu2+ was synthesized and characterised by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR). Various concentrations of this catalyst was used to catalyse aquathermolysis of medium heavy crude oil (API gravity = 29.40o) at temperature of 200oC for three hours (3h). The oil sample(s) were characterised before and after aquathermolysis reaction using FT-IR. SARA analysis was carried out using column chromatography and the sulphur content, kinematic viscosity, density and API gravity were also determined. The original viscosity of the fresh crude oil was 9.8799 m2/s, after the reaction without catalyst; the viscosity was reduced to 8.8125 m2/s (10.80% reduction). When Cu2+ was used at optimum concentration, it was further reduced to 7.7339 m2/s (21.61% reduction).  The catalyst reduced the sulphur content by 4.37% and it was reduced by 2.77% when no catalyst was used. Also, API gravity was increased by 1.02% without catalyst while it was reduced by 2.72% when the catalyst was used. The results indicate that the percentage by weight of asphaltenes and resins were reduced due to cleavage on carbon to heteroatom bonds while that of aromatics and saturates were increased. The compared results with previous researches strongly confirmed that this catalyst possessed good catalytic activity owing to its strong viscosity reduction properties

Selection of optimum chromium oxide-based catalysts for propane oxidehydrogenation

Propane oxidative dehydrogenation has been studied at 350-500°C, 1.0 bar and feed flow rate of 75 cm3/min over several supported chromium oxide-based catalysts. Effects of various chromium loadings, different supports, catalyst precursors and reaction conditions were investigated in an attempt to select an optimum catalyst for the reaction. Chromium oxides of different loadings ranging from 0.1 to 20 wt.% on γ-Al2O3 were tested. At 450°C, 10 wt.% loading exhibited propane conversion of 19%. γ-Al2O3 gave the best performance when MgO, TiO2, SiO2 and γ-Al2O3 were tested as supports. As a precursor, Cr(NO3)3•9H2O exhibited the best results compared with K2Cr2O7, CaCr2O7, Na2Cr2O7, Cr2SO4•12H2O and CrO3. Effects of reaction temperatures and feed compositions were also evaluated on a 10 wt.% Cr-Al-O catalyst. The maximum selectivity to propene obtained was 61% while the yield was 18%. The 10 wt.% Cr-Al-O catalyst was characterized by X-ray diffraction patterns (XRD), temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) which confirmed the presence of both Cr3+ and Cr6+ in the calcined catalyst and, also, the predominance of Cr3+ in the spent catalyst..

Oxidehydrogenation of propane over Mn-P-O catalyst: Effects of oxygen partial pressure

Manganese phosphate catalyst was prepared and tested for the catalytic oxidative dehydrogenation of natural gas components such as propane to propylene at 1 atm and 450°-550°C. In the temperature range, the propane conversion changed from 4.1 to 40.7%, the selectivity to propylene showed insignificant change at 41%. The products obtained were propylene, ethylene, methane, CO2, and CO. Selectivity to propylene could be improved by employing low or moderate oxygen partial pressure. .King Fahd University of Petroleum and Minerals, KFUPM, Japan Petroleum Industry, JP

Oxidative dehydrogenation of propane over supported chromium-molybdenum oxides catalysts

Catalytic oxidative dehydrogenation of propane to propylene was studied on alumina-supported chromium-molybdenum oxides catalysts - 10 wt% Cr xMo(1-x)/γ-Al2O3 (where x=0-1). The catalysts are active for the reaction. Increase in the amount of molybdenum in the catalysts decreases the reducibility and changes the nature of the lattice oxygen in the catalyst as indicated by TPR and XPS data. The catalysts with lower reducibilities exhibits corresponding increase in the propylene selectivities. Alkali metals (Li, K, Cs)-doped 10 wt% Cr 0.8Mo0.2 (alkali/CrMo weight ratio of 0-0.175), shows maxima in both propane degrees of conversion and propylene yields in the ratio ranges explored. One of the catalysts (Cs/CrMo=0.125) exhibits propane conversion of 15.1% and selectivity to propylene of 64.5% at 420 °C. This is among the most promising catalysts reported for oxidative dehydrogenation of propane.

Oxidative dehydrogenation of propane over supported chromium-molybdenum oxides catalysts

Catalytic oxidative dehydrogenation of propane to propylene was studied on alumina-supported chromium-molybdenum oxides catalysts - 10 wt% Cr xMo(1-x)/γ-Al2O3 (where x=0-1). The catalysts are active for the reaction. Increase in the amount of molybdenum in the catalysts decreases the reducibility and changes the nature of the lattice oxygen in the catalyst as indicated by TPR and XPS data. The catalysts with lower reducibilities exhibits corresponding increase in the propylene selectivities. Alkali metals (Li, K, Cs)-doped 10 wt% Cr 0.8Mo0.2 (alkali/CrMo weight ratio of 0-0.175), shows maxima in both propane degrees of conversion and propylene yields in the ratio ranges explored. One of the catalysts (Cs/CrMo=0.125) exhibits propane conversion of 15.1% and selectivity to propylene of 64.5% at 420 °C. This is among the most promising catalysts reported for oxidative dehydrogenation of propane.

Activity of CoMo/Υ-Al2O3 as a catalyst in hydrodesulfurization: Effects of Co/Mo ratio and drying condition

A series of Υ-alumina-supported cobalt-molybdenum hydrodesulfurization catalysts have been prepared with different ratios of cobalt to molybdenum (0.0-1.0) and under different drying temperatures (323, 373 and 423 K). The active components ions were loaded on the alumina via an incipient wetness impregnation method. The catalysts were converted to active sulfide form using dimethyldisulfide. Hydrodesulfurization (HDS) of dibenzothiophene (DBT) was tested at 550-683 K and 10 atm. Samples of the catalysts were characterized using SEM and XPS techniques. Changes in grain sizes and binding energy due to the cobalt-molybdenum interactions have been observed. The catalyst activities based on dibenzothiophene conversion rate constants and product (biphenyl BP and cyclohexylbenzene CHB) distributions, depended strongly on the Co/Mo ratios. CHB/BP ratio as high as 0.2 was obtained for Co/Mo of 0.2-0.4, while for higher Co/Mo ratios, no CHB was observed. The ratio of about 0.4 exhibited the highest rate constant. The drying temperature was found to improve the activities, with the lowest temperature showing the best performance in terms of dibenzothiophene degree of conversion. Such results suggest that cobalt and molybdenum are associated in a fixed proportion and that their distribution on the support surface, which in turn improves catalyst performance, could be modified by the catalyst preparation conditions

Microwave-Assisted Adsorptive Desulfurization of Model Diesel Fuel Using Synthesized Microporous Rare Earth Metal-Doped Zeolite Y

The microwave-assisted adsorptive desulfurization of model fuel (thiophene in n-heptane) was investigated using a synthesized rare earth metal-doped zeolite Y (RE Y). Crystallinity of the synthesized zeolite was 89.5%, the silicon/aluminium (Si/Al) molar ratio was 5.2, the Brunauer–Emmett–Teller (BET) surface area was 980.9 m2/g, and the pore volume and diameter was 0.3494 cm3/g and 1.425 nm, respectively. The results showed that the microwave reactor could be used to enhance the adsorptive desulfurization process with best efficiency of 75% at reaction conditions of 100 °C and 15 minutes. The high desulfurization effect was likely due to the higher efficiency impact of microwave energy in the interaction between sulfur in thiophene and HO-La(OSiAl)