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.