Effect of gallium, aluminium, and chromium on silica supported V-Mg-O catalysts during oxidative dehydrogenation of propane: Kinetic study

The oxidative dehydrogenation （ODH） of propane was conducted on gallium, aluminum, and chromium doped Si30VMgO catalysts. On doping, the concentrations of the phases responsible for the activity and selectivity increased in their concentrations. The reaction studies were conducted in a tubular steel reactor at temperatures of 753, 783, 813, and 843 K and atmospheric pressure. The total flow rates of the feed were chosen as 30, 40, 50, and 60 ml/min. The propane to oxygen ratios were chosen at 1 ： 1, 2 ： 1, and 3 ： 1, respectively. The effect of various dopants on the activity and selectivity of the catalysts was studied. Deactivation studies were conducted over all the catalysts. The kinetic data were analyzed in terms of power law models and Langmuir-Hinshelwood （LH） models. The kinetic data results were analyzed by comparing the effect of dopants. Statistical model discrimination was done for the proposed models. AIC and BIC criteria were used for discrimination of the models.     

Kinetics of Oxidative Dehydrogenation of Propance over a VMgO Catalyst

The reaction kinetics of the oxidative dehydrogenation of propane was studied at 475-550oC over a VMgO catalyst. Vanadium-magnesium-oxides are among the most selective and active catalysts for the dehydrogenation of propane to propylene. Selectivity to propylene up to about 60% was obtained at 10% conversion, but the selectivity decreased with increasing conversion. No oxygenates were detected, the only by-products were CO and CO2. The reaction rate of propane was found to be first order in propane and close to zero order in oxygen, which is in agreement with a Mars van Krevelen mechanism with the activation of the hydrocarbon as the rate determining step. The activation energy of the conversion of propane was found to be 122±6 kJ/mol.     

Oxidative dehydrogenation of propane under steady-state and transient regimes over alumina-supported catalysts prepared from mixed V_2W_4O_（19）~（4-） hexametalate precursors

An integrated approach combining the development of an innovative catalyst and the research of a set of adequate operating conditions for the propane oxidative dehydrogenation (ODH) is described. The experimental set-up, specially designed for steady-state and transient studies is presented. The preparation method, the characterization and the performances in steady-state and transient regimes of catalysts based on V_2W_4O_(19)~(4-) Lindqvist isopolyanion used as a precursor and supported on alumina are reported. The influence of the preparation method of the catalyst and the role of water in the feed gas are more particularly discussed.