Kinetic modeling of oxidative dehydrogenation of propane with CO2 over MoOx/La2O3-Al2O3 in a fluidized bed

A 4-step kinetic model of CO2-assisted oxidative dehydrogenation (ODH) of propane to C-2/C-3 olefins over a novel MoOx/La2O3-gamma Al2O3 catalyst was developed. Kinetic experiments were conducted in a CREC Riser Simulator at various reaction temperatures (525-600 degrees C) and times (15-30 s). The catalyst was highly selective towards propylene at all combinations of the reaction conditions. Langmuir-Hinshelwood type kinetics were formulated considering propane ODH, uni- and bimolecular cracking of propane to produce a C-1-C-2 species. It was found that the one site type model adequately fitted the experimental data. The activation energy for the formation of propylene (67.8 kJ/mol) is much lower than that of bimolecular conversion of propane to ethane and ethylene (303 kJ/mol) as well as the direct cracking of propane to methane and ethylene (106.7 kJ/mol). The kinetic modeling revealed the positive effects of CO2 towards enhancing the propylene selectivity over the catalyst.