ANALYSIS OF THE SURFACE-ENHANCED HOMOGENEOUS REACTION DURING OXIDATIVE DEHYDROGENATION OF PROPANE OVER A V-MG-O CATALYST

The nature of the desorbed species that caused surface-initiated gas-phase reactions on a V-Mg-O catalyst during the oxidation of propane was investigated by modeling the reactions in the post-catalytic reactor (reactor volume downstream of the catalyst) with elementary reactions of the oxidative pyrolysis of propane. The elementary reactions reported in the literature that were used consisted of 37 elementary reactions and 20 chemical species. The rate constants were chosen so that the computed and experimental propane conversions and product distributions in the oxidative pyrolysis reaction were in good agreement at conversions up to 35% at 574-degrees-C and 25% at 558-degrees-C. With the use of these elementary reactions and rate constants, the conversions and product distributions in the postcatalytic reactor were calculated assuming different desorbed reactive intermediates which included propyl, ethyl, methyl, and OH radicals. After comparison of the results of the calculation with those from experiments, it was concluded that propyl radicals were the most likely species that desorbed from a V-Mg-O catalyst surface, although OH radicals were also possible candidates. The rate of propyl radical desorption was estimated to be 23% of the rate of reaction of propane on the catalyst surface at 570-degrees-C and 5% at 556-degrees-C.