Oxidative dehydrogenation of propane on Mg-V-Al mixed oxides

Vanadium-magnesium mixed oxides have been prepared by thermal decomposition of decavanadate-intercalated Mg, Al layered double hydroxides (LDHs), MgAlVO-LDH, and by impregnation of MgO (mixed, MgAlVO-I, or not, MgVO-I, with Al2O3) with an aqueous decavanadate solution. The activity of catalyst MgAlVO-LDH in oxidative dehydrogenation of propane is higher than that measured for the mixed oxides obtained by conventional impregnation. However, the largest normalised conversion measured over sample MgAlVO-I is assigned to the higher surface density of V centers, which are stabilised along the reaction runs. Normalised selectivity and conversion profiles show that propene is first formed and then oxidized to CO on catalyst MgAlVO-I, a process favoured by the high acidity of this solid. However, catalyst MgVO-I, with a medium strength surface acidity, is rapidly deactivated, forming CO2, by coke deposition on exposed V sites. The low selectivity to propene of catalyst MgAlVO-LDH is related to its low surface density of V sites.

Vanadium-magnesium mixed oxides have been prepared by thermal decomposition of decavanadate-intercalated Mg, Al LDHs and by impregnation of MgO or without Al2O3 with a decavanadate solution, and they have tested for ODH of propane. The differences observed for the catalytic behaviour are mainly related to their acid properties, increased by Al3+ decreasing the selectivity to propene.Figure optionsDownload as PowerPoint slide