Oxidative Dehydrogenation of Isobutane on CrOx/Oxide Support Catalysts: Effect of Potassium on Physicochemical and Catalytic Properties

A series of catalysts containing CrOx (equivalent to 1 theoretical monolayer of Cr2O3) on Al2O3, TiO2, SiO2 and MgO supports, with and with out the potassium additive, have been prepared, characterized by different methods and tested in oxidative dehydrogenation, ODH, of isobutane. Addition of potassium did not affect the structure of the catalysts. It led to a slight decrease in the total activity for all the catalysts and anincrease in the selectivity to isobutene only for the CrOx/TiO2 system. A decrease for CrOx/Al2O3 and Cr/SiO2, on the potassium doping and practically no change in selectivity for CrOx/MgO catalysts, were observed. For all the studied catalysts the K additive decreased the acidity, increased the basicity and decreased the reducibility. No clear correlations between the selectivty and the acid-base properties or reducibility were found. The total activity decreases with the increasing electronegativity of the support cation, except for CrMgO catalyst.