EFFECT OF ALKALI-METALS ADDITIVES TO V2O5 TIO2 CATALYST ON PHYSICOCHEMICAL PROPERTIES AND CATALYTIC PERFORMANCE IN OXIDATIVE DEHYDROGENATION OF PROPANE/

The effect of alkali metal additives Li, K, and Iib to V2O5/TiO2 catal yst on the rate of catalyst reduction with propane and reoxidation wit h oxygen, sorption of propene, and the electron work function has been examined. The results have been correlated with the catalytic perform ance in oxidative dehydrogenation, ODH, of propane. It has been found that the rates of reduction, reoxidation and the ODH of propane decrea se in the order: VTi > LiVTi > KVTi > RbVTi. The activation energies o f the reduction and reoxidation are not, however, affected by the pres ence of the alkali metals. The same sequence has been observed for the work function values of the catalysts. It is argued that alkali metal poisons the centres of the hydrocarbon activation. The yield and sele ctivity to propene in the ODH of propane increase, however, for the pr omoted catalysts, following the above sequence. This effect is ascribe d to the decrease in the heat of the propene adsorption, which is due to the increase in the basicity and decrease in acidity on the promote d catalysts.