INFLUENCE OF CONDITIONS OF PLATINUM-VANADIUM-ALUMINA CATALYST PREPARATION ON THE ACTIVITY AND SELECTIVITY IN DEHYDROGENATION AND HYDROGENOLYSIS OF LOWER ALKANES

The influence of the conditions of treatment of a modified support and Pt-V/Al2O3 catalysts with various V/Pt atomic ratios and the influenc e of catalyst preparation procedure on their performance in dehydrogen ation and hydrogenolysis of propane and ethane were studied. It was fo und that V in Pt-V/Al2O3 catalysts acts as an inhibitor or promotor fo r Pt in the alkane conversion depending on the conditions of prelimina ry treatment (oxidative or reductive) of the modified support. The sel ectivity to propene in propane dehydrogenation increases from 82% (on nonmodified Pt/Al2O3) to 94-98% (on the samples whose support (NH4VO3/ Al2O3 with vanadium content from 1 to 10 at. %) was oxidatively treate d at 400-900 degrees C. The same effect is observed when the supports are reductively treated at [V] greater than or equal to 5 at. % and <6 00 degrees C. The activity of the catalysts obtained by co-impregnatio n decreases after oxidative treatment. On the oxidatively treated cata lysts, ethane dehydrogenation predominates (selectivity to ethylene re aches 96%). On the reductively treated samples the cleavage of the C-C bond is the main process (the selectively to methane reaches 63%). Th e efficiency of Pt-V/Al2O3 catalysts can be controlled by varying the conditions of treatment of the modified support or by changing the V/P t atomic ratio.