Effect of thermal treatment of the Al2O3 and TiO2 supports on properties of dispersed chromium oxide in oxidative dehydrogenation of isobutane

Chromium oxide has been dispersed on Al2O3 and TiO2 supports, heated betwee n 500-1200 degreesC, and the catalysts obtained have been tested in oxidati ve dehydrogenation of isobutane at 280 degreesC. For the CrOx/Al2O3 system the thermal treatment of alumina, which leads to the decrease in the specif ic surface area and polymorphic transformations of the initial gamma -Al2O3 into theta, Delta and alpha modifications, does not affect the catalytic p erformance of the catalysts in the reaction under study. On the other hand, the transformation of anatase-TiO2 into rutile-TiO2, occurring on heating at 1000 degreesC, leads to catalysts of a higher activity and selectivity t o isobutene. Amelioration of the catalytic properties for CrOx/rutile-TiO2, as compared with CrOx/anatase-TiO2 catalysts, has been ascribed to changes in the structure of the CrOx active centres, evidenced by ESR.