Chromium oxide supported on different Al2O3 supports: Catalytic propane dehydrogenation

Chromium oxide was supported on different commercial aluminas. Their charac teristics were assessed by different techniques (X-ray diffraction, X-ray p hotoelectron, laser Raman, and electron paramagnetic resonance spectroscopi es, and Brunauer-Emmett-Teller surface, temperature-programmed reduction, a nd temperature-programmed desorption measurements). The variation of the Cr 3+/Cr6+ ratio was accounted for by the interaction between the chromium pha se and the support. The tendency of Cr3+ to form aggregates such as Cr2O3 w as induced by the support. The features of the support exert-an influence u pon chromium stabilization both in its oxidation states 6+ and 3+ and in th e coordination of surface chromia species. The total acid sites and the oxi dized chromium have a marked effect on activity and selectivity at initial operation times.