Amorphous silica-alumina as robust support for catalytic dehydrogenation of propane: Effect of Si/Al ratio on nature and dispersion of Cr active sites

Abstract

The effect of amorphous silica-alumina (ASA) with Si/Al ratios of 0.01, 0.1, 1, and 3 on the catalytic performance of chromium catalysis in the propane dehydrogenation reaction were studied. The characterization results reveal that the Si/Al ratio significantly affects the nature and dispersion of chromium species, reducibility, the surface concentration of Cr3+, and acidity. ASA catalysis with Si/Al ratios of 0.1 and 0.01 showed a remarkable increase in Cr6+ species and the lowest α-Cr2O3, which have the highest propane conversion (with initial propylene yield of 60 and 57, respectively) due to the reduction of surface monochromate Cr6+ species, which are the precursor of coordinatively unsaturated active sites (c.u.s.) to active Cr3+ species. Si/Al increase to the values of 1 and 3 can restrict the access of reactants to active Cr species due to the decrease in chromium reduction and increase in α-Cr2O3.