Different alkali metals promoted Cr/Al2O3 catalysts for propane dehydrogenation

Unmodified Cr/Al2O3 and Cr/Al2O3 doping with different alkali metals (Li, Na, K) were prepared by the incipient wetness impregnation method. The surface elements of all the catalysts are evenly distributed and well loaded, and the addition of alkali metals does not change the crystal structure and surface texture. Both Cr6+ and Cr3+ species exist on all catalysts, and the addition of alkali metals can increase the amount of Cr6+ species, and Cr6+ species are basically converted into active Cr3+ species in the reaction thus increasing the initial propane conversion in the reaction. The addition of alkali metals reduced the amount of total acid sites and the strong acid sites of the catalyst, thus inhibiting the occurrence of side reactions and the formation of carbon deposition, and reducing the deactivation rate of the catalyst. Cr-0.5Na/Al2O3 exhibited the best catalytic performance and the lowest carbon deposition.