Improved Performance of Commercial Catalyst 13 wt % Cr-?-Al2O3 for Direct Ethane Dehydrogenation to Ethylene

For the improvement of commercial catalyst 13 wt % Cr-gamma-Al2O3 for the dehydrogenation of light alkanes to olefins, 13 wt % Cr-x wt % Ce-gamma-Al2O3 catalysts with x equaling 0, 2.5, 5, 7.5, and 10, named as 0Ce, 2.5Ce, 5Ce, 7.5Ce, and 10Ce, are prepared by the incipient wetness impregnation method, characterized by X-ray diffraction, transmission electron microscopy, Raman, UV-vis, X-ray photoelectron spectroscopies, and temperature-programmed reduction and evaluated for ethane dehydrogenation to ethylene. Their performance increases with Ce addition to 5 wt % and then decreases and attenuates with time. 5Ce demonstrates the highest dehydrogenation activity and better regeneration ability than 0Ce. It is found that the as prepared 5Ce contains more active amorphous Cr6+ species and less crystalline Cr3+ species (alpha-Cr2O3) than 0Ce, other than the Ce species of CeO2. The reasons for the better dehydrogenation and regeneration performance of 5Ce are that the CeO2 particles in 5Ce physically separate the Cr species, promoting the formation of Cr6+ species, preventing their aggregation and migration to form less active alpha-Cr2O3 and inactive alpha-(Cr, Al)2O3, and preserving more active Cr6+ species in the as-prepared and regenerated catalysts.