Enhanced performance of Ca-doped Pt/γ-Al_2O_3 catalyst for cyclohexane dehydrogenation

摘要

The promotion effects of Ca on catalytic performance of Ca-doped Pt/Al_2O_3 catalyst were investigated by varying Ca content and impregnation orders. The Ca-doped Pt/Al_2O_3 catalyst with atomic rate Ca/Pt = 5 exhibited the highest catalytic activity and stability. Detailed analyses show that low Ca content (Ca/Pt < 5) could not efficiently promote hydrogen spillover from Pt-Al interface to the support and reduce the strong acid sites on the support. However, high Ca content (Ca/Pt > 5) decreases the initial activity due to the coverage of Ca on the support and increases the amount of Pt strongly interacting with Ca, which inhibits Pt reduction. Furthermore, the Ca promotion effect is more pronounced when Ca is added prior to Pt due to surface modification of Ca on Al_O_3 support. This modified catalyst possesses more dispersed Pt, lower acidity and larger amount of spilled-over hydrogen.