Effect of addition of tin on the catalytic properties of Pt/ZSM-5 catalyst in propane dehydrogenation

The influence of Sn promoter on the catalytic performance of Pt/ZSM-5 in propane dehydrogenation was investigated by using microreactor tests combined with thermogravimetry (TG), H2 chemisorption and temperatureprogrammed reduction (TPR)．It has been shown that addition of tin component to the supported Pt/ZSM-5 catalyst can improve the catalytic selectivity and stability in propane dehydrogenation, and the catalytic activity and selectivity both increase with increasing Sn loading. When the Sn/Pt molar ratio of PtSn/ZSM-5 catalyst was larger than 6.5, the catalytic activity and H2 uptake remarkably decreased. This might be correlated to the deep reduction of tin oxide to its metallic state as a result of weakening the interaction of excessive tin oxide with ZSM-5 support. For the supported PtSn/ZSM-5 catalyst (0.5% Pt, SiO2/Al2O3 mol ratio is 108), the optimum Sn/Pt mol ratio is 3.0 ~ 6.0.