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.