Isolated Sn on mesoporous silica as a highly stable and selective catalyst for the propane dehydrogenation

Tin oxide supported on silica (SnO2/SiO2) were prepared by incipient-wetness impregnation method and examined for propane dehydrogenation at 600 degrees C. The physicochemical properties of SnO2/SiO2 were characterized by N-2-physisorption, XRD, UV-vis-DRS and H-2-TPR. The results indicate that, at Sn loading <= 1.78 wt%, SiO2 contains a uniform distribution of Sn as isolated species in tetrahedral coordination, while crystalline SnO2 together with isolated Sn species are found for the higher Sn loadings. The reducibility of various Sn species was studied by a combination of XPS, H-2-TPR, and reduction-reoxidation-TPR techniques. The results reveal that after high-temperature H-2 reduction, crystalline SnO2 is fully reduced to metallic Sn, whereas isolated Sn are stabilized in the Sn2+ state with high dispersion due to a strong interaction between isolated Sn and support. Catalytic activity tests showed that these Sn2+ species exhibits both high activity and stability for propane dehydrogenation.