Propane dehydrogenation over Ce-containing ZSM-5 supported platinum–tin catalysts: Ce concentration effect and reaction performance analysis

Abstract

Ce-containing ZSM-5 zeolites were hydrothermally synthesized and then used as supports for platinum–tin catalysts in propane dehydrogenation. To study the location of the Ce species and the effects of Ce concentration on the catalyst structure, the as-prepared catalysts were characterized by several techniques, including XRD, nitrogen adsorption, SEM, TEM, UV-vis, FT-IR, NH₃-TPD, XPS, H₂-TPD, TPR and TPO analyses. It is found that parts of the cerium species can be incorporated into the framework of ZSM-5 zeolites, thus influencing the morphologies and textural properties of the supports. The use of the Ce-modified material promotes the dispersion of metallic particles, improves the catalytic ability to adsorb hydrogen at low temperature and enhances the interaction of Sn species and the support. As a result, the active sites can be stabilized and higher amounts of Sn species exist in oxidative states. Moreover, the substitution of Ce decreases the strength of the weak acidity and facilitates the migration of coke from metal active sites to the support. During the process of reaction, the variation of Ce content mainly affects the occurrence of hydrogenolysis and hydrogenation side reactions. In the present work, the optimal content of Ce in the support is 0.76 wt%, which results in the highest reaction activity and the stability in the reaction of propane dehydrogenation.