Improved catalytic performance of CrOx catalysts supported on foamed Sn-modified alumina for propane dehydrogenation

To better understand influences of surface properties of supports on distributed Cr active sites of Cr-based catalysts with high Cr loading, foamed alumina modified by Sn was prepared to support CrOx catalysts for propane dehydrogenation. N2 adsorption-desorption, TEM, XRD, FTIR, UV–vis, Raman, XPS, NH3-TPD, Py-IR and H2-TPR were carried out to elucidate catalyst structures. The foamable alumina is formed by using soft template, and tin added in preparing process changes micro-micelle formation to generate more complex cavity structure. The Sn doped into alumina framework and dispersed on support surface changes the surface properties, such as surface hydroxyl group and isoelectric point, promoting the formation of more active polymeric chromate on the surface, thus the CrOx supported on modified alumina presents high activity of propane dehydrogenation and good catalyst stability, comparing with unmodified CrOx/alumina catalyst. The added Sn obviously inhibits the formation of coke deposition due to decreased strong acid sites, Cr sites density and Cr3+ content on the surface of the catalysts.