The roles of CeyZr1-yO2 in propane dehydrogenation: Enhancing catalytic stability and decreasing coke combustion temperature

Abstract

The influence of CeyZr1-yO2 content (0 < y < 1) in Pt-Sn/xCeZr-Al catalysts, where x was the weight percentage of (Ce + Zr) and calculated as [mass of (Ce + Zr)] x 100/[mass of (Ce + Zr + Al2O3)], on stability and regeneration temperature in propane dehydrogenation was studied using a fixed-bed reactor at 600 degrees C and 1 bar of pressure. The XRD data revealed that CeyZr1-yO2 phases were formed over xCeZr-Al (x not equal 0) supports and the concentration of Zr4+ ions in these phases increased when the CeyZr1-yO2 content was increased. The band of oxygen vacancies characterized by Raman spectra at ca. 620-645 cm(-1) was strongly dependent on catalyst processing; introduction of metal (Pt, Sn) and/or re-calcination created more oxygen vacancies in the catalysts. The XRD patterns and XPS data of the reduced Pt-Sn/xCeZr-Al catalysts did not indicate the formation of Pt-Sn alloys. The XPS and CO-IR spectra demonstrated that Pt became more electron deficient with increasing CeyZr1-yO2 content. The higher catalytic stability and lower coke combustion temperature (regeneration temperature) were obtained with a higher CeyZr1-yO2 content in Pt-Sn/xCeZr-Al catalysts. (C) 2012 Elsevier B.V. All rights reserved.