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)]×100/[mass of (Ce+Zr+Al2O3)], on stability and regeneration temperature in propane dehydrogenation was studied using a fixed-bed reactor at 600°C and 1bar of pressure. The XRD data revealed that CeyZr1−yO2 phases were formed over xCeZr-Al (x≠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. 620–645cm−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.