Ethane oxidative dehydrogenation by CO2 over stable CsRu/CeO2 catalyst

Oxidative and non-oxidative ethane dehydrogenation were studied and compared over Cs-promoted Ru/CeO2 catalyst. The presence of CO2 improved the ethane conversion to ethylene and led to the formation of C3 and C4 olefins as well. The olefin selectivity and yield in ODH were affected by reaction variables including CO2/C2H6 ratio, temperature, and feed rate. The CsRu/CeO2 remained stable activity for 93 days under reactive conditions wherein intermittent shutdowns and startups were performed. Mechanistically, the interaction between Cs and Ru with ceria in the crystalline structure facilitated reduction and oxidation cycles. It was postulated that Ce3+ had a strong tendency to react with CO2 to form Ce4+, whereas Ce4+ was reduced by hydrogen from ethane dehydrogenation to form Ce3+. The redox cycle can be repeated during the ODH reaction keeping the catalyst active. Furthermore, in the ODH reaction, the CsRu/CeO2 catalyst exhibited resistance to carbon deposition, evidenced by the carbon balance measurement.