Effect of Ce doping of a Co/Al₂O₃ catalyst on hydrogen production via propane steam reforming

We synthesized cerium-doped cobalt-alumina (Co_xCe_y/Al₂O₃) catalysts for the propane steam reforming (PSR) reaction. Adding cerium introduces oxygen vacancies, and the oxygen transfer capacity of the Ce promoter favors CO to CO₂ conversion during PSR, inhibiting coke deposition and promoting hydrogen production. The best PSR activity was achieved at 700°C using the Co_0.85Ce_0.15/Al₂O₃ catalyst, which showed 100% propane (C₃H₈) conversion and about 75% H₂ selectivity, and 6% CO, 5% CO₂, and 4% CH₄ were obtained. In contrast, the H₂ selectivity of the base catalyst, Co/Al₂O₃, is 64%. The origin of the difference in activity was the lower C₃H₈ gas desorption temperature of the Co_0.85Ce_0.15/Al₂O₃ catalyst compared to that of the Co/Al₂O₃ catalyst; thus, the PSR occurred at low temperatures. Furthermore, more CO was adsorbed on the Co_0.85Ce_0.15/Al₂O₃ catalyst, and subsequently, desorbed as CO₂. The activation energy for water desorption from the Co_0.85Ce_0.15/Al₂O₃ catalyst was 266.96 kJ/mol, higher than that from Co/Al₂O₃. Furthermore, the water introduced during the reaction probably reacted with CO on the Co_0.85Ce_0.15/Al₂O₃ catalyst, increasing CO₂ generation. Finally, we propose a mechanism involving the Co_0.85Ce_0.15/Al₂O₃ catalyst, wherein propane is reformed on Co_xCe_y sites, forming H_2, and CO, followed by the conversion of CO to CO₂ by water on CeO₂ sites.