CO2 methanation over alumina-supported cobalt oxide and carbide synthesized by reverse microemulsion method

Abstract

In the past age, CO2 conversion catalysts have gained attention due to various environmental issues caused by CO2 emission. Catalytic reduction of CO2 using renewable hydrogen as reductant to produce renewable fuels is considered as a potential solution to store the surplus renewable energy and reduce the CO2 emission. Alumina-supported cobalt oxide and cobalt carbide catalysts prepared by reverse microemulsion (RME) method were investigated for CO2 methanation. Results showed that the prepared catalysts were nanosized particles ranged from 5-15 nm. XRD, BET, SEM and TEM were used for catalysts characterization and TPR was conducted to study the reducibility. The catalytic performance of these catalysts was studied by CO2 methanation reaction. At 400 °C, 3 bar, under a 60,000 mL gcat-1 h-1 flow (H2:CO2=4:1), the selectivity to methane on alumina-supported cobalt carbide catalysts can reach 0.96 and the conversion of CO2 was 0.78, showing high catalytic activity and mild reaction condition. With increasing pressure, the conversion of CO2, as well as the selectivity to CH4 both increased and reached 0.91 and 0.98 respectively at 11 bar showing excellent performance towards CO2 methanation. In-situ FTIR was used to study the mechanism of the reaction on alumina-supported cobalt catalysts. The pathway from CO2 to methane and adsorbed intermediates on catalysts were investigated. Intermediates and adsorbed species on the catalysts were investigated during the reaction. At lower temperature and lower gas concentration, CO2 was adsorbed on the surface as carbonates. When the reaction condition was achieved, adsorbed CO2 started to be reacted to CO and CH4 and intermediate species started to appear.