Enhanced low-temperature performance of CO2 methanation over mesoporous Ni/Al2O3-ZrO2 catalysts

Abstract

Abstract Converting carbon dioxide to value-added chemicals has been attracted much attention, whereas direct hydrogenation of CO2 to synthetic natural gas (SNG) at a lower temperature remains a big challenge. Mesoporous Al2O3-ZrO2 modified Ni catalysts were prepared via a single-step epoxide-driven sol-gel method for CO2 methanation. Almost 100% selectivity of CH4 with 77% CO2 conversion were obtained at a lower temperature of 300 °C, and no catalyst deactivation was observed in 100 h. Different characterization methods including N2 adsorption-desorption, H2-TPR, H2-TPD, XRD, XPS, and TEM were combined together to explore the interaction of Ni-ZrO2 and Al2O3-ZrO2. Incorporation of ZrO2 into Ni/Al2O3 weakened the Ni-Al2O3 interaction via the combination of Al2O3-ZrO2 solid solution, promoting the reduction and dispersion of NiO phase. The adding of higher Zr loading increased the amount of active metallic nickel sites and oxygen vacancies on the composite support, improving obviously the lower temperature catalytic activity and CH4 selectivity. Higher Ni species loading further resulted in the formation of active Ni sites and improved the low-temperature CO2 methanation performance. Moreover, the enhanced stability of the Al2O3-ZrO2 support and oxygen vacancies provided by the ZrO2 promoter could help to promote the catalytic stability.