Highly active Ni/CeO2/SiO2 catalyst for low-temperature CO2 methanation: Synergistic effect of small Ni particles and optimal amount of CeO2

Abstract

CO2 methanation is of great significance to CO2 utilization. However, it is challenging to prepare Ni-based catalysts with superior low-temperature activity via a simple method. In this work, a highly active Ni/CeO2/SiO2 catalyst is developed by a combustion-impregnation method, and the synergistic effect of active sites for H2 and CO2 activation are studied. The research results show that highly dispersed Ni particles (6 nm) are obtained by this method with an instantaneous reaction. As a result of the increased number of Ni active sites, the catalyst exhibits improved catalytic activity. Moreover, addition of CeO2 promoter further improves the low-temperature activity. First, it enhances the catalyst reducibility, creating more Ni active sites for H2 dissociation. Second, the surface oxygen vacancies formed on CeO2 facilitate CO2 activation. Therefore, the best performance of 63% CO2 conversion and 99% CH4 selectivity at 250 °C is achieved on the Ni-5Ce catalyst with small Ni particles and optimal amount of CeO2 promoter. With higher CeO2 content, Ni-7.5Ce catalyst displays decreased catalyst reducibility and catalytic activity. Therefore, it can be concluded that a proper ratio between both types of sites is crucial for CO2 methanation.