Effect of SiO2 on the CO Selective Methanation over SiO2/Ni‐ZrO2 Catalysts

Abstract

AbstractCO selective methanation is a reliable and efficient method for deep CO removal from H2‐rich reformate gases in proton exchange membrane fuel cell (PEMFC). In this study, a series of SiO2/Ni‐ZrO2 catalysts with different mass fractions of SiO2 was prepared for CO selective methanation, and the structures and surface chemical properties of Ni‐ZrO2 could be controlled by SiO2. It was found that SiO2 greatly increased the specific surface areas of the catalyst and the dispersion of supported metallic Ni, which endowed the catalyst with higher active Ni surface area and then increased the adsorption quantity of CO, which improved the conversion of CO at low temperature. More importantly, the SiO2 weakened the surface basicity over the Ni‐ZrO2 catalyst, and thus decreased the strength and quantity of CO2 adsorption, which greatly inhibited the methanation of CO2, leading to the higher selectivity for CO methanation. However, the strength of CO adsorption was found to be more related to the methanation of CO, which would be weakened by SiO2 in the catalysts. Meanwhile, the SiO2 increased the strength of H2 adsorption over Ni surface. Therefore, excess SiO2 added into Ni‐ZrO2 enhanced the competitive adsorption between CO and H2 molecules over Ni surface, which weakened CO adsorption, resulting in the increase of CO outlet concentration.