Effect of catalyst properties on selectivity in CO2 methanation with coupling pathway of RWGS and CO methanation

Abstract

The multiplicity of catalyst structures and modification strategies makes possible different reaction pathways and selectivity of CO₂ methanation, and the reaction mechanism is also controversial. In this work, La-modified LN/AZ catalyst and La–Ce co-modified LCN/AZ catalyst were prepared by the same method and used to investigate the influencing factors of the catalytic activity and selectivity of CO₂ methanation. The characterization results show that the Ni precursor states, Ni⁰ dispersion, surface oxygen vacancies, and acidity in the two catalysts were different. Through catalytic activity tests, kinetics and in situ DRIFTS analysis, the overall reaction pathway was investigated on the two catalysts through sequential reverse water–gas shift (RWGS) reaction to CO and CO methanation. Over the LCN/AZ catalyst, the high density of surface oxygen vacancies and weakly basic sites significantly promoted CO₂ activation, while the CH₄ selectivity was low. This is due to modification by Ce resulting in the failure of the Ni precursor to form a perovskite structure, which ultimately undermined the synergistic effect between the support and the active sites.