Mechanistic study of the effect of chlorine on selective CO methanation over Ni alumina-based catalysts

The effect of residual chlorine of alumina-supported Ni catalysts on the selective CO methanation reaction was investigated. By chloride addition to the catalyst, CO₂methanation and the reverse water gas-shift reaction were significantly suppressed in the course of the reaction. FTIR measurements for CO₂adsorption on a series of modified catalysts with various chlorine-containing additives revealed that chlorine suppressed the dissociation of CO₂on the catalyst surface, which led to the formation of adsorbed CO species. The FTIR results combined with TPD measurements for CO₂desorption indicates that chlorine adsorbed on Ni metal diminished the formation of carboxylate species on the same surface under flowing CO₂conditions. Through the present study, the controlling factor for the selective methanation of CO by chlorine was clarified in high CO₂concentration-containing hydrogen rich gas.