Enhanced reactive CO2 species formation via V2O5-promoted Ni/KCC-1 for low temperature activation of CO2 methanation

Abstract

Application of CO₂ methanation, especially in CO₂-rich gas fields, could potentially provide additional value to the synthetic natural gas production. In this study, highly active vanadium (V₂O₅)-promoted Ni/KCC-1 catalysts with 5% nickel content were prepared using a co-impregnation method for CO₂ methanation reaction. The influence of V₂O₅ on the textural properties, basicity and reducibility of the 5Ni/KCC-1 catalysts was systematically investigated. It was found that addition of V₂O₅ enhances the basicity of the catalysts; however, it decreases the surface area and pore volume. The amphoteric properties of V₂O₅ provide additional adsorption sites of CO₂ producing more reactive unidentate CO₂ adsorbed species. The presence of V₂O₅ also improved the dispersion and exposed more Ni species. This leads to an increased amount of reducible NiO species. Compared to 5Ni/KCC-1, the V₂O₅-Ni/KCC-1 series were active at lower temperature. The light off temperature for V₂O₅-Ni/KCC-1 was 423 K compared to 473 K for 5Ni/KCC-1. At 623 K, the 7.5V₂O₅-Ni/KCC-1 reaches 94.4% CO₂ conversion, 15% higher than 5Ni/KCC-1. The presence of O₂ negatively affects the catalytic activity as O₂ interferes with the CO₂ adsorption sites. The analysis of variance (ANOVA) indicates that the reaction temperature heavily influences the CH₄ yield followed by the reduction temperature and H₂ : CO₂ ratio. The optimized conditions by the RSM are a reduction temperature of 696.9 K, a reaction temperature of 766.5 K and a H₂ : CO₂ ratio of 5.1.