Influence of support composition (MZr₄O₂) of Cu−based catalysts on activity in CO₂ hydrogenation to methanol

Hydrogenation of carbon dioxide to methanol can not only achieve the control of carbon emission, but also reduce the consumption of fossil energy, which is one of the effective ways to realize the utilization of CO₂ resources. Copper-based catalysts are capable of catalyzing the conversion of CO₂ hydrogenation to methanol at high temperature and high pressure, but the traditional copper-based catalysts suffer from the problems of weak CO₂ activation ability, low selectivity of methanol as the target product, and poor stability of oxide-loaded activated copper species, and so on. Therefore, the development of highly efficient, stable and novel copper-based catalysts is an important part of the research in the reaction of methanol synthesis by CO₂ hydrogenation. In this study, four copper-based catalysts supported by zirconium bimetallic oxides, namely Cu/TiZr₄O₂, Cu/ZnZr₄O₂, Cu/GaZr₄O₂, and Cu/CeZr₄O₂, are synthesized and tested in CO₂ hydrogenation experiments for methanol production. The results show that the Cu/TiZr₄O₂ catalysts with TiZr₄O₂ oxides as carriers have good catalytic activity. Characterization analyses show that the H₂ reduced Cu/TiZr₄O₂ catalysts have a large number of unsaturated Cu species （Cu⁰） on the surface, which combined with abundant oxygen vacancies and surface alkaline sites to promote the adsorption and activation of CO₂ and H₂. The smaller Cu particle size, larger Cu specific surface area and dispersion combined to promote H₂ activation. The excellent physicochemical properties enable the Cu/TiZr₄O₂ catalyst to exhibit good catalytic activity. In addition the reaction mechanism suggests that formate species are key intermediates in the synthesis of methanol from CO₂ hydrogenation catalyzed by Cu/TiZr₄O₂ catalysts.