Catalytic activity and reaction mechanism of CO₂ hydrogenation to methanol catalyzed by solid solution

Solid solution catalyst has good catalytic activity in the study of CO₂ hydrogenation to methanol, due to its changes of features like solid solution strengthening, lattice distortion and solid solution structure. Solid solution strengthening can effectively improve the thermal stability of the catalyst, so that it can maintain stable catalytic performance under high temperature and high pressure conditions. Lattice distortion can adjust the electronic structure and surface active site of the catalyst, enhance the interfacial structural interaction and promote the adsorption and activation of reactant molecules. The solid solution structure can create more oxygen vacancies and form bimetallic site synergistic effect, which makes the key intermediate of the reaction more stable in the process of activating CO₂ at high temperature, so as to effectively inhibit the generation of CO. The controversy on the mechanism of CO₂ hydrogenation to methanol mainly focuses on two intermediates: formate species (HCOO*) and carboxyl group species (COOH*). Among them, solid solution catalysts are more inclined to formate mechanism, which considers formate (HCOO*) and methoxy (CH₃O*) as key intermediates in the reaction. Gallium zirconium, indium zirconium and zinc zirconium are the three most common solid solution catalysts. The catalytic activity and reaction mechanism of these three catalysts are summarized. Finally, the problems existing in the field of CO₂ hydrogenation of solid solution catalyst to methanol are discussed and prospected.