Research progress on the monolithic catalyst for hydrogenation of CO₂ to methane

Carbon dioxide (CO₂) can be efficiently converted and utilized through the CO₂ methanation reaction, which has significant potential benefits for the environment and the economy. The contradiction between the thermodynamics and kinetics of the CO₂ methanation reaction process leads to low CO₂ conversion at 200−350 °C and low methane selectivity at 350−500 °C. The utilization of catalysts can solve the contradiction between kinetics and thermodynamics, achieving high CO₂ methanation efficiency at low temperatures. However, the poor thermal conductivity of powder catalysts leads to the rapid accumulation of heat, resulting in the formation of hot spots, which can cause the sintering or even deactivation of active species. To solve this problem, researchers have focused on monolithic catalysts with integrated reaction systems. This review categorizes the monolithic catalysts into two main groups based on their unique characteristics, namely structured catalysts and catalytic membrane reactors. The characteristics of these monolithic catalysts, commonly used support materials, preparation techniques, and their applications in the CO₂ methanation reaction are discussed in depth. These studies provide theoretical basis and practical guidance for the design and optimization of structured catalysts and catalytic membrane reactors. Finally, challenges and prospects in the application of monolithic catalysts for the CO₂ methanation reaction are proposed for the future development.