Selectivity control by zeolites during methanol-mediated CO2 hydrogenation processes

Abstract

The thermocatalytic conversion of CO₂ with green or blue hydrogen into valuable energy and commodity chemicals such as alcohols, olefins, and aromatics emerges as one of the most promising strategies for mitigating global warming concerns in the future. This process can follow either a CO₂-modified Fischer–Tropsch synthesis route or a methanol-mediated route, with the latter being favored for its high product selectivity beyond the Anderson–Schulz–Flory distribution. Despite the progress of the CO₂-led methanol-mediated route over bifunctional metal/zeolite catalysts, challenges persist in developing catalysts with both high activity and selectivity due to the complexity of CO₂ hydrogenation reaction networks and the difficulty in controlling C–O bond activation and C–C bond coupling on multiple active sites within zeolites. Moreover, the different construction and proximity modes of bifunctionality involving redox-based metallic sites and acidic zeolite sites have been explored, which have not been systematically reviewed to derive reliable structure–reactivity relationships. To bridge this “knowledge gap”, in this review, we will provide a comprehensive and critical overview of contemporary research on zeolite-confined metal catalysts for alcohol synthesis and zeolite-based bifunctional tandem/cascade catalytic systems for C₂₊ hydrocarbons synthesis in CO₂ hydrogenation via the methanol-mediated route. Accordingly, special emphasis will be placed on evaluating how confinement and proximity effects within the “redox-acid” bifunctional systems influence the reaction outcomes, particularly regarding product selectivity, which has also been analyzed from the mechanistic standpoint. This review will also examine the synergistic interactions among various catalyst components that govern catalysis, offering valuable insights for the rational design of new or improved catalyst systems. By discussing current challenges and recognizing future opportunities in CO₂ hydrogenation using zeolite-based bifunctional catalysis, this review aims to contribute to the advancement of sustainable and efficient processes for CO₂ valorization.