Selectivity control by zeolites during methanol-mediated CO₂ hydrogenation processes.

Area of Science:

• Catalysis
• Chemical Engineering
• Materials Science
• Sustainable Chemistry

Background:

• Carbon dioxide (CO2) conversion with hydrogen is a key strategy for mitigating global warming and producing valuable chemicals.
• The methanol-mediated route for CO2 hydrogenation offers higher product selectivity compared to traditional methods.
• Developing bifunctional metal/zeolite catalysts for CO2 hydrogenation faces challenges in achieving high activity and selectivity due to complex reaction networks and control over active sites.

Purpose of the Study:

• To provide a comprehensive review of zeolite-confined metal catalysts and zeolite-based bifunctional systems for CO2 hydrogenation via the methanol-mediated route.
• To critically evaluate the influence of confinement and proximity effects in 'redox-acid' bifunctional systems on reaction outcomes, particularly product selectivity.
• To analyze mechanistic aspects and synergistic interactions among catalyst components for rational catalyst design.

Main Methods:

• Literature review and critical analysis of contemporary research on zeolite-confined metal catalysts and bifunctional tandem/cascade catalytic systems.
• Evaluation of structure-reactivity relationships derived from experimental and theoretical studies.
• Mechanistic analysis of CO2 hydrogenation pathways, focusing on C-O bond activation and C-C bond coupling.

Main Results:

• Confinement and proximity effects within bifunctional systems significantly influence product selectivity in CO2 hydrogenation.
• Synergistic interactions between metallic and zeolite sites are crucial for optimizing catalytic performance.
• Understanding these effects provides insights into controlling selectivity towards alcohols and C2+ hydrocarbons.

Conclusions:

• Zeolite-based bifunctional catalysis presents a viable pathway for efficient and selective CO2 valorization.
• Further research is needed to bridge knowledge gaps in structure-reactivity relationships for rational catalyst design.
• This review offers valuable insights for developing advanced catalysts for sustainable CO2 hydrogenation processes.