Green Catalysts for High-Temperature Reactions: Mechanistic Insights and Sustainable Advances in Hydrogenation, Cracking, and Reforming

Green catalysts are increasingly being explored as sustainable alternatives to traditional catalytic systems. Their use in high-temperature processes remains unexplored. This review concentrates on building green catalysts for applications like hydrogenation, dehydrogenation, thermal cracking, and reforming. The systematic classification of green catalysts by sustainability metrics and catalytic functionality is also done and critically examines major catalytic modes, metal-centered, acid/base driven, and bifunctional catalysis, emphasizing their distinct mechanistic features. Additionally, detailed mechanistic insights into each high-temperature reaction are presented. It covers recent advancements in metals readily available on Earth, systems devoid of metal, redox-active supports providing stability at high temperatures, coke resistance, and environmental safety. Using synthesis techniques, structure-function correlations, and density functional theory (DFT) insights, the review elucidates the influence of a material's structure on its catalytic performance under demanding conditions. Unlike other reviews, this review emphasizes the molecular and structural requirements of high-temperature catalysis. It reveals significant knowledge gaps in lifecycle sustainability, operando characterization, and scalability. Along with a strategy for the following generation of green catalytic systems employed in high-energy environments, the review also includes future directions in green catalyst design. This roadmap highlights pathways of designing thermally stable, regenerable, eco-friendly catalyst structures and the incorporation of DFT-controlled predictive technologies to accelerate the finding of the next-generation green catalytic structures.