Recent advancements in thermocatalytic hydrogenation of syngas and carbon dioxide into LPG through heterogeneous catalysis

Abstract

Liquefied petroleum gas (LPG), primarily composed of propane and butane, is a versatile, clean-burning fuel with lower CO₂ emissions compared to coal and oil. Conventionally produced as a byproduct of natural gas processing and crude oil refining, LPG faces sustainability challenges due to its dependency on fossil fuels. Recent advances in heterogeneous catalysis offer alternative pathways for LPG synthesis from syngas and CO₂ hydrogenation, presenting opportunities to diversify feedstocks and mitigate greenhouse gas emissions. This review critically examines both the direct route, involving a single-stage reactor, and the indirect route, using a two-stage reactor, for LPG production, with an emphasis on hybrid catalysts that couple methanol synthesis-active phases with acidic zeolites to enable sequential conversion. Particular attention is given to various metal-based catalysts, including Cu, Pd, In, Fe, and Zn, as well as catalyst design strategies such as core-shell structures, promoter incorporation, and zeolite modifications. The impact of operating parameters on activity, selectivity, and stability is also examined. A comparative analysis highlights the advantages of direct, one-step processes in terms of energy efficiency and scalability, while indirect, multi-step routes offer greater control over product distribution. Finally, the review outlines key challenges, including catalyst deactivation, water tolerance, and process integration, and discusses future directions toward sustainable, high-selectivity LPG production from renewable carbon resources.