Research progress on catalysts for the synthesis of higher alcohols from syngas

Catalytic conversion of syngas (CO+H₂) into low-carbon alcohols (C₂₊alcohols) in C₁ chemistry is of great strategic significance to alleviate the global energy crisis, particularly for the resource utilization of agricultural and forestry wastes. Clean and efficient utilization of coal and natural gas can be realized with high atomic economy and low carbon dioxide emissions in green carbon science and the recycling economy. This study systematically reviewed the recent research progress on catalysts to synthesize higher alcohols from syngas, with emphasis on the reaction mechanisms and high-efficiency catalysts. The synergistic effect of bifunctional active sites dominated the adsorption and conversion pathways of CO at the mechanism level. Dissociative adsorption sites promoted carbon chain growth for non-dissociative adsorption sites, facilitating the formation of oxygen-containing intermediates. Alkali metal promoters (Li, Na, and K) and key process parameters (H₂/CO ratio, reaction temperature, pressure) effectively regulated the generation of key intermediates and the distribution of target products. A multi-system pattern was found in the catalyst field, such as Mo-based, Rh-based, modified methanol synthesis, modified Fischer-Tropsch synthesis and Cu-based bimetallic catalysts. CO conversion rate, C₂₊ alcohol selectivity and catalyst stability were significantly improved after component regulation, structural (core-shell, confinement structures) and promoter modification. Industrial application also included single-tube tests, 100-ton pilot-scale experiments and 1000-ton industrial sideline demonstrations. Cu-based catalysts achieved over 85% in CO conversion and C₂₊ alcohol selectivity of 70%. Mo-based catalysts maintained stability for up to 1 700 h. Techno-economic analysis showed that green hydrogen accounted for 58%-83% of the total production cost, while non-noble metal catalysts reduced the preparation cost by 30%-50%, compared with noble metal catalysts; Agricultural waste gasification increased the system energy efficiency to 43.0%, indicating a significant reduction in greenhouse gas emissions. Some challenges included the synchronous high CO conversion and C₂₊ alcohol selectivity, harsh high-temperature and high-pressure reaction conditions, insufficient catalyst stability, and weak adaptability to agricultural application. Future research priorities should be placed on the precise design of non-noble metal catalysts suitable for agricultural waste-derived syngas, atomic-level mechanism analysis via in-situ characterization and DFT calculations, optimization for agricultural carbon sequestration and green hydrogen, and large-scale engineering. Technical barriers between basic research and agricultural applications can be broken to accelerate the industrialization of syngas-to-low-carbon-alcohol technology. The findings can provide strong support for clean energy production and the carbon circular economy in the resource utilization of agricultural wastes.