Structure-performance interplay of rhodium-based catalysts for syngas conversion to ethanol

Abstract

Ethanol as a fuel additive and energy carrier has been received much attention recently due to the importance of carbon neutralization and reduction of carbon emissions. The current ethanol product strongly relies on grain fermentation, which competes with human food. The conversion of syngas (a mixture of CO and H₂) to ethanol has provided an alternative route that avoids competition with food. In this process, rhodium nanoparticle catalysts have exhibited unique catalytic properties, but there is still a gap in meeting the demand. The performances of these catalysts are strongly related to the geometric and electronic structures of the Rh species, where the controlled cleavage of C–O in CO, hindered deep hydrogenation to methane, and selective C–C coupling to ethanol are highly desirable. This review discusses the reaction mechanism of Rh-catalyzed ethanol production from syngas and summarizes the recent progress in Rh catalysts related to improving catalytic activity, ethanol selectivity, and durability. Based on these results, the structure-performance interplay of rhodium-based catalysts is briefly concluded. Particularly, zeolite-fixed Rh-based nanoparticles are highlighted, which might guide the development of more efficient catalysts via Rh-zeolite synergism.