Hydroxyl-mediated ethanol selectivity of CO ₂ hydrogenation†

Abstract

This paper describes the promotional effect of hydroxyl groups over RhFeLi/TiO ₂ catalysts for the ethanol synthesis via CO ₂ hydrogenation.

Abstract

Oxide-supported Rh nanoparticles have been widely used for CO ₂ hydrogenation, especially for ethanol synthesis. However, this reaction operates under high pressure, up to 8 MPa, and suffers from low CO ₂ conversion and alcohol selectivity. This paper describes the crucial role of hydroxyl groups bound on Rh-based catalysts supported on TiO ₂ nanorods (NRs). The RhFeLi/TiO ₂ NR catalyst shows superior reactivity (≈15% conversion) and ethanol selectivity (32%) for CO ₂ hydrogenation. The promoting effect can be attributed to the synergism of high Rh dispersion and high-density hydroxyl groups on TiO ₂ NRs. Hydroxyls are proven to stabilize formate species and protonate methanol, which is easily dissociated into *CH _x , and then CO obtained from the reverse water–gas shift reaction (RWGS) is inserted into *CH _x to form CH ₃CO*, followed by CH ₃CO* hydrogenation to ethanol.

Notes

†Electronic supplementary information (ESI) available: Experimental details and supporting figures and tables. See DOI: 10.1039/c8sc05608k