Flame Synthesis of Cu/ZnO-CeO Catalysts: Synergistic Metal-Support Interactions Promote CHOH Selectivity in CO Hydrogenation.

The hydrogenation of CO to CHOH is an important reaction for future renewable energy scenarios. Herein, we compare Cu/ZnO, Cu/CeO, and Cu/ZnO-CeO catalysts prepared by flame spray pyrolysis. The Cu loading and support composition were varied to understand the role of Cu-ZnO and Cu-CeO interactions. CeO addition improves Cu dispersion with respect to ZnO, owing to stronger Cu-CeO interactions. The ternary Cu/ZnO-CeO catalysts displayed a substantially higher CHOH selectivity than binary Cu/CeO and Cu/ZnO catalysts. The high CHOH selectivity in comparison with a commercial Cu-ZnO catalyst is also confirmed for Cu/ZnO-CeO catalyst prepared with high Cu loading (∼40 wt %). In situ IR spectroscopy was used to probe metal-support interactions in the reduced catalysts and to gain insight into CO hydrogenation over the Cu-Zn-Ce oxide catalysts. The higher CHOH selectivity can be explained by synergistic Cu-CeO and Cu-ZnO interactions. Cu-ZnO interactions promote CO hydrogenation to CHOH by Zn-decorated Cu active sites. Cu-CeO interactions inhibit the reverse water-gas shift reaction due to a high formate coverage of Cu and a high rate of hydrogenation of the CO intermediate to CHOH. These insights emphasize the potential of fine-tuning metal-support interactions to develop improved Cu-based catalysts for CO hydrogenation to CHOH.