Role of Co2C in ZnO‐promoted Co Catalysts for Alcohol Synthesis from Syngas. Issue 2 (27th December 2018)

• Record Type: Journal Article
• Authors: Singh, Joseph A.; Hoffman, Adam S.; Schumann, Julia; Boubnov, Alexey; Asundi, Arun S.; Nathan, Sindhu S.; Nørskov, Jens; Bare, Simon R.; Bent, Stacey F.
• Is Part Of: ChemCatChem. Volume 11:Issue 2(2019)
• Page Start: 799
• Page End: 809
• Publication Date: 2018-12-27
• Subjects: Higher alcohol synthesis -- in situ characterization -- EXAFS modelling -- cobalt carbide -- density functional theory; Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.201801724
• Languages: English
• ISSNs: 1867-3880

Abstract

Abstract: Controlling selectivity is a key goal in the design of a heterogeneous catalyst. Herein, we present detailed characterization and activity of silica‐supported cobalt catalysts modified by atomic layer deposition of ZnO. After reduction, the resulting catalysts exhibit substantial selectivity towards alcohol production during CO hydrogenation compared to catalysts containing only cobalt. The prepared catalysts have up to 46 % selectivity toward alcohols with 39 % of the alcohols corresponding to ethanol and other higher alcohols, albeit with reduced activity. In situ characterization of the catalyst by X‐ray diffraction and X‐ray absorption spectroscopy reveals details on the structural evolution in syngas, CO+H2, and shows that ZnO promotion of Co results in the formation of Co2 C under catalytic conditions. A mechanism is proposed, supported by density functional theory calculations, which explains Co2 C formation by the blocking of Co step sites by Zn species. The ZnO acts a dual promoter both by facilitating Co2 C formation and by modifying the resulting Co2 C. The Co2 C formed from the ZnO‐promoted Co catalysts displays improved thermal stability and selectivity compared with similar Co2 C catalysts without Zn. Abstract : Staying active for alcohol! In situ X‐ray absorption spectroscopy, X‐ray diffraction and DFT calculations have been used to elucidate the active phase of an ALD‐ZnO‐modified Co catalyst for the synthesis of higher alcohols from syngas, which is identified as a Zn‐modified Co2 C.