Understanding Support Effects of ZnO‐Promoted Co Catalysts for Syngas Conversion to Alcohols Using Atomic Layer Deposition. Issue 2 (3rd December 2020)

• Record Type: Journal Article
• Authors: Nathan, Sindhu S.; Asundi, Arun S.; Singh, Joseph A.; Hoffman, Adam S.; Boubnov, Alexey; Hong, Jiyun; Bare, Simon R.; Bent, Stacey F.
• Is Part Of: ChemCatChem. Volume 13:Issue 2(2021)
• Page Start: 770
• Page End: 781
• Publication Date: 2020-12-03
• Subjects: cobalt carbide -- support effects -- oxygenate synthesis -- in situ XANES -- syngas; Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.202001630
• Languages: English
• ISSNs: 1867-3880

Abstract

Abstract: Co2 C, an emerging catalyst for the conversion of syngas to oxygenates, shows support‐sensitive behavior that has not yet been fully explained. Here, we characterize Co catalysts modified with ZnO atomic layer deposition on SiO2, carbon, CeO2, and Al2 O3 supports. We find that under syngas conditions, ZnO‐promoted Co transforms into Co2 C on SiO2, carbon, and CeO2, but not on Al2 O3 . Moreover, the support affects the extent of carburization: while the SiO2 ‐supported catalyst carburizes completely, carbon‐ and CeO2 ‐supported catalysts show incomplete conversion of Co to Co2 C. These three catalysts also exhibit different oxygenate selectivities. In contrast, the modified Al2 O3 ‐supported catalyst retains the Fischer‐Tropsch catalytic properties of metallic Co. By depositing increasing amounts of Al2 O3 by ALD on the SiO2 support, decreasing Co2 C formation and oxygenate selectivity occurs. In‐situ XANES reveals that Al2 O3 prevents Co2 C formation by enabling the ZnO to restructure into ZnAl2 O4 during reduction. Thus, in addition to modifying the active catalyst phase, the promoter can also strongly interact with the support, significantly impacting catalyst performance. Abstract : Co2 C formation and reactivity is support sensitive. Co catalysts modified by ZnO atomic layer deposition show varied carbide formation, activity, and oxygenate selectivity in syngas reaction depending on the support. Using Al2 O3 ALD and in situ XANES to probe the Al2 O3 ‐supported catalyst system further, we observe a unique promoter‐support interaction that inhibits cobalt carbide formation.