Influence of CO on the Activation, O‑Vacancy Formation, and Performance of Au/ZnO Catalysts in CO2 Hydrogenation to Methanol

• Published in: The journal of physical chemistry letters Vol. 10; no. 13; pp. 3645 - 3653
• Main Authors: Abdel-Mageed, Ali M, Klyushin, Alexander, Knop-Gericke, Axel, Schlögl, Robert, Behm, R. Jürgen
• Format: Journal Article
• Language: English
• Published: American Chemical Society 05.07.2019
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.9b00925

The impact of CO on the activation and reaction characteristics of Au/ZnO catalysts in methanol synthesis from a CO2/H2 mixture was studied by kinetic, near ambient pressure X-ray photoelectron spectroscopy and X-ray absorption spectroscopy at the O K-edge, together with in situ Foureir transform infrared measurements. Transient measurements under up to industrial reaction conditions (50 bar, 240 °C) show a pronounced transient increase of the activity for methanol formation from CO2/H2 after exposure to a CO/H2 reaction gas mixture, while the steady-state activity is similar to that observed directly after oxidative pretreatment. For the reaction in CO/H2, the much longer activation phase is accompanied by formation of CO2 due to reaction of CO with the ZnO catalyst support. This leads to O-vacancy formation on the support at an extent significantly higher than in CO2/H2. The consequences of these findings on the mechanistic understanding of methanol formation from CO2/H2 on Au/ZnO and for ZnO-supported catalysts in general are discussed.