title: Methanol synthesis via CO₂ hydrogenation over a Au/ZnO catalyst: an isotope labelling study on the role of CO in the reaction process.
abstract: Methanol synthesis for chemical energy storage, via hydrogenation of CO2 with H2 produced by renewable energies, is usually accompanied by the undesired formation of CO via the reverse water-gas shift reaction. Aiming at a better mechanistic understanding of methanol formation from CO2/H2 on highly selective supported Au/ZnO catalysts we have investigated the role of CO in the reaction process using isotope labelling experiments. Using (13)C-labelled CO2, we found for reaction at 5 bar and 240 °C that (i) the methanol formation rate is significantly higher in CO2-containing gas mixtures than in a CO2-free mixture and (ii) in mixtures containing both CO2 and CO methanol formation from CO increases with the CO content up to 1% CO, and then remains at 20% of the total methanol formation up to a CO2/CO ratio of 1/1, making CO2 the preferred carbon source in these mixtures. A shift in the preferred carbon source for MeOH from CO2 towards CO is observed with increasing reaction temperatures between 240 °C and 300 °C. At even higher temperatures CO is expected to become the dominant carbon source. The consequences of these findings for the application of Au/ZnO catalysts for chemical storage of renewable energies are discussed.
authors.affiliation: Institute of Surface Chemistry and Catalysis, Ulm University, Albert-Einstein-Allee 47, D-89081 Ulm, Germany. juergen.behm@uni-ulm.de.
authors.forename: Yeusy
authors.initials: Y
authors.lastname: Hartadi
authors.affiliation: Institute of Surface Chemistry and Catalysis, Ulm University, Albert-Einstein-Allee 47, D-89081 Ulm, Germany. juergen.behm@uni-ulm.de.
authors.forename: Daniel
authors.initials: D
authors.lastname: Widmann
authors.affiliation: Institute of Surface Chemistry and Catalysis, Ulm University, Albert-Einstein-Allee 47, D-89081 Ulm, Germany. juergen.behm@uni-ulm.de.
authors.forename: R Jürgen
authors.initials: RJ
authors.lastname: Behm