Chinese Journal of Catalysis ›› 2019, Vol. 40 ›› Issue (11): 1741-1748.DOI: 10.1016/S1872-2067(19)63348-6

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Zr(IV) surface sites determine CH3OH formation rate on Cu/ZrO2/SiO2-CO2 hydrogenation catalysts

Erwin Lama, Kim Larmiera,c, Shohei Tadaa,d, Patrick Wolfa, Olga V. Safonovab, Christophe Copéreta   

  1. a ETH Zürich, Department of Chemistry and Applied Biosciences, Vladimir-Prelog-Weg 1-5, CH 8093, Zürich, Switzerland;
    b Paul Scherrer Institute, CH-5232 Villigen, Switzerland;
    c IFP Energies Nouvelles, Rond-Point de l'échangeur de Solaize, BP3, 69360 Solaize, France;
    d Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113-8656 Tokyo, Japan
  • Received:2019-01-12 Revised:2019-03-05 Online:2019-11-18 Published:2019-09-06
  • Contact: Christophe Copéret
  • Supported by:
    E.L., K.L., P.W., and S.T. are supported by the SCCER-Heat and Energy Storage program. We acknowledge PSI Super-XAS for beamtime and thank Dr. Maarten Nachtegaal (PSI) for assistance and ScopeM at ETH Zürich for the use of their electron microscopy facilities and Dr. Dmitry Lebedev (ETH) for TEM.

Abstract: Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carried out on the Cu and Zr K-edge. Under reaction conditions, Cu remains metallic, while Zr is present in three types of coordination environment associated with 1) bulk ZrO2, 2) coordinatively saturated and 3) unsaturated Zr(IV) surface sites. The amount of coordinatively unsaturated Zr surface sites can be quantified by linear combination fit of reference X-Ray absorption near edge structure (XANES) spectra and its amount correlates with CH3OH formation rates, thus indicating the importance of Zr(IV) Lewis acid surface sites in driving the selectivity toward CH3OH. This finding is consistent with the proposed mechanism, where CO2 is hydrogenated at the interface between the Cu nanoparticles that split H2 and Zr(IV) surface sites that stabilizes reaction intermediates.

Key words: CO2 hydrogenation, ZrO2/SiO2 supported Cu nanoparticles, Lewis acidic surface sites, In situ X-ray absorption spectroscopy