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A highly selective and stable ZnO-ZrO2 solid solution catalyst for CO2 hydrogenation to methanol

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Science Advances  06 Oct 2017:
Vol. 3, no. 10, e1701290
DOI: 10.1126/sciadv.1701290
  • Fig. 1 Catalytic performance of the ZnO-ZrO2 catalyst.

    (A) Dependence of catalytic performance at 320°C on the Zn/(Zn + Zr) molar ratio. Inset: purple, normalized activities for ZnO, 13% ZnO-ZrO2, and ZrO2 by specific surface area; dark yellow, normalized activities for mechanically mixed ZnO and ZrO2 in the same composition. (B) Catalytic performance at the reaction temperatures from 200° to 380°C with H2/CO2 = 3:1 and 4:1. (C) Catalyst stability test in 550 hours. (D) Catalyst stability toward the S-containing molecules (50 ppm H2S or SO2 in Ar) and annealing. In S experiments, there are two gas paths: one is 50 ppm H2S(SO2)/Ar and the other is CO2/H2/Ar. Pulsing experiment was carried out by turning on the S gas for 30 min and 60 min and then turning off after the CO2 + H2 reaction reached its steady state. After several pulses, the two gas paths were turned on simultaneously. Standard reaction conditions: 5.0 MPa, H2/CO2 = 3:1, 320°C, GHSV = 24,000 ml/(g hour), using a tubular fixed-bed reactor with the 13% ZnO-ZrO2 catalyst.

  • Fig. 2 Structural characterization of the ZnO-ZrO2 catalyst.

    (A) XRD patterns of ZnO-ZrO2. (B) High-resolution transmission electron microscopy (HRTEM) and (C) aberration-corrected scanning TEM–high-angle annular dark-field images and element distribution of 13% ZnO-ZrO2. (D) Raman spectra of ZnO-ZrO2 with 244-nm laser (solid line), 266-nm laser (pink dot line), and 325-nm laser (dark yellow dot line). (E) Zn concentration in the surface region of ZnO-ZrO2 measured by XPS. (F) Schematic description of the ZnO-ZrO2 solid solution catalyst model.

  • Fig. 3 CO2 adsorption and H2 activation.

    (A) CO2-TPD on ZnO, ZrO2, and 13% ZnO-ZrO2 normalized by specific surface area. Inset: purple, normalized CO2 adsorption below 320°C; dark yellow, normalized activities for mechanically mixed ZnO and ZrO2 in the same composition as 13% ZnO-ZrO2. (B) H2-D2 exchange reaction on ZnO, ZrO2, and 13% ZnO-ZrO2 at 280°C. Purple, normalized rate by specific surface area; dark yellow, normalized activities for mechanically mixed ZnO and ZrO2 in the same composition as 13% ZnO-ZrO2.

  • Fig. 4 Characterization of surface species.

    (A) In situ DRIFT spectra of surface species formed from the CO2 + H2 reaction. (B) DRIFT-MS of CO2 + H2 and CO2 + D2 reactions on 13% ZnO-ZrO2. (C) In situ DRIFT spectra of surface species from CO2 + H2 and subsequently switched to D2. (D) DRIFT-MS of CO2 + H2 and subsequently switched to D2. Reaction conditions: 13% ZnO-ZrO2 catalyst, 0.1 MPa, 280°C, 10 ml/min CO2 + 30 ml/min H2 (D2).

  • Fig. 5 DFT calculations.

    Reaction diagram [energy (E) and Gibbs free energy (G) at a typical reaction temperature of 593 K] of CO2 hydrogenation to methanol on the (101) surface of the tetragonal ZnO-ZrO2 model.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/10/e1701290/DC1

    table S1. The BET results of catalysts and intrinsic property.

    table S2. The catalytic performance of mechanically mixed and supported catalysts.

    table S3. DRIFT peak assignments of the surface species for the CO2 + H2(D2) reaction on 13% ZnO-ZrO2.

    fig. S1. The dependence of methanol selectivity on the Zn/(Zn + Zr) molar ratio at a 10% CO2 conversion.

    fig. S2. The effect of pressure, H2/CO2 ratio, and GHSV on CO2 hydrogenation.

    fig. S3. XRD patterns of ZnO-ZrO2 catalysts.

    fig. S4. HRTEM of the 13% ZnO-ZrO2 catalyst.

    fig. S5. The UV-vis absorbance and Raman spectra of ZnO-ZrO2.

    fig. S6. XPS of ZnO, ZrO2, and 13% ZnO-ZrO2.

    fig. S7. H2-TPR of ZnO, ZrO2, and 13% ZnO-ZrO2.

    fig. S8. XRD of mechanically mixed and supported catalysts.

    fig. S9. DRIFT results of CO2 + H2 substituted by CO2 + D2.

    fig. S10. Structure of ZrO2 and ZnO-ZrO2.

    fig. S11. Local geometries of the reaction intermediates of CO2 hydrogenation to methanol via formate on the ZnO-ZrO2 (101) surface.

    fig. S12. Local geometries of the reaction intermediates of CO2 hydrogenation to methanol via CO on the ZnO-ZrO2 (101) surface.

    fig. S13. Structure of ZnO.

    fig. S14. Hartree potential of the Zn-terminated ZnO (0001) surface calculated by different dipole correction methods.

    fig. S15. Local geometries of the reaction intermediates on the ZnO (0001) surface.

    fig. S16. Reaction diagram of CO2 hydrogenation to CH3OH via formate on the Zn-terminated ZnO (0001) surface.

    fig. S17. The catalytic performance contrast of the ZnO-ZrO2 catalyst for CO2 + H2 and CO + H2.

    fig. S18. The catalytic performance contrast of Cu/ZnO/Al2O3 and ZnO-ZrO2 catalysts for CO2 hydrogenation.

    fig. S19. The stability test of the Cu/ZnO/Al2O3 catalyst.

  • Supplementary Materials

    This PDF file includes:

    • table S1. The BET results of catalysts and intrinsic property.
    • table S2. The catalytic performance of mechanically mixed and supported catalysts.
    • table S3. DRIFT peak assignments of the surface species for the CO2 + H2(D2) reaction on 13% ZnO-ZrO2.
    • fig. S1. The dependence of methanol selectivity on the Zn/(Zn + Zr) molar ratio at a 10% CO2 conversion.
    • fig. S2. The effect of pressure, H2/CO2 ratio, and GHSV on CO2 hydrogenation.
    • fig. S3. XRD patterns of ZnO-ZrO2 catalysts.
    • fig. S4. HRTEM of the 13% ZnO-ZrO2 catalyst.
    • fig. S5. The UV-vis absorbance and Raman spectra of ZnO-ZrO2.
    • fig. S6. XPS of ZnO, ZrO2, and 13% ZnO-ZrO2.
    • fig. S7. H2-TPR of ZnO, ZrO2, and 13% ZnO-ZrO2.
    • fig. S8. XRD of mechanically mixed and supported catalysts.
    • fig. S9. DRIFT results of CO2 + H2 substituted by CO2 + D2.
    • fig. S10. Structure of ZrO2 and ZnO-ZrO2.
    • fig. S11. Local geometries of the reaction intermediates of CO2 hydrogenation to methanol via formate on the ZnO-ZrO2 (101) surface.
    • fig. S12. Local geometries of the reaction intermediates of CO2 hydrogenation to methanol via CO on the ZnO-ZrO2 (101) surface.
    • fig. S13. Structure of ZnO.
    • fig. S14. Hartree potential of the Zn-terminated ZnO (0001) surface calculated by different dipole correction methods.
    • fig. S15. Local geometries of the reaction intermediates on the ZnO (0001) surface.
    • fig. S16. Reaction diagram of CO2 hydrogenation to CH3OH via formate on the Zn-terminated ZnO (0001) surface.
    • fig. S17. The catalytic performance contrast of the ZnO-ZrO2 catalyst for CO2 + H2 and CO + H2.
    • fig. S18. The catalytic performance contrast of Cu/ZnO/Al2O3 and ZnO-ZrO2 catalysts for CO2 hydrogenation.
    • fig. S19. The stability test of the Cu/ZnO/Al2O3 catalyst.

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