Interaction of hydrogen with Cu–Zn mixed oxide model methanol synthesis catalyst

• The Cu2+ in the (Cu,Zn)O mixed oxide reversibly interacts with H2 giving 2H+.
• Protons are stabilized as OH−-groups, which are reactive hydrogen species.
• Exposure of (Cu,Zn)O to air prior to the reduction affects the reduction kinetics.
• Carbonate ad-anions decompose to CO2 via formates in the presence of hydrogen.

Interaction of hydrogen with model Cu–Zn methanol synthesis catalyst prepared by decomposition of mixed hydroxicarbonate is studied by inelastic neutron scattering, in situ FTIR/MS, and thermal analysis. Reduced (Cu0.08,Zn0.92)O mixed oxide accumulates 6H/Cu, mainly as hydride, hydroxyl and formate species. The reduction of copper in the (Cu,Zn)O mixed oxide occurs via a reversible redox interaction with H2 and absorption of protons as OH−-groups with ν = 3250 cm−1 and δ ≈ 1430–1480 cm−1. Kinetic and thermodynamic parameters of this process are evaluated. The weight loss during the reduction is due to the decomposition of the residual carbonate groups to CO2 via formate intermediates, which occurs in the presence of hydrogen. Exposure of (Cu,Zn)O to air prior to the reduction strongly affects the kinetic parameters of the reduction process.

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