Hydrogenation reactions occurring on the surface of a copper/zirconia (Cu:Zr ) 30:70 atom %) catalyst, which had previously been loaded by adsorption of formic acid, CO, and CO2, have been studied by means of in situ diffuse reflectance FTIR spectroscopy. Besides characterizing the reactivity of adsorbates, the dynamics of CO and CO2/hydrogen reactant mixtures has been monitored over both the prereduced and unreduced catalyst, with the aim of acquiring information on the methanol synthesis mechanism. Surface formates, which have previously been identified as intermediates in the catalytic reduction of carbon oxides yielding methane, appear to be spectator species in methanol synthesis over ZrO2 supported catalysts. The latter synthesis, when using CO2 as the reactant, starts from surface carbonate, which is first reduced to yield adsorbed carbon monoxide and water. The desired methanol product is generated via surfacebound formaldehyde and methoxy species.

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