Surface Species in CO and CO₂Hydrogenation over Copper/Zirconia:  On the Methanol Synthesis Mechanism

Abstract

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.

Effect of pressure on the mechanisms of the CO2/H2 reaction on a CO-precipitated CuO/ZnO/Al2O3 catalyst

“…This species was commonly detected in experiments [26,27]. (ii) The pathway involves the reverse water-gas-shift (RWGS, reaction 4) reaction, where CO 2 is first converted to CO which is then hydrogenated to form methanol (reaction 2).…”

A Brief Review of Carbon Dioxide Hydrogenation to Methanol Over Copper and Iron Based Catalysts

“…(3)) [31]. As well as, the redox mechanism for the RWGS reaction can be easily modeled through the following scheme:…”

Fine tuning of the sizes and phases of ZrO2 nanocrystals

“…Zirconia (or doped zirconia) dispersed in ceramics has long been applied to increase the fracture toughness, strength, and hardness [1 3]. A widely used catalyst and catalyst support, zirconia catalyzes alcohol dehydration [4,5], CO/CO 2 hydrogenation [6], alkane isomerization [7], selective oxidation of alcohols and alkanes [8,9], hydrogenation of olefins [10], and isomerization of olefi ns and epoxides [11,12]. Different zirconia phases (monoclinic and tetragonal) exhibit different catalyst selectivities, such as in the selective hydrogenation of CO and alkane isomerization reactions [13 15].…”