Effects of oxide carriers on surface functionality and process performance of the Cu–ZnO system in the synthesis of methanol via CO2 hydrogenation

Physicochemical properties and CO2-to-methanol hydrogenation functionality (TR, 453–513 K; PR, 0.1–5.0 MPa) of Al2O3-, ZrO2-, and CeO2-supported Cu–ZnO catalysts are systematically addressed. Carriers control texture and metal surface exposure (MSA), while characterization of steady-state catalysts shows extensive CO2 and H2 coverage regardless of MSA, proving a crucial influence of the oxide carrier on the adsorption properties of the Cu–ZnO system. The kinetic dependence on pCO2 and pH2 confirms that dioxo-methylene intermediate hydrogenation is the rate-determining step (r.d.s.) at P < 0.1 MPa, while a low kinetic dependence on pressure (0.3–0.5) signals that product desorption is the r.d.s. at P > 0.1 MPa. The influence of flow rate on selectivity pattern discloses that CH3OH is the primary reaction product at T < 473 K, while at higher temperatures, CO forms by consecutive decomposition of methanol (MD) and parallel reverse water–gas shift (RWGS). Textural and chemical effects of the zirconia carrier confer superior performance on the Cu–ZnO/ZrO2 system, attaining a space time yield (STY) of 1.2 image at 10% conversion per pass.