Modulation of Al2O3 and ZrO2 composite in Cu/ZnO-based catalysts with enhanced performance for CO2 hydrogenation to methanol

Abstract

Cu/ZnO/Al2O3 catalysts have been widely applied as industrial catalysts for methanol synthesis from syngas, but suffers low activity for CO2 hydrogenation to methanol. This study establishes highly active Cu catalysts through modulation of the composite of Al2O3 and ZrO2 in Cu/ZnO-based catalysts. The composition of Al2O3 and ZrO2 impacts the Cu dispersion, exposed surface area of Cu, the Cu0/(Cu0+Cu+) ratio and surface basicity. An appropriate content of Al2O3 and ZrO2 presents the higher Cu surface area, desirable ratio of Cu0/(Cu0+Cu+) and moderate-strong basic sites for effective CO2 adsorption/activation, giving rise to higher space-time yield of methanol (up to 648 gCH3OH·kgcat−1·h−1) than the commercial Cu catalyst. STY of methanol can be correlated with Cu surface area and Cu0/(Cu0+Cu+) ratio under the investigated conditions. The mechanistic analysis demonstrates that surface formate and methoxy species are the major intermediates. The methanol formation principally follows the formate-methoxy intermediate pathway.