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CO2 hydrogenation to methanol was conducted using a set of activated carbon-supported Cu/ZnO/Al2O3 catalysts (CCZA) prepared by an incipient wetness impregnation approach. The effect of the Cu/Al ratio on the physicochemical properties of the catalysts, as well as their catalytic performance, were investigated. As Cu/Al ratio increased, the metallic Cu surface area displayed a reducing trend from 6.88 to 4.18 m2∙gcat−1, while the CO2 adsorption capacity exhibited an increasing trend. Meanwhile, aluminum content will have an important effect on the catalysts' reducibility and, thus, on their catalytic performance. The CCZA-2.7-de catalyst demonstrated the highest selectivity to methanol at 83.75% due to the excellent distribution and synergistic effect of copper and zinc. Although the CO2 conversion of CCZA-2.2-de and CCZA-3.5-de exceeded 10%, the CH3OH selectivity was less than 60%, which may be attributed to the larger particle sizes of ZnO and poor interactions in Cu–Zn. The present study offers a novel approach to increase the number of active sites, optimize the activated carbon-aided Cu/ZnO/Al2O3 catalyst's composition, and finally elucidate the mechanism for CO2 hydrogenation to methanol. [ABSTRACT FROM AUTHOR]

Cu/ZnO/Al 2 O 3 catalysts have been widely applied as industrial catalysts for methanol synthesis from syngas, but suffers low activity for CO 2 hydrogenation to methanol. This study establishes highly active Cu catalysts through modulation of the composite of Al 2 O 3 and ZrO 2 in Cu/ZnO-based catalysts. The composition of Al 2 O 3 and ZrO 2 impacts the Cu dispersion, exposed surface area of Cu, the Cu0/(Cu0+Cu+) ratio and surface basicity. An appropriate content of Al 2 O 3 and ZrO 2 presents the higher Cu surface area, desirable ratio of Cu0/(Cu0+Cu+) and moderate-strong basic sites for effective CO 2 adsorption/activation, giving rise to higher space-time yield of methanol (up to 648 g CH3OH ·kg cat −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. [Display omitted] • An appropriate amount of Al 2 O 3 and ZrO 2 favors the production of methanol. • The conversion rate of CO 2 is positively correlated with S Cu. • The relatively high content of Cu0 showed higher activity. • The increase of the number of moderate basic sites contributes to the improvement of CO 2 conversion rate. • The CO 2 hydrogenation to methanol followed the formate intermediate pathway. [ABSTRACT FROM AUTHOR]