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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]

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]

Note: The source of the background picture is from website. [Display omitted] • K 3 PO 4 could adjust Cu+/(Cu0 + Cu+) and promote catalytic performance greatly. • By regression analysis, Fe2+, Cu0, and medium base site show linear relation to C 2+ OH STY. • Significance level of above three factors follows Cu0＞Fe2+＞medium base sequence. • Conversion of Fe0 to Fe 3 C or Fe 3 O 4 leads to activity decrease. CO 2 hydrogenation to C 2+ OH is an effective way to diminish CO 2 emissions. Although challenges still exist in large-scale applications, CuFeZn catalysts attract extensive attention due to their low-cost. Herein, CuFeZn catalysts are modified by different amounts of K 3 PO 4 , (KP) 0.1 CuFeZn exhibits an excellent catalytic performance (total alcohols selectivity of 15.76 % at CO 2 conversion of 38.10 %, C 2+ OH/ROH fraction of 94.23 %, and C 2+ alcohols space–time-yield (STY) of 53.81 mg·mL−1·h−1). Combined with a series of characterization results, it is found that the effect of K 3 PO 4 is complex, and the proportion of Fe2+, Cu0 and medium base shows perfect linear relation to STY of C 2+ OH. The significance level of the above three factors is in the following sequence: Cu0＞Fe2+＞medium base. The introduction of K 3 PO 4 decreases the proportion of Fe2+ (active site for RWGS, the competitive reaction for C–C coupling) and increases the proportion of Cu+/(Cu++Cu0) (Cu+ is the active site for C–C coupling) due to the synergistic effect of Cu0 and Cu+, thereby improving the synthesis of C 2+ OH. Moreover, conversion of Fe0 to Fe 3 C or Fe 3 O 4 plays negative roles in the stability of the catalysts. [ABSTRACT FROM AUTHOR]