CO hydrogenation to isobutyl alcohol is a promising route for CO transformation to high value-added products. However, the formation mechanism of isobutyl alcohol is complex, and its synthesis requires complex catalysts and harsh reaction conditions, which hinders the identification of active sites. Herein, we efficiently synthesized isobutyl alcohol under mild conditions over a simple Cu–ZrO2 catalyst by decreasing the Cu loading. The space–time yield (STY) of isobutyl alcohol using an optimal CZ-0.11 catalyst was as high as 61.3 g·Lcat–1·h–1 with a CO conversion of 19.2%, far surpassing the STY of the state-of-the-art isobutyl alcohol synthesis (44.6 g·Lcat–1·h–1) under harsh conditions. Decreasing the Cu loading increased the distribution of smaller Cu particles and clarified the structure–activity relationship of Cu–Zr interactions for isobutyl alcohol synthesis. The enhanced Cu–Zr interaction led to the formation of more electron-deficient Cu species on the CZ-0.11 catalyst, which enriched the linearly adsorbed CO on Cu, as demonstrated by in situ diffuse reflectance infrared Fourier-transform spectroscopy. Experimental and theoretical results revealed that coupling of the bicarbonate species on ZrO2 with the linearly adsorbed CO species on electron-deficient Cu clusters promoted the formation of C2 intermediates and finally produced isobutyl alcohol through rapid β-addition. These insights into the active sites for CO hydrogenation to isobutyl alcohol may guide further catalyst designs.
Yu Hao Wang,Wen Gui Gao,Hua Wang,Yan E. Zheng,Wei Na,Kong Zhai Li
A series of Cu–ZrO2 (CZ) catalysts with different surface area, copper surface area (SCu), oxygen vacancy concentration, and interaction between Cu and ZrO2 features were synthesized. The factors that could affect catalytic activity of CO2 hydrogenation to methanol were investigated. The interaction between Cu and ZrO2 is crucial for determining the catalytic activity. The catalyst possessing the strongest interaction between Cu and ZrO2, exhibited the optimum catalytic activity. The evolution of carbonaceous species and pyridine adsorption over CZ catalysts were investigated using in situ DRIFT spectroscopy. It is found that the hydrogenation of formate species is a rate-limiting step and H spillover plays an important role. The hydrogenation of formate species and H spillover are strongly dependent on the interaction. These results provide a new way of understanding the activity dependence and reaction mechanism of CO2 hydrogenation to methanol over CZ catalysts.
Yuewen Shao,Tingting Wang,Kai Sun,Zhanming Zhang,Lijun Zhang,Qingyin Li,Shu Zhang,Guangzhi Hu,Xun Hu
Oxides with different crystal phases can have important effects on the configuration of surface atoms, which can further affect the distribution of hydrogenation sites and acidic sites as well as the competitions of these varied types of catalytic sites. This could be potentially used to tailor the distribution of the products. In this study, zirconium oxides with different crystal phases supported copper catalysts were prepared for the hydrogenation of the biomass-derived furfural, vanillin, etc. The results showed that both calcination temperature and Cu species affected the shift of zirconia from tetragonal phase to the monoclinic phase. Monoclinic zirconia supported copper catalyst can effectively catalyze the hydrogenation of furfural to furfuryl alcohol via hydrogenation route due to its low amount of Brønsted acidic sites, although the surface area and the exposed metallic Cu surface area were much lower than the tetragonal zirconia supported copper catalyst. Zirconia with tetragonal or tetragonal/monoclinic phases supported copper catalysts contain abundant acidic sites and especially the Brønsted acidic sites, which catalyzed mainly the conversion of furfural via the acid-catalyzed routes such as the acetalization, rather than the hydrogenation. The acidic sites over the Cu/ZrO 2 catalyst played more predominant roles than the hydrogenation sites in determining the conversion of the organics like furfural and vanillin.
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