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Abstract: A mild strategy to form ethylene glycol via photocatalytic C-C coupling of methanol and formaldehyde was developed with high atomic efficiency over M/TiO2 under UV-light irradiation. The presence of both methanol and formaldehyde significantly enhanced the formation of ethylene glycol with selectivity of 80%. A radical reaction mechanism for the photocatalytic C-C coupling of methanol and formaldehyde into ethylene glycol was proposed based on electron spin resonance and isotope labeling experiment as well as quantum chemical calculations.Graphical Abstract: [ABSTRACT FROM AUTHOR]

A series of industrial related Cu/ZnO/AlO methanol catalysts with different compositions were prepared by parallel coprecipitation method at neutral condition. The structural properties were characterized through BET, XRD, TEM, TPD and TPR, and the catalytic performances were evaluated on a 4-tube stainless steel continuous flow fixed-bed microreactor. The influence of composition on performances was investigated. The results show that AlO increases the long-term stability of catalysts due to stabilizing effect, meanwhile, Al also promotes the formation of zincian malachite phase as the precursor during coprecipitation and aging. Furthermore, AlO surface acidity also affects the byproducts selectivity. Cu/Zn ratio influences the activity of catalysts which could be traced back to precursor phases. ZnO also affects the long-term stability probably derived from its spacing effect. Taking activity, long-term stability and product purity all into consideration, an optimized composition was found to be with 2.8 ≤ n(Cu)/ n(Zn) ≤ 3.0 and 10 ≤ n(Al) ≤ 12, over which the performances are better than that of commercial C307 catalyst in our experiments. Graphical Abstract: [ABSTRACT FROM AUTHOR]

A series of Cu/ZnO/Al 2 O 3 catalysts with the total weight percentage of Cu and ZnO from 9.94 wt.% to 44.5 wt.% have been prepared by ammonia deposition −precipitation method and tested for methanol synthesis from CO 2 hydrogenation. A Cu/Zn/Al layered double hydroxides (LDHs) precursor can be formed in situ on the surface of microspherical Al 2 O 3 which acts as both support and sole source of Al 3+ cations. With increase of total Cu and ZnO loading, the dispersion of copper and reducibility of CuO decline continuously, while the exposed copper surface area increases gradually. In addition, the formation of LDHs results in a stronger both basicity and acid strength on the catalyst surface. It is found that the CO 2 conversion increases linearly with increase of the Cu and ZnO loading. The methanol selectivity for the catalyst with low total metal loading (9.94 wt.%) is much lower than those for other catalysts, though it increases with increasing loading, which can be mainly assigned to the much smaller Cu particle size (<5 nm) and the higher ratio of isolated CuO phase. Moreover, the Cu/ZnO/Al 2 O 3 catalyst with relatively high total metal loading (44.50 wt.%) still exhibits a considerable stable catalytic performance due to the formation of LDH structure. [ABSTRACT FROM AUTHOR]

A series of fluorinated Cu/Zn/Al/Zr hydrotalcite-like compounds are synthesized by incorporation of different amount of (AlF 6 ) 3− into hydrotalcite-like sheets. The fluorine-modified Cu/ZnO/Al 2 O 3 /ZrO 2 catalysts are then obtained by calcination and reduction of fluorinated precursors. With increasing of F/Al atomic ratios, the Cu particle size increases continuously and the Cu surface area and dispersion decrease gradually, as well as the amount of moderately and strongly basic sites first increases significantly and then decreases. The catalytic performance for the methanol synthesis from CO 2 hydrogenation is examined. The change of CO 2 conversion is small when F/Al ≤ 0.8, while the CO 2 conversion decreases remarkably with further increase of fluorine content. It is also found that the CH 3 OH selectivity is closely related to the distribution of basic sites and the selectivity of CH 3 OH takes a volcanic trend with increased fluorine content. The introduction of suitable amount of (AlF 6 ) 3− into the hydrotalcite-like structure can enhance the methanol yield markedly and the fluorine-modified catalysts with F/Al = 0.83 affords the substantial stability and the best catalytic performance. [ABSTRACT FROM AUTHOR]

Cu/Zn/Al/Zr catalysts with Cu 2+ :Zn 2+ :Al 3+ :Zr 4+ = 2:1: x :0.1 ( x = 0.6–1.5) were prepared from hydrotalcite-like precursors by co-precipitation method and tested for the CO 2 hydrogenation to methanol. Both Cu/Zn/Al/Zr hydrotalcite-like and malachite phase were formed at low Al content. However, with the increase of Al content, the yield of hydrotalcite-like phase increased and phase-pure Cu/Zn/Al/Zr hydrotalcite-like compound was obtained for x ≥ 0.9. In addition, both the specific surface area and the dispersion of Cu increased gradually with the increase of Al, while the exposed Cu surface area first increased until Al content was 27.9 mol%, then decreased. The results of catalytic test for CO 2 hydrogenation revealed that Cu/Zn/Al/Zr catalysts via phase-pure hydrotalcite-like compounds exhibited much better catalytic performance with higher CO 2 conversion and CH 3 OH selectivity compared with the catalyst derived from mixed phase (hydrotalcite-like and malachite). The Cu/Zn/Al/Zr catalysts with Cu 2+ :Zn 2+ :Al 3+ :Zr 4+ = 2:1:1.2:0.1 resulting from phase-pure hydrotalcite-like precursors afforded the substantial stability and the best catalytic performance. [ABSTRACT FROM AUTHOR]

Highlights: [•] Introduction of fluorine shows a significant influence on properties of catalysts. [•] The lower CO2 conversion is attributed to the decrease of exposed Cu surface area. [•] The TOF increase significantly owing to the higher amount of easily reducible CuO. [•] The CH3OH selectivity highly increases due to the increase of strongly basic sites. [•] The introduction of fluorine is beneficial for the production of methanol. [ABSTRACT FROM AUTHOR]

A series of Cu–Zn–Al–Zr precursor materials are prepared by coprecipitation at different pH values (6.0–11.0) and treated under hydrothermal condition. Zincian malachite is formed as the main phase at the low pH of 6.0 and 7.0, and is replaced by hydrotalcite-like phases with increasing the pH. After calcination and reduction of precursors, Cu/ZnO/Al 2 O 3 /ZrO 2 catalysts are obtained and tested for methanol synthesis from CO 2 hydrogenation at the reaction temperature of 463 K. With increasing pH, the Cu particle size first increases until pH 9.0 and then decreases. Compared with the sample resulting from well-crystallized zincian malachite (pH 7.0), the catalysts derived from phase-pure hydrotalcite-like precursors (pH ≥ 9.0) exhibit lower BET specific surface area and lower specific Cu surface area. In addition, due to the smaller of Cu particle size and the stronger interaction among Cu and ZnO, the catalytic activity for the Cu/ZnO/Al 2 O 3 /ZrO 2 catalysts via the hydrotalcite-like precursors is higher than that for the catalysts derived from zincian malachite precursors at low reaction temperature. A maximum CH 3 OH yield of 0.087 g gcat −1 h −1 with the CO 2 conversion of 10.7% and the CH 3 OH selectivity of 81.8% at 463 K and 5.0 MPa is obtained over the Cu/ZnO/Al 2 O 3 /ZrO 2 catalyst prepared at pH 9.0. [ABSTRACT FROM AUTHOR]

The core–shell catalysts with Cu and Cu/ZnO nanoparticles coated by mesoporous silica shells are prepared for CO 2 hydrogenation to methanol. With the confined effect of silica shell, the size of Cu nanoparticles is only about 5.0 nm, which results in high activity for CO 2 conversion. The CH 3 OH selectivity is enhanced significantly with the introduction of ZnO. The core–shell structured catalysts endow the Cu nanoparticles trapped inside with excellent anti-aggregation and no deactivation is observed with time-on-stream. Therefore, the core–shell Cu/ZnO@m-SiO 2 catalyst exhibits the maximum CH 3 OH yield with high stability. [ABSTRACT FROM AUTHOR]

Abstract: Fluorine-modified Cu/Zn/Al/Zr catalysts were prepared by calcination of the fluorine-containing Cu/Zn/Al/Zr hydrotalcite-like compounds and tested for CO2 hydrogenation to methanol. The results revealed that the CH3OH selectivity was greatly improved by the remarkable increase of the proportion of strongly basic sites, while the CO2 conversion decreased slightly. It is also found that the activity of catalysts is closely related to the synergy between the Cu and basic sites. The CH3OH yield for the fluorine-modified Cu/Zn/Al/Zr catalysts was higher than that for the fluorine-free catalysts; thus, the introduction of fluorine favored the methanol formation. [Copyright &y& Elsevier]

Abstract: A series of La–M–Cu–Zn–O (M = Y, Ce, Mg, Zr) based perovskite-type catalysts are prepared by sol–gel method and characterized by XRD, BET, TPR, N2O-adsorption, XPS and TPD techniques. The results indicate that all the catalysts exhibit La2CuO4 perovskite structure. The addition of Ce, Mg and Zr lead to smaller particles, lower reduction temperature, higher Cu dispersion, larger amount of hydrogen desorption at low temperature and more amount of basic sites. However, Y has less affects on the physicochemical properties. The catalysts derived from perovskite-type precursors show high selectivity for methanol, which is correlated with the Cuα+ species that exists in the reduced catalysts. More exposed Cu surface area is favorable for high CO2 conversion. [Copyright &y& Elsevier]

Abstract: A series of Cu/Zn/Al/Zr catalyst derived from hydrotalcite-containing precursors were prepared by introducing the Cu2+ at different stages of Zn/Al/Zr hydrotalcite-like compounds formation and reconstruction and the catalytic performance for the synthesis of methanol from CO2 hydrogenation was examined. The results showed that the physicochemical properties of the catalysts, such as the Cu2+ content located in the layer structure of precursor, the exposed Cu surface area, the Cu+ and Cu0 content on the reduced surface and the ratio of Cu+/Cu0 were greatly influenced by the Cu2+ introduction procedure. The Cu/Zn/Al/Zr catalyst prepared by adding the Cu2+ into the precursor at the reconstructed stage exhibited the best catalytic performance due to the highest exposed Cu surface area and the ratio of Cu+/Cu0. [Copyright &y& Elsevier]