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A series of Cu-ZnO-ZrO2 (CCZ) catalysts were prepared by the solvothermal method with different solvothermal times (1 h, 3 h, 6 h, and 12 h). The physicochemical properties of these catalysts and the catalytic performance for CO2 hydrogenation to methanol were studied. The highest methanol yield was achieved when the solvothermal time was 6 h (CCZ-6). Furthermore, we found that the copper surface area (SCu) increases and then decreases with an increase in the solvothermal time and that there is a strong correlation between the methanol yield and the SCu. This research highlights the crucial influence of the solvothermal time on the structure and catalytic behavior of Cu-ZnO-ZrO2 catalysts, providing a valuable reference for the development of efficient catalysts. [ABSTRACT FROM AUTHOR]

A series of CuO-ZnO–ZrO2 (CZZ) catalysts were synthesized via a solvothermal method. The effects of four saturated monohydric alcohols (methanol, ethanol, n-propanol, and n-butanol) as solvents on the physicochemical properties and catalytic performance for the direct synthesis of methanol from CO2 hydrogenation of the prepared catalysts were investigated. N2 physical adsorption, X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray (EDX) spectroscopy mapping, reactive N2O adsorption, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction by H2 (H2-TPR), and temperature programmed desorption (H2-TPD, CO2-TPD) techniques were used to characterize the catalysts. The results indicate that the catalyst prepared with methanol as solvent (CZZ-M) has the smallest Cu crystallites and the largest metallic Cu surface area, thus exhibiting the highest methanol yield of 7.4% at 240 °C, 3.0 MPa, H2:CO2 of 3 (v/v), and GHSV of 2400 mL/(gcat·h). [ABSTRACT FROM AUTHOR]

Abstract Three CuO-ZnO-ZrO 2 -M x O y (CZZM, M = Cr, Mo and W) mixed oxides were prepared by a co-precipitation method and tested as catalysts for methanol synthesis from CO 2 hydrogenation. The catalysts were characterized by XRD, N 2 adsorption/desorption, XPS, reactive N 2 O adsorption, H 2 -TPR, and CO 2 -TPD techniques. The results indicated that the methanol selectivity and yield of the CuO-ZnO-ZrO 2 catalyst noticeably increased by the additions of MoO 3 and WO 3 , but slightly decreased by Cr 2 O 3 doping. Combining with the characterization results, the difference in methanol yield over the three catalysts can be attributed to the differences in their BET specific surface areas (S BET) and adsorption capacities for CO 2 , while the methanol selectivity is closely correlated to the ratio of surface contents of Zn to Cu, as well as the fraction of strong basic sites in the total basic sites of the investigated catalysts. Graphical abstract Image 1 Highlights • CuZnZrM (M = Cr/Mo/W) mixed oxides were used for methanol synthesis from CO 2 and H 2. • The CuO-ZnO-ZrO 2 -WO 3 catalyst shows the highest activity and methanol selectivity. • Methanol yield is related to the S BET and CO 2 adsorption capacity of the catalyst. • Methanol selectivity is closely related to the surface composition and basicity. [ABSTRACT FROM AUTHOR]

A series of WO 3 modified CuO-ZnO-ZrO 2 mixed oxides with different WO 3 contents (0–20 at.%) were prepared by co-precipitation method and used as catalyst for methanol synthesis from CO 2 hydrogenation. The effects of WO 3 content on the physicochemical and catalytic properties of the CuO-ZnO-ZrO 2 -WO 3 catalysts were investigated by X-ray diffraction, X-ray photoelectron spectra, temperature-programed reduction of hydrogen, temperature-programed desorption of CO 2 , N 2 adsorption and desorption, reactive N 2 O adsorption, and activity testing. The results indicated that both CO 2 conversion and methanol selectivity of the CuO-ZnO-ZrO 2 catalyst was enhanced by the addition of small amounts (2 and 5 at.%) of WO 3 . However, the activity was significantly decreased by the addition of excessive WO 3 (20 at.%). The activity was closely related to the specific surface area of metallic Cu ( S Cu ), amount of weak basic sites, and reducibility of the catalyst. [ABSTRACT FROM AUTHOR]

The influence of TiO 2 , ZrO 2 , and TiO 2 –ZrO 2 mixed oxide on the catalytic performance of CuO–ZnO catalyst in the methanol synthesis from CO 2 hydrogenation was studied. The catalysts were prepared by oxalate co-precipitation method and characterized by TGA, N 2 adsorption, XRD, reactive N 2 O adsorption, XPS, H 2 -TPR, H 2 -TPD, and CO 2 -TPD techniques. Characterization results reveal that all the additives improve the CuO dispersion in the catalyst body and increase the Cu surface area and adsorption capacities of CO 2 and H 2 . The results of catalytic test reveal that the additives increase both the CO 2 conversion and methanol selectivity, and TiO 2 –ZrO 2 mixed oxide is more effective than single components of TiO 2 or ZrO 2 . Moreover, the activity of methanol synthesis is correlated directly with CO 2 adsorption capacity over the catalysts. [ABSTRACT FROM AUTHOR]

A series of CuO–ZnO–ZrO 2 catalysts are synthesized by a surfactant-assisted co-precipitation method and tested for the synthesis of methanol from CO 2 hydrogenation. The effects of calcination temperature on the physicochemical properties of as-prepared catalysts are investigated extensively by TG-DSC, N 2 adsorption/desorption, XRD, N 2 O chemisorption, SEM/TEM, EDX, XPS, TPR, H 2 -TPD and CO 2 -TPD techniques. The results show that the size of copper particles increases with the increase in calcination temperature, leading to the decrease in turnover frequency (TOF) for methanol formation. Moreover, compared with the counterparts prepared by the conventional co-precipitation method, the CuO–ZnO–ZrO 2 catalysts prepared by this novel method show significantly high methanol selectivity. The superior property of the prepared CuO–ZnO–ZrO 2 catalyst can be attributed to the formation of more amounts of Cu–ZnO x and/or Cu–ZrO x species resulted from the homogeneous element distribution, intimate interface contact of Cu species with ZnO and/or ZrO 2 , and to porous structure with larger pore size. [ABSTRACT FROM AUTHOR]

A series of CuO-ZnO-TiO2 catalysts with various TiO2 loadings were prepared by using a co-precipitation method. The prepared catalysts were characterized by using X-ray diffraction (XRD), N2 adsorption, reactive N2O adsorption, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), hydrogen temperature programmed desorption (H2-TPD), and CO2-TPD techniques, and tested the extent of methanol synthesis from carbon dioxide (CO2) hydrogenation. The results indicate that the addition of TiO2 to the CuO-ZnO catalyst makes the copper species exist in an amorphous-like structure or in much smaller crystallites, which promotes the reduction of CuO. Upon increasing the TiO2 loading, the metallic Cu surface area ( SCu) of the catalyst rises first and then decreases, exhibiting a maximum at a TiO2 loading of 10 %. The results of the catalytic experiments reveal that the addition of TiO2 favors the production of methanol, and an optimum catalytic activity is obtained at a TiO2 loading of 10 %. Moreover, the methanol yield increases linearly with the SCu of the catalysts, thereby indicating that the addition of TiO2 enhances the SCu but not the intrinsic activity. [ABSTRACT FROM AUTHOR]

Abstract: A series of Cu/ZrO2 catalysts with various La loadings for methanol synthesis from CO2 hydrogenation were prepared by a urea–nitrate combustion method. The catalysts were characterized with N2 adsorption, XRD, reactive N2O adsorption, XPS, TPR, H2-TPD and CO2-TPD techniques, and tested for methanol synthesis from CO2 hydrogenation. With increasing La loading, the Cu surface area increases first and then decreases, whereas the amount of basic site over catalysts increases continuously. The results of catalytic test reveal that a linear relationship exists between the conversion of CO2 and the Cu surface area. Moreover, it is found for the first time that the selectivity to methanol is related to the distribution of basic site on the catalyst surface. The presence of La favors the production of methanol, and the optimum catalytic activity is obtained when the amount of La doping is 5% of the total amount of Cu2+ and Zr4+. [Copyright &y& Elsevier]

Abstract: Cu/ZnO/ZrO2 catalysts were prepared by a route of solid-state reaction and tested for the synthesis of methanol from CO2 hydrogenation. The effects of calcination temperature on the physicochemical properties of as-prepared catalysts were investigated by N2 adsorption, XRD, TEM, N2O titration and H2-TPR techniques. The results show that the dispersion of copper species decreases with the increase in calcination temperature. Meanwhile, the phase transformation of zirconia from tetragonal to monoclinic was observed. The highest activity was achieved over the catalyst calcined at 400°C. This method is a promising alternative for the preparation of highly efficient Cu/ZnO/ZrO2 catalysts. [Copyright &y& Elsevier]

Abstract: A series of CuO–ZnO–ZrO2 (CZZ) catalysts were synthesized by a glycine–nitrate combustion method and characterized by XRD, BET, N2O chemisorption, SEM and TPR techniques. The results show that the physicochemical properties of the catalysts are strongly influenced by the fuel content used in the combustion process. The dispersion of CuO exhibits an inverse-volcano variation trend with an increase in the glycine amount from 50% to 150% of the stoichiometry. The relationship between physiochemical properties and the fuel content is discussed in detail in terms of combustion temperature. The catalytic performance for the synthesis of methanol from CO2 hydrogenation was examined. The CZZ catalyst exhibits an optimum catalytic activity when 50% of stoichiometric amount of glycine was used. The turnover frequency has been calculated for various CZZ catalysts, and it reveals that the catalytic activities depend not only on the surface area of metallic copper but also on the phase state of ZrO2. [Copyright &y& Elsevier]

Abstract: Various CuO–ZnO–ZrO2 (CZZ) catalysts have been synthesized by urea–nitrate combustion method and their performances for methanol synthesis from CO2 hydrogenation have been investigated. The effects of urea/nitrate ratio on physicochemical and catalytic properties were studied by XRD, BET, H2-TPR and reactive N2O adsorption techniques. The results show that when 50% of stoichiometric amount of urea was used, the CZZ catalyst exhibited an optimum catalytic behavior. The combustion method was found to be a simple, fast and valuable route for the preparation of CZZ catalyst for methanol synthesis from CO2 hydrogenation. [Copyright &y& Elsevier]

Abstract: A series of γ-Al2O3 samples modified with various contents of sulfate (0–15wt.%) and calcined at different temperatures (350–750°C) were prepared by an impregnation method and physically admixed with CuO–ZnO–Al2O3 methanol synthesis catalyst to form hybrid catalysts. The direct synthesis of dimethyl ether (DME) from syngas was carried out over the prepared hybrid catalysts under pressurized fixed-bed continuous flow conditions. The results revealed that the catalytic activity of SO4 2−/γ-Al2O3 for methanol dehydration increased significantly when the content of sulfate increased to 10wt.%, resulting in the increase in both DME selectivity and CO conversion. However, when the content of sulfate of SO4 2−/γ-Al2O3 was further increased to 15wt.%, the activity for methanol dehydration was increased, and the selectivity for DME decreased slightly as reflected in the increased formation of byproducts like hydrocarbons and CO2. On the other hand, when the calcination temperature of SO4 2−/γ-Al2O3 increased from 350°C to 550°C, both the CO conversion and the DME selectivity increased gradually, accompanied with the decreased formation of CO2. Nevertheless, a further increase in calcination temperature to 750°C remarkably decreased the catalytic activity of SO4 2−/γ-Al2O3 for methanol dehydration, resulting in the significant decline in both DME selectivity and CO conversion. The hybrid catalyst containing the SO4 2−/γ-Al2O3 with 10wt.% sulfate and calcined at 550°C exhibited the highest selectivity and yield for the synthesis of DME. [Copyright &y& Elsevier]

A series of Cu@ZrO 2 -U framework catalysts derived from Cu@UiO-67 precursors with adjustable copper loadings were constructed by the deposition-precipitation method, and the catalytic activities of methanol synthesis via CO 2 hydrogenation were investigated. The optimized 20-Cu@ZrO 2 -U catalyst showed the best catalytic activity. At 3 MPa and 260 °C, the space-time yield of CH 3 OH (STY CH3OH) reached 2.28 mmol CH3OH /(g cat ·h), which was 3.5 times higher than that of 20-Cu/ZrO 2. The catalyst of 20-Cu@ZrO 2 -U also showed good stability during the 100-h time on stream test. The catalysts were further characterized by XRD, N 2 sorption, TEM, XPS, H 2 -TPR, CO 2 /H 2 -TPD and in situ DRIFTS. The characterization results showed that the stable ZrO 2 framework derived from UiO-67 is propitious to the confine of copper nanoparticles and formation of Cu+-ZrO 2 interfacial sites, which should be responsible for the excellent performance of methanol synthesis. Moreover, in situ DRIFTS was used to probe that the methanol synthesis via CO 2 hydrogenation over 20-Cu@ZrO 2 -U follows a HCOO∗-intermediated reaction pathway. [Display omitted] • A novel Cu@ZrO 2 -U framework catalyst was constructed by Cu@UiO-67 precursor strategy. • The optimized catalyst of 20-Cu@ZrO 2 -U was shown to form rich Cu+-ZrO 2 interfaces. • The methanol yield of 20-Cu@ZrO 2 -U was 3.5 times higher than 20-Cu/ZrO 2 catalyst. • The methanol productivity depends on the ratio of Cu+/Cu0 regulated by Cu+-ZrO 2 interface. • The methanol synthesis mechanism of Cu@ZrO 2 -U follows a HCOO∗-intermediate pathway. [ABSTRACT FROM AUTHOR]

In this study, a series of Cu–Ce 1-x Zr x O 2 (x = 0, 0.2, 0.5, 0.8, 1) catalysts were prepared by an eco-friendly and facile solid-phase grinding method. The effect of different Ce/Zr molar ratios on the performance of Cu–Ce 1-x Zr x O 2 catalysts for CO 2 hydrogenation to methanol was investigated. The results showed that the Cu–Ce 0.5 Zr 0·5 O 2 catalyst had the best catalytic performance, with CO 2 conversion of 15.2 % and methanol yield of 7.5 % at GHSV = 3600 mL/(g cat ·h)); when GHSV was increased to 20,000 mL/(g cat ·h), the space-time yield of methanol reached 270.8 g CH3OH /(kg cat ·h). X-ray diffraction (XRD), scanning electron microscope (SEM), N 2 adsorption-desorption, N 2 O chemisorption, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction by H 2 (H 2 -TPR), and temperature programmed desorption (H 2 -TPD, CO 2 -TPD) techniques were used to characterize the catalysts, and the higher reactivity of Cu–Ce 0.5 Zr 0·5 O 2 can be attributed to more Cu0 species, defect oxygen and basic sites. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) results revealed that the hydrogenation of CO 2 to methanol occurred through the formate intermediate pathway. This work proposed an eco-friendly and facile method for the preparation of high-performance Cu-based catalysts and the systematic study provided a deep insight for the development of high-performance Cu-based catalysts for methanol synthesis from CO 2 hydrogenation. [ABSTRACT FROM AUTHOR]

A serials of copper catalysts supported on TiO 2 modified with different amount of MgO were prepared by an impregnation method and tested for methanol synthesis from CO 2 hydrogenation. The physico-chemical properties of the catalysts were characterized using XRD, N 2 physisorption, N 2 O titration, XPS, H 2 -TPR and CO 2 -TPD techniques. With the increase in amount of MgO, the Cu surface area initially increases and then decreases. The modification of TiO 2 with MgO hinders the interaction between CuO and TiO 2 , resulting in a decline in the reducibility of CuO. Furthermore, the number and strength of the moderate and strong basic sites over the surface of catalyst increase with increasing MgO loading. The catalyst exhibits an optimum catalytic activity as the content of MgO is 1 wt%. The CO 2 conversion is determined by the Cu specific surface area and the interaction between CuO and TiO 2 , and the CH 3 OH selectivity is related to the surface basicity of catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu/ZnO x particles were encapsulated in UiO-66 by deposition–precipitation method. • Both of metal loading and Cu/Zn mole ratio can regulate the Cu-Zn interaction. • The amount of Cu/ZnO x interfaces is related to the methanol synthesis performance. A series of Cu-Zn catalysts encapsulated by Zr-based metal–organic frameworks (UiO-66) with various metal loadings and Cu/Zn mole ratios were prepared by the deposition–precipitation method, and the catalytic activities were investigated by CO 2 hydrogenation to methanol. The results showed that Cu-Zn@UiO-66 catalyst with Cu-Zn loading of 35 wt% and Cu/Zn mole ratio of 2.5 had the best catalytic activity. At 240 °C and 3 MPa, this catalyst gave the excellent catalytic activity with the highest methanol yield of 9.1%, and showed good reaction stability during 100-hour catalytic test. The catalysts were characterized by N 2 -sorption, XRD, TEM, XPS, H 2 -TPR and CO 2 -TPD. Such excellent performance benefits from the ultrasmall nanoparticles (NPs) and abundant Cu/ZnO x interfaces confined in the UiO-66, and the strong interaction between Cu and ZnO promotes the CO 2 conversion and methanol synthesis. [ABSTRACT FROM AUTHOR]