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To achieve the near-zero carbon emissions from chemical looping hydrogen generation (CLHG) power plant, two novel systems were proposed in this study: one integrates CLHG with ammonia decomposition for hydrogen production (ADHP) and CO 2 hydrogenation to methanol (CHM), while the other integrates CLHG with CHM and CO 2 compression storage (CCS). The performance of these two integrated systems was evaluated through analyses of economy, energy, exergy, and ecology (4E). The findings reveal that the CLHG-CHM-CCS system is more economically competitive and environmentally favorable than the CLHG-ADHP-CHM system. Its maximum net present value increases by 2.373×108 $, and annual CO 2 emissions decreases by 361.401 t. Meanwhile, the system's profitable allowable maximum purchasing price of natural gas increases by 0.036 $/Nm3, while its minimum selling price of methanol decreases by 47.583 $/t. However, the CLHG-ADHP-CHM system exhibits improvements in both energy efficiency and exergy efficiency, with improvements of 1.88% and 2.34%, respectively, compared to the CLHG-CHM-CCS system. Moreover, reactors within the CLHG subsystem account for 42.60% of its total exergy loss, offering a potential 3.275 MW improvement. • Two novel CLHG-based systems for achieving near-zero carbon emissions were proposed. • Economy, energy, exergy and ecology analysis for the systems was carried out. • CLHG-CHM-CCS system proved to be more economical. • Carbon capture rates for both systems exceed 99.5%. • Reactors within the CLHG subsystem account for 42.60% of its total exergy loss. [ABSTRACT FROM AUTHOR]

Cu/ZnO/C–P were prepared via the deposition-precipitation for CO 2 hydrogenation to methanol. At 280 °C, Cu/ZnO/C–P reached the maximum methanol space-time yield (STY) of 0.66 g CH3OH ·g cat −1·h−1, significantly higher than Cu/ZnO (0.48 g CH3OH ·g cat −1·h−1). The addition of C–P escalated the reduction of Cu2+ and made Cu/ZnO interface much tighter. Phosphorus-doped Carbon (C–P) was not only favorable for the formation of Cu/ZnO contact interfaces and boosted Cu0 amount at the Cu/ZnO interfaces, but also further strengthened the interaction between Cu0 and ZnO. Cu0/ZnO interfaces also improved the adsorption and activation of CO 2 and H 2 , eventually advanced methanol formation. The variation trend between methanol STY and Cu0 species content at the Cu/ZnO interface was in good agreement with each other. Cu0 species strongly interacted with ZnO at the Cu/ZnO contact interfaces may be indispensable for methanol generation on Cu/ZnO/C–P. The Cu0/ZnO interface serves as the active center to efficiently escalate CO 2 hydrogenation to methanol. [Display omitted] • Phosphorus-doped carbon materials were synthesized using a simple hydrothermal method. • C–P promoted the generation of Cu/ZnO interfaces and enhanced the interaction between Cu0 and ZnO. • Cu0/ZnO interfaces were the active sites of Cu/ZnO/C–P for CO 2 hydrogenation to methanol. • Cu/ZnO modified by appropriate amount of C–P promoted the methanol formation. [ABSTRACT FROM AUTHOR]

Converting CO2 into methanol on a large scale is of great significance in the sustainable methanol economy. Zirconia species are considered to be an essential support in Cu‐based catalysts due to their excellent properties for CO2 adsorption and activation. However, the evolution of Zr species during the reaction and the effect of their structure on the reaction pathways remain unclear. Herein, single‐site Zr species in an amorphous SiO2 matrix are created by enhancing the Zr−Si interaction in Cu/ZrO2‐SiO2 catalysts. In situ X‐ray absorption spectroscopy (XAS) reveals that the coordination environment of single‐site Zr is sensitive to the atmosphere and reaction conditions. We demonstrate that the CO2 adsorption occurs preferably on the interface of Cu and single‐site Zr rather than on ZrO2 nanoparticles. Methanol synthesis in reverse water‐gas‐shift (RWGS)+CO‐hydro pathway is verified only over single‐dispersed Zr sites, whereas the ordinary formate pathway occurs on ZrO2 nanoparticles. Thus, it expands a non‐competitive parallel pathway as a supplement to the dominant formate pathway, resulting in the enhancement of Cu activity sixfold and twofold based on Cu/SiO2 and Cu/ZrO2 catalysts, respectively. The establishment of this dual‐channel pathway by single‐site Zr species in this work opens new horizons for understanding the role of atomically dispersed oxides in catalysis science. [ABSTRACT FROM AUTHOR]

Methanol formation from CO2 hydrogenation attracts great attention in view of utilization of carbon resources. However, CO2 transformation to methanol is challenging because of the thermodynamic equilibrium restriction and water‐caused catalyst deactivation. It is desired, therefore, to develop highly active, selective and stable catalysts for CO2 hydrogenation to methanol. Herein, we propose a novel tandem catalyst composed of Cu−ZnO−Al2O3−ZrO2 (CZAZ) and Cu−MOR for highly selective conversion of CO2 to methanol. During CO2 hydrogenation by the CZAZ catalyst, the by‐product methane is continuously transformed to methanol through reaction with water via the Cu−MOR catalyst, thus enhancing CO2 conversion and methanol selectivity. Under mild reaction conditions (200 °C and 3.0 MPa), high CO2 conversion (40.7 %) and methanol selectivity (97.6 %) are achieved, outperforming state‐of‐the‐art CO2 hydrogenation catalysts. Further, water‐caused deactivation of the catalyst through aggregation and densification is suppressed owing to water consumption via methane oxidation to methanol, validating a high CZAZ/Cu−MOR tandem catalyst stability. [ABSTRACT FROM AUTHOR]

Carbon coated In 2 O 3 hollow tube catalysts embedded with ultra-low content ZnO quantum dots (QDs) were synthesized for CO 2 hydrogenation to methanol. [Display omitted] • Carbon coated In 2 O 3 hollow tubes embedded with ultra-low content ZnO QDs were obtained. • The QD heterojunction boosted the CO 2 adsorption and accelerated the electron transfer from In3+ to Zn2+. • The carbon acted as a medium for hydrogen spillover and promoted the electron transfer. • ZnO QDs facilitated the H 2 dissociation and activation. • The highest methanol STY could reach 0.98 g MeOH h−1 g cat −1 on ZnO-In 2 O 3 -II at 350 °C and 3 MPa. CO 2 hydrogenation coupled with renewable energy to produce methanol is of great interest. Carbon coated In 2 O 3 hollow tube catalysts embedded with ultra-low content ZnO quantum dots (QDs) were synthesized for CO 2 hydrogenation to methanol. ZnO-In 2 O 3 -II catalyst had the highest CO 2 and H 2 adsorption capacity, which demonstrated the highest methanol formation rate. When CO 2 conversion was 8.9%, methanol selectivity still exceeded 86% at 3.0 MPa and 320 °C, and STY of methanol reached 0.98 g MeOH h−1g cat −1 at 350 °C. The ZnO/In 2 O 3 QDs heterojunctions were formed at the interface between ZnO and In 2 O 3 (2 2 2). The ZnO/In 2 O 3 heterojunctions, as a key structure to promote the CO 2 hydrogenation to methanol, not only enhanced the interaction between ZnO and In 2 O 3 as well as CO 2 adsorption capacity, but also accelerated the electron transfer from In3+ to Zn2+. ZnO QDs boosted the dissociation and activation of H 2. The carbon layer coated on In 2 O 3 surface played a role of hydrogen spillover medium, and the dissociated H atoms were transferred to the CO 2 adsorption sites on the In 2 O 3 surface through the carbon layer, promoting the reaction of H atoms with CO 2 more effectively. In addition, the conductivity of carbon enhanced the electron transfer from In3+ to Zn2+. The combination of the ZnO/In 2 O 3 QDs heterojunctions and carbon layer greatly improved the methanol generation activity. [ABSTRACT FROM AUTHOR]

The Cu/CeO2-nanopolyhedrals and pure Cu/CeO2-nanorods with different sizes were synthesized for CO2 hydrogenation to methanol. With increasing the percentage composition of CeO2 nanorods, the surface concentrations of Cu+, Ce3+ and oxygen vacancies were gradually enhanced. However, the amount of surface Cu+ species and oxygen vacancies would be decreased instead if the size of pure CeO2 nanorods was too large. The variation tendency of catalytic performance for CO2 hydrogenation to methanol was well consistent with that of Cu+ species and oxygen vacancies. Cu/CeO2 nanorods with small size exhibited the strongest interaction in Cu-CeO2 interface and the highest methanol production activity among all Cu/CeO2 nano-catalysts. The small size of CeO2-nanorods obtained at NaOH concentration of 10 mol/L, hydrothermal temperature of 80 °C and hydrothermal time of 24 h showed the best catalytic performance (XCO2 = 5.8%, SCH3OH = 92.0%, YCH3OH = 5.3%) at 280 °C and 3 MPa. The stronger interaction accelerated the charge transfer between CuOx species and CeO2 nanorods, which produced the larger amount of surface Cu+ species and oxygen vacancies. The synergistic effect between reduced Cu species and oxygen vacancies improved methanol selectivity and was responsible for CO2 hydrogenation to methanol. [ABSTRACT FROM AUTHOR]

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• A novel system for near-complete utilization of captured CO 2 from CLHG was proposed. • The process modeling and parametric analysis for the system was performed. • The multi-objective optimization for the system was conducted. • The economy, energy and ecology analysis for the optimized system was carried out. • The system had an energy efficiency of 64.42% and a CO 2 utilization rate of 99.63%. To fully utilize the captured carbon dioxide (CO 2) from chemical looping hydrogen generation (CLHG), this study proposes a novel system that integrates it with ammonia decomposition for hydrogen production (ADHP) and CO 2 hydrogenation to methanol (CHM). A comprehensive analysis, encompassing parametric examination of major decision variables, multi-objective optimization for the system, as well as subsequent economy, energy, and ecology (3E) evaluations for the optimized system, were conducted. The findings reveal that the system can achieve optimal methanol production cost, net output power, and energy efficiency of 426.37 $/t, 56.762 MW, and 64.42 %, respectively. The optimized system demonstrates remarkable efficiency in capturing and utilizing CO 2 , boasting capture and utilization rates of 99.77 % and 99.63 %, respectively. Consequently, the energy derived from methanol product constitutes 79.92 % of the total output energy of 491.208 MW. Moreover, given that methane costs and methanol product revenue account for 43.01 % and 91.89 % respectively, of the annual total production cost of 2.933 × 108 $ and total revenue of 3.113 × 108 $, it is crucial to ensure that the purchasing price of methane remains under 0.2879 $/Nm3 and the selling price of methanol stays above 455.22 $/t to maintain profitability of the optimized system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electron-rich interface was created by introduction of TiO 2 into Al 2 O 3 support. • Adsorption and activation of CO 2 and carbonyl species are enhanced. • The reaction rate controlling step for RWGS pathway changed. • RWGS pathway becomes the dominant pathway. • Cu 13 /Ga-AT is a promising catalyst for CO 2 directional hydrogenation to methanol. Density functional theory investigations on CO 2 hydrogenation to methanol mechanisms over Cu 13 cluster loaded catalyst were performed. The results indicate that introducing TiO 2 into Al 2 O 3 promoted the residual electrons from Al 2 O 3 surface directionally transmitted to the interface formed by the loaded Cu 13 cluster and the support surface, thus created the electron-rich active interface. Incorporating single atom Ga promoter further gathered the residual electrons and stabilized the loaded Cu 13 clusters. The electron-rich property of the active interface promoted the chemical adsorption and activation of both CO 2 and the generated carbonyl species. Further favors the hydrogenating of carbonyl intermediates to methanol and effectively enhances the methanol selectivity. Moreover, CO 2 priors to hydrogenated to methanol via reverse water gas shift pathway over Cu 13 /Ga-AT computational model with changed reaction rate controlling step with reduced activation energy. This work offers a simple approach for efficient copper-based methanol synthesis catalysts through control of interface electron structure. [ABSTRACT FROM AUTHOR]

[Display omitted] • The structure of ZnO-In 2 O 3 HT-I catalyst promoted the creation of ZnO-In 2 O 3 solid solution. • The high quality oxygen vacancies on the surface of ZnO-In 2 O 3 solid solution favored methanol formation. • The solid solution strengthened electron transfer from Zn2+ to In3+, promoting localized electron imbalance. • The formate was the intermediate species for methanol formation on ZnO-In 2 O 3 solid solution. • The highest STY of methanol could reach 1.12 g MeOH h-1g cat -1 on ZnO-In 2 O 3 HT-I catalyst. Three ZnO-In 2 O 3 solid solution hollow tube catalysts with different microstructure were synthesized for CO 2 hydrogenation to methanol. ZnO could maintain In 2 O 3 hollow tube structure from being destroyed during the reaction, and the ZnO-In 2 O 3 solid solution could be in-situ formed on three catalysts during CO 2 hydrogenation reaction. Especially, the structure of ZnO-In 2 O 3 HT-I was most conducive to the creation of ZnO-In 2 O 3 solid solution. The ZnO-In 2 O 3 solid solution promoted electron transfer from ZnO to In 2 O 3 , resulting in an increase in the electron density of In 2 O 3 surface and local electron imbalance around the oxygen vacancy. ZnO facilitated electron delocalization in surface lattice oxygen. The surface electrons were transferred and concentrated on surface oxygen vacancy, which enhanced the electron density of surface oxygen vacancy especially for ZnO-In 2 O 3 HT-I catalyst. The "quality" of surface oxygen vacancy was raised, which boosted the adsorption and activation of H 2 and CO 2. The density functional theory (DFT) findings suggested that ZnO-In 2 O 3 solid solution caused the energy barrier of formate species to be lowered and those of carboxylate species to be raised, which was more favorable for methanol generation. Combined experimental and DFT data proved that the CO 2 hydrogenation to methanol proceeded via formate reaction route. Among the three ZnO-In 2 O 3 catalysts, ZnO-In 2 O 3 HT-I showed the highest methanol formation activity with 13.9% CO 2 conversion and 68% methanol selectivity at 350 °C, and the methanol space–time yield (STY) reached 1.12 g MeOH h−1 g cat −1. [ABSTRACT FROM AUTHOR]

• A theoretical study of the structure, electronic, and reaction mechanism of CO 2 to methanol on In 3 Ru(212) surfaces with different surface In/Ru ratio. • In 3 Ru could achieve high methanol selectivity by adding a H 2 O into each elementary step because it benefits the O H formation process. Designing high-performance catalyst is vital in the field of CO 2 methanolization. In this study, two In 3 Ru surfaces (In 3 Ru_i and In 3 Ru_r) were employed as computational models and the density functional theory was applied to study the influence of surface In/Ru ratio on their surface morphologies, reaction mechanisms and catalysis performance for methanol synthesis. Surface characterization reveals that In 3 Ru_i is higher in surface In/Ru ratio than In 3 Ru_r, and such difference facilitates CO 2 adsorption on In 3 Ru_r. Being different in surface In/Ru ratio, two surfaces exhibit distinct variations in the reaction mechanism of methanol formation. For In 3 Ru_i, the "Formate" pathway dominates the first CO 2 activation step which leads to methanol production. On the other hand, In 3 Ru_r prefers the "reverse water-gas shift" pathway (RWGS) in the initial step of CO 2 activation, but this mechanism is unable to generate CH 3 OH due to the kinetic limitation of CO* hydrogenation. Based on the microkinetic modeling, In 3 Ru_i is superior in both CO 2 production rate and CH 3 OH selectivity than the other one, suggesting higher surface In/Ru ratio benefits methanol formation, which complies well with the experiment. Overall, our study offers a new perspective with respect to how surface morphology of the bimetallic catalyst influences the reaction mechanisms of CO 2 hydrogenation. [Display omitted] [ABSTRACT FROM AUTHOR]

Cu/ZnO-based catalysts have been extensively and intensively studied for CO 2 hydrogenation to methanol due to their relatively superior catalytic performance. However, the mediocre methanol selectivity over Cu/ZnO-based catalysts has not been disclosed mainly because the predominant by-product CO formation activity fails to arouse any attention, significantly deterring the further catalyst optimization. The ZnOx-Cu nanoparticles (NP)-ZnO interface, derived from strong metal-support interactions (SMSI), has been recognized to be more active for methanol formation compared with the classical direct contact Cu-ZnO interface. In order to disclose the origin of the mediocre methanol selectivity, these two types of Cu-ZnO interfaces have been designed and constructed through carefully manipulating the synthesis and heat pre-treatment conditions of the powder model catalysts. Then, methanol and CO formation behaviors over these two interfaces have been explored thoroughly in actual reaction conditions. Finally, the origin of the mediocre methanol selectivity over Cu/ZnO-based catalysts has been proposed. This work provides unique insights for designing efficient Cu/ZnO-based catalysts with high methanol selectivity and yield and puts forward an effective strategy to investigate the catalytic behaviors over different interfaces in actual reaction conditions. [Display omitted] • The direct contact Cu-ZnO interface and the ZnOx-Cu nanoparticles (NP)-ZnO interface are successfully constructed. • The methanol and CO formation behaviors over the two interfaces have been explored. • The ZnOx-Cu NP-ZnO interface plays paramount roles in methanol formation. • The mediocre S MeOH of Cu/ZnO-based catalysts originates from the severe CO formation over the ZnOx-Cu NP-ZnO interface. • Rational designing powder model catalysts to simulate interfaces contributes to revealing their actual reaction behaviors. [ABSTRACT FROM AUTHOR]

CO2 valorization through chemical reactions attracts significant attention due to the mitigation of greenhouse gas effects. This article covers the catalytic hydrogenation of CO2 to methanol and dimethyl ether using Cu-Ho-Ga containing ZSM-5 and g-Al2O3 at atmospheric pressure and at temperatures of 210 °C and 260 °C using a CO2:H2 feed ratio of 1:3 and 1:9. In addition, the thermodynamic limitations of methanol and DME formation from CO2 was investigated at a temperature range of 100-400 °C. Cu-Ho-Ga/g-Al2O3 catalyst shows the highest formation rate of methanol (90.3 µmolCH3OH/gcat/h ) and DME (13.2 µmolDME/gcat/h) as well as the highest selectivity towards methanol and DME (39.9 %) at 210 °C using a CO2:H2 1:9 feed ratio. In both the thermodynamic analysis and reaction results, the higher concentration of H2 in the feed and lower reaction temperature resulted in higher DME selectivity and lower CO production rates. [ABSTRACT FROM AUTHOR]

Converting CO 2 into methanol on a large scale is of great significance in the sustainable methanol economy. Zirconia species are considered to be an essential support in Cu-based catalysts due to their excellent properties for CO 2 adsorption and activation. However, the evolution of Zr species during the reaction and the effect of their structure on the reaction pathways remain unclear. Herein, single-site Zr species in an amorphous SiO 2 matrix are created by enhancing the Zr-Si interaction in Cu/ZrO 2 -SiO 2 catalysts. In situ X-ray absorption spectroscopy (XAS) reveals that the coordination environment of single-site Zr is sensitive to the atmosphere and reaction conditions. We demonstrate that the CO 2 adsorption occurs preferably on the interface of Cu and single-site Zr rather than on ZrO 2 nanoparticles. Methanol synthesis in reverse water-gas-shift (RWGS)+CO-hydro pathway is verified only over single-dispersed Zr sites, whereas the ordinary formate pathway occurs on ZrO 2 nanoparticles. Thus, it expands a non-competitive parallel pathway as a supplement to the dominant formate pathway, resulting in the enhancement of Cu activity sixfold and twofold based on Cu/SiO 2 and Cu/ZrO 2 catalysts, respectively. The establishment of this dual-channel pathway by single-site Zr species in this work opens new horizons for understanding the role of atomically dispersed oxides in catalysis science., (© 2023 Wiley-VCH GmbH.)

Cr 2 O 3 was applied to study the modification of In 2 O 3 based catalysts for CO 2 hydrogenation to methanol reaction. Combined with X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), etc., the structure of the catalysts was characterized. The reaction performances for CO 2 hydrogenation to methanol were evaluated on a stainless-steel fix-bed reactor. The results showed that solid solutions were formed for the Cr 2 O 3 promoted In 2 O 3 catalysts. The important role of electronic interaction between Cr 2 O 3 and In 2 O 3 was revealed in the hydrogenation reaction. In 1.25 Cr 0.75 O 3 sample exhibited the highest methanol yield, which was 2.8 times higher than that of pure In 2 O 3 . No deactivation was observed for In 1.25 Cr 0.75 O 3 sample during the 50 hours of reaction. The improved catalytic performance may be due to the formation of the solid solutions and the highest amount of oxygen vacancies., (© 2023 Wiley-VCH GmbH.)

As part of concepts for chemical energy storage of excess chemical energy produced from renewable sources, we investigated the performance of CuO/ZnO catalysts supported on mesoporous carbon to convert CO2 hydrogenation to methanol. In this work, mesoporous carbon was used as the catalyst support for CuO-ZnO catalysts. Four catalysts with different precipitated precursors were synthesized and analyzed by N2-physisorption, X-ray diffraction (XRD), thermogravimetric analysis (TG-DTG), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that catalyst CZ-in situ had the highest turnover frequency (TOF) (2.8 × 10−3 s−1) and methanol production rate (0.8 mmol g−1·h−1). The catalysts for co-precipitation of copper and zinc on carbon precursors are more active. Cu/ZnO domains that are accessible to the reactant gas are another reason for the catalysts being active. The Cu-ZnO interface is crucial to methanol catalyst activity.

CO 2 hydrogenation to methanol plays an increasingly important role in fields of chemical engineering, energy generation and H 2 /CO 2 utilization, and the prohibitive costs result partially from the high operating pressures required for practical application. Thus, a hybrid catalyst/adsorbent consisting of Cu-ZnO-ZrO 2 supported on hydrotalcite (named CZZ@HT) was synthesized, characterized and analyzed in this study with the intent that the adsorbent hydrotalcite would enhance the local concentration of CO 2 and assist in catalyst dispersion. The as-prepared CZZ@HT catalyst containing 43.4 wt% of CuO-ZnO-ZrO 2 in the form of well dispersed nanoparticles possessed a considerable BET surface area and external surface area after reduction. A remarkable copper dispersion of 58.7% was thereby achieved. This reduced catalyst displayed elevated uptakes of H 2 O and CO 2 at 473 K compared to the reference adsorbent-free catalyst and presented enhanced adsorption capacities of CO 2 at reaction temperatures due to collective effects of physisorption and chemisorption. Catalysis experiments on a fixed bed reactor using the rCZZ@HT catalyst showed a methanol selectivity of 83.4% and a S MeOH /S CO ratio of 5.0 in products. A control experiment in which hydrotalcite was replaced with quartz (named rCZZ&QS) showed considerably lower conversion at low pressure and demonstrated the enhancing effect of the hydrotalcite support. The new catalyst could achieve the same methanol productivity as the control catalyst at 2.45 MPa lower reaction pressure. This lower pressure corresponds to a ∼61.3% savings in energy consumption for compression. Accordingly, the CZZ@HT is a promising candidate for CO 2 hydrogenation to methanol at moderate pressures. • A hybrid catalyst/adsorbent consisting of Cu-ZnO-ZrO 2 and hydrotalcite was prepared. • The catalyst showed elevated uptakes of H 2 O and CO 2 compared to adsorbent-free catalyst. • The enhancing effects of the hydrotalcite support on methanol selectivity were verified. • A ∼61.3% savings in energy consumption for compression was achieved. [ABSTRACT FROM AUTHOR]

CO2 hydrogenation to methanol is one of the main and valuable catalytic reactions applied on Cu/ZnO-based catalysts; the interface formed through Zn migration from ZnO support to the surface of Cu nanoparticle (ZnOx-Cu NP-ZnO) has been reported to account for methanol synthesis from CO2 hydrogenation. However, the accompanied reverse water gas shift (RWGS) reaction significantly decreases methanol selectivity and deactivates catalysts soon. Inhibition of RWGS is thus of great importance to afford high yield of methanol. The clear understanding of the reactivity of RWGS reaction on both the direct contact Cu-ZnO interface and ZnOx-Cu NP-ZnO interface is essential to reveal the low methanol selectivity in CO2 hydrogenation to methanol and look for efficient catalysts for RWGS reaction. Cu doped plate ZnO (ZnO:XCu) model catalysts were prepared through a hydrothermal method to simulate direct contact Cu-ZnO interface and plate ZnO supported 1 wt % Cu (1Cu/ZnO) catalyst was prepared by wet impregnation for comparison in RWGS reaction. Electron paramagnetic resonance (EPR), XRD, SEM, Raman, hydrogen temperature-programmed reduction (H2-TPR) and CO2 temperature-programmed desorption (CO2-TPD) were employed to characterize these catalysts. The characterization results confirmed that Cu incorporated into ZnO lattice and finally formed direct contact Cu-ZnO interface after H2 reduction. The catalytic performance revealed that direct contact Cu-ZnO interface displays inferior RWGS reaction reactivity at reaction temperature lower than 500 °C, compared with the ZnOx-Cu NP-ZnO interface; however, it is more stable at reaction temperature higher than 500 °C, enables ZnO:XCu model catalysts superior catalytic activity to that of 1Cu/ZnO. This finding will facilitate the designing of robust and efficient catalysts for both CO2 hydrogenation to methanol and RWGS reactions.

• MIL-68(In)-derived In 2 O 3 with different morphologies and sizes was applied to CO 2 hydrogenation to methanol. • Self-assembled MIL-68(In)-derived perfect In 2 O 3 hollow tubes were successfully synthesized by appropriate 0.5 M NaOAc. • The perfect In 2 O 3 hollow tube composed of ordered arranged nanoparticles was most beneficial to generate of oxygen vacancies. • The more perfect and regular the structure of In 2 O 3 hollow tubes, the higher the methanol formation activity. MIL-68(In)-derived In 2 O 3 hollow tubes with different morphology and size using MIL-68(In) as a template were prepared at different NaOAc concentrations and applied to CO 2 hydrogenation to methanol. The size of a series of MIL-68(In) gradually decreased with increasing NaOAc concentration. Too large or small diameter of MIL-68(In) (NaOAc at 0.2 M or 1 M) led to the collapse of corresponding derivative In 2 O 3 tubular structure and only haphazardly accumulated In 2 O 3 nanoparticles were retained. However, the In 2 O 3 hollow tubular-like structure could be obtained when NaOAc concentrations were in the range of 0.4 M to 0.65 M. Interestingly, the self-assembly MIL-68(In)-0.5 M-derived In 2 O 3 with the most regular and perfect hollow tube structure was composed of ordered arrangement of In 2 O 3 nanoparticles at 0.5 M NaOAc, which exhibited much higher methanol synthesis performance than that of other In 2 O 3 catalysts. The lowest surface reduction temperature led to oxygen vacancies easily exposed on In 2 O 3 -0.5 M hollow tube surface. The space confinement effect further enhanced the reaction efficiency of oxygen vacancies, and adsorption capacity of CO 2 was enhanced to improve the methanol yield. It achieved a CO 2 conversion of 14.0%, while methanol selectivity remained at 65%. The space-time yield was up to 1.07 g MeOH h-1g cat -1, showing excellent methanol activity. [ABSTRACT FROM AUTHOR]

Carbon neutrality is spurring worldwide impetus on the exploration of CO 2 hydrogenation to methanol, but groundbreaking catalyst presents a grand challenge. An outstanding InNi 3 C 0.5 /Fe 3 O 4 catalyst is tailored by finely tuning the electronic metal-support interaction (EMSI) that is controlled by Fe 3 O 4 precursor. The one using Fe 3 O 4 - N (from ferric nitrate) stands out against the ones using Fe 3 O 4 - A (ferrous acetate) and Fe 3 O 4 - C (ferric chloride), achieving a turnover frequency (421.6 h−1) 2.3–3.1 times as high as that of the two others. There is a correlation between the oxygen deficiency of Fe 3 O 4 and the EMSI-governed activity. The EMSI effect is enhanced substantially by the highly oxygen-deficient Fe 3 O 4 - N. Enhanced EMSI makes InNi 3 C 0.5 electron-enriched and thus enables CO 2 to be dissociated easily. The InNi 3 C 0.5 /Fe 3 O 4 - N achieves a high methanol space time yield of 2.60 g MeOH g cat −1 h−1 with 92.0% methanol selectivity at 325 °C and 6.0 MPa. This catalyst is also highly anti-sintering and anti-sulfur poisoning. [Display omitted] • Active, selective and stable InNi 3 C 0.5 /Fe 3 O 4 is developed for the CO 2 -to-methanol. • The catalyst activity is linked with electronic metal-support interaction (EMSI). • The EMSI is governed by Fe 3 O 4 precursor dependent oxygen vacancy. • Enhanced EMSI makes InNi 3 C 0.5 electron-enriched and thus favors CO 2 activation. • A high STY of 2.60 g MeOH g cat −1 h−1 is obtainable with 92.0% methanol selectivity. [ABSTRACT FROM AUTHOR]

Hydrogenation of CO 2 to valuable chemicals has the potential to mitigate the elevated CO 2 level and depletion of fossil fuel problems. Herein, bamboo powder (BP) assisted synthesis of Co 3 O 4 -In 2 O 3 catalysts was applied for efficient CO 2 hydrogenation to methanol (MeOH). Under reaction stabilization, Co 3 O 4 in BP-modified catalyst has a stronger interaction with In 2 O 3 , and will be transformed into amorphous Co0 and inactive Co 3 InC 0.75 (the weight fraction of Co 3 InC 0.75 in the catalyst is 69 wt%). In contrast, without assistance of BP, crystalline Co0 is formed and the mass content of Co 3 InC 0.75 also reaches 61 wt%. Density function theory calculation gives the information that H 2 molecules are more easily adsorbed and dissociated on amorphous Co0 compared to crystalline Co0, which further facilitates the oxygen vacancy formation of In 2 O 3. On the other hand, in situ DRIFTs confirms that MeOH synthesis over the Co 3 O 4 -In 2 O 3 catalyst follows the dual-site model. That is, active Co0 and oxygen vacancies are both important, in which the former is associated with H 2 dissociation while the latter is closely relatively to CO 2 activation. Besides, K+ species originated from BP in BP-modified catalyst favor CO production, and the negative role can be eliminated by an easy HCl washing. As a result, at the sacrification of some decreased Co0 but with higher reactive amorphous Co0, BP-1-mediated biosynthesis of Co 3 O 4 -In 2 O 3 (BP treated in pH = 1) attains a better MeOH space-time yield of 13.39 mmol g cat −1 h−1 at 300 °C and 4 MPa. Moreover, the above catalyst shows excellent stability with almost no deactivation in a continuous run of 100 h. [Display omitted] • With the help of BP, amorphous Co0 was formed during reaction reconstruction. • Amorphous Co0 has stronger interaction with In 2 O 3 than crystalline Co0. • H 2 molecules are more easily adsorbed and dissociated on amorphous Co0. • A methanol space-time yield of 13.39 mmol g cat −1 h−1 was reached over Co-In oxide at 300 °C and 4 MPa. [ABSTRACT FROM AUTHOR]

• Distributions of In 2 O 3 in ZrO 2 are explored to prepare binary oxide. • In 2 O 3 /ZrO 2 obtained by precipitation-coating has the enhanced exposure of In 2 O 3. • In 2 O 3 surface exposure contributes to CO 2 adsorption and activation. • Synergistic interface effect allows the carbonate-formate-methoxy pathway. • Methanol selectivity exceeds 86% and CO 2 conversion is 7.5%. Four different compositing strategies were explored to synthesize In 2 O 3 /ZrO 2 binary composite oxides with the goal of optimizing the interaction between the two phases and the degree of In 2 O 3 surface exposure. The composite oxide prepared by the precipitation-coating method demonstrated the highest exposure area of In 2 O 3 (S In = 6.22 m2·g−1). In contrast, the composite oxide prepared by the co-precipitation method caused In 2 O 3 to form a bulk dispersion structure with ZrO 2 , resulting in the lowest In 2 O 3 exposure area (S In = 1.56 m2·g−1). The incorporation of an In 2 O 3 phase in ZrO 2 inhibited the excessive formation of oxygen vacancies compared with pure In 2 O 3 , improving the catalytic performance for hydrogenation of CO 2 to methanol. The 10% In 2 O 3 /m-ZrO 2 composite prepared by the precipitation-coating method had excellent catalytic performance and stability: the CO 2 conversion was 7.5%, the space-time yield (STY) of methanol reached 0.398 g MeOH ·h−1·g cat −1, and the catalytic performance did not significantly decline after a reaction time of 120 h. The results of experimental and simulation calculation verify that In 2 O 3 surface exposure contributes to CO 2 adsorption and activation. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and DFT calculation were used to show that oxygen vacancy defects in the In 2 O 3 /m-ZrO 2 composite oxides helped stabilize formate intermediates and that methanol synthesis followed a carbonate-formate-methoxy pathway. [Display omitted] [ABSTRACT FROM AUTHOR]

A defect-free water permeable membrane for water/gases separation under extremely harsh conditions to be applied in CO 2 hydrogenation to methanol. [Display omitted] • The membrane could separate H 2 O from H 2 , CO 2 and CH 3 OH at T ≥ 200 ℃ and P ≥ 20 bar. • Defect-free membrane is synthesized by a template-free method with low-cost. • DFT analysis provides more insights to explain the water separation behavior. CO 2 hydrogenation to methanol is a high value-added way for CO 2 utilization. However, the conversion of CO 2 to methanol is severely limited by the thermodynamic equilibrium. Using water permeable membranes to simultaneously remove the by-product (H 2 O) during the reaction can overcome this limitation, and enhance CO 2 conversion and methanol yield. In this work, a defect-free NaA zeolite membrane supported on an alumina hollow fiber substrate was fabricated via a totally template-free method with the capability to scale up at a low cost in the future. Furthermore, the as-synthesized membrane can effectively separate water from other small gas molecules (H 2 and CO 2) under extremely harsh conditions (T ≥ 200 ℃ and P ≥ 20 bar), with a water flux up to 4.8 × 10-7 mol m−2 s−1 Pa−2 and superior separation factor for H 2 O/H 2 (>10000), H 2 O/CO 2 (>10000) and H 2 O/CH 3 OH (>300). With this remarkable separation performance, this zeolite membrane is promising to be applied in CO 2 hydrogenation to methanol. Moreover, DFT analysis provides more insights to explain the water separation behavior of this membrane. [ABSTRACT FROM AUTHOR]

Catalytic CO 2 hydrogenation to methanol is one of the important reactions for environmental-related applications. Pd/CeO 2 catalysts with four different ceria morphologies, i.e. polyhedral, rod, cube and polygonal, and 5 wt% Pd loading were synthesized, and their catalytic characteristics and reaction mechanism were studied. Combining the results of N 2 physisorption, XRD, Raman, CO 2 -TPD, Py-TPD and H 2 -TPR analyses suggests that PdO and Pd x Ce 1−x O 2-δ linkages are present in the Pd/CeO 2 catalysts, which have different interactions with different exposed planes. Pd functionalized ceria with polyhedral morphology denoted as Pd/CeO 2 -NPH shows the highest specific surface area with exposed facets ({111}+{110}), responsible for the formation of more oxygen vacancy and higher extent of surface oxygen mobility, and higher number of acidic-basic sites on the catalysts surface, which contributed to improved catalytic activity and selectivity. XRD and Raman spectroscopy results revealed strong metal-support interactions for the most active catalyst by forming the Pd x Ce 1−x O 2-δ linkage, which improved the formation of surface oxygen vacancies and CO 2 activation on the CeO 2 support and promoted dissociation of H 2 on the Pd metal. In-situ DRIFTS examination provided clear evidence for the formate reaction pathway of methanol synthesis. From a mechanistic point of view, the decomposition of surface carbonate species resulted in the formation of formate, which was further hydrogenated to form crucial methoxy species followed by methanol and CO as reaction products. [Display omitted] • Catalytic CO 2 hydrogenation to methanol over Pd/CeO 2 solids was investigated. • High specific surface area of CeO 2 contributed to improved catalytic performance. • Pd/CeO 2 with exposed {111}+{110} facets enabled higher activity and selectivity. • Increased surface acidity and basicity facilitated selective methanol production. • In-situ DRIFTS examination provided clear evidence for the formate reaction pathway. [ABSTRACT FROM AUTHOR]

• Y 2 O 3 -doped Cu/ZnO catalyst exhibited superior catalytic activity in CO 2 hydrogenation. • Highly dispersed Cu and ZnO species with small crystal size were generated after introduction of Y 2 O 3. • The doping of Y 2 O 3 greatly improved the CO 2 and H 2 adsorption amounts. Revealing the origin of the enhanced performance on yttria (Y 2 O 3) promoted Cu/ZnO based catalyst for methanol synthesis via CO 2 hydrogenation is still challenging. To shed light upon the promotion effect of Y 2 O 3 modifier on binary Cu/ZnO catalyst for CO 2 hydrogenation reaction, a ternary Cu/ZnO/Y 2 O 3 catalyst was synthesized via a citric acid coordination-assisted strategy. The developed Cu/ZnO/Y 2 O 3 catalyst exhibited a remarkably higher Weight-time yeild of methanol (236.8 g MeOH g cat −1∙ h −1) and methanol selectivity (81.1%) in comparison to Cu/ZnO catalyst (159.6 g MeOH g cat −1∙ h −1 and 73.9%, respectively). Various characterizations results have uncovered the enhanced catalytic activity of Cu/ZnO/Y 2 O 3 catalyst for methanol synthesis was associated with small size and highly dispersed Cu species and abundant surface adsorption sites as well as more Cu-ZnO interfaces with strong interaction. Moreover, the Cu/ZnO/Y 2 O 3 catalyst displayed a superior weight-time yield of methanol with a time-on-stream of 100 h in comparison with classic Cu/ZnO catalyst. We anticipate that this basic design strategy will provide a novel alternative to expand opportunities to explore scalable, cost-effective catalysts for industrial methanol synthesis. [Display omitted] [ABSTRACT FROM AUTHOR]

As part of concepts for chemical energy storage of excess chemical energy produced from renewable sources, we investigated the performance of CuO/ZnO catalysts supported on mesoporous carbon to convert CO2 hydrogenation to methanol. In this work, mesoporous carbon was used as the catalyst support for CuO-ZnO catalysts. Four catalysts with different precipitated precursors were synthesized and analyzed by N2-physisorption, X-ray diffraction (XRD), thermogravimetric analysis (TG-DTG), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that catalyst CZ-in situ had the highest turnover frequency (TOF) (2.8 × 10−3 s−1) and methanol production rate (0.8 mmol g−1·h−1). The catalysts for co-precipitation of copper and zinc on carbon precursors are more active. Cu/ZnO domains that are accessible to the reactant gas are another reason for the catalysts being active. The Cu-ZnO interface is crucial to methanol catalyst activity. [ABSTRACT FROM AUTHOR]

a) Methanol synthesis process from CO 2 and H 2. b) Conventional methanol production route from natural gas where natural gas is first converted to syngas and then to methanol. • Conventional and green methanol production are compared. • Maximization of reactor productivity, CO 2 utilization, and hydrogen conversion were considered. • The higher the H 2 /CO to the methanol reactor, the higher gas consumption in the conventional route. • The optimal path configuration depends on the objective function chosen. In this paper, CO 2 hydrogenation to methanol is investigated with three objective functions, i.e. maximization of reactor productivity, CO 2 utilization, and hydrogen conversion. Key performance indicators of methanol production via conventional and CO 2 hydrogenation routes are compared. The results suggest that the methanol production rate with an inlet H 2 /CO 2 of 3 is ca. 59 % greater than the case with the inlet H 2 /CO 2 composition of 2. The overall hydrogen and CO 2 conversion of the cases with the inlet H 2 /CO 2 of 3 is greater than the reactor system with the inlet H 2 /CO 2 of 2. For each objective function criteria, the analysis shows that increasing the H 2 /CO 2 to the methanol reactor increases the natural gas consumption in the conventional route and the higher the inlet H 2 /CO 2 ratio, the higher the CO 2 emission is. If the inlet hydrogen is produced via water electrolysis, the CO 2 emission of the CO 2 hydrogenation process route will be negative. [ABSTRACT FROM AUTHOR]

In this study, a comparative study was conducted on the three reactor types (the adiabatic, water-cooled and gas-cooled reactor) employed for the traditional syngas to methanol (STM) process to investigate their potential applications to the STM process with the CO 2 -rich feed gas or the CO 2 hydrogenation to methanol (CTM) process. The temperature profiles in the axial and radial directions particularly the hot-spot temperatures, operating conditions and methanol yields for the reactors have been investigated using the thermodynamic analysis, the CFD method and the pseudo-homogeneous model. The capital costs for CTM process with the three reactor types have also been evaluated. Compared with the traditional STM process, the STM process with the CO 2 -rich feed gas and CTM process exhibited reduced hot-spot temperatures. The simulation results showed that the single-bed adiabatic (without internal cooling) reactor and the gas-cooled reactor exhibited potentials for the CTM process, where the hot-spot temperatures the hot-spot temperatures in the reactors can be within the typical operating temperature range (e.g., 220–280 °C) for the catalyst. Regarding the comparison of the three reactor types for the CTM process, the water-cooled reactor showed advantages in terms of efficient heat removal, low hot-spot temperature and relatively wide range of inlet temperature for control. The adiabatic reactor and the gas-cooled reactor demonstrated a relatively low and medium performance, and also a relatively low and medium capital cost, respectively, which indicates the potentials of the two reactor types in a small-scale CTM process. [ABSTRACT FROM AUTHOR]

CO2 hydrogenation to methanol is one of the main and valuable catalytic reactions applied on Cu/ZnO-based catalysts; the interface formed through Zn migration from ZnO support to the surface of Cu nanoparticle (ZnOx-Cu NP-ZnO) has been reported to account for methanol synthesis from CO2 hydrogenation. However, the accompanied reverse water gas shift (RWGS) reaction significantly decreases methanol selectivity and deactivates catalysts soon. Inhibition of RWGS is thus of great importance to afford high yield of methanol. The clear understanding of the reactivity of RWGS reaction on both the direct contact Cu-ZnO interface and ZnOx-Cu NP-ZnO interface is essential to reveal the low methanol selectivity in CO2 hydrogenation to methanol and look for efficient catalysts for RWGS reaction. Cu doped plate ZnO (ZnO:XCu) model catalysts were prepared through a hydrothermal method to simulate direct contact Cu-ZnO interface and plate ZnO supported 1 wt % Cu (1Cu/ZnO) catalyst was prepared by wet impregnation for comparison in RWGS reaction. Electron paramagnetic resonance (EPR), XRD, SEM, Raman, hydrogen temperature-programmed reduction (H2-TPR) and CO2 temperature-programmed desorption (CO2-TPD) were employed to characterize these catalysts. The characterization results confirmed that Cu incorporated into ZnO lattice and finally formed direct contact Cu-ZnO interface after H2 reduction. The catalytic performance revealed that direct contact Cu-ZnO interface displays inferior RWGS reaction reactivity at reaction temperature lower than 500 °C, compared with the ZnOx-Cu NP-ZnO interface; however, it is more stable at reaction temperature higher than 500 °C, enables ZnO:XCu model catalysts superior catalytic activity to that of 1Cu/ZnO. This finding will facilitate the designing of robust and efficient catalysts for both CO2 hydrogenation to methanol and RWGS reactions. [ABSTRACT FROM AUTHOR]

In this study, highly loaded CuO (65.2 wt%) on ZrO2 support was prepared by flame spray pyrolysis, and the effects of their particle sizes and ZrO2 crystallinity on CO2 hydrogenation to methanol were investigated. By varying the precursor feed rate (1–10 mL min−1), the crystallite size (3–7 nm) and the crystallinity of tetragonal ZrO2 were controlled. After H2 reduction at 300°C, the Cu species in the catalysts, prepared at the feed rate = 2–10 mL min−1, were converted to Cu particles (approximately 10–20 nm); however, the size and crystallinity of ZrO2 remained the same. The activity and selectivity of the catalysts prepared at the feed rate = 2–3 mL min−1 were higher than those of the catalysts prepared at the feed rates = 5–10 mL min−1, because the smaller ZrO2 particles in the former provided more surface to stabilize small Cu particles and from interfacial Cu‐ZrO2 sites (active sites). [ABSTRACT FROM AUTHOR]