Highest Methanol Yield Research Articles

Exploring the Effect of the Solvothermal Time on the Structural Properties and Catalytic Activity of Cu-ZnO-ZrO2 Catalysts Synthesized by the Solvothermal Method for CO2 Hydrogenation to Methanol

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.

Enhanced photocatalytic CO2 reduction to methanol by modulating valence states of copper in CuSrTiO3

Manipulating the oxidation states of transition metals is an ideal solution to achieve selective generation of different products and copper is widely used in CO2 photocatalytic reduction to methanol. However, the understanding on the effects of valence states of copper species in SrTiO3 on its structure and the selectivity of the corresponding product in CO2 photocatalysis are currently still limited. Here, copper-doped SrTiO3 nanofibers with different controllable ratios of Cu+/Cu2+ and Cu+/Cu0 were prepared by the combination of the electrospinning with the in-situ reduction method. The proportion of copper with different valence states (Cu+/Cu2+ and Cu+/Cu0) was changed by rationally adjusting the time of hydrogen reduction. The presence of monovalent copper facilitated the generation of reactive intermediates, thereby enhancing its photocatalytic activity. The copper-doped SrTiO3 nanofibers obtained after 3 h of hydrogen reduction (STCu0.08-H-3 h) had the highest proportion of Cu+/Cu2+ and Cu+/Cu0 with the highest methanol yield (6.96 μmol·g−1·h−1). Methanol generation rate and Cu+/Cu2+ ratio of STCu0.08-H-xh (x = 1, 2, 3, 4,5) with different hydrogen reduction time were proven to be linearly positively correlated. Furthermore, theoretical investigation and in-situ CO2 infrared spectrum deeply understood the difference of CO2 adsorption behavior and CO2 activation over Cu2+ and Cu+ of STCu0.08-H-3 h photocatalyst and the reaction intermediates involved in the photocatalytic CO2 reduction to methanol.

Integrated production of methanol and biochar from bagasse and plastic waste: A three-in-one solution for carbon sequestration, bioenergy production, and waste valorization

The shift from fossil fuels to renewable energy is a crucial strategy to achieve carbon neutrality. However, the methanol industry relies heavily on fossil fuels. Alternative feedstocks, such as biomass and plastics, still face many challenges. Biomass is hydrogen-deficient and cannot achieve a high methanol yield, while plastic gasification consumes too much energy. Accordingly, this research proposed a new method to synergistically co-produce methanol and biochar from bagasse pyrolysis and plastic waste gasification. This innovative approach was assessed using techno-economic analysis and hybrid life-cycle assessment based on sugarcane bagasse resources in Guangxi province as a case study and compared with the other four scenarios. The results indicated that the novel method exhibits huger economic and environmental benefits with a low payback period of 6.32 years and a low global warming potential of −1875.41 kg CO2-eq/t. However, the high total capital cost is the primary potential obstacle to widespread promotion. Spatial-temporal analysis shows that Chongzuo and Laibin have the most tremendous methanol production potential and economic and environmental benefits due to their high bagasse production. This study contributes to biomass utilization and plastic waste management by proposing a synergistic process and offers multiple benefits for carbon sequestration, energy security, and waste valorization.

Regulating Au coverage for the direct oxidation of methane to methanol

The direct oxidation of methane to methanol under mild conditions is challenging owing to its inadequate activity and low selectivity. A key objective is improving the selective oxidation of the first carbon-hydrogen bond of methane, while inhibiting the oxidation of the remaining carbon-hydrogen bonds to ensure high yield and selectivity of methanol. Here we design ultrathin PdxAuy nanosheets and revealed a volcano-type relationship between the binding strength of hydroxyl radical on the catalyst surface and catalytic performance using experimental and density functional theory results. Our investigations indicate a trade-off relationship between the reaction-triggering and reaction-conversion steps in the reaction process. The optimized Pd3Au1 nanosheets exhibits a methanol production rate of 147.8 millimoles per gram of Pd per hour, with a selectivity of 98% at 70 °C, representing one of the most efficient catalysts for the direct oxidation of methane to methanol.

The origin of the mediocre methanol selectivity of Cu/ZnO-based catalysts for methanol synthesis from CO2 hydrogenation

Cu/ZnO-based catalysts have been extensively and intensively studied for CO2 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.

Direct oxidation of methane to methanol using CuMoO4.

Upgrading methane into methanol or other high value-added chemicals is not only beneficial to mitigate the greenhouse effect, but also provides basic raw materials for industrial production. Nowadays, most research is limited to zeolite systems, and it is a considerable challenge to extend the support to metal oxides while achieving a high yield of methanol. In this paper, we take advantage of impregnation methods to synthesise a novel Cu/MoO3 catalyst, which can convert methane to methanol in the gaseous phase. At 600 °C, the Cu(2)/MoO3 catalyst can achieve a maximum STYCH3OH of 47.2 μmol (g-1 h-1) with a molar ratio CH4 : O2 : H2O = 5 : 1.4 : 10. Consequences of SEM, TEM, HRTEM and XRD substantiate that Cu is incorporated into the lattice of MoO3 to form CuMoO4. And transmission infrared spectroscopy, Raman spectroscopy together with XPS characterization techniques confirm the generation of CuMoO4, which is the main active site provider. This work provides a new support platform for Cu-based catalyst research in the methane-to-methanol system.

0D/2D CeO2/BiVO4 S-scheme photocatalyst for production of solar fuels from CO2

The production of hydrocarbon fuels is essential for the energy market to develop a green and sustainable environment. However, new pathways are being developed to accelerate energy production to fulfill energy demands. Here, we have developed an efficient 0D/2D CeO2/BiVO4 S-scheme heterojunction for producing methanol from CO2 in visible illuminance. The developed heterojunction photocatalyst demonstrated the excellent yield of methanol and the production of CO and CH4 in small amounts. The high yield of methanol refers to the effective charge separation and good basic sites at the heterojunction photocatalyst due to the CeO2 content, which facilitates the accommodation of CO2 molecules more efficiently at the CeO2 surface and provides a higher yield of methanol than CeO2 and BiVO4 alone. In addition, the effective charge separation between CeO2 and BiVO4 provided excellent yields of C1 solar fuels. The characteristic properties of the synthesized photocatalysts were examined using various spectroscopic and microscopic techniques. Also, the recovered photocatalyst exhibited relatively similar activity without leaching the metal content after five consecutive runs under identical experimental conditions.

Recent Insights into Cu-Based Catalytic Sites for the Direct Conversion of Methane to Methanol.

Direct conversion of methane to methanol is an effective and practical process to improve the efficiency of natural gas utilization. Copper (Cu)-based catalysts have attracted great research attention, due to their unique ability to selectively catalyze the partial oxidation of methane to methanol at relatively low temperatures. In recent decades, many different catalysts have been studied to achieve a high conversion of methane to methanol, including the Cu-based enzymes, Cu-zeolites, Cu-MOFs (metal-organic frameworks) and Cu-oxides. In this mini review, we will detail the obtained evidence on the exact state of the active Cu sites on these various catalysts, which have arisen from the most recently developed techniques and the results of DFT calculations. We aim to establish the structure-performance relationship in terms of the properties of these materials and their catalytic functionalities, and also discuss the unresolved questions in the direct conversion of methane to methanol reactions. Finally, we hope to offer some suggestions and strategies for guiding the practical applications regarding the catalyst design and engineering for a high methanol yield in the methane oxidation reaction.

Facet-dependent catalytic activity of CeO2 toward methanol synthesis from methane

The relationship between CeO2 morphology (nano rods, NR; nano cubes, NC; nano octahedra, NO) and methanol synthesis from methane at low reaction temperature was studied by using density functional theory (DFT) and experiments. CeO2(110) displays the lowest energy barriers among CeO2(100), CeO2(111) and CeO2(110) surfaces due to the strongest hybridization between O 2p orbital of OH and Ce 4f orbital. As a result, CeO2-NR has the highest methanol yield (1.52 μmol/gcat) compared with CeO2-NC (0.60 μmol/gcat) and CeO2-NO (0.66 μmol/gcat) at 453 K and 101325 Pa. These results show that methanol synthesis from methane at low reaction temperature on CeO2 is a morphology sensitive reaction.

Dimethyl ether (DME) synthesis from CO2 and H2 through ethanol-assisted methanol synthesis and methanol dehydration

Two steps of dimethyl ether (DME) synthesis from CO2 and H2 in a batch reactor were studied, including CO2 hydrogenation to methanol through ethanol-assisted method and methanol dehydration to DME. Additions of 10 wt% ZrO2, Al2O3 and ZrO2–Al2O3 into Cu/ZnO were investigated in low-temperature methanol synthesis using ethanol as catalytic solvent. Suitable zeolite (ZSM-5 and ferrierite) for methanol dehydration was also determined. Ethanol-assisted method offered high methanol yield and Cu/ZnO/ZrO2 catalyst provided the highest CO2 conversion (82.1%) and methanol yield (60.8%) at 150 °C and 50 bar since ZrO2 decreased CuO crystallite sizes and increased surface areas of the catalyst. For methanol dehydration to DME, zeolite's strong acidity related to DME formation. The Cu/ZnO/ZrO2 - Ferrierite provided the highest DME productivity at 0.44 mmolDME/gcat. In addition, DME synthesis from CO2 and H2 through ethanol-assisted methanol synthesis and methanol dehydration can be a potential method to simultaneously produce DME and ethylene. Under the operating conditions, ethylene was produced as a valued by-product of 5.65 mmolEthylene/gcat from dehydration of ethanol. In this study, rather high methanol yield was obtained from ethanol-assisted method. However, DME yield can be further improved by increasing synthesis temperature.

Low-temperature alcohol-assisted methanol synthesis from CO2 and H2: The effect of alcohol type

Carbon dioxide (CO2) conversion to higher-value products is a promising pathway to mitigate CO2 emissions. Methanol is a high-value-chain chemical in industries that can be produced through CO2 hydrogenation, which is an exothermic reaction. Due to thermodynamic limitations, a typical synthesis temperature between 250 °C and 300 °C results in a low conversion of CO2 at equilibrium. To enhance the CO2 conversion, high pressures of 50–100 bar are required, which inevitably causes the process to be energy-intensive. In this study, an alternative method called alcohol-assisted methanol synthesis is investigated. In this method, alcohol is used as a catalytic solvent and helps decrease the reaction temperature and pressure (150 °C and 50 bar) and significantly increases methanol yield. Ethanol is used as the alcohol due to its reactivity, providing a high methanol yield (47.80%) with 63.93% CO2 conversion and 67.54% methanol selectivity. However, due to unwanted side reactions, ethanol generates ethyl acetate as a byproduct that forms an azeotrope with methanol, leading to difficulty in product purification. The effects of alcohol type (molecular weight and structure), including ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, iso-butanol, tert-butanol and 1-pentanol, on CO2 conversion, methanol yield and byproducts are investigated. It is found that smaller-molecule alcohols provide a higher methanol yield. Moreover, n-alcohols provide a higher methanol yield than branched alcohols, and the byproducts of the reaction with n-alcohols do not form an azeotrope with methanol. Therefore, 1-propanol is compared with ethanol providing 26.55% methanol yield, 69.02% CO2 conversion and 70.82% methanol selectivity.

Effect of work-function and morphology of heterostructure components onCO2reduction photo-catalytic activity ofMoS2-Cu2Oheterostructure

Photocatalysis possesses a high potential to utilize solar energy to meet the rising energy demands, however it suffers from various challenges such as fast recombination of the photo-generated electron–hole pairs and low thermodynamic reaction feasibility in the low band-gap materials. Rationally engineered heterostructure photocatalysts possess higher activity compared to their individual components primarily due to spatial separation of photo-generated electron–hole pairs. In this work, we synthesized several MoS 2 -Cu 2 O heterostructures, by modulating the electronic and structural properties of the heterostructure components. Heterostructures formed using MoS 2 with p-type intrinsic conductivity has shown higher photocatalytic activity, with methanol production yield up to 76 μ mol.g cat − 1 . h − 1 , compared to n-type MoS 2 -based heterostructures due to direct Z-scheme and type-II charge transfer mechanism of photo-generated electron–hole pairs respectively. Further, heterostructures formed with Cu 2 O nanoparticles of cubic morphology with dominantly { 100 } facets shows (a) higher binding affinity with MoS 2 (b) lower recombination of photo-generated electron–hole pairs and (c) higher methanol yield, compared to Cu 2 O nanoparticles with cubo-octahedron morphology with dominantly { 111 } facets. This study highlights the important role of work-function and morphology of the heterostructure components in modulating the photo-activity and paves the way for the rational engineering of heterostructure photocatalysts. • Multiple MoS 2 -Cu 2 O heterostructures are studied for CO 2 photo-reduction activity. • Intrinsic conductivity and work function of MoS 2 is altered by introducing defects. • Two types of Cu 2 O with cubic and cubo-octahedron morphology are synthesized. • p-type MoS 2 -based heterostructure shows Z-scheme mechanism and high photoactivity. • Cubic Cu 2 O shows better CO 2 adsorption and interfacial interaction with MoS 2 .

Evaluation of Au/ZrO2 Catalysts Prepared via Postsynthesis Methods in CO2 Hydrogenation to Methanol

Au nanoparticles supported on ZrO2 enhance its surface acidic/basic properties to produce a high yield of methanol via the hydrogenation of CO2. Amorphous ZrO2-supported 0.5–1 wt.% Au catalysts were synthesized by two methods, namely deposition precipitation (DP) and impregnation (IMP), characterized by a variety of techniques, and evaluated in the process of CO2 hydrogenation to methanol. The DP-method catalysts were highly advantageous over the IMP-method catalyst. The DP method delivered samples with a large surface area, along with the control of the Au particle size. The strength and number of acidic and basic sites was enhanced on the catalyst surface. These surface changes attributed to the DP method greatly improved the catalytic activity when compared to the IMP method. The variations in the surface sites due to different preparation methods exhibited a huge impact on the formation of important intermediates (formate, dioxymethylene and methoxy) and their rapid hydrogenation to methanol via the formate route, as revealed by means of in situ DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) analysis. Finally, the rate of formation of methanol was enhanced by the increased synergy between the metal and the support.

Enhanced performance and stability of Cu/ZnO catalyst by introducing MgO for low-temperature methanol synthesis using methanol itself as catalytic promoter

Catalytic conversion of CO2-containing syngas to methanol is one of important processes in industry. However, realizing high space time yield (STY) of methanol at low reaction temperature remains a challenge. Herein, ternary Cu/ZnO/MgO catalysts were prepared via co-precipitation and tested for low-temperature methanol synthesis via autocatalysis of methanol. The effects of Mg2+ ion and MgO content on the formation and composition of the precipitated precursors, as well as on the physicochemical properties of the calcined and the reduced catalysts were systemically investigated and discussed. The structure–activity relationships were disclosed by detailed catalysts characterization. Compared to Cu/ZnO, the total carbon turnover frequency (TOF) and space time yield (STY) of methanol on Cu/ZnO/MgO remarkably increased from 17.8 to 20.0 h−1 and from 425.2 to 538.3 g/kg∙h−1, respectively. Besides, Cu/ZnO/MgO kept its activity for 180 h without deactivation, which was much more stable than Cu/ZnO. In comparison with commercial Cu/ZnO/Al2O3 and other Cu-based catalysts reported in the literatures for methanol synthesis from syngas, Cu/ZnO/MgO catalyst with Cu/Zn/Mg molar ratio of 1:1:0.05 displayed much higher space time yield (STY) of methanol. In addition, the reaction conducted in the presence of methanol promoter exhibited much lower apparent activation energy than that of the reaction carried out without methanol promoter, indicating a catalytic and promotional role of methanol during low-temperature methanol synthesis reaction. The current work provided not only a hopeful strategy for enhancing activity and stability of Cu/ZnO catalyst, but also a sustainable low-temperature methanol synthesis route using methanol itself as catalytic promoter.

Efficient Role of Nanosheet-Like Pr2O3 Induced Surface-Interface Synergistic Structures over Cu-Based Catalysts for Enhanced Methanol Production from CO2 Hydrogenation.

In a complex heterogeneous metal-catalyzed reaction process, unique cooperative effects between metal sites and surface-interface active sites, as well as favorable synergy between surface-interface active sites, can play crucial roles in improving their catalytic performances. In this work, a ZnO-modified Cu-based catalyst over defect-rich Pr2O3 nanosheets for high-efficiency CO2 hydrogenation to produce methanol was successfully constructed. It was demonstrated that an as-fabricated nanosheet-like Cu-based catalyst presented several structural advantages including the formation of highly dispersive Cu0 sites and the coexistence of abundant defective Pr3+-Vo-Pr3+ structures (Vo: oxygen vacancy) and interfacial Cu-O-Pr sites. Combining structural characterization and catalytic reaction results with density functional theory calculations, it was clearly unveiled that the synergy between surface defective structures and Cu-Pr2O3 interfaces over the catalyst remarkably promoted the adsorption of CO2 and CO intermediate, thus boosting the CO2 hydrogenation simultaneously via both the formate intermediate pathway and the intense reverse water-gas shift reaction-derived CO hydrogenation pathway, along with a high space-time yield of methanol of 0.395 gMeOH·gcat-1·h-1 under mild reaction conditions (260 °C and 3.0 MPa). The study provides a new strategy to construct high-performance Cu-based catalysts for high-efficiency CO2 hydrogenation to produce methanol and a deep understanding of the promotional roles of synergy between surface-interface active sites in the CO2 hydrogenation.

Cover Feature: The Influence of UiO‐bpy Skeleton for the Direct Methane‐to‐Methanol Conversion on Cu@UiO‐bpy: Importance of the Encapsulation Effect (ChemCatChem 23/2021)

The Cover Feature shows that CuxOx clusters are confined in the UiO-bpy skeleton. In their Full Paper, L. Fu, M. Yuan et al. use Cu@UiO-bpy, which shows high methanol yield and stability in the direct methane-to-methanol conversion. Once the UiO-bpy framework is destroyed, the active sites of small CuxOx clusters will grow into CuO nanoparticles due to the thermal movement during the reaction. As a result, the catalyst is deactivated. The results show that the encapsulation effect of UiO-bpy skeleton is the key factor for catalyst stability. More information can be found in the Full Paper by L. Fu, M. Yuan et al.

The Influence of UiO‐bpy Skeleton for the Direct Methane‐to‐Methanol Conversion on Cu@UiO‐bpy: Importance of the Encapsulation Effect

AbstractThe influence of UiO‐bpy skeleton for the direct methane‐to‐methanol conversion on Cu@UiO‐bpy is studied by experiment and DFT. It is found that Cu@UiO‐bpy shows high methanol yield and stability. However, if the UiO‐bpy skeleton is destroyed, the active sites of small CuxOx clusters grow into CuO nanoparticles due to the thermal movement during the reaction. As a result, the catalyst is deactivated. In other words, the encapsulation effect is a key factor for catalyst stability, which prevents the growth of CuxOx clusters. In addition, the encapsulation effect of UiO‐bpy skeleton affects the morphology and size of CuxOx clusters, of which small CuxOx clusters are beneficial for methane conversion.

Construction of Low-Cost Z-Scheme Heterostructure Cu2 O/PCN for Highly Selective CO2 Photoreduction to Methanol with Water Oxidation.

Solar-driven CO2 reaction with water oxidation into alcohols represents a promising approach to achieve real artificial photosynthesis. However, rapid recombination of photogenerated carriers seriously restricts the development of artificial photosynthesis. Herein, a facile method is explored to construct low-cost Z-Scheme heterostructure Cu2 O/polymeric carbon nitride (PCN) by in situ growth of Cu2 O hollow nanocrystal on PCN. The protective PCN layer and Z-schematic charge flow can make robust Cu2 O/PCN photocatalysts, and the spatial separation of electrons and holes with high redox potentials of ECB (-1.15eV) and EVB (1.65eV) versus NHE can efficiently drive CO2 photoreduction to methanol in pure water, which is further confirmed by DFT calculation. The Z-scheme heterostructure Cu2 O/PCN exhibits a high methanol yield of 276µmol g-1 in 8 h with ca. 100% selectivity, much superior to that of isolated Cu2 O and PCN, and all the reported Cu2 O-based heterostructures. This work provides a unique strategy to efficiently and selectively promote the conversion of CO2 and H2 O into high-value chemicals by constructing a low-cost Z-scheme heterostructure.

Photocatalytic CO2 reduction with new band gap energy evaluation from spectroscopic relationship of graphene-Mg2CuSnCoO6 composite bridged with organics

A new structure of graphene-Mg 2 CuSnCoO 6 composite bridged with gallic acid (GMG) was synthesized with a novel method. Band gap energy of the newly synthesized nanocomposite was evaluated with a laser-wavelength region and DRS method. Evaluation and analysis were based on the relationship among XRD, HRTEM, XPS, Raman scattering, and computer simulated model structure. Changes in the structure of graphene or graphene-based composite were associated with location changes of the valence band and the conduction band. Electron density was used to confirm the number of electrons by computer simulation. Finally, such graphene-Mg 2 CuSnCoO 6 -gallic acid nanocomposite was used for photocatalytic CO 2 reduction into methanol. Under UV-light irradiation, the highest methanol yield was 5.576% with 0.6 g of scavenger. This work might offer a promising strategy for measuring band gap energies of different types of semiconductors. • Synthesis of new-structured Graphene-Mg 2 CuSnCoO 6 composite bridged with Gallic acid. • The evaluation of new band gap energy value. • Photocatalytic activity for the CO 2 reduction by novel ternary nanocomposite. • The high methanol production rate with scavengers. • High stability and photocatalytic efficient properties for production of solar fuel.

Methane oxidation to methanol over copper-containing zeolite

Methane oxidation to methanol over copper-containing zeolite