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The present study was aimed to convert CO2 into methanol which not only addresses the potential solution for controlling the CO2 concentration level in the atmosphere but also offers an alternative approach for the production of renewable energy source. In this perspective, a hybrid photocatalyst, PANI@CuFe2O4 was synthesized, characterized and used as a photocathode for photoelectrocatalytic (PEC) reduction of CO2 to methanol in aqueous medium at an applied potential of −0.4 V vs NHE under visible light irradiation. The combination of PANI with CuFe2O4 greatly increased the PEC CO2 reduction to methanol owing to enhance the CO2 chemisorption capacity by the photocathode surface and at the same time facilitated the separation of photogenerated electron-hole (e−/h+) pairs. The incident photon to current efficiency (IPCE) and quantum efficiency (QE) for methanol formation in PEC CO2 reduction could be achieved as 7.1 and 24.0% respectively. The rate of formation of methanol in PEC CO2 reduction was found as 49.3 μmol g−1h−1 with 73% Faradaic efficiency. Compared to photocatalytic reaction, the PEC results demonstrated that the applied potential could effectively separate the photogenerated e−/h+ pairs and therefore, enhanced the PEC CO2 reduction activity of the hybrid photocatalyst.

CO2 hydrogenation to methanol is becoming a potential route for reducing CO2 emission, benefiting from the worldwide growth of renewable energy for H2 production. In this work, the ZnO-ZrO2 solid solution catalysts with ordered mesoporous structure were constructed by the evaporation-induced self-assembly (EISA) process using triblock copolymer P123 as the template. The 20% ZnO-ZrO 2 catalyst prepared by the evaporation-induced self-assembly process shows a methanol formation rate of 22.1 mmol·h-1·gcat-1 at 320°C, 5.5 MPa, which is 1.35 times that of the catalyst prepared by co-precipitation. Characterizations prove that the EISA catalysts have larger specific surface areas and more sites for the activation of CO2 and H2, which are related to the higher CO2 conversion.

Continuous catalytic methanol production from methane is reported on Cu-SSZ-39 using N2O as an oxidant. Through optimization of CH4, N2O and H2O partial pressures, a methanol formation rate of 499 μmolCH3OH g−1 h−1 and a methanol selectivity of 34% is achieved.

Mo2C-Based catalysts constitute a promising class of materials for CO2 hydrogenation to high added-value products. In this work, we show that methanol formation can be significantly enhanced by the addition of Cu. Moreover, the preparation method of the Cu–Mo2C catalysts can significantly affect the catalytic performance. Synthesis via the sol–gel auto-combustion route leads not only to the most active material, achieving 30 mol% CO2 conversion at 325 °C and 45 bar, but also to the most selective towards methanol (∼50 C-mol% at 5 mol% conversion). This performance is slightly inferior for the catalyst prepared with the solvothermal method. Conversely, the catalyst synthesized with the solid state route presents by a long way the worst activity and selectivity in the reaction. We show with spectroscopy and temperature programed studies that Cu addition and the synthesis method modify the population, type and strength of the sites available for CO2 and H2 activation on the surface and hence the catalytic performance. The results suggest that strong interaction between the Cu and Mo2C phases and formation of Mo2C–Cu+ interfaces are required for the efficient hydrogenation of CO2 to methanol.

Developing catalysts with high activity and high selectivity toward methanol, and elucidating the structure-activity relationship, are important in the area of CO2 hydrogenation. Herein, a simple ultrasonic-assisted impregnation modification method, which modifies a CuZnZr catalyst for methanol synthesis from CO2, is reported. The results show high methanol selectivity (97.1%) and a CO2 conversion of 10.7%, in the presence of the catalyst modified with CuBr2 (CuZnZr/CuBr2). Furthermore, detailed investigations of the structure-activity relationship demonstrate that the CuBr2 modification influences both the catalyst surface properties and catalyst morphology. In particular, residual Br, as a CuBr phase, is stabilized on the catalyst surface and is able to significantly passivate the reverse water-gas shift activity on the Cu surface; therefore, CO formation on the Cu surface is almost completely suppressed. The catalytic evaluation and IR data support the formate pathway mechanism in the presence of the CuZnZr/CuBr2 catalyst to synthesize methanol from CO2.

The kinetics of AlO+ + CH4 are studied from 300-500 K using a selected-ion flow tube. At all temperatures the reaction proceeds near the Langevin-Gioumousis-Stevenson collision rate with two product channels: hydrogen atom abstraction (AlOH+ + CH3, 86 ± 5%) and methanol formation (Al+ + CH3OH, 14 ± 5%). Density functional calculations show the key Al-CH3OH+ intermediate is formed barrierlessly via a mechanism unique to aluminum, avoiding the rate-limiting step common to other MO+. The reaction of Al2O3+ + CH4 follows a similar mechanism to that for AlO+ through to the key intermediate; however, the conversion to methanol occurs only for AlO+ due to favorable energetics attributed to a weaker Al+-CH3OH bond. Importantly, that bond strength may be tuned independent of competing product channels by altering the acidity of the Al with electron-withdrawing or donating groups, indicating a key design criteria to develop a real world Al-atom catalyst.

Cu oxo nanoclusters hosted in microporous solids have emerged in the past decades as promising materials for catalyzing the selective conversion of methane to methanol. In this minireview, we highlight the activity of Cu-zeolite materials in the selective oxidation of methane to methanol, and discuss the mechanism of this reaction over different Cu-oxo structural proposals. We aim to offer a comprehensive picture of recently published spectroscopy and theoretical studies which tackled the structure–activity relationships of Cu-oxo nanoclusters. Here it is discussed how the topological diversity of zeolites and other factors influence the formation and stabilization of Cu-oxo motifs, as well as their ability to activate CH4 at mild temperatures. Finally, we also give a brief overview on the catalytic performance of Cu-oxo clusters hosted in metal organic frameworks. At the end of this minireview, we summarize the main conclusions extracted from the literature evaluation, and we provide a brief outlook on the research opportunities in this field.

Insight into the detailed mechanism of the Sabatier reaction on iron is essential for the design of cheap, environmentally benign, efficient and selective catalytic surfaces for CO2 reduction. Earlier attempts to unravel the mechanism of CO2 reduction on pure metals including inexpensive metals focused on Ni and Cu; however, the detailed mechanism of CO2 reduction on iron is not yet known. We have, thus, explored with spin-polarized density functional theory calculations the relative stabilities of intermediates and kinetic barriers associated with methanation of CO2 via the CO and non-CO pathways on the Fe (111) surface. Through the non-CO (formate) pathway, a dihydride CO2 species (H2CO2), which decomposes to aldehyde (CHO), is further hydrogenated into methoxy, methanol and then methane. Through the CO pathway, it is observed that the CO species formed from dihydroxycarbene is not favorably decomposed into carbide (both thermodynamically and kinetically challenging) but CO undergoes associative hydrogenation to form CH2OH which decomposes into CH2, leading to methane formation. Our results show that the transformation of CO2 to methane proceeds via the CO pathway, since the barriers leading to alkoxy transformation into methane are high via the non-CO pathway. Methanol formation is more favored via the non-CO pathway. Iron (111) shows selectivity towards CO methanation over CO2 methanation due to differences in the rate-determining steps, i.e., 91.6 kJ mol−1 and 146.2 kJ mol−1, respectively.

The possibility of producing synthesis gas with an H2 : CO ratio of 2.0 or higher by the gasification of mechanically activated mixtures of biomass and tar was shown. A copper–zinc catalyst was synthesized, and its morphological characteristics were studied using electron microscopy and BET adsorption methods. It was established that the use of the synthesized catalyst makes it possible to obtain methanol from synthesis gas. Selectivity for methanol formation decreased with the synthesis temperature; in this case, the conversion of synthesis gas and carbon dioxide increased.

Made available in DSpace on 2020-12-12T01:31:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 Many studies are focused on the development of materials for converting carbon dioxide into multicarbon oxygenates such as methanol and ethanol, because of their higher energy density and wider applicability. In this work, TiO2 nanotubes (NT/TiO2) were modified with CuxO nanoparticles in order to investigate the contribution of different ratio of Cu2O/CuO and its distribution over NT/TiO2 for CO2 photoelectro-conversion to methanol. The photoelectrodes were built by anodization process to obtain NT/TiO2 layer, and the decoration with CuxO hybrid system was carried out by electrodeposition process, using Na2SO4 or acid lactic as electrolyte, followed by annealing at different temperatures. X-ray photoelectron spectroscopy analysis revealed the predominance of Cu+1 and Cu+2 at 150 °C and 300 °C, respectively. X-ray diffraction and scanning electron microscopy indicated that under lactic acid solution, the oxide nanoparticles exhibited small size, cubic shape, and uniform distribution on the nanotube wall. While under Na2SO4 electrolyte, large nanoparticles with two different morphologies, octahedral and cubic shapes, were deposited on the top of the nanotubes. All modified electrodes converted CO2 in methanol in different quantities, identified by gas chromatograph. However, the NT/TiO2 modified with CuO/Cu2O (80:20) nanoparticles using lactic acid as electrolyte showed better performance in the CO2 reduction to methanol (0.11 mmol L−1) in relation to the other electrodes. In all cases, a blend among the structures and nanoparticle morphologies were achieved and essential to create new site of reactions what improved the use of light irradiation, minimization of charge recombination rate and promoted high selectivity of products. Department of Chemical Engineering Institute of Environmental Science Chemistry and Pharmaceutical Federal University of São Paulo (UNIFESP), Rua São Nicolau, 210 Unesp National Institute for Alternative Technologies of Detection Toxicological Evaluation and Removal of Micropollutants and Radioactives (INCT-DATREM) Institute of Chemistry, P.O. Box 355 Institute of Chemistry São Paulo State University (UNESP), R. Francisco Degni 55 Unesp National Institute for Alternative Technologies of Detection Toxicological Evaluation and Removal of Micropollutants and Radioactives (INCT-DATREM) Institute of Chemistry, P.O. Box 355 Institute of Chemistry São Paulo State University (UNESP), R. Francisco Degni 55

The reaction pathway of high-pressure CO2 hydrogenation over a Cu/ZnO/Al2O3 catalyst is investigated through the gradients of reactants/products concentration and catalyst temperature within the catalytic reactor. This study reveals that methanol is formed through direct CO2 hydrogenation at low temperature, while above 260 °C methanol formation is mediated via CO which is formed by reverse water-gas shift reaction.

Made available in DSpace on 2018-12-11T17:35:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Aiming a selective reduction of CO2 to methanol, a p-n junction semiconductor was constructed based on CuO nanospheres (NsCuO) deposited at TiO2 nanotubes (NtTiO2). The NtTiO2/NsCuO material demonstrated smaller charge transfer resistance, smaller flat band potential and wider optical absorption when compared with NtTiO2 and/or Ti/TiO2 nanoparticles coated by higher size particles of CuO (Ti/TiO2/CuO). The selective reduction of dissolved CO2 to methanol was promoted at lower potential of +0.2 V and UV–vis irradiation in 0.1 mol L−1 K2SO4 electrolyte pH 8 with 57% of faradaic efficiency. Even though the performance of the nanostructured material NtTiO2/NsCuO was similar to the non-completely nanostructured material Ti/TiO2/CuO (0.1 mmol L−1 methanol), the conversion to methanol has been significantly increased when hydroxyls (0.62 mmol L−1) and holes scavengers (0.71 mmol L−1), such as p-nitrosodimethylaniline (RNO) or glucose, respectively, were added in the supporting electrolyte. It indicates that photogenerated electron/hole pairs are spatially separated on p-n junction electrodes, which produces effective electrons and long-life holes, influencing the products formed in the reaction. A schematic representation of the heterojunction effect on the photoelectrocatalytic CO2 reduction is proposed under the semiconductor and each supporting electrolyte, which improves the knowledge about the subject. São Paulo State University (UNESP) Institute of Chemistry, R. Francisco Degni 55 São Paulo State University (UNESP) Institute of Chemistry, R. Francisco Degni 55 FAPESP: 2008/10449-7 FAPESP: 2013/25343-8

A massive search for chemical routes leading to methanol formation in gas phase has been conducted using computational chemistry, at the CBS-QB3 level of theory. The calculations were performed at five different temperatures (100, 80, 50, 20, and 10 K) and at three pressures (0.1, 0.01, and 0.001 atm) for each temperature. The search was focused on identifying reactions with the necessary features to be viable in the interstellar medium (ISM). A searching strategy was applied to that purpose, which allowed to reduce an initial set of 678 possible reactions to a subset of 11 chemical routes that are recommended, for the first time, as potential candidates for contributing to methanol formation in the gas phase of the ISM. They are all barrier-less, and thus they are expected to take place at collision rates. Hopefully, including these reactions in the currently available models, for the gas-phase methanol formation in the ISM, would help improving the predicted fractional abundance of this molecule in dark clouds. Further investigations, especially those dealing with grain chemistry and electronic excited states, would be crucial to get a complete picture of the methanol formation in the ISM.

CO2 hydrogenation to methanol receives great attention recently not only in conventional CO hydrogenation process but also in CO2 and H2 storage technologies. CO2 can be converted to methanol by catalytic hydrogenation, and it is supposed that CO2 is hydrogenated to methanol via hydrocarboxyl (COOH) intermediate (rWGSR route) rather than formate (HCOO) intermediate. It was reported that CeOx/Cu(111) surface stabilizes COOH intermediate, which consecutively results in lower activation energy for methanol formation than on Cu(111) and Cu / ZnO ( 000 1 ¯ ) surfaces. The activity of Cu/CeO2 catalysts can be further enhanced by Pd addition, because it can enhance reducibility of Cu site. In this study, therefore, Cu/CeO2 and Pd–Cu/CeO2 catalysts were applied to CO2 hydrogenation to methanol. Pd-promoted Cu/CeO2 catalysts achieved higher methanol productivity than Cu/CeO2 catalyst due to the increase in CO2 conversion. Because methanol productivity over Pd weight (mmolMeOH/gPd·h) simply decreased as the amount of Pd increased, it is considered that the enhanced activity of Pd–Cu/CeO2 catalysts mainly resulted from the increase in the reactivity of active Cu sites. The dispersion and surface concentration of Cu increased due to the interaction with highly-dispersed Pd, and Cu sites were more reduced by Pd promotion due to electron donation from Pd. Pd promotion also generated more reduced CeO2 surface. These promoting effects of Pd was the highest in the catalyst containing 1 wt.% Pd (1Pd–10Cu/CeO2), because further increase in the amount of loaded Pd lowered the textural properties of catalyst. As a result, methanol productivity was enhanced in Pd-promoted Cu/CeO2 catalysts and the highest in 1Pd–10Cu/CeO2 catalyst.

This paper reports on the formation of methanol (MeOH) during conventional oxygen delignification (OD) of four typical alkaline pulps, namely, southern pine kraft pulp (SP-KP), wheat straw soda pulp (WS-SP), and eucalyptus kraft pulp (E-KP) with κ numbers (KN) of 32.8 and 16.9 (E-KP32.8 and E-KP16.9). Based on the mass transfer effect of MeOH and a proposed demethoxylation reaction pathway of lignin, two kinds of kinetic models were proposed to predict MeOH formation. The results show that the two-stage pseudo kinetic model with a first-order rate equation is adequate, which was further modified to a first-order kinetic model by means of which MeOH formation during OD of the pulps can be effectively predicted. Finally, the single set of kinetic parameters for the WS-SP, E-KP32.8, and E-KP16.9 pulps was calculated. The proposed kinetic model is considered as a valuable tool for the prediction and control of MeOH formation during OD of various alkaline pulps.

Methanol formation from [Cp*IrIII(NHC)Me(CD2Cl2)]+ occurs quantitatively at room temperature with air (O2) as the oxidant and ethanol as a proton source. A rare example of a diiridium bimetallic complex, [(Cp*Ir(NHC)Me)2(μ-O)][(BArF4)2], 3, was isolated and shown to be an intermediate in this reaction. The electronic absorption spectrum of 3 features a broad observation at ∼660 nm, which is primarily responsible for its blue color. In addition, 3 is diamagnetic and can be characterized by NMR spectroscopy. Complex 3 was also characterized by X-ray crystallography and contains an IrIV–O–IrIV core in which two d5 Ir(IV) centers are bridged by an oxo ligand. DFT and MCSCF calculations reveal several important features of the electronic structure of 3, most notably, that the μ-oxo bridge facilitates communication between the two Ir centers, and σ/π mixing yields a nonlinear arrangement of the μ-oxo core (Ir–O–Ir ∼ 150°) to facilitate oxygen atom transfer. The formation of 3 results from an Ir oxo/oxyl interme...

Morinda citrifolia is used in traditional medicine. Pectinmethylesterases (PME) is an enzyme that responsible for the degradation of pectin. The current was aimed to extract PME from M. citrifolia (MPME) and compared with commercial PME, and studied the temperature mediated inactivation of PME. The results revealed that the optimum time, pH, and temperature of MPME was found as 5 min, pH 7, and 30°C, respectively. The pretreatment of M. citrifolia for 5 min at 100°C can significantly prevent the methanol formation. Further detailed study on the purification and characterization of MPME and the influence of pretreatment of M. citrifolia on methanol formation under progress.

We present experimental constraints on the insertion of oxygen atoms into methane to form methanol in astrophysical ice analogs. In gas-phase and theoretical studies this process has previously been demonstrated to have a very low or non-existent energy barrier, but the energetics and mechanisms have not yet been characterized in the solid state. We use a deuterium UV lamp filtered by a sapphire window to selectively dissociate O2 within a mixture of O2:CH4 and observe efficient production of CH3OH via O(1D) insertion. CH3OH growth curves are fit with a kinetic model, and we observe no temperature dependence of the reaction rate constant at temperatures below the oxygen desorption temperature of 25K. Through an analysis of side products we determine the branching ratio of ice-phase oxygen insertion into CH4: ~65% of insertions lead to CH3OH with the remainder leading instead to H2CO formation. There is no evidence for CH3 or OH radical formation, indicating that the fragmentation is not an important channel and that insertions typically lead to increased chemical complexity. CH3OH formation from O2 and CH4 diluted in a CO-dominated ice similarly shows no temperature dependence, consistent with expectations that insertion proceeds with a small or non-existent barrier. Oxygen insertion chemistry in ices should therefore be efficient under low-temperature ISM-like conditions, and could provide an important channel to complex organic molecule formation on grain surfaces in cold interstellar regions such as cloud cores and protoplanetary disk midplanes.

The photochemical conversion of methane into methanol from H2O2 aqueous solution as well as the effect of the addition mode were studied. Direct addition of different amounts H2O2 leads to increasing methanol production at the first stage of the reaction. The excess of H2O2 would lead to the reactive oxygen species scavenging and the subsequent O2 production. It was also corroborated that extra hydroxyl radicals in the aqueous medium do not improve the formation of methanol but a noticeable increase in the formation of HCOOH with respect to methanol was evidenced. In contrast, dosing addition at relatively low rates leads to constant methane consumption towards methanol. Methanol formation would be in this case in equilibrium with further oxidation to HCOOH or CO2. This suggests that only a controlled constant availability of HO’s at low concentration can enhance the performance of methanol generation in the photochemical process., The financial support from MINECO/FEDER through CTQ2014-60524-R project is fully acknowledged.

article i nfo 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.

Hydrogenation of CO 2 is challenging from both economic and environmental view points. In the present study, density functional theory (DFT) method was employed to investigate the reaction mechanism of methanol synthesis from CO 2 hydrogenation. Two possible reaction pathways were proposed, where hydrogenation of CO 2 led to intermediate HOCO free radical, followed by the formation of intermediate HCOOH or CO, finally resulting in the methanol formation. The results showed that the preferred pathway was CO 2 → CO → H 2 CO → CH 3 OH, whose enthalpy energy is −35.389788 kJ/mol. The calculated results of the configuration and the enthalpy energy of classic molecules were in good agreement with the values in literature, which indicated that the results should be reliable.

Current CuZnO methanol synthesis technology may be improved by development of a catalyst allowing a “once through” methanol synthesis step. A Raney copper/alkoxide catalyst has been reported in the patent literature operating at 50 bar and 120 °C. We report here the effect of temperature, pressure, Raney copper concentration and CH3OK concentration by orthogonal array design on this catalyst system. A synergistic effect on catalyst activity and methanol formation has been observed between CH3OK and Raney copper.

A series of [Cp*Ir(III)(R-bpy)Cl]Cl (R-bpy = 4,4'-di-R-2,2'-bipyridine; R = CF3, H, Me, tBu, OMe) complexes was prepared and studied for catalytic formic acid disproportionation. The relationship between the electron donating strength of the bipyridine substituents and methanol production of the corresponding complexes was analyzed; the unsubstituted (R = H) complex was the most selective for methanol formation.

The main dynamic characteristics of biochemical methanol formation by the oxidation of methane using a biocatalyst were studied. The biocatalyst is based on cells of bacteria Methylosinus sporium B-2121, both suspended in a medium and immobilized in the poly(vinyl alcohol) cryogel. The change in the methane concentration and the biocatalyst amount affects the productivity of the system, the maximal concentration of methanol in the cultural liquid, and the rate of methanol accumulation. The most part of the dynamic characteristics are described by extremal curves. The experimental conditions were optimized prior to experiments. The use of the immobilized biocatalyst makes it possible to enhance the productivity of the process more than fivefold compared to that of the free cells and to achieve the highest methanol concentration in the medium: 62±2 mg L−1.

Methanol decomposition on metals has been subject of several theoretical studies, usually concentrating on a particular set of reactions in the main reaction path. In this work, we present an extensive study that considers all potential elementary steps for four close-packed surfaces including Cu, Ru, Pt, and Pd that shows the different behaviors and alternative routes through which the decomposition can take place by theoretical methods, including dispersion contributions. Decomposition follows different paths on these metals; while Cu would produce CH2O, CO is the major product for the other metals. In addition, coverage effects might change the first step in Pt and Ru from methylenic to alcohol H activation. Alternatively the reaction network can be inspected for the formation of methanol from CO and hydrogen. Under these conditions, Cu generates CH2O and only at very high H coverages is methanol likely to appear. On Pd, methanol formation and CHOH dissociation compete, thus leading to an inefficient process. A similar path takes place for Pt. For Ru the lateral paths leading to C−O breaking can occur at several points in the reaction network, never reaching CH3OH. A compilation of the results with comparable computational setups presents a detailed database that can be added to the thermodynamics and kinetics for other reactions, such as methanation, with which they share a common list of reactions, or employed when analyzing larger alcohols such as those derived from biomass.

The hydrogen-bonded hexamolybdoplatinate tetramer [H23(PtMo6O24)4]9− was reacted with methanol to yield a new methylated hexamolybdoplatinate. X-ray diffraction analysis revealed that the methylate...