Methanol Formation Research Articles

Solvothermal Synthesis of Medium-Entropy Oxide Spheres for Thermocatalytic Conversion of CO2 to Methanol.

New chemical compositions and structures for medium- and high-entropy oxides (HEOs) currently represent a promising new avenue in materials research for a wide range of applications including catalysis, energy storage, and ceramics. To speed up further development, synthesis methods for multicationic oxides are needed for controlling features like morphology, porosity, and chemical compositions. In this work, mesoporous spinel oxide spheres with five cations are synthesized using solvothermal synthesis techniques. The targeted chemistry included Co, Al, Fe, and Cr as the first four cations, where the fifth cation was varied by increasing cation radii (Ga, In, Yb, Ho, or Ce). After calcination, all as-synthesized precursors led to mesoporous oxide spheres with spinel oxide structures. In order to demonstrate an example of applicability for targeting different M3+ cations, the sample containing Co, Al, Fe, Cr, and In was tested in a model reaction of thermocatalytic CO2 hydrogenation and is shown to be active with a preference to methanol formation (58% selectivity, 7.8% conversion at 300 °C). The synthesis of multicationic mesoporous spheres appears to be quite flexible in terms of possible M3+ cations compositions and is a potential material to combine targeted chemistry for applications like catalysis.

Tailored pore-confined single-site iron(III) catalyst for selective CH4 oxidation to CH3OH or CH3CO2H using O2.

Direct oxidation of methane to valuable oxygenates like alcohols and acetic acid under mild conditions poses a significant challenge due to high C‒H bond dissociation energy, facile overoxidation to CO and CO2 and the intricacy of C-H activation/C-C coupling. In this work, we develop a multifunctional iron(III) dihydroxyl catalytic species immobilized within a metal-organic framework (MOF) for selective methane oxidation into methanol or acetic acid at different reaction conditions using O2. The active-site isolation of monomeric FeIII(OH)2 species at the MOF nodes, their confinement within the porous framework, and their electron-deficient nature facilitate chemoselective C‒H oxidation, yielding methanol or acetic acid with high productivities of and , respectively. Experiments and theoretical calculations suggest that methanol formation occurs via a FeIII-FeI-FeIII catalytic cycle, whereas CH3CO2H is produced via hydrocarboxylation of in-situ generated CH3OH with CO2 and H2, and direct CH4 carboxylation with CO2.

Amino Acid-Based Ionic Liquids-aided CO2 Hydrogenation to Methanol.

This study explored the use of amino acid-based ionic liquids to facilitate the conversion of carbon dioxide (CO2) into methanol through catalytic hydrogenation. Combining tetrabutylammonium L-argininate (TBA·Arg) with the ruthenium Ru-MACHO-BH complex, allowed achieving significant yields of methanol under optimized conditions. By systematically varying key reaction parameters, we demonstrate that the TBA·Arg ionic liquid promotes the efficient hydrogenation pathway leading to methanol formation, thus offering a sustainable approach to CO2 valorization. These findings underscore the potential of amino acid-based ionic liquids in catalyzing the transformation of CO2 into valuable chemicals, contributing to carbon mitigation efforts.

Role of H2O2 as Oxidant and H2O as Co-catalyst over Anatase-TiO2 (101) for Conversion of Methane to Methanol.

Computations based on density functional theory are carried out to examine the mechanism of photocatalytic oxidation of methane to methanol with H2O2 as oxidant and water as co-catalyst over anatase TiO2 (101) surface. The reaction proceeds with hydrogen abstraction from methane followed by the formation of surface methoxy species, which is reduced to methanol. We compare the reaction energetics for C-H dissociation in the presence and absence of surface defect, but find no discernible impact of O-vacancy on methane oxidation. In comparison, hydroxyl produced as a result of H2O2 or H2O photo-decomposition dramatically reduces the barrier for CH3-H bond cleavage. The reaction proceeds further by the reduction of surface methoxy group and is the rate-limiting step for methanol formation. Additionally, we find that methyl can also react with water to form methanol with a considerably lower barrier, suggesting an active involvement of water for methanol formation. We also study the role of water as a co-catalyst and observe significant reduction in barriers, facilitated by alternate pathway for proton transfer. The reaction pathways presented provide valuable in- sights into the mechanism of methane oxidation in the presence of H2O2 as oxidant and demonstrate the rate-enhancing role of water for these steps.

Exploring complete catalytic cycle of methane oxidation to methanol on Cu2O2 stabilized within MIL-53(Al) framework: A combined DFT and microkinetic study

Although inspiration from copper-based natural enzymes has shown promise in improving catalyst design for methane-to-methanol (MTM) oxidation, high productivity, and selectivity under mild conditions remain a significant challenge. This study constructs the dinuclear copper (Cu2) species stabilized within the metal-organic framework (MOF), MIL-53(Al), containing Cu as efficient catalytic sites and explores the ability of different oxidants (O2, N2O, and H2O2) to oxidize Cu2 into the dicopper-oxo (Cu2O2) species using density functional theory (DFT) calculations. Our results indicate the kinetic and thermodynamic favorability of Cu2O2 species formation using O2 as an oxidant within the MIL-53(Al) framework. Furthermore, the thermal stability of Cu2O2/MIL-53(Al) has been verified via ab initio molecular dynamics (AIMD) calculations. The kinetics of the complete MTM oxidation cycle over Cu2O2/MIL-53(Al) have been studied using both DFT and microkinetic simulation methods. The present study predicts that the C-H activation on the Cu2O2/MIL-53(Al) has a low free energy barrier (0.77 eV) and that the high stability of CH3 and its very low free energy barrier in the C-O coupling step favors the methanol formation over the formaldehyde. More importantly, Cu2O2/MIL-53(Al) exhibits high methanol selectivity owing to the inhibition of CH3 dehydrogenation and low methanol desorption energy (0.21 eV). Microkinetic simulations confirm the methanol production under relatively mild reaction conditions (200–280 K and 1 bar). This work provides insights into the feasibility of selective MTM oxidation over this family of MOF under mild conditions.

Trimetallic Alloys as an Electrocatalyst for Fuel Cells: The Case of Methyl Formate on Pt3Pd3Sn2.

The shift toward renewable energy sources plays a central role in the quest for a circular economy. In this context, methyl formate (MF) has garnered attention as a compelling hydrogen carrier and alternative fuel, because of its remarkable characteristics (energy density, ease of storage and transport, and low boiling point). In this study, DFT calculations supported by online electrochemical mass spectroscopy (OE-MS) were performed to investigate the MF electro-oxidation (MFEO) on Pt3Pd3Sn2 (111). The DFT calculations provide insight into the role of Pt, Pd, and Sn atoms in MFEO. Pt and Pd together provide a preferred active site for initiating MFEO through the O-H bond scission, and Sn plays an essential role in the mitigation of CO through oxygenation or water activation. By comparing the reaction energies and activation barriers for all possible reactions in MFEO, the suggested path necessitates a minimum energy of 0.14 eV to initiate the MFEO. This value was supported by the experimental results, showing that the oxidation wave of MF starts at 0.15 V (70 °C). Density functional theory (DFT) results, supported by OE-MS, indicate that the hydrolysis of MF prior to MFEO is not preferred on Pt3Pd3Sn2 (111) surfaces, although the formation of methanol is plausible via a CH3O intermediate. Among the three small organic molecules (SOMs) studied─MF, methanol, and formic acid─MF has the lowest activation energy for the initial bond breaking that starts the whole oxidation process (0.13 eV), compared to formic acid (0.45 eV) and methanol (0.61 eV); thus, MF is the preferred fuel on Pt3Pd3Sn2 (111).

Cobalt Tetracationic 3,4-Pyridinoporphyrazine for Direct CO2 to Methanol Conversion Escaping the CO Intermediate Pathway.

Molecular catalysts offer a unique opportunity to implement different chemical functionalities to steer the efficiency and selectivity for the CO2 reduction for instance. Metalloporphyrins and metallophthalocyanines are under high scrutiny since their most classic derivatives the tetraphenylporphyrin (TPP) and parent phthalocyanine (Pc), have been used as the molecular platform to install, hydrogen bonds donors, proton relays, cationic fragments, incorporation in MOFs and COFs, to enhance the catalytic power of these catalysts. Herein, we examine the electrocatalytic properties of the tetramethyl cobalt (II) tetrapyridinoporphyrazine (CoTmTPyPz) for the reduction of CO2 in heterogeneous medium when adsorbed on carbon nanotubes (CNT) at a carbon paper (CP) electrode. Unlike reported electrocatalysis with cobalt based phthalocyanine where CO was advocated as the two electron and two protons reduced intermediate on the way to the formation of methanol, we found here that CoTmTPyPz does not reduce CO to methanol. Henceforth, ruling out a mechanistic pathway where CO is a reaction intermediate.

Cobalt Tetracationic 3,4‐Pyridinoporphyrazine for Direct CO2 to Methanol Conversion Escaping the CO Intermediate Pathway

AbstractMolecular catalysts offer a unique opportunity to implement different chemical functionalities to steer the efficiency and selectivity for the CO2 reduction for instance. Metalloporphyrins and metallophthalocyanines are under high scrutiny since their most classic derivatives the tetraphenylporphyrin (TPP) and parent phthalocyanine (Pc), have been used as the molecular platform to install, hydrogen bonds donors, proton relays, cationic fragments, incorporation in MOFs and COFs, to enhance the catalytic power of these catalysts. Herein, we examine the electrocatalytic properties of the tetramethyl cobalt (II) tetrapyridinoporphyrazine (CoTmTPyPz) for the reduction of CO2 in heterogeneous medium when adsorbed on carbon nanotubes (CNT) at a carbon paper (CP) electrode. Unlike reported electrocatalysis with cobalt based phthalocyanine where CO was advocated as the two electron and two protons reduced intermediate on the way to the formation of methanol, we found here that CoTmTPyPz does not reduce CO to methanol. Henceforth, ruling out a mechanistic pathway where CO is a reaction intermediate.

Enhanced photoelectrochemical CO2 reduction activity towards selective generation of alcohols over CuxO/SrTiO3 heterojunction photocathodes

Photoelectrochemical reduction (PECR) of CO2 to value-added chemicals and fuels will reduce the dependency on fossil fuels, also it will solve environmental issues that arise due to greenhouse gases. A heterojunction of CuxO/SrTiO3 with varying post-annealing temperature ranges from 300 to 600 °C (CS300-600) was synthesized by overlying the spin-coated SrTiO3 on electrodeposited Cu2O over the FTO glass substrate. The synthesized photoelectrode's crystallinity and phase formation significantly varied by varying the post-annealing temperature, which was characterized via XRD and Raman spectroscopy. Optical, morphological, type of heterojunction formation and elemental surface oxidation states of photoelectrodes were studied through UV–visible DRS spectrum, FE-SEM, and XPS analysis respectively. Electrocatalytic analysis such as Linear Sweep Voltammetry (LSV), and Electrochemical Impedance Spectrometry (EIS) was employed, thus it conforms to the highest photocurrent density (−1.38 mA/cm2 at −0.6V vs. Ag/AgCl), and low charge transfer resistance (RCT=0.412 kΩ) at the electrode-electrolyte interfaces for CS500 photoelectrode as compared to others photoelectrodes. PECR of CO2 to liquid product formation was evaluated by applying different potential ranges (0 to −0.6 V vs. Ag/AgCl). Highest methanol formation of 48.69 μmol.cm−2hr−1, which is approximately 9 times enhanced as compared to the pure Cu2O (5.62 μmol.cm−2hr−1) photoelectrode at 0 V vs Ag/AgCl for CS500 heterojunction. Optimization of overlaying SrTiO3 synthesis temperature for crystallization formation on Cu2O and applied photoelectrode potential findings could pave the way for designing other new heterojunction types for selective liquid alcohol production.

Enhanced CO2 hydrogenation reaction by Tuning interfacial Cu/ZnOx through synergistic interactions in the precursors

The Cu/ZnO/Al2O3 is a typical industrial catalyst for water–gas-shift reaction and methanol synthesis, and is also gaining momentum in CO2 hydrogenation reaction. The dynamic evolution of the phases and microstructures of the precursor of this catalyst leads to a notable synergistic effect that defines its overall catalytic function and performance. To gain insights into the role and interaction between the relevant precursors, we compared Cu/ZnO/Al2O3 catalysts using a conventional co-precipitation and a fractional precipitation method, where the latter one shows an enhanced Cu/ZnOx interface due to a thorough and strong interaction between two components in the precursor. The ZnOx decoration on Cu with unsaturated Znδ+ species boosted the methanol formation to a rate of 508 gCH3OH‧kgcat−1‧h−1 with 58 % selectivity at 513 K and 3 MPa. This work provides mechanistic insights into the synergistic interplay between the involved phases in the Cu/ZnO/Al2O3 catalyst.

Insight into the synergistic effect between plasma and oxygen vacancy in direct oxidation of CH4 to CH3OH by molecular O2 at mild condition

The direct conversion of methane into the value-added chemical methanol using molecular oxygen was investigated via plasma catalysis under mild condition. An efficient synergistic effect between plasma and catalyst was achieved using an oxygen vacancy-rich ZnO/Al2O3 catalyst. A high methanol selectivity of 48.5 % and a high synergy factor of 2.1 could be achieved simultaneously over ZnO/Al2O3 R300 catalyst. The presence of oxygen vacancies played a crucial role in methanol formation. A close relationship between oxygen vacancy content and methanol selectivity was established. In situ DRIFT and optical emission spectra were employed to identify key intermediates, and a plausible reaction mechanism was proposed. The CH3 and CH3O species were the key intermediates on the catalyst surface. The oxygen vacancy could efficiently adsorb the O radicals and accelerate the formation of CH3O species. This work offers insights into the rational engineering of efficient catalyst for plasma catalysis process.

Ab initio calculations of high-entropy clusters for oxygen reduction and evolution as well as CO2 reduction reactions

This study introduces a design concept for a high-entropy cluster (HEC) comprising of Fe, Co, Ni, Cu, and Rh metals supported on nitrogen-doped graphene. Five different configurations including CoNiCuRh@FeN4, FeNiCuRh@CoN4, FeCoCuRh@NiN4, FeCoNiRh@CuN4, as well as; FeCoNiCu@RhN4 with the mixing entropy change of ΔSmix = 0.14 meV/K were considered. The positive dissociation potential and negative formation energy suggested the electrochemical and thermodynamic stabilities of these materials. According to density functional theory (DFT + U) calculations, the CoNiCuRh@FeN4 catalyst led to the overpotentials of 0.37 VRHE, 0.37 VRHE, and 0.24 VRHE for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and CO2 reduction reaction (CO2RR) towards CO production, respectively. It was determined that, FeN4 acted as an active site, while CoNiCuRh-HEC behaved as the modulator. Also, FeNiCuRh@CoN4 catalyst led to the CO2RR overpotential of 0.35 VRHE towards CH3OH formation where CoN4 acted as the active site, and FeNiCuRh-HEC species acted as the modulator surpassing the activity of single-atom catalysts (SAC). Moreover, the density of states (DOS) and charge transfer analyses suggested that, the presence of a high-entropy cluster may enhance the charge transfer and stabilize the reaction intermediates, toward selective methanol formation. Therefore, a DFT-based strategy to design a high-entropy cluster was developed through electrochemistry and beyond.

Single-step conversion of methane-steam to methanol on single-atom Cu1/γ-Al2O3 catalyst prepared via electrostatic anchoring

Direct conversion of methane to methanol in heterogeneous catalysis is of paramount importance but remains a challenging issue in improving catalytic activity and selectivity. Here, we report that Cu single-atom sites anchored on γ-Al2O3 oxides (Cu1/γ-Al2O3) using surface electrostatic adsorption, are highly active (methanol yield of ∼47 mmol/molCu/h) and stable in continuous conversion of methane-steam to methanol at 200 °C, comparable to most of the state-of-the-art Cu-zeolite catalysts. The combined DFT calculation and isotope labeling experiments reveal the methane-to-methanol reaction pathway on Cu single-atom sites and methanol formation is the rate limiting step. The further theoretical study indicates that single Cu atom as active site can preferentially activate methane C-H bond instead of methanol and has larger advantage for highly-selective methanol yield compared with [Cu(II)-OH]+ and [CuOCu]2+ active sites. Our molecular-level findings on Cu1/γ-Al2O3 single-atom catalyst pave the way to prepare better non-zeolite catalysts for methane to methanol.

Activity of bimetallic PdIn/CeO2 catalysts tuned by thermal reduction for improving methanol synthesis via CO2 hydrogenation

AbstractSynergistic Pd–In2O3 catalysts are promising candidates for producing methanol via CO2 hydrogenation, and the metal phases in them can be tuned by thermal reduction treatment affecting the catalytic activity significantly. This work presents a comprehensive investigation to gain an insight into the effect of thermal reduction temperature on the variation and interaction of Pd and In2O3 phases supported on CeO2 (viz., PdIn/CeO2) and their correlations with CO2 hydrogenation toward methanol synthesis. The findings show that Pd/In‐rich PdIn alloys and In2O3 with relatively strong interaction are key phases (by reducing the PdIn/CeO2 at 300°C) for promoting methanol formation, leading to a high selectivity to methanol at 78.9% and space–time yield (STY) of 3.6 gCH3OH gPdIn−1 h−1. A further increase in reduction temperature (from 300 to 500°C) promoted the formation of homogenized PdIn intermetallic alloys with significantly poor ability for H2 dissociation and CO2 activation, and hence poor methanol yield.

CO2 hydrogenation to methanol over Pt functionalized Hf-UiO-67 versus Zr-UiO-67.

Sustainable methanol formation from CO2/H2 is potentially a key process in the post-fossil chemical industry. In this study, Hf- and Zr-based metal-organic framework (MOF) materials with UiO-67 topology, functionalized with Pt nanoparticles, have been tested for CO2 hydrogenation at 30 bar and 170-240°C. The highest methanol formation rate, 14 molmethanol molPt-1 h-1, was obtained over a Hf-based catalyst, compared with the maximum of 6.2 molmethanol molPt-1 h-1 for the best Zr-based analogue. However, changing the node metal did not significantly affect product distribution or apparent activation energy for methanol formation (44-52 kJ mol-1), strongly indicating that the higher activity of the Hf-based analogues is associated with a higher number of active sites. Both catalysts showed stable catalytic performance during testing under kinetic conditions, but the addition of 2 vol% water to the feed induced catalyst deactivation, in particular the Hf-MOFs. Interestingly, mainly methanol and methane formation rates decreased, while CO formation rates were less affected by deactivation. No direct correlation was found between catalytic stability and framework stability (crystallinity, specific surface area). Experimental and computational studies suggest that water adsorption strength to the MOF node may affect the relative catalytic stability of Hf-UiO-67-Pt versus Zr-UiO-67-Pt methanol catalysts.This article is part of the discussion meeting issue 'Green carbon for the chemical industry of the future'.

Bifunctional Au@UiO‐67‐bpy‐Cu Plasmonic Nanostructures for the Solar‐Driven CO2 Reduction to Methanol

AbstractPhotocatalytic CO2 reduction is gaining more interest as a sustainable route to produce methanol, a key starting material in the synthesis of many chemicals and a potential energy carrier. Here, metal‐organic frameworks (MOFs) are used as platforms to integrate plasmonic Au nanospheres and Cu active centers in joint bifunctional hybrid photocatalysts. The methodology followed in obtaining stable Au@UiO‐67‐bpy‐Cu MOFs is based on synthesizing Au@UiO‐67‐bypiridine (bpy) MOFs through a core‐shell procedure, and then modifying them with Cu ions after their coordination with the bpy ligands. This gains the final structure regular coverage of active metal centers that can be excited by the interaction with the plasmonic nanospheres. In the absence of Au, the system demonstrates selectivity toward the formation of methanol under hole scavenger‐free conditions owing to the excitation of the bpy‐Cu complex with visible light. The obtained yield duplicates upon Au nanospheres incorporation as a result of the injection of hot electrons, excited by surface‐mediated intraband processes, to the bpy‐Cu states, thus increasing their CO2 reduction efficiency. Additionally, the catalytic activity remains stable during four consecutive cycles.

Dual-engine-driven realizing high-yield synthesis of Para-Xylene directly from CO2-containing syngas

The direct synthesis of light aromatics, especially para-xylene (p-X), from syngas/CO2 is drawing strong interest, but improving the space-time yield (STY) of p-X is a significant challenge. Here, a dynamic “dual-engine-driven” (DED) catalytic system is designed by combining two partners of ZnCr and FeMn (named “dual-engine”) with Z5@SiO2 capsule zeolite. The DED catalyst of 1.0%FeMn&[ZnCr&Z5@SiO2] shows an extremely higher p-X STY of 36.1 gp-x·kgcat-1·h-1, about eight times higher than that of [ZnCr&Z5]. DED manipulates ZnCr engine for methanol formation and drives FeMn engine for light olefins generation together, and then the formed methanol and light olefins are coordinately converted in situ into p-X-rich aromatics over Z5@SiO2. The DED model boosts the driving force for syngas/CO2 conversion, simultaneously concerting the cooperation of “dual-engine” for p-X generation, resulting in extremely high STY of p-X. This study achieves non-petroleum p-X production at industrial-relevant level and advances knowledge in designing innovative heterogeneous catalysts.

Regulated Photocatalytic CO2-to-CH3OH Pathway by Synergetic Dual Active Sites of Interlayer.

Herein, composites of nanosheets with van der Waals contacts are employed to disclose how the interlayer-microenvironment affects the product selectivity of carbon dioxide (CO2) photoreduction. The concept of composites of nanosheets with dual active sites is introduced to manipulate the bonding configuration and promote the thermodynamic formation of methanol (CH3OH). As a prototype, the CoNi2S4-In2O3 composites of nanosheets are prepared, in which high-resolution transmission electron microscopy imaging, X-ray photoelectron spectroscopy spectra, and zeta potential tests confirm the presence of van der Waals contacts rather than chemical bonding between the In2O3 nanosheets and the CoNi2S4 nanosheets within the composite. The fabricated CoNi2S4-In2O3 composites of nanosheets exhibit the detection of the key intermediate *CH3O during CO2 photoreduction through in situ Fourier transform infrared spectra, while the In2O3 nanosheets and CoNi2S4 nanosheets alone do not show this capability, further verified by the density functional theory calculations. Accordingly, the CoNi2S4-In2O3 composites of nanosheets show the ability to produce CH3OH, whereas the CoNi2S4 and In2O3 nanosheets solely generate carbon monoxide products from CO2 photoreduction.

The influence of La incorporation on the performance of the CuxCeyLa1-(x+y)O2-δ catalysts for CO2 hydrogenation to methanol

The effect of La incorporation on the catalytic performance of Cu–CeO2 for CO2 hydrogenation to methanol was investigated. The increase of the CeO2 lattice constant and shift in the F2g band from Raman spectroscopy confirmed La incorporation into the CeO2 lattice. The La atomic percent of ≤ 19 % was the upper limit for the amount of La incorporated fully into the CeO2 lattice without any phase segregation. XPS results of Cu0.25Ce0.56La0.19O2-δ assumed to have full La incorporation, showed a maximum concentration of oxygen vacancies that facilitated CO2 adsorption and conversion to methanol.The lattice fringes from HRTEM and lattice expansion confirmed that Cu was located on the catalyst surface for the synthesized catalysts. Cu0.25Ce0.56La0.19O2-δ showed an improvement in the methanol space-time yield when the temperature was increased from 260 °C to 280 °C, in contrast to the catalysts with excess La on the surface. The descriptors for the methanol production were the availability of oxygen vacancies and the metal-metal oxide interaction (Cu–CexLa1−xO2-δ and Cu–La2O2CO3). The smaller metallic Cu crystallite size for Cu0.25Ce0.19La0.56O2-δ suggested increased interactions between Cu0 and the CexLa1−xO2-δ support, which was conducive for methanol formation. The highest performance of Cu0.25Ce0.56La0.19O2-δ at a higher temperature of 280 °C and pressure of 50 bar with a methanol space-time yield of 55.2 gCH3OH.kgcatal.h−1 was attributed to the excellent thermal stability of the formed CexLa1−xO2-δ solid solution support interacting with Cu which prevented sintering.

Electrochemical CO2 Reduction by Cobalt(II)2,9,16,23-tetra(amino)phthalocyanine: Enhancement Effect of Active Sites toward Methanol Formation

Electrochemical CO₂ Reduction by Cobalt(II)2,9,16,23-tetra(amino)phthalocyanine: Enhancement Effect of Active Sites toward Methanol Formation