Partial Oxidation Of Methanol Research Articles

Breaking Continuously Packed Bimetallic Sites to Singly Dispersed on Nonmetallic Support for Efficient Hydrogen Production.

We have synthesized Pt1Zn3/ZnO, also termed 0.01 wt %Pt/ZnO-O2-H2, as a catalyst containing singly dispersed single-atom bimetallic sites, also called a catalyst of singly dispersed bimetallic sites or a catalyst of isolated single-atom bimetallic sites. Its catalytic activity in partial oxidation of methanol to hydrogen at 290 °C is found to be 2-3 orders of magnitude higher than that of Pt-Zn bimetallic nanoparticles supported on ZnO, 5.0 wt %Pt/ZnO-N2-H2. Selectivity for H2 on Pt1Zn3/ZnO reaches 96%-100% at 290-330 °C, arising from the uniform coordination environment of single-atom Pt1 in singly dispersed single-atom bimetallic sites, Pt1Zn3 on 0.01 wt %Pt/ZnO-O2-H2, which is sharply different from various coordination environments of Pt atoms in coexisting PtxZny (x ≥ 0, y ≥ 0) sites on Pt-Zn bimetallic nanoparticles. Computational simulations attribute the extraordinary catalytic performance of Pt1Zn3/ZnO to the stronger adsorption of methanol and the lower activation barriers in O-H dissociation of CH3OH, C-H dissociations of CH2O to CO, and coupling of intermediate CO with atomic oxygen to form CO2 on Pt1Zn3/ZnO as compared to those on Pt-Zn bimetallic nanoparticles. It demonstrates that anchoring uniform, isolated single-atom bimetallic sites, also called singly dispersed bimetallic sites on a nonmetallic support can create new catalysts for certain types of reactions with much higher activity and selectivity in contrast to bimetallic nanoparticle catalysts with coexisting, various metallic sites MxAy (x ≥ 0, y ≥ 0). As these single-atom bimetallic sites are cationic and anchored on a nonmetallic support, the catalyst of singly dispersed single-atom bimetallic sites is different from a single-atom alloy nanoparticle catalyst. The critical role of the 0.01 wt %Pt in the extraordinary catalytic performance calls on fundamental studies of the profound role of a trace amount of a metal in heterogeneous catalysis.

Periodic open cellular structures (POCS) as catalyst support for intensified heat transport in the partial oxidation of methanol to formaldehyde

Heat transport in catalytic reactors is one of the most important factors in reactor design, especially for highly endo- or exothermic reactions. The limited thermal conductivity of randomly packed beds can be significantly improved when alternative catalyst supports are used. A new generation thereof are periodic open cellular structures (POCS), which are used in this study as catalyst support for the partial oxidation of methanol to formaldehyde, an exothermic gas phase reaction. A comparison to traditional packed bed reactors revealed that a POCS made of the highly conductive alloy AlSi10Mg can significantly reduce the hot-spot temperature, allowing almost isothermal operation at optimal reaction conditions. The improved temperature control allows for operation with higher methanol inlet concentrations and wall temperatures as compared to the commercial process. The beneficial heat transport properties of POCS were used to conduct isothermal kinetic measurements at elevated temperature. Based on these findings and the design freedom of additive manufacturing, an optimized cellular structure was designed and fabricated, which improved the heat transport especially in the critical inlet section of the reactor.

A joint strategy for CO2 reduction and CH3OH oxidation at electrode to CO + CH4 and methylal in ionic liquid

Electrochemical reduction reaction of CO2 (CO2eRR) in aqueous electrolyte currently encounters with sluggish oxygen evolution at anode and hydrogen evolution as a competing reaction at cathode. A Cu-FeOx-N-doped carbon composite (CFCN) prepared by facile pyrolysis of Cu-Fe salts and melamine was used as cathode, associated with Pt sheet anode to perform CO2eRR to CO + CH4 and partial oxidation of methanol to methylal (DMM) in ionic liquid-methanol electrolyte solution. The electrolysis exhibits efficient red-ox activity with higher average FEDMM (59.9%) for DMM within 24 h and high momentary FEC1 (87.2%) for CO + CH4 at 24 h, specifically, realizing red-ox reactions couple for synchronously producing high-valued chemicals, DMM and CO + CH4. Besides, the composite also demonstrates high saturation magnetization (110 emu/g). The catalytic role and contribution of the various components such as metal Cu, CuOx and Fe3O4 nanocrystallines constituting the composite for CO2eRR and to magnetic property were examined. The catalyst possesses high run stability for CO2eRR as the electrolysis has continuously performed for 120 h.

Investigation on formaldehyde generation characteristics and influencing factors of PODE/methanol dual-fuel combustion mode.

Polyoxymethylene dimethyl ether (PODE) and methanol are important low-carbon substitutable fuels for reducing carbon emissions in internal combustion engines. In the research, the impacts of methanol ratio, injection timing, and intake temperature on HCHO generation and emission were investigated using both engine tests and numerical simulations. Results suggest that an increase in methanol ratio suppresses auto-ignition tendency of PODE, leading to the increase of ignition delay period, pressure peak, and heat release rate peak inside the cylinder. The decrease in in-cylinder combustion temperature contributes to an increase in HCHO emission due to partial oxidation of methanol in the cylinder and exhaust pipe. While the injection timing is gradually postponed from -10 °CA ATDC to 2 °CA ATDC, in-cylinder high-temperature area decreases, the quantity of unburned methanol increases, but part of HCHO is converted to HCO due to H radical influence, resulting in 72% increased HCHO emission. With the increment of intake temperature, the oxidation and decomposition of in-cylinder methanol accelerate, leading to an improvement in combustion stability, more uniform temperature distribution, and a decrease in unburned methanol, which results in lower HCHO emission. When the intake temperature is rose from 30 to 60 °C, HCHO emission decreases by 11.2%.

Paired Electrosynthesis of Formaldehyde Derivatives from CO2 Reduction and Methanol Oxidation

AbstractUtilizing CO2‐derived formaldehyde derivatives for fuel additive or polymer synthesis is a promising approach to reduce net carbon dioxide emissions. Existing methodologies involve converting CO2 to methanol by thermal hydrogenation, followed by electrochemical or thermochemical oxidation to produce formaldehyde. Adding to the conventional methanol oxidation pathway, we propose a new electrochemical approach to simultaneously generate formaldehyde derivatives at both electrodes by partial methanol oxidation and the direct reduction of CO2. To achieve this, a method to directly reduce CO2 to formaldehyde at the cathode is required. Still, it has been scarcely reported previously due to the acidity of the formic acid intermediate and the facile over‐reduction of formaldehyde to methanol. By enabling the activation and subsequent stabilization of formic acid and formaldehyde respectively in methanol solvent, we were able to implement a strategy where formaldehyde derivatives were generated at the cathode alongside the anode. Further mechanism studies revealed that protons supplied from the anodic reaction contribute to the activation of formic acid and the stabilization of the formaldehyde product. Additionally, it was found that the cathodic formaldehyde derivative Faradaic efficiency can be further increased through prolonged electrolysis time up to 50 % along with a maximum anodic formaldehyde derivative Faradaic efficiency of 90 %.

Paired Electrosynthesis of Formaldehyde Derivatives from CO2 Reduction and Methanol Oxidation.

Utilizing CO2 -derived formaldehyde derivatives for fuel additive or polymer synthesis is a promising approach to reduce net carbon dioxide emissions. Existing methodologies involve converting CO2 to methanol by thermal hydrogenation, followed by electrochemical or thermochemical oxidation to produce formaldehyde. Adding to the conventional methanol oxidation pathway, we propose a new electrochemical approach to simultaneously generate formaldehyde derivatives at both electrodes by partial methanol oxidation and the direct reduction of CO2 . To achieve this, a method to directly reduce CO2 to formaldehyde at the cathode is required. Still, it has been scarcely reported previously due to the acidity of the formic acid intermediate and the facile over-reduction of formaldehyde to methanol. By enabling the activation and subsequent stabilization of formic acid and formaldehyde respectively in methanol solvent, we were able to implement a strategy where formaldehyde derivatives were generated at the cathode alongside the anode. Further mechanism studies revealed that protons supplied from the anodic reaction contribute to the activation of formic acid and the stabilization of the formaldehyde product. Additionally, it was found that the cathodic formaldehyde derivative Faradaic efficiency can be further increased through prolonged electrolysis time up to 50 % along with a maximum anodic formaldehyde derivative Faradaic efficiency of 90 %.

Enhancing catalytic performance and hot electron generation through engineering metal-oxide and oxide-oxide interfaces

Interfaces are of utmost importance in catalytic reactions, influencing reaction kinetics and electron transfer processes. However, investigations in combined interfaces of metal-oxide and oxide-oxide at heterogeneous catalysts still have challenges due to their complex structure. Herein, we synthesized well-defined Co3O4 and CeO2 cubes with distinct facets and investigated their catalytic performance when deposited on a Pt-thin film, focusing on the influence of metal-oxide and oxide-oxide interfaces. Catalytic measurements demonstrated that the CeO2/Pt interface significantly enhanced turnover frequency (TOF) and selectivity for partial methanol oxidation compared to Co3O4/Pt and bare Pt. Notably, the CeO2/Co3O4/Pt nanodevice exhibited improved partial oxidation selectivity, highlighting the role of the CeO2/Co3O4 interface in methyl formate production. Chemicurrent measurements demonstrate enhanced hot electron generation due to increased overall TOF and partial oxidation production. We also conducted near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) analysis, revealing a higher concentration of Ce3+ ions and increased oxygen vacancies in the CeO2/Co3O4/Pt catalyst, suggesting oxygen migration from CeO2 to Co3O4, leading to methoxy species stabilization and promoting methyl formate formation.

Electrosynthesis of ethylene glycol from C1 feedstocks in a flow electrolyzer

Ethylene glycol is a widely utilized commodity chemical, the production of which accounts for over 46 million tons of CO2 emission annually. Here we report a paired electrocatalytic approach for ethylene glycol production from methanol. Carbon catalysts are effective in reducing formaldehyde into ethylene glycol with a 92% Faradaic efficiency, whereas Pt catalysts at the anode enable formaldehyde production through methanol partial oxidation with a 75% Faradaic efficiency. With a membrane-electrode assembly configuration, we show the feasibility of ethylene glycol electrosynthesis from methanol in a single electrolyzer. The electrolyzer operates a full cell voltage of 3.2 V at a current density of 100 mA cm−2, with a 60% reduction in energy consumption. Further investigations, using operando flow electrolyzer mass spectroscopy, isotopic labeling, and density functional theory (DFT) calculations, indicate that the desorption of a *CH2OH intermediate is the crucial step in determining the selectively towards ethylene glycol over methanol.

Nanoporous Gold: From Structure Evolution to Functional Properties in Catalysis and Electrochemistry

Nanoporous gold (NPG) is characterized by a bicontinuous network of nanometer-sized metallic struts and interconnected pores formed spontaneously by oxidative dissolution of the less noble element from gold alloys. The resulting material exhibits decent catalytic activity for low-temperature, aerobic total as well as partial oxidation reactions, the oxidative coupling of methanol to methyl formate being the prototypical example. This review not only provides a critical discussion of ways to tune the morphology and composition of this material and its implication for catalysis and electrocatalysis, but will also exemplarily review the current mechanistic understanding of the partial oxidation of methanol using information from quantum chemical studies, model studies on single-crystal surfaces, gas phase catalysis, aerobic liquid phase oxidation, and electrocatalysis. In this respect, a particular focus will be on mechanistic aspects not well understood, yet. Apart from the mechanistic aspects of catalysis, best practice examples with respect to material preparation and characterization will be discussed. These can improve the reproducibility of the materials property such as the catalytic activity and selectivity as well as the scope of reactions being identified as the main challenges for a broader application of NPG in target-oriented organic synthesis.

Paired Electrosynthesis of Formic Acid from CO2 and Formaldehyde from Methanol

Electrochemical carbon dioxide (CO2) reduction provides a pathway to sustainable chemicals. However, the high electrical energy demand is still a major challenge. Cathodic (CO2) reduction is typically paired with the anodic oxygen evolution reaction (OER), which is energy intensive with limited added value. In this experimental work, we replace OER with partial methanol oxidation to reduce the energy demand while producing formaldehyde and formic acid as value-added chemicals. We investigate methanol oxidation on metallic and oxidized platinum and the paired process with CO2 reduction to formic acid in an electrochemical flow cell. Methanol oxidation on oxidized platinum was more selective to formaldehyde than on metallic platinum but required a higher potential. In the paired process, we achieved a current efficiency for formaldehyde of up to 58% on oxidized platinum at 75 mA cm–2 and 1.8 V vs RHE reaching a concentration of 1.14 mol L–1 formaldehyde. The current efficiency for formaldehyde and formic acid combined reached up to 89%. Methanol oxidation was not affected by pairing, while the current efficiency of CO2 reduction decreased. We report the first production of formaldehyde beyond mechanistic studies by electrochemical methanol oxidation and demonstrate paired CO2 reduction with formaldehyde as primary anodic product.

A methanol autothermal reforming system for the enhanced hydrogen production: Process simulation and thermodynamic optimization

Methanol autothermal reforming is a potential way to produce hydrogen that can be used for vehicle power batteries like PEMFC. Combining a reformer with a combustor to produce substantial hydrogen is promising, but the challenge of heat transfer efficiency between the reformer and combustor must be considered. Furthermore, the complexity of the system structure is not conducive to its large-scale operation level. In this paper, a novel methanol autothermal reforming hydrogen production system without catalytic combustion was built and developed, aiming to produce hydrogen-rich gas with low CO concentration. Process simulation and thermodynamic optimization on the target system were detailedly performed using Aspen Plus software and parameter sensitivity analysis methods. In addition, a methanol autothermal reforming hydrogen production system using catalytic combustion was taken as the reference system. The results indicated that the novel system could achieve a self-sustaining operation by the coupled methanol partial oxidation and steam reforming. And the product gas contained very low CO concentration (<10 ppm) due to the combined effects of water-gas shifting and CO preferential oxidation reactions. It was verified that under the maximal exergy efficiency condition, the exergy efficiency of the novel system is not significantly improved compared with the reference system, but the hydrogen yield is increased by about 27.65%, the thermal efficiency is increased by about 17.51%, and the exergy loss when generating unit molar H2 is reduced by 20.53 kJ/mol; Under the condition of maximum hydrogen yield, the indicators of the novel system also perform better. Notably, the reformer is the main exergy loss source in the novel system, which provides a theoretical basis for further optimization of parameter configuration. This work will be beneficial to researchers who study the miniaturization design of the integrated system of methanol hydrogen production coupled vehicle power battery.

Kinetic Coupling of Redox and Acid Chemistry in Methanol Partial Oxidation on Vanadium Oxide Catalysts

Kinetic, isotopic, and spectroscopic studies establish the active site requirements for three kinetically coupled catalytic cycles catalyzed by redox, Brønsted, and Lewis acid–base sites, which occur during methanol and oxygen reactions on titania-supported vanadium oxide catalysts. The initial activation of methanol during its oxidative dehydrogenation to formaldehyde restricts the overall turnovers─this reaction proceeds via CH3OH dissociative adsorption followed by a kinetically relevant C–H bond scission of the CH3O intermediate on V–O redox site pairs found at the interface of VOx and TiO2. The Gibbs free energy change of these two steps (ΔGads and ΔG⧧, respectively) both decrease as V–O–V coordination decreases and V–O–Ti coordination increases, leading to higher turnovers per surface vanadium as VOx dispersion increases, except the extreme case of isolated VO4. Coupled kinetically with the oxidative dehydrogenation cycle is the Brønsted acid-catalyzed cycle that forms dimethoxymethane─this cycle proceeds via methanol- and formaldehyde-derived CH3OCH2OH adsorption to Brønsted sites at the VOx–TiO2 interface, followed by its kinetically relevant C–O bond scission. Its turnovers also increase with VOx dispersion following the same trend as the oxidative dehydrogenation cycle but at a much faster rate, so the reaction can readily approach chemical equilibrium. Alongside the other two catalytic cycles is the Tishchenko reaction that forms methyl formate from two formaldehyde molecules, produced by the methanol oxidative dehydrogenation cycle, on exposed Ti4+–O2– Lewis acid–base pairs uncovered by VOx─this cycle proceeds via kinetically relevant intermolecular C–O bond formation followed by a rapid 1,3-hydride shift. The interplay of coexisting redox, Brønsted, and Lewis sites, each with its unique catalytic roles, leads to different rates and yields of the three products. The active site structure and mechanistic knowledge established here allow us to optimize the product ratios required for downstream synthesis of larger oxygenates.

From molecular adsorption to decomposition of methanol on various ZnO facets: A periodic DFT study

Methanol is an interesting and important molecule to study because of its potential to replace existing fuels. It is also a prominent hydrogen source which can be used to generate hydrogen in-situ. ZnO is widely used as catalyst in synthesis of methanol from CO2 at industrial scale. In this work, we demonstrate that the same catalyst could be used for MeOH decomposition. We have investigated interaction of methanol with various flat and stepped facets of ZnO by employing Density Functional Theory (DFT). Two flat [(101¯0) and (112¯0)] and two stepped [(101¯3) and (112¯2)] facets are studied in detail for methanol adsorption. Chemisorption of MeOH with varying strength is common to all four facets. Most importantly spontaneous dissociation of O-H bond of methanol is observed on all facets except (112¯0). Our DFT calculations reveal that molecular adsorption is favored on flat facets, while dissociation is favored on step facets. Also, (101¯0) facet undergoes substantial reconstruction upon MeOH adsorption. Activation of C-H bond along with strengthening of C-O bond on ZnO facets suggest partial oxidation of methanol. With our DFT investigations, we dig deeper into the underlying electronic structure of various facets of ZnO and provide rationale for the observed facet dependent interaction of ZnO with MeOH.

Hydrogen production optimization from methanol partial oxidation via ultrasonic sprays using response surface methodology and analysis of variance

Hydrogen production via partial oxidation of methanol (POM) in an ultrasonic spray system was studied experimentally, using an h-BN-Pt/Al2O3 catalyst with ultra-low Pt contents (0.2 wt%). The effects of oxygen-to-methanol (O2/C) ratio, methanol flow rate, and gas hourly space velocity (GHSV) of air and carrier gas on H2 yield were examined. Compared to conventional spray systems, the ultrasonic spray system could produce more uniformly dispersed methanol and thus further enhance the POM reaction. The results showed a higher O2/C ratio (0.8) enhanced the POM, which poses higher CH3OH conversion, higher reaction temperature, and lower CO and CH4 productions. The CO2 concentration was mainly affected by GHSV and CH3OH flow rate. A higher GHSV led to a quicker retention time for the reactants in the catalyst bed, and a lower CH3OH flow rate deteriorates the CO2 concentration. Based on the Box Behnken design (BBD) from response surface methodology (RSM) and analysis of variance (ANOVA), the optimal operating conditions are found to be O2/C ratio = 0.8, CH3OH flow rate = 0.7 mL min−1, and GHSV = 10 000 h−1. Combining these conditions, the predicted maximum H2 yield is 1.635 mol‧(mol CH3OH)−1 which is close to the experimental value of 1.646 mol‧(mol CH3OH)−1. The RSM and ANOVA not only resulted in a quadratic response surface regression model and significant regression coefficients but also indicated CH3OH flow rate being the primary factor.

Understanding of photocatalytic partial oxidation of methanol to methyl formate on surface doped La(Ce)[sbnd]TiO2: Experiment and DFT calculation

The photocatalytic partial oxidation of methanol to methyl formate (MF) under visible light irradiation on surface doped La(Ce)TiO2 was studied by the experimentation and DFT calculation. The La or Ce atoms could be doped in the surface lattice of TiO2 to form the bond of La(Ce)OTi but could not be doped in the body of TiO2. The crystal size of TiO2 was restrained from growth due to the surface lattice distortion resulted from La(Ce) bonding with surface oxygen. The band structure and surface hydroxyls can be tuned by the La or Ce distribution on the surface of TiO2. The rare earth on the surface of TiO2 can form impurity levels in the valence band and conduction band, reduce the band gap, change surface electron states, decrease the potential energy for surface hydroxyl formation, and reduce the energy barriers of the transition states from methoxy via formaldehyde to MF. The doped catalyst exhibited superior methanol conversion and MF selectivity in photocatalytic partial oxidation of methanol to MF under visible light irradiation. The surface hydroxyl group plays an important role in the reaction and were positively related to the methanol conversion and MF selectivity. The La doped catalysts exhibited better methanol conversion and MF selectivity than the Ce doped catalysts due to the faster recoverable surface hydroxyls and lower energy barriers to transition states. This study may contribute to design new visible light responsive catalyst for photocatalytic partial oxidation reaction and provide applicable green route to MF synthesis.

Silver catalysts for the partial oxidation of alcohols

The review analyzes state of the art in the partial oxidation of alcohols to carbonyl compounds over Ag catalysts, including the partial oxidation of methanol to formaldehyde, oxidation of ethylene glycol to glyoxal, and oxidation of ethanol to acetaldehyde. For the methanol oxidation process, conditions for implementing the BASF and ICI technologies are considered and the entire chain of transformations from natural gas to formaldehyde is estimated in terms of exergy. When considering modern kinetic studies for the partial oxidation of alcohols on silver, some recent publication are analyzed, particularly those devoted to the application of a ring-shaped reactor to suppress the homogeneous steps of formaldehyde decomposition, the development of a new approach to simulation of the process taking into account different reactivity of the catalyst, and the creation of a simulator to calculate the methanol oxidation process using a neural network with a genetic algorithm. Main steps in the development of a technology for the partial oxidation of ethylene glycol to glyoxal on Ag catalysts are briefly described. The author analyzes modern experimental and theoretical works devoted to the formation mechanisms of oxygencontaining active sites on the silver surface and their involvement in the conversion of alcohols to carbonyl compounds, as well as the new Ag-containing catalytic compositions.

Iron molybdate catalysts synthesised via dicarboxylate decomposition for the partial oxidation of methanol to formaldehyde

Iron molybdate catalysts were prepared using a sol gel route with malonic acid and oxalic acid and their performance for the selective oxidation of methanol to formaldehyde was evaluated.

Understanding of Photocatalytic Partial Oxidation of Methanol to Methyl Formate on Surface Doped La(Ce)-Tio2: Experiment and Dft Calculation

Understanding of Photocatalytic Partial Oxidation of Methanol to Methyl Formate on Surface Doped La(Ce)-Tio2: Experiment and Dft Calculation

Methanol oxidation on Au(332): methyl formate selectivity and surface deactivation under isothermal conditions

Surface deactivation for partial methanol oxidation to methyl formate on Au(332) under oxygen-deficient conditions at low temperatures suggests a small number of highly active sites for methyl formate formation.

Heterogeneity of oxygen reactivity: key for selectivity of partial methanol oxidation on gold surfaces.

Recent evidence for low-temperature oxidation of methyl formate on Au(332) may affect the selectivity of gold catalysts during partial oxidation of methanol. Under isothermal conditions, overoxidation of methyl formate is significantly slower than methanol oxidation which can be attributed to special oxygen species required for overoxidation.