Methanol Dehydrogenation Reaction Research Articles

Efficient CuZn/SiO2 lamellar catalysts for methanol dehydrogenation: New insights into the role of zinc

CuZn/SiO2 lamellar catalysts are obtained through the introduction of zinc oxide with different amount to Cu/SiO2 prepared by the ammonia-evaporation method and investigated for the dehydrogenation of methanol to methyl formate. The 20CuZn/SiO2 catalyst showed the best catalytic activity with a methanol conversion of 44.5% and a selectivity to methyl formate of ~92.7% at 300 °C and 0.2 MPa. The reason for this excellent activity could be ascribed to the strong interaction between Cu and ZnO, which promoted the decomposition of the copper phyllosilicate precursor to release copper oxide and thereby achieved more active Cu0 species upon reduction on the catalyst surface. In addition, the agglomeration of Cu species was mainly responsible for the slight decline in the methanol conversion in ZnO modified Cu based catalysts for the methanol dehydrogenation reaction.

Analysis of integrated system for ammonia synthesis and methyl formate production in the thermally coupled reactor

In this study, the simultaneous production of ammonia and methyl formate (MF) in a thermally coupled reactor has been investigated. Since the ammonia synthesis reaction is associated with heat release, and the production of MF is an endothermic reaction, the ammonia production reaction supplies the heat required for MF's reaction in the proposed reactor. To justify the suggested model's accuracy, the results are verified with the same condition's experimental data. This reactor's benefits include the elimination of ammonia synthesis inter-stage coolers, and reduced energy consumption. Also, exchanged heat causes significant improvements in both equilibrium reactions and enhanced process performance. On the other hand, by the novel configuration reactor, the methanol dehydrogenation reaction's hydrogen supplied about 21.57% of the required hydrogen in ammonia production feed. Eventually, the effect of input parameters on reactor performance investigates by using the sensitivity analysis and optimization process. It also found that about 34.66% of required hydrogen in ammonia synthesis feeds by methanol dehydrogenation reaction in optimum conditions supplied.

Second Sphere Ligand Promoted Organoiridium Catalysts for Methanol Dehydrogenation under Mild Conditions

AbstractHydrogen produced from renewable resources is a potential source of clean energy. And Methanol is a liquid at room temperature and has a hydrogen content of up to 12.6 wt%, makes it a promising hydrogen source and can provide great benefits for sustainable hydrogen production. In this work, the modification of the picolinic acid ligand along with changes in the type and substituent position of the groups enhances the activity in iridium‐catalyzed methanol dehydrogenation catalysis. These second sphere ligand modifications are found to be effective for achieving highly active organoiridium catalysts for methanol dehydrogenation reaction under mild conditions, i. e. 1 atm, 78 °C, with a weak base and without using an organic solvent, exhibiting a TOF of 377 h−1. The electronic population analysis of each ligand is theoretically calculated, which shows that catalytic activity is dramatically affected by modifications to the metal's secondary coordination sphere environment, and the high activity originates from appropriate coordination by the picolinic acid ligand and carboxylic acid moiety in addition to the hydroxyl functionality. Moreover, kinetic experiments suggest that the C−H bond of methanol is linked to the iridium core and broken in the rate‐determining step of the reaction. This study will be valuable for catalyst development in the field of methanol dehydrogenation.

Over-faradaic hydrogen production in methanol electrolysis cells

A new alcohol electrolyser concept (Methanol Over-Faradaic Electrolyser: MOFE) has been developed to achieve over-faradaic H2 production rates, which were experimentally measured. In a first stage, this outstanding phenomenon was investigated in an alkaline membrane electrolyser. Secondly, a membrane-less electrolyser was used to simplify and implement this concept in practical configurations. The obtained results demonstrated that the experimentally measured over-faradaic H2 production rates on the cathode were due to the coupling of the electrocatalytic hydrogen production via methanol electrolysis (hydrogen evolution reaction) with the catalytic methanol dehydrogenation reaction. The kinetic of the latter reaction is drastically enhanced upon polarization due to the phenomenon of Electrochemical Promotion of Catalysis (EPOC), in liquid phase conditions. Hence, the K+ ions supplied to the Pd/C catalyst-cathode from the liquid electrolyte under polarization conditions promote the chemisorption of intermediate species, activating the catalytic hydrogen production via methanol dehydrogenation reaction on the active Pd sites. Thus, the synergy between these two processes (electrocatalytic + catalytic) lowers the overall energy requirements of the hydrogen produced below the typical values found for conventional alcohol electrolysis cells. These results demonstrate, for the first time, the possibility to produce an “over-faradaic” H2 production rate in a liquid phase electrolysis cell, which is of great interest in view of enhancing the energetic efficiency and the power requirements for hydrogen production via electrolysis of organic molecules.

Comparison of O–H and C–H activation of methanol on Ni-based cluster: a DFT investigation

Using the density functional theory, the initial dehydrogenation of methanol on NixMy (M = Ni, Co, Fe, Mn, Cr, x + y = 4, y = 1, 2) clusters is investigated. Two adsorption and dehydrogenation mechanisms of methanol are studied: one proceeds along the C–H scission and another begins with the breaking of the O-H bond. The adsorption sites of methanol on the Ni or M sites of the NixMy clusters are considered. The adsorption of methanol on Ni4 cluster is stronger than those on bimetallic clusters, while the initial dehydrogenation barriers on NixMy clusters are lower than that on Ni4 cluster. The comparable energy barriers of two pathways (O–H or C–H dissociation) on Ni-based clusters indicate that these two paths are quite competitive. In addition, the Ni2M2 clusters show superior activation performance compared with the Ni3M clusters, especially for Ni2Mn2 and Ni2Cr2 clusters. The effects of alloyed metal on the catalytic activity of Ni for methanol initial dehydrogenation, including the adsorption energy, O–H or C–H bond scission barrier and frontier molecular orbital levels, are discussed. It can be concluded that the addition of Co, Fe, Mn and Cr to Ni catalyst is able to enhance the activity of the methanol dehydrogenation reaction.

Methanol dehydrogenation reaction at Au@Pt catalysts: Insight into the methanol electrooxidation

The electrochemical methanol oxidation reaction (MOR) has received considerable attention because of its importance in the development of fuel cells. Recently, bimetallic Au-Pt catalyst systems were developed as efficient MOR electrocatalysts. In this work, we investigated the methanol dehydrogenation reaction (MDHR, CH3OH → CO + 2H2) on the Au@Pt core-shell surfaces using an in situ surface-enhanced Raman spectroscopy (SERS) technique. The CO intermediates produced by the MDHR and adsorbed on the Pt surfaces play an important role in the electrochemical MOR. The formation of CO on Au@Pt surfaces during the MDHR was examined as a function of the coverage and thickness of the Pt layers on Au. The effect of the electrode potential applied to the Au@Pt surface on the MDHR behavior was also investigated. The SERS results regarding the MDHR behaviors on the different Pt layers on Au surfaces could provide rational comparisons of the electrochemical MOR activities of the Au@Pt and Pt/C catalysts that can be evaluated differently depending on the contact time between the electrode and methanol and the scan rate. The present work provides insight into the electrocatalytic activity of bimetallic core-shell catalysts from the mechanistic perspective.

Exploring the mechanisms of aqueous methanol dehydrogenation catalyzed by defined PNP Mn and Re pincer complexes under base-free as well as strong base conditions

The mechanisms of aqueous methanol dehydrogenation reaction catalyzed by defined Mn and Re pincer complexes under different conditions were computed.

Kinetic studies of methanol dehydrogenation. Part III: carbon-supported copper catalysts

The kinetics of methanol dehydrogenation over carbon-supported copper catalyst was studied. The catalyst was prepared by the incipient wetness impregnation of carbonaceous graphite-like material Sibunit with aqueous solution of copper nitrate. The resulting Cu/C samples were calcined and reduced in a hydrogen flow within temperature interval of 200–400 °C. Experiments were carried out in a flow-through fixed-bed tubular reactor. Observable rate constants were determined for the reactions of methanol dehydrogenation to methyl formate and methyl formate decomposition on carbon monoxide and hydrogen. The process of methanol dehydrogenation in a tubular reactor was simulated by means of mathematical modeling. The estimation of kinetic parameters in accordance with experimental data obtained for the Cu/C sample reduced at 300 °C has allowed us to consider the reversibility of methanol dehydrogenation reaction.

Kinetic studies of methanol dehydrogenation. Part II: copper on silica–montmorillonite composite

The kinetics of methanol dehydrogenation over copper catalyst supported on silica–montmorillonite composite was studied. The samples of the catalyst were prepared by incipient wetness impregnation followed by drying, calcination and reduction in hydrogen flow in a temperature range 200–400 °C. Kinetic studies were performed in a flow fixed-bed reactor. Observed rate constants were determined for the reactions of methanol dehydrogenation into methyl formate and methyl formate decomposition on carbon monoxide and hydrogen. An increase in the reduction temperature was shown to have no significant effect on the catalytic properties. Numerical methods were used to calculate the kinetic constants with consideration of reversibility of methanol dehydrogenation reaction the sample reduced at 300 °C.

A Heat Exchanger Reactor Equipped with Membranes to Produce Dimethyl Ether from Syngas and Methyl Formate and Hydrogen from Methanol

The energy crisis of the century is a motivation to present processes with higher energy efficiency for production of clean and renewable resources of energy. Hence, a catalytic heat exchanger reactor for production of dimethyl ether (DME) from syngas, and hydrogen and methyl formate (MF) from methanol is investigated in the present study. The proposed configuration is equipped with two different membranes for in-situ separation of products. Syngas is converted to DME through an exothermic reaction and it supplies a part of required energy for the methanol dehydrogenation reaction. Produced water in the exothermic side and produced hydrogen in the endothermic side are separated by using appropriate perm-selective membranes. In-situ separation of products makes the equilibrium reactions proceed toward higher conversion of reactants. A mathematical model based on reasonable assumptions is developed to evaluate molar and thermal behavior of the configuration. Performance of the system is aimed to enhance by obtaining optimum operating conditions. In this regard, Genetic Algorithm is applied. Performance of the heat exchanger double membrane reactor working under optimum conditions (OTMHR) is compared with a heat exchanger reactor without membrane (THR). OTMHR promotes methanol conversion to MF to %87.2, carbon monoxide conversion to %95.8 and hydrogen conversion to %64.6.

Reactivity of a Ruthenium-Carbonyl Complex in the Methanol Dehydrogenation Reaction.

Finding new catalysts for the release of molecular hydrogen from methanol is of high relevance in the context of the development of sustainable energy carriers. Herein, we report that the ruthenium complex Ru(salbinapht)(CO)(Pi‐Pr3) {salbinapht=2‐[({2′‐[(2‐hydroxybenzyl)amino]‐[1,1′‐binaphthalen]‐2‐yl}imino)methyl]phenolato} (2) catalyzes the methanol dehydrogenation reaction in the presence of base and water to yield H2, formate, and carbonate. Dihydrogen is the only gas detected and a turnover frequency up to 55 h−1 at 82 °C is reached. Complex 2 bears a carbonyl ligand that is derived from methanol, as is demonstrated by labeling experiments. The carbonyl ligand can be treated with base to form formate (HCOO−) and hydrogen. The nature of the active species is further shown not to contain a CO ligand but likely still possesses a salen‐derived ligand. During catalysis, formation of Ru(CO)2(H)2(P‐iPr3)2 is occasionally observed, which is also an active methanol dehydrogenation catalyst.

Investigation of thermally double coupled double membrane heat exchanger reactor to produce dimethyl ether and methyl formate

Owing to concerns associated with energy consumption and energy intensive methods in the chemical industries, the present study aims to investigate production of some downstream products of natural gas in a recuperative configuration. Accordingly, simultaneous production of dimethyl ether from methanol and syngas and also methyl formate from methanol is investigated in a catalytic heat-exchanger reactor assisted with water perm-selective membranes. Dimethyl ether synthesis from methanol and syngas are exothermic reactions supplying required energy for the methanol dehydrogenation reaction. Produced waters in both exothermic sides are eliminated from reaction media by permeation through the perm-selective membranes equipped on the inner and outer surfaces of the reactor. A feasibility study is implemented through a mathematical model based on mass and energy balance. Genetic algorithm as a powerful method in nonlinear optimization problems is applied to obtain optimum operating conditions. 97% methanol conversion to dimethyl ether, 66% methanol conversion to methyl formate and 17% hydrogen conversion are the advancements of the proposed thermally double-coupled double-membrane reactor working under optimum conditions.

Optimal conditions in converting methanol to dimethyl ether, methyl formate, and hydrogen utilizing a double membrane heat exchanger reactor

Following importance of investigating new sources of energy with highly efficient processes, a new configuration for simultaneous production of high purity dimethyl ether (DME), hydrogen and methyl formate (MF) is numerically studied in this work. In this regard, a catalytic heat-exchanger reactor assisted with two different membranes for methanol conversion and in-situ separation of products is simulated. The interesting feature of this system is utilizing only one feedstock (i.e. methanol) to produce different valuable products. Methanol is dehydrated through an exothermic reaction and supplies required energy for the methanol dehydrogenation reaction. Produced water in the exothermic side and produced hydrogen in the endothermic side are separated by permeation to particular membranes. A steady state one-dimensional plug flow model is developed to evaluate molar and thermal behavior of the system. Optimum operating conditions are determined applying genetic algorithm as a powerful optimization method. The proposed configuration working under optimum conditions promotes methanol conversion to DME to % 95.1 and methanol conversion to MF to % 99.6 providing high purity products in the output streams.

Nanocomposites on the basis of layered silicates as the catalysts for the dehydrogenation of methanol

The methanol dehydrogenation reaction has been studied over impregnated copper-containing catalysts. A silica-montmorillonite nanocomposite has been used as the support for these systems. The catalyst’s features were found to depend strongly on the distance of the interlayer spacing within the structure of montmorillonite. The textural changes taking place in the support affect the accessibility of the active sites of the catalyst for methanol. The optimal temperature of the reductive pretreatment in hydrogen atmosphere required for the preparation of an active and durable enough nanocomposite-based catalyst was found to be 300°C.

Fabricating polystyrene fiber-dehydrogenase assemble as a functional biocatalyst

Immobilization of the enzymes on nano-structured materials is a promising approach to enhance enzyme stabilization, activation and reusability. This study aimed to develop polystyrene fiber-enzyme assembles to catalyze model formaldehyde to methanol dehydrogenation reaction, which is an essential step for bioconversion of CO2 to a renewable bioenergy. We fabricated and modified electrospun polystyrene fibers, which showed high capability to immobilize dehydrogenase for the fiber-enzyme assembles. Results from evaluation of biochemical activities of the fiber-enzyme assemble showed that nitriation with the nitric/sulfuric acid ratio (v/v, 10:1) and silanization treatment delivered desirable enzyme activity and long-term storage stability, showing great promising toward future large-scale applications.

Analysis of sulfur-induced selectivity changes for anhydrous methanol dehydrogenation on Ni(100) surfaces

The absorption of sulfur on the Ni(100) surface has been reported to influence its product selectivity for methanol dehydrogenation. While dehydrogenation on the clean Ni(100) surface primarily produces a mixture of carbon monoxide and hydrogen, preadsorption of 0.25–0.33 monolayers of sulfur shifts the selectivity to mainly formaldehyde and hydrogen. Density functional theory calculations of clean and sulfur-modified Ni(100) surfaces demonstrate that sulfur destabilizes methanol dehydrogenation reaction intermediates in a manner consistent with this shift in selectivity. Microkinetic modeling of the reaction system further indicates that these changes alter the reaction selectivities from CO to CH2O production in the steady state. The reaction selectivities of metal alloy surfaces, which also have heterogeneous surface morphologies, are hypothesized to be influenced in a similar manner as these S/Ni(100) surfaces.

Hydrogen Generation from Alcohols Catalyzed by Ruthenium−Triphenylphosphine Complexes: Multiple Reaction Pathways

We report a comprehensive density functional theory (DFT) study of the mechanism of the methanol dehydrogenation reaction catalyzed by [RuH(2)(H(2))(PPh(3))(3)]. Using the B97-D dispersion-corrected functional, four pathways have been fully characterized, which differ in the way the critical beta-hydrogen transfer step is brought about (e.g., by prior dissociation of one PPh(3) ligand). All these pathways are found to be competitive (DeltaG(++) = 27.0-32.1 kcal/mol at 150 degrees C) and strongly interlocked. The reaction can thus follow multiple reaction channels, a feature which is expected to be at the origin of the good kinetics of this system. Our results also point to the active role of PPh(3) ligands, which undergo significant conformational changes as the reaction occurs, and provide insights into the role of the base, which acts as a "co-catalyst" by facilitating proton transfers within active species. Activation barriers decrease on going from methanol to ethanol and 2-propanol substrates, in accord with experiment.

Possible reaction pathway in methanol dehydrogenation on Pt and Ag surfaces/clusters starting from O–H scission: Dipped adcluster model study

The mechanism of the methanol dehydrogenation reaction on a Pt surface has been investigated using the dipped adcluster model (DAM) combined with density-functional theory (DFT) calculations. Starting from O–H bond scission, methanol decomposes to form CO exothermically on the Pt surface, where the Pt-dσ orbital effectively interacts with the O–H antibonding orbital. The donative interaction of the Pt-dσ orbitals was found to be important for catalytic activation on the Pt surface. The reaction pathway starting from C–H bond scission has a larger activation barrier and, therefore, is less kinetically favorable. Electron transfer from the bulk, which is included in the present DAM calculation, plays an important role in the reaction pathway from O–H bond scission, in particular for the dehydrogenation of formaldehyde. On the other hand, the Ag surface has been shown to be effective for formaldehyde synthesis, because formaldehyde desorbs spontaneously from the Ag surface. The present reaction has also been examined and discussed in view of the nanoscale clusters and nanorods.

Characterization of Cu/SiO 2 catalysts prepared by ion exchange for methanol dehydrogenation

A series of copper on silica catalysts prepared by using the ion exchange methods with copper loading between 0.45 and 3 wt% have been studied by means of different techniques such as TPR, EPR, XANES, XRD, XRF, BET and methanol dehydrogenation reaction. The TPR patterns showed two well-defined peaks with maxima between 250–350°C and 600–650°C. The first one (peak I) corresponds to two contributions: (i) the one step reduction (Cu 2+ to Cu 0) of a low interacted species (S 1), and (ii) the partial reduction (Cu 2+ to Cu 1+) of a highly dispersed and surface interacted species (S 2). The second TPR peak (peak II) observed at a higher temperature corresponds to the second step reduction (Cu 1+ to Cu 0) of the S 2 species. In addition, it has been found out that Cu 0 and not Cu 2+ is the active site for methanol dehydrogenation to methyl formate.