Partial Oxidation Of Methanol Research Articles

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.

Synthesis of Mesoporous Cu-Ni/Al2O4 Catalyst for Hydrogen Production via Hydrothermal Reconstruction Route

Mesoporous Cu-Ni/Al2O4 catalyst of high surface area (176 m2g−1) is synthesized through a simple hydrothermal reconstruction process by using low-cost activated alumina as the aluminate source without organic templates. The desired mesoporous structure of the catalyst is formed by the addition of Cu2+ and Ni2+ metal ions in the gel solution of the activated alumina followed by hydrothermal treatment at 70 °C and calcination at temperatures in the range of 600 to 800 °C. To consider the environmental concern, we found the concentration of the Cu2+ and Ni2+ ion in the residual filtrate is less than 0.1 ppm which satisfies the effluent standard in Taiwan (<1.0 ppm). The effects of the pH value, hydrothermal treatment time, and calcination temperature on the structure, morphology and surface area of the synthesized Cu-Ni/Al2O4 composites are investigated as well. In addition, the Cu-Ni/Al2O4 catalyst synthesized at pH 9.0 with a hydrothermal treatment time of 24 h and a calcination temperature of 600 °C is used for hydrogen production via the partial oxidation of methanol. The conversion efficiency is found to be >99% at a reaction temperature of around 315 °C, while the H2 yield is 1.99 mol H2/mol MeOH. The catalyst retains its original structure and surface area following the reaction process, and is thus inferred to have a good stability. Overall, the hydrothermal reconstruction route described herein is facile and easily extendable to the preparation of other mesoporous metal-alumina materials for catalyst applications.

Investigation of fuel composition and efficiency of solid oxide fuel cell with different methanol pretreating technologies

ABSTRACT In this paper, fuel composition and efficiency of solid oxide fuel cell with different methanol pretreating technologies are investigated. High concentrations of H2 and CO can be produced by methanol pretreatment at high temperature, whereas high concentration of methane can be produced at low temperature under the thermodynamic equilibrium condition. For steam reforming of methanol, high cell efficiency can be obtained, whereas for partial oxidation of methanol, the cell efficiency decreases most obviously compared with other pretreating technologies with the increase of O/C ratio. When the O/C ratio is 1.5, the cell efficiencies are 55.89% for steam reforming of methanol, 50.83% for autothermal reforming of methanol, and 45.77% for partial oxidation of methanol at 80% equivalent fuel utilization and 1073 K. When the O/C ratio increases to 2.5, the cell efficiency decreases slowly to 52.01% for steam reforming of methanol, whereas rapidly to 21.68% for partial oxidation of methanol at 80% equivalent fuel utilization and 1073 K. According to the calculated results under the thermodynamic equilibrium condition, suitable pretreating technology and O/C ratio for methanol pretreatment can be selected for the operation of solid oxide fuel cell, which can lead to the high efficiency and good stability of solid oxide fuel cell.

Methanol to Formaldehyde: An Overview of Surface Studies and Performance of an Iron Molybdate Catalyst

Formaldehyde is a primary chemical in the manufacturing of various consumer products. It is synthesized via partial oxidation of methanol using a mixed oxide iron molybdate catalyst (Fe2(MoO4)3–MoO3). This is one of the standard energy-efficient processes. The mixed oxide iron molybdate catalyst is an attractive commercial catalyst for converting methanol to formaldehyde. However, a detailed phase analysis of each oxide phase and a complete understanding of the catalyst formulation and deactivation studies is required. It is crucial to correctly formulate each oxide phase and influence the synthesis methods precisely. A better tradeoff between support and catalyst and oxygen revival on the catalyst surface is vital to enhance the catalyst’s selectivity, stability, and lifetime. This review presents recent advances on iron molybdate’s catalytic behaviour for formaldehyde production—a deep recognition of the catalyst and its critical role in the processes are highlighted. Finally, the conclusion and prospects are presented at the end.

Optimization for hydrogen production from methanol partial oxidation over Ni–Cu/Al2O3 catalyst under sprays

In this work, a novel Ni–Cu/Al2O3 catalyst is used to trigger the partial oxidation of methanol (POM) for hydrogen production. This reaction system also employed ultrasonic sprays to aid in dispersing methanol fuel. The prepared catalyst is analyzed by scanning electron microscope (SEM), energy-dispersive X-ray (EDX) spectroscopy, and X-ray diffraction (XRD) to explore the catalyst's surface structure, elemental composition, and physical structure, respectively. The Box-Behnken design (BBD) of response surface methodology (RSM) is utilized for experimental design to achieve process optimization. The operating parameters comprise the O2/C molar ratio (0.5–0.7), preheating temperature (150–250 °C), and weight percent (wt%) of Ni (10–30%) in the catalyst. The results show that methanol conversion is 100% in all the operating conditions, while the reaction temperature for H2 production ranges from 160 to 750 °C, stemming from heat released by POM. The significance and suitability of operating conditions are also analyzed by analysis of variance (ANOVA). It indicates that the highest H2 yield is 2 mol (mol CH3OH)−1, occurring at O2/C = 0.5, preheating temperature = 150 °C, and Ni wt% = 10. Compared with the commercial h-BN-Pt/Al2O3 catalyst, the prepared Ni–Cu/Al2O3 catalysts have higher activity for H2 production. The O2/C ratio is the most influential factor in the H2 yield. Moreover, the interaction of the O2/C ratio and Ni content is sound, reflecting that changing Ni content in the catalyst will affect the trend of H2 yield under each O2/C.

Harnessing of Diluted Methane Emissions by Direct Partial Oxidation of Methane to Methanol over Cu/Mordenite.

The upgrading of diluted methane emissions into valuable products can be accomplished at low temperatures (200 °C) by the direct partial oxidation of methanol over copper-exchanged zeolite catalysts. The reaction has been studied in a continuous fixed-bed reactor loaded with a Cu–mordenite catalyst, according to a three-step cyclic process: adsorption of methane, desorption of methanol, and reactivation of the catalyst. The purpose of the work is the use of methane emissions as feedstocks, which is challenging due to their low methane concentration and the presence of oxygen. Methane concentration had a marked influence on methane adsorption and methanol production (decreased from 164 μmol/g Cu for pure methane to 19 μmol/g Cu for 5% methane). The presence of oxygen, even in low concentrations (2.5%), reduced methane adsorption drastically. However, methanol production was only affected slightly (average decrease of 9%), concluding that methane adsorbed on the active centers yielding methanol is not influenced by oxygen.

Formaldehyde Selectivity in Methanol Partial Oxidation on Silver: Effect of Reactive Oxygen Species, Surface Reconstruction, and Stability of Intermediates

Selective oxidation reactions on heterogeneous silver catalysts are essential for the mass production of numerous industrial commodity chemicals. However, the nature of active oxygen species in such reactions is still debated. To shed light on the role of different oxygen species, we studied the methanol oxidation reaction on Ag(111) single-crystal model catalyst surfaces containing two dissimilar types of oxygen (electrophilic, Oe and nucleophilic, On). X-ray photoelectron spectroscopy and low energy electron diffraction experiments suggested that the atomic structure of the Ag(111) surface remained mostly unchanged after accumulating low Oe coverage at 140 K. Temperature-programmed reaction spectroscopic investigation of low coverages of Oe on Ag(111) revealed that Oe was active for methanol oxidation on Ag(111) with a high selectivity toward formaldehyde (CH2O) production. High surface oxygen coverages, on the other hand, triggered a reconstruction of the Ag(111) surface, yielding Ag oxide domains, which catalyzes methanol total oxidation to CO2 and decreases the formaldehyde selectivity. This important finding indicates a trade-off between CH2O selectivity and methanol conversion, where 93% CH2O selectivity can be achieved for an oxygen surface coverage of θO = 0.08 ML (ML = monolayer) with moderate methanol conversion, while methanol conversion could be boosted by a factor of ∼4 for θO = 0.26 ML with a suppression of CH2O selectivity to 50%. Infrared reflection absorption spectroscopy results and density functional theory calculations indicated that Ag oxide contains dissimilar adsorption sites for methoxy intermediates, which are also energetically less stable than that of the unreconstructed Ag(111). The current findings provide important molecular-level insights regarding the surface structure of the oxidized Ag(111) model catalyst directly governing the competition between different reaction pathways in methanol oxidation reaction, ultimately dictating the reactant conversion and product selectivity.

Partial oxidation of methanol to formaldehyde in an annular reactor

A structured reactor with annular configuration was applied for studying methanol oxidation to formaldehyde over silver. By eliminating gas phase reactions, high formaldehyde selectivity (93–97%) was obtained at low methanol and oxygen conversion under practically isothermal reaction conditions. CH2O and CO2 were the only carbon containing products, and both may be claimed as primary products along with H2. It also proves that CO is formed by homogenous decomposition of CH2O and should not be considered a main precursor to CO2, as assumed in several reaction mechanisms. The analysis of H2/CO2 ratio as a function of temperature provides an estimate of contributions from dehydrogenation and partial oxidation of methanol, and clearly suggests presence of a dehydrogenation pathway to CH2O. Extracting kinetic parameters is challenging due to a correlation between activity, oxygen dissolution, and silver restructuring and morphology and its dependence on temperature. Nevertheless, the data indicate 1st order with respect to oxygen. Conditioning by reaction at high temperature followed by a temperature ramp was performed to minimize the impact of a gradually changing Ag catalyst. The resulting Arrhenius analysis implies two distinct regions of activity. The apparent activation energy was estimated to 41 kJ/mol for the high temperature region, a value close to the activation energy for oxygen diffusion in silver at high temperature. The investigation demonstrates benefits of using an annular reactor configuration in bridging lab scale investigations with industrial conditions. Collecting reaction data at low oxygen conversion is enabled, which has not been achievable in conventional lab scale reactors this far.

Modified iron-molybdate catalysts with various metal oxides by a mechanochemical method: enhanced formaldehyde yield in methanol partial oxidation

A mechanochemical method was employed to prepare modified iron molybdate catalysts with various metal salts as precursors. The physicochemical properties of the iron molybdate catalysts were characterized, and their performances in catalyzing the reaction from methanol to formaldehyde (HCHO) were evaluated. Iron molybdate catalysts doped with Co(NO3)2 · 6H2Oand Al(NO3)3 · 9H2O resulted in high HCHO yields. Compared with a commercial catalyst, the HCHO yields in the reaction with the modified catalyst at an optimal Co/Mo molar ratio reached 97.37%. According to chemical state analysis, the formation of CoO and the efficient decrease in the MoO3 sublimation rate could be important factors enhancing the HCHO yield in reactions catalyzed with iron molybdate doped with different Co/Mo mole ratios.

The facet effect of ceria nanoparticles on platinum dispersion and catalytic activity of methanol partial oxidation.

The effect of platinum-supported nano-shaped ceria catalysts on methanol partial oxidation and methyl formate product selectivity has been investigated. A Pt-supported CeO2 nanocube catalyst had a higher turnover frequency than nanosphere catalysts; however, nanosphere catalysts showed higher selectivity towards methyl formate. The observed ceria shape effect in catalysis was associated with the shape-dependent Pt dispersion and its oxidation states. Furthermore, in situ studies revealed that the reduced platinum and mono-dentate methoxy group were responsible for the higher turnover frequency.

Near-Surface Imaging of the Multicomponent Gas Phase above a Silver Catalyst during Partial Oxidation of Methanol

Fundamental chemistry in heterogeneous catalysis is increasingly explored using operando techniques in order to address the pressure gap between ultrahigh vacuum studies and practical operating pressures. Because most operando experiments focus on the surface and surface-bound species, there is a knowledge gap of the near-surface gas phase and the fundamental information the properties of this region convey about catalytic mechanisms. We demonstrate in situ visualization and measurement of gas-phase species and temperature distributions in operando catalysis experiments using complementary near-surface optical and mass spectrometry techniques. The partial oxidation of methanol over a silver catalyst demonstrates the value of these diagnostic techniques at 600 Torr (800 mbar) pressure and temperatures from 150 to 410 °C. Planar laser-induced fluorescence provides two-dimensional images of the formaldehyde product distribution that show the development of the boundary layer above the catalyst under different flow conditions. Raman scattering imaging provides measurements of a wide range of major species, such as methanol, oxygen, nitrogen, formaldehyde, and water vapor. Near-surface molecular beam mass spectrometry enables simultaneous detection of all species using a gas sampling probe. Detection of gas-phase free radicals, such as CH3 and CH3O, and of minor products, such as acetaldehyde, dimethyl ether, and methyl formate, provides insights into catalytic mechanisms of the partial oxidation of methanol. The combination of these techniques provides a detailed picture of the coupling between the gas phase and surface in heterogeneous catalysis and enables parametric studies under different operating conditions, which will enhance our ability to constrain microkinetic models of heterogeneous catalysis. (Less)

Hydrogen production from partial oxidation and autothermal reforming of methanol from a cold start in sprays

Hydrogen is a noticeable clean fuel that can be applied in power generation and transport. Hydrogen production from methanol via thermochemical methods has been widely studied and used. In these methods, autothermal reforming (ATR) simultaneously contains endothermic steam reforming and exothermic partial oxidation of methanol (POM), The latter can help start the experiment and provide heat for the former. This study aims to perform methanol ATR by sprays via an h-BN-Pt catalyst without preheating, mainly focusing on the effects of operating conditions on hydrogen production and methanol conversion. Meanwhile, the comparison between ATR and POM of methanol is also carried out. The results of POM indicate that the highest H2 and CO concentrations are obtained at the air-to-methanol molar ratio (O2/C) of 0.7, and the CH3OH conversion can reach 100%. However, through the ATR process, the methanol conversion reaches 60% at O2/C = 0.7 with steam-to-methanol molar ratio (S/C) of 1.5. At S/C = 0.5, it is observed that the CH3OH conversion is up to 100% with increasing the O2/C ratio, and the H2 yield is higher than that of POM. The effects of S/C and O2/C ratios on ATR indicate that the CH3OH conversion and reaction temperature are significantly increased with decreasing the S/C ratio and increasing the O2/C ratio. Overall, the H2 yield from ATR at S/C of 0.5 and O2/C of 0.7 is highest with 1.697 mol (mol CH3OH)−1.

Reforming of methanol to produce hydrogen over the Au/ZnO catalyst

Gold particle with an average size of dAu ~ 4 nm was dispersed on ZnO by the deposition precipitation method. The fabricated Au/ZnO catalyst was used to produce hydrogen from reforming of methanol. Four reforming reactions, i.e., decomposition of methanol (DM), steam reforming of methanol (SRM), partial oxidation of methanol (POM) and oxidative steam reforming of methanol (OSRM), were evaluated in a fixed bed reactor. A reaction temperature of TR > 623 K was required for catalyzing reactions of DM and SRM. Interestingly, high methanol conversion (CMeOH > 90%) was found from reforming reactions of POM and OSRM at an amazing low temperature of TR < 473 K. Besides, a presentable hydrogen yield (RH2 ~ 2.4) and a low selectivity of CO (SCO ~ 1%) were simultaneously attained from the reaction of OSRM. Therefore, the low temperature OSRM reaction over the Au/ZnO catalyst is suggested as a friendly reforming process for on-board production of hydrogen.

Au/Ce0.5Zr0.5O2 catalysts for hydrogen production via partial oxidation of methanol

Effects of ZrO2 addition to the Au/CeO2 and the pretreatment methods of the catalysts on the partial oxidation of methanol (POM) were investigated. ZrO2 addition to Au/CeO2 catalyst led to (i) formation of a Ce0.5Zr0.5O2 solid solution; (ii) enhancement of lattice oxygen reducibility of the Ce0.5Zr0.5O2 support; and (iii) formation of surface Auδ+ (δ = 1 or 3) species coexisting with Au0 nanoparticles. Catalytic evaluation showed that the highest hydrogen selectivity was achieved over Au/Ce0.5Zr0.5O2 at 270 °C. The reductive pretreatment could improve the hydrogen selectivity and methanol conversion as well. At higher reaction temperature Auδ+ clusters in Au/Ce0.5Zr0.5O2 catalyst activated the O‒H bond in the adsorbed CH3‒Oδ−‒Hδ+ due to the interaction between Auδ+ and Oδ−‒Hδ+ of methanol that favors the release of H+ proton, and thus benefits the H2 selectivity enhancement. Some oxygen vacancies in the catalysts evidenced by XPS analysis participated in the formation of active surface oxygen species that promoted CO oxidation to CO2 on Au0 nanoparticles A reaction mechanism of POM involving in the methanol surface adsorption on Auδ+ species, O‒H bond activation, and CO oxidation on Au0 nanoparticles and oxygen defects was proposed.

Atomic-Scale Structure and Catalysis on Positively Charged Bimetallic Sites for Generation of H2.

Here, we report that a cationic bimetallic site consisting of one Pd and three Zn atoms (Pd1Zn3) supported on ZnO (Pd1Zn3/ZnO) exhibits an extraordinarily high catalytic activity for the generation of H2 through methanol partial oxidation (MPO) that is 2-3 orders of magnitude higher than that of a metallic Pd-Zn site on Pd-Zn nanoalloy (Pd-Zn/ZnO). Computational studies uncovered that the positively charged Pd atom of the subnanometer Pd1Zn3 bimetallic site largely decreases the activation barrier for dehydrogenation of methanol as compared to a metallic Pd atom of Pd-Zn alloy, thus switching the rate-determining step of MPO from methanol dehydrogenation over a Pd-Zn alloy with high barrier to the O2 dissociation step on a cationic Pd1Zn3 site with a low barrier, which is supported by our kinetics studies. The significantly higher catalytic activity and selectivity for H2 production over a cationic bimetallic site suggest a new approach to design bimetallic catalysts.

MODEL AND SIMULATION OF PARTIAL OXIDATION OF METHANOL TO FORMALDEHYDE ON FeO/MoO3 CATALYST IN A CATALYTIC FIXED BED REACTOR

A two-dimensional mathematical model was developed for a porous heterogeneous catalytic fixed bed reactor. The model took into account the effect of heat generated by adsorption of reactants on the catalyst surface and heat transfer from the fluid phase to the surroundings which have significant effect on reactor performance especially at reactor hotspot. The developed model predicted the partial oxidation of methanol to formaldehyde on FeO/MoO3 catalyst, a complex reaction system. Excellent agreement was achieved when the resultant simulated results were compared with experimental data in the literature. The proposed model predicted the location of hotspot at a dimensionless distance of 0.4413 (= 0.0309 m) the same as the experiment value but with a temperature of 619 K compared with experimental value of 622 K. The conventional heterogeneous and pseudo-homogeneous models predicted the hotspot temperature to be about 8 K and 34 K lower than the experimental value respectively.