Liquid phase oxidation of toluene is an environmental benign route for the production of benzoic acid.In a φ48mm bubble column reactor,the commercial process of toluene liquid phase oxidation was conducted with Co(CH...Liquid phase oxidation of toluene is an environmental benign route for the production of benzoic acid.In a φ48mm bubble column reactor,the commercial process of toluene liquid phase oxidation was conducted with Co(CH3COO)2.4H2O as catalyst.The Co2+ concentration [Co2+] was determined by extraction spectrophotometry and hereby the Co3+ concentration [Co3+] was obtained by mass balance.The results showed that [Co3+] reached the maximum at about 25-30min.[Co3+] increased with increasing Co catalyst amount at total Co concentration<150 mg.L-1 of toluene.The conversion of toluene,yield and selectivity of benzoic acid increased with the increasing [Co3+/Co2+] max.A high [Co3+] and a high [Co3+]/[Co2+] ratio are beneficial to the reaction.展开更多
Pt/CeO2–ZrO2–SnO2/γ-Al2O3 catalysts were prepared by co-precipitation and wet impregnation methods for catalytic oxidation of acetaldehyde to acetic acid in water. In the present catalysts, Pt and CeO2–ZrO2–SnO2 ...Pt/CeO2–ZrO2–SnO2/γ-Al2O3 catalysts were prepared by co-precipitation and wet impregnation methods for catalytic oxidation of acetaldehyde to acetic acid in water. In the present catalysts, Pt and CeO2–ZrO2–SnO2 were successfully dispersed on the γ-Al2O3 support.Dependences of platinum content and reaction time on the selective oxidation of acetaldehyde to acetic acid were investigated to optimize the reaction conditions for obtaining both high acetaldehyde conversion and highest selectivity to acetic acid. Among the catalysts, a Pt（6.4 wt.%）/Ce0.68Zr0.17Sn0.15O2.0（16 wt.%）/γ-Al2O3 catalyst showed the highest acetaldehyde oxidation activity. On this catalyst, acetaldehyde was completely oxidized after the reaction at 0°C for 8 hr, and the selectivity to acetic acid reached to 95%and higher after the reaction for 4 hr and longer.展开更多
During the liquid-phase oxidation of p-xylene,over-oxidation of reactant,intermediates and solvent to carbon dioxide and carbon monoxide is generally known as the burning side reaction.Batch and semi-continuous experi...During the liquid-phase oxidation of p-xylene,over-oxidation of reactant,intermediates and solvent to carbon dioxide and carbon monoxide is generally known as the burning side reaction.Batch and semi-continuous experiments were carried out,and the experimental data of the burning side reaction were analyzed and reported in this paper.The results showed that the rates of burning side reactions were proportional to the rates of the main reaction,but decreased with the increasing concentrations of reactant and intermediates.The inter-stimulative and competitive relationship between the burning side reaction and the main reaction was confirmed,and the rates of the burning side reaction could be described with some key indexes of the main reaction.According to the mechanism of the side reactions and the kinetics model of main reaction which were proposed and tested in the previous papers,a kinetic model of the burning side reactions involving some key indexes of the main reaction was developed,and the parameters were determined by data fitting of the COx rate curves.The obtained kinetic model could describe the burning side reactions adequately.展开更多
The effect of liquid-phase oxidation impurities on the solubility of water in hydrocarbon fuels was studied.The results show that the concentration of polar surfactant molecules in the first region increases(true solu...The effect of liquid-phase oxidation impurities on the solubility of water in hydrocarbon fuels was studied.The results show that the concentration of polar surfactant molecules in the first region increases(true solution)during fuel oxidation,and since the oxidation groups(-COOH,-O=O,-OH,etc.)have similar dipole momentμ,the dielectric loss tangent tanδincreases linearly in this region with surfactant concentration.Upon further oxidation,micelle structures begin to form at a certain point.Micelle formation leads to a sharp decrease in the dipole moment attributable to the monomer unitμ/n,where nis the number of molecules in a micelle.A several-fold decrease in the dipole moment leads to a sharp drop in tanδ.Upon further increase in the number and size of micelles,the dipole moment remains practically unchanged,and the dielectric loss tangent begins to increase linearly again with surfactant concentration.If the critical concentration for micelle formation is achieved upon further oxidation of hydrocarbon liquids,micelle formation processes occur spontaneously in the solution,and the true solution becomes a colloidal system(sol).The resulting micelles are structured with hydrocarbon radicals of molecules toward the outside and hydrophilic(polar)groups toward the inside.Water molecules are located inside micelles and held so securely that water molecules do not aggregate as temperature decreases.The reason for significant differences in the equilibrium solubility of water in hydrocarbon fuels is the different oxidation factors of product samples,resulting from the accumulation of various concentrations of oxidation products,which are natural surfactants,in hydrocarbon fuels.展开更多
To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretre...To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretreatment was employed to construct a Ta_(2)O_(5)ceramic layer on the Ta12W alloy surface.Subsequently,a slurry spraying-vacuum sintering method was used to prepare a Si-Cr-Ti-Zr coating on the pretreated substrate.Comparative studies were conducted on the microstructure,phase composition,and isothermal oxidation resistance(at 1600℃)of the as-prepared coatings with and without the micro-arc oxidation ceramic layer.The results show that the Ta_(2)O_(5)layer prepared at 400 V is more continuous and has smaller pores than that prepared at 350 V.After microarc oxidation pretreatment,the Si-Cr-Ti-Zr coating on Ta12W alloy consists of three distinct layers:an upper layer dominated by Ti_(5)Si_(3),Ta_(5)Si_(3),and ZrSi;a middle layer dominated by TaSi_(2);a coating/substrate interfacial reaction layer dominated by Ta_(5)Si_(3).Both the Si-Cr-Ti-Zr coatings with and without the Ta_(2)O_(5)ceramic layer do not fail after isothermal oxidation at 1600℃for 5 h.Notably,the addition of the Ta2O5 ceramic layer reduces the high-temperature oxidation rate of the coating.展开更多
The limited high-temperature oxidation resistance of Mg alloys is a key factor restricting their development and application.The addition of some rare earth elements(REs),owing to their unique physical and chemical pr...The limited high-temperature oxidation resistance of Mg alloys is a key factor restricting their development and application.The addition of some rare earth elements(REs),owing to their unique physical and chemical properties,can significantly enhance the oxidation resistance of Mg alloys.Based on our previous study,we conclude that REs such as Gd,Y,and Ce enhance the oxidation resistance of Mg-RE alloys.This article comprehensively reviews recent research progress on high-temperature oxidation behavior and the potential mechanism in Mg-RE alloys.Based on the thermodynamic and kinetic analyses,the evolution of the complex oxide system formed during the high-temperature oxidation of Mg-RE alloys is first summarized.The diffusion behavior and concentration control mechanisms of REs during the oxidation process and how these mechanisms affect the sustained growth of the oxide film and antioxidant properties were elucidated.Moreover,the different structures of the oxide films were classified,and their properties were discussed.Finally,this paper introduces the applications of commonly used REs in Mg alloys and frontier research on their oxidation mechanisms.Based on the above review,we propose that future research perspectives can be explored in terms of expanding the experimental temperature range for oxidation tests,optimizing the chemical composition by adding trace REs to study their synergistic mechanism,revealing the underlying oxidation mechanism through advanced in situ microscopic characterization methods,and investigating the mechanical properties of oxide films using diverse approaches.展开更多
Platinum group metals have high melting points,strong corrosion resistance,stable chemical properties,and low oxygen permeability in high-temperature oxygen-containing environments.As thermal protective coating materi...Platinum group metals have high melting points,strong corrosion resistance,stable chemical properties,and low oxygen permeability in high-temperature oxygen-containing environments.As thermal protective coating materials,they have gained essential applications in the aerospace field and have excellent prospects for application in frontier military fields,such as protecting hot-end components of hypersonic aircraft.This research reviewed the latest research progress of platinum group metal coatings with hightemperature oxidation resistance,including coating preparation techniques,oxidation failure,and alloying modification.The leading preparation techniques of current platinum group metal coatings were discussed,as well as the advantages and disadvantages of various existing preparation techniques.Besides,the intrinsic properties,failure forms,and failure mechanisms of coatings of single platinum group metal in high-temperature oxygen-containing environments were analyzed.On this basis,the necessity,main methods,and main achievements of alloying modification of platinum group metals were summarized.Finally,the future development of platinum group coatings with high-temperature oxidation resistance was discussed and prospected.展开更多
Fine-grained nuclear graphite is a key material in high-temperature gas-cooled reactors(HTGRs).During air ingress accidents,core graphite components undergo severe oxidation,threatening structural integrity.Therefore,...Fine-grained nuclear graphite is a key material in high-temperature gas-cooled reactors(HTGRs).During air ingress accidents,core graphite components undergo severe oxidation,threatening structural integrity.Therefore,understanding the oxidation behavior of nuclear graphite is essential for reactor safety.The influence of oxidation involves multiple factors,including temperature,sample size,oxidant,impurities,filler type and size,etc.The size of the filler particles plays a crucial role in this study.Five ultrafine-and superfine-grained nuclear graphite samples(5.9-34.4μm)are manufactured using identical raw materials and manufacturing processes.Isothermal oxidation tests conducted at 650℃-750℃ are used to study the oxidation behavior.Additionally,comprehensive characterization is performed to analyze the crystal structure,surface morphology,and nanoscale to microscale pore structure of the samples.Results indicate that oxidation behavior cannot be predicted solely based on filler grain size.Reactive site concentration,characterized by active surface area,dominates the chemical reaction kinetics,whereas pore tortuosity,quantified by the structural parameterΨ,plays a key role in regulating oxidant diffusion.These findings clarify the dual role of microstructure in oxidation mechanisms and establish a theoretical and experimental basis for the design of high-performance nuclear graphite capable of long-term service in high-temperature gas-cooled reactors.展开更多
Electrocatalytic glucose oxidation to high-value chemicals provides a sustainable route for biomass valorization.NiCo-based catalysts have emerged as promising candidates for glucose oxidation reaction owing to the in...Electrocatalytic glucose oxidation to high-value chemicals provides a sustainable route for biomass valorization.NiCo-based catalysts have emerged as promising candidates for glucose oxidation reaction owing to the intrinsic activity of Ni and Co catalytic centers.However,the dynamic evolution and atomic-scale synergy between these centers remain elusive.Herein,we fabricated NiCo_(2)O_(4)nanosheets supported on nickel foam,where Ni preferentially occupies tetrahedral sites to regulate the electronic configuration of octahedral Co.Experimental and theoretical results demonstrate that the incorporation of tetrahedral Ni induces low-to-intermediate spin transition in octahedral Co,thereby optimizing eg orbital occupancy and stabilizing active sites.This spin-state engineering establishes Ni-Co synergistic catalytic centers for the selective oxidation of glucose to formate(FA).At higher potential(≥1.4 V vs.RHE),octahedral Co undergoes reconstruction into excessive active CoOOH and CoO_(2)species,resulting in glucose overoxidation to CO_(2)and intensified competitive oxygen evolution.In contrast,at lower potentials(<1.4 V vs.RHE),tetrahedral Ni facilitates electron delocalization across the Ni–O–Co lattice,thereby stabilizing octahedral Co for glucose adsorption and oxidation.Subsequently,a coupled electrocatalytic system was constructed,achieving 80.7%FA yield with 91.3%Faradaic efficiency(FE)at NiCo_(2)O_(4)anode and H2 evolution rate of 696μmol h^(−1)with 99.9%FE at Pt cathode for 2 h under 1.35 V vs.RHE.This work provides a deep insight into spin-state regulation of the catalytic center,offering valuable guidance for rational catalyst design.展开更多
Selective depression of pyrite remains a major bottleneck in copper flotation,particularly when high-pyrite ores are processed and saline water is used.In such environments,conventional approaches using lime and inert...Selective depression of pyrite remains a major bottleneck in copper flotation,particularly when high-pyrite ores are processed and saline water is used.In such environments,conventional approaches using lime and inert grinding media often fail to discriminate ef-fectively between pyrite and valuable copper minerals due to strong copper activation on pyrite surfaces.This study introduced a novel approach using inorganic radicals generated from peroxymonosulfate(PMS)to selectively oxidize and depress pyrite.Flotation tests with synthetic high-pyrite ore blends showed that PMS significantly reduced pyrite recovery while maintaining or improving chalcopyrite flot-ation.Ethylenediaminetetraacetic acid(EDTA)extraction confirmed selective oxidation of pyrite,and electron paramagnetic resonance(EPR)spectroscopy identified hydroxyl(·OH)and sulfate(SO_(4)^(·-))radicals as the dominant reactive species.Iron ions from grinding me-dia and mineral surfaces were identified as key activators of PMS.A major insight was pyrite’s dual role,acting both as a radical scav-enger and an activator,which made it highly reactive and susceptible to radical-induced oxidation.This process converted surface copper-sulfur species into copper hydroxides,effectively suppressing pyrite flotation.While previous studies have applied EPR to detect radicals in simplified activator/precursor systems,this study provides the first direct mechanistic evidence of radical-driven selectivity in flotation by detecting inorganic radicals in a complex flotation slurry,thereby demonstrating their persistence under industrially relevant conditions and establishing a foundation for more effective and targeted flotation strategies.展开更多
Electrocatalytic oxidation of glycerol for value-added chemicals is a superior strategy to utilize the excess glycerol produced in the biodiesel industry.Pd is one of the few active catalysts for alkaline glycerol oxi...Electrocatalytic oxidation of glycerol for value-added chemicals is a superior strategy to utilize the excess glycerol produced in the biodiesel industry.Pd is one of the few active catalysts for alkaline glycerol oxidation reaction(GOR);however,glycerol inevitably dissociates and converts to carbon dioxide on the Pd surface,which results in its low total Faradaic efficiency(FE)for high-value-added products.Herein,a series of Pd/C and Pd10Bix/C catalysts were synthesized to investigate the GOR pathway.The Pd10Bi3/C catalyst with optimal Bi content achieved an excellent GOR mass activity of 7.5±0.2 A mgPd−1 and an outstanding total FE of 90%±3%,which are much higher than those values on Pd/C(1.2±0.2 A mgPd−1 for mass activity and 63%±4%for total FE).Combined results of in-situ attenuated total reflection surface enhanced infrared absorption spectroscopy and density functional theory calculations show that Bi suppresses the dissociation of glycerol through the“shielding effect”of Bi to the adjacent Pd sites,which weakens the adsorption strength of GOR intermediates on those sites.This work provides a new insight into the GOR mechanism and puts forward a valid strategy for the rational design of catalysts to enable the transformation of glycerol into high-value-added products.展开更多
The methanol oxidation reaction(MOR)to formic acid offers a promising alternative to the anodic oxygen evolution reaction(OER)in water electrolysis.However,the development of efficient and cost-effective catalysts rem...The methanol oxidation reaction(MOR)to formic acid offers a promising alternative to the anodic oxygen evolution reaction(OER)in water electrolysis.However,the development of efficient and cost-effective catalysts remains a primary challenge.In this study,an enhancement in catalytic MOR performance is achieved through the incorporation of Mn atoms with unsaturated t_(2g)orbitals into Ni_(3)Se_(4).Comprehensive experimental analyses and theoretical calculations reveal that substituting Ni with Mn induces strong electron-withdrawing effects,effectively modulating the local coordination environment of the metal centers.The presence of Mn also elongates Ni–Se(O)bonds,which reduces eg orbital occupancy and modifies the spin state of the material.Electrochemical measurements demonstrate that electrodes based on this optimized material exhibit a high spin state and deliver excellent catalytic activity,achieving a MOR current density up to∼190 mA cm^(−2)at 1.6 V.This performance enhancement is attributed to the favorable electronic configuration and reduced reaction energy barriers associated with the high-spin state.展开更多
The three-dimensional(3D) Pd-based nanoflower structures,assembled from two-dimensional(2D)nanosheets,are characterized by their stable and ordered configurations.These structures have been extensively designed as ano...The three-dimensional(3D) Pd-based nanoflower structures,assembled from two-dimensional(2D)nanosheets,are characterized by their stable and ordered configurations.These structures have been extensively designed as anode materials for fuel cells.However,the exploration of trimetallic nanoflowers with porous architectures remains limited.In this study,we present a straightforward one-step solvothermal method for the synthesis of trimetallic Pd Cu Ni porous nanoflowers(PNFs).Leveraging several unique advantages,such as an open superstructure,high porosity,and enhanced electronic interactions among the trimetals,the resulting Pd Cu Ni PNFs demonstrate significantly improved electrochemical performance,with mass activities reaching 5.94 and 10.14 A/mg for the ethanol oxidation reaction(EOR)and the ethylene glycol oxidation reaction(EGOR),respectively.Furthermore,the Pd Cu Ni PNFs exhibit optimized d-band centers and the most negative onset oxidation potential,indicating enhanced antitoxicity and stability.This study not only provides a novel perspective on the synthesis of 3D porous nanomaterials but also highlights the potential application value of trimetallic nanoalloys in catalysis.展开更多
Alzheimer’s disease(AD)is a complex neurodegenerative disorder associated with changes in inflammation,oxidative stress,and gut microbiota composition.Butyrolactone Ⅰ(BTL-Ⅰ),a fungal metabolite,has shown anti-infla...Alzheimer’s disease(AD)is a complex neurodegenerative disorder associated with changes in inflammation,oxidative stress,and gut microbiota composition.Butyrolactone Ⅰ(BTL-Ⅰ),a fungal metabolite,has shown anti-inflammatory,microbiota regulating,and memory-improving potentials in previous in vitro and AlCl3-induced zebrafish studies.However,its effects of memory-improving and gutbrain axis regulating on Aβ-induced mammalian AD models have not been explored.In this study,intragastric administrated BTL-Ⅰ ameliorated cognitive deficits related to recognition and spatial memory impaired by Aβ_(1-42)intracerebroventricular injection in mice.BTL-Ⅰ maintained gut microbiota balance by increasing the abundance of Blautia,Muribaculaceae,Bacteroides,Akkermansia,etc.,and decreasing CAG-352,Clostridia UCG-014,different Lachnospiraceae groups,etc.,and Firmicutes/Bacteroidota ratio and elevated the levels of short-chain fatty acids.Additionally,it alleviated intestinal oxidative stress,inflammatory responses,and pathological damage.Furthermore,BTL-I reversed Aβ_(1-42)-induced activation of microglia and astrocytes in the hippocampus and inhibited the elevated oxidative stress and proinflammatory cytokines in both plasma and brain.The correlation analysis between the regulated taxa and biomarkers supports the role of gut microbiota in adjusting inflammation,oxidative stress,and memory.In conclusion,BTL-I may serve as a valuable drug lead for treating Alzheimer’s disease by systematically inhibiting microbiota imbalance,inflammation,and oxidative stress along the gut-brain axis.展开更多
TiB_(2)coatings can significantly enhance the high-temperature oxidation resistance of molybdenum,which would broaden the application range of molybdenum and alloys thereof.However,traditional methods for preparing Ti...TiB_(2)coatings can significantly enhance the high-temperature oxidation resistance of molybdenum,which would broaden the application range of molybdenum and alloys thereof.However,traditional methods for preparing TiB_(2)coatings have disadvantages such as high equipment costs,complicated processes,and highly toxic gas emissions.This paper proposes an environmentally friendly method,which requires inexpensive equipment and simple processing,for preparing TiB_(2)coating on molybdenum via electrophoretic deposition within Na3AlF6-based molten salts.The produced TiB_(2)layer had an approximate thickness of 60μm and exhibited high density,outstanding hardness(38.2 GPa)and robust adhesion strength(51 N).Additionally,high-temperature oxidation experiments revealed that,at900℃,the TiB_(2)coating provided effective protection to the molybdenum substrate against oxidation for 3 h.This result indicates that the TiB_(2)coating prepared on molybdenum using molten salt electrophoretic deposition possesses good high-temperature oxidation resistance.展开更多
Investigating structural and hydroxyl group effects in electrooxidation of alcohols to value-added products by solid-acid electrocatalysts is essential for upgrading biomass alcohols.Herein,we report efficient electro...Investigating structural and hydroxyl group effects in electrooxidation of alcohols to value-added products by solid-acid electrocatalysts is essential for upgrading biomass alcohols.Herein,we report efficient electrocatalytic oxidations of saturated alcohols(C_(1)-C_(6))to selectively form formate using Ni Co hydroxide(Ni Co-OH)derived Ni Co_(2)O_(4)solid-acid electrocatalysts with balanced Lewis acid(LASs)and Brønsted acid sites(BASs).Thermal treatment transforms BASs-rich(89.6%)Ni Co-OH into Ni Co_(2)O_(4)with nearly equal distribution of LASs(53.1%)and BASs(46.9%)which synergistically promote adsorption and activation of OH-and alcohol molecules for enhanced oxidation activity.In contrast,BASs-enriched Ni Co-OH facilitates formation of higher valence metal sites,beneficial for water oxidation.The combined experimental studies and theoretical calculation imply the oxidation ability of C1-C6alcohols increases as increased number of hydroxyl groups and decreased HOMO-LUMO gaps:methanol(C_(1))<ethylene glycol(C_(2))<glycerol(C3)<meso-erythritol(C4)<xylitol(C5)<sorbitol(C6),while the formate selectivity shows the opposite trend from 100 to 80%.This study unveils synergistic roles of LASs and BASs,as well as hydroxyl group effect in electro-upgrading of alcohols using solid-acid electrocatalysts.展开更多
Liquid-phase oxidation of toluene with air has become the main technology for producing benzoic acid in a reactor at present. Based on the kinetic model of the toluene oxidation process obtained from laboratory and ma...Liquid-phase oxidation of toluene with air has become the main technology for producing benzoic acid in a reactor at present. Based on the kinetic model of the toluene oxidation process obtained from laboratory and mass balance of key component, a novel model is established to simulate the industrial toluene oxidation process, in which the effects of benzaldehyde and benzyl alcohol are considered and the kinetic parameters are revised by industrial data. The simulation results show that the error of benzoic acid yield is within 3.5%. Based on the simulation model, to maximize the benzoic acid yield, an optimization model is proposed to optimize the operating parameters, including toluene feed-in mass flux and temperature. The optimization result indicates that on the allowable operating conditions the maximum benzoic acid yield obtained with the reaction temperature at 167.2 C an the mass flux at 104.1 t·h^- 1 is greater than the current one, which can be used to guide industrial reactor s operation.展开更多
In this study, liquid-phase aerobic oxidation of toluene catalyzed by Mn–Mo oxide was conducted in a 1.0 L batch reactor. The macroscopic kinetics of toluene consumption and benzaldehyde generation at 413–443 K were...In this study, liquid-phase aerobic oxidation of toluene catalyzed by Mn–Mo oxide was conducted in a 1.0 L batch reactor. The macroscopic kinetics of toluene consumption and benzaldehyde generation at 413–443 K were obtained from a combination of experimental observation and hypothetical models. The results clearly showed that both the oxidation rate of toluene and generation rate of the aromatic product were proportional to the concentration of the substrate, the partial pressure of oxygen and the surface area of the catalyst. The energy barrier of toluene oxidation to benzyl alcohol was the highest(≈ 81 kJ mol^(-1)), while that of benzyl alcohol oxidation to benzaldehyde was the lowest(≈ 57 kJ mol^(-1)). Moreover, the activation energy of further oxidation of benzaldehyde in an acetic acid solvent was only slightly lower(≈ 1.9 kJ mol^(-1)) than that of toluene oxidation. Significantly, the transformation of benzyl alcohol indeed contributed to the generation of benzaldehyde and this step conformed to a first-order parallel-consecutive model. Increased reaction temperature and residence time favored the transformation of benzyl alcohol to benzaldehyde. In addition, doping with molybdenum at Mn/Mo = 3/1 enhanced the catalytic performance of the heterogeneous catalyst and was attributed to the presence of a synergetic effect between different metal cations. Regarding the microscopic kinetics, the LH-OS-ND mechanism(Langmuir–Hinshelwood adsorption of reagents on the same type of active sites and non-dissociative adsorption of oxygen) was verified as responsible for the heterogeneous oxidation of toluene. Oxygen and benzaldehyde were weakly adsorbed(Δ H_(ads,Oxy) ≈^(-1)5 kJ mol^(-1), Δ H _(ads)0,Bald) ≈-30 kJ mol^(-1)), but showed strong mobility(Δ S_(ads,Oxy) ≈-22 J mol^(-1) K^(-1)), Δ S_(ads,Bald) ≈-39 J mol^(-1) K^(-1)). The fundamental intrinsic rates were deduced based on the LH-OS-ND mechanism and showed great consistency with the macroscopic results.展开更多
The selective oxidation of methanol to methyl formate is one of the most attractive processes to obtain value-added methanol-downstream products.The development of highly efficient and stable catalysts is critical for...The selective oxidation of methanol to methyl formate is one of the most attractive processes to obtain value-added methanol-downstream products.The development of highly efficient and stable catalysts is critical for this transformation.In this study,a series of MIL-88B(Fe_(x),Co_(1‒x))bimetallic catalysts with different Fe/Co molar ratios were prepared through a one-pot hydrothermal method.X-ray diffraction,scanning electron microscopy,high-resolution transmission electron microscopy,energy dispersive spectroscopy,Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy,N2 adsorption-desorption,and inductively coupled plasma-mass spectrometry characterization were performed to elucidate the structure of the catalysts.The activity of the catalysts were assessed in the one-step oxidation of methanol to methyl formate with H_(2)O_(2)in a liquid-phase batch reactor.The results show that the MIL-88B(Fe_(x),Co_(1‒x))catalysts exhibit uniform needle-like morphologies with an average length and width of 400-600 nm and 100-150 nm,respectively.Co^(2+)is incorporated into the framework by partially replacing Fe^(3+)in MIL-88B.Moreover,the catalyst efficiently promoted the conversion of methanol to methyl formate.When MIL-88B(Fe_(0.7),Co_(0.3))catalyst was used with a molar ratio of H_(2)O_(2)to methanol of 0.5 at 80℃for 60 min,34.8%methanol conversion was achieved,and the selectivity toward methyl formate was 67.6%.The catalysts also showed great stability with a steady conversion and selectivity even after four cycles.The preliminary oxidation mechanism was also studied.It was determined that H_(2)O_(2)is first adsorbed on the Fe^(3+)sites and subsequently activates these sites.Methanol is adsorbed by the O atoms of the framework through hydrogen bonding and is gradually oxidized to formic acid.Subsequently,formic acid reacts with the residual methanol at the Fe^(3+)and Co^(2+)Lewis acid sites to form methyl formate.展开更多
Hydrogen sulfide in rural biogas was removed with liquid-phase catalytic oxidation.By using rare earth as catalyst,and sulfosalicylic acid as stabilizer,H2S purification efficiency could increase as high as 96%,and su...Hydrogen sulfide in rural biogas was removed with liquid-phase catalytic oxidation.By using rare earth as catalyst,and sulfosalicylic acid as stabilizer,H2S purification efficiency could increase as high as 96%,and sulfur capacity of the composite solution was about 3 g/L.The results show that purification efficiency was affected by catalyst addition,pH,experimental temperature,and sulfur capacity.The parameters effects on catalytic oxidation were studied,and the optimized conditions were that Fe3+ concentration 0.08 mg/L,reaction temperature 70°C,pH 9.0,with a absorption solution volume of 50 mL,a gas flow rate 200 mL/min,and H2S mass concentration of 1.58-2.02 mg/m3.展开更多
基金Supported by the National Natural Science Foundation of China （20576081, 20736009） and the Ph.D. Programs Foundation of Ministry of Education of China （20070610128）.
文摘Liquid phase oxidation of toluene is an environmental benign route for the production of benzoic acid.In a φ48mm bubble column reactor,the commercial process of toluene liquid phase oxidation was conducted with Co(CH3COO)2.4H2O as catalyst.The Co2+ concentration [Co2+] was determined by extraction spectrophotometry and hereby the Co3+ concentration [Co3+] was obtained by mass balance.The results showed that [Co3+] reached the maximum at about 25-30min.[Co3+] increased with increasing Co catalyst amount at total Co concentration<150 mg.L-1 of toluene.The conversion of toluene,yield and selectivity of benzoic acid increased with the increasing [Co3+/Co2+] max.A high [Co3+] and a high [Co3+]/[Co2+] ratio are beneficial to the reaction.
文摘Pt/CeO2–ZrO2–SnO2/γ-Al2O3 catalysts were prepared by co-precipitation and wet impregnation methods for catalytic oxidation of acetaldehyde to acetic acid in water. In the present catalysts, Pt and CeO2–ZrO2–SnO2 were successfully dispersed on the γ-Al2O3 support.Dependences of platinum content and reaction time on the selective oxidation of acetaldehyde to acetic acid were investigated to optimize the reaction conditions for obtaining both high acetaldehyde conversion and highest selectivity to acetic acid. Among the catalysts, a Pt（6.4 wt.%）/Ce0.68Zr0.17Sn0.15O2.0（16 wt.%）/γ-Al2O3 catalyst showed the highest acetaldehyde oxidation activity. On this catalyst, acetaldehyde was completely oxidized after the reaction at 0°C for 8 hr, and the selectivity to acetic acid reached to 95%and higher after the reaction for 4 hr and longer.
基金Supported by the Natural National Science Foundation of China （20080672） and the Research Fund for the Doctoral Program of Higher Education of China （200803351111）.
文摘During the liquid-phase oxidation of p-xylene,over-oxidation of reactant,intermediates and solvent to carbon dioxide and carbon monoxide is generally known as the burning side reaction.Batch and semi-continuous experiments were carried out,and the experimental data of the burning side reaction were analyzed and reported in this paper.The results showed that the rates of burning side reactions were proportional to the rates of the main reaction,but decreased with the increasing concentrations of reactant and intermediates.The inter-stimulative and competitive relationship between the burning side reaction and the main reaction was confirmed,and the rates of the burning side reaction could be described with some key indexes of the main reaction.According to the mechanism of the side reactions and the kinetics model of main reaction which were proposed and tested in the previous papers,a kinetic model of the burning side reactions involving some key indexes of the main reaction was developed,and the parameters were determined by data fitting of the COx rate curves.The obtained kinetic model could describe the burning side reactions adequately.
文摘The effect of liquid-phase oxidation impurities on the solubility of water in hydrocarbon fuels was studied.The results show that the concentration of polar surfactant molecules in the first region increases(true solution)during fuel oxidation,and since the oxidation groups(-COOH,-O=O,-OH,etc.)have similar dipole momentμ,the dielectric loss tangent tanδincreases linearly in this region with surfactant concentration.Upon further oxidation,micelle structures begin to form at a certain point.Micelle formation leads to a sharp decrease in the dipole moment attributable to the monomer unitμ/n,where nis the number of molecules in a micelle.A several-fold decrease in the dipole moment leads to a sharp drop in tanδ.Upon further increase in the number and size of micelles,the dipole moment remains practically unchanged,and the dielectric loss tangent begins to increase linearly again with surfactant concentration.If the critical concentration for micelle formation is achieved upon further oxidation of hydrocarbon liquids,micelle formation processes occur spontaneously in the solution,and the true solution becomes a colloidal system(sol).The resulting micelles are structured with hydrocarbon radicals of molecules toward the outside and hydrophilic(polar)groups toward the inside.Water molecules are located inside micelles and held so securely that water molecules do not aggregate as temperature decreases.The reason for significant differences in the equilibrium solubility of water in hydrocarbon fuels is the different oxidation factors of product samples,resulting from the accumulation of various concentrations of oxidation products,which are natural surfactants,in hydrocarbon fuels.
基金National Natural Science Foundation of China(52071274)Key Research and Development Projects of Shaanxi Province(2023-YBGY-442)Science and Technology Nova Project-Innovative Talent Promotion Program of Shaanxi Province(2020KJXX-062)。
文摘To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretreatment was employed to construct a Ta_(2)O_(5)ceramic layer on the Ta12W alloy surface.Subsequently,a slurry spraying-vacuum sintering method was used to prepare a Si-Cr-Ti-Zr coating on the pretreated substrate.Comparative studies were conducted on the microstructure,phase composition,and isothermal oxidation resistance(at 1600℃)of the as-prepared coatings with and without the micro-arc oxidation ceramic layer.The results show that the Ta_(2)O_(5)layer prepared at 400 V is more continuous and has smaller pores than that prepared at 350 V.After microarc oxidation pretreatment,the Si-Cr-Ti-Zr coating on Ta12W alloy consists of three distinct layers:an upper layer dominated by Ti_(5)Si_(3),Ta_(5)Si_(3),and ZrSi;a middle layer dominated by TaSi_(2);a coating/substrate interfacial reaction layer dominated by Ta_(5)Si_(3).Both the Si-Cr-Ti-Zr coatings with and without the Ta_(2)O_(5)ceramic layer do not fail after isothermal oxidation at 1600℃for 5 h.Notably,the addition of the Ta2O5 ceramic layer reduces the high-temperature oxidation rate of the coating.
基金supported by the Key R&D Program of Shandong Province,China(No.2025CXGC 010412)the National Key Research and Development Program of China(No.2022YFB3709300)the National Natural Science Foundation of China(No.U21A2048).
文摘The limited high-temperature oxidation resistance of Mg alloys is a key factor restricting their development and application.The addition of some rare earth elements(REs),owing to their unique physical and chemical properties,can significantly enhance the oxidation resistance of Mg alloys.Based on our previous study,we conclude that REs such as Gd,Y,and Ce enhance the oxidation resistance of Mg-RE alloys.This article comprehensively reviews recent research progress on high-temperature oxidation behavior and the potential mechanism in Mg-RE alloys.Based on the thermodynamic and kinetic analyses,the evolution of the complex oxide system formed during the high-temperature oxidation of Mg-RE alloys is first summarized.The diffusion behavior and concentration control mechanisms of REs during the oxidation process and how these mechanisms affect the sustained growth of the oxide film and antioxidant properties were elucidated.Moreover,the different structures of the oxide films were classified,and their properties were discussed.Finally,this paper introduces the applications of commonly used REs in Mg alloys and frontier research on their oxidation mechanisms.Based on the above review,we propose that future research perspectives can be explored in terms of expanding the experimental temperature range for oxidation tests,optimizing the chemical composition by adding trace REs to study their synergistic mechanism,revealing the underlying oxidation mechanism through advanced in situ microscopic characterization methods,and investigating the mechanical properties of oxide films using diverse approaches.
文摘Platinum group metals have high melting points,strong corrosion resistance,stable chemical properties,and low oxygen permeability in high-temperature oxygen-containing environments.As thermal protective coating materials,they have gained essential applications in the aerospace field and have excellent prospects for application in frontier military fields,such as protecting hot-end components of hypersonic aircraft.This research reviewed the latest research progress of platinum group metal coatings with hightemperature oxidation resistance,including coating preparation techniques,oxidation failure,and alloying modification.The leading preparation techniques of current platinum group metal coatings were discussed,as well as the advantages and disadvantages of various existing preparation techniques.Besides,the intrinsic properties,failure forms,and failure mechanisms of coatings of single platinum group metal in high-temperature oxygen-containing environments were analyzed.On this basis,the necessity,main methods,and main achievements of alloying modification of platinum group metals were summarized.Finally,the future development of platinum group coatings with high-temperature oxidation resistance was discussed and prospected.
基金supported by the National Key Research and Development Program of China(2024YFA1612900)the National Natural Science Foundation of China(Grant No.52103365 and No.12375270)the Guangdong Innovative and Entrepreneurial Research Team Program,China(Grant No.2021ZT09L227).
文摘Fine-grained nuclear graphite is a key material in high-temperature gas-cooled reactors(HTGRs).During air ingress accidents,core graphite components undergo severe oxidation,threatening structural integrity.Therefore,understanding the oxidation behavior of nuclear graphite is essential for reactor safety.The influence of oxidation involves multiple factors,including temperature,sample size,oxidant,impurities,filler type and size,etc.The size of the filler particles plays a crucial role in this study.Five ultrafine-and superfine-grained nuclear graphite samples(5.9-34.4μm)are manufactured using identical raw materials and manufacturing processes.Isothermal oxidation tests conducted at 650℃-750℃ are used to study the oxidation behavior.Additionally,comprehensive characterization is performed to analyze the crystal structure,surface morphology,and nanoscale to microscale pore structure of the samples.Results indicate that oxidation behavior cannot be predicted solely based on filler grain size.Reactive site concentration,characterized by active surface area,dominates the chemical reaction kinetics,whereas pore tortuosity,quantified by the structural parameterΨ,plays a key role in regulating oxidant diffusion.These findings clarify the dual role of microstructure in oxidation mechanisms and establish a theoretical and experimental basis for the design of high-performance nuclear graphite capable of long-term service in high-temperature gas-cooled reactors.
基金financially supported by the National Natural Science Foundation of China(22472199)Chinese Universities Scientific Fund(15055009)and Central University Guided Funds for Building World-Class Universities(Disciplines)and Advancing Characteristic Development.The authors extend their gratitude to Theoretical and Computational Chemistry Team(from Scientific Compass www.shiyanjia.com)for providing invaluable assistance.
文摘Electrocatalytic glucose oxidation to high-value chemicals provides a sustainable route for biomass valorization.NiCo-based catalysts have emerged as promising candidates for glucose oxidation reaction owing to the intrinsic activity of Ni and Co catalytic centers.However,the dynamic evolution and atomic-scale synergy between these centers remain elusive.Herein,we fabricated NiCo_(2)O_(4)nanosheets supported on nickel foam,where Ni preferentially occupies tetrahedral sites to regulate the electronic configuration of octahedral Co.Experimental and theoretical results demonstrate that the incorporation of tetrahedral Ni induces low-to-intermediate spin transition in octahedral Co,thereby optimizing eg orbital occupancy and stabilizing active sites.This spin-state engineering establishes Ni-Co synergistic catalytic centers for the selective oxidation of glucose to formate(FA).At higher potential(≥1.4 V vs.RHE),octahedral Co undergoes reconstruction into excessive active CoOOH and CoO_(2)species,resulting in glucose overoxidation to CO_(2)and intensified competitive oxygen evolution.In contrast,at lower potentials(<1.4 V vs.RHE),tetrahedral Ni facilitates electron delocalization across the Ni–O–Co lattice,thereby stabilizing octahedral Co for glucose adsorption and oxidation.Subsequently,a coupled electrocatalytic system was constructed,achieving 80.7%FA yield with 91.3%Faradaic efficiency(FE)at NiCo_(2)O_(4)anode and H2 evolution rate of 696μmol h^(−1)with 99.9%FE at Pt cathode for 2 h under 1.35 V vs.RHE.This work provides a deep insight into spin-state regulation of the catalytic center,offering valuable guidance for rational catalyst design.
基金support from the Australian Research Council(ARC)Linkage Project(No.LP230100166).
文摘Selective depression of pyrite remains a major bottleneck in copper flotation,particularly when high-pyrite ores are processed and saline water is used.In such environments,conventional approaches using lime and inert grinding media often fail to discriminate ef-fectively between pyrite and valuable copper minerals due to strong copper activation on pyrite surfaces.This study introduced a novel approach using inorganic radicals generated from peroxymonosulfate(PMS)to selectively oxidize and depress pyrite.Flotation tests with synthetic high-pyrite ore blends showed that PMS significantly reduced pyrite recovery while maintaining or improving chalcopyrite flot-ation.Ethylenediaminetetraacetic acid(EDTA)extraction confirmed selective oxidation of pyrite,and electron paramagnetic resonance(EPR)spectroscopy identified hydroxyl(·OH)and sulfate(SO_(4)^(·-))radicals as the dominant reactive species.Iron ions from grinding me-dia and mineral surfaces were identified as key activators of PMS.A major insight was pyrite’s dual role,acting both as a radical scav-enger and an activator,which made it highly reactive and susceptible to radical-induced oxidation.This process converted surface copper-sulfur species into copper hydroxides,effectively suppressing pyrite flotation.While previous studies have applied EPR to detect radicals in simplified activator/precursor systems,this study provides the first direct mechanistic evidence of radical-driven selectivity in flotation by detecting inorganic radicals in a complex flotation slurry,thereby demonstrating their persistence under industrially relevant conditions and establishing a foundation for more effective and targeted flotation strategies.
基金supported by the National Natural Science Foundation of China(Grant number 22172112)and the Fundamental Research Funds for the Central Universities.
文摘Electrocatalytic oxidation of glycerol for value-added chemicals is a superior strategy to utilize the excess glycerol produced in the biodiesel industry.Pd is one of the few active catalysts for alkaline glycerol oxidation reaction(GOR);however,glycerol inevitably dissociates and converts to carbon dioxide on the Pd surface,which results in its low total Faradaic efficiency(FE)for high-value-added products.Herein,a series of Pd/C and Pd10Bix/C catalysts were synthesized to investigate the GOR pathway.The Pd10Bi3/C catalyst with optimal Bi content achieved an excellent GOR mass activity of 7.5±0.2 A mgPd−1 and an outstanding total FE of 90%±3%,which are much higher than those values on Pd/C(1.2±0.2 A mgPd−1 for mass activity and 63%±4%for total FE).Combined results of in-situ attenuated total reflection surface enhanced infrared absorption spectroscopy and density functional theory calculations show that Bi suppresses the dissociation of glycerol through the“shielding effect”of Bi to the adjacent Pd sites,which weakens the adsorption strength of GOR intermediates on those sites.This work provides a new insight into the GOR mechanism and puts forward a valid strategy for the rational design of catalysts to enable the transformation of glycerol into high-value-added products.
基金financially supported by the Sichuan Science and Technology Program(Grant No.2025NSFSC0139)the China Postdoctoral Science Foundation(Grant No.2023MD734228)+5 种基金The authors extend their gratitude to Ms.Zhou Yuke(from Scientific Compass www.shiyanjia.com)for providing invaluable assistance with the XPS analysis.ICN2 acknowledges funding from Generalitat de Catalunya 2021SGR00457This study is part of the Advanced Materials programme and was supported by MCIN with funding from European Union NextGenerationEU(PRTR-C17.I1)by Generalitat de Catalunya(In-CAEM Project)The authors thank the support from the project AMaDE(PID2023-149158OB-C43)funded by MCIN/AEI/10.13039/501100011033/and by“ERDF A way of making Europe”,by the“European Union”.ICN2 is supported by the Severo Ochoa program from Spanish MCIN/AEI(Grant No.:CEX2021-001214-S)is funded by the CERCA Programme/Generalitat de Catalunya.Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program.JY has received funding from the CSC-UAB PhD scholarship program.ICN2 is founding member of e-DREAM[87].
文摘The methanol oxidation reaction(MOR)to formic acid offers a promising alternative to the anodic oxygen evolution reaction(OER)in water electrolysis.However,the development of efficient and cost-effective catalysts remains a primary challenge.In this study,an enhancement in catalytic MOR performance is achieved through the incorporation of Mn atoms with unsaturated t_(2g)orbitals into Ni_(3)Se_(4).Comprehensive experimental analyses and theoretical calculations reveal that substituting Ni with Mn induces strong electron-withdrawing effects,effectively modulating the local coordination environment of the metal centers.The presence of Mn also elongates Ni–Se(O)bonds,which reduces eg orbital occupancy and modifies the spin state of the material.Electrochemical measurements demonstrate that electrodes based on this optimized material exhibit a high spin state and deliver excellent catalytic activity,achieving a MOR current density up to∼190 mA cm^(−2)at 1.6 V.This performance enhancement is attributed to the favorable electronic configuration and reduced reaction energy barriers associated with the high-spin state.
基金supported by the National Natural Science Foundation of China (No.52274304)。
文摘The three-dimensional(3D) Pd-based nanoflower structures,assembled from two-dimensional(2D)nanosheets,are characterized by their stable and ordered configurations.These structures have been extensively designed as anode materials for fuel cells.However,the exploration of trimetallic nanoflowers with porous architectures remains limited.In this study,we present a straightforward one-step solvothermal method for the synthesis of trimetallic Pd Cu Ni porous nanoflowers(PNFs).Leveraging several unique advantages,such as an open superstructure,high porosity,and enhanced electronic interactions among the trimetals,the resulting Pd Cu Ni PNFs demonstrate significantly improved electrochemical performance,with mass activities reaching 5.94 and 10.14 A/mg for the ethanol oxidation reaction(EOR)and the ethylene glycol oxidation reaction(EGOR),respectively.Furthermore,the Pd Cu Ni PNFs exhibit optimized d-band centers and the most negative onset oxidation potential,indicating enhanced antitoxicity and stability.This study not only provides a novel perspective on the synthesis of 3D porous nanomaterials but also highlights the potential application value of trimetallic nanoalloys in catalysis.
基金Supported by the Guangdong Provincial Natural Science Foundation(No.2022A1515010783)the Sustainable Development Program of Shenzhen Science and Technology Major Program(No.KCXFZ20240903093925033)+4 种基金the Guangdong Provincial Special Project in Science and Technology(No.2021A05240)the Special Project in Key Fields of Guangdong Provincial Higher Education Institutions(No.2021ZDZX2064)the Basic Research Project of Shenzhen Science and Technology Innovation Commission(No.JCYJ20220530162014032)the Zhanjiang Marine Youth Talent Innovation Project(No.2022E05010)the Program for Scientific Research Start-up Funds of Guangdong Ocean University(Nos.R18008,060302042201)。
文摘Alzheimer’s disease(AD)is a complex neurodegenerative disorder associated with changes in inflammation,oxidative stress,and gut microbiota composition.Butyrolactone Ⅰ(BTL-Ⅰ),a fungal metabolite,has shown anti-inflammatory,microbiota regulating,and memory-improving potentials in previous in vitro and AlCl3-induced zebrafish studies.However,its effects of memory-improving and gutbrain axis regulating on Aβ-induced mammalian AD models have not been explored.In this study,intragastric administrated BTL-Ⅰ ameliorated cognitive deficits related to recognition and spatial memory impaired by Aβ_(1-42)intracerebroventricular injection in mice.BTL-Ⅰ maintained gut microbiota balance by increasing the abundance of Blautia,Muribaculaceae,Bacteroides,Akkermansia,etc.,and decreasing CAG-352,Clostridia UCG-014,different Lachnospiraceae groups,etc.,and Firmicutes/Bacteroidota ratio and elevated the levels of short-chain fatty acids.Additionally,it alleviated intestinal oxidative stress,inflammatory responses,and pathological damage.Furthermore,BTL-I reversed Aβ_(1-42)-induced activation of microglia and astrocytes in the hippocampus and inhibited the elevated oxidative stress and proinflammatory cytokines in both plasma and brain.The correlation analysis between the regulated taxa and biomarkers supports the role of gut microbiota in adjusting inflammation,oxidative stress,and memory.In conclusion,BTL-I may serve as a valuable drug lead for treating Alzheimer’s disease by systematically inhibiting microbiota imbalance,inflammation,and oxidative stress along the gut-brain axis.
基金supported by the Original Exploratory Program of the National Natural Science Foundation of China(No.52450012)。
文摘TiB_(2)coatings can significantly enhance the high-temperature oxidation resistance of molybdenum,which would broaden the application range of molybdenum and alloys thereof.However,traditional methods for preparing TiB_(2)coatings have disadvantages such as high equipment costs,complicated processes,and highly toxic gas emissions.This paper proposes an environmentally friendly method,which requires inexpensive equipment and simple processing,for preparing TiB_(2)coating on molybdenum via electrophoretic deposition within Na3AlF6-based molten salts.The produced TiB_(2)layer had an approximate thickness of 60μm and exhibited high density,outstanding hardness(38.2 GPa)and robust adhesion strength(51 N).Additionally,high-temperature oxidation experiments revealed that,at900℃,the TiB_(2)coating provided effective protection to the molybdenum substrate against oxidation for 3 h.This result indicates that the TiB_(2)coating prepared on molybdenum using molten salt electrophoretic deposition possesses good high-temperature oxidation resistance.
基金the financial support from the National Natural Science Foundation of China(52172110,52472231,52311530113)Shanghai"Science and Technology Innovation Action Plan"intergovernmental international science and technology cooperation project(23520710600)+1 种基金Science and Technology Commission of Shanghai Municipality(22DZ1205600)the Central Guidance on Science and Technology Development Fund of Zhejiang Province(2024ZY01011)。
文摘Investigating structural and hydroxyl group effects in electrooxidation of alcohols to value-added products by solid-acid electrocatalysts is essential for upgrading biomass alcohols.Herein,we report efficient electrocatalytic oxidations of saturated alcohols(C_(1)-C_(6))to selectively form formate using Ni Co hydroxide(Ni Co-OH)derived Ni Co_(2)O_(4)solid-acid electrocatalysts with balanced Lewis acid(LASs)and Brønsted acid sites(BASs).Thermal treatment transforms BASs-rich(89.6%)Ni Co-OH into Ni Co_(2)O_(4)with nearly equal distribution of LASs(53.1%)and BASs(46.9%)which synergistically promote adsorption and activation of OH-and alcohol molecules for enhanced oxidation activity.In contrast,BASs-enriched Ni Co-OH facilitates formation of higher valence metal sites,beneficial for water oxidation.The combined experimental studies and theoretical calculation imply the oxidation ability of C1-C6alcohols increases as increased number of hydroxyl groups and decreased HOMO-LUMO gaps:methanol(C_(1))<ethylene glycol(C_(2))<glycerol(C3)<meso-erythritol(C4)<xylitol(C5)<sorbitol(C6),while the formate selectivity shows the opposite trend from 100 to 80%.This study unveils synergistic roles of LASs and BASs,as well as hydroxyl group effect in electro-upgrading of alcohols using solid-acid electrocatalysts.
文摘Liquid-phase oxidation of toluene with air has become the main technology for producing benzoic acid in a reactor at present. Based on the kinetic model of the toluene oxidation process obtained from laboratory and mass balance of key component, a novel model is established to simulate the industrial toluene oxidation process, in which the effects of benzaldehyde and benzyl alcohol are considered and the kinetic parameters are revised by industrial data. The simulation results show that the error of benzoic acid yield is within 3.5%. Based on the simulation model, to maximize the benzoic acid yield, an optimization model is proposed to optimize the operating parameters, including toluene feed-in mass flux and temperature. The optimization result indicates that on the allowable operating conditions the maximum benzoic acid yield obtained with the reaction temperature at 167.2 C an the mass flux at 104.1 t·h^- 1 is greater than the current one, which can be used to guide industrial reactor s operation.
基金supported by the National Natural Science Foundation of China (No. 21376163)
文摘In this study, liquid-phase aerobic oxidation of toluene catalyzed by Mn–Mo oxide was conducted in a 1.0 L batch reactor. The macroscopic kinetics of toluene consumption and benzaldehyde generation at 413–443 K were obtained from a combination of experimental observation and hypothetical models. The results clearly showed that both the oxidation rate of toluene and generation rate of the aromatic product were proportional to the concentration of the substrate, the partial pressure of oxygen and the surface area of the catalyst. The energy barrier of toluene oxidation to benzyl alcohol was the highest(≈ 81 kJ mol^(-1)), while that of benzyl alcohol oxidation to benzaldehyde was the lowest(≈ 57 kJ mol^(-1)). Moreover, the activation energy of further oxidation of benzaldehyde in an acetic acid solvent was only slightly lower(≈ 1.9 kJ mol^(-1)) than that of toluene oxidation. Significantly, the transformation of benzyl alcohol indeed contributed to the generation of benzaldehyde and this step conformed to a first-order parallel-consecutive model. Increased reaction temperature and residence time favored the transformation of benzyl alcohol to benzaldehyde. In addition, doping with molybdenum at Mn/Mo = 3/1 enhanced the catalytic performance of the heterogeneous catalyst and was attributed to the presence of a synergetic effect between different metal cations. Regarding the microscopic kinetics, the LH-OS-ND mechanism(Langmuir–Hinshelwood adsorption of reagents on the same type of active sites and non-dissociative adsorption of oxygen) was verified as responsible for the heterogeneous oxidation of toluene. Oxygen and benzaldehyde were weakly adsorbed(Δ H_(ads,Oxy) ≈^(-1)5 kJ mol^(-1), Δ H _(ads)0,Bald) ≈-30 kJ mol^(-1)), but showed strong mobility(Δ S_(ads,Oxy) ≈-22 J mol^(-1) K^(-1)), Δ S_(ads,Bald) ≈-39 J mol^(-1) K^(-1)). The fundamental intrinsic rates were deduced based on the LH-OS-ND mechanism and showed great consistency with the macroscopic results.
文摘The selective oxidation of methanol to methyl formate is one of the most attractive processes to obtain value-added methanol-downstream products.The development of highly efficient and stable catalysts is critical for this transformation.In this study,a series of MIL-88B(Fe_(x),Co_(1‒x))bimetallic catalysts with different Fe/Co molar ratios were prepared through a one-pot hydrothermal method.X-ray diffraction,scanning electron microscopy,high-resolution transmission electron microscopy,energy dispersive spectroscopy,Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy,N2 adsorption-desorption,and inductively coupled plasma-mass spectrometry characterization were performed to elucidate the structure of the catalysts.The activity of the catalysts were assessed in the one-step oxidation of methanol to methyl formate with H_(2)O_(2)in a liquid-phase batch reactor.The results show that the MIL-88B(Fe_(x),Co_(1‒x))catalysts exhibit uniform needle-like morphologies with an average length and width of 400-600 nm and 100-150 nm,respectively.Co^(2+)is incorporated into the framework by partially replacing Fe^(3+)in MIL-88B.Moreover,the catalyst efficiently promoted the conversion of methanol to methyl formate.When MIL-88B(Fe_(0.7),Co_(0.3))catalyst was used with a molar ratio of H_(2)O_(2)to methanol of 0.5 at 80℃for 60 min,34.8%methanol conversion was achieved,and the selectivity toward methyl formate was 67.6%.The catalysts also showed great stability with a steady conversion and selectivity even after four cycles.The preliminary oxidation mechanism was also studied.It was determined that H_(2)O_(2)is first adsorbed on the Fe^(3+)sites and subsequently activates these sites.Methanol is adsorbed by the O atoms of the framework through hydrogen bonding and is gradually oxidized to formic acid.Subsequently,formic acid reacts with the residual methanol at the Fe^(3+)and Co^(2+)Lewis acid sites to form methyl formate.
基金Project(2008ZX07105-002) supported by the Erhai Lake Project of National Science and Technology Major Project in the 11th Five years Plan of China
文摘Hydrogen sulfide in rural biogas was removed with liquid-phase catalytic oxidation.By using rare earth as catalyst,and sulfosalicylic acid as stabilizer,H2S purification efficiency could increase as high as 96%,and sulfur capacity of the composite solution was about 3 g/L.The results show that purification efficiency was affected by catalyst addition,pH,experimental temperature,and sulfur capacity.The parameters effects on catalytic oxidation were studied,and the optimized conditions were that Fe3+ concentration 0.08 mg/L,reaction temperature 70°C,pH 9.0,with a absorption solution volume of 50 mL,a gas flow rate 200 mL/min,and H2S mass concentration of 1.58-2.02 mg/m3.
