α-Bi2O3 powders were prepared from nanometer Bi powders through low-temperature oxidation at less than 873.15 K. XRD, SEM, TEM and HRTEM were used to characterize the structure and morphology of Bi powders and Bi2O3 ...α-Bi2O3 powders were prepared from nanometer Bi powders through low-temperature oxidation at less than 873.15 K. XRD, SEM, TEM and HRTEM were used to characterize the structure and morphology of Bi powders and Bi2O3 particles. Kinetic studies on the bismuth oxidation at low-temperatures were carried out by TGA method. The results show that bismuth beads should be reunited and oxidized to become irregular Bi2O3 powders. The bismuth oxidation follows shrinking core model, and its controlling mechanism varies at different reaction time. Within 0-10 min, the kinetics is controlled by chemical reaction, after that it is controlled by O2 diffusion in the solid α-Bi2O3 layer. The apparent activation energy is determined as 55.19 kJ/mol in liquid-phase oxidation.展开更多
We report the investigation on the low-temperature oxidation of cyclohexane in a jet-stirred reactor over 500-742 K. Synchrotron vacuum ultraviolet photoionization mass spectrometry （SVUV-PIMS） was used for identify...We report the investigation on the low-temperature oxidation of cyclohexane in a jet-stirred reactor over 500-742 K. Synchrotron vacuum ultraviolet photoionization mass spectrometry （SVUV-PIMS） was used for identifying and quantifying the oxidation species. Major products, cyclic olefins, and oxygenated products including reactive hydroperoxides and high oxygen compounds were detected. Compared with n-alkanes, a narrow low-temperature window （-80 K） was observed in the low-temperature oxidation of cyclohexane. Besides, a kinetic model for cyclohexane oxidation was developed based on the CNRS model [Combust. Flame 160, 2319 （2013）], which can better capture the experimental results than previous models. Based on the modeling analysis, the 1,5-H shift dominates the crucial isomerization steps of the first and second O2 addition products in the low-temperature chain branching process of cyclohexane. The negative temperature coefficient behavior of cyclohexane oxidation results from the reduced chain branching due to the competition from chain inhibition and propagation reactions, i.e. the reaction between cyclohexyl radical and O2 and the de- composition of cyclohexylperoxy radical, both producing cyclohexene and HO2 radical, as well as the decomposition of cyclohexylhydroperoxy radical producing hex-5-en-l-al and OH radical.展开更多
Light crude oil from the lower member of the Paleogene Xiaganchaigou Formation of Gaskule in Qinghai Oilfield was selected to carry out thermal kinetic analysis experiments and calculate the activation energy during t...Light crude oil from the lower member of the Paleogene Xiaganchaigou Formation of Gaskule in Qinghai Oilfield was selected to carry out thermal kinetic analysis experiments and calculate the activation energy during the oil oxidation process.The oxidation process of crude oi l in porous medium was modeled by crude oil static oxidation experiment,and the component changes of crude oil before and after low-temperature oxidation were compared through Fourier transform ion cy-clotron resonance mass spectrometry and gas chromatography;the dynamic displacement experiment of oxygen-reduced air was combined with NMR technology to analyze the oil recovery degree of oxygen-reduced air flooding.The whole process of crude oil oxidation can be divided into four stages:light hydrocarbon volatilization,low-temperature oxidation,fuel deposition,and high temperature oxidation;the high temperature oxidation stage needs the highest activation energy,followed by the fuel deposition stage,and the low-temperature oxidation stage needs the lowest activation energy;the concentration of oxygen in the reaction is negatively correlated with the activation energy required for the reaction;the higher the oxygen concentration,the lower the average activation energy required for oxidation reaction is;the low-temperature oxidation reaction between crude oil and air generates a large amount of heat and CO,CO_(2) and CH4,forming flue gas drive in the reservoir,which has certain effects of mixing phases,reducing viscosity,lowering interfacial tension and promoting expansion of crude oil,and thus helps enhance the oil recovery rate.Under suitable reservoir temperature condition,the degree of recovery of oxygen-reduced air flooding is higher than that of nitrogen flooding for all scales of pore throat,and the air/oxygen-reduced air flooding de-velopment should be preferred.展开更多
Correlations among free radicals, apparent activation energy, and functional groups during lowtemperature oxidation of Jurassic coal in Northern Shaanxi were investigated by examining three coal samples collected from...Correlations among free radicals, apparent activation energy, and functional groups during lowtemperature oxidation of Jurassic coal in Northern Shaanxi were investigated by examining three coal samples collected from the Ningtiaota, Jianxin, and Shigetai coal mines. Free radical concentrations at less than 120 ℃ were investigated by electron spin resonance experiments while the thermogravimetric experiments were conducted to analyze apparent activation energies. In addition, Fourier transform infrared spectroscopy was employed to study the spectrum of functional groups generated in coal. The results indicated that, in decreasing order, the apparent activation energies were Shigetai 〉Jianxin 〉 Ningtiaota, indicating that, from 50 to 120 ℃, the Ningtiaota coal sample most easily absorbed and reacted with oxygen while the most resistant was the Shigetai coal sample. Free radical concentrations and line heights increased with increased temperature, and the line width and Lande factor showed irregular fluctuations. Functional group variations were different among these coals, and the phenol and alcohol-associated OHs, carboxyls, and aromatic ring double bonds might have had a major impact on free radical concentrations. These results were meaningful for better consideration and management of coal oxidation at low temperatures.展开更多
The aim of this paper is to analyze the change in the active structure of lignite during the process of lowtemperature oxidation by constructing a molecular structure model for lignite. Using quantum computation combi...The aim of this paper is to analyze the change in the active structure of lignite during the process of lowtemperature oxidation by constructing a molecular structure model for lignite. Using quantum computation combined with experimental results of proximate analysis, ultimate analysis, Fourier transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS), a structural model for the large molecular structure was constructed. By analyzing the bond lengths in the model molecule, the evolution law for the active structure of lignite was predicted for the process of low-temperature oxidation. In low-temperature oxidation,alkanes and hydroxyls are the primary active structures observed in lignite, though ether may also react. These active functional groups react with oxygen to release heat, thereby speeding up the reaction between coal and oxygen. Finally, the content of various functional groups in the process of lignite low-temperature oxidation was analyzed by infrared analysis, and the accuracy of the model was verified.展开更多
The low-temperature catalytic oxidation of heavy crude oil（Xinjiang Oilfield,China） was studied using three types of catalysts including oil-soluble,watersoluble,and dispersed catalysts.According to primary screenin...The low-temperature catalytic oxidation of heavy crude oil（Xinjiang Oilfield,China） was studied using three types of catalysts including oil-soluble,watersoluble,and dispersed catalysts.According to primary screening,oil-soluble catalysts,copper naphthenate and manganese naphthenate,are more attractive,and were selected to further investigate their catalytic performance in in situ upgrading of heavy oil.The heavy oil compositions and molecular structures were characterized by column chromatography,elemental analysis,and Fourier transform infrared spectrometry before and after reaction.An Arrhenius kinetics model was introduced to calculate the rheological activation energy of heavy oil from the viscosity-temperature characteristics.Results show that the two oil-soluble catalysts can crack part of heavy components into light components,decrease the heteroatom content,and achieve the transition of reaction mode from oxygen addition to bond scission.The calculated rheological activation energy of heavy oil from the fitted Arrhenius model is consistent with physical properties of heavy oil（oil viscosity and contents of heavy fractions）.It is found that the temperature,oil composition,and internal molecular structures are the main factors affecting its flow ability.Oil-soluble catalyst-assisted air injection or air huff-n-puff injection is a promising in situ catalytic upgrading method for improving heavy oil recovery.展开更多
The oxidation behavior of molybdenum disilicide （MoSi2） powders at 400, 500, and 600℃ for 12 h in air were investigated by using X-ray diffraction （XRD） and transmission electron microscopic （TEM） techniques. S...The oxidation behavior of molybdenum disilicide （MoSi2） powders at 400, 500, and 600℃ for 12 h in air were investigated by using X-ray diffraction （XRD） and transmission electron microscopic （TEM） techniques. Significant changes were observed in volume, mass, and color. Especially at 500℃, the volume expansion was found to be as high as 7-8 times, the color changed from black to yellow-white, and the mass gain was about 169.34% after 8 h, with SiO2 and MoO3 as main reaction products. The gains in volume and mass were less at 400 and 600℃ compared with those at 500℃, probably due to the less reaction rate at 400℃ and the formation of silica glass scale at 600℃, which would protect the matrix and restrain the diffusion of oxygen and molybdenum. Thus, the accelerated oxidation behavior of MoSi2 powder appeared at 500℃ and the volume expansion was the sign of accelerated oxidation.展开更多
The low-temperature wet oxidation behavior of semi-dry desulfurization ash from iron ore sintering flue gas in ammonium citrate solution was investigated for efficiently utilizing the low-quality desulfurization ash.T...The low-temperature wet oxidation behavior of semi-dry desulfurization ash from iron ore sintering flue gas in ammonium citrate solution was investigated for efficiently utilizing the low-quality desulfurization ash.The effects of the ammonium citrate concentration,oxidation temperature,solid/liquid ratio,and oxidation time on the wet oxidation behavior of desulfurization ash were studied.Simultaneously,the oxidation mechanism of desulfurization ash was revealed by means of X-ray diffraction,Zeta electric resistance,and X-ray photoelectron spectroscopy(XPS)analysis.Under the optimal conditions with ammonium citrate,the oxidation ratio of CaSO_(3)was up to the maximum value(98.49%),while that of CaSO_(3)was only 8.92%without ammonium citrate.Zeta electric resistance and XPS results indicate that the dissolution process of CaSO_(3)could be significantly promoted by complexation derived from the ammonium citrate hydrolysis.As a result,the oxidation process of CaSO_(3)was transformed from particle oxidation to SO_(3)^(2−)ion oxidation,realizing the rapid transformation of desulfurization ash from CaSO_(3)to CaSO_(4)at low temperature.It provides a reference for the application of semi-dry desulfurization ash and contributes to sustainable management for semi-dry desulfurization ash.展开更多
Low-temperature oxidation(LTO)is the main reaction that affects fuel formation in the in-situ combustion process,which has important significance for the subsequent combustion propulsion and the successful extraction ...Low-temperature oxidation(LTO)is the main reaction that affects fuel formation in the in-situ combustion process,which has important significance for the subsequent combustion propulsion and the successful extraction of crude oil.In this study,heavy oil was subjected to LTO reactions at different temperatures.Three types of reaction products with varying oxidation depths were characterized in terms of the number of oxygen atoms and the polarity of the molecule to reveal the low-temperature oxidation process of the heavy oil.Ketone compounds and acid polyoxides in the oil phase and deep oxidation products with a higher number of oxygen atoms in the coke were identified with increasing oxidation depth.The experimental results showed that the oxidation reaction of the heavy oil changed from kinetic-controlled to diffusion-controlled in the open oxidation system of the heavy oil as the oxidation depth increased.The oxidation reaction of the oil phase reached a maximum and stable value in oxygen content.The molecular compositions of the ketone compound and acid polyoxide did not change significantly with further increase in reaction temperature.The molecular compositions of the deep oxidation products with a higher number of oxygen atoms in the coke phase changed significantly.The coke precursor molecules with a lower oxygen content and condensation degree participated in the coke formation,and the oxidation reaction pathway and the complexity of the oxidation product component also increased.展开更多
Using Fourier Transform Infrared(FTIR)combined with an adiabatic oxidation test,temperature-programmed oxidation and gas analysis,we studied the changes of active functional groups during low-temperature oxidation of ...Using Fourier Transform Infrared(FTIR)combined with an adiabatic oxidation test,temperature-programmed oxidation and gas analysis,we studied the changes of active functional groups during low-temperature oxidation of lignite,gas coal,fat coal and anthracite.During slow low-temperature heat accumulation,aliphatic hydrocarbons,such as methyl and methylene,are attacked by oxygen atoms absorbed by pores on coal surfaces,generating unstable solid intermediate carbon-oxygen complexes,which then decompose into gaseous products(CO,CO_(2))and stable solid complexes.At the accelerated oxidation stage,the stable complexes begin to decompose in large amounts and provided new active sites for further oxidation,while the aliphatic structures gained energy and fell from the benzene rings to produce C_(x)H_(y)and H_(2).展开更多
This work aimed at investigating the crucial factor in building and maintaining the combustion front during in-situ combustion(ISC),oxidized coke and pyrolyzed coke.The surface morphologies,elemental contents,and non-...This work aimed at investigating the crucial factor in building and maintaining the combustion front during in-situ combustion(ISC),oxidized coke and pyrolyzed coke.The surface morphologies,elemental contents,and non-isothermal mass losses of the oxidized and pyrolyzed cokes were thoroughly examined.The results indicated that the oxidized coke could be combusted at a lower temperature compared to the pyrolyzed coke due primarily to their differences in the molecular polarity and microstructure.Kinetic triplets of coke combustion were determined using iso-conversional models and one advanced integral master plots method.The activation energy values of the oxidized and pyrolyzed cokes varied in the range of 130-153 k J/mol and 95-120 kJ/mol,respectively.The most appropriate reaction model of combustion of the oxidized and pyrolyzed cokes followed three-dimensional diffusion model(D_(3)) and random nucleation and subsequent growth model(F_(1)),respectively.These observations assisted in building the numerical model of these two types of cokes to simulate the ISC process.展开更多
The catalytic oxidation of ethyl acetate(EA)was studied over CuO/CeO_(2) catalysts which were prepared by ball milling with different precursors(copper oxide,cerium acetate,cerium dioxide,copper acetate and cerium hyd...The catalytic oxidation of ethyl acetate(EA)was studied over CuO/CeO_(2) catalysts which were prepared by ball milling with different precursors(copper oxide,cerium acetate,cerium dioxide,copper acetate and cerium hydroxide).The CuO/CeO_(2) catalyst(O-A)prepared with copper oxide and cerium acetate as precursors shows very high catalytic activity that 100%EA conversion is achieved at low temperature of 220℃.It is found that specific surface area(112.8 m^(2)/g),particle size of CuO(3.5 nm)and proportion of oxygen vacancies are prominent on the O-A catalyst.Oxygen vacancies in CeO_(2)support are beneficial to enhancing the adsorption and activation of the oxygen.More finely dispersed CuO particles and oxygen vacancies which are derived from the synergistic interaction of Cu-Ce species play an important role in the catalytic oxidation of EA.展开更多
Effective control of gas-phase pollutants(volatile organic compounds(VOCs)and CO)is critical to human health and the ecological environment.Catalytic oxidation is one of the most promising technologies for achieving e...Effective control of gas-phase pollutants(volatile organic compounds(VOCs)and CO)is critical to human health and the ecological environment.Catalytic oxidation is one of the most promising technologies for achieving efficient volatile organic compounds and CO emission control.The subnano cluster catalyst can not only provide catalytic sites with multiple metal atoms,but also maintain full utilization efficiency.Almost all metal atoms in highly dispersed clusters can be used for adsorption and conversion of reactants.Recently,various types of sub-nano clusters,including subnano cluster oxides,have been developed and demonstrated excellent performance in low-temperature gas-phase pollutants combustion.In this mini review,we systematically summarize the structure,physicochemical properties,characterization,and applications of sub-nano cluster catalysts in catalytic oxidation of CO,methane,propane,propylene,toluene and its derivatives,formaldehyde and chlorinated volatile organic compounds.Finally,we have analyzed and discussed the problems and challenges faced by sub-nano cluster catalysts in both basic research and practical applications,providing a scientific basis for the design,synthesis,and application of efficient heterogeneous catalysts for CO and VOCs oxidation.展开更多
The investigation of low-temperature oxidation(LTO) of crude oil within tight shale holds significant importance due to its implications for subsequent oxidation reactions and enhanced oil recovery in the process of a...The investigation of low-temperature oxidation(LTO) of crude oil within tight shale holds significant importance due to its implications for subsequent oxidation reactions and enhanced oil recovery in the process of air injection.In this study,the tight shale sample underwent oxidation at various LTO temperatures,followed by an analysis of the resulting gas composition.Furthermore,the oxidized oil was separated from the tight shale and subjected to characte rization using electron paramagnetic resonance,nuclear magnetic resonance,and negative ion electrospray Fourier transform-ion cyclotron resonance mass spectrometry techniques.The primary focus was on examining the distinct LTO reaction pathways observable across different temperature ranges.The findings demonstrated a correlation between LTO temperature and the concentration of free radicals,which predominantly resided on aromatic hydrocarbons,alkanes,and oxygen atoms.Additionally,the proton count of polycyclic aromatic hydrocarbons exhibited a continuous increase from 83 to 350℃,suggesting intensified aromatization and condensation reactions involving aliphatic and aromatic compounds.With rising LTO temperature,the molecular structure of O2compounds underwent significant transformations,characterized by increased condensation degree and a decrease in low carbon nu mber molecular structu res,while higher equivale nt double bonds and carbon number molecular structures became more prevalent.The LTO reaction pathways of shale oil included cycle paths 1,2,and 3.The influence of cycle path 1 diminished at temperatures ranging from 83 to 150℃ and 250 to 350℃ whereas the significance of cycle paths 2 and 3 increased,resulting in an overall escalation of the oxidation rate with temperature elevation.It was observed that the shale oil LTO process exhibited a negative temperature coefficient within the temperature range of150 to 250℃,emphasizing the criticality of overcoming the energy barrier in this region to achieve stable combustion.This comprehensive investigation provides valuable insights into the mechanisms underlying LTO in crude oil confined within tight shale.展开更多
This study focused on improving the cathode performance of Ba_(0.6)Sr_(0.4)Co_(0.85)Nb_(0.15)O_(3-δ)(BSCN)-based perovskite materials through molybdenum(Mo)doping.Pure BSCN and Mo-modified-BSCN—Ea_(0.6)Sr_(0.4)Co_(0...This study focused on improving the cathode performance of Ba_(0.6)Sr_(0.4)Co_(0.85)Nb_(0.15)O_(3-δ)(BSCN)-based perovskite materials through molybdenum(Mo)doping.Pure BSCN and Mo-modified-BSCN—Ea_(0.6)Sr_(0.4)Co_(0.85)Nb_(0.1)Mo_(0.05)O_(3-δ)(B S CNM_(0.05)),Ba_(0.6)Sr_(0.4)Co_(0.85)Nb_(0.05)Mo_(0.1)O_(3-δ)(BSCNM_(0.1)),and Ba_(0.6)Sr_(0.4)Co_(0.85)Mo_(0.15)O_(3-δ)(BSCM)—with Mo doping contents of 5mol%,10mol%,and15mol%,respectively,were successfully prepared using the sol-gel method.The effects of Mo doping on the crystal structure,conductivity,thermal expansion coefficient,oxygen reduction reaction(ORR)activity,and electrochemical performance were systematically evaluated using X-ray diffraction analysis,thermally induced characterization,electrochemical impedance spectroscopy,and single-cell performance tests.The results revealed that Mo doping could improve the conductivity of the materials,suppress their thermal expansion effects,and significantly improve the electrochemical performance.Surface chemical state analysis using X-ray photoelectron spectroscopy revealed that 5mol%Mo doping could facilitate a high adsorbed oxygen concentration leading to enhanced ORR activity in the materials.Density functional theory calculations confirmed that Mo doping promoted the ORR activity in the materials.At an operating temperature of 600℃,the BSCNM_(0.05)cathode material exhibited significantly enhanced electrochemical impedance characteristics,with a reduced area specific resistance of 0.048Ω·cm~2,which was lower than that of the undoped BSCN matrix material by 32.39%.At the same operating temperature,an anode-supported single cell using a BSCNM_(0.05)cathode achieved a peak power density of 1477 mW·cm^(-2),which was 30.71%,56.30%,and 171.50%higher than those of BSCN,BSCNM_(0.1),and B SCM,respectively.The improved ORR activity and electrochemical performance of BSCNM_(0.05)indicate that it can be used as a cathode material in low-temperature solid oxide fuel cells.展开更多
Electrochemical reaction is emerging as a powerful approach for glucose detection and biomass conversion.However,it has been rarely explored for glucose detection and biomass conversion into valueadded chemicals.Previ...Electrochemical reaction is emerging as a powerful approach for glucose detection and biomass conversion.However,it has been rarely explored for glucose detection and biomass conversion into valueadded chemicals.Previously reported glucose oxidase reduction(GOR)catalysts exhibit issues such as low activity,limited detection range,poor sensitivity,and overreliance on noble metals.Here,we employ an impregnation method to load transition metal nickel onto carbon nanotubes(CNT)and fabricated Ni/CNT30 catalyst via a discharge process.Ni/CNT30 catalyst exhibits a remarkably high catalytic activity of up to 3336.7μA·cm^(-2)·mmol^(-1)·L,a detection limit of 2.43μmol·L^(-1),outstanding stability,and excellent resistance to impurities and interference,surpassing other noble metal-based and oxide-based materials.Hence,this material provides a new approach for the preparation of glucose sensors to achieve precise mobile measurement of glucose concentration and biofuel cells in future.展开更多
The development of efficient low-load platinum catalysts for CO oxidation is critical for large-scale industrial applications and environmental protection.In this study,a strategy of N_(2)treatment triggered the self-...The development of efficient low-load platinum catalysts for CO oxidation is critical for large-scale industrial applications and environmental protection.In this study,a strategy of N_(2)treatment triggered the self-reforming into fully exposed Pt cluster catalysts was proposed.By adjusting the coordination environment of Pt species on the defect support through N_(2)treatment,the CO catalytic activity was significantly enhanced,achieving complete CO oxidation at 130℃with a Pt loading of only 0.1 wt.%.The turnover frequency of N_(2)-treated Pt_(FEC)/Ti-D at 160℃was 18.3 times that of untreated Pt_(SA)/Ti-D.Comprehensive characterization results indicated that the N_(2)treatment of the Pt single-atom defect catalyst facilitated the reconfiguration and evolution of the defect structure,leading to the aggregation of Pt single atoms into fully exposed Pt clusters.Notably,these fully exposed Pt clusters exhibited a reduced coordination of Pt–O in the first coordination shell compared to single atoms,which resulted in the formation of Pt–Pt metal coordination.This unique coordination structure enhanced the adsorption and activation of CO and O_(2)on the catalyst,thereby resulting in exceptionally low-temperature CO oxidation activity.This work demonstrates a promising strategy for the design,synthesis,and industrial application of efficient low-platinum load catalysts.展开更多
Over recent decades,fuel cell technologies have emerged as viable solutions to address the energy and environmental challenges stemming from fossil fuel dependence.Especially,ammonia has gained increasing attention as...Over recent decades,fuel cell technologies have emerged as viable solutions to address the energy and environmental challenges stemming from fossil fuel dependence.Especially,ammonia has gained increasing attention as an attractive alternative to hydrogen,offering comparable energy density while maintaining carbon-free characteristics,along with superior storage and transport properties that give direct ammonia fuel cells(DAFCs)distinct safety advantages over hydrogen-based systems.Central to this technology is the anodic ammonia oxidation reaction(AOR),where platinum(Pt)remains the most efficient catalyst after years of intensive research.This review offers a comprehensive overview of Ptbased AOR electrocatalysts with potential for application in low-temperature DAFCs.Following an introductory section highlighting key historical developments and catalytic breakthroughs,a fundamental understanding of low-temperature DAFC operation and AOR mechanisms is systematically presented.Subsequently,it outlines the advancements in Pt-based catalysts from simple monometallic systems to sophisticated multimetallic alloys and composites,highlighting material innovations and performance enhancements.Afterward,key challenges and future research directions for advancing AOR electrocatalysts are identified,with the aim of providing valuable guidance for developing practical,highperformance,and low-temperature DAFC systems.展开更多
A series of Au/Co_(x)Fe_(3-x)O_(4) catalysts was synthesized using the sol-deposition method by depositing 2–5 nm Au particles on Fe-doped Co_(3)O_(4).Co_(2)FeO_(4),with a Co/Fe molar ratio of 2:1,exhibited higher sp...A series of Au/Co_(x)Fe_(3-x)O_(4) catalysts was synthesized using the sol-deposition method by depositing 2–5 nm Au particles on Fe-doped Co_(3)O_(4).Co_(2)FeO_(4),with a Co/Fe molar ratio of 2:1,exhibited higher specific surface area,Co^(3+)/Co^(2+)ratio,and oxygen vacancy content compared to Co_(3)O_(4).As a result,it displayed better performance in CO oxidation,achieving a total conversion temperature(T100)of 96℃.Au greatly improved the catalytic efficiency of all Co_(x)Fe_(3-x)O_(4) samples,with the 0.2%Au/Co_(2)FeO_(4) catalyst achieving a further decrease in T100 to 73℃.Stability tests conducted at room temperature on the 1%Au/Co_(x)Fe_(3-x)O_(4) catalysts demonstrated a slowed deactivation rate after Fe-doping.The reaction pathway for CO oxidation catalyzed by Au/Co_(2)FeO_(4) followed the Mars-van Krevelen mechanism.展开更多
基金Project (2006BAB02B05-04- 01/02) supported by the National Key Technologies R&D Program of China
文摘α-Bi2O3 powders were prepared from nanometer Bi powders through low-temperature oxidation at less than 873.15 K. XRD, SEM, TEM and HRTEM were used to characterize the structure and morphology of Bi powders and Bi2O3 particles. Kinetic studies on the bismuth oxidation at low-temperatures were carried out by TGA method. The results show that bismuth beads should be reunited and oxidized to become irregular Bi2O3 powders. The bismuth oxidation follows shrinking core model, and its controlling mechanism varies at different reaction time. Within 0-10 min, the kinetics is controlled by chemical reaction, after that it is controlled by O2 diffusion in the solid α-Bi2O3 layer. The apparent activation energy is determined as 55.19 kJ/mol in liquid-phase oxidation.
基金supported by the National Natural Science Foundation of China(No.91641205,No.51622605,No.91541201)the Shanghai Science and Technology Committee(No.17XD1402000)
文摘We report the investigation on the low-temperature oxidation of cyclohexane in a jet-stirred reactor over 500-742 K. Synchrotron vacuum ultraviolet photoionization mass spectrometry （SVUV-PIMS） was used for identifying and quantifying the oxidation species. Major products, cyclic olefins, and oxygenated products including reactive hydroperoxides and high oxygen compounds were detected. Compared with n-alkanes, a narrow low-temperature window （-80 K） was observed in the low-temperature oxidation of cyclohexane. Besides, a kinetic model for cyclohexane oxidation was developed based on the CNRS model [Combust. Flame 160, 2319 （2013）], which can better capture the experimental results than previous models. Based on the modeling analysis, the 1,5-H shift dominates the crucial isomerization steps of the first and second O2 addition products in the low-temperature chain branching process of cyclohexane. The negative temperature coefficient behavior of cyclohexane oxidation results from the reduced chain branching due to the competition from chain inhibition and propagation reactions, i.e. the reaction between cyclohexyl radical and O2 and the de- composition of cyclohexylperoxy radical, both producing cyclohexene and HO2 radical, as well as the decomposition of cyclohexylhydroperoxy radical producing hex-5-en-l-al and OH radical.
文摘Light crude oil from the lower member of the Paleogene Xiaganchaigou Formation of Gaskule in Qinghai Oilfield was selected to carry out thermal kinetic analysis experiments and calculate the activation energy during the oil oxidation process.The oxidation process of crude oi l in porous medium was modeled by crude oil static oxidation experiment,and the component changes of crude oil before and after low-temperature oxidation were compared through Fourier transform ion cy-clotron resonance mass spectrometry and gas chromatography;the dynamic displacement experiment of oxygen-reduced air was combined with NMR technology to analyze the oil recovery degree of oxygen-reduced air flooding.The whole process of crude oil oxidation can be divided into four stages:light hydrocarbon volatilization,low-temperature oxidation,fuel deposition,and high temperature oxidation;the high temperature oxidation stage needs the highest activation energy,followed by the fuel deposition stage,and the low-temperature oxidation stage needs the lowest activation energy;the concentration of oxygen in the reaction is negatively correlated with the activation energy required for the reaction;the higher the oxygen concentration,the lower the average activation energy required for oxidation reaction is;the low-temperature oxidation reaction between crude oil and air generates a large amount of heat and CO,CO_(2) and CH4,forming flue gas drive in the reservoir,which has certain effects of mixing phases,reducing viscosity,lowering interfacial tension and promoting expansion of crude oil,and thus helps enhance the oil recovery rate.Under suitable reservoir temperature condition,the degree of recovery of oxygen-reduced air flooding is higher than that of nitrogen flooding for all scales of pore throat,and the air/oxygen-reduced air flooding de-velopment should be preferred.
基金supported by the Key Projects of the National Natural Science Foundation of China (Nos. 51504187, 51774233, and 51704226)Shaanxi Province Industrial Science and Technology Research Project (No. 2016GY-192)the China Postdoctoral Science Foundation (No. 2016-M-590963)
文摘Correlations among free radicals, apparent activation energy, and functional groups during lowtemperature oxidation of Jurassic coal in Northern Shaanxi were investigated by examining three coal samples collected from the Ningtiaota, Jianxin, and Shigetai coal mines. Free radical concentrations at less than 120 ℃ were investigated by electron spin resonance experiments while the thermogravimetric experiments were conducted to analyze apparent activation energies. In addition, Fourier transform infrared spectroscopy was employed to study the spectrum of functional groups generated in coal. The results indicated that, in decreasing order, the apparent activation energies were Shigetai 〉Jianxin 〉 Ningtiaota, indicating that, from 50 to 120 ℃, the Ningtiaota coal sample most easily absorbed and reacted with oxygen while the most resistant was the Shigetai coal sample. Free radical concentrations and line heights increased with increased temperature, and the line width and Lande factor showed irregular fluctuations. Functional group variations were different among these coals, and the phenol and alcohol-associated OHs, carboxyls, and aromatic ring double bonds might have had a major impact on free radical concentrations. These results were meaningful for better consideration and management of coal oxidation at low temperatures.
基金Supported by the Fundamental Research Funds for the Central Universities(2017XKQY066)
文摘The aim of this paper is to analyze the change in the active structure of lignite during the process of lowtemperature oxidation by constructing a molecular structure model for lignite. Using quantum computation combined with experimental results of proximate analysis, ultimate analysis, Fourier transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS), a structural model for the large molecular structure was constructed. By analyzing the bond lengths in the model molecule, the evolution law for the active structure of lignite was predicted for the process of low-temperature oxidation. In low-temperature oxidation,alkanes and hydroxyls are the primary active structures observed in lignite, though ether may also react. These active functional groups react with oxygen to release heat, thereby speeding up the reaction between coal and oxygen. Finally, the content of various functional groups in the process of lignite low-temperature oxidation was analyzed by infrared analysis, and the accuracy of the model was verified.
基金supported by the National Natural Science Foundation of China (No. 51404202)Sichuan Youth Science and Technology Fund (No. 2015JQ0038)the Scientific Research Starting Project of Southwest Petroleum University (No. 2014QHZ001)
文摘The low-temperature catalytic oxidation of heavy crude oil（Xinjiang Oilfield,China） was studied using three types of catalysts including oil-soluble,watersoluble,and dispersed catalysts.According to primary screening,oil-soluble catalysts,copper naphthenate and manganese naphthenate,are more attractive,and were selected to further investigate their catalytic performance in in situ upgrading of heavy oil.The heavy oil compositions and molecular structures were characterized by column chromatography,elemental analysis,and Fourier transform infrared spectrometry before and after reaction.An Arrhenius kinetics model was introduced to calculate the rheological activation energy of heavy oil from the viscosity-temperature characteristics.Results show that the two oil-soluble catalysts can crack part of heavy components into light components,decrease the heteroatom content,and achieve the transition of reaction mode from oxygen addition to bond scission.The calculated rheological activation energy of heavy oil from the fitted Arrhenius model is consistent with physical properties of heavy oil（oil viscosity and contents of heavy fractions）.It is found that the temperature,oil composition,and internal molecular structures are the main factors affecting its flow ability.Oil-soluble catalyst-assisted air injection or air huff-n-puff injection is a promising in situ catalytic upgrading method for improving heavy oil recovery.
基金This work was financially supported by the National Natural Science Foundation of China (No.50025412)
文摘The oxidation behavior of molybdenum disilicide （MoSi2） powders at 400, 500, and 600℃ for 12 h in air were investigated by using X-ray diffraction （XRD） and transmission electron microscopic （TEM） techniques. Significant changes were observed in volume, mass, and color. Especially at 500℃, the volume expansion was found to be as high as 7-8 times, the color changed from black to yellow-white, and the mass gain was about 169.34% after 8 h, with SiO2 and MoO3 as main reaction products. The gains in volume and mass were less at 400 and 600℃ compared with those at 500℃, probably due to the less reaction rate at 400℃ and the formation of silica glass scale at 600℃, which would protect the matrix and restrain the diffusion of oxygen and molybdenum. Thus, the accelerated oxidation behavior of MoSi2 powder appeared at 500℃ and the volume expansion was the sign of accelerated oxidation.
基金the National Natural Science Foundation of China(NSFC)(Grant Nos.51704004 and 51674002)the Natural Science Foundation of Anhui Province(Grant No.1808085QE133).
文摘The low-temperature wet oxidation behavior of semi-dry desulfurization ash from iron ore sintering flue gas in ammonium citrate solution was investigated for efficiently utilizing the low-quality desulfurization ash.The effects of the ammonium citrate concentration,oxidation temperature,solid/liquid ratio,and oxidation time on the wet oxidation behavior of desulfurization ash were studied.Simultaneously,the oxidation mechanism of desulfurization ash was revealed by means of X-ray diffraction,Zeta electric resistance,and X-ray photoelectron spectroscopy(XPS)analysis.Under the optimal conditions with ammonium citrate,the oxidation ratio of CaSO_(3)was up to the maximum value(98.49%),while that of CaSO_(3)was only 8.92%without ammonium citrate.Zeta electric resistance and XPS results indicate that the dissolution process of CaSO_(3)could be significantly promoted by complexation derived from the ammonium citrate hydrolysis.As a result,the oxidation process of CaSO_(3)was transformed from particle oxidation to SO_(3)^(2−)ion oxidation,realizing the rapid transformation of desulfurization ash from CaSO_(3)to CaSO_(4)at low temperature.It provides a reference for the application of semi-dry desulfurization ash and contributes to sustainable management for semi-dry desulfurization ash.
基金supported by the National Key R&D Program of China(2018YFA0702400)the PetroChina Exploration&Production Company(KS2020-01-05).
文摘Low-temperature oxidation(LTO)is the main reaction that affects fuel formation in the in-situ combustion process,which has important significance for the subsequent combustion propulsion and the successful extraction of crude oil.In this study,heavy oil was subjected to LTO reactions at different temperatures.Three types of reaction products with varying oxidation depths were characterized in terms of the number of oxygen atoms and the polarity of the molecule to reveal the low-temperature oxidation process of the heavy oil.Ketone compounds and acid polyoxides in the oil phase and deep oxidation products with a higher number of oxygen atoms in the coke were identified with increasing oxidation depth.The experimental results showed that the oxidation reaction of the heavy oil changed from kinetic-controlled to diffusion-controlled in the open oxidation system of the heavy oil as the oxidation depth increased.The oxidation reaction of the oil phase reached a maximum and stable value in oxygen content.The molecular compositions of the ketone compound and acid polyoxide did not change significantly with further increase in reaction temperature.The molecular compositions of the deep oxidation products with a higher number of oxygen atoms in the coke phase changed significantly.The coke precursor molecules with a lower oxygen content and condensation degree participated in the coke formation,and the oxidation reaction pathway and the complexity of the oxidation product component also increased.
基金Financial support for this work provided by the National Natural Science Foundation of China(No.50674088)is deeply appreciated
文摘Using Fourier Transform Infrared(FTIR)combined with an adiabatic oxidation test,temperature-programmed oxidation and gas analysis,we studied the changes of active functional groups during low-temperature oxidation of lignite,gas coal,fat coal and anthracite.During slow low-temperature heat accumulation,aliphatic hydrocarbons,such as methyl and methylene,are attacked by oxygen atoms absorbed by pores on coal surfaces,generating unstable solid intermediate carbon-oxygen complexes,which then decompose into gaseous products(CO,CO_(2))and stable solid complexes.At the accelerated oxidation stage,the stable complexes begin to decompose in large amounts and provided new active sites for further oxidation,while the aliphatic structures gained energy and fell from the benzene rings to produce C_(x)H_(y)and H_(2).
基金supported by Chinese Postdoctoral Science Foundation (2021M692696)the National Science and Technology Project (2016ZX05058-003-017)Sichuan Science and Technology Program (2021YFH0081)。
文摘This work aimed at investigating the crucial factor in building and maintaining the combustion front during in-situ combustion(ISC),oxidized coke and pyrolyzed coke.The surface morphologies,elemental contents,and non-isothermal mass losses of the oxidized and pyrolyzed cokes were thoroughly examined.The results indicated that the oxidized coke could be combusted at a lower temperature compared to the pyrolyzed coke due primarily to their differences in the molecular polarity and microstructure.Kinetic triplets of coke combustion were determined using iso-conversional models and one advanced integral master plots method.The activation energy values of the oxidized and pyrolyzed cokes varied in the range of 130-153 k J/mol and 95-120 kJ/mol,respectively.The most appropriate reaction model of combustion of the oxidized and pyrolyzed cokes followed three-dimensional diffusion model(D_(3)) and random nucleation and subsequent growth model(F_(1)),respectively.These observations assisted in building the numerical model of these two types of cokes to simulate the ISC process.
基金Project supported by the Shanghai Rising-Star Program(21QA1406600)the NSFC-Zhejiang Joint Fund for Integration of Industrialization and Diversification(U1809214)Zhoushan City Science&Technology Research Project(2019C21012).
文摘The catalytic oxidation of ethyl acetate(EA)was studied over CuO/CeO_(2) catalysts which were prepared by ball milling with different precursors(copper oxide,cerium acetate,cerium dioxide,copper acetate and cerium hydroxide).The CuO/CeO_(2) catalyst(O-A)prepared with copper oxide and cerium acetate as precursors shows very high catalytic activity that 100%EA conversion is achieved at low temperature of 220℃.It is found that specific surface area(112.8 m^(2)/g),particle size of CuO(3.5 nm)and proportion of oxygen vacancies are prominent on the O-A catalyst.Oxygen vacancies in CeO_(2)support are beneficial to enhancing the adsorption and activation of the oxygen.More finely dispersed CuO particles and oxygen vacancies which are derived from the synergistic interaction of Cu-Ce species play an important role in the catalytic oxidation of EA.
基金supported by the National Natural Science Foundation of China(No.22506042)the Natural Science Foundation of Henan Province(Nos.252300421710 and 252300421552)the High level Talent Research Launch Fund of Henan University of Technology(No.2024BS061).
文摘Effective control of gas-phase pollutants(volatile organic compounds(VOCs)and CO)is critical to human health and the ecological environment.Catalytic oxidation is one of the most promising technologies for achieving efficient volatile organic compounds and CO emission control.The subnano cluster catalyst can not only provide catalytic sites with multiple metal atoms,but also maintain full utilization efficiency.Almost all metal atoms in highly dispersed clusters can be used for adsorption and conversion of reactants.Recently,various types of sub-nano clusters,including subnano cluster oxides,have been developed and demonstrated excellent performance in low-temperature gas-phase pollutants combustion.In this mini review,we systematically summarize the structure,physicochemical properties,characterization,and applications of sub-nano cluster catalysts in catalytic oxidation of CO,methane,propane,propylene,toluene and its derivatives,formaldehyde and chlorinated volatile organic compounds.Finally,we have analyzed and discussed the problems and challenges faced by sub-nano cluster catalysts in both basic research and practical applications,providing a scientific basis for the design,synthesis,and application of efficient heterogeneous catalysts for CO and VOCs oxidation.
基金supported by National Natural Science Founda tion of China(No.52204049)Open Fund(PLN020-23)of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Southwest Petroleum University)Ministry of Science and Higher Education of the Russian Federation under Agreement No.075-15-2022-299 within the framework of the development pro gram for a world-class Research Center“Efficient development of the global liquid hydrocarbon reserves”.
文摘The investigation of low-temperature oxidation(LTO) of crude oil within tight shale holds significant importance due to its implications for subsequent oxidation reactions and enhanced oil recovery in the process of air injection.In this study,the tight shale sample underwent oxidation at various LTO temperatures,followed by an analysis of the resulting gas composition.Furthermore,the oxidized oil was separated from the tight shale and subjected to characte rization using electron paramagnetic resonance,nuclear magnetic resonance,and negative ion electrospray Fourier transform-ion cyclotron resonance mass spectrometry techniques.The primary focus was on examining the distinct LTO reaction pathways observable across different temperature ranges.The findings demonstrated a correlation between LTO temperature and the concentration of free radicals,which predominantly resided on aromatic hydrocarbons,alkanes,and oxygen atoms.Additionally,the proton count of polycyclic aromatic hydrocarbons exhibited a continuous increase from 83 to 350℃,suggesting intensified aromatization and condensation reactions involving aliphatic and aromatic compounds.With rising LTO temperature,the molecular structure of O2compounds underwent significant transformations,characterized by increased condensation degree and a decrease in low carbon nu mber molecular structu res,while higher equivale nt double bonds and carbon number molecular structures became more prevalent.The LTO reaction pathways of shale oil included cycle paths 1,2,and 3.The influence of cycle path 1 diminished at temperatures ranging from 83 to 150℃ and 250 to 350℃ whereas the significance of cycle paths 2 and 3 increased,resulting in an overall escalation of the oxidation rate with temperature elevation.It was observed that the shale oil LTO process exhibited a negative temperature coefficient within the temperature range of150 to 250℃,emphasizing the criticality of overcoming the energy barrier in this region to achieve stable combustion.This comprehensive investigation provides valuable insights into the mechanisms underlying LTO in crude oil confined within tight shale.
基金financially supported by the National Natural Science Foundation of China(No.22309067)the Open Project Program of the State Key Laboratory of Materials-Oriented Chemical Engineering,China(No.KL21-05)the Marine Equipment and Technology Institute,Jiangsu University of Science and Technology,China(No.XTCX202404)。
文摘This study focused on improving the cathode performance of Ba_(0.6)Sr_(0.4)Co_(0.85)Nb_(0.15)O_(3-δ)(BSCN)-based perovskite materials through molybdenum(Mo)doping.Pure BSCN and Mo-modified-BSCN—Ea_(0.6)Sr_(0.4)Co_(0.85)Nb_(0.1)Mo_(0.05)O_(3-δ)(B S CNM_(0.05)),Ba_(0.6)Sr_(0.4)Co_(0.85)Nb_(0.05)Mo_(0.1)O_(3-δ)(BSCNM_(0.1)),and Ba_(0.6)Sr_(0.4)Co_(0.85)Mo_(0.15)O_(3-δ)(BSCM)—with Mo doping contents of 5mol%,10mol%,and15mol%,respectively,were successfully prepared using the sol-gel method.The effects of Mo doping on the crystal structure,conductivity,thermal expansion coefficient,oxygen reduction reaction(ORR)activity,and electrochemical performance were systematically evaluated using X-ray diffraction analysis,thermally induced characterization,electrochemical impedance spectroscopy,and single-cell performance tests.The results revealed that Mo doping could improve the conductivity of the materials,suppress their thermal expansion effects,and significantly improve the electrochemical performance.Surface chemical state analysis using X-ray photoelectron spectroscopy revealed that 5mol%Mo doping could facilitate a high adsorbed oxygen concentration leading to enhanced ORR activity in the materials.Density functional theory calculations confirmed that Mo doping promoted the ORR activity in the materials.At an operating temperature of 600℃,the BSCNM_(0.05)cathode material exhibited significantly enhanced electrochemical impedance characteristics,with a reduced area specific resistance of 0.048Ω·cm~2,which was lower than that of the undoped BSCN matrix material by 32.39%.At the same operating temperature,an anode-supported single cell using a BSCNM_(0.05)cathode achieved a peak power density of 1477 mW·cm^(-2),which was 30.71%,56.30%,and 171.50%higher than those of BSCN,BSCNM_(0.1),and B SCM,respectively.The improved ORR activity and electrochemical performance of BSCNM_(0.05)indicate that it can be used as a cathode material in low-temperature solid oxide fuel cells.
基金supported by the National Natural Science Foundation of China(22408225 and 22478241)the Postdoctoral Fellowship Program of CPSF(GZC20240999).
文摘Electrochemical reaction is emerging as a powerful approach for glucose detection and biomass conversion.However,it has been rarely explored for glucose detection and biomass conversion into valueadded chemicals.Previously reported glucose oxidase reduction(GOR)catalysts exhibit issues such as low activity,limited detection range,poor sensitivity,and overreliance on noble metals.Here,we employ an impregnation method to load transition metal nickel onto carbon nanotubes(CNT)and fabricated Ni/CNT30 catalyst via a discharge process.Ni/CNT30 catalyst exhibits a remarkably high catalytic activity of up to 3336.7μA·cm^(-2)·mmol^(-1)·L,a detection limit of 2.43μmol·L^(-1),outstanding stability,and excellent resistance to impurities and interference,surpassing other noble metal-based and oxide-based materials.Hence,this material provides a new approach for the preparation of glucose sensors to achieve precise mobile measurement of glucose concentration and biofuel cells in future.
基金supported by the National Natural Science Foundation of China(52170118,52322004,52230002)the China Postdoctoral Science Foundation(2024M763296).
文摘The development of efficient low-load platinum catalysts for CO oxidation is critical for large-scale industrial applications and environmental protection.In this study,a strategy of N_(2)treatment triggered the self-reforming into fully exposed Pt cluster catalysts was proposed.By adjusting the coordination environment of Pt species on the defect support through N_(2)treatment,the CO catalytic activity was significantly enhanced,achieving complete CO oxidation at 130℃with a Pt loading of only 0.1 wt.%.The turnover frequency of N_(2)-treated Pt_(FEC)/Ti-D at 160℃was 18.3 times that of untreated Pt_(SA)/Ti-D.Comprehensive characterization results indicated that the N_(2)treatment of the Pt single-atom defect catalyst facilitated the reconfiguration and evolution of the defect structure,leading to the aggregation of Pt single atoms into fully exposed Pt clusters.Notably,these fully exposed Pt clusters exhibited a reduced coordination of Pt–O in the first coordination shell compared to single atoms,which resulted in the formation of Pt–Pt metal coordination.This unique coordination structure enhanced the adsorption and activation of CO and O_(2)on the catalyst,thereby resulting in exceptionally low-temperature CO oxidation activity.This work demonstrates a promising strategy for the design,synthesis,and industrial application of efficient low-platinum load catalysts.
基金supported by the National Natural Science Foundation of China(No.52401284)the Natural Science Foundation of Jiangsu Province(No.BK20240957)+1 种基金the Key Research and Development Program of Nantong(No.GZ2024005)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX25_3677)。
文摘Over recent decades,fuel cell technologies have emerged as viable solutions to address the energy and environmental challenges stemming from fossil fuel dependence.Especially,ammonia has gained increasing attention as an attractive alternative to hydrogen,offering comparable energy density while maintaining carbon-free characteristics,along with superior storage and transport properties that give direct ammonia fuel cells(DAFCs)distinct safety advantages over hydrogen-based systems.Central to this technology is the anodic ammonia oxidation reaction(AOR),where platinum(Pt)remains the most efficient catalyst after years of intensive research.This review offers a comprehensive overview of Ptbased AOR electrocatalysts with potential for application in low-temperature DAFCs.Following an introductory section highlighting key historical developments and catalytic breakthroughs,a fundamental understanding of low-temperature DAFC operation and AOR mechanisms is systematically presented.Subsequently,it outlines the advancements in Pt-based catalysts from simple monometallic systems to sophisticated multimetallic alloys and composites,highlighting material innovations and performance enhancements.Afterward,key challenges and future research directions for advancing AOR electrocatalysts are identified,with the aim of providing valuable guidance for developing practical,highperformance,and low-temperature DAFC systems.
基金supported by the Fundamental Research Program of Shanxi Province of China(202203021211103,202303021212172,202403021211196).
文摘A series of Au/Co_(x)Fe_(3-x)O_(4) catalysts was synthesized using the sol-deposition method by depositing 2–5 nm Au particles on Fe-doped Co_(3)O_(4).Co_(2)FeO_(4),with a Co/Fe molar ratio of 2:1,exhibited higher specific surface area,Co^(3+)/Co^(2+)ratio,and oxygen vacancy content compared to Co_(3)O_(4).As a result,it displayed better performance in CO oxidation,achieving a total conversion temperature(T100)of 96℃.Au greatly improved the catalytic efficiency of all Co_(x)Fe_(3-x)O_(4) samples,with the 0.2%Au/Co_(2)FeO_(4) catalyst achieving a further decrease in T100 to 73℃.Stability tests conducted at room temperature on the 1%Au/Co_(x)Fe_(3-x)O_(4) catalysts demonstrated a slowed deactivation rate after Fe-doping.The reaction pathway for CO oxidation catalyzed by Au/Co_(2)FeO_(4) followed the Mars-van Krevelen mechanism.
