We adopted the solution impregnation route with aluminum dihydrogen phosphate solution as liquid medium for effective surface modification on graphite substrate.The mass ratio of graphite to Al(H_(2)PO_(4))_(3) change...We adopted the solution impregnation route with aluminum dihydrogen phosphate solution as liquid medium for effective surface modification on graphite substrate.The mass ratio of graphite to Al(H_(2)PO_(4))_(3) changed from 0.5:1 to 4:1,and the impregnation time changed from 1 to 7 h.The typical composite phase change thermal storage materials doped with the as-treated graphite were fabricated using form-stable technique.To investigate the oxidation and anti-oxidation behavior of the impregnated graphite at high temperatures,the samples were put into a muffle furnace for a cyclic heat test.Based on SEM,EDS,DSC techniques,analyses on the impregnated technique suggested an optimized processing conditions of a 3 h impregnation time with the ratio of graphite:Al(H_(2)PO_(4))_(3) as 1:3 for graphite impregnation treatment.Further investigations on high-temperature phase change heat storage materials doped by the treated graphite suggested excellent oxidation resistance and thermal cycling performance.展开更多
Influence of three different preparation methods, i.e. impregnation, coprecipitation, and inverse coprecipitation, on the preferential oxidation of CO in excess hydrogen （PROX） over CuO-CeO2 catalysts has been inves...Influence of three different preparation methods, i.e. impregnation, coprecipitation, and inverse coprecipitation, on the preferential oxidation of CO in excess hydrogen （PROX） over CuO-CeO2 catalysts has been investigated and CuO-CeO2 catalysts are characterized using BET, XPS, XRD, UV Raman, and TPR techniques. The results show that the catalysts prepared by coprecipitation have smaller particle sizes, well-dispersed CuOx species, more oxygen vacancies, and are more active in the PROX than those prepared by the other methods. However. the inverse coprecipitation depresses the catalytic performance of CuO-CeO2 catalysts and causes the growth of CuO-CeO2 because of different pH value in the precipitation process.展开更多
A series of SnO2‐based catalysts modified by Mn, Zr, Ti and Pb oxides with a Sn/M （M=Mn, Zr, Ti and Pb） molar ratio of 9/1 were prepared by a co‐precipitation method and used for CH4 and CO oxidation. The Mn3＋, ...A series of SnO2‐based catalysts modified by Mn, Zr, Ti and Pb oxides with a Sn/M （M=Mn, Zr, Ti and Pb） molar ratio of 9/1 were prepared by a co‐precipitation method and used for CH4 and CO oxidation. The Mn3＋, Zr4＋, Ti4＋and Pb4＋cations are incorporated into the lattice of tetragonal rutile SnO2 to form a solid solution structure. As a consequence, the surface area and thermal stability of the catalysts are improved. Moreover, the oxygen species of the modified catalysts become easier to be reduced. Therefore, the oxidation activity over the catalysts was improved, except for the one modified by Pb oxide. Manganese oxide demonstrates the best promotional effects for SnO2. Using an X‐ray diffraction extrapolation method, the lattice capacity of SnO2 for Mn2O3 was 0.135 g Mn2O3/g SnO2, which indicates that to form stable solid solution, only 21%Sn4＋cations in the lattice can be maximally replaced by Mn3＋. If the amount of Mn3＋cations is over the capacity, Mn2O3 will be formed, which is not favorable for the activity of the catalysts. The Sn rich samples with only Sn‐Mn solid solution phase show higher activity than the ones with excess Mn2O3 species.展开更多
The Cu-Zr-Ce-O catalysts prepared using the coprecipitation method exhibited better catalytic performance for CO selective oxidation. The Cu-Zr-Ce-O catalysts pretreated with different methods were studied by CO-TPR a...The Cu-Zr-Ce-O catalysts prepared using the coprecipitation method exhibited better catalytic performance for CO selective oxidation. The Cu-Zr-Ce-O catalysts pretreated with different methods were studied by CO-TPR and XPS techniques. The results showed that the Cu-Zr-Ce-O catalyst pretreated with oxygen exhibited the best catalytic performance and had the widest operating temperature window, with CO conversion above 99% from 160 to 200 ℃. The O2 pretreatment caused an enrichment of the oxygen storaged on the Cu active species and promoted the conversion of adsorbed oxygen into surface lattice oxygen. It also improved the amount of Cu＋/Cu^2＋ ionic pair, and then facilitated the formation of CuO active species on the catalyst for selective CO oxidation.展开更多
The removal of hydrogen sulfide from gas plays an important role in rational utilization of resources and environ- mental protection. In this paper, the process of hydrogen sulfide removal by wet oxidation method in a...The removal of hydrogen sulfide from gas plays an important role in rational utilization of resources and environ- mental protection. In this paper, the process of hydrogen sulfide removal by wet oxidation method in a rotating packed bed was investigated in a scale for treating 10 000 Nm3/h of gas. On the basis of studying the influence of the species and con- centration of alkali source, the liquid/gas volume ratio, the high gravity factor, and the hydrogen sulfide content in feed gas on the desulfurization effect, the suitable technological conditions were obtained. The hydrogen sulfide removal efficiency could reach 98.0% under these conditions. The results of continuous operation of process facilities showed that the high gravity method has many merits including higher desulfurization rate, good stability in operation, lower liquid/gas volume ratio, greater operation elasticity, and apparent energy saving effects.展开更多
The CuO-CeO2 catalyst prepared by chelating method has a superior catalytic performance for the preferential oxidation of CO in rich hydrogen, compared with the CuO-CeO2 catalyst prepared by coprecipitation method. Th...The CuO-CeO2 catalyst prepared by chelating method has a superior catalytic performance for the preferential oxidation of CO in rich hydrogen, compared with the CuO-CeO2 catalyst prepared by coprecipitation method. The CO conversions over these catalysts, at 120 ℃ and 120000 ml/（g-h） in the absence of CO2 and H2O, are 99.6% and 88.6%, respectively, and the selectivity of O2 over these catalysts is very close （i.e. 51.3% and 55.8%, respectively）. The influence of certain factors such as hydrogen concentration, carbon monoxide concentration, H2O, O2/CO ratios, and space velocity on the catalytic performance of CuO-CeO2 catalyst prepared by chelating method is also studied. The results show that the addition of hydrogen and H2O has a negative effect on the catalytic performance of CuO-CeO2 catalyst, however, the variation of space velocity and the O2/CO ratio causes a comparatively slight influence.展开更多
High-temperature oxidation is an important property to evaluate thermal protection materials. However, since oxidation is a complex process involving microstructure evolution, its quantitative analysis has always been...High-temperature oxidation is an important property to evaluate thermal protection materials. However, since oxidation is a complex process involving microstructure evolution, its quantitative analysis has always been a challenge. In this work, a phase field method （PFM） based on the thermodynamics theory is developed to simulate the oxidation behavior and oxidation induced growth stress. It involves microstructure evolution and solves the problem of quantitatively computational analysis for the oxidation behavior and growth stress. Employing this method, the diffusion process, oxidation performance, and stress evolution axe predicted for Fe-Cr-A1-Y alloys. The numerical results agree well with the experimental data. The linear relationship between the maximum growth stress and the environment oxygen concentration is found. PFM provides a powerful tool to investigate high-temperature oxidation in complex environments.展开更多
The traditional automotive catalytic converter using commercial ceramic honeycomb carriers has many problems such as high back pressure,low engine efficiency,and high usage of precious metals.This study proposes a fou...The traditional automotive catalytic converter using commercial ceramic honeycomb carriers has many problems such as high back pressure,low engine efficiency,and high usage of precious metals.This study proposes a four-channel catalytic micro-reactor based on alumina hollow fiber membrane,which uses phase inversion method for structural molding and regulation.Due to the advantages of its carrier,it can achieve lower ignition temperature under low noble metal loading.With Pd/CeO_(2) at a loading rate of 2.3%(mass),the result showed that the reaction ignition temperature is even less than 160℃,which is more than 90℃ lower than the data of commercial ceramic substrates under similar catalyst loading and airspeed conditions.The technology in turn significantly reduces the energy consumption of the reaction.And stability tests were conducted under constant conditions for 1000 h,which proved that this catalytic converter has high catalytic efficiency and stability,providing prospects for the design of innovative catalytic converters in the future.展开更多
The influence of different cooking and smoking methods (boiling, frying, frying + boiling, hot and cold smoking) on oxidation and fatty acid composition of catfish (Arius maculatus) commercialized on the Wouri river c...The influence of different cooking and smoking methods (boiling, frying, frying + boiling, hot and cold smoking) on oxidation and fatty acid composition of catfish (Arius maculatus) commercialized on the Wouri river coast was evaluated including commonly used analytical indexes (peroxide and acid values)and physical analysis by Fourier transform infrared (FTIR) spectroscopy. The mean moisture, protein, ash and fat contents of raw fish were 75.88 ± 0.55;64.24 ± 0.14;10.98 ± 0.31 and 23.02 ± 0.88 respectively. All these treatments provoke the modification of the quality indexes. Lipid deterioration, thermolysis and lipid oxidation occurred throughout the treatment. Peroxide value decreased for all cooked and smoked catfish, while free fatty acids of smoked sample increased. The FTIR applied to evaluate lipid oxidation in extracted lipid clearly provided a better picture of the oxidation progress and led to a similar conclusion with chemical analysis. Boiled, bleaching hot and bleaching cold smoking were found to be the suitable treatment methods for catfish because they gave it a high nutritive value compared to other smoking methods.展开更多
The oil oxidation characteristics of the whole temperature regions from 30 ℃ to 600 ℃ during oil reservoir air injection were revealed by experiments. The whole oil oxidation temperature regions were divided into fo...The oil oxidation characteristics of the whole temperature regions from 30 ℃ to 600 ℃ during oil reservoir air injection were revealed by experiments. The whole oil oxidation temperature regions were divided into four different parts: dissolving and inflation region, low temperature oxidation region, medium temperature oxidation region and high temperature oxidation region. The reaction mechanisms of different regions were explained. Based on the oil oxidation characteristics and filed tests results, light oil reservoirs air injection development methods were divided into two types: oxygen-reducing air flooding and air flooding;heavy oil reservoirs air injection in-situ combustion development methods were divided into two types: medium temperature in-situ combustion and high temperature in-situ combustion. When the reservoir temperature is lower than 120 ℃, oxygen-reducing air flooding should be used for light oil reservoir development. When the reservoir temperature is higher than 120 ℃, air flooding method should be used for light oil reservoir development. For a normal heavy oil reservoir, when the combustion front temperature is lower than 400 ℃, the development method is medium temperature in-situ combustion. For a heavy oil reservoir with high oil resin and asphalting contents, when the combustion front temperature is higher than 450 ℃, the development method at this condition is high temperature in-situ combustion. Ten years field tests of air injection carried out by PetroChina proved that air has advantages in technical, economical and gas source aspects compared with other gas agents for oilfield gas injection development. Air injection development can be used in low/super-low permeability light oil reservoirs, medium and high permeability light oil reservoirs and heavy oil reservoirs. Air is a very promising gas flooding agent.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
Co3O4 catalysts prepared with different precipitants（NH3·H2O,KOH,NH4HCO3,K2CO3 and KHCO3）were investigated for the oxidation of formaldehyde（HCHO）.Among these,KHCO3-precipitated Co3O4（KHCO3-Co） was the most...Co3O4 catalysts prepared with different precipitants（NH3·H2O,KOH,NH4HCO3,K2CO3 and KHCO3）were investigated for the oxidation of formaldehyde（HCHO）.Among these,KHCO3-precipitated Co3O4（KHCO3-Co） was the most active low-temperature catalyst,and was able to completely oxidize HCHO at the 100-ppm level to CO2 at 90℃.In situ diffuse reflectance infrared spectroscopy demonstrated that hydroxyl groups on the catalyst surface were regenerated by K~＋ and CO3^（2-）,thus promoting the oxidation of HCHO.Moreover,H2-temperature programmed reduction and X-ray photoelectron spectroscopy showed that employing KHCO3 as the precipitant increased the Co^3＋/Co^2＋molar ratio on the surface of the Co3O4 catalyst,thus further promoting oxidation.Structural characterization revealed that catalysts precipitated with carbonate or bicarbonate reagents exhibited greater specific surface areas and pore volumes.Overall,these data suggest that the high activity observed during the Co3O4 catalyzed oxidation of HCHO can be primarily attributed to the presence of K~＋ and CO3^（2-） on the Co3O4 surface and the favorable Co^3＋/Co^2＋ ratio.展开更多
A molten salt method was developed to prepare porous La1‐xSrxMn0.8Fe0.2O3 （0≤ x ≤ 0.6） micro‐spheres using hierarchical porous δ‐MnO2 microspheres as a template in eutectic NaNO3‐KNO3. X‐ray diffraction patt...A molten salt method was developed to prepare porous La1‐xSrxMn0.8Fe0.2O3 （0≤ x ≤ 0.6） micro‐spheres using hierarchical porous δ‐MnO2 microspheres as a template in eutectic NaNO3‐KNO3. X‐ray diffraction patterns showed that single phase LaMn0.8Fe0.2O3 with good crystallinity was syn‐thesized at 450℃ after 4 h. Transmission electron microscope images exhibited that the LaMn0.8Fe0.2O3 sample obtained at 450？？ after 4 h possessed a porous spherical morphology com‐posed of aggregated nanocrystallites. Field emission scanning electron microscope images indicated that the growth of the porous LaMn0.8Fe0.2O3 microspheres has two stages. SEM pictures showed that a higher calcination temperature than 450？？ had an adverse effect on the formation of a po‐rous spherical structure. The LaMn0.8Fe0.2O3 sample obtained at 450？？ after 4 h displayed a high BET surface area of 55.73 m2/g with a pore size of 9.38 nm. Fourier transform infrared spectra suggested that Sr2＋ions entered the A sites and induced a decrease of the binding energy between Mn and O. The CO conversion with the La1‐xSrxMn0.8Fe0.2O3 （0≤x≤0.6） samples indicated that the La0.4Sr0.6Mn0.8Fe0.2O3 sample had the best catalytic activity and stability. Further analysis by X‐ray photoelectron spectroscopy demonstrated that Sr2＋doping altered the content of Mn4＋ions, oxygen vacancies and adsorbed oxygen species on the surface, which affected the catalytic performance for CO oxidation.展开更多
A series of rare earth hydroxide and oxide nanoparticles have been prepared by precipitation method with alcohol as the dispersive and protective reagent. Transmission electron microscope （TEM） images indicate that ...A series of rare earth hydroxide and oxide nanoparticles have been prepared by precipitation method with alcohol as the dispersive and protective reagent. Transmission electron microscope （TEM） images indicate that the particles are spherical in shape and smaller than 100 nm in size. The crystallite sizes of cubic Ln2O3 have lanthanide shrinking effect, while average crystal lattice distortion rates possess lanthanide swelling effect. The diffraction peak intensity of heavy rare earth oxide nanometer powders is remarkably stronger than that of light rare earth oxide nanometer powders. The variation of diffraction intensity with atomic number presents an inverted W type, forming a double peak structure. Fourier transform infrared （FTIR） spectrums reveal that Ln2O3 nanopowders have higher surface activity than that of ordinary Ln2O3 powders. The UV-vis spectra show that Ln-O bond of these particles is slightly blue-shifted, and its absorption intensity decreases.展开更多
A carbon supported Pd（Pd/C） catalyst used as the anodic catalyst in the direct formic acid fuel cells（DFAFC） was prepared via the improved complex reduction method with sodium ethylenediamine tetracetate（EDTA） a...A carbon supported Pd（Pd/C） catalyst used as the anodic catalyst in the direct formic acid fuel cells（DFAFC） was prepared via the improved complex reduction method with sodium ethylenediamine tetracetate（EDTA） as stabilizer and complexing agent. This method is very simple. The average size of the Pd particles in the Pd/C catalyst prepared with the improved complex reduction method is as small as about 2.1 nm and the Pd particles in the Pd/C catalyst possess an excellent uniformity. The Pd/C catalyst shows a high electrocatalytic activity and stability for the formic acid oxidation.展开更多
The orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore with NaOH aiming to comprehensively utilize zinc oxide ore.The optimized reaction conditions were molar ratio of NaOH to zinc...The orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore with NaOH aiming to comprehensively utilize zinc oxide ore.The optimized reaction conditions were molar ratio of NaOH to zinc oxide ore 6:1,roasting temperature 450°C,holding time 150 min.The molar ratio of NaOH to zinc oxide ore was the most predominant factor affecting the extraction ratios of zinc oxide and silica.The mineral phase transformations were investigated by testing the phases of specimens obtained at different temperatures.The process was that silica reacted with molten NaOH to form Na_2SiO_3 at first,then transformed into Na_4SiO_4 with temperature rising.ZnCO_3 and its decomposing product ZnO reacted with NaOH to form Na_2ZnO_2.Na_2ZnSiO_4was also obtained.The reaction rate was investigated using unreacted shrinking core model.Two models used were chemical reaction at the particle surface and diffusion through the product layer.The results indicated that the reaction rate was combine-controlled by two models.The activation energy and frequency factor were obtained as 24.12 k J/mol and 0.0682,respectively.展开更多
Gradiently denitrated gun propellant(GDGP)prepared by a“gradient denitration”strategy is obviously superior in progressive burning performance to the traditional deterred gun propellant.Currently,the preparation of ...Gradiently denitrated gun propellant(GDGP)prepared by a“gradient denitration”strategy is obviously superior in progressive burning performance to the traditional deterred gun propellant.Currently,the preparation of GDGP employed a tedious two-step method involving organic solvents,which hinders the large-scale preparation of GDGP.In this paper,GDGP was successfully prepared via a novelty and environmentally friendly one-step method.The obtained samples were characterized by FT-IR,Raman,SEM and XPS.The results showed that the content of nitrate groups gradiently increased from the surface to the core in the surface layer of GDGP and the surface layer of GDGP exhibited a higher compaction than that of raw gun propellant,with a well-preserved nitrocellulose structure.The denitration process enabled the propellant surface with regressive energy density and good progressive burning performance,as confirmed by oxygen bomb and closed bomb test.At the same time,the effects of different solvents on the component loss of propellant were compared.The result showed that water caused the least component loss.Finally,the stability of GDGP was confirmed by methyl-violet test.This work not only provided environmentally friendly,simple and economic preparation of GDGP,but also confirmed the stability of GDGP prepared by this method.展开更多
The electrochemical methanol oxidation reaction(MOR) is of paramount importance for direct methanol fuel cell(DMFC) application, where efficient catalysts are required to facilitate the complicated multiple charge tra...The electrochemical methanol oxidation reaction(MOR) is of paramount importance for direct methanol fuel cell(DMFC) application, where efficient catalysts are required to facilitate the complicated multiple charge transfer process. The catalyst support not only determines the dispersion status of the catalysts particles, but also exerts great influence on the electronic structure of the catalysts, thereby altering its intrinsic activity. Herein, we demonstrated that nitrogen atoms, assisted by the pre-treatment of carbon matrix with oxidants, can be easily doped into carbon nanotubes at low temperature. The obtained nitrogen-doped carbon nanotubes can effectively improve the dispersion of the supported platinum nanoparticles and facilitate the MOR by modifying the electronic structure of platinum atoms,through catalyst-support interaction.展开更多
FeOx-SiO2 catalysts prepared by a sol-gel method were studied for the selective oxidation of methane by oxygen. A single-pass formaldehyde yield of 2.0% was obtained over the FeOx-SiO2 with an iron content of 0.5 wt% ...FeOx-SiO2 catalysts prepared by a sol-gel method were studied for the selective oxidation of methane by oxygen. A single-pass formaldehyde yield of 2.0% was obtained over the FeOx-SiO2 with an iron content of 0.5 wt% at 898 K. This 0.5 wt% FeOx-SiO2 catalyst demonstrated significantly higher catalytic performances than the 0.5 wt% FeOx/SiO2 prepared by an impregnation method. The correlation between the catalytic performances and the characterizations with UV-Vis and H2-TPR suggested that the higher dispersion of iron species in the catalyst prepared by the sol-gel method was responsible for its higher catalytic activity for formaldehyde formation. The modification of the FeOx-SiO2 by phosphorus enhanced the formaldehyde selectivity, and a single-pass formaldehyde yield of 2.4% could be attained over a P-FeOx-SiO2 catalyst （P/Fe = 0.5） at 898 K. Raman spectroscopic measurements indicated the formation of FePO4 nanoclusters in this catalyst, which were more selective toward formaldehyde formation.展开更多
In this paper, a new computational method for improving the accuracy of numerically computed solutions is introduced. The computational method is based on the one-step method and conserved quantities of holonomic syst...In this paper, a new computational method for improving the accuracy of numerically computed solutions is introduced. The computational method is based on the one-step method and conserved quantities of holonomic systems are considered as kinematical constraints in this method.展开更多
基金Funded by Scientific and Technological Innovation Project of Carbon Emission Peak and Carbon Neutrality of Jiangsu Province(No.BE2022028-4)。
文摘We adopted the solution impregnation route with aluminum dihydrogen phosphate solution as liquid medium for effective surface modification on graphite substrate.The mass ratio of graphite to Al(H_(2)PO_(4))_(3) changed from 0.5:1 to 4:1,and the impregnation time changed from 1 to 7 h.The typical composite phase change thermal storage materials doped with the as-treated graphite were fabricated using form-stable technique.To investigate the oxidation and anti-oxidation behavior of the impregnated graphite at high temperatures,the samples were put into a muffle furnace for a cyclic heat test.Based on SEM,EDS,DSC techniques,analyses on the impregnated technique suggested an optimized processing conditions of a 3 h impregnation time with the ratio of graphite:Al(H_(2)PO_(4))_(3) as 1:3 for graphite impregnation treatment.Further investigations on high-temperature phase change heat storage materials doped by the treated graphite suggested excellent oxidation resistance and thermal cycling performance.
文摘Influence of three different preparation methods, i.e. impregnation, coprecipitation, and inverse coprecipitation, on the preferential oxidation of CO in excess hydrogen （PROX） over CuO-CeO2 catalysts has been investigated and CuO-CeO2 catalysts are characterized using BET, XPS, XRD, UV Raman, and TPR techniques. The results show that the catalysts prepared by coprecipitation have smaller particle sizes, well-dispersed CuOx species, more oxygen vacancies, and are more active in the PROX than those prepared by the other methods. However. the inverse coprecipitation depresses the catalytic performance of CuO-CeO2 catalysts and causes the growth of CuO-CeO2 because of different pH value in the precipitation process.
基金supported by the National Natural Science Foundation of China (21263015,21567016 and 21503106)the Education Department Foundation of Jiangxi Province (KJLD14005 and GJJ150016)the Natural Science Foundation of Jiangxi Province (20142BAB213013 and 20151BBE50006),which are greatly acknowledged by the authors~~
文摘A series of SnO2‐based catalysts modified by Mn, Zr, Ti and Pb oxides with a Sn/M （M=Mn, Zr, Ti and Pb） molar ratio of 9/1 were prepared by a co‐precipitation method and used for CH4 and CO oxidation. The Mn3＋, Zr4＋, Ti4＋and Pb4＋cations are incorporated into the lattice of tetragonal rutile SnO2 to form a solid solution structure. As a consequence, the surface area and thermal stability of the catalysts are improved. Moreover, the oxygen species of the modified catalysts become easier to be reduced. Therefore, the oxidation activity over the catalysts was improved, except for the one modified by Pb oxide. Manganese oxide demonstrates the best promotional effects for SnO2. Using an X‐ray diffraction extrapolation method, the lattice capacity of SnO2 for Mn2O3 was 0.135 g Mn2O3/g SnO2, which indicates that to form stable solid solution, only 21%Sn4＋cations in the lattice can be maximally replaced by Mn3＋. If the amount of Mn3＋cations is over the capacity, Mn2O3 will be formed, which is not favorable for the activity of the catalysts. The Sn rich samples with only Sn‐Mn solid solution phase show higher activity than the ones with excess Mn2O3 species.
基金supported by the National Nature Science Foundation of China (Project No.20576023)the Natural Science Foundation of Guangdong Province (Project No.06025660).
文摘The Cu-Zr-Ce-O catalysts prepared using the coprecipitation method exhibited better catalytic performance for CO selective oxidation. The Cu-Zr-Ce-O catalysts pretreated with different methods were studied by CO-TPR and XPS techniques. The results showed that the Cu-Zr-Ce-O catalyst pretreated with oxygen exhibited the best catalytic performance and had the widest operating temperature window, with CO conversion above 99% from 160 to 200 ℃. The O2 pretreatment caused an enrichment of the oxygen storaged on the Cu active species and promoted the conversion of adsorbed oxygen into surface lattice oxygen. It also improved the amount of Cu＋/Cu^2＋ ionic pair, and then facilitated the formation of CuO active species on the catalyst for selective CO oxidation.
基金the Shanxi Provin-cial Youth Science and Technology Research Fund (No.2008021009-2) for the financial support to this project
文摘The removal of hydrogen sulfide from gas plays an important role in rational utilization of resources and environ- mental protection. In this paper, the process of hydrogen sulfide removal by wet oxidation method in a rotating packed bed was investigated in a scale for treating 10 000 Nm3/h of gas. On the basis of studying the influence of the species and con- centration of alkali source, the liquid/gas volume ratio, the high gravity factor, and the hydrogen sulfide content in feed gas on the desulfurization effect, the suitable technological conditions were obtained. The hydrogen sulfide removal efficiency could reach 98.0% under these conditions. The results of continuous operation of process facilities showed that the high gravity method has many merits including higher desulfurization rate, good stability in operation, lower liquid/gas volume ratio, greater operation elasticity, and apparent energy saving effects.
基金The work was supported by the National Basic Research Program of China (973 Program, No. 2004CB719504)
文摘The CuO-CeO2 catalyst prepared by chelating method has a superior catalytic performance for the preferential oxidation of CO in rich hydrogen, compared with the CuO-CeO2 catalyst prepared by coprecipitation method. The CO conversions over these catalysts, at 120 ℃ and 120000 ml/（g-h） in the absence of CO2 and H2O, are 99.6% and 88.6%, respectively, and the selectivity of O2 over these catalysts is very close （i.e. 51.3% and 55.8%, respectively）. The influence of certain factors such as hydrogen concentration, carbon monoxide concentration, H2O, O2/CO ratios, and space velocity on the catalytic performance of CuO-CeO2 catalyst prepared by chelating method is also studied. The results show that the addition of hydrogen and H2O has a negative effect on the catalytic performance of CuO-CeO2 catalyst, however, the variation of space velocity and the O2/CO ratio causes a comparatively slight influence.
基金Project supported by the National Natural Science Foundation of China (Nos. 90505015 and10702035)
文摘High-temperature oxidation is an important property to evaluate thermal protection materials. However, since oxidation is a complex process involving microstructure evolution, its quantitative analysis has always been a challenge. In this work, a phase field method （PFM） based on the thermodynamics theory is developed to simulate the oxidation behavior and oxidation induced growth stress. It involves microstructure evolution and solves the problem of quantitatively computational analysis for the oxidation behavior and growth stress. Employing this method, the diffusion process, oxidation performance, and stress evolution axe predicted for Fe-Cr-A1-Y alloys. The numerical results agree well with the experimental data. The linear relationship between the maximum growth stress and the environment oxygen concentration is found. PFM provides a powerful tool to investigate high-temperature oxidation in complex environments.
基金funded by the Natural Science Foundation of Jiangsu Province(BK20210252)。
文摘The traditional automotive catalytic converter using commercial ceramic honeycomb carriers has many problems such as high back pressure,low engine efficiency,and high usage of precious metals.This study proposes a four-channel catalytic micro-reactor based on alumina hollow fiber membrane,which uses phase inversion method for structural molding and regulation.Due to the advantages of its carrier,it can achieve lower ignition temperature under low noble metal loading.With Pd/CeO_(2) at a loading rate of 2.3%(mass),the result showed that the reaction ignition temperature is even less than 160℃,which is more than 90℃ lower than the data of commercial ceramic substrates under similar catalyst loading and airspeed conditions.The technology in turn significantly reduces the energy consumption of the reaction.And stability tests were conducted under constant conditions for 1000 h,which proved that this catalytic converter has high catalytic efficiency and stability,providing prospects for the design of innovative catalytic converters in the future.
文摘The influence of different cooking and smoking methods (boiling, frying, frying + boiling, hot and cold smoking) on oxidation and fatty acid composition of catfish (Arius maculatus) commercialized on the Wouri river coast was evaluated including commonly used analytical indexes (peroxide and acid values)and physical analysis by Fourier transform infrared (FTIR) spectroscopy. The mean moisture, protein, ash and fat contents of raw fish were 75.88 ± 0.55;64.24 ± 0.14;10.98 ± 0.31 and 23.02 ± 0.88 respectively. All these treatments provoke the modification of the quality indexes. Lipid deterioration, thermolysis and lipid oxidation occurred throughout the treatment. Peroxide value decreased for all cooked and smoked catfish, while free fatty acids of smoked sample increased. The FTIR applied to evaluate lipid oxidation in extracted lipid clearly provided a better picture of the oxidation progress and led to a similar conclusion with chemical analysis. Boiled, bleaching hot and bleaching cold smoking were found to be the suitable treatment methods for catfish because they gave it a high nutritive value compared to other smoking methods.
文摘The oil oxidation characteristics of the whole temperature regions from 30 ℃ to 600 ℃ during oil reservoir air injection were revealed by experiments. The whole oil oxidation temperature regions were divided into four different parts: dissolving and inflation region, low temperature oxidation region, medium temperature oxidation region and high temperature oxidation region. The reaction mechanisms of different regions were explained. Based on the oil oxidation characteristics and filed tests results, light oil reservoirs air injection development methods were divided into two types: oxygen-reducing air flooding and air flooding;heavy oil reservoirs air injection in-situ combustion development methods were divided into two types: medium temperature in-situ combustion and high temperature in-situ combustion. When the reservoir temperature is lower than 120 ℃, oxygen-reducing air flooding should be used for light oil reservoir development. When the reservoir temperature is higher than 120 ℃, air flooding method should be used for light oil reservoir development. For a normal heavy oil reservoir, when the combustion front temperature is lower than 400 ℃, the development method is medium temperature in-situ combustion. For a heavy oil reservoir with high oil resin and asphalting contents, when the combustion front temperature is higher than 450 ℃, the development method at this condition is high temperature in-situ combustion. Ten years field tests of air injection carried out by PetroChina proved that air has advantages in technical, economical and gas source aspects compared with other gas agents for oilfield gas injection development. Air injection development can be used in low/super-low permeability light oil reservoirs, medium and high permeability light oil reservoirs and heavy oil reservoirs. Air is a very promising gas flooding agent.
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supported by the National Natural Science Foundation of China(21577088)~~
文摘Co3O4 catalysts prepared with different precipitants（NH3·H2O,KOH,NH4HCO3,K2CO3 and KHCO3）were investigated for the oxidation of formaldehyde（HCHO）.Among these,KHCO3-precipitated Co3O4（KHCO3-Co） was the most active low-temperature catalyst,and was able to completely oxidize HCHO at the 100-ppm level to CO2 at 90℃.In situ diffuse reflectance infrared spectroscopy demonstrated that hydroxyl groups on the catalyst surface were regenerated by K~＋ and CO3^（2-）,thus promoting the oxidation of HCHO.Moreover,H2-temperature programmed reduction and X-ray photoelectron spectroscopy showed that employing KHCO3 as the precipitant increased the Co^3＋/Co^2＋molar ratio on the surface of the Co3O4 catalyst,thus further promoting oxidation.Structural characterization revealed that catalysts precipitated with carbonate or bicarbonate reagents exhibited greater specific surface areas and pore volumes.Overall,these data suggest that the high activity observed during the Co3O4 catalyzed oxidation of HCHO can be primarily attributed to the presence of K~＋ and CO3^（2-） on the Co3O4 surface and the favorable Co^3＋/Co^2＋ ratio.
基金supported by the National Science Foundation for Young Scientists of China (51202171)~~
文摘A molten salt method was developed to prepare porous La1‐xSrxMn0.8Fe0.2O3 （0≤ x ≤ 0.6） micro‐spheres using hierarchical porous δ‐MnO2 microspheres as a template in eutectic NaNO3‐KNO3. X‐ray diffraction patterns showed that single phase LaMn0.8Fe0.2O3 with good crystallinity was syn‐thesized at 450℃ after 4 h. Transmission electron microscope images exhibited that the LaMn0.8Fe0.2O3 sample obtained at 450？？ after 4 h possessed a porous spherical morphology com‐posed of aggregated nanocrystallites. Field emission scanning electron microscope images indicated that the growth of the porous LaMn0.8Fe0.2O3 microspheres has two stages. SEM pictures showed that a higher calcination temperature than 450？？ had an adverse effect on the formation of a po‐rous spherical structure. The LaMn0.8Fe0.2O3 sample obtained at 450？？ after 4 h displayed a high BET surface area of 55.73 m2/g with a pore size of 9.38 nm. Fourier transform infrared spectra suggested that Sr2＋ions entered the A sites and induced a decrease of the binding energy between Mn and O. The CO conversion with the La1‐xSrxMn0.8Fe0.2O3 （0≤x≤0.6） samples indicated that the La0.4Sr0.6Mn0.8Fe0.2O3 sample had the best catalytic activity and stability. Further analysis by X‐ray photoelectron spectroscopy demonstrated that Sr2＋doping altered the content of Mn4＋ions, oxygen vacancies and adsorbed oxygen species on the surface, which affected the catalytic performance for CO oxidation.
文摘A series of rare earth hydroxide and oxide nanoparticles have been prepared by precipitation method with alcohol as the dispersive and protective reagent. Transmission electron microscope （TEM） images indicate that the particles are spherical in shape and smaller than 100 nm in size. The crystallite sizes of cubic Ln2O3 have lanthanide shrinking effect, while average crystal lattice distortion rates possess lanthanide swelling effect. The diffraction peak intensity of heavy rare earth oxide nanometer powders is remarkably stronger than that of light rare earth oxide nanometer powders. The variation of diffraction intensity with atomic number presents an inverted W type, forming a double peak structure. Fourier transform infrared （FTIR） spectrums reveal that Ln2O3 nanopowders have higher surface activity than that of ordinary Ln2O3 powders. The UV-vis spectra show that Ln-O bond of these particles is slightly blue-shifted, and its absorption intensity decreases.
基金Supported by the "863" Program of Science and Technology Ministry of China(Nos.2006AA05Z137, 2007AA05Z143 and 2007AA05Z159)National Natural Science Foundation of China(Nos.20433060, 20473038, 20573057 and 20703043)the Natural Science Foundation of Jiangsu Province, China(No.BK2006224).
文摘A carbon supported Pd（Pd/C） catalyst used as the anodic catalyst in the direct formic acid fuel cells（DFAFC） was prepared via the improved complex reduction method with sodium ethylenediamine tetracetate（EDTA） as stabilizer and complexing agent. This method is very simple. The average size of the Pd particles in the Pd/C catalyst prepared with the improved complex reduction method is as small as about 2.1 nm and the Pd particles in the Pd/C catalyst possess an excellent uniformity. The Pd/C catalyst shows a high electrocatalytic activity and stability for the formic acid oxidation.
基金Projects(51774070,51204054)supported by the National Natural Science Foundation of ChinaProject(N150204009)supported by the Ministry of Education Basic Scientific Research Business Expenses,ChinaProject(2007CB613603)supported by the National Basic Research Program of China
文摘The orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore with NaOH aiming to comprehensively utilize zinc oxide ore.The optimized reaction conditions were molar ratio of NaOH to zinc oxide ore 6:1,roasting temperature 450°C,holding time 150 min.The molar ratio of NaOH to zinc oxide ore was the most predominant factor affecting the extraction ratios of zinc oxide and silica.The mineral phase transformations were investigated by testing the phases of specimens obtained at different temperatures.The process was that silica reacted with molten NaOH to form Na_2SiO_3 at first,then transformed into Na_4SiO_4 with temperature rising.ZnCO_3 and its decomposing product ZnO reacted with NaOH to form Na_2ZnO_2.Na_2ZnSiO_4was also obtained.The reaction rate was investigated using unreacted shrinking core model.Two models used were chemical reaction at the particle surface and diffusion through the product layer.The results indicated that the reaction rate was combine-controlled by two models.The activation energy and frequency factor were obtained as 24.12 k J/mol and 0.0682,respectively.
文摘Gradiently denitrated gun propellant(GDGP)prepared by a“gradient denitration”strategy is obviously superior in progressive burning performance to the traditional deterred gun propellant.Currently,the preparation of GDGP employed a tedious two-step method involving organic solvents,which hinders the large-scale preparation of GDGP.In this paper,GDGP was successfully prepared via a novelty and environmentally friendly one-step method.The obtained samples were characterized by FT-IR,Raman,SEM and XPS.The results showed that the content of nitrate groups gradiently increased from the surface to the core in the surface layer of GDGP and the surface layer of GDGP exhibited a higher compaction than that of raw gun propellant,with a well-preserved nitrocellulose structure.The denitration process enabled the propellant surface with regressive energy density and good progressive burning performance,as confirmed by oxygen bomb and closed bomb test.At the same time,the effects of different solvents on the component loss of propellant were compared.The result showed that water caused the least component loss.Finally,the stability of GDGP was confirmed by methyl-violet test.This work not only provided environmentally friendly,simple and economic preparation of GDGP,but also confirmed the stability of GDGP prepared by this method.
基金supported by the National Natural Science Foundation of China (21433003, 21633008)the Jilin Province Science and Technology Development Program (20150101066JC, 20160622037JC, 20170203003SF, and 20170520150JH)the Hundred Talents Program of the Chinese Academy of Sciences and the Recruitment Program of Foreign Experts (WQ20122200077)
文摘The electrochemical methanol oxidation reaction(MOR) is of paramount importance for direct methanol fuel cell(DMFC) application, where efficient catalysts are required to facilitate the complicated multiple charge transfer process. The catalyst support not only determines the dispersion status of the catalysts particles, but also exerts great influence on the electronic structure of the catalysts, thereby altering its intrinsic activity. Herein, we demonstrated that nitrogen atoms, assisted by the pre-treatment of carbon matrix with oxidants, can be easily doped into carbon nanotubes at low temperature. The obtained nitrogen-doped carbon nanotubes can effectively improve the dispersion of the supported platinum nanoparticles and facilitate the MOR by modifying the electronic structure of platinum atoms,through catalyst-support interaction.
基金supported by the National Natural Science Foundation of China (Nos.20625310,20773099 and 20873110)the National Basic Programof China (No. 2005CB221408)the National Science Fund for Talent Training in Basic Science (No.J0630429)
文摘FeOx-SiO2 catalysts prepared by a sol-gel method were studied for the selective oxidation of methane by oxygen. A single-pass formaldehyde yield of 2.0% was obtained over the FeOx-SiO2 with an iron content of 0.5 wt% at 898 K. This 0.5 wt% FeOx-SiO2 catalyst demonstrated significantly higher catalytic performances than the 0.5 wt% FeOx/SiO2 prepared by an impregnation method. The correlation between the catalytic performances and the characterizations with UV-Vis and H2-TPR suggested that the higher dispersion of iron species in the catalyst prepared by the sol-gel method was responsible for its higher catalytic activity for formaldehyde formation. The modification of the FeOx-SiO2 by phosphorus enhanced the formaldehyde selectivity, and a single-pass formaldehyde yield of 2.4% could be attained over a P-FeOx-SiO2 catalyst （P/Fe = 0.5） at 898 K. Raman spectroscopic measurements indicated the formation of FePO4 nanoclusters in this catalyst, which were more selective toward formaldehyde formation.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10572021 and 10372053）, and the Fundamental Research Foundation of Beijing Institute of Technology （BIT-UBF-200507A4206）.
文摘In this paper, a new computational method for improving the accuracy of numerically computed solutions is introduced. The computational method is based on the one-step method and conserved quantities of holonomic systems are considered as kinematical constraints in this method.
