Hierarchical layer-stacking Mn-Ce composite oxide with mesoporous structure was firstly prepared by a simple precipitation/decomposition procedure with oxalate precursor and the complete catalytic oxidation of VOCs（b...Hierarchical layer-stacking Mn-Ce composite oxide with mesoporous structure was firstly prepared by a simple precipitation/decomposition procedure with oxalate precursor and the complete catalytic oxidation of VOCs（benzene, toluene and ethyl acetate） were examined. The Mn-Ce oxalate precursor was obtained from metal salt and oxalic acid without any additives. The resulting materials were characterized by X-ray diffraction（XRD）, Brunauer-Emmett-Teller（BET）, scanning electron microscopy（SEM）, energy dispersive X-ray spectroscopy（EDX）, hydrogen temperature programmed reduction（H2-TPR） and X-ray photoelectron spectroscopy（XPS）. Compared with Mn-Ce composite oxide synthesized through a traditional method（Na2CO3 route）, the hierarchical layer-stacking Mn-Ce composite oxide exhibited higher catalytic activity in the complete oxidation of volatile organic compounds（VOCs）. By means of testing, the data revealed that the hierarchical layer-stacking Mn-Ce composite oxide possessed superior physiochemical properties such as good low-temperature reducibility, high manganese oxidation state and rich adsorbed surface oxygen species which resulted in the enhancement of catalytic abilities.展开更多
Photocatalysis is a promising technology for purification of indoor air by oxidation of volatile organic compounds.This study provides a comprehensive analysis of the adsorption and photo-oxidation of surface-adsorbed...Photocatalysis is a promising technology for purification of indoor air by oxidation of volatile organic compounds.This study provides a comprehensive analysis of the adsorption and photo-oxidation of surface-adsorbed acetone on three SrTiO_(3)morphologies:cubes(for which exclusively{100}facets are exposed),{110}-truncated cubes,and{100}-truncated rhombic dodecahedrons,respectively,all prepared by hydrothermal synthesis.In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy shows that cubic crystals contain a high quantity of surface-OH groups,enabling significant quantities of adsorbed acetone in the form ofη^(1)-enolate when exposed to gas phase acetone.Contrary,{110}facets exhibit fewer surface-OH groups,resulting in relatively small quantities of adsorbedη^(1)-acetone,without observable quantities of enolate.Interestingly,acetate and formate signatures appear in the spectra of cubic,surfaceη^(1)-enolate containing,SrTiO_(3)upon illumination,while besides acetate and formate,the formation of(surface)formaldehyde was observed on truncated cubes,and dodecahedrons,by conversion of adsorbedη^(1)-acetone.Time-Resolved Photoluminescence studies demonstrate that the lifetimes of photogenerated charge carriers vary with crystal morphology.The shortest carrier lifetime(τ_(1)=33±0.1 ps)was observed in{110}-truncated cube SrTiO_(3),likely due to a relatively strong built-in electric field promoting electron transport to{100}facets and hole transport to{110}facets.The second lifetime(τ_(2)=259±1 ps)was also the shortest for this morphology,possibly due to a higher amount of surface trap states.Our results demonstrate that SrTiO_(3)crystal morphology can be tuned to optimize performance in photocatalytic oxidation.展开更多
Sulfur dioxide(SO_(2))frequently coexist with volatile organic compounds(VOCs)in exhaust gas.The competitive adsorption of SO_(2) and VOCs can adversely affect the efficiency of catalytic combustion,leading to catalys...Sulfur dioxide(SO_(2))frequently coexist with volatile organic compounds(VOCs)in exhaust gas.The competitive adsorption of SO_(2) and VOCs can adversely affect the efficiency of catalytic combustion,leading to catalyst poisoning and irreversible loss of activity.To investigate the impact of sulfur poisoning on the catalysts,we prepared the MnO_(2)/Beta zeolite,and a corresponding series of sulfur-poisoned catalysts through in-situ thermal decomposition of(NH_(4))_(2)SO_(4).The decrease in toluene catalytic activity of poisoned MnO_(2)/Beta zeolite primarily results from the conversion of the active species MnO_(2) to MnSO_(4).However,the crystal structure and the porous structure of MnO_(2)/Beta zeolite were stable,and original structure was still maintained when 1.6%(mass)sulfur species were introduced.Furthermore,the extra-framework Al of Beta zeolite could capture sulfur species to generate Al2(SO_(4))_(3),thereby reducing sulfur species from reacting with Mn^(4+) active sites.The combination of sulfur and Beta zeolite was found to directly produce new strong-acid sites,thus effectively compensating for the effect of reduced Mn4+active species on the catalytic activity.展开更多
Micro-mesoporous ZSM-5 zeolites were obtained by the post-treatment of tetrahydroxy ammonium hydroxide(TPAOH) solution with different concentration.The hierarchical pore structure formed during the desilication proces...Micro-mesoporous ZSM-5 zeolites were obtained by the post-treatment of tetrahydroxy ammonium hydroxide(TPAOH) solution with different concentration.The hierarchical pore structure formed during the desilication process facilitates the dispersion of Pt nanoparticles and Pt/ZSM-5 catalysts exhibit rather high catalytic activity for the deep oxidation of various VOCs at low temperature.The catalyst treated with TPAOH of 0.1 mol/L(Pt/ZSM-5(0.1)) shows the lowest degradation temperature(T90%) of 128 and 142℃, respectively for benzene and n-hexane.Compared with the untreated Pt/ZSM-5 catalyst, the abundant mesopores, small Pt particle size and finely dispersed Pt contribute to the superior catalytic activity and stability of the Pt/ZSM-5 catalysts for VOCs removal.More importantly, the existence of H_(2)O in the feed gases hardly affected the activity of Pt/ZSM-5(0.1) catalyst at the low reaction temperature of 128℃, which is very important for VOCs low-temperature removal in the future practical applications.展开更多
Different zeolites supported Pt catalystswithmicro-mesoporous structurewere prepared by organic base tetrapropylammonium hydroxide(TPAOH)treatment and their catalytic oxidation activity for various volatile organic co...Different zeolites supported Pt catalystswithmicro-mesoporous structurewere prepared by organic base tetrapropylammonium hydroxide(TPAOH)treatment and their catalytic oxidation activity for various volatile organic compounds(VOCs)were evaluated.The results reveal that the synergistic effect between Pt nanoparticles and surface acid sites plays an important role in VOCs low-temperature removal.The small size and high dispersion of Pt nanoparticles on the surface of the zeolites would promote the catalytic oxidation of aromatics and alkanes over the Pt/zeolite catalysts,while strong acidity and abundant acid sites of catalysts are in favour of the oxidation of the VOCs containingNandOheteroatoms.In addition,it was found that Pt/ZSM-5 catalyst exhibits the highest oxidation activity for various VOCs low-temperature removal amongst all the catalysts due to the balance of both Pt dispersion and abundant acid sites in the catalyst.This comprehensive consideration should be very helpful when designing and preparing novel catalysts for the low-temperature removal of VOCs.展开更多
In this work,cathode materials of spent lithium-ion ternary batteries are recovered and used as metal precursor to prepare multi-metal oxides MnO_(x)(SY)and GdMnO_(3)(SY)via combustion method and sol-gel method,respec...In this work,cathode materials of spent lithium-ion ternary batteries are recovered and used as metal precursor to prepare multi-metal oxides MnO_(x)(SY)and GdMnO_(3)(SY)via combustion method and sol-gel method,respectively.Furthermore,a series of MnO_(x)(SY)-n and GdMnO_(3)(SY)-n(n=0.05,0.10,1.00,4.00,n represents the dilute HNO_(3) concentration)catalysts are fabricated by acid treatment of MnO_(x)(SY)and GdMnO_(3)(SY)samples and catalytic activities of oxygenated VOCs oxidation over all the prepared catalysts are investigated.Catalytic evaluation results show that acid-treated MnO_(x)(SY)-0.10 and GdMnO_(3)(SY)-0.05 samples perform the optimum VOCs removal efficiency respectively,which may be attributed to their obvious enhancement of physicochemical properties.In detail,Mn O_(x)(SY)-0.10 and GdMnO_(3)(SY)-0.05 samples exhibit the larger specific surface area,bigger amount of surface high-valence metal ions(Mn^(4+),Co^(3+),Ni^(3+)),more abundant adsorbed oxygen species and better low-temperature reducibility,which can play a crucial role in the significant improvement of VOCs oxidation.In situ DRIFTS results imply that the possible main intermediates are-OCO,-COO and-C-O species produced during VOCs oxidation.Possible by-products are further determined via TD/GC-MS analysis.展开更多
The catalytic oxidation of volatile organic compounds(VOCs)is of considerable significance for the sustainable development of the chemical industry;thus,considerable efforts have been devoted to the exploration of eff...The catalytic oxidation of volatile organic compounds(VOCs)is of considerable significance for the sustainable development of the chemical industry;thus,considerable efforts have been devoted to the exploration of efficient catalysts for use in this reaction.In this regard,the development and utilization of single-atom catalysts(SACs)in VOCs decomposition is a rapidly expanding research area.SACs can be employed as potential catalysts for oxidizing VOC molecules due to their optimal utilization efficiency,unique atomic bonding structures,and unsaturated orbits.Progress has been achieved,while the challenges surrounding precise regulation of the microstructures of SACs for improving their low-temperature efficiency,stability,and product selectivity under practical conditions are remaining.Therefore,elucidating structure-performance relationships and establishing intrinsic modulating mechanisms are urgently required for guiding researchers on how to synthesize effective and stable functional SACs proactively.Herein,recent advances in the design and synthesis of functional SACs for application in the catalytic oxidation of VOCs are summarized.The experimental and theoretical studies revealing higher efficiency,stability,and selectivity of as-prepared functional SACs are being highlighted.Accordingly,the future perspectives in terms of promising catalysts with multi-sized composite active sites and the illustration of intrinsic mechanism are proposed.The rapid intelligent screening of applicable SACs and their industrial applications are also discussed.展开更多
To date,investigations onto the regulation of reactants mass transfer has been paid much less attention in environmental catalysis.Herein,we demonstrated that by rationally designing the adsorption sites of multi-reac...To date,investigations onto the regulation of reactants mass transfer has been paid much less attention in environmental catalysis.Herein,we demonstrated that by rationally designing the adsorption sites of multi-reactants,the pollutant destruction efficiency,product selectivity,reaction stability and secondary pollution have been all affected in the catalytic chlorobenzene oxidation(CBCO).Experimental results revealed that the co-adsorption of chlo robenzene(CB)and gaseous O_(2)at the oxygen vacancies of CeO_(2)led to remarkably high CO_(2)generation,owning to their short mass transfer distance on the catalyst surface,while their separated adsorptions at Bronsted HZSM-5 and CeO_(2)vacancies resulted in a much lower CO_(2)generation,and produced significant polychlorinated byproducts in the off-gas.Howeve r,this separated adsorption model yielded superior long-term stability for the CeO_(2)/HZSM-5 catalyst,owning to the protection of CeO_(2)oxygen vacancies from Cl poisoning by the preferential adsorption of CB on the Bronsted acidic sites.This work unveils that design of environmental catalysts needs to consider both of the catalyst intrinsic property and reactant mass transfer;investigations of the latter could pave a new way for the development of highly efficient catalysts towards environmental pollution control.展开更多
Volatile organic compounds(VOCs)oxidation processes play a very important role in atmospheric chemistry,and the chemical reactions are expressed in various manners in chemical mechanisms.To gain an improved understand...Volatile organic compounds(VOCs)oxidation processes play a very important role in atmospheric chemistry,and the chemical reactions are expressed in various manners in chemical mechanisms.To gain an improved understanding of VOCs evolution during oxidation processes and evaluate the discrepancies of VOCs oxidation schemes among different mechanisms,we used the total VOC reactivity as a diagnostic and evaluated tool to explore the differences for six widely used chemical mechanisms.We compared the total VOC reactivity evolution under high-NO_(x)xconditions for several sets of precursors,including n-pentane,toluene,ethene,isoprene and a mixture of 57 Photochemical Assessment Monitoring Stations(PAMS)species in a 0-D photochemical box model.Inter-comparison of total VOC reactivity of individual precursor simulations showed discrepancies to different extent of the oxidation schemes among the studied mechanisms,which are mainly attributed to the different lumping approaches for organic species.The PAMS simulation showed smaller discrepancy than individual precursor cases in terms of total VOC reactivity.SAPRC07 and RACM2 performances are found to better match the MCM for simulation of total VOC reactivity.Evidences suggest that the performance in simulating secondary organic products,OH concentrations and NO_(x)concentrations are related to the OH reactivity discrepancies among various chemical mechanisms.Information in this study can be used in selection of chemical mechanisms to better model OH reactivity in different environments.The results in this study also provide directions to further improve the ability in modelling total VOC reactivity with the chemical mechanisms.展开更多
Improving catalytic performance is a yet still challenge in thermal catalytic oxidation.Herein,uniform mesoporous MnO_(2) nanospheresupported bimetallic Pt–Pd nanoparticles were successfully fabricated via a SiO_(2) ...Improving catalytic performance is a yet still challenge in thermal catalytic oxidation.Herein,uniform mesoporous MnO_(2) nanospheresupported bimetallic Pt–Pd nanoparticles were successfully fabricated via a SiO_(2) template strategy for the total catalytic degradation of volatile organic compounds at low temperature.The introduction of mesopores into the MnO_(2) support induces a large specific surface area and pore size,thus providing numerous accessible active sites and enhanced diffusion properties.Moreover,the addition of a secondary noble metal can adjust the O_(ads)/O_(latt) molar ratios,resulting in high catalytic activity.Among them,the catalyst having a Pt/Pd molar ratio of 7:3 exhibits optimized catalytic activity at a weight hourly space velocity of 36,000 mL g^(-1) h^(-1),reaching 100%toluene oxidation at 175℃ with a lower activation energy(57.0 kJ mol^(-1))than the corresponding monometallic Pt or non-Pt-based catalysts(93.8 kJ mol^(-1) and 214.2 kJ mol^(-1)).Our findings demonstrate that the uniform mesoporous MnO_(2) nanosphere-supported bimetallic Pt–Pd nanoparticles catalyst is an effective candidate for application in elimination of toluene.展开更多
OMS-2 nanorod catalysts were synthesized by a hydrothermal redox reaction method using Mn SO4（OMS-2-SO4） and Mn（CH3COO）2（OMS-2-AC） as precursors. SO4^2--doped OMS-2-AC catalysts with different SO4^2-concentratio...OMS-2 nanorod catalysts were synthesized by a hydrothermal redox reaction method using Mn SO4（OMS-2-SO4） and Mn（CH3COO）2（OMS-2-AC） as precursors. SO4^2--doped OMS-2-AC catalysts with different SO4^2-concentrations were prepared next by adding（NH4）2SO4solution into OMS-2-AC samples to investigate the effect of the anion SO4^2-on the OMS-2-AC catalyst. All catalysts were then tested for the catalytic oxidation of ethanol. The OMS-2-SO4 catalyst synthesized demonstrated much better activity than OMS-2-AC. The SO4^2-doping greatly influenced the activity of the OMS-2-AC catalyst, with a dramatic promotion of activity for suitable concentration of SO4^2-（SO4/catalyst = 0.5% W/W）. The samples were characterized by X-ray diffraction（XRD）, field emission scanning electron microscopy（FE-SEM）, transmission electron microscopy（TEM）, X-ray photoelectron spectroscopy（XPS）,inductively coupled plasma optical emission spectroscopy（ICP-OES）, NH3-TPD and H2-TPR techniques. The results showed that the presence of a suitable amount of SO4^2-species in the OMS-2-AC catalyst could decrease the Mn–O bond strength and also enhance the lattice oxygen and acid site concentrations, which then effectively promoted the catalytic activity of OMS-2-AC toward ethanol oxidation. Thus it was confirmed that the better catalytic performance of OMS-2-SO4 compared to OMS-2-AC is due to the presence of some residual SO4^2-species in OMS-2-SO4 samples.展开更多
Cu-Mn, Cu-Mn-Ce, and Cu-Ce mixed-oxide catalysts were prepared by a citric acid sol-gel method and then characterized by XRD, BET, H_2-TPR and XPS analyses. Their catalytic properties were investigated in the toluene ...Cu-Mn, Cu-Mn-Ce, and Cu-Ce mixed-oxide catalysts were prepared by a citric acid sol-gel method and then characterized by XRD, BET, H_2-TPR and XPS analyses. Their catalytic properties were investigated in the toluene combustion reaction. Results showed that the Cu-Mn-Ce ternary mixed-oxide catalyst with 1：2：4 mole ratios had the highest catalytic activity, and 99% toluene conversion was achieved at temperatures below 220°C. In the Cu-Mn-Ce catalyst, a portion of Cu and Mn species entered into the Ce O2 fluorite lattice, which led to the formation of a ceria-based solid solution. Excess Cu and Mn oxides existed on the surface of the ceria-based solid solution. The coexistence of Cu-Mn mixed oxides and the ceria-based solid solution resulted in a better synergetic interaction than the Cu-Mn and Cu-Ce catalysts, which promoted catalyst reducibility, increased oxygen mobility, and enhanced the formation of abundant active oxygen species.展开更多
A compilation of new advances made in the research?eld of laboratory reaction kinetics in China’s Key Development Project for Air Pollution Formation Mechanism and Control Technologies was presented.These advances ar...A compilation of new advances made in the research?eld of laboratory reaction kinetics in China’s Key Development Project for Air Pollution Formation Mechanism and Control Technologies was presented.These advances are grouped into six broad,interrelated categories,including volatile organic compound(VOC)oxidation,secondary organic aerosol(SOA)formation,new particle formation(NPF)and gas-particle partitioning,ozone chemistry,model parameters,and secondary inorganic aerosol(SIA)formation,highlighting the laboratory work done by Chinese researchers.For smog chamber applications,the current knowledge gained from laboratory studies is reviewed,with emphasis on summarizing the oxidation mechanisms of long-chain alkanes,aromatics,alkenes,aldehydes/ketones in the atmosphere,SOA formation from anthropogenic emission sources,and oxidation of aromatics,isoprene,and limonene,as well as SIA formation.For?ow tube applications,atmospheric oxidation mechanisms of toluene and methacrolein,SOA formation from limonene oxidation by ozone,gas-particle partitioning of peroxides,and sulfuric acid-water(H2SO4-H2O)binary nucleation,methanesulfonic acid-water(MSA-H2O)binary nucleation,and sulfuric acid-ammonia-water(H2SO4-NH3-H2O)ternary nucleation are discussed.展开更多
Catalytic oxidation is widely used in pollution control technology to remove volatile organic compounds. In this study, Pd/ZSM-5 catalysts with different Pd contents and acidic sites were prepared via the impregnation...Catalytic oxidation is widely used in pollution control technology to remove volatile organic compounds. In this study, Pd/ZSM-5 catalysts with different Pd contents and acidic sites were prepared via the impregnation method. All the catalysts were characterized by means of N2 adsorption- desorption, X-ray fluorescence （XRF）, HE temperature programmed reduction （H2-TPR）, and NH3 temperature programmed desorption （NH3-TPD）. Their catalytic performance was investigated in the oxidation of butyl acetate experiments. The by-products of the reaction were collected in thermal desorption tubes and identified by gas chromatography/mass spectrometry. It was found that the increase of Pd content slightly changed the catalytic activity of butyl acetate oxidation according to the yield of CO2 achieved at 90%, but decreased the cracking by-products, whereas the enhancement of strong acidity over Pd-based catalysts enriched the by-product species. The butyl acetate oxidation process involves a series of reaction steps including protolysis, dehydrogenation, dehydration, cracking, and isomerization. Generally, butyl acetate was cracked to acetic acid and 2- methylpropene and the latter was an intermediate of the other by-products, and the oxidation routes of typical by-products were proposed. Trace amounts of 3-methylpentane, hexane, 2-methylpentane, pentane, and 2-methylbutane originated from iso4merization and protolysis reactions.展开更多
A novel method was presented for synthesis of ZnO and ZnO-CuO composites in the form of nanowires, nanorods and nanoflakes on oxidized silicon substrates. Further, the use of the synthesized nanostructures for gas sen...A novel method was presented for synthesis of ZnO and ZnO-CuO composites in the form of nanowires, nanorods and nanoflakes on oxidized silicon substrates. Further, the use of the synthesized nanostructures for gas sensing was demonstrated. Pure brass （Cu0.65-Zn0.35） films were deposited on oxidized Si substrate by radio frequency （RF） diode sputtering. Subsequently, these films having thickness in the range of 100-200 nm were oxidized in different oxidizing ambient in the temperature range of 300-550 ℃. The effect of temperature, time and oxidizing ambient on the growth of nanostructures was investigated by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and photoluminescence （PL） techniques. The nanostructures surface was analyzed by X-ray photoelectron spectroscopy （XPS）. The synthesized nanowires had diameter in the range of 60-100 nm and length up to 50 μm. Based on these observations, the growth mechanism has been suggested. For the nanorods, the diameter was observed to be -150 nm. Samples having dense nanowires, nanorods and nanoflakes were used as a gas sensing material. The performance Of the sensor was investigated for different nanostructured materials for various volatile organic compounds （VOCs）, It was observed that ZnO- CuO nanoflakes were more sensitive to VOC sensing compared to ZnO nanowires and nanorods.展开更多
Since the discovery of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs)in the process of municipal solid waste incineration(MSWI),a large number of researches have been conducted to reveal their formation ...Since the discovery of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs)in the process of municipal solid waste incineration(MSWI),a large number of researches have been conducted to reveal their formation mechanisms and emission characteristics.As one of national priority control pollutants,chlorinated organics are inclined to transfer into PCDD/Fs in the heterogeneously catalyzed process,which has been considered to be one of great challenges in environmental catalysis.However,so far direct evidences to support such a conversion process are insufficient,and the reaction mechanisms are lack of exploration.This study investigated the catalytic elimination of chlorobenzene(CBz)over a range of industrially applied active species including Pt,Ru,V,Ce and Mn oxides,and explored their reaction byproducts,chlorine adsorption/desorption behaviors and PCDD/F formations.We found that all of these species could generate the PCDD/Fs,amongst which,Mn species were the most active for PCDD/F formation.Approximately 140 ng I-TEQg-1 PCDD/Fs were detected on the Mn-CNT surface after ageing at250℃for 30 h.Even using the dichloromethane(DCM)as a precursor,significant PCDD/Fs were still detected.The Ru and V species were shown to generate much less polychlorinated byproducts and PCDD/Fs,owning to their sufficiently high abilities in Cl desorption,which were through the semi-Deacon and Br(?)nsted H reactions,respectively.展开更多
A series of hierarchical macro-/mesoporous silica supports （MMSs） were successfully synthesized using dual-templating technique employing polystyrene （PS） spheres and the Pluronic P123 surfactant. Pd was next load...A series of hierarchical macro-/mesoporous silica supports （MMSs） were successfully synthesized using dual-templating technique employing polystyrene （PS） spheres and the Pluronic P123 surfactant. Pd was next loaded on the hierarchical silica supports via colloids precipitation method. Physicochemical properties of the synthesized samples were characterized by various techniques and all catalysts were tested for the total oxidation of o-xylene. Among them, the Pd/MMS-b catalyst with tetraethoxysilane/polystyrene weight ratio of 1.0 exhibited superior catalytic activity, and under a higher gas hourly space velocity （GHSV） of 70000 h^-1, the 90% conversion of o-xylene has been obtained at around 200℃. The BET and SEM results indicated that Pd/MMS- b catalyst possesses high surface area and large pore volume, and well-ordered, interconnected macropores and 2D hexagonally mesopores hybrid network. This novel ordered hierarchical porous structure was highly beneficial to the dispersion of active sites Pd nanoparticles with less aggregation, and facilitates diffusion of reactants and products. Furthermore, the Pd/MMS-b catalyst possessed good stability and durability.展开更多
基金supported by Strategic Project of Science and Technology of Chinese Academy of Sciences(XDB05050000)the National Natural Science Foundation of China(51272253)
文摘Hierarchical layer-stacking Mn-Ce composite oxide with mesoporous structure was firstly prepared by a simple precipitation/decomposition procedure with oxalate precursor and the complete catalytic oxidation of VOCs（benzene, toluene and ethyl acetate） were examined. The Mn-Ce oxalate precursor was obtained from metal salt and oxalic acid without any additives. The resulting materials were characterized by X-ray diffraction（XRD）, Brunauer-Emmett-Teller（BET）, scanning electron microscopy（SEM）, energy dispersive X-ray spectroscopy（EDX）, hydrogen temperature programmed reduction（H2-TPR） and X-ray photoelectron spectroscopy（XPS）. Compared with Mn-Ce composite oxide synthesized through a traditional method（Na2CO3 route）, the hierarchical layer-stacking Mn-Ce composite oxide exhibited higher catalytic activity in the complete oxidation of volatile organic compounds（VOCs）. By means of testing, the data revealed that the hierarchical layer-stacking Mn-Ce composite oxide possessed superior physiochemical properties such as good low-temperature reducibility, high manganese oxidation state and rich adsorbed surface oxygen species which resulted in the enhancement of catalytic abilities.
基金Advanced Research Center for Chemical Building Blocks,ARC CBBC,which is co-foundedco-financed by the Dutch Research Council(NWO)and the Netherlands Ministry of Economic Affairs and Climate Policy.
文摘Photocatalysis is a promising technology for purification of indoor air by oxidation of volatile organic compounds.This study provides a comprehensive analysis of the adsorption and photo-oxidation of surface-adsorbed acetone on three SrTiO_(3)morphologies:cubes(for which exclusively{100}facets are exposed),{110}-truncated cubes,and{100}-truncated rhombic dodecahedrons,respectively,all prepared by hydrothermal synthesis.In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy shows that cubic crystals contain a high quantity of surface-OH groups,enabling significant quantities of adsorbed acetone in the form ofη^(1)-enolate when exposed to gas phase acetone.Contrary,{110}facets exhibit fewer surface-OH groups,resulting in relatively small quantities of adsorbedη^(1)-acetone,without observable quantities of enolate.Interestingly,acetate and formate signatures appear in the spectra of cubic,surfaceη^(1)-enolate containing,SrTiO_(3)upon illumination,while besides acetate and formate,the formation of(surface)formaldehyde was observed on truncated cubes,and dodecahedrons,by conversion of adsorbedη^(1)-acetone.Time-Resolved Photoluminescence studies demonstrate that the lifetimes of photogenerated charge carriers vary with crystal morphology.The shortest carrier lifetime(τ_(1)=33±0.1 ps)was observed in{110}-truncated cube SrTiO_(3),likely due to a relatively strong built-in electric field promoting electron transport to{100}facets and hole transport to{110}facets.The second lifetime(τ_(2)=259±1 ps)was also the shortest for this morphology,possibly due to a higher amount of surface trap states.Our results demonstrate that SrTiO_(3)crystal morphology can be tuned to optimize performance in photocatalytic oxidation.
基金supported by the National Natural Science Foundation of China(21577094)the Zhejiang Public Welfare Technology Research Project(LGG19B070003).
文摘Sulfur dioxide(SO_(2))frequently coexist with volatile organic compounds(VOCs)in exhaust gas.The competitive adsorption of SO_(2) and VOCs can adversely affect the efficiency of catalytic combustion,leading to catalyst poisoning and irreversible loss of activity.To investigate the impact of sulfur poisoning on the catalysts,we prepared the MnO_(2)/Beta zeolite,and a corresponding series of sulfur-poisoned catalysts through in-situ thermal decomposition of(NH_(4))_(2)SO_(4).The decrease in toluene catalytic activity of poisoned MnO_(2)/Beta zeolite primarily results from the conversion of the active species MnO_(2) to MnSO_(4).However,the crystal structure and the porous structure of MnO_(2)/Beta zeolite were stable,and original structure was still maintained when 1.6%(mass)sulfur species were introduced.Furthermore,the extra-framework Al of Beta zeolite could capture sulfur species to generate Al2(SO_(4))_(3),thereby reducing sulfur species from reacting with Mn^(4+) active sites.The combination of sulfur and Beta zeolite was found to directly produce new strong-acid sites,thus effectively compensating for the effect of reduced Mn4+active species on the catalytic activity.
基金supported by a grant from the National Key Research and Development Program of China (No.2016YFC0204300)the Nature Science Foundation of China (No.21477109)。
文摘Micro-mesoporous ZSM-5 zeolites were obtained by the post-treatment of tetrahydroxy ammonium hydroxide(TPAOH) solution with different concentration.The hierarchical pore structure formed during the desilication process facilitates the dispersion of Pt nanoparticles and Pt/ZSM-5 catalysts exhibit rather high catalytic activity for the deep oxidation of various VOCs at low temperature.The catalyst treated with TPAOH of 0.1 mol/L(Pt/ZSM-5(0.1)) shows the lowest degradation temperature(T90%) of 128 and 142℃, respectively for benzene and n-hexane.Compared with the untreated Pt/ZSM-5 catalyst, the abundant mesopores, small Pt particle size and finely dispersed Pt contribute to the superior catalytic activity and stability of the Pt/ZSM-5 catalysts for VOCs removal.More importantly, the existence of H_(2)O in the feed gases hardly affected the activity of Pt/ZSM-5(0.1) catalyst at the low reaction temperature of 128℃, which is very important for VOCs low-temperature removal in the future practical applications.
基金supported by a grant from the National Key Research and Development Program of China (No. 2016YFC0204300)the Nature Science Foundation of China (No. 21477109)
文摘Different zeolites supported Pt catalystswithmicro-mesoporous structurewere prepared by organic base tetrapropylammonium hydroxide(TPAOH)treatment and their catalytic oxidation activity for various volatile organic compounds(VOCs)were evaluated.The results reveal that the synergistic effect between Pt nanoparticles and surface acid sites plays an important role in VOCs low-temperature removal.The small size and high dispersion of Pt nanoparticles on the surface of the zeolites would promote the catalytic oxidation of aromatics and alkanes over the Pt/zeolite catalysts,while strong acidity and abundant acid sites of catalysts are in favour of the oxidation of the VOCs containingNandOheteroatoms.In addition,it was found that Pt/ZSM-5 catalyst exhibits the highest oxidation activity for various VOCs low-temperature removal amongst all the catalysts due to the balance of both Pt dispersion and abundant acid sites in the catalyst.This comprehensive consideration should be very helpful when designing and preparing novel catalysts for the low-temperature removal of VOCs.
基金supported by the National Natural Science Foundation of China(Grant numbers 21876107,21607103)。
文摘In this work,cathode materials of spent lithium-ion ternary batteries are recovered and used as metal precursor to prepare multi-metal oxides MnO_(x)(SY)and GdMnO_(3)(SY)via combustion method and sol-gel method,respectively.Furthermore,a series of MnO_(x)(SY)-n and GdMnO_(3)(SY)-n(n=0.05,0.10,1.00,4.00,n represents the dilute HNO_(3) concentration)catalysts are fabricated by acid treatment of MnO_(x)(SY)and GdMnO_(3)(SY)samples and catalytic activities of oxygenated VOCs oxidation over all the prepared catalysts are investigated.Catalytic evaluation results show that acid-treated MnO_(x)(SY)-0.10 and GdMnO_(3)(SY)-0.05 samples perform the optimum VOCs removal efficiency respectively,which may be attributed to their obvious enhancement of physicochemical properties.In detail,Mn O_(x)(SY)-0.10 and GdMnO_(3)(SY)-0.05 samples exhibit the larger specific surface area,bigger amount of surface high-valence metal ions(Mn^(4+),Co^(3+),Ni^(3+)),more abundant adsorbed oxygen species and better low-temperature reducibility,which can play a crucial role in the significant improvement of VOCs oxidation.In situ DRIFTS results imply that the possible main intermediates are-OCO,-COO and-C-O species produced during VOCs oxidation.Possible by-products are further determined via TD/GC-MS analysis.
基金financially supported by the National Natural Science Foundation of China(Nos.22276145,2187613921922606)+1 种基金National Key R&D Program of China(No.2022YFB4101500)China Postdoctoral Science Foundation(No.2023M732783)。
文摘The catalytic oxidation of volatile organic compounds(VOCs)is of considerable significance for the sustainable development of the chemical industry;thus,considerable efforts have been devoted to the exploration of efficient catalysts for use in this reaction.In this regard,the development and utilization of single-atom catalysts(SACs)in VOCs decomposition is a rapidly expanding research area.SACs can be employed as potential catalysts for oxidizing VOC molecules due to their optimal utilization efficiency,unique atomic bonding structures,and unsaturated orbits.Progress has been achieved,while the challenges surrounding precise regulation of the microstructures of SACs for improving their low-temperature efficiency,stability,and product selectivity under practical conditions are remaining.Therefore,elucidating structure-performance relationships and establishing intrinsic modulating mechanisms are urgently required for guiding researchers on how to synthesize effective and stable functional SACs proactively.Herein,recent advances in the design and synthesis of functional SACs for application in the catalytic oxidation of VOCs are summarized.The experimental and theoretical studies revealing higher efficiency,stability,and selectivity of as-prepared functional SACs are being highlighted.Accordingly,the future perspectives in terms of promising catalysts with multi-sized composite active sites and the illustration of intrinsic mechanism are proposed.The rapid intelligent screening of applicable SACs and their industrial applications are also discussed.
基金financially supported by the National Key R&D Program of China(No.2016YFC0202200)the National Natural Science Foundation of China(Nos.21777140,21922607)the Outstanding Youth Project of Zhejiang Natural Science Foundation(No.LR19E080004)。
文摘To date,investigations onto the regulation of reactants mass transfer has been paid much less attention in environmental catalysis.Herein,we demonstrated that by rationally designing the adsorption sites of multi-reactants,the pollutant destruction efficiency,product selectivity,reaction stability and secondary pollution have been all affected in the catalytic chlorobenzene oxidation(CBCO).Experimental results revealed that the co-adsorption of chlo robenzene(CB)and gaseous O_(2)at the oxygen vacancies of CeO_(2)led to remarkably high CO_(2)generation,owning to their short mass transfer distance on the catalyst surface,while their separated adsorptions at Bronsted HZSM-5 and CeO_(2)vacancies resulted in a much lower CO_(2)generation,and produced significant polychlorinated byproducts in the off-gas.Howeve r,this separated adsorption model yielded superior long-term stability for the CeO_(2)/HZSM-5 catalyst,owning to the protection of CeO_(2)oxygen vacancies from Cl poisoning by the preferential adsorption of CB on the Bronsted acidic sites.This work unveils that design of environmental catalysts needs to consider both of the catalyst intrinsic property and reactant mass transfer;investigations of the latter could pave a new way for the development of highly efficient catalysts towards environmental pollution control.
基金supported by the National Natural Science Foundation of China(No.41877302)Guangdong Natural Science Funds for Distinguished Young Scholar(No.2018B030306037)+2 种基金the National Key R&D Plan of China(No.2019YFE0106300)Guangdong Innovative and Entrepreneurial Research Team Program(No.2016ZT06N263)supported by the Special Fund Project for Science and Technology Innovation Strategy of Guangdong Province(No.2019B121205004)
文摘Volatile organic compounds(VOCs)oxidation processes play a very important role in atmospheric chemistry,and the chemical reactions are expressed in various manners in chemical mechanisms.To gain an improved understanding of VOCs evolution during oxidation processes and evaluate the discrepancies of VOCs oxidation schemes among different mechanisms,we used the total VOC reactivity as a diagnostic and evaluated tool to explore the differences for six widely used chemical mechanisms.We compared the total VOC reactivity evolution under high-NO_(x)xconditions for several sets of precursors,including n-pentane,toluene,ethene,isoprene and a mixture of 57 Photochemical Assessment Monitoring Stations(PAMS)species in a 0-D photochemical box model.Inter-comparison of total VOC reactivity of individual precursor simulations showed discrepancies to different extent of the oxidation schemes among the studied mechanisms,which are mainly attributed to the different lumping approaches for organic species.The PAMS simulation showed smaller discrepancy than individual precursor cases in terms of total VOC reactivity.SAPRC07 and RACM2 performances are found to better match the MCM for simulation of total VOC reactivity.Evidences suggest that the performance in simulating secondary organic products,OH concentrations and NO_(x)concentrations are related to the OH reactivity discrepancies among various chemical mechanisms.Information in this study can be used in selection of chemical mechanisms to better model OH reactivity in different environments.The results in this study also provide directions to further improve the ability in modelling total VOC reactivity with the chemical mechanisms.
基金financial support provided by the National Key R&D Program of China(2017YFC0210901,2017YFC0210906)National Natural Science Foundation of China(51573122,21722607,21776190)+2 种基金Natural Science Foundation of the Jiangsu Higher Education Institutions of China(17KJA430014,17KJA150009)the Science and Technology Program for Social Development of Jiangsu(BE2015637)the project supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)。
文摘Improving catalytic performance is a yet still challenge in thermal catalytic oxidation.Herein,uniform mesoporous MnO_(2) nanospheresupported bimetallic Pt–Pd nanoparticles were successfully fabricated via a SiO_(2) template strategy for the total catalytic degradation of volatile organic compounds at low temperature.The introduction of mesopores into the MnO_(2) support induces a large specific surface area and pore size,thus providing numerous accessible active sites and enhanced diffusion properties.Moreover,the addition of a secondary noble metal can adjust the O_(ads)/O_(latt) molar ratios,resulting in high catalytic activity.Among them,the catalyst having a Pt/Pd molar ratio of 7:3 exhibits optimized catalytic activity at a weight hourly space velocity of 36,000 mL g^(-1) h^(-1),reaching 100%toluene oxidation at 175℃ with a lower activation energy(57.0 kJ mol^(-1))than the corresponding monometallic Pt or non-Pt-based catalysts(93.8 kJ mol^(-1) and 214.2 kJ mol^(-1)).Our findings demonstrate that the uniform mesoporous MnO_(2) nanosphere-supported bimetallic Pt–Pd nanoparticles catalyst is an effective candidate for application in elimination of toluene.
基金financially supported by the National Natural Science Foundation of China (No. 21422706)the Program of the Ministry of Science and Technology of China (No. 2012AA062702)
文摘OMS-2 nanorod catalysts were synthesized by a hydrothermal redox reaction method using Mn SO4（OMS-2-SO4） and Mn（CH3COO）2（OMS-2-AC） as precursors. SO4^2--doped OMS-2-AC catalysts with different SO4^2-concentrations were prepared next by adding（NH4）2SO4solution into OMS-2-AC samples to investigate the effect of the anion SO4^2-on the OMS-2-AC catalyst. All catalysts were then tested for the catalytic oxidation of ethanol. The OMS-2-SO4 catalyst synthesized demonstrated much better activity than OMS-2-AC. The SO4^2-doping greatly influenced the activity of the OMS-2-AC catalyst, with a dramatic promotion of activity for suitable concentration of SO4^2-（SO4/catalyst = 0.5% W/W）. The samples were characterized by X-ray diffraction（XRD）, field emission scanning electron microscopy（FE-SEM）, transmission electron microscopy（TEM）, X-ray photoelectron spectroscopy（XPS）,inductively coupled plasma optical emission spectroscopy（ICP-OES）, NH3-TPD and H2-TPR techniques. The results showed that the presence of a suitable amount of SO4^2-species in the OMS-2-AC catalyst could decrease the Mn–O bond strength and also enhance the lattice oxygen and acid site concentrations, which then effectively promoted the catalytic activity of OMS-2-AC toward ethanol oxidation. Thus it was confirmed that the better catalytic performance of OMS-2-SO4 compared to OMS-2-AC is due to the presence of some residual SO4^2-species in OMS-2-SO4 samples.
基金the financial support from the Natural Science Foundation of China (No. 21107096)Zhejiang Provincial Natural Science Foundation of China (No. Y14E080008)+1 种基金the Commission of Science and Technology of Zhejiang province (No. 2013C03021)the Specialized Research Fund for the Doctoral Program of Higher Education (No. 20133317110004)
文摘Cu-Mn, Cu-Mn-Ce, and Cu-Ce mixed-oxide catalysts were prepared by a citric acid sol-gel method and then characterized by XRD, BET, H_2-TPR and XPS analyses. Their catalytic properties were investigated in the toluene combustion reaction. Results showed that the Cu-Mn-Ce ternary mixed-oxide catalyst with 1：2：4 mole ratios had the highest catalytic activity, and 99% toluene conversion was achieved at temperatures below 220°C. In the Cu-Mn-Ce catalyst, a portion of Cu and Mn species entered into the Ce O2 fluorite lattice, which led to the formation of a ceria-based solid solution. Excess Cu and Mn oxides existed on the surface of the ceria-based solid solution. The coexistence of Cu-Mn mixed oxides and the ceria-based solid solution resulted in a better synergetic interaction than the Cu-Mn and Cu-Ce catalysts, which promoted catalyst reducibility, increased oxygen mobility, and enhanced the formation of abundant active oxygen species.
基金supported by the National Key Research and Development Program of China(No.2019YFC0214801)。
文摘A compilation of new advances made in the research?eld of laboratory reaction kinetics in China’s Key Development Project for Air Pollution Formation Mechanism and Control Technologies was presented.These advances are grouped into six broad,interrelated categories,including volatile organic compound(VOC)oxidation,secondary organic aerosol(SOA)formation,new particle formation(NPF)and gas-particle partitioning,ozone chemistry,model parameters,and secondary inorganic aerosol(SIA)formation,highlighting the laboratory work done by Chinese researchers.For smog chamber applications,the current knowledge gained from laboratory studies is reviewed,with emphasis on summarizing the oxidation mechanisms of long-chain alkanes,aromatics,alkenes,aldehydes/ketones in the atmosphere,SOA formation from anthropogenic emission sources,and oxidation of aromatics,isoprene,and limonene,as well as SIA formation.For?ow tube applications,atmospheric oxidation mechanisms of toluene and methacrolein,SOA formation from limonene oxidation by ozone,gas-particle partitioning of peroxides,and sulfuric acid-water(H2SO4-H2O)binary nucleation,methanesulfonic acid-water(MSA-H2O)binary nucleation,and sulfuric acid-ammonia-water(H2SO4-NH3-H2O)ternary nucleation are discussed.
基金supported by the National High Technology Research and Development Program of China(No.2012AA063101)the National Basic Research Program of China(No.2010CB732300)the"Strategic Priority Research Program"of the Chinese Academy of Sciences(No.XDB05050200)
文摘Catalytic oxidation is widely used in pollution control technology to remove volatile organic compounds. In this study, Pd/ZSM-5 catalysts with different Pd contents and acidic sites were prepared via the impregnation method. All the catalysts were characterized by means of N2 adsorption- desorption, X-ray fluorescence （XRF）, HE temperature programmed reduction （H2-TPR）, and NH3 temperature programmed desorption （NH3-TPD）. Their catalytic performance was investigated in the oxidation of butyl acetate experiments. The by-products of the reaction were collected in thermal desorption tubes and identified by gas chromatography/mass spectrometry. It was found that the increase of Pd content slightly changed the catalytic activity of butyl acetate oxidation according to the yield of CO2 achieved at 90%, but decreased the cracking by-products, whereas the enhancement of strong acidity over Pd-based catalysts enriched the by-product species. The butyl acetate oxidation process involves a series of reaction steps including protolysis, dehydrogenation, dehydration, cracking, and isomerization. Generally, butyl acetate was cracked to acetic acid and 2- methylpropene and the latter was an intermediate of the other by-products, and the oxidation routes of typical by-products were proposed. Trace amounts of 3-methylpentane, hexane, 2-methylpentane, pentane, and 2-methylbutane originated from iso4merization and protolysis reactions.
基金National Agricultural Innovation Project(NAIP)Indian Council of Agricultural Research(ICAR)for their financial support under the project C10125(component-4)
文摘A novel method was presented for synthesis of ZnO and ZnO-CuO composites in the form of nanowires, nanorods and nanoflakes on oxidized silicon substrates. Further, the use of the synthesized nanostructures for gas sensing was demonstrated. Pure brass （Cu0.65-Zn0.35） films were deposited on oxidized Si substrate by radio frequency （RF） diode sputtering. Subsequently, these films having thickness in the range of 100-200 nm were oxidized in different oxidizing ambient in the temperature range of 300-550 ℃. The effect of temperature, time and oxidizing ambient on the growth of nanostructures was investigated by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and photoluminescence （PL） techniques. The nanostructures surface was analyzed by X-ray photoelectron spectroscopy （XPS）. The synthesized nanowires had diameter in the range of 60-100 nm and length up to 50 μm. Based on these observations, the growth mechanism has been suggested. For the nanorods, the diameter was observed to be -150 nm. Samples having dense nanowires, nanorods and nanoflakes were used as a gas sensing material. The performance Of the sensor was investigated for different nanostructured materials for various volatile organic compounds （VOCs）, It was observed that ZnO- CuO nanoflakes were more sensitive to VOC sensing compared to ZnO nanowires and nanorods.
基金financially supported by the National Natural Science Foundation of China(Nos.21777140,21922607)the Outstanding Youth Project of Zhejiang Natural Science Foundation(No.LR19E080004)。
文摘Since the discovery of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs)in the process of municipal solid waste incineration(MSWI),a large number of researches have been conducted to reveal their formation mechanisms and emission characteristics.As one of national priority control pollutants,chlorinated organics are inclined to transfer into PCDD/Fs in the heterogeneously catalyzed process,which has been considered to be one of great challenges in environmental catalysis.However,so far direct evidences to support such a conversion process are insufficient,and the reaction mechanisms are lack of exploration.This study investigated the catalytic elimination of chlorobenzene(CBz)over a range of industrially applied active species including Pt,Ru,V,Ce and Mn oxides,and explored their reaction byproducts,chlorine adsorption/desorption behaviors and PCDD/F formations.We found that all of these species could generate the PCDD/Fs,amongst which,Mn species were the most active for PCDD/F formation.Approximately 140 ng I-TEQg-1 PCDD/Fs were detected on the Mn-CNT surface after ageing at250℃for 30 h.Even using the dichloromethane(DCM)as a precursor,significant PCDD/Fs were still detected.The Ru and V species were shown to generate much less polychlorinated byproducts and PCDD/Fs,owning to their sufficiently high abilities in Cl desorption,which were through the semi-Deacon and Br(?)nsted H reactions,respectively.
基金This work was financially supported by the National Natural Science Foundation （Grant Nos. 21337003 and 21477149）, and the Strategic Priority Research Program of the Chinese Academy of Sciences （XDB05050200）.
文摘A series of hierarchical macro-/mesoporous silica supports （MMSs） were successfully synthesized using dual-templating technique employing polystyrene （PS） spheres and the Pluronic P123 surfactant. Pd was next loaded on the hierarchical silica supports via colloids precipitation method. Physicochemical properties of the synthesized samples were characterized by various techniques and all catalysts were tested for the total oxidation of o-xylene. Among them, the Pd/MMS-b catalyst with tetraethoxysilane/polystyrene weight ratio of 1.0 exhibited superior catalytic activity, and under a higher gas hourly space velocity （GHSV） of 70000 h^-1, the 90% conversion of o-xylene has been obtained at around 200℃. The BET and SEM results indicated that Pd/MMS- b catalyst possesses high surface area and large pore volume, and well-ordered, interconnected macropores and 2D hexagonally mesopores hybrid network. This novel ordered hierarchical porous structure was highly beneficial to the dispersion of active sites Pd nanoparticles with less aggregation, and facilitates diffusion of reactants and products. Furthermore, the Pd/MMS-b catalyst possessed good stability and durability.
