Platinum/cerium-zirconium-sulfate（Pt/Ce-Zr-SO_4^（2-）） catalysts were prepared by wetness impregnation.Catalytic activities were evaluated from the combustion of propene and CO.Sulfate（SO_4^（2-））addition improv...Platinum/cerium-zirconium-sulfate（Pt/Ce-Zr-SO_4^（2-）） catalysts were prepared by wetness impregnation.Catalytic activities were evaluated from the combustion of propene and CO.Sulfate（SO_4^（2-））addition improved the catalytic activity significantly.When using Pt/Ce-Zr-SO_4^（2-） with 10 wt%SO_4^（2-）,the temperature for 90%conversion of propene and CO decreased by 75℃ compared with Pt/Ce-Zr.The conversion exceeded 95%at 240℃ even after 0.02%sulfur dioxide poisoning for 20 h.Temperature-programmed desorption of CO and X-ray photoelectron spectroscopy analyses revealed an improvement in Pt dispersion onto the Ce-Zr-SO_4^（2-） support,and the increased number of Pt particles built up more Pt^（-）-（SO_4^（2-））^（-） couples,which resulted in excellent activity.The increased total acidity and new Bronsted acid sites on the surface provided the Pt/Ce-Zr-SO_4^（2-） with good sulfur resistance.展开更多
Two continuously regenerating diesel particulate filter （CRDPF） with different configurations and one particles oxidation catalyst （POC） were employed to perform experiments in a controlled laboratory setting to e...Two continuously regenerating diesel particulate filter （CRDPF） with different configurations and one particles oxidation catalyst （POC） were employed to perform experiments in a controlled laboratory setting to evaluate their effects on NO2, smoke and particle number emissions. The results showed that the application of the after-treatments increased the emission ratios of NO2/NOx significantly. The results of smoke emissions and particle number （PN） emissions indicated that both CRDPFs had sufficient capacity to remove more than 90% of total particulate matter （PM） and more than 97% of solid particles. However, the POC was able to remove the organic components of total PM, and only partially to remove the carbonaceous particles with size less than 30 nm. The negligible effects of POC on larger particles were observed due to its honeycomb structure leads to an inadequate residence time to oxidize the solid particles or trap them. The particles removal efficiencies of CRDPFs had high degree of correlations with the emission ratio of NO2/NOx. The PN emission results from two CRDPFs indicated that more NO2 generating in diesel oxidation catalyst section could obtain the higher removal efficiency of solid particles. However this also increased the risk of NO2 exposure in atmosphere.展开更多
A molecular [Ru(bda)]-type(bda = 2,2’-bipyridine-6,6’-dicarboxylate) water oxidation catalyst with 4-vinylpyridine as the axial ligand(Complex 1) was immobilized or co-immobilized with 1-(trifluoromethyl)-4-vinylben...A molecular [Ru(bda)]-type(bda = 2,2’-bipyridine-6,6’-dicarboxylate) water oxidation catalyst with 4-vinylpyridine as the axial ligand(Complex 1) was immobilized or co-immobilized with 1-(trifluoromethyl)-4-vinylbenzene(3 F) or styrene(St) blocking units on the surface of glassy carbon(GC) electrodes by electrochemical polymerization, in order to prepare the corresponding poly-1@GC, poly-1+P3 F@GC, and poly-1+PSt@GC functional electrodes. Kinetic measurements of the electrode surface reaction revealed that [Ru(bda)] triggers the O–O bond formation via(1) the radical coupling interaction between the two metallo-oxyl radicals(I2 M) in the homo-coupling polymer(poly-1), and(2) the water nucleophilic attack(WNA) pathway in poly-1+P3 F and poly-1+PSt copolymers. The comparison of the three electrodes revealed that the second coordination sphere of the water oxidation catalysts plays vital roles in stabilizing their reaction intermediates, tuning the O–O bond formation pathways and improving the water oxidation reaction kinetics without changing the first coordination structures.展开更多
Decomposition mass loss and pyrolysis products analyses of particles sampled at various locations along the tailpipe of a Euro-IV diesel engine were performed using a thermo gravimetry in conjunction with Fourier tran...Decomposition mass loss and pyrolysis products analyses of particles sampled at various locations along the tailpipe of a Euro-IV diesel engine were performed using a thermo gravimetry in conjunction with Fourier transformation infrared spectrometrymass spectrum.Diesel particles were collected at the same location with and without diesel oxidation catalyst(DOC)mounted on the test engine separately.The three poles in thermal gravity-differential thermal gravity images suggested that the decomposition process of diesel particles could be divided into three stages which correspond to the decompositions of lower boiling substances,higher boiling substances and soot respectively.It is noticed that no matter whether DOC was mounted or not,the further the particles were sampled away from the engine block,the lower the peak temperatures and the heavier the mass losses within the first two stages,which indicated that the soluble organic fraction in the particle samples increased and therefore lowering the activation energy of thermal decomposition.Hydroxyl,ammonia,C_xH_y fragments,benzene,toluene,and phenol were found to be the primary products of particle decomposition,which didn’t change with the location of particle sample point.The employment of DOC increased the activation energy for particle oxidation and resulted in a higher peak temperature and lower mass loss within the first-stage.Moreover,the C=O stretching bands of aldehyde and ketone at 1771 cm-1 was only detected without a DOC,while the N02 peak at 1634 cm-1 was solely noticed with the presence of DOC.Compared to the first-stage pyrolysis products,more polycyclic aromatic hydrocarbons and less C_xH_y fragments were seen in the second-stage.展开更多
Formaldehyde（HCHO）is carcinogenic and teratogenic,and is therefore a serious danger to human health.It also adversely affects air quality.Catalytic oxidation is an efficient technique for removing HCHO.The developme...Formaldehyde（HCHO）is carcinogenic and teratogenic,and is therefore a serious danger to human health.It also adversely affects air quality.Catalytic oxidation is an efficient technique for removing HCHO.The development of highly efficient and stable catalysts that can completely convert HCHO at low temperatures,even room temperature,is important.Supported Pt and Pd catalysts can completely convert HCHO at room temperature,but their industrial applications are limited because they are expensive.The catalytic activities in HCHO oxidation of transition-metal oxide catalysts such as manganese and cobalt oxides with unusual morphologies are better than those of traditional MnO2,Co3O4,or other metal oxides.This is attributed to their specific structures,high specific surface areas,and other factors such as active phase,reducibility,and amount of surface active oxygens.Such catalysts with various morphologies have great potential and can also be used as catalyst supports.The loading of relatively cheap Ag or Au on transition-metal oxides with special morphologies potentially improves the catalytic activity in HCHO removal at room temperature.The preparation and development of new nanocatalysts with various morphologies and structures is important for HCHO removal.In this paper,research progress on precious-metal and transition-metal oxide catalyst systems for HCHO oxidation is reviewed; topics such as oxidation properties,structure–activity relationships,and factors influencing the catalytic activity and reaction mechanism are discussed.Future prospects and directions for the development of such catalysts are also covered.展开更多
Low‐temperature CO oxidation is important for both fundamental studies and practical applica‐tions. Supported gold catalysts are generally regarded as the most active catalysts for low‐temperature CO oxidation. The...Low‐temperature CO oxidation is important for both fundamental studies and practical applica‐tions. Supported gold catalysts are generally regarded as the most active catalysts for low‐temperature CO oxidation. The active sites are traditionally believed to be Au nanoclusters or nanoparticles in the size range of 0.5–5 nm. Only in the last few years have single‐atom Au catalysts been proved to be active for CO oxidation. Recent advances in both experimental and theoretical studies on single‐atom Au catalysts unambiguously demonstrated that when dispersed on suitable oxide supports the Au single atoms can be extremely active for CO oxidation. In this mini‐review, recent advances in the development of Au single‐atom catalysts are discussed, with the aim of illus‐trating their unique catalytic features during CO oxidation.展开更多
The catalytic wet air oxidation of aniline over Ru catalysts supported on modified Ti 2 （Ti 2, Ti0.9Ce0.1O2, Ti0.9Zr0.1O2） is investigated. A series of characterization techniques are conducted to deter...The catalytic wet air oxidation of aniline over Ru catalysts supported on modified Ti 2 （Ti 2, Ti0.9Ce0.1O2, Ti0.9Zr0.1O2） is investigated. A series of characterization techniques are conducted to determine the relationship between the physico-chemical properties and the catalytic performance. As a result of the good metal dispersion and large number of surface oxygen species, the Ru/Ti0.9 Zr0.1O2 catalyst presents the best catalytic activity among the tested samples. The effects of the operating conditions on the reaction are investigated and the optimal reaction conditions are determined. Based on the relationship between the by-products concentration and the reaction time, the reaction path for the catalytic oxidation of aniline is established. Carbonaceous deposits on the surface of the support are known to be the main reason for catalyst deactivation. The catalysts maintain a constant activity even after three consecutive cycles.展开更多
Polycrystalline SnO2 fine powder consisting of nano-particles （SnO2-NP）, SnO2 nano-sheets （SnO2-NS）, and SnO2 containing both nano-rods and nano-particles （SnO2-NR＋NP） were prepared and used for CO oxidation. S...Polycrystalline SnO2 fine powder consisting of nano-particles （SnO2-NP）, SnO2 nano-sheets （SnO2-NS）, and SnO2 containing both nano-rods and nano-particles （SnO2-NR＋NP） were prepared and used for CO oxidation. SnO2-NS possesses a mesoporous structure and has a higher surface area, larger pore volume, and more active species than SnO2-NP, and shows improved activity. In contrast, although SnO2-NR＋NP has only a slightly higher surface area and pore volume, and slightly more active surface oxygen species than SnO2-NP, it has more exposed active （110） facets, which is the reason for its improved oxidation activity. Water vapor has only a reversible and weak influence on SnO2-NS, therefore it is a potential catalyst for emission control processes.展开更多
Water oxidation, as a mandatory reaction of solar fuels conversion systems, requires the use of light absorbers with electronic properties that are well matched with those of the multi-electron catalyst in order to ac...Water oxidation, as a mandatory reaction of solar fuels conversion systems, requires the use of light absorbers with electronic properties that are well matched with those of the multi-electron catalyst in order to achieve high efficiency. Molecular light absorbers offer flexibility in fine tuning of orbital energetics,and metal oxide nanoparticles have emerged as robust oxygen evolving catalysts. Hence, these material choices offer a promising approach for the development of photocatalytic systems for water oxidation.However, efficient charge transfer coupling of molecular light absorbers and metal oxide nanoparticle catalysts has proven a challenge. Recent new approaches toward the efficient coupling of these components based on synthetic design improvements combined with direct spectroscopic observation and kinetic evaluation of charge transfer processes are discussed.展开更多
The effects of a diesel oxidation catalytic （DOC） converter on diesel engine emissions were investigated on a diesel bench at various loads for two steady-state speeds using diesel fuel and B20. The DOC was very eff...The effects of a diesel oxidation catalytic （DOC） converter on diesel engine emissions were investigated on a diesel bench at various loads for two steady-state speeds using diesel fuel and B20. The DOC was very effective in hydrocarbon （HC） and CO oxidation. Approximately 90%-95% reduction in CO and 36%-70% reduction in HC were realized using the DOC. Special attention was focused on the effects of the DOC on elemental carbon （EC） and organic carbon （OC） fractions in fine particles （PM2.5） emitted from the diesel engine. The carbonaceous compositions of PM2.5 were analyzed by the method of thermal/optical reflectance （TOR）. The results showed that total carbon （TC）, OC and EC emissions for PM2.5 from diesel fuel were generally reduced by the DOC. For diesel fuel, TC emissions decreased 22%-32% after the DOC depending on operating modes. The decrease in TC was attributed to 35%-97% decrease in OC and 3%-65% decrease in EC emissions. At low load, a significant increase in the OC/EC ratio of PMz.5 was observed after the DOC. The effect of the DOC on the carbonaceous compositions in PM2.5 from B20 showed different trends compared to diesel fuel. At low load, a slight increase in EC emissions and a significant decrease in OC/EC ratio of PM2.5 after DOC were observed for B20.展开更多
CePO4 （in particular, monoclinic CePO4） has been rarely used to make supported catalysts. Herein, monoclinic CeP04 nanoparticles were prepared by calcining hexagonal CePO4 nanomds （prepared by precipitation） in ai...CePO4 （in particular, monoclinic CePO4） has been rarely used to make supported catalysts. Herein, monoclinic CeP04 nanoparticles were prepared by calcining hexagonal CePO4 nanomds （prepared by precipitation） in air at 900 ℃. Monoclinic CePO4 nanowires were prepared by calcining hexagonal CePO4 nanowires （prepared by hydrothermal synthesis at 150 ℃） in air at 900 ℃. Both monoclinic CePO4 materials were used to support Rh2O3 by impregnation using Rh（NO3）3 as a precursor （followed by calcination）. The catalytic performance of Rh2O3/monoclinic CePO4 composite materials in N2O decomposition and CO oxidation was investigated. It was found that Rh2O3 supported on monoclinic CePO4 nanowims was much more active than Rh2O3 supported on monoclinic CePO4 nanoparticles. The stability of catalysts as a function of reaction time on stream was studied in both reactions. The influence of co-fed CO2, O2, and H2O on the catalytic activity in N20 decomposition was also studied. These catalysts were characterized by employing N2 adsorption-desorption, ICP-OES, XRD, TEM, XPS, H2-TPR, O2-TPD, and CO2-TPD. The correlation between physicochemical properties and catalytic properties was discussed.展开更多
A series of K-promoted Pt/Al2O3 catalysts were tested for CO oxidation. It was found that the addition of K significantly enhanced the activity. A detailed kinetic study showed that the activation energies of the K-co...A series of K-promoted Pt/Al2O3 catalysts were tested for CO oxidation. It was found that the addition of K significantly enhanced the activity. A detailed kinetic study showed that the activation energies of the K-containing catalysts were lower than those of the K-free ones, particularly for catalysts with high Pt contents （51.6 k）/mol for 0.42K-2.0Pt/Al2O3 and 6：3.6 kJ/mol for 2.0Pt/Al2O3 ）. The CO reaction orders were higher for the K-containing catalysts （about -0.2） than for the K-free ones （about -0.5）, with the former having much lower equilibrium constants for CO adsorption than the latter. In situ Fourier-transform infrared spectroscopy showed that surface CO desorption from the 0.42K-2.0Pt/Al2O3 catalyst was easier than from 2.0Pt/Al2O3. The promoting effect of K was therefore caused by weakening of the interactions between CO and surface Pt atoms. This decreased coverage of the catalyst with CO and facilitated competitive O2 chemisorption on the Pt surface, and significantly lowered the reaction barrier between chemisorbed CO and O2 species.展开更多
The nanometer CeO2 powder was prepared by the method of microwave-assisted heating hydrolysis,and the nanometer CeO2-supported or ordinary CeO2-supported vanadia catalysts with different vanadium loadings(atomic ratio...The nanometer CeO2 powder was prepared by the method of microwave-assisted heating hydrolysis,and the nanometer CeO2-supported or ordinary CeO2-supported vanadia catalysts with different vanadium loadings(atomic ratios:100V/Ce=0.1,1,4,10,and 20) were prepared by an incipient-wetness impregnation method.Spectroscopic techniques(XRD,FT-IR,Raman and UV-Vis DRS) were utilized to characterize the structures of VOx/CeO2 catalysts.The results showed that the structures of CeO2-supported vanadium oxide catalysts de...展开更多
The selective oxidation of n-butane to maleic anhydride (MA) on a vanadium-phosphorus oxide (VPO) catalyst was studied using on-line gas-chromatography combined with mass spectrometry(GC-MS) and transient response tec...The selective oxidation of n-butane to maleic anhydride (MA) on a vanadium-phosphorus oxide (VPO) catalyst was studied using on-line gas-chromatography combined with mass spectrometry(GC-MS) and transient response technique. The reaction intermediates, buterie and furan, were found in the reaction effluent under near industrial feed condition (3% butane+15%O2), while dihydrofuran was detected at high butane concentration (12% butane, 5%O2). Some intermediates of MA decomposition were also identified. Detection of these intermediates shows that the vanadium phosphorus oxides are able to dehydrogenate butane to butene, and butene further to form MA. Based on these observations, a modified scheme of reaction network is proposed. The transient experiments show that butane in the gas phase may directly react with oxygen both on the surface and from the metal oxide lattice, without a proceeding adsorption step. Gas phase oxygen can be adsorbed and transformed to surface lattice oxygen but it can not participate in selective oxidation. Adsorbed oxygen leads to deep oxidation, while lattice oxygen leads to selective oxidation.展开更多
Experiments were conducted in a fixed-bed reactor containing a commercial V2O5/WO3/TiO2 catalyst to investigate mercury oxidation in the presence of HCl and O2. Mercury oxidation was improved significantly in the pres...Experiments were conducted in a fixed-bed reactor containing a commercial V2O5/WO3/TiO2 catalyst to investigate mercury oxidation in the presence of HCl and O2. Mercury oxidation was improved significantly in the presence of HCl and O2, and the Hg^0 oxidation efficiencies decreased slowly as the temperature increased from 200 to 400℃. Upon pretreatment with HCl and O2 at 350℃, the catalyst demonstrated higher catalytic activity for Hg^0 oxidation. Notably,the effect of pretreatment with HCl alone was not obvious. For the catalyst treated with HCl and O2, better performance was observed with lower reaction temperatures. The results showed that both HCl and Hg^0 were first adsorbed onto the catalyst and then reacted with O2 following its adsorption, which indicates that the oxidation of Hg^0 over the commercial catalyst followed the Langmuir–Hinshelwood mechanism. Several characterization techniques, including Hg^0temperature-programmed desorption（Hg-TPD） and X-ray photoelectron spectroscopy（XPS）, were employed in this work. Hg-TPD profiles showed that weakly adsorbed mercury species were converted to strongly bound species in the presence of HCl and O2. XPS patterns indicated that new chemisorbed oxygen species were formed by the adsorption of HCl, which consequently facilitated the oxidation of mercury.展开更多
Several Mo-V-Te-O mixed metal oxides catalysts with different dopant were prepared and used for catalytic oxidation propane to acrolein. It was revealed that the addition of P could greatly improve the performance of ...Several Mo-V-Te-O mixed metal oxides catalysts with different dopant were prepared and used for catalytic oxidation propane to acrolein. It was revealed that the addition of P could greatly improve the performance of the Mo-V-Te-O catalyst. The catalysts were examined by XRD and H2-TPR. The XRD characteristic of the Mo-V-Te-P-O showed that the addition of P could aggrandize the (V0.07Mo0.93)5O14 phase. H2-TPR illuminated that the MoV0.3Te0.23P0.15On catalyst took on the best redox ability.展开更多
Ce_(x)Co_(y)Cuzoxide composite catalysts were prepared by using polyethylene glycol, citrate sol-gel method combined with PMMA template for the oxidation of o-xylene. The catalysts were characterized by the Xray diffr...Ce_(x)Co_(y)Cuzoxide composite catalysts were prepared by using polyethylene glycol, citrate sol-gel method combined with PMMA template for the oxidation of o-xylene. The catalysts were characterized by the Xray diffraction(XRD), H2-temperature programmed reduction(H2-TPR), X-ray photoelectron spectroscopy(XPS) and Fourier transform infrared spectroscopy(FT-IR), etc. The catalytic activity for o-xylene was investigated. The catalytic degradation pathway and mechanism of o-xylene were inferred. The results show that Ce O_(2)is mainly present on the surface of all catalysts. The surface area of Ce_(2)Co1Cu1is up to 77.2 m^(2)/g, and the average pore size is 10.62 nm. It exhibits redox and sufficient Ce^(4+)and Ce^(^(3+)), and reactive oxygen species, and has maximum O-H and C=O in the five catalyst samples. The catalytic activity of Ce2Co1Cu1is the best at low temperature, with the T50and T90values of 235 and 258°C at a space velocity of 32000 h-1, respectively. The o-xylene is oxidized to o-methyl benzaldehyde, and then further oxidized to o-methylbenzoic acid, and finally CO_(2)and H2O are formed.展开更多
Copper-ceria sheets catalysts with different loadings of copper（2 wt.%, 5 wt.% and 10 wt.%） supported on ceria nanosheets were synthesized via a depositioneprecipitation（DP） method. The prepared catalysts were sys...Copper-ceria sheets catalysts with different loadings of copper（2 wt.%, 5 wt.% and 10 wt.%） supported on ceria nanosheets were synthesized via a depositioneprecipitation（DP） method. The prepared catalysts were systematically characterized with various structural and textural detections including X-ray diffraction（XRD）, Raman spectra, transmission electron microscopy（TEM）, X-ray absorption fine structure（XAFS）, and temperature-programmed reduction by hydrogen（H2-TPR）, and tested for the CO oxidation reaction. Notably, the sample containing 5 wt.% of Cu exhibited the best catalytic performance as a result of the highest number of active CuO species on the catalyst surface. Further increase of copper content strongly affects the dispersion of copper and thus leads to the formation of less active bulk CuO phase, which was verified by XRD and H2-TPR analysis. Moreover, on the basis of in-situ diffuse reflectance infrared Fourier transform spectroscopy（in-situ DRIFTS） results, the surface Cu~＋ species, which are derived from the reduction of Cu^（2＋）, are likely to play a crucial role in the catalyzing CO oxidation.Consequently, the superior catalytic performance of the copper-ceria sheets is mainly attributed to the highly dispersed CuOx cluster rather than Cu-[Ox]-Ce structure, while the bulk CuO phase is adverse to the catalytic activity of CO oxidation.展开更多
The aerobic oxidation of glycerol provides an economically viable route to glyceraldehyde, dihydroxyacetone and glyceric acid with versatile applications, for which monometallic Pt, Au and Pd and bimetallic Au-Pt, Au-...The aerobic oxidation of glycerol provides an economically viable route to glyceraldehyde, dihydroxyacetone and glyceric acid with versatile applications, for which monometallic Pt, Au and Pd and bimetallic Au-Pt, Au- Pd and Pt-Pd catalysts on TiO2 were examined under base-free conditions. Pt exhibited a superior activity relative to Pd, and Au-Pd and Pt-Pd while Au was essentially inactive. The presence of Au on the Au-Pt/TiO2 catalysts led to their higher activities （normalized per Pt atom） in a wide range of Au/Pt atomic ratios （i.e. 1/3-7/1 ）, and the one with the Au/Pt ratio of 3/1 exhibited the highest activity. Such promoting effect is ascribed to the increased electron density on Pt via the electron transfer from Au to Pt, as characterized by the temperature-programmed desorption of CO and infra-red spectroscopy for CO adsorption. Meanwhile, the presence of Au on Au-Pt/TiO2, most like due to the observed electron transfer, changed the product selectivity, and facilitated the oxidation of the secondary hydroxyl groups in glycerol, leading to the favorable formation of dihydroxyacetone over glyceraldehyde and glyceric acid that were derived from the oxidation of the primary hydroxyl groups. The synergetic effect between Au and Pt demonstrates the feasibility in the efficient oxidation of glycerol to the targeted products, for example, by rational tuning of the electronic properties of metal catalysts.展开更多
This study was focused on the influence of active oxygen on the performance of Pt/CeO2 catalysts for CO oxidation. A series of CeO2 supports with different contents of active oxygen were obtained by adding surfactant ...This study was focused on the influence of active oxygen on the performance of Pt/CeO2 catalysts for CO oxidation. A series of CeO2 supports with different contents of active oxygen were obtained by adding surfactant at different synthesis steps. 0.25 wt% Pt was loaded on these CeO2 supports by incipientwetness impregnation methods. The catalysts were characterized by N2 adsorption, X-ray diffraction（XRD）, high-resolution transmission electron microscopy（HRTEM）, H2 temperature-programmed reduction（H2-TPR）, dynamic oxygen storage capacity（DOSC） and in-situ DRIFTS technologies. For S-f supports, the surfactant was added into the solution before spray-drying in the synthesis process, which facilitates more active oxygen formation on the surface of CeO2. After loading Pt, the more active oxygen on CeO2 contributes to dispersing Pt species and enhancing the CO oxidation activity. As for the aged samples,Pt-R-h shows the highest activity above 190 ℃ because of the presence of more partly oxidized Pt^（δ＋） species. Thus the activity is also influenced by the states of Pt and the Pt^（δ＋） species may contribute to the high activity at elevated temperature.展开更多
基金supported by the National Natural Science Foundation of China(21506194,21676255)the Provincial Natural Science Foundation of Zhejiang Province(LY16B070011)the Commission of Science and Technology of Zhejiang Province(2017C33106,2017C03007)~~
文摘Platinum/cerium-zirconium-sulfate（Pt/Ce-Zr-SO_4^（2-）） catalysts were prepared by wetness impregnation.Catalytic activities were evaluated from the combustion of propene and CO.Sulfate（SO_4^（2-））addition improved the catalytic activity significantly.When using Pt/Ce-Zr-SO_4^（2-） with 10 wt%SO_4^（2-）,the temperature for 90%conversion of propene and CO decreased by 75℃ compared with Pt/Ce-Zr.The conversion exceeded 95%at 240℃ even after 0.02%sulfur dioxide poisoning for 20 h.Temperature-programmed desorption of CO and X-ray photoelectron spectroscopy analyses revealed an improvement in Pt dispersion onto the Ce-Zr-SO_4^（2-） support,and the increased number of Pt particles built up more Pt^（-）-（SO_4^（2-））^（-） couples,which resulted in excellent activity.The increased total acidity and new Bronsted acid sites on the surface provided the Pt/Ce-Zr-SO_4^（2-） with good sulfur resistance.
基金supported by the National Natural Science Foundation of China (No. 50876013)
文摘Two continuously regenerating diesel particulate filter （CRDPF） with different configurations and one particles oxidation catalyst （POC） were employed to perform experiments in a controlled laboratory setting to evaluate their effects on NO2, smoke and particle number emissions. The results showed that the application of the after-treatments increased the emission ratios of NO2/NOx significantly. The results of smoke emissions and particle number （PN） emissions indicated that both CRDPFs had sufficient capacity to remove more than 90% of total particulate matter （PM） and more than 97% of solid particles. However, the POC was able to remove the organic components of total PM, and only partially to remove the carbonaceous particles with size less than 30 nm. The negligible effects of POC on larger particles were observed due to its honeycomb structure leads to an inadequate residence time to oxidize the solid particles or trap them. The particles removal efficiencies of CRDPFs had high degree of correlations with the emission ratio of NO2/NOx. The PN emission results from two CRDPFs indicated that more NO2 generating in diesel oxidation catalyst section could obtain the higher removal efficiency of solid particles. However this also increased the risk of NO2 exposure in atmosphere.
文摘A molecular [Ru(bda)]-type(bda = 2,2’-bipyridine-6,6’-dicarboxylate) water oxidation catalyst with 4-vinylpyridine as the axial ligand(Complex 1) was immobilized or co-immobilized with 1-(trifluoromethyl)-4-vinylbenzene(3 F) or styrene(St) blocking units on the surface of glassy carbon(GC) electrodes by electrochemical polymerization, in order to prepare the corresponding poly-1@GC, poly-1+P3 F@GC, and poly-1+PSt@GC functional electrodes. Kinetic measurements of the electrode surface reaction revealed that [Ru(bda)] triggers the O–O bond formation via(1) the radical coupling interaction between the two metallo-oxyl radicals(I2 M) in the homo-coupling polymer(poly-1), and(2) the water nucleophilic attack(WNA) pathway in poly-1+P3 F and poly-1+PSt copolymers. The comparison of the three electrodes revealed that the second coordination sphere of the water oxidation catalysts plays vital roles in stabilizing their reaction intermediates, tuning the O–O bond formation pathways and improving the water oxidation reaction kinetics without changing the first coordination structures.
基金supported by the Open Research Program of State Key Laboratory of Engine Combustion(No.K2018-11)the National Nature Science Foundation of China(No.51806015)the National Engineering Laboratory for Mobile Source Emission Control Technology(No.NELMS2018A17)
文摘Decomposition mass loss and pyrolysis products analyses of particles sampled at various locations along the tailpipe of a Euro-IV diesel engine were performed using a thermo gravimetry in conjunction with Fourier transformation infrared spectrometrymass spectrum.Diesel particles were collected at the same location with and without diesel oxidation catalyst(DOC)mounted on the test engine separately.The three poles in thermal gravity-differential thermal gravity images suggested that the decomposition process of diesel particles could be divided into three stages which correspond to the decompositions of lower boiling substances,higher boiling substances and soot respectively.It is noticed that no matter whether DOC was mounted or not,the further the particles were sampled away from the engine block,the lower the peak temperatures and the heavier the mass losses within the first two stages,which indicated that the soluble organic fraction in the particle samples increased and therefore lowering the activation energy of thermal decomposition.Hydroxyl,ammonia,C_xH_y fragments,benzene,toluene,and phenol were found to be the primary products of particle decomposition,which didn’t change with the location of particle sample point.The employment of DOC increased the activation energy for particle oxidation and resulted in a higher peak temperature and lower mass loss within the first-stage.Moreover,the C=O stretching bands of aldehyde and ketone at 1771 cm-1 was only detected without a DOC,while the N02 peak at 1634 cm-1 was solely noticed with the presence of DOC.Compared to the first-stage pyrolysis products,more polycyclic aromatic hydrocarbons and less C_xH_y fragments were seen in the second-stage.
基金supported by the National Natural Science Foundation of China(21325731,51478241,21221004)~~
文摘Formaldehyde（HCHO）is carcinogenic and teratogenic,and is therefore a serious danger to human health.It also adversely affects air quality.Catalytic oxidation is an efficient technique for removing HCHO.The development of highly efficient and stable catalysts that can completely convert HCHO at low temperatures,even room temperature,is important.Supported Pt and Pd catalysts can completely convert HCHO at room temperature,but their industrial applications are limited because they are expensive.The catalytic activities in HCHO oxidation of transition-metal oxide catalysts such as manganese and cobalt oxides with unusual morphologies are better than those of traditional MnO2,Co3O4,or other metal oxides.This is attributed to their specific structures,high specific surface areas,and other factors such as active phase,reducibility,and amount of surface active oxygens.Such catalysts with various morphologies have great potential and can also be used as catalyst supports.The loading of relatively cheap Ag or Au on transition-metal oxides with special morphologies potentially improves the catalytic activity in HCHO removal at room temperature.The preparation and development of new nanocatalysts with various morphologies and structures is important for HCHO removal.In this paper,research progress on precious-metal and transition-metal oxide catalyst systems for HCHO oxidation is reviewed; topics such as oxidation properties,structure–activity relationships,and factors influencing the catalytic activity and reaction mechanism are discussed.Future prospects and directions for the development of such catalysts are also covered.
文摘Low‐temperature CO oxidation is important for both fundamental studies and practical applica‐tions. Supported gold catalysts are generally regarded as the most active catalysts for low‐temperature CO oxidation. The active sites are traditionally believed to be Au nanoclusters or nanoparticles in the size range of 0.5–5 nm. Only in the last few years have single‐atom Au catalysts been proved to be active for CO oxidation. Recent advances in both experimental and theoretical studies on single‐atom Au catalysts unambiguously demonstrated that when dispersed on suitable oxide supports the Au single atoms can be extremely active for CO oxidation. In this mini‐review, recent advances in the development of Au single‐atom catalysts are discussed, with the aim of illus‐trating their unique catalytic features during CO oxidation.
基金supported by the National Natural Science Foundation of China(21333003,21577034)National Basic Research Program of China(2013CB933200)+1 种基金National High Technology Research and Development Program of China(2015AA034603)the Fundamental Research Funds for the Central Universities(WJ1514020)~~
文摘The catalytic wet air oxidation of aniline over Ru catalysts supported on modified Ti 2 （Ti 2, Ti0.9Ce0.1O2, Ti0.9Zr0.1O2） is investigated. A series of characterization techniques are conducted to determine the relationship between the physico-chemical properties and the catalytic performance. As a result of the good metal dispersion and large number of surface oxygen species, the Ru/Ti0.9 Zr0.1O2 catalyst presents the best catalytic activity among the tested samples. The effects of the operating conditions on the reaction are investigated and the optimal reaction conditions are determined. Based on the relationship between the by-products concentration and the reaction time, the reaction path for the catalytic oxidation of aniline is established. Carbonaceous deposits on the surface of the support are known to be the main reason for catalyst deactivation. The catalysts maintain a constant activity even after three consecutive cycles.
基金supported by the National Natural Science Foundation of China (21263015)the Education Department of Jiangxi Province (KJLD14005)the Natural Science Foundation of Jiangxi Province(20151BBE50006,20122BAB203009)~~
文摘Polycrystalline SnO2 fine powder consisting of nano-particles （SnO2-NP）, SnO2 nano-sheets （SnO2-NS）, and SnO2 containing both nano-rods and nano-particles （SnO2-NR＋NP） were prepared and used for CO oxidation. SnO2-NS possesses a mesoporous structure and has a higher surface area, larger pore volume, and more active species than SnO2-NP, and shows improved activity. In contrast, although SnO2-NR＋NP has only a slightly higher surface area and pore volume, and slightly more active surface oxygen species than SnO2-NP, it has more exposed active （110） facets, which is the reason for its improved oxidation activity. Water vapor has only a reversible and weak influence on SnO2-NS, therefore it is a potential catalyst for emission control processes.
基金supported by the Director,Office of Science,Office of Basic Energy Sciences,Division of Chemical,Geological and Biosciences of the U.S.Department of Energy under Contract No.DE-AC02-05CH11231
文摘Water oxidation, as a mandatory reaction of solar fuels conversion systems, requires the use of light absorbers with electronic properties that are well matched with those of the multi-electron catalyst in order to achieve high efficiency. Molecular light absorbers offer flexibility in fine tuning of orbital energetics,and metal oxide nanoparticles have emerged as robust oxygen evolving catalysts. Hence, these material choices offer a promising approach for the development of photocatalytic systems for water oxidation.However, efficient charge transfer coupling of molecular light absorbers and metal oxide nanoparticle catalysts has proven a challenge. Recent new approaches toward the efficient coupling of these components based on synthetic design improvements combined with direct spectroscopic observation and kinetic evaluation of charge transfer processes are discussed.
基金This work was financially supported by the National Science Fund for Distinguished Young Scholars of China （No. 20625722） and the National Natural Science Foundation of China （Grant No. 20807025）. We would also like to thank Prof. Yunshan Ge from Beijing Institute of Technology for the significant in-kind support on the engine test and thank Mr. Charles N. Freed for useful comments on this work.
文摘The effects of a diesel oxidation catalytic （DOC） converter on diesel engine emissions were investigated on a diesel bench at various loads for two steady-state speeds using diesel fuel and B20. The DOC was very effective in hydrocarbon （HC） and CO oxidation. Approximately 90%-95% reduction in CO and 36%-70% reduction in HC were realized using the DOC. Special attention was focused on the effects of the DOC on elemental carbon （EC） and organic carbon （OC） fractions in fine particles （PM2.5） emitted from the diesel engine. The carbonaceous compositions of PM2.5 were analyzed by the method of thermal/optical reflectance （TOR）. The results showed that total carbon （TC）, OC and EC emissions for PM2.5 from diesel fuel were generally reduced by the DOC. For diesel fuel, TC emissions decreased 22%-32% after the DOC depending on operating modes. The decrease in TC was attributed to 35%-97% decrease in OC and 3%-65% decrease in EC emissions. At low load, a significant increase in the OC/EC ratio of PMz.5 was observed after the DOC. The effect of the DOC on the carbonaceous compositions in PM2.5 from B20 showed different trends compared to diesel fuel. At low load, a slight increase in EC emissions and a significant decrease in OC/EC ratio of PM2.5 after DOC were observed for B20.
基金Supported by the National Natural Science Foundation of China(21177028,21477022)
文摘CePO4 （in particular, monoclinic CePO4） has been rarely used to make supported catalysts. Herein, monoclinic CeP04 nanoparticles were prepared by calcining hexagonal CePO4 nanomds （prepared by precipitation） in air at 900 ℃. Monoclinic CePO4 nanowires were prepared by calcining hexagonal CePO4 nanowires （prepared by hydrothermal synthesis at 150 ℃） in air at 900 ℃. Both monoclinic CePO4 materials were used to support Rh2O3 by impregnation using Rh（NO3）3 as a precursor （followed by calcination）. The catalytic performance of Rh2O3/monoclinic CePO4 composite materials in N2O decomposition and CO oxidation was investigated. It was found that Rh2O3 supported on monoclinic CePO4 nanowims was much more active than Rh2O3 supported on monoclinic CePO4 nanoparticles. The stability of catalysts as a function of reaction time on stream was studied in both reactions. The influence of co-fed CO2, O2, and H2O on the catalytic activity in N20 decomposition was also studied. These catalysts were characterized by employing N2 adsorption-desorption, ICP-OES, XRD, TEM, XPS, H2-TPR, O2-TPD, and CO2-TPD. The correlation between physicochemical properties and catalytic properties was discussed.
基金financially supported by the National Natural Science Foundation of China(21173195)~~
文摘A series of K-promoted Pt/Al2O3 catalysts were tested for CO oxidation. It was found that the addition of K significantly enhanced the activity. A detailed kinetic study showed that the activation energies of the K-containing catalysts were lower than those of the K-free ones, particularly for catalysts with high Pt contents （51.6 k）/mol for 0.42K-2.0Pt/Al2O3 and 6：3.6 kJ/mol for 2.0Pt/Al2O3 ）. The CO reaction orders were higher for the K-containing catalysts （about -0.2） than for the K-free ones （about -0.5）, with the former having much lower equilibrium constants for CO adsorption than the latter. In situ Fourier-transform infrared spectroscopy showed that surface CO desorption from the 0.42K-2.0Pt/Al2O3 catalyst was easier than from 2.0Pt/Al2O3. The promoting effect of K was therefore caused by weakening of the interactions between CO and surface Pt atoms. This decreased coverage of the catalyst with CO and facilitated competitive O2 chemisorption on the Pt surface, and significantly lowered the reaction barrier between chemisorbed CO and O2 species.
基金supported by the National Natural Science Foundation of China (20803093,20833011,20525621)the Doctor Select Foundation for the University of State Education Ministry (200804251016)+1 种基金the Beijing Outstanding Ph.D.Thesis Foundation (YB 20091141401)the Hi-Tech Research and Development Program (863) of China (SQ2009AA06Z3488052)
文摘The nanometer CeO2 powder was prepared by the method of microwave-assisted heating hydrolysis,and the nanometer CeO2-supported or ordinary CeO2-supported vanadia catalysts with different vanadium loadings(atomic ratios:100V/Ce=0.1,1,4,10,and 20) were prepared by an incipient-wetness impregnation method.Spectroscopic techniques(XRD,FT-IR,Raman and UV-Vis DRS) were utilized to characterize the structures of VOx/CeO2 catalysts.The results showed that the structures of CeO2-supported vanadium oxide catalysts de...
基金Supported by the National Natural Science Foundation of China (No. 29792073-3).
文摘The selective oxidation of n-butane to maleic anhydride (MA) on a vanadium-phosphorus oxide (VPO) catalyst was studied using on-line gas-chromatography combined with mass spectrometry(GC-MS) and transient response technique. The reaction intermediates, buterie and furan, were found in the reaction effluent under near industrial feed condition (3% butane+15%O2), while dihydrofuran was detected at high butane concentration (12% butane, 5%O2). Some intermediates of MA decomposition were also identified. Detection of these intermediates shows that the vanadium phosphorus oxides are able to dehydrogenate butane to butene, and butene further to form MA. Based on these observations, a modified scheme of reaction network is proposed. The transient experiments show that butane in the gas phase may directly react with oxygen both on the surface and from the metal oxide lattice, without a proceeding adsorption step. Gas phase oxygen can be adsorbed and transformed to surface lattice oxygen but it can not participate in selective oxidation. Adsorbed oxygen leads to deep oxidation, while lattice oxygen leads to selective oxidation.
基金supported by the National Basic Research Program(973)of China(No.2013CB430005)the Special Research Funding for Public Benefit Industries from National Ministry of Environmental Protection(No.201309018)the National Hi-Tech Research and Development Program(863)of China(No.2013AA065404)
文摘Experiments were conducted in a fixed-bed reactor containing a commercial V2O5/WO3/TiO2 catalyst to investigate mercury oxidation in the presence of HCl and O2. Mercury oxidation was improved significantly in the presence of HCl and O2, and the Hg^0 oxidation efficiencies decreased slowly as the temperature increased from 200 to 400℃. Upon pretreatment with HCl and O2 at 350℃, the catalyst demonstrated higher catalytic activity for Hg^0 oxidation. Notably,the effect of pretreatment with HCl alone was not obvious. For the catalyst treated with HCl and O2, better performance was observed with lower reaction temperatures. The results showed that both HCl and Hg^0 were first adsorbed onto the catalyst and then reacted with O2 following its adsorption, which indicates that the oxidation of Hg^0 over the commercial catalyst followed the Langmuir–Hinshelwood mechanism. Several characterization techniques, including Hg^0temperature-programmed desorption（Hg-TPD） and X-ray photoelectron spectroscopy（XPS）, were employed in this work. Hg-TPD profiles showed that weakly adsorbed mercury species were converted to strongly bound species in the presence of HCl and O2. XPS patterns indicated that new chemisorbed oxygen species were formed by the adsorption of HCl, which consequently facilitated the oxidation of mercury.
文摘Several Mo-V-Te-O mixed metal oxides catalysts with different dopant were prepared and used for catalytic oxidation propane to acrolein. It was revealed that the addition of P could greatly improve the performance of the Mo-V-Te-O catalyst. The catalysts were examined by XRD and H2-TPR. The XRD characteristic of the Mo-V-Te-P-O showed that the addition of P could aggrandize the (V0.07Mo0.93)5O14 phase. H2-TPR illuminated that the MoV0.3Te0.23P0.15On catalyst took on the best redox ability.
基金Project supported by the Zhejiang Provincial Natural Science Foundation of China (LY20E080003)。
文摘Ce_(x)Co_(y)Cuzoxide composite catalysts were prepared by using polyethylene glycol, citrate sol-gel method combined with PMMA template for the oxidation of o-xylene. The catalysts were characterized by the Xray diffraction(XRD), H2-temperature programmed reduction(H2-TPR), X-ray photoelectron spectroscopy(XPS) and Fourier transform infrared spectroscopy(FT-IR), etc. The catalytic activity for o-xylene was investigated. The catalytic degradation pathway and mechanism of o-xylene were inferred. The results show that Ce O_(2)is mainly present on the surface of all catalysts. The surface area of Ce_(2)Co1Cu1is up to 77.2 m^(2)/g, and the average pore size is 10.62 nm. It exhibits redox and sufficient Ce^(4+)and Ce^(^(3+)), and reactive oxygen species, and has maximum O-H and C=O in the five catalyst samples. The catalytic activity of Ce2Co1Cu1is the best at low temperature, with the T50and T90values of 235 and 258°C at a space velocity of 32000 h-1, respectively. The o-xylene is oxidized to o-methyl benzaldehyde, and then further oxidized to o-methylbenzoic acid, and finally CO_(2)and H2O are formed.
基金Project supported by the National Natural Science Foundation of China(21301107,21501109)the Excellent Young Scientists Fund from NSFC(21622106)+3 种基金the Taishan Scholar Project of Shandong Province of China,China Postdoctoral Science Foundation(2014M551891,2015T80706)Doctoral Funding of Shandong Province of China(BS2014CL008)Specialized Research Fund for the Doctoral Program of Higher Education(20130131120009)Postdoctoral Innovation Project Foundation of Shandong Province(201301008)
文摘Copper-ceria sheets catalysts with different loadings of copper（2 wt.%, 5 wt.% and 10 wt.%） supported on ceria nanosheets were synthesized via a depositioneprecipitation（DP） method. The prepared catalysts were systematically characterized with various structural and textural detections including X-ray diffraction（XRD）, Raman spectra, transmission electron microscopy（TEM）, X-ray absorption fine structure（XAFS）, and temperature-programmed reduction by hydrogen（H2-TPR）, and tested for the CO oxidation reaction. Notably, the sample containing 5 wt.% of Cu exhibited the best catalytic performance as a result of the highest number of active CuO species on the catalyst surface. Further increase of copper content strongly affects the dispersion of copper and thus leads to the formation of less active bulk CuO phase, which was verified by XRD and H2-TPR analysis. Moreover, on the basis of in-situ diffuse reflectance infrared Fourier transform spectroscopy（in-situ DRIFTS） results, the surface Cu~＋ species, which are derived from the reduction of Cu^（2＋）, are likely to play a crucial role in the catalyzing CO oxidation.Consequently, the superior catalytic performance of the copper-ceria sheets is mainly attributed to the highly dispersed CuOx cluster rather than Cu-[Ox]-Ce structure, while the bulk CuO phase is adverse to the catalytic activity of CO oxidation.
基金supported by the National Basic Research Program of China (2011CB201400 and 2011CB808700)the National Natural Science Foundation of China (21373019, 21173008 and 21433001)
文摘The aerobic oxidation of glycerol provides an economically viable route to glyceraldehyde, dihydroxyacetone and glyceric acid with versatile applications, for which monometallic Pt, Au and Pd and bimetallic Au-Pt, Au- Pd and Pt-Pd catalysts on TiO2 were examined under base-free conditions. Pt exhibited a superior activity relative to Pd, and Au-Pd and Pt-Pd while Au was essentially inactive. The presence of Au on the Au-Pt/TiO2 catalysts led to their higher activities （normalized per Pt atom） in a wide range of Au/Pt atomic ratios （i.e. 1/3-7/1 ）, and the one with the Au/Pt ratio of 3/1 exhibited the highest activity. Such promoting effect is ascribed to the increased electron density on Pt via the electron transfer from Au to Pt, as characterized by the temperature-programmed desorption of CO and infra-red spectroscopy for CO adsorption. Meanwhile, the presence of Au on Au-Pt/TiO2, most like due to the observed electron transfer, changed the product selectivity, and facilitated the oxidation of the secondary hydroxyl groups in glycerol, leading to the favorable formation of dihydroxyacetone over glyceraldehyde and glyceric acid that were derived from the oxidation of the primary hydroxyl groups. The synergetic effect between Au and Pt demonstrates the feasibility in the efficient oxidation of glycerol to the targeted products, for example, by rational tuning of the electronic properties of metal catalysts.
基金Project supported by the National key research and development program(2016YFC0204901)the National Natural Science Foundation of China(21576207)+1 种基金the Introduction Of Talent and Technology Cooperation Plan Of Tianjin(14RCGFGX00849)GM Global Research&Development(GAC 1539)
文摘This study was focused on the influence of active oxygen on the performance of Pt/CeO2 catalysts for CO oxidation. A series of CeO2 supports with different contents of active oxygen were obtained by adding surfactant at different synthesis steps. 0.25 wt% Pt was loaded on these CeO2 supports by incipientwetness impregnation methods. The catalysts were characterized by N2 adsorption, X-ray diffraction（XRD）, high-resolution transmission electron microscopy（HRTEM）, H2 temperature-programmed reduction（H2-TPR）, dynamic oxygen storage capacity（DOSC） and in-situ DRIFTS technologies. For S-f supports, the surfactant was added into the solution before spray-drying in the synthesis process, which facilitates more active oxygen formation on the surface of CeO2. After loading Pt, the more active oxygen on CeO2 contributes to dispersing Pt species and enhancing the CO oxidation activity. As for the aged samples,Pt-R-h shows the highest activity above 190 ℃ because of the presence of more partly oxidized Pt^（δ＋） species. Thus the activity is also influenced by the states of Pt and the Pt^（δ＋） species may contribute to the high activity at elevated temperature.
