Against the backdrop of global energy and environmental crises,the technology of CO_(2)hydrogenation to produce methanol is garnering widespread attention as an innovative carbon capture and utilization solution.Bimet...Against the backdrop of global energy and environmental crises,the technology of CO_(2)hydrogenation to produce methanol is garnering widespread attention as an innovative carbon capture and utilization solution.Bimetallic oxide catalysts have emerged as the most promising research subject in the field due to their exceptional catalytic performance and stability.The performance of bimetallic oxide catalysts is influenced by multiple factors,including the selection of carrier materials,the addition of promoters,and the synthesis process.Different types of bimetallic oxide catalysts exhibit significant differences in microstructure,surface active sites,and electronic structure,which directly determine the yield and selectivity of methanol.Although bimetallic oxide catalysts offer significant advantages over traditional copper-based catalysts,they still encounter challenges related to activity and cost.In order to enhance catalyst performance,future investigations must delve into microstructure control,surface modification,and reaction kinetics.展开更多
The elimination of pollutants from diesel exhaust has received widespread research attention as they cause serious air pollution and pose a threat to human health.Catalytic post-treatment technology is one of the most...The elimination of pollutants from diesel exhaust has received widespread research attention as they cause serious air pollution and pose a threat to human health.Catalytic post-treatment technology is one of the most effective and universal technologies to treat diesel exhaust pollutants.The design and development of efficient and low-cost catalysts is the key factor to realize the wide application of catalytic post-treatment technology.Cerium(Ce)-based oxides with specific morphologies are widely used to eliminate pollutants in diesel vehicle exhaust due to their unique physical and chemical properties,such as high catalytic activity,low cost and non-toxicity.In this review,the preparation methods of Cebased oxide materials with specific morphologies,such as nanoparticles,nanocubes,nanorods,nanofibers,and multi-stage pores,are introduced in detail,and the research progress on using these catalysts for the removal of carbon monoxide,hydrocarbons,soot particles,nitrogen oxides,and other pollutants from diesel exhaust is reviewed in detail.Finally,the unresolved issues associated with using Ce-based oxide catalysts with a specific morphology to catalytically remove pollutants from diesel exhaust are highlighted,and future application prospects and development directions are discussed.展开更多
The widespread use of diesel engines results in significant environmental contamination due to emitted pollutants,particularly soot particles.These pollut-ants are detrimental to public health.At present,one of the mo...The widespread use of diesel engines results in significant environmental contamination due to emitted pollutants,particularly soot particles.These pollut-ants are detrimental to public health.At present,one of the most effective ways to remove soot particles is the catalytic diesel particulate filter after-treatment tech-nology,which requires the catalyst to have superior low temperature activity.Compared with cerium oxide which is widely used,cobalt oxide in transition metal oxides has been widely studied in recent years because of its high redox ability and easy to control morphology.This paper elaborates on the influence of modification techniques such as doping,loading,and solid solution on the catalytic performance of cobalt-based catalysts in soot oxidation.Along the same lines,it further reviews the research progress on cobalt-based oxide catalysts with specific dimensional structures and morphologies in soot oxidation.Finally,it provides an outlook on the challenges faced by the theoretical basis and applied research of cobalt-based catalysts in soot oxidation.展开更多
A series of Mn-Cu mixed oxide catalysts were prepared by precipitation method. The catalysts were characterized by N2 adsorp- tion-desorption, H2-TPR and XPS. When the loading ratio of manganese oxides to copper oxide...A series of Mn-Cu mixed oxide catalysts were prepared by precipitation method. The catalysts were characterized by N2 adsorp- tion-desorption, H2-TPR and XPS. When the loading ratio of manganese oxides to copper oxides was 8：2 or 7：3, the catalysts possessed better catalytic activity, and benzene was converted completely at 558 K. Results of H2-TPR showed that the loading of a small amount of copper oxides decreased the reduction temperature of catalysts. Results of XPS showed that the loading of a small amount of copper oxides increased the proportion of manganese and defective oxygen on the surface of catalysts, and stabilized manganese at higher oxidation state. And the catalyst with the loading ratio 7：3 was a little worse than 8：2, since the interaction between manganese oxides and copper oxides is too strong, copper oxides migrate to the surface of catalysts and manganese oxides in excess are immerged.展开更多
This short review paper aims at assembling the present state of the art of the multiuses of metal oxides in heterogeneous catalysis, concerning liquid and gaseous phases of the reactant mixtures on solid catalysts. It...This short review paper aims at assembling the present state of the art of the multiuses of metal oxides in heterogeneous catalysis, concerning liquid and gaseous phases of the reactant mixtures on solid catalysts. It includes the description of the main types of metal oxide catalysts, of their various preparation procedures and of the main reactions catalysed by them (acid-base type, selective and total oxidations, bi-functional catalysis, photocatalysis, biomass treatments, environmental catalysis and some of the numerous industrial applications). Challenges and prospectives are also discussed.展开更多
The electrochemical oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) are fundamental processes in a range of energy conversion devices such as fuel cells and metal–air batteries. ORR and OER both hav...The electrochemical oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) are fundamental processes in a range of energy conversion devices such as fuel cells and metal–air batteries. ORR and OER both have significant activation barriers, which severely limit the overall performance of energy conversion devices that utilize ORR/OER. Meanwhile, ORR is another very important electrochemical reaction involving oxygen that has been widely investigated. ORR occurs in aqueous solutions via two pathways: the direct 4-electron reduction or 2-electron reduction pathways from O_(2) to water(H_2O) or from O_(2) to hydrogen peroxide(H_2O_(2)). Noble metal electrocatalysts are often used to catalyze OER and ORR, despite the fact that noble metal electrocatalysts have certain intrinsic limitations, such as low storage. Thus, it is urgent to develop more active and stable low-cost electrocatalysts, especially for severe environments(e.g., acidic media). Theoretically, an ideal oxygen electrocatalyst should provide adequate binding to oxygen species. Transition metals not belonging to the platinum group metal-based oxides are a low-cost substance that could give a d orbital for oxygen species binding. As a result, transition metal oxides are regarded as a substitute for typical precious metal oxygen electrocatalysts. However, the development of oxide catalysts for oxygen reduction and oxygen evolution reactions still faces significant challenges, e.g., catalytic activity, stability, cost, and reaction mechanism. We discuss the fundamental principles underlying the design of oxide catalysts, including the influence of crystal structure, and electronic structure on their performance. We also discuss the challenges associated with developing oxide catalysts and the potential strategies to overcome these challenges.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
Alkali metal K in exhaust gas has a deactivation effect on NH_(3)-SCR catalysts.In this work,it is discovered that the addition of Ho on CeTi catalyst can remarkably strengthen its K tolerance.The conclusions of Bruna...Alkali metal K in exhaust gas has a deactivation effect on NH_(3)-SCR catalysts.In this work,it is discovered that the addition of Ho on CeTi catalyst can remarkably strengthen its K tolerance.The conclusions of Brunauer-Emmett-Teller(BET),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),NH_(3) temperature programmed desorption(NH_(3)-TPD)and H_(2)temperature programmed reduction(H_(2)-TPR)analyses demonstrate that the enhancement of K resistance mainly originates from its stronger surface acidity and redox capability,the higher concentration of Ce^(3+)species and surface chemisorbed oxygen.In situ DRIFT analysis reveals that the introduction of Ho on CeTi can remarkably improve the adsorption of NH_(3) and NO_(x) species on catalyst surface,accompanied by the intensified reactivity of ad-NH_(3) species,which should also administer to improve the K resistance.展开更多
Binary metal oxide（MnOx-A/TiO2）catalysts were prepared by adding the second metal to manganese oxides supported on titanium dioxide（TiO2）,where,A indicates Fe2O3,WO3,MoO3,and Cr2O3.Their catalytic activity,N2 sele...Binary metal oxide（MnOx-A/TiO2）catalysts were prepared by adding the second metal to manganese oxides supported on titanium dioxide（TiO2）,where,A indicates Fe2O3,WO3,MoO3,and Cr2O3.Their catalytic activity,N2 selectivity,and SO2 poisonous tolerance were investigated.The catalytic performance at low temperatures decreased in the following order：Mn-W/TiO2〉Mn-Fe/TiO2〉Mn-Cr/TiO2〉Mn-Mo/TiO2,whereas the N2 selectivity decreased in the order：Mn-Fe/TiO2〉Mn-W/TiO2〉Mn-Mo/TiO2〉Mn-Cr/TiO2.In the presence of 0.01%SO2 and 6%H2O,the NOx conversions in the presence of Mn-W/TiO2,Mn-Fe/TiO2,or Mn-Mo/TiO2 maintain 98.5%,95.8%and 94.2%, respectively,after 8 h at 120°C at GHSV 12600 h？ 1 .As effective promoters,WO3 and Fe2O3 can increase N2 selectivity and the resistance to SO2 of MnOx/TiO2 significantly.The Fourier transform infrared（FTIR）spectra of NH3 over WO3 show the presence of Lewis acid sites.The results suggest that WO3 is the best promoter of MnOx/TiO2,and Mn-W/TiO2 is one of the most active catalysts for the low temperature selective catalytic reduction of NO with NH3.展开更多
Supported manganese oxide catalysts were prepared by incipient wetness impregnation method for methane catalytic combustion, and effects of the support （Al2O3, SiO2 and TiO2） and Mn loading were investigated. These ...Supported manganese oxide catalysts were prepared by incipient wetness impregnation method for methane catalytic combustion, and effects of the support （Al2O3, SiO2 and TiO2） and Mn loading were investigated. These catalysts were characterized with N2 adsorption, X-ray diffraction, X-ray photoelectron spectroscopy and temperature-programmed reduction techniques. Methane conversion varied in a large range depending on supports or Mn loading. Al2O3 supported 15% Mn catalyst exhibited better activity toward methane catalytic oxidation. The manganese state and oxygen species played an important role in the catalytic performance,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
As one of the most important water pollutants, ammonia nitrogen emissions have increased year by year, which has attracted people＇s attention. Catalytic ozonation technology, which involves production of ·OH rad...As one of the most important water pollutants, ammonia nitrogen emissions have increased year by year, which has attracted people＇s attention. Catalytic ozonation technology, which involves production of ·OH radical with strong oxidation ability, is widely used in the treatment of organic-containing wastewater. In this work, MgO-Co3O4 composite metal oxide catalysts prepared with different fabrication conditions have been systematically evaluated and compared in the catalytic ozonation of ammonia（50 mg/L） in water. In terms of high catalytic activity in ammonia decomposition and high selectivity for gaseous nitrogen, the catalyst with MgO-Co3O4 molar ratio 8：2, calcined at 500°C for 3 hr, was the best one among the catalysts we tested, with an ammonia nitrogen removal rate of 85.2% and gaseous nitrogen selectivity of44.8%. In addition, the reaction mechanism of ozonation oxidative decomposition of ammonia nitrogen in water with the metal oxide catalysts was discussed. Moreover, the effect of coexisting anions on the degradation of ammonia was studied, finding that SO2-4 and HCO-3 could inhibit the catalytic activity while CO2-3 and Br-could promote it. The presence of coexisting cations had very little effect on the catalytic ozonation of ammonia nitrogen. After five successive reuses, the catalyst remained stable in the catalytic ozonation of ammonia.展开更多
Sulphur-containing aromatic nitro compounds were rapidly reduced to the corresponding amines in high yields by employing hydrazine hydrate as a hydrogen donor in the presence of iron oxide hydroxide catalyst. It was w...Sulphur-containing aromatic nitro compounds were rapidly reduced to the corresponding amines in high yields by employing hydrazine hydrate as a hydrogen donor in the presence of iron oxide hydroxide catalyst. It was worth noting that the catalyst exhibited extremely high activity. The reduction could be completed within 20-50 min and the yields were up to 97-99 %.展开更多
A novel molecular probe for identifying properties of supported transition metals and metal oxides catalysts was established.The catalytic mechanism of transition metals was proposed.
The relations between catalytic activities and compositions of the systems Mg_xZn_(1-x)Fe_2O_4, Co_xZn_(1-x)Fe_2O_4, Co_xMg_(1-x)Fe_2O_4, Cd_xZn_(1-x)Fe_2O_4 and Mg_xZn_(1-x)Fe_2O_4·0.17Fe_2O_3 have been studied ...The relations between catalytic activities and compositions of the systems Mg_xZn_(1-x)Fe_2O_4, Co_xZn_(1-x)Fe_2O_4, Co_xMg_(1-x)Fe_2O_4, Cd_xZn_(1-x)Fe_2O_4 and Mg_xZn_(1-x)Fe_2O_4·0.17Fe_2O_3 have been studied by flow differential reactor, XRD, and derivative IR techniques. It has been found that the appropriate normal-inverse spinel combination substantially increases the activity for the title raction. The structure of the active site and the role of the bivalent cation in the title catalyst have been inferred.展开更多
A series of catalysts on the basis of 10 wt.% CuO/y-AI203, 10 wt.% CuO ＋ 10 wt.% Cr2O3/y-AI203 and 15 wt.% MnO2/y -A1203 have been prepared and modified by CeO2 with contents up to 20 wt.%. Physico-chemical propertie...A series of catalysts on the basis of 10 wt.% CuO/y-AI203, 10 wt.% CuO ＋ 10 wt.% Cr2O3/y-AI203 and 15 wt.% MnO2/y -A1203 have been prepared and modified by CeO2 with contents up to 20 wt.%. Physico-chemical properties of the catalysts were determined by the methods of BET Adsorption, XRD, and TPR. Oxidative activity of the catalysts was studied at the temperature range 90-220 ℃and CO concentration of 3 mol.%. Addition of CeO2 led to changes in physico-chemical properties of the catalysts and formation of novel active centres that increased the activity of CuO and Cr203 containing catalysts, but decreased the activity of those, containing MnO2. The catalyst sample containing 10 wt.% CuO and 15 wt.% CeO2 has been shown to be the best one for complete conversion of CO. At the given conditions on this catalyst the complete oxidation of CO to CO2 occurred at 130 ~C during more than 500 h.展开更多
To understand the catalytic conversion of lignin into high-value products,lignin depolymerization was performed using a layered polymetallic oxide(CuMgAlO_(x))catalyst.The effects of the conversion temperature,hydroge...To understand the catalytic conversion of lignin into high-value products,lignin depolymerization was performed using a layered polymetallic oxide(CuMgAlO_(x))catalyst.The effects of the conversion temperature,hydrogen pressure,and reaction time were studied,and the ability of CuMgAlO_(x)to break the C–O bond was evaluated.The CuMgAlO_(x)(Mg/Al=3:1)catalyst contained acidic sites and had a relatively homogeneous elemental distribution with a high pore size and specific surface area.Theβ-O-4 was almost completely converted by disassociating the C–O bond,resulting in yields of 14.74%ethylbenzene,47.58%α-methylphenyl ethanol,and 36.43%phenol.The highest yield of lignin-derived monophenols was 85.16%under reaction conditions of 280℃ and 3 Mpa for 4 h.As the reaction progressed,depolymerization and condensation reactions occurred simultaneously.Higher temperatures(>280℃)and pressures(>3 Mpa)tended to produce solid char.This study establishes guidelines for the high-value application of industrial lignin in the catalytic conversion of polymetallic oxides.展开更多
Metal(oxide)-zeolite bifunctional catalysts have been the subject of considerable attention from researchers in both academic and industry,due to their superior activity and stability in various heterogeneous catalyti...Metal(oxide)-zeolite bifunctional catalysts have been the subject of considerable attention from researchers in both academic and industry,due to their superior activity and stability in various heterogeneous catalytic processes[1–3].Based on the different metal loading sites,these bifunctional catalysts can be categorized as follows:(a)metal species loaded on the outer surface of zeolite crystals,(b)metal species encapsulated within the channels or cavities of zeolites,and(c)metal species incorporated into the zeolite framework(Fig.1).Metal species in type(b)and(c)samples are stabilized by the zeolite frameworks,resulting in excellent thermal and hydrothermal stability during catalytic reactions,especially under harsh conditions,as well as unique shape-selectivity.However,the complex synthesis procedures make large-scale preparation of these catalysts impractical.In contrast,a type(a)sample can be achieved via the simple impregnation;nevertheless,migration of metal species and their aggregation into larger particles often occur during the calcination and reduction processes.展开更多
Catalytic wet air oxidation(CWAO)is one of the most promising technologies for pollution abatement.Developing catalysts with high activity and stability is crucial for the application of the CWAO process.The Mn/Ce com...Catalytic wet air oxidation(CWAO)is one of the most promising technologies for pollution abatement.Developing catalysts with high activity and stability is crucial for the application of the CWAO process.The Mn/Ce com-plex oxide catalysts for CWAO of high concentration phenol-containing wastewater were prepared by coprecipitation.The catalyst preparation conditions were optimized by using an orthogonal layout method and single-factor experimental analysis.The Mn/Ce serial catalysts were characterized by Brunauer-Emmett-Teller(BET)analysis and the metal cation leaching was measured by inductively coupled plasma torch-atomic emission spectrometry(ICP-AES).The results show that the catalysts have high catalytic activities even at a low temperature(80°C)and low oxygen partial pressure(0.5 MPa)in a batch reactor.The metallic ion leaching is comparatively low(Mn<6.577 mg/L and Ce<0.6910 mg/L,respectively)in the CWAO process.The phenol,COD_(Cr),and TOC removal efficiencies in the solution exceed 98.5%using the optimal catalyst(named CSP).The new catalyst would have a promising application in CWAO treatment of high concentration organic wastewater.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
文摘Against the backdrop of global energy and environmental crises,the technology of CO_(2)hydrogenation to produce methanol is garnering widespread attention as an innovative carbon capture and utilization solution.Bimetallic oxide catalysts have emerged as the most promising research subject in the field due to their exceptional catalytic performance and stability.The performance of bimetallic oxide catalysts is influenced by multiple factors,including the selection of carrier materials,the addition of promoters,and the synthesis process.Different types of bimetallic oxide catalysts exhibit significant differences in microstructure,surface active sites,and electronic structure,which directly determine the yield and selectivity of methanol.Although bimetallic oxide catalysts offer significant advantages over traditional copper-based catalysts,they still encounter challenges related to activity and cost.In order to enhance catalyst performance,future investigations must delve into microstructure control,surface modification,and reaction kinetics.
基金Project supported by National Key R&D Program of China(2022YFB3506200,2022YFB3504100)National Natural Science Foundation of China(22372107,22072095,U1908204)+2 种基金Excellent Youth Science Foundation of Liaoning Province(2022-YQ-20)Shenyang Science and Technology Planning Project(22-322-3-28)University Joint Education Project for China-Central and Eastern European Countries(2021097)。
文摘The elimination of pollutants from diesel exhaust has received widespread research attention as they cause serious air pollution and pose a threat to human health.Catalytic post-treatment technology is one of the most effective and universal technologies to treat diesel exhaust pollutants.The design and development of efficient and low-cost catalysts is the key factor to realize the wide application of catalytic post-treatment technology.Cerium(Ce)-based oxides with specific morphologies are widely used to eliminate pollutants in diesel vehicle exhaust due to their unique physical and chemical properties,such as high catalytic activity,low cost and non-toxicity.In this review,the preparation methods of Cebased oxide materials with specific morphologies,such as nanoparticles,nanocubes,nanorods,nanofibers,and multi-stage pores,are introduced in detail,and the research progress on using these catalysts for the removal of carbon monoxide,hydrocarbons,soot particles,nitrogen oxides,and other pollutants from diesel exhaust is reviewed in detail.Finally,the unresolved issues associated with using Ce-based oxide catalysts with a specific morphology to catalytically remove pollutants from diesel exhaust are highlighted,and future application prospects and development directions are discussed.
基金National Natural Science Foundation of China,Grant/Award Number:22406050Top-Notch Personnel Fund of Henan Agricultural University,Grant/Award Number:30501029+2 种基金Natural Science Foundation of Henan Province,Grant/Award Number:232300420293Science and Technology Project of China Tobacco Shaanxi Industrial Co.,Ltd,Grant/Award Number:2024610000340104Postgraduate Education Reform and Quality Improvement Project of Henan Province,Grant/Award Number:YJS2024JD17。
文摘The widespread use of diesel engines results in significant environmental contamination due to emitted pollutants,particularly soot particles.These pollut-ants are detrimental to public health.At present,one of the most effective ways to remove soot particles is the catalytic diesel particulate filter after-treatment tech-nology,which requires the catalyst to have superior low temperature activity.Compared with cerium oxide which is widely used,cobalt oxide in transition metal oxides has been widely studied in recent years because of its high redox ability and easy to control morphology.This paper elaborates on the influence of modification techniques such as doping,loading,and solid solution on the catalytic performance of cobalt-based catalysts in soot oxidation.Along the same lines,it further reviews the research progress on cobalt-based oxide catalysts with specific dimensional structures and morphologies in soot oxidation.Finally,it provides an outlook on the challenges faced by the theoretical basis and applied research of cobalt-based catalysts in soot oxidation.
基金Project supported by National Natural Science Foundation of China (20773090)the National High Technology Research and Development Program of China (863 Program, 2006AA06Z347)the Youth Fund of Sichuan University (2008119)
文摘A series of Mn-Cu mixed oxide catalysts were prepared by precipitation method. The catalysts were characterized by N2 adsorp- tion-desorption, H2-TPR and XPS. When the loading ratio of manganese oxides to copper oxides was 8：2 or 7：3, the catalysts possessed better catalytic activity, and benzene was converted completely at 558 K. Results of H2-TPR showed that the loading of a small amount of copper oxides decreased the reduction temperature of catalysts. Results of XPS showed that the loading of a small amount of copper oxides increased the proportion of manganese and defective oxygen on the surface of catalysts, and stabilized manganese at higher oxidation state. And the catalyst with the loading ratio 7：3 was a little worse than 8：2, since the interaction between manganese oxides and copper oxides is too strong, copper oxides migrate to the surface of catalysts and manganese oxides in excess are immerged.
文摘This short review paper aims at assembling the present state of the art of the multiuses of metal oxides in heterogeneous catalysis, concerning liquid and gaseous phases of the reactant mixtures on solid catalysts. It includes the description of the main types of metal oxide catalysts, of their various preparation procedures and of the main reactions catalysed by them (acid-base type, selective and total oxidations, bi-functional catalysis, photocatalysis, biomass treatments, environmental catalysis and some of the numerous industrial applications). Challenges and prospectives are also discussed.
基金the Natural Science Foundation of China (22005250)National Key R D Program of China (2022YFB2502000)FWO (12ZV320N)。
文摘The electrochemical oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) are fundamental processes in a range of energy conversion devices such as fuel cells and metal–air batteries. ORR and OER both have significant activation barriers, which severely limit the overall performance of energy conversion devices that utilize ORR/OER. Meanwhile, ORR is another very important electrochemical reaction involving oxygen that has been widely investigated. ORR occurs in aqueous solutions via two pathways: the direct 4-electron reduction or 2-electron reduction pathways from O_(2) to water(H_2O) or from O_(2) to hydrogen peroxide(H_2O_(2)). Noble metal electrocatalysts are often used to catalyze OER and ORR, despite the fact that noble metal electrocatalysts have certain intrinsic limitations, such as low storage. Thus, it is urgent to develop more active and stable low-cost electrocatalysts, especially for severe environments(e.g., acidic media). Theoretically, an ideal oxygen electrocatalyst should provide adequate binding to oxygen species. Transition metals not belonging to the platinum group metal-based oxides are a low-cost substance that could give a d orbital for oxygen species binding. As a result, transition metal oxides are regarded as a substitute for typical precious metal oxygen electrocatalysts. However, the development of oxide catalysts for oxygen reduction and oxygen evolution reactions still faces significant challenges, e.g., catalytic activity, stability, cost, and reaction mechanism. We discuss the fundamental principles underlying the design of oxide catalysts, including the influence of crystal structure, and electronic structure on their performance. We also discuss the challenges associated with developing oxide catalysts and the potential strategies to overcome these challenges.
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Project supported by the National Key R&D Program of China(2018YFB0605002)。
文摘Alkali metal K in exhaust gas has a deactivation effect on NH_(3)-SCR catalysts.In this work,it is discovered that the addition of Ho on CeTi catalyst can remarkably strengthen its K tolerance.The conclusions of Brunauer-Emmett-Teller(BET),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),NH_(3) temperature programmed desorption(NH_(3)-TPD)and H_(2)temperature programmed reduction(H_(2)-TPR)analyses demonstrate that the enhancement of K resistance mainly originates from its stronger surface acidity and redox capability,the higher concentration of Ce^(3+)species and surface chemisorbed oxygen.In situ DRIFT analysis reveals that the introduction of Ho on CeTi can remarkably improve the adsorption of NH_(3) and NO_(x) species on catalyst surface,accompanied by the intensified reactivity of ad-NH_(3) species,which should also administer to improve the K resistance.
文摘Binary metal oxide（MnOx-A/TiO2）catalysts were prepared by adding the second metal to manganese oxides supported on titanium dioxide（TiO2）,where,A indicates Fe2O3,WO3,MoO3,and Cr2O3.Their catalytic activity,N2 selectivity,and SO2 poisonous tolerance were investigated.The catalytic performance at low temperatures decreased in the following order：Mn-W/TiO2〉Mn-Fe/TiO2〉Mn-Cr/TiO2〉Mn-Mo/TiO2,whereas the N2 selectivity decreased in the order：Mn-Fe/TiO2〉Mn-W/TiO2〉Mn-Mo/TiO2〉Mn-Cr/TiO2.In the presence of 0.01%SO2 and 6%H2O,the NOx conversions in the presence of Mn-W/TiO2,Mn-Fe/TiO2,or Mn-Mo/TiO2 maintain 98.5%,95.8%and 94.2%, respectively,after 8 h at 120°C at GHSV 12600 h？ 1 .As effective promoters,WO3 and Fe2O3 can increase N2 selectivity and the resistance to SO2 of MnOx/TiO2 significantly.The Fourier transform infrared（FTIR）spectra of NH3 over WO3 show the presence of Lewis acid sites.The results suggest that WO3 is the best promoter of MnOx/TiO2,and Mn-W/TiO2 is one of the most active catalysts for the low temperature selective catalytic reduction of NO with NH3.
基金supported by the New Century Excellent Talent Project of China (NCET-05-0783).
文摘Supported manganese oxide catalysts were prepared by incipient wetness impregnation method for methane catalytic combustion, and effects of the support （Al2O3, SiO2 and TiO2） and Mn loading were investigated. These catalysts were characterized with N2 adsorption, X-ray diffraction, X-ray photoelectron spectroscopy and temperature-programmed reduction techniques. Methane conversion varied in a large range depending on supports or Mn loading. Al2O3 supported 15% Mn catalyst exhibited better activity toward methane catalytic oxidation. The manganese state and oxygen species played an important role in the catalytic performance,
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 the National Natural Science Foundation of China (Nos. 51164014 and 51568023)
文摘As one of the most important water pollutants, ammonia nitrogen emissions have increased year by year, which has attracted people＇s attention. Catalytic ozonation technology, which involves production of ·OH radical with strong oxidation ability, is widely used in the treatment of organic-containing wastewater. In this work, MgO-Co3O4 composite metal oxide catalysts prepared with different fabrication conditions have been systematically evaluated and compared in the catalytic ozonation of ammonia（50 mg/L） in water. In terms of high catalytic activity in ammonia decomposition and high selectivity for gaseous nitrogen, the catalyst with MgO-Co3O4 molar ratio 8：2, calcined at 500°C for 3 hr, was the best one among the catalysts we tested, with an ammonia nitrogen removal rate of 85.2% and gaseous nitrogen selectivity of44.8%. In addition, the reaction mechanism of ozonation oxidative decomposition of ammonia nitrogen in water with the metal oxide catalysts was discussed. Moreover, the effect of coexisting anions on the degradation of ammonia was studied, finding that SO2-4 and HCO-3 could inhibit the catalytic activity while CO2-3 and Br-could promote it. The presence of coexisting cations had very little effect on the catalytic ozonation of ammonia nitrogen. After five successive reuses, the catalyst remained stable in the catalytic ozonation of ammonia.
文摘Sulphur-containing aromatic nitro compounds were rapidly reduced to the corresponding amines in high yields by employing hydrazine hydrate as a hydrogen donor in the presence of iron oxide hydroxide catalyst. It was worth noting that the catalyst exhibited extremely high activity. The reduction could be completed within 20-50 min and the yields were up to 97-99 %.
文摘A novel molecular probe for identifying properties of supported transition metals and metal oxides catalysts was established.The catalytic mechanism of transition metals was proposed.
基金Project supported by National Natural Science Foundation of P. R. China.
文摘The relations between catalytic activities and compositions of the systems Mg_xZn_(1-x)Fe_2O_4, Co_xZn_(1-x)Fe_2O_4, Co_xMg_(1-x)Fe_2O_4, Cd_xZn_(1-x)Fe_2O_4 and Mg_xZn_(1-x)Fe_2O_4·0.17Fe_2O_3 have been studied by flow differential reactor, XRD, and derivative IR techniques. It has been found that the appropriate normal-inverse spinel combination substantially increases the activity for the title raction. The structure of the active site and the role of the bivalent cation in the title catalyst have been inferred.
文摘A series of catalysts on the basis of 10 wt.% CuO/y-AI203, 10 wt.% CuO ＋ 10 wt.% Cr2O3/y-AI203 and 15 wt.% MnO2/y -A1203 have been prepared and modified by CeO2 with contents up to 20 wt.%. Physico-chemical properties of the catalysts were determined by the methods of BET Adsorption, XRD, and TPR. Oxidative activity of the catalysts was studied at the temperature range 90-220 ℃and CO concentration of 3 mol.%. Addition of CeO2 led to changes in physico-chemical properties of the catalysts and formation of novel active centres that increased the activity of CuO and Cr203 containing catalysts, but decreased the activity of those, containing MnO2. The catalyst sample containing 10 wt.% CuO and 15 wt.% CeO2 has been shown to be the best one for complete conversion of CO. At the given conditions on this catalyst the complete oxidation of CO to CO2 occurred at 130 ~C during more than 500 h.
基金supported by the National Natural Science Fund for Distinguished Young Scholars(52125601).
文摘To understand the catalytic conversion of lignin into high-value products,lignin depolymerization was performed using a layered polymetallic oxide(CuMgAlO_(x))catalyst.The effects of the conversion temperature,hydrogen pressure,and reaction time were studied,and the ability of CuMgAlO_(x)to break the C–O bond was evaluated.The CuMgAlO_(x)(Mg/Al=3:1)catalyst contained acidic sites and had a relatively homogeneous elemental distribution with a high pore size and specific surface area.Theβ-O-4 was almost completely converted by disassociating the C–O bond,resulting in yields of 14.74%ethylbenzene,47.58%α-methylphenyl ethanol,and 36.43%phenol.The highest yield of lignin-derived monophenols was 85.16%under reaction conditions of 280℃ and 3 Mpa for 4 h.As the reaction progressed,depolymerization and condensation reactions occurred simultaneously.Higher temperatures(>280℃)and pressures(>3 Mpa)tended to produce solid char.This study establishes guidelines for the high-value application of industrial lignin in the catalytic conversion of polymetallic oxides.
基金financially supported by the National Key R&D Program of China(2024YFE0101100)the National Natural Science Foundation of China(22475112,22305132,22305155)+1 种基金the China Postdoctoral Science Foundation(2023M732323)the Postdoctoral Fellowship Program of CPSF(GZC20231679).
文摘Metal(oxide)-zeolite bifunctional catalysts have been the subject of considerable attention from researchers in both academic and industry,due to their superior activity and stability in various heterogeneous catalytic processes[1–3].Based on the different metal loading sites,these bifunctional catalysts can be categorized as follows:(a)metal species loaded on the outer surface of zeolite crystals,(b)metal species encapsulated within the channels or cavities of zeolites,and(c)metal species incorporated into the zeolite framework(Fig.1).Metal species in type(b)and(c)samples are stabilized by the zeolite frameworks,resulting in excellent thermal and hydrothermal stability during catalytic reactions,especially under harsh conditions,as well as unique shape-selectivity.However,the complex synthesis procedures make large-scale preparation of these catalysts impractical.In contrast,a type(a)sample can be achieved via the simple impregnation;nevertheless,migration of metal species and their aggregation into larger particles often occur during the calcination and reduction processes.
基金This work was supported by the National High-Tech Research and Development Program of China(Grant No.2002AA601260)。
文摘Catalytic wet air oxidation(CWAO)is one of the most promising technologies for pollution abatement.Developing catalysts with high activity and stability is crucial for the application of the CWAO process.The Mn/Ce com-plex oxide catalysts for CWAO of high concentration phenol-containing wastewater were prepared by coprecipitation.The catalyst preparation conditions were optimized by using an orthogonal layout method and single-factor experimental analysis.The Mn/Ce serial catalysts were characterized by Brunauer-Emmett-Teller(BET)analysis and the metal cation leaching was measured by inductively coupled plasma torch-atomic emission spectrometry(ICP-AES).The results show that the catalysts have high catalytic activities even at a low temperature(80°C)and low oxygen partial pressure(0.5 MPa)in a batch reactor.The metallic ion leaching is comparatively low(Mn<6.577 mg/L and Ce<0.6910 mg/L,respectively)in the CWAO process.The phenol,COD_(Cr),and TOC removal efficiencies in the solution exceed 98.5%using the optimal catalyst(named CSP).The new catalyst would have a promising application in CWAO treatment of high concentration organic wastewater.
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.
