The local coordination environment of catalysts has been investigated ftor an extended period to obtain enhanced catalytic performance.Especially with the advancement of single-atom catalysts(SACs),research on the coo...The local coordination environment of catalysts has been investigated ftor an extended period to obtain enhanced catalytic performance.Especially with the advancement of single-atom catalysts(SACs),research on the coordination environment has been advanced to the atomic level.The surrounding coordination atoms of central metal atoms play important roles in their catalytic activity,selectivity and stability.In recent years,remarkable improvements of the catalytic performance of SACs have been achieved by the tailoring of coordination atoms,coordination numbers and second-or higher-coordination shells,which provided new opportunities for the further development of SACs.In this review,the characterization of coordination environment,tailoring of the local coordination environment,and their related adjustable catalytic performance will be discussed.We hope this review will provide new insights on further research of SACs.展开更多
In recent decades,the environmental protection and long-term sustainability have become the focus of attention due to the increasing pollution generated by the intense industrialization.To overcome these issues,enviro...In recent decades,the environmental protection and long-term sustainability have become the focus of attention due to the increasing pollution generated by the intense industrialization.To overcome these issues,environmental catalysis has increasingly been used to solve the negative impact of pollutants emission on the global environment and human health.Supported platinum-metal-group(PGM)materials are commonly utilized as the state-of-the-art catalysts to eliminate gaseous pollutants but large quantities of PGMs are required.By comparison,single-atom site catalysts(SACs)have attracted much attention in catalysis owing to their 100%atom efficiency and unique catalytic performances towards various reactions.Over the past decade,we have witnessed burgeoning interests of SACs in heterogeneous catalysis.However,to the best of our knowledge,the systematic summary and analysis of SACs in catalytic elimination of environmental pollutants has not yet been reported.In this paper,we summarize and discuss the environmental catalysis applications of SACs.Particular focus was paid to automotive and stationary emission control,including model reaction(CO oxidation,NO reduction and hydrocarbon oxidation),overall reaction(three-way catalytic and diesel oxidation reaction),elimination of volatile organic compounds(formaldehyde,benzene,and toluene),and removal/decomposition of other pollutants(Hg0 and SO3).Perspectives related to further challenges,directions and design strategies of single-atom site catalysts in environmental catalysis were also provided.展开更多
Volatile organic compounds（VOCs） are a major component in air pollutants and pose great risks to both human health and environmental protection. Currently, VOC abatement in industrial applications is through the use...Volatile organic compounds（VOCs） are a major component in air pollutants and pose great risks to both human health and environmental protection. Currently, VOC abatement in industrial applications is through the use of activated carbons as adsorbents and oxide-supported metals as catalysts. Notably, activated carbons easily adsorb water, which strongly hinders the adsorption of VOCs; conventional oxides typically possess relatively low surface areas and random pores, which effectively influence the catalytic conversion of VOCs. Zeolites, in contrast with activated carbons and oxides, can be designed to have very uniform and controllable micropores, in addition to tailored wettability properties, which can favor the selective adsorption of VOCs. In particular, zeolites with selective adsorptive properties when combined with catalytically active metals result in zeolite-supported metals exhibiting significantly improved performance in the catalytic combustion of VOCs compared with conventional oxide-supported catalysts. In this review, recent developments on VOC abatement by adsorptive and catalytic techniques over zeolite-based materials have been briefly summarized.展开更多
Coal-fired utility boilers are now identified as the largest source of mercury in the United States. There is speculation that the installation of selective catalytic reduction （SCR） system for reduction of NOx can ...Coal-fired utility boilers are now identified as the largest source of mercury in the United States. There is speculation that the installation of selective catalytic reduction （SCR） system for reduction of NOx can also prompt the oxidation and removal of mercury. In this paper, tests at six full-scale power plants with similar type of the SCR systems are conducted to investigate the effect of the SCR on the transformation of mercury speciation. The results show that the SCR system can achieve more than 70%-80% oxidation of elemental mercury and enhance the mercury removal ability in these units. The oxidation of elemental mercury in the SCR system strongly depends on the coal properties and the operation conditions of the SCR systems. The content of chloride in the coal is the key factor for the oxidization process and the maximum oxidation of elemental mercury is found when chloride content changes from 400 to 600 ppm. The sulfur content is no significant impact on oxidation of elemental mercury.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
The effects of rare earth（RE）on the structure,acidity,and catalytic performance of HZSM-5 zeolite were investigated.A series of RE/HZSM-5 catalysts,containing 7.54% RE（RE=La,Ce,Pr,Nd,Sm,Eu or Gd）,were prepared by ...The effects of rare earth（RE）on the structure,acidity,and catalytic performance of HZSM-5 zeolite were investigated.A series of RE/HZSM-5 catalysts,containing 7.54% RE（RE=La,Ce,Pr,Nd,Sm,Eu or Gd）,were prepared by the impregnation of the ZSM-5 type zeolites（Si/Al=64：1）with the corresponding RE nitrate aqueous solutions.The catalysts were characterized by means of FT-IR,UV-Vis,NH3-TPD,and IR spectroscopy of adsorbed pyridine.The catalytic performances of the RE/HZSM-5 for the catalytic cracking of mixed butane to light olefins were also measured with a fixed bed microreactor.The results revealed that the addition of light rare earth metal on the HZSM-5 catalyst greatly enhanced the selectivity to olefins,especially to propylene,thus increasing the total yield of olefins in the catalytic cracking of butane.Among the RE-modified HZSM-5 samples,Ce/HZSM-5 gave the highest yield of total olefins,and Nd/HZSM-5 gave the highest yield of propene at a reaction temperature of 600℃.The presence of rare earth metal on the HZSM-5 sample,not only modified the acidic properties of HZSM-5 including the amount of acid sites and acid type,that is,the ratio of L/B（Lewis acid/Brnsted acid）,but also altered the basic properties of it,which in turn promoted the catalytic performance of HZSM-5 for the catalytic cracking of butane.展开更多
Cu-Mn, Cu-Mn-Ce, and Cu-Ce mixed-oxide catalysts were prepared by a citric acid sol-gel method and then characterized by XRD, BET, H_2-TPR and XPS analyses. Their catalytic properties were investigated in the toluene ...Cu-Mn, Cu-Mn-Ce, and Cu-Ce mixed-oxide catalysts were prepared by a citric acid sol-gel method and then characterized by XRD, BET, H_2-TPR and XPS analyses. Their catalytic properties were investigated in the toluene combustion reaction. Results showed that the Cu-Mn-Ce ternary mixed-oxide catalyst with 1：2：4 mole ratios had the highest catalytic activity, and 99% toluene conversion was achieved at temperatures below 220°C. In the Cu-Mn-Ce catalyst, a portion of Cu and Mn species entered into the Ce O2 fluorite lattice, which led to the formation of a ceria-based solid solution. Excess Cu and Mn oxides existed on the surface of the ceria-based solid solution. The coexistence of Cu-Mn mixed oxides and the ceria-based solid solution resulted in a better synergetic interaction than the Cu-Mn and Cu-Ce catalysts, which promoted catalyst reducibility, increased oxygen mobility, and enhanced the formation of abundant active oxygen species.展开更多
As a class of famous carbon materials,biochars(BCs)and their derivative materials with excellent physicochemical properties and diversified functionalities present great potential in wastewater treatment fields.This r...As a class of famous carbon materials,biochars(BCs)and their derivative materials with excellent physicochemical properties and diversified functionalities present great potential in wastewater treatment fields.This review focuses on the latest development in reported biochar-based materials as superior adsorbents or catalysts for removing harmful organic contaminants from wastewater.The construction and properties of biochar-based materials are briefly introduced at the beginning.As one of the major factors affecting the properties of BCs,the wide diversity of feedstocks,such as agricultural and forest residues,industrial by-products as well as municipal wastes,endows BCs different chemical compositions and structures.Woody and herbaceous BCs usually have higher carbon contents,larger surface areas and strong aromaticity,which is in favor of the organic contaminant removal.Driven by the desire of more cost-effective materials,several types of biochar-based hybrid materials,such as magnetic BC composites(MBC),nanometal/nanometallic oxides/hydroxide BC composites and layered nanomaterial-coated BCs,as well as physically/chemically activated BCs,have also been developed.With the help of foreign materials,these types of hybrid BCs have excellent capacities to remove a wide range of organic contaminants,including organic dyestuff,phenols and chemical intermediates,as well as pharmaceutically active compounds,from aquatic solutions.Depending on the different types of biochar-based materials,organic contaminants can be removed by different mechanisms,such as physical adsorption,electrostatic interaction,π-πinteraction and Fenton process,as well as photocatalytic degradation.In summary,the low cost,tunable surface chemistry and excellent physical-chemical properties of BCs allow it to be a potential material in organic contaminant removal.The combination of BCs with foreign materials endows BCs more functionalities and broader development opportunities.Considering the urgent demand of practical wastewater treatment,we展开更多
With growing demand for propylene and increasing production of propane from shale gas,the technologies of propylene production,including direct dehydrogenation and oxidative dehydrogenation of propane,have drawn great...With growing demand for propylene and increasing production of propane from shale gas,the technologies of propylene production,including direct dehydrogenation and oxidative dehydrogenation of propane,have drawn great attention in recent years.In particular,direct dehydrogenation of propane to propylene is regarded as one of the most promising methods of propylene production because it is an on-purpose technique that exclusively yields propylene instead of a mixture of products.In this critical review,we provide the current investigations on the heterogeneous catalysts(such as Pt,CrOx,VOx,GaOx-based catalysts,and nanocarbons)used in the direct dehydrogenation of propane to propylene.A detailed comparison and discussion of the active sites,catalytic mechanisms,influencing factors(such as the structures,dispersions,and reducibilities of the catalysts and promoters),and supports for different types of catalysts is presented.Furthermore,rational designs and preparation of high-performance catalysts for propane dehydrogenation are proposed and discussed.展开更多
Ce-ZrO2 is a widely used three-way catalyst support. Because of the large surface area and excellent redox quality, Ce-ZrO2 may have potential application in selective catalytic reduction （SCR） systems. In the prese...Ce-ZrO2 is a widely used three-way catalyst support. Because of the large surface area and excellent redox quality, Ce-ZrO2 may have potential application in selective catalytic reduction （SCR） systems. In the present work, Ce-ZrO2 was introduced into a low-temperature SCR system and CeO2 and ZrO2 supports were also introduced to make a contrastive study. Mn/CeO2, Mn/ZrO2 and Mn/Ce-ZrO2 were prepared by impregnating these supports with Mn（NO3）2 solution, and have been characterized by N2-BET, XRD, TPR, TPD, XPS, FT-IR and TG. The activity and resistance to SO2 and H2O of the catalysts were investigated. Mn/Ce-ZrO2 and Mn/CeO2 were proved to have better low-temperature activities than Mn/ZrO2, and yielded 98.6% and 96.8% NO conversion at 180℃, respectively. This is mainly because Mn/Ce-ZrO2 and Mn/CeO2 had higher dispersion of manganese oxides, better redox properties and more weakly adsorbed oxygen species than Mn/ZrO2. In addition, Mn/Ce-ZrO2 showed a good resistance to SO2 and H2O and presented 87.1% NO conversion, even under SO2 and H2O treatment for 6 hours, and the activity of Mn/Ce-ZrO2 was almost restored to its original level after cutting off the injection of SO2 and H2O. This was due to the weak water absorption and weak sulfation process on the surface of the catalyst.展开更多
Different transition metals were used to modify V2O5-based catalysts （M-V, M = Cu, Fe, Mn, Co） on TiO2 via impregnation, for the selective reduction of NO with NH3. The introduced metals induced high dispersion in t...Different transition metals were used to modify V2O5-based catalysts （M-V, M = Cu, Fe, Mn, Co） on TiO2 via impregnation, for the selective reduction of NO with NH3. The introduced metals induced high dispersion in the vanadium species and the formation of vanadates on the TiO2 support, and increased the amount of surface acid sites and the strength of these acids. The strong acid sites might be responsible for the high N2 selectivity at higher temperatures. Among these catalysts, Cu-V/TiO2 showed the highest activity and N2 selectivity at 225-375 ~C. The results of X-ray photo- electron spectroscopy, NH3-temperature-programmed desorption, and in-situ diffuse reflectance infrared Fourier transform spectroscopy suggested that the improved performance was probably due to more active surface oxygen species and increased strong surface acid sites. The outstanding activity, stability, and SO2/H2O durability of Cu-V/TiO2 make it a candidate to be a NOx removal catalyst for stationary flue gas.展开更多
Since the ferromagnetic(Fe_(3)O_(4))nanoparticles were firstly reported to exert enzyme-like activity in 2007,extensive research progress in nanozymes has been made with deep investigation of diverse nanozymes and rap...Since the ferromagnetic(Fe_(3)O_(4))nanoparticles were firstly reported to exert enzyme-like activity in 2007,extensive research progress in nanozymes has been made with deep investigation of diverse nanozymes and rapid development of related nanotechnologies.As promising alterna-tives for natural enzymes,nanozymes have broadened the way toward clinical medicine,food safety,environmental monitoring,and chemical production.The past decade has witnessed the rapid development of metal-and metal oxide-based nanozymes owing to their remarkable physicochemical proper-ties in parallel with low cost,high stability,and easy storage.It is widely known that the deep study of catalytic activities and mechanism sheds sig-nificant influence on the applications of nanozymes.This review digs into the characteristics and intrinsic properties of metal-and metal oxide-based nanozymes,especially emphasizing their catalytic mechanism and recent applications in biological analysis,relieving inflammation,antibacterial,and cancer therapy.We also conclude the present challenges and provide insights into the future research of nanozymes constituted of metal and metal oxide nanomaterials.展开更多
A monolithic series of Cu-Mn-Ce oxides supported on cordierites with different Cu/Mn/Ce molar ratios were prepared by the in-situ sol-gel method without any binder. The catalysts were characterized by scanning electro...A monolithic series of Cu-Mn-Ce oxides supported on cordierites with different Cu/Mn/Ce molar ratios were prepared by the in-situ sol-gel method without any binder. The catalysts were characterized by scanning electron microscopy （SEM）, energy dispersive spectrometer （EDS）, X-ray diffraction （XRD）, and Brunauer-Emmett-Teller method （BET） and examined in the catalytic combustion of volatile organic compounds （VOCs）. The results showed that the well-dispersed nanometer particles of mixed oxides adhered firmly to the cordierite surface. Cu0.15Mn0.3Ce55/cordierite was identified as the most active catalyst. Compared with commercial Pd/Al2O3, Cu0.15Mn0.3Ce55/cordierite showed higher activities for the combustion of various types of VOCs, especially for oxy-derivative compounds which could be lighted off below 200 ℃.展开更多
A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=l/3 and calcined ...A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=l/3 and calcined at 300 ℃ shows a superior activity for NO oxidation to NO2. On Ce（1）Mn（3）Ti catalyst, 58% NO conversion was obtained at 200 ℃ and 85% NO conversion at 250 ℃ with a GHSV of 41000 h-1, which was much higher than that over MnOx/TiO2 catalyst （48% at 250 ℃）. Characterization results implied that the higher activity of Ce（1）Mn（3）Ti could be attributed to the enrichment of well-dispersed MnO2 on the surface and the abundance of Mn3＋ and Zi3＋ species. The addition of Ce into MnO2/TiO2 could improve oxygen storage capacity and facilitate oxygen mobility of the catalyst as shown by PL and ESR, so that its activity for NO oxidation could be enhanced. The effect of H2O and SO2 on the catalyst activity was also investigated.展开更多
The monodispersed Co nanoparticles were successfully prepared by means of hydrogen plasma method in inert atmosphere. The particle size, specific surface area, crystal structure and morphology of the samples were char...The monodispersed Co nanoparticles were successfully prepared by means of hydrogen plasma method in inert atmosphere. The particle size, specific surface area, crystal structure and morphology of the samples were characterized by transmission electron microscopy （TEM）, BET equation, X-ray diffraction （XRD）, and the corresponding selected area electron diffraction （SAED）. The catalytic effect of Co nanoparticles on the decomposition of ammonium perchlorate （AP） was investigated by differential thermal analyzer （DTA）. Compared with the thermal decomposition of pure AP, the addition of Co nanoparticles （2%-10%, by mass） decreases the decomposition temperature of AP by 145.01-155.72℃. Compared with Co3O4 nano-particles and microsized Co particles, the catalytic effect of Co nanoparticles for AP is stronger. Such effect is attributed to the large specific surface area and its interaction of Co with decomposition intermediate gases. The present work provides useful information for the application of Co nanoparficles in the AP-based propellant.展开更多
Most of volatile organic compounds （VOCs） are harmful to the atmosphere and human health. Cata‐lytic combustion is an effective way to eliminate VOCs. The key issue is the availability of high per‐formance catalys...Most of volatile organic compounds （VOCs） are harmful to the atmosphere and human health. Cata‐lytic combustion is an effective way to eliminate VOCs. The key issue is the availability of high per‐formance catalysts. Many catalysts including transition metal oxides, mixed metal oxides, and sup‐ported noble metals have been developed. Among these catalysts, the porous ones attract much attention. In this review, we focus on recent advances in the synthesis of ordered mesoporous and macroporous transition metal oxides, perovskites, and supported noble metal catalysts and their catalytic oxidation of VOCs. The porous catalysts outperformed their bulk counterparts. This excel‐lent catalytic performance was due to their high surface areas, high concentration of adsorbed oxy‐gen species, low temperature reducibility, strong interaction between noble metal and support and highly dispersed noble metal nanoparticles and unique porous structures. Catalytic oxidation of carbon monoxide over typical catalysts was also discussed. We made conclusive remarks and pro‐posed future work for the removal of VOCs.展开更多
基金the National Key R&D Program of China(Nos.2018YFA0702003 and 2016YFA0202801)the National Natural Science Foundation of China(Nos.51631001,51872030,21890383,21671117,21871159,21901135,51702016,and 51501010)+1 种基金Beijing Institute of Technology Research Fund Program for Young ScholarsBeijing Municipal Science&Technology Commission(No.Z191100007219003).
文摘The local coordination environment of catalysts has been investigated ftor an extended period to obtain enhanced catalytic performance.Especially with the advancement of single-atom catalysts(SACs),research on the coordination environment has been advanced to the atomic level.The surrounding coordination atoms of central metal atoms play important roles in their catalytic activity,selectivity and stability.In recent years,remarkable improvements of the catalytic performance of SACs have been achieved by the tailoring of coordination atoms,coordination numbers and second-or higher-coordination shells,which provided new opportunities for the further development of SACs.In this review,the characterization of coordination environment,tailoring of the local coordination environment,and their related adjustable catalytic performance will be discussed.We hope this review will provide new insights on further research of SACs.
基金This work was supported by the China Postdoctoral Science Foundation(No.2020M670355)the National Key R&D Program of China(No.2018YFA0702003)+2 种基金the National Natural Science Foundation of China(Nos.21890383,21671117,and 21871159)the Science and Technology Key Project of Guangdong Province of China(No.2020B010188002)Beijing Municipal Science&Technology Commission(No.Z191100007219003).
文摘In recent decades,the environmental protection and long-term sustainability have become the focus of attention due to the increasing pollution generated by the intense industrialization.To overcome these issues,environmental catalysis has increasingly been used to solve the negative impact of pollutants emission on the global environment and human health.Supported platinum-metal-group(PGM)materials are commonly utilized as the state-of-the-art catalysts to eliminate gaseous pollutants but large quantities of PGMs are required.By comparison,single-atom site catalysts(SACs)have attracted much attention in catalysis owing to their 100%atom efficiency and unique catalytic performances towards various reactions.Over the past decade,we have witnessed burgeoning interests of SACs in heterogeneous catalysis.However,to the best of our knowledge,the systematic summary and analysis of SACs in catalytic elimination of environmental pollutants has not yet been reported.In this paper,we summarize and discuss the environmental catalysis applications of SACs.Particular focus was paid to automotive and stationary emission control,including model reaction(CO oxidation,NO reduction and hydrocarbon oxidation),overall reaction(three-way catalytic and diesel oxidation reaction),elimination of volatile organic compounds(formaldehyde,benzene,and toluene),and removal/decomposition of other pollutants(Hg0 and SO3).Perspectives related to further challenges,directions and design strategies of single-atom site catalysts in environmental catalysis were also provided.
基金supported by the Fundamental Research Funds for the Central Universities(2015XZZX004-04)Zhejiang Provincial Natural Science Foundation(LR15B030001)~~
文摘Volatile organic compounds（VOCs） are a major component in air pollutants and pose great risks to both human health and environmental protection. Currently, VOC abatement in industrial applications is through the use of activated carbons as adsorbents and oxide-supported metals as catalysts. Notably, activated carbons easily adsorb water, which strongly hinders the adsorption of VOCs; conventional oxides typically possess relatively low surface areas and random pores, which effectively influence the catalytic conversion of VOCs. Zeolites, in contrast with activated carbons and oxides, can be designed to have very uniform and controllable micropores, in addition to tailored wettability properties, which can favor the selective adsorption of VOCs. In particular, zeolites with selective adsorptive properties when combined with catalytically active metals result in zeolite-supported metals exhibiting significantly improved performance in the catalytic combustion of VOCs compared with conventional oxide-supported catalysts. In this review, recent developments on VOC abatement by adsorptive and catalytic techniques over zeolite-based materials have been briefly summarized.
基金Project supported by the National Basic Research Program (973) of China (No. 2006CB2003)the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Personnel Ministry.
文摘Coal-fired utility boilers are now identified as the largest source of mercury in the United States. There is speculation that the installation of selective catalytic reduction （SCR） system for reduction of NOx can also prompt the oxidation and removal of mercury. In this paper, tests at six full-scale power plants with similar type of the SCR systems are conducted to investigate the effect of the SCR on the transformation of mercury speciation. The results show that the SCR system can achieve more than 70%-80% oxidation of elemental mercury and enhance the mercury removal ability in these units. The oxidation of elemental mercury in the SCR system strongly depends on the coal properties and the operation conditions of the SCR systems. The content of chloride in the coal is the key factor for the oxidization process and the maximum oxidation of elemental mercury is found when chloride content changes from 400 to 600 ppm. The sulfur content is no significant impact on oxidation of elemental mercury.
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.
基金Project supported by the National Basic Research Program of China(2004CB2178062005CB221402)+1 种基金the National NaturalScience Foundation of China(20373043)Young Scientists Innovation Foundation of CNPC(04E7025)
文摘The effects of rare earth（RE）on the structure,acidity,and catalytic performance of HZSM-5 zeolite were investigated.A series of RE/HZSM-5 catalysts,containing 7.54% RE（RE=La,Ce,Pr,Nd,Sm,Eu or Gd）,were prepared by the impregnation of the ZSM-5 type zeolites（Si/Al=64：1）with the corresponding RE nitrate aqueous solutions.The catalysts were characterized by means of FT-IR,UV-Vis,NH3-TPD,and IR spectroscopy of adsorbed pyridine.The catalytic performances of the RE/HZSM-5 for the catalytic cracking of mixed butane to light olefins were also measured with a fixed bed microreactor.The results revealed that the addition of light rare earth metal on the HZSM-5 catalyst greatly enhanced the selectivity to olefins,especially to propylene,thus increasing the total yield of olefins in the catalytic cracking of butane.Among the RE-modified HZSM-5 samples,Ce/HZSM-5 gave the highest yield of total olefins,and Nd/HZSM-5 gave the highest yield of propene at a reaction temperature of 600℃.The presence of rare earth metal on the HZSM-5 sample,not only modified the acidic properties of HZSM-5 including the amount of acid sites and acid type,that is,the ratio of L/B（Lewis acid/Brnsted acid）,but also altered the basic properties of it,which in turn promoted the catalytic performance of HZSM-5 for the catalytic cracking of butane.
基金the financial support from the Natural Science Foundation of China (No. 21107096)Zhejiang Provincial Natural Science Foundation of China (No. Y14E080008)+1 种基金the Commission of Science and Technology of Zhejiang province (No. 2013C03021)the Specialized Research Fund for the Doctoral Program of Higher Education (No. 20133317110004)
文摘Cu-Mn, Cu-Mn-Ce, and Cu-Ce mixed-oxide catalysts were prepared by a citric acid sol-gel method and then characterized by XRD, BET, H_2-TPR and XPS analyses. Their catalytic properties were investigated in the toluene combustion reaction. Results showed that the Cu-Mn-Ce ternary mixed-oxide catalyst with 1：2：4 mole ratios had the highest catalytic activity, and 99% toluene conversion was achieved at temperatures below 220°C. In the Cu-Mn-Ce catalyst, a portion of Cu and Mn species entered into the Ce O2 fluorite lattice, which led to the formation of a ceria-based solid solution. Excess Cu and Mn oxides existed on the surface of the ceria-based solid solution. The coexistence of Cu-Mn mixed oxides and the ceria-based solid solution resulted in a better synergetic interaction than the Cu-Mn and Cu-Ce catalysts, which promoted catalyst reducibility, increased oxygen mobility, and enhanced the formation of abundant active oxygen species.
基金support from the National Key Research and Development Program of China(2017YFA0207002)the National Natural Science Foundation of China(21836001,21607042)the Fundamental Research Funds for the Central Universities(2018ZD11,2018MS114).
文摘As a class of famous carbon materials,biochars(BCs)and their derivative materials with excellent physicochemical properties and diversified functionalities present great potential in wastewater treatment fields.This review focuses on the latest development in reported biochar-based materials as superior adsorbents or catalysts for removing harmful organic contaminants from wastewater.The construction and properties of biochar-based materials are briefly introduced at the beginning.As one of the major factors affecting the properties of BCs,the wide diversity of feedstocks,such as agricultural and forest residues,industrial by-products as well as municipal wastes,endows BCs different chemical compositions and structures.Woody and herbaceous BCs usually have higher carbon contents,larger surface areas and strong aromaticity,which is in favor of the organic contaminant removal.Driven by the desire of more cost-effective materials,several types of biochar-based hybrid materials,such as magnetic BC composites(MBC),nanometal/nanometallic oxides/hydroxide BC composites and layered nanomaterial-coated BCs,as well as physically/chemically activated BCs,have also been developed.With the help of foreign materials,these types of hybrid BCs have excellent capacities to remove a wide range of organic contaminants,including organic dyestuff,phenols and chemical intermediates,as well as pharmaceutically active compounds,from aquatic solutions.Depending on the different types of biochar-based materials,organic contaminants can be removed by different mechanisms,such as physical adsorption,electrostatic interaction,π-πinteraction and Fenton process,as well as photocatalytic degradation.In summary,the low cost,tunable surface chemistry and excellent physical-chemical properties of BCs allow it to be a potential material in organic contaminant removal.The combination of BCs with foreign materials endows BCs more functionalities and broader development opportunities.Considering the urgent demand of practical wastewater treatment,we
基金supported by the National Natural Science Foundation of China(21421001,21573115)the Fundamental Research Funds for the Central Universities(63185015)the Foundation of State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering(2017-K13)~~
文摘With growing demand for propylene and increasing production of propane from shale gas,the technologies of propylene production,including direct dehydrogenation and oxidative dehydrogenation of propane,have drawn great attention in recent years.In particular,direct dehydrogenation of propane to propylene is regarded as one of the most promising methods of propylene production because it is an on-purpose technique that exclusively yields propylene instead of a mixture of products.In this critical review,we provide the current investigations on the heterogeneous catalysts(such as Pt,CrOx,VOx,GaOx-based catalysts,and nanocarbons)used in the direct dehydrogenation of propane to propylene.A detailed comparison and discussion of the active sites,catalytic mechanisms,influencing factors(such as the structures,dispersions,and reducibilities of the catalysts and promoters),and supports for different types of catalysts is presented.Furthermore,rational designs and preparation of high-performance catalysts for propane dehydrogenation are proposed and discussed.
基金supported by the National Natural Science Foundation of China (No. 51176077,50976050)the Tianjin Municipal Natural Science Foundation Project(No. 12JCZDJC29300)
文摘Ce-ZrO2 is a widely used three-way catalyst support. Because of the large surface area and excellent redox quality, Ce-ZrO2 may have potential application in selective catalytic reduction （SCR） systems. In the present work, Ce-ZrO2 was introduced into a low-temperature SCR system and CeO2 and ZrO2 supports were also introduced to make a contrastive study. Mn/CeO2, Mn/ZrO2 and Mn/Ce-ZrO2 were prepared by impregnating these supports with Mn（NO3）2 solution, and have been characterized by N2-BET, XRD, TPR, TPD, XPS, FT-IR and TG. The activity and resistance to SO2 and H2O of the catalysts were investigated. Mn/Ce-ZrO2 and Mn/CeO2 were proved to have better low-temperature activities than Mn/ZrO2, and yielded 98.6% and 96.8% NO conversion at 180℃, respectively. This is mainly because Mn/Ce-ZrO2 and Mn/CeO2 had higher dispersion of manganese oxides, better redox properties and more weakly adsorbed oxygen species than Mn/ZrO2. In addition, Mn/Ce-ZrO2 showed a good resistance to SO2 and H2O and presented 87.1% NO conversion, even under SO2 and H2O treatment for 6 hours, and the activity of Mn/Ce-ZrO2 was almost restored to its original level after cutting off the injection of SO2 and H2O. This was due to the weak water absorption and weak sulfation process on the surface of the catalyst.
基金supported by the National Natural Science Foundation of China (21303099)the National Basic Research Program of China(973 Program,2014CB660803)+1 种基金the Shanghai Municipal Education Commission(14ZZ097, B.3704713001)the Research Fund for Innovation Program of Shanghai University (K.10040713003)~~
文摘Different transition metals were used to modify V2O5-based catalysts （M-V, M = Cu, Fe, Mn, Co） on TiO2 via impregnation, for the selective reduction of NO with NH3. The introduced metals induced high dispersion in the vanadium species and the formation of vanadates on the TiO2 support, and increased the amount of surface acid sites and the strength of these acids. The strong acid sites might be responsible for the high N2 selectivity at higher temperatures. Among these catalysts, Cu-V/TiO2 showed the highest activity and N2 selectivity at 225-375 ~C. The results of X-ray photo- electron spectroscopy, NH3-temperature-programmed desorption, and in-situ diffuse reflectance infrared Fourier transform spectroscopy suggested that the improved performance was probably due to more active surface oxygen species and increased strong surface acid sites. The outstanding activity, stability, and SO2/H2O durability of Cu-V/TiO2 make it a candidate to be a NOx removal catalyst for stationary flue gas.
基金the supports of the National Foundational Basic Research Project of China(2017YFA0205301)National Nature Scientific Foundation Innovation Team of China(81921002)+6 种基金National Nature Scientific foundation of China(8202010801,81903169,81803094,81602184,81822024 and 81571729)Shanghai Municipal Commission of Economy and Information Technology Fund(No.XC-ZXSJ-02-2016-05)the medical engineering cross project of Shanghai Jiao Tong University(YG2017Z D05)the Project of Thousand Youth Talents from Chinathe National Key Research and Development Program of China(2017YFC1200904)the financial support of China Postdoctoral Science Foundation(2020TQ0191)Shanghai Engineering Research Center for Intelligent Diagnosis and Treatment Instrument(No.15DZ2252000)。
文摘Since the ferromagnetic(Fe_(3)O_(4))nanoparticles were firstly reported to exert enzyme-like activity in 2007,extensive research progress in nanozymes has been made with deep investigation of diverse nanozymes and rapid development of related nanotechnologies.As promising alterna-tives for natural enzymes,nanozymes have broadened the way toward clinical medicine,food safety,environmental monitoring,and chemical production.The past decade has witnessed the rapid development of metal-and metal oxide-based nanozymes owing to their remarkable physicochemical proper-ties in parallel with low cost,high stability,and easy storage.It is widely known that the deep study of catalytic activities and mechanism sheds sig-nificant influence on the applications of nanozymes.This review digs into the characteristics and intrinsic properties of metal-and metal oxide-based nanozymes,especially emphasizing their catalytic mechanism and recent applications in biological analysis,relieving inflammation,antibacterial,and cancer therapy.We also conclude the present challenges and provide insights into the future research of nanozymes constituted of metal and metal oxide nanomaterials.
基金Project supported by National Natural Science Foundation of China (21107096)Zhejiang Provincial Natural Science Foundation (Y5090202)
文摘A monolithic series of Cu-Mn-Ce oxides supported on cordierites with different Cu/Mn/Ce molar ratios were prepared by the in-situ sol-gel method without any binder. The catalysts were characterized by scanning electron microscopy （SEM）, energy dispersive spectrometer （EDS）, X-ray diffraction （XRD）, and Brunauer-Emmett-Teller method （BET） and examined in the catalytic combustion of volatile organic compounds （VOCs）. The results showed that the well-dispersed nanometer particles of mixed oxides adhered firmly to the cordierite surface. Cu0.15Mn0.3Ce55/cordierite was identified as the most active catalyst. Compared with commercial Pd/Al2O3, Cu0.15Mn0.3Ce55/cordierite showed higher activities for the combustion of various types of VOCs, especially for oxy-derivative compounds which could be lighted off below 200 ℃.
基金supported by the National Natural Science Foundation of China (Grant No. 51078185)
文摘A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=l/3 and calcined at 300 ℃ shows a superior activity for NO oxidation to NO2. On Ce（1）Mn（3）Ti catalyst, 58% NO conversion was obtained at 200 ℃ and 85% NO conversion at 250 ℃ with a GHSV of 41000 h-1, which was much higher than that over MnOx/TiO2 catalyst （48% at 250 ℃）. Characterization results implied that the higher activity of Ce（1）Mn（3）Ti could be attributed to the enrichment of well-dispersed MnO2 on the surface and the abundance of Mn3＋ and Zi3＋ species. The addition of Ce into MnO2/TiO2 could improve oxygen storage capacity and facilitate oxygen mobility of the catalyst as shown by PL and ESR, so that its activity for NO oxidation could be enhanced. The effect of H2O and SO2 on the catalyst activity was also investigated.
基金Supported by the National Natural Science Foundation of China （50306008, 50602024）.
文摘The monodispersed Co nanoparticles were successfully prepared by means of hydrogen plasma method in inert atmosphere. The particle size, specific surface area, crystal structure and morphology of the samples were characterized by transmission electron microscopy （TEM）, BET equation, X-ray diffraction （XRD）, and the corresponding selected area electron diffraction （SAED）. The catalytic effect of Co nanoparticles on the decomposition of ammonium perchlorate （AP） was investigated by differential thermal analyzer （DTA）. Compared with the thermal decomposition of pure AP, the addition of Co nanoparticles （2%-10%, by mass） decreases the decomposition temperature of AP by 145.01-155.72℃. Compared with Co3O4 nano-particles and microsized Co particles, the catalytic effect of Co nanoparticles for AP is stronger. Such effect is attributed to the large specific surface area and its interaction of Co with decomposition intermediate gases. The present work provides useful information for the application of Co nanoparficles in the AP-based propellant.
基金supported by the National High Technology Research and Development Program (863 Program,2015AA034603)the National Natural Science Foundation of China (21377008,201077007,20973017)+1 种基金Foundation on the Creative Research Team Construction Promotion Project of Beijing Municipal InstitutionsScientific Research Base Construction-Science and Technology Creation Platform National Materials Research Base Construction~~
文摘Most of volatile organic compounds （VOCs） are harmful to the atmosphere and human health. Cata‐lytic combustion is an effective way to eliminate VOCs. The key issue is the availability of high per‐formance catalysts. Many catalysts including transition metal oxides, mixed metal oxides, and sup‐ported noble metals have been developed. Among these catalysts, the porous ones attract much attention. In this review, we focus on recent advances in the synthesis of ordered mesoporous and macroporous transition metal oxides, perovskites, and supported noble metal catalysts and their catalytic oxidation of VOCs. The porous catalysts outperformed their bulk counterparts. This excel‐lent catalytic performance was due to their high surface areas, high concentration of adsorbed oxy‐gen species, low temperature reducibility, strong interaction between noble metal and support and highly dispersed noble metal nanoparticles and unique porous structures. Catalytic oxidation of carbon monoxide over typical catalysts was also discussed. We made conclusive remarks and pro‐posed future work for the removal of VOCs.
