The use of fossil fuels significantly contributes to excess CO_(2) emissions.Catalytic hydrogenation of CO_(2) to dimethyl ether(DME)is an effective method for CO_(2) recycling,offering both environmental and economic...The use of fossil fuels significantly contributes to excess CO_(2) emissions.Catalytic hydrogenation of CO_(2) to dimethyl ether(DME)is an effective method for CO_(2) recycling,offering both environmental and economic benefits.Zeolites,known for their efficiency as solid catalysts,are widely utilized in the chemical industries.Bifunctional catalysts based on zeolites have gained attention for their applications in CO_(2) hydrogenation to DME.This review discusses key factors affecting the catalytic performance of zeolites,including topologies,Si/Al ratio,crystal size,and the proximity of metallic species to the zeolite catalysts.Although bifunctional catalytic systems enhance the conversion of CO_(2) to DME,they also lead to high CO selectivity at elevated temperatures,which can limit both DME yield and selectivity.We present recent advancements in the development of bifunctional catalysts for the direct hydrogenation of CO_(2) to DME,providing insights for designing optimized catalysts for tandem reaction systems.展开更多
The selective catalytic reduction(SCR)of NO_(x) by NH3 is one of the most mature technologies for NO_(x) treatment.Catalysts are the main factors affecting denitrification efficiency.Zeolites as low-tempe rature NH3-S...The selective catalytic reduction(SCR)of NO_(x) by NH3 is one of the most mature technologies for NO_(x) treatment.Catalysts are the main factors affecting denitrification efficiency.Zeolites as low-tempe rature NH3-SCR catalysts have been extensively studied in the past few years.In this work,the mechanism of zeolites for NH3-SCR reaction was reviewed and the denitrification performances of zeolite catalysts prepared by different methods were compared.The effects of sulfur and water poisoning on zeolite catalysts in NH3-SCR reaction were also analyzed.Several ways to address the problems in lowtemperature NH3-SCR reaction were discussed.Hopefully,this review could provide a fundamental understanding of SCR reaction on zeolite catalysts and pave the way toward similar studies to realize its commercial applications.展开更多
To reduce greenhouse gas emission from oil and gas production,it is essential to better convert methane to useful chemicals(rather) than to flare it.Conversion of methane to liquid oxygenates(mainly methanol) has attr...To reduce greenhouse gas emission from oil and gas production,it is essential to better convert methane to useful chemicals(rather) than to flare it.Conversion of methane to liquid oxygenates(mainly methanol) has attracted extensive attention and countless efforts have been made;however,running this reaction in a green,efficient,and practical way has remained elusive.The novel catalyst and oxidants play a critical role in activating methane and converting it to oxygenates(methanol).In this review,the work of commonly used oxidants for methane partial oxidation have been summarized,in which,earth abundant oxidants,O;and H;O are promising.Moreover,H;or CO can activate O;to produce H;O;that catalyzes methane partial oxidation more efficiently and selectively than O;or H;O.Therefore,the work of using reducing agent,such as CO and H;have been reviewed,focusing on rational catalyst design that features multifunction(H;O;production and CH;activation).The novel catalyst design has advanced this reaction towards practicality with green oxidants and H;using zeolites-based catalyst.Environmentally friendly zeolite preparation methods and novel two-dimensional(2 D) zeolites that can reduce waste,improve synthesis and catalytical performance substantially are also reviewed in this work to provide insights for a more comprehensive approach to meet the environment protection needs.展开更多
For the first time the preparation of the N-doped TiO2-coated NaY zeolite membrane（N-doped TiO2/NaY zeolite membrane） as an electrode material for photoelectrocatalysis has been achieved and reported.The XRD, SEM, U...For the first time the preparation of the N-doped TiO2-coated NaY zeolite membrane（N-doped TiO2/NaY zeolite membrane） as an electrode material for photoelectrocatalysis has been achieved and reported.The XRD, SEM, UV–vis and XPS techniques were used to characterize the structure of the N-doped TiO2/NaY zeolite membrane. The results verified that the surface of the N-doped TiO2/NaY zeolite membrane was coated by TiO2 nanoparticles of ca. 20 nm size and exhibited a distinct red-shift in the UV–vis spectra compared to N-doped TiO2. The photoelectrocatalysis performance of the N-doped TiO2/NaY zeolite membrane electrode was evaluated by phenol degradation. The results revealed it is a promising novel electrode material for application of photoelectrocatalysis in the removal of organic contaminants in waste water.展开更多
Ti02 coatings on natural feather zeolite are respectively prepared by a collosol （Sol-gel） method and two powder coating methods with deionizod water or dehydrated ethanol as a dispersant. During degradation of orth...Ti02 coatings on natural feather zeolite are respectively prepared by a collosol （Sol-gel） method and two powder coating methods with deionizod water or dehydrated ethanol as a dispersant. During degradation of orthomono- chlorphenol solutions by ultraviolet, the strong adsorption capability of the zeolite results in increased concentration of substrate on its surface. The Ti（h film coated on feather zeolite further enhances the photocatalytic activity. The TiO~ film on the zeolite prepared by the Sol-gel method is found more effective as a catalyst than that by two powder coating methods.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 catalytic hydrogenation of p-nitrophenol to p-aminophenol was investigated over Ni/TiO2 catalysts prepared by a liquid-phase chemical reduction method. The catalysts were characterized by inductively coupled plasm...The catalytic hydrogenation of p-nitrophenol to p-aminophenol was investigated over Ni/TiO2 catalysts prepared by a liquid-phase chemical reduction method. The catalysts were characterized by inductively coupled plasma (ICP), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and temperature-programmed reduction (TPR). Results show that the titania structure has favorable influence on physio-chemical and catalytic properties of Ni/TiO2 catalysts. Compared to commercial Raney nickel, the catalytic activity of Ni/TiO2 catalyst is much superior, irrespective of the titania structure. The catalytic activity of anatase titania supported nickel catalyst Ni/TiO2(A) is higher than that of rutile titania supported nickel catalyst Ni/TiO2(R), possibly because the reduction of nickel oxide to metallic nickel for Ni/TiO2(A) is easier than that for Ni/TiO2(R) at similar reaction conditions.展开更多
A series of catalysts were prepared by doping different loadings of CeO2 over TiO2-SiO2-WO3 and used for the selective catalytic reduction of NOx by NH3. The experimental results showed that the selective catalytic re...A series of catalysts were prepared by doping different loadings of CeO2 over TiO2-SiO2-WO3 and used for the selective catalytic reduction of NOx by NH3. The experimental results showed that the selective catalytic reduction（SCR） performance and SO2-resistant ability of TiO2-SiO2-WO3 were greatly enhanced by the introduction of cerium. The catalyst containing 10% CeO2 showed the highest NO conversion in a wide temperature range and good N2 selectivity with broad operation temperature window at the gas hourly space velocity（GHSV） of 30000 h–1, which was a very promising catalyst for NOx abatement from diesel engine exhaust. The catalysts were characterized by X-ray diffraction（XRD）, scanning electron microscopy with energy dispersive X-ray spectroscopy（SEM-EDS）, N2 adsorption-desorption（BET） and X-ray photoelectron spectroscopy（XPS）. The characterization results showed that the bigger pore radius, higher surface atomic concentration and dispersion of Ce and the abundant adsorbed oxygen on the surface of catalyst contributed to the best NH3-SCR performance of CeO2/TiO2-SiO2-WO3 catalyst containing 10% CeO2.展开更多
NOx emission abatement catalysts V 2O 5 supported on various TiO 2 including anatase, rutile and mixture of both were investigated with various physico\|chemical measurements such as BET, NH\-3\|TPD, NARP, XRD and ...NOx emission abatement catalysts V 2O 5 supported on various TiO 2 including anatase, rutile and mixture of both were investigated with various physico\|chemical measurements such as BET, NH\-3\|TPD, NARP, XRD and so on, and the effect of TiO\-2 surface properties on the SCR(selective catalytic reduction) activity of V\-2O\-5/TiO\-2 catalysts was studied. It was found that the TiO\-2 surface properties had strong affect on the SCR activity of V\-2O\-5/TiO\-2 catalysts. The stronger acidic property resulted in the higher exposure of active sites as well as the higher SCR activity.展开更多
The effects of atmospheres and precursors on MnOx/TiO2 catalysts were studied, which were prepared by the impregnation method and tested for their NOx conversion activity in ammonia selective catalytic reduction （NH3...The effects of atmospheres and precursors on MnOx/TiO2 catalysts were studied, which were prepared by the impregnation method and tested for their NOx conversion activity in ammonia selective catalytic reduction （NH3-SCR） reactions. Results showed that the manganese carbonate （MC） precursor caused mainly Mn2O3, while the manganese nitrate （MN） precursor resulted primarily in MnO2 and the manganese sulfate （MS） precursor was unchanged. The manganese acetate （MA） precursor leaded obtaining a mixture of Mn2O3 and Mn304. NOn conversion decreased in the following order： MA/TiO2 〉 MC/TiO2 〉 MN/TiO2 〉 MS/TiO2 〉 P25, with a calcination temperature of 773 K in air. Catalysts that were prepared by MA and calcined in oxygen performed strong interaction between Ti and Mn, while MnTiO3 was observed. Compared to the catalysts calcined in nitrogen, those calcined in oxygen had larger diameter and smaller surface area and pore. Catalysts that were prepared by MA and calcined in nitrogen tended to gain higher denitration rates than those in air, since they could be prepared with significant specific surface areas. NO., conversion decreased with calcination atmospheres： Nitrogen〉 Air〉 Oxygen. Meanwhile, amorphous Mn2O3 turned into crystalline Mn2O3, when the temperatures increased from 673 to 873 K.展开更多
Series of Mn/TiO2 catalysts modified with various contents of Nd for low-temperature SCR were synthesized.It can be found that the appropriate amount of Nd can markedly reduce the take-off temperature of Mn/TiO2 catal...Series of Mn/TiO2 catalysts modified with various contents of Nd for low-temperature SCR were synthesized.It can be found that the appropriate amount of Nd can markedly reduce the take-off temperature of Mn/TiO2 catalyst to 80℃and NOx conversion is stabilized over 90%in the wide temperature range of 100-2600 C.0.1 Nd-Mn/Ti shows higher N2 selectivity and better SO2 resistance than Mn/Ti catalyst.The results reveal that Nd-doped Mn/TiO2 catalyst exhibits larger BET surface area and better dispersion of active component Mn2O3.XPS results indicate that the optimal 0.1 Nd-Mn/Ti sample possesses higher concentration of Mn4+and larger amount of adsorbed oxygen at the surface compared with the unmodified counterpart.In situ DRIFTS show that the surface acidity is evidently increased after adding Nd,especially,the Lewis acid sites,and the intermediate(-NH2)is more stable.The reaction mechanism over Mn/Ti and 0.1 Nd-Mn/Ti catalysts obey the Eley-Rideal(E-R)mechanisms under low temperature reaction conditions.H2-TPR results show that Nd-Mn/TiO2 catalyst exhibits better lowtemperature redox properties.展开更多
In this work,syngas methanation over Ni-W/TiO2-SiO2catalyst was studied in a fluidized-bed reactor(FBR)and its performance was compared with a fixed-bed reactor(FIXBR).The effects of main operating variables including...In this work,syngas methanation over Ni-W/TiO2-SiO2catalyst was studied in a fluidized-bed reactor(FBR)and its performance was compared with a fixed-bed reactor(FIXBR).The effects of main operating variables including feedstock gases space velocity,coke content,bed temperature and sulfur-tolerant stability of 100 h life were investigated.The structure of the catalysts was characterized by XRD,N2adsorptiondesorption and TEM.It is found that under same space velocity from 5000 h 1to 25000 h 1FBR gave a higher CH4yield,lower coke content,and lower bed temperature than those obtained in FIXBR.Ni-W/TiO2-SiO2catalyst possessed excellent sulfur-tolerant stability on the feedstock gases less than 500 ppm H2S in FBR.The carbon deposits formed on the spent catalyst were in the form of carbon fibers in FBR,while in the form of dense accumulation distribution appearance in FIXBR.展开更多
A series of V2O5‐WO3/TiO2‐ZrO2,V2O5‐WO3/TiO2‐CeO2,and V2O5‐WO3/TiO2‐CeO2‐ZrO2 catalysts were synthesized to improve the selective catalytic reduction(SCR)performance and the K‐poisoning resistance of a V2O5‐W...A series of V2O5‐WO3/TiO2‐ZrO2,V2O5‐WO3/TiO2‐CeO2,and V2O5‐WO3/TiO2‐CeO2‐ZrO2 catalysts were synthesized to improve the selective catalytic reduction(SCR)performance and the K‐poisoning resistance of a V2O5‐WO3/TiO2 catalyst.The physicochemical properties were investigated by using XRD,BET,NH3‐TPD,H2‐TPR,and XPS,and the catalytic performance and K‐poisoning resistance were evaluated via a NH3‐SCR model reaction.Ce^4+and Zr^4+co‐doping were found to enhance the conversion of NOx,and exhibit the best K‐poisoning resistance owing to the largest BET‐specific surface area,pore volume,and total acid site concentration,as well as the minimal effects on the surface acidity and redox ability from K poisoning.The V2O5‐WO3/TiO2‐CeO2‐ZrO2 catalyst also presents outstanding H2O+SO2 tolerance.Finally,the in situ DRIFTS reveals that the NH3‐SCR reaction over the V2O5‐WO3/TiO2‐CeO2‐ZrO2 catalyst follows an L‐H mechanism,and that K poisoning does not change the reaction mechanism.展开更多
In this work, the effectiveness of V2O5-WO3/TiO2 catalysts modified with different CeO2 contents by impregnation and co-precipitation methods on the selective catalytic reduction of NOxby NH3 have been studied compara...In this work, the effectiveness of V2O5-WO3/TiO2 catalysts modified with different CeO2 contents by impregnation and co-precipitation methods on the selective catalytic reduction of NOxby NH3 have been studied comparatively by various experimental techniques. The results showed that the NO conversion of V2O5-WO3/CeO2-TiO2 catalysts modified by co-precipitation method obviously increased with the Ce doping contents in the studied range below 20%（All Ce contents are in mass fractions）, but the NO conversion of V2O5-WO3/CeO2/TiO2 catalysts modified by impregnation methods was lower than V2O5-WO3/CeO2-TiO2 catalysts especially beyond 2.5% Ce doping contents. The V2O5-WO3/CeO2-TiO2 catalysts showed better SCR activity, wider reaction window, and higher sulfur and water resistance. The characterization results elucidated that the modified catalysts by co-precipitation method exhibited higher specific surface area, much better dispersity of Ce component, more Ce^（3＋）species and more Br？nsted acid sites than that by impregnation. The vacancies caused by more Ce^（3＋）species were favorable for more NO oxidation to NO2, and the interaction between Ce species and WOxspecies generated more Br？nsted acid sites. It could be supposed that dispersed Ce Oxspecies and WOxspecies offered more second active centers respectively to adsorb oxygen and activate ammonia as co-catalysis to the primary active center of V ions, thus facilitated the better SCR activity of modified V2O5-WO3/CeO2-TiO2 catalysts by coprecipitation methods. The co-precipitation methods with Ce component were more suitable for production of modified commercial V2O5-WO3/TiO2 catalysts.展开更多
IrO2 and IrRuOx(Ir:Ru 60:40 at%),supported by 50 wt%onto titania nanotubes(TNTs)and(3 at%Nb)Nb-doped titania nanotubes(Nb-TNTs),as electrocatalysts for the oxygen evolution reaction(OER),were synthesized and character...IrO2 and IrRuOx(Ir:Ru 60:40 at%),supported by 50 wt%onto titania nanotubes(TNTs)and(3 at%Nb)Nb-doped titania nanotubes(Nb-TNTs),as electrocatalysts for the oxygen evolution reaction(OER),were synthesized and characterized by means of structural,surface analytical and electrochemical techniques.Nb doping of titania significantly increased the surface area of the support from 145(TNTs)to 260 m2g-1(Nb-TNTs),which was significantly higher than those of the Nb-doped titania supports previously reported in the literature.The surface analytical techniques showed good dispersion of the catalysts onto the supports.The X-ray photoelectron spectroscopy analyses showed that Nb was mainly in the form of Nb(IV)species,the suitable form to behave as a donor introducing free electrons to the conduction band of titania.The redox transitions of the cyclic voltammograms,in agreement with the XPS results,were found to be reversible.Despite the supported materials presented bigger crystallite sizes than the unsupported ones,the total number of active sites of the former was also higher due to their better catalyst dispersion.Considering the outer and the total charges of the cyclic voltammograms in the range 0.1–1.4 V,stability and electrode potentials at given current densities,the preferred catalyst was Ir O2 supported on the Nb-TNTs.The electrode potentials corresponding to given current densities were between the smallest ones given in the literature despite the small oxide loading used in this work and its Nb doping,thus making the Nb-TNTs-supported IrO2 catalyst a promising candidate for the OER.The good dispersion of IrO2,high specific surface area of the Nb-doped supports,accessibility of the electroactive centers,increased stability due to Nb doping and electron donor properties of the Nb(IV)oxide species were considered the main reasons for its good performance.展开更多
Developing methods for efficient product/catalyst separation and catalyst recycling is meaningful in multi-phase catalytic reactions. Here, we reported a p H-responsive emulsion system stabilized by interfacially acti...Developing methods for efficient product/catalyst separation and catalyst recycling is meaningful in multi-phase catalytic reactions. Here, we reported a p H-responsive emulsion system stabilized by interfacially active TiO2 nanoparticles for achieving in situ product/catalyst separation and catalyst recycling. In this system, emulsification and demulsification process could be easily engineered through tuning the p H values. The emulsion droplets were destroyed completely at a p H value of 3–4, and the solid catalyst distributed in the aqueous phase could be used to the next reaction cycle after removal of the organic product and adjusting the p H to 7–8. Such a p H triggered switchable Pickering emulsion catalytic system not only shows good recyclability of the solid catalyst but also high catalytic efficiency,and could be recycled more than 10 cycles.展开更多
Nanometer SnO2 particles were synthesized by sol-gel dialytic processes and used as a support to prepare CuO supported catalysts via a deposition-precipitation method. The samples were characterized by means of TG-DTA...Nanometer SnO2 particles were synthesized by sol-gel dialytic processes and used as a support to prepare CuO supported catalysts via a deposition-precipitation method. The samples were characterized by means of TG-DTA, XRD, H2-TPR and XPS. The catalytic activity of the CuO/TiO2-SnO2 catalysts was markedly depended on the loading of CuO, and the optimum CuO loading was 8 wt.% （Tloo = 80 ℃）. The CuO/TiO2-SnO2 catalysts exhibited much higher catalytic activity than the CuO/TiO2 and CuO/SnO2 catalysts. H2-TPR result indicated that a large amount of CuO formed the active site for CO oxidation in 8 wt.% CuO/TiO2-SnO2 catalyst.展开更多
Five Cu-ZSM-5 catalysts were obtained by treating Na-ZSM-5(Si/Al ratio=15)with aqueous solutions of differ-ent Cu precursors(CuCl_(2),Cu(NO_(3))2,CuSO_(4),Cu(CH_(3)COO)2,and ammoniacal copper(II)complex ion).After bei...Five Cu-ZSM-5 catalysts were obtained by treating Na-ZSM-5(Si/Al ratio=15)with aqueous solutions of differ-ent Cu precursors(CuCl_(2),Cu(NO_(3))2,CuSO_(4),Cu(CH_(3)COO)2,and ammoniacal copper(II)complex ion).After being pretreated in flowing He at 500℃to form active Cu+,these catalysts exhibited quite different activities in cata-lytic decomposition of N_(2)O.CZM-AC(II)(prepared by ammoniacal copper(II)complex ion)with 9.4 wt%Cu con-tent was the most active among these Cu-ZSM-5 catalysts,achieving almost complete N_(2)I conversion at 400℃.CZM-CA(prepared using Cu(CH_(3)COO)2 as the Cu precursor)with 2.8 wt%Cu content was the second most active catalyst among these Cu-ZSM-5 catalysts,achieving almost complete N_(2)I conversion at 425℃.CZM-CC,CZM-CN,and CZM-CS prepared by using CuCl_(2),Cu(NO_(3))2,or CuSO_(4)as the Cu precursor with similar Cu contents(≈1.7 wt%)were the least active among these Cu-ZSM-5 catalysts,achieving ca.90%N_(2)O conversion at 500℃.XRD,ICP,SEM,TEM,EDX-mapping,and CO-IR experiments were conducted to characterize relevant samples.The superior activity of CZM-AC(II)can be attributed to the high contents of total Cu+and dimeric Cu+among these samples.The influence of co-fed O2 or H2O on the catalytic performance of typical samples was also studied.展开更多
The influence of calcination temperature on the structure and catalytic behavior of Ni/TiO2-SiO2 catalyst, for CO2 reforming of methane to synthesis gas under atmospheric pressure, was investigated. The results showed...The influence of calcination temperature on the structure and catalytic behavior of Ni/TiO2-SiO2 catalyst, for CO2 reforming of methane to synthesis gas under atmospheric pressure, was investigated. The results showed that the Ni/TiO2-SiO2 catalyst calcined at 700 ℃ had high and stable activity while the catalysts calcined at 550 and 850 ℃ had low and unstable activity. Depending on the calcination temperature, one, two, or three of the following Ni-containing species, NiO, Ni2.44Ti0.72Si0.07O4, and NiTiO3 were identified by combining the temperature programmed reduction （TPR） and X-ray diffraction （XRD） results. Their reducibility decreased in the sequence： NiO〉Ni2.44Ti0.72Si0.07O4〉NiTiO3. It suggests that high and stable activities observed over the Ni/TiO2-SiO2 catalyst calcined at 700 ~C were induced by the formation of Ni2.44Ti0.72Si0.07O4 and smaller NiO species crystallite size.展开更多
基金the National Key Research and Development Program of China(2021YFA1500401)the National Natural Science Foundation of China(22288101)the‘111 Center’(B17020)for supporting this work.
文摘The use of fossil fuels significantly contributes to excess CO_(2) emissions.Catalytic hydrogenation of CO_(2) to dimethyl ether(DME)is an effective method for CO_(2) recycling,offering both environmental and economic benefits.Zeolites,known for their efficiency as solid catalysts,are widely utilized in the chemical industries.Bifunctional catalysts based on zeolites have gained attention for their applications in CO_(2) hydrogenation to DME.This review discusses key factors affecting the catalytic performance of zeolites,including topologies,Si/Al ratio,crystal size,and the proximity of metallic species to the zeolite catalysts.Although bifunctional catalytic systems enhance the conversion of CO_(2) to DME,they also lead to high CO selectivity at elevated temperatures,which can limit both DME yield and selectivity.We present recent advancements in the development of bifunctional catalysts for the direct hydrogenation of CO_(2) to DME,providing insights for designing optimized catalysts for tandem reaction systems.
基金the Sichuan Science and Technology Program(No.2019YFS0495-02)。
文摘The selective catalytic reduction(SCR)of NO_(x) by NH3 is one of the most mature technologies for NO_(x) treatment.Catalysts are the main factors affecting denitrification efficiency.Zeolites as low-tempe rature NH3-SCR catalysts have been extensively studied in the past few years.In this work,the mechanism of zeolites for NH3-SCR reaction was reviewed and the denitrification performances of zeolite catalysts prepared by different methods were compared.The effects of sulfur and water poisoning on zeolite catalysts in NH3-SCR reaction were also analyzed.Several ways to address the problems in lowtemperature NH3-SCR reaction were discussed.Hopefully,this review could provide a fundamental understanding of SCR reaction on zeolite catalysts and pave the way toward similar studies to realize its commercial applications.
文摘To reduce greenhouse gas emission from oil and gas production,it is essential to better convert methane to useful chemicals(rather) than to flare it.Conversion of methane to liquid oxygenates(mainly methanol) has attracted extensive attention and countless efforts have been made;however,running this reaction in a green,efficient,and practical way has remained elusive.The novel catalyst and oxidants play a critical role in activating methane and converting it to oxygenates(methanol).In this review,the work of commonly used oxidants for methane partial oxidation have been summarized,in which,earth abundant oxidants,O;and H;O are promising.Moreover,H;or CO can activate O;to produce H;O;that catalyzes methane partial oxidation more efficiently and selectively than O;or H;O.Therefore,the work of using reducing agent,such as CO and H;have been reviewed,focusing on rational catalyst design that features multifunction(H;O;production and CH;activation).The novel catalyst design has advanced this reaction towards practicality with green oxidants and H;using zeolites-based catalyst.Environmentally friendly zeolite preparation methods and novel two-dimensional(2 D) zeolites that can reduce waste,improve synthesis and catalytical performance substantially are also reviewed in this work to provide insights for a more comprehensive approach to meet the environment protection needs.
基金supported by the Talent Introduction Fund of Yangzhou University(2012),Jiangsu Province Science and Technology Support Project(No.BE2014613)Six Big Peak Talent in Jiangsu Province(No.2014-XCL-013)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘For the first time the preparation of the N-doped TiO2-coated NaY zeolite membrane（N-doped TiO2/NaY zeolite membrane） as an electrode material for photoelectrocatalysis has been achieved and reported.The XRD, SEM, UV–vis and XPS techniques were used to characterize the structure of the N-doped TiO2/NaY zeolite membrane. The results verified that the surface of the N-doped TiO2/NaY zeolite membrane was coated by TiO2 nanoparticles of ca. 20 nm size and exhibited a distinct red-shift in the UV–vis spectra compared to N-doped TiO2. The photoelectrocatalysis performance of the N-doped TiO2/NaY zeolite membrane electrode was evaluated by phenol degradation. The results revealed it is a promising novel electrode material for application of photoelectrocatalysis in the removal of organic contaminants in waste water.
文摘Ti02 coatings on natural feather zeolite are respectively prepared by a collosol （Sol-gel） method and two powder coating methods with deionizod water or dehydrated ethanol as a dispersant. During degradation of orthomono- chlorphenol solutions by ultraviolet, the strong adsorption capability of the zeolite results in increased concentration of substrate on its surface. The Ti（h film coated on feather zeolite further enhances the photocatalytic activity. The TiO~ film on the zeolite prepared by the Sol-gel method is found more effective as a catalyst than that by two powder coating methods.
基金Natural Science Foundation of Anhui Province(1908085ME127)Research Foundation of the Institute of Environmentfriendly Materials and Occupational Health(Wuhu),Anhui University of Science and Technology(ALW2021YF11)。
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 Basic Research Program (No.2003CB615702) and the National Natural Science Foundation of Chin(No.20436030).
文摘The catalytic hydrogenation of p-nitrophenol to p-aminophenol was investigated over Ni/TiO2 catalysts prepared by a liquid-phase chemical reduction method. The catalysts were characterized by inductively coupled plasma (ICP), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and temperature-programmed reduction (TPR). Results show that the titania structure has favorable influence on physio-chemical and catalytic properties of Ni/TiO2 catalysts. Compared to commercial Raney nickel, the catalytic activity of Ni/TiO2 catalyst is much superior, irrespective of the titania structure. The catalytic activity of anatase titania supported nickel catalyst Ni/TiO2(A) is higher than that of rutile titania supported nickel catalyst Ni/TiO2(R), possibly because the reduction of nickel oxide to metallic nickel for Ni/TiO2(A) is easier than that for Ni/TiO2(R) at similar reaction conditions.
基金supported by the National Natural Science Foundation of China(21173153)the National High Technology Research and Development Program of China(863 project)(2013AA065304)
文摘A series of catalysts were prepared by doping different loadings of CeO2 over TiO2-SiO2-WO3 and used for the selective catalytic reduction of NOx by NH3. The experimental results showed that the selective catalytic reduction（SCR） performance and SO2-resistant ability of TiO2-SiO2-WO3 were greatly enhanced by the introduction of cerium. The catalyst containing 10% CeO2 showed the highest NO conversion in a wide temperature range and good N2 selectivity with broad operation temperature window at the gas hourly space velocity（GHSV） of 30000 h–1, which was a very promising catalyst for NOx abatement from diesel engine exhaust. The catalysts were characterized by X-ray diffraction（XRD）, scanning electron microscopy with energy dispersive X-ray spectroscopy（SEM-EDS）, N2 adsorption-desorption（BET） and X-ray photoelectron spectroscopy（XPS）. The characterization results showed that the bigger pore radius, higher surface atomic concentration and dispersion of Ce and the abundant adsorbed oxygen on the surface of catalyst contributed to the best NH3-SCR performance of CeO2/TiO2-SiO2-WO3 catalyst containing 10% CeO2.
文摘NOx emission abatement catalysts V 2O 5 supported on various TiO 2 including anatase, rutile and mixture of both were investigated with various physico\|chemical measurements such as BET, NH\-3\|TPD, NARP, XRD and so on, and the effect of TiO\-2 surface properties on the SCR(selective catalytic reduction) activity of V\-2O\-5/TiO\-2 catalysts was studied. It was found that the TiO\-2 surface properties had strong affect on the SCR activity of V\-2O\-5/TiO\-2 catalysts. The stronger acidic property resulted in the higher exposure of active sites as well as the higher SCR activity.
基金Funded by the National "Twelfth Five-Year" Plan for Science&Technology Support of China(No.2011BAE29B02))
文摘The effects of atmospheres and precursors on MnOx/TiO2 catalysts were studied, which were prepared by the impregnation method and tested for their NOx conversion activity in ammonia selective catalytic reduction （NH3-SCR） reactions. Results showed that the manganese carbonate （MC） precursor caused mainly Mn2O3, while the manganese nitrate （MN） precursor resulted primarily in MnO2 and the manganese sulfate （MS） precursor was unchanged. The manganese acetate （MA） precursor leaded obtaining a mixture of Mn2O3 and Mn304. NOn conversion decreased in the following order： MA/TiO2 〉 MC/TiO2 〉 MN/TiO2 〉 MS/TiO2 〉 P25, with a calcination temperature of 773 K in air. Catalysts that were prepared by MA and calcined in oxygen performed strong interaction between Ti and Mn, while MnTiO3 was observed. Compared to the catalysts calcined in nitrogen, those calcined in oxygen had larger diameter and smaller surface area and pore. Catalysts that were prepared by MA and calcined in nitrogen tended to gain higher denitration rates than those in air, since they could be prepared with significant specific surface areas. NO., conversion decreased with calcination atmospheres： Nitrogen〉 Air〉 Oxygen. Meanwhile, amorphous Mn2O3 turned into crystalline Mn2O3, when the temperatures increased from 673 to 873 K.
基金Project supported by the Key Research and Development Projects of Jiangsu Province(BE2017716)National Key R&D Program of China(2017YFB0603201)Environmental Nonprofit Industry Research subject(2016YFC0208102)。
文摘Series of Mn/TiO2 catalysts modified with various contents of Nd for low-temperature SCR were synthesized.It can be found that the appropriate amount of Nd can markedly reduce the take-off temperature of Mn/TiO2 catalyst to 80℃and NOx conversion is stabilized over 90%in the wide temperature range of 100-2600 C.0.1 Nd-Mn/Ti shows higher N2 selectivity and better SO2 resistance than Mn/Ti catalyst.The results reveal that Nd-doped Mn/TiO2 catalyst exhibits larger BET surface area and better dispersion of active component Mn2O3.XPS results indicate that the optimal 0.1 Nd-Mn/Ti sample possesses higher concentration of Mn4+and larger amount of adsorbed oxygen at the surface compared with the unmodified counterpart.In situ DRIFTS show that the surface acidity is evidently increased after adding Nd,especially,the Lewis acid sites,and the intermediate(-NH2)is more stable.The reaction mechanism over Mn/Ti and 0.1 Nd-Mn/Ti catalysts obey the Eley-Rideal(E-R)mechanisms under low temperature reaction conditions.H2-TPR results show that Nd-Mn/TiO2 catalyst exhibits better lowtemperature redox properties.
文摘In this work,syngas methanation over Ni-W/TiO2-SiO2catalyst was studied in a fluidized-bed reactor(FBR)and its performance was compared with a fixed-bed reactor(FIXBR).The effects of main operating variables including feedstock gases space velocity,coke content,bed temperature and sulfur-tolerant stability of 100 h life were investigated.The structure of the catalysts was characterized by XRD,N2adsorptiondesorption and TEM.It is found that under same space velocity from 5000 h 1to 25000 h 1FBR gave a higher CH4yield,lower coke content,and lower bed temperature than those obtained in FIXBR.Ni-W/TiO2-SiO2catalyst possessed excellent sulfur-tolerant stability on the feedstock gases less than 500 ppm H2S in FBR.The carbon deposits formed on the spent catalyst were in the form of carbon fibers in FBR,while in the form of dense accumulation distribution appearance in FIXBR.
基金supported by the National Natural Science Foundation of China(21876168,21507130)the Key Projects for Common Key Technology Innovation in Key Industries in Chongqing(cstc2016zdcy-ztzx0020-01)+2 种基金the Chongqing Science&Technology Commission(cstc2016jcyjA0070,cstckjcxljrc13)the Open Project Program of Chongqing Key Laboratory of Catalysis and Functional Organic Molecules from Chongqing Technology and Business University(1456029)the Graduate Innovation Project of Chongqing Technology and Business University(yjscxx201803-028-22)~~
文摘A series of V2O5‐WO3/TiO2‐ZrO2,V2O5‐WO3/TiO2‐CeO2,and V2O5‐WO3/TiO2‐CeO2‐ZrO2 catalysts were synthesized to improve the selective catalytic reduction(SCR)performance and the K‐poisoning resistance of a V2O5‐WO3/TiO2 catalyst.The physicochemical properties were investigated by using XRD,BET,NH3‐TPD,H2‐TPR,and XPS,and the catalytic performance and K‐poisoning resistance were evaluated via a NH3‐SCR model reaction.Ce^4+and Zr^4+co‐doping were found to enhance the conversion of NOx,and exhibit the best K‐poisoning resistance owing to the largest BET‐specific surface area,pore volume,and total acid site concentration,as well as the minimal effects on the surface acidity and redox ability from K poisoning.The V2O5‐WO3/TiO2‐CeO2‐ZrO2 catalyst also presents outstanding H2O+SO2 tolerance.Finally,the in situ DRIFTS reveals that the NH3‐SCR reaction over the V2O5‐WO3/TiO2‐CeO2‐ZrO2 catalyst follows an L‐H mechanism,and that K poisoning does not change the reaction mechanism.
基金Project supported by the Guangxi Natural Science Foundation(2014GXNSFAA118057)Guangxi Science and Technology Planning Project(AB16380276)
文摘In this work, the effectiveness of V2O5-WO3/TiO2 catalysts modified with different CeO2 contents by impregnation and co-precipitation methods on the selective catalytic reduction of NOxby NH3 have been studied comparatively by various experimental techniques. The results showed that the NO conversion of V2O5-WO3/CeO2-TiO2 catalysts modified by co-precipitation method obviously increased with the Ce doping contents in the studied range below 20%（All Ce contents are in mass fractions）, but the NO conversion of V2O5-WO3/CeO2/TiO2 catalysts modified by impregnation methods was lower than V2O5-WO3/CeO2-TiO2 catalysts especially beyond 2.5% Ce doping contents. The V2O5-WO3/CeO2-TiO2 catalysts showed better SCR activity, wider reaction window, and higher sulfur and water resistance. The characterization results elucidated that the modified catalysts by co-precipitation method exhibited higher specific surface area, much better dispersity of Ce component, more Ce^（3＋）species and more Br？nsted acid sites than that by impregnation. The vacancies caused by more Ce^（3＋）species were favorable for more NO oxidation to NO2, and the interaction between Ce species and WOxspecies generated more Br？nsted acid sites. It could be supposed that dispersed Ce Oxspecies and WOxspecies offered more second active centers respectively to adsorb oxygen and activate ammonia as co-catalysis to the primary active center of V ions, thus facilitated the better SCR activity of modified V2O5-WO3/CeO2-TiO2 catalysts by coprecipitation methods. The co-precipitation methods with Ce component were more suitable for production of modified commercial V2O5-WO3/TiO2 catalysts.
文摘IrO2 and IrRuOx(Ir:Ru 60:40 at%),supported by 50 wt%onto titania nanotubes(TNTs)and(3 at%Nb)Nb-doped titania nanotubes(Nb-TNTs),as electrocatalysts for the oxygen evolution reaction(OER),were synthesized and characterized by means of structural,surface analytical and electrochemical techniques.Nb doping of titania significantly increased the surface area of the support from 145(TNTs)to 260 m2g-1(Nb-TNTs),which was significantly higher than those of the Nb-doped titania supports previously reported in the literature.The surface analytical techniques showed good dispersion of the catalysts onto the supports.The X-ray photoelectron spectroscopy analyses showed that Nb was mainly in the form of Nb(IV)species,the suitable form to behave as a donor introducing free electrons to the conduction band of titania.The redox transitions of the cyclic voltammograms,in agreement with the XPS results,were found to be reversible.Despite the supported materials presented bigger crystallite sizes than the unsupported ones,the total number of active sites of the former was also higher due to their better catalyst dispersion.Considering the outer and the total charges of the cyclic voltammograms in the range 0.1–1.4 V,stability and electrode potentials at given current densities,the preferred catalyst was Ir O2 supported on the Nb-TNTs.The electrode potentials corresponding to given current densities were between the smallest ones given in the literature despite the small oxide loading used in this work and its Nb doping,thus making the Nb-TNTs-supported IrO2 catalyst a promising candidate for the OER.The good dispersion of IrO2,high specific surface area of the Nb-doped supports,accessibility of the electroactive centers,increased stability due to Nb doping and electron donor properties of the Nb(IV)oxide species were considered the main reasons for its good performance.
基金the Natural Science Foundation of China (Nos. 21733009, 21573136, and U1510105)the Key Scientist and Technology Program of Shanxi Province (No. 20150313003-1)Shanxi Scholarship Council of China (No. 2015-003)
文摘Developing methods for efficient product/catalyst separation and catalyst recycling is meaningful in multi-phase catalytic reactions. Here, we reported a p H-responsive emulsion system stabilized by interfacially active TiO2 nanoparticles for achieving in situ product/catalyst separation and catalyst recycling. In this system, emulsification and demulsification process could be easily engineered through tuning the p H values. The emulsion droplets were destroyed completely at a p H value of 3–4, and the solid catalyst distributed in the aqueous phase could be used to the next reaction cycle after removal of the organic product and adjusting the p H to 7–8. Such a p H triggered switchable Pickering emulsion catalytic system not only shows good recyclability of the solid catalyst but also high catalytic efficiency,and could be recycled more than 10 cycles.
基金supported by the National Natural Science Foundation of China (20771061 and 20871071)the 973 Program (2005CB623607)Science and Technology Commission Foundation of Tianjin (08JCYBJC00100 and 09JCYBJC03600)
文摘Nanometer SnO2 particles were synthesized by sol-gel dialytic processes and used as a support to prepare CuO supported catalysts via a deposition-precipitation method. The samples were characterized by means of TG-DTA, XRD, H2-TPR and XPS. The catalytic activity of the CuO/TiO2-SnO2 catalysts was markedly depended on the loading of CuO, and the optimum CuO loading was 8 wt.% （Tloo = 80 ℃）. The CuO/TiO2-SnO2 catalysts exhibited much higher catalytic activity than the CuO/TiO2 and CuO/SnO2 catalysts. H2-TPR result indicated that a large amount of CuO formed the active site for CO oxidation in 8 wt.% CuO/TiO2-SnO2 catalyst.
基金Supported by the National Natural Science Foundation of China(Grant No.21477022)
文摘Five Cu-ZSM-5 catalysts were obtained by treating Na-ZSM-5(Si/Al ratio=15)with aqueous solutions of differ-ent Cu precursors(CuCl_(2),Cu(NO_(3))2,CuSO_(4),Cu(CH_(3)COO)2,and ammoniacal copper(II)complex ion).After being pretreated in flowing He at 500℃to form active Cu+,these catalysts exhibited quite different activities in cata-lytic decomposition of N_(2)O.CZM-AC(II)(prepared by ammoniacal copper(II)complex ion)with 9.4 wt%Cu con-tent was the most active among these Cu-ZSM-5 catalysts,achieving almost complete N_(2)I conversion at 400℃.CZM-CA(prepared using Cu(CH_(3)COO)2 as the Cu precursor)with 2.8 wt%Cu content was the second most active catalyst among these Cu-ZSM-5 catalysts,achieving almost complete N_(2)I conversion at 425℃.CZM-CC,CZM-CN,and CZM-CS prepared by using CuCl_(2),Cu(NO_(3))2,or CuSO_(4)as the Cu precursor with similar Cu contents(≈1.7 wt%)were the least active among these Cu-ZSM-5 catalysts,achieving ca.90%N_(2)O conversion at 500℃.XRD,ICP,SEM,TEM,EDX-mapping,and CO-IR experiments were conducted to characterize relevant samples.The superior activity of CZM-AC(II)can be attributed to the high contents of total Cu+and dimeric Cu+among these samples.The influence of co-fed O2 or H2O on the catalytic performance of typical samples was also studied.
文摘The influence of calcination temperature on the structure and catalytic behavior of Ni/TiO2-SiO2 catalyst, for CO2 reforming of methane to synthesis gas under atmospheric pressure, was investigated. The results showed that the Ni/TiO2-SiO2 catalyst calcined at 700 ℃ had high and stable activity while the catalysts calcined at 550 and 850 ℃ had low and unstable activity. Depending on the calcination temperature, one, two, or three of the following Ni-containing species, NiO, Ni2.44Ti0.72Si0.07O4, and NiTiO3 were identified by combining the temperature programmed reduction （TPR） and X-ray diffraction （XRD） results. Their reducibility decreased in the sequence： NiO〉Ni2.44Ti0.72Si0.07O4〉NiTiO3. It suggests that high and stable activities observed over the Ni/TiO2-SiO2 catalyst calcined at 700 ~C were induced by the formation of Ni2.44Ti0.72Si0.07O4 and smaller NiO species crystallite size.
