Vanadium-titanium-based catalysts are the most widely used industrial materials for NO_x removal from coal-fired power plants. Owing to their relatively poor low-temperature deNO_x activity, low thermal stability, ins...Vanadium-titanium-based catalysts are the most widely used industrial materials for NO_x removal from coal-fired power plants. Owing to their relatively poor low-temperature deNO_x activity, low thermal stability, insufficient Hg^0 oxidation activity, SO_2 oxidation, ammonia slip, and other disadvantages,modifications to traditional vanadium-titanium-based selective catalytic reduction（SCR）catalysts have been attempted by many researchers to promote their relevant performance. This article reviewed the research progress of modified vanadium-titanium-based SCR catalysts from seven aspects, namely,（1） improving low-temperature deNO_x efficiency,（2） enhancing thermal stability,（3） improving Hg^0 oxidation efficiency,（4） oxidizing slip ammonia,（5） reducing SO_2 oxidation,（6） increasing alkali resistance, and（7） others. Their catalytic performance and the influence mechanisms have been discussed in detail. These catalysts were also divided into different categories according to their modified components such as noble metals（e.g., silver, ruthenium）, transition metals（e.g., manganese, iron, copper, zirconium, etc.）, rare earth metals（e.g., cerium, praseodymium）,and other metal chlorides（e.g., calcium chloride, copper chloride） and non-metals（fluorine,sulfur, silicon, nitrogen, etc.）. The advantages and disadvantages of these catalysts were summarized.Based on previous studies and the author＇s point of view, doping the appropriate modified components is beneficial to further improve the overall performance of vanadium-titanium-based SCR catalysts. This has enormous development potential and is a promising way to realize the control of multiple pollutants on the basis of the existing flue gas treatment system.展开更多
Titania-based composite catalysts were prepared through a sol-gel route employing multi-walled carbon nanotubes with different diameters. The materials were characterized using thermogravimetric analysis, nitrogen ads...Titania-based composite catalysts were prepared through a sol-gel route employing multi-walled carbon nanotubes with different diameters. The materials were characterized using thermogravimetric analysis, nitrogen adsorption-desorption isotherm, powder X-ray diffraction, scanning electron microscopy, and diffuse reflectance UV-Vis absorption spectra. The application of the catalysts to photocatalytic degradation of phenol was tested under UV-Vis irradiation. A synergetic effect on phenol removal was observed in case of composite catalysts, which was evaluated in terms of apparent rate constant, total organic carbon removal and photonic efficiency.展开更多
Nanostructured titanium dioxides were synthesized via various post-treatments of titanate nanofibers obtained from titanium precursors by hydrothermal reactions. The microstructures of TiO2 and supported Ru/TiO2 catal...Nanostructured titanium dioxides were synthesized via various post-treatments of titanate nanofibers obtained from titanium precursors by hydrothermal reactions. The microstructures of TiO2 and supported Ru/TiO2 catalysts were characterized with X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray analysis, and nitrogen adsorption isotherms. The phase structure, particle size, morphology, and specific surface area were determined. The supported Ru catalysts were applied for the selective methanation of CO in a hydrogen-rich stream. The results indicated that the Ru catalyst supported on rutile and TiO2-B exhibited higher catalytic performance than the counterpart supported on anatase, which suggested the distinct interaction between Ru nanoparticles and TiO2 resulting from different crystalline phases and morphology.展开更多
TiO2/V2O5 catalyst doped with rare earth ions was prepared by sol-gel method. Titanium tetrapropoxide and vanadium pentoxide were used as precursor of the composite catalyst and rare earth ions were used as dopant. Th...TiO2/V2O5 catalyst doped with rare earth ions was prepared by sol-gel method. Titanium tetrapropoxide and vanadium pentoxide were used as precursor of the composite catalyst and rare earth ions were used as dopant. The crystal phases, crystalline sizes, microstructure, absorption spectra of doped composite catalyst were studied by XRD, EDS, FT-IR and UV-Vis. Photoactivity of the prepared catalyst under ultraviolet irradiation were evaluated by degradation of methyl orange （MO） in aqueous solution. It is shown that the prepared catalyst is composed of anatase and futile. The rare earth ions are highly dispersed in composite catalyst. All the doped catalysts appear higher photocatalytic activity than TiO2/V2O5 catalyst and catalyst doped with Ce^4＋ present the best activity to MO.展开更多
Precise,efficient copolymerizations of ethylene with cyclic olefins[norbornene(NBE),cyclopentene(CPE)]using nonbridged half-titanocenes of type,Cp TiCl_2(L)(Cp =cyclopentadienyl group,L=aryloxo,ketimide)-MAO catalyst ...Precise,efficient copolymerizations of ethylene with cyclic olefins[norbornene(NBE),cyclopentene(CPE)]using nonbridged half-titanocenes of type,Cp TiCl_2(L)(Cp =cyclopentadienyl group,L=aryloxo,ketimide)-MAO catalyst systems have been summarized.CpTiCl_2(N=C Bu_2)exhibited both remarkable catalytic activity and efficient NBE incorporation for ethylene/NBE copolymerization:the NBE incorporation by Cp TiCl_2(X)(X=N=C Bu_2,O-2,6- Pr_2C_6H_3; Cp =Cp,C_5Me_5,indenyl)was related to the calculated coordination ene...展开更多
The effect of chemical composition of highly active supported Ziegler-Natta catalysts with controlled morphology on the MWD of PE has been studied.It was shown the variation of transition metal compound in the MgCl_2-...The effect of chemical composition of highly active supported Ziegler-Natta catalysts with controlled morphology on the MWD of PE has been studied.It was shown the variation of transition metal compound in the MgCl_2-supported catalyst affect of MWD of PE produced in broad range:Vanadium-magnesium catalyst(VMC)produce PE with broad and bimodal MWD(M_w/M_n=14-21).MWD of PE,produced over titanium-magnesium catalyst(TMC)is narrow or medium depending on Ti content in the catalyst(M_w/M_n=3.1-4.8).The oxidation ...展开更多
The aim of this work was to investigate the effects of calcination/acid-activation on the composition, structure, and photocatalytic （PC） reduction property of an anodic oxidation TiO2/Ti film catalyst. The surface ...The aim of this work was to investigate the effects of calcination/acid-activation on the composition, structure, and photocatalytic （PC） reduction property of an anodic oxidation TiO2/Ti film catalyst. The surface morphology and phase composition were examined by scanning electron microscopy and X-ray diffraction. The catalytic property of the film catalysts was evaluated through the removal rate of potassium chromate during the PC reduction process. The results showed that the film catalysts were composed of anatase and rutile TiO2 with a micro-porous surface structure. The calcination treatment increased the content of TiO2 in the film, changed the relative ratio of anatase and rutile TiO2, and decreased the size of the micro pores of the film catalysts. The removal rate of potassium chromate was related to the technique parameters of calcination/acid-activation treatment. When the anodic oxidation TiO2/Ti film catalyst was calcined at 873 K for 30 min and then acid-activated in the concentrated H2SO4 for 60 min, it presented the highest catalytic property, with the removal rate of potassium chromate of 96.3% during the PC reduction process under the experimental conditions.展开更多
A monocyclopentadienyl titanium complex containing 8-quinolinolato (QCpTiCl_2) was synthesized. Its activities in ethylene polymerization at various Al/Ti molar ratios, different temperatures and activation time were ...A monocyclopentadienyl titanium complex containing 8-quinolinolato (QCpTiCl_2) was synthesized. Its activities in ethylene polymerization at various Al/Ti molar ratios, different temperatures and activation time were investigated. The activity with a Al/Ti molar ratio of 500 exhibited a maximum of 2.8×10~5 g/(mol.h) at 30℃. The activation time of QCpTiCl_2 with MAO before polymerization also plays a role on the activity. The structural properties of the produced polyethylene (molecular weight, molecular weight distribution and melting point) were discussed. Kinetic behaviors of ethylene polymerization with the QCpTiCl_2/MAO system at different Al/Ti molar ratios were studied. For the QCpTiMeCl/MAO system and the CpTiMe_2Cl/MAO system, binding energies of the examined intermediates were calculated by quantum-mechanical method based on ADF program, respectively. It is confirmed that the chlorinebridged adduct formed by the reaction of QCpTiMeCl with MAO is thermodynamically steady. In the case of the QCpTiMeCl/MAO system, olefin-separated ion pair (OSIP) mechanism is much favorable than ion-pair dissociation (IPD) mechanism. The experimental result on the CpTiMe_2Cl/MAO system showed lower activity for ethylene polymerization than that on the QCpTiMeCl/MAO system, which revealed that the CpTiMe_2Cl/MAO system is unfavorable to form active species with ethylene.展开更多
Ti-containing mesoporous silica materials(Ti-MSs) with isolated tetrahedrally coordinated Ti species have been widely applied in bulk molecular catalysis. Herein, Ti-MSs were synthesized using anionic surfactant SDS a...Ti-containing mesoporous silica materials(Ti-MSs) with isolated tetrahedrally coordinated Ti species have been widely applied in bulk molecular catalysis. Herein, Ti-MSs were synthesized using anionic surfactant SDS as the co-template. The SDS molecular assembled structures can interact with silica species through the interface hydrogen bonds leading to the formation of mesoporous silica structure with compact Ti-O bonds, lower hydrophilicity and low template cost. The influence of adding SDS as the co-template on the oxidation of styrene with aqueous H_2O_2 as the oxidant was investigated. Ti-MSs using SDS as the co-template showed better catalytic performance as compared with mesoporous titanium silicate synthesized with CTAB serving as the sole template. Moreover, the Ti-MSs synthesized at a Ti/Si ratio of 0.005 demonstrated an optimized performance for styrene oxidation with styrene conversion improved by 14.8%, benzaldehyde selectivity improved by 13.7% and styrene oxide selectivity improved by 9.2% when the reaction time was 6 h.展开更多
Three mono-cyclopentadienyl metal complexes, [C_6H_4O_2]CpTiCl (Ⅰ),[C_(12)H_8O_2]CpTiCl (Ⅱ), and [C_(20)H_(12)O_2] CpTiCl (Ⅲ), were prepared via the reactions ofcyclopentadienyl titanium trichloride with catechol, ...Three mono-cyclopentadienyl metal complexes, [C_6H_4O_2]CpTiCl (Ⅰ),[C_(12)H_8O_2]CpTiCl (Ⅱ), and [C_(20)H_(12)O_2] CpTiCl (Ⅲ), were prepared via the reactions ofcyclopentadienyl titanium trichloride with catechol, 2,2i-bisphenol, and 2,2'-bisnaphthol,respectively. In the presence of a moderate amount of methylaluminoxane (MAO), the complexesexhibited catalytic activities for ethylene polymerization. Complex Ⅰ showed the highest activityat Al/Ti molar ratio of 500 at the temperature of 30℃. With increasing of polymerizationtemperature, catalytic activities and molecular weight of the obtained polyethylene tended todecrease, and molecular weight distribution of polyethylene became narrower. With the molecularsimulation method, the charges on titanium atoms of complexes Ⅰ, Ⅱ, and Ⅲ, and the bond anglesformed by Ti and bisphenoxy ligands were calculated. It was concluded that the smaller the netcharge on Ti and the smaller the angle of O1―Ti―O2, the higher the activity of the complex.展开更多
Catalysts of carbon monoxide oxidation were synthesized by deposition of platinum on titanium nitride (TiN). Two substrates with an average particle size of 18 and 36 nm were obtained by hydrogen reduction of titanium...Catalysts of carbon monoxide oxidation were synthesized by deposition of platinum on titanium nitride (TiN). Two substrates with an average particle size of 18 and 36 nm were obtained by hydrogen reduction of titanium tetrachloride in a stream of microwave plasma of nitrogen. The surface of the catalysts was studied by X-ray photoelectron spectroscopy (XPS). The data obtained by us in the present work indicate the presence of oxynitride as a transition layer between nitride and oxide. It was found that the CO oxidation rate on the 9 - 15 wt.% Pt loaded TiN catalysts is 120 times higher than that on the platinum black with a specific surface of 30 m<sup>2</sup>/g. Increase in the reaction rate of CO oxidation on Pt/TiN catalysts as compared to platinum black can be associated with both an increase in the concentration of CO molecules adsorbed and a decrease in the activation energy of the reaction. Catalysts are promising for use in catalytic air purification systems.展开更多
he deactivation of highly active multicomponent oxide LiLa_0.5 Ti_0.5 O_(2+λ) cata-lyst at high reaction temperatures has been studied. The surface and bulk structureof the catalyst were characterized by means of XRD...he deactivation of highly active multicomponent oxide LiLa_0.5 Ti_0.5 O_(2+λ) cata-lyst at high reaction temperatures has been studied. The surface and bulk structureof the catalyst were characterized by means of XRD, IR, XPS, BET, O_2-TPD,SEM etc.. The results show that the deactivation of the catalyst at high reactiontemperatures is mainly due to the loss of surface lithium. As a result , the diffusionof lithium from bulk to surface leads to the decompositiqn of the active phase con-taining lithium, which lowers tlie number of oxygen vacancies and decreases themobility of lattice oxygen.展开更多
基金supported by the Science and Technology Plan Project of Hebei Province of China(16273703D)the Fundamental Research Funds for the Central Universities(2015ZD24,2017XS123)~~
文摘Vanadium-titanium-based catalysts are the most widely used industrial materials for NO_x removal from coal-fired power plants. Owing to their relatively poor low-temperature deNO_x activity, low thermal stability, insufficient Hg^0 oxidation activity, SO_2 oxidation, ammonia slip, and other disadvantages,modifications to traditional vanadium-titanium-based selective catalytic reduction（SCR）catalysts have been attempted by many researchers to promote their relevant performance. This article reviewed the research progress of modified vanadium-titanium-based SCR catalysts from seven aspects, namely,（1） improving low-temperature deNO_x efficiency,（2） enhancing thermal stability,（3） improving Hg^0 oxidation efficiency,（4） oxidizing slip ammonia,（5） reducing SO_2 oxidation,（6） increasing alkali resistance, and（7） others. Their catalytic performance and the influence mechanisms have been discussed in detail. These catalysts were also divided into different categories according to their modified components such as noble metals（e.g., silver, ruthenium）, transition metals（e.g., manganese, iron, copper, zirconium, etc.）, rare earth metals（e.g., cerium, praseodymium）,and other metal chlorides（e.g., calcium chloride, copper chloride） and non-metals（fluorine,sulfur, silicon, nitrogen, etc.）. The advantages and disadvantages of these catalysts were summarized.Based on previous studies and the author＇s point of view, doping the appropriate modified components is beneficial to further improve the overall performance of vanadium-titanium-based SCR catalysts. This has enormous development potential and is a promising way to realize the control of multiple pollutants on the basis of the existing flue gas treatment system.
基金ACKNOWLEDGMENT This work was supported Science Foundation of China by the National Natural （No.20703042）.
文摘Titania-based composite catalysts were prepared through a sol-gel route employing multi-walled carbon nanotubes with different diameters. The materials were characterized using thermogravimetric analysis, nitrogen adsorption-desorption isotherm, powder X-ray diffraction, scanning electron microscopy, and diffuse reflectance UV-Vis absorption spectra. The application of the catalysts to photocatalytic degradation of phenol was tested under UV-Vis irradiation. A synergetic effect on phenol removal was observed in case of composite catalysts, which was evaluated in terms of apparent rate constant, total organic carbon removal and photonic efficiency.
基金V. ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.20703042）, the National Basic Research Program of China （No.2010 CB923300）, USTC-NSRL Association Funding （No.KY 2060030009）, and Fundamental Research Funds for the Central Universities （No.WK2060030010）.
文摘Nanostructured titanium dioxides were synthesized via various post-treatments of titanate nanofibers obtained from titanium precursors by hydrothermal reactions. The microstructures of TiO2 and supported Ru/TiO2 catalysts were characterized with X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray analysis, and nitrogen adsorption isotherms. The phase structure, particle size, morphology, and specific surface area were determined. The supported Ru catalysts were applied for the selective methanation of CO in a hydrogen-rich stream. The results indicated that the Ru catalyst supported on rutile and TiO2-B exhibited higher catalytic performance than the counterpart supported on anatase, which suggested the distinct interaction between Ru nanoparticles and TiO2 resulting from different crystalline phases and morphology.
基金Project supported by the National Natural Science Foundation of China (50571003)
文摘TiO2/V2O5 catalyst doped with rare earth ions was prepared by sol-gel method. Titanium tetrapropoxide and vanadium pentoxide were used as precursor of the composite catalyst and rare earth ions were used as dopant. The crystal phases, crystalline sizes, microstructure, absorption spectra of doped composite catalyst were studied by XRD, EDS, FT-IR and UV-Vis. Photoactivity of the prepared catalyst under ultraviolet irradiation were evaluated by degradation of methyl orange （MO） in aqueous solution. It is shown that the prepared catalyst is composed of anatase and futile. The rare earth ions are highly dispersed in composite catalyst. All the doped catalysts appear higher photocatalytic activity than TiO2/V2O5 catalyst and catalyst doped with Ce^4＋ present the best activity to MO.
基金Grant-in-Aid for Scientific Research(B)from the Japan Society for the Promotion of Science(JSPS,No.18350055).
文摘Precise,efficient copolymerizations of ethylene with cyclic olefins[norbornene(NBE),cyclopentene(CPE)]using nonbridged half-titanocenes of type,Cp TiCl_2(L)(Cp =cyclopentadienyl group,L=aryloxo,ketimide)-MAO catalyst systems have been summarized.CpTiCl_2(N=C Bu_2)exhibited both remarkable catalytic activity and efficient NBE incorporation for ethylene/NBE copolymerization:the NBE incorporation by Cp TiCl_2(X)(X=N=C Bu_2,O-2,6- Pr_2C_6H_3; Cp =Cp,C_5Me_5,indenyl)was related to the calculated coordination ene...
文摘The effect of chemical composition of highly active supported Ziegler-Natta catalysts with controlled morphology on the MWD of PE has been studied.It was shown the variation of transition metal compound in the MgCl_2-supported catalyst affect of MWD of PE produced in broad range:Vanadium-magnesium catalyst(VMC)produce PE with broad and bimodal MWD(M_w/M_n=14-21).MWD of PE,produced over titanium-magnesium catalyst(TMC)is narrow or medium depending on Ti content in the catalyst(M_w/M_n=3.1-4.8).The oxidation ...
基金supported by the National High Technology Research and Development Program of China (No. 2007AA03Z337)the Harbin Special Creation Foundation for Science and Technology of Fellow in China (No. 2006RFQXG032)
文摘The aim of this work was to investigate the effects of calcination/acid-activation on the composition, structure, and photocatalytic （PC） reduction property of an anodic oxidation TiO2/Ti film catalyst. The surface morphology and phase composition were examined by scanning electron microscopy and X-ray diffraction. The catalytic property of the film catalysts was evaluated through the removal rate of potassium chromate during the PC reduction process. The results showed that the film catalysts were composed of anatase and rutile TiO2 with a micro-porous surface structure. The calcination treatment increased the content of TiO2 in the film, changed the relative ratio of anatase and rutile TiO2, and decreased the size of the micro pores of the film catalysts. The removal rate of potassium chromate was related to the technique parameters of calcination/acid-activation treatment. When the anodic oxidation TiO2/Ti film catalyst was calcined at 873 K for 30 min and then acid-activated in the concentrated H2SO4 for 60 min, it presented the highest catalytic property, with the removal rate of potassium chromate of 96.3% during the PC reduction process under the experimental conditions.
基金The work is sub sidized by Special Funds for Major State Basis Research Projects of China(No.G1999064801)
文摘A monocyclopentadienyl titanium complex containing 8-quinolinolato (QCpTiCl_2) was synthesized. Its activities in ethylene polymerization at various Al/Ti molar ratios, different temperatures and activation time were investigated. The activity with a Al/Ti molar ratio of 500 exhibited a maximum of 2.8×10~5 g/(mol.h) at 30℃. The activation time of QCpTiCl_2 with MAO before polymerization also plays a role on the activity. The structural properties of the produced polyethylene (molecular weight, molecular weight distribution and melting point) were discussed. Kinetic behaviors of ethylene polymerization with the QCpTiCl_2/MAO system at different Al/Ti molar ratios were studied. For the QCpTiMeCl/MAO system and the CpTiMe_2Cl/MAO system, binding energies of the examined intermediates were calculated by quantum-mechanical method based on ADF program, respectively. It is confirmed that the chlorinebridged adduct formed by the reaction of QCpTiMeCl with MAO is thermodynamically steady. In the case of the QCpTiMeCl/MAO system, olefin-separated ion pair (OSIP) mechanism is much favorable than ion-pair dissociation (IPD) mechanism. The experimental result on the CpTiMe_2Cl/MAO system showed lower activity for ethylene polymerization than that on the QCpTiMeCl/MAO system, which revealed that the CpTiMe_2Cl/MAO system is unfavorable to form active species with ethylene.
基金financially supported by the Scientific Research Foundation of Shandong University of Science and Technology for Recruited Talents (No. 2014RCJJ017)
文摘Ti-containing mesoporous silica materials(Ti-MSs) with isolated tetrahedrally coordinated Ti species have been widely applied in bulk molecular catalysis. Herein, Ti-MSs were synthesized using anionic surfactant SDS as the co-template. The SDS molecular assembled structures can interact with silica species through the interface hydrogen bonds leading to the formation of mesoporous silica structure with compact Ti-O bonds, lower hydrophilicity and low template cost. The influence of adding SDS as the co-template on the oxidation of styrene with aqueous H_2O_2 as the oxidant was investigated. Ti-MSs using SDS as the co-template showed better catalytic performance as compared with mesoporous titanium silicate synthesized with CTAB serving as the sole template. Moreover, the Ti-MSs synthesized at a Ti/Si ratio of 0.005 demonstrated an optimized performance for styrene oxidation with styrene conversion improved by 14.8%, benzaldehyde selectivity improved by 13.7% and styrene oxide selectivity improved by 9.2% when the reaction time was 6 h.
基金The work is supported by Special Funds for State Major Basic Research Projects of China(No.G1999064801)
文摘Three mono-cyclopentadienyl metal complexes, [C_6H_4O_2]CpTiCl (Ⅰ),[C_(12)H_8O_2]CpTiCl (Ⅱ), and [C_(20)H_(12)O_2] CpTiCl (Ⅲ), were prepared via the reactions ofcyclopentadienyl titanium trichloride with catechol, 2,2i-bisphenol, and 2,2'-bisnaphthol,respectively. In the presence of a moderate amount of methylaluminoxane (MAO), the complexesexhibited catalytic activities for ethylene polymerization. Complex Ⅰ showed the highest activityat Al/Ti molar ratio of 500 at the temperature of 30℃. With increasing of polymerizationtemperature, catalytic activities and molecular weight of the obtained polyethylene tended todecrease, and molecular weight distribution of polyethylene became narrower. With the molecularsimulation method, the charges on titanium atoms of complexes Ⅰ, Ⅱ, and Ⅲ, and the bond anglesformed by Ti and bisphenoxy ligands were calculated. It was concluded that the smaller the netcharge on Ti and the smaller the angle of O1―Ti―O2, the higher the activity of the complex.
文摘Catalysts of carbon monoxide oxidation were synthesized by deposition of platinum on titanium nitride (TiN). Two substrates with an average particle size of 18 and 36 nm were obtained by hydrogen reduction of titanium tetrachloride in a stream of microwave plasma of nitrogen. The surface of the catalysts was studied by X-ray photoelectron spectroscopy (XPS). The data obtained by us in the present work indicate the presence of oxynitride as a transition layer between nitride and oxide. It was found that the CO oxidation rate on the 9 - 15 wt.% Pt loaded TiN catalysts is 120 times higher than that on the platinum black with a specific surface of 30 m<sup>2</sup>/g. Increase in the reaction rate of CO oxidation on Pt/TiN catalysts as compared to platinum black can be associated with both an increase in the concentration of CO molecules adsorbed and a decrease in the activation energy of the reaction. Catalysts are promising for use in catalytic air purification systems.
文摘he deactivation of highly active multicomponent oxide LiLa_0.5 Ti_0.5 O_(2+λ) cata-lyst at high reaction temperatures has been studied. The surface and bulk structureof the catalyst were characterized by means of XRD, IR, XPS, BET, O_2-TPD,SEM etc.. The results show that the deactivation of the catalyst at high reactiontemperatures is mainly due to the loss of surface lithium. As a result , the diffusionof lithium from bulk to surface leads to the decompositiqn of the active phase con-taining lithium, which lowers tlie number of oxygen vacancies and decreases themobility of lattice oxygen.
