In this study,different loadings of x%Ni_(2)P/γ-Al_(2)O_(3)(x=6%,9%,12%,15%,18%)catalysts with aluminum oxide(Al_(2)O_(3))as the carrier,nickel chloride(NiCl2)as the nickel(Ni)source,and ammonium hypophosphite(NH_(4)...In this study,different loadings of x%Ni_(2)P/γ-Al_(2)O_(3)(x=6%,9%,12%,15%,18%)catalysts with aluminum oxide(Al_(2)O_(3))as the carrier,nickel chloride(NiCl2)as the nickel(Ni)source,and ammonium hypophosphite(NH_(4)H_(2)PO_(2))as the phosphorus(P)source were prepared by the equal volume impregnation method to investigate the effects of different loadings on the performance of the selective hydrogenation of diolefins and thiol etherification in LPG.The physicochemical properties of the catalysts were characterized by XRD,BET,SEM,TEM,H_(2)-TPR,and XPS,and the catalytic activity of the catalysts was evaluated in a fixed-bed microreactor.The results showed that a change in the loading affected the catalyst crystalline phase structure and size,specific surface area,P coverage,active phase dispersion,and catalytic activity.At 6%,9%,and 12%loadings the catalysts had an Ni phase but there was no obvious Ni_(2)P phase in the nickel phosphide;at 15%loading a single Ni_(2)P phase was obtained,and at 18%loading both Ni_(2)P and Ni1_(2)P_(5) phases appeared.There was a P enrichment on the catalyst surface,and the higher the loading the more P species were enriched on the surface,but some of the P was lost during the catalyst reduction process due to the production of phosphine(PH3)gas.The 15%Ni_(2)P/γ-Al_(2)O_(3) catalyst had the largest Ni/Al ratio and the best dispersion.The Ni_(2)P active phase size was small at about 4.25 nm and Ni_(2)P was uniformly dispersed on the catalyst surface without agglomeration.The 15%Ni_(2)P/γ-Al_(2)O_(3) catalyst had the best catalytic activity at a pressure of 2.0 MPa,a liquid hourly space velocity(LHSV)of 3.0 h-1,and a hydrogen to hydrocarbon ratio of 12.The 1,3-butadiene conversion was 97.45%and the methanethiol removal was 100%at a temperature of 140℃.展开更多
Catalytic properties of MnOx-FeOx complex oxide (hereafter denoted as Mn-Fe) catalysts modified with different loadings of chromium oxide were investigated by using the combination of physico-cbemical techniques, su...Catalytic properties of MnOx-FeOx complex oxide (hereafter denoted as Mn-Fe) catalysts modified with different loadings of chromium oxide were investigated by using the combination of physico-cbemical techniques, such as N2 physisorption, X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), in situ Fourier transform infrared spectroscopy (in situ FT-IR) and temperature-programmed reduction (TPR) and their catalytic activities were evaluated with the selective catalytic reduction (SCR) of NOx by NH3. It was found that with the addition of Cr, more NO could be removed in the low-temperature window (below 120 ℃). Among the tested catalysts, Mn-Fe- Cr (2 : 2 : 1) catalyst exhibited the best catalytic performance at 80 ℃ with the NO conversion higher than 90%. The combination of the reaction and characterization results indicated that (1) the strong interaction among tertiary metal oxides existed in the catalysts when Cr was appropriately added, which made the active components better dispersed with less agglomeration and sintering and the largest BET specific surface area could be obtained; (2) Cr improved the low-temperature reducibility of the catalyst and promoted the formation of the active intermediate (-NH3+), which favored the low-temperature SCR reaction.展开更多
Binary metal oxide(MnOx-A/TiO2)catalysts were prepared by adding the second metal to manganese oxides supported on titanium dioxide(TiO2),where,A indicates Fe2O3,WO3,MoO3,and Cr2O3.Their catalytic activity,N2 sele...Binary metal oxide(MnOx-A/TiO2)catalysts were prepared by adding the second metal to manganese oxides supported on titanium dioxide(TiO2),where,A indicates Fe2O3,WO3,MoO3,and Cr2O3.Their catalytic activity,N2 selectivity,and SO2 poisonous tolerance were investigated.The catalytic performance at low temperatures decreased in the following order:Mn-W/TiO2〉Mn-Fe/TiO2〉Mn-Cr/TiO2〉Mn-Mo/TiO2,whereas the N2 selectivity decreased in the order:Mn-Fe/TiO2〉Mn-W/TiO2〉Mn-Mo/TiO2〉Mn-Cr/TiO2.In the presence of 0.01%SO2 and 6%H2O,the NOx conversions in the presence of Mn-W/TiO2,Mn-Fe/TiO2,or Mn-Mo/TiO2 maintain 98.5%,95.8%and 94.2%, respectively,after 8 h at 120°C at GHSV 12600 h? 1 .As effective promoters,WO3 and Fe2O3 can increase N2 selectivity and the resistance to SO2 of MnOx/TiO2 significantly.The Fourier transform infrared(FTIR)spectra of NH3 over WO3 show the presence of Lewis acid sites.The results suggest that WO3 is the best promoter of MnOx/TiO2,and Mn-W/TiO2 is one of the most active catalysts for the low temperature selective catalytic reduction of NO with NH3.展开更多
In this study,we used a simple impregnation method to prepare Fe-Ce-O_x catalysts and tested them regarding their low-temperature(200-300 ℃) selective catalytic reduction(SCR) of NO using NH_3.We investigated the eff...In this study,we used a simple impregnation method to prepare Fe-Ce-O_x catalysts and tested them regarding their low-temperature(200-300 ℃) selective catalytic reduction(SCR) of NO using NH_3.We investigated the effects of Fe/Ce molar ratio,the gas hourly space velocity(GHSV),the stability and SO_2/H_2O resistance of the catalysts.The results showed that the FeCe(1:6)O_x(Ce/Fe molar ratio is 1:6) catalyst,which has some ordered parallel channels,exhibited good SCR performance.The FeCe(1:6)O_x catalyst had the highest NO conversion with an activity of 94-99%at temperatures between 200 and300 ℃ at a space velocity of 28,800 h^(-1).The NO conversion for the FeCe(1:6)O_x catalyst also reached 80-98%between 200 and 300 ℃ at a space velocity of204,000h^(-1).In addition,the FeCe(1:6)O_x catalyst demonstrated good stability in a 10-h SCR reaction at200-300 ℃.Even in the presence of SO_2 and H_2O,the FeCe(1:6)O_x catalyst exhibited good SCR performance.展开更多
The feasibility and technologies of comprehensive recovery of tin, zinc, arsenic and iron from the complex iron ores by selective chlorination roasting were studied by thermodynamic analysis and roasting experiments. ...The feasibility and technologies of comprehensive recovery of tin, zinc, arsenic and iron from the complex iron ores by selective chlorination roasting were studied by thermodynamic analysis and roasting experiments. Investigation shows that the product pellets with the compression strength of 2625N/P, the tumble index of 97.26%, the abrasion index of 1.35%, tin, arsenic and zinc residue of 0.043%, 0.046% and 0.058% respectively can be achieved if balling a concentrate containing 0.39% tin, 0.40% arsenic and 0.28% with addition of 8% coke breeze and 0.5% CaCl2 and roasting the pellets at 10601080℃ for 40min. The volatilization of tin, arsenic and zinc is 91.75%, 93.42% and 81.12% respectively. The performances of the product pellets are able to meet the requirements of blast furnace ironmaking.展开更多
The metal oxide catalyst was prepared by loading MnOx and FeOx on carbon nano-tubes (CNTs) with impregnation method. Then the catalyst was characterized by BET and XPS, and the effect of adding FeOx on MnOx/CNTs catal...The metal oxide catalyst was prepared by loading MnOx and FeOx on carbon nano-tubes (CNTs) with impregnation method. Then the catalyst was characterized by BET and XPS, and the effect of adding FeOx on MnOx/CNTs catalyst at the low-temperature selective catalytic reduction of NO with NH3 was investigated. The results showed that the active components were loaded suc-cessfully and easily on the carriers by impregnation. The Mn-Fe/CNTs catalyst was chose 10% Fe(NO3)3 solution to impregnate Mn-Fe/CNTs. The species of active components loaded on the catalyst were Fe2O3. The different concentration of impregnant solution played an important role for NO conversion in SCR with NH3. With the increase of the concentration of impregnant solution, the NO conversion of catalysts was increasing initially then decreasing.展开更多
Vanadium extraction of vanadium-bearing titanomagnetite was investigated by selective chlorination. Thermodynamics analyses on the interactive reactions among related species in the system were made before the experim...Vanadium extraction of vanadium-bearing titanomagnetite was investigated by selective chlorination. Thermodynamics analyses on the interactive reactions among related species in the system were made before the experiments. Some fundamental experiments for extracting vanadium by FeCl_x as chlorinating agent were conducted over the temperature range of 900-1300 K under air or oxygen atmosphere. The results show that vanadium can be extracted by the selective chlorination, using FeCl_x, based on thermodynamic analysis and experiment. Vanadium extraction ratio first increases with the increase of temperature, and then decreases with the increase of temperature over the range of 900-1300 K under air or oxygen atmosphere. The higher molar ratio of FeCl_3 to oxides(n_(chl):n_(oxd)) reacting with FeCl_3, the higher ratio of vanadium extraction. Under oxygen atmosphere, the vanadium extraction ratio is up to 32% at 1100 K for 2 h by using FeCl_3 as chlorinating agent.展开更多
A series of Mn-based catalysts, MnOx, MnOx-CeO, Pd-Mn-Ce, MnOx/AC were prepared. And their performances for NO low-temperature SCR were investigated in this study. The NO conversion is about 90% at 100 ℃ on MnOx-CeOa...A series of Mn-based catalysts, MnOx, MnOx-CeO, Pd-Mn-Ce, MnOx/AC were prepared. And their performances for NO low-temperature SCR were investigated in this study. The NO conversion is about 90% at 100 ℃ on MnOx-CeOand almost all NO can be converted at 120 ℃. Similar results are also observed in the tests on MnOx-CeO/AC. The excellent low-temperature catalytic activity of modified Mn-based catalysts, which may be mainly due to the oxygen storage function of CeO, can improve the oxygen flow on the catalysts surface. Then the oxidation of NO to NO2 is accelerated, which is the key step of NO SCR.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
A series of N-doped graphene(NG)and TiO_2 supported MnO_x–CeO_2 catalysts were prepared prepared by a hydrothermal method.The catalysts with different molar ratios of Mn/Ce(6:1,10:1,15:1)were investigated for the low...A series of N-doped graphene(NG)and TiO_2 supported MnO_x–CeO_2 catalysts were prepared prepared by a hydrothermal method.The catalysts with different molar ratios of Mn/Ce(6:1,10:1,15:1)were investigated for the low-temperature selective catalytic reduction(SCR)of NO_x with NH_3.The synthesized catalysts were characterized by HRTEM,SEM,XRD,BET,XPS,and NH_3-TPD technologies.The characterization results indicated that manganese and cerium oxide particles dispersed on the surface of the TiO_2–NG support uniformly,and that manganese and cerium oxides existed in different valences on the surface of the TiO_2–NG support.At Mn element loading of 8 wt%,MnO_x–CeO_2(10:1)/TiO_2–1%NG displayed superior activity and improved SO_(2 )resistance.On the basis of the catalyst characterization,excellent catalytic performance and SO_2 tolerance at low temperature were attributed to the high content of manganese with high oxidation valence,extensive oxidation of NO into NO_2 by CeO_2 and strong NO adsorption capacity,and electron transfer of N-doped graphene.展开更多
Mn-based catalysts have exhibited promising performance in low-temperature selective catalytic reduction of NOx with NH_(3)(NH_(3)-SCR).However,challenges such as H_(2)O-or SO_(2)-induced poisoning to these catalysts ...Mn-based catalysts have exhibited promising performance in low-temperature selective catalytic reduction of NOx with NH_(3)(NH_(3)-SCR).However,challenges such as H_(2)O-or SO_(2)-induced poisoning to these catalysts still remain.Herein,we report an efficient strategy to prepare the dual single-atom Ce-Ti/MnO_(2)catalyst via ball-milling and calcination processes to address these issues.Ce-Ti/MnO_(2)showed better catalytic performance with a higher NO conversion and enhanced H_(2)O-and SO_(2)-resistance at a lowtemperature window(100−150°C)than the MnO_(2),single-atom Ce/MnO_(2),and Ti/MnO_(2)catalysts.The in situ infrared Fourier transform spectroscopy analysis confirmed there is no competitive adsorption between NOx and H_(2)O over the Ce-Ti/MnO_(2)catalyst.The calculation results showed that the synergistic interaction of the neighboring Ce-Ti dual atoms as sacrificial sites weakens the ability of the active Mn sites for binding SO_(2)and H_(2)O but enhances their binding to NH_(3).The insight obtained in this work deepens the understanding of catalysis for NH_(3)-SCR.The synthesis strategy developed in this work is easily scaled up to commercialization and applicable to preparing other MnO_(2)-based single-atom catalysts.展开更多
It is fascinating to explore the distribution of CO_(2)hydrogenation products regulated by heterogeneous catalysts,as both the chemical state of surface metals and structure of the support itself of the supported cata...It is fascinating to explore the distribution of CO_(2)hydrogenation products regulated by heterogeneous catalysts,as both the chemical state of surface metals and structure of the support itself of the supported catalysts may affect the performance of CO_(2)hydrogenation.Herein,the complete switching of CO_(2)hydrogenation products from CH4 to CO can be realized by induction of Cl into Ru/TiO_(2)catalyst.Density functional theory(DFT)calculations indicated that Cl ions were mainly located on the Ru metal sites of Ru/TiO_(2)catalysts.Bader charge analysis and Ru 3p X-ray photoelectron spectra(XPS)results suggested that electrons transferred from Ru to Cl,resulting in the decrease of electron density of Ru.In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)of CO_(2)hydrogenation and CO adsorption proved that with the increase of the Cl ion content,the adsorption of CO on the catalyst surface was significantly weakened,and resulted in the high CO selectivity.Our work demonstrates the role of Cl ions in regulating the distribution of CO_(2)hydrogenation products,and provides new ideas for regulating other catalytic processes.展开更多
文摘In this study,different loadings of x%Ni_(2)P/γ-Al_(2)O_(3)(x=6%,9%,12%,15%,18%)catalysts with aluminum oxide(Al_(2)O_(3))as the carrier,nickel chloride(NiCl2)as the nickel(Ni)source,and ammonium hypophosphite(NH_(4)H_(2)PO_(2))as the phosphorus(P)source were prepared by the equal volume impregnation method to investigate the effects of different loadings on the performance of the selective hydrogenation of diolefins and thiol etherification in LPG.The physicochemical properties of the catalysts were characterized by XRD,BET,SEM,TEM,H_(2)-TPR,and XPS,and the catalytic activity of the catalysts was evaluated in a fixed-bed microreactor.The results showed that a change in the loading affected the catalyst crystalline phase structure and size,specific surface area,P coverage,active phase dispersion,and catalytic activity.At 6%,9%,and 12%loadings the catalysts had an Ni phase but there was no obvious Ni_(2)P phase in the nickel phosphide;at 15%loading a single Ni_(2)P phase was obtained,and at 18%loading both Ni_(2)P and Ni1_(2)P_(5) phases appeared.There was a P enrichment on the catalyst surface,and the higher the loading the more P species were enriched on the surface,but some of the P was lost during the catalyst reduction process due to the production of phosphine(PH3)gas.The 15%Ni_(2)P/γ-Al_(2)O_(3) catalyst had the largest Ni/Al ratio and the best dispersion.The Ni_(2)P active phase size was small at about 4.25 nm and Ni_(2)P was uniformly dispersed on the catalyst surface without agglomeration.The 15%Ni_(2)P/γ-Al_(2)O_(3) catalyst had the best catalytic activity at a pressure of 2.0 MPa,a liquid hourly space velocity(LHSV)of 3.0 h-1,and a hydrogen to hydrocarbon ratio of 12.The 1,3-butadiene conversion was 97.45%and the methanethiol removal was 100%at a temperature of 140℃.
基金supported by Jiangsu Natural Science Foundation (No. BK2012347)the National High Technology and Development Program of China (863 Programs, No.2007AA061802)
文摘Catalytic properties of MnOx-FeOx complex oxide (hereafter denoted as Mn-Fe) catalysts modified with different loadings of chromium oxide were investigated by using the combination of physico-cbemical techniques, such as N2 physisorption, X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), in situ Fourier transform infrared spectroscopy (in situ FT-IR) and temperature-programmed reduction (TPR) and their catalytic activities were evaluated with the selective catalytic reduction (SCR) of NOx by NH3. It was found that with the addition of Cr, more NO could be removed in the low-temperature window (below 120 ℃). Among the tested catalysts, Mn-Fe- Cr (2 : 2 : 1) catalyst exhibited the best catalytic performance at 80 ℃ with the NO conversion higher than 90%. The combination of the reaction and characterization results indicated that (1) the strong interaction among tertiary metal oxides existed in the catalysts when Cr was appropriately added, which made the active components better dispersed with less agglomeration and sintering and the largest BET specific surface area could be obtained; (2) Cr improved the low-temperature reducibility of the catalyst and promoted the formation of the active intermediate (-NH3+), which favored the low-temperature SCR reaction.
文摘Binary metal oxide(MnOx-A/TiO2)catalysts were prepared by adding the second metal to manganese oxides supported on titanium dioxide(TiO2),where,A indicates Fe2O3,WO3,MoO3,and Cr2O3.Their catalytic activity,N2 selectivity,and SO2 poisonous tolerance were investigated.The catalytic performance at low temperatures decreased in the following order:Mn-W/TiO2〉Mn-Fe/TiO2〉Mn-Cr/TiO2〉Mn-Mo/TiO2,whereas the N2 selectivity decreased in the order:Mn-Fe/TiO2〉Mn-W/TiO2〉Mn-Mo/TiO2〉Mn-Cr/TiO2.In the presence of 0.01%SO2 and 6%H2O,the NOx conversions in the presence of Mn-W/TiO2,Mn-Fe/TiO2,or Mn-Mo/TiO2 maintain 98.5%,95.8%and 94.2%, respectively,after 8 h at 120°C at GHSV 12600 h? 1 .As effective promoters,WO3 and Fe2O3 can increase N2 selectivity and the resistance to SO2 of MnOx/TiO2 significantly.The Fourier transform infrared(FTIR)spectra of NH3 over WO3 show the presence of Lewis acid sites.The results suggest that WO3 is the best promoter of MnOx/TiO2,and Mn-W/TiO2 is one of the most active catalysts for the low temperature selective catalytic reduction of NO with NH3.
基金supported by the National Natural Science Foundation of China (No.21206108)Tianjin Municipal Science and Technology Commission (No.14JCYBJC21200)
文摘In this study,we used a simple impregnation method to prepare Fe-Ce-O_x catalysts and tested them regarding their low-temperature(200-300 ℃) selective catalytic reduction(SCR) of NO using NH_3.We investigated the effects of Fe/Ce molar ratio,the gas hourly space velocity(GHSV),the stability and SO_2/H_2O resistance of the catalysts.The results showed that the FeCe(1:6)O_x(Ce/Fe molar ratio is 1:6) catalyst,which has some ordered parallel channels,exhibited good SCR performance.The FeCe(1:6)O_x catalyst had the highest NO conversion with an activity of 94-99%at temperatures between 200 and300 ℃ at a space velocity of 28,800 h^(-1).The NO conversion for the FeCe(1:6)O_x catalyst also reached 80-98%between 200 and 300 ℃ at a space velocity of204,000h^(-1).In addition,the FeCe(1:6)O_x catalyst demonstrated good stability in a 10-h SCR reaction at200-300 ℃.Even in the presence of SO_2 and H_2O,the FeCe(1:6)O_x catalyst exhibited good SCR performance.
文摘The feasibility and technologies of comprehensive recovery of tin, zinc, arsenic and iron from the complex iron ores by selective chlorination roasting were studied by thermodynamic analysis and roasting experiments. Investigation shows that the product pellets with the compression strength of 2625N/P, the tumble index of 97.26%, the abrasion index of 1.35%, tin, arsenic and zinc residue of 0.043%, 0.046% and 0.058% respectively can be achieved if balling a concentrate containing 0.39% tin, 0.40% arsenic and 0.28% with addition of 8% coke breeze and 0.5% CaCl2 and roasting the pellets at 10601080℃ for 40min. The volatilization of tin, arsenic and zinc is 91.75%, 93.42% and 81.12% respectively. The performances of the product pellets are able to meet the requirements of blast furnace ironmaking.
文摘The metal oxide catalyst was prepared by loading MnOx and FeOx on carbon nano-tubes (CNTs) with impregnation method. Then the catalyst was characterized by BET and XPS, and the effect of adding FeOx on MnOx/CNTs catalyst at the low-temperature selective catalytic reduction of NO with NH3 was investigated. The results showed that the active components were loaded suc-cessfully and easily on the carriers by impregnation. The Mn-Fe/CNTs catalyst was chose 10% Fe(NO3)3 solution to impregnate Mn-Fe/CNTs. The species of active components loaded on the catalyst were Fe2O3. The different concentration of impregnant solution played an important role for NO conversion in SCR with NH3. With the increase of the concentration of impregnant solution, the NO conversion of catalysts was increasing initially then decreasing.
基金Projects(51374061,51074040)supported by the National Natural Science Foundation of ChinaProject(201202064)supported by the Natural Science Foundation of Liaoning Province,ChinaProject(N120402004)supported by the Fundamental Research Funds for the Central Universities,China
文摘Vanadium extraction of vanadium-bearing titanomagnetite was investigated by selective chlorination. Thermodynamics analyses on the interactive reactions among related species in the system were made before the experiments. Some fundamental experiments for extracting vanadium by FeCl_x as chlorinating agent were conducted over the temperature range of 900-1300 K under air or oxygen atmosphere. The results show that vanadium can be extracted by the selective chlorination, using FeCl_x, based on thermodynamic analysis and experiment. Vanadium extraction ratio first increases with the increase of temperature, and then decreases with the increase of temperature over the range of 900-1300 K under air or oxygen atmosphere. The higher molar ratio of FeCl_3 to oxides(n_(chl):n_(oxd)) reacting with FeCl_3, the higher ratio of vanadium extraction. Under oxygen atmosphere, the vanadium extraction ratio is up to 32% at 1100 K for 2 h by using FeCl_3 as chlorinating agent.
基金the Key Project of the National Natural Science Foundation of China (20437010)the Natural Science Foundation of Yunnan Province (2007E184M)the Science Foundation of the Education Department of Yunnan Province(07C11400)
文摘A series of Mn-based catalysts, MnOx, MnOx-CeO, Pd-Mn-Ce, MnOx/AC were prepared. And their performances for NO low-temperature SCR were investigated in this study. The NO conversion is about 90% at 100 ℃ on MnOx-CeOand almost all NO can be converted at 120 ℃. Similar results are also observed in the tests on MnOx-CeO/AC. The excellent low-temperature catalytic activity of modified Mn-based catalysts, which may be mainly due to the oxygen storage function of CeO, can improve the oxygen flow on the catalysts surface. Then the oxidation of NO to NO2 is accelerated, which is the key step of NO SCR.
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.
基金financially supported by the Program of Frontier Exploration Fund of China Building Materials Academy,"the whole process of air pollution control on new technology research" (No. 2016YFC0209302)
文摘A series of N-doped graphene(NG)and TiO_2 supported MnO_x–CeO_2 catalysts were prepared prepared by a hydrothermal method.The catalysts with different molar ratios of Mn/Ce(6:1,10:1,15:1)were investigated for the low-temperature selective catalytic reduction(SCR)of NO_x with NH_3.The synthesized catalysts were characterized by HRTEM,SEM,XRD,BET,XPS,and NH_3-TPD technologies.The characterization results indicated that manganese and cerium oxide particles dispersed on the surface of the TiO_2–NG support uniformly,and that manganese and cerium oxides existed in different valences on the surface of the TiO_2–NG support.At Mn element loading of 8 wt%,MnO_x–CeO_2(10:1)/TiO_2–1%NG displayed superior activity and improved SO_(2 )resistance.On the basis of the catalyst characterization,excellent catalytic performance and SO_2 tolerance at low temperature were attributed to the high content of manganese with high oxidation valence,extensive oxidation of NO into NO_2 by CeO_2 and strong NO adsorption capacity,and electron transfer of N-doped graphene.
基金We gratefully acknowledge the financial supports from the National Natural Science Foundation of China(Nos.52070180,51938014,and 21802054)the Science Research Project of the Ministry of Education of the Heilongjiang Province of China(No.145109102)+2 种基金the Beijing Chenxi Environmental Engineering Co.,Ltd.Z.Z.thanks the financial support of Guangdong Key discipline fund for this collaborationY.J.thanks the financial supports from the Outstanding Youth cultivation program of Beijing Technology and Business University(No.19008021144)Research Foundation for Advanced Talents of Beijing Technology and Business University(No.19008020159).
文摘Mn-based catalysts have exhibited promising performance in low-temperature selective catalytic reduction of NOx with NH_(3)(NH_(3)-SCR).However,challenges such as H_(2)O-or SO_(2)-induced poisoning to these catalysts still remain.Herein,we report an efficient strategy to prepare the dual single-atom Ce-Ti/MnO_(2)catalyst via ball-milling and calcination processes to address these issues.Ce-Ti/MnO_(2)showed better catalytic performance with a higher NO conversion and enhanced H_(2)O-and SO_(2)-resistance at a lowtemperature window(100−150°C)than the MnO_(2),single-atom Ce/MnO_(2),and Ti/MnO_(2)catalysts.The in situ infrared Fourier transform spectroscopy analysis confirmed there is no competitive adsorption between NOx and H_(2)O over the Ce-Ti/MnO_(2)catalyst.The calculation results showed that the synergistic interaction of the neighboring Ce-Ti dual atoms as sacrificial sites weakens the ability of the active Mn sites for binding SO_(2)and H_(2)O but enhances their binding to NH_(3).The insight obtained in this work deepens the understanding of catalysis for NH_(3)-SCR.The synthesis strategy developed in this work is easily scaled up to commercialization and applicable to preparing other MnO_(2)-based single-atom catalysts.
基金the National Natural Science Foundation of China(No.22072176)the Key Laboratory of Magnetic Molecules and Magnetic Information Materials,Ministry of Education(No.MMMM-202001)+1 种基金the Shanxi Science and Technology Department(No.20210302123012)the Award Foundation for Excellent PhD Graduates Work in Shanxi Province(No.SQ2019005).
文摘It is fascinating to explore the distribution of CO_(2)hydrogenation products regulated by heterogeneous catalysts,as both the chemical state of surface metals and structure of the support itself of the supported catalysts may affect the performance of CO_(2)hydrogenation.Herein,the complete switching of CO_(2)hydrogenation products from CH4 to CO can be realized by induction of Cl into Ru/TiO_(2)catalyst.Density functional theory(DFT)calculations indicated that Cl ions were mainly located on the Ru metal sites of Ru/TiO_(2)catalysts.Bader charge analysis and Ru 3p X-ray photoelectron spectra(XPS)results suggested that electrons transferred from Ru to Cl,resulting in the decrease of electron density of Ru.In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)of CO_(2)hydrogenation and CO adsorption proved that with the increase of the Cl ion content,the adsorption of CO on the catalyst surface was significantly weakened,and resulted in the high CO selectivity.Our work demonstrates the role of Cl ions in regulating the distribution of CO_(2)hydrogenation products,and provides new ideas for regulating other catalytic processes.