In this work we prepared several CeO2-TiO2 catalysts for the NH3-SCR reactionusing co-precipitation with assistance of microwave irradiation.The catalytic NH3-SCR activities over CeO2-TiO2 catalysts at low temperature...In this work we prepared several CeO2-TiO2 catalysts for the NH3-SCR reactionusing co-precipitation with assistance of microwave irradiation.The catalytic NH3-SCR activities over CeO2-TiO2 catalysts at low temperatures are largely enhanced by the treatment of microwave irradiation,the operation temperature window is also broadened.For better understanding the promotion mechanism,the catalyst prepared by conventional co-precipitation with and without microwave irradiation treatment was characterized with H2-TPR,NH3-TPD,XPS,XRD and BET.Microwave irradiation treatment accelerates the crystallite rate of CeO2-TiO2 catalysts,and greatly enlarges their surface area by adjusting their microstructures.The resistance to SO2 and H2O is also improved via regulating the hierarchical pore structure by the microwave irradiation.Microwave irradiation treatment can also improve the redox property and increase the acid sites over the catalyst surfaces.The result of in situ DRIFTS suggests that the microwave irradiation treatment generates more Br?nsted acid sites on CeO2-TiO2-2 h catalyst,helpful in SCR reactions.XPS results show that after microwave irradiation on the CeO2-TiO2 catalysts,the surface demonstrates an elevated concentration of chemisorbed oxygen,consequently leading to better oxidation of NO to NO2.Additionally,the molar ratio of Ce3+/Ce4+has been elevated after being treated by microwave irradiation,a vital factor in enhancing the NH3-SCR activities.展开更多
The structure and catalytic desulfurization characteristics of CeO2-TiO2 mixed oxides were investigated by means ofX-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and catalytic activity tests. Acco...The structure and catalytic desulfurization characteristics of CeO2-TiO2 mixed oxides were investigated by means ofX-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and catalytic activity tests. According to the results, a CeO2-TiO2solid solution is formed when the mole ratio of cerium to titanium n(Ce):n(Ti) is 5:5 or greater, and the most suitable n(Ce):n(Ti) isdetermined as 7:3, over which the conversion rate of SO2 and the yield of sulfur at 500℃ reach 93% and 99%, respectively.According to the activity testing curve, Ce0.7Ti0.3O2 (n(Ce):n(Ti)=7:3) without any pretreatment can be gradually activated by reagentgas after about 10 min, and reaches a steady activation status 60 min later. The XPS results of Ce0.7Ti0.3O2 after different time ofSO2+CO reaction show that CeO2 is the active component that offers the redox couple Ce4+/Ce3+ and the labile oxygen vacancies, andTiO2 only functions as a catalyst structure stabilizer during the catalytic reaction process. After 48 h of catalytic reaction at 500℃,Ce0.7Ti0.3O2 still maintains a stable structure without being vulcanized, demonstrating its good anti-sulfur poisoning performance.展开更多
Ce-Zr-Al-Nd2O3 (CZAN) support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffTaction (XRD), low temperature nitrogen adsorption-desorption,...Ce-Zr-Al-Nd2O3 (CZAN) support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffTaction (XRD), low temperature nitrogen adsorption-desorption, oxygen pulsing technique, H2-temperamre programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The Pd-only three-way catalysts (Pd-TWC) supported on these materials were prepared by incipient wetness method and studied by activity tests. The results demonstrated that the CZAN supports obtained by the two methods showed better structural, textural and redox properties than the CZA without Nd2O3, and the addition of Nd203 improved the catalytic activity of TWC. Especially, the CZAN-i support prepared by impregnation method had better thermal stability and redox property. Meanwhile, the Pd/CZAN-i catalyst exhibited the best catalytic performance. XPS measurements indicated that the Nd-modified samples possessed more Ce3+ and oxygen vacancies on the surface of samples, which led to a better redox property. The excellent redox property of support materials helped to improve the catalytic activity of TWC.展开更多
CeO2-TiO2 catalysts prepared by different methods were investigated for deep oxidation of 1,2-dichloroethane(DCE),as a typical representative of the chlorinated volatile organic compounds(CVOCs).Characterization analy...CeO2-TiO2 catalysts prepared by different methods were investigated for deep oxidation of 1,2-dichloroethane(DCE),as a typical representative of the chlorinated volatile organic compounds(CVOCs).Characterization analysis reveals that CeO2-TiO2 catalysts prepared by sol-gel and coprecipitation methods exhibit higher specific area,CeO2 and TiO2 particles are highly dispersed into each other and the reducibility and mobility of active oxygen species are obviously promoted due to the strong interaction between the two catalysts CeO2 and TiO2,resulting in higher catalytic activity for DCE oxidation to and less chlorinated byproduct.The high calcination temperature would lead to the formation of a new monoclinic phase Ce0.3Ti0.7O2 and sintering,which is the main reason for the catalytic activity for DCE oxidation markedly decreases.展开更多
A series of catalysts consisting of three‐dimensionally ordered macroporous(3DOM)x‐CeO2/Al2O3‐supported Au nanoparticles(x=2,10,20,and40wt%)were successfully synthesized using a reduction‐deposition method.These c...A series of catalysts consisting of three‐dimensionally ordered macroporous(3DOM)x‐CeO2/Al2O3‐supported Au nanoparticles(x=2,10,20,and40wt%)were successfully synthesized using a reduction‐deposition method.These catalysts were characterized using scanning electron microscopy,the Brunauer‐Emmett‐Teller method,X‐ray diffraction,transmission electron microscopy,ultraviolet‐visible spectroscopy,and temperature‐programmed reduction by H2.Au nanoparticles of mean particle size5nm were well dispersed and supported on the inner walls of uniform macropores.The3DOM structure improved the contact efficiency between soot and the catalyst.An Al‐Ce‐O solid solution was formed in the multilayer support,i.e.,x‐CeO2/Al2O3,by the incorporation of Al3+ions into the CeO2lattice,which resulted in the creation of extrinsic oxygen vacancies.Strong interactions between the metal(Au)and the support(Ce)increased the amount of active oxygen species,and this promoted soot oxidation.The catalytic performance in soot combustion was evaluated using a temperature‐programmed oxidation technique.The presence of CeO2nanolayers in the3DOM Au/x‐CeO2/Al2O3catalysts clearly improved the catalytic activities in soot oxidation.Among the prepared catalysts,3DOM Au/20%CeO2/Al2O3showed high catalytic activity and stability in diesel soot oxidation.展开更多
The influence of sulfation on Pd/Ce0.75Zr0.25O2, Pd/Ce O2-Ti O2 and Pd/Ce O2 was investigated. Physical structure and chemical properties of different catalysts were characterized by N2 adsorption, X-ray diffraction(...The influence of sulfation on Pd/Ce0.75Zr0.25O2, Pd/Ce O2-Ti O2 and Pd/Ce O2 was investigated. Physical structure and chemical properties of different catalysts were characterized by N2 adsorption, X-ray diffraction(XRD), CO chemisorption, X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FT-IR) and X-ray fluorescence(XRF). After 10 h SO2 sulfation, it was found that the decrement on CO oxidation catalytic activity was limited on Pd/Ce0.75Zr0.25O2 compared to Pd/Ce O2-Ti O2 and Pd/Ce O2. It demonstrated that Pd/Ce0.75Zr0.25O2 was more sulfur resistant compared to the other two catalysts. After sulfur exposure, catalyst texture was not much influenced as shown by N2 adsorption and XRD, and surface Pd atoms were poisoned indicated by CO chemisorption results. Pd/Ce0.75Zr0.25O2 and Pd/Ce O2-Ti O2 exhibited less sulfur accumulation compared to Pd/Ce O2 in the sulfation process. Furthermore, XPS results clarified that surface sulfur amount, especially surface sulfates amount on the sulfated catalysts was more crucial for the deactivation in sulfur containing environment.展开更多
CeO2-TiO2 films and CeO2-TiO/SnO2:Sb (6 mol%) double films were deposited on glass substrates by radio-frequency magnetron sputtering (R.F. Sputtering), using SnO2:Sb(6 mol%) target, and CeO2- TiO2 targets wit...CeO2-TiO2 films and CeO2-TiO/SnO2:Sb (6 mol%) double films were deposited on glass substrates by radio-frequency magnetron sputtering (R.F. Sputtering), using SnO2:Sb(6 mol%) target, and CeO2- TiO2 targets with different molar ratio of CeO2 to TiO2 (CeO2:TiO2-0:1.0; 0.1:0.9; 0.2:0.8; 0.3:0.7; 0.4:0.6; 0.5:0.5; 0.6:0.4; 0.7:0.3; 0.8:0.2; 0.9:0.1; 1.0:0). The films are characterized by UV-visible transmission and infrared reflection spectra, scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. The obtained results show that the amorphous phases composed of CeO2-TiO2 play an important role in absorbing UV, there are Ce^3-, Ce^4- and Ti^4- on the surface of the films; the glass substrates coated with CeO2-TiO2 (Ce/Ti=0.5:0.5; 0.6:0.4)/SnO2:Sb(6 mol%) double films show high absorbing UV(〉99), high visible light transmission (75%) and good infrared reflection (〉70%). The sheet resistance of the films is 30-50 Ω/□. The glass substrates coated with the double functional films can be used as window glass of buildings, automobile and so on.展开更多
基金Project supported by the National Natural Science Foundation of China(21577005)the National Key Research and Development Program of China(2016YFB0600400)
摘要In this work we prepared several CeO2-TiO2 catalysts for the NH3-SCR reactionusing co-precipitation with assistance of microwave irradiation.The catalytic NH3-SCR activities over CeO2-TiO2 catalysts at low temperatures are largely enhanced by the treatment of microwave irradiation,the operation temperature window is also broadened.For better understanding the promotion mechanism,the catalyst prepared by conventional co-precipitation with and without microwave irradiation treatment was characterized with H2-TPR,NH3-TPD,XPS,XRD and BET.Microwave irradiation treatment accelerates the crystallite rate of CeO2-TiO2 catalysts,and greatly enlarges their surface area by adjusting their microstructures.The resistance to SO2 and H2O is also improved via regulating the hierarchical pore structure by the microwave irradiation.Microwave irradiation treatment can also improve the redox property and increase the acid sites over the catalyst surfaces.The result of in situ DRIFTS suggests that the microwave irradiation treatment generates more Br?nsted acid sites on CeO2-TiO2-2 h catalyst,helpful in SCR reactions.XPS results show that after microwave irradiation on the CeO2-TiO2 catalysts,the surface demonstrates an elevated concentration of chemisorbed oxygen,consequently leading to better oxidation of NO to NO2.Additionally,the molar ratio of Ce3+/Ce4+has been elevated after being treated by microwave irradiation,a vital factor in enhancing the NH3-SCR activities.
摘要The structure and catalytic desulfurization characteristics of CeO2-TiO2 mixed oxides were investigated by means ofX-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and catalytic activity tests. According to the results, a CeO2-TiO2solid solution is formed when the mole ratio of cerium to titanium n(Ce):n(Ti) is 5:5 or greater, and the most suitable n(Ce):n(Ti) isdetermined as 7:3, over which the conversion rate of SO2 and the yield of sulfur at 500℃ reach 93% and 99%, respectively.According to the activity testing curve, Ce0.7Ti0.3O2 (n(Ce):n(Ti)=7:3) without any pretreatment can be gradually activated by reagentgas after about 10 min, and reaches a steady activation status 60 min later. The XPS results of Ce0.7Ti0.3O2 after different time ofSO2+CO reaction show that CeO2 is the active component that offers the redox couple Ce4+/Ce3+ and the labile oxygen vacancies, andTiO2 only functions as a catalyst structure stabilizer during the catalytic reaction process. After 48 h of catalytic reaction at 500℃,Ce0.7Ti0.3O2 still maintains a stable structure without being vulcanized, demonstrating its good anti-sulfur poisoning performance.
基金Project supported by National Natural Science Foundation of China (20773090, 20803049)the Specialized Research Fund for the Doctoral Program of Higher Education (20070610026, 200806100009)
摘要Ce-Zr-Al-Nd2O3 (CZAN) support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffTaction (XRD), low temperature nitrogen adsorption-desorption, oxygen pulsing technique, H2-temperamre programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The Pd-only three-way catalysts (Pd-TWC) supported on these materials were prepared by incipient wetness method and studied by activity tests. The results demonstrated that the CZAN supports obtained by the two methods showed better structural, textural and redox properties than the CZA without Nd2O3, and the addition of Nd203 improved the catalytic activity of TWC. Especially, the CZAN-i support prepared by impregnation method had better thermal stability and redox property. Meanwhile, the Pd/CZAN-i catalyst exhibited the best catalytic performance. XPS measurements indicated that the Nd-modified samples possessed more Ce3+ and oxygen vacancies on the surface of samples, which led to a better redox property. The excellent redox property of support materials helped to improve the catalytic activity of TWC.
基金Project supported by the National Natural Science Foundation of China(21477109)National Key Research and Development Program of China(2016YFC0204300)。
摘要CeO2-TiO2 catalysts prepared by different methods were investigated for deep oxidation of 1,2-dichloroethane(DCE),as a typical representative of the chlorinated volatile organic compounds(CVOCs).Characterization analysis reveals that CeO2-TiO2 catalysts prepared by sol-gel and coprecipitation methods exhibit higher specific area,CeO2 and TiO2 particles are highly dispersed into each other and the reducibility and mobility of active oxygen species are obviously promoted due to the strong interaction between the two catalysts CeO2 and TiO2,resulting in higher catalytic activity for DCE oxidation to and less chlorinated byproduct.The high calcination temperature would lead to the formation of a new monoclinic phase Ce0.3Ti0.7O2 and sintering,which is the main reason for the catalytic activity for DCE oxidation markedly decreases.
基金supported by the National High Technology Research and Development Program of China(863 Program,2015AA034603)the National Natural Science Foundation of China(21477146,21673142 and 21303263)+2 种基金the Beijing Nova Program(Z141109001814072)the Specialized Research Fund for the Doctoral Program of Higher Education(20130007120011)the Science Foundation of China University of Petroleum-Beijing(YJRC-2013-13,2462013BJRC003)~~
摘要A series of catalysts consisting of three‐dimensionally ordered macroporous(3DOM)x‐CeO2/Al2O3‐supported Au nanoparticles(x=2,10,20,and40wt%)were successfully synthesized using a reduction‐deposition method.These catalysts were characterized using scanning electron microscopy,the Brunauer‐Emmett‐Teller method,X‐ray diffraction,transmission electron microscopy,ultraviolet‐visible spectroscopy,and temperature‐programmed reduction by H2.Au nanoparticles of mean particle size5nm were well dispersed and supported on the inner walls of uniform macropores.The3DOM structure improved the contact efficiency between soot and the catalyst.An Al‐Ce‐O solid solution was formed in the multilayer support,i.e.,x‐CeO2/Al2O3,by the incorporation of Al3+ions into the CeO2lattice,which resulted in the creation of extrinsic oxygen vacancies.Strong interactions between the metal(Au)and the support(Ce)increased the amount of active oxygen species,and this promoted soot oxidation.The catalytic performance in soot combustion was evaluated using a temperature‐programmed oxidation technique.The presence of CeO2nanolayers in the3DOM Au/x‐CeO2/Al2O3catalysts clearly improved the catalytic activities in soot oxidation.Among the prepared catalysts,3DOM Au/20%CeO2/Al2O3showed high catalytic activity and stability in diesel soot oxidation.
基金supported by the Introduction of Talent and Technology Cooperation Plan of Tianjin(14RCGFGX00849)
摘要The influence of sulfation on Pd/Ce0.75Zr0.25O2, Pd/Ce O2-Ti O2 and Pd/Ce O2 was investigated. Physical structure and chemical properties of different catalysts were characterized by N2 adsorption, X-ray diffraction(XRD), CO chemisorption, X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FT-IR) and X-ray fluorescence(XRF). After 10 h SO2 sulfation, it was found that the decrement on CO oxidation catalytic activity was limited on Pd/Ce0.75Zr0.25O2 compared to Pd/Ce O2-Ti O2 and Pd/Ce O2. It demonstrated that Pd/Ce0.75Zr0.25O2 was more sulfur resistant compared to the other two catalysts. After sulfur exposure, catalyst texture was not much influenced as shown by N2 adsorption and XRD, and surface Pd atoms were poisoned indicated by CO chemisorption results. Pd/Ce0.75Zr0.25O2 and Pd/Ce O2-Ti O2 exhibited less sulfur accumulation compared to Pd/Ce O2 in the sulfation process. Furthermore, XPS results clarified that surface sulfur amount, especially surface sulfates amount on the sulfated catalysts was more crucial for the deactivation in sulfur containing environment.
基金the program for Changjiang Scholars and Innovative Research Team in University (No.IRT0547
摘要CeO2-TiO2 films and CeO2-TiO/SnO2:Sb (6 mol%) double films were deposited on glass substrates by radio-frequency magnetron sputtering (R.F. Sputtering), using SnO2:Sb(6 mol%) target, and CeO2- TiO2 targets with different molar ratio of CeO2 to TiO2 (CeO2:TiO2-0:1.0; 0.1:0.9; 0.2:0.8; 0.3:0.7; 0.4:0.6; 0.5:0.5; 0.6:0.4; 0.7:0.3; 0.8:0.2; 0.9:0.1; 1.0:0). The films are characterized by UV-visible transmission and infrared reflection spectra, scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. The obtained results show that the amorphous phases composed of CeO2-TiO2 play an important role in absorbing UV, there are Ce^3-, Ce^4- and Ti^4- on the surface of the films; the glass substrates coated with CeO2-TiO2 (Ce/Ti=0.5:0.5; 0.6:0.4)/SnO2:Sb(6 mol%) double films show high absorbing UV(〉99), high visible light transmission (75%) and good infrared reflection (〉70%). The sheet resistance of the films is 30-50 Ω/□. The glass substrates coated with the double functional films can be used as window glass of buildings, automobile and so on.