Activity and stability of 1%Pd-0.2%Pt/Al2O3 and 1%Pd-0.2%Pt/0.6%Ce/Al2O3 catalysts prepared by impregnation method for catalytic combustion of methane in air were investigated. The catalysts before and after reaction ...Activity and stability of 1%Pd-0.2%Pt/Al2O3 and 1%Pd-0.2%Pt/0.6%Ce/Al2O3 catalysts prepared by impregnation method for catalytic combustion of methane in air were investigated. The catalysts before and after reaction were characterized by BET, CO chemisorption, XRD and XPS techniques. Results showed that the presence of Ce significantly increased the activity and thermal stability of the Pd-Pt/Al2O3 catalyst towards methane combustion, which could be attributed to more highly-dispersed active PdO particles over the Pd-Pt/Ce/Al2O3 catalyst surface as well as the retarded sintering of PdO and the maintained oxidized state of surface Pd during the combustion process in the presence of Ce.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
Alkali metal K in exhaust gas has a deactivation effect on NH_(3)-SCR catalysts.In this work,it is discovered that the addition of Ho on CeTi catalyst can remarkably strengthen its K tolerance.The conclusions of Bruna...Alkali metal K in exhaust gas has a deactivation effect on NH_(3)-SCR catalysts.In this work,it is discovered that the addition of Ho on CeTi catalyst can remarkably strengthen its K tolerance.The conclusions of Brunauer-Emmett-Teller(BET),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),NH_(3) temperature programmed desorption(NH_(3)-TPD)and H_(2)temperature programmed reduction(H_(2)-TPR)analyses demonstrate that the enhancement of K resistance mainly originates from its stronger surface acidity and redox capability,the higher concentration of Ce^(3+)species and surface chemisorbed oxygen.In situ DRIFT analysis reveals that the introduction of Ho on CeTi can remarkably improve the adsorption of NH_(3) and NO_(x) species on catalyst surface,accompanied by the intensified reactivity of ad-NH_(3) species,which should also administer to improve the K resistance.展开更多
The Cu-Zr-Ce-O catalysts prepared using the coprecipitation method exhibited better catalytic performance for CO selective oxidation. The Cu-Zr-Ce-O catalysts pretreated with different methods were studied by CO-TPR a...The Cu-Zr-Ce-O catalysts prepared using the coprecipitation method exhibited better catalytic performance for CO selective oxidation. The Cu-Zr-Ce-O catalysts pretreated with different methods were studied by CO-TPR and XPS techniques. The results showed that the Cu-Zr-Ce-O catalyst pretreated with oxygen exhibited the best catalytic performance and had the widest operating temperature window, with CO conversion above 99% from 160 to 200 ℃. The O2 pretreatment caused an enrichment of the oxygen storaged on the Cu active species and promoted the conversion of adsorbed oxygen into surface lattice oxygen. It also improved the amount of Cu＋/Cu^2＋ ionic pair, and then facilitated the formation of CuO active species on the catalyst for selective CO oxidation.展开更多
A Ce（0.3）TiOxoxide carrier was synthesized via a sol–gel process,and Ce（0.3）TiOxsupported metal（M=Cd,Mn,Fe,W,Mo）oxide catalysts were prepared by the method of incipient-wetness impregnation.The catalysts were c...A Ce（0.3）TiOxoxide carrier was synthesized via a sol–gel process,and Ce（0.3）TiOxsupported metal（M=Cd,Mn,Fe,W,Mo）oxide catalysts were prepared by the method of incipient-wetness impregnation.The catalysts were characterized by means of X-ray diffraction（XRD）,Brunauer–Emmett–Teller（BET）analysis,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,Fourier transform infrared（FT–IR）spectroscopy,UV–Visdiffusereflectancespectroscopy（UV–VisDRS）,and Temperature-programmed reduction with H2（H2-TPR）.The catalytic activities for de-NO（x ）were evaluated by the NH3-SCR reaction.Among all the catalysts tested,the 2 wt.%Cd/Ce（0.3）TiOxcatalyst exhibited the best NH3-SCR performance,with a wide temperature window of 250–450℃ for NO conversion above 90%.Moreover,the catalyst showed N2 selectivity greater than 99%from 200 to 450℃.展开更多
In this investigation, Pt–Ba–Ce/c-Al2O3 catalysts were prepared by incipient wetness impregnation and experiments were performed to evaluate the influence of H2 on the evolution mechanism of nitrogen oxides (NOx) st...In this investigation, Pt–Ba–Ce/c-Al2O3 catalysts were prepared by incipient wetness impregnation and experiments were performed to evaluate the influence of H2 on the evolution mechanism of nitrogen oxides (NOx) storage and reduction (NSR). The physical and chemical properties of the Pt–Ba–Ce/c- Al2O3 catalysts were studied using a combination of characterization techniques, which showed that PtOx, CeO2, and BaCO3, whose peaks were observed in X-ray diffraction (XRD) spectra, dispersed well on the c-Al2O3, as shown by transmission electron microscope (TEM), and that the difference between Ce3+ and Ce4+, as detected by X-ray photoelectron spectroscopy (XPS), facilitated the migration of active oxygen over the catalyst. In the process of a complete NSR experiment, the NOx storage capability was greatly enhanced in the temperature range of 250–350℃, and reached a maximum value of 315.3μmol·gcat^-1 at 350℃, which was ascribed to the increase in NO2 yield. In a lean and rich cycling experiment, the results showed that NOx storage efficiency and conversion were increased when the time of H2 exposure (i.e., 30, 45, and 60 s) was extended. The maximum NOx conversion of the catalyst reached 83.5% when the duration of the lean and rich phases was 240 and 60 s, respectively. The results revealed that increasing the content of H2 by an appropriate amount was favorable to the NSR mechanism due to increased decomposition of nitrate or nitrite, and the refreshing of trapping sites for the next cycle of NSR.展开更多
The metal oxides CuMnCe and CeY washcoats on cordierite were prepared using an impregnation method, and then used as support for the active Pt component to prepare the Pt/CuMnCe and Pt/CeY monolithic catalysts for the...The metal oxides CuMnCe and CeY washcoats on cordierite were prepared using an impregnation method, and then used as support for the active Pt component to prepare the Pt/CuMnCe and Pt/CeY monolithic catalysts for the deep oxidation of VOCs. In comparison with the Pt/CeY, CuMnCe, and CeY monolithic catalysts, the Pt/CuMnCe monolithic catalyst shows an excellent performance for toluene,ethyl acetate,and n-hexane oxidation and the Tis low to 216, 200 and 260 ℃,respectively. The active components Pt/PtO and CuMnCe result in a better synergetic interaction, which promote the catalyst reducibility, increase the oxygen mobility, and enhance the adsorption and activation of organic molecules.展开更多
A monolithic series of Cu-Mn-Ce oxides supported on cordierites with different Cu/Mn/Ce molar ratios were prepared by the in-situ sol-gel method without any binder. The catalysts were characterized by scanning electro...A monolithic series of Cu-Mn-Ce oxides supported on cordierites with different Cu/Mn/Ce molar ratios were prepared by the in-situ sol-gel method without any binder. The catalysts were characterized by scanning electron microscopy （SEM）, energy dispersive spectrometer （EDS）, X-ray diffraction （XRD）, and Brunauer-Emmett-Teller method （BET） and examined in the catalytic combustion of volatile organic compounds （VOCs）. The results showed that the well-dispersed nanometer particles of mixed oxides adhered firmly to the cordierite surface. Cu0.15Mn0.3Ce55/cordierite was identified as the most active catalyst. Compared with commercial Pd/Al2O3, Cu0.15Mn0.3Ce55/cordierite showed higher activities for the combustion of various types of VOCs, especially for oxy-derivative compounds which could be lighted off below 200 ℃.展开更多
The Ce-Zr-La-O solid solution was prepared by the sol-gel method. Thestructure and the redox behavior of Ce-Zr-La-O solid solution and CuO/Ce-Zr-La-O catalysts wereinvestigated by using XRD, Raman and TPR techniques. ...The Ce-Zr-La-O solid solution was prepared by the sol-gel method. Thestructure and the redox behavior of Ce-Zr-La-O solid solution and CuO/Ce-Zr-La-O catalysts wereinvestigated by using XRD, Raman and TPR techniques. The result shows that the reduction capabilityof Ce_(0.7)Zr_(0.3-y)La_yO solid solution is related to content of La. Appropriate content of La canenhance the redox capability of the solid solution. The oxidation activity of the CuO (6 percent)/Ce_(0.7)Zr_(0.15)La_(0.15)O catalyst is the highest. CuO, which finely dispersed and interacted withthe support, is the site of oxidation activity.展开更多
Ce x Ti 1- x O 2 mixed oxides of different mole ratios ( x =0, 0.1, 0.2～0.9, 1.0) were prepared by co precipitation of TiCl 4 with Ce(NO 3) 3 and then loaded with different amounts of CuO. The effe...Ce x Ti 1- x O 2 mixed oxides of different mole ratios ( x =0, 0.1, 0.2～0.9, 1.0) were prepared by co precipitation of TiCl 4 with Ce(NO 3) 3 and then loaded with different amounts of CuO. The effects of CuO on NO+CO reaction were investigated, and the structure and reductive properties of various CuO/Ce x Ti 1- x O 2 were characterized by the methodologies of BET, TPR and XRD. The results show that different Ce/Ti mole ratios and calcination temperatures induce changes of structure and reductive properties of the Ce x Ti 1- x O 2 mixed oxides. When x =0.1～0.5, amorphous CeTi 2O 6 phase mainly forms at 650 ℃ compared to the formation of CeTi 2O 6 which crystallizes at 800 ℃. When x >0.6, some TiO 2 enters the CeO 2 lattice and a CeO 2 TiO 2 solid solution is formed. The activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 650 ℃ is largely affected by the x values, which is the highest when x =0.3, 0.4 and 0.9. The NO conversion reaches 70% at a reaction temperature of 150 ℃. By comparison, the x values have little effect on the activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 800 ℃ . There are strong interactions between CuO and CeTi 2O 6, i.e., formation of the CeTi 2O 6 phase shifts the CuO reduction peak temperature from 380 to 200 ℃, and CuO, in turn, shifts the CeTi 2O 6 reduction peak temperature from 600 to 300 ℃.展开更多
The three way catalysts (TWCs) promoters (Ce Zr)O 2, (Pr Ce Zr)O 2 and (Pr Zr)O 2 were prepared by sol gel like method. They were characterized by XRD, EXAFS and BET surface area determination. The reduction ...The three way catalysts (TWCs) promoters (Ce Zr)O 2, (Pr Ce Zr)O 2 and (Pr Zr)O 2 were prepared by sol gel like method. They were characterized by XRD, EXAFS and BET surface area determination. The reduction features of the promoters were measured by temperature programmed reduction (TPR) of H 2 to access the potential for the promoters containing praseodymia as oxygen storage component in three way catalyst. The (Pr Zr)O 2 cubic solid solution is formed at high temperature up to 800 ℃, which makes it more reducible than the (Ce Zr)O 2 solid solution. For the (Pr Ce Zr)O 2 samples, the ternary solid solution plays an important role in the reduction process. The performance of the three way catalysts with fully formulated Pt, Pd and Rh is proceeded by using both light off temperature under a stoichiometric gas composition and the conversion of CO, C 3H 6 and NO under changing air/fuel ratio at a constant reaction temperature 400 ℃ . The results indicate that a small amount of praseodymia doping into (Ce Zr)O 2 favors the light off temperature of C 3H 6 and NO, and all the catalysts containing praseodymia obviously exhibits enhanced width of S value for NO conversion at lean region ( S ≥1.00).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
基金supported by the National High Technology Research and Development Program (863) of China (No.2010AA064904)
文摘Activity and stability of 1%Pd-0.2%Pt/Al2O3 and 1%Pd-0.2%Pt/0.6%Ce/Al2O3 catalysts prepared by impregnation method for catalytic combustion of methane in air were investigated. The catalysts before and after reaction were characterized by BET, CO chemisorption, XRD and XPS techniques. Results showed that the presence of Ce significantly increased the activity and thermal stability of the Pd-Pt/Al2O3 catalyst towards methane combustion, which could be attributed to more highly-dispersed active PdO particles over the Pd-Pt/Ce/Al2O3 catalyst surface as well as the retarded sintering of PdO and the maintained oxidized state of surface Pd during the combustion process in the presence of Ce.
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Project supported by the National Key R&D Program of China(2018YFB0605002)。
文摘Alkali metal K in exhaust gas has a deactivation effect on NH_(3)-SCR catalysts.In this work,it is discovered that the addition of Ho on CeTi catalyst can remarkably strengthen its K tolerance.The conclusions of Brunauer-Emmett-Teller(BET),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),NH_(3) temperature programmed desorption(NH_(3)-TPD)and H_(2)temperature programmed reduction(H_(2)-TPR)analyses demonstrate that the enhancement of K resistance mainly originates from its stronger surface acidity and redox capability,the higher concentration of Ce^(3+)species and surface chemisorbed oxygen.In situ DRIFT analysis reveals that the introduction of Ho on CeTi can remarkably improve the adsorption of NH_(3) and NO_(x) species on catalyst surface,accompanied by the intensified reactivity of ad-NH_(3) species,which should also administer to improve the K resistance.
基金supported by the National Nature Science Foundation of China (Project No.20576023)the Natural Science Foundation of Guangdong Province (Project No.06025660).
文摘The Cu-Zr-Ce-O catalysts prepared using the coprecipitation method exhibited better catalytic performance for CO selective oxidation. The Cu-Zr-Ce-O catalysts pretreated with different methods were studied by CO-TPR and XPS techniques. The results showed that the Cu-Zr-Ce-O catalyst pretreated with oxygen exhibited the best catalytic performance and had the widest operating temperature window, with CO conversion above 99% from 160 to 200 ℃. The O2 pretreatment caused an enrichment of the oxygen storaged on the Cu active species and promoted the conversion of adsorbed oxygen into surface lattice oxygen. It also improved the amount of Cu＋/Cu^2＋ ionic pair, and then facilitated the formation of CuO active species on the catalyst for selective CO oxidation.
基金financially supported by the National Natural Science Foundation of China (Nos. 21673290, u1162103 and 21376261)the National Hi-Tech Research and Development Program (863) of China (No. 2015AA034603)the China Offshore Oil Fund (No. LHYJYKJSA2016002)
文摘A Ce（0.3）TiOxoxide carrier was synthesized via a sol–gel process,and Ce（0.3）TiOxsupported metal（M=Cd,Mn,Fe,W,Mo）oxide catalysts were prepared by the method of incipient-wetness impregnation.The catalysts were characterized by means of X-ray diffraction（XRD）,Brunauer–Emmett–Teller（BET）analysis,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,Fourier transform infrared（FT–IR）spectroscopy,UV–Visdiffusereflectancespectroscopy（UV–VisDRS）,and Temperature-programmed reduction with H2（H2-TPR）.The catalytic activities for de-NO（x ）were evaluated by the NH3-SCR reaction.Among all the catalysts tested,the 2 wt.%Cd/Ce（0.3）TiOxcatalyst exhibited the best NH3-SCR performance,with a wide temperature window of 250–450℃ for NO conversion above 90%.Moreover,the catalyst showed N2 selectivity greater than 99%from 200 to 450℃.
基金the National Natural Science Foundation of China (51676090)the Natural Science Foundation of Jiangsu Province (BK20150513), and the Six Talent Peaks Project in Jiangsu Province.
文摘In this investigation, Pt–Ba–Ce/c-Al2O3 catalysts were prepared by incipient wetness impregnation and experiments were performed to evaluate the influence of H2 on the evolution mechanism of nitrogen oxides (NOx) storage and reduction (NSR). The physical and chemical properties of the Pt–Ba–Ce/c- Al2O3 catalysts were studied using a combination of characterization techniques, which showed that PtOx, CeO2, and BaCO3, whose peaks were observed in X-ray diffraction (XRD) spectra, dispersed well on the c-Al2O3, as shown by transmission electron microscope (TEM), and that the difference between Ce3+ and Ce4+, as detected by X-ray photoelectron spectroscopy (XPS), facilitated the migration of active oxygen over the catalyst. In the process of a complete NSR experiment, the NOx storage capability was greatly enhanced in the temperature range of 250–350℃, and reached a maximum value of 315.3μmol·gcat^-1 at 350℃, which was ascribed to the increase in NO2 yield. In a lean and rich cycling experiment, the results showed that NOx storage efficiency and conversion were increased when the time of H2 exposure (i.e., 30, 45, and 60 s) was extended. The maximum NOx conversion of the catalyst reached 83.5% when the duration of the lean and rich phases was 240 and 60 s, respectively. The results revealed that increasing the content of H2 by an appropriate amount was favorable to the NSR mechanism due to increased decomposition of nitrate or nitrite, and the refreshing of trapping sites for the next cycle of NSR.
基金Project supported by the National Natural Science Foundation of China(21506194,21676255)the Natural Science Foundation of Zhejiang Province(Y16B070011)the Commission of Science and Technology of Zhejiang Province(2017C03007,2017C33106)
文摘The metal oxides CuMnCe and CeY washcoats on cordierite were prepared using an impregnation method, and then used as support for the active Pt component to prepare the Pt/CuMnCe and Pt/CeY monolithic catalysts for the deep oxidation of VOCs. In comparison with the Pt/CeY, CuMnCe, and CeY monolithic catalysts, the Pt/CuMnCe monolithic catalyst shows an excellent performance for toluene,ethyl acetate,and n-hexane oxidation and the Tis low to 216, 200 and 260 ℃,respectively. The active components Pt/PtO and CuMnCe result in a better synergetic interaction, which promote the catalyst reducibility, increase the oxygen mobility, and enhance the adsorption and activation of organic molecules.
基金Project supported by National Natural Science Foundation of China (21107096)Zhejiang Provincial Natural Science Foundation (Y5090202)
文摘A monolithic series of Cu-Mn-Ce oxides supported on cordierites with different Cu/Mn/Ce molar ratios were prepared by the in-situ sol-gel method without any binder. The catalysts were characterized by scanning electron microscopy （SEM）, energy dispersive spectrometer （EDS）, X-ray diffraction （XRD）, and Brunauer-Emmett-Teller method （BET） and examined in the catalytic combustion of volatile organic compounds （VOCs）. The results showed that the well-dispersed nanometer particles of mixed oxides adhered firmly to the cordierite surface. Cu0.15Mn0.3Ce55/cordierite was identified as the most active catalyst. Compared with commercial Pd/Al2O3, Cu0.15Mn0.3Ce55/cordierite showed higher activities for the combustion of various types of VOCs, especially for oxy-derivative compounds which could be lighted off below 200 ℃.
文摘The Ce-Zr-La-O solid solution was prepared by the sol-gel method. Thestructure and the redox behavior of Ce-Zr-La-O solid solution and CuO/Ce-Zr-La-O catalysts wereinvestigated by using XRD, Raman and TPR techniques. The result shows that the reduction capabilityof Ce_(0.7)Zr_(0.3-y)La_yO solid solution is related to content of La. Appropriate content of La canenhance the redox capability of the solid solution. The oxidation activity of the CuO (6 percent)/Ce_(0.7)Zr_(0.15)La_(0.15)O catalyst is the highest. CuO, which finely dispersed and interacted withthe support, is the site of oxidation activity.
文摘Ce x Ti 1- x O 2 mixed oxides of different mole ratios ( x =0, 0.1, 0.2～0.9, 1.0) were prepared by co precipitation of TiCl 4 with Ce(NO 3) 3 and then loaded with different amounts of CuO. The effects of CuO on NO+CO reaction were investigated, and the structure and reductive properties of various CuO/Ce x Ti 1- x O 2 were characterized by the methodologies of BET, TPR and XRD. The results show that different Ce/Ti mole ratios and calcination temperatures induce changes of structure and reductive properties of the Ce x Ti 1- x O 2 mixed oxides. When x =0.1～0.5, amorphous CeTi 2O 6 phase mainly forms at 650 ℃ compared to the formation of CeTi 2O 6 which crystallizes at 800 ℃. When x >0.6, some TiO 2 enters the CeO 2 lattice and a CeO 2 TiO 2 solid solution is formed. The activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 650 ℃ is largely affected by the x values, which is the highest when x =0.3, 0.4 and 0.9. The NO conversion reaches 70% at a reaction temperature of 150 ℃. By comparison, the x values have little effect on the activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 800 ℃ . There are strong interactions between CuO and CeTi 2O 6, i.e., formation of the CeTi 2O 6 phase shifts the CuO reduction peak temperature from 380 to 200 ℃, and CuO, in turn, shifts the CeTi 2O 6 reduction peak temperature from 600 to 300 ℃.
文摘The three way catalysts (TWCs) promoters (Ce Zr)O 2, (Pr Ce Zr)O 2 and (Pr Zr)O 2 were prepared by sol gel like method. They were characterized by XRD, EXAFS and BET surface area determination. The reduction features of the promoters were measured by temperature programmed reduction (TPR) of H 2 to access the potential for the promoters containing praseodymia as oxygen storage component in three way catalyst. The (Pr Zr)O 2 cubic solid solution is formed at high temperature up to 800 ℃, which makes it more reducible than the (Ce Zr)O 2 solid solution. For the (Pr Ce Zr)O 2 samples, the ternary solid solution plays an important role in the reduction process. The performance of the three way catalysts with fully formulated Pt, Pd and Rh is proceeded by using both light off temperature under a stoichiometric gas composition and the conversion of CO, C 3H 6 and NO under changing air/fuel ratio at a constant reaction temperature 400 ℃ . The results indicate that a small amount of praseodymia doping into (Ce Zr)O 2 favors the light off temperature of C 3H 6 and NO, and all the catalysts containing praseodymia obviously exhibits enhanced width of S value for NO conversion at lean region ( S ≥1.00).
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)
文摘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.
