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
A series of CexPr1-xO2-δ (x=0, 0.5, 0.9, 1.0) mixed oxide calcined at different temperatures were synthesized by sol-gel method and characterized by Raman, XRD and O2-TPD techniques. When x=0.9, only a cubic phase Ce...A series of CexPr1-xO2-δ (x=0, 0.5, 0.9, 1.0) mixed oxide calcined at different temperatures were synthesized by sol-gel method and characterized by Raman, XRD and O2-TPD techniques. When x=0.9, only a cubic phase CeO2 is observed. When x=0.5, the compound was combined by Pr6O11 and CeO2 mixed oxides. For CexPr1-xO2-δ (x=0.5, 0.9)samples 465 cm-1 Raman peak is attributed to the Raman active F2g mode of CeO2. The broad peak at about 570 cm-1 can be linked to lattice defects resulting in oxygen vacancies. The crystallite size of the samples increased as increasing the calcined temperature. But the increased value of Ce0.9Pr0.1O2-δ and Ce0.5Pr0.5O2-δ is smaller than single CeO2 and Pr6O11 obviously. It reveals that the insertion of Pr atom into the ceria lattice could enhance the sintering resistance and thermal stability of the mixed oxides. Calcination temperatures had great effect on the peak intensity for CeO2 but less effect on Ce0.8Pr0.2O2-δ in Raman spectra, and it may be caused by the colors transformation of the mixed oxides. The result of O2-TPD experiment indicates that the formation of solid solution has elevation the stabilization and thermal stability of the mixed oxides.展开更多
A series of La1-xCexMnO3+δ(x=D,0.05,0.1,0.2,and 0.3)perovskites and Mn-Ce mixed oxides were prepared.Their physico-chemical properties were systematically characterized and the NO oxidation activities of the catalyst...A series of La1-xCexMnO3+δ(x=D,0.05,0.1,0.2,and 0.3)perovskites and Mn-Ce mixed oxides were prepared.Their physico-chemical properties were systematically characterized and the NO oxidation activities of the catalysts were investigated.The La0.9Ce0.1MnO3+δhas the best activity among all of the catalysts,with a maximum NO conversion of 85%at 300℃.The characterization results indicate that the doping of Ce improves the properties of the perovsidtes in terms of the specific surface area,the average valence state of Mn ions,the number of reactive oxygen species and the NOx desorption behaviors.The Mn-Ce mixed oxide calcined at 500℃shows a similar NO oxidation activity with La0.9Ce0.1MnO3+δ.However,the activity of the mixed oxide obtained at 750℃decreases a lot,which results from the loss of active sites and active oxygen species.展开更多
A series of CexPr1-xO2-δ mixed oxides were synthesized by sol-gel met hod and characterized by Raman and XRD techniques. When x value was changed from 1.0 to 0.5, only a cubic phase CeO2 was observed. The samples wer...A series of CexPr1-xO2-δ mixed oxides were synthesized by sol-gel met hod and characterized by Raman and XRD techniques. When x value was changed from 1.0 to 0.5, only a cubic phase CeO2 was observed. The samples were very well cr ystallized on decreasing x from 0.50 to 0.99. For CexPr1-xO2-δ samples 465 cm-1 and 1 150 cm-1 Raman peaks are attributed to the Raman active F2g mode of CeO2. The broad peak at about 570 cm-1 in the region of 0.3 ≤ x ≤ 0.99 can be linke d to lattice defects resulting in oxygen vacancies. The new band at about 195 cm -1 may be attributed to the asymmetric vibration caused by the formation of oxyg en vacancies. Calcination temperatures had great effect on the peak intensity fo r CeO2 but less effect on Ce0.8Pr0.2O2-δ in Raman spectra. It might be due to t he transformation of the colors for the mixed oxides, the insertion of Pr atom i nto the ceria lattice could enhance the sintering resistance and thermal stabili ty of the mixed oxides.展开更多
Ce_（1–x）La_xO_y solid solution was simply prepared using mixed rare earth chloride（RECl_3·x H_2O, RE=Ce, La99%, containing unseparated Ce and La from rare earth metallurgical industry） as precursor by ultras...Ce_（1–x）La_xO_y solid solution was simply prepared using mixed rare earth chloride（RECl_3·x H_2O, RE=Ce, La99%, containing unseparated Ce and La from rare earth metallurgical industry） as precursor by ultrasonic-assisted co-precipitation method with different ultrasonic frequencies（CLf, f=200, 400, 600, 800, 1000 Hz）. A compared Ce_（1–x）La_xO_y solid solution（CL＊） was also prepared by the same mothod with 10% less precipitant. X-ray diffraction results confirmed the formation of Ce1–xLaxOy solid solution, and the crystal structures of these catalysts were not very sensitive to ultrasonic frequency and precipitant amount. However, both of the factors had obvious effect on morphology and surface area of CL, and precipitant amount seem to play a more crucial role than ultrasonic frequency for Ce_（1–x）La_xO_y solid solution preparation. When soot and catalyst were tight contacted, the peak temperature（Tpeak） of soot oxidation and oxygen reducing temperature for CLf catalysts decreased linearly with increasing surface area. Under loose contact condition, the Tpeak had obvious negative correlation with H_2 consumption. It was inferred that good reducibility of the Ce_（1–x）La_xO_y solid solution favored the soot oxidation reaction. The Ce_（1–x）La_xO_y solid solution prepared from unseparated rare earth chloride showed a good soot oxidaiton activity. Controlling the preparation conditions to prepare a CL catalyst would high surface area will enhance its reducibility and activity.展开更多
Using SnxTi1-xO2 as carriers, CuO/Sn0.9Zi0.1O2 and CuO/Sn0.7Ti0.3O2 catalysts with different loading amounts of copper oxide （CuO） were prepared by an impregnation method. The catalytic properties of CuO/Sn0.9Ti0.1O...Using SnxTi1-xO2 as carriers, CuO/Sn0.9Zi0.1O2 and CuO/Sn0.7Ti0.3O2 catalysts with different loading amounts of copper oxide （CuO） were prepared by an impregnation method. The catalytic properties of CuO/Sn0.9Ti0.1O2 and CuO/Sn0.7Zi0.3O2 were examined using a microreactor-gas chromatography （GC） NO＋CO reaction system and the methods of BET （Brun- auer-Emmett-Teller）, TG-DTA （themogravimetric and differential thermal analysis）, X-ray diffraction （XRD） and H2-temperature programmed reduction （TPR）. The results showed that NO conversions of Sn0.9Zi0.1O2 and Sn0.7Ti0.3O2 were 47.2% and 43.6% respectively, which increased to 95.3% and 90.9% at 6 wt% CuO loading. However, further increase in CuO loading caused a decrease in the catalytic activity. The nitrogen adsorption-desorption isotherm and pore-size distribution curve of Sn0.9Zi0.1O2 and Sn0.7Ti0.3O2 represented type IV of the BDDT （Brunauer, Deming, Deming and Teller） system and a typical mesoporous sample. There were two CuO diffraction peaks （2θ 35.5° and 38.7°）, and the diffraction peak areas increased with increasing CuO loading. TPR analysis also detected three peaks （α, β and γ） from the CuO-loaded catalysts, suggesting that the α peak was the reduction of the highly dispersed copper oxide, the β peak was the reduction of the isolated copper oxide, and the y peak was the reduction of crystal phase copper oxide. In addition, a fourth peak （5） of the catalysts meant that the SnxTi1-xO2 mixed oxides could be reductive.展开更多
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A series of CexPr1-xO2-δ (x=0, 0.5, 0.9, 1.0) mixed oxide calcined at different temperatures were synthesized by sol-gel method and characterized by Raman, XRD and O2-TPD techniques. When x=0.9, only a cubic phase CeO2 is observed. When x=0.5, the compound was combined by Pr6O11 and CeO2 mixed oxides. For CexPr1-xO2-δ (x=0.5, 0.9)samples 465 cm-1 Raman peak is attributed to the Raman active F2g mode of CeO2. The broad peak at about 570 cm-1 can be linked to lattice defects resulting in oxygen vacancies. The crystallite size of the samples increased as increasing the calcined temperature. But the increased value of Ce0.9Pr0.1O2-δ and Ce0.5Pr0.5O2-δ is smaller than single CeO2 and Pr6O11 obviously. It reveals that the insertion of Pr atom into the ceria lattice could enhance the sintering resistance and thermal stability of the mixed oxides. Calcination temperatures had great effect on the peak intensity for CeO2 but less effect on Ce0.8Pr0.2O2-δ in Raman spectra, and it may be caused by the colors transformation of the mixed oxides. The result of O2-TPD experiment indicates that the formation of solid solution has elevation the stabilization and thermal stability of the mixed oxides.
基金Project supported by the National Key R&D Program of China(2016YFE0126600 and 2017YFC0211002)。
文摘A series of La1-xCexMnO3+δ(x=D,0.05,0.1,0.2,and 0.3)perovskites and Mn-Ce mixed oxides were prepared.Their physico-chemical properties were systematically characterized and the NO oxidation activities of the catalysts were investigated.The La0.9Ce0.1MnO3+δhas the best activity among all of the catalysts,with a maximum NO conversion of 85%at 300℃.The characterization results indicate that the doping of Ce improves the properties of the perovsidtes in terms of the specific surface area,the average valence state of Mn ions,the number of reactive oxygen species and the NOx desorption behaviors.The Mn-Ce mixed oxide calcined at 500℃shows a similar NO oxidation activity with La0.9Ce0.1MnO3+δ.However,the activity of the mixed oxide obtained at 750℃decreases a lot,which results from the loss of active sites and active oxygen species.
文摘A series of CexPr1-xO2-δ mixed oxides were synthesized by sol-gel met hod and characterized by Raman and XRD techniques. When x value was changed from 1.0 to 0.5, only a cubic phase CeO2 was observed. The samples were very well cr ystallized on decreasing x from 0.50 to 0.99. For CexPr1-xO2-δ samples 465 cm-1 and 1 150 cm-1 Raman peaks are attributed to the Raman active F2g mode of CeO2. The broad peak at about 570 cm-1 in the region of 0.3 ≤ x ≤ 0.99 can be linke d to lattice defects resulting in oxygen vacancies. The new band at about 195 cm -1 may be attributed to the asymmetric vibration caused by the formation of oxyg en vacancies. Calcination temperatures had great effect on the peak intensity fo r CeO2 but less effect on Ce0.8Pr0.2O2-δ in Raman spectra. It might be due to t he transformation of the colors for the mixed oxides, the insertion of Pr atom i nto the ceria lattice could enhance the sintering resistance and thermal stabili ty of the mixed oxides.
基金Project supported by National Natural Science Foundation of China(21403015)the Program of the General Research Institute for Nonferrous Metals(53515)
文摘Ce_（1–x）La_xO_y solid solution was simply prepared using mixed rare earth chloride（RECl_3·x H_2O, RE=Ce, La99%, containing unseparated Ce and La from rare earth metallurgical industry） as precursor by ultrasonic-assisted co-precipitation method with different ultrasonic frequencies（CLf, f=200, 400, 600, 800, 1000 Hz）. A compared Ce_（1–x）La_xO_y solid solution（CL＊） was also prepared by the same mothod with 10% less precipitant. X-ray diffraction results confirmed the formation of Ce1–xLaxOy solid solution, and the crystal structures of these catalysts were not very sensitive to ultrasonic frequency and precipitant amount. However, both of the factors had obvious effect on morphology and surface area of CL, and precipitant amount seem to play a more crucial role than ultrasonic frequency for Ce_（1–x）La_xO_y solid solution preparation. When soot and catalyst were tight contacted, the peak temperature（Tpeak） of soot oxidation and oxygen reducing temperature for CLf catalysts decreased linearly with increasing surface area. Under loose contact condition, the Tpeak had obvious negative correlation with H_2 consumption. It was inferred that good reducibility of the Ce_（1–x）La_xO_y solid solution favored the soot oxidation reaction. The Ce_（1–x）La_xO_y solid solution prepared from unseparated rare earth chloride showed a good soot oxidaiton activity. Controlling the preparation conditions to prepare a CL catalyst would high surface area will enhance its reducibility and activity.
基金Project (No. Y504131) supported by the Natural Science Foundation of Zhejiang Province, China
文摘Using SnxTi1-xO2 as carriers, CuO/Sn0.9Zi0.1O2 and CuO/Sn0.7Ti0.3O2 catalysts with different loading amounts of copper oxide （CuO） were prepared by an impregnation method. The catalytic properties of CuO/Sn0.9Ti0.1O2 and CuO/Sn0.7Zi0.3O2 were examined using a microreactor-gas chromatography （GC） NO＋CO reaction system and the methods of BET （Brun- auer-Emmett-Teller）, TG-DTA （themogravimetric and differential thermal analysis）, X-ray diffraction （XRD） and H2-temperature programmed reduction （TPR）. The results showed that NO conversions of Sn0.9Zi0.1O2 and Sn0.7Ti0.3O2 were 47.2% and 43.6% respectively, which increased to 95.3% and 90.9% at 6 wt% CuO loading. However, further increase in CuO loading caused a decrease in the catalytic activity. The nitrogen adsorption-desorption isotherm and pore-size distribution curve of Sn0.9Zi0.1O2 and Sn0.7Ti0.3O2 represented type IV of the BDDT （Brunauer, Deming, Deming and Teller） system and a typical mesoporous sample. There were two CuO diffraction peaks （2θ 35.5° and 38.7°）, and the diffraction peak areas increased with increasing CuO loading. TPR analysis also detected three peaks （α, β and γ） from the CuO-loaded catalysts, suggesting that the α peak was the reduction of the highly dispersed copper oxide, the β peak was the reduction of the isolated copper oxide, and the y peak was the reduction of crystal phase copper oxide. In addition, a fourth peak （5） of the catalysts meant that the SnxTi1-xO2 mixed oxides could be reductive.
