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
The effects of ceria and zirconium oxides additions to alumina-supported palladium catalysts on methane combustion behavior were investigated. The structure and TPR/TPO properties were studied by XRD, TPR, TPO techniq...The effects of ceria and zirconium oxides additions to alumina-supported palladium catalysts on methane combustion behavior were investigated. The structure and TPR/TPO properties were studied by XRD, TPR, TPO techniques. The results show that the addition of Ce-Zr oxides improves the thermal stability of alumina and PdO. The Pd/Ce0.2Zr0.8/Al2O3 exhibits the highest activity and thermal stability for methane combustion.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
The transition metals （Cu, Co, and Fe） were applied to modify Ni/Ce0.2Zr0.1Al0.7Oδ catalyst. The effects of transition metals on the catalytic properties of Ni/Ce0.2Zr0.1Al0.7Oδ autothermal reforming of methane we...The transition metals （Cu, Co, and Fe） were applied to modify Ni/Ce0.2Zr0.1Al0.7Oδ catalyst. The effects of transition metals on the catalytic properties of Ni/Ce0.2Zr0.1Al0.7Oδ autothermal reforming of methane were investigated. The Ni-supported catalysts were characterized by XRD, TPR and XPS. Tests in autothermal reforming of methane to hydrogen showed that the addition of transition metals （Cu and Co） significantly increased the activity of catalyst under the conditions of lower reaction temperature, and Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδ was found to have the highest conversion of CH4 among all catalysts in the operation temperatures ranging from 923 K to 1023 K. TPR, XRD and XPS measurements indicated that the cubic phases of CexZr1-xO2 solid solution were formed in the preparation process of catalysts. Strong interaction was found to exist between NiO and CexZr1-xO2 solid solution. The addition of Cu improved the dispersion of NiO, inhibited the formation of NiAl2O4, and thus significantly promoted the activity of the catalyst Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδ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.
文摘The effects of ceria and zirconium oxides additions to alumina-supported palladium catalysts on methane combustion behavior were investigated. The structure and TPR/TPO properties were studied by XRD, TPR, TPO techniques. The results show that the addition of Ce-Zr oxides improves the thermal stability of alumina and PdO. The Pd/Ce0.2Zr0.8/Al2O3 exhibits the highest activity and thermal stability for methane combustion.
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This work was supported by Guangdong Natural Science Foundation of China (030514)Science and Technology Programs of Guangdong Province of China (2004B33401006)
文摘The transition metals （Cu, Co, and Fe） were applied to modify Ni/Ce0.2Zr0.1Al0.7Oδ catalyst. The effects of transition metals on the catalytic properties of Ni/Ce0.2Zr0.1Al0.7Oδ autothermal reforming of methane were investigated. The Ni-supported catalysts were characterized by XRD, TPR and XPS. Tests in autothermal reforming of methane to hydrogen showed that the addition of transition metals （Cu and Co） significantly increased the activity of catalyst under the conditions of lower reaction temperature, and Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδ was found to have the highest conversion of CH4 among all catalysts in the operation temperatures ranging from 923 K to 1023 K. TPR, XRD and XPS measurements indicated that the cubic phases of CexZr1-xO2 solid solution were formed in the preparation process of catalysts. Strong interaction was found to exist between NiO and CexZr1-xO2 solid solution. The addition of Cu improved the dispersion of NiO, inhibited the formation of NiAl2O4, and thus significantly promoted the activity of the catalyst Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδ
