Dynamic oxygen storage and release capability （OSC） measurement apparatus was designed to evaluate the OSC performance of ceria-based oxygen storage material. The optimum measurement condition was at a frequency of ...Dynamic oxygen storage and release capability （OSC） measurement apparatus was designed to evaluate the OSC performance of ceria-based oxygen storage material. The optimum measurement condition was at a frequency of 0.1 Hz with the inlet gas-flow sequence CO （5S）→O2（5S）→CO→O2 and a flow rate of 300 ml·min^-1. Under this condition, similar regular square wave in the inlet and outlet of the reactor was obtained to guarantee the reliability of the dynamic OSC results. The dynamic OSC performance of the CeO2 and Ce0.67Zr0.33O2 mixed oxide prepared using the citric sol-gel method was studied at the optimum measurement condition with focus on both quantitative and qualitative analyses, The results reveal distinctly that Ce0.67Zr0.33O2 had better dynamic OSC performance because of its higher oxygen migration rate than CeO2. Under dynamic conditions, two CO2 production peaks occurred corresponding to the CO pulse and the O2 pulse, respectively, during the entire cycle. The intensity and ratio between the two CO2 productions were highly influenced by temperature and frequency indicating complex surface phenomena during the oxygen storage/release process, As a result, this set-up can be applied to the evaluation of ceria-based material on the OSC performance.展开更多
The NO oxidation reaction was studied over MnOx-CeO2 catalysts prepared by co-precipitation, impregnation and mechanical mixing method, respectively. It was found that the co-precipitation was the most active and a 60...The NO oxidation reaction was studied over MnOx-CeO2 catalysts prepared by co-precipitation, impregnation and mechanical mixing method, respectively. It was found that the co-precipitation was the most active and a 60% NO conversion was achieved at 250 oC. X-ray diffraction （XRD）, Brumauer-Emmett （BET）, H2-temperature programmed reduction （H2-TPR） and oxygen storage capacity （OSC） techniques were employed to characterize the physical and chemical properties of the catalysts. XRD results showed that amorphous MnOx or Mn-O-Ce solid solution existed in co-precipitation and impregnation prepared sample, while crystalline MnOx was found in mechanical mixing catalyst. A larger surface area was observed on co-precipitation prepared catalyst compared to those prepared by impregnation and mechanical mixing. The strong interaction between MnOx and CeO2 enhanced the reducibility of the oxides and increased the amount of Mn4＋ and activated oxygen, which are favorable for NO oxidation to NO2.展开更多
La1-x Cax MnO3 （x=0-0.3） perovskite-type oxides were synthesized by citrate sol-gel method. The physical and chemical properties were characterized by X-ray diffraction （XRD）, Brumauer-Emmett-Teller method （BET）...La1-x Cax MnO3 （x=0-0.3） perovskite-type oxides were synthesized by citrate sol-gel method. The physical and chemical properties were characterized by X-ray diffraction （XRD）, Brumauer-Emmett-Teller method （BET）, X-ray photoelectron spectroscopy （XPS）, NO＋O2 -TPD （temperature-programmed desorption）, activated oxygen evaluation and H2 -TPR （temperature-programmed reduction） technologies. The results showed that NO catalytic oxidation activity was significantly improved by Ca substitution, especially for lower temperature activity. The La0.9 Ca0.1 MnO 3 sample showed the maximum conversion of 82% at 300 oC. The monodentate nitrates played a crucial role for the formation of NO2 . The reducibility of Mn 4＋ ions and reactivity of activated oxygen were favorable for the catalytic performances of NO oxidation.展开更多
基金Project supported by the National"973"Project (2004CB719503) and the Programfor New Century Excellent Talents in University
文摘Dynamic oxygen storage and release capability （OSC） measurement apparatus was designed to evaluate the OSC performance of ceria-based oxygen storage material. The optimum measurement condition was at a frequency of 0.1 Hz with the inlet gas-flow sequence CO （5S）→O2（5S）→CO→O2 and a flow rate of 300 ml·min^-1. Under this condition, similar regular square wave in the inlet and outlet of the reactor was obtained to guarantee the reliability of the dynamic OSC results. The dynamic OSC performance of the CeO2 and Ce0.67Zr0.33O2 mixed oxide prepared using the citric sol-gel method was studied at the optimum measurement condition with focus on both quantitative and qualitative analyses, The results reveal distinctly that Ce0.67Zr0.33O2 had better dynamic OSC performance because of its higher oxygen migration rate than CeO2. Under dynamic conditions, two CO2 production peaks occurred corresponding to the CO pulse and the O2 pulse, respectively, during the entire cycle. The intensity and ratio between the two CO2 productions were highly influenced by temperature and frequency indicating complex surface phenomena during the oxygen storage/release process, As a result, this set-up can be applied to the evaluation of ceria-based material on the OSC performance.
基金supported by National High Technology Research and Development Program of China(863Program,2011AA03A405)grant support from GM Global Research & Development
文摘The NO oxidation reaction was studied over MnOx-CeO2 catalysts prepared by co-precipitation, impregnation and mechanical mixing method, respectively. It was found that the co-precipitation was the most active and a 60% NO conversion was achieved at 250 oC. X-ray diffraction （XRD）, Brumauer-Emmett （BET）, H2-temperature programmed reduction （H2-TPR） and oxygen storage capacity （OSC） techniques were employed to characterize the physical and chemical properties of the catalysts. XRD results showed that amorphous MnOx or Mn-O-Ce solid solution existed in co-precipitation and impregnation prepared sample, while crystalline MnOx was found in mechanical mixing catalyst. A larger surface area was observed on co-precipitation prepared catalyst compared to those prepared by impregnation and mechanical mixing. The strong interaction between MnOx and CeO2 enhanced the reducibility of the oxides and increased the amount of Mn4＋ and activated oxygen, which are favorable for NO oxidation to NO2.
基金Project supported by National High Technology Research and Development Program of China(863Program,2011AA03A405)
文摘La1-x Cax MnO3 （x=0-0.3） perovskite-type oxides were synthesized by citrate sol-gel method. The physical and chemical properties were characterized by X-ray diffraction （XRD）, Brumauer-Emmett-Teller method （BET）, X-ray photoelectron spectroscopy （XPS）, NO＋O2 -TPD （temperature-programmed desorption）, activated oxygen evaluation and H2 -TPR （temperature-programmed reduction） technologies. The results showed that NO catalytic oxidation activity was significantly improved by Ca substitution, especially for lower temperature activity. The La0.9 Ca0.1 MnO 3 sample showed the maximum conversion of 82% at 300 oC. The monodentate nitrates played a crucial role for the formation of NO2 . The reducibility of Mn 4＋ ions and reactivity of activated oxygen were favorable for the catalytic performances of NO oxidation.
