Cu/CeO2-ZrO2 catalysts for water-gas shift （WGS） reaction were prepared with co-precipitation method, and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of...Cu/CeO2-ZrO2 catalysts for water-gas shift （WGS） reaction were prepared with co-precipitation method, and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of N2 physical adsorption analysis, XRD and H2-TPR. The results indicate that the BET surface areas of the catalysts are increased in varying degrees due to the presence of ZrO2. With increasing ZrO2 content, the pore size distribution is centered on 1.9 nm. ZrO2 can efficiently restrain the growth of Cu crystal particles. The appropriate amount of ZrO2 in the Cu/CeO2 catalysts can help the catalyst keep better copper dispersion in the WGS reaction, which can lead to both higher catalytic activity and better thermal stability. When ZrO2 content is 10% （atom fraction）, Cu/CeO2-Zr02 catalyst reaches a CO conversion rate of 73.7% at the reaction temperature of 200℃.展开更多
CeO2 was synthesized via sol-gel process and used as supporter to prepare CuO/CeO2, Cu/CeO2 catalysts by impregnation method. The catalytic properties and characterization of CeO2, CuO/CeO2 and Cu/CeO2 catalysts were ...CeO2 was synthesized via sol-gel process and used as supporter to prepare CuO/CeO2, Cu/CeO2 catalysts by impregnation method. The catalytic properties and characterization of CeO2, CuO/CeO2 and Cu/CeO2 catalysts were examined by means of a microreactor-GC system, HRTEM, XRD, TPR and XPS techniques. The results show that CuO has not catalytic activity and the activity of CeO2 is quite low for CO oxidation. However, the catalytic activity of CuO/CeO2 and Cu/ CeO2 catalysts increases significantly. Furthermore, the activity of CuO/CeO2 is higher than that of Cu/CeO2 catalysts.展开更多
Composite supports CeO2-ZrO2-Al2O3（CZA） and CeO2-ZrO2-Al2O3-La2O3（CZALa） were prepared by co-precipitation method. Palladium catalysts were prepared by impregnation and their purification ability for CH4, CO and N...Composite supports CeO2-ZrO2-Al2O3（CZA） and CeO2-ZrO2-Al2O3-La2O3（CZALa） were prepared by co-precipitation method. Palladium catalysts were prepared by impregnation and their purification ability for CH4, CO and NOx in the mixture gas simulated the exhaust from natural gas vehicles （NGVs） operated under stoichiometric condition was investigated. The effect of La2O3 on the physicochemical properties of supports and catalysts was characterized by various techniques. The characterizations with X-ray diffraction （XRD） and Raman spectroscopy revealed that the doping of La2O3 restrained effectively the sintering of crystallite particles, maintained the crystallite particles in nanoscale and stabilized the crystal phase after calcination at 1000 ℃. The results of N2-adsorption, H2-temperatnre-programmed reduction （H2-TPR） and oxygen storage capacity （OSC） measurements indicated that La2O3 improved the textural properties, reducibility and OSC of composite supports. Activity testing results showed that the catalysts exhibit excellent activities for the simultaneous removal of methane, CO and NOx in the simulated exhaust gas. The catalysts supported on CZALa showed remarkable thermal stability and catalytic activity for the three pollutants, especially for NOx. The prepared palladium catalysts have high ability to remove NOx, CH4 and CO, and they can be used as excellent catalysts for the purification of exhaust from NGVs operated under stoichiometric condition. The catalysts reported in this work also have significant potential in industrial application because of their high performance and low cost.展开更多
The Pd-only catalysts for motorcycle were prepared by impregnating CeO2-ZrO2-Al2O3 and CeO2-ZrO2+Al2O3 with PdCl2 aqueous solution and characterized by X-ray diffraction (XRD), oxygen storage capacity (OSC) and H2-tem...The Pd-only catalysts for motorcycle were prepared by impregnating CeO2-ZrO2-Al2O3 and CeO2-ZrO2+Al2O3 with PdCl2 aqueous solution and characterized by X-ray diffraction (XRD), oxygen storage capacity (OSC) and H2-temperature-programmed reduction (H2-TPR) methods. The XRD result indicated that the CeO2-ZrO2-Al2O3 compound prepared by co-precipitation formed a single solid solution and had good thermal stability, and Pd phase was not observed in all catalysts. The TPR results showed that the reduction temperature of Pd/CeO2-ZrO2-Al2O3 catalyst was lower than that of Pd/CeO2-ZrO2+Al2O3 catalyst whether they were fresh or aged catalysts. The Pd/CeO2-ZrO2-Al2O3 exhibited high three-way catalytic activity at low temperature, high thermal stability, and wide working window, suggesting a great potential for applications.展开更多
Three series of CeO2/CuO samples were prepared by impregnation method and characterized by XRD, N2 adsorption-desorption, temperatureprogrammed reduction （TPR）, XPS and TEM techniques. In comparison with the samples...Three series of CeO2/CuO samples were prepared by impregnation method and characterized by XRD, N2 adsorption-desorption, temperatureprogrammed reduction （TPR）, XPS and TEM techniques. In comparison with the samples prepared with CuO as initial support, the samples with Cu（OH）2 as initial support have higher reducibilities and smaller relative TPR peak areas, and also larger specific surface areas at calcina- tion temperatures of 400 ℃--600 ℃. As a result, Cu（OH）2 is better than CuO as initial support for preferential oxidation of CO in excess H2 （CO-PROX）. The best catalytic performance was achieved on the sample calcined at 600 ℃ and with an atomic ratio of Ce/Cu at 40%. XPS analyses indicate that more interface linkages Ce-O-Cu could be formed when it was calcined at 600 ℃. And the atomic ratio of Ce/Cu at 40% led to a proper reducibility for the sample as illustrated by the TPR measurements.展开更多
CeO2-promoted Ni/Al2O3-ZrO2 （Ni/Al2O3-ZrO2-CeO2） catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO2 was studied by infrared s...CeO2-promoted Ni/Al2O3-ZrO2 （Ni/Al2O3-ZrO2-CeO2） catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO2 was studied by infrared spectroscopy （IR）, thermal gravimetric analysis （TGA）, microscopic analysis, X-ray diffraction （XRD） and temperature-programmed reduction （TPR）. The catalytic performance for CO2 reforming of methane to synthesis gas was investigated in a continuous-flow micro-reactor under atmospheric pressure. TGA, IR, XRD and microscopic analysis show that the catalysts prepared by the direct sol-gel process consist of Ni particles with a nanostructure of around 5 nm and an amorphous-phase composite oxide support. There exists a chemical interaction between metallic Ni particles and supports, which makes metallic Ni well dispersed, highly active and stable. The addition of CeO2 effectively improves the dispersion and the stability of Ni particles of the prepared catalysts, and enhances the adsorption of CO2 on the surface of catalysts. The catalytic tests for methane reforming with CO2 to synthesis gas show that the Ni/Al2O3-ZrO2-CeO2 catalysts show excellent activity and stability compared with the Ni/Al2O3 catalyst. The excellent catalytic activity and stability of the Ni/Al2O3-ZrO2-CeO2 are attributed to the highly, uniformly and stably dispersed small metallic Ni particles, the high reducibility of the Ni oxides and the interaction between metallic Ni particles and the composite oxide supports.展开更多
The oxidative properties and characterization of CuO, CeO 2 and CuO/CeO 2 cata lysts were examined by means of a CO micro-reactor GC system, TPR, XPS and X-r ay diffraction Rietveld methods. The results show that ei...The oxidative properties and characterization of CuO, CeO 2 and CuO/CeO 2 cata lysts were examined by means of a CO micro-reactor GC system, TPR, XPS and X-r ay diffraction Rietveld methods. The results show that either CuO or CeO 2 ac tivity is quite low for CO oxidation. However, when CuO and CeO 2 are mixed, the oxidative activity of the catalyst increases significantly, probably owing to the valency status of copper species (Cu 2+ and Cu+) on the CeO 2 surfa ce, the dispersion and reducibility. XPS surface analysis shows that CuO loading is very important in forming of either Cu 2+ or Cu+. Rietveld analysis s hows that some CuO, which has smaller ion radius than Ce 4+, enters the Ce O 2 lattice after CuO and CeO 2 are mixed. When the CuO loading reaches 5.0%, the size of CuO crystals is a minimum (6.1 nm) and the micro-strain value i s a maximum (2.86×10 -3), resulting in high surface energy and the best ac tivity for CO oxidation.展开更多
Pt-CeO2-ZrO2/MgO （Pt-CZ/MgO） catalysts with 0.8 wt% Pt, 3.0 wt% CeO2 and 3.0 wt% ZrO2 were prepared by wet impregnation method. Support MgO was obtained using ion exchange resin method or using commercial MgO. XRD, ...Pt-CeO2-ZrO2/MgO （Pt-CZ/MgO） catalysts with 0.8 wt% Pt, 3.0 wt% CeO2 and 3.0 wt% ZrO2 were prepared by wet impregnation method. Support MgO was obtained using ion exchange resin method or using commercial MgO. XRD, BET, SEM, TEM, DTA-TG and CO2-TPD were used to characterize the catalysts. CH4-CO2 reforming to synthesis gas （syngas） was performed to test the catalytic behavior of the catalysts. The catalyst Pt-CZ/MgO-IE（D） prepared using ion exchange resin exhibits more regular structure, smaller and more unique particle sizes, and stronger basicity than the catalyst Pt-CZ/MgO prepared from commercial MgO. At 1073 K and atmospheric pressure, Pt-CZ/MgO-IE（D） catalyst has a higher activity and greater stability than Pt-CZ/MgO catalyst for CH4-CO2 reforming reaction at high gas hourly space velocity of 36000 mL/（g.h） with a stoichiometric feed of CH4 and C02. Activity measurement and characterization results demonstrate that modification of the support using ion exchange resin method can promote the surface structural property and stability, therefore enhancing the activity and stability for CH4-CO2 reforming reaction.展开更多
文摘Cu/CeO2-ZrO2 catalysts for water-gas shift （WGS） reaction were prepared with co-precipitation method, and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of N2 physical adsorption analysis, XRD and H2-TPR. The results indicate that the BET surface areas of the catalysts are increased in varying degrees due to the presence of ZrO2. With increasing ZrO2 content, the pore size distribution is centered on 1.9 nm. ZrO2 can efficiently restrain the growth of Cu crystal particles. The appropriate amount of ZrO2 in the Cu/CeO2 catalysts can help the catalyst keep better copper dispersion in the WGS reaction, which can lead to both higher catalytic activity and better thermal stability. When ZrO2 content is 10% （atom fraction）, Cu/CeO2-Zr02 catalyst reaches a CO conversion rate of 73.7% at the reaction temperature of 200℃.
基金Projected supported by the National Natural Science Foundation of China (20271028) and Tianjin Natural Science Foundation(033602511)
文摘CeO2 was synthesized via sol-gel process and used as supporter to prepare CuO/CeO2, Cu/CeO2 catalysts by impregnation method. The catalytic properties and characterization of CeO2, CuO/CeO2 and Cu/CeO2 catalysts were examined by means of a microreactor-GC system, HRTEM, XRD, TPR and XPS techniques. The results show that CuO has not catalytic activity and the activity of CeO2 is quite low for CO oxidation. However, the catalytic activity of CuO/CeO2 and Cu/ CeO2 catalysts increases significantly. Furthermore, the activity of CuO/CeO2 is higher than that of Cu/CeO2 catalysts.
基金supported by the National Natural Science Foundation of China (No. 20773090, 20803049)the National High Technology Researchand Development Program of China (863 Program, No. 2006AA06Z347)the Specialized Research Fund for the Doctoral Program of Higher Education(20070610026)
文摘Composite supports CeO2-ZrO2-Al2O3（CZA） and CeO2-ZrO2-Al2O3-La2O3（CZALa） were prepared by co-precipitation method. Palladium catalysts were prepared by impregnation and their purification ability for CH4, CO and NOx in the mixture gas simulated the exhaust from natural gas vehicles （NGVs） operated under stoichiometric condition was investigated. The effect of La2O3 on the physicochemical properties of supports and catalysts was characterized by various techniques. The characterizations with X-ray diffraction （XRD） and Raman spectroscopy revealed that the doping of La2O3 restrained effectively the sintering of crystallite particles, maintained the crystallite particles in nanoscale and stabilized the crystal phase after calcination at 1000 ℃. The results of N2-adsorption, H2-temperatnre-programmed reduction （H2-TPR） and oxygen storage capacity （OSC） measurements indicated that La2O3 improved the textural properties, reducibility and OSC of composite supports. Activity testing results showed that the catalysts exhibit excellent activities for the simultaneous removal of methane, CO and NOx in the simulated exhaust gas. The catalysts supported on CZALa showed remarkable thermal stability and catalytic activity for the three pollutants, especially for NOx. The prepared palladium catalysts have high ability to remove NOx, CH4 and CO, and they can be used as excellent catalysts for the purification of exhaust from NGVs operated under stoichiometric condition. The catalysts reported in this work also have significant potential in industrial application because of their high performance and low cost.
基金Project supported by the National High Technology Research and Development Program of China (863 Program,2006AA06Z347)the Specialized Research Fund for the Doctoral Program of Higher Education (20070610026)
文摘The Pd-only catalysts for motorcycle were prepared by impregnating CeO2-ZrO2-Al2O3 and CeO2-ZrO2+Al2O3 with PdCl2 aqueous solution and characterized by X-ray diffraction (XRD), oxygen storage capacity (OSC) and H2-temperature-programmed reduction (H2-TPR) methods. The XRD result indicated that the CeO2-ZrO2-Al2O3 compound prepared by co-precipitation formed a single solid solution and had good thermal stability, and Pd phase was not observed in all catalysts. The TPR results showed that the reduction temperature of Pd/CeO2-ZrO2-Al2O3 catalyst was lower than that of Pd/CeO2-ZrO2+Al2O3 catalyst whether they were fresh or aged catalysts. The Pd/CeO2-ZrO2-Al2O3 exhibited high three-way catalytic activity at low temperature, high thermal stability, and wide working window, suggesting a great potential for applications.
文摘Three series of CeO2/CuO samples were prepared by impregnation method and characterized by XRD, N2 adsorption-desorption, temperatureprogrammed reduction （TPR）, XPS and TEM techniques. In comparison with the samples prepared with CuO as initial support, the samples with Cu（OH）2 as initial support have higher reducibilities and smaller relative TPR peak areas, and also larger specific surface areas at calcina- tion temperatures of 400 ℃--600 ℃. As a result, Cu（OH）2 is better than CuO as initial support for preferential oxidation of CO in excess H2 （CO-PROX）. The best catalytic performance was achieved on the sample calcined at 600 ℃ and with an atomic ratio of Ce/Cu at 40%. XPS analyses indicate that more interface linkages Ce-O-Cu could be formed when it was calcined at 600 ℃. And the atomic ratio of Ce/Cu at 40% led to a proper reducibility for the sample as illustrated by the TPR measurements.
基金supported by the National Natural Science Foundation of China (NO. 20976013, 21006057)
文摘CeO2-promoted Ni/Al2O3-ZrO2 （Ni/Al2O3-ZrO2-CeO2） catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO2 was studied by infrared spectroscopy （IR）, thermal gravimetric analysis （TGA）, microscopic analysis, X-ray diffraction （XRD） and temperature-programmed reduction （TPR）. The catalytic performance for CO2 reforming of methane to synthesis gas was investigated in a continuous-flow micro-reactor under atmospheric pressure. TGA, IR, XRD and microscopic analysis show that the catalysts prepared by the direct sol-gel process consist of Ni particles with a nanostructure of around 5 nm and an amorphous-phase composite oxide support. There exists a chemical interaction between metallic Ni particles and supports, which makes metallic Ni well dispersed, highly active and stable. The addition of CeO2 effectively improves the dispersion and the stability of Ni particles of the prepared catalysts, and enhances the adsorption of CO2 on the surface of catalysts. The catalytic tests for methane reforming with CO2 to synthesis gas show that the Ni/Al2O3-ZrO2-CeO2 catalysts show excellent activity and stability compared with the Ni/Al2O3 catalyst. The excellent catalytic activity and stability of the Ni/Al2O3-ZrO2-CeO2 are attributed to the highly, uniformly and stably dispersed small metallic Ni particles, the high reducibility of the Ni oxides and the interaction between metallic Ni particles and the composite oxide supports.
文摘The oxidative properties and characterization of CuO, CeO 2 and CuO/CeO 2 cata lysts were examined by means of a CO micro-reactor GC system, TPR, XPS and X-r ay diffraction Rietveld methods. The results show that either CuO or CeO 2 ac tivity is quite low for CO oxidation. However, when CuO and CeO 2 are mixed, the oxidative activity of the catalyst increases significantly, probably owing to the valency status of copper species (Cu 2+ and Cu+) on the CeO 2 surfa ce, the dispersion and reducibility. XPS surface analysis shows that CuO loading is very important in forming of either Cu 2+ or Cu+. Rietveld analysis s hows that some CuO, which has smaller ion radius than Ce 4+, enters the Ce O 2 lattice after CuO and CeO 2 are mixed. When the CuO loading reaches 5.0%, the size of CuO crystals is a minimum (6.1 nm) and the micro-strain value i s a maximum (2.86×10 -3), resulting in high surface energy and the best ac tivity for CO oxidation.
基金supported by the National Natural Science Foundation of China (No. 20873013)
文摘Pt-CeO2-ZrO2/MgO （Pt-CZ/MgO） catalysts with 0.8 wt% Pt, 3.0 wt% CeO2 and 3.0 wt% ZrO2 were prepared by wet impregnation method. Support MgO was obtained using ion exchange resin method or using commercial MgO. XRD, BET, SEM, TEM, DTA-TG and CO2-TPD were used to characterize the catalysts. CH4-CO2 reforming to synthesis gas （syngas） was performed to test the catalytic behavior of the catalysts. The catalyst Pt-CZ/MgO-IE（D） prepared using ion exchange resin exhibits more regular structure, smaller and more unique particle sizes, and stronger basicity than the catalyst Pt-CZ/MgO prepared from commercial MgO. At 1073 K and atmospheric pressure, Pt-CZ/MgO-IE（D） catalyst has a higher activity and greater stability than Pt-CZ/MgO catalyst for CH4-CO2 reforming reaction at high gas hourly space velocity of 36000 mL/（g.h） with a stoichiometric feed of CH4 and C02. Activity measurement and characterization results demonstrate that modification of the support using ion exchange resin method can promote the surface structural property and stability, therefore enhancing the activity and stability for CH4-CO2 reforming reaction.
