The Ni-CeO2/Al2O3 catalysts with a nickel content of 15 wt% prepared via impregnating boehmite were found to be highly active and stable for methanation of carbon dioxide with hydrogen at a H2/CO2 molar ratio of 4. Th...The Ni-CeO2/Al2O3 catalysts with a nickel content of 15 wt% prepared via impregnating boehmite were found to be highly active and stable for methanation of carbon dioxide with hydrogen at a H2/CO2 molar ratio of 4. The effects of CeO2 content and reaction temperature on the performance of the Ni-CeO2/Al2O3 catalysts were studied in detail. The results showed that the catalytic performance was strongly dependent on the CeO2 content in Ni-CeO2/Al2O3 catalysts and that the catalysts with 2 wt% CeO2 had the highest catalytic activity among the tested ones at 350 ℃. The XRD and H2-TPR characterizations revealed that the addition of CeO2 decreased the reduction temperature by altering the interaction between Ni and Al2O3, and improved the reducibility of the catalyst. Preliminary stability test of 120 h on stream over the Ni-2CeO2/Al2O3 catalyst at 350 ℃ revealed that the catalyst was much better than the unpromoted one.展开更多
Ni catalysts supported on various mixed oxides of Al2O3 with rare earth oxide and transitional metal oxides were synthesized. The studies focused on the measurement of the autothermal reforming of methane to hydrogen ...Ni catalysts supported on various mixed oxides of Al2O3 with rare earth oxide and transitional metal oxides were synthesized. The studies focused on the measurement of the autothermal reforming of methane to hydrogen over Ni catalysts supported on the mixed oxide ZrxCe30-xAl70Oδ （x-=5, 10, 15）. The catalytic performance of Ni/Zr10Ce20Al70Oδ was better than that of other catalysts. XRD results showed that the addition of Zr to Ni/Ce30Al70Oδ prevented the formation of NiAl2O4 and facilitated the dispersion of NiO. Effects of CuO addition to Zr10Ce20Al70Oδ were also investigated. The activity of Ni catalyst supported on CuO-ZrO2-CeO2-Al2O3 was somewhat affected and the Ni/Cu5Zr10Ce20Al65Oδ showed the best catalytic performance with the highest CH4 conversion, yield of H2, selectivity for H2 and H2/CO production ratio in operation temperatures ranging from 650 to 750 ℃.展开更多
The decomposition of methane on Ni/α-Al_2O_3 modified by La_2O_3 and CeO_2with different contents has been investigated and the ralationship between methane decomposition andremoval of carbon by CO_2 over these catal...The decomposition of methane on Ni/α-Al_2O_3 modified by La_2O_3 and CeO_2with different contents has been investigated and the ralationship between methane decomposition andremoval of carbon by CO_2 over these catalyst has also been studied by pulse-chromatography. Thecatalysts were characterized by TPR and XRD. It was shown that Ni/α-Al_2O_3 could be promoted byadding La_2O_3, and the carbon species produced over this catalyst was activated and eliminated byCO_2. But CeO_2 would suppress the decomposition of methane over Ni crystallite. Both La_2O_3 andCeO_2 can inhibit aggregation of the Ni particles. Decomposition of methane over the Ni-basedcatalysts is structure sensitive to a certain extent.展开更多
The Ni/CeO_2-ZrO_2-Al_2O_3 catalyst with different Al_2O_3 and NiO contentswere prepared by hydrothermal synthesis method. The catalytic performance for CO_2 reforming of CH_4reaction, the interaction among components...The Ni/CeO_2-ZrO_2-Al_2O_3 catalyst with different Al_2O_3 and NiO contentswere prepared by hydrothermal synthesis method. The catalytic performance for CO_2 reforming of CH_4reaction, the interaction among components and the relation between Ni content and catalyst surfacebasicity were investigated. Results show that the interaction between NiO and Al_2O_3 is strongerthan that between NiO and CeO_2-ZrO_2. The addition of Al_2O_3 can prevent the formation of largemetallic Ni ensembles, increase the dispersion of Ni, and improve catalytic activity, but excessAl_2O_3 causes the catalyst to deactivate easily. The interaction between NiO and CeO_2 results inmore facile reduction of surface CeO_2. The existence of a small amount of metallic Ni can increasethe number of basic sites. As metallic Ni may preferentially reside on the strong basic sites,increasing Ni content can weaken the catalyst basicity.展开更多
A series of novel Ni/CeOe-Al2O3 composite catalysts were synthesized by one-step citric acid complex method, The as-synthesized catalysts were characterized by N2 physical adsorption/desorption, X-ray diffraction （XR...A series of novel Ni/CeOe-Al2O3 composite catalysts were synthesized by one-step citric acid complex method, The as-synthesized catalysts were characterized by N2 physical adsorption/desorption, X-ray diffraction （XRD）, Fourier transform infrared （FT-IR） spectroscopy, hydrogen temperature-programmed reduction （Hz-TPR）, X-ray photoelectron spectroscopy （XPS） and thermogravimetry analysis （TGA）. The effects of nickel content, calcination and reaction temperatures, gas hourly space velocity （GHSV） and inert gas dilution of N2 on their performance of catalytic partial oxidation of methane （CPOM） were investigated. Catalytic activity test results show that the highest methane conversion （〉85%）, the best selectivities to carbon monoxide （〉87%） and to hydrogen （〉95%）, the excellent stability and perfect Hz/CO ratio （2.0） can be obtained over Ni/CeO2-Al2O3 with 8 wt% Ni content calcined at 700 ℃ under the reaction condition of 750 ℃, CH4/O2 ratio of 2 ： 1 and gas hourly space velocity of 12000 mL.h-1 .g-1. Characterization results show that the good catalytic performance of this composite catalyst can be contributed to its large specific surface area （~108 m2.g-1）, small crystallite size, easy reducibility and low coking rate.展开更多
基金supported by the National High Technology Research and Development Program of China(Grant No.2006AA11A189)Science and Technology Commission of Shanghai Municipality(Grant No.07DZ12036,and08DZ12064)Shanghai Pujiang Program(Grant No.08PJ1405900)
文摘The Ni-CeO2/Al2O3 catalysts with a nickel content of 15 wt% prepared via impregnating boehmite were found to be highly active and stable for methanation of carbon dioxide with hydrogen at a H2/CO2 molar ratio of 4. The effects of CeO2 content and reaction temperature on the performance of the Ni-CeO2/Al2O3 catalysts were studied in detail. The results showed that the catalytic performance was strongly dependent on the CeO2 content in Ni-CeO2/Al2O3 catalysts and that the catalysts with 2 wt% CeO2 had the highest catalytic activity among the tested ones at 350 ℃. The XRD and H2-TPR characterizations revealed that the addition of CeO2 decreased the reduction temperature by altering the interaction between Ni and Al2O3, and improved the reducibility of the catalyst. Preliminary stability test of 120 h on stream over the Ni-2CeO2/Al2O3 catalyst at 350 ℃ revealed that the catalyst was much better than the unpromoted one.
基金The project is supported by Guangdong Provincial Natural Science Foundation of China(030514)Science and Technology Plan of Guangdong Province(2004B33401006)
文摘Ni catalysts supported on various mixed oxides of Al2O3 with rare earth oxide and transitional metal oxides were synthesized. The studies focused on the measurement of the autothermal reforming of methane to hydrogen over Ni catalysts supported on the mixed oxide ZrxCe30-xAl70Oδ （x-=5, 10, 15）. The catalytic performance of Ni/Zr10Ce20Al70Oδ was better than that of other catalysts. XRD results showed that the addition of Zr to Ni/Ce30Al70Oδ prevented the formation of NiAl2O4 and facilitated the dispersion of NiO. Effects of CuO addition to Zr10Ce20Al70Oδ were also investigated. The activity of Ni catalyst supported on CuO-ZrO2-CeO2-Al2O3 was somewhat affected and the Ni/Cu5Zr10Ce20Al65Oδ showed the best catalytic performance with the highest CH4 conversion, yield of H2, selectivity for H2 and H2/CO production ratio in operation temperatures ranging from 650 to 750 ℃.
文摘The decomposition of methane on Ni/α-Al_2O_3 modified by La_2O_3 and CeO_2with different contents has been investigated and the ralationship between methane decomposition andremoval of carbon by CO_2 over these catalyst has also been studied by pulse-chromatography. Thecatalysts were characterized by TPR and XRD. It was shown that Ni/α-Al_2O_3 could be promoted byadding La_2O_3, and the carbon species produced over this catalyst was activated and eliminated byCO_2. But CeO_2 would suppress the decomposition of methane over Ni crystallite. Both La_2O_3 andCeO_2 can inhibit aggregation of the Ni particles. Decomposition of methane over the Ni-basedcatalysts is structure sensitive to a certain extent.
文摘The Ni/CeO_2-ZrO_2-Al_2O_3 catalyst with different Al_2O_3 and NiO contentswere prepared by hydrothermal synthesis method. The catalytic performance for CO_2 reforming of CH_4reaction, the interaction among components and the relation between Ni content and catalyst surfacebasicity were investigated. Results show that the interaction between NiO and Al_2O_3 is strongerthan that between NiO and CeO_2-ZrO_2. The addition of Al_2O_3 can prevent the formation of largemetallic Ni ensembles, increase the dispersion of Ni, and improve catalytic activity, but excessAl_2O_3 causes the catalyst to deactivate easily. The interaction between NiO and CeO_2 results inmore facile reduction of surface CeO_2. The existence of a small amount of metallic Ni can increasethe number of basic sites. As metallic Ni may preferentially reside on the strong basic sites,increasing Ni content can weaken the catalyst basicity.
基金supported by the National Natural Science Foundation of China(Grants No.21067004 and No.21263005)the Technological Foundation of Jiangxi Province Education Office(No.GJJ12344)+1 种基金the Young Science and Technolgy Project of Jiangxi Province(No.20133BAB21003)the Young Scientist Training Project of Jiangxi Province(No.20122BCB23015)
文摘A series of novel Ni/CeOe-Al2O3 composite catalysts were synthesized by one-step citric acid complex method, The as-synthesized catalysts were characterized by N2 physical adsorption/desorption, X-ray diffraction （XRD）, Fourier transform infrared （FT-IR） spectroscopy, hydrogen temperature-programmed reduction （Hz-TPR）, X-ray photoelectron spectroscopy （XPS） and thermogravimetry analysis （TGA）. The effects of nickel content, calcination and reaction temperatures, gas hourly space velocity （GHSV） and inert gas dilution of N2 on their performance of catalytic partial oxidation of methane （CPOM） were investigated. Catalytic activity test results show that the highest methane conversion （〉85%）, the best selectivities to carbon monoxide （〉87%） and to hydrogen （〉95%）, the excellent stability and perfect Hz/CO ratio （2.0） can be obtained over Ni/CeO2-Al2O3 with 8 wt% Ni content calcined at 700 ℃ under the reaction condition of 750 ℃, CH4/O2 ratio of 2 ： 1 and gas hourly space velocity of 12000 mL.h-1 .g-1. Characterization results show that the good catalytic performance of this composite catalyst can be contributed to its large specific surface area （~108 m2.g-1）, small crystallite size, easy reducibility and low coking rate.
