The activity and thermal stability of Pd/Al2O3 and Pd/（Al2O3＋MOx） （M=Ca, La, Ce） palladium catalysts in the reaction of complete oxidation of methane are presented in this study. The catalyst supports were prepar...The activity and thermal stability of Pd/Al2O3 and Pd/（Al2O3＋MOx） （M=Ca, La, Ce） palladium catalysts in the reaction of complete oxidation of methane are presented in this study. The catalyst supports were prepared by sol-gel method and they were dried either conventionally or with supercritical carbon dioxide. Then they were impregnated with palladium nitrate solution. The catalysts with unmodified alumina had a high surface area. The activity and thermal stability of the aluminasupported catalyst was also very high. The introduction of calcium, lanthanum, or cerium oxide into alumina support caused a decrease of the surface area in the way dependent on the support precursor drying method. These modifiers decreased the activity of palladium catalysts, and they required higher temperatures for the complete oxidation of methane than unmodified Pd/Al2O3. The improvement of the palladium activity by lanthanum and cerium support modifier was observed only at low temperatures of the reaction.展开更多
The carbon nanotubes supported palladium(Pd/CNT)nanocatalysts were modified by cerium oxides/ hydroxides and their catalytic performances for methanol oxidation were evaluated.Electrochemical measurements indicate tha...The carbon nanotubes supported palladium(Pd/CNT)nanocatalysts were modified by cerium oxides/ hydroxides and their catalytic performances for methanol oxidation were evaluated.Electrochemical measurements indicate that the introduction of cerium remarkably improves the catalytic activity of Pd/CNT catalysts towards methanol oxidation.X-Ray photoelectron spectra results reveal an interaction between palladium and cerium oxides.It is also observed that cerium-modified catalysts have excellent poison resistances,which is attributed to the poison-removal ability of cerium oxides/hydroxides.The highly oxidized cerium oxides/hydroxides have a strong ability to inhibit the accumulation of carbonaceous intermediates on the active sites of Pd catalysts.展开更多
Barium oxide was developed successfully to modify palladium catalysts supported on CeO2-ZrO2-La2O3-Al2O3（CZLA） compound oxides by impregnation method. N2 adsorption（BET）, X-ray diffraction（XRD）, H2-temperature-p...Barium oxide was developed successfully to modify palladium catalysts supported on CeO2-ZrO2-La2O3-Al2O3（CZLA） compound oxides by impregnation method. N2 adsorption（BET）, X-ray diffraction（XRD）, H2-temperature-programmed reduction（H2-TPR） and X-ray photoelectron spectroscopy（XPS） were employed to characterize the influence of BaO on the physicochemical properties of catalyst. And catalytic activity tests for methanol, CO, C3H8 and NO conversion were evaluated. Catalytic activity results showed that BaO had a positive effect on the conversion of all pollutants. H2-TPR results suggested that the addition of BaO increased the reductive ability of the palladium catalysts. The XPS results indicated that doping BaO also improved the dispersion of Pd species and increased the amounts of Ce3＋ on the Pd-Ba/CZLA catalyst surface, which led to a better redox property. The excellent redox property helped to improve the catalytic activities toward all the pollutants over Pd-based catalysts.展开更多
文摘The activity and thermal stability of Pd/Al2O3 and Pd/（Al2O3＋MOx） （M=Ca, La, Ce） palladium catalysts in the reaction of complete oxidation of methane are presented in this study. The catalyst supports were prepared by sol-gel method and they were dried either conventionally or with supercritical carbon dioxide. Then they were impregnated with palladium nitrate solution. The catalysts with unmodified alumina had a high surface area. The activity and thermal stability of the aluminasupported catalyst was also very high. The introduction of calcium, lanthanum, or cerium oxide into alumina support caused a decrease of the surface area in the way dependent on the support precursor drying method. These modifiers decreased the activity of palladium catalysts, and they required higher temperatures for the complete oxidation of methane than unmodified Pd/Al2O3. The improvement of the palladium activity by lanthanum and cerium support modifier was observed only at low temperatures of the reaction.
基金the National Natural Science Foundation of China(No.21273152).
文摘The carbon nanotubes supported palladium(Pd/CNT)nanocatalysts were modified by cerium oxides/ hydroxides and their catalytic performances for methanol oxidation were evaluated.Electrochemical measurements indicate that the introduction of cerium remarkably improves the catalytic activity of Pd/CNT catalysts towards methanol oxidation.X-Ray photoelectron spectra results reveal an interaction between palladium and cerium oxides.It is also observed that cerium-modified catalysts have excellent poison resistances,which is attributed to the poison-removal ability of cerium oxides/hydroxides.The highly oxidized cerium oxides/hydroxides have a strong ability to inhibit the accumulation of carbonaceous intermediates on the active sites of Pd catalysts.
基金Project supported by the National Natural Science Foundation of China(51209024)the Key Program of Education Department of Sichuan Province(14ZA0163)Air Environmental Modeling and Pollution Controlling Key Laboratory of Sichuan Higher Education Institutes(KYTZ201219)
文摘Barium oxide was developed successfully to modify palladium catalysts supported on CeO2-ZrO2-La2O3-Al2O3（CZLA） compound oxides by impregnation method. N2 adsorption（BET）, X-ray diffraction（XRD）, H2-temperature-programmed reduction（H2-TPR） and X-ray photoelectron spectroscopy（XPS） were employed to characterize the influence of BaO on the physicochemical properties of catalyst. And catalytic activity tests for methanol, CO, C3H8 and NO conversion were evaluated. Catalytic activity results showed that BaO had a positive effect on the conversion of all pollutants. H2-TPR results suggested that the addition of BaO increased the reductive ability of the palladium catalysts. The XPS results indicated that doping BaO also improved the dispersion of Pd species and increased the amounts of Ce3＋ on the Pd-Ba/CZLA catalyst surface, which led to a better redox property. The excellent redox property helped to improve the catalytic activities toward all the pollutants over Pd-based catalysts.
