Nickel catalysts supported on CeO2-ZrO2-CeO2,ZrO2-Al2O3 and Al2O3 were prepared and characterized by means of X-ray diffraction(XRD),BET areas,H2 temperature-programmed reduction(H2-TPR),and X-ray photoelectron sp...Nickel catalysts supported on CeO2-ZrO2-CeO2,ZrO2-Al2O3 and Al2O3 were prepared and characterized by means of X-ray diffraction(XRD),BET areas,H2 temperature-programmed reduction(H2-TPR),and X-ray photoelectron spectroscopy(XPS).Through the test of catalytic partial oxidation of methane(CPOM),Ni/CeO2-ZrO2-Al2O3 displayed the highest activity,which resulted from its largest BET area and best NiO dispersion.Furthermore,Ni/CeO2-ZrO2-Al2O3 maintained a long-time stability in CPOM,which was attributed to its best coking resistance among all the prepared catalysts.展开更多
Fixed-bed reactors for the catalytic partial oxidation of methane (CPOM) to produce synthesis gas still pose hot spots problems.Microreactor is a good alternative reactor proposed to resolve these problems.In this p...Fixed-bed reactors for the catalytic partial oxidation of methane (CPOM) to produce synthesis gas still pose hot spots problems.Microreactor is a good alternative reactor proposed to resolve these problems.In this paper,synthesis gas (hydrogen and carbon monoxide) production was investigated by a two-dimensional numerical model of single microchannel.Computational fluid dynamic (CFD) modeling with detailed chemistry was conducted to understand the CPOM on platinum (Pt) catalyst.Gas inlet velocity,microchannel pressure,and fuel to air ratio (F/A) are selected as the effective parameters on microchannel performance.Study results show that Reynolds number has considerable effect on methane conversion,hydrogen to carbon monoxide ratio (H2/CO),and product distribution.Increasing gas inlet velocity causes all the above parameters to decrease.It is noted that increasing microchannel pressure and decreasing the ratio of fuel to air cause the decrease of the H2/CO ratio.展开更多
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
A nickel nanowire catalyst was prepared by a hard template method, and characterized by transmission electron microscopy (TEM), N2 physical adsorption, X-ray photoelectron spectrometry (XPS), X-ray diffraction (...A nickel nanowire catalyst was prepared by a hard template method, and characterized by transmission electron microscopy (TEM), N2 physical adsorption, X-ray photoelectron spectrometry (XPS), X-ray diffraction (XRD) and H2 temperature-programmed reduction (H2-TPR). The catalytic properties of the nanowire catalyst in the partial oxidation of methane to syngas were compared with a metallic Ni catalyst which was prepared with nickel sponge. The characterization results showed that the nickel nanowire catalyst had high specific surface area and there was more NiO phase in the nickel nanowire catalyst than in the metallic Ni catalyst. The reaction results showed that the nickel nanowire catalyst had high CH4 conversion and selectivities for H2 and CO under low space velocity.展开更多
基金Project supported by State Key Fundamental Research Project(G1999022400)
文摘Nickel catalysts supported on CeO2-ZrO2-CeO2,ZrO2-Al2O3 and Al2O3 were prepared and characterized by means of X-ray diffraction(XRD),BET areas,H2 temperature-programmed reduction(H2-TPR),and X-ray photoelectron spectroscopy(XPS).Through the test of catalytic partial oxidation of methane(CPOM),Ni/CeO2-ZrO2-Al2O3 displayed the highest activity,which resulted from its largest BET area and best NiO dispersion.Furthermore,Ni/CeO2-ZrO2-Al2O3 maintained a long-time stability in CPOM,which was attributed to its best coking resistance among all the prepared catalysts.
文摘Fixed-bed reactors for the catalytic partial oxidation of methane (CPOM) to produce synthesis gas still pose hot spots problems.Microreactor is a good alternative reactor proposed to resolve these problems.In this paper,synthesis gas (hydrogen and carbon monoxide) production was investigated by a two-dimensional numerical model of single microchannel.Computational fluid dynamic (CFD) modeling with detailed chemistry was conducted to understand the CPOM on platinum (Pt) catalyst.Gas inlet velocity,microchannel pressure,and fuel to air ratio (F/A) are selected as the effective parameters on microchannel performance.Study results show that Reynolds number has considerable effect on methane conversion,hydrogen to carbon monoxide ratio (H2/CO),and product distribution.Increasing gas inlet velocity causes all the above parameters to decrease.It is noted that increasing microchannel pressure and decreasing the ratio of fuel to air cause the decrease of the H2/CO ratio.
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 financial supports by the National High Technology Research and Development Program of China (863 Program) under Grant No. 2007AA05Z104 and 2006AA05Z115key project of Tianjin Natural Science Foundation under Grant No. 07 JCZDJC00200 are gratefully acknowledged
文摘A nickel nanowire catalyst was prepared by a hard template method, and characterized by transmission electron microscopy (TEM), N2 physical adsorption, X-ray photoelectron spectrometry (XPS), X-ray diffraction (XRD) and H2 temperature-programmed reduction (H2-TPR). The catalytic properties of the nanowire catalyst in the partial oxidation of methane to syngas were compared with a metallic Ni catalyst which was prepared with nickel sponge. The characterization results showed that the nickel nanowire catalyst had high specific surface area and there was more NiO phase in the nickel nanowire catalyst than in the metallic Ni catalyst. The reaction results showed that the nickel nanowire catalyst had high CH4 conversion and selectivities for H2 and CO under low space velocity.