Diannan Gao

Catalytic combustion of methane over Pd/MWCNTs under lean fuel conditions

Abstract The raw multi-walled carbon nanotubes (MWCNTs) were treated with nitric acid. The shift of the surface functional groups on the MWCNTs was observed with XPS. The Pd/MWCNTs catalysts were synthesized by the ultrasonic impregnation method. The total contents of oxygen, hydroxyl and carbonyl groups were measured. The dispersion and size distribution of Pd particles were characterized with TEM. The dependence of Pd dispersion on the oxygen-containing functional groups was validated. The effect of pretreatment on the catalytic activity and stability for methane combustion was investigated under lean fuel conditions. It is shown that the catalytic activity depends on the valence state and particle size of palladium. The transformation from Pd to PdO possibly caused the decrease in the catalytic activity. Another factor inducing deactivation is Pd particle aggregation. The reaction mechanism for methane combustion over the Pd/MWCNTs catalyst is postulated on the basis of the intermediate species detected by in-situ FT-IR spectroscopy.

Effect of support calcination temperature on the catalytic properties of Ru/Ce0.8Zr0.2O2 for methanation of carbon dioxide

Abstract A series of Ru/Ce 0.8 Zr 0.2 O 2 catalysts were prepared by the impregnation method with Ce 0.8 Zr 0.2 O 2 homoprecipitated and calcined at different temperatures as supports. The supports and the catalysts were characterized with TG-DSC, BET and H 2 -TPR techniques. It was shown that the Ce 0.8 Zr 0.2 O 2 calcined at 500°C formed Ce-Zr solid solution and had a proper surface area and pore opening and a weak interaction with Ru species, leading to a significant increase in the catalytic activity. A suitable reduction methods promoted distribution of active species. The Ru/Ce 0.8 Zr 0.2 O 2 prepared with the Ce 0.8 Zr 0.2 O 2 calcined at 500°C showed high activity after calcination at 400°C and successive reduction with H 2 N·NH 2 ·H 2 O and H 2 . It gave a H 2 conversion of 93.57%, approaching to the equilibrium value under the conditions of 290°C, 0.1 MPa, 10000 h −1 and H 2 /CO 2 molar ratio of 3.5.

In-Situ FT-IR Study on Methane Combustion over Pd/NiAl 2 O 4 Catalyst: In-Situ FT-IR Study on Methane Combustion over Pd/NiAl 2 O 4 Catalyst

The mechanism of methane combustion on Pd/NiAl 2 O 4 catalyst was studied by in-situ FT-IR spectroscopy. The results showed that the transformation from formate to carbonate was the rate-determining step for the reaction. After reaction under lean fuel condition, the active site of pre-reduced catalyst was still Pd-PdO mixed phase. The existence of metal Pd would convert O 2 to O 2 – species, which would facilitate the transformation from formate to carbonate.

Methane Combustion over Pd/Al 2 O 3 Catalyst: Effect of Cal-cination Temperature: Methane Combustion over Pd/Al 2 O 3 Catalyst: Effect of Cal-cination Temperature

The effect of calcination temperature for the support and catalyst on the catalytic properties of the Pd/Al2O3 catalyst for lean methane combustion was investigated.The Pd/Al2O3 catalyst was prepared by the impregnation method using Al2O3 support calcined at 500–1300℃.All catalyst samples were characterized by X-ray diffraction,transmission electron microscopy,surface area measurements,temperature-programmed desorption of NH3,and temperature-programmed oxidation of O2.Calcination temperature significantly affected the catalyst activity and stability.As the calcination temperature increased,the structure of the support and the amount and intensity of the acid sites changed obviously,and the dispersion of the active component and the interaction between the support and active component decreased.The proper calcination temperature for the Al2O3 support was 1100℃,and the optimal calcination temperature for the Pd/Al2O3 was 200℃.This catalyst showed high thermal stability and catalytic activity.