Acta Phys. -Chim. Sin. ›› 2008, Vol. 24 ›› Issue (11): 2108-2113.doi: 10.1016/S1872-1508(08)60080-7

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Catalytic Combustion of Methane over CeO2-MOx (M=La3+, Ca2+) Solid Solution Promoted Pd/γ-Al2O3 Catalysts

XIAO Li-Hua, SUN Kun-Peng, XU Xian-Lun   

  1. State Key Laboratory Breeding Base of Green-Chemistry Synthesis Technology, Institute of Resources and Environment Catalysis, Zhejiang University of Technology, Hangzhou 310032, P. R. China; State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, P. R. China
  • Received:2008-04-14 Revised:2008-06-27 Published:2008-11-10
  • Contact: XIAO Li-Hua

Abstract: Solid solution CeO2-MOx (M=La3+, Ca2+) promoted Pd/γ-Al2O3 catalysts were prepared by a deposition-precipitation method. The structural properties were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. The results showed that Mn+ ions incorporated into CeO2 lattice and solid solutions formed in Pd/γ-Al2O3-CeO2-MOx catalysts. The formation of solid solution was confirmed by the change in lattice parameters of CeO2 and the shift of 2θ angles as compared with pure CeO2. A strain formed in the O2- sub-lattice of CeO2 was revealed by Raman analyses, which decreased the intensity of the Raman-active band at around 463 cm-1 owing to the F2g symmetric stretching of Ce—O bond. The appearance of a new band at 615 cm-1 (in the case of Pd/γ-Al2O3-CeO2-CaO) and a shoulder at 320 cm-1 (in the case of Pd/γ-Al2O3-CeO2-La2O3) was also confirmed. Ionic Pdδ+ species were formed in the catalysts, which exhibited higher binding energies (0.5-0.6 eV higher for Pd 3d5/2) than that of normal PdO. The catalysts showed high activity and stability for low temperature methane combustion. 10% and 100% conversions of methane could be obtained at temperatures of 254 and 340 ℃, respectively, over Pd/γ-Al2O3-CeO2-La2O3 catalyst under an hourly space velocity of 50000 h-1.

Key words: CeO2-MOx solid solution, Pd/γ-Al2O3 catalyst, Catalytic methane combustion, XRD, Raman, XPS