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 Pdγ-Al2O3-CeO2-Mox catalysts. The formation of solid solution was confirmed by the change in lattice parameters of CeO2 and the shift of 20 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.%采用沉积-沉淀法制备了固溶体CeO2-MOx=(M=La3+,Ca2+)改性的Pd/γ-Al2O3催化剂,利用XRD、Raman和XPS对催化剂进行了表征.结果表明,金属(M)离子进入CeO2的晶格,形成CeO2-MOx固溶体,Raman谱上463cm-1处对应于Ce-O键的F2g对称伸缩振动强度降低.其中,样品Pd/γ-Al2O3CeO2-CaO在615 cm-1处出现一小峰,样品Pd/γ-Al2O3-CeO2-La2O3在320cm-1处出现的肩峰,都表明固溶体CeO2-MOx的形成使O2-亚晶格结构对称性降低.XPS分析表明,固溶体改性的Pd/γ-Al2O3催化剂中Pd的3d5/2结合能比正常价态的PdO的结合能高出0.5-0.6 eV,形成了一种高度离子化的.与载体具有强相互作用的Pd物种.催化甲烷燃烧实验证明,固溶体CeO2-MOx(M=La3+,Ca2+)改性的Pd/γ-Al2O3催化剂的低温活性和稳定性均高于未经改性的Pd/γ-Al2O3催化剂和仅用CeO2改性的Pd/γAl2O3催化剂,在空速为50000 h-1时,可使1%CH4-99%空气(体积分数)混合气中甲烷的10%转化温度降至254℃,转化率100%时的转化温度降至340℃.
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