CeO_2^-MO_x(M=La^(3+),Ca^(2+))改性Pd/γ-Al_2O_3催化甲烷燃烧性能(英文)  

Catalytic Combustion of Methane over CeO_2^-MO_x (M=La^(3+),Ca^(2+)) Solid Solution Promoted Pd/γ-Al_2O_3 Catalysts

作　　者：肖利华[1] 孙鲲鹏[2] 徐贤伦[2] 

机构地区：[1]浙江工业大学催化研究所,绿色化学合成技术国家重点实验室培育基地,杭州310032 [2]中国科学院兰州化学物理研究所,羰基合成与选择氧化国家重点实验室,兰州730000

出　　处：《物理化学学报》2008年第11期2108-2113,共6页Acta Physico-Chimica Sinica

摘　　要：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-Al2O3-CeO2-CaO在615cm-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0.5-0.6eV,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/γ-Al2O3催化剂,在空速为50000h-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℃.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.

关 键 词：CeO2-MOx固溶体 Pd/γ-Al2O3催化剂 甲烷催化燃烧 XRD RAMAN XPS 

分 类 号：O643.36[理学—物理化学]