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)

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℃.

Effect of water vapor on the CO and CH_4 catalytic oxidation over CeO_2-MO_x (M=Cu, Mn, Fe, Co, and Ni) mixed oxide

CeO2-MOx (M=Cu, Mn, Fe, Co, and Ni) mixed oxide catalysts were prepared by a citric acid complexation-combustion method. CeO2-MOx solid solutions could be formed with M cations doping into CeO2 lattice, while NiO and Co3O4 phases were detected on the surface of CeO2-NiO and CeO2-Co3O4 by Raman spectroscopy. The presence of M in CeO2 could obviously promote its catalytic activity for CH4 catalytic combustion and CO oxidation. Among the prepared samples, CeO2-CuO exhibited the best performance for CO oxidatio...

CuO/CeO_2-MO_x(M=Co,Mn,Al和La)催化剂富氢条件下CO氧化性能的研究

研究了MOx(M=Co,Mn,Al和La)对CuO/CeO2催化剂富氢条件下CO选择性氧化性能的影响,并运用XRD,XPS,BET,TPR和TPD等手段对催化剂进行了表征。结果表明,MnOx和Co3O4的引入能提高CuO/CeO2催化剂富氢条件下CO选择性氧化的活性,其中以MnOx的改性效果最好,80℃时CO转化率达58%,140℃为100%。与其他CuO/CeO2-MOx催化剂相比,CuO/CeO2-MnOx催化剂中活性组分与载体的相互作用较强,铜原子外电子云密度升高,表面Cu和晶格氧含量较多,CO的吸附量较大。