关键词: 甲烷催化氧化, 铈锆钇固溶体, 负载型Ag₂O催化剂, 滞后回线, 虫孔状介孔材料

Abstract: Highly-specific-surface-area wormhole-like mesoporous Ce_0.6Zr_0.35Y_0.05O₂(CZY) solid solution nanoparticles with a cubic crystal structure were synthesized by using a modified co-precipitation strategy with hexadecyltrimethyl ammonium bromide as the template, and the CZY-loaded 0.2%—2.0% Ag₂O catalysts were prepared with the incipient wetness impregnation method. The physicochemical properties of these materials were characterized with XRD, HRSEM, HRTEM/SAED, H₂-TPR and XPS techniques. We also examined the catalytic performance of the Ag₂O/CZY catalysts for the total oxidation of methane. It is found that among the x% Ag₂O/CZY(x=0.2—2.0) catalysts, the one at x=2.0 showed the best catalytic activity: under the conditions of n(CH₄)/n(O₂)=1:4, space velocity=50000 h^-1 and reaction temperature=600 ℃, methane could be oxidized completely to carbon dioxide and water, furthermore over this catalyst the hysteresis pheno-menon of methane conversion versus temperature during the processes of temperature rise and drop was basically eliminated. On the basis of the above results, we concluded that the good catalytic performance of Ag₂O/CZY is associated with the formation of three-dimensional wormhole-like mesoporous structure, larger specific surface area, stronger oxygen storage and release ability, and the stabilization of active phase Ag₂O by CZY.

Key words: Catalytic methane oxidation, Ceria-zirconia-yttia solid solution, Supported silver oxide catalyst, Hysteresis curve, Wormhole-like mesoporous materials