三维虫孔状介孔纳米粒子Ag2O/Ce0.6Zr0.35Y0.05O2的制备、表征及其对甲烷氧化反应的催化性能

以十六烷基三甲基溴化铵(CTAB)为模板剂, 采用改进的共沉淀法合成了高比表面积的虫孔状介孔Ce0.6Zr0.35Y0.05O2(CZY)立方晶相结构的纳米粒子, 用浸渍法制备了Ag2O质量分数为0.2%—4.0%的Ag2O/CZY催化剂, 以XRD, HRSEM, HRTEM/SAED, H2-TPR和XPS等表征手段测定了CZY 和Ag2O/CZY催化剂的物化性质, 考察了其对甲烷氧化反应的催化性能. 结果表明, 质量分数为2.0%的Ag2O/CZY催化剂在空速为50000 h-1、甲烷/氧气摩尔比为1:4和反应温度为600 ℃的条件下, 可使甲烷完全氧化成CO2和H2O, 且基本上消除了在升温、降温过程中甲烷转化率随温度变化的“滞后回线”现象. 可见, Ag2O/CZY的优良催化性能与CZY具有发达的三维虫孔状介孔结构、较大的比表面积、较强的储释氧能力及其稳定活性相Ag2O等因素有关.

Synthesis, Characterization and Catalytic Properties of Three-dimensional Wormhole-like Mesoporous Ag2O/Ce0.6Zr0.35Y0.05O2 Nanoparticles in Methane Oxidation

Highly-specific-surface-area wormhole-like mesoporous Ce0.6Zr0.35Y0.05O2(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.