三维有序大孔H3PW12O40-SiO2功能材料的制备、表征及催化性能研究

以杂多酸 H₃PW₁₂O₄₀ (PW₁₂)与正硅酸乙酯(TEOS)混合溶胶, 采用胶晶模板法结合煅烧去除模板工艺, 成功地制备了PW₁₂/SiO₂物质的量比在1/10～1/40之间的三维有序大孔(3DOM) PW₁₂-SiO₂催化剂. 经SEM, N₂吸附, XRD和FTIR等研究表明, PW₁₂含量较低的样品, 大孔结构三维规整性十分好. 在410 ℃氧化分解胶晶的条件下, PW₁₂基本保持一级Keggin结构. PW₁₂在样品中以分子簇或微晶存在, 其大小随含量增加而增大. PW₁₂高含量时, 其含氧键的FTIR振动与纯PW₁₂的基本一致, 但低含量时含氧键振动有一定偏移, 显示PW₁₂/SiO₂相互作用较显著. 样品酸性随杂多酸含量增加而增加, 但PW₁₂/SiO₂物质的量比超过1/30时酸性便减小, 呈火山型曲线变化规律. 对1-十二烯烷基化反应的催化活性随PW₁₂/SiO₂物质的量比的变化与酸性变化有相同的规律. 但所有样品的催化反应活性均远高于纯PW₁₂, 并且有良好的重复使用性能, 使用4次后仍保持新鲜催化剂活性的78%.

Preparation, Characterization and Catalytic Activity of Three-dimensionally Ordered Macroporous H3PW12O40-SiO2 Functionalized Materials

By templation via in-situ sol-gel transformation, with calcination (410 ℃) to remove the colloidal crystals, three-dimensionally ordered macroporous (3DOM) H₃PW₁₂O₄₀ (PW₁₂)-SiO₂ functional-ized materials with different PW₁₂/SiO₂ molar ratios in a range of 1/10～1/40 were prepared. The nature of the functionalized materials has been characterized by SEM, N₂ adsorption, XRD and FTIR techniques. The results revealed that the macropores were ar-rayed highly periodically and connected with one another by small windows. The walls of the macropores were of microporous configuration. H₃PW₁₂O₄₀ was chemically combined with the support and still maintained its primary Keggin structure. The acidity of the materials showed a change with a volcano curve as PW₁₂ loading increased. High catalytic activity could be found with the samples for the alkylation of benzene with 1-dodecene, and their catalytic activity also demonstrated a similar change to the acidity. A significant recyclability could also be observed with the catalyst: having been reused for 4 times, it retained 78% reactivity compared with the fresh one.