Direct room-temperature synthesis of methyl-functionalized Ti-MCM-41 nanoparticles and their catalytic performance in epoxidation
Direct room-temperature synthesis of methyl-functionalized Ti-MCM-41 nanoparticles and their catalytic performance in epoxidation
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DOI：
10.1016/j.jcat.2009.01.013
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发表时间：
2009-04-01
影响因子：
7.3
通讯作者：
Jacobs, Pierre A.
中科院分区：
文献类型：
--
作者：
Lin, Kaifeng;Pescarmona, Paolo P.;Jacobs, Pierre A.
以正硅酸乙酯和甲基烷氧基硅烷为原料，采用稀溶液法制备了粒径为80~160 nm的甲基功能化纳米颗粒(Me-Ti-MCM-41 NP)。表征结果表明，纳米粒子中存在有序的六方介孔结构和四面体的钛物种。在叔丁基过氧化氢和H_2O_2-Me水溶液环氧化环己烯的反应中，与普通粒径的Ti-MCM-41和未功能化的Ti-MCM-41纳米粒子相比，Ti-MCM-41纳米粒子对环己烯具有更高的转化率和初始反应速率。同时，在H_2O_2水溶液中，环己烯环氧化物有较高的选择性。结果表明，在Me-Ti-MCM-41NP催化剂上，环氧环己烷与水的水解度降低。从催化剂颗粒的纳米尺寸和表面甲基化两个方面讨论了Me-Ti-MCM-41NP的催化性能的改善。用叔丁基氢过氧化氢溶液通过洗涤和焙烧的方法对Me-Ti-MCM-41 NP进行再生。(C)2009 Elsevier Inc.保留所有权利。
Methyl-functionalized Ti-MCM-41 nanoparticles with a size of 80 to 160 nm (Me-Ti-MCM-41 NP) were directly prepared via a dilute solution route by the co-condensation of tetraethoxysilane and methylalkoxysilanes in sodium hydroxide medium at room temperature. The characterization results showed the existence of ordered hexagonal mesoporous structure and tetrahedral Ti species in the nanoparticles. In the epoxidation of cyclohexene with tert-butyl hydroperoxide and aqueous H2O2 Me, Ti-MCM-41 NP samples displayed higher turnover frequencies (TOFs) for cyclohexene and initial reaction rates compared to Ti-MCM-41 and methyl-functionalized Ti-MCM-41 with normal particle size and to non-functionalized Ti-MCM-41 nanoparticles. Simultaneously a higher selectivity for cyclohexene epoxide was observed in the case of aqueous H2O2. suggesting that the hydrolysis of cyclohexene epoxide with water is reduced on Me-Ti-MCM-41 NP samples. The improved catalytic behavior of Me-Ti-MCM-41 NP is discussed both in terms of the nanosize and methylation of the surface of the catalyst particles The. regeneration of Me-Ti-MCM-41 NP with tert-butyl hydroperoxide solution was evaluated via washing and calcination approaches. (C) 2009 Elsevier Inc. All rights reserved.