Effects of oxidant and solvent on the liquid-phase cyclohexane oxidation catalyzed by Ce-exchanged zeolite Y
Effects of oxidant and solvent on the liquid-phase cyclohexane oxidation catalyzed by Ce-exchanged zeolite Y
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DOI：
10.1016/s0926-860x(00)00496-8
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发表时间：
2000-10-16
影响因子：
5.5
通讯作者：
Schuchardt, U
中科院分区：
文献类型：
--
作者：
Pires, EL;Magalhaes, JC;Schuchardt, U
以Ce（III）交换的Y型分子筛（Si：Al=12.5）为催化剂，叔丁基过氧化氢（I-BHP）和过氧化氢（H2 O2）为氧原子供体，在温和条件下（T=343 K，24 h）研究了几种溶剂对环己烷氧化制环己醇和环己酮的影响。结果表明，环己烷转化率的高低顺序为：无溶剂> 1，2-二氯乙烷>二氯甲烷>丙酮>乙腈>吡啶。使用t-BHP作为氧化剂，观察到正己醛形成为副产物，并且当使用具有更碱性特征的溶剂（例如乙腈和吡啶）时，选择性增加。以H_2O_2为氧化剂的反应选择性高，主要产物为环己醇，但转化率低。浸出实验表明，均相Ce ~（3+）对催化剂的活性没有影响。然而，该催化剂在回收实验中失活，可能是由于羧酸的形成，其阻塞孔入口和/或络合到活性位点。(C)2000 Elsevier Science B. V.保留所有权利。
The effect of several solvents on the cyclohexane oxidation to cyclohexanol and cyclohexanone under mild conditions (T=343 K, 24h) using zeolite Y (Si:Al=12.5) exchanged with Ce(III) as catalyst, and tert-butyl-hydroperoxide (I-BHP) and hydrogen peroxide (H2O2) as oxygen atom donors was studied. The results show that higher cyclohexane conversions are obtained in the following order: no solvent>1,2-dichloroethane>dichloromethane>acetone>acetonitrile>pyridine. Using t-BHP as oxidant, n-hexanal formation is observed as by-product and the selectivity increases when solvents with more basic characteristics (e.g. acetonitrile and pyridine) are used. Reactions with H2O2 as oxidant are highly selective yielding cyclohexanol as the major product, however, the conversion is low. Leaching experiments show that homogeneous Ce3+ is not responsible for the catalytic activity. However, the catalyst is deactivated in recycling experiments, probably due to the formation of carboxylic acids, which block the pore entrances and/or complex to the active sites. (C) 2000 Elsevier Science B.V. All rights reserved.