Styrene oxidation by manganese Schiff base complexes in zeolite structures
Styrene oxidation by manganese Schiff base complexes in zeolite structures
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DOI：
10.1016/j.molcata.2006.05.070
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发表时间：
2006-10
影响因子：
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通讯作者：
M. A. D. Silva;C. Freire;B. Castro;J. Figueiredo
中科院分区：
文献类型：
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作者：
M. A. D. Silva;C. Freire;B. Castro;J. Figueiredo
以叔丁基过氧化氢为氧源，以锰（III） salen配合物为催化剂，在均相介质中包封在NaX和NaY沸石中，研究了苯乙烯的氧化反应。苯乙烯氧化生成苯甲醛、苯乙烯氧化物和苯乙醛，并含有少量苯基-1,2-乙烷二醇；还观察到一些聚合物的形成。在均相介质中，两种具有甲氧基功能化配体的配合物在环氧苯乙烯和苯甲醛中表现出相似的苯乙烯转化率和化学选择性。固定化后，[Mn(3-MeOsalen)]@X在60℃常压下表现出最高的催化活性，在环氧苯乙烯和苯甲醛中具有最高的化学选择性。在催化反应过程中没有观察到包封的金属配合物的浸出，氮吸附分析和SEM显微照片提供了金属配合物在沸石笼内而不是在其外表面上的包裹的支持。采用最活跃的非均相催化剂[Mn(3-MeOsalen)]@X考察了反应机理，研究了底物、催化剂浓度和温度等不同反应参数对烯烃转化率和环氧苯乙烯收率的影响。此外，用电子能谱法对[Mn(3-MeOsalen)CH3COO]催化苯乙烯的均相氧化进行了监测，结果表明，自由基机制涉及过氧化物锰作为催化剂的活性中间体。
Styrene oxidation was investigated using manganese(III) salen complexes as catalysts in homogeneous media and encapsulated in NaX and NaY zeolites using tert-butylhydroperoxide as the oxygen source. The oxidation of styrene led to formation of benzaldehyde, styrene oxide and phenylacetaldehyde, with minor amounts of phenyl-1,2-ethane-diol; some polymer formation was also observed. In homogeneous media, both complexes with ligands functionalized with methoxyl groups showed similar styrene conversions and chemoselectivities in styrene epoxide and benzaldehyde. Upon immobilization, [Mn(3-MeOsalen)]@X showed the highest catalytic activity at 60°C and atmospheric pressure, and the highest chemoselectivities in styrene epoxide and benzaldehyde. No leaching of the encapsulated metal complexes was observed during the catalytic reactions and support for the entrapment of metal complexes inside the zeolite cages and not on their external surfaces was provided by nitrogen adsorption analyses and SEM micrographs. The reaction mechanism was investigated using the most active heterogeneous catalyst, [Mn(3-MeOsalen)]@X, and the influence of various reaction parameters, such as substrate, catalyst concentration and temperature, on alkene conversion and styrene epoxide yield have been studied. Furthermore, the homogeneous oxidation of styrene using [Mn(3-MeOsalen)CH3COO] was monitored by electronic spectroscopy, the results suggesting a free radical mechanism involving a peroxomanganese species as the catalyst active intermediate.