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研究了一种可循环并且环境友好的催化体系:[π-C_5H_5N(CH_2)_(15)CH_3]_3[PMoW_3O_(24)] /过氧化氢/乙酸乙酯/烯烃.此体系不仅可以催化烯烃的环氧化反应,而且避免了对含氯溶剂的使用.反应在过氧化氢/乙酸乙酯的两相体系中进行,可以将多种烯烃转化为相应的环氧化物,且产率较高.此催化剂具有反应控制相转移的特征,反应结束后可以回收再利用.采用Raman, IR,31P MAS NMR和31P NMR等手段对新鲜及重复使用过的催化剂进行表征.结果表明:新鲜催化剂[π-C5H5N(CH2)15CH3]3[PMoW3O24]是一种混合物,含有多种过氧磷钼钨酸盐,如{PO4[MoO(O2)2]4}3 -, [(PO4){Mo3WO20}]3 -, [(PO4){Mo2W2O20}]3 -,[ (PO4){MoW3O20}]3 -和{PO4[WO(O2)2]4}3 -.当过氧化氢被完全消耗后,这些小的活性物种就会聚合成具有混合多原子的Keggin型杂多阴离子,形成M-Ob-M (M =W或Mo)和M-Oc-M键.
A new type of catalytic system that can be recycled and environment-friendly has been studied: [π-C_5H_5N (CH_2) _ (15) CH_3] _3 [PMoW_3O_ (24)] / hydrogen peroxide / ethyl acetate / , And avoids the use of chlorinated solvents.The reaction is carried out in a two-phase system of hydrogen peroxide / ethyl acetate to convert a number of olefins to the corresponding epoxies with high yields The catalyst has the characteristics of reaction controlled phase transfer and can be recycled after the reaction is finished.The fresh and reused catalysts were characterized by means of Raman, IR, 31P MAS NMR and 31P NMR.The results showed that the catalyst [π (PO4) {Mo3WO20}] is a mixture containing a variety of peroxophosphomolybdenum tungstates such as {PO4 [MoO (O2) 2] 4} 3- 3 -, [(PO4) {Mo2W2O20}] 3 -, [(PO4) {MoW3O20}] 3- and {PO4 [WO (O2) 2] 4} 3-. When hydrogen peroxide is completely consumed, these small Of active species will polymerize into Keggin-type heteropolyanions with mixed polyatoms, forming M-Ob-M (M = W or Mo) and M-Oc-M bonds.