MCM-41介孔分子筛固载Schiff碱钴配合物催化烯烃环氧化

Epoxidations of Alkenes Catalyzed by Cobalt Schiff Base Complex Immobilized on MCM-41 Molecular Sieves

以3-甲基氨丙基三甲氧基硅烷为偶联剂,采用多步接枝法将Schiff碱钴配合物Co(CBP-PHEN-Sal)共价键联到MCM-41介孔分子筛的表面,制备了固载催化剂Co(CBP-PHEN-Sal)-MCM-41。X射线衍射、傅里叶变换红外光谱、漫反射紫外-可见光谱、N2吸附-脱附表征结果显示,Co(CBP-PHEN-Sal)被成功地固载于MCM-41介孔分子筛的孔道中,且MCM-41介孔分子筛的结构特征保持不变。在异丁醛存在下,以分子氧为氧化剂,固载催化剂Co(CBP-PHEN-Sal)-MCM-41在环己烯的环氧化反应中较均相催化剂Co(CBP-PHEN-Sal)表现出更高的催化活性,且可重复使用。在Co(CBP-PHEN-Sal)-MCM-41催化剂用量25.0mg、乙腈10mL、环己烯5mmol、异丁醛10mmol、25℃、0.1MPa、5h的反应条件下,环己烯的转化率达78.3%,环氧化物的选择性达84.8%。

A cobalt Schiff base complex, Co （CBP-PHEN-Sal） was covalently bonded to silica surface of MCM-41 molecular sieve by multi-step grafting using（3-methylamino）propyltrimethoxysilane as coupling agent to immobilize the complex. The prepared immobilized Co（CBP-PHEN-Sal）-MCM-41 was used as catalyst in epoxidation of cyclohexene with molecular O2 as oxidant. The catalyst was characterized by means of XRD, FTIR, DR UV-Vis, N2 adsorption-desorption. The cobalt Schiff base complex was proved to be immobilized inside channels of MCM-41 molecular sieves. The textural characteristics of the support were kept intact after immobilization. The immobilized catalyst Co （ CBP- PHEN-Sal）-MCM-41 showed higher catalytic activity than homogeneous counterpart Co （CBP-PHEN- Sal） in epoxidation of cyclohexene. The immobilized catalyst could be reused four times without significant loss of activity. Under reaction conditions of 25. 0 mg Co （CBP-PHEN-Sal）-MCM-41 catalyst, 10 mL acetorlitrile, 5 mmol cyclohexene, in presence of 10 mmol isobutylaldehyde, 25℃, 0.1 MPa and 5 h, conversion of cyclohexene was 78.3% and selectivity to epoxide was 84.8%.