介孔氧化铝复合材料负载铂催化剂上丙酮酸乙酯的不对称氢化反应

Asymmetric Hydrogenation of Ethyl Pyruvate on Chirally Modified Pt Catalysts Supported on Al_2O_3@FDU-14 Mesoporous Composites

采用固相研磨法制备了有序介孔树脂FDU-14孔道限阈分散的Al2O3复合材料Al2O3@FDU-14.以其为载体,采用浸渍法制备了4.0%Pt/Al2O3@FDU-14催化剂,并利用X射线衍射、透射电子显微镜和N2吸附等手段对催化剂进行了表征.结果表明,Pt/Al2O3@FDU-14催化剂保持了FDU-14的介孔结构特征.经手性分子辛可尼定修饰后,考察了该催化剂在丙酮酸乙酯不对称氢化反应中的催化性能.当复合材料载体中Al2O3含量为5%~15%时,Al2O3主要以无定形态均匀分布于FDU-14孔道内.随着催化剂中Al2O3含量增加,丙酮酸乙酯不对称氢化反应的活性和产物的光学选择性都有所提高,其中后者最高可达80%ee.Al2O3的引入可降低FDU-14介孔树脂材料表面的电子密度,有利于辛可尼定在催化剂表面的吸附,因此,Pt/Al2O3@FDU-14催化剂手性诱导能力比Pt/FDU-14强.

A series of Al2O3@FDU-14 composites with different alumina loadings were prepared using a solid state grinding method. The 4% Pt catalysts supported on Al2O3@FDU-14 were prepared by impregnation using H2PtCl6. X-ray diffraction, transmission electron microscopy, and nitrogen adsorption characterization of the Pt/Al2O3@FDU-14 catalysts indicated that the mesoporous features of the FDU-14 mesopolymer were retained. The Pt/Al2O3@FDU-14 catalysts were used in the asymmetric hydrogenation of ethyl pyruvate after they were chirally modified with cinchonidine. For Al2O3 loading from 5% to 15%, Al2O3 was uniformly dispersed inside the mesoporous channels of FDU-14 host. Ethyl pyruvate conversion and their ee values increased with increasing alumina loading, with a highest ee value of 80%. It was suggested that the alumina coating inside the mesoporous channels of FDU-14 decreased the surface electronic density of the FDU-14 mesopolymer so that cinchonidine can be easily adsorbed on the surface of Pt/Al2O3@FDU-14 catalysts. As compared with chirally modified Pt/FDU-14 catalysts, chirally modified Pt/Al2O3@FDU-14 catalysts gave higher ee values.