Asymmetric Hydrogenation of Ethyl Pyruvate on Chirally Modified Pt Catalysts Supported on Al2O3@FDU-14 Mesoporous Composites

Abstract

A series of Al 2 O 3 @FDU-14 composites with different alumina loadings were prepared using a solid state grinding method. The 4% Pt catalysts supported on Al 2 O 3 @FDU-14 were prepared by impregnation using H 2 PtCl 6 . X-ray diffraction, transmission electron microscopy, and nitrogen adsorption characterization of the Pt/Al 2 O 3 @FDU-14 catalysts indicated that the mesoporous features of the FDU-14 mesopolymer were retained. The Pt/Al 2 O 3 @FDU-14 catalysts were used in the asymmetric hydrogenation of ethyl pyruvate after they were chirally modified with cinchonidine. For Al 2 O 3 loading from 5% to 15%, Al 2 O 3 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/Al 2 O 3 @FDU-14 catalysts. As compared with chirally modified Pt/FDU-14 catalysts, chirally modified Pt/Al 2 O 3 @FDU-14 catalysts gave higher ee values. 以碳包铁纳米晶 (Fe@C) 为载体, 采用浸渍法制备了一种磁可分离的 Pd/Fe@C 催化剂, 并运用 X 射线荧光光谱、透射电镜、X 射线衍射和 X 射线光电子能谱对催化剂进行了表征. 结果表明, 纳米 Pd 颗粒的粒径分布在 4∼10 nm, 平均粒径约为 7 nm, Pd 物种以 Pd 0 为主, 其 Pd 3 d 5/2 结合能为 335.6 eV. 将该催化剂应用于苯甲醇选择性氧化反应, 考察了催化剂用量、溶剂、温度对反应的影响以及催化剂的循环使用性能. 结果表明, 催化剂可使苯甲醇高选择性生成苯甲醛, 在催化剂用量 (摩尔分数) 为 0.5%、乙腈为溶剂、80 o C 常压 O 2 条件下, 苯甲醇的氧化反应效果最佳 (苯甲醇转化率为 96%, 苯甲醛选择性为 95%). 催化剂易于磁分离和回收, 循环使用 4 次仍保持较佳的催化性能. Cinchonidine modified Pt/Al2O3@FDU-14 gave a higher ee value than a Pt/FDU-14 catalyst for the chiral hydrogenation of ethyl pyruvate, which was due to cinchonidine adsorption on the alumina coating.