奎宁修饰型Pt/Al_2O_3催化丙酮酸乙酯的不对称加氢反应

在常压下以乙酸为溶剂,采用奎宁修饰型Pt/Al2O3为加氢催化剂,考察了修饰剂浓度及氢化温度对丙酮酸乙酯不对称加氢反应对映选择性和反应速率的影响,并于优化条件下研究了修饰型催化剂的稳定性、循环使用及再生。结果表明:修饰剂浓度有一适宜值,低温有利于不对称加氢反应;反应体系中底物丙酮酸乙酯的存在对修饰剂奎宁的深度加氢具有抑制作用;催化剂的一次再生使催化反应的不对称性增强,经二次再生后则降低产物的对映选择性。

Asymmetric Hydrogenation of Ethyl Pyruvate over Quinine Modified Pt/Al_2O_3 Catalyst

Under atmospheric pressure, the effects of the quinine concentration and hydrogenation temperature on the enantioselectivity and reaction rate were investigated in the asymmetric hydrogenation of ethyl pyruvate over quinine modified Pt/Al_2O_3 catalyst in acetic acid.The stability of the quinine modified Pt/Al_2O_3 catalyst and its reuse and regeneration were studied under the optimized conditions.The results show that there is an appropriate value for modifier concentration; low temperature is beneficial to the asymmetric reaction; the existence of ethyl pyruvate in reaction system can inhibit the further hydrogenation of modifier quinine.The enantioselectivity of product can increase using the Pt/Al_2O_3 catalyst regenerated first but decrease using the catalyst regenerated secondly.