【摘要】 采用奎宁修饰的Pt/Al2O3为催化剂,研究了在常压下,乙酸溶剂中丙酮酸乙酯的不对称加氢反应.考察了奎宁修饰剂浓度、反应温度、预修饰时间、底物起始浓度及氧的加入对丙酮酸乙酯不对称氢化反应初始过渡期(ITP)特征的影响.结果表明,在不对称氢化反应的初期,存在对映选择性随底物转化率的增加而不断升高的现象(即ITP现象),反应条件的变化能不同程度地改变ITP特征,在奎宁修饰催化剂时加入O2能明显提高催化剂对产物的对映选择性,改善ITP现象.ITP特征取决于反应起始阶段反应体系中各组分在催化剂表面的相互作用及达到平衡的速度,其实质是手性修饰型催化剂表面的重排过程.更多还原

【Abstract】 The asymmetric hydrogenation of ethyl pyruvate over the Pt/Al2O3 catalyst modified by quinine was studied under atmospheric pressure in acetic acid.The effects of quinine modifier concentration,reaction temperature,pre-modification time,initial substrate concentra-tion,and O2 addition on the character of the initial transient period(ITP) of reaction were investigated.The results showed that the enanti-oselectivity of product gradually increases with the increase of the reactant conversion in the ITP of hydrogenation reaction,which is entitled as an ITP phenomenon.The reaction conditions would affect the character of ITP.Adding O2 during the modification of the catalyst by qui-nine can significantly increase the enantioselectivity of product and improve the ITP phenomenon.The character of ITP depends on the in-teractions among various components on the surface of catalyst and the speed to achieve equilibration at the beginning of reaction,and its essence is a restructuring process for the chiral surface of modified catalyst.更多还原