中文摘要：

使用胶体沉积法制备了具有不同钯粒径、不同氧化物载体的负载型钯催化剂,系统地研究了α,β-不饱和酸的多相不对称氢化反应中的钯粒径和载体效应.结果表明钯粒径仅影响反应的活性而与对映体选择性无关.这是由于在较小的钯粒子上存在较多的边,角等区域,而这些区域具有较高的双键加氢活性,因而在较小的粒子上具有较高的氢化反应速率但是粒径的变化并没有改变手性修饰剂与反应中间体的吸附模式.载体的酸性对反应的活性和对映体选择性都有促进作用,说明酸性载体有利于反应中间体的吸附.

英文摘要：

Effects of Pd particle size and support acidity on enantioselective hydrogenation of a,fl-unsaturated carboxylic acids were systematically studied using Pd nanoparticles with different size immobilized on various oxides. Small Pd parti- cles showed higher activity in the hydrogenation of （E）-2-methyl-2-pentenoic acid due to the larger fraction of edge sites which were more active in olefin hydrogenation; but they did not change the reaction mechanism and/or the adsorption mode of reaction intermediates. Similar correlations in the hydrogenation of （E）-2-methyl-2-butenoic acid and 2-acetamidoacrylic acid further confirmed that the size of Pd particles only mediated the activity but did not alter the enantioselectivity. On the other hand, the activity and the enantioselectivity were strongly dependent on the acidity of the support. The TOF and the ee value followed the order TiO2 〉 y-A1203 〉 SiO2 〉 CeO2, suggesting that the acidic support favored the adsorption of the reac- tion intermediates.