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用浸渍法制备了一系列γ-Al2O3负载的Pt、Ir单金属及不同Pt/Ir比例的双金属催化剂,在辛可尼定修饰下用于对2-氧-4-苯基丁酸乙酯不对称加氢合成(R)-2-羟基-4-苯基丁酸乙酯反应.运用XRD、TEM、TPR、XPS、UV-Vis等表征手段,对催化剂的物化性质进行了研究,并对Pt、Ir金属表面辛可尼定手性诱导机理进行了初步探讨.结果表明,金属组分在催化剂上分散均匀,无团聚现象,平均粒径为3～4 nm;Pt-Ir/γ-Al2O3上Pt、Ir组分以单质形式存在;Ir作为低活性物种,在Pt/γ-Al2O3催化剂掺杂Ir组分遮盖和稀释了催化剂表面总体Pt活性位点数目,降低了Pt-Ir/γ-Al2O3催化剂加氢性能.辛可尼定在Pt、Ir表面的不同吸附行为(吸附方式、吸附强度、吸附构象)影响EOPB不对称加氢活性和对映选择性.
A series of γ-Al2O3 supported Pt, Ir monometallics and different Pt / Ir bimetallic catalysts were prepared by impregnation method. The catalysts were used for the synthesis of ethyl 2-oxo-4-phenylbutyrate Asymmetric hydrogenation of ethyl (R) -2-hydroxy-4-phenylbutyrate was carried out. The physico-chemical properties of the catalyst were studied by XRD, TEM, TPR, XPS and UV- The chiral induction mechanism of cinchonidine on Pt and Ir metal surfaces was discussed. The results showed that the metal components dispersed uniformly on the catalyst without agglomeration and the average particle size was 3 ~ 4 nm. The Pt-Ir / γ-Al2O3 Pt and Ir on the Pt / γ-Al2O3 catalyst were doped with Ir to cover and dilute the Pt active sites on the catalyst surface, reducing the Pt-Ir / γ- Al2O3 Hydrogenation Performances The different adsorption behaviors of cinchonidine on Pt and Ir surfaces (adsorption mode, adsorption strength and adsorption conformation) affect the asymmetric hydrogenation activity and enantioselectivity of EOPB.