摘要
将PVP保护的铑纳米簇合物负载于钛硅分子筛上制得了负载型Rh/PVP TS 1催化剂 .以辛可尼定 (CD)作为手性诱导剂时 ,考察了预处理和修饰条件 ,如溶剂、温度、氢压、修饰气体及反应时间等因素对催化丙酮酸甲酯不对称加氢反应性能的影响 .以THF为溶剂 ,催化剂在 140℃和 5 0MPa的氢气中进行预处理 1h ,并在c(CD) =4 0mmol/L ,2 0℃和 5 0MPa的氢气中修饰 0 5h后 ,在 2 0℃和 7 0MPa的氢气中反应 1h ,丙酮酸甲酯的转化率和对映选择性分别为 40 8%和 39 9%.
This paper describes the effects of pretreatment and modification conditions of TS-1-supported rhodium nanocluster on the enantioselective hydrogenation of methyl pyruvate. The PVP-stabilized rhodium nanocluster was prepared using RhCl 3·3H 2O and PVP which were dissolved in a mixed solution of distilled water, ethanol and i-propanol ( V(H 2O)∶ V(EtOH)∶ V(i-PrOH)=1∶3∶6).The solution was refluxed at 90 ℃ for 3 h and then evaporated to dryness and redispersed in ethanol. The ethanol solution was stirred with the required amount of TS-1 at room temperature. After filtration, the TS-1-supported rhodium nanocluster was washed and dried. The cinchonidine, which is used as the chiral modification reagent, not only induces the enantioselectivity, but also accelerates greatly the hydrogenation. The reaction rate is accelerated about 13 times when the concentration of cinchonidine (CD) in the solution is about 4.0 mmol/L. Although the conversion of methyl pyruvate is high in the mixed solution of THF and i-propanol ( V(THF)/ V(i-PrOH)=1), the ee value is not high. THF is the excellent solvent for this reaction in order to obtain higher enantioselectivity. The optimum pretreatment conditions are p(H 2)=5.0 MPa, θ=140 ℃, t=1.0 h and the optimum modification conditions are p(H 2)=5.0 MPa, θ=20 ℃, t=30 min and c(CD)=4.0 mmol/L. The above-mentioned procedure is favorable for the stabilization of catalytic active species and the formation of chiral environment. The hydrogenation conversion of methyl pyruvate and ee value of the product can reach 40.8% and 39.9% under the reaction conditions of p(H 2)=7.0 MPa, θ=20 ℃ and t=1 h, respectively.
出处
《催化学报》
SCIE
EI
CAS
CSCD
北大核心
2003年第8期619-623,共5页
关键词
铑
纳米簇
辛可尼定
丙酮酸甲酯
不对称加氢
乳酸甲酯
rhodium, nanocluster, cinchonidine, methyl pyruvate, enantioselective hydrogenation, methyl lactate
