Design Of Novel Metal Catalyst And Kinetic Kinetic Resolution Of α - Phenylethylamine By Its Binding Enzyme

The resolution of chiral compounds is a challenging and significant research task. Dynamic kinetic resolution (DKR), combining the racemization of chiral compounds and the kinetic resolution of enantiomers, makes the theoretical yield could reach100%, which accords with the concept of "Green Chemistry". The commercial lipase we used possesses high activity for the kinetic resolution of a-phenylethylamine; therefore, the present research focuses on both the preparation of racemization catalyst and the combination with lipase for the DKR of a-phenylethylamine. MOF materials are favored by the scientists since it was developed owing to its super-large specific surface area. Among them, the MIL-101was often used as an excellent catalyst support because of the super-large specific surface area, large pore size, as well as good hydrothermal stability.In this thesis, we developed a series of Pd-based catalysts and investigated their catalytic properties by using the DKR of a-phenylethylamine as a probe reaction. The relationship of the catalytic activity to the structure was established. According to this theme, our work had been carried out as follows in the text:(1) The Pd/MIL-101was prepared by impregnation method. Its activity was studied when used in DKR of a-phenylethylamine. Thanks to the super-large specific surface area of the MIL-101, the Pd loaded over the MIL-101was highly dispersed, resulting in higher activity in the DKR of a-phenylethylamine relative to other reference Pd catalysts. Due to the presence of Lewis acid sites in the framework of MIL-101, the Pd/MIL-101could not achieve a high selectivity during the DKR process. To resolve this problem, we added Na2CO3into the DKR system. This could improve the selectivity to80%without any decrease in the conversion.(2) In order to further increase the selectivity, we tried to change the surface acidity of the support through grafting amino group in the frameworks of MIL-101to produce the NH2-MIL-101. The amino group in the MIL-101can not only reduce the surface content of Lewis acid sites, but also improve the disperse degree of the Pd nanoparticles. The experiments showed that Pd/NH2-MIL-101can obviously increase the selectivity for the DKR of a-phenylethylamine in compared with Pd/MIL-101and inhibit the formation of the by-product. Moreover, the Pd/NH2-MIL-101can reduce the reaction time from24h to18h owing to its high activity. Recycling test revealed that the as-prepared Pd/NH2-MIL-101can be used repetitively for7times, indicating good stability.(3) Pd-Ni nanoparticles was prepared by co-reduction of Pd(acac)2and Ni(acac)2. It was found that the synergistic effect of Pd and Ni caused a higher activity than single Pd in the racemization of a-phenylethylamine. But, the activity of the Pd-Ni catalyst in DKR reaction reduced because of the deactivation of the lipase when contacting with Ni. To tackle this problem, a core-shell Pd-Ni@SiCO2catalyst (Pd-Ni nanoparticles encapsuled by porous silica) was prepared. Using this catalyst, the reactants can pass freely through the porous shell; meawhile, the Pd-Ni core can be prevented from contacting with lipase. The comparison of the performances of bimetallic catalyst with that of the mechanical mixing displayed the observed promotional effect of the synergistic effect of Pd and Ni.