| Chiral amino alcohols are very important organic small molecule compounds and excellent organic synthesis catalysts,which have been widely applied in pharmaceutical synthesis,fine chemicals and,chiral resolution of racemic mixtures,etc.Therefore,the synthesis of chiral amino alcohols with high optically activity has extremely important meanings.In this thesis,a series of L-phenylalanine esters with different ester group substituents(or protection of amino group)were used as the reaction substrates,to study the adaptability or versatility of the Cu/ZnO/Al2O3 catalyst for their hydrogenation to chiral L-phenylalaninol,and the DFT calculation was used to further clarify the reaction mechanism over the Cu/ZnO/Al2O3 catalyst for this title reaction.In addition,the alumina support was pretreated in the acid or base solution and at higher temperature,to investigate the effects of the acid-base properties and textural properties of Al2O3 on the catalytic performance of the catalyst.The main results obtained are described as follows.1.A series of L-phenylalanine esters with different ester group substituents(or protection of amino group)were used as the substrates for their catalytic hydrogenation over the CuZn0.3Mg0.1 AlOx catalyst.The results show that the presence of amino group at the a-position of the carboxy group in a-amino acid esters is essential for this catalytic hydrogenation,and the catalytic activity of this Cu/ZnO/Al2O3 catalyst is correlated with the electron-donor properties and geometrical restrictions of the ester group substituents of substrates.2.The DFT theoretical calculation was employed to study the adsorption configuration and adsorption sites of substrate adsorbed on the catalyst surface,and speculate the possible reaction mechanism and reaction intermediates.The results show that the substrate adsorbed on the active sites of the catalyst surface mainly by two functional groups:the amino group(-NH2)absorbed on the Al2O3,and the carbonyl group(C=O)oxygen and alkoxy group(RO-)oxygen absorbed on the boundary of Cu and γ-Al2O3(100)facet.This catalytic hydrogenation undergoes the formation of a hemiacetal intermediate,the cleavage of the C-O bond by reacting with dissociated H to directly attain an aldehyde ad-species and methoxy ad-species,and the aldehyde ad-species is instantly hydrogenated to the desired amino alcohols.3.After Al2O3 was treated in different acid or base solutions,its effect on the catalytic activity of Cu-ZnO/Al2O3 catalyst was investigated.The results show that,Cu-ZnO spported oin Al2O3 treated in H3PO4 solution showed the lowest activity,and the catalyst on Al2O3 treated in NH3 H2O showed better activity.After Al2O3 support was hydrothermally treated in 3 wt%of NH3 H2O solution at 200 0C,the Cu-ZnO/Al2O3 catalyst showed the best activity.The catalytic activity of Cu-ZnO/Al2O3 catalyst is related not only to SCu but also to other factors,such as the reducibility of CuO species and the surface acidity of catalyst.The Cu-ZnO/Al2O3 catalyst for L-phenylalaninol synthesis with higher SCu,easily reducible CuO species,proper number of acidity sites,lower density of acidity sites and higher proportion of weak acidity sites were responsible for its high activity.4.The effect of the calcination temperature of Al2O3 and Al2O3 from different factories on the catalytic performance of the Cu-ZnO/Al2O3 catalyst for the title reaction was investagted.The results show that,the Cu-ZnO/Al2O3 catalyst prepared with Al2O3 calcined at 450 ℃show best activity,and with the increase in the calcination temperature of Al2O3,the activity of corresponding catalyst decreased,due to the decrease in the specific surface area of Al2O3 and the crystalline phase of Al2O3 transformed.There is difference in the catalytic activity between the Cu-ZrnO/Al2O3 catalysts prepared with Al2O3 from different factories,among them,the catalyst prepated with Al2O3 support provided by Wenzhou alumina Co.Ltd.showed the best activity. |
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