Salen-Co And Sharpless-Ti Grafted On Nano-Silica And Core-shell Silica Surfaces

Enantioselective epoxidation of olefins is great important for synthesis of many chemical intermediates which enrich chiral carbon,such as chiral alcohols , chiral alcohol amines and chiral dialcohols.There are two general catalytic systems for enantioselective epoxidation of olefins,Sharpless Ti and Jacbensen Salen-Mn. The former system is fitted for allylic alcohols and the latter is effective for nonfunctional alkenes.In the thesis, inorganic-organic hybrid carriers which consist of nano-silica core and styrene and methyl acrylate copolymers shell (or styrene and vinyl acetate shell )were synthesised by suspension polymerization. The shell layer properties of the core-shell carriers could be adjusted by varying the ratio of two monomer.The results were as follows:(1)By means of chemically grafting method, Salen-Co complex has been successfully bond onto the surfaces of nano-silica and inorganic-organic hybrid carriers which consist of nano-silica core and styrene and methyl acrylate copolymers shell. The prepared catalysts were characterized by FT-IR, TG-DTA and TEM. The characterization results indicated that the shell layer properties of the core-shell carriers could be adjusted by varying the ratio of two monomer, the shell with the majority of poly-styrene was gradually transmitted to be characteristic of poly methyl acrylate with increasing methyl acrylate. In catalyzing the epoxidation of cyclohexene, the Co complexes grafted the core-shell carriers showed a higher catalytic activity than the nano-silica, this is mainly due to the former having a better affinity to the substrate than the latter. However, in catalyzing the epoxidation of E-stilbene, the reversed results were obtained. This is likely that the strong affinity between thecore-shell catalysts and E-stilbene is unfavorable of catalytic recycles.(2)Last chiral salen-Co complexes were grsfted the surfaces of nano-silica and inorganic-organic hybrid carriers which consist of nano-silica core and styrene and methyl acrylate copolymers shell on the basis of the second chapter of results. The prepared catalysts were characterized by FT-IR, TG-DTA and TEM. The epoxidation of E-stilbene was employed to check the catalytic performances of these catalysts.(3) Titantium tartrate complexes have been successfully grafted onto nano-silica surfaces and core-shell carriers surfaces which have nano-silica core and vinyl acetate copolymers shell by means of chemically bonding methods. The prepared catalysts were characterized by FT-IR, TG-DSC. The characterization results confirmed the organic-inorganic composite particles which consist of an inorganic core surrounded by a polymer shell were successfully synthesized by suspension polymerization and Ti tartrate complex was bonded to the surfaces of the carriers. The epoxidation of cyclohexene was employed to check the catalytic performances of these catalysts.The recovered catalysts can be recycled two times without significant loss of activity. These indicate that Salen-Mn complexes and Titantium tartrate complexes have been steadily bond to the carriers.