Preparation Of Cellulose-based Salen Complex And Study On Catalytic Epoxidation Of ?-Pinene

Natural olefin alpha-pinene,one of the main components in turpentine,can be applied to the synthesis of pinene oxide.The epoxy compounds are significant synthetic intermediate materials used in the preparation of spices and pharmaceuticals.Compared to other catalytic systems,homogeneous Salen complex,which are not sensitive to moisture and air,exhibits excellent catalytic activity and enantioselectivity for the epoxidation of many natural olefins.However,reusability is still the major problem among the developed catalysts.From the perspective of industrialization,homogeneous catalysts are not ideal and economic catalysts.In contrast,the immobilization of homogeneous catalysts endows the catalysts with attractive features,such as allowing the catalysts can be recycled,the reaction products separation easily,what is more,heterogeneous catalysts can meet the requirements of continuous production of industrialization.Therefore,the most effective method is immobilizing the salen complex on various solid supports.Inorganic carrier,organic synthetic polymer,natural polymer are three kinds of carriers.Compared with other carriers,natural polymer materials with cheap,environmentally friendly,biodegrade,has been widely used in the catalyst load.In this research,two novel heterogeneous cellulose-based Salen catalysts were synthesized by simple modification and characterization of natural polymeric cellulose,and were used to catalyze the epoxidation of?-pinene.The main research is as follows:1.Ethylenediamine cellulose was prepared through the reaction of chloro and amine,and the dialdehyde cellulose was prepared by oxidation.The two functional celluloses were characterized by means of FT-IR,Elemental analyze and scanning electron microscope?SEM?.Research shows that two kinds of functional cellulose were prepared successfully.Moreover,through single factor investigation,the optimal reaction conditions of ethylenediamine cellulose were obtained.2.The homogeneous Salen catalyst and two cellulose-based Salen catalysts were prepared respectively.The three catalysts were characterized by FT-IR,X-ray photoelectron spectroscopy?XPS?,inductively coupled plasma?ICP?,scanning electron microscopy?SEM?and simultaneous thermal analyzer?TGA?.The research shows that three kinds of Salen catalysts have been successfully sythesized.3.Three Salen type catalysts were applied to the epoxidation of?-pinene.The effects of oxygen source,reaction temperature,reaction time,active metal center,the amount of cocatalyst and the solvent on the epoxidation of?-pinene were investigated by single factor experiments on two cellulose-based Salen catalysts.The optimum reaction conditions are 3.6 mmol catalyst,8 mmol?-pinene,0.75 mol isobutyraldehyde,30 ml acetonitrile,reaction temperature 25°C,reaction time 3 h,O₂?flow rate 5 ml/min?and active metal center Mn.Under these conditions,the conversions are both above 99%,and the selectivities of epoxy pinane are over 83%.4.Emphasis was placed on the number of recycling of two cellulose-based Salen catalysts and the experiments were magnified 10 and 25 times.The results show that both of Salen catalysts have good stability,the number of repeated use of 6 times and 8times,respectively.After several cycles,Salen catalysts still have a high catalytic conversion and selectivity.After the experiment is enlarged,the catalytic effect remains stable,which provides a theoretical basis for industrialization in the future.5.Compares the reported literature about catalytic activity and number of cycles of the heterogeneous Salen catalyst,the heterogeneous catalysts in this study show that the two kinds of cellulose-based Salen catalyst in this study have good catalytic activity,while the high recycling rate.