Investigation On The Synthesis Of Cyclic Carbonates From Olefins

CO₂ is the main greenhouse gas,but also cheap and abundant C1 resources.The synthesis of cyclic carbonates with CO₂ as raw material is a green and economical route.The catalyst of high activity and environmental friendly is the focus of this field.In this thesis,we studied the synthesis of cyclic carbonates using olefins as the starting materials,under the combined action of oxidant and CO₂.The main idea was to design efficient catalysts system and use green oxidant,to achieve the conversion under mild conditions.In this process,epoxide and halohydrin can both act as the main intermediate;however,the latter consumes equivalents of halogenated reagents and generates waste salt.So we mainly studied the green routes with epoxide as the intermediate.The main contents are as followed.?1?Novel schiff base complexes were synthesized and used as catalysts of cyclic carbonates.Ni,Fe and Cu complexes of salicylaldehyde-glycine?Sal-Gly?schiff base ligands were synthesized through a simple method.Sal-Gly-Ni and Sal-Gly-Fe?Cl?can promote the direct synthesis of styrene carbonate from styrene tert-butyl hydroperoxide?TBHP?and atmospheric CO₂.The operations of"one-pot,two-step"and"one-pot,one step"were both suitable and the highest yield of styrene carbonate was 78%.5-Chlorosalicylaldehyde-glycine copper?BIT-C?has a three-dimensional structure with hexagonal poles,which can catalyze a variety of epoxides and CO₂ to synthesize cyclic carbonates?84⁹9%yields?at atmospheric pressure and near room temperature?35⁶0oC?.BIT-C has a wide range of applicability to halogen-containing co-catalysts.In addition,using BIT-C to capture and converse CO₂ from air directly is also feasible.It was observed that BIT-C could be dissociated under the effect of co-catalyst and generated copper-containing fragments with different degree of polymerization.Kinetic studies and DFT calculations showed that?CuL?₂ was the truly catalytically active species,of which a single Cu center involved in the activation of CO₂ molecule and epoxide molecule synchronously.?2?A method for the synthesis of cyclic carbonates catalyzed by commercial organic moleculeswasdeveloped.UsingH₂O₂asthegreenoxidantand2,2,2-trifluoroacetophenone as the catalyst,a variety of olefins converted to epoxides at room temperature with high selectivity.This reaction was a phase-transfer oxidation between organic phase and the aqueous phase,and the epoxides could further convert to cyclic carbonates through removing the aqueous phase and adding CO₂ and the co-catalyst Bu₄NBr.The highest yield of 1-hexene carbonate was up to 91%.It was found that nucleophilesstronglyinhibitedtheepoxidationofolefinscatalyzedby2,2,2-trifluoroacetophenone,includingthesubstituentsofolefinsandthe halogen-containing co-catalyst..So the synthesis strategy of“one-pot,two-step”was used to achieve the optimal conversion efficiency.?3?The process of continuous synthesis of cyclic carbonate in fixed bed-slurry reactor was developed.The microporous titanosilicate molecular sieve?TS-1?was used as olefin epoxidation catalyst and the metal organic framework Cr-MIL-101 was used as CO₂cycloaddition catalyst,to synthesize cyclic carbonates from olefin-H₂O₂-CO₂.Firstly,the continuous flow of olefin and H₂O₂ passed through TS-1 in fixed-bed reactor at the appropriate space velocity and obtained a solution containing epoxides.After drying,the solution was transferred into the slurry reactor and CO₂ was charged,using Cr-MIL-101 as a one-component catalyst to promote the conversion of CO₂ to cyclic carbonate.At the end of the reaction,the solution was discharged out of reactor by the internal pressure,and Cr-MIL-101 powder was precipitated and filtered in the reactor.TS-1 and Cr-MIL-101 can be regenerated by calcination and hot solvent treatment,respectively.This method is suitable for the conversion of common olefins such as propylene.Green oxidiant H₂O₂ and halogen-free,heterogeneous catalysts were used to reduce the environmental pollution and the cost of separation.Meanwhile,the conversion of CO₂ to high value chemicals was realized.This approach had application values and a potential of industrialization.