A Study On Green Synthesis Of Cyclic Carbonate From CO₂

Carbon dioxide is a greenhouse gas.It can also be used as a cheap and abundant C1resource.Using CO₂ as a raw material to synthesize cyclic carbonate is one of the most promising ways to utilize CO₂,which also can conducive to our country’s goals of achieving peak carbon dioxide emissions and carbon neutrality.Cyclic carbonates are high-value chemicals with the character of high boiling point,low toxicity,stable structure,and biodegradability.Therefore,it is widely used in lithium battery electrolyte,dispersant in printing and textile industry,monomer for synthesizing polycarbonate and intermediate of other chemical products.Therefore,epoxides and olefins as substrates to synthesis cyclic carbonates.The first part of this work is the synthesis of propylene carbonate based on the cycloaddition reaction of propylene oxide and CO₂.A series of Bmim Cl-based deep eutectic solvents（DESs）were prepared by melting method for this reaction.The composition ratio of DESs affects the hydrogen bonding,which in turn affects the activity of the reaction.In this regard,a series of DESs with different ratios were synthesised.Under the optimized reaction conditions,the yield of PC was about 98.0%over Bmim Cl/BA/GA（7/1/1,molar ratio）.In addition,the Bmim Cl-based ternary DESs are easy to recycle and indicates excellent reusability.The mechanism of epoxide activated by hydrogen bonds and epoxide ring opening was proposed.The Bmim Cl-based ternary DESs will be viewed as an innovative system for cycloaddition of CO₂ with epoxides and it will supply a novel class of DESs for other possible applications.In order to overcome the high price,high toxicity,difficulty in transportation and storage of epoxides,the epoxide precursor styrene was used as the reactant to synthesize cyclic carbonate through oxidative carboxylation reaction in the second work.A series of catalysts were designed using MIL-101-NH₂ as support.The successful synthesis of the catalyst was proved by XRD,FT-IR,BET and other characterization methods.With 70%mass fraction of tert-butyl hydroperoxide（TBHP）as the oxygen source,the catalytic performance of different catalysts for the oxidative carboxylation of styrene was investigated.By optimizing the reaction conditions,59.9%yield of styrene carbonate was obtained under the optimal conditions.This step-by-step method provides a new idea for constructing the catalyst required for the tandem reaction.Although good results were obtained in the second job,the stability of the catalyst was poor and the synthesis process of the catalyst was complicated.A series of Ce O₂ with different Cu contents or different other metals were synthesized by simple hydrothermal method,were used as a catalyst for styrene oxidative carboxylation reaction.Through the addition of urea in the synthesis process,a metal-doped porous Ce O₂ catalyst was prepared.TEM,XRD and XPS were used to confirm the successful synthesis of the catalyst.The doping of Cu creates a new redox cycle(Cu⁺+Ce⁴⁺?Cu²⁺+Ce³⁺).Under the optimal reaction conditions（temperature,pressure,catalyst dosage,etc.）,10Cu/Ce catalyst can get 57.4%yield of styrene carbonate.The results of this study opened up a new way for the design of high-efficiency oxidation carboxylation catalyst.