Application Of Functionalized Deep Eutectic Solvents In Separation And Conversion Of CO₂ And SO₂ Gase

At present,the use of fossil fuels associated with a large amount of acid gases CO₂and SO₂has caused great harm to the environment and human health.The development of efficient CO₂and SO₂capture and conversion technology is an effective way to reduce air pollution,and it is also related to the sustainable development of mankind.The key to realizing the efficient capture and conversion of CO₂and SO₂lies in the design of effective capture and conversion media.The existing capture and conversion technologies cannot meet the requirements of new green chemical processes due to many bottlenecks.Therefore,it is urgent to develop new efficient and green capture and conversion methods of CO₂and SO₂.As ionic liquids（ILs）,deep eutectic solvents（DESs）are new green solvents that are easy to prepare,cheap and easy to obtain,and have excellent application prospects in gas separation and conversion.Based on this,this paper closely focuses on the two purposes of"efficient capture"or"low energy conversion",designs and synthesizes a variety of functional DESs for the capture and conversion of CO₂and SO₂gases,focuses on the structure-activity relationship of DESs in gas capture and catalytic conversion,and establishes a variety of effective methods for the separation and conversion of CO₂and SO₂gases.The specific research contents are as follows:（1）The cycloaddition reaction of CO₂and epoxide to prepare cyclic carbonate is one of the important ways of CO₂organic conversion.This process has been widely studied in the field of catalysis,but the low cost and environmental protection of catalyst is still a challenging topic.In this paper,a series of DESs catalytic systems based on proton ionic liquids/amines were designed and synthesized.Through the synergistic catalysis between them,CO₂is successfully converted into cyclic carbonate at room temperature.The reaction conditions are milder than most of the reported catalysts.The mechanism study confirmed that the synergistic catalysis between proton ionic liquid and amine is the key reason for the realization of CO₂cycloaddition conversion.（2）In order to realize the"greenness"of the catalyst required for CO₂cycloaddition conversion,a series of biocompatibility platform molecules such as choline,glycerol,malic acid,malonic acid,and succinic acid were used as raw materials to synthesize a series of bio-based DESs and used to catalyze the cycloaddition reaction of CO₂and epoxides.The effects of functional group structure of DESs,hydrogen bond donor and acceptor ratio,reaction temperature,pressure and water content on the catalytic activity of bio-based DESs were investigated in detail.The results show that Ac Ch Br-LMA（2:1）has the best catalytic activity,the yields of various cyclic carbonates can reach 66%～99%at 80^oC and 1 bar,and the DESs also show excellent cycle performance.（3）In terms of SO₂capture and conversion,four kinds of multi active site DESs were prepared for SO₂capture and transformation by using the strong electric absorption ability of chloride ion in 1-ethyl-3-methylimidazole chloride（Emim Cl）and the weak alkaline property of amide.The results show that Emim Cl-DMU（2:1）can absorb SO₂up to 1.26 g/g（20^oC and1 bar）,and exhibits excellent reversible absorption performance.The mechanism study shows that there is charge transfer between SO₂and DESs,and the structure of DESs does not change before and after SO₂absorption.In addition,the absorbed SO₂was successfully transformed into a high value-added DABCO·2SO₂complex by using DESs as the phase transfer medium,and it was verified that the complex can be used in the synthesis of N-aminosulfonamide and sulfonamide derivatives instead of SO₂.（4）Cycloaddition of SO₂and epoxides to cyclic sulfites is another green route to SO₂conversion.Inspired by the cycloaddition of CO₂catalyzed by proton ionic liquids（PILs）,protonated imidazolium salts are used as hydrogen bond acceptors and various imidazole derivatives to prepare imidazolyl DESs,which are used for SO₂absorption and conversion.The results show that the SO₂uptake of[MIm H][Cl]-2MIm（1:1）is as high as 1.45 g/g,which is the highest SO₂uptake reported so far.In particular,SO₂absorbed by DESs can directly react with epoxides to form cyclic sulfites at 30^oC,realizing the process coupling of SO₂absorption and conversion.