The Design And Systhesis Of Superbase Ionic Liquid-Based Deep Eutectic Solvents For Improving CO₂ Absorption

Carbon dioxide?CO₂?is a harmful greenhouse gas to the environment and the main culprit of global warming.However,the development of efficient methods for CO₂ absorption and separation is still a great challenge.Ionic liquids?ILs?have emerged as promising solvents for CO₂ separation due to adjustable structures and good affinity toward CO₂.Most of the functional ILs have the problems of high viscosity,complex synthesis steps and high desorption temperature,so the solvent with simple synthesis steps and low viscosity has the prospect of industrial application.In this work,the above problems are solved by the synthesis of IL-based DESs.The specific innovative results are as follows:?1?Design synthesis and CO₂ absorption performance of superbase ionic liquid:Four superbase ILs,including 1,8-Diazabicyclo[5,4,0]undec-7-ene imidazole?[HDBU][Im]?,1,8-Diazabicyclo[5,4,0]undec-7-ene indole?[HDBU][Ind]?,1,8-Diazabicyclo[5,4,0]undec-7-ene 1,2,4-triazole?[HDBU][Triz]?and1,8-Diazabicyclo[5,4,0]undec-7-ene 2-Hydroxypyridine?[HDBU][2-OP]?with low molecular weight of cation were synthesized by one step.The viscosity,density,thermal decomposition temperature,melting points and absorption performance of ILs at 40?and 100 k Pa were studied.The results showed that the viscosity and density of ILs decrease with the increase of temperature,and the thermal decomposition temperature of ILs are not very high.It is necessary to control the industrial use temperature reasonably.[HDBU][Im]shows the lowest melting point?-62??.The absorption capacity of[HDBU][Im]at 40?and 100 k Pa is as high as0.194 g CO₂/g IL,but the viscosity of ILs increase in the absorption process,and the final formation of gelatinous state is not beneficial to mass transfer of CO₂,so the absorption time is long.?2?Design and synthesis of IL-based DESs and high efficiency absorption of CO₂:To solve the above problems,four superbase ILs were designed as hydrogen bond acceptor?HBA?and further combined with ethylene glycol?EG?as hydrogen Sbond donor?HBD?to form novel IL-DES was proposed for efficient and reversible absorption of CO₂.The results indicated that both excellent recyclability and high CO₂ mass capacity up to 0.141g CO₂/g DES under 40?and 100 k Pa were achieved by[HDBU][Im]/EG with mass ratio of 7:3,and the value is much higher than most of reported IL-based DESs.The superior CO₂ absorption and desorption performance were attributed to the synergistic interaction between both IL,EG and CO₂ to form carbamate and carbonate by FTIR and NMR.This work provides a feasible method for designing IL-based solvents in CO₂ separation applications.?3?Based on the operation of the small test device of ammonia carbon separation by IL method:On this basis,the separation project of ammonia?NH₃?and carbon dioxide?CO₂?was carried out.The small test device was insulated,the calibration of gas mass flowmeter and material pump,the determination of purified gas detection method and the optimization of process operation parameters.The designed and synthesized IL can selectively absorb NH₃ and separate it from CO₂.The concentration of ammonia after absorption is below 1000-3000 ppm,which provides enlarged data for IL-DESs absorb CO₂.In conclusion,the[HDBU][Im]/EG with the mass ratio of 7:3 can effectively solve the viscosity problem in the absorption process and has a high mass absorption.Secondly,the designed IL can successfully separate NH₃ and CO₂.After separation,the concentration of NH₃ in the tail gas is 1000-3000 ppm,which meets the emission standard of industrial tail gas.