Tuning the Structures of Ionic Liquids for Highly Efficient Gas Capture and Utilization

Author:Chen Kai Hong

Supervisor:wang cong min donald jdarensbourg


Degree Year:2018





The standard for industrial waste gas becomes increasingly strict,when we realize the importance of environmental protection.In industry,traditional methods for air purification bear plenty of drawbacks.It is a challenge work to develop an efficient method for gas capture while overcome these disadvantages.Ionic liquids(ILs)have been proved to be the ideal absorbent for many gases because of their unique properties,such as negligible vapor pressure,wide liquid temperature range,reusable,high thermal stability,tunable structure,etc.Several strategies,by tuning their structures,have been developed in CO2 or SO2 absorption and CO2 capture and utilization(CCU)at the same time.Thanks to their outstanding performance in CO2 absorption,ILs are found can accelerate many CCU processes even under mild conditions.In this work,we investigate the influence of ILs on gas absorption and utilization systematically by tuning their structures and properties.First,the effect of basicity and substituents for ILs on SO2 absorption is investigated under simulated flue gas.The results disclose that the basicity of ILs is the key to determine their SO2 absorption capacity,while the relationship between the SO2 available absorption and its absorption enthalpy is a volcano plot.A new IL with low molecular weight is designed for SO2 absorption under 2000 ppm,according to the thermodynamic analysis and DFT calculation.In the meantime,this IL has high SO2 absorption capacity and reusability.In addition,we report the NO absorption by using ILs for the first time.NO absorption capacity for[P66614][Tetz]is more than 4.5 molNO·molIL-1,but it is very low for[P66614][Tf2N].Moreover,absorption kinetics exhibits two different trends in this process.Through combining of experimental results,DFT calculation,NMR and FT-IR spectra,results show that there are two absorption sites in[P66614][Tetz].In the reaction between propargylic alcohols and CO2,we use ILs with different basicity as cocatalyst,in order to find out the effect of basicity on this CCU process.It is found that the basicity of ILs can determine its activity significantly.Strong basicity will lead to poor selectivity,while weak basicity gives low activity.In the copolymerization of oxirane and CO2,we develop a new betaine functional catalyst that has high activity and selectivity.Through a combination of control experiments,MALDI-TOF analyzing and DFT calculations,co-catalyst is found significant in this catalyst system.Importantly,these catalysts also have high activity and selectivity in the synthesis of poly(styrene carbonate)and poly(2-vinyloxirane carbonate).Base on the relationship between pKa and catalytic activity,DFT calculation is utilized to predict the activity of anions in CCU process.This prediction is in good agreement with experimental results in the synthesis of 3(2H)-furanone.Furthermore,the effect of cations on this reaction is further investigated by using 1H NMR spectra analysis and DFT calculations.To realise NO controlled-release under particular conditions,sulfamic acid and aminocarboxylic acid functionalized ILs are designed and showed high NO absorbtion capacity.Their NO absorbtion capacity is found related to the chain length of anions and cation species.What’s more,the NO absorbed by these ILs can release at 37 ℃ and pH 7.4 in 0.1 M phosphate buffer,with half-time period ranging from 211 min to 1591 min.The reason to different NO release rates is also investigated by DFT calculation.In summary,we investigate the effect of basicity of ILs on the SO2 capture under simulated flue gas,NO absorption and CCU process,by finely tuning their structures.The basicity of ILs is found to influence their ability dramatically.Based on this result,we then design the efficient ILs for gas capture and utilization.In addition,a new kind of betaine functional Co(Ⅲ)catalyst,taking ILs as precursor,is also synthesis for copolymerization of oxirane and CO2.Finally,we realise the first IL-based NO donor and the half-time period of NO releasing can be tuned by tuning the structure of ILs.