Molecular Dynamics Simulation And Application Of Imidazole-type Ionic Liquids In Gas/liquid-liquid Mass Transfer Process

Ionic liquids（ILs）,as a new solvent,has many advantages such as low volatility and adjustable structure,and has been widely used in green synthesis,gas absorption and separation in recent years.Due to the complex anions and cations of ILs and hydrogen bond donor-acceptor combinations of deep eutectic solvents（DESs）,their effects in gas/liquid-liquid mass transfer process are quite different.It is of great significance to study the diffusion properties and aggregation behavior in the process of carbon capture and the separation of low carbon alcohols through the multi-scale combination of molecular dynamics simulation（MD）,experiment,process simulation and life cycle assessment.The structure and kinetic properties of acidic gases such as CO₂ and H₂S in imidazolyl ILs are investigated by means of quantum chemistry and MD.The combined design of ethanolamine DES hydrogen bond donor and acceptor and molar ratio of the two are also designed.The deviation between simulated ILs density and experimental density is less than 5%,which verifies the accuracy of force field parameters and analysis results.The total non-bond interaction force,radial distribution function and spatial distribution function of different molecules after dynamic equilibrium are calculated.The results of interaction energy showed that the total non-bond interaction force between Ch Cl:MEA（1:6）and CO₂ is-3674.88 k J·mol^-1,which is higher than that between Ch Cl:MEA（1:7）and Ch Cl:MEA（1:8）,and the total non-bond interaction force between MEA and CO₂ accounted for 76.87%of the total of DES.Compared with the commonly used absorbent 10%MEA in industry,the absorbent increased about 4.2times.Kinetic analysis results show that two different MEA molecules in Ch Cl:MEA（1:6）interact directly through hydrogen bonds between NH₂/NH₂,NH₂/OH and OH/OH groups,CO₂ is distributed in the gap around the MEA without Ch Cl,and the structure of Ch Cl:MEA（1:6）almost does not change before and after absorption.Considering temperature,viscosity and solvent cost,it is recommended to use 10%Ch Cl:MEA（1:6）in industry.The order of diffusion coefficients is MDEA<[BMIM][PF₆]<[BMIM][BF₄]<[HMIM][TF₂N]<[BMIM][TF₂N]<[EMIM][TF₂N].Considering the viscosity,heat capacity and toxicity of ionic liquid comprehensively,[EMIM]⁺is easy to crystallize at low temperature,which increases the cost of temperature control,so[BMIM][TF₂N]is chosen as absorbent.The life cycle assessment method is used to evaluate the actual carbon emission reduction and energy consumption increase of the new imidazole-type ILs process for acid gas removal.The life cycle environment analysis and comparison of the three kinds of ILs carbon removal and storage processes during the solvent production and use stage showed that 90%of the waste compounds are discharged during the preparation of basic materials.The impact of the improved process on the environment is only 33-36%of that of the basic process,and the CO₂ emission of the carbon capture and storage process for waste heat recovery is only 2.03 kg CO₂ eq/t in its life cycle.CML2000 is used to analyze the environmental impacts of GWP,ADP,ODP,HTP,AP,EP,POCP,FAETP and TETP in CCS-IL process.Except ADP,Li NTf₂ is the main part of other environmental impact indicators.The input energy of anion precursors is 15 times that of cationic precursors,and anion production is the main cause of environmental burden.A combination of phase equilibrium calculation,MD and process simulation was used to realize the efficient green separation of low carbon alcohol azeotropic compounds with imidazole ILs.The effect of temperature,pressure and cation type on CO₂ solubility is consistent with the experimental results.The extraction efficiency decreases significantly when the temperature increases from 25℃to 60℃.The high room temperature efficiency is conducive to the energy saving and consumption reduction of the process,and the extraction capacity of IL is not affected by the initial low carbon alcohol concentration,so that IL can be used in a wider range of low carbon alcohol separation.The lowest annual total cost of[BMIM][HSO₄]extraction process is17.31%lower than that of traditional process,and the GWP and EP were 86.1%and85.0%lower,respectively,which showed good sustainable development advantages.