Screening Ionic Liquid As Solvents For Capturing CO₂ Based On Molecule Simulation

The global climate warming problem caused by the increased carbon dioxide (CO2) in the atmosphere has been paid much attention all over the world. A lot of studies have found that ionic liquids (ILs) are good absorbents for CO2 capture. However, a large number of ionic liquids have been synthesized at present, and apparently, it will cost too long a period to select a suitable ionic liquid for absorbing CO2 by experimentally measuring the solubility of CO2 in ionic liquids. To address the above questions, a straightforward computational way based on quantum mechanics and statistical thermodynamics theories for the prediction of ILs' absorption capacity is presented in this work.For physical absorption, the parameters that affect ILs'absorption capacity are focused. It is proved that the COSMO-RS theory could well verify conclusions derived from other methods, for example molecule dynamic simulation. The simplified and easy-to-handle process demonstrates the superiority of COSMO-RS theory.For chemical absorption, GaussianO3W combined with COSMOtherm softwares were used to calculate three kinds of free energiesΔG,ΔEsol andΔGrsolution. According to the calculated results, ifΔG>0, absorption capacity of the ionic liquid is quite low; ifΔEsol>-36KJ/mol, the absorption capacity is below 1 mol CO2/mol IL, which means there is little need to synthesis this IL; ifΔEsol<-60KJ/mol, which demonstrates high absorption capability, thenΔGrsolution could be calculated to further assess this kind of ionic liquid.