Simultaneous absorption of CO2 and H2S by [Emim][Ac]: The competition mechanism

In this work, ionic liquid (IL), 1-ethyl-3-methylimidazolium acetate ([Emim][Ac]) was used for simultaneous absorption of H2S and CO2 from mixed gases. According to the results, there was a competitive relationship between H2S and CO2. The CO2 capacity of simultaneous absorption, less than 0.010 mol/mol IL is much lower than that of individual absorption, 0.294 mol/mol IL, at 40 degrees C and 101 kPa with 50 vol% CO2 in gases. And the H2S/CO2 selectivity during individual absorption (Sideal) was significantly different from that during simultaneous absorption (Ssim). Ssim could reach 75.3, which was about 40 times of Sideal. The increase of temperature can increase Sideal, but has almost no obvious influence on Ssim. The decrease of volume fraction can increase Sideal, but decrease Ssim. The competitive mechanism in [Emim][Ac] is proposed and verified by the characterization, quantum chemical (QC) calculation and molecular dynamics (MD) simulation. The results show that the presence of H2S prevented the formation of "carbene" in [Emim][Ac] that can react with CO2 for chemical absorption. This work provides new insights into simultaneous absorption of H2S and CO2 by ILs.