Determination of Absorption Rate and Capacity of CO₂ in Ionic Liquids at Atmospheric Pressure by Thermogravimetric Analysis

Abstract

Here, a cheap and fast way to measure the CO2 absorption rate and capacity through thermogravimetric analysis (TGA) is proposed. The absorption of CO2 in 11 ILs varying in anion, cation, alkyl chain length, and C2 methylation was then investigated. Three parameters comprehensively characterizing the absorption capacity and kinetics, including the absorption capacity (x), the initial absorption rate (r10), and the degree of difficulty to reach phase equilibrium (t0.9), were proposed as the standards to evaluate the potential of ILs for CO2 capture. Results show that the correlation between absorption capacity and the degree of difficulty to reach phase equilibrium is complicated. However, ILs with higher absorption capacity usually have a higher initial absorption rate, suggesting a simple way to estimate absorption capacity just by determining initial absorption rate for less than 10 min. More importantly, ILs with the acetate ([Ac]) anions have an advantage in x, r10, and t0.9 over other ILs, indicating that [Ac]-based ILs are promising candidates for CO2 capture in practice.