Gas–Liquid Mass Transfer Characteristics of CO₂ Absorption in Azole-Functionalized Ionic Liquid Anhydrous Solvents

Ionic liquids (ILs)-based solvent absorption is a promising green and low regenerative energy consumption technology for CO2 capture. Various functionalized ILs with highly efficient performance have been developed in academia, and the research focuses on thermodynamic properties such as CO2 solubility, gas–liquid equilibrium, and reaction heat. Kinetic studies of CO2 in ILs are also important to evaluate their potential for industrial applications, which need to be studied further. In this work, the mass transfer characteristics of three azole-based IL anhydrous solvents were studied in a wetted-wall column (WWC). At 313.15 K, the total mass transfer coefficient (KG) of fresh [HDBU][Im]/EG, [Cho][Im]/EG, and [Cho][Triz]/EG was 5.40, 2.32, and 0.80 mmol/(m2·s·kPa), respectively. The KG of the three solvents increased along with increase in the temperature. Conversely, when the CO2 loading in the solvent increased, KG decreased. At the initial stage of absorption, the mass transfer resistance of [HDBU][Im]/EG was mainly in the gas phase and then gradually changed to liquid phase. However, due to the excessive viscosity of [Cho][Im]/EG and [Cho][Triz]/EG, the mass transfer resistance was mainly concentrated in the liquid phase. The enhancement factor (E) of [HDBU][Im]/EG was higher than 159, indicating that it had good chemical reaction ability, thereby improving the mass transfer ability. The KG of [HDBU][Im]/EG is 92.12, 307.01, and 117.48% higher than MEA/H2O, MDEA/PZ/H2O, and MEA/AEEA/H2O at 313.15 K, respectively. This work showed that [HDBU][Im]/EG had a good mass transfer performance and great potential in future industrial applications. At the same time, the mass transfer law was summarized to provide theoretical support for CO2 capture technology and reactor design.