Acetylcholine-based deep eutectic solvents for highly efficient SO2 absorption, selective separation from CO2 and their mechanism
Ruizhong Lu, Songqi Ma, Yang Zhai, Zeyu Geng, Zhi Jin, Yong Fu, Wei Wang, Yun Xu
Abstract
The development of deep eutectic solvents (DESs)-based absorbents for selective uptake of SO 2 from CO 2 (SO 2 /CO 2 , g/g) is of interest to flue-gas desulfurization (FGD). In this work, a series of DESs are designed through acetylcholine chloride (ACC) as hydrogen bond acceptor (HBA) and ethylene glycol (EG), 1,3-propylene glycol (1, 3-PDO), glycerol (Gly), polyethylene glycol 200 (PEG200) and triethylene glycol (TG) as hydrogen bond donors (HBDs). All the DESs display good thermal stability under 150 °C and competitive capacities of SO 2 . ACC/PEG200 (1:1) is remarkable due to their absorption capacity of SO 2 to 3.5 mol/mol (P = 1.0 bar, T = 303.2 K). All DESs show excellent selectivity separation of SO 2 from CO 2 more than 100, for example, up to 335 in ACC/TG (1:1). In this work, the relative mechanism reveals that DESs absorption of SO 2 combining physisorption and chemisorption via a reaction equilibrium thermodynamic model and theoretical calculation. Furthermore, ACC/TG (1:1) maintains the reversible absorption capacity of SO 2 after five absorption/desorption cycles. Considering high SO 2 absorption capacity, desired selectivity, and excellent recyclability, DESs in this study are considered recyclable green absorbers, which can be potentially applied to SO 2 capture towards CO 2 mixture.