Investigating the SO2 absorption behavior of pyrimidine-based deep eutectic solvents via a dual-site thermodynamic model

Abstract

Deep eutectic solvents (DESs), composed of hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs), are widely used in flue gas desulfurization due to their excellent SO 2 absorption properties. In this work, 14 DESs with 2-Aminopyrimidine (AmPyr), 2-Chloropyrimidine, 2-Bromopyrimidine, 4-Amino-2-hydroxypyrimidine, 2,4-Dihydroxypyrimidine, 4,6-Diaminopyrimidene, 2-Aminopyrazine, or 3-Aminopyridazine as HBDs with 1-Ethyl-3-methylimidazolium Chloride (C 2 mimCl) or 1-Ethyl-3-methylimidazolium Bromide as HBAs have been successfully prepared and used for SO 2 absorption. Among them, C 2 mimCl-7 + AmPyr exhibited the highest SO 2 absorption (19.032 mol•kg -1 , at 298.15 K and 1.0 bar), rapid gas-liquid equilibrium time within 40 s, and exceptional ideal selectivity of 528.7 for SO 2 /CO 2 . After 30 cycles of absorption-desorption, the SO 2 absorption capacity remained as high as 18.265 mol•kg -1 . A dual-site reaction equilibrium thermodynamic model (DS-RETM) was established for absorption behavior analysis. Using C 2 mimCl-7 + AmPyr as a case study, Henry's constant, equilibrium constants, and other thermodynamic parameters were determined. DS-RETM fitting further enabled visualization of the potential absorption behavior of each DESs component, facilitating comparison of HBAs and HBDs effects on SO 2 absorption. This study offers new insights into the development of high-performance flue gas desulfurization absorbents and introduces a novel model for thermodynamic analysis of SO 2 absorption in DESs.