Synergistic SO2 absorption in N-methyl ethanolamine/thiocyanate blends: Thermodynamic insights and energy optimization

Traditional amine scrubbing for SO 2 capture typically dilutes alcohol amines with water to improve mass transfer, resulting in high volatility and desorption energy consumption. Inspired by the exceptional properties of ionic liquid (IL) 1-ethyl-3-methylimidazolium thiocyanate ([EMIM][SCN]), we herein propose substituting water with [EMIM][SCN] in a novel SO 2 absorbent system based on N -methyl ethanolamine (MDEA). MDEA acts as the primary SO 2 absorbent, while [EMIM][SCN] serves as an auxiliary absorption component and physical properties regulator. Performance evaluations reveal that MDEA-[EMIM][SCN] achieves high thermal stability (~483.15 K), low viscosity (~26 mPa s), excellent absorption capacity (~1.64 mol/kg at 298.15 K and 2000 ppm SO 2 ), high SO 2 /CO 2 selectivity (~101), and low desorption energy (approximately −95.6 kJ/mol). Thermodynamic modeling illustrates MDEA and [EMIM][SCN] contribute independently to absorption. Optimal energy consumption was determined by the proposed objective function. This work exemplifies the non-aqueous alkanolamine/IL system for SO 2 capture, offering a promising approach for developing efficient, low-energy SO 2 absorbents.