Rapid and high-capacity absorption of SO2 by deep eutectic solvents bound to tertiary amine sites

Abstract

Rapid and efficient absorption of SO2 by deep eutectic solvents (DESs) is highly desirable but extremely challenging. In this work, novel DESs bound to several tertiary amine sites were synthesized by mixing methylated polyethyleneimine (mPEI) and tris(2-(2-methoxyethoxy)ethyl)amine (TDA) at different mass ratios (2:1, 1:1, and 1:2). The synthesized DESs with low viscosity achieved efficient SO2 absorption. In particular, excellent absorption capacities were achieved within a short period (0.44 g·g−1 at 0.5 min and 0.75 g·g−1 at 1.0 min) by mPEI-TDA (1:2) at 293 K and 1 bar. The uptake results are superior to those of most DESs and ILs in the current literature. Furthermore, mPEI-TDA (1:2) had an excellent SO2/CO2 selectivity up to 89.1 at 293 K and 1 bar. Moreover, the SO2 absorption achieved using DESs is highly reversible since the absorption capacity did not decrease significantly even after 10 cycles (absorption at 293 K and 1 bar, desorption at 353 K and 0.1 kPa under vacuum for 2 h). Overall, this work indicates that designing a DES containing several tertiary amine sites with low viscosity can be an effective method for realizing fast and efficient desulfurization of flue gas.