(398ar) Efficient Absorption of SO2 in Flue Gas By Environmentally Benign Functional Deep Eutectic Solvents

Kai Zhang¹, Shuhang Ren¹, Yucui Hou², Ying Sun¹, Weize Wu^1,*

¹State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China

²Department of Chemistry, Taiyuan Normal University, Taiyuan 030031, China

Sulfur dioxide (SO₂) mainly emitted from flue gas badly effects on environment. Deep eutectic solvents (DESs), which is a combination of a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD) through hydrogen bond, are considered as a new kind of solvents with many advantages such as low vapor pressure, easy preparation and low price. In this work, we found DESs could be designed with a function to absorb low concentration SO₂ from simulated flue gas. Two kinds of DES, which can efficiently and reversibly absorb SO₂, based on betaine (Bet) and L-carnitine (L-car) as HBA and ethylene glycol (EG) or water as HBD were prepared with different ratios of HBA to HBD. 2% SO₂ solubility in DESs were 0.332 mol SO₂ / mol HBA for Bet + EG DES and 0.820 mol SO₂ / mol HBA for L-car + EG DES with n_HBA:n_HBD = 1:3, and 0.155 mol SO₂ / mol HBA for Bet + H₂O DES and 0.606 mol SO₂ / mol HBA for L-car + H₂O DES with m_HBA:m_HBD = 1:1, at 40 ^oC. SO₂ solubility increased with increasing SO₂ concentration and decreasing temperature. Meanwhile, the absorption capacities in DESs did not change after 5 absorption/desorption cycles. FTIR, ¹H NMR and ¹³C NMR results indicated that there are strong acid–base interactions between SO₂ and −COO^– on HBA. DESs based on Bet and L-car as HBA and EG or water as HBD are promising absorbents in the application of SO₂ capture.

The project is financially supported by the National Natural Science Foundation of China (No. 21176020 and 21306007), and the Research Fund for the Doctoral Program of Higher Education of China (No. 20130010120005).

Keywords: Absorption; SO₂; flue gas; Functionalization; Deep eutectic solvent