Effective Absorption Mechanism of SO₂ and NO₂ in the Flue Gas by Ammonium-Bromide-Based Deep Eutectic Solvents

Abstract

Simultaneous capture of SO 2 and NO x from flue gas is critical for coal-fired power generation. In this study, environmentally friendly and high-performance deep eutectic solvents based on ethylene glycol and ammonium bromide were designed to capture SO 2 and NO 2 simultaneously. The SO 2 and NO 2 absorption performances and absorption mechanisms were systematically investigated by 1 H NMR and Fourier transform infrared (FT-IR) spectroscopy in combination with ab initio calculations using Gaussian software. The results showed that EG-TBAB DESs can absorb low concentrations of SO 2 and NO 2 from the flue gas simultaneously at low temperatures (≤50 °C). 1 H NMR, FT-IR, and simulation results indicate that SO 2 and NO 2 are absorbed by forming EG-TBAB-SO 2 –NO 2 complexes, Br – is the main active site for NO 2 absorption, and NO 2 is more active in an EG-TBAB-NO 2 –SO 2 complex than SO 2 . EG-TBAB DESs exhibit outstanding regeneration capability, and absorption capacities remain unchanged after five absorption–desorption cycles. The fundamental understanding of simultaneous capture of SO 2 and NO 2 from this study enables DES structures to be rationally designed for efficient and low-cost desulfurization and denitrification reagents.

Mechanism of synergistic removal of NO and SO2 by sodium bicarbonate

“…In addition to the peaks of Na 2 CO 3 at 863 and 1450 cm −1 , the characteristic peaks corresponding to Na 2 SO 4 appear at 618 and 1140 cm −1 , while that of NaNO 3 is at 1381 cm −1 , implying that the reaction products of NaHCO 3 with SO 2 and NO mainly include Na 2 CO 3 , Na 2 SO 4 and NaNO 3 . [25][26][27] The reaction products were then characterized by XPS, and the high-resolution spectra of S 2p and N 1s were illustrated in Fig. 5.…”