Guanidinium-based dicarboxylic acid ionic liquids for SO2 capture

BACKGROUND Ionic liquids (ILs) have been widely used in the field of SO 2 separation for gases. In this study, two kinds of guanidinium-based dicarboxylic acid ionic liquids including [1,1,3,3-tetramethylguanidinium][Poly(ethylene glycol) bis(carboxymethyl) ether] ([TMG][PBE]) and [1,1,3,3-tetramethylguanidinium] [Suberic acid] ([TMG][SUB]) were synthesized, and their absorption and desorption performance of SO 2 were investigated. RESULTS The saturated molar ratio of SO 2 to [TMG][PBE] and [TMG][SUB] were 8.74 and 5.96 mol SO 2 per mole ILs at 25 °C, respectively. [TMG][PBE] saturated with SO 2 was easier to desorb and could be recycled at least 5 times without loss of initial performance, while the ability to absorb SO 2 by [TMG][SUB] was gradually weakened after desorption. The absorption mechanism is discussed. Results showed that SO 2 could interact not only with the amino group on the cation but also with the methylene bonded to the carbonyl carbon on the anion for [TMG][SUB]. As for [TMG][PBE], SO 2 could interact with the ether group by S-O ligand interaction, instead of interacting with the methylene group bonded to the carbonyl carbon on the anion. [TMG][PBE] show good performance for SO 2 capture. CONCLUSION The anion of dicarboxylic acid-based ILs plays an important role in absorption/desorption of SO 2 on the basis of the experimental results. © 2016 Society of Chemical Industry