Guanidinium-based dicarboxylic acid ionic liquids for SO sub(2) capture

BACKGROUND Ionic liquids (ILs) have been widely used in the field of SO sub(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] [Subericacid] ([TMG) were synthesized, and their absorption and desorption performance of SO sub(2) were investigated. RESULTS The saturated molar ratio of SO sub(2) to [TMG][PBE] and [TMG] were 8.74 and 5.96 mol SO sub(2) per mole ILs at 25 degree C, respectively. [TMG][PBE] saturated with SO sub(2) was easier to desorb and could be recycled at least 5 times without loss of initial performance, while the ability to absorb SO sub(2) by [TMG] was gradually weakened after desorption. The absorption mechanism is discussed. Results showed that SO sub(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]. As for [TMG][PBE], SO sub(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 sub(2) capture. CONCLUSION The anion of dicarboxylic acid-based ILs plays an important role in absorption/desorption of SO sub(2) on the basis of the experimental results.