Guanidinium-based ionic liquids for sulfur dioxide sorption

Three guanidinium-based ionic liquids (GBILs) including [1,1,3,3-tetramethylguanidinium][phenol] ([TMG][PHE]), [1,1,3,3-tetramethylguanidinium][2,2,2-trifluoroethanol] ([TMG][TE]) and [1,1,3,3-tetramethylguanidinium][imidazole] ([TMG][IM]) were synthesized and their absorption and desorption of sulfur dioxide were investigated, respectively. The saturated molar ratio of SO2 to GBILs varied from 2.24 to 3.16 at 40 °C with high absorption rate. The absorption mechanism might be that SO2 reacts with the –NH2 group on the cation and then a new –SO2H group is formed. The new GBILs could absorb SO2 by both physical and chemical interactions while physical absorption does play an important role at the experimental conditions under investigation.

► Three new guanidinium-based ionic liquids (GBILs) were synthesized.
► The SO2 absorption/desorption properties of the GBILs were examined.
► The SO2 absorption capacity of the GBILs are significantly larger than that for CO2.
► The GBILs absorb SO2 by both physical and chemical interactions.
► Physical absorption plays an important role at the experimental conditions.