Physically bound and chemically grafted activated carbon supported 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-ethyl-3-methylimidazolium acetate ionic liquid absorbents for SO2/CO2 gas separation

Absorption separation of SO2 from a SO2/CO2/O2/N2 gas mixture was examined by preparing and testing four different Supported Ionic Liquid Phase absorbents (SILPs) on functionalized and pristine, microporous carbon substrates. In particular, ionic liquids(ILs) 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-ethyl-3-methylimidazolium acetate, capturing acidic gases (CO2 and SO2) by physisorption and chemisorption respectively, were immobilized into the porous structure of an activated carbon substrate, either by physical imbibition, or chemical grafting. Absorption capacities and SO2/CO2, SO2/O2 selectivities were determined by means of a fixed bed breakthrough experiment, in a range of pressures and temperatures. The target was to elucidate the applicability of the prepared SILPs for flue gas desulfurization and conclude on the influence of chemical grafting and competitive SO2, CO2 chemisorption on the performance and stability of the SILPs under cyclic absorption/regeneration tests. Results showed that the SILPs with acetate ionic liquid were highly effective, but could not preserve their enhanced absorption and separation performance after regeneration. On the contrary, SILPs prepared with the physisorbing IL exhibited remarkable stability accompanied with satisfactory performance.