Diamine-Anchored Polystyrene Resins for Reversible SO₂ Adsorption

Abstract

Diamine-anchored Merrifield resins ([DAMR]-CH3SO3; DA = diamine, MR = Merrifield resin, X = Cl, CH3SO3, and (CF3SO2)(2)N), synthesized from the reactions of Merrifield resin with a tertiary diamine selected from N,N,N'N'-tetramethylethylenediamine (TMEDA), 1,4-dimethylpiperazine (DMP), and 1,4-diazabicyclo[2,2,2]octane (DABCO), were found to exhibit excellent performance as SO2 adsorbents under both hydrous and dry conditions. Under dry conditions, the molar SO2 adsorption capacity of [DAMR]X was greatly affected by the nucleophilicity of the anion but was rarely influenced by the type of diamine anchored on the cation. In contrast, under hydrous conditions, the SO2 adsorption and desorption behaviors on [DAMR]X were strongly affected by the basicity of the diamine on the cation, [DAMR](+). Spectroscopic and experimental results suggest that in the presence of water SO2 is adsorbed on [DAMR]X as a bisulfite species, and the formation and the stability of the bisulfite species increase with the increasing basicity of the diamine of [DAMR]+. SO2 adsorbed on [DABCOMR]X was found to completely desorb at 80 degrees C, irrespective of the presence of water.