Abstract:

The anion-functionalization strategy has been proposed and applied for the synthesis of macro-porous resins [IRA-900][An], thus realizing anultra-high SO₂ adsorption capacity (>10 mmol·g^-1) at 101.3 kPa and 20 ℃. Compared with the normal azole-based anion-functionalized resins, the poly(imidazolyl)borate anion-functionalized resin [IRA-900][B(Im)₄] exhibited an outstanding adsorption capacity at low SO₂ partial pressures (10.62 mmol·g^-1 at 20 ℃ and 10.13 kPa). From the results of the IR spectrum investigation and DFT calculations, the multiple-site adsorption mechanism was verified. On account of the unique tetrahedral configuration of [B(im)₄], the conjugation and electronic communication between the electronegative nitrogen atoms were disrupted, making them behave as local reactive sites. Therefore, at least four electronegative nitrogen atoms could be provided by one [B(im)₄] to react with SO₂ without evident adsorption enthalpy deterioration (from -50.6 kJ·mol^-1 to -37.2 kJ·mol^-1) during the continuous SO₂ capture; this was responsible for the ultra-high SO₂ adsorption capacity achieved by [IRA-900][B(Im)₄] at low partial pressures. Moreover, the thermal stability and reversibility of [IRA-900][B(Im)₄] for SO₂ capture and desorption were investigated. Six cycles where the adsorption was carried out at 20 ℃ and 10.13 kPa and the regeneration was performed at 70 ℃ demonstrated the adequate reversibility of [IRA-900][B(Im)₄] for SO₂ capture, showing the resin's great potential for industrial desulfurization. Thus, the anion-functionalization strategy and multiple-site adsorption behavior provide new perspectives to realize effective SO₂ capture from flue gas.

Key words: Anion functionalized, Macro-porous resins, Poly(imidazolyl)borate anion, Multiple-site, SO₂ capture