Glycidol-modified PEI: a highly selective adsorbent for SO2 in the presence of CO2

Abstract

Amine-containing CO₂ adsorbents are highly sensitive to the presence of SO₂ in the feed gas, even in minute amounts. It is thus necessary to remove SO₂ quantitatively prior to CO₂ capture. To this end, we developed a silica-supported polyethylenimine (GD-PEI/S) adsorbent containing only tertiary amines via quantitative glycidol functionalization. The novel material was characterized by infra-red (IR) and nuclear magnetic resonance (NMR) spectroscopy, and by thermogravimetric analysis (TGA). In the presence of a gas mixture containing 5 ppm SO₂ and more than a 2 × 10⁴ higher concentration of CO₂, the GD-PEI/S material adsorbed SO₂ quantitatively until near saturation, with no CO₂ uptake, indicating that the adsorbent exhibits 100% SO₂ selectivity versus CO₂, even in the presence of very high CO₂/SO₂ ratios. Furthermore, the SO₂ uptake of the adsorbent almost doubled in the presence of humidity, possibly due to increased diffusion of SO₂. Under recycling conditions, GD-PEI/S showed good reversibility in the presence of both dry and humid SO₂ at low and high SO₂ concentrations.