Gas Separation and Purification by Polymeric Adsorbents: Flue Gas Desulfurization and SO₂ Recovery with Styrenic Polymers

High-surface-area polystyrenic sorbents possess all necessary properties for flue gas and tail gas desulfurization: high SO₂ adsorption capacity and diffusion rate, high SO₂/CO₂ selectivity, and hydrophobicity. NO chemisorbs on these polymers at room temperature, but the NO-treated polymers retain all of the above properties. Model simulations show that pressure swing adsorption cycles using these NO-treated polymers can effectively remove well over 90% of the SO₂ from the flue gases and, at the same time, generate SO₂-concentrated desorption products containing well over 5% by volume of SO₂. The desorption products can be readily converted to elemental sulfur. Aromatic rings comprise the major fraction of the polymer surface area. Infrared spectroscopic analysis indicates that NO chemisorbs by interactions with the π electrons in the aromatic rings on the polymer surface. The existence of lone-pair electrons in the SO₂ molecule enables it to interact with the π electrons of the aromatic rings much more strongly than CO₂, leading to the high SO₂/CO₂ selectivity.