Probing the Adsorption/Desorption of CO sub(2) on Amine Sorbents by Transient Infrared Studies of Adsorbed CO sub(2) and C sub(6)H sub(6)

CO sub(2) diffusion limitations and readsorption of desorbed CO sub(2) during removal from immobilized amine sorbents could significantly reduce the effectiveness of CO sub(2) capture processes. To decouple CO sub(2) diffusion from desorption/readsorption on silica and tetraethylenepentamine (TEPA)/silica sorbents, a new transient diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) method was carried out by using benzene as a surrogate probe molecule. Comparison of the infrared intensity profiles of adsorbed CO sub(2) and Si-OH (which adsorbs benzene) revealed that slow rates of CO sub(2) uptake and desorption are a result of (i) CO sub(2) diffusion through an interconnected network produced from CO sub(2) adsorbed inside of the amine/silica sorbent pores and (ii) readsorption of CO sub(2) on the amine sites inside of the pores and at the external surface of the sorbents. High rates of CO sub(2) adsorption/desorption onto/from the immobilized amine sorbents could be achieved by sorbents with low amine density at the external surfaces and pore mouths.