SO-Resistant Amine-Containing CO Adsorbent with a Surface Protection Layer.

Amine-containing solids are promising adsorbents for CO capture, but they suffer from irreversible poisoning by the highly acidic SO in flue gas. Here, we demonstrate a facile strategy to inhibit SO poisoning. We first prepared an amine-containing adsorbent by impregnating polyethyleneimine (PEI) into porous silica. The PEI located at the external surface of the adsorbent was selectively alkylated with epoxide so that amines were fully converted to tertiary amines. As opposed to that onto primary and secondary amines, SO adsorption onto tertiary amines is fully reversible. Therefore, during the flue gas adsorption, SO is reversibly captured by the tertiary-amine-rich layer and then desulfurized CO is adsorbed onto PEI beneath this layer. The resultant adsorbent showed insignificant loss of CO adsorption capacity (8.52%) even after 1000 CO adsorption-desorption cycles in the presence of 50 ppm SO, whereas conventional PEI/silica showed severe capacity loss (65.1%) due to irreversible SO poisoning.