Hydrophobic functionalized amine-impregnated resin for CO2 capture in humid air

Water vapor in air significantly affects the CO 2 separation performance of solid amine sorbents. Although moisture benefits the CO 2 adsorption process, the co-adsorbed H 2 O in amine sorbents leads to extra regeneration energy consumption, which challenges the application of solid amine sorbents for direct air capture. Reducing H 2 O adsorption and improving the CO 2 /H 2 O selectivity of solid amine sorbents are fundamental solutions. This work clarified the more prominent hydrophilic contribution of polyethylenimine (PEI) layers than support resins for amine-impregnated sorbents. Then, we identified the phenyl group as the preferred additive to enhance the hydrophobic properties of PEI-impregnated sorbents using an orthogonal test. The introduction of hydrophobic phenyl groups reduced the average water vapor adsorption per amine group by more than 50% and increased the CO 2 /H 2 O selectivity of the amine resin sorbents by 68%–89%, resulting in lower heat requirement caused by H 2 O desorption. Despite the modification reduced CO 2 uptake, a modest CO 2 capacity of 1.47–1.6 mmol/g was detected of BZ13.5–40%R20 in a representative air condition (28 °C, relative humidity 50%). In addition, BZ13.5–40%R20 showed stable CO 2 capacity in 10 consecutive temperature swing adsorption cycles (desorption at 70 °C, N 2 stripping) in laboratory.