Effect of nitrogen group on selective separation of CO2/N2 in porous polystyrene

•Successful modification of porous poly-styrene by doping nitrogen groups.•Illustration of the effect of nitrogen group on CO2 adsorption.•A linear correlation of CO2/N2 selectivity with nitrogen content.•A new performance parameter for adsorbent selection and evaluation.

Hyper-crosslinked porous polystyrene adsorbents were successfully synthesized from 4-nitrobenzyl chloride using the Friedel–Crafts alkylation reaction. These porous polymer samples were characterized by SEM, TEM, FT-IR and TGA for their morphology, surface functionality and thermal stability. Nitrogen adsorption and desorption at 77 K were used for characterizing their pore textural properties. The adsorption properties of CO2 and N2 were determined volumetrically at 298 K and gas pressures up to 10 bar. The experimental results showed that the porous polymer adsorbents have a relatively high N-content (up to 1.05%), a large BET surface area (up to 1275 m2/g) and a large pore volume (up to 1.338 cm3/g). It was observed that both pore texture and N-content in the porous polymers are equally important for adsorbing CO2. The equilibrium selectivity for CO2/N2 separation on the five samples is well correlated with the N-content and micropore volume percentage in the polymers, and the N-content strongly affects the adsorbent selection parameter. Adding N-functional group in porous polymer adsorbents is an effective way for improving their capability for CO2/N2 separation. Using the CO2 adsorption capacity alone is not sufficient for evaluating adsorbents, and the adsorbent selection parameter is calculated to screen adsorbents for CO2 capture from flue gas.

Graphical abstractEffect of nitrogen content on CO2/N2 separation selectivity.Figure optionsDownload full-size imageDownload as PowerPoint slide