Nitrogen-rich hyper-crosslinked polymers for low-pressure CO₂ capture

A series of poly[methacrylamide-co-(ethylene glycol dimethacrylate)] (poly(MAAM-co-EGDMA)) porous polymeric particles with high CO₂-philicity, referred to as HCP-MAAMs, were synthesised for CO₂ capture. The polymers with a MAAM-to-EGDMA molar ratio from 0.3 to 0.9 were inherently nitrogen-enriched and exhibited a high affinity towards selective CO₂ capture at low pressures. A techno-economic model based on a 580 MW_el supercritical coal-fired power plant scenario was developed to evaluate the performance of the synthesised adsorbents. The presence and density of NH₂ moieties within the polymer network were determined using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The thermogravimetric analysis (TGA) showed that the polymers were thermally stable up to 515–532 K. The maximum CO₂ adsorption capacity at 273 K was 1.56 mmol/g and the isosteric heat of adsorption was 28–35 kJ/mol. An increase in the density of amide groups within the polymer network resulted in a higher affinity towards CO₂ at low pressure. At a CO₂:N₂ ratio of 15:85, CO₂/N₂ selectivity at 273 K was 52 at 1 bar and reached 104 at ultra-low CO₂ partial pressure. The techno-economic analysis revealed that retrofitting a HCP-MAAM-based CO₂ capture system led to a net energy penalty of 7.7–8.0%_HHV points, which was noticeably lower than that reported for MEA or chilled ammonia scrubbing capture systems. The specific heat requirement was superior to the majority of conventional solvents such as MDEA-PZ and K₂CO₃. Importantly, the economic performance of the HCP-MAAM retrofit scenario was found to be competitive to chemical solvent scrubbing scenarios.