CO2 capture performance and environmental impact of copolymers of ethylene glycol dimethacrylate with acrylamide, methacrylamide and triallylamine

Cross-linked polymer networks of ethylene glycol dimethacrylate (EGDMA) with methacrylamide (MAAM), acrylamide (AAm) and triallylamine (TAAm) were synthesised by free radical bulk copolymerisation and their CO2 capture capacities, selectivities, and environmental impacts were compared. At 273 K and CO2 pressure of 1 bar, poly(EGDMA-co-MAAM) copolymer, formed at the MAAM:EGDMA molar ratio of 0.6:1 using acetonitrile (ACN) as the diluent and azobisisobutyronitrile (AIBN) as the initiator, exhibited an adsorption capacity of 1.45 mmol/g. The CO2/N2 selectivity of this copolymer was 53 at 273 K and atmospheric pressure, with a CO2:N2 molar ratio of 15:85, while CO2 purity of the product stream was over 90%. Thermogravimetric analysis revealed high thermal stability of all synthesised polymers up to 573 K. The polymer fabricated from TAAm exhibited the lowest isosteric heat of adsorption, between 31 and 27 kJ mol-1, which could be due to the lowest nitrogen content, and low affinity of tertiary amine groups towards CO2. The life cycle assessment revealed that poly(EGDMA-co-AAm) had the lowest environmental impact followed by poly(EGDMA-co-MAAM). ACN was found to be the main environmental burden followed by methacrylic acid and allyl chloride, used in the synthesis of monomers and crosslinker, respectively.