Development of polystyrene adsorbents functionalized with heterocyclic ligands for selective adsorption of CO2 from CH4 and N2

• Synthesis of novel functionalized polystyrene adsorbents with multiple sites for interaction with CO2.
• The six member aromatic heterocyclic ligands functionalized polystyrene adsorbents show enhanced separation factors as compared to aliphatic and saturated heterocyclic functionalized polystyrene adsorbents.
• Lewis acid–Lewis base interaction is prominent mechanism for separation of CO2 from CH4 and N2.

Equilibrium adsorption studies of CO2, CH4 and N2 were carried out with polystyrene based adsorbent, functionalized with heterocyclic ligands, viz. citrazinic acid (CA), 4-hydroxymethyl pyridine (MP) and 2,6-bis-imidazo-1-yl-pyridine-4-carboxylic acid (BIMP) using batch adsorption and pulse chromatography technique. The equilibrium uptakes of CO2, CH4 and N2 for all the adsorbents were determined at atmospheric and high pressures. The equilibrium adsorption constants and selectivities were estimated by fitting of experimental chromatograms obtained from pulse chromatography studies into linear equilibrium dispersive chromatography model using gPROMS. The BIMP functionalized polystyrene adsorbent showed the highest equilibrium uptake and selectivity for CO2.