Amine Modification of Binder-Containing Zeolite 4A Bodies for Post-Combustion CO₂ Capture

In the current study, a new type of composite adsorbent was synthesized by amine modification of binder-containing zeolite 4A bodies and its potential application in the post-combustion CO₂ capture was evaluated. A wide range of aliphatic straight chain amines such as propylamine (PA), butylamine (BA), pentylamine (PEA), and their respective branched chain amines, iso-propylamine (IPA), iso-butylamine (IBA), and iso-pentylamine (IPEA), were used in a smaller fraction to modify binder-containing zeolite 4A bodies. The synthesized materials were characterized by various spectro-analytical techniques to elucidate the effect of amine modification on physicochemical properties of binder-containing zeolite 4A bodies and its reactivity for CO₂ capture. Among all of the studied hybrid adsorbents, the iso-butylamine-modified binder-containing zeolite 4A bodies (IBA-Z4A) exhibited excellent CO₂ adsorption performance with a maximum adsorption capacity of 2.56 mmol g^–1 at 25 °C and 1 bar of pressure. Notably, IBA-Z4A also demonstrated excellent purity (98%) and remarkably high CO₂/N₂ selectivity (335) as compared to the pristine binder-containing zeolite 4A bodies (24). Such enhanced CO₂ adsorption capacity and high CO₂/N₂ selectivity values for IBA-Z4A can be attributed to the symbiotic interactions between CO₂ and amines governed by the basicity, electron density at the N atom of amines, and the steric effect of adsorbing molecules (CO₂ and N₂) at the adsorbent surface. Notably, IBA-Z4A also displayed a marginal isosteric heat of adsorption for CO₂ (51 kJ mol^–1) along with the encouraging thermochemical cyclic stability over five consecutive CO₂ adsorption–desorption cycles at 25 °C and 1 bar, believed to be the best suited for post-combustion CO₂ capture.