CO2 and N2 adsorption in alkali metal ion exchanged X-Faujasite: Grand canonical Monte Carlo simulation and equilibrium adsorption studies

• Published in: Microporous and mesoporous materials 2012-11, Vol.162, p.143-151
• Main Authors: Pillai, Renjith S., Peter, Sunil A., Jasra, Raksh Vir
• Format: Article
• Language: English
• Subjects: Adsorption; Alkali metal cation exchange; Chemistry; Colloidal state and disperse state; Exact sciences and technology; Flue gas; General and physical chemistry; Grand canonical Monte Carlo simulation; Ion-exchange; Porous materials; Surface physical chemistry; Zeolite X; Zeolites: preparations and properties
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2011.12.039

The adsorption capacity of CO2 in alkali metal ion exchanged zeolites increased on increasing cationic radius, whereas for N2 the adsorption capacity decreased on increasing extra framework cationic radius. These adsorption capacities are depended on the shielding effect of the initially adsorbed molecules in the zeolite cavity and also the basicity of the zeolite framework. [Display omitted] ► CO2 and N2 adsorption in zeolite X by GCMC calculations and experimentally. ► CO2 adsorption increases with increase in extra framework cation radius. ► The basicity of the zeolite framework influences the CO2 adsorption capacity. Adsorption of CO2 and N2 was studied in alkali metal cation exchanged zeolite X samples experimentally as well as theoretically employing volumetric measurements and grand canonical Monte Carlo simulation respectively. Adsorption capacities for CO2 in the cation exchanged samples were observed to be higher compared to those for N2. CO2 adsorption capacities per unit cell were observed to increase with ion exchange from lithium to cesium in alkali metal series, whereas these were observed to decrease for N2. The isosteric heat of adsorption data reflect stronger interactions of CO2 and N2 molecules with alkali metal cation exchanged zeolite X following the order of the electronegativities of exchanged cations. Simulation of adsorption isotherms of CO2 and N2 showed that the adsorbed molecules were located in the proximity to the extra framework alkali metal cations inside the super cage of zeolite X. Simulated adsorption isotherms and heats of adsorption data for both CO2 and N2 in alkali metal cation exchanged zeolite X match reasonably well with the experimental values particularly at initial adsorbate concentrations.