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

Adsorption of CO2 and N-2 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 N-2. 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 N-2. The isosteric heat of adsorption data reflect stronger interactions of CO2 and N-2 molecules with alkali metal cation exchanged zeolite X following the order of the electronegativities of exchanged cations. Simulation of adsorption isotherms of CO2 and N-2 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 N-2 in alkali metal cation exchanged zeolite X match reasonably well with the experimental values particularly at initial adsorbate concentrations. (C) 2012 Elsevier Inc. All rights reserved.