Enhancement of CO2/CH4 Adsorptive Selectivity by Functionalized Faujasite Zeolite

In this work, we have modified a synthesized Y-type zeolite (Si/Al = 2.5), with three different amines to investigate the influence of adsorbent’s surface modification on CO2 selectivity over CH4. The pristine and amine-functionalized NaY zeolites were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) analysis, and N2 adsorption. The results showed that the structure of zeolite was preserved after amine modification. The adsorption capacity of CO2 and CH4 on these adsorbents was measured by the volumetric method at 298 K and 348 K. In comparison to CH4, CO2 was preferentially adsorbed on these adsorbents. the results demonstrated that incorporation of amines into zeolites structure improved significantly the selectivity towards carbon dioxide so that the optimal selectivity of CO2 over CH4 reached to 4.04 on zeolite modified with 2-methylaminoethanol at 348 K. Chemical interaction between adsorbate and sorbents as well as the steric effects were assessed to be the main reasons of high selective adsorption of carbon dioxide on amine-functionalized zeolites. Two of the most common adsorption models, the Langmuir and Sips isotherms, were used to correlate the experimental data of CO2 adsorption on the adsorbents The results revealed that the amine-functionalized NaY zeolites could be a good sorbent for use in flue and natural gas separation processes.