Enhancing the CO2, CH4, and N2 adsorption and kinetic performance on FAU zeolites for CO2 capture from flue gas by metal incorporation technique

Various metals including alkali (Na+, K+), alkaline earth (Mg2+ and Ca2+), and transition metals (Cu2+ and Fe3+) were successfully incorporated into the structure of faujasite zeolites (X and Y) by novel post-synthesis modification method. The effect of metal-doping on the CO2, CH4, and N2 adsorption and kinetic performance in the context of flue gas carbon capture and natural gas purification was examined by four approaches; (i) the impact on structural properties was examined by XRD, FTIR, UV–visible, H2-TPR, FESEM, EDX Dot-Mapping, and BET analysis; (ii) the influence on the CO2, CH4, and N2 adsorption capacity was acquired by volumetric method up to 100 kPa at 25 °C (iii) the effect on binary CO2/CH4 and CO2/N2 selectivity was determined by the Henry constant and IAST selectivity; (iv) the micropore - macropore kinetic model was utilized to study the influence on diffusion coefficients. The dual-site Langmuir-Freundlich (DSLF) isotherm was found to be the best adaptability to the experimental isotherms data. The results showed an extraordinary increase in CO2 absorption capacity to 4.9 and 7 for KX and KY, respectively. Faujasite zeolite with a lower Si/Al ratio (zeolite X) outperforms CO2/CH4 and CO2/N2 separation performance than higher ones (zeolite Y). Among all samples, KX showed the highest CO2/CH4 and CO2/N2 IAST selectivity with values of 61 and 152 at 100 kPa, respectively, in addition to the highest diffusion coefficients for CH4 and N2. The incorporated potassium metal into the faujasite zeolites showed promising sorbents for the separation of CO2 from flue gas and natural gas streams.