Adsorption separation of CO2/CH4 on the synthesized NaA zeolite shaped with montmorillonite clay in natural gas purification process

In this study, the effects of parameters such as crystallization time and temperature on the phase and morphology of NaA zeolite prepared by hydrothermal method were investigated. The textural properties of the synthesized zeolites were characterized using XRD, SEM, FTIR and BET analyses. The findings revealed that the optimum time and temperature of NaA preparation to be 20 h and 363 K, respectively. The adsorption experiments of CO2 and CH4 by synthesized and commercial NaA zeolites were carried out at three temperatures (277, 290 and 310 K) for pressures up to 10 bar. The experimental data were analyzed using Langmuir and Sips equations, and the Sips model better described the experimental data. It was found that the synthesized NaA had BET specific surface area of 222.8 m2 g-1 and pore volume of 0.096 cm3 g-1. Also, the adsorption capacities of 5.2 and 2.6 mmolg−1 were obtained for CO2 and CH4 by the synthesized samples, respectively. Comparing with commercial sample, the synthesized zeolite showed higher adsorption capacities for CO2 and CH4 under the same condition. The heat of adsorption at zero coverage of CO2 and CH4 on the synthesized NaA zeolite were found to be 48.5 and 24.4 kJ mol-1, respectively. The ideal CO2/CH4 selectivity of the synthesized and commercial zeolites were 7.1 and 6.4, respectively, at atmospheric pressure and 290 K. The dynamic adsorption experiments of CO2/CH4 gas mixture confirmed that the synthesized NaA zeolite had more promising performance for the separation of CO2/CH4 compared to the commercial zeolite.