Molecular simulation of characteristics for water adsorption on ZSM-5 type zeolite doped by lithium ion

The grand canonical assemblage Monte Carlo (GCMC) method was used to calculate the adsorption heat of HZSM-5 zeolite. The results are in good agreement with the experimental data reported in the literature. Then the adsorption isotherms of water by Li+ exchanged ZSM-5 zeolite were simulated. Based on these facts, adsorption of water on LinZSM-5 zeolite with various molar ratios n(Si)/n(Al) is predicted. The simulation results indicate that the n(Si)/n(Al) ratio of the zeolite framework greatly affects the water adsorption and adsorption isotherms. The adsorption amount decreases as the n(Si)/n(Al) ratio increases, and the free volume is even greater. The adsorbed water molecules are located around Li cations and Al atoms on the zeolite framework and a main sorption site for water in LinZSM-5 zeolite. The ZSM-5 zeolite modified by Li cations can decrease the isosteric heat effectively. At the same loading, the adsorption heat decreases as the n(Si)/n(Al) ratio increases.