Abstract: Using the configurational bias Monte Carlo (CBMC) simulation method, the adsorption behavior of n-heptane on MFI type zeolites (ZSM-5) was systematically studied. Over a wide temperature range (303—623 K) and pressure range (0.5—10 kPa), adsorption isotherms, isobars, adsorption heat, and adsorption site distributions were examined. The results indicate that n-heptane adsorption on MFI type zeolites follows the dual Langmuir adsorption isotherm model. At low pressures, the interactions between molecules and the framework are strong, and the adsorption amount rises rapidly. With increasing temperature, the adsorption amount decreases significantly, and the distribution of adsorption sites undergoes a configurational change. Heat of adsorption analysis shows that at low temperatures adsorption is influenced by intermolecular cooperative effects, whereas at high temperatures it is mainly controlled by the framework potential field. Especially under high temperature conditions of 623 K, n-heptane molecules exhibit pronounced shape-selective adsorption characteristics, preferentially occupying straight channels with smaller spatial hindrance and deeper potential wells, while the adsorption density in sinusoidal channels is very low. This study systematically elucidates the mechanism by which temperature and pressure affect the adsorption capacity and spatial distribution of n-heptane on MFI type zeolites, deepening the understanding of alkane adsorption behavior within zeolite channels and providing a theoretical basis for the optimized design of related adsorption separation and catalytic processes.

Key words: configurational biased Monte Carlo, n-heptane, MFI type zeolite, adsorption, dual Langmuir adsorption isotherm model