Computing adsorption isotherms for benzene, toluene, and p-xylene in heulandite zeolite

When computer simulations were performed in the grand canonical ensemble, a dsorption isotherms for benzene, toluene, and p-xylene in Heulandite zeolit e were constructed. Nitrogen adsorption was simulated to test a feasible co mputational strategy. Simulations were performed at three temperatures (200 , 298, and 473 K), at pressures ranging from 0 to 200 kPa, and at water con tents ranging from 0% to 4%, It was found that the adsorption of the organi c species was not significantly affected by increasing the pressure over 10 kPa. Also, increasing the water content of the zeolite reduced the adsorpt ion of these aromatics significantly. On the other hand, as the temperature was increased the amount of adsorbed material was only slightly affected. To access adsorption selectivity information, various mixtures of the aroma tics were studied. Results from the simulations show that adsorption of ben zene was higher than that of toluene, and toluene adsorption was higher tha n that of p-xylene. A relation between the electronic environment; of the m olecular species and the amount of adsorbed material was established. The r esults obtained are compared with experimental data available on other synt hetic and natural zeolites.