The grand canonical ensemble Monte Carlo simulation is used for investigating the adsorption, heat of adsorption and distributions of thiophene and benzene on MFI and MOR type zeolites. The calculated amount absorbed of thiophene on MFI is good agreement with the experimental data at high ratio of Si/Al. The calculated results show the amount absorbed of thiophene on MFI is much more than that on MOR under coequal conditions. The distribution of the thiophene over various channels for MFI shows adsorption capacity of the intersections of straight and zig zag channels appears preferable to the other channels. The 12-membered ring channels for MOR accommodate all thiophene molecules; however, in the other channels, the density of distribution of thiophene molecules is very low. Binary systems were studied to understand the siting and segregation of the molecules. We found that the thiophene/benzene system obeys the competition classification, because both species prefer the intersections. In this case the thiophene adsorbs more strongly, pushing benzene into the zig zag channels. (c) 2006 Elsevier B.V. All rights reserved.