In this work, we demonstrate the efficiency of force field energy minimization technique to study the adsorption and diffusion behavior of large molecules inside the micropores of zeolites. Molecular modeling studies for diffusion of alkylbenzene molecules, namely, ethylbenzene, p-diethylbenzene, isobutylbenzene, and o-, m-, and p-isobutylethylbenzene in various zeolites, such as faujasite, zeolite L, mazzite, and mordenite, indicate that mordenite is a good catalyst for selective synthesis of p-isobutylethylbenzene. The periodic variations of interaction energy between the molecules and zeolite framework in the calculated diffusion energy profiles are used to predict the energy barrier for diffusion. Force field energy minimization calculations for the cage to cage diffusion of the alkylbenzenes in faujasite show no significant diffusional energy barrier for any of the molecule. Zeolite L shows a very small selectivity toward p-isobutylethylbenzene which is due to a rapid change in minimum energy configuration as the molecules diffuse along the pore. In the case of mazzite, a high diffusional energy barrier is observed for o-isobutylethylbenzene compared to m-and p-isomers. Calculations of the diffusion energy profiles for the molecules in mordenite show that there is negligible energy barrier for the diffusion of p-isobutylethylbenzene, whereas an energy barrier of 17.95 kJ/mol exists for diffusion of m-isobutylethylbenzene and a significantly large energy barrier of 95.69 kJ/mol exists for o-isobutylethylbenzene. Thus, the efficiency of shape selective production of p-isobutylethylbenzene in these zeolites will be in the order faujasite similar to zeolite L < mazzite < mordenite. The adsorption of the molecules in general are energetically favorable when the alkyl groups have maximum interaction with the surface of the zeolite pores.