A recently developed dual ensemble Monte Carlo (DE-MC) simulation has been applied to the study of pervaporation of a Lennard-Jones (LJ) fluid mixture, modeled for an ethanol and water mixture, occurring in MFI-type silicalite membrane. From the simulation results for the binary system, it is indicated that ethanol LJ molecules can readily enter the membrane pore, whereas no water LJ molecules penetrate into the pore, resulting in the formation of an adsorbed phase with the silanol groups on the external surface. The molecular density profile obtained for the binary system clearly reveals the adsorption site of ethanol, and it was found that the amount of adsorbed ethanol in the membrane decreases linearly from the feed side to the vacuum side. The total extent of ethanol adsorption in the membrane pore from the binary mixture is smaller than that from the pure liquid component when the ethanol activity is the same. These observed behaviors are in qualitative agreement with experimental observations.