Binary adsorption of benzene-ethylene in ZSM-5 under supercritical conditions has been studied by grand canonical Monte Carlo simulation.The adsorption isotherm of benzene in ZSM-5 increases at low pressures, then achieves equilibrium gradually, and decreases slightly at high pressures.Localization of benzene molecules in ZSM-5 is mainly in the interconnections of sinusoidal and straight channels covering different pressures.This observation is in agreement with the "commensurate freezing" phenomenon taking place in the interconnections of the two types of channels.In contrast, adsorption and localization of ethylene molecules are distinctly different from that of benzene.The adsorption isotherm of ethylene rises with pressure, and localization of ethylene molecules varies dramatically with pressure.Furthermore, the effect of the feed ratio of benzene/ethylene under supercritical conditions has been investigated.Simulation results indicate that the mean loading of benzene is almost unchanged, while the mean loading of ethylene decreases with the increase of the feed ratio of benzene/ethylene.The two curves of the mean loadings intersect at the feed ratio of benzene/ethylene about 3:1, which corresponds to equimolecular adsorption of benzene and ethylene in the pores of ZSM-5, and is in favor of the mechanism of alkylation of benzene with ethylene.Moreover, it is found that localization of benzene molecules is in the interconnections of two types of channels.On the other hand, localization of ethylene molecules is in the sinusoidal and straight channels, rather than the interconnections, under supercritical conditions.In addition, it is found that different feed ratios of benzene/ethylene have little effect on localizations of benzene and ethylene molecules in the pores of ZSM-5.

Key words: supercritical condition, ZSM-5, Monte Carlo simulation, mixture adsorption of benzene and ethylene