| Grand Canonical Monte Carlo(GCMC),Equilibrium Molecular Dynamics(EMD) and Quantum Mechanics were used to investigate the sorption and diffusion behavior of water, methanol ,ethanol and their mixtures in MFI membranes. We used COMPASS force field in Molecular Mechanics and Molecular Dynamics simulation, and used Density Functional Theory (DFT) method in Quantum Mechanics simulation.The permeation of ethanol/water through the silicalite membrane was taken as an example to analyze the adsorption isotherms and the adsorption sites of ethanol, water and their mixtures by using the parameters we obtained. The effect of concentration on diffusion coefficients was studied by simulation. In addition, we explained the hydrophobicity of the silicalite membrane on molecular level. Based on the adsorption and diffusion simulations, we used the permeation theory to analyze the permeability of pure water and ethanol at different activity.Then, we used Molecular Dynamics simulation to investigate the diffusion behavior of water, methanol and their mixtures in MFI membranes. In this calculation, Al substitutions were carried out at several T2 sites in the silicalite simulation cell, and we thus obtained the H-ZSM-5 structure model. We analyzed the different diffusion behavior of water, methanol in the silicalite and H-ZSM-5, and their displacements in the H-ZSM-5 as a function of the simulation time. In addition, we explained the effect of concentration and temperature on the hydrogen bonds between diffusion molecules by analyzing the radial distribution functions between molecules.At last, based on Quantum Mechanics simulation, we investigated the variations of structure, Mulliken charge and vibration frequency before and after water adsorption on three different channels in the H-ZSM-5 by using Density Functional Theory. And we obtained the order of adsorption energy is : intersectional channel> straight channel> sinusoidal channel.
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