Molecular Dynamics Simulation Of Adsorption And Separation Through Zeolite Membrane

There are strong incentives for simulating, at the molecular level, the thermodynamics and dynamics of sorbed phases of pure gases or mixtures in zeolites, because oftentimes complicated experimental measurements can be guided or even replaced by a rigorously designed computer experiment. Computational techniques are the adequate methods to investigate microscopic characters of membranes and mechanisms of permeation. Particularly, molecular dynamics (MD) allows the description of the dynamic behavior of the transport mechanism. Recent development in Monte Carlo (MC) and molecular dynamics (MD) simulation techniques, coupled with the availability of high performance computing facilities, have enabled the determination of the adsorption and diffusion characteristics of a variety of molecules in different zeolites with a reasonable degree of accuracy and reliability. A molecular dynamics simulation method is an efficient tool for understanding quantitatively and qualitatively structure-property relations, elucidating the mechanisms of microscopic phenomena, and even retrieving quantitative information about zeolite-sorbate systems. Recently, it has become possible to predict the behavior of the guest molecule in membranes and the membrane performance by molecular simulation techniques.Contents and novelties of this work listed as follows:1. In the present study, we investigated the adsorption and permeation process of carbon dioxide and methane through the DDR type zeolite membrane using the MD calculations. Molecular dynamics simulations were carried out to determine the adsorption isotherm and permeation mechanism including self-diffusivities of CH₄ and CO₂ both for pure components and in 50-50 mixtures for a range of molar loadings DDR zeolites. The phenomenon that sorption energy distribution with loading was referred to explain the mechanism of adsorption and permeation of guests through zeolites, which is the first novelty. The model of single gases adsorbed in DDR membrane can be described by Langmuir theory veraciously. Adsorption on the DDR membrane is favorable for CO2 in their equal mixture. All the quantities agreements of parameters obtained from simulation can prove that the parameters and the model of adsorption are feasible in the sorption simulation.2. The effect of the crystal axial tropism to the separate selectivity on CO₂/CH₄ binary was researched. The diffusion of CO₂ and CH₄ was contrasted follow the three directions XYZ in DDR membrane, the results prove that, CO₂ was propitious to diffused in the X direction; however, it has the feebleness in the Z direction. Correspondingly, CH₄ has the least diffusivity in the X direction. Thereby, the DDR membrane has a good separate performance in the X direction for CO₂/CH₄ binary.3. In this paper, we try to model the intracrystalline region structure of zeolite, and apply molecular dynamics (MD) and Monte Carlo (MC) simulation techniques to investigate the effect of intracrystalline region structure on the diffusivity and adsorption parameter for ethanol/water in silicalite. We focused on the effect of the intracrystalline region on sorption and permeation properties. The self-diffusion coefficients of ethanol and water in the pure are also estimated by molecular dynamic in the intracrystalline model. These results indicate the importance of considering the effect of an intracrystalline region on the permeability in zeolite membranes.