Adsorption And Diffusion Of Benzene-Propylene System In Supercritical Condition In MCM-22 And Benzene In Swnts With Method Of Molecular Simulation

This thesis is made up of two relatively independent parts, i.e. adsorption and diffusion of light hydrocarbons and benzene in MCM-22 and benzene in nanotubes.Porous nano-materials and confined fluids constitute complicated systems in chemical engineering field. The fantastic phase behavior of confined fluids is an important factor to the application of porous nano-materials in chemical engeneering and other fields. In this thesis, two kinds of materials were chosen to study (i.e. MCM-22 and quasi-one dimension SWNTs). Among the microporous materials, MCM-22 zeolites are outstanding for their special characteristics and widespread used. The use of microporous materials for the alkylation of benzene with propylene to produce cumene is studied in this thesis. The strong confinement of small-diameter SWNT to benzene molecules inside and the diffusion behavior of benzene molecules within the SWNT are also studied.In the simulation of light hydrocarbons in MCM-22 zeolite, the grand canonical Monte Carlo (GCMC) method and an all-atom forcfield model are used. Pure and binary component sorption equilibria are discussed. The results show good agreement with predictions made using the Ideal Adsorbed Solution (IAS) theory. Compared with other zeolites, the selectivity of MCM-22 in binary component is higher. The systems of methane-ethane and methane-propane behave ideally within MCM-22 zeolite.The methods of grand canonical Monte Carlo and molecular dynamics are used for investing the positions of benzene and propylene adsorbed in the zeolite MCM-22 and their diffusion behavior. The energies distributions and mass distributions show that propylene molecules are adsorbed in 10-MR channels of MCM-22 by preference and most benzene molecules are in 12-MR supercages. But with increase of the mole fraction of benzene molecules in the mixture, the number of benzene molecules in 10-MR channels also increase obviously. The simulations are performed at the super critical condition of the mixture, while the mole fraction of the mixture component varies. The critical points of mixture are determined using PR equation. The adsorption results show that the mole fraction of benzene molecules is ~0.5 in MCM-22 when NC6H6/NC3H6=5/1 or 4/1 in bulk phase, indicating that the two mole fractions in mixture are better than others for alkylation of benzene with propylene to produce cumene. Then the MD simulations are employed to analyze the dynamic diffusion process of benzene and propylene in zeolite. The results show that the diffusion coefficients of benzene and propylene molecules in MCM-22 would not change significantly with the varying of the mole fraction. The grand canonical Monte Carlo method is used to adsorption of benzene molecules in single walled carbon nanotubes(SWNT) in triangle array of different diameter(0.95nm, 1.42nm, 1.89nm, 3.77nm). Benzene preferably load in the center and parallel the centre shaft of SWNT when σ=0.95nm, showing strong confinement of small-diameter SWNT. With the increase of diameter of SWNT, monolayer or multilayer benzene molecules cylindrical shell will form within it. When the diameter is 3.77nm, benzene molecules not only load in SWNT but can reach the space formed by three neighboring SWNT neighbor each other.