Vapor-liquid Equilibrium Of Ethylene And Vinyl Acetate By Gibbs Ensemble Monte Carlo Simulation

Vinyl acetate is an important raw material of organic synthesis, and vinyl acetate ismainly produced by the technology of ethylene. The phase equilibrium data of vinylacetate system is lacking, resulting in much difficulty in the relevant development andresearch work. Gibbs ensemble Monte Carlo (GEMC) method by Towhee softwarewas used in this paper to study the phase equilibrium of vinyl acetate and ethylenesystem.Firstly, after adding bond and non-bond parameters of CHo=c(sp2) atom group tothe general TraPPE-UA force field, Gibbs ensemble Monte Carlo method was used tosimulate the phase equilibrium of pure vinyl acetate and binary system of ethyleneand vinyl acetate. The deviations between simulated and experimental values weremuch large, showing that the force field described molecular interaction incorrect andthe force field parameters should be modified.In order to modify the force field parameters, researches on charge distribution,frontier orbitals and molecular interaction for vinyl acetate were done, showing thatthe properties of the lacking TraPPE-UA force field parameters of carbon atom wasrelatively actively, and the force field parameters for the atom were crucial. Themethod of quantum chemistry was used to compute the interaction energy betweenpairs of vinyl acetates and the results were fitted to Lennard-Jones12-6function. Andthe force field parameters were modified.The modified force field was used to calculate the vapor-liquid phase equilibriumof ethylene and vinyl acetate at the temperature of303.15K and the pressure of310kPa,724kPa and1138kPa. The deviations between the simulated andexperimental values were obviously reduced. This result showed that the modifiedintermolecular non-bond parameters described the vapor-liquid phase equilibrium ofvinyl acetate system more accurately.Finally, the modified force field was used to predict the vapor-liquid equilibrium ofethylene and vinyl acetate system at atmospheric pressure and the temperature from293.15K to353.15K, providing basic data for production equipment of vinyl acetate.