Study On The Vapor-liquid Phase Equilibrium Of Chain-fluids With Gibbs Ensemble Monte Carlo Simulation

Phase equilibria of liquids and their mixtures is always an issue in chemical engineering. With the development of chemical technical, molecular simulation has already been used in the computing of fluids'phase equilibrium properties. Gibbs ensemble Monte Carlo simulation is a direct computer modeling way to simulate the vapor-liquid phase equilibria of fluids. It can decrease the computing time, and it is simpler than indirect Monte Carlo simulation since the simulation way needn't compute a number of chemical potential and the simulation of vapor-liquid phase equilibria can be completed in once.In our work, Gibbs Ensemble Monte Carlo simulation has been used successfully to simulate the vapor-liquid phase equilibrium for binary systems, such as the pure component and mixtures of n-alkane and the 1-alkene at a series of pressures and temperatures by computer program—Visual Fortran95. Based on the TraPPE, NERD molecular force field models, we adjusted some Lennard-Jones parameters in the potential models of the n-alkane to calculate the short range potential energy among electric charges and the potential energy among molecules. At the same time, long-range corrections and Ewald Summation techniques have been used respectively to calculate no-charge long range intermolecular interactions and long range charge-charge interactions in the simulations.Compared to the experiment data, the simulating results have some error. Such as , the saturated vapor pressure of the ethane and propene system, our result is lower the experiment results at a percentage of 5.7% and 3.3% respectively, the result of the n-octane and 1-hexene is higher at a percentage of 16% and 15%, for the n-dodecane and 1-octadecene system, the results of boiling point overestimate at 10K. All the systems still are in good agreement with each other and the method is feasible. According to the paper, the experiences about studying the vapor-liquid phase equilibrium of more complicated hydrocarbon and the thermodynamics of more complicated mixtures has been obtained.