Vapor-liquid Phase Equilibrium Simulation For N-formylmorpholine Extractive Distillation System

To obtain high purity aromatic products, the vapor-liquid equilibrium data ofextraction agent with aromatic or non-aromatic compounds are important basicinformation in the design and optimization process of aromatic extractive distillation.In order to get vapor-liquid equilibrium data, experiment is a conventional method.N-Formylmorpholine is commonly used as a distillation agent in the extractivedistillation, its boiling point is largely different from C6~C8aromatic andnon-aromatic compound, so it is difficult to measure the vapor-liquid equilibrium datausing experiment method. Molecular simulation is a modern approach for predictingthe vapor-liquid phase equilibrium of pure fluids and mixtures. And Gibbs EnsembleMonte Carlo method become more and more important in the vapor-liquidequilibrium data calculations by ignoring the chemical potential and the phaseboundary.Force field is the key factor in the Gibbs Ensemble Monte Carlo method. Theaccuracy of the simulation depends on the force field function and parameters.N-Formylmorpholine is a cyclic molecule, compared to the chain molecules, it ismore difficult to obtain the complexity force field parameters. Therefore the methodto get vapor-liquid equilibrium data of cyclic compound by using computer is still inits fancy.For the purpose of solving the problem of lacking parameters forN-formylmorpholine in the TraPPE-UA force field?the dihedral angle and chargeparameters are calculated by quantum chemistry method, together with the migratingparameters from the literature?the force field for N-formylmorpholine is constructed.The newly constructed force field is then used to calculate the vapor-liquid phaseequilibrium of N-Formylmorpholine/hexane binary system. The simulation resultsconfirm that the new force field and the simulation methods for N-formylmorpholine/hexane binary system are applicative.Through the electronic property analysis of N-formylmorpholine?we find thecrucial group of N-formylmorpholine in the contribution of Vander Waals interactionforce. By the method of detecting particles, the non-bonding interaction force iscalculated and the Vander Waals parameter is optimized. The quantized intramolecular parameters and modified Vander Waals parameteris used to calculate the vapor-liquid phase equilibrium of N-Formylmorpholine/hexane at the temperature of393.15K and the pressure of227.23~389.52kPa.Compared to the experimental data, the simulation results show that the new forcefield for N-Formylmorpholine can be used to describe the vapor-liquid phaseequilibrium of N-Formylmorpholine more accurately.Using the modified force field for N-Formylmorpholine, we predict thevapor-liquid equilibrium of N-Formylmorpholine/hexane, N-Formylmorpholine/benzene and N-Formylmorpholine/2,4-dimethylpentane binary system at normalpressure and expect it can play a guiding role in the design of aromatic extractivedistillation process.