Determination, Modeling Correlation And Prediction For Isothermal Vapor-Liquid Equilibria Of Binary Systems

To provide the phase equilibrium data and the corresponding models for the development and simulation of the technological process in factories, and to suggest some experimental information for the theoretical improvement of models, the vapor-liquid equilibrium (VLE) of three binary systems containing hydrogen-bonding associating fluids (n-propyl acetate+ acetic acid, acetic acid+p-xylene, di-isopropyl ether+phenol) were studied in this paper.A static total pressure method was applied to measuring the vapor pressure of five pure fluids (n-propyl acetate, acetic acid, p-xylene, phenol and di-isopropyl ether) and the corresponding three binary mixtures at different temperatures and feeding compositions. The liquid and vapor phase compositions for the three binary mixtures were calculated by a modified Peng-Robinson equation of state (MPR-EoS) and activity coefficient models (NRTL, Wilson and UNIQUAC equation) combining with the mass balance equations. And the complete VLE data were obtained. The MPR-EoS was used for vapor phase, and for liquid phase it was using the activity coefficient models which show the same satisfactory calculation results.The cubic plus association (CPA) model was employed to correlate the isothermal VLE data of the three binary systems. And the calculation results were agreed with the experimental data well which means that the CPA model is fit for the systems in this work.The COSMOtherm software based on COSMO-RS model, and COSMO-SAC model developed from COSMO-RS, were both used to predict the VLE data of the three binary systems. The results predicted by COSMOtherm software combining with the ".cosmo files" from VT 2005 Sigma Profile Database or Gaussian 03 calculation, both of them can present an appearance or tendency of azeotropy for VLE, and have a certain deviation from experimental results and different prediction performance for different systems. While, the former predicted vapor pressure was always lower than that predicted by the latter. The COSMO-SAC model with the data from VT 2005 Sigma Profile Database gave satisfactory results. By the comparison between the three predictions, it was concluded that the results from COSMO-SAC model was best, and that from COSMOtherm software had a certain deviation between the predicted and experimental data, and theσ-profiles obtained from different quantum chemical calculation had an important effect on the prediction for VLE.