Measurement And Study On The Density And Vapor-liquid Equilibrium For Mixtures Related PTA Process At Elevated Temperature And Pressure

Liquid densities and vapor-liquid phase equilibrium data of pure compound and their mixtures are needed for the design of chemical processes involving heat and mass transfers or fluid mechanics, and are indispensable for PTA process. This thesis is partially supported by Chinese Petroleum Chemical Engineering Company. It includes the measurement and research of density and vapor-liquid phase equilibrium data related to the production of PTA.PTA is manufactured under pressure condition. Comparing to the atmospheric pressure, it is more difficult to measure the physical properties at high temperature and pressure. The data that related to the high temperature and pressure are even scarce. In addition, as the solvent, acetic acid is an important component in the PTA process. The strong corrosion of the acetic acid makes it difficult to select and design the measurement apparatus. In this paper, a new piezometric densimeter was designed and manufactured by ourselves. The main part of this densimeter is a thick-walled glass capillary, which can resist corrosion and can bear up to 10.0MPa in pressure and 573.15K in temperature. With the densimeter, the reliability of it was confirmed with literature data. The liquid densities of p-xylene-acetic acid, o-xylene-acetic acid, and m-xylene-acetic acid were measured by this densimeter at T from 313.15K to 473.15K and p from 0.20 to 2.0MPa. Excess molar volumes were calculated by the measurement results and being fitted by the Redlich-Kister equation. A flow-type apparatus for measuring vapor-liquid phase equilibrium under high pressures was also set up. The main part of this apparatus is made by titanium, which has good corrosion resistence. The design working pressure and temperature are 10.0MPa and 573.15K. The reliable and accurate of this apparatus were also proved. The VLE data of p-xylene-acetic acid, o-xylene-acetic acid, and m-xylene-acetic acid were measured by this apparatus at T from 433.15K to 473.15K. These results provide adequate and reliable data for PTA engineering design.CPA-EOS, HBT model and ISH2 model were selected to calculate and estimated the liquid densities of xylenes-acetic acid binary mixtures under experimental conditions. The HBT model and ISH2 model were modified and used to estimate the liquid densities of xylenes-acetic acid binary mixtures. Compared to the original models, the estimation results of the two modified models are both better than the original models, especially the m-HBT model. Wilson and NRTL models were used to correlate the VLE experimental data, and the corresponding model parameters were regressed also. It can be found from the correlation results that both models can get good correlation accuracy.Interaction parameters of the A-UNIFAC model corresponding to the ACCH2-CH2 groups and ACCH2-COOH groups were obtained by fitting the experimental data. A mA-UNIFAC model was proposed based on A-UNIFAC model. The interaction parameters of the mA-UNIFAC model were also obtained by fitting the literature data. The experimental VLE data were calculated and estimated by A-UNIFAC and mA-UNIFAC models. The results show that mA-UNIFAC model has the similar calculation accuracy as A-UNIFAC model. In the aspect of predicting vapor phase compositions the accuracy of mA-UNIFAC model is better.