| Acrylic acid as an organic acid used in polymer synthesis, is the important chemical raw material. Acrylic acid and its polymer products are widely used in industry. So the production and purification of acrylic acid have a very high economic efficiency. The core technologies are the patents of large chemical companies in the world. In industrial production, accurate and reliable phase equilibrium data are required in design, innovation and optimization of chemical separation process, while researching in the thermodynamics, the measurement and study of the phase equilibria is also very important content.In this study, vapor-liquid equilibrium data for water - acetic acid, water - acrylic acid and acetic acid - acrylic acid binary systems were measured at 20kPa by using a circulating vapor-liquid equilibra still. Vapor-liquid equilibrium data for water - acetic acid - acrylic acid ternary system also were measured at 20kPa.Because strong association occurs in the systems containing acrylic acid and acetic acid, the fugacitiy coefficients of components in the vapor phase were calculated by Virial equation and the Hayden-O'Connell correlation. Non-ideal nature of the liquid phase, including acids'association effect were all due to be corrected in the liquid phase activity coefficients. NRTL, UNIQUAC and Wilson activity coefficient models were used for correlating the three binary VLE data, the corresponding optimal interaction parameters were calculated. Also the results of correlation were given: The temperature's average relative deviations for water-acrylic acid system were respective 0.1676%, 0.1723%, 0.1887%, the average relative deviations of water's vapor composition were repective 8.9364%, 8.9419%, 9.1846%; the temperature's average relative deviations for water-acetic acid system were respective 0.0894 %, 0.09419%, 0.1084%, the average relative deviations of water's vapor composition were repective 3.6023%, 4.3298%, 4.2238%; The temperature's average relative deviations for acetic acid-acrylic acid system were respective 0.0907%, 0.0897%, 0.0929%, the average relative deviations of acetic acid's vapor composition were repective 2.7996%, 2.7663%, 2.7381%.Finally, with the binary interaction parameters, respectively, NRTL and UNIQUAC activity coefficient models , VLE data of water - acetic acid - acrylic acid ternary system at 20kPa were predicted and compared with experimental data: The temperature's average relative deviations were respective 0.92%,1.00%; the average relative deviations of water's vapor composition were repective 10.64%,11.11%; the average relative deviations of acetic acid's vapor composition were repective 11.79%,13.21%; the average relative deviations of acylic acid's vapor composition were repective 20.17%,20.60%. The prediction showed satisfactory results, which can provide the reliable thermodynamic data for process improvement of acrylic acid's purification. |
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