Phase Equilibrium Of Acetic Acid System

For a long time, the treatment of acetic-acid contained wastewater has been a technical problem that plagued many enterprises. Study of the effective separation of water and acetic acid can not only bring economic and social benefits, but also play an important role in the development of chemical separation, chemical industry and environmental protection disciplines.In industrial production, a large number of accurate and reliable data of fluid phase equilibrium are a required condition of the design, reconstruction, innovation, and choosing optimum process condition, meanwhile, in the field of chemical engineering, the measurement of fluid equilibrium data and the study of thermodynamic model is also very important content.In this study, we adopt the improved ROSE kettle to measure the VLE(Vapor-liquid equilibrium) data of acetic acid / vinyl acetate system and acetic acid / vinyl acetate / water system (immiscible region) at normal pressure. Also we protract the x-y phase diagram and the T-x-y phase diagram.When we associate and forecast the experimental data, we are faced a problem, as acetic acid is a strong associated material, the equilibrium relations are very complex that not only contained the phase equilibrium relationship between the components monomers, but also contained the relationship between associations and the chemical equilibrium between associated components and its monomers. So in the progress of association, we synthesized the two-molecule-association and three-molecule-association in the phase equilibrium. And we adopted the modified UNIQUAC equation to calculate the apparent activity coefficient of liquid phase, finally to calculate the fugacity. Meanwhile, we proofread the non-ideal property of gas phase by modified VIRIAL equation and R-K equation to calculate the real fugacity coefficient. As a result, we associated the experimental VLE data of AC(acetic acid)/VAC(vinyl acetate) system and calculated the equilibrium temperature and the composition of the two phase, also we protracted the x-y figure and T-x-y figure. By the way, we also calculated the temperature deviations and the deviations of two phase composition, and got the coefficients and of modified UNIQUAC equation. On the other hand, we forecasted the VLE data of AC/VAC/Water system by modified-VIRIAL-equation andΔu 12Δu21 modified-R-K-equation used in vapor phase and by modified-Wilson-equation and modified-UNIQUAC-equation respectively, also calculated the the average error and RMS error.The association phenomena also exited in liquid-liquid phase equilibrium system, so in this investigation we measured the LLE(Liquid-liquid equilibrium) data of n-decane/AC/water system, vacuum residue(n-decane solution)/AC/water system at 30℃,50℃,70℃and drew the curve of AC distribution coefficients in oil and water phases.