Binary vapour-liquid equilibria for oxygen-containing compounds.

In this study, there was a need for VLE data for systems of oxygen-containing organic compounds. Experimental VLE data are presented for the following binary systems: a) 2-propanone (1) + 2-butanol (2) at 333.15K, 353.15K and 373.15K b) 2-propanone (1) + n-propanoic acid (2) at 333.15K, 353.15K and 373.15K c) 1-propanol (1) + n-butanoic acid (2) at 333.15K and 353.15K A test system (cyclohexane + ethanol at 323.15K) was measured to confirm the accuracy of the method and apparatus. With the exception of the test system, data for all the other binary systems investigated in this study are currently not available in the open literature. The dynamic recirculating stills of Joseph (2001) and Reddy (2006) were utilised to undertake the measurements. The experimental vapour pressure data measured in this study and the results obtained for the highly non-ideal test system were in excellent agreement with the literature data. It was thus concluded that the apparatus and operating procedures used were capable of producing highly accurate VLE data and confidence in the new data measured was obtained. Thermodynamic consistency testing was performed on the experimental VLE data using the point test (Van Ness et al., 1973), which provided an indication of the data’s quality and reliability. The data were thereafter subjected to data correlation to enable interpolation of the data and extrapolation to conditions other than those measured. Appropriate thermodynamic models (taking into account vapour-phase association in particular) were correlated to the data using the combined approach to VLE ( - method). For the calculation of the fugacity coefficients, three methods were used viz. the virial EOS and the Hayden-O’Connell correlation (1975); chemical theory and the Nothnagel et al. Formulation (1973); and the VPA/IK-CAPE EOS (Abbott and Van Ness, 1992). Three activity coefficients models were also used viz. the Wilson (1964) model; the NRTL model (Renon and Prausnitz, 1968); and the UNIQUAC model (Abrams and Prausnitz, 1975). In general, the models fitted the data well and the model parameters that were acquired are included. Theoretical developments involving associating components are ongoing.