High-Pressure Vapor-Liquid and Vapor-Liquid-Liquid Equilibria in the Carbon Dioxide + 1-Nonanol System Catinca Secuianu, Viorel Feroiu, Dan Geană Dept. of Applied Physical Chemistry and Electrochemistry Introduction Thermodynamic knowledge of the high-pressure phase behavior of carbon dioxide + alcohol mixtures is essential for the design and implementation of many chemical and biotechnological processes. In this work the fluid phase behavior of the binary system carbon dioxide + 1-nonanol has been measured. The experimental data were modelled with the SRK-EOS coupled with the Huron-Vidal infinite dilution (HVID) mixing rules and with the MHV2-UNIFAC ‘87. Experimental work Phase behavior measurements were made in a high-pressure visual cell with variable volume based on the static-analytical method. A detailed description of the apparatus and experimental procedure was presented in an earlier paper [1]. Vapor-liquid and vapor-liquid-liquid equilibria data for the carbon dioxide + 1-nonanol system at , , , and K up to bar were determined. The three-phase equilibrium data and the upper critical endpoint were measured. Modelling The Soave-Redlich-Kwong (SRK) equation of state coupled with the Huron-Vidal infinite dilution (HVID) mixing rules [2] was used to predict the complex phase behavior (Critical curve, LLV line, isothermal VLE, and VLLE). The SRK-MHV2-UNIFAC ’87 model was applied to predict the VLE at constant temperatures. Results Conclusions References [1] Secuianu, C., Feroiu, V., Geană, D., J. Chem. Eng. Data 48 (2003) 1384 [2] Feroiu, V., Geană, D., Fluid Phase Equilib., 120 (1996) 1 [3] Scheidgen, A., Ph. D. Thesis, Ruhr University, Bochum (1997) [4] Secuianu, C., Feroiu,V., Geană, D., J. Chem. Eng. Data 49 (2004) 1635 [5] Secuianu, C., Ph. D. Thesis, Politehnica University, Bucharest (2004) Some experimental results are presented in the table and the figures below. The calculated curves are also included. A visual high-pressure variable volume static-analytic apparatus was used to obtain VLE and VLLE data. As also confirmed by the measurements of Scheidgen, the phase behavior of the mixture of carbon dioxide + 1-nonanol can be attributed to type III. The SRK/HVID model is successful in modeling qualitatively the complicated topology of the phase behavior of the system under study. The presented system in this work is a part of an extended study about binary mixtures containing carbon dioxide + alcohols [1, 4-5]. P-T fluid phase diagram of carbon dioxide (1) + 1-nonanol (2) P-T projection of the three phase curve Pressure-composition data for carbon dioxide + 1-nonanol at K Pressure-composition data for carbon dioxide (1) + 1-nonanol (2) Experimental results and correlations with SRK/HVID EOS Experimental results and predictions with SRK/MHV2-UNIFAC EOS Table 1. Experimental and calculated temperatures-compositions of the three-phase curve The experimental fluid phase behavior of the carbon dioxide + 1- nonanol shows that the system presents a type III phase diagram. VLE data at temperatures between and K were correlated with SRK/HVID and a linear dependence of the HVID parameters with the inverse temperature was obtained. The values of HVID parameters from the linear correlation were used to predict VLE, VLLE, critical curve, and LLV line. The topology of phase behavior is reliable predicted. Constant values of the parameters with the temperature were also tested. The predictions of VLE with SRK-MHV2-UNIFAC show a significant disagreement with the experimental data.