Ternary mixtures phase equilibrium, distillation

Similar patterns of behavior can be observed in reactive distillation columns or other integrated reaction separation processes with fast reversible reactions [11, 23] as illustrated in Fig. 5.3 for a pure rectifying column with a ternary mixture and a reaction of type 2B A + C taking place in the liquid phase. However, due to the reaction equilibrium the profiles consist of a single concentration front, which is clearly different from the nonreactive problem illustrated in Fig. 5.2. 

A residue curve map (RCM) consists of a plot of the phase equilibrium of a mixture submitted to distillation in a batch vessel at constant pressure. RCM is advantageous for analyzing ternary mixtures. More exactly, a residue curve shows explicitly the evolution of the residual liquid of a mixture submitted to batch distillation. 

In this study, the phase equilibrium in the binary mixtures that are expected to be found in the flash distillation was modeled with the Predictive Soave-Redlich-Kwong (PSRK) equation of state [4], using modified molecular parameters r and q. Five binary ethanol + congener mixtures were considered for new yield values for parameters r and q. The congeners considered were acetic acid, acetaldehyde, furfural, methanol, and 1-pentanol. Subsequently, the model was validated with the water + ethanol binary system, and the 1 -pentanol + ethanol + water, 1-propanol + ethanol + water, and furfural + ethanol + water ternary systems. 

As illustrated throughout this section, process simulators have extensive facilities for preparing phase-equilibrium diagrams T-x-y, P-x-y, x-y,... ), and residue curve maps and binodal curves for ternary systems. In addition, related but independent packages have been developed for the synthesis and evaluation of distillation trains involving azeotropic mixtures. These include SPLIT by Aspen Technology, Inc., and DISTIL by Hyprotech (now Aspen Technology, Inc., which contains MAYFLOWER developed by M.F. Doherty and M.F. Malone at the University of Massachusetts). 

For their negligible vapor pressure and low toxicity, ILs are, in theory, an excellent alternative for being used for the extraction of aromatic compounds by means an environmental friendly procedure and where the distillation step is not required. In 2001, Azko Novel patented a procedure for the extraction of an aromatic compound from an aliphatic phase using ILs (Shyu et al, 2001). To this point many papers have been published about studies of liquid-liquid equilibrium in mixtures of aliphatic and aromatic hydrocarbons (Letcher et al., 2003, Letcher et al., 2005) and in the last years Spanish researchers have focused in these equilibria and in physicochemical aspects of two ternary systems comprising aliphatic/aromatic/ILs compounds (a-e. Gonzalez et al., 2010, a- b. Pereiro et al., 2009, a-c. Arce et al., 2009, a-b. Arce, 2008, Alonso, 2008, a-b. Garcia et al., 2008, Garcia et al., 2010, a-b. Pereira, et al., 2010). 

This study was undertaken to obtain the necessary vapor-liquid equilibrium data and to determine the distillation requirements for recovering solvent for reuse from the solvent-water mixture obtained from adsorber regeneration. Previous binary vapor-liquid equilibrium data (2, 3) indicated two binary azeotropes (water-THF and water-MEK) and a two phase region (water-MEK). The ternary system was thus expected to be highly nonideal. 

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