Binary LLE

DAT This file contains the data for each binary LLE system. 

First header Standard polymer abbreviation/Standard solvent name Second header columns  

10 Number average molecular weight of the polymer 20 Weight average molecular weight of the polymer 50 Experimental method used 

80 Year of publication (Must match columns 29-31 in SOURCES.DAT) 

LST This file has a list of binary systems in this data base. First line - total number of systems. 

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Binary liquid-liquid equilibria are usually represented as temperature-vol-ume fraction diagrams. These diagrams give the mutual solubilities in the two coexisting liquid phases, as functions of temperature. Figure 2F-3 illustrates six types of phase behavior that have been observed in binary LLE. A horizontal line intersects the phase boundary curve at two points which give the compositions of the two phases in equilibrium at the corresponding temperature. 

In the general description of LLE, any number of species may be considered, and pressure may be a significant variable. We treat here a simpler (but important) special case, that of binary LLE either at constant pressure or at reduced temperatures low enough that the effect of pressure on the activity coefficients may be ignored. With but one independent mole fraction per phase. 

Table of systems where binary LLE data were published only in graphical form as phase diagrams or related figures ... 

Figure 5.67 Observed temperature dependences of binary LLE [3] (a) 1-butanol (1)-water (2), (b) tetrahydrofuran (1)-water (2), (c) dipropylamine (l)-water (2), (d) n-hexane (l)-water (2), (e) benzene (l)-sulfur (2).

While the calculation of binary LLE can be performed graphically, the calculation of LLE for ternary and higher systems has to be performed iteratively. One possible procedure for a multicomponent system is shown in Figure 5.73 in the form of a flow diagram. The method takes into account the isoactivity conditions (Eq. (5.73)) and the material balance. 

For systems of type II, if the mutual binary solubility (LLE) data are known for the two partially miscible pairs, and if reasonable vapor-liquid equilibrium (VLE) data are known for the miscible pair, it is relatively simple to predict the ternary equilibria. For systems of type I, which has a plait point, reliable calculations are much more difficult. However, sometimes useful quantitative predictions can be obtained for type I systems with binary data alone provided that... 

Figure 16 shows observed and calculated VLE and LLE for the system benzene-water-ethanol. In this unusually fortunate case, predictions based on the binary data alone (dashed line) are in good agreement with the experimental ternary data. Several factors contribute to this good agreement VLE data for the mis-... 

Guffey and Wehe (1972) used excess Gibbs energy equations proposed by Renon (1968a, 1968b) and Blac)c (1959) to calculate multicomponent LLE. They concluded that prediction of ternary data from binary data is not reliable, but that quarternary LLE can be predicted from accurate ternary representations. Here, we carry these results a step further we outline a systematic procedure for determining binary parameters which are suitable for multicomponent LLE. 

Type B. Components 1 and 2 are only partly miscible with each other. Both 1 and 2 are completely miscible with all other components in the system (3 through m). Components 3 through m are also miscible in all proportions. Both binary and ternary data are needed for a reliable description of the multicomponent LLE ... 

LLE provided that care is taken in obtaining optimum binary para-... 

Many well-known models can predict ternary LLE for type-II systems, using parameters estimated from binary data alone. Unfortunately, similar predictions for type-I LLE systems are not nearly as good. In most cases, representation of type-I systems requires that some ternary information be used in determining optimum binary parameter. 

Mixture property Define the model to be used for liquid activity coefficient calculation, specify the binary mixture (composition, temperature, pressure), select the solute to be extracted, the type of phase equilibrium calculation (VLE or LLE) and finally, specify desired solvent performance related properties (solvent power, selectivity, etc.)... 

In the second case, where LLE are lacking, VLE data are used to fit the parameters in the UNIQUAC model. These parameters, for the three binaries, were obtained from the literature in which VLE data were given at the following temperatures ... 

The thermodynamic data needed to calculate the 1-octanol/water partitioning is the LLE in the ternary system, in binary phases ... 

The LLE of twenty binary systems containing [CglTj30ClT2-Cilm][BFJ with aliphatic hydrocarbons (n-pentane, n-hexane, n-heptane, or n-octane) and aromatic hydrocarbons (benzene, toluene, ethylbenzene, o-xylene, m-xylene, or p-xylene) were presented [78]. Also, the mixtures of [CglTj30ClT2-Qlm][Tf2N]... 

The LLE for ILs and common solvents such as alcohols is very important for developing ILs for liquid-liquid extraction processes. Previous studies in many laboratories have shown this potential. Most of the measured mixtures were of IL + short chain alcohol) binary systems. It is well known that an increase in the alkyl chain length of the alcohol resulted in an increase in the UCST. Nevertheless, the solubilities of many ILs were measured in 1-octanol (important value for the description of bioaccumulation) [14,50-54, 79,98-100,112,127,133]. The other short chain alcohols were pointed out earlier. 

In addition to the experimental results of phase equilibria, the correlation with the widely known GE models was assigned to. It was indicated by many authors that SLE, LLE, and VLE data of ILs can be correlated by Wilson, NRTL, or UNIQUAC models [52,54,64,79,91-101,106,112,131,134]. For the LLE experimental data, the NRTL model is very convenient, especially for the SLE/LLE correlation with the same binary parameters of nonrandom two-liquid equation for mixtures of two components. For the binary systems with alcohols the UNIQUAC equation is more adequate [131]. For simplicity, the IL is treated as a single neutral component in these calculations. The results may be used for prediction in ternary systems or for interpolation purposes. In many systems it is difficult to obtain experimentally the equilibrium curve at very low solubilities of the IL in the solvent. Because this solubility is on the level of mole fraction 10 or 10 , sometimes only... 

Binary System. The first task is to examine the characteristics of the 2-propanol—water-phase equilibria (VLE, LLE, SLE) to determine the compositions of interest and any critical features. 2-Propanol forms a minimum boiling azeotrope with water (80.4°C at 101.3 kPa (760 torr), 68 mol % 2-propanol). The azeotrope is between the feed and the IPA product and is a distillation boundary, thus it is impossible to obtain both desired products from any single-feed... 

As a demonstration of quantitative LLE calculations, we now consider in more detail some of the binary mixtures that we have discussed qualitatively in section 6.3. In Fig. 6.13 we see the excess Gibbs free energy of mixing Gex, the heat of mixing Hex, and the excess entropy of mixing Sex for mixtures of acetone and... 

The phase diagram for the partially miscible binaries water/2-ethylhexanol and water/lauric acid can be described satisfactorily by UNIQUAC with binary interaction parameters from LLE data plus the azeotropic point This procedure allows accurate prediction of the liquid-liquid split, while preserving sufficient accuracy for VLE. The interaction parameters are given in Tables 8.5 and 8.6. 

The binary mixture parameter has been fitted to VLE data for 29 systems its values are in Table 1. It should be noted that is independent of temperature and always very close to unity. The calculation of phase equilibria was performed by means of the algorithm of Deiters [8, 9], The reproduction of VLE data and the predictions of LLE data, of excess volumes, of virial coefficients are very good for all 29 binary mixtures investigated [3]. 

An excellent discussion of the thermodynamics of LLE systems has been given by Sorensen and Arlt (1979,1980) and Sorensen et al. (1979). The following section is adapted from these references. Consider a binary liquid mixture of + n2 moles at fixed temperature and pressure. The necessary and sufficient condition for equilibrium is that the total Gibbs free energy of mixing, AG, for the mixture is a minimum with respect to all possible changes... 

Binary and ternary polymer-solution LLE data may be correlated using any of the models described in Section 3 and the methods for computing LLE compositions and estimation of parameters presented in Sections 4 and 5. 

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