Methanol vapor-liquid equilibria

Such a process depends upon the difference in departure from ideally between the solvent and the components of the binary mixture to be separated. In the example given, both toluene and isooctane separately form nonideal liquid solutions with phenol, but the extent of the nonideality with isooctane is greater than that with toluene. When all three substances are present, therefore, the toluene and isooctane themselves behave as a nonideal mixture and then-relative volatility becomes high. Considerations of this sort form the basis for the choice of an extractive-distillation solvent. If, for example, a mixture of acetone (bp = 56.4 C) and methanol (bp = 64.7°Q, which form a binary azeotrope, were to be separated by extractive distillation, a suitable solvent could probably be chosen from the group of aliphatic alcohols. Butanol (bp = 117.8 Q, since it is a member of the same homologous series but not far removed, forms substantially ideal solutions with methanol, which are themselves readily separated. It will form solutions of positive deviation from ideality with acetone, however, and the acetone-methanol vapor-liquid equilibria will therefore be substantially altered in ternary mixtures. If butanol forms no azeotrope with acetone, and if it alters the vapor-liquid equilibrium of acetone-methanol sufficiently to destroy the azeotrope in this system, it will serve as an extractive-distillation solvent. When both substances of the binary mixture to be separated are themselves chemically very similar, a solvent of an entirely different chemical nature will be necessary. Acetone and furfural, for example, are useful as extractive-distillation solvents for separating the hydrocarbons butene-2 and a-butane. 

You want to separate methanol and water into a distillate containing 90 mol% methanol and a bottoms containing 5 mol% methanol. Vapor liquid equilibrium data for ... 

Figure 15 shows results for a difficult type I system methanol-n-heptane-benzene. In this example, the two-phase region is extremely small. The dashed line (a) shows predictions using the original UNIQUAC equation with q = q. This form of the UNIQUAC equation does not adequately fit the binary vapor-liquid equilibrium data for the methanol-benzene system and therefore the ternary predictions are grossly in error. The ternary prediction is much improved with the modified UNIQUAC equation (b) since this equation fits the methanol-benzene system much better. Further improvement (c) is obtained when a few ternary data are used to fix the binary parameters. 

Application of the algorithm for analysis of vapor-liquid equilibrium data can be illustrated with the isobaric data of 0th-mer (1928) for the system acetone(1)-methanol(2). For simplicity, the van Laar equations are used here to express the activity coefficients. 

Vapor-Liquid Equilibrium Data Reduction for Acetone(1)-Methanol(2) System (Othmer, 1928)... 

Propylene oxide is a colorless, low hoiling (34.2°C) liquid. Table 1 lists general physical properties Table 2 provides equations for temperature variation on some thermodynamic functions. Vapor—liquid equilibrium data for binary mixtures of propylene oxide and other chemicals of commercial importance ate available. References for binary mixtures include 1,2-propanediol (14), water (7,8,15), 1,2-dichloropropane [78-87-5] (16), 2-propanol [67-63-0] (17), 2-methyl-2-pentene [625-27-4] (18), methyl formate [107-31-3] (19), acetaldehyde [75-07-0] (17), methanol [67-56-1] (20), ptopanal [123-38-6] (16), 1-phenylethanol [60-12-8] (21), and / /f-butanol [75-65-0] (22,23). 

Figure 14.4 Vapor-liquid equilibrium data and calculated values for the propane-methanol system [reprinted from the Canadian Journal of Chemical Engineering with permission].

Table 14.9 Vapor-Liquid Equilibrium Data for the Methanol (l)-Isobutane...

Hong, J.H. and Kobayashi, R., "vapor-Liquid Equilibrium Studies for the carbon Dioxide-Methanol System", Fluid Phase Equilibria. 41,269-276 (1988). 

Schwartzentruber J., F. Galivel-Solastiuk and H. Renon, "Representation of the Vapor-Liquid Equilibrium of the Ternary System Carbon Dioxide-Propane-Methanol and its Binaries with a Cubic Equation of State. A new Mixing Rule", Fluid Phase Equilibria, 38,217-226 (1987). 

Other companies (e.g., Hoechst) have developed a slightly different process in which the water content is low in order to save CO feedstock. In the absence of water it turned out that the catalyst precipitates. Clearly, at low water concentrations the reduction of rhodium(III) back to rhodium(I) is much slower, but the formation of the trivalent rhodium species is reduced in the first place, because the HI content decreases with the water concentration. The water content is kept low by adding part of the methanol in the form of methyl acetate. Indeed, the shift reaction is now suppressed. Stabilization of the rhodium species and lowering of the HI content can be achieved by the addition of iodide salts. High reaction rates and low catalyst usage can be achieved at low reactor water concentration by the introduction of tertiary phosphine oxide additives.8 The kinetics of the title reaction with respect to [MeOH] change if H20 is used as a solvent instead of AcOH.9 Kinetic data for the Rh-catalyzed carbonylation of methanol have been critically analyzed. The discrepancy between the reaction rate constants is due to ignoring the effect of vapor-liquid equilibrium of the iodide promoter.10... 

Table 9. Vapor-Liquid Equilibrium Data Correlation for Methanol-Water-NaBr system at 298.15°K... 

Another type of ternary electrolyte system consists of two solvents and one salt, such as methanol-water-NaBr. Vapor-liquid equilibrium of such mixed solvent electrolyte systems has never been studied with a thermodynamic model that takes into account the presence of salts explicitly. However, it should be recognized that the interaction parameters of solvent-salt binary systems are functions of the mixed solvent dielectric constant since the ion-molecular electrostatic interaction energies, gma and gmc, depend on the reciprocal of the dielectric constant of the solvent (Robinson and Stokes, (13)). Pure component parameters, such as gmm and gca, are not functions of dielectric constant. Results of data correlation on vapor-liquid equilibrium of methanol-water-NaBr and methanol-water-LiCl at 298.15°K are shown in Tables 9 and 10. 

Kurihara, K., Takimoto, Y., Ochi, K., and Kojima, K. Vapor-liquid equilibrium data for the quaternary system acetone + chloroform-t methanol -t benzene at 101.3 kPa, J. Chem. Eng. Data, 45(5) 792-795, 2000. 

Resa, J.M., Gonzalez, C., de Eandaluce, S.O., andLanz, J. Vapor-liquid equilibrium of binary mixtures containing methanol + propyl acetate, methanol + isopropyl acetate, vinyl acetate + propyl acetate, and vinyl acetate + isopropyl acetate at 101.3... 

A procedure is presented for correlating the effect of non-volatile salts on the vapor-liquid equilibrium properties of binary solvents. The procedure is based on estimating the influence of salt concentration on the infinite dilution activity coefficients of both components in a pseudo-binary solution. The procedure is tested on experimental data for five different salts in methanol-water solutions. With this technique and Wilson parameters determined from the infinite dilution activity coefficients, precise estimates of bubble point temperatures and vapor phase compositions may be obtained over a range of salt and solvent compositions. 

A method of prediction of the salt effect of vapor-liquid equilibrium relationships in the methanol-ethyl acetate-calcium chloride system at atmospheric pressure is described. From the determined solubilities it is assumed that methanol forms a preferential solvate of CaCl296CH OH. The preferential solvation number was calculated from the observed values of the salt effect in 14 systems, as a result of which the solvation number showed a linear relationship with respect to the concentration of solvent. With the use of the linear relation the salt effect can be determined from the solvation number of pure solvent and the vapor-liquid equilibrium relations obtained without adding a salt. 

The salt effect is attributable to the formation of preferential solvation from the standpoint of molecular structure. In other words, when calcium chloride, which dissolves readily in methanol but very little in ethyl acetate, was added to the methanol-ethyl acetate system to saturation, calcium chloride formed with methanol the preferential solvate which may be written CaCl2 6CH30H. It was also shown from the observation of solubility that the solvated methanol molecules did not participate in the vapor-liquid equilibrium. 

Many papers concerning salt effect on vapor-liquid equilibrium have been published. The systems formed by alcohol-water mixtures saturated with various salts have been the most widely studied, with those based on the ethyl alcohol-water binary being of special interest (1-6,8,10,11). However, other alcohol mixtures have also been studied methanol (10,16,17,20,21,22), 1-propanol (10,12,23,24), 2-propanol (12,23,25,26), butanol (27), phenol (28), and ethylene glycol (29,30). Other binary solvents studied have included acetic acid-water (22), propionic acid-water (31), nitric acid-water (32), acetone-methanol (33), ethanol-benzene (27), pyridine-water (25), and dioxane-water (26). 

Maher, P. J., and B. D. Smith, Vapor-liquid equilibrium data for binary systems of chlorobenzene with acetone, acetonitrile, ethyl acetate, ethylbenzene, methanol and 1-pentene , J. Chem. Eng. Data, 24, 363-377 (1979). 

Jacoby, R.H., Vapor-Liquid Equilibrium Data for Use of Methanol in Preventing Gas Hydrates, in Proc. Gas Hydrocarbon. Control Conference. University of Oklahoma, Norman, OK (1953). 

Cervenkova, I., Boublik, T. (1982) Vapor pressure, refractive indices and densities at 20.0°C and vapor-liquid equilibrium at 101.325 kPa in the tert-amyl methyl ether-methanol system. Utzcht. Prague 1982—reference from Boublik et al. 1984. 

Vapor/liquid equilibrium data for the system l -dichloromethane(l)/methanol(2) at -as follows ... 

Table 3 Isothermal Vapor-Liquid Equilibrium results for Methanol-Water...

Donald F. Othmer while at Eastman Kodak during the 1920 s experimented using salts to concentrate acetic acid (14). He also developed an industrial process for distilling acetone from its azeotrope with methanol by passing a concentrated calcium chloride brine down the rectification column (15). Pure acetone was condensed overhead, and acetone-free methanol was recovered in a separate still from the brine which was then recycled. The improved Othmer recirculation still (16) has been the apparatus generally favored by investigators who have studied the effects of salts on vapor-liquid equilibrium. 

VER chart, 372 Vapor-liquid equilibrium data acetone/methanol, 416 acetone/water, 416,423 butadiene, 420... 

All calculations were carried out at T = 313.15 K. The vapor-liquid equilibrium (VLB) data for the ternary mixture and the corresponding binaries were taken from [32]. The excess volume data for the ternary mixture A,A-dimethylformamide-methanol-water and binary mixtures A, A-dimethylformamide-methanol and methanol-water were taken from [33], and the excess volume data for the binary mixture A,A-dimethylformamide-water from [34]. There are no isothermal compressibility data for the ternary mixture, but the contribution of compressibility to the binary KBls is almost negligible far from the critical point [6]. For this reason, the compressibilities in binary and ternary mixtures were taken to be equal to the ideal compressibilities, and were calculated from the isothermal compressibilities of the pure components as follows ... 

Zielkiewicz, J. Oracz, P. Vapor-liquid equilibrium in the ternary system Ai,V-dimethylformamide-methanol-water at 313.15 K. Fluid Phase Equilib. 1990, 59, 279-290. 

Hall, D. J. Mash, C. 1. Pemberton, R. C. Vapor liquid equilibriums for the systems water—methanol, water—ethanol, and water—methanol-ethanol at 298.15 K determined by a rapid transpiration method. NPL Report Chem. 1979, 95, 36. 

FIGURE 2. Solubilities of naphthalene (S is the mole fraction of naphthalene) in the mixtures a) methanol + water and b) ethanol + water. The experimental data (0) were taken from Ref. (2). The solid lines represent the solubilities of naphthalene predicted using equation M4. The Wilson constants were taken from Gmeling s vapor-liquid equilibrium compilation (2 ). Thus, the only solubilities in pure water and cosolvents were used for prediction. 

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