Calculation aqueous ethanol mixtures

The use of digital computers to carry out complete calculations in the design of separation processes has been the goal of many. To do this effectively, suitable methods for phase equilibria and tray-to-tray distillation calculations are required. Results calculated by the application of such methods to dehydrate aqueous ethanol mixtures using ethylene glycol as the extractive distillation solvent is discussed below. A brief review of the methods used for phase equilibria and enthalpies is followed by a discussion of the results from distillation calculations. These are compared for extractive distillation with corresponding results obtained by azeotropic distillation with n-pentane. 

Calculations for the extractive distillation of aqueous ethanol mixtures containing 85.64% m ethanol have been carried out with the aid of a UNIVAC 1108 computer. The computer program calculates all phase equilibria and tray-to-tray material and heat balances for each component... 

A sample calculation is given showing the use of the program to calculate the azeotropic distillation of aqueous ethanol mixtures using the entrainer n-pentane (KNTRL 2, Option 7). 

The limiting conductivity of the standard electrolyte El in pure solvent A, A i = (Xg = 0), and the coefficients a and b for some representative examples of water-rich and cosolvent-rich mixtures are shown in Table 6.4. The values for other electrolytes E2 may then be calculated from Equations 6.3. The standard deviations in the limiting conductivities calculated according to Equation 6.4 do not exceed 3 S-cm mol". As an illustration, the Agj = (Xg) values of numerous electrolytes E2 referred to E1 = KC1 in aqueous ethanol mixtures according to Equation 6.3 are shown in Figure 6.2. Up to single curve is obtained. 

J- for Hydroxide Solutions in Aqueous Ethanol. From the pK2(H20) values and values of log CArCH(OH)cr/CArCHO a a given Coh- in a given solvent mixture, it is possible to calculate J- values for the solvent mixture under consideration using Equation 1 where pKw is the autoprotolytic constant of water and pK2(H20) is inserted for pK2- This definition expresses J values with reference to a standard state in pure water, and therefore basicities of sodium hydroxide solutions in mixed solvents can be compared to basicities of sodium hydroxide solutions in water by J values. 

Work-Up and Isolation Replace the beaker with a large dish or pan containing about 200 ml of 50% aqueous ethanol and unwind the nylon rope into the wash solution. After stirring the mixture gently, decant the wash solution, and transfer the polymer to a filter on a Buchner funnel. Press the polymer as dry as possible, and then place it in your desk until the next laboratory period. When the nylon is thoroughly dry, weigh it and calculate the yield. Note how the bulk of polymer is affected upon drying. 

A polymer(ll) solution in O.IM 15% aqueous ethanolic NaOH was made such that the polymer concentration was 0.05 g/L. To obtain a clear solution it was necessary to heat the mixture at 70-80°C or 2-3 hours. The spectrum of the clear solution was recorded and the amount of each oxime, 8 and 5, determined. From this, the molecular weight of the polymer was calculated using the equations described above. Yields of 8 and 5 were quantitative for each polymer. 

FIGURE 9A Values of hi — h°) for ethanol (species a) and water (species b) calculated from measured heats of mixing. The two sets of curves, from the lowest to the highest, correspond to 298.15, 323.15, 331.15, 343.15, 363.15, and 383.15 K. The triangles and circles are comparisons to data from another author. (From Larkin, J. A. Thermodynamic properties of aqueous nonelectrolyte mixtures, I excess enthalpy for water + ethanol at 298.15 to 383.15 K. J. Chem. Thermodyn. 7 137-148 (1975). Reproduced hy permission of the puhhsher.)... 

Kinetic solvent isotope effect as a measure of electrophilic solvent assistance to bromide ion departure limiting value Br- = 1.35 in MeOL. From h>r and kinetic data in water, methanol, ethanol and their aqueous mixtures. c( aqEtoH/ AcOH>r measurement of nucleophilic solvent assistance. Calculated from data in Ruasse and Dubois (1975) and Ruasse et al. (1978). Ruasse and Lefebvre (1984). - Ruasse and Lefebvre (unpublished results). "Ruasse (1985). 

Let us suppose that the acetic acid content of the final aqueous solution is 5%, corresponding to a ratio of approximately 1 mol of CH3COOH to 60 mol of H2O. As the yield of reaction 2.1 will be near 100% (recall that reaction 2.2 is rather exothermic, implying a very high equilibrium constant see section 2.9), the same value will be used for the molar ratio (H2 O) / n (C 2115OII), despite the increased total amount of substance of water in the reaction products. In the present case, the difference of 1 mol of water between the product and the reactant mixtures has a negligible enthalpic effect. The enthalpies associated with the solution of ethanol and acetic acid in 60 mol of water are derived from literature data [17] as Asin//(1) = -10.0 0.1 kJ mol-1 and Asin//(3) = —1.0 0.1 kJ mol-1. This calculation will be detailed in section 2.5. 

In 1977 De Santis et al. (J5) as well as Heidemann et al. ( ) calculated the gas-phase fugacities in the systems HjO-air and H2O-N2-CO2 by equation of state in these calculations the liquid phase was not included. One of the authors (7J showed in 1978 that aqueous systems with some inert gases and alkanes as well as H2S and C02 could be represented by an equation of state if the molecular weight of water was artificially increased. An extension of this method applied to alcohols was found to be only partially successful. Gmehling et al. (8) treated polar fluids such as alcohols, ketones and water as monomer-dimer mixtures using Donohue s equation of state (9) various systems including water-methanol and water-ethanol were succussfully represented. 

A solution of ( )-l-(l-naphthyl)-l-ethanol (2.416 g, 14.0 mmol), DIPEA (1.93 mL, 10.5 mmol) and catalyst 45 (74 mg, 0.28 mmol) in CHCl (14 mL) was stirred at 0 for 15 min then treated with (n-Pr0)20 (1.35 mL, 10.5 mmol). The mixture was stirred at 0 for 10 h, at which time it was quenched with MeOH (10 mL), allowed to warm slowly and left for 1 h at room temperature. The reaction mixture was diluted with CH Clj, washed twice with 1 M HCl, then twice with saturated aqueous NaHCO, and dried (NaSO ). The solution was concentrated in vacuo and purified by PC on silica gel (Et O/hexanes, 1/19 —> 1/4) to give the ester (1.672 g, 52%, 82.5% ee by chiral-HPLC), and the alcohol (1.091 g, 45%, 98.8% ee by chiral-HPLC). The calculated selectivity value at 54.5% conversion was s = 52.3. The aqueous phase obtained during the work up was basified with 0.5 M NaOH and repeatedly extracted with CH Cl (until the aqueous phase was pale-yeUow), the extract was dried (Na SO ), concentrated in vacuo, and purified by FC on sfiica gel (i-PrOH/hexanes, 1/19 -> 1/9) to provide 50 mg of recovered catalyst 45 (68%). 

At the 4th day of the fermentation 2.5 g compactin substrate is added in sterile filtered aqueous solution. Calculated for the volume of the broth 0.5-1.0% glucose was added into the culture depending on the pH in the form of 50% solution sterilized at 121°C for 25 min in parallel with the substrate feeding. After 24 hours the compactin substrate is consumed from the culture (is detected by HPLC) and was converted to pravastatin. By lyophilization of the aqueous residue 1.3 g pravastatin was obtained. The chromatographically pure product was crystallized from a mixture of ethanol and ethyl acetate. Melting point 170-173°C (decomp.). 

A solution is prepared which contains 5 X 10 mol of europium(III) chloride in 200 ml. of water. Since this chloride is quite hygroscopic, it is convenient to dilute a calculated volume of standardized ca. 0.5 M aqueous solution to 200 ml. Alternatively, 0.880 g. (2.5 X 10 mol) of europium (III) oxide is dissolved in a small excess of 6 M hydrochloric acid. The resultant solution is evaporated to a small volume to remove excess hydrochloric acid and ultimately diluted to 200 ml. To the solution of europium (III) chloride is added, with stirring, a solution of 4.0 g. (an excess) of benzoylacetone in 50 ml. of 95% ethanol. The resulting suspension is stirred with a magnetic stirring bar while 15 ml. of molar aqueous ammonia is added dropwise over a period of 2 hours. The mixture of product and excess benzoylacetone is filtered, washed with water, and dried in a vacuum desiccator to give approximately 4.4 g. of solid. 

Gutbezahl and Grunwald considered liquid-junction potentials between a solution of aqueous potassium chloride and solutions of acids in ethanol-water mixtures both theoretically and experimentally. They concluded that for mixtures containing up to 33% ethanol the liquid-junction potential should be 6 mV or less. For solvents containing higher percentages of alcohol, the liquid-junction potential increases rapidly—25 mV for 50%, 44 mV for 65%, and 75 mV for 80% ethanol. These numerical values should not be interpreted too literally, particularly as the composition approaches 100% ethanol. Calculated liquid-junction potentials contain an indeterminate term that involves all quantities other than those arising from unequal transfer activity coefficients (such as dipole orientation effects). 

Aminabhavi, T.M., Gopalakrishna, B., 1995. Density, viscosity, refractive index, and speed of sound in aqueous mixtures of A,A-dimethylformamide, dimethylsulfoxide, A,A-dimethylace-tamide, acetonitrile, ethylene glycol, diethylene glycol, 1,4-dioxane, tetrahydrofuran, 2-methoxyethanol, and 2-ethoxy-ethanol at 298.15 K. J. Chem. Eng. Data 40, 856-861. Barzegar-Jalali, M., Jouyban-Gharamaleki, A., 1996. Models for calculating solubility in binary solvent systems. Int. J. Pharm. 140, 237-246. 

The solubility of sulphamethoxypyridazine in ethanol-water mixtures represents a rare kind of drug solubility in an aqueous mixed solvent, because it exhibits two solubility maxima on the curve solubility versus mixed solvent composition (Escalera et al., 1994). It is of interest to verify if such behavior satisfies the thermodynamic consistency criterion. The values of D were calculated using Eq. (11), and... 

Once the interaction energies were obtained, they were used to calculate the parameters in the UNIQUAC and Wilson models given by Eq. (24). To test the validity of the method, low-pressure vapor-liquid equilibrium (VLE) predictions were made for several binary aqueous systems. The calculations were done using the usual method assuming an ideal vapor phase (Sandler, 1999). Figures 7 and 8 show the low-pressure VLE diagrams for the binary aqueous mixtures of ethanol and acetone [see Sum and Sandler (1999a,b) for results for additional systems and values of the... 

An initial mixture consists of equal masses of 90 wt % aqueous solution of acid and 95 wt % solution of ethanol. For constant-volume conditions calculate the conversion of acid to ester for various times of reaction. Assuming complete miscibility, estimate the equilibrium conversion. 

This crude acid (28 g) is heated in water (120 ml) for 2.5 h under reflux. The resulting AT-acetyltryptophan is less soluble that the starting acid and gradually crystallizes from the reaction mixture. Sodium hydroxide (16 g, 0.4 mole) in water (40 ml) is next added and the solution is boiled for 20 h under reflux. It is then treated with charcoal, filtered, and acidified with glacial acetic acid (24 g, 0.4 mole), this causing immediate formation of a white precipitate. The mixture is kept for 12 h in a refrigerator, after which the precipitate is collected and dissolved in aqueous sodium hydroxide (5 g in 200 ml). This solution is treated with charcoal and filtered. 95% ethanol (100 ml) is added to the filtrate which is then warmed to 70°, acidified with glacial acetic acid (7.5 ml), and cooled slowly. Tryptophan, which separates as plate-like crystals, is filtered off, washed successively with water (2 x 40 ml), ethanol (2 x 40 ml), and ether (2 x 30 ml). The yield is 81 % calculated on the ester product (14 g), and the m.p. is 272-280° (dec.) after recrystallization from 33 % ethanol. 

---