Vapor-liquid equilibrium data butanol/water

Table 8-2. Vapor-liquid equilibrium data for water and n-butanol at 1 atm mol% water... 

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). 

FIG. 13-8 Vapor-liquid equilibrium data for an n-butanol-water system at 101.3 kPa (1 atm) phase splitting and heterogeneous-azeotrope formation. 

The Non-Random, Two Liquid Equation was used in an attempt to develop a method for predicting isobaric vapor-liquid equilibrium data for multicomponent systems of water and simple alcohols—i.e., ethanol, 1-propanol, 2-methyl-l-propanol (2-butanol), and 3-methyl-l-butanol (isoamyl alcohol). Methods were developed to obtain binary equilibrium data indirectly from boiling point measurements. The binary data were used in the Non-Random, Two Liquid Equation to predict vapor-liquid equilibrium data for the ternary mixtures, water-ethanol-l-propanol, water-ethanol-2-methyl-1-propanol, and water-ethanol-3-methyl-l-butanol. Equilibrium data for these systems are reported. 

The direct measurement of vapor-liquid equilibrium data for partially miscible mixtures such as 3-methyl-l-butanol-water is difficult, and although stills have been designed for this purpose (9, 10), the data was indirectly obtained from measurements of pressure, P, temperature, t, and liquid composition, x. It was also felt that a test of the validity of the NRTL equation in predicting the VLE data for the ternary mixtures would be the successful prediction of the boiling point. This eliminates the complicated analytical procedures necessary in the direct measurement of ternary VLE data. 

Table III. Vapor—Liquid Equilibrium Data at 760 mm. Hg 3-Methyl-1-Butanol (1)—Water (2)...

The vapor-liquid equilibrium data for the 3-methyl-l-butanol-water system are shown in Table III and Figure 4. The boiling point measurements agreed with those reported in Timmermans (13). The value of a = 0.45 as suggested by Renon and Prausnitz (8) for alcohol-water systems was not suitable. Various other values of a were tried, and a value of a. = 0.3 was found to agree best. This fit can be established by using the method described to test the consistency of the equations—i.e., the... 

Figure 4. Vapor-liquid equilibrium data at 760 mm Hg. 3-Methyl-l-Butanol (1)-Water (2).

Ternary System. The values of all binary parameters used in predicting the ternary data are shown in Table IV. The predicted values of the vapor-liquid equilibrium data—i.e.9 the boiling point, and the composition of the vapor phase, y, for given values of the liquid composition, x, are presented in Tables V, VI, and VII. Also shown are the measured boiling points for the given values of the liquid composition. The RMSD value between the predicted and measured boiling points for the systems water-ethanol-l-propanol, water-ethanol-2-methyl-l-propanol, and water-ethanol-2-methyl-l-butanol are 0.23°C, 0.69°C, and 2.14°C. It seems therefore that since the NRTL equation successfully predicts temperature, the predicted values of y can be accepted confidently. 

Example 4.6 Mixtures of water and 1-butanol (n-butanol) form two-liquid phases. Vapor-liquid equilibrium and liquid-liquid equilibrium for the water-1-butanol system can be predicted by the NRTL equation. Vapor pressure coefficients in bar with temperature in Kelvin for the Antoine equation are given in Table 4.136. Data for the NRTL equation are given in Table 4.14, for a pressure of 1 atm6. Assume the gas constant R = 8.3145 kJ-kmoL -K-1. 

Darwish, N. A. Al-Anber, Z. A. Vapor-liquid equilibrium measurements and data analysis of tert-butanol - isobutanol and tert-butanol - water binaries at 94.9 kPa. Fluid Phase Equilib. 1997, 131, 287-295. 

Dl. A mixture of water and n-butanol is being processed in an enriching column coupled to a total condenser and a liquid-liquid setder. The feed is a saturated vapor that is 28 mol% water. Feed rate is 100 kmol/h. The distillate product is the water phase from the liquid-liquid setder. The butanol phase in the setder is refluxed to the enriching column as a saturated liquid. Operation is at 1.0 atm and CMO is valid. An external reflux ratio of L/D = 4.0 is used. Equilibrium data are in Table 8-2. 

D5. We have a saturated vapor feed that is 80.0 mol% water and 20.0 mol% butanol. Feed rate is 200.0 kmol/h. This feed is condensed and sent to a liquid-liquid separator. The water layer is taken as the water product, W, and the butanol (top) layer is sent to a stripping column which has a partial reboiler. The bottoms from this stripping column is the butanol product, which should contain 4.0 mol% water. The vapor leaving the stripping column is condensed and sent to the setder. Equilibrium data are in Table 8-2. Find ... 

D13. We are separating water from n-butanol in a system with two feeds. Feed l[Fi = 100 kmol/h, z = 0.84(mole fraction water), saturated vapor] is mixed with the vapor leaving the top of the column before it is sent to the total condenser and then to the liquid-liquid setder. Feed 2 [F2 = 80 kmol/h, Z2 = 0.20(mole fraction water), saturated liquid] is fed within the column. The column has a partial reboiler and CMO is valid. The top layer from the liquid-liquid settler (xq = 0.573 mole fraction water) is sent as reflux to the distillation column. The bottom layer = 0.975 mole fraction water) is the distillation product. Pressure p = 1.0 atm, reflux is a saturated liquid, V/B = 1.5, Xj t = 0.04 mole fraction water. Equilibrium data are in Table 8-2. 

D21. A distillation column is separating water fromn-butanol at 1 atmosphere pressure. Equilibrium data are in Table 8-2. The distillation system is similar to Figure 8-3A and has a partial reboiler, a total condenser and a liquid-liquid settler. The bottom layer from the settler (rich in water with x = 0.975) is taken as the distillate product. The top layer (x = 0.573) is returned to the column as a saturated liquid reflux. The feed is 40.0 mol% water, is a saturated vapor and flows at 500.0 kmol/h. The bottoms is 0.04 mole frac water. Use a boilup ratio of V/B = 0.5. Assume CMO is valid. Step off stages from the bottom up. Find the optimum feed stage location and the total number of equilibrium stages needed. 

D15. We wish to batch distill 100 kmol of a mixture of n-butanol and water. The system consists of a batch still pot plus 1 equilibrium stage. The system is at one atmosphere. The feed is 48 mol% water and 52 mol% butanol. The distillate vapor is condensed and sent to a liquid-liquid settler. The water rich product (0.975 mole fraction water) is taken as the distillate product and the butanol rich layer (0.573 mole fraction water) is refluxed to the column. We desire a final still pot mole fraction of 0.08 water. Energy is added at a constant rate to the still pot thus, V = constant. Note that the distillate product is a constant mole fraction. The reflux ratio increases as the distillate vapor mole fraction decreases during the course of the batch distillation. Equilibrium data are given in Table 8-2. 

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