Azeotropic calculated

For azeotrope calculation specify that the designed compound should not form azeotropes with any of the compounds in the mixture. 

Convergence is usually accomplished in 2 to 4 iterations. For example, an average of 2.6 iterations was required for 9 bubble-point-temperature calculations over the complete composition range for the azeotropic system ehtanol-ethyl acetate. Standard initial estimates were used. Figure 1 shows results for the incipient vapor-phase compositions together with the experimental data of Murti and van Winkle (1958). For this case, calculated bubble-point temperatures were never more than 0.4 K from observed values. 

Revised material in Section 5 includes an extensive tabulation of binary and ternary azeotropes comprising approximately 850 entries. Over 975 compounds have values listed for viscosity, dielectric constant, dipole moment, and surface tension. Whenever possible, data for viscosity and dielectric constant are provided at two temperatures to permit interpolation for intermediate temperatures and also to permit limited extrapolation of the data. The dipole moments are often listed for different physical states. Values for surface tension can be calculated over a range of temperatures from two constants that can be fitted into a linear equation. Also extensively revised and expanded are the properties of combustible mixtures in air. A table of triple points has been added. 

Ideal Adsorbed Solution Theory. Perhaps the most successful approach to the prediction of multicomponent equiUbria from single-component isotherm data is ideal adsorbed solution theory (14). In essence, the theory is based on the assumption that the adsorbed phase is thermodynamically ideal in the sense that the equiUbrium pressure for each component is simply the product of its mole fraction in the adsorbed phase and the equihbrium pressure for the pure component at the same spreadingpressure. The theoretical basis for this assumption and the details of the calculations required to predict the mixture isotherm are given in standard texts on adsorption (7) as well as in the original paper (14). Whereas the theory has been shown to work well for several systems, notably for mixtures of hydrocarbons on carbon adsorbents, there are a number of systems which do not obey this model. Azeotrope formation and selectivity reversal, which are observed quite commonly in real systems, ate not consistent with an ideal adsorbed... 

Binary azeotropic systems are reported for all three derivatives (9). The solubiHties of benzyl chloride, benzal chloride, and ben zotricbl oride in water have been calculated by a method devised for compounds with significant hydrolysis rates (10). 

Fig. 15. Isobaric vapor—liquid—liquid (VLLE) phase diagrams for the ethanol—water—benzene system at 101.3 kPa (D-D) representHquid—Hquid tie-lines (A—A), the vapor line I, homogeneous azeotropes , heterogeneous azeotropes Horsley s azeotropes, (a) Calculated, where A is the end poiat of the vapor line and the numbers correspond to boiling temperatures ia °C of 1, 70.50 2, 68.55 3, 67.46 4, 66.88 5, 66.59 6, 66.46 7, 66.47, and 8, the critical poiat, 66.48. (b) Experimental, where A is the critical poiat at 64.90°C and the numbers correspond to boiling temperatures ia °C of 1, 67 2, 65.5 3, 65.0 ...

In most cases, systems deviate to a greater or lesser extent from Raoult s law, and vapour pressures may be greater or less than the values calculated. In extreme cases (e.g. azeotropes), vapour pressure-composition curves pass through maxima or minima, so that attempts at fractional distillation lead finally to the separation of a constantboiling (azeotropic) mixture and one (but not both) of the pure species if either of the latter is present in excess. 

Copolymerizations were performed at 70 C using an ampoule technique similar to that used for MMA. Monomers were purified by distillation. Most of the runs had an initial weight fraction styrene of 0.767 and 1.45 mole % AIBN initiator. Also utilized is one run using 0.235 wt. fraction styrene (0.350 mole % AIBN) and one at 0.557 (1.45 mole % AIBN). Gruber and Knell (10) used both the former compositions. The latter one is the calculated azeotropic composition using their values of the reactivity ratios. 

If the composition (or flow-rate) of one stream is fixed by internal or external constraints, this may fix the composition and flows of other process streams. In Chapter 1, the relationship between the process variables, the design variables and design equations was discussed. If sufficient design variables are fixed by external constraints, or by the designer, then the other stream flows round a unit will be uniquely determined. For example, if the composition of one product stream from a distillation column is fixed by a product specification, or if an azeotrope is formed, then the other stream composition can be calculated directly from the feed compositions see Section 2.10. The feed composition would be fixed by the outlet composition of the preceding unit. 

Step 8 Set up the calculations for any values which are design constraints. For example, the overheads, recycle flow, from the second column which should approximate to the azeotropic composition see Table 4.4. The calculations giving the composition of this stream are shown in Figure 4.19a. 

This should approximate to the azeotropic composition (9 per cent alcohol, 91 per cent water). The flow of any component in this stream is given by multiplying the feed to the column (X5k) by the split-fraction coefficient for the recycle stream (a 15/.). The calculated flows for each component are shown in Table 4.4. 

If a binary system forms an azeotrope, the activity coefficients can be calculated from a knowledge of the composition of the azeotrope and the azeotropic temperature. At the azeotropic point the composition of the liquid and vapour are the same, so from equation 8.31 ... 

The values of the activity coefficients determined at the azeotropic composition can be used to calculate the coefficients in the Wilson equation (or any other of the three-suffix equations) and the equation used to estimate the activity coefficients at other compositions. Horsley (1973) gives an extensive collection of data on azeotropes. 

Solution To determine the location of the azeotrope for a specified pressure, the liquid composition has to be varied and a bubble-point calculation performed at each liquid composition until a composition is identified, whereby X = y,-. Alternatively, the vapor composition could be varied and a dew-point calculation performed at each vapor composition. Either way, this requires iteration. Figure 4.5 shows the x—y diagram for the 2-propanol-water system. This was obtained by carrying out a bubble-point calculation at different values of the liquid composition. The point where the x—y plot crosses the diagonal line gives the azeotropic composition. A more direct search for the azeotropic composition can be carried out for such a binary system in a spreadsheet by varying T and x simultaneously and by solving the objective function (see Section 3.9) ... 

Thus, if the saturated vapor pressure is known at the azeotropic composition, the activity coefficient can be calculated. If the composition of the azeotrope is known, then the compositions and activity of the coefficients at the azeotrope can be substituted into the Wilson equation to determine the interaction parameters. For the 2-propanol-water system, the azeotropic composition of 2-propanol can be assumed to be at a mole fraction of 0.69 and temperature of 353.4 K at 1 atm. By combining Equation 4.93 with the Wilson equation for a binary system, set up two simultaneous equations and solve Au and A21. Vapor pressure data can be taken from Table 4.11 and the universal gas constant can be taken to be 8.3145 kJ-kmol 1-K 1. Then, using the values of molar volume in Table 4.12, calculate the interaction parameters for the Wilson equation and compare with the values in Table 4.12. 

Levy SG, Van Dongen DB and Doherty MF (1985) Design and Synthesis of Homogeneous Azeotropic Distillation 2. Minimum Reflux Calculations for Non-ideal and Azeotropic Columns, Ind Eng Chem Fund, 24 463. 

Polyurethane networks were prepared from polyoxypropylene (POP) triols(Union Carbide Niax Polyols) after removal of water by azeotropic distillation with benzene. For Niax LHT 240, the number-average molecular weight determined by VPO was 710 and the number-average functionality fn, calculated from Mjj and the content of OH groupSj determined by using excess phenyl isocyanate and titration of unreacted phenyl isocyanate with dibutylamine, was 2.78 the content of residual water was 0.02 wt.-%. For the Niax LG-56, 1 =2630, fn=2.78, and the content of H2O was 0.02wt.-%. The triols were reacted with recrystallized 4,4"-diphenylmethane diisocyanate in the presence of 0.002 wt.-% dibutyltin dilaurate under exclusion of moisture at 80 C for 7 days. The molar ratio r0H = [OH]/ [NCO] varied between 1.0 and 1.8. For dry samples, the stress-strain dependences were measured at 60 C in nitrogen atmosphere. The relaxation was sufficiently fast and no extrapolation to infinite time was necessary. 

Single crystal x-ray diffraction studies showed that the crystals of halcinonide recrystallized from tz-propyl alcohol-water azeotrope (79 22) are orthorhombic and belong to the gpace group P2 2 2, with unit ell constants of a = 10.007 A, = 11.875 A ana Q = 19.460 A. Density is 1.330 gm/cm2 3, as measured by flotation in a hexane-carbon tetrachloride gradient. The molecular weight calculated from the unit cell volume and density is 461 daltons (theoretical is 455 daltons). 

Azeotrope/miscibility calculations Specify if the solvent must or must nor form azeotropes, miscibility as a liquid solution, solid precipitation, etc. 

It can be noted from Fig. 2a that ProCAMD needed only 1.97 seconds to generate 5614 molecular structures and after evaluating them ended-up with 111 feasible candidates. The time also includes the process calculations related to miscibility, azeotrope verification as well as solvent loss and selectivity. 

Azeotrope/Miscibility Calculations j Biodegradation Calculations Temperature depd. props. j Mixture Properties... 

Norman, W. S. Trans. Inst. Chem. Eng. 23 (1945) 66. The dehydration of ethanol by azeotropic distillation. Ibid. 89. Design calculations for azeotropic dehydration columns. 

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