# 11 – applications of thermodynamics in separation technology

### Textbook Examples:

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11.02          Azeotropic Points in the Quaternary System Benzene – Cyclohexane – Acetone – Ethanol Using Mod. UNIFAC (p. 483)
Mathcad (2001) – Solution as XPS

11.03          Azeotropic Points in the Quaternary System Carbon Dioxide – Ethane – Hydrogen Sulfide – Propane Using VTPR (p. 483)

11.04          Residue Curves for Acetone – Benzene – Cyclohexane Using the Wilson
Model (p. 487)
Excel VBA Ternary Plot

Mathcad (2001) – Solution as XPS

11.05          Effect of NMP on the Separation Factor of the Mixture Benzene –
Cyclohexane Using mod. UNIFAC (p. 497)
Mathcad (2001) – Solution as XPS

P11.01        Effect of Different Entrainers on the Separation 1,3-Butadiene – 1-Butene Using Modified UNIFAC
For the separation of butadiene-1,3 from the C4-fraction of the steam cracker by extractive distillation various entrainers are used. Calculate the separation factor between butadiene-1,3 (x1 = 0.25) and 1-butene (x2 = 0.25)  at a temperature of 50°C using the mod. UNIFAC model to get an impression about the selectivity of the following entrainers (3): NMP, Acetonitrile, DMF (x3=0.5).

P11.02      Effect of NMP on the Separation Factor Between Benzene and
Cyclohexane Using Wilson
Check with the help of the Wilson equation, how the separation factor a12 between
benzene(1) and cyclohexane(2) is altered in the presence of 50 (70) mol-% NMP(3) at 60 °C.
Wilson parameters, molar volumes and vapor pressures of NMP at 60 °C:

Dl13   = –205.34 K
Dl31  = 414.16 K
Dl23  = 321.30 K
Dl32  = 436.34 K
v
3      = 96.44 cm3 mol–1
P3s    = 0.47 kPa.
The additionally required Wilson parameters and pure component
properties are given in Table 5.10 and in Appendix A respectively.

P11.03      Separation Factor Between Acetone and Water Using NRTL
Calculate the separation factor for the system acetone (1 ) – water (2) for an acetone concentration of  x1 = 0.95 at 50°C and at 1 atm with the help of the NRTL equation assuming ideal vapor phase behavior. Binary interaction parameters for NRTL can be found in Table 5.9. All other properties and parameters are given in Appendix A.

P11.04      Azeotropic Composition Benzene-Water From Vapor Pressure Data
In the free DDBSP Explorer Edition, search for all mixture data for the system benzene – water. Due to very limited miscibility in the liquid phase, the system shows heteroazeotropic behavior. Estimate the azeotropic composition using the vapor pressure correlations given in Appendix A and compare the results to the experimental data.