1. Unit Operations Lecture 20 1 7 Nov 2012

2. McCabe-Thiele – AZ diagrams 2 Ethanol – Water Binary (1.013 bar):

3. Overview 3 Review rigorous methods / RADFRAC Multicomponent systems: o Residue curves o DSTWU / RADFRAC o Rules of thumb Complex (Enhanced) distillation Column internals Batch distillation

4. Azeotropic Distillation 4 Perry’s 8 th ed.

5. Azeotropic Distillation 5 Water with (binary system at atmospheric P): methanol- no azeotrope ethanol- azeotrope propanol- azeotrope In-class exercise: using Aspen Plus, explore if we can use distillation to separate the binary mixture of water and n-butanol.

6. Heterogeneous Azeotropic Distillation 6 VLLE (NRTL)

7. Heterogeneous Azeotropic Distillation 7 Perry’s 8 th ed.

8. 8 Residue Curve Maps

9. Complex Multicomponent Systems 9

10. Pressure Swing Distillation 10

11. Pressure Swing Distillation 11

12. Complex or Enhanced Distillation 12 Extractive Distillation o Higher boiling solvent o Enters near top of column o Interacts with other components to affect volatility or activity coefficients Homogeneous Azeotropic Distillation o Add entrainer that forms min/max boiling point AZ w/ 1 or more of feed compds o Added near top or bottom, depending upon if AZ is min or max BP Heterogeneous Azeotropic Distillation o Add entrainer to form min BP heterogeneous azeotrope (EtOH-H2O + benzene) Pressure – Swing Distillation o For pressure sensitive azeotropes and distillation boundaries Salt Distillation o Alter relative volatilities of feed compds by dissolving a soluble ionic salt into the reflux Steam Distillation o Steam is added to reduce temperature of distilling organic mixture Reactive Distillation o add reactant &/or catalyst to cause a reversible/selective reaction with one of the feed components o Reaction and distillation occur in same vessel

13. Reactive Distillation 13 Esterification of acetic acid with ethanol to ethyl acetate and water

14. Column Internals 14

15. Column Internals 15