2. Mohammad Javad Hosseinishahi Dastjerdi Distillation Dr.H.S.Ghaziaskar

3. Vacuum Distillation Molecular Distillation Molecular Sublimation Lyophilization (Freeze Drying) 1

4. Vacuum Distillation 2

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6. 150 Perform Vacuum Distillation a if the liquid boils above 150 ̊ C Boiling Point Vapor pressure = External pressure Reduced pressure = Lower boiling point 4

7. Vacuum Distillation 5

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11. If you find a leak 1.Turn off vacuum 2. Introduce air 3. Regrease the joints 4. Try again 9

12. Vacuum Distillation 10

13. 11 Vacuum Distillation

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15. Vacuum Distillation Example summery: bp at 760 torr = 320 ̊ C Pressure = 0.5 torr Expected bp =120 ̊ C 13

16. When finished with the vacuum distillation: 1) Remove the heat source 2) Introduce air 3) Stop Stirring 4) Remove the flask 14 Vacuum Distillation

17. Molecular Distillation 15

18. What is mean free path of molecules ? Molecular Distillation What is molecular distillation ? When molecular distillation is performed ? 16

19. Molecular Distillation Difference between molecular distillation an ordinary vacuum distillation 1) The liquid condensed is not allowed to flow back into the sample 2) The pressure reduced that a molecule has a good chance of reaching the condenser surface without hitting another molecule 3) The ratios at which different component molecules distilled is proportional to: 4)No equilibrium exists between the vapor and condensed phase. Ideal distillation conditions are attained when the rate of evaporation is equal to the rate of condensation. 17

20. Molecular Distillation Laboratory- scale molecular still 18

21. Diagram of the commercial molecular still Molecular Distillation 19

22. Molecular Distillation Commercial stills The rate of distillation depends on how fast material from below the surface can get to surface. Commercial stills provide a large evaporating surface and a continuous process ( fresh surface). - Falling Film Stills - Wiped Film still - Centrifugal stills 20

23. ASAHI Molecular Distillation Apparatus are designed for distillation of heat-sensitive substances, such as vitamins and fine chemicals, in very high vacuum range of 5.0 x 10 -3 -10 -8 mmHg. Moreover, oxidation of the distillation is eliminated since it is operated in high vacuum conditions. Molecular Distillation 21

24. Applications of Molecular Distillation -Removal of odors and colors from plasticizers -vitamin recovery -Isolation of natural oils -Purification of drugs -Distillation of waxes and fatty acids -Isolation of perfumes -Deodorizing oils -Solvent stripping -Remove color bodies from materials of high molecular weight -Stripping monomer from polymer -Concentrating fruit juices and …. Molecular Distillation 22

25. Theory Langmuir ‘s method to determine the maximum amount of material that can be distill P=pressure in dynes/cm2 M=m.w T=temperature(K) W=amount of distillated in grams/sec/cm2 p=vapor pressure (torr) Molecular Distillation 23

26. Evaporative Coefficient (f) 1) The fraction of molecules reaching the condenser without collision 2) The fraction that collides first and how many reach the condenser 3) Those that have collided and reach the condenser by random motion (f) considers three factors: Equation to more closely represent what actually take place D=diffusivity of the organic molecules in an air atmosphere The lower vacuum,the higher D d=distance in cm from evaporation surface to the condensing surface Molecular Distillation 24

27. Referring to langmuir ‘s equation : A nomograph used to estimate the rate of molecular distillation Example: Molecular distillation at 600 K,M=700,p=0.001,f=0.1 6.3E-6 25 Molecular Distillation

28. Molecular Sublimation 26

29. Molecular Sublimation What is Sublimation ? High Purity in sublimation External Pressure =Vapor pressure  in lower melting point 27

30. -Theoretically, all compounds can be sublimed, However, for most compounds, the triple point is at such a low pressure and temperature, that sublimation is not practical. SublimandSublimate -The subliming temperature at reduced pressure is usually several degrees below the melting point,so less compound destruction occurs during a sublimation than during a distillation. Molecular Sublimation 28

31. Entrainer Sublimation - Sublimation can be speeded up by passing an inert gas ( Carrier or entrainer) - The purpose of this gas is to reduce the partial pressure of the sublimate 29

32. Entrainer sublimators Molecular Sublimation 30

33. Differences between a Molecular Distillation and a Sublimation at low pressure 1) The molecular distillation goes from solid to liquid to gas,which usually requires more energy than a sublimation. 2) The surface of the subliming compound is continuously renewed by evaporation,convection,or diffusion.thus a sublimation in many cases is faster and more economical. Molecular Sublimation 31

34. Lyophilization (Freeze Drying) 32

35. What is Lyophilization(Freeze Drying) ? -This works well heat sensitive materials. Lyophilization (Freeze Drying) 33

36. History -The Incas prepared their food by drying it on mountain tops. -1890 R.Altman was report microscopic investigation -1942 (WWII), freeze drying was developed on a large scale for processing blood plasma. -1949, used for food. A freeze dried material undergoes fewer adverse changes than other methods. The product requires simpler storage and transportation system and if sealed under vacuum or an inert gas, usually retain most of its biological and physical characteristics indefinitely. Lyophilization (Freeze Drying) 34

37. Process -Frozen to a temperature just below its lowest eutectic. -Vacuum of from 4-6 torr. The heat loss by subliming water usually will keep material frozen. (reduced the water content about 90%) in large-scale commercial applications,heat must be applied to provide the sublimation energy -Reduced pressure to a few tenths of torr to remove bound water Lyophilization (Freeze Drying) 35 Freeze Rate Effects slow freezing  large ice crystals fast freezing  tiny crystals

38. A: Freeze drying sample holder B: Freeze drying connecting valve C: multi port condenser A B C Techniques Lyophilization (Freeze Drying) 36

39. Laboratory- scale 37

40. Commercial scale 38

41. --dehydrating frozen foods Lyophilization (Freeze Drying) 39

42. Taxi-Dry Lyophilization (Freeze Drying) 40

43. --Freeze Dried Floral Art & Keepsakes --Freeze-drying in the mycological collection Lyophilization (Freeze Drying) 41

44. -Clifton E.Melon :Chemical Separations Principles,Techniques,and Experiments; -Georg Wilhelm Oetjen : Freeze Drying www.Ocw.mit.edu Refrence 42