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SUPERCRITICAL FLUIDS FOR SEPARATION

SUPERCRITICAL FLUIDS FOR SEPARATION. Objectives. What for do we need phase equilibrium? Design of solvent cycle (process). Objectives. Solubility of the compounds Change of solubility with process conditions Capacity of the solvent Solubility of solvent in condensed phase

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SUPERCRITICAL FLUIDS FOR SEPARATION

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  1. SUPERCRITICAL FLUIDS FOR SEPARATION

  2. Objectives What for do we need phase equilibrium? Design of solvent cycle (process)

  3. Objectives Solubility of the compounds Change of solubility with process conditions Capacity of the solvent Solubility of solvent in condensed phase Distribution of compounds between the phases (separation factor, selectivity) Two-phase area What do we need to know about phase equilibrium?

  4. Objectives For what type of systems (chemical compounds) do we need phase equilibrium? CO2, C3H8, H2O, .... (gases) Paraffins, glycerides, vitamins, ... Terpenes, sesquiterpenes, mono-, di-, tri- .... ....

  5. Extraction with Supercritical Fluids Flow scheme of gas extraction (SFE) The need for phase equilibria: Solubility, K-factor, Separation factor, Two-phase region

  6. Solubility of quartz in water Kennedy 1950

  7. Poynting-effect Vapor pressure enhancement E.U. Franck 1956 ____ 25 oC, ------ 500 oC P02/P01 VL

  8. Poynting-Factor System: Ethanol - Water, 343 K Ethanol Water kPa 10 1.0022 1.0006 1000 1.022 1.0065 10000 1.2425 1.0667

  9. Density CO2 (calc. Bender EOS)

  10. Vapour Pressure vs. Temperature

  11. Influences on Solute Concentration in Gaseous Phase Density of supoercritical Fluid responsible for solvent power (increasing with pressure, decreasing with temperature) Hydrostatic pressure enhances effective vapour pressure (Poynting effect, small) Temperature increases vapour pressure (exponentially, big effect)

  12. Solubility of Caffeine in CO2 Gährs 1984 Ebeling, Franck 1984 Johannsen, Brunner 1994

  13. Solubility of Naphthalene in Ethylene Tsekhanskaja 1964 Solubility [g/l]

  14. Oleic acid - ethylene Brunner 1978

  15. Solubility of oleic acid in various gases Brunner 1978

  16. Solubility of Triglycerides in sc Gases Triglycerides of palm oil Brunner 1978

  17. Solubility in sc CO2

  18. Solubility of Xanthines in dry sc CO2 Johannsen and Brunner 1994

  19. P,T,x-diagram of a binary system

  20. P,x-diagram ethane - heptane Kay 1938

  21. T,x-diagram ethane - heptane Kay 1938

  22. Phase equilibria of a binary system Melting point temperature of B higher than critical temperature of A

  23. Phase equilibrium in a binary system Melting point temperature of B higher than critical temperature of A; Interrupted critical curve.

  24. P,T- projections of phase boundary lines

  25. Phase behaviour of a ternary system Temperature dependence Pressure dependence

  26. CO2 - benzene - oleic acid

  27. Ethylene - DMF - C18 fatty acids

  28. Solubility Enhancement by a Modifier

  29. Solubility Enhancement by Entrainer (Modifier) Schmitt 1984

  30. Solubility of Caffeine in CO2 Influence of nitrogen Gährs 1984

  31. Solubility of Phenanthrene in CO2 Influence of propane Prausnitz, Joshi 1984

  32. Phase Equilibrium in a Ternary System Brunner 1983

  33. Solubility in a gas with a modifier Influence of temperature Brunner 1983

  34. Separation Factor Influence of entrainer Brunner 1983

  35. Separation Factor Influence of concentration Brunner 1983

  36. Three Phase Equilibrium

  37. P,T-diagrams of Complex Mixtures

  38. Measuring Phase Equilibrium

  39. Measuring Phase Equilibrium

  40. Modeling of Phase Equilibrium with EOS HPW modification of RK-EOS

  41. Thermodynamic Equilibrium Gas-Liquid Phase Equilibrium Two different ways: A = standard fugacity i = activity coefficient: gE-models) B = fugacity coefficient: Equations of state

  42. Calculation of Phase Equilibrium • VLE-Calculation: • With the simplification: • since • : 

  43. Phase Equilibrium: Non Ideal Solutions High pressure Low pressure

  44. Concentration dependence of separation factor  P = 101 kPa  = 1   = 1 Chloroform - acetone Methanol - water

  45. Concentration dependence of separation factor

  46. Phase Equilibrium Limiting values of the partition coefficient K T = const. VLE T = const. VLE xsf = const. xsf = solvent free concentrations in liquid phase

  47. Phase Equilibrium Limiting values of separation factor  Binary system i-j in a multicomponent system At low pressure Binär:

  48. Murphy´s Law of Thermodynamics THINGS GET WORSE UNDER PRESSURE

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