Supercritical Fluid Extraction-Introduction, Components, Modes, Advantages, Disadvantages, applications

1. SUPERCRITICAL FLUID
EXTRACTION
PRAGATI SINGHAM
PhD (I Year)

2. CONTENTS
• Introduction to SCF
– Properties of SCF
– Historical background
• Supercritical fluid Extraction (SFE)
– Components of SFE
– Critical properties of selected substances
– Modes of SFE
• Methods of developments of SFE
• Objectives for commercialization
• Advantages
• Limitations
• Precautions
• Applications

3. SUPERCRITICAL ??
Supercritical Fluid
Supercritical Fluid
Extraction - SFE
CRITICAL POINT
Triple point
Fig. 1 Typical Pressure-Temperature of a substance
At a certain temperature and pressure condition, liquid and vapour phases of a substance
become indistinguishable. Known as CRITICAL CONDITION
Substances above critical point- “SUPERCRITICAL FLUIDS” (SCF)
Pc
Tc

4. PROPERTIES OF SCF
• Physical and thermal properties of SCFs are in between pure
liquid and gas, hence can also be known as ‘Compressible
liquids’ or ‘dense gases’
• Changes in properties are for a SCF are as follows:
– Liquid like densities (100-1000 times greater than gases)
– Diffusivities higher than liquids (10-3 and 10-4cm2/s)
– Good solvating power
– Reduction in surface tension
– Low viscosity (10-100 times less than liquid)
– Gas like compressibility properties
Therefore they posses high penetrating power

5. HISTORICAL BACKGROUND
• Solvent properties of SCF were first reported well over 100
years ago in 1879 by Hannay and Hogarth, (measured
solubility of inorganic salts in supercritical ethanol)
• Since 1980s and 1990s SCF has been used in several industrial
processes.

6. SUPERCRTICAL FLUID EXTRACTION

7. SUPERCRITICAL FLUID EXTRACTION (SFE)
Solvent extraction method
Solvent
(pass through)
Solids
Dissolves solute
Supercritical fluid extraction
Supercritical Solvent
(pass through)
Solids
Dissolves solute
Extract Raffinate (solvent) Extract Raffinate (SC solvent)
Hence can say that it resembles solvent extraction process

8. SUPERCRITICAL FLUID EXTRACTION (SFE)
CONTD..
Supercritical fluid extraction is the process of separating
one component from another (the matrix)
using supercritical fluids as the extracting solvent

9. SUPERCRITICAL FLUID EXTRACTION (SFE)
CONTD..
Steps: Introduction of feed into extractor (solid feed)
or extractor in modified column either co-currently or counter-currently
Formation of mobile phase: mixing of solutes with supercritical
fluid.
Exposure of mobile phase to pressures (50-500 atm) and
temperatures (ambient to 300°C) near or above the critical
point for enhancing the mobile phase solvating power.
Isolation of dissolved solute by precipitation
Eg. CO2 in vapour form is compressed into a liquid before
becoming supercritical and then extraction takes place.

10. COMPONENTS OF SFE
1. Fluid reservoir (gas cylinder in case of CO2)
2. Pump
– Reciprocating pump
– Syringe pump (pulse-free flow at large range of flow rates)
3. Extraction cell/column (stationary phase)
– Usually stainless steel Chamber or vessel in compartment
– Capable of withstanding high pressure (300-600 atm) [for
solids]
– Open tubular capillary columns or packed columns
[liquids]

11. COMPONENTS CONTD..
4. Restrictor
– Maintaining pressure change inside the extraction vessel
Two types-
– fixed (linear restrictor, tapered desire, integral restrictor,
ceramic frit restrictor, metal restrictor)
– Variable (variable nozzle, back pressure regulator)
5. Collector (trapping system)
6. Detectors (flame ionization detector of gas chromatography)

12. SFE WITH RECYCLING (TRAPPING SYSTEM)
Recycling of SFE can be done-
1. Reduction of pressure - SCF unable to dissolve the solute,
separation of sold under gravity and the gas at low pressure
is compressed back to the supercritical conditions.

13. SFE WITH RECYCLING (TRAPPING
SYSTEM)CONTD…
2. Reduction of temperature - solute drops and recovery of
solvent without recompression
3. Pumping SCF to expansion tank - where it becomes gas
resulting in very less solubility i.e. separation of solute. Spent
gases are then recompressed and recycled. Heat exchangers
are used to maintain temperature and prevent excessive
cooling at throttling valve called as Joule-Kelvin effect.

14. SFE WITH RECYCLING (TRAPPING SYSTEM)
CONTD…
• Pumping SCF to expansion tank

15. CRITICAL PROPERTIES OF SELECTED
SUBSTANCES

16. SUPERCRITICAL CO2

17. MODES OF SFE
STATIC EXTRACTION MODE
(steady state)
• Sample matrix is soaked in a
fixed amount of
supercritical fluid
• Can be compared to a
teabag in a cup of water
DYNAMIC EXTRACTION MODE
(non-steady)
• Supercritical fluid
continuously passes
through the sample matrix
• Analogous to coffee maker

18. SFE CONTD..
• Sample Matrix Parameters that influence SFE:
– Particle size and shape
– Surface area and porosity
– Moisture content
– Changes in morphology
– Sample size
– Extractables level
• The parameters effect on solubility:
– The vapour pressure of the component
– Interaction with the supercritical fluid
– Temperature, pressure, density and additives

19. METHOD DEVELOPMENT FOR SFE

20. OBJECTIVES FOR COMMERCIALIZATION
• Separation of multiple solutes (as solubility of solute in
supercritical solvent may be a function of temperature and
pressure)
• Use of entrainers/modifiers an enhance versatility and
efficiency. Eg. CO2 mixed with 1-10% of methanol to solubilise
more polar solutes.

21. MULTIPLE SOLUTES IN SFE
Separation of solutes is by using a two-stage process.
Method
• First extraction: similar to single stage (soluble-dissolved, less
soluble- left)
• Second extraction: dissolution of the remaining solute in the
solid in the solvent will result in the isolation
Solid Solute
(Extract)
Solvent First Extraction Second Extraction References
Dried
Ginger
Ginger flavor CO2 79 Bars and 30◦C 246 Bars and 40◦C. Yonei, Y, et al J. Sup.
Fl. 8:156–161,
1995).
Coriander
seeds
Flavor CO2 , (Celery
powder &
sage)
250 Bars and 40◦C. 70 Bars and
20◦C
Catchpoole, O.J. et al.
J. Sup. Fl. 9:273–279,
1996
Egg yolk Phospholipids CO2 , (CO2
ethanol 5%)
414 Bars and 45◦C. 414 Bars and 45◦C Shah A. et al. J. Sup.
Fl. 30:303–313, 2004

22. MODIFIERS FOR SFE

23. ADVANTAGES
• Elimination of organic solvents i.e. reduces the risk of storage.
• Rapid (due to fast back-diffusion of analytes in the SCF
reduces the extraction time since the complete extraction
step is performed in about 20 min)
• Suitable for extraction and purification of compounds having
low volatility present in solid or liquid
• Susceptible to thermal degradation (low operating conditions)

24. ADVANTAGES CONTD…
• Complete separation of solvent from extract and raffinate
• Continuous process
• Low handling cost
• Solvent recovery is easy
• Versatile and efficient (use of co-solvents and co-solutes)

25. LIMITATIONS
• Prolonged time (penetration of SCF into the interior of a solid
is rapid, but solute diffusion from the solid into the SCF).
• Modeling is inaccurate
• Scale is not possible (due to absence of fundamental,
molecular-based model of solutes in SCF)
• Expensive
• Consistency & reproducibility may vary in continuous
production

26. PRECAUTIONS
• Adequate contact time
(for penetration of solvent into solid particles and diffusion of
solute from inside the solid particles to solvent)
• Equilibrium should be achieved
(i.e. proper flow of solvent such that concentration of dissolved
solutes in the solvent phase will be below the solubility of
solute in solvent)

27. APPLICATIONS
Food science
• Fat and oil samples in meat, egg, meals, chocolate,
dairy products, seeds and food snacks,
Natural products
• Flavors & spices of ginger, eucalyptus, soyabean,
coffee, soybean, basil, lime peels, potato chips,
popcorn
By-products recovery
• Fruit and vegetable waste

28. REFERENCES
• Sairam, P., Ghosh, S., Jena, S., Rao, K.N.V. and Banji, D. (2012)
Supercritical Fluid Extraction (SFE)-An Overview Asian J. Res.
Pharm. Sci.; Vol. 2: Issue 3, Pg 112-120.
• Das, S. supercritical fluid extraction, module 10. NPTEL.
• Jonin, T.M., Adjadj, L. P and Rizvi, S.S. Food Engineering. Vol
III. Encyclopedia of Life Suport System (EOLSS).
• Toledo , Supercritical fluid extraction. Chapter Extraction.
Third Edition. pp 528-531

29. THANKYOU
For stepping forward towards Green Chemistry…