Supercritical fluids are substances above their critical temperature and pressure, where they can penetrate solids like gases but dissolve materials like liquids. Common supercritical fluids are CO2 and H2O. Supercritical fluids have good solvent properties and are used in many applications like extraction, particle synthesis, and chemical reactions. They are useful for extracting food and flavorings, producing nanoparticles for pharmaceuticals, and improving oil recovery from reservoirs.

1. SUPER CRITICAL
FLUIDS
AND ITS
APPLICATIONS
Clyde Jonathan D’Silva

2. INTRODUCTION
 Definition: Supercritical
Fluid is any substance at a
temperature and pressure
above its Critical point.
 Example: Commonly used
Supercritical fluids are CO2 &
H2O.
 Phase Diagram:
Define SCF by Phase diagram

3. Few SCF

4. PROPERTIES OF SCF
 Can penetrate solids like gas.
 Dissolves materials like liquid.
 There is no surface tension in SCF.
 It has a very good solvent property.
 In supercritical environment only one phase
exists and hence no liquid-gas phase
boundary.
 Close to the critical point, small changes in
pressure or temperature result in large
changes in density, allowing many properties

5.  All supercritical fluids are completely miscible
with each other.
 So for a mixture, single phase can be
guaranteed if the critical point of the mixture is
exceeded.
 The critical point of a binary mixture can be
estimated as the arithmetic mean of the critical
temperatures and pressures of the two
components,
 Tc(mix) = (mole fraction A) x TcA + (mole fraction
B) x TcB.

6.  Most important properties is the solubility of
material in the fluid. Solubility in a SCF tends
to increase with density of the fluid (at const.
temp.).
 Since density increases with pressure,
solubility tends to increase with pressure. At
constant density, solubility will increase with
temperature.
 However, close to the critical point, the density
can drop sharply with a slight increase in
temperature.

7. NATURAL OCCURRENCE
 Submarine -Volcanoes:
Steam & gases which are
releases from the volcanoes are
in high pressure (about 300atm)
& temperature (>275*C).
 Planetary –atmosphere:
Many planets atmosphere is
Supercritical environment for
some fluid. Like –Venus, Jupiter
etc.

8. APPLICATIONS

9. EXTRACTION
• Basic procedure:
Partition volatile substances by contacting
Supercritical Fluid with feed material.
Soluble material dissolve into the
Supercritical Fluid.
The extracted component then separated by
changing pressure & temperature.
Finally the SCF recompressed & recycled.
Process of SFE by flow diagram

11. Why we use SFE?
 Advantages:
 It is relatively rapid for low viscosity & high diffusivity of SCF
 Easily recoverable by changing pressure and temp.
 Non-toxic solvents leave no harmful residue.
 Can be selective by controlling density.
 High boiling components are extracted at relatively low temp.
• Uses:
 IT is largely used in Food & Flavouring industry.
 This method is used for Decaffenication of tea & coffee.
 Extraction of essential oils, aroma materials from spices etc.

12. NANO-PARTICLE
SYNTHESIS
 Supercritical Fluid Precipitation technology produces
particles with Nano-dimension.
 Supercritical fluids provide a number of ways of
achieving this by rapidly exceeding the saturation point
of a solute by dilution, depressurization or a combination
of these.
 These processes occur faster in supercritical fluids than
in liquids, promoting nucleation over crystal growth and
yielding very small and regularly sized particles.
 Recent supercritical fluids have shown the capability to
reduce particles up to a range of 5-2000 nm
 This technique is largely used in Pharmaceutical
industry

13. MICRONIZATION
 Micronization is the process of reducing the
average diameter of a solid material's
particles. Usually, the term micronization is
used when the particles that are produced are
only a few micrometres in diameter.
 However, modern applications (usually in the
pharmaceutical industry) require average
particle diameters of the nanometer scale.

14.  Modern methods using supercritical fluids in
the micronization process are
1. RESS process (Rapid Expansion of
Supercritical Solutions)
2. SAS method (Supercritical Anti-Solvent)
3. PGSS method (Particles from Gas Saturated
Solutions).

15. RESS METHOD
 The SCF is used to dissolve the solid material
under high pressure and temperature, thus
forming a homogeneous supercritical phase.
 The solution is expanded through a nozzle and
small particles are formed.
 At the rapid expansion point right at the
opening of the nozzle there is a sudden
pressure drop that forces the dissolved
material (the solid) to precipitate out of the
solution.

16.  The crystals that are instantly formed enclose
a small amount of the solvent that, due to the
expansion, changes from supercritical fluid to
its normal state (usually gas), thus breaking
the crystal from inside-out. At the same time,
further reduction of size is achieved while the
forming and breaking crystals collide with each
other at the vicinity of the nozzle. The particles
that are formed this way have a diameter of a
few hundreds of nanometers.

18. SAS METHOD
 In the SAS method, the solid material is
dissolved in an organic solvent and a
supercritical fluid is then also forced by means
of pressure to dissolve in the system. In this
way, the volume of the system is expanded,
thus lowering the density, and therefore also
the solubility of the material of interest is
decreased. As a result, the material
precipitates out of the solution as a solid with a
very small particle diameter.

20. PGSS METHOD
 In the PGSS method the solid material is
melted and the supercritical fluid is dissolved
in it, like in the case of the SAS method.
However, in this case the solution is forced to
expand through a nozzle, and in this way
nanoparticles are formed.

22.  In all three methods described, the effect that
causes the small diameter of the solid particles
is the supersaturation that occurs at the time of
the particle formation
 The PGSS method has the advantage that
because of the supercritical fluid, the melting
point of the solid material is reduced. Therefore,
the solid melts at a lower temperature than the
normal melting temperature at ambient pressure
 These processes also do not demand long
processing times, like the case in the traditional

23. Carbon capture and storage and Enhanced oil
recovery
 Supercritical carbon dioxide is used to
enhance oil recovery in mature oil fields.
 The CO2 is separated from other flue gases
either pre- or post-combustion, compressed to
the supercritical state, and injected into
geological storage, possibly into existing oil
fields to improve yields.

24. Chemical Reactions
 Changing the conditions of the reaction
solvent can allow separation of phases for
product removal, or single phase for reaction.
 Rapid diffusion accelerates diffusion controlled
reactions.
 Temperature and pressure can tune the
reaction down preferred pathways, e.g., to
improve yield of a particular chiral
isomer.There are also significant
environmental benefits over conventional
organic solvents.

25. Impregnation and dyeing
 Impregnation is the converse of extraction.
 A substance is dissolved in the supercritical
fluid, the solution flowed past a solid substrate,
and is deposited on or dissolves in the
substrate.
 Dyeing, which is readily carried out on polymer
fibres such as polyester using disperse (non-
ionic) dyes, is a special case of this.

26. Biodiesel production
 Conversion of vegetable oil to biodiesel is via
a transesterification reaction, where the
triglyceride is converted to the methyl ester
plus glycerol. This is usually done using
methanol and caustic or acid catalysts, but can
be achieved using supercritical methanol
without a catalyst.
 This has the advantage of allowing a greater
range and water content of feedstocks (in
particular, used cooking oil), the product does
not need to be washed to remove catalyst, and

27. Generation of pharmaceutical Co-
crystals
 SCF act as a new media for the generation of novel
crystalline forms of APIs (Active Pharmaceutical
Ingredients) named as pharmaceutical cocrystals.
 Supercritical fluid technology offers a new platform
that allows a single-step generation of particles that
are difficult or even impossible to obtain by
traditional techniques.
 The generation of pure and dried new cocrystals
can be achieved due to unique properties of SCFs
by using different supercritical fluid properties:
supercritical CO2 solvent power, anti-solvent effect
and its atomization enhancement.

28. Supercritical fluid
chromatography
 Supercritical fluid chromatography (SFC) can be
used on an analytical scale, where it combines
many of the advantages of High performance
liquid chromatography (HPLC) and Gas
chromatography (GC).
 It can be used with non-volatile and thermally
labile analytes (unlike GC) and can be used with
the universal flame ionization detector (unlike
HPLC), as well as producing narrower peaks
due to rapid diffusion

29.  In practice, the advantages offered by SFC have
not been sufficient to displace the widely used
HPLC and GC, except in a few cases such as
chiral separations and analysis of high-
molecular-weight hydrocarbons.
 For manufacturing, efficient preparative
simulated moving bed units are available.
 The purity of the final products is very high, but
the cost makes it suitable only for very high-
value materials such as pharmaceuticals.

30. Dry Cleaning
 Supercritical carbon dioxide (SCD) can be
used instead of PERC (perchloroethylene) or
other undesirable solvents for dry cleaning.
 Detergents that are soluble in carbon dioxide
improve the solvating power of the solvent.
 Disadvantage: Supercritical carbon dioxide
sometimes intercalates into buttons, and,
when the SCD is depressurized, the buttons
pop, or break apart.

31. Refrigeration
 Supercritical carbon dioxide is also an important
emerging refrigerant, being used in new, low-carbon
solutions for domestic heat pumps.
 These systems are undergoing continuous
development with SCD heat pumps already being
successfully marketed in Asia.
 Some systems developed by consortium of
companies including Mitsubishi in Japan, develop
high-temperature domestic water with small inputs
of electric power by moving heat into the system
from their surroundings. Their success makes a
future use in other world regions possible.

32. Supercritical water power
generation
 The efficiency of a heat engine is ultimately dependent
on the temperature difference between heat source and
sink (Carnot cycle).
 To improve efficiency of power stations the operating
temperature must be raised. Using water as the working
fluid, this takes it into supercritical conditions.
Efficiencies can be raised from about 39% for subcritical
operation to about 45% using current technology.
 Supercritical water reactors (SCWRs) are promising
advanced nuclear systems that offer similar thermal
efficiency gains.
 Carbon dioxide can also be used in supercritical cycle
nuclear plants, with similar efficiency gains

33. Supercritical water oxidation
 Uses supercritical water to oxidize hazardous
waste, eliminating production of toxic
combustion products that burning can
produce.

34. Antimicrobial Properties
 Beside other highly compressed fluids
particularly CO2 at high pressures has
antimicrobial properties.
 While its effectiveness has been shown for
various applications, the mechanism of
inactivation have not been fully understood.

35. THANK YOU!