4. INTRODUCTION
• A switchable solvent (New generation solvent) is a green solvent where one
of its characteristics can be switched from one form to another.
• These could be conductivity, polarity, solubilizing capability or viscosity.
• Switchable-polarity solvents are solvents that can switch reversibly between
One form that is miscible with water to another that forms biphasic mixture
with water.
• Switchable solvents are more advantageous than conventional solvents as
media for reactions or separation due to its properties especially in multi-
step chemical process that requires more steps.
4
5. INTRO. CONT….
• This increase the production cost and environmental waste for the
entire process.
• However, a switchable solvent could carryout more than one step
before it needs to be replaced.
• Whereby, the solvent go from a relatively low polarity into another
that is more polar with the addition of CO2.
5
6. Principle and Mechanisms of Switchable
polarity solvent polarity
• First, they both require CO2 as the switching agent,
• Which can be switched back by its removal with heat
Or N2.
• Typically conversion of the SPS from its non-polar to polar form can be affected
by simple addition of 1bar CO2 pressure.
• Reversing from its polar again to its non-polar form is completed by bubbling
Nitrogen through the medium.
•
6
7. Cont….
• Though, application to a commercially viable process requires further
considerations of such factors as reaction vessel design, separation of
solvent whether in polar or non-polar form.
• Application of adequate Co2 pressure, and supply of inert gas for
reversing to non-polar form.
• Above all, the process steps for recovery of the target source are most
as are the overall economic considerations.
7
10. SYNTHESIS OF SWITCHABLE SOLVENT
• SPS mainly includes amidine derivatives and tertiary amine
compounds.
• But tertiary amines were easier to switch compared to amidines.
Hence, amidines are very difficult to synthesize.
• To find appropriate tertiary amine type Sps, reserchers had concluded
that amines has Log K between 1.2 and 2.5 and PKA above 9.5 so that
it displays typical SPS behavior.
10
12. Advantages of SPS
1. It has few chemical steps in chemical processes and separations
when compared with conventional solvents that involves multi-step
chemical process, which increase the production cost and
environmental waste for the entire process.
2. It is non-toxic and less hazardous
3. It is relatively cheap
4. The use of switchable solvents in combination with water has been
proposed as an alternative to distillation for solvent removal that do
not require the use of volatile compounds.
12
13. Advantages Cont…
5. This method has been exploited as a method for removing solvent
from products such as Soybean oil, Algae oil, bitumen and high density
polystyrene powder.
6. It is used as an efficient method for extraction, separation and
recovery
7. It is used in non-polluting, non-wasteful chemical processes and
method that are environmentally friendly for chemical processing and
separation.
13
14. Limitations of SPS
• Amidines are not easy to synthesize as well not easy in switching its
polarity.
• Inadequate supply of CO2 and N2/ heat may not switch the polarity of
the solvent to the desired form.
• It needs back extraction, hence lead to low enhancement factor.
• Some times using high conc. Of NaOH leads to wastage of analytes
which are based hydrolysed.
14
15. Testing for switchable Behavior
• To confirm the switchable miscibility, Amines were mixed with water
in a 1:1 volume ratio.
• If two phases were observed, CO2 was bubbled into the solution
through a gas dispersion tube for 2 hours
• If the mixture become mono-phasic, N2 was bubbled into the solution
through a gas dispersion tube for 2 hours, while the solution was
heated to 65C.
• If the mixture become biphasic again, the amine was classified as a
switchable polarity solvent.
15
16. Some Instruments compatible with SPS
• GC-MS
• GC-FID
• HPLC
• NMR
• Atomic Absorption Spectroscopy (FAAS and GFAAS)
• ICP-MS
• ICP-OES
• FT-IR….. ETC
16
24. CONCLUSION
• Solvents play an incredibly important role in large scale chemical
reaction.
• SPS is a novel and efficient method for extraction, separation and
other chemical processes which provide non-toxic, non-waste and
environmentally friendly process.
• SPS may prove to be a class of solvent that offers energy and material
efficiencies greater then existing solvents that needs further
exploitation to improve the efficiency of the process as a green
chemical process.
24
25. Reference
• Boyd, A.R., Champagne, P., McGinn, P.J., MacDougall, K.M., Melanson, J.E.,
Jessop, P.G., 2012. Switchable hydrophilicity solvents for lipid extraction from
microalgae for biofuel production. Bioresour. Technol. 118, 628–632.
• Devereux, J.M., Payne, K.R., Peeling, E.R.A., 1957. 555. Catalytic hydrogenation.
Part I. The hydrogenation of unsaturated amines over platinic oxide. J. Chem. Soc.
(Resumed), 2845–2851.
• Frenna, V., Vivona, N., Consiglio, G., Spinelli, D., 1985. Amine basicities in benzene
and in water. J. Chem. Soc. Perkin Trans. 2, 1865–1868.
• Fu, D., Farag, S., Chaouki, J., Jessop, P.G., 2014. Extraction of phenols from lignin
microwave-pyrolysis oil using a switchable hydrophilicity solvent. Bioresour.
Technol. 154, 101–108. Hall, N.F., Sprinkle, M.R., 1932.
• Relations between the structure and strength of certain organic bases in aqueous
solution. J. Am. Chem. Soc. 54, 3469–3485. Hansen, C.M., 2004. Polymer
additives and solubility parameters. Prog. Org. Coat. 51, 109–112.
25
