The document summarizes information about oligoglycerols, including their types (linear, branched, cyclic), history, synthesis methods, analysis techniques, applications in polymer production, food industry and cosmetics, commercialization, and future scope. Oligoglycerols are synthesized from glycerol and have various industrial and commercial uses. Further research is needed to develop more sustainable and economical production methods.

1. Sumeet Brar
Chemical engineer

2. Contents
• Glycerol
• Oligoglycerol and its types
• History
• Synthesis of different types of Oligoglycerols
• Laboratory preparation & purification
• Analysis of composition of Oligoglycerols by GC
• Applications
• Commercialization
• Future Scope
• Conclusion
• Refrences

3. Glycerol
• Glycerol ( also called glycerine or glycerin) is a simple
polyol compound. It is a colorless, odorless, viscous liquid that
is sweet-tasting and non-toxic.
• The glycerol backbone is found in all lipids known as
triglycerides. Glycerol is a considered green feedstock due to
its bioavailability.
• An enormous quantity of glycerol is being produced by the
oleochemical and biodiesel industry and is used as a base
chemical for the production of value added products.
• Glycerol has three hydroxyl groups that are responsible for its
solubility in water and its hydroscopic nature.
• It has enormous applications in the food industry,
pharmaceutical and personal care.

4. Structure
• Although achiral, glycerol is prochiral with respect to reactions
of one of the two primary alcohols.
• The name of the compound having the formula is C3H5(OH)3(1)
glycerol, (2) ethylene glycol, (3) propene, (4) propanoic acid.

5. Oligoglycerol
• Oligoglycerols may also be considered as superior building
blocks for polymerization or polycondensation reactions in
comparison to the monomer as the latter leads to low
molecular weight reaction products which have a considerable
effect on the properties of the macromolecular compounds.
Linear oligoglycerol
Branched oligoglycerol
Cyclic oligoglycerol

6. • The general structural formula for oligoglycerol can be
sketched as
• where n=0 results in diglycerol, n=1 in triglycerol, n=2 in
tetraglycerol etc., including branched isomers formed by
reaction of secondary hydroxyls

7. < Linear
< Branched (prim-sec)
< Branched (sec-sec)

8. < Cyclic

9. History
• Oligoglycerol is one of the most versatile and valuable
chemical substances known to man. In the modern era, it was
identified in 1779, by Swedish chemist Carl W Scheele, who
discovered a new transparent, syrupy liquid by heating olive oil
with litharge (PbO, used in lead glazes on ceramics). It is
completely soluble in water and alcohols, is slightly soluble in
many common solvents such as ether and dioxane, but is
insoluble in hydrocarbons.
• Separation of oligoglycerol mixtures into their components is
difficult by direct distillation. But, it was recognized as early as
1947 by Wittcoff that diisopropylidene diglycerol could readily
be removed by fractional distillation from an acetonated
polyglycerol mixture

10. Synthesis of Linear Oligoglycerol
• Linear di- and triglycerols are
known compounds of
oligoglycerol.
• In order to assess the action of
the catalyst in the process of
oligomerization of glycerol a
temperature of 140 °C was
selected for the assessment of
the influence of the catalyst
using a molar ratio of 3%
H2SO4, H3PO4 or NaOH, in a
reaction.

11. Synthesis of Branched Oligomer
• Unlike the linear oligoglycerols, branched compounds cannot
easily be synthesised using a general convergent method. As
the number of possible structures corresponding to each
degree of polymerisation rapidly becomes high (12 isomeric
compounds for n=3, 360 for n=5), a selection of targets had to
be decided upon and different strategies had to be developed
in order to synthesise the branched oligomers.

12. • Synthesis of prim-sec dimer precursors 14 and 15:
1.Benzaldehyde, DMF, CSA, 70 °C, 1 h (68%);
2.KOH, H2O, TBAI, 80 °C, 48 h (80%)

14. • Synthesis of racemic prim-sec dimer 18a from protected
precursor 15:
MeOH, 10% Pd/C, H2, room temp., 1 atm, 24 h (88%)

15. Laboratory Preparation &
Purification of Oligoglycerols
• Glycerol (28.5 times of NAOH) and sodium hydroxide (3.5 wt%
based on the glycerol) added to a three-neck flask equipped
with a condenser.
• The reaction was performed under nitrogen to prevent the
dehydration of glycerol to acrolein. The mixture was reacted for
3.5 h at 250°C and 400 rpm. After reaction, it cooled down to
room temperature, and the crude oligoglycerols are purified
using molecular distillation (MD).
• The glycerol was removed and the heavy phase was collected
under the following conditions:
evaporator temperature 120°C,
condenser temperature 50°C,
evaporator vacuum pressure 5.0 Pa, and
 roller speed 300 rpm.

16. • The high polyglycerol (n≥4) removed from the heavy phase of
MD has been collected, and the light phase containing
oligoglycerols was obtained using the following conditions:
evaporator temperature 170°C,
condenser temperature 60°C,
evaporator vacuum pressure 1.0 Pa, and
roller speed 300 rpm.

17. Analysis of the oligoglycerol
composition by GC
• The composition of oligoglycerols were analyzed by gas
chromatography. According to a modified method described by
Prof. Xiao in 2001. The GC analysis was carried out on an
Agilent GC 7820A instrument (Agilent Technologies Inc.,
America), equipped with a flame ionization detector (FID) and a
capillary column of AT-Wax (15 m×0.32 mm, 0.25 μm). The
injector temperature was 280 °C and was used in the split
mode with a split ratio of 20:1. FID was kept at 280 °C and the
flow rate of the carrier gas (N2) was kept at 30 mL·min−1.

18. • The oven temperature was programmed from 120 °C to 260 °C
as follows:
Rising from 120 °C to 165 °C at a rate of 60 °C·min−1 and held
for 4 min,
to 230 °C at a rate of 60 °C·min−1 and held for 2 min,
 to 260 °C at a rate of 10 °C·min−1 and held for 3 min.
The percentage content of each oligoglycerol was calculated
assuming the same response factor.

19. Applications
• Polymer production :In the polymer industry oligoglycerol is
included in the production of plasticizer in polyvinyl alcohol
films or starch-based biodegradable thermoplastic
compositions, and is used in the manufacture of polyurethanes
and polyesters.

20. • Food industry: oligoglycerol is also
used in the production of fatty acid ester
emulsifiers, and is part of food additives.
Often, oligoglycerol is further processed to
derivatives. The abundant reaction is the
esterification of oligoglycerol with fatty
acids to mono-, di-, tri- and tetraester.
This reaction can be accomplished with or
without basic catalysts and leads in
general to a mixture of ester compounds.
These ester exhibit lipophilic/hydrophilic
properties and are favourably included as
emulsifier in the food industry, specifically
in bakery products and oleomargarine.

21. • Cosmetics : In cosmetics, oligoglycerol is ingredient in
personal care formulations. It enhances fragrance and flavour
impact and longevity in products such as toothpastes,
mouthwashes and deodorant sticks. The rate of menthol
evaporation is reduced when dissolved in oligoglycerol instead
of glycerol. With the refractive index higher than glycerol,
oligoglycerol has additional benefits in the formulation of clear
gels. Transparent emulsions are obtained when the aqueous
and oily phases have the same refractive indices. The use of
higher refractive index ingredients, such as oligoglycerol, in the
aqueous phase allows the evaporation of more water, leading
to a reduction in cost. It also results in products with better
optical clarity.

22. Commercialization
• Currently, the amount of oligoglycerol that goes annually into
technical applications is around 30 000 tonnes and is expected
to grow at an annual rate of 2.8%.
• Most of the oligoglycerol marketed today meets the stringent
requirements of the United States Pharmacopeia (USP) and
the Food Chemicals Codex (FCC).
• However, technical grades of oligoglycerol that are not certified
as USP or FCC quality are also found. Also available is Food
Grade Kosher glycerol, which has been prepared and
maintained in compliance with the customs of the Jewish
religion.
•

23. • In 2015, the data on the
market of glycerol
oligomers or polymers are
hardly available. One
estimation for application
of oligoglycerol in food
industry 2015. Nearly
59% are allotted to bakery
products, 29% to
confectionery, 5% to
oleomargarine, 1.5% to
chocolate, 1.5% to ice
cream and 4% to others.

24. Future Scope
• Further research work is needed to combine the benefits from
shape-selective solid catalysts offering a tuned pore system,
and high stability under reaction conditions, with reaction
engineering tools of process intensification thus allowing high
conversion degrees of glycerol at high selectivity of the desired
products. This would make a sustainable high-yield process to
di- and triglycerol by glycerol oligomerization economically
attractive, and would represent an environmentally benign
reaction route in comparison to the current epichlorohydrin
process.

25. Conclusion
• The glycerol chemistry is a subject to continuous change
striving for catalyzed selective conversion in value-added
products. For many applications in cosmetics and food industry
pure glycerol can favourably be replaced by its oligomers,
above all linear diglycerol and triglycerol. Solid catalysts with
specific microporous (crystalline) structures or ordered
mesoporous surface-rich silica or aluminosilicates are
applicable, besides dense oxides of alkaline earth metals.
• Alternatively, the reaction engineering can be modified.
Traditionally, the reaction is performed in batch mode, needing
relatively long reaction times for a complete glycerol conversion
and a correspondingly long residence time of the desired
products in contact with the catalyst.

26. • Since the glycerol oligomerization is a consecutive reaction, the
desired diglycerol and triglycerol are further converted to higher
oligomers at longer reaction times and progressive glycerol
conversion. Using a reactor setup similar to reactive distillation,
where glycerol is evaporated under reduced pressure and
back-condensed on the top of a reactive section containing a
superacidic polymer, high selectivity to diglycerol could be
achieved, even at nearly complete conversion of glycerol.

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