Transesterification, mechanism of trans esterification, importance of transesterification, conclusion and references

1. Transesterification of milk fat
for production of biodiesel
Presented by:
M Archana
MDK 1702
Dairy Chemistry
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2. Contents
Introduction
Definition of Transesterification
Transesterification reactions and its mechanism
Transesterification of milk fat by using dairy waste
(scum)
Importance and applications of transesterification
Conclusion
References
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3. Introduction
 The limited fossil fuel resources along with the need to reduce
Green House Gas emissions were a major impulse to the
development of alternative fuels.
 As a result, increased attention has been given to biofuels, such as
biodiesel, that can be used as an alternative fuel in compression–
ignition engines.
 Its production from renewable resources, such as vegetable oils
and animal fats, makes it biodegradable and non-toxic also, it
contributes to the reduction of CO2 emissions, because it
comprises a closed carbon cycle.
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4. Transesterification
 Generally, biodiesel is produced by means of transesterification.
 Transesterification is the reaction of a lipid with an alcohol to
form esters and a by-product, glycerol.
 It is, in principle, the action of one alcohol displacing another
from an ester, referred to as alcoholysis (cleavage by an alcohol).
 The reaction is reversible, and thus an excess of alcohol is usually
used to force the equilibrium to the product side.
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5. Transesterification definition
 Transesterification is the general term used to describe the
important class of organic reactions where an ester is transformed
into another ester through interchange of the alkoxy moiety. When
the original ester is reacted with an alcohol, produces an another
esters and the process is called transesterification or alcoholysis.
RCOOR’ + R”OH RCOOR” + R’OH
 Transesterification consists of a sequence of three consecutive
reversible reactions. The first step is the conversion of triglycerides
to diglycerides, followed by the conversion of diglycerides to
monoglycerides, and finally monoglycerides into glycerol, yielding
one ester molecule from each glyceride at each step.
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6. Transesterification reaction
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7.  The catalyst used has a significant effect on the reaction, raising the
rate notably.
 It is known that basic catalysts require short times to complete the
reaction even at room temperature, while acid catalysts, such as
sulfuric acid, require higher temperatures (100ºC) and longer
reaction times (3 – 4 h).
 The alkalis that are used generally include sodium and potassium
hydroxides, carbonates, and alkoxides such as methoxide, ethoxide,
propoxide, and butoxide.
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8. Biodiesel production process flow line
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9. Mechanism of transesterification process
 Short-chain alcohols such as methanol, ethanol, and butanol are the most
frequently employed.
 Ethanol can be produced from agricultural renewable resources, thereby
attaining total independence from petroleum-based alcohols. Also,
ethanol, as an extraction solvent, is preferable over methanol because of
its much higher dissolving power for oils.
 For this cause, ethanol is sometimes used as an suitable alcohol for the
transesterification of vegetables oils. Therefore, producing ethyl esters
rather than methyl esters is of considerable interest, because, in addition
to the entirely agricultural nature of the ethanol, the extra carbon atom
provided by the ethanol molecule slightly increases the heat content and
the cetane(C16 H34 aliphatic hydrocarbon) number.(A performance rating
of diesel fuel corresponding to the percentage of cetane in a mixture with
isocetane (or, formerly, methylnaphthalene) that would have the same
performance.)
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10. Transesterification of milk fat by using dairy waste (scum)
Annual production of milk in India is approx. 150 MT per year.
Raw chilled milk of cow and buffalo milk are standardized to
market milk, milk products such as butter, ghee, cream, peda,
paneer, cheese, yoghurt, ice-cream etc.
During these process enormous quantity of water is used for
washing equipments, sterilization and good housekeeping.
Due to this residual butter and related fat which are washed and get
collected in ETP as scum.
Scum is less dense floating solid mass formed by a mixture fat,
lipids, proteins and other organic compounds.
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11. A large dairy, which produces 5lakh litres of milk per day will
produce approx. 200-300 kg of effluent scum per day.
If this scum is disposed to solid waste disposal site or by
incinerating causes economic waste increases BOD and COD
values and pollutes the environment.
To avoid these problems this scum is utilising in the further
production of bio-diesel by a process called transesterification.
There are 4 methods for the production of bio-diesel they are
 Direct use and blending
 Micro-emulsification
 Pyrolysis
 Transesterification
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12. Transesterification is the displacement of alcohol from an ester by
another alcohol
Overall transesterification reaction was given by three consecutive
and reversible reactions are believed to occur.
This reaction is widely used to reduce the viscosity of triglycerides
derived from renewable feedstock such as vegetable oil and animal
derived fat for use in compression engine.
Catalyst is used to increase the transesterification reaction rate and
yield.
Excess alcohol is used to make possible to complete the reversible
reaction.
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13. Methanol is preferred for the production of biodiesel by using dairy
scum because of its low cost, physical and chemical advantages
(polar and short chain).
It can quickly reacts with triglycerides and alkaline catalysts such
as NaOH or KOH.
In methanolysis formation of emulsion were quick and easily
breakdown triglyceride to form glycerol rich bottom layer and
methyl ester rich upper layer.
Transesterification occurs 4000 times faster in presence of alkaline
catalysts than the same amount of acid catalysts used.
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14. In transesterification the starting temperature of the column is
160ºC and increased to 7.5ºC per minute to a final temperature of
240ºC (win-chrome software).
Chemical composition of dairy scum oil:
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15. Transesterification reaction setup:
The transesterification reaction was carried out in a system consists
of a 1L double-necked round bottom flask, which was put inside the
heat jacked.
Thermostat was a part of heat jacket to maintain the temperature of
the reactant at a desired value and the reaction was carried out at
desired temperature.
Methanol has a boiling point of 65ºC, which vaporizes at elevated
temperatures during the reaction.
To prevent the loss of methanol during reaction, a water-cooled
condenser was used to condense the vapours and reflux it back to
the reactor.
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16. The condenser also helps in maintaining the atmospheric pressure
inside the reactor.
The side neck was used for fixing condenser, in order to achieve
perfect contact between the reagents and the oil during
transesterification process, they must be stirred well at a constant
rate.
Transesterification process:
The reactor was charged with a dairy waste scum oil, which was
stirred and pre-heated at different temperatures.
After this a solution of KOH and methanol (CH3OH) was added.
The reaction conditions was varied to obtain a large range of methyl
esters yield.
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17. Heating and stirring was then stopped, neutralised with acetic acid
and the product was allowed to separate into two phases.
Separation:
After completion of the reaction the product is transferred into a
separating funnel for certain time interval for phase separation
(approx. 12hrs).
Since the solubility of the methyl ester is low and it floats on the
surface, and the glycerine tends to collect at the bottom.
Washing:
Washing is a process that removes the entrained glycerol, catalyst,
soaps and excess methanol.
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18. Free glycerine in the product is from transesterification reaction,
when esters are completely washed with water and there should be
a trace amount of methanol left since alcohol is more soluble in
water than in bio-diesel.
The washing process also removes soaps and residual catalysts.
The mixing of ester with water should be gentle to reduce the loss
of ester due to formation of emulsion that could increase separation
time.
To reduce the washing cycles the initial washing was done by
diluted acetic acid continued by distilled water until the lower layer
had a pH of similar to the pH of distilled water indicating that the
biodiesel is free from catalyst.
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19. Drying:
Water in fuel causes 2 problems they are it can cause corrosion of
engine and another is microbial growth.
Drying suggests the possible separation of water from biodiesel.
Drying helps to remove dispersed and dissolved water in biodiesel
which cause poor combustion plugging and smoke in optimal
engine performance.
Drying was performed in hot air oven at 105ºC as long as the water
content reduces below 0.05% as per ASTM
Drying also removes traces of methanol.
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20. line diagram for manufacture of biodiesel
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21. General Properties of Biodiesel
Calorific value- 37.27 MJ/kg
Color- Varies from Golden to Dark Brown
Flash point- >130 °C, >266 °F
Density- ~ 0.88 g/cm³
High boiling point
Low vapor pressure
Immiscible with water
No sulphur content
High Cetane number
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22. Properties of dairy scum based biodiesel:
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23. Biodiesel producing countries
 Brazil
 Argentina
 Colombia
 Malasia
 Indonesia
 China
 Singapore
 Russia
 Southafrica
 India (10th )
 Philippines
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24. Applications of transesterification
Used in Vehicles
Railway uses
Aircraft uses
As a heating oil
For cleaning oil spill
In generators
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25. Conclusion
By knowing about the biodiesel as a fuel we came to know that,
biodiesel is the today's best alternatives for the fossils fuels like
diesel and gasoline.
It can be used in vehicles with some modification in the vehicle.
Production of biodiesel is easy as compared to the fossil fuels, also
it is easy to handle and less pollutant than that of fossil fuels.
Biodiesel is environment friendly and human friendly.
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26. References
Srikanth H.V., Venkatesh J., Sharanappa Godiganur.,
Venkateswaran S., Bhaskar Manne.2017.Bio-Based Diluents
Improve Cold Flow Properties of Dairy Washed Milk-Scum
Biodiesel.international journal of renewable energy.P.1-21
Sivakumar P., Anabarsu K., Ranganathan S.2011.Bio-diesel
production by alakli catalyzed transesterification of dairy waste
scum.journal of fuel.P.147-151
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