Biodiesel, its Characteristics, Biodiesel Production, Its advantages and limitations

1. BIODIESEL PRODUCTION
PROCESSES
Dr. Ajay Singh Lodhi
Assistant Professor
College of Agriculture, Balaghat
Jawahar Lal Krishi Vishwa Vidyalaya, Jabalpur (M.P.)

2. METHOD OF BIODIESEL PRODUCTION
 An adaptation of the vegetable oil as a Compression
Ignition (CI) engines fuel can be done by four methods
 Pyrolysis;
 Micro-emulsification;
 Dilution; and
 Transesterification.

3. PYROLYSIS
 The pyrolysis refers to a chemical change caused by the
application of thermal energy in the absence of air or
nitrogen. The liquid fractions of the thermally
decomposed vegetable oils are likely to approach diesel
fuels.
 The pyrolyzate has a lower viscosity, flash point, and
pour point than diesel fuel and equivalent calorific values.
The cetane number of the pyrolyzate is lower.
 The pyrolyzed vegetable oils contain acceptable amounts
of sulfur, water and sediments and give acceptable
copper corrosion values but unacceptable ash, carbon
residual and pour point.

4. MICRO-EMULSIFICATION
 The formation of micro emulsion is one of the potential
solutions for solving the problem of vegetable oil viscosity.
 Micro-emulsions are defined as transparent,
thermodynamically stable colloidal dispersion.
 The droplet diameters in micro-emulsions range from 100
to 1000 Å. Microemulsion can be made of vegetable oils
with an ester and dispersant (co solvent), or of vegetable
oils, and alcohol and a surfactant and a cetane improver,
with or without diesel fuels. All micro-emulsions with
butanol, hexanol and octanol met the maximum viscosity
requirement for diesel fuel.
 The 2-octanol was found to be an effective amphiphile in
the micellar solubilization of methanol in triolein and
soybean oil.

5. DILUTION
 The dilution of vegetable oils can be accomplished with
such material as diesel fuels, solvent or ethanol.
 Dilution results in the reduction of viscosity and density of
vegetable oils. The addition of 4% ethanol to diesel fuel
increases the brake thermal efficiency, brake torque and
brake power, while decreasing the brake specific fuel
consumption.
 Since the boiling point of ethanol is less than that of diesel
fuel, it could assist the development of the combustion
process through an unburned blend spray.

6. TRANSESTERIFICATION
 Transesterification is the method of biodiesel production
from oils and fats and can be carried out by two ways.
 (a) Catalytic Transesterification.
 (b) Supercritical Methanol Transesterification
Catalytic Transesterification
 The “Catalytic Transesterification” process is the reaction
of a triglyceride (fat/oil) with an alcohol in the presence of
some catalyst to form esters and glycerol.
 A triglyceride has a glycerin molecule as its base with
three long chain fatty acids attached. The characteristics
of the oil/fat are determined by the nature of the fatty acids
attached to the glycerin. The nature of the fatty acids can
in turn affect the characteristics of the biodiesel.

7. The products of the reaction of biodiesel
A successful transesterification reaction is signified by the
separations of the ester and glycerol layer after the reaction
time. The heavier, co-product, glycerol settles out and may
be sold as it is or it may be purified for use in other
industries, e.g. the pharmaceutical, cosmetics etc.

8. ACID CATALYZED TRANSESTERIFICATION
 The acid catalyzed process is the reaction of a triglyceride
(fat/oil) with an alcohol in the presence of acid catalyst,
preferably sulphonic and sulphuric acids to form esters
(biodiesel) and glycerol.
 These catalysts give very high yields in alkyl esters, but
the reactions are slow, requiring, typically, temperatures
above 100°C.
 The acid-catalyzed transesterification should be carried
out in the absence of water, in order to avoid the
competitive formation of carboxylic acids which reduce the
yields of alkyl esters.

9. ALKALINE CATALYZED TRANSESTERIFICATION
 The alkaline catalyzed transesterification process is the
reaction of a triglyceride (fat/oil) with an alcohol in the presence
of an alkaline catalyst such as alkaline metal alkoxides and
hydroxides as well as sodium or potassium carbonates to form
esters (biodiesel) and glycerol.
 The alkaline catalyzed transesterification of vegetable oil
proceeds faster than the acid catalyzed reaction. Due to this
reason, together with the fact that the alkaline catalysts are less
corrosive than acidic compounds, industrial processes usually
favor alkaline catalysts, such as alkaline metal alkoxides and
hydroxides as well as sodium or potassium carbonates.
 But the presence of water and high amount of free acid gives
rise to saponification of oil and therefore, incomplete reaction
during the alkaline transesterification process with subsequent
formation of emulsion and difficulty in separations of glycerol.

10. LIPASE CATALYZED TRANSESTERIFICATION
 The lipase catalyzed transesterification process is the
reaction of a triglyceride (fat/oil) with an alcohol in the
presence of lipase enzyme as a catalyst to form esters
(biodiesel) and glycerol.
 In lipase catalyzed process no complex operations are
needed not only for the recovery of glycerol but also in the
elimination of catalyst and soap.
 This is an environmentally more attractive option to the
conventional process. However, the reaction yields as well
as the reaction times are still unfavorable compared to the
alkaline catalyzed reaction systems.

11. SUPER CRITICAL TRANSESTERIFICATION
 The simple transesterification processes discussed above are
confronted with two problems, i.e. the processes are relatively
time consuming and needs separations of the catalyst and
saponified impurities from the biodiesel.
 The first problem is due to the phase separations of the
vegetable oil/ alcohol mixture, which may be dealt with by
vigorous stirring. These problems are not faced in the
supercritical method of transesterification.
 This is perhaps due to the fact that the tendency of two phase
formation of vegetable oil/alcohol mixture is not encountered
and a single phase is found due to decrease in the dielectric
constant of alcohol in the supercritical state (at 340°C and 43
MPa). As a result, the reaction was found to be complete in a
very short time within 2-4 mins.
 Further, since no catalyst is used, the purification of biodiesel is
much easier, trouble free and environment friendly (Demirbas,
2005).

12. BIODIESEL PREPARATIOSNS BY CATALYTIC
TRANSESTERIFICATION METHOD
 Refined corn oil, palm oil, waste cooking cotton seed and rice
bran oils were esterified by the transesterification method.
Transesterification is otherwise known as alcoholysis. It is the
reaction of fat or oil with alcohol to yield esters and glycerin.
 Transesterification of selected oils was carried out by heating
the oil. In this process, alcohol combines with triglyceride
molecule from acid to form glycerol and ester. The glycerol is
then removed by density separations.
 Simple alcohols are used for transesterification and this
process is usually carried out with a basic catalyst (NaOH,
KOH) in the complete absence of water.
 Transesterification decreases the viscosity of oil, making it
similar to diesel fuel in characteristics. A catalyst is used to
improve the reaction rate and yield. Transesterification of
triglycerides using alcohol is shown in Figure.

13. Biodiesel production process by transesterification method

14.  The “catalytic
transesterification” process
is the reaction of a
triglyceride (fat/oil) with an
alcohol in the presence of
acidic, alkaline or lipase as
catalyst to form mono alkyl
ester (i.e. Biodiesel) and
glycerol. Alkaline catalyzed
transesterification is the
fastest and require simple
setup Therefore, in current
the study, the SVO of
selected oils was
transesterified with methyl
alcohol in the presence of
strong alkaline sodium
hydroxide catalyst in a batch
type transesterification
reactor.
Schematic sketch of
transesterification reactor

15.  To prepare biodiesel from SVO of selected oils, first, the sodium
hydroxide is added to methyl alcohol to form sodium-methoxide;
simultaneously oil is heated in a separate vessel to remove
moisture.
 Moisture free oil is kept in the inner vessel of transesterification
reactor, and subjected to heat and stirring. When the
temperature of the oil reaches 60°C, then sodium methoxide is
mixed into the oil and the reaction mixture is stirred for more
than one hour until separation of glycerol is started.
 Separation of glycerol is checked by taking a small sample of
reactant in a test tube. When separation of glycerol starts then
stirring is stopped and the reaction mixture is transferred to a
separate container.
 After 8 hours the reaction mixture is separated into the methyl
esters in the upper layer and the glycerol in the lower layer. The
methyl esters are decanted and washed three times with warm
distilled water to remove traces of soap and other impurities. The
final product obtained is good quality biodiesel.

16. Bio-Diesel Production
(TNAU biodiesel pilot plant)
 For the esterification of Jatropha oil, alkaline-based
catalyst is used in this plant.
 The Jatropha oil is blended with alcohol and catalyst
mixture.
 The oil extracted from the seeds of Jatropha is mixed with
methanol catalyst mixture at a proportion under a particular
temperature.
 This solution is continuously stirred for two hours.
 During the above process, glycerol present in the solution
separate out, which when settled can be separated out. For
settling, three separate tanks are provided in the plant.
 After removing the glycerol, the liquid biodiesel is
transferred to washing tank, where the fuel is washed twice
and the purified biodiesel is obtained.

17. By using the this
unit, about 250
litres of biodiesel
could be produced
in a day.
The cost of the
unit is approx 1.5
lakhs.
This could be
reduced by
appropriate
substitutions in the
existing plant.
Depending upon
the need, the size
of the unit can be
scaled up to get
higher capacity.

19. Mechanics of the transesterification process
 Take 50 litres of Jatropha oil in the container and pump oil from inlet tank to
biodiesel reactor by using inlet pump (10 minutes)
 Switch ON for heater of biodiesel reactor
 Take 20 per cent of methanol and 1 per cent of sodium hydroxide (by
weight of oil) in the chemical mixing tank. Ensure that gate valve for
chemical tank is in closed position before filling of methanol into tank
 Switch ON for stirrer of chemical mixing tank (15 minutes) to produce the
sodium methoxide solution
 After reaching reaction temperature 60 deg. C, the sodium methoxide is
send to biodiesel reactor by opening of gate valve and close the valve.
 Switch ON for main stirrer of biodiesel reactor and reaction is continued for
about 2 hours
 After reaction time is completed, open the gate valve for glycerol settling
tank and the biodiesel and glycerol mixer is send to the glycerol settling
tank (by using storage switch)
 Allow the biodiesel mixture in glycerol settling tanks for 12 hours
 Before feeding of raw biodiesel, fill 100 litres of water in the washing tank
 Remove the glycerol from settling tank and biodiesel is sent to washing
tank by opening gate
 Switch ON the aerator for 30 minutes. Allow the sample for 3 hours and
remove the biodiesel from washing tank
 Heat the biodiesel for 20 minutes to remove the moisture.

20. POST PRODUCTION PROCESS
Refining (Cleaning)
 The esters recovered from the reaction mixture are refined
to meet the requirements of ASTM D 6751-2. The topics
include: biodiesel/glycerol separation, ester washing, ester
drying, other ester treatments and additization.
Biodiesel/glycerol separation
 The biodiesel /glycerol separation is typically the first step of
product recovery in most biodiesel processes.
 The separation process is based on the facts that fatty acid
alcohol esters and glycerol are sparingly mutually soluble,
and that there is a significant difference in density between
the ester and glycerol phases. The presence of methanol in
one or both phases affects the solubility of ester in glycerol
and glycerol in ester.

21.  The biodiesel washing step is used to neutralize any residual
catalyst, to remove any soaps formed during the esterification
reaction and to remove residual free glycerol and methanol.
 Ester drying is required to meet the stringent limits on the
amount of water present in the final biodiesel product. In
addition, there may be other treatments used to reduce color
bodies in the fuel, remove sulfur and phosphorus from the fuel,
or to remove glycerides.
 Additization is the addition of materials that have a specific
functionality that modifies one or more fuel properties. Examples
include cloud point/pour point additives, antioxidants, or other
stability enhancing agents.
 Fatty acid alcohol esters have a density of about 0.88 gm/cc,
while the glycerol phase has a density on the order of 1.05
gm/cc, or more. The glycerol density depends on the amount of
methanol, water, and catalyst in the glycerol. This density
difference is sufficient for the use of simple gravity separation
techniques for two phases.
 Any of the three categories of the equipments viz., Decanter
system or Centrifuge System or Hydro cyclone can be used to
separate the ester and glycerol phases.

22. Thank You