31-07-2012, 04:44 PM
BIODIESEL PRODUCTION FROM MUTTON TALLOW
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INTRODUCTION
Biodiesel is an alternative fuel for diesel engines that is
receIVIng great attention worldwide as it reduces the
dependence on petroleum products, the energy crisis, global
climate changes and environmental pollution. Biodiesel and
its blends can be used in diesel engines without any major
modification. It is defined by ASTM that it is a fuel composed
of Mono alkyl esters of long-chain fatty acids derived from
renewable vegetable oils or animal fats(Ma and Hanna, 1999,
Srivastava and Prasad, 2000). Chemical Biodiesel can be
produced by transesterification, which is a three step
reversible reaction that converts the intial triglycerides into a
mixture of Fatty acid Methyl Ester(FAME) and glycerol in the
presence of a catalyst usually homogeneous bases such as
NaOH, KOH, or their alkoxides (Han et ai, 2009). Although
Vegetable oil esters have certain advantages such as lower
viscosity, lower flask point, higher vapour pressure and easier
processing relative to animal fatty acid esters, hence they are
non-economical and non-feasible due to the prohibitive cost.
Moreover, the use of vegetable oil leads to shortage of food
while use of animal fat for human consumption is a health
hazard. Drawbacks of using animal fat as a raw material for
Biodiesel production is its physical properties which could be
eliminated by adding necessary amount of alcohol, catalyst for
a required period of time. In the present work, we intent to
produce methyl esters from the waste mutton fat and to
optimise the reaction variables.
MATERIALS AND METHODS
The mutton fat was obtained from a slaughter house. The fat
was washed, cleaned with deionised water and was free of
flesh. The solid fat was melted at around 65° C . This was
then filtered, centrifuged and decanted to remover other
suspended particles. The processed fat which was
homogeneous in nature was stored in air tight opaque plastic
jars to prevent oxidation. The free fatty acid (FFA) of the and
mutton fat was determined and found to be 12.4 mg of
KOH/gm of fat. All the analytical grade reagents were
bought from the local chemical supplier.
TRANSESTERlF1CATlON
Biodiesel production from mutton fat consist of two steps: Acid
esterification (Step I) and alkali transesterification (Step 2) as the
acid value of mutton fat is more than 2%. The parameters such as
alcohol to oil molar ratio, catalyst amount, reaction temperature and
reaction time were analysed. As the mutton fat had an initial acid
value of 12.4 mg KOHJg, which is far above the 1% limit for
satisfactory transesterification reaction using alkaline catalyst.
Therefore, FFA levels were first reduced in a multi-step pretreatment
process using acid catalyst (H2S04 1% v/v) to reduce the acid value
of Mutton fat below 1%. KOHJg. Experiments were conducted in a
laboratory-scale setup which considered of 250cc glass flasks with air
tight caps and a water cooled condenser that returned any vaporized
methanol to the reacting mixture. The flasks were kept in an oil bath
maintained at 60° C, just below the boiling point of methanol. The
mixture was stirred using an agitator at the same rate for all runs. The
same setup was also used for the alkaline catalysed transesterification
reaction. At various time the progress of the reaction was monitored
by measuring the acid value.
CONCLUSION
The study on the biodiesel productin process optimization of mutton
fat showed that the quantity of catalyst, amount of methanol, reaction
temperature and reaction time are the main factors affecting the
production of methyl esters. The optimal values of these parameters
for achieving maximum conversion of oil to esters depended on the
chemical and physical properties of these fats. The following
conclusions are drawn from the study.
1. Addition of excess catalyst causes more triglycerides
participation in the saponification reaction leading to a
marked reduction in the ester yield
2. Biodiesel production process is incomplete when the
methanol a,mount is less than the optimal value. Operating
beyond the optimal value, the ester yield would not be
increased but will result in additional cost for methanol
recovery.
3. Sufficient reaction time should be allowed to ensure
complete conversion of triglycerides into esters. However,
excess reaction time did not promote the conversion but
favours the reverse reaction of transesterification which
resulted in a reduction of ester yield.
4. The optimal reaction conditions for production of methyl
esters from mutton fat are established as follows. The
reaction time of 90 min at 60°C, 6: 1 molar ratio of
methanol to oil and 0.39 gms of KOHlgm of oil for mutton
fat for 50ml of mutton fat.
5. Results of present study clearly demonstrated that the use
of mutton fats is very suitable as low cost feed stocks for
biodiesel production.