6. Discussion
In this research article, we have presented two mathematical
models of transesterification reaction of Jatropha Curcas oil with
alcohol using base catalyst and enzyme catalyst separately with
the help of some basic assumptions. Different time dependant concentration
of substrate, catalysts, complexes, intermediates and
products have been calculated numerically for both the cases.
Our results show that mass transfer in enzymatic transesterification
of Jatropha oil depends mainly on agitation speed and amount
of enzyme. Therefore, effect of enzyme and agitation speed on biodiesel
productivity in terms of mass transfer and reaction time is
determined using Pontryagin Minimum Principle. Biodiesel yield
is significantly influenced by agitation speed and reaction time.
Biodiesel is produced from vegetable oil through a refinery process
called transesterification. Presently, the industrial production
of biodiesel fuel is performed by alcoholysis of oil using alkaline
catalysts. But there are some problems associated with the chemical
transesterification of vegetable oil. In chemical transesterification
high reaction temperature (50–60 C) and stirrer rotation
(600 rpm) are needed. Higher temperature and higher stirring
enhance saponification reaction also. It complicates purification
process and reduces the biodiesel production. A major economic
disadvantage in chemical alcoholysis is that the purification of
glycerol is very difficult and costly. Chemical catalyst, which is
removed with glycerol layer, cannot be reused. Ethanol can be produced
from biomass and is less toxic, but conventional alcoholysis
with ethanol gives lower yields.
To overcome the problems associated with chemical catalysis
for production of biodiesel, enzymatic processes using lipases have
been developed. Enzymatic transesterification has attracted much
attention for biodiesel production as it produces high purity product.
Separation from the by-product, glycerol, is very easy. But the
cost of enzyme remains a barrier for its industrial implementation.
In order to increase the cost effectiveness of the process, the
enzyme is reused by immobilizing in a suitable biomass support
particle and that has resulted in considerable increase in efficiency.
Inhibition of enzyme by methanol can be avoided giving control on
stirring. Reaction rate in this process is very slow due to mass
transfer resistance. For cost effective production of biodiesel
through enzyme catalyzed reaction, we have applied control
approach on mixing intensity and we have seen that control measures
have a great impact on reaction system for the maximum