205
temperature = 393 K. The catalyst synthesized at optimum conditions gave maximum conversion (~95%) of oleic acid due to the highest total acid density
(5.56 mmol/g), surface area (641 m
2
/g), and mesoporous structure. Further, it was
observed that the synthesized catalyst may be reused up to 20 cycles after washing
with n-hexane.
5 Conclusions
Waste vegetable oils and non-edible oils are the best feedstock for biodiesel production to lower the cost and to avoid the ethical issues in using virgin vegetable oils.
Moreover, to dampen the disadvantages of the conventional biodiesel production
processes such as limited interphase mass transfer, sensitivity to free fatty acids in
the feedstock, slow reaction rates, and rigorous anhydrous conditions, a phase transfer catalyst can be explored. Conventional single-step base (KOH and NaOH)catalyzed transesterification process requires free fatty acid content in the oil to be
less than 3 wt%. Waste vegetable oils contain water, and a slightly higher amount of
free fatty acids is not a good feedstock for biodiesel production through the conventional route. The addition of phase transfer catalysts such as TMAB can enhance the
mass transfer between the reactants and lower down the methanol requirement.
Non-edible oils containing a very high amount of free fatty acids (usually much
greater than 3 wt%) are also not suitable for biodiesel production through the conventional route. The addition of TMAB enhances the mass transfer between the
reactants which results in a higher yield of biodiesel. However, due to the presence
of a very high amount of free fatty acids in non-edible oils, there is a large tendency
of reaction between the FFA and the base catalyst rather than the reaction between
triglycerides and methanol or free fatty acid and methanol. The addition of TMAB
does not offer any advantage in such cases. Therefore, the content of free fatty acids
in the oil needs to be reduced before transesterification. This raises the need for a
two-step biodiesel production process in which the first step would be esterification.
Among various techniques, esterification is the volume-efficient process to lower
the free fatty acids and uses concentrated sulfuric acid in a homogeneous form. To
mitigate the drawbacks of a conventional homogeneous esterification process, a
non-catalytic esterification route can be explored.
Concentrated sulfuric acid is associated with several drawbacks, and the noncatalytic route requires elevated reaction conditions which are associated with the
high cost of production. Due to these drawbacks, research efforts are focused on the
low-cost solid acid catalysts, which offer an environmentally benign and economically feasible biodiesel production process. The combination of low-quality feedstock and mild reaction conditions can lower the biodiesel cost to a substantial
extent. Moreover, the solid acid catalysts like novel corncob-based solid acid catalyst offer huge eco-friendly benefits together with the recyclability and reusability.
Catalytic and Non-Catalytic Methods for Biodiesel Production
temperature = 393 K. The catalyst synthesized at optimum conditions gave maximum conversion (~95%) of oleic acid due to the highest total acid density
(5.56 mmol/g), surface area (641 m
2
/g), and mesoporous structure. Further, it was
observed that the synthesized catalyst may be reused up to 20 cycles after washing
with n-hexane.
5 Conclusions
Waste vegetable oils and non-edible oils are the best feedstock for biodiesel production to lower the cost and to avoid the ethical issues in using virgin vegetable oils.
Moreover, to dampen the disadvantages of the conventional biodiesel production
processes such as limited interphase mass transfer, sensitivity to free fatty acids in
the feedstock, slow reaction rates, and rigorous anhydrous conditions, a phase transfer catalyst can be explored. Conventional single-step base (KOH and NaOH)catalyzed transesterification process requires free fatty acid content in the oil to be
less than 3 wt%. Waste vegetable oils contain water, and a slightly higher amount of
free fatty acids is not a good feedstock for biodiesel production through the conventional route. The addition of phase transfer catalysts such as TMAB can enhance the
mass transfer between the reactants and lower down the methanol requirement.
Non-edible oils containing a very high amount of free fatty acids (usually much
greater than 3 wt%) are also not suitable for biodiesel production through the conventional route. The addition of TMAB enhances the mass transfer between the
reactants which results in a higher yield of biodiesel. However, due to the presence
of a very high amount of free fatty acids in non-edible oils, there is a large tendency
of reaction between the FFA and the base catalyst rather than the reaction between
triglycerides and methanol or free fatty acid and methanol. The addition of TMAB
does not offer any advantage in such cases. Therefore, the content of free fatty acids
in the oil needs to be reduced before transesterification. This raises the need for a
two-step biodiesel production process in which the first step would be esterification.
Among various techniques, esterification is the volume-efficient process to lower
the free fatty acids and uses concentrated sulfuric acid in a homogeneous form. To
mitigate the drawbacks of a conventional homogeneous esterification process, a
non-catalytic esterification route can be explored.
Concentrated sulfuric acid is associated with several drawbacks, and the noncatalytic route requires elevated reaction conditions which are associated with the
high cost of production. Due to these drawbacks, research efforts are focused on the
low-cost solid acid catalysts, which offer an environmentally benign and economically feasible biodiesel production process. The combination of low-quality feedstock and mild reaction conditions can lower the biodiesel cost to a substantial
extent. Moreover, the solid acid catalysts like novel corncob-based solid acid catalyst offer huge eco-friendly benefits together with the recyclability and reusability.
Catalytic and Non-Catalytic Methods for Biodiesel Production