Effect of Temperature on the Conversion of Triolein to Biodiesel Via a Heterogeneous Acid-Catalyzed Interesterification Reaction

Abstract

With the increase
of environment protection consciousness and decrease of petroleum reserves, the
search for alternatives energy has gained much attention. Biodiesel is a
potential energy source that has grown in importance over recent years, as an
alternative to petroleum based diesel fuel. Biodiesel has several benefits,
such as reducing the greenhouse gas emissions. And it can be produced from
varies of vegetable oils and animal fats, such as soybean and sunflower. The
industrial production of biodiesel is by a transesterification reaction between
triglycerides (found in oils and fats) and methanol in the presence of a
catalyst. Stoichiometrically, 3 mol of FAME (fatty acid methyl ester) and 1 mol
of glycerol are produced from every 1 mol of triglyceride. One of the main
drawbacks of this process is the production of low-purity glycerol. Glycerol is
limited in its application and has reached market saturation. Theoretically,
glycerol by-production can be prevented by an alternative reaction,
interesterification where triglycerides are reacted with methyl acetate instead
of methanol. The stoichiometry remains identical but the replacement of
methanol with methyl acetate produces triacetin as a byproduct instead of
glycerol. Triacetin has been shown to have various positive applications after
its purification. It can be used as a fuel additive and its mixture with FAME
shows no detrimental effects on fuel properties. However, interesterification
reaction has a lower reaction rate compared to transesterification, which
limits the industrial applications of interesterification. In this project,
triolein, a symmetrical triglyceride, was selected as the feedstock. Ferric
sulfate worked as a heterogeneous acid catalyst to increase the reaction rate.
The yield of methyl oleate/ethyl oleate via interesterification reaction was
determined at different temperature with different combination of reactants to
demonstrate the effect of temperature on the conversion of triolein to FAME. The
highest yield of FAME was found to be approximately 70% at 120 ºC with 20:1
MAOMR and 7.5 wt% catalyst loading.