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.