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Abstract
This study evaluated the production of fatty acid ethyl esters from fish oil using ultrasonic energy and alkaline catalysts dissolved in ethanol. The feasibility of fatty acid ethyl ester production was determined using an ultrasonic bath and probe, and between 0.5 and 1% KOH (added to the fish oil). Furthermore, factors such as ultrasonic device (bath and probe), catalyst (KOH and C^sub 2^H^sub 5^ ONa), temperature (20 and 60 °C), and duration of exposure (10-90 min) were assessed. Sodium ethoxide was found to be a more efficient catalyst than KOH when transesterifying fish oil. Ultrasonic energy applied for greater than 30 min at 60 °C using 0.8% of C^sub 2^H^sub 5^ONa as a catalyst transesterified over 98% fish oil triglycerides to fatty acid ethyl esters. It is reasonable to conclude that the yield of fatty acid ethyl esters produced by applying ultrasonic energy to fish oil is related to the sonication time. Due to increases in the surface area contact between the reactants and the catalyst, ultrasonic energy has the potential to reduce the production time required by a conventional large-scale commercial transesterification method that uses agitation as a way of mixing.
Keywords Transesterification * Ultrasonic energy * Fish oil * Polyunsaturated fatty acids * Base catalysts Fatty acid ethyl esters
Introduction
Biodiesel refers to the fatty acid alkyl esters that are produced from vegetable oils or animal fats in the presence of an alcohol and a catalyst, and the most common method used to produce it is through transesterification of oil [1, 2]. It has been proposed that the transesterification occurs in three steps: (1) reaction of triglycerides (TG) and alcohol leading to diglycerides (DG) and one monoester; (2) DG react with alcohol and produce monoglycerides (MG) and monoester, and (3) MG react with alcohol and produce glycerol and monoester [3-5]. The complete mechanism to convert TG to glycerol and monoesters has complicated kinetics since the process comprises not less than twelve reaction equilibria [6].
Transesterification can be catalyzed by enzymes, acid, or base. However, both enzyme and acid catalysis are generally slower than the more commonly used base catalysts [7]. On me commercial scale, the common alkali catalysts are NaOH and KOH because of their low cost [6]. Stoichiometrically, transesterification...