Ethanolysis of fish oil via optimized protocol and purification by dry washing of crude ethyl esters

Abstract

In this research work, fatty acid ethyl ester (biodiesel) was successfully developed from fish oil. The acid value of fish oil used is 1.23 mg KOH/g. As a result, transesterification of fish oil with ethanol was performed via one-step transesterification, namely alkaline-catalyzed transesterification using potassium hydroxide (KOH) as a catalyst. The influence of transesterification variables including amount of KOH, ethanol to oil molar ratio, reaction temperature, reaction time and type of the alkali catalyst on yield of fish oil ethyl esters (FOEE) were investigated. The dry washing method which used the activated carbon produced from de-oiled fish waste was used to purify the crude ethyl esters. The best yield of FOEE (98.04% ∼ 97.11% w/w ester content) was obtained at 0.75% wt. KOH, 9:1 ethanol to oil molar ratio, 70 °C reaction temperature and 60 min of reaction. The fuel properties of FOEE were complied with the limits prescribed in the ASTM D6751 standards and EN 14214, where applicable. The viscosity of the produced ethyl ester was found much lower than those reported for the ethyl esters produced from various feedstocks. The transesterification of fish oil with ethanol followed first order kinetics and the activation energy was found to be 14.45 kJ/mol.