Kinetics of Biodiesel Production from Soya Bean Soap Stock

Abstract

Low quality lipids such as soyabeanrsoapstock, a by-product of vegetable oil processing can be used as a viable feedstock for the production of biodiesel due to its high yield capacity, availability, and low cost. Sodium hydroxide and methanol were used as catalyst and solvent respectively while n–hexane was added as a co-solvent. Kinetics of the transesterification reaction mechanismfor soyabeansoapstock with and without co-solvent (n-hexane) was carried out using models proposed by Singh & Fernando, (2007) to determine the reaction order and rate constant at different temperatures (45°C, 55°C and 65°C). Similar rate constants were obtained (with and without co-solvent) though with slightly different R2 values showing that n-hexane does not distort the chemistry of the reaction. Negative and very low R2 values obtained at temperatures 45°C and 65°C further affirms 55°C as the optimum temperature for the reaction. An activation energy of 74 KJ/mol and frequency factor of 2.9 was also obtained. Findings from the studyshows that soyabeansoapstock is a viable feedstock for the production of biodiesel and n-hexane was a suitable co-solvent in the transesterification of low quality lipids (soyabean soap stock). A rate constant of 0.0008 min-1 and reaction order of 2 was obtained for the transesterification reaction.