Kittiphoom Suppalakpanya, Sukritthira Ratanawilai, Ruamporn Nikhom, and Chakrit Tongurai

pp. 79 - 86

Abstract

The esterification of free fatty acids (FFA) in vegetable oils with alcohol using an acid catalyst is a promising method
to convert FFA into valuable ester and obtain a FFA-free oil that can be further transesterified using alkali bases. In this
work, the direct esterification reaction of FFA in crude palm oil to ethyl ester by continuous microwave was studied and the
effects of the main variables involved in the process, amount of catalyst, reaction time and the molar ratio oil/ alcohol, were
analyzed. The optimum condition for the continuous esterification process was carried out with a molar ratio of oil to ethanol
1:6, using 1.25%wt of H₂
SO₄
/oil as a catalyst, microwave power of 78 W and a reaction time 90 min. This esterification process
shows that the amount of FFA was reduced from 7.5%wt to values around 1.4 %wt. Similar results were obtained following
conventional heating at 70°C, but only after a reaction time of 240 min. The esterified crude palm oil is suitable to perform the
transesterification process. Transesterification of the esterified palm oil has been accomplished with a molar ratio of oil to
ethanol of 1:8.5, 2.5%wt of KOH as a catalyst, a microwave power of 78 W, and a reaction time of 7 min. In addition, the
problem of glycerin separation was solved by mixing 10%wt of pure glycerin into the ethyl ester to induce the glycerin from
the reaction to separated. This two-step esterification and transesterification process provided a yield of 78%wt with an
ester content of 97.4%wt. The final ethyl ester product met with the specifications stipulated by ASTM D6751-02.