Comparison of Biodiesel Production from High Free Fatty Acid, Crude Coconut Oil via Saponification followed by Transesterification or a Two-Stage Process

Abstract

Saponification followed by a transesterification process (SFT) or a two-stage process (TSP) were investigated for biodiesel production from high free fatty acid (FFA), crude coconut oil. In SFT, the effects of the concentration of NaOH solution on free fatty acid reduction were investigated. The oil
from saponification after cleaning was used as a raw material to produce biodiesel. For TSP, the effects of methanol and H₂SO₄ on free fatty acid reduction were determined using various amounts of methanol catalyzed by H₂SO₄ and with different amounts of H₂SO₄ in methanol. Then, the de-acidified oil was used to produce biodiesel. All reactions were carried out at 60°C and monitored by titration and thin layer chromatography/flame ionization detection. The suitable conditions of SFT for obtaining 99% by weight methyl ester content were: 15 v% of water, 36 v% of methanol and 19.9 %wt/v of NaOH, yielding 45.6% in 26 h. Like methyl ester concentration, TSP could produce 86.6% yield of biodiesel under 5 v% of H2SO4, 37 v% of methanol and 2.5 %wt/v of NaOH in 14.25 h. Finally, the biodiesel cost was approximately 57.09 and 32.02 THB/L by SFT and TSP, respectively. Therefore, TSP was considered more suitable for producing biodiesel from high FFA crude coconut oil because it was quicker, cheaper and produced a higher yield.