Production of Methyl ester from Coconut Oil using Heterogeneous K/γ-Al2O3 under Microwave Irradiation

Abstract

Methyl esters derived from coconut oil are very interesting to study because they contain free fatty acids , so most methyl esters (70%) can be bio-kerosene and the rest can be biodiesel. Trans-esterification triglyceride generally using a homogeneous KOH catalyst but this process requires a long catalyst separation process through washing and drying process. The use of heterogeneous catalysts in the production of methyl esters can remove the washing and drying processes, but trans-esterification reactions with heterogeneous catalysts require severe conditions, whereas at low temperatures and atmospheric conditions, the methyl ester yield is relatively low. Using microwave-irradiated trans-esterification reactions with heterogeneous catalysts, it is expected to be much faster and can obtained higher yields. Therefore, in this study we prepare a heterogeneous catalyst K/γ-Al₂O₃ using solution KOH that impregnated in catalyst support γ-Al₂O₃, and catalyst obtained are characterized by XRD, BET dan SEM. Our objective was to compare the yield of methyl esters obtained through the trans-esterification process of coconut oil assisted by microwave using a heterogeneous K/γ-Al₂O₃ catalyst with yield obtained using a homogeneous KOH catalyst. The batch process was carried out at atmospheric pressure with variation of K/γ-Al₂O₃ catalyst concentration (0.5, 1.0, 1.5, 2.0, 2.5%) and microwave power (100, 264 and 400 W). The experimental results show that the methyl ester yield increases with increasing of microwave power, catalyst concentration and reaction time. However, the yield of methyl esters obtained by the K/γ-Al₂O₃ heterogeneous catalyst process are relatively easy to separate rather than using a homogeneous KOH catalyst.