Abstract
Biodiesel is a renewable, carbon neutral liquid fuel produced from vegetable oils or animal fats with alcohol via catalytic transesterification reaction. Conventionally, alkaline-catalysed transesterification using convective heating takes long time to complete. Alkaline catalysts used are usually non-recyclable, environmentally unfriendly and could react with free fatty acids to form soap. Recently, ionic liquids have been shown to be effective in catalyzing transesterification. Furthermore, microwave irradiation has been shown to boost heat transfer to the reactants, making the reaction time shorter than the conventional heating. In this work, biodiesel production from microwave-irradiated transesterification of palm oils with methanol using a green ionic liquid was investigated. The ionic liquid (ChOH) was synthesized from choline chloride (ChCl) with potassium hydroxide (KOH) and characterized by Fourier transform infrared spectroscopy. The batch experiments were setup and carried out in an 800 W microwave oven with a flask reactor connected to a condenser. The continuous experiments were setup and carried out with a polytetrafluoroethylene (Teflon) tubing connected to a Teflon valve and a pump. Operating condition was oil to methanol ratio (1:15), reaction time (8 min), power of microwave (800 W), and catalyst loading (4 wt%). Methyl ester content was determined by gas chromatography and mass spectrometer. From the findings, it was shown that the ionic liquid was effective in catalysing transesterification of palm oils. Microwave heating proved to accelerate the reaction in short time. The methyl ester content was found to be 87 and 82 % for the batch and continuous experiments. The ester content was quite low, compared to the conventional heating. Further investigation was needed to find high biodiesel yield. The ChOH could also be reused several times but its effectiveness to produce biodiesel may be degraded, in comparison with the fresh catalyst.
