Optimization and kinetic study of non-catalytic transesterification of palm oil under subcritical condition using microwave technology

The main transesterification used in industries involves the reaction with basic catalysts that caused unwanted soap formation, and time-consuming as post-treatment is needed. This creates the need for the utilization of a non-catalytic transesterification reaction under subcritical condition for the transformation of palm oil into biodiesel. This study evaluates the potential of using microwave technology to implement the non-catalytic transesterification for the efficient production of biodiesel. Response surface methodology (RSM) was implemented to maximise the non-catalytic biodiesel yield based on three variables: Dimethyl carbonate (DMC) to oil molar ratio, reaction temperature and reaction time. A maximum biodiesel yield of 86% was obtained with DMC to oil molar ratio of 9.5:1 at 167 °C after 2.5 hr of reaction. Also, its activation energy and pre-exponential factor were 44.88 kJ/mol and 7.88 × 10³ min⁻¹, respectively. Biodiesel quality that satisfies the EN14214 biodiesel standard was successfully produced under subcritical condition in the absence of catalysts via this microwave processing technology. This new processing method will enhance the biodiesel production and feasibility in terms of simplicity and less production step. Besides, it needs lower power consumption compared to non-catalytic supercritical method, which brings slight enhancement in cost reduction.