Highly effective microwave plasma application for catalyst-free and low temperature hydrogenation of biodiesel

Abstract

Partially hydrogenated biodiesel or partially hydrogenated fatty acid methyl ester (H-FAME) derived from palm oil has been successfully synthesized using a microwave plasma system equipped with negative high voltage at low temperature without the use of a catalyst. The impact of the process parameters such as hydrogen gas feed flow rate, microwave power, reaction temperature, negative high voltage and reaction time on FAME composition and product properties were studied. It was found that the optimal condition for the highest conversion of polyunsaturated FAMEs was 8.5 L/min hydrogen flow rate, 500 W microwave power, 30 °C reaction temperature, 60 kV negative high voltage and 3 h of reaction time. The oxidation stability increased from 12.5 to 21.6 h and no trans C18:1 formation was detected. Further we found that the microwave plasma system equipped with negative high voltage can also be applied to effectively hydrogenate other chemicals at low temperatures without using a catalyst.