Combustion dynamics of biodiesel produced by supercritical methanol transesterification

• Plant oil with more unsaturated fatty acids exhibits higher FAME production rate.
• Biodiesel with more C = C double bonds presents higher ignition temperature.
• Biodiesel with more FAMEs presents lower combustion activation energy.

The fatty acid methyl ester (FAME) compositions and combustion characteristics of the biodiesel produced from three plant oils under different supercritical methanol conditions were investigated by gas chromatography and thermobalance analyzers. When the reaction temperature increased from 255 to 300 °C, the conversion efficiency of rapeseed oil into FAMEs in biodiesel increased from 13% to 98%. Such increase resulted in an improved combustion property of rapeseed biodiesel with decreasing combustion activation energy from 143.6 to 84.2 kJ/mol. The ignition temperatures of the biodiesel produced from rapeseed, soybean and palm oils gradually decreased from 257.6 to 240.2 and 238.0 °C, which implied that the biodiesel with more C = C double bonds had higher ignition temperature. The ignition temperature of biodiesel was lower than that of raw plant oil, but higher than that of petroleum diesel.