Numerical simulation of hotspot in polyol ester production using microwave-assisted reaction

• Heat and electromagnetic field distributions were analysed and visualised. • The electric field and power absorbed by the sample were affected by the polarity of TMPE. • The electric field and power absorbed by the sample were 1.92×10 4 V/m and 1.38×10 7 W/m 3 . • Hotspots were primarily located in the upper corner of the TMPE sample • Dielectric properties and frequency significantly influence microwave absorption and heat conversion. The complex distribution of electric field and heat transfer in microwave heating causes unfavorable hotspots in a microwave-assisted transesterification process. This local overheating may reduce product yield significantly, thereby highlighting the importance of mixing during microwave-assisted biolubricant production. This study investigated the distribution of electric field in the microwave-assisted transesterification of palm oil methyl ester (PME) and trimethylolpropane (TMP) for biolubricant trimethylolpropane ester (TMPE) production, as well as the temperature profile and the power absorbed, using COMSOL Multiphysics 4.2. The electric field and power absorbed by the sample were 1.92×10 4 V/m and 1.38×10 7 W/m 3 , respectively, which are highly affected by the polarity of TMPE. Hotspots were observed and were primarily located in the upper corner of the TMPE sample, and a significant redistribution of the electromagnetic field within the oven cavity was measured. This study also concluded that the dielectric properties of the TMPE sample layer and frequency are highly influential factors for microwave absorption and heat conversion. This study can provide insight into the future design of microwave-assisted transesterification to enhance product yield and scale up microwave reactors.