Novel microwave reactor equipment using internal transmission line (INTLI) for efficient liquid phase chemistries: A study-case of polyester preparation

In this work, we demonstrate the application of a novel type of microwave equipment using internal transmission line (INTLI) to liquid phase chemistries. Contrary to common cavity-based microwave equipment, where the reactor is exposed to a standing microwave field formed in a confined space, the INTLI technology allows for irradiation of the liquid phase from the interior of the reactor, thereby enabling better coupling of the microwave energy with the liquid mixture. The model reaction system studied is a polyesterification reaction of industrial relevance. The INTLI reactor is compared with a common type of multimode cavity in terms of specific energy consumption. The total specific energy consumption with the INTLI reactor is considerably lower owing to the ability to optimize/adapt the microwave power dissipated in the liquid mixture and to minimize the lost (reflected) power that is scattered off the liquid mixture and sent back toward the magnetron. For the studied reactor system and conditions, the total energy consumption with the INTLI reactor was up to a factor two lower (at the beginning of the reaction) compared to the multimode cavity. Optimized (lower) usage of microwave power during the process and effective scale up possibility are inherent advantages of the INTLI reactor technology over cavity-based microwave equipment.