Double-layer packed bed used for heating non-polar liquid under microwave irradiation

There are some reports showing that microwave heating has a positive effect on the non-polar reaction liquid with polar solute. For the continuous-flow microwave heating of non-polar reaction liquid, the methods such as the addition of a high-loss dielectric material are generally used, but there is a problem that the temperature of the fluid will continue to rise, which cannot be maintained within a stable range. In this paper, a novel double-layer packed bed is designed in order to solve the above problem. The double-layer packed bed is divided into a heating layer and a thermostatic layer: the packing of heating layer is composed of the high-loss dielectric material; the packing of thermostatic layer is composed of a mixture of the high-loss and low-loss dielectric material in a certain proportion. Both the experimental and simulation results verified that the non-polar liquid temperature can rapidly rise to the preheating temperature in the heating layer and remain stable in the thermostatic layer while passing through the double-layer packed bed under microwave irradiation. The practicality of the double-layer packed bed was exemplified in the continuous synthesis of geranyl butyrate that proceeded more rapidly under microwave irradiation than conventional heating.