This paper reports the state of the art of the microwave super-heated boiling phenomenon. When a liquid is heated by microwaves, the temperature increases rapidly to reach a steady temperature while refluxing. It happens that this steady state temperature can be up to 40 K higher than the boiling point of the liquid. With the same reactor, overheating is not observed under conventional heating. The bulk temperature of a microwaved solvent under boiling depends on many factors: physical properties of the solvent, reactor geometry, mass flow, heat flow, and electric field distribution. The influence of these factors is studied and discussed. The kinetics of homogeneous organic reactions shows an extension of Arrhenius behaviour into the superheated temperature region. Reaction rate enhancement of order 10-100 can thus be achieved, which is normally only possible under pressure. Finally, we present a model predicting reaction kinetics and yields under classical and microwave heating, based on predicted temperature profiles in agreement with experimental data.
|Journal||Chemical Engineering & Technology|
|Publication status||Published - 2001|