Basics of Microwave Heating and Recent Advances

Abstract

Since the late 1980s, the scientific community has been attracted toward the application of microwave energy as an alternative method of heating due to its advantages over conventional heating technologies. In fact, differently from conventional heating technologies, the microwave heating mechanism is a volumetric process in which heat is generated within the material itself, and, consequently, it can be very rapid and selective. In this way, the microwave-susceptible material can absorb the energy of the microwaves. The application of the microwave heating technique to a chemical process can lead to both a reduction in processing time as well as an increase in the production rate, which is obtained by enhancing the chemical reactions and results in energy saving. Microwave radiation has been used for the synthesis and sintering of materials for more than 20 years; the future challenges will be, among others, the development of processes with lower greenhouse gas (e.g., CO2) emissions and the discovery of novel energy-saving catalytic reactions. A natural choice in such efforts would be the combination of catalysis and microwave radiation. The main aim of this chapter is to provide an overview of the basics of microwave heating and the recent advances in microwave reactors. The chapter is divided into three principal sections: (i) an introduction to microwave chemistry and microwave materials processing; (ii) a description of the loss mechanisms and microwave-specific effects in heterogeneous catalysis; and (iii) new challenges and recent advances in microwave reactors.