This article reviews, albeit non-exhaustively, recent research of chemical reactions induced by microwave radiation in heterogeneous catalytic systems, a field that has been rather active since the 1990s. Results have shown that acceleration of chemical reactions by the microwave method cannot be achieved with conventional heating under otherwise identical temperature conditions. The interaction(s) between the microwave radiation fields and the catalyst appears to be at the origin of such a facilitator effect. Accordingly, the article examines process enhancement in heterogeneous catalytic systems exposed to microwave radiation, particularly on such reactions as the dehydrogenation of methane and other hydrocarbons, and the synthesis of 4-methylbiphenyl by the Suzuki–Miyaura cross-coupling reaction. Also examined are the usage of suitable reactors for carrying out microwave-assisted heterogeneous catalysis, and the role of hot spots that are sometimes encountered in microwave chemistry.

Attempts to generate plasma in liquids have been successful and various devices have been proposed.

Organic reactions driven by microwaves have been subjected for several years to some enigmatic phenomenon referred to as the microwave effect, an effect often mentioned in microwave chemistry but seldom understood. We identify this microwave effect as an electromagnetic wave effect that influences many chemical reactions. In this article, we demonstrate its existence using three different types of microwave generators with dissimilar oscillation characteristics. We show that this effect is operative in photocatalyzed TiO₂ reactions; it negatively influences electro-conductive catalyzed reactions, and yet has but a negligible effect on organic syntheses. The relationship between this electromagnetic wave effect and chemical reactions is elucidated from such energetic considerations as the photon energy and the reactions’ activation energies.