Role of microwaves in heterogeneous catalytic systems

TLDR

Microwave‑induced reactions in heterogeneous catalytic systems have been actively studied since the 1990s. The article investigates how microwave exposure enhances processes such as methane dehydrogenation and 4‑methylbiphenyl synthesis via Suzuki–Miyaura cross‑coupling in heterogeneous catalysis. It examines suitable reactor designs for microwave‑assisted catalysis and the influence of hot spots that can arise during microwave heating. Microwave irradiation accelerates reactions beyond what conventional heating achieves at the same temperature, likely due to interactions between the microwave field and the catalyst, and the study highlights the importance of reactor choice and hot‑spot management.

Abstract

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.