A TM01-mode microwave reactor for highly uniform coal pyrolysis: Multiphysics modelling and mechanistic insights

Precise reaction kinetics from mechanistic studies are critical for the rational design and scale-up of industrial microwave pyrolysis reactors. However, the non-uniform field in commonly used multimode microwave oven reactors severely compromises this objective by distorting reaction kinetics, product distributions, and yield consistency. To overcome this challenge, we developed a TM 01 -mode single-mode reactor that achieves exceptional heating uniformity (temperature variation coefficient < 0.12) by leveraging an azimuthally symmetric electric field. This design eliminates angular hotspots and ensures consistent energy deposition, thereby enabling attribution of physicochemical changes to specific temperatures and thus allowing quantitative tracking of pyrolysis stages. A Multiphysics model incorporating temperature-dependent dielectric and thermal properties was established to investigate the heating performance and guide the reactor's geometrical optimization. The model's predictive capability was evidenced by the close alignment of simulated and experimental temperature distributions, providing a validated tool for reactor design and process optimization. The high thermal uniformity of the reactor allowed the gas evolution to be more clearly resolved over distinct pyrolysis temperature regimes: CO 2 release (20–300 °C) from oxygen-functional groups, CH 4 generation (300–600 °C) from aliphatic chain scission, and a dominant H 2 yield (79 vol%) from aromatic condensation (>600 °C). This work provides both a reliable platform for mechanistic studies in microwave pyrolysis, and a predictive Multiphysics model for the design of scale-up reactors in industrial applications.