Microwave irradiation can intensify catalytic chemistry by selective and controlled microwave-catalytic packed-bed interaction. However, turning it to reality from laboratory to practical applications is hindered by challenges in the reactor design and scale-up. Here, we present a novel, rectangular traveling-wave microwave reactor (RTMR) and provide an easy-to-handle, 3-step design procedure of such reactor. The multiphysics model couples the electromagnetic field, heat transfer, and fluid dynamics in order to optimize the geometrical parameters and operational conditions for the microwave-assisted heterogeneous catalysis. The results show that the microwave energy input/output ports should be well-positioned and matched; otherwise, it would significantly decrease energy efficiency. In terms of microwave transmission, the RTMR presents a mix between the standing wave and the traveling-wave systems. Gas space velocity and input temperature significantly affect the temperature profile, and gas–solid temperature can present no significant difference under certain gas–solid contact.

Interfacial wettability adjustment is a new method for intensifying vapor–liquid mass transfer process. Contact angle effect has been well investigated but not complete due to interfacial wettability consisting of both static behavior (contact angle) and dynamic behavior (contact angle hysteresis). Here, methods of adjusting contact angle hysteresis (CAH) were proposed, and then, the CAH effect on the hydrodynamics was investigated. A multiscale analysis of CAH effect, from interfacial force and wettability to single-bubble and gas–liquid two-phase flow inside the foam to bubble swarm hydrodynamics, was conducted, and thus, the hydrodynamic performance criteria were derived. The interfaces had similar contact angles, whereas a significant difference in the CAH was prepared by using the developed sol dip-coating and spray coating methods. Subsequent experiments revealed that lower CAH can decrease the pressure drop, homogenize the gas distribution, and increase the weeping rate, which are consistent with the derived criteria.

The paper discusses the currents status and future perspectives of the utilization of microwaves, as a selective and locally controlled heating method, in heterogeneous catalytic flow reactors. Various factors related to the microwave-catalyst interaction and the design of microwave-assisted catalytic reactor systems are analyzed. The analysis clearly shows the superiority of the traveling-wave systems over the mono-mode and multi-mode cavity-based systems when it comes to the design and application of microwave flow reactors at relevant production scales.