Rapid control of hydrogen permeation in Pd membrane reactor by magnetic-field-induced heating under microwave irradiation

A microwave (MW) heating system induced by a magnetic field was designed and applied for uniform heating of a Pd membrane selectively through hydrogen. This system aimed to control the temperature of the membrane and the hydrogen permeation rate. Although the conventional dielectric heating by MWs is not suitable for metal membranes because of the reflection of MWs, a magnetic field can excite the surface current (eddy current) and causes Joule heating. First, this was successfully achieved for thin metal films in a frequency-variable single-mode MW reactor system with a cylindrical cavity. The temperature of the surface was controlled precisely by a resonance frequency autotracking function. Then, for the control of the hydrogen permeation rate through the Pd membrane, this system was applied to a pore-filling-type Pd membrane where the Pd nanoparticles were filled in the nanospace void of the Al2O3 support tube, suggesting high durability. The temperature of Pd membrane could be quickly and precisely controlled due to direct heating by this MW system. Hydrogen permeation rate was well controlled associated with the temperature of the membrane.