2020 Volume 4 Pages 16-23
Microwaves selectively heat solid catalysts and allow enhancement of fixed-bed flow reactions. In this study, microwave in situ and operando Raman spectroscopy and resonance frequency were performed for real-time monitoring of the oxidation state of the tungsten oxide (WO3) catalyst during microwave irradiation. First, the enhancement of catalytic dehydration and dehydrogenation over WO3 catalyst was demonstrated under microwave irradiation. Operando Raman spectroscopy revealed that the remarkable reduction occurred at the surface of the WO3 catalyst. We further applied in situ resonance frequency for real-time monitoring of oxidation state of WOx during model oxidation reaction of WO2 to WO3. We found that the oxidation state of WOx determined by the in situ resonance frequency was comparable to that obtained by XRD. However, the changes in the resonance frequency should be considered carefully because it is also affected by the volume and temperature of the samples.