In situ / operando analysis of dehydration reaction of 2-propanol by WO₃ catalysis under microwave irradiation

Abstract

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 WO_x during model oxidation reaction of WO₂ to WO₃. We found that the oxidation state of WO_x 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.