Operando Raman Spectroscopy of the Microwave-Enhanced Catalytic Dehydration of 2‑Propanol by WO₃

Operando Raman spectroscopy was performed to understand the mechanism of a microwave (MW)-enhanced fixed-bed catalytic reaction. An MW operando Raman spectroscopy system was constructed by integrating a Raman spectroscopy probe (785 nm) with a single-mode (TM₁₁₀) MW cavity resonator equipped with a semiconductor MW generator. MW heating enhanced the dehydration of 2-propanol to diisopropyl ether and propylene by +54 to +60% under the air flow condition. In the argon flow condition, the conversion of 2-propanol was further enhanced by +71 to +83% with >99.9% selectivity toward propylene when MW heating was used. Operando Raman spectroscopy revealed that MW irradiation enhances the reduction of the WO₃ surface and exhibits intense light emission, especially under the argon flow condition. The enhanced generation of WO_3–x species on the surface of the WO₃ catalyst should be, therefore, a key factor in the enhancement of the dehydration of 2-propanol under MW irradiation.