Novel Sensing Technology for Real-Time Detection of Carbon Deposition on a Solid Catalyst Using the Resonance Frequency Shift of Single-Mode Microwave

We report a novel approach for the real-time and highly sensitive detection of carbon deposition on solid catalysts using the resonance frequency shift of a single-mode microwave. Using a microwave reactor system, the change in dielectric constant within the cavity was observed. Since the dielectric constant of catalysts and absorption of the microwave by the catalysts increase with carbon deposition, we hypothesized that shifts in the resonance frequency could be used to characterize carbon deposition. We evaluated the efficacy of the proposed method using ethanol steam reforming as a model reaction with various steam-to-carbon ratios, and the results were validated by comparison with thermogravimetry and scanning electron microscopy analyses. The increased sensitivity of the method compared with thermogravimetry for carbon deposition detection was demonstrated (100 ppm order of carbon can be detected). The proposed method can be extended to other catalytic conversions of various hydrocarbons in which carbon deposition causes severe catalyst degradation.