Direct detection of coke deposits on fixed bed catalysts by electrical sensors

The activity and the rate of deactivation of heterogeneous fixed bed catalysts are substantially influenced by the formation of coke deposits. In the chemical industry, especially in refineries and in petrochemical processes, the continuous direct and in situ monitoring of the level of the coke load in a catalytic reactor would be an additional controlling instrument of high value. In order to contribute to the development of such sensors, a representative pellet of an alumina-based chromium-oxide-coated catalyst was used in this work as a model system. The pellet was contacted and electrically measured by impedance spectroscopy. By combination with a gravimetrical method, a clear relationship between coke loading and the respective electrical signal could be observed, both during coke formation and during the regeneration by coke burn-off.