Real-Time Quantitative Operando Raman Spectroscopy of a CrOx/Al2O3 Propane Dehydrogenation Catalyst in a Pilot-Scale Reactor

Abstract

Combined operando UV/vis-Raman spectroscopy has been used to study the deactivation of CrOx/Al2O3 catalyst extrudates in a pilot scale propane dehydrogenation reactor. For this purpose, UV/vis and Raman optical fiber probes have been designed, constructed and tested. The light absorption measured by operando UV/vis spectroscopy was used to correct for the effect of catalyst darkening. This makes operando Raman spectroscopy a quantitative technique to follow the formation of coke deposits on-line during the first hour of catalytic propane dehydrogenation process. The probe was used to study the coke deposition at the top and bottom of the reactor. Differences in the rate of coke deposition were observed, which were related to the local temperature of the catalyst bed. The chemical nature of the coke deposits formed on a catalyst extrudate, as expressed by the D-1/G ratio, was independent of reaction time as well as of the position of the catalyst extrudate within the reactor bed.