Monitoring Chromia/Alumina Catalysts in Situ during Propane Dehydrogenation by Optical Fiber UV–Visible Diffuse Reflectance Spectroscopy

A continuous-flow reactor system with in situ monitoring of the catalyst was developed. The catalyst surface was analyzed by collecting UV–visible diffuse reflectance spectra through an optical fiber placed in the catalyst bed. The system was tested with a series of chromia/alumina catalysts (1 wt% Cr) under the conditions of propane dehydrogenation. The fast reduction of Cr6+ to Cr3+ under propane stream could be detected. Increase in the catalytic activity with the alumina pretreatment temperature was tentatively ascribed to the presence of θ-alumina, and decrease in the activity during calcination to incorporation of Cr3+ inside the alumina support.