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 theta -alumina, and decrease in the activity during calcination to incorporation of Cr3+ inside the alumina support. (C) 2001 Academic Press.