In situ characterisation of carbon-containing species formed on chromia/alumina during propane dehydrogenation

The formation of carbon-containing species was studied during propane dehydrogenation on a chromia/alumina catalyst with 13.5 wt% chromium. The deposition was monitored by in situ DRIFT spectroscopy combined with mass spectrometry, and by in situ Raman spectroscopy combined with gas chromatography. The reduction of chromates by propane resulted in the formation of adsorbed acetone, formates, and acetates. Acetates/carboxylates and hydrocarbon species—aliphatic, unsaturated/aromatic, and graphite-like species—were present under dehydrogenation conditions. The deposition of the hydrocarbon species was gradual, consistent with the continuous deactivation of the catalyst observed during the measurements. Hydrogen prereduction of the chromia/alumina catalyst slowed the formation of acetates/carboxylates, but it had no detectable effect on the deposition of the hydrocarbon species.