A TPD Study of Chromium Catalysts Supported on an Oxidized and Nonoxidized Activated Carbon

A commercial activated carbon was oxidized with nitric acid and both the untreated and the oxidized activated carbon were used as supports for Cr catalysts, which was deposited on them by adsorption from aqueous solution using either chromium nitrate or ammonium chromate as precursor salts. The samples so obtained were heat treated in He flow up to 1200 K following the evolution of CO and CO2 by mass spectrometry. Results found show that during this treatment the CO disproportionation reaction takes place only in those supported catalysts obtained from the oxidized activated carbon. This reaction was catalyzed by Cr2O3 which is formed during the heat treatment. After He treatment up to 1200 K, the samples were treated in a He-O-2 flow (10 vol % of oxygen) at 573 K for 5 min. Results found show that Cr2O3 supported on the untreated carbon presented a higher dispersion than that supported on the oxidized one.