INVESTIGATION OF IRON-OXIDE CHROMIA ALUMINA AEROGELS FOR THE SELECTIVE CATALYTIC REDUCTION OF NITRIC-OXIDE BY AMMONIA

The selective catalytic reduction of nitric oxide by ammonia over iron oxide-chromia-alumina aerogels was studied over the temperature range of 423 to 750 K. The highest activities were observed for Fe/Cr/Al materials with a 60% conversion at 720 K for a reactor flow velocity of 1008 m3/h-kg. Oxygen significantly enhanced the reaction rate as explained by a redox mechanism. Infrared characterization showed weak adsorption of nitric oxide on the preoxidized materials and quite strong adsorption on the reduced material; ammonia adsorption was strong on both oxidized and reduced materials. Observation of interaction between adsorbed nitric oxide and ammonia (when ammonia was added to reduced catalysts which held preadsorbed nitric oxide) provided insight into the reaction mechanism. © 1991.