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Investigation of Novel Iron Oxide-Chromia on Alumina or Magnesia Aerogel Catalysts for the Selective Reduction of Nitric Oxide by Ammonia
Published online by Cambridge University Press: 28 February 2011
Abstract
A series of iron oxide-chromia on alumina and iron oxide on magnesia materials were made by the aerogel process. These materials had high surface areas (300 to 700 m2/g) and demonstrated good activity for the selective reduction of nitric oxide by ammonia.
A combination of 4 parts Fe to 1 Part Cr gave the best catalyst for the reaction. Fe-Cr to alumina ratios were varied from 0.1 to 0.4. Activity per unit weight increased with increasing Fe-Cr/A12O3 ratios, however, activity per unit Fe-Cr favored the lower Fe-Cr to alumina ratios.
The fresh material from the autoclave was found reduced (Fe3O4) and initially had poor activity for the selective reduction of nitric oxide by ammonia (525 ppm NO & 525 ppm NH3 in air feed conditions). However, after several testing cycles, in which the catalyst was in continuous contact with oxygen (as air), activity improved dramatically. Upon removal from the reactor the material had a distinct color change (from brown to reddish brown) and magnetic properties were lost. This suggests that Fe2O3 is part of the active site for the selective reduction of nitric oxide by ammonia. At higher temperatures activity decreased because of a competing reaction, ammonia oxidation to nitric oxide.
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- Copyright © Materials Research Society 1988
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