CATALYTIC REDUCTION OF NITRIC-OXIDE ON PDO-MOO3 GAMMA-AL2O3

The activity and selectivity of PdO-MoO3/gamma-Al2O3 catalysts containing 2% Pd and 20% Mo for the reduction of nitric oxide by carbon monoxide, by hydrogen, and by a mixture of CO + H-2 was investigated in the presence of different amounts of oxygen at reaction temperatures from 25 to 550-degrees-C. Results are compared with PdO/gamma-Al2O3, MoO3/gamma-Al2O3, and a commercial Pt-Rh catalyst. The palladium determines the performance of PdO-MoO3/gamma-Al2O3 under oxygen free reaction conditions up to 400-degrees-C, not-withstanding the high loading of the molybdena. At higher temperatures the molybdena can improve the performance of the catalyst, especially at slightly oxidizing conditions. Neither the activity nor the selectivity of PdO-MoO3/gamma-Al2O3 resemble those of the monometallic catalysts in the presence of oxygen when CO + H-2 is used for reduction. In the case of the present catalyst in fresh condition, nitric oxide is reduced selectively to nitrogen and nitrous oxide with a conversion > 70% at temperatures from 300 to 550-degrees-C under either slightly reducing or slightly oxidizing conditions.