Study of NO Formation During NH3 Oxidation Reaction Over a Cu-SAPO-34 SCR catalyst

Ammonia oxidation to N-2 over a Cu-SAPO-34 SCR catalyst was studied with the intent of determining if the mechanism is the direct oxidation of NH3 to N-2 or proceeds through a two-step pathway where NH3 is oxidized to NO, with the NO then reacting with available NH3 through the SCR reaction to produce N-2. NH3 oxidation data show that some NO is indeed formed and the NO selectivity is dependent on the amount of NH3 adsorbed on the surface, and thus on the adsorption time and temperature. This is due to the ratio of NO formed to adsorbed NH3 downstream along the monolith channel. NO selectivity increased as the amount of NH3 adsorbed on the catalyst surface decreased. Overall, the data demonstrate that NH3 to N-2 can occur via the NO intermediate pathway, with subsequent reduction by NH3 to N-2. [GRAPHICS]