Fe2O3/γ-Al2O3 and NiO/γ-Al2O3 catalysts for the selective catalytic oxidation of ammonia

Ammonia, a significant atmospheric pollutant, requires effective emission control due to its inherent toxicity and the generation of secondary pollutants like particulate matter. This control can be achieved through various methods, including catalytic processes. Therefore, our study focuses on evaluating the potential of catalysts based on iron oxide and nickel oxide supported on gamma-Al2O3 for the selective catalytic oxidation of NH3 to N-2 (NH3-SCO). The gamma-Al2O3 was obtained by thermal decomposition of aluminum hydroxide, and 5 or 10 wt% of Fe or Ni was added through wetness incipient impregnation. XRD diffractograms confirmed the formation of the gamma-Al2O3 phase. XRD, H-2-TPR, and UV-vis DRS data showed the presence of Fe2O3, NiO, and NiAl2O4 in the catalysts. Introducing metal oxides onto the support led to a drop in the specific area, pore size, pore volume, and NH3 desorption, which was higher for the catalysts containing Fe. The catalysts were active in NH3-SCO, and the insertion of Fe or Ni was essential because it promoted a significant increase in the NH3 conversion (similar to 75 % Fe and similar to 55 % Ni), compared to pure support (similar to 8 %), mainly from 400 degrees C. However, doubling the metal content has not resulted in a considerable increase in NH3 conversion. The N-2 selectivity was higher for the catalysts containing Ni (similar to 85 %) from 400 degrees C compared to catalysts containing Fe (similar to 76 %). Such behavior was due to the larger surface area of the Ni-containing catalysts. Despite that, the 5Fe/gamma-Al2O3 catalyst emerged as the most effective option for NH3-SCO applications, combining higher NH3 conversion and good N-2 selectivity.