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 γ–Al 2 O 3 for the selective catalytic oxidation of NH 3 to N 2 (NH 3 -SCO). The γ–Al 2 O 3 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 γ–Al 2 O 3 phase. XRD, H 2 -TPR, and UV–vis DRS data showed the presence of Fe 2 O 3 , NiO, and NiAl 2 O 4 in the catalysts. Introducing metal oxides onto the support led to a drop in the specific area, pore size, pore volume, and NH 3 desorption, which was higher for the catalysts containing Fe. The catalysts were active in NH 3 -SCO, and the insertion of Fe or Ni was essential because it promoted a significant increase in the NH 3 conversion (∼75 % Fe and ∼55 % Ni), compared to pure support (∼8 %), mainly from 400 °C. However, doubling the metal content has not resulted in a considerable increase in NH 3 conversion. The N 2 selectivity was higher for the catalysts containing Ni (∼85 %) from 400 °C compared to catalysts containing Fe (∼76 %). Such behavior was due to the larger surface area of the Ni-containing catalysts. Despite that, the 5Fe/γ–Al 2 O 3 catalyst emerged as the most effective option for NH 3 -SCO applications, combining higher NH 3 conversion and good N 2 selectivity. [Display omitted] • Thermal decomposition of Al(OH) 3 was effectively to obtain γ-Al 2 O 3 with mild and strong acid sites. • H 2 -TPR and UV–vis DRS data showed the formation of Fe 2 O 3 , or NiO in catalysts. • XRD showed NiAl 2 O 4 peaks in Ni/γ-Al 2 O 3. • The increasing in the metal content in catalysts did not considerably contribute in NH 3 conversion and N 2 selectivity. • At 500 °C, NH 3 conversion for 5Fe/γ-Al 2 O 3 reached 75 % and a selectivity of 80 % for N 2 formation. [ABSTRACT FROM AUTHOR]