Promotional effect of Mn modification on DeNO_x performance of Fe/nickel foam catalyst at low temperature

Manganese (Mn)-modified ferric oxide/nickel foam (Fe/Ni) catalysts were prepared using Ni as a carrier, Fe and Mn as active components to study NH₃-SCR of NO_x at low temperature. The effects of different Fe loads and Mn-modified Fe/Ni catalysts on the DeNO_x activity were investigated. Results show that when the amount of Fe is 10%, Fe/Ni catalyst has the highest NO_x conversion. For the Mn-modified Fe/Ni catalysts, the NO_x conversions firstly increase and then decrease with the Mn loading amount increasing. 3MnFe/Ni catalyst shows high NO_x conversions, which reach 98.4-100% at 120-240 °C. The characterization analyses reveal that Mn-modified Fe/Ni catalysts increase the FeO_x dispersion on Ni surface, improve significantly the valence ratio of the Fe³⁺/Fe²⁺, the content of lattice oxygen which promotes the catalyst storage and exchange oxygen capacity at low temperature, and the number of Brønsted active acid sites on the catalyst surface, and enhance the low-temperature redox capacity. These factors remarkably increase the NO_x conversions at low temperature. Especially, 3Mn10Fe/Ni catalyst not only has excellent DeNO_x activity but also has better water resistance. However, the anti-SO₂ poisoning performance needs to be improved. To further analyze the reason why different catalysts show different DeNO_x performance, the reaction kinetics was also explored.