Reducing the NOx emissions during NH3 oxidation with Nickel modified Fe2O3-a promising cost-effective and environmentally friendly catalyst for NH3 combustion

Abstract

Ammonia is considered to be a green energy due to its carbon-free footprint, high energy density, cheap transport costs and so on. However, the problem of NOx (mainly NO/NO2) emissions especially at high temperature (>800 °C) inhibits the energy utilization progress of NH3 (Such as NH3 combustion). So, catalytic combustion of NH3 is supposed to be a promising method to solve this problem but there is a rare report on that. The NOx emissions or N2 selectivity performances in the NH3 oxidation process with different catalyst was conducted with Density functional theory (DFT) and experimental studies. Results showed that, when Fe2O3 was used as catalyst, the conversion efficiency of NH3 was 96.2%, and the selectivity of N2 was 97.7%, which was higher than oxidation of NH3 without catalyst. DFT simulation showed that NH3 and O2 can be separately adsorbed on Fe (top) of Fe2O3 (001), the adsorption of NH3 and O2 were enhanced when they were put on Fe (top) of Fe2O3 (001) at the same time. Meanwhile, the length of inter-atomic bond increased thus creating oxygen vacancy, which promoted the oxidation of NH3. Finally, a Ni modified Fe-based catalyst (NiO10%/Fe2O330%/Al2O360%), full of oxygen vacancy (confirmed with X-ray photoelectron spectroscopy (XPS)), was fabricated with impregnation method. The adsorption of NH3 and O2 were further enhanced (confirmed by DFT simulation), the NH3 conversion efficiency and the N2 selectivity were stably improved to 96.8% and 100%.