In Situ Spectroscopic Studies of NH₃ Oxidation of Fe-Oxide/Al₂O₃

Abstract

Simple temperature-regulated chemical vapor deposition was used to disperse iron oxide nanoparticles on porous Al2O3 to create an Fe-oxide/Al2O3 structure for catalytic NH3 oxidation. The Fe-oxide/Al2O3 achieved nearly 100% removal of NH3, with N2 as a major reaction product at temperatures above 400 °C and negligible NO x emissions at all experimental temperatures. The results of a combination of in situ diffuse reflectance infrared Fourier-transform spectroscopy and near-ambient pressure–near-edge X-ray absorption fine structure spectroscopy suggest a N2H4-mediated oxidation mechanism of NH3 to N2 via the Mars–van Krevelen pathway on the Fe-oxide/Al2O3 surface. As a catalytic adsorbentan energy-efficient approach to reducing NH3 levels in living environments via adsorption and thermal treatment of NH3no harmful NO x emissions were produced during the thermal treatment of the NH3-adsorbed Fe-oxide/Al2O3 surface, while NH3 molecularly desorbed from the surface. A system with dual catalytic filters of Fe-oxide/Al2O3 was designed to fully oxidize this desorbed NH3 to N2 in a clean and energy-efficient manner.