Soot oxidation and NOx reduction over BaAl2O4 catalyst

This study addresses soot oxidation and NOx reduction over a BaAl2O4 catalyst. By XRD analysis, the catalyst was shown to be of spinel structure. Temperature Programmed Oxidation (TPO) and Constant Temperature Oxidation (CTO) at 673 K show that the presence of O2 decreases the ignition temperature of soot, and it enhances the conversion of NOx to N2 and N2O. The kinetic features of soot oxidation in the TPO test are similar to that in the TG–DTA analysis. Analysis by Diffuse Reflectance Fourier Infrared Transform Spectroscopy (DRIFTS) indicates that the nitrates formed from NOx adsorption and the C(O) intermediates from soot oxidation are the key precursors of the redox process between soot and NOx over surfaces of the BaAl2O4 catalyst. Moreover, DRIFTS tests suggest that nitrates act as the principal oxidants for C(O) oxidation, through which nitrates are reduced to N2 and N2O. The O2 in the gas mixture presents a positive effect on the conversion of NOx to N2 and N2O by promoting the oxidation of nitrites into nitrates species.