Removal of Gaseous Ammonia in Pt-Rh Binary Catalytic Oxidation

Abstract

In this study, the oxidation of ammonia (NH3) to form nitrogen was investigated by selective catalytic oxidation (SCO) over a Pt-Rh binary catalyst fabricated by the incipient wetness impregnation process in a tubular fixed-bed flow quartz reactor (TFBR). The catalysts were analysed by three-dimensional excitation-emission fluorescent matrix (EEFM) spectroscopy, UV-Vis absorption, dynamic light-scattering (DLS), zeta potential measurements, and linear sweep voltammograms (LSV). At optimum conditions, namely, a temperature of 673 K and an oxygen content of 4%, nearly 100% of the NH3 was removed by catalytic oxidation over the Pt-Rh binary catalyst. The main product of the NH3-SCO process was N2. Additionally, for the freshly prepared Pt-Rh binary catalyst, three peaks (at 235/295 nm, 245/315 nm, and 240/365 nm) were observed via EEFM; however, the peak with the highest emission wavelength disappeared over time as Pt-Rh binary catalyst was exhausted by NH3. These results show that EEFM spectroscopy, which enhances intrinsic emission Pt clusters in the Pt-Rh binary catalyst, is an effective method for characterizing this catalyst in catalytic treatment systems. The UV-Vis absorption spectra revealed that the bands associated with such octahedral platinum (IV) species were observed at about 350 nm. Moreover, the LSV reversible redox ability may explain the significant activity of the catalysts.