Reduction of NOx by H2 on Pt/WO3/ZrO2 catalysts in oxygen-rich exhaust

This work addresses the low-temperature NOx abatement under oxygen-rich conditions using H2 as reductant. For this purpose Pt/ZrO2 and Pt/WO3/ZrO2 catalysts are developed and characterised by temperature-programmed desorption of H2 (H2-TPD), N2 physisorption (BET) and powder X-ray diffraction (PXRD). The most active catalyst is a Pt/WO3/ZrO2 pattern with a Pt load of 0.3 wt.% and a W content of 11 wt.%. This material reveals high deNOx activity below 200 °C and high overall N2 selectivity of about 90%. Additionally, the catalyst exhibits outstanding hydrothermal stability as well as resistance against SOx. Furthermore, the transfer from the powder level to real honeycomb systems leads to promising performance as well.Diffuse reflectance Fourier transform infrared spectroscopic studies, kinetic modelling of temperature-programmed desorption of O2 (O2-TPD) and NOx-TPD examinations indicate that the pronounced H2-deNOx performance of the Pt/WO3/ZrO2 catalyst is related to the electronic interaction of WO3 with the precious metal. The tungsten promoter increases the electron density on the Pt thus activating the sample for H2-deNOx and N2 formation, respectively. Contrary, NOx surface species formed on the WO3/ZrO2 support are not supposed to be involved in the H2-deNOx reaction.