Reduction of NO x by H2 on Pt/WO3/ZrO2 catalysts in oxygen-rich exhaust

Abstract: This work addresses the low-temperature NO x 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 0.3wt.% and a W content of 11wt.%. This material reveals high deNO x activity below 200°C and high overall N2 selectivity of about 90%. Additionally, the catalyst exhibits outstanding hydrothermal stability as well as resistance against SO x . 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 NO x -TPD examinations indicate that the pronounced H2-deNO x 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-deNO x and N2 formation, respectively. Contrary, NO x surface species formed on the WO3/ZrO2 support are not supposed to be involved in the H2-deNO x reaction. [Copyright &y& Elsevier]