The mechanism of reduction of NO with H2 in strongly oxidizing conditions (H2-SCR) on a novel Pt/MgO-CeO2 catalyst:: Effects of reaction temperature

Steady State Isotopic Transient Kinetic Analysis (SSITKA) experiments using on-line Mass Spectrometry (MS) and in situ Diffuse Reflectance Infrared Fourier-Transform Spectroscopy (DRIFTS) have been performed to study essential mechanistic aspects of the Selective Catalytic Reduction of NO by H-2 under strongly oxidizing conditions (H-2-SCR) in the 120-300 degrees C range over a novel 0.1 wt % Pt/MgO-CeO2 catalyst. The N-path of reaction from NO to the N-2 gas product was probed by following the (NO)-N-14/H2O2 -> (NO)-N-15/H-2/O-2 switch (SSITKA-MS and SSITKA-DRIFTS) at 1 bar total pressure. It was found that the N-pathway of reaction involves the formation of two active NO (x) species different in structure, one present on MgO and the other one on the CeO2 support surface. Inactive adsorbed NO (x) species were also found on both the MgO-CeO2 support and the Pt metal surfaces. The concentration (mol/g cat) of active NO (x) leading to N-2 was found to change only slightly with reaction temperature in the 120-300 degrees C range. This leads to the conclusion that other intrinsic kinetic reasons are responsible for the volcano-type conversion of NO versus the reaction temperature profile observed.