In situ DRIFTS characterization of wet-impregnated and sol–gel Pd/TiO 2 for NO reduction with CH 4

Abstract

The adsorption/desorption behavior of 2%Pd/TiO 2 catalysts synthesized by wet-impregnation and modified sol–gel techniques were examined in NO–CH 4–O 2 reaction using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The catalyst prepared by the modified sol–gel method showed significantly higher resistance toward oxygen while maintaining a 100% NO conversion. Under NO+CH 4+O 2 flow, the main adsorbed NO species was identified as the linearly adsorbed NO on metallic palladium (Pd 0–NO) at high temperatures. On the oxidized sample, the major NO species was found to be a bridged nitrate species. Pd 0–NO species was suggested to react with CH x to form surface NH x species. Over the sol–gel catalyst, the peak intensity for Pd 0–NO species was much higher than that over the impregnated catalyst. The DRIFTS data seem to suggest that this species could play a role in reduction of NO with CH 4 over Pd/TiO 2 catalysts.