Catalytic reduction of N2O and NO2 with methane over sol–gel palladium-based catalysts

Pd/TiO2 and Gd-doped Pd/TiO2 prepared through a ‘one-pot’ sol–gel method are shown to be active for the reduction of both N2O and NO2 using CH4 as a reducing agent under excess O2 conditions. In previous studies these catalysts were shown to effectively reduce NO with CH4, however activity was strongly dependant on the oxidation state of Pd. Through the electropositive nature of Gd, Pd was maintained in metallic state under higher oxygen concentrations compared to the Gd-free catalysts. Characterization through XPS and in situ DRIFTS studies indicate that in the reduction of NO2, even under excess oxygen, a significant portion of the surface Pd is maintained in the active metallic state.

Graphical abstractPd/TiO2 and Gd-doped Pd/TiO2 prepared through a ‘one-pot’ sol–gel method are shown to be active for the reduction of both N2O and NO2 using CH4 as a reducing agent under excess O2 conditions. In the figure presented here surface species formed during the sequential introduction of NO2, CH4, O2 are monitored through DRIFTS. These results provide evidence of a CH4-nitrate interaction during the reduction of NO2. These catalysts are quite active and selective to N2. Figure optionsDownload full-size imageDownload as PowerPoint slide