Adsorption and Oxidation of NH3 and NO over Sol-Gel-Derived CuO-CeO2-MnOx/γ-Al2O3 Catalysts

CuO-CeO2-MnOx/gamma-Al2O3 granular catalysts were synthesized by the sol-gel method. Performance of the CuO-CeO2-MnOx/gamma-Al2O3 catalyst was explored in a fixed bed adsorption system. The optimum temperature range for NO reduction over the CuO-CeO2-MnOx/gamma-Al2O3 catalyst was 200-450 degrees C. The catalysts maintained nearly 100% NO conversion effectivity at 350 degrees C. Comprehensive tests were carried out to study the behavior of NH3 and NO over the catalyst in the presence of oxygen. The NH3 oxidation experiments showed that both NO and N2O were produced gradually with the temperature raising. The catalysts in this experiment had a relatively stronger oxidation property on NH3, which improved the activity at low temperature. The over-oxidation of NH3 at high temperature is the main reason causing the decrease of NO conversion. The NO oxidation experiments revealed that NO was oxidized to NO2 over the catalysts. The NH3 and NO desorption experiments proved that NH3 and NO were adsorbed on CuO-CeO2-MnOx/gamma-Al2O3 catalysts. NH3/O-2 and NO/O-2 adsorption processes on the catalyst and the transient response of NH3 and NO were investigated by in situ diffuse reflectance infrared transform spectroscopy (DRIFTS) to study the mechanism. It was found that the selective catalytic reduction (SCR) reaction on the CuO-CeO2-MnOx/gamma-Al2O3 catalyst accorded not only the Eley-Rideal echanism but also the Langmuir-Hinshel wood hypothesis. The adsorbed NO may contribute to the high activity of the catalyst.