Physico-Chemical Property and Catalytic Activity of a CeO2-Doped MnOx-TiO2 Catalyst with SO2 Resistance for Low-Temperature NH3-SCR of NOx

The effects of CeO2 addition on the catalytic activity and the SO2 resistance of CeO2-doped MnOx-TiO2 catalysts were investigated for the low-temperature selective catalytic reduction (SCR) with NH3 of NOx emissions in marine applications. The most active catalyst was obtained from 30 wt% CeO2-MnOx-TiO2 catalyst in the whole temperature range of 100-300 degrees C at a low gas hourly space velocity (GHSV) of 10,000 h-1, and its de-NOx efficiency was higher than 90% over 250 degrees C. The enhanced catalytic activity may contribute to the dispersion state and catalytic acidity on the catalyst surface, and the highly dispersed Mn and Ce on the nano-scaled TiO2 catalyst affects the increase of Lewis and Bronsted acid sites. A CeO2-rich additive on MnOx-TiO2 could provide stronger catalytic acid sites, associated with NH3 adsorption and the SCR performance. As the results of sulfur resistance in flue gas that contains SO2, the de-NOx efficiency of MnOx-TiO2 decreased by 15% over 200 degrees C, whereas that of 30 wt% ceria-doped catalyst increased by 14-21% over 150 degrees C. The high SO2 resistance of CeO2-MnOx-TiO2 catalysts that resulted from the addition of ceria suppressed the formation of Mn sulfate species, which led to deactivation on the surface of nano-catalyst.