Si-modified Mn–Ce oxide catalysts for selective catalytic reduction of NOx with NH3 at low temperatures.

Si-modified Mn–Ce oxide catalysts were prepared by a co-precipitation method for the selective catalytic reduction of NOx with NH3 (NH3-SCR). The doping of Si can improve significantly the NOx conversion and N2 selectivity of the Mn–Ce oxide catalysts above 150 °C. The catalyst with Mn : Ce : Si = 4 : 5 : 1 molar ratio (Mn4Ce5Si1) showed excellent SCR activity at low temperatures, with NOx conversion above 80% at 110–230 °C. The further acid modification could broaden the operating temperature window of Mn4Ce5Si1, and Mn4Ce5Si1-1%S exhibited higher deNOx efficiency (>90%) from 100 to 260 °C. The Si modification increased the specific surface area and surface acidity, and facilitated the NO/NH3 adsorption, thus enhancing the low-temperature activity through both Langmuir–Hinshelwood (L–H) and Eley–Rideal (E–R) pathways. The N2O production over Mn–Ce oxide catalysts through the L–H mechanism was much lower than via the E–R mechanism. [ABSTRACT FROM AUTHOR]