Experimental parameters for the preparation of Mn/TiO2 catalysts by ultrasonic spray pyrolysis method for selective catalytic reduction of NOx at low temperature

Mn/TiO2 series selective catalytic reduction (SCR) catalysts with regular spherical shape could be obtained by ultrasonic spray pyrolysis method. The investigation of experimental parameters, such as decomposition temperature and the type and flow rate of carrier gas, showed that a high and stable NOx conversion at 70% could be achieved at 180 °C when the ultrasonic spray pyrolysis temperature was 500 °C and N2 was used as a carrier gas with a flow rate of 2 L/min. The physical and chemical properties of the catalysts were characterized by X-ray diffraction, SEM, and H2-TPR, revealing that a regular spherical structure, a small amount of Mn2O3 crystals, and high redox ability were the important factors affecting the activity of the catalyst. With these properties, Mn(0.5)/TiO2 (500 °C, N2, 2 L/min) exhibited more than 90% conversion at 240 °C with N2 selectivity above 96%.