Ce regulated surface properties of Mn/SAPO-34 for improved NH-SCR at low temperature.

Ce modified MnO /SAPO-34 was prepared and investigated for low-temperature selective catalytic reduction of NO with ammonia (NH-SCR). The 0.3Ce-Mn/SAPO-34 catalyst had nearly 95% NO conversion at 200-350 °C at a space velocity of 10 000 h. Microporous SAPO-34 as the support provided the catalyst with increased hydrothermal stability. XPS and H-TPR results proved that the Mn and O content increased after incorporation of Ce, this promoted the conversion of NO at low temperature a 'fast SCR' route. NH-TPD measurements combined oxidation experiments of NO, NH indicated the reduction of both the surface acidity and the amount of acid sites, which effectively decreased the NH oxditaion to NO or NO at elevated temperature and promoted the catalytic selectivity for nitrogen. A redox cycle between manganese oxide and Ce was assumed for the active oxygen transfer and facilitated the catalyst durability.