Ce regulated surface properties of Mn/SAPO-34 for improved NH 3 -SCR at low temperature.

Ce modified MnO x /SAPO-34 was prepared and investigated for low-temperature selective catalytic reduction of NO x with ammonia (NH 3 -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 -1 . Microporous SAPO-34 as the support provided the catalyst with increased hydrothermal stability. XPS and H 2 -TPR results proved that the Mn 4+ and O α content increased after incorporation of Ce, this promoted the conversion of NO at low temperature via a 'fast SCR' route. NH 3 -TPD measurements combined oxidation experiments of NO, NH 3 indicated the reduction of both the surface acidity and the amount of acid sites, which effectively decreased the NH 3 oxditaion to NO or N 2 O 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.