Recent Progress on Low-Temperature Selective Catalytic Reduction of NO(x) with Ammonia.

Selective catalytic reduction of nitrogen oxides (NO(x)) with ammonia (NH(3)-SCR) has been implemented in response to the regulation of NO(x) emissions from stationary and mobile sources above 300 °C. However, the development of NH(3)-SCR catalysts active at low temperatures below 200 °C is still needed to improve the energy efficiency and to cope with various fuels. In this review article, recent reports on low-temperature NH(3)-SCR catalysts are systematically summarized. The redox property as well as the surface acidity are two main factors that affect the catalytic activity. The strong redox property is beneficial for the low-temperature NH(3)-SCR activity but is responsible for N(2)O formation. The multiple electron transfer system is more plausible for controlling redox properties. H(2)O and SO(x), which are often found with NO(x) in flue gas, have a detrimental effect on NH(3)-SCR activity, especially at low temperatures. The competitive adsorption of H(2)O can be minimized by enhancing the hydrophobic property of the catalyst. Various strategies to improve the resistance to SO(x) poisoning are also discussed.