Effect of W Doping on NH₃ Selective Catalytic Reduction Performance over Sm1–xWxMn₂O₅: A Modification Strategy for a NO Oxidation Catalyst

A novel design strategy of the catalyst for selective catalytic reduction of NO x with NH 3 (NH 3 -SCR) by modifying the NO oxidation catalyst has been investigated. The Sm 1– x W x Mn 2 O 5 catalyst was synthesized by doping tungsten in SmMn 2 O 5, an excellent NO oxidation catalyst. The relationship between the catalytic performance at a low temperature and the properties (redox and acidity) has been explored by several characterization methods. It is concluded that the substitution of samarium with 1% tungsten (Sm 0.99 W 0.01 Mn 2 O 5 ) can maintain the structure of mullite as well as increase acid sites, by which the proper redox property and abundant surface acidity could be subtly regulated. The NO conversion and N 2 selectivity at a low temperature are simultaneously improved, successfully widening the temperature window of efficient catalysis. The intermediates, nitrites/nitrite precursors, have also been revealed by the chemical trap method, which are of great importance to both the activity and selectivity of NH 3 -SCR at a low temperature.