Characterization and FTIR Studies of MnOx−CeO2 Catalyst for Low-Temperature Selective Catalytic Reduction of NO with NH3

• DOI: 10.1021/jp048431h
• Publication Date: 2004-09-30T05:30:27Z
• Authors: Gongshin Qi; Ralph T. Yang
• Keywords: Coprecipitation; Selective catalytic reduction; Temperature-programmed reduction

A series of high-activity manganese−cerium oxide catalysts for the low-temperature (373−453 K) selective catalytic reduction (SCR) NOx with ammonia were prepared. They prepared by using citric acid method (CA), coprecipitation (CP), and impregnation (IM) characterized XRD, ESR, XPS, FTIR techniques. sample CA method, MnOx(0.3)−CeO2(923), showed highest activity. XRD results that catalyst had smallest particle size weakest peak intensity. Using ESR Mn4+, Mn3+, Mn2+ species found after calcination in air. Three kinds Mn phases existed MnOx−CeO2 method: (1) aggregated Mn2O3 on CeO2 support, (2) highly dispersed strong interactions CeO2, (3) atoms incorporated into lattice. The distribution depends preparation methods. Any oxygen vacancy formed lattice caused incorporation adsorbs activates molecular to form active species. Thus, high activity MnOx(0.3)−CeO2(923) is attributed more formed. Ammonia molecules adsorbed onto NH4+ coordinated NH3. At same time, NH2 was observed because H-abstraction. NO2, nitrite, nitrate oxidation NO. mechanistic pathway this reaction proposed basis earlier findings obtained work. initial step adsorption NH3 Lewis sites, then, formed, followed between NO produce N2 H2O. Possible intermediates are proposed, all could transform NH2NO, which further react