New SCR Catalysts Based on Mn Supported on Simple or Mixed Aerogel Oxides: Effect of Sulfates Addition

New SCR catalysts based on Mn supported on simple or mixed aerogel oxides (Mn/ZrO2, Mn/CeO2-ZrO2 and Mn/CeO2-ZrO2-SO42−) were prepared for selective catalytic reduction of nitrogen oxide by ammonia (NO-SCR by NH3). One step sol gel method followed by supercritical drying process were used for elaborating the catalytic supports, however, Mn species were incorporated into aerogels via impregnation method. Structural, textural, acidic and redox properties of samples were studied using XRD; BET and porosity measurements; NH3-TPD and H2-TPR techniques. The results revealed that Mn/ZrO2 and Mn/CeO2-ZrO2 solids develop mesoporous texture, good crystallinity of zirconia tetragonal phase and nano-sized particles but exhibit a poor NO-SCR activity. The addition of SO42− induces a disorder in ZrO2 structure but it generates very active strong acid sites for the high temperature NO reduction. 100% NO conversion into N2 was achieved above 400 °C over the new Mn/CeO2-ZrO2-SO42− catalytic system.