New Mn-TiO2 aerogel catalysts for the low-temperature selective catalytic reduction of NOx

• Published in: Journal of sol-gel science and technology 2021-02, Vol.97 (2), p.302-310
• Main Authors: Arfaoui, Jihene, Ghorbel, Abdelhamid, Petitto, Carolina, Delahay, Gerard
• Format: Article
• Language: English
• Subjects: Aerogels; Ammonia; Anatase; Catalysis; Catalysts; Ceramics; Chemical reduction; Chemical Sciences; Chemistry and Materials Science; Composites; Conversion; cryogels; etc.; Glass; Inorganic Chemistry; Low temperature; Materials Science; Nanotechnology; Natural Materials; Nitrous oxide; Optical and Electronic Materials; Original Paper: Nano- and macroporous materials (aerogels; Oxidation; Porosity; Properties (attributes); Selective catalytic reduction; Sol-gel processes; Surface layers; Titanium dioxide; Valence; xerogels
• ISSN: 0928-0707; 1573-4846
• DOI: 10.1007/s10971-020-05451-4

A new series of Mn-based catalysts (Mn-TiO 2 , Ce-Mn-TiO 2 , Mn-TiO 2 -SO 4 2 – , and Ce-Mn-TiO 2 -SO 4 2– ) were successfully elaborated using the sol–gel method associated with supercritical drying approach for the low-temperature NO-SCR by NH 3 . The physicochemical properties of aerogel powders were examined by XRD, N 2 -Physisorption at 77 K, NH 3 -TPD, H 2 -TPR, and DRUV-Vis spectroscopy. It was shown that all the catalysts develop essentially the diffraction peaks of TiO 2 anatase phase and are characterized by a nanometer size (ranging between ~5 and 9 nm), developed mesoporous texture, high surface area (S BET  > 104 m 2 /g) and large porosity (V PT  > 0.24 cm 3 /g). The incorporation of Ce and/or SO 4 2– influences differently the structural, textural, acidic, and redox properties of Mn-derived sol–gel catalysts and consequently affects their SCR activity. High NO conversions (>75%) into essentially N 2 O are obtained at low temperatures (150–270 °C) over Mn-TiO 2 and Ce-Mn-TiO 2 aerogel systems. The addition of sulfate modifies the nature of Mn species and noticeably reduces the low-temperature reactivity of catalysts ( T   300 °C) leading to highly active and N 2 -selective Mn-TiO 2 -SO 4 2– and Ce-Mn-TiO 2 -SO 4 2– sulfated catalysts. Above 90% NO conversion into N 2 (100%) was reached, in the NO-SCR by NH 3 , over the new Ce-Mn-TiO 2 -SO 4 2– aerogel catalyst, in the 450–500 °C temperature range. Highlights New Mn-TiO 2 , Ce-Mn-TiO 2 , Mn-TiO 2 −SO 4 2− and Ce-Mn-TiO 2 -SO 4 2− SCR aerogel catalysts. Mn-TiO 2 and Ce-Mn-TiO 2 exhibit high NO conversion into N 2 O between 150 and 270 °C. Ce slightly modifies the physicochemical properties of Mn based catalysts. SO 4 2− affects nature, oxidation state, dispersion of Mn species and NO-SCR activity. Mn-TiO 2 −SO 4 2− and Ce-Mn-TiO 2 −SO 4 2− exhibit high NO conversion into N 2 at T > 300 °C.