High Resistance of SO2 and H2O over Monolithic Mn-Fe-Ce-Al-O Catalyst for Low Temperature NH3-SCR

Abstract

Monolithic Mn-Fe-Ce-Al-O catalyst with honeycomb cordierite ceramic as a carrier was reported for the first time for low temperature deNO_x application. In the reaction of selective catalytic reduction (SCR) of NO with NH₃, a NO conversion of above 80% at 100 °C was obtained. Notably, the catalyst also showed excellent resistance against SO₂ and H₂O. About 60% NO conversion was maintained after successive operation in the mixed stream of SO₂ and H₂O for 168 h. The Brunner−Emmet−Teller (BET) measurement, SEM, EDS, thermogravimetric analysis (TG), FT-IR, and XPS results of the used catalysts indicated that certain amounts of ammonium sulfate was formed on the surface of the catalyst. XPS results revealed that partial of Fe²⁺ was oxidized to Fe³⁺ during the reaction process, and Fe²⁺ species have strong redox ability, which can explain the decrease in activity after reaction. In addition, SO₂ and H₂O induced a transformation of Ce from Ce⁴⁺ to Ce³⁺ on the surface of the catalyst, which increased the amount of chemisorbed oxygen. Owing to these factors, the addition of Ce and Fe species contributes to excellent resistance of the catalyst to SO₂ and H₂O.