Transition metals (Co, Zr, Ti) modified iron-samarium oxide as efficient catalysts for selective catalytic reduction of NOx at low-temperature.

Graphical abstract Highlights • The iron-samarium oxide catalyst was modified by Zr, Co and Ti. • Ti 0.15 Sm 0.075 Fe 0.775 O x -350 showed 95% NO conversion between 150 and 300 °C. • The effects of GHSV, KCl and SO 2 on NH 3 -SCR activity were investigated. • Surface acidity of samples were analyzed evidently by Py-IR and NH 3 -TPD. Abstract A series of iron-samarium mixed oxide catalysts modified by zirconium, cobalt and titanium were prepared by co-precipitation method, and the effects of modified transition metal species and calcination temperature in preparation process on NH 3 -SCR activity were investigated. The catalysts were characterized by TG-DSC, SEM, EDS-mapping, BET, XRD, XPS, PY-IR, NH 3 -TPD, O 2 -TPD and in situ DRIFTS. We also investigated the effects of gas hourly space velocity (GHSV), KCl, water vapor and SO 2 on NH 3 -SCR activity over the optimal catalyst. The results indicated that the addition of transition metal could alter the activity of iron-samarium mixed oxide catalyst. In all the samples tested, titanium was illustrated to be the most suitable assistant that could increase surface acid species and acid amount, meanwhile broaden the reaction temperature window and improved the N 2 selectivity. Moreover, Ti 0.15 Sm 0.075 Fe 0.775 O x -350 sample possessed best NO conversion rate and excellent resistance to water vapor and SO 2. However, The NH 3 -SCR activity of K/Ti 0.15 Sm 0.075 Fe 0.775 O x -350 was much lower than that of the fresh Ti 0.15 Sm 0.075 Fe 0.775 O x -350. Furthermore, in situ DRIFT study verified the NH 3 -SCR reaction of Ti 0.15 Sm 0.075 Fe 0.775 O x -350 involved both E–-R mechanism and L–-H mechanism. [ABSTRACT FROM AUTHOR]