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The introduction of WO 3 species on to FeTiO x catalysts led to the formation of Fe(3+n)+-O-W(6−n)+ and Ti(4+n)+-O-W(6−n)+ structures, increasing the ratio of chemical adsorbed oxygen, surface W-OH species, which were beneficial to the NH 3 -SCR reaction. [Display omitted] • The catalytic activity of FeTiO x was improved after the loading of WO 3 species. • The amount and strength of Brønsted acid sites was enhanced. • Fe(3+n)+-O-W(6−n)+ raised the count of chemical adsorbed oxygen, surface W-OH species. A series of WO 3 modified iron-titanate mixed metal oxides catalysts (the molar ratio of Fe/Ti = 4:1) were synthesized by conventional impregnation method and tested for selective catalytic reduction of NO x by NH 3. The addition of WO 3 species could enhance the catalytic performance of FeTiO x and 6 W/FeTiO x showed optimal activity with above 80 % NO conversion under a wide operating temperature window of 200–400 °C. It also exhibited excellent stability in the presence of H 2 O and SO 2 at 250 °C, even as low as 225 °C, which provided a suitable deNO x candidate for stationary sources. The characterization methods including XRD, BET, XPS, H 2 -TPR, NH 3 -TPD, NO-TPD and in situ DRIFTs were used to investigate the structure and surface properties of catalysts and their influence on the catalytic activity. The results demonstrated that the impregnation of WO 3 species led to the strong electronic inductive effects between Fe3+and W6+, Ti4+ and W6+ in the forms of Fe(3+n)+-O-W(6−n)+ and Ti(4+n)+-O-W(6−n)+ structures, increasing the ratio of chemical adsorbed oxygen species, surface OH-, which were stimulative to low-temperature NH 3 -SCR reaction. The increased amount of surface Brønsted acid sites mainly came from W-OH species. Besides, the reaction pathway over 6 W/FeTiO x mainly followed Eley-Rideal mechanism at 225 °C through the reaction between gaseous NO and adsorbed NH 3 species. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The addition of TiO 2 improves the physicochemical property of Mn/CZ-NR catalyst. • Catalytic activity of Mn/CZ-NR catalyst is obviously enhanced by TiO 2 modification. • TiO 2 modification can inhibit the generation of N 2 O over Mn/CZ-NR catalyst. • Mn-Ti/CZ-NR catalyst exhibits excellent H 2 O + SO 2 tolerance in NH 3 -SCR reaction. Abstract In the present work, we chose MnO x /CeO 2 -ZrO 2 nanorod (i.e. , Mn/CZ-NR) as a benchmark catalyst, and used TiO 2 as a modifier with the purpose of inhibiting the formation of N 2 O (by-product) as well as further enhancing the catalytic activity and H 2 O + SO 2 tolerance of Mn/CZ-NR catalyst. These samples were characterized by TEM, HRTEM, XRD, Raman, H 2 -TPR, XPS, NH 3 -TPD, and in situ DRIFTS. De NO x performance and H 2 O + SO 2 tolerance of these samples were evaluated by low-temperature NH 3 -SCR reaction. The obtained results show that the TiO 2 modified catalyst (i.e. , Mn-Ti/CZ-NR) exhibits higher catalytic activity than Mn/CZ-NR catalyst due to larger amount of oxygen vacancy accompanied with more Ce3+, higher ratios of Mn4+ and surface adsorbed oxygen species, as well as the improvement of surface acidity. Furthermore, TiO 2 modification effectively inhibits the non-selective oxidation of NH 3 to N 2 O through appropriately weakening the redox property of Mn/CZ-NR catalyst, which is beneficial to the enhancement of N 2 selectivity. Finally, Mn-Ti/CZ-NR catalyst exhibits excellent H 2 O + SO 2 tolerance, which indicates that it has the potential to be used for practical low-temperature de NO x application. [ABSTRACT FROM AUTHOR]

• The competitive adsorption between SO 2 and NO x is the main reason for the decrease of activity in low temperature. • The formation and consumption of ABS reach a dynamic equilibrium, making the negative effect on the SCR activity limited. • The accumulation of ferric sulfate species enhances the surface acidity and promotes E-R pathway, further facilitating the activity. • The higher the temperature, the more SO 4 2− accumulated, and the rapider climbing rate of the catalytic activity. SO 2 poisoning of NH 3 -SCR catalysts at low temperature (< 300 °C) is still an austere challenge. In this work, γ-Fe 2 O 3 was taken as a model catalyst and the effect of reaction temperature on the catalytic activity in the presence of SO 2 were fully revealed. SO 2 introduction has no negative effect on the activity at 300 °C, which gradually improves with the extension of time. While for 225−275 °C, the activity decreases firstly and then increases slowly. The formatted sulfate species inhibits the adsorption of NO x , cuts off L-H reaction pathway and leads to the initial decline. While the deposited ammonium bisulfate (ABS) can be consumed continuously by NO + O 2 , implying the formation and consumption of ABS have reached a dynamic equilibrium. Moreover, the formation of ferric sulfate species results in the enhancement of surface acidity, which leads to the promotion of the E-R reaction pathway and further facilitates the increase of activity. [ABSTRACT FROM AUTHOR]