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A series of NiFe mixed oxide catalysts were prepared via calcining hydrotalcite-like precursors for the selective catalytic reduction of nitrogen oxides (NOx) with NH3 (NH3-SCR). Multiple characterizations revealed that catalytic performance was highly dependent on the phase composition, which was vulnerable to the calcination temperature. The MOx phase (M = Ni or Fe) formed at a lower calcination temperature would induce more favorable contents of Fe2+ and Ni3+ and as a result contribute to the better redox capacity and low-temperature activity. In comparison, NiFe2O4 phase emerged at a higher calcination temperature, which was expected to generate more Fe species on the surface and lead to a stable structure, better high-temperature activity, preferable SO2 resistance, and catalytic stability. The optimum NiFe-500 catalyst incorporated the above virtues and afforded excellent denitration (DeNOx) activity (over 85% NOx conversion with nearly 98% N2 selectivity in the region of 210–360 °C), superior SO2 resistance, and catalytic stability.

The speculated mechanism of the SCR reaction over the NiTi-LDO catalyst and the synergetic catalytic effect between Ni and Ti.

A series of Ni4‐xMnxTi1Oy mixed metal oxides (Ni4‐xMnxTi1‐LDO) catalysts originated from layered double hydroxides (LDHs) were fabricated and evaluated in the selective catalytic reduction of NO with NH3 (NH3‐SCR). To optimize the denitrification performance, the redox capability of catalysts was adjusted by calcining the Ni4‐xMnxTi1‐LDHs precursors with different Mn loading at different temperatures. The results revealed that calcination temperature was the secondary factor while the molar ratio of Mn to Ni was the main factor for influencing the redox properties. Among Ni4‐xMnxTi1‐LDO catalysts, the Ni2Mn2Ti1‐LDO catalyst afforded the optimal DeNOx behavior with above 90 % NOx conversion and 95 % selectivity of N2 as well as superior SO2 resistance in the wide temperature region of 150–360 °C. Multiple characterizations indicated that exceptional catalytic performance of Ni2Mn2Ti1‐LDO catalyst was highly dependent on the suitable redox capability resulted from moderate concentration of Ni3+, Mn4+ and chemisorbed oxygen Oβ in catalysts surface.

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