NOx Removal by Selective Catalytic Reduction with Ammonia over a Hydrotalcite-Derived NiFe Mixed Oxide

Abstract

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 Role of Nitrate on the Sol-Gel Spread Self-Combustion Process and Its Effect on the NH3-SCR Activity of Magnetic Iron-Based Catalyst

“…As can be observed, the isotherm of Fe 85 Ce 10 W 5 -CP-CA(NA1.0) can be recognized as a type IV N2 adsorption/desorption isotherm according to the International Union of Pure and Applied Chemistry (IUPAC) classification, and it presents mainly meso-pores (2-50 nm), however, the hysteresis loops of Fe85Ce10W5-CP-CA(NA1.0) and Fe85Ce10W5-CP-CA are the H2 and H1 type [32,34], respectively. This demonstrates that the removal of nitrate promotes the formation of meso-pores in magnetic, and the Fe85Ce10W5-CP-CA catalyst shows uniform and regular meso-pores, which was confirmed by the results of the pore diameter distribution in Figure 5B [35]. Interesting, the Brunauer-Emmett and Teller (BET) surface area of Fe 85 Ce 10 W 5 -CP-CA was 90.85 m 2 /g, a little smaller than that of Fe 85 Ce 10 W 5 -CP-CA(NA 1.0 ) (93.13 m 2 /g), as shown in Table 2.…”

NH3‐SCR Performance Enhancement of LDHs‐Based NiMnFe‐Mixed Oxides by Two‐Phase Coexistence and Cooperation

“…Just as the catalytic results presented, the Ni 3 Mn 1 Fe 1 ‐600 catalyst showed the most satisfactory DeNO x results. It can be seen from Figure S2 that the DeNO x efficiency of NiMnFe−T catalysts was better at low temperature range than NiFe‐LDO catalyst of our previously reported, which should be ascribed to Mn species redox behavior . Furthermore, the effect of GHSV on the DeNO x performance of Ni 3 Mn 1 Fe 1 ‐600 catalyst was also investigated Figure S3, ESI†).…”

“…Besides, it was also discovered that the strong interaction between the Ni and Mn species in the NiMn bi‐metal oxides could lead to great catalytic activities of NO x removal . Apart from that, our preliminary research found that NiFe mixed oxide afforded superior SO 2 resistance and catalytic stability in the application of NH 3 ‐SCR due to the creation of redox cycle resulting from the electron transfer between Ni and Fe, whereas the low‐temperature DeNO x activity was not very satisfactory . Thus, introducing Mn species into the NiFe system might be promising to improve NH 3 ‐SCR activity in the low temperature zone.…”

The Influence of the Support on the Activity of Mn–Fe Catalysts Used for the Selective Catalytic Reduction of NOx with Ammonia

“…In the automotive industry, hydrocarbons are initially preferred as reductors as they are present in the exhaust gas, but not many catalysts are active for the reaction and most of them have problems related to the hydrothermal stability of the materials [7]. Ammonia is the other alternative selected by the industry and a high efficiency [8,9] can be obtained when ammonia or its precursor (urea) are used for the NO x -SCR.…”