Highly selective catalytic reduction of NO via SO2/H2O-tolerant spinel catalysts at low temperature
2016
Cai, Xuanxuan | Sun, Wei | Xu, Chaochao | Cao, Limei | Yang, Ji
Selective catalytic reduction of NO X by hydrogen (H₂-SCR) in the presence of oxygen has been investigated over the NiCo₂O₄ and Pd-doped NiCo₂O₄ catalysts under varying conditions. The catalysts were prepared by a sol-gel method in the presence of oxygen within 50–350 °C and were characterized using XRD, BET, EDS, XPS, Raman, H₂-TPR, and NH₃-TPD analysis. The results demonstrated that the doped Pd could improve the catalyst reducibility and change the surface acidity and redox properties, resulting in a higher catalytic performance. The performance of NiCo₁.₉₅Pd₀.₀₅O₄ was consistently better than that of NiCo₂O₄ within the 150–350 °C range at a gas hourly space velocity (GHSV) of 4800 mL g⁻¹ h⁻¹, with a feed stream containing 1070 ppm NO, 10,700 ppm H₂, 2 % O₂, and N₂ as balance gas. The effects of GHSV, NO/H₂ ratios, and O₂ feed concentration on the NO conversion over the NiCo₂O₄ and NiCo₁.₉₅Pd₀.₀₅O₄ catalysts were also investigated. The two samples similarly showed that an increase in GHSV from 4800 to 9600 mL h⁻¹ g⁻¹, the NO/H₂ ratio from 1:10 to 1:1, and the O₂ content from 0 to 6 % would result in a decrease in NO conversion. In addition, 2 %, 5 %, and 8 % H₂O into the feed gas had a slightly negative influence on SCR activity over the two catalysts. The effect of SO₂ on the SCR activity indicated that the NiCo₁.₉₅Pd₀.₀₅O₄ possesses better SO₂ tolerance than NiCo₂O₄ catalyst does. Graphical abstract The NiCo₁.₉₅Pd₀.₀₅O₄ catalyst achieved over 90 % NO conversion with N₂ selectivity of 100 % in the 200∼250 °C range than the maximum 40.5 % NO conversion over NiCo₂O₄ with N₂ selectivity of approximately 80 % in 350 °C.
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