Investigation of low-temperature selective catalytic reduction of NOx with ammonia over Cr-promoted Fe/AC catalysts

Ge, Tingting; Zhu, Baozhong; Sun, Yunlan; Song, Weiyi; Fang, Qilong; Zhong, Yuxiu

Investigation of low-temperature selective catalytic reduction of NOx with ammonia over Cr-promoted Fe/AC catalysts

2019

Fe/activated coke (AC) and Cr-Fe/AC catalysts with AC as a supporter and Cr and Fe as active components were prepared by an impregnation method for low-temperature selective catalytic reduction (SCR) of NO with NH₃. The effects of Cr addition and its concentrations on the deNOₓ performance of Fe/AC catalysts were studied at low temperature. The Cr addition promotes the low-temperature SCR activity of the 8Fe/AC catalyst and the 8Fe6Cr/AC catalyst has the best low-temperature SCR deNOₓ performance, which the NOₓ conversions are greater than 90% at 160–240 °C. The 8Fe6Cr/AC catalyst has good water resistance. However, when 100 ppm SO₂ was introduced into the reaction gas, its deNOₓ efficiency drops to 45% at 180 °C. To clarify the specific effects of Cr addition on the NOₓ conversions and sulfur poisoning, the Cr-Fe/AC catalysts were characterized by X-ray diffraction, BET, H₂ temperature-programmed reduction, NH₃ temperature-programmed desorption, X-ray photoelectron spectroscopy, and Fourier infrared spectroscopy. The addition of Cr into Fe/AC catalysts greatly increases the BET surface area and the number of weak and medium-strong acid sites on the catalyst surface and improves the ratio of Fe³⁺/Fe²⁺. These factors enhance the NOₓ conversion of 8Fe/AC catalyst. The formed sulfates and hydrogen sulfates cover the active sites on the catalyst surface, which lead to the sulfur poisoning of the 8Fe6Cr/AC catalyst. Graphical abstract

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