Effect of iron minerals during coaling on the transformation of NO in the presence of NH3: Take pyrite as an example
2020
Shu, Daobing | Chen, Tianhu | Zou, Xuehua | Li, Mengxue | Wang, Can | Wang, Hanlin | Han, Zhengyan | Liu, Haibo
Pyrite, a naturally occurring mineral, can be found extensively in coal. The change in the pyrite structure that occurs during coaling process, the ability of the pyrite-derived α-Fe₂O₃ to convert NO in the presence of NH₃ before catalyst bed and the kinetic study were investigated in this work. The pyrite-derived α-Fe₂O₃ was obtained by calcining at 500, 600, 700, 800 °C and was characterized by the X-ray diffraction (XRD), N₂ physisorption, the X-ray photoelectron spectrometer (XPS), the scanning electron microscope (SEM), UV–visible near-infrared spectroscopy (UV–vis DRS), the temperature-programmed desorption of ammonia (NH₃-TPD) and the in situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS). The results indicated that the α-Fe₂O₃ derived from natural pyrite exhibited an affirmative effect on NO conversion in the presence of NH₃ at reaction temperatures of 200–450 °C, particularly at 350 °C, the pyrite-derived α-Fe₂O₃ displayed the best efficiency for the NO conversion. In addition, the formed sulfate derived from the oxidation of pyrite enhanced the NO conversion at the temperature of 300–450 °C, while hinder the NO conversion at 200–275 °C. The in-situ DRIFTS and kinetic studies demonstrated that both the Eley-Rideal and Langmuir-Hinshelwood mechanism contributed to the selective catalytic reduction (SCR) of NO when the reaction temperature was over 200 °C, while selective catalytic oxidization (CO) happened over 300 °C. This study favored the understanding of the NO behavior in flue gas pipeline after sprawling NH₃ and the mechanism of NO conversion before the catalyst bed.
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