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Low-temperature De-NO x technology is a new topic in the area of flue gas treatment. This paper presents experimental studies on selective catalytic reduction (SCR) of NO x from synthetic flue gas over iron-based catalysts with ammonia in a fluidized reactor. The iron-based catalysts used in the experiments are particles of Fe 3 O 4 and c-Fe 2 O 3 , and they are analyzed by X-ray diffraction (XRD) and Mössbauer spectroscopy, before and after reaction. It is observed that the efficiency of De-NO x with c-Fe 2 O 3 catalyst is high at temperatures from 200-290°C and the maximum efficiency is seen to exceed 90 % at 250°C. The effects of magnetic fields on SCR De-NO x using c-Fe 2 O 3 particles as catalysts are also studied by applying uniform and coaxial magnetic fields to the fluidized bed. The results suggest that SCR De-NO x on c-Fe 2 O 3 catalyst is fit for operation below 200°C in the fluidized reactor in conjunction with the effects of magnetic fields. IntroductionSelective catalytic reduction (SCR) of NO x is an effective flue gas cleaning technology, which can reduce NO x with high efficiency [1][2][3]. Currently, SCR De-NO x is normally undertaken at medium to high temperatures varying from 350-450°C. However, the temperature of the flue gas discharged from the boiler is reduced to 200°C, since the flue gas cools down when it passes through the boiler economizer and the air preheater. Therefore, it is difficult for the tail end configurations to apply SCR De-NO x technologies developed under middle to high temperature conditions in practical situations. Moreover, the De-NO x catalysts can be poisoned by SO 2 , and thus, one should remove SO 2 in the flue gas before the De-NO x process proceeds. Unfortunately, the temperature of the flue gas after desulfurization is normally below 200°C. In such instances, if the operation temperatures of De-NO x catalysts are in the medium to high temperature range, the flue gas must be reheated by heat exchange, and this results in even further energy consumption. Hence, it is important to develop a low temperature De-NO x technology and determine the catalysts that can be used in such low temperature De-NO x processes. However, most of the suitable catalysts currently available are expensive metal oxides, e.g., Mn-based [4-8], Cu-based [9][10][11][12], and Cebased [3,13] catalysts. In addition to the high costs involved in applying these metal-based catalysts to industry, the heavy metal-based catalysts will cause further pollution to the environment if their disposal is not undertaken properly.Therefore, in the current context, the SCR De-NO x from synthetic flue gas is investigated in a fluidized reactor based on magnetic iron-based catalysts, such as Fe 3 O 4 and Fe 2 O 3 . These iron-based catalysts are fairly cheap and less hazardous compared to the above-mentioned metal oxide catalysts. Furthermore, a magnetically fluidized bed is configured by applying uniform and axial magnetic fields to the fluidized bed, and the effects of magnetic fields on SCR De-NO x are rese...

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The catalysts used in the selective catalytic reduction (SCR) of NOx with NH3 were prepared from γFe2O3 nanoparticles. The NH3‐SCR activity measurement was carried out in a fixed bed reactor. The adsorption characteristics of γFe2O3 nano‐catalysts to NH3 and NO were studied with in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements. Experimental activity measurement indicated that γFe2O3 used as a SCR de‐NOx catalyst exhibited excellent low‐temperature SCR de‐NOx performance. The DRIFTS measurements showed that there existed both NH4+ bonded to Brønsted acid sites and coordinated NH3 bonded to Lewis acid sites on the catalyst surface. Coordinated NH3 was the main adsorption product. O2 promoted H‐abstraction from coordinated NH3 to form NH2 species, as well as O2 greatly enhancing the adsorption of NO on the catalyst surface to form nitrate species and absorbed NO2. Possible reaction paths with the γFe2O3 catalyst were proposed as follows: the SCR process mainly formed NH2 from H‐abstraction of coordinated NH3 which reacted with NO to form N2 and H2O at high and medium temperatures. At low temperatures, however, the formation of adsorbed NO2 resulted from NO oxidation by O2 over Fe3+ sites played an important role. NH4NO3 and (NH4+)2NO2 as the key intermediate products reacted with NO to form N2 and H2O at low temperatures.

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