Abstract
The selective catalytic reduction of NO with NH3 at low temperatures has been investigated with natural iron ore catalysts. Four iron ore raw materials from different locations were taken and processed to be used as catalysts. The methods of X-ray diffraction (XRD), X-ray fluorescence (XRF), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR), ammonia temperature-programmed desorption (NH3-TPD), scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) were used to characterize the materials. The results showed that the sample A (comprised mainly of α-Fe2O3 and γ-Fe2O3), calcined at 250 °C, achieved excellent selective catalytic reduction (SCR) activity (above 80% at 170–350 °C) and N2 selectivity (above 90% up to 250 °C) at low temperatures. Suitable calcination temperature, large surface area, high concentration of surface-adsorbed oxygen, good reducibility, lots of acid sites and adsorption of the reactants were responsible for the excellent SCR performance of the iron ore. However, the addition of H2O and SO2 in the feed gas showed some adverse effects on the SCR activity. The FT-IR analysis indicated the formation of sulfate salts on the surface of the catalyst during the SCR reaction in the presence of SO2, which could cause pore plugging and result in the suppression of the catalytic activity.
Highlights
Current global major environmental problems, such as smog, rain, fine particle pollution, and ozone depletion are credited to nitrogen oxides (NOx, x = 1, 2) [1]
The addition of H2 O and SO2 in the feed gas showed some adverse effects on the selective catalytic reduction (SCR) activity
The results showed that the sample A which calcined at 250 ◦ C achieved excellent SCR
Summary
In the modern era, a lot of focus is given to the removal of NOx by the researchers. To meet these stringent regulations of NOx abatement for point sources (coal-fired power plants), selective catalytic reduction (SCR) of NOx with ammonia (NH3 ) has become the most effective and extensively used NOx reduction technology [3]. Other issues include high activity for the oxidation of SO2 to SO3 [6], the formation of N2 O at high temperatures [7] and the toxicity of vanadium to the environment [8]. Environmental catalysis has put great efforts into the development of V-free NH3 -SCR catalysts
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