Promotional effect of tungsten modification on magnetic iron oxide catalyst for selective catalytic reduction of NO with NH3

Abstract

A novel tungsten-doped magnetic iron oxide catalyst was fabricated for selective catalytic reduction of NOx with NH3 (NH3-SCR), which was supported by carbon-included magnetic materials of Fe2O3–-H synthesized by the solution combustion followed by the oxidization of hydrogen peroxide. As a consequence, the thermal stability of γ-Fe2O3 crystallites located in the magnetic support is significantly enhanced. Meanwhile, the irreversible transformation of Fe2O3 crystallites from γ-phase to α-phase during the annealing process at high temperatures (i.e. 400 °C) is restrained to a large extent. In addition, the magnetic W/Fe2O3 catalyst presents a superb porous structure with higher BET surface area and pore volume due to the anti-sintering effect of tungsten doping on the magnetic Fe2O3. In this regard, the surface acidity as well as the molar ratio of the surface-adsorbed oxygen is substantially augmented, leading to a remarkable improvement of the redox ability of the active bulk species in the catalyst. It is worth mentioning that the promotions in thermal stability and redox ability is affected by the doping amount of tungsten in the catalyst, the molar ratio of glucose/urea/iron, and the ignition temperature for synthesizing the magnetic iron oxide support. The experiments revealed that with a doping amount of 7.5 wt%, a molar ratio of glucose/urea/iron of 5:20:8, and an ignition temperature of 400 °C, the NH3-SCR activity of the novel catalyst could be optimized.