Microwave-Pyrolysis-Assisted Preparation of Magnetic Iron-Titanium Mixed Oxide Catalyst for Selective Catalytic Reduction of NOx with NH3

A kind of magnetic iron-titanium oxide catalyst for selective catalytic reduction (SCR) of NOx with NH3 is obtained by the microwave-pyrolysis co-precipitation method. This catalyst is characterized in detail by various techniques such as X-ray diffraction, N2 adsorption–desorption, X-ray photoelectron spectroscopy, temperature-programmed reduction of H2, and temperature-programmed desorption of NH3/NO to investigate the influence of titanium oxide addition on the NH3-SCR activity of magnetic iron oxide. Furthermore, the NH3-SCR reaction mechanism over magnetic iron-titanium oxide is also revealed. The NH3-SCR activity over magnetic iron oxide is enhanced by the addition of titanium oxide, especially the low-temperature activity. The addition of titanium oxide depresses the oxidization of γ-Fe2O3 to α-Fe2O3 in the precursor obtained through microwave-pyrolysis co-precipitation during the aging process, and also reduces the absorption ability of SO42− to the precursor. The crystallite of iron oxide in magnetic Fe1-xTixOz-500 (x = 0.25, 0.5, and 0.75) catalysts is mainly γ-Fe2O3. Among these magnetic catalysts, magnetic Fe0.75Ti0.25Oz-500 has two distinctive peaks in the pore size distribution curve and more active iron-based sites on its surface for NH3-SCR reaction. This catalyst shows the highest NH3-SCR activity. The NH3-SCR reaction over magnetic Fe0.75Ti0.25Oz-500 at low-temperature obeys both the Eley–Rideal mechanism and the Langmuir–Hinshelwood mechanism.