Highly selective catalytic reduction of NOx by MnOx-CeO2-Al2O3 catalysts prepared by self-propagating high-temperature synthesis.

We first present preparation of MnOx-CeO2-Al2O3 catalysts with varying Mn contents through a self-propagating high-temperature synthesis (SHS) method, and studied the application of these catalysts to the selective catalytic reduction of NOx with NH3 (NH3-SCR). Using the catalyst with 18 wt.% Mn (18MnCe1Al2), 100% NO conversion was achieved at 200°C and a gas hourly space velocity of 15384hr-1, and the high-efficiency SCR temperature window, where NO conversion is greater than 90%, was widened to a temperature range of 150-300°C. 18MnCe1Al2 showed great resistance to SO2 (100 ppm) and H2O (5%) at 200°C. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller (BET) analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and H2 temperature programmed reduction. The characterization results showed that the surface atomic concentration of Mn increased with increasing Mn content, which led to synergism between Mn and Ce and improved the activity in the SCR reaction. 18MnCe1Al2 has an extensive pore structure, with a BET surface area of approximately 135.4m2/g, a pore volume of approximately 0.16cm3/g, and an average pore diameter of approximately 4.6 nm. The SCR reaction on 18MnCe1Al2 mainly followed the Eley-Rideal mechanism. The performances of the MnOx-CeO2-Al2O3 catalysts were good, and because of the simplicity of the preparation process, the SHS method is applicable to their industrial-scale manufacture.