Highly dispersed MnOx–FeOx supported by silicalite-1 for the selective catalytic reduction of NOx with NH3 at low temperatures

Abstract

A silicalite-1-based catalyst with highly dispersed manganese and iron oxides was synthesized by the wet impregnation method for the selective catalytic reduction (SCR) of NO_x with NH₃ at low temperatures. The optimized catalyst demonstrated over 90% NO_x conversion efficiency between 135 and 270 °C with a space velocity of 35 000 h⁻¹, which can be attributed to the well-developed porous structure of silicalite-1 and the synergistic effects between silicalite-1 and supported metal oxide active sites. In addition, the porous structure and the addition of FeO_x greatly promoted the dispersion of MnO_x nanoparticles, which further improves the efficiency of SCR. Moreover, the reaction route for the NH₃-SCR reaction was further investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). The corresponding test results indicate that the reaction route follows both Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) mechanisms.