Effect of iron loading on the performance and structure of Fe/ZSM-5 catalyst for the selective catalytic reduction of NO with NH3.

Abstract

A series of Fe/ZSM-5 catalysts with different Fe contents were prepared by impregnation method. The catalysts were characterized by TEM, XRD, H2 temperature-programed reduction (H2-TPR), temperature-programed desorption of ammonia (NH3-TPD), and in situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), and the catalytic activity test was also carried out on selective catalytic reduction (SCR) denitration device. Results showed that the single metal iron-supported ZSM-5 catalyst has high deNOx activity in the medium-high temperature range, and the optimal loading of Fe active component is 10wt%; the deNOx efficiency over 80% at the range of 350-450°C and 431°C reaches the maximum of 96.91%. Iron species can be finely dispersed on the surface of the carrier as amorphous oxides, and the crystalline structure of zeolite is retained. The significant redox performance, highly dispersed nanoparticles, and rich Lewis acid sites on the surface of catalyst are favorable for the SCR denitration reaction. Fe/ZSM-5 10wt% catalyst has rich Lewis acid sites and less B acid sites and Lewis acidic sites play an important role during the reaction. Only Eley-Rideal (E-R) mechanism existed during the NH3-SCR reaction process, and there is no denitration reaction being accomplished by L-H mechanism at 150°C.