Investigation of the interactions in CeO2–Fe2O3 binary metal oxides supported on ZSM-5 for NO removal by CO in the presence of O2, SO2 and steam

Abstract

ZSM-5 series catalysts with different metal contents were prepared for NO removal by CO in the presence of O₂, SO₂ and steam via an impregnation method. The flash catalysts and used catalysts were characterized via XRD, BET, XPS, NH₃-TPD, CO-TPR and in situ DRIFTS and their activities were tested in a fixed-bed reactor. The 10Ce–10Fe catalyst exhibited stable NO conversion of over 90% within the temperature range from 320 °C to 650 °C, and it has superior resistance to O₂, SO₂ and steam. The ZSM-5 structure was retained after loading Fe and Ce, and diffraction peaks of Fe₂O₃ and CeO₂ were observed in the XRD spectra with an increase in the metal content. The specific surface area and pore volume of Ce–Fe/ZSM-5 decreased, and its average pore diameter increased. The Ce–Fe/ZSM-5 catalysts possess chemisorbed oxygen and lattice oxygen, and their various cations (Fe³⁺/Fe²⁺ and Ce⁴⁺/Ce³⁺) promote the production of oxygen vacancies, which are beneficial for the activation of N–O. The strong acid sites and some medium-strong acid sites are involved in the catalytic reaction as the active sites for Ce–Fe/ZSM-5 in NH₃-TPD. The interaction between Fe₂O₃ and CeO₂ (Ce³⁺ + Fe³⁺ ↔ Ce⁴⁺ + Fe²⁺) in the Ce–Fe/ZSM-5 catalyst improves its catalytic performance, reducing property, resistance to O₂, SO₂ and steam, and service life.