Unraveling NH3-SCR performance and the role of Fe and Cu over the supported TNU-9 catalysts

Abstract

Enlarging reaction temperature and raising the resistance of SO2 and H2O for NH3-SCR is still a challenge. Meanwhile, the role of Fe and Cu over the supported TNU-9 catalysts is not so clear either for NH3-SCR reaction. Aiming at the above-mentioned problems, Fe and Cu bimetallic co-doped TNU-9 catalysts were prepared by solution ion-exchanged method and the effect of the exchanged order of Fe and Cu on NH3-SCR activity was conducted. What's more, the resistance of SO2/H2O and DFT calculations are also investigated. As a comparison, the activity Fe/T9 and Cu/T9 were examined. The reason that the different activity of Fe and Cu was also explained through DFT calculations. The glorious catalyst, Cu-2Fe/T9 synthesized via exchanging Cu first for twice and then Fe for once, demonstrated outstanding catalytic performance with the NOx conversion ca. 100 % at 225–450 °C and exceeding 80 % in the temperature range of 200–500 °C. It was attributed to minimizing the oxidation of Fe2+. And the most amazing thing was that Cu-2Fe/T9 had better the resistance of SO2 and worse the resistance of H2O than Cu/T9 at 225 °C. It was because that SO2 was more easily adsorbed at the Fe site, resulting in Fe protecting the active site Cu and the sulfation also provided more strong acidic sites, which were confirmed by DFT calculations and NH3-TPD. In addition, monomeric iron was more susceptible to water and the migration of ion-exchanged iron aggregated to form metal oxide clusters.