Significantly enhanced Pb resistance of a Co-modified Mn–Ce–Ox/TiO2 catalyst for low-temperature NH3-SCR of NOx

Abstract

Lead (Pb) is one of the heavy metal elements which have an obvious deactivation effect on catalysts for selective catalytic reduction (SCR) of NO_x with NH₃. In this study, it was found that cobalt (Co) modification induced a significant enhancement of the Pb resistance of the Mn–Ce–O_x/TiO₂ catalyst. The fresh and Pb-poisoned catalysts were prepared by an impregnation method and characterized by ICP-OES, XRD, N₂ adsorption, XPS, H₂-TPR, NH₃- and NO-TPD, NO oxidation reaction, and in situ DRIFTS. The results indicated that the introduction of Pb to the Mn–Ce–O_x/TiO₂ catalyst could promote the crystallization of MnO₂ and/or CeO₂, reduce the catalyst specific surface area, and decrease the relative concentrations of Mn⁴⁺ and Ce³⁺ on the catalyst surface. In addition, the presence of Pb in the Mn–Ce–O_x/TiO₂ catalyst could result in the decrease of reducibility, adsorption capacities for NH₃ and NO, and oxidation ability for NO to NO₂. However, modification of the Mn–Ce–O_x/TiO₂ catalyst with Co could greatly alleviate these negative effects resulting from Pb doping, thus markedly improving the Pb resistance of the Mn–Ce–O_x/TiO₂ catalyst.