Selective catalytic reductive removal of NOx with decreased interference from SO2 and H2O by use of Sm-modified SmxCo0.05-xCe0.05Ti0.9Oy catalysts

Abstract

This work presents a novel and highly efficient NH₃-SCR catalyst, Sm-modified CoCeTiO_x, synthesized by a simple one-step sol-gel method. The optimum Sm_0.03Co_0.02Ce_0.05Ti_0.9O_x catalyst with a high BET surface area shows more than 90% NO conversion and nearly 100 % N₂ selectivity at 180-440 °C. We investigated the relationship between Sm content and surface reactivity using NH₃-TPD, H₂-TPR, XPS, and in-situ DRIFTS. It demonstrated that the Sm-doping could precisely regulate the acidity and redox ability of the Sm_aCo_0.05-aCe_0.05Ti_0.9O_x catalyst. Sm helped develop paths for fast electron transport, in which a charge transfer bridge was built between the Ce and Co, largely favoring the redox cycle. The nature of the acid sites, NO_x adsorption, and the reactivity of surface adsorption species was characterized via in-situ DRIFTS. Moreover, the addition of Sm weakened the adsorption capacity of SO₂ on the catalyst surface. We found that the electron transfer between SO₂ and the activity sites was hindered on the modified catalyst.

Keywords: Nitrogen oxides; Selective catalytic reduction with NH(3); Sm influence; SmCoCeTiO(x) oxide; improved SO(2) resistance.