Mechanistic study of better K-resistance on Mn/TiO2 catalysts with preferentially exposed anatase {0 0 1} facets in low-temperature NH3-SCR

Abstract

The presence of alkali metals in the flue gas can physically and chemically poison the catalyst, leading to catalyst deactivation. In this paper, Mn/TiO2 catalysts with exposed TiO2 {001} (NS) and TiO2 {101} (NP) facets are studied for potassium poisoning. It was found that Mn/TiO2-NS exhibited higher denitrification efficiency and tolerance to potassium compared to Mn/TiO2-NP. Experimental characterizations and DFT calculations showed that the NH3-SCR reaction on the surface of both fresh Mn/TiO2-NS and Mn/TiO2-NP catalysts was controlled by the E-R and L-H mechanisms. The presence of K species did not decrease the specific surface area of Mn/TiO2-NS catalyst. Under the same K poisoning condition, Mn/TiO2-NS was able to retain more surface acidic sites and surface active species, whose reaction was still controlled by the E-R and L-H mechanisms. While the adsorption and activation of NO on the Mn/TiO2-NP surface was severely inhibited by the presence of K, resulting in the L-H mechanism blocked.