The effect of alkali metal over Mn/TiO2 for low-temperature SCR of NO with NH3 through DRIFT and DFT.

Mn/TiO 2 catalysts has been shown excellent selective catalyst reduction (SCR) activity at low temperature. However, the exhaust gases in some plant contained alkali metal compounds after dust removal, which showed a serious poisoning effect on activity of Mn/TiO 2 catalyst. Our previous work showed that the poisoning effect of potassium on catalyst was most serious among these alkali elements. In the study, in situ diffuse reflectance infrared transform spectroscopy (DRIFT) and density function theory plus dispersion (DFT-D) calculation were used to investigate the mechanism how the potassium species have a negative impact on Mn/TiO 2 catalytic. The results indicated that there were two reasons for that alkali metal elements make the Mn/TiO 2 catalyst inactive. The first one is that the amount of NH 3 adsorption was on the Lewis acid sites, which was main active substances for the reduction of NO. The second one is that the electrons tend to occupy high energy states under effect of potassium, which resulted in decrease of oxidative capacity of catalyst. [ABSTRACT FROM AUTHOR]