Development of the bifunctional catalyst Mn—Fe—Beta for selective catalytic reduction of nitrogen oxides*

The catalytic properties of the Mn-Fe-Beta system with Mn contents in the range 0.1–16 wt.% were studied in the selective catalytic reduction (SCR) of NOx with ammonia. The catalyst structure was investigated using IR spectra of adsorbed NO, temperature-programmed reduction with hydrogen (H2-TPR), X-ray diffraction analysis, and ESR. The use of manganese as a promoter substantially increases the activity of iron-containing catalysts in the SCR of NOx with ammonia. At low contents (<2 wt.%), Mn exists in the cation form and the catalytic activity of the Mn-Fe-Beta system does not increase. At a higher content of Mn, clusters MnOx begin to form, which are highly active in the oxidation of NO to NO2 and the low-temperature catalytic activity of the Mn-Fe-Beta system increases. The observed increase in the low-temperature catalytic activity in the process of SCR of NOx with ammonia is related to a change in the reaction route. The MnOx clusters favor the oxidation of NO and the iron cations facilitate the reaction of “fast” SCR.