Mn–Ce/beta “bifunctional” catalyst for the selective catalytic reduction of nitrogen oxides with ammonia

The properties of the Mn–Ce/Beta zeolite catalyst in the selective catalytic reduction (SCR) of NOx have been investigated. The introduction of Ce leads to a marked increase in the NOx conversion at 100–250°C. The data of this study are consistent with the “bifunctional” pathway of SCR suggested for Mn/Beta, which consists of two stages—NO oxidation to NO2 over the oxide component and “fast” SCR over the zeolite. The increased activity of Mn–Ce/Beta at the NO-to-NO2 oxidation stage is due to the formation of MnCeOx mixed oxides enhancing the mobility of lattice oxygen. The determining role is played by the activity of the zeolite component in the “fast” SCR reaction.