Supported manganese catalysts for the selective catalytic reduction of nitrogen oxides with ammonia - Part II. Catalytic experiments

Manganese-promoted active carbons have been studied as catalysts for select ive catalytic reduction with ammonia. Activity, selectivity and stability d epend on the preparation procedure, the choice of the precursors and the ch emistry of the starting support. The highest activity in the low-temperatur e region was shown by samples prepared from manganese nitrate. An even (nea r monolayer) distribution of manganese species led to nitrogen as the sole product, and bigger manganese oxide crystallites resulted, additionally, in N2O as a by-product. Manganese addition did not influence the stability of active carbons except those prepared from potassium permanganate where inc reased gasification due to the presence of potassium was observed at higher temperatures. Side reactions: ammonia oxidation and direct decomposition o f nitric oxide are also discussed.