Manganese supported catalysts for selective catalytic reduction of nitrogen oxides with ammonia - Part 1 - Characterization

The preparation of active carbons promoted with manganese was studied with low temperature argon sorption techniques temperature-programmed desorption and X-ray photoelectron spectroscopy. As supports, unoxidized and oxidatively pretreated carbons were used. The introduction of active material was accomplished by an adsorption method using solutions of KMnO4, KMnO4 + H2SO4 or Mn(NO3)(2). The oxidation state of the active phase and its distribution depended on the precursor and the amount/type of oxygen surface functionalities of their support. KMnO4 solutions led to the precipitation of Mn2O3/MnO2 crystallites, mostly on the outer surface of active carbon particles. Mn(NO3)(2) solutions, when introduced onto unpretreated support, resulted in Mn3O4/MnO2 as large aggregates. When H2SO4 was added to KMnO4 solution, small clusters with a broad distribution of sizes were deposited. A monolayer coverage of manganese species could only be obtained when active carbon was pretreated in an oxidizing environment strong enough to produce a considerable amount of carboxylic functionalities. Additionally, the preparation procedures influenced the textural properties.