Synthesis and characterization of cryptomelane- and birnessite-type oxides: Precursor effect

Manganese oxide systems were prepared in the form of laminar octahedral compounds (birnessites) or octahedral molecular sieves (cryptomelanes) in order to test their efficiency as catalysts for the abatement of volatile organic compounds. Gelation routes and redox–reflux methods with different precursors were chosen such as KMnO4/glucose, KMnO4/polyvinyl alcohol for birnessites and KMnO4/Mn-oxalate, KMnO4/Mn-sulphate and KMnO4/Mn-acetate for cryptomelanes. Birnessite, prepared using glucose as the reducing agent, showed a high activity in the total oxidation of acetone in spite of the moderate surface area. Cryptomelanes, prepared from Manganese carboxylates, present the classical fibrous morphology with a high surface area and were extremely active for acetone total oxidation.