Alumina-Supported Manganese Catalysts for Soot Combustion Prepared by Thermal Decomposition of KMnO4

Abstract

Alumina-supported manganese catalysts with cryptomelane and/or birnessite structure have been prepared using a simple method based on the thermal decomposition of potassium permanganate. The samples have been characterized by XRD, FTIR, TGA, DSC, N 2 adsorption at −196 °C, SEM, H 2 -TPR and XPS, and their catalytic activity for soot combustion has been tested and compared to that of a reference Pt/alumina catalyst. The thermal decomposition of alumina-supported KMnO 4 yields a mixture of supported birnessite and potassium manganate which is the most effective, among those prepared, to lower the soot combustion temperature. However, this material is not useful for soot combustion because the accelerating effect is not based on a catalytic process but on the oxidation of soot by potassium manganate. A suitable soot combustion catalyst is obtained after potassium manganate is removed by water washing, yielding only the birnessite phase OPEN ACCESSCatalysts 2012, 2 353 on the γ-Al 2 O 3 support. This birnessite phase can be transformed into cryptomelane by calcination at 600 °C. These two samples, γ-Al 2 O 3 -supported birnessite and cryptomelane are suitable catalysts for soot combustion in NO x /O 2 mixtures, as their catalytic activity is based on the NO 2 -assited mechanism, that is, both catalysts accelerate the oxidation of NO to NO 2 and NO 2 promotes soot oxidation. The soot combustion temperatures obtained with these birnessite/cryptomelane alumina-supported catalysts are similar to that obtained with the reference Pt/alumina catalyst.

Nanostructured Potassium-Manganese Oxides Decorated with Pd Nanoparticles as Efficient Catalysts for Low-Temperature Soot Oxidation

“…The significance of these results is in achieving the thermal conditions relevant for soot combustion in the temperature of real Diesel exhaust gases. The observed activity of the catalysts is comparable or better than found in literature [24,40,41]. In all tested conditions Pd/OL was the most active catalyst, achieving 50% soot conversion at 385, 450 and 541 °C for tight, loose + NO and loose contact conditions.…”

Dosimeter-Type NOx Sensing Properties of KMnO4 and Its Electrical Conductivity during Temperature Programmed Desorption

“…Given the ability of KMnO 4 /La-Al 2 O 3 to detect either NO or NO 2 , the oxidizing properties of KMnO 4 /La-Al 2 O 3 are demonstrated to be sufficient to convert NO to NO 2 prior to nitrate formation. This is consistent with MnO x , as a product of KMnO 4 decomposition [25,27], being known as an effective oxidizing agent in NO x reduction catalysts [22,24,33,34,36,44]. The contribution of MnO x to the NO x sorption capacity at 380 °C cannot be excluded [45–48].…”

“…The KMnO 4 /La-Al 2 O 3 powder was prepared by multiple infiltration of an aqueous solution of KMnO 4 into the La-Al 2 O 3 powder, followed by drying at 100 °C and calcination at 600 °C for 5 h. Upon thermal decomposition KMnO 4 is known to form various potassium- and manganese-containing compounds, like K 2 MnO 4 and K 3 MnO 4 , as well as manganese oxide MnO x existing in different oxidation states [22,24–30]. The decomposition of KMnO 4 is reported by Boldyrev [25,26] to become noticeable in the temperature range from 205 to 280 °C.…”

Surface Modification of Alumina Nanoparticles: A Dispersion Study in Organic Media

“…2c) is related to the presence of vinyl double bonds (C=C) of trimethoxyvinylsilane coated on the surface of alumina NPs. 35 The observed band at 1016 cm -1 is due to the stretching frequency of Si-O in silane. 36 These observations in FT-IR spectra confirm that the surface of Al 2 O 3 NPs is modified by oleic acid and TMVS.…”