Screening investigations into the effect of cryptomelane doping with 3d transition metal cations on the catalytic activity in soot oxidation, NO2 formation and SO2 resistance
Monika Fedyna, Piotr Legutko, Joanna Gryboś, Janusz Janas, Xuehua Yu, Zhen Zhao, Andrzej Kotarba, Zbigniew Sojka
Abstract
The cryptomelane catalysts containing transition metal (M/K-OMS-2, M = Cu, Ni, Co, Cr and Fe) was synthesized and characterized by XRD, TEM/EDX, XRF, XPS, Raman, H2-TPR corroborated by potassium thermal desorption measurements. The catalysts were tested for soot oxidation in tight and loose contact modes in various conditions: O2, O2 + NO, O2 + SO2, O2 + NO + SO2. The alterations in the soot oxidation activity were discussed in terms of manganese average oxidation number, NO2 formation during the combustion and potassium release, which are modified by the dopants. It was shown that the strong effect of dopants on the NO2 formation is different in absence and presence of soot, and varies with the type of the sot-catalyst contact, being well corelated with the concurrent CO2 formation. Sulphur resistance can be enhanced by doping of the cryptomelane. The most efficient is the catalyst containing segregated mixed cobalt-manganese spinel phase.