Promoted cobalt oxide catalyst on the metallic structured reactor filling for VOC combustion as an alternative to noble metal catalysts

VOC combustion is a demanding process for both the reactor and the catalyst design. As we have proved in recent papers the diffusional limitation of reaction rate that occurs during combustion may be overcome by designing the metallic microstructures used as reactor internals. Their application on an industrial scale depends on the development of an efficient method of catalyst layering on metallic supports and the optimisation of a fine catalyst structure which would not change the elaborated microstructure geometry. In this study we propose the Langmuir-Blodgett (LB) film method to deposit various metals (Al, Co) in the form of catalyst organic precursors. The film forming abilities of the precursors were checked by surface pressure measurements upon film compression, Brewster Angle Microscopy and by the monolayers stability measurements. The amount of the deposited materials was controlled by the LB parameters and verified by the TG measurements. The catalyst obtained in this way were characterized at various stages of the preparation by SEM/XFS, XPS, AFM and RM methods and tested in n-hexane combustion. Oxidation of the Al washcoat precursor led to the formation of γ-Al₂O₃ improving the properties of the Al₂O₃ layer (α phase) developed on the pre-calcined CrAl carrier. Oxidation of cobalt stearate deposited on the CrAl produced dispersed Co₃O₄ spinel. The cobalt catalysts were active in combustion showing resistance to sintering. Compared to standard Pt supported catalyst it demonstrated twice as low activation energy (50 kJ/mol).