Engineering and chemical aspects of the preparation of microstructured cobalt catalyst for VOC combustion

VOC combustion is a demanding process for both reactor and catalyst design. The microstructural reactor made of wire gauze was studied by us as an alternative to ceramic monoliths. The reactor evaluation was based on modeling heat and mass transfer through the selected microstructures. Chromium-aluminum and chromium-nickel steel was surveyed in terms of their applicability for carrier manufacturing and catalyst depositing. The alumina washcoat and cobalt catalyst were deposited as organic precursors using Langmuir-Blodgett (LB) method. The amount of deposited materials was controlled by the LB parameters and verified by TG measurements. The carriers were characterized at various stages of the preparation by SEM/EDX, XPS 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 precalcined CrAl carrier. Oxidation of cobalt stearate deposited on the CrAl gave dispersed Co3O4 spinel. Although the obtained cobalt catalyst in an oxidized state initiated n-hexane combustion at higher temperature (370 °C) than an industrial Pt/Al2O3 catalyst used as a reference, it had twice as low activation energy (50 kJ/mol).