Low-temperature carbon monoxide and propane total oxidation by nanocrystalline cobalt oxides

Abstract

Pure CoO(OH), with intra particulate porosity up to 76%, was synthesized by an innovative aqueous precipitation method, starting either from nitrate or sulfate salts. Microstructural and chemical properties were characterized by powder X-ray diffraction (XRD), thermogravimetry (TG) and differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The primary particles (10–15 nm) are self-organized in monolayer building hexagonal nano-platelets (50–200 nm) which are arranged randomly creating large pores. CoO(OH) was converted in Co3O4 by heating in air at 250 °C. This treatment did not modify the porosity but increased the specific surface area, which became close to 100 m2/g. The catalytic activity for CO and C3H8 total oxidation was better for Co3O4 than for CoO(OH). Besides, at high conversion rate, catalysts prepared from sulfate precursor showed a superior activity for C3H8 oxidation than those prepared from nitrate. This effect can be explained by the improved accessibility of reactants to the surface of the catalysts which exhibit a larger porosity. To our knowledge, the activity values presented here are the highest reported in literature for C3H8 total oxidation.