The NiO/Al2O3-CaO, CuO/Al2O3-CaO and CoO/Al2O3-CaO catalytic systems were investigated for the decomposition of ozone. Each of the three different Al2O3-CaO carriers was obtained after treatment of the initial precursor at 1100 °C for 2, 4 and 6 h, respectively, to examine the effect of annealing on support calcination. AAS, XRD, XPS, EPR, SEM and BET were applied for sample characterization. The carrier comprises a mixture of corundum α-Al2O3, θ-Al2O3 and Ca3Al2O3. The XRD spectra of the active phases of the catalysts show the existence of Co3O4, NiO, Ni2O3 and CuO. The SEM micrographs reveal spherical particles for the NiO/Al2O3–CaO sample. In contrast, the CoO/Al2O3–CaO sample exhibits a morphology composed of wool-like fibers and perpendicularly oriented plate-like structures. The CuO/Al2O3–CaO sample consists not only of fibrous structures but also of distinct, separated aggregates. The obtained catalysts have highly developed specific surface areas. Their catalytic activity depends on the calcination conditions of the support, and the best results are observed after 2h treatment for all of the investigated samples due to the smaller crystallite size and higher specific surface area. The activity of the investigated catalysts for the ozone decomposition reaction follows the order NiO/Al2O3-CaO > CoO/Al2O3-CaO > CuO/Al2O3-CaO.
Milenova et al. (Sat,) studied this question.