NO oxidation over supported cobalt oxide catalysts

摘要

NO oxidation was conducted over cobalt oxides supported on various supports such as SiO_2, ZrO_2, TiO_2, and CeO_2. The N_2 physisorption, an inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), NO chemisorptions, the temperature-programmed desorption (TPD) with a mass spectroscopy after NO or CO chemisorptions were conducted to characterize catalysts. Among tested catalysts, Co_3O_4 supported on ceria with a high surface area showed the highest catalytic activity. This catalyst showed superior catalytic activity to unsupported Co_3O_4 with a high surface area and 1 wt% Pt/γ-Al_2O_3. For ceria-supported Co_3O_4, the catalytic activity, the NO uptake at 298 K and the dispersion of Co_3O_4 increased with increasing the surface area of CeO_2. The active participation of the lattice oxygen in NO oxidation could not be observed. On the other hand, the lattice oxygen participated in the CO oxidation over the same catalyst. The deactivation was observed over Co_3O_4/CeO_2 and 1 wt% Pt/γ-Al_2O_3 in the presence of SO_2 in a feed. 1 wt% Pt/γ-Al_2O_3 was deactivated by SO, more rapidly compared with Co_3O_4/CeO_2.