Nanostructured metal oxides obtained by means polymerization-combustion at low temperature for COÂ selective oxidation

We investigated the synthesis of nanosized Co3O4, NiO and CuO oxides by the polymerization-combustion method and evaluated in the selective oxidation of CO. These materials were characterized before and after catalytic test under specific conditions by X-ray diffraction, scanning electron microscopy, temperature programmed reduction, Raman spectroscopy and Diffuse reflectance infrared Fourier transform spectroscopy. For isoconversion the activity follows the order: Co3O4>NiO > CuO. The intrinsic activities under isothermal conditions at 100 °C are: 0.20 × 10−3 s−1 for the Co3O4 and 0.08 × 10−3 s−1 for NiO and CuO. Therefore, the activity of the Co3O4, is 3 times higher than for NiO and CuO. The XRD and Raman analyses after catalytic test confirm the existence of a partial reduction of oxides to the metallic phase and no evidence of carbon deposition over surface materials. In the case of nickel oxide the analyzed sample shows the metallic phase of nickel and in the case of copper oxide the sample presents a high grade of reduction. XRD results confirm the presence of Cu2O and metallic Cu. Finally, results showed that these oxide catalysts present a high resistance to carbonaceous formation under present reaction conditions and confirm the effectiveness of polymerization-combustion technique for synthesis of active high catalyst in the selective oxidation of CO.