Co3O4-MnOx oxides supported on SBA-15 for CO and VOCs oxidation

Mono- and bi-component cobalt and manganese samples were prepared by two-solvent'' technique using SBA15 as a support. The obtained materials were characterized by SAXS (Small angle X-Ray scattering), N-2 adsorption-desorption, X-ray diffraction, TEM (Transmission Electron Microscopy), X-ray photoelectron spectroscopy (XPS), TPR (Temperature-programmed reduction) and O-2-TPD (Oxygen Temperature-programmed desorption). The catalytic properties were tested in the complete oxidation of propane, n-hexane, and carbon monoxide. The modification of the SBA-15 materials with Co, Mn or simultaneously with both cobalt and manganese does not change significantly the mesoporous structure, however its pores are partially blocked by the oxides, resulting in the decrease in the specific surface area and in the pore volume. In the case of mono component Co-SBA-15, the clusters of Co3O4 are on the surface and they are partially located inside the pore system of SBA-15 while for Mn-SBA-15 sample, the oxide phases preferentially fill up the channels of SBA-15 forming nanowires. The mixed oxide nanowires are formed in the channels of CoMn-SBA-15 material along with small nanoparticles, aggregated outside of the channels. The mesoporous structure and morphology of SBA-15, type of oxide phases and the size of the oxide particles remain almost unchanged after tests in reaction of complete n-hexane oxidation and this is valid for all studied samples. The observed resistance towards agglomeration can be attributed to the mesoporous structure. On the other hand, after reaction the surface concentration of different cobalt and manganese species undergoes significant changes, except for the sample with equimolar Co:Mn ratio. The most active catalyst among bi-component Co-Mn samples in all studied reactions is the catalyst where the Co:Mn molar ratio is 1:0.5, which can be explained by the formation of finely divided oxides, thus ensuring highest reducibility and oxygen mobility.