Peculiar redox properties of SBA-15 supported copper ferrite catalysts promoting total oxidation of a model volatile organic air pollutant

Copper ferrite is an ideal catalyst for total oxidation of VOCs due to its peculiar, reversible redox properties. By rationally designing mono- and bimetal Cu/Fe catalysts with metal content of 10 wt.% supported on SBA-15 silica, high activity in total oxidation of toluene as a model VOC compound could be achieved. The key parameters for the formation of copper ferrite on the silica support are the Cu/Fe atomic ratio of 1:2 and the pore size of the SBA-15. Using temperature-programmed reduction and spectroscopic methods, such as Mössbauer, diffuse reflectance UV–Vis and FT-IR, in addition to detecting oxides, we could observe ionic metal species and strong interaction with the silica surface depending on the applied temperatures (350–450 °C) and gas media (air, NO/He) for salt decomposition. It was found that heat treatment in air resulted in stronger interaction with the silica wall, whereas NO/He pretreatment favored the formation of finely dispersed copper ferrite nanoparticles. The formation of ferrite nanoparticles ensures Cu 2+ /Fe 3+ pairs in the catalyst providing easier release of oxygen, which is necessary for the activation of toluene. It was also found that the SBA-15 supported copper ferrite catalysts preserve the special redox properties of the bulk material. They show high activity and stability with time on stream, or by reduction-reoxidation treatment. It can be attributed also to the fact, that metal oxide species confined in the mesopores are more resistant to agglomeration during the catalytic test.