Toluene oxidation on chromium- and copper-modified SiO2 and SBA-15

Copper- and chromium-modified SiO2 and SBA-15 materials, prepared by a wet impregnation technique, were investigated using X-ray diffraction (XRD), N2 physisorption, temperature-programmed reduction (TPR-DTG), temperature-programmed oxidation (TPO-DTG), UV–vis diffuse reflectance EPR and FT-IR spectroscopy. Their catalytic behavior was studied in the total oxidation of toluene. The supports had decisive role on the nature and dispersion of the formed metal species. The presence of chromium and copper species, mainly in tetrahedral coordination, was observed for the modified SBA-15 samples, while a significant amount of metal oxides is registered for the modified SiO2 ones. More finely dispersed chromium and copper species were formed on the bi-component copper- and chromium-containing SBA-15 catalysts and possessed higher activity in total oxidation of toluene. The optimal metal oxide content for highly active and selective SBA-15-supported catalyst was found to be 3 wt.% chromium and 7 wt.% copper.

It was found that the type of the generated metal oxide species depends on the type of support used. The mesoporous support favors the formation of tetrahedrally coordinated copper and chromium oxide species which are highly active in toluene oxidation. The appropriate metal oxide content in order to obtain highly active catalyst is 3 wt.% chromium and 7 wt.% copper supported on SBA-15.Figure optionsDownload high-quality image (47 K)Download as PowerPoint slide