Catalytic Combustion of Toluene over Co3O4 loaded on ZrSn1−xFexO4−δ

Toluene is one of the volatile organic compounds which are harmful to the environment and human health. One promising approach to eliminate toluene is catalytic combustion. Although precious metal based catalysts are known to show high activity for toluene combustion, the high price of the precious metals has restricted their widespread applications. In this study, precious-metal-free catalysts of Co3O4/ZrSn1−xFexO4−δ were synthesized for toluene combustion. Here, scrutinyite-type ZrSnO4 was focused as a promoter which can supply active oxygen species from inside the lattice toward the Co3O4 activator. In addition, Fe2+/3+ ions were introduced into the ZrSnO4 lattice to enhance the oxygen supply ability owing to the improvement of redox properties and the formation of oxygen vacancies for smooth oxide ion migration. The oxygen supply from the ZrSn1−xFexO4−δ lattice facilitated toluene oxidation on Co3O4, and the highest catalytic activity was obtained for the 19 wt% Co3O4/ZrSn0.93Fe0.07O4−δ (Co3O4/ZSF0.07) catalyst, where the complete combustion was realized at the temperature as low as 250 °C. The toluene combustion reaction over Co3O4/ZSF0.07 is considered to proceed along a typical route of the rapid transformation of toluene into the intermediates (benzyl alcohol, benzaldehyde, benzoate, and maleic anhydride) and finally the formation of carbon dioxide and water.