Preparation and Characterization of SnO2-Based Composite Metal Oxides: Active and Thermally Stable Catalysts for CH4 Oxidation

A series of SnO₂-based catalysts modified by Fe, Cr and Mn were prepared by the combination of redox reaction and co-precipitation methods, and applied to catalytic CH₄ oxidation. The modified catalysts show generally higher activity than the unmodified SnO₂. XRD analysis indicates that Fe, Cr and Mn cations could be incorporated into the lattice of rutile SnO₂ (cassiterite) to form solid solution structure. As a result, more reducible and active oxygen species was formed in the samples, as substantiated by the H₂-TPR results. Moreover, the specific surface areas of the modified catalysts are much higher than that of pure SnO₂ and their crystallite sizes are smaller, indicating they are more resistant to thermal sintering. Indeed, the high specific surface areas and the formation of more active oxygen species in the modified samples are believed to be the predominant reasons leading to their enhanced CH₄ oxidation activity. Eventually, it is noted that SnCrO displays not only remarkable CH₄ oxidation activity, but also potent resistance to SO₂ and water deactivation, which makes it a promising catalyst with the potential to be applied in some real CH₄ oxidation processes.