CH4 deep oxidation over active and thermally stable catalysts based on Sn–Cr composite oxide

Abstract

Catalysts based on Sn–Cr composite oxide (SnCr) and modified with sulfate or a small amount of Pd were prepared and studied for CH₄ deep oxidation. XRD suggests that a solid solution may be formed between Sn and Cr. As a result, the thermal stability of SnCr catalyst is significantly enhanced, and more active oxygen species are formed in it, thus leading to improved activity. The addition of sulfate into SnCr binary oxide (SnCr–SO₄²⁻) promotes its activity markedly, perhaps due to further increased thermal stability, higher surface area and the formation of strong acid sites, which were previously found to be favorable for hydrocarbon activation. Pd supported on SnCr (Pd/SnCr) shows much higher activity than SnCr, which is close to SnCr–SO₄²⁻. The main reason leading to the enhanced activity, however, is ascribed to the superior performance of Pd itself for CH₄ oxidation, and the synergism between Pd and tin oxide. Pd/SnCr–SO₄²⁻ exhibits slightly higher activity than SnCr–SO₄²⁻ and Pd/SnCr with the same Pd loading. Ultimately, it is noted that SnCr–SO₄²⁻ displays not only superior CH₄ oxidation activity, but also excellent resistance to sulfur poisoning and long term stable performance, indicating that it is a promising catalyst with the potential to be applied in some real CH₄ oxidation processes.