Physicochemical and catalytic properties of sol gel-prepared copper-chromium oxides

Nanostructured copper-chromium oxides were prepared by the sol–gel process (SG) and were characterised by elemental analysis, thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and by their activity in methane combustion. A comparative study was made with copper chromites commercial catalysts. The as-synthesised copper chromites sample exhibited higher specific surface area (248 m² g⁻¹) with respect to commercial solids (42 m² g⁻¹). The surface quantitative analysis evidenced a Cr⁶⁺ enrichment for the SG catalyst (Cr⁶⁺/Cr³⁺=0.56) with respect to commercial sample (0.39), while the ratio of copper species Cu²⁺/(Cu° + Cu⁺) was the same in both solids. Catalytic activity of SG solids in methane combustion was found to be comparable to that of Pt/Al₂O₃ and superior to that of commercial copper chromites tested under the same conditions.