Nano-gold supported on Fe₂O₃: a highly active catalyst for low temperature oxidative destruction of methane green house gas from exhaust/waste gases

Abstract

A number of nano-gold catalysts were prepared by depositing gold on different metal oxides (viz. Fe₂O₃, Al₂O₃, Co₃O₄, MnO₂, CeO₂, MgO, Ga₂O₃ and TiO₂), using the homogeneous deposition precipitation (HDP) technique. The catalysts were evaluated for their performance in the combustion of methane (1 mol% in air) at different temperatures (300-600°C) for a GHSV of 51,000 h^-1. The supported nano-gold catalysts have been characterized for their gold loading (by ICP) and gold particle size (by TEM/HRTEM or XRD peak broadening). Among these nano-gold catalysts, the Au/Fe₂O₃ (Au loading = 6.1% and Au particle size = 8.5 nm) showed excellent performance. For this catalyst, temperature required for half the methane combustion was 387°C, which is lower than that required for Pd(1%)/Al₂O₃ (400°C) and Pt(1%)/Al₂O₃ (500°C) under identical conditions. A detailed investigation on the influence of space velocity (GHSV = 10,000-100,000 cm³ g^-1 h^-1) at different temperatures (200-600°C) on the oxidative destruction of methane over the Au/Fe₂O₃ catalyst has also been carried out. The Au/Fe₂O₃ catalyst prepared by the HDP method showed much higher methane combustion activity than that prepared by the conventional deposition precipitation (DP) method. The XPS analysis showed the presence of Au in the different oxidation states (Au⁰, Au¹⁺ and Au³⁺) in the catalyst.