Total oxidation catalysts based on manganese or copper oxides and platinumor palladium II: Activity, hydrothermal stability and sulphur resistance

Deactivation of catalysts based on either manganese oxides, copper oxides, platinum, palladium or combinations of these metal oxides and noble metals supported on gamma-alumina was studied. The activity of the catalysts for t he oxidation of carbon monoxide, naphthalene and methane, in a mixture rese mbling the flue gases from wood combustion, was measured before and after e xposure of the catalysts either to a temperature of 900 degrees C in the pr esence of steam or to sulphur dioxide. Most of the mixed catalysts were mor e resistant to hydrothermal and sulphur treatments than the catalysts with a single active component. After the hydrothermal treatment the activity of the MnOx catalyst was enhanced. When Pt is combined with MnOx or CuOx, the loss of activity of Pt was decreased during the hydrothermal treatment. Al so, the hydrotreated mixed MnOx-Pd and CuOx-Pd catalysts were more active t han the treated Pd catalyst for the oxidation of methane. After sulphur tre atment, the activities of the mixed MnOx-Pt (Pt: 0.05 mol%), MnOx-Pd and Cu Ox-Pd catalysts were improved for the oxidation of carbon monoxide and naph thalene. Among the catalysts studied, the MnOx-Pt, CuOx-Pt and CuOx-Pd cata lysts, with a metal oxide and a noble metal loading of 10 and 0.1 mol%/gamm a-alumina, respectively had the best combination of activity, thermal stabi lity and resistance to sulphur treatment. (C) 1999 Elsevier Science B.V. Al l rights reserved.