Modifications of Pt/alumina combustion catalysts by barium addition II. Properties of aged catalysts Original Research Article

Resistance of platinum deposited onto alumina and barium modified alumina, towards ageing at 1200°C has been studied experimentally in the catalytic combustion of butane. With pure alumina, ageing has a tremendous effect on both the surface area of the support and metal dispersion which induces severe loss of activity. High temperature calcination of Ptsingle bondBa/Al2O3 samples leads to a solid state reaction leading first to BaO · Al2O3, then to BaO · 6Al2O3. The latter phase is strongly heat resistant inhibiting α-Al2O3 transformation. Despite surface area preservation, platinum is not stabilised on this support: metallic dispersion is very low, as evidenced by the formation of very large particles. Unexpectedly, activity is enhanced on such sintered catalyst. Some hypothesis concerning active species have been proposed to explain this activity enhancement. It is suggested that some kind of mobile superficial oxygen atom may be responsible for the activity.