The determination of accessible Pt metal fraction in Pt±Sn/Al2O3 reforming catalyst

Abstract

An attempt has been made to provide a simple method for the determination of accessible Pt metal fraction in Pt±Sn/Al2O3 catalyst. The complications in Pt±Sn/Al2O3 system arise mainly due to uncertainties involved in the oxidation states of tin: Sn0, Sn2 and Sn4 in the reduced catalyst. H2, O2 chemisorption/titrations originally applied to Pt/Al2O3 were extended to the Pt±Sn/Al2O3 system. Two oxygen titration cycles OT1 and OT2 at room temperature were carried out using a dynamic pulse ¯ow technique. Only part of the total Sn in the catalyst is reduced to Sn0 (15%), which contributes to oxygen uptake. While OT1 is a linear function of the Sn content in the catalyst, the second oxygen titration OT2 gives the accessible Pt metal fraction only. It has been concluded that oxygen chemisorption/titrations at temperatures higher than ambient under dynamic conditions are not reliable for the determination of metal dispersions. # 1998 Elsevier Science B.V