CHARACTERIZATION OF STRUCTURE AND CATALYTIC ACTIVITY OF PT-SN CATALYSTS SUPPORTED IN AL2O3, SIO2 AND TIO2

In this work we characterized two types of Pt-Sn bimetallic catalysts: a 'model' catalyst made by sequentially evaporating the two metals on a planar SiO2 film deposited on a 3 mm gold grid and a series of 'rea l' catalysts prepared by the impregnation method on SiO2, TiO2 and Al2 O3 and were called 'real' catalysts. Lattice spacings from high resolu tion electron micrographs exhibited differences between the 'model' an d the 'real' catalysts, implying that the preparation method affects t he formation of different chemical phases. We observed the formation o f core-shell morphologies in both 'model' and 'real' catalysts, which implies the segregation and formation of different phases at the surfa ce of the particles. The 'real' catalysts were also studied with X-ray diffraction to compare the chemical phases formed with the HREM measu rements. We used dehydrogenation of cyclohexane as a test reaction to study the catalytic behaviour of the Pt when we add Sn. Catalysts at d ifferent atomic concentrations were prepared in order to observe the c hanges in activity and selectivity. (C) 1998 Elsevier Science B.V. All rights reserved.