TRANSFORMATION OF CARBON-COMPOUNDS ON GRAPHIMET CATALYSTS .9. STRUCTURAL-PROPERTIES AND CATALYTIC ACTIVITY OF PD-GRAPHIMET

A comparative study of pristine and thermally treated (medium-temperat ure reduction, MTR, 573 K, 1 h) Pd-graphimet was carried out to establ ish the changes arising in structure and catalytic activity. The struc tural investigation was performed by means of BET surface area analysi s, transmission electron microscopy, small-angle X-ray scattering and H-2 titration. In order to distinguish between the hydrogenation and i somerization sites of the samples, the single turnover reaction of l-b utene was applied. For pristine Pd-graphimet, the experimental evidenc e confirmed the presence of interlayer metal and surface metal particl es of different sizes. Although the catalytic activity was clearly att ributable to the 1-2 nm surface Pd crystallites, the interlayer metal content also had an influence on the reaction through deintercalation which first started at 323 K. Nevertheless, the effect of MTR was foun d to be far more pronounced: all the inserted Pd atoms underwent migra tion and a moderate sintering of the surface Pd crystallites took plac e. Data on the transformation of l-butene indicated that Pd-graphimet was similar in effect to supported Pd catalysts.