Platinum/silica and platinum/alumina of low metal content and rather high dispersion have been silylated by treatment with hexamethyldisilazane in oxygen carrier or in hydrogen carrier at 100°. Hydrogenations on silylated and unsilylated catalysts have been studied in a liquid-phase batch reactor at 20° with cyclopentene and di-tert-butylacetylene and in a pulse reactor at -46.5° with ethylene. In the most straightforward case, the hydrogenation of cyclopentene, silylation in oxygen reduces the rate only about 20%. It is concluded that hydrogenation is predominantly confined to the surface of metallic platinum under our conditions, that is, that reaction of olefin with hydrogen atoms which have migrated from platinum to the surface of silica is of minor importance and that provision of a new channel of supply of olefin to the surface of platinum by initial adsorption of olefin on silica is similarly of low importance.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry