CATALYTIC ACTIVITY AND CHARACTERIZATION OF PT/SIO2 CATALYSTS PREPARED BY THE SOL-GEL METHOD

Platinum on silica catalysts have been prepared by adding [PtCl6]-2 to tetraethoxysilane (TEOS). After hydrolysis and condensation a gel is formed. The addition of platinum into the gel has an important effect on the surface area of the solid (up to 1,100 m2 m/g). The catalysts with a low metal concentration (less-than-or-equal-to 0.5 wt %) are active for the hydrogenation of alkenes but not for the hydrogenation of aromatics. A support effect can be proposed to explain the low activity for benzene and ortho-xylene hydrogenation. In ortho-xylene hydrogenation, as far as deactivation by thiophene is concerned, sol-gel platinum catalysts are more resistant to poisoning than impregnated catalysts.