HYDROGENOLYSIS OF METHYLCYCLOPENTANE AND ISOMERIZATION OF 2-METHYLPENTANE OVER WELL CHARACTERIZED SILICA-SUPPORTED PLATINUM-RUTHENIUM CATALYSTS

The hydrogenolysis of methylcyclopentane and the isomerization of 2-me thylpentane were studied over Pt-Ru bimetallic catalysts prepared usin g either H2PtCl6 and RuCl3 (Series A) or from Pt(NH3)(4)(NO3)(2) and R u(NH3)(6)Cl-3 (Series B). Energy-dispersive X-ray spectroscopy (EDXS) studies showed that the catalysts prepared using the amine precursors were 100% bimetallic. Image defocussing studies suggest that approxima tely 20% of the particles prepared using the chloride precursors were monometallic, At temperatures at which only ruthenium is active (413 K ), the formation of C-1 to C-5 products was depressed over Pt-Ru bimet allic clusters, Tertiary-secondary carbon-carbon bond cleavage approac hes that observed for ruthenium while secondary-secondary carbon-carbo n bond cleavage is closer to that observed for platinum, The isomeriza tion of 2MP at 493 K is representative of Pt-Ru activated dual sites s ince platinum is inactive at this temperature and ruthenium leads to e xtensive degradation of the molecule. The contribution of the cyclic m echanism was obtained using C-13 labelled species. A synergistic effec t was observed for the catalysts prepared using amine precursors. This is explained by considering an increase in the number of PtRu dual su rface sites.