PLATINUM SUPPORTED ON [60]FULLERENE-GRAFTED SILICA AS A NEW POTENTIALCATALYST FOR HYDROGENATION

A Pt-based catalyst supported on a silica grafted with [60]fullerene w as prepared and evaluated in the liquid-phase hydrogenation of cinnama ldehyde. Silanization of a large-pore silica was carried out with diet hoxymethylsilane. [60]Fullerene was anchored on the modified silica th rough a hydrosilylation reaction with Si-H bonds, mediated by a Pt-0 K arsted catalyst. IR, Si-29 and C-13 MAS NMR spectroscopies, and N-2 ad sorption-desorption provided evidence that [60]fullerene was covalentl y bonded onto the silica surface. [60]Fullerene was released at ca 950 , 750, and 800 K in He, air, and H-2, respectively, even in the presen ce of 0.8 wt% Pt. The very high density of [60]fullerene grafting conf ers a strong hydrophobic character to the surface. A fairly good selec tivity to cinnamyl alcohol was observed on this catalyst at cinnamalde hyde conversion above 90%. This behavior might be better explained by a specific interaction between the phenyl ring of cinnamaldehyde and t he grafted [60]fullerene film than by a modification of the Pt d-band. The IR spectroscopy of adsorbed CO did not provide any evidence of an enhanced, or reduced, back-donation to 2 pi antibonding orbitals of CO, with respect to classical supported Pt catalysts. (C) 1998 Academi c Press.