Development of [60] fullerene supported on silica catalysts for the photo-oxidation of alkenes

Simple or successive incipient wetness impregnation followed by heating at 180 degrees C is proved an efficient preparation method for dispersing effectively onto the silica surface various amounts of C-60 in the range 1-4% (w/w). BET, XRD, DRS, TGA, microelectrophoresis and photoluminescence have been used to characterize the photocatalysts prepared. A high dispersion was obtained for the quite stable supported C-60 phase, comprised mainly from relatively small or medium size C-60 clusters/aggregates. The photocatalytic activity was assessed in the singlet oxygen oxidation of alkenes by examining the photo-oxygenation of 2-methyl-2-heptene as a probe reaction. The catalytic tests were carried out at 0-5 degrees C in CH3CN, under oxygen atmosphere and using a 300 W xenon lamp as the light source. The heterogeneous catalysts obtained were proved to be active in the photocatalytic oxidation of olefins via a O-1(2) ene reaction. The catalysts exhibited significant conversion, turnover number and turnover frequency values, substantially higher than those achieved over the unsupported C-60. The conversion increases with the amount of the supported C-60 up to a value equal to 3% (w/w) and then it decreases whereas turnover number and turnover frequency decreases monotonically as the amount of the supported C-60 increases. The easy separation of these solid catalysts from the reaction mixture, the high activity and stability as well as the retained activity in subsequent catalytic cycles, make these supported catalysts suitable for a small-scale synthesis of fine chemicals. (C) 2009 Elsevier B.V. All rights reserved.