Performance of Gold Nanoparticles Supported on Carbon Nanotubes for Selective Oxidation of Cyclooctene with Use of O2 and TBHP

Gold nanoparticles supported on multi-walled carbon nanotubes (Au/CNTs) were developed for the selective epoxidation of cyclooctene with oxygen and small amount of tert-butyl hydroperoxide (O₂-TBHP). We found that the Au/CNTs could provide the best combination of selectivity and conversion in comparison with the supported gold catalysts with several other carriers like active carbon, graphite, TiO₂, SiO₂ and Al₂O₃. The conversion of cyclooctene and the selectivity to epoxide increased with the amount of TBHP, but both reached almost maxima when the TBHP amount was higher than 5.0 mol% of cyclooctene. The CNTs-supported gold nanoparticles with mean sizes ranging from 3.1 to 15.0 nm could be prepared by using sol-immobilization method. The Au/CNTs catalysts with smaller gold particle size were related to higher epoxide yield, indicating a size effect of gold nanoparticles on the catalytic performance. The results suggested that the epoxidation of cyclooctene over the Au/CNTs with use of O₂-TBHP would be structure-sensitive.