Performance of Gold Nanoparticles Supported on Carbon Nanotubes for Selective Oxidation of Cyclooctene with Use of O 2 a
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Performance of Gold Nanoparticles Supported on Carbon Nanotubes for Selective Oxidation of Cyclooctene with Use of O2 and TBHP Bodong Li • Ping He • Guangquan Yi Haiqiang Lin • Youzhu Yuan
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Received: 30 July 2009 / Accepted: 21 September 2009 / Published online: 30 September 2009 Ó Springer Science+Business Media, LLC 2009
Abstract 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 structuresensitive. Keywords Supported gold catalyst Carbon nanotube Epoxidation Cyclooctene Gold size effect
B. Li P. He G. Yi H. Lin Y. Yuan (&) State Key Laboratory of Physical Chemistry of Solid Surfaces, National Engineering Laboratory for Green Chemical Productions of Alcohols-Ethers-Esters, College of Chemistry and Chemical Engineering, Xiamen University, 361005 Xiamen, People’s Republic of China e-mail: [email protected]
1 Introduction Supported gold nanoparticles have been extensively studied as catalysts for a wide range of oxidation reactions including low-temperature CO oxidation, alkene epoxidation, and aerobic oxidation of alcohols in both gas- and liquid-phase under relatively mild conditions [1–14]. In the case of selective oxidation of higher olefins catalyzed by supported gold catalysts, Choudhary et al. [15–19] and subsequently Yin et al. [20–22] have shown that gold nanoparticles supported on a range of carriers are active for the epoxidation of styrene using tert-butyl hydroperoxide (TBHP). About 50% selectivity to styrene oxide is achieved using this approach. Hutchings et al. [23] have showed that gold nanoparticles supported on graphite could selectively epoxidize a variety of alkenes using oxygen as an oxidant under the help of a catalytic amount of TBHP or H2O2. The effects of support, the amount of TBHP or H2O2, the additives like Bi and the catalyst preparation methods were investigated in their work. A careful selection of reaction solvent like 1,2,3,5-tetramethylbenzene was necessary in order to obtain higher yield. Quite recently, Hutchings et al. [24] reported that the epoxidation of cylcooctene over Au/graphite catalyst under mild and sol
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