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Journal of Zhejiang University SCIENCE A
ISSN 1673-565X(Print), 1862-1775(Online), Monthly
2016 Vol.17 No.12 P.1000-1012
Green epoxidation of cyclooctene with molecular oxygen over an ecofriendly heterogeneous polyoxometalate-gold catalyst Au/BW11/Al2O3
Abstract: An ecofriendly heterogeneous polyoxometalate (POM)-gold catalyst Au/BW11/Al2O3 was synthesized and used for solvent-free epoxidation of cyclooctene under mild reaction conditions using molecular oxygen as an oxidant and t-butyl hydroperoxide (TBHP) as an initiator. The catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), induced coupled plasma optical emission spectrometry (ICP-OES), and Brunauer-Emmett-Teller (BET). The catalyst showed good conversion and high selectivity without use of solvents or environmentally harmful oxidants. Moreover, the catalyst is recyclable up to three cycles with no significant loss in selectivity towards epoxide.
Key words: Nano gold, Polyoxometalates (POMs), POM-gold catalyst, Cyclooctene epoxidation, Molecular oxygen
创新点：1. 把纳米金颗粒和多金属氧酸盐（即BW11）结合并负载在固体载体上制备出了一种新型复合催化剂材料；2. 采用分子氧作为氧化剂而不是传统的有机酸或者过氧酸；3. 在温和条件下可获得良好的转化率和较高的环氧化物选择性；4. 催化反应体系未使用有机溶剂；5. 催化剂稳定并可循环使用。
方法：1. 根据文献中所述方法制备BW11；2. 采用标准沉积沉淀法合成Au/Al2O3；3. 采用湿式浸渍法制备催化剂Au/BW11/Al2O3；4. 环辛烯环氧化使用叔丁基过氧化氢（TBHP）作为引发剂，氧气作为氧化剂，在高压反应釜中进行反应；5. 采用扫描电镜和X射线衍射等对催化剂进行表征。
结论：1. 提高焙烧温度可改善催化反应性能；2. 随着催化剂量增加到0.2 g，转化率也随之增加（图8）；3. 反应的最佳温度为80 °C（表1）；4. 随着反应时间的增加直到24 h，转化率逐渐增加，环氧化物选择性也增加到约87%（图9）；5. 催化剂可适用于多种氧化剂（表2）；6. 无溶剂下转化率和选择性相对较大（表3）；7. 催化剂可以有效活化分子氧和环辛烯；8. 催化剂可以再生，在使用三次后，其活性损失不大。
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DOI:
10.1631/jzus.A1500332
CLC number:
TQ032.4
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On-line Access:
2016-12-06
Received:
2015-12-09
Revision Accepted:
2016-06-16
Crosschecked:
2016-11-24