Gold Nanoparticles Stabilized by Task-Specific Oligomeric Ionic Liquid for Styrene Epoxidation Without Using VOCs as Sol
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Gold Nanoparticles Stabilized by Task-Specific Oligomeric Ionic Liquid for Styrene Epoxidation Without Using VOCs as Solvent Lirong Luo Æ Ningya Yu Æ Rong Tan Æ Yong Jin Æ Dulin Yin Æ Donghong Yin
Received: 8 March 2009 / Accepted: 13 April 2009 / Published online: 23 May 2009 Ó Springer Science+Business Media, LLC 2009
Abstract An oligomer of ionic liquid containing imidazolium and disulfide groups, which is miscible with the ionic liquid of [Bmim]PF6, was synthesized and used to stabilize gold nanoparticles. As such, epoxidation of styrene could be catalyzed by the oligomeric ionic liquidstabilized gold nanoparticles in the nonvolatile [Bmim]PF6 without using any VOC as solvent. Under optimum reaction conditions, a styrene conversion of 100% with the selectivity to styrene oxide of 90% was obtained. Keywords Gold nanoparticles Ionic liquid Styrene Epoxidation
1 Introduction Since Haruta’s [1] pioneering work in 1987 on the extraordinary catalytic activity of nanoscale gold particles for CO oxidation, gold nanoparticles have been shown to be highly active catalysts for many important industrial reactions, such as low temperature CO oxidation [2–4], alcohol oxidation [5–10], hydrogenation of a,b-unsaturated aldehydes [11], direct formation of hydrogen peroxide
L. Luo N. Yu (&) R. Tan Y. Jin D. Yin D. Yin Key Lab of Sustainable Resources Processing and Advanced Materials of Hunan Province, Institute of Fine Catalysis and Synthesis, Hunan Normal University, 410081 Changsha, Hunan, People’s Republic of China e-mail: [email protected] Y. Jin D. Yin (&) Technology Center, China Tobacco Hunan Industrial Corporation, 410014 Changsha, Hunan, People’s Republic of China e-mail: [email protected]
[12, 13], and epoxidation/oxidation of alkenes [14–20]. Owing to easy agglomeration of nanoparticle, these gold nanoparticles are generally stabilized by solid supports in catalytic reactions, especially in liquid-phase epoxidation/ oxidation. Although the supported solid catalysts show good activity in some liquid-phase reactions [5–10, 14–17], the potential inaccessibility of the substrate to the catalytic active sites in the reaction system involving solid catalyst has stimulated researchers to use liquid stabilizer as an alternative solution [21–24]. On the other hand, liquidphase epoxidation/oxidation catalyzed by solid gold nanoparticle catalysts usually employ volatile organic compounds (VOCs) as solvents, such as benzene [14–16], methylcyclohexane [17], and 1,2,3,5-tetramethylbenzene [18]. The toxic and/or hazardous properties of such volatile solvents will limit the applications of these systems with respect to environmental law. Hence, it is still highly desirable for academic and business circles to develop efficient and environmentally benign gold nanoparticle catalytic system for liquid-phase epoxidation/oxidation [9, 21, 22]. Ionic liquids (ILs), especially those based on imidazolium cation, seem well positioned to address the challenge of developing efficient and environmentally benign gold na
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