The Applications Of Ionic Liquids In The Preparation And Catalytic Performances Of Gold Nanoparticles

Room-temperature ionic liquids (RTILs), which offer favorable ionicenvironments for some reactions, have attracted much interest in reducingor eliminating environmental pollutions caused by solvents. On the otherhand, lots of researches of gold nanoparticles indicated that their catalyticactivity depends on the particle size correlated with the preparationmethod. Unfortunately, gold nanoparticles easily aggregated in catalyticreactions, resulting in quick loss of activity. In this dissertation, theapplications of ionic liquids in the preparation and catalytic performancesof gold nanoparticles were investigated. The main contents discussedwere as follows:1. A series of RTILs were synthesized and used as solvents togetherwith water for the synthesis of epithiochlorohydrin. The transformation ofepichlorohydrin to epithiochlorohydrin was effectively catalyzed by thesesystems via an oxygen-sulfur exchange process with potassiumthiocyanate under mild conditions. It was found that the conversion andselectivity were as high as 99.1% and 97.0%, respectively, when thereaction was performed in [Bmim]PF₆H₂O catalysis-solvent system at 15℃for 4 h. Furthermore, the ionic liquids could be conveniently recoveredfor recycled use at least four times without obvious loss in activity. 2. A novel thioether-functionalized ionic liquid (TFIL) was synthesizedvia the reaction of epithiochlorohydrin and methylimidazolium, and usedfor the preparation of gold nanoparticles (GNPs) in water or1-n-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF₆). TheGNPs stabilized by the thioether-functionalized ionic liquid(GNPs-TFIL)were characterized by FT-IR, UV-vis spectra and transmission electronmicroscopy (TEM), FT-IR spectra showed that the GNPs-TFIL stillremained the structure of the TFIL after GNPs being stabilized by theTFIL, The UV-vis spectra of the GNPs-TFIL prepared in water and[Bmim]PF₆ displayed an interface resonance absorption appearing around530 nm and 526 nm, repectively, which suggest the formation ofnanometer gold particles in TFIL. TEM observation showed that thenano-Au particles in GNPs-TFIL prepared in [Bmim]PF₆ possessedsmaller average size with more uniform particle size distribution incomparison with that prepared in water.3. The obtained GNPs-TFIL were used as a catalyst in the epoxidationof styrene in [Bmim]PF₆ for the first time and exhibited high catalyticactivity The conversion of styrene and the selectivity of styrene oxidewere as high as 100% and 88.5%, respectivety. when the reaction wasperformed at 45℃for 6h using 3-chloroperoxybenzoic acid (m-CPBA)as oxidant, Also, the GNPs could be easily reused.