Synthesis And Applications Of Room Temperature Ionic Liquids

In this paper, four kinds of room temperature ionic liquids (RTIL) are prepared. Their electric conductivity and electrochemical window, which play an important role in the applications of ionic liquids to electrodeposition and electroplating of active metals, are determined.The intermediates N-butylpyridium chloride(BPC) and l-butyl-3-methylimidazolium chloride([bmim]Cl) for the synthesis of ionic liquids are prepared by the reactions between N-butyl halide and pyridium or N-methylimidazolium. Acidic, basic and neutral BPC-AlCl3 ionic liquids are prepared by directly mixing BPC and AlCl3 with different ratios of BPC to AlCl3 under inert atmosphere. For other ionic liquids such as N-butylpyridium tetrafluoride (BPBF4), l-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BFi|) and l-butyl-3-methylimidazolium hydrogen sulphate ([bmim][HSO4]), they are synthesized through anion exchange reactions in acetonitrile medium. Their chemical structures are determinedby H NMR, IR and Raman spectra, respectively.The electrochemical window of the ionic liquids synthesized is measured by Cyclic Voltammogram. The chemical potential windows of the RTILs prepared are 3.4V, 4.0V, 2.25V, 3.1V, 2.2V and 2.2V for acidic, neutral and basic A1C13-BPC, BPBF4, [bmim]BF4 and [bmim][HSO4] RTILs respectively. The electrochemical windows of these ionic liquids are broader than of water (1.229V), so some active metals such as aluminium can be electrolysed in these ionic liquids.The electric conductivity of the RTILs is measured at different temperatures. The electric conductivity is increased with increasing temperature. It is shown that the sequence of electric conductivity can be expressed as Ka>Kb>Kc>Kd>Ke>Kf, where Ka kb kc, Kd Ke and Kf are electric conductivity for [bmim]BF4, BPBF4, acidic, basic and neutral AlCl3-BPC and [bmim][HSO4] RTILs, respectively. Moreover, the relations of electric conductivity and temperature can be described with Arrhenius equation.The viscosity of BPBF4, [bmim]BF4 and [bmim][HSO4] RTILs is determined at 22℃. It is demonstrated that [bmim]BF4 ionic liquid has better fluidity than BPBF4, and [bmim][HSO4 ] is the worst in fluidity among them.