Preparation,Property Of Ionic Liquids And Investigation Of Crystal For Vitamin C

Room temperature ionic liquids (ILs) are organic salts composed of cations and anions that are liquids at conditions near room temperature. Known as environmentally benign solvents, ILs are attracting a great deal of attention as possible replacement for traditional volatile organic solvents. Their application has involved in many fields, such as organic syntheses, catalytic reactions and multiphase separations. The key functions of ILs are possible to be tuned by varying the nature of the cations and anions, 1 in which two important groups are those based on imidazolium and pyridinium cations. While the focus of researches on ILs has predominantly been on their applicability as solvents for reactions and separations, the physicochemicai properties of ILs and their mixtures with organic or inorganic solvents have not been studied much. The study of properties is important in order to obtain sufficient information to predict properties and characteristics of ILs, and the lack of physical property data and fundamental understanding of ILs prevent their further application to industry.2In this work, data of densities and viscosities of mixtures consisting of water and l-ethyl-3-methylimidaloziurn tetrafluoroborate ([emim][BF4]) were measured over the entire range of their compositions at different temperatures (293.15, 298.15, 303.15, 308.15, 313.15, 318.15, 323.15 K). The excess molar volume VE and viscosity derivation .A n. of this binary system have been obtained and fitted to the Redlich-Kister equation. The effects of water content and temperature on the physical properties were analyzed, and the interactions and structures were discussed in terms of the behavior of excess molar volume VE and viscosity derivation . . of [emim][BF4]-H2O mixture.In IL solution, the experiments of single crystals growth were carried out on growth rates of different orientations ([010], [001] and [100]) for vitamin C. Under various temperatures and supersaturations, the directional growth rates were measured. The kinetic parameters wereregressed by least-square method and verified by significance test. Crystals are often in the form of rod. And the effects of solvent on directional growths were analyzed according to steric effect of solvent molecules and hydrogen bond interaction at solution-crystal interface.Growth of vitamin C single crystals were studied by direct observation. In flowing solution, the linear growth rates of three directions ([010], [001], [100]) were measured for vitamin C-IL system. The experiments were designed as orthogonal test to investigate the effect extent of factors. Comparing with temperature and velocity, supersaturation is the most important factor. And the relationships between growth and supersaturation were different with crystal directions, which obviously show anisotropy. The magnitude orders of G[010], G[001], G[100]and their dependences on supersaturation (g1010], g[001], g[100]) were in good agreement with analysis of maximum difference. The effect of solution diffusion could be neglected and crystal growth was controlled by surface reaction.