Preparation And Application Of Novel Deep Eutectic Solvents

Recently, it was shown that substituted quaternary ammonium salts with urea or carboxylicacids can form eutectics, which are liquid at ambient temperature and exhibit interesting solventproperties. This kind of solvents, termed deep eutectic solvent (DES), possess much benefit thatthose traditional ionic liquids based on imidazolium salts do not have:(1) the preparationprocedure of these eutectic mixtures is very simple, only needs to mix two different compoundsmechanically and requires no medium;(2) They are very cheap due to the low cost of rawmaterials;(3) DES is expected to have good biocompatibility since quaternary ammonium saltssuch as choline iodide was used as an additive in chicken feed.(4)100%reaction mass efficiencyand zero emission in the synthesis are achieved and which is relatively environmentally benign.They find use in electrochemical applications, in separation sciences as solvents for extractionprocesses, for gas chromatography as a stationary phase, as well as in mass spectrometry.However, the application in large-scale have been very limited due to issues with high viscosityand melting point. Based on the application of DES, a series of correlative experiments werecarried out in this study. The preparation and physical properties of DES, such as viscosity,conductivity, density and refractive index were determined. In addition, the preparation ofhollow nickel spheres was studied by an improved self-catalytic reduction method using DES assolvent.In this paper, novel deep eutectic solvents (DES) were successfully prepared with1-butyl-3-methylimidazolium chloride ([Bmim]Cl) and dicarboxylic acids (malonic acid, succinicacid, glutaric acid or adipic acid) as raw materials. All DES are colorless transparent liquid atroom temperature. The influence of the molar ratio of [Bmim]Cl and dicarboxylic acids on thepreparation of DES were studied. The Interaction of [Bmim]Cl and dicarboxylic acids werestudied by FTIR. The physical properties of DES, such as viscosity, conductivity, density andrefractive index were determined. The influence of temperature, carbon number of dicarboxylicacids and molar ratio of dicarboxylic acids in DES system on the physical properties wasinvestigated. The results showed that they cannot form the uniform transparent liquid when the molar ratios of ([Bmim]Cl) is less than1in the system. When the molar ratios of [Bmim]Cl andadipic acid is1:1, the system can only form uniform transparent liquid under the condition ofheating.When the composition was constant, the viscosity of all investigated DESs decreased rapidlywith increasing of temperature and the conductivity increased with increasing of temperature.When the temperature was constant, the carbon number of dicarboxylic acids showed differentinfluence on viscosity and conductivity according to molar ratio with odd-even effect and packingeffect. The temperature dependence of viscosity and conductivity was investigated throughsystemically quantitative analysis using Arrhenius equation and VTF equation. The activationenergy of viscous flow (E,48~84kJ·mol-1) and activation energy of the ionic conductivity (Eσ,37~73kJ·mol-1) were calculated by Arrhenius plots. In the temperature range of298.15~333.15K,the temperature dependence of viscosity and conductivity both showed a well accordance withVTF models (all R>0.9999) than Arrhenius models. The range of density was1.1153～1.1725g/cm3when the temperature is25℃. The densities of DES also decreased linearly withincreasing of temperature when the composition was constant. Excess molar volumes (VE) ofDESs were all positive. The contribution of dicarboxylic acids on VEis more than [Bmim]Cl. Therefractive index of DES (at298.15K) decreased with increasing of molar ratio of dicarboxylicacids in DES system. The refractive indexes showed a similar trend to densities with increasing ofcarbon number in dicarboxylic acids.The hollow nickel sphere was perepared using ChCl:2Urea as solvent, NiCl26H2O,Ni(NO3)26H2O, NiSO46H2O as the source of nickel, and sodium hypophosphite (NaH2PO2) asa reducing agent. The influence of nickel source and their concentration, temperature, amount ofwater, the concentration and dosage of the reducing agent on the preparation of hollow nickelspheres were studied. It showed that nickel source and their concentration, temperature, amount ofwater, the concentration and dosage of the reducing agent have great influence on the preparationof hollow nickel spheres. The hollow nickel spheres are prepared with Ni(NO3)26H2O are betterthan NiCl26H2O and NiSO46H2O. The surface morphology of hollow nickel spheres changedsignificantly with increasing of concentration. Therefore, the best preparation conditions forhollow nickel spheres is:0.05mol/L Ni(NO3)26H2O,150℃, the dosage of water is1ml, thedosage of0.4mol/L NaH2PO2is5ml (based on5ml solvent). In conclusion, novel deep eutectic solvents (DES) were successfully prepared with1-butyl-3-methylimidazolium chloride ([Bmim]Cl) and dicarboxylic acids as raw materials. Thehollow nickel spheres were prepared by an autocatalytic reduction method using DES as solvent.The preparation process, which is simple and controllable, cheap raw materials, zero emission inthe synthesis and environmentally benign, are achieved. The subject is not only importantsignificance in preparation and development of deep eutectic solvents, but also promotes theeutectic solvent large-scale application in terms of the preparation of nickel hollow spheres.