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An experimental part

1.1 Instruments and reagents

N icolet A vatar 330 FT-IR spectrophotometer, N icolet Evolution 300 UV-visible spectrophotometer, USA Nicolet (N icolet) company; DDS212A digital conductivity meter, Shanghai Hongyi Instrument Co., Ltd.; Agilent GC6890 gas chromatograph, USA Agilent Technologies, Inc.; M ettler2Toledo AL 204 electronic analytical balance, Shanghai Science and Technology Co., Ltd.; KQ 250B Ultrasonic cleaner, Kunshan Ultrasonic Instrument Co., Ltd..

Sodium tetrafluoroborate, n-butyl bromide, CP, Sinopharm Chemical Reagent Co., Ltd.; N 2 methylimidazole, AR, A lfa A esar A Johnson M atthey Company (USA); dichloromethane, AR, Shanghai Chemical Reagent Co. company; ethyl acetate, AR, Tianjin Chemical Reagent Co.; ethanol, methanol, AR, China Shanghai revitalization of a chemical plant.

1.2 Ionic Liquids

Out in 100 mL two-necked flask, 01055 mol-methylimidazole, ultrasonic (the oscillation frequency is 40 kHz) was slowly added dropwise processing state 0105 mol 12 bromide, during the addition of about 10 m in, the reaction 115 h. Purified product was 80 ℃ vacuum dried 6 h to give a yellow viscous liquid, 232 butyl methylimidazolium bromide 12 (Br), 99% yield.

Was dissolved in 30 mL of acetone Br, adding 1417 g N aBF 4, at 55 ℃ water bath, ultrasonic response 2 h. Vacuum filtered to remove a white solid material, the mother liquor to recover the acetone by distillation under reduced pressure to give a pale yellow BF 4, produced rate of 92%.

1.3 Determination of the viscosity

At a temperature of 303 K, using an Ubbelohde viscometer viscosity of ionic liquid, according to the formula (1) to calculate the viscosity of the ionic liquid, three parallel experiments, the mean value.

1. 4 BF 4 Determination of conductivity

Respectively, acetone, ethanol and ethyl acetate as the solvent, the preparation of a series of concentrations of BF 4 solution, at a certain temperature, the magnetic stirring after 10 m in measured conductivity.

1. 5BF 4 catalyzed esterification and gas chromatography

Conditions for BF 4 as catalyst, the oleic acid and methanol, acetic acid and isoamyl alcohol molar ratio of 115:1 to the esterification reaction, 80 ℃ a magnetic stirring the reaction time and the product was quantitatively analyzed by gas chromatography.

Gas chromatography analysis conditions: American Agilent GC6890 gas chromatograph, F ID detector, polyethylene glycol bonded capillary (25 m × 0120 mm × 0120Λm), column temperature 210 ℃, carrier gas: N 2, 015 mL m in. Detector temperature: 250 ℃; inlet temperature: 250 ℃. The injection volume 1ΛL.

2 Results and discussion

2.1 Ultrasonic assisted synthesis ionic liquids

In the absence of nitrogen conditions, using Ultrasonic vibration, 55 ℃ water bath heated reaction 115 h and 2 h preparation Br (yield 99%) and BF 4 (yield 92%). Compared with the conventional method (the first step reaction time is generally requires about 48 h, the reaction under nitrogen), the reaction time is much shorter, the reaction temperature is lower, the reaction without nitrogen, and the yield considerably. Same structure as alkyl chloride, dialkyl imidazole synthesis time to be extended, which is due to different due to differences in the reactivity of halogenated hydrocarbons.

2.2 Spectral Analysis

2.2. 1 UV spectrum ultraviolet absorption spectrum, the solvent of the ionic liquid absorption wavelength, absorption coefficient of the fine structure will have an impact. Should avoid absorption bands in the ultraviolet region with a solvent, so as not to affect the ionic liquid absorption band observed. Methanol as solvent used in this study, can reduce the strong ion conductive polymer.

At room temperature (25 ℃). Shows: methanol as solvent, BF 4 wavelength of UV absorption 213 nm, the wavelength of the transmittance at 233 nm increased rapidly.

2.2. 2 IR spectrum measured using KBr ionic liquid BF infrared spectrum.

2.3 Determination of the viscosity measured at 303 K of water, Br, and BF 4 viscosity. Shows: room temperature ionic liquid viscosity greatly.

Br BF 4 with a viscosity of water at the same temperature were the viscosity and 53157 times 65152 times. The viscosity of the ionic liquid to the structure of the cationic and anionic: When the same cation, the anion is smaller, the greater the viscosity of the experimental data with this agreement.

2.4 Determination of Conductivity

Debye's law based, selection of ethyl acetate, ethanol and acetone as the measuring solvent, the preparation of the ionic liquid solution with different concentrations.

Conductivity meter after calibration, measured at different temperatures conductivity of the solution. BF 4 in different solvents (ethyl acetate, ethanol and acetone), and the molar conductivity at different temperatures. Shows: the solution temperature, the conductivity of the solution increased, the conductivity increases. Relationship between molar conductivity and temperature can be expressed as: + m = aT + b, where, a, b are the slope and intercept of a straight line.

In different solvents, there are large differences in conductivity. This is because BF 4 in different solvents solvation different structure and different polarity solvents, solvents solvation BF 4 are also different. BF 4 in different solvents molar conductivity of the order: acetone, ethanol, ethyl acetate. BF 4 in acetone solvent, the characteristics of a strong electrolyte. Molar conductivity variation with concentration and conductivity with different changes in the concentration, when the concentration decreases, the mutual interaction between the particles weakened, anion and cation movement speed increases, so the molar conductivity increases.

Limiting molar conductivity can not be measured directly from the experiment, because the infinite dilution solution itself is an extreme solution, but can be accurately measured molar conductivity, and then extrapolated to a concentration of 0, ie the molar conductivity at infinite dilution solution. Typically when the concentration of 01001 molL - 1 or less, + m and c in Equation between (3) + m = + ∞ m (1-Βc 1 2) (3) Formula (3): In a certain temperature , for a given electrolyte and solvent, Β is a constant.

Shows: With the c 1 2 increases, the molar conductivity is decreasing. And in different solvents, which reduces to different degrees. Fig pushed by extrapolation to a concentration of 0, in a polar solvent, more complete ionization, + ∞ m large, and in a weak polar solvent, ionic liquid may be present in a compact form ion pairs, leading + ∞ m small.

2. 5BF 4 catalytic properties

BF 4 Synthesis of isoamyl alcohol and acetic acid and oleic acid and methanol reaction results (molar ratio of 115:1, the mass ratio of 0106:1 and an acid catalyst, reaction temperature 80 ℃).

Notes: a gas chromatography workstation provides data; b by caustic washing, drying and distillation of the data processing calculations.

By the known: BF 4 Catalytic Synthesis of Isoamyl Acetate Catalyzed effects than synthetic oil methyl ester. This indicates that the catalytic BF 4 easier esterification of lower carboxylic acids, lower carboxylic acid esters of the catalytic synthesis has a good potential, its optimal catalytic conditions for further study.

3 Conclusion

a. the mechanical Ultrasonic cavitation can increase the interaction between molecules, to improve the reaction efficiency to ultrasonic BF 4 Synthesis of ionic liquids is conducive to shorten the reaction time. Reaction with acetone as a solvent, the solvent recyclable, in accordance with the "green chemistry" requirement, and is conducive to the purification of ionic liquids. Synthesis reaction time from 24 ~ 48 h shortened to 4 h, the method has mild reaction conditions, the reaction speed, energy consumption end, the product easy purification and so on.

b. BF 4 molar conductivity increases with increasing temperature, with the concentration increases. In different solvents as solvent molecules on the anion and cation solvation is different, the molar conductivity are quite different, indicating that BF 4 in different solvents can occur completely or partially ionized.

c. the BF 4 catalyst acid and alcohol in the esterification reaction, no side reactions such as oxidation, BF 4 recycled, reused. BF 4 with an alcohol, an acid has good compatibility with a catalytic esterification.

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