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(Nicolet-5700) in the wavenumber range of 400~4000 cm−1. Percentage
content of elements which composed the products was observed by using
an elemental analysis (Vario EL CUBE).
The [Emim] Ac solution of TATB was scanned using a FTIR spec-
trometer (Nicolet-5700) in the wavenumber range of 400~4000 cm−1
to investigate how [Emim] Ac dissolved TATB. Thermal behaviors of
the recycled TATB were detected using a synchrotherm reactor
(SDT Q600) in nitrogen atmosphere (velocity of flow: 30 ml/min),
heating range from 25°C to 1000°C (heating rate: 20°C/min). Morphol-
ogies of the recycled TATB were observed using a scanning electron
microscope (TM-1000), so as to compare with those of untreated TATB.
3. Results and discussion
3.1. One-pot synthesis of [Emim] Ac
In this work, the one-pot method was proposed to synthesize [Emim]
Ac using 1-methylimidazole and bromethyl as starting materials. It is
necessary to optimize the reaction conditions in order to improve the
[Emim] Ac synthesis efficiency.
Fig. 1. Hydrogen bonding of TATB.
Calorimetry (DSC). Finally the dissolution mechanism of TATB in
ionic liquids was illustrated by FTIR analysis.
3.1.1. Influence of reactant ratio on yield
According to the literature [14–15], reactant ratio plays an impor-
tant role in this reaction. So by fixing the reaction temperature at 65°C
and the reaction time of 24 h, five comparative experiments have
been carried out with the following bromethyl:1-methylimidazole:
lead acetate ratios: 2:2:1, 2.4:2:1, 3:2:1, 3.6:2:1, and 4:2:1, whose
results are shown in Fig. 3. It can be concluded from Fig. 3 that the
optimized materials ratio (bromethyl:1-methylimidazole:lead acetate)
is 3.6:2:1 and the yield could reach 84.4% at this ratio.
2. Materials and experiment
2.1. Reagent and equipment
1-Methylimidazole (LR) was provided by Chengdu Kelong Chemical
Reagent Company [Sichuan Province, China]. Bromethyl (AR) and Lead
acetate (AR) were purchased from Tianjin Chemical Reagent Co., Ltd.
ethyl acetate (AR) was produced from Chengdu Institute of Chemical Re-
agent. Vacuum drying oven (DZF6053) and rotary evaporator(R-201)
were produced by Shanghai Hengyi Scientific Instrument Co., Ltd.
3.1.2. Influence of reaction temperature on yield
While the reactant ratio and the reaction time are fixed to 3.6:2:1 and
24 h, respectively, Fig. 4 gives the reaction yields of four different reaction
temperatures (40°C, 50°C, 60°C, and 70°C). It is clear from Fig. 4 that the
yield of the produce increase with the temperature from 40°C to 60°C.
But when the temperature exceeds 60°C, the yield slightly decreases.
The color of solution becomes deeper with the temperature upto 70°C, in-
dicate that it is bromethyl’s volatilization and [Emim] Ac’s decomposition
overabundance at 70°C, resulting from the superheating of reaction sys-
tem. In order to get a higher yield, the optimized reaction temperature
had better be 60°C and at this temperature the yield reaches 87.4%.
2.2. Synthesis of [Emim] Ac by one-pot method
1-Methylimidazole (8.20 g, 0.1 mol), an excess of bromethyl (13.08 g,
0.12 mol) and propanetriol solution of lead acetate (containing lead
acetate: 16.23 g, 0.05 mol) were added to the three-opening flask
with a reflux and stirring device at 60°C, in a constant temperature
water bath. The synthetic route was shown in Fig. 2. After 20 hours,
the solution cooled to the room temperature, and the white precipi-
tated was removed by suction filtration. The clear solution was
washed with pure ethyl acetate (EtOAc) (30 ml) many times. At last,
the aim product was obtained by vacuum rotary evaporation at 60°C
for 2 hours. [Emim] Ac: 87%: UV–vis ([Emim] Ac)λmax: 214.0 nm; IR ν:
3433, 3146, 3085, 1572, 1170, 621 cm-1; Anal. calcd for [Emim] Ac:
C 56.47, N 16.47, H 8.24; found C 56.55, N 16.50, H 8.16.
3.1.3. Influence of reaction time on yield
Based on the above experimental results, the influence of reaction
time on product yield is investigated at 60 °C and with the ratio being
3.6:2:1, and the yields of five different reaction times are displayed in
Fig. 5. It can be seen from Fig. 5 that the product yield improves from
14 h to 20 h but decreases slightly from 20 h to 24 h, displaying that
the optimal reaction time is 20 h and at this reaction time the yield
reaches 86.8%.
2.3. Characterization
Absorption spectrum of the product was measured on a UV–vis
spectrophotometer (UV-3150) in the wavelength range of 200~800 nm.
All the images were obtained in the 1 cm quartz cuvette using deionized
water as the background. FTIR spectra were taken on a FTIR spectrometer
3.2. Dissolution of TATB in ionic liquids
Table 1 summarizes the measured solubility of TATB in [Xmim]Y
(X=−CH2CH3, –(CH2)3CH3, and –(CH2)7CH3; Y=Cl−, HSO4−, and
Fig. 2. One-pot synthesis route of 1-ethyl-3-methylimidazolium acetate.
Zhu
