CN112125848A - Method for synthesizing imidazole ionic liquid under assistance of ultrasonic waves and application - Google Patents

Method for synthesizing imidazole ionic liquid under assistance of ultrasonic waves and application Download PDF

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CN112125848A
CN112125848A CN202010982185.6A CN202010982185A CN112125848A CN 112125848 A CN112125848 A CN 112125848A CN 202010982185 A CN202010982185 A CN 202010982185A CN 112125848 A CN112125848 A CN 112125848A
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ionic liquid
ultrasonic
imidazole
imidazole ionic
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CN112125848B (en
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刘向荣
宋长磊
赵顺省
杨再文
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Xian University of Science and Technology
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    • C07D233/00—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings
    • C07D233/54—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings having two double bonds between ring members or between ring members and non-ring members
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Abstract

The invention provides a method for synthesizing imidazole ionic liquid with the assistance of ultrasonic waves and application thereof, belonging to the technical field of organic matter synthesis, wherein the synthesis method comprises the following steps: adding 0.1-0.3 mol of 1-methylimidazole into a solvent for dissolving, adding 0.05-0.2 mol of 1, 4-dibromobutane, carrying out ultrasonic reaction for 1-4 h under the conditions that the ultrasonic frequency is 100-400W and the ultrasonic temperature is 30-80 ℃, carrying out rotary evaporation at the temperature of 60-80 ℃ to remove the solvent, cooling, washing, carrying out suction filtration, and drying to obtain the imidazole ionic liquid. The method can improve the synthesis efficiency of the imidazole ionic liquid.

Description

Method for synthesizing imidazole ionic liquid under assistance of ultrasonic waves and application
Technical Field
The invention belongs to the technical field of organic matter synthesis, and particularly relates to a method for synthesizing imidazole ionic liquid under the assistance of ultrasonic waves and application thereof.
Background
The fossil energy structure in China is characterized by rich coal, poor oil and less gas, the coal resources in China are rich, the varieties are complete, and the coal occupies a main position in the energy consumption structure in China. As coal yields continue to increase, the importance of coal mine safety is more prominent. Coal spontaneous combustion is one of typical coal mine disasters, and not only can waste coal resources and pollute the environment, but also threatens the life safety of workers in a mine. Therefore, the flame retardant research of coal has important significance for protecting the life and property safety of the nation and people.
In recent years, in order to suppress the harm caused by spontaneous combustion of coal, many scholars at home and abroad develop different types of flame retardants to suppress spontaneous combustion of coal. The ionic liquid is a novel environment-friendly flame retardant and becomes a research hotspot at home and abroad. The research on the ionic liquid flame retardant is mainly focused on the imidazole ionic liquid, because the imidazole ionic liquid has better flame retardant property to coal, scholars enhance the flame retardant property of the imidazole ionic liquid by changing the length of a cationic side chain and the type of anions in the imidazole ionic liquid, and have less research on improving a process method to improve the flame retardant property of the ionic liquid. In addition, imidazole ionic liquid synthesized by the currently adopted water bath method has poor inhibitory effect on coal spontaneous combustion.
Disclosure of Invention
Aiming at the problem that the imidazole ionic liquid synthesized by the existing water bath method has poor inhibitory effect on spontaneous combustion of coal, the invention provides a method for synthesizing imidazole ionic liquid by ultrasonic wave assistance and application thereof, and the specific technical scheme is as follows:
a method for synthesizing imidazole ionic liquid with the assistance of ultrasonic waves comprises the following steps:
adding 0.1-0.3 mol of 1-methylimidazole into a solvent for dissolving, adding 0.05-0.2 mol of 1, 4-dibromobutane, carrying out ultrasonic reaction for 1-4 h under the conditions that the ultrasonic frequency is 100-400W and the ultrasonic temperature is 30-80 ℃, carrying out rotary evaporation at the temperature of 60-80 ℃ to remove the solvent, cooling, washing, carrying out suction filtration, and drying to obtain the imidazole ionic liquid.
Further limiting, the steps specifically include:
adding 0.1-0.3 mol of 1-methylimidazole into a solvent for dissolving, adding 0.05-0.2 mol of 1, 4-dibromobutane, carrying out ultrasonic reaction for 2.5h under the conditions that the ultrasonic frequency is 200W and the ultrasonic temperature is 60 ℃, removing the solvent by rotary evaporation at 70 ℃, cooling, washing, carrying out suction filtration, and drying to obtain the imidazole ionic liquid.
Further defined, the solvent is ethanol.
Further limiting, the washing solution used for washing and suction filtration is ethyl acetate.
Further defined, the drying conditions are: drying for 20-30 h at 40-50 ℃.
The imidazole ionic liquid prepared by the method for synthesizing the imidazole ionic liquid by ultrasonic assistance.
The imidazole ionic liquid is applied to the aspect of inhibiting spontaneous combustion of coal.
The method for verifying the imidazole ionic liquid in the aspect of inhibiting the spontaneous combustibility of coal is characterized by comprising the following steps: preparing 20 wt% imidazole ionic liquid solution, mixing 8-12 g coal sample with 80-120 ml imidazole ionic liquid solution, carrying out ultrasonic reaction for 2-3 hours at the ultrasonic frequency of 250-350W and the ultrasonic temperature of 70-90 ℃, washing the coal sample to be neutral, drying, and preparing the verified coal sample.
Further, the washing liquid used for washing is distilled water.
Further defined, the drying conditions are: drying the mixture for 40 to 50 hours at the temperature of 50 to 30 ℃.
Compared with the prior art, the invention has the beneficial effects that:
1. the method for synthesizing the imidazole ionic liquid under the assistance of the ultrasonic waves accelerates the cavitation effect formed in a reaction system and the chemical reaction rate by using the ultrasonic waves for assistance, and the yield of the imidazole ionic liquid can be improved to 94.97% by using the method for ultrasonic reaction for 2.5 hours under the conditions that the ultrasonic frequency is 200W and the ultrasonic temperature is 60 ℃, so that the synthesis efficiency of the imidazole ionic liquid is greatly improved.
2. The imidazole ionic liquid prepared by the method disclosed by the invention can be used for inhibiting the spontaneous combustibility of the coal sample, so that the ignition point of the coal sample can be increased from 401.2 ℃ to 433.1 ℃.
3. The mixed solution of the imidazole ionic liquid and the coal sample is treated under the assistance of ultrasonic waves, so that ash in the coal sample can be effectively removed, the carbon-hydrogen ratio of the coal sample is improved, the fraction of the coal sample is reduced, and the coalification degree of the coal sample is improved.
Drawings
FIG. 1 is the effect of ultrasonic frequency on imidazole ionic liquid yield;
FIG. 2 is the effect of ultrasonic temperature on imidazole ionic liquid yield;
FIG. 3 is the effect of ultrasound time on imidazole ionic liquid yield;
FIG. 4 is a nuclear magnetic resonance hydrogen spectrum of the imidazole-based ionic liquid prepared in example 1;
FIG. 5 is a nuclear magnetic resonance carbon spectrum of the imidazole-based ionic liquid prepared in example 1;
FIG. 6 is an infrared spectrum of the imidazole-based ionic liquid prepared in example 1;
FIG. 7 is a TG-DTG graph of a coal sample;
FIG. 8 is a TG-DTG graph of an imidazole ionic liquid treated coal sample under water bath stirring;
FIG. 9 is a TG-DTG graph of a coal sample treated by the ultrasonic-assisted imidazole ionic liquid.
Detailed Description
The technical solutions of the present invention will be further explained below with reference to the drawings and examples, but the present invention is not limited to the embodiments described below.
A method for synthesizing imidazole ionic liquid with the assistance of ultrasonic waves comprises the following steps:
adding 0.1-0.3 mol of 1-methylimidazole into a solvent for dissolving, adding 0.05-0.2 mol of 1, 4-dibromobutane, carrying out ultrasonic reaction for 1-4 h under the conditions that the ultrasonic frequency is 100-400W and the ultrasonic temperature is 30-80 ℃, carrying out rotary evaporation at the temperature of 60-80 ℃ to remove the solvent, cooling, washing, carrying out suction filtration, and drying to obtain the imidazole ionic liquid.
The method for synthesizing the imidazole ionic liquid under the assistance of the ultrasonic waves comprises the following steps:
adding 0.1-0.3 mol of 1-methylimidazole into a solvent for dissolving, adding 0.05-0.2 mol of 1, 4-dibromobutane, carrying out ultrasonic reaction for 2.5h under the conditions that the ultrasonic frequency is 200W and the ultrasonic temperature is 60 ℃, removing the solvent by rotary evaporation at 70 ℃, cooling, washing, carrying out suction filtration, and drying to obtain the imidazole ionic liquid. The solvent is ethanol. The washing liquid used for washing and suction filtration is ethyl acetate. The drying conditions were: drying for 20-30 h at 40-50 ℃.
The imidazole ionic liquid is prepared by the method for synthesizing the imidazole ionic liquid under the assistance of the ultrasonic waves.
The imidazole ionic liquid is applied to the aspect of inhibiting spontaneous combustion of coal.
The method for verifying the imidazole ionic liquid in the aspect of inhibiting the spontaneous combustibility of coal comprises the following steps: preparing 20 wt% imidazole ionic liquid solution, mixing 8-12 g coal sample with 80-120 ml imidazole ionic liquid solution, carrying out ultrasonic reaction for 2-3 hours at the ultrasonic frequency of 250-350W and the ultrasonic temperature of 70-90 ℃, washing the coal sample to be neutral, drying, and preparing the verified coal sample. The washing liquid used for washing is distilled water. The drying conditions were: drying the mixture for 40 to 50 hours at the temperature of 50 to 30 ℃.
Example 1
The embodiment of the invention relates to a method for synthesizing imidazole ionic liquid with the assistance of ultrasonic waves, which comprises the following steps:
adding 0.2mol of 1-methylimidazole into a 100ml beaker, adding 50ml of ethanol for dissolving, adding 0.1mol of 1, 4-dibromobutane, carrying out ultrasonic reaction for 2.5h under the conditions that the ultrasonic frequency is 200W and the ultrasonic temperature is 60 ℃, carrying out rotary evaporation at 70 ℃ after the ultrasonic reaction is finished to remove ethanol to obtain yellow oily liquid, cooling to gradually generate white solid, repeatedly carrying out suction filtration and washing for 3 times by using ethyl acetate, and drying in a vacuum drying oven at 50 ℃ for 24 hours to obtain the imidazole ionic liquid.
Example 2
The embodiment of the invention relates to a method for synthesizing imidazole ionic liquid with the assistance of ultrasonic waves, which comprises the following steps:
adding 0.1mol of 1-methylimidazole into a 100ml beaker, adding 50ml of ethanol for dissolving, adding 0.05mol of 1, 4-dibromobutane, carrying out ultrasonic reaction for 4 hours at the ultrasonic frequency of 100W and the ultrasonic temperature of 60 ℃, carrying out rotary evaporation at the temperature of 60 ℃ after the ultrasonic reaction is finished to remove ethanol to obtain yellow oily liquid, cooling to gradually generate white solid, repeatedly carrying out suction filtration and washing for 4 times by using ethyl acetate, and drying in a vacuum drying oven at the temperature of 40 ℃ for 20 hours to obtain the imidazole ionic liquid.
Example 3
The embodiment of the invention relates to a method for synthesizing imidazole ionic liquid with the assistance of ultrasonic waves, which comprises the following steps:
adding 0.3mol of 1-methylimidazole into a 100ml beaker, adding 50ml of ethanol for dissolving, adding 0.2mol of 1, 4-dibromobutane, carrying out ultrasonic reaction for 3 hours at the ultrasonic frequency of 400W and the ultrasonic temperature of 30 ℃, carrying out rotary evaporation at 80 ℃ after the ultrasonic reaction is finished to remove ethanol to obtain yellow oily liquid, cooling to gradually generate white solid, repeatedly carrying out suction filtration and washing for 5 times by using ethyl acetate, and drying in a vacuum drying oven at 45 ℃ for 30 hours to obtain the imidazole ionic liquid.
Example 4
The embodiment of the invention relates to a method for synthesizing imidazole ionic liquid with the assistance of ultrasonic waves, which comprises the following steps:
adding 0.15mol of 1-methylimidazole into a 100ml beaker, adding 50ml of ethanol for dissolving, adding 0.15mol of 1, 4-dibromobutane, carrying out ultrasonic reaction for 2h at the ultrasonic frequency of 300W and the ultrasonic temperature of 50 ℃, carrying out rotary evaporation at the temperature of 65 ℃ after the ultrasonic reaction is finished to remove ethanol to obtain yellow oily liquid, cooling to gradually generate white solid, repeatedly carrying out suction filtration and washing for 4 times by using ethyl acetate, and drying in a vacuum drying oven at the temperature of 48 ℃ for 28 hours to obtain the imidazole ionic liquid.
Example 5
The embodiment of the invention relates to a method for synthesizing imidazole ionic liquid with the assistance of ultrasonic waves, which comprises the following steps:
adding 0.25mol of 1-methylimidazole into a 100ml beaker, adding 50ml of ethanol for dissolving, adding 0.18mol of 1, 4-dibromobutane, carrying out ultrasonic reaction for 1h at the ultrasonic frequency of 200W and the ultrasonic temperature of 40 ℃, carrying out rotary evaporation at 75 ℃ after the ultrasonic reaction is finished to remove ethanol to obtain yellow oily liquid, cooling to gradually generate white solid, repeatedly carrying out suction filtration and washing for 5 times by using ethyl acetate, and drying for 26 hours in a vacuum drying oven at 45 ℃ to obtain the imidazole ionic liquid.
Influence of ultrasonic frequency on the yield of the imidazole ionic liquid of the invention:
adding 0.2mol of 1-methylimidazole into a 100ml beaker, adding 50ml of ethanol for dissolving, adding 0.1mol of 1, 4-dibromobutane, carrying out ultrasonic reaction for 2 hours at an ultrasonic frequency of 100-400W and an ultrasonic temperature of 50 ℃, carrying out rotary evaporation at 70 ℃ after the ultrasonic reaction is finished to remove ethanol to obtain yellow oily liquid, cooling to gradually generate white solid, repeatedly carrying out suction filtration and washing for 3 times by using ethyl acetate, and drying in a vacuum drying oven at 50 ℃ for 24 hours to obtain the imidazole ionic liquid. Referring to fig. 1, with the increase of ultrasonic power, the yield of the imidazole-based ionic liquid shows a tendency of increasing slowly after increasing suddenly, and when the power reaches 200W, an inflection point appears, the yield is 87.25%, and after 200W, the yield of the imidazole-based ionic liquid is almost unchanged, because when the ultrasonic power reaches a certain value, the reaction rate of the system is already maximized, and the increase of the ultrasonic power to the yield of the product is not obvious. Therefore, the optimal ultrasonic power is 200W from the viewpoint of energy saving.
Influence of ultrasonic temperature on imidazole ionic liquid yield:
adding 0.2mol of 1-methylimidazole into a 100ml beaker, adding 50ml of ethanol for dissolving, adding 0.1mol of 1, 4-dibromobutane, carrying out ultrasonic reaction for 2 hours at the ultrasonic frequency of 200W and the ultrasonic temperature of 30-80 ℃, carrying out rotary evaporation at 70 ℃ after the ultrasonic reaction is finished to remove ethanol to obtain yellow oily liquid, cooling to gradually generate white solid, repeatedly carrying out suction filtration and washing for 3 times by using ethyl acetate, and drying in a vacuum drying oven at 50 ℃ for 24 hours to obtain the imidazole ionic liquid. Referring to fig. 2, the yield of the imidazole ionic liquid increases with the increase of the reaction temperature within the temperature range of 30-80 ℃, the yield reaches the maximum value of 92.39% at the temperature of 60 ℃, and the yield basically does not change at the temperature of 60 ℃, because the reaction rate of the reaction system reaches the maximum value when the temperature of the reaction system reaches a certain value, and the increase of the temperature is not obvious to the increase of the reaction rate. Therefore, the optimum reaction temperature for this experiment was 60 ℃ from the viewpoint of energy saving and maximizing the yield.
Influence of ultrasonic time on imidazole ionic liquid yield:
adding 0.2mol of 1-methylimidazole into a 100ml beaker, adding 50ml of ethanol for dissolving, adding 0.1mol of 1, 4-dibromobutane, carrying out ultrasonic reaction for 1-4 h under the conditions that the ultrasonic frequency is 200W and the ultrasonic temperature is 60 ℃, carrying out rotary evaporation at 70 ℃ after the ultrasonic reaction is finished to remove ethanol to obtain yellow oily liquid, cooling to gradually generate white solid, repeatedly carrying out suction filtration and washing for 3 times by using ethyl acetate, and drying in a 50 ℃ vacuum drying oven for 24 hours to obtain the imidazole ionic liquid. Referring to fig. 3, the yield of the imidazole ionic liquid increases with the increase of the reaction time within the range of 1-4 h, an inflection point appears when the ultrasonic time exceeds 2.5h, the yield reaches 94.97% to the maximum, and the yield is basically unchanged when the reaction time is greater than 2.5h, because the reaction is completed in the system after the reaction time reaches 2.5h, the influence of the increase of the ultrasonic time on the yield of the product is not great, so from the viewpoint of the reaction efficiency, the optimal ultrasonic time is selected to be 2.5h in the experiment.
Nuclear magnetic resonance characterization of the imidazole-based ionic liquids prepared in example 1:
0.005g of the imidazole ionic liquid synthesized in example 1 was put into a nuclear magnetic tube, 0.50mL of deuterated DMSO was added by a pipette, the tube was shaken continuously until the sample was dissolved sufficiently, and then the tube was put into a Bruker advanced DRX-400 nuclear magnetic resonance spectrometer1H NMR、13C NMR measurement, see FIGS. 4 and 5, obtained data as1H NMR(400MHz,DMSO-d6)(ppm):9.29(s,2H),7.83(d,2H),7.75(d,2H),4.25(t,4H),3.86(s,6H),1.79(m,4H).13C NMR(101MHz,DMSO-d6) (ppm) 137.10,124.11,122.72,48.37,36.30, 26.50. The nuclear magnetic resonance H spectrum and C spectrum results of the imidazole ionic liquid accord with theoretical values, which shows that the target ionic liquid is successfully synthesized.
Infrared spectroscopic characterization of the imidazole-based ionic liquid prepared in example 5:
placing a certain amount of KBr in a 120 ℃ blast drying oven for drying for 4 hours, adding the dried KBr and imidazole ionic liquid into an agate mortar, fully grinding, pressing the KBr into a transparent sheet under the pressure of 10t by using a pressing die and an oil press, continuously scanning for 32 times on an infrared spectrometer, wherein the test range is 400-4000 cm-1Referring to FIG. 6, it can be seen that 3452cm-1The absorption peak of (A) is caused by the stretching vibration of free-OH, indicating that the sample containsThere is moisture. 3076cm-1The absorption peak is the stretching vibration of C-H bond in imidazole ring; and 2955cm-1And 2860cm-1The absorption peak at is-CH31633cm of antisymmetric telescopic vibration-1And 1573cm-1The absorption peak is the stretching vibration of C ═ C in the imidazole ring, 1458cm-1The absorption peak is the skeleton vibration of imidazole ring, 1331cm-1The absorption peak at is-CH21163cm of deformation vibration-1The absorption peak at is-CH2Off-plane rocking vibration of 856cm-1、791cm-1And 621cm-1The absorption peak at (A) is an in-plane bending vibration of the C-H bond. The infrared spectrum result shows that the synthesized imidazole ionic liquid has characteristic absorption peaks in the structure, which indicates that the target ionic liquid is successfully synthesized.
Crushing and screening raw coal, selecting raw coal with the particle size of 0.075-0.2mm as an experimental coal sample, drying the experimental coal sample at 25 ℃ under a vacuum condition for 48 hours, sealing and storing for later use, and performing industrial analysis and element analysis, wherein the results are shown in table 1.
Experimental coal samples were validated with the imidazole-based ionic liquid prepared in example 1 under water bath agitation:
20.00g of the imidazole-based ionic liquid prepared in example 1 was weighed into a 100mL volumetric flask, distilled water was added to the scale mark to prepare a 20% wt solution, 10g of a coal sample was mixed with 100mL of the imidazole-based ionic liquid solution prepared in example 1 (ratio: 1:10), and the mixture was magnetically stirred for 3 hours in a water bath at 80 ℃. After stirring, the coal sample is repeatedly washed by distilled water until the eluate is neutral. The washed experimental coal sample was dried in a vacuum oven at 50 ℃ for 48 hours, and subjected to industrial analysis and elemental analysis, the results of which are shown in table 1.
Experimental coal samples were validated with the imidazole-based ionic liquid prepared in example 1 under sonication:
verification 1: weighing 20.00g of the imidazole ionic liquid prepared in example 1, adding the imidazole ionic liquid into a 100mL volumetric flask, adding distilled water to a scale mark to prepare a solution with the concentration of 20 wt%, mixing a 10g coal sample with 100mL of the imidazole ionic liquid solution prepared in example 1 (the ratio is 1:10), carrying out ultrasonic reaction for 3 hours at the ultrasonic frequency of 300W and the ultrasonic temperature of 80 ℃, and repeatedly flushing the coal sample with distilled water after the ultrasonic reaction is finished until an eluate is neutral. The washed experimental coal sample was dried in a vacuum oven at 50 ℃ for 48 hours to prepare a verification coal sample 1, and industrial analysis and elemental analysis were performed, with the results shown in table 1.
And (3) verification 2: weighing 20.00g of the imidazole ionic liquid prepared in example 1, adding the imidazole ionic liquid into a 100mL volumetric flask, adding distilled water to a scale mark to prepare a solution with the concentration of 20 wt%, mixing 8g of a coal sample with 80mL of the imidazole ionic liquid solution prepared in example 1 (the ratio is 1:10), carrying out ultrasonic reaction for 2 hours at the ultrasonic frequency of 250W and the ultrasonic temperature of 70 ℃, and repeatedly flushing the coal sample with distilled water after the ultrasonic reaction is finished until an eluate is neutral. The washed experimental coal sample was dried in a vacuum oven at 50 ℃ for 48 hours to prepare a test coal sample 2.
And (3) verification: weighing 20.00g of the imidazole ionic liquid prepared in example 1, adding the imidazole ionic liquid into a 100mL volumetric flask, adding distilled water to a scale mark to prepare a solution with the concentration of 20 wt%, mixing a 12g coal sample with 120mL of the imidazole ionic liquid solution prepared in example 1 (the ratio is 1:10), carrying out ultrasonic reaction for 2.5 hours at the ultrasonic frequency of 350W and the ultrasonic temperature of 90 ℃, and repeatedly flushing the coal sample with distilled water after the ultrasonic reaction is finished until an eluate is neutral. The washed experimental coal sample was dried in a vacuum oven at 50 ℃ for 48 hours to prepare a test coal sample 3.
Table 1: industrial and elemental analysis of experimental coal samples
Figure BDA0002687960010000061
Figure BDA0002687960010000071
In table 1: mad: moisture, air drying base; a. thed: ash, dry basis; vdaf: volatilizing, and drying the ashless base; FCdaf: fixing carbon, and drying an ashless base; stad: and (4) sulfur content.
As can be seen from table 1, after the ionic liquid treatment under the assistance of ultrasonic waves, the ash content and the moisture content of the experimental coal sample are greatly reduced, and the fixed carbon content is increased, which indicates that the ash content in the experimental coal sample can be effectively removed through the ultrasonic-assisted ionic liquid treatment. The elemental analysis results show that: after the ultrasonic-assisted ionic liquid is treated, the carbon content of the experimental coal sample is increased, and the hydrogen content and the sulfur content are reduced, which shows that the carbon-hydrogen ratio of the experimental coal sample can be improved, the sulfur content in the coal can be removed, and the coalification degree can be improved by the ultrasonic-assisted ionic liquid treatment.
Thermogravimetric experiments on experimental coal samples and imidazole-based ionic liquids prepared in example 1
Respectively weighing 5.0mg of an experimental coal sample, 5.0mg of an experimental coal sample treated by imidazole ionic liquid prepared under the existing water bath stirring condition and 5.0mg of an experimental coal sample treated by imidazole ionic liquid prepared under the ultrasonic auxiliary condition in example 1, adding the experimental coal sample into an alumina crucible, and heating the experimental coal sample from room temperature to 800 ℃ at a heating rate of 10 ℃/min in an air atmosphere, so as to analyze the self-ignition characteristic of the experimental coal sample, wherein the air flow in the experiment is 25 mL/min. Referring to fig. 7-9, according to the characteristics of the coal spontaneous combustion process, the characteristic temperature points of spontaneous combustion of the experimental coal sample obtained from the TG-DTG curve are: critical temperature point (T)1) Cracking temperature point (T)2) Ignition point (T)3) Maximum thermogravimetric peak temperature value (T)4) Burnout point (T)5). The TG-DTG curve was divided into the following 4 phases: RT to T1Temperature section: during the process, the water in the experimental coal sample is lost, and the quality is rapidly reduced; t is1～T2Stage (2): investigating the primary gases, e.g. CH, in coal samples4、CO2When the analysis occurs, the quality is slowly reduced; t is2～T3Stage (2): in the slow oxidation stage of the experimental coal sample, small molecules in the experimental coal sample gradually start to crack, part of active groups start to be separated, and the quality is reduced to a certain degree; t is3～T5Stage (2): the rapid oxidation stage of the experimental coal sample, namely the spontaneous combustion stage of the experimental coal sample, the active structure in the experimental coal sample rapidly reacts to release CO and CO2Waiting for the gas, the quality decreases rapidly. The heat characterization temperature points are shown in Table 2.
Table 2: TG-DTG characteristic temperature point of experimental coal sample and treated imidazole ionic liquid
Figure BDA0002687960010000072
The thermogravimetric experiment result shows that compared with the experimental coal sample, the experimental coal sample treated by the imidazole ionic liquid under the water bath stirring condition has the dry cracking temperature point (T)2) Ignition point (T)3) Point of maximum rate of thermal weight loss (T)4) And burnout point (T)5) Both increase, which increases the ignition point of the experimental coal sample from 401.1 ℃ to 427.6 ℃ and the maximum weight loss rate point from 461.2 ℃ to 495.5 ℃. Under the ultrasonic-assisted condition, the ignition point of the experimental coal sample treated by the imidazole ionic liquid is 433.1 ℃, the maximum weight loss rate point is 504.3 ℃, and the ignition point and the maximum weight loss rate point are both larger than those of the experimental coal sample treated by the imidazole ionic liquid under the water bath stirring condition. The above analysis shows that the imidazole ionic liquid prepared under the ultrasonic-assisted condition has a very good inhibition effect on spontaneous combustion of coal.
The ultrasonic reaction apparatus used for the ultrasonic reaction of the above-described embodiment and verification process was an ultrasonic cell disruptor, model number C43-1000, manufactured by shanghai allen electronics technologies ltd.
The raw coal of the experimental coal sample can be brown coal, anthracite, lean coal, coking coal, fat coal, coking coal, gas fat coal, gas coal, medium-caking coal, weak-caking coal, non-caking coal, long-flame coal and the like.

Claims (10)

1. A method for synthesizing imidazole ionic liquid with the assistance of ultrasonic waves is characterized by comprising the following steps:
adding 0.1-0.3 mol of 1-methylimidazole into a solvent for dissolving, adding 0.05-0.2 mol of 1, 4-dibromobutane, carrying out ultrasonic reaction for 1-4 h under the conditions that the ultrasonic frequency is 100-400W and the ultrasonic temperature is 30-80 ℃, carrying out rotary evaporation at the temperature of 60-80 ℃ to remove the solvent, cooling, washing, carrying out suction filtration, and drying to obtain the imidazole ionic liquid.
2. The method for synthesizing imidazole ionic liquids with the assistance of ultrasonic waves according to claim 1 is characterized by comprising the following steps:
adding 0.1-0.3 mol of 1-methylimidazole into a solvent for dissolving, adding 0.05-0.2 mol of 1, 4-dibromobutane, carrying out ultrasonic reaction for 2.5h under the conditions that the ultrasonic frequency is 200W and the ultrasonic temperature is 60 ℃, removing the solvent by rotary evaporation at 70 ℃, cooling, washing, carrying out suction filtration, and drying to obtain the imidazole ionic liquid.
3. The ultrasonic-assisted synthesis method of imidazole ionic liquids according to claim 1 or 2, characterized in that the solvent is ethanol.
4. The method for synthesizing imidazole ionic liquids with the assistance of ultrasonic waves as claimed in claim 3, wherein the washing solution used for washing and suction filtration is ethyl acetate.
5. The method for synthesizing imidazole ionic liquids assisted by ultrasonic waves according to claim 1 or 2, wherein the drying conditions are as follows: drying for 20-30 h at 40-50 ℃.
6. The imidazole ionic liquid prepared by the method for synthesizing imidazole ionic liquid assisted by ultrasonic waves according to claim 5.
7. The use of imidazole-based ionic liquids as claimed in claim 6 for inhibiting the spontaneous combustibility of coal.
8. The method for verifying the inhibition of the spontaneous combustibility of coal by the imidazole-based ionic liquid according to claim 7, is characterized by comprising the following steps: preparing 20 wt% imidazole ionic liquid solution, mixing 8-12 g coal sample with 80-120 ml imidazole ionic liquid solution, carrying out ultrasonic reaction for 2-3 hours at the ultrasonic frequency of 250-350W and the ultrasonic temperature of 70-90 ℃, washing the coal sample to be neutral, drying, and preparing the verified coal sample.
9. The method for verifying the inhibition of the spontaneous combustibility of coal by using the imidazole ionic liquids according to claim 8, wherein the washing liquid used for washing is distilled water.
10. The method for verifying the inhibition of the spontaneous combustibility of coal by the imidazole-based ionic liquid according to claim 9, wherein the drying conditions are as follows: drying the mixture for 40 to 50 hours at the temperature of 50 to 30 ℃.
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