Preparation process of 1-butyl-3-methylimidazolium bromide

Abstract

The invention relates to the technical field of chemical synthesis, and provides a preparation process of 1-butyl-3-methylimidazolium bromide, which comprises the following steps: S1, placing N-methylimidazole and n-butyl bromide in a reaction kettle, introducing inert gas, adding a modified ferrite accelerant, stirring, and reacting for 2-3 hours; carrying out microwave-ultrasonic combined reaction to obtain a product for later use; s2, adding the product in the step S1 into a solvent, stirring, and standing to obtain a solid 1 and a liquid for later use; and S3, carrying out rotary evaporation on the liquid obtained in the step S2 to obtain a solid 2, combining the solid 2 and the solid 1 obtained in the step S2, washing with ethyl acetate, and drying to obtain the 1-butyl-3-methylimidazolium bromide. The preparation process of the 1-butyl-3-methylimidazolium bromide provided by the invention has the characteristics of high yield, high purity, high production rate and high stability, and has better commercial application value.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and in particular to a preparation process of 1-butyl-3-methylimidazolium bromide. Background Art

[0002] Ionic liquids are substances composed of ions that are liquid at room temperature or near room temperature. Compared with traditional solvents, ionic liquids have the advantages of being non-flammable, non-explosive, non-oxidizable, thermally stable, and environmentally friendly. They not only provide a new field for chemical research, but also provide a new approach to solving environmental pollution problems caused by modern industry. Therefore, ionic liquids have been widely used in separation processes, chemical reaction processes, drug development, electrochemistry, and other fields.

[0003] Imidazole ionic liquids are widely used in the extraction of flavonoids from natural products. Among them, 1-butyl-3-methylimidazolium bromide is the most widely used due to its simple synthesis and low cost. At the same time, 1-butyl-3-methylimidazolium bromide can also be used as an important intermediate for the synthesis of other ionic liquids. Therefore, the research on the production process of 1-butyl-3-methylimidazolium bromide has become increasingly important.

[0004] At present, the synthesis methods of 1-butyl-3-methylimidazolium bromide are mainly solvent reflux method and microwave-assisted synthesis method. The solvent reflux method is simple to operate, but takes a long time; while the microwave-assisted synthesis method has problems such as excessive reaction and poor temperature control during the synthesis process. Based on this, the existing preparation process of 1-butyl-3-methylimidazolium bromide has the problems of long time consumption, difficult to control reaction conditions, poor stability, and unsatisfactory yield and purity.

[0005] Patent CN 107698514A discloses a method for preparing 1-butyl-3-methylimidazolium bromide. The method for preparing 1-butyl-3-methylimidazolium bromide disclosed in the application is synthesized from bromobutyl and N-methylimidazole under heating and stirring conditions, and has the advantages of high yield and low production cost, but the reaction time takes about 1 hour, and there is still a disadvantage of being time-consuming.

[0006] Therefore, there is an urgent need in the market for a preparation process of 1-butyl-3-methylimidazolium bromide with high yield, high purity, fast production rate and high stability. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention selects a process for synthesizing 1-butyl-3-methylimidazolium bromide by microwave method as a basis, optimizes the microwave method into a microwave-ultrasound combined method, adds a modified ferrite promoter, and optimizes the synthesis steps and reaction conditions of the process, thereby solving the problems of long time consumption, poor stability, and unsatisfactory yield and purity in the existing preparation process of 1-butyl-3-methylimidazolium bromide.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] The present invention provides a process for preparing 1-butyl-3-methylimidazolium bromide, comprising the following steps:

[0010] S1, placing N-methylimidazole and n-butyl bromide in a reaction kettle, introducing an inert gas, adding a modified ferrite promoter, and subjecting the reaction to a microwave-ultrasound combined reaction to obtain a product for standby use;

[0011] S2, adding the product of step S1 into a solvent, stirring, and standing to obtain a solid 1 and a liquid for standby use;

[0012] S3, taking the liquid of step S2 and performing rotary evaporation to obtain solid 2, combining solid 2 and solid 1 of step S2, washing with ethyl acetate, and drying to obtain 1-butyl-3-methylimidazolium bromide.

[0013] In some embodiments of the present invention, the molar ratio of N-methylimidazole to n-butyl bromide in step S1 is 1:(1.05-1.2).

[0014] Preferably, the molar ratio of N-methylimidazole to n-butyl bromide in step S1 is 1:1.1.

[0015] In some embodiments of the present invention, the mass ratio of N-methylimidazole to modified ferrite promoter in step S1 is 1:(0.04-0.1).

[0016] Preferably, the mass ratio of N-methylimidazole to modified ferrite promoter in step S1 is 1:0.07.

[0017] In some embodiments of the present invention, the method for preparing the modified ferrite promoter in step S1 comprises the following steps:

[0018] (1) adding ammonium persulfate to concentrated sulfuric acid, stirring for 10-20 min, adding natural flake graphite in 3-5 portions, ultrasonicating for 20-40 min, standing, washing, and drying to obtain expanded graphite for later use;

[0019] (2) taking the expanded graphite of step (1), adding magnesium boride and DMF, stirring for 20-40 min, drying, adding boron oxide, heating to 1250-1350° C. in an inert atmosphere, introducing ammonia, reacting for 20-40 min, and obtaining modified expanded graphite for standby use;

[0020] (3) Take the modified expanded graphite of step (2), add deionized water, ultrasonicate for 1-2h, add barium nitrate, samarium nitrate and ferric nitrate, stir for 30-50min, add citric acid, stir for 2-3h, add ammonia water dropwise to adjust the pH to 6.5-7.5, dry, calcine and grind to obtain a modified ferrite promoter.

[0021] In some embodiments of the present invention, in step (2), the mass ratio of expanded graphite to boron oxide is 1:(0.4-0.8).

[0022] Preferably, in step (2), the mass ratio of expanded graphite to boron oxide is 1:0.6.

[0023] In some embodiments of the present invention, in step (3), the mass ratio of modified expanded graphite, barium nitrate, samarium nitrate and ferric nitrate is 1:(2-3):(0.3-0.4):(13-15).

[0024] Preferably, in step (3), the mass ratio of modified expanded graphite, barium nitrate, samarium nitrate and ferric nitrate is 1:2.5:0.34:14.

[0025] The present application adopts a microwave-ultrasound combined method to synthesize 1-butyl-3-methylimidazolium bromide. Furthermore, the applicant synthesizes a modified ferrite promoter based on ferrite to make 1-butyl-3-methylimidazolium bromide absorb microwaves better, thereby improving the yield and synthesis rate of 1-butyl-3-methylimidazolium bromide. Among many ferrite materials, barium ferrite, as a magnetic loss type absorbing material, has high coercivity, strong magnetic loss performance and good impedance matching, making it a good microwave absorption promoter. However, barium ferrite has a large density, a narrow absorption band and a low absorption intensity, which limits its development in the field of microwave absorption.

[0026] On the one hand, the applicant uses expanded graphite and barium ferrite for compounding. Expanded graphite has excellent electrical conductivity, large specific surface area, low density and good chemical stability, which can make up for the shortcomings of barium ferrite to a large extent. In addition, the loose and porous worm-like structure in the expanded graphite is conducive to the construction of a conductive network and multiple reflections and scattering of electromagnetic waves, which can play a role in synergistically promoting the absorption of microwaves. Furthermore, the applicant uses boron oxide as a boron source, ammonia as a nitrogen source and magnesium boride as a catalyst to synthesize modified expanded graphite. By controlling the in-situ growth of boron nitride between the layers of expanded graphite, CN covalent bonds are formed, and vertical heat transfer paths are constructed between the graphite layers, thereby improving the thermal conductivity of the expanded graphite, which is conducive to the synthesis of 1-butyl-3-methylimidazolium bromide. It plays an auxiliary heat dissipation role in the process, effectively avoiding the problem of decomposition of the product 1-butyl-3-methylimidazolium bromide due to excessive system temperature, thereby improving the yield and purity of 1-butyl-3-methylimidazolium bromide; on the other hand, the applicant uses samarium nitrate to form a rare earth metal samarium-doped barium ferrite structure, and the superexchange effect is increased by replacing barium ions with samarium ions, thereby increasing the conductivity of the modified ferrite promoter, improving the dielectric loss, and improving the microwave absorption capacity of the barium iron oxide; further, the doping of samarium element improves the melting point and stability of the modified ferrite promoter, and can play the role of a dispersant, making the barium ferrite more stable, stably and quickly promoting the synthesis of 1-butyl-3-methylimidazolium bromide, and improving its preparation yield.

[0027] In some embodiments of the present invention, in the microwave-ultrasound combined reaction in step S1, the reaction temperature is 55-65°C, the microwave power is 190-210W, and the ultrasound power is 90-110W.

[0028] Preferably, in the microwave-ultrasound combined reaction in step S1, the reaction temperature is 60° C., the microwave power is 200W, and the ultrasound power is 100W.

[0029] In some embodiments of the present invention, the time of the microwave-ultrasound combined reaction in step S1 is 160-190 s.

[0030] Preferably, the time of the microwave-ultrasound combined reaction in step S1 is 175 s.

[0031] The applicant selected microwave and ultrasonic combined reaction to synthesize 1-butyl-3-methylimidazolium bromide, and by controlling the power of microwave and ultrasonic waves, the two synergistically promoted the synthesis of 1-butyl-3-methylimidazolium bromide, thereby solving the problem of violent reaction but low yield of traditional microwave methods, and improving the yield and shortening the reaction time of the preparation process of 1-butyl-3-methylimidazolium bromide.

[0032] In some embodiments of the present invention, in step S2, the solvent is anhydrous ethanol.

[0033] The applicant selected anhydrous ethanol as the product separation solvent in step S2. 1-butyl-3-methylimidazolium bromide can be dissolved in anhydrous ethanol, while the prepared modified ferrite promoter cannot be dissolved in anhydrous ethanol, thus achieving the effect of successfully separating the modified ferrite promoter and improving the purity of 1-butyl-3-methylimidazolium bromide.

[0034] In some embodiments of the present invention, the yield of 1-butyl-3-methylimidazolium bromide prepared by the preparation process described in the above technical solution is not less than 99.8%, and the purity is not less than 99.5%.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The present invention provides a process for preparing 1-butyl-3-methylimidazolium bromide, which is based on a microwave process, optimizes the microwave process to a microwave-ultrasound combined process, adds a modified ferrite promoter, and optimizes the synthesis steps and reaction conditions of the process, so that the process for preparing 1-butyl-3-methylimidazolium bromide has the characteristics of high yield, high purity, fast production rate and high stability.

[0037] (2) The present invention synthesizes a modified ferrite promoter based on ferrite so that 1-butyl-3-methylimidazolium bromide can better absorb microwaves and achieve the effect of auxiliary heat dissipation, thereby improving the yield, purity and production rate of 1-butyl-3-methylimidazolium bromide.

[0038] (3) The present invention adopts a microwave-ultrasound combined method to prepare 1-butyl-3-methylimidazolium bromide. By controlling the reaction temperature and the power of microwave and ultrasound, the preparation process of 1-butyl-3-methylimidazolium bromide has the characteristics of high production rate and high yield.

[0039] (4) The yield of 1-butyl-3-methylimidazolium bromide obtained by the preparation process of the present invention is not less than 99.8%, and the purity is not less than 99.5%. DETAILED DESCRIPTION

[0040] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, but not to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0041] In the following examples, except for the modified ferrite promoter, the other compound monomers and related reagents used can be purchased from the market, among which natural flake graphite was purchased from Jiangxi Shuobang New Material Technology Co., Ltd.

[0042] Preparation Example 1

[0043] The synthesis method of modified ferrite promoter A comprises the following steps:

[0044] (1) 15 g of ammonium persulfate was added to 9 g of 98 wt% concentrated sulfuric acid, stirred for 15 min, 3 g of natural flake graphite was added in 4 portions, stirred until uniform after each addition, ultrasonicated for 30 min, allowed to stand for 24 h, washed with deionized water 3 times, and dried at 80° C. for 12 h to obtain expanded graphite for use;

[0045] (2) taking 1 g of the expanded graphite of step (1), adding 2.5 g of magnesium boride and 200 ml of DMF, stirring for 30 min, drying at 80 ° C for 12 h, adding 0.6 g of boron oxide, heating to 1300 ° C in an argon atmosphere, passing ammonia at 100 ml / min for 2 min, reacting for 30 min, and obtaining modified expanded graphite for standby use;

[0046] (3) Take 1 g of the modified expanded graphite of step (2), add 100 ml of deionized water, ultrasonicate for 1.5 h, add 2.5 g of barium nitrate, 0.34 g of samarium nitrate and 14 g of ferric nitrate, stir for 40 min, add 3 g of citric acid, stir for 2.5 h, add 25 wt % ammonia water to adjust the pH to 7.0, dry at 105 ° C for 12 h, calcine at 300 ° C for 4 h, grind for 2 min, and obtain modified ferrite promoter A.

[0047] Preparation Example 2

[0048] The specific implementation method of the modified ferrite promoter B is the same as that of the modified ferrite promoter A, except that in step (2), the mass of boron oxide is replaced by 0.3 g.

[0049] Preparation Example 3

[0050] The specific implementation manner of the modified ferrite promoter C is the same as that of the modified ferrite promoter A, except that in step (3), the mass of the modified expanded graphite is replaced with 0.8 g.

[0051] Preparation Example 4

[0052] The specific implementation method of modified ferrite promoter D is the same as that of modified ferrite promoter A, except that in step (3), the mass of samarium nitrate is replaced by 0.2 g.

[0053] Example 1

[0054] A preparation process of 1-butyl-3-methylimidazolium bromide comprises the following steps:

[0055] S1. Place 0.1 mol of N-methylimidazole and 0.11 mol of n-butyl bromide in a reaction kettle, introduce nitrogen, add 0.58 g of modified ferrite promoter A, and perform microwave-ultrasonic combined reaction at 60° C. for 175 s to obtain a product for standby use.

[0056] Among them, the power of microwave is 200W, and the power of ultrasound is 100W;

[0057] S2, adding the product of step S1 into 100 ml of anhydrous ethanol, stirring for 30 min, standing for 24 h, to obtain solid 1 and liquid for standby use;

[0058] S3. Take the liquid from step S2 and perform rotary evaporation to obtain solid 2. Combine solid 2 and solid 1 from step S2, wash with ethyl acetate three times, and dry at 60° C. for 12 h to obtain 1-butyl-3-methylimidazolium bromide.

[0059] Example 2

[0060] A preparation process of 1-butyl-3-methylimidazolium bromide comprises the following steps:

[0061] S1. 0.1 mol N-methylimidazole and 0.105 mol n-butyl bromide were placed in a reaction kettle, nitrogen was introduced, 0.33 g of modified ferrite promoter A was added, and microwave-ultrasound combined reaction was performed at 55° C. for 190 s to obtain a product for standby use.

[0062] Among them, the power of microwave is 190W, and the power of ultrasound is 90W;

[0063] S2, adding the product of step S1 into 100 ml of anhydrous ethanol, stirring for 30 min, standing for 24 h, to obtain solid 1 and liquid for standby use;

[0064] S3. Take the liquid from step S2 and perform rotary evaporation to obtain solid 2. Combine solid 2 and solid 1 from step S2, wash with ethyl acetate three times, and dry at 60° C. for 12 h to obtain 1-butyl-3-methylimidazolium bromide.

[0065] Example 3

[0066] A preparation process of 1-butyl-3-methylimidazolium bromide comprises the following steps:

[0067] S1. Place 0.1 mol N-methylimidazole and 0.12 mol n-butyl bromide in a reaction kettle, introduce nitrogen, add 0.82 g modified ferrite promoter A, and perform microwave-ultrasound combined reaction at 65° C. for 160 s to obtain a product for standby use.

[0068] Among them, the power of microwave is 210W, and the power of ultrasound is 110W;

[0069] S2, adding the product of step S1 into 100 ml of anhydrous ethanol, stirring for 30 min, standing for 24 h, to obtain solid 1 and liquid for standby use;

[0070] S3. Take the liquid from step S2 and perform rotary evaporation to obtain solid 2. Combine solid 2 and solid 1 from step S2, wash with ethyl acetate three times, and dry at 60° C. for 12 h to obtain 1-butyl-3-methylimidazolium bromide.

[0071] Example 4

[0072] This embodiment provides a preparation process of 1-butyl-3-methylimidazolium bromide. The specific implementation method is the same as that of Example 1, except that the mass of the modified ferrite promoter A in step S1 is 0.2 g.

[0073] Example 5

[0074] This embodiment provides a preparation process of 1-butyl-3-methylimidazolium bromide. The specific implementation method is the same as that of Example 1, except that the mass of the modified ferrite promoter A in step S1 is 1 g.

[0075] Example 6

[0076] This embodiment provides a preparation process of 1-butyl-3-methylimidazolium bromide. The specific implementation method is the same as that of Example 1, except that the microwave-ultrasound combined reaction in step S1 is replaced by microwave reaction.

[0077] The microwave reaction temperature, power and time are the same as those in Example 1.

[0078] Example 7

[0079] This embodiment provides a preparation process of 1-butyl-3-methylimidazolium bromide. The specific implementation method is the same as that of Example 1, except that the microwave-ultrasound combined reaction in step S1 is replaced by ultrasonic reaction.

[0080] The ultrasonic reaction temperature, power and time are the same as those in Example 1.

[0081] Example 8

[0082] This embodiment provides a preparation process of 1-butyl-3-methylimidazolium bromide. The specific implementation method is the same as that of Example 1, except that the modified ferrite promoter B replaces the modified ferrite promoter A in equal amounts.

[0083] Example 9

[0084] This embodiment provides a preparation process of 1-butyl-3-methylimidazolium bromide. The specific implementation method is the same as that of Example 1, except that the modified ferrite promoter C replaces the modified ferrite promoter A in equal amounts.

[0085] Example 10

[0086] This embodiment provides a preparation process of 1-butyl-3-methylimidazolium bromide. The specific implementation method is the same as that of Example 1, except that the modified ferrite promoter D replaces the modified ferrite promoter A in equal amounts.

[0087] Comparative Example 1

[0088] This comparative example provides a preparation process of 1-butyl-3-methylimidazolium bromide, and the specific implementation method is the same as that of Example 1, except that the modified ferrite promoter A is replaced by an equal amount of barium ferrite.

[0089] Performance Testing

[0090] The yield and purity of the 1-butyl-3-methylimidazolium bromide described in the above Examples 1-10 and Comparative Example 1 were tested, and the test results are shown in Table 1.

[0091] The yield of 1-butyl-3-methylimidazolium bromide is obtained by the yield calculation formula, that is, yield (%) = actual yield / theoretical yield × 100%;

[0092] The purity was measured by HPLC.

[0093] Table 1

[0094] Group Yield purity Example 1 99.92％ 99.76％ Example 2 99.90％ 99.74％ Example 3 99.87％ 99.71％ Example 4 97.32％ 96.32％ Example 5 97.34％ 96.28％ Example 6 97.20％ 99.53％ Example 7 97.15％ 99.50％ Example 8 95.21％ 94.51％ Example 9 95.23％ 94.53％ Example 10 95.12％ 94.25％ Comparative Example 1 94.35％ 93.59％

[0095] It can be seen from the data in Table 1 that the 1-butyl-3-methylimidazolium bromide in Examples 1-3 of the present invention has the characteristics of high yield and high purity as a whole. Among them, Example 4-5 changes the ratio between the modified ferrite promoter and N-methylimidazole in step S1, so that the microwave cannot be well absorbed during the synthesis of 1-butyl-3-methylimidazolium bromide, resulting in a decrease in the yield and purity of 1-butyl-3-methylimidazolium bromide; Example 6-7 uses a separate microwave reaction and ultrasonic reaction instead of a microwave-ultrasonic combined reaction, so that microwaves and ultrasound cannot synergistically promote the synthesis of 1-butyl-3-methylimidazolium bromide, resulting in 1-butyl-3-methylimidazolium bromide. The yield of 1-butyl-3-methylimidazolium bromide decreased, but had little effect on the purity; Examples 8-10 changed the amount of the main modifying substance added in the modified ferrite promoter, so that the microwave absorption intensity of the modified ferrite promoter was not effectively improved, thereby showing a decrease in the yield and purity of 1-butyl-3-methylimidazolium bromide; Comparative Example 1 is a conventional ferrite absorber barium ferrite replacing the modified ferrite promoter A in equal amounts, and the test found that the yield and purity of the prepared 1-butyl-3-methylimidazolium bromide both showed poor results.

[0096] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A process for preparing 1-butyl-3-methylimidazolium bromide, characterized in that: The following steps are involved: S1, placing N-methylimidazole and n-butyl bromide in a reaction kettle, introducing an inert gas, adding a modified ferrite promoter, and subjecting the reaction to a microwave-ultrasound combined reaction to obtain a product for standby use; S2, adding the product of step S1 into a solvent, stirring, and standing to obtain a solid 1 and a liquid for standby use; S3, taking the liquid of step S2 and performing rotary evaporation to obtain solid 2, combining solid 2 and solid 1 of step S2, washing with ethyl acetate, and drying to obtain 1-butyl-3-methylimidazolium bromide.

2. The process for preparing 1-butyl-3-methylimidazolium bromide according to claim 1, characterized in that: The molar ratio of N-methylimidazole to n-butyl bromide in step S1 is 1:(1.05-1.2).

3. The preparation process of 1-butyl-3-methylimidazolium bromide according to claim 1, characterized in that: The mass ratio of N-methylimidazole to modified ferrite promoter in step S1 is 1:(0.04-0.1).

4. The process for preparing 1-butyl-3-methylimidazolium bromide according to claim 1, characterized in that: The preparation method of the modified ferrite promoter in step S1 comprises the following steps: (1) adding ammonium persulfate to concentrated sulfuric acid, stirring for 10-20 min, adding natural flake graphite in 3-5 portions, ultrasonicating for 20-40 min, standing, washing, and drying to obtain expanded graphite for later use; (2) taking the expanded graphite of step (1), adding magnesium boride and DMF, stirring for 20-40 min, drying, adding boron oxide, heating to 1250-1350° C. in an inert atmosphere, introducing ammonia, reacting for 20-40 min, and obtaining modified expanded graphite for standby use; (3) Take the modified expanded graphite of step (2), add deionized water, ultrasonicate for 1-2h, add barium nitrate, samarium nitrate and ferric nitrate, stir for 30-50min, add citric acid, stir for 2-3h, add ammonia water dropwise to adjust the pH to 6.5-7.5, dry, calcine and grind to obtain a modified ferrite promoter.

5. The process for preparing 1-butyl-3-methylimidazolium bromide according to claim 4, characterized in that: In the step (2), the mass ratio of expanded graphite to boron oxide is 1:(0.4-0.8).

6. The process for preparing 1-butyl-3-methylimidazolium bromide according to claim 4, characterized in that: In the step (3), the mass ratio of modified expanded graphite, barium nitrate, samarium nitrate and ferric nitrate is 1:(2-3):(0.3-0.4):(13-15).

7. The process for preparing 1-butyl-3-methylimidazolium bromide according to claim 1, characterized in that: In the microwave-ultrasound combined reaction in step S1, the reaction temperature is 55-65° C., the microwave power is 190-210W, and the ultrasound power is 90-110W.

8. The process for preparing 1-butyl-3-methylimidazolium bromide according to claim 1, characterized in that: The time of the microwave-ultrasound combined reaction in step S1 is 160-190s.

9. The process for preparing 1-butyl-3-methylimidazolium bromide according to claim 1, characterized in that: In the step S2, the solvent is anhydrous ethanol.

10. The process for preparing 1-butyl-3-methylimidazolium bromide according to any one of claims 1 to 9, characterized in that: The yield of the prepared 1-butyl-3-methylimidazolium bromide is not less than 99.8%, and the purity is not less than 99.5%.