CN108623823B - Composite ionic liquid and preparation method and application thereof - Google Patents
Composite ionic liquid and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a composite ionic liquid and a preparation method and application thereof, wherein the composite ionic liquid comprises the following components: 90-110 parts by mass of 1-butyl-3-methylimidazole chlorine salt, 5-15 parts by mass of bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt and 5-15 parts by mass of bis-1, 4-bis [1- (3-methylimidazole) ] butyl diperchlorate salt. Experiments show that: the composite ionic liquid can obviously reduce the dissolving temperature and the dissolving time of cellulose, improve the solubility of the cellulose, obviously reduce the degradation rate of the cellulose, has excellent dissolving performance on the cellulose, and can be used for dissolving the cellulose; in addition, the preparation process disclosed by the invention is economical and practical, simple in preparation process, low in cost, free of any organic solvent, environment-friendly and pollution-free, free of special equipment and harsh conditions, easy to realize industrial production and high in application value.
Description
Technical Field
The invention relates to an ionic liquid, a preparation method and application thereof, in particular to a composite ionic liquid, a preparation method and application thereof in cellulose dissolution.
Background
Cellulose is a polysaccharide which is widely distributed and has the largest content in the nature, accounts for more than 50 percent of the carbon content in the plant, and is one of the most abundant natural organic matters in the nature. The cellulose is mainly derived from plants, such as cotton, wood, cotton linter, wheat straw, reed, hemp, mulberry bark and the like, wherein the cellulose content of the cotton is close to 100 percent and is the natural purest cellulose source, and the cellulose accounts for 40 to 50 percent, 10 to 30 percent of hemicellulose and 20 to 30 percent of lignin in the common wood.
As a degradable green biomaterial, natural fiber gradually plays an increasingly important role due to its superior properties of light weight, degradability, low price, high modulus, high strength and the like. Due to the characteristics of self-aggregation structure, namely, a large number of hydrogen bonds exist in molecules and among molecules, and the cellulose has high crystallinity, the cellulose is difficult to dissolve in conventional solvents (such as water and most organic solvents) and further development and utilization of the cellulose are limited. Therefore, the cellulose is dissolved by developing an effective cellulose solvent to obtain a cellulose solution, so that the regeneration and the functionalization of the cellulose are realized, the method is an important way for effectively utilizing the cellulose, and great revolution is brought to the cellulose industry.
Several cellulose solvent systems have been developed including N, N-dimethylacetamide/lithium chloride (DMAc/LiCl), N-dimethylformamide/dinitrogen tetroxide (DMF/N2O4), N-methyl-N-oxomorpholine (NMMO), dimethyl sulfoxide/tetrabutylammonium fluoride (DMSO/TBAF) and molten salt hydrates (e.g., LiClO)4·3H2O、LiSCN·2H2O), but the solvent systems have the defects of strong toxicity, high cost, difficult recycling of the solvent, unstable use process and the like, and are not suitable for industrial production.
Under certain conditions, cellulose reacts with water, an oxygen bridge is broken during reaction, water molecules are added at the same time, and the cellulose is changed into short-chain molecules from long-chain molecules until the oxygen bridge is completely broken to become glucose. Therefore, there are many reports on the preparation of cellulose solution by hydrolysis, and the current hydrolysis method usually uses inorganic acid to hydrolyze cellulose, and the inorganic acid used is sulfuric acid, hydrochloric acid, phosphoric acid, etc., among which, sulfuric acid is most commonly used, and sulfuric acid and hydrochloric acid are used in certain proportion. However, the preparation of cellulose solution by inorganic acid hydrolysis has the disadvantages of large acid consumption, difficult treatment of waste liquid, large water consumption for washing products, serious pollution and high cost, and is not suitable for industrial production.
Therefore, the search for suitable solvents and the economic and environment-friendly dissolution processing of cellulose are always the goals pursued. The ionic liquid is a salt existing in a liquid state at room temperature or near room temperature, has the liquidity of the liquid and the chemical activity of the salt, and has a plurality of unique properties, such as designable structure, wide liquid range, vapor pressure close to zero, non-flammability, high thermal stability and chemical stability, and the like. At present, ionic liquid has made many advances in the aspects of separation process, catalysis, organic synthesis, electrochemistry and the like, and is considered to be a novel environment-friendly green medium with wide application prospect in green synthesis and clean production.
In recent years, ionic liquids have attracted considerable attention for the dissolution and processing of cellulose. The ionic liquid is used as a medium to prepare the regenerated cellulose material, has the advantages of environmental friendliness, short production period, convenient solvent recovery and the like, and is a novel method for processing cellulose with great potential. Chinese patents CN 200610078784.5, cn200680012598.x, CN200710085298.0, CN201310158819.6, etc. disclose methods for dissolving cellulose with ionic liquids, respectively, but the ionic liquids for dissolving cellulose in the above patents have not good dissolving performance for cellulose: the dissolving temperature is higher in the dissolving process, and is usually about 100 ℃ or even as high as 150 ℃; the dissolution time is long, and is usually 2-48 hours, even up to 72 hours; the solubility is low; in addition, cellulose is degraded to a certain degree in the dissolving process; severely limiting the industrial production thereof.
In order to improve the solubility of the ionic liquid to cellulose, two main ways are currently adopted:
one is to develop a new ionic liquid; chinese patent CN201210141931.4 discloses a hydroxyl-containing divalent imidazole type ionic liquid, which is used for dissolving prepared cellulose solution when the ionic liquid is used for dissolving cellulose, the mass percentage of the cellulose in the solution can reach 30%, and the cellulose degradation is very small in the dissolving process, but when the ionic liquid is used for dissolving the cellulose, the dissolving temperature is still high (90-170 ℃), the energy consumption is high, and the industrial production is not facilitated;
the other is that the solubility of the ionic liquid to the cellulose is improved by auxiliary means; the adopted means comprises ultrasonic oscillation, microwave heating, acid or alkali pretreatment and the like, for example, Chinese patent 201410404512.4 discloses a method for dissolving cellulose by ionic liquid, which comprises the steps of firstly pretreating natural wood fibers by using an alkali solution and an acid solution, then mixing the ionic liquid and the pretreated cellulose, adding the mixture into an emulsifying machine for shearing, and finally performing ultrasonic treatment for bubble removal to obtain a cellulose/ionic liquid homogeneous phase solution system; the method adopts auxiliary means such as alkali solution and acid solution pretreatment, shearing of an emulsifying machine, ultrasonic treatment and the like, so that cellulose is not degraded in the dissolving process, but the method has the disadvantages of complex process, more energy consumption and no contribution to industrial production.
In summary, although the ionic liquid as a green solvent shows a good development situation in cellulose dissolution, there are still many disadvantages, and therefore, there is a need to develop an ionic liquid having excellent solubility to cellulose to promote industrial application of the ionic liquid.
Disclosure of Invention
In view of the above problems in the prior art, the present invention aims to provide a composite ionic liquid, and a preparation method and applications thereof, so as to expand the variety and applications of ionic liquids.
In order to achieve the purpose, the invention adopts the following technical scheme:
a composite ionic liquid is prepared from the following components:
1-butyl-3-methylimidazolium chloride salt: 90-110 parts by mass;
bis 1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt: 5-15 parts by mass;
bis 1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride: 5-15 parts by mass;
mixing to obtain; wherein:
the chemical structural formula of the bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt is as follows:
the chemical structural formula of the bi-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride is as follows:
a method for preparing the composite ionic liquid comprises the following steps:
firstly, 1-butyl-3-methylimidazole chlorine salt, bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt and bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride perchlorate are uniformly mixed according to the proportion, and then the mixture is stirred and reacted for 5 to 15 hours at the temperature of 110 to 130 ℃.
Preferably, the preparation of the bis 1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt comprises the following steps: dropwise adding N-methylimidazole into 1, 4-dichlorobutane at the temperature of 65-85 ℃ under the protection of inert gas, and then carrying out reflux reaction for 12-72 hours.
More preferably, the molar ratio of 1, 4-dichlorobutane to N-methylimidazole is 1:1 to 1: 1.5.
As a further preferable mode, the inert gas is nitrogen or argon.
Preferably, the preparation of the bis 1, 4-bis [1- (3-methylimidazole) ] butyl diperchlor comprises the following steps:
firstly, dissolving the bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt and the lithium perchlorate in water, then stirring and reacting for 12-48 hours at the temperature of 75-85 ℃, then cooling to room temperature, and continuing stirring for 5-15 hours at room temperature.
In a further preferred embodiment, the molar ratio of the bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt to the lithium perchlorate is 1:1 to 1: 1.5.
The composite ionic liquid can be used for dissolving cellulose.
Preferably, the operation of dissolving cellulose by using the composite ionic liquid comprises the following steps: adding cellulose into a composite ionic liquid-water mixed solution with the mass fraction of 20-100 wt% (preferably 50-98 wt%), and stirring for 5-30 minutes (preferably 10-25 minutes) at 50-100 ℃ (preferably 50-80 ℃) to obtain a uniform and transparent solution.
The prepared cellulose ionic liquid solution can be used for preparing a cellulose finished product by subsequent spinning, wherein the concentration of the cellulose is preferably 5-30 wt% (preferably 10-25 wt%).
Compared with the prior art, the invention has the following remarkable beneficial effects:
the invention prepares a novel composite ionic liquid by compounding 1-butyl-3-methylimidazole chlorine salt, bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt and bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt, and experimental results show that: when the composite ionic liquid is used for dissolving cellulose, the dissolving temperature can be obviously reduced, the dissolving time can be shortened, the solubility of the cellulose can be improved, the degradation rate of the cellulose can be obviously reduced, the composite ionic liquid has excellent dissolving performance on the cellulose, can be used for preparing a fiber composite material by dissolving the cellulose, and the variety and the application range of the ionic liquid are enlarged; in addition, the preparation process is economical and practical, the preparation process is simple, the cost is low, any organic solvent is not required to be used, the environment is friendly, no pollution is caused, special equipment and harsh conditions are not required, the industrial production is easy to realize, and the application value is very high.
Detailed Description
The technical scheme of the invention is further detailed and completely explained by combining the embodiment, the application example and the comparative example.
Example 1
Preparation of mono-bis 1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt:
slowly dropping 1.2mol of N-methylimidazole into 1mol of 1, 4-dichlorobutane at the temperature of 80 ℃ under the protection of nitrogen, after the dropping is finished, refluxing for 72 hours to finish the reaction, cooling the reaction liquid to room temperature, washing the obtained product with diethyl ether to remove unreacted raw materials to obtain a white solid substance, namely the bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt (the HPLC purity is 98.8%, and the yield is 88%).
Preparation of di, di 1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride:
dissolving 1mol of bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride and 1.2mol of lithium perchlorate in 1L of water, stirring and reacting at 80 ℃ for 36 hours, cooling to room temperature, continuing stirring at room temperature for 12 hours, dispersing the reaction solution into chloroform with the same volume, separating, washing a chloroform phase with water until the water phase has no chloride ions, and concentrating the chloroform phase under reduced pressure to obtain a colorless transparent liquid, namely bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride (the HPLC purity is 98.9%, and the yield is 78%).
Thirdly, preparing the composite ionic liquid:
uniformly mixing 100g of 1-butyl-3-methylimidazole chlorine salt, 10g of bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt and 10g of bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt, stirring and reacting at 120 ℃ for 12 hours, finishing the reaction, and cooling to room temperature to obtain the composite ionic liquid.
Application example 1
Preparing a composite ionic liquid-water mixed solution with the mass fraction of 85 wt%, adding wood pulp fiber with the polymerization degree of 1050 into the prepared composite ionic liquid-water mixed solution, stirring and reacting for 30 minutes at 80 ℃, removing volatile impurities and bubbles in a cellulose solution by decompression in the process to obtain a uniform and transparent cellulose ionic liquid solution, and determining the yield of 99.1% after the cellulose in the solution is regenerated.
Comparative example 1.1
Dissolving 1-butyl-3-methylimidazolium chloride in deionized water to prepare 85 wt% of 1-butyl-3-methylimidazolium chloride-water mixed solution, then adding wood pulp fiber with the polymerization degree of 1050 into the 1-butyl-3-methylimidazolium chloride-water mixed solution, stirring and reacting for 5 hours at 120 ℃, decompressing in the process to remove volatile impurities and bubbles in the cellulose solution to obtain uniform and transparent cellulose ionic liquid solution, and determining the yield of 92.5% after the cellulose in the solution is regenerated.
Comparative example 1.2
Dissolving bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride in deionized water to prepare 85 wt% of a mixed solution of bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride and water, adding wood pulp fiber with the polymerization degree of 1050 into the mixed solution of bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride and water, stirring and reacting for 6 hours at 120 ℃, and removing volatile impurities and bubbles in the cellulose solution under reduced pressure in the process to obtain a uniform and transparent cellulose ionic liquid solution, wherein the yield is 92.3% after the cellulose in the solution is regenerated.
Comparative example 1.3
Dissolving the bis-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride in deionized water to obtain 85 wt% of a mixed solution of the bis-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride and water, adding wood pulp fiber with the polymerization degree of 1050 into the mixed solution of the bis-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride and water, stirring and reacting for 6 hours at 120 ℃, and removing volatile impurities and bubbles in the cellulose solution under reduced pressure in the process to obtain a uniform and transparent cellulose ion liquid solution, wherein the yield is 93% after the cellulose in the solution is regenerated.
Application example 2
Dissolving the prepared composite ionic liquid in deionized water to prepare a composite ionic liquid-water mixed solution with the mass fraction of 75 percent by weight, then adding cotton linters with the polymerization degree of 850 into the composite ionic liquid-water mixed solution, stirring and reacting for 25 minutes at 70 ℃, removing volatile impurities and air bubbles in a cellulose solution by decompression in the process to obtain a uniform and transparent cellulose ionic liquid solution, and determining the cellulose in the solution after regeneration, wherein the yield is 99.3 percent.
Comparative example 2.1
Dissolving 1-butyl-3-methylimidazolium chloride in deionized water to prepare 75 wt% of 1-butyl-3-methylimidazolium chloride-water mixed solution, adding cotton linters with the polymerization degree of 850 into the 1-butyl-3-methylimidazolium chloride-water mixed solution, stirring and reacting for 5 hours at 110 ℃, decompressing in the process to remove volatile impurities and bubbles in the cellulose solution to obtain uniform and transparent cellulose ionic liquid solution, and determining the cellulose in the solution after regeneration, wherein the yield is 94.5%.
Comparative example 2.2
Dissolving the bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride in deionized water to prepare 75 wt% of a bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride-water mixed solution, adding cotton linters with the polymerization degree of 850 into the bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride-water mixed solution, stirring and reacting for 5 hours at 110 ℃, removing volatile impurities and bubbles in a cellulose solution under reduced pressure in the process to obtain a uniform and transparent cellulose ionic liquid solution, and determining the yield of 95% after the cellulose in the solution is regenerated.
Comparative example 2.3
Dissolving the bi-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloronate in deionized water to prepare 75 wt% of the bi-1, 4-bis [1- (3-methylimidazole) ] butyl diperchloronate-water mixed solution, then adding cotton linters with the polymerization degree of 850 into the bi-1, 4-bis [1- (3-methylimidazole) ] butyl diperchloronate-water mixed solution, stirring and reacting for 5 hours at 110 ℃, and removing volatile impurities and bubbles in the cellulose solution under reduced pressure in the process to obtain a uniform and transparent cellulose ion liquid solution, wherein the yield is 94.6% after the cellulose in the solution is regenerated.
As can be seen from application examples 1 and 2 and comparative examples 1 and 2, when the composite ionic liquid provided by the invention is used for dissolving cellulose, the dissolving temperature and the dissolving time are both obviously reduced, and the cellulose degradation rate in the dissolving process is also obviously reduced.
Application example 3
Dissolving the prepared composite ionic liquid in deionized water to prepare a 70 wt% composite ionic liquid-water mixed solution, then adding the bamboo pulp with the polymerization degree of 585 into the composite ionic liquid-water mixed solution, stirring and reacting for 15 minutes at 50 ℃, and removing volatile impurities and air bubbles in the cellulose solution by decompression in the process to obtain a uniform and transparent cellulose ionic liquid solution, wherein the concentration of cellulose in the solution is 22 wt%.
Comparative example 3.1
Dissolving 1-butyl-3-methylimidazolium chloride in deionized water to prepare 70 wt% of 1-butyl-3-methylimidazolium chloride-water mixed solution, then adding the bamboo pulp with the polymerization degree of 585 into the 1-butyl-3-methylimidazolium chloride-water mixed solution, stirring and reacting for 2 hours at 100 ℃, and removing volatile impurities and bubbles in the cellulose solution by pressure reduction in the process to obtain uniform and transparent cellulose ionic liquid solution, wherein the concentration of cellulose in the solution is 11.5 wt%.
Comparative example 3.2
Dissolving bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride in deionized water to prepare 70 wt% of bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride-water mixed solution, then adding bamboo pulp with the polymerization degree of 585 into the bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride-water mixed solution, stirring and reacting for 2 hours at 100 ℃, and removing volatile impurities and bubbles in the cellulose solution under reduced pressure in the process to obtain the uniform and transparent cellulose ionic liquid solution, wherein the concentration of cellulose in the solution is 11.6 wt%.
Comparative example 3.3
Dissolving bis-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride in deionized water to prepare 70 wt% of bis-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride-water mixed solution, adding bamboo pulp with the polymerization degree of 585 into the bis-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride-water mixed solution, stirring and reacting for 2 hours at 100 ℃, and removing volatile impurities and bubbles in the cellulose solution by pressure reduction in the process to obtain uniform and transparent cellulose ion liquid solution, wherein the concentration of cellulose in the solution is 11.5 wt%.
Application example 4
Dissolving the prepared composite ionic liquid in deionized water to prepare a composite ionic liquid-water mixed solution with the weight of 60%, then adding the cotton pulp with the polymerization degree of 1080 into the composite ionic liquid-water mixed solution, stirring and reacting for 10 minutes at 80 ℃, and removing volatile impurities and bubbles in the cellulose solution by decompression in the process to obtain a uniform and transparent cellulose ionic liquid solution, wherein the concentration of cellulose in the solution is 20 wt%.
Comparative example 4.1
Dissolving 1-butyl-3-methylimidazolium chloride in deionized water to prepare 60 wt% of 1-butyl-3-methylimidazolium chloride-water mixed solution, then adding cotton pulp with the polymerization degree of 1080 into the 1-butyl-3-methylimidazolium chloride-water mixed solution, stirring and reacting for 3 hours at 130 ℃, and removing volatile impurities and bubbles in the cellulose solution by pressure reduction in the process to obtain uniform and transparent cellulose ionic liquid solution, wherein the concentration of cellulose in the solution is 7.0 wt%.
Comparative example 4.2
Dissolving bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride in deionized water to prepare 60 wt% of bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride-water mixed solution, then adding cotton pulp with the polymerization degree of 1080 into the bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride-water mixed solution, stirring and reacting for 3 hours at 130 ℃, and removing volatile impurities and bubbles in the cellulose solution under reduced pressure in the process to obtain the uniform and transparent cellulose ionic liquid solution, wherein the concentration of cellulose in the solution is 7.0 wt%.
Comparative example 4.3
Dissolving bis-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride in deionized water to prepare 60 wt% of bis-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride-water mixed solution, adding cotton pulp with the polymerization degree of 1080 into the bis-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride-water mixed solution, stirring and reacting for 3 hours at 130 ℃, and removing volatile impurities and bubbles in the cellulose solution by decompression in the process to obtain uniform and transparent cellulose ion liquid solution, wherein the concentration of cellulose in the solution is 7.1 wt%.
Application example 5
Adding cotton pulp with the polymerization degree of 1080 into pure composite ionic liquid (namely, no water is added into the composite ionic liquid), stirring and reacting for 15 minutes at 75 ℃, and decompressing in the process to remove volatile impurities and bubbles in the cellulose solution to obtain uniform and transparent cellulose ionic liquid solution, wherein the concentration of cellulose in the solution is 20.5 wt%.
Comparative example 5.1
Adding cotton pulp with the polymerization degree of 1080 into 1-butyl-3-methylimidazolium chloride, stirring and reacting for 3 hours at the temperature of 120 ℃, and decompressing in the process to remove volatile impurities and bubbles in the cellulose solution to obtain a uniform and transparent cellulose ionic liquid solution, wherein the concentration of cellulose in the solution is 7.5 wt%.
Comparative example 5.2
Adding cotton pulp with the polymerization degree of 1080 into bis (1, 4-bis (1- (3-methylimidazole)) butyl dichloride salt, stirring and reacting for 3 hours at the temperature of 120 ℃, and removing volatile impurities and bubbles in a cellulose solution by decompression in the process to obtain a uniform and transparent cellulose ionic liquid solution, wherein the concentration of cellulose in the solution is 7.6 wt%.
Comparative example 5.3
Adding cotton pulp with the polymerization degree of 1080 into the bi-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloronate, stirring and reacting for 3 hours at the temperature of 120 ℃, and decompressing in the process to remove volatile impurities and bubbles in the cellulose solution to obtain a uniform and transparent cellulose ionic liquid solution, wherein the concentration of the cellulose in the solution is 7.6 wt%.
As can be seen from application examples 3, 4 and 5 and comparative examples 3, 4 and 5, when the composite ionic liquid is used for dissolving cellulose, the dissolving temperature can be obviously reduced, the dissolving time can be shortened, the solubility of the cellulose in the dissolving process is obviously increased, and the degradation rate of the cellulose is obviously reduced.
The cellulose ionic liquid solution prepared by dissolving the cellulose in the application example can be used for a subsequent spinning process according to a conventional process to prepare a cellulose finished product; in addition, the composite ionic liquid in the application example can be recycled without special treatment, the composite ionic liquid can be recycled for more than 200 times, and the single loss is less than or equal to 0.5 percent.
In summary, the following steps: the invention prepares a novel composite ionic liquid by compounding 1-butyl-3-methylimidazole chlorine salt, bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt and bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt, when the obtained composite ionic liquid is used for dissolving cellulose, a uniform and transparent cellulose ionic liquid solution can be obtained under the conditions that the dissolving temperature is 50-100 ℃ and the dissolving time is 5-30 minutes without auxiliary means such as ultrasonic treatment, microwave heating, acid-base pretreatment and the like, the dissolving temperature can be obviously reduced, the dissolving time is shortened, the solubility is also obviously improved, and meanwhile, the degradation rate of the cellulose is greatly reduced in the dissolving process, therefore, the novel composite ionic liquid provided by the invention has excellent dissolving performance to the cellulose, the cellulose dissolving agent can be used for dissolving cellulose, and the applicable cellulose range is wide; in the process of dissolving cellulose, the ionic liquid does not need any organic solvent, has no vapor pressure and no volatile pollution, greatly reduces the volatilization loss of the solvent, and avoids the defects that the traditional solvent corrodes equipment and pollutes the environment; in addition, the preparation process is economical and practical, the preparation process is simple, the cost is low, any organic solvent is not required to be used, the environment is friendly, no pollution is caused, special equipment and harsh conditions are not required, the industrial production is easy to realize, the application value is extremely high, and compared with the prior art, the preparation method has the advantages of remarkable progress and unexpected effect.
Finally, it should be pointed out here that: the above is only a part of the preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention, and the insubstantial modifications and adaptations of the present invention by those skilled in the art based on the above description are intended to be covered by the present invention.
Claims (7)
1. The composite ionic liquid is characterized by comprising the following components:
90-110 parts by mass of 1-butyl-3-methylimidazole chloride salt;
5-15 parts by mass of bis (1, 4-bis [1- (3-methylimidazole) ] butyl dichloride;
5-15 parts by mass of bis (1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride);
mixing to obtain; wherein:
the chemical structural formula of the bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt is as follows:
the chemical structural formula of the bi-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride is as follows:
2. a process for preparing the composite ionic liquid of claim 1, characterized in that: firstly, 1-butyl-3-methylimidazole chlorine salt, bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt and bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride perchlorate are uniformly mixed according to the proportion, and then the mixture is stirred and reacted for 5 to 15 hours at the temperature of 110 to 130 ℃.
3. The method of claim 2, wherein the bis-1, 4-bis [1- (3-methylimidazole) ] butyldichloride salt is prepared by the steps of: dropwise adding N-methylimidazole into 1, 4-dichlorobutane at the temperature of 65-85 ℃ under the protection of inert gas, and then carrying out reflux reaction for 12-72 hours.
4. The method of claim 3, wherein: the molar ratio of the 1, 4-dichlorobutane to the N-methylimidazole is 1: 1-1: 1.5.
5. The method of claim 2, wherein the bis-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichlorate is prepared by the steps of:
firstly, dissolving the bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt and the lithium perchlorate in water, then stirring and reacting for 12-48 hours at the temperature of 75-85 ℃, then cooling to room temperature, and continuing stirring for 5-15 hours at room temperature.
6. The method of claim 5, wherein: the molar ratio of the bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt to the lithium perchlorate is 1: 1-1: 1.5.
7. The use of the composite ionic liquid of claim 1 in cellulose dissolution, wherein the operation of dissolving cellulose with the composite ionic liquid of claim 1 comprises the following steps: adding cellulose into a composite ionic liquid-water mixed solution with the mass fraction of 60-100 wt%, and stirring for 5-30 minutes at 50-100 ℃ to obtain a uniform and transparent solution.
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| "Effects of Water Concentration on the Structural and Diffusion Properties of Imidazolium-Based Ionic Liquid−Water Mixtures";Amir A. Niazi et al.;《J.Phys.Chem.B》;20130109;第117卷;第1378-1388页 * |
| "Theoretical Insights into the Role of Water in the Dissolution of Cellulose Using IL/Water Mixed Solvent Systems";Ramakrishnan Parthasarathi et al.;《J.Phys.Chem.B》;20150925;第119卷;第14339-14349页 * |
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