Ionic liquid copolymer with temperature response in trioxymethylene aqueous solution and preparation method thereof

Abstract

The invention discloses a phosphate ionic liquid copolymer responding to temperature in a trioxymethylene aqueous solution and a preparation method of the phosphate ionic liquid copolymer. The preparation method comprises the following specific steps: regulating and controlling the mixing ratio of 1-alkenyl-3-alkyl imidazole dimethyl phosphate and N-isopropylacrylamide or acrylamide, controlling the reaction temperature at 60-100 DEG C, reacting for 10-48 hours, dialyzing in a dialysis bag, and drying in vacuum after dialyzing to obtain the temperature-responsive phosphate ionic liquid copolymer. The phosphate ionic liquid copolymer provided by the invention shows a reversible upper critical solution temperature in a trioxymethylene aqueous solution. The phosphate ionic liquid copolymer prepared by the method has a wide application prospect in the field of separation and stimuli-responsive materials.

Description

[Technical field]

[0001] The invention belongs to the field of separation and recovery of ionic copolymers and relates to a temperature-sensitive phosphate polyionic liquid copolymer and a preparation method thereof. [Background technology]

[0002] Ionic liquids have a certain application potential in the fields of separation and catalysis due to their designable structure, strong molecular recognition ability and low volatility, but their high synthesis cost and difficulty in recycling limit the promotion and application of ionic liquids. On the basis of retaining the specific functional groups of ionic liquids, ionic liquids are constructed into ionic liquid copolymers with temperature-sensitive properties, which is a low-cost and efficient recycling method.

[0003] CN 110028388 B discloses a method for separating tetrafluoropropanol and water azeotropes by extractive distillation using a hydrophilic ionic liquid (EMIMAc, EMIMCl, EMIMBr). The method comprises the following steps: the strong interaction between the ionic liquid and tetrafluoropropanol breaks the azeotrope formed by the tetrafluoropropanol and water, thereby achieving separation of the tetrafluoropropanol and water. However, the operating temperature of the ionic liquid recovery flash tank is 120 to 240° C., which is a relatively high recovery temperature. At this temperature, the ionic liquid begins to thermally decompose.

[0004] CN 108440493 B discloses an azeotropic system for separating trioxymethylene and water by extractive distillation using an ionic liquid as an extractant. Although the ionic liquid disclosed in the patent has good thermal stability and high-temperature long-cycle stability, it is difficult to reach 97% (mass fraction) when the ionic liquid extractant is recovered, and a small amount of water will remain.

[0005] Therefore, providing a low-temperature and efficient ionic liquid recovery method has become an urgent problem to be solved in the art. [Summary of the invention]

[0006] [Technical issues to be solved]

[0007] In order to solve the problems of high energy consumption and low separation efficiency in the recovery of ionic liquids, the present invention provides a recovery method for ionic liquids with low energy consumption and high recovery rate by constructing a temperature-sensitive ionic liquid copolymer.

[0008] [Technical solution]

[0009] The technical solution of the present invention is a method for preparing a phosphate ionic liquid copolymer that responds to temperature in a trioxymethylene aqueous solution, and the synthesis steps are:

[0010] (1) Synthesis of ionic liquid monomer 1-alkenyl-3-alkyl imidazole phosphate: 1-alkenyl imidazole and trialkyl phosphate are mixed at a molar ratio of 1:1 to 1.5, and reacted at 60 to 100° C. with magnetic stirring for 10 to 48 hours. After the reaction is completed, wash with ether or ethyl acetate 3 to 5 times to remove unreacted raw materials, and vacuum dry at 60 to 100° C. for 10 to 48 hours to obtain a light yellow oily liquid;

[0011] (2) Synthesis of thermosensitive phosphate ionic liquid copolymer: Before the reaction, nitrogen was purged for 30 to 90 minutes to remove dissolved oxygen in the alcohol solvent. RAFT polymerization was used, deoxygenated alcohol was used as solvent, AIBN was used as chain initiator, ((ethoxy)carbonyl)thio)acetic acid was used as chain transfer agent, ionic liquid monomer and N-isopropylacrylamide or acrylamide were added in proportion, the solution was sealed and placed at 60 to 80°C with continuous stirring for 10 to 48 hours. After the reaction, anhydrous alcohol was used as solvent and dialyzed in a dialysis bag with a molecular weight cutoff of 1000 for 48 hours. The anhydrous alcohol was replaced every 6 to 12 hours to remove impurities. After the dialysis, the ethanol was removed by rotary evaporation, and vacuum dried at 60 to 100°C for 10 to 48 hours to obtain a light yellow solid, which is a phosphate ionic liquid copolymer;

[0012] Preferably, the 1-vinyl imidazole in step (1) is one of 1-vinyl imidazole and 1-propylene imidazole;

[0013] Preferably, the trialkyl phosphate described in step (1) is one of trimethyl phosphate, triethyl phosphate and tributyl phosphate;

[0014] Preferably, the ionic liquid monomer and N-isopropylacrylamide or acrylamide described in step (2) are mixed in a molar ratio of 1:1 to 10;

[0015] Preferably, the anhydrous alcohol in step (2) is a solvent such as methanol, ethanol, propanol, isopropanol, or a mixed alcohol solvent;

[0016] Preferably, the number average molecular weight (Mn) of the phosphate ionic liquid copolymer in step (2) is 5000 <Mn<40000。

[0017] The phosphate ionic liquid copolymer synthesized according to the above method was dissolved in a trioxymethylene aqueous solution, and its temperature-sensitive properties were measured at different temperatures using a variable temperature ultraviolet spectrophotometer, such as Figure 1 shown.

[0018] Preferably, the concentration of trioxymethylene is in the range of 1% to 20% (mass fraction).

Brief Description of the Drawings

[0019] Figure 1 This is a diagram showing the temperature response of phosphate ionic liquid copolymers.

[0020] Figure 2 The temperature sensitivity of the copolymer synthesized with ionic liquid monomer: N-isopropylacrylamide = 1:3 in trioxymethylene aqueous solution.

[0021] Figure 3 The temperature sensitivity of the copolymer synthesized with ionic liquid monomer: N-isopropylacrylamide = 1:6 in trioxymethylene aqueous solution.

[0022] Figure 4 The temperature sensitivity of the copolymer synthesized with ionic liquid monomer: acrylamide = 1:2 in trioxymethylene aqueous solution.

[0023] Figure 5 The temperature sensitivity of the copolymer synthesized with ionic liquid monomer: acrylamide = 1:4 in trioxymethylene aqueous solution.

[0024] Figure 6 This is a SEM image of solid particles generated from phosphate ionic liquid copolymers at low temperature. [Specific implementation method]

[0025] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description in conjunction with the accompanying drawings and embodiments.

[0026] Example 1: Synthesis of thermosensitive phosphate ionic liquid copolymer: Before the reaction, nitrogen was purged for 35 minutes to remove dissolved oxygen in the alcohol solvent. RAFT polymerization was used, deoxygenated alcohol was used as solvent, AIBN was used as chain initiator, ((ethoxy)carbonyl)thio)acetic acid was used as chain transfer agent, ionic liquid monomer and N-isopropylacrylamide or acrylamide were added in proportion, the solution was sealed and placed at 60°C for continuous stirring for 15 hours, after the reaction was completed, anhydrous alcohol was used as solvent, and dialyzed in a dialysis bag with a molecular weight cutoff of 1000 for 48 hours, and the anhydrous alcohol was replaced every 7 hours to remove impurities. After the dialysis was completed, the ethanol was removed by rotary evaporation, and vacuum dried at 65°C for 20 hours to obtain a light yellow solid, which is a phosphate ionic liquid copolymer, such as Figure 2 shown.

[0027] Example 2: Synthesis of thermosensitive phosphate ionic liquid copolymer: Before the reaction, nitrogen was purged into the solution for 50 minutes to remove dissolved oxygen in the alcohol solvent. RAFT polymerization was used, deoxygenated alcohol was used as solvent, AIBN was used as chain initiator, ((ethoxy)carbonyl)thio)acetic acid was used as chain transfer agent, ionic liquid monomer and N-isopropylacrylamide or acrylamide were added in proportion, the solution was sealed and placed at 70°C for continuous stirring for 25 hours, after the reaction was completed, anhydrous alcohol was used as solvent, and dialyzed in a dialysis bag with a molecular weight cutoff of 1000 for 48 hours, and anhydrous alcohol was replaced every 9 hours to remove impurities. After the dialysis was completed, ethanol was removed by rotary evaporation, and vacuum dried at 75°C for 30 hours to obtain a light yellow solid, which was a phosphate ionic liquid copolymer, such as Figure 3 shown.

[0028] Example 3: Synthesis of thermosensitive phosphate ionic liquid copolymer: Before the reaction, nitrogen was purged for 65 minutes to remove dissolved oxygen in the alcohol solvent. RAFT polymerization was used, deoxygenated alcohol was used as solvent, AIBN was used as chain initiator, ((ethoxy)carbonyl)thio)acetic acid was used as chain transfer agent, ionic liquid monomer and N-isopropylacrylamide or acrylamide were added in proportion, the solution was sealed and placed at 75°C for continuous stirring for 35 hours, after the reaction was completed, anhydrous alcohol was used as solvent, and dialyzed in a dialysis bag with a molecular weight cutoff of 1000 for 48 hours, and anhydrous alcohol was replaced every 10 hours to remove impurities. After the dialysis was completed, the ethanol was removed by rotary evaporation, and vacuum dried at 85°C for 40 hours to obtain a light yellow solid, which was a phosphate ionic liquid copolymer, such as Figure 4 shown.

[0029] Example 4: Synthesis of thermosensitive phosphate ionic liquid copolymer: Before the reaction, nitrogen was purged for 80 minutes to remove dissolved oxygen in the alcohol solvent. RAFT polymerization was used, deoxygenated alcohol was used as solvent, AIBN was used as chain initiator, ((ethoxy)carbonyl)thio)acetic acid was used as chain transfer agent, ionic liquid monomer and N-isopropylacrylamide or acrylamide were added in proportion, the solution was sealed and placed at 80°C for continuous stirring for 45 hours, after the reaction was completed, anhydrous alcohol was used as solvent, and dialyzed in a dialysis bag with a molecular weight cutoff of 1000 for 48 hours, and the anhydrous alcohol was replaced every 12 hours to remove impurities. After the dialysis was completed, the ethanol was removed by rotary evaporation, and vacuum dried at 95°C for 45 hours to obtain a light yellow solid, which is a phosphate ionic liquid copolymer, such as Figure 5 shown.

Claims

1. A phosphate ionic liquid copolymer that responds to temperature in a trioxymethylene aqueous solution, characterized in that: The main chain structure of the ionic liquid polymer is shown below: Among them, R1 is CH3-, CH3CH2-, CH3(CH2)3-, and n:m is 1:1~10.

2. The temperature-responsive phosphate ionic liquid copolymer in trioxymethylene aqueous solution according to claim 1, characterized in that: The comonomers selected are ionic liquid and N-isopropylacrylamide or acrylamide; The cationic raw material of the ionic liquid comonomer is one of vinyl imidazole and acryl imidazole, and the anionic raw material is one of trimethyl phosphate, triethyl phosphate and tributyl phosphate.

3. The temperature-responsive phosphate ionic liquid copolymer in trioxymethylene aqueous solution according to claims 1 and 2, characterized in that: The ionic liquid monomer and N-isopropylacrylamide or acrylamide are mixed in a molar ratio of 1:1 to 10, the reaction temperature is 60°C to 80°C, and the reaction time is 10 to 48 hours to obtain a reaction intermediate product; The intermediate product is dissolved in a solvent such as methanol, ethanol, propanol, isopropanol or several mixed alcohol solvents, and dialyzed in a dialysis bag with a molecular weight cutoff of 1000 for 48 hours to obtain a reaction product. After the reaction product is vacuum dried to remove alcohols, the temperature-responsive phosphate ionic liquid copolymer is obtained.

4. The temperature-responsive phosphate ionic liquid copolymer in trioxymethylene aqueous solution according to claim 1, characterized in that: The number average molecular weight of phosphate ionic liquid copolymer (Mn) is 5000 <Mn <40000.

5. The temperature-responsive phosphate ionic liquid copolymer in trioxymethylene aqueous solution according to claim 1, characterized in that: The concentration range of trioxymethylene in the trioxymethylene aqueous solution is 1% to 20% (mass fraction).

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