Preparation and application of indicating color-changing adsorption heat storage composite material

Abstract

The invention discloses a color-changing indicating adsorption heat storage composite material and a preparation method thereof. The composite material comprises polypropylene acrylamide hydrogel, ionic liquid and a cobalt chloride color-changing indicating agent. The preparation process comprises the following steps: firstly, adding cobalt chloride into a polyacrylamide precursor; then gelatinizing at a certain temperature to synthesize the indicating discoloration polyacrylamide hydrogel; preparing an ionic liquid into an ionic liquid aqueous solution, and dipping the ionic liquid aqueous solution into the polyacrylamide hydrogel to prepare a final product. The product prepared by the invention has the performance of indicating discoloration, displays pink after absorbing water and is blue black after high-temperature desorption, plays a monitoring role, and avoids invalid work of an adsorption heat storage material. The material has high adsorption capacity and high heat storage density, and has important significance in the field of adsorption heat storage.

Description

Technical Field

[0001] The present invention relates to the field of energy storage composite materials, and more particularly to an indicator color-changing adsorption heat storage composite material and a preparation method thereof. Background Art

[0002] With the rapid development of science and technology, environmental problems have become increasingly prominent, and clean and renewable energy sources have been widely used. However, both wind energy and solar energy have the characteristics of discontinuity and instability. To solve this problem, heat energy storage is considered an effective method to adjust the time difference and space difference of energy supply and demand.

[0003] Adsorption heat storage has the advantages of high energy storage density, stable output temperature, strong short-term and long-term energy storage capabilities, etc., and has now begun to be widely studied and used. The characteristics of the adsorption heat storage system are closely related to the characteristics of the adsorption material. As is well known, metal halide inorganic hydrates, metal-organic framework materials, and porous materials have all been studied as adsorption heat storage materials. They spontaneously capture water vapor molecules in the air through physical or chemical adsorption to release heat, and store energy by releasing water vapor under heating conditions. The water vapor adsorption capacity determines the heat storage performance of the material. Therefore, it is very necessary to develop a high-performance adsorbent with high water absorption. Hydrogel is a typical hygroscopic material with hydrophilicity and a three-dimensional network, which can accommodate abundant water and is an ideal adsorption heat storage material. However, the slow hygroscopicity of hydrogel materials results in low efficiency of the materials in the adsorption heat storage system, and the colorless characteristic of hydrogel materials causes the hydrogel materials to be used for too long because it is difficult to be detected visually.

[0004] Therefore, to solve the problems of hydrogel materials in adsorption heat storage applications, the present invention provides an indicator color-changing adsorption heat storage composite material and a preparation method thereof, using a high water-absorbing acrylamide material as a water storage support, an ionic liquid material as a water-absorbing material, and cobalt chloride as a color-changing indicator material, which not only solves the problem of slow water absorption rate of hydrogel materials, but also provides a color-changing indicator adsorption heat storage material. Summary of the Invention

[0005] The primary object of the present invention is to provide an indicator color-changing adsorption heat storage composite material, which can be used in the field of heat storage.

[0006] Another object of the present invention is to provide a preparation method of the above-mentioned indicator color-changing adsorption heat storage composite material. The technical solution adopted by the composite material is specifically as follows:

[0007] (1) Synthesis of polyacrylamide hydrogel (PAM): Add acrylamide (AM) powder into deionized water, and then successively add N,N'-methylenebisacrylamide (BIS), N,N,N',N'-tetramethylethylenediamine (TMEDA, also known as tetramethylethylenediamine), cobalt chloride powder (CoCl2). Ultrasonic for more than 5 min until the solid is completely dissolved and the liquid is evenly mixed; Purge the mixed precursor solution with nitrogen for more than 10 min to remove dissolved oxygen, and then add ammonium persulfate (APS) powder to initiate polymerization. After mixing evenly, let the solution stand at a certain temperature to complete gelation;

[0008] (2) Synthesis of ionic liquid temperature - indicating hydrogel: Wash the PAM hydrogel obtained in (1) with deionized water to remove unreacted reactants to obtain a pure hydrogel; Then immerse the purified hydrogel in an ionic liquid aqueous solution overnight to load the ionic liquid to obtain the ionic liquid temperature - indicating hydrogel.

[0009] Furthermore, in step (1), the mass ratio of AM to BIS powder should be 100 - 70:1. The concentration of AM in deionized water is 0.2 - 0.25 g / mL.

[0010] Furthermore, in step (1), the concentration of TMEDA in deionized water is 0.01 - 0.05 mg / mL.

[0011] Furthermore, in step (1), the CoCl2 powder needs to be pretreated by grinding before use. After CoCl2 is added to the solution, the concentration of CoCl2 in deionized water is 0.0008 - 0.009 g / mL.

[0012] Furthermore, in step (1), the concentration of APS powder in deionized water is 0.025 - 0.041 g / mL.

[0013] Furthermore, in step (1), let the solution stand at a certain temperature to complete gelation, the temperature is 60 - 70 °C, the time is 4 - 5 h or more, and it is synthesized under a nitrogen atmosphere.

[0014] Furthermore, the ionic liquid described in step (2) includes but is not limited to one or more of 1,3 - dimethylimidazolium dimethylphosphate ([DMIM][DMP]), 1 - ethyl - 3 - methylimidazolium acetate ([EMIM][Ac]), 1 - ethyl - 3 - methylimidazolium diethylphosphate ([EMIM][DEP]), and 1 - ethyl - 3 - methylimidazolium ethyl sulfate ([EMIM][EtSO4]).

[0015] Further, for the preparation of the ionic liquid aqueous solution described in step (2), the ratio of the ionic liquid to water should be the ionic liquid: the maximum water absorption of the ionic liquid at 85% humidity.

[0016] The product prepared by the present invention has the property of indicating color change. It shows pink after water absorption and turns blue-black after desorption at high temperature, playing a monitoring role to avoid the ineffective operation of the adsorption heat storage material. The material has high adsorption capacity and high heat storage density, which is of great significance in the field of adsorption heat storage.

[0017] Compared with the existing technology, the beneficial effects of the present invention are as follows:

[0018] (1) The present invention uses ionic liquid as the adsorption heat storage material. On the premise of ensuring high adsorption capacity and high heat storage density, it can ensure the thermal cycle stability of the material and avoid precipitation and aggregation caused by the use of chemical adsorbents. It has good compatibility with hydrogel materials and has high and fast water vapor adsorption characteristics at high humidity, improving the problem of low adsorption rate of hydrogel materials.

[0019] (2) The present invention uses polyacrylamide hydrogel as the loading material, which has the characteristics of high porosity, excellent biocompatibility and reliable chemical stability. The existence of the hydrogel network enables the composite material to store water and prevent leakage after water absorption, avoiding the problems of large fluidity and easy leakage of ionic liquid and water during the heat storage process.

[0020] (3) Cobalt chloride in the indicator color-changing adsorption heat storage composite material of the present invention has the property of moisture-sensitive intelligent color change. Cobalt ions are introduced into the hydrogel through coordination bonds formed with the amide groups of the polymer chain. The color change caused by different numbers of hydrated water molecules can monitor the current working condition of the adsorption heat storage material and avoid the ineffective operation of the adsorption heat storage material.

[0021] (4) The indicator color-changing adsorption heat storage composite material prepared by the present invention is used as the adsorption heat storage material. Compared with the traditional adsorption heat storage material, it not only has a higher enthalpy value, but also the color indication effect improves the efficiency of the material in adsorption heat storage applications, having good prospects and application value. Brief Description of the Drawings

[0022] Attached Figure 1 is a physical picture of the indicator color-changing adsorption heat storage composite material before and after water absorption in Example 1 of the present invention. Attached Figure 2 is the adsorption kinetics of the indicator color-changing adsorption heat storage composite material in Example 1 of the present invention at 25°C and RH80%. Attached Figure 3 Adsorption rate curve of the indicator color-changing adsorption heat storage composite material in Example 1 of the present invention at 25°C and RH80%. Detailed Embodiments

[0023] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0024] CoCl2 needs to be pretreated by grinding before use to make it into CoCl2 powder;

[0025] Example 1

[0026] (1) Synthesis of polyacrylamide hydrogel (PAM): Weigh 2.4 g of acrylamide (AM) powder and add it to a small beaker containing 12 mL of deionized water. Then, successively add 24 mg of N,N'-methylenebisacrylamide (BIS), 12 μL of N,N-tetramethylethylenediamine (TMEDA), and 0.01 g of cobalt chloride powder (CoCl2). Each time a drug is added, it is ultrasonically treated for 8 min to completely dissolve the solid and evenly mix the liquid. Bubble the mixed precursor solution with nitrogen for 10 min to remove dissolved oxygen. Then, add 0.5 g of ammonium persulfate (APS) powder to the deoxygenated solution, mix evenly, seal it with a rubber stopper, and place the solution in a nitrogen atmosphere and let it stand in an oil bath at 60 °C for 5 h to complete gelation.

[0027] (2) Synthesis of ionic liquid indicator color-changing adsorption heat storage composite material: Select [EMIM][Ac] to prepare an ionic liquid aqueous solution, and the concentration of the ionic liquid is 39.4 wt%. Then, wash the PAM hydrogel obtained in (1) 5 times with deionized water to remove unreacted reactants to obtain a pure hydrogel. Then, immerse the pure hydrogel in an excess of ionic liquid aqueous solution for 10 h, and take out the hydrogel loaded with ionic liquid to obtain the ionic liquid indicator color-changing adsorption heat storage composite material.

[0028] (4) Product measurement: Use a thermostatic and humidity-controlled box and an electronic analytical balance to measure the leakage performance and water absorption performance of the ionic liquid indicator color-changing adsorption heat storage composite material; use a SUPERSCAN SSX-550 electron microscope (Japan) to observe the morphology of the final product, and the working pressure of the scanning electron microscope is 20 kV; use a constant comprehensive thermal analyzer to measure the desorption latent heat of the ionic liquid indicator color-changing adsorption heat storage composite material. All measurements are carried out in a nitrogen environment, and the heating or cooling rate is 5 °C / min. About 5 mg of the ionic liquid indicator color-changing adsorption heat storage composite material is placed in an open porcelain crucible and heated from room temperature 25 °C to 120 °C for 19 min, and the water vapor is completely desorbed and evaporated. Finally, after measurement, in an environment of 25 °C and RH80%, the composite material can adsorb 0.92 g / g of water vapor within 1200 min, the heat storage density is 2760 J / g, it has an indicator color-changing effect, and the liquid will not leak out of the hydrogel within 4 days.

[0029] Example 2

[0030] The process and conditions are the same as those in Example 1, except that the addition amount of CoCl2 powder in step (1) of Example 1 is changed to 0.1 g, and the rest are the same as those in Example 1, obtaining an ionic liquid indicator color-changing adsorption heat storage composite material. Finally, it is measured that in an environment of 25 °C and RH80%, 0.88 g / g of water vapor can be adsorbed within 1200 min, the heat storage density is 2440 J / g, it has an indicator color-changing effect, and the liquid will not leak out of the hydrogel within 4 days.

[0031] Example 3

[0032] The process and conditions are the same as those in Example 1, except that the addition amount of APS powder in step (1) of Example 1 is changed to 0.3 g, and the time for standing the solution in the oil bath is changed to 6 h, and the rest are the same as those in Example 1, obtaining an ionic liquid indicator color-changing adsorption heat storage composite material. Finally, it is measured that in an environment of 25 °C and RH80%, 0.90 g / g of water vapor can be adsorbed within 1200 min, the heat storage density is 2635 J / g, it has an indicator color-changing effect, and the liquid will not leak out of the hydrogel within 4 days.

Claims

1. A preparation method of an indicator color-changing adsorption heat storage composite material, characterized in that It includes the following steps: (1) Synthesize polyacrylamide hydrogel (PAM): Add acrylamide (AM), N,N'-methylenebisacrylamide (BIS), N,N,N',N'-tetramethylethylenediamine (TMEDA), and cobalt chloride powder (CoCl2) into water and dissolve them into a liquid to obtain a precursor solution; Bubble the mixed precursor solution with nitrogen for more than 10 minutes to remove dissolved oxygen, then add ammonium persulfate (APS) powder to initiate polymerization. After mixing evenly, let the solution stand in a nitrogen atmosphere at a certain temperature to complete gelation; The temperature is 60 - 70 °C (preferably 60 - 65 °C, more preferably 60 - 62 °C), and the time is 4 - 5 hours (preferably 4.5 - 5 hours, more preferably 4.75 - 5 hours); (2) Synthesize an ionic liquid indicator color-changing adsorption heat storage composite material: Wash the PAM hydrogel obtained in (1) with water to remove unreacted reactants to obtain a pure hydrogel; Then immerse the pure hydrogel in an excessive ionic liquid aqueous solution for 8 - 16 hours (preferably 12 - 16 hours, more preferably 12 - 14 hours), and take out the hydrogel after loading the ionic liquid to obtain the ionic liquid indicator color-changing adsorption heat storage composite material.

2. The preparation method according to claim 1, characterized in that: In the step (1), the mass ratio of AM to BIS should be 100 - 70:1, preferably 100 - 80:1, more preferably 100 - 90:1; The concentration of AM in deionized water is 0.2 - 0.25 g / mL, preferably 0.2 - 0.23 g / mL, more preferably 0.2 - 0.22 g / mL; In the step (1), the concentration of TMEDA in deionized water is 0.01 - 0.05 mg / mL, preferably 0.01 - 0.03 mg / mL, more preferably 0.01 - 0.02 mg / mL; In the step (1), after CoCl2 is added to the solution, the concentration of CoCl2 in deionized water is 0.0008 - 0.009 g / mL, preferably 0.0008 - 0.001 g / mL, more preferably 0.0008 - 0.0009 g / mL.

3. The preparation method according to claim 1, characterized in that: In the step (1), the concentration of APS powder in water is 0.025 - 0.042 g / mL, preferably 0.035 - 0.042 g / mL, more preferably 0.040 - 0.042 g / mL.

4. The preparation method according to claim 1, characterized in that: In the step (2), the ionic liquid includes but is not limited to one or more of 1,3-dimethylimidazolium dimethylphosphate ([DMIM][DMP]), 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]), 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]), and 1-ethyl-3-methylimidazolium ethyl sulfate ([EMIM][EtSO4]).

5. The preparation method according to claim 1 or 4, characterized in that: For the preparation of the ionic liquid aqueous solution in the step (2), the mass ratio of ionic liquid to water should be 1:5 - 1:6, preferably 1:5 - 1:1.

52.

6. The preparation method according to any one of claims 1-5, characterized in that: In the step (1), the specific process is as follows: synthesize polyacrylamide hydrogel (PAM): add acrylamide (AM) powder into deionized water, and then successively add N,N'-methylenebisacrylamide (BIS), N,N,N',N'-tetramethylethylenediamine (TMEDA), cobalt chloride powder (CoCl2), and ultrasonicate for more than 5 min until the solids are completely dissolved and the liquid is evenly mixed; bubble the mixed precursor solution with nitrogen for more than 10 min to remove dissolved oxygen, then add ammonium persulfate (APS) powder to initiate polymerization, and after mixing evenly, let the solution stand at a certain temperature to complete gelation.

7. An indicator color-changing adsorption heat storage composite material obtained by the preparation method according to any one of claims 1-6.

8. An application of the indicator color-changing adsorption heat storage composite material according to claim 7 as an adsorption heat storage material or a water absorption and dehumidification material.

9. The application according to claim 8, characterized in that: The composite material described above includes polyacrylamide hydrogel, ionic liquid, and cobalt chloride. The polyacrylamide hydrogel serves as a support, which can store water and prevent water leakage; the ionic liquid serves as an adsorption heat storage material, which can spontaneously absorb water vapor in the air and has high adsorption capacity and high heat storage density; cobalt chloride serves as an indicator color-changing material, which shows pink after the composite material absorbs water and turns blue-black after desorption at a high temperature of 60 - 80 °C, playing a monitoring role. The three are compounded and can be used in an adsorption heat storage system to avoid the ineffective operation of the adsorption heat storage material.

Images