Supramolecular phase change material for long-term storage and controllable release of heat energy as well as preparation method and application of supramolecular phase change material

Abstract

The invention discloses a supramolecular phase change material for long-term storage and controllable release of heat energy as well as a preparation method and application of the supramolecular phase change material. Ethyl pillar [5] arene is subjected to vacuum activation, and the obtained activated supramolecular phase change material shows controllable heat energy release in a thermal cycle process; and the stored heat energy can be released only by heating again. In addition, heat absorbed in the melting process can be stored at room temperature for more than 180 days, so that long-term storage is realized. The phase change material has the characteristics of high latent heat energy density, controllable and switchable heat energy release, long heat storage time, heat stability and the like, and has great attraction in the field of heat energy. Meanwhile, the synthesis process is simple to operate and low in equipment requirement; higher latent heat and controllable heat energy release are realized; the heat energy storage time is long.

Description

Technical Field

[0001] The present invention relates to the technical field of phase change materials, and more particularly to a supramolecular phase change material for long-term storage and controllable release of thermal energy, and a preparation method and application thereof. Background Art

[0002] With the increasing demand for energy in human production and life, the development and utilization of environmentally friendly sustainable renewable energy such as solar energy, wind energy, geothermal energy, and tidal energy has become a research hotspot since the world energy crisis in the 1970s. However, the intermittent and unstable nature of renewable energy has restricted its use in some key areas. Therefore, the development of efficient, long-term and stable energy storage technologies is of great significance for the utilization of renewable energy. Thermal energy storage, as a promising energy storage technology to solve the contradiction between energy supply and demand, has been well explored. Among them, phase change materials are considered to be ideal thermal energy storage media because they absorb and release a large amount of latent heat during the phase change process. Different types of phase change materials, such as inorganic salts, organic polyols and aliphatics, can store heat within different operating temperature ranges.

[0003] Although these phase change materials can absorb large amounts of heat energy during heating, the absorbed heat energy is spontaneously released due to spontaneous cold crystallization when cooled. Therefore, a higher storage temperature is required to avoid spontaneous heat energy release, which greatly limits the universal applicability of thermal energy storage. In addition, long-term thermal energy storage can further extend the storage period, eliminate the intermittent problem of renewable energy technology, and enable thermal energy systems to operate stably regardless of weather conditions and transportation distances. However, even with the use of complex insulating materials, more than 30% of the latent heat stored in these phase change materials will gradually be lost to the environment within a few months (Energy Storage Mater. 46, 192-222). This uncontrollable heat energy release and short energy storage time are major obstacles to the utilization of traditional phase change materials for thermal storage. Chinese patent publication number CN104140786A discloses a composite phase change thermal storage material. This material uses a porous material with high thermal conductivity as a supporting skeleton, and a low-melting-point metal or a low-melting-point metal with added nanoparticles is distributed in the pores of the porous material. This composite phase change material is complex to prepare and its heat energy release is uncontrollable. Chinese patent publication number CN113416289A discloses a bio-based benzoxazine organic phase-change material. The preparation method involves subjecting a uniformly mixed reaction system containing a biomass phenolic compound, a biomass amine compound, and paraformaldehyde to a solvent-free Mannich reaction to produce the bio-based benzoxazine organic phase-change material. Similarly, the organic phase-change material releases uncontrollable heat energy.

[0004] Therefore, it is urgent to develop phase change materials with simple synthesis, long-term thermal energy storage and controllable release. Summary of the Invention

[0005] In view of the limitations of traditional phase change materials such as uncontrollable heat energy release and short energy storage time, the present invention provides a supramolecular phase change material for long-term storage and controllable release of heat energy, as well as its preparation method and application. Ethyl pillar[5]arene (EtP5) is vacuum activated to obtain an activated supramolecular phase change material (EtP5α), which realizes long-term storage and controllable release of heat energy. The excellent heat storage capacity enables EtP5α to be used at room temperature for more than 180 days without heat loss.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for preparing a supramolecular phase change material for long-term storage and controllable release of thermal energy, comprising the following steps: adding ethyl pillar[5]arene to a solvent, heating to boiling, and dropwise adding the solvent until all of the solvent is dissolved, storing the resulting solution at 273K for 12 hours, then filtering and collecting the precipitated crystals, and heating and activating the crystals in a vacuum environment to obtain the supramolecular phase change material;

[0008] The chemical structure of the supramolecular phase change material is shown below:

[0009]

[0010] Optionally, the phase change temperature of the supramolecular phase change material is 421K-434K, and the phase change latent heat is 86.5 J / g.

[0011] Optionally, the solvent is acetone.

[0012] Optionally, the temperature of the heating activation is 393K, and the time of the heating activation is 10 hours.

[0013] Optionally, the preparation method of the ethyl pillar [5] aromatic hydrocarbon is as follows: 1,4-diethoxybenzene is dissolved in a chloroform solution, paraformaldehyde is added, and the resulting suspension is stirred at 25°C for 20 minutes; then, boron trifluoride etherate is added to the solution, and the mixture is stirred at 25°C for 20 minutes, and water is added to terminate the reaction. The organic phase is separated and washed with a saturated NaHCO3 aqueous solution, and the crude product is purified by column chromatography to obtain the obtained product.

[0014] The present invention also discloses a supramolecular phase change material for long-term storage and controllable release of thermal energy obtained by the above-mentioned preparation method. The chemical structure of the supramolecular phase change material is shown in the following formula:

[0015]

[0016] The present invention also discloses the use of a supramolecular phase change material for long-term storage and controllable release of thermal energy prepared by the above-mentioned preparation method in thermal energy storage materials.

[0017] The implementation of the present invention will have the following beneficial effects:

[0018] The supramolecular phase change material (EtP5α) provided by the embodiments of the present invention exhibits controllable heat release during thermal cycling, and the stored heat energy can only be released by reheating. In addition, the heat absorbed during the melting process can be stored at room temperature for more than 180 days, enabling long-term storage. EtP5α phase change material has the characteristics of high latent heat energy density, controllable and switchable heat energy release, long heat storage time and thermal stability, making it extremely attractive in the field of thermal energy.

[0019] At the same time, the synthesis process of the present invention is simple to operate and has low equipment requirements; it has high latent heat and controllable heat energy release; and the heat energy storage time is long. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is an SEM image of the supramolecular phase change material prepared in Example 1 of the present invention.

[0021] Figure 2 This is the DSC curve of the supramolecular phase change material prepared in Example 1 of the present invention.

[0022] Figure 3 This is a POM image of the supramolecular phase change material prepared in Example 1 of the present invention.

[0023] Figure 4 This is the DSC curve of the supramolecular phase change material prepared in Example 1 of the present invention after storage for 180 days.

[0024] Figure 5 This is the thermal stability curve of the supramolecular phase change material prepared in Example 1 of the present invention.

[0025] Figure 6 This is the crystal structure of the supramolecular phase change material prepared in Example 1 of the present invention.

[0026] Figure 7 This is the NMR image of EtP5 prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to specific examples, but the present invention is not limited thereto in any way.

[0028] The present invention discloses a method for preparing a supramolecular phase change material for long-term storage and controllable release of thermal energy, comprising the following steps: adding ethyl pillar[5]arene to a solvent, heating to boiling, and adding the solvent dropwise until the solvent is completely dissolved; storing the resulting solution at 273K for 12 hours; then filtering and collecting the precipitated crystals; and heating and activating the crystals in a vacuum environment to obtain a supramolecular phase change material; the chemical structure of the supramolecular phase change material is shown below:

[0029]

[0030] In a specific embodiment, the phase change temperature of the supramolecular phase change material is 421K-434K and the phase change latent heat is 86.5 J / g.

[0031] In a specific embodiment, the preparation method of ethyl pillar[5]arene is as follows: 1,4-diethoxybenzene is dissolved in a chloroform solution, paraformaldehyde is added, and the resulting suspension is stirred at 25°C for 20 minutes; then, boron trifluoride etherate is added to the solution, and the mixture is stirred at 25°C for 20 minutes, and water is added to terminate the reaction. The organic phase is separated and washed with a saturated aqueous solution of NaHCO3. The crude product is purified by column chromatography to obtain the product.

[0032] In one embodiment, the solvent is acetone.

[0033] In a specific embodiment, the temperature of the heating activation is 393K, and the heating activation time is 10 hours.

[0034] The present invention also discloses a supramolecular phase change material for long-term storage and controllable release of thermal energy obtained by the above-mentioned preparation method. The chemical structure of the supramolecular phase change material is shown in the following formula:

[0035]

[0036] The present invention also discloses the use of a supramolecular phase change material for long-term storage and controllable release of thermal energy prepared by the above-mentioned preparation method in thermal energy storage materials.

[0037] The following are specific embodiments

[0038] Example 1

[0039] The method for preparing the supramolecular phase change material for long-term storage and controllable release of thermal energy of this embodiment comprises the following steps:

[0040] (1) Preparation of ethyl post[5]arene (EtP5): 1,4-diethoxybenzene (6.00 g, 36 mmol) was dissolved in 300 ml of chloroform solution and paraformaldehyde (1.08 g, 36 mmol) was added. The suspension was stirred at 25°C for 20 min to crush the larger paraformaldehyde particles. Then, boron trifluoride etherate (4.5 ml, 36 mmol) was added to the solution. After stirring at 25°C for 20 min, water was added to terminate the reaction. The organic phase was separated and washed with saturated aqueous NaHCO3 solution. The crude product was purified by column chromatography (dichloromethane / petroleum ether).

[0041] (2) Weigh 2 g of ethyl column [5] arene and place it in 20 mL of acetone. Heat to boiling, add acetone dropwise until it is completely dissolved, store the solution at 273 K overnight (more than 12 h), collect the precipitated crystals by filtration, and dry the obtained crystals in vacuum at 393 K for 10 h to obtain a white powder, denoted as EtP5α, with the chemical structure shown below. The crystal structure is as follows: Figure 6 As shown:

[0042]

[0043] The product characterization data prepared in this example are as follows: Figure 7 As shown:

[0044] EtP5, 1 HNMR (600MHz, CDCl3, 298K, ppm) δ6.74 (s, 10H), 3.85 (q, 20H), 3.76 (s, 10H), 1.27 (t, 30H).

[0045] Test Case

[0046] (1) The morphology was observed using a scanning electron microscope. Figure 1 As shown, the EtP5α phase change material is in a regularly dispersed block morphology.

[0047] (2) Differential Scanning Calorimetry (DSC) Measurements: The thermal properties of the EtP5α phase change material were measured using differential scanning calorimetry (DSC) using a TA-Discovery DSC25 instrument calibrated with indium and zinc standards. For the EtP5α phase change material, the sample was heated from 293 to 473 K under a nitrogen flow. The programmed rate for all heating and cooling processes was 10 K / min. The stored heat energy and the controllable exothermic temperature were determined based on the relevant peaks of the DSC curve.

[0048] Get EtP5 α The phase change characteristics of phase change materials are as follows: DSC curve Figure 2 As shown. During the melting process EtP5 αThe phase change material absorbs 86.5 J / g of heat energy and stores it well during cooling. α Phase change materials must be heated above 363 K to trigger EtP5 α Phase change materials cool and crystallize, releasing the stored latent heat. This heat storage performance is controllable, which makes EtP5 α Phase change materials have great potential in thermal energy storage applications.

[0049] (3) Polarizing microscope (POM) test

[0050] Direct observation of melting and crystallization behavior during heating and cooling cycles by optical microscopy, e.g. Figure 3 As shown in Figure 2, POM results show that the EtP5α phase-change material is in a solid phase at temperatures between 298K and 408K. When the temperature is above 413K, the EtP5α phase-change material begins to melt and gradually crystallizes into colorful block crystals. When the EtP5α phase-change material is heated to 435K, it completely melts. As the temperature decreases, the EtP5α phase-change material undergoes a glass transition to a transparent amorphous state without birefringence. When the EtP5α phase-change material after the glass transition is further heated to 353K, it gradually crystallizes into colored flake crystals.

[0051] (4) Long-term heat storage test

[0052] The EtP5α phase change material after the thermal cycle test was placed for 180 days and then subjected to a DSC test to investigate whether there was any latent heat loss.

[0053] The DSC data measured after 180 days of storage are as follows: Figure 4 As shown, it was observed that the EtP5α phase change material released 92.3% of the latent heat by induced cold crystallization in the temperature range of 350-370K, with low latent heat loss.

[0054] (5) Thermal stability test

[0055] The thermal stability of EtP5α was analyzed by TG. The TG curve of EtP5α showed that the weight loss was negligible (less than 2%) below 500K, indicating that it has good thermal stability.

[0056] The above-described embodiments merely represent several implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a supramolecular phase change material for long-term storage and controlled release of thermal energy, characterized in that: The following steps are involved: Ethyl pillar[5]arene is added to a solvent, heated to boiling, and the solvent is added dropwise until all of the solvent is dissolved, the obtained solution is stored at 273K for 12 hours, and then the precipitated crystals are collected by filtration, and the crystals are heated and activated in a vacuum environment to obtain the supramolecular phase change material; The chemical structure of the supramolecular phase change material is shown below:

2. The preparation method according to claim 1, characterized in that The phase change temperature of the supramolecular phase change material is 421K-434K, and the phase change latent heat is 86.5 J / g.

3. The preparation method according to claim 1, characterized in that The preparation method of the ethyl pillar [5] aromatic hydrocarbons comprises the following steps: Dissolve 1,4-diethoxybenzene in chloroform solution, add paraformaldehyde, and stir the resulting suspension at 25°C for 20 minutes; then, add boron trifluoride etherate to the solution, continue stirring at 25°C for 20 minutes, add water to terminate the reaction, separate the organic phase, and wash with saturated NaHCO3 aqueous solution. The crude product is purified by column chromatography to obtain the product.

4. The preparation method according to claim 1, characterized in that The solvent is acetone.

5. The preparation method according to claim 1, characterized in that The temperature of the heating activation is 393K, and the time of the heating activation is 10 hours.

6. A supramolecular phase change material for long-term storage and controlled release of thermal energy obtained by the preparation method according to any one of claims 1 to 5, characterized in that: The chemical structure of the supramolecular phase change material is shown below:

7. Use of the supramolecular phase change material for long-term storage and controllable release of thermal energy obtained by the preparation method according to any one of claims 1 to 5 in thermal energy storage materials.

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