Phase change heat storage material and preparation method thereof

Abstract

The invention provides a phase change heat storage material and a preparation method thereof, and belongs to the technical field of phase change materials, and the specific preparation method comprises the following steps: adding a titanate substance into a liquid paraffin phase change material to obtain a phase change mixed solution; adding an ethanol aqueous solution containing a catalyst for a titanium source into the pretreated boehmite to obtain a boehmite catalytic precursor solution; and uniformly mixing the boehmite catalytic precursor liquid and the phase change mixed liquid, adding the load carrier, heating, vacuumizing, preserving heat, pressurizing and vacuumizing repeatedly for 3-5 times to obtain the phase change heat storage material, and the pretreated boehmite is prepared by treating boehmite with oleic acid. The phase change heat storage material prepared by the invention has good heat storage performance and heat transfer capability, and can maintain relatively high phase change latent heat and heat-conducting property after being used for many times.

Description

Technical Field

[0001] The present invention belongs to the technical field of phase change materials, and in particular relates to a phase change heat storage material and a preparation method thereof. Background Art

[0002] Phase change thermal storage materials are special chemical materials that can store and release heat through their own phase change process. Ideal phase change thermal storage materials have large latent heat and high thermal conductivity. They can quickly absorb and release large amounts of heat during the phase change process, while maintaining a stable phase change process during melting.

[0003] Paraffin is an organic phase change material with high latent heat of phase change, strong chemical inertness, and a suitable phase change temperature. However, it has problems such as poor thermal conductivity and easy leakage, which makes the material transfer heat slowly when storing and releasing energy, and the heat storage efficiency is significantly reduced. In the existing technology, the heat transfer efficiency and easy leakage problem of paraffin-based phase change materials can be improved by combining paraffin with a porous matrix and adding high thermal conductivity materials. However, since the volume of paraffin before and after melting differs by nearly one-tenth, the large difference in volume change can cause the porous structure of the matrix to shrink and rupture, and the effective components are prone to aggregation and accumulation, making it difficult to evenly disperse, affecting the cyclic stability of the phase change process. After repeated use, the thermal conductivity and latent heat of phase change of paraffin-based phase change materials decrease significantly. Summary of the Invention

[0004] In order to solve the problems existing in the background technology, the present invention provides a phase change heat storage material and a preparation method thereof, which can effectively improve the leakage problem of paraffin-based phase change materials, and at the same time enable the paraffin-based phase change materials to have excellent cycle stability, and maintain a high thermal conductivity and phase change latent heat after multiple uses.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing a phase change heat storage material comprises the following steps:

[0007] S1. The paraffin is heated and melted to obtain a liquid organic phase change material, the titanate substance and the emulsifier are added to the liquid organic phase change material, mixed uniformly to obtain a phase change mixture;

[0008] S2. An ethanol aqueous solution containing a titanium source catalyst was added to the pretreated boehmite, stirred and soaked for 1-3h to obtain a boehmite catalytic precursor liquid, wherein the mass ratio of the pretreated boehmite, the titanium source catalyst, and the ethanol aqueous solution is 10:0.8-1.2:40-60;

[0009] S3. Add boehmite catalytic precursor liquid and the phase change mixed liquid of step S1 into the reactor, mix them evenly, add the load carrier, increase the temperature of the reactor to 75-85°C, evacuate the reactor to a negative pressure, keep it warm, increase the pressure of the reactor to a positive pressure, and then evacuate it to a negative pressure, repeat the operation 3-5 times, keep it warm for 1-3 hours, and under vacuum, reduce the temperature of the reactor to room temperature, discharge the material, and obtain a phase change heat storage material.

[0010] The pretreated boehmite is prepared by treating with oleic acid.

[0011] Furthermore, the preparation of the pretreated boehmite comprises the following steps:

[0012] Oleic acid and ethanol are added into a reactor in a mass ratio of 1:3-5, mixed evenly, and flake boehmite is added. The temperature is raised to 50-60° C., and an acidic solution is slowly added dropwise to adjust the pH to 2-4. The mixture is stirred for 2-4 hours, cooled to room temperature, filtered, washed with deionized water, and vacuum dried to obtain pretreated boehmite.

[0013] Furthermore, the titanate substance in step S1 is one or a mixture of two or more of tetrabutyl titanate, tetraethyl titanate and isopropyl titanate.

[0014] Furthermore, in step S1, the amount of titanate added is 4-6% of the mass of the organic phase change material.

[0015] Furthermore, in step S2, the catalyst for the titanium source is one of sulfuric acid and hydrochloric acid or a mixture of two or more.

[0016] Furthermore, in step S3, the mass ratio of the phase change mixed liquid to the boehmite catalytic precursor liquid is 10:0.5-1.

[0017] Furthermore, in step S3, the load carrier is expanded perlite.

[0018] Furthermore, in the preparation of the pretreated boehmite, the acidic solution is one or a mixture of two or more of sulfuric acid, hydrochloric acid and phosphoric acid.

[0019] Furthermore, in the preparation of the pretreated boehmite, the particle size of the lamellar boehmite is 0.15-0.5 microns.

[0020] This application has the following beneficial effects:

[0021] 1. The phase change heat storage material provided by the present invention has a simple preparation process, which overcomes the various shortcomings of the prior art, such as poor wall material strength, low thermal conductivity, packaging efficiency, and low phase change latent heat. The obtained phase change heat storage material has good heat storage performance and heat transfer capacity, and can maintain high phase change latent heat and thermal conductivity after repeated use.

[0022] 2. The present invention fills the titanium dioxide shell in the form of a liquid precursor together with melted liquid paraffin in the carrier pores, and then treats it with boehmite carrying a catalyst to solidify it in the pores to form a titanium dioxide shell structure, which can coat the paraffin. At the same time, boehmite is a flaky material and can seal the paraffin phase change material that is not completely coated. A strong structural system is established by the titanium dioxide shell and boehmite to achieve comprehensive wrapping of the paraffin phase change material, avoid structural defects such as pore wall collapse caused by volume changes during the phase change process, effectively prevent liquid leakage, and at the same time, the wrapping of the paraffin phase change material by the titanium dioxide shell plays a role in enhancing heat transfer. The phase change material finally obtained can maintain a high phase change latent heat and thermal conductivity.

[0023] 3. Pre-treatment of boehmite can form a functional base film on the surface of boehmite, forming effective adsorption sites, so that it has good adhesion to the liquid paraffin phase change material, inducing the titanium source precursor in the liquid paraffin to solidify into a coating shell, which helps to form a multi-layer all-round coating structure, enhance the stability of the coating structure, and significantly improve the phase change latent heat retention rate of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 , a comparative trend diagram of the internal thermal conductivity and phase change latent heat of the phase change heat storage materials prepared in Examples 1-5 of the present invention and Comparative Examples 1-3 before 100 melting cycles;

[0025] Figure 2 , a comparative trend diagram of the internal thermal conductivity and phase change latent heat retention rate of the phase change heat storage materials prepared in Examples 1-5 of the present invention and Comparative Examples 1-3 after 100 melting cycles. DETAILED DESCRIPTION

[0026] The present application is further described in detail below with reference to the embodiments.

[0027] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0028] Example 1

[0029] A phase change heat storage material is prepared by the following steps:

[0030] S1. Paraffin wax (paraffin wax from Rubitherm, Germany, with a phase change temperature of 34°C) was heated to 55°C to melt to obtain a liquid organic phase change material. Tetrabutyl titanate and Tween 80 were added to the liquid organic phase change material and mixed to obtain a phase change mixture, wherein the amounts of tetrabutyl titanate and Tween 80 added were 5% and 2% by mass of the organic phase change material, respectively.

[0031] S2. To the pretreated boehmite was added a 0.5 mol / L aqueous ethanol solution of sulfuric acid containing a titanium source catalyst, wherein the ethanol aqueous solution was 80% by mass, stirred and soaked for 2h to obtain a boehmite catalytic precursor liquid, wherein the mass ratio of the pretreated boehmite, titanium source catalyst, and ethanol aqueous solution was 10:1:50;

[0032] S3. Add boehmite catalytic precursor liquid and the phase change mixed liquid of step S1 into the reactor, the mass ratio of the phase change mixed liquid to the boehmite catalytic precursor liquid is 10:0.8, mix them evenly, add expanded perlite, the mass ratio of expanded perlite to the phase change mixed liquid is 1:1, raise the temperature of the reactor to 80°C, evacuate the reactor to a pressure of -0.1MPa, keep warm, raise the pressure of the reactor to 0.2MPa, then evacuate to -0.1MPa, repeat the operation 4 times, keep warm for 2h, lower the temperature of the reactor to room temperature under vacuum, discharge the material, and obtain a phase change heat storage material.

[0033] The preparation of the pretreated boehmite comprises the following steps:

[0034] Oleic acid and ethanol were added to a reactor in a mass ratio of 1:4, and mixed evenly to obtain a treatment liquid. Lamellar boehmite with a particle size of 0.15-0.5 microns was added, and the amount of the lamellar boehmite added was 10% of the mass of the treatment liquid. The temperature was raised to 55° C., and hydrochloric acid was slowly added dropwise to adjust the pH to 3. The mixture was stirred and reacted for 3 hours. The mixture was cooled to room temperature, filtered, washed with deionized water, and vacuum dried to obtain pretreated boehmite.

[0035] Example 2

[0036] A phase change heat storage material is prepared by the following steps:

[0037] S1. Paraffin wax (paraffin wax from Rubitherm, Germany, with a phase change temperature of 34°C) was heated to 50°C to melt to obtain a liquid organic phase change material. Tetraethyl titanate and Tween 80 were added to the liquid organic phase change material and mixed thoroughly to obtain a phase change mixture, wherein the amounts of tetraethyl titanate and Tween 80 added were 4% and 2% by mass of the organic phase change material, respectively.

[0038] S2. To the pretreated boehmite was added an ethanol aqueous solution containing 1 mol / L hydrochloric acid, wherein the ethanol aqueous solution was 80% by mass, stirred and soaked for 1h to obtain a boehmite catalytic precursor liquid, wherein the mass ratio of the pretreated boehmite, the titanium source catalyst, and the ethanol aqueous solution was 10:0.8:40;

[0039] S3. Add boehmite catalytic precursor liquid and the phase change mixed liquid of step S1 into the reactor, the mass ratio of the phase change mixed liquid to the boehmite catalytic precursor liquid is 10:0.5, mix them evenly, add expanded perlite, the mass ratio of expanded perlite to the phase change mixed liquid is 1:1, raise the temperature of the reactor to 75°C, evacuate the reactor to a pressure of -0.1MPa, keep warm, raise the pressure of the reactor to 0.2MPa, then evacuate to -0.1MPa, repeat the operation 3 times, keep warm for 1h, lower the temperature of the reactor to room temperature under vacuum, discharge the material, and obtain a phase change heat storage material.

[0040] The preparation of the pretreated boehmite comprises the following steps:

[0041] Oleic acid and ethanol were added to a reactor in a mass ratio of 1:3, and mixed evenly to obtain a treatment liquid. Lamellar boehmite with a particle size of 0.15-0.5 microns was added, and the amount of the lamellar boehmite added was 10% of the mass of the treatment liquid. The temperature was raised to 50° C., and an acidic solution was slowly added dropwise to adjust the pH to 2. The mixture was stirred for reaction for 2 hours, cooled to room temperature, filtered, washed with deionized water, and vacuum dried to obtain pretreated boehmite.

[0042] Example 3

[0043] A phase change heat storage material is prepared by the following steps:

[0044] S1. Paraffin wax (paraffin wax is a phase change paraffin wax from Rubitherm, Germany, with a phase change temperature of 34°C) is heated to 60°C to melt to obtain a liquid organic phase change material. Titanate-based substances, isopropyl titanate and Tween 80, are added to the liquid organic phase change material and mixed to obtain a phase change mixture, wherein the amounts of isopropyl titanate and Tween 80 added are 6% and 2% by mass of the organic phase change material, respectively.

[0045] S2. To the pretreated boehmite was added an ethanol solution containing 0.5 mol / L sulfuric acid, wherein the ethanol aqueous solution was 80% by mass, stirred and soaked for 3h to obtain a boehmite catalytic precursor solution, wherein the mass ratio of the pretreated boehmite, titanium source catalyst, and ethanol aqueous solution was 10:1.2:60;

[0046] S3. Add boehmite catalytic precursor liquid and the phase change mixed liquid of step S1 into the reactor, the mass ratio of the phase change mixed liquid to the boehmite catalytic precursor liquid is 10:1, mix them evenly, add expanded perlite, the mass ratio of expanded perlite to the phase change mixed liquid is 1:1, raise the temperature of the reactor to 85°C, evacuate the reactor to a pressure of -0.1MPa, keep warm, raise the pressure of the reactor to 0.2MPa, then evacuate to -0.1MPa, repeat the operation 5 times, keep warm for 3h, lower the temperature of the reactor to room temperature under vacuum, discharge the material, and obtain a phase change heat storage material.

[0047] The preparation of the pretreated boehmite comprises the following steps:

[0048] Oleic acid and ethanol were added to a reactor in a mass ratio of 1:5, and mixed evenly to obtain a treatment liquid. Lamellar boehmite with a particle size of 0.15-0.5 microns was added, and the amount of the lamellar boehmite added was 10% of the mass of the treatment liquid. The temperature was raised to 60° C., and an acidic solution was slowly added dropwise to adjust the pH to 4. The mixture was stirred and reacted for 4 hours. The mixture was cooled to room temperature, filtered, washed with deionized water, and vacuum dried to obtain pretreated boehmite.

[0049] Example 4

[0050] A phase change heat storage material is prepared by the following steps:

[0051] S1. Paraffin wax (paraffin wax from Rubitherm, Germany, with a phase change temperature of 34°C) was heated to 50°C to melt to obtain a liquid organic phase change material. Tetrabutyl titanate and Tween 80 were added to the liquid organic phase change material and mixed thoroughly to obtain a phase change mixture, wherein the amounts of tetrabutyl titanate and Tween 80 added were 6% and 2% by mass of the organic phase change material, respectively.

[0052] S2. To the pretreated boehmite was added an ethanol aqueous solution containing 1 mol / L hydrochloric acid, wherein the ethanol aqueous solution was 80% by mass, stirred and soaked for 3h to obtain a boehmite catalytic precursor liquid, wherein the mass ratio of the pretreated boehmite, titanium source catalyst, and ethanol aqueous solution was 10:0.8:60;

[0053] S3. Add boehmite catalytic precursor liquid and the phase change mixed liquid of step S1 into the reactor, the mass ratio of the phase change mixed liquid to the boehmite catalytic precursor liquid is 10:0.5, mix them evenly, add expanded perlite, the mass ratio of expanded perlite to the phase change mixed liquid is 1:1, raise the temperature of the reactor to 85°C, evacuate the reactor to a pressure of -0.1MPa, keep warm, raise the pressure of the reactor to 0.2MPa, then evacuate to -0.1MPa, repeat the operation 3 times, keep warm for 3h, lower the temperature of the reactor to room temperature under vacuum, discharge the material, and obtain a phase change heat storage material.

[0054] The preparation of the pretreated boehmite comprises the following steps:

[0055] Oleic acid and ethanol were added to a reactor in a mass ratio of 1:3, and mixed evenly to obtain a treatment liquid. Lamellar boehmite with a particle size of 0.15-0.5 microns was added, and the amount of the lamellar boehmite added was 10% of the mass of the treatment liquid. The temperature was raised to 60° C., and an acidic solution was slowly added dropwise to adjust the pH to 4. The mixture was stirred for reaction for 2 hours, cooled to room temperature, filtered, washed with deionized water, and vacuum dried to obtain pretreated boehmite.

[0056] Example 5

[0057] A phase change heat storage material is prepared by the following steps:

[0058] S1. Paraffin wax (paraffin wax from Rubitherm, Germany, with a phase change temperature of 34°C) was heated to 60°C to melt to obtain a liquid organic phase change material. Tetraethyl titanate and Tween 80 were added to the liquid organic phase change material and mixed thoroughly to obtain a phase change mixture, wherein the amounts of tetraethyl titanate and Tween 80 added were 4% and 2% by mass of the organic phase change material, respectively.

[0059] S2. To the pretreated boehmite was added an ethanol solution containing 0.5 mol / L sulfuric acid, wherein the ethanol aqueous solution was 80% by mass, stirred and soaked for 1 h to obtain a boehmite catalytic precursor solution, wherein the mass ratio of the pretreated boehmite, titanium source catalyst, and ethanol aqueous solution was 10:1.2:40;

[0060] S3. Add boehmite catalytic precursor liquid and the phase change mixed liquid of step S1 into the reactor, the mass ratio of the phase change mixed liquid to the boehmite catalytic precursor liquid is 10:1, mix them evenly, add expanded perlite, the mass ratio of expanded perlite to the phase change mixed liquid is 1:1, raise the temperature of the reactor to 75°C, evacuate the reactor to a pressure of -0.1MPa, keep warm, raise the pressure of the reactor to 0.2MPa, then evacuate to -0.1MPa, repeat the operation 5 times, keep warm for 1h, lower the temperature of the reactor to room temperature under vacuum, discharge the material, and obtain a phase change heat storage material.

[0061] The preparation of the pretreated boehmite comprises the following steps:

[0062] Oleic acid and ethanol were added to a reactor in a mass ratio of 1:5, and mixed evenly to obtain a treatment liquid. Lamellar boehmite with a particle size of 0.15-0.5 microns was added, and the amount of the lamellar boehmite added was 10% of the mass of the treatment liquid. The temperature was raised to 50° C., and an acidic solution was slowly added dropwise to adjust the pH to 2. The mixture was stirred and reacted for 4 hours. The mixture was cooled to room temperature, filtered, washed with deionized water, and vacuum dried to obtain pretreated boehmite.

[0063] Comparative Example 1

[0064] The only difference of this comparative example 1 is that in step S1, tetrabutyl titanate is replaced with titanium dioxide. The specific contents are as follows:

[0065] S1. Paraffin is heated to 55°C to melt to obtain a liquid organic phase change material, titanium dioxide and Tween 80 are added to the liquid organic phase change material, and mixed to obtain a phase change mixture;

[0066] Comparative Example 2

[0067] The only difference of this comparative example is that the boehmite is not pretreated, that is, the pretreated boehmite in step S2 is replaced by ordinary lamellar boehmite.

[0068] Comparative Example 3

[0069] The only difference of this comparative example is that tetrabutyl titanate is replaced by titanium dioxide, and the boehmite is not pretreated.

[0070] Proven effectiveness

[0071] The thermal conductivity of the phase change thermal storage material carrier was tested in accordance with the standard GB / T10297-2015. The phase change latent heat of the phase change thermal storage material was tested using a differential calorimeter scanner model DSC-300C produced by Shanghai Jiezhun Instrument Co., Ltd. The phase change thermal storage material to be tested was subjected to 100 cycles of endothermic melting and exothermic crystallization. The residence time after each endothermic and exothermic cycle was 3 hours. The internal thermal conductivity and phase change latent heat retention of the phase change thermal storage material before and after the melting cycle were tested. The test results are shown in Table 1 and the attached Figure 1 As shown:

[0072] Table 1

[0073]

[0074] Result Analysis

[0075] Analyze Examples 1-5 and Comparative Examples 1-3, and combine the data in Table 1 and Figure 1-2 It can be seen that the phase change heat storage material prepared in the present invention has good heat storage performance (phase change latent heat of more than 114.6 J / g) and heat transfer capacity (thermal conductivity of more than 0.41 W / (m·K)). After 100 melting cycles, it can still maintain a relatively high phase change latent heat and thermal conductivity.

[0076] Combining the data in Table 1 and Figure 1-2, an analysis of Example 1 and Comparative Examples 1-3 shows that the addition of tetrabutyl titanate can not only improve the thermal conductivity and phase change latent heat of the phase change heat storage material, but also improve its cyclic stability. After multiple melting cycles, the phase change heat storage material maintains a relatively high thermal conductivity and phase change latent heat retention rate; the pretreatment of boehmite can improve the phase change latent heat of the phase change heat storage material and the phase change latent heat retention rate after multiple melting cycles to a certain extent, and there is a synergistic effect between the two, which can synergistically improve the phase change latent heat retention rate of the phase change heat storage material after multiple melting cycles.

[0077] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0078] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a phase change heat storage material, characterized in that: The following steps are involved: S1. The paraffin is heated and melted to obtain a liquid organic phase change material, the titanate substance and the emulsifier are added to the liquid organic phase change material, mixed uniformly to obtain a phase change mixture; S2. An ethanol aqueous solution containing a titanium source catalyst was added to the pretreated boehmite, stirred and soaked for 1-3h to obtain a boehmite catalytic precursor liquid, wherein the mass ratio of the pretreated boehmite, the titanium source catalyst, and the ethanol aqueous solution was 10:0.8-1.2:40-60, and the pretreated boehmite was prepared by treating boehmite with oleic acid; S3. Add boehmite catalytic precursor liquid and the phase change mixed liquid of step S1 into the reactor, mix them evenly, add the load carrier, increase the temperature of the reactor to 75-85°C, evacuate the reactor to a negative pressure, keep it warm, increase the pressure of the reactor to a positive pressure, and then evacuate it to a negative pressure, repeat the operation 3-5 times, keep it warm for 1-3 hours, and under vacuum, reduce the temperature of the reactor to room temperature, discharge the material, and obtain a phase change heat storage material.

2. The method for preparing a phase change thermal storage material according to claim 1, wherein: The preparation of the pretreated boehmite in step S2 comprises the following steps: Oleic acid and ethanol are added into a reactor in a mass ratio of 1:3-5, mixed evenly, and flake boehmite is added. The temperature is raised to 50-60° C., and an acidic solution is slowly added dropwise to adjust the pH to 2-4. The reaction is stirred for 2-4 hours, cooled to room temperature, filtered, washed with water, and vacuum dried to obtain pretreated boehmite.

3. The method for preparing a phase change thermal storage material according to claim 1, wherein: In step S1, the titanate substance is one or a mixture of two or more of tetrabutyl titanate, tetraethyl titanate and isopropyl titanate.

4. The method for preparing a phase change thermal storage material according to claim 1, wherein: In step S1, the amount of titanate added is 4-6% of the mass of the organic phase change material.

5. The method for preparing a phase change thermal storage material according to claim 1, wherein: In step S2, the catalyst for the titanium source is one of sulfuric acid and hydrochloric acid or a mixture of two or more.

6. The method for preparing a phase change heat storage material according to claim 1, characterized in that: In step S3, the mass ratio of the phase change mixed liquid to the boehmite catalytic precursor liquid is 10:0.5-1.

7. The method for preparing a phase change thermal storage material according to claim 1, wherein: In step S3, the load carrier is expanded perlite.

8. The method for preparing a phase change thermal storage material according to claim 2, wherein: The acidic solution is one or a mixture of two or more of sulfuric acid, hydrochloric acid and phosphoric acid.

9. The method for preparing a phase change thermal storage material according to claim 2, wherein: The particle size of the lamellar boehmite is 0.15-0.5 microns.

10. A phase change heat storage material, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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