Chitin-based phase change composite aerogel as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of phase change energy storage, and discloses chitin-based phase change composite aerogel as well as a preparation method and application thereof. The preparation method comprises the following steps: dispersing chitin powder into an alkali metal hydroxide aqueous solution, carrying out reflux treatment, and washing and dispersing with water to obtain a chitin dispersion liquid; adjusting the pH value of the chitin dispersion liquid to 2-4, and mechanically grinding to obtain a chitin nanofiber suspension; mixing a part of the chitin nanofiber suspension with solid paraffin, heating to melt the solid paraffin, and performing ultrasonic treatment to obtain a chitin-based paraffin emulsion; uniformly mixing another part of the chitin nanofiber suspension with the chitin-based paraffin emulsion to obtain a mixed solution; and pre-cooling the mixed solution, and freeze-drying to obtain the chitin phase change composite aerogel. The preparation method provided by the invention can effectively retain the porous structure of the polymer aerogel, so that the prepared butyl-based phase-change composite aerogel can simultaneously ensure the coexistence of heat preservation and heat insulation properties and heat storage properties.

Description

Technical Field

[0001] The present invention relates to the technical field of phase change energy storage, and in particular to a chitin-based phase change composite aerogel and a preparation method and application thereof. Background Art

[0002] Phase change materials can absorb and release a large amount of heat through phase change, realizing the storage and recovery of thermal energy. They have attracted much attention due to their negligible temperature changes. They can improve the efficiency of thermal energy utilization, reduce the imbalance between thermal energy supply and demand, and have excellent energy storage and release performance.

[0003] Traditional phase change materials are mostly solid-liquid phase change materials, which have high latent heat capacity and stable physical and chemical properties, and are a good choice for energy management systems. However, solid-liquid phase change materials undergo a phase change from solid to liquid when absorbing or releasing latent heat, which makes solid-liquid phase change materials have obvious disadvantages as heat storage bodies, including easy leakage and low thermal conductivity, which greatly limits the application scope and application prospects of phase change materials.

[0004] In order to solve the above technical problems, those skilled in the art have proposed a new phase change material based on polymer aerogel and organic phase change material, and the prior art mainly obtains a polymer organic phase change composite block material by immersing the polymer aerogel in an organic phase change material melt, and then heating to remove the unadsorbed organic phase change material. However, the above preparation method is difficult to effectively retain the porous structure of the polymer aerogel, resulting in the inability of the prepared polymer organic phase change composite material to simultaneously ensure the coexistence of thermal insulation and heat storage performance. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a chitin-based phase change composite aerogel and a preparation method and application thereof.

[0006] The chitin-based phase change composite aerogel and its preparation method and application of the present invention are achieved through the following technical solutions:

[0007] The first object of the present invention is to provide a method for preparing a chitin-based phase change composite aerogel, comprising the following steps:

[0008] Step 1, dispersing chitin powder into an alkali metal hydroxide aqueous solution, then subjecting the solution to a reflux treatment, centrifuging, and then washing and dispersing the solution with water to obtain a chitin dispersion.

[0009] Step 2, adjusting the pH of the chitin dispersion to 2-4, and then performing mechanical grinding to obtain a chitin nanofiber suspension.

[0010] Step 3, taking a portion of the chitin nanofiber suspension and mixing it with solid paraffin to obtain a solid-liquid mixture; heating the solid-liquid mixture to melt the solid paraffin; and then performing ultrasonic treatment to obtain a chitin-based paraffin emulsion.

[0011] Step 4, taking another portion of the chitin nanofiber suspension and mixing it with the chitin-based paraffin emulsion to obtain a mixed solution; precooling the mixed solution and then freeze-drying it to obtain a chitin phase change composite aerogel.

[0012] In the above step 1, it should be noted that the present invention adds the alkali metal hydroxide in the form of an alkali metal hydroxide aqueous solution, so that the alkali metal hydroxide aqueous solution provides OH by reflux treatment. - , in order to provide an alkaline environment for the subsequent deacetylation reaction of chitin, thereby allowing the provided OH - It can react with some acetylamino groups in chitin to generate amino groups -NH 2 , which makes some amino groups in the chitin molecule easily cationic, making its subsequent degree of fibrillation higher.

[0013] In some preferred embodiments of the present invention, the alkali metal hydroxide is NaOH or KOH.

[0014] In order to achieve the above technical effects, in some preferred embodiments of the present invention, the mass ratio of the chitin powder to the alkali metal hydroxide is 1-5:1-5, so as to ensure that the OH provided by the alkali metal hydroxide - It can react with part of the acetylamino groups in chitin to generate amino groups. In some more preferred embodiments of the present invention, the mass ratio of the chitin powder to the alkali metal hydroxide is 1:1 to 5. In some more preferred embodiments of the present invention, the mass ratio of the chitin powder to the alkali metal hydroxide is 1:4.

[0015] In order to ensure that the water provided in the alkali metal hydroxide aqueous solution can fully disperse the chitin powder, in some preferred embodiments of the present invention, the dispersant used is water, and the total amount of water in the alkali metal hydroxide aqueous solution and the amount of water added during dispersion can be used to prepare the chitin powder to form a chitin dispersion with a concentration of 1wt% to 1.2wt%, so that it can be used after dilution.

[0016] The present invention realizes the deacetylation reaction of chitin by reflux treatment at high temperature and can be continuously carried out, and in some preferred embodiments of the present invention, the temperature of the reflux treatment is 100°C to 200°C, and the reflux time is 5h to 10h. In some more preferred embodiments of the present invention, the temperature of the reflux treatment is preferably 100°C to 150°C, more preferably 150°C. In some more preferred embodiments of the present invention, the reflux time of the reflux treatment is preferably 5h to 7h, more preferably 6h.

[0017] In the above step 2, it should be noted that the present invention considers that the cationization of the amino groups on the surface of chitin can help nanofibrillation through electrostatic repulsion, so the pH of the chitin dispersion is first adjusted to 2-4 before mechanical grinding. Chitin undergoes deacetylation reaction under the action of alkali to remove part of the acetyl group at the C2 position, and the exposed amino groups form positive charges in the acidic solution and are further dispersed into nanofibers.

[0018] In some preferred embodiments of the present invention, a grinder is used for mechanical grinding, and the rotation speed of the mechanical grinding is 1000 rpm to 2000 rpm, preferably 1000 rpm to 1500 rpm, and more preferably 1500 rpm. In some preferred embodiments of the present invention, the gap of the mechanical grinding is -1 to -2, preferably -1 to -1.5, and more preferably -1.5.

[0019] In some preferred embodiments of the present invention, acetic acid is used to adjust the pH of the chitin dispersion. Compared with other acids, acetic acid is less corrosive and safer.

[0020] In some preferred embodiments of the present invention, the concentration of the chitin nanofiber suspension is 0.5wt% to 1wt%. In some more preferred embodiments of the present invention, the concentration of the chitin nanofiber suspension is preferably 0.5wt% to 0.8wt%, more preferably 0.8wt%.

[0021] In some preferred embodiments of the present invention, the pH of the chitin dispersion is adjusted to 2-3, more preferably 3.

[0022] In the above step 3, it should be noted that the present invention first takes a portion of the chitin nanofiber suspension, mixes it with solid paraffin, and then heats the solid paraffin to melt and preliminarily mix it with the chitin nanofiber suspension; then ultrasound is performed to allow the chitin nanofibers to wrap the paraffin to form composite microspheres, thereby obtaining a chitin-based paraffin emulsion.

[0023] In some preferred embodiments of the present invention, when preparing the solid-liquid mixture, the mass ratio of the solid paraffin to the chitin nanofiber suspension is 1-5:1-5, so as to achieve the control of the yield and size of the composite microspheres in the chitin-based paraffin emulsion, and ensure that the surface and interior of the obtained composite microspheres have a rich porous network structure. In some more preferred embodiments of the present invention, the mass ratio of the solid paraffin to the chitin nanofiber is preferably 1-3:3-5, more preferably 1:5.

[0024] In some preferred embodiments of the present invention, the melting point of the solid paraffin used is 58°C to 64°C.

[0025] In some preferred embodiments of the present invention, the heating temperature is 80°C to 120°C. In some more preferred embodiments of the present invention, the heating temperature is preferably 100°C to 120°C, more preferably 100°C.

[0026] In some more preferred embodiments of the present invention, the heating time is 0.5h to 2h, preferably 0.5h to 1h, more preferably 1h.

[0027] In some preferred embodiments of the present invention, an ultrasonic crusher is used for ultrasonication, so as to fully mix the chitin nanofiber suspension and the melted paraffin by ultrasound. In some more preferred embodiments of the present invention, the ultrasonic power of the ultrasonication is 5W / mL to 10W / mL, preferably 5W / mL to 6W / mL, and more preferably 6W / mL. The ultrasonication time of the ultrasonication is 5min to 20min, preferably 5min to 10min, and more preferably 10min.

[0028] In the above step 4, it should be noted that, in some preferred embodiments of the present invention, when preparing the mixed solution, the volume ratio of the chitin-based paraffin wax emulsion to the chitin nanofiber suspension is 2 to 8: 2 to 8. In some more preferred embodiments of the present invention, the volume ratio of the chitin-based paraffin wax emulsion to the chitin nanofiber suspension is preferably 2 to 8: 8, more preferably 2: 8.

[0029] In some preferred embodiments of the present invention, the precooling temperature is -20°C to -10°C, preferably -20°C to -15°C, more preferably -20°C. The precooling freezing time is 10h to 20h, preferably 12h to 20h, more preferably 12h.

[0030] In some preferred embodiments of the present invention, the freeze-drying temperature is -30°C to -60°C, preferably -50°C to -60°C, more preferably -50°C. The freeze-drying time is 48h to 96h, preferably 72h to 96h, more preferably 72h.

[0031] The second object of the present invention is to provide a chitin-based phase change composite aerogel prepared by the preparation method of the chitin-based phase change composite aerogel.

[0032] It should be noted that the latent heat enthalpy of the chitin-based phase change composite aerogel prepared in the present invention is 135.78 J / g to 197.54 J / g.

[0033] The third object of the present invention is to provide an application of the chitin-based phase change composite aerogel in phase change energy storage.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] In the present invention, the alkali metal hydroxide is added in the form of an alkali metal hydroxide aqueous solution, so that after the chitin powder is dispersed in the alkali metal hydroxide aqueous solution, the OH provided by the alkali metal hydroxide aqueous solution is refluxed. - It can react with some acetylamino groups in chitin to generate amino groups -NH 2 , which makes some amino groups in chitin molecules easy to be cationized, so that the subsequent fiberization degree becomes higher. The present invention first adjusts the pH of the chitin dispersion to 2-4, and then performs mechanical grinding treatment, so that the cationization of the amino groups on the surface of chitin helps nanofibrillation through electrostatic repulsion. Then take a part of the chitin nanofiber suspension, mix it with solid paraffin, and heat it to melt the solid paraffin and preliminarily mix it with the chitin nanofiber suspension; then perform ultrasound to make the chitin nanofiber wrap the paraffin to form composite microspheres, and then obtain a chitin-based paraffin emulsion; take another part of the chitin nanofiber suspension and mix it with the chitin-based paraffin emulsion to obtain a mixed solution; pre-cool the mixed solution and freeze-dry it to obtain a chitin phase change composite aerogel. That is, the present invention adopts the Pickering emulsion template method, firstly compounds chitin fiber with paraffin to form a chitin-based paraffin emulsion containing composite microspheres, and then compounds the chitin fiber with another part of chitin fiber to prepare a chitin-based phase change composite aerogel, so that the chitin-based phase change composite aerogel prepared by the present invention can effectively retain the porous structure of the polymer aerogel, and then the prepared chitin-based phase change composite aerogel can simultaneously ensure the coexistence of thermal insulation and heat storage performance, so as to obtain a chitin-based phase change composite aerogel with excellent thermal regulation ability, good mechanical properties, strong morphological stability and excellent cyclic thermal performance.

[0036] The chitin-based phase-change composite aerogel prepared by the present invention has a stable porous network structure, and it has been tested and verified that the chitin-based phase-change composite aerogel prepared by the present invention has good mechanical properties, the maximum compressive stress can reach 5.56MPa, and it can withstand a load about 500 times heavier than its own weight without deformation, and the thermal conductivity is low, only 53mW / mK to 65mW / mK, which can be used as an excellent thermal insulation material. In terms of thermal stability, the composite aerogel can show excellent morphological stability at 80°C, no liquid leakage occurs after 20 heating / cooling cycles, and no liquid leakage occurs when placed at 100°C for 48 hours, and the latent heat enthalpy value can reach 197.54J / g, which can be used as an excellent energy storage material. A series of experiments have proved that the aerogel has great application value in phase change energy storage. Combined with its excellent thermal insulation performance, strong mechanical properties, high heat capacity, good stability and reusable properties, the composite phase change aerogel material has broad application prospects in temperature regulation of intelligent buildings, aviation equipment, heat storage and heat generation devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The Young's modulus and yield strength test results of the chitin-based phase change composite aerogels of Examples 1 to 4 of the present invention and Comparative Example 1 are shown.

[0038] Figure 2 These are the test results of thermal conductivity of the chitin-based phase change composite aerogels of Examples 1 to 4 of the present invention.

[0039] Figure 3 These are the test results of the thermal regulation performance of the chitin-based phase change composite aerogels of Examples 1 to 4 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention will be described clearly and completely below.

[0041] Example 1

[0042] This embodiment provides a chitin-based phase change composite aerogel, which is prepared by the following steps:

[0043] Step 1, preparing chitin dispersion:

[0044] 20 g of chitin powder was dispersed in 400 mL of a 20 wt% NaOH aqueous solution, and then boiled and refluxed at 150° C. for 6 h. The reactant was cooled and centrifuged, washed with deionized water for 3 times, and dispersed to a concentration of about 1 wt% to obtain a chitin dispersion.

[0045] Step 2, preparing chitin nanofiber suspension:

[0046] Acetic acid was added dropwise to the chitin dispersion obtained in step 1 to keep the pH of the chitin suspension at 3. Subsequently, a high-performance grinder was used for grinding at a grinding speed of 1500 rpm and a grinding gap of -1.5 to adjust the suspension concentration to 0.8 wt % to obtain a chitin nanofiber suspension.

[0047] Step 3, preparing chitin-based paraffin emulsion:

[0048] Take a portion of the chitin nanofiber suspension with a concentration of 0.8wt% obtained in step 2; add solid paraffin with a melting point of 62-64°C to the chitin nanofiber suspension with a concentration of 0.8wt%, the mass ratio of solid paraffin to 0.8wt% chitin nanofiber suspension being 1:5, and heat at 100°C to melt the paraffin. Ultrasonicate the chitin nanofiber / paraffin mixture with an ultrasonic cell crusher peptide tip intermittent pulse, the power is 6W / mL, the working interval time is 5s, and the ultrasound is 6min to obtain a chitin-based paraffin emulsion.

[0049] Step 4, forming chitin phase change composite aerogel:

[0050] Take another portion of the chitin nanofiber suspension with a concentration of 0.8wt% obtained in the above step 2, stir and mix it evenly with the chitin-based paraffin emulsion obtained in step 3 at a volume ratio of 8:2, freeze the obtained mixture at -20°C, and then freeze-dry it in a freeze dryer at -50°C for 72h to obtain a chitin phase change composite aerogel.

[0051] Example 2

[0052] This embodiment provides a chitin-based phase change composite aerogel, which is prepared by the following steps:

[0053] Step 1, preparing chitin dispersion:

[0054] 20 g of chitin powder was dispersed in 400 mL of a 20 wt% NaOH aqueous solution, and then boiled and refluxed at 150° C. for 6 h. The reactant was cooled and centrifuged, washed with deionized water for 3 times, and dispersed to about 1 wt% to obtain a chitin dispersion.

[0055] Step 2, preparing chitin nanofiber suspension:

[0056] Acetic acid was added dropwise to the chitin dispersion obtained in step 1 to keep the pH of the chitin suspension at 3. Subsequently, a high-performance grinder was used for grinding at a grinding speed of 1500 rpm and a grinding gap of -1.5 to adjust the suspension concentration to 0.8 wt % to obtain a chitin nanofiber suspension.

[0057] Step 3, preparing chitin-based paraffin emulsion:

[0058] Take a portion of the chitin nanofiber suspension with a concentration of 0.8wt% obtained in step 2 above; add solid paraffin with a melting point of 62-64°C to the chitin nanofiber suspension with a concentration of 0.8wt%, the mass ratio of solid paraffin to 0.8wt% chitin nanofiber suspension being 1:5, and heat at 100°C to melt the paraffin. Ultrasonicate the chitin nanofiber / paraffin mixture with an ultrasonic cell crusher peptide tip intermittent pulse, the power is 6W / mL, the working interval time is 5s, and the ultrasonic time is 6min. Obtain a chitin-based paraffin emulsion.

[0059] Step 4, forming chitin phase change composite aerogel:

[0060] Take another portion of the chitin nanofiber suspension with a concentration of 0.8wt% obtained in the above step 2, stir and mix it evenly with the chitin-based paraffin emulsion obtained in step 3 at a volume ratio of 6:4, freeze the obtained mixture at -20°C, and then freeze-dry it in a freeze dryer at -50°C for 72h to obtain a chitin phase change composite aerogel.

[0061] Example 3

[0062] This embodiment provides a chitin-based phase change composite aerogel, which is prepared by the following steps:

[0063] Step 1, preparing chitin dispersion:

[0064] 20 g of chitin powder was dispersed in 400 mL of a 20 wt% NaOH aqueous solution, and then boiled and refluxed at 150° C. for 6 h. The reactant was cooled and centrifuged, washed with deionized water for 3 times, and dispersed to about 1 wt% to obtain a chitin dispersion.

[0065] Step 2, preparing chitin nanofiber suspension:

[0066] Acetic acid was added dropwise to the chitin dispersion obtained in step 1 to keep the pH of the chitin suspension at 3. Subsequently, a high-performance grinder was used for grinding at a grinding speed of 1500 rpm and a grinding gap of -1.5 to adjust the suspension concentration to 0.8 wt % to obtain a chitin nanofiber suspension.

[0067] Step 3, preparing chitin-based paraffin emulsion:

[0068] Take a portion of the chitin nanofiber suspension with a concentration of 0.8wt% obtained in step 2 above; add solid paraffin with a melting point of 62-64°C to the chitin nanofiber suspension with a concentration of 0.8wt%, the mass ratio of solid paraffin to 0.8wt% chitin nanofiber suspension being 1:5, and heat at 100°C to melt the paraffin. Ultrasonicate the chitin nanofiber / paraffin mixture with an ultrasonic cell crusher peptide tip intermittent pulse, the power is 6W / mL, the working interval time is 5s, and the ultrasonic time is 6min. Obtain a chitin-based paraffin emulsion.

[0069] Step 4, forming chitin phase change composite aerogel:

[0070] Take another portion of the chitin nanofiber suspension with a concentration of 0.8wt% obtained in the above step 2, stir and mix it evenly with the chitin-based paraffin emulsion obtained in step 3 at a volume ratio of 4:6, freeze the obtained mixture at -20°C, and then freeze-dry it in a freeze dryer at -50°C for 72h to obtain a chitin phase change composite aerogel.

[0071] Example 4

[0072] This embodiment provides a chitin-based phase change composite aerogel, which is prepared by the following steps:

[0073] Step 1, preparing chitin dispersion:

[0074] 20 g of chitin powder was dispersed in 400 mL of a 20 wt% NaOH aqueous solution, and then boiled and refluxed at 150° C. for 6 h. The reactant was cooled and centrifuged, washed with deionized water for 3 times, and dispersed to about 1 wt% to obtain a chitin dispersion.

[0075] Step 2, preparing chitin nanofiber suspension:

[0076] Acetic acid was added dropwise to the chitin dispersion obtained in step 1 to keep the pH of the chitin suspension at 3. Subsequently, a high-performance grinder was used for grinding at a grinding speed of 1500 rpm and a grinding gap of -1.5 to adjust the suspension concentration to 0.8 wt % to obtain a chitin nanofiber suspension.

[0077] Step 3, preparing chitin-based paraffin emulsion:

[0078] Take a portion of the chitin nanofiber suspension with a concentration of 0.8wt% obtained in step 2 above; add solid paraffin with a melting point of 62-64°C to the chitin nanofiber suspension with a concentration of 0.8wt%, the mass ratio of solid paraffin to 0.8wt% chitin nanofiber suspension being 1:5, and heat at 100°C to melt the paraffin. Ultrasonicate the chitin nanofiber / paraffin mixture with an ultrasonic cell crusher peptide tip intermittent pulse, the power is 6W / mL, the working interval time is 5s, and the ultrasonic time is 6min. Obtain a chitin-based paraffin emulsion.

[0079] Step 4, forming chitin phase change composite aerogel:

[0080] Take another portion of the chitin nanofiber suspension with a concentration of 0.8wt% obtained in the above step 2, stir and mix it evenly with the chitin-based paraffin emulsion obtained in step 3 at a volume ratio of 2:8, freeze the obtained mixture at -20°C, and then freeze-dry it in a freeze dryer at -50°C for 72h to obtain a chitin phase change composite aerogel.

[0081] Comparative Example 1

[0082] This comparative example provides a chitin-based aerogel, which is prepared by the following steps:

[0083] Step 1, preparing chitin dispersion:

[0084] 20 g of chitin powder was dispersed in 400 mL of a 20 wt% NaOH aqueous solution, and then boiled and refluxed at 150° C. for 6 h. The reactant was cooled and centrifuged, washed with deionized water for 3 times, and dispersed to about 1 wt% to obtain a chitin dispersion.

[0085] Step 2, preparing chitin nanofiber suspension:

[0086] Acetic acid was added dropwise to the chitin dispersion obtained in step 1 to keep the pH of the chitin suspension at 3. Subsequently, a high-performance grinder was used for grinding at a grinding speed of 1500 rpm and a grinding gap of -1.5 to adjust the suspension concentration to 0.8 wt % to obtain a chitin nanofiber suspension.

[0087] Step 3, forming chitin phase change composite aerogel:

[0088] The chitin nanofiber suspension with a concentration of 0.8 wt% obtained in step 2 above was frozen at -20°C, and then freeze-dried in a freeze dryer at -50°C for 72 hours to obtain a chitin phase change composite aerogel.

[0089] That is, the difference between this comparative example and Example 1 is only that:

[0090] In this comparative example, no chitin-based paraffin emulsion was added.

[0091] Experimental part

[0092] (I) Mechanical properties test

[0093] The present invention tests the chitin-based phase change composite aerogels of Examples 1 to 4 and Comparative Example 1 respectively according to the national standards GB / T 22315-2008 and GB / T 28905-2022 for Young's modulus and yield strength, and the test results are as follows: Figure 1 shown.

[0094] Figure 1 The Young's modulus and yield strength test results of the chitin-based phase change composite aerogels of Examples 1 to 4 of the present invention and Comparative Example 1 are shown.

[0095] Depend on Figure 1 It can be seen from the test results that the Young's modulus and yield strength of the chitin-based phase change composite aerogels of Examples 1 to 4 are higher than those of Comparative Example 1, which indicates that the chitin-based phase change composite aerogels prepared by the preparation method of the present invention have excellent mechanical properties.

[0096] Furthermore, by comparing the test results of the Young's modulus and yield strength of the chitin-based phase change composite aerogels of Examples 1 to 4, it can be seen that with the increase of the content of the chitin-based paraffin emulsion, the Young's modulus and yield strength of the chitin-based phase change composite aerogels of Examples 1 to 4 increase accordingly, and among them, the Young's modulus of the chitin-based phase change composite aerogel of Example 1 is 189 KPa, and the yield strength is 19.9 KPa, and the chitin-based phase change composite aerogel of Example 4 has the highest Young's modulus of 435 KPa, and the yield strength is 61.5 KPa, which is about twice that of the chitin-based phase change composite aerogel of Example 1.

[0097] In addition, it should be noted that when the chitin-based paraffin emulsion is further added on the basis of Example 4 during the exploration process of the present invention, the Young's modulus and yield strength of the obtained chitin-based phase change composite aerogel are reduced. Therefore, considering the comprehensive factors of cost and performance, the volume ratio of the chitin-based paraffin emulsion to the chitin nanofiber suspension is limited to the range of 2 to 8:2 to 8.

[0098] (II) Thermal insulation performance test

[0099] The present invention tests the thermal conductivity of the chitin-based phase change composite aerogels of Examples 1 to 4 according to the national standard GB / T 32064-2015, and the test results are as follows: Figure 2 shown.

[0100] Figure 2 These are the test results of thermal conductivity of the chitin-based phase change composite aerogels of Examples 1 to 4 of the present invention.

[0101] Depend on Figure 2 It can be seen from the test results that the thermal conductivity of the chitin-based phase change composite aerogels of Examples 1 to 4 varies in the range of 53 mW / mK to 64 mW / mK, which indicates that the chitin-based phase change composite aerogels prepared by the preparation method of the present invention have excellent thermal insulation properties and are helpful for energy saving.

[0102] By further analyzing the increasing trend of the thermal conductivity of the chitin-based phase change composite aerogels of Examples 1 to 4, it can be seen that as the content of the chitin-based paraffin emulsion increases, the thermal conductivity of the chitin-based phase change composite aerogel also increases, and this increase can be explained as higher density leading to higher thermal conductivity. Since the thermal conductivity is low, the porous structure provides the chitin phase change composite aerogel with good thermal insulation performance, which helps to save energy.

[0103] (III) Thermal regulation performance test

[0104] The present invention also tests the thermal regulation performance of the chitin-based phase change composite aerogels of Examples 1 to 4 and Comparative Example 1 according to the national standard GB / T 22232-2008, and the test results are as follows: Figure 3 shown.

[0105] Figure 3 These are the test results of the thermal regulation performance of the chitin-based phase change composite aerogels of Examples 1 to 4 of the present invention and Comparative Example 1.

[0106] Depend on Figure 3 It can be seen from the test results that the more the chitin-based paraffin emulsion content in Examples 1 to 4 and Comparative Example 1 is, the lower the heating rate of the surface temperature of the composite aerogel is, and the lower the maximum temperature after the temperature stabilizes is. This is mainly because the absorption of energy by paraffin inhibits the temperature rise, which confirms the thermal stability of the chitin phase change composite aerogel.

[0107] (IV) Phase change latent heat performance test

[0108] The present invention also tests the phase change latent heat of the chitin-based phase change composite aerogels in Examples 1 to 4 and Comparative Example 1 during the melting and crystallization processes, and the test results are shown in Table 1.

[0109] Table 1 Melting temperature (Tm), crystallization temperature (Tc) and transition enthalpy (ΔH) of chitin phase change composite aerogels

[0110] <![CDATA[T m (℃)]]> <![CDATA[ΔH m (J / g)]]> <![CDATA[T c (℃)]]> <![CDATA[ΔH c (J / g)]]> Example 1 60.21 135.78 56.56 135.23 Example 2 60.20 143.38 56.77 141.61 Example 3 60.33 169.52 56.31 169.96 Example 4 (1 cycle) 60.29 197.54 56.65 197.16 Example 4 (25 cycles) 60.08 196.52 56.55 197.03 Example 4 (50 cycles) 60.05 195.19 56.72 194.83

[0111] From the test results in Table 1, it can be seen that as the content of chitin-based paraffin emulsion increases, the phase change enthalpy of the chitin phase change composite aerogel increases. In order to investigate the cyclic performance of the composite aerogel, 50 melting and crystallization cycles were performed on Example 4. The important thermal parameters of Example 4 are melting point temperature (T m ), crystallization temperature (T c ) and latent heat (ΔH) remained essentially unchanged after 50 cycles, indicating that the three-dimensional network structure formed by the chitin nanofibers was strong and had a good encapsulation effect. Therefore, the chitin phase change composite aerogel of the present invention has a high energy density and good thermal stability and can be used for thermal energy storage applications.

[0112] Obviously, the above embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for preparing a chitin-based phase change composite aerogel, characterized in that: The following steps are involved: The chitin powder is dispersed in an alkali metal hydroxide aqueous solution, followed by reflux treatment, solid-liquid separation and washing, and the precipitate is dispersed with a dispersant to obtain a chitin dispersion; The pH of the chitin dispersion is adjusted to 2-4, followed by mechanical grinding to convert the chitin into chitin nanofibers to obtain a chitin nanofiber suspension; Taking a portion of the chitin nanofiber suspension and mixing it with solid paraffin to obtain a solid-liquid mixture; heating the solid-liquid mixture to melt the solid paraffin; then performing ultrasonic treatment so that the chitin nanofibers wrap the paraffin to form composite microspheres, thereby obtaining a chitin-based paraffin emulsion; Another part of the chitin nanofiber suspension is mixed with the chitin-based paraffin emulsion to obtain a mixed solution; the mixed solution is precooled and then freeze-dried to obtain a chitin phase change composite aerogel.

2. The method for preparing the chitin-based phase change composite aerogel according to claim 1, characterized in that: The concentration of the chitin dispersion is 1 wt% to 1.2 wt%.

3. The method for preparing the chitin-based phase change composite aerogel according to claim 1, characterized in that: The concentration of the chitin nanofiber suspension is 0.5 wt% to 1 wt%.

4. The method for preparing the chitin-based phase change composite aerogel according to claim 1, characterized in that: When preparing the solid-liquid mixture, the mass ratio of the solid paraffin to the chitin nanofiber suspension is 1-5:1-5.

5. The method for preparing the chitin-based phase change composite aerogel according to claim 1, characterized in that: When preparing the mixed solution, the chitin-based paraffin emulsion The volume ratio of the chitin nanofiber suspension is 2-8:2-8.

6. The method for preparing the chitin-based phase change composite aerogel according to claim 1, characterized in that: The mass ratio of the chitin powder to the alkali metal hydroxide in the alkali metal hydroxide aqueous solution is 1-5:1-5.

7. The method for preparing the chitin-based phase change composite aerogel according to claim 1, characterized in that: The temperature of the reflux treatment is 100° C. to 200° C., and the reflux time is 5 h to 10 h.

8. The method for preparing the chitin-based phase change composite aerogel according to claim 1, characterized in that: The rotation speed of the mechanical grinding process is 1000 rpm to 2000 rpm, and the gap is -1 to -2.

9. A chitin-based phase-change composite aerogel prepared by the method for preparing a chitin-based phase-change composite aerogel according to any one of claims 1 to 8.

10. Use of the chitin-based phase change composite aerogel according to claim 9 in phase change energy storage.

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