Chitin-based phase-change composite aerogel and its preparation method and application

Abstract

The present invention belongs to the field of phase change energy storage technology, and discloses a chitin-based phase change composite aerogel, its preparation method, and application. The preparation method is as follows: chitin powder is dispersed in an alkali metal hydroxide aqueous solution, refluxed, and then washed and dispersed with water to obtain a chitin dispersion; the pH of the chitin dispersion is adjusted to 2-4 and then mechanically ground to obtain a chitin nanofiber suspension; a portion of the chitin nanofiber suspension is mixed with solid paraffin and heated to melt the solid paraffin, followed by ultrasonic treatment to obtain a chitin-based paraffin emulsion; another portion of the chitin nanofiber suspension is mixed with the chitin-based paraffin emulsion to obtain a mixed solution; the mixed solution is pre-cooled and then freeze-dried to obtain a chitin phase change composite aerogel. The preparation method of the present invention can effectively retain the porous structure of the polymer aerogel, so that the prepared chitin-based phase change composite aerogel can simultaneously ensure the coexistence of thermal insulation and heat storage properties.

Description

Technical Field

[0001] The present invention relates to the technical field of phase change energy storage technology, 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 large amounts 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 (PCMs) are mostly solid-liquid (SLC) PCMs. These materials have high latent heat capacity and stable physical and chemical properties, making them a good choice for energy management systems. However, SLC PCMs undergo a phase change from solid to liquid when absorbing or releasing latent heat. This results in significant drawbacks as heat storage media, including leakage and low thermal conductivity, which greatly limits the scope and prospects of their application.

[0004] To address the aforementioned technical issues, those skilled in the art have proposed a novel phase-change material based on polymer aerogel and an organic phase-change material. Existing techniques primarily involve impregnating the polymer aerogel in a melt of the organic phase-change material, then heating to remove the unabsorbed organic phase-change material, to produce a polymer-organic phase-change composite block material. However, this preparation method struggles 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 maintain both thermal insulation and heat storage properties. 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 the solution, and 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 -NH2, which makes some amino groups in the chitin molecules easily cationic, making the subsequent degree of fiberization 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 some 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 used in the alkali metal hydroxide aqueous solution and the amount of water added during dispersion is sufficient to prepare the chitin powder into a chitin dispersion with a concentration of 1 wt% to 1.2 wt%, so that it can be diluted for use.

[0016] The present invention achieves a chitin deacetylation reaction by reflux treatment at a high temperature, and in some preferred embodiments of the present invention, the reflux treatment temperature is 100°C to 200°C, and the reflux time is 5 hours to 10 hours. In some more preferred embodiments of the present invention, the reflux treatment temperature is preferably 100°C to 150°C, more preferably 150°C. In some more preferred embodiments of the present invention, the reflux treatment time is preferably 5 hours to 7 hours, more preferably 6 hours.

[0017] In step 2 above, 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. 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 0.5 wt% to 1 wt%. In some more preferred embodiments of the present invention, the concentration of the chitin nanofiber suspension is preferably 0.5 wt% to 0.8 wt%, more preferably 0.8 wt%.

[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 melts the solid paraffin by heating to preliminarily mix it evenly 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 wax to the chitin nanofiber suspension is 1-5:1-5, so as to achieve control over the yield and size of the composite microspheres in the chitin-based paraffin wax emulsion and, similarly, ensure that the resulting composite microspheres have a rich porous network structure on the surface and inside. In some more preferred embodiments of the present invention, the mass ratio of the solid paraffin wax to the chitin nanofibers 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 0.5 h to 2 h, preferably 0.5 h to 1 h, more preferably 1 h.

[0027] In some preferred embodiments of the present invention, ultrasonication is performed using an ultrasonic disruptor to thoroughly mix the chitin nanofiber suspension and the melted paraffin wax. In some more preferred embodiments of the present invention, the ultrasonication power is 5 W / mL to 10 W / mL, preferably 5 W / mL to 6 W / mL, and more preferably 6 W / mL. The ultrasonication time is 5 min to 20 min, preferably 5 min to 10 min, and more preferably 10 min.

[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 pre-cooling temperature is -20°C to -10°C, preferably -20°C to -15°C, more preferably -20°C. The pre-cooling 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 above-mentioned 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 -NH2, which facilitates the cationization of some amino groups in the chitin molecule, thereby increasing its subsequent fibrillation degree. The present invention first adjusts the pH of the chitin dispersion to 2-4, then mechanically grinds it to allow the cationization of the amino groups on the chitin surface to promote nanofibrillation through electrostatic repulsion. A portion of the chitin nanofiber suspension is then mixed with solid paraffin wax. The solid paraffin wax is then melted by heating and initially mixed with the chitin nanofiber suspension. Ultrasound is then applied to allow the chitin nanofibers to wrap around the paraffin wax to form composite microspheres, thereby producing a chitin-based paraffin wax emulsion. Another portion of the chitin nanofiber suspension is then mixed with the chitin-based paraffin wax emulsion to form a mixed solution. The mixed solution is pre-cooled and freeze-dried to produce a chitin phase-change composite aerogel. That is, the present invention adopts the Pickering emulsion template method, first compounding chitin fibers and paraffin to form a chitin-based paraffin emulsion containing composite microspheres, and then compounding the chitin-based paraffin emulsion with another part of chitin fibers 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 further the prepared chitin-based phase change composite aerogel can simultaneously ensure the coexistence of thermal insulation and heat storage performance, thereby obtaining 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. Tests have shown that the chitin-based phase-change composite aerogel prepared by the present invention has excellent mechanical properties, with a maximum compressive stress of 5.56 MPa, and can withstand loads approximately 500 times heavier than its own weight without deformation. It also has a low thermal conductivity of only 53mW / mK to 65mW / mK, making it an excellent thermal insulation material. In terms of thermal stability, the composite aerogel exhibits excellent morphological stability at 80°C, with no liquid leakage after 20 heating / cooling cycles and no liquid leakage after being placed at 100°C for 48 hours. Its latent heat enthalpy can reach 197.54J / g, making it 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 reusability, 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 These are the test results of Young's modulus and yield strength of the chitin-based phase change composite aerogels of Examples 1 to 4 of the present invention and Comparative Example 1.

[0038] Figure 2 These are the thermal conductivity test results 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% aqueous NaOH solution, and then refluxed at 150° C. for 6 h. The reaction mixture was cooled, centrifuged, and washed three times with deionized water 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 maintain the pH of the chitin suspension at 3. Subsequently, the chitin suspension was ground using a high-performance grinder 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 0.8 wt% chitin nanofiber suspension obtained in step 2 above; add solid paraffin wax with a melting point of 62-64°C to the 0.8 wt% chitin nanofiber suspension, with the mass ratio of solid paraffin wax to 0.8 wt% chitin nanofiber suspension being 1:5. Heat at 100°C to melt the paraffin wax. Ultrasonicate the chitin nanofiber / paraffin wax mixture using an ultrasonic cell disruptor with intermittent pulses at a power of 6 W / mL, a 5-second interval, and for 6 minutes to obtain a chitin-based paraffin wax emulsion.

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

[0050] Another portion of the chitin nanofiber suspension with a concentration of 0.8 wt% obtained in step 2 was taken and mixed evenly with the chitin-based paraffin emulsion obtained in step 3 at a volume ratio of 8:2. The resulting mixture was frozen at -20°C and then freeze-dried in a freeze dryer at -50°C for 72 h 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% aqueous solution of NaOH, and then refluxed at 150° C. for 6 h. The reaction mixture was cooled, centrifuged, and washed three times with deionized water to obtain a chitin dispersion of approximately 1 wt%.

[0055] Step 2, preparing chitin nanofiber suspension:

[0056] Acetic acid was added dropwise to the chitin dispersion obtained in step 1 to maintain the pH of the chitin suspension at 3. Subsequently, the chitin suspension was ground using a high-performance grinder 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 0.8 wt% chitin nanofiber suspension obtained in step 2 above; add solid paraffin wax with a melting point of 62-64°C to the 0.8 wt% chitin nanofiber suspension, with the mass ratio of solid paraffin wax to 0.8 wt% chitin nanofiber suspension being 1:5. Heat at 100°C to melt the paraffin wax. Ultrasonicate the chitin nanofiber / paraffin wax mixture using an ultrasonic cell disruptor with intermittent pulses at a power of 6 W / mL, a 5-second interval, and a sonication time of 6 minutes. This yields a chitin-based paraffin wax emulsion.

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

[0060] Another portion of the chitin nanofiber suspension with a concentration of 0.8 wt% obtained in step 2 was taken and mixed evenly with the chitin-based paraffin emulsion obtained in step 3 at a volume ratio of 6:4. The resulting mixture was frozen at -20°C and then freeze-dried in a freeze dryer at -50°C for 72 h 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% aqueous solution of NaOH, and then refluxed at 150° C. for 6 h. The reaction mixture was cooled, centrifuged, and washed three times with deionized water to obtain a chitin dispersion of approximately 1 wt%.

[0065] Step 2, preparing chitin nanofiber suspension:

[0066] Acetic acid was added dropwise to the chitin dispersion obtained in step 1 to maintain the pH of the chitin suspension at 3. Subsequently, the chitin suspension was ground using a high-performance grinder 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 0.8 wt% chitin nanofiber suspension obtained in step 2 above; add solid paraffin wax with a melting point of 62-64°C to the 0.8 wt% chitin nanofiber suspension, with the mass ratio of solid paraffin wax to 0.8 wt% chitin nanofiber suspension being 1:5. Heat at 100°C to melt the paraffin wax. Ultrasonicate the chitin nanofiber / paraffin wax mixture using an ultrasonic cell disruptor with intermittent pulses at a power of 6 W / mL, a 5-second interval, and a sonication time of 6 minutes. This yields a chitin-based paraffin wax emulsion.

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

[0070] Another portion of the chitin nanofiber suspension with a concentration of 0.8 wt% obtained in step 2 was taken and mixed evenly with the chitin-based paraffin emulsion obtained in step 3 at a volume ratio of 4:6. The resulting mixture was frozen at -20°C and then freeze-dried in a freeze dryer at -50°C for 72 h 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% aqueous solution of NaOH, and then refluxed at 150° C. for 6 h. The reaction mixture was cooled, centrifuged, and washed three times with deionized water to obtain a chitin dispersion of approximately 1 wt%.

[0075] Step 2, preparing chitin nanofiber suspension:

[0076] Acetic acid was added dropwise to the chitin dispersion obtained in step 1 to maintain the pH of the chitin suspension at 3. Subsequently, the chitin suspension was ground using a high-performance grinder 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 0.8 wt% chitin nanofiber suspension obtained in step 2 above; add solid paraffin wax with a melting point of 62-64°C to the 0.8 wt% chitin nanofiber suspension, with the mass ratio of solid paraffin wax to 0.8 wt% chitin nanofiber suspension being 1:5. Heat at 100°C to melt the paraffin wax. Ultrasonicate the chitin nanofiber / paraffin wax mixture using an ultrasonic cell disruptor with intermittent pulses at a power of 6 W / mL, a 5-second interval, and a sonication time of 6 minutes. This yields a chitin-based paraffin wax emulsion.

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

[0080] Another portion of the chitin nanofiber suspension with a concentration of 0.8 wt% obtained in step 2 was taken and mixed evenly with the chitin-based paraffin emulsion obtained in step 3 at a volume ratio of 2:8. The resulting mixture was frozen at -20°C and then freeze-dried in a freeze dryer at -50°C for 72 h 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% aqueous solution of NaOH, and then refluxed at 150° C. for 6 h. The reaction mixture was cooled, centrifuged, and washed three times with deionized water to obtain a chitin dispersion of approximately 1 wt%.

[0085] Step 2, preparing chitin nanofiber suspension:

[0086] Acetic acid was added dropwise to the chitin dispersion obtained in step 1 to maintain the pH of the chitin suspension at 3. Subsequently, the chitin suspension was ground using a high-performance grinder 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 was frozen at -20°C, and then freeze-dried in a freeze dryer at -50°C for 72 h 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] (1) Mechanical properties test

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

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

[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 chitin-based paraffin emulsion content, 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. The Young's modulus of the chitin-based phase change composite aerogel of Example 4 is the highest, which is 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 was 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 were 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] (2) 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 respectively 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 thermal conductivity test results 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] Further analysis of the increasing thermal conductivity of the chitin-based phase-change composite aerogels from Examples 1 to 4 reveals that the thermal conductivity of the chitin-based phase-change composite aerogels increases with increasing chitin-based paraffin wax emulsion content. This increase can be explained by the higher thermal conductivity resulting from higher density. Due to the low thermal conductivity, the porous structure of the chitin-based phase-change composite aerogels provides excellent thermal insulation, contributing to energy conservation.

[0103] (3) 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 higher the chitin-based paraffin emulsion content in Examples 1 to 4 and Comparative Example 1, the lower the heating rate of the composite aerogel surface temperature, and the lower the maximum temperature after the temperature stabilizes. This is mainly because the absorption of energy by paraffin inhibits the temperature rise, confirming the thermal stability of the chitin phase change composite aerogel.

[0107] (4) 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 of 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] The test results in Table 1 show that the phase change enthalpy of the chitin phase change composite aerogel increases with the increase of the chitin-based paraffin emulsion content. 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 the melting point temperature (T m ), crystallization temperature (T c ) and latent heat (ΔH) remained essentially unchanged after 50 cycles, demonstrating the strong three-dimensional network structure formed by the chitin nanofibers and their good encapsulation effect. Therefore, the chitin phase-change composite aerogel of this invention possesses high energy density and good thermal stability, making it suitable for thermal energy storage applications.

[0112] Obviously, the above embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making 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: Dispersing chitin powder in an alkali metal hydroxide aqueous solution, followed by reflux treatment, solid-liquid separation and washing, and dispersing the precipitate with a dispersant to obtain a chitin dispersion; The chitin dispersion is adjusted to a pH of 2 to 4, followed by mechanical grinding to convert the chitin into chitin nanofibers, thereby obtaining 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; and then performing ultrasonic treatment to allow the chitin nanofibers to wrap the paraffin to form composite microspheres, thereby obtaining a chitin-based paraffin emulsion; Another portion of the chitin nanofiber suspension is mixed with the chitin-based paraffin emulsion to obtain a mixed solution; the mixed solution is pre-cooled 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, wherein: 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, wherein: 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, wherein: 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, wherein: When preparing the mixed solution, the chitin-based paraffin emulsion The volume ratio of the chitin nanofiber suspension to 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, wherein: 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, wherein: 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, wherein: 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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