Preparation method of banana nanocellulose-montmorillonite aerogel / paraffin composite phase change material
By using banana nanocellulose-montmorillonium aerogel to support paraffin phase change materials, nanocellulose-montmorillonium aerogel/paraffin composite phase change materials were prepared, which solved the problem of rapid heat release of existing phase change materials and achieved the goal of achieving rapid heat transfer. Long-term heat release and low-cost production effect.
Patent Information
- Application Number
- CN202411303644.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-19
- Publication Date
- 2025-02-25
AI Technical Summary
The heat of existing phase change materials is quickly released during the heat release process, resulting in the inability to achieve long-term heat release and is costly.
Banana nanocellulose-montmorillonium aerogel as the support material and paraffin as the phase change material, and paraffin is loaded into the aerogel by vacuum impregnation method to prepare nanocellulose-montmorillonium aerogel/paraffin composite phase change Material.
Long-term heat release of nanocellulose-montmorillonium aerogel/paraffinium composite phase change material is achieved. The heat can be continuously released for 8 hours after the light is over, and it is cheap and green and environmentally friendly.
Smart Images
Figure CN119505817A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of textile materials, and specifically relates to a preparation method of a banana nanocellulose-montmorillonite aerogel / paraffin composite phase change material. Background Art
[0002] Cellulose-based aerogel raw materials are widely available, and banana hemp is abundant in reserves and is green and environmentally friendly. Phase change materials have latent heat of phase change, and the use of phase change energy storage technology is one of the effective means to store and improve the utilization rate of solar energy. However, single phase change materials have limited applications due to defects such as easy leakage, poor thermal conductivity, and poor light-heat conversion. Using banana hemp to prepare nanocellulose aerogel as a carrier of phase change materials is low-cost, biodegradable, and can increase the added value of banana hemp.
[0003] Shu prepared nanocellulose / graphene aerogels and vacuum-assisted paraffin impregnation to prepare shape-stable phase change materials at 200 mW / cm 2 The temperature can reach 75.5℃ under irradiation of light for 50min, and the exothermic time is only 10min; Shen prepared a shape-stable phase change material of cellulose nanofiber / carbon nanotube aerogel loaded with paraffin wax, which can reach 75.5℃ under 469mW / cm 2 The temperature reached 95°C for 30 minutes under light irradiation, and the exothermic time was only 16 minutes; Xu prepared cellulose nanofiber / polypyrrole aerogel, and vacuum-assisted paraffin-impregnated shape-stable phase change material. 2 The temperature reached 80°C after 20 minutes of irradiation under light, and the heat release time was 42 minutes. The addition of materials such as graphene, carbon nanotubes and polypyrrole can improve the light-to-heat conversion efficiency of shape-stable phase change materials. However, the excessively high thermal conductivity causes the heat of shape-stable phase change materials to be released quickly during the heat release process. Therefore, the search for a preparation method for phase change energy storage materials that can achieve long-term heat release and low cost has attracted much attention.
[0004] The invention uses banana nanocellulose-montmorillonite aerogel as a supporting material and paraffin as a phase change material to prepare a nanocellulose-montmorillonite aerogel / paraffin composite phase change material capable of releasing heat for a long time. Summary of the invention
[0005] Based on the above description, the present invention aims to propose a preparation method of a composite phase change material with paraffin as phase change material and banana nanocellulose-montmorillonite aerogel as supporting material, which can release heat for a long time, thereby increasing the added value of raw banana hemp and reducing environmental pollution.
[0006] The technical solutions used in the present invention are as follows:
[0007] Step 1: Preparation of banana nanocellulose
[0008] The raw banana hemp is crushed by a crusher, and the raw banana hemp powder is extracted with benzene alcohol by a Soxhlet extractor. The raw banana hemp powder is bleached with sodium chlorite, and the hemicellulose is removed in a potassium hydroxide solution. Finally, the cellulose is washed and dried to obtain the cellulose.
[0009] Step 2: Preparation of Nanocellulose-Montmorillonite Aerogel
[0010] Cellulose and montmorillonite are placed in deionized water for homogenization, and then polyvinyl alcohol is added, and the mixture is heated and stirred in a water bath for a period of time. The obtained suspension is placed in a freeze dryer and freeze-dried to obtain nanocellulose-montmorillonite aerogel.
[0011] Step 3: Preparation of nanocellulose-montmorillonite aerogel / paraffin composite phase change material
[0012] The nanocellulose-montmorillonite aerogel and excess paraffin are placed in a vacuum oven and heated to allow the paraffin to be impregnated into the aerogel, followed by drying and cooling to obtain a nanocellulose-montmorillonite aerogel / paraffin composite phase change material.
[0013] In the above technical solution, further, in step 1, the preparation method of the banana nanocellulose is:
[0014] The raw banana hemp is crushed by a crusher and then filtered by a sieve to obtain raw hemp powder with a particle diameter less than 280 μm; the raw hemp powder is extracted with benzene alcohol by a Soxhlet extractor, and the volume ratio of benzene alcohol is 2:1; the raw hemp powder is bleached by a 1wt% sodium chlorite solution, acetic acid is added to adjust the pH value to 3-5, and a magnetic stirrer is used to stir for 1 hour at a temperature of 65-85°C, and the above steps are repeated 6 times; then a 5wt% potassium hydroxide solution is used to remove hemicellulose, and cellulose is washed and dried to obtain cellulose.
[0015] In the above technical solution, further, in step 2, the preparation method of nanocellulose-montmorillonite aerogel is:
[0016] 1g of cellulose and montmorillonite were respectively placed in deionized water, and the mass of montmorillonite was 0.5-3.5g. The mixture was homogenized for 10-20min, polyvinyl alcohol was added thereto, and the mixture was placed in a constant temperature heating magnetic stirrer at a temperature of 80-100°C, and stirred to obtain a nanocellulose-montmorillonite suspension. The suspension was placed in a freeze dryer at a temperature of -60°C, and freeze-dried to obtain a nanocellulose-montmorillonite aerogel.
[0017] In the above technical solution, further, in step 3, the aerogel obtained in step 2 and excess paraffin are placed in a vacuum oven and heated at a temperature of 60 to 80° C., and then cooled and dried to obtain a nanocellulose-montmorillonite aerogel / paraffin composite phase change material.
[0018] Compared with the prior art, the present invention has the following beneficial effects:
[0019] (1) The present invention uses banana hemp as a raw material to prepare nanocellulose-montmorillonite aerogel, which is green, environmentally friendly, low-cost, and easy to mass produce.
[0020] (2) The nanocellulose-montmorillonite aerogel of the present invention has low density, dense pores, high porosity, and high paraffin loading rate.
[0021] (3) The nanocellulose-montmorillonite aerogel of the present invention has a three-dimensional network structure, which can significantly improve the heat release time of the nanocellulose-montmorillonite aerogel / paraffin composite phase change material and can be used for photothermal conversion of solar energy. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The following drawings are only intended to illustrate and explain the present invention, and are not intended to limit the scope of the present invention.
[0023] Figure 1 is a scanning electron microscope image of an embodiment.
[0024] Figure 2 It is a comparison table of porosity, density and loading rate of the embodiments.
[0025] Figure 3 Schematic diagram of thermal conductivity of the embodiment.
[0026] Figure 4 1 is the light-to-heat conversion curve of the embodiment. DETAILED DESCRIPTION
[0027] The present invention will be described in detail below in conjunction with the embodiments and drawings.
[0028] Example: Preparation of nanocellulose-montmorillonite aerogel / paraffin composite phase change material, the steps are as follows:
[0029] (1) Preparation of banana nanocellulose
[0030] The banana raw hemp was cut into pieces of about 2 cm, crushed by a pulverizer, and then filtered using a sieve to obtain raw hemp powder with particles less than 280 μm; the raw hemp powder was extracted with benzene alcohol using a Soxhlet extractor, the volume ratio of the benzene / ethanol mixed solution was 2:1, the solid-liquid ratio was 1:30 (g / mL), the time was 6 hours, and the temperature was 90°C; the raw hemp powder was bleached with a 1wt% sodium chlorite solution, the solid-liquid ratio was 1:65 (g / mL), acetic acid was added to adjust the pH value to 4, and a magnetic stirrer was used for stirring and heating, the time was 1 hour, the temperature was 75°C, and the above steps were repeated 6 times; hemicellulose was removed using a 5wt% potassium hydroxide solution, the solid-liquid ratio was 1:30 (g / mL), the time was 2 hours, and the temperature was 90°C. The cellulose was washed and dried to obtain cellulose.
[0031] (2) Preparation of Nanocellulose-Montmorillonite Aerogel
[0032] 1g of cellulose was added to 0.5g, 1.5g, and 2.5g of montmorillonite in 100ml of deionized water, and 0.4g of polyvinyl alcohol was added after homogenization for 15min. Polyvinyl alcohol will make the nanocellulose and montmorillonite more tightly combined. Then the mixture was placed in a 90℃ water bath and stirred with a magnetic stirrer for 1h to obtain a nanocellulose-montmorillonite suspension. The suspension was placed in a freeze dryer and freeze-dried at -60℃ for 48h to obtain three types of nanocellulose-montmorillonite aerogels. The three types of nanocellulose-montmorillonite aerogels were recorded as CM0.5, CM1.5, and CM2.5 according to the different masses of montmorillonite added.
[0033] (3) Preparation of nanocellulose-montmorillonite aerogel / paraffin composite phase change materials
[0034] The aerogel obtained in step 2 and excess paraffin were placed in a vacuum oven and heated at 70°C for 1 hour. After heating, they were placed in a dryer for cooling to obtain three composite phase change materials, which were respectively recorded as CMP0.5, CMP1.5, and CMP2.5 according to the different montmorillonite contents.
[0035] Under the microscope with the same magnification, the microscopic morphology of CMP0.5, CMP1.5 and CMP2.5 is a compact and uniform lamellar structure, which is conducive to the adhesion of paraffin. And as the montmorillonite content increases, the lamellar structure becomes more compact, as shown in Figure 2. Figure 1 shown.
[0036] The concentration of montmorillonite has an effect on the loading rate. The loading rate of composite nanocellulose-montmorillonite aerogel is about 1000%. Figure 2 shown.
[0037] As a clay mineral material with negative surface charge, montmorillonite has excellent adsorption capacity and moderate thermal conductivity. As the montmorillonite content increases, the thermal conductivity of the nanocellulose-montmorillonite aerogel / paraffin composite phase change material increases, and the heat storage capacity is improved. Figure 3 shown.
[0038] Nanocellulose-montmorillonite aerogel / paraffin composite phase change material, banana nanocellulose aerogel is a compact porous lamellar structure that is conducive to the attachment of paraffin. As the montmorillonite content increases, the paraffin attachment rate gradually increases. The paraffin attachment rates of the embodiments CMP0.5, CMP1.5 and CMP2.5 all reach more than 1000%. The thermal conductivity of the nanocellulose-montmorillonite aerogel / paraffin composite phase change material increases with the increase of the montmorillonite content. The thermal conductivity of pure paraffin is 0.06W / (m·K), while the thermal conductivity of CMP0.5, CMP1.5 and CMP2.5 increases to 0.082, 0.154 and 0.186W / (m·K), respectively. When illuminated, the temperature of the nanocellulose-montmorillonite aerogel / paraffin composite phase change material rises, and the heating rate is significantly higher than that of pure paraffin. The nanocellulose-montmorillonite aerogel / paraffin composite phase change material has a temperature inflection point at the paraffin phase change temperature. After 60 minutes of illumination, the temperature of pure paraffin is only 46.4°C, while the temperatures of CMP0.5 and CMP2.5 reach above 50°C and 70°C, respectively, and the temperature of CMP2.5 reaches above 80°C. When the paraffin undergoes a phase change, the nanocellulose-montmorillonite aerogel / paraffin composite phase change material can store more heat; when the illumination is stopped, the nanocellulose-montmorillonite aerogel / paraffin composite phase change material begins to release heat, the temperature drops rapidly, and a plateau representing heat release appears near the paraffin phase change temperature, while pure paraffin does not. Thanks to the excellent structural design, montmorillonite can improve the heat storage capacity and photothermal conversion performance of the nanocellulose-montmorillonite aerogel / paraffin composite phase change material. The material of the present invention releases heat for up to 8 hours after the illumination ends. Figure 4 As shown in the figure, from top to bottom, they are the temperature change curves of CMP2.5, CMP1.5, CMP0.5, and paraffin. However, the nanocellulose aerogel-graphene / paraffin phase change composite prepared by Shu, the shape-stable phase change material of cellulose nanofiber / carbon nanotube aerogel loaded with paraffin prepared by Shen, and the shape-stable phase change material of cellulose nanofiber / polypyrrole aerogel loaded with paraffin prepared by Xu are only 10min, 16min, and 42min, respectively.
[0039] The present invention adopts paraffin as phase change material and loads it into nanocellulose-montmorillonite aerogel (CM) by vacuum impregnation to prepare a composite phase change material (CMP) with long-term heat release. CMP has good light-heat conversion and suitable thermal conductivity, can store heat energy and release heat energy for a long time, and release heat in a lightless environment after the illumination ends, and the time can reach 8 hours.
[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A preparation method of banana nanocellulose-montmorillonite aerogel / paraffin composite phase change material, comprising the following steps: Step 1: Preparation of banana nanocellulose-montmorillonite aerogel 1g of banana nanocellulose and different masses of montmorillonite were respectively placed in 100ml of deionized water and homogenized for 15min. After the treatment, 0.4g of polyvinyl alcohol was added thereto, and the mixture was placed in a water bath at 90°C and stirred with a magnetic stirrer for 1h to obtain a nanocellulose-montmorillonite suspension. Polyvinyl alcohol can make the nanocellulose and montmorillonite more closely combined. The suspension was placed in a freeze dryer and freeze-dried for 48h at -60°C to obtain a banana nanocellulose-montmorillonite aerogel (CM). Step 2: Preparation of banana nanocellulose-montmorillonite aerogel / paraffin composite phase change material Banana nanocellulose-montmorillonite aerogel (CM) and excess paraffin were placed in a vacuum oven, heated at 70°C for 1 h, and then cooled in a desiccator to obtain a composite phase change material (CMP).