Biomass-based shape-stabilized phase change material for building wall thermal insulation and preparation method thereof

Abstract

The application discloses a biomass-based shaped phase change material for building wall thermal insulation and a preparation method thereof, and belongs to the technical field of building energy saving. The biomass-based shaped phase change material for building wall thermal insulation is a porous carrier loaded with a eutectic phase change material. The porous carrier is loaded with the eutectic phase change material in a vacuum-assisted infiltration mode. The porous carrier is obtained by modifying a biomass subjected to acid etching treatment. The biomass-based shaped phase change material for building wall thermal insulation has low cost, is easy to purchase and manufacture, effectively solves the problem of easy leakage of the eutectic phase change material, has good thermal performance, low thermal conductivity and low thermal diffusivity, and can effectively enhance the thermal inertia of the building wall.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building energy saving, in particular to a biomass-based shaped phase change material for building wall thermal insulation and a preparation method thereof. BACKGROUND

[0002] Building energy consumption is increasing day by day, which exacerbates the consumption of traditional energy, causes serious resource shortage and environmental pollution, etc. Therefore, developing building energy saving and consumption reduction technology and improving energy utilization efficiency is an important measure to alleviate energy consumption.

[0003] Phase change materials have high enthalpy and approximately constant temperature during heat storage / release process, and can reduce indoor heat / cold dissipation, stabilize indoor temperature fluctuation and improve building energy system operation efficiency when applied to building walls. Organic solid-liquid phase change materials have the advantages of low supercooling degree, no phase separation, stable chemical properties and small volume change during phase change, and are ideal materials for building wall thermal insulation. However, organic solid-liquid phase change materials are prone to leakage during phase change, which can pollute the wall and cause safety hazards, greatly restricting the practical application of organic solid-liquid phase change materials.

[0004] At present, porous materials are mainly used to adsorb organic phase change materials to prevent leakage, such as using expanded perlite as a carrier to encapsulate myristic acid / paraffin to prepare a shaped phase change material with a melting temperature of 40.39℃ and a melting enthalpy of 106.87J / g, which can be applied to building envelope structures in high temperature areas and has good stability.

[0005] For example, nano-SiO2 is used as a carrier to prepare a composite phase change material, and the corresponding melting temperature and melting enthalpy are 36.2℃ and 182.1J / g, respectively, which makes the thermal inertia of the building maintenance structure better.

[0006] However, whether expanded perlite or SiO2 is used as a carrier, both have high cost, which is not conducive to the large-scale application of building energy saving and maintenance structures. SUMMARY

[0007] An advantage of the present application is to provide a biomass-based shaped phase change material for building wall thermal insulation and a preparation method thereof, wherein the porous carrier is obtained by modifying the biomass treated by acid etching. The biomass is abundant in nature, has the advantages of easy-to-control physical and chemical properties and low price. After removing the minerals by acid etching treatment, the biomass can produce additional pore structure to provide storage space for eutectic phase change materials, thereby solving the problem of easy leakage of eutectic phase change materials. In addition, the biomass treated by acid etching can be doped with nitrogen on the surface of the porous carrier through modification, thereby being able to induce hydrogen bond to enhance the adsorption capacity of eutectic phase change materials and further prevent the leakage of eutectic phase change materials. Therefore, the biomass-based shaped phase change material and the preparation method thereof provided by the present application not only have the advantages of low cost and easy procurement, but also have good thermal performance, low thermal conductivity and low thermal diffusivity, which can effectively prevent or greatly reduce the leakage of eutectic phase change materials and enhance the thermal inertia of building walls.

[0008] To achieve at least one of the above advantages of the present application, in a first aspect, the present application provides a biomass-based shaped phase change material for building wall thermal insulation, wherein the biomass-based shaped phase change material is a porous carrier loaded with eutectic phase change materials, wherein the porous carrier is loaded with the eutectic phase change materials by vacuum-assisted infiltration, and wherein the porous carrier is obtained by modifying the biomass treated by acid etching.

[0009] In a second aspect, the present application further provides a preparation method of the aforementioned biomass-based shaped phase change material for building wall thermal insulation, which comprises the following steps in sequence:

[0010] Mixing at least two organic phase change materials to obtain eutectic phase change materials;

[0011] Mixing the biomass treated by acid etching with a nitrogen-containing compound, and then pyrolyzing in a non-oxidizing atmosphere to obtain a biomass porous carrier;

[0012] Loading the eutectic phase change materials on the biomass porous carrier to obtain the biomass-based shaped phase change material for building wall thermal insulation.

[0013] According to an embodiment of the present application, the organic phase change materials include caprylic acid, capric acid, lauric acid, palmitic acid, myristic acid, stearic acid, myristyl alcohol, palmitol, stearyl alcohol and paraffin.

[0014] According to an embodiment of the present application, the preparation method of the eutectic phase change materials comprises the following steps:

[0015] First, the organic phase change materials are melted and mixed, and then stirred at a high temperature for 2-2.5 hours, wherein the stirring temperature is higher than the melting temperature of the organic phase change materials, and then ultrasonic-assisted mixing is performed;

[0016] The heating / cooling is repeated 4-7 times in the last cycle.

[0017] According to an embodiment of the present application, the biomass is any one or more of a mixture of chitin, lignin, straw, chitosan and chitooligosaccharide.

[0018] According to an embodiment of the present application, the acid etching method comprises:

[0019] The biomass is immersed in an acid solution with a concentration of 0.5-1.2 mol / L for 24 h, wherein the acid solution is sulfuric acid, hydrochloric acid, nitric acid, acetic acid or carbonic acid.

[0020] According to an embodiment of the present application, after the biomass is immersed in the acid solution and left for 24 h, the biomass is washed with deionized water until neutral, and then dried to obtain a biomass precursor, and then the biomass precursor is mixed with a nitrogen-containing compound by mechanical mixing, wherein the nitrogen-containing compound is urea, thiourea, ammonium chloride or ammonium carbonate.

[0021] According to an embodiment of the present application, the pyrolysis in a non-oxidizing atmosphere is specifically that the biomass precursor mixture is placed in a 300-500℃ tube furnace for co-pyrolysis, wherein the tube furnace has a heating rate of 5-10℃ / min, and the biomass porous carrier is obtained after holding for 3-4 h, wherein the non-oxidizing atmosphere uses argon, nitrogen, helium or krypton.

[0022] According to an embodiment of the present application, the loading of the eutectic phase change material on the biomass porous carrier is specifically loading the eutectic phase change material by vacuum-assisted infiltration, comprising the following steps:

[0023] The eutectic phase change material is heated in anhydrous ethanol to above the melting point, then the biomass porous carrier is added and stirred until uniform, and then the ethanol is evaporated, and the mixture is soaked in a vacuum heating box at-0.1 to-0.05 MPa for 6-8 h.

[0024] According to an embodiment of the present application, the mass ratio of the eutectic phase change material to the biomass porous carrier is 1:1-1.5.

[0025] These and other objects, features and advantages of the present application will become apparent with reference to the following detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A comparison diagram of the thermal conductivity, thermal diffusivity and specific heat of the shaped phase change materials prepared in Examples 1-3 and Comparative Examples of the present application is shown.

[0027] Figure 2The shape stability test results of the shaped phase change materials prepared in Examples 1-3 and Comparative Examples of the present application are shown in the schematic diagram.

[0028] Figure 3 The thermal stability test results of the shaped phase change materials prepared in Examples 1-3 and Comparative Examples of the present application are shown in the schematic diagram.

[0029] Figure 4 The cyclic use stability test results of the shaped phase change materials prepared in Example 3 of the present application are shown in the schematic diagram. DETAILED DESCRIPTION

[0030] The following description is provided so that others skilled in the art can have the best possible understanding of the application. The preferred embodiments described in the following description are only examples of the application. Those skilled in the art can make other obvious modifications and variations within the spirit and scope of the application. The basic principles defined in the following description can be applied to other embodiments, variations, improvements, equivalents and other technical solutions without departing from the spirit and scope of the application.

[0031] Those skilled in the art should understand that in the disclosure of the specification, the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are based on the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore, the above terms cannot be understood as a limitation of the application.

[0032] It can be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of one element can be one, and in another embodiment, the number of the element can be multiple, and the term "one" cannot be understood as a limitation on the number.

[0033] Biomass (such as straw, lignin, chitin, etc.) as a natural renewable resource, has a wide source and low cost, at the same time, a large amount of biomass materials are produced in China every year, but most of them are treated as agricultural and forestry waste, not only resulting in high treatment cost, but also easily causing environmental pollution.

[0034] Therefore, can biomass be converted and used for building walls to avoid the risk of leakage of conventional organic solid-liquid phase change materials during phase change?

[0035] The first aspect of the present application provides a biomass-based shaped phase change material for building wall thermal insulation, wherein the biomass-based shaped phase change material is a porous carrier loaded with eutectic phase change material, wherein the porous carrier is loaded with the eutectic phase change material by vacuum-assisted infiltration, and the porous carrier is obtained by modification treatment of biomass treated by acid etching.

[0036] The biomass is pyrolyzed under a non-oxidizing atmosphere to obtain a porous carrier with developed pore structure. The porous carrier is rich in functional groups such as hydroxyl and amino groups, which can form hydrogen bonds with the functional groups of the eutectic phase change material, effectively adsorbing the eutectic phase change material at the micro level. Therefore, the problem of easy leakage of the eutectic phase change material during phase change can be solved, the production cost of the shaped phase change material can be greatly reduced, and the shaped phase change material can be widely applied in building walls. In addition, the biomass-based porous carrier has excellent chemical inertness and good compatibility with the eutectic phase change material, thereby prolonging the service life of the shaped phase change material.

[0037] The second aspect of the present application further provides a preparation method of a biomass-based shaped phase change material for building wall thermal insulation, which comprises the following steps in sequence:

[0038] First, at least two organic phase change materials are mixed to obtain a eutectic phase change material, wherein the organic phase change materials include caprylic acid, capric acid, lauric acid, palmitic acid, myristic acid, stearic acid, myristyl alcohol, palmitol, stearyl alcohol and paraffin wax. That is, two or three, or even four or more of the above organic phase change materials are mixed to obtain the eutectic phase change material. The preparation method of the eutectic phase change material comprises the following steps: melting and mixing the organic phase change materials, then stirring at a high temperature for 2-2.5 hours, wherein the stirring temperature is higher than the melting temperature of the organic phase change materials, then ultrasonic-assisted mixing, and then cyclic heating / cooling 4-7 times, wherein one cycle is heating first and then cooling, and the heating and cooling cycles are repeated 2, 3, 4 or even 10 times in the present application.

[0039] Then, the biomass treated by acid etching is mixed with a nitrogen-containing compound, and then pyrolyzed in a non-oxidizing atmosphere to obtain a biomass porous carrier. The biomass is any one or a mixture of more than one of chitin, lignin, straw, chitosan and chitooligosaccharide. The acid etching method comprises: immersing the biomass in an acid solution for 24 hours, and the concentration of the acid solution is 0.5-1.2 mol / L. The acid solution is sulfuric acid, hydrochloric acid, nitric acid, acetic acid or carbonic acid. Therefore, the mineral matter in the biomass can be removed by the acid solution to produce pore structure and provide storage space for the eutectic phase change material, thereby solving the problem of easy leakage of the eutectic phase change material.

[0040] Finally, the eutectic phase change material is loaded on the biomass porous carrier to obtain the biomass-based shaped phase change material for building wall thermal insulation.

[0041] Preferably, the biomass is subjected to acid immersion and then washed with deionized water to neutralize after standing for 24 hours, and then dried to obtain a biomass precursor, and then the biomass precursor is mixed with a nitrogen-containing compound by mechanical mixing, wherein the nitrogen-containing compound is urea, thiourea, ammonium chloride or ammonium carbonate, and the nitrogen-containing compound and the biomass precursor are co-pyrolyzed in a non-oxidizing atmosphere, and the nitrogen atoms can be doped on the surface of the biomass porous carrier to induce hydrogen bonding, thereby enhancing the adsorption capacity of the eutectic phase change material and further preventing leakage of the eutectic phase change material.

[0042] Further preferably, the co-pyrolysis in a non-oxidizing atmosphere is specifically placing the biomass precursor mixture in a tube furnace at 300-500°C, and the tube furnace has a heating rate of 5-10°C / min, and the biomass porous carrier is obtained after holding for 3-4 hours, and the non-oxidizing atmosphere uses argon, nitrogen, helium or krypton.

[0043] Preferably, the loading of the eutectic phase change material on the biomass porous carrier is specifically loading the eutectic phase change material by vacuum-assisted infiltration, including the following steps:

[0044] The eutectic phase change material is heated to above the melting point in anhydrous ethanol, and then the biomass porous carrier is added and stirred until uniform, and then the ethanol is evaporated, and the mixture is soaked in a vacuum heating box at -0.1 to -0.05 MPa for 6-8 hours.

[0045] Preferably, the mass ratio of the eutectic phase change material to the biomass porous carrier is 1:1-1.5.

[0046] The detailed preparation method of the biomass-based shaped phase change material for building wall thermal insulation is as follows:

[0047] (1) 10 g of biomass is immersed in an acid solution of 0.5-1.2 mol / L and stirred for 30-100 min, and then left to stand at room temperature for 24 hours, and then washed with deionized water to neutralize, and dried to obtain a biomass precursor;

[0048] (2) The biomass precursor obtained in step (1) is mixed with a modifier in a mortar at a mass ratio of 1:1-1.5 and continuously ground for 25-40 min to obtain a biomass precursor mixture;

[0049] (3) The biomass precursor mixture obtained in step (2) is placed in a tube furnace, a non-oxidizing gas flow of 100 mL / min is set, and linear heating from room temperature to 300-500℃ at a rate of 5-10℃ / min is performed, and after holding for 3-4 h, natural cooling to room temperature is performed to obtain a biomass porous carrier;

[0050] (4) After melting, the organic phase change material A and the organic phase change material B are poured into a beaker, stirred at 80℃ for 2-2.5 h with ultrasonic-assisted mixing, and then heated / cooled 4-7 times in cycles to obtain a eutectic phase change material;

[0051] (5) The eutectic phase change material is added to ethanol, heated at 50℃ for 30 min until completely melted, and then the porous carrier is added according to a mass ratio of 1:1-1.5 of the eutectic phase change material to the biomass porous carrier, stirred for 3-4 h, and then the suspension is evaporated at 80℃ to remove ethanol, and after cooling to room temperature, a solid mixture is obtained;

[0052] (6) The mixture obtained in step (5) is heated in a vacuum heating box at 50℃ for 30 min, the pressure in the box is reduced to -0.1 to -0.05 MPa, and vacuum infiltration is performed for 6-8 h;

[0053] (7) The mixture in step (6) is naturally cooled under normal pressure, and then broken using a breaker to obtain a biomass-based shaped phase change material for building wall thermal insulation.

[0054] Example 1

[0055] (1) 10 g of chitin is immersed in a 1 mol / L hydrochloric acid solution and stirred for 60 min, then left to stand at room temperature for 24 h, and then washed with deionized water until neutral, and dried to obtain a chitin precursor;

[0056] (2) The chitin precursor obtained in step (1) is continuously ground in a mortar with urea at a mass ratio of 1:0.5 for 25 min until mixed uniformly to obtain a chitin precursor mixture;

[0057] (3) The chitin precursor mixture obtained in step (2) is placed in a tube furnace, a nitrogen flow of 100 mL / min is set, and linear heating from room temperature to 400℃ at a rate of 5℃ / min is performed, and after holding for 3 h, natural cooling to room temperature is performed to obtain a chitin porous carrier CC;

[0058] (4) After melting, decanoic acid and stearic acid are poured into a beaker at a mass ratio of 4:1, stirred at 80℃ for 2 h with ultrasonic-assisted mixing, and then heated / cooled 4 times in cycles to obtain a eutectic phase change material CA-SA;

[0059] (5) LA-SA was added to ethanol, heated at 50°C for 30 min until completely melted, then CC was added according to the mass ratio of eutectic phase change material to porous carrier being 1:1, stirred for 4 h, and then the suspension was evaporated at 80°C to dry the ethanol, and a solid mixture was obtained after cooling to room temperature;

[0060] (6) The mixture obtained in step (5) was heated in a vacuum heating box at 50°C for 30 min, the pressure in the box was reduced to -0.05 MPa, and vacuum infiltration was performed for 8 h;

[0061] (7) The mixture in step (6) was naturally cooled under normal pressure, and then broken using a breaker to obtain a chitin-based shape-stabilized phase change material CC / CA-SA for building wall thermal insulation.

[0062] Example 2

[0063] (1) 10 g of lignin was immersed in a 1 mol / L hydrochloric acid solution and stirred for 100 min, then left to stand at room temperature for 24 h, and then washed with deionized water until the lignin was neutral, and dried to obtain a lignin precursor;

[0064] (2) The lignin precursor obtained in step (1) was continuously ground in a mortar with ammonium chloride according to a mass ratio of 1:3 for 40 min until the mixture was uniform, to obtain a lignin precursor mixture;

[0065] (3) The lignin precursor mixture obtained in step (2) was placed in a tube furnace, the nitrogen flow was set to 100 mL / min, and the temperature was linearly increased from room temperature to 500°C at a rate of 8°C / min, and then naturally cooled to room temperature after holding for 4 h to obtain a lignin porous carrier CL;

[0066] (4) Lauric acid and stearic acid were melted, poured into a beaker according to a mass ratio of 3:1, stirred at 80°C for 2.5 h with ultrasonic assistance, and then heated / cooled 7 times in a cycle to obtain a eutectic phase change material LA-SA;

[0067] (5) LA-SA was added to ethanol, heated at 50°C for 30 min until completely melted, then CL was added according to the mass ratio of eutectic phase change material to porous carrier being 1:1, stirred for 3 h, and then the solution was evaporated at 80°C to dry the ethanol, and a solid mixture was obtained after cooling to room temperature;

[0068] (6) The mixture obtained in step (5) was heated in a vacuum heating box at 50°C for 30 min, the pressure in the box was reduced to -0.08 MPa, and vacuum infiltration was performed for 6 h;

[0069] (7) The mixture in step (6) is naturally cooled under normal pressure, and then broken by using a breaker to obtain a lignin-based shaped phase change material CL / LA-SA for building wall thermal insulation.

[0070] Example 3

[0071] (1) 10 g of straw was immersed in a 1 mol / L acidic solution and stirred for 60 min, then left to stand at room temperature for 24 h, and then washed with deionized water until neutral, and dried to obtain a straw precursor;

[0072] (2) The straw precursor obtained in step (1) was continuously ground in a mortar with ammonium chloride at a mass ratio of 1:3 for 30 min until mixed uniformly to obtain a straw precursor mixture;

[0073] (3) The straw porous carrier precursor mixture obtained in step (2) was placed in a tube furnace, and the nitrogen flow was set to 100 mL / min, and linearly heated from room temperature to 400℃ at a rate of 10℃ / min, and then naturally cooled to room temperature after holding for 3 h to obtain a straw porous carrier CS;

[0074] (4) Lauric acid and stearic acid were melted, poured into a beaker at a mass ratio of 3:1, stirred at 80℃ for 2 h with ultrasonic assisted mixing, and then heated / cooled 6 times in cycles to obtain a eutectic phase change material LA-SA;

[0075] (5) The LA-SA was added to ethanol, heated at 50℃ for 30 min until completely melted, and then the porous carrier was added at a mass ratio of eutectic phase change material to porous carrier of 2:3, stirred for 4 h, and then the solution was evaporated at 80℃ to remove ethanol, and cooled to room temperature to obtain a solid mixture;

[0076] (6) The mixture obtained in step (5) was heated in a vacuum heating box at 50℃ for 30 min, and the pressure in the box was reduced to -0.1 MPa, and vacuum infiltrated for 6 h;

[0077] (7) The mixture in step (6) was naturally cooled under normal pressure, and then broken by using a breaker to obtain a straw-based shaped phase change material CS / LA-SA for building wall thermal insulation.

[0078] Comparative Example

[0079] To further demonstrate the superiority of the preparation process and material performance in the present application, a shaped phase change material was prepared according to the method of Example 3, except that the straw porous carrier was not subjected to acid etching and modification treatment, and the specific steps were as follows:

[0080] (1) 10 g of straw was continuously ground in a mortar for 30 min and then placed in a tube furnace. The nitrogen flow rate was set to 100 mL / min, and the temperature was linearly increased from room temperature to 400°C at a rate of 10°C / min. After holding for 3 h, the temperature was naturally cooled to room temperature to obtain the unmodified straw porous carrier NS.

[0081] (2) After melting lauric acid and stearic acid, they were poured into a beaker according to a mass ratio of 3:1, stirred at 80°C for 2 h with ultrasonic-assisted mixing, and then heated / cooled 6 times in a cycle to obtain the eutectic phase change material LA-SA.

[0082] (3) After LA-SA was added to ethanol and heated at 50°C for 30 min until completely melted, the porous carrier was added according to a mass ratio of eutectic phase change material to porous carrier of 2:3, stirred for 4 h, and then the solution was evaporated at 80°C to remove ethanol. After cooling to room temperature, a solid mixture was obtained.

[0083] (4) The mixture obtained in step (3) was heated in a vacuum heating box at 50°C for 30 min, the pressure in the box was reduced to -0.1 MPa, and vacuum infiltration was performed for 6 h.

[0084] (5) The mixture in step (4) was naturally cooled under normal pressure, and then crushed using a crusher to obtain the unmodified straw-based shaped phase change material NS / LA-SA.

[0085] Thermal performance test

[0086] (1) The biomass-based shaped phase change materials prepared in Examples 1-3 were subjected to thermal performance testing: the shaped phase change material was placed in a differential scanning calorimeter (DSC), and the temperature of the shaped phase change material was increased from 25°C to 60°C at a set heating rate and atmosphere (5°C / min; nitrogen) to obtain a DSC curve. The thermal performance parameters of the shaped phase change material were calculated based on the DSC curve, as shown in Table 1. The melting temperature of CC / CA-SA was 26.2°C, which was within the comfortable temperature range of the human body; the melting enthalpy was 58.55 J / g, which was suitable for use in building walls to suppress indoor temperature fluctuations. The melting temperatures of CL / LA-SA and CS / LA-SA were 32.4°C and 31.2°C, respectively, and the melting enthalpies were 74.88 J / g and 62.61 J / g, respectively, which were suitable for use in building walls in high-temperature regions.

[0087] (2) The biomass-based shaped phase change materials obtained in Examples 1-3 were subjected to thermal constant testing. The test results are as follows Figure 1As shown, the thermal conductivity of CC / CA-SA is 0.262 W / (m·K), the thermal conductivity of CL / LA-SA is 0.287 W / (m·K), and the thermal conductivity of CS / LA-SA is 0.220 W / (m·K), which indicates that the prepared biomass-based shaped phase change material has very low thermal conductivity and low heat transfer rate, and can be completely used for building wall insulation, which is beneficial to prevent heat / cold dissipation and enhance the thermal inertia of building walls.

[0088] (3) The shape stability of the biomass-based shaped phase change materials obtained in Examples 1-3 was detected by heating experiments. The eutectic phase change material and the biomass-based shaped phase change material were heated in a 50°C drying oven for 2 h, and the shape stability was detected by Figure 2 It can be seen that the shape of the eutectic phase change material changes obviously after heating, and there is a serious leakage problem, while the shape of the prepared biomass-based shaped phase change material does not change after heating, and there is no leakage phenomenon or only a very small leakage phenomenon, which indicates that the biomass porous carrier solves the problem of easy leakage of the eutectic phase change material.

[0089] (4) The thermal stability of the biomass-based shaped phase change materials obtained in Examples 1-3 was evaluated by thermogravimetric analysis (TGA). From Figure 3 It can be seen that the TG curves of CC / CA-SA, CL / LA-SA and CS / LA-SA have weight loss temperatures of 148.5°C, 176.5°C and 166.2°C, respectively, which indicates that the biomass-based shaped phase change material does not have weight loss within its melting temperature range, and has good thermal stability.

[0090] (5) The straw-based shaped phase change material in Example 3 was subjected to cyclic heating / cooling treatment, and its cyclic use was analyzed. From Figure 4 It can be seen that after 200 cycles of heating / cooling, the DSC curves of the material are almost the same, and the melting enthalpy of CS / LA-SA before and after the cycle is only reduced by 0.72%, and the thermal performance remains stable, which reflects that the straw-based shaped phase change material has an ideal service life.

[0091] (6) Comparison of CS / LA-SA and NS / LA-SA in Example 3 and Comparative Example. From Figure 1 and Figure 2It can be seen that the thermal performance parameters of CS / LA-SA and NS / LA-SA are similar, but the thermal conductivity and thermal diffusivity of NS / LA-SA are higher, and obvious leakage occurs after heating. It can be seen that the biggest feature of the biomass-based shaped phase change material for building wall insulation is that the biomass porous carrier treated by acid etching and modification can ensure the thermal performance of the shaped phase change material, reduce the thermal conductivity and thermal diffusivity, effectively prevent the leakage of eutectic phase change material, and is more conducive to reducing the indoor heat / cold dissipation, thereby enhancing the thermal inertia of the building wall.

[0092] Table 1 Thermal performance parameters of the shaped phase change materials in Examples 1-3 and Comparative Examples

[0093]

[0094] Those skilled in the art will understand that the above description and the embodiments of the present application shown in the drawings are only examples and do not limit the present application. The advantages of the present application have been fully and effectively achieved. The functions and structural principles of the present application have been shown and described in the embodiments, and the embodiments of the present application can be any modification or modification without departing from the principles.

Claims

1. A biomass-based form-stable phase change material for building wall thermal insulation, characterized in that, The biomass-based shaped phase change material is a porous carrier loaded with eutectic phase change material, wherein the porous carrier is loaded with the eutectic phase change material by vacuum-assisted infiltration, and the porous carrier is obtained by modification treatment of biomass subjected to acid etching treatment. The preparation method of the biomass-based shaped phase change material for building wall thermal insulation comprises the following steps in sequence: mixing at least two organic phase change materials to obtain eutectic phase change material; mixing biomass subjected to acid etching treatment with nitrogen-containing compounds, and then pyrolyzing in a non-oxidizing atmosphere to obtain a biomass porous carrier; loading the eutectic phase change material on the biomass porous carrier to obtain the biomass-based shaped phase change material for building wall thermal insulation; The organic phase change material includes octanoic acid, decanoic acid, lauric acid, palmitic acid, myristic acid, stearic acid, myristyl alcohol, palmitol, stearyl alcohol and paraffin.

2. The method for preparing the biomass-based shaped phase change material for building wall thermal insulation according to claim 1, characterized in that, The preparation method of the biomass-based shaped phase change material for building wall thermal insulation comprises the following steps in sequence: mixing at least two organic phase change materials to obtain eutectic phase change material; mixing biomass subjected to acid etching treatment with nitrogen-containing compounds, and then pyrolyzing in a non-oxidizing atmosphere to obtain a biomass porous carrier; loading the eutectic phase change material on the biomass porous carrier to obtain the biomass-based shaped phase change material for building wall thermal insulation.

3. The preparation method according to claim 2, characterized in that, The organic phase change material includes octanoic acid, decanoic acid, lauric acid, palmitic acid, myristic acid, stearic acid, myristyl alcohol, palmitol, stearyl alcohol and paraffin.

4. The preparation method according to claim 3, characterized in that, The preparation method of the eutectic phase change material comprises the following steps: firstly, melting and mixing the organic phase change material, then stirring at high temperature for 2-2.5 hours, wherein the stirring temperature is higher than the melting temperature of the organic phase change material, and then ultrasonic-assisted mixing; finally, cyclic heating / cooling 4-7 times.

5. The preparation method according to claim 2, characterized in that, The biomass is any one or a mixture of more than one of chitin, lignin, straw, chitosan and chitooligosaccharide.

6. The preparation method according to claim 5, characterized in that, The acid etching treatment method comprises: immersing the biomass in an acidic solution for 24 hours, and the concentration of the acidic solution is 0.5-1.2 mol / L, wherein the acidic solution is sulfuric acid, hydrochloric acid, nitric acid, acetic acid or carbonic acid.

7. The preparation method according to claim 6, characterized in that, After the biomass is subjected to acid immersion and is left for 24 hours, it is washed with deionized water until it is neutral, and then it is dried to obtain a biomass precursor, and then the biomass precursor is mixed with nitrogen-containing compounds by mechanical mixing, wherein the nitrogen-containing compounds are urea, thiourea, ammonium chloride or ammonium carbonate.

8. The method of claim 7, wherein the step of preparing is characterized by, The pyrolysis in a non-oxidizing atmosphere is specifically placing the biomass precursor mixture in a 300-500℃ tube furnace for co-pyrolysis, wherein the heating rate of the tube furnace is 5-10℃ / min, and the biomass porous carrier is obtained after holding for 3-4 hours, and the non-oxidizing atmosphere uses argon, nitrogen, helium or krypton.

9. The preparation method according to claim 2, characterized in that, The loading of the eutectic phase change material on the biomass porous carrier is specifically loading the eutectic phase change material by vacuum-assisted infiltration, The preparation method of the biomass-based shaped phase change material for building wall thermal insulation comprises the following steps in sequence: mixing at least two organic phase change materials to obtain eutectic phase change material; mixing biomass subjected to acid etching treatment with nitrogen-containing compounds, and then pyrolyzing in a non-oxidizing atmosphere to obtain a biomass porous carrier; loading the eutectic phase change material on the biomass porous carrier to obtain the biomass-based shaped phase change material for building wall thermal insulation. The eutectic phase change material is heated to above the melting point in anhydrous ethanol, then the biomass porous carrier is added and stirred until uniform, and then the ethanol is evaporated, and the mixture is soaked in a vacuum heating box at-0.1 to-0.05 MPa for 6 to 8 hours.

10. The method of claim 9, wherein the step of preparing is characterized by, The mass ratio of the eutectic phase change material to the biomass porous carrier is 1:1 to 1.5.

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