Highly graphitized charcoal-based photo-thermal conversion and storage thermochemical material and preparation method thereof
By loading thermochemical materials onto graphitized biochar-based materials, the problems of low spectral absorption, low thermal conductivity, easy liquid decomposition and leakage, and poor cycle stability of traditional thermochemical materials have been solved, achieving efficient solar thermal conversion and storage.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-04-07
AI Technical Summary
Existing thermochemical materials suffer from low spectral absorption, low thermal conductivity, slow reaction kinetics, easy liquid decomposition and leakage, and poor cycle stability, which limits the efficient capture, conversion and storage of solar energy.
Using highly graphitized biochar-based materials as a carrier, thermochemical materials are loaded onto the graphitized biochar framework with oriented fiber structure and hierarchical pore characteristics, and then vacuum impregnated with metal salt catalysts to prepare composite materials with high spectral absorption, excellent thermal conductivity and mechanical stability.
It achieves efficient full-spectrum photothermal conversion and storage, has a high thermochemical material loading capacity, good cycle stability, and possesses rapid thermochemical reaction kinetics and mechanical structural stability, making it suitable for large-scale applications.
Smart Images
Figure CN121801546A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a biochar-based photothermal conversion and storage thermochemical material, particularly a highly graphitized biochar-based photothermal conversion and storage thermochemical material, and also to a method for preparing the above material. Background Technology
[0002] Solar energy is considered one of the most promising alternative energy sources due to its wide distribution, massive total amount, and green, pollution-free nature. However, the inherent drawbacks of solar radiation, such as its intermittency, fluctuations, and low energy density, severely limit its application potential. Therefore, developing efficient, reliable, and low-cost large-scale solar energy conversion and storage technologies is crucial to overcoming its development bottlenecks and realizing a high proportion of renewable energy applications in the future.
[0003] Thermochemical thermal energy storage technology, relying on reversible chemical reactions to store energy, boasts outstanding advantages such as extremely high energy density (5-10 times that of sensible thermal energy storage) and low heat loss during long-term storage, making it considered one of the most promising thermal energy storage methods. Storing solar energy as thermal energy through thermochemical thermal energy storage and providing continuous supply when needed can effectively alleviate the problems of intermittency, fluctuation, and low energy density in solar energy utilization. However, thermochemical materials are difficult to directly capture and convert solar energy due to their low spectral absorption rates. Furthermore, traditional thermochemical materials generally suffer from poor cycle stability (such as material pulverization and agglomeration), low thermal conductivity, slow reaction kinetics, and susceptibility to liquefaction, severely limiting their practical application. Therefore, there is an urgent need to develop a new type of thermochemical material to overcome its inherent defects and achieve efficient photothermal conversion and storage.
[0004] Combining thermochemical materials with porous supports provides a new approach to solving the above-mentioned bottlenecks. Common porous supports include silica gel, zeolite, diatomaceous earth, vermiculite, and expanded graphite. The following key issues remain in existing technologies: 1) Most existing porous carriers lack a hierarchical pore structure. Macropores are beneficial for loading high-volume thermochemical materials, achieving a higher overall heat storage density; while micropores and mesopores facilitate water vapor transport and diffusion, achieving higher thermochemical reaction kinetics, while preventing salt liquefaction and leakage; 2) Porous carriers generally have poor thermal conductivity (except for expanded graphite), thus greatly limiting the heat transfer rate and heat storage / release power; 3) Common porous carriers have low spectral absorption rates, making it difficult to directly utilize solar thermal energy; 4) Some composite thermochemical heat storage materials have poor mechanical properties, and are prone to breakage and pulverization after multiple heat storage / release cycles, greatly limiting the material's service life. For example, silica gel pulverizes after multiple cycles; composite materials made from porous frameworks such as diatomaceous earth and expanded graphite prepared by granulation and pressing are prone to cracking and breakage after heating cycles. Summary of the Invention
[0005] Purpose of the invention: To address the problems of low spectral absorption, low thermal conductivity, slow reaction kinetics, easy liquid decomposition and leakage, and poor cycle stability of traditional thermochemical materials in the prior art, the purpose of this invention is to provide a novel, inexpensive, highly graphitized biochar-based photothermal conversion and storage thermochemical material and its preparation method, which can directly achieve efficient capture, conversion and storage of solar energy.
[0006] Technical solution: The highly graphitized biochar-based photothermal conversion and storage thermochemical material of the present invention has a structure of graphitized biochar framework supporting thermochemical material, wherein the mass fraction of thermochemical material is 60%~90% and the mass fraction of graphitized biochar framework is 10%~40%; its framework is an oriented fiber structure and exhibits significant hierarchical pore characteristics, wherein the proportion of mesopores mainly of 2-50 nm is significant.
[0007] The thermochemical materials include one or a combination of several of the following: MgCl2 • 6H2O, SrCl2 • 6H2O, SrBr2 • 6H2O, CaCl2 • 6H2O, LiCl • 2H2O, MgSO4 • 7H2O, K2CO3 • 1.5H2O, Na2S • 5H2O, LiOH • H2O, CaBr2 • 6H2O, Ce(SO4)2• 6H2O, LaCl3• 7H2O, LiNO3• 3H2O, Na2S2O3• 5H2O, Zn(NO3)2• 6H2O, CaSO4•2H2O, and Al2(SO4)3•18H2O.
[0008] The graphitized biochar framework has an oriented fibrous structure and a hierarchical porous structure. Using biological solid waste as a precursor, the graphitization degree is greater than 90%. The preparation method includes the following steps:
[0009] (1) The biological solid waste precursor was washed with deionized water and then dried.
[0010] (2) Dissolve the graphitization catalyst in water to prepare a graphite catalytic solution, and soak the biological solid waste precursor in the aqueous solution of the graphitization catalyst for 24 hours and then take it out and dry it.
[0011] (3) Use a tube furnace to heat to 900℃~1500℃ in an argon or nitrogen atmosphere at a heating rate of 5~10℃ / min, and hold for 2~5 hours;
[0012] (4) After cooling to room temperature, soak in hydrochloric acid for 12-24 hours to remove impurities such as catalysts. Then wash repeatedly with deionized water and dry to obtain highly graphitized biochar.
[0013] The biological solid waste precursors include biomass such as pine wood, balsa wood, straw, loofah, coconut shell, sugarcane, or bamboo; the graphitization catalyst is one or more transition element salts containing iron (Fe), cobalt (Co), nickel (Ni), chromium (Cr), or manganese (Mn).
[0014] In step (3), the mass ratio of the biological solid waste precursor to the graphitization catalyst is 1:4 to 1:0.05.
[0015] In step (4), the concentration of hydrochloric acid is 0.1~0.2 mol / L.
[0016] The preparation method of the above-mentioned highly graphitized biochar-based photothermal conversion and storage thermochemical materials includes the following steps:
[0017] (1) Preparation of graphitized biochar framework;
[0018] (2) Dissolve the anhydrous salt of the thermochemical material in water to prepare a saturated solution;
[0019] (3) The graphitized biochar-based framework is placed in a solution and vacuum impregnated for 6 to 12 hours. After drying, dehydration and cooling, a highly graphitized biochar-based photothermal conversion and storage thermochemical material is obtained.
[0020] The vacuum degree during the vacuum impregnation process is 0~10kPa; step (3) is repeated to increase the loading of thermochemical materials on the graphitized biochar framework, and the number of repetitions is 1~3 times.
[0021] Invention Principle: The highly graphitized biochar-based photothermal conversion and storage thermochemical material of this invention uses a highly graphitized biochar framework with a special oriented fiber structure and hierarchical pore characteristics as a carrier. Thermochemical materials are loaded into the fiber structure and hierarchical pore structure of the carrier, wherein the hierarchical pores are mainly mesopores of 2-50 nm. The highly graphitized biochar-based framework is prepared by graphitization catalytic modification of biological precursors. Through the dissolution and release of amorphous carbon by the graphitization catalyst, it can be achieved at a relatively low temperature (1500°C). o Highly graphitized biochar-based frameworks with a graphitization degree of over 90% were obtained (below 3000°C). The ordered graphite crystal structure significantly improved the three-dimensional thermal conductivity and solar spectral absorptivity of the biochar-based framework. However, traditional high-temperature graphitization methods require temperatures reaching approximately 3000°C. o C. Furthermore, the porous properties of biochar-based frameworks can be optimized through metal graphitization catalysis, with mesopore (2-50 nm) pore volumes increasing from 0.039 cm³. 3 / g increased to 0.106 cm 3The high density of biochar not only facilitates the transport and diffusion of water vapor, giving the composite material excellent thermochemical reaction kinetics, but also provides the biochar-based framework with excellent resistance to liquid degradation due to the capillary forces of the mesopores, preventing leakage and spillage of the thermochemical material. The biochar-based framework composite photothermal conversion and storage thermochemical material prepared based on graphitization catalytic modification possesses excellent properties such as high heat storage density, rapid thermochemical reaction kinetics, efficient photothermal capture, rapid heat transfer, and stable mechanical structure.
[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The material of the present invention can realize full-spectrum photothermal conversion and storage, and its light absorption rate is as high as 95%; (2) The loading of thermochemical materials in the material reaches more than 60%; (3) The material of the present invention has good cycle stability and thermochemical reaction rate; (4) The graphitized biochar skeleton in the material is prepared from biological solid waste, the preparation method is simple and the graphitization degree is high, and it has good economic and large-scale preparation potential. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the preparation process of the highly graphitized biochar-based photothermal conversion and storage thermochemical material of the present invention;
[0024] Figure 2 The full-spectrum absorption characteristics of the biochar-based photothermal conversion and storage thermochemical material of the present invention;
[0025] Figure 3 The images are scanning electron microscope (SEM) images of the internal microstructure of the highly graphitized biochar-based photothermal conversion and storage thermochemical material of the present invention, wherein (a) is a longitudinal section SEM image and (b) is a transverse section SEM image.
[0026] Figure 4 The highly graphitized biochar-based photothermal conversion and storage thermochemical material of the present invention and the water vapor adsorption curve (a) and saturated adsorption capacity (b) of the comparative example are shown.
[0027] Figure 5 The thermal conductivity diagrams of the highly graphitized biochar-based photothermal conversion and storage thermochemical material of the present invention and comparative examples are shown.
[0028] Figure 6 The liquid hydrolysis resistance of the highly graphitized biochar-based photothermal conversion and storage thermochemical material of this invention was tested against other materials.
[0029] Figure 7 The structural stability of the highly graphitized biochar-based photothermal conversion and storage thermochemical material of this invention was tested against other materials. Detailed Implementation
[0030] The technical solution of the present invention will be further described below with reference to the embodiments. The test materials used in the embodiments can all be purchased through conventional means.
[0031] Example 1
[0032] The highly graphitized biochar-based photothermal conversion and storage thermochemical material of the present invention is prepared from magnesium sulfate, pine wood, etc., and its preparation method includes the following steps:
[0033] (1) Preparation of highly graphitized biochar-based framework: Pine wood was selected, rinsed with clean water, and dried in an 80℃ drying oven for 2 hours for later use. A graphitization catalyst was prepared by using ferric nitrate and pine wood in a mass ratio of 1:2. The pine wood was immersed in the graphitization catalyst solution for 24 hours, then removed and dried in a 105℃ drying oven for 6 hours. The dried pine wood blocks were placed in a tube furnace for graphitization catalysis, with nitrogen gas introduced at a rate of 50 mL / min, and the temperature increased to 1500℃ at a rate of 10℃ / min. After holding at this temperature for 2 hours, the temperature was lowered to room temperature. 0.2 mol / L dilute hydrochloric acid was prepared, and the graphitized framework was completely immersed in the dilute hydrochloric acid solution. After thorough acid washing and water washing, a highly graphitized biochar-based framework was obtained.
[0034] (2) Preparation of photothermal conversion and storage thermochemical materials: Prepare a 30 wt% magnesium sulfate solution;
[0035] (3) The highly graphitized biochar skeleton was placed in magnesium sulfate solution for vacuum impregnation for 6 hours with a vacuum degree of 0.1 bar; then it was placed in a drying oven at 210°C for 2 hours and cooled to obtain photothermal conversion and storage thermochemical material.
[0036] Example 2
[0037] The highly graphitized biochar-based photothermal conversion and storage thermochemical material of the present invention is prepared from calcium chloride, balsa wood, etc., and its preparation method includes the following steps:
[0038] (1) Preparation of highly graphitized biochar-based framework: Balsa wood was selected, rinsed with clean water, and dried in an 80℃ drying oven for 2 hours for later use. Ferric nitrate and balsa wood were used as graphitization catalysts at a mass ratio of 1:1. Balsa wood was immersed in the graphitization catalyst solution for 24 hours, then removed and dried in a 105℃ drying oven for 6 hours. The dried balsa wood was placed in a tube furnace for graphitization catalysis, with nitrogen gas introduced at a rate of 50 mL / min, and the temperature increased to 1300℃ at a rate of 10℃ / min. After holding at this temperature for 2 hours, the temperature was lowered to room temperature. 0.2 mol / L dilute hydrochloric acid was prepared, and the graphitized framework was completely immersed in the dilute hydrochloric acid solution. After thorough acid washing and water washing, a highly graphitized biochar-based framework was obtained.
[0039] (2) Preparation of photothermal conversion and storage thermochemical materials: Prepare a 45wt% calcium chloride solution;
[0040] (3) The graphitized biochar skeleton was placed in a calcium chloride solution for vacuum impregnation for 6 hours with a vacuum degree of 0.1 bar; then it was placed in a drying oven at 210°C for 2 hours and cooled to obtain a photothermal conversion and storage thermochemical material.
[0041] Example 3
[0042] The highly graphitized biochar-based photothermal conversion and storage thermochemical material of the present invention is prepared from magnesium sulfate, coconut shell, etc., and its preparation method includes the following steps:
[0043] (1) Preparation of highly graphitized biochar-based framework: Coconut shells were selected, rinsed with clean water, and dried in an 80℃ drying oven for 2 hours for later use. The graphitization catalyst was prepared by using nickel nitrite and coconut shells at a mass ratio of 1:2. The coconut shells were immersed in the graphitization catalyst solution for 24 hours, removed, and dried in a 105℃ drying oven for 6 hours. The dried coconut shells were placed in a tube furnace for graphitization catalysis, with nitrogen gas introduced at a rate of 50 mL / min, and the temperature was increased to 1100℃ at a rate of 10℃ / min. After holding at the temperature for 2 hours, the temperature was lowered to room temperature. 0.2 mol / L dilute hydrochloric acid was prepared, and the graphitized framework was completely immersed in the dilute hydrochloric acid solution. After thorough acid washing and water washing, a highly graphitized biochar-based framework was obtained.
[0044] (2) Preparation of photothermal conversion and storage thermochemical materials: Prepare a 30wt% magnesium sulfate solution;
[0045] (3) The graphitized biochar skeleton was placed in magnesium sulfate solution for vacuum impregnation for 6 hours with a vacuum degree of 0.1 bar; then it was placed in a drying oven at 210°C for 2 hours and cooled to obtain photothermal conversion and storage thermochemical materials.
[0046] Comparative Example 1
[0047] A composite material, prepared from magnesium sulfate, pine wood, etc., is prepared by the following steps:
[0048] (1) Preparation of biochar-based framework: Select pine wood, rinse it with clean water and dry it in an 80℃ drying oven for 2 hours. Place the dried pine wood in a tube furnace for carbonization, introduce nitrogen gas at 50 mL / min, heat it to 1500℃ at a rate of 10℃ / min, keep it at the temperature for 2 hours and then cool it to room temperature to obtain biochar-based framework;
[0049] (2) Preparation of photothermal conversion and storage thermochemical materials: Prepare a 30wt% magnesium sulfate solution, place the biochar skeleton in the solution for vacuum impregnation for 6h, vacuum degree 0.1bar; then place it in a drying oven at 210℃ for 2h, and cool it to obtain the product.
[0050] Comparative Example 2
[0051] A composite material, prepared from magnesium sulfate, activated carbon felt, etc., is prepared by means of the following steps:
[0052] Prepare a 30 wt% magnesium sulfate solution, immerse the activated carbon felt in the solution under vacuum for 6 hours at a vacuum degree of 0.1 bar; then dry it in a drying oven at 210℃ for 2 hours, and obtain the final product after cooling.
[0053] Comparative Example 3
[0054] A composite material, prepared from magnesium sulfate, activated carbon particles, etc., is prepared by means of the following steps:
[0055] Prepare a 30 wt% magnesium sulfate solution, place activated carbon particles in the solution and vacuum impregnate for 6 hours at a vacuum degree of 0.1 bar; then dry in a drying oven at 210℃ for 2 hours, and obtain the final product after cooling.
[0056] like Figure 1 As shown, after soaking the biological solid waste precursor in a graphite catalyst, a highly graphitized biochar framework is obtained through high-temperature graphitization catalysis. The graphitized biochar-based framework is then placed in a thermochemical material solution for vacuum impregnation and drying to obtain a highly graphitized biochar-based photothermal conversion and storage thermochemical material.
[0057] like Figure 2 As shown, the material can achieve full-spectrum photothermal conversion and storage, with a light absorption rate as high as 95%.
[0058] like Figure 3 The images shown are scanning electron microscope (SEM) images of the internal microstructure of the material in Example 1. (a) is a longitudinal section SEM image of Example 1, and (b) is a transverse section SEM image of Example 1. Due to the hierarchical porous structure of the highly graphitized biochar framework, this structure facilitates the full filling of the pores by the thermochemical material solution, resulting in a thermochemical material loading rate of over 60%.
[0059] like Figure 4As shown, (a) is the adsorption curve of Example 1 and Comparative Examples 1, 2, and 3, and (b) is the bar chart of saturated adsorption capacity of Example 1 and Comparative Examples 1, 2, and 3. By observing the slope of the adsorption curve in Figure (a), the superior performance of the highly graphitized biochar-based photothermal conversion and storage thermochemical material prepared in Example 1 in improving the thermochemical reaction rate is evident (the curve slope of Example 1 is the best). This indicates that the hierarchical porous structure of the highly graphitized biochar framework has a large specific surface area, and its continuous channel structure can enhance the heat and mass transfer of the reactant gases, thereby improving the thermochemical reaction kinetics and heat storage / release power. Furthermore, from... Figure 4 As can be seen in (b), Example 1 has the highest water vapor saturation adsorption capacity, indicating that the material has the strongest water vapor adsorption capacity and thermochemical heat storage capacity.
[0060] like Figure 5 As shown, the continuous thermally conductive pathway structure of the graphitized biochar framework of the material is beneficial to the heat transfer process, and its thermal conductivity can reach 1.48 W / (m·K).
[0061] like Figure 6 As shown, the hierarchical porous structure of Example 2 exhibits excellent resistance to liquid hydrolysis, preventing CaCl2 leakage above saturated humidity. This demonstrates the resistance to liquid hydrolysis of the highly graphitized biochar-based photothermal conversion and storage thermochemical material of the present invention. In contrast, the CaCl2 / carbon felt material has a porous structure dominated by macropores, which makes it difficult to adsorb liquid-hydrolyzed CaCl2, leading to leakage problems.
[0062] like Figure 7 As shown, Example 2 maintained structural stability after 5 heat storage / heat release cycles, while the CaCl2 / silica gel material showed pulverization after 5 cycles, indicating the structural stability of the highly graphitized biochar-based photothermal conversion and storage thermochemical material of the present invention after multiple cycles.
Claims
1. A highly graphitized biochar-based photothermal conversion and storage thermochemical material, characterized in that, The material is a graphitized biochar framework supported by thermochemical materials, wherein the mass fraction of thermochemical materials is 60% to 90% and the mass fraction of graphitized biochar framework is 10% to 40%, wherein the thermochemical materials are supported in the hierarchical porous structure of graphitized biochar framework.
2. The highly graphitized biochar-based photothermal conversion and storage thermochemical material according to claim 1, characterized in that, The thermochemical materials include one or a combination of several of the following: MgCl2 • 6H2O, SrCl2 • 6H2O, SrBr2 • 6H2O, CaCl2 • 6H2O, MgSO4 • 7H2O, K2CO3 • 1.5H2O, Na2S • 5H2O, LiOH • H2O, LiCl • 2H2O, CaBr2 • 6H2O, Ce(SO4)2 • 6H2O, LaCl3 • 7H2O, LiNO3 • 3H2O, Na2S2O3 • 5H2O, Zn(NO3)2 • 6H2O, CaSO4 • 2H2O, and Al2(SO4)3 • 18H2O.
3. The highly graphitized biochar-based photothermal conversion and storage thermochemical material according to claim 1, characterized in that, The graphitized biochar uses biological solid waste as a precursor, has a graphitization degree of over 90%, and its skeleton is a directional fiber structure with significant hierarchical porosity.
4. The highly graphitized biochar-based photothermal conversion and storage thermochemical material according to claim 3, characterized in that, The preparation method of the graphitized biochar framework includes the following steps: (1) The biological solid waste precursor was washed with deionized water and then dried. (2) Dissolve the graphitization catalyst in water to prepare a graphite catalytic solution, and soak the biological solid waste precursor in the aqueous solution of the graphitization catalyst for 24 hours and then take it out and dry it. (3) Use a tube furnace to heat to 900℃~1500℃ in an argon or nitrogen atmosphere at a heating rate of 5~10℃ / min, and hold for 2~5 hours; (4) After cooling to room temperature, soak in hydrochloric acid for 12-24 hours to remove impurities such as catalysts. Then wash repeatedly with deionized water and dry to obtain highly graphitized biochar.
5. The highly graphitized biochar-based photothermal conversion and storage thermochemical material according to claim 4, characterized in that, The biological solid waste precursors include pine wood, balsa wood, straw, loofah, coconut shell, sugarcane, or bamboo; the graphitization catalyst is one or more transition element salts containing iron, cobalt, nickel, chromium, or manganese.
6. The highly graphitized biochar-based photothermal conversion and storage thermochemical material according to claim 4, characterized in that, In step (3), the mass ratio of the biological solid waste precursor to the graphitization catalyst is 1:4 to 1:0.
05.
7. The highly graphitized biochar-based photothermal conversion and storage thermochemical material according to claim 4, characterized in that, In step (4), the concentration of hydrochloric acid is 0.1~0.2 mol / L.
8. A method for preparing the highly graphitized biochar-based photothermal conversion and storage thermochemical material as described in claim 1, characterized in that, Includes the following steps: (1) Preparation of graphitized biochar framework; (2) Dissolve the anhydrous salt of the thermochemical material in water to prepare a saturated solution; (3) The graphitized biochar-based framework is placed in a solution and vacuum impregnated for 6 to 12 hours. After drying, dehydration and cooling, a highly graphitized biochar-based photothermal conversion and storage thermochemical material is obtained.
9. The preparation method according to claim 8, characterized in that, The vacuum degree during the vacuum impregnation process is 0~10kPa.
10. The preparation method according to claim 8, characterized in that, Repeat step (3) to increase the loading of thermochemical materials on the graphitized biochar framework.