Copper-zinc-based heat storage material and preparation method thereof
By combining the redox cycle of copper-zinc based thermal storage materials with renewable energy electrolysis for hydrogen production, the problems of sintering at high temperatures and poor thermal conductivity of copper-based thermal storage materials have been solved, achieving efficient heat storage and release, extending the cycle life of the materials and improving the stability of the system.
Patent Information
- Application Number
- CN202511098371.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-23
- Publication Date
- 2025-11-18
AI Technical Summary
Existing copper-based thermal storage materials are prone to sintering at high temperatures, have poor thermal conductivity, and poor thermal shock resistance of particles, resulting in short cycle life. Furthermore, the oxides have low heat transfer performance, which affects the stability and efficiency of energy storage systems.
A copper-zinc based thermal storage material is prepared by doping copper oxide with aluminum oxide and zinc active components. The reduction exothermic reaction of copper oxide and the oxidation exothermic reaction of elemental copper are utilized, combined with the hydrogen and oxygen generated in the process of hydrogen production by electrolysis of water in renewable energy, to prepare a porous copper-zinc based material, which prevents sintering and improves thermal conductivity.
It achieves efficient heat storage and release, the material operates stably in the range of 300-900℃, extends cycle life, avoids material breakage and sintering, and improves the energy storage efficiency of the system.
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Figure CN120966437A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of thermal storage materials, and in particular to a copper-zinc based thermal storage material and its preparation method. Background Technology
[0002] Renewable energy, a clean and recyclable energy source, is currently a hot topic in energy research and application. However, renewable energy sources, typically represented by wind, solar, and tidal power, are unstable in time and space due to natural factors. Therefore, achieving stable and continuous output of renewable energy and its full utilization remains a significant challenge. Energy storage technology is a key solution to the mismatch between renewable energy supply and demand in time and space. It utilizes electrical, chemical, mechanical, or thermal energy to store renewable energy and output it stably when needed. One such method is generating electricity from renewable energy, then electrolyzing water to produce hydrogen and oxygen, and utilizing these gases. However, in this approach, while hydrogen is used in many scenarios, the oxygen produced during water electrolysis is mostly released. Furthermore, hydrogen storage and transportation require dehydration and drying. This makes the process complex and inefficient. Therefore, if the hydrogen and oxygen produced during renewable energy generation and water electrolysis are utilized efficiently without complex purification processes, the operating costs of this approach will be significantly reduced. Thermal energy storage technology is an important branch of energy storage technology. Currently, thermal energy storage technology is mainly divided into three forms: sensible heat, latent heat of phase change, and chemical reaction thermal energy storage. Thermochemical energy storage is based on the possible exothermic and endothermic behaviors of chemical reactions to achieve the storage and release of heat.
[0003] Utilizing chemical energy to store renewable energy not only results in high energy density but also allows for long-term storage at high temperatures, facilitating maintenance and management. Among the reported thermochemical reaction thermal storage systems, high-temperature thermochemical thermal storage technology based on metal oxides achieves energy storage through redox reactions between metal oxides of different valence states. This results in high storage temperatures (>800℃), high storage densities (>500kJ / kg), and abundant resources (copper-based, manganese-based, etc.). Among these, copper-based thermal storage materials have a faster reaction rate and higher storage density, but suffer from performance degradation due to sintering at high temperatures. However, these systems share common problems: (1) The redox reaction between copper oxide and elemental copper releases heat during valence state transformation, which can easily lead to the sintering of highly dispersed copper compounds, resulting in performance degradation. (2) The oxides have low thermal conductivity and poor heat transfer. (3) The particles have poor thermal shock resistance. During temperature changes, the temperature fluctuations, coupled with the influence of water vapor, can easily cause particle pulverization, increasing the pressure drop of the thermal storage device and preventing long-term system operation.
[0004] To address these issues, a proposed solution involves doping copper oxide with aluminum oxide to improve its cycling performance. However, this copper oxide-alumina-doped system showed a re-oxidation rate of approximately 80% after 120 cycles, and while the cycle life increased somewhat, it remained unsatisfactory.
[0005] Other heat storage materials are mainly classified into crystalline hydrates, metal hydroxides (Mg(OH)₂, Ca(OH)₂, etc.), metal hydrides, and metal carbonates. Different chemical heat storage materials can be selected based on the operating temperature range of the storage system. Mg(OH)₂ is a commonly studied material in the heat storage temperature range of 200–400℃. However, pure magnesium oxide / magnesium hydroxide heat storage materials have poor heat transfer performance, reducing the overall efficiency of the system. Furthermore, the sintering of magnesium oxide during hydration leads to larger grains and smaller pore volumes, resulting in very low circulating heat storage and release efficiency. Summary of the Invention
[0006] To address the problems existing in current thermal storage materials and circulation systems, this invention combines a copper-zinc based thermal storage material oxidation-reduction cycle with a renewable energy system for producing hydrogen and oxygen through water electrolysis. By utilizing the exothermic reduction of copper oxide and the exothermic oxidation of elemental copper, the hydrogen and oxygen produced during the renewable energy water electrolysis process are fully utilized, achieving highly efficient heat storage. The oxidation-reduction reactions and the amounts of exothermic heat are shown below.
[0007] The reduction of copper oxide by hydrogen (H2) is exothermic, and the equation is:
[0008] CuO + H2 → Cu + H2O (liquid) -128.5 kJ.
[0009] The reaction of copper with oxygen to form copper oxide is also exothermic, and the equation is:
[0010] 2Cu(s)+O2(g)→2CuO(s)-314.6kJ
[0011] This process requires minimal changes to existing energy storage systems and can be directly embedded into the existing system as a module, rapidly improving the energy storage performance of the original system.
[0012] This invention discloses a copper-zinc based thermal storage material, comprising a copper active component, a zinc active component, a carrier, and additives. The carrier is a mixed-phase compound containing aluminum whose specific surface area has been adjusted by a pore-conditioning agent. The additives are alumina formed by impregnating and loading aluminum sol onto the carrier. The additives, copper, and zinc active components are jointly supported on the carrier. The mass percentage of each component in the thermal storage material is as follows:
[0013] Copper active component: 15-35%, zinc active component: 1-8%, carrier and additives: balance.
[0014] Furthermore, the mass percentages of each component in the heat storage material are as follows: copper active component: 20-35%, zinc active component: 3-6%, and carrier and additives: balance.
[0015] The copper active component is a copper oxide, and the zinc active component is a zinc oxide.
[0016] The pore conditioner is calcium hydroxide, which forms calcium hexaaluminate during the high-temperature sintering process with aluminum-containing compounds.
[0017] The aluminum-containing compound used as the carrier is one or more of aluminum hydroxide, boehmite, and γ-phase alumina.
[0018] The carrier is a mixed-phase material, including α-phase alumina, θ-phase alumina and calcium hexaaluminate, wherein the calcium hexaaluminate content is 9%-38%.
[0019] The aluminum-containing compounds used as the support have a specific surface area of 50-190 m² / g without pore conditioning. After pore conditioning, the specific surface area of the support increases to 60-260 m² / g, representing an increase of 10-70 m² / g. Increasing the specific surface area is beneficial for improving the loading of the active component. The calcium hexaaluminate phase content of the support was tested using XRF. Depending on the sintering temperature of the heat storage material, the α-phase can be increased accordingly, resulting in a more stable structure, but the increase in specific surface area will be correspondingly reduced.
[0020] Furthermore, this invention also discloses a method for preparing copper-zinc based thermal storage materials, comprising the following steps:
[0021] (1) According to a certain ratio, the aluminum-containing compound and the pore conditioner are mixed with water evenly, extruded into shape, and then calcined at high temperature to obtain the carrier;
[0022] (2) Prepare copper source solution and zinc source solution, mix them, add aluminum sol and mix evenly, then impregnate the carrier treated in step 1 at room temperature and then dry it.
[0023] (3) The mixture obtained in step (2) is calcined to obtain a copper-zinc based heat storage material;
[0024] In step (1), the feeding ratio of aluminum compound and pore conditioner is: aluminum compound: pore conditioner: Al2O3: CaO = 23.5-72:1 (molar ratio, calculated as Al2O3 and CaO). The solid content of the mixture after adding water in step (1) is 30-60%. The amount of additive added is: carrier: aluminum sol (calculated as alumina) = 8.5-9.5:1 (mass ratio). The aluminum sol is loaded onto the carrier together with the copper-zinc active components, which acts as a separator for the active components, making the heat storage material less prone to sintering.
[0025] The copper source is one or more of copper nitrate, copper chloride, copper acetate, copper oxalate, and copper sulfate. The zinc source is one or more of zinc nitrate, zinc chloride, zinc acetate, zinc oxalate, and zinc sulfate. The concentration of the copper solution is 0.1–1 mol / L, the concentration of the zinc solution is 0.1–1 mol / L, and the atomic ratio of copper to zinc is 1.9–44.5. The amount of carrier 1 added in step (2) is: carrier: copper and zinc oxides (calculated based on the total amount of copper and zinc oxides) = 0.97–3.94:1 (mass ratio).
[0026] In step (2), the impregnation reaction is carried out using equal-volume impregnation. The first impregnation is performed based on the saturated water absorption capacity of the carrier, followed by standing for 2-48 hours. After impregnation, the carrier is dried at 120-140℃ for 2-5 hours. Then, the second impregnation is performed, repeating the first impregnation step multiple times. The amount of the mixture containing copper solution, zinc solution, and aluminum sol added each time is evenly distributed according to the number of impregnation cycles.
[0027] The sintering temperature of step (1) is 900-1350℃ and the sintering time is 1-4 hours; the sintering temperature of step (3) is 400-600℃ and the sintering time is 1-4 hours.
[0028] The beneficial effects of this invention are
[0029] 1. The heat storage body prepared by the present invention has a porous structure. Its supported copper-zinc based material can undergo a reduction reaction with hydrogen and then an oxidation reaction with oxygen (or air). Heat can be released in these reaction processes, realizing the accumulation and storage of heat, and can stably achieve oxidation and reduction cycle for a long time.
[0030] 2. Adding aluminum sol to the impregnation solution allows it to penetrate and impregnate the carrier, immobilizing it together with the active components on the carrier. This acts as a separator for the active components, further preventing sintering.
[0031] 3. The heat storage material of the present invention can operate stably in the range of 300-900℃.
[0032] 4. The entire system can withstand drastic temperature changes, and the heat storage material will not crack during long-term operation, and the copper it supports will not sinter. Attached Figure Description
[0033] Figure 1 These are the XRD patterns of the carriers used in Examples 1, 2, and 3;
[0034] Figure 2 This is the hydrogen consumption of the heat storage material in Example 1 after 70 H2-TPR cycles; Detailed Implementation
[0035] Example 1:
[0036] (1) Boehmite and calcium hydroxide were mixed evenly with water to a solid content of 30%. The feed amount was calculated according to Al2O3:CaO = 24:1 (molar ratio). The mixture was extruded and calcined at 1080℃. The initial calcination temperature was room temperature, the heating rate was 10℃ / min, and the high temperature holding time at 1100℃ was 5h. The resulting mixture had a phase composition of 31.5% (mass percentage) of calcium hexaaluminate phase, with the remainder being α-phase alumina and θ-phase alumina. The XRD analysis spectrum is shown in [reference needed]. Figure 1 The specific surface area was measured to be 100 m² / g using a physical adsorption analyzer.
[0037] (2) Prepare an aqueous solution of 10g copper nitrate (Cu(NO3)2·3H2O) (concentration of 0.4mol / L) and prepare an aqueous solution of 2g zinc nitrate (Zn(NO3)2·6H2O) (concentration of 0.4mol / L). After mixing, add 7.1g aluminum sol (alumina content of 22% in aluminum sol) and mix evenly.
[0038] Based on the saturated water absorption of the carrier, the above mixed impregnation solution was divided into multiple portions and subjected to multiple equal-volume impregnation reactions at room temperature with 14g of carrier 1 treated in step 1. Each time, the mixture was allowed to stand for 12 hours and then dried at 140℃ for 2 hours.
[0039] (3) The mixture obtained in step (2) is calcined at 500°C for 2 hours to obtain copper-zinc based heat storage material.
[0040] Example 2:
[0041] (1) Aluminum hydroxide and calcium hydroxide were mixed evenly with water, with a solid content of 40%. The feed amount was calculated according to Al2O3:CaO = 30:1 (molar ratio). The mixture was extruded and calcined at 1050℃. The initial calcination temperature was room temperature, the heating rate was 10℃ / min, and the high temperature holding time was 8h. The resulting mixture had a phase composition of 22% (mass percentage) calcium hexaaluminate, with the remainder being α-alumina and θ-alumina. The XRD analysis spectrum is shown in [reference needed]. Figure 1 The specific surface area was measured to be 145 m² / g using a physical adsorption analyzer.
[0042] (2) Prepare an aqueous solution of 11.25g copper nitrate (Cu(NO3)2·3H2O) (concentration of 0.5mol / L) and prepare an aqueous solution of 2.5g zinc sulfate (ZnSO4·7H2O) (concentration of 0.5mol / L). After mixing, add 6.1g aluminum sol (alumina content of 22% in aluminum sol) and mix evenly.
[0043] Based on the saturated water absorption of the carrier, the above mixed impregnation solution was divided into multiple portions and subjected to multiple equal-volume impregnation reactions at room temperature with 12.1g of carrier treated in step 1. Each time, the mixture was allowed to stand for 28 hours and then dried at 120℃ for 3 hours.
[0044] (3) The mixture obtained in step (2) is calcined at 500°C for 3 hours to obtain copper-zinc based heat storage material.
[0045] Example 3:
[0046] (1) Boehmite and calcium hydroxide were mixed evenly with water to a solid content of 50%, and the feed ratio was Al2O3:CaO = 40:1 (molar ratio). The mixture was extruded and calcined at 1000℃. The initial calcination temperature was room temperature, the heating rate was 10℃ / min, and the high temperature holding time was 5h. The resulting mixture contained 16% (mass percentage) calcium hexaaluminate, with the remainder being α-alumina and θ-alumina. The XRD analysis spectrum is shown in [reference needed]. Figure 1 The specific surface area was measured to be 205 m² / g using a physical adsorption analyzer.
[0047] (2) Prepare an aqueous solution of 13.75g copper acetate (Cu(NO3)2·3H2O) (concentration of 0.3mol / L) and prepare an aqueous solution of 2.5g zinc nitrate (Zn(NO3)2·6H2O) (concentration of 0.3mol / L). After mixing, add 6.6g aluminum sol (alumina content of 22% in aluminum sol) and mix evenly.
[0048] Based on the saturated water absorption of the carrier, the above mixed impregnation solution was divided into multiple portions and subjected to multiple equal-volume impregnation reactions at room temperature with 13.1g of carrier treated in step 1. Each time, the mixture was allowed to stand for 30 hours and then dried at 120℃ for 4 hours.
[0049] (3) The mixture obtained in step (2) is calcined at 550°C for 2 hours to obtain copper-zinc based heat storage material.
[0050] Figure 1 The XRD patterns were compared with standard patterns. The 2θ angles were: 25.60°, 35.15°, 37.78°, 43.35°, 52.54°, 57.49°, 66.50°, and 68.20°, which belonged to α-Al₂O₃; 20.15°, 22.07°, 32.19°, 32.69°, 34.16°, 36.21°, 39.38°, 42.83°, 45.08°, 60.27°, and 67.31°, which belonged to calcium hexaaluminate; and broad peaks between 44-47° and 66-69°, which belonged to θ-Al₂O₃.
[0051] Example 4:
[0052] The thermal storage material was evaluated using a chemisorption analyzer. 0.3 g (40-60 mesh) of the thermal storage material obtained in Example 1 was loaded into the reactor for H2-TPR testing. The reaction temperature ranged from 50℃ to 750℃, and the hydrogen consumption was calculated. After the reaction, a 5% O2-A2 equilibrium gas was introduced for re-oxidation, followed by another H2-TPR test. The hydrogen consumption was recorded after multiple cycles. Figure 2 The hydrogen consumption of the sample in Example 1 was calculated after 70 H2-TPR cycles. The results of the 70 repeated hydrogen consumption experiments show that the hydrogen consumption decays slowly, indicating that the sample has strong resistance to thermal sintering and good stability.
Claims
1. A copper-zinc based thermal storage material, characterized in that... The material comprises a copper active component, a zinc active component, a carrier, and additives. The carrier is a mixed-phase compound containing aluminum, the specific surface area of which has been adjusted by a pore-conditioning agent. The additives are alumina formed by impregnating and loading aluminum sol onto the carrier. The additives, copper, and zinc active components are supported together on the carrier. The mass percentages of each component in the heat storage material are as follows: Copper active component: 15-35%, zinc active component: 1-8%, carrier and additives: balance.
2. The copper-zinc based thermal storage material according to claim 1, characterized in that... The pore conditioning agent is calcium hydroxide.
3. The copper-zinc based thermal storage material according to claim 2, characterized in that... The aluminum-containing compound is one or more of aluminum hydroxide, boehmite, and γ-phase alumina.
4. The copper-zinc based thermal storage material according to claim 3, characterized in that... The support is a mixed-phase material, including α-phase alumina, θ-phase alumina, and calcium hexaaluminate phase. The specific surface area of the support after pore conditioning is 60-260 m². 2 / g.
5. A method for preparing a copper-zinc based thermal storage material according to any one of claims 1-4, comprising the following steps: (1) According to a certain ratio, the aluminum-containing compound and the pore conditioner are mixed with water evenly, extruded into shape, and then calcined at high temperature to obtain the carrier; (2) Prepare copper source solution and zinc source solution, mix them, add aluminum sol and mix evenly, then impregnate the carrier treated in step 1 at room temperature and then dry it. (3) The mixture obtained in step (2) is calcined to obtain copper-zinc based heat storage material.
6. The copper-zinc based thermal storage material according to claim 5, characterized in that... In step (1), the feeding ratio of aluminum compound and pore conditioner is: aluminum compound: pore conditioner = 23.5-72:1 (molar ratio, calculated based on the Al2O3 and CaO contained).
7. A copper-zinc based heat storage material according to claim 5, characterized in that... The amount of additive added is carrier: aluminum sol (calculated as alumina) = 8.5-9.5:1 (mass ratio).
8. The copper-zinc based thermal storage material according to claim 5, characterized in that... The copper source is one or more of copper nitrate, copper chloride, copper acetate, copper oxalate, and copper sulfate.
9. A copper-zinc based thermal storage material according to claim 5, characterized in that... The zinc source is one or more of zinc nitrate, zinc chloride, zinc acetate, zinc oxalate, and zinc sulfate.
10. The method for preparing the copper-zinc based thermal storage material according to claim 5, characterized in that... The roasting temperature in step (1) is 900-1350℃ and the roasting time is 1-4 hours.
11. The method for preparing the copper-zinc based thermal storage material according to claim 5, characterized in that... The roasting temperature in step (3) is 400-600℃ and the roasting time is 1-4 hours.