A manganese-iron-aluminum co-doped calcium oxide material, a preparation method therefor and applications thereof

Abstract

The application discloses a manganese-iron-aluminum co-doped calcium oxide material and a preparation method and application thereof, and comprises the following steps: (1) preparing a manganese-iron-aluminum co-doped calcium oxide material precursor; (2) calcining the precursor obtained in the step (1) to obtain the co-doped calcium oxide material, which is CaalphaMnbetaFegAldelta, wherein alpha, beta, gamma and delta are molar ratios of corresponding metal elements in raw materials. The doped elements in the material prepared by the method are uniformly dispersed in the material, and the material exhibits long-time stability in the reaction process. The method can be applied to the preparation of most metal oxides which need to be co-doped with one or more metal elements.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of solar photo-thermal power generation, and particularly relates to a manganese-iron-aluminum co-doped calcium oxide material and a preparation method and application thereof. BACKGROUND

[0002] New energy such as solar energy, wind energy and tidal energy has quite high research value, but has obvious defects such as low energy density, discontinuity and instability, and therefore needs to be combined with energy storage. In actual application, heat energy can be stored into a system in three ways: sensible heat storage (SHS) realizes energy storage by heating a storage medium, and releases heat generated by cooling of the medium to generate power. Latent heat storage (LHS) realizes energy storage and release through a phase change process of a storage medium. Thermochemical energy storage (TCES) is based on a reversible thermochemical reaction, and realizes energy storage and release through endothermic and exothermic processes of the reversible reaction. Compared with the other two storage methods, the TCES method has the advantages of high energy storage density, wide working temperature range and long storage time, and is particularly suitable for concentrated solar power generation.

[0003] The CaCO3 / CaO cyclic energy storage material itself has a relatively high energy storage density, but its large-scale application still faces many challenges, such as easy sintering of the material due to the reaction at high temperature, resulting in a decrease in the energy storage density, etc. The current CaCO3 / CaO cyclic energy storage material usually uses a mechanical mixing method to realize element doping, for example, a ball mill is used to mechanically mix raw materials, and the energy storage material prepared by this kind of method generally has problems such as uneven distribution of elements, easy sintering and deactivation under high temperature conditions, and the material performance usually starts to decrease after stable maintenance for dozens of cycles. SUMMARY

[0004] In order to overcome the defects existing in the prior art, the application provides a manganese-iron-aluminum co-doped calcium oxide material and a preparation method and application thereof. The doped elements in the material prepared by the method are uniformly dispersed in the material, and the material exhibits long-term stability during the reaction process. The method can be applied to the preparation of most metal oxides which need to be co-doped with one or several metal elements.

[0005] In order to achieve the above purpose, the technical scheme adopted by the application is:

[0006] A manganese-iron-aluminum co-doped calcium oxide material, comprising calcium oxide and a composite oxide of calcium, manganese, iron and aluminum, wherein the manganese-iron-aluminum co-doped calcium oxide material is obtained by calcining a mixture of metal precursors Ca(NO3)2, Mn(NO3)2, Fe(NO3)3 and Al(NO3)3 with a reducing agent and a binder, and has a formula of CaαMnβFeγAlδ, wherein α, β, γ and δ are the molar ratios of the corresponding metal elements in the raw materials.

[0007] The manganese-iron-aluminum co-doped calcium oxide material has a sponge-like porous bulk body formed by aggregation of a large number of 1-2 nm particles.

[0008] The molar ratio of each doping element to calcium element is 0-1:5.

[0009] The manganese-iron-aluminum co-doped calcium oxide material has high activity and good stability in the energy storage cycle.

[0010] The composite oxide plays a role in improving the stability and light absorption of the material.

[0011] A preparation method of a manganese-iron-aluminum co-doped calcium oxide material, comprising the following steps:

[0012] (1) preparing a manganese-iron-aluminum co-doped calcium oxide material precursor;

[0013] (2) calcining the precursor obtained in step (1) to obtain the manganese-iron-aluminum co-doped calcium oxide material.

[0014] In step (1), the oxidizing calcium precursor, the doping metal (manganese, iron and aluminum) precursor, the reducing agent and the binder are placed in a mortar and continuously ground until the raw materials form a uniform paste, thereby obtaining the manganese-iron-aluminum co-doped calcium oxide material precursor.

[0015] In step (1), the mass ratio of the reducing agent to the binder is 1:1-1.25, and the amount of the binder added is preferably such that the raw materials are uniformly mixed into a paste without being dispersed into powder or flowing liquid.

[0016] In step (1), the molar ratio of each doping element to calcium element is 0-1:5.

[0017] In step (1), the oxidizing calcium precursor includes but is not limited to calcium nitrate and its hydrate, and can also be one of calcium chloride, calcium bromide, calcium acetate, calcium permanganate and calcium gluconate. When a calcium salt other than calcium nitrate is used, 2 times the amount of nitric acid or ammonium nitrate of the calcium element needs to be additionally added as an oxidizing agent.

[0018] The metal precursor doped in step (1) includes but is not limited to nitrates of manganese, iron and aluminum and common hydrates thereof, and can also be one or more of water-soluble salts thereof.

[0019] The reducing agent in step (1) is used to promote the combustion reaction of the precursor. The reducing agent is one of reducing organic matters such as urea, aminoacetic acid, hydrazine, citric acid, glucose, sucrose, carbohydrazide, oxalyl dihydrazide, acetylacetone and hexamethylenetetramine.

[0020] The binder in step (1) is water-soluble starch.

[0021] In step (2), the paste-like precursor obtained in step (1) is transferred to a boat and subjected to two-stage calcination in a muffle furnace under an air atmosphere, first heated to 500-800 DEG C and kept for 20 min-2 h, and then heated to 850-900 DEG C and calcined for 2-4 h.

[0022] In the first sintering step, the mixture is combusted in an air environment at a temperature of 500 DEG C or higher to remove the organic matter to form a powder; in the second sintering step, the powder is sintered in an oxygen environment at a temperature of 850 DEG C or higher to form a composite metal oxide.

[0023] The manganese-iron-aluminum co-doped calcium oxide material can realize thermochemical energy storage cycle under high temperature conditions.

[0024] The manganese-iron-aluminum co-doped calcium oxide material is applied to solar thermochemical energy storage, and the energy storage principle is that heat energy is converted into chemical energy for storage through the process of CaCO3 calcination and decomposition into CaO and CO2, energy is released through the process of recombination of CaO and CO2 to form CaCO3, manganese, iron and aluminum elements do not directly participate in the energy storage reaction, and mainly play a role in improving the stability of the material, and the specific reaction is:

[0025]

[0026] The application of the manganese-iron-aluminum co-doped calcium oxide material is to carry out energy storage cycle performance test under an Ar-CO2 atmosphere at 800 DEG C. Taking a typical test process as an example, 0.1 g of sample is loaded into a quartz tube reactor, Ar (50 sccm) is continuously introduced as a carrier gas, the tube furnace is heated, the heating rate is 10-15 DEG C / min, CO2 (50 sccm) is introduced for the first carbonation after being raised to 800 DEG C, the carbonation process lasts for 10 min, then the CO2 gas is cut off, and a calcination process of 6 min is started, that is, one cycle is completed, the above carbonation-calcination cycle is repeated, and the output gas component is detected by using an online mass spectrometer.

[0027] The beneficial effects of the present application are:

[0028] In order to realize long-period stability of the solar energy thermo-chemical energy storage material, the self-combustion method is used for material preparation, the uniform distribution of the doped elements in the calcium oxide material is realized, and the gas generated in the combustion process is used to form uniform pores in the material, the doped elements and the calcium oxide form stable composite oxides after calcination, the sintering resistance of the material is significantly improved, and the energy storage performance of the material is significantly improved. At the same time, the addition of manganese and iron elements significantly improves the light absorption capacity of the material. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is an XRD schematic diagram of Ca10Mn1Al1.

[0030] Figure 2 is an absorbance comparison diagram of CaO, Ca10Mn1Al1, Ca10Mn1Fe1Al1.

[0031] Figure 3 is a stability schematic diagram of Ca10Mn1Fe1Al1 at 800 DEG C for 400 energy storage cycles.

[0032] Figure 4 is a stability schematic diagram of Ca10Mn1Fe1Al2 at 800 DEG C for 1900 energy storage cycles.

[0033] Figure 5 is an SEM schematic diagram of Ca10Mn1Fe1Al1.

[0034] Figure 6 is an EDS-mapping schematic diagram of Ca10Mn1Fe1Al1. DETAILED DESCRIPTION

[0035] The application will be further described in detail below with reference to the accompanying drawings.

[0036] Example 1

[0037] The application provides a manganese-iron-aluminum co-doped calcium oxide material and a preparation method thereof, which comprises the following steps:

[0038] (1) The co-doped calcium oxide material precursor with 0 content of iron element: 0.5668g of Ca(NO)2·4H2O, 0.0598g of Mn(NO)2·4H2O, 0.09g of Al(NO)3·9H2O, 0.776g of urea and 0.97g of water-soluble starch are weighed in a mortar, and continuous grinding is performed until the raw materials become paste, and then the grinding is continuously performed for a period of time until the materials are uniformly mixed.

[0039] (2) The paste obtained in (1) is transferred to a porcelain boat and placed in a muffle furnace for continuous two-stage calcination under an air atmosphere (ramped to 800 DEG C at a rate of 10 DEG C / min, held for 20 min; then ramped to 900 DEG C at a rate of 10 DEG C / min, calcined for 2 h), to obtain Ca10Mn1Al1.

[0040] Ca10Mn1Al1 is a brown dispersed powder in macroscopic morphology, which can be used for solar thermochemical energy storage and can be subjected to energy storage cycle performance test at 800 DEG C under an Ar-CO2 atmosphere.

[0041] Example 2

[0042] The application provides a manganese-iron-aluminum co-doped calcium oxide material and a preparation method thereof, which comprises the following steps:

[0043] (1) A co-doped calcium oxide material precursor with an aluminum element content of 0: 0.5668 g of Ca(NO)2.4H2O, 0.0598 g of Mn(NO)2.4H2O, 0.097 g of Fe(NO)3.9H2O, 0.776 g of urea and 0.97 g of water-soluble starch are weighed in a mortar, and grinding is continuously performed until the raw materials become a paste, and the grinding is continuously performed for a period of time until the raw materials are uniformly mixed.

[0044] (2) The paste obtained in (1) is transferred to a porcelain boat and placed in a muffle furnace for continuous two-stage calcination under an air atmosphere (ramped to 800 DEG C at a rate of 10 DEG C / min, held for 20 min; then ramped to 900 DEG C at a rate of 10 DEG C / min, calcined for 2 h), to obtain Ca10Mn1Fe1.

[0045] Ca10Mn1Fe1 is a brown-black dispersed powder in macroscopic morphology, which can be used for solar thermochemical energy storage and can be subjected to energy storage cycle performance test at 800 DEG C under an Ar-CO2 atmosphere.

[0046] Example 3

[0047] The application provides a manganese-iron-aluminum co-doped calcium oxide material and a preparation method thereof, which comprises the following steps:

[0048] (1) A co-doped calcium oxide material precursor with an aluminum element content of 0: 0.5668 g of Ca(NO)2.4H2O, 0.0598 g of Mn(NO)2.4H2O, 0.097 g of Fe(NO)3.9H2O, 0.776 g of urea and 0.97 g of water-soluble starch are weighed in a mortar, and grinding is continuously performed until the raw materials become a paste, and the grinding is continuously performed for a period of time until the raw materials are uniformly mixed.

[0049] (2) The paste obtained in (1) is transferred to a porcelain boat, and two-stage calcination is continuously carried out in a muffle furnace under an air atmosphere (ramped to 800 DEG C at a rate of 10 DEG C / min, kept for 20 min; then ramped to 900 DEG C at a rate of 10 DEG C / min, calcined for 2 h), to obtain Ca10Mn1Fe1Al1.

[0050] Ca10Mn1Fe1Al1 is a brown-black dispersed powder in macroscopic morphology, and can be used for solar thermochemical energy storage, and can be subjected to energy storage cycle performance test at 800 DEG C under an Ar-CO2 atmosphere.

[0051] Example 4

[0052] The application provides a manganese-iron-aluminum co-doped calcium oxide material and a preparation method thereof, and comprises the following steps:

[0053] (1) A manganese-iron-aluminum co-doped calcium oxide material precursor: 0.5668 g of Ca(NO)2.4H2O, 0.0598 g of Mn(NO)2.4H2O, 0.097 g of Fe(NO)3.9H2O, 0.18 g of Al(NO)3.9H2O, 0.776 g of urea and 0.97 g of water-soluble starch are weighed in a mortar, and grinding is continuously carried out until the raw materials become a paste, and the grinding is continuously carried out for a period of time until the mixture is uniform.

[0054] (2) The paste obtained in (1) is transferred to a porcelain boat, and two-stage calcination is continuously carried out in a muffle furnace under an air atmosphere (ramped to 800 DEG C at a rate of 10 DEG C / min, kept for 20 min; then ramped to 900 DEG C at a rate of 10 DEG C / min, calcined for 2 h), to obtain Ca10Mn1Fe1Al2.

[0055] Ca10Mn1Fe1Al2 is a brown-black dispersed powder in macroscopic morphology, and can be used for solar thermochemical energy storage, and can be subjected to energy storage cycle performance test at 800 DEG C under an Ar-CO2 atmosphere.

[0056] Example 5

[0057] The application provides a method for testing the thermochemical energy storage performance of a manganese-iron-aluminum co-doped calcium oxide material.

[0058] The performance of the energy storage material was evaluated by using a quartz tube fixed bed reactor with an inner diameter of 8 mm. In a typical test process, 0.1 g of sample was loaded into the reactor, heated by a tube furnace, and Ar (50 sccm) was continuously introduced as the carrier gas at a reaction temperature of 800°C and a heating rate of 10-15°C / min. After the temperature was raised to 800°C, CO2 (50 sccm) was introduced for the first carbonation, and the carbonation process lasted for 10 min. After the CO2 gas was cut off, calcination was performed for 6 min, i.e., one cycle was completed. The above carbonation-calcination cycle was repeated, and the output gas components were detected by using an online mass spectrometer.

[0059] The energy storage density was calculated as follows:

[0060]

[0061] wherein D i is the energy storage density of the material in the i th energy storage cycle (kJ / kg), V i,cal and V m respectively refer to the amount of carbon dioxide released in the i th calcination step (STP L) and the molar volume of the gas under standard conditions (22.4 STP L / mol). is the molar enthalpy of reaction (178 kJ / mol). m sample is the mass of the sample (kg)

[0062] Figure 1 is the XRD diagram of Ca10Mn1Fe1Al1, the peak shape is sharp, and the crystallinity is high.

[0063] Figure 2 is the absorbance comparison diagram of CaO, Ca10Mn1Al1, and Ca10Mn1Fe1Al1. After adding Mn and Fe, the light absorption capacity of the material is significantly improved.

[0064] Figure 3 is the stability diagram of Ca10Mn1Fe1Al1 at 800°C for 400 energy storage cycles. The initial energy storage density can reach 1555 kJ / kg, and no performance decline is observed in 400 cycles.

[0065] Figure 4 is the stability diagram of Ca10Mn1Fe1Al2 at 800°C for 1900 energy storage cycles. The initial energy storage density can reach 1200 kJ / kg, and no performance decline is observed in 900 cycles. The performance only decreases by 23% after 1900 cycles.

[0066] Figure 5 is the SEM diagram of Ca10Mn1Fe1Al1. The micro-morphology of the material is a large number of 10-50 nm particles aggregated to form a sponge-like porous block.

[0067] Figure 6 The EDS-mapping diagram of Ca10Mn1Fe1Al1 shows that various metal elements in the material are uniformly distributed.

[0068] Element doping is an effective means to improve the stability and light absorption of thermochemical energy storage materials, and in the application, the dispersibility of the doping elements in calcium oxide can be significantly improved by the self-combustion method, thereby further improving the stability of the thermochemical energy storage materials.

Claims

1. A manganese iron aluminum co-doped calcium oxide material, characterized in that, The manganese-iron-aluminum co-doped calcium oxide material is obtained from metal precursors Ca(NO3)2, Mn(NO3)2, Fe(NO3)3 and Al(NO3)3, and the manganese-iron-aluminum co-doped calcium oxide material obtained by mixing the metal precursors with a reducing agent and a binder and calcining is CaαMnβFeγAlδ, wherein α, β, γ and δ are the molar ratios of the corresponding metal elements in the raw materials; The manganese-iron-aluminum co-doped calcium oxide material has a sponge-like porous bulk body formed by aggregation of a large number of 1-2 nm particles; The molar ratio of each doping element to calcium element is 0-1:5; The reducing agent is one of urea, aminoacetic acid, hydrazine, citric acid, glucose, sucrose, carbohydrazide, oxalyl dihydrazide, acetylacetone and hexamethylenetetramine; the binder is water-soluble starch; and the calcination is two-stage calcination, i.e., first heating to 500-800 ℃ and keeping for 20 min-2 h, and then heating to 850-900 ℃ and calcining for 2-4 h.

2. The method of claim 1, wherein the manganese, iron and aluminum co-doped calcium oxide material is prepared by the steps of: preparing a solution of manganese ions, iron ions and aluminum ions; adding a calcium compound to the solution; and precipitating the manganese, iron and aluminum co-doped calcium oxide material from the solution. The method comprises the following steps: (1) preparing a manganese-iron-aluminum co-doped calcium oxide material precursor; (2) calcining the precursor obtained in step (1) to obtain a manganese-iron-aluminum co-doped calcium oxide material.

3. The method for preparing a manganese-iron-aluminum co-doped calcium oxide material according to claim 2, characterized in that, In step (1), the oxidizing calcium precursor, the doping metal precursor, the reducing agent and the binder are placed in a mortar and continuously ground until the raw materials form a uniform paste, thereby obtaining the manganese-iron-aluminum co-doped calcium oxide material precursor.

4. The method for preparing a manganese-iron-aluminum co-doped calcium oxide material according to claim 2, characterized in that, In step (1), the mass ratio of the reducing agent to the binder is 1:1-1.25, and the amount of the binder added is appropriate to make the raw materials uniformly mixed into a paste without being dispersed into powder or flowing liquid. In step (1), the molar ratio of each doping element to calcium element is 0-1:

5.

5. The method for preparing a manganese-iron-aluminum co-doped calcium oxide material according to claim 4, characterized in that, In step (1), the oxidizing calcium precursor is one of calcium chloride, calcium bromide, calcium acetate, calcium permanganate and calcium gluconate, and when a calcium salt other than calcium nitrate is used, 2 times the amount of nitric acid or ammonium nitrate of the calcium element is additionally added as an oxidizing agent. In step (1), the doping metal precursor is one or more of nitrate salts of manganese, iron and aluminum and their common hydrates. In step (1), the reducing agent is one of urea, aminoacetic acid, hydrazine, citric acid, glucose, sucrose, carbohydrazide, oxalyl dihydrazide, acetylacetone and hexamethylenetetramine. In step (1), the binder is water-soluble starch.

6. The method for preparing a manganese-iron-aluminum co-doped calcium oxide material according to claim 3, characterized in that, In step (2), the paste precursor obtained in step (1) is transferred to a porcelain boat and subjected to two-stage calcination in a muffle furnace under an air atmosphere, i.e., first heating to 500-800 ℃ and keeping for 20 min-2 h, and then heating to 850-900 ℃ and calcining for 2-4 h. In the first sintering step, the mixture is combusted in an air environment at a temperature ≥500 ℃ to remove the organic matter to form a powder; and in the second sintering step, the powder is sintered in an oxygen environment at a temperature ≥850 ℃ to form a composite metal oxide.

7. The manganese iron aluminum co-doped calcium oxide material produced by the method of any one of claims 2-6, characterized by, The method can realize a thermochemical energy storage cycle under high-temperature conditions.

8. The manganese iron aluminum co-doped calcium oxide material produced by the method of any one of claims 2-6, characterized by, The manganese-iron-aluminum co-doped calcium oxide material is applied to solar thermochemical energy storage, heat energy is converted into chemical energy for storage through the process of CaCO3 calcination and decomposition into CaO and CO2, and energy release is realized through the process of recombination of CaO and CO2 to form CaCO3, and the manganese-iron-aluminum elements do not directly participate in the energy storage reaction, and the specific reaction is: The application of the manganese-iron-aluminum co-doped calcium oxide material is to carry out energy storage cycle performance test at 800 DEG C under Ar-CO2 atmosphere.

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