CN114291833A - Preparation method of magnesium nitrate and magnesium nitrate-based multi-element molten salt - Google Patents

Preparation method of magnesium nitrate and magnesium nitrate-based multi-element molten salt Download PDF

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Publication number
CN114291833A
CN114291833A CN202210019522.0A CN202210019522A CN114291833A CN 114291833 A CN114291833 A CN 114291833A CN 202210019522 A CN202210019522 A CN 202210019522A CN 114291833 A CN114291833 A CN 114291833A
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China
Prior art keywords
magnesium nitrate
molten salt
nitrate
heating
based multi
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CN202210019522.0A
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Inventor
王敏
钟远
李锦丽
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Qinghai Institute of Salt Lakes Research of CAS
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Qinghai Institute of Salt Lakes Research of CAS
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Priority to CN202210019522.0A priority Critical patent/CN114291833A/en
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    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01FCOMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F5/00Compounds of magnesium
    • C01F5/38Magnesium nitrates
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09KMATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K5/00Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
    • C09K5/08Materials not undergoing a change of physical state when used
    • C09K5/10Liquid materials
    • C09K5/12Molten materials, i.e. materials solid at room temperature, e.g. metals or salts

Abstract

The invention discloses a preparation method of magnesium nitrate and magnesium nitrate-based multi-element molten salt, which comprises the following steps: putting an open container containing magnesium nitrate hexahydrate or a multi-element molten salt mixture containing magnesium nitrate hexahydrate into a heating device for vacuum heating dehydration; and then putting the dehydrated product into an anhydrous oxygen-free glove box for crushing to obtain the magnesium nitrate or the magnesium nitrate-based multi-element molten salt. The preparation method provided by the invention can effectively reduce the content of alkali type magnesium nitrate in the magnesium nitrate and magnesium nitrate-based multi-component molten salt, can obtain high-purity magnesium nitrate or magnesium nitrate-based multi-component molten salt at a lower temperature in a shorter time, and simultaneously, the obtained magnesium nitrate or magnesium nitrate-based multi-component molten salt has a higher decomposition temperature.

Description

Preparation method of magnesium nitrate and magnesium nitrate-based multi-element molten salt
The invention is a divisional application with the application number of 201910485889.X and the application date of 2019, 06 and 05, and the invention name is 'a preparation method of magnesium nitrate and magnesium nitrate-based multi-component molten salt'.
Technical Field
The invention relates to the field of molten nitrate salts, in particular to a method for preparing magnesium nitrate and magnesium nitrate-based multi-element molten salt.
Background
With the increasing demand of energy, opportunities and challenges are brought to the development of clean energy such as nuclear energy and solar energy. The heat storage medium can not be conducted regardless of nuclear energy or solar energy. The heat transfer medium with good performance not only can ensure the efficient transmission and utilization of heat, but also can improve the safety coefficient of the whole heat transfer system.
Molten salt (molten salt for short) is the form of salt under melting, and is a mature heat transfer and storage material which is applied more in the current solar thermal power station. Because of the high melting point of pure salt, the molten salt with industrial applicability is generally a mixture with eutectic point prepared by different proportions of several inorganic salts.
The magnesium nitrate based multi-element molten salt system takes magnesium nitrate, sodium nitrate, potassium nitrate and other nitrates as components, and molten salt mixtures with eutectic points are prepared by different proportions. The magnesium nitrate-based molten salt has the advantages of low melting point, low cost, high decomposition temperature and the like, and is a molten salt with application prospect. The existing magnesium nitrate hexahydrate dehydration technology needs higher dehydration temperature and time, and the content of alkaline magnesium nitrate in a dehydration product is high, so that the decomposition temperature of the prepared magnesium nitrate and magnesium nitrate-based multi-element molten salt is reduced. The magnesium nitrate exists stably in the atmospheric environment in the form of magnesium nitrate hexahydrate, and anhydrous magnesium nitrate can be prepared by a method of removing crystallization water by heating. During the heating dehydration, due to thermodynamic limitation, magnesium nitrate is inevitably subjected to hydrolysis reaction, and a mixture of magnesium nitrate and basic magnesium nitrate is obtained. Above 330 c decomposition occurs to magnesium oxide and nitrogen oxide gases.
How to reduce the hydrolysis side reaction of magnesium nitrate and improve the purity of anhydrous magnesium nitrate is always a difficult point of the magnesium nitrate hexahydrate dehydration technology.
Disclosure of Invention
The invention aims to provide a preparation method of magnesium nitrate and magnesium nitrate-based multi-element molten salt, which aims to solve the problems in the prior art.
In order to achieve the above object, according to one aspect of the present invention, there is provided a method for preparing magnesium nitrate, comprising the steps of:
(1) heating and dehydrating magnesium nitrate hexahydrate in a vacuum environment;
(2) and (2) putting the product obtained in the step (1) into an anhydrous oxygen-free glove box for crushing to obtain the magnesium nitrate.
Further, magnesium nitrate hexahydrate is placed in an open container and crushed uniformly before the step (1).
Further, the heating apparatus used in step (1) comprises a vacuum-heatable muffle furnace.
Further, the heating temperature is controlled to be 150-300 ℃ during the heating dehydration in the step (1).
Further, the heating rate in the step (1) is 1-10 ℃/min during heating and dehydration.
Further, the heating time in the step (2) is 0.5-12 h during heating and dehydration.
Further, the vacuum degree of the vacuum environment in the step (2) is controlled to be-0.05 to-0.1 Mpa.
Another object of the present invention is to provide a method for preparing a magnesium nitrate-based multi-component molten salt, which specifically comprises:
(a) uniformly mixing a polybasic molten salt mixture containing magnesium nitrate hexahydrate in an open container;
(b) heating and dehydrating the multi-element molten salt mixture in a vacuum environment;
(c) and (c) putting the product obtained in the step (b) into an anhydrous oxygen-free glove box for crushing to obtain the magnesium nitrate-based multi-element molten salt.
Further, the magnesium nitrate based multi-element molten salt is a mixture of magnesium nitrate hexahydrate and any one or more of sodium nitrate, potassium nitrate, lithium nitrate, calcium nitrate, cesium nitrate, sodium nitrite and potassium nitrite.
Compared with the prior art, the invention has the beneficial effects that:
(1) the magnesium nitrate hexahydrate dehydration temperature in the preparation method of the magnesium nitrate and magnesium nitrate based multi-element molten salt is low and the time is short.
(2) The preparation method provided by the invention can reduce the hydrolysis side reaction of magnesium nitrate, and the prepared magnesium nitrate and magnesium nitrate-based multi-element molten salt have high purity of magnesium nitrate and low content of basic magnesium nitrate; and reducing the occurrence of decomposition reactions.
(3) The decomposition temperature of the magnesium nitrate and magnesium nitrate-based multi-element molten salt prepared by the method is obviously improved.
Detailed Description
In view of the defects in the prior art, the inventor of the present invention provides a technical scheme of the present invention through long-term research and a great deal of practice, wherein hydrolysis characteristics in a dehydration process of magnesium nitrate hexahydrate are mainly utilized, and a vacuum heating method is adopted to dehydrate a mixture of magnesium nitrate hexahydrate and a multi-component molten salt containing magnesium nitrate hexahydrate so as to prepare magnesium nitrate and magnesium nitrate-based multi-component molten salt.
The technical solutions of the present invention will be described in detail below with reference to several embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All embodiments obtained by a person skilled in the art based on the embodiments of the present invention without any inventive step are within the scope of the present invention.
Example 1
Placing the container containing magnesium nitrate hexahydrate in a muffle furnace capable of being heated under vacuum at-0.05 MPa, heating to 300 deg.C at 10 deg.C/min for 0.5 hr, grinding in a sealed glove box, sampling, and analyzing Mg2+And (4) content. Tests show that the basic magnesium nitrate content is 3.5 percent, and the magnesium nitrate content is 96.5 percent. The sample was tested to have a decomposition temperature of 390.6 ℃.
Example 2
Placing the container containing magnesium nitrate hexahydrate in a muffle furnace capable of being heated under vacuum at-0.1 MPa, heating to 150 deg.C at a rate of 1 deg.C/min, heating at 150 deg.C for 12 hr, grinding in a glove box, sampling, and analyzing Mg2+And (4) content. Tests show that the basic magnesium nitrate content is 2.8 percent, and the magnesium nitrate content is 97.2 percent. The sample was tested to have a decomposition temperature of 391.5 ℃.
Example 3
Putting the container filled with the magnesium nitrate hexahydrate into a vacuum drying device capable of being heated in vacuumIn the box, the vacuum degree is controlled at-0.06 MPa, then the temperature is raised to 250 ℃ at the speed of 5 ℃/min, the mixture is heated for 2h at 250 ℃, and the mixture is taken out to be ground in a glove box, sampled and analyzed for Mg2+And (4) content. Tests show that the basic magnesium nitrate content is 3.2 percent, and the magnesium nitrate content is 96.8 percent. The sample was tested to have a decomposition temperature of 390.9 ℃.
Example 4
Putting a container filled with magnesium nitrate hexahydrate, sodium nitrate and potassium nitrate (mass ratio of 1: 2: 1) into a muffle furnace capable of being heated in vacuum, controlling the vacuum degree at-0.06 MPa, heating to 250 ℃ at the speed of 5 ℃/min, heating for 2h at 250 ℃, taking out, grinding in a glove box, sampling and analyzing Mg2+And (4) content. Tests show that the basic magnesium nitrate content is 0.5 percent, and the magnesium nitrate content is 99.5 percent. The sample was tested to have a decomposition temperature of 468.8 ℃.
Example 5
Putting a container filled with magnesium nitrate hexahydrate, sodium nitrate, potassium nitrate and calcium nitrate (mass ratio of 1: 2: 1: 0.5) into a muffle furnace capable of being heated in vacuum, controlling the vacuum degree at-0.06 MPa, heating to 250 ℃ at the speed of 5 ℃/min, heating for 2h at 250 ℃, taking out, grinding in a glove box, sampling and analyzing Mg2+And (4) content. Tests show that the basic magnesium nitrate content is 0.4 percent, and the magnesium nitrate content is 99.6 percent. The sample was tested to have a decomposition temperature of 490.2 ℃.
Comparative example 1
Placing the container containing magnesium nitrate hexahydrate in muffle furnace, heating to 300 deg.C at 10 deg.C/min under normal pressure, heating at 300 deg.C for 0.5h, taking out, grinding in glove box, sampling, and analyzing Mg2+The content of the basic magnesium nitrate is 7.8 percent, and the content of the magnesium nitrate is 92.2 percent. The sample was tested to have a decomposition temperature of 385.6 ℃.
Comparative example 2
And (3) putting the container filled with the magnesium nitrate hexahydrate into a muffle furnace, heating to 150 ℃ at the speed of 1 ℃/min under normal pressure, and heating at 150 ℃ for 12 hours until the dehydrated product is still liquid, which indicates that the dehydration is incomplete.
Comparative example 3
And (3) putting the container filled with the magnesium nitrate hexahydrate into a muffle furnace, heating to 250 ℃ at the speed of 5 ℃/min under normal pressure, and heating at 250 ℃ for 2 hours until the dehydrated product is still liquid, which indicates that the dehydration is incomplete.
Comparative example 4
Putting a container filled with magnesium nitrate hexahydrate, sodium nitrate and potassium nitrate (mass ratio of 1: 2: 1) into a muffle furnace, heating to 300 ℃ at a speed of 5 ℃/min under normal pressure, heating at 300 ℃ for 2h, taking out, grinding in a glove box, sampling and analyzing Mg2+The content of the basic magnesium nitrate is 7.9 percent, and the content of the magnesium nitrate is 92.1 percent. The sample was tested to have a decomposition temperature of 461.8 ℃.
Comparative example 5
Placing a container filled with magnesium nitrate hexahydrate, sodium nitrate, potassium nitrate and calcium nitrate (mass ratio of 1: 2: 1: 0.5) into a muffle furnace capable of being heated in vacuum, heating to 250 ℃ at the speed of 5 ℃/min under normal pressure, heating for 2h at 250 ℃, taking out, grinding in a glove box, sampling and analyzing Mg2+The content of the basic magnesium nitrate is 6.5 percent, and the content of the magnesium nitrate is 93.5 percent. The sample was tested to have a decomposition temperature of 475.2 ℃.
The results show that the magnesium nitrate content of the magnesium nitrate and the magnesium nitrate-based multi-element molten salt prepared by the method is obviously improved, and the decomposition temperature is also improved.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (2)

1. A method for preparing magnesium nitrate, which is characterized by comprising the following steps:
(1) firstly, putting magnesium nitrate hexahydrate in an open container, uniformly crushing, and then heating and dehydrating the magnesium nitrate hexahydrate in a vacuum environment, wherein the used heating equipment is a muffle furnace capable of being heated in vacuum, the heating temperature is controlled within the range of 150-300 ℃ during heating and dehydrating, the heating rate is 1-10 ℃/min during heating and dehydrating, the heating time is 0.5-12 h during heating and dehydrating, and the vacuum degree of the vacuum environment is controlled at 0.05-0.1 Mpa;
(2) and (2) putting the product obtained in the step (1) into an anhydrous oxygen-free glove box for crushing to obtain the magnesium nitrate.
2. A preparation method of magnesium nitrate based multi-element molten salt is characterized by comprising the following steps:
(a) uniformly mixing a polybasic molten salt mixture containing magnesium nitrate hexahydrate in an open container;
(b) heating and dehydrating the multi-element molten salt mixture in a vacuum environment;
(c) and (c) putting the product obtained in the step (b) into an anhydrous oxygen-free glove box, and crushing to obtain the magnesium nitrate-based multi-element molten salt, wherein the magnesium nitrate-based multi-element molten salt is a mixture of magnesium nitrate hexahydrate and any one or more of sodium nitrate, potassium nitrate, lithium nitrate, calcium nitrate, cesium nitrate, sodium nitrite and potassium nitrite.
CN202210019522.0A 2019-06-05 2019-06-05 Preparation method of magnesium nitrate and magnesium nitrate-based multi-element molten salt Pending CN114291833A (en)

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CN106219581A (en) * 2016-07-22 2016-12-14 中国科学院青海盐湖研究所 A kind of method utilizing selection absorption method to prepare magnesium nitrate
GB201816380D0 (en) * 2018-10-08 2018-11-28 Sunamp Ltd Group II metal nitrate based compositions for use as phase change materials

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