JP2019189483A - Method for producing sodium borohydride - Google Patents

Abstract

To provide a method for producing sodium borohydride that can inhibit the production efficiency of sodium borohydride from being lowered even in use of a moisture-containing sodium metaborate as a raw material.SOLUTION: A method for producing sodium borohydride is provided which sequentially comprises (1A) a step where an airtight container is filled with a non-oxidizing gas after or before the airtight container is charged with a moisture-containing sodium metaborate with a particle diameter of 100 μm or less and aluminum; (2A) a step where with the airtight container having its inside heated and kept at 200°C or higher, a moisture adhering to sodium metaborate and to aluminum and hydration water of sodium metaborate are released to be vaporized; and (3A) a step where with the airtight container having its inside heated to 280 to 550°C, sodium metaborate and the aluminum are rolling-crushed with the use of a crushing medium, and a residual moisture within the airtight container is allowed to react with the aluminum for conversion into a hydrogen gas and aluminum oxide.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing sodium borohydride, and more particularly to a method for producing sodium borohydride from sodium metaborate.

  While hydrogen fuel is attracting attention as an alternative energy to fossil fuel, sodium borohydride is a promising hydrogen carrier as a hydrogen storage and transport and hydrogen generation source. In order to disseminate sodium borohydride as a hydrogen carrier to society, it is necessary to establish an optimal manufacturing method with the mass production technology in mind.

  As a conventional method for producing sodium borohydride, for example, Patent Document 1 discloses a method for producing sodium borohydride by reacting trialkylborate with sodium aluminum hydride. However, in this method, it is necessary to convert boric acid to trialkyl borate in advance and to react sodium, aluminum, and hydrogen to produce sodium aluminum hydride, so that the manufacturing process is complicated.

  Moreover, in patent document 2, manufacture of sodium borohydride which has a process which makes sodium metaborate and granular aluminum react by carrying out rolling grinding | pulverization using a grinding | pulverization medium in a hydrogen atmosphere, and obtaining sodium borohydride. A method is disclosed. Although this manufacturing method is a more simplified manufacturing method, it has the following problems. That is, the anhydrous sodium metaborate, which is a raw material, is used after being purified by a method in which sodium metaborate hydrate is heated to evaporate and remove water. However, normally available sodium metaborate is a tetrahydrate, and the water content is as high as 52.2%, and bumping may occur during heating. Furthermore, powdered anhydrous sodium metaborate dried and solidified after heating needs to be fine powder because the particles are hard, large in size and low in reactivity. However, sodium metaborate has a high affinity for water, and when it is made finer, it is easier to absorb moisture. When fine powder anhydrous sodium metaborate that has absorbed moisture is used as a raw material, the reaction with moisture is always prioritized and the production reaction rate of sodium borohydride decreases. Thus, when the sodium metaborate containing a water | moisture content is used as a raw material, since the production | generation efficiency of sodium borohydride falls, the improvement is calculated | required.

  Furthermore, Patent Document 3 discloses a method for producing sodium borohydride (borohydride compound), which comprises using a compound containing boron and oxygen together with a specific Lewis base, aluminum, and hydrogen. Although sodium metaborate is illustrated as a compound containing boron and oxygen, the water content of sodium metaborate is not considered in this method as well, and the same problem as the problem shown in Patent Document 2 is held.

Japanese Patent No. 2809666 International Publication No. 2015/190403 JP 2009-256180 A

  The present invention has been made in view of the above-described conventional problems, and even when sodium metaborate containing water is used as a raw material, sodium borohydride that can suppress a decrease in production efficiency of sodium borohydride. It aims at providing the manufacturing method of.

As a result of intensive studies, the present inventors have obtained the following knowledge. That is, the aluminum grains are plastically deformed by the energy of collision of the grinding media, and when a solid other than aluminum is sandwiched between the aluminum grains and the grinding media, the aluminum is plastically deformed due to the driving effect and the surface area is increased. As a result, the oxide film covering the surface of the aluminum grains is destroyed, and a new surface portion is formed. The new surface portion is an aluminum background without an oxide film. And in the new surface part of aluminum, it contacts and reacts with solids, such as gas, such as water and hydrogen, and sodium metaborate, in atmosphere. Under an atmosphere in which hydrogen gas and water are present, the new surface portion of aluminum first reacts preferentially with water to produce an aluminum oxide film and hydrogen gas on the surface. Accordingly, in the case of sodium metaborate containing adhering water or hydrate, the adhering water is vaporized at 1 atm 100 ° C. or higher, and the water of all hydrates is vaporized at 280 ° C. or higher, and remains in the vaporized water and sodium metaborate. Moisture reacts with new surface parts of aluminum. When the moisture in the atmosphere disappears through this reaction, sodium metaborate can be kept in an anhydrous state. The new surface portion of aluminum then reacts with anhydrous sodium metaborate and hydrogen gas to produce sodium borohydride. That is, according to this knowledge, in the production of sodium borohydride, it is possible to avoid the influence of moisture contained in sodium metaborate, and therefore it is possible to suppress a decrease in production efficiency of sodium borohydride.
Means for solving the above problems are as follows.

The method for producing sodium borohydride according to the first aspect of the present invention comprises:
(1A) A step of filling the inside of the sealed container with a non-oxidizing gas after or before charging sodium metaborate containing water and having a particle size of 100 μm or less and aluminum in the sealed container;
(2A) A process of heating and holding the inside of the sealed container at 200 ° C. or more to release and vaporize the attached moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate,
(3A) heating the inside of the sealed container to 280 to 550 ° C., rolling and grinding sodium metaborate and aluminum with a grinding medium, and reacting residual moisture in the sealed container with aluminum to convert into hydrogen gas and aluminum oxide;
Are included sequentially.

  In the method for producing sodium borohydride according to the first aspect of the present invention, after the step (3A), (4A) the inside of the sealed container is heated to 200 to 550 ° C., and the hydrogen gas pressure is set to 0.3 to It is preferable to further include a step of rolling and crushing sodium metaborate and aluminum with a crushing medium while setting the pressure to 10 MPa.

In the method for producing sodium borohydride according to the first aspect of the present invention, the mass of aluminum in the step (1A) is preferably larger than the sum of the following mass X1 and mass Y1.
Mass X1: Mass of aluminum assumed to react in an equimolar amount with sodium metaborate charged in the step (1A) Mass Y1: From normal temperature to 600 ° C. by thermogravimetric measurement of sodium metaborate in the step (1A) The weight reduction rate of the product multiplied by 0.828 and the mass X1

  In the method for producing sodium borohydride according to the first aspect of the present invention, the mass of aluminum charged in the step (1A) is greater than or equal to the mass of aluminum that reacts with the residual moisture in the sealed container in the step (3A). And a step of additionally charging a short amount of aluminum that is equal to or less than the mass of the total amount of aluminum necessary for the reaction with residual moisture and the reaction for forming sodium borohydride, as defined in (3A). It can be provided immediately after the process.

The method for producing sodium borohydride according to the second aspect of the present invention comprises:
(1B) a step of containing sodium metaborate containing water and having a particle size of 100 μm or less and aluminum in a sealed container;
(2B) The inside of the sealed container is heated to 200 ° C. or more, and the attached moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate are released and vaporized, and the moisture is removed by degassing the inside of the sealed container. Process,
(3B) A step of heating the inside of the sealed container to 280 to 550 ° C., rolling and grinding sodium metaborate and aluminum with a grinding medium, and reacting residual moisture in the sealed container with aluminum to convert it into hydrogen gas and aluminum oxide. ,
Are included sequentially.

  In the method for producing sodium borohydride according to the second aspect of the present invention, after the step (3B), (4B) the inside of the sealed container is heated to 200 to 550 ° C., and the hydrogen gas pressure is set to 0.3 to It is preferable to further include a step of rolling and grinding the sodium metaborate and the aluminum with a grinding medium while setting the pressure to 10 MPa.

  In the method for producing sodium borohydride according to the second aspect of the present invention, the mass of aluminum in the step (1B) is changed from the room temperature to 600 ° C. in the mass of sodium metaborate charged in the step (1B). It is preferable to be equivalent to the mass of aluminum assumed to react with the remaining sodium metaborate minus the mass corresponding to the decreasing rate in an equimolar amount.

  In any of the aspects of the method for producing sodium borohydride of the present invention, the average particle diameter of aluminum in the step (1A) or (1B) is preferably 1 μm or more and 10 mm or less.

  In any of the aspects of the method for producing sodium borohydride according to the present invention, before step (1A) or (1B), sodium metaborate containing water and having a particle size of 100 μm or less and aluminum are mixed. A step of obtaining a mixture is provided, and in the step (1A) or (1B), the mixture can be used in place of sodium metaborate containing water and aluminum. In this case, the mixture can be pellets.

  In any of the aspects of the method for producing sodium borohydride of the present invention, the grinding medium can be a ceramic ball.

  In any of the aspects of the method for producing sodium borohydride according to the present invention, the reaction between the residual moisture and aluminum in the step (3A) or (3B) is performed at the time when the pressure change in the sealed container no longer occurs or the pressure It is preferable to continue until the point at which the value decreases.

  ADVANTAGE OF THE INVENTION According to this invention, even if it uses the sodium metaborate containing a water | moisture content as a raw material, the manufacturing method of sodium borohydride which can suppress the production | generation efficiency of sodium borohydride can be provided.

It is a TG-DTA chart of sodium metaborate tetrahydrate from room temperature to 600 ° C. It is a TG-DTA chart of the used sodium metaborate powder (<100 μm) from room temperature to 600 ° C. It is a fragmentary sectional view which shows an example of the airtight container used in this embodiment. It is a graph which shows the manufacture process in the manufacturing method of the sodium borohydride of this embodiment. It is a graph which shows the manufacturing process in the manufacturing method of sodium borohydride including the heating deaeration process.

<First Embodiment>
The manufacturing method of the sodium borohydride of 1st this embodiment is (1A) It charges after charging sodium metaborate containing water and a particle size of 100 micrometers or less, and aluminum in an airtight container. (2A) The inside of the sealed container is heated to 200 ° C. or higher to release the adhering moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate. (3A) The inside of the sealed container is heated to 280 to 550 ° C., and the sodium metaborate and aluminum are rolled and pulverized with a grinding medium, and the residual moisture in the sealed container is reacted with aluminum to form hydrogen gas and aluminum oxide. It is characterized by sequentially including the steps of conversion.
Below, each process is explained in full detail.

[Step (1A)]
In the step (1A), the inside of the sealed container is filled with a non-oxidizing gas after or before charging sodium metaborate having a particle size of 100 μm or less and aluminum in the sealed container. It is a process. Hereinafter, “sodium metaborate” means “sodium metaborate containing water and having a particle size of 100 μm or less” unless otherwise indicated, except when referred to as “anhydrous sodium metaborate”.
In the step (1A), the raw material is mainly prepared and charged. By filling the inside of the sealed container with a non-oxidizing gas, the moisture content in the air on the surface oxidized coating of sodium metaborate and aluminum is reduced. Adhesion can be prevented. The timing for filling the inside of the sealed container with the non-oxidizing gas may be after the raw materials are charged into the sealed container or before charging. Note that examples of the non-oxidizing gas include hydrogen gas, rare gas, and the like, or a vacuum state is possible.

  As a sealed container, it has heat resistance and pressure resistance that can withstand 550 ° C. (heating temperature in the process of (4A)) and 10 MPa, can be secured with a gas filled space, and is rolled and crushed with a grinding medium. A container provided with at least the stirring means is used. Details of such a sealed container will be described later.

  The sodium metaborate used as a raw material contains water, and this “water” refers to water contained by hydration water, water attached to the surface, and anhydrous sodium metaborate powder reacting with water. Sodium metaborate can be obtained, for example, by hydrolyzing sodium borohydride. Sodium metaborate is usually a tetrahydrate, but it may contain water of hydration in other proportions. In the present embodiment, any sodium metaborate can be used regardless of whether or not moisture is attached to the surface of the sodium metaborate.

  In the present embodiment, sodium metaborate having a particle size of 100 μm or less is used. However, if it exceeds 100 μm, the production efficiency of sodium borohydride is reduced. The sodium metaborate having a particle size of 100 μm or less can be obtained by pulverizing to a certain degree and then passing through a sieve having an opening of 100 μm. In order to further improve the production efficiency of sodium borohydride, it is preferable to use sodium metaborate having a smaller particle size. For that purpose, a sieve having an opening of less than 100 μm may be used for the powder of sodium metaborate.

  The mass of sodium metaborate charged in the step (1A) can be determined according to the desired amount of sodium borohydride produced. However, since sodium metaborate contains moisture as described above, it is necessary to estimate more in consideration of the reduced mass of the moisture.

  As aluminum used as a raw material, fragments such as powder material and scrap material can be used. For example, scrap pieces such as chips and waste materials can be used as the aluminum piece, but it is preferable to select an aluminum fragment having a metal impurity content that is less noble than aluminum.

  Here, the mass of the aluminum charged in the step (1A) will be considered. Part of aluminum does not contribute to the formation of sodium borohydride, which is the final product, because it reacts with water vaporized from sodium metaborate or the like in the step (3A) to form aluminum oxide. Therefore, an extra amount of aluminum that reacts with moisture released in the process is required. If there is not a sufficient amount of aluminum, in the step (4A), there is a shortage of aluminum that reacts with anhydrous sodium metaborate, and sodium borohydride may not be generated sufficiently. Also, for example, in the step (3A), when all the aluminum reacts with the water vaporized from sodium metaborate to become aluminum oxide, in the step (4A), aluminum is insufficient, so the reaction itself is It will be stagnant.

  In all the steps in the present embodiment, the amount of water that reacts with aluminum corresponds to the amount of water from adhering water and hydrate, most of which is vaporized from sodium metaborate. Anhydrous sodium metaborate is known to be stable in heating from room temperature to about 900 ° C, and the proportion of water vaporized (mass fraction) in the raw material sodium metaborate is from normal temperature to 600 ° C. This corresponds to a low thermal weight ratio when heated. Assuming that the mass of aluminum necessary for the total reaction between the vaporized water and the reduced amount of anhydrous sodium metaborate is “A”, “A” is the mass of aluminum that reacts with the reduced amount of anhydrous sodium metaborate “B”. The mass of aluminum that reacts with moisture “D” is added (A = B + D). When the mass of anhydrous sodium metaborate as a raw material is “E” and the thermal weight loss rate (%) is “C”, the amount of aluminum “D” that reacts with moisture is expressed by D = (C / 100) × E. . The amount of aluminum “B” that reacts with the reduced amount of anhydrous sodium metaborate is represented by (1−C / 100) × E × 0.547. Here, 0.547 is a mass ratio of aluminum that reacts with an equal amount of anhydrous sodium metaborate. That is, the mass “A” of all the aluminum necessary for the reaction is A = (1−C / 100) × E × 0.547 + (C / 100) × E. 828 × C / 100) × 0.547 × E. That is, if the thermal weight reduction rate “C” of the raw material sodium metaborate is measured, the mass of aluminum necessary for all reactions can be calculated. Therefore, when it is assumed that the anhydrous sodium metaborate mass “E” of the raw material does not contain moisture, from 1 + 0.828 × C / 100 with respect to the amount of Al “0.547 × E” that reacts in an equal amount to this It is preferable to use a large proportion of aluminum as a raw material.

From the above, it is preferable that the mass of aluminum in the step (1A) is larger than the sum of the following mass X1 and mass Y1.
Mass X1: Mass of aluminum assumed to react with equimolar amount of sodium metaborate charged in the step (1A) Mass Y1: From normal temperature to 600 by thermogravimetric measurement of sodium metaborate in the step (1A) Mass obtained by multiplying the rate of thermal weight loss up to 0 ° C by 0.828 and mass X1

  As moisture other than the above, there are moisture and hydrated oxide film covering the surface of aluminum. However, the thickness of the normal oxide film of non-corroded aluminum is about 0.5 to 1 nm, which is 1/1000 or less of the thickness of the raw material aluminum, and the amount of water is negligibly small. Can do.

On the other hand, the average particle size of the aluminum to be charged is preferably 1 μm or more and 10 mm or less. When the particle size is small, the specific surface area is large and the initial reaction with moisture, the reaction rate between sodium metaborate and hydrogen is fast, and when the particle size is large, rolling crushing is continuously maintained and the reaction between sodium metaborate and hydrogen. Speed is difficult to decrease. However, if it is less than 1 μm, dust explosion tends to occur and it becomes difficult to handle, and the particles tend to adhere to each other, and the particles tend to harden. On the other hand, if the thickness is less than 1 μm, the room for rolling and grinding may be reduced, and the reaction opportunity with sodium metaborate may be reduced, resulting in a reduction in reaction yield. When the average particle diameter is larger than 10 mm, the specific surface area per mass is decreased, the reaction area is decreased, and the reaction rate at the initial stage of rolling and grinding may be extremely decreased. The average particle size is more preferably 10 μm or more and 5 mm or less.
The average particle diameter is obtained as a particle diameter having a sphere equivalent diameter by a laser diffraction particle size distribution measuring apparatus.

  There is no restriction | limiting in particular in the temperature in the airtight container in the process of (1A), What is necessary is just to be less than 100 degreeC. Since the inside of the sealed container does not need to be heated, it can be set to room temperature. In order to avoid a reaction between sodium metaborate and moisture in the air, it is necessary to quickly seal the container after charging the raw materials.

  The process (2A) can be started immediately after the completion of the process (1A), and the process (2A) may be started after an arbitrary time has elapsed.

[Step (2A)]
The step (2A) is a step in which the inside of the reaction vessel is heated and held at 200 ° C. or higher, and the attached moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate are released and vaporized. Although the adhering moisture exists not only in sodium metaborate but also in an oxide film covering aluminum in a trace amount, both can be vaporized in the step (2A). Also, from thermogravimetric analysis, at 1 atm, the release temperature of sodium metaborate hydrated water is 280 ° C. Therefore, the heating conditions for releasing sodium metaborate hydrated water are preferably 280 ° C. or higher. . As the holding time, a holding time of 10 minutes or more is preferable, and the holding time can be reduced by setting the heating temperature in the range of 300 ° C. to 550 ° C. in order to increase the release rate of hydrated water.

[Step (3A)]
In the step (3A), the inside of the sealed container is heated to 280 to 550 ° C., and sodium metaborate and aluminum are rolled and crushed with a grinding medium, and the residual moisture in the sealed container is reacted with aluminum to form hydrogen gas and aluminum oxide. This is the process of conversion. That is, this step is a step of removing moisture from the reaction system by reacting the moisture vaporized in the step (2A), that is, the residual moisture in the sealed container and aluminum. In this step, aluminum and moisture react to produce aluminum oxide and hydrogen gas. More specifically, the oxide film on the aluminum surface is broken, and the aluminum exposed to the new surface reacts with moisture in the atmosphere to form an aluminum oxide film and hydrogen gas. The reaction between moisture and aluminum is shown by the following reaction formula.
2Al + 3H ₂ O → Al ₂ O ₃ + 3H ₂
The heating condition in the step (3A) is sufficient if it is 100 ° C. or higher at which moisture hardly condenses, but if it is 280 ° C. or higher, the sodium metaborate hydrate completely releases water and the aluminum Since the strength is reduced, rolling and grinding are facilitated, and the reactivity between water and aluminum is increased, moisture in the atmosphere can be removed in a shorter time.

FIG. 1 shows a TG-DTA chart of sodium metaborate tetrahydrate from room temperature to 600 ° C. From FIG. 1, weight loss accompanied by an endothermic peak due to dehydration can be seen with increasing temperature. And when it exceeds 276 degreeC, since weight loss and an endothermic peak are not seen and there is no weight loss, it is thought that the sodium metaborate hydrate discharge | released water completely. That is, as described above, sodium metaborate tetrahydrate can remove moisture if the heating temperature is 280 ° C. or higher.
Similarly, FIG. 2 shows a TG-DTA chart of the used sodium metaborate powder (100 μm>) containing moisture. From FIG. 2, a gentle weight loss is observed even in a temperature range higher than 280 ° C. (280 ° C. to 600 ° C.). Since no endothermic peak is observed, it is presumed that the moisture taken into the amorphous form gradually dehydrated as the temperature rose. It can be seen that anhydrous sodium metaborate has a high reactivity with moisture when powdered, and it is difficult to release moisture even at high temperatures. Moisture from the hydrate and adhering water is removed from sodium metaborate by heating at 280 ° C. or higher, and the water held to 280 ° C. or higher in powdered sodium metaborate is removed by reacting the moisture with aluminum by rolling and grinding. be able to.

  The reaction between the residual moisture and aluminum in the step (3A) is preferably continued until the pressure change (increase) in the sealed container stops or the pressure decreases. In the step (3A), aluminum and moisture react as described above, and the pressure increases due to the generation of hydrogen gas. However, when the reaction ends, the pressure increase due to hydrogen gas ends. That is, since the reaction is not completed until the end of the pressure change (rise) or the pressure decreases, it is preferable to continue the step (3A) until that time. In other words, it can be determined that the step (3A) is finished when the pressure rise in the sealed container ends or the pressure decreases.

  Examples of the pulverizing medium used for rolling and pulverizing include those having a ball shape, a rod shape, and the like. Of these, a ball shape is preferable. In the case of a ball shape, the ball diameter is preferably larger than the particle diameter of the aluminum to be charged. In addition, regarding the material of the grinding medium, an existing material such as ceramic or stainless steel can be appropriately selected. Above all, the ceramic balls are free from metal contamination. For this reason, it is preferable to use ceramic balls as the grinding medium, and specifically to use alumina balls.

  The mass of aluminum charged in the step (1A) is greater than or equal to the mass of aluminum that reacts with the residual moisture in the hermetic container in the step (3A), and the reaction with the residual moisture and the formation of sodium borohydride. When the amount is less than or equal to the mass of the total amount of aluminum required for the above, a step of additionally charging a shortage of aluminum with respect to the total amount of aluminum can be provided immediately after the step (3A). Here, “immediately after the step (3A)” means a period from the end of the step (3A) to the start of the step (4A).

  The mass of the deficient aluminum to be added later in the step (3A) is the deficiency relative to the mass of aluminum necessary for the entire reaction, that is, the mass “A” of the total aluminum necessary for all the reactions described above. = (1 + 0.828 × C / 100) × 0.547 × E) minus the mass of the aluminum charged in (1A). When the step (4A) is advanced, the sodium metaborate dehydrated in the steps (1A) to (3A) and the newly added aluminum are rolled and pulverized with a pulverizing medium. React in atmosphere to produce sodium borohydride.

[Step (4A)]
In the present embodiment, sodium borohydride can be generated by providing the next step (4A) after the above step (3A) is completed. It is sandwiched between grinding media and plastically deformed. Furthermore, the surface oxide film covering the aluminum surface is broken, and the new aluminum surface is contacted and collided with dehydrated sodium metaborate in a hydrogen atmosphere. Progresses. As sodium borohydride is produced, the amount of hydrogen in the reaction vessel decreases, but the reaction rate increases by increasing the hydrogen gas pressure. The reaction here is shown by the following reaction formula. In the rolling pulverization, a pulverization aid having higher hardness than aluminum may be charged. If the grinding aid is harder than the starting materials aluminum and sodium metaborate, it is easily pressed into aluminum and the grinding speed is improved, and the mass transfer of solid sodium metaborate and sodium borohydride is facilitated to improve the reaction speed. As the grinding aid, for example, aluminum oxide is preferable.
4Al + 6H ₂ + 3NaBO ₂ → 3NaBH ₄ + 2Al ₂ O ₃

  In the step (4A), as the sealed container, the sealed container used in (1A) to (3A) may be used as it is, or another sealed container may be used. That is, the steps (1A) to (3A) and the step (4A) may proceed as steps in one sealed container, or may be steps in two separate sealed containers. In particular, when the process is carried out in two separate sealed containers, considering the mass of aluminum that reacts with the total water vaporized in the process (2A), the aluminum deficient in the process (4A) is reduced to (3A). It is preferable to provide an additional charging step between the steps (4A) and (4A). The mass of aluminum to be additionally charged can be obtained as described above.

  The hydrogen gas pressure maintained in the step (4A) is preferably in the range of 0.3 to 10 MPa, more preferably in the range of 1 to 10 MPa. By setting the hydrogen gas pressure to 0.3 to 10 MPa, the production efficiency of sodium borohydride is excellent, and a reaction vessel and equipment having excellent pressure resistance are not required, and an increase in equipment cost can be suppressed. .

  In the step (4A), the heating temperature is preferably 200 to 550 ° C. in order to sufficiently advance the reaction. By setting the heating temperature to 200 to 550 ° C., a sufficient reaction rate is obtained, the production efficiency of sodium borohydride is excellent, and sublimation of the produced sodium borohydride is suppressed, and a sufficient recovery rate is obtained.

In (4A), the grinding medium used for rolling and grinding is the same as the grinding medium described in the step (3A).
Note that the rolling pulverization is performed by stirring the pulverization medium. The higher the stirring speed at that time, the larger the mass of the stirring medium, or the higher the reaction temperature, the shorter the time lag until the reaction. be able to.

  By the steps (1A) to (4A) described above, sodium borohydride can be generated.

<Second Embodiment>
The method for producing sodium borohydride of the second embodiment includes (1B) a step of charging sodium metaborate containing water and aluminum into a sealed container, and (2B) heating the inside of the sealed container to 200 ° C. or higher. Holding, releasing and vaporizing the adhering moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate and degassing the inside of the sealed container, (3B) 280-550 in the sealed container It is characterized by sequentially including a step of heating to ° C., rolling and grinding sodium metaborate and aluminum with a grinding medium, and reacting residual water in the sealed container with aluminum to convert it into hydrogen gas and aluminum oxide.

In the second embodiment, the major difference from the first embodiment is that in the step (2B), the attached moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate are released and vaporized, and the sealed container is The point is to remove moisture by deaeration. In the second embodiment, since water is removed in the step (2B), the water remaining in the step (3B) is less than the water remaining in the step (3A) of the first embodiment. Therefore, in the second embodiment, the amount of aluminum to be reacted with moisture can be reduced, and the necessary minimum mass of aluminum as a raw material is different from that in the first embodiment.
Below, it demonstrates in each process.

[Step (1B)]
The step (1B) is a step of charging sodium metaborate containing water and aluminum into a sealed container. The step (1B) is a step of mainly preparing and charging raw materials, and is different from the step (1A) in that the inside of the sealed container is not filled with a non-oxidizing gas. The raw materials sodium metaborate and aluminum are the same as those in the first embodiment.

In the second embodiment, as described above, since moisture is removed by deaeration in the step (2B), there is little residual moisture in the step (3B). Therefore, the mass of the aluminum charged in the step (1B) can be made smaller than that in the first embodiment. Specifically, in the first embodiment, an aluminum mass having a ratio of greater than 1 + 0.828 × C / 100 with respect to the mass “B” of aluminum when it is assumed to react with the raw material sodium metaborate in an equimolar amount. In contrast to the raw material, in the second embodiment, aluminum having a mass ratio equivalent to 1-C / 100 may be used as the raw material.
Therefore, the mass of aluminum in the step (1B) is equal to the remaining sodium metaborate obtained by subtracting the mass corresponding to the thermal weight reduction rate of 600 ° C. from the mass of sodium metaborate charged in the step (1B). The mass is preferably equivalent to the mass of aluminum assumed to react in moles.
In addition, “equivalent” in “... equal to the mass of aluminum assumed to react with sodium metaborate in an equimolar amount” means not only the case where they are equal, but also the case where there is a difference of ± 5%. .

  The process (2B) can be started immediately after the completion of the process (1B), and the process (2B) may be started after an arbitrary time has elapsed.

[Step (2B)]
In the step (2B), the inside of the sealed container is heated and held at 200 ° C. or more, the attached moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate are released and vaporized, and the inside of the sealed container is degassed to obtain moisture. This is a step of removing. In this step, the adhering moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate are vaporized, but the step (2A) of the first embodiment in that the moisture is removed by deaeration. Is different. Deaeration can be performed, for example, by connecting a vacuum pump or a suction pump to the sealed container and sucking the gas in the sealed container. It is desirable that the deaeration is continuously performed after the raw materials are charged.
In addition, the suitable conditions of the heating temperature in this process are the same as the process of (2A) of 1st Embodiment.

[Step (3B)]
In the step (3B), the inside of the sealed vessel is heated to 280 to 550 ° C., and sodium metaborate and aluminum are rolled and crushed with a grinding medium, and the residual moisture in the sealed vessel is reacted with aluminum to react with hydrogen gas and aluminum oxide. It is a process to convert to. This step is the same as the step (3A) in the first embodiment, and the preferred mode is also the same, so the description is omitted. In the description of the step (3A) in the first embodiment, replacing (3A) with (3B) is justified as the description of the step (3B) in the second embodiment.

  In the present embodiment, sodium borohydride can be generated by providing the next step (4B) after the above step (3B) is completed.

  As described above, in this embodiment, sodium borohydride can be efficiently produced by the steps (1B) to (3B) even when sodium metaborate containing moisture is used as a raw material. And sodium borohydride can be produced | generated by the process of the following (4B), for example using the sodium metaborate obtained by the process of (1B)-(3B). In addition, the process of (4B) may be performed continuously after the process of (3B) is completed, or may be performed after being transferred to another container.

[Step (4B)]
Step (4B) is a step of rolling and crushing sodium metaborate and aluminum with a grinding medium while heating the inside of the sealed container to 200 to 550 ° C. and setting the hydrogen gas pressure to 0.3 to 10 MPa. This step is the same as the step (4A) in the first embodiment, and the preferred mode is also the same, so the description is omitted. In the description of the process (4A) in the first embodiment, replacing (4A) with (4B) is justified as the description of the process (4B) in the second embodiment.

  By the steps (1B) to (4B), sodium borohydride can be generated.

In any of the first and second embodiments described above, sodium metaborate and aluminum may be charged separately in a sealed container or sequentially as a mixture containing them. . When charging as a mixture, a step of obtaining a mixture by mixing sodium metaborate and aluminum is provided before the step (1A) or (1B). In the step (1A) or (1B), metaboric acid is provided. Sodium and aluminum are preferably charged into the reaction vessel in the form of the mixture. By mixing aluminum and sodium metaborate in advance and using the mixed raw materials, sodium metaborate is easily driven into aluminum in the rolling and grinding process, and the degree of generation of new aluminum surfaces increases. The reaction rate can be increased.
Moreover, when making aluminum and sodium metaborate into a mixture, it can also carry out dispersion | distribution mixing in advance, and can also be made into a pellet by applying a pressure. Pellets have advantages such as less moisture absorption and better handling than powders.

  Next, an example of an airtight container that can be used in the present embodiment is shown, but in the present embodiment, the present invention is not limited to the following.

  A sealed container 10 shown in FIG. 3 has a round-bottomed cylindrical container body 12 and a detachable disk-shaped lid 14 that seals the container body 12. A heater 16 capable of adjusting the temperature is disposed outside the lower portion of the container body 12, and the contents of the container body 12 are heated by the heater 16. In addition, an O-ring 18 is disposed on the upper end surface of the container body 12 so as to be in close contact with the lid portion 14 and ensure internal airtightness. When the lid portion 14 is closed, the lid portion 14 is The container body 12 is in close contact with the O-ring 18. FIG. 3 shows a state in which a large number of grinding media 40 are introduced into the container body 12.

  The lid portion 14 has an opening at the center thereof, a cylindrical portion is erected in the vicinity of the opening, and a motor 20 is disposed on the upper side of the cylindrical portion. A rotating shaft of the motor 20 is provided with a stirring rod 22 having a plurality of stirring portions 22 </ b> A. When the lid portion 14 is attached to the container main body 12, the tip of the stirring rod 22 reaches a lower region inside the container main body 12. That is, when the motor 20 is driven, the stirring rod 22 rotates and the contents of the container body 12 are stirred. When the raw material is charged into the container body 12 and the stirring rod 22 is rotated, the raw material is rolled and ground due to the presence of a large number of grinding media 40.

  The lid portion 14 further includes a pipe 24 and a pipe 30 communicating with the inside of the container body 12, and the pipe 24 is connected to a hydrogen gas supply source (not shown) via a hydrogen gas supply valve 26. The exhaust valve 28 is connected to a vacuum pump (not shown). That is, when the hydrogen gas supply valve 26 is opened, hydrogen gas is supplied into the interior 12, and when the exhaust valve 28 is opened, the interior of the container body 12 is evacuated. The pipe 30 is connected to a pressure gauge 32, and the pressure inside the container body 12 can be known by the pressure gauge 32.

Hereinafter, the present embodiment will be described in more detail with reference to examples, but the present embodiment is not limited thereto.
In the following, Examples 1-2, Reference Examples 1-2, and Comparative Examples 1-2 correspond to the first embodiment, and Examples 3-5 correspond to the second embodiment.

[Example 1]
(A) Step (1A) The sodium metaborate powder which was pulverized and passed through a sieve having an opening of 100 μm was subjected to TG measurement from room temperature to 600 ° C. The weight reduction rate due to moisture was 5.3%. After 1.962 g of this sodium metaborate containing moisture and 1.133 g of aluminum having an average particle diameter of 30 μm increased by 5.5% with respect to the same amount of sodium metaborate and equimolar aluminum, at room temperature. Then, it was charged in the sealed container shown in FIG. Next, after the inside of the sealed container was connected to a vacuum pump and deaerated, it was filled with hydrogen gas (non-oxidizing gas).

(B) Step (2A) The inside of the sealed container was heated to 300 ° C., and the attached moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate were released and vaporized. The heating time at this time was 40 minutes.

(C) Step (3A) While heating the inside of the sealed container to 300 ° C., rotating the stirring rod in the sealed container, using an alumina ball having a diameter of 5 mm as a grinding medium, rolling and grinding at a stirring rotational speed of 1150 rpm. Then, the residual moisture in the sealed container was reacted with aluminum and converted into hydrogen gas and aluminum oxide to remove the residual moisture. In addition, the completion | finish of this process was complete | finished and stirred when the pressure rise in an airtight container no longer arises. The stirring time was 63 minutes.

(D) Step (4A) The hydrogen gas valve was opened, the inside of the sealed container was filled with hydrogen gas, and rolled and pulverized with a pulverization medium for 5 hours while being heated to 310 ° C. The initial hydrogen gas pressure at this time was 0.81 MPa.
As described above, sodium borohydride was obtained.

  After the completion of the step (4A), the reaction rate was calculated from the decrease in the hydrogen gas pressure. The amount of decrease was calculated by calculating the difference from the minimum pressure under the reaction conditions from the maximum gas pressure and converting it to the hydrogen gas volume (molar amount). As a result, the reaction rate was 35%. Moreover, when the content rate of sodium borohydride in a reaction product was calculated | required by the iodine titration method as shown below, it was 34%.

~ Iodine titration method ~
(1) A sample (reaction product) 50 mg was weighed to the order of 0.1 mg and collected in a weighing bottle.
(2) The sample collected in (1) was transferred to a 200 ml conical flask with a stopper. To this conical flask equipped with a stopper, 40 ml of NaOH solution having a concentration of 20 g / L was added and heated on a water bath to completely decompose unreacted aluminum powder.
(3) After cooling to room temperature, 20.0 ml of 0.05M iodine solution was added with a whole pipette, stoppered and left in the dark for 15 minutes.
(4) 3 ml of hydrochloric acid was added and shaken well, followed by titration with 0.1 M sodium thiosulfate.
(5) The titration was completed when the purple color of iodine changed to colorless.
(6) A blank test was performed without adding the sample, and the sodium borohydride content was calculated. The formula used for calculating the content is shown below.
<Calculation formula for obtaining sodium borohydride content>
NaBH ₄ (mass%) = {(A−B) × 0.1 × f × 37.83 / 8} / C × 100
The variables and constants in the above formula are as follows.
A: 0.1M sodium thiosulfate solution titration value for blank test (ml)
B: 0.1M sodium thiosulfate solution titration value of sample solution (ml)
f: Factor of 0.1 M sodium thiosulfate solution C: Amount of sample collected (mg)
37.83: Molecular weight of sodium borohydride (g / mol)
8: Normality of 1 mol / L sodium borohydride solution (N)

[Example 2]
(A) Step (1A) The sodium metaborate powder which was pulverized and passed through a sieve having an opening of 100 μm was subjected to TG measurement from room temperature to 600 ° C. The weight reduction rate due to moisture was 5.3%. After mixing 1.970 g of this sodium metaborate containing water with 1.125 g of aluminum having an average particle diameter of 10 μm increased by 4.4% with respect to the equivalent amount of sodium metaborate and equimolar aluminum, at room temperature Then, it was charged in the sealed container shown in FIG. The sealed container was closed, and the inside of the sealed container was connected to a vacuum pump for deaeration. Next, the inside of the sealed container was filled with hydrogen gas to 0.5 MPa.

(B) Step (2A) The inside of the sealed container was heated to 500 ° C., and the attached moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate were released and vaporized.

(C) Step (3A) While heating the inside of the sealed container to 500 ° C., rotating the stirring rod in the sealed container, using an alumina ball having a diameter of 5 mm as a grinding medium, rolling and grinding at a stirring rotational speed of 250 rpm. Then, the residual moisture in the sealed container was reacted with aluminum and converted into hydrogen gas and aluminum oxide to remove the residual moisture. In addition, the completion | finish of this process stopped stirring, when the pressure rise in an airtight container no longer arises. The stirring time was 48 minutes.

(D) Step (4A) The inside of the sealed container was filled with hydrogen gas and heated and pulverized for 70 minutes with a grinding medium at a stirring rotational speed of 300 rpm while being heated to 510 ° C. The hydrogen gas pressure at the beginning of the reaction in the step (4A) was 0.97 MPa.
As described above, sodium borohydride was obtained. In addition, the process of (2A)-(4A) of a present Example is corresponded to a series of processes shown in FIG.

  After the completion of the step (4A), the reaction rate was calculated from the decrease in the hydrogen gas pressure. The amount of decrease was calculated by calculating the difference from the minimum pressure under the reaction conditions from the maximum gas pressure and converting it to the hydrogen gas volume (molar amount). As a result, the reaction rate was 32%. The content of sodium borohydride in the reaction product was determined in the same manner as in Example 1 and found to be 33%.

[Example 3]
(A) Step (1B) The sodium metaborate powder which was pulverized and passed through a sieve having an opening of 100 μm was subjected to TG measurement from room temperature to 600 ° C. The weight reduction rate due to moisture was 4.2%. After mixing 1.980 g of this sodium metaborate containing water and 1.980 g of aluminum having an average particle diameter of 30 μm increased by 4.3% with respect to the equivalent amount of aluminum and its mass of sodium metaborate, at room temperature The sample was placed in a sealed container shown in FIG. Next, the inside of the sealed container was connected to a vacuum pump to be evacuated, filled with 0.1 Mpa of Ar, and then connected again to a vacuum pump of 1 torr> to make a vacuum.

(B) Step (2B) The inside of the sealed container was heated to 395 ° C., and the attached moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate were released and vaporized, followed by vacuum degassing. It cooled after deaeration.

Step (c) (3B) The hydrogen gas valve is opened and the inside of the sealed container is filled with hydrogen gas, heated to 310 ° C., and a 5 mmφ SUS304 stainless steel ball is used as the grinding medium, and the stirring rod in the sealed container is 1150 rpm. The residual water was removed by rotating, rolling and crushing, reacting the residual water with aluminum and converting it to hydrogen gas and aluminum oxide. In addition, the completion | finish of this process stopped stirring, when the pressure rise in an airtight container no longer arises. The stirring time was 1 minute.

(D) Step (4B) Following the step (3B), the mixture was heated to 310 ° C. and rolled and ground for about 5 hours with a grinding medium at a stirring rotational speed of 1150 rpm. At this time, the hydrogen gas pressure at the initial stage of the reaction was 0.75 MPa.
As described above, sodium borohydride was obtained.

  After the completion of the step (4B), the reaction rate was calculated from the decrease in the hydrogen gas pressure. The amount of decrease was calculated by calculating the difference from the minimum pressure under the reaction conditions from the maximum gas pressure and converting it to the hydrogen gas volume (molar amount). As a result, the reaction rate was 37%.

[Example 4]
(A) Step (1B) The sodium metaborate powder which was pulverized and passed through a sieve having an opening of 100 μm was subjected to TG measurement from room temperature to 600 ° C. The weight reduction rate due to moisture was 7.8%. After mixing 1.971 g of this sodium metaborate containing moisture and 1.079 g of aluminum having an average particle diameter of 30 μm increased by 0.1% with respect to the same amount of aluminum and its mass of sodium metaborate, at room temperature The sample was placed in a sealed container shown in FIG. Next, the inside of the sealed container was connected to a vacuum pump to be evacuated, and then filled with 0.1 Mpa of Ar. Next, the vacuum was again connected to a vacuum pump of 1 torr>.

(B) Step (2B) The inside of the sealed container was heated to 302 ° C., and the attached moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate were released and vaporized, followed by vacuum degassing. The heat degassing time was 40 minutes. It cooled after deaeration.

(C) Step (3B) With the hydrogen gas valve opened, the sealed container is filled with hydrogen gas and heated to 310 ° C., and the stirring rod in the sealed container is rotated at 600 rpm using the same grinding medium as in Example 1. Then, the residual water was removed by rolling and crushing, reacting the residual water with aluminum and converting it to hydrogen gas and aluminum oxide. In addition, the completion | finish of this process stopped stirring, when the pressure rise in an airtight container no longer arises. The stirring time was 8 minutes.

(D) Step (4B) Following the step (3B), the mixture was heated to 310 ° C. and rolled and ground for about 5 hours with a grinding medium at a stirring rotational speed of 1150 rpm. The hydrogen gas pressure at the initial stage of the reaction at this time was 0.806 MPa. The decrease in hydrogen gas pressure was two steps. The increase in the reaction rate in the second stage is due to the fact that the unreacted layer adhering to the wall of the closed reaction vessel dropped and the rolling and grinding reaction accelerated again.
As described above, sodium borohydride was obtained.

  After the completion of the step (4B), the reaction rate was calculated from the decrease in the hydrogen gas pressure. The amount of decrease was calculated by calculating the difference from the minimum pressure under the reaction conditions from the maximum gas pressure and converting it to the hydrogen gas volume (molar amount). As a result, the reaction rate was 43%. In addition, the process of (2B)-(4B) of a present Example is corresponded to a series of processes shown in FIG.

[Example 5]
(A) Step (1B) The sodium metaborate powder which was pulverized and passed through a sieve having an opening of 100 μm was subjected to TG measurement from room temperature to 600 ° C. The weight reduction rate due to moisture was 4.2%. After 0.760 g of this sodium metaborate containing moisture and 0.42 g of aluminum having an average particle diameter of 30 μm increased by 1.0% with respect to the same amount of sodium metaborate as the mass, and at room temperature The sample was placed in a sealed container shown in FIG. Next, the inside of the sealed container was connected to a vacuum pump of 1 torr> to make a vacuum.

(B) Step (2B) The inside of the sealed container was heated to 230 ° C., and the attached moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate were released and vaporized, followed by vacuum deaeration. It cooled after deaeration.

Step (c) (3B) The hydrogen gas valve is opened, the inside of the sealed container is filled with hydrogen gas, heated to 280 ° C., and a 5 mmφ SUS304 stainless steel ball is used as the grinding medium, and the stirring rod in the sealed container is 1150 rpm. The residual water was removed by rotating, rolling and crushing, reacting the residual water with aluminum and converting it to hydrogen gas and aluminum oxide. In addition, the completion | finish of this process stopped stirring, when the pressure rise in an airtight container no longer arises. The stirring time was 3.5 minutes.

(D) Step (4B) Following the step (3B), the mixture was heated to 238 ° C. and rolled and ground for about 7 hours with a grinding medium at a stirring rotational speed of 1150 rpm. The hydrogen gas pressure at the beginning of the reaction at this time was 0.65 MPa.
As described above, sodium borohydride was obtained.

  After the completion of the step (4B), the reaction rate was calculated from the decrease in the hydrogen gas pressure. The amount of decrease was calculated by calculating the difference from the minimum pressure under the reaction conditions from the maximum gas pressure and converting it to the hydrogen gas volume (molar amount). As a result, the reaction rate was 38%.

  From the above Examples 1 to 5, it can be seen that sodium borohydride could be produced with sufficient production efficiency even when sodium metaborate containing water was used as a raw material.

[Reference Example 1]
(A) Step (1A) The sodium metaborate powder which was pulverized and passed through a sieve having an opening of 100 μm was subjected to TG measurement from room temperature to 600 ° C. The weight reduction rate due to moisture was 5.3%. After mixing 1.963 g of this sodium metaborate containing water and 1.020 g of aluminum having an average molar diameter of 30 μm as anhydrous sodium metaborate, it was placed in a sealed container shown in FIG. 3 at room temperature. I was charged. Next, after the inside of the sealed container was connected to a vacuum pump and deaerated, it was filled with hydrogen gas (non-oxidizing gas).

(B) Step (2A) The inside of the sealed container was heated to 300 ° C., and the attached moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate were released and vaporized. The heating time at this time was 40 minutes.

(C) Step (3A) While heating the inside of the sealed container to 310 ° C., rotating the stirring rod in the sealed container, using an alumina ball having a diameter of 5 mm as a grinding medium, rolling and grinding at a stirring rotational speed of 1150 rpm. Then, the residual moisture in the sealed container was reacted with aluminum and converted into hydrogen gas and aluminum oxide to remove the residual moisture. In addition, the completion | finish of this process was complete | finished and stirred when the pressure rise in an airtight container no longer arises. The stirring time was 76 minutes.

(D) Step (4A) The hydrogen gas valve was opened, the inside of the sealed container was filled with hydrogen gas, and rolled and pulverized with a pulverization medium for 5 hours while being heated to 310 ° C. The initial hydrogen gas pressure at this time was 0.801 MPa.
As described above, sodium borohydride was obtained.

  After the completion of the step (4A), the reaction rate was calculated from the decrease in the hydrogen gas pressure. The amount of decrease was calculated by calculating the difference from the minimum pressure under the reaction conditions from the maximum gas pressure and converting it to the hydrogen gas volume (molar amount). As a result, the reaction rate was 22%. Moreover, when the content rate of sodium borohydride in a reaction product was calculated | required like Example 1, it was 23%. In Reference Example 1, it is considered that the reaction rate was low because the amount of the raw material aluminum was small as compared with Examples 1-5.

[Reference Example 2]
(A) Step (1A) The sodium metaborate powder which was pulverized and passed through a sieve having an opening of 100 μm was subjected to TG measurement from room temperature to 600 ° C. The weight reduction rate due to moisture was 7.8%. After mixing 1.980 g of this sodium metaborate containing moisture and 1.080 g of aluminum having an average particle diameter of 30 μm reduced by 0.3% with respect to the equivalent amount of sodium metaborate and equimolar aluminum, at room temperature Then, it was charged in the sealed container shown in FIG. Next, after the inside of the sealed container was connected to a vacuum pump and deaerated, it was filled with hydrogen gas (non-oxidizing gas).

(B) Step (2A) The inside of the sealed container was heated to 500 ° C., and the attached moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate were released and vaporized. The heating time at this time was 60 minutes.

(C) Step (3A) While heating the sealed container to 500 ° C., rotating the stirring rod in the sealed container, using an alumina ball having a diameter of 5 mm as a grinding medium, rolling and grinding at a stirring rotational speed of 300 rpm. Then, the residual moisture in the sealed container was reacted with aluminum and converted into hydrogen gas and aluminum oxide to remove the residual moisture. In addition, the completion | finish of this process was complete | finished and stirred when the pressure rise in an airtight container no longer arises. The stirring time was 65 minutes.

(D) Step (4A) The hydrogen gas valve was opened, the inside of the sealed container was filled with hydrogen gas, and heated and pulverized with a grinding medium for 1 hour while being heated to 510 ° C. The initial hydrogen gas pressure at this time was 1.05 MPa.
As described above, sodium borohydride was obtained.

  After the completion of the step (4A), the reaction rate was calculated from the decrease in the hydrogen gas pressure. The amount of decrease was calculated by calculating the difference from the minimum pressure under the reaction conditions from the maximum gas pressure and converting it to the hydrogen gas volume (molar amount). As a result, the reaction rate was 16%. In Reference Example 2, it is considered that the reaction rate was low because the amount of raw material aluminum was even smaller than that in Reference Example 1.

  The reason why the reaction rates of Reference Examples 1 and 2 were low in spite of including the steps (1A) to (3A) in the first embodiment is that the raw material aluminum is small as described above. Naturally, if the amount of raw materials is small, the reaction rate is low, and the effects of the steps (1A) to (3A) of this embodiment are not denied. In Reference Example 1, the reaction rate can be increased by increasing the amount of aluminum used in the step (1A) or adding an aluminum deficiency immediately after the step (3A).

[Comparative Example 1]
(A) Step (1A) The mixture was coarsely pulverized and passed through a sieve having an opening of 100 μm, and sodium metaborate on the sieve was subjected to TG measurement from room temperature to 600 ° C. The weight reduction rate due to moisture was 3.7%. After mixing 1.942 g of this sodium metaborate containing water and 1.096 g of aluminum having an average particle diameter of 30 μm increased by 3.2% with respect to the weight of aluminum equivalent to the mass of sodium metaborate, at room temperature. Then, it was charged in the sealed container shown in FIG. Next, the inside of the sealed container was connected to a vacuum pump and deaerated.

(B) Step (2A) The hydrogen gas valve is opened, the inside of the sealed container is filled with hydrogen gas, the inside of the sealed container is heated to 308 ° C., water adhering to sodium metaborate and aluminum, and hydrated water of sodium metaborate And were vaporized.

(C) Step (3A) While heating to 308 ° C., using a 5 mmφ alumina ball as a grinding medium, rotating the stirring rod in the sealed container at 1150 rpm, rolling and grinding, reacting the residual moisture with aluminum, hydrogen gas Residual moisture was removed by converting to aluminum oxide. In addition, the completion | finish of this process stopped stirring, when the pressure rise in an airtight container no longer arises. The stirring time was 57 minutes.

(D) Step (4A) Following the step (3A), the mixture was heated to 310 ° C. and rolled and ground for about 5 hours with a grinding medium at a stirring rotational speed of 300 rpm. At this time, the hydrogen gas pressure at the initial stage of the reaction was 0.795 MPa.
As described above, sodium borohydride was obtained.

  After the completion of the step (4A), the reaction rate was calculated from the decrease in the hydrogen gas pressure. The amount of decrease was calculated by calculating the difference from the minimum pressure under the reaction conditions from the maximum gas pressure and converting it to the hydrogen gas volume (molar amount). As a result, the reaction rate was 3.7%. In Comparative Example 1, it is considered that the reaction rate was low because sodium metaborate having a particle size of more than 100 μm was used as a raw material.

[Comparative Example 2]
(A) Step (1A) The sodium metaborate powder which was pulverized and passed through a sieve having an opening of 100 μm was subjected to TG measurement from room temperature to 600 ° C. The weight reduction rate due to moisture was 5.3%. Without mixing 1.979 g of this sodium metaborate containing moisture and 1.059 g of aluminum having an average particle diameter of 30% less by 2.2% with respect to its equivalent amount of sodium metaborate and aluminum, at room temperature, FIG. 3 was charged in a closed container. Next, after the inside of the sealed container was connected to a vacuum pump and deaerated, it was filled with hydrogen gas (non-oxidizing gas).

(B) Step (2A) The inside of the sealed container was heated to 230 ° C., and the attached moisture of sodium metaborate and aluminum and the hydrated water of sodium metaborate were released and vaporized. The heating time at this time was 40 minutes.

(C) Step (3A) While heating the sealed container to 230 ° C., rotating the stirring rod in the sealed container, using an alumina ball having a diameter of 5 mm as a grinding medium, rolling and grinding at a stirring rotation speed of 300 rpm. Then, the residual moisture in the sealed container was reacted with aluminum and converted into hydrogen gas and aluminum oxide to remove the residual moisture. In addition, the completion | finish of this process was complete | finished and stirred when the pressure rise in an airtight container no longer arises. The stirring time was 168 minutes.

(D) Step (4A) The hydrogen gas valve was opened, the inside of the sealed container was filled with hydrogen gas, and heated and pulverized with a pulverization medium for 17 hours while being heated to 230 ° C. The initial hydrogen gas pressure at this time was 0.66 MPa.
As described above, sodium borohydride was obtained.

  After the completion of the step (4A), the reaction rate was calculated from the decrease in the hydrogen gas pressure. The amount of decrease was calculated by calculating the difference from the minimum pressure under the reaction conditions from the maximum gas pressure and converting it to the hydrogen gas volume (molar amount). As a result, the reaction rate was 13%. In Comparative Example 2, it is considered that the reaction rate was low because the heating temperature in the step (3A) was low (230 ° C.).

  From the above examples, it can be seen that the time required for dehydration of water from the sodium metaborate powder containing water becomes shorter as the heating temperature is increased and as the stirring speed is increased, the time lag until the reaction starts. Moreover, it turns out that it will become still shorter if it heat-evacuates in the same container.

  Next, referring to FIG. 4 and FIG. 5, the time required for manufacturing is compared between the manufacturing method of sodium borohydride of the present embodiment and the conventional manufacturing method of sodium borohydride. FIG. 4 shows a process of steps ((2A) to (4A)) in the manufacturing method of the present embodiment, and FIG. 5 includes a step of performing heat deaeration in advance in the reaction vessel. 4 and 5, the horizontal axis indicates time, and the vertical axis varies depending on the graph, and indicates the hydrogen gas pressure (MPa), the temperature in the container (° C.), or the stirring rotation speed (rpm).

  In FIG. 4, the process of (2A) is about 1 hour from the start to the temperature raising period from 500 ° C. until the maximum pressure of 0.97 Mpa is reached after the start of rolling and grinding at 250 rpm. Forty-eight minutes is the step (3A), and after that, the stirring rotation speed is set to 300 rpm and the hydrogen gas pressure starts to decrease for about one hour (4A). That is, it is understood that it takes about 3 hours from the introduction of the raw material into the sealed container to the end of the production of sodium borohydride.

  On the other hand, in FIG. 4, the time axis value before 0.0 in the graph is a step of heating and degassing the attached water and hydrated water of sodium metaborate. Then, after filling with hydrogen gas, heating, rolling and crushing, water remaining in the raw material powder is dehydrated. Although the heating and degassing process of (2A) in FIG. 5 becomes longer, the rolling pulverization and dehydration process of (3B) is significantly shorter than the process of (3A) in FIG. . Thereafter, the mixture is rolled and ground to react the raw material mixture to produce sodium borohydride.

Claims (12)

(1A) A step of filling the inside of the sealed container with a non-oxidizing gas after or before charging sodium metaborate having a particle size of 100 μm or less and aluminum in the sealed container,
(2A) A step of heating and holding the inside of the sealed container at 200 ° C. or more to release and vaporize the adhering moisture of the sodium metaborate and the aluminum and the hydrated water of the sodium metaborate,
(3A) The inside of the sealed container is heated to 280 to 550 ° C., the sodium metaborate and the aluminum are rolled and pulverized with a grinding medium, and the residual moisture in the sealed container is reacted with the aluminum to generate hydrogen gas and aluminum oxide. The process of converting to
The manufacturing method of sodium borohydride which contains these one by one.   After the step (3A), (4A) the inside of the sealed container is heated to 200 to 550 ° C. and the hydrogen gas pressure is set to 0.3 to 10 MPa, and the sodium metaborate and the aluminum are crushed. The method for producing sodium borohydride according to claim 1, further comprising a step of rolling and pulverizing by the method. The manufacturing method of sodium borohydride of Claim 1 or 2 which makes mass of aluminum in the process of said (1A) larger mass than the sum of the following mass X1 and mass Y1.
Mass X1: Mass of aluminum assumed to react with equimolar amount of sodium metaborate charged in the step (1A) Mass Y1: From normal temperature to 600 by thermogravimetric measurement of sodium metaborate in the step (1A) Mass obtained by multiplying the weight loss rate up to 0 ° C by 0.828 and mass X1   The mass of aluminum charged in the step (1A) is not less than the mass of aluminum that reacts with the residual moisture in the sealed container in the step (3A), and the reaction with the residual moisture and sodium borohydride. The step of additionally charging a short amount of aluminum that is not more than the mass of the total amount of aluminum required for the reaction of the production of the above-mentioned total aluminum is provided immediately after the step (3A). The manufacturing method of sodium borohydride of any one of these. (1B) a step of containing sodium metaborate containing water and having a particle size of 100 μm or less and aluminum in a sealed container;
(2B) The inside of the sealed container is heated and maintained at 200 ° C. or more, and the adhered water of the sodium metaborate and the aluminum and the hydrated water of the sodium metaborate are discharged and vaporized, and the inside of the sealed container is deaerated. Removing water,
(3B) The inside of the sealed container is heated to 280 to 550 ° C., the sodium metaborate and the aluminum are rolled and pulverized with a grinding medium, and the residual moisture in the sealed container is reacted with aluminum to generate hydrogen gas and aluminum oxide. The process of converting to
The manufacturing method of sodium borohydride which contains these one by one.   After the step (3B), (4B) the inside of the sealed container is heated to 200 to 550 ° C. and the hydrogen gas pressure is set to 0.3 to 10 MPa, and the sodium metaborate and the aluminum are crushed. The method for producing sodium borohydride according to claim 5, further comprising a step of rolling and pulverizing by the method.   The mass of aluminum in the step (1B) is the same as the remaining sodium metaborate obtained by subtracting the mass corresponding to the thermal weight reduction rate of 600 ° C. from the mass of sodium metaborate charged in the step (1B). The method for producing sodium borohydride according to claim 5 or 6, wherein the mass is equivalent to the mass of aluminum assumed to react in moles.   The method for producing sodium borohydride according to any one of claims 1 to 7, wherein an average particle diameter of aluminum in the step (1A) or (1B) is 1 µm or more and 10 mm or less.   Before the step (1A) or (1B), a step of obtaining a mixture by mixing sodium metaborate containing water and aluminum is provided, and in the step (1A) or (1B), metaborate containing water The method for producing sodium borohydride according to any one of claims 1 to 8, wherein the mixture is used instead of sodium and aluminum.   The method for producing sodium borohydride according to claim 9, wherein the mixture is a pellet.   The method for producing sodium borohydride according to any one of claims 1 to 10, wherein the grinding medium is a ceramic ball.   The reaction between residual moisture and aluminum in the step (3A) or (3B) is continued until the time when the pressure change in the sealed container stops or the pressure decreases. 2. A method for producing sodium borohydride according to item 1.

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