JP7559199B2 - Sodium borohydride manufacturing method and sodium borohydride manufacturing apparatus - Google Patents

Description

The present invention relates to a hydrogen fixation method and a hydrogen fixation device.

Hydrogen is an important material in many chemical processes, and in recent years it is expected to be used as a clean energy source, including in fuel cells for automobiles.

When hydrogen is used as an energy source, a method of using sodium borohydride (NaBH ₄ ) as a hydrogen storage material that fixes hydrogen has been studied (Patent Document 1). This sodium borohydride easily undergoes a hydrolysis reaction with water to produce hydrogen and sodium metaborate, and therefore the efficient use of energy sources can be achieved by extracting hydrogen gas and reusing sodium metaborate.

In Patent Document 1, a mixture containing sodium metaborate (NaBO ₂ ) and metallic aluminum is heated in a hydrogen atmosphere to generate protide (H ⁻ ) on the surface of the metallic aluminum, thereby producing sodium borohydride as a hydrogen storage material (represented by the following formula (1)).
NaBO ₂ +4/3Al+2H ₂ → NaBH ₄ +2/3Al ₂ O ₃ ...(1)

JP 2014-181174 A

As mentioned above, in the production of sodium borohydride in Patent Document 1, sodium metaborate and aluminum are mixed together, so it was necessary to separate the aluminum oxide by-product after the reaction.

The present invention aims to provide a hydrogen fixation method and device that achieves excellent reaction efficiency between sodium metaborate and hydrogen without using a catalyst.

The present invention solves the above problems by any one of the following [1] to [6].
[1] A hydrogen fixation method for immobilizing hydrogen by bringing sodium metaborate into contact with hydrogen gas in a reaction vessel containing sodium metaborate to generate sodium borohydride;
[2] The hydrogen fixation method according to the above [1], wherein a catalyst is not contained in a reaction vessel;
[3] The hydrogen fixation method according to the above [1] or [2], wherein the temperature in the reaction vessel is 100 to 500° C.;
[4] The hydrogen fixation method according to any one of the above [1] to [3], wherein the hydrogen gas is generated by a reaction between a metal having hydrogen storage capacity and water vapor;
[5] A hydrogen fixation device comprising a reaction vessel for introducing sodium metaborate, a hydrogen gas supplying means for supplying hydrogen gas to the reaction vessel, and a reaction control means for reacting the supplied hydrogen gas with sodium metaborate in the reaction vessel;
[6] The hydrogen fixation device according to the above [5], wherein the hydrogen gas supply means is a means for supplying hydrogen gas generated by a reaction between a metal having hydrogen storage capacity and water vapor under pressurized conditions.

The present invention provides a hydrogen fixation method and device that achieves excellent reaction efficiency between sodium metaborate and hydrogen without using a catalyst.

1 is a schematic diagram showing a configuration of an apparatus used to carry out a hydrogen fixation method according to at least one embodiment of the present invention. FIG. 2 is a schematic diagram for explaining the structure of a reaction vessel used in carrying out the hydrogenation fixation method.

The following describes an embodiment of the present invention with reference to the attached drawings. The following description of the effects is one aspect of the effects of the embodiment of the present invention, and is not limited to those described here.

[First embodiment]
The first embodiment of the hydrogen fixation method of the present invention will be outlined below. The hydrogen fixation method of the present invention is a method for fixing hydrogen by hydrogenation of sodium metaborate (NaBO ₂ ), and is represented by the following chemical reaction formula (1).
NaBO ₂ +4H ₂ → NaBH ₄ +2H ₂ O...(1)

The above reaction is carried out by contacting hydrogen gas under pressurized conditions in a reaction vessel filled with sodium metaborate to proceed with the reaction and produce sodium borohydride. Figure 1 is a schematic diagram showing the configuration of an apparatus used to carry out a hydrogen fixation method corresponding to at least one embodiment of the present invention. The hydrogen fixation apparatus 100 comprises at least a reaction vessel 1 into which sodium metaborate is introduced, a hydrogen gas supplying means 2 that supplies hydrogen gas to the reaction vessel 1, and a reaction control means 4 that reacts the supplied hydrogen gas with sodium metaborate in the reaction vessel 1.

(Sodium Metaborate)
The sodium metaborate, which is the metal boron salt used as the raw material, may be a hydrate or anhydrous. For example, a step of removing the hydrate of sodium metaborate to obtain anhydrous sodium metaborate may be included as a pre-stage of contacting sodium metaborate with hydrogen. The removal method is not particularly limited, but it can be removed by heating, for example.

Sodium metaborate can be reacted by directly adding raw material powder to the reaction vessel 1. Alternatively, the reaction vessel 1 may be equipped with a raw material tank so that a predetermined amount can be automatically added from the tank.

In this first embodiment, we will describe in detail how the raw material sodium metaborate is filled into a cartridge, and then this cartridge is automatically loaded into a reaction vessel (described below) and subjected to a reaction.

By subjecting the reaction to a reaction in a cartridge filled with sodium borohydride, the sodium borohydride produced by the reaction in the cartridge can be easily used as a hydrogen source. In other words, since the sodium borohydride produced reacts easily with water to produce hydrogen, it is possible to use the cartridge as it is, for example, as a hydrogen source for fuel cells installed in fuel cell vehicles.

The shape of the cartridge 3 is not particularly limited, but it is preferably cylindrical in order to transport and use the filled sodium borohydride as a hydrogen generation source. In addition, the material of the cartridge 3 is preferably a stainless steel metal or a resin that is heat-resistant and hydrogen-resistant, in order to prevent the sodium borohydride from coming into contact with moisture during transportation and to withstand the pressure of the hydrogen gas that is generated.

(Reaction vessel)
The reactor 1 may be of any shape as long as the inner wall is made of a material resistant to the hydrogenation reaction. The reactor 1 may be equipped with a cooling device 6 for cooling the reactor when the temperature inside the reactor exceeds a predetermined range. The reactor 1 may also be appropriately equipped with an interlock mechanism (not shown) that prevents the reactor from operating unless sodium metaborate, the raw material, is charged, and with safety devices such as grounding the entire reactor 1 and providing a safety valve 7 for adjusting the pressure inside the reactor 1.

As shown in FIG. 2, the reaction vessel 1 includes a lid 22 with a hydrogen gas supply port 21, and a reaction chamber 23 with a cartridge holder 24 for holding a cartridge 3. The figure shows four cartridges held vertically, but it may be configured to hold a larger number of cartridges depending on the volume of the reaction chamber 23, or to hold the cartridges horizontally.

The reaction chamber 23 may be equipped with a heating means such as a heater for heating the cartridge 3 and the entire reaction chamber 23, and a temperature sensor. It may also be equipped with a cooling means such as water cooling. Furthermore, a stirring blade for stirring the sodium metaborate and hydrogen gas in the reaction chamber 23 may be provided at the bottom of the reaction chamber 23. By reacting while stirring under heated conditions, the hydrogen fixation reaction can be efficiently progressed. It is also preferable that the reaction in the reaction chamber 23 is controlled by a control means described below.

(Hydrogen gas supply means)
The reaction vessel 1 is equipped with a hydrogen gas supply means 2 for supplying hydrogen gas used in the reaction. Hydrogen gas is filled in, for example, a tank 5, and hydrogen gas with an adjusted flow rate is passed from this tank 5 through a hydrogen gas filter device 8 or the like to adjust the hydrogen gas concentration. The hydrogen gas with the adjusted concentration is supplied to the reaction vessel 1 as appropriate via a mass flow meter 9 or an electromagnetic valve 10. The mass flow meter 9 adjusts the flow rate, and the electromagnetic valve 10 is used to adjust the intake and exhaust of hydrogen gas into the reaction vessel.

The tank 5, hydrogen gas filter device 8, mass flow meter 9, solenoid valve 10, and the above-mentioned cooling device 6 are all connected to the reaction control means 4, and the temperature, pressure, and hydrogen gas concentration in the reaction vessel 1 during the hydrogenation reaction are controlled so that the reaction proceeds efficiently. This control may be automated by prior input.

In the present invention, it is desirable that the hydrogen gas filled in the tank 5 is hydrogen gas generated by a reaction between a metal having hydrogen storage capacity and water vapor. Specifically, the hydrogen gas is generated by a reaction between a metal M having hydrogen storage capacity and high-pressure water vapor by the by-product hydrogen production method described in JP 2017-190275 A, which generates an oxide of the metal M, M _α O _β (α and β are each an integer of 1 to 4, and α and β may be the same or different). By making it possible to supply the hydrogen gas generated by such a reaction to the tank 5 through piping, the efficiency of the entire plant can be improved.

The metal M is preferably a pelletized granular metal, and is preferably at least one metal selected from the group consisting of magnesium, aluminum, and iron.

The temperature of the high-pressure steam is adjusted appropriately depending on the metal M used. The reaction of the above formula (1) proceeds when the temperature of the steam in contact with the metal M is equal to or higher than the melting point of the metal M used. Therefore, when the metal M is magnesium, the temperature of the steam when it comes into contact with magnesium is preferably 650°C or higher, when the metal M is aluminum, the temperature of the steam when it comes into contact with aluminum is preferably 660°C or higher, and when the metal M is iron, the temperature of the steam when it comes into contact with iron is preferably 1535°C or higher.

The hydrogen gas generated by the reaction between the metal with hydrogen storage capacity and high-pressure steam is stored in tank 5, and the supply flow rate of hydrogen gas to reaction vessel 1 is adjusted.

(Reaction Control Means)
The reaction control means 4 adjusts the temperature and pressure within the reaction vessel 1 mainly by adjusting the amount of hydrogen gas supplied from the tank 5 to the reaction vessel 1 and by heating the reaction chamber, in order to progress the reaction between the supplied hydrogen gas and sodium metaborate within the reaction vessel 1.

In the present invention, the hydrogen fixation reaction represented by the above reaction formula (1) can be sufficiently promoted by contacting hydrogen gas with sodium metaborate, even without the presence of a catalyst such as aluminum or magnesium that is mixed with sodium metaborate in the reaction vessel 1 as in the conventional method.

The temperature inside the reaction vessel is preferably 100°C or higher, more preferably 200°C or higher, and even more preferably 300°C or higher. The temperature inside the reaction vessel is preferably 500°C or lower, more preferably 400°C or lower, and even more preferably 350°C or lower. Although it depends on the internal pressure of the reaction vessel 1, by setting the temperature inside the reaction vessel 1 within this temperature range, the hydrogen fixation reaction can be efficiently carried out.

(Method of fixing hydrogen)
A specific flow of a hydrogen fixation method using the hydrogen fixation apparatus having the above-mentioned configuration will be described.

First, the cartridge 3 filled with the raw material sodium metaborate is held in the cartridge holder 24 inside the reaction vessel 2. This operation can be performed automatically.

The lid 22 of the reaction vessel 1 is closed to seal the reaction vessel 1. Hydrogen gas is started to be supplied into the reaction vessel 1 from the hydrogen gas supply means connected to the reaction vessel 1 through the hydrogen gas supply port 21. When the pressure inside the reaction vessel 1 reaches a predetermined pressure, the inside of the reaction vessel 1 is heated until the reaction chamber 23 and cartridge 3 reach a predetermined temperature. While controlling the heating conditions to maintain the predetermined temperature, the supply of hydrogen gas continues until 4 moles of hydrogen gas are mixed with 1 mole of sodium metaborate.

By carrying out the hydrogenation as described above, sodium borohydride is produced. The reaction amount of sodium metaborate added can be roughly estimated from the total hydrogen gas flow rate supplied to the reaction vessel.

Once the reaction is complete, the cartridge can be removed from the reaction vessel, completing the entire process. A mechanism for automatically removing the cartridge may be installed as a method for removing the cartridge from the reaction vessel. A new cartridge is then installed, and the immobilization method can be carried out continuously.

(Other processes)
Since the produced sodium borohydride has high reactivity, for example, a step of creating a vacuum inside the reaction vessel 1 using a vacuum generating device 11 after the hydrogenation reaction may be provided. Also, a step of filling a vessel such as a cartridge with sodium borohydride may be provided.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Example 1
As a raw material, three cylindrical cartridges with a diameter of 20 cm were filled with sodium metaborate. The top lid of the reaction vessel was opened, and all the cartridges were mounted in the predetermined positions (cartridge holders) in the reaction vessel. Next, hydrogen gas was supplied from the hydrogen gas supply means 2 into the reaction vessel 1. The hydrogen gas used was stored in the tank 5 by a reaction between a separate magnesium metal and high-pressure steam.

The cartridge and the reaction vessel were heated so that the temperature of the sodium borate and hydrogen gas packed in the cartridge reached 200°C, and the reaction system was then maintained at 200°C. When 4 moles or more of hydrogen gas per mole of sodium metaborate packed in the cartridge 3 was supplied from the hydrogen gas supply means 2 to the reaction vessel 1, the supply of hydrogen gas was stopped and the reaction was terminated. The reaction hydrogenated the sodium metaborate, yielding sodium borohydride, and immobilizing hydrogen.

According to the hydrogen fixation method and hydrogen fixation device of the present invention, only the raw material sodium metaborate reacts with hydrogen gas in the reaction vessel to produce sodium borohydride, making it useful for efficient production of sodium borohydride without the need for a separation process as in the past.

100 Hydrogen fixation device 1 Reaction vessel 2 Hydrogen gas supply means 3 Cartridge 4 Reaction control means

Claims (6)

a hydrogen gas supplying step of supplying hydrogen gas under pressurized conditions to a reaction vessel containing sodium metaborate (except for a reaction vessel containing both sodium metaborate and a catalyst);
and a generating step of generating sodium borohydride by reacting the supplied hydrogen gas and sodium metaborate in the reaction vessel according to the following chemical reaction formula (1).
Method for producing sodium borohydride.
NaBO ₂ +4H ₂ → NaBH ₄ +2H ₂ O...(1) The temperature in the reaction vessel in the production step is 100 to 500° C.;
The method for producing sodium borohydride according to claim 1. The hydrogen gas supplying step supplies hydrogen gas generated by a reaction between a metal having hydrogen storage capacity and water vapor.
The method for producing sodium borohydride according to claim 1 or 2. A cooling step of cooling the inside of the reaction vessel by a cooling device.
The method for producing sodium borohydride according to any one of claims 1 to 3. The hydrogen gas supplying step supplies hydrogen gas from a tank filled with hydrogen gas into the reaction vessel while adjusting the flow rate via a mass flow meter.
The method for producing sodium borohydride according to any one of claims 1 to 4. A reaction vessel into which sodium metaborate is charged (excluding those into which sodium metaborate and a catalyst are charged together);
a hydrogen gas supply means for supplying hydrogen gas under pressurized conditions to the reaction vessel;
The reaction vessel is for reacting the supplied hydrogen gas with sodium metaborate according to the following chemical reaction formula (1) to produce sodium borohydride.
Sodium borohydride manufacturing equipment.
NaBO ₂ +4H ₂ → NaBH ₄ +2H ₂ O...(1)

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