JP2023112931A - Method for producing magnesium hydride - Google Patents

Abstract

To provide a method for producing magnesium hydride which improves the reactivity of magnesium and can carry out hydrogenation treatment even in a state where the pressure of hydrogen gas is kept low.SOLUTION: There is provided a method for producing magnesium hydride which comprises: a pulverization step of pulverizing magnesium by adding a fatty acid; and a hydrogenation step of hydrogenating the pulverized magnesium by heating the magnesium to a temperature of 140°C or more and less than the decomposition temperature of magnesium hydride in a reaction vessel to which hydrogen gas is supplied so as to keep the pressure 5 atmospheres or less, wherein the pulverization step is performed under an atmosphere of nitrogen gas and the pulverized magnesium is not allowed to contact with oxygen until the hydrogenation step has been completed.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for producing magnesium hydride.

In recent years, hydrogen has been attracting attention as an energy source, and magnesium hydride is available as a method for storing the hydrogen.

Further, in Patent Document 1, a raw material powder containing magnesium as a main component is held in a hydrogen gas atmosphere enclosed in an enclosure, the pressure of the hydrogen gas atmosphere in the enclosure is maintained at a predetermined pressure, The temperature of the hydrogen gas atmosphere in the enclosure is raised from room temperature, and the temperature of the hydrogen gas atmosphere in the enclosure is increased to the equilibrium curve of the reaction in which elemental magnesium and hydrogen molecules combine to form magnesium hydride and the reverse reaction. By maintaining a temperature that is higher than the temperature corresponding to the predetermined pressure above and the temperature difference from the temperature corresponding to the predetermined pressure on the equilibrium curve is within 100 ° C. for a predetermined first period, the surface of the raw material powder Then, without returning the temperature of the hydrogen gas atmosphere in the enclosure to room temperature, lower than the temperature corresponding to the predetermined pressure on the equilibrium curve and corresponding to the predetermined pressure on the equilibrium curve A method for producing a magnesium-based hydride is disclosed in which a magnesium-based hydride is produced from a raw material powder by maintaining a temperature within 100° C. from the temperature for a predetermined second period.

That is, in Patent Document 1, at a temperature higher than the temperature corresponding to the predetermined pressure on the equilibrium curve of the reaction in which magnesium and hydrogen molecules are combined to form magnesium hydride and the reverse reaction, the predetermined pressure on the equilibrium curve A first feature is that the temperature difference from the temperature corresponding to is within 100° C. is maintained for a predetermined first period.

Due to this first feature, in Patent Document 1, thermal decomposition of magnesium hydroxide (Mg(OH) ₂ ) formed on the surface of magnesium (Mg) proceeds, and magnesium oxide (MgO ) is also reduced by hydrogen molecules, the film on the surface of magnesium (Mg) is removed, and it becomes possible to rapidly react with hydrogen (H ₂ ).

Further, in Patent Document 1, the temperature of the hydrogen gas atmosphere is lower than the temperature corresponding to the predetermined pressure on the equilibrium curve without returning to room temperature, and the temperature difference from the temperature corresponding to the predetermined pressure on the equilibrium curve is A second feature is that the temperature is maintained within 100° C. for a predetermined second period.

Due to this second feature, in Patent Document 1, high-purity magnesium hydride ( MgH ₂ ) can be obtained.

JP-A-2008-44832

By the way, in Patent Literature 1, looking at the examples, the hydrogen gas pressure during the hydrogenation is set to a pressure atmosphere of 10 atmospheres (about 1 MPa) or more.

Patent document 1 also explains that the pressure should be at least 6 atmospheres or more in order to produce magnesium hydride within a realistic time range.

However, the specifications (for example, pressure resistance performance, etc.) required for an apparatus that performs processing in a high-pressure hydrogen gas atmosphere are severe.

Therefore, it is desired to improve the reactivity of magnesium and realize a technology that enables hydrotreating even when the pressure of hydrogen gas is kept low.

The present invention has been made in view of such circumstances, and provides a method for producing magnesium hydride that can improve the reactivity of magnesium and can be hydrotreated even when the pressure of hydrogen gas is kept low. for the purpose.

In order to achieve the above objects, the present invention is grasped by the following configurations.
(1) The method for producing magnesium hydride of the present invention includes a pulverizing step of pulverizing magnesium by adding fatty acid, and pulverizing in a reaction vessel supplied with hydrogen gas so as to maintain a pressure of 5 atmospheres or less. A hydrogenation step of heating the magnesium to a temperature of 140 ° C. or higher and less than the decomposition temperature of magnesium hydride to hydrogenate it, and the pulverizing step is performed in an atmosphere of nitrogen gas, and the pulverized Magnesium is not exposed to oxygen until the end of the hydrogenation step.

(2) In the configuration of (1) above, the nitrogen gas is supplied from a nitrogen generator that generates nitrogen gas with a purity of 99.9% or more from the atmosphere.

(3) In the configuration of (1) or (2) above, the amount of the fatty acid added in the grinding step is 3% by mass or more of the total mass of the magnesium and the fatty acid.

ADVANTAGE OF THE INVENTION According to this invention, the reactivity of magnesium is improved and the manufacturing method of the magnesium hydride which can be hydrogenated even in the state which kept the pressure of hydrogen gas low can be provided.

1 is a perspective view of a pulverizer used in a pulverization step of a first embodiment according to the present invention; FIG. It is a perspective view showing the state where the hood of the crusher of the first embodiment according to the present invention is opened. 1 is a perspective view of a crushing container of a first embodiment according to the present invention; FIG. 1 is an exploded perspective view of a crushing container of a first embodiment according to the present invention; FIG. 1 is a side view showing a hydrogenation furnace of a first embodiment according to the present invention; FIG. 4 is a flow chart showing the procedure of the hydrogenation step of the first embodiment according to the present invention. 4 is a graph showing the boundary line of decomposition formation of magnesium hydride obtained by thermodynamic calculation.

EMBODIMENT OF THE INVENTION Hereinafter, with reference to an accompanying drawing, the form (henceforth, embodiment) for implementing this invention is demonstrated in detail.
In addition, the same code|symbol is attached|subjected to the same element through the whole description of embodiment.

(First embodiment)
The method for producing magnesium hydride according to the first embodiment of the present invention includes a pulverizing step of adding fatty acid and pulverizing magnesium before pulverization (hereinafter, sometimes simply referred to as magnesium), and 5 atmospheres or less. A hydrogenation step of heating and hydrogenating the pulverized magnesium to a temperature of 140 ° C. or more and less than the decomposition temperature of magnesium hydride in a reaction vessel supplied with hydrogen gas so as to maintain the pressure of Prepare.

For this reason, as equipment, a crusher 1 (see FIG. 1) for carrying out the crushing step and a hydrogenation furnace 8 (see FIG. 5) for carrying out the hydrogenation step are used. After describing the crusher 1 and the hydrogenation furnace 8 (including the work procedure in the hydrogenation furnace 8), specific examples will be described.

(Crusher)
FIG. 1 is a perspective view of a pulverizer 1 used in the pulverization step of the first embodiment according to the present invention, and FIG. 2 shows a state in which the hood 3 of the pulverizer 1 of the first embodiment of the present invention is opened. 3 is a perspective view of the crushing container 4 of the first embodiment according to the present invention, and FIG. 4 is an exploded perspective view of the crushing container 4 of the first embodiment according to the present invention. .
The pulverizer 1 used in the first embodiment described below is a planetary ball mill manufactured by Fritsch.

As shown in FIGS. 1 and 2, the pulverizer 1 used in the first embodiment includes a pulverizer body 2 for controlling rotation of a detachably fixed pulverization container 4 (see FIG. 2), and a pulverizer A hood 3 that is connected to the main body 2 with a hinge structure so as to be openable and closable and that can cover the crushing container 4 is provided.

As shown in FIG. 1, the crusher body 2 includes a condition input unit 21 for inputting conditions for controlling the rotation of the crushing container 4, and an emergency stop button 22. As shown in FIG.

As shown in FIGS. 3 and 4, the crushing container 4 constitutes a container for containing an object to be crushed (not shown) and spherical crushing media (not shown) for promoting crushing. , a bottomed crushing container main body 41 having an upper opening, and a lid portion 42 closing the upper opening of the crushing container main body 41 .

As shown in FIG. 4, the crushing container main body 41 has a groove portion 411 in which the O-ring 5 is arranged in the edge portion on the upper opening side, and a screw portion formed radially outwardly of the groove portion 411 to which a screw is screwed. and a screw hole 412 .
In addition, a total of four screwing holes 412 are provided at a pitch of 90° in the circumferential direction.

On the other hand, the lid portion 42 has a through hole 421 provided with a counterbore for accommodating the screw head on the outer surface (see FIG. 3).
The through hole 421 is for passing the threaded portion of the screw into the crushing container main body 41 when the lid portion 42 is screwed to the crushing container main body 41, so the through hole 421 is provided. The positions (distance from the center, etc.) correspond to the threaded holes 412 of the crushing container main body S41. are provided individually.

An object to be crushed (not shown) and spherical crushing media (not shown) for promoting crushing are accommodated in the crushing container main body 41, and the lid portion 42 holds the O-ring 5 on the crushing container main body 41 side. When a screw (not shown) is screwed into the screw engagement hole 412 of the crushing container main body 41 through the through hole 421 from the lid portion 42 side so as to press the object to be crushed (not shown) and Spherical grinding media (not shown) that promote grinding are housed in the grinding container 4 in a completely sealed state.

In this way, after the object to be crushed (not shown) and the spherical crushing media (not shown) that promotes crushing are accommodated in the crushing container 4, as shown in FIG. The container 4 is fixed to the crusher main body 2, the hood 3 of the crusher main body 2 is closed as shown in FIG. Then press the crushing start button to start crushing.

Specifically, when the pulverization start button is pressed, the rotation of the pulverization container 4 itself is started, and in the pulverization container 4 that is in a sealed state, the pulverization media for promoting pulverization by rotational force, specifically, , a hard ball (for example, a 5 mmφ high-hardness ball (SUS440C, hard ball such as chromium steel)) and magnesium, which is an object to be pulverized, are vigorously agitated, and pulverization proceeds.

As described above, since the crushing container 4 is configured to be completely sealed, outside air does not enter during crushing.

Therefore, an object to be crushed (not shown) and spherical crushing media (not shown) for promoting crushing are placed in the crushing container main body 41, and the lid portion is screwed to the crushing container main body 41 with a screw (not shown). If the work of fixing 42 is performed in a glove box in an argon gas atmosphere, the inside of the crushing container 4 becomes an argon gas atmosphere, and the crushing can be performed in the argon gas atmosphere.

An object to be crushed (not shown) and spherical crushing media (not shown) for promoting crushing are placed in the crushing container main body 41, and the crushing container main body 41 is screwed (not shown) to the lid. If the work of fixing 42 is performed in a glove box having a nitrogen gas atmosphere, the inside of the grinding container 4 becomes a nitrogen gas atmosphere, and grinding can be performed in the nitrogen gas atmosphere.

When the crushing process is completed, the crushing container 4 is removed from the crusher main body 2 again, the crushing container 4 is moved into the glove box, and the crushed material is transferred to an airtight bottle that can prevent outside air from entering inside the glove box. to collect the crushed material.

If this recovery work is performed in a glove box with an argon gas atmosphere, the pulverized material will be stored in an airtight bottle filled with argon gas, and it will be performed in a glove box with a nitrogen gas atmosphere. For example, ground material would be stored in an airtight bottle filled with nitrogen gas.

In addition, as will be described later, when magnesium, which is an object to be pulverized, is contained in the pulverization container 4, a pulverization step of adding fatty acid and pulverizing magnesium can be performed, and hydrogenation efficiency can be improved. It can be highly reactive ground magnesium.

The reason for the high reactivity is that fatty acids have a carboxyl group, and the oxygen of the metal oxide (for example, the oxygen of the oxide film formed on the surface of magnesium) reacts with the carboxyl group to Therefore, it is surmised that this kind of reaction contributes to the formation of pulverized magnesium with good hydrogenation efficiency and high reactivity. be done.
It is believed that fatty acids also react with metals themselves to form metal soaps.

For example, fatty acids to be added include butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, icosanoic acid, Henicosanoic acid, docosanoic acid, tetracosanoic acid, hexacosanoic acid, octacosanoic acid, triacontanoic acid, and the like can be preferably used.

However, if the alkyl chain is short, the hydrophobicity becomes weak and it tends to absorb moisture, so it is necessary to handle it so that it does not absorb moisture. It is thought that the melting of fatty acids does not occur with the rise, making it difficult to add to magnesium.

From this, the fatty acid has a total carbon number of about 7 to 30, that is, heptanoic acid (7 carbon atoms), octanoic acid (8 carbon atoms), nonanoic acid (9 carbon atoms), decanoic acid (9 carbon atoms), number 10), dodecanoic acid (12 carbon atoms), tetradecanoic acid (14 carbon atoms), pentadecanoic acid (15 carbon atoms), hexadecanoic acid (16 carbon atoms), heptadecanoic acid (17 carbon atoms), octadecanoic acid (18 carbon atoms ), icosanoic acid (20 carbons), henicosanoic acid (21 carbons), docosanoic acid (22 carbons), tetracosanoic acid (24 carbons), hexacosanoic acid (26 carbons), octacosanoic acid (28 carbons), Triacontanoic acid (30 carbon atoms), etc. are considered more suitable.

(hydrogenation furnace)
FIG. 5 is a side view showing the hydrogenation furnace 8 of the first embodiment according to the invention.
In addition, FIG. 5 illustrates the heating furnace 81 as a cross-sectional view so that the explanation can be easily understood.
In addition, FIG. 5 only shows the mounting position of the clamp 824 with a dotted line for easy understanding of the explanation, and what is actually used is a commercially available clamp for clamping a NW standard flange.

As shown in FIG. 5, the hydrogenation furnace 8 detachably receives a reaction vessel 82 for hydrogenating pulverized magnesium and the reaction vessel 82, and adjusts the temperature in the reaction vessel 82 to A heating furnace 81 that can be heated to a temperature and a flexible gas pipe FGP that is controlled to maintain the pressure of hydrogen gas at a predetermined pressure is connected to a reaction vessel 82 so that the hydrogen gas can be supplied. A pressure adjustment tank 83 is provided.

The reaction vessel 82 has a flange portion 8211 supported by the heating furnace 81 on the outer periphery in the middle in the vertical direction, and has a reaction vessel main body 821 whose upper side is open so that crushed magnesium can be accommodated, and the upper opening is closed. an O-ring 823 that is arranged at the edge of the opening side of the reaction container main body 821 and is sandwiched between the reaction container main body 821 and the lid portion 822 to maintain airtightness; and a clamp 824 that is fixed so as to be pressed by the lid portion 822 .

The lid portion 822 is provided with a needle valve N1 detachable from the flexible gas pipe FGP, and has an intake/exhaust port 8221 that can be opened and closed by operating the needle valve N1.

The heating furnace 81 includes a heat-insulating housing 811 having an opening for receiving the reaction vessel main body 821, a heater section 812 provided inside the heat-insulating housing 811, and a temperature controller for controlling the heater section 812 at a set temperature. (not shown), and the opening for receiving the reaction container main body 821 is set to have an inner diameter slightly smaller than the outer diameter of the flange portion 8211 so that the flange portion 8211 of the reaction container main body 821 can be supported.

However, the opening for receiving the reaction container main body 821 is set to have an inner diameter larger than the body outer diameter of the reaction container main body 821 so that the reaction container main body 821 can be received.

Note that the temperature controller controls a temperature measuring unit (for example, a thermocouple) that measures the temperature of the heater unit 812, and controls the power supplied to the heater unit 812 based on the temperature measurement result to maintain the set temperature. and a power control unit.

The pressure regulating tank 83 is a stainless steel tank with a sealed structure for confining gas, and is equipped with a mounting port PT1 for mounting a digital pressure gauge DP for measuring the pressure inside the tank, and an on-off valve OCB2. A hydrogen gas receiving port PT2 for receiving hydrogen gas and an on-off valve OCB3 are attached, and an argon gas receiving port PT3 for receiving argon gas and a needle valve N2 are attached to allow the gas in the tank to flow into the reaction vessel. A gas supply port PT4 to which a flexible gas pipe FGP for sending to 82 is connected, and a vacuum pump P2 equipped with an on-off valve OCB5 and used to replace the gas in the tank. and a port PT5.

In addition, the supply of hydrogen gas to the pressure adjustment tank 83 is performed by decompressing the hydrogen gas to a pressure of 0.2 to 0.3 MPa, which is the operating pressure of the mass flow controller, by the decompression valve of the hydrogen gas cylinder B2 of high pressure gas. The hydrogen gas is supplied through a mass flow controller MFC-H for hydrogen gas connected to the receiving port PT2 of .

In addition, the argon gas is supplied to the pressure adjustment tank 83. The argon gas is decompressed to a pressure of 0.2 to 0.3 MPa, which is the operating pressure of the mass flow controller, by the decompression valve of the argon gas cylinder B3 of high pressure gas. The argon gas is supplied via an argon gas mass flow controller MFC-A connected to the receiving port PT3 of .

The hydrogenation furnace 8 is equipped with a control device for controlling the gas supply. Specifically, the control device uses a sequencer PLC, which is a controller capable of constructing a control program. ing.
In FIG. 5, the sequencer PLC, the digital pressure gauge DP, the hydrogen gas mass flow controller MFC-H, and the argon gas mass flow controller MFC-A are connected by dash-dotted lines. This indicates that they are connected by a signal line that transmits a signal.

As a sequencer PLC control program, the mass flow controller to be operated and the flow rate are specified on the sequencer PLC liquid crystal screen, and the mass flow controller specified to flow the flow rate (mass flow controller MFC-H for hydrogen gas, mass flow controller MFC-H for argon gas, A direct input mode that controls the operation of the mass flow controller MFC-A), and a mass flow controller to be operated and the upper and lower limits of pressure are specified on the liquid crystal screen of the sequencer, and the output value of the digital pressure gauge DP indicates the lower limit of pressure. and a pressure control mode for performing control to supply gas at a preset flow rate to a designated mass flow controller when the pressure falls below.

In the pressure control mode, when the output value of the digital pressure gauge DP reaches the upper limit of the pressure due to gas supply, the operation of the mass flow controller is stopped to stop the gas supply.

Further, in the above description, the configuration has been described in which argon gas can be supplied to the hydrogenation furnace 8, but there is no problem even if the argon gas is changed to nitrogen gas.
In this case, the high-pressure argon gas cylinder B3 is changed to a high-pressure nitrogen cylinder or a nitrogen generator that generates nitrogen gas with a purity of 99.9% or more from the atmosphere, and the argon gas mass flow controller MFC-A is replaced. , the mass flow controller should be changed to a nitrogen gas mass flow controller.

(Working procedure in the hydrogenation furnace)
Next, a working procedure (a procedure of the hydrogenation step) using the hydrogenation furnace 8 as described above will be described.
FIG. 6 is a flow chart showing the procedure of the hydrogenation step of the first embodiment according to the present invention.
In the following description, a configuration in which argon gas is supplied to the hydrogenation furnace 8 will be described. It should be understood by replacing the part with nitrogen gas.

Before explaining the procedure of the hydrogenation step, it is assumed that the pressure adjustment tank 83 and the reaction vessel 82 are filled with argon gas at atmospheric pressure. It is assumed that the on-off valves OCB2, OCB3, and OCB5 attached to PT3 and exhaust port PT5 are closed.
It is also assumed that the needle valves N1 and N2 attached to the intake/exhaust port 8221 of the lid portion 822 and the gas supply port PT4 are also closed.

(Step 1)
First, the reaction vessel 82 is removed from the hydrogenation furnace 8 (S1).
Specifically, the connection between the needle valve N1 attached to the intake/exhaust port 8221 of the lid portion 822 and the flexible gas pipe FGP is released, and the reaction vessel 82 is removed from the hydrogenation furnace 8. .

By disconnecting the connection, outside air (atmosphere) enters the flexible gas pipe FGP. is in the closed state, external air does not enter the reaction container 82 .
Similarly, since the needle valve N2 is also closed, outside air does not enter the pressure regulation tank 83.

(Step 2)
Next, the removed reaction container 82 is placed in the glove box, and the object to be crushed (specifically, crushed magnesium) crushed in the crushing step is accommodated in the reaction container 82 (S2).

Specifically, the clamp 824 of the reaction vessel 82 is removed in the glove box, the lid 822 is removed from the reaction vessel main body 821, and crushed magnesium is introduced into the reaction vessel main body 821 through the upper opening of the reaction vessel main body 821.
Subsequently, a lid portion 822 is installed so as to close the upper opening of the reaction container main body 821, and a clamp 824 is attached so that the outside air (atmospheric air) does not enter the reaction container 82 and is sealed.

In this glove box, when the pulverized magnesium is stored in the reaction vessel 82, if the inside of the glove box is set to an argon gas atmosphere, the reaction vessel 82 containing the pulverized magnesium is filled with argon gas. become.

Similarly, when the glove box is used to store the pulverized magnesium in the reaction vessel 82, if the inside of the glove box is kept in a nitrogen gas atmosphere, the reaction vessel 82 containing the pulverized magnesium is filled with nitrogen gas. become a state.

(Step 3)
Next, the reaction vessel 82 containing the pulverized magnesium is attached again to the heating furnace 8 (S3).
Specifically, as shown in FIG. 5, the reaction vessel 82 in which the atmospheric gas is enclosed in the glove box is installed so that the flange portion 8211 of the reaction vessel main body 821 is supported by the heat insulating housing 811, The needle valve N1 attached to the intake/exhaust port 8221 of the lid portion 822 is connected to the flexible gas pipe FGP.

(Step 4)
Next, the outside air (atmosphere) mixed in the flexible gas pipe FGP, the argon gas in the pressure adjustment tank 83, and the gas in the reaction vessel 82 are evacuated to make it possible to fill with hydrogen gas. is vacuumed (S4).

First, the vacuum pump P2 is driven, the on-off valve OCB5 attached to the exhaust port PT5 is opened, and the argon gas in the pressure adjustment tank 83 is started to be exhausted.

Subsequently, the needle valve N2 attached to the gas supply port PT4 is opened to exhaust outside air (atmosphere) mixed in the flexible gas pipe FGP.

Then, the operator waits in this state for a while until the outside air (atmosphere) mixed in the flexible gas pipe FGP is completely exhausted.

After sufficiently evacuating in this way (for example, after evacuating to about several Pa), the needle valve N1 attached to the intake/exhaust port 8221 of the lid portion 822 is slowly turned to open. state.

The reason why the needle valve N1 attached to the intake/exhaust port 8221 is slowly turned to open is that the gas in the reaction vessel 82 is gently exhausted so that the pulverized magnesium in the reaction vessel 82 is not sucked. to do

(Step 5)
When the inside of the reaction vessel 82 becomes a vacuum state, a hydrogenation treatment is performed by heating the pulverized magnesium to a temperature at which hydrogenation proceeds in a hydrogen gas atmosphere (S5).

First, before hydrogen gas is actually supplied and hydrogenation treatment is performed, the heater part 812 of the heating furnace 81 is turned on while vacuuming is continued to start heating the pulverized magnesium.
The set temperature of the heater part 812 may be the temperature for heating to a temperature suitable for hydrogenating pulverized magnesium.

Specifically, when the pressure of the hydrogen gas is about 90 kPa (about 0.9 atm), the heating temperature for hydrogenation is 140° C., because the hydrogenation reaction rapidly slows down below 140° C. Since the hydrogenation efficiency is relatively good in the range of about 220°C ± 40°C, in the first embodiment, the set temperature of the heater unit 812 is set to 220°C for the pulverized magnesium. Set the temperature to heat.

In this way, by starting heating in a vacuum state, the excess fatty acid added in the grinding process adhering to the surface of the ground magnesium is removed, and the hydrogenation efficiency decreases due to the effect of the fatty acid. can be prevented.

However, if the amount of fatty acid added is not large, the heat treatment of heating the pulverized magnesium while vacuuming may be omitted.
That is, the heating may be started after the hydrogen gas is supplied first.

Next, after closing the on-off valve OCB5 attached to the exhaust port PT5 and stopping the driving of the vacuum pump P2, the on-off valve OCB2 attached to the hydrogen gas receiving port PT2 is opened, Start the pressure control mode of the sequencer PLC.

In the first embodiment, the pressure of hydrogen gas is controlled to about 90 kPa (about 0.9 atmospheres), so the upper and lower limits of the pressure to be controlled are set to a lower limit of 89 kPa and an upper limit of 91 kPa, respectively. When the output value of the digital pressure gauge DP reaches 91 kPa, the driving of the hydrogen gas mass flow controller MFC-H is stopped, and the supply of hydrogen gas is stopped.

As the hydrogenation progresses, hydrogen gas is taken into the pulverized magnesium, so the pressure in the pressure regulation tank 83 decreases and the output value of the digital pressure gauge DP becomes 89 kPa.

Then, the hydrogen gas mass flow controller MFC-H is driven again, and hydrogen gas is supplied until the output value of the digital pressure gauge DP reaches 91 kPa.

In this way, while maintaining the pressure of the hydrogen gas atmosphere at about 90 kPa, the pulverized magnesium is heated to about 220° C. and hydrogenation is performed for a predetermined time. , the pressure control mode of the sequencer PLC is terminated, and the hydrogenation process ends.

(Step 6)
After the hydrogenation process is completed, the hydrogenated material (magnesium hydride) is taken out. , argon gas is replaced (S6).

Specifically, after closing the open/close valve OCB2 attached to the hydrogen gas receiving port PT2, the vacuum pump P2 is driven and the open/close valve OCB5 attached to the exhaust port PT5 is opened.

After the vacuum is sufficiently drawn, the open/close valve OCB5 attached to the exhaust port PT5 is closed to stop the vacuum pump P2, and the open/close valve OCB3 attached to the argon gas receiving port PT3 is closed. Open and supply argon gas until atmospheric pressure is reached.

When the argon gas filling is completed until the pressure of the pressure adjustment tank 83 and the reaction vessel 82 reaches the atmospheric pressure, the supply of argon gas is stopped, and the open/close valve OCB3 attached to the argon gas receiving port PT3 is closed. close.

At this time, the needle valve N1 attached to the intake/exhaust port 8221 of the lid 822 of the reaction vessel 82 and the needle valve N2 attached to the gas supply port PT4 of the pressure adjustment tank 83 are closed, Complete the gas replacement work.

(Step 7)
When the gas replacement is finished, magnesium hydride, which is the material after hydrogenation, is taken out (S7).
Magnesium hydride is relatively stable even in the atmosphere unless it is exposed to moisture, so it is not necessary to carry out the reaction in the glove box used to store the pulverized magnesium in the reaction vessel 82 .

However, if you work in a glove box, you can take out magnesium hydride in an environment with extremely low humidity, so store magnesium hydride in a glove box with nitrogen gas or argon gas You may perform the operation|work which collects in a bottle etc.

Thus, when the magnesium hydride, which is the post-hydrogenation material, is removed from the reaction vessel 82, the hydrogenation step is completed.

Here, the hydrogen gas atmosphere and heating conditions for the hydrogenation treatment will be briefly described.
FIG. 7 is a graph showing the boundary line of decomposition formation of magnesium hydride obtained by thermodynamic calculation.
Note that the temperature on the decomposition boundary line may be referred to as the decomposition boundary temperature.
In the graph shown in FIG. 7, the vertical axis indicates the pressure (unit: Pa) of the hydrogen gas atmosphere, and the horizontal axis indicates the temperature (unit: ° C.). It has become.

In other words, on the right side (high temperature side) of the decomposition production boundary line BL of magnesium hydride, magnesium hydride decomposes into a state of magnesium and hydrogen gas, and on the left side (low temperature side), decomposition of magnesium hydride occurs. This is the region in which the production reaction proceeds to form magnesium hydride if magnesium and hydrogen gas are present.

In the first embodiment, the pressure of the hydrogen gas atmosphere is about 90 kPa, which is slightly lower than 100000 Pa, and the temperature on the boundary line BL for decomposition of magnesium hydride is around 280.degree.

However, since the actual heating temperature is about 220° C., the temperature may be about 60° C. lower than the temperature on the boundary line BL of decomposition formation of magnesium hydride.

From this, for example, in the case of treatment in a hydrogen gas atmosphere of 5 atm (5 atmospheres) indicated by the dotted line on the graph, the temperature on the decomposition production boundary line BL of magnesium hydride is about 350 ° C. It is thought that the heating temperature of 300° C. or less may suffice.

On the other hand, as shown in the prior art document, if the treatment is performed at a temperature about 50° C. higher than the temperature on the decomposition production boundary line BL of magnesium hydride, treatment in a hydrogen gas atmosphere of 5 atm (5 atm) is required. In the case of , it is heated to a temperature of 400° C. or higher, and in this case, radiant heat becomes dominant.

A metal material such as stainless steel is generally used for the reaction vessel 82. However, if stainless steel or the like is used, radiation is reflected, which reduces heat transfer efficiency and increases energy loss. be done.

However, by performing the pulverization step of adding fatty acid and pulverizing magnesium, it is unnecessary to treat at a temperature about 50 ° C. higher than the temperature on the decomposition production boundary line BL of magnesium hydride as shown in the prior art document. , it is possible to produce sufficiently high-purity magnesium hydride.

Therefore, if the pressure of the hydrogen gas atmosphere in the hydrogenation step is set to 5 atm (5 atmospheres) or less, the hydrogenation treatment can be performed at a low temperature range of about 400° C. to 100° C. or more, where radiant heat is dominant, and energy efficiency is improved. Good hydrotreating can be realized.

Furthermore, since it is possible to process at a relatively low pressure of 5 atm (5 atmospheres) or less, there is no need to increase the thickness of the reaction vessel 82 for pressure resistance performance, so heat is transmitted well and pulverization is efficient. Since it is possible to heat the magnesium that has been heated, the energy efficiency is considered to be good in this respect as well.

On the other hand, according to thermodynamic calculations, magnesium hydride can exist stably even at low temperatures, but there is no reaction rate factor in thermodynamic calculations. The decrease in pressure seen in the hydrogenation process due to absorption of gas is significantly slowed.

For this reason, it is preferable to heat magnesium to a temperature of 140° C. or higher in the hydrogenation treatment of the hydrogenation step.

Specifically, the line indicated by the dashed-dotted line in the graph of FIG. By doing so, magnesium hydride will not decompose at a temperature of 140°C.

Therefore, in the hydrogenation step, it is preferable to heat the pulverized magnesium to a temperature of 140° C. or more and less than the decomposition temperature of magnesium hydride under a hydrogen gas pressure of 500 Pa or more and 5 atmospheres or less. By doing so, the treatment can be performed in a temperature range 100° C. or more lower than 400° C. where the influence of radiant heat is strong, and since there is no need to increase the thickness of the reaction vessel 82, the heat can pass through well and the treatment can be performed with good energy efficiency. can be done.

For example, when the pressure of the hydrogen gas in the hydrogenation step is less than 0.2 MPa, even periodic inspection is not required legally, and in promoting hydrogenation, a high pressure, such as 30 kPa (about 0.3 Atmospheric pressure) or more is preferable, and the hydrogenation treatment in the hydrogenation step is more preferably performed by heating the pulverized magnesium under a hydrogen gas pressure of 30 kPa or more and less than 0.2 MPa.

Next, Example 1 and Comparative Example 1 will be described.
In the pulverization steps of Example 1 and Comparative Example 1, in both cases, as the pulverization condition, a hard ball made of high hardness stainless steel (SUS440C) having a diameter of 5 mm was inserted so as to occupy 1/3 of the internal volume of the pulverization container 4. , and 70 g of magnesium having an average particle size of 180 μm was added so as to occupy ⅓ of the internal volume.

Further, when magnesium was put into the pulverizing container 4, octadecanoic acid was added as a fatty acid, and a pulverizing step was performed in which the fatty acid was added and the magnesium was pulverized.

Specifically, in both Example 1 and Comparative Example 1, magnesium (70 g) and octadecanoic acid (3.684 g) were placed in the crushing vessel 4, and the total amount of magnesium and octadecanoic acid combined was Add 5% by mass (wt%) of octadecanoic acid (fatty acid) in the mass (73.684 g), add 5% by mass (wt%) of octadecanoic acid in the total mass, and grind the magnesium. I made it

In both Example 1 and Comparative Example 1, the crusher 1 was operated at a rotational speed of 330 rpm for 1 hour and then stopped for 1 hour, which was performed 24 times for crushing. The rotation time of the container 4 was set to 24 hours.

The reason why the operation is stopped for one hour after the operation for one hour is to suppress the temperature rise of the pulverizing container 4 for pulverization. It is

In Example 1, the work of putting magnesium, fatty acid, and hard spheres into the crushing container 4 was performed in a glove box with a nitrogen gas atmosphere, so that the atmosphere in the crushing container 4 was changed to nitrogen gas, and the crushing process was performed. was performed in an atmosphere of nitrogen gas.

In addition, when creating a nitrogen gas atmosphere in the glove box, a nitrogen generator (manufactured by Hitachi Industrial Equipment Systems Co., Ltd.) that generates nitrogen gas with a purity of 99.9% from the atmosphere was inserted into the gas receiving port of the glove box. Nitrogen gas is supplied, and the oxygen concentration display of the oxygen concentration meter installed in the glove box is set to display 0%. I did the work to put in.

In Example 1, the operation of collecting the pulverized magnesium in an airtight bottle after pulverization was also performed in a glove box in a nitrogen gas atmosphere with nitrogen gas from a nitrogen generator.

On the other hand, in Comparative Example 1, the operation of putting magnesium, fatty acid, and rigid spheres into the grinding container 4 was performed in a glove box with an argon gas atmosphere, so that the atmosphere in the grinding container 4 was changed to argon gas, and the grinding process was performed. was performed under an argon gas atmosphere.

In order to create an argon gas atmosphere inside the glove box, the gas receiving port of the glove box is supplied with argon gas from a high-purity argon cylinder. displayed 0%, and in this state, magnesium, fatty acid, and rigid spheres were put into the crushing container 4 .

In Comparative Example 1, the operation of collecting the pulverized magnesium in an airtight bottle after pulverization was also performed in a glove box in an argon gas atmosphere with argon gas from a high-purity argon cylinder.

Subsequently, the hydrogenation step of the pulverized magnesium of Example 1 and Comparative Example 1 was carried out according to the procedure described above.

However, in Example 1, the operation of transferring the pulverized magnesium from the airtight bottle to the reaction vessel 82 of the hydrogenation furnace 8, that is, the pulverized magnesium in the airtight bottle is accommodated in the reaction vessel 82 of the hydrogenation furnace 8. The containing process was performed in a glove box with a nitrogen gas atmosphere, and the containing process was performed under the nitrogen gas atmosphere.

On the other hand, in Comparative Example 1, the work of transferring the pulverized magnesium from the airtight bottle to the reaction vessel 82 of the hydrogenation furnace 8, that is, the accommodation of the pulverized magnesium in the airtight bottle into the reaction vessel 82 of the hydrogenation furnace 8 The processing was performed in a glove box set to an argon gas atmosphere, and the containing processing was performed under an argon gas atmosphere.

Note that the specific conditions for the hydrogenation treatment are the same in both Example 1 and Comparative Example 1.
Specifically, at a temperature setting for heating to 220° C. suitable for hydrogenation of pulverized magnesium, the heater part 812 is turned on while in a vacuumed state, and the vacuumed state is maintained until the set temperature is reached. is maintained, hydrogen gas is supplied when the set temperature is reached, and the pressure of the hydrogen gas atmosphere is kept at about 90 kPa (about 0.9 atm) to perform heating (hydrogenation) for 4 hours, After the heater part 812 was turned off, after cooling to room temperature, hydrogenated magnesium was taken out.

As can be seen from the above description, in Example 1, the pulverized magnesium from the pulverization step to the end of the hydrogenation step was in contact with only nitrogen gas and hydrogen gas, and in Comparative Example 1, from the pulverization step Until the end of the hydrogenation process, the pulverized magnesium was exposed only to argon gas and hydrogen gas.

Therefore, in both Example 1 and Comparative Example 1, from the pulverization step to the end of the hydrogenation step, it was handled so as not to be exposed to the atmosphere, and the pulverized magnesium was Until then, it is kept out of contact with oxygen, so that the reactivity of magnesium, which has been enhanced by the pulverization process, is not degraded by the influence of the atmosphere (mainly oxygen).

Subsequently, the pulverized magnesium after hydrogenation of Example 1 and Comparative Example 1 was each subjected to an X-ray diffractometer (XRD device), and the hydrogenation rate, that is, the hydrogenation rate in the pulverized magnesium after hydrogenation As a result of determining the content of magnesium, the average hydrogenation rate of Example 1 was 22.8% by mass (wt%), and the average hydrogenation rate of Comparative Example 1 was 7.6% by mass (wt%). Ta.

In addition, the average hydrogenation rate is the particle size variation in pulverized magnesium, and the hydrogenation efficiency is considered to depend on the particle size. Although hydrogenation is considered to progress, it means that the hydrogenation rate is an average hydrogenation rate that includes variation in particle size without performing sieving or the like.

Since the hydrogenation reaction is thought to proceed from the surface of the pulverized magnesium toward the center, the result of Example 1 was 22.8% by mass (wt%) from the surface of the entire pulverized magnesium. ) is thought to have progressed to a depth at which the hydrogenation rate of ) can be achieved.

Therefore, the magnesium is atomized to particles having a diameter about twice as deep as the progressed depth, specifically, the particle size (average particle size) of magnesium is reduced to about 1/13 of the pulverized magnesium in Example 1 Then, under the same hydrogenation conditions as in Example 1, it is expected that nearly 100% by mass (wt %) of magnesium hydride will be obtained.

For example, in a planetary ball mill, the larger the diameter of the hard spheres for promoting pulverization, the faster the pulverization speed and the larger the critical particle size achieved in pulverization. Although the pulverization speed is slow, the critical particle size achieved by pulverization is small.
From this, it is considered that a higher hydrogenation rate can be obtained by performing additional pulverization using rigid spheres with a small diameter.

In general, it is said that the presence of a nitride film or an oxide film on the surface of magnesium makes it difficult for hydrogenation to occur. The hydrogenation efficiency did not deteriorate even when the hydrogenation was carried out in an atmosphere of nitrogen gas, and surprisingly, the hydrogenation efficiency was better than that of pulverization in argon gas.

It should be noted that generating nitrogen gas with a nitrogen generator is cheaper than purchasing and using nitrogen gas in a gas cylinder.
Therefore, when the amount of nitrogen gas used increases due to the size of the pulverizer, etc., the running cost can be greatly reduced, so when using nitrogen gas, it is recommended to use nitrogen gas generated by a nitrogen generator preferable.

Further, in Example 1, the accommodation process of accommodating the pulverized magnesium in the reaction vessel 82 of the hydrogenation furnace 8 was also performed under a nitrogen gas atmosphere. The hydrogenation efficiency does not deteriorate even if the work is performed.

Next, Example 2 in which the amount of fatty acid added in the pulverization step is increased will be described.
In Example 2, octadecanoic acid was used as the fatty acid, and the magnesium used was the same as in Example 1.

In Example 2, by putting magnesium (70 g) and octadecanoic acid (6.923 g) into the crushing vessel 4, 9 masses out of the total mass (76.923 g) of magnesium and octadecanoic acid % (wt %) of octadecanoic acid was added to grind the magnesium.

In addition, Example 2 is the same as Example 1 except that the amount of fatty acid added is different from Example 1.

In other words, Example 2 is the same as Example 1 except that the addition amount of fatty acid is different from the pulverization step to the hydrogenation step.

Then, the pulverized magnesium after hydrogenation in Example 2 was subjected to an X-ray diffraction device (XRD device) to determine the hydrogenation rate, that is, the content of magnesium hydride in the pulverized magnesium after hydrogenation. The average hydrogenation rate was 54.2 mass % (wt%), and by increasing the amount of fatty acid added, a higher hydrogenation rate than in Example 1 was able to be obtained.

In this way, increasing the amount of fatty acid added in the pulverization process greatly improves the reactivity of the pulverized magnesium. is assumed to take longer.

In addition, although fatty acids liquefy at the temperature during pulverization, if excessively added, the liquefied fatty acids act as a lubricating liquid that reduces the frictional resistance during pulverization, and there is a risk that the pulverization speed will decrease.

Therefore, the amount of fatty acid to be added is preferably 15% by mass or less, more preferably 14% by mass or less, of the total mass of magnesium and fatty acid.

On the other hand, fatty acids have the effect of suppressing the aggregation of magnesium that has been pulverized during the pulverization process. is good.

Also, looking at Example 1 and Example 2, since the hydrogenation rate improves when the amount of fatty acid added in the pulverization process is increased, in the pulverization process, the total mass of magnesium and fatty acid It is preferable to add 4% by mass or more of fatty acid, and the amount added is 5% by mass or more, 6% by mass or more, 7% by mass or more, 8% by mass or more, 9% by mass or more, and 10% by mass or more. It is preferable that there are many.

Although specific embodiments have been described above, the present invention is not limited to specific embodiments.
In the above, the case where a ball mill device is used for the pulverizer 1 is explained, but for example, a bead mill device capable of continuous processing for the purpose of large-scale pulverization such as Ashizawa Fine Tech Co., Ltd., Nippon Coke Industry Co., Ltd. is used as the pulverizer 1. may be used.

A bead mill capable of continuous processing naturally has an airtight structure to prevent the pulverized powder from scattering outside, but it is not a completely sealed structure. In addition to the use of gas, in order to suppress the decrease in reactivity of pulverized magnesium that has increased reactivity, a large amount of air (mainly oxygen in the atmosphere) is suppressed from entering the pulverizing section and pulverized powder collecting section. of nitrogen gas must be supplied, and in such a case, if the nitrogen gas generated by the nitrogen generator is used, the running cost can be greatly reduced.

As described above, the present invention is not limited to specific embodiments, and appropriately modified and improved versions are also included in the technical scope of the present invention. It is clear from the description of the claims.

1 Crusher 2 Crusher main body 21 Condition input unit 22 Emergency stop button 3 Hood 4 Crushing container 41 Crushing container main body 411 Groove 412 Threaded hole 42 Lid 421 Through hole 5 O-ring 8 Hydrogenation furnace 81 Heating furnace 811 Thermal insulation housing Body 812 Heater 82 Reaction vessel 821 Reaction vessel main body 8211 Flange 822 Lid 8221 Intake/exhaust port 823 O-ring 824 Clamp 83 Pressure adjustment tank B1 High-pressure gas cylinder B2 Hydrogen gas cylinder B3 Argon gas cylinder BL Decomposition boundary line DP Digital pressure gauge FGP Gas Piping MFC-A Argon gas mass flow controller MFC-H Hydrogen gas mass flow controller N, N1, N2 Needle valves OCB2, OCB3, OCB5 Open/close valves P1, P2 Vacuum pump PLC Sequencer PT1 Mounting port PT2 Receiving port PT3 Receiving port PT4 Gas supply port PT5 Exhaust port

Claims (3)

A method for producing magnesium hydride,
A pulverizing step of adding fatty acid to pulverize magnesium;
Hydrogenation in which the pulverized magnesium is heated to a temperature of 140 ° C. or more and less than the decomposition temperature of magnesium hydride in a reaction vessel to which hydrogen gas is supplied so as to maintain the pressure at 5 atmospheres or less. comprising a process and
The pulverization step is performed in an atmosphere of nitrogen gas,
A method for producing magnesium hydride, wherein the pulverized magnesium is not exposed to oxygen until the completion of the hydrogenation step. 2. The method for producing magnesium hydride according to claim 1, wherein the nitrogen gas is supplied from the atmosphere from a nitrogen generator that produces nitrogen gas with a purity of 99.9% or more. 3. The magnesium hydride according to claim 1 or 2, wherein the amount of the fatty acid added in the grinding step is 3% by mass or more in the total mass of the magnesium and the fatty acid. Production method.