JP3365483B2 - Method for producing high-pressure hydrogen gas by electrolysis of water - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing high-pressure hydrogen gas by electrolyzing water in a subcritical state or a supercritical state.

[0002]

2. Description of the Related Art Usually, electrolysis of water using a solid electrolyte membrane as a diaphragm is called steam electrolysis, and it is 500 to 1
Water vapor at about 000 ° C. is sent to the surface of the electrode formed on the surface of the diaphragm to perform electrolysis. There are two types of solid electrolyte membranes, hydrogen permeable type and oxygen permeable type. When a hydrogen-permeable solid electrolyte membrane is used, water is decomposed into oxygen and hydrogen ions on the negative electrode surface of the solid electrolyte membrane, and hydrogen ions diffuse inside the solid electrolyte membrane and migrate to the positive electrode side to hydrogen gas. Become. On the other hand, when an oxygen-permeable solid electrolyte membrane is used, the water decomposition reaction occurs on the negative electrode surface of the solid electrolyte membrane to generate hydrogen, and oxygen diffuses inside the solid electrolyte membrane and migrates to the positive electrode side. Becomes oxygen gas.

[0003]

However, in the above-described conventional steam electrolysis method, since water is supplied to the electrode surface in the state of low-pressure steam, the contact efficiency between water molecules and the electrode is low and the reaction becomes insufficient. There's a problem. Further, when producing hydrogen gas at a higher pressure, it is necessary to pressurize the hydrogen gas generated by electrolysis. An object of the present invention is to provide a method for easily producing high-pressure hydrogen gas with high electrolysis efficiency.

[0004]

As shown in FIGS. 1 and 3, the invention according to claim 1 is divided into negative electrode chambers 16a and 16b and positive electrode chamber 17 by oxygen permeable type solid electrolyte membranes 14a and 14b. Negative electrode chambers 16a, 16 in the reaction vessel 13
b, and a step of supplying water into the negative electrode chambers 16a and 16b to electrolyze the water in a subcritical or supercritical state to generate hydrogen gas in the negative electrode chambers 16a and 16b and oxygen gas in the positive electrode chamber 17. Steps for producing each and the negative electrode chambers 16a, 16
b In the resulting subcritical or supercritical state containing hydrogen gas
By reducing either or both of the water pressure or temperature, high-pressure hydrogen gas by electrolysis of water and a step of taking out the <br/> high-pressure hydrogen gas in the water of the subcritical or supercritical state Is a manufacturing method. Since water in the subcritical state or supercritical state has a relatively excellent diffusion capacity,
The hydrogen gas generated on the surfaces of the electrodes 23 of 6a and 16b quickly forms a homogeneous phase with water. As a result, the adsorption of hydrogen gas on the surface of the electrode 23 is reduced and the hydrogen generation efficiency is increased. Further, since the pressure of water in the subcritical state or the supercritical state is high, the frequency of collision of water molecules with the electrodes increases. Further, after electrolysis, high-pressure hydrogen gas can be obtained without providing special pressurizing means.

The invention according to claim 2 is the invention according to claim 1, and as shown in FIGS. 1 and 2, the oxygen permeable first and second solid electrolyte membranes 14a, 1 are provided in the reaction vessel 13.
4b are provided so as to partition the reaction vessel 13 with a space between each other, and the first and second portions are provided outside the both diaphragms 14a and 14b.
Negative electrode chambers 16a, 16b of the two diaphragms 14a, 1
4b is a method for producing high-pressure hydrogen gas by electrolysis of water in which the positive electrode chamber 17 is formed. Two negative electrode chambers 16a and 1
By providing 6b, the effective reaction area between water and the electrode is further increased, and the amount of hydrogen gas generated is increased.

The invention according to claim 3 is the invention according to claim 1, and as shown in FIG. 1, after cooling the residual liquid from which high-pressure hydrogen gas has been taken out, the water to be supplied to the negative electrode chambers 16a, 16b is changed. This is a method for producing high-pressure hydrogen gas by electrolysis of added water. The residual liquid obtained by extracting the high-pressure hydrogen gas is reused as a part of the electrolytic solution.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the subcritical state of water is a temperature of 200 to 374 ° C. and 160 to 215 kg.
It means the state of water at a pressure of / cm ² . The supercritical state of water is a temperature of 374 to 400 ° C. and 215 to 3
It means the state of water at a pressure of 00 kg / cm ² . Below the lower limits of temperature and pressure in the subcritical state, the reaction is slow and the electrolysis efficiency is poor. Further, if the upper limits of temperature and pressure in the supercritical state are exceeded, the reaction container is overloaded, which is also inefficient.

When carrying out the method for producing high-pressure hydrogen gas according to the present invention, for example, an apparatus as shown in FIG. 1 is used. First, water (H ₂ O) is supplied to the water tank 12 via the valve 11. The water stored in the water tank 12 is the reaction container 1
3 is supplied. The reaction container 13 has a first oxygen-permeable type
And, the second solid electrolyte membranes 14a and 14b are provided so as to partition the reactor 13 with a space therebetween. As a result, the first and second negative electrode chambers 16a and 16b are formed outside the diaphragms 14a and 14b, and the positive electrode chamber 17 is formed between the diaphragms 14a and 14b. Anode chamber 1 of reaction vessel 13
The water in the water tank 12 is pressurized by the pump 19a via the valve 18a and the preheaters 21a, 21b
It is heated in b and is pumped into a subcritical state or a supercritical state. Anode chambers 16a and 16b are provided around the reaction vessel 13.
A heater 22 for heating the water inside is provided, whereby the water maintains a subcritical state or a supercritical state in the reaction vessel 13.

As shown in detail in FIG. 2, a negative electrode 23 is formed on the outer surface of both diaphragms 14a and 14b in the reaction vessel 13, and a positive electrode 2 is formed on the inner surface of both diaphragms 14a and 14b.
4 is formed. The negative electrode 23 and the positive electrode 24 are connected to a power supply 27, respectively. A heater 22 is provided on the outer surface of the peripheral wall 20 of the reaction container 13. As the oxygen-permeable first and second solid electrolyte membranes 14a and 14b, yttria-stabilized zirconia having a porous (ZrO ₂ ) _0.92 (Y ₂ O ₃ ) _0.08 composition or the like is used. As a material for forming the negative electrode 23, a mixture of yttria-stabilized zirconia and nickel and a noble metal such as platinum are used. As a material forming the positive electrode 24, a conductive perovskite oxide such as lanthanum trioxide trioxide is used. The electrode is formed like a film on the surface of the diaphragm. Further, since supercritical water has a relatively excellent diffusing ability, the use of a porous electrode has the advantage of increasing the effective reaction surface area of the electrode and increasing the reaction efficiency.

When the negative electrode 23 and the positive electrode 24 are energized in this state, water is electrolyzed on the surface of the negative electrode 23 as shown by the following equation, and hydrogen gas (H ₂
Gas) is generated. On the other hand, oxygen passes through the solid electrolyte membranes 14a and 14b as O ²⁻ ions as shown by the arrow in FIG. 2 and moves to the positive electrode chamber 17 to become oxygen gas (O ₂ gas). As a result, hydrogen gas and water are accumulated in the negative electrode chambers 16a and 16b, and oxygen gas is accumulated in the positive electrode chamber 17. Negative electrode chamber 16a, 16b: H ₂ O + 2e ⁻ → 1 /
2H ₂ ↑ + O ^{2 −} positive electrode chamber 17: O ^{2 −} → 1 / 2O ₂ ↑ + 2e ⁻ Water containing hydrogen gas generated in the negative electrode chambers 16a, 16b is taken out from the reaction vessel 13, and the pressure reducing valves 28a, 28b are turned on. It is sent to the separation tank 29 of hydrogen and water via. Here, pressure reducing valve 2
By lowering the pressure at 8a and 28b, water and high-pressure hydrogen gas are separated. The separated high-pressure hydrogen gas is sent to and stored in the high-pressure hydrogen storage tank 32 via the valve 31. The water separated from the hydrogen gas in the hydrogen / water separation tank 29 is cooled by the cooler 33, pressurized by the pump 34, collected in the water tank 12, and reused as the electrolytic solution in the reaction container 13. On the other hand, the oxygen gas accumulated in the positive electrode chamber 17 is continuously taken out from the reaction container 13 via the valve 36 and the suction pump 35 and stored in an oxygen storage tank (not shown).

In FIGS. 1 and 2, the reaction vessel 13 is partitioned by the first and second solid electrolyte membranes 14a and 14b which are separated from each other to form two negative electrode chambers 16a and 16b and a single positive electrode chamber 17. ing. However, the present invention is not limited to the reaction vessel 13 having such a structure,
For example, as shown in FIG. 3, the reaction vessel 13 is partitioned by a single oxygen-permeable solid electrolyte membrane 14c to form a single negative electrode chamber 16c on one of the partition surfaces, and a single negative electrode chamber 16c on the other partition surface. The positive electrode chamber 17 may be formed. In the reaction vessel 13 thus configured, water is pressure-fed into the negative electrode chamber 16c through the valve 37 in a subcritical state or a supercritical state, and the water is supplied to the negative electrode 23 and the positive electrode 24 formed on the surface of the solid electrolyte membrane 14c. When energized, water is electrolyzed on the surface of the negative electrode 23 to generate hydrogen gas in the negative electrode chamber 16c, and oxygen is converted to O ²⁻ ions as solid electrolyte membrane 14 as shown by the arrow in FIG.
After passing through c, it becomes oxygen gas in the positive electrode chamber 17. Negative electrode chamber 1
The water containing hydrogen gas generated in 6c is taken out from the reaction vessel 13 through the valve 38 and then sent to the hydrogen / water separation tank. On the other hand, the oxygen gas accumulated in the positive electrode chamber 17 is taken out from the positive electrode chamber 17 through the valve 39 and stored as described above. 3 that are the same as those in FIG. 2 indicate the same components.

[0012]

As described above, according to the present invention, water is supplied to the negative electrode chamber in the reaction vessel 13 which is divided into the negative electrode chamber and the positive electrode chamber by the oxygen permeable type solid electrolyte membrane, and the negative electrode chamber Water is electrolyzed in a subcritical state or a supercritical state to generate hydrogen gas in the negative electrode chamber and oxygen gas in the positive electrode chamber, respectively, and in a subcritical state or a supercritical state containing hydrogen gas generated in the negative electrode chamber . By reducing the pressure or temperature of water , or both , a subcritical state or supercritical state
Since the high-pressure hydrogen gas contained in the water in the state was taken out, the hydrogen gas generated on the electrode surface of the negative electrode chamber quickly diffuses and dissolves in the water that is the electrolytic solution, and the adsorption of hydrogen gas on the electrode surface Decrease and the electrolysis efficiency increases. After electrolysis, high-pressure hydrogen gas can be obtained without providing any special pressurizing means.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a high-pressure hydrogen gas production apparatus of the present invention.

FIG. 2 is a configuration diagram for explaining the action of electrolysis by enlarging the reaction container in the apparatus of FIG.

FIG. 3 is a configuration diagram showing another embodiment of a reaction container.

[Explanation of symbols]

12 aquarium 13 Reaction vessel 14a, 14b Oxygen-permeable solid electrolyte membrane 16a, 16b negative electrode chamber 17 Positive electrode chamber 29 Hydrogen and water separation tank 32 High-pressure hydrogen storage tank

Continuation of the front page (72) Inventor Den Kenjun, Naka-machi, Naka-gun, Naka-gun, Ibaraki Prefecture 6-person, Mukaiyama, No. 1002 14 Mitsubishi Materials Corporation Naka Energy Laboratory (72) Inventor Kenji Nishimura Naka-machi, Naka-gun, Ibaraki Prefecture 14 in 1002, Mukaiyama, Mitsuyama, Mitsubishi Materials Corporation, Naka Energy Laboratory (56) References JP-A-9-228085 (JP, A) JP-A-9-3680 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C25B 1/00-15/08

Claims (3)

(57) [Claims] 1. An oxygen-permeable solid electrolyte membrane (14a, 14b)
By the step of supplying water into the negative electrode chamber (16a, 16b) in the reaction vessel (13) divided into the negative electrode chamber (16a, 16b) and the positive electrode chamber (17), the negative electrode chamber (16a, 16b) A step of producing hydrogen gas in the negative electrode chamber (16a, 16b) and oxygen gas in the positive electrode chamber (17) by electrolyzing the water in a subcritical state or a supercritical state, respectively, and the negative electrode chamber (16a, 16b) by lowering one or both of water pressure or temperature of the subcritical or supercritical state containing hydrogen gas generated in the subcritical state or supercritical
A method of producing high-pressure hydrogen gas by electrolysis of water, comprising the step of extracting high-pressure hydrogen gas contained in water in a critical state . 2. A first and a second oxygen-permeable solid electrolyte membranes (14a, 14b) are provided in the reaction vessel (13) so as to partition the reaction vessel (13) with a space therebetween. First and second negative electrode chambers (16a, 16b) are formed on the outside of both diaphragms,
The method for producing high-pressure hydrogen gas according to claim 1, wherein a positive electrode chamber (17) is formed between the both diaphragms. 3. The high-pressure hydrogen gas is taken out and the residual liquid is cooled and then added to water supplied to the negative electrode chambers (16a, 16b).
A method for producing a high-pressure hydrogen gas as described.