JPS6077102A - Production of hydrogen - Google Patents

Abstract

PURPOSE:To produce high-purity H2 in high efficiency with shortened steps, by transferring O2 in steam to an O2-acceptor through a membrane made of a solid electrolyte containing ZrO2, etc., represented by a specific formula, and having electrical conductivity with oxygen ion. CONSTITUTION:A cell is furnished with a membrane made of a solid electrolyte having oxygen ion conductivity and represented by the general formula (ZrO2)100-x(MF3)x (M is Y and X is 13-25; or M is Yb and x is 16-25; X is mol%). The cell is heated at a high temperature, and is supplied with an O2- acceptor (e.g. CO gas) to the inner side and steam to the outer side of the cell. The O2 in steam is transferred to the CO gas by this process. High-purity H2 can be produced in high efficiency with shortened steps.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing hydrogen, particularly a method for producing hydrogen using a novel oxygen ion conductive solid electrolyte having high permselective properties for oxygen.

Reflecting the energy situation in recent years, various methods have been proposed for obtaining hydrogen, such as methods for obtaining it by electrolyzing the inexhaustible water, and methods for obtaining hydrogen by decomposing hydrocarbons and the like using various methods.

However, all of these methods involve considerably complicated steps, require high equipment costs, and are not necessarily efficient means of obtaining high-purity hydrogen.

Recently, stabilized zirconia doped with calcium oxide or yttrium oxide, which has the property of selectively permeating oxygen, has been used for partition walls, and carbon oxide or methane gas has been used as an oxygen acceptor, and high-temperature (approximately 700 degrees Celsius) water vapor has been used. A method of decomposing hydrogen to obtain high-purity hydrogen has been proposed.

This method is used in residential units as a means of shortening the process, reducing costs, and efficiently obtaining high-purity hydrogen compared to conventional methods, but the conductivity of the stabilized zirconia used as the partition wall is not necessarily sufficient. In addition, in practical use? O
It has the property of not being able to transfer oxygen sufficiently unless it is placed at a high temperature of O'C or higher, and there are considerable problems in practical use, such as the fact that there are considerable restrictions on the materials used, especially when electrodes are used. There is.

In order to eliminate such problems, the inventors of the present invention have conducted various studies and found that the object can be achieved by using a fluorinated oxide having a specific composition in place of stabilized zirconia.

Thus, the present invention provides a method in which a substance capable of accepting water vapor is present on one side of the diaphragm and a substance capable of accepting oxygen is present on the other side, and oxygen in water molecules is transferred to the oxygen-accepting substance through the membrane.
In the method of decomposing water vapor to obtain hydrogen, the diaphragm is of the general formula % % 13-25, or M-Yb x ~ 18-25,
The present invention provides a method for producing hydrogen characterized by using an oxygen ion conductive solid electrolyte (X is mol%).

Examples of the oxygen-accepting substance used in the present invention include carbon oxide and hydrocarbons such as methane and ethane, and one or more of these can be used as appropriate.

The amount of these substances to be used is strictly determined by the difficulty of the substance in accepting oxygen, the amount of hydrogen to be obtained, the reactivity per unit time, etc., but in general, it is 0.1% of the amount of water vapor supplied. It is appropriate to adopt a value of about 10 times.

In the present invention, if the composition deviates from the above-mentioned range, the conductivity will be significantly lowered, the composition will be non-uniform, and the thermal shock resistance will be lowered, which is not practical.

When the composition is within the above range, the conductivity and sinterability are almost stable or constant, and the composition has sufficient practicality. And when M is yttrium (Y) from the viewpoint of material properties and economic efficiency! -14~1B, if M is ytterbium (Yb)! It is particularly preferable to use -17 to 19.

The method for producing a conductive substance according to the present invention is as follows: zirconium oxide and yttrium fluoride or ytterbium fluoride can be ground and mixed, respectively, and held at 1100 to 1400°C for about 3 hours in an inert gas atmosphere.
ZrOz )85 (YF3 )+5 is 0.
．． 85 mol c) ZrO2 and 0.15 mol (7) YF3
It can be easily obtained by pulverizing and mixing and baking the mixture at 1200° C. for about 3 hours in an argon atmosphere. Also, ZrO+, ZrF4, Y2O3 and Yb2O3
It can also be produced by firing and sintering a mixture of the following. However, in this case, since ZrF4 is relatively volatile,
Care must be taken because the loss of ZrF4 and the target composition may not be achieved accurately.

In addition, these solid electrolytes can be shaped using, for example, plasma spraying, vacuum evaporation, sputtering, etc. to obtain a thin film, and hot pressing, etc. to obtain a relatively thick shape.
Rubber press method.

A hot isostatic pressure sintering method or the like can be appropriately employed.

The thickness of the solid electrolyte used in the present invention is generally 1. ~5
Approximately m11 is appropriate. If the thickness is less than the above range, gas leakage is likely to occur due to non-uniformity, while if it exceeds the above range, resistance loss may become significantly large, which is not preferable.

Further, the material of the anode used in the present invention includes, for example, a metal material such as platinum, silver, and cobalt, and a perovskite material such as LaCoO3, and the material of the cathode includes, for example, a metal material such as platinum, silver, and nickel, and a metal material such as LaCoO3. Perovskite-based oxide materials and the like can be appropriately employed.

In addition, it is necessary for gas to permeate through both the anode and the anode, and for this reason, the physical properties of these electrodes include porous, semi-molten, and other materials that have good adhesion to the solid electrolyte. is appropriate. Further, it is generally appropriate to employ the thickness of these electrodes to be about several thousand to about 100 hi.

These electrodes can be provided on the solid electrolyte by means such as screen printing or sputtering.

Next, the present invention will be explained by examples.

Example 1 20.88 moles of ZrO and 30.14 moles of YF were pulverized and mixed using a ball mill, and then molded into pellets with a diameter of 20 mm and a thickness of 2 cm using a rubber press method.

This was fired at 1200°C for 3 hours in an argon atmosphere.
The X-ray diffraction diagram of this sintered body was as shown in FIG. 1, and the composition was (ZrO2) 0.86 (YF3) 0.14. After baking PT powder on both sides of this pellet,
A PT lead wire was attached and the whole was attached to one end of a sintered alumina tube using alumina cement to produce a steam electrolysis cell. This cell was inserted into an electric furnace having a quartz core tube, and heated and maintained at 600°C. Carbon monoxide gas was supplied to the inside at a flow rate of 50 mA/min, and water vapor-saturated argon gas was supplied to the outside at a flow rate of 25 m1/min.

After 1 hour, the amount of hydrogen produced was measured and was 0.3 lmat.
The time was 7 minutes (calculated as room temperature).

Example 2 020.82 moles of Zr0 and 30.18 moles of YbF were mixed, molded, and fired in the same manner as in Example 1. x of this sintered body
The Vi diffraction diagram is as shown in the t52 diagram, and the composition is (Z
r02)o, B2(YbF3)ols. A steam electrolytic cell was prepared using this, and the amount of hydrogen produced was measured under the same conditions as in Example 1. The result was 0.2 lmol.
It was 7 minutes.

[Brief explanation of drawings]

Figure 1.2 is an X-ray diffraction diagram of the composition used in the present invention shown in the Examples. Procedural amendment is a formality) February 1980 J Branch Commissioner of the Japan Patent Office Mr. Kazuo Wakasugi 1, Indication of the case 1982 Patent Application No. 180428 2, Name of the invention Process for producing hydrogen 3, Person making the amendment Related Patent Applicant Address No. 2, Marunouchi 2-chome, Chiyoda-ku, Tokyo Name (
004) Asahi Glass Co., Ltd. 8, Contents of the amendment: Engraving of the details (no changes to the contents) and above

Claims (1)

[Claims] 1. A method for decomposing water vapor to obtain hydrogen by allowing a substance capable of accepting water vapor to exist on one side of a diaphragm and oxygen in the other, and transferring oxygen in the water vapor to the oxygen-accepting substance through the membrane, As a diaphragm, the general formula (ZrO
2) 100”4 (MF3)! (However, M=Y Teatte!=13~25° or -Yb and x=IB~
25. A method for producing hydrogen characterized by using an oxygen ion conductive solid electrolyte represented by (X is mol%).