JP2009184886A - Composition, hydrogen production apparatus and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition which is capable of homogenously and efficiently bringing an inorganic hydride in contact with water, producing hydrogen at a required rate and achieving a high hydrogen storage density, by solving the problem associated with a hydrogen-generating reaction conducted using a high concentration of an inorganic hydride, wherein a foam product that is 20 times larger in volume than the introduced inorganic hydride is formed and accumulates around the inorganic hydride. <P>SOLUTION: The composition comprises the inorganic hydride, a metal chloride and water, wherein the inorganic hydride, the metal chloride and the water are reactive and contact with each other, to produce hydrogen. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a composition for generating hydrogen to be supplied to an apparatus that requires hydrogen such as a fuel cell, a hydrogen generator, and a fuel cell system that generates electric power using the hydrogen.

  Due to the recent increase in energy problems and environmental problems, there is an increasing expectation for hydrogen as a clean fuel other than fossil fuels. However, hydrogen has problems in all aspects such as production, storage, transportation, and utilization technology, and development of handling technology is urgent.

  Examples of the power generation device using hydrogen include a fuel cell and an internal combustion engine. These power generators cover all types of industries such as regional distributed power sources, buildings, homes, automobiles, and portable devices. In any case, it is necessary to supply a predetermined amount of hydrogen promptly, and particularly in automobiles and portable devices, the hydrogen supply device and the hydrogen generating material have a high hydrogen storage density because of the space for installing the power generation device. It is demanded.

  Conventionally, a method of hydrolyzing an inorganic hydride called chemical hydride is known as a method for maintaining hydrogen at a high hydrogen storage density. For example, lithium borohydride, sodium borohydride, lithium aluminum hydride, and sodium aluminum hydride, which are inorganic hydrides, are dissolved in an alkaline aqueous solution, and the aqueous solution is supplied to and contacted with a precious metal catalyst to generate hydrogen. A method for causing a reaction and a method for causing a hydrogen generation reaction by supplying water or alcohol to an inorganic hydride are known (see, for example, Patent Document 1).

  According to this technique, the hydrogen storage density can be 10 wt%. Other hydrogen storage methods, for example, the hydrogen storage density of hydrogen storage alloys is at most about 3 wt%, and the effectiveness of the hydrogen storage density of inorganic hydrides is clear.

Taking sodium borohydride as an example, the reaction conditions of a hydrolyzable inorganic hydride will be described. Sodium borohydride generates hydrogen in the following reaction.
NaBH ₄ + 2H ₂ O => NaBO ₂ + 4H ₂
Thus, in terms of stoichiometry, sodium borohydride reacts with approximately the same weight of water, but in practice, a large excess of water is added to improve the reaction efficiency. There is a disclosure of the invention that the ratio of the weight of water to the weight of inorganic hydride is preferably 0.5 to 2.22 (see, for example, Patent Document 2). This ratio is from the point of hydrogen release characteristics when the inorganic hydride is made into an aqueous solution, but a hydrogen storage density of 6 to 10 wt% is obtained, and in this respect also, the composition is highly effective.
JP2003-206101A (page 4-6, FIG. 1) Japanese Patent Laid-Open No. 2002-201001

  However, as is conventional, when an inorganic hydride is subjected to a hydrogen generation reaction at a high concentration, a foam-like product is formed. The volume of the foam-like product may be 20 times that of the charged inorganic hydride. This is a phenomenon that occurs because a product is generated while entraining the generated hydrogen, and the bubbles are maintained without being broken. The reason is considered to be related to the hydration property of the product sodium metaborate and the viscosity generated by the intermolecular interaction. Therefore, this foam-like product stays around the inorganic hydride, and the reaction is hindered, resulting in a problem that complicated control is required to obtain a desired hydrogen generation rate. In addition, a space for containing the foam-like product is required in the hydrogen generator, which causes a problem that the hydrogen storage density per volume is reduced.

  On the other hand, this phenomenon is not observed when the water weight ratio is 10 or more. However, an increase in the water weight ratio causes the hydrogen storage density to be 2% or less, resulting in a problem that the hydrogen storage density is reduced.

  The present invention has been made in view of the above circumstances, and the present invention does not produce a foam-like product when an inorganic hydride and water are mixed, and uniformly and efficiently produces an inorganic hydride and water. An object of the present invention is to provide a composition and a hydrogen generator which can be brought into contact with each other to generate hydrogen at a required rate and have a high hydrogen storage density.

  It is another object of the present invention to provide a fuel cell system having a high energy density by using the hydrogen generated here as a fuel.

  In order to achieve the above object, a composition according to claim 1 of the present invention is a first composition comprising an inorganic hydride, a metal chloride, and water, wherein the inorganic hydride, the metal chloride The water and the water are reactants that contact each other and generate hydrogen.

  Thereby, no foam-like product is generated at the time of the hydrogen generation reaction, or even if it is generated, bubbles are broken rapidly. Accordingly, the volume of the foam product does not increase around the composition, and the mutual contact of the composition can proceed smoothly, so that a uniform reaction rate can be easily obtained.

  The inorganic hydride is a metal hydride or an inorganic hydride. In particular, the inorganic hydride is preferably a boron hydride salt. The metal of the salt and the metal of the metal hydride are preferably alkali metals or alkaline earth metals. Examples thereof include sodium borohydride, potassium borohydride, lithium aluminum hydride, lithium hydride, sodium hydride, magnesium hydride, calcium hydride and the like.

  The metal chloride is particularly preferably a fourth period transition metal. Applicable substances include iron chloride, cobalt chloride, and nickel chloride.

  The metal chloride is mixed in a molar ratio of 0.001 to 0.07 with respect to the water.

  Thereby, the foam breaking effect of the foam-like product by the metal chloride can be obtained particularly.

  A second composition comprising the first composition and an acid, wherein the first composition and the acid are reactants that come into contact with each other to generate hydrogen.

  As a result, the hydrogen generation rate can be increased. It has become possible to improve the hydrogen generation rate that has been possible by using a large amount of water without using a large amount of water.

  The acid is mixed at a molar ratio of 0.005 to 0.2 with respect to the water.

  According to this composition ratio, the hydrogen generation rate is remarkably improved, so that it can be easily used.

  The acid is preferably a non-volatile acid. This is to prevent the volatile components of the acid from being mixed into the generated hydrogen and the decrease in acidity. Examples of the acid include citric acid, succinic acid, malic acid, fumaric acid, maleic acid, malonic acid and other organic acids and sulfuric acid.

  The metal chloride is mixed in a molar ratio of 0.004 or more and 0.04 or less with respect to the water.

  According to this, the foam breaking effect when an acid is added is particularly high.

  The metal chloride is mixed with the water in a weight ratio of 0.007 or more and 0.5 or less.

  Thereby, the foam breaking effect of the foam-like product by the metal chloride can be obtained particularly.

  A second composition comprising the first composition and an acid, wherein the first composition and the acid are reactants that come into contact with each other to generate hydrogen.

  As a result, the hydrogen generation rate can be increased. It has become possible to improve the hydrogen generation rate that has been possible by using a large amount of water without using a large amount of water.

  The acid is mixed with the water at a weight ratio of 0.05 to 1.3.

  According to this composition ratio, the hydrogen generation rate is remarkably improved, so that it can be easily used.

  The metal chloride is mixed in a weight ratio of 0.03 or more and 0.3 or less with respect to the water.

  According to this, the foam breaking effect when an acid is added is particularly high.

  It is characterized by comprising a reaction section for containing the composition in a container and bringing the compositions into contact with each other to cause a hydrogen generation reaction, and a hydrogen discharge port.

  Thereby, since it is hard to produce | generate a foam-like product in a hydrogen generator, the space for accommodating this becomes unnecessary, and it becomes possible to make a hydrogen generator small. A hydrogen generator having a high hydrogen storage density can be obtained.

  The hydrogen generator, a flow path for passing hydrogen, and a power generation unit in which hydrogen moved through the flow path reacts by an electrochemical reaction, connecting the hydrogen discharge port of the hydrogen generator and the flow path, Electricity is generated using hydrogen generated by the hydrogen generator.

  As a result, a fuel cell system having a small volume of the hydrogen generator can be formed, so that a high energy density can be achieved.

  As described above, in the present invention, the first composition is composed of an inorganic hydride, a metal chloride, and water, and the inorganic hydride, the metal chloride, and the water are in contact with each other to form hydrogen. Was a reaction product. Further, the molar ratio of metal chloride to water was defined as 0.001 or more and 0.07 or less, and an acid was further added to form a second composition. As a result, the volume of the product produced when forming the composition can be kept small, and it is difficult to form the product foam around the composition. It became possible to produce a reaction with good controllability as a material.

  Moreover, since a hydrogen generator and a fuel cell system were formed using this composition, it became possible to provide a high energy density apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the table of FIG. The composition of this embodiment is composed of sodium borohydride, water, and various metal chlorides and acids shown in the table as inorganic hydrides. No. 1 to No. Ten embodiment examples up to 10 and three comparative examples from Comparative Example 1 to Comparative Example 3 are shown, and the weight ratio of metal chloride and acid to water contained in the composition is described. In the rightmost column of the table, the ratio of the volume of the product to the composition is described, and the effectiveness of this embodiment is shown.

  The volume ratio of the product to the composition in the table was evaluated by the following two methods. In the first method, metal chloride, acid, and water are mixed in the weight ratio shown in the table to make an aqueous solution, and this aqueous solution is supplied in small portions to solid sodium borohydride to form a composition. I went. A hydrogen generation reaction occurred when the aqueous solution was supplied, and hydrogen and a product were obtained. The volume of this product was divided by the total volume of the initial composition to calculate the volume ratio of the product to the composition.

  As a second method, sodium borohydride and water are mixed to form an aqueous hydride solution, and this is supplied in small amounts to the metal chloride and acid prepared in the weight ratio shown in the table. It formed. As in the first method, a hydrogen generation reaction occurred when an aqueous solution was supplied, and hydrogen and a product were obtained. The volume of this product was divided by the total volume of the initial composition to calculate the volume ratio of the product to the composition.

  In the comparative example, all the products expanded to a volume of 20 times or more with respect to the initial composition. The product was so viscous that it was difficult to break the bubble, and it contained hydrogen as bubbles, resulting in an enormous volume.

  On the other hand, in the composition of this embodiment, the volume ratio of the product to the composition was 13 times or less, and the effect of reducing the volume of the product was increased. In particular, in the combination of the weight ratio of nickel chloride 0.6 and malic acid 0.33, or nickel chloride 0.10 and citric acid 0.33, the volume ratio was 1.2 times and hardly expanded.

  As a result of the evaluation by the first method and the second method, in the composition under the same conditions, the volume of the product was almost equal.

It is a table | surface which shows the combination of the metal chloride and acid of the composition by this invention shown in embodiment, a weight ratio, and the volume ratio of a product.

Claims (11)

A first composition comprising an inorganic hydride, a metal chloride, and water,
The inorganic hydride, the metal chloride, and the water are reactants that contact each other to generate hydrogen.   The composition according to claim 1, wherein the metal chloride is mixed in a molar ratio of 0.001 to 0.07 with respect to the water. A second composition comprising the first composition and an acid,
3. The composition according to claim 2, wherein the first composition and the acid are reactants that contact each other to generate hydrogen.   4. The composition according to claim 3, wherein the acid is mixed with the water in a molar ratio of 0.005 or more and 0.2 or less.   The composition according to claim 4, wherein the metal chloride is mixed with the water in a molar ratio of 0.004 or more and 0.04 or less.   The composition according to claim 1, wherein the metal chloride is mixed in a weight ratio of 0.007 to 0.5 with respect to the water. A second composition comprising the first composition and an acid,
The composition according to claim 6, wherein the first composition and the acid are reactants that contact each other to generate hydrogen.   The composition according to claim 7, wherein the acid is mixed in a weight ratio of 0.05 to 1.3 with respect to the water.   The composition according to claim 8, wherein the metal chloride is mixed with the water in a weight ratio of 0.03 or more and 0.3 or less.   A hydrogen generator, comprising: a reaction section that contains the composition according to any one of claims 1 to 9 and causes the composition to contact each other to cause a hydrogen generation reaction; and a hydrogen discharge port.   The hydrogen generator according to claim 10, a flow path for passing hydrogen, and a power generation unit in which hydrogen moved through the flow path reacts by an electrochemical reaction, and the hydrogen discharge port of the hydrogen generator and the hydrogen generator A fuel cell system, wherein the fuel cell system is connected to a flow path and generates power using hydrogen generated by the hydrogen generator.

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