JP2008214538A - Cyclic guanidine-based proton exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material for an electrochemical device which exhibits proton conductivity even in unmoistened conditions, for example, a proton exchanger suitable for a solid electrolyte of a fuel cell, an electrolyte in the field of batteries and the like. <P>SOLUTION: Provided is a proton exchanger containing a salt prepared from a cyclic guanidine compound represented by formula (1) and a Broensted acid. In the formula, R<SP>1</SP>, R<SP>2</SP>and R<SP>3</SP>indicate each independently an alkyl, aryl, alkenyl, hydroxyalkyl, alkoxyalkyl, acyloxyalkyl, acyl group or hydrogen and n indicates an integer of ≥1 and ≤6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a novel proton exchanger that functions even under non-humidified conditions, and more particularly to a proton exchanger that can be used in electrochemical devices such as batteries and electrolytes.

  A perfluorocarbon sulfonic acid membrane or the like is used as an electrolyte membrane of a conventional polymer solid electrolyte fuel cell (Patent Document 1). The perfluorocarbon sulfonic acid membrane has a drawback that it cannot be used in a dry state because water contained in the membrane becomes a proton conduction path (Non-patent Document 1). In order to improve proton conductivity in a dry state, various materials such as a silica-dispersed perfluorosulfonic acid membrane (Patent Literature 2), an inorganic-organic composite membrane (Patent Literature 3), a phosphoric acid doped graft membrane (Patent Literature 4), etc. Attempts have been made. However, in any of these methods, water in the membrane is essential to show proton conductivity, and it has not been an essential solution to the problem of proton conduction under non-humidified conditions.

  Therefore, development of a proton conductor that does not require water has been demanded, and the use of an ionic liquid has been proposed as an example. An ionic liquid is a general term for compounds having a melting point of 100 ° C. or less composed of a combination of an anion and a cation, and it is proposed that necessary characteristics can be expressed by a combination of ions according to the purpose (non-patent). Reference 1). As its use, utilization to a reaction solvent, a battery electrolyte, a lubricant, a heat medium, etc. has been proposed (Non-Patent Document 2).

Several proposals have also been made for proton exchangers mainly used for fuel cells. For example, a proton exchange membrane using an aprotic ionic liquid composed of a nitrogen-containing quaternary salt such as a quaternary ammonium salt, quaternary pyridinium salt, or quaternary imidazolium salt and a polymer material having an ion exchange group (Patent Literature) 5-7), a proton exchange solution by using a protic ionic liquid composed of an imidazole compound, a membrane (Patent Document 8), and the like. However, the conductivity under non-humidified conditions shown in these examples is about 10 ⁻⁴ to 10 ⁻³ S / cm at the highest, and improvement is necessary for use as a non-humidified proton exchanger. It was. Proton exchange liquids and membranes using imidazole ionic liquids with hydrogen fluoride compounds as anions have been proposed as having high conductivity, but when using this material, handling of hydrogen fluoride is difficult. It is assumed to be a problem.

  Although these ionic liquids have been proposed to exhibit the necessary characteristics by combining ions according to the purpose as described above, in most developments, quaternary imidazolium and alicyclic compounds are proposed. At present, quaternary ammonium, quaternary alkylammonium and the like are used, and a breakthrough with a new skeleton has been required.

  Thus, as a result of the search for a new skeleton for the purpose of ion-conducting materials, the present inventors have found that the specificity of the cyclic guanidine compound on the chemical structure, that is, 1) electron delocalized structure, 2) nitrogen We focused on the fact that the skeleton contains many atoms that allow proton capture such as atoms. However, the applications of guanidine compounds so far have been raw materials for pharmaceuticals, dyes, paints, photographic agents, raw materials for additives to polymer materials, and the like. As a report on the electrochemical characteristics of the guanidine compound, there is a report on the quaternary guanidine compound in which hexaalkylguanidine is used as a cation (Non-patent Document 3). However, this report is limited to the contents related to the dye-sensitized solar cell. It has been difficult to use as a proton conductor. Examples of reports of protic guanidine compounds that can be used as proton conductors include salts of tetramethylguanidine and Bronsted acid (Patent Document 9, Non-Patent Document 4). The effect of the cyclic guanidine compound was not clear.

JP-A-7-90111 Japanese Unexamined Patent Publication No. 6-11827 JP 2000-90946 A Japanese Patent Laid-Open No. 2001-213987 JP 2003-257484 A JP 2004-31307 A JP 2004-311212 A WO2003-083981 Publication JP 2004-253357 A Chem. & Eng. News, May 15, 2000 issue Functional creation and application of ionic liquids, NTS Corporation 2004 Synthetic Communication, Vol.34, pp3083-3089 (2004) Appl.Phys.A, 79, 73-77 (2004)

  An object of the present invention is to provide a cyclic guanidine protonic ionic liquid having proton conductivity under non-humidified conditions.

  Thus, as a result of intensive studies to solve such problems, the present inventors have found that a salt obtained from a cyclic guanidine derivative and an acid has high proton conductivity, and have reached the present invention.

（式中、R¹、R²及びR³は、独立にアルキル基、アリール基、アルケニル基、ヒドロキシアルキル基、アルコキシアルキル基、アシルオキシアルキル基、アシル基又は水素を示す。ｎは１以上、６以下の整数を示す。） The present invention is a proton exchanger characterized by containing a salt obtained from a cyclic guanidine compound represented by the following formula (1) and a Bronsted acid.

(Wherein R ¹ , R ² and R ³ independently represent an alkyl group, an aryl group, an alkenyl group, a hydroxyalkyl group, an alkoxyalkyl group, an acyloxyalkyl group, an acyl group or hydrogen. N is 1 or more, 6 The following integers are shown.)

  Moreover, the present invention is a proton exchange membrane obtained by forming a proton exchanger into a membrane shape. Furthermore, the present invention is a fuel cell comprising a solid polymer electrolyte membrane made of a proton exchange membrane. Furthermore, the present invention is an electrolyte for an electrochemical cell characterized by having a proton exchanger.

Preferred embodiments of the present invention are as follows.
1) The proton exchanger is made of a salt obtained by reacting the cyclic guanidine compound represented by the formula (1) with a Brönsted acid in an equivalent amount.
2) A salt obtained from a cyclic guanidine compound and a Bronsted acid is retained in a gelled material composed of a polymer compound as a proton exchanger.

  Hereinafter, the present invention will be described in more detail.

The cyclic guanidine compound used in the present invention is represented by the formula (1). In the formula, R ₁ , R ₂ and R ₃ independently represent an alkyl group, aryl group, alkenyl group, hydroxyalkyl group, alkoxyalkyl group, acyloxyalkyl group, acyl group or hydrogen. Preferred examples of the alkyl group include C1-C12 alkyl groups. Preferred examples of the aryl group include 6-membered aromatic hydrocarbon groups. The alkenyl group is preferably a C2 to C6 alkenyl group, and examples thereof include a vinyl group and an allyl group. As the hydroxyalkyl group, a hydroxyalkyl group having C1 to C6 is preferable, and examples thereof include a hydroxyethyl group, a hydroxypropyl group, a hydroxybutyl group, a hydroxypentyl group, and a hydroxyhexyl group. The alkoxyalkyl group is preferably a lower alkoxyalkyl group, for example, methoxymethyl group, methoxyethyl group, methoxypropyl group, methoxybutyl group, ethoxyethyl group, ethoxypropyl group, ethoxybutyl group, propyloxyethyl group, isopropyl Examples include a pyroxyethyl group, isopropyloxypropyl group, butoxyethyl group, butoxypropyl group, butoxybutyl group. Acyloxyalkyl groups include formyloxyalkyl group, acetyloxyalkyl group, propionyloxyalkyl group, butyryloxyalkyl group, isobutyryloxyalkyl group, valeryloxyalkyl group, isovaleryloxyalkyl group, pivaloyl Examples thereof include an oxyalkyl group, an acryloyloxyalkyl group, a methacryloyloxyalkyl group, and a benzoyloxyalkyl group. Examples of the acyl group include formyl group, acetyl group, propionyl group, butyryl group, isobutyryl group, valeryl group, isovaleryl group, pivaloyl group, acryloyl group, methacryloyl group, and benzoyl group. n represents an integer of 1 or more and 6 or less, preferably an integer of 2 to 4.

  The proton exchanger of the present invention contains a salt obtained by reacting a cyclic guanidine compound represented by the above formula (1) with a Bronsted acid (hereinafter sometimes abbreviated as G-B salt).

  As the Bronsted acid, either an organic Bronsted acid or an inorganic Bronsted acid can be used. Examples of the inorganic Bronsted acid include sulfuric acid, phosphoric acid, boric acid, and heteropolyacid. Organic Bronsted acids include carboxylic acids such as acetic acid, formic acid, and trifluoroacetic acid, alkyl sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, and octanesulfonic acid, trifluoromethanesulfonic acid, perfluorobutanesulfonic acid, and perfluorooctane. Examples thereof include fluorine-containing sulfonic acids such as sulfonic acid and fluorine-containing alkylsulfonic acid imides such as bis (trifluoromethanesulfonic acid) imide (hereinafter also referred to as imide acids). Alkyl sulfonic acids, fluorine-containing alkyl sulfonic acids, alkyl carboxylic acids (RCOOH) or imide acids are preferred. Here, the alkyl preferably has 1 to 6 carbon atoms.

  The cyclic guanidine compound represented by the formula (1) acts as a base, and a GB salt is obtained by a neutralization reaction with a Bronsted acid. As a specific method thereof, a generally known acid-base neutralization reaction method can be used. Since 1 mol of the cyclic guanidine compound represented by the formula (1) is calculated as 1 equivalent of a base, 1 equivalent of Bronsted acid is required to neutralize 1: 1. However, either can be used in excess. In this case, a preferable range is 0.5 to 2 equivalents of Bronsted acid with respect to 1 mol of the cyclic guanidine compound. A salt obtained by using 1 equivalent of Bronsted acid with respect to 1 mol of the cyclic guanidine compound has a high G-B salt concentration, so that the performance of the proton exchanger is excellent.

The neutralization reaction method is obtained by reacting the cyclic guanidine compound represented by the formula (1) and Bronsted acid by dissolving or mixing them in a solvent. For example, N- (1,3-dimethyl-2-imidazolidinylidene) -1-propanamine as the cyclic guanidine compound and bis (trifluoromethanesulfonic acid) imide as the Bronsted acid are used in equimolar amounts, respectively. By acting in the reaction, a bis (trifluoromethanesulfonic acid) imide salt of N- (1,3-dimethyl-2-imidazolidinylidene) -1-propanamine represented by the formula (2) can be obtained.

  Since the G-B salt itself has proton exchange ability, it can be used as a proton exchanger of the present invention. Moreover, it can also be used as an active ingredient of a proton exchanger.

  The proton exchanger is used in liquid or solid form. When used in a liquid state, when the G-B salt becomes a liquid at the use temperature, it may be used as it is or may be used by mixing other components. When the G-B salt becomes a solid, it can be used by dissolving in a suitable solvent. The solvent that can be used is a solvent having a boiling point equal to or higher than the use temperature of the GB salt, and is not particularly limited as long as the GB salt dissolves and does not inhibit proton conductivity. Alcohols, aromatic hydrocarbons represented by toluene, aliphatic hydrocarbons represented by hexane, dimethylformamide, dimethylacetamide, dimethylimidazolidinone, N-methylpyrrolidone, dimethylsulfoxide, etc. And aprotic polar solvents.

  When the proton exchanger is used in a solid state, when the G-B salt becomes a solid at the use temperature, it may be used as it is. For example, it can be used as a solid electrolyte without a solvent.

  A proton exchanger of the present invention can also be obtained by combining a gelling material comprising a polymer compound and a G-B salt. In this case, it can also be used as a polymer gel electrolyte. As the production method, the polymer compound and GB salt exemplified below are directly added, dissolved by heating, cooled, or mixed and molded in a suitable organic solvent, and then the solvent is removed by a method such as drying under reduced pressure. Obtained by distillation. The polymer compound is not limited as long as it can solidify GB salt, but polyvinyl polymer compounds such as polyvinyl chloride, polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride, polyoxymethylene, polyethylene oxide, Examples thereof include polyether polymer compounds such as polypropylene oxide, polyamide compounds such as nylon 6 and nylon 66, polyester compounds such as polyethylene terephthalate, and polycarbonate compounds. Furthermore, it is also possible to make a composite by crosslinking these polymerizable precursors, for example, a polymerizable compound such as acrylate. It is also possible to obtain a polymer compound complex by polymerizing monomers in a G-B salt-containing solution.

すなわち、環状尿素化合物に対して塩化ホスホリル等の塩素化剤を作用させた後に、１級脂肪族アミンを作用させて所望の環状グアニジン化合物を方法である。 The cyclic guanidine compound represented by the formula (1) can be easily produced by a known method. For example, it can be obtained by the following reaction formula shown in Inorg. Chem. 2005, 44, p1704-1712.

That is, a desired cyclic guanidine compound is produced by allowing a primary aliphatic amine to act after a chlorinating agent such as phosphoryl chloride is allowed to act on the cyclic urea compound.

    Although the preferable specific example of the cyclic guanidine compound represented by Formula (1) is shown below, it is not limited to these. The number described below the chemical formula is the chemical formula number.

  The proton exchanger of the present invention can be one in which a GB salt is held in a gelled material made of a polymer compound, and can be made into a proton exchange membrane by forming this into a membrane. . The proton exchange membrane is suitable as a solid polymer electrolyte membrane material for a fuel cell having a solid polymer electrolyte membrane.

  The proton exchanger of the present invention has a function as a proton conductor. Applications of the proton exchanger of the present invention include, in addition to the fuel cell material applications described above, ion exchange membrane applications, and pharmaceutical applications (such as exchanging Na ions for protons in the form of biological membranes).

  The proton exchanger of the present invention is suitable for materials for electrochemical devices that take advantage of proton conductivity under unhumidified conditions, which has been difficult until now, such as solid electrolytes for fuel cells and electrolytes in the battery field.

Hereinafter, the present invention will be described in more detail with reference to examples.
The proton conductivity in the examples was measured by the AC impedance method.

Example 1
Toluene (5 ml), dimethylimidazolidinone (50 mmol) and phosphoryl chloride (15 mmol, 0.3 eq) were dissolved at room temperature in a nitrogen atmosphere, and then stirred at 65 ° C. After 20 hours, the mixture was cooled to 0 ° C., dichloromethane (15 ml) was added, n-propylamine was added, and the mixture was heated and stirred at 55 ° C. After 4 hours, the mixture was cooled, an aqueous sodium hydroxide solution was added, and the mixture was extracted with dichloromethane. The dichloromethane layer was concentrated, and the residue was purified by an alumina column to give N- (1,3-dimethyl-2-imidazolidinylidene) -1-propanamine as a yellow oil.
The results of 1H-NMR (CDCl3) measurement are shown in FIG. 1H-NMR (CDCl3); 3.55 (s, 4H), 3.34 (t, 2H, J = 7.56Hz), 3.10 (s, 6H), 1.71 (dt, 6H, J = 7.56, 7.56Hz), 0.89 (t , 3H, J = 7.56Hz)

  The obtained N- (1,3-dimethyl-2-imidazolidinylidene) -1-propanamine (10 mmol) was added to a methanol solution of bis (trifluoromethanesulfonic acid) imide (10 mmol) and stirred at room temperature. After 30 minutes, the solvent was distilled off to obtain bis (trifluoromethanesulfonic acid) imide salt of N- (1,3-dimethyl-2-imidazolidinylidene) -1-propanamine as an oil. Table 1 shows the results of the proton conductivity of this salt obtained by the AC impedance method.

Example 2
In Example 1, except that n-butylamine was used in place of n-propylamine, the same operation as in Example 1 was performed to obtain a corresponding cyclic guanidine compound, which was combined with bis (trifluoromethanesulfonic acid) imide. The reaction gave bis (trifluoromethanesulfonic acid) imide salt as an oil. Table 2 shows the results of the proton conductivity of this salt obtained by the AC impedance method. FIG. 2 shows the 1H-NMR (CDCl3) measurement results of the cyclic guanidine compound.

Example 3
In Example 1, except that n-dodecylamine was used in place of n-propylamine, the same operation as in Example 1 was performed to obtain a corresponding cyclic guanidine compound, which was combined with bis (trifluoromethanesulfonic acid) imide. To give a bis (trifluoromethanesulfonic acid) imide salt as an oil. Table 3 shows the results of the proton conductivity of this salt obtained by the AC impedance method. FIG. 3 shows the 1H-NMR (CDCl3) measurement results of the cyclic guanidine compound.

Example 4
In Example 1, except that ethanolamine was used instead of n-propylamine, the same operation as in Example 1 was performed to obtain a corresponding cyclic guanidine compound, which was reacted with bis (trifluoromethanesulfonic acid) imide. To give bis (trifluoromethanesulfonic acid) imide salt as an oil. Table 3 shows the results of the proton conductivity of this salt obtained by the AC impedance method. FIG. 4 shows the 1H-NMR (CDCl3) measurement results of the cyclic guanidine compound.

Example 5
As shown in FIG. 5, the N- (1,3) obtained in Example 1 was placed in a U-shaped glass cell in which platinum electrodes 1 and 2 were disposed at both ends and a gas bubbling tube 3 was disposed on the platinum electrode 1 side. The bis (trifluoromethanesulfonic acid) imide salt of -dimethyl-2-imidazolidinylidene) -1-propanamine was added. A direct current power source was connected so that the electrode 1 was a positive electrode and the electrode 2 was a negative electrode, and nitrogen gas or hydrogen was circulated from the gas bubbling tube 3 to conduct an energization test. The results of the current test are shown in FIG.

  When nitrogen was circulated through the gas bubbling pipe 3, almost no current flowed as shown in FIG. 6, but when hydrogen was circulated, current flowed according to the voltage. That is, it is considered that the proton generated at the electrode 1 becomes hydrogen at the electrode 2 under the flow of hydrogen. From this, it was confirmed that the GB salt as a proton conductor of the present invention functions as a proton conductor.

NMR chart of the cyclic guanidine compound obtained in Example 1 NMR chart of the cyclic guanidine compound obtained in Example 2 NMR chart of the cyclic guanidine compound obtained in Example 3 NMR chart of the cyclic guanidine compound obtained in Example 4 Schematic diagram of an apparatus for evaluating the performance as a proton conductor Diagram showing the relationship between voltage and current when hydrogen or nitrogen gas is passed

Explanation of symbols

  1: platinum electrode, 2: platinum electrode, 3: gas bubbling tube

Claims (6)

Following formula (1)

(Wherein R ¹ , R ² and R ³ independently represent an alkyl group, an aryl group, an alkenyl group, a hydroxyalkyl group, an alkoxyalkyl group, an acyloxyalkyl group, an acyl group or hydrogen. N is 1 or more, 6 A proton exchanger comprising a salt obtained from a cyclic guanidine compound represented by the following formula: and a Bronsted acid.   2. The proton exchanger according to claim 1, comprising a salt obtained by reacting the cyclic guanidine compound represented by the formula (1) with a Bronsted acid in an equivalent amount.   The proton exchanger according to claim 1, wherein a salt obtained from a cyclic guanidine compound and a Bronsted acid is held in a gelling material comprising a polymer compound.   A proton exchange membrane obtained by forming the proton exchanger according to claim 3 into a membrane shape.   A fuel cell comprising a solid polymer electrolyte membrane comprising the proton exchange membrane according to claim 4.   An electrolyte for an electrochemical cell comprising the proton exchanger according to claim 1.

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