JPH05238739A - Method for oxidizing reduced polyoxo anionic compound - Google Patents

Abstract

PURPOSE:To smooth the reaction at the time of oxidizing a reduced polyoxo anionic compd. with oxygen in a liq. phase by using a golden metal as the catalyst. CONSTITUTION:A polyoxo anionic compd. (contg. polyoxo anion and one or >=2 kinds of cations) is reduced by a reducing agent in a liq. phase or electrochemically reduced in a liq. phase. The reduction product is dissolved by 0.01-80wt.% in water, a liq. mixed with a polar solvent or a liq. mixed with a mineral acid, and a golden metal (metallic gold, a mixture of gold and 1 kind of other metals and/or alloy) is used as the catalyst by 0.0001-50 mols per mol of the compd. Oxygen is used as the oxidizing agent, and the oxygen in excess of >=2 mols is introduced. The reaction is carried out at 0-200 deg.C and at a pressure ranging from atmospheric pressure to high pressures. The partial pressure of oxygen is controlled between atmospheric pressure and 50kg/cm<2>, and the reaction time is determined in accordance with the conditions.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for oxidizing a reduced polyoxoanion compound with a catalyst.

[0002]

2. Description of the Related Art Polyoxoanion compounds are extremely important compounds as industrial catalysts in the chemical industry.

Generally, polyoxoanion compounds are strong oxidizing agents, and it is known that many of their redox reactions are reversible. For example, G.I. A. Tsig
dinos et al. (Topp. Curr. Chem., 7
6, 1 (1978)) reported that the redox reaction was reversible from cyclic voltammetry measurement of a heteropolyoxoanion composed of phosphorus, molybdenum and the like. Further, in this redox reaction, it is known that the reduced polyoxoanion compound is reversibly oxidized by an oxidant, particularly oxygen, in the solution.

For example, K. I. Matveev et al. (Ki
net. Katal. , 18,862 (1977)),
, P. Argitis et al. (Inorg. Chem.,
25, 4386, (1986)) report that a reduced heteropolyoxoanion consisting of phosphorus, molybdenum and vanadium is reversibly oxidized by oxygen. In addition, E. Papaconstantinou
(J. Chem. Soc. Chem. Commun.,
12 (1982)) report that a reduced heteropolyoxoanion consisting of phosphorus and molybdenum is reversibly oxidized by oxygen.

[0005]

However, the above cited document (Inorg. Chem., 25, 4386,
(1986), page 4388, left column, lines 49 to 51,
J. Chem. Soc. Chem. Commun. , 1
2 (1982) page 13, right column, lines 19-30), and C.I. L. Hill et al. (J. Am. Che
m. Soc. , 107, 5148 (1985), 515.
As described on page 2, left column, lines 14 to 22) and the like, there is a problem that the oxidation reaction of the reduced polyoxoanion compound has a slow reaction rate and does not proceed smoothly. Therefore, for example, in a process using a polyoxoanion compound as a catalyst and the like, it has been desired to develop a method for smoothly oxidizing a reduced polyoxoanion compound with oxygen in a liquid phase.

[0006]

[Means for Solving the Problems] In view of the current situation,
The present inventors have made detailed studies on the oxidation reaction of the reduced polyoxoanion compound. As a result, surprisingly, the inventors have found the novel fact that the oxidation reaction of the reduced polyoxoanion compound progresses more smoothly when a gold metal is used as a catalyst, and completed the present invention.

That is, the present invention is a method of oxidizing a reduced polyoxoanion compound with oxygen in a liquid phase, wherein a gold metal is used as a catalyst, and a method of oxidizing a reduced polyoxoanion compound is characterized. Regarding

The present invention will be described in more detail below.

In the present invention, the polyoxoanion compound is, for example, M. T. Heterop by Pope
ol y and Isopoly Oxometala
As described in tes, it refers to those containing a polyoxoanion and one kind or two or more kinds of cations (counter cations).

The polyoxoanion constituting the polyoxoanion compound is represented by the following general formula (1) (hereinafter abbreviated as formula (1)). _{[X x L a M b N} c O z] -m ··· (1) where, X is P, B, Si, As, Ge, Se, Te,
An element selected from I, Co, Mn and Cu, and L and M
And N represent an element independently selected from Mo, W, V, Nb, Ta and Re, and O represents an oxygen element. In general, the polyoxoanion is composed of an isopolyoxoanion produced by condensation of oxygen acids of the transition metals L, M, and N in formula (1) and an oxygen acid of the transition metals L, M, and N with the heteroatom X as the center. And a heteropolyoxoanion generated by condensation of oxygen by a condensed acid group sharing oxygen with each other. As the polyoxoanion, a single metal component type in which all L, M, and N elements are the same and a mixed coordination type in which two or more different L, M, and N elements are different are known. x is 0 in the isopolyoxoanion, and x is a natural number in the heteropolyoxoanion. m represents the valence of the polyoxoanion. a, b, c, z, and m are positive integers, and a + b + c is 2 or more. Further, the heteropolyoxoanion having the hetero atom X at the center is characterized by its structure. For example, in the formula (1), x = 1, a + b +
For c = 12 and z = 40, three MO ₆ octahedra (M
= Mo, W, V, etc.) share an edge to form M ₃ O ₁₃ , and these four atoms form one hetero atom X (X = P, Si).
It is known to have a so-called "Keggin structure" that surrounds the same). Further, in the formula (1), x
= 2, a + b + c = 18, z = 62 is the above M
_{It is known that 3} O ₁₃ 6 has a so-called "Dawson structure" in which two heteroatoms X are surrounded.

Among the polyoxoanions, examples of the isopolyoxoanion in which x = 0 in the formula (1) include, for example, [Mo ₇ O ₂₄ ] ⁶⁻ , [W ₁₀ O ₃₂ ] ^4- [Mo ₄ V _{8 ^{O 40] 8-, [Mo 3}} V 3 O 19] 5- [Mo 6 V 2 O 26] 6-, [Mo 6 V 6 O 36] 6- [W 7 Mo 3 V 2 O 36] 2-, [Mo ₈ V ₄ O ₃₆ ]
^4- etc. can be mentioned.

Among the polyoxoanions, in the formula (1), x is represented as a heteropolyoxoanion.
= 1, for example, [SiMo ₁₂ O ₄₀ ] ⁴⁻ ,
[SiMo ₈ W ₄ O ₄₀ ] ^4- , [SiW ₁₂ O ₄₀ ]
^4- , [PMo ₁₂ O ₄₀ ] ^3- , [PMo ₄ W ₈ O
₄₀ ] ³⁻ , [PMo ₆ W ₆ O ₄₀ ] ³⁻ , [PMo ₈
W ₄ O ₄₀ ] ³⁻ , [PMo ₆ V ₆ O ₄₀ ] ⁹⁻ , [P
^{_{Mo 8 V 4 O 40] 7-}} , [PMo 9 V
₃ O ₄₀ ] ⁶⁻ , [PMo ₁₀ V ₂ O ₄₀ ] ⁵⁻ , [P
Mo ₁₁ VO ₄₀ ] ^4- , [PW ₁₂ O ₄₀ ] ^3- ,
[PW ₁₁ VO ₄₀ ] ^4- , [PW ₁₀ V ₂ O ₄₀ ]
^5- , [GeMo ₁₂ O ₄₀ ] ^4- , [GeMo ₈ W ₄
O ₄₀ ] ⁴⁻ , etc. When x = 2, for example, [P ₂ Mo
₁₈ O ₆₂ ] ⁶⁻ , [P ₂ W ₁₈ O ₆₂ ] ⁶⁻ , [P ₂
Mo ₂ W ₁₅ VO ₆₂ ] ⁷⁻ , [P ₂ Mo ₅ W ₁₂ VO
₆₂ ] ⁷⁻ , [As ₂ W ₁₈ O ₆₂ ] ⁶⁻ , and the like.

In the present invention, the polyoxoanion may be either an isopolyoxoanion or a heteropolyoxoanion, but a heteropolyoxoanion stable in a reversible redox reaction is more preferable. In formula (1), X and L, M, and N may be elements independently selected from the above-mentioned elements, and L, M, and
The elements of N may all be the same or may be two or more different elements, but X or P or Si may be L,
As M and N, an element selected from Mo, W and V is preferable.

In the present invention, the polyoxoanion may be of the above-mentioned single metal component type or mixed coordination type. Further, the polyoxoanion has various structures such as the heteropolyoxoanion is known to have various structures such as Keggin structure and Dawson structure. It does not matter even if it has a different structure. In general, polyoxoanions are often known to be in dissociation equilibrium with polyoxoanions having a plurality of different compositions and structures in a solution. It may be in a dissociation equilibrium state of polyoxoanions having a plurality of different compositions and structures.

On the other hand, many cation species are known as counter cations for polyoxoanion compounds. For example, H ⁺ , various metal ions, for example, L
Alkali metal ions such as i ⁺ , Na ⁺ and K ⁺ , Ca
Alkaline earth metal ions such as ²⁺ and Mg ²⁺ , and nonmetallic cations such as onium such as ammonium ion and alkylammonium ion (secondary to quaternary ammonium ion) are known. In the present invention,
These counter cations may be one kind selected from these counter cations, or two or more kinds.

In general, polyoxoanion compounds often have water of crystallization.
The polyoxoanion compound may contain water of crystallization.

In the present invention, the reduced polyoxoanion compound is a reduced polyoxoanion compound obtained by reducing the polyoxoanion compound. It is known that the reaction of reducing a polyoxoanion compound is generally a reaction of reducing a polyoxoanion to generate a reduced polyoxoanion. Therefore, the reduced polyoxoanion compound includes the reduced polyoxoanion and the counter cation. The reduced polyoxoanion is represented by the following general formula (2) (hereinafter abbreviated as formula (2)). _{[X x L a M b N} c O z] -m-n ··· (2) wherein, X, L, M, N , O , and, x, a, b, c ,
z and m represent the same element or number as in formula (1). Further, n represents the number of reducing electrons of the reduced polyoxoanion, and usually n is 0 <n ≦ 6.

The reduced polyoxoanion has 1, 2, 3, 4, 5, 6 electrons corresponding to the values of n = 1, 2, 3, 4, 5, 6 in the formula (2), respectively. Represents a reduced polyoxoanion. Examples of these reduced polyoxoanions include those obtained by reducing the aforementioned isopolyoxoanion and those obtained by reducing the heteropolyoxoanion.

In the present invention, the reduced electron number n of the reduced polyoxoanion is not necessarily a positive integer. This is because, in a mixture of reduced polyoxoanions having different reduction electron numbers of n = 1 to 6, n may not be an apparent integer. Further, the reduced polyoxoanion and the non-reduced polyoxoanion may coexist. Moreover, even if the electrons generated in the reduced polyoxoanion and present in the reduced polyoxoanion are localized in the specific metal constituting the polyoxoanion, the electrons are distributed in the entire polyoxoanion. It does not matter which is delocalized. Further, the reduced polyoxoanion may be in a dissociation equilibrium state of the reduced polyoxoanion having a plurality of different compositions or structures, where the reduced polyoxoanion has a different number of reducing electrons. It may be dissociated into a reduced polyoxoanion or a non-reduced polyoxoanion.

On the other hand, in the case of preparing a reduced polyoxoanion compound by reducing the polyoxoanion compound, a part of the reducing agent described later becomes a counter cation of the reduced polyoxoanion compound. In the present invention, a part of the reducing agent may be a counter cation or may be replaced with a counter cation of the polyoxoanion compound before undergoing reduction.

In the present invention, the reduced polyoxoanion compound can be prepared by reducing the polyoxoanion compound by a known method. For example, hydrogen or organic compounds such as hydrazine, oxalic acid, citric acid, ascorbic acid, aldehydes, alcohols, ketones, sodium borohydride, ferrous sulfate, cuprous chloride, stannous chloride, etc. A polyoxoanion compound reduced by a method of reducing in a liquid phase with a reducing agent such as a metal salt, a metal such as copper or iron, or a method of reducing in a liquid phase by giving an electron by an electrochemical method Can be obtained. In the present invention, the reduced polyoxoanion compound may be reduced by any of these methods. In these methods, a reducing polyoxoanion compound having a desired number of reducing electrons can be obtained by changing the reducing conditions, the amount of the reducing agent and the like.

In addition, the various reduced polyoxoanion compounds include those having water of crystallization.

In the present invention, the reduced polyoxoanionic compound thus prepared can be oxidized in the presence of the catalyst of the present invention. In the present invention, the above-mentioned oxidation of the reduced polyoxoanion compound means that the reduced electron number of the reduced polyoxoanion compound decreases. Therefore, the reduced polyoxoanion compound is oxidized, and the reduced polyoxoanion compound in a more oxidized state, or the original polyoxoanion compound, and a mixed equilibrium state thereof may be used. ..

In the present invention, a gold metal is used as a catalyst for the reaction of oxidizing the reduced polyoxoanion compound. Gold-based metals are gold metals or mixtures and / or alloys of gold metals with one or more other metals.
When the gold-based metal is a mixture and / or alloy of gold metal and one or more other metals, examples of the other metal include noble metals such as platinum, silver, palladium, rhodium, ruthenium, iridium, and copper, Examples include base metals such as lead, bismuth, and indium. When the gold-based metal is a mixture and / or alloy of gold metal and one or more other metals, when the other metal is a noble metal, the content of the gold metal is 2
% By weight or more, preferably 10% by weight or more, and
When the other metal is a base metal, the content of the gold metal is 0.5% by weight or more, preferably 5% by weight or more.

The gold metal is a gold compound, for example, an inorganic salt such as gold chloride, gold iodide, gold bromide, gold sulfide, gold cyanide or gold hydroxide, tetrachloroauric acid, potassium tetrachloroaurate, or tetrachloro. Complex salts such as sodium aurate, ammonium tetrachloroaurate, potassium dicyanoaurate, etc., such as hydrogen, organic compounds such as hydrazine, sodium citrate, alcohol, etc., inorganic salts such as lithium aluminum hydride, sodium borohydride etc. It can be obtained by reducing with a reducing agent. The reduction of the gold compound may be carried out in a solution by dissolving the gold compound in a solvent such as water or alcohol.

When the gold-based metal is a mixture and / or alloy of gold metal and one or more other metals, the gold-based metal is an inorganic salt of gold metal and another metal, that is, the above-mentioned noble metal or base metal. A physical mixture of an organic salt or a complex salt obtained by reducing the salt with the reducing agent, or the gold compound and one or more other metals, salts of other metals and / or complex salts. A mixture obtained by dissolving or mixing in the solvent at the same time or separately, and reducing with the reducing agent, or
It is an alloy obtained by subjecting these mixtures to a known alloying treatment.

In the present invention, the gold-based metal may be supported on a carrier. As the carrier on which the gold-based metal is supported,
There is no particular limitation, and any of a neutral carrier, an acidic carrier, and a basic carrier can be used. For example, examples of the neutral carrier include silica and activated carbon, examples of the acidic carrier include alumina and zeolite, and examples of the basic carrier include zirconia, magnesia, and titania. Among these, silica and activated carbon are particularly preferable.

In the present invention, the method of supporting the gold-based metal on the carrier includes, for example, an impregnation method, a coprecipitation method, physical mixing,
The method is not particularly limited as long as it is a known method for preparing a metal-supported catalyst such as adsorption of metal fine particles, but an impregnation method is simple and preferable. As a method of preparing the gold metal-supported catalyst by the impregnation method, for example, a method of obtaining gold metal from the gold compound can be applied. For example, a desired amount of the gold compound is
It is dissolved in a solvent such as water or alcohol, a carrier is added to the obtained gold compound solution, and then the solvent is distilled off. The solvent may be distilled off by raising the temperature or under reduced pressure. The solvent can be distilled off and then dried, and the gold compound can be reduced by using the reducing agent to obtain a gold metal-supported catalyst. Further, in the case of a mixture and / or alloy of gold metal and one or more other metals, in the method for preparing a gold metal-supported catalyst, one or more other metals, salts or complex salts of other metals, Add each separately or at the same time,
It can be prepared by reduction or by a known alloying treatment.

In these gold-based metal-supported catalysts, the supporting ratio of the gold metal component is not particularly limited, but usually 0.1 to 10% by weight as the gold metal, or one or more of the gold metal and the carrier. 0.1 to 20% by weight as a mixture and / or alloy with other metals is preferred.

In the method of the present invention, the reaction is performed in a batch system,
Any method such as a semi-batch method or a continuous method may be used. Usually, normal pressure or pressure batch method, normal pressure or pressure semi-batch method, or normal pressure or continuous pressure A method etc. can be adopted.

In the present invention, the abundance ratio of the gold-based metal used as the catalyst and the reduced polyoxoanion-based compound is not particularly limited. For example, in the case of a batch reaction or a semi-batch reaction, Gold-based metal 0.0001-5 per mol of reduced polyoxoanion compound
The amount is 0 mol, preferably 0.0002 to 20 mol, and more preferably 0.0005 to 5 mol.

In the present invention, the oxidation reaction of the reduced polyoxoanionic compound can be carried out in a solution in which they are dissolved. Any solvent can be used as this solvent as long as it can dissolve the reduced polyoxoanion compound. Usually, water can be used, and the solvent can be used in an aqueous solution. In the present invention, the water solvent may be used alone, or acetonitrile, γ-butyrolactone, dimethylformamide, methyl ethyl ketone, sulfolane, ethanol, tert-butyl alcohol, dioxane,
A polar solvent such as acetic acid may be mixed. Further, if necessary, a mineral acid such as sulfuric acid, nitric acid, phosphoric acid or hydrochloric acid may be appropriately added.

The concentration of the reduced polyoxoanion compound is not particularly limited as long as it becomes a solution under the oxidation reaction conditions, but is usually 0.01 to 80% by weight.
The oxidation reaction can be performed at a concentration of about (saturated solution).

In the present invention, the oxidation reaction of the reduced polyoxoanion compound is carried out by allowing oxygen to coexist as an oxidizing agent. There are no particular restrictions on the oxygen that can be used, but normally, pure oxygen, oxygen such as air, or oxygen diluted with an inert gas such as argon can be used. It is also possible to coexist with an oxidizing agent or the like in which oxygen has already been activated such as organic peracid and hydrogen peroxide. The abundance ratio of oxygen and the reduced polyoxoanion compound is not particularly limited, but is usually an excess of 2 mol or more in molar ratio with respect to the reduced polyoxoanion compound in the present oxidation reaction. A quantity of oxygen can be present. Since oxygen is consumed in the oxidation reaction, it is possible to appropriately supplement oxygen to carry out the reaction. In the method of supplementing oxygen, the abundance ratio does not have to be an excessive amount.

The reaction temperature in the present invention is not particularly limited, but is usually 0 to 200 ° C., preferably 30 to
It is 150 ° C. The reaction pressure can be appropriately selected within a wide range from normal pressure to high pressure, and is usually from normal pressure to 10
The range is about 0 kg / cm ² . At this time, the partial pressure of oxygen can be appropriately selected within the range of atmospheric pressure to about 50 kg / cm ² .

The reaction time in the present invention depends on the kind of reduced polyoxoanion compound, the amount of catalyst, the reaction pressure,
Since it depends on the reaction conditions such as the reaction temperature, the reaction method and the like, it cannot be defined unconditionally, but an industrially practicable reaction time can be selected. For example, in the case of a batch reaction, the reaction can be carried out within a few minutes to a few hours.

Further, the catalyst can be recovered after the reaction and used again in the oxidation reaction. In this case, if the catalyst is partially deactivated, it may be reused in the oxidation reaction after being activated by calcination and reduction if necessary.

[0038]

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

In the following Examples and Comparative Examples, the degree of progress of the oxidation reaction is represented by the oxidation rate of the reduced polyoxoanion compound shown below. The oxidation rate of the reduced polyoxoanion compound is calculated by the following formula (3). Oxidation rate of reduced polyoxoanion compound (%) = (A−B) × 100 / A (3) where A and B are A = reduced polyoxoanion compound before oxidation reaction Number of reducing electrons of compound B = number of reducing electrons of reduced polyoxoanion compound after oxidation reaction. However, when the reduced polyoxoanion compound is completely oxidized by the oxidation reaction to become a non-reduced polyoxoanion compound, B
= 0.

In the above formula (3), the oxidation rate (%) of the reduced polyoxoanion compound is decreased by the ratio of the number of reduced electrons of the reduced polyoxoanion compound being oxidized. The closer the value is to 100%, the more the oxidation reaction proceeds.

The number of reducing electrons is determined by KM of the reduced polyoxoanion compound before and after the reaction.
It was performed by titration with an nO ₄ solution or measurement of ultraviolet-visible-near infrared absorption spectrum.

Example 1 Tetrachloroauric acid tetrahydrate (HAuCl ₄ .4H ₂ O) was dissolved in 40 ml of water, and 3 g of activated carbon pulverized to 200 mesh or less was added thereto. Water was removed under reduced pressure using a rotary evaporator, and the obtained paste was dried under reduced pressure at 80 ° C. for 2 hours and further at 110 ° C. for 2 hours to obtain a catalyst powder. This was reduced under a stream of 10% hydrogen (remaining nitrogen) to prepare gold-activated carbon (Au / C, carrying 2.5% by weight of gold metal).

In a 500 ml four-necked flask equipped with a dropping funnel, a reflux condenser, a 100 ° C. thermometer, and a magnetic stirrer, H ₃ PM was added as a polyoxoanion compound.
o ₆ W ₆ O ₄₀ / 30H ₂ O (manufactured by Japan Inorganic Chemical Company) 14
4.66 g (50 mmol) and 100 ml of water were added to dissolve the polyoxoanion compound. 50 ml of water
In addition, 1.25 g of H ₂ NNH ₂ · H ₂ O (25 mmo
l) was dissolved and placed in a dropping funnel. This was added dropwise to the above polyoxoanion compound aqueous solution under N ₂ atmosphere while stirring over 30 minutes. 6 hours at 40 ° C for 3 hours
The polyoxoanion compound was reduced by heating and stirring at 0 ° C. for 1 hour. The solution after the reaction was dark blue. After the reaction solution was cooled to room temperature, 0.2 mol of the reduced polyoxoanion compound was obtained by diluting with water.
/ L aqueous solution. From the titration with the KMnO ₄ solution, the number of reducing electrons of the obtained reduced polyoxoanion compound was 2 electrons. In this manner, a 0.2 mol / l 2 electron-reduced polyoxoanion compound H ₅ PMo ₆ W ₆ O ₄₀ aqueous solution was obtained.

The above-mentioned 0.2 mol / l 2 electron-reduced polyoxoanion compound H ₅ PMo ₆ W ₆ O ₄₀
30 ml of an aqueous solution (containing a 2-electron-reduced polyoxoanion compound H ₅ PMo ₆ W ₆ O ₄₀ 6.0 mmol) and the above-prepared gold-activated carbon (Au / C, gold metal 2.5 weight) as a catalyst % Carrying) 0.4727 g
Was charged in a 100 ml autoclave with a stirring blade made of Teflon, oxygen 4 kg / cm ² (absolute pressure) was injected, and the reaction was carried out at 60 ° C. for 30 minutes while stirring at a stirring speed of 800 rpm. In this reaction, oxygen was supplied and supplemented so that the pressure during the reaction became constant. After completion of the reaction, the reaction solution was allowed to cool and then titrated with a KMnO ₄ solution. As a result, the oxidation rate of the polyoxoanion compound reduced by this reaction was 67.4%.

That is, the polyoxoanion compound H ₅ PMo ₆ W ₆ O ₄₀ which has been reduced by two electrons by this reaction
This means that the reduced electrons of are no longer 67.4%.

Comparative Example 1 The same reaction as in Example 1 was carried out except that gold-activated carbon was not added in the oxidation of the reduced polyoxoanion compound. as a result,
The oxidation rate of the reduced polyoxoanion compound is 1.
It was 8%.

Example 2 The same reaction as in Example 1 was carried out except that the reaction temperature was 80 ° C. As a result, the oxidation rate of the reduced polyoxoanion compound was 77.2%.
Met.

Example 3 In Example 1, the amount of gold-activated carbon was 0.0236 g in the oxidation of the reduced polyoxoanion compound.
And the same reaction as in Example 1 except that the reaction temperature was 100 ° C. As a result, the oxidation rate of the reduced polyoxoanion compound was 46.1%.

Example 4 The same reaction as in Example 3 was carried out except that the reaction temperature in the oxidation of the reduced polyoxoanion compound was 120 ° C. As a result, the oxidation rate of the reduced polyoxoanion compound was 54.6.
%Met.

Example 5 Tetrachloroauric acid tetrahydrate (HAuCl ₄ .4H ₂ O) was dissolved in 40 ml of water, and silica gel (Carriert 50 manufactured by Fuji Devison Co., Ltd.) was pulverized to 100 to 200 mesh. 10 g of the product was added and dried using a 60 ° C warm bath. This was reduced under a stream of 10% hydrogen (remaining nitrogen) to prepare gold-silica (Au / SiO ₂ , supporting 0.5% by weight of gold metal).

In Example 1, 0.2364 g of the above-prepared gold-silica (Au / SiO ₂ , supporting 0.5% by weight of gold metal) instead of gold-activated carbon in the oxidation of the reduced polyoxoanion compound. The same reaction as in Example 1 was carried out except that the above was used. As a result, the oxidation rate of the reduced polyoxoanion compound was 10.9%.
Met.

Example 6 In a 500 ml four-necked flask equipped with a dropping funnel, a reflux condenser, a 100 ° C. thermometer, and a magnetic stirrer, H ₃ PMo ₁₂ O _40.
29H ₂ O (Nippon Inorganic Chemicals Co., Ltd.) 11.74 g (5 mm
ol) and 100 ml of water were added to dissolve the polyoxoanion compound. H ₂ NNH ₂ · H _{2 in} 50 ml of water
0.250 g (5 mmol) of O was dissolved and placed in a dropping funnel. This was added dropwise to the above polyoxoanion compound aqueous solution under N ₂ atmosphere while stirring over 30 minutes. Furthermore, the polyoxoanion compound was reduced by heating and stirring at 40 ° C. for 3 hours and at 60 ° C. for 3 hours.
The solution after the reaction was dark blue. After the reaction solution was cooled to room temperature, water and H ₃ PO ₄ were added to prepare a reduced polyoxoanion compound as a 0.02 mol / l aqueous solution (containing 1 wt% H ₃ PO ₄ ). did.
From the titration with the KMnO ₄ solution, the number of reducing electrons of the obtained reduced polyoxoanion compound was 4 electrons. In this way, 0.02 mol / l 4 electron-reduced polyoxoanion compound H ₇ PMo ₁₂ O
₄₀ aqueous solution (containing 1 wt% H ₃ PO ₄ ) was obtained.

The above-mentioned 0.02 mol / l 4 electron-reduced polyoxoanion compound H ₇ PMo ₁₂ O ₄₀
30 ml of an aqueous solution (containing 1 wt% H ₃ PO ₄ ) (4-electron reduced polyoxoanion compound H ₇ PMo ₁₂
(O ₄₀ 0.60 mmol content), and 0.4727 g of gold-activated carbon (Au / C, carrying 2.5% by weight of gold metal) prepared in Example 1 as a catalyst were charged in a 100 ml autoclave equipped with a Teflon stirring blade. , Oxygen 4kg
/ Cm ² (absolute pressure) was injected, and the mixture was reacted at 60 ° C. for 5 minutes while stirring at a stirring speed of 800 rpm. In this reaction, oxygen was supplied and supplemented so that the pressure during the reaction became constant. After completion of the reaction, the reaction solution was allowed to cool, and the reaction solution was KMnO ₄
When titrated with a solution, the oxidation rate of the polyoxoanion compound reduced by this reaction was 100%.

That is, the number of reducing electrons of the polyoxoanion compound H ₇ PMo ₁₂ O ₄₀ reduced by four electrons by this reaction is 100%.

Comparative Example 2 Example 6 was repeated except that no gold-activated carbon was added in the oxidation of the reduced polyoxoanion compound and the reaction time was 30 minutes.
Reaction exactly the same as was performed. As a result, the oxidation rate of the reduced polyoxoanion compound was 21.5%.

Example 7 In a 500 ml four-necked flask equipped with a dropping funnel, a reflux condenser, a 100 ° C. thermometer, and a magnetic stir bar, H ₅ PMo ₁₀ V ₂ O was added as a polyoxoanion compound.
₄₀ · _31H 2 O (Nippon Muki Chemical Co., Ltd.) 114.79g
(50 mmol) and 100 ml of water were added to dissolve the polyoxoanion compound. 50 ml of water, H ₂ NN
1.25 g (2.5 mmol) of H ₂ · H ₂ O was dissolved and placed in a dropping funnel. This was added dropwise to the above polyoxoanion compound aqueous solution under N ₂ atmosphere while stirring over 30 minutes. Furthermore, the polyoxoanion compound was reduced by heating and stirring at 40 ° C. for 3 hours and at 60 ° C. for 3 hours. The solution after the reaction was deep blue-green. The reaction solution was cooled to room temperature and then diluted with water to prepare a reduced polyoxoanion compound as a 0.2 mol / l aqueous solution.

From the visible-near infrared absorption spectrum measurement, the number of reducing electrons of the obtained reduced polyoxoanion compound was 2 electrons. In this way, 0.2 mol
/ L2-electron reduced polyoxoanion compound H ₇
A PMo ₁₀ V ₂ O ₄₀ aqueous solution was obtained.

The above-mentioned 0.2 mol / l 2 electron-reduced polyoxoanion compound H ₇ PMo ₁₀ V ₂ O
₄₀ aqueous solution 30 ml (two-electron reduced polyoxoanion compound H ₇ PMo ₁₀ V ₂ O ₄₀ 6.0 mm
ol) and gold-activated carbon prepared in Example 1 as a catalyst (Au / C, supporting 2.5% by weight of gold metal).
4727 g was charged into a 100 ml autoclave equipped with a Teflon stirring blade, oxygen 4 kg / cm ² (absolute pressure) was pressure-injected, and the mixture was stirred at a stirring speed of 800 rpm for 3 at 60 ° C.
Reacted for 0 minutes. In this reaction, oxygen was supplied and supplemented so that the pressure during the reaction became constant. After completion of the reaction, the reaction solution was allowed to cool and the visible-near infrared absorption spectrum of the reaction solution was measured. As a result, the oxidation rate of the polyoxoanion compound reduced by this reaction was 39.0%.

That is, a polyoxoanion compound H ₇ PMo ₁₀ V ₂ O which has been reduced by two electrons by this reaction
The reduced electrons of ₄₀ are 39.0% gone.

Comparative Example 3 The same reaction as in Example 7 was carried out except that gold-activated carbon was not added in the oxidation of the reduced polyoxoanion compound. as a result,
The oxidation rate of the reduced polyoxoanion compound is 1
It was 4.8%.

[0061]

INDUSTRIAL APPLICABILITY In the present invention, a polyoxoanion compound reduced by using a gold metal as a catalyst can be smoothly oxidized by oxygen.

The oxidation of a reduced polyoxoanion compound, which has been a problem in the past, can be catalytically promoted by the present invention, and the present invention uses a polyoxoanion compound as a catalyst. It has a very high utility value industrially in processes and the like.

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Claims (1)

[Claims] 1. A method for oxidizing a reduced polyoxoanion compound in a liquid phase, wherein a gold metal is used as a catalyst.