JP2006290727A - Heteropolyacid, acid catalyst comprising heteropolyacid, and method for producing heteropolyacid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel compound which has a sufficiently large number of H<SP>+</SP>ions per molecule, and therefore exhibits a higher catalytic activity than a conventional heteropolyacid and is stable as a catalyst and to provide a method for producing the novel compound in a good yield. <P>SOLUTION: The heteropolyacid is represented by formula (1). Formula (1) is H<SB>d</SB>[P<SB>2</SB>W<SB>a</SB>V<SB>b</SB><SP>V</SP>V<SB>c</SB><SP>IV</SP>O<SB>62</SB>]×(xH<SB>2</SB>O) (wherein a is an integer of 15 to 17; b and c are each an integer of 0 to 3; a+b+c=18; b+c is an integer of 1 to 3; d is an integer equal to 6+b+2c; x is an integer of 1 to 100; V<SP>V</SP>is a pentavalent vanadium atom; and V<SP>IV</SP>is a tetravalent vanadium atom). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a novel heteropolyacid that can be used as an acid catalyst and a method for producing the same.

  The heteropolyacid salt has a structure in which skeleton constituent atoms such as W and Mo are coordinated through an oxygen atom around a heteroatom such as P, Si and As coordinated with four oxygen atoms. It is known that the heteropolyacid salt having such a structure can be partially substituted with a different metal by deleting a part of the skeleton constituent atoms. Such a deficient heteropolyacid salt and a heteropolyacid salt substituted with a different oxidation metal having a lower oxidation number have a negative charge density on the surface, which is higher than that of a normal heteropolyacid salt. Has been used as.

  There are many examples of missing and substituted heteropolyacid salts, many of which are used as oxidation catalysts. For example, an oxidation reaction of alcohol by a Ru substituent is known (Patent Document 1).

However, it is important as an industrial application and has been put into practical use in many cases as an acid catalyst using a free acid type heteropolyacid in which the partner cation is exchanged with H ⁺ . For example, ring-opening polymerization of tetrahydrofuran is mentioned (Patent Document 2).

Many examples of heteropolyacids as acid catalysts that are useful for industrial applications often use unsubstituted free acid types. For _{example, H 3 [PW 12 O 40} ], H 3 [PMo 12 O 40], H 4 [SiW 12 O 40], H 4 [SiMo 12 O 40] , and the like.

JP 2003-261493 A (Claims) JP 59-215320 A (Example)

However, the negative charges of these heteropolyacids are −3 and −4, and the number of partner cations H ⁺ is limited to 3 or 4. When a heteropolyacid is used as the acid catalyst, the catalytic activity depends on the number of H ⁺ contained in the heteropolyacid, so that a heteropolyacid having a large number of H ⁺ per molecule is desired in order to improve the catalyst performance. Yes.

  Furthermore, it is known that these heteropolyacids show significant deterioration in the activity of acid catalysis while performing the catalysis.

Accordingly, an object of the present invention is to provide a novel compound that has a sufficiently large number of H ⁺ per molecule, exhibits higher catalytic activity than conventional heteropolyacids, and has high stability as a catalyst.

  Another object of the present invention is to provide a catalyst using the novel compound.

  Another object of the present invention is to provide an efficient method for producing the novel compound.

The heteropolyacid of the present invention that solves the above problems is represented by the general formula (1).
_{H d [P 2 W a V} b V V c IV O 62] · xH 2 O ··· (1)
[Wherein, a is an integer of 15 to 17, and b and c are integers of 0 to 3. Further, a + b + c is 18, and b + c is an integer of 1 to 3. d is an integer represented by 6 + b + 2c. x is an integer of 1 to 100. V ^V represents a pentavalent vanadium atom, and V ^IV represents a tetravalent vanadium atom. ]

Moreover, the heteropolyacid of this invention is shown by General formula (2).
_{H g [P 1 W e V} f V O 40] · xH 2 O ··· (2)
[Wherein e is an integer from 9 to 11, and f is an integer from 1 to 3. E + f is 12. g is an integer represented by 3 + f. x is an integer of 1 to 100. V ^V represents a pentavalent vanadium atom. ]

  The acid catalyst of the present invention is composed of the heteropolyacid.

In addition, the method for producing a heteropolyacid according to the present invention comprises producing the ether adduct of the heteropolyacid according to claim 1 by a treatment including the following steps (A) and (B), and then adding ether from the ether adduct. To be removed.
(A) Step of making aqueous solution of heteropolyacid salt represented by general formula (3) acidic with hydrochloric acid or sulfuric acid (B) Step of adding ether to aqueous solution of heteropolyacid salt represented by general formula (3) K _d [P ^{_{2 W a V b V V c}} IV O 62] · xH 2 O ··· (3)
[Wherein, a is an integer of 15 to 17, and b and c are integers of 0 to 3. Further, a + b + c is 18, and b + c is an integer of 1 to 3. d is an integer represented by 6 + b + 2c. x is an integer of 1 to 100. V ^V represents a pentavalent vanadium atom, and V ^IV represents a tetravalent vanadium atom. ]

Moreover, the method for producing a heteropolyacid according to the present invention comprises producing an ether adduct of the heteropolyacid according to claim 2 by treatment including the following steps (C) and (D), and then adding ether from the ether adduct. To be removed.
(C) Step of making aqueous solution of heteropolyacid salt represented by general formula (4) acidic with hydrochloric acid or sulfuric acid (D) Step of adding ether to aqueous solution of heteropolyacid salt represented by general formula (4) K _g [P ^{_{1 W e V f V O 40}} ] · xH 2 O ··· (4)
[Wherein e is an integer from 9 to 11, and f is an integer from 1 to 3. E + f is 12. g is an integer represented by 3 + f. x is an integer of 1 to 100. V ^V represents a pentavalent vanadium atom. ]

The heteropolyacid of the present invention has more H ⁺ than known heteropolyacids, and a part of the basic skeleton is substituted with a vanadium atom having a lower oxidation number, so that the catalytic activity of the anion portion can be enhanced. Therefore, the synergistic effect with H ⁺ can show a much higher catalytic activity than conventionally known heteropolyacids.

  Furthermore, the stability of the catalyst is also improved, and after the separation and recovery, the catalytic reaction can be performed again, and the thermal stability is excellent, and the catalyst can exist stably up to 600 ° C.

  Moreover, according to the method for producing a heteropolyacid of the present invention, a heteropolyacid having the excellent characteristics as described above can be produced efficiently.

  Hereinafter, embodiments of the present invention will be described.

The heteropolyacid of the present invention is characterized by comprising the general formula (1).
_{H d [P 2 W a V} b V V c IV O 62] · xH 2 O ··· (1)
[Wherein, a is an integer of 15 to 17, and b and c are integers of 0 to 3. Further, a + b + c is 18, and b + c is an integer of 1 to 3. d is an integer represented by 6 + b + 2c. x is an integer of 1 to 100. V ^V represents a pentavalent vanadium atom, and V ^IV represents a tetravalent vanadium atom. ]

Specific examples of the heteropolyacid represented by the general formula (1) include H ₇ [P ₂ W ₁₇ V ₁ ^V O ₆₂ ] · xH ₂ O, H ₈ [P ₂ W ₁₆ V ₂ ^V O ₆₂ ] · xH. ₂ O, H ₈ [P ₂ W ₁₇ V ₁ ^IV O ₆₂ ] xH ₂ O, H ₉ [P ₂ W ₁₅ V ₃ ^V O ₆₂ ] xH ₂ O, H ₉ [P ₂ W ₁₆ V ₁ ^V V ₁ ^IV O ₆₂ ] xH ₂ O, H ₁₀ [P ₂ W ₁₆ V ₂ ^IV O ₆₂ ] x H ₂ O, H ₁₀ [P ₂ W ₁₅ V ₂ ^V V ₁ ^IV O ₆₂ ] xH ₂ O, H _{11 [P 2 W 15 V 1} V V 2 IV O 62] · xH 2 O, H 12 [P 2 W 15 V 3 IV O 62] · xH 2 O and the like. In any case, x is an integer of 1 to 100, V ^V represents a pentavalent vanadium atom, and V ^IV represents a tetravalent vanadium atom.

  Such a heteropolyacid of general formula (1) can be produced from a heteropolyacid salt of general formula (3) which is a precursor.

_{K d [P 2 W a V} b V V c IV O 62] · xH 2 O ··· (3)
[Wherein, a is an integer of 15 to 17, and b and c are integers of 0 to 3. Further, a + b + c is 18, and b + c is an integer of 1 to 3. d is an integer represented by 6 + b + 2c. x is an integer of 1 to 100. V ^V represents a pentavalent vanadium atom, and V ^IV represents a tetravalent vanadium atom. ]

Specific examples of the heteropolyacid salt represented by the general formula (3) include K ₇ [P ₂ W ₁₇ V ₁ ^V O ₆₂ ] · xH ₂ O, K ₈ [P ₂ W ₁₆ V ₂ ^V O ₆₂ ] · xH ₂ O, K ₈ [P ₂ W ₁₇ V ₁ ^IV O ₆₂ ] xH ₂ O, K ₉ [P ₂ W ₁₅ V ₃ ^V O ₆₂ ] xH ₂ O, K ₉ [P ₂ W ₁₆ V ₁ ^V V ₁ ^IV O ₆₂ ] · xH ₂ O, K ₁₀ [P ₂ W ₁₆ V ₂ ^IV O ₆₂ ] · xH ₂ O, K ₁₀ [P ₂ W ₁₅ V ₂ ^V V ₁ ^IV O ₆₂ ] · xH ₂ O, _{K 11 [P 2 W 15 V} 1 V V 2 IV O 62] · xH 2 O, K 12 [P 2 W 15 V 3 IV O 62] · xH 2 O and the like. In any case, x is an integer of 1 to 100, V ^V represents a pentavalent vanadium atom, and V ^IV represents a tetravalent vanadium atom.

To produce the heteropolyacid of the general formula (1), first, hydrochloric acid or sulfuric acid is added to an aqueous solution containing the heteropolyacid salt of the general formula (3) in a container such as a beaker, and the aqueous solution is made acidic with hydrochloric acid or sulfuric acid. To do. The amount of hydrochloric acid or sulfuric acid to be added is not particularly limited, but it is preferable to add such an amount that the H ⁺ concentration in the aqueous solution is 9 mol / L or more. When the concentration of hydrochloric acid or sulfuric acid is lower than this concentration, the heteropolyacid does not completely produce the ether adduct described later, causing a decrease in the yield of the target product.

  Next, ether is added in a separatory funnel to produce an ether adduct of the heteropolyacid of general formula (1). The amount of ether to be added is not particularly limited, but it is preferable to add two or more times by volume with respect to the aqueous solution containing the heteropolyacid salt. If the amount of ether to be added is small, the heteropolyacid does not completely form the ether adduct, which causes the yield of the target product to decrease. The ether can be used without particular limitation as long as it does not hinder the workability. For example, diethyl ether or the like can be used.

  The step of adding hydrochloric acid or sulfuric acid to the aqueous solution containing the heteropolyacid salt of the general formula (3) to make it acidic with hydrochloric acid or sulfuric acid and the step of adding ether may be mixed in steps.

  At the stage where the ether adduct is formed, it is separated into three phases of an ether phase, an aqueous phase and an ether adduct-containing phase in a separatory funnel. The ether adduct-containing phase is the lowermost phase, which is separated and dried under vacuum to remove water and the added ether, whereby the heteropolyacid of the general formula (1) can be produced.

The heteropolyacid salt represented by the general formula (3) can be produced according to the following documents (A), (B), and (C).
(A) R.A. G. Finke, B.M. Rapko, R.A. J. et al. Saxton, P.M. J. et al. Domaille, “J. Am. Chem. Soc.”, USA, 1986, 108, p. 2947
(B) M.M. Abbessi, R.A. Contant, R.A. Thouvennot, G.M. Herve, “Inorg. Chem.”, USA, 1991, No. 30, p. 1595
(C) S.M. P. Harmalker, M.M. A. Leparulo, M.M. T. T. et al. Pope, “J. Am. Chem. Soc.”, USA, 1983, No. 105, p. 4286

Moreover, the heteropolyacid of this invention consists of General formula (2).
_{H g [P 1 W e V} f V O 40] · xH 2 O ··· (2)
[Wherein e is an integer from 9 to 11, and f is an integer from 1 to 3. E + f is 12. g is an integer represented by 3 + f. x is an integer of 1 to 100. V ^V represents a pentavalent vanadium atom. ]

Specific examples of the heteropolyacid represented by the general formula (2) include H ₆ [P ₁ W ₉ V ₃ ^V O ₄₀ ] · xH ₂ O, H ₅ [P ₁ W ₁₀ V ₂ ^V O ₄₀ ] · xH. ₂ O, H ₄ [P ₁ W ₁₁ V ₁ ^V O ₄₀ ] · xH ₂ O. In any case, x is an integer of 1 to 100, and V ^V represents a pentavalent vanadium atom.

  Such a heteropolyacid of the general formula (2) can be produced from a heteropolyacid salt of the general formula (4) which is a precursor.

_{K g [P 1 W e V} f V O 40] · xH 2 O ··· (4)
[Wherein e is an integer from 9 to 11, and f is an integer from 1 to 3. E + f is 12. g is an integer represented by 3 + f. x is an integer of 1 to 100. V ^V represents a pentavalent vanadium atom. ]

Specifically, the heteropolyacid salt represented by the general formula (4) includes K ₆ [P ₁ W ₉ V ₃ ^V O ₄₀ ] · xH ₂ O, K ₅ [P ₁ W ₁₀ V ₂ ^V O ₄₀ ] · _{xH 2 O, K 4 [P} 1 W 11 V 1 V O 40] · xH 2 O and the like. In any case, x is an integer of 1 to 100, and V ^V represents a pentavalent vanadium atom.

To produce the heteropolyacid represented by the general formula (2), first, hydrochloric acid or sulfuric acid is added to an aqueous solution containing the heteropolyacid salt of the general formula (4) in a container such as a beaker, and the aqueous solution is acidified with hydrochloric acid or sulfuric acid Let it be acidic. The amount of hydrochloric acid or sulfuric acid to be added is not particularly limited, but it is preferable to add such an amount that the H ⁺ concentration in the aqueous solution is 4 mol / L or more. When the concentration of hydrochloric acid or sulfuric acid is lower than this concentration, the heteropolyacid does not completely produce the ether adduct described later, causing a decrease in the yield of the target product.

  Next, ether is added in a separatory funnel to form an ether adduct of the heteropolyacid of general formula (2). The amount of ether to be added is not particularly limited, but it is preferable to add two or more times by volume with respect to the aqueous solution containing the heteropolyacid salt. If the amount of ether to be added is small, the heteropolyacid does not completely form the ether adduct, which causes the yield of the target product to decrease. The ether can be used without particular limitation as long as it does not hinder the workability. For example, diethyl ether or the like can be used.

  The step of adding hydrochloric acid or sulfuric acid to the aqueous solution containing the heteropolyacid salt of the general formula (4) to make it acidic with hydrochloric acid or sulfuric acid and the step of adding ether may be mixed in steps.

  At the stage where the ether adduct is formed, it is separated into three phases of an ether phase, an aqueous phase and an ether adduct-containing phase in a separatory funnel. The ether adduct-containing phase is the lowermost phase, which is separated and dried under vacuum to remove water and the added ether, whereby the heteropolyacid of the general formula (2) can be produced.

The heteropolyacid salt represented by the general formula (4) can be produced according to the following document (D).
(D) P.I. J. et al. Domaille, “J. Am. Chem. Soc.”, USA, 1986, 106, p. 7777

  The greatest feature of the method for producing the heteropolyacids of the above general formulas (1) and (2) is that a specific precursor is used, so that unlike a conventional ether extraction method, a free acid type heteropolyacid is used. This is the point where molecular design of acid is possible. In addition, in the conventional method, many impurities are mixed, but in the method of the present invention, a single species can be easily obtained.

  The acid catalyst of the present invention is characterized by comprising the heteropolyacids of the above general formulas (1) and (2).

The acid catalyst of the present invention has a composition in which the heteropolyacid has a large amount of H ⁺ per molecule, and a part of the basic skeleton is substituted with a vanadium atom having a low oxidation number, thereby enhancing the catalytic activity of the anion moiety. Therefore, the synergistic effect with H ⁺ can show a much higher catalytic activity than conventionally known heteropolyacids. Furthermore, the stability of the catalyst is also improved, and after the separation and recovery, the catalytic reaction can be performed again, and the thermal stability is excellent, and the catalyst can exist stably up to 600 ° C.

  Examples of the catalytic reaction using the acid catalyst of the present invention include esterification reaction, alkylation reaction, acylation reaction of various compounds, alkene hydration reaction, alkene oxidation reaction, and the like.

  The acid catalyst of the present invention can be recovered by filtration, centrifugation or the like after the reaction.

[Example 1]
First, according to the above-mentioned document (A), a heteropolyacid salt represented by the general formula (5) was produced.

K ₉ [P ₂ W ₁₅ V ₃ ^V O ₆₂ ] · 24H ₂ O (5)

  Next, 3.0 g of the obtained heteropolyacid salt of the general formula (5) was dissolved in 60 mL of hot water. The aqueous solution was allowed to cool to room temperature and stirred in an ice bath for 15 minutes. To the aqueous solution was added 20 mL of 95% sulfuric acid to make the aqueous solution acidic with sulfuric acid, followed by stirring for 10 minutes.

  The aqueous solution was then transferred to a separatory funnel and 300 mL of diethyl ether was added and stirred vigorously. After standing for 30 minutes, the liquid separated into three phases. The bottom phase was taken out and dissolved in 10 mL of pure water. Subsequently, after making it dry with a rotary evaporator, 1.22g of compound 1 was obtained by making it vacuum-dry.

  About the obtained compound 1, IR and NMR measurement were performed. The results are shown below.

<IR (KBr)>
1227m, 1088s, 1061W, 1019W, 953vs, 920m, 817vs, 742s, 598W, 528m cm ^-1

^<31 P NMR>
(26.0 ° C, D ₂ O): δ-6.97, -13.7 ppm

< ⁵¹ V NMR>
(24.3 ° C., D ₂ O): δ-581.9 ppm

< ¹⁸³ W NMR>
(22.7 ° C., D ₂ O): δ-142.0 (3W), −171.0 (6W), −196.4 (6W) ppm

From the above IR and NMR measurement results, Compound 1 is a heteropolyacid, H ₉ [P ₂ W ₁₅ V ₃ ^V O ₆₂ ] · xH ₂ O, and obtained as a single species that maintains this polyacid structure. You can see that Subsequently, when the mass change to 500 degreeC was measured for the compound 1 by TG / DTA, 13.0% reduction | decrease was recognized with respect to the whole mass, and it turned out that x of the compound 1 is 33. From the above results, in Example 1, heteropolyacid H ₉ [P ₂ W ₁₅ V ₃ ^V O ₆₂ ] · 33H ₂ O was obtained, and a single species maintaining this polyacid structure was obtained. It was confirmed that In addition, the yield of the heteropolyacid of Example 1 was 52.0%.

[Comparative Example 1]
As the heteropolyacid of Comparative Example 1, H ₃ [PW ₁₂ O ₄₀ ] · 12H ₂ O was prepared.

  The heteropolyacids of Example 1 and Comparative Example 1 were used as acid catalysts for cyclohexene hydration as described below, and the catalytic activity was evaluated. The results are shown in Table 1. The numerical value in the table is TON. TON is an index indicating catalytic activity, and is calculated by TON = reaction product (mol) / catalyst amount (mol). The higher the TON, the higher the activity as a catalyst.

<Evaluation of catalytic activity>
In the Schlenk tube, 29.6 mmol of the reaction substrate cyclohexene was weighed, and 10.2 μmol of the heteropolyacid selected from Example 1 and Comparative Example 1 was added thereto. The reaction vessel was adjusted to 60 ° C., the inside of the Schlenk tube was replaced with Ar gas, and the reaction was followed, and TON after 3 hours and 24 hours was evaluated. The reaction product was confirmed by gas chromatography. The reaction product was only cyclohexanol.

  As is apparent from the results in Table 1, it can be seen that cyclohexanol was produced in Example 1, whereas almost no formation was produced in Comparative Example 1.

  Further, the heteropolyacid of Example 1 could be recovered by filtration and could be reused as a catalyst.

  From the above results, it was found that the heteropolyacid of Example 1 is useful as an acid catalyst. Moreover, according to the manufacturing method of the heteropolyacid of Example 1, the heteropolyacid excellent in catalyst activity was able to be manufactured efficiently.

[Example 2]
First, according to the said literature (D), the heteropolyacid salt shown by General formula (6) was manufactured.

K ₆ [P ₁ W ₉ V ₃ ^V O ₄₀ ] · 6H ₂ O (6)

  Next, 9.0 g of the obtained heteropolyacid salt of the general formula (6) was dissolved in 60 mL of a hydrochloric acid aqueous solution having a pH of 2.2. To the solution, 60 mL of 12M hydrochloric acid was added and stirred for 10 minutes.

  The aqueous solution was then transferred to a separatory funnel and 600 mL of diethyl ether was added and stirred vigorously. After standing for 30 minutes, the liquid separated into three phases. The bottom phase was taken out and dissolved in 10 mL of pure water. Subsequently, after making it dry with a rotary evaporator, 1.75g of compound 2 was obtained by making it vacuum-dry.

  About the obtained compound 2, IR and NMR measurement were performed. The results are shown below.

<IR (KBr)>
1086 s, 1054 m, 966 s, 889 m, 796 s, 597 w, 522 w cm ⁻¹

^<31 P NMR>
(23.2 ° C., D ₂ O): δ-13.9 ppm

< ⁵¹ V NMR>
(23.1 ° C., D ₂ O): δ-571.7 ppm

From the above IR and NMR measurement results, Compound 2 is obtained as a heteropolyacid, H ₆ [P ₁ W ₉ V ₃ ^V O ₄₀ ] · xH ₂ O, and as a single species that maintains this polyacid structure. You can see that Subsequently, when the mass change to 500 degreeC was measured for the compound 2 by TG / DTA, the reduction | decrease of 4.17% was recognized with respect to the whole mass, and it turned out that x of the compound 2 is 6. From the above results, in Example 2, the heteropolyacid H ₆ [P ₁ W ₉ V ₃ ^V O ₄₀ ] · 6H ₂ O was obtained, and a single species maintaining this polyacid structure was obtained. It was confirmed that The yield of heteropolyacid in Example 2 was 21.3%.

  The heteropolyacid of Example 2 obtained in this way had catalytic activity. Moreover, according to the method for producing a heteropolyacid of Example 2, a heteropolyacid having catalytic activity could be produced efficiently.

  Further, the heteropolyacid of Example 2 could be recovered by filtration and could be reused as a catalyst.

Claims (5)

A heteropolyacid represented by the general formula (1).
_{H d [P 2 W a V} b V V c IV O 62] · xH 2 O ··· (1)
[Wherein, a is an integer of 15 to 17, and b and c are integers of 0 to 3. Further, a + b + c is 18, and b + c is an integer of 1 to 3. d is an integer represented by 6 + b + 2c. x is an integer of 1 to 100. V ^V represents a pentavalent vanadium atom, and V ^IV represents a tetravalent vanadium atom. ] A heteropolyacid represented by the general formula (2).
_{H g [P 1 W e V} f V O 40] · xH 2 O ··· (2)
[Wherein e is an integer from 9 to 11, and f is an integer from 1 to 3. E + f is 12. g is an integer represented by 3 + f. x is an integer of 1 to 100. V ^V represents a pentavalent vanadium atom. ]   An acid catalyst comprising the heteropolyacid according to claim 1 or 2. The method for producing a heteropolyacid according to claim 1, wherein the ether adduct of the heteropolyacid according to claim 1 is produced by a treatment including the following steps (A) and (B), and then the ether is removed from the ether adduct. .
(A) Step of making aqueous solution of heteropolyacid salt represented by general formula (3) acidic with hydrochloric acid or sulfuric acid (B) Step of adding ether to aqueous solution of heteropolyacid salt represented by general formula (3) K _d [P ^{_{2 W a V b V V c}} IV O 62] · xH 2 O ··· (3)
[Wherein, a is an integer of 15 to 17, and b and c are integers of 0 to 3. Further, a + b + c is 18, and b + c is an integer of 1 to 3. d is an integer represented by 6 + b + 2c. x is an integer of 1 to 100. V ^V represents a pentavalent vanadium atom, and V ^IV represents a tetravalent vanadium atom. ] The method for producing a heteropolyacid according to claim 2, wherein the ether adduct of the heteropolyacid according to claim 2 is produced by a treatment including the following steps (C) and (D), and then the ether is removed from the ether adduct. .
(C) Step of making aqueous solution of heteropolyacid salt represented by general formula (4) acidic with hydrochloric acid or sulfuric acid (D) Step of adding ether to aqueous solution of heteropolyacid salt represented by general formula (4) K _g [P ^{_{1 W e V f V O 40}} ] · xH 2 O ··· (4)
[Wherein e is an integer from 9 to 11, and f is an integer from 1 to 3. E + f is 12. g is an integer represented by 3 + f. x is an integer of 1 to 100. V ^V represents a pentavalent vanadium atom. ]