JPH072214B2 - Regeneration method of palladium nitrate chelate complex catalyst - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for regenerating a palladium nitrate chelate complex catalyst.

BACKGROUND OF THE INVENTION A chelate complex of a palladium salt formed from a palladium salt and a basic bidentate ligand such as 1,10-phenanthroline or 2,2′-bipyridine is oxidatively coupled to an o-phthalic acid diester. It has been proposed to use it as a catalyst in the production of biphenyltetracarboxylic acid tetraester (JP-A-60-51150 and JP-A-60-150150).
-51151).

It has already been known that a catalyst composed of a palladium salt, a basic bidentate ligand and a copper salt can be used when oxidatively coupling an o-phthalic acid diester to produce a biphenyltetracarboxylic acid tetraester. There is.

Since the above oxidative coupling reaction is carried out at a high temperature, when the above components are simply added as a mixture when the catalyst is added, the palladium salt decomposes and precipitates as metallic palladium with lost catalytic activity. There is. On the other hand, since the complex formed from the palladium salt and the basic bidentate ligand has excellent thermal stability, it can be advantageously used without depositing metallic palladium in the above oxidative coupling reaction. In the above-mentioned JP-A-60-51151, it is described that when an inorganic acid palladium salt, particularly palladium nitrate, is used as the palladium salt, a chelate complex of the palladium salt, which is more excellent in thermal stability, can be obtained. .

The method for producing a chelate complex of a palladium salt described in the above publication is a method of reacting palladium nitrate with an equimolar amount of a basic bidentate ligand. A palladium nitrate monochelate complex represented by L · Pd (NO ₃ ) ₂ ... [II] (wherein L represents a basic bidentate ligand) is obtained. However, when the basic bidentate ligand is used in excess with respect to palladium nitrate in the above method, the general formula [I]; L ₂ · Pd (NO ₃ ) ₂ ... [I] (where L is , Which represents a basic bidentate ligand).

According to the study of the present inventor, both of the above two kinds of complexes can be used as catalysts for the above oxidative coupling reaction, but the palladium nitrate bis chelate complex is derived from the palladium nitrate monochelate complex. Period (time required for the reaction rate to become sufficiently high after the start of the reaction)
Turned out to be long.

Produced by a known method for producing a biphenyltetracarboxylic acid tetraester by subjecting an o-phthalic acid diester to an oxidative coupling reaction in the presence of a catalyst composed of a chelate complex formed from palladium nitrate and a basic bidentate ligand. The target substance, biphenyltetracarboxylic acid tetraester, is extracted from the reaction solution, and palladium is also recovered as a palladium nitrate solution. Then, this palladium nitrate solution and 1,10-phenanthroline, 2,2 '
-A chelate reaction with a basic bidentate ligand such as bipyridine to convert it into a palladium nitrate chelate complex (regeneration),
It is generally practiced to use this again as a catalyst.

In the catalyst regeneration step, in the reaction between the palladium nitrate and the basic bidentate ligand, the basic bidentate ligand is used in an excessive amount in order to effectively utilize the recovered palladium nitrate. However, according to the study by the present inventor, when the basic bidentate ligand is excessively used as described above, the amount of the basic bidentate ligand remaining in the palladium nitrate recovered from the reaction solution is increased. It was also found that the amount of basic bidentate ligand was considerably excessive, and in that case, the obtained palladium nitrate chelate complex was a mixture of the monochelate complex and the bis chelate complex. When a mixture of such a monochelate complex and a bis-chelate complex is used as a regenerating catalyst, as is clear from the above-mentioned new finding of the present inventors, when a catalyst containing only a monochelate complex is used. Compared to, there is a drawback that the induction period becomes longer.

[Object of the Invention] The present invention is directed to oxidative coupling reaction of o-phthalic acid diester in the presence of a chelate complex formed from palladium nitrate and 1,10-phenanthroline or 2,2′-bipyridine to give biphenyltetracarboxylic acid. An object of the present invention is to provide a method for regenerating a palladium nitrate chelate complex catalyst having high catalytic ability, using a solution containing palladium nitrate recovered from a reaction solution in which an acid tetraester is produced.

SUMMARY OF THE INVENTION The present invention provides biphenyltetracarboxylic acid by oxidative coupling reaction of o-phthalic acid diester in the presence of a chelate complex formed from palladium nitrate and 1,10-phenanthroline or 2,2′-bipyridine. A solution containing palladium nitrate recovered from the reaction solution in which the acid tetraester was produced, and 1,10-phenanthroline or 2,2'-
A mixture of a palladium nitrate bis chelate complex obtained by a chelation reaction with bipyridine and a palladium nitrate monochelate complex, and 1 to 2 times the molar amount of palladium nitrate with respect to the palladium nitrate bis chelate complex contained in the mixture, in an aqueous solution. The method for regenerating a palladium nitrate chelate complex catalyst comprises obtaining a product consisting of a palladium nitrate monochelate complex.

In the present invention, the palladium nitrate bis chelate complex is a complex represented by the following formula.

L ₂ · Pd (NO ₃ ) ₂ (where L is 1,10-phenanthroline or 2,2 ′
-Means bipyridine. ) Further, the palladium nitrate monochelate complex is a complex represented by the following formula.

L · Pd (NO ₃ ) ₂ (L has the same meaning as above.) [Detailed Description of the Invention] The present invention was formed from palladium nitrate and 1,10-phenanthroline or 2,2′-bipyridine. When regenerating a palladium nitrate chelate complex catalyst using a solution containing palladium nitrate recovered from a reaction solution in which an o-phthalic acid diester is oxidatively coupled in the presence of a chelate complex to produce a biphenyltetracarboxylic acid tetraester In addition, it can be advantageously used for the purpose of obtaining a complex catalyst having a high catalytic ability such as shortening the induction period in the catalytic reaction. That is, the object of the regeneration treatment of the present invention is a chelation reaction between a solution containing palladium nitrate recovered from a reaction solution in which a biphenyltetracarboxylic acid tetraester is produced and 1,10-phenanthroline or 2,2′-bipyridine. It is a mixture of a palladium nitrate bis chelate complex and a palladium nitrate monochelate complex obtained by.

The mixture may contain copper together with a palladium component, and means a palladium salt, a basic bidentate ligand (in the present invention, 1,10-phenanthroline, 2,2′-bipyridine, or a mixture thereof). ) And a copper salt as a catalyst, oxidative coupling of o-phthalic acid diester to produce biphenyltetracarboxylic acid tetraester was carried out, and metallic palladium was recovered from a mixture of metallic palladium and metallic copper recovered from the reaction solution. A mixture of a mono-complex and a bis-complex formed by using a basic bidentate ligand in an equimolar amount with respect to metallic palladium upon regeneration as a catalyst for the oxidative coupling reaction can also be mentioned. Regarding the method of regenerating metallic palladium as a catalyst for the oxidative coupling reaction from the mixture of metallic palladium and metallic copper recovered from the reaction solution, detailed description is given in Example 4 of JP-A-60-102939. is there.

The method of the present invention comprises reacting a bis complex in the above mixture with equimolar or more (but not more than 2 times the molar amount) of palladium nitrate in an aqueous solution to form a monocomplex. Characterize.

The above palladium nitrate is preferably used as an aqueous solution. By using palladium nitrate as an aqueous solution, the aqueous solution can be conveniently used as a solvent for each of the above complexes. The above palladium nitrate aqueous solution may be prepared by dissolving palladium nitrate in water. However, since palladium nitrate has a deliquescent property, metallic palladium (also called palladium black) is dissolved in concentrated nitric acid and then diluted with water. It is preferably prepared by The metal palladium can be easily obtained by reducing palladium tide such as palladium chloride, palladium sulfate, and palladium acetate. The concentration of concentrated nitric acid is preferably 50% or more,
More preferably, it is 60% or more. The amount used is sufficient to dissolve metallic palladium and the solution shows acidity, and usually it is in the range of 150 to 1000 ml per mol of metallic palladium. When the dissolution of metallic palladium is insufficient, the metallic palladium may be reduced and activated. For the activation method of the above-mentioned metallic palladium, see Japanese Patent Publication No. 53-20.
A detailed description is given in Japanese Patent No. 009. The above palladium metal is dissolved in concentrated nitric acid, and water is added to dilute it to prepare an aqueous palladium nitrate solution. The amount of dilution water is not particularly limited, but 100 to 1000 ml is sufficient for 10 g of metallic palladium.

A mixture containing a bis complex is added to the palladium nitrate aqueous solution. The amount of palladium nitrate used needs to be equimolar or more to the bis complex, and is preferably in the range of 1 to 2 times, particularly 1 to 1.2 times the molar amount.
Palladium nitrate may be used in excess, but it is disadvantageous because the amount of dissolved palladium tends to increase.
Further, when the amount of palladium nitrate used is less than the equimolar amount with respect to the bis complex, the product is a mixture of the mono complex and the bis complex, which is not preferable.

Then, the above aqueous solution is heated at 20 to 250 ° C, preferably 20 to 100 ° C.
Heat to the range of 10 and react for 10 minutes to 10 hours. After completion of the reaction, the reaction solution is acidified with nitric acid to completely precipitate the monocomplex, and then the complex is filtered and separated and recovered.

Palladium is dissolved in the filtrate after filtering the complex. This palladium can be recovered by the method described in Japanese Patent Application No. 62-316433.

It was recovered from the reaction liquid in which the biphenyltetracarboxylic acid tetraester was produced by oxidatively coupling the o-phthalic acid diester using the above-mentioned catalyst composed of the palladium salt, the basic bidentate ligand and the copper salt. When the monocomplex is regenerated from the mixture of metallic palladium and metallic copper, in addition to the palladium nitrate-basic bidentate ligand complex, a copper nitrate-basic bidentate ligand complex is further formed, and the product is obtained. May be a mixture of these various complexes. Also for the copper nitrate-basic bidentate ligand complex, in the same manner as the method for converting the palladium bis chelate complex into the palladium monochelate complex, the basic bidentate ligand coordinated to the copper complex is used. The palladium monochelate complex can be converted by reacting palladium nitrate in an equimolar amount or more with respect to the amount of the palladium monochelate complex formed.

[Effect of the Invention] By the method of the present invention, an o-phthalic acid diester is subjected to an oxidative coupling reaction in the presence of a chelate complex formed from palladium nitrate 1,10-phenanthroline or 2,2'-bipyridine to effect biphenyl tetra- A solution containing palladium nitrate recovered from the reaction solution which produced a carboxylic acid tetraester, and 1,10-phenanthroline or 2,
A mixture of a palladium nitrate bis chelate complex and a palladium nitrate monochelate complex obtained by a chelation reaction with 2′-bipyridine, by an industrially easy operation,
It can be converted into a palladium nitrate monochelate complex to obtain only a monocomplex containing substantially no bis complex.

Next, examples of the present invention will be described.

Example 1 2 g of a mixture of palladium and copper recovered from a dimerization reaction solution of o-phthalic acid ester was dissolved in 5 ml of concentrated nitric acid,
Dilution with water gave a total of 104 g of aqueous solution. It was confirmed by atomic absorption spectrometry that the aqueous solution contained 1.64% by weight of palladium and 0.29% by weight of copper.
13 g of this aqueous solution contain 2 mmol of palladium nitrate and 0.6 mmol of copper nitrate.

To 13 g of the above aqueous solution, 0.510 of 1,10-phenanthroline-hydrate was added.
g (2.6 mmol) was added and heated at 80 ° C. for 30 minutes.
The reaction solution was allowed to cool, then 10 mL of 0.5N nitric acid was added, and the precipitated solid
0.905 g was collected by filtration. The results of elemental analysis of the solid are shown for the elemental composition of mono (1,10-phenanthroline) dinitratopalladium (abbreviated as monocomplex) and bis (1,10-phenanthroline) dinitratopalladium (abbreviated as biscomplex). Shown together with calculated values.

CHN experimental value 37.72 2.16 14.49 calculated value for mono-complex 35.10 1.96 13.65 calculated value for bis-complex 48.79 2.73 14.22 (mono-complex: C ₁₂ H ₈ N ₄ O ₆ Pd = 410.62) (bis-complex: C ₂₄ H ₁₆ N ₆ O ₆ Pd = 590.83) From the elemental analysis and IR spectrum, it was found that the above solid was a mixture of a monocomplex and a biscomplex (monocomplex: biscomplex = 76: 24, molar ratio).

5 ml of an aqueous solution containing 0.069 g (0.3 mmol) of palladium nitrate
0.5 g of the yellow solid obtained above was added to, and the mixture was refluxed for 1 hour. After allowing the reaction solution to cool, 0.5 ml of 6N-nitric acid was added to obtain 0.510 g of a yellow solid. The IR spectrum of this solid was consistent with the authentic mono (1,10-phenanthroline) dinitratopalladium. Next, the result of elemental analysis of this solid is shown.

CHN experimental value 35.33 1.90 13.69 calculated value 35.10 1.96 13.65 (C ₁₂ H ₈ N ₄ O ₆ Pd = 410.62) [Reference Example 1] 5 ml of an aqueous solution containing 0.046 g (0.2 mmol) of paradium nitrate.
To this, 0.118 g (0.2 mmol) of bis (1,10-phenanthroline) dinitratopalladium was added, and the mixture was refluxed for 1 hour. After allowing the reaction solution to cool, 0.5 ml of 6N-nitric acid was added to obtain 0.154 g of a yellow solid. The IR spectrum of this solid was consistent with the authentic mono (1,10-phenanthroline) dinitratopalladium. The yield was 94%. Next, the result of elemental analysis of this solid is shown.

CHN experimental value 35.55 1.94 13.92 calculated value 35.10 1.96 13.65 (C ₁₂ H ₈ N ₄ O ₆ Pd = 410.62) The bis (1,10-phenanthroline) dinitratopalladium used above was synthesized as follows. did.

Mono (1,10-phenanthroline) dinitratopalladium
2.053 g (5 mmol) and 1,10-phenanthroline-hydrate
1.031 g (5.2 mmol) was dissolved in 50 ml acetic acid and the solution was refluxed for 1 hour. After cooling, the precipitate was filtered, washed with chloroform, dried, and bis (1,10-phenanthroline).
2.750 g of dinitratopalladium was obtained (yield 93%). Recrystallization from water gave yellow plate crystals. Next, the results of elemental analysis of the yellow plate crystals are shown.

CHN experimental value 48.96 2.73 14.49 calculated value 48.79 2.73 14.22 (C ₂₄ H ₁₆ N ₆ O ₆ Pd = 590.83) [Reference Example 2] 10 ml of an aqueous solution containing 0.115 g (0.5 mmol) of paradimium nitrate.
And bis (2,2'-bipyridine) dinitratopalladium
0.271 g (0.5 mmol) was added and the mixture was refluxed for 30 minutes. After allowing the reaction solution to cool, 0.5 ml of 6N-nitric acid was added to give a yellow solid 0.3.
67g was obtained. The IR spectrum of this solid was consistent with the authentic mono (2,2'-bipyridine) dinitratopalladium. The yield was 95%. Next, the results of elemental analysis are shown.

C H N were used in the experimental value 31.20 2.07 14.53 Calculated _{31.07 2.08 14.49 (C 10 H 8} N 4 O 6 Pd = 386.60) above, bis (2,2'-bipyridine) dinitrate tiger DOO palladium, as follows Synthesized.

Mono (2,2'-bipyridine) dinitratopalladium 0.773
g (2 mmol) and 0.328 g (2.1 mmol) of 2,2'-bipyridine were dissolved in 20 ml of methanol, and the solution was refluxed for 30 minutes. After allowing to cool, the precipitate is filtered and washed with chloroform,
After drying, 0.964 g of bis (2,2′-bipyridine) dinitratopalladium was obtained (yield 89%). Next, the results of elemental analysis are shown.

C H N Found 44.73 2.94 15.80 Calculated _{44.26 2.97 15.48 (C 20 H 16} N 6 O 6 Pd = 542.79) [ Reference Example 3] palladium complex 0.4 mmol and copper acetate - a monohydrate 0.12 mmol using the catalyst, o -Dimethyl phthalate (hereinafter,
Abbreviated as DMP) 119 g 300 ml of air in a 300 ml flask
The mixture was aerated for minutes and the oxidative coupling reaction was carried out at 220 ° C. with stirring at 500 rpm.

In the attached drawings, there are two types of DMP in the case of using mono (1,10-phenanthroline) dinitratopalladium (circle) and bis (1,10-phenanthroline) dinitratopalladium (x) as the palladium complex. 3,3 ′ by quantification,
The time-dependent change curve of the yield of tetramethyl 4,4'-biphenyl tetracarboxylic acid is shown.

From the change in the slope of the curve when using each complex,
It is clear that the bis complex has a longer induction period than the mono complex.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the results of the oxidative coupling reaction of dimethyl o-phthalate using a palladium complex as a catalyst.
A time-dependent change curve of the yield of 3 ', 4,4'-biphenyltetracarboxylic acid tetramethyl is shown, in which a circle indicates a palladium complex with mono ((1,10-phenanthroline) dinitratopalladium, and a cross indicates Shows the case where bis (1,10-phenanthroline) dinitratopalladium was used.

Claims (2)

[Claims] 1. An oxidative coupling reaction of o-phthalic acid diester in the presence of a chelate complex formed from palladium nitrate and 1,10-phenanthroline or 2,2'-bipyridine to give biphenyltetracarboxylic acid tetraester. A solution containing palladium nitrate recovered from the produced reaction solution and 1,10-phenanthroline or 2,2 '
An aqueous solution of a mixture of a palladium nitrate bis chelate complex obtained by a chelation reaction with bipyridine and a palladium nitrate monochelate complex, and 1 to 2 moles of palladium nitrate with respect to the palladium nitrate bis chelate complex contained in the mixture. A method for regenerating a palladium nitrate chelate complex catalyst, which comprises reacting in a solution to obtain a product comprising a palladium nitrate monochelate complex. 2. A mixture of a palladium nitrate bis-chelate complex and a palladium nitrate mono-chelate complex and a palladium nitrate bis-chelate complex contained in the mixture are 1 to 1.
The method for regenerating a palladium nitrate chelate complex catalyst according to claim 1, which comprises reacting with a 2-fold molar amount of palladium nitrate in an aqueous solution to obtain a product consisting of a palladium nitrate monochelate complex.