JPH0639453B2 - Method for producing 3,3 ', 4,4'-biphenyltetracarboxylic acid tetraester - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing 3,3 ′, 4,4′-buphenyltetracarboxylic acid tetraester.

BACKGROUND OF THE INVENTION It is known that biphenyltetracarboxylic acid tetraesters are obtained by dimerizing o-phthalic acid diesters. For example, JP-A-60-51150 and JP-A-60-51150.
No. 51151 discloses that, in the presence of a catalyst containing a divalent palladium salt, a gas containing molecular oxygen is supplied to a reaction system under conditions where a solvent is substantially absent.
Biphenyl which selectively undergoes oxidative coupling reaction of o-phthalic acid diester under the temperature condition of ℃ to obtain 3,3 ′, 4,4′-biphenyltetracarboxylic acid tetraester (hereinafter abbreviated as s-BPTT) A method for producing a tetracarboxylic acid tetraester is described.

According to the above method, s-BP can be selectively used as a dimer.
In addition to TT, 2,3,3 ′, 4′-biphenyltetracarboxylic acid tetraester (hereinafter abbreviated as a-BPTT), biphenyltricarboxylic acid triester,
High-boiling compounds are produced as by-products. Of these, s-BP
TT is important as one of the raw materials for the monomers of the aromatic polyimide, and it is desirable to generate it in the highest possible purity. In particular, according to the research conducted by the present inventor, the by-produced biphenyltricarboxylic acid triester is 3,3 ′, 4,
If it is mixed with 4'-biphenyltetracarboxylic acid tetraester, it will be a hindrance to the production of polyimide by the subsequent copolymerization reaction, and it will be difficult to obtain a high molecular weight polyimide.

Therefore, in the above-mentioned dimerization reaction, a method for suppressing the formation of by-products such as biphenyl tricarboxylic acid triester is desired.

OBJECT OF THE INVENTION It is an object of the present invention to provide an improved process for producing highly pure 3,3 ', 4,4'-biphenyltetracarboxylic acid tetraester.

SUMMARY OF THE INVENTION In the present invention, an o-phthalic acid diester is supplied to a reaction system in the presence of a catalyst containing a divalent palladium salt and a gas containing molecular oxygen in a substantially solvent-free condition. While 1
When the dimerization of the o-phthalic acid diester is carried out by heating at 40 to 260 ° C., a low boiling point compound which is a by-product during the progress of the reaction is mixed with a part of the o-phthalic acid diester and a gas per 1000 reaction liquid,
3,3 ', 4,4'-biphenyltetracarboxylic acid characterized by continuously distilling out of the reaction system while feeding at 5 to 500 / hour, and replenishing the reaction system with o-phthalic acid diester. The present invention relates to a method for producing an acid tetraester.

DETAILED DESCRIPTION OF THE INVENTION The present invention is carried out in the absence of a solvent, in the presence of a catalyst containing a divalent palladium salt, while supplying a gas containing molecular oxygen to the reaction system. It can be advantageously applied to a diester dimerization reaction.

Examples of the o-phthalic acid diester that can be used in the dimerization reaction of the present invention include o-phthalic acid or its anhydride, or its halide and a compound having a hydroxyl group at the terminal (for example, lower aliphatic alcohol, aromatic alcohol, etc.). Any diester compound obtained by reacting with
For example, dimethyl o-phthalate, diethyl o-phthalate, dipropyl o-phthalate, dibutyl o-phthalate,
O-phthalic acid di-lower alkyl ester having 1 to 5 carbon atoms such as o-phthalic acid dipentyl can be preferably mentioned. The present invention can be applied particularly advantageously when using o-dimethyl phthalate.

Examples of the catalyst containing a divalent palladium salt that can be used in the dimerization reaction of the present invention include a catalyst containing a divalent palladium salt, a copper salt and a basic bidentate ligand.

The divalent palladium salt forming the catalyst is a palladium salt of an aliphatic carboxylic acid or an inorganic acid. Examples of the aliphatic carboxylic acid palladium salt include palladium formate, palladium acetate, palladium propionate, palladium butyrate, palladium valerate and the like, but palladium acetate is preferred. Examples of the inorganic acid palladium salt include palladium chloride, palladium sulfate, palladium sulfite, palladium nitrate, palladium nitrite, and palladium phosphate, with palladium nitrate being preferred.

Examples of the copper salt forming the catalyst include copper salts of organic acids or inorganic acids, or copper chelate salts of β-diketones. The copper salt of an organic acid has 1 to 5 carbon atoms.
The copper salts of aliphatic mono- or dicarboxylic acids, such as copper formate, copper acetate, copper propionate, copper butyrate, copper valerate, and copper oxalate can be mentioned, but copper acetate is preferable. Examples of the copper salt of an inorganic acid include copper sulfate, copper sulfite, copper nitrate, copper nitrite, and copper phosphate, but copper nitrate is preferable. Examples of the copper chelate salt of β-diketones include copper chelate salts such as acetylacetone, benzoylacetone and trifluoroacetone.

The basic bidentate ligand that constitutes the above catalyst is 2,
2'-biquinoline, bathocuproine, neocuproine,
Banphenanthroline, o-phenanthroline, 2,
Although 2'-bipyridine and the like can be mentioned, o-phenanthroline and 2,2'-bipyridine are preferable.

The present invention can be particularly preferably applied when a catalyst composed of palladium acetate or palladium nitrate, copper acetate and o-phenanthroline is used.

The above-mentioned dimerization reaction is carried out under atmospheric pressure while supplying a gas containing molecular oxygen to the reaction system in the absence of a solvent in the presence of the above catalyst,
It is carried out by heating the o-phthalic acid diester to 140 to 260 ° C. As the gas containing molecular oxygen supplied to the reaction system, pure oxygen gas may be used as it is, or in order to prevent the risk of explosion, etc., an oxygen-containing gas diluted with a substantially inert gas or Air may be used. At that time, the oxygen partial pressure in the reaction system is preferably in the range of 0.01 to 200 atm, particularly 0.05 to 50 atm.

The unreacted o-phthalic acid diester, dimerization product, low-boiling acid and low-boiling ester exist in the reaction system obtained by dimerization of o-phthalic acid diester under the above-mentioned conditions.

The dimerization product is produced by oxidative coupling of o-phthalic acid diester, and includes a-BPTT, biphenyl tricarboxylic acid triester, and high boiling point compounds, in addition to the main product, s-BPTT.

The low-boiling acid and low-boiling ester are considered to be by-produced from o-phthalic acid diester, and although the reaction mechanism is unknown, they tend to accelerate the production of biphenyltricarboxylic acid triester.

Examples of the low-boiling acid include benzoic acid, phthalic acid and phthalic anhydride, and examples of the low-boiling ester include benzoic acid ester, salicylic acid ester and o-toluic acid ester.

A gas containing the above-mentioned molecular oxygen, from a porous plate or a large number of nozzles provided at the bottom of the reaction tank used for the reaction,
By bubbling and feeding, a low-boiling acid and a low-boiling ester that promote the formation of the biphenyltricarboxylic acid triester are distilled along with the gas.

In order to efficiently distill the above low boiling point acid and low boiling point ester, the gas is added in an amount of 5 to 5 per 1000 reaction liquids.
It is supplied at 500 / hour, preferably 10 to 100 / hour.

The above-mentioned components distilled along with the gas are removed to the outside of the reaction system. The distillate component contains unreacted o-phthalic acid diester in addition to low-boiling acid and low-boiling ester. The o-phthalic acid diester can be subjected to a dimerization reaction again by washing the distillate with an alkali such as an aqueous solution of caustic caustic for purification. Of course, the replenishing o-phthalic acid diester may be entirely new.

When the distillate component is removed to the outside of the reaction system, the amount of o-phthalic acid diester corresponding to the distillate component is insufficient in the reaction system.
The supply is necessary. The replenishment of the o-phthalic acid diester to the reaction system may be carried out continuously or intermittently. However, it is desirable that the replenishment of the o-phthalic acid diester to the reaction system be carried out continuously so as to substantially compensate the amounts (volume) of the o-phthalic acid diester and the low boiling point compound distilled from the reaction system. . When such a replenishment method is used, the liquid level of the reaction liquid in the reaction tank is always kept substantially constant, which is preferable for the progress of the reaction.

[Effect of the Invention] By the method of the present invention, low-boiling acids and esters present in the reaction system can be effectively removed by distillation, so that by-products of biphenyltricarboxylic acid triesters are suppressed in the dimerization reaction. , S-BPTT yield can be improved.

Next, examples and comparative examples of the present invention will be shown.

[Example 1] o-Dimethyl phthalate 2100 (2500 kg), palladium acetate 1884 g, copper acetate-hydrate 501 g, o
-Phenanthroline (1512 g) was placed in a reaction vessel, and the reaction was carried out at 230 ° C for 10 hours while bubbling air from the lower portion of the reaction vessel at 100 Nm ³ / hr to produce tetramethyl biphenyltetracarboxylate. During the reaction, all the distillate was removed to the outside of the reaction vessel, and simultaneously, dimethyl o-phthalate was continuously supplied to the reaction vessel at 250 / hour (297 kg / hour).

Samples were taken from the reaction tank 6 hours, 8 hours, and 10 hours after the start of the reaction to examine the composition of the product. The results are shown in Table 1.

[Comparative Example 1] The same as Example 1 except that the distillate during the reaction was condensed and the condensed product was returned to the reaction tank without any particular separation operation, while the replenishment of o-dimethyl phthalate was not performed. In the same manner, tetramethyl biphenyl tetracarboxylate was produced.

Samples were taken from the reaction tank 6 hours, 8 hours, and 10 hours after the start of the reaction to examine the composition of the product. The results are shown in Table 1.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A 64-56649 (JP, A) JP-A 64-90154 (JP, A) JP-A 64-68342 (JP, A) JP-A 64-- 56646 (JP, A) Actually open 64-68341 (JP, U)

Claims (4)

[Claims] 1. An o-phthalic acid diester in the substantially absence of a solvent, 140 to 260 in the presence of a catalyst containing a divalent palladium salt while supplying a gas containing molecular oxygen to the reaction system. When the o-phthalic acid diester is dimerized by heating to 0 ° C., a low boiling point compound, which is a by-product during the progress of the reaction, together with a part of the o-phthalic acid diester, a gas is added to the reaction solution in an amount of 5 to 5 3,3 ', 4,4'-biphenyltetracarboxylic acid tetracarboxylic acid characterized by continuously distilling out of the reaction system while supplying at 500 / hour, and replenishing o-phthalic acid diester to the reaction system. Method for producing ester. 2. The method according to claim 1, wherein the o-phthalic acid diester is continuously supplied to the reaction system.
Process for producing 3 ', 4,4'-biphenyltetracarboxylic acid tetraester. 3. The replenishment of o-phthalic acid diester to the reaction system is carried out continuously so as to substantially replenish the amounts of o-phthalic acid diester and low boiling point compound distilled from the reaction system. 3,3 ', 4,4'-in the range 1
Method for producing biphenyl tetracarboxylic acid tetraester. 4. The o-phthalic acid diester supplied to the reaction system is an o-phthalic acid diester purified from a mixture of a low boiling point compound distilled out of the reaction system and the o-phthalic acid diester. 3, 3 ', 4, described in the range 1
Process for producing 4'-biphenyltetracarboxylic acid tetraester.