JP2001288149A - Method for separating and recovering diaryl carbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To separate and recover a diaryl carbonate by selective crystallization of the diaryl carbonate from a mixed solution (A) consisting essentially of the diaryl carbonate and an aromatic hydroxy compound. SOLUTION: A diaryl carbonate is selectively crystallized by adding solvent (B) capable of compatibilizing with the aromatic hydroxy compound and having 7.0-10.0 solubility parameter δS (the subscript S means a solvent) to the above mixed solution (A) to separate and recover the diaryl carbonate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for separating and recovering diaryl carbonate. More specifically, a specific solvent is added to a mixed solution of a diaryl carbonate and an aromatic hydroxy compound to perform a crystallization operation to selectively crystallize the diaryl carbonate, and to separate a high-purity diaryl carbonate from the mixed solution. Regarding the method of collecting. Further, the present invention relates to a method for separating and recovering diaryl carbonate when the mixed solution is a solution generated by a reaction for obtaining diaryl carbonate.

[0002]

2. Description of the Related Art Aromatic polycarbonates are widely used as engineering plastics having excellent heat resistance and transparency. As a method for producing the aromatic polycarbonate, an interfacial polymerization method in which an aromatic dihydroxy compound is reacted with phosgene and a melt transesterification method in which an aromatic dihydroxy compound and a diaryl carbonate are polymerized in a molten state are generally known. . But,
The former has a problem in using a large amount of a halogen-based solvent such as methylene chloride which is environmentally problematic. In this regard, the latter can solve this problem, but depending on the purity of the diaryl carbonate used, problems such as a decrease in polymerization activity and coloring of the aromatic polycarbonate occur. Therefore, various studies have been made on a method for separating and recovering high-purity diaryl carbonate from a reaction mixture solution.

[0003] Further, as a method for producing a diaryl carbonate, various methods are known, including a method of performing a carbonylation reaction of an aromatic hydroxy compound with carbon monoxide and molecular oxygen in the presence of a catalyst. In general, the carbonylation reaction requires a complex catalyst system,
Also, since the catalyst is expensive, furthermore, the catalyst remaining in the diaryl carbonate causes a decrease in purity,
Various studies have been made on the separation and recovery and recirculation.

JP-A-6-172270 teaches that a 1: 1 crystal adduct of diphenyl carbonate and phenol is produced from a reaction solution containing a catalyst by a suspension crystallization method and separated from the reaction solution. are doing. In this method, in order to obtain and separate a crystalline adduct in a high yield, the concentration of diphenyl carbonate contained in the reaction solution is limited to a narrow range of 50 to 70% by weight. Furthermore, this crystal adduct obtained by filtration contains a catalyst-containing residue, and in the subsequent purification (distillation, etc.) of the crystal adduct, the remaining catalyst component may have an adverse effect such as decomposition of diphenyl carbonate. is there. It has also been proposed to wash the crystalline adduct with a mixed solution of 9% water and 91% phenol prior to heating under reduced pressure to separate the phenol, which removes most of the crystalline adduct. Not only will it dissolve, but it will also increase the amount of water in the crystalline adduct, causing hydrolysis during distillation for the purpose of isolating diphenyl carbonate,
It may reduce the yield of diphenyl carbonate.

[0005] The content of diphenyl carbonate is 5
When a reaction solution having a concentration of less than 0% by weight is treated by the above-described method, a distillation operation or the like for the purpose of concentrating the reaction solution must be performed. However, when this operation is performed, in addition to the above-mentioned disadvantages, deactivation of the catalyst due to thermal load also occurs.

As another technique utilizing suspension crystallization, there is another technique disclosed in Japanese Patent Application Laid-Open No. Hei 10-45680. The method performs suspension crystallization by cooling the reaction mixture solution containing the diaryl carbonate and inoculating the inoculum at the beginning of the crystallization. The obtained crystal is composed of a diaryl carbonate and an aromatic hydroxy compound, separated from the catalyst-containing mother liquor, and then washed with a mixture of the diaryl carbonate and the aromatic hydroxy compound, or with the aromatic hydroxy compound alone. And the mother liquor containing the catalyst are recycled and reused in the next reaction. However, since a considerable amount of the aromatic hydroxy compound is mixed in the crystal obtained by this method, the subsequent purification (distillation, etc.) for isolating the diaryl carbonate is necessary to obtain a high-purity diaryl carbonate. Inevitable.

[0007] As described above, in the conventional method, it is inevitable that the quality of the product decreases due to the low separation efficiency of the diaryl carbonate from the reaction mixture solution, and the cost of the recovery apparatus increases.
Further, a large amount of separation energy was required.

[0008]

SUMMARY OF THE INVENTION Accordingly, the present invention relates to a method for separating and recovering a diaryl carbonate using a crystallization method, which avoids the incorporation of an aromatic hydroxy compound into a crystal and reduces the content of the diaryl carbonate in the crystal. It is an object to provide a method for improvement. Still another object of the present invention is to provide a method for producing a diaryl carbonate using a reaction for obtaining a diaryl carbonate in the presence of a catalyst, in which a catalyst system is recovered with a high space-time yield and recycled. .

[0009]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and have reached the following invention. In the following description, diphenyl carbonate (hereinafter, referred to as DPC) may be selected as the diaryl carbonate and phenol may be selected as the aromatic hydroxy compound, but the present invention is not limited to these.

The present inventors started by comparing the solubility of DPC and phenol using the solubility parameter derived from the concept of KLHoy's molar traction (J. Paint Technol., 42, 76) (1970). Was. Hoy calculates the molar traction constant G for several types of atoms and groups by vapor pressure measurement.
And the following formula (V)

[0011]

Δ = dΣG / M (V) (where δ is the solubility parameter, d is the density, G is the molar traction constant, and M is the molecular weight), and the solubility is determined from the molecular structural formula. It states that the value of the parameter can be estimated. See the original report for further details regarding the calculation of the value of δ.

When the solubility parameters of DPC and phenol are calculated by this method, the solubility parameter δdpc of DPC (subscript dpc means DPC) is 10.2
5. The solubility parameter δph of phenol (subscript ph means phenol) is 9.73. Note that the value at 20 ° C. is used as the value of d. The difference between these values is close to 0.52, which means that these two components are easily compatible. From these results, the inventors have found that it is difficult to isolate DPC from a mixed solution of these two components using a crystallization operation.

The inventors of the present invention have conducted intensive studies on isolating DPC using a crystallization operation. As a result, when a specific amount of a third component solvent having a specific solubility parameter was added to the mixed solution, the apparent amount of the third component solvent was reduced. Above, it was found that there was an effect of lowering the solubility parameter δph of phenol. More surprisingly, it has been found that the amount of phenol occluded or adsorbed in the DPC crystal, which has conventionally been a problem, is significantly reduced.

That is, the present invention relates to the following formula (I)

A diaryl carbonate represented by R—O—CO—O—R (I) wherein R is selected from substituted or unsubstituted C ₆ -C ₁₅ aryl; The following formula (II)

[0015]

Embedded image R—OH (II) (the definition of R in the formula is the same as that of the formula (I)) is compatible with the aromatic hydroxy compound in the mixed solution (A) of the aromatic hydroxy compound. The solubility parameter is 7.
A solvent (B) in the range of 0 to 10.0 is added, and the diaryl carbonate is selectively crystallized and separated and recovered.

In the formulas (I) and (II), the substituent which can be introduced into the aromatic ring of R is, for example, an alkyl group having 1 to 10 carbon atoms such as --CH ₃ or --C ₂ H ₅ , or halogen. Etc., and can be substituted once or twice. R in the formula
Is preferably substituted or unsubstituted phenyl. R is particularly preferably unsubstituted aryl, and phenyl, biphenylyl, naphthyl and anthryl are preferred.
R is particularly preferably phenyl.

In the formula, R is HO—C ₆ H ₄ —C (CH ₃ ) ₂
Structures such as —C ₆ H ₄ — may also be included. That is, ROH also includes aromatic dihydroxy compounds such as bisphenol A.

The aromatic hydroxy compound is at least one compound represented by the above ROH, and is particularly preferably an aromatic monohydroxy compound.

The solubility parameter and amount of the solvent (B) are determined by the following formula (III):

Δsah = δsWs / (Ws + Wah) + δahWah / (Ws + Wah) (III) (wherein W is weight, subscript s is the solvent, ah is an aromatic hydroxy compound, and sah is the solvent) And the aromatic hydroxy compound.) Has a solubility parameter δsah defined by the following formula (IV):

[0020]

Δdac−δsah ≧ 0.6 (IV) (where the subscript dac represents a diaryl carbonate, and sah represents a mixed solution of the solvent and the aromatic hydroxy compound). Stipulated.

Here, the formula (III) is a formula relating to the solubility parameter and the weight fraction of the aromatic hydroxy compound and the solvent (B), and the value of δsah calculated from this formula is It represents the value of the overall solubility parameter of the mixed solution of the solvent (B). Formula (IV) is a conditional formula for selectively crystallizing a diaryl carbonate.

The value on the left side of the formula (IV) means the solubility of the diaryl carbonate in the mixed solution of the solvent (B) and the aromatic hydroxy compound, and the larger the value is, the more the diaryl carbonate is isolated. Is effective.

Further, the addition of the solvent (B) apparently
This has the effect of lowering the melting point of the aromatic hydroxy compound, and can extend the crystallization operation temperature range. The solvent (B)
The melting point of itself is at least the melting point of the aromatic hydroxy compound, preferably 41 ° C. or less, more preferably 15 ° C.
It is recommended that:

As the solvent (B) satisfying the above conditions, for example, C ₅ -C ₈ cycloaliphatic hydrocarbon, aromatic hydrocarbon, preferably cyclohexane or toluene,
Or xylene, aliphatic ethers C ₃ -C _6, preferably diethyl ether, aliphatic ketones, preferably acetone or methyl ethyl ketone or alcohols of methyl isobutyl ketone, and C ₁ -C _3, preferably methyl alcohol, Or ethyl alcohol, or isopropyl alcohol. In the present invention, at least one kind is selected from such solvents.

The addition of the solvent (B) apparently shifts the eutectic point of the diaryl carbonate-aromatic hydroxy compound system to a lower temperature side and a lower diaryl carbonate-containing concentration side. Isolation of diaryl carbonate from a mixed solution having a diaryl carbonate-containing concentration is possible. Therefore, the recommended concentration range of the diaryl carbonate contained in the mixed solution (A) is 5 to 95% by weight, preferably 7 to 70% by weight.
%, More preferably 10 to 50% by weight.

The stirring during the crystallization operation is performed by using the mixed solution (A).
It is suitable for solving the above-mentioned problem relating to occlusion of impurities due to the concentration distribution of. However, according to the present invention, the addition of the solvent (B) improves the uniformity of the mixed solution (A), so that the crystallization operation does not need to be particularly performed under stirring.
The reaction may be carried out in a state where the mixed solution (A) to which the solvent (B) is added is allowed to stand.

Based on the above, the present invention can be carried out, for example, by the following formula (I)

## STR5 ## A diaryl carbonate represented by R--O--CO--OR (I) wherein R is selected from substituted or unsubstituted C ₆ -C ₁₅ aryl is obtained. In the process, the following formula (II)

[0028]

R-OH (II) (wherein R is the same as defined in the formula (I)) in the presence of carbon monoxide, molecular oxygen and a catalyst. It can be preferably applied to a method of selectively crystallizing diaryl carbonate from solution (C) produced by a reaction for obtaining diaryl carbonate by oxidative carbonylation to obtain a diaryl carbonate.

The residue (D) after separating and recovering the diaryl carbonate is a mixture of the solvent (B), the aromatic hydroxy compound, and the catalyst. The aromatic hydroxy compound and the catalyst in the residue (D) can be reused in a process for producing a diaryl carbonate. Therefore, the catalyst-containing solution (E) obtained by removing the solvent (B) from the residue (D) after the crystallization operation is recycled to the reaction tank for obtaining the diaryl carbonate.

The catalyst system used in the reaction for obtaining the diaryl carbonate includes a platinum group catalyst (ruthenium, rhodium, palladium, osmium, iridium, platinum, preferably ruthenium, palladium, platinum, more preferably palladium), a cocatalyst ( Manganese, cobalt, copper, cerium, preferably manganese, and lead;
At least one is selected from tin, preferably lead, and quaternary salts (tetrabutylammonium bromide, tetrabutylammonium chloride, tetraphenylphosphoryl chloride, preferably tetrabutylammonium bromide).

The platinum group catalyst is used in the form of a metal or a compound of a metal, for example, in the case of palladium, in the form of a palladium metal or a zero-valent or divalent palladium compound. Containing halogen salts such as palladium chloride and palladium bromide, salts of inorganic acids such as palladium nitrate, complex salts such as palladium acetylacetonate, oxides or hydroxides, or olefins such as carbon monoxide, amines, phosphines or halogens These metals or compounds can be used in the form of a complex compound. Further, these metals or compounds can be used in a suitable support, for example, activated carbon, silica gel, alumina, metal oxides such as titanium oxide and zirconium oxide, metal composite oxides such as perovskite, and silicon. It may be in a state of being carried on a carbide or the like such as a carbide. Pre majority with their support may be a state of being separated off.

The cocatalyst is at least one, preferably two or more, compounds selected from manganese, cobalt, copper, cerium, lead and tin compounds, each of which is an oxide,
Hydroxide, acetylacetonate salt, acetate salt, chloride,
Used in the form of bromide and the like. Preferred combinations of two or more metal compounds are, for example, manganese compounds and lead compounds, cobalt compounds and lead compounds, cerium compounds and lead compounds, cerium compounds, tin compounds and copper compounds, manganese compounds, cerium compounds, tin compounds and copper And the like.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description, DPC is again selected as a diaryl carbonate and phenol is selected as an aromatic hydroxy compound, but the present invention is not limited to these.

DPC is produced by a carbonylation reaction of phenol with carbon monoxide and molecular oxygen in the presence of the catalyst, and the resulting reaction mixture is introduced into a suitable crystallization apparatus. The obtained reaction mixture solution is 10 to 50
It is a mixed solution containing DPC by weight.

The crystallization apparatus used here is, for example, a stirrer crystallization apparatus as described in JP-A-10-45680, or a bundle tube as described in JP-A-10-59904. A crystallization device and the like are not limited to these.

The mixed solution obtained by adding the solvent to the introduced reaction mixed solution is 80 to 40 ° C., preferably 60 to 40 ° C.
From 30 to -30 ° C, preferably from 30 to 0 ° C.
When cooled to a temperature range of ° C., DPC is selectively crystallized by the effect of the added solvent, and surprisingly high purity DPC crystals are obtained.

Thus, at the end of the crystallization operation, the phenol, the catalyst, and the solvent are present as residues in addition to the DPC crystals. The slurry-like mixed solution is separated into the DPC crystals and the residue using a centrifugal separator or the like.

The phenol and the catalyst are recycled to the DPC formation reaction. In recycling, the solvent needs to be removed from the residue, and for the removal, an operation such as simple distillation is applied.

[0039]

The present invention will be described in detail with reference to the following examples.
The present invention is not limited to these.

[Example 1] The crystallization apparatus used was a cylindrical vertical glass vessel (empty volume 50 cc) and had no stirring apparatus. After introducing 10.0 g of DPC powder and 10.0 g of phenol powder into this container, the container was immersed in an oil bath and heated to 50 ° C. to melt both powders. Acetone (δs = 7.59, melting point:
(−94.7 ° C.) 4.0 g, and the mixture was gradually cooled from 45 ° C. to 20 ° C. When the crystallization was completed, the crystal and the residue were extracted from the extraction port at the bottom of the vessel, and the crystal was separated by a membrane filter. As a result of quantitative analysis of DPC contained in the thus obtained crystal using gas chromatography, the DPC concentration of the obtained crystal was 97.2% by weight.

Example 2 As in Example 1, a crystallization apparatus using a cylindrical vertical glass container (empty volume: 50 cc) and having a horseshoe-type stirring apparatus was used. D in this container
10.0 g of PC powder and 10.0 g of phenol powder
After this, the container is immersed in an oil bath and
To melt both powders. 4.0 g of acetone (δs = 7.59, melting point: -94.7 ° C) was added to the melt, and the mixture was gradually cooled from 45 ° C to 20 ° C while stirring at 10 rpm. When the crystallization was completed, the crystal and the residue were extracted from the extraction port at the bottom of the vessel, and the crystal was separated by a membrane filter. Using gas chromatography, the DPC contained in the crystal thus obtained
As a result of quantitative analysis, the DPC concentration of the obtained crystal was 96.5% by weight.

Example 3 DPC 6.0 g, phenol 1
Except having set it to 4.0 g, it carried out similarly to Example 1. The DPC concentration of the obtained crystal was 96.5% by weight.

Example 4 The container described in Example 1 was added with D
After introducing 10.0 g of PC powder, 10.0 g of phenol powder and 0.2 g of tetrabutylammonium bromide, this container was immersed in an oil bath and heated to 50 ° C. to melt all the powders. 8.0 g of ethyl alcohol (δs = 8.65, melting point-114.5 ° C.) was added to this melt.
Was added, and the mixture was gradually cooled from 45 ° C to 20 ° C. When the crystallization was completed, the crystal and the residue were extracted from the extraction port at the bottom of the vessel, and the crystal was separated by a membrane filter. The DPC concentration of the obtained crystal was measured in the same manner as in Example 1. The amount of tetrabutylammonium bromide contained in the residue was quantified by adding silver nitrate to precipitate silver bromide and weighing the precipitate. The DPC concentration of the obtained crystal was 98.1%, and the amount of tetrabutylammonium bromide contained in the residue was 99.2% of the amount contained in the mixed solution before crystallization.

Example 5 8.0 g of DPC, phenol 1
The procedure was performed in the same manner as in Example 4 except that the amount was 2.0 g. The DPC concentration of the obtained crystal was 97.6% by weight, and the amount of tetrabutylammonium bromide contained in the residue was 98.3% of the amount contained in the mixed solution before crystallization.

Example 6 0.2 g of palladium acetylacetonate, 250.0 g of phenol, 0.5 g of lead oxide were placed in a stainless steel autoclave (empty volume: 500 cc).
g, manganese acetylacetonate 0.35 g, and tetrabutylammonium bromide 5.0 g. Keeping the vessel 80 ° C., nitrogen was replaced in the order of carbon monoxide, a further vessel with carbon monoxide 8.0 Kg / cm ²
Pressurized. Thereafter, carbon monoxide 2.5 L / min,
The reaction was started by flowing oxygen simultaneously at a flow rate of 0.125 L / min. As a result of continuing the reaction for 3 hours, 17.9% of DPC was formed on a phenol basis. 20 g of the reaction mixture thus obtained was collected and introduced into a cylindrical vertical glass container (empty volume: 50 cc) without a stirrer, and further 10 g of methyl alcohol (δs = 9.23, melting point:
(−97.49 ° C.) and gradually cooled from 45 ° C. to 20 ° C. When the crystallization was completed, the crystal and the residue were extracted from the extraction port at the bottom of the vessel, and the crystal was separated by a membrane filter. The measurement of the DPC concentration of the obtained crystal and the measurement of the amount of tetrabutylammonium bromide contained in the residue were performed in the same manner as in Example 4. The DPC concentration of the obtained crystal was 98.0%, and the amount of tetrabutylammonium bromide contained in the residue was 98.8% of the amount contained in the mixed solution before crystallization.

[0046]

According to the present invention, there is provided a method for separating and recovering a diaryl carbonate using a crystallization method, in which an aromatic hydroxy compound is prevented from being mixed into a crystal, and the content of the diaryl carbonate in the crystal is improved. Can be. Further, in a method for producing a diaryl carbonate using a reaction for obtaining a diaryl carbonate in the presence of a catalyst, it is possible to recover the catalyst system with high space-time yield and reuse it in circulation. That is, according to the present invention,
Energy and equipment costs required for separating the diaryl carbonate and the catalyst can be greatly reduced.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Go Muraoka 2-1 Hinode-cho, Iwakuni-shi, Yamaguchi Prefecture Teijin Limited Iwakuni Research Center (72) Inventor Eiyoshi Zenzato 2-1 Hinode-cho, Iwakuni-shi, Yamaguchi Prefecture Teijin Iwakuni Research Center F term (reference) 4H006 AA02 AD15 BB11 BB14 BB15 BB16 BJ50 4H039 CA66 CF30

Claims (13)

[Claims] 1. The following formula (I): R--O--CO--OR (I) wherein R is selected from substituted or unsubstituted C ₆ -C ₁₅ aryl. And an aromatic hydroxy compound represented by the following formula (II): R-OH (II) (wherein R has the same definition as in formula (I)) To a mixed solution (A) containing
It is compatible with the aromatic hydroxy compound, that is, the solubility parameter δs (subscript s means a solvent) is 7.0 to 1
A method for separating and recovering diaryl carbonate, comprising adding a solvent (B) in a range of 0.0, selectively crystallizing the diaryl carbonate, and separating and recovering the same. 2. An amount of the solvent (B) to be added is represented by the following formula (III): δsah = δsWs / (Ws + Wah) + δahWah / (Ws + Wah) (III) , Suffix s represents the solvent, ah represents an aromatic hydroxy compound, and sah represents a mixed solution of the solvent and the aromatic hydroxy compound.) The solubility parameter δsah defined by the following formula (IV): Δdac−δsah ≧ 0.6 (IV) (where the subscript dac represents a diaryl carbonate and sah represents a mixed solution of the solvent and an aromatic hydroxy compound). The method according to claim 1, wherein 3. The method according to claim 1, wherein the concentration of the diaryl carbonate in the mixed solution (A) is in the range of 5 to 95% by weight. 4. The method according to claim 3, wherein the concentration of the diaryl carbonate in the mixed solution (A) is in the range of 7 to 70% by weight. 5. The method according to claim 4, wherein the concentration of the diaryl carbonate in the mixed solution (A) is in the range of 10 to 50% by weight. 6. The method according to claim 1, wherein the solvent (B) has a melting point of 15 ° C. or lower. 7. The solvent (B) wherein the solvent (B) is a C ₅ -C ₈ cycloaliphatic hydrocarbon, an aromatic hydrocarbon, a C ₃ -C ₆ aliphatic ether, an aliphatic ketone, and a C ₁ -C 6. _It is at least one selected from the group consisting of alcohols of claim 3.
7. The method according to any one of 6. 8. The solvent (B) is at least one selected from the group consisting of cyclohexane, toluene, xylene, diethyl ether, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl alcohol, ethyl alcohol, and isopropyl alcohol. The method according to any one of claims 1 to 7. 9. The method according to claim 1, wherein the crystallization operation is performed while stirring the mixed solution of the mixed solution (A) and the solvent (B). 10. The method according to claim 1, wherein the crystallization operation is performed by allowing the mixed solution of the mixed solution (A) and the solvent (B) to stand. 11. A mixed solution (C) formed by a reaction of oxidatively carbonylating an aromatic hydroxy compound in the presence of carbon monoxide, molecular oxygen and a catalyst to obtain a diaryl carbonate. The method according to claim 1, wherein 12. A solution (E) containing a catalyst obtained by removing the solvent (B) from the residue (D) after the crystallization operation.
Is recycled to the reactor for obtaining the diaryl carbonate. 13. The method according to claim 11, wherein the catalyst contained in the solution (C) formed by the reaction is at least one selected from a platinum group catalyst, a cocatalyst, and a quaternary salt. .