JPH09100256A - Production of diaryl carbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a diaryl carbonate, capable of producing the diaryl carbonate in a high yield, while preventing the by- production of an aryl chloroformate. SOLUTION: This method for producing the diaryl carbonate by reacting an aromatic hydroxy compound with phosgene in the presence of a catalyst in a liquid phase, the characteristic comprises performing the reaction in the following two processes. [The first process]: the aromatic hydroxyl compound is reacted with phosgene to convert >=90% of the aromatic hydroxy compound into the reaction product. [The second process]: the reaction product of the first process is mixed with the aromatic hydroxyl compound in a stoichiometric amount corresponding to the aryl chloroformate contained in the reaction product or in a larger amount and subsequently converted into the diaryl carbonate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a diaryl carbonate. More specifically, the present invention relates to a method for producing a diaryl carbonate in which by-product of aryl chloroformate, which is difficult to separate, is suppressed.

[0002]

2. Description of the Related Art It is known that diaryl carbonate can be obtained by reacting an aromatic hydroxy compound with a carbonyl halide. For example, U.S. Pat. No. 2,837,555 proposes performing solventless condensation in the presence of tetramethylammonium halide as a catalyst. However, this method requires a relatively large amount of catalyst and a relatively high temperature of 180 to 215 ° C. in order to obtain an economical reaction rate, which is thermally unstable. There is a risk of decomposition of tetramethylammonium halide. In addition, phosgene is consumed at a much higher rate than required stoichiometrically.

Japanese Unexamined Patent Publication (Kokai) No. 4-308553 proposes to use aluminum chloride and to carry out the above reaction in a temperature range of 100 to 150 ° C. Although this method gives good yields, it has difficulties in separating the catalyst from its product. In fact, these aluminum compounds have a certain degree of volatility, which can lead to thermal decomposition reactions caused by these aluminum compounds, which lead to impurities, poor quality and poor yields. It will be.

Further, Japanese Patent Publication No. 58-50977 discloses
The present invention relates to a method for producing a diaryl carbonate by reacting an aromatic hydroxy compound with phosgene in the presence of a catalytic amount of a nitrogen-containing heterocyclic base. This method is reported to be simpler and give better yields than the method described above. However, even in this method, the DPC production rate by the reaction of phenyl chloroformate, which is an intermediate product of diphenyl carbonate (hereinafter sometimes abbreviated as DPC), and phenol is higher than that of phenyl chloroformate. Since it does not have a sufficient rate, a small amount of phenyl chloroformate remains with DPC at the end of the reaction. Such residual phenyl chloroformate is extremely disadvantageous in industrial practice. That is, since the boiling points of DPC and phenyl chloroformate are close to each other, it is difficult to separate and purify DPC by distillation, and further, the mixing of an acidic compound such as phenyl chloroformate into DPC causes coloring of DPC. Has been pointed out (see Japanese Patent Laid-Open No. 7-138208).

[0005]

As described above, in industrial DPC production, there are many inadequacies in the process, and the content of aryl chloroformate, which is a contaminant and is not easily separated, is suppressed. From the viewpoint of advantage, it was a problem to obtain the target DPC.

[0006]

As a result of intensive studies in view of the above-mentioned circumstances, the present invention has found that it is effective to carry out a reaction in two specific steps, and arrived at the present invention.
That is, the present invention provides a method for producing a diaryl carbonate by reacting an aromatic hydroxy compound with phosgene in the liquid phase in the presence of a catalyst, wherein the aromatic hydroxy compound is reacted with phosgene to give 9
Aromatic hydroxy compound is added to the reaction product of the first step of 0% or more conversion; A second step of converting a chloroformate to a diaryl carbonate; and a method for producing a diaryl carbonate.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The reaction method according to the present invention is carried out in two steps, in which a phosgenation reaction of an aromatic hydroxy compound is carried out in the first step, and then, in a second step, the arylchloro compound produced in the first step is carried out. It consists of reacting a formate with a separately added aromatic hydroxy compound to convert it to the desired diaryl carbonate.

A suitable aromatic hydroxy compound used as a raw material in the method of the present invention is represented by the following formula (I): Ar-OH (I) [wherein Ar represents phenyl, naphthyl, anthryl, phenanthryl, indanyl or Represents a tetrahydronaphthyl group or represents a group derived from a 5- or 6-membered aromatic heterocyclic compound having 1 or 2 heteroatoms selected from the N, O and S groups, wherein the homologous The cyclic group or heterocyclic group may be substituted with 1 or 2 substituents, for example, a linear or branched C ₁ -C ₄ -alkyl group, a linear or branched C ₁ -C ₄ -alkoxy group Often, these are phenyl, cyano and halogen (eg F,
Cl, Br) may be substituted, and here, further, these heterocyclic groups may be linked to a fused benzene ring].

Examples of the aromatic monohydroxy compound represented by the above formula (I) include phenol; o-, m-
And p-cresol, o-, m- and p-isopropylphenol; corresponding halogeno or alkoxyphenols, such as p-chlorophenol or p-methoxyphenol; monohydroxy compounds of naphthalene, anthracene and phenanthrene; 4-hydroxypyridine And hydroxyquinoline. Phenols which may be optionally substituted are preferably used, and phenol is particularly preferably used.

The catalyst used in this reaction is not particularly limited, but the catalyst preferably used is a nitrogen-containing aromatic heterocyclic compound in which a nitrogen atom is present in an aromatic 5- or 6-membered ring. . Specifically, the following compounds can be mentioned. Pyridine; quinoline; isoquinoline; picoline; acridine; pyrazine; pyritadi; pyrimidine; and the benzene ring is, for example, alkyl, carbalkoxy,
It may be substituted with an inert group such as halogen,
Corresponding benzene heterocyclic compounds; oxazines; thiazines such as phenothiazine;
Triazines such as 6-trimethyltriazine; compounds of this type substituted by alkyl, alkoxy, carbachoxy or halogen, such as 2-methyl-imidazole; and, for example, benzimidazole, benzotriazole, benzothiazole, Corresponding benzoheterocyclic compound. Among these, preferred catalysts are pyridine; quinoline; picoline; imidazoles; benzimidazoles; pyrazoles; triazoles and benzotriazoles.

These catalysts are usually used in the range of 0.01 to 20% on a mol% basis based on the aromatic hydroxy compound. A more preferable catalyst concentration range is 0.1 to 10
Mol%, and the most preferred range is 1 to 5 mol%.

In an industrially preferred embodiment of the process according to the present invention, a complete mixing tank type reactor is used as a reaction apparatus, and in the first step, in the liquid phase in the presence of a catalyst, an aromatic hydroxy compound is usually added. Phosgene is introduced in an amount of 0.4 to 1.5, preferably 0.5 to 0.7, relative to 1 mol of the aromatic hydroxy compound, and hydrogen chloride formed during the reaction is optionally, continuously or The reaction is carried out while removing it discontinuously. The supply of phosgene is stopped when the aromatic hydroxy compound is converted to 90% or more, preferably 95 to 100%. Then, in the second step, the reaction product of the first step has a stoichiometric amount or more corresponding to the aryl chloroformate in the reaction product, preferably 1 to 5 mol per 1 mol of aryl chloroformate. Thus, an aromatic hydroxy compound is added to convert the aryl chloroformate to a diaryl carbonate. By such a two-step reaction, the amount of aryl chloroformate in the final reaction product can be 2 mol% or less, and further 1% or less, based on 1 mol of the diaryl carbonate.

The method according to the present invention can employ either a batch reaction system or a continuous reaction system. The reaction can be carried out at any temperature as long as the catalyst does not decompose and remains stable. The temperature range is usually 60 to 250 ° C,
Preferably 100 to 180 ° C., more preferably 130 to 180 ° C.
It is 180 ° C. In the method of the present invention, both steps are performed in the liquid phase. It is preferably carried out in the molten state, at a reaction temperature above the melting point of the aromatic hydroxy compound and the diaryl carbonate. If desired, a solvent may be used, and aliphatic and aromatic hydrocarbons such as pentane, hexane, octane, benzene, isomeric xylenes, diethylbenzene, alkylnaphthalenes,
Biphenyl; halogenated hydrocarbons, such as solvents such as dichloromethane, trichloroethylene and the like can be mentioned.

The final reaction solution obtained through the above two steps is separated from the product and the catalyst by a conventional separation method such as distillation. The obtained crude diaryl carbonate may be further purified depending on the use, for example, by distillation, washing with water or crystallization.

[0015]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples as long as the gist of the present invention is not exceeded. Note that D
The molar percentages of PC, phenol, and phenyl chloroformate were defined as follows.

[0016]

(Equation 1)

Embodiment 1 FIG. [First step] 10 equipped with a stirrer and a reflux condenser
4 ml of phenol (0.
502 mol) and 3 mol% of imidazole with respect to phenol were charged and heated under N ₂ flow to raise the temperature. 150 ° C
At that point, phosgene was bubbled continuously for 65 minutes at a flow rate of 0.6 g / min. A total of 0.39 mol of phosgene was fed to the reaction system. The composition (molar percentage) of the obtained reaction product was 86.9 mol% DPC,
Phenyl chloroformate was 12.4 mol% and phenol was 0.6 mol%. At this time, the conversion rate of the aromatic hydroxy compound was 99.0%.

[Second Step] To the above reaction product, 6.6 g (0.07 mol) of phenol was added, and the reaction was carried out at 150 ° C. for 1 hour while bubbling N ₂ . The composition (molar percentage) of the final reaction liquid was 98.6 mol% DPC, 1 mol% phenol, and 0.3 mol% phenyl chloroformate. The by-product rate of phenyl chloroformate was 0.3% based on the charged phenol.
The DPC yield was 98.0%.

Comparative Example 1 [Step A] As in the first step of Example 1, phenol 4 was used.
7.0 g (0.50 mol), 3 mol% based on phenol
Was heated to 150 ° C. under N ₂ flow, and 0.6 g / min of phosgene was continuously bubbled for 65 minutes. A total of 0.39 mol of phosgene was fed to the reaction system. The composition of the reaction solution (molar percentage) obtained by the phosgenation reaction was 85.9 mol% DPC, 14.0 mol% phenyl chloroformate, and a trace amount of phenol. At this time, the conversion rate of the aromatic hydroxy compound was 99.5%.

[Step B] The reaction solution obtained in step A was stopped by supplying phosgene, and left standing at 150 ° C. for 30 minutes under stirring.
Then, while bubbling N ₂ , it was left for 1.5 hours while slowly cooling from 150 ° C. to 100 ° C. The liquid composition (molar percentage) of the final reaction liquid obtained in the step B was 89.0% DPC and 11. Phenyl chloroformate, respectively.
It was 0% and phenol 0%.

Example 2 [First Step] 10 equipped with a stirrer and a reflux condenser
In 0 ml of glass Kolben, 47 g of phenol (0.
5 mol) and 3 mol% of mixed picoline with respect to phenol were charged, and the mixture was heated and heated in an N ₂ atmosphere. When 150 ° C was reached, phosgene was continuously fed for 90 minutes at a flow rate of 0.3 g / min. A total of 0.275 mol of phosgene was fed to the reaction system. The composition of the reaction liquid (molar percentage) obtained in the phosgenation step was DPC 89.8%, phenyl chloroformate 8.0%, and phenol 2.3%, respectively. The conversion rate of the aromatic hydroxy compound at this time is 9
It was 7.9%.

[Second Step] 2.7 g (0.029 mol) of phenol was newly added to the reaction product obtained in the phosgenation step.
Was added and the mixture was allowed to stand for 0.5 hour at 150 ° C. under stirring conditions. Then, while bubbling N ₂ , it was left for 1.5 hours while slowly cooling from 150 ° C. to 100 ° C. The liquid composition (mol percentage) of the final reaction liquid thus obtained was 97.3% DPC, 0.9% phenyl chloroformate, and 1.7% phenol. The yield of DPC was 94.2% based on the charged phenol, and the by-product ratio of phenyl chloroformate was 0.9%.

Comparative Example 2 [Step A] The same phosgenation reaction as in the first step of Example 2 was carried out to give a composition of 91.0 mol% DPC, 7.4 mol% phenylchloroformate and 1.6 mol% phenol. A reaction mixture consisting of (molar percentage) was obtained. Total amount is 0.
275 mol of phosgene was fed to the reaction system. At this time, the conversion rate of the aromatic hydroxy compound was 98.5%.

[Step B] The same treatment as in Example 2 was carried out without newly adding phenol, and the final reaction liquid composition (mol percentage) was 94.1 mol% DPC, 4.8 mol% phenylchloroformate, and Phenol 1.0
Mole%. The finally obtained reaction results were a DPC yield of 90.6% and a phenylchloroformate byproduct rate of 4.6% based on the charged phenol.

[0025]

INDUSTRIAL APPLICABILITY When the aromatic hydroxy compound and phosgene are reacted in the liquid phase in the presence of a catalyst to produce a diaryl carbonate, by employing the specific two-step reaction according to the present invention, the desired diaryl carbonate can be obtained. The yield of carbonate is increased, and the by-product of aryl chloroformate is suppressed. Thus, the process of the present invention is such that there is little residual aryl chloroformate in the crude reaction product which adversely affects the quality of the diaryl carbonate while at the same time obtaining the desired diaryl carbonate in maximum yield. It has a great advantage that the treatment of the purification step of the crude reaction product is greatly simplified, which is extremely advantageous industrially.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Furuto Kurosaki, Yawatanishi-ku, Kitakyushu, Fukuoka Prefecture Mitsubishi Chemical Co., Ltd. Kurosaki Development Laboratory

Claims (4)

[Claims] 1. A method for producing a diaryl carbonate by reacting an aromatic hydroxy compound and phosgene in a liquid phase in the presence of a catalyst, wherein the aromatic hydroxy compound is reacted with phosgene to give 90% of the aromatic hydroxy compound.
% In the first step; and to the reaction product of the first step, an aromatic hydroxy compound is added so that the stoichiometry is equal to or more than the aryl chloroformate in the reaction product. A second step of converting a formate into a diaryl carbonate; 2. The method according to claim 1, wherein the conversion rate of the aromatic hydroxy compound in the first step is 95 to 100%. 3. The method according to claim 1, wherein the aromatic hydroxy compound added in the second step is 1 to 5 (molar ratio) with respect to the aryl chloroformate in the reaction product of the first step. 4. The method according to claim 1, wherein the amount of the aryl chloroformate in the reaction product of the second step is 2 mol% or less based on 1 mol of the diaryl carbonate.