JP3220973B2 - Preparation of diaryl carbonate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a diaryl carbonate useful as a raw material for producing a polycarbonate.

[0002]

2. Description of the Related Art As a method for producing a diaryl carbonate, a method of reacting phosgene with an aromatic hydroxy compound in the presence of an alkali (Japanese Patent Laid-Open No. 62-190146).
And a method of transesterifying a dialkyl carbonate with an aromatic hydroxy compound in the presence of a catalyst (JP-B-56-42577 and JP-B-1-558).
No. 8 is well known. However, the former method using phosgene is not necessarily industrially excellent because phosgene itself is a highly toxic compound and a large amount of alkali is used. In addition, the latter transesterification method, as described in many patents relating to this method, does not have a sufficient reaction rate despite the use of a highly active catalyst. There is a problem that a device is required.

As another method, a method for producing a diaryl carbonate by decarbonylating a diaryl oxalate is known, but this method has a problem that it is industrially disadvantageous due to a high reaction temperature. ing. That is, in a method of producing diphenyl carbonate (diphenyl carbonate) by boiling diphenyl oxalate (diphenyl oxalate) in a distillation flask without a catalyst (Organic Synthesis Association, 5, 47 (1948), 70),
Since the reaction temperature is high, phenol and carbon dioxide are by-produced, and the yield of diphenyl carbonate (diphenyl carbonate) decreases. Conversely, if the reaction temperature is low, diphenyl carbonate (diphenyl carbonate) is hardly obtained (Comparative Example 1). , 2).

Further, a method has been proposed in which an oxalate diester is heated in the liquid phase at 50 to 150 ° C. in the presence of an alcoholate catalyst to produce a carbonate diester (US Pat. No. 4,544,507). As shown in the Examples, what is obtained as the main product is the starting material diphenyl oxalate, and the desired diphenyl carbonate cannot be obtained (see Comparative Example 3).

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for easily producing a diaryl carbonate without using phosgene which is a highly toxic compound. That is, an object of the present invention is to provide a method for producing a diaryl carbonate from diaryl oxalate, which method can produce the diaryl carbonate with a high yield.

[0006]

The object of the present invention is achieved by a process for producing a diaryl carbonate, which comprises subjecting a diaryl oxalate to a decarbonylation reaction in a liquid phase in the presence of an alkaline earth metal catalyst.

[0007]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a diaryl carbonate is formed by a decarbonylation reaction of a diaryl oxalate represented by the following formula.

[0008]

Embedded image (Wherein, Ar represents an aryl group)

The aryl group includes (1) a phenyl group, (2) as a substituent, (a) an alkyl group having 1 to 12 carbon atoms such as a methyl group and an ethyl group, (b) a methoxy group,
An alkoxy group having 1 to 12 carbon atoms such as an ethoxy group, (c)
Examples include a nitro group or (d) a substituted phenyl group having a halogen atom such as a fluorine atom and a chlorine atom, and (3) a naphthyl group.

The substituted phenyl group includes various isomers.
These isomers include (a) 2- (or 3-, 4-)
2- having an alkyl group having 1 to 12 carbon atoms such as a methylphenyl group and a 2- (or 3-, 4-) ethylphenyl group;
(Or 3-, 4-) alkylphenyl group or (b) 2-
(Or 3-, 4-) methoxyphenyl group, 2- (or 3)
A 2- (or 3-, 4-) alkoxyphenyl group having an alkoxy group having 1 to 12 carbon atoms, such as-, 4-) ethoxyphenyl group or (c) 2- (or 3-, 4-) nitrophenyl Or a (d) 2- (or 3-, 4-) halophenyl group having a halogen atom such as a 2- (or 3-, 4-) fluorophenyl group or a 2- (or 3-, 4-) chlorophenyl group And the like.

Examples of the alkaline earth metal catalyst include alkaline earth metals such as magnesium, calcium, strontium, barium and the like, and compounds thereof. Usually, the compounds are preferably used. Examples of the alkaline earth metal compounds include (a) halides of alkaline earth metals such as magnesium chloride, calcium chloride, strontium chloride, barium chloride, magnesium bromide, calcium bromide, strontium bromide, and barium bromide; (B) magnesium oxalate, calcium oxalate, strontium oxalate, barium oxalate, magnesium formate,
Calcium formate, strontium formate, barium formate,
Alkaline earth metal salts of aliphatic mono- or dicarboxylic acids such as magnesium acetate, calcium acetate, strontium acetate and barium acetate, and (c) oxides of alkaline earth metals such as magnesium oxide, calcium oxide, strontium oxide and barium oxide And (d) magnesium hydroxide,
Examples include hydroxides of alkaline earth metals such as calcium hydroxide. The above alkaline earth metal catalyst may be used after previously heat-treated at 100 to 600 ° C. in an inert gas such as nitrogen gas.

The alkaline earth metal catalyst is generally used as an alkaline earth metal in an amount of 0.0 to the diaryl oxalate.
It is used in an amount of from 0.01 to 50 mol%, preferably from 0.01 to 40 mol%. The catalyst may be used singly or as a mixture of two or more kinds, or may be used after being dissolved or suspended in a reaction solution. When the alkaline earth metal catalyst is used in a suspended state, a carrier in which an alkaline earth metal or a compound thereof is supported on a carrier such as alumina such as γ-alumina, silica, silica alumina, or zeolite may be used. The loading amount of the alkaline earth metal or a compound thereof is usually 0.1 to 50 mol%, preferably 0.5 to 20 mol%, as the alkaline earth metal relative to the carrier.

The decarbonylation reaction of the diaryl oxalate is carried out by placing the diaryl oxalate and the alkaline earth metal catalyst in a reactor (eg, a stirred tank) at 100 to 450 ° C.
Preferably 160-400 ° C, more preferably 180-
It is carried out by heating in the liquid phase at 350 ° C, especially 180-300 ° C. At this time, diaryl carbonate is generated from diaryl oxalate according to the above reaction formula, and carbon monoxide is generated as a by-product. The reaction pressure is increased when the reaction temperature exceeds the boiling point of the diaryl oxalate, but is usually normal pressure or reduced pressure. A solvent is not particularly required in the decarbonylation reaction, and examples thereof include sulfolane, N-methylpyrrolidone, dimethylimidazolidone, 1,3-dimethyl-3,
An aprotic polar solvent such as 4,5,6-tetrahydro-2 (1H) -pyrimidinone can be appropriately used. After the reaction, the produced diaryl oxalate is separated and purified by distillation or the like.

[0014]

Next, the present invention will be described specifically with reference to examples and comparative examples. The yield (mol%) of diphenyl carbonate was determined based on the charged diphenyl oxalate.

EXAMPLE 1 16.4 mm of diphenyl oxalate was placed in a 50 ml glass flask equipped with a thermometer, a stirrer and a reflux condenser.
ol (3.97 g) and magnesium chloride (MgCl ₂ ) 0.82 mmol (0.02 g) as an alkaline earth metal catalyst.
78g) and heated to 260 ° C.
While removing generated carbon monoxide outside the system,
The mixture was heated for a time to carry out a decarbonylation reaction. After the reaction,
The reaction solution is cooled to room temperature and subjected to gas chromatography (column temperature: 100 to 180 ° C, inlet temperature: 170 ° C).
As a result, diphenyl carbonate was found to be 2.
5 mmol (0.54 g) was produced. The yield of diphenyl carbonate was 15.3%, and its selectivity (the ratio of diphenyl carbonate to consumed diphenyl oxalate) was 83.9 mol%. In addition, generation of diphenyl carbonate from diphenyl oxalate by the analysis operation was not recognized.

Comparative Example 1 A reaction and analysis were carried out in the same manner as in Example 1 except that no alkaline earth metal catalyst was used. As a result, generation of diphenyl carbonate was not recognized.

Examples 2 to 7 The procedure of Example 1 was repeated except that the alkaline earth metal catalyst was replaced with the compound shown in Table 1 and the amount of diphenyl oxalate charged and the reaction temperature were changed as shown in Table 1. Reaction and analysis were performed as in 1. Table 1 shows the results.

Comparative Example 2 In Example 1, 20.7 m of diphenyl oxalate was used.
The reaction and the analysis were carried out in the same manner as in Example 1 except that the reaction temperature was changed to 330 ° C., and the alkaline earth metal catalyst was not used. As a result, 0.84 mmol of diphenyl carbonate was produced (yield: 4.1%).

Comparative Example 3 An internal volume 90 having a gas exhaust pipe and a thermometer and a stirrer
20.7 mmol (5.0 g) of diphenyl oxalate, 3.8 mmol (0.5 g) of potassium phenolate and 5.0 g of tetrahydrofuran were placed in a ml stainless steel reactor, heated to 100 ° C., and then heated to normal pressure. The mixture was heated at this temperature for 3 hours to carry out a decarbonylation reaction. When the analysis was performed in the same manner as in Example 1, formation of diphenyl carbonate was not recognized. Table 1 shows the results of Examples and Comparative Examples.

[0020]

[Table 1]

[0021]

Industrial Applicability According to the present invention, diaryl carbonate useful as a raw material for polycarbonate can be produced from diaryl oxalate at a lower reaction temperature which is industrially suitable as compared with a known diaryl oxalate boiling method for decarbonylation. It can be manufactured with good yield. In addition, since phosgene, which is a highly toxic compound, is not used, diaryl carbonate can be easily and safely produced.

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI // C07B 61/00 300 C07B 61/00 300 (56) References JP-A-8-333307 (JP, A) JP-A-8 JP-A-325207 (JP, A) JP-A-8-325206 (JP, A) JP-A-9-255628 (JP, A) JP-A-51-75044 (JP, A) (58) Fields investigated (Int. . ^7, DB name) C07C 68/00 C07C 69/96 C07B 61/00 300 B01J 23/02 B01J 27/138 B01J 31/04 CASREACT (STN)

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein the diaryl oxalate is an alkaline earth
Metal halides, aliphatic mono- or dicarboxylic acids
A process for producing a diaryl carbonate, wherein a decarbonylation reaction is carried out in a liquid phase in the presence of an alkaline earth metal salt or an alkaline earth metal oxide .