JP3206425B2 - Method for producing diaryl carbonate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 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 Application Laid-Open No. 62-190146, etc.) or a method of using a dialkyl carbonate and an aromatic hydroxy compound as a catalyst Method of transesterification in the presence (JP-B-56)
Japanese Patent No. 42577, Japanese Patent Publication No. 1-5588, etc.)
Is well known. However, the former method using phosgene is not always industrially excellent because phosgene itself is a highly toxic compound and a large amount of alkali is used. In addition, the latter transesterification method does not have a sufficient reaction rate in spite of using a highly active catalyst as described in many patents relating to this method. There is a problem that the device is required.

As another method, a method is known in which a diaryl oxalate is subjected to a decarbonylation reaction to produce a diaryl carbonate. However, this method has a problem that the yield of the desired diaryl carbonate is extremely low. . That is,
A method for producing diphenyl carbonate by boiling diphenyl oxalate in a distillation flask (Journal of the Society of Organic Synthesis, 5, pp. 47)
(1948), 70), which is also shown in the reaction formula described in this document, produces phenol as a by-product as isolated as a by-product, and further produces carbon dioxide as a by-product to produce the desired diphenyl carbonate. There is a problem that the yield is extremely low.

An oxalate diester (oxalic acid diester) is added to an alcoholate catalyst in the presence of 50 to 15 to 15 to 15%.
A method for producing a carbonate diester (carbonic acid diester) by heating to 0 ° C. in a liquid phase has also been proposed (USP
In this method, as shown in Examples in the publication, even if diphenyl oxalate (diphenyl oxalate) is heated in the presence of a potassium phenoxide catalyst, the product obtained as a main product is a raw material. The desired diphenyl carbonate (diphenyl carbonate) cannot be obtained.

[0005]

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 a diaryl oxalate, which method can produce the diaryl carbonate with a high yield.

[0006]

The object of the present invention is attained by a process for producing a diaryl carbonate, which comprises subjecting a diaryl oxalate to a decarbonylation reaction in the gas phase at 330 to 800 ° C.

[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, (b) 2-
(Or 3-, 4-) methoxyphenyl group, 2- (or 3)
-, 4-) ethoxyphenyl group or other 2- (or 3-, 4-) alkoxyphenyl group having an alkoxy group having 1 to 12 carbon atoms, (c) 2- (or 3-, 4-) nitrophenyl group , (D) a 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; No.

[0011] In the decarbonylation reaction of diaryl oxalate, the diaryl oxalate is supplied to a gas phase reaction tube, and 33
It is carried out by heating in the gas phase at 0 to 800 ° C, preferably 400 to 700 ° C, more preferably 450 to 650 ° C. At this time, according to the above reaction formula, diaryl carbonate is generated from diaryl oxalate, and carbon monoxide is generated. If the reaction temperature is lower than 330 ° C., almost no decarbonylation reaction occurs. If the reaction temperature is higher than 800 ° C., the yield of diaryl carbonate decreases, which is not preferable.

For the supply of diaryl oxalate, for example, a diaryl oxalate dissolved in a solid, a melt or a solvent is vaporized in advance by a vaporizer or a vaporization layer, and is introduced into a reaction tube together with an inert gas such as nitrogen gas. This is done by: The supply amount of the diaryl oxalate is usually 0.1 to 10000 g / l · hr, preferably 10 to 1000 g / l · hr, per unit volume (l) and unit time (hr) of the reaction tube in the predetermined temperature range. is there. Also, the space velocity of the gas containing the vaporized inert gas such as oxalic acid diaryl and nitrogen gas is usually 10～10000Hr ^-1, preferably 100~6000hr ^-1. The reaction pressure is preferably normal pressure or reduced pressure.

The reaction tube is preferably filled with a filler inert to this reaction in order to improve the thermal contact of the diaryl oxalate. As the inert filler, quartz or α-alumina having no acid point, hydroxyl group or the like is preferable. As the reaction tube, for example, a reaction tube made of stainless steel, iron, or quartz can be used. After the reaction, the produced diaryl carbonate 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 diaryl carbonate was determined for diaryl oxalate.

Example 1 A thermocouple for temperature measurement was attached to a side wall, an inner diameter of 6.5 mm,
A quartz bead (3
mmφ), and the whole reaction tube was heated to 610 ° C. while flowing nitrogen gas under normal pressure. Then, under normal pressure,
The reaction was started by vaporizing diphenyl oxalate at 200 ° C. in a vaporizer and introducing it into the reaction tube together with nitrogen gas (50 ml / min) (reaction temperature: 610 ° C.). The total nitrogen gas flow during the reaction was 75 ml / min. During the reaction, about 6 ml / mi of sulfolane was supplied to the outlet of the reaction tube in order to dissolve and collect the products and the like that came out of the reaction tube.
n. 1.5 g of diphenyl oxalate (6.2 m
mol) for 4 hours to carry out the reaction, and then subject the product to gas chromatography (column temperature: 130 to 170).
(C, inlet temperature: 180 ° C), it was found that 0.90 g (4.2 mmol) of diphenyl carbonate was produced. The yield of diphenyl carbonate was 67.7%, and the ratio (selectivity) of diphenyl carbonate to consumed diphenyl oxalate was 83 mol%. In addition, the formation of diphenyl carbonate from diphenyl oxalate by the analytical operation was not recognized.

Example 2 In Example 1, the entire reaction tube was heated to 570 ° C., and then diphenyl oxalate was vaporized to obtain nitrogen gas (10 m
l / min) and introduced into the reaction tube together with 1.70 g (7.0 mmol) of diphenyl oxalate in 5 hours (reaction temperature: 570 ° C.).
The reaction and analysis were performed in the same manner as described above. The total flow rate of the nitrogen gas during the reaction was 20 ml / min. As a result, 0.71 g (3.3 mmol) of diphenyl carbonate was produced (yield: 47.1%).

Example 3 An inner diameter of 10 m provided with a temperature measurement insertion pipe and a gas introduction pipe.
Quartz beads (3 mmφ) were filled in the upper five-sixth part of a 300 mm long, 300 mm quartz reaction tube, and the quartz beads filled part was heated to 600 ° C. while flowing nitrogen gas under normal pressure. Next, the reaction was started by evaporating the melt of diphenyl oxalate under normal pressure and introducing it into the reaction tube (reaction temperature: 600 ° C.). During the reaction, 250
While supplying sulfolane to the position of mm at a rate of 20 ml / min, products and the like adhering to the vessel wall were dissolved and collected.
0.80 g (3.3 mmol) of diphenyl oxalate in 1
After the reaction was carried out by supplying over a period of time, analysis was performed in the same manner as in Example 1 to find that 0.34 g (1.6 g) of diphenyl carbonate was obtained.
0 mmol) (yield: 48.5%).

Example 4 A reaction and analysis were carried out in the same manner as in Example 3 except that the portion filled with quartz beads was heated to 700 ° C. (reaction temperature: 700 ° C.). As a result, the amount of diphenyl carbonate was 0.1.
15 g (0.71 mmol) was produced (yield: 2
1.5%).

Example 5 An inner diameter of 10 m provided with a temperature measurement insertion pipe and a gas introduction pipe.
Quartz beads (3 mmφ) were filled in the upper five-sixth part of a 300 mm long, 300 mm quartz reaction tube, and the quartz beads filled part was heated to 400 ° C. while flowing nitrogen gas under normal pressure. Next, the reaction was started by evaporating the melt of diphenyl oxalate under normal pressure and introducing it into the reaction tube (reaction temperature: 400 ° C.). During the reaction, while the sulfolane was supplied at a rate of 10 ml / min to a position 250 mm from the top of the reaction tube, the products and the like adhering to the vessel wall were dissolved and collected.
2.1 g (8.8 mmol) of diphenyl oxalate in 2
After the reaction was carried out by supplying the mixture over a period of time, the same analysis as in Example 1 was carried out.
9 mmol) (yield: 9.0%).

Comparative Example 1 A reaction and analysis were carried out in the same manner as in Example 5 except that the portion filled with quartz beads was heated to 300 ° C. (reaction temperature: 300 ° C.). As a result, diphenyl carbonate was only slightly generated.

Example 6 A stainless steel reaction tube having an inner diameter of 20 mm and a length of 750 mm in which a thermocouple for temperature measurement was attached to a side wall was filled with 30 ml of α-alumina (2 mmφ), and α was added while flowing nitrogen gas under normal pressure. Heating the alumina-filled part to 500 ° C.
Next, the reaction was started by evaporating diphenyl oxalate under normal pressure and introducing it into the reaction tube together with nitrogen gas (100 ml / min) (reaction temperature: 500 ° C.). During the reaction, about 30 ml / m of acetonitrile was added from the bottom of the reaction tube.
While supplying the product in, products and the like adhering to the vessel wall were dissolved and collected. 3.5 g of diphenyl oxalate (14.5
(mmol) for 2 hours to conduct a reaction, and analyzed in the same manner as in Example 1. As a result, diphenyl carbonate was found to be 1.65.
g (7.7 mmol) (yield: 53.1).
%). Table 1 shows the results of Examples 1 to 5 and Comparative Example 1.

[0022]

[Table 1]

Comparative Example 2 5.0 g (20.7 g) of diphenyl oxalate was placed in a 100 ml glass reactor equipped with a thermometer, a stirrer and a reflux condenser.
mmol), the space in the container was replaced with argon gas, and the temperature was raised to 330 ° C. Then, the mixture was heated (boiled) in a liquid phase at normal pressure and at this temperature for 3 hours to perform a decarbonylation reaction. After completion of the reaction, the vessel was cooled to room temperature and analyzed in the same manner as in Example 1.
18 g (0.84 mmol) was produced (yield: 4.
1%).

Comparative Example 3 An internal volume 90 having a gas exhaust pipe, a thermometer, and a stirrer
5.0 g (20.7 mmol) of diphenyl oxalate, 0.5 g (3.8 mmol) of potassium phenolate and 5.0 g of tetrahydrofuran were placed in a ml stainless steel reactor, and the space in the vessel was replaced with argon gas. Thereafter, the temperature was raised to 100 ° C. Then, the mixture was heated in the liquid phase at this temperature under normal pressure for 1.25 hours to carry out a decarbonylation reaction. After completion of the reaction, the vessel was cooled to room temperature and analyzed in the same manner as in Example 1. As a result, formation of diphenyl carbonate was not observed.

[0025]

According to the present invention, diaryl carbonate can be easily produced from diaryl oxalate with good yield without using phosgene which is a highly toxic compound.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Yoshifumi Yamamoto, 1978 Kogushi, Oji, Ube City, Yamaguchi Prefecture Inside Ube Research Institute, Ube Industries, Ltd. Ube Industries, Ltd., Ube Research Laboratory (72) Inventor Toshio Kurato, 1978 Kogushi, Oji, Ube City, Yamaguchi Prefecture 5 Ube Industries, Ltd. Ube Research Laboratory Examiner Tomoko Anabuki (56) References JP 8-325207 ( JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 68/00 C07C 69/96 CASREACT (STN)

Claims (1)

(57) [Claims] 1. A diaryl oxalate at 400 to 800 ° C.
And producing a diaryl carbonate by heating in the gas phase to carry out a decarbonylation reaction.