JP2001247518A - Method of producing diaryl carbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process of producing diaryl carbonate from an aromatic monohydroxy compound and phosgene by using a catalyst comprising an aromatic nitrogen-containing heterocyclic compound, in which the diaryl carbonate can be produced at a high conversion ratio in an industrially advantageous manner, the by-produced hydrogen chloride is converted into chlorine, and the converted chlorine is reused in phosgene production process. SOLUTION: This method of producing diaryl carbonate is characterized by including four steps of: (1) a diaryl carbonate production step for subjecting an aromatic monohydroxy compound and phosgene to condensation reaction at a temperature of 80 deg.C to 180 deg.C in the presence of an aromatic nitrogen- containing heterocyclic compound catalyst to obtain the diaryl carbonate; (2) a purification step for removing impurities from a hydrogen chloride gas by- produced upon the condensation reaction; (3) a chlorine recovery step for recovering chlorine usable for the production of phosgene from the purified hydrogen chloride gas; and (4) a phosgene production step for reacting the recovered chlorine with carbon monoxide to obtain phosgene usable in the diaryl carbonate production step.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a diaryl carbonate. More specifically, the present invention relates to a method for producing diaryl carbonate, which converts by-produced hydrogen chloride into chlorine by the phosgene method and uses it again for producing phosgene.

[0002]

2. Description of the Related Art Diaryl carbonate is used in large quantities as a raw material for producing aromatic polycarbonate by transesterification with bisphenol A. Among the methods for obtaining diaryl carbonate, a method for obtaining diaryl carbonate from dialkyl carbonate and recovering and recycling alkyl alcohol as a by-product is well known. There is a disadvantage that the aromatic polycarbonate is colored by a generated impurity or a cross-linking reaction is caused, and improvement has been desired.

[0003] On the other hand, as a method for obtaining a diaryl carbonate from phosgene, a number of methods are known for a reaction using a homogeneous catalyst or a heterogeneous catalyst. In these methods, for example, an aryl salicylate having a boiling point very close to that of the diaryl carbonate is used. However, problems such as recovery of the catalyst in the case of byproducts and homogeneous catalysts, and elution of metal components in the case of heterogeneous catalysts have not been solved. In the method using activated carbon as a catalyst, there is no problem of elution of metal components,
It does not have an industrially advantageous reaction rate.

It is also known that a diaryl carbonate can be obtained by reacting an aromatic monohydroxy compound with phosgene. 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 requires a relatively high temperature of 180 to 215 ° C. in order to obtain an economical reaction rate, which is not suitable for thermally unstable reaction. There is a risk of decomposition of the tetramethylammonium halide. In addition, phosgene is consumed at a much higher rate than required stoichiometrically.

In Japanese Patent Publication No. 50-50977, 1 mole of phosgene is added at a temperature of 40 to 180 ° C. to 2 moles of an aromatic monohydroxy compound (phenol) using an aromatic nitrogen-containing heterocyclic compound as a catalyst. A method for producing a diaryl carbonate (diphenyl carbonate) by performing a reaction accompanied by elimination of hydrogen chloride in a solvent, if necessary, at a lower temperature than the method described in the above-mentioned U.S. Patent, and It is disclosed that the reaction is performed at twice or more the reaction rate.

The method described in Japanese Patent Publication No. 50-50977 is industrially excellent for the above-mentioned reason. In this method, phenyl chloroformate, which is an intermediate product of diphenyl carbonate, and phenol are used. Since the rate of formation of diphenyl carbonate by the reaction is not sufficient compared to the rate of formation of phenyl chloroformate, a small amount of phenyl chloroformate remains with diphenyl carbonate at the end of the reaction. Such residual phenyl chloroformate adversely affects the aromatic polycarbonate as described above.

In order to industrially obtain a high-quality polycarbonate, a process for producing a high-purity diaryl carbonate containing no aryl chloroformate has been studied, and an aromatic monohydroxy compound and phosgene are converted to an aromatic nitrogen-containing heterocyclic compound catalyst. Wherein phosgene is reacted with 0.44 to 0.5 equivalents to 1 equivalent of the aromatic monohydroxy compound to convert unreacted diaryl carbonate and aryl chloroformate into 1 equivalent of the aromatic monohydroxy compound. An aryl monohydroxy compound is produced in an equivalent amount or less, and the reaction solution obtained in this step is subjected to a dehydrochlorination reaction between the aryl chloroformate and the aromatic monohydroxy compound to produce a diaryl carbonate. It has been found that this can be achieved through a stepwise reaction process (Japanese Unexamined Patent Publication No.
279714). The document also describes that hydrochloric acid produced as a by-product is reused in the plant, but does not describe the purpose of use. The present invention relates to this recycling, a closed cycle as a method for producing diaryl carbonate,
That is, the present invention provides an ideal process for utilizing by-produced hydrogen chloride as phosgene again.

In a method for producing a diaryl carbonate from an aromatic monohydroxy compound and phosgene using an aromatic nitrogen-containing heterocyclic compound as a catalyst, a high conversion is industrially advantageous and a diaryl carbonate is obtained from a dialkyl carbonate. Since there is no salicylic acid-based impurity as in the method and the separation from by-product monomers is easy, diaryl carbonate with extremely high purity can be obtained with high efficiency.

On the other hand, methods for converting hydrogen chloride into chlorine have been studied for many years, and in particular, an extremely large number of applications have been filed for an oxidation reaction using a chromium oxide catalyst (JP-B-6-15402, JP-B-5-15402). No.-3402, Tokuhei 5-
No. 3403, No. 5-3405, No. 5-340
No. 6, Japanese Patent Publication No. 5-69042, Japanese Patent Publication No. 6-17203
Recently, many applications have been filed for reactions using a ruthenium oxide catalyst (Japanese Patent Application Laid-Open No. 9-67).
No. 103, JP-A-10-194705, JP-A-10-194
182104, JP-A-10-338502, JP-A-11-180701, and JP-A-2000-34105. All of these documents describe a technique for converting hydrogen chloride into chlorine, and do not teach use of the converted chlorine, particularly conversion of phosgene to diaryl carbonate.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a diaryl carbonate from an aromatic monohydroxy compound and phosgene using an aromatic nitrogen-containing heterocyclic compound as a catalyst. It is an object of the present invention to provide a process for producing diaryl carbonate, converting hydrogen chloride produced as a by-product into chlorine, and then reusing it during the phosgene production process.

[0011]

Means for Solving the Problems The present inventors have determined the purity of hydrogen chloride required for the reaction for converting hydrogen chloride to chlorine, the purity of the obtained chlorine for use in the production of phosgene, and the purity of the obtained chlorine. As a result of intensive studies on the purity required for reacting the phosgene with the aromatic monohydroxy compound with the aromatic monohydroxy compound, and on the concentration of impurities generated in order to form a closed cycle process and the purging destination thereof, the present invention has been reached.

That is, the gist of the present invention resides in a method for producing a diaryl carbonate, comprising the following four steps. 1) An aromatic monohydroxy compound and phosgene are reacted at a reaction temperature of 80 ° C. in the presence of an aromatic nitrogen-containing heterocyclic compound catalyst.
A diaryl carbonate production process for obtaining a diaryl carbonate by condensation reaction at 180 ° C .; 2) a purification process for removing impurities from hydrogen chloride gas by-produced in the condensation reaction; 3) a phosgene production process from the purified hydrogen chloride gas A chlorine recovery step of obtaining a usable chlorine, and 4) a phosgene production step of reacting the recovered chlorine with carbon monoxide to obtain phosgene usable in a diaryl carbonate production step.

Further, another aspect of the present invention includes the following features. a) In the chlorine recovery step, 0.1 mol per 1 mol of hydrogen chloride is used.
A reaction temperature of 300 ° C to 500 ° C using oxygen of 25 mol or more.
The oxidation reaction of hydrogen chloride is carried out at ℃ in the presence of a chromium oxide catalyst. b) After removing hydrogen chloride and water from the crude chlorine gas obtained by the above oxidation reaction, it is compressed and liquefied to obtain chlorine that can be used in the phosgene production process, while recovering chlorine in the gas from unliquefied gas. Then, the recovered chlorine gas is circulated to the compressed liquefaction. c) The remaining oxygen-containing gas from which the chlorine has been recovered is partially discharged as waste gas, and the remainder is recycled to the oxidation reaction. d) In another chlorine recovery step, an aqueous solution of hydrogen chloride having a predetermined concentration, which is prepared by absorbing purified hydrogen chloride gas into water, is electrolyzed. e) After removing water from the crude chlorine gas obtained by the electrolysis, it is compressed and liquefied to obtain chlorine which can be used in the phosgene production step. At this time, a part of the circulating catholyte of the electrolytic cell is purified. Used for absorbing hydrogen chloride gas. f) In another chlorine recovery step, 0.25 mol or more of oxygen is used per 1 mol of hydrogen chloride, and the reaction temperature is 200
An oxidation reaction of hydrogen chloride is performed at ~ 400 ° C in the presence of a ruthenium oxide catalyst. g) Hydrogen chloride and water are removed from the crude chlorine gas obtained in the above oxidation reaction, and then compressed and liquefied to obtain chlorine that can be used in the phosgene production process, while unliquefied oxygen-containing gas partially contains It is discharged as waste gas and the remainder is recycled to the oxidation reaction. h) In the phosgene production step, the crude phosgene gas obtained by the reaction of chlorine and carbon monoxide is cooled and liquefied to obtain phosgene usable in the diaryl carbonate production step, while the unliquefied gas is obtained by completely decomposing phosgene. , Is discharged as waste gas.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Each step of the present invention can be represented by the following chemical formula.

Embedded image

(Where PhOH is phenol, PCF
Represents phenyl chloroformate, and DPC represents diphenyl carbonate. )

The details of the present invention are described below. 1) Catalyst for producing diaryl carbonate : The catalyst used for the condensation reaction between the aromatic monohydroxy compound and phosgene is an aromatic nitrogen-containing heterocyclic compound having a 6-membered or 5-membered skeleton. Hetero atoms other than nitrogen in the ring (sulfur, oxygen, or secondary nitrogen atoms)
May be included. Further, the heterocyclic group may be condensed with another aromatic heterocyclic group or an aromatic carbocyclic group.

An example of such a catalyst is as follows. Pyridine, quinoline, isoquinoline, picoline, acridine, pyrazine, pyrimidine, imidazole, 2-
Methylimidazole, 2-methoxypyridine and 2-hydroxypyridine, preferably pyridine, α-picoline, β, γ-mixed picoline, isoquinoline, 2-hydroxypyridine and imidazole. Further, the above-mentioned compound formed into a polymer such as polyvinyl pyridine can be used in the same manner.

The amount of the catalyst is preferably 0.1 to 10 mol%, more preferably 0.5 to 5 mol%, based on the aromatic monohydroxy compound as the substrate. Is preferred. Also, these catalysts rapidly change to the corresponding hydrochloride salts in the reaction mixture. Therefore, even when used in the reaction in the form of a hydrochloride, exactly the same reactivity and selectivity can be obtained. It is also possible to use a strong acid salt such as bromate, sulfate and nitrate. Weak acid salts such as formate, acetate, phosphate, caproate, and pivalate can be substituted because they easily change to hydrochloride during the reaction.

Aromatic monohydroxy compound: The aromatic monohydroxy compound used in the present invention includes, for example, phenol, cresol (isomer) and isopropylphenol (isomer), chlorophenol (isomer) and methoxyphenol Halogenated phenols such as (isomer) and alkoxyphenols are exemplified. Further, it is a heterocyclic monohydroxy compound having a 5- or 6-membered ring which may be condensed with or substituted by an aromatic cyclic group, for example, 4-hydroxyquinoline. In particular, phenol is preferably used.

Condensation reaction: An aromatic monohydroxy compound and phosgene are reacted in the presence of an aromatic nitrogen-containing heterocyclic compound catalyst at a reaction temperature of 80 to 180 ° C., preferably 120 to 1 ° C.
React at 60 ° C. If the reaction temperature is too high, the generation of by-products increases, and if it is too low, the reaction rate is too slow, which is not preferable. Usually, phosgene gas is introduced into a molten mixture of an aromatic monohydroxy compound and an aromatic nitrogen-containing heterocyclic compound catalyst while sufficiently stirring the mixture.

The amount of phosgene introduced is preferably 1 mol or less per 1 mol of the aromatic monohydroxy compound.
0.4-0.5 mol is more preferred. The stoichiometric amount is 0.5 mol, but by controlling the amount of phosgene introduced to a stoichiometric amount or less, an unreacted aromatic monohydroxy compound inevitably remains, and the reaction intermediate aryl chloro The reaction for forming a diaryl carbonate between the formate and the aromatic monohydroxy compound is accelerated, and a reaction mixture containing almost no arylchloroformate which has a bad influence on the production of a colorless polycarbonate can be obtained. At that time, if necessary, nitrogen gas is blown into the reaction mixture after the introduction of phosgene to remove hydrogen chloride, which is a by-product of the condensation reaction, out of the system, whereby the diaryl carbonate formation reaction can be further promoted. .

2) Purification step: hydrogen chloride : Hydrogen chloride gas by-produced in the condensation reaction between the aromatic monohydroxy compound and phosgene is not only an unreacted aromatic monohydroxy compound but also a bromo-substituted product or tetrachloride as impurities. It contains various organic impurities such as by-products such as carbon. Therefore, hydrogen chloride gas is used in the next chlorine recovery process.
It is necessary to remove these impurities in order to be able to use without trouble. As a method thereof, it is preferable that organic impurities are adsorbed and removed by contact with an adsorbent such as activated carbon. When activated carbon is used, if it is adsorbed and removed while passing through an activated carbon tower filled with activated carbon having a large pore volume, organic impurities can be almost completely removed, and purified hydrogen chloride gas of high purity can be obtained. The temperature of this adsorption treatment is preferably low, usually 80 ° C. or lower, preferably 1 ° C.
Perform at 0-40 ° C. The gas flow rate during the adsorption process is
Considering the adsorption efficiency, the lower is better, the SV (volume speed) is usually about several hundred / hr, preferably 200 / hr or less. Other methods for reducing the content of organic impurities include a liquefied distillation method, a washing method with a high boiling point solvent, a cryogenic separation method, and the like, and these methods can be used in combination.

3) Chlorine recovery step: Chlorine: Various means can be applied from the above purified hydrogen chloride gas to obtain chlorine that can be used in the next phosgene production step. A method based on an oxidation reaction using a catalyst and a method based on electrolysis are generally used. Recently, a method using a ruthenium oxide catalyst which can perform an oxidation reaction at a lower temperature with a smaller amount of a catalyst due to its high catalytic activity has been found. a) Oxidation reaction In the oxidation reaction of hydrogen chloride using a chromium oxide catalyst, purified hydrogen chloride gas and oxygen gas are reacted at a reaction temperature of 300 ° C.
It is carried out by contacting the solid catalyst at a temperature of up to 500 ° C., but the contact system may be any of a fixed bed, a fluidized bed and a moving bed. The ratio of hydrogen chloride and oxygen used for the oxidation reaction is
0.25 mol or more of oxygen is used per 1 mol of hydrogen chloride. If the amount of oxygen used is small, the catalyst cannot always be maintained under an oxygen atmosphere, and the catalytic activity is undesirably reduced. However, if the amount is too large, it is necessary to reinforce the facility for reusing excess oxygen, so that about 0.3 to 1 mol is usually sufficient. The crude chlorine gas obtained by the oxidation reaction contains unreacted hydrogen chloride and oxygen in addition to the water produced as a by-product of the oxidation reaction. Is subjected to sulfuric acid dehydration and then liquefied under compression to obtain purified high-purity liquefied chlorine that can be used in the phosgene production step. In actual use, this liquefied chlorine is evaporated and supplied as chlorine gas to the phosgene production process described later.
Since the unliquefied gas contains a significant amount of chlorine in addition to oxygen, it is usually absorbed in carbon tetrachloride to recover chlorine, or recovered by PSA separation. The recovered chlorine is circulated to the compressed liquefaction after being vaporized. On the other hand, the remaining oxygen-containing gas from which chlorine has been recovered is used to remove accompanying carbon tetrachloride by, for example, absorbing it into a sodium sulfite solution. , And the remainder is recycled to the oxidation reaction and reused. Since the oxidation reaction of hydrogen chloride using a ruthenium oxide catalyst has high activity, a method similar to the oxidation reaction using a chromium oxide catalyst described above can be employed except that the reaction temperature is set to 200 to 400 ° C.

B) Electrolysis The electrolysis of hydrogen chloride is carried out by electrolyzing an aqueous solution of hydrogen chloride having a predetermined concentration, which is prepared by absorbing purified hydrogen chloride gas into water. The concentration of hydrogen chloride in the aqueous solution of hydrogen chloride suitable for electrolysis is 10 to 40% by weight, preferably 15 to 30% by weight. If the concentration is too high, the conductivity decreases, the cell voltage increases, and the cell voltage is too low. In addition, the consumption of graphite anode and the amount of generated oxygen increase, which is not preferable. As a result of the electrolysis, crude hydrogen gas is collected at the cathode, and crude chlorine gas is collected at the anode. Since the crude chlorine gas generated in the anode chamber contains accompanying water and a small amount of hydrogen chloride, when this is cooled to condense and remove water, hydrogen chloride is also condensed and removed as dilute hydrochloric acid. After the water is removed, compression liquefaction yields liquefied chlorine that can be used in the phosgene production process. In actual use, this liquefied chlorine is evaporated and supplied as chlorine gas to the phosgene production process described later. The dilute hydrochloric acid is reused for preparing an aqueous solution of hydrogen chloride having a predetermined concentration as an electrolytic solution.

Since the crude hydrogen gas generated in the cathode chamber contains entrained water and a small amount of hydrogen chloride, when this is cooled to condense and remove water, part of the hydrogen chloride is also condensed and removed as dilute hydrochloric acid. Is done. The diluted hydrochloric acid is reused for preparing an aqueous solution of hydrogen chloride having a predetermined concentration as an electrolytic solution, while uncondensed hydrogen chloride is neutralized and removed to obtain a purified hydrogen gas. Thus, it is preferable that a part of the circulating catholyte in the electrolytic cell is used for absorbing the purified hydrogen chloride gas. The amount used is determined so as to achieve a predetermined concentration in consideration of the balance with the amounts of various types of hydrochloric acid used for preparing the aqueous hydrogen chloride solution.

4) Phosgene production step: phosgene: The reaction between the recovered chlorine and carbon monoxide is as follows:
Usually, a gas mixture of carbon monoxide and chlorine is passed through a column packed with activated carbon, thereby obtaining phosgene which can be used in a diaryl carbonate production process. As a result of the reaction, the highest temperature range is 300 ° C to 400 ° C.
, But the outlet gas temperature becomes 1 by external cooling with cooling water.
It is adjusted so as to be 00 ° C. or less. The crude phosgene gas obtained by the reaction is cooled to 0 ° C. or lower by a heat exchanger, condensed, and stored as liquefied phosgene that can be used in the diaryl carbonate production process. In actual use, the liquefied phosgene is evaporated and supplied as phosgene gas to the diaryl carbonate production step. Generally, it is often stored temporarily as liquefied phosgene, but without liquefaction,
The mixture containing the carbon monoxide gas is sent to the next diaryl carbonate production step, where the carbon monoxide gas can be treated as an off-gas. On the other hand, the unliquefied gas, after completely decomposing phosgene using, for example, an aqueous solution of caustic soda,
Released into the atmosphere as waste gas. In order to obtain phosgene with high purity, the reaction is always performed with the carbon monoxide / chlorine ratio being 1 or more, but in order to reduce the off-gas (improve the phosgene unit consumption), the ratio should be as close to 1 as possible. , Unreacted chlorine remains. As a purification method, it is desirable to perform adsorption removal using activated carbon. Other impurities include carbon tetrachloride, chloroform, and halides such as methylene chloride.These compounds are removed at the stage of phosgene distillation before being subjected to the reaction, or are mixed with the aromatic monohydroxy compound of the next step. A method is employed in which the by-product gas (hydrogen chloride) after the reaction is removed at the stage of purification.

Carbon monoxide: For producing phosgene, various methods have been known for a long time, such as a coke partial oxidation method, a methanol decomposition method and an LNG reforming method, for producing carbon monoxide which is reacted with chlorine. In any method, separation from carbon dioxide is inevitable, and carbon disulfide and carbonyl sulfide, which are partially contaminated, are converted to hydrogen sulfide with a Claus catalyst, and then desorbed and removed with caustic soda in a decarbonation and desulfurization tower for purification. . For a small amount of the remaining sulfur compound, there is a method of using zinc oxide to remove by adsorption.

[0028]

The present invention will be described by the following examples.
The present invention is not limited to the following examples. Example 1 Each step will be described with reference to FIG. CO Production Carbon dioxide gas (1) and oxygen gas (2) at a temperature of 20 ° C. were respectively supplied to a CO generating furnace (4) at 2.06 Nm ³ / hr.
Coke (3) 2.2 while supplying 13 Nm ³ / hr
3 kg / hr is burned, and crude CO gas (carbon monoxide: 6
5.2% by volume, carbon dioxide: 27.8% by volume, water: 7.
0% by volume, hydrogen: trace, COS: 1000 ppm,
Hydrogen sulfide: 500 ppm, carbon disulfide: 100 ppm,
Dust) was obtained at 5.28 Nm ³ / hr. Generator (4)
Was cooled with demineralized water because of high temperature, and the produced gas was adjusted to 250 ° C. The pressure of the generated gas is increased to 3500 mmAq by a blower, dust is removed by a filter (5), and then supplied to a Claus catalyst tower (6) to hydrolyze impurities COS and carbon disulfide to hydrogen sulfide. And air-cooled to 60 ° C. The resulting gas (carbon monoxide: 63.4% by volume,
Carbon dioxide: 27.0% by volume, water: 9.7% by volume, hydrogen: trace, COS: 10 ppm, hydrogen sulfide: 169
0 ppm) is sent to a decarboxylation desulfurization tower (7) and is brought into countercurrent contact with an aqueous potassium carbonate solution (8) to perform decarboxylation and desulfurization, and then a trace amount of a sulfur compound (COS: 10 ppm) remaining.
Was heated to 120 ° C. to adsorb and remove, and then supplied to a zinc oxide tower (9). The adsorption purified gas is cooled down to 40 ° C,
After the pressure was increased to 5.0 kg / cm ² G by a compressor (10), the purified CO gas (13) (carbon monoxide: 96.9% by volume, hydrogen) was passed through a decarbonation tower (11) and a dehydration tower (12). : 3.1% by volume, carbon dioxide: trace, water: trace) at 3.55 Nm ³ / hr.

Production of phosgene A mixed gas (chlorine: 99.8) of the above-mentioned purified CO gas (13), recovered chlorine gas (14) recovered from hydrogen chloride described later, and chlorine gas (15) generated by a salt electrolysis method. Volume%, oxygen: 0.2 volume%)
³ / hr, 3.33 Nm ³ / hr to the gas mixer,
The mixed gas was sent to the phosgene reactor (16).
The reactor (16) consisted of a column packed with granular activated carbon, and was a multitubular device capable of removing heat by cooling water to remove heat generated by the reaction. The reaction was performed at a pressure of 3.9 kg / cm.
^The adjustment was performed at ² G and a temperature of 70 ° C. 3.63 Nm ³
/ Hr crude phosgene gas (phosgene: 9
1.0% by volume, carbon monoxide: 5.1% by volume, hydrogen chloride:
1.7% by volume, hydrogen: 2.0% by volume, carbon dioxide: 0.1%
2% by volume) enter condenser (17) and -5
C., liquefied phosgene at 14.5 kg / hr and stored. The phosgene concentration in the storage tank (18) is 9
9.7 wt% or more, and hydrogen chloride is contained as an impurity in an amount of 0.1%.
A trace amount of 3 wt% of carbon tetrachloride was detected. After evaporation (19), the liquefied phosgene was used as purified phosgene gas (20) in the production of diphenyl carbonate. On the other hand, the residual gas leaving the condenser (17) (carbon monoxide: 52.3% by volume, phosgene: 12.1% by volume, hydrogen chloride: 11.2% by volume, hydrogen: 22.4% by volume, carbon dioxide : 1.9% by volume) is a sodium hydroxide aqueous solution (2%) at 0.33 Nm ³ / hr.
The phosgene was supplied to the circulating detoxification column 1), and after completely decomposing phosgene, the waste gas (22) was discharged to the atmosphere.

Production of diphenyl carbonate About 30.0 kg of molten phenol (23) at a temperature of 50 ° C.
/ Hr (0.319 kmol / hr) and the catalyst pyridine (24) at 0.757 kg / hr (0.00957 km
ol / hr), the temperature was raised to 150 ° C. while continuously supplying the first reactor (25). While sufficiently stirring, purified phosgene gas (20) (3.286 Nm ^{3 /} hr: 0.1467) corresponding to a 0.46 molar ratio of the supplied phenol.
kmol / hr) was continuously supplied to the first reactor (25). The reaction mixture flowing out of the first reactor was supplied to the second reactor (26) via an overflow pipe in a gas-liquid mixed phase. The second reactor is also adjusted to 150 ° C. with sufficient stirring, and the reaction solution is supplied to a degassing tower (27). In the degassing tower, a push-off reaction between phenylchloroformate and phenol, which are intermediates, is performed. To complete, countercurrent contact with nitrogen gas (28) was performed at 160 ° C. A reaction mixture (29) was obtained at a flow rate of 34.9 kg / hr from the bottom of the degassing column, and after the composition was sufficiently stabilized, the reaction mixture was analyzed by gas chromatography to find that diphenyl carbonate was 8%.
9.9% by weight was produced and almost 100% of the phosgene feed was converted to diphenyl carbonate. On the other hand, the reaction exhaust gas from the second reactor (26) and the nitrogen-containing exhaust gas from the degassing tower (27) are mixed, cooled in a condenser (30) in which SK oil circulates at about 40 ° C., and condensed. The liquid was returned to the second reactor (26) and the gas was further cooled to 10 ° C. with brine. 97.8% hydrogen chloride as the exhaust gas after cooling
In addition to 7% by weight, crude hydrogen chloride gas (32) containing 0.04% by weight of phenol, 2.09% by weight of nitrogen and a trace amount of carbon tetrachloride was supplied at about 10.59 kg / hr (6.54 N
m ³ / hr).

Chlorine Recovery The crude hydrogen chloride gas (32) by-produced in the production of diphenyl carbonate is fed into an activated carbon tower (33) filled with granular coal-based activated carbon at 30 ° C. at 10.59 kg / hr.
(Equivalent to SV = 500 / hr) to remove organic impurities such as phenol and carbon tetrachloride by adsorption. 2.04 kg / hr of oxygen gas (34) (oxygen: 99.6% by weight,
Nitrogen: 0.4% by weight) and 3.81 kg / hr of oxygen-containing circulating gas (35) from the abatement tower (47) described later (oxygen:
(65.9% by weight, nitrogen: 34.1% by weight) was fed into a heater so as to have a ratio of 0.5 mole of oxygen to 1 mole of the raw material hydrogen chloride, and 200 moles of heated steam. C. and fed to the fluidized bed reactor (36). The fluidized-bed reactor (36) is a cylindrical reactor made of Ni-lined having a diameter of about 0.15 m and a height of about 2 m, into which chromium nitrate is precipitated by aqueous ammonia, and converted into SiO _2. About 6.5 kg of a chromium oxide catalyst calcined by adding about 10 wt% of silica gel was used. The oxidation reaction was performed at 400 ° C.

Oxidation product gas (chlorine: 42.9% by weight, hydrogen chloride: 18.9% by weight, nitrogen: 9.3% by weight, oxygen:
17.9% by weight, water: 10.9% by weight)
At a flow rate of kg / hr, the mixture was fed into a chromium recovery / hydrogen chloride gas absorption tower (37) comprising a lower chromium recovery section and an upper hydrogen chloride gas absorption section. In the chromium recovery section, water is continuously sprinkled from the upper part, and the vaporized and scattered matter of hydrogen chloride and chromium as the main component of the catalyst are washed with water, and about 0.1% is continuously obtained from the lower part.
An 8% by weight aqueous chromium solution was taken out. The product gas that passed through the chromium recovery section was sent to a hydrogen chloride gas absorption section filled with a 1-inch Raschig ring, and water at 25 ° C. was supplied from above to perform countercurrent washing. The water was washed in the hydrogen chloride gas absorption part, and the hydrogen chloride gas in the gas was absorbed and removed.
° C product gas (chlorine: 60.5% by weight, nitrogen: 13.3%)
% By weight, oxygen: 25.7% by weight, water: 0.5% by weight, hydrogen chloride: trace) was cooled to 20 ° C. by a cooler and fed to a sulfuric acid washing tower (38) filled with a filler. Sent in.
In the sulfuric acid washing tower (38), 98% sulfuric acid was continuously supplied from above at a rate of 0.15 kg / hr together with circulating sulfuric acid to carry out countercurrent washing and dehydration of the produced gas.

The gas produced at 50 ° C. (chlorine: 60.9% by weight, nitrogen: 13.4% by weight, oxygen: 25.8% by weight) exiting the sulfuric acid washing tower (38) at 11.44 kg / hr is described later. Chlorine-containing circulating gas (39) from the evaporating solvent recovery tower (46)
After being compressed by being fed into a compressor (40), the mixture was cooled by a cooler (41) and supplied to a distillation column (42). In the distillation column, liquefied chlorine is distilled, impurities in the liquefied chlorine are distilled off from the top together with residual gas such as oxygen, and liquid chlorine (chlorine: 99.99% by weight, oxygen: 0.01 weight%)
Was taken out to the storage tank (43) at a flow rate of 6.96 kg / hr. After the chlorine was evaporated, it was recycled as a recovered chlorine gas (14) to the phosgene production process. On the other hand, unliquefied gas (chlorine: 42.3% by weight,
Nitrogen: 19.7% by weight, oxygen: 38.0% by weight) is sent to the absorption tower (45) to recover chlorine, and is returned from the solvent recovery tower (46) supplied from the upper part to be tetrachloride. Bring countercurrent contact with carbon. The carbon tetrachloride solution that has absorbed chlorine and is discharged from the absorption tower (45) is sent to the solvent recovery tower (46), where the chlorine is vaporized, whereby chlorine is recovered with a yield of almost 100%. did it. As described above, the chlorine-containing circulating gas (39) discharged from the top of the solvent recovery tower (46) is mixed with the product gas exiting the sulfuric acid washing tower (38), compressed and cooled, and then sent to the distillation tower (42). Supplied. On the other hand, gas not absorbed by carbon tetrachloride and discharged from the top of the absorption tower (45) (chlorine: trace, carbon tetrachloride: 0.2% by weight, nitrogen:
(34.1% by weight, oxygen: 65.8% by weight) is harmed with a sodium sulfite solution (48), and then 85% of the oxidized gas is used as an oxygen-containing circulating gas (35) to oxidize hydrogen chloride gas as described above. For use, it was recycled to the fluidized bed reactor, and the remainder was discharged to the atmosphere as waste gas (49).

Example 2 Example 1 was the same as Example 1 except that only the chlorine recovery step was changed as described below, ie, the chlorine recovery was carried out by electrolysis of an aqueous hydrogen chloride solution. Production of diphenyl carbonate was carried out in exactly the same manner as described above. As a result, almost 100% of phosgene was consumed, and a predetermined concentration (89.9% by weight) of diphenyl carbonate was obtained stably at 34.9 kg / hr.

Hereinafter, description will be made with reference to FIG. Chlorine recovery Crude hydrogen chloride gas by-produced by the production of diphenyl carbonate (hydrogen chloride: 97.87% by weight, phenol:
0.04% by weight, nitrogen: 2.09% by weight, carbon tetrachloride:
(Trace) was measured at 30.degree. C. at 10.59 kg / hr (SV = 500 / hr) in a column packed with granular coal-based activated carbon.
), And organic impurities such as phenol and carbon tetrachloride were adsorbed and removed. The hydrogen chloride gas from which organic substances have been completely removed is fed into an absorption tower (50), and water (51) supplied from the top of the tower and circulating catholyte (17% by weight) of an electrolytic cell supplied from the middle stage of the tower. Hydrochloric acid (28.0% by weight, water: 7%)
2.0% by weight) at a flow rate of 77.61 kg / hr. The gas not absorbed by the absorption tower (50) is sent to the abatement tower (52) and is abated by countercurrent contact with the aqueous caustic soda solution (53), and then the waste gas (54) is released into the atmosphere. Discharged.

The 28% by weight hydrochloric acid (55) generated in the absorption tower (50) is collected in a hydrochloric acid storage tank (56), of which 32% is condensed water in hydrogen gas (58) generated from the cathode and It was mixed with a part of the circulating catholyte (17% by weight hydrochloric acid), adjusted to 21% by weight hydrochloric acid, cooled to 60 ° C., and supplied to the cathode chamber (−) of the electrolytic cell (57). The remainder of 28% by weight hydrochloric acid was mixed with condensed water in the chlorine gas (64) generated at the anode and the circulating anolyte, and adjusted to 22% by weight hydrochloric acid.
C. and cooled and supplied to the anode chamber (+) of the electrolytic cell (57).
The electrolytic cell (57) is a cathode chamber (-) with a polyvinyl chloride diaphragm.
And an anode chamber (+), each having a graphite electrode, and a bipolar electrolytic cell having a transformer and a rectifier. 80 ° C., 4.15 kA / m ² , 1.95 V
The electrolysis was carried out.

Crude hydrogen gas (58) generated in the cathode chamber (hydrogen: 15.7% by weight, hydrogen chloride: 3.4% by weight, water: 8)
0.9% by weight) is cooled to 41 ° C. in a cooling tower (60). The dilute hydrochloric acid condensed at that time is 28% by weight as described above.
After mixing with hydrochloric acid and circulating catholyte, the mixture was supplied to the cathode compartment (-). The cooled hydrogen gas is sent to a neutralization tower (61) and neutralized with a caustic soda aqueous solution (62) to further remove accompanying hydrogen chloride, and purified hydrogen gas (63) (hydrogen: 98.5) Weight, water: 1.5% by weight) 0.29k
g / hr. Crude chlorine gas (64) (chlorine: 86.7% by weight, hydrogen chloride: 0.5% by weight, water: 12.7% by weight) generated in the anode chamber was passed through a cooling tower (66) to 41.
Cool to ° C. The dilute hydrochloric acid condensed at that time was mixed with 28% by weight hydrochloric acid and the circulating anolyte as described above, and then supplied to the anode chamber (+). The cooled chlorine gas was sent to a drying tower (67) in which concentrated sulfuric acid (68) was circulated in order to further remove accompanying water. The dried chlorine gas is pressurized and cooled by a compressor (69) and a condenser (70), and is liquefied and purified chlorine (71) (chlorine: 100.0% by weight).
Was taken out to a chlorine storage tank (72) at 10.0 kg / hr. After liquefied chlorine was vaporized in the evaporator (73), it was recycled to the phosgene production process as recovered chlorine gas (14).

Example 3 In Example 1, only the step of recovering chlorine among the following steps was changed as follows. That is, diphenyl carbonate was produced in exactly the same manner as in Example 1 except that the chlorine recovery by the oxidation reaction of hydrogen chloride using a ruthenium oxide catalyst was replaced. As a result, almost 100% of the phosgene is consumed and stably at a predetermined concentration (89.
94.9% by weight of diphenyl carbonate).
hr.

Hereinafter, description will be made with reference to FIG. Chlorine recovery Crude hydrogen chloride gas by-produced by the production of diphenyl carbonate (hydrogen chloride: 97.87% by weight, phenol:
0.04% by weight, nitrogen: 2.09% by weight, carbon tetrachloride:
(Trace) was measured at 30.degree. C. at 10.59 kg / hr (SV = 500 / hr) in a column packed with granular coal-based activated carbon.
), And organic impurities such as phenol and carbon tetrachloride were adsorbed and removed. Hydrogen chloride gas from which organic matter was completely removed was 2.27 kg / hr of oxygen gas (74) (oxygen:
99.6% by weight, nitrogen: 0.4% by weight) and an oxygen-containing circulating gas (75) to be described later were fed into a fixed-bed reactor (76) (77) composed of two continuous stages. . The fixed bed reactor was a multitubular reactor made of Ni lining, and filled with a titanium oxide-supported ruthenium oxide catalyst obtained by the following method. Catalyst preparation, a mixed solution consisting of ruthenium chloride aqueous solution and sodium hydroxide aqueous solution,
An aqueous urea solution is poured into an aqueous solution of titanium tetrachloride, heated, and the obtained white precipitate is dropped into a suspension of water.The black precipitate obtained after addition of nitric acid is washed, filtered, and calcined to form a powder. Thus, a ruthenium oxide catalyst supporting titanium oxide was obtained. The oxidation reaction is performed at 370 ° C. at 0.8 atm,
The step was performed at 280 ° C. The oxidation product gas in which about 95% of the hydrogen chloride has reacted is sent to a hydrogen chloride gas absorption tower (79) via a heat exchanger (78), where the unreacted hydrogen chloride and the generated water are washed with water, and the bottom of the tower is washed. About 17% hydrochloric acid aqueous solution (80) was recovered. The gas obtained from the top was subjected to countercurrent washing and dehydration with 98% sulfuric acid (82) in a dehydration column (81). The product gas (mixed gas of chlorine, oxygen, and nitrogen) after the dehydration is sent to a compressor (83) and cooled to −35 ° C. to obtain liquefied chlorine at 9.78 kg / hr. After evaporation in the exchanger (84), the recovered chlorine gas (14)
Recycled to the phosgene production process. On the other hand, the unliquefied gas passed through a storage tank (85) and a condenser (86), was partially neutralized, discharged to the atmosphere (87), and the remainder was recycled to the oxidation reaction.

[0040]

According to the process of the present invention, by converting hydrogen chloride by-produced in the process of producing diaryl carbonate to chlorine and then reusing it for phosgene production, it is possible to provide an ideal closed cycle process for producing diaryl carbonate. It is.

[Brief description of the drawings]

FIG. 1 is a flow sheet diagram showing all the steps of producing a diaryl carbonate.

FIG. 2 is a flow sheet diagram showing a chlorine recovery step.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carbon dioxide gas 2 Oxygen gas 3 Coke 4 CO generation furnace 5 Filter 6 Claus catalyst tower 7 Decarbonation desulfurization tower 8 Potassium carbonate aqueous solution 9 Zinc oxide tower 10 Compressor 11 Decarbonation tower 12 Dehydration tower 13 Pure CO gas 14 Recovery chlorine gas 15 Chlorine Gas 16 phosgene reactor 17 condenser 18 storage tank 19 evaporator 20 purified phosgene gas 21 caustic soda aqueous solution 22 waste gas 23 phenol 24 pyridine 25 first reactor 26 second reactor 27 degassing tower 28 nitrogen gas 29 reaction product 30 condenser 31 Condenser 32 Crude hydrogen chloride gas 33 Activated carbon tower 34 Oxygen gas 35 Oxygen-containing circulating gas 36 Fluidized bed reactor 37 Chromium recovery / hydrogen chloride gas absorption tower 38 Sulfuric acid washing tower 39 Chlorine-containing circulating gas 40 Compressor 41 Cooler 42 Distillation Tower 43 Storage tank 44 Evaporator 45 Absorption tower Reference Signs List 6 solvent recovery tower 47 abatement tower 48 sodium sulfite aqueous solution 49 waste gas 50 absorption tower 51 water 52 abatement tower 53 caustic soda aqueous solution 54 waste gas 55 hydrochloric acid 56 hydrochloric acid storage tank 57 electrolytic tank 58 crude hydrogen gas 59 catholyte storage tank 60 cooling tower 61 Neutralizing tower 62 Caustic soda aqueous solution 63 Purified hydrogen gas 64 Crude chlorine gas 65 Anolyte storage tank 66 Cooling tower 67 Drying tower 68 Concentrated sulfuric acid 69 Compressor 70 Condenser 71 Liquefied purified chlorine 72 Chlorine storage tank 73 Evaporator 74 Oxygen gas 75 Oxygen-containing circulating gas 76 Fixed bed reactor (first stage) 77 Fixed bed reactor (second stage) 78 Heat exchanger 79 Hydrogen chloride gas absorption tower 80 17% hydrochloric acid water 81 Dehydration tower 82 98% sulfuric acid 83 Compressor 84 Heat exchanger 85 Storage tank 86 Condenser 87 Purge gas

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4H006 AA02 AC13 AC48 AD10 BA51 BC10 BD34 BD51 BD52 BJ10 KA52 4H039 CA66 CD10

Claims (10)

[Claims] 1. A method for producing a diaryl carbonate, comprising the following four steps. 1) An aromatic monohydroxy compound and phosgene are reacted at a reaction temperature of 80 ° C. in the presence of an aromatic nitrogen-containing heterocyclic compound catalyst.
A diaryl carbonate production process for obtaining a diaryl carbonate by condensation reaction at 180 ° C .; 2) a purification process for removing impurities from hydrogen chloride gas by-produced in the condensation reaction; 3) a phosgene production process from the purified hydrogen chloride gas A chlorine recovery step of obtaining a usable chlorine, and 4) a phosgene production step of reacting the recovered chlorine with carbon monoxide to obtain phosgene usable in a diaryl carbonate production step. 2. In the chlorine recovery step, 0.25 mol or more of oxygen is used per 1 mol of hydrogen chloride, and the reaction temperature is 200 to
The method for producing a diaryl carbonate according to claim 1, wherein the oxidation reaction of hydrogen chloride is performed at 400 ° C in the presence of a ruthenium oxide catalyst. 3. The crude chlorine gas obtained by the oxidation reaction is subjected to removal of hydrogen chloride and water, and then compressed and liquefied to obtain chlorine which can be used in the phosgene production step. The method according to claim 2, wherein the part is discharged as waste gas and the remainder is recycled to the oxidation reaction. 4. In the chlorine recovery step, 0.25 mol or more of oxygen is used per 1 mol of hydrogen chloride at a reaction temperature of 300 ° C.
The method for producing a diaryl carbonate according to claim 1, wherein the oxidation reaction of hydrogen chloride is carried out at a temperature of up to 500 ° C in the presence of a chromium oxide catalyst. 5. A crude chlorine gas obtained by an oxidation reaction, wherein hydrogen chloride and water are removed, and then compressed and liquefied to obtain chlorine which can be used in a phosgene production process. 5. The method for producing a diaryl carbonate according to claim 4, wherein the recovered chlorine gas is circulated to the compressed liquefaction. 6. The method for producing a diaryl carbonate according to claim 5, wherein the remaining oxygen-containing gas from which chlorine has been recovered is partially discharged as waste gas, and the remainder is recycled to the oxidation reaction. 7. The diaryl carbonate according to claim 1, wherein in the chlorine recovery step, an aqueous solution of hydrogen chloride having a predetermined concentration, which is prepared by absorbing purified hydrogen chloride gas into water, is electrolyzed. Production method. 8. After removing water from the crude chlorine gas obtained by the electrolysis, it is compressed and liquefied to obtain chlorine which can be used in the phosgene production step. The method for producing a diaryl carbonate according to claim 7, wherein the method is used for absorbing purified hydrogen chloride gas. 9. In the phosgene production step, crude phosgene gas obtained by the reaction of chlorine and carbon monoxide is cooled and liquefied to obtain phosgene which can be used in the diaryl carbonate production step.
The method for producing a diaryl carbonate according to any one of claims 1 to 8, wherein the unliquefied gas is exhausted as waste gas after completely decomposing phosgene. 10. A method for producing an aromatic polycarbonate, comprising reacting a diaryl carbonate obtained by the method according to any one of claims 1 to 9 with a dihydroxy compound.