JPH09169704A - Production of diaryl carbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously obtain the subject compound in a high production rate, while reducing the deterioration of a catalyst used herein and the loss of the product in post treating processes. SOLUTION: This method for producing the diaryl carbonate comprises reacting a dialkyl carbonate of the formula: R<1> OCO2 R<2> (R<1> , R<2> are each an alkyl) (e.g. dimethyl carbonate) with an aromatic hydroxy compound of the formula: ArOH (Ar is an aryl) in the presence of a catalyst to produce an alkylaryl carbonate and the diaryl carbonate, preliminarily distilling the reaction product solution to separate a catalyst-containing solution (a catalyst concentration of 10-99wt.%), separating the residual reaction solution into low boiling point components and high boiling point components by a distillation operation, and further distilling the high boiling point components. The catalyst used herein includes AlX3 (X is a halogen, an acetoxy, etc.), TiX4 , VOX3 , ZnX2 , FeX3 , and SnR4- NXN (N is an integer of 1-3).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a diaryl carbonate, and more particularly to a method for efficiently producing a diaryl carbonate from a dialkyl carbonate and an aromatic hydroxy compound. Diaryl carbonate as various chemical raw materials,
In particular, it is a very useful compound as a raw material for polycarbonate.

[0002]

2. Description of the Related Art It is well known that a dialkyl carbonate is reacted with an aromatic hydroxy compound to produce a diaryl carbonate, and these reaction formulas are represented by the following formulas.

[0003]

[Chemical 1]

Although these reactions are equilibrium reactions, in particular, the reactions of the formulas (1) and (2) are very largely biased toward the original system and the reaction rate is not fast. Was industrially produced with great difficulty. Several proposals have been made to improve this. In other words, it is mainly related to the reaction system such as catalyst development for increasing the reaction rate, reactive distillation method, continuous multi-stage distillation method, use of vertical reaction tank, etc., and the focus is on improving the reaction rate, conversion rate and yield. It was being done. However, the post-treatment process such as separation/recovery of raw materials and catalysts has hardly been regarded as a problem.

The catalyst used in this reaction system is usually dissolved in the reaction solution under the reaction conditions and has a higher boiling point than that of the diaryl carbonate. Therefore, in order to obtain a high-purity diaryl carbonate from the reaction product solution. For this purpose, a method of first removing the low boiling point component from the reaction solution by distillation and then separating the diaryl carbonate and the catalyst by distillation is usually considered.

Therefore, in order to reduce the manufacturing cost,
The key points are efficient separation/recovery of the catalyst, reduction of loss in the post-treatment process of the product diaryl carbonate, and reduction of equipment cost/utility cost due to high temperature/high pressure/high vacuum. As a method for separating the catalyst and the diaryl carbonate by a method other than distillation, for example, a reaction solution containing the catalyst is heated at 120° C.
Below, there is a method of cooling to separate the catalyst-containing material (JP-A-6-9506). In this method, the reaction product liquid after cooling and separating the catalyst has to be heated again in order to distill away the product diaryl carbonate,
The heat efficiency is poor. Therefore, as a method for separating the catalyst and the diaryl carbonate, the general distillation operation is the most efficient overall. Since the boiling point of diaryl carbonate is as high as 300°C or higher, and the vapor pressure of the catalyst is lower than that of diaryl carbonate, in order to suppress thermal decomposition, alteration, and heaviness due to high temperature, a considerably high vacuum distillation of about several Torr is performed. There is a need. Although the temperature and pressure conditions vary depending on the type and concentration of the catalyst, for example, using Ti(OC ₆ H ₅ ) ₄ which is one of the typical catalysts of this reaction,
When the pressure is 20 Torr and the catalyst concentration is 70% by weight, the liquid temperature reaches about 250°C. In the case of the (C ₄ H ₉ ) ₂ SnO catalyst, the liquid temperature reaches about 240° C. under the same conditions. It was found that at such a high temperature, deterioration due to thermal decomposition of the catalyst, deterioration of the diaryl carbonate of the product, and loss due to heaviness are likely to occur, and the by-product thereof also has an adverse effect on the catalytic activity. In order to lower the temperature, there are methods of increasing the degree of vacuum and lowering the catalyst concentration. In the case of carrying out, the degree of pressure reduction of 20 to 30 Torr or less is required, and therefore the equipment cost greatly increases. If you do
A large amount of diaryl carbonate is extracted together with the catalyst and recycled to the reaction system, and more raw materials are required to produce a predetermined amount of diaryl carbonate. Further, if the catalyst concentration in the reaction section is lowered, a sufficient reaction rate cannot be obtained.

[0007]

The present invention has been made from the above viewpoint, and can be obtained continuously from dialkyl carbonate and aromatic hydroxy compound in a high yield,
Moreover, it is an object of the present invention to provide a method for producing a diaryl carbonate capable of reducing catalyst deterioration and loss of a target product in a post-treatment step.

[0008]

As a result of earnest studies, the present inventors have found that by incorporating a step of separating a raw material and a product from a catalyst by preliminary distillation after the reaction step,
The inventors have completed the present invention by finding that the objects of the above invention can be effectively achieved. That is, the present invention provides a method for producing a diaryl carbonate by reacting a dialkyl carbonate with an aromatic hydroxy compound, wherein the production is carried out by the following steps. [Step 1]: Dialkyl carbonate and aromatic hydroxy compound are reacted in the presence of a catalyst to obtain alkyl aryl carbonate or diaryl carbonate, and dialkyl carbonate as a raw material, aromatic hydroxy compound, generated alkyl aryl carbonate, diaryl carbonate, and A step of extracting a reaction product liquid containing a catalyst, [step 2]: from the reaction product liquid extracted from step 1,
A step of separating the catalyst-containing liquid by preliminary distillation and supplying the remaining reaction product liquid to the next step 3, [step 3]: diluting the reaction product liquid from step 2 mainly by a dialkyl carbonate, an aromatic hydroxy compound, And a step of separating a low-boiling-point component consisting of alkylaryl carbonate and a high-boiling-point component mainly consisting of diaryl carbonate and a catalyst, and [Step 4]: further distilling the high-boiling point component from Step 3 to contain a diaryl carbonate and a catalyst. The process of separating into liquid.

[0009]

[In the formula, R ¹ and R ² each represent an alkyl group, and they may be the same or different from each other. ]

The alkyl group represented by R ¹ and R ² is linear,
It may be branched or cyclic, and particularly has 1 carbon atom.
Those of 10 are preferable. Specific examples thereof include methyl group, ethyl group, n-propyl group, isopropyl group, n-
Examples thereof include a butyl group, isobutyl group, sec-butyl group, t-butyl group, n-pentyl group, isopentyl group, n-hexyl group and isohexyl group.

Specific examples of the dialkyl carbonate represented by the above formula (4) include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, dipentyl carbonate, dihexyl carbonate, dicyclohexyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, Methyl butyl carbonate, ethyl propyl carbonate,
Examples thereof include ethyl butyl carbonate and propyl butyl carbonate, and among these, dimethyl carbonate is particularly preferable.

The aromatic hydroxy compound which is another reaction raw material in the method of the present invention is represented by the following formula (5). ArOH (5) [In the formula, Ar represents an aryl group having or not having a substituent. Such Ar represents an aryl group such as a phenyl group or a naphthyl group, and an appropriate substituent may be introduced into the aryl group. Here, as the substituent, for example, a halogen atom such as a chlorine atom or a bromine atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group,
An alkyl group having 1 to 6 carbon atoms such as an isobutyl group, a sec-butyl group, a t-butyl group, a methoxy group, an ethoxy group,
Examples thereof include an alkoxy group having 1 to 6 carbon atoms such as an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group and a t-butoxy group, a nitro group and a cyano group. One of these substituents may be introduced, or two or more thereof may be introduced.

Specific examples of the aromatic hydroxy compound represented by the above formula (5) include phenol, α-naphthol, β-naphthol, various cresols, various chlorophenols, various ethylphenols, various n-propylphenols, various types. Examples include isopropylphenol, various butylphenols, various methoxyphenols, various ethoxyphenols, various n-propoxyphenols, various isopropoxyphenols, various butoxyphenols, various nitrophenols, various cyanophenols, various xylenols, and the like. Is preferred.

As the catalyst used in the present invention, any catalyst may be used as long as it accelerates the reaction for producing an alkylaryl carbonate from a dialkyl carbonate and an aromatic hydroxy compound and a diaryl carbonate from the alkylaryl carbonate. You can For example, (C ₄ H ₉ ) ₂ SnO, (C ₆ H ₅ )
_{2 SnO, (C 4 H 9} ) 2 Sn (OC 6 H 5) 2, (C
_{4 H 9) 2 Sn (OCH} 3) 2, (C 4 H 9) 2 Sn
_{(OC 2 H 5) 2,} (C 4 H 9) 2 Sn (OC 6 H 5)
Organotin compounds such as O(OC ₆ H ₅ )Sn(C ₄ H ₉ ) ₂ ; PbO, Pb(OC ₆ H ₅ ) ₂ , Pb(OCOCH
₃ ) ₂ etc. lead compounds; Zr(acac) ₄ , ZrO ₂ etc. zirconium compounds; AlX ₃ , TiX ₄ , VO
X ₃ , VX ₅ , ZnX ₂ , FeX ₃ , SnR _4-N X
Examples thereof include Lewis acids such as _N (where X represents a halogen atom, an acetoxy group, an alkoxy group, and an aryloxy group, and N represents an integer of 1 to 3). Among these, Ti(OCH ₃ ) ₄ and Ti(OC ₂ H ₅ ) ₄ are particularly preferable.
Such as titanium tetraalkoxide, titanium tetraphenoxide, (C ₄ H ₉ ) ₂ Sn(OC ₆ H ₅ ) ₂ , (C ₄ H
₉ ) Dialkyltin compounds such as ₂ Sn(OCH ₃ ) ₂ .

In the present invention, the diaryl carbonate is, as shown below, a reaction step (step 1), a catalyst pre-separation step (2), a raw material recovery step (3), a product purification step.
It is produced by a process comprising a catalyst separation step (4). (Step 1) Reaction Step The reaction method may be either a batch method or a continuous method, but a solution containing by-products alkanol and dialkyl carbonate is sequentially withdrawn from the top of the tower, and a liquid containing the product from the bottom of the tower. The reaction is performed while extracting the so-called
It is efficient to use the reactive distillation method. Specifically, a two-stage method in which a reaction vessel equipped with a distillation column is used in the front and rear stages is preferable.

The reaction temperature varies depending on the kind of raw material used, but is usually 100 to 230° C., preferably 1
It is carried out in the range of 50 to 230°C. When the temperature is lower than 100°C, the reaction rate is slow and the reaction equilibrium is further biased toward the raw material system side, which is not preferable. It is not preferable because the catalyst is likely to deteriorate.

The reaction pressure may be reduced pressure, normal pressure or increased pressure, although it varies depending on the type of raw material used, reaction temperature, raw material composition, type of catalyst and catalyst concentration, and is usually 0.1 to 10 atm. .. The residence time of the reaction liquid in the reaction tank is usually 0.1 to 10 hours.
If it is less than 0.1 hours, the reaction does not proceed sufficiently, and if it is more than 10 hours, side reactions occur simultaneously, and the selectivity of the target compound decreases, which is not preferable.

Regarding the charging ratio of the raw materials, the aromatic hydroxy compound/dialkyl carbonate (molar ratio) is usually 0.01 to 100, preferably 0.1 to 50, including the recycling amount. If the molar ratio is too large,
If it is too small, the yields of alkylaryl carbonate and diaryl carbonate are low, and a large amount of unreacted raw material is recycled, which is inefficient.

The amount of catalyst used depends on the activity of the catalyst used.
Although it is different, the raw material to be supplied to the reaction tank is dialkyl carbonate.
Normally 1x for bonbonate (including recycled)
10 ^-Four~ 5 times the molar amount. Preferably 1×10^-3~ 1
It is twice the mole. 1 x 10^-FourIf the amount is less than twice the mole, the reaction speed
It is slow and inefficient. If the molar ratio exceeds 5 times,
It is preferable because the amount of by-products such as rukyryl aryl ether increases.
Not good. When converted to the catalyst concentration in the reaction solution, it is usually
0.01-20% by weight, preferably 0.1-10%
%.

(Step 2) Catalyst Preliminary Separation Step In the step 2, preliminary distillation such as flash distillation is carried out under the conditions of a pressure of 20 Torr to 1 atm and a tower bottom temperature of 150 to 230° C. In the step of separating the catalyst, the catalyst concentration of the separated catalyst-containing liquid is usually 10 to 9
The content is 9% by weight, preferably 30 to 98% by weight, more preferably 50 to 95% by weight. If it is less than 10% by weight, a large amount of diaryl carbonate is extracted together with the catalyst, resulting in poor efficiency. If it exceeds 99% by weight, the amount of catalyst separated from the reaction solution is extremely small and the effect of preliminary separation is reduced. .. The reaction product liquid from which the catalyst-containing liquid has been separated is subjected to the next step 3, and it is preferable from the viewpoint of efficiency that a part or all of the separated catalyst liquid is recycled to step 1. In addition, the reaction liquid supplied to the step 3 has a total amount of dialkyl carbonate, aromatic hydroxy compound, alkylaryl carbonate and diaryl carbonate of 50.
˜99% by weight.

(Step 3) Raw Material Recovery Step In the step 3, a liquid containing a dialkyl carbonate as a raw material, an aromatic hydroxy compound and an alkylaryl carbonate as an intermediate product (low boiling point component) is used by using a distillation column (raw material recovery column). ) Is distilled from the top of the column, and a liquid (high boiling point component) containing the diaryl carbonate and the catalyst is extracted from the bottom of the column and separated.

The bottom temperature of the raw material recovery tower is usually 100 to 23.
The pressure in the tower is 0° C., and the pressure in the tower is usually reduced pressure (20 Torr) to increased pressure (10 atm). The low boiling point component from step 3 is
For efficiency, some or all of them are recycled to step 1. The high boiling point component is supplied to step 4, and the catalyst concentration of the high boiling point component is usually 0.1 to 30% by weight. If it is less than 0.1% by weight, diaryl carbonate cannot be sufficiently distilled out in the step 2 and the efficiency is poor. When it exceeds 30% by weight, the degree of reduced pressure (about 2
In order to separate the catalyst from the diaryl carbonate at 0 Torr), a high column bottom temperature (230° C. or higher) is required. Along with this, deterioration of the diaryl carbonate and deterioration of the catalyst occur, which is not preferable.

(Step 4) Product Refining/Catalyst Separation Step In the step 4, a distillation column (product column) is used to distill the target diaryl carbonate from the top, and a solvent amount of diaryl carbonate is contained from the bottom. This is a step of extracting the catalyst-containing liquid. The bottom temperature of the product tower is usually 230°C or lower. If the temperature exceeds 230°C, alteration of the diaryl carbonate and deterioration of the catalyst may occur, which is not preferable.

The quality of the diaryl carbonate distilled out is such that the content of the entrained catalyst is 1 ppm by weight or less. When the amount of the catalyst is more than 1 ppm by weight, coloring of the product and deterioration of the quality of the polycarbonate using this as a raw material are caused, which is not preferable. The catalyst-containing liquid from the bottom of the step 4 is partially or entirely recycled to the step 1 for efficiency.

The type of the distillation column used in the steps 1, 3, and 4 may be any general distillation apparatus such as a packed column or a plate column. Further, the number of plates (theoretical plate number in the case of a packed column, the number of plate plates in the case of a plate column) is usually 3 to 50. The reflux ratio is usually in the range of 0.1 to 10.
If it is too small, the separation performance deteriorates, and if it is too large, the required heat energy becomes excessive, which is not preferable.

In this way, the diaryl carbonate is obtained in high yield. When dimethyl carbonate and phenol are used as raw materials, diphenyl carbonate is obtained.

[0026]

[Reference example]

(Activity evaluation) In a 200 ml three-necked flask equipped with a cooling tube, 0.10 mmol of tetraphenoxytitanium was charged as a catalyst, 1.0 mol of phenol was further charged, and the mixture was immersed in an oil bath at 170° C. and then dimethyl carbonate. Was added to start the reaction. The reaction liquid in the flask was sampled at a predetermined time interval, and the liquid composition was analyzed by gas chromatography. The catalytic activity was evaluated from the production rate of methylphenyl carbonate at the initial stage of the reaction. As a result, the initial methylphenyl carbonate production rate was 0.12 mmol/min.

Comparative Example 1 A distillation column packed in the upper part of the (pre-reaction stage) (column diameter: 1 inch, column height: 5)
In a 2 liter autoclave (reaction tank) made of SUS equipped with dimethyl carbonate, phenol and tetraphenoxytitanium (molar ratio 1:2:0.01) at a rate of 0.52 kg/hr. The liquid was supplied while controlling the liquid volume in the reaction tank to 0.50 liter, and the reaction was carried out under the conditions of a temperature of 191° C. and a pressure of 1.7 kg/cm ² . The catalyst concentration in the reaction solution was 2.6% by weight. From the top of the distillation column, a low boiling point component containing methanol, dimethyl carbonate and phenol was added at a reflux ratio of 1,0.2.
It was continuously withdrawn at a rate of 2 kg/hr. On the other hand, 7.2% by weight of methylphenyl carbonate from the bottom of the reaction tank
(22 g/hr), 0.30 kg/h of a product liquid containing 0.1% by weight of diphenyl carbonate (0.4 g/hr)
It was continuously extracted at a rate of r and supplied to the reaction tank at the subsequent stage.

(Post-reaction) The reaction liquid of the same type as that of the reaction front stage is supplied with the product liquid of the front stage at a rate of 0.30 kg/hr while controlling the liquid volume in the reaction tank to 0.50 liter,
The reaction was carried out under the conditions of a temperature of 190° C. and a pressure of 1.1 kg/cm ² . From the top of the distillation column, a low boiling point component containing methanol, dimethyl carbonate and phenol was added at a reflux ratio of 1,
It was continuously extracted at a rate of 0.22 kg/hr. On the other hand, from the bottom of the reaction tank, methyl phenyl carbonate 5.8
Wt% (4.7 g/hr), diphenyl carbonate 2
A product liquid containing 5% by weight (20 g/hr) and 9.6% by weight of tetraphenoxytitanium (7.8 g/hr) was continuously withdrawn at a rate of 0.081 kg/hr.

(Catalyst recovery): In the case where pre-distillation was not carried out, a packed column having a height of 10 cm and a reflux valve were attached 20.
A 0 ml flask was charged with 0.1 liter of the product solution extracted from the bottom of the reaction tank at the latter stage of the reaction, and batch type vacuum distillation was carried out. The diphenyl carbonate/tetraphenoxytitanium (weight ratio) in the charged product liquid was 2.6. Dimethyl carbonate, phenol, methylphenyl carbonate, diphenyl carbonate and the like were distilled off while gradually raising the liquid temperature in the flask under the conditions of a vacuum degree of 20 Torr and a reflux ratio of 1. Internal temperature is 25
When the temperature reached 0°C, the distillation was stopped and the composition of the residual liquid in the flask was analyzed. The diphenyl carbonate/tetraphenoxytitanium (weight ratio) in the residual liquid was 0.5. In addition, by-products such as phenyl salicylate are 0.4% by weight (gas chromatographic analysis) with respect to the amount of raw material charged, and the molecular weight is 50
0.09 wt% of heavy substances of 0 or more (GPC analysis) was produced. 0.01 mmol of the catalyst remaining in the flask was sampled, and the activity was evaluated in the same manner as in Reference Example. as a result,
The initial methylphenyl carbonate production rate was 0.07 mmol/min, and the activity was significantly deteriorated as compared with the reference example.

Example 1 (Catalyst Recovery): When Preliminary Distillation was Performed The product liquid after the reaction of Comparative Example 1 was heated to 200° C. and continuously fed to a 1-liter SUS flash drum for flashing. Distillation was performed. The pressure inside the flash drum was controlled to maintain a pressure of 20 Torr. When the liquid extracted from the bottom of the flash drum was analyzed for composition, diphenyl carbonate/tetraphenoxytitanium (weight ratio) was 0.04, and the catalyst concentration was 95% by weight. The catalyst recovery rate (catalyst amount extracted from bottom/catalyst amount supplied) was 79%. In addition, by-products such as phenyl salicylate are 0.0
1% by weight (gas chromatographic analysis) and 0.02% by weight (GPC analysis) of heavy substances having a molecular weight of 500 or more were produced. 5-20T of the fraction extracted from the upper part of the flash drum
Diphenyl carbonate was fractionally distilled under the conditions of an orr and a column bottom temperature of 150 to 230° C. to fractionally fractionate the jephenyl carbonate, and the titanium concentration therein was measured to be 1 ppm by weight or less.

0.10 mmol of the catalyst extracted from the bottom of the flash drum was sampled, and the activity was evaluated in the same manner as in Reference Example. As a result, the initial methylphenyl carbonate production rate was 0.12 mmol/min, and no activity deterioration was observed as compared with the reference example.

[0032]

Industrial Applicability According to the present invention, a diaryl carbonate and an aromatic hydroxy compound can be used as raw materials to continuously obtain a diaryl carbonate in a high yield, and catalyst deterioration and loss of a target product in a post-treatment process can be prevented. It can be reduced.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01J 27/138 B01J 27/138 X 31/04 31/04 X C07C 68/06 C07C 68/06 Z // C07B 61/00 300 C07B 61/00 300 (72) Inventor Nobuo Fujikawa 1280, Kamizumi, Sodegaura-shi, Chiba Idemitsu Kosan Co., Ltd.

Claims (5)

[Claims] 1. A method for producing a diaryl carbonate by reacting a dialkyl carbonate with an aromatic hydroxy compound, wherein the production is carried out by the following steps. [Step 1]: A dialkyl carbonate and an aromatic hydroxy compound are reacted in the presence of a catalyst to obtain an alkylaryl carbonate and a diaryl carbonate, and a raw material dialkyl carbonate, an aromatic hydroxy compound, the produced alkylaryl carbonate, a diaryl carbonate, and A step of extracting a reaction product liquid containing a catalyst, [step 2]: from the reaction product liquid extracted from step 1,
A step of separating the catalyst-containing liquid by preliminary distillation and supplying the remaining reaction product liquid to the next step 3, [step 3]: diluting the reaction product liquid from step 2 mainly by a dialkyl carbonate, an aromatic hydroxy compound, And a step of separating a low-boiling-point component consisting of alkylaryl carbonate and a high-boiling-point component mainly consisting of diaryl carbonate and a catalyst, and [Step 4]: further distilling the high-boiling point component from Step 3 to contain a diaryl carbonate and a catalyst. The process of separating into liquid. 2. The method for producing a diaryl carbonate according to claim 1, wherein the catalyst-containing liquid separated from the step 2 has a catalyst concentration of 10 to 99% by weight. 3. The method for producing a diaryl carbonate according to claim 1, wherein a part or all of the catalyst-containing liquid separated from step 2 is recycled to step 1. 4. The catalyst is AlX ₃ , TiX ₄ , VOX ₃ ,
VX ₅ , ZnX ₂ , FeX ₃ and SnR _4-N X _N (where X is a halogen atom, an acetoxy group, an alkoxy group,
The method for producing a diaryl carbonate according to claim 1, wherein the diaryl carbonate is at least one selected from a Lewis acid represented by an aryloxy group and N is an integer of 1 to 3. 5. 5. The method for producing a diaryl carbonate according to claim 1, wherein the catalyst is titanium tetraalkoxide or titanium tetraphenoxide.