JPH06263694A - Production of diarylcarbonate - Google Patents

Abstract

PURPOSE:To industrially advantageously obtain the subject compound useful as a raw material for polycarbonates, etc., by reacting a dialkyl carbonatye with an aromatic hydroxy compoud in a multistage continuous reaction system comprising plural reaction tanks connected to each other in series and equipped with distillation towers, respectively. CONSTITUTION:A dialkyl carbonate and an aromatic hydroxy compound are continuously fed into the first multistage continuous reaction system comprising plural reaction tanks 1-5 arranged in series and equipped with distillation towers 14, respectively, brought into contact with a catalyst in each reaction tank and reacted with each other. The produced alcohol is continuously discharged from the tops of the distillation towers to the outside through a pipe 9. The reaction product is also continuously discharged from the final reaction tank 5 in a liquid state, continuously charged into the second multistage reaction system comprising reaction tanks 10, 11 arranged in series and equipped with distillation towers, respectively, and brought into contact with a catalyst in each reaction tank. The produced low boiling compounds such as dialkyl carbonate are discharged from the tops of the distillation towers through the line 12 to the outside, and high boiling compounds containing the product are discharged through a pipe 13 to afford the objective diallyl carbonate in a high yield.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a diaryl carbonate. More specifically, it relates to a method for efficiently producing a diaryl carbonate from a dialkyl carbonate and an aromatic hydroxy compound. Diaryl carbonate is a very useful compound as various chemical raw materials, especially as a raw material for polycarbonate.

[0002]

BACKGROUND OF THE INVENTION It is well known to react an alkylhydroxycarbonate with an aromatic hydroxy compound to produce an alkylaryl carbonate, and further a diaryl carbonate or a mixture thereof, and these reactions are represented by the following formula. .

[0003]

[Chemical 1]

However, it is known that these reactions are equilibrium reactions, and in particular, the reactions of the formulas (1) and (2) are very largely biased toward the original system. Also, the reaction speed is not fast. On the other hand, the reaction of the formula (3) has both equilibrium and kinetic advantages over the reactions of the above two formulas. Therefore, it is extremely difficult to produce a diaryl carbonate by these reactions, and some proposals have been made as a method for solving it.

As a method for increasing the reaction rate, there is a method for developing a highly active catalyst. In the reaction of the formula (1), for example, a Lewis acid such as Ti or Al or a compound capable of forming a Lewis acid (JP-A-51-105032, JP-A-56-123948 and JP-A-56-123949) , Tin compounds such as organic tin alkoxide and organic tin oxide (JP-A-54-48733)
JP-A-54-63023, JP-A-60-169444, JP-A-60-
19445, JP-A-62-277345 and JP-A-1-265063), salts or alkoxides of alkali metal or alkaline earth metal (JP-A-56-25138), lead compounds (JP-A-56-25138). 57-176932), complexes of metals such as copper, iron and zirconium (JP-A-57-183745), titanic acid esters (JP-A-58-185536), Lewis acids and proton acids. Mixture (JP-A-60-173016), S
Compounds such as c, Mo, Mn, Bi, Te, etc.
265064), ferric acetate (JP-A 61-172852), aluminum metal (JP-A 4-7035), aluminate compound (JP-A 4-122451), etc. is there. Regarding the reaction of formula (3), Ti and A
Lewis acid or a compound capable of forming a Lewis acid (JP-A-51-75044), a polymeric tin compound (JP-A-60-169444), a general formula RX (═O) OH (R
Is an organic residue, X is a compound represented by Sn or Ti) (JP-A-60-169445), a mixture of a Lewis acid and a protonic acid (JP-A-60-173016), and a lead catalyst (JP-A-60-173016). 1-9
3560), titanium and zirconium compounds (JP-A-1-
265063), compounds such as Sc, Mo, Mn, Bi, Te (Japanese Patent Laid-Open No. 1-265064) and the like are used. However, there was no case where the reaction rate was greatly improved and the diaryl carbonate was produced in a high yield. That is, it is important to improve the reaction rate by improving the activity of the catalyst, but it can be said that the study on the reaction equilibrium was insufficient.

In an attempt to transfer the equilibrium to the production system as much as possible, a method of distilling off the alcohol produced as a by-product with an azeotropic agent (Japanese Patent Laid-Open Nos. 54-48732 and 61-291545).
JP-A No. 58-185536, a method of adsorbing and removing with a molecular sieve (JP-A-58-185536), and a method of increasing the reaction temperature (JP-A 1-265062, JP-A 1-265063 and JP-A 1-265064).
However, the method using an azeotropic agent complicates the process due to its recovery and separation and the effect is not great, and the method using a molecular sieve requires a large amount of use and desorption operation is required. Alternatively, it was not suitable as an industrial method because the effect was not sufficient even in the reaction at high temperature and the increase of by-products was observed.

As a reaction system, it is known to use a so-called reactive distillation apparatus in which a distillation column is provided in the upper part of the reactor in order to distill off by-produced alcohol from the reaction mixture. Used in Examples (JP-A-56-123948, JP-A-56-25138, JP-A-60-16-16)
9444, JP 60-19445, JP 60-173016, JP 61-172852, JP 61-291545, and JP 62-2.
77345 publication). However, the content of any description is for a batch reaction tank, and a method for continuously producing a diaryl carbonate at a high reaction rate in a high yield has not been known.

Further, a low boiling point component containing an alcohol, which is a by-product, is withdrawn while a dialkyl carbonate and an aromatic hydroxy compound are reacted in a continuous multi-stage distillation column, while a high boiling point component containing an alkylaryl carbonate is continuously discharged from the bottom of the column. A method has been proposed in which the diaryl carbonate is continuously extracted from the bottom of the column while feeding it to another continuous multi-stage distillation column and similarly causing the reaction in the distillation column. Kaihei 4-9358, JP-A-4-21
1038, JP-A-4-224547, JP-A-4-230242 and JP-A-4-35951). However, this method has an essential problem in achieving a high yield. That is, as described above, the above reaction (particularly the formula (1)) is extremely difficult in terms of equilibrium theory. Therefore, in order to obtain the target diaryl carbonate in a high yield, the by-produced alcohol is removed from the reaction system to the limit. Although it has to be distilled off, in the method, since the reaction is carried out in the distillation column, there is always a gas-liquid equilibrium of the produced alcohol, and in order to obtain a high yield, the alcohol in the reaction solution is To reduce the concentration to the limit, it is necessary to take an extremely large number of stages in the distillation column. Furthermore, since the selectivity decreases due to the concurrent occurrence of this reaction with the progress of the reaction, the optimum reaction conditions differ in each reaction step, but there is a drawback that it is difficult to cope with the condition changes in this method. is there.

[0009]

The object of the present invention is not to have the above-mentioned drawbacks as a method for producing a diaryl carbonate, and to continuously produce a diaryl carbonate from a dialkyl carbonate and an aromatic hydroxy compound at a high reaction yield and selectivity. It is to provide a method for producing carbonate.

[0010]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that a reaction between a dialkyl carbonate and an aromatic hydroxy compound is carried out by connecting a plurality of reaction vessels equipped with a distillation column in series. It was found that it is possible to produce a diaryl carbonate with a high yield and a high selectivity by carrying out in two multi-stage continuous reaction systems configured by connecting to each other. That is, according to the method of the present invention, since the reaction part is divided into a plurality of fractions, it is possible to reduce the alcohol concentration in the reaction solution to the utmost limit by gradually distilling off the by-product alcohol. It has become possible to significantly improve the carbonate yield. Further, they have found that the alkyl aromatic ether, which is a by-product of the sequential reaction of dialkyl carbonate, can be significantly reduced by lowering the reaction temperature in the subsequent reaction tank, and completed the present invention.

The method of the present invention is a method for producing a diaryl carbonate by reacting a dialkyl carbonate with an aromatic hydroxy compound, wherein the reaction is carried out by the following steps. : [First step]: The dialkyl carbonate and the aromatic hydroxy compound are continuously introduced into the first reaction tank of the first multistage continuous reaction system constituted by connecting a plurality of reaction tanks each equipped with a distillation column in series. It is supplied and reacted by contacting with a catalyst in each reaction tank, and the produced alcohol is continuously extracted from the top of the distillation column attached to each reaction vessel to the outside of the system, while the produced alkylaryl carbonate and diaryl carbonate are liquified. A step of continuously withdrawing from the final reaction tank through a continuous reaction tank in a phase state, and [ Step 2]: Second multi-stage continuous reaction system constituted by connecting a plurality of reaction tanks each equipped with a distillation column with the liquid extracted from the final reaction tank of the first step containing the produced alkylaryl carbonate and diaryl carbonate Is continuously supplied into the first reaction tank of the above, and the low boiling point compound having a dialkyl carbonate as a main component, which is produced by bringing into contact with the catalyst in each reaction tank to react, is added to the top of the distillation column attached to each reaction tank. Is continuously extracted from the system to the outside of the system, and on the other hand, the high boiling point compound containing the produced diaryl carbonate is continuously withdrawn in the liquid phase state from the final reaction tank through successive reaction tanks.

According to another aspect of the present invention, in order to efficiently withdraw the alcohol produced in the first step, a dialkyl carbonate as a raw material and a low-boiling organic compound inert to the reaction (for example, Benzene, toluene, hexane, heptane, etc.) and inert gases (eg nitrogen,
One or more substances selected from helium, argon, etc.) are introduced into all or a part of the reaction tank of the first multistage continuous reaction system, and this is taken out as a gas phase from the top of the attached distillation column to carry out the reaction. The alcohol produced can be removed entrained.

According to another aspect of the present invention, in order to accelerate the progress of the reaction in the second step, an aromatic hydroxy compound, a low-boiling organic compound inert to the reaction, and an inert gas are used as the first component. The low boiling point compound containing dialkyl carbonate as a main component can be removed together by introducing the compound into the first reaction tank of the two-stage continuous reaction system and the like and extracting it as a gas phase from the top of the distillation column.

According to another preferred aspect of the present invention, in the first step, the reaction temperature is lowered according to the subsequent stage of each reaction vessel, while in the second step, the reaction temperature is reduced to the subsequent stage of each reaction vessel. By increasing the reaction temperature accordingly, the yield of the desired diaryl carbonate can be increased.

In the method of the present invention, the first step of obtaining an alkylaryl carbonate and a diaryl carbonate by the transesterification reaction of a dialkyl carbonate with an aromatic hydroxy compound, and a bimolecular transesterification reaction of the produced alkylaryl carbonate ( The second step of obtaining a diaryl carbonate by a homogenization reaction). Since the first step is an equilibrium reaction that is remarkably biased toward the original system as shown in the above formula (1), the efficiency of distilling the by-product alcohol out of the reaction system greatly affects the reaction rate and the yield. . In order to increase the efficiency of distillation, the reaction temperature should be raised and the starting material dialkyl carbonate, a substance selected from the above-mentioned inert gases and low boiling organic compounds should be introduced, and this should be passed from the reaction vessel through the distillation column to the top of the column. It is preferable to increase the area of the gas-liquid interface by extracting the alcohol and remove the produced alcohol together. However, if the reaction temperature is high, the production of alkyl aromatic ether increases as a sequential reaction, and therefore the reaction temperature must be lowered to suppress this. Therefore, at a low reaction rate, the space-time yield is increased by maintaining the reaction at a temperature as high as possible to increase the reaction rate, while at the stage of a high reaction rate, the reaction temperature is lowered and the catalyst amount is increased if necessary to increase the reaction rate. It is preferable to suppress the decrease. For that purpose, it is effective to maintain a higher reaction temperature in the former stage and lower the temperature in the latter stage in a reaction vessel in which a plurality of reactors are connected.

The second step is the reaction represented by the above formulas (2) and (3). The reaction of the formula (2) is mainly compared with the formula (3) because the equilibrium is largely biased to the original system and the reaction rate is lower than that of the formula (3).
Is the main reaction in the second step. Formula (2), Formula (3)
Since it is an equilibrium reaction, it is necessary to distill off the produced alcohol and dialkyl carbonate in order to proceed the reaction. In order to increase the efficiency of distillation, the reaction temperature should be high, and aromatic hydroxy compounds, low boiling point organic compounds inert to the reaction, and substances selected from inert gases such as nitrogen, helium, and argon should be used first. It is effective to introduce the dialkyl carbonate into all or a part of the reaction tank of the two-stage continuous reaction system, and to withdraw the dialkyl carbonate produced in the reaction together by withdrawing from the reaction tank to the outside of the system through the attached distillation column. is there. The unreacted dialkyl carbonate in the first step is usually removed through a distillation column attached to the first reaction tank of the second step, but between the first step and the second step, an ordinary continuous distillation column or flash is used. It is also possible to install a distillation column or the like and remove the unreacted dialkyl carbonate by distillation in advance and supply it to the second step. Formula (3)
Since the reaction (1) can be performed at a higher rate and yield as compared with the reaction of the formula (1), the efficiency of the first step in the method of the present invention determines the overall productivity.

The dialkyl carbonate used as the reaction raw material in the method of the present invention is represented by the following formula (4). R ¹ OCO ₂ R ² (4) (In the formula, R ¹ and R ² are an alkyl group having 1 to 10 carbon atoms,
Represents an alkenyl group having 2 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms or an aralkyl group having 7 to 12 carbon atoms, and R ¹ and R ² may be the same or different. Specific examples include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diallyl carbonate, dihexyl carbonate, dioctyl carbonate, dicyclohexyl carbonate, dibenzyl carbonate, methyl ethyl carbonate, ethylene carbonate and propylene carbonate. Among these, dimethyl carbonate and diethyl carbonate are particularly preferably used.

The aromatic hydroxy compound, which is the other reaction raw material in the method of the present invention, is represented by the formula (5). ArOH (5) (In the formula, Ar represents an aromatic group having 1 to 20 carbon atoms.) Specific examples thereof include phenol, cresol, cyclohexylphenol, and naphthol. Particularly preferred among these is phenol.

The alkylaryl carbonate referred to in the present invention is represented by the formula (6). R ³ OCO ₂ Ar (6) (wherein, Ar represents the same as the equation (5). Or is R ³ is the formula
It represents the same as R ¹ or R ² in (4). Specific examples include methyl phenyl carbonate, ethyl phenyl carbonate, propyl phenyl carbonate, allyl tolyl carbonate, methyl cumyl carbonate, methyl methoxy phenyl carbonate, and methyl naphthyl carbonate. Particularly preferred among these are methylphenyl carbonate and ethylphenyl carbonate.

The diaryl carbonate which is the object compound of the present invention is represented by the formula (7). (ArO) ₂ CO (7) (In the formula, Ar represents the same as the formula (5).) Specifically, it represents diphenyl carbonate, ditolyl carbonate, dinaphthyl carbonate or the like. Particularly preferred is diphenyl carbonate.

The catalyst used in the present invention may be any catalyst 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 an alkylaryl carbonate. Is possible. For example, Bu ₂ SnO, Ph ₂ SnO, Bu
₂ Sn (OPh) ₂ , Bu ₂ Sn (OCH ₃ ) ₂ , Bu ₂ Sn (O
Et) ₂ , Bu ₂ Sn (OPh) O (OPh) SnBu ₂ and other tin compounds; PbO, Pb (OPh) ₂ , Pb (OCOCH
Lead compounds such as ₃ ) ₂ ; aluminum compounds such as AlCl ₃ and Al (OPh) ₃ ; titanium compounds such as TiCl ₃ and Ti (OPr) ₃ ; zirconium compounds such as Zr (acac) ₄ and ZrO _2. . Of these, tin compounds and lead compounds are particularly preferable.

The reaction tank used in the method of the present invention is a reaction tank having a distillation column on the upper part thereof. A plurality of the reaction vessels are connected in series to form a multi-stage continuous reaction system. The first multistage continuous reaction system in the first step and the second in the second step
Each of the multi-stage continuous reaction systems has about 2 to 10 reaction vessels, but the number of reaction vessels can be arbitrarily determined depending on the reaction conditions. In general, the number of reaction vessels may be small because the reaction in the second step is reactionally and kinetically faster. In order to efficiently distill off the alcohol and dialkyl carbonate produced in the reaction tank to favor the reaction equilibrium,
The distillation column preferably has two or more stages, usually about 10 to 50 stages. As the distillation column, either a plate column type or a packed column type can be used. The stirring system of the reaction tank may be any system as long as the interface between the gas and the liquid is made as large as possible and the produced light boiling components can be efficiently distilled off to the gas phase. In particular,
Examples include those equipped with a stirrer, stirring by pump circulation, or bubble stirring by gas passage. The bubbles used for stirring the bubbles are low-boiling organic compounds that are inert to the reaction so that the low-boiling alcohol produced in the reaction can be efficiently taken out in the reaction tank and taken out in the vapor phase. Examples include compounds and gases such as nitrogen, helium, and argon.

In the first step, a reboiler is installed in each reaction tank, and a dialkyl carbonate gas blown through the reboiler can also be preferably used. In addition, in the second step, the aromatic hydroxy compound is introduced and withdrawn in the gas phase, it is possible to efficiently withdraw the dialkyl carbonate. The liquid containing alcohol and dialkyl carbonate extracted from the top of the distillation column of each reaction tank in the first step can be reused as a reaction substrate in the first step after the alcohol is fractionally removed. Further, since the liquid extracted from the top of the distillation column of the downstream reaction tank in the first step has a relatively low alcohol concentration, it may be circulated and fed to the upstream reaction tank without purification. At this time, it is preferable to circulate and feed the reaction solution to two or more upstream reaction tanks. On the other hand, the liquid containing the dialkyl carbonate and the aromatic hydroxy compound extracted in the second step can be recycled to the first step after purification or as a reaction raw material as it is. In addition, the liquid extracted from the second step can be efficiently produced as a target diaryl carbonate by purification or crystallization using an ordinary distillation column.

In a preferred embodiment of the present invention, an aromatic hydroxy compound and a dialkyl carbonate in which a predetermined amount of a catalyst is dissolved are continuously supplied to the first reaction tank of the first multistage continuous reaction system. From the reaction tank, the produced alcohol and the dialkyl carbonate are continuously distilled off from the top of the distillation column equipped. On the other hand, the inert gas is continuously introduced from the lower part of the reaction tank. To further increase the yield, the product solution is continuously withdrawn from the lower part of the reaction tank,
It is fed to the second reactor and the reaction is continued in the same manner. In this way, the reaction is carried out in multiple stages until the desired yield is obtained. The withdrawal liquid from the last reaction vessel mainly consisted of dialkyl carbonate, alkylaryl carbonate, diaryl carbonate, aromatic hydroxy compound, and catalyst, and this withdrawal liquid was second
It is sent to the first reaction tank of the multistage continuous reaction system. On the other hand, in the first reaction system, the liquid consisting of the dialkyl carbonate and alcohol withdrawn from the top of the distillation column of each reaction tank is
It can be used as it is or after purification and removal of alcohol as a reaction substrate in the first step.

The reaction product liquid supplied from the first reaction system to the second reaction system is further reacted in the same manner as in the first step. The reaction is completed while continuously distilling off the unreacted dialkyl carbonate in the first step and the dialkyl carbonate produced in the disproportionation reaction in the second step from the top of the distillation column. The product liquid from the final reaction tank of the second reaction system mainly comprises diaryl carbonate, aromatic hydroxy compound and catalyst. Pure diphenyl carbonate can be obtained by purifying this product solution by a usual distillation process or crystallization. Further, the liquid extracted from the distillation column in the second reaction system, which is mainly composed of the dialkyl carbonate and the aromatic hydroxy compound, can be recycled and reused as the raw material of the first step.

The general reaction conditions in the first step are as follows. The supply molar ratio of the dialkyl carbonate and the aromatic hydroxy compound is 1 to 100, preferably 1 to 1
It is 0. The larger the molar ratio, the higher the reaction yield but the lower the productivity, which is not preferable. Reaction temperature is 50-3
00 ° C is preferably 100 to 250 ° C. The higher the reaction temperature is, the higher the reaction rate is, but it is not preferable because the by-products such as alkyl aromatic ethers are increased or the reaction pressure is increased. Further, in order to reduce the amount of by-product aromatic alkyl ether, the reaction temperature on the rear side of the multi-stage reaction tank is 5 to 50 ° C., preferably 10 ° C. from the front side.
It is more effective to lower the temperature by -30 ° C. The pressure in the reactor is
It depends on the types of the dialkyl carbonate and the aromatic carbonate, and the reaction temperature, but usually 1 to 50.
Atmospheric pressure, preferably 2 to 20 atmospheric pressure. In order to efficiently distill off the alcohol, the vapor pressure of the reaction solution is usually set to 0.1 to 10 atm, preferably 0.5 to 3 atm higher than the vapor pressure of the reaction solution at the reaction temperature used. The amount of the catalyst is 0.0001 to 10 mol%, preferably 0.0001 to 5 mol% based on the aromatic hydroxy compound. When used in large amounts, the amount of by-products such as alkyl aromatic ethers tends to increase.
The residence time in each reaction tank depends on the reaction temperature, the aromatic hydroxy compound concentration and the amount of catalyst, but is usually 0.1 to 5
It's time.

The general reaction conditions in the second step are as follows. The molar ratio of the alkylaryl carbonate to the aromatic hydroxy compound varies depending on the supply molar ratio of the dialkyl carbonate to the aromatic hydroxy compound and the reaction rate of the aromatic hydroxy compound in the first step, but is usually in the range of 0.5 to 10. is there. Further, since the reaction between the aromatic hydroxy compound and the alkylaryl carbonate is extremely slow, the production of the diaryl carbonate by the disproportionation reaction of the alkylaryl carbonate is usually given priority, and the unreacted aromatic hydroxy compound may be treated as a solvent. The reaction temperature is 50 to 300 ° C., preferably 100.
~ 250 ° C. Further, in order to further increase the reaction rate, it is more effective to increase the reaction temperature on the rear side of the multi-stage reaction tank in which the amount of by-produced alkylaryl ether is smaller than that on the front side by 5 to 50 ° C, preferably 10 to 30 ° C. is there. The pressure in the reactor varies depending on the types of aromatic hydroxy compound and alkylaryl carbonate used, and the reaction temperature, but usually 0.001 to 2 atm in order to efficiently distill off the dialkyl carbonate produced as a by-product. The pressure is preferably 0.01 to 1 atm. If you reduce the pressure too much,
It is not preferable because the reaction rate decreases due to the decrease in the reaction temperature. Although the catalyst used in the first step may be used as it is in the second step as it is, the catalyst is used in an amount of 0.000 relative to the alkylaryl carbonate in the liquid introduced.
You may add a catalyst of 01-10 mol%, preferably 0.0001-5 mol%. The catalyst species added here is the first
It may be the same as or different from that used in the process. The residence time in each reaction tank depends on the reaction temperature and the amount of catalyst, but is usually 0.1 to 5 hours.

In the first step and the second step of the present invention, it is not always necessary to use a solvent, but ethers, aliphatic hydrocarbons, aromatic hydrocarbons and the like are used as a solvent inert to the reaction. be able to.

[0029]

EXAMPLES The present invention will be specifically described with reference to the following examples. Example 1 For the production of diphenyl carbonate, the multistage continuous reaction apparatus shown in FIG. 1 was used. The first multi-stage continuous reaction system consists of five reaction tanks, each of which is a 0.5 L stainless steel autoclave equipped with a packed distillation column having an inner diameter of 30 mmφ and a height of 30 cm. Dimethyl carbonate, phenol, and dibutyltin oxide were added to the first reaction tank at a molar ratio of 4: 1: 0.0.
It was continuously fed at a rate of 0.3 L / h so as to be 3. Further, nitrogen gas was supplied to each reaction tank at 0.5 L / min. The reaction temperature was 180 ° C. and the reaction pressure was 9.5 atm. On the other hand, dimethyl carbonate which was azeotropically distilled with the produced methanol was continuously withdrawn from the top of the distillation column from each reaction tank. In order to control the height of the liquid surface, the same amount of dimethyl carbonate as the liquid extracted from the top of the distillation column was continuously introduced from the bottom of each reaction tank. 0.3L / from the 5th reaction tank
The product liquid extracted in h was 0.70 per 1 L.
It contained mols of methylphenyl carbonate and 0.01 mol of diphenyl carbonate. Therefore, the conversion rate of phenol in the first step is 30.0%. Next, the above-mentioned product liquid was introduced into the first reaction tank of the second multistage continuous reaction system composed of two reaction tanks. Each of the reaction tanks is an autoclave made of stainless steel of 0.5 L and has an inner diameter of 30 mm.
It is equipped with a packed tower of φ and a height of 30 cm. Unreacted and produced dimethyl carbonate was reacted while being extracted from the top of each distillation column. When the product solution extracted at 50 ml / h from the second reaction tank was analyzed, the conversion of methylphenyl carbonate was 100% and the selectivity to diphenyl carbonate was 98%.

Example 2 The multistage continuous reactor shown in FIG. 2 was used. As the dimethyl carbonate continuously introduced into the first reaction tank of the first reaction system, the liquid extracted from the top of the distillation column of the fourth reaction tank of the first reaction system is used, and the second reaction tank of the first reaction system is used. As the dimethyl carbonate continuously introduced into the reactor, the liquid extracted from the top of the distillation column of the fifth reaction tank of the first reaction system is used to supplement the shortage with dimethyl carbonate, and the third, fourth and fifth reactions are also performed. Dimethyl carbonate was supplied to the tank at a rate of 0.11 L / h, and the liquid extracted from the top of the distillation column of each reaction tank of the second reaction system was used as a part of the raw material of the first step. The reaction was carried out as in Example 1. The produced liquid from the fifth reaction tank of the first reaction system contained 0.
It contained 61 mol of methylphenyl carbonate and 0.01 mol of diphenyl carbonate. Therefore the first
The conversion of phenol in the process is 26.3%. Further, when the product liquid after the completion of the second step was analyzed, the conversion rate of methylphenyl carbonate was 100% and the selectivity to diphenyl carbonate was 98%.

[0031]

INDUSTRIAL APPLICABILITY According to the present invention, a diaryl carbonate can be continuously produced in high yield from a dialkyl carbonate and an aromatic hydroxy compound.

[Brief description of drawings]

FIG. 1 is a schematic view of an example of a process for explaining a first embodiment of the present invention.

FIG. 2 is a schematic view of an example process for explaining Example 2 of the present invention.

[Explanation of symbols]

1 1st multistage continuous reaction system 1st reaction tank 2 1st multistage continuous reaction system 2nd reaction tank 3 1st multistage continuous reaction system 3rd reaction tank 4 1st multistage continuous reaction system 4th reaction tank 5 1 5th reaction tank of multi-stage continuous reaction system 6,7 Introducing pipe of dialkyl carbonate, aromatic hydroxy compound or catalyst 8 Inert gas introducing pipe 9, 12 Extraction conduit 10 First reaction tank of 2nd multi-stage continuous reaction system 11 Second reaction tank of second multi-stage continuous reaction system 13 Diaryl carbonate extraction tube 14 Distillation column

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masashi Inaba 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Co., Ltd. Yokkaichi Research Institute

Claims (8)

[Claims] 1. A method for producing a diaryl carbonate by reacting a dialkyl carbonate with an aromatic hydroxy compound, wherein the reaction is carried out by the following steps. [First step]: The dialkyl carbonate and the aromatic hydroxy compound are continuously supplied into the first reaction tank of the first multistage continuous reaction system configured by connecting a plurality of reaction tanks each equipped with a distillation column in series. Then, the reaction is carried out by contacting with a catalyst in each reaction tank, and the produced alcohol is continuously taken out of the system from the top of the distillation column attached to each reaction tank, while the produced alkylaryl carbonate and diaryl carbonate are in a liquid phase. In the state, a step of continuously withdrawing from the final reaction vessel through a continuous reaction vessel, and [second step]: withdrawing liquid from the first step final reaction vessel containing the produced alkylaryl carbonate and diaryl carbonate, respectively. Is continuously supplied into the first reaction tank of the second multi-stage continuous reaction system which is constituted by connecting a plurality of reaction tanks equipped with a distillation column in series. Then, the low boiling point compound having a dialkyl carbonate as a main component is continuously extracted from the top of the distillation column attached to each reaction vessel to the outside of the system by contacting with a catalyst in each reaction vessel to generate one. The step of continuously withdrawing the high boiling point compound containing the diaryl carbonate from the final reaction tank in a liquid phase state through the continuous reaction tanks. 2. One or more substances selected from the group consisting of a raw material dialkyl carbonate, a low-boiling organic compound inert to the reaction, and an inert gas, in all or part of the reaction tank of the first multistage continuous reaction system. The method according to claim 1, wherein the alcohol produced in the reaction is entrained and removed by introducing it in a gas phase or a liquid phase and withdrawing it from the top of the distillation column attached to the reaction vessel to the outside of the system. 3. One or more substances selected from the group consisting of aromatic hydroxy compounds, low-boiling organic compounds inert to the reaction, and inert gas in the first reaction tank of the second multi-stage continuous reaction system in the gas phase or The method according to claim 1, wherein the low-boiling compound containing dialkyl carbonate as a main component is entrained and removed by continuously introducing it in a liquid phase from the top of a distillation column attached to the reaction vessel to the outside of the system. 4. The method according to claim 1, wherein a part or all of the distillate from the top of the distillation column of each reaction tank of the second multistage continuous reaction system is circulated and fed to the reaction tank of the first multistage continuous reaction system. 5. A part or all of the distillate from the top of the distillation column of each reaction tank of the first multistage continuous reaction system is circulated and fed to the reaction tank upstream of the first multistage continuous reaction system. The method described. 6. The method according to claim 1, wherein, in the first step, the reaction temperature is lowered in the subsequent stage of each reaction tank. 7. The method according to claim 1, wherein in the second step, the reaction temperature is increased in the subsequent stage of each reaction tank. 8. The method of claim 1 wherein the aromatic hydroxy compound is phenol and the diaryl compound is diphenyl carbonate.