JP4623413B2 - Continuous production of diaryl carbonate - Google Patents

Description

  The present invention relates to a method for producing a diaryl carbonate by deCO reaction of diaryl oxalate, and more specifically, a diaryl oxalate is deCO-reacted in the presence of a deCO catalyst to form a reaction mixture containing the diaryl carbonate. A continuous reaction of diaryl carbonate, comprising continuously performing a reaction step of generating, an evaporation step of evaporating an evaporation component containing diaryl carbonate as a main component from the reaction mixture, and a step of returning the evaporation residue mixture of the evaporation step to the reaction step It relates to the manufacturing method.

Patent Document 1 and Patent Document 2 include a reaction step in which a diaryl oxalate is de-CO-reacted in the presence of a de-CO catalyst typified by an organophosphorus compound catalyst to form a reaction mixture containing a diaryl carbonate, An evaporation step of evaporating an evaporation component containing diaryl carbonate as a main component from the reaction mixture, and a step of returning the evaporation residue mixture containing the de-CO catalyst produced in the evaporation step to the reaction step are sequentially performed. A continuous production process is described.
Japanese Patent Laid-Open No. 10-109962 Japanese Patent Laid-Open No. 11-246489

  As described above, a reaction step in which diaryl oxalate is de-CO-reacted in the presence of a de-CO catalyst to form a reaction mixture containing diaryl carbonate, and an evaporation component containing diaryl carbonate as a main component from the reaction mixture. A method for continuously producing a diaryl carbonate by continuously performing an evaporation step for evaporation and a step for returning an evaporation residue mixture containing a de-CO catalyst produced in the evaporation step to the reaction step is already known. According to this study, depending on the amount of a specific component contained in the evaporation residue mixture containing the de-CO catalyst returned from the evaporation step to the reaction step, the de-CO catalyst from the reaction mixture in the reaction step or the evaporation step is determined. Precipitation and the like occurred, and it was found that the reaction efficiency and evaporation efficiency for the production of diaryl carbonate are likely to deteriorate.

  Accordingly, the present invention provides a reaction step in which a diaryl oxalate is de-CO-reacted in the presence of a de-CO catalyst to form a reaction mixture containing diaryl carbonate, and an evaporation component containing diaryl carbonate as a main component from the reaction mixture. The main object of the present invention is to provide an improved process for continuously producing a diaryl carbonate by continuously carrying out an evaporation step for evaporating water and a step of returning an evaporation residue mixture containing a de-CO catalyst produced in the evaporation step to the reaction step. And

The present invention provides a reaction step in which a diaryl oxalate is de-CO-reacted in the presence of a de-CO catalyst to form a reaction mixture containing diaryl carbonate, and an evaporation component containing diaryl carbonate as a main component is evaporated from the reaction mixture. In a continuous process for producing a diaryl carbonate comprising continuously performing an evaporation step and a step of returning the evaporation residue mixture of the evaporation step to the reaction step, the diaryl carbonate contained in the evaporation residue mixture returned to the reaction step from the evaporation step A continuous production method of diaryl carbonate, characterized in that the production of a by-product consisting of an aromatic carboxylic acid ester having a high boiling point is maintained in the range of 20 to 35% by weight and is continuously produced in a time exceeding 500 hours. is there.

  By the improved continuous production method of diaryl carbonate of the present invention, the reaction step and the evaporation step can be carried out without causing troubles such as precipitation of a de-CO catalyst from the reaction mixture, and the yield of the produced diaryl carbonate can be increased. There is no reduction. Therefore, the improved continuous production method of diaryl carbonate of the present invention is highly practical as an industrial production method of diaryl carbonate.

  First, an outline of a method for continuously producing diaryl carbonate by deCO reaction of diaryl oxalate will be described with reference to FIG. 1 of the accompanying drawings.

  The deCO reaction of the diaryl oxalate is carried out in a reactor (3) to which a deCO reaction catalyst supply line (1) and a diaryl oxalate (DPO, etc.) supply line (2) are connected. That is, in this reactor, diaryl carbonate (such as DPC) is produced from diaryl oxalate in the presence of a de-CO catalyst. DPO represents diphenyl oxalate, and DPC represents diphenyl carbonate.

  A reaction mixture discharge line (4) is connected to the lower part of the reactor (3), and a CO gas discharge line (8) is connected to the upper part of the reactor (3). The reaction mixture of the de-CO reaction is continuously supplied from the reaction mixture discharge line (4) to the evaporator (5). In the evaporator (5), an evaporation component mainly composed of diaryl carbonate (target product) in the reaction mixture is evaporated, and an evaporation fraction supply line (9) connected to the upper part of the evaporator (5) is connected. To be supplied to the distillation purification process.

  At the bottom of the evaporator (5) in the evaporation zone, an evaporation residue mixture mainly composed of a de-CO catalyst and a hardly volatile reaction by-product remains. Therefore, this evaporation residue mixture is extracted from the evaporator and reacted. A recycling line (6) for recycling to the vessel (3) is connected. Further, a purge liquid discharge line (7) is connected in the middle of the recycle line (6), and a part of the evaporation residue mixture is purged (discharged) out of the system.

  According to the study of the present inventor, in the above evaporation residue mixture, in addition to the de-CO catalyst, the raw material diaryl oxalate, and the main product diaryl carbonate, some organic carboxylic acids having higher boiling points than some diaryl carbonates. Ester compound is mixed as a hardly volatile by-product, and by adjusting the amount of this volatile by-product mixed in the evaporation residue mixture, deposition of the de-CO catalyst from the reaction mixture during the de-CO reaction or during the evaporation operation It was found that the desired reaction and evaporation can be carried out without causing oxidization, which makes it possible to carry out continuous production of diaryl carbonate smoothly and while maintaining a high acquisition rate of diaryl carbonate. did.

  A representative example of a hardly volatile by-product mainly composed of an organic carboxylic acid ester compound which is a problem in the evaporation residue mixture is a reaction by-product having a boiling point higher than that of diaryl carbonate, and its molecular weight distribution is 300 to 800. The reaction by-products (particularly aromatic carboxylic acid ester compounds) having an average molecular weight in the range of 400 to 600. Next, reaction by-products mixed in such an evaporation residue mixture will be described.

  In the de-CO reaction, a p-hydroxybenzoic acid aryl ester compound represented by the following chemical formula B1 is represented by the Fries rearrangement reaction from diaryl carbonate or diaryl oxalate (p-hydroxybenzoic acid when R in chemical formula B1 is all hydrogen atoms). And an o-hydroxybenzoic acid aryl ester compound represented by the following chemical formula B2 (or phenyl salicylate (POB) when all of R in the chemical formula B2 are hydrogen atoms): Benzoic acid aryl ester compounds are by-produced. Next, most of the hydroxybenzoic acid aryl ester compounds are subjected to a transesterification reaction, a polycondensation reaction, or a depolymerization with a diaryl carbonate, a diaryl oxalate, or the hydroxybenzoic acid aryl ester compound itself. A variety of organic carboxylic acid ester compounds are by-produced.

  As described above, in the de-CO reaction, the hydroxybenzoic acid aryl ester compound represented by the chemical formula B1 or B2 by-produced from diaryl carbonate or diaryl oxalate is converted into the following by transesterification with diaryl carbonate or diaryl oxalate. Or an aryl (p- (or o-) aryloxycarbonylaryl) carbonate compound represented by the chemical formula C1 or C2 or an aryl (p- (or o-) aryloxy represented by the chemical formula D1 or D2. Carbonylaryl) oxalate compounds and the like are produced.

  In the chemical formulas C1 and C2, when all R are hydrogen atoms, the chemical formula C1 represents phenyl (p-phenoxycarbonylphenyl) carbonate (PCPC), and the chemical formula C2 represents phenyl (o-phenoxycarbonylphenyl) carbonate. (OPCPC).

  In the chemical formulas D1 and D2, when all R are hydrogen atoms, the chemical formula D1 represents phenyl (p-phenoxycarbonylphenyl) oxalate (PCPO), and the chemical formula D2 represents phenyl (o-phenoxycarbonylphenyl) oxalate. (OPCPO) is shown.

  The organic carboxylic acid ester compound which is the main component of the hardly volatile by-product is the aryl (aryloxycarbonylaryl) carbonate compound represented by the chemical formulas C1 and C2, and the aryl (aryloxycarbonylaryl) represented by the chemical formulas D1 and D2. The oxalate compound is further formed by condensation polymerization with the hydroxybenzoic acid aryl ester compound represented by the chemical formulas B1 and B2, or the product is depolymerized, resulting in the organic carboxylic acid ester compound having the aforementioned average molecular weight. In some cases.

  Examples of the organic carboxylic acid ester compound include, for example, a polycondensation polymer represented by the following chemical formulas I and I ′ produced by self-condensation of a p-hydroxybenzoic acid aryl ester compound represented by the chemical formula B1, or A condensation polymer represented by the chemical formula II or III produced by condensation polymerization with diaryl carbonate or diaryl oxalate is also included.

  Regarding the o-hydroxybenzoic acid aryl ester compound represented by the chemical formula B2, a condensation polymer similar to the p-hydroxybenzoic acid aryl ester compound represented by the chemical formula B1 is produced, and these condensation polymers are also represented by the organic carboxylic acid ester. Included in compounds.

  In the above chemical formulas I, I ′, II and III, R is the same as defined above, n and m are integers of 1 to 5, and A is —CO— or —CO—CO. -Is shown. In the chemical formulas I and I ′ and the chemical formula II, when n or m is 1, the compound is represented by the chemical formula B1, the chemical formula C1, and the chemical formula D1.

  In the continuous production method of the present invention, when the evaporation component is evaporated from the reaction mixture in the evaporator, the evaporation ratio is adjusted, or the remaining reaction mixture foreign matter (evaporation residue mixture) from which the evaporation component has evaporated is removed. The amount of the hardly volatile by-product in the evaporation residue mixture is adjusted to 20 to 35% by weight, for example, by purging a part of it during recycling to the reactor again. The purge amount of the evaporation residue mixture is preferably an amount that provides a purge rate of about 1 to 20% by volume, particularly about 5 to 15% by volume of the evaporation residue mixture extracted from the evaporator.

  When the evaporation residue mixture recycled to the reaction process has a low content of hardly volatile by-products, it becomes difficult for the reaction mixture to uniformly dissolve the catalyst component for de-CO in the reactor and the evaporator, In some cases, the catalyst may be deposited, the de-CO reaction cannot be performed stably, and in order to maintain a low content of volatile by-products, a large amount of the evaporation residue mixture being recycled is purged. In addition to the hardly volatile by-products, unreacted diaryl oxalate, reaction product diaryl carbonate and catalyst are discharged out of the system in a considerable amount. Is inappropriate.

  On the other hand, when the content of the hardly volatile by-product in the evaporation residue mixture recycled to the reaction process becomes higher than 40% by weight, the reaction mixture generated in the reaction process has a high viscosity, and in particular, the evaporation components are evaporated in the evaporation region. Since the viscosity of the evaporation residue mixture after the treatment becomes high and handling such as recycling becomes difficult, it is not suitable. In addition, it is preferable that the vaporization component recycled to the reaction process has a viscosity in the range of about 5 to 1000 centipoise, particularly in the range of about 10 to 500 centipoise at 150 ° C.

Further, the evaporation residue mixture recycled from the evaporation step to the reaction step has the content of hardly volatile by-products adjusted as described above, and the concentration of diaryl oxalate is 30% by weight or more, and further 40 %. %, Particularly 50% by weight or more, and the concentration of the de-CO catalyst is preferably 40% by weight or less, more preferably 30% by weight or less.

  In the above de-CO reaction, the reaction temperature is preferably 100 to 450 ° C., more preferably 160 to 400 ° C., and particularly preferably 180 to 350 ° C., and the reaction pressure is not particularly limited. The conditions can be selected as appropriate. The time for which the reaction mixture stays in the reactor (retention time) is not particularly limited as long as the diaryl carbonate can be produced in a high yield.

  When no reaction solvent is used in the de-CO reaction, the diaryl oxalate concentration in the reaction mixture in the reaction step (reaction mixture sent from the reactor to the evaporator) is 2 to 15% by weight, particularly 5 to 12%. It is preferable to adjust so that it may be about weight%. The de-CO reaction can be carried out batchwise or continuously, but industrially it is preferably carried out continuously.

  The reactor (3) used for the above-mentioned de-CO reaction can be any one as long as it can produce diaryl carbonate by de-CO-reacting diaryl oxalate to produce carbon monoxide (gas) as a by-product. It can also be used in the form of For example, a single tank type or multi-tank type fully mixed reactor (stirring tank), a multi-tube heat exchange type tube reactor or a tower reactor can be mentioned. In the case of a tube-type or column-type reactor, a packing or a baffle for improving mixing may be installed, and a wet wall type reactor can also be mentioned.

  Any evaporator can be used as long as it can evaporate an evaporation component such as diaryl carbonate from the reaction mixture of the de-CO reaction and supply it to the purification zone. For example, evaporation such as an evaporator, a thin film evaporator, a falling film evaporator, etc. A vessel is preferred.

  When evaporating an evaporation component such as diaryl carbonate from the reaction mixture containing diaryl carbonate in the evaporation zone, the evaporation temperature is preferably 150 to 200 ° C., particularly 160 to 180 ° C., the evaporation pressure is 200 torr or less, It is preferably 100 torr or less, particularly 1 to 60 torr.

  The recycling line (6) may be directly connected to the reactor (3), but as shown in FIG. 1, it is connected to the supply line (2) for raw material DPO or the like. Then, the evaporation residue mixture may be mixed with the raw material DPO or the like and recycled to the reactor (3).

  The diaryl carbonate contained in the evaporation component by the method of the present invention is preferably then subjected to a distillation purification step. In this distillation purification process, the evaporating fraction flowing out from the upper part of the evaporator (5) is, as shown in FIG. 1, a distillation purification process having a first distillation column (10), a second distillation column (12) and the like. It supplies to a 1st distillation column (10). Then, the distillation purification operation of the evaporation component is started, the light fraction is removed from the outflow line (11) connected to the top of the first distillation column (10), and the first distillation column (10) From the bottom of the column, a can liquid containing a target product such as DPC is extracted and supplied to the second distillation column (12) for purification by distillation, and the extraction line (13) at the bottom of the second distillation column (12). Distilled carbon dioxide such as DPC distilled and removed from the product effluent line (14) connected to the top of the second distillation column (12). Get the product.

  As the de-CO catalyst used in the present invention, an organic phosphorus compound is suitable, and the details of the de-CO catalyst composed of such an organic phosphorus compound are described in Patent Document 1 and Patent Document 2 described above.

  In the present invention, when an organic phosphorus compound other than the halide described in the above-mentioned literature is used as a catalyst, it is particularly preferable to add an organic or inorganic halogen compound to cause a de-CO reaction. For example, as shown in FIG. It is preferable to supply an organic or inorganic halogen compound to the reactor from a halogen compound supply line (15) connected to the raw material supply line (2). Accordingly, the reaction mixture may contain such an organic or inorganic halogen compound. As the organic or inorganic halogen compound, for example, compounds described in JP-A-8-333307 can be used.

  Examples of the diaryl oxalate that is a starting material for producing the diaryl carbonate of the present invention include those in which the aryl group is a phenyl group, a substituted phenyl group, a naphthyl group, or the like. These aryl groups include, for example, a substituent such as an alkoxy group having a C 1-12 alkyl group (methyl group, ethyl group, etc.) or a C 1-12 alkoxy group (methoxy group, ethoxy group, etc.). The diaryl oxalate is an oxalic acid diester having an aryl group having the above-mentioned substituent, and these are various isomers of o-, m-, and p-. There may be.

  Examples of the diaryl oxalate include diphenyl oxalate, bis (p-methylphenyl) oxalate, bis (p-methoxyphenyl) oxalate, bis (p-nitrophenyl) oxalate, and bis (p-chlorophenyl) oxalate. Specific examples thereof include dinaphthyl oxalate, and diphenyl oxalate is most preferred.

  In this invention, the evaporation residue mixture extracted from the evaporator (5) is purged from the purge liquid discharge line (7), and the remainder is sent to the reactor (3) through the recycle line (6) (circulation supply). And an organic phosphorus compound (catalyst), raw material (diaryl oxalate), and, if necessary, an organic or inorganic halogen compound is required through the respective supply lines (1), (2), and (15). When the amount is replenished and the recycling supply is started, the supply amount of the catalyst (organophosphorus compound) to the reactor (3) is adjusted, and the evaporation residue mixture, raw material and catalyst supplied to the reactor (3) are adjusted. It is preferable to control the catalyst concentration in the mixed solution. At this time, it is preferable to continuously perform the decarbonylation reaction by adjusting the supply amount of the raw material (diaryl oxalate) to the reactor (3) as necessary.

  As shown in FIG. 1, purification of the evaporating component containing diaryl carbonate obtained by evaporating from the evaporator (5) is performed by first and second distillation columns (particularly 5 to 50) having a certain number of theoretical plates (particularly 5 to 50). A further purified diaryl carbonate product can be obtained by distillation purification using a packed column, a plate column, or the like.

  Next, the present invention will be specifically described with reference to examples and comparative examples. The production of diphenyl carbonate was performed according to the process diagram shown in FIG. 1, the product was analyzed by liquid chromatography, and the molecular weight of the hardly volatile by-product was measured by GPC analysis.

[Example 1]
In the continuous production apparatus as shown in the schematic process in FIG. 1, from a glass-lined stirring tank having an internal volume of 250 L (a two-tank connection type of the stirring tank, connected from the first tank to the second tank with an overflow pipe) Into the de-CO reactor (3), diphenyl oxalate and tetraphenylphosphonium chloride (1.5% by weight with respect to diphenyl oxalate) were charged, and the jacket of the de-CO reactor (3) was heated through a heating medium, The deCO reaction was carried out with stirring.

  When the conversion rate of the first reactor in the de-CO reactor (3) is about 60% and the conversion rate of the second tank is about 80%, diphenyl oxalate and tetraphenylphosphonium chloride (diphenyl oxalate) 1.5% by weight) was continuously fed from each of the feed lines (1) and (2) to the first reactor. Moreover, in said de-CO reaction, the temperature (reaction temperature) in a de-CO reactor was adjusted to 225 degreeC in each tank, and the reaction temperature was maintained.

The de-CO reaction mixture withdrawn from the de-CO reactor (3) is fed to the glass-lined evaporator (5) having an internal volume of 100 L via the reaction mixture take-out line (4), and is fed to the evaporator jacket. While evaporating evaporating components such as diphenyl carbonate at a reduced pressure of 6 kPaA through steam and extracting it, the de-CO reaction mixture was evaporated and concentrated (evaporation rate 40-60%).
The evaporation component obtained by evaporation of the above-mentioned de-CO reaction mixture was about 90% by weight of diphenyl carbonate, about 9% by weight of diphenyl oxalate, and about other impurities such as phenol, methylphenylphenyl carbonate, phenyl parachlorobenzoate and the like. 1% by weight, and the evaporation component was obtained at a rate of 45 to 50 kg / hr.

  On the other hand, the evaporation residue mixture (residual liquid or concentrated liquid) containing the phosphonium salt component derived from the de-CO catalyst and the hardly volatile by-product (residual liquid or concentrated liquid) is transferred to the first reactor (3) via the recycle line (6). Recycled. In addition, when recycling the evaporation residue mixture to the reactor (3), chloroform (amount corresponding to about 10 mol% with respect to the catalyst component in the concentrate) was continuously added from the supply line (15).

Moreover, the catalyst feed to the reactor was stopped when the evaporation residue mixture (including the catalyst) began to be recycled to the reactor (3). In this state, since a phenomenon that a small amount of the catalyst was precipitated in the evaporation residue mixture (concentrated liquid) inside the evaporator (5) was sometimes observed, the concentration rate was temporarily slightly reduced (evaporation rate 30 to 40). %) And operated.
As described above, when the evaporation rate was low, the amount of diphenyl oxalate fed to the reactor (3) was adjusted accordingly.

  In this state, continuous de-CO reaction was continued. However, since the accumulation of impurities (non-volatile by-products) gradually increased, a part of the evaporation residue mixture recycled to the reactor (3) after 300 hours Was continuously purged out of the system at a rate of 0.42 kg / hr (purge rate: 0.7%). Simultaneously with the start of this purge, replenishment of the same amount of catalyst as the amount of catalyst extracted by this purge was started into the reactor.

As a result of continuously performing the de-CO reaction while maintaining the above reaction conditions, the mixture of evaporation residues (5) in the evaporator (5) at the time when the composition of the reaction mixture became almost stable (about 500 hours after the start of the continuous reaction) ( Analyzed values of the concentrate were 52.40% by weight of diphenyl carbonate, 15.64% by weight of diphenyl oxalate, 0.06% by weight of phenol, 2.96% by weight of tetraphenylphosphonium chloride (phosphonium component), etc. The high-boiling by-product (hardly volatile by-product) was 28.94% by weight.
In this state, the de-CO reaction was carried out continuously for 3 months. However, the liquid composition of the evaporation residue mixture (concentrated liquid) was almost constant, and the catalyst was precipitated in the evaporation residue mixture during the evaporation operation of the reaction mixture. Therefore, the de-CO reaction could be carried out while maintaining a stable state.

  In the de-CO reaction after about 500 hours from the start of the continuous reaction, no catalyst precipitation phenomenon in the reaction zone (especially in the evaporator) was observed at this stage in the reaction conditions. The evaporation component (evaporation fraction) obtained by evaporation of the de-CO reaction mixture in the evaporator (5) was 88.54% by weight of diphenyl carbonate, 9.71% by weight of diphenyl oxalate, phenol, methyl carbonate. Other impurities such as phenylphenyl and phenyl parachlorobenzoate were 1.75% by weight, and were obtained at a rate of about 48 kg / hr.

  As a result, the reaction selectivity from diphenyl oxalate to diphenyl carbonate in this continuously performed reaction system was 99.5%, which was obtained by purging the evaporation residue mixture (concentrated liquid) extracted from the evaporator. The acquisition rate including loss was 98.8%.

  In addition, when GPC (gel permeation chromatography) analysis was performed about the evaporation residue mixture (concentrated liquid) obtained from the evaporator in the state in which the above-mentioned de-CO reaction is a steady state, it is a hardly volatile by-product. Has a molecular weight distribution in the range of 350 to 800, but most of it has a molecular weight of 400 to 600. Further, the viscosity of the evaporation residue mixture (concentrated liquid) recycled to the reactor was as low as about 10 cp (150 ° C.) even at the concentration of the hardly volatile by-product, and there was no problem in operation.

[Comparative Example 1]
In the same manner as in Example 1, continuous production of diphenyl carbonate by de-CO of diphenyl oxalate was started, and 1.0 kg / hour of the evaporation residue mixture (concentrated liquid) recycled to the reactor 100 hours after the start of the reaction. (Purge rate: 1.5%) A part of the evaporation residue mixture was continuously purged out of the system. Simultaneously with the start of the purge, replenishment of the same amount of catalyst as the amount of catalyst extracted by the purge was started to the reactor.
The analytical value of the evaporation residue mixture (concentrate) in the evaporator when the composition of the reaction mixture in this de-CO reaction was almost stabilized (about 250 hours after the start of continuous reaction) was 64.99% by weight of diphenyl carbonate, Diphenyl oxalate is 19.87% by weight, phenol is 0.07% by weight, tetraphenylphosphonium chloride (phosphonium component) is 2.91% by weight, and other by-products (hardly volatile by-products) are 12.16% by weight. there were.

Further, the evaporation component (concentrated liquid) obtained by evaporation of the de-CO reaction mixture was 87.46% by weight of diphenyl carbonate, 10.84% by weight of diphenyl oxalate, phenol, methyl phenyl phenyl carbonate, phenyl parachlorobenzoate. The other impurities were 1.70% by weight and were obtained at a rate of about 47 kg / hour.
As a result, when the de-CO reaction is continuously performed as described above, the reaction selectivity from diphenyl oxalate to diphenyl carbonate is 99.5%, including loss due to partial purge of the evaporation residue mixture. The rate was 97.5%. Further, in this state, the catalyst precipitation phenomenon in the evaporation residue mixture (concentrated liquid) in the evaporator is not completely eliminated, and there is a considerable problem in the stability of the reaction operation.

[Comparative Example 2]
The amount of purging a part of the evaporation residue mixture (concentrated liquid) extracted from the evaporator and recycled to the reactor was further increased from that in Comparative Example 1 to 2.5 kg / hour (purge rate: 3.7%). When continuous production of diphenyl carbonate was continued in the same manner as in No. 1, precipitation of the catalyst became more prominent, and clogging in piping and valves also occurred. The concentration of the hardly volatile by-product in the evaporation residue mixture (concentrated liquid) at this time was about 5% by weight.

FIG. 1 is a flowchart illustrating the process of the continuous production method of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Catalyst supply line 2 Raw material (DPO) supply line 3 Reactor 4 Reaction mixture extraction line 5 Evaporator 6 Evaporation residue mixture recycling line 7 Purge liquid discharge line 8 CO discharge line 9 Evaporating distillate supply line 10 Distillation column 12 Distillation column 14 Product (DPC) outflow line

Claims (6)

A reaction step in which diaryl oxalate is de-CO-reacted in the presence of a de-CO catalyst to form a reaction mixture containing diaryl carbonate, an evaporation step in which an evaporation component containing diaryl carbonate as a main component is evaporated from the reaction mixture, and In the continuous production method of diaryl carbonate comprising continuously performing the step of returning the evaporation residue mixture of the evaporation step to the reaction step, the boiling point is higher than that of the diaryl carbonate contained in the evaporation residue mixture returned to the reaction step from the evaporation step A method for continuously producing diaryl carbonate, characterized in that the amount of reaction by-product comprising an aromatic carboxylic acid ester is maintained in the range of 20 to 35% by weight and continuously produced in a time exceeding 500 hours.   Maintaining the amount of reaction by-products having a boiling point higher than that of the diaryl carbonate contained in the evaporation residue mixture returned from the evaporation step to the reaction step, adjusting the ratio between the evaporation component and evaporation residue mixture generated in the evaporation step and / or part The continuous process for producing a diaryl carbonate according to claim 1, which is carried out by removing a typical evaporation residue mixture out of the system. The process for continuously producing a diaryl carbonate according to claim 1 or 2, wherein the aromatic carboxylic acid ester contained in the evaporation residue mixture has a molecular weight distribution in the range of 300 to 800. The process for continuously producing a diaryl carbonate according to claim 1 or 2, wherein the aromatic carboxylic acid ester contained in the evaporation residue mixture has an average molecular weight in the range of 400 to 600. The continuous production method of a diaryl carbonate according to any one of claims 1 to 4, wherein the diaryl oxalate is diphenyl oxalate and the diaryl carbonate is diphenyl carbonate. The continuous production method of a diaryl carbonate according to any one of claims 1 to 5, wherein the de-CO catalyst is an organophosphorus compound.

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