Method for producing diaryl carbonates

Abstract

To provide a method for producing diaryl carbonates that can reduce heat consumption while suppressing the by-production of phenyl salicylate. [Solution] A continuous manufacturing method comprising: a second reaction distillation step in which a dialkyl carbonate and an aromatic monohydroxy compound are continuously supplied to a first continuous multi-stage distillation column, catalytic reaction and distillation are carried out simultaneously to extract high-boiling-point components, and the mixture is supplied to a second continuous multi-stage distillation column, where catalytic reaction and distillation are carried out simultaneously to extract high-boiling-point components; a first purification step in which the extracted high-boiling-point components are supplied to a high-boiling-point substance separation column and separated by distillation into low-boiling-point components and high-boiling-point components; a second purification step in which the low-boiling-point components are supplied to a purification column and separated by distillation into three components: top component, side-cut component, and bottom component; a first circulation step in which the low-boiling-point components are supplied to the first continuous multi-stage distillation column; a thin-film evaporation step in which the high-boiling-point components are supplied to a thin-film evaporator and separated into low-boiling-point components and high-boiling-point components; and a second circulation step in which the high-boiling-point components are supplied to the first continuous multi-stage distillation column / second continuous multi-stage distillation column.

Description

[Technical Field]

[0001] This invention relates to a method for producing diaryl carbonates. [Background technology]

[0002] In the presence of a homogeneous catalyst, the reaction mixture obtained from a transesterification reaction using a dialkyl carbonate and an aromatic monohydroxy compound as raw materials usually contains various reaction by-products. In particular, if diaryl carbonates that do not sufficiently reduce high-boiling point by-products, such as phenyl salicylate, xanthones, phenyl methoxybenzoate, and 1-phenoxycarbonyl-2-phenoxycarboxyphenylene, which have higher boiling points than the target diaryl carbonate, are used as raw materials for transesterification polycarbonates, it can cause discoloration and deterioration of physical properties. Therefore, it is preferable to reduce these impurities as much as possible.

[0003] As a way to solve these problems, for example, Patent Document 1 proposes a method for stably producing high-purity diphenyl carbonate industrially in large quantities (e.g., 1 ton or more per hour) over a long period of time (e.g., 1000 hours or more) for a long period of time, by including a dialkyl carbonate production step (II) of producing dialkyl carbonates and diols using a reaction distillation column having a specific structure, a step (II) of producing diphenyl carbonate using two reaction distillation columns having a specific structure, and a step (III) of obtaining high-purity diphenyl carbonate using a high-boiling-point substance separation column A and a diphenyl carbonate purification column B.

[0004] Furthermore, Patent Document 2 proposes a manufacturing method in which the reaction performance of the first and second continuous multi-stage distillation columns can be improved, heat consumption reduced, and catalyst replenishment suppressed by setting the mass concentration ratio of diphenyl carbonate (DPC) to high-boiling-point substance (HB) in the bottom component of the high-boiling-point substance separation column (DPC / HB) to 0.1 to 1.0, and the mass concentration ratio of diphenyl carbonate to catalyst (DPC / catalyst) to 1.0 to 10.0. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2007 / 072705 [Patent Document 2] International Publication No. 2023 / 068288 [Overview of the project] [Problems that the invention aims to solve]

[0006] In the method described in Patent Document 1, in the first continuous multistage distillation column, an alkyl carbonate (e.g., dimethyl carbonate (DMC)) and phenol (PhOH) are reacted in the presence of a catalyst to produce an alkylaryl carbonate (e.g., methylphenyl carbonate (MPC)) and an alcohol (e.g., methanol (MeOH)). In the second continuous multistage distillation column, a diaryl carbonate (e.g., diphenyl carbonate (DPC)) and a dialkyl carbonate (e.g., dimethyl carbonate (DMC)) are produced by a disproportionation reaction of the alkylaryl carbonate (e.g., methylphenyl carbonate (MPC)). For example, this is represented by the following reaction equation. [ka]

[0007] After the disproportionation reaction, the high-boiling reaction mixture in the second continuous multi-stage distillation column, which contains diaryl carbonate (e.g., diphenyl carbonate (DPC)), is distilled in a high-boiling substance separation column and a diphenyl carbonate purification column. Here, the bottom components of the high-boiling substance separation column are supplied to the first and second continuous multi-stage distillation columns, thereby recycling the catalyst necessary for the reaction.

[0008] The bottom components of high-boiling-point substance separation columns contain a large amount of high-boiling-point substances. Therefore, in order to suppress the increase in the concentration of high-boiling-point substances in the system, at least a portion of the bottom components are usually discarded without being recycled.

[0009] In the method described in Patent Document 1, the reaction efficiency of the raw materials is insufficient in both the first continuous multi-stage distillation column and the second continuous multi-stage distillation column. Therefore, in order to produce the target diaryl carbonate, a large amount of the raw materials, dialkyl carbonate and aromatic monohydroxy compounds, must be circulated, which presents challenges in terms of energy efficiency.

[0010] Reducing the amount of diaryl carbonate entrained in the recycled catalyst reduces the amount of diaryl carbonate returned to the first and second continuous multi-stage distillation columns, shifting the equilibrium of the transesterification reaction toward the generation of diaryl carbonate and thus increasing the reaction efficiency. However, in the method described in Patent Document 2, if the operating temperature of the high-boiling-point substance separation column is increased to facilitate the evaporation of diaryl carbonate and reduce the amount recycled, the concentration of phenyl salicylate, a high-boiling-point byproduct, tends to increase. Phenylen salicylate is difficult to separate from diaryl carbonate because their boiling points are close, and it is undesirable as it can cause discoloration and deterioration of the properties of diaryl carbonate.

[0011] Therefore, the present invention aims to provide a method for producing diaryl carbonates that can reduce heat consumption while suppressing the by-production of phenyl salicylate. [Means for solving the problem]

[0012] The present invention encompasses the following embodiments. <1> A method for continuously producing a diaryl carbonate, comprising: continuously feeding a dialkyl carbonate and an aromatic monohydroxy compound into a first continuous multi-stage distillation column, and simultaneously performing a reaction and distillation in the presence of a catalyst to obtain a low-boiling component F containing alcohol H , H , 2H , H , 2L , H , , L , , , , L , L , 2H , H , , 1H , L , 2L , , S , , continuously withdrawn from the upper part of the column, and a high-boiling component F containing an alkylaryl carbonate 1H continuously withdrawn from the lower part of the column, and a first reactive distillation step; feeding the high-boiling component F 1H Into a second continuous multi-stage distillation column, and simultaneously performing a reaction and distillation in the presence of a catalyst to obtain a low-boiling component F containing a dialkyl carbonate 2L continuously withdrawn from the upper part of the column, and a high-boiling component F containing a diaryl carbonate 2H continuously withdrawn from the lower part of the column, and a second reactive distillation step; feeding the high-boiling component F 2H continuously into a high-boiling substance separation column, and continuously distilling and separating it into a low-boiling component A containing a diaryl carbonate L and a high-boiling component A containing a catalyst H and a first purification step; feeding the low-boiling component A L continuously into a diaryl carbonate purification column, and continuously distilling and separating it into three components: a top component B L a side-cut component B containing a diaryl carbonate S and a bottom component B H and a second purification step; feeding the low-boiling component F 2L continuously into the first continuous multi-stage distillation column, and a first circulation step; feeding the high-boiling component A H into a thin-film evaporator, and separating it into a low-boiling component C L and a high-boiling component C H and a thin-film evaporation step; feeding the high-boiling component C H continuously into the first continuous multi-stage distillation column and / or the second continuous multi-stage distillation column, and a second circulation step; A method for producing a diaryl carbonate comprising. <2> The aforementioned low boiling point component C L This includes a third circulation step of continuously supplying the above-mentioned high-boiling-point substance separation column, <1> The manufacturing method described above. <3> In the thin-film evaporation process, the temperature conditions are 193°C to 203°C, and the pressure conditions are 500 Pa to 3000 Pa. <1> or <2> The manufacturing method described above. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a method for producing diaryl carbonate that reduces heat consumption and suppresses the by-production of phenyl salicylate. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram showing an example of a continuous multi-stage distillation column T0. An internal structure consisting of a perforated plate tray is installed inside the shell. [Figure 2] This is a schematic diagram showing an example of a first continuous multi-stage distillation column. An internal is installed inside the shell. [Figure 3] This is a schematic diagram showing an example of a second continuous multi-stage distillation column. Inside the shell, there is an internal structure consisting of ordered packing at the top and a perforated plate tray at the bottom. [Figure 4] This is a schematic diagram showing an example of a thin-film evaporator. [Figure 5] This is a schematic diagram showing an example of an apparatus in which a first continuous multi-stage distillation column 101 and a second continuous multi-stage distillation column 201 are connected. [Figure 6] This is a schematic diagram showing an example of an apparatus having a high-boiling-point substance separation column A, a diaryl carbonate purification column B, and a thin-film evaporator C. [Figure 7] This is a schematic diagram showing an example of a apparatus that connects a high-boiling-point substance separation column A and a diaryl carbonate purification column B. [Modes for carrying out the invention]

[0015] The embodiments of the present invention (hereinafter referred to as "these embodiments") will be described in detail below, with reference to the drawings as necessary. However, the present invention is not limited thereto, and various modifications are possible without departing from its essence. In the drawings, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to those shown.

[0016] Numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described stepwise in this specification, the upper or lower limit of a numerical range in one step can be arbitrarily combined with the upper or lower limit of a numerical range in another step.

[0017] Modifiers such as "first," "second," and "third" may be used to distinguish elements, but such modifiers do not necessarily indicate any specific order.

[0018] The manufacturing method of this embodiment is a method for continuously producing diaryl carbonate, Dialkyl carbonates and aromatic monohydroxy compounds are continuously supplied into the first continuous multi-stage distillation column, and the reaction and distillation are carried out simultaneously in the presence of a catalyst, producing a low-boiling point component F containing alcohol. 1L The high-boiling point component F containing alkylaryl carbonate is continuously extracted from the top of the column. 1H The first reaction distillation step involves continuously extracting the material from the lower part of the column, The aforementioned low boiling point component F 1L The mixture is continuously supplied into the second continuous multi-stage distillation column, and the reaction and distillation are carried out simultaneously in the presence of a catalyst, producing a low-boiling point component F containing dialkyl carbonate. 2L The high-boiling point component F containing diaryl carbonate is continuously extracted from the top of the tower. 2H The second reaction distillation step involves continuously extracting the material from the lower part of the column, The aforementioned high-boiling point component F 2H The low-boiling component A, which contains diaryl carbonate, is continuously supplied to the high-boiling-point substance separation column. L And, high boiling point component A containing a catalystH The first purification step involves continuous distillation separation, The aforementioned low boiling point component A L This is continuously supplied to the diaryl carbonate purification column, and the top component B L Side cut component B containing diaryl carbonate S and base component B H The second purification step involves sequentially distilling and separating the three components, The aforementioned low boiling point component F 2L A first circulation step involves continuously supplying the above into the first continuous multi-stage distillation column, The aforementioned high boiling point component A H The low boiling point component C is supplied to the thin film evaporator. L And, high boiling point component C H The thin film evaporation process separates the two into, The aforementioned high boiling point component C H A second circulation step, which continuously supplies the first continuous multi-stage distillation column and / or the second continuous multi-stage distillation column, Includes.

[0019] The diaryl carbonate production method of this embodiment, due to the above-mentioned features, has the effect of reducing heat consumption and suppressing the by-production of phenyl salicylate. Although the mechanism by which these effects are achieved is not clear, the inventors of the present invention posit the following.

[0020] High-boiling-point component A in a high-boiling-point substance separation column H However, when supplied to the first continuous multi-stage distillation column and / or the second continuous multi-stage distillation column and recycled as a catalyst, high boiling point component A H This includes not only catalysts but also diaryl carbonates and other high-boiling-point substances. In this process, high-boiling-point component A is recycled to the first and / or second continuous multi-stage distillation column. H It was revealed that the diaryl carbonate contained in the product unfavorably affects the formation of diaryl carbonate in the equilibrium of the transesterification reaction in the first and / or second continuous multistage distillation column.

[0021] The method for producing diaryl carbonate in this embodiment involves high boiling point component AH Using a thin-film evaporator, the high-boiling point component C H And, low boiling point component C L It has a thin-film evaporation process that separates the high-boiling point component C. H This is high-boiling point component A H It contains most of the catalyst and most of the high-boiling-point material, and low-boiling-point component C L It contains most diaryl carbonates and substances with lower boiling points than diaryl carbonates. High boiling point component C H By supplying this to the first and / or second continuous multi-stage distillation column, the concentration of diaryl carbonate in the recycled composition can be reduced. As a result, in the first continuous multi-stage distillation column, alkylaryl carbonate is produced by the reaction of dialkyl carbonate with an aromatic monohydroxy compound, and then diaryl carbonate is produced by the reaction of alkylaryl carbonate with an aromatic monohydroxy compound. In this reaction equilibrium, the production of diaryl carbonate becomes more favorable, and as alkylaryl carbonate is consumed, the production of alkylaryl carbonate becomes more favorable. Furthermore, in the second continuous multi-stage distillation column, reducing the concentration of diaryl carbonate in the recycled composition makes the production of diaryl carbonate more favorable in terms of reaction equilibrium.Therefore, the method for producing diaryl carbonate in this embodiment is thought to reduce the amount of heat used for the reaction in the first and / or second continuous multi-stage distillation column, and furthermore, to suppress the production of phenyl salicylate.

[0022] In the thin-film evaporation process, the low-boiling point component C is separated. L It is preferable to continuously supply the resulting material directly to the high-boiling-point substance separation column (third circulation process). In the third circulation process, it may also be recycled to the bottom of the high-boiling-point substance separation column.

[0023] Furthermore, as a method to reduce the concentration of diaryl carbonate in the catalyst recycled in the first and / or second continuous multi-stage distillation column, it is usually considered to raise the bottom temperature of the high-boiling point substance separation column. However, this method is undesirable because it increases the concentration of phenyl salicylate in the bottom component. Therefore, it is considered that by introducing the thin-film evaporation process as described above, the reaction performance can be improved while suppressing the generation of phenyl salicylate.

[0024] Furthermore, it is preferable that the temperature conditions in the thin-film evaporation process are between 193°C and 203°C, and the pressure conditions are between 500 Pa and 3000 Pa. By performing the thin-film evaporation process under these conditions, the amount of heat consumed can be significantly reduced.

[0025] According to the diaryl carbonate production method of this embodiment, by improving the reaction performance, it is possible to reduce, for example, the amount of recirculation between the dialkyl carbonate and the aromatic monohydroxy compound. Consequently, the amount of energy used in the first recirculation step can also be suppressed.

[0026] In this embodiment, a high-boiling-point substance refers to a substance with a boiling point higher than that of diaryl carbonate, excluding the catalyst.

[0027] (Dialkyl carbonate manufacturing process) This embodiment may include a step (hereinafter also referred to as the "dialkyl carbonate production step") for continuously producing dialkyl carbonates and diols from, for example, a cyclic carbonate and an aliphatic monohydric alcohol in order to obtain the dialkyl carbonate as a raw material. The reaction in the dialkyl carbonate production step is a reversible transesterification reaction represented by the following formula. Diols are produced together with the alkyl carbonate.

[0028] [ka]

[0029] (In the formula, R 1 R represents a divalent group -(CH2)m- (where m is an integer from 2 to 6), and one or more of its hydrogen atoms may be substituted by alkyl or aryl groups having 1 to 10 carbon atoms. 2 (This represents a monovalent aliphatic group having 1 to 12 carbon atoms, and one or more of its hydrogen atoms may be substituted with alkyl or aryl groups having 1 to 10 carbon atoms.)

[0030] Examples of cyclic carbonates include alkylene carbonates such as ethylene carbonate and propylene carbonate, 1,3-dioxacyclohexa-2-one, and 1,3-dioxacyclohepta-2-one. Among these, alkylene carbonates are preferred, ethylene carbonate and propylene carbonate are more preferred, and ethylene carbonate is even more preferred. It is preferable that the cyclic carbonate is produced by the reaction of an alkylene oxide such as ethylene oxide, propylene oxide, or styrene oxide with carbon dioxide.

[0031] Furthermore, the aliphatic monohydric alcohol used has a lower boiling point than the diols produced. Preferably, the aliphatic monohydric alcohol is an alcohol having 1 to 6 carbon atoms. Examples of alcohols having 1 to 6 carbon atoms include methanol, ethanol, propanol (each isomer), and butanol (each isomer). Among these, methanol and ethanol are preferred, with methanol being more preferred.

[0032] In the reaction distillation process for dialkyl carbonate production, any method is acceptable for introducing the catalyst into the reaction distillation column. For example, in the case of a homogeneous catalyst that dissolves in the reaction solution under reaction conditions, the catalyst can be introduced into the reaction distillation column by continuously supplying it to the column. Alternatively, in the case of a heterogeneous catalyst that does not dissolve in the reaction solution under reaction conditions, the catalyst can be introduced into the reaction system by placing a solid catalyst in the reaction distillation column. A combination of these methods is also acceptable.

[0033] The catalyst is not particularly limited, but examples include alkali metals, alkaline earth metals, alkali metal and alkaline earth metal hydrides, hydroxides, alkoxides, aryloxides, amidides and other basic compounds, alkali metal and alkaline earth metal carbonates, bicarbonates, organic acid salts and other basic compounds, tertiary amines, nitrogen-containing heteroaromatic compounds, cyclic amidines, thallium compounds, tin compounds, zinc compounds, aluminum compounds, titanium compounds, phosphorus compounds, zirconium compounds, lead and lead-containing compounds, lead oxides, lead sulfides, lead hydroxides, zinc salts, lead salts, lead carbonates and their basic salts, alkoxy leads, aryloxy leads, lead salts of organic acids and their carbonates and basic salts, organic lead compounds, lead alloys, lead minerals, and hydrates of these lead compounds. Among these, alkali metals are preferred. Examples of alkali metals include lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, and barium.

[0034] These compounds can be used as homogeneous catalysts when dissolved in reaction raw materials, reaction mixtures, or reaction by-products, and can be used as solid catalysts when they do not dissolve. Furthermore, it is also preferable to pre-dissolve these compounds in reaction raw materials, reaction mixtures, or reaction by-products, or to use a mixture obtained by reacting with these compounds as a homogeneous catalyst.

[0035] Furthermore, ion exchangers such as anion exchange resins having tertiary amino groups, ion exchange resins having amide groups, ion exchange resins having at least one exchange group among sulfonic acid groups, carboxylic acid groups, and phosphate groups, and solid strong basic anion exchangers having quaternary ammonium groups as exchange groups; and solid inorganic compounds such as silica, silica-alumina, silica-magnesia, aluminosilicate, gallium silicate, various zeolites, various metal exchange zeolites, and ammonium exchange zeolites are used as catalysts.

[0036] As solid catalysts, solid strongly basic anion exchangers having quaternary ammonium groups as exchange groups are particularly preferred. Such solid strongly basic anion exchangers are not particularly limited, but examples include strongly basic anion exchange resins having quaternary ammonium groups as exchange groups, cellulose strongly basic anion exchangers having quaternary ammonium groups as exchange groups, and inorganic support-supported strongly basic anion exchangers having quaternary ammonium groups as exchange groups. Strongly basic anion exchange resins having quaternary ammonium groups as exchange groups are not particularly limited, but for example, styrene-based strongly basic anion exchange resins are preferably used.

[0037] The amount of catalyst used in the dialkyl carbonate manufacturing process varies depending on the type of catalyst used. When a homogeneous catalyst that dissolves in the reaction solution under reaction conditions is continuously supplied, the amount of catalyst is preferably 0.0001 to 50% by mass, more preferably 0.005 to 20% by mass, and even more preferably 0.01 to 10% by mass, relative to the total mass of the cyclic carbonate and aliphatic monohydric alcohol supplied as raw materials. Furthermore, when a solid catalyst is installed and used in a distillation column, the amount of catalyst is preferably 0.01 to 75% by volume, more preferably 0.05 to 60% by volume, and even more preferably 0.1 to 60% by volume, relative to the empty volume of the distillation column.

[0038] In the dialkyl carbonate manufacturing process, the raw material may contain the product dialkyl carbonate and / or diols. The content of dialkyl carbonate is preferably 0 to 40% by mass, more preferably 0 to 30% by mass, and even more preferably 0 to 20% by mass in the raw material. The content of diols is preferably 0 to 10% by mass, more preferably 0 to 7% by mass, and even more preferably 0 to 5% by mass in the raw material.

[0039] In the dialkyl carbonate manufacturing process, not only newly introduced raw materials into the reaction system may be used, but also cyclic carbonates and / or aliphatic monohydric alcohols recovered in this process and / or other processes may be used as raw materials. Other processes include, for example, the first reaction distillation process, in which aliphatic monohydric alcohols are produced as by-products and recovered. These recovered by-product aliphatic monohydric alcohols may typically include dialkyl carbonates, aromatic monohydroxy compounds, alkylaryl ethers, and the like.

[0040] In the dialkyl carbonate production process, the molar ratio of aliphatic monohydric alcohol to cyclic carbonate (aliphatic monohydric alcohol / cyclic carbonate) in the raw materials supplied to the reaction distillation column is preferably 0.01 to 1000, more preferably 2 to 20, even more preferably 3 to 15, and even more preferably 5 to 12.

[0041] In the dialkyl carbonate manufacturing process, for example, when continuously producing approximately 0.4 tons or more of dialkyl carbonate per hour, the minimum amount of cyclic carbonate continuously supplied is typically 0.44P tons / hr relative to the amount of dialkyl carbonate to be produced (P tons / hr).

[0042] The continuous multi-stage distillation column T0 used in the dialkyl carbonate manufacturing process is not particularly limited, but for example, as shown in Figure 1, it has a cylindrical body 7 with a body length L0 (cm) and a body inner diameter D0 (cm), and has an internal structure 6 with n0 stages inside, with an inner diameter d at the top of the column or near the top of the column. 01 (cm) Gas outlet 1, at the bottom of the tower 5 or near the bottom of the tower with an inner diameter d 02 (cm) liquid outlet 2, one or more first inlets 3-a, 3-b, 3-c, 3-d, and / or 3-e below the gas outlet 1 and in the upper and / or middle part of the column, and one or more second inlets 4-a and / or 4-b above the liquid outlet 2 and in the middle and / or lower part of the column, L0, D0, L0 / D0, n0, D0 / d 01 , D0 / d 02However, examples of continuous multi-stage distillation columns that satisfy equations (1) to (6) are given. Equation (1): 2100 ≤ L0 ≤ 8000 (more preferably 2300 ≤ L0 ≤ 6000, even more preferably 2500 ≤ L0 ≤ 5000) Equation (2): 180 ≤ D0 ≤ 2000 (more preferably 200 ≤ D0 ≤ 1000, even more preferably 210 ≤ D0 ≤ 800) Equation (3): 4 ≤ L0 / D0 ≤ 40 (more preferably 5 ≤ L0 / D0 ≤ 30, even more preferably 7 ≤ L0 / D0 ≤ 20) Equation (4): 10 ≤ n0 ≤ 120 (more preferably 30 ≤ n0 ≤ 100, even more preferably 40 ≤ n0 ≤ 90) Formula (5): 3≦D0 / d 01 ≤20 (more preferably 4 ≤ D0 / d 01 ≤15, more preferably 5 ≤D0 / d 01 ≤13) Formula (6): 5≦D0 / d 02 ≤30 (more preferably 7 ≤ D0 / d 02 ≤25, more preferably 9 ≤D0 / d 02 ≤20)

[0043] In this embodiment, the term "top of the column or the upper part of the column near the top" refers to the portion from the top of the column downwards to approximately 0.25 L0, and the term "bottom of the column or the lower part of the column near the bottom" refers to the portion from the bottom of the column upwards to approximately 0.25 L0. (In the first and second continuous multistage distillation columns, these are 0.25 L1 and 0.25 L2, respectively, and in the high-boiling-point substance separation column A and diaryl carbonate purification column B, these are 0.25 L A and 0.25L B (That is the case.)

[0044] By using a continuous multi-stage distillation column T0 that simultaneously satisfies equations (1) to (6), dialkyl carbonates can be stably produced from cyclic carbonates and aliphatic monohydric alcohols on an industrial scale, preferably at a rate of 0.4 tons or more per hour, with high reaction rate, high selectivity, and high productivity, for long periods of time, for example, 1000 hours or more, preferably 3000 hours or more, and even more preferably 5000 hours or more. The reason why the dialkyl carbonate production process enables the production of dialkyl carbonates and diols on an industrial scale with such excellent effects is not clear, but it is presumed to be due to the combined effect brought about when the conditions of equations (1) to (6) are combined. The preferred ranges for each factor are shown below.

[0045] Satisfying equation (1) results in a good reaction rate, allowing the desired production volume to be achieved and equipment costs to be reduced. Satisfying equation (2) allows the desired production volume to be achieved while equipment costs to be reduced. Satisfying equation (3) improves operational stability, allows for lower temperatures at the bottom of the column, suppresses side reactions, and tends to improve selectivity. Satisfying equation (4) improves the reaction rate, allowing the desired production volume to be achieved and equipment costs to be reduced. Satisfying equation (5) reduces equipment costs, suppresses the leakage of gas components from the system, and facilitates stable operation. Satisfying equation (6) reduces equipment costs, relatively reduces the amount of liquid extracted, facilitates stable operation, and further reduces erosion, thereby suppressing corrosion of the equipment.

[0046] Furthermore, the continuous multi-stage distillation column T0 used in the dialkyl carbonate manufacturing process 01 and d 02 It is even more preferable if equation (28) is satisfied. 1 ≤ d 01 / d 02 ≦ 5 Equation (28).

[0047] In the context of dialkyl carbonate manufacturing processes, long-term stable operation means that for 1,000 hours or more, preferably 3,000 hours or more, and more preferably 5,000 hours or more, operation can be continued in a steady state based on the operating conditions without flooding, pipe clogging or erosion, and a predetermined amount of dialkyl carbonate and diols is produced while maintaining high reaction rate, high selectivity, and high productivity.

[0048] The continuous multistage distillation column T0 used in the dialkyl carbonate manufacturing process is preferably a distillation column having trays and / or packing as its internals. In this embodiment, "internals" refers to the part of the distillation column where gas and liquid actually come into contact. Such trays are not particularly limited, but examples of preferred trays include bubble trays, perforated plate trays, valve trays, counterflow trays, super flak trays, max flak trays, etc. As packing materials, irregular packing materials such as Raschig rings, Lessing rings, Pall rings, Berl saddles, Interox saddles, Dixon packing, McMahon packing, Helipak, etc., and regular packing materials such as Melapack, Gempack, Technopack, Flexipak, Sulzer packing, Goodroll packing, Glitch grid, etc. A multistage distillation column having both a tray section and a section filled with packing material can also be used. In this embodiment, the term "number of stages in the internals" refers to the number of trays in the case of trays, and to the theoretical number of stages in the case of packing material. Therefore, in the case of a multi-stage distillation column that has both a tray section and a section filled with packing material, the number of stages is the sum of the number of trays and the theoretical number of stages.

[0049] In the dialkyl carbonate manufacturing process, high reaction rates, high selectivity, and high productivity tend to be achieved regardless of whether a tray-type continuous multistage distillation column or a packed column-type continuous multistage distillation column is used, with the internal structure consisting of trays and / or packing having a predetermined number of stages. A tray-type distillation column with trays as the internal structure is more preferable. Furthermore, a perforated plate tray having a perforated plate section and a downcomer section is particularly superior in terms of the relationship between function and equipment cost.

[0050] Furthermore, the perforated plate tray has a perforated plate area of ​​1 m². 2 It is preferable to have 100 to 1000 holes per unit area. The number of holes in the perforated plate tray corresponds to the area of ​​the perforated plate section per square meter. 2 Preferably, there are 120 to 900 holes, and more preferably 150 to 800 holes. Also, the cross-sectional area per hole in the perforated plate tray is preferably 0.5 to 5 cm². 2 More preferably 0.7 to 4 cm 2 And more preferably 0.9 to 3 cm 2 Furthermore, the perforated plate tray has a perforated plate area of ​​1 m². 2 It has 100 to 1000 holes per unit, and the cross-sectional area of ​​each hole is 0.5 to 5 cm². 2 It is even more preferable that it be so.

[0051] Furthermore, the opening ratio of the perforated plate tray is preferably 1.5 to 15%, more preferably 1.7 to 13%, and even more preferably 1.9 to 11%. Here, the opening ratio of the perforated plate tray represents the ratio of the total cross-sectional area of ​​all holes in the perforated plate (total cross-sectional area) to the area of ​​the perforated plate portion (including the total cross-sectional area of ​​all holes). The area of ​​the perforated plate portion and / or the total cross-sectional area of ​​all holes may differ in each perforated plate tray, but even in this case, it is preferable that the opening ratio of each perforated plate tray is within the above range. The number of holes in the perforated plate portion may be the same for all perforated plates, or it may be different for all perforated plates.

[0052] In the process of producing dialkyl carbonates, for example, a cyclic carbonate and an aliphatic monohydric alcohol, which are the raw materials, are continuously supplied into a continuous multi-stage distillation column containing a catalyst. The reaction and distillation are carried out simultaneously in the column, and the low-boiling point reaction mixture containing the produced dialkyl carbonate is continuously withdrawn as a gas from the top of the column, while the high-boiling point reaction mixture containing diols is continuously withdrawn as a liquid from the bottom of the column, thereby continuously producing dialkyl carbonates and diols.

[0053] Furthermore, in the dialkyl carbonate manufacturing process, to continuously supply the raw materials, cyclic carbonate and aliphatic monohydric alcohol, into a continuous multi-stage distillation column T0, the raw materials may be supplied as a mixture or separately, in liquid and / or gaseous form, from one or more inlets located below the gas outlet at the top of the distillation column but in the upper or middle part of the column. Alternatively, a preferred method is to supply the cyclic carbonate or a raw material containing a large amount thereof in liquid form from an inlet in the upper or middle part of the distillation column, and the aliphatic monohydric alcohol or a raw material containing a large amount thereof in gaseous form from an inlet located above the liquid outlet at the bottom of the distillation column but in the middle or lower part of the column.

[0054] The reaction time of the transesterification reaction carried out in the dialkyl carbonate manufacturing process is considered to correspond to the average residence time of the reaction solution in the continuous multi-stage distillation column T0. This varies depending on the shape and number of stages of the distillation column's internals, the amount of raw materials supplied, the type and amount of catalyst, and the reaction conditions, but is usually 0.1 to 20 hours, preferably 0.5 to 15 hours, and more preferably 1 to 10 hours.

[0055] The reaction temperature in the dialkyl carbonate manufacturing process varies depending on the type of raw material compound and the type and amount of catalyst used, but is usually 30 to 300°C, preferably 40 to 250°C, more preferably 50 to 200°C, and even more preferably 60 to 150°C. Furthermore, the bottom temperature of the distillation column in the dialkyl carbonate manufacturing process is preferably 150°C or lower, more preferably 130°C or lower, even more preferably 110°C or lower, and even more preferably 100°C or lower. High reaction rates, high selectivity, and high productivity can be achieved even at such low bottom temperatures.

[0056] The reaction pressure is typically 1 Pa to 2 × 10⁻⁶. 7 Pa, preferably 10 3 Pa~10 7 Pa, fua10 4 Pa~5×10 6 It will be conducted within the Pa range.

[0057] Furthermore, the reflux ratio of the continuous multi-stage distillation column T0 in the dialkyl carbonate production process is usually 0 to 10, preferably 0.01 to 5, and more preferably 0.05 to 3.

[0058] The materials used to construct the continuous multi-stage distillation column T0 in the dialkyl carbonate manufacturing process are mainly metallic materials such as carbon steel and stainless steel, but stainless steel is preferred in terms of the quality of the dialkyl carbonates and diols produced.

[0059] (First reaction distillation step, and second reaction distillation step) In this embodiment, the production method involves continuously supplying a dialkyl carbonate and an aromatic monohydroxy compound into a first continuous multi-stage distillation column, and simultaneously carrying out the reaction and distillation in the presence of a catalyst to obtain a low-boiling point component F containing alcohol. 1L The high-boiling point component F containing alkylaryl carbonate is continuously extracted from the top of the column. 1H A first reaction distillation step in which the substance is continuously extracted from the lower part of the column, and The aforementioned high-boiling point component F 1H The mixture is continuously supplied into the second continuous multi-stage distillation column, and the reaction and distillation are carried out simultaneously in the presence of a catalyst, producing a low-boiling point component F containing dialkyl carbonate. 2L The high-boiling point component F containing diaryl carbonate is continuously extracted from the top of the tower. 2H It has a second reaction distillation step in which the material is continuously extracted from the lower part of the column.

[0060] The dialkyl carbonate used in the first reaction distillation step is not particularly limited, but examples include those represented by the following formula. [ka] Here, R 2 This is as stated above.

[0061] As for dialkyl carbonates, R 2Dialkyl carbonates in which the alkyl group has 4 or fewer carbon atoms are preferred. Examples of dialkyl carbonates include dimethyl carbonate, diethyl carbonate, dipropyl carbonate (each isomer), and dibutyl carbonate (each isomer). Among these, dimethyl carbonate is preferred. Furthermore, dialkyl carbonates produced in a substantially halogen-free state are preferred, for example, those produced from a substantially halogen-free alkylene carbonate and a substantially halogen-free alcohol. Here, substantially halogen-free means a halogen content of 1 ppb or less.

[0062] Aromatic monohydroxy compounds are compounds represented by the formula: ArOH (wherein Ar is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms). Examples of Ar include phenyl groups and substituted phenyl groups in which at least one hydrogen atom is substituted with an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms. Among these, phenyl groups are preferred.

[0063] Diaryl carbonates are compounds represented by the formula: ArOCOOAr (wherein Ar is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms).

[0064] In the first reaction distillation step, the molar ratio of dialkyl carbonate to aromatic monohydroxy compound (dialkyl carbonate / aromatic monohydroxy compound) is preferably 0.1 to 10. Within this range, the amount of unreacted raw materials remaining is small relative to the desired production amount of diaryl carbonate, making the process efficient and reducing the energy required to recover them. In this sense, the molar ratio is more preferably 0.5 to 5, more preferably 0.8 to 3, and even more preferably 1 to 2. Here, the molar ratio refers to the value obtained by converting the total supply amount (t / h) of raw materials supplied to the first continuous multistage distillation column and high-boiling-point components recycled from the thin-film evaporation step into molar ratio.

[0065] In this embodiment, it is preferable to continuously produce 1 ton or more of high-purity diaryl carbonate per hour.

[0066] Therefore, in the first reaction distillation step, the minimum amount of aromatic monohydroxy compound continuously supplied is typically 8 Q tons / hr relative to the amount of high-purity diaryl carbonate to be produced (Q tons / hr).

[0067] The dialkyl carbonate and aromatic monohydroxy compound may be of high purity, but they may also contain other compounds, such as compounds and reaction by-products generated in the first and / or second continuous multi-stage distillation column. When carried out industrially, it is preferable to use, in addition to the dialkyl carbonate and aromatic monohydroxy compound newly introduced into the reaction system, compounds recovered from the first and / or second continuous multi-stage distillation column as raw materials.

[0068] Low boiling point component F 2L It is preferable that the concentration of alkylaryl carbonate in the mixture is 1% by mass or less. Low boiling point component F 2L When the concentration of alkylaryl carbonate in the mixture is 1% by mass or less, the conversion rate of dimethyl carbonate in the first continuous multi-stage distillation column tends to improve. As a result, the amount of low-boiling-point mixture continuously supplied from the second continuous multi-stage distillation column to the first continuous multi-stage distillation column is reduced, and consequently, the amount of steam used in both the first and second continuous multi-stage distillation columns tends to decrease. From a similar perspective, low-boiling-point component F 2L The concentration of alkylaryl carbonate in the mixture is preferably 0.01 to 0.5% by mass, and more preferably 0.01 to 0.3% by mass. In this embodiment, the low boiling point component F 2L The concentration of alkylaryl carbonate in the mixture can be measured by the method described in the examples below.

[0069] In this industrially implemented embodiment, the raw materials supplied to the first continuous multi-stage distillation column preferably contain alcohols, alkylaryl carbonates, diaryl carbonates, alkylphenyl ethers, etc., and may also preferably contain small amounts of high-boiling point by-products such as phenyl carbonate, Fries transition products of diaryl carbonates, and their derivatives. In this embodiment, for example, when methylphenyl carbonate and diaryl carbonate are produced using dimethyl carbonate as the dialkyl carbonate and unsubstituted phenol as the aromatic monohydroxy compound, the raw materials preferably contain reaction products such as methyl alcohol, methylphenyl carbonate, and diphenyl carbonate, and may also contain small amounts of reaction by-products such as anisole, phenyl salicylate, methyl salicylate, and high-boiling point by-products derived therefrom.

[0070] Furthermore, the diaryl carbonate produced is preferably used to manufacture aromatic polycarbonates by polymerization with aromatic dihydroxy compounds. However, this polymerization reaction produces a large amount of aromatic monohydroxy compounds as by-products, which are recovered. From the viewpoint of resource utilization, it is preferable to use the aromatic monohydroxy compounds produced as by-products of the polymerization reaction as raw materials in the first reaction distillation step.

[0071] The diaryl carbonate produced in this embodiment is obtained by a transesterification reaction between a dialkyl carbonate and an aromatic monohydroxy compound. This transesterification reaction includes a reaction in which one or two alkoxy groups of the dialkyl carbonate are exchanged with the phenoxy group of the aromatic monohydroxy compound, thereby removing alcohols, and a disproportionation reaction, which is a transesterification reaction between two molecules of the resulting alkylaryl carbonate, converting it into diaryl carbonate and dialkyl carbonate. In the first continuous multistage distillation column of the first reaction distillation step, mainly alkylaryl carbonate is obtained, and in the second continuous multistage distillation column of the second reaction distillation step, diaryl carbonate and dialkyl carbonate are obtained mainly by the disproportionation reaction of this alkylaryl carbonate. It is preferable that the diaryl carbonate obtained in the second reaction distillation step does not contain any halogens. Such diaryl carbonate is useful, for example, as a raw material when industrially producing aromatic polycarbonates. This is because even if halogens are present in the polymerization raw materials in an amount less than, for example, 1 ppm, they will inhibit the polymerization reaction, hinder the stable production of aromatic polycarbonates, and cause a decrease in the physical properties and discoloration of the resulting aromatic polycarbonates.

[0072] <Catalyst> The catalyst used in the first and / or second reaction distillation steps is not particularly limited, but can be selected from, for example, the following compounds: <Lead compounds> Lead oxides such as PbO, PbO2, and Pb3O4; Lead sulfides such as PbS and Pb2S; Lead hydroxides such as Pb(OH)2 and Pb2O2(OH)2; Na2PbO2, K2PbO2, NaHPbO2, KHPbO2, and other malite salts; Lead salts such as Na2PbO3, Na2H2PbO4, K2PbO3, K2[Pb(OH)6], K4PbO4, Ca2PbO4, and CaPbO3; Lead carbonates such as PbCO3, 2PbCO3·Pb(OH)2, and their basic salts; Lead salts of organic acids such as Pb(OCOCH3)2, Pb(OCOCH3)4, and Pb(OCOCH3)2·PbO·3H2O, as well as their carbonates and basic salts; Organolead compounds such as Bu4Pb, Ph4Pb, Bu3PbCl, Ph3PbBr, Ph3Pb (or Ph6Pb2), Bu3PbOH, and Ph3PbO (where Bu represents a butyl group and Ph represents a phenyl group). Alkoxy lead compounds such as Pb(OCH3)2, (CH3O)Pb(OPh), and Pb(OPh)2, and aryl oxy lead compounds; Lead alloys such as Pb-Na, Pb-Ca, Pb-Ba, Pb-Sn, and Pb-Sb; Lead minerals such as borenite and senaenite, and hydrates of these lead compounds; <Compounds of copper group metals> Salts and complexes of copper group metals such as CuCl, CuCl2, CuBr, CuBr2, CuI, CuI2, Cu(OAc)2, Cu(acac)2, copper oleate, Bu2Cu, (CH3O)2Cu, AgNO3, AgBr, silver picrate, AgC6H6ClO4, [AuC≡CC(CH3)3]n, and [Cu(C7H8)Cl]4 (acac represents an acetylacetone chelate ligand). <Alkali metal complexes> Alkali metal complexes such as Li(acac) and LiN(C4H9)2; <Zinc complex> Zinc complexes such as Zn(acac)2; <Cadmium complexes> Cadmium complexes such as Cd(acac)2; <Compounds of iron group metals> Fe(C 10 Complexes of iron group metals such as H8)(CO)5, Fe(CO)5, Fe(C4H6)(CO)3, Co(mesitylene)2(PEt2Ph)2, CoC5F5(CO)7, Ni-π-C5H5NO, and ferrocene; <Zirconium complex> Zirconium complexes such as Zr(acac)4 and zirconocene; <Lewis acid compounds> Lewis acids such as AlX3, TiX3, TiX4, VOX3, VX5, ZnX2, FeX3, SnX4 (where X is a halogen, acetoxy group, alkoxy group, aryloxy group), and transition metal compounds that generate Lewis acids; <Organotin compound> (CH3)3SnOCOCH3, (C2H5)3SnOCOC6H5, Bu3SnOCOCH3, Ph3SnOCOCH3, Bu2Sn(OCOCH3)2, Bu2Sn(OCOC 11 H 23 )2, Ph3SnOCH3, (C2H5)3SnOPh, Bu2Sn(OCH3)2, Bu2Sn(OC2H5)2, Bu2Sn(OPh)2, Ph2Sn(OCH3)2, (C2H5)3SnOH, Ph3SnOH, Bu2SnO, (C8H 17 )2SnO, Bu2SnCl2, BuSnO(OH) and other organotin compounds; Metal-containing compounds such as these are used as catalysts.

[0073] The catalyst used in this embodiment is preferably one containing metals such as Pb, Cu, Zn, Fe, Co, Ni, Al, Ti, V, and Sn, and is a homogeneous catalyst that dissolves in the reaction system. Therefore, catalyst species in which these metal components are bonded to organic groups are preferably used. Of course, these catalyst components may have reacted with organic compounds present in the reaction system, such as aliphatic alcohols, phenols, alkylphenyl carbonates, diphenyl carbonates, dialkyl carbonates, etc., or they may have been heat-treated with the raw materials or products prior to the reaction. The catalyst used in this embodiment is preferably one that has high solubility in the reaction solution under the reaction conditions. In this sense, preferred catalysts include, for example, PbO, Pb(OH)2, Pb(OPh)2; TiCl4, Ti(OMe)4, (MeO)Ti(OPh)3, (MeO)2Ti(OPh)2, (MeO)3Ti(OPh), Ti(OPh)4; SnCl4, Sn(OPh)4, Bu2SnO, Bu2Sn(OPh)2; FeCl3, Fe(OH)3, Fe(OPh)3, etc., or catalysts obtained by treating these with phenol or a reaction solution. The catalyst used in the first continuous multi-stage distillation column and the catalyst used in the second continuous multi-stage distillation column may be of the same type or different types.

[0074] In this embodiment, it is particularly preferable to use halogen-free raw materials and catalysts. In this case, the diaryl carbonate produced is halogen-free and therefore useful as a raw material for the industrial production of polycarbonate by transesterification. This is because even if halogen is present in the polymerization raw material in an amount less than, for example, 1 ppm, it can inhibit the polymerization reaction, degrade the physical properties of the resulting polycarbonate, or cause discoloration.

[0075] The first continuous multi-stage distillation column 101, for example as shown in Figure 2, has a cylindrical body with a body length L1 (cm) and an internal diameter D1 (cm), and has an internal structure with n1 stages, with an internal diameter d at the top of the column or near the top of the column. 11 (cm) gas outlet 11, at the bottom of the tower 16 or nearby, inner diameter d12 A continuous multi-stage distillation column having a liquid outlet 12 (in cm), one or more third inlets 13 and / or 14 at a position below the gas outlet 11 and in the upper part and / or middle part of the column, and one or more fourth inlets 15 at a position above the liquid outlet 12 and in the middle part and / or lower part of the column, where L1, D1, L1 / D1, n1, D1 / d 11 , D1 / d 12 is preferably a continuous multi-stage distillation column that satisfies the following formulas (7) to (12) respectively. 1500 ≦ L1≦ 8000 Formula (7) 100 ≦ D1≦ 2000 Formula (8) 2 ≦ L1 / D1≦ 40 Formula (9) 20 ≦ n1≦ 120 Formula (10) 5 ≦ D1 / d 11 ≦ 30 Formula (11) 3 ≦ D1 / d 12 ≦ 20 Formula (12)

[0076] Further, the second continuous multi-stage distillation column 201 has, for example, as shown in FIG. 3, a cylindrical body having a body length L2 (cm) and a body inner diameter D2 (cm), and has an internal structure with the number of stages n2. It has a gas outlet 21 with an inner diameter d 21 (cm) at the top of the column or in the upper part of the column near it, a liquid outlet 22 with an inner diameter d 22 (cm) at the bottom of the column 26 or in the lower part of the column near it, and is a continuous multi-stage distillation having one or more fifth inlets 23 and / or 24 at a position below the gas outlet 21 and in the upper part and / or middle part of the column, and one or more sixth inlets 25 at a position above the liquid outlet 22 and in the middle part and / or lower part of the column, where L2, D2, L2 / D2, n2, D2 / d 21 , D2 / d 22 is preferably a continuous multi-stage distillation column that satisfies the following formulas (13) to (18) respectively. 1500 ≦ L2≦ 8000 Formula (13) 100 ≦ D2≦ 2000 Formula (14) 2 ≦ L2 / D2≦ 40 Formula (15) 10 ≦ n2≦ 80 Formula (16) 2 ≦ D2 / d21 ≦ 15 Equation (17) 5 ≤ D2 / d 22 ≦ 30 Equation (18)

[0077] By using a first continuous multistage distillation column and a second continuous multistage distillation column that simultaneously satisfy all of formulas (7) to (18), diaryl carbonates can be stably produced from dialkyl carbonates and aromatic monohydroxy compounds on an industrial scale, preferably at a rate of about 0.85 tons or more per hour, more preferably 1 ton or more, with high selectivity and high productivity, for a long period of time, preferably 2000 hours or more, more preferably 3000 hours or more, and even more preferably 5000 hours or more. The reason why the method of this embodiment enables the production of aromatic carbonates on an industrial scale with such excellent effects is not clear, but it is presumed to be due to the combined effect brought about when the conditions of formulas (7) to (18) are combined. The preferred ranges for each factor constituting the continuous multistage distillation column are shown below.

[0078] When L1(cm) and L2(cm) are both 1500 or more, the reaction rate improves, and the desired production volume can be achieved. Furthermore, in order to reduce equipment costs while ensuring a reaction rate that can achieve the desired production volume, it is preferable to set L1 and L2 to 8000 or less. More preferable ranges for L1(cm) and L2(cm) are 2000≦L1≦6000 and 2000≦L2≦6000, respectively, and even more preferable are 2500≦L1≦5000 and 2500≦L2≦5000.

[0079] The desired production volume can be achieved when D1 (cm) and D2 (cm) are each 100 or greater. Furthermore, in order to reduce equipment costs while achieving the desired production volume, it is preferable to set D1 and D2 to 2000 or less. More preferable ranges for D1 (cm) and D2 (cm) are 150 ≤ D1 ≤ 1500 and 150 ≤ D2 ≤ 1500, respectively, and even more preferable are 200 ≤ D1 ≤ 1000 and 200 ≤ D2 ≤ 1000, respectively.

[0080] In addition, in the first and second continuous multi-stage distillation columns, as long as D1 and D2 are within the above range, the inner diameter may be the same from the top to the bottom of the column, or it may be different in parts. For example, in these continuous multi-stage distillation columns, the inner diameter of the top of the column may be smaller or larger than the inner diameter of the bottom of the column.

[0081] When L1 / D1 and L2 / D2 are each 2 or greater, or 40 or less, stable operation becomes easier. In particular, when they are 40 or less, it is possible to suppress the pressure difference between the top and bottom of the column from becoming too large, which not only facilitates long-term stable operation but also allows for lower temperatures at the bottom of the column, thus suppressing side reactions and tending to improve selectivity. More preferable ranges for L1 / D1 and L2 / D2 are 2≦L1 / D1≦30 and 2≦L2 / D2≦30, respectively, and even more preferable are 2≦L1 / D1≦15 and 2≦L2 / D2≦15.

[0082] When n1 is 20 or greater, the reaction rate improves, allowing the desired production volume to be achieved in the first continuous multi-stage distillation column. Furthermore, to reduce equipment costs while ensuring a reaction rate that can achieve the desired production volume, it is preferable to set n1 to 120 or less. Moreover, when n1 is 120 or less, it is possible to suppress the pressure difference between the top and bottom of the column from becoming too large, which not only facilitates long-term stable operation of the first continuous multi-stage distillation column but also allows the temperature at the bottom of the column to be lowered, thereby suppressing side reactions and tending to improve selectivity. A more preferable range for n1 is 30 ≤ n1 ≤ 100, and even more preferable is 40 ≤ n1 ≤ 90.

[0083] Furthermore, when n2 is 10 or greater, the reaction rate improves, allowing the desired production volume to be achieved in the second continuous multi-stage distillation column. In addition, to reduce equipment costs while ensuring a reaction rate that can achieve the desired production volume, it is preferable to set n2 to 80 or less. Moreover, when n2 is 80 or less, it is possible to suppress the pressure difference between the top and bottom of the column from becoming too large, which not only facilitates long-term stable operation of the second continuous multi-stage distillation column but also allows the temperature at the bottom of the column to be lowered, which tends to suppress side reactions and improve selectivity. A more preferable range for n2 is 15 ≤ n2 ≤ 60, and even more preferable is 20 ≤ n2 ≤ 50.

[0084] D1 / d 11 A value of 5 or higher reduces the equipment costs of the first continuous multi-stage distillation column and suppresses the release of gaseous components into the system, thus facilitating stable operation of the first continuous multi-stage distillation column. A value of 30 or lower results in a relatively larger amount of gaseous components being extracted, which not only facilitates stable operation but also tends to improve the reaction rate. A more preferable value is D1 / d. 11 The range is 8 ≤ D1 / d 11 ≤25, and more preferably 10 ≤ D1 / d 11 The value is ≤20. Also, D2 / d 21 A D2 / d ratio of 2 or higher can reduce the equipment costs of the second continuous multi-stage distillation column and suppress the release of gaseous components into the system, thus facilitating stable operation of the second continuous multi-stage distillation column. A D2 / d ratio of 15 or lower results in a relatively larger amount of gaseous components being extracted, which not only facilitates stable operation but also tends to improve the reaction rate. A more preferable D2 / d ratio is 2 or higher. 21 The range is 5 ≤ ​​D² / d 21 ≤ 12, and more preferably 3 ≤ D² / d 21 The value is ≤ 10.

[0085] D1 / d 12 A value of 3 or higher reduces the equipment cost of the first continuous multi-stage distillation column, relatively reduces the amount of liquid extracted, and facilitates stable operation of the first continuous multi-stage distillation column. A value of 20 or lower suppresses a rapid increase in flow velocity at the liquid outlet and piping, making erosion less likely and suppressing corrosion of the equipment. A more preferable D1 / d value is 3 or higher. 12The range is 5 ≤ ​​D1 / d 12 ≤ 18, and more preferably 7 ≤ D1 / d 12 ≤ 15. Also, D2 / d 22 A value of 5 or higher reduces the equipment cost of the second continuous multi-stage distillation column, relatively reduces the amount of liquid extracted, and facilitates stable operation of the second continuous multi-stage distillation column. A value of 30 or lower suppresses a rapid increase in flow velocity at the liquid outlet and piping, making erosion less likely and suppressing corrosion of the equipment. A more preferable D2 / d value is 5 or higher. 22 The range is 7 ≤ D² / d 22 ≤25, and more preferably 9 ≤ D² / d 22 The value is ≤20.

[0086] Furthermore, in the first reaction distillation step, d 11 and d 12 and satisfy equation (29), and d 21 and d 22 It is even more preferable if it satisfies formula (30). 1≦d 12 / d 11 ≦5 Equation (29) 1≦d 21 / d 22 ≦6 Formula (30)

[0087] In the first reaction distillation process, long-term stable operation means that for 1,000 hours or more, preferably 3,000 hours or more, and more preferably 5,000 hours or more, operation can be continued in a steady state based on the operating conditions without flooding, weeping, pipe blockage or erosion, and a predetermined amount of diaryl carbonate is produced while maintaining high selectivity.

[0088] In the second reaction distillation step, the goal is to produce diaryl carbonate with high selectivity and stability over a long period of time, preferably with a high productivity of 1 ton or more per hour, more preferably with 2 tons or more per hour, and even more preferably with 3 tons or more per hour. In addition, in the first and second reaction distillation steps, L1, D1, L1 / D1, n1, D1 / d of the first continuous multistage distillation column 11 D1 / d12 These are 2000≦L1≦6000, 150≦D1≦1000, 3≦L1 / D1≦30, 30≦n1≦100, and 8≦D1 / d 11 ≤25, 5 ≤D1 / d 12 ≤ 18, and L2, D2, L2 / D2, n2, D2 / d of the second continuous multistage distillation column. 21 , D2 / d 22 These are 2000≦L2≦6000, 150≦D2≦1000, 3≦L2 / D2≦30, 15≦n2≦60, and 2.5≦D2 / d respectively. 21 ≤12, 7 ≤D² / d 22 When the value is ≤25, it is possible to produce at least 2 tons per hour, more preferably 2.5 tons per hour, and even more preferably 3 tons per hour of diaryl carbonate.

[0089] Furthermore, in the first and second reaction distillation steps, L1, D1, L1 / D1, n1, D1 / d of the first continuous multistage distillation column 11 D1 / d 12 These are 2500≦L1≦5000, 200≦D1≦800, 5≦L1 / D1≦15, 40≦n1≦90, and 10≦D1 / d respectively. 11 ≤25, 7 ≤D1 / d 12 ≤ 15, and L2, D2, L2 / D2, n2, D2 / d of the second continuous multistage distillation column. 21 , D2 / d 22 These are 2500≦L2≦5000, 200≦D2≦800, 5≦L2 / D2≦10, 20≦n2≦50, and 3≦D2 / d 21 ≤10, 9 ≤D² / d 22 If the value is ≤20, it is possible to produce at least 3 tons per hour, preferably at least 3.5 tons per hour, and more preferably at least 4 tons per hour of diaryl carbonate.

[0090] In this embodiment, the selectivity of the diaryl carbonate is relative to the reacted aromatic monohydroxy compound, and is preferably 95% or higher, more preferably 97% or higher, and even more preferably 98% or higher, achieving a high selectivity.

[0091] The first and second continuous multistage distillation columns preferably have trays and / or packing as internals. In this embodiment, "internals" refers to the part of the distillation column where gas-liquid contact actually occurs. As such trays, those described in the section on the dialkyl carbonate manufacturing process are preferred. The "number of internal stages" is as described above.

[0092] In the first continuous multi-stage distillation column of the first reaction distillation step, a reaction mainly to produce alkylaryl carbonates from dialkyl carbonates and aromatic monohydroxy compounds is carried out. Since this reaction has an extremely small equilibrium constant and a slow reaction rate, a tray-type distillation column with trays as the internal structure is more preferable as the first continuous multi-stage distillation column used for reaction distillation. In the second continuous multi-stage distillation column of the second reaction distillation step, a reaction mainly to disproportionate alkylaryl carbonates is carried out. This reaction also has a small equilibrium constant and a slow reaction rate. However, as the second continuous multi-stage distillation column used for reaction distillation, a distillation column having both packing and trays as the internal structure is more preferable. Furthermore, as the second continuous multi-stage distillation column, it is preferable to have packing at the top and trays at the bottom. The packing for the second continuous multi-stage distillation column is preferably ordered packing, and among ordered packings, Melapak is particularly preferred.

[0093] Furthermore, the trays installed in the first and second continuous multi-stage distillation columns are preferably perforated trays having a perforated plate section and a downcomer section, considering the relationship between function and equipment cost. The number of holes in the perforated plate section of the perforated tray is preferably 1 m² in area. 2 The number of holes is 100 to 1000 per square meter, with a more preferable number per square meter area. 2 The number is 120 to 900 per unit, and more preferably 150 to 800 per unit.

[0094] Furthermore, the cross-sectional area of ​​each hole in the perforated plate tray is 0.5 to 5 cm². 2Preferably, the cross-sectional area per hole is preferably 0.7 to 4 cm². 2 And more preferably 0.9 to 3 cm 2 Furthermore, the perforated plate tray has a perforated plate area of ​​1 m². 2 It has 100 to 1000 holes per unit, and the cross-sectional area of ​​each hole is 0.5 to 5 cm². 2 This is particularly preferable.

[0095] Low-boiling point component F containing alcohol in the first continuous multi-stage distillation column of the first reaction distillation step 1L In addition to the alcohols produced in the reaction, the compound typically contains dialkyl carbonates, aromatic monohydroxy compounds, alkylaryl ethers, and may also contain small amounts of alkylaryl carbonates and diaryl carbonates. Low boiling point component F 1L It can be extracted from the top of the column, but it is preferable to extract it from the top of the column. Low boiling point component F 1L While it can be used as is as an aliphatic monohydric alcohol in the dialkyl carbonate manufacturing process, it is preferable to use it as a raw material in the dialkyl carbonate manufacturing process after reducing the amount of substances with a higher boiling point than the alcohol produced by distillation or the like. It is particularly preferable that a mixture of this alcohol and the dialkyl carbonate be used as an aliphatic monohydric alcohol in the dialkyl carbonate manufacturing process.

[0096] In the first reaction distillation step, the dialkyl carbonate and aromatic monohydroxy compound may be continuously supplied into the first continuous multi-stage distillation column in liquid and / or gaseous form from one or more inlets located below the gas outlet at the top of the column but in the upper or middle part of the column, or the raw material containing a large amount of aromatic monohydroxy compound may be supplied in liquid form from the inlet at the top of the first distillation column, and the raw material containing a large amount of dialkyl carbonate may be supplied in gaseous form from an inlet located at the bottom of the column but above the liquid outlet at the bottom of the first distillation column.

[0097] Furthermore, in the second reaction distillation step, the high-boiling point component F1H The material is continuously supplied to the second continuous multi-stage distillation column, but the supply location is below the gas outlet at the top of the second continuous multi-stage distillation column. It is preferable that the material be supplied in liquid and / or gaseous form from one or more inlets located at the top or middle of the column. Furthermore, it is preferable that the second continuous multi-stage distillation column has a packing section at the top and a tray section at the bottom. When using such a distillation column, it is preferable that at least one inlet be located between the packing section and the tray section. Also, if the packing consists of two or more regular packings, it is preferable to install inlets at the intervals that make up these regular packings.

[0098] Furthermore, in the first and second reaction distillation steps, it is also preferable to perform a reflux operation in which the gas extraction components from the top of the first and second continuous multi-stage distillation columns are condensed, and then a portion of them is returned to the top of each distillation column. In this case, the reflux ratio of the first continuous multi-stage distillation column is 0 to 10, and the reflux ratio of the second continuous multi-stage distillation column is preferably 0.01 to 10, more preferably 0.08 to 5, and even more preferably 0.1 to 2. A reflux ratio of 0 in the first continuous multi-stage distillation column, where no reflux operation is performed, is also a preferred embodiment.

[0099] In the first reaction distillation step, any method of introducing the catalyst into the first continuous multi-stage distillation column is acceptable, but it is preferable to supply the catalyst into the distillation column from a position above the middle section of the first continuous multi-stage distillation column. Furthermore, it is preferable to supply the catalyst so that the reaction solution comes into contact with the catalyst in a region of at least 7 stages, preferably 10 stages, and more preferably 15 stages or more of the first continuous multi-stage distillation column. In this case, the catalyst solution, in which the catalyst is dissolved in the raw materials or reaction solution, may be introduced together with the raw materials, or the catalyst solution may be introduced from a separate inlet from the raw materials. In this embodiment, the amount of catalyst used in the first continuous multi-stage distillation column varies depending on the type of catalyst used, the type and ratio of raw materials, and the reaction conditions such as reaction temperature and reaction pressure, but is preferably 0.0001 to 30% by mass, more preferably 0.0005 to 10% by mass, and even more preferably 0.001 to 1% by mass, as a percentage of the total mass of the raw materials.

[0100] Furthermore, in the second reaction distillation step, any method is acceptable for introducing the catalyst into the second continuous multi-stage distillation column, but it is preferable to supply it into the distillation column from a position above the middle section of the second continuous multi-stage distillation column. In this case, the catalyst solution may be introduced together with the raw materials or reaction liquid, or the catalyst solution may be introduced from a separate inlet from the raw materials. In this embodiment, the amount of catalyst used in the second continuous multi-stage distillation column varies depending on the type of catalyst used, the type and ratio of raw materials, the reaction temperature, and the reaction pressure, but is preferably 0.0001 to 30% by mass, more preferably 0.0005 to 10% by mass, and even more preferably 0.001 to 1% by mass, as a percentage of the total mass of the raw materials.

[0101] The catalyst used in the first continuous multi-stage distillation column and the catalyst used in the second continuous multi-stage distillation column may be of the same type or different types, but preferably the same type of catalyst is used. More preferably, the catalyst is of the same type and can dissolve in both reaction solutions. In this case, the catalyst usually contains a high-boiling point component F 1H The catalyst is supplied to the second continuous multi-stage distillation column in a dissolved state. It is also possible to add additional catalyst to the second continuous multi-stage distillation column as needed.

[0102] The reaction time of the transesterification reaction carried out in the first and second reaction distillation steps is considered to correspond to the average residence time of the reaction solution in the first and second continuous multi-stage distillation columns, respectively. This reaction time varies depending on the shape and number of stages of the internal structure of each distillation column, the amount of raw material supplied, the type and amount of catalyst, and the reaction conditions, but is usually 0.01 to 10 hours, preferably 0.05 to 5 hours, and more preferably 0.1 to 3 hours, in both the first and second continuous multi-stage distillation columns.

[0103] The reaction temperature in the first continuous multi-stage distillation column varies depending on the type of raw material compound and the type and amount of catalyst used, but is usually in the range of 100 to 350°C. Increasing the reaction temperature is preferable to increase the reaction rate, but high reaction temperatures are undesirable because they also increase the likelihood of side reactions, such as the formation of alkylphenyl ethers as by-products. In this sense, the preferred reaction temperature in the first continuous multi-stage distillation column is in the range of 130 to 280°C, more preferably 150 to 260°C, and even more preferably 180 to 250°C.

[0104] The reaction temperature in the second continuous multi-stage distillation column varies depending on the type of starting compound and the type and amount of catalyst used, but is usually in the range of 100 to 350°C. While it is preferable to raise the reaction temperature to increase the reaction rate, higher reaction temperatures also increase the likelihood of side reactions, such as alkylphenyl ethers and the formation of Fries transition reaction products and derivatives of alkylaryl carbonates and diaryl carbonates, which are the starting compounds and products, and are therefore undesirable. In this sense, the preferred reaction temperature in the second continuous multi-stage distillation column is in the range of 130 to 280°C, more preferably 150 to 260°C, and even more preferably 180 to 250°C.

[0105] Furthermore, the reaction pressure of the first continuous multi-stage distillation column varies depending on the type and composition of the raw material compounds used, the reaction temperature, etc., but the first continuous multi-stage distillation column can be under reduced pressure, atmospheric pressure, or pressurized pressure. The usual top pressure of the column is 0.1 Pa ~ 2 × 10⁻⁶ 7 Pa, preferably 10 5 Pa~10 7 Pa, ffer2×10 5 Pa~5×10 6 This is within the range of Pa.

[0106] The reaction pressure in the second continuous multistage distillation column varies depending on the type and composition of the raw material compounds used, the reaction temperature, etc., but it can be reduced pressure, atmospheric pressure, or pressurized pressure. The usual top pressure of the column is 0.1 Pa ~ 2 × 10⁻⁶ 7 Pa, preferably 10 3 Pa~10 6 Pa, comfort5×10 3 Pa~105 This is within the range of Pa.

[0107] Furthermore, two or more distillation columns can be used as the first continuous multi-stage distillation column in the first reaction distillation step. In this case, the two or more distillation columns can be connected in series, in parallel, or in a combination of series and parallel connections. Furthermore, two or more distillation columns can be used as the second continuous multi-stage distillation column in the second reaction distillation process. In this case, the two or more distillation columns can be connected in series, in parallel, or in a combination of series and parallel connections.

[0108] The materials that make up the first and second continuous multi-stage distillation columns are mainly metallic materials such as carbon steel and stainless steel, but stainless steel is preferred in terms of the quality of the aromatic carbonate produced. Furthermore, it is preferable that the wetted parts at the bottom of the second continuous multi-stage distillation column be made of a material mainly composed of Fe, with Mo at least 2% by mass and Cr at least 18% by mass. When such a material is used for the wetted parts at the bottom of the second continuous multi-stage distillation column, corrosion of the distillation column tends to be suppressed even when the concentration of high-boiling-point substances in the components at the bottom of the second continuous multi-stage distillation column is increased. More preferably, the composition of the material for the wetted parts at the bottom of the second continuous multi-stage distillation column is 60-72% by mass of Fe, 2-3% by mass of Mo, and 16-18% by mass of Cr. In this embodiment, the main component means 40% by mass or more, preferably 50% by mass or more, and more preferably 60% by mass.

[0109] (1st circulation process) The manufacturing method of this embodiment uses low boiling point component F 2L The process has a first circulation step in which the low boiling point component F is continuously supplied into the first continuous multi-stage distillation column. 2L The material may be supplied directly to the first continuous multi-stage distillation column, or it may be supplied after some of its components have been separated. This process allows for the effective utilization of dialkyl carbonates and unreacted raw materials produced in the disproportionation reaction.

[0110] (First purification step and second purification step) The manufacturing method of the present embodiment is High-boiling component F 2H is continuously supplied to a high-boiling substance separation column, and a low-boiling component A containing diaryl carbonate L and a high-boiling component A containing a catalyst H are continuously separated by distillation into a first purification step, The low-boiling component A L is continuously supplied to a diaryl carbonate purification column, and the top component B L S a side-cut component B containing diaryl carbonate S and a bottom component B H and a second purification step of continuously separating into three components, and has.

[0111] High-boiling component F 2H is mainly composed of diaryl carbonate, but usually also contains reaction raw materials such as alkyl aryl carbonate, a small amount of high-boiling by-products and a catalyst. Therefore, from the viewpoint of obtaining high-purity diaryl carbonate from the high-boiling component F 2H the first purification step and the second purification step are carried out. In the first purification step and the second purification step, high-purity diaryl carbonate can be obtained as the side-cut component B S .

[0112] In addition, in the first purification step, the low-boiling component A L is further separated into a top component A T and a side-cut component A containing diaryl carbonate S in a high-boiling substance separation column. That is, the first purification step is a step of continuously supplying the high-boiling component F 2H to a high-boiling substance separation column, and continuously separating into three components of a top component A T a side-cut component A containing diaryl carbonate S and a high-boiling component A containing a catalyst H and may be.

[0113] The high-boiling substance separation column A, for example, has a cylindrical body with a length L A (cm) and an inner diameter D A (cm), and is a continuous multi-stage distillation column having internals with a number of stages n A inside. It is preferable that L A , D A , and n A respectively satisfy the following formulas (19) to (21) in the continuous multi-stage distillation column. 800 ≦ L A ≦ 3000 Formula (19) 100 ≦ D A ≦ 1000 Formula (20) 20 ≦ n A ≦ 100 Formula (21)

[0114] The diaryl carbonate purification column B, for example, has a cylindrical body with a length L B (cm) and an inner diameter D B (cm), and has a structure with internals inside. It has an inlet B1 in the middle of the column and a side cut extraction port B2 between the inlet B1 and the bottom of the column. The number of internal stages from the inlet B1 to the upper part is n B1 , the number of internal stages between the inlet B1 and the side cut extraction port B2 is n B2 , and the number of internal stages from the side cut extraction port B2 to the lower part is n B3 . It is a continuous multi-stage distillation column where the sum of the number of each stage (n B1 [[ID= forty]]+n B2 +n B3 ) is n B . It is preferable that L B , D B , n B1 , n B2 , n B3 , n B respectively satisfy the following formulas (22) to (27) in the continuous multi-stage distillation column. 1000 ≦ L B ≦ 5000 Formula (22) 100 ≦ D B ≦ 1000 Formula (23) 5 ≦ n B1 ≦ 20 Formula (24) 12 ≤ n B2 ≦ 40 Equation (25) 3 ≤ n B3 ≦ 15 Equation (26) 20 ≤ n B ≦ 70 Equation (27)

[0115] By satisfying all of these conditions simultaneously, the high boiling point component F 2H From this, high-purity diaryl carbonate can be produced stably over a long period of time on an industrial scale of more than 1 ton per hour. The production time is, for example, 2000 hours or more, preferably 3000 hours or more, and more preferably 5000 hours or more. The reason why such excellent effects are obtained by implementing the method of this embodiment is not clear, but it is presumed to be the effect brought about when a high-boiling-point substance separation column A and a diaryl carbonate purification column B that satisfy the conditions of equations (19) to (27) are combined. The preferred ranges for each factor are shown below.

[0116] L A When (cm) is 800 or higher, there is more headroom in the internal height that can be installed inside high-boiling-point substance separation column A, which tends to improve separation efficiency. Also, in order to reduce equipment costs while achieving the desired separation efficiency, L A It is preferable to make it 3000 or less. More preferable L A The range (cm) is 1000 ≤ L A ≤2500, and more preferably 1200 ≤L A The value is ≤2000.

[0117] D A If (cm) is 100 or more, the desired production volume can be achieved. Also, in order to reduce equipment costs while achieving the desired production volume, D A It is preferable to make it 1000 or less. A more preferable D A The range (cm) is 200 ≤ D A ≤900, and more preferably 250 ≤D A The value is ≤ 850.

[0118] n AWhen n is 20 or higher, the separation efficiency improves, and the desired high purity can be achieved. Also, in order to reduce equipment costs while achieving the desired separation efficiency, A It is preferable to make n 100 or less. A If n is 100 or less, it is possible to suppress the pressure difference between the top and bottom of the column from becoming too large, which not only facilitates long-term stable operation of high-boiling-point substance separation column A, but also allows for lower temperatures at the bottom of the column, which tends to suppress side reactions. A more preferable n A The range is 22≦n A ≤70, and more preferably 25 ≤ n A The value is ≤60.

[0119] L B When (cm) is 1000 or more, there is more headroom in the internal height that can be installed inside diaryl carbonate purification column B, which tends to improve separation efficiency. Also, in order to reduce equipment costs while achieving the desired separation efficiency, L B It is preferable to make it 5000 or less. More preferable L B The range (cm) is 1500 ≤ L B ≤4000, and more preferably 1700 ≤L B The value is ≤ 3500.

[0120] D B If (cm) is 100 or more, the desired production volume can be achieved. Also, in order to reduce equipment costs while achieving the desired production volume, D B It is preferable to make it 1000 or less. A more preferable D B The range (cm) is 150 ≤ D B ≤900, and more preferably 200 ≤D B The value is ≤ 800.

[0121] n B When n is 20 or higher, the overall separation efficiency of the tower improves, making it possible to achieve the desired high purity. Furthermore, in order to reduce equipment costs while achieving the desired separation efficiency, n B It is preferable to make n 70 or less. BWhen n is 70 or less, the pressure difference between the top and bottom of the column can be suppressed, which not only facilitates long-term stable operation of diaryl carbonate purification column B, but also allows for lower temperatures at the bottom of the column, which tends to suppress side reactions. B The range is 25≦n B ≤ 55, and more preferably 30 ≤ n B The value is ≤50. Furthermore, in order to obtain the desired high-purity diaryl carbonate stably over a long period of time, n B1 , n B2 , n B3 Each of these is 5≦n B1 ≤20, 12 ≤n B2 ≤40, 3 ≤n B3 It is preferable that the range is ≤15. A more preferable range is 7 ≤ n B1 ≤15, 12 ≤n B2 ≤30, 3 ≤n B3 The value is ≤ 10.

[0122] Note that the high-boiling-point substance separation column A has a bottom temperature (T A )185~280℃, top pressure (P A It is preferable to operate at 500 to 20000 Pa.

[0123] T A If the temperature is above 185°C, there is no need to lower the top pressure of the tower, so there is no need for equipment to maintain a high vacuum, and the equipment can be made smaller. A If the temperature is below 280°C, the formation of high-boiling point by-products during distillation tends to be suppressed. A The temperature range is 190-240°C, and more preferably 195-230°C.

[0124] P A If the pressure is 500 Pa or higher, there is no need for large equipment to maintain a high vacuum, P A When the pressure is below 20,000 Pa, the distillation temperature tends to be lower, which can suppress by-products. A more preferable P A The pressure is in the range of 700 to 15000 Pa, and more preferably in the range of 1000 to 13000 Pa.

[0125] Diaryl carbonate purification column B, bottom temperature (T B )185~280℃, top pressure (P B It is preferable to operate at 500 to 20000 Pa.

[0126] T B If the temperature is above 185°C, there is no need to lower the top pressure of the tower, so there is no need for equipment to maintain a high vacuum, and the equipment can be made smaller. B If the temperature is below 280°C, the formation of high-boiling point by-products during distillation tends to be suppressed. B The temperature range is 190-240°C, and more preferably 195-230°C.

[0127] P B If the pressure is 500 Pa or higher, there is no need for large equipment to maintain a high vacuum, P B When the pressure is below 20,000 Pa, the distillation temperature tends to be lower, which can suppress by-products. A more preferable P B The pressure is in the range of 700 to 15000 Pa, and more preferably in the range of 1000 to 13000 Pa.

[0128] Furthermore, in the high-boiling-point substance separation column A and the diaryl carbonate purification column B, D A and D B As long as it is within the above range, the inner diameter may be the same from the top to the bottom of the column, or it may have different inner diameters in parts. For example, in these continuous multi-stage distillation columns, the inner diameter of the top of the column may be smaller or larger than the inner diameter of the bottom of the column.

[0129] High-boiling point substance separation column A and diaryl carbonate purification column B are preferably distillation columns having trays and / or packing as internals. The trays described in the section on the dialkyl carbonate production process are preferred.

[0130] The high-boiling substance separation column A preferably has packing as an internal component. Further, the packing is preferably structured packing. Also, the diaryl carbonate purification column B preferably has packing as an internal component, and more preferably one or more units of structured packing.

[0131] High-boiling component F 2H usually contains 0.05 to 2% by mass of dialkyl carbonate, 1 to 20% by mass of aromatic monohydroxy compound, 0.05 to 2% by mass of alkyl phenyl ether, 10 to 45% by mass of alkyl aryl carbonate, 50 to 80% by mass of diaryl carbonate, 0.1 to 5% by mass of high-boiling by-products, and 0.001 to 5% by mass of catalyst. High-boiling component F 2H is preferably continuously supplied from the second reactive distillation step directly to the high-boiling substance separation column A as it is.

[0132] High-boiling component F 2H The composition of high-boiling component F varies depending on the conditions of the transesterification reaction between dialkyl carbonate and aromatic monohydroxy compound, the type and amount of catalyst, etc. However, as long as the transesterification reaction is carried out under certain conditions, a reaction mixture with a substantially constant composition can be produced, so the composition of the reaction mixture supplied to the high-boiling substance separation column A is substantially constant. However, according to the first purification step and the second purification step, as long as the composition of the reaction mixture is within the above range, even if it fluctuates, it can be separated with substantially the same separation efficiency.

[0133] In the first purification step, to continuously supply high-boiling component F 2H into the high-boiling substance separation column A, it may be supplied in a liquid state from one or several inlets installed below the middle part of the high-boiling substance separation column A, or it may be supplied into the column through the reboiler from a pipe provided at the bottom of the reboiler of the high-boiling substance separation column A. The amount of the bottom liquid of the second continuous multi-stage distillation column supplied to the high-boiling substance separation column A varies depending on the production amount of the high-purity diaryl carbonate to be produced, the concentration of diaryl carbonate in the reaction mixture, the separation conditions of the high-boiling substance separation column A, etc., but is usually about 2 tons / hr or more, preferably about 6 tons / hr or more, and more preferably about 10 tons / hr or more.

[0134] High boiling point component F 2H The high-boiling-point substance separation column separates the top component A T Side cut component A containing diaryl carbonate S , and high boiling point component A H When distilling and separating into these three components, the top component A T It contains diaryl carbonates and unreacted raw materials, alkylaryl ethers, alkylaryl carbonates, and most of the compounds with lower boiling points than diaryl carbonates, and side cut component A S It contains most diaryl carbonates, compounds with lower boiling points than the diaryl carbonates mentioned above, and high-boiling-point component A H It contains small amounts of diaryl carbonate, a catalyst, and high-boiling point by-products. Note that high-boiling point component A H It may also be a component of the base of the tower.

[0135] High boiling point component A H The concentration of diaryl carbonate in is preferably 9 to 38% by mass. Also, high boiling point component A H In this process, the mass concentration ratio (DPC / HB) of diaryl carbonate to high-boiling-point substance is preferably 0.2 to 0.8, from the viewpoint of controlling the bottom temperature of the high-boiling-point substance separation column to a range where evaporation in the reboiler is possible.

[0136] High boiling point component A H It may contain a small amount of alkylaryl carbonate. High boiling point component A H These organic substances within help dissolve the catalytic components and keep them in a liquid state. High boiling point component A H This is continuously supplied to the thin-film evaporator C and used for the thin-film evaporation process described later.

[0137] High boiling point component A H The composition of high-boiling-point component A changes depending on the operating conditions of high-boiling-point component separation column A, but in high-boiling-point component separation column A, the composition of high-boiling-point component A remains almost constant. H Since this can be manufactured, high-boiling-point component A is supplied to the thin-film evaporator C. HThe composition is almost constant. However, the high-boiling-point component A H If the composition remains within the above range, separation can be achieved with nearly the same separation efficiency even if it fluctuates.

[0138] By-products and catalyst components with higher boiling points than diaryl carbonates such as phenyl salicylate, xanthones, phenyl methoxybenzoate, and 1-phenoxycarbonyl-2-phenoxycarboxyphenylene are almost completely separated into high-boiling-point component A in a high-boiling-point substance separation column. H It is separated as follows.

[0139] Side cut component A S One of the features of this embodiment is that the content of high-boiling point by-products can be easily reduced to typically 200 ppm or less, preferably 100 ppm or less, and more preferably 50 ppm or less.

[0140] In addition, high-boiling-point component F is supplied to the high-boiling-point substance separation column. 2H Although it depends on the composition, typically 20-35% by mass of the continuously supplied liquid is the top component A. T It is continuously extracted from the top of the tower, and 55-65% by mass is side-cut component A. S It is continuously extracted from the side-cut extraction port, and 10-25% by mass is high-boiling point component A. H They are extracted sequentially as follows.

[0141] Side cut component A S It typically contains 0.01 to 5% by mass of aromatic monohydroxy compounds, 0.05 to 0.5% by mass of alkylphenyl ethers, 1 to 20% by mass of alkylaryl carbonates, 800 to 99% by mass of diaryl carbonates, and high-boiling point by-products in an amount of 200 ppm or less, preferably 100 ppm or less, and more preferably 50 ppm.

[0142] Also, the top component A T The alkylaryl carbonates and diaryl carbonates in the mixture are preferably recovered by returning them to the second continuous multi-stage distillation column.

[0143] In the first purification step, the reflux ratio of the high-boiling-point substance separation column A is preferably 0.01 to 10, more preferably 0.08 to 5, and even more preferably 0.1 to 3.

[0144] In the first purification process, side cut component A S The amount of high boiling point component F 2H The amount is typically around 55-65% by mass, and this is continuously supplied to the diaryl carbonate purification column B from the inlet 61 located in the middle of the column, and then used for the second purification process described later.

[0145] In the second purification process, low boiling point component A L This is continuously supplied to the diaryl carbonate purification column, and the top component B L Side cut component B containing diaryl carbonate S and base component B H The three components are separated by continuous distillation. Low boiling point component A L This is side cut component A S It is preferable that this be the case.

[0146] Side-cut component A supplied to the diaryl carbonate purification column S All components with lower boiling points than diaryl carbonates contained in it are apex component B L The liquid is continuously drawn from the top of the tower, and small amounts of liquid are continuously drawn from the bottom of the tower.

[0147] Tower top component B L It contains a small amount of diaryl carbonate, which is usually 1 to 9% by mass, preferably 3 to 8% by mass, relative to the supplied diaryl carbonate. This is the top component B L The diaryl carbonate inside is the top component B. L It is separated and recovered in another distillation column, but it is also a preferred method to separate it as a bottom component of this other distillation column and recover it by returning it to a high-boiling-point substance separation column and / or diaryl carbonate purification column.

[0148] Tower bottom component B H It contains diaryl carbonates and small amounts of high-boiling point by-products concentrated to less than a few percent. Bottom component B extracted from the bottom of the column. H One of the features of this embodiment is that the amount of diaryl carbonate in the mixture is very small, and this amount is typically 0.05 to 7% by mass relative to the supplied diaryl carbonate.

[0149] From the side-cut extraction opening 70, side-cut component B S High-purity diaryl carbonate is continuously extracted at a flow rate of typically 1 ton / hr or more, preferably 3 ton / hr or more, and more preferably 5 ton / hr or more. This amount typically corresponds to about 80-90% of the diaryl carbonate supplied to the diaryl carbonate purification column.

[0150] In the second purification process, side-cut components (B S The purity of the diaryl carbonate obtained as is is usually 99.9% or higher, preferably 99.99% or higher, and more preferably 99.999% or higher. In this embodiment, high purity means 99.9% or higher.

[0151] Side cut component (B S In the high-purity diaryl carbonate obtained as ), the content of phenyl salicylate is preferably 30 ppm or less, more preferably 10 ppm or less, and even more preferably 1 ppm or less.

[0152] Regarding the content of high-boiling-point impurities in the resulting high-purity diaryl carbonate, xanthones are 30 ppm or less, preferably 10 ppm or less, and more preferably 1 ppm or less; phenyl methoxybenzoate is 30 ppm or less, preferably 10 ppm or less, and more preferably 1 ppm or less; and 1-phenoxycarbonyl-2-phenoxycarboxyphenylene is 30 ppm or less, preferably 10 ppm or less, and more preferably 5 ppm or less. The total content of these high-boiling-point by-products is 100 ppm or less, preferably 50 ppm or less, and more preferably 10 ppm or less.

[0153] In this embodiment, the purity and impurity content of the diaryl carbonate can be measured by the method described in the examples below.

[0154] In the second purification step, the reflux ratio of diaryl carbonate purification column B is preferably 0.01 to 10, more preferably 0.1 to 8, and even more preferably 0.5 to 5.

[0155] (Thin film evaporation process) This embodiment relates to high boiling point component A H The low boiling point component C is supplied to the thin film evaporator. L And, high boiling point component C H It has a thin-film evaporation step that separates the low-boiling point component C. L And, high boiling point component C H The two can be separated continuously.

[0156] The thin-film evaporator, for example as shown in Figure 4, has a cylindrical body 74 with a length L3 (cm) and an inner diameter D3 (cm), and has a heat transfer area S inside. CL (m 2 It has a condensing section 75 having a capacitor 78, and a heat transfer area S outside the body section 74. CH (m 2 ) has a jacket 77 and a wiper 76 that rotates near the wall surface of the body 74, and the rotation of the wiper 76 forms a thin film from the supply liquid, L3, D3, S CL S CHHowever, it is preferable that the thin-film evaporator C1 satisfies the following equations (30) to (33). Note that high boiling point component A is introduced from the inlet 71. H It supplies low boiling point component C L After evaporation, it is concentrated in the condenser 78 and extracted from the outlet 73 of the concentration section 75, and the high-boiling point component C H It is extracted from outlet 72. 1000 ≦ L3 ≦ 10000 Formula (30) 500≦D3≦2000 Formula (31) 1 ≤ S CL ≦ 100 Formula (32) 1 ≤ S CH ≦ 100 Formula (33)

[0157] When L3(cm) is 1000 or more, the desired supply amount can be processed. Furthermore, in order to reduce equipment costs while processing the desired supply amount, it is preferable to set L3 to 10000 or less. A more preferable range for L3(cm) is 1500 ≤ L3 ≤ 8000, and even more preferable is 2000 ≤ L3 ≤ 7000.

[0158] When D3(cm) is 500 or more, the desired supply amount can be processed. Furthermore, to reduce equipment costs while processing the desired supply amount, it is preferable to set D3 to 2000 or less. A more preferable range for D3(cm) is 700≦D3≦1900, and even more preferable is 800≦D3≦1800.

[0159] S CL (m 2 If ) is 1 or more, the desired supply quantity can be processed. Also, in order to reduce equipment costs while processing the desired supply quantity, S CL It is preferable to make it 100 or less. A more preferable S CL (m 2 The range of ) is 5≦S CL ≤90, and more preferably 10 ≤S CL The value is ≤70.

[0160] S CH is 1m 2As a result, separation efficiency is improved, and the desired catalyst concentration can be achieved in the high-boiling point components obtained in the thin-film evaporator. Furthermore, in order to reduce equipment costs while ensuring separation efficiency that can achieve the desired catalyst concentration, S CH 100m 2 The following is preferable. More preferable S CH 3-50m 2 And more preferably, 5 to 30 m 2 It is within the range.

[0161] In the thin film evaporation process, the thin film evaporator is heated to a temperature (T C ) 185~280℃, pressure (P C It is preferable to operate under conditions of 500 to 20000 Pa.

[0162] T C If the temperature is above 185°C, there is no need to lower the operating pressure further, so there is no need for equipment that maintains a high vacuum, and the equipment can be made smaller. C If the temperature is 280°C or lower, heat consumption can be suppressed. A more preferable T C The temperature range is 190-240°C, and more preferably 193-203°C.

[0163] P C If the pressure is 500 Pa or higher, there is no need for large equipment to maintain a high vacuum, P C When the pressure is below 20,000 Pa, the distillation temperature tends to be lower, which can suppress by-products. A more preferable P C The pressure is in the range of 700 to 10000 Pa, and more preferably in the range of 500 to 3000 Pa.

[0164] High boiling point component A H Typically, it contains 0.01-10% by mass of alkylaryl carbonate, 8-45% by mass of diaryl carbonate, 40-80% by mass of high-boiling point byproducts, and 1-10% by mass of catalyst, so this high-boiling point component A H It is preferable to continuously supply this directly to the thin-film evaporator C.

[0165] (2nd circulation process) This embodiment is a high-boiling point component C H The process includes a second circulation step in which the high-boiling-point component C is continuously supplied into the first continuous multi-stage distillation column and / or the second continuous multi-stage distillation column. H The entire amount or a portion thereof is continuously supplied to the first and / or second continuous multi-stage distillation column as a catalyst component for the transesterification reaction. This step allows for effective utilization of the transesterification catalyst.

[0166] (3rd circulation process) This embodiment is based on the low boiling point component C L It is preferable to include a third circulation step in which the material is continuously supplied to a high-boiling-point substance separation column. Having this step allows for effective utilization of the diaryl carbonate separated and recovered in the thin-film evaporation step.

[0167] The materials used to constitute the high-boiling-point substance separation column, diaryl carbonate purification column, and thin-film evaporator in this embodiment are mainly metallic materials such as carbon steel and stainless steel, but stainless steel is preferred in terms of the quality of the diaryl carbonate produced.

[0168] The amount of high-purity diaryl carbonate produced by this embodiment is preferably 1 ton or more per hour, more preferably 2 tons or more, and even more preferably 3 tons or more. Thus, according to this embodiment, high-purity diaryl carbonate can be produced on an industrial scale. In this embodiment, "industrial scale" means 1 ton or more per hour.

[0169] By implementing the method of this embodiment, such high-purity diaryl carbonate can be stably produced for a long period of time, for example, preferably 2000 hours or more, more preferably 3000 hours or more, and even more preferably 5000 hours or more. Therefore, this embodiment is an extremely effective method for the industrial production of high-purity diaryl carbonate. [Examples]

[0170] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0171] [Analysis method] The composition of each component was analyzed by gas chromatography. The gas chromatography analysis was performed using the internal standard method, with toluene used as the internal standard. Equipment: Agilent 7890A Column: Agilent J&W DB-1 (Length 30m x ID 0.25mm x Film 0.25μm) Carrier gas: He, flow rate 2.0 mL / min Inlet temperature: 250℃ Injection volume: 1.0μL Oven temperature: Hold at 50°C for 2 minutes, then increase the temperature to 300°C at a rate of 10°C / minute and hold for 8 minutes. Injection method: Split method, split ratio 20 Detector: FID, Temperature: 300℃

[0172] 0.1 g of each sampled component was weighed, and 0.04 g (all weighed to an accuracy of 0.1 mg) of 5 mL of acetonitrile was added to prepare a sample solution for gas chromatography. The prepared solution was filtered through a 0.45-0.50 μm polytetrafluoroethylene (PTFE) membrane filter. The relationship between the peak area ratio and concentration ratio of DPC and the internal standard (toluene) was determined by measuring DPC and toluene with known concentrations beforehand, and the gas chromatography measurements of the bottom-of-column components were corrected. The remaining amount [mass%] obtained by subtracting the DPC concentration [mass%] obtained by gas chromatography measurement from 100 [mass%] represents the amount of high-boiling point substance (HB) and catalyst.

[0173] The catalyst concentration was measured by decomposing various high-boiling point organic components with microwaves, then measuring the metal concentration [mass%] of the catalyst using an ICP emission spectrometer (ICP), and calculating the amount of catalyst [mass%] from the molecular weight of the catalyst.

[0174] The halogen content in the side-cut components of diaryl carbonate purification column B was measured by ion chromatography.

[0175] <Example 1> <First continuous multi-stage distillation column 101> As the first continuous multistage distillation column 101, the specifications are as shown in Figure 2: L1 = 3300 cm, D1 = 710 cm, L1 / D1 = 4.6, n1 = 80, D1 / d 11 =17, D1 / d 12 A continuous multi-stage distillation column with a ratio of 9 was used. In this example, the internal cross-sectional area per pore was approximately 1.5 cm². 2 , Number of holes = approx. 250 pieces / m 2 A perforated plate tray having the following properties was used.

[0176] <Second continuous multi-stage distillation column 201> As the second continuous multistage distillation column 201, the specifications are as shown in Figure 3: L2 = 3100 cm, D2 = 710 cm, L2 / D2 = 4.4, n2 = 30, D2 / d 21 =3.85, D2 / d 22 A continuous multi-stage distillation column with a cross-sectional area of ​​11.1 was used. In this example, two Melapak units (total theoretical stage count of 11 stages) were installed at the top as internals, and the cross-sectional area per hole was approximately 1.3 cm² at the bottom. 2 , Number of holes = approx. 250 pieces / m 2 A perforated plate tray having the following properties was used.

[0177] <High boiling point substance separation column A> As high-boiling point substance separation column A, L A =1700cm, D A =650cm, and as internal, n A A continuous multi-stage distillation column equipped with 30 Melapacks was used.

[0178] <Diaryl carbonate purification column B> As diaryl carbonate purification column B, L B =2500cm, D B = 540cm, as internal, n B1 =12, n B2 =18, nB3 A continuous multi-stage distillation column was used, equipped with three Melapak units with a value of 5.

[0179] <Thin film evaporator C> As the thin-film evaporator C, as shown in Figure 4, L3 = 3900 cm, D3 = 1600 cm, S CL =30m 2 S CH = 15m 2 A thin-film evaporator was used.

[0180] <Production of Diphenyl Carbonate> Diphenyl carbonate was produced using an apparatus consisting of a first continuous multi-stage distillation column 101 and a second continuous multi-stage distillation column 201 connected together as shown in Figure 5, and an apparatus consisting of a high-boiling-point substance separation column A1, a diaryl carbonate purification column B1, and a thin-film evaporator C1 as shown in Figure 6. Raw material 1, consisting of phenol / dimethyl carbonate = 1.9 (mass ratio), was continuously introduced in liquid form at a flow rate of 177 tonnes / hr from the inlet 31 of the first continuous multi-stage distillation column 101. Meanwhile, raw material 2, consisting of dimethyl carbonate / phenol = 3.2 (mass ratio), was continuously introduced in gaseous form at a flow rate of 185 tonnes / hr from the inlet 32 ​​of the first continuous multi-stage distillation column 101. The molar ratio of the raw materials introduced into the first continuous multi-stage distillation column 101 was dimethyl carbonate / phenol = 1.25. The catalyst was Pb(OPh)2, and high-boiling-point component C was introduced from the outlet 72 of the thin-film evaporator C1 so that it was present in the liquid of the first continuous multi-stage distillation column 101 at a concentration of approximately 100 ppm. H The high-boiling-point component F was continuously introduced at a flow rate of 195 kg / hr into the inlet 33 of the first continuous multi-stage distillation column 101. In the first continuous multi-stage distillation column 101, the high-boiling-point component F was extracted in liquid form from the bottom 38 of the column. 1H A portion of the water was heated by the heat exchanger 39 and returned to the bottom of the column through the inlet 40. In the first continuous multi-stage distillation column 101, the temperature at the bottom of the column was 231°C, and the pressure at the top of the column was 6.5 × 10⁻⁶. 5 Continuous reaction distillation was carried out under conditions of Pa and reflux ratio of 0. Low-boiling point components F in the first continuous multi-stage distillation column 101 containing methyl alcohol, dimethyl carbonate, phenol, etc. 1LThe gaseous components F from the top of the column 34 were continuously extracted, passed through the heat exchanger 35, and then extracted from the outlet 37 at a flow rate of 177 tons / hr, with the remainder returned to the first continuous multi-stage distillation column 101 through the inlet 36. Meanwhile, the high-boiling-point components F from the first continuous multi-stage distillation column 101, which include methylphenyl carbonate, dimethyl carbonate, phenol, diphenyl carbonate, catalyst, etc., were also extracted. 1H The liquid was continuously extracted from the base 38 of the tower.

[0181] After 24 hours, a stable steady state was reached, and the high-boiling-point component F from the bottom 38 of the first continuous multi-stage distillation column 101 was released. 1H A portion of the solution was continuously supplied at a flow rate of 183 tons / hr through an inlet 41 located between the Melapack and the perforated plate tray of the second continuous multi-stage distillation column 201. In the second continuous multi-stage distillation column 201, Pb(OPh)2 was present as the catalyst, the temperature at the bottom of the column was 208°C, and the pressure at the top of the column was 3 × 10⁻⁶ 4 Continuous reaction distillation was carried out under conditions of Pa and reflux ratio of 0.3. In the second continuous multi-stage distillation column 201, the high-boiling point component F was extracted in liquid form from the bottom 47 of the column. 2H A portion of the water was heated by the heat exchanger 48 and returned to the bottom of the column through the inlet 49. Stable steady-state operation was achieved after 24 hours. Low-boiling point components F, containing 37% by mass of dimethyl carbonate, 58% by mass of phenol, and 0.4% by mass of methylphenyl carbonate, were introduced from the top 43 of the second continuous multi-stage distillation column 201. 2L The mixture was continuously extracted, passed through the heat exchanger 44, and then extracted from the outlet 46 at a flow rate of 158 tons / hr. The remainder was returned to the second continuous multi-stage distillation column 201 through the inlet 45. Meanwhile, from the bottom of the column 47, high-boiling-point components F, containing 31% by mass of methylphenyl carbonate and 50% by mass of diphenyl carbonate, were extracted. 2H The low-boiling point component F of the second continuous multi-stage distillation column 201 was continuously extracted from outlet 50. 2L The mixture was continuously supplied from the inlet 31 to the first continuous multi-stage distillation column 101 (first circulation process). At this time, the amount of newly supplied dimethyl carbonate and phenol was the low boiling point component F 2L After considering the composition and quantity of the above-mentioned raw materials 1 and 2, adjustments were made to maintain their composition and quantity.

[0182] After 24 hours, a stable steady state was reached, and the high-boiling-point component F from the bottom 47 of the second continuous multi-stage distillation column 201 was removed. 2H A portion of it was continuously introduced at a rate of 44 tons / hr into the inlet 51 of the high-boiling-point substance separation column A1. The temperature at the bottom of the column (T A ) at 203℃, pressure at the top of the tower (P A The pressure was set to 1700 Pa, and continuous distillation was carried out at a reflux ratio of 3.5. In the high-boiling-point substance separation column A1, the high-boiling-point component A was extracted in liquid form from the bottom 57 of the column. H A portion of the mixture was heated by a heat exchanger 58 and returned to the bottom of the column through an inlet 59. At this time, the composition of the bottom of the high-boiling-point substance separation column A1 was 33% by mass of diphenyl carbonate, 63% by mass of high-boiling-point substance, 4% by mass of catalyst, and 1% by mass of phenyl salicylate.

[0183] From the top 53 of the high-boiling point substance separation column A1, the top component A T The material was continuously extracted, and the flow rate at outlet 56 was 13.6 tons / hr. Column top component A T A portion of it passed through the heat exchanger 54 and was returned to the high-boiling-point substance separation column A1 through the inlet 55. Column top component A T It was then continuously introduced from the outlet 56 through a conduit (not shown) to the bottom of the second continuous multi-stage distillation column 201. From the outlet 60 of the high-boiling point substance separation column A1, side-cut component A S It was continuously extracted at a flow rate of 27.9 tons / hr. Sidecut component A S It was then continuously introduced from the inlet 61 into the diaryl carbonate purification column B1. High-boiling-point component A was introduced from the bottom 57 of the high-boiling-point substance separation column A1. H The high-boiling-point component A is extracted in succession. H A portion of this was continuously introduced at a rate of 9.8 tons / hr into the inlet 71 of the thin-film evaporator C1.

[0184] In diaryl carbonate purification column B1, the temperature at the bottom of the column (T B ) at 183℃, pressure at the top of the tower (P B The pressure was set to 1700 Pa, and continuous distillation was carried out at a reflux ratio of 2.6, passing the top component B through the extraction port 65. LThe material is continuously extracted at a rate of 2.5 tons / hr, and the bottom component B is passed through the extraction port 69. H The material is continuously extracted at a rate of 1.8 tons / hr, and side-cut component B is passed through the extraction port 70. S It was continuously extracted at a rate of 23.5 tons / hr. Column top component B was extracted from column top 62 of diaryl carbonate purification column B1. L A portion of it was returned to the diaryl carbonate purification column B1 through the inlet 64 after passing through the heat exchanger 63. In the diaryl carbonate purification column B1, the bottom component B was extracted in liquid form from the bottom 66 of the column. H A portion of the water was heated by the heat exchanger 67 and returned to the bottom of the tower through the inlet 68.

[0185] In thin film evaporator C1, the temperature (T C ) at 196℃, pressure (P B ) is set to 1600 Pa and distillation is carried out continuously, and the high-boiling point component C is extracted from the extraction port 72. H The low-boiling point component C was continuously extracted at a rate of 7.0 tons / hr from the extraction port 73. L It was continuously extracted at a rate of 2.8 tons / hr. High boiling point component C H Of this amount, 31.2 kg / hr was discharged from the system to maintain the concentration of the generated high-boiling-point substance at 63 mass%. The remaining 6.9 tons / hr was introduced into the inlet 33 of the first continuous multi-stage distillation column 101 and the inlet 42 of the second continuous multi-stage distillation column. Low-boiling-point component C L This was then continuously introduced from the inlet 52 to the bottom of the high-boiling-point substance separation column A.

[0186] The composition of each component after 24 hours when the system was completely stable was as follows: Bottom components of the first continuous multistage distillation column 101: methylphenyl carbonate 14.0% by mass, diphenyl carbonate 0.5% by mass. Side-cut components of high-boiling point substance separation column A1: methylphenyl carbonate 9% by mass, diphenyl carbonate 91% by mass. The content of phenyl salicylate, xanthone, and phenyl methoxybenzoate in the side-cut components of diaryl carbonate purification column B1 was all 1 ppm or less, and 1-phenoxycarbonyl-2-phenoxycarboxyphenylene was 4 ppm. Also, the side-cut component B of diaryl carbonate purification column B1S The halogen content inside was less than 1 ppb. Therefore, the side cut component B of diaryl carbonate purification column B1 is S The purity of diphenyl carbonate in this process was found to be 99.999% or higher. The production rate of this high-purity diphenyl carbonate (DPC) was 24.0 tons per hour. At this time, the conversion rates of dimethyl carbonate (DMC) and methylphenyl carbonate (MPC) in the first continuous multi-stage distillation column 101 and the second continuous multi-stage distillation column 201 were 9.0% and 67.8%, respectively. The heat required for the first continuous multi-stage distillation column 101, the second continuous multi-stage distillation column 201, the high-boiling-point substance separation column A1, and the thin-film evaporator C1 were 20612 kW, 18623 kW, 5337 kW, and 334 kW, respectively, for a total of 44906 kW. In addition, the makeup catalyst replenishment rate to replace the catalyst discharged from the bottom of the high-boiling-point substance separation column A1 was 6 kg / hr.

[0187] Continuous operation was carried out under these conditions for a long period. The production volume and purity of diphenyl carbonate, as well as the steam consumption of the first continuous multi-stage distillation column 101 and the second continuous multi-stage distillation column 201, and the amount of makeup catalyst supplied remained virtually unchanged after 500 hours, 2000 hours, 4000 hours, 5000 hours, and 6000 hours.

[0188] <Example 2> Diphenyl carbonate was produced using the same apparatus as in Example 1. In this case, the temperature of the thin-film evaporator C1 was set to 192°C and the pressure to 1600 Pa. All other conditions were the same as in Example 1. As a result, phenyl salicylate at the bottom of high-boiling point substance separation column A1 was 1% by mass, and side-cut component B of diaryl carbonate purification column B1 was also present. S The phenyl salicylate content was less than 1 ppm.

[0189] As a result, the conversion rates of dimethyl carbonate (DMC) and methylphenyl carbonate (MPC) in the first continuous multi-stage distillation column 101 and the second continuous multi-stage distillation column 201 were 9.0% and 67.8%, respectively. The heat required for the first continuous multi-stage distillation column 101, the second continuous multi-stage distillation column 201, the high-boiling-point substance separation column A1, and the thin-film evaporator C1 were 20772 kW, 18783 kW, 5337 kW, and 174 kW, respectively, for a total of 45066 kW.

[0190] <Example 3> Diphenyl carbonate was produced using the same apparatus as in Example 1. In this experiment, the temperature of the thin-film evaporator C1 was set to 204°C and the pressure to 1600 Pa. All other conditions were the same as in Example 1. As a result, phenyl salicylate at the bottom of high-boiling point substance separation column A1 was 1% by mass, and side-cut component B of diaryl carbonate purification column B1 was also present. S The phenyl salicylate content was less than 1 ppm. As a result, the conversion rates of dimethyl carbonate (DMC) and methylphenyl carbonate (MPC) in the first continuous multi-stage distillation column 101 and the second continuous multi-stage distillation column 201 were 9.0% and 67.8%, respectively. The heat required for the first continuous multi-stage distillation column 101, the second continuous multi-stage distillation column 201, the high-boiling-point substance separation column A1, and the thin-film evaporator C1 were 20,587 kW, 18,598 kW, 5,337 kW, and 544 kW, respectively, for a total of 45,066 kW.

[0191] <Example 4> Diphenyl carbonate was produced using the same apparatus as in Example 1. In this experiment, the temperature of the thin-film evaporator C1 was set to 196°C and the pressure to 4000 Pa. All other conditions were the same as in Example 1. As a result, phenyl salicylate at the bottom of high-boiling point substance separation column A1 was 1% by mass, and side-cut component B of diaryl carbonate purification column B1 was also present. S The phenyl salicylate content was less than 1 ppm. As a result, the conversion rates of dimethyl carbonate (DMC) and methylphenyl carbonate (MPC) in the first continuous multi-stage distillation column 101 and the second continuous multi-stage distillation column 201 were 9.0% and 67.8%, respectively. The heat required for the first continuous multi-stage distillation column 101, the second continuous multi-stage distillation column 201, the high-boiling-point substance separation column A1, and the thin-film evaporator C1 were 20772 kW, 18783 kW, 5337 kW, and 174 kW, respectively, for a total of 45066 kW.

[0192] <Comparative Example 1> Diphenyl carbonate was produced using an apparatus consisting of a first continuous multi-stage distillation column 101 and a second continuous multi-stage distillation column 201 connected together, as shown in Figure 5, and an apparatus consisting of a high-boiling-point substance separation column A1 and a diaryl carbonate purification column B1, as shown in Figure 7. The apparatus does not have a thin-film evaporator C1, and no operation related to it was performed. Here, raw material 1, consisting of phenol / dimethyl carbonate = 1.9 (mass ratio), was continuously introduced in liquid form at a flow rate of 183 ton / hr from the inlet 31 of the first continuous multi-stage distillation column 101, and raw material 2, consisting of dimethyl carbonate / phenol = 3.6 (mass ratio), was continuously introduced in gaseous form at a flow rate of 185 ton / hr from the inlet 32 ​​of the first continuous multi-stage distillation column 101. Other conditions were the same as in Example 1. As a result, the phenyl salicylate content at the bottom of high-boiling-point substance separation column A1 was 1% by mass, and the phenyl salicylate content in the side-cut components of diaryl carbonate purification column B1 was less than 1 ppm. As a result, the conversion rates of dimethyl carbonate (DMC) and methylphenyl carbonate (MPC) in the first continuous multi-stage distillation column 101 and the second continuous multi-stage distillation column 201 were 8.8% and 67.6%, respectively. The heat required for the first continuous multi-stage distillation column 101, the second continuous multi-stage distillation column 201, and the high-boiling-point substance separation column A1 were 21,297 kW, 19,159 kW, and 5,337 kW, respectively, for a total of 45,793 kW. The production volume of high-purity diphenyl carbonate (DPC) was 23.5 tons per hour.

[0193] <Comparative Example 2> Diphenyl carbonate was produced using the same apparatus as in Comparative Example 1. At this time, the temperature at the bottom of the high-boiling-point substance separation column A1 is (T A The temperature was set to 216°C. Other conditions were the same as in Comparative Example 1. As a result, the bottom components of high-boiling-point substance separation column A1 were 24% by mass of diphenyl carbonate, 71% by mass of high-boiling-point substance, 3% by mass of catalyst, and 2% by mass of phenyl salicylate. In addition, the side-cut components of diaryl carbonate separation column B1 were (B S The phenyl salicylate concentration in the solution was 6 ppm. The required heat for the first continuous multi-stage distillation column 101, the second continuous multi-stage distillation column 201, and the high-boiling point substance separation column A1 were 20,612 kW, 18,623 kW, and 5,671 kW, respectively, for a total of 44,906 kW.

[0194] Table 1 shows the conditions and results for Examples 1-4 and Comparative Examples 1-2.

[0195] [Table 1] [Industrial applicability]

[0196] The present invention provides an industrial method for producing diaryl carbonate, which is used as a raw material for polycarbonate and the like. [Explanation of symbols]

[0197] 1, 11, 21…Gas outlets, 2, 12, 22…Liquid outlets, 3-a, 3-b, 3-c, 3-d, 3-e…First inlet, 4-a, 4-b…Second inlet, 5…Bottom of column, 6…Internal, 7, 74…Body, 13…Third inlet, 15…Fourth inlet, 16…Bottom of column, 23…Fifth inlet, 25…Sixth inlet, 26…Bottom of column, 31, 32, 33, 36, 40, 41, 42, 45, 49, 51, 52, 55, 59, 61, 64, 68, 71…Inlets 34, 43, 53, 62… Top section of the column, 35, 39, 40, 48, 54, 58, 63, 67… Heat exchanger, 37, 46, 50, 56, 60, 65, 69, 70, 72, 73… Outlet, 38, 47, 57, 66… Bottom section of the column, 75… Concentration section, 76… Wiper, 77… Jacket, 78… Condenser, 101… First continuous multi-stage distillation column, 201… Second continuous multi-stage distillation column, A, A1… High boiling point substance separation column, B, B1… Diaryl carbonate purification column, C, C1… Thin film evaporator

Claims

1. A method for continuously producing diaryl carbonates, Dialkyl carbonates and aromatic monohydroxy compounds are continuously supplied into the first continuous multi-stage distillation column, and the reaction and distillation are carried out simultaneously in the presence of a catalyst, producing a low-boiling point component F containing alcohol. 1L The high-boiling point component F containing alkylaryl carbonate is continuously extracted from the top of the column. 1H The first reaction distillation step involves continuously extracting the material from the lower part of the column, The aforementioned high-boiling point component F 1H The mixture is continuously supplied into the second continuous multi-stage distillation column, and the reaction and distillation are carried out simultaneously in the presence of a catalyst, producing a low-boiling point component F containing dialkyl carbonate. 2L The high-boiling point component F containing diaryl carbonate is continuously extracted from the top of the tower. 2H The second reaction distillation step involves continuously extracting the material from the lower part of the column, The aforementioned high-boiling point component F 2H The low-boiling component A, which contains diaryl carbonate, is continuously supplied to the high-boiling-point substance separation column. L And, high boiling point component A containing the catalyst H The first purification step involves continuous distillation separation, The low-boiling component A L is continuously supplied to a diaryl carbonate purification column, and the overhead component B L , the side-cut component B containing diaryl carbonate S and the bottom component B H are continuously separated by distillation into three components, and a second purification step The low boiling point component F 2L A first circulation step involves continuously supplying the following into the first continuous multi-stage distillation column: The aforementioned high boiling point component A H The low boiling point component C is supplied to the thin film evaporator. L And, high boiling point component C H The thin film evaporation process separates the two into, The aforementioned high boiling point component C H A second circulation step, which continuously supplies the first continuous multi-stage distillation column and / or the second continuous multi-stage distillation column, A method for producing diaryl carbonates containing [the specified substance].

2. The aforementioned low boiling point component C L The manufacturing method according to claim 1, comprising a third circulation step of continuously supplying to the high-boiling-point substance separation column.

3. The manufacturing method according to claim 1 or 2, wherein the temperature conditions in the thin film evaporation step are 193°C or higher and 203°C or lower, and the pressure conditions are 500 Pa or higher and 3000 Pa or lower.

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