Method for producing diphenyl carbonate

Abstract

A method for producing diphenyl carbonate, comprising a first purification step, in which a diphenyl-carbonate-containing reaction mixture obtained by a specific step is continuously introduced into a high-boiling-point-substance separation tower A to continuously separate the mixture by distillation into a top fraction (AT) containing diphenyl carbonate and a bottoms fraction (AB) containing a catalyst, a specific second purification step, and two specific circulation steps, wherein in the bottoms fraction (AB) from the high-boiling-point-substance separation tower A, the mass concentration ratio of diphenyl carbonate to high-boiling-point substances, DPC / HB, is 0.1-1.0 and the mass concentration ratio of the diphenyl carbonate to the catalyst, DPC / catalyst, is 1.0-10.0.

Description

Diphenyl carbonate manufacturing method

[0001] The present invention relates to a method for producing diphenyl carbonate.

[0002] The reaction mixture obtained by the transesterification reaction using dialkyl carbonate and phenol as raw materials in the presence of a homogeneous catalyst usually contains various reaction by-products, but if diphenyl carbonate in which high-boiling by-products such as phenyl salicylate, xanthone, phenyl methoxybenzoate, and 1-phenoxycarbonyl-2-phenoxycarboxy-phenylene, which have boiling points higher than those of the target diphenyl carbonate, have not been reduced to a sufficient level or lower, is used as a raw material for transesterification polycarbonate, this will cause coloration and deterioration in physical properties. Therefore, it is preferable to reduce these impurities as much as possible. As a method for solving these problems, for example, Patent Document 1 proposes a method for stably producing high-purity diphenyl carbonate, which is necessary for producing high-quality, high-performance aromatic polycarbonates from cyclic carbonate and phenol, in large quantities (e.g., 1 ton or more per hour) on an industrial scale over a long period of time (e.g., 1,000 hours or more, preferably 3,000 hours or more, and more preferably 5,000 hours or more) by a method comprising the steps of: step (I) of producing a dialkyl carbonate and a diol using a reactive distillation column having a specific structure; step (II) of producing diphenyl carbonate using two reactive distillation columns having specific structures; and step (III) of obtaining high-purity diphenyl carbonate using a heavy-ends cut column A and a diphenyl carbonate purification column B.

[0003] International Publication No. 2007 / 072705

[0004] In the method described in Patent Document 1, in a first continuous multi-stage distillation column, an alkyl carbonate (e.g., dimethyl carbonate (DMC)) and phenol (PhOH) are reacted in the presence of a catalyst to produce an alkyl aryl carbonate (e.g., methyl phenyl carbonate (MPC)) and an aliphatic alcohol (e.g., methanol (MeOH)), and in a second continuous multi-stage 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 alkyl aryl carbonate (e.g., methyl phenyl carbonate (MPC)). For example, this is shown in the following reaction formula: (First continuous multi-stage distillation column) DMC + PhOH ⇔ MPC + MeOH (Second continuous multi-stage distillation column) 2MPC ⇔ DPC + DMC After the disproportionation reaction, the heavy-boiling reaction mixture from the second continuous multi-stage distillation column containing diaryl carbonate (e.g., diphenyl carbonate (DPC)) is distilled in a heavy-ends cut column A and a diphenyl carbonate purification column B. Here, the column bottom component (A Ｂ The catalyst required for the reaction is recycled by supplying the bottom component (A) to the first continuous multi-stage distillation column and the second continuous multi-stage distillation column. Ｂ Therefore, in order to prevent the concentration of high boiling point substances from increasing in the system, the bottom component (A Ｂ) is discarded without being recycled. In the method described in Patent Document 1, the reaction results in both the first and second continuous multi-stage distillation columns are insufficient, and in order to produce the target diphenyl carbonate, it is necessary to circulate large amounts of the raw materials, dialkyl carbonate and phenol. Therefore, in the method described in Patent Document 1, it is necessary to improve the reaction results in the first and second continuous multi-stage distillation columns in order to reduce the circulation energy. On the other hand, in the method described in Patent Document 1, it is possible to increase the catalyst concentration in the bottom liquid of the heavy-ends cut column A in order to improve the reaction results, but increasing the catalyst concentration increases catalyst loss, which poses a problem of increasing the need for catalyst replenishment. Therefore, an object of the present invention is to provide a method for producing diphenyl carbonate that can reduce heat consumption and suppress the amount of catalyst replenishment.

[0005] The present inventors have conducted extensive research to find a specific method for achieving the above object, and as a result have arrived at the present invention. That is, the present invention is as follows.

[0006] [1] A method for continuously producing diphenyl carbonate, comprising the steps of continuously supplying a dialkyl carbonate and a phenol into a first continuous multi-stage distillation column in the presence of a catalyst, simultaneously carrying out reaction and distillation in the first continuous multi-stage distillation column, continuously withdrawing a first column low-boiling reaction mixture containing produced alcohols in a gaseous state from an upper portion of the first continuous multi-stage distillation column, and continuously withdrawing a first column high-boiling reaction mixture containing produced alkyl phenyl carbonate in a liquid state from a lower portion of the first continuous multi-stage distillation column, thereby continuously producing alkyl phenyl carbonate; a step of continuously supplying the first column high-boiling reaction mixture into a second continuous multi-stage distillation column in the presence of a catalyst, simultaneously carrying out reaction and distillation in the second continuous multi-stage distillation column, continuously withdrawing the second column low-boiling reaction mixture containing the produced dialkyl carbonates in a gaseous state from the top of the second continuous multi-stage distillation column, and continuously withdrawing the second column high-boiling reaction mixture containing the produced diphenyl carbonate in a liquid state from the bottom of the second continuous multi-stage distillation column, thereby continuously producing diphenyl carbonate; and continuously introducing the second column high-boiling reaction mixture containing diphenyl carbonate into a heavy-ends cut column A, and continuously withdrawing a column top component (A) containing diphenyl carbonate. Ｔ ) and a column bottom component (A Ｂ a first purification step of continuously distilling and separating the top component (A Ｔ ) is continuously introduced into a diphenyl carbonate purification column B having a side cut withdrawal port, and the column top component (B Ｔ ), side cut component (B Ｓ ) and the bottom component (B Ｂ ) by successive distillation separation into three components, Ｓ a second purification step of obtaining diphenyl carbonate as the bottom component (A); a first circulation step of continuously supplying the second column low-boiling point reaction mixture into a first continuous multi-stage distillation column; Ｂ a second circulation step of continuously supplying a portion of the bottom component (A) of the heavy-ends cut column A into the first continuous multi-stage distillation column and / or the second continuous multi-stage distillation column; Ｂ ) contains diphenyl carbonate (DPC) and high boiling point substances (HB), and the column bottom component (A Ｂ[2] A method for producing diphenyl carbonate, wherein the mass concentration ratio of diphenyl carbonate to high-boiling substances (DPC / HB) in the column bottom component (A) is 0.1 to 1.0, and the mass concentration ratio of diphenyl carbonate to the catalyst (DPC / catalyst) is 1.0 to 10.0. Ｂ [3] The production method according to [1], wherein the concentration of diphenyl carbonate in the second column low-boiling point reaction mixture is 9 to 38 mass%. [3] The production method according to [1] or [2], wherein a material containing Fe as a main component, 2 mass% or more of Mo, and 18 mass% or less of Cr is used for the liquid-contacting part of the lower part of the second continuous multi-stage distillation column. [4] The production method according to any of [1] to [3], wherein the concentration of alkyl aryl carbonate in the second column low-boiling point reaction mixture is 1 mass% or less. [5] (a) The first continuous multi-stage distillation column has a length L １ (cm), inner diameter D １ (cm) cylindrical body, and has n stages inside １ The column has an internal structure with an internal diameter of d １１ A gas outlet with an inner diameter of d (cm) is provided at the bottom of the tower or at a lower part of the tower close to the bottom. １２ (cm) of liquid withdrawal port, one or more third inlets below the gas withdrawal port in the upper and / or middle part of the column, and one or more fourth inlets above the liquid withdrawal port in the middle and / or lower part of the column, １ , D １ , L １ / D １ , n １ , D １ / d １１ , D １ / d １２ respectively satisfy the following formulas (7) to (12), and 1500≦L １ ≦ 8000 Formula (7) 100 ≦ D １ ≦ 2000 Formula (8) 2 ≦ L １ / D １ ≦ 40 Formula (9) 20 ≦ n １ ≦ 120 Formula (10) 5 ≦ D１ / d １１ ≦ 30 Formula (11) 3 ≦ D １ / d １２ ≦ 20 Equation (12) (b) The second continuous multi-stage distillation column has a length L ２ (cm), inner diameter D ２ (cm) cylindrical body, and has n stages inside ２ The column has an internal structure with an internal diameter of d ２１ A gas outlet with an inner diameter of d (cm) is provided at the bottom of the tower or at a lower part of the tower close to the bottom. ２２ (cm) of liquid withdrawal port, one or more fifth inlets below the gas withdrawal port in the upper and / or middle part of the column, and one or more sixth inlets above the liquid withdrawal port in the middle and / or lower part of the column, ２ , D ２ , L ２ / D ２ , n ２ , D ２ / d ２１ , D ２ / d ２２ respectively satisfy the following formulas (13) to (18), and 1500≦L ２ ≦ 8000 Formula (13) 100 ≦ D ２ ≦ 2000 Formula (14) 2 ≦ L ２ / D ２ ≦ 40 Formula (15) 10 ≦ n ２ ≦ 80 Formula (16) 2 ≦ D ２ / d ２１ ≦ 15 Formula (17) 5 ≦ D ２ / d ２２ ≦ 30 Formula (18) (c) The high boiling point substance separation column A has a length L Ａ (cm), inner diameter D Ａ (cm) cylindrical body, and has n stages inside Ａ A continuous multi-stage distillation column having an internal of L Ａ , DＡ , n Ａ respectively satisfy the following formulas (19) to (21), and 800≦L Ａ ≦ 3000 Formula (19) 100 ≦ D Ａ ≦ 1000 Formula (20) 20 ≦ n Ａ ≦ 100 Formula (21) (d) The diphenyl carbonate purification column B has a length L Ｂ (cm), inner diameter D Ｂ The column has a cylindrical body with a diameter of 1.5 cm and an internal structure. １ , the inlet B １ Between the tower bottom and the side cut outlet B ２ and inlet B １ The number of internal stages at the top is n Ｂ１ , inlet B １ and side cut outlet B ２ The number of internal stages between Ｂ２ , Side cut outlet B ２ The number of internal stages at the bottom is n Ｂ３ The total number of stages (n Ｂ１ +n Ｂ２ +n Ｂ３ ) is n Ｂ A continuous multi-stage distillation column in which L Ｂ , D Ｂ , n Ｂ１ , n Ｂ２ , n Ｂ３ , n Ｂ The method according to any one of [1] to [4], wherein L satisfies the following formulas (22) to (27), respectively: 1000≦L Ｂ ≦ 5000 Formula (22) 100 ≦ D Ｂ ≦ 1000 Formula (23) 5 ≦ n Ｂ１ ≦ 20 Formula (24) 12 ≦ n Ｂ２ ≦ 40 Formula (25) 3 ≦ n Ｂ３≦ 15 Formula (26) 20 ≦ n Ｂ ≦ 70 Formula (27)

[0007] According to the present invention, it is possible to provide a method for producing diphenyl carbonate that can reduce the amount of heat used and the amount of catalyst replenishment.

[0008] Continuous multi-stage distillation column T ０ FIG. 1 is a schematic diagram showing an example of a first continuous multi-stage distillation column. An internal consisting of sieve trays is installed inside the body. FIG. 2 is a schematic diagram showing an example of a second continuous multi-stage distillation column. An internal consisting of structured packing is installed in the upper part of the body and sieve trays in the lower part. FIG. 3 is a schematic diagram showing an example of an apparatus in which a first continuous multi-stage distillation column and a second continuous multi-stage distillation column are connected. FIG. 4 is a schematic diagram showing an example of an apparatus in which a heavy ends cut column A and a diphenyl carbonate purification column B are connected.

[0009] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited to this, and various modifications are possible within the scope of the gist of the present invention. 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 of the drawings are not limited to those shown in the drawings.

[0010] The method for producing diphenyl carbonate of this embodiment is a method for continuously producing diphenyl carbonate, comprising the steps of continuously supplying a dialkyl carbonate and a phenol into a first continuous multi-stage distillation column in the presence of a catalyst, simultaneously carrying out reaction and distillation in the first continuous multi-stage distillation column, continuously withdrawing a first-column low-boiling reaction mixture containing produced alcohols in a gaseous state from an upper part of the first continuous multi-stage distillation column, and continuously withdrawing a first-column high-boiling reaction mixture containing produced alkyl phenyl carbonate in a liquid state from a lower part of the first continuous multi-stage distillation column, thereby continuously producing alkyl phenyl carbonate; a step of continuously supplying the first column high-boiling reaction mixture into a second continuous multi-stage distillation column in the presence of a catalyst, simultaneously carrying out reaction and distillation in the second continuous multi-stage distillation column, continuously withdrawing the second column low-boiling reaction mixture containing the produced dialkyl carbonates in a gaseous state from the top of the second continuous multi-stage distillation column, and continuously withdrawing the second column high-boiling reaction mixture containing the produced diphenyl carbonate in a liquid state from the bottom of the second continuous multi-stage distillation column, thereby continuously producing diphenyl carbonate; and continuously introducing the second column high-boiling reaction mixture containing diphenyl carbonate into a heavy-ends cut column A, and continuously withdrawing a column top component (A) containing diphenyl carbonate. Ｔ ) and a column bottom component (A Ｂ a first purification step of continuously distilling and separating the top component (A Ｔ ) is continuously introduced into a diphenyl carbonate purification column B having a side cut withdrawal port, and the column top component (B Ｔ ), side cut component (B Ｓ ) and the bottom component (B Ｂ ) by successive distillation separation into three components, Ｓ a second purification step of obtaining diphenyl carbonate as the bottom component (A); a first circulation step of continuously supplying the second column low-boiling point reaction mixture into a first continuous multi-stage distillation column; Ｂ a second circulation step of continuously supplying a portion of the bottom component (A) of the heavy-ends cut column A into the first continuous multi-stage distillation column and the second continuous multi-stage distillation column; Ｂ) contains diphenyl carbonate (hereinafter also referred to as "DPC") and high boiling point substances (hereinafter also referred to as "HB"), and the column bottom component (A Ｂ ) the mass concentration ratio of diphenyl carbonate to high boiling point substances (DPC / HB) is 0.1 to 1.0, and the mass concentration ratio of diphenyl carbonate to catalyst (DPC / catalyst) is 1.0 to 10.0.

[0011] The diphenyl carbonate production method of the present embodiment, due to the above-mentioned characteristics, has the effect of reducing the amount of heat used and suppressing the amount of catalyst replenishment. The mechanism by which such effects are achieved is not clear, but the present inventors speculate as follows.

[0012] The bottom component of the heavy ends cut column A (A Ｂ ) is recycled to the first continuous multi-stage distillation column and the second continuous multi-stage distillation column, and typically contains not only the catalyst but also diphenyl carbonate and high-boiling substances. In the method for producing diphenyl carbonate of this embodiment, Ｂ By increasing the concentration of high boiling point substances in the column bottom component (A), the concentration of diphenyl carbonate contained in the recycled liquid is reduced, and as described above, Ｂ The mass concentration ratio (DPC / HB) of diphenyl carbonate to high-boiling substances in the bottom component (AB) is controlled within a predetermined range. This favors the production of diphenyl carbonate in terms of reaction equilibrium, particularly in the second continuous multi-stage distillation column, and it is believed that the diphenyl carbonate production method of this embodiment can improve reaction performance. On the other hand, if the mass concentration ratio (DPC / HB) of diphenyl carbonate to high-boiling substances in the bottom component (AB) is reduced too much, the temperature of the bottom of the high-boiling separation column becomes too high, making evaporation in the reboiler impossible. From this perspective, the mass concentration ratio (DPC / HB) of diphenyl carbonate to high-boiling substances in the bottom component (AB) is preferably 0.2 to 0.8, and more preferably 0.3 to 0.6.

[0013] Furthermore, as described above, the bottom component (A ＢIt is believed that by controlling the mass concentration ratio of diphenyl carbonate to the catalyst (DPC / catalyst) in the column bottom component (A) within a predetermined range, it is possible to improve the above-mentioned reaction results while suppressing the amount of catalyst replenishment. Ｂ The mass concentration ratio of diphenyl carbonate to the catalyst (DPC / catalyst) in the column bottom component (A) is preferably 7.0 to 9.5, more preferably 8.0 to 9.0. Ｂ The concentration of diphenyl carbonate in the bottom component (A) is preferably 9 to 38 mass%, more preferably 19 to 36 mass%, and even more preferably 28 to 34 mass%. Ｂ When the concentration of diphenyl carbonate in the above-mentioned range, the amount of heat used tends to be further reduced and the amount of catalyst replenishment tends to be further suppressed.

[0014] According to the diphenyl carbonate production method of the present embodiment, by improving the reaction performance, it is possible to reduce the amounts of dialkyl carbonate and phenol recycled, for example, and accordingly reduce the amount of energy used in the first recycling step.

[0015] In the first circulation step, for example, steam is used in the first continuous multi-stage distillation column and the second continuous multi-stage distillation column to boil the dialkyl carbonate and phenol to the top of the column, thereby forming a circulation. Therefore, by reducing the circulation amount, the amount of energy used in the first continuous multi-stage distillation column and the second continuous multi-stage distillation column can be reduced.

[0016] The bottom component of the heavy ends cut column A (A Ｂ In order to adjust the mass concentration ratio of diphenyl carbonate to high boiling points (DPC / HB) in the heavy-ends cut column to 0.1 to 1.0, it is necessary to boil the DPC at the bottom of the column up to the top of the column, as compared with the conventional method. Therefore, for example, the mass concentration ratio (DPC / HB) can be adjusted to fall within the above-mentioned range by lowering the pressure in the heavy-ends cut column compared with the conventional method.

[0017] In addition, the bottom component (A ＢIn order to make the mass concentration ratio of diphenyl carbonate to the catalyst (DPC / catalyst) in the column bottom component (A) 1.0 to 10.0, it is usually sufficient to reduce the amount of catalyst present. Reducing the amount of catalyst present tends to increase the above-mentioned mass concentration ratio (DPC / HB). However, since the reaction in the first continuous multi-stage distillation column and the second continuous multi-stage distillation column decreases, the mass concentration ratio (DPC / catalyst) can be adjusted to within the above-mentioned range by, for example, reducing the DPC concentration rather than reducing the amount of catalyst present. Note that in this embodiment, the column bottom component (A Ｂ The concentrations of diphenyl carbonate (DPC), high boiling point substances (HB) and catalyst in the above mixture can be measured by the method described in the Examples below.

[0018] In this embodiment, the high-boiling substance refers to a substance having a boiling point higher than that of diphenyl carbonate, excluding catalysts.

[0019] In this embodiment, the method for obtaining the raw material dialkyl carbonate is not particularly limited, but for example, step (I) may be carried out to continuously produce dialkyl carbonate and diols from a cyclic carbonate and an aliphatic monohydric alcohol on an industrial scale. The reaction in step (I) is a reversible transesterification reaction represented by the following formula:

[0020]

[0021] (In formula 1, R １ is a divalent group -(CH ２ )m- (m is an integer of 2 to 6), and one or more hydrogen atoms may be substituted with an alkyl group or an aryl group having 1 to 10 carbon atoms. ２ represents a monovalent aliphatic group having 1 to 12 carbon atoms, one or more hydrogen atoms of which may be substituted with an alkyl group or aryl group having 1 to 10 carbon atoms.

[0022] As such a cyclic carbonate, for example, alkylene carbonates such as ethylene carbonate and propylene carbonate, 1,3-dioxacyclohex-2-one, 1,3-dioxacyclohept-2-one, etc. are preferably used, and ethylene carbonate and propylene carbonate are more preferably used from the viewpoint of easy availability, and ethylene carbonate is particularly preferably used.

[0023] The aliphatic monohydric alcohols used have a boiling point lower than that of the diols produced. Therefore, although the boiling point may vary depending on the type of cyclic carbonate used, examples include methanol, ethanol, propanol (each isomer), allyl alcohol, butanol (each isomer), 3-buten-1-ol, amyl alcohol (each isomer), hexyl alcohol (each isomer), heptyl alcohol (each isomer), octyl alcohol (each isomer), nonyl alcohol (each isomer), decyl alcohol (each isomer), undecyl alcohol (each isomer), dodecyl alcohol (each isomer), cyclopentanol, cyclohexanol, cycloheptanol, cyclooctanol, and methylcyclopentanol. (each isomer), ethylcyclopentanol (each isomer), methylcyclohexanol (each isomer), ethylcyclohexanol (each isomer), dimethylcyclohexanol (each isomer), diethylcyclohexanol (each isomer), phenylcyclohexanol (each isomer), benzyl alcohol, phenethyl alcohol (each isomer), phenylpropanol (each isomer), and the like. Furthermore, these aliphatic monohydric alcohols may be substituted with a substituent such as a halogen, a lower alkoxy group, a cyano group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, or a nitro group.

[0024] Among these aliphatic monohydric alcohols, alcohols having 1 to 6 carbon atoms are preferably used, and alcohols having 1 to 4 carbon atoms, such as methanol, ethanol, propanol (each isomer), and butanol (each isomer), are more preferred. When ethylene carbonate or propylene carbonate is used as the cyclic carbonate, methanol and ethanol are preferred, and methanol is particularly preferred.

[0025] When performing the reactive distillation in step (I), any method may be used to cause a catalyst to be present in the reactive distillation column. For example, in the case of a homogeneous catalyst that dissolves in the reaction liquid under reaction conditions, the catalyst can be continuously supplied into the reactive distillation column to cause the catalyst to be present in the liquid phase in the reactive distillation column. Alternatively, in the case of a heterogeneous catalyst that does not dissolve in the reaction liquid under reaction conditions, a solid catalyst can be placed in the reactive distillation column to cause the catalyst to be present in the reaction system. Alternatively, a combination of these methods may be used.

[0026] When a homogeneous catalyst is continuously supplied to a reactive distillation column, it may be supplied simultaneously with the cyclic carbonate and / or the aliphatic monohydric alcohol, or may be supplied to a position different from that of the raw material. Since the reaction actually proceeds in the distillation column in a region below the catalyst supply position, it is preferable to supply the catalyst to a region between the top of the column and a position slightly below the raw material supply position. The number of stages in which the catalyst is present is preferably 5 or more, more preferably 7 or more, and even more preferably 10 or more.

[0027] When a heterogeneous solid catalyst is used, the number of stages in which the catalyst is present is preferably 5 or more, more preferably 7 or more, and even more preferably 10 or more. A solid catalyst that also functions as a packing for a distillation column can also be used.

[0028] The catalyst used in step (I) is not particularly limited, and examples thereof include: alkali metals and alkaline earth metals such as lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, and barium; basic compounds such as hydrides, hydroxides, alkoxides, aryloxides, and amides of alkali metals and alkaline earth metals; basic compounds such as carbonates, bicarbonates, and organic acid salts of alkali metals and alkaline earth metals; tertiary amines such as triethylamine, tributylamine, trihexylamine, and benzyldiethylamine; Nitrogen-containing heteroaromatic compounds such as N-alkylpyrrole, N-alkylindole, oxazole, N-alkylimidazole, N-alkylpyrazole, oxadiazole, pyridine, alkylpyridine, quinoline, alkylquinoline, isoquinoline, alkylisoquinoline, acridine, alkylacridine, phenanthroline, alkylphenanthroline, pyrimidine, alkylpyrimidine, pyrazine, alkylpyrazine, triazine, and alkyltriazine; cyclic amidines such as diazabicycloundecene (DBU) and diazabicyclononene (DBN); thallium compounds such as thallium oxide, thallium halides, thallium hydroxide, thallium carbonate, thallium nitrate, thallium sulfate, and organic acid salts of thallium; Tin compounds such as tributyl methoxy tin, tributyl ethoxy tin, dibutyl dimethoxy tin, diethyl diethoxy tin, dibutyl diethoxy tin, dibutyl phenoxy tin, diphenyl methoxy tin, dibutyl tin acetate, tributyl tin chloride, and tin 2-ethylhexanoate; zinc compounds such as dimethoxy zinc, diethoxy zinc, ethylene dioxy zinc, and dibutoxy zinc; aluminum compounds such as aluminum trimethoxide, aluminum triisopropoxide, and aluminum tributoxide; titanium compounds such as tetramethoxy titanium, tetraethoxy titanium, tetrabutoxy titanium, dichlorodimethoxy titanium, tetraisopropoxy titanium, titanium acetate, and titanium acetylacetonate;Phosphorus compounds such as trimethylphosphine, triethylphosphine, tributylphosphine, triphenylphosphine, tributylmethylphosphonium halide, trioctylbutylphosphonium halide, and triphenylmethylphosphonium halide; zirconium compounds such as zirconium halides, zirconium acetylacetonate, zirconium alkoxides, and zirconium acetate; lead and lead-containing compounds, for example, PbO, PbO; ２ , Pb ３ O ４ Lead oxides such as PbS, Pb ２ S ３ , PbS ２ Lead sulfides such as Pb(OH) ２ , Pb ３ O ２ (OH) ２ , Pb ２ [PbO ２ (OH) ２ ], Pb ２ O(OH) ２ Lead hydroxides such as Na ２ PbO ２ , K. ２ PbO ２ , NaHPbO ２ , KHPbO ２ Natrium salts such as; ２ PbO ３ , Na ２ H ２ PbO4, K ２ PbO ３ , K. ２ [Pb(OH) ６ ], K ４ PbO ４ , Ca ２ PbO ４ , CaPbO ３ Plumbates such as PbCO ３ , 2PbCO ３ Pb(OH) ２ lead carbonates and their basic salts; Pb(OCH ３ ) ２ , (CH ３ O) Pb(OPh), Pb(OPh) ２Alkoxy lead compounds, aryloxy lead compounds, such as Pb(OCOCH ３ ) ２ , Pb(OCOCH ３ ) ４ , Pb(OCOCH ３ ) ２ PbO 3H ２ Lead salts of organic acids such as HCl, ... ４ Pb, Ph ４ Pb, Bu ３ PbCl, Ph ３ PbBr, Ph ３ Pb (or Ph ６ Pb ２ ), Bu ３ PbOH, Ph ２ Examples include organic lead compounds such as PbO (Bu represents a butyl group and Ph represents a phenyl group); lead alloys such as Pb—Na, Pb—Ca, Pb—Ba, Pb—Sn, and Pb—Sb; lead minerals such as aragonite and aragonite, and hydrates of these lead compounds.

[0029] These compounds can be used as homogeneous catalysts when they are soluble in the reaction raw materials, reaction mixture, reaction by-products, etc., and can be used as solid catalysts when they are insoluble. Furthermore, it is also a preferred method to dissolve these compounds in the reaction raw materials, reaction mixture, reaction by-products, etc. in advance, or to use a mixture obtained by dissolving the compounds through reaction as a homogeneous catalyst.

[0030] Further, ion exchangers such as anion exchange resins having a tertiary amino group, ion exchange resins having an amide group, ion exchange resins having at least one exchange group selected from sulfonic acid group, carboxylic acid group, and phosphoric acid group, and solid strongly basic anion exchangers having a quaternary ammonium group as an exchange group; and solid inorganic compounds such as silica, silica-alumina, silica-magnesia, aluminosilicate, gallium silicate, various zeolites, various metal-exchanged zeolites, and ammonium-exchanged zeolites can be used as catalysts.

[0031] A particularly preferred solid catalyst is a solid strongly basic anion exchanger having a quaternary ammonium group as an exchange group. Examples of such a solid strongly basic anion exchanger include, but are not limited to, a strongly basic anion exchange resin having a quaternary ammonium group as an exchange group, a cellulose strongly basic anion exchanger having a quaternary ammonium group as an exchange group, and an inorganic carrier-supported strongly basic anion exchanger having a quaternary ammonium group as an exchange group. Examples of strongly basic anion exchange resins having a quaternary ammonium group as an exchange group include, but are not limited to, styrene-based strongly basic anion exchange resins. Styrenic strongly basic anion exchange resins are strongly basic anion exchange resins based on a copolymer of styrene and divinylbenzene and having a quaternary ammonium group (type I or type II) as an exchange group, and are, for example, represented by the following formula:

[0032]

[0033] In the formula, X represents an anion, and typically, X is F － , Cl － ,Br － , I － , HCO ３ － , CO ３ ２－ , C.H. ３ CO ２ － , HCO ２ － , I.O. ３ － , BrO ３ － , ClO3 － At least one anion selected from the group consisting of － ,Br － , HCO ３ － , CO ３ ２－ The resin matrix may be of either a gel type or a macroreticular type (MR type), but the MR type is particularly preferred because of its high resistance to organic solvents.

[0034] The strongly basic cellulose anion exchanger having a quaternary ammonium group as an exchange group is not particularly limited, but examples thereof include —OCH ２ CH ２ NR ３ Examples of such cellulose include those having an exchange group X, where R represents an alkyl group, typically methyl, ethyl, propyl, or butyl, preferably methyl or ethyl, and X represents an anion as described above.

[0035] The inorganic carrier-supported strong basic anion exchanger having quaternary ammonium groups as exchange groups is a strong basic anion exchanger in which the surface hydroxyl groups -OH of the inorganic carrier are partially or completely modified to form quaternary ammonium groups -O(CH ２ )nNR ３ X is introduced. Here, R and X are as described above. n is usually an integer of 1 to 6, and preferably n=2. The inorganic support is not particularly limited, but for example, silica, alumina, silica-alumina, titania, zeolite, etc. can be used, preferably silica, alumina, and silica-alumina, and particularly preferably silica. Any method can be used to modify the surface hydroxyl groups of the inorganic support.

[0036] Commercially available solid strongly basic anion exchangers having quaternary ammonium groups as exchange groups can also be used. In this case, they can be pretreated by ion exchange with the desired anion species before use as a transesterification catalyst.

[0037] In addition, solid catalysts composed of macroreticular and gel-type organic polymers having at least one nitrogen-containing heterocyclic group bonded thereto, or inorganic supports having at least one nitrogen-containing heterocyclic group bonded thereto, are also preferably used as transesterification catalysts. Furthermore, solid catalysts in which some or all of these nitrogen-containing heterocyclic groups have been converted into quaternary salts are also used. Solid catalysts such as ion exchangers can also function as packings.

[0038] The amount of catalyst used in step (I) varies depending on the type of catalyst used, but when a homogeneous catalyst that dissolves in the reaction liquid under the reaction conditions is continuously supplied, the catalyst is typically used in an amount of 0.0001 to 50 mass%, preferably 0.005 to 20 mass%, and more preferably 0.01 to 10 mass%, expressed as a ratio to the total mass of the cyclic carbonate and aliphatic monohydric alcohol that are the feed materials. When a solid catalyst is used by placing it in the distillation column, the catalyst is preferably used in an amount of 0.01 to 75 volume%, preferably 0.05 to 60 volume%, and more preferably 0.1 to 60 volume%, based on the empty volume of the distillation column.

[0039] In step (I), the continuous multi-stage distillation column T ０ There are no particular limitations on the method for continuously supplying the raw materials, cyclic carbonate and aliphatic monohydric alcohol, to the distillation column, and any supply method may be used as long as they can be brought into contact with the catalyst in at least five stages, preferably seven stages, and more preferably ten stages or more of the distillation column. That is, the cyclic carbonate and the aliphatic monohydric alcohol can be continuously supplied from the number of inlets required for the stages of the continuous multi-stage distillation column that satisfy the above conditions. Furthermore, the cyclic carbonate and the aliphatic monohydric alcohol may be introduced into the same stage of the distillation column, or may be introduced into different stages.

[0040] The raw materials, cyclic carbonate and aliphatic monohydric alcohol, are fed to the continuous multi-stage distillation column T in the form of a liquid, a gas, or a mixture of a liquid and a gas. ０ In addition to supplying the raw material to the distillation column in this manner, it is also a preferred method to additionally supply a gaseous raw material intermittently or continuously from the lower part of the distillation column. Another preferred method is to continuously supply the cyclic carbonate in a liquid state or in a gas-liquid mixed state to the distillation column at a stage above the stage where the catalyst is present, and to continuously supply the aliphatic monohydric alcohol in a gaseous and / or liquid state to the lower part of the distillation column. In this case, it is of course acceptable for the cyclic carbonate to contain an aliphatic monohydric alcohol.

[0041] In step (I), the feedstock may contain the product dialkyl carbonate and / or diols. The dialkyl carbonate content is typically 0 to 40 mass%, preferably 0 to 30 mass%, and more preferably 0 to 20 mass%, expressed in mass% of the dialkyl carbonate in the aliphatic monohydric alcohol / dialkyl carbonate mixture, and the diols content is typically 0 to 10 mass%, preferably 0 to 7 mass%, and more preferably 0 to 5 mass%, expressed in mass% of the cyclic carbonate / diol mixture.

[0042] When the reaction of step (I) is carried out industrially, it is preferable that, in addition to the cyclic carbonate and / or aliphatic monohydric alcohol newly introduced into the reaction system, substances mainly composed of cyclic carbonate and / or aliphatic monohydric alcohol recovered in this step and / or other steps can be used as raw materials for these. Other steps include, for example, step (II) in which diphenyl carbonate is produced from dialkyl carbonate and phenol. In step (II), aliphatic monohydric alcohol is by-produced and recovered. This recovered by-product aliphatic monohydric alcohol usually contains dialkyl carbonate, phenol, alkylaryl ether, etc., and may also contain small amounts of alkylaryl carbonate, diphenyl carbonate, etc. The by-product aliphatic monohydric alcohol can be used as the raw material for step (I) as is, or can be used as the raw material for step (I) after reducing the amount of substances with a boiling point higher than that of the aliphatic monohydric alcohol by distillation or the like.

[0043] Furthermore, the preferred cyclic carbonate used in step (I) is one produced by the reaction of an alkylene oxide such as ethylene oxide, propylene oxide, or styrene oxide with carbon dioxide, and therefore a cyclic carbonate containing a small amount of these compounds can also be used as the raw material in step (I).

[0044] In step (I), the ratio of the amount of cyclic carbonate to the aliphatic monohydric alcohols supplied to the reactive distillation column varies depending on the type and amount of the transesterification catalyst and the reaction conditions. Typically, the aliphatic monohydric alcohols can be supplied in a molar ratio of 0.01 to 1000 times the amount of cyclic carbonate supplied. In order to increase the reaction rate of the cyclic carbonate, it is preferable to supply an excess of at least 2 times the amount of the aliphatic monohydric alcohols, but if used in too large an excess, the equipment must be larger. In this sense, the molar ratio of the aliphatic monohydric alcohols to the cyclic carbonate is preferably 2 to 20, more preferably 3 to 15, and even more preferably 5 to 12. If a large amount of unreacted cyclic carbonate remains, it will react with the product diols to by-produce polymers such as dimers and trimers. Therefore, when carried out industrially, it is preferable to reduce the amount of unreacted cyclic carbonate remaining as much as possible.

[0045] In step (I), for example, when about 0.4 ton or more of dialkyl carbonate is continuously produced per hour, the minimum amount of cyclic carbonate continuously supplied relative to the amount of dialkyl carbonate to be produced (P ton / hr) is usually 0.44 P ton / hr, preferably 0.42 P ton / hr, more preferably 0.4 P ton / hr. In even more preferable cases, it can be less than 0.39 P ton / hr.

[0046] The continuous multi-stage distillation column T used in step (I) ０ is not particularly limited, but for example, as shown in FIG. ０ (cm), inner diameter D ０ (cm) cylindrical body, and has n stages inside ０ The column has an internal structure with an internal diameter of d ０１ A gas outlet with an inner diameter of d (cm) is provided at the bottom of the tower or at a lower part of the tower close to the bottom. ０２ (cm) of liquid withdrawal port, one or more first inlets below the gas withdrawal port in the upper and / or middle part of the column, and one or more second inlets above the liquid withdrawal port in the middle and / or lower part of the column, ０ , D０ , L ０ / D ０ , n ０ , D ０ / d ０１ , D ０ / d ０２ However, examples of the continuous multi-stage distillation column include those satisfying the following formulas (1) to (6): 2100 ≦ L ０ ≦ 8000 Formula (1) 180 ≦ D ０ ≦ 2000 Formula (2) 4 ≦ L ０ / D ０ ≦ 40 Formula (3) 10 ≦ n ０ ≦ 120 Formula (4) 3 ≦ D ０ / d ０１ ≦ 20 Formula (5) 5 ≦ D ０ / d ０２ ≦ 30 Formula (6).

[0047] The term "top of the tower or the upper part of the tower close to the top" used in this embodiment refers to the area about 0.25 L below the top of the tower. ０ The term "lower part of the column at or near the bottom of the column" refers to the part up to about 0.25 L above the bottom of the column. ０ (In the first and second continuous multi-stage distillation columns, 0.25 L is used.) １ and 0.25L ２ and in the heavy-ends cut column A and the diphenyl carbonate purification column B, 0.25 L, respectively. Ａ and 0.25L Ｂ It is.)

[0048] A continuous multi-stage distillation column T that simultaneously satisfies equations (1), (2), (3), (4), (5), and (6) ０By using this process, dialkyl carbonates can be stably produced from cyclic carbonates and aliphatic monohydric alcohols at rates of preferably 0.4 tons or more per hour and / or diols at rates of preferably 0.26 tons or more per hour on an industrial scale with high reaction rates, high selectivity, and high productivity, for long periods of time, for example, 1,000 hours or more, preferably 3,000 hours or more, and more preferably 5,000 hours or more. The reason why carrying out step (I) enables the production of dialkyl carbonates and diols on an industrial scale with such excellent effects is unclear, but it is presumed to be due to the combined effect brought about by the combination of the conditions of formulas (1) to (6). The preferred ranges for each factor are shown below.

[0049] L ０ When the reaction rate is 2100 or more, the reaction rate is good and the desired production amount can be achieved. In addition, in order to reduce the equipment cost while ensuring a reaction rate that can achieve the desired production amount, L ０ It is preferable to set L to 8000 or less. ０ The range of (cm) is 2300≦L ０ ≦6000, and more preferably 2500≦L ０ ≦5000.

[0050] D ０ If the diameter of the nozzle is 180 or more, the desired production volume can be achieved. ０ It is preferable to set D to 2000 or less. ０ (cm) range is 200≦D ０ ≦1000, and more preferably 210≦D ０ ≦800.

[0051] L ０ / D ０ When L is 4 or more or 40 or less, stable operation becomes easy, especially when L ０ / D ０When L is 40 or less, the pressure difference between the top and bottom of the column can be prevented from becoming too large, which not only facilitates long-term stable operation but also makes it possible to lower the temperature in the lower part of the column, thereby suppressing side reactions and tending to improve the selectivity. ０ / D ０ The range is 5≦L ０ / D ０ ≦30, and more preferably 7≦L ０ / D ０ ≦20.

[0052] n ０ If n is 10 or more, the reaction rate is improved, and the desired production amount can be achieved. In order to reduce the equipment cost while ensuring a reaction rate that can achieve the desired production amount, ０ It is preferable to set n to 120 or less. ０ When n is 120 or less, the pressure difference between the top and bottom of the column can be prevented from becoming too large, which not only facilitates long-term stable operation but also makes it possible to lower the temperature in the bottom of the column, suppress side reactions, and tends to improve the selectivity. ０ The range is 30≦n ０ ≦100, and more preferably 40≦n ０ ≦90.

[0053] D ０ / d ０１ When the ratio is 3 or more, not only can the equipment cost be reduced but also the outflow of gas components to the outside of the system can be suppressed, and stable operation can be facilitated. When the ratio is 20 or less, the amount of gas components extracted becomes relatively large, and not only can stable operation be facilitated but also the reaction rate tends to be improved. ０ / d ０１ The range is 4≦D ０ / d ０１ ≦15, and more preferably 5≦D ０ / d ０１ ≦13.

[0054] D ０ / d ０２If D is 5 or more, not only can the equipment cost be reduced, but also the amount of liquid drawn off is relatively small, facilitating stable operation, and if D is 30 or less, a sudden increase in the flow rate at the liquid drawing port and piping can be prevented, erosion is less likely to occur, and corrosion of the equipment can be suppressed. ０ / d ０２ The range is 7≦D ０ / d ０２ ≦25, and more preferably 9≦D ０ / d ０２ ≦20.

[0055] Furthermore, the continuous multi-stage distillation column T used in step (I) ０ The d ０１ and the d ０２ It is more preferable if 1 ≦ d satisfies the formula (28). ０１ / d ０２ ≦ 5 Formula (28).

[0056] The long-term stable operation in step (I) means that operation can be continued in a steady state based on the operating conditions for 1,000 hours or more, preferably 3,000 hours or more, and more preferably 5,000 hours or more without flooding, clogging of piping, or erosion, and that predetermined amounts of dialkyl carbonate and diols are produced while maintaining high reaction rate, high selectivity, and high productivity.

[0057] The selectivity of dialkyl carbonate and diols in step (I) refers to the selectivity of the reacted cyclic carbonate, and in this embodiment, a high selectivity of typically 95% or more can be achieved, preferably 97% or more, and more preferably 99% or more. Furthermore, the reaction rate in step (I) typically refers to the reaction rate of the cyclic carbonate, and in this embodiment, the reaction rate of the cyclic carbonate can be increased to 95% or more, preferably 97% or more, more preferably 99% or more, even more preferably 99.5% or more, and even more preferably 99.9% or more. The ability to achieve a high reaction rate while maintaining such high selectivity is one of the excellent features of step (I).

[0058] The continuous multi-stage distillation column T used in step (I) ０Preferably, the distillation column has trays and / or packings as internals. In this embodiment, the term "internal" refers to the portion of the distillation column where gas and liquid actually come into contact. Examples of such trays include, but are not limited to, bubble trays, perforated trays, valve trays, countercurrent trays, Superfrac trays, and Maxfrac trays. Examples of packing include random packings such as Raschig rings, Lessing rings, Pall rings, Berl saddles, Intalox saddles, Dixon packing, McMahon packing, and Helipack, and structured packings such as Melapak, Gempack, Technopack, Flexipak, Sulzer packing, Goodroll packing, and Glitch grid. Multi-stage distillation columns having both tray sections and sections packed with packings can also be used. In this embodiment, the term "internal stage number" refers to the number of trays in the case of trays, and the theoretical number of stages in the case of packings. Therefore, in the case of a multi-stage distillation column having both a tray section and a section filled with packing, the number of stages is the sum of the number of trays and the number of theoretical stages.

[0059] In step (I) of reacting a cyclic carbonate with an aliphatic monohydric alcohol, whether a tray-type continuous multi-stage distillation column and / or a packed column-type continuous multi-stage distillation column whose internal is made of trays and / or packings having a predetermined number of stages is used, tends to achieve a high reaction rate, high selectivity, and high productivity. A tray-type distillation column whose internal is a tray is more preferred. Furthermore, a sieve tray having a sieve tray section and a downcomer section is particularly excellent in terms of functionality and equipment costs. And, the sieve tray has a sieve tray section with an area of ​​1 m ２ It is preferable that the number of holes is 100 to 1000 per square meter. A more preferable number of holes is 100 to 1000 per square meter. ２ The number of holes per hole in the sieve tray is preferably 120 to 900, more preferably 150 to 800. The cross-sectional area per hole in the sieve tray is preferably 0.5 to 5 cm. ２ The more preferable cross-sectional area per hole is 0.7 to 4 cm ２ and more preferably 0.9 to 3 cm ２Furthermore, the area of ​​the perforated tray is 1 m ２ It has 100 to 1000 holes per hole, and the cross-sectional area of ​​each hole is 0.5 to 5 cm ２ It is particularly preferred if

[0060] Furthermore, the aperture ratio of the sieve tray is preferably 1.5 to 15%. A more preferred aperture ratio is 1.7 to 13%, and even more preferred is 1.9 to 11%. Here, the aperture ratio of the sieve tray refers to the ratio of the cross-sectional area of ​​all the holes present in the sieve tray (total hole cross-sectional area) to the area of ​​the sieve plate portion (including the total hole cross-sectional area). The area and / or the total hole cross-sectional area of ​​the sieve plate portion may differ among the sieve trays, but even in this case, it is preferable that the aperture ratio of each sieve tray be within the above-mentioned range. The number of holes in the sieve plate portion may be the same or different among all the sieve plates.

[0061] When carrying out step (I), for example, the starting materials, cyclic carbonate and aliphatic monohydric alcohols, are continuously supplied to a continuous multi-stage distillation column in the presence of a catalyst, reaction and distillation are carried out simultaneously in the column, and the resulting low-boiling reaction mixture containing dialkyl carbonate is continuously withdrawn in a gaseous state from the top of the column, and the high-boiling reaction mixture containing diols is continuously withdrawn in a liquid state from the bottom of the column, thereby continuously producing dialkyl carbonate and diols.

[0062] In step (I), the raw materials, cyclic carbonate and aliphatic monohydric alcohols, are separated in a continuous multi-stage distillation column T ０ In order to continuously supply the aliphatic monohydric alcohols into the distillation column, the raw materials may be supplied in liquid and / or gaseous form as a raw material mixture or separately from one or more inlets located below the gas outlet at the top of the column but in the upper or middle section of the column. Alternatively, it is also a preferred method to supply the cyclic carbonate or a raw material containing a large amount of the cyclic carbonate in liquid form from an inlet at the upper or middle section of the column, and supply the aliphatic monohydric alcohols or a raw material containing a large amount of the cyclic carbonate in gaseous form from an inlet located above the liquid outlet at the bottom of the column but in the middle or lower section of the column.

[0063] The reaction time of the transesterification reaction carried out in step (I) is ０ This is considered to correspond to the average residence time of the reaction liquid within the distillation column, which varies depending on the shape and number of plates of the internals of the distillation column, the amount of raw material supplied, the type and amount of catalyst, reaction conditions, etc., but is usually 0.1 to 20 hours, preferably 0.5 to 15 hours, and more preferably 1 to 10 hours.

[0064] The reaction temperature in step (I) varies depending on the type of raw material compound used and the type and amount of catalyst, but is typically 30 to 300°C. Increasing the reaction temperature is preferable to increase the reaction rate, but high reaction temperatures also make side reactions more likely to occur. A preferred reaction temperature is 40 to 250°C, more preferably 50 to 200°C, and even more preferably 60 to 150°C. In this embodiment, reactive distillation can be carried out at a column bottom temperature of 150°C or less, preferably 130°C or less, more preferably 110°C or less, and even more preferably 100°C or less. One of the excellent features of step (I) is that a high reaction rate, high selectivity, and high productivity can be achieved even at such a low column bottom temperature. The reaction pressure varies depending on the type and composition of the raw material compound used, the reaction temperature, etc., but may be reduced pressure, atmospheric pressure, or increased pressure, and is typically 1 Pa to 2 x 10 ７ Pa, preferably 10 ３ Pa to 10 ７ Pa, more preferably 10 ４ Pa ~ 5 x 10 ６ The pressure is in the range of Pa.

[0065] In addition, the continuous multi-stage distillation column T ０ The reflux ratio is usually 0 to 10, preferably 0.01 to 5, and more preferably 0.05 to 3.

[0066] The continuous multi-stage distillation column T used in step (I) ０ The material constituting the reactor is mainly a metal material such as carbon steel or stainless steel, but stainless steel is preferred from the viewpoint of the quality of the dialkyl carbonate and diols to be produced.

[0067] In the production method of this embodiment, dialkyl carbonate and phenol are continuously supplied into a first continuous multi-stage distillation column in the presence of a catalyst, reaction and distillation are simultaneously carried out in the first continuous multi-stage distillation column, the first column low-boiling reaction mixture containing the produced alcohols is continuously withdrawn in a gaseous state from the top of the first continuous multi-stage distillation column, and the first column high-boiling reaction mixture containing the produced alkyl phenyl carbonate is continuously withdrawn in a liquid state from the bottom of the first continuous multi-stage distillation column, thereby continuously producing alkyl phenyl carbonate. The process comprises the steps of continuously supplying a first-column high-boiling reaction mixture to a second continuous multi-stage distillation column in the presence of a catalyst, simultaneously carrying out reaction and distillation in the second continuous multi-stage distillation column, continuously withdrawing the second-column low-boiling reaction mixture containing the resulting dialkyl carbonates in a gaseous state from the top of the second continuous multi-stage distillation column, and continuously withdrawing the second-column high-boiling reaction mixture containing the resulting diphenyl carbonate in a liquid state from the bottom of the second continuous multi-stage distillation column (hereinafter also referred to as "step (II)"). The dialkyl carbonate used in step (II) is not particularly limited, but examples thereof include those represented by the following formula shown in Chemical Formula 1 above. Here, R ２ is as described above.

[0068] Such an R ２The dialkyl carbonate having the formula (I) is not particularly limited, and examples thereof include dimethyl carbonate, diethyl carbonate, dipropyl carbonate (each isomer), diallyl carbonate, dibutenyl carbonate (each isomer), dibutyl carbonate (each isomer), dipentyl carbonate (each isomer), dihexyl carbonate (each isomer), diheptyl carbonate (each isomer), dioctyl carbonate (each isomer), dinonyl carbonate (each isomer), didecyl carbonate (each isomer), dicyclopentyl carbonate, Examples of the carbonates include cyclohexyl carbonate, dicycloheptyl carbonate, dibenzyl carbonate, diphenethyl carbonate (each isomer), di(phenylpropyl) carbonate (each isomer), di(phenylbutyl) carbonate (each isomer), di(chlorobenzyl) carbonate (each isomer), di(methoxybenzyl) carbonate (each isomer), di(methoxymethyl) carbonate, di(methoxyethyl) carbonate (each isomer), di(chloroethyl) carbonate (each isomer), and di(cyanoethyl) carbonate (each isomer).

[0069] Among these, R ２ is a halogen-free dialkyl carbonate consisting of an alkyl group having 4 or less carbon atoms, and dimethyl carbonate is particularly preferred. Furthermore, among the preferred dialkyl carbonates, even more preferred are dialkyl carbonates produced in a state in which they are substantially free of halogen, such as those produced from an alkylene carbonate that is substantially free of halogen and an alcohol that is substantially free of halogen.

[0070] The phenol used in step (II) is represented by the following general formula, and is a compound in which a hydroxyl group is directly bonded to a phenyl group (Ph). In some cases, a substituted phenol in which the phenyl group is substituted with a lower alkyl group or a lower alkoxy group can also be used: PhOH

[0071] In this embodiment, phenol that is substantially free of halogen is preferably used. Therefore, the diphenyl carbonate referred to in this embodiment is represented by the following general formula: PhOCOOPh

[0072] The molar ratio of dialkyl carbonate to phenol used as a raw material in step (II) is preferably 0.1 to 10. Within this range, the amount of unreacted raw material remaining for a given production amount of the desired diphenyl carbonate is reduced, which is efficient and also reduces the energy required to recover them. In this sense, this molar ratio is more preferably 0.5 to 5, more preferably 0.8 to 3, and even more preferably 1 to 2.

[0073] In this embodiment, it is preferable to continuously produce 1 ton or more of high-purity diphenyl carbonate per hour.

[0074] Therefore, the minimum amount of phenol to be continuously supplied in step (II) is usually 15 tonnes / hr, preferably 13 tonnes / hr, more preferably 10 tonnes / hr, relative to the amount (tonnes / hr) of high purity diphenyl carbonate to be produced. In even more preferable cases, it can be less than 8 tonnes / hr.

[0075] The dialkyl carbonate and phenol used as raw materials in step (II) may each be of high purity, but may also contain other compounds, for example, compounds or reaction by-products produced in the first continuous multi-stage distillation column and / or the second continuous multi-stage distillation column. When carried out industrially, these raw materials are preferably recovered from the first continuous multi-stage distillation column and / or the second continuous multi-stage distillation column in addition to the dialkyl carbonate and phenol newly introduced into the reaction system. In the method of this embodiment, a first circulation step is carried out in which the top component, which is the second-column low-boiling reaction mixture in the second continuous multi-stage distillation column, is continuously fed into the first continuous multi-stage distillation column. In this case, the second-column low-boiling reaction mixture may be fed directly to the first continuous multi-stage distillation column, or may be fed after separating some of the components.

[0076] The concentration of alkyl aryl carbonate in the second column low-boiling reaction mixture is preferably 1% by mass or less. When the concentration of alkyl aryl carbonate in the second column low-boiling reaction mixture is 1% by mass or less, the conversion of dimethyl carbonate in the first continuous multi-stage distillation column tends to improve, and as a result, the amount of low-boiling mixture from the second continuous multi-stage distillation column continuously fed into the first continuous multi-stage distillation column is reduced, and the amount of steam used in the first continuous multi-stage distillation column and the second continuous multi-stage distillation column also tends to be reduced. From the same perspective, the concentration of alkyl aryl carbonate in the second column low-boiling reaction mixture is preferably 0.01 to 0.5% by mass, more preferably 0.01 to 0.3% by mass. In this embodiment, the concentration of alkyl aryl carbonate in the second column low-boiling reaction mixture can be measured by the method described in the Examples below.

[0077] In this embodiment, which is carried out industrially, the raw material supplied to the first continuous multi-stage distillation column preferably contains alcohols, alkyl phenyl carbonate, diphenyl carbonate, alkyl phenyl ether, etc., and further preferably contains small amounts of high-boiling by-products such as the product phenyl carbonate or diphenyl carbonate Fries rearrangement products or derivatives thereof. In this embodiment, for example, when methyl phenyl carbonate and diphenyl carbonate are produced using dimethyl carbonate as the dialkyl carbonate and unsubstituted phenol as the phenol raw materials, the raw material preferably contains the reaction products methyl alcohol, methyl phenyl carbonate, and diphenyl carbonate, and may further contain small amounts of the reaction by-products anisole, phenyl salicylate, methyl salicylate, and high-boiling by-products derived therefrom.

[0078] The diphenyl carbonate obtained by the production method of this embodiment is preferably used to produce an aromatic polycarbonate by polymerization with an aromatic dihydroxy compound, but a large amount of phenol is produced as a by-product and recovered in this polymerization step, and it is preferable to use this by-product phenol as a raw material in step (II) of this embodiment.

[0079] The diphenyl carbonate produced in step (II) is obtained by a transesterification reaction between a dialkyl carbonate and a phenol. This transesterification reaction involves the exchange of one or two alkoxy groups of the dialkyl carbonate with the phenoxy groups of the phenol, resulting in the release of alcohols, and a disproportionation reaction between two molecules of the resulting alkyl phenyl carbonate, converting the diphenyl carbonate to a dialkyl carbonate. In the first continuous multi-stage distillation column in step (II), alkyl phenyl carbonate is primarily obtained, and in the second continuous multi-stage distillation column, diphenyl carbonate and dialkyl carbonate are primarily obtained by the disproportionation reaction of this alkyl phenyl carbonate. The diphenyl carbonate obtained in step (II) preferably contains no halogens. Such diphenyl carbonate is useful, for example, as a raw material for the industrial production of aromatic polycarbonates. This is because the presence of halogens in the polymerization raw materials, even in an amount less than 1 ppm, inhibits the polymerization reaction and the stable production of aromatic polycarbonate, and further causes a decrease in the physical properties of the produced aromatic polycarbonate and discoloration.

[0080] The catalyst used in the first continuous multi-stage distillation column and / or the second continuous multi-stage distillation column in step (II) is not particularly limited, and may be selected from, for example, the following compounds: <Lead compounds> Lead oxides such as PbO, PbO2, Pb3O4; Lead sulfides such as PbS and Pb2S; Lead hydroxides such as Pb(OH)2 and Pb2O2(OH)2; Lead nitides such as Na2PbO2, K2PbO2, NaHPbO2, KHPbO2; Plumbates such as Na2PbO3, Na2H2PbO4, K2PbO3, K2[Pb(OH)6], K4PbO4, Ca2PbO4, CaPbO3; Lead carbonates and basic salts thereof such as PbCO3, 2PbCO3.Pb(OH)2; 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; organic lead compounds (Bu represents a butyl group and Ph represents a phenyl group) such as Bu4Pb, Ph4Pb, Bu3PbCl, Ph3PbBr, Ph3Pb (or Ph6Pb2), Bu3PbOH, and Ph3PbO; alkoxyleads and aryloxyleads such as Pb(OCH3)2, (CH3O)Pb(OPh), and Pb(OPh)2; lead alloys such as Pb-Na, Pb-Ca, Pb-Ba, Pb-Sn, and Pb-Sb; lead minerals such as hohenite and sachalinenite, 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≡C-C(CH3)3]n, [Cu(C7H8)Cl]4 (where acac represents an acetylacetone chelate ligand); <Alkali metal complexes> Alkali metal complexes such as Li(acac) and LiN(C4H9)2; <Zinc complexes> Zinc complexes such as Zn(acac)2; <Cadmium complexes> Cadmium complexes such as Cd(acac)2; <Iron group metal compounds> Fe(C 10Complexes of iron group metals such as Fe(CO)(H8), Fe(CO)(CO), Fe(C4H6)(CO), Co(mesitylene)(PEt2Ph), CoC5F5(CO), Ni-π-C5H5NO, and ferrocene; <Zirconium complexes> Zirconium complexes such as Zr(acac) and zirconocene; <Lewis acid compounds> AlX3, TiX3, TiX4, VOX3, VX5, ZnX2, FeX3, and SnX 4 (wherein X is a halogen, an acetoxy group, an alkoxy group, or an aryloxy group), and Lewis acids and transition metal compounds that generate Lewis acids; <Organotin compounds> (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, organotin compounds such as BuSnO(OH); and metal-containing compounds such as

[0081] The catalyst used in this embodiment preferably contains a metal such as Pb, Cu, Zn, Fe, Co, Ni, Al, Ti, V, or 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 be reacted with organic compounds present in the reaction system, such as aliphatic alcohols, phenols, alkylphenyl carbonates, diphenyl carbonates, or dialkyl carbonates, or may be heat-treated with raw materials or products prior to the reaction. The catalyst used in this embodiment is preferably one that is highly soluble in the reaction solution under the reaction conditions. In this sense, preferred catalysts include, for example, PbO, Pb(OH) 2 , Pb(OPh) 2 ; TiCl 4 , and Ti(OMe) 4 . ４ , (MeO)Ti(OPh) ３ , (MeO) ２Ti(OPh) ２ , (MeO) ３ Examples of the catalyst include Ti(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 liquid, etc. 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 the same type or different types.

[0082] In this embodiment, it is particularly preferable to use raw materials and catalysts that do not contain halogen, and in this case, the diphenyl carbonate produced is completely halogen-free and therefore useful as a raw material for industrially producing polycarbonate by the transesterification method, because the presence of halogens in the polymerization raw materials, even in amounts less than 1 ppm, can inhibit the polymerization reaction and can deteriorate the physical properties of the produced polycarbonate or cause coloration.

[0083] The first continuous multi-stage distillation column used in step (II) has a length L １ (cm), inner diameter D １ (cm) cylindrical body, and has n stages inside １ The column has an internal structure with an internal diameter of d １１ A gas outlet with an inner diameter of d (cm) is provided at the bottom of the tower or at a lower part of the tower close to the bottom. １２ (cm) of liquid withdrawal port, one or more third inlets below the gas withdrawal port in the upper and / or middle part of the column, and one or more fourth inlets above the liquid withdrawal port in the middle and / or lower part of the column, １ , D １ , L １ / D １ , n １ , D １ / d １１ , D １ / d １２ are preferably continuous multi-stage distillation columns that satisfy the following formulas (7) to (12): 1500 ≦ L １≦ 8000 Formula (7) 100 ≦ D １ ≦ 2000 Formula (8) 2 ≦ L １ / D １ ≦ 40 Formula (9) 20 ≦ n １ ≦ 120 Formula (10) 5 ≦ D １ / d １１ ≦ 30 Formula (11) 3 ≦ D １ / d １２ ≦ 20 Formula (12)

[0084] The second continuous multi-stage distillation column used in step (II) has a length L ２ (cm), inner diameter D ２ (cm) cylindrical body, and has n stages inside ２ The column has an internal structure with an internal diameter of d ２１ A gas outlet with an inner diameter of d (cm) is provided at the bottom of the tower or at a lower part of the tower close to the bottom. ２２ (cm) of liquid withdrawal port, one or more fifth inlets below the gas withdrawal port in the upper and / or middle part of the column, and one or more sixth inlets above the liquid withdrawal port in the middle and / or lower part of the column, ２ , D ２ , L ２ / D ２ , n ２ , D ２ / d ２１ , D ２ / d ２２ are preferably continuous multi-stage distillation columns satisfying the following formulas (13) to (18): 1500 ≦ L ２ ≦ 8000 Formula (13) 100 ≦ D ２ ≦ 2000 Formula (14) 2 ≦ L ２ / D ２ ≦ 40 Formula (15) 10 ≦ n ２≦ 80 Formula (16) 2 ≦ D ２ / d ２１ ≦ 15 Formula (17) 5 ≦ D ２ / d ２２ ≦ 30 Formula (18)

[0085] By using a first continuous multi-stage distillation column and a second continuous multi-stage distillation column that simultaneously satisfy all of the formulas (7) to (18), diphenyl carbonate can be produced from dialkyl carbonate and phenol at an industrial scale of about 0.85 tons or more, preferably 1 ton or more per hour, with high selectivity and high productivity, for example, for a long period of time of 2000 hours or more, preferably 3000 hours or more, and 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 multi-stage distillation column used in step (II) are shown below.

[0086] L １ (cm) and L ２ When the reaction rate (cm) is 1500 or more, the reaction rate is improved, and the desired production amount can be achieved. In addition, in order to reduce the equipment cost while ensuring a reaction rate that can achieve the desired production amount, １ and L ２ It is preferable that each of L is 8000 or less. １ (cm) and L ２ The range of (cm) is 2000≦L １ ≦6000 and 2000≦L ２ ≦6000, and more preferably 2500≦L １ ≦5000 and 2500≦L ２ ≦5000.

[0087] D １ (cm) and D ２When each of the diameters (cm) is 100 or more, the desired production volume can be achieved. In addition, in order to reduce the equipment cost while achieving the desired production volume, １ and D ２ It is preferable that each of D is 2000 or less. １ (cm) and D ２ The range of (cm) is 150≦D １ ≦1000 and 150≦D ２ ≦1000, and more preferably, 200≦D １ ≦800 and 200≦D ２ ≦800.

[0088] In the first continuous multi-stage distillation column and the second continuous multi-stage distillation column, D １ and D ２ As long as the inner diameter is within the above range, the column may have the same inner diameter from the top to the bottom, or the inner diameter may vary partially. For example, in these continuous multi-stage distillation columns, the inner diameter of the column upper portion may be smaller or larger than the inner diameter of the column lower portion.

[0089] L １ / D １ and L ２ / D ２ When each of these is 2 or more or 40 or less, stable operation is facilitated. In particular, when it is 40 or less, the pressure difference between the top and bottom of the column can be prevented from becoming too large, which not only facilitates long-term stable operation but also allows the temperature at the bottom of the column to be lowered, which can suppress side reactions and tends to improve selectivity. More preferred L １ / D １ and L ２ / D ２ The range of each is 3≦L １ / D １ ≦30 and 3≦L ２ / D ２ ≦30, and more preferably 5≦L １ / D １ ≦15 and 5≦L ２ / D ２ ≦15.

[0090] n １When n is 20 or more, the reaction rate is improved, and the desired production amount can be achieved in the first continuous multi-stage distillation column. In addition, in order to reduce the equipment cost while ensuring a reaction rate that can achieve the desired production amount, １ It is preferable to set n to 120 or less. １ When n is 120 or less, the pressure difference between the top and bottom of the column can be prevented 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 in the lower part of the column to be lowered, which can suppress side reactions and tends to improve the selectivity. １ The range is 30≦n １ ≦100, and more preferably 40≦n １ ≦90.

[0091] Also, n ２ When n is 10 or more, the reaction rate is improved, and the desired production amount can be achieved in the second continuous multi-stage distillation column. In addition, in order to reduce the equipment cost while ensuring a reaction rate that can achieve the desired production amount, ２ It is preferable to set n to 80 or less. ２ When n is 80 or less, the pressure difference between the top and bottom of the column can be prevented 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 in the lower part of the column to be lowered, which tends to suppress side reactions and improve selectivity. ２ The range is 15≦n ２ ≦60, and more preferably 20≦n ２ ≦50.

[0092] D １ / d １１ When the ratio is 5 or more, the equipment costs for the first continuous multi-stage distillation column can be reduced and the leakage of gas components out of the system can be suppressed, facilitating stable operation of the first continuous multi-stage distillation column. When the ratio is 30 or less, the amount of gas components extracted becomes relatively large, facilitating stable operation and also tending to improve the reaction rate. １ / d １１ The range is 8≦D １ / d １１ ≦25, and more preferably 10≦D １ / d １１≦20. ２ / d ２１ When the ratio is 2 or more, the equipment costs for the second continuous multi-stage distillation column can be reduced and the leakage of gas components out of the system can be suppressed, facilitating stable operation of the second continuous multi-stage distillation column. When the ratio is 15 or less, the amount of gas components extracted becomes relatively large, facilitating stable operation and also tending to improve the reaction rate. ２ / d ２１ The range is 5≦D ２ / d ２１ ≦12, and more preferably 3≦D ２ / d ２１ ≦10.

[0093] D １ / d １２ When D is 3 or more, the equipment costs for the first continuous multi-stage distillation column can be reduced, the amount of liquid withdrawn is relatively small, and stable operation of the first continuous multi-stage distillation column can be facilitated. When D is 20 or less, a sudden increase in the flow rate at the liquid withdrawal port and piping can be prevented, erosion is less likely to occur, and corrosion of the equipment can be suppressed. １ / d １２ The range is 5≦D １ / d １２ ≦18, and more preferably 7≦D １ / d １２ ≦15. ２ / d ２２ When D is 5 or more, the equipment costs for the second continuous multi-stage distillation column can be reduced, the amount of liquid withdrawn is relatively small, and stable operation of the second continuous multi-stage distillation column can be facilitated. When D is 30 or less, a sudden increase in the flow rate at the liquid withdrawal port and piping can be prevented, erosion is less likely to occur, and corrosion of the equipment can be suppressed. ２ / d ２２ The range is 7≦D ２ / d ２２ ≦25, and more preferably 9≦D ２ / d ２２ ≦20.

[0094] Furthermore, in step (II), the d １１ and the d １２ and satisfy the formula (29), and ２１and the d ２２ It is more preferable if 1≦d satisfies the formula (30). １２ / d １１ ≦5 Formula (29) 1≦d ２１ / d ２２ ≦6 Formula (30)

[0095] The long-term stable operation in step (II) means that operation can be continued in a steady state based on the operating conditions for 1,000 hours or more, preferably 3,000 hours or more, and more preferably 5,000 hours or more without flooding, weeping, clogged pipes, erosion, or the like, and a predetermined amount of diphenyl carbonate is produced while maintaining high selectivity.

[0096] In step (II), diphenyl carbonate is produced stably over a long period of time with high productivity of preferably 1 ton or more per hour, with high selectivity, more preferably 2 tons or more per hour, and even more preferably 3 tons or more per hour. １ , D １ , L １ / D １ , n １ , D １ / d １１ , D １ / d １２ are respectively 2000≦L １ ≦6000, 150≦D １ ≦1000, 3≦L １ / D １ ≦30, 30≦n １ ≦100, 8≦D １ / d １１ ≦25, 5≦D １ / d １２ ≦18, and the L of the second continuous multi-stage distillation column ２ , D ２ , L ２ / D ２ , n ２ , D ２ / d ２１ , D ２ / d ２２ are respectively 2000≦L２ ≦6000, 150≦D ２ ≦1000, 3≦L ２ / D ２ ≦30, 15≦n ２ ≦60, 2.5≦D ２ / d ２１ ≦12, 7≦D ２ / d ２２ When the ratio is ≦25, the amount of diphenyl carbonate produced is 2 tons or more per hour, preferably 2.5 tons or more per hour, and more preferably 3 tons or more per hour.

[0097] Furthermore, in step (II), the L of the first continuous multi-stage distillation column １ , D １ , L １ / D １ , n １ , D １ / d １１ , D １ / d １２ are respectively 2500≦L １ ≦5000, 200≦D １ ≦800, 5≦L １ / D １ ≦15, 40≦n １ ≦90, 10≦D １ / d １１ ≦25, 7≦D １ / d １２ ≦15, and the L of the second continuous multi-stage distillation column ２ , D ２ , L ２ / D ２ , n ２ , D ２ / d ２１ , D ２ / d ２２ are respectively 2500≦L ２ ≦5000, 200≦D ２ ≦800, 5≦L ２ / D ２ ≦10, 20≦n ２ ≦50, 3≦D ２ / d ２１ ≦10, 9≦D ２ / d ２２When the ratio is ≦20, the amount of diphenyl carbonate produced is 3 tons or more per hour, preferably 3.5 tons or more per hour, and more preferably 4 tons or more per hour.

[0098] The selectivity of diphenyl carbonate in step (II) is based on the reacted phenol, and in step (II), a high selectivity of 95% or more can usually be achieved, preferably 97% or more, and more preferably 98% or more.

[0099] The first and second continuous multi-stage distillation columns used in step (II) are preferably distillation columns having trays and / or packings as internals. In this embodiment, the term "internal" refers to the portion of the distillation column where gas and liquid actually come into contact. Such trays are preferably those described in the section on step (I). The "number of internal stages" is as described above.

[0100] In the first continuous multi-stage distillation column in step (II), a reaction to produce alkyl phenyl carbonate from dialkyl carbonate and phenol is primarily carried out. Because this reaction has an extremely small equilibrium constant and a slow reaction rate, a plate-type distillation column with trays as the internal is more preferred as the first continuous multi-stage distillation column used for reactive distillation. In the second continuous multi-stage distillation column, a disproportionation reaction of the alkyl phenyl carbonate is primarily carried out. This reaction also has a small equilibrium constant and a slow reaction rate. However, a distillation column having both packings and trays as the internal is more preferred as the second continuous multi-stage distillation column used for reactive distillation. Furthermore, a second continuous multi-stage distillation column with packings installed in the upper part and trays installed in the lower part is preferred. The packing of the second continuous multi-stage distillation column is preferably structured packing, and among structured packings, Melapack is particularly preferred.

[0101] Furthermore, the trays installed in each of the first and second continuous multi-stage distillation columns are particularly excellent in terms of functionality and equipment costs when they have a sieve tray section and a downcomer section. ２It is preferable that the number of holes is 100 to 1000 per square meter. A more preferable number of holes is 100 to 1000 per square meter. ２ The number of particles is preferably 120 to 900, and more preferably 150 to 800.

[0102] The cross-sectional area of ​​each hole in the perforated tray is 0.5 to 5 cm ２ The more preferable cross-sectional area per hole is 0.7 to 4 cm ２ and more preferably 0.9 to 3 cm ２ Furthermore, the area of ​​the perforated tray is 1 m ２ It has 100 to 1000 holes per hole, and the cross-sectional area of ​​each hole is 0.5 to 5 cm ２ It is particularly preferred if

[0103] When carrying out step (II), the starting materials, dialkyl carbonate and phenol, are continuously supplied to a first continuous multi-stage distillation column in the presence of a catalyst, reaction and distillation are carried out simultaneously in the first continuous multi-stage distillation column, the first-column low-boiling reaction mixture containing the produced alcohols is continuously withdrawn in gaseous form from the top of the first continuous multi-stage distillation column, the first-column high-boiling reaction mixture containing the produced alkyl phenyl carbonate is continuously withdrawn in liquid form from the bottom of the first continuous multi-stage distillation column, the first-column high-boiling reaction mixture is continuously supplied to a second continuous multi-stage distillation column in the presence of a catalyst, reaction and distillation are carried out simultaneously in the second continuous multi-stage distillation column, the second-column low-boiling reaction mixture containing the produced dialkyl carbonates is continuously withdrawn in gaseous form from the top of the second continuous multi-stage distillation column, and the second-column high-boiling reaction mixture containing the produced diphenyl carbonate is continuously withdrawn in liquid form from the bottom of the second continuous multi-stage distillation column, thereby continuously producing diphenyl carbonate.

[0104] As described above, this raw material may contain reaction by-products such as alcohols, alkyl phenyl carbonates, diphenyl carbonates, alkyl phenyl ethers, high-boiling compounds, etc. In consideration of the equipment and costs required for separation and purification in other steps, in the case of this embodiment that is actually carried out industrially, it is preferable that these compounds are contained in small amounts.

[0105] The top component of the first continuous multi-stage distillation column in step (II) usually contains dialkyl carbonate, phenol, alkyl aryl ether, etc. in addition to the alcohols produced in the reaction, and may also contain small amounts of alkyl aryl carbonate, diphenyl carbonate, etc. This top component of the first continuous multi-stage distillation column can be used as is as the aliphatic monohydric alcohol in step (I), but it is preferable to use it as the raw material for step (I) after reducing the amount of contained substances with a boiling point higher than that of the produced alcohol by distillation, etc. It is particularly preferable to use a mixture of this alcohol and dialkyl carbonate as the aliphatic monohydric alcohol in step (I).

[0106] In step (II), the starting materials, dialkyl carbonate and phenol, can be continuously supplied into the first continuous multi-stage distillation column by supplying them in liquid and / or gaseous form from one or more inlets located below the upper gas outlet port of the first distillation column but in the upper or middle portion of the column; alternatively, it is also a preferred method to supply the phenol-rich starting material in liquid form from an inlet located in the upper portion of the first distillation column, and supply the dialkyl carbonate-rich starting material in gaseous form from an inlet located above the lower liquid outlet port of the first distillation column but in the lower portion of the column.

[0107] In step (II), the first column high-boiling reaction mixture containing alkyl phenyl carbonate continuously withdrawn from the bottom of the first continuous multi-stage distillation column is continuously supplied to the second continuous multi-stage distillation column. The supply position is lower than the gas outlet at the top of the second continuous multi-stage distillation column, and it is preferable to supply the mixture in liquid and / or gaseous form from one or several inlets installed at the top or middle of the column. Furthermore, when a distillation column having a packing section at the top and a tray section at the bottom, which is a preferred embodiment of this embodiment, is used as the second continuous multi-stage distillation column, it is preferable that at least one inlet is installed between the packing section and the tray section. Furthermore, when the packing consists of two or more structured packings, it is also a preferred method to install an inlet at the interval between these structured packings.

[0108] In addition, in step (II), it is also a preferred method to condense the components extracted from the tops of the first and second continuous multi-stage distillation columns and then return a portion of the components to the top of each distillation column through a reflux operation. 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 in the range of 0.01 to 10, preferably 0.08 to 5, and more preferably 0.1 to 2. A reflux ratio of 0, in which no reflux operation is performed in the first continuous multi-stage distillation column, is also a preferred embodiment.

[0109] In step (II), any method for providing a homogeneous catalyst in the first continuous multi-stage distillation column may be used, but it is preferable to supply the catalyst into the distillation column from a position above the middle of the first continuous multi-stage distillation column. It is also preferable to supply the catalyst so that the reaction solution contacts the catalyst in 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 dissolved in the raw material or the reaction solution may be introduced together with the raw material, or this catalyst solution may be introduced from an inlet separate from the raw material. In this embodiment, the amount of catalyst used in the first continuous multi-stage distillation column varies depending on reaction conditions such as the type of catalyst used, the type and amount ratio of the raw materials, reaction temperature, and reaction pressure, but is typically 0.0001 to 30% by mass, preferably 0.0005 to 10% by mass, and more preferably 0.001 to 1% by mass, expressed as a ratio to the total mass of the raw materials.

[0110] In step (II), any method may be used to cause the homogeneous catalyst to be present in the second continuous multi-stage distillation column, but it is preferable to supply the catalyst to the distillation column from a position above the middle of the second continuous multi-stage distillation column. In this case, the catalyst solution dissolved in the raw material or reaction liquid may be introduced together with the raw material, or this catalyst solution may be introduced from an inlet separate from the raw material. In this embodiment, the amount of catalyst used in the second continuous multi-stage distillation column varies depending on reaction conditions such as the type of catalyst used, the type and amount ratio of the raw materials, the reaction temperature, and the reaction pressure, but is usually 0.0001 to 30% by mass, preferably 0.0005 to 10% by mass, and more preferably 0.001 to 1% by mass, expressed as a proportion of the total mass of the raw materials.

[0111] In step (II), 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 the same type or different types, but preferably the same type of catalyst is used. More preferably, the catalyst is the same type and can be dissolved in both reaction solutions. In this case, the catalyst is usually dissolved in the high-boiling point reaction mixture of the first continuous multi-stage distillation column, extracted from the bottom of the first distillation column together with alkyl phenyl carbonate, etc., and supplied directly to the second continuous multi-stage distillation column, which is a preferred embodiment. It is also possible to add a new catalyst to the second continuous multi-stage distillation column as needed.

[0112] The reaction time for the transesterification reaction carried out in step (II) is considered to correspond to the average residence time of the reaction liquid in each of the first and second continuous multi-stage distillation columns. This reaction time varies depending on the internal shape and number of stages 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 each of the first and second continuous multi-stage distillation columns.

[0113] The reaction temperature of 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 typically 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 make side reactions more likely to occur, increasing the amount of by-products such as alkyl phenyl ethers, for example. 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.

[0114] The reaction temperature of the second 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 also more likely to cause side reactions, and are undesirable because they increase the production of by-products such as alkyl phenyl ethers, Fries rearrangement reaction products of the raw materials and products such as alkyl phenyl carbonates and diphenyl carbonates, and their derivatives. 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.

[0115] The reaction pressure in 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 may be operated at reduced pressure, atmospheric pressure, or elevated pressure. The column top pressure is usually 0.1 Pa to 2 × 10 ７ Pa, preferably 10 ５ Pa to 10 ７ Pa, more preferably 2×10 ５ Pa ~ 5 x 10 ６ The range is 0.2 Pa.

[0116] The reaction pressure in the second continuous multi-stage distillation column varies depending on the type and composition of the raw material compounds used, the reaction temperature, etc., but may be reduced pressure, normal pressure, or increased pressure. Usually, the column top pressure is 0.1 Pa to 2 × 10 ７ Pa, preferably 10 ３ Pa to 10 ６ Pa, more preferably 5×10 ３ Pa to 10 ５ The range is 0.2 Pa.

[0117] Two or more distillation columns can be used as the first continuous multi-stage distillation column in step (II). In this case, two or more distillation columns can be connected in series, in parallel, or in a combination of series and parallel. Furthermore, two or more distillation columns can be used as the second continuous multi-stage distillation column in step (II). In this case, two or more distillation columns can be connected in series, in parallel, or in a combination of series and parallel.

[0118] The materials constituting the first and second continuous multi-stage distillation columns used in step (II) are primarily metal materials such as carbon steel and stainless steel, but stainless steel is preferred from the perspective of the quality of the aromatic carbonate produced. Furthermore, it is preferable to use a material containing Fe as the main component, 2% by mass or more of Mo, and 18% by mass or less of Cr for the liquid-contacting portion of the lower part of the second continuous multi-stage distillation column. Using such a material for the liquid-contacting portion of the lower part of the second continuous multi-stage distillation column tends to suppress corrosion of the distillation column even if the concentration of high-boiling-point substances in the components in the lower part of the second continuous multi-stage distillation column is increased. The composition of the material for the liquid-contacting portion of the lower part of the second continuous multi-stage distillation column is more preferably 60 to 72% by mass of Fe, 2 to 3% by mass of Mo, and 16 to 18% by mass of Cr. In this embodiment, "main component" means 40% by mass or more, preferably 50% by mass or more, and more preferably 60% by mass.

[0119] In the production method of this embodiment, the second column high-boiling reaction mixture containing diphenyl carbonate is continuously introduced into the heavy-ends cut column A, and the top component (A) containing diphenyl carbonate is Ｔ ) and a column bottom component (A Ｂ a first purification step of continuously distilling and separating the top component (A Ｔ ) is continuously introduced into a diphenyl carbonate purification column B having a side cut withdrawal port, and the column top component (B Ｔ ), side cut component (B Ｓ ) and the bottom component (B Ｂ ) by successive distillation separation into three components, Ｓ and a second purification step of obtaining diphenyl carbonate as the purified product (hereinafter, the first and second purification steps are also collectively referred to as "step (III)").

[0120] The second column high-boiling reaction mixture continuously withdrawn in liquid form from the bottom of the second continuous multi-stage distillation column in step (II) is mainly composed of diphenyl carbonate, but usually also contains unreacted alkyl phenyl carbonate, a small amount of unreacted raw materials, small amounts of high-boiling by-products and catalyst components. Therefore, a purification step (III) is carried out from the viewpoint of obtaining high-purity diphenyl carbonate from the second column high-boiling reaction mixture. In step (III), two distillation columns (heavy-ends cut column A and diphenyl carbonate purification column B having a side cut outlet) are used, and in heavy-ends cut column A, a column top component (A) mainly composed of unreacted alkyl phenyl carbonate, a small amount of unreacted raw materials and diphenyl carbonate is extracted. Ｔ ) and a small amount of high-boiling by-products and / or catalyst components as the main component (A Ｂ ) and the top component (A Ｔ ) is continuously fed to a diphenyl carbonate purification column B, and in the diphenyl carbonate purification column B, a column top component (B Ｔ ), side cut component (B Ｓ ), and the bottom component (B Ｂ ) and the side cut component (B Ｓ ) to obtain high-purity diphenyl carbonate.

[0121] In step (III), the heavy-ends cut column A has a length L Ａ (cm), inner diameter D Ａ (cm) cylindrical body, and has n stages inside Ａ A continuous multi-stage distillation column having an internal of L Ａ , D Ａ , n Ａ are preferably continuous multi-stage distillation columns satisfying the following formulas (19) to (21): 800 ≦ L Ａ ≦ 3000 Formula (19) 100 ≦ D Ａ ≦ 1000 Formula (20) 20 ≦ n Ａ ≦ 100 Formula (21)

[0122] The diphenyl carbonate purification column B has, for example, a length L Ｂ (cm), inner diameter D Ｂ The column has a cylindrical body with a diameter of 1.5 cm and an internal structure. １ , the inlet B １ Between the tower bottom and the side cut outlet B ２ and inlet B １ The number of internal stages at the top is n Ｂ１ , inlet B １ and side cut outlet B ２ The number of internal stages between Ｂ２ , Side cut outlet B ２ The number of internal stages at the bottom is n Ｂ３ The total number of stages (n Ｂ１ +n Ｂ２ +n Ｂ３ ) is n Ｂ A continuous multi-stage distillation column in which L Ｂ , D Ｂ , n Ｂ１ , n Ｂ２ , n Ｂ３ , n Ｂ are preferably continuous multi-stage distillation columns satisfying the following formulas (22) to (27): 1000 ≦ L Ｂ ≦ 5000 Formula (22) 100 ≦ D Ｂ ≦ 1000 Formula (23) 5 ≦ n Ｂ１ ≦ 20 Formula (24) 12 ≦ n Ｂ２ ≦ 40 Formula (25) 3 ≦ n Ｂ３ ≦ 15 Formula (26) 20 ≦ n Ｂ ≦ 70 Formula (27)

[0123] By simultaneously satisfying all of these conditions, high-purity diphenyl carbonate tends to be stably produced from the second column high-boiling reaction mixture containing diphenyl carbonate obtained in step (II) on an industrial scale at a rate of 1 ton or more per hour, for long periods of time, for example, 2,000 hours or more, preferably 3,000 hours or more, and more preferably 5,000 hours or more. The reason why the method of this embodiment enables the production of high-purity diphenyl carbonate on an industrial scale with such excellent effects is not clear, but it is presumed to be due to the effect achieved by combining a heavy-ends cut column A and a diphenyl carbonate purification column B that satisfy the conditions of equations (19) to (27). The preferred ranges for each factor are shown below.

[0124] L Ａ When the L (cm) is 800 or more, there is a margin in the height of the internals that can be installed inside the heavy ends cut column A, and therefore the separation efficiency tends to improve. Ａ It is preferable to set L to 3000 or less. Ａ The range of (cm) is 1000≦L Ａ ≦2500, and more preferably 1200≦L Ａ ≦2000.

[0125] D Ａ If the diameter of the nozzle is 100 or more, the desired production volume can be achieved. Ａ It is preferable to set D to 1000 or less. Ａ (cm) range is 200≦D Ａ ≦600, and more preferably 250≦D Ａ ≦450.

[0126] n Ａ If n is 20 or more, the separation efficiency is improved, and the desired high purity can be achieved. In addition, in order to achieve the desired separation efficiency while reducing the equipment cost, Ａ It is preferable that n is 100 or less. ＡWhen n is 100 or less, the pressure difference between the top and bottom of the column can be prevented from becoming too large, which not only facilitates long-term stable operation of the heavy-ends cut column A but also makes it possible to lower the temperature in the lower part of the column, which tends to suppress side reactions. Ａ The range is 30≦n Ａ ≦70, and more preferably 35≦n Ａ ≦60.

[0127] L Ｂ When the L (cm) is 1000 or more, there is a margin in the height of the internal that can be installed inside the diphenyl carbonate purification column B, and therefore the separation efficiency tends to improve. Ｂ It is preferable to set L to 5000 or less. Ｂ The range of (cm) is 1500≦L Ｂ ≦3000, and more preferably 1700≦L Ｂ ≦2500.

[0128] D Ｂ If the diameter of the nozzle is 100 or more, the desired production volume can be achieved. Ｂ It is preferable to set D to 1000 or less. Ｂ (cm) range is 150≦D Ｂ ≦500, and more preferably 200≦D Ｂ ≦400.

[0129] n Ｂ If n is 20 or more, the separation efficiency of the column as a whole is improved, and the desired high purity can be achieved. Ｂ It is preferable to set n to 70 or less. Ｂ When n is 70 or less, the pressure difference between the top and bottom of the column can be prevented from increasing, which not only facilitates long-term stable operation of the diphenyl carbonate purification column B but also makes it possible to lower the temperature in the lower part of the column, which tends to suppress side reactions. Ｂ The range is 25≦n Ｂ ≦55, and more preferably 30≦nＢ Furthermore, in order to stably obtain diphenyl carbonate of the desired high purity for a long period of time, n Ｂ1 , n Ｂ２ , n Ｂ３　 are respectively 5≦n Ｂ１ ≦20, 12≦n Ｂ２ ≦40, 3≦n Ｂ３ It is preferable that the range of n is 7≦n≦15. A more preferable range is 7≦n Ｂ１ ≦15, 12≦n Ｂ２ ≦30, 3≦n Ｂ３ ≦10.

[0130] When carrying out this embodiment, the heavy-ends cut column A has a column bottom temperature (T Ａ ) 185-280°C, top pressure (P Ａ The diphenyl carbonate purification column B is operated at a column bottom temperature (T Ｂ ) 185-280°C, top pressure (P Ｂ ) It is preferable to operate at 1000 to 20000 Pa.

[0131] T Ａ If the temperature is 185°C or higher, there is no need to lower the pressure at the top of the column, so there is no need to use equipment that maintains a high vacuum, and the equipment can be made smaller. Ａ If the temperature is 280°C or lower, the generation of high-boiling by-products during distillation tends to be suppressed. Ａ is 190 to 240°C, more preferably 195 to 230°C.

[0132] P Ａ When the pressure is 1000 Pa or more, there is no need to use a large facility to maintain a high vacuum. Ａ When the pressure is 20,000 Pa or less, the distillation temperature is low and the generation of by-products tends to be suppressed. Ａ is in the range of 2000 to 15000 Pa, and more preferably in the range of 3000 to 13000 Pa.

[0133] T Ｂ If the temperature is 185°C or higher, there is no need to lower the pressure at the top of the column, so there is no need to use equipment that maintains a high vacuum, and the equipment can be made smaller.Ｂ If the temperature is 280°C or lower, the generation of high-boiling by-products during distillation tends to be suppressed. Ｂ is 190 to 240°C, more preferably 195 to 230°C.

[0134] P Ｂ When the pressure is 1000 Pa or more, there is no need to use a large facility to maintain a high vacuum. Ｂ When the pressure is 20,000 Pa or less, the distillation temperature is low and the generation of by-products tends to be suppressed. Ｂ is in the range of 2000 to 15000 Pa, and more preferably in the range of 3000 to 13000 Pa.

[0135] In addition, in the heavy ends cut column A and the diphenyl carbonate purification column B, D Ａ and D Ｂ As long as the inner diameter is within the above range, the column may have the same inner diameter from the top to the bottom, or the inner diameter may vary partially. For example, in these continuous multi-stage distillation columns, the inner diameter of the column upper portion may be smaller or larger than the inner diameter of the column lower portion.

[0136] The heavy-ends cut column A and the diphenyl carbonate purification column B used in step (III) are preferably distillation columns each having trays and / or packings as internals. In this embodiment, the internals refer to the portion of the distillation column where gas and liquid actually come into contact. Such trays are preferably those described in the section on step (I). The "number of internal stages" is as defined above.

[0137] The heavy-ends cut column A in step (III) preferably has packing as an internal, more preferably structured packing, and the diphenyl carbonate purification column B preferably has packing as an internal, more preferably one or more structured packing units.

[0138] The high-boiling reaction mixture continuously withdrawn from the bottom of the second continuous multi-stage distillation column in step (II) typically contains 0.05 to 2 mass% of dialkyl carbonate, 1 to 20 mass% of phenol, 0.05 to 2 mass% of alkyl phenyl ether, 10 to 45 mass% of alkyl phenyl carbonate, 50 to 80 mass% of diphenyl carbonate, 0.1 to 5 mass% of high-boiling by-products, and 0.001 to 5 mass% of catalyst. Therefore, it is preferable to continuously supply this continuously withdrawn bottoms liquid as it is to the high-boiling separation column A in step (III).

[0139] The composition of the reaction mixture varies depending on the conditions for the transesterification reaction of dialkyl carbonate with phenol, the type and amount of catalyst, etc., but as long as the transesterification reaction is carried out under certain conditions, a reaction mixture of approximately constant composition can be produced, and therefore the composition of the reaction mixture supplied to heavy-ends cut column A is approximately constant. However, in step (III), as long as the composition of the reaction mixture falls within the above range, separation can be performed with approximately the same separation efficiency even if the composition fluctuates. This is one of the features of step (III) used in this embodiment.

[0140] In step (III), the bottoms of the second continuous multi-stage distillation column in step (II) can be continuously supplied to heavy-ends cut column A by supplying the bottoms in liquid form from one or more inlets installed below the middle of separation column A, or alternatively, it is also preferred to supply the bottoms to the column via a reboiler from a pipe installed below the reboiler of separation column A. The amount of the bottoms of the second continuous multi-stage distillation column supplied to heavy-ends cut column A varies depending on the production amount of high-purity diphenyl carbonate to be produced, the concentration of diphenyl carbonate in the reaction mixture, the separation conditions of separation column A, etc., but is usually at least about 2 ton / hr, preferably at least about 6 ton / hr, and more preferably at least about 10 ton / hr.

[0141] The high-boiling reaction mixture of the second continuous multi-stage distillation column continuously supplied to the heavy-ends cut column A is divided into a column top component (A) consisting of a majority of diphenyl carbonate and a majority of unreacted raw materials, alkyl phenyl ethers, alkyl phenyl carbonates, and other compounds having boiling points lower than that of diphenyl carbonate. Ｔ), and a bottom component (A) containing a small amount of diphenyl carbonate, a catalyst, and high-boiling by-products. Ｂ The bottom component (A Ｂ A small amount of alkyl phenyl carbonate may be contained in the bottom component. These organic substances in the bottom component help to dissolve the catalyst components and keep them in a liquid state. Ｂ ) is normally continuously supplied as it is to the first continuous multi-stage distillation column and / or the second continuous multi-stage distillation column in step (II) as a catalyst component for the transesterification reaction and recycled for reuse, but in some cases it is separated from the organic matter in a catalyst recovery step, regenerated as a catalyst, and recycled for reuse.

[0142] In step (III), by-products having a boiling point higher than that of diphenyl carbonate, such as phenyl salicylate, xanthone, phenyl methoxybenzoate, and 1-phenoxycarbonyl-2-phenoxycarboxyphenylene, and catalyst components are almost completely separated in the heavy ends cut column A into the bottom component (A Ｂ ) and the top component (A Ｔ One of the features of step (III) is that the content of the ammonium nitrate in the top component (A) can be easily controlled to usually 200 ppm or less, preferably 100 ppm or less, and more preferably 50 ppm or less. Ｔ One of the features of step (III) is that the top component (A) is hardly contained in the reaction mixture introduced therein, and most of the diphenyl carbonate in the reaction mixture introduced therein can be withdrawn from the top of the column. In step (III), 95% or more, preferably 96% or more, and more preferably 98% or more of the diphenyl carbonate in the reaction mixture continuously fed to heavy ends cut column A can be withdrawn from the top of the column. Furthermore, in step (III), although it depends on the composition of the high-boiling reaction mixture of the second continuous multi-stage distillation column fed to separation column A, usually 90 to 97% by mass of the liquid continuously fed therein is the top component (A). Ｔ ) is continuously withdrawn from the top of the column, and 10 to 3 mass % is withdrawn as the bottom component (A Ｂ ) is continuously extracted from the bottom of the column. ＴThe composition of the dialkyl carbonate is usually 0.05 to 1 mass % of dialkyl carbonate, 1 to 10 mass % of phenol, 0.05 to 0.5 mass % of alkyl phenyl ether, 20 to 40 mass % of alkyl phenyl carbonate, and 50 to 80 mass % of diphenyl carbonate, and the content of high-boiling by-products is usually 200 ppm or less, preferably 100 ppm or less, and more preferably 50 ppm.

[0143] In the step (III), the reflux ratio of the heavy ends cut column A is in the range of 0.01 to 10, preferably 0.08 to 5, and more preferably 0.1 to 3.

[0144] A column top component (A) continuously extracted from the top of the heavy ends cut column A Ｔ The amount of the high-boiling point reaction mixture from the second continuous multi-stage distillation column supplied to the separation column A is usually about 90 to 97% as described above, and this is continuously supplied to the diphenyl carbonate purification column B from an inlet B1 provided in the middle of the column B, and the column top component (B Ｔ ), side cut component (B Ｓ ), bottom component (B Ｂ The top component (A) of the separation column A fed to the purification column B is continuously separated into three components. Ｔ All of the components with boiling points lower than diphenyl carbonate contained in the column top component (B Ｔ ) is continuously withdrawn from the top of the column, and a small amount of liquid is continuously withdrawn from the bottom of the column. Ｔ A small amount of diphenyl carbonate is contained in the top component (B), and the amount thereof is usually 1 to 9%, preferably 3 to 8%, based on the amount of diphenyl carbonate fed. Ｔ The diphenyl carbonate in the column top component (B Ｔ ) and recovered in another distillation column for separating the diphenyl carbonate purifying component A. Alternatively, it is also preferred to separate the diphenyl carbonate purifying component A as a bottom component in this other distillation column and recover it by returning it to the heavy ends cut column A and / or the diphenyl carbonate purifying column B.

[0145] Bottom component (B ＢThe bottom component (B) is composed of diphenyl carbonate and a small amount of high-boiling by-products concentrated to a few percent. Ｂ One of the features of this embodiment is that the amount of diphenyl carbonate in the diphenyl carbonate ester is very small, and the amount is usually 0.05 to 0.5% based on the amount of diphenyl carbonate supplied.

[0146] High-purity diphenyl carbonate is continuously withdrawn from the side cut withdrawal port B2 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 90 to 96% of the diphenyl carbonate supplied to the purification column B.

[0147] In step (III), the side cut component (B Ｓ The purity of the diphenyl carbonate obtained as diphenyl carbonate diol is usually 99.9% or more, preferably 99.99% or more, and more preferably 99.999% or more. In the present embodiment, "high purity" means 99.9% or more, preferably 99.99% or more, and more preferably 99.999% or more. The contents of high-boiling impurities in the high-purity diphenyl carbonate obtained when steps (II) and (III) are carried out using dimethyl carbonate and phenol as raw materials are as follows: phenyl salicylate is 30 ppm or less, preferably 10 ppm or less, and more preferably 1 ppm or less; xanthone is 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-phenoxycarboxy-phenylene is 30 ppm or less, preferably 10 ppm or less, and more preferably 5 ppm or less. The total content of these high-boiling by-products is 100 ppm or less, preferably 50 ppm or less, and more preferably 10 ppm or less. In this embodiment, the purity and impurity contents of diphenyl carbonate can be measured by the methods described in the Examples below.

[0148] Furthermore, in this embodiment, raw materials and catalysts that do not normally contain halogen are used, and therefore the halogen content of the obtained diphenyl carbonate is 0.1 ppm or less, preferably 10 ppb or less, and more preferably 1 ppb or less (outside the detection limit of ion chromatography).

[0149] In the step (III), the reflux ratio of the diphenyl carbonate purification column B is in the range of 0.01 to 10, preferably 0.1 to 8, and more preferably 0.5 to 5.

[0150] The materials constituting the heavy-ends cut column A, diphenyl carbonate purification column B, and liquid-contacting parts used in this embodiment are mainly metal materials such as carbon steel and stainless steel, but stainless steel is preferred from the viewpoint of the quality of the diphenyl carbonate to be produced.

[0151] By carrying out the method of this embodiment, high-purity diphenyl carbonate, which is necessary for producing a high-quality, high-performance aromatic polycarbonate from a cyclic carbonate and phenol, can be produced on an industrial scale, preferably at a rate of 1 ton or more per hour, more preferably 2 tons or more, and even more preferably 3 tons or more. In this embodiment, industrial scale means 1 ton or more per hour, preferably 2 tons or more, and even more preferably 3 tons or more. Furthermore, the diphenyl carbonate obtained by carrying out the method of this embodiment has a halogen content of preferably 0.1 ppm or less, more preferably 10 ppb or less, and even more preferably 1 ppb or less, and impurities with a boiling point higher than that of diphenyl carbonate are preferably 100 ppm or less, more preferably 50 ppm or less, and even more preferably 10 ppm or less. By carrying out the method of this embodiment, such high-purity diphenyl carbonate can be stably produced for a long period of time, for example, preferably 2,000 hours or more, more preferably 3,000 hours or more, and even more preferably 5,000 hours or more. Therefore, this embodiment is a highly effective method for industrially producing high-purity diphenyl carbonate.

[0152] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0153] [Analysis method] Bottom component (A Ｂ The concentrations of diphenyl carbonate (DPC), high boiling point material (HB), and catalyst in the first column, the concentration of alkyl aryl carbonate in the low boiling point reaction mixture in the second column, and the purity of diphenyl carbonate, the content of impurities, and other compositions were analyzed by gas chromatography. The gas chromatography analysis was performed by the internal standard method, and toluene was used as the internal standard. Apparatus: Agilent 7890A Column: Agilent J&W DB-1 (Length 30 m × I.D. 0.25 mm × Film 0.25 μm) Carrier gas: He Flow rate: 2.0 mL / min Injection port temperature: 250°C Injection amount: 1.0 μL Oven temperature: After holding at 50°C for 2 minutes, the temperature was increased to 300°C at a rate of 10°C / min and held for 8 minutes Injection method: Split method, split ratio 20 Detector: FID Temperature 300°C Sampled column bottom component (A Ｂ 0.1 g of DPC was weighed, and 0.04 g (each 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, the concentrations of which were known in advance, and the gas chromatography measurement value of the bottom component was corrected. The remaining amount [mass %] obtained by subtracting the DPC concentration [wt %] obtained by gas chromatography measurement from 100 [mass %] represents the amount of high boiling point material (HB) and catalyst. The catalyst concentration was measured by decomposing the organic matter of the bottom component (AB) using microwaves, measuring the metal concentration [mass %] of the catalyst using an ICP atomic emission spectrometer (ICP), and calculating the catalyst amount [mass %] from the molecular weight of the catalyst. The halogen content in the side cut fraction from diphenyl carbonate purification column B was measured by ion chromatography.

[0154] Example 1 First continuous multi-stage distillation column 101 As a first continuous multi-stage distillation column, the L １ = 3300 cm, D １ = 500 cm, L １ / D １ = 6.6, n １ = 80, D １ / d １１ = 17, D １ / d １２ In this example, a continuous multi-stage distillation column with a cross-sectional area per hole of approximately 1.5 cm was used. ２ , Number of holes = approximately 250 pieces / m ２ As the second continuous multi-stage distillation column, a perforated tray having a L ２ = 3100 cm, D ２ = 500 cm, L ２ / D ２ = 6.2, n ２ = 30, D ２ / d ２１ = 3.85, D ２ / d2 ２ In this example, a continuous multi-stage distillation column with a cross-sectional area per hole of about 1.3 cm was used. In this example, two Melapak units (total theoretical number of plates: 11) were installed at the top as internals, and a ２ , Number of holes = approximately 250 pieces / m ２ A perforated tray having a structure similar to that shown in FIG. 5 was used. The lower liquid-contacting portion was made of a material containing 2.5 mass % of Mo and 17 mass % of Cr. Test pieces, Test Piece 1 containing no Mo and 19 mass % of Cr, and Test Piece 2 containing 0.15 mass % of Mo and 0.4 mass % of Cr, were placed in the lower liquid-contacting portion. <Heavy-ends cut column A> A heavy-ends cut column A having a structure similar to that shown in FIG. 5 was used. Ａ = 1700 cm, D Ａ = 340 cm, and as internal, n Ａ A continuous multi-stage distillation column equipped with a Melapak of 30 was used. <Diphenyl carbonate purification column B> As the diphenyl carbonate purification column B, a L Ｂ = 2200 cm, D Ｂ= 280 cm, internal, n Ｂ１ = 12, n Ｂ２ = 18, n Ｂ３ A continuous multi-stage distillation column equipped with three Melapaks with a mass ratio of 1.5 was used. <Production of Diphenyl Carbonate> Diphenyl carbonate was produced using an apparatus connected to a first continuous multi-stage distillation column 101 and a second continuous multi-stage distillation column 201 as shown in FIG. 4, and an apparatus consisting of a heavy-ends cut column A and a diphenyl carbonate purification column B as shown in FIG. 5. Feedstock 1, consisting of a phenol / dimethyl carbonate ratio of 1.9 (mass ratio), was continuously introduced in liquid form through the upper inlet 11 of the first continuous multi-stage distillation column 101 at a flow rate of 57 tons / hr. Meanwhile, feedstock 2, consisting of a dimethyl carbonate / phenol ratio of 3.6 (mass ratio), was continuously introduced in gaseous form through the lower inlet 12 of the first continuous multi-stage distillation column 101 at a flow rate of 58 tons / hr. The molar ratio of the feedstocks introduced into the first continuous multi-stage distillation column 101 was dimethyl carbonate / phenol = 1.35. The catalyst used was Pb(OPh) ２ The distillation column was continuously introduced from the bottom 11 of the heavy-ends cut column A into the upper inlet 11 of the first continuous multi-stage distillation column 101 at a flow rate of 188 kg / hr so ​​as to achieve a concentration of about 100 ppm in the liquid of the first continuous multi-stage distillation column 101. In the first continuous multi-stage distillation column 101, the temperature at the bottom of the column was 225°C and the pressure at the top of the column was 7 x 10 ５ Reactive distillation was carried out continuously under conditions of a pressure of 1 Pa and a reflux ratio of 0. The first-column low-boiling reaction mixture from first continuous multi-stage distillation column 101, containing methyl alcohol, dimethyl carbonate, phenol, etc., was continuously withdrawn in a gaseous state from column top 13, passed through heat exchanger 14, and withdrawn from withdrawal port 16 at a flow rate of 39 tons / hr. Meanwhile, the first-column high-boiling reaction mixture from first continuous multi-stage distillation column 101, containing methyl phenyl carbonate, dimethyl carbonate, phenol, diphenyl carbonate, the catalyst, etc., was continuously withdrawn in a liquid state from inlet 21 via column bottom 17. After 24 hours, a stable steady state was reached, and the first-column high-boiling reaction mixture from column bottom 17 of first continuous multi-stage distillation column 101 was continuously fed, as is, into second continuous multi-stage distillation column 201 through raw material inlet 21, which was installed between the Melapack and the perforated tray, at a flow rate of 75 tons / hr. In the second continuous multi-stage distillation column 201, Pb(OPh)２ The temperature at the bottom of the column was 210°C, and the pressure at the top of the column was 3 x 10 ４ Reactive distillation was carried out continuously under conditions of a pressure of 100 Pa and a reflux ratio of 0.3. Stable steady-state operation was achieved after 24 hours. A second-column low-boiling reaction mixture containing 35% by mass of dimethyl carbonate, 56% by mass of phenol, and 0.5% by mass of methyl phenyl carbonate was continuously withdrawn from the top 23 of the second continuous multi-stage distillation column 201, and the flow rate at the withdrawal port 26 was 62 tons / hr. A second-column high-boiling reaction mixture containing 38% by mass of methyl phenyl carbonate and 56% by mass of diphenyl carbonate was continuously withdrawn from the bottom 27. The second-column low-boiling reaction mixture of the second continuous multi-stage distillation column 201 was continuously supplied to the first continuous multi-stage distillation column 101 from the inlet 11 (first circulation step). At this time, the amount of dimethyl carbonate and phenol newly supplied was adjusted to maintain the composition and amount of the second-column low-boiling reaction mixture, taking into account the composition and amount of the second-column low-boiling reaction mixture. After 24 hours, a stable steady state was reached, and the second column heavy-boiling reaction mixture from the bottom 27 of the second continuous multi-stage distillation column 201 was continuously introduced as it was into the inlet A1 of the heavy-ends cut column A at a rate of 13.1 tons / hr. Ａ ) at 206°C, and the pressure at the top of the column (P Ａ The distillation was carried out continuously at a reflux ratio of 0.6 and a pressure of 1700 Pa. The composition of the bottom of the heavy-ends cut column A was 33% by mass of diphenyl carbonate, 63% by mass of high-boiling substances, and 4% by mass of the catalyst. Ｂ ), the mass concentration ratio of diphenyl carbonate (DPC) to heavy-boiling points (HB) (DPC / HB) was 0.5, and the mass concentration ratio of diphenyl carbonate (DPC) to the catalyst (DPC / catalyst) was 8.3. From the top 13 of the heavy-ends cut column A, a column top component (A Ｔ The overhead component (A) was continuously extracted at a rate of 12.9 tons / hr. Ｔ ) was continuously introduced directly into the diphenyl carbonate purification column B from the inlet B1. From the bottom of the heavy-ends cut column A, the column bottom component (A Ｂ) was continuously withdrawn at a rate of 200 kg / hr. Of this, 12 kg / hr was discharged to the outside of the system in order to maintain the concentration of the produced high boiling point substances at 63 mass %. The remaining 188 kg / hr was introduced into the upper inlet 11 of the first continuous multi-stage distillation column 101 (second circulation step). In the diphenyl carbonate purification column B, the temperature at the bottom of the column (T Ｂ ) at 213°C, and the pressure at the top of the column (P Ｂ ) to 5000 Pa, and distillation was carried out continuously at a reflux ratio of 1.5. Ｔ ) was continuously extracted at a rate of 5.7 tons / hr, and the bottom component (B Ｂ ) is continuously extracted at a rate of 30 kg / hr, and a side cut component (B Ｓ) was continuously extracted at a rate of 7.2 tons / hr. 24 hours after the system had completely stabilized, the compositions of the components were as follows: Bottom component of first continuous multi-stage distillation column 101: 18.2 mass% methyl phenyl carbonate, 2.4 mass% diphenyl carbonate. Top component of heavy-ends cut column A: 8 mass% of substances with boiling points lower than methyl phenyl carbonate, 34 mass% methyl phenyl carbonate, 58 mass% diphenyl carbonate. Top component of diphenyl carbonate purification column B: 18 mass% of substances with boiling points lower than methyl phenyl carbonate, 78 mass% methyl phenyl carbonate, 4 mass% diphenyl carbonate. Bottom component of diphenyl carbonate purification column B: 95 mass% diphenyl carbonate, 5 mass% high-boiling substances. The contents of phenyl salicylate, xanthone, and phenyl methoxybenzoate in the side cut component of diphenyl carbonate purification column B were all 1 ppm or less, and 1-phenoxycarbonyl-2-phenoxycarboxy-phenylene was 4 ppm. Furthermore, the halogen content in the side cut component of diphenyl carbonate purification column B was 1 ppb or less. This indicates that the purity of the diphenyl carbonate obtained from the side cut of diphenyl carbonate purification column B was 99.999% or more. Furthermore, the production rate of this high-purity diphenyl carbonate (DPC) was 7.2 tons per hour. At this time, the conversion rates of dimethyl carbonate (DMC) in the first continuous multi-stage distillation column 101 and methyl phenyl carbonate (MPC) in the second continuous multi-stage distillation column 201 were 10% and 74%, respectively, and the steam consumption rates of the first continuous multi-stage distillation column 101 and the second continuous multi-stage distillation column 201 were 15.1 tons / hr and 12.4 tons / hr, respectively. Furthermore, the makeup catalyst replenishment rate for replenishing the catalyst discharged from the bottom of heavy ends column A to the outside of the system was 2 kg / hr. Long-term continuous operation was carried out under these conditions. The production amount and purity of diphenyl carbonate, as well as the steam consumption and makeup catalyst replenishment rates of the first continuous multi-stage distillation column 101 and the second continuous multi-stage distillation column 201, remained substantially unchanged after 500 hours, 2000 hours, 4000 hours, 5000 hours, and 6000 hours. Furthermore, no corrosion was observed at all in the liquid-contacting lower portion of second continuous multi-stage distillation column 201.On the other hand, corrosion was observed on test pieces 1 and 2, and particularly severe corrosion was observed on test piece 2.

[0155] Example 2 Diphenyl carbonate was produced using the same apparatus as in Example 1. At this time, the concentration of methyl phenyl carbonate in the second column low-boiling point reaction mixture at the top of the second continuous multi-stage distillation column 201 was set to 2.0% by mass. As a result, the concentration of methyl phenyl carbonate at the bottom of the first continuous multi-stage distillation column 101 was 18.2% by mass, but the concentration of diphenyl carbonate was 2.2% by mass. As a result, in order to produce 7.2 tons of diphenyl carbonate per hour, it was necessary to continuously introduce raw material 1 consisting of a phenol / dimethyl carbonate = 1.9 (mass ratio) from the upper inlet 11 of the first continuous multi-stage distillation column 101 in liquid form at a flow rate of 58 tons / hr, and raw material 2 consisting of a dimethyl carbonate / phenol = 3.6 (mass ratio) from the lower inlet 12 of the first continuous multi-stage distillation column 101 in gaseous form at a flow rate of 60 tons / hr. As a result, the conversion rates of dimethyl carbonate (DMC) in the first continuous multi-stage distillation column 101 and methyl phenyl carbonate (MPC) in the second continuous multi-stage distillation column 201 were 9.8% and 72%, respectively, and the steam consumption rates of the first continuous multi-stage distillation column 101 and the second continuous multi-stage distillation column 201 were 15.4 tons / hr and 12.7 tons / hr, respectively.

[0156] Comparative Example 1 Diphenyl carbonate was produced using the same apparatus as in Example 1. At this time, the composition of the bottom of the heavy-ends cut column A was 58 mass % diphenyl carbonate, 38 mass % high boiling point substances, and 4 mass % catalyst component. That is, the bottom component (A Ｂ), the mass concentration ratio (DPC / HB) of diphenyl carbonate (DPC) to high boiling point substances (HB) was 1.5, and the mass concentration ratio (DPC / catalyst) of diphenyl carbonate (DPC) to the catalyst was 14.5. As a result, the concentration of methyl phenyl carbonate at the bottom of the first continuous multi-stage distillation column 101 was 18.2 mass%, but the concentration of diphenyl carbonate was 0.8 mass%. As a result, in order to produce 7.2 tons of diphenyl carbonate per hour, it became necessary to continuously introduce feedstock 1 consisting of a phenol / dimethyl carbonate = 1.9 (mass ratio) in liquid form from the upper inlet 11 of the first continuous multi-stage distillation column 101 at a flow rate of 63 tons / hr, and feedstock 2 consisting of a dimethyl carbonate / phenol = 3.6 (mass ratio) in gas form from the lower inlet 12 of the first continuous multi-stage distillation column 101 at a flow rate of 64 tons / hr. Furthermore, in order to maintain the concentration of high boiling points at 38% by mass, it became necessary to discharge the heavy-ends cut column A from the bottom at a flow rate of 20 kg / hr to the outside of the system. As a result, the conversion rates of dimethyl carbonate (DMC) in the first continuous multi-stage distillation column 101 and methyl phenyl carbonate (MPC) in the second continuous multi-stage distillation column 201 both deteriorated by 10% compared to Example 1, and the amounts of steam used in the first continuous multi-stage distillation column 101 and the second continuous multi-stage distillation column 201 also increased by 9% and 10%, respectively, compared to Example 1. Furthermore, the amount of make-up catalyst replenished to replenish the catalyst discharged from the bottom of heavy-ends cut column A to the outside of the system also increased by 1.5 times compared to Example 1.

[0157] Comparative Example 2 Diphenyl carbonate was produced using the same apparatus as in Example 1. At this time, the composition of the bottom of the heavy-ends cut column A was 56 mass % diphenyl carbonate, 37 mass % high boiling point substances, and 7 mass % catalyst component. That is, the bottom component (A Ｂ ), the mass concentration ratio of diphenyl carbonate (DPC) to high boiling point substances (HB) (DPC / HB) was 1.5, and the mass concentration ratio of diphenyl carbonate (DPC) to catalyst (DPC / catalyst) was 8.3. As a result, in order to maintain the concentration of high boiling point substances at 37 mass%, the bottom component (AＢ As a result, the amount of makeup catalyst replenished to make up for the catalyst discharged from the bottom of heavy-ends cut column A to the outside of the system became 3.5 times that in Example 1.

[0158] Comparative Example 3 Diphenyl carbonate was produced using the same apparatus as in Example 1. At this time, the composition of the bottom of the heavy-ends cut column A was 35 mass % diphenyl carbonate, 63 mass % high-boiling substances, and 2 mass % catalyst component. That is, the bottom component (A Ｂ ), the mass concentration ratio (DPC / HB) of diphenyl carbonate (DPC) to high boiling point substances (HB) was 0.5, and the mass concentration ratio (DPC / catalyst) of diphenyl carbonate (DPC) to the catalyst was 14.5. As a result, the concentration of methyl phenyl carbonate at the bottom of the first continuous multi-stage distillation column 101 was 18.2 mass%, but the concentration of diphenyl carbonate was 0.8 mass%. As a result, in order to produce 7.2 tons of diphenyl carbonate per hour, it became necessary to continuously introduce feedstock 1 consisting of a phenol / dimethyl carbonate = 1.9 (mass ratio) in liquid form from the upper inlet 11 of the first continuous multi-stage distillation column 101 at a flow rate of 63 tons / hr, and feedstock 2 consisting of a dimethyl carbonate / phenol = 3.6 (mass ratio) in gas form from the lower inlet 12 of the first continuous multi-stage distillation column 101 at a flow rate of 64 tons / hr. As a result, the conversion rate of dimethyl carbonate (DMC) in the first continuous multi-stage distillation column 101 and the conversion rate of methyl phenyl carbonate (MPC) in the second continuous multi-stage distillation column 201 both deteriorated by 10% compared to Example 1, and the amounts of steam used in the first continuous multi-stage distillation column 101 and the second continuous multi-stage distillation column 201 also increased by 9% and 10%, respectively, compared to Example 1.

[0159] Example 3 Diphenyl carbonate was produced using the same equipment and production method as in Example 1, except that the catalyst was replaced with the catalyst described in Example 1 of WO 2011 / 105442. (Preparation of Titanium-Containing Composition) 7 kg of tetrabutoxytitanium (manufactured by DuPont, product name: Tyzor TnBT) was charged under a nitrogen atmosphere into a 60 L batch reactor equipped with a stirrer, heater, and distillation column, followed by 14 kg of phenol previously purified by distillation. Next, the mixture in the batch reactor was heated to 180°C using a heater at atmospheric pressure and reacted. n-Butanol generated by the reaction was recovered from the top of the distillation column. The batch reactor was then depressurized to approximately 53 kPa, and n-butanol was recovered. The batch reactor was then returned to atmospheric pressure, approximately 18 kg of diphenyl carbonate was charged, and the mixture in the reactor was heated to approximately 190°C. Next, the batch reactor was depressurized to approximately 1.3 kPa, and diphenyl carbonate containing low-boiling components was distilled off to obtain a titanium-containing composition. Diphenyl carbonate was added so that the titanium concentration of the obtained titanium-containing composition was 5% by mass. The titanium-containing composition was heated at 200°C for approximately 48 hours to serve as a reaction catalyst for the production of diphenyl carbonate. The titanium-containing composition catalyst was continuously introduced from the bottom 11 of heavy-ends cut column A into the upper inlet 11 of first continuous multi-stage distillation column 101 at a flow rate of 188 kg / hr so ​​that the titanium-containing composition catalyst was approximately 100 ppm in the liquid of first continuous multi-stage distillation column 101.

[0160] Example 4 Diphenyl carbonate was produced using the same apparatus and production method as in Example 2, except that the catalyst was changed to the same catalyst as in Example 3.

[0161] The conditions and results of Examples 1 to 4 and Comparative Examples 1 to 3 are shown in Table 1.

[0162] This application is based on a Japanese patent application (Patent Application No. 2021-172658) filed on October 21, 2021, the contents of which are incorporated herein by reference.

[0163] By carrying out the method of the present invention, for example, high-purity diphenyl carbonate, which is necessary for producing high-quality, high-performance aromatic polycarbonates, can be produced on an industrial scale at a rate of 1 ton or more per hour, preferably 2 ton or more, and more preferably 3 ton or more, while reducing heat consumption and suppressing the amount of catalyst replenishment. Furthermore, high-purity diphenyl carbonate having a halogen content of 0.1 ppm or less, preferably 10 ppb or less, and a higher-boiling impurity content than diphenyl carbonate of 100 ppm or less, preferably 50 ppm or less, and more preferably 10 ppm or less can be stably produced for a long period of time, for example, 2,000 hours or more, preferably 3,000 hours or more, and more preferably 5,000 hours or more. Therefore, the present invention is an extremely effective method for industrially producing high-purity diphenyl carbonate.

[0164] (Figure 1) 1: Gas outlet, 2: Liquid outlet, 3-a to 3-e: Inlet, 4-a to 4-b: Inlet, 5: Head, 6: Internal, 7: Body, 10: Continuous multi-stage distillation column, L ０ : Body length (cm), D ０ : inner diameter of body (cm), d ０１ : inner diameter of gas outlet (cm), d ０２ : inner diameter of liquid outlet (cm) (Figs. 2, 3 and 4) 1: gas outlet, 2: liquid outlet, 3: inlet, 4: inlet, 5: end plate, L １ and L ２ : Body length (cm), D １ and D １ : inner diameter of body (cm), d １１ and d ２１ : inner diameter of gas outlet (cm), d １２ and d ２２: inner diameter of liquid withdrawal port (cm), 101: first continuous multi-stage distillation column, 201: second continuous multi-stage distillation column, 11, 12, 21: inlet, 13, 23: column top gas withdrawal port, 14, 24, 18, 28: heat exchanger, 17, 27: column bottom liquid withdrawal port, 16, 26: column top component withdrawal port, 31: second continuous multi-stage distillation column column bottom component withdrawal port (FIG. 5) A1, B1: inlet, B2: outlet, 11: bottom component outlet of heavy-ends cut column A, 13, 23: overhead gas outlet, 14, 24, 18, 28: heat exchangers, 15, 25: reflux liquid inlet, 16: overhead component outlet of heavy-ends cut column A, 17, 27: bottom liquid outlet, 26: overhead component outlet of diphenyl carbonate purification column B, 31: bottom component outlet of diphenyl carbonate purification column B, 33: side-cut component outlet of diphenyl carbonate purification column B

Claims

1. A method for continuously producing diphenyl carbonate, comprising the steps of continuously supplying a dialkyl carbonate and phenol into a first continuous multi-stage distillation column in the presence of a catalyst, simultaneously carrying out reaction and distillation in the first continuous multi-stage distillation column, continuously withdrawing the first column low-boiling reaction mixture containing the produced alcohols in a gaseous state from the top of the first continuous multi-stage distillation column, and continuously withdrawing the first column high-boiling reaction mixture containing the produced alkyl phenyl carbonate in a liquid state from the bottom of the first continuous multi-stage distillation column, thereby continuously producing alkyl phenyl carbonate; a step of continuously supplying the first column high-boiling reaction mixture into a second continuous multi-stage distillation column in the presence of a catalyst, simultaneously carrying out reaction and distillation in the second continuous multi-stage distillation column, continuously withdrawing the second column low-boiling reaction mixture containing the produced dialkyl carbonates in a gaseous state from the top of the second continuous multi-stage distillation column, and continuously withdrawing the second column high-boiling reaction mixture containing the produced diphenyl carbonate in a liquid state from the bottom of the second continuous multi-stage distillation column, thereby continuously producing diphenyl carbonate; and continuously introducing the second column high-boiling reaction mixture containing diphenyl carbonate into a heavy-ends cut column A, and continuously withdrawing a column top component (A) containing diphenyl carbonate. Ｔ ) and a column bottom component (A Ｂ a first purification step of continuously separating the top component (A) from the top component (A); Ｔ ) is continuously introduced into a diphenyl carbonate purification column B having a side cut withdrawal port, and the column top component (B Ｔ ), side cut component (B Ｓ ) and the bottom component (B Ｂ ) by successive distillation separation into three components, Ｓ a second purification step of obtaining diphenyl carbonate as the second column low-boiling point reaction mixture; a first circulation step of continuously supplying the second column low-boiling point reaction mixture into a first continuous multi-stage distillation column; and Ｂ a second circulation step of continuously supplying a portion of the bottom component (A) of the heavy-ends cut column A into the first continuous multi-stage distillation column and / or the second continuous multi-stage distillation column; Ｂ ) contains diphenyl carbonate (DPC) and high boiling point substances (HB), and the column bottom component (A Ｂ wherein the mass concentration ratio of diphenyl carbonate to high-boiling substances (DPC / HB) is 0.1 to 1.0 and the mass concentration ratio of diphenyl carbonate to catalyst (DPC / catalyst) is 1.0 to 10.

0.

2. The bottom component (A Ｂ 2. The method according to claim 1, wherein the concentration of diphenyl carbonate in the reaction mixture is 9 to 38 mass%.

3. The manufacturing method described in claim 1 or 2, wherein the liquid-contacting portion at the bottom of the second continuous multi-stage distillation column is made of a material containing Fe as the main component, 2 mass% or more of Mo, and 18 mass% or less of Cr.

4. The production method according to claim 1 or 2, wherein the concentration of alkyl aryl carbonate in the second column low-boiling point reaction mixture is 1 mass % or less.

5. (a) The first continuous multi-stage distillation column has a length L １ (cm), inner diameter D １ (cm) cylindrical body, and has n stages inside １ The column has an internal structure with an internal diameter of d １１ A gas outlet with an inner diameter of d (cm) is provided at the bottom of the tower or at a lower part of the tower close to the bottom. １２ (cm) of liquid withdrawal port, one or more third inlets below the gas withdrawal port in the upper and / or middle part of the column, and one or more fourth inlets above the liquid withdrawal port in the middle and / or lower part of the column, １ , D １ , L １ / D １ , n １ , D １ / d １１ , D １ / d １２ respectively satisfy the following formulas (7) to (12), and 1500≦L １ ≦ 8000 Formula (7) 100 ≦ D １ ≦ 2000 Formula (8) 2 ≦ L １ / D １ ≦ 40 Formula (9) 20 ≦ n １ ≦ 120 Formula (10) 5 ≦ D １ / d １１ ≦ 30 Formula (11) 3 ≦ D １ / d １２ ≦ 20 Equation (12) (b) The second continuous multi-stage distillation column has a length L ２ (cm), inner diameter D ２ (cm) cylindrical body, and has n stages inside ２ The column has an internal structure with an internal diameter of d ２１ A gas outlet with an inner diameter of d (cm) is provided at the bottom of the tower or at a lower part of the tower close to the bottom. ２２ (cm) of liquid withdrawal port, one or more fifth inlets below the gas withdrawal port in the upper and / or middle part of the column, and one or more sixth inlets above the liquid withdrawal port in the middle and / or lower part of the column, ２ , D ２ , L ２ / D ２ , n ２ , D ２ / d ２１ , D ２ / d ２２ respectively satisfy the following formulas (13) to (18), and 1500≦L ２ ≦ 8000 Formula (13) 100 ≦ D ２ ≦ 2000 Formula (14) 2 ≦ L ２ / D ２ ≦ 40 Formula (15) 10 ≦ n ２ ≦ 80 Formula (16) 2 ≦ D ２ / d ２１ ≦ 15 Formula (17) 5 ≦ D ２ / d ２２ ≦ 30 Formula (18) (c) The high boiling point substance separation column A has a length L Ａ (cm), inner diameter D Ａ (cm) cylindrical body, and has n stages inside Ａ A continuous multi-stage distillation column having an internal of L Ａ , D Ａ , n Ａ respectively satisfy the following formulas (19) to (21), and 800≦L Ａ ≦ 3000 Formula (19) 100 ≦ D Ａ ≦ 1000 Formula (20) 20 ≦ n Ａ ≦ 100 Formula (21) (d) The diphenyl carbonate purification column B has a length L Ｂ (cm), inner diameter D Ｂ The column has a cylindrical body with a diameter of 1.5 cm and an internal structure. １ , the inlet B １ Between the tower bottom and the side cut outlet B ２ and inlet B １ The number of internal stages at the top is n Ｂ１ , inlet B １ and side cut outlet B ２ The number of internal stages between Ｂ２ , Side cut outlet B ２ The number of internal stages at the bottom is n Ｂ３ The total number of stages (n Ｂ１ +n Ｂ２ +n Ｂ３ ) is n Ｂ A continuous multi-stage distillation column in which L Ｂ , D Ｂ , n Ｂ１ , n Ｂ２ , n Ｂ３ , n Ｂ The method according to claim 1 or 2, wherein L satisfies the following formulas (22) to (27), respectively: 1000≦L Ｂ ≦ 5000 Formula (22) 100 ≦ D Ｂ ≦ 1000 Formula (23) 5 ≦ n Ｂ１ ≦ 20 Formula (24) 12 ≦ n Ｂ２ ≦ 40 Formula (25) 3 ≦ n Ｂ３ ≦ 15 Formula (26) 20 ≦ n Ｂ ≦ 70 Formula (27)

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