Method for producing carbonate having aryl group

Abstract

Provided is a method for producing a carbonate having an aryl group, the production method comprising: a reaction / distillation step for continuously supplying a feedstock, which contains dialkyl carbonate and hydroxyaryl, into a reaction distillation column A in which an ester exchange reaction catalyst is present, simultaneously carrying out a reaction and distillation in the column A, continuously extracting a fraction AU containing alkyl alcohol and dialkyl carbonate from the upper part of the column A, and continuously extracting, in a liquid state, a fraction AL containing hydroxyaryl, alkyl aryl carbonate, and diaryl carbonate from a lower part of the column A; an extractive distillation step for supplying, from an upper part of an extractive distillation column B, an extractant containing hydroxyaryl as a main component, supplying a mixture containing alkyl alcohol and dialkyl carbonate from a lower part of the column B, carrying out extractive distillation, extracting a fraction BU containing alkyl alcohol as a main component from the upper part of the column B, and extracting, from the lower part of the column B, a fraction BL containing dialkyl carbonate and hydroxyaryl; and a step for continuously supplying the fraction BL to the column A.

Description

Method for producing carbonates having aryl groups

[0001] The present invention relates to a method for producing a carbonate having an aryl group.

[0002] Carbonates containing aryl groups, including diaryl carbonates, are important raw materials for producing polycarbonates, the most popular engineering plastics. Diaryl carbonates can be produced by reacting hydroxyaryls with phosgene or by transesterification of alkylene carbonates with alkyl alcohols.

[0003] In the method for producing alkylene carbonate from alkyl alcohol, the transesterification reaction has a very small equilibrium constant, and therefore the alkyl alcohol produced as the reaction proceeds inhibits the progress of the transesterification reaction. Therefore, it is necessary not only to reduce the alkyl alcohol content in the dialkyl carbonate in the raw material as much as possible, but also to discharge the produced alkyl alcohol from the reaction system, where it is continuously withdrawn as a low-boiling reaction mixture together with unreacted dialkyl carbonate.

[0004] The extracted low-boiling reaction mixture must be separated from the alkyl alcohol in order to re-feed the unreacted dialkyl carbonate to the reactive distillation column. However, because alkyl alcohol and dialkyl carbonate form an azeotropic mixture at normal pressure, separation by conventional methods is difficult. Several methods for separating these by distillation have been proposed. For example, Patent Document 1 proposes a separation method that utilizes the change in the azeotropic composition of methanol and dimethyl carbonate due to pressure application. Furthermore, Patent Documents 2 and 3 propose an extractive distillation method using phenol as the extracting solvent, and Patent Document 4 proposes an extractive distillation method using propylene carbonate as the extracting solvent.

[0005] International Publication No. WO 2006 / 035642 International Publication No. WO 2016 / 151488 JP 2001-064235 A JP 2009-527530 A

[0006] However, the distillation methods described in Patent Documents 1 to 4 require pressurization or an additional step of separating the mixture of dialkyl carbonate and extraction solvent again before feeding the unreacted dialkyl carbonate back into the reactive distillation column, which is disadvantageous in that the system becomes complicated and increases the capital investment cost, as well as in terms of energy consumption.

[0007] The problem to be solved by the present invention is to provide a method for producing a carbonate having an aryl group by transesterification of a dialkyl carbonate and a hydroxyaryl, which method reduces the burden of purifying a fraction containing alkyl alcohol and dialkyl carbonate that are by-produced.

[0008] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that by subjecting a fraction containing alkyl alcohol and dialkyl carbonate discharged from a reactive distillation column to extractive distillation using an extractant containing a hydroxyaryl, it is possible to efficiently separate the alkyl alcohol and reuse the mixture of dialkyl carbonate and extractant as a raw material in the reactive distillation column without further separation, thereby arriving at the present invention.

[0009] That is, the present invention includes the following embodiments: <1> A method for producing a carbonate having an aryl group, comprising continuously supplying a raw material containing a dialkyl carbonate and a hydroxyaryl into a reactive distillation column A in which a transesterification catalyst is present, and simultaneously carrying out reaction and distillation in the column A, thereby obtaining a fraction A containing an alkyl alcohol and a dialkyl carbonate. Ｕ is continuously withdrawn from the top of the column A, and fraction A containing hydroxyaryl, alkylaryl carbonate and diaryl carbonate is obtained. Ｌ a reactive distillation step in which an extractant mainly containing hydroxyaryl is supplied from the top of extractive distillation column B, and a mixture containing alkyl alcohol and dialkyl carbonate is supplied from the bottom of column B, and extractive distillation is performed to obtain a fraction B mainly containing alkyl alcohol. Ｕis withdrawn from the top of the column B, and a fraction B containing dialkyl carbonate and hydroxyaryl is withdrawn. Ｌ extracting the fraction B from the bottom of the column B; Ｌ <2> A method for producing a carbonate having an aryl group, comprising: a step of continuously supplying the fraction A to the column A. Ｕ The method further comprises a step of separating the hydroxyaryl-based liquid fraction from a mixture containing alkyl alcohol and dialkyl carbonate, the liquid fraction containing hydroxyaryl as a main component being supplied from an upper portion of an extractive distillation column B, and the mixture containing alkyl alcohol and dialkyl carbonate being supplied from a lower portion of the column B in the extractive distillation step, and extractive distillation is carried out to obtain a fraction B containing alkyl alcohol as a main component. Ｕ is withdrawn from the top of the column B, and a fraction B containing dialkyl carbonate and hydroxyaryl is withdrawn. Ｌ The method according to <1>, wherein the fraction B is extracted from the bottom of the column B. <3> The method according to <1>, wherein the fraction B is extracted from the bottom of the column B. Ｌ <4> The method according to <1> or <2>, wherein the total content of dialkyl carbonate and hydroxyaryl in the fraction B is 80 mass% or more. Ｌ <5> The method according to any one of <1> to <4>, wherein the content of alkyl alcohol in the column B is 10% by mass or less. <6> The method according to any one of <1> to <5>, wherein the column top pressure of the column B is 0.5 MPaG or less. <7> The method according to any one of <1> to <6>, wherein the column top temperature of the column B is 100°C or less. <8> The method according to any one of <1> to <6>, wherein the dialkyl carbonate is dimethyl carbonate. <9> The method according to any one of <1> to <8>, wherein the mixture in the extractive distillation step is separated into the fraction A separated in the column A. Ｕ <9> The method according to any one of <1> to <7>, wherein the fraction A is derived from Ｕ is continuously fed into a continuous multi-stage distillation column C, and a fraction C containing alkyl alcohol and dialkyl carbonate is obtained. Ｕ and fraction C containing hydroxyaryl as the main component. ＬIn the extractive distillation step, the fraction C is separated into Ｕ is supplied as the mixture from the bottom of the column B, and the fraction C Ｌ The method according to <8>, wherein the fraction A separated in the column A is supplied as the extractant from the top of the column B. <10> The method according to <8>, wherein the fraction A separated in the column A is supplied as the extractant from the top of the column B. Ｕ A portion of the liquid fraction A is condensed. Ｕｌ and gas fraction A Ｕｇ a first condensation step of separating the gaseous fraction A into Ｕｇ a second condensation step of further condensing the fraction A Ｕｌ is distilled and purified in the column C, and the fraction C Ｕ is supplied as the mixture from the bottom of the column B, and the fraction C Ｌ is supplied as the extractant from the top of the column B, and the condensed fraction A Ｕｇ and supplying the fraction B as the mixture from the bottom of the column B. <11> In the extractive distillation step, the column B has a distillation purification section above the supply position of the extractant, and Ｕ <12> The method according to any one of <1> to <9>, wherein a raw material containing an alkylene carbonate and an alkyl alcohol is continuously supplied to a reactive distillation column G in the presence of an ester exchange reaction catalyst, and reaction and distillation are simultaneously carried out in the column G, thereby obtaining a fraction G containing a dialkyl carbonate and an alkyl alcohol. Ｕ and extracting the fraction G from the top of the column G. Ｕ is introduced into the column B. <13> The method according to <12>, wherein the alkyl alcohol used as a raw material in the dialkyl carbonate production step is derived from the fraction BU.

[0010] According to the present invention, there can be provided a method for producing a carbonate having an aryl group by transesterification of a dialkyl carbonate and a hydroxyaryl, which method reduces the burden of purifying a fraction containing the by-produced alkyl alcohol and the dialkyl carbonate.

[0011] FIG. 1 is a schematic diagram of an apparatus for producing a carbonate having an aryl group. FIG. 2 is a schematic diagram of a reactive distillation column A. FIG. 3 is a schematic diagram of an apparatus for producing a carbonate having an aryl group. FIG. 4 is a schematic diagram of an apparatus for producing a carbonate having an aryl group. FIG. 5 is a schematic diagram of an apparatus for producing a dialkyl carbonate and a carbonate having an aryl group. FIG. 6 is a schematic diagram of an apparatus for producing a carbonate having an aryl group. FIG. 7 is a schematic diagram of an apparatus for producing a dialkyl carbonate and a carbonate having an aryl group.

[0012] 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.

[0013] The method according to this embodiment is a method for producing a carbonate having an aryl group, comprising continuously supplying a raw material containing a dialkyl carbonate and a hydroxyaryl into a reactive distillation column A in which a transesterification catalyst is present, and simultaneously carrying out reaction and distillation in the column A, thereby obtaining a fraction A containing an alkyl alcohol and a dialkyl carbonate. Ｕ is continuously withdrawn from the top of column A, and fraction A containing hydroxyaryl, alkylaryl carbonate and diaryl carbonate is obtained. Ｌ a reactive distillation step in which an extractant mainly composed of hydroxyaryl is supplied from the top of an extractive distillation column B, and a mixture containing alkyl alcohol and dialkyl carbonate (hereinafter, the mixture used in the extractive distillation step is also referred to as "mixture Bs") is supplied from the bottom of the column B, and extractive distillation is performed to obtain a fraction B mainly composed of alkyl alcohol. Ｕ is withdrawn from the top of the column B, and a fraction B containing dialkyl carbonate and hydroxyaryl is withdrawn. Ｌ extracting the fraction B from the bottom of the column B;Ｌ to the column A. According to this embodiment, in a method for producing a carbonate having an aryl group by transesterification from a dialkyl carbonate and a hydroxyaryl, a method for producing a carbonate having an aryl group can be provided that reduces the purification load of a fraction containing by-produced alkyl alcohol and dialkyl carbonate.

[0014] In this embodiment, fraction A containing alkyl alcohol and dialkyl carbonate extracted in the reactive distillation step Ｕ In the extractive distillation process, fraction B containing alkyl alcohol as the main component is obtained. Ｕ and fraction B containing dialkyl carbonate and hydroxyaryl. Ｌ Fraction B is separated. Ｌ The dialkyl carbonate and hydroxyaryl contained in fraction B are raw materials in the reactive distillation process. Ｌ By continuously supplying this to column A, it is reused as a raw material for the reactive distillation step, so that a carbonate having an aryl group can be efficiently produced while simplifying the purification step.

[0015] The meanings of various terms used in this embodiment are as follows: "Upper" means a position above the midpoint of the distillation column. "Lower" means a position below the midpoint of the distillation column. "Major component" means a component that accounts for more than 50 mass%. "Carbonate having an aryl group" means a carbonate compound that has one or two aryl groups, such as diaryl carbonate or aryl alkyl carbonate. Pressures ending in "G" (e.g., "MPaG") mean gauge pressure.

[0016] The method according to this embodiment will be described below using the apparatus shown in FIG. 1 as an example. As shown in FIG. 1, the apparatus for producing a carbonate having an aryl group includes a reactive distillation column A, a continuous multi-stage distillation column C, and an extractive distillation column B. The reactive distillation column A is equipped with a reboiler A1 that adds heat to the components at the bottom of the distillation column. The apparatus may also include a multi-stage concentrator D that condenses the gaseous fraction produced from the reactive distillation column A. The continuous multi-stage distillation column C is equipped with a reboiler C1 that adds heat to the components at the bottom of the distillation column. The apparatus may also include a concentrator E that condenses the gaseous fraction produced from the continuous multi-stage distillation column C. The extractive distillation column B is equipped with a reboiler B1 that adds heat to the components at the bottom of the distillation column. The apparatus may also include a concentrator F that condenses the gaseous fraction produced from the extractive distillation column B. Each step will be described in detail below.

[0017] <Reactive distillation step> In the method according to this embodiment, a raw material containing a dialkyl carbonate and a hydroxyaryl is continuously supplied to a reactive distillation column A in which a transesterification catalyst is present, and reaction and distillation are simultaneously carried out in the column A to obtain a fraction A containing an alkyl alcohol and a dialkyl carbonate. Ｕ is continuously withdrawn from the top of column A, and fraction A containing hydroxyaryl, alkylaryl carbonate and diaryl carbonate is obtained. Ｌ is continuously extracted from the bottom of column A.

[0018] [Feedstock] The feedstock supplied to the reactive distillation column A contains a dialkyl carbonate and a hydroxyaryl.

[0019] (Dialkyl Carbonate) The dialkyl carbonate used as a raw material is, for example, (R １ O)CO(OR ２ ) (wherein, R １ and R ２are each independently an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms. Examples of dialkyl carbonates include dimethyl carbonate (hereinafter also referred to as "DMC"), diethyl carbonate (hereinafter also referred to as "DEC"), dipropyl carbonate, dibutyl carbonate, dihexyl carbonate, dioctyl carbonate, dicyclohexyl carbonate, dibenzyl carbonate, and methyl ethyl carbonate. Among these, dimethyl carbonate and diethyl carbonate are preferred.

[0020] (Hydroxyaryl) Examples of the hydroxyaryl used as a raw material include compounds represented by ArOH (wherein Ar represents an aromatic group having 1 to 20 carbon atoms). Examples of the hydroxyaryl include phenol, o-, m-, or p-cresol, o-, m-, or p-ethylphenol, o-, m-, or p-propylphenol, o-, m-, or p-methoxyphenol, 2,6-dimethylphenol, 2,4-dimethylphenol, 3,4-dimethylphenol, o-, m-, or p-chlorophenol, 1-naphthol, and 2-naphthol. Among these, phenol is preferred. The raw material of this embodiment may be derived from biomass. Examples include DMC, DEC, and methyl ethyl carbonate obtained using bioethanol or biomethanol as raw materials.

[0021] The mass ratio of dialkyl carbonate / hydroxyaryl to be fed into the reactive distillation column A as the raw material is preferably 0.1 to 1.0, more preferably 0.2 to 0.9, and even more preferably 0.3 to 0.8.

[0022] The mass ratio of dialkyl carbonate / hydroxyaryl in the raw material and fraction BL supplied into reactive distillation column A is preferably 0.5 to 3, more preferably 0.8 to 2.5, and even more preferably 1.0 to 2.0.

[0023] [Transesterification Catalyst] The transesterification catalyst used in this embodiment is not particularly limited, but for example, Bu ２ SnO, Ph ２ SnO, (C ８ H １７ ) ２ SnO, Bu ２ Sn(OPh) ２ , Bu ２ Sn(OCH ３ ) ２ , Bu ２ Sn(OEt) ２ , Bu ２ Sn(OPh)O(OPh)SnBu ２ Tin compounds such as PbO, Pb(OPh) ２ , Pb(OCOCH ３ ) ２ lead compounds such as AlX ３ , TiX ３ , TiX ４ , ZnX ２ , FeX ３ , SnX ４ , VX ５ (wherein X represents a halogen, an acetoxyl group, an alkoxyl group, or an aryloxy group). More specifically, examples of the transesterification catalyst include AlCl ３ , Al(OPh) ３ , TiCl ４ , Ti(OPh) ４ , Ti(OEt) ４ , Ti(OPr) ４ , Ti(OBu) ４ Lewis acid compounds such as Zr(acac) ４ , ZrO ２ Zirconium compounds such as CuCl, CuCl ２ ,CuBr,CuBr ２ , CuI, CuI ２ , Cu(OAc) ２ (wherein acac represents an acetylacetone ligand, and Ac represents an acetyl group) etc. Among these, tin compounds or titanium compounds are preferred.

[0024] [Reactive distillation column A] Figure 2 is a schematic diagram of reactive distillation column A. Here, an example using a continuous multi-stage distillation column 10 as reactive distillation column A will be described. The continuous multi-stage distillation column 10 has a structure in which end plates 5 are disposed above and below a cylindrical body 7 having a length L (cm) and an inner diameter D (cm), and an internal 6 having n stages inside. The top of the column or the upper part of the column near it has an inner diameter d １ A gas outlet 1 having an inner diameter of d (cm) is provided at the bottom of the column or at the bottom of the column near the bottom. ２ (cm) liquid withdrawal port 2, one or more first inlets 3 located below the gas withdrawal port 1 in the upper and / or middle portion of the column, and one or more second inlets 4 located above the liquid withdrawal port 2 in the lower portion of the column, but various conditions must be satisfied in order to simultaneously carry out not only distillation but also reaction and to produce at least 1 ton of aromatic carbonate per hour stably for a long period of time. Note that, because Figure 2 shows one embodiment of a continuous multi-stage distillation column, the arrangement of internal 6 is not limited to the configuration shown in Figure 2.

[0025] The reactive distillation column A is preferably a distillation column having at least one internal selected from the group consisting of trays and packings. Here, "internal" refers to the portion of the distillation column where gas-liquid contact actually occurs. Examples of trays include bubble trays, perforated trays, valve trays, countercurrent trays, Super Frac trays, and Max Frac 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 Melapack, Gempack, Technopack, Flexipak, Sulzer packing, Goodroll packing, and Glitch grid.

[0026] A multi-stage distillation column having both trays and a section packed with packing may also be used. Note that the "number of internal stages n" means the number of trays in the case of a tray column, and means the number of theoretical stages in the case of a packing column.

[0027] The transesterification reaction between dialkyl carbonate and hydroxyaryl has an extremely small equilibrium constant and a slow reaction rate. Therefore, a plate-type distillation column having a tray as the internal is more preferable as the continuous multi-stage distillation column used in the reactive distillation column A. Furthermore, a sieve tray having a sieve tray section and a downcomer section is preferable. The sieve tray has an area of ​​1 m ２ The number of holes in the perforated plate is preferably 100 to 1000 per square meter of the perforated plate. ２ The number of holes per hole is preferably 120 to 900, more preferably 150 to 800. The cross-sectional area per hole of the sieve tray is preferably 0.5 to 5 cm. ２ and more preferably 0.7 to 4 cm ２ and more preferably 0.9 to 3 cm ２ The perforated tray has a perforated plate area of ​​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 preferable that:

[0028] Any method may be used to cause the transesterification catalyst to be present in the reactive distillation column A, but when the transesterification catalyst is in a solid form that is insoluble in the reaction liquid, it may be fixed in the column by being installed in a stage in the reactive distillation column A or by being installed in the form of a packing. In the case of a transesterification catalyst that dissolves in the raw material or the reaction liquid, it is preferable to supply it into the distillation column from above the middle part of the distillation column.

[0029] The material constituting the reactive distillation column A is not particularly limited, but examples thereof include metal materials such as carbon steel and stainless steel. Among these, stainless steel is preferred.

[0030] [Conditions] The amount of transesterification catalyst varies depending on reaction conditions such as the type of transesterification catalyst used, the types and quantitative ratios of raw materials, reaction temperature, and reaction pressure, but is usually 0.0001 to 30% by mass, preferably 0.005 to 10% by mass, and more preferably 0.001 to 1% by mass, relative to the total mass of the raw materials.

[0031] The reaction time for the transesterification reaction is usually 0.1 to 10 hours, preferably 0.3 to 5 hours, and more preferably 0.5 to 3 hours.

[0032] The reaction temperature is usually 100 to 350° C., preferably 130 to 280° C., more preferably 150 to 260° C., and even more preferably 180 to 250° C. The reaction temperature means the temperature at the bottom of the column.

[0033] The reaction pressure is usually 0.1 to 2 × 10 ７ Pa, preferably 10 ５ ~10 ７ Pa, more preferably 2×10 ５ ~5 x 10 ６ The reaction pressure here means the pressure at the top of the column.

[0034] Fraction A separated by the reactive distillation process Ｕ is withdrawn from the upper part of column A, preferably from the top of column A. Ｕ is usually in gaseous form when withdrawn from column A. Ｕ Fraction A contains alkyl alcohols and dialkyl carbonates. Ｕ The total content of alkyl alcohol and dialkyl carbonate in fraction A may contain hydroxyaryl. Ｕ The alkyl alcohol content is preferably 40 to 90% by mass, more preferably 50 to 80% by mass, and even more preferably 60 to 70% by mass. Ｕ The dialkyl carbonate content is preferably 0.1 to 20 mass%, more preferably 1 to 15 mass%, and even more preferably 2 to 10 mass%. Ｕ The hydroxyaryl content is preferably 40 to 90 mass%, more preferably 50 to 80 mass%, and even more preferably 60 to 70 mass%. Ｕ The anisole content is preferably 10 to 60% by mass, more preferably 20 to 50% by mass, and even more preferably 25 to 40% by mass.Ｕ The content is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0035] Fraction A separated by the reactive distillation process Ｌ is withdrawn from the lower part of column A, preferably from the bottom of column A. Ｌ is usually in liquid form when withdrawn from column A. Ｌ The total content of hydroxyaryl, alkylaryl carbonate and diaryl carbonate in fraction A is 100%. Ｌ The alkyl aryl carbonate content in fraction A is preferably 30 to 90 mass%, more preferably 45 to 80 mass%, and even more preferably 55 to 70 mass%. Ｌ The diaryl carbonate content is preferably 1 to 40 mass%, more preferably 5 to 30 mass%, and even more preferably 10 to 20 mass%. Ｌ The hydroxyaryl content is preferably 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, and even more preferably 0.3 to 1% by mass. Ｌ The content is preferably 30 to 60% by mass, more preferably 40 to 50% by mass, and even more preferably 45 to 55% by mass.

[0036] In the method for producing a carbonate having an aryl group according to this embodiment, a carbonate having an aryl group including the alkylaryl carbonate and diaryl carbonate described above is produced. Ｌ may be further purified to increase the purity of the carbonate having an aryl group.

[0037] The content of carbonate having an aryl group is ＬThe mass ratio is preferably 1 to 40 mass%, more preferably 5 to 30 mass%, and even more preferably 10 to 20 mass%. When the objective is to obtain an alkylaryl carbonate among carbonates having an aryl group, the mass ratio of alkylaryl carbonate / diaryl carbonate is preferably 2 or more, more preferably 10 or more, and even more preferably 15 or more. The upper limit of the mass ratio of alkylaryl carbonate / diaryl carbonate is not particularly limited, but it may be, for example, 100 or less.

[0038] In the method according to this embodiment, fraction A Ｕ The liquid fraction containing hydroxyaryl as a main component is supplied as the extractant from the top of an extractive distillation column B, and in the extractive distillation step, the fraction containing alkyl alcohol and dialkyl carbonate is supplied as the mixture Bs from the bottom of the column B, and extractive distillation is performed to obtain a fraction B containing alkyl alcohol as a main component. Ｕ is withdrawn from the top of the column B, and a fraction B containing dialkyl carbonate and hydroxyaryl is withdrawn. Ｌ is preferably withdrawn from the bottom of the column B. By including such a step, the purification load of the fraction containing the by-produced alkyl alcohol and dialkyl carbonate can be further reduced. Specifically, the separation step can be realized by a distillation step and / or a condensation step (first condensation step and second condensation step) described below. The liquid fraction containing hydroxyaryl as a main component may be directly obtained in the condensation step and supplied from the bottom of the column B, or may be supplied from the bottom of the column B after undergoing a distillation step.

[0039] <Distillation Step> In the method according to this embodiment, the fraction A Ｕ is continuously fed into a continuous multi-stage distillation column C, and a fraction C containing alkyl alcohol and dialkyl carbonate is obtained. Ｕ and fraction C containing hydroxyaryl as the main component. ＬIn the case where the distillation step is included, the extractive distillation step preferably includes a distillation step of separating the fraction C into the fraction C. Ｕ is fed from the bottom of column B, and fraction C Ｌ is supplied as an extractant from the top of column B. By having this distillation step, fraction C containing hydroxyaryl as a main component can be obtained. Ｌ and using it as an extractant in the extractive distillation step, extractive distillation can be carried out at low temperature and low pressure without introducing an external hydroxyaryl, and the amount of dialkyl carbonate discharged together with the alkyl alcohol can be reduced while reducing the purification load.

[0040] As the continuous multi-stage distillation column C, the continuous multi-stage distillation column exemplified in the description of the reactive distillation column A above may be used.

[0041] [Conditions] The column bottom temperature in the distillation step is preferably 80 to 350°C, more preferably 90 to 280°C, and even more preferably 100 to 200°C.

[0042] The pressure at the top of the column in the distillation step is preferably 0.5 MPaG or less, more preferably 0.1 MPaG or less, and even more preferably 0.01 MPaG or less.

[0043] Fraction C separated by distillation process Ｕ is withdrawn from the top of column C, preferably from the top of column C. Ｕ is usually in gaseous form when withdrawn from column C. Ｕ Fraction C contains alkyl alcohols and dialkyl carbonates. Ｕ The total content of alkyl alcohol and dialkyl carbonate in fraction C may contain hydroxyaryl to reduce the load on the distillation process. Ｕ The alkyl alcohol content is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. ＵThe dialkyl carbonate content is preferably 0.1 to 20 mass%, more preferably 0.5 to 15 mass%, and even more preferably 1 to 10 mass%. Ｕ The hydroxyaryl content is preferably 40% by mass or more, more preferably 60% by mass or more, and even more preferably 80 to 95% by mass. Ｕ The content is preferably 1 to 40% by mass, more preferably 2 to 35% by mass, and even more preferably 3 to 20% by mass.

[0044] Fraction C separated by distillation process Ｌ is withdrawn from the bottom of column C, preferably from the bottom of column A. Ｌ is usually in liquid form when withdrawn from column C. Ｌ The main component of fraction C is hydroxyaryl. Ｌ Of these, the content is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0045] <Condensation Step> In the method according to this embodiment, prior to the distillation step, fraction A separated in column A is Ｕ A portion of the liquid fraction A is condensed. Ｕｌ and gas fraction A Ｕｇ a first condensation step of separating the gaseous fraction A into Ｕｇ In addition, when the first condensation step and the second condensation step are performed, fraction A is preferably further condensed. Ｕｌ is distilled and purified in column C, and fraction C Ｕ is fed as mixture Bs from the bottom of column B, and fraction C Ｌ is preferably fed as an extractant from the top of column B, and the condensed fraction A Ｕｇis preferably supplied as a mixture Bs from the bottom of the column B. The first condensation step and the second condensation step are carried out, for example, by a multi-stage concentrator D shown in FIG. 1 . By including the first condensation step and the second condensation step, the amount of the fraction introduced into the distillation step is reduced, and by previously fractionally condensing the fraction, aryl alkyl ethers and hydroxyaryls, which have boiling points higher than those of the alkyl alcohol and dialkyl carbonate, are preferentially condensed, and a liquid fraction A rich in aryl alkyl ethers and hydroxyaryls is obtained. Ｕｌ can be supplied to the continuous multi-stage distillation column C, thereby reducing the load on the distillation step.

[0046] <Extractive distillation step> In the method according to this embodiment, an extractant containing hydroxyaryl as a main component is supplied from the top of an extractive distillation column B, and a mixture Bs containing alkyl alcohol and dialkyl carbonate is supplied from the bottom of the column B, and extractive distillation is performed to obtain a fraction B containing alkyl alcohol as a main component. Ｕ is withdrawn from the top of column B, and fraction B containing dialkyl carbonate and hydroxyaryl is withdrawn. Ｌ The extractive distillation step includes an extractive distillation step in which fraction B is extracted from the bottom of column B. By including the extractive distillation step, it is possible to reduce the burden of purifying the by-produced alkyl alcohol and dialkyl carbonate. In the extractive distillation step, an extractant containing hydroxyaryl as the main component is used, and fraction B is extracted from the bottom of column B. Ｌ contains dialkyl carbonate and hydroxyaryl, and fraction B Ｌ can be used as the raw material for column A. The "mixture Bs" may contain alkyl alcohol and dialkyl carbonate, for example, fraction C Ｕ , fraction A Ｕｇ , supplementary raw material B Ｍ , and combinations thereof.

[0047] As the extractive distillation column B, the continuous multi-stage distillation column exemplified in the description of the reactive distillation column A above may be used.

[0048] In the extractive distillation step, column B has a distillation purification section above the extractant supply position, and fraction B ＵIt is preferable to extract the fraction B from above the distillation purification section. Ｕ The methanol concentration in the mixture can be increased.

[0049] The mixture Bs introduced into the column B contains alkyl alcohol and dialkyl carbonate. The mixture Bs is the fraction A separated in the column A. Ｕ The mixture Bs may be a supplementary raw material B containing the dialkyl carbonate that is insufficient in the column A. Ｍ may be introduced from the outside.

[0050] [Conditions] The column bottom temperature in the extractive distillation step is preferably 80 to 350°C, more preferably 90 to 280°C, and even more preferably 100 to 200°C. The column top temperature in the extractive distillation step is preferably 100°C or lower, more preferably 90°C or lower, and even more preferably 80°C or lower. The lower limit of the column top temperature is not particularly limited, but is equal to or higher than the boiling point of the alkyl alcohol, for example, 64°C or higher in the case of methanol.

[0051] The column top pressure in the extractive distillation step is preferably 0.5 MPaG or less, more preferably 0.1 MPaG or less, and even more preferably 0.01 MPaG or less.

[0052] Fraction B separated by the extractive distillation process Ｕ is withdrawn from the top of column B, preferably from the top of column B. Ｕ Fraction B is usually in gaseous form when withdrawn from column B. Ｕ Fraction B is mainly composed of alkyl alcohol. Ｕ Fraction B may contain dialkyl carbonate to reduce the load on the distillation process. Ｕ The dialkyl carbonate content in fraction B is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. Ｕ The content is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, and even more preferably 1 to 10% by mass.

[0053] Fraction B separated by the extractive distillation process Ｌ is withdrawn from the lower part of column B, preferably from the bottom of column B. Ｌ Fraction B is usually in liquid form when withdrawn from column B. Ｌ The total content of dialkyl carbonate and hydroxyaryl is 100%. Ｌ The dialkyl carbonate content in fraction B is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. Ｌ The hydroxyaryl content is preferably 30 to 90% by mass, more preferably 40 to 80% by mass, and even more preferably 50 to 70% by mass. Ｌ The alkyl alcohol content is preferably 10 to 60% by mass, more preferably 20 to 50% by mass, and even more preferably 30 to 40% by mass. Ｌ The content is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less.

[0054] In the method according to this embodiment, fraction B Ｌ The step of continuously supplying fraction B to column A is included. Ｌ However, the aryl group-containing carbonate can be efficiently produced by recycling it as a raw material for column A.

[0055] Examples of carbonates having an aryl group that can be obtained by the method according to this embodiment include diaryl carbonates and aryl alkyl carbonates, and more specifically, diphenyl carbonate and phenyl methyl carbonate.

[0056] The carbonates having these aryl groups are obtained from fraction A obtained in the reactive distillation step. Ｌ The purification method is not particularly limited, and can be carried out by a known method.

[0057] <Dialkyl Carbonate Production Process> In the method according to this embodiment, a raw material containing an alkylene carbonate and an alkyl alcohol is continuously supplied to a reactive distillation column G in which a transesterification catalyst is present, and reaction and distillation are simultaneously carried out in the column G, thereby obtaining a fraction G containing a dialkyl carbonate and an alkyl alcohol. Ｕ It is preferable to have a dialkyl carbonate production process in which fraction G is extracted from the top of column G. Ｕ It is preferable to introduce the fraction G into column B. Ｕ is introduced into column B and subjected to an extractive distillation process carried out in column B. Here, fraction G Ｕ By introducing into column B, the shortage of dialkyl carbonate can be compensated for, and transesterification in the reactive distillation step proceeds efficiently.

[0058] The alkyl alcohol used as a raw material in the dialkyl carbonate manufacturing process is fraction B in the extractive distillation process. Ｕ Thus, fraction B is preferably derived from Ｕ By recycling these as raw materials, resources can be used effectively.

[0059] In the method according to this embodiment, before the dialkyl carbonate production step, alkyl alcohol is decarbonated. ２ The alkyl alcohol is introduced into column H, and CO ２ When carbon dioxide is introduced into the transesterification reactor, the transesterification reaction is inhibited and the reaction rate decreases. By including this step, it is possible to prevent the reaction rate from decreasing. ２ In column H, fraction B Ｕ It is preferable to introduce an alkyl alcohol by introducing the following.

[0060] A method having a dialkyl carbonate production step will be described using an example in which the apparatus shown in Figure 5 is used. Since the apparatus shown in Figure 5 is basically the same as the apparatus shown in Figure 1, the same symbols are used for the common components and their explanations will be omitted. In the apparatus shown in Figure 5, ２A column H and a reactive distillation column G are provided.

[0061] The raw materials in the dialkyl carbonate production process include alkylene carbonate and alkyl alcohol.

[0062] (Alkylene Carbonate) Examples of the alkylene carbonate include ethylene carbonate, propylene carbonate, etc. Among these, ethylene carbonate is preferred.

[0063] (Alkyl Alcohol) The alkyl alcohol may be, for example, an alkyl alcohol having 1 to 4 carbon atoms. Examples of the alkyl alcohol include methanol, ethanol, various propanols, various butanols, etc. Among these, methanol is preferred.

[0064] The mass ratio of alkyl alcohol / alkylene carbonate supplied as raw materials to the reactive distillation column G is preferably 1 to 7, more preferably 1.5 to 5, and even more preferably 2 to 4.

[0065] The transesterification catalyst used in the reactive distillation column G is a compound consisting of a mixture of an alkali metal and ethylene glycol. Furthermore, in this homogeneous catalyst, the mass ratio of the alkali metal to ethylene glycol (alkali metal / ethylene glycol) is 0.05 to 0.5, preferably 0.1 to 0.4, and more preferably 0.2 to 0.3. When the mass ratio of the alkali metal to ethylene glycol (alkali metal / ethylene glycol) is within the above range, the production of dialkyl carbonate and diols can be promoted while the production of impurities can be suppressed. Furthermore, the catalyst concentration (in terms of alkali metal concentration) relative to the cyclic carbonate (e.g., ethylene carbonate (EC)) supplied to the reactive distillation column G is 0.05 to 2.0% by mass. The alkali metal is not particularly limited, but examples include lithium, potassium, sodium, and cesium, with potassium and sodium being preferred.

[0066] As the reactive distillation column G, the continuous multi-stage distillation column exemplified in the description of the reactive distillation column A above may be used.

[0067] [Conditions] The amount of transesterification catalyst varies depending on reaction conditions such as the type of transesterification catalyst used, the types and quantitative ratios of raw materials, reaction temperature, and reaction pressure, but is usually 0.0001 to 30% by mass, preferably 0.005 to 10% by mass, and more preferably 0.001 to 5% by mass, relative to the total mass of the raw materials.

[0068] The reaction time for the transesterification reaction is usually 0.1 to 20 hours, preferably 0.5 to 15 hours, and more preferably 1 to 10 hours.

[0069] The reaction temperature is usually 40 to 250° C., preferably 50 to 200° C., more preferably 60 to 150° C., and even more preferably 70 to 130° C. The reaction temperature means the temperature at the bottom of the column.

[0070] The reaction pressure is usually 1 to 2 × 10 ６ Pa, preferably 10 ３ ~10 ６ Pa, more preferably 10 ４ ~5 x 10 ５ The reaction pressure here means the pressure at the top of the column.

[0071] Fraction G separated by the dialkyl carbonate production process Ｕ is withdrawn from the top of column G, preferably from the top of column G. Ｕ is typically in gaseous form when withdrawn from column G.

[0072] Fraction G Ｕ comprises a dialkyl carbonate and an alkyl alcohol.

[0073] The total content of dialkyl carbonate and alkyl alcohol is Ｕ The dialkyl carbonate content is preferably 90 to 100 mass%, more preferably 95 to 100 mass%, and even more preferably 98 to 100 mass%. Ｕ The alkyl alcohol content is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, and even more preferably 50 to 60% by mass.Ｕ Of these, the content is preferably 30 to 90% by mass, more preferably 40 to 80% by mass, and even more preferably 50 to 70% by mass.

[0074] Fraction G separated by the dialkyl carbonate production process Ｌ is withdrawn from the lower part of the column G, preferably from the bottom of the column G. Ｌ is usually in liquid form when withdrawn from column G. Ｌ The alkylene diol is an alkyl dialcohol derived from alkylene carbonate produced by transesterification of alkylene carbonate with alkyl alcohol. The alkylene diol content is determined by the following formula: Ｌ The content is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more.

[0075] The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to the following examples.

[0076] Example 1 In Example 1, the apparatus shown in Figure 1 was used. The reactive distillation column A had an inner diameter of 5000 mm and was packed with a perforated tray (cross-sectional area per hole = approximately 1.5 cm ２ , Number of holes = approximately 250 pieces / m ２ ), the number of trays was 80, and the raw materials shown in Table 1 were fed from the top of the column, fraction B Ｌ The fraction A was introduced from the bottom of the column. A two-stage condenser was used as the multi-stage concentrator D. The continuous multi-stage distillation column C had an inner diameter of 1100 mm, structured packing (Melapack) and 10 theoretical plates. Ｕｌ The extractive distillation column B had an inner diameter of 2100 mm, structured packing (Melapac), and 40 theoretical plates. Ｌ The 17th theoretical plate from the top is the mixture Bs, and the fraction A is Ｕｇ and fraction C Ｕ The theoretical plate is the 29th plate from the top, and supplementary raw material B Ｍ was introduced from the 36th theoretical plate from the top of column A.Ｕ is the fraction A which has been partially condensed by 8.5 wt% in the first stage of the multi-stage concentrator D and turned into a liquid. Ｕｌ The remaining fraction is condensed in the second stage to form a liquid fraction A. Ｕｇ Fraction A Ｕｌ is continuously separated by distillation in column C at a column top pressure of 0 MPaG, a column bottom temperature of 185°C, a column top temperature of 88°C, and a reflux ratio of 1.2, and fraction C is obtained from the column top. Ｕ , fraction C from the bottom of the column Ｌ Fraction C was continuously withdrawn. Ｌ is supplied from the top of column B as an extraction solvent, and fraction A Ｕｇ and fraction C Ｕ was fed from the bottom of tower B. On the other hand, in order to make up for the shortage of dimethyl carbonate in tower A, supplementary raw material B Ｍ The column B was continuously separated by distillation at a column top pressure of 0 MPaG, a column bottom temperature of 120°C, a column top temperature of 64°C, and a reflux ratio of 2.0. Ｕ , fraction B from the bottom of the column Ｌ Fraction B was continuously withdrawn. Ｌ Fraction B had almost the same composition as the feedstock for column A and was recycled as the feedstock. Ｕ was used as a raw material for reacting with ethylene carbonate to produce dimethyl carbonate and ethylene glycol. The energy consumption in reboiler B1 of column B was 3200 Mcal / h, and the energy consumption in reboiler C1 of column C was 330 Mcal / h.

[0077] In Example 2, the apparatus shown in Figure 3 was used. In this example, the equipment configurations of towers A and C were the same as in Example 1, and tower B had an inner diameter of 2700 mm, structured packing (Melapack) as the packing, and the number of theoretical plates was 24. Fraction C was used as the extractant. Ｌ The first theoretical plate is the mixture Bs, and the fraction A is the mixture Bs. Ｕｇ and fraction C Ｕ The theoretical plate is the 13th plate from the top, and supplementary raw material B Ｍ was introduced from the 20th theoretical plate from the top of column A. Ｕ is the fraction A which has been partially condensed by 8.5 wt% in the first stage of the multi-stage concentrator D and turned into a liquid. ＵｌThe remaining fraction is condensed in the second stage to form a liquid fraction A. Ｕｇ Fraction A Ｕｌ is continuously separated by distillation in column C at a column top pressure of 0 MPaG, a column bottom temperature of 185°C, a column top temperature of 88°C, and a reflux ratio of 1.2, and fraction C is obtained from the column top. Ｕ , fraction C from the bottom of the column Ｌ Fraction C was continuously withdrawn. Ｌ is supplied from the top of column B as an extraction solvent, and fraction A Ｕｇ and fraction C Ｕ was fed from the bottom of tower B. On the other hand, in order to make up for the shortage of dimethyl carbonate in tower A, supplementary raw material B Ｍ The column B was continuously separated by distillation at a column top pressure of 0 MPaG, a column bottom temperature of 119°C, a column top temperature of 67°C, and a reflux ratio of 5.5. Ｕ , fraction B from the bottom of the column Ｌ Fraction B was continuously withdrawn. Ｌ Fraction B had almost the same composition as the feedstock for column A, and was recycled as the feedstock. Ｕ After further distillation purification to remove high-boiling components such as anisole, phenol, and methyl phenyl carbonate, the crude oil was reacted with ethylene carbonate to produce dimethyl carbonate and ethylene glycol. The energy consumption in the reboiler B1 of column B was 5,800 Mcal / h, and the energy consumption in the reboiler C1 of column C was 300 Mcal / h.

[0078] [Example 3] In Example 3, the apparatus shown in Figure 4 was used. The apparatus used in this example did not have the multi-stage concentrator D, and the column A had the same configuration as in Example 1. The column C had an inner diameter of 4000 mm in the concentrating section and 1100 mm in the stripping section, and the packing was structured packing (Melapack). The theoretical number of plates was 10. Ｕ The column B had an inner diameter of 2500 mm, structured packing (Melapack), and 40 theoretical plates. Ｌ The 17th theoretical plate from the top is the mixture Bs, and the fraction C Ｕ The theoretical plate is the 29th plate from the top, and supplementary raw material B Ｍwas introduced from the 36th theoretical plate from the top of column A. Ｕ is continuously separated by distillation in column C at a column top pressure of 0 MPaG, a column bottom temperature of 189°C, a column top temperature of 97°C, and a reflux ratio of 0.3, and fraction C is obtained from the column top. Ｕ , fraction C from the bottom of the column Ｌ Fraction C was continuously withdrawn. Ｌ is supplied from the top of column B as an extraction solvent, and fraction C Ｕ was fed from the bottom of tower B. On the other hand, in order to make up for the shortage of dimethyl carbonate in tower A, supplementary raw material B Ｍ The column B was continuously separated by distillation at a column top pressure of 0 MPaG, a column bottom temperature of 120°C, a column top temperature of 64°C, and a reflux ratio of 1.1. Ｕ , fraction B from the bottom of the column Ｌ Fraction B was continuously withdrawn. Ｌ Fraction B had almost the same composition as the feedstock for column A, and was recycled as the feedstock. Ｕ was used as a raw material for reacting with ethylene carbonate to produce dimethyl carbonate and ethylene glycol. The energy consumption in reboiler B1 of column B was 4700 Mcal / h, and the energy consumption in reboiler C1 of column C was 620 Mcal / h.

[0079] [Example 4] In Example 4, the apparatus shown in Figure 5 was used. The apparatus configuration of the reactive distillation column A was the same as in Example 1. The continuous multi-stage distillation column C had an inner diameter of 1400 mm, structured packing (Melapack), and 10 theoretical plates. Ｕｌ The extractive distillation column B had an inner diameter of 3500 mm, structured packing (Melapack), and 40 theoretical plates. Ｌ The 17th theoretical plate from the top is the mixture Bs, and the fraction A is Ｕｇ and fraction C Ｕ The theoretical plate is the 29th plate from the top, and supplementary raw material B Ｍ was introduced from the 36th theoretical plate from the top of column A. Ｕis the fraction A which has been partially condensed by 19 wt% in the first stage of the multi-stage concentrator D and turned into a liquid. Ｕｌ The remaining fraction is condensed in the second stage to form a liquid fraction A. Ｕｇ Fraction A Ｕｌ is continuously separated by distillation in column C at a column top pressure of 0 MPaG, a column bottom temperature of 185°C, a column top temperature of 86°C, and a reflux ratio of 1.2, and fraction C is obtained from the column top. Ｕ , fraction C from the bottom of the column Ｌ Fraction C was continuously withdrawn. Ｌ is supplied from the top of the extractive distillation column as an extracting solvent, and fraction A Ｕｇ and fraction C Ｕ was supplied from the bottom of the extractive distillation column. Meanwhile, in order to make up for the dimethyl carbonate shortage in column A, ethylene carbonate and methanol were used as raw materials and reacted in reactive distillation column G, where a transesterification catalyst was present. The resulting fraction containing dimethyl carbonate and methanol was supplied as supplementary raw material B. Ｍ The fraction was fed from the bottom of column B. In column B, continuous distillation separation was carried out at a column top pressure of 0 MPaG, a column bottom temperature of 120°C, a column top temperature of 64°C, and a reflux ratio of 1.4, and fraction B was fed from the top of the column. Ｕ , fraction B from the bottom of the column Ｌ Fraction B was continuously withdrawn. Ｌ Fraction B had almost the same composition as the feedstock for column A and was recycled as the feedstock. Ｕ was used as a raw material for reacting with ethylene carbonate to produce dimethyl carbonate and ethylene glycol. The energy consumption in reboiler B1 of column B was 9800 Mcal / h, and the energy consumption in reboiler C1 of column C was 760 Mcal / h.

[0080]

[0081] Comparative Example 1 In Comparative Example 1, the apparatus shown in Figure 6 was used. The apparatus configuration of the reactive distillation column A was the same as in Example 1. The continuous multi-stage distillation column K had an inner diameter of 1200 mm in the enrichment section and 1800 mm in the stripping section, and the packing was a perforated tray (cross-sectional area per hole = approximately 1.3 cm ２ , Number of holes = approximately 550 pieces / m ２ ), the number of trays was 55 in the concentration section and 16 in the stripping section, and fraction A ＵThe tray is the 55th tray from the top, and the supplementary material B Ｍ was introduced from the 63rd tray from the top of the column. Ｕ was totally condensed to a liquid by condenser J and continuously fed to column K. On the other hand, in order to make up for the shortage of dimethyl carbonate in column A, supplementary raw material B was Ｍ The column K was continuously separated by distillation at a column top pressure of 0.98 MPaG, a column bottom temperature of 227°C, a column top temperature of 140°C, and a reflux ratio of 3.0. Ｕ , fraction K from the bottom of the column Ｌ The fractions K and K were continuously withdrawn. Ｌ The composition of fraction K was almost the same as that of the feed to column A, and this fraction was recycled and reused as the feed. Ｕ was used as a raw material for reacting with ethylene carbonate to produce dimethyl carbonate and ethylene glycol. The energy consumption in the reboiler K1 of column K was 4300 Mcal / h.

[0082] [Comparative Example 2] In Comparative Example 2, the apparatus shown in Figure 7 was used. The apparatus configuration of reactive distillation column A was the same as in Comparative Example 1. The apparatus configuration of continuous multi-stage distillation column K was the same as in Comparative Example 1 except for the concentration section of 2700 mm and the stripping section of 3200 mm. Fraction A continuously extracted as a gas from the top of column A was Ｕ was totally condensed to a liquid by condenser J and continuously supplied to column K. On the other hand, in order to make up for the dimethyl carbonate shortage in column A, ethylene carbonate and methanol were used as raw materials and reacted in reactive distillation column G in the presence of an ester exchange reaction catalyst, and the resulting fraction containing dimethyl carbonate and methanol was fed to supplementary raw material B. Ｍ The fraction K was continuously separated by distillation at a column top pressure of 0.98 MPaG, a column bottom temperature of 227°C, a column top temperature of 140°C, and a reflux ratio of 3.0. Ｕ , fraction K from the bottom of the column Ｌ The fractions K and K were continuously withdrawn. Ｌ The composition of fraction K was almost the same as that of the feed to column A, and this fraction was recycled and reused as the feed. Ｕwas used as a raw material for reacting with ethylene carbonate to produce dimethyl carbonate and ethylene glycol. The energy consumption in the reboiler K1 of column K was 12,000 Mcal / h.

[0083]

[0084] A Reactive distillation column B Extractive distillation column C Continuous multi-stage distillation column D Multi-stage concentrator E, F Concentrator G Reactive distillation column H CO2 removal ２ Tower A1, B1, C1 Reboiler

Claims

1. A method for producing a carbonate having an aryl group, comprising continuously supplying a raw material containing a dialkyl carbonate and a hydroxyaryl to a reactive distillation column A in which a transesterification catalyst is present, and simultaneously carrying out reaction and distillation in the column A to obtain a fraction A containing an alkyl alcohol and a dialkyl carbonate. Ｕ is continuously withdrawn from the top of the column A, and a fraction A containing hydroxyaryl, alkylaryl carbonate and diaryl carbonate is obtained. Ｌ A reactive distillation step in which an extractant mainly composed of hydroxyaryl is supplied from the top of an extractive distillation column B, and a mixture containing alkyl alcohol and dialkyl carbonate is supplied from the bottom of the column B to perform extractive distillation, thereby obtaining a fraction B mainly composed of alkyl alcohol. Ｕ is withdrawn from the top of the column B, and a fraction B containing dialkyl carbonate and hydroxyaryl is withdrawn. Ｌ from the bottom of said column B; and Ｌ to said column A.

2. The fraction A Ｕ 2. The method according to claim 1, further comprising a step of separating the hydroxyaryl-based distillate from the extractive distillation column B into a liquid fraction mainly composed of hydroxyaryl and a fraction containing alkyl alcohol and dialkyl carbonate, wherein the liquid fraction mainly composed of hydroxyaryl is supplied as the extractant from an upper portion of an extractive distillation column B, and in the extractive distillation step, the fraction containing alkyl alcohol and dialkyl carbonate is supplied as the mixture from a lower portion of the column B.

3. The fraction B Ｌ The method according to claim 1, wherein the total content of the dialkyl carbonate and the hydroxyaryl in the above formula (1) is 80 mass% or more.

4. The fraction B Ｌ The method according to claim 1, wherein the content of the alkyl alcohol in the above is 10% by mass or less.

5. The method according to claim 1, wherein the top pressure of the column B is 0.5 MPaG or less.

6. The method according to claim 1, wherein the top temperature of said column B is 100° C. or less.

7. The method of claim 1, wherein the dialkyl carbonate is dimethyl carbonate.

8. In the extractive distillation step, the mixture is separated in the column A into the fraction A. Ｕ The method according to any one of claims 1 to 7, wherein the product is derived from 9. The fraction A Ｕ is continuously fed into a continuous multi-stage distillation column C, and a fraction C containing an alkyl alcohol and a dialkyl carbonate is obtained. Ｕ and fraction C mainly composed of hydroxyaryl. Ｌ In the extractive distillation step, the fraction C is separated into Ｕ is supplied as the mixture from the bottom of the column B, and the fraction C is Ｌ is fed as the extractant from the top of column B.

10. The fraction A separated in the column A Ｕ A part of the liquid fraction A is condensed. Ｕｌ and gas fraction A Ｕｇ a first condensation step of separating the gaseous fraction A into Ｕｇ A second condensation step of further condensing the fraction A. Ｕｌ is distilled and purified in the column C, and the fraction C Ｕ is supplied as the mixture from the bottom of the column B, and the fraction C is Ｌ is supplied as the extractant from the top of the column B, and the condensed fraction A is Ｕｇ is fed as said mixture from the bottom of said column B.

11. In the extractive distillation step, the column B has a distillation purification section above the supply position of the extractant, and the fraction B Ｕ The method according to any one of claims 1 to 7, wherein the distillation purification section is separated from the above-mentioned distillation purification section.

12. A raw material containing an alkylene carbonate and an alkyl alcohol is continuously fed into a reactive distillation column G in which an ester exchange reaction catalyst is present, and reaction and distillation are simultaneously carried out in the column G to obtain a fraction G containing a dialkyl carbonate and an alkyl alcohol. Ｕ from the top of the column G; Ｕ The process according to any one of claims 1 to 7, wherein the first and second columns are introduced into column B.

13. The alkyl alcohol used as a raw material in the dialkyl carbonate production process is the fraction B. Ｕ The method of claim 12, wherein the

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