JPH04230242A - Continuous production of diaryl carbonate - Google Patents

Abstract

PURPOSE:To continuously produce a diaryl carbonate and a dialkyl carbonate from an alkyl aryl carbonate in high yield and selectivity. CONSTITUTION:An alkyl aryl carbonate is supplied to a continuous multistage distillation column, the liquid flowing down in the column is extracted and introduced to an outer reactor, the obtained reaction liquid is introduced to a stage above the extraction stage to effect the distillation of the liquid under circulation and the objective diaryl carbonate is continuously extracted from the bottom of the column.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous process for producing diaryl carbonates. More specifically, the present invention relates to a method for continuously producing diaryl carbonate and dialkyl carbonate from alkylaryl carbonate.

0002

BACKGROUND OF THE INVENTION The production of diaryl carbonates and dialkyl carbonates from alkylaryl carbonates is well known. For example, when one type of alkylaryl carbonate represented by RO(CO)OAr (R represents an alkyl group and Ar represents an aryl group) is used as the alkylaryl carbonate, the reaction is as shown in Chemical formula 1. This is an intramolecular transesterification reaction (disproportionation reaction).

0003

[Chemical formula 1]

Of course, if two types of alkylaryl carbonates are used, the corresponding diaryl carbonate and dialkyl carbonate can be obtained in addition to the disproportionation reaction. However, this reaction is an equilibrium reaction, and in addition to the fact that the equilibrium is biased toward the original system, the reaction rate is slow, so it takes a lot of effort to industrially produce diaryl carbonates using this method. It was fraught with difficulties.

Several proposals have been made to improve this, most of which concern the development of catalysts to increase the reaction rate. Such catalysts include, for example, catalyst compositions selected from Lewis acids and transition metal compounds capable of generating Lewis acids [JP-A-51-75
No. 044 (West German Patent Publication No. 2552907,
U.S. Pat. No. 4,045,464)], polymeric tin compound [JP-A-60-169444 (U.S. Pat. No. 4,554,110)], general formula R-X (=O)
A compound represented by OH (wherein X is selected from Sn and Ti, and R is selected from monovalent hydrocarbon oxy groups) [
JP-A-60-169445 (U.S. Patent No. 4552)
704 specification)], a mixture of Lewis acid and protonic acid [
JP-A-60-173016 (U.S. Patent No. 4609)
501 specification)], lead (JP-A-1-93560), titanium and zirconium compounds (JP-A-1-2650)
62), tin compounds (Japanese Unexamined Patent Publication No. 1-265063), compounds of Sc, Mo, Mn, Bi, Te, etc. (Japanese Unexamined Patent Application No. 1-265064).

[0006] Among the above-mentioned inventions proposed so far, a preferred reaction method is to separate the dialkyl carbonate produced as a by-product from the reaction from the raw materials, products, or coexisting solvents. It is also known to use a device in which a column having a distillation or fractional distillation function is added to the upper part of the reactor in order to remove the water by distillation.
Examples of JP-A-169444 (U.S. Pat. No. 4,554,110), Examples of JP-A-60-169445 (U.S. Pat. No. 4,552,704), JP-A-6
0-173016 (U.S. Pat. No. 4,609,501), JP-A-51-75044].

However, in these methods,
In either case, it is clear that the reaction takes place only in the reactor where the catalyst is present. It is also clear that the distillation column section provided at the top of the reactor is used to separate the dialkyl carbonates produced in the reactor from other components present in the reactor. In other words, the reactive distillation method in these previous methods uses an apparatus in which a reaction part and a distillation part exist separately, and the distillation column part only performs distillation and does not perform any reaction. This is the method to do so. In these methods, the reaction is carried out in the liquid phase in the reactor, but it is not until the by-produced low-boiling dialkyl carbonates are extracted from the liquid phase into the gas phase via the gas-liquid interface. The reaction equilibrium shifts toward the production system, and the reaction progresses. However, the reactors used in these methods are tank-type and the gas-liquid interface area is as small as the cross-sectional area of the reactor, so it is known that the reaction is slow. For example, in the example of JP-A-51-75044, the reaction is carried out in a batchwise manner over a period of 4 hours.

However, it is also known that alkylaryl carbonates, which are raw materials, easily produce alkylaryl ethers through decarboxylation. In fact, in the examples of JP-A-51-75044 mentioned above, it is described that phenylethyl ether and anisole are produced as by-products, and the long-time reaction leads to side reactions of the alkylaryl carbonate products. This is undesirable because it causes Therefore, conventional reaction methods have problems in that the reaction rate is substantially low and that the products undergo side reactions.

[0009] In the embodiments of the above-mentioned patents that have been proposed so far, a batch method is used in which the raw material alkylaryl carbonate and the catalyst are initially charged in a reactor and then reacted. Therefore, no continuous reaction system has been disclosed so far in which alkylaryl carbonate is continuously supplied to a reactor and products and catalysts are continuously extracted.

0010

[Problems to be Solved by the Invention] The present invention is capable of continuously producing diaryl carbonates at high reaction rate and high selectivity, without the drawbacks of the methods proposed so far. This was done with the purpose of providing a method to do so.

[0011]

[Means for Solving the Problems] In producing diaryl carbonate and dialkyl carbonate from alkylaryl carbonate in the presence of a catalyst, the present inventors conducted a reaction using a continuous multi-stage distillation column equipped with an external reactor. The present inventors have discovered that a method of conducting distillation and distillation is an excellent method that can easily achieve the above object, and based on this knowledge, they have completed the present invention.

That is, in producing diaryl carbonate and dialkyl carbonate from alkylaryl carbonate in the presence of a catalyst, the alkylaryl carbonate as a raw material compound is continuously fed into a continuous multi-stage distillation column. , the liquid flowing down inside the column is extracted from a side outlet provided in the middle stage and/or the lowest stage of the distillation column, and after being introduced into a reactor provided outside the distillation column and reacted, the liquid is removed from the outlet. Circulating it to the distillation column by introducing it into a stage higher than a certain stage,
While reacting in the reactor or both in the reactor and in the distillation column, dialkyl carbonate as a by-product is continuously extracted in gaseous form by distillation, and the resulting diaryl carbonate is continuously extracted in liquid form from the bottom of the column. This is a continuous production method for diaryl carbonate, which is characterized by the continuous extraction of diaryl carbonate.

The alkylaryl carbonate used as a raw material compound in the present invention is represented by the following formula.

[0014]

[Case 2]

In the present invention, the dialkyl carbonate produced as a by-product is extracted in gaseous form, and the product diaryl carbonate is extracted in liquid form from the bottom of the column. Therefore, the alkylaryl carbonates used in the present invention are those in which the boiling point of the by-produced dialkyl carbonates is lower than the boiling point of the product diaryl carbonates.

For example, methylphenyl carbonate, ethylphenyl carbonate, propylphenyl carbonate (various isomers), methyltolyl carbonate (various isomers), ethyltolyl carbonate (various isomers)
, propylphenyl carbonate (various isomers), propyltolyl carbonate (various isomers), butylphenyl carbonate (various isomers), methylxylyl carbonate (various isomers), ethylxylyl carbonate (
various isomers), benzyl xylyl carbonate, methyl (hydroxyphenyl) carbonate (various isomers),
Ethyl (hydroxyphenyl) carbonate (various isomers), methoxycarbonyloxybiphenyl (various isomers), methyl (hydroxybiphenyl) carbonate (
various isomers), methyl-2-(hydroxyphenyl)propylphenyl carbonate (various isomers), ethyl-
Examples include 2-(hydroxyphenyl)propylphenyl carbonate (various isomers), and preferably R1
is an alkyl group having 1 to 4 carbon atoms, and Ar1 is a mono- or divalent aromatic group having 6 to 10 carbon atoms, and more preferably methylphenyl carbonate is used. These alkylaryl carbonates can be used alone or as a mixture. Cross-reaction products may also be produced when mixtures are used as raw materials.

The diaryl carbonate referred to in the present invention is an alkylaryl carbonate in which one alkyl group is substituted with an aromatic group, and is represented by the following formula.

[0018]

[Chemical formula 3]

For example, diphenyl carbonate, ditolyl carbonate (various isomers), phenyltolyl carbonate (various isomers), di(ethylphenyl) carbonate (various isomers), phenyl (ethylphenyl) carbonate (various isomers), dinaphthyl carbonate (various isomers), di(hydroxyphenyl) carbonate (
various isomers), di[2-(hydroxyphenylpropyl)phenyl]carbonate (various isomers), and the like.

The dialkyl carbonate referred to in the present invention is represented by the following formula.

[0021]

[C4]

For example, dimethyl carbonate, diethyl carbonate, dipropyl carbonate (various isomers)
, dibutyl carbonate (various isomers), dihexyl carbonate (various isomers), diheptyl carbonate (
various isomers), dicyclopentyl carbonate, dicyclohexyl carbonate, ethyl methyl carbonate,
Examples include methylpropyl carbonate (various isomers), methylbutyl carbonate (various isomers), ethylpropyl carbonate (various isomers), ethylbutyl carbonate (various isomers), dibenzyl carbonate, and the like.

As the catalyst used in the present invention, any catalyst can be used as long as it can produce diaryl carbonates and dialkyl carbonates from alkylaryl carbonates. For example, (lead compounds) lead oxides such as PbO, PbO2, Pb3 O4; lead sulfides such as PbS, Pb2 S; Pb(OH)2
, Pb2 O2 (OH)2 and other lead hydroxides; Na2
PbO2, K2PbO2, NaHPbO2, K
Namarites such as HPbO2; Na2 PbO3,
Na2 H2PbO4 , K2 PbO3 , K2 [
Pb(OH)6], K4 PbO4, Ca2 Pb
Lead salts such as O4, CaPbO3, etc.; PbCO3
,2PbCO3 ・Pb(OH)2 and other lead carbonates and their basic salts; Bu4 Pb, Ph4 Pb, Bu
3 PbCl, Ph3 PbBr, Ph3 Pb (or Ph6 Pb2 ), Bu3 PbOH, Ph3 Pb
Organic lead compounds such as O (Bu is a butyl group, Ph is a phenyl group); Pb(OCH3)2, (CH3O
) Alkoxyleads such as Pb(OPh), Pb(OPh)2, aryloxyleads; Pb-Na, Pb-Ca,
Lead alloys such as Pb-Ba, Pb-Sn, Pb-Sb;
Hydrates of lead minerals such as baenite and senaenite, and hydrates of these lead compounds; (copper compounds) CuCl, CuCl2, CuBr, CuBr2, C
uI2, Cu(OAc)2, Cu(acac)2,
Copper oleate, Bu2 Cu, (CH3 O)2 Cu
, AgNO3 , AgBr, silver picrate, AgC6
H6ClO4 , Ag (bulbaren)3 NO3 , [
AuC≡CC(CH3)3]n[Cu[C7H
8) Salts and complexes of copper group metals such as Cl]4 (acac
represents an acetylacetone chelate ligand); (alkali metal complex) Li (acac), LiN (C
4 H9) Complexes of alkali metals such as 2; (complexes of zinc) Complexes of zinc such as Zn(acac)2; (complexes of cadmium) Complexes of cadmium such as Cd(acac)2; (compounds of iron group metals) Fe(C10H8)(CO)5
,Fe(CO)5 ,Fe(C4H6)(CO)
3, Co (mesitylene)2 (PEt2 Ph)2,
CoC5 F6 (CO)7 , Ni-π-C5 H5
Complexes of iron group metals such as NO and ferrocene; (Zirconium complexes) Zirconium complexes such as Zr(acac)4 and zirconocene; (Lewis acid compounds) AlX3, TiX3, TiX
4, VOX3, VX5, ZnX2, FeX3
, SnX4 , (where X is halogen, acetoxy group,
Lewis acids such as alkoxy groups and aryloxy groups) and transition metal compounds that generate Lewis acids; (organotin compounds) (CH3)3 SnOCOCH3
, (C2 H5 )3 SnOCOC6 H5 ,B
u3 SnOCOCH3 , Ph3 SnOCOCH3
,Bu2Sn(OCOCH3)2,Bu2Sn
(OCOC11H23)2 , Ph3 SnOCH3
, (C2 H5 )3 SnOPh, Bu2 Sn(O
CH3)2,Bu2Sn(OC2H5)2
,Bu2 Sn(OPh)2 ,Ph2 Sn(OCH
3)2,(C2H5)3SnOH,Ph3
SnOH, Bu2 SnO, (C8 H17)2 Sn
Organotin compounds such as O, Bu2 SnCl2, BuSnO(OH); (Solid catalyst) Solid catalysts such as silica, alumina, titania, silica titania, zinc oxide, zirconium oxide, gallium oxide, zeolite, rare earth oxides; Solid catalysts whose surface acid sites have been modified by methods such as silylation are used.

These catalysts may or may not be soluble in the reaction solution under the reaction conditions. Further, these catalysts can be used by being mixed with a compound or carrier that is inert to the reaction, or by being supported on these. Of course, these catalyst components may be reacted with organic compounds present in the reaction system, such as alkylaryl carbonates, diaryl carbonates, dialkyl carbonates, etc., or they may be reacted with raw materials or products prior to the reaction. It may be heat-treated.

Preferably, PbO, PbO2, Pb3
Lead oxides such as O4; Pb(OH)2, Pb2 O
2 Lead hydroxides such as (OH)2; PbCO3, 2P
bCO3 ・Pb(OH)2 and other lead carbonates and their basic salts; Pb(OCH3)2, (CH3O)
These are lead compounds such as alkoxyleads such as Pb(OPh) and Pb(OPh)2, and aryloxyleads, as well as those obtained by reacting these lead compounds with organic compounds present in the reaction system. It is also preferable to use a lead compound that has been heat-treated with a raw material or product prior to the reaction.

The continuous multi-stage distillation column used in the present invention is:
A distillation column having multiple distillation stages of two or more stages,
Any type of distillation column may be used as long as it is capable of continuous distillation (the number of plates in a distillation column in the present invention refers to the number of plates in the case of a plate column; For other distillation columns, the number of theoretical plates is indicated.) Such continuous multi-stage distillation columns include, for example, plate column types using trays such as bubble bell trays, perforated plate trays, valve trays, and countercurrent trays, as well as those using Raschig rings, Lessing rings, Paul rings, Berl saddles, and inter-stage distillation columns. Any type of column that is normally used as a continuous multi-stage distillation column can be used, such as a packed column type packed with various types of packing such as Rocks saddle, Dixon packing, McMahon packing, Helipak, Sulzer packing, Melapak, etc. can do. Furthermore, a distillation column having both a tray section and a section filled with packing material is also preferably used. Furthermore, when a solid catalyst is used, a packed column type distillation column in which the solid catalyst is used as part or all of the packing is also preferably used.

In the method of the present invention, when reacting an alkylaryl carbonate in the presence of a catalyst to produce the corresponding diaryl carbonate, the alkylaryl carbonate is continuously fed into a continuous multi-stage distillation column, and the inside of the column is A part or most of the liquid flowing down was extracted from the side outlet provided in the middle stage and/or the bottom stage of the distillation column, and introduced into a reactor provided outside the distillation column to react. Afterwards, it is circulated to the distillation column by introducing it into the circulation inlet provided in the stage above the stage where the extraction port is located, and the water inside the reactor or inside the reactor and inside the distillation tower is circulated. While reacting in both, the dialkyl carbonate produced by the reaction is continuously extracted in gaseous form from the distillation column by distillation, and the diaryl carbonate produced is continuously extracted in liquid form from the bottom of the column. However, an arbitrary number of side outlet ports can be provided in the side of the continuous multi-stage distillation column between the intermediate stage and/or the bottom stage of the distillation column. Also,
Any number of circulation inlets may be provided as long as they are located above the corresponding side outlet. If multiple side outlet ports are provided, the liquid extracted from two or more different side outlet ports can be combined and introduced into the reactor, or if multiple reactors are used, two or more different side outlet ports may be combined. The reaction liquid taken out from the reactor can also be combined and then introduced to the circulation inlet. Also,
These can also be combined.

[0028] Preferably, when there are two or more reactors provided outside the continuous multi-stage distillation column, and the stages connected to the reactors and each provided with a liquid outlet from the distillation column are different from each other. More preferably, there are two or more reactors provided outside the continuous multistage distillation column, and the stages connected to the reactors are each provided with a liquid outlet from the distillation column, and This is the case when the stages of the circulation inlet provided in the distillation column for circulating from the reactor to the distillation column are different stages.

In the present invention, a reactor is provided between the side outlet of the continuous multi-stage distillation column and the circulation inlet to the distillation column, but this reactor may be of any flow type. For example, a tubular reactor, a stirred tank type flow reactor, etc. may be used. In the method of the present invention, it is necessary to have a catalyst present at least in these reactors, and in addition, it is also preferable to have a catalyst present inside the continuous multi-stage distillation column.

[0030] Any method may be used to make the catalyst present in the reactor or in the reaction system consisting of the reactor and the continuous multi-stage distillation column. In the case of a homogeneous catalyst that dissolves in the reactor and/or the distillation column, the catalyst can be present in the reaction system by continuously supplying the catalyst to the reactor and/or the distillation column, or the catalyst can be present in the reaction system under the reaction conditions. In the case of a heterogeneous catalyst that does not dissolve in the reaction system, the catalyst can be present in the reaction system by placing a solid catalyst in the reactor or both in the reactor and in the distillation column. For example, a solid catalyst may be placed in the reactor and/or the distillation column, and a homogeneous catalyst may also be used.

In the method of the present invention, a raw material compound consisting of an alkylaryl carbonate is continuously fed into a continuous multi-stage distillation column. A compound may be introduced into the distillation column as a reaction liquid. Further, the raw material compound can be introduced into any stage of the distillation column and/or any reactor through any number of inlets. The raw material compound is supplied as a liquid, a gas, or a gas-liquid mixture of a liquid and a gas.

In addition to continuously feeding the raw material compound into the continuous multi-stage distillation column and/or the reactor, the gaseous raw material compound may be intermittently or continuously supplied from the bottom of the distillation column. Supplying is also a preferred method. These feedstocks may contain dialkyl carbonate or diaryl carbonate products, but since this reaction is reversible, if the concentration of these products is too high, the reaction rate of the raw materials will decrease. This is not preferable because it lowers the

Although the reason why the method of the present invention exhibits higher yield and higher selectivity in a shorter reaction time than conventional techniques is not clear, it is presumed to be as follows. That is, although the reaction of the present invention is an equilibrium reaction as represented by Chemical Formula 1, the equilibrium is extremely biased toward the original system. Therefore, in order to increase the reaction rate of raw materials, the dialkyl carbonate (Chemical formula 5) produced as a result of the reaction is usually evaporated from the reaction solution into the gas phase, so that the concentration of dialkyl carbonate in the reaction solution is reduced to the equilibrium concentration. It is necessary to make it as low as possible.

[0034]

[C5]

However, the reaction rate described in the prior art using a reaction vessel equipped with a distillation column was unable to increase the reaction rate. The reason for this is that the reaction site is not only limited to the part of the reaction vessel where the catalyst is present, but also that the gas-liquid interface area is large enough to evaporate the dialkyl carbonate produced by the reaction from the liquid in the reaction vessel to the gas phase. This is because it is small.

On the other hand, in the method of the present invention, part or most of the liquid to be reacted, which is continuously flowing down the continuous multi-stage distillation column, is provided in the middle stage and/or the lowest stage of the distillation column. A method in which the distillate is extracted from a side outlet, introduced into a reactor installed outside the distillation column, reacted, and then circulated to the distillation column by being introduced into a stage above the stage where the outlet is located. Therefore, the reaction mixture with increased product concentration leaving the reactor is introduced into a distillation column with a large gas-liquid interface area, and is repeatedly brought into contact with the vapor rising from below inside the distillation column. , the low-boiling point products in the reaction liquid can be efficiently evaporated into the vapor phase, and the concentration of the low-boiling point reaction products in the liquid mixture flowing down the distillation column can be efficiently reduced in a short time. As a result, diaryl carbonates can be obtained in high yields in a short time.

[0037] Furthermore, in a reaction method using a reaction vessel with a distillation column installed at the top, the reaction rate cannot be increased, so the residence time in the reaction vessel is long, and as a result, side reactions proceed and the selectivity is increased. However, according to the method of the present invention, it is possible to obtain a product in a short residence time, which is thought to increase the selectivity. In the present invention, the by-produced dialkyl carbonate is extracted in gaseous form. The gaseous extract may be dialkyl carbonate alone or may be a mixture with alkylaryl carbonate as a raw material. It may also contain a small amount of diaryl carbonates. The outlet for gas consisting of dialkyl carbonate, etc. in a continuous multi-stage distillation column can be provided at any position other than the bottom of the column, but the concentration of by-product dialkyl carbonate in the vapor phase is usually higher at the top of the column. . Therefore, it is preferable to provide a gas extraction port between the raw material supply position and the top of the tower or at the top of the tower, and more preferably at the top of the tower.

In the present invention, the product diaryl carbonates are extracted in liquid form from the bottom of a continuous multi-stage distillation column. The liquid extract may be an aromatic carbonate alone or may be a mixture with an alkylaryl carbonate as a raw material. It may also contain a small amount of dialkyl carbonate. When a homogeneous catalyst is used as a catalyst, the catalyst is contained in the liquid extract.

[0039] Further, an outlet for extracting a liquid consisting of diaryl carbonates, etc. from the distillation column is provided at the bottom of the column. In the present invention, the lower part of the column is usually between the raw material supply position and the column bottom, or the column bottom, and preferably the column bottom. In the present invention, the velocity of the flowing liquid and the rising vapor velocity in the distillation column vary depending on the type of distillation column used, and when a packed column is used, depending on the type of packing, but they are usually carried out within a range that does not cause flooding. be done.

[0040] In the present invention, part or most of the liquid flowing down the stage in the distillation column where the side outlet is provided is extracted from the side outlet provided at the middle stage and/or the lowest stage. and introduced into the reactor. The residence time in the reactor is usually 0.001 to 100 hours, preferably 0.001 to 100 hours.
．． The heating time is preferably 0.03 to 50 hours, more preferably 0.01 to 10 hours.

In the present invention, in addition to the reaction in the reactor, the reaction can also be carried out in a continuous multi-stage distillation column if necessary.
This is the preferred method. In this case, the amount of diaryl carbonate produced also depends on the amount of hold-up liquid in the distillation column. In other words, when using distillation columns with the same column height and column diameter, a distillation column with higher liquid holdup will have a longer average residence time of the reaction liquid inside the distillation column, that is, a longer reaction time inside the distillation column. preferable.

However, if the liquid holdup is too high, the residence time becomes long, making it easy for side reactions to proceed and flooding to occur. Therefore,
The amount of hold-up liquid in the distillation column used in the present invention may vary depending on the distillation conditions and the type of distillation column, but it is expressed as the volume ratio of the amount of hold-up liquid to the empty column volume of the distillation column.
Usually, it is carried out at 0.005 to 0.75. In the present invention, the residence time of the reaction solution in the distillation column may vary depending on the reaction conditions, but is usually 0.001 to 50 hours, preferably 0.01 to 10 hours.

In the present invention, increasing the reflux ratio increases the efficiency of distilling dialkyl carbonate into the vapor phase, so that the concentration of dialkyl carbonate in the vapor to be extracted can be increased. However, if the reflux ratio is increased too much, the required thermal energy becomes excessive, which is not preferable. Further, since the dialkyl carbonate can be concentrated after being extracted from the distillation column, it is not necessary to reflux the dialkyl carbonate. Therefore, the reflux ratio is usually 0 to
20 is used, preferably 0 to 10 is used.

[0044] In carrying out the present invention, the reaction temperature varies depending on the type of raw materials used, but is usually 50 to 350°C.
, preferably at a temperature of 100 to 250°C. Furthermore, when the reaction is carried out both in the reactor and in the distillation column, the reactions can be carried out at different reaction temperatures and reaction pressures. The reaction pressure varies depending on the type of raw materials used and the reaction temperature, but it may be reduced pressure, normal pressure, or increased pressure, and is usually 1 mmHg to 200 kg/cm2.
It will be held in

As described above, in the method of the present invention, since the reactor is provided outside the continuous multi-stage distillation column, reaction conditions of temperature and pressure different from the distillation conditions (temperature, pressure) can be adopted, and two reactors can be used. When the above-mentioned reactors are provided, each has a feature that different reaction conditions can be adopted. In the present invention, it is not necessary to use a solvent, but in order to facilitate the reaction operation, suitable inert solvents such as ethers, aliphatic hydrocarbons, aromatic hydrocarbons, halogenated Aliphatic hydrocarbons, halogenated aromatic hydrocarbons, etc. can be used as the reaction solvent.

In the present invention, an inert gas such as nitrogen, helium, or argon may be coexisting in the reaction system as a substance inert to the reaction. In addition, an inert gas or a low-boiling organic compound inert to the reaction may be supplied in gaseous form to the reactive distillation column for the purpose of accelerating the removal of by-product aliphatic alcohol. In the present invention, dialkyl carbonate and diaryl carbonate, which are reaction products, may be contained in the raw materials, but since this reaction is a reversible reaction, if the concentration of dialkyl carbonate or diaryl carbonate is too high, This is not preferable because it lowers the reaction rate of the raw materials. Therefore, usually, the amount of dialkyl carbonate and diaryl carbonate in the raw material is preferably 20 mol % or less, more preferably 10 mol % or less, based on the alkylaryl carbonate that is the raw material.

[0047] The amount of the catalyst used in the present invention may vary depending on the activity of the catalyst used, but when the catalyst is continuously fed to the reaction system, the amount of the catalyst used in the present invention is usually adjusted to Expressed as 0.
0001 to 50% by weight. In addition, when using a solid catalyst, it is usually 10 to 1
00%, preferably 50-100% by volume. Further, when a solid catalyst is installed inside the distillation column, the amount of catalyst used is 0.01 to 75% by volume based on the empty column volume of the distillation column.

[0048]

[Examples] The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. The catalyst concentration was analyzed using ICP [high-frequency inductively coupled plasma emission spectrometer (manufactured by Seiko Denshi Co., Ltd.)].

[0049]

[Example 1] 1 20 kg of phenol and 4 kg of lead monoxide
A catalyst (catalyst A) was prepared by heating at 80° C. for 10 hours and distilling off the produced water together with phenol. Diaryl carbonate was produced using an apparatus as shown in FIG. The number of reactors is four. Reactor A, B, C
, D, each had an internal volume of 0.5 liters, and each was filled with stainless steel Dixon patching (6 mmφ) as a filling material. Methylphenyl carbonate (MPC) and catalyst were placed 1 m from the top (17) of a continuous multi-stage distillation column consisting of a packed column with a column height of 4 m and a column diameter of 3 inches, packed with the same packing as that of the reactor. A mixture consisting of A was continuously supplied in liquid form from the raw material introduction pipe (2) via the preheater 5 and the raw material introduction pipe (6).

The liquid flowing down the distillation column was extracted from a side outlet provided at an intermediate stage of the distillation column, and then introduced into each reactor. The reaction proceeded in the reactor, and the reaction solution, in which the diaryl carbonate concentration and the dialkyl carbonate concentration were increased, was circulated to the distillation column from the circulation inlet. The concentration of dialkyl carbonate in the liquid flowing down the distillation column decreased as it came into contact with the vapor rising from the bottom of the distillation column toward the top. The amount of heat required for distillation was supplied by heating the bottom liquid in the reboiler (10). The gas distilled from the top (17) was condensed in a condenser (13) via a gas withdrawal conduit (12). A portion of the condensate was refluxed to the distillation column (1) via the inlet pipe (15), and the remainder was extracted through the degas conduit (16). A low-boiling component containing dimethyl carbonate, which is a low-boiling reaction product, was obtained from this condensate.

High-boiling components, including catalyst components and diphenyl carbonate (DPC), were also withdrawn from the bottom (18) via conduits (8) and (19). The conditions of the reaction and the results after steady state are shown in Tables 1 and 2. In the table, the amount of diaryl carbonate produced is expressed in grams per hour and per kilogram of tower bottom liquid. The selectivity of diaryl carbonate is expressed based on the alkylaryl carbonate of the raw material. Wt% represents weight%.

[0052]

Example 2 An apparatus as shown in FIG. 2 was used. There are 6 reactors, and instead of using a reboiler, methylphenyl carbonate (MPC) is introduced through the evaporator (9) and through the introduction tubes (3) and (7) to supply the amount of heat required for distillation. Other than the above, the reaction and distillation were carried out under the same conditions as in Example 1. The reaction conditions and the results after steady state are shown in Tables 1 and 2.

[0053]

[Example 3] γ-Alumina (manufactured by JGC Corporation, product number N611N
) was filled into a quartz glass cylinder (length 100 cm, diameter 10 cm), and then the cylinder was placed in a tube furnace. After purging with nitrogen, the γ-alumina was dried by heating at 200° C. for 5 hours. Next, 50 m of a benzene solution (20 wt%) of tetramethoxysilane was poured into the cylinder heated to 200°C.
γ-Alumina was treated by adding at a flow rate of 1/hr for 10 hours. A catalyst (catalyst B) was prepared by cooling in a nitrogen atmosphere.

Diaryl carbonate was produced by reaction and distillation in the same manner as in Example 1, except that catalyst B was used as the packing for reactors A, B, C, D and distillation column 1. The reaction conditions and the results after steady state are shown in Tables 1 and 2.

[0055]

[Comparative Example 1] A distillation column (63) with a column height of 1 m and a column diameter of 1 inch [filled with stainless steel Dickson packing (6 mmφ)] and an agitator (71) shown in FIG. liter autoclave reaction vessel (62
), 12.6 kg of liquid with the same composition as used in Example 1
was charged from the introduction tube (61). While stirring, pour the reaction vessel (
62) using an electric furnace (70) until the liquid temperature reaches 1.
The reaction was carried out at a constant temperature of 95°C. The gas distilled off from the top (69) of the distillation column (63) is passed through the conduit (64
) and then condensed in a condenser (65). A portion of the condensate was refluxed through the inlet pipe (67), and the remainder was continuously extracted from the conduit (68) at a rate of 1.0 kg/hr. The reflux ratio was 2.1. After the start of extraction, the reaction was carried out for 3 hours, and 3.0 kg of condensate was extracted. Reaction pot (62)
After cooling, the reaction liquid was taken out from the conduit (72), and its weight was 9.6 kg. The ratio of the amount of condensate drawn out and the amount of liquid drawn out from the reaction vessel in this comparative example is the same as the ratio of the amount of condensed liquid drawn out and the amount of bottom liquid drawn out in Example 1. Moreover, the distillation rate is also the same.

As a result of analysis, it was found that 66.8% by weight of diphenyl carbonate (DPC) was produced in the reaction solution. 1
Diphenyl carbonate (per kg of reaction solution per hour)
The production amount of DPC) was 219 g/kg/hr. The selectivity of diphenyl carbonate (DPC) based on methylphenyl carbonate was 95%. Furthermore, when the condensate was analyzed, anisole, a reaction by-product, was detected. The anisole selectivity based on methylphenyl carbonate was 5%. Comparing this result with Example 1, it is found that the method of the present invention yields diaryl carbonate (DP
It shows that C) can be obtained in high yield and high selectivity.

[0057]

[Table 1]

[0058]

[Table 2]

[0059]

According to the method of the present invention, diaryl carbonates can be obtained continuously in high yield and high selectivity using alkylaryl carbonate as a raw material.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an example process for implementing the invention.

FIG. 2 is a schematic diagram of an example process for implementing the invention.

FIG. 3 is a schematic diagram of a reaction apparatus used in Comparative Example 1.

[Explanation of symbols]

1
Continuous multistage distillation column 2, 3, 6, 7
Raw material introduction pipe 5

Preheater 8, 19
Bottom liquid extraction conduit 9
Distillation column 10

reboiler 11
Bottom liquid introduction pipe 12, 14, 16
Gas extraction conduit 13
Condenser 15

Condensate introduction pipe 17
Tower top 18

Tower bottom A, B, C, D, E, F
Reactor 20, 22, 24, 26
, 28, 30 Side outlet 21, 23, 25, 27, 29, 31 Circulation inlet 61
Raw material introduction pipe 62

Reaction pot 63
Distillation column 64, 66, 68
Distillate gas extraction conduit 65
condenser 67

Condensate introduction pipe 69
Tower top 70

Electric furnace 71
Stirrer 7
2
Reaction liquid extraction conduit

Claims (1)

[Claims] Claim 1: In producing diaryl carbonate and dialkyl carbonate from alkylaryl carbonate in the presence of a catalyst, the alkylaryl carbonate is continuously fed into a continuous multistage distillation column, and the liquid flowing down inside the column is It is extracted from a side outlet provided in the middle stage and/or the lowest stage of the distillation column, and introduced into a reactor provided outside the distillation column for reaction. The dialkyl carbonate produced by the reaction is circulated to the distillation column by introducing it into the circulation inlet provided in the reactor, or while reacting both in the reactor and in the distillation column. 1. A method for continuously producing diaryl carbonates, which comprises continuously extracting diaryl carbonate in gaseous form from the distillation column by distillation, and continuously extracting the produced diaryl carbonate in liquid form from the bottom of the column.