JPH0791235B2 - Continuous production method of diaryl carbonate - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a continuous process for producing diaryl carbonate. More specifically, it relates to a method for continuously producing a diaryl carbonate and a dialkyl carbonate from an alkylaryl carbonate.

[0002]

The production of diaryl carbonates and dialkyl carbonates from alkyl aryl carbonates is well known. For example, when using one kind of alkyl aryl carbonate represented by Chemical formula 1,
The reaction is an intramolecular transesterification reaction represented by Chemical formula 2, and can be said to be a disproportionation reaction.

[0003]

[Chemical 1] (R is an alkyl group, Ar is an aryl group)

[0004]

[Chemical 2]

Of course, when two or more kinds of alkylaryl carbonates are used, the corresponding diaryl carbonate can be obtained by an intermolecular transesterification reaction and an intramolecular transesterification reaction. However, since this reaction is an equilibrium reaction, and the equilibrium is biased toward the original system, and the reaction rate is slow, it is very difficult to industrially produce diaryl carbonates by this method. It was difficult. Several proposals have been made to improve this, most of which relate to catalyst development to increase the reaction rate. As such a catalyst, for example, a composition selected from a Lewis acid and a transition metal compound capable of generating a Lewis acid (JP-A-51-750).
44), polymeric tin compounds (JP-A-60-1).
No. 69444), a compound represented by the general formula R—X (═O) OH (wherein X is selected from Sn and Ti, and R is selected from a monovalent hydrocarbon oxy group) Sho 6
No. 0-169445), a physical mixture of at least one Lewis acid and at least one protonic acid (JP-A-60-173016), (JP-A-1-93356).
No. 0), tin compounds (JP-A 1-265063), compounds such as Sc, Mo, Mn, Bi, Te (JP-A 1-265064) and the like have been proposed.

Among the inventions proposed so far, the preferred reaction method is to separate the dialkyl carbonates by-produced by the reaction from the raw materials, products or coexisting solvents by distillation. Are known (Japanese Patent Laid-Open No. 169444/1985, Japanese Patent Laid-Open No.
No. 169445 and JP-A No. 60-173016), for that purpose, it is also known that a distillation column capable of refluxing is added to the reactor to carry out distillation while reacting (JP-A No. 5-5945).
1-75044).

However, in these methods,
In each case, it is clear that the reaction only takes place in the reactor in which 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 the other components present in the reactor.

That is, using a device in which a reaction part and a distillation part are present separately from the reactive distillation methods in these prior methods, only distillation is carried out in the distillation column part and no reaction is carried out at all. It is a method characterized by that. As described above, in these methods, the reaction is carried out in the liquid phase in the reactor, but the low boiling point dialkyl carbonate produced as a by-product is first extracted from the liquid phase to the gas phase through the gas-liquid interface. The equilibrium of the reaction shifts to the production system side, and the reaction proceeds.

However, the reactor used in these methods is of a tank type, and since the gas-liquid interface area is as small as the cross-sectional area of the reactor, it is known that the reaction is slow. There is. For example, in the example of JP-A-51-75044, the reaction is carried out in a batch reaction for 4 hours. However, it is also known that alkylaryl carbonates easily produce an alkylaryl ether by a decarboxylation reaction. In fact, it is described in the above-mentioned JP-A-51-75044 that phenylethyl ether and anisole are produced as by-products, and a long-term reaction is caused by a side reaction of the product diaryl carbonate. It is not preferable because it will happen.
Therefore, the conventional reaction method has problems that the reaction rate is substantially low and that the product undergoes a side reaction.

Further, in the examples of the above-mentioned patents which have been proposed so far, a batch system is used in which the alkylaryl carbonate and the catalyst are first reacted in the reactor as it is. Therefore, a continuous reaction system in which the alkylaryl carbonate is continuously fed to the reactor and the diaryl carbonate is continuously withdrawn has not been disclosed at all.

[0011]

DISCLOSURE OF THE INVENTION The present invention does not have such drawbacks of the methods proposed so far, and continuously produces a diaryl carbonate at a high reaction rate and a high selectivity. The purpose is to provide a method.

[0012]

DISCLOSURE OF THE INVENTION The present inventors have described a reactive distillation method in which a diaryl carbonate and a dialkyl carbonate are produced from an alkyl aryl carbonate in the presence of a catalyst, in which reaction is carried out in a continuous multistage distillation column. The inventors have found that the method is an excellent method that can easily achieve the object, and have completed the present invention based on this finding.

That is, according to the present invention, when a diaryl carbonate and a dialkyl carbonate are produced from an alkyl aryl carbonate in the presence of a catalyst, the alkyl aryl carbonate is continuously fed into a continuous multi-stage distillation column to perform continuous multi-stage distillation. While reacting by contacting with a catalyst in the column, by-product dialkyl carbonate is continuously withdrawn in a gaseous state by distillation, and the produced diaryl carbonate is continuously withdrawn in liquid form from the lower part of the column. Is a continuous manufacturing method of.

The alkylaryl carbonate used in the present invention is represented by Chemical formula 3.

[0015]

[Chemical 3] (R ¹ represents an alkyl group, an alicyclic group or an aralkyl group, and Ar ¹ represents a monovalent directional group.)

Such R ¹ is, for example, methyl,
Ethyl, propyl (each isomer), allyl, butyl (each isomer), butenyl (each isomer), pentyl (each isomer), hexyl (each isomer), heptyl (each isomer),
Alkyl groups such as octyl (each isomer), nonyl (each isomer), decyl (each isomer), cyclohexylmethyl;
Alicyclic groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl; benzyl,
Examples include aralkyl groups such as phenethyl (each isomer), phenylpropyl (each isomer), phenylbutyl (each isomer), and methylbenzyl (each isomer).

The alkyl group, alicyclic group and aralkyl group may be substituted with other substituents such as a lower alkyl group, a lower alkoxy group, a cyano group and a halogen atom, or an unsaturated bond may be formed. You may have. Examples of Ar ¹ include phenyl, tolyl (each isomer), xylyl (each isomer), trimethylphenyl (each isomer), tetramethylphenyl (each isomer), ethylphenyl (each isomer). ), Propylphenyl (each isomer), butylphenyl (each isomer), diethylphenyl (each isomer), methylethylphenyl (each isomer), pentylphenyl (each isomer), hexylphenyl (each isomer) , Cyclohexylphenyl (each isomer)
Such as phenyl groups and various alkylphenyl groups; various alkoxyphenyl groups such as methoxyphenyl (each isomer), ethoxyphenyl (each isomer), butoxyphenyl (each isomer); fluorophenyl (each isomer) ), Chlorophenyl (each isomer), bromophenyl (each isomer), chloro (methyl) phenyl (each isomer), dichlorophenyl (each isomer), and various halogenated phenyl groups; Phenyl groups; naphthyl (each isomer), methylnaphthyl (each isomer), dimethylnaphthyl (each isomer), chloronaphthyl (each isomer),
Naphthyl groups such as methoxynaphthyl (each isomer), cyanonaphthyl (each isomer) and various substituted naphthyl groups; pyridyl (each isomer), coumaryl (each isomer), quinolyl (each isomer), methylpyridyl ( Each isomer), chloropyridyl (each isomer), methylcoumaryl (each isomer), methylquinolyl (each isomer), and various substituted and unsubstituted heteroaromatics.

[0018]

[Chemical 4] [However, A is a mere bond, or -O-, -S-, -C
O -, - SO ₂ - ₂ divalent group such as or Alkylene groups or substituted alkylene groups such as R ⁴ ,
R ⁵ , R ⁶ and R ⁷ are each a hydrogen atom, a lower alkyl group, a cycloalkyl group, an aryl group or an aralkyl group, which may be optionally substituted with a halogen atom or an alkoxy group), or Represents a cycloalkylene group (wherein k is an integer of 3 to 11 and the hydrogen atom may be substituted with a lower alkyl group, an aryl group, a halogen atom, etc.), and the aromatic ring is a lower alkyl group. It may be substituted with a substituent such as a group, a lower alkoxy group, an ester group, a hydroxyl group, a nitro group, a halogen or a cyano group. ]

Examples of such alkyl aryl carbonates include methyl phenyl carbonate, ethyl phenyl carbonate, propyl phenyl carbonate (each isomer), allyl phenyl carbonate, butyl phenyl carbonate (each isomer), pentyl phenyl carbonate (each isomer). ), Hexyl phenyl carbonate (each isomer), heptyl phenyl carbonate (each isomer), octyl tril carbonate (each isomer), nonyl (ethyl phenyl) carbonate (each isomer), decyl (butyl phenyl) carbonate (each isomer) Body), methyl tolyl carbonate (each isomer), ethyl tolyl carbonate (each isomer), propyl tolyl carbonate (each isomer), butyl tolyl carbonate (each isomer), allyl tolyl carbonate Bonate (each isomer), methyl xylyl carbonate (each isomer), methyl (trimethylphenyl) carbonate (each isomer), methyl (chlorophenyl) carbonate (each isomer), methyl (nitrophenyl) carbonate (each isomer) ), Methyl (methoxyphenyl) carbonate (each isomer), methyl cumyl carbonate (each isomer), methyl (naphthyl) carbonate (each isomer), methyl (pyridyl) carbonate (each isomer), ethyl cumyl carbonate (Each isomer), methyl (benzoylphenyl) carbonate (each isomer), ethyl xylyl carbonate (each isomer),
Benzyl xylyl carbonate, methyl (hydroxyphenyl) carbonate (each isomer), ethyl (hydroxyphenyl) carbonate (each isomer), methoxycarbonyloxybiphenyl (each isomer), methyl (hydroxyphenyl) carbonate (each isomer) , Methyl-2
-(Hydroxyphenyl) propylphenyl carbonate (each isomer), ethyl-2- (hydroxyphenyl)
Propylphenyl carbonate (each isomer) and the like can be mentioned.

Of these alkylaryl carbonates, those in which R ¹ is an alkyl group having 1 to 4 carbon atoms and Ar ¹ is an aromatic group having 6 to 10 carbon atoms are used, more preferably methyl. Phenyl carbonate is used. These alkylaryl carbonates can be used alone or as a mixture. Corresponding cross-reaction products can also be produced when the mixture is used as raw material.

The diaryl carbonate produced by the present invention is a compound in which one alkyl group of an alkylaryl carbonate is substituted with an aromatic group and is represented by Chemical formula 5.

[0022]

[Chemical 5] (Ar ¹ is as described above, and Ar ² and Ar ⁴ are divalent aromatic groups having the same skeleton as Ar ¹ and are bonded to another atom via oxygen. Ar ³ is Ar ¹ and The same aromatic group is represented, and m and n respectively independently represent 1 or 2.)

Examples of such a diaryl carbonate include diphenyl carbonate, ditolyl carbonate (each isomer), phenyltolyl carbonate (each isomer), di (ethylphenyl) carbonate (each isomer), phenyl (ethylphenyl). ) Carbonate (each isomer), Dinaphthyl carbonate (each isomer), Di (hydroxyphenyl) carbonate (each isomer), Di [2
-(Hydroxyphenylpropyl) phenyl] carbonate (each isomer) and the like can be mentioned.

The dialkyl carbonate produced by the present invention is represented by Chemical formula 6.

[0025]

[Chemical 6] (R ¹ is as described above, R ² is an alkyl group, an alicyclic group,
It represents an aralkyl group, and R ¹ and R ² may be the same or different. )

For example, dimethyl carbonate, diethyl carbonate, dipropyl carbonate (each isomer),
Diallyl carbonate, dibutenyl carbonate (each isomer), dibutyl carbonate (each isomer), dipentyl carbonate (each isomer), dihexyl carbonate (each isomer), diheptyl carbonate (each isomer),
Dioctyl carbonate (each isomer), dinonyl carbonate (each isomer), didecyl carbonate (each isomer), dicyclopentyl carbonate, dicyclohexyl carbonate, dicycloheptyl carbonate, dibentyl carbonate, diphenethyl carbonate (each isomer) ), Di (phenylpropyl) carbonate (each isomer), di (phenylbutyl) carbonate (each isomer), di (chlorobenzyl) carbonate (each isomer), di (methoxybenzyl) carbonate (each isomer), Di (methoxymethyl) carbonate (each isomer), di (methoxyethyl) carbonate (each isomer), di (chloroethyl) carbonate (each isomer),
Di (cyanoethyl) carbonate (each isomer), methylethylcarbonate, methylpropylcarbonate (each isomer), methylbutylcarbonate (each isomer), ethylpropylcarbonate (each isomer), ethylbutylcarbonate (each isomer) , Dibenzyl carbonate,
Examples thereof include ethylene carbonate and propylene carbonate.

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

The catalyst used in the present invention may be one which can produce diaryl carbonates and dialkyl carbonates by intramolecular transesterification (disproportionation reaction) and / or intermolecular transesterification of alkylaryl carbonates. Anything can be used. For example, (lead compound) lead oxides such as PbO, PbO ₂ , Pb ₃ O ₄ ; PbS,
Lead sulfides such as Pb ₂ S; Pb (OH) ₂ , Pb ₂ O
Lead hydroxides such as ₂ (OH) ₂ ; Na ₂ PbO ₂ , K ₂ P
Namarites such as bO ₂ , NaHPO ₂ , KHPbO ₂ ; Na ₂ PbO ₃ , Na ₂ H ₂ PbO ₄ , K ₂ PbO
₃ , K ₂ [Pb (OH) ₆ ], K ₄ PbO ₄ , Ca ₂ P
Lead salts such as bO ₄ , CaPbO ₃ ; PbCO ₃ , 2P
Lead carbonates such as bCO ₃ and Pb (OH) ₂ and basic salts thereof; Bu ₄ Pb, Ph ₄ Pb, Bu ₃ PbCl, P
h ₃ PbBr, Ph ₃ Pb (or Ph ₆ Pb ₂ ), Bu
Organic lead compounds such as ₃ PbOH and Ph ₃ PbO (Bu represents a butyl group, Ph represents a phenyl group); Pb (OCH
₃ ) ₂ , (CH ₃ O) Pb (OPh), Pb (OPh)
Alkoxyleads such as ₂ ; Aryloxyleads; Pb-N
a, Pb-Ca, Pb-Ba, Pb-Sn, Pb-Sb
Alloys of lead such as; Houenite Lead minerals such as senaenite and hydrates of these lead compounds, (copper compounds) CuCl, CuCl ₂ , CuBr, CuBr ₂ , Cu
I, CuI ₂ , Cu (OAc) ₂ , Cu (aca
c) ₂ , copper oleate, Bu ₂ Cu, (CH ₃ O) ₂ C
u, AgNO ₃ , AgBr, silver picrate, AgC ₆ H
₆ ClO ₄ , Ag (bulvarene) ₃ NO ₃ , [AuC≡
C—C (CH ₃ ) ₃ ] _n [Cu (C ₇ H ₈ ) Cl] _{4 and} other copper group metal salts and complexes (acac represents an acetylacetone chelate ligand), (alkali metal complex) Li ( acac) Lin (C ₄ H ₉ ) ₂ or other alkali metal complex, (Zinc complex) Zn (acac) ₂ or similar zinc complex, (Cadmium complex) Cd (acac) ₂ or similar cadmium complex, ( Compound of iron group metal) Fe (C ₁₀ H ₈ ) (CO) ₅ , Fe (CO) ₅ , Fe
(C ₄ H ₆ ) (CO) ₃ , Co (mesitylene) ₂ (PE
t ₂ Ph) ₂ , CoC ₅ F ₆ (CO) ₇ , Ni-π-C
₅ H ₅ NO, iron group metal complexes such as ferrocene, (zirconium complex) Zr (acac) ₄ , zirconium such as zirconocene, (Lewis acid compounds) AlX ₃ , TiX ₃ , TiX ₄ , VOX ₃ , VX ₅ , Z
_{nX 2, FeX 3, SnX 4} ( wherein X is halogen, acetoxyl group, alkoxy group, an aryl group) a transition metal compound capable of generating a Lewis acid and a Lewis acid such as, (organotin compounds) (CH _{3) 3} SnOCOCH ₃ , (C ₂ H ₅ ) ₃ SnO
COC ₆ H ₅ , Bu ₃ SnOCOCH ₃ , Ph ₃ SnO
COCH ₃ , Bu ₂ Sn (OCOCH ₃ ) ₂ , Bu ₂ S
n (OCOC ₁₁ H ₂₃ ) ₂ , Ph ₃ SnOCH ₃ , (C _{2
H 5) 3 SnOPh, Bu 2} Sn (OCH 3) 2, Bu
₂ Sn (OC ₂ H ₅ ) ₂ , Bu ₂ Sn (OPh) ₂ , P
h ₂ Sn (OCH ₃ ) ₂ , (C ₂ H ₅ ) ₃ SnOH, P
_{h 3 SnOH, Bu 2 SnO,} (C 8 H 17) 2 SnO
Organotin compounds such as H, Bu ₂ SnCl ₂ , BuSnO (OH), (solid catalyst) solid catalysts such as silica, alumina, titania, silica-titania, zinc oxide, zirconium oxide, gallium oxide, zeolite, oxides of rare earths; Those obtained by modifying the surface acid points of these solid catalysts by a method 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 mixing with a compound or carrier which is inert to the reaction, or by being supported on them. Of course, these catalyst components may be those reacted with organic compounds existing in the reaction system, for example, alkylaryl carbonates, diaryl carbonates, dialkyl carbonates, etc., or raw materials or products prior to the reaction. It may be heat-treated at.

Among these catalysts, particularly preferably used are lead oxides such as PbO, PbO ₂ and Pb ₃ O ₄ ; lead hydroxides such as Pb (OH) ₂ and Pb ₂ O ₂ (OH) _2. PbCO ₃ , 2PbCO ₃ .Pb (OH) _{2 and} other lead carbonates and basic salts thereof; Pb (OCH ₃ ) ₂ ,
(CH ₃ O) Pb (OPh), Pb (OPh) _{2 and} other alkoxy lead compounds, aryloxy lead compounds and other lead compounds, and these lead compounds reacted with organic compounds present in the reaction system. Those obtained by heat-treating these lead compounds with raw materials or products prior to the reaction are also preferably used.

The continuous multi-stage distillation column used in the present invention is
A distillation column having a number of distillation stages having two or more stages,
Any number may be used as long as continuous distillation is possible (in the present invention, the number of distillation column columns means, in the case of a plate column, the number of plate columns, and it is a packed column. The formula and the number of theoretical plates for other distillation columns are shown. Examples of such a continuous multi-stage distillation column include a tray column type using trays such as bubble bell trays, perforated plate trays, valve trays, countercurrent trays, Raschig rings, Lessing rings, Pall rings, Berlu saddles, and interludes. Use any type of column that is normally used as a continuous multi-stage distillation column, such as a packed column type filled with various packing such as Rox saddle, Dickson packing, McMahon packing, Helipack, Sulzer packing, Melapak, etc. can do. Further, a distillation column having both a tray part and a part filled with packing material is also preferably used. When a solid catalyst is used, a packed column distillation column in which the solid catalyst is a part or all of the packing is also preferably used.

The reaction of the present invention is usually carried out in the liquid phase,
For example, in the case of an exchange reaction (disproportionation reaction) to an intramolecular ester using one kind of alkylaryl carbonate, it is an equilibrium reaction represented by the general formula (I) in Chemical formula 7. When two or more kinds of alkylaryl carbonates are used, the equilibrium reaction represented by the general formula (II) in Chemical formula 7 is used.

[0033]

[Chemical 7] (R ^1, R ² is as defined above Ar ⁵ is Ar ¹ and similar aromatic group Ar ¹ may be the same as .Ar ^x, Ar ^y
Are independently Ar ¹ and Ar ⁵ , and R ^x and R ^y are independently R ¹ and R ² . )

In the process of the present invention, these reactions are carried out in a continuous multi-stage distillation column in the presence of a catalyst, and more preferably in a plurality of stages in the presence of a catalyst, and at the same time, a low boiling point produced by the reaction is produced. The method is characterized by using a reactive distillation column system in which the product is separated from the reaction system by distillation. This method enables continuous production of aromatic carbonate with high yield and high selectivity.

Although the exact reason why the method of the present invention has a higher reaction rate than the conventional method and dramatically improves the yield (or productivity) and the selectivity, it is not clear, but the following facts are obtained. Presumed. The reactions of the present invention represented by the above general formulas (I) and (II) are all equilibrium reactions, and both equilibria are extremely biased toward the original system. Therefore, in any of the reactions, in order to increase the reaction rate, it is necessary to remove the by-product (usually dialkyl carbonate), which is a low boiling point product, from the reaction solution as quickly as possible.

However, it has been impossible to increase the reaction rate in the reaction system described in the prior art, which uses a reaction vessel having a distillation column installed above. The reason for this is that not only the reaction field is limited to the part of the reaction vessel where the catalyst is present, but also the low boiling point product produced by the reaction is vaporized from the liquid in the reaction vessel to the vapor phase. This is because the boundary area is small.

On the other hand, in the method of the present invention, the catalyst is allowed to exist in a wide range in the continuous multi-stage distillation column, and the reaction can proceed in a wide area having a very large gas-liquid interface area. In this area, the supplied reaction liquid is
The vapor rising from the bottom and gas-liquid contact are repeated, and while distilling, reacting and flowing down. At this time, the low boiling point product evaporates from the reaction solution into the vapor phase.

As a result, each component in the continuous multi-stage distillation column has a concentration distribution, and the concentration of diaryl carbonate, which is usually a high boiling point product, in the liquid is the highest in the stage where the catalyst is present. As it goes from the lower part to the lower part of the column, it has a distribution that gradually increases, while the concentration of dialkyl carbonate, which is a low boiling point product, in the liquid usually has a distribution that gradually decreases from the upper part to the lower part of the column, It is possible to make the concentration in the liquid very low near the bottom of the tower. In the vapor phase, the concentration of dialkyl carbonate gradually increases from the bottom of the column to the top of the column.

In the present invention, these reactions proceed in the continuous multi-stage distillation column in this way. However, considering the arbitrary position of this reaction region, the reaction solution was close to the equilibrium composition as a result of the reaction. It is considered that the vapor phase is in a state close to a vapor-liquid equilibrium state with respect to the reaction liquid. Therefore, when the reaction solution remains in this position, the reaction does not proceed any further, but in reality, the reaction solution flows down to make vapor-liquid contact with the vapor phase having a low boiling point and a lower concentration of the reaction product. Thereby, the reaction can be further advanced, and the concentration of the high-boiling-point product, the diaryl carbonate, in the reaction solution can be further increased.

The conventional method of carrying out the reaction in a reaction kettle having a distillation tower installed above is to advance the reaction only in the reaction kettle, and the distillation tower simply discharges the gas phase from the gas-liquid interface in the reaction kettle. It only plays the role of separating the low boiling point product vapor and the low boiling point raw material compound vapor, causing the low boiling point raw material compound to flow down in a liquid state, and returning it to the reaction vessel. Therefore, it is considered that the reason why the method of the present invention has an excellent effect as compared with the conventional method is mainly due to the following points.

The gas-liquid interfacial area can be made very large as compared with the reaction system using a reaction vessel, and as a result, the mass transfer of the low boiling point product, which is a by-product, to the vapor phase is easy. The reaction liquid in the continuous multi-stage distillation column flows down while reacting by repeating vapor-liquid contact with vapor rising from below. Therefore, it is possible to increase the reaction rate between the starting material and the reactant, even though it is a continuous method (in the continuous method of continuously extracting the target aromatic carbonate by the conventional reaction method using a reaction vessel, It is difficult to increase the reaction rate, and in fact, no method has been proposed so far to carry out continuously. In order to increase the reaction rate by this method, it is necessary to carry out the reaction for a long time in a batch system).

As the vapor rising in the continuous multi-stage distillation column rises, it rises while repeating vapor-liquid contact with the liquid to be processed. Therefore, the thermal energy of steam is effectively used. In the present invention, it is essential that the catalyst is present in the continuous multi-stage distillation column, and more preferably, the catalyst is present in two or more stages in the continuous multi-stage distillation column.

Any method may be used for allowing the catalyst to be present in such a continuous multi-stage distillation column. For example, in the case of a homogeneous catalyst which dissolves in the reaction solution under the reaction conditions, the distillation is carried out. By continuously supplying the catalyst to the tower,
The catalyst can be present in the reaction system, or in the case of a heterogeneous catalyst that does not dissolve in the reaction solution under the reaction conditions, the catalyst can be present in the reaction system by arranging the solid catalyst in the distillation column. Alternatively, a combination of these methods may be used.

When the homogeneous catalyst is continuously supplied to the distillation column, it may be mixed with the alkylaryl carbonate as a raw material and supplied at the same time as the supply of the raw material, or at a stage different from the position where the raw material is supplied. May be supplied to. Further, the catalyst may be supplied to any position as long as it has at least one or more stages from the bottom of the column. However, since the reaction actually progresses in the distillation column is usually the region below the position where the catalyst is supplied, it is necessary to supply the catalyst to the region between the top of the column and the raw material supply position. Is preferred. Further, when a heterogeneous solid catalyst is used, the catalyst can be packed in a required amount at any position in the distillation column, and the theoretical layer of the layer in which the catalyst is present may be at least one theoretical stage. , Preferably two or more stages. This solid catalyst also has an effect as a packing for the distillation column.

Further, in the area where the catalyst does not exist in the distillation column, it functions only as a normal distillation column such as concentration of reaction products. In the method of the present invention, an alkylaryl carbonate is continuously supplied to a continuous multi-stage distillation column, and in the distillation column, a reaction is carried out in the presence of a catalyst, and at the same time, a low-boiling-point product, a dialkyl carbonate, is produced. Is continuously withdrawn from the upper part of the distillation column in a gaseous state by distillation, and the high-boiling product diaryl carbonate is continuously withdrawn from the lower part of the distillation column in a liquid form,
It is characterized by continuously producing diaryl carbonates.

The method for continuously supplying the alkylaryl carbonate to the continuous multi-stage distillation column is not particularly limited, and they can be used as a catalyst in a region of at least one stage, preferably two or more stages of the distillation column. Any method may be used as long as it can be brought into contact. That is, the alkylaryl carbonate can be continuously fed from the required number of inlets to the stages satisfying the above-mentioned conditions of the continuous multi-stage distillation column, and the starting material and the reaction substance can be supplied to the distillation column. May be introduced in the same stage, or may be introduced in different stages.

The portion above the raw material supply position serves only as a normal distillation column of the dialkyl carbonate concentration column. The raw material is supplied to the continuous multi-stage distillation column as a liquid, vapor or a mixture of liquid and vapor. Further, in addition to supplying the raw material to the continuous multi-stage distillation column by liquid or vapor, additionally supplying the raw material vapor to the lower part of the reaction column means that the concentration of dialkyl carbonate in the vapor phase rising in the continuous multi-stage distillation column is substantially increased. It is a preferable method because it has the effect of lowering the temperature.

In the present invention, the by-produced dialkyl carbonate is extracted in the form of gas. The gaseous extract may be dialkyl carbonate alone or may be a mixture with the alkylaryl carbonate as a raw material. It may contain a small amount of diaryl carbonates. The extraction port for the gas consisting of dialkyl carbonate or the like in the continuous multi-stage distillation column can be provided at any position other than the bottom of the column, but the concentration of the dialkyl carbonate produced as a by-product in the vapor phase is usually higher in the upper part of the column. high. Therefore, it is preferable to provide a gas extraction port between the raw material supply position and the top of the column or at the top of the column, and more preferably at the top of the column.

In the present invention, the product diaryl carbonates are withdrawn in liquid form from the lower part of the continuous multistage distillation column. The liquid extract may be a diaryl carbonate alone or a mixture with an alkylaryl carbonate as a raw material. It may contain a small amount of dialkyl carbonate. When a homogeneous catalyst is used as the catalyst, the liquid extract contains the catalyst. The outlet for the liquid containing diaryl carbonate or the like in the continuous multi-stage distillation column is provided at the bottom of the column. In the present invention, the lower part of the tower is usually between the raw material supply position and the bottom of the tower or the bottom of the tower, preferably the bottom of the tower.

In carrying out the reactive distillation in the present invention,
The descending reaction liquid velocity and ascending vapor velocity in the continuous multi-stage distillation column differ depending on the type of the continuous multi-stage distillation column used and the type of packing when a packed column is used, but usually do not cause flatting. It is carried out in a range. In the present invention, when the reflux ratio is increased, the distillation efficiency of the dialkyl carbonate into the vapor phase is increased, so that the concentration of the dialkyl carbonate in the extracted vapor can be increased.

However, if the reflux ratio is increased too much, the required thermal energy becomes excessive, which is not preferable. Further, the concentration of the dialkyl carbonate may be carried out after the dialkyl carbonate is taken out from the reactive distillation column, so that the reflux is not always necessary. Therefore, the reflux ratio is usually 0 to 20, preferably 0 to 10. Since the reaction in the present invention occurs in the continuous multi-stage distillation column, the amount of diaryl carbonate produced depends on the hold-up liquid amount in the continuous multi-stage distillation column. That is, when using a continuous multi-stage distillation column having the same column height and the same column diameter, a continuous multi-stage distillation column having a high liquid holdup is preferable in that the average residence time of the reaction liquid, that is, the reaction time becomes long.

However, when the liquid holdup is too high, the retention time becomes long, so that side reactions easily proceed and flatting easily occurs. Therefore, the hold-up liquid amount of the continuous multi-stage distillation column used in the present invention may vary depending on the reactive distillation conditions and the type of the continuous multi-stage distillation column, but is a volume ratio of the hold-up liquid amount to the empty column volume of the continuous multi-stage distillation column. Expressed, usually 0.005
~ 0.75.

In carrying out the present invention, the reaction temperature is usually 50 to 350, though it varies depending on the kind of raw material used.
C., preferably in the range of 100 to 250.degree. Also,
The reaction pressure varies depending on the type of raw material used and the reaction temperature, but is usually 0.00001 to 200 kg / cm ² . The residence time of the reaction liquid in the continuous multi-stage distillation column in the present invention 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, it is not always necessary to use a reaction solvent, but a suitable inert solvent such as ethers, aliphatic hydrocarbons and aromatic hydrocarbons is used for the purpose of facilitating the reaction operation. , Halogenated aliphatic hydrocarbons, halogenated aromatic hydrocarbons and the like can be used as a reaction solvent. In the present invention, an inert gas such as nitrogen, helium or argon may be allowed to coexist in the reaction system as a substance inert to the reaction. Further, for the purpose of accelerating the removal of the by-produced dialkyl carbonate, an inert gas or a low-boiling organic compound inert to the reaction may be introduced from the lower part of continuous multistage distillation or the like.

In the present invention, the raw material may contain an aromatic hydroxy compound, a reaction product such as a diaryl carbonate, or a by-product such as a dialkyl carbonate. Since it is a reversible reaction, if the concentration of dialkyl carbonate or diaryl carbonate is too high, the reaction rate of the raw material is lowered, which is not preferable. Therefore, usually, the amount of the dialkyl carbonate and the diaryl carbonate in the raw material is preferably 20 mol% or less, more preferably 10 mol% or less, based on the alkylaryl carbonate.

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 supplied to the reaction system, it is usually expressed as a ratio based on the weight of dialkyl carbonate, Used at 0.0001 to 50% by weight. When the solid catalyst is installed and used in continuous multistage distillation or the like, a catalyst amount of 0.01 to 75% by volume relative to the empty column volume in continuous multistage distillation or the like is used.

[0057]

EXAMPLES The present invention will be specifically described below with reference to examples.

[0058]

Example 1 A continuous column comprising a pressure regulator (10) as shown in FIG. 1 and filled with Dickson packing (6 mmφ) made of stainless steel as a packing material and having a tower height of 4 m and a diameter of 3 inches. A mixture consisting of methylphenyl carbonate and a catalyst was introduced into the continuous multi-stage distillation column (3) from the inlet (1) to the continuous multi-stage distillation column (3) at a position 1 m from the top of the multi-stage distillation column (3) through a preheater (2). And heated by a reboiler for reaction. The reaction conditions are shown in Table 1.

As a result of the reaction, the bottom of the continuous multistage distillation column (9)
A liquid containing diphenyl carbonate as a reaction product was obtained from the column bottom liquid outlet (6). The results of the reaction are shown in Tables 1 and 2. The condensate obtained by condensing the gas distilled from the gas outlet (7) provided at the tower top (8) in the condenser (5) is partially refluxed, and the rest is condensed liquid outlet. (7 ')
Extracted from. Dimethyl carbonate, a by-product of the reaction, was obtained from this condensate. This condensate contained a side reaction product, anisole. The anisole selectivity is 0.
It was 7%.

[0060]

Comparative Example 1 As shown in FIG. 3, a distillation column (14) having a tower height of 1 m and a diameter of 1 inch [having a pressure regulator (22) and being filled with stainless Dickson packing (6 mmφ)] was used. Volume 15 with stirrer (20) on the lid
A liter reactor (13) was charged with raw materials and catalysts having the same composition as used in Example 1 through the inlet (12) 12.6.
I charged kg.

Stirrer (20) until the liquid temperature reaches 195 ° C.
The reaction was started by raising the temperature using an electric furnace (19) with stirring. When the liquid temperature becomes constant,
The condensate obtained by condensing the gas distilled from the gas outlet (15) provided at the top (21) of the distillation column (14) in the condenser (16) is partially refluxed and the rest is condensed. It was continuously withdrawn from the liquid outlet (17) at a rate of 1.0 kg / hr. The reflux ratio was 2.1. The reaction was carried out for 3 hours after the start of extraction, and 3.0 kg of the condensate was extracted.

After cooling the reaction kettle, the reaction liquid was extracted from the discharge port (18), and the weight was 9.6 kg. The ratio of the amount of condensed withdrawal and the amount of liquid withdrawn from the reaction vessel in this comparative example is the same as the ratio of the amount of condensed withdrawal and the amount of liquid withdrawn from the bottom in Example 1. As a result of analysis, 67.2% by weight of diphenyl carbonate was formed in the reaction solution. The amount of diphenyl carbonate produced per 1 kg of the reaction solution per hour was 224 g / kg · hr. The selectivity of diphenyl carbonate based on methyl phenyl carbonate was 95%.

When the condensate was analyzed, anisole which was a by-product of the reaction was detected. Anisole selectivity based on methylphenyl carbonate was 5%. Comparison of this result with Example 1 shows that the method of the present invention provides diaryl carbonate in high yield and high selectivity.

[0064]

Examples 2 to 7 Experiments were conducted under the reaction conditions shown in Table 1 using the same apparatus as used in Example 1. The results are shown in Table 2.

[0065]

[Embodiment 8] As shown in FIG. 2, a continuous column comprising a pressure regulator (10) and a Dickson packing (6 mmφ) made of stainless steel as a packing material and having a tower height of 4 m and a diameter of 3 inches. A mixture of methylphenyl carbonate and a catalyst is continuously introduced in a liquid state into the reactive distillation column (3) from an inlet (1) through a preheater (2) to a position 1 m from the top of the multistage distillation column (3). Then, methyl phenyl carbonate was introduced from the inlet (1 '), and was fed in gaseous form to the bottom (9) of the continuous multistage distillation column (3) via the evaporator (4'). The reaction conditions are shown in Table 3.

As a result of the reaction, a liquid containing diphenyl carbonate as a reaction product was obtained from the bottom of the continuous multistage distillation column. In addition, dimethyl carbonate as a by-product of the reaction was obtained from the liquid obtained by condensing the gas distilled from the top of the column in the condenser (5). The results of the reaction are shown in Table 4.

[0067]

Examples 9 to 10 Using the same equipment as used in Example 8, the reaction was carried out under the reaction conditions shown in Table 3. The results are shown in Table 4.

[0068]

Example 11 As a continuous multi-stage distillation column, instead of a packed column, a plate column having a column height of 6 m and a column diameter of 10 inches equipped with a sieve tray having 20 plates was used, and the column was fed to a position 0.5 m from the top of the column. The reaction was performed in the same manner as in Example 8 except that the reaction was performed under the reaction conditions shown in Table 3. The results are shown in Table 4.

[0069]

[Table 1]

[0070]

[Table 2]

[0071]

[Table 3]

[0072]

[Table 4]

The symbols used in the table have the following meanings. In the table, the amount of diaryl carbonate produced and the selectivity are shown in the following (Note). PhOH Phenol Pb (OPh) ² Diphenoxy Lead Bu ₂ SnO Dibutyltin Oxide Ti (OPh) ₄ Tetraphenoxy Titanium MPC Methylphenylcarbonate MTC Methyltolylcarbonate EPC Ethylphenylcarbonate DPC Diphenylcarbonate DTC Ditolylcarbonate (Note) It is expressed in g per 1 hour of the bottom liquid of the column per hour.

The selectivity of the diaryl carbonate is based on the alkyl aryl carbonate.

[0075]

Industrial Applicability According to the method of the present invention, diaryl carbonates can be continuously obtained in high yield and high selectivity from alkyl aryl carbonates as raw materials.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a continuous multistage distillation apparatus of the present invention.

FIG. 2 is a schematic view showing an example of a continuous multistage distillation apparatus of the present invention.

FIG. 3 is a schematic diagram of a reactive distillation column used in Comparative Example 1.

[Simple explanation of symbols]

 1, 1 ', 12 Inlet 2 Preheater 3 Continuous multi-stage distillation column 4 Reboiler 4'Evaporator 5,16 Condenser 6 Bottom liquid outlet 7,15 Gas outlet 7', 17 Condensate outlet 8,22 Tower top 9 Tower bottom 10,22 Pressure regulator 11,23 Gas-liquid separator 13 Reactor kettle 14 Distillation column 18 Discharge port 19 Electric furnace 20 Stirrer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B01J 27/232 31/02 101 31/04 31/12 31/22 C07B 61/00 300

Claims (3)

[Claims] 1. When a diaryl carbonate and a dialkyl carbonate are produced from an alkylaryl carbonate in the presence of a catalyst, the alkylaryl carbonate is continuously fed into a continuous multi-stage distillation column, and the catalyst is fed into the continuous multi-stage distillation column. Continuous production of a diaryl carbonate characterized in that the by-produced dialkyl carbonate is continuously withdrawn in a gaseous state by distillation while being reacted by contacting with the product, and the produced diaryl carbonate is continuously withdrawn in a liquid state from the lower part of the tower. Method. 2. The method according to claim 1, wherein the catalyst is present by continuously feeding a homogeneous catalyst to a continuous multistage distillation column. 3. The method according to claim 1, wherein the catalyst is a solid catalyst, and the catalyst is present by arranging the solid catalyst inside a continuous multistage distillation column.