JPH0791236B2 - Continuous production method for aromatic carbonates - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a continuous process for producing aromatic carbonates. More specifically, it relates to a method for efficiently and continuously producing an aromatic carbonate composed of an alkylaryl carbonate, a diaryl carbonate or a mixture thereof by reacting a dialkyl carbonate with an aromatic hydroxy compound.

[0002]

It is well known that an aromatic carbonate composed of an alkylaryl carbonate, a diaryl carbonate or a mixture thereof can be obtained by reacting a dialkyl carbonate with an aromatic hydroxy compound. For example, using the compound represented by Chemical formula 1 as the dialkyl carbonate

[0003]

[Chemical 1]

ArOH as an aromatic hydroxy compound
When an aromatic monohydroxy compound represented by (Ar is a monovalent aromatic group) is used, the reaction is represented by Chemical formula 2.

[0005]

[Chemical 2]

However, all of these reactions are equilibrium reactions, and the equilibrium is extremely biased toward the original system, and the reaction rate is slow. Manufacturing was enormously difficult. Several proposals have been made to improve this, most of which relate to catalyst development to increase the reaction rate. Examples of such a catalyst include Lewis acids such as transition metal halides or compounds that produce Lewis acids [JP-A-51-105032, JP-A-56-123948, JP-A-56-56].
No. 123949 (West German Patent Publication No. 252841)
2, British Patent No. 1499530, US Pat. No. 4,182,726)], tin compounds such as organic tin alkoxides and organic tin oxides [JP-A-54-48].
733 (West German Patent Publication No. 2736062)
No.), JP-A-54-63023, JP-A-60-1.
69444 (US Pat. No. 4,554,110) and JP-A-60-169445 (US Pat. No. 4).
No. 552704), JP-A-62-277645, JP-A-1-265063], alkali metal or alkaline earth metal salts and alkoxides (JP-A-56-25138), and lead compounds. (JP-A-57
-176932), complexes of metals such as copper, iron and zirconium (JP-A-57-183745), titanates (JP-A-58-185536 (US Pat. No. 4,410,464)). ], A mixture of a Lewis acid and a protonic acid [JP-A-60-173016 (US Pat. No. 4,609,501)], Sc, Mo, M
Compounds such as n, Bi and Te (Japanese Patent Laid-Open No. 1-265064)
JP-A-61-172852), ferric acetate (JP-A-61-272852), and the like have been proposed.

Another attempt to improve the yield of aromatic carbonates in these reactions is to shift the equilibrium toward the production system as much as possible. As such a method, for example, in a reaction between dimethyl carbonate and phenol, a by-produced methanol is azeotropically distilled off together with an azeotrope-forming agent [JP-A-54-48732 (West German Patent). Publication No. 2736
No. 063, U.S. Pat. No. 4,252,737), JP-A-61-291545], and a method of removing by-produced methanol by adsorbing it with a molecular sieve [JP-A-58-185536 (US Patent). No. 41046
No. 4)]] has been proposed.

Further, as a preferable reaction system in the inventions proposed so far, alcohols by-produced by the reaction are separated and distilled off from the raw materials or products or the coexisting solvents. In order to achieve this, it is also known to use an apparatus in which columns having distillation and fractional distillation functions are added to the upper part of the reactor [JP-A-56-123948 (US Pat. No. 4,182,726)]. Example,
Examples of JP-A-56-25138, JP-A-60-
169444, Examples of (US Pat. No. 4,554,110), JP-A-60-169445 (US Pat. No. 4,552,704), JP-A-6
No. 0-173016 (U.S. Pat. No. 4,609,501), JP-A 61-172852, JP-A 61-291545, JP-A 62-277345. Example of].

However, in these methods,
In each case, it is clear that the reaction only proceeds 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 only used to separate the alcohols produced in the reactor from the other components present in the reactor. This is described in detail in JP-A-61-291545,
According to this, for example, "for such a reaction, usually, while using a reactive distillation in which a distillation column is added to the reactor to carry out the reaction in the reactor at the bottom of the column, the boiling point is lower than that of the carbonate produced from the top of the column A reactive distillation method of distilling off methanol is adopted "(the same specification, page 1, right column, lines 12 to 17).

That is, the reactive distillation in the above-mentioned methods uses only an apparatus in which a reaction portion and a distillation portion exist separately, and only the distillation is performed in the distillation column portion, and the reaction is not performed at all. It is a method characterized by that.
Thus, in these methods, the reaction is carried out in the liquid phase in the reactor, but the low boiling point alcohol by-produced is extracted from the liquid phase to the gas phase through the gas-liquid interface, and then the reaction is equilibrated. Shifts to the production system side, and the reaction proceeds.

However, since the reactor used in these methods is of a tank type and the gas-liquid interfacial area is as small as the cross-sectional area of the reactor, it is known that the reaction is very slow. For example, JP-A-61-291
In the examples of JP-A-54545 and JP-A-54-48732 and JP-A-54-48733, the reaction takes a batch-type reaction for a long time of 8 to 45 hours. In such a method that takes a long time, not only side reactions of the raw materials and intermediates but also side reactions of the produced aromatic carbonates are likely to occur, resulting in a decrease in selectivity.

Further, in the conventional method called reactive distillation, which uses an apparatus in which a reaction portion and a distillation portion are separately provided, Japanese Patent Application Laid-Open No. 61-291545 (page 3, left lower column, line 4) is disclosed. ~ Line 9) "Reactive distillation can be performed either batchwise or continuously, but in the case of transesterification of dimethyl carbonate with phenol, the reaction rate is slow and continuous. However, the batch method is preferable because it requires a large amount of equipment. ”In fact, in all the examples of the above-mentioned patents proposed so far, dialkyl carbonate and aromatic hydroxy are used. At least one of the raw material compounds (usually an aromatic hydroxy compound, which is a high boiling point compound) is reacted with the catalyst initially as it is charged in the reactor. A switch system. Therefore, a continuous reaction system in which a raw material compound is continuously supplied and a product is continuously extracted has not been disclosed at all.

[0013]

SUMMARY OF THE INVENTION The present invention does not have the drawbacks of the methods proposed so far, and the aromatic carbonates can be continuously reacted at a high reaction rate and a high selectivity. It is made for the purpose of providing a manufacturing method.

[0014]

Means for Solving the Problems In producing a diaryl carbonate from a dialkyl carbonate and an aromatic hydroxy compound in the presence of a catalyst, the present inventors have described a reactive distillation system in which a reaction is carried out inside a continuous multistage distillation column. The present invention has been completed based on the finding that it is an excellent method that can easily achieve the object.

That is, according to the present invention, when a dialkyl carbonate and an aromatic hydroxy compound are reacted in the presence of a catalyst to produce an aromatic carbonate composed of an alkylaryl carbonate, a diaryl carbonate or a mixture thereof, a raw material compound is used. An aliphatic alcohol produced as a by-product while continuously supplying the dialkyl carbonate and the aromatic hydroxy compound into a continuous multi-stage distillation column and causing the catalyst and the raw material compound to contact each other in the distillation column. Is continuously extracted in a gaseous state by distillation, and the produced aromatic carbonates are continuously extracted in a liquid state from the lower part of the tower, and a continuous process for producing aromatic carbonates is provided.

The dialkyl carbonate used as the raw material compound in the present invention is represented by Chemical formula 3.

[0017]

[Chemical 3] (R ¹ and R ² represent an alkyl group, an alicyclic group or an aralkyl group, R ¹ and R ² may be the same or different, and R ¹ and R ² may be a ring. It may be a constituent component.)

Examples of R ¹ and R ² are methyl, ethyl, propyl (each isomer), allyl, butyl (each isomer), butenyl (each isomer), pentyl (each isomer), hexyl. (Each isomer), heptyl (each isomer), octyl (each isomer), nonyl (each isomer), decyl (each isomer), an alkyl group such as cyclohexylmethyl; cyclopropyl, cyclobutyl, cyclopentyl,
Alicyclic groups such as cyclohexyl and cycloheptyl; aralkyl groups such as benzyl, phenethyl (each isomer), phenylpropyl (each isomer), phenylbutyl (each isomer), methylbenzyl (each isomer), etc. . In addition,
In these alkyl groups, alicyclic groups, and aralkyl groups, other substituents such as a lower alkyl group, a lower alkoxy group, a cyano group and a halogen may be substituted,
It may have an unsaturated bond.

Examples of the dialkyl carbonate having R ¹ and R ² include dimethyl carbonate, diethyl carbonate, dipropyl carbonate (each isomer), diallyl carbonate, dibutenyl carbonate (each isomer), dibutyl carbonate ( Each isomer), dipentyl carbonate (each isomer), dihexyl carbonate (each isomer), diheptyl carbonate (each isomer), dioctyl carbonate (each isomer), dinonyl carbonate (each isomer), didecyl carbonate ( Each isomer), dicyclopentyl carbonate, dicyclohexyl carbonate, dicycloheptyl carbonate, dibenzyl carbonate, diphenethyl carbonate (each isomer), di (phenylpropyl) carbonate (each isomer), di Phenylbutyl) carbonate (each isomer), di (chlorobenzyl) carbonate (each isomer), di (methoxybenzyl) carbonate (each isomer), di (methoxymethyl) carbonate, di (methoxyethyl) carbonate (each isomer) Body), di (chloroethyl) carbonate (each isomer), di (dianoethyl)
Carbonate (each isomer), methylethyl carbonate, methylpropyl carbonate (each isomer), methylbutyl carbonate (each isomer), ethylpropyl carbonate (each isomer), ethylbutyl carbonate (each isomer), dibenzyl carbonate , Ethylene carbonate, propylene carbonate and the like are used.

Among these dialkyl carbonates,
What is preferably used in the present invention is a dialkyl carbonate in which each of R ¹ and R ² is an alkyl group having 4 or less carbon atoms, and dimethyl carbonate is particularly preferable. The aromatic hydroxy compound which is the raw material compound used in the present invention is represented by the general formula Ar ¹ CH (2) (Ar ¹ represents a monovalent aromatic group), and the aromatic group is Any one may be used as long as it is directly bonded to a hydroxy group. Examples of such 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), Phenyl groups and various alkylphenyl groups such as cyclohexylphenyl (each isomer); 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 Various halogenated phenyl groups such as phenyl (each isomer), dichlorophenyl (each isomer); various substituted phenyl groups shown in Chemical formula 4; naphthyl (each isomer), methylnaphthyl (each isomer), dimethylnaphthyl (Each isomer), chloronaphthyl (each isomer), methoxynaphthyl (each isomer), cyanonaphthyl (each isomer) and other naphthyl groups and various substituted naphthyl groups; pyridine (each isomer), coumaryl (each isomer) Isomers), quinolyl (each isomer), methylpyridyl (each isomer), chlorpyridyl (each isomer), methylcoumaryl (each isomer), methylquinolyl (each isomer), and other substituted and unsubstituted heteroaromatics Group groups and the like can be mentioned.

[0021]

[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 the aromatic hydroxy compound having Ar ¹ include phenol; cresol (each isomer), xylenol (each isomer), trimethylphenol (each isomer), tetramethylphenol (each isomer). ), Ethylphenol (each isomer), propylphenol (each isomer), butylphenol (each isomer), diethylphenol (each isomer), methylethylphenol (each isomer), methylpropylphenol (each isomer) , Various alkylphenols such as dipropylphenol (each isomer), methylbutylphenol (each isomer), pentylphenol (each isomer), hexylphenol (each isomer), cyclohexylphenol (each isomer); methoxyphenol ( Each isomer), ethoxyphenol (each isomer) ) Etc .; various substituted phenols represented by Chemical formula 5; naphthol (each isomer) and various substituted naphthols; hydroxypyridine (each isomer), hydroxycoumarin (each isomer), hydroxyquinoline (each) Heteroaromatic hydroxy compounds such as isomers) are used.

[0023]

[Chemical 5] (A is as described above.)

Aromatic dihydroxy compounds having two hydroxyl groups, for example, hydroquinone, resorcin, catechol, dihydroxynaphthalene, dihydroxyanthracene and their alkyl-substituted hydroxy compounds; Can be used.

[0025]

[Chemical 6] (However, A is as described above, and the aromatic ring may be substituted with a substituent such as a lower alkyl group, a lower alkoxy group, an ester group, a nitro group or a cyano group.)

Among these aromatic hydroxy compounds,
In the present invention, an aromatic monohydroxy compound in which Ar ¹ is an aromatic group having 6 to 10 carbon atoms is preferably used, and phenol is particularly preferable. Further, the alkyl aryl carbonate referred to in the present invention is
1 of the dialkyl carbonate represented by the formula (1)
In which one alkyl group is substituted with an aromatic group,
Is represented by.

[0027]

[Chemical 7] (R ³ is R ¹ or R ² , and R ¹ , R ² and Ar ¹ are as described above.)

When the aromatic hydroxy compound is an aromatic dihydroxy compound Ar ² (OH) ₂ (4) having two hydroxyl groups, the compound represented by Chemical formula 8 is also included in the alkyl carbonate.

[0029]

[Chemical 8] (R ³ is as described above, Ar ² represents a divalent aromatic group having the same skeleton as Ar ^1, and m represents 1 or 2.)

Examples of such alkylaryl carbonates include methylphenyl carbonate, ethylphenyl carbonate, propylphenyl carbonate (each isomer), allylphenyl carbonate, butylphenyl carbonate (each isomer), pentylphenyl 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 (tolylmethylphenyl) carbonate (each isomer), methyl (chlorophenyl) carbonate (each isomer), methyl (nitrophenyl) carbonate (each isomer) Body), 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 (hydroxybiphenyl) carbonate (each isomer) , Methyl 2
Examples include-(hydroxyphenyl) propylphenyl carbonate (each isomer) and ethyl 2- (hydroxyphenyl) propylphenyl carbonate (each isomer).

The diaryl carbonate referred to in the present invention is a compound in which two alkyl groups of a dialkyl carbonate are substituted with an aromatic group and is represented by Chemical formula 9.

[0032]

[Chemical 9] (Ar ¹ , Ar ² and m are as described above, Ar ³ is Ar ¹
Represents an aromatic group similar to that described in, and Ar ⁴ is Ar
^It represents the same divalent aromatic group as described in 2. Further, n represents 1 or 2. )

Examples of such diaryl carbonates 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.

In the present invention, the aliphatic alcohol produced is withdrawn in a gaseous state, and the aromatic carbonate produced is withdrawn in liquid form from the lower part of the column. Therefore, in the present invention,
The dialkyl carbonate and the aromatic hydroxy compound are used in a combination such that the boiling point of the produced aliphatic alcohol is lower than the boiling point of the product aromatic carbonate.

As such a preferable combination, the dialkyl carbonate represented by the formula (1) and the formula (2) are used.
Alternatively, in the aromatic hydroxy compound represented by the formula (4), R ¹ and R ² may be an alkyl group having 1 to 4 carbon atoms, and Ar ¹ or Ar ² may be an aromatic group having 6 to 10 carbon atoms. can give. A particularly preferred combination is when the dialkyl carbonate is dimethyl carbonate and the aromatic hydroxy compound is phenol. In this case, the alkyl aryl carbonate produced is methyl phenyl carbonate and the siaryl carbonate is diphenyl carbonate.

Any catalyst can be used in the present invention as long as it can produce an aromatic carbonate composed of an alkylallyl carbonate, a diaryl carbonate or a mixture thereof by reacting a dialkyl carbonate with an aromatic hydroxy compound. Can be used. For example, (lead compounds) 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 , NaHPbO ₂ and KHPbO ₂ ; Na ₂ PbO ₃ , Na ₂ H ₂ PbO ₄ and K ₂ Pb
O ₃ , K ₂ [Pb (OH) ₆ ], K ₄ PbO ₄ , Ca ₂
Lead salts such as PbO ₄ and CaPbO ₃ ; PbCO ₃ and 2
Lead carbonates such as PbCO ₃ · Pb (OH) ₂ and their basic compounds; Pb (OCOCH ₃ ) ₂ and Pb (OCOC)
H ₃ ) ₄ , Pb (OCOCH ₃ ) ₂ · PbO · 3H ₂ O
Lead salts of organic acids and their carbonates and basic salts; Bu ₄
Pb, Ph ₄ Pb, Bu ₃ PbC1, Ph ₃ PbBr,
Ph ₃ Pb (or Ph ₆ Pb ₂ ), Bu ₃ PbOH, P
Organic lead compounds such as h ₃ PbO (Bu is a butyl group, Ph
Represents a phenyl group); Pb (OCH ₃ ) ₂ , (CH ₃
O) Pb (OPh), Pb (OPh) _{2 and} other alkoxy leads, aryloxy leads; Pb-Na, Pb-Ca,
Lead alloys such as Pb-Ba, Pb-Sn and Pb-Sb;
Lead minerals such as houenite and senaenite, and hydrates of these lead compounds; (Copper group metal compounds) CuCl, CuCl ₂ , CuBr, CuBr ₂ , Cu
I, CuI ₂ , Cu (OAc) ₂ , Cu (aca
c) ₂ , copper oleinate, Bu ₂ Cu, (CH ₃ O) ₂
Cu, AgNO ₃ , AgBr, silver picrate, AgC ₆
H ₆ CIO ₄ Ag (pulparene) ₃ NO ₃ , [AuC≡
C-C _{(CH 3)} 3] _{n [Cu (C 7} H 8) Cl] ₄ such as copper group metal salts and complexes of (acac represents acetylacetone chelate ligand); (complex of an alkali metal) Li ( acac), a complex of alkali metal such as LiN (C ₄ H ₉ ) ₂ ; (complex of zinc) complex of zinc such as Zn (acac) ₂ ; (complex of cadmium) complex of cadmium such as Cd (acac) ₂ ; (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 (PEt
_{2 Ph) 2, CoC 5 F} 6 (CO) 7, Ni-π-C 5
Complexes of iron group metals such as H ₅ NO and ferrocene; (zirconium complex) Zr (acac) ₄ , zirconium complexes such as zirconocene; (Lewis acid compounds) AlX ₃ , TiX ₃ , TiX ₄ , VOX ₃ , VX. ₅ , Z
nX ₂ , FeX ₃ , SnX ₄ (where X is a halogen, an acetoxy group, an alkoxy group, or an aryloxy group)
Transition metal compounds that generate Lewis acids and Lewis acids and the like; (organotin _{compound) (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 (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 Bu ₂ SnCl ₂ and 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 the solid catalyst 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 by these. Of course, even if these catalyst components are reacted with organic compounds existing in the reaction system, for example, aliphatic alcohols, aromatic hydroxy compounds, alkylaryl carbonates, diaryl carbonates, dialkyl carbonates, etc. It may be heat-treated with a raw material or a product before the reaction.

Among these catalysts, lead oxides such as PbO, PbO ₂ and Pb ₃ O ₄ are particularly preferably used;
_{Pb (OH) 2, Pb 2} O 2 (OH) lead hydroxide such as _{2; PbCO 3, 2PbCO 3 ·} Pb (OH) carbonates ₂ such as lead and its basic salts; Pb _{(OCH 3) 2} ，
(CH ₃ O) Pb (OPh), Pb (OPh) _{2 and} other alkoxyleads; aryloxyleads 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
It is a distillation column having two or more stages of distillation, and may be any one as long as continuous distillation is possible (the number of stages of the distillation column in the present invention refers to that of a plate column). In this case, the number of trays is shown, and the number of theoretical plates is shown for packed column type and other distillation columns.). As such a continuous vertical distillation column, for example, a bubble column tray, a perforated plate tray, a valve tray, a tray column type using a tray such as a countercurrent tray, Raschig ring, Lessing ring, ball ring, Berlu saddle, Any type that is normally used as a continuous multi-stage distillation column, such as a packed column type filled with various packings such as Interlocks saddle, Dickson packing, McMahon packing, Helipack, Sulzer packing, Melapak, etc. Can be used. Further, a distillation column having both a tray part and a part filled with packing material is also preferably used. Also,
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 a liquid phase. For example, when a symmetrical dialkyl carbonate (R ¹ = R ² ) is used as the dialkyl carbonate and an aromatic monohydroxy compound is used as the aromatic hydroxy compound,
The equilibrium reaction is represented by the following chemical formula 9.

[0041]

[Chemical 10]

In the method of the present invention, these reactions are carried out in a continuous multi-stage distillation column in the presence of a catalyst, more preferably in a plurality of plates 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, and this method enables continuous production of aromatic carbonate with high yield and high selectivity for the first time.

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 reaction, in order to increase the reaction rate, it is necessary to remove by-products (usually aliphatic alcohols), which are low-boiling products produced by the reaction, from the reaction solution as quickly as possible.

However, it has been impossible to increase the reaction rate by the reaction system using the reaction vessel having the distillation column installed at the upper part as described in the prior art. 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 where the gas-liquid interface seat is very large. 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 the alkylaryl carbonate and / or diaryl carbonate, which is usually a high boiling point product, in the liquid is such that the catalyst is present. The distribution of the fatty alcohol, which is a low boiling point product, in the liquid gradually increases from the top of the column to the bottom of the column. It has a decreasing distribution, and it is possible to make the concentration in the liquid very low near the bottom of the tower. Further, in the vapor phase, the concentration of the aliphatic alcohol gradually increases from the lower part of the column to the upper part of the column.

In the present invention, these reactions proceed in the continuous multi-stage distillation column in this manner. Considering any position in this reaction region, however, the reaction solution approaches 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, if 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 lower than the concentration of the low boiling point reaction product. Thus, the reaction can be further advanced to further increase the concentration of the aromatic carbonates, which are high boiling point products, in the reaction liquid.

The conventional method of carrying out the reaction in a reaction vessel having a distillation column installed above is to proceed the reaction only in the reaction vessel, and the distillation column simply discharges from the gas-liquid interface in the reaction vessel to the gas phase. 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 type 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 while repeating liquid phase contact with the vapor rising from below. Therefore, it is possible to increase the reaction rate of the raw material compound in spite of being a continuous method (in the continuous method of continuously extracting the target aromatic carbonate by the conventional reaction method using a reaction vessel, the reaction rate of the raw material compound is It has been difficult to raise the temperature, and in fact, no method has been proposed so far to continuously carry out the reaction. 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 liquid-vapor contact with the descending liquid. 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 vapor column. Alternatively, a combination of these methods may be used.

When a homogeneous catalyst is fed to the distillation column,
The raw material may be mixed with either or both of the dialkyl carbonate and the aromatic hydroxy compound and supplied at the same time as the supply of the raw material, or at a stage different from the supply position of the raw material. 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, the reaction actually progresses in the distillation column is
Usually, since it is a region below the position where the catalyst is supplied, it is preferable to supply the catalyst to a region between the tower top and the raw material supply position. 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 at least two stages or more.

This solid catalyst also has an effect as a packing for a distillation column. 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. The method of the present invention comprises continuously supplying a dialkyl carbonate and an aromatic hydroxy compound to a continuous multi-stage distillation column, in which the reaction is carried out in the presence of a catalyst, and at the same time, a low boiling point produced by the reaction is produced. The aliphatic alcohol, which is the product, is continuously withdrawn in a gaseous state from the upper part of the distillation column by distillation, and the aromatic carbonate, which is a high-boiling product, is continuously withdrawn in the liquid form, from the lower part of the distillation column. It is characterized by continuously producing carbonates.

The method for continuously supplying the dialkyl carbonate and the aromatic hydroxy compound to the continuous multi-stage distillation column is not particularly limited, and they are at least one stage, preferably two or more stages in the distillation column. In the area of
Any method may be used as long as it can be brought into contact with the catalyst. That is, the dialkyl carbonate and the aromatic hydroxy compound can be continuously supplied from the required number of inlets to the stages satisfying the above conditions of the continuous multi-stage distillation column, and the starting material and the reactant are It may be introduced into the same stage of the distillation column,
They may be introduced in different stages.

The dialkyl carbonate and the aromatic hydroxy compound are continuously supplied in the form of liquid, gas or a mixture of liquid and gas. As described above, in addition to continuously supplying the dialkyl carbonate and the aromatic hydroxy compound to the continuous multi-stage distillation column, the gaseous dialkyl carbonate and / or the aromatic hydroxy compound is additionally added from the bottom of the distillation column. Discontinuous or continuous feeding is also a preferable method.

Of the raw materials consisting of the dialkyl carbonate and the aromatic hydroxy compound, the raw material having a higher boiling point is continuously supplied to the distillation column in a liquid or gas-liquid mixed state in a stage above the stage in which the catalyst is present. However, a method of continuously supplying a raw material having a lower boiling point in a gaseous state from the lower portion of the distillation column is also a preferable method. In this case, it does not matter if the low boiling point raw material is contained in the high boiling point raw material supplied from the upper portion.

These feed materials may contain products such as aliphatic alcohols, alkylaryl carbonates and diaryl carbonates, but since this reaction is a reversible reaction, the concentration of these products If it is too high, the reaction rate of the raw material is lowered, which is not preferable. The amount ratio of the dialkyl carbonate and the aromatic hydroxy compound supplied to the continuous multi-stage distillation column can be changed depending on the kind and amount of the catalyst and the reaction conditions, but usually,
The aromatic hydroxy compound is preferably supplied in a molar ratio of 0.01 to 1000 times with respect to the dialkyl carbonate in the raw material.

In the present invention, the aliphatic alcohol, which is a low boiling point product, is continuously withdrawn from the distillation column in the form of gas, which is a product having a lower boiling point than the reaction in the continuous multistage distillation column. In this case, the gaseous extract may be an aliphatic alcohol alone, a mixture with a raw material compound, or a small amount of a high boiling point product. From the continuous multi-stage distillation column, the outlet for extracting the gaseous substance containing the low boiling point product can be provided at any position other than the bottom of the column, but the concentration of the low boiling point product in the vapor phase is usually It increases as it goes to the top. Therefore, it is preferable to provide an outlet for the gaseous substance between the raw material supply position and the top of the column or at the top of the column, more preferably at the top of the column. A so-called reflux operation may be performed in which the gaseous component extracted in this manner is liquefied by cooling or the like and a part of it is returned to the upper part of the distillation column. When the reflux ratio is increased by this reflux operation, the distillation efficiency of the low boiling point product into the vapor phase is increased, so that the concentration of the low boiling point product in the extracted gas component can be increased. However, if the reflux ratio is increased too much, the required thermal energy becomes large, which is not preferable. Therefore, the reflux ratio is usually 0 to 20,
Preferably, 0-10 is used.

The aromatic carbonates produced according to the present invention are continuously withdrawn as a high boiling point product in a liquid form from the lower part of the continuous multistage distillation column. In this case, the liquid extract may be a high boiling point product alone, a mixture with a starting compound, or a small amount of a low boiling point product. When a catalyst having a high boiling point that can be dissolved in the reaction solution under the reaction conditions is used, the liquid extract also contains the catalyst. An extraction port for extracting a liquid substance containing a high boiling point product from a continuous multi-stage distillation column is provided at the bottom of the column,
Particularly preferably, it is provided in the lower part of the tower. The liquid substance thus extracted may be returned to the lower part of the distillation column in a gaseous or gas-liquid mixture state by heating a part of it with a boiler.

The amount of the catalyst used in the present invention includes the type of catalyst used, the type of continuous multi-stage distillation column, the type of dialkyl carbonate and the aromatic hydroxy compound and the ratio thereof,
It depends on the reaction conditions such as reaction temperature and reaction pressure, but when the catalyst is continuously supplied to the reaction zone of the continuous multi-stage distillation column, the total weight of the feedstock such as dialkyl carbonate and aromatic hydroxy compound is used. It is usually used in an amount of 0.0001 to 50% by weight. When the solid catalyst is used by being installed in a continuous multi-stage distillation column, 0.01% of the empty column volume of the distillation column is used.
A catalyst amount of ˜75% by volume is preferably used.

In the present invention, since the reaction takes place in the continuous multi-stage distillation column in which a catalyst is present, the amount of the reaction product produced usually depends on the amount of the holdup liquid in the distillation column. That is, when the distillation column having the same column height and the same column diameter is used, a distillation column having a large amount of hold-up liquid is preferable in the sense that the retention time of the reaction liquid, that is, the reaction time can be relatively lengthened.

However, when the amount of the hold-up liquid is too large, the retention time becomes long, so that side reactions easily proceed and flooding easily occurs. Therefore, the hold-up liquid amount of the distillation column used in the present invention may vary depending on the distillation conditions and the type of the distillation column, but is expressed by the volume ratio of the hold-up liquid amount to the empty column volume of the continuous multi-stage distillation column, and usually, It is performed at 0.005 to 0.75.

Further, in the present invention, the average residence time of the reaction liquid in the continuous multi-stage distillation column varies depending on the reaction conditions, the type of the multi-stage continuous distillation column and the internal structure (for example, types of trays and packings). It is usually 0.001 to 50 hours, preferably 0.01 to 10 hours, more preferably 0.05 to 5 hours. The reaction temperature is the temperature in the continuous multi-stage distillation column, and although it varies depending on the types of the raw material compounds, the dialkyl carbonate and the aromatic hydroxy compound, it is generally 50 to 350 ° C, preferably 100 to 280 ° C. The reaction pressure may be any of reduced pressure, normal pressure and increased pressure, although it varies depending on the type of raw material compound used, reaction temperature, etc., and is usually 0.1 mmHg to 200 kg
/ Cm ² range.

In the present invention, it is not always necessary to use a solvent, but a suitable inert solvent such as ethers, aliphatic hydrocarbons and aromatic hydrocarbons for the purpose of facilitating the reaction operation and the like. , Halogenated aliphatic hydrocarbons,
A halogen aromatic hydrocarbon or the like can be used as a reaction solvent. Further, as a substance inert to the reaction, an inert gas such as nitrogen, helium, or argon may be allowed to coexist in the reaction system, and a continuous multistage distillation column for the purpose of accelerating the distillation of the low boiling point by-product to be produced. From the lower part, the above-mentioned inert gas or the low-melting point organic compound inert to the reaction may be introduced in a gaseous state.

In order to specifically explain the present invention, the reactor will be exemplified below, but the present invention is not limited thereto. For example, as shown in FIG. 1, a raw material mixture composed of a dialkyl carbonate and an aromatic hydroxy compound is introduced from an introduction pipe (2) through a preheater (5) to a reboiler (1
0) and a condenser (13) are continuously introduced into a continuous multistage distillation column (1), and the bottom liquid is reboiler (10).
The reaction and distillation are carried out by heating with.
A liquid component containing aromatic carbonates, which is a high-boiling product produced in the presence of a catalyst in the continuous multi-stage distillation column, is continuously withdrawn from the lower part of the column as a column bottom liquid via a conduit (19). Further, a gas phase component containing a low boiling point product which is a reaction by-product is continuously withdrawn as a top gas from the conduit (12) and condensed in a condenser (13).
It is continuously withdrawn from the conduit (16) as the top of the column.
It is also possible to reflux a part of the overhead liquid from the introduction pipe (15) to the upper part of the continuous multistage distillation column.

Further, as shown in FIG. 2, the raw material mixture consisting of the dialkyl carbonate and the aromatic hydroxy compound is continuously introduced into the continuous multistage distillation column (1) from the introduction pipe (2) through the preheater (5). At the same time, one of the starting compounds having a lower boiling point is introduced through the introduction pipe (7) and vaporized in the evaporator (9), and then the continuous multistage distillation column (1)
The reaction and distillation are carried out by continuously introducing from the lower part of. A liquid component containing an aromatic carbonate, which is a high-boiling product produced in the presence of a catalyst inside the continuous multi-stage distillation column, is continuously withdrawn from the lower part of the column through a conduit (19) as a bottom liquid. Further, a gas phase component containing a low boiling point product which is a reaction by-product is continuously withdrawn as a top gas from a conduit (12) and condensed in a condenser (13), and then the top is supplied from a conduit (16). It is continuously withdrawn as a liquid.

[0065]

EXAMPLES Next, the present invention will be specifically described by way of 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 KK)].

[0066]

Example 1 As shown in FIG. 1, Dickson packing (6 mmφ) made of stainless steel was filled as a filling material. Dimethyl carbonate at a position 1 m from the top of the continuous multistage distillation column consisting of a packed column having a column height of 4 m and a column diameter of 3 inches,
A mixture of phenol and catalyst was continuously fed in liquid form from the introduction pipe (2) through the preheater (5) into the distillation column (1). The amount of heat required for reactive distillation was supplied by heating the lower liquid of the column with a reboiler. The reaction conditions are shown in Table 1. As a result of the reaction, a liquid containing the catalyst components and the reaction products, methylphenyl carbonate and diphenyl carbonate, was obtained from the bottom (18) of the distillation column through conduits (8) and (19). The results of the reaction are shown in Table 2. Also,
This reaction liquid contained 0.02% by weight of anisole, which is considered to be produced by a side reaction (decarboxylation reaction) of methylphenyl carbonate. The results show that the phenol-based anisole selectivity is 0.8%. A conduit (12) provided at the top (17) of the tower
The gas distilled from was condensed in the condenser (13). A part of the condensate was refluxed to the distillation column (1) via the conduit (15), and the rest was extracted from the conduit (16). From this condensate, low boiling point reaction product methanol was obtained.

The reaction conditions are shown in Table 1 and the reaction results are shown in Table 2.

[0068]

[Comparative Example 1] A distillation column (63) having a tower height of 1 m and a diameter of 1 inch shown in FIG. 3 [filled with stainless Dickson packing (6 mmφ)] and a stirrer (71), capacity 15 L autoclave type reaction kettle (6
2) Liquid 12.6k having the same composition as that used in Example 1
g was charged via conduit (61). The reaction was carried out while heating the reaction vessel (62) using an electric furnace (70) with stirring so that the liquid temperature was kept constant at 204 ° C. The gas distilled from the top (69) of the distillation column (63) is fed through a conduit (6).
Part of the condensate condensed in condenser (65) via 4) was refluxed via conduit (67) and the rest was continuously withdrawn from conduit (68) at a rate of 2.1 kg / hr. . The reflux ratio was 0.8. When 4.2 kg of the condensate was withdrawn, the reaction vessel (62) was cooled and the reaction solution was introduced into the conduit (7).
When extracted from 2), the weight was 8.4 kg. The ratio of the amount of charged liquid to the amount of liquid remaining in the kettle in this comparative example was the same as the ratio of the amount supplied from the introduction pipe (2) and the amount discharged from the bottom liquid from the conduit (19) in Example 1. It was

The distilling rate of the distillate obtained by condensing the gas components was also the same. As a result of the analysis, methylphenyl carbonate was 1.8% by weight, diphenylcarbonate was 0.01% by weight, and anisole was 0.07% by weight in the reaction solution.
Was included. The amount of aromatic carbonate produced per kg of the reaction solution per hour was 9 g / kg · hr for methylphenyl carbonate and 0.05 g / kg · hr for diphenyl carbonate. The selectivity of aromatic carbonate based on phenol was 94% for methylphenyl carbonate and 1% for diphenyl carbonate.
The selectivity of the by-product anisole based on phenol was 5%. As a result of performing the same reaction for 4 hours, the selectivity of by-product anisole was 7%.

The results of Example 1 show that the amount of methylphenyl carbonate produced is 34 g / kg · hr (selectivity 97%).
And the amount of diphenyl carbonate produced is 0.5 g / k
g · hr (selectivity 2%) and by-product anisole selectivity 0.8% (constant without change over time), so a batch-type reaction kettle with a distillation column simply installed at the top Compared with the method (Comparative Example 1), the method of the present invention is capable of continuously producing aromatic carbonate at a high reaction rate with high yield (high production amount per unit time), high selectivity. It turns out to be an excellent method.

[0071]

Examples 2 to 4 Experiments were conducted using the same equipment as in Example 1 under the reaction conditions shown in Table 1. The results are shown in Table 2.

[0072]

Example 5 As shown in FIG. 2, a continuous multi-stage distillation column (1) composed of a packed column having a column height of 4 m and a column diameter of 3 inches, filled with stainless Dickson packing (6 mmφ) as a packing material. A mixture of dimethyl carbonate, phenol and a catalyst was continuously fed in a liquid state into the distillation column (1) from an inlet pipe (2) through a preheater (5) to a position 1 m from the top, and dimethyl carbonate containing phenol. Was introduced from an introduction pipe (7), and was supplied to the bottom of the distillation column (1) in a gaseous state via an evaporator (9). The reaction conditions are shown in Table 2. As a result of the reaction, a liquid containing methylphenyl carbonate and diphenyl carbonate as reaction products was obtained from the bottom of the distillation column. Further, methanol, which is a low boiling point product, was obtained from the liquid obtained by condensing the gas distilled from the top of the column in the condenser (13). The results are shown in Tables 3 and 4.

[0073]

Examples 6 to 9 Using the same equipment as used in Example 5, the reaction was carried out under the reaction conditions shown in Table 3. The results are shown in Table 4.

[0074]

Example 10 Instead of a packed column as a continuous multi-stage distillation 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. Example 5 except that the reaction was carried out under the reaction conditions shown in Table 3.
The reaction was performed in the same manner as in. The results are shown in Table 4.

[0075]

[Table 1]

[0076]

[Table 2]

[0077]

[Table 3]

[0078]

[Table 4]

The symbols in the table have the following meanings, and the amount of aromatic carbonate produced and the selectivity are shown in the following (Note). DMC: Dimethyl carbonate DEC: Diethyl carbonate PhOH: Phenol Pb (OPh) ₂ : Diphenoxy lead Ti (OPh) ₄ : Tetraphenoxy titanium Bu ₂ SnO: Dibutyltin oxide MPC: Methylphenyl carbonate MTC: Methyltolyl carbonate EPC: Ethylphenyl carbonate DPC : Diphenyl carbonate DTC: ditolyl carbonate wt%: wt% (Note) The amount of aromatic carbonate produced is expressed in g per hour per 1 kg of the bottom liquid.

The selectivity of the aromatic carbonate is based on the starting aromatic hydroxy compound.

[0081]

According to the method of the present invention, an aromatic carbonate composed of an alkyl carbonate, a diaryl carbonate or a mixture thereof is continuously obtained with a high yield and a high selectivity from a dialkyl carbonate and an aromatic hydroxy compound as raw materials. be able to.

[Brief description of drawings]

1 is a schematic diagram of an example process for practicing the present invention.

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

FIG. 3 is a schematic view of a reaction device used in Comparative Example 1.

[Explanation of symbols]

 1 Continuous multi-stage distillation column 2, 7, 15 Introducing pipe 5 Preheater 8, 12, 16, 19 Conduit 9 Evaporator 10 Reboiler 13 Condenser 17 Top of column 18 Bottom of bottom 61, 67 Introducing pipe 62 Reactor 63 Distillation column 64, 68, 72 conduit 65 condenser 69 tower top 70 electric furnace 71 stirrer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location B01J 27/122 27/125 27/232 27/236 29/06 31/02 101 31/04 31 / 12 31/20 31/22 C07B 61/00 300

Claims (3)

[Claims] 1. A dialkyl which is a raw material compound for producing an aromatic carbonate composed of an alkylaryl carbonate, a diaryl carbonate or a mixture thereof by reacting a dialkyl carbonate with an aromatic hydroxy compound in the presence of a catalyst. The carbonate and the aromatic hydroxy compound are continuously fed into a continuous multi-stage distillation column, and the catalyst and the raw material compound are brought into contact in the distillation column to cause a reaction, while the aliphatic alcohol produced as a by-product is distilled. A continuous process for producing aromatic carbonates, characterized in that the aromatic carbonates are continuously withdrawn in a gaseous state and the produced aromatic carbonates are continuously withdrawn in a liquid state from the lower part of the tower. 2. The method according to claim 1, wherein the catalyst is present by continuously feeding the homogeneous catalyst to a continuous multistage distillation column. 3. The catalyst is a solid catalyst, and the solid catalyst is placed inside a continuous multistage distillation column so that the catalyst is present.
The method of claim 1.