JP2000072721A - Supply of catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply a catalyst by a method for causing a small amount of a by-product and not requiring the preliminary preparation of the catalyst in reacting a dialkyl carbonate with an aromatic hydroxyl compound by supplying a specific catalytic precursor. SOLUTION: In obtaining (C) a diaryl carbonate by reacting (A) a dialkyl carbonate (e.g. dibutyl carbonate) with (B) an aromatic hydroxyl compound (e.g. phenol), (E) a titanium tetraalkoxide having the same alkyl group as that of the component A [Ti(OR)4 (R is the same alkyl as that of the component A and is a 2-6C alkyl)] (e.g. titanium tetra-n-butoxide is supplied as a catalytic precursor in stead of supplying (D) a titanium tetraaryl oxide being a catalyst. Since the supplied component E is rapidly converted into the component D in the system, the catalyst can be readily supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for supplying a catalyst. More specifically, the present invention relates to a method for supplying a catalyst in a reaction for producing a diaryl carbonate from a dialkyl carbonate and an aromatic hydroxy compound.

[0002]

2. Description of the Related Art It is known that titanium tetraphenoxide is used as a catalyst in a process for producing a diaryl carbonate by a transesterification reaction between an aromatic hydroxy compound and a dialkyl carbonate and a disproportionation reaction of an alkylaryl carbonate (Japanese Patent Laid-Open Publication No. H11-163873). Showa 5
1-105032, JP-A-51-75044). However, since the catalyst is a solid at ordinary temperature, its operability is poor and it is difficult to obtain. As a method for preparing the catalyst, a method for preparing titanium tetraphenoxide from titanium tetraethoxide and phenol (J. Indian Chl.
em. Soc., Vol. 38, No. 3, 1961), and a method of preparing and supplying titanium tetraphenoxide by reacting titanium oxide with phenol (Japanese Patent Laid-Open No.
0-43606) have been proposed. However, any of the methods required an apparatus and a process for preparing the catalyst.

Further, as a method for producing diaryl carbonate using titanium tetraalkoxide as a catalyst, a method for producing diphenyl carbonate from phenylmethyl carbonate using titanium tetramethoxide as a catalyst (JP-A-51-75044), A method of reacting carbonate and phenol in the presence of a titanium tetraisopropoxide catalyst
-105032).

[0004] However, titanium tetramethoxide is
It is solid at room temperature, has poor operability, and is expensive. on the other hand,
Titanium tetraisopropoxide is a liquid at room temperature, has excellent operability, and is easily available. However, as a result of investigations by the present inventors, titanium tetraalkoxide is:
By reacting with an aromatic hydroxy compound, or an alkylaryl carbonate, or a diaryl carbonate in a reaction system, it becomes a titanium tetraaryl oxide or an adduct of the aromatic hydroxy compound. When the groups are different, it is apparent that by-products having different alkyl groups are mixed in the alkyl alcohol, dialkyl carbonate and alkyl aryl carbonate, which is a problem in recycling the alkyl alcohol, dialkyl carbonate and alkyl aryl carbonate. It became.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for supplying a catalyst which has a small amount of by-products and requires no preparatory preparation in view of the above-mentioned problems.

[0006]

Means for Solving the Problems The present inventors have intensively studied a method for producing a diaryl carbonate from a dialkyl carbonate and an aromatic hydroxy compound in order to solve the above-mentioned problems. As a result, if instead of supplying titanium tetraaryl oxide as a catalyst, if titanium tetraalkoxide corresponding to the alkyl group of the dialkyl carbonate used as a raw material is supplied, it is quickly converted into titanium tetraaryl oxide in the system, which is convenient. Has been found to be able to supply the catalyst. Furthermore, since the alkyl alcohol by-produced from titanium tetraalkoxide is the same as the alkyl alcohol produced by the reaction, it has been found that mixing of by-products having different alkyl groups can be avoided, and the present invention has been achieved.

That is, the present invention relates to [A] a titanium tetraalkyl carbonate represented by the general formula (5) comprising a dialkyl carbonate represented by the general formula (1) and an aromatic hydroxy compound represented by the general formula (2). A step of reacting an aryl oxide or an adduct thereof with an aromatic hydroxy compound as a catalyst to produce an alkylaryl carbonate represented by the general formula (3), [B] a dialkyl represented by the above general formula (1) By distilling off the carbonate, the alkylaryl carbonate produced in the above step is disproportionated in the presence of the same catalyst as in step [A] to produce a diaryl carbonate represented by the general formula (4). The same alkyl group as the dialkyl carbonate used as the raw material in the method for producing a diaryl carbonate comprising the two steps of A titanium tetraalkoxide represented by the general formula (6) is supplied as a catalyst precursor, and a titanium tetraaryl oxide represented by the general formula (5) or an aromatic hydroxy compound thereof is used as a catalyst in the system. The present invention relates to a method for supplying a catalyst, which is used after being converted into an adduct.

Embedded image RO—CO—OR (1) ArOH (2) RO—CO—OAr (3) ArO—CO—OAr (4) Ti (OAr) ₄ (5) Ti (OR) ₄ (6) (Formula 2) In the formula, R represents an alkyl group having 2 to 6 carbon atoms, and Ar represents an unsubstituted or a phenyl group substituted by an alkyl group, an alkoxy group, or a halogen.
Throughout the formulas (1) to (6), the same symbols indicate the same substituents. )

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The dialkyl carbonate as a raw material of the present invention is a dialkyl carbonate having an alkyl group having 2 to 6 carbon atoms, specifically, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, dipentyl carbonate. And various isomers of dihexyl carbonate.

The aromatic hydroxy compound as the other raw material of the present invention is phenol and phenol substituted with an alkyl group, an alkoxy group, a halogen, etc.
Specifically, phenol, cresol (each isomer), xylenol (each isomer), ethylphenol (each isomer), methoxyphenol (each isomer), fluorophenol (each isomer), chlorophenol (each isomer) ) Are exemplified.

The compound supplied as a catalyst precursor in the present invention is a titanium tetraalkoxide represented by Ti (OR) ₄ , wherein R is the same as the alkyl group of the dialkyl carbonate used as a raw material. If a dialkyl carbonate and an alkyl group with a different titanium alkoxide are used, the resulting alkyl alcohol, dialkyl carbonate and alkylaryl carbonate are mixed with different alkyl groups,
Decrease purity. Further, when these are recycled without being separated and titanium tetraalkoxide is replenished, alkyl carbonates having different alkyl groups gradually accumulate, which causes a reduction in yield.

R is an alkyl group having 2 to 6 carbon atoms. Titanium tetramethoxide, in which R is methyl, is expensive, is solid at ordinary temperature and has poor operability, so that the effect of this supply method is poor. On the other hand, titanium tetraalkoxides having 2 to 6 carbon atoms are excellent in operability because they are liquid at ordinary temperature, and particularly, titanium tetraethoxide, titanium tetraisopropoxide, titanium tetra n-propoxide, and titanium tetra n- Butoxide, titanium tetraisobutoxide and the like are inexpensive and readily available.

The method for producing a diaryl carbonate used in the present invention comprises the steps of: [A] reacting a dialkyl carbonate with an aromatic hydroxy compound using titanium tetraaryl oxide or an adduct of the aromatic hydroxy compound as a catalyst, A step of producing a carbonate, and [B] a step of disproportionating the alkylaryl carbonate produced in the above step in the presence of the same catalyst as in the step [A] to produce a dialkyl carbonate and a diaryl carbonate. Become.

This reaction can be carried out by either a batch system or a continuous system. When the step [A] and the step [B] are performed in a batch system, the step [B] can be performed in the same reactor after the step [A] is performed. When the above two steps are performed in a continuous manner, at least two reactors are used, and the step [A] and the step [B] are performed in separate reactors. In both the step [A] and the step [B], it is preferable to use a reactor provided with a distillation column at the top, and the reaction can also be performed in the distillation column.

In the step [A], the reaction is carried out by distilling off the alkyl alcohol. The distillated alkyl alcohol is reacted with urea or carbon monoxide and can be recycled as dialkyl carbonate. Therefore, it is preferable that the alkyl alcohol to be distilled has a high purity.

In the step [B], the reaction is carried out by distilling off the dialkyl carbonate. The dialkyl carbonate distilled off is preferably reused as a raw material in the step [A].

The titanium tetraalkoxide can be supplied alone to the reactor in the step [A] or the step [B], or can be supplied together with the liquid charged in the step [A] or the step [B]. In this case, the charge in step [A] is a mixture of an aromatic hydroxy compound and a dialkyl carbonate, and may further contain a recycled catalyst, an alkyl alcohol, a small amount of an alkylaryl carbonate and a diaryl carbonate. good. Further, the charged liquid in the step [B] refers to the liquid in the step [A].
Reaction solution.

The supplied titanium tetraalkoxide becomes a titanium aryl oxide corresponding to the aryl group of the aromatic hydroxy compound used as a raw material or an adduct of the aromatic hydroxy compound in the reaction system, and acts as a catalyst. The used catalyst is preferably returned to the step [A] and reused. Normally,
In order to prevent deactivation of the catalyst and accumulation of by-products, a part of the solution containing the catalyst to be reused is removed outside the reaction system, and titanium tetraalkoxide is supplied for the purpose of replenishing the removed catalyst. If there is no catalyst to be reused, the entire amount of the catalyst can be covered by titanium tetraalkoxide.

The total amount of the titanium tetraalkoxide and the catalyst to be recycled is 0.01 to 10 mol% based on the dialkyl carbonate used as the raw material in the step [A].
It is preferable to adjust so that

This reaction is preferably carried out at a reaction temperature of about 160 to 250 ° C. If the reaction temperature is too low, the reaction is slow, and if the reaction temperature is too high, decomposition of carbonates and generation of by-products are observed. The pressure is suitably in the range of the above reaction temperature in the range of 0.001 to 0.5 MPa for distilling off the alkyl alcohol or dialkyl carbonate.

[0020]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. In this example, when the term "butyl" is simply used, n-
Butyl shall be indicated.

Example 1 A glass-made distillation column equipped with a vacuum jacket (Sulzer Lab packing, inner diameter 50 mmφ, height of packed section 1100 m)
m) was connected to the top of a 5-liter round bottom flask and charged with 862 g of dibutyl carbonate, 932 g of phenol and 16.8 g of titanium tetrabutoxide. The mixture was heated by a mantle heater while stirring at 300 rpm with a mechanical stirrer. The temperature at the bottom of the tower is 191 ° C
After the reflux was started, total reflux was performed for 10 minutes, and then distillation was started at a reflux ratio of 30. Starting from the start of the distillation, the reaction was started, and the butyl phenyl carbonate yield (mol%) based on the charged dibutyl carbonate was analyzed by gas chromatography. As a result, 1
2.3%, 18.6% in 60 minutes, 22.5% in 90 minutes,
It was 27.4% at 120 minutes and 30.0% at 150 minutes. The amount of the distillate was 131 g, butanol 128 g,
It contained 3 g of phenol. The temperature at the bottom of the column at the start of the distillation was 192 ° C, and the temperature after 150 minutes was 197 ° C. 150 minutes after the start of the reaction, the reflux ratio was set to 0.2, and the reaction pressure was gradually lowered from normal pressure to 450 mmHg, whereby mainly unreacted phenol and dibutyl carbonate were distilled off. After 40 minutes, almost unreacted phenol and dibutyl carbonate were distilled off. At this time, the temperature at the bottom of the tower was 205 ° C. Therefore, dibutyl carbonate was mainly distilled off while gradually reducing the reaction pressure to 100 mmHg. Set the reflux ratio to 0.2 and then 2
After a lapse of time, the reaction was terminated, and the reaction mixture was analyzed. As a result, 133 g of diphenyl carbonate was produced. At this time, the temperature at the bottom of the tower was 207 ° C. The amount of the distillate was 1460 g, 668 g of dibutyl carbonate and 774 phenol.
g, butanol 18 g.

COMPARATIVE EXAMPLE 1 Except that 20.8 g of titanium tetraphenoxide was used instead of 16.8 g of titanium tetrabutoxide,
The reaction and analysis were performed in the same manner as in Example 1. As a result, the butyl phenyl carbonate yield was 12.3 in 30 minutes of the reaction.
%, 18.7% at 60 minutes, 24.0% at 90 minutes, 120
Min was 26.4% and 150 min was 30.3%. The temperature at the bottom of the column at the start of the distillation was 192 ° C, and the temperature after 150 minutes was 197 ° C. Further, the amount of diphenyl carbonate produced after the completion of the reaction was 135 g. The reaction rate was almost the same as in Example 1 using titanium tetrabutoxide as a catalyst.

Comparative Example 2 A reaction and analysis were carried out in the same manner as in Example 1 except that 1001 g of diisoamyl carbonate was used instead of 862 g of dibutyl carbonate. As a result, the yield of isoamylphenyl carbonate was 16.9% in 30 minutes, 21.4% in 60 minutes, 24.9% in 90 minutes, and 28.0% in 120 minutes.
0% and 29.9% at 150 minutes. The temperature at the bottom of the column at the start of the distillation was 195 ° C, and the temperature after 150 minutes was 20 ° C.
1 ° C. The amount of the distillate was 133 g, which contained 114 g of isoamyl alcohol, 15 g of phenol, and 4 g of butanol as a by-product. Further, similarly to Example 1, the reaction was performed for 2 hours while the reflux ratio was set to 0.2 and the pressure was gradually reduced to 100 mmHg. At this time, the temperature at the bottom of the tower was 209 ° C. The amount of the distillate was 1610 g, 15 g of isoamyl alcohol and 746 of phenol.
g, 688 g of diisoamyl carbonate and 134 g of isoamylphenyl carbonate, as well as 24 g of isoamylbutyl carbonate and 3 g of butylphenyl carbonate as by-products. The amount of diphenyl carbonate produced after the completion of the reaction was 93 g.

Example 2 The reaction solution of Example 1 was distilled at 200 ° C. and 10 mmHg to obtain 29.2 g of a catalyst residue. 20% by weight of this catalyst residue was removed, and 3.4 g of titanium tetrabutoxide was added to obtain a recycled catalyst. Further, 1460 g of the distillate from Example 1 (dibutyl carbonate 66
Contains 8 g, 774 g of phenol and 18 g of butanol. ), 194 g of dibutyl carbonate and 158 g of phenol were additionally used as raw materials. The reaction and analysis were conducted in the same manner as in Example 1. As a result, the yield of butylphenyl carbonate was 14.8% in 30 minutes of the reaction, and 18.8 in 60 minutes.
%, 22.6% in 90 minutes, 27.1% in 120 minutes, 15
It was 31.2% at 0 minutes. The temperature at the bottom of the column at the start of the distillation was 193 ° C, and the temperature after 150 minutes was 197 ° C. After the reaction was completed, the amount of diphenyl carbonate produced was 134 g.

Example 3 Using the reaction solution of Example 2, an experiment for recycling the catalyst was carried out in the same manner as in Example 2. As a result, the yield of butyl phenyl carbonate was 13.8% in 30 minutes of the reaction, 18.9% in 60 minutes, 22.6% in 90 minutes, and 27.20 in 120 minutes.
2%, 31.2% at 150 minutes. The temperature at the bottom of the column at the start of the distillation was 193 ° C, and the temperature after 150 minutes was 19 ° C.
7 ° C. Further, the amount of diphenyl carbonate produced after the completion of the reaction was 142 g. Comparing the production rate of butylphenyl carbonate and the production amount of diphenyl carbonate in Examples 1, 2, and 3, it can be seen that the catalyst can be satisfactorily replenished without lowering the activity of the catalyst.

[0026]

According to the method of the present invention, in producing a diaryl carbonate from a dialkyl carbonate having an alkyl group of 2 to 6 carbon atoms and an aromatic hydroxy compound, it is possible to prepare the diaryl carbonate by a method with a small amount of by-products without any preliminary preparation. A catalyst can be supplied.

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Claims (6)

[Claims] 1. A method for producing a diaryl carbonate from a dialkyl carbonate and an aromatic hydroxy compound, wherein titanium tetraalkoxy having the same alkyl group as the dialkyl carbonate is supplied as a catalyst precursor. Supply method. 2. [A] A titanium tetraaryl oxide represented by the general formula (5) comprising a dialkyl carbonate represented by the general formula (1) and an aromatic hydroxy compound represented by the general formula (2): Alternatively, a step of producing an alkylaryl carbonate represented by the general formula (3) by reacting the adduct with the aromatic hydroxy compound as a catalyst, [B] distilling the dialkyl carbonate represented by the general formula (1) A process of disproportionating the alkylaryl carbonate produced in the above step in the presence of the same catalyst as in the step [A] to produce a diaryl carbonate represented by the general formula (4). In a method for producing a diaryl carbonate comprising two steps, a general formula having the same alkyl group as the dialkyl carbonate used as a raw material The titanium tetraalkoxide represented by 6) is supplied as a catalyst precursor, and is converted into a titanium tetraaryl oxide represented by general formula (5) or an adduct thereof with an aromatic hydroxy compound as a catalyst in the system. A method for supplying a catalyst, characterized in that it is used after being used. Embedded image RO—CO—OR (1) ArOH (2) RO—CO—OAr (3) ArO—CO—OAr (4) Ti (OAr) ₄ (5) Ti (OR) ₄ (6) (formula In the formula, R represents an alkyl group having 2 to 6 carbon atoms, and Ar represents an unsubstituted or a phenyl group substituted by an alkyl group, an alkoxy group, or a halogen.
Throughout the formulas (1) to (6), the same symbols indicate the same substituents. ) 3. The above-mentioned general formula (1) distilled off in the step [B]
The method for supplying a catalyst according to claim 2, wherein the dialkyl carbonate represented by the formula is reused as a raw material in the step [A]. 4. The method according to claim 2, wherein the reaction is carried out in a batch reactor having a distillation column on top. 5. The method according to claim 2, wherein R is an n-butyl group. 6. The method according to claim 2, wherein said Ar is a phenyl group.