JP2001058974A - Production of diaryl carbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently obtain a diaryl carbonate by imparting fixed agitation driving force in reaction of an aromatic monohydroxy compound with phosgene and/or an aryl chloroformate. SOLUTION: When reacting an aromatic monohydroxy compound (e.g. phenol or the like) with phosgene and/or an aryl chloroformate in the presence of an aromatic heterocyclic nitrogen-containing basic compound (e.g. pyridine or the like), motive power of >=250 kgf.m/L is imparted as agitation driving force (P/q) per a unit flow rate in a reactor which is calculated by the formula: P/q=Np.ρ.n3.d5/q [Np is an agitation driving force constant; ρ is a specific gravity (kg/m3) of a reactional liquid; n is a number of revolution (rps) of an agitator; d is a diameter (m) of gyration of an agitator; q is a flow rate (L/s) of a reactional liquid]. Raw materials are continuously fed into a first reactor 1 and agitation driving force is imparted by an agitator 31 preferably at 120-190 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a stable and high-quality diaryl carbonate. The diaryl carbonate obtained in the present invention is useful as a raw material for producing an aromatic polycarbonate by a melt transesterification method.

[0002]

2. Description of the Related Art A method for obtaining a diaryl carbonate by reacting an aromatic monohydroxy compound with phosgene and / or an aryl chloroformate in the presence of an aromatic heterocyclic nitrogen-containing basic compound is well known ( For example, see JP-A-58-50977). In this method, one mole of phosgene is used for 2 moles of an aromatic monohydroxy compound (phenol) at a temperature of 40 to 180 ° C. and, if necessary, in a solvent, using 2 moles of an aromatic monohydroxy compound (phenol), using an aromatic nitrogen-containing heterocyclic compound as a catalyst. A condensation reaction involving elimination of hydrogen chloride is performed to produce diaryl carbonate (diphenyl carbonate). However, compared to the production rate of phenyl chloroformate, which is an intermediate product of diphenyl carbonate, the production rate of diphenyl carbonate by the reaction between the chloroformate and phenol is not sufficient. For this reason, a small amount of the chloroformate remains at the end of the reaction, lowering the purity of the diaryl carbonate, and adversely affecting the production of a non-colored aromatic polycarbonate.

As an improvement of this manufacturing method, Japanese Patent Laid-Open No.
JP-A-7250 and JP-A-9-278714 describe that a reaction under specific conditions can effectively reduce the remaining amount of a chloroformate. That is, upon the reaction between the aromatic monohydroxy compound and phosgene, the chloroformate is produced in an equivalent amount or less with respect to the unreacted aromatic monohydroxy compound, and the chloroformate in the obtained reaction solution is further converted to the chloroformate. A technique for reacting with an unreacted monohydroxy compound to convert substantially the entire amount to a diaryl carbonate is described.

Further, Japanese Patent Application Laid-Open No. Hei 10-245366 discloses that the quality of a diaryl carbonate obtained as described above includes steps of neutralization, washing and distillation based on hydrolyzable chlorine contained in a product. It is described that good quality can be maintained after passing through. In addition, Japanese Patent Application Laid-Open No. H11-5766 describes a cleaning condition, and Japanese Patent Application Laid-Open No. H11-5767 describes a method in which cleaning water is reused.

[0005]

As described above, various effective methods for reducing the amount of chlorine and the amount of chlorine contained in a trace amount have been proposed, and it is recognized that the problem of the quality of diaryl carbonate has been almost solved. . However, when diaryl carbonate production is carried out industrially according to these methods, how to effectively use the raw material phosgene,
No particularly effective means has been proposed for conversion to products. For example, at the stage of increasing the scale of the reaction system, the same reaction efficiency cannot be ensured if the reaction tank is increased in proportion to the increasing supply amount of phosgene. Cannot be expected to increase the amount corresponding to the scale. In the case of phosgene which comes in gaseous contact with other liquid reactants in the reaction vessel, it is impossible to make the gas linear velocity the same as on a small scale, and the reduction in reaction efficiency caused by this is compensated by other means. It was essential. That is, when a diaryl carbonate is obtained by reacting an aromatic monohydroxy compound with phosgene and / or an aryl chloroformate in the presence of an aromatic heterocyclic nitrogen-containing basic compound, the reaction efficiency of phosgene is improved. It was an important issue to do so.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies in order to solve this problem, and as a result, by applying a constant stirring power, gaseous phosgene can be more effectively used for the reaction. And completed the present invention. An object of the present invention is to provide conditions under which phosgene can be used most efficiently in the production of diaryl carbonate.

The gist of the present invention is to provide a process for producing a diaryl carbonate, which comprises reacting an aromatic monohydroxy compound with phosgene and / or an aryl chloroformate in the presence of an aromatic heterocyclic nitrogen-containing basic compound. The stirring power (P / q) per unit flow rate in the reactor at the time of the reaction determined in (1) is 250
(Kgf · m / l) or more. P / q = Np · ρ · n ³ · d ⁵ / q (kgf · m / l) (1) Np: stirring power constant, ρ: specific gravity of reaction solution (kg / m
m ³ ), n: number of revolutions of the stirrer (rps), d: blade diameter of the stirrer (m), q: flow rate of the reaction solution (l / sec)

[0008]

DETAILED DESCRIPTION OF THE INVENTION Raw materials and auxiliary materials Aromatic monohydroxy compound: The aromatic monohydroxy compound is a compound in which a hydroxy group is directly bonded to an aromatic ring, and alkylphenols such as phenol, cresol and butylphenol; Aryl phenols, halogenated phenols and phenols having an alkyl or aryl group bonded through a hetero atom can be used. Aryl Chloroformate: As the aryl chloroformate, the chloroformate of the aromatic monohydroxy compound can be used.

Phosgene: As phosgene, pure phosgene containing no impurities such as methylene chloride, carbon tetrachloride and chlorine is preferred. The amount of phosgene introduced is preferably 1.0 mol or less, more preferably 0.4 to 0.5 mol, per 1.0 mol of the aromatic monohydroxy compound. The stoichiometric amount is 0.5 mol, but by controlling the introduced amount of phosgene to a stoichiometric amount or less, an unreacted aromatic monohydroxy compound inevitably remains, and the reaction intermediate aryl The reaction of forming a diaryl carbonate between the chloroformate and the aromatic monohydroxy compound is promoted,
An industrial grade colorless polycarbonate is obtained.

Aromatic heterocyclic nitrogen-containing basic compound or a salt thereof: As the aromatic heterocyclic nitrogen-containing basic compound used as a catalyst, a 5-membered ring or a 6-membered ring whose nitrogen atom is aromatic is used.
A basic nitrogen compound that is present in a membered ring and does not have a functional group (for example, an amino group or a hydroxy group) that easily forms a strong bond with phosgene or a carbonate under the reaction conditions; May have other hetero atoms such as oxygen and sulfur in addition to the nitrogen atom. Specific examples of such catalysts are pyridine, quinoline, picoline, imidazoles, benzimidazoles, pyrazoles, triazoles and benzotriazoles.

The aromatic heterocyclic nitrogen-containing basic compound catalyst (hereinafter, may be abbreviated as “basic catalyst”) may be used.
It immediately changes to the corresponding hydrochloride in the reaction mixture. Since this hydrochloride is in dissociation equilibrium with the free basic catalyst, a salt of the basic catalyst,
For example, inorganic acid salts such as hydrochloride and sulfate, and organic acid salts such as formate and acetate can be used. These catalysts, based on 1.0 mole of the aromatic monohydroxy compound,
It is preferably used in an amount of from 0.001 to 0.20 mol, more preferably from 0.01 to 0.10 mol.

Alkali: As the alkali used as a neutralizing agent for the hydrochloride type basic catalyst, there can be used hydroxides of sodium, potassium, calcium and barium, and sodium and ammonium salts of carbonic acid and phosphoric acid.

Flow Sheet An example of the method for producing a diaryl carbonate of the present invention will be described with reference to the flow sheet of FIG. In the figure, 1 is a first reactor, 2 is a second reactor, 3 is a third reactor, 4 is a neutralization tank,
5 is a separation tank, 6 is a distillation apparatus, 11, 12, 13 and 14
Are pipes for introducing an aromatic monohydroxy compound, an aromatic heterocyclic nitrogen-containing basic compound or a salt thereof, phosgene and an inert gas, 21, 22, 23, 24, 25, and 2, respectively.
6 and 27 are pipes for discharging the first reactor reaction mixture, the second reactor exhaust gas, the second reactor effluent, the third reactor exhaust gas, the third reactor effluent, the neutralizing solution and the separated organic phase, respectively. 31,
Reference numerals 32, 33, and 34 denote stirrers installed in the first reactor, the second reactor, the third reactor, and the neutralization tank, respectively.

Reaction: Heated and melted aromatic monohydroxy compound (11), aromatic heterocyclic nitrogen-containing basic compound or its salt (12) and gaseous phosgene (13) are mixed in a first reactor (1). The reaction is carried out at a temperature of 120 to 190 ° C. while stirring (31). At this time, phosgene (13) is introduced into the liquid phase in the reactor as shown. Further, the aromatic heterocyclic nitrogen-containing basic compound or its salt (12) may be introduced as a mixture with a part or all of the aromatic monohydroxy compound (11) melted by heating.

The reaction mixture in the first reactor is continuously discharged in a gas-liquid dispersed state, introduced into a second reactor (2) via a pipe (21), and further stirred (32) to further proceed the reaction to produce phosgene. Improve conversion. The second reactor exhaust gas is mainly composed of hydrogen chloride generated by the reaction and unreacted phosgene, is discharged from the pipe (22), and is purged out of the system via a condenser (not shown). Therefore, it is important to improve the phosgene consumption rate.

The liquid discharged from the second reactor is discharged from the pipe (23), further introduced into the third reactor (3), and stirred (33).
Under the above, an inert gas (14) such as nitrogen gas is blown to remove hydrogen chloride gas dissolved in the liquid, and a push-off reaction of a chloroformate (a reaction to a diaryl carbonate by an equilibrium reaction with an aromatic monohydroxy compound) is performed. Conversion). The third reactor exhaust gas is hydrogen chloride entrained by an inert gas, and is discharged from the pipe (24). The hydrogen chloride is purified if necessary and reused as recovered hydrochloric acid. The inert gas can be recycled to the reactor after recovering the hydrochloric acid. In the case of two reactors, the second reactor can be omitted and the operation can be performed with the first reactor and the third reactor.

Separation / recovery: In the mixture after completion of the reaction,
It contains diaryl carbonate, unreacted aromatic monohydroxy compound, trace impurities and hydrochloride of aromatic heterocyclic nitrogen-containing basic compound which is a catalyst, and the content of chlorine depends on the amount of the catalyst used. 300-60,000pp
m. The third reactor effluent (25) is supplied to a neutralization tank (4), and is brought into contact with an aqueous alkali solution introduced separately (not shown) under stirring (34) to neutralize the hydrochloride. The neutralized solution is introduced into a separation tank (5) via a pipe (26), where it is separated into an organic phase and an aqueous phase. The organic phase is extracted and further brought into contact with hot water, and then is again passed through the separation tank. Separate into organic and aqueous phases. Chlorine is removed with the aqueous phase.

The organic phase finally separated is connected to a pipe (27).
To a distillation unit (6), where by distillation
The free basic catalyst, unreacted aromatic monohydroxy compound and diaryl carbonate are separated and recovered. The distillation is carried out at 1 to 100 torr in order to suppress the decomposition of diallyl carbonate due to heating during the distillation, and practically 5 to 50 t.
Preferred is vacuum distillation of orr. The distillation apparatus may be composed of a plurality of distillation columns (not shown). For example, in order to easily and efficiently recover a basic catalyst, light boilers (unreacted aromatic monohydroxy compound, free aromatic heterocyclic nitrogen-containing basic compound and water, etc.) are separated in the first distillation column. Then, the high-boiling impurities and the product diaryl carbonate may be separated in the second distillation column.

The production of the diaryl carbonate of the present invention may be a continuous type or a batch type (batch type).

Stirring power: In the method for producing a diaryl carbonate of the present invention, the reaction between the aromatic monohydroxy compound and phosgene is usually carried out in the form of gas-liquid contact. Therefore, when phosgene gas is introduced into a reaction solution containing an aromatic monohydroxy compound in which a basic catalyst is dissolved and both reaction materials are brought into contact with each other and reacted, it is important to diffuse the phosgene gas into the reaction solution. However, when the gas supply linear velocity is increased, a phenomenon of “blowing through” in which the gas passes through the reaction solution without being substantially diffused occurs. When trying to avoid this phenomenon,
It is necessary to limit the gas supply rate or use a large number of reactors, all of which result in a small production volume per reactor volume. The gas supply rate is an important issue because it affects the capacity of the production facility. On a small scale such as an experimental facility, there is no problem if the linear velocity is limited to 0.1 cm / sec or less, but a linear scale of 0.5 cm / sec or more on a practical scale, and a linear velocity of 1 cm / sec thereon. At the order of 10 cm / sec, "blowing through" is inevitable, and it is necessary to consider stirring power and other diffusion improvement measures.

In the method for producing a diaryl carbonate of the present invention, the stirring power (P / q) per unit flow rate of the reaction solution in the reactor in which the reaction proceeds, which is determined by the following equation (1), is not less than a certain limit value. It is necessary to provide power. P / q = Np · ρ · n ³ · d ⁵ / q (kgf · m / l) (1) Np: stirring power constant, ρ: specific gravity of reaction solution (kg / m
m ³ ), n: number of revolutions of the stirrer (rps), d: blade diameter of the stirrer (m), q: flow rate of the reaction solution (l / sec) Specifically, stirring power per unit flow rate (P / Q) is at least 250 (kgf · m / l), preferably 300
(Kgf · m / l) or more, more preferably 350 (kg
(fmm / l) or more must be transmitted to the reaction solution. If only a power lower than this limit is given, it means that the reaction is still in the diffusion-controlled region and the phosgene reaction efficiency has not reached the maximum. In order to ensure that the reaction rate is within the range of the rate control and to make the reaction efficiency of phosgene independent of the power, the value of the power to be supplied is preferably set to the above preferable value or more preferable value.

In the method of the present invention, since the reaction is carried out under acidic conditions of hydrochloric acid, it is difficult to use ordinary stainless steel as a material for the reactor and the stirring blade, and in general, it must be made of glass lining or Teflon lining. . as a result,
R is inevitably taken at the edge of the stirring blade, and the stirring efficiency becomes poor. Even in such a situation, in order to react phosgene in a gaseous form with high efficiency, a stirring power exceeding the above-mentioned limit value is required.

As the kind of the stirring blade, any type can be used as long as it can improve the gas dispersion efficiency. A general turbine blade, a Faudler blade, a disk turbine blade, a full zone blade (Shinko Pantech) ), Max blend wings and the like are preferably used.

However, no matter which type of blade is used, the load power of the reaction liquid consisting of the aromatic monohydroxy compound, the arylchloroformate and the diarylcarbonate is proportional to the load power relative to the rotational speed in the actual liquid system. Since the stirrer does not rise with such a gradient, a considerable amount of stirring rotation and a contrivance of gas dispersion are required to apply the stirring power. For example, it is preferable to provide a baffle to improve the stirring and mixing. Also, to improve gas dispersion efficiency,
The number of phosgene introduction holes is preferably as large as possible. In general, it is preferable to use a blown tube having a fine hole in a Teflon tube or a glass ball filter having a fine hole.

Scale-up: As a means for detecting that a constant stirring power has been added to the reaction, a torque meter is installed on a small-scale stirring shaft and the power value is actually measured. Next, a calculated power value is obtained by the above equation (1),
The Np value (equipment constant) is calculated by comparing the two power values. Using this Np, a load power value when the scale-up is performed in a similar manner is calculated, and if it is confirmed that the load power value is larger than the limit value, the scale-up is possible.
Thus, by using the required power value as an indicator of scale-up, the production of diaryl carbonate can be scaled up to an industrial level.

[0026]

The present invention will be described below in more detail with reference to Examples and Comparative Examples. Examples 1 to 3 A glass-made reaction vessel with a jacket connected to an oil circulation type external heating device (with an internal volume of 0.85 liters, an overflow pipe was installed at a position of 410 ml of actual liquid, tower cross-sectional area of the vessel = 57 cm ²⁾ ) Were connected three in a row. An exhaust pipe with a condenser for removing generated hydrochloric acid gas to the outside of the system was connected to the second and third reaction vessels. 420 g / hr of molten phenol and 17 g / hr of pyridine (pyridine /
The temperature was raised to 150 ° C. while continuously supplying phenol (equivalent to 5 mol%) to the first reaction vessel. A glass disk turbine two-stage blade was used as a stirring blade, and phosgene (212 g / hr) having a 0.48 mole ratio of phenol to be supplied was continuously supplied to the first reaction vessel at the stirring rotation speed shown in Table 1. did. Table 1 shows the phosgene linear velocity and phosgene conversion at this time.
It was shown to. At this time, the power value read from the torque meter attached to the stirrer is compared with the power value calculated from the above formula (1) based on the stirring speed and the blade diameter.
The value was calculated to be 5.2.

The reaction mixture flowing out of the first reaction vessel is
The reaction mixture was supplied to the second reactor via an overflow pipe, and the reaction mixture flowing out of the second reactor was similarly supplied to the third reactor. The reaction mixture flowing out of the third reactor was withdrawn into a glass receiver. The third reactor was provided with a nitrogen gas blowing pipe, and continuously supplied with nitrogen gas into the reaction mixture to degas residual hydrochloric acid.

The same composition was neutralized by adding a 5% by weight aqueous solution of sodium hydroxide at 85 ° C., allowed to stand, and then an aqueous phase and an organic phase were separately extracted. The pH after the addition of the aqueous sodium hydroxide solution was 9. The extracted organic phase is again
After washing with demineralized water at the same temperature, the mixture was allowed to stand, and then the aqueous phase and the organic phase were separately extracted.

The separated organic phase was purified by distillation in a vacuum distillation column filled with Sulzer packing (manufactured by Sumitomo Heavy Industries). In the first distillation, phenol, pyridine and water, which are light boiling components, were expelled, and in the subsequent distillation, diphenyl carbonate was distilled and purified.

The purity of the diphenyl carbonate thus obtained is analyzed by gas chromatography and liquid chromatography.
5 g was added to 10 ml of toluene, dissolved at room temperature, 10 ml of ultrapure water (ion-exchanged water containing no Cl) was added, and the mixture was stirred for 10 minutes at 1000 rpm using a magnetic stirrer. Analyzed graphically.

Examples 4 to 6 A jacketed glass-lined reaction vessel connected to an oil circulation type external heating device (with an internal volume of 60 liters, an overflow pipe was installed at a position of 29 liters of actual liquid, column cross-sectional area in vessel = 962 cm ² ) were continuously connected. An exhaust pipe with a condenser for removing generated hydrochloric acid gas to the outside of the system was connected to the second reaction vessel. About 29 l / hr (phenol 29.7 kg / hr, phenol 29.7 kg / hr,
While continuously supplying the first reaction vessel with pyridine (corresponding to 1.24 kg / hr), the temperature was raised to 150 ° C. Using a Teflon disk turbine blade as a stirring blade, phosgene (15.0 kg / hr) of 0.48 mol ratio of supplied phenol was continuously supplied to the first reaction vessel at a stirring rotation speed shown in Table 1. did. The phosgene linear speed and phosgene conversion at this time are shown in Table 1. In Table 1, the numerical value calculated using the small-scale Np value of 5.2 obtained in Example 1 and the numerical formula (1) is used as the stirring power value (P / q).
As shown. Subsequent operations were performed in the same manner as in Example 1.

Examples 7 to 9 Under the same conditions as in Example 4, the supply time of each raw material was reduced by half, so that the residence time in each reaction tank was set to 2 hours.

Comparative Examples 1-2 The same operation as in Example 1 was carried out using the apparatus used in Example 1 except that the stirring speed was changed as shown in Table 1.

Comparative Examples 3 and 4 The same operation as in Example 4 was performed using the apparatus used in Example 4 except that the stirring rotation speed shown in Table 1 was changed.

Comparative Example 5 The same operation as in Example 7 was carried out except that the stirring time shown in Table 1 was changed to the residence time of Example 7.

[0036]

[Table 1]

Thus, even when the reactor is scaled up (the linear speed of phosgene is improved), it is found that the reaction can be changed from diffusion-controlled to reaction-controlled if there is a load power exceeding a certain stirring power. . On the other hand, when the load power is in a diffusion-controlled state, the conversion of phenol is low and the conversion of phosgene is low, resulting in a very lossy reaction.

[0038]

According to the process for producing diaryl carbonate of the present invention, stable and high-quality diaryl carbonate can be obtained in high yield, and the scale of the reactor can be increased.

[Brief description of the drawings]

FIG. 1 is a flow sheet diagram showing a method for producing a diaryl carbonate of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st reactor 2 2nd reactor 3 3rd reactor 4 Neutralization tank 5 Separation tank 6 Distillation apparatus 11-14 Pipe for introduction 21-27 Pipe for discharge 31-34 Stirrer

Continued on the front page (72) Inventor Narutoshi Hyodo 1-1 Kurosaki Castle Stone, Yawatanishi-ku, Kitakyushu City, Fukuoka Prefecture Inside the Kurosaki Office of Mitsubishi Chemical Corporation (72) Inventor Eiji Fujimoto 1-1-1, Kurosaki Castle Stone, Yawata-Nishi-ku, Kitakyushu City, Fukuoka Prefecture Mitsubishi F-term (reference) in Kurosaki Office of Chemical Co., Ltd. 4H006 AA02 AC48 BA52 BA69 BC40 BD83 BD84 BE52 KA52 KA53 4H039 CA66 CD10 CD20 CE10

Claims (4)

[Claims] 1. A process for producing a diaryl carbonate, which comprises reacting an aromatic monohydroxy compound with phosgene and / or an aryl chloroformate in the presence of an aromatic heterocyclic nitrogen-containing basic compound. The required stirring power (P / q) per unit flow rate in the reactor at the time of the reaction is 250 (kgf · m / l).
A method for producing a diaryl carbonate, which provides the above power. P / q = Np · ρ · n ³ · d ⁵ / q (kgf · m / l) (1) Np: stirring power constant, ρ: specific gravity of reaction solution (kg / m
m ³ ), n: number of revolutions of the stirrer (rps), d: blade diameter of the stirrer (m), q: flow rate of the reaction solution (l / sec) 2. A stirring power (P / q) of 300 (kgf)
The method for producing a diaryl carbonate according to claim 1, wherein a power of at least (m / l) is applied. 3. The process for producing a diaryl carbonate according to claim 2, wherein a reactor made of glass lining and / or Teflon (registered trademark) equipped with a stirrer having stirring blades is used. 4. The method for producing a diaryl carbonate according to claim 2, wherein the reaction is performed at a blowing speed of 0.5 cm / sec or more as the linear speed of phosgene.