JPH0782206A - Production of fluorenone - Google Patents

Abstract

PURPOSE:To improve the production process for fluorenone by oxidizing fluorene dispersed in a mixture of agueous sodium hydroxide and an organic solvent immiscible with water with molecular oxygen in the presence of a quaternary ammonium salt. CONSTITUTION:An organic solvent having 80 to 150 deg.C standard boiling point such as toluene is used to effect oxidation reaction at a temperature lower than 100 deg.C so that the water vaporized during the oxidation reaction is accompanied by the exhaust gas after and removed out of the reactor. The oxidation reaction is accelerated and the reaction mixture can reeadily be separated into the oil phase and the aqueous phase and the recovered sodium hydroxide solution can be reused without concentration and the consumption of the catalyst can be saved. The product can readily be separated from the solvent by single distillation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing fluorenone (more strictly speaking, 9-fluorenone) which is useful as a raw material and a modifier for resins, and more specifically, it is a liquid phase oxidation of fluorene with molecular oxygen to produce fluorenone. To a method of manufacturing.

[0002]

2. Description of the Related Art Although various methods have been conventionally known for producing fluorenone, they are contained in coal tar and by-product oil obtained by dealkylation of alkyl aromatic compounds such as toluene. The method of oxidizing fluorene is industrially promising because raw materials are available at low cost. The production of fluorenone by the oxidation of fluorene is a reaction in which two hydrogen atoms bonded to the only saturated carbon atom (9-position) of fluorene are eliminated and replaced with an oxo group (= O) as shown in the following formula. Therefore, water is produced as a byproduct of the oxidation.

[0003]

[Chemical 1]

As a method for producing fluorenone by oxidizing fluorene, chemical oxidation with an oxidizing agent such as nitric acid, potassium permanganate and potassium dichromate is described in the literature. In addition, there are problems in terms of environment and hygiene, and it is unsuitable for industrial production.

On the other hand, both the vapor phase method and the liquid phase method are known for the oxidation of fluorene by molecular oxygen.
Method for obtaining fluorenone by catalytic gas phase oxidation of fluorene
(For example, JP-A-60-233028), since it is oxidized at a high temperature of 330 to 450 ° C., oxidative decomposition products such as phthalic anhydride and maleic anhydride are by-produced, and the yield is 90% or less. And not enough.

As a method of oxidizing with molecular oxygen in the liquid phase,
Although a method using a combination of Cr and / or Co ions and N, N-dialkyl lower saturated fatty acid amide as a catalyst has been proposed (Japanese Patent Laid-Open No. 56-32430), the conversion of fluorene cannot be increased. There is a problem in terms of productivity.

A liquid-phase oxidation method using dimethylsulfoxide (DMSO) or hexamethylphosphoramide (HMPA) as a solvent in the presence of potassium tert-butoxide is also known [Yoshio Kamiya “Organic Oxidation Reaction-Autoxidation Theory and Applications ”, 1973 (Gihodo)]. However, there are problems that a large amount of potassium tert-butoxide, which is expensive and unrecoverable, is required, and DMSO and HMPA used as solvents have high boiling points and are water-soluble, so that recovery is difficult.

As a liquid-phase oxidation method in which this problem is solved, a quaternary salt is prepared in a heterogeneous mixed solvent consisting of an aqueous solution of caustic soda and a water-immiscible high-boiling organic solvent such as α-methylnaphthalene and quinoline. A method of oxidizing fluorene with molecular oxygen in the presence thereof has been proposed (JP-A-53-98948). This method uses an inexpensive aqueous caustic soda solution and a quaternary salt in place of the expensive potassium tert-butoxide,
Instead of DMSO and HMPA as the organic solvent, a high boiling point solvent such as α-methylnaphthalene which is immiscible with water and is relatively easy to recover is used.

However, it takes 48 hours to complete the reaction, the reaction rate is slow, and it takes a long time to perform static liquid separation between the organic layer and the aqueous layer after the stirring is stopped after the reaction. Also, since a high boiling point solvent is used, the difference in boiling point between the solvent and fluorenone is small, and precision distillation is required when recovering the solvent. Furthermore, since water is by-produced by the oxidation of fluorenone, the caustic soda aqueous solution recovered as an aqueous layer by stationary separation has a reduced caustic soda concentration, and in order to be used repeatedly, it is concentrated to remove water. However, there still remains a problem that hinders industrialization.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide an industrially advantageous method for producing fluorenone. A more specific object is to provide a method suitable for industrialization in the production of fluorenone by oxidizing fluorene using the above-mentioned caustic soda aqueous solution, quaternary salt and organic solvent, without the above-mentioned problems of the prior art. That is.
Specifically, it is to provide a method for producing fluorenone, which has a short reaction time and liquid separation time, facilitates solvent recovery, and does not require concentration of an aqueous solution of caustic soda.

[0011]

DISCLOSURE OF THE INVENTION The present inventors have proposed that fluorene is added to molecular oxygen in the presence of a quaternary ammonium salt in a heterogeneous mixed solvent of a caustic aqueous solution and an organic solvent incompatible with water. As a result of repeated studies on a method of producing fluorenone by liquid-phase oxidation with water, an organic solvent having a lower boiling point than that used so far was used, and water evaporated from the reaction system during the oxidation reaction was allowed to accompany the oxidizing exhaust gas. It has been found that the above object can be achieved by removing it outside the oxidation reactor by the above method, and arrived at the present invention.

Here, the gist of the present invention is to blow molecular oxygen into a fluorene-containing raw material in the presence of a quaternary ammonium salt in a stirred heterogeneous mixed solvent consisting of a caustic aqueous solution and an organic solvent. In the method of producing fluorenone by oxidation, the standard boiling point of the organic solvent is
It is an organic solvent that is incompatible with water at 80 to 150 ° C, and the oxidation reaction is performed at a temperature of 100 ° C or less, and the water evaporated from the reaction mixture during the oxidation reaction is entrained in the oxidation reaction exhaust gas and discharged outside the oxidation reactor. A method for producing fluorenone, which comprises removing the fluorenone.

Here, the standard boiling point is 1 atm (760 Torr)
The boiling point below. The organic solvent incompatible with water means an organic solvent which is substantially insoluble in water.
In a preferred embodiment, after completion of the oxidation reaction, the reaction solution is allowed to stand and separate to separate into an oil layer and an aqueous layer, and the aqueous caustic alkali solution of the aqueous layer is used as it is for the next oxidation reaction.

According to the present invention, the rate of oxidation reaction is significantly increased, and the time required for static separation after the oxidation reaction is also significantly reduced. Further, since water evaporated during the reaction is removed from the reaction system, it is not necessary to concentrate the caustic aqueous solution separated from the organic solvent layer after the reaction, or the load thereof is significantly reduced. Furthermore, since the boiling point of the organic solvent is low, the organic solvent can be recovered from the reaction product fluorenone by simple distillation instead of precision distillation. Therefore,
All the problems of the above-mentioned conventional techniques are solved.

Fluorene, which is a starting material, is contained in coal tar at a ratio of about 1.6% by weight, and is also contained in dealkylated by-product oil such as toluene and xylene. The fluorene-containing raw material used in the present invention is isolated and purified from a fraction containing fluorene such as a high boiling point fraction of coal tar and the above-mentioned by-product oil (fluorene-containing oil), for example, purity.
Although 95% by weight or more of fluorene may be used, the fluorene-containing oil may be directly used as a fluorene-containing raw material without being refined. In that case, the fluorene content in the raw material is not particularly limited, but in view of productivity in the oxidation and purification steps, it is preferably 30% by weight or more, and particularly preferably 40% by weight or more. It is one of the advantages of the present invention that a high yield can be obtained even when such an unpurified fluorene-containing raw material is used.

As the caustic aqueous solution, an aqueous solution of sodium hydroxide, potassium hydroxide, calcium hydroxide or the like can be used, but an aqueous sodium hydroxide solution is usually used. The concentration of the caustic aqueous solution is not particularly limited, but it is usually preferably in the range of 20 to 50% by weight, particularly preferably in the range of 35 to 45% by weight. If it is less than 20% by weight, the oxidation rate of fluorene tends to decrease and the productivity decreases. If it exceeds 50% by weight, caustic crystals may be precipitated during the oxidation reaction, which does not affect the oxidation of fluorene itself, but the liquid separation operation at the time of stationary separation after the oxidation reaction becomes complicated. Although the amount of the caustic aqueous solution used is not particularly limited, it is usually 1/10 to 10 times by weight and 1/10 to 1 times by weight the total weight of the organic layer (fluorene-containing raw material + organic solvent). Is preferred. If the amount is too small, the reaction rate will decrease, and if it is too large, it is uneconomical.

The organic solvent is used to dissolve the raw material fluorene. In the present invention, an organic solvent which is incompatible with water and has a normal boiling point of 80 to 150 ° C is used. 2 organic solvents
It may be a mixed solvent of two or more species. In the case of a mixed solvent, the boiling point of the mixture may be within the above range. A solvent with a standard boiling point lower than 80 ° C has a large effect of removing water from the oxidation reactor, but has a large load for cooling and condensing the vapor that is evaporated together with water and distilled out of the oxidation reactor system. Cannot be adopted for. A solvent having a normal boiling point of higher than 150 ° C. is not suitable for the present invention because it has a small effect of removing water from the oxidation reactor and reduces the reaction rate.

The following are examples of solvents that satisfy the above requirements and can be used in the present invention (normal boiling points in parentheses): benzene (80 ° C.), toluene (111 ° C.), xylene (138 to 144).
Aromatic hydrocarbons such as (° C), n-heptane (98 ° C), n
-Aliphatic hydrocarbons such as octane (126 ° C), alicyclic hydrocarbons such as methylcyclohexane (101 ° C), halogenated aromatic compounds such as chlorobenzene (132 ° C), 1,2
-Halogenated aliphatic compounds such as dichloroethane (83 ° C). Particularly preferred solvents are toluene and xylene.

The amount of the organic solvent used is preferably in the range of 1/2 to 10 times by weight, particularly 1 to 3 times by weight, based on 1 part by weight of the fluorene-containing raw material. If this amount is less than 1/2 weight, less water will be removed from the oxidation reactor during the reaction.
On the other hand, the use of a large amount of organic solvent in excess of 10 times by weight does not adversely affect the oxidation reaction itself, but increases the volume efficiency of the oxidation reaction and the load of solvent recovery, which is economically disadvantageous.

In the present invention, the quaternary ammonium salt is used as the phase transfer catalyst because the oxidation reaction is carried out in the heterogeneous phase reaction system consisting of the caustic aqueous solution and the organic solvent. The quaternary ammonium salt is a compound represented by the general formula [R] ₄ N ⁺ X ⁻ . Ammonium salts useful as catalysts in the present invention are compounds where each R is alkyl or alkylphenyl (eg, benzyl, etc.). However, four Rs may be the same as or different from each other. X ⁻ means an anion such as a halogen ion (Cl ⁻ , Br ⁻ , I ⁻ ), a hydroxide ion (OH ⁻ ), a hydrogen sulfate ion (HSO ₄ ⁻ ).

Specific examples of suitable quaternary ammonium salts include tetra-n-butylammonium bromide, tetraethylammonium hydroxide, trimethylbenzylammonium hydroxide, distearyldimethylammonium chloride, lauryltrimethylammonium chloride, benzyllauryl chloride. Dimethylammonium, tetra-n-butylammonium hydrogen sulfate, tetra-n-butylammonium iodide and the like can be mentioned.

The amount of the quaternary ammonium salt used is preferably within the range of 1/1000 to 1/10 mol with respect to 1 mol of fluorene in the raw material. If it is less than 1/1000 mol, the oxidation rate of fluorene will be slow, and if it is added in excess of 1/10 mol, further increase in the oxidation rate will be slight, which is economically disadvantageous.

As the molecular oxygen as the oxidant of the present invention, exhaust gas containing molecular oxygen such as combustion exhaust gas can be used, but normally, air, oxygen, or a gas obtained by diluting oxygen or air with an inert gas is used. To use.

The oxidation reaction is carried out at a temperature of 100 ° C. or lower. The reaction temperature is preferably 30 to 100 ° C, more preferably 50 to 80 ° C.
Is the range. When the reaction temperature is lower than 30 ° C, the oxidation rate of fluorene becomes slow. If the reaction temperature exceeds 100 ° C,
The decomposition of the quaternary ammonium salt becomes remarkable.

The reaction pressure is not particularly limited, and may be normal pressure (atmospheric pressure), reduced pressure, or increased pressure. The reaction temperature and pressure may be selected according to the boiling point of the organic solvent so that water will evaporate at a suitable rate together with the organic solvent. Therefore, even if pressure is applied, the pressure is up to 5 kg / cm ² G because excessive pressurization slows down the removal rate of water.

The reaction is continued until there is virtually no uptake of oxygen or there is no unreacted fluorene. Also, the reaction was interrupted while leaving fluorene,
It is also possible to collect unreacted fluorene together with an organic solvent and use it as a raw material for the next oxidation.

The oxidation reaction can be carried out batchwise, semi-batchwise, or continuously. The batch system is suitable when the production amount is small, and the continuous system is suitable when the production amount is large. In any case, the heterogeneous mixed solvent of the caustic aqueous solution and the organic solvent introduced into the oxidation reactor is stirred at a sufficient speed to increase the contact area between fluorene dissolved in the organic solvent and the caustic aqueous solution. . In practice, a mixture of a fluorene-containing raw material, a quaternary ammonium salt, a caustic aqueous solution and an organic solvent is stirred, and a molecular oxygen-containing gas is blown into this stirred mixture to carry out an oxidation reaction. The gas not used in the reaction is discharged from the oxidation reactor as oxidizing exhaust gas.

The flow rate of the molecular oxygen-containing gas can be set with the upper limit of the flow rate at which the oxygen concentration in the oxidizing exhaust gas becomes a concentration within the explosion range (usually 8% by volume or less) in coexistence with the organic solvent vapor used.

According to the present invention, the water and the organic solvent evaporated from the reaction mixture are entrained in the oxidizing exhaust gas and removed outside the oxidation reactor. The aqueous phase of the reaction system is an aqueous solution of caustic alkali having a concentration of 20 to 50% by weight, and when this aqueous solution is simply heated, the water cannot be evaporated unless it is heated to a temperature considerably higher than 100 ° C due to an increase in boiling point. However, in the present invention, the boiling point is lowered by azeotropy due to the coexistence of an organic solvent having a relatively low boiling point, and by blowing an oxygen-containing gas, the reaction temperature is as low as 30 to 100 ° C. Water can be evaporated. Thus, by removing water from the reactor during the reaction, it is possible to prevent the concentration of the caustic aqueous solution from being diluted during the reaction, and to prevent the reaction rate from decreasing. The amount of water removed is preferably at least half the amount of water by-produced during the reaction.

The exhaust gas distilled from the oxidation reactor is cooled to condense the organic solvent and water vapor entrained in it. The uncondensed gas is discharged to the outside of the equipment system after removing a small amount of the remaining organic solvent vapor with a scrubber or the like, if necessary. The condensed liquid is separated into oil and water by a decanter or the like, and separated into an oil layer and a water layer. The water layer is discharged to the outside of the facility system after being subjected to wastewater treatment if necessary. The oil layer may be returned to the reactor as an organic solvent, or alternatively, fresh organic solvent may be replenished. When the amount of organic solvent is large, it is not always necessary to replenish the evaporated component.

After the completion of the oxidation reaction, the reaction liquid extracted from the reactor was allowed to stand and separate into an oil layer (mainly organic solvent + product).
And water layer (mainly caustic aqueous solution). The low-boiling point organic solvent used in the present invention generally has a lower viscosity and density than a high-boiling point solvent, so that it can be easily separated from an aqueous solution of caustic alkali, and the time required for separation can be greatly shortened. In the case of the batch system or the semi-batch system, it is also possible to perform static separation in the oxidation reactor.

Since the caustic aqueous solution recovered in this way is less diluted with water produced as a by-product during the reaction, it can be used as it is for the next oxidation reaction without any treatment such as concentration. Of course, if necessary, addition of an operation such as concentration to the caustic aqueous solution for adjusting the concentration does not impair the significance of the present invention.

Most of the quaternary ammonium salt used as a catalyst is present in an aqueous solution of caustic alkali. Therefore, if a treatment such as concentration is applied, the quaternary ammonium salt decomposes in the course of this treatment. However, the significance of the present invention is great.

On the other hand, the separated oil phase is, if necessary,
After treatment such as washing with water or a caustic aqueous solution, the organic solvent is recovered by distillation or the like. For the distillation operation, since the organic solvent has a low boiling point and the difference in boiling point between the product and fluorenone is large, simple distillation is generally sufficient, and the operating pressure may be atmospheric pressure, but the heat source used for the distillation, the cooling medium, etc. Depending on the limitation, it is also possible to use under pressure or under pressure. Further, both batch distillation and continuous distillation are possible.

Of course, the recovered organic solvent can be reused. If necessary, the distillation residue can be purified by distillation, crystallization, recrystallization, complex formation, extraction, adsorption or the like to obtain fluorenone having a desired purity.

[0036]

EXAMPLES The present invention will be described in detail below with reference to Examples and Comparative Examples. In Examples and Comparative Examples,% means% by weight unless otherwise specified.

(Example 1) A. A reflux condenser having a receiver for moisture measurement, a gas introduction pipe,
In a 500 ml jacketed flask equipped with a thermometer and an induction stirrer, a fluorene-containing oil (fluorene content of 89%
%) 28 g (150 mmol), 100 g of toluene, 30 g of 40% sodium hydroxide aqueous solution, 1.18 g (1.5 mmol) of distearyldimethylammonium chloride (manufactured by Kao, trade name Kotamine D86P) as a quaternary ammonium salt, and a stirrer While vigorously stirring at 50 ° C., dilute air with oxygen concentration of 7% by volume and dilute air with a flow rate of 0.3 liter / min.
Oxidized at 0 ° C and atmospheric pressure.

The water measuring receiver used had the structure shown in FIG. 1, and when the separated condensate became more than a certain amount, the upper oil layer (organic solvent) overflowed to cause oxidation in the oxidation reactor. I was supposed to go back to a flask.

The oxygen concentration in the exhaust gas was 4% by volume at the start of the reaction, but became 7% by volume after 6 hours, so the supply of dilution air was stopped. 2.7 g of water was distilled in the receiver for measuring water content. Stop stirring and allow the reaction mixture in the flask to
After standing for a minute, the layers were separated into an oil layer and an aqueous layer. The oil layer was subjected to simple distillation under normal pressure to recover toluene. When the distillation residue (31.7 g) after the toluene recovery was analyzed by gas chromatography, the content of fluorenone was 81%.
(The yield of fluorenone was 95 mol%), but unreacted fluorene was not detected.

B. The aqueous layer separated from the oil layer of the reaction solution
After returning to the jacketed flask used in A, 28 g of the same fluorene-containing oil as above, 140 g of toluene, and 0.59 g (0.75 mmol) of ketamine D86P were added, and the second reaction was carried out in the same manner as above. After the same time as above
Since the oxygen concentration of the exhaust gas became 7% by volume, the supply of dilution air was stopped.

Thereafter, the same operation as in A was performed to obtain a distillation residue (31.9 g) after recovery of toluene. When analyzed by gas chromatography, the fluorenone content was 80% (fluorenenone yield 94 mol%), and fluorene was not detected. Therefore, in the second reaction in which the recovered sodium hydroxide solution was used as it was without being concentrated, excellent reaction results almost equivalent to those in the first reaction could be obtained.

Comparative Example 1 A. An oxidation reaction was performed in the same manner as in Example 1 except that the moisture measuring receiver was removed from the reflux condenser. In this case, all of the toluene vapor and steam removed from the reactor along with the exhaust gas are cooled and condensed by the reflux condenser and returned to the flask. The oxygen concentration in the exhaust gas was 4% by volume at the start of the reaction.
After 9 hours, the volume reached 7% by volume, so the supply of dilution air was stopped. Then, the reaction solution was separated by standing and then distilled in the same manner as in Example 1 to recover the solvent. The distillation residue contained fluorenone in a yield of 93 mol%.

B. The aqueous layer recovered by the stationary separation was added to the above A.
The flask was returned to the flask (without a receiver for measuring water content), and the second oxidation reaction was performed in the same manner as in Example 1B. After 5 hours from the start of oxidation, oxygen absorption was not observed. When a small amount of the reaction liquid was sampled and the oil layer was analyzed by gas chromatography, residual fluorenone was observed.
The oxidation was started again by adding 1.18 g of 86P. After 7 hours, the oxygen concentration of the exhaust gas became 7% by volume, so the supply of dilution air was stopped and the same treatment as above was performed. The yield of fluorenone contained in the distillation residue after recovery of toluene was 90 mol%.
Met.

(Comparative Example 2) Same as A of Example 1 except that the organic solvent was changed from toluene to methylnaphthalene (1-methylnaphthalene 52.6%, 2-methylnaphthalene 46.5%, normal boiling point 241 to 242 ° C). Oxidation of fluorene was carried out. The oxygen concentration in the exhaust gas was 5% by volume at the start of the reaction, but became 7% by volume after 11 hours, so the supply of dilution air was stopped. 2.9 g of water was distilled in the receiver for measuring water content.

The stirring was stopped and the mixture was allowed to stand overnight, but the oil layer and the water layer were poorly separated, and an intermediate layer (emulsion layer) was formed. Only the oil layer was subjected to precision distillation at a reflux ratio of 10 in a rectification column with 20 theoretical plates under a reduced pressure of 100 mmHg. Gas chromatographic analysis of the distillation residue (28.8 g) remaining after collecting the distilled methylnaphthalene revealed a fluorenone content of 76% (81 mol% yield of fluorenone), and unreacted fluorene was detected. Was not done.

From these results, when the organic solvent has a high boiling point exceeding 150 ° C., precision distillation is required to recover the organic solvent, and the effects of the present invention such as reduction of reaction time and liquid separation time can be obtained. That is, the yield is also decreased.

[0047]

As described above, according to the method of the present invention,
95% fluorene while keeping the oxidation rate high
%, The reaction time is remarkably shortened as compared with the conventional oxidation method in a heterogeneous mixed solvent. In addition, since the caustic aqueous solution obtained by separating after the oxidation reaction can be repeatedly used without adding treatment such as concentration, productivity is improved and consumption of the quaternary ammonium salt of the catalyst is suppressed. be able to. Furthermore, since the organic solvent has a low boiling point and the difference in boiling point between the product and fluorenone is sufficient, the organic solvent can be recovered from the product after the reaction by simple distillation, and the liquid is separated from the aqueous layer. Since the process is completed in a short time, productivity is improved also in this respect. Therefore, as a whole, it can be said that the method of the present invention is very suitable for industrialization.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the structure of a moisture measuring receiver used in an example.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiji Takeuchi, No. 3, Hikari, Oshima, Kashima-machi, Kashima-gun, Ibaraki Prefecture Sumikin Kako Co., Ltd.

Claims (2)

[Claims] 1. A fluorenone is oxidized by blowing molecular oxygen into a fluorene-containing raw material in the presence of a quaternary ammonium salt in a stirred heterogeneous mixed solvent consisting of an aqueous caustic alkali solution and an organic solvent to oxidize fluorenone. In the method for producing, the organic solvent is an organic solvent that is incompatible with water having a normal boiling point of 80 to 150 ° C, the oxidation reaction is performed at a temperature of 100 ° C or lower, and water evaporated from the reaction mixture is oxidized during the oxidation reaction. A method for producing fluorenone, which is characterized in that it is removed from the oxidation reactor by being entrained in a reaction exhaust gas. 2. After the completion of the oxidation reaction, the reaction solution is allowed to stand and separate to separate into an oil layer and an aqueous layer, and the caustic aqueous solution of the aqueous layer is used as it is for the next oxidation reaction.
The method of claim 1.