JP2000007598A - Recovery of phenol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recovering phenols, reduced in phenols lost by being distributed into water layer in a step for separating and recovering phenols from an aqueous solution of an alkali containing sodium phenolate. SOLUTION: In this method for separating and recovering phenols from an aqueous solution of an alkali containing sodium phenolate, a mixed solution obtained by adding cumene and/or α-methylstyrene to an aqueous solution of an alkali is added to an alkali solution of alkali is neutralized with a mineral acid or the aqueous solution is previously neutralized with a mineral acid and then, cumene and/or α-ethylstyrene is added thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a synthetic resin, a pesticide,
The present invention relates to the separation and recovery of phenol, which is useful as an intermediate for the production of dyes, medicines, and the like, from an aqueous alkaline solution.

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed as methods for synthesizing phenol. Among these methods, a cumene phenol production process for synthesizing phenol using cumene as a starting material is generally put to practical use. This cumene process oxidizes cumene with oxygen or air to produce cumene hydroperoxide (hereinafter referred to as “cumene hydroperoxide”).
Abbreviated as "CHP") and then subjecting the resulting CHP to a decomposition reaction in the presence of a mineral acid catalyst to obtain phenol and acetone.

[0003] In recent years, in a phenol plant for producing phenol, this cumene process, which has mild reaction conditions and is excellent in economic efficiency, has become the mainstream of phenol production in the world. The phenol production process by the cumene method is roughly divided into an oxidation system, a concentration system, a crevage system, a neutralization system, a purification system, and a recycling system. The cumene hydroperoxide obtained by oxidizing cumene is cleaved by a mineral acid ( Cleavage), in the neutralization step,
Neutralizes catalyst mineral acids. This neutralization of mineral acid usually contains sodium phenolate (hereinafter abbreviated as “phenate”) which is extracted with alkaline water to recover phenol in each step such as caustic soda and purification system and is recycled. An alkaline aqueous solution or the like is used. After the neutralized liquid is separated from oil and water, a part of the aqueous layer is taken out of the system as wastewater. The water (wastewater) obtained by separation contains a small amount of valuables such as phenol, and it is useful to establish a recovery method industrially from an economic viewpoint. Although it is desirable to recover almost completely from the viewpoint of environmental problems, phenate water obtained from each step of the cumene phenol plant is recycled to a neutralization tank, neutralized with a mineral acid, and then separated into oil and water. In the method in which the neutralized salt is recovered in the aqueous layer, phenol in the wastewater distributed into the aqueous layer and discharged out of the system cannot be suppressed due to equilibrium. Therefore, various methods for separating and recovering phenol from wastewater containing phenol alone have been studied.

Conventionally, as a method for treating phenol-based wastewater, incineration treatment, activated sludge treatment, solvent extraction, and adsorption have been known. As a method for industrially recovering phenols, a solvent extraction method and an adsorption method are generally used. In the conventional solvent extraction method, a trace amount of phenol remains in the wastewater after the treatment, and a secondary treatment such as an activated sludge treatment or an incineration treatment is further required. In addition, since a part of the extraction solvent is transferred to a water tank, a method of heating and evaporating the solvent for recovery operation is employed. This operation requires a large amount of energy and has a problem that the operation itself is very complicated. Examples of such an example are as follows.
For example, Japanese Patent Application Laid-Open No. 4-41465 discloses a method for recovering phenol using, as an extractant, DPC purified in an aqueous layer containing inorganic salts and a small amount of phenols in a diphenyl carbonate (DPC) production process.
On the other hand, as a method for recovering phenol in wastewater by an adsorption treatment method, a method using activated carbon as an adsorbent is disclosed in Japanese Unexamined Patent Application Publication No. Hei.
No. 146838. However, since the phenol-containing wastewater generated in this process contains a trace amount of organic acids such as formic acid and acetic acid, the organic acids may be concentrated in the phenols desorbed and recovered. Furthermore, in the activated carbon adsorption method, since the adsorption power is strong, in order to elute the adsorbed phenol, not only had to use an alkali such as caustic soda, but also had to go through steps such as neutralization and extraction. . Further, for example, Japanese Patent Application Laid-Open No. 3-117651 discloses a method for separating and recovering phenol from phenol-containing wastewater in a 2,6-dimethylphenol production step, using a styrene / divinylbenzene-based synthetic resin adsorbent. A method for recovering phenol has been disclosed. However, even in this method, not only the adsorption capacity of the synthetic resin is limited, but also complicated steps such as resin regeneration are required.
Further, it is known that the alkali salt generated in the neutralization step causes various troubles downstream of the neutralization step. In other words, a reboiler is provided in the concentration tower or distillation tower provided downstream of each neutralization step,
When this reboiler heats the oil flowing through the process,
There is a problem that sodium salts and the like generated by the neutralization are deposited on the tube surface and cause fouling of the reboiler.

[0005] Therefore, conventionally, an alkali salt such as a sodium salt has been removed from a process by various fluid treatment apparatuses. One of such methods is removal of an alkali salt such as a sodium salt by a filled filter medium, but this method has a problem that the filter medium used can maintain its performance only for a short period of time.

[0006]

The existing solvent extraction method described above is not economically preferable because not only the extraction effect is insufficient, but also the extraction solvent used is dissolved in wastewater. In addition, the adsorption treatment method not only complicates the apparatus due to the necessity of the regeneration step, but also has a problem in its adsorption capacity when using synthetic resin and is insufficient for industrialization. was there.

Further, in the conventional treatment for neutralizing a phenate-containing aqueous alkali solution with a mineral acid, the amount of phenol distributed in the aqueous layer increases, and the loss increases, which is not economically preferable. However, the phenol is separated and recovered from the alkaline aqueous solution containing phenate while minimizing the loss of phenol, and the recovered phenol contains a small amount of acetone. It is possible to increase the yield of phenol, and the economic merit is great.

Accordingly, an object of the present invention is to provide a method for recovering phenol which reduces the amount of phenol distributed and lost in an aqueous layer in a step of separating and recovering phenol from an aqueous alkali solution containing phenate. .

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have obtained a mixed solution obtained by adding cumene and / or α-methylstyrene to an alkaline aqueous solution containing phenate. And even cumene and / or
Alternatively, it has been surprisingly found that by performing a neutralization treatment with a mineral acid before and after the addition of α-methylstyrene, the phenol concentration in the aqueous layer of the treatment liquid decreases. Further, by adjusting the salt concentration and pH of the strong acid and strong alkali in the obtained aqueous layer of the neutralized solution to a specific range, the sodium salt in the oil layer which causes trouble in the distillation step can also be reduced. And completed the present invention.

That is, the present invention relates to a method for separating and recovering phenols from an aqueous alkali solution containing sodium phenolate, wherein a mixed solution obtained by adding cumene and / or α-methylstyrene to the aqueous alkali solution is mixed with a mineral acid. Or a method of recovering phenols, which comprises neutralizing the aqueous alkali solution with a mineral acid before adding cumene and / or α-methylstyrene.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

In the present invention, the cumene and / or α-methylstyrene added to the aqueous alkali solution containing sodium phenolate may be a step containing cumene and / or α-methylstyrene produced in each step of a phenol production plant. Liquid can be used. For example, in the crude phenol solution after acid cleavage, acetone is firstly distilled off by a distillation column (crude acetone column), and cumene and α-methylstyrene are further distilled off by a downstream distillation column (hydrocarbon column). ). A process solution containing this cumene or α-methylstyrene can be used. The concentration of cumene and / or α-methylstyrene in the process liquid at this time is 10 to 100% by weight.
Are preferred. If the concentration of cumene and / or α-methylstyrene in the process liquid is lower than 10% by weight, the amount added to the alkaline aqueous solution containing phenate is undesirably increased. The component may be a single component of cumene or α-methylstyrene or a mixture of two or more types.

Further, the concentration of cumene and / or α-methylstyrene in the treatment solution or the mixed solution in the present invention is preferably in the range of 3 to 30% by weight. If the added amount of cumene and / or α-methylstyrene is lower than 3% by weight, not only sufficient effect cannot be obtained, but also the boundary between oil and water becomes unclear and the separation efficiency decreases. On the other hand, when the added amount of cumene and / or α-methylstyrene is higher than 30% by weight, the load on the distillation column (steam amount) for separating / recovering the added oil layer component increases, which is economically undesirable. . Therefore, it is more preferably in the range of 5 to 20% by weight, and most preferably in the range of 8 to 15% by weight.

Examples of the salt of a strong acid and a strong alkali in the present invention include sodium chloride, potassium chloride, sodium sulfate and potassium sulfate. In the cumene phenol production process, a large amount of sodium sulfate is generated by neutralization of sulfuric acid used for decomposing cumene hydroperoxide with caustic soda, and it is preferable to use this.

The salt concentration of the strong acid and the strong alkali adjusted in the present invention can be in the range of 20 to 32% by weight based on the amount of the aqueous solution after the neutralization treatment. If the salt concentration is lower than 20% by weight, the amount of phenol or acetone contained in the neutralized wastewater increases, which is not economically preferable. On the other hand, when the salt concentration is 32
If the concentration is higher than% by weight, solidification may occur in various pipes, which is not preferable. Thus, preferably 22
-30% by weight, more preferably 23-28% by weight.

As the mineral acid used to neutralize the aqueous alkali solution containing phenate, sulfuric acid is usually used.
Further, the concentration of the acid used is not particularly limited, but may be 50 to 98.
It is preferred to use those by weight. When the pH needs to be finely adjusted, the concentration of the acid used is preferably lower than the concentration of the acid used for the neutralization, for example, 10% by weight. The amount of these acids used is appropriately determined depending on the phenate and alkali content in the aqueous alkali solution containing the phenate to be neutralized. Use up to 1.5 equivalents.

The pH of the aqueous layer after the neutralization treatment is preferably in the range of 3.0 to 7.8. To prevent corrosion of the equipment in the downstream distillation process or to eliminate the need for a neutralization device, PH should be 3.
The pH is preferably 0 or more, and the pH is preferably 7.8 or less in order to complete the neutralization and reduce the loss of phenol.

The neutralization temperature is not particularly limited, but is usually carried out at around normal temperature. However, implementation at other temperatures is also included in the scope of the present invention.

The phenate-containing aqueous alkali solution and cumene and / or α-methylstyrene used in the present invention are effective when mixed before use before neutralization or when mixed after neutralization. Either method can be used.

The effect of the method of the present invention can be exhibited in both a batch system and a flow system as an embodiment.

Hereinafter, the present invention will be described in detail with reference to examples.

[0022]

EXAMPLE 1 An aqueous solution of phenate (32.9% by weight of phenate, 6.1% by weight of sodium hydroxide, pH 1) obtained from a recycling system of a phenol production plant using a cumene method was placed in a 100 ml screw tube.
50 g of 2) was collected, and 5 g of cumene was added as an oil layer (corresponding to a concentration of 9% by weight in the mixture). Next, a 98% by weight aqueous solution of sulfuric acid was added to the mixture to neutralize it while cooling and stirring. The pH was finely adjusted with a 10% by weight aqueous sulfuric acid solution. Neutralization was considered to be completed when the pH reached around 7. Further, distilled water was added to the neutralized solution so that the concentration of sodium sulfate in the aqueous layer became about 21% by weight. The resulting neutralized solution was stirred in a water bath heated to 40 ° C. in advance using a magnetic stirrer at 30 sec / time for 6 times at 5 minute intervals, and then allowed to stand for 30 minutes. The oil / water layer thus obtained was separated by a separating funnel, and sodium ions and sulfate ions in the oil layer were measured by an ion chromatograph equipped with a Shim-pack IC-A3 column. Also,
The amount of water in the oil layer was analyzed with a Karl Fischer moisture meter. Further, the phenol concentrations in the aqueous layer and the oil layer were analyzed by gas chromatography.

As a result of various analyses, sodium ion and sulfate ion in the oil layer were 605 ppm and 94 ppm, respectively. The phenol concentration in the water layer and the water concentration in the oil layer were 0.80% by weight and 8.0% by weight, respectively. Table 1 shows the results.

Example 2 Example 1 was repeated, except that 5 g of α-methylstyrene was added to an aqueous alkali solution containing phenol instead of 5 g of cumene.
Was carried out in the same manner as described above.

As a result of various analyses, sodium ion and sulfate ion in the oil layer were 1100 ppm and 94.5 ppm, respectively. The phenol concentration in the water layer and the water concentration in the oil layer were 0.77% by weight and 7.3% by weight, respectively. Table 1 shows the results.

Example 3 Instead of 5 g of cumene, 2.5 g of cumene, α-methylstyrene
The procedure was carried out in the same manner as in Example 1, except that 2.5 g (corresponding to a total concentration of 9% by weight in the mixture) of the phenate-containing aqueous alkali solution was added.

As a result of various analyses, sodium ions and sulfate ions in the oil layer were 808 ppm and 94.5 ppm, respectively. The phenol concentration in the water layer and the water concentration in the oil layer were 0.78% by weight and 7.7% by weight, respectively. Table 1 shows the results.

Example 4 The procedure of Example 1 was repeated, except that instead of 5 g of cumene, 7.5 g of cumene (corresponding to a concentration of 13% by weight in the mixture) was added to an aqueous alkali solution containing phenate.

As a result of various analyses, sodium ion and sulfate ion in the oil layer were 490 ppm and 74 ppm, respectively. The phenol concentration in the water layer and the water concentration in the oil layer were 0.70% by weight and 6.9% by weight, respectively. Table 1 shows the results.

Example 5 Example 1 was repeated except that 5 g of cumene was added to an alkaline aqueous solution containing phenate which had been previously neutralized with an aqueous sulfuric acid solution.
Was carried out in the same manner as described above.

As a result of various analyses, sodium ion and sulfate ion in the oil layer were 615 ppm and 95 ppm, respectively. The phenol concentration in the water layer and the water concentration in the oil layer were 0.80% by weight and 7.9% by weight, respectively. Table 1 shows the results.

Example 6 Instead of 5 g of cumene, an oil layer containing cumene or α-methylstyrene (composition: cumene 67.0) obtained from a purification system (hydrocarbon tower) in a cumene phenol production process.
%, Α-methylstyrene 28.7%, phenol,
Acetone, hydroxyacetone and water were detected) 5g
(Corresponding to a concentration of 9% by weight in the mixed solution) was carried out in the same manner as in Example 1 except that an aqueous alkaline solution containing phenol was added.

As a result of various analyses, sodium ions and sulfate ions in the oil layer were 755 ppm and 94 ppm, respectively. The phenol concentration in the water layer and the water concentration in the oil layer were 0.78% by weight and 7.6% by weight, respectively. Table 1 shows the results.

Example 7 The procedure of Example 1 was repeated, except that 15 g of cumene (corresponding to a concentration of 23% by weight in the mixture) was added to an aqueous alkaline solution containing phenol instead of 5 g of cumene.

As a result of various analyses, sodium ion and sulfate ion in the oil layer were 345 ppm and 51 ppm, respectively. The phenol concentration in the water layer and the water concentration in the oil layer were 0.56% by weight and 6.3% by weight, respectively. Table 2 shows the results.

Comparative Example 1 The same procedure as in Example 1 was carried out except that cumene was not added to the aqueous alkali solution containing phenate.

As a result of various analyses, sodium ion and sulfate ion in the oil layer were 1700 ppm and 252 ppm, respectively. The phenol concentration in the water layer and the water concentration in the oil layer were 1.12% by weight and 18.1% by weight, respectively. Table 2 shows the results.

Example 8 Instead of 5 g of cumene, 15 g of cumene (corresponding to a concentration of 23% by weight in the mixture) was added to an aqueous phenol-containing aqueous alkali solution, and sulfuric acid in a neutralized liquid aqueous layer was further distilled water. The sodium concentration was 25.8% by weight. Further, the procedure was performed in the same manner as in Example 1 except that the pH was adjusted to 3.5 with an aqueous sulfuric acid solution.

As a result of various analyses, sodium ion and water in the oil layer were 55 ppm and 4.9% by weight, respectively. The phenol concentration in the aqueous layer was 0.38% by weight.
Table 2 shows the results.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

According to the present invention, the alkali aqueous solution is neutralized with a mineral acid before and after adding cumene and / or α-methylstyrene to the aqueous phenate-containing aqueous alkali solution, so that the aqueous solution layer of the processing liquid can be neutralized. The phenol concentration in the oil layer is reduced by specifying the salt concentration and pH of the strong acid and strong alkali in the aqueous layer of the neutralized solution obtained by neutralizing the aqueous phenate-containing alkali solution with a mineral acid. Can be reduced. Thereby, phenol loss in the neutralized wastewater can be reduced. Furthermore, fouling (clogging) of the tube of the reboiler in the distillation step is suppressed, and the number of cleaning shutdowns is drastically reduced.

Continued on the front page (72) Inventor Yoshihiro Sezaki 1-6-6 Takasago, Takaishi-shi, Osaka Mitsui Chemicals, Inc. (72) Inventor Masami 1-6-6 Takasago, Takaishi-shi, Osaka Mitsui Chemicals, Inc. (72) Inventor Shigeki Nagamatsu 1-6-6 Takasago, Takaishi-shi, Osaka Mitsui Chemicals, Inc. (72) Inventor Takayuki Shiga 1-6-6 Takasago, Takaishi-shi, Osaka Mitsui Chemicals, Inc.

Claims (5)

[Claims] 1. A method for separating and recovering phenols from an aqueous alkali solution containing sodium phenolate, wherein a mixed solution obtained by adding cumene and / or α-methylstyrene to the aqueous alkali solution is neutralized with a mineral acid; A method for recovering phenols, comprising neutralizing the aqueous alkali solution with a mineral acid in advance and then adding cumene and / or α-methylstyrene. 2. A treatment solution obtained by neutralizing a mixed solution obtained by adding cumene and / or α-methylstyrene to an aqueous alkali solution containing sodium phenolate with a mineral acid, or treating the aqueous alkali solution with a mineral acid beforehand. Of cumene and / or a mixed solution to which α-methylstyrene has been added,
Cumene and / or α-methylstyrene concentration in the oil layer is 3 to
The method for recovering phenol according to claim 1, wherein the amount is in the range of 30% by weight. 3. A treatment solution obtained by neutralizing a mixed solution obtained by adding cumene and / or α-methylstyrene to an aqueous alkali solution containing sodium phenolate with a mineral acid, or treating the aqueous alkali solution with a mineral acid beforehand. The method for recovering phenol according to claim 1, wherein the salt concentration of the strong acid and the strong alkali in the aqueous layer of the mixed solution to which cumene and / or α-methylstyrene are added after the addition is 20 to 32% by weight. 4. A treatment solution obtained by neutralizing a mixed solution obtained by adding cumene and / or α-methylstyrene to an aqueous alkali solution containing sodium phenolate with a mineral acid, or treating the aqueous alkali solution with a mineral acid beforehand. The method for recovering phenol according to claim 1, wherein the pH of the aqueous layer of the mixed solution obtained by adding cumene and / or α-methylstyrene after the addition is adjusted to 3.0 to 7.8. 5. The method according to claim 3, wherein the salt of the strong acid and the strong alkali is sodium sulfate.