JPS647058B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for purifying phenols.
More specifically, the present invention relates to a method for purifying cumene crude phenols using an extractive distillation method. Phenol, m
The industrial production of phenols such as -cresol and p-cresol is generally well known as the cumene process. The phenols separated from the crude phenols, which are the acid-catalyzed cleavage products, by ordinary distillation contain various harmful impurities, although their freezing point is close to the theoretical freezing point. There is. These impurities cause undesirable coloration when phenols are sulfonated with concentrated sulfuric acid or treated with chlorine, thus preventing their use in applications where high quality is required. It turns out. Conventionally, many methods have been proposed for separating highly pure phenols from crude phenols produced by the cumene process. Among these methods, crude phenols are subjected to extractive distillation using polyalkylene glycol or its ether, impurities and unreacted substances are distilled off from the top of the distillation column, and then purified by distillation from the bottom extraction mixture. The method of separating phenols (Japanese Patent Publication No. 36-5713) is considered to be one of the industrially superior methods. However, even with such an extractive distillation method, impurities that cause coloring cannot be completely removed. One embodiment of the extractive distillation method when the phenols are phenols will be described in detail with reference to FIG. 1 of the drawings. First, the reaction mixture obtained by cleavage of cumene hydroperoxide with an acid catalyst is neutralized with an alkali, and the oil layer separated from the aqueous layer is fed to a deacetonization tower through line 1, and is then cleaved from the top of this tower through line 2. A low-boiling fraction such as acetone is separated and then led to an acetone purification column (not shown) to produce purified acetone. On the other hand, from the bottom of the column, a fraction from which low-boiling fractions such as acetone have been removed is extracted through line 3 and supplied to a vacuum distillation column. From the top of this vacuum distillation column, line 4
Cumene, water, etc. may be distilled off using a line 5, and a portion thereof may be refluxed to a vacuum distillation column via a line 5. A phenol-containing fraction is extracted from the bottom of the vacuum distillation column via line 7 and is supplied to the distillation column. From the bottom of this distillation column, substances with higher boiling points than phenol are removed via line 8, and the crude phenol fraction from the top of the column is introduced via line 9 into the extractive distillation column. Note that the arrangement order of the vacuum distillation column and the distillation column used before the extractive distillation column can also be reversed. The fraction fed to the extractive distillation column is brought into countercurrent contact with the polyalkylene glycols freshly fed via line 10 and recycled via line 14, and the phenols extracted into this solvent are passed through the column. Impurities that are not extracted by the solvent are led to the distillation column from the bottom via line 11, and are passed from the top to line 12.
removed from the system by Purified phenol, which is distilled in this distillation column and separated from polyalkylene glycols, is taken out from the top of the column through line 13 and used as a product. On the other hand, the extraction solvent is
It is circulated from the bottom of the column to the extractive distillation column via line 14. In such a series of extractive distillation columns, even if high-boiling substances such as fractions with higher boiling points than phenol are removed from the bottom of the distillation column, these fractions are entrained in the top fraction, even if only slightly. , these high-boiling fractions are partially removed from the top of the next extractive distillation column, while the remaining part is withdrawn from the bottom of the column together with the extraction solvent and fed to the distillation column. - Gradual accumulation of this undesirable high-boiling fraction between the distillation columns results in a deterioration of the quality of purified phenol obtained from the distillation columns. Therefore, in order to prevent the accumulation of these high-boiling fractions, the present inventors extracted a portion of the fraction that does not substantially contain the extraction solvent at an intermediate stage of the distillation column.
An attempt was made to completely remove the high-boiling fraction from the bottom of the distillation column by returning it to the column ~, but after long-term operation, colored components accumulated in the system, mixed into the purified phenol, and the This could not be a solution to the problem since the quality would deteriorate. Therefore, the present inventors also investigated known methods for removing components that cause coloration of crude phenol, specifically, Japanese Patent Publication No. 39-622 and Japanese Patent Publication No. 37-1989.
Using the method described in Publication No. 11664, we applied a treatment method using an acidic catalyst to remove benzofuran, which is a coloring component, in the stage before the distillation column that removes high-boiling substances, but the acid cleavage of cumene hydroperoxide Due to the presence of unresolved traces of the salts formed upon neutralization of the product, and also due to the presence of tar components formed during the acid cleavage of cumene hydroperoxide, acidic catalysts, e.g. When treated with a solid acid, the catalytic function of this solid acid decreased rapidly.
It was acknowledged that the intended objectives could not be fully achieved. In view of this background, the present inventors further conducted various studies to solve this problem, and found that a portion of the fraction containing substantially no extraction solvent was extracted from a distillation column that fractionated a mixture of phenols and extraction solvent. By extracting it, treating it with an acidic catalyst, and recycling this acid-treated product as it is or after adding distillation to the previous process, it is possible to obtain high-quality and stable phenols. I found out what I can do. Therefore, the present invention relates to a method for purifying phenols, which involves extraction from a distillation column that fractionates a mixture of phenols and an extraction solvent when purifying crude phenols using the cumene method using an extractive distillation method. A part of the fraction containing substantially no solvent is extracted, treated with an acidic catalyst, and the acid-treated product is subjected to a high-boiling point removal process or a hydroperoxide treatment in combination with the above-mentioned process. This is carried out by circulating the process at any stage between the acid cleavage step and the acid cleavage step. Here, the distillate that does not substantially contain extraction solvent is defined as a fraction containing approximately 1000 ppm or less of extraction solvent.
Preferably the fraction is about 500 ppm or less. If this fraction contains a large amount of extraction solvent, the extraction solvent may partially change in quality when it comes into contact with an acidic catalyst (for example, diethylene glycol changes to dioxane due to the action of acid), or the fraction after acid treatment may be The extraction solvent that is entrained when circulating through the process is removed from the system in the high-boiling point removal process, resulting in unfavorable results such as loss of extraction solvent. The purified phenolic fraction itself, which should be obtained as a product as a fraction that does not substantially contain such extraction solvent, is obtained as a product.
Although it can be used in a proportion of about 1 to 20 parts by weight per 100 parts by weight, it is preferable to use a higher boiling point fraction from a lower stage than the number of stages in the distillation column from which this purified phenol fraction is distilled. Such a higher boiling point fraction is generally extracted in a proportion of about 1 to 20 parts by weight, preferably about 3 to 15 parts by weight, based on 100 parts by weight of the purified phenol fraction, and fed to the acid treatment step.
If the amount extracted is too small, a sufficient purification effect cannot be expected; on the other hand, if more is extracted, a larger amount of phenols will be recycled, or a larger amount of phenols will be subjected to distillation of the acid-treated product. As a result, a large amount of work is required and it is not economical. Acidic catalysts used to treat fractions substantially free of these extraction solvents include sulfuric acid, hydrochloric acid, phosphoric acid; p-toluenesulfonic acid, phenolsulfonic acid, trichloroacetic acid; aluminum chloride, boron trifluoride, and Ether complex compounds; silica-alumina, activated clay, bentonite, montmolinite and acid-treated products thereof; solid acids such as phosphoric acid-diatomaceous earth; acidic ion exchange resins such as sulfonated styrene-divinylbenzene resin, etc. are used. Among them, the use of solid acids is extremely preferred from the viewpoint of ease of post-treatment. Although these acidic catalysts vary widely depending on the type of catalyst and other conditions, they are generally used in a proportion of about 0.005 to 10% by weight of the fraction to be treated, and solid acid catalysts are When processing in a continuous manner as a fixed bed, the liquid hourly space velocity (LHSV) is approximately 1 to
30, preferably within the range of about 3 to 10.
Treatment with acidic catalysts can also be carried out batchwise, but
It is preferable to carry out the process in a continuous manner, and most preferably to carry out in a continuous manner as a fixed bed using the solid acid catalyst described above. The processing temperature ranges from room temperature to approx.
250°C, preferably in the range of about 120-180°C, for example in the case of phenol its boiling point (181.8°C)
At temperatures above , pressure treatment is required. Furthermore, processing under pressure conditions lower than atmospheric pressure is also possible. The treatment time is generally about 1 to 60 minutes. The fraction that does not substantially contain the acidic catalyst and the extraction solvent may be recycled as is, but the distillation operation is performed to distill purified phenol from the top of the column to obtain product phenol. You can also cycle through this. The bottom fraction thus treated with an acidic catalyst or further subjected to a distillation operation can be used in any step of the high boiler removal step or any stage between this step and the hydroperoxide acid cleavage step, preferably a high boiler. It is recycled to the material removal process. As a result of treatment with such an acidic catalyst, color-causing substances with boiling points and solubility close to those of phenols, which cannot be completely removed even by extractive distillation, become high-boiling substances. By recycling the process or previous steps, the high boilers formed are easily removed;
It is thought that high-quality phenols can now be obtained because the color-causing substances that conventionally accumulated between the distillation column and the extractive distillation column are removed. To explain the present invention with reference to the drawings, Fig. 2 is a flow sheet of an embodiment of the invention in which the acid-treated product is directly circulated, and Fig. 3 is a flow sheet of an embodiment of the invention in which the acid-treated product is circulated after being distilled. 1, and the symbols ~ and 7 to 14 indicate the same things as in FIG. The crude phenolic fraction fed from the distillation column to the extractive distillation column via line 9 is preferably converted from acid cleavage products to low-boiling fractions such as acetone, cumene, α-methylstyrene, etc. by a stepwise distillation operation. Water and other high-boiling substances such as acetophenone, cumylphenol, α-methylstyrene dimer, tar components, and salts are removed. The polyalkylene glycols freshly supplied via line 10 and recycled via line 14 include one or more lower polyalkylene glycols with a higher boiling point than the phenols or their ethers, such as diethylene glycol; Triethylene glycol, dipropylene glycol, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol propyl ether, diethylene glycol butyl ether, etc. are used, and diethylene glycol, diethylene glycol propyl ether, diethylene glycol butyl ether, etc. are particularly preferably used. The amount of these used varies depending on the amount of impurities in the crude phenol fraction, the quality of the desired purified phenols, etc., but in general, it is about 1 part by weight of the crude phenol fraction.
It ranges from 0.1 to 3 parts by weight, preferably about 0.3 to 1 part by weight. Extractive distillation can be performed in various ways depending on the type of phenol and the type of extraction solvent, but in the case of phenol, it is carried out under reduced pressure conditions of atmospheric pressure to about 10 mmHg (absolute pressure). It will be done. Through this extractive distillation operation, most of the phenols along with the extraction solvent are taken out from the bottom of the extractive distillation column via line 11, and in the case of phenols, hydrocarbons such as cumene and α-methylstyrene are removed. In addition, most of the impurities such as acetophenone, mesityl oxide, 2-methyl-benzofuran, and hydroxyacetone are removed from the top of the column through line 1.
2, it is discharged out of the system. In the distillation column, phenols and extraction solvent are fractionally distilled, with purified phenols coming from line 13, and a fraction containing substantially no extraction solvent coming from line 15 (this fraction is purified phenols). (sometimes from line 13), and the extraction solvent is removed from line 14 in a state containing some phenols. In addition, the purified phenol that becomes the product has an extraction solvent content that is below the detection limit of gas chromatography (approx.
Distillation operation is carried out so that the concentration is 30 ppm or less. The fraction substantially free of extraction solvent is treated with an acid in an acid treatment device, and then circulated through a line 16 to a supply line 7 to the distillation column, where it is treated as a bottom fraction of the distillation column with high boiling point substances. is discharged from the system through line 8 (Fig. 2). Alternatively, the acid-treated product is
Purified phenols are sent to the distillation column via line 16 and fractionated, and are obtained via line 17, while other fractions are circulated via line 18, and high-boiling fractions are removed from line 8. (Figure 3). In the distillation operation using this distillation column, the impurities contained in the phenols treated with acid in the acid treatment device have a high boiling point, so it is easy to separate the phenols, and therefore entrainment can be avoided. It can be carried out effectively using any type of distillation column, and has good sulfonation values with recoveries of about 70-95% of the feed when operated at atmospheric pressure or under reduced pressure. Purified phenols can be obtained from line 17. When such a distillation operation is added, it is possible to avoid the disadvantage that, if not carried out, heating would be required twice in the distillation column and in order to purify the phenols, which would result in loss of utility. I can do it. Ultimately, whether or not to add such a distillation operation is determined from the relative viewpoint of the distillation cost in the distillation column and the cost of increased use. Next, the present invention will be explained with reference to examples. Comparative Example According to the embodiment shown in FIG. 1, cumene crude phenol was purified by extractive distillation. The acid cleavage product obtained by decomposing the cumene hydroperoxide solution obtained by oxidizing cumene with a sulfuric acid catalyst is neutralized with an alkali, and then the aqueous layer is removed, and the mixture is passed through a distillation column to produce acetone and lower The boiling point fraction was removed to obtain a fraction having the following composition. Phenols 56% by weight Cumene 15 Water 16 α-methylstyrene 6.0 Acetophenone 1.5 Carbinol 0.5 High boilers 5.0 This fraction was fed to a vacuum distillation column with 70 plates at a rate of 30 parts by weight per hour, and the internal pressure was approximately 200 mmHg. , vacuum distillation was carried out under the conditions of a top temperature of 64°C and a bottom temperature of 178°C. From the top of the column, mainly water, cumene, and their accompanying impurities were distilled off, while from the bottom of the column a distillate with the following composition was distilled off. min Phenol 84% by weight Cumene 0.1 α-Methylstyrene 3.2 High boilers 12.3 were taken out at a rate of 20 parts by weight per hour, and then the high boilers were removed by distilling the phenol fraction in a distillation column. This crude phenol fraction is fed at a rate of 17.5 parts by weight per hour to the central stage of a 54-plate extractive distillation column, and brought into countercurrent contact with circulating diethylene glycol introduced from the top of the column at a rate of 19.5 parts by weight per hour. For extractive distillation, the top temperature is 92℃ and the bottom temperature is 192℃.
It was carried out under the following conditions. From the top of the column, impurities such as α-methylstyrene, cyclohexanol, and ketones that cannot be extracted by diethylene glycol are removed, while from the bottom of the column, a diethylene glycol solution from which phenol has been extracted is taken out at a rate of 36 parts by weight per hour. , is fed to the distillation column. In this distillation column, distillation was carried out at a top temperature of 116°C, and purified phenol was taken out from the top of the column at a rate of 16.5 parts by weight per hour.The sulfonation value of the purified phenol thus obtained was 85%. Ta. This sulfonation value is 45% for 20ml of sample phenol.
℃ for 10 minutes on a water bath, then quickly mixed with 20 ml of concentrated sulfuric acid, left at room temperature for 1 minute, and then in water for 5 minutes, and the sample was transferred to a 20 mm cell.
The transmittance at a wavelength of 532 mμ was measured using a photoelectric colorimeter, and the value is expressed as a percentage, and the larger the value, the better the quality of the phenol. Example 1 According to the embodiment shown in FIG. 2, crude phenol produced by the cumene process was purified by extractive distillation. In the comparative example, 14
A fraction with a diethylene glycol content of 275 ppm is extracted from the liquid phase portion of the tray in the upper stage at a ratio of 1 part by weight per 16.5 parts by weight of purified phenol distilled from the top of the column. The solution was passed through a packed drum filled with 0.17 parts by volume (1 part by volume is 1 m ³ when 1 part by weight is 1 ton) under the following acid treatment conditions. The thus acid-treated product was mixed with the feed 7 from the vacuum distillation column, and a distillation operation was performed in the distillation column to remove high-boiling substances from the bottom of the column. The crude phenol fraction from which high boilers have been removed in this way is fed at a rate of 18.5 parts by weight per hour to the central stage of a 54-plate extractive distillation column, and is introduced from the top of the column at a rate of 21 parts by weight per hour. in countercurrent contact with circulating diethylene glycol. Extractive distillation is carried out in the same manner as in the comparative example, and 38.5 parts by weight of the phenol-extracted diethylene glycol solution taken out from the bottom of the column is fed to the distillation column. Through distillation in this distillation column carried out at a top temperature of 116° C., purified phenol was taken out from the top of the column at a rate of 16.5 parts by weight per hour, and the sulfonation value of the purified phenol thus obtained was measured. Examples 2 to 7 In Example 1, purification was carried out by adjusting the liquid hourly space velocity (LHSV) by changing the amount of activated clay packed into the packed drum, and by varying the treatment temperature. The results obtained in Examples 1 to 7 are shown in Table 1 below.

[Table] Examples 8 to 11 Purification was carried out in Example 1 with various changes in the acidic catalyst and other treatment conditions. The results obtained are shown in Table 2 below.

[Table] Alumina
9 Silica 〃 〃 〃
10 Acidic clay 〃 〃 94
11 Alumina 〃 200 95
Example 12 In the comparative example, 20% per hour from the bottom of the distillation column
A total of 20.2 parts by weight/hour of the fraction taken out at a rate of 1 part by weight and the fraction recycled at a rate of 0.2 parts by weight from the distillation column described below at a rate of 0.2 parts by weight/hour is distilled in a distillation column to remove high boiling point substances, The crude phenolic fraction is fed to an extractive distillation column and brought into countercurrent contact with recycled diethylene glycol introduced from the top of the column at a rate of 20 parts by weight per hour. From the top of the extractive distillation column, 1.0 parts by weight of impurities not extracted by the extraction solvent are removed every hour, while from the bottom of the column, a diethylene glycol solution containing phenol is removed every hour.
A proportion of 36.7 parts by weight is taken out and fed to the distillation column. In this distillation column, purified phenol is taken out from the top of the column at a rate of 15.7 parts by weight per hour, and the sulfonation value of the purified phenol thus obtained is 95%, which becomes product phenol. Note that these distillation operating conditions are almost the same as those in the comparative example. In this way, 15.7 parts by weight of purified phenol was distilled out per hour, and in the same manner as in Example 1, 1 part by weight of a higher boiling point fraction was distilled out per hour and treated with acid. 20 stages), the top pressure was 135 mmHg, the temperature was 134°C, and the bottom temperature was 149°C.
Distillation is carried out under the conditions of 0.8 parts by weight of purified phenol per hour. The sulfonation value of this purified phenol is 98%, which is the product phenol. 0.2 parts by weight/hour of the bottom fraction of this distillation column is recycled to the distillation column as described above.

[Brief explanation of drawings]

FIG. 1 is a flow sheet of a conventional method, and FIGS. 2 and 3 are flow sheets of a method for purifying crude phenols using the cumene process by extractive distillation according to the method of the present invention. In these drawings, the symbols indicate a distillation column, a vacuum distillation column, a distillation column, an extractive distillation column, a distillation column, an acid treatment device, and a distillation column, respectively.

Claims (1)

[Claims] 1. When purifying phenols produced by the cumene process by extractive distillation, a portion of the fraction containing substantially no extraction solvent is extracted from a distillation column that fractionates a mixture of phenols and extraction solvent. Purification of phenols, characterized by extracting them, treating them with an acidic catalyst, and circulating the acid-treated product to a high boiler removal step or any stage of the process between this step and a hydroperoxide acid cleavage step. Method. 2. The phenol according to claim 1, wherein the same fraction as the purified phenol fraction obtained as a product is used as the fraction substantially free of extraction solvent extracted for acidic catalyst treatment. refining methods. 3. The method according to claim 1, wherein a fraction having a higher boiling point than the purified phenolic fraction obtained as a product is used as the fraction containing substantially no extraction solvent extracted for acidic catalyst treatment. Method for purifying phenols. 4 The extracted amount of the fraction that does not substantially contain the extraction solvent is the purified phenolic fraction obtained as a product.
The method for purifying phenols according to claim 2 or 3, wherein the amount is about 1 to 20 parts by weight per 100 parts by weight. 5. When purifying the crude phenols produced by the cumene process by the extractive distillation method, a part of the fraction containing substantially no extraction solvent is extracted from the distillation column that fractionates the mixture of the phenols and the extraction solvent, and the fraction is heated using an acidic catalyst. This acid-treated product is subjected to a distillation operation, and the fraction other than purified phenols is subjected to a high-boiling point removal step or an arbitrary step between this step and a hydroperoxide acid cleavage step. A method for purifying phenols, characterized by circulation. 6. The phenol according to claim 5, wherein the same fraction as the purified phenol fraction obtained as a product is used as the fraction substantially free of extraction solvent extracted for acidic catalyst treatment. refining methods. 7. The method according to claim 5, wherein a fraction having a higher boiling point than the purified phenolic fraction obtained as a product is used as the fraction containing substantially no extraction solvent extracted for acidic catalyst treatment. Method for purifying phenols. 8 The extracted amount of the fraction that does not substantially contain the extraction solvent is the purified phenolic fraction obtained as a product.
The method for purifying phenols according to claim 6 or 7, wherein the amount is about 1 to 20 parts by weight per 100 parts by weight.