JPS6126890B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for purifying phenols. A widely known method is to oxidize an alkyl aromatic compound with molecular oxygen to form a hydroperoxide, which is then decomposed in the presence of an acid catalyst to produce phenols. Generally speaking, the greater the number of alkyl groups in the raw alkyl aromatic compound, the more
Furthermore, the higher the boiling point of the product phenols, the more difficult it is to separate and purify the desired phenols. For this reason, several separation and purification methods such as distillation, extraction, recrystallization, and adsorbent treatment are often used in combination. Regarding adsorbent treatment, activated carbon treatment is effective in removing trace amounts of impurities, but when applied to highly oxidizable phenols such as hydroquinone, it may cause the phenols to become colored. Therefore, there are problems in using it industrially. The present inventors investigated a method for preventing the above-mentioned coloring and effectively removing trace impurities when treating phenols with activated carbon, and as a result, developed the following method. That is, the present invention is a method for purifying phenols, which is characterized by bringing phenols into contact with activated carbon that has been subjected to acid treatment and reduction treatment. In the present invention, phenols containing impurities are treated with activated carbon, and the phenols are not only those obtained by the acid decomposition method of aromatic hydroperoxides, but also those produced by any other method. It may be. For example, it may be obtained by methods such as fractional distillation of tar, alkali melting, aniline oxidation, electrooxidation of phenol, and peroxide oxidation. Examples of the phenols include phenol, cresol, isopropylphenol, xylenol, catechol, resorcinol, hydroquinone, naphthol, cumylphenol, and phloroglumine. Phenols are particularly susceptible to oxidation,
For example, hydroquinone, catechol, resolmin,
Remarkable effects can be obtained when applied to naphthol or their nuclear substituted derivatives. In the present invention, activated carbon used for purifying phenols is subjected to acid treatment and reduction treatment in advance. Although the acid treatment and the reduction treatment may be performed sequentially, it is usually preferable to perform them simultaneously using a compound that has both actions. Examples of such compounds include acidic substances having reducing ability, such as reducing organic acids. More specifically, reducing organic acids such as oxalic acid, ascorbic acid, and formic acid are preferably used. Other examples include combinations of organic acids or inorganic acids other than those mentioned above and reducing agents such as hydrogen, sodium bisulfite, sodium thiosulfate, and sodium dithionite. In the acid treatment, it is preferable to use an acidic substance in the form of an aqueous solution, and the concentration thereof is arbitrary, but a sufficient effect can be observed even if it is used as a dilute aqueous solution of 10 to 10 ⁴ ppm. Further, the treatment temperature is preferably about 10 to 100°C. In acid treatment, the pH of the treated water is 4.
It is best to do this to the extent that: The activated carbon preferably has many relatively large pores; for example, one having an equilibrium adsorption capacity for erythrosine red of 0.2 g/g-activated carbon or more (equilibrium concentration 0.3 g/g) can be suitably used. When treating phenols with activated carbon, it is advantageous to dissolve the phenols in a suitable solvent. Such solvents include water, ketones, hydrocarbons, alcohols, etc., and the phenols are preferably dissolved at a concentration of, for example, about 5 to 60% by weight. This solution contains stabilizers for phenols,
For example, adding a small amount of an acidic compound such as oxalic acid, sulfuric acid, citric acid, ascorbic acid, etc. is more effective in preventing discoloration. In order to prevent fine powder from being mixed with phenols, it is preferable to use activated carbon in granular form, and fine powder should be removed by washing with water before starting use or prior to acid treatment or reduction treatment. It is desirable to keep it. Activated carbon treatment is usually advantageously carried out by passing phenols through a packed tower filled with activated carbon, and by using multiple such packed towers, the cycle of regeneration and use can be carried out smoothly. be able to. In the above usage method, the processing temperature is about 10 to 90℃, and the LHSV is
Purification can be carried out satisfactorily at a time of about 0.5 to 30 hr ^-1 . According to the present invention, there is no coloring of phenols;
It is possible to effectively remove trace amounts of impurities. Phenols treated in this manner also have the advantage of having very little tendency to color even after long-term storage. Next, the present invention will be explained in more detail with reference to examples. Example 1 Calgon activated carbon (CPG grade) 40 was placed in a stainless steel double tube with an inner diameter of 27 m/m and a height of 520 m/m.
80°C hot water was flowed from the top onto the activated carbon layer at a rate of 600ml/hr for 30 minutes. Then, 80°C hot water containing 500 ppm of oxalic acid was flowed from the top at a rate of 600 ml/hr. During this time, the pH of the liquid flowing out from the bottom through the activated carbon layer was measured over time.
When the pH reached 3.7, the flow of oxalic acid water was stopped. The time required for the distribution of oxalic acid was 1.2 hours. Contains 25wt% crude hydroquinone and 50ppm oxalic acid immediately after stopping the distribution of oxalic acid aqueous solution.
Hydroquinone was purified by flowing an 80°C hydroquinone aqueous solution from the top at a rate of 600 ml/hr (LHSV=7.5 hr ^-1 ). The absorbance of the purified hydroquinone aqueous solution flowing out from the bottom was measured, and at the same time, the hydroquinone that precipitated by cooling to 30°C was separated, and the absorbance of this crystal was also measured. Table 1 shows the changes in each absorbance. The outer shell of the activated carbon packed tower was kept at 80°C during the entire operation period.
The inside was kept at 80℃ by running hot water.

【table】

[Table] Examples 2 and 3 The same operation as in Example 1 was performed except that the activated carbon shown in Table 2 was used as the activated carbon. In both cases, 420 m of hydroquinone aqueous solution after activated carbon treatment
The absorbance at μ (measured by the method described in Table 1) is
The absorbance at 420 mμ of the hydroquinone crystals crystallized from the treated solution for 0 to 7 hours (measured by the method described in Table 1) was 0.017 (Example 2) and 0.016 (Example 3), respectively.

[Table] Example 4 Instead of the pretreatment with an oxalic acid aqueous solution in Example 1, the treatment solution was treated with water containing 1000 ppm formic acid.
The same operation as in Example 1 was performed except that the pretreatment was performed until the pH was 3.8. 420mμ of hydroquinone aqueous solution after activated carbon treatment
The absorbance (measured by the method described in Table 1) was 0.021 at 30 minutes, 0.019 at 60 minutes, 0.020 at 3 hours, and 0.021 at 7 hours after the start of hydroquinone treatment. Example 5 The same device used in Example 1 was filled with 40 g of activated carbon manufactured by Calgon (CAL grade) and poured from the top.
Hot water at 80°C was flowed through the activated carbon bed for 30 minutes at a rate of 600 ml/hr. Next, a 0.2wt% aqueous hydrochloric acid solution warmed to 80℃ was poured at a rate of 600ml/hr for 1 hour, and then
Activated carbon was pretreated by flowing hot water at 80°C containing 0.1 wt% sodium thiosulfate at a rate of 600 ml/hr for 1.5 hours. Immediately thereafter, an 80°C aqueous hydroquinone solution containing 25 wt% crude hydroquinone and 50 ppm oxalic acid was flowed at a rate of 600 ml/hr to purify hydroquinone. The absorbance at 420 mμ of the activated carbon-treated hydroquinone aqueous solution (measured by the method described in Table 1) was 30 mμ after the start of the hydroquinone treatment.
It was 0.018 at 60 minutes, 0.015 at 60 minutes, 0.016 at 3 hours, and 0.015 at 7 hours. Comparative Example 1 Example 1 except that the activated carbon was not treated with the 500 ppm oxalic acid aqueous solution in Example 1.
I performed the same operation as . The hydroquinone aqueous solution after the activated carbon treatment has a pale yellow-red color, and the absorbance at 420 mμ (measured by the method described in Table 1) is 0.090 at 30 minutes after the start of the hydroquinone treatment, 0.055 at 1 hour, and 0.055 at 3 hours. It was 0.043 at the time. Comparative Example 2 Activated carbon manufactured by Mitsui Coke Co., Ltd. (BL-
The same operation as in Example 5 was performed except that 40 g of 1030) was used and that the activated carbon treatment with an aqueous sodium thiosulfate solution was not performed. Hydroquinone aqueous solution after activated carbon treatment shows yellow-red color,
The absorbance at 420 mμ (measured using the method described in Table 1) was determined at 30 minutes after the start of hydroquinone treatment.
0.10, 0.091 at 60 minutes, 0.085 at 3 hours
showed that. Example 6 In the same manner as in Example 1, a crude resorcinol aqueous solution (resorcinol concentration 50%) was used instead of the crude hydroquinone aqueous solution. The absorbance of the crude aqueous resorcin solution before activated carbon treatment (absorbance at 420 mμ measured using a 50 m/m cell for a solution diluted 10 times with water) is 0.021, while the absorbance of the aqueous resorcin solution after activated carbon treatment ( (measured in the same manner as in the case of the crude resorcin aqueous solution) was 0.005 or less. Example 7 In the same manner as in Example 1, instead of the crude hydroquinone aqueous solution, a crude phloroglucin aqueous solution (phloroglucin concentration 15 wt%) was treated. Absorbance of crude phloroglucin aqueous solution before activated carbon treatment (absorbance of 420 mμ for diluted 6 times with water)
(measured using a 10 m/m cell) was 0.107, whereas the absorbance of the phloroglucin aqueous solution after activated carbon treatment (measured using the same method as the crude phloroglucin aqueous solution) was 0.04 or less. Example 8 After the pretreatment of activated carbon with an oxalic acid aqueous solution in Example 1, only hot water was passed through the activated carbon layer to wash the remaining oxalic acid, and then a 25 wt % crude hydroquinone aqueous solution containing no oxalic acid was added to Example 1.
Activated carbon treatment was performed in the same manner as above. The absorbance at 420 mμ of the hydroquinone aqueous solution after treatment is
It was less than 0.02. Comparative Examples 3-4 50 ppm of oxalic acid was added to a 25wt% crude hydroquinone aqueous solution (80°C) with an absorbance of 0.09, and the change in absorbance was examined, but the absorbance did not change to 0.09 and there was no decolorizing effect by oxalic acid. Comparative Example 4 When 100 ppm of sodium dithionite was added to a 25wt% crude hydroquinone aqueous solution (80°C) with an absorbance of 0.09 and the absorbance was examined, the absorbance was 0.08.

Claims (1)

[Scope of Claims] 1. A method for purifying phenols, which comprises bringing phenols into contact with activated carbon that has been subjected to acid treatment and reduction treatment. 2. The method according to claim 1, wherein the acid treatment and reduction treatment are performed with an acidic substance having reducing ability. 3. The method according to claim 1, characterized in that the phenols to be brought into contact contain an acidic compound.