JPS6216443A - Method of purifying phenol - Google Patents

Abstract

PURPOSE:In purifying a crude phenol containing a thiol as an purity, to improve qualities without causing problems of clogging of device and coloring, by combining oxidizing agent treatment with alkali metallic hydroxide treatment to contact an alkali metallic hydroxide. CONSTITUTION:A crude phenol containing a thiol as an impurity is fed from the line 1 to the contact part 2 and brought into contact with an alkali metallic hydroxide (preferably aqueous solution of caustic soda is used) fed from the line 3. The amount of caustic soda used is preferably an amount to make the crude phenol in the line 4 sent from the contact part 2 into 6.5-8.5 pH. The crude phenol is mixed with an oxidizing agent from the fine 6 in the blending part 5. Then, the blend is fed to the dehydrating column 7 and water is extracted from the line 8. The dehydrated crude phenol is fed to the flash column 10 of reduced pressure type with the column bottom kept at <=120 deg.C and a heavy material is removed from the line 12, to give the aimed compound from the line 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for purifying phenols, and particularly to a method for recovering high-quality phenols, cresols, etc. from crude phenols containing thiols.

[Prior art 1] Tar oil, liquefied coal oil, coal gasified condensate oil, etc. obtained by distilling coal tar, cerite tar, oil gas tar, etc. contain phenols such as phenol, cresols, and xylenol. These substances are purified and recovered.

However, the crude phenols obtained from the above raw materials such as tar oil contain a large amount of impurities such as carboxylic acids, bases, and thiols, and especially thiols such as alkylmercaptans and thiophenols. Since it causes coloration and odor, it is desirable to remove this as much as possible. Therefore, the applicant proposed a purification method in which thiols are removed by first adding an oxidizing agent to the crude phenols to make them heavier (
JP-A No. 59-210.038).

[Problems to be Solved by the Invention] The method of removing thiols by making them heavier with an oxidizing agent in crude phenols exhibits superior effects compared to other conventional purification methods. However, when the crude phenols treated with an oxidizing agent are purified and distilled using this method, there are problems such as clogging of the equipment and coloring of the obtained product phenols over time.

Therefore, as a result of various studies on methods for solving these problems, the present inventors solved the above problems by combining oxidizing agent treatment and alkali metal hydroxide treatment in which alkali metal hydroxide is brought into contact with each other. The present invention was achieved by discovering that the problem can be solved.

[Means for Solving the Problems] That is, the present invention, when purifying crude phenols containing thiols, treats the crude phenols with an oxidizing agent to make the thiols heavier. This is a method for purifying phenols in which oxidizing agent treatment and alkali metal hydroxide treatment are carried out by contacting with an alkali metal hydroxide, followed by distillation to remove heavy substances, followed by purification distillation.

The crude phenols used in the present invention contain thiols, and preferably, in order to recover crude phenols from tar oil, coal liquefied oil, coal gas condensate oil, etc., the phenols are first extracted by alkaline extraction. It is a crude phenol obtained by separating it as a salt and then decomposing it with an acid.

Such crude phenols contain carboxylic acids, pitch, and bases as impurities in addition to thiols, so it is preferable to remove these carboxylic acids, pitch, and bases before treatment with an oxidizing agent. Perform impurity removal treatment to separate and remove. The treatment method for removing carboxylic acid, pitch, and bases may be any conventionally known method, but it is preferable to use carbonated alkaline water washing, such as washing with carbonated alkaline water such as soda carbonate, as the decarboxylic acid treatment. As the debasing treatment, a cation exchange resin treatment in which the resin is brought into contact with a cation exchange resin such as a styrene-divinylbenzene copolymer type having a sulfonic acid group is preferable.

Various oxidizing agents such as hydrogen peroxide, permanganate, nitric acid, air, and ozone can be used as oxidizing agents to make the thiols contained in crude phenols heavier. These oxidizing agents can be used alone or in combination of two or more. Hydrogen peroxide and the combination of hydrogen peroxide and air reciprocation using air are particularly preferred because they do not generate sludge during distillation and do not cause problems with equipment corrosion. The amount of the oxidizing agent used in this oxidizing agent treatment is 3.5% based on the thiols contained in the crude phenols as raw materials. OOOppm
Below, preferably 1. The excess should preferably be within the range of Oo o ppn+, and the treatment temperature is from room temperature to 190°C, preferably from room temperature to 80°C.

Before, during, or after the above-mentioned oxidizing agent treatment, an alkali metal hydroxide treatment is performed in which the material is brought into contact with an alkali metal hydroxide. Examples of the alkali metal hydroxide used here include caustic soda and caustic potash, but caustic soda is preferred from the viewpoint of ease of availability and handling.

In addition, this alkali metal hydroxide is preferably used as an aqueous solution of about 5 to 50%, and the amount used is at least the chemical equivalent of a free acid such as a carboxylic acid if it exists, and the alkali metal hydroxide. As hydroxide, usually 20
0-20.0001)pm.

Preferably 500-10. OOppm. The amount of the alkali metal hydroxide used is preferably controlled by the pH value, and in that case, the pH of the crude phenol after adding the alkali metal hydroxide is usually 5 to 10, preferably 6 to 9, More preferably, it is controlled to be 6.5 to 8.5. If this pH value is less than 5, the effect of adding alkali metal hydroxide will not be sufficiently exhibited;
Addition to a value greater than 0 increases the production of alkali phenolate.

The alkali metal hydroxide treatment may be carried out before, during, or after the thiols are made heavy with an oxidizing agent.
It is necessary to do this before removing heavy substances, and optimally before carrying out weighting with an oxidizing agent.

From the crude phenols whose pH has been adjusted by the alkali metal hydroxide treatment in this manner, heavy substances such as heavy substances produced by weighting or alkali metal salts are removed. The method for removing heavy substances is not particularly limited, but is preferably a flash heating method which can be carried out at a relatively low temperature and in a short period of time. This removal of heavy substances is preferably carried out at a temperature of 140° C. or lower, preferably 130° C. or lower, in order to prevent decomposition of the heavy thiols.

During actual operation, prior to the removal of the heavy materials mentioned above,
It is preferable to remove the moisture contained in the crude phenols. This water content can be removed by a conventionally known method, for example, using a dehydration tower. When removing this contained moisture, it is preferable to carry out the removal at a temperature of 140°C or lower, preferably 120°C or lower.

The crude phenols from which heavy substances have been removed are then purified and distilled by conventional methods and separated into several fractions to produce product phenols such as phenol, O-cresol, and In/p-cresol.

[Example] Hereinafter, the method of the present invention will be explained based on an example carried out according to the flow sheet shown in the attached drawings.

100 parts by weight of crude phenols (containing 600 ppm of thiophenols in terms of total sulfur content) after decarboxylic acid treatment, depitching treatment, and debasing treatment were added to line 1.
1,250p of 25% caustic soda aqueous solution as NaOH was charged into the contact part 2 from the line 3.
The pH of the crude phenols in the line 4 exiting from the contacting section 2 is adjusted to 8.4, and the crude phenols are transferred to the line 6 in the mixing section 5.
30% hydrogen peroxide solution charged from 1 as H2O2
．． 1501) l) l) The thiophenols contained in the crude phenols are converted into secondary phenols, and then charged to the dehydration tower 7 whose bottom temperature is maintained at 100°C or less, and the top of the tower is Moisture is drawn out from line 8, and 100 parts of dehydrated crude phenols are drawn from line 9 at the bottom of the tower, and the dehydrated crude phenols are transported to the bottom of the tower at a temperature of 1.
95 parts by weight of mixed phenols from which heavy components have been removed are charged into a vacuum-type flash column 10 maintained at 20° C. or lower, and extracted from the column top line 11.
From this, 5 parts by weight of the above-mentioned heavy components were extracted. Purification was carried out continuously for about one month using the method of this example, during which time the thermal temperature V
No equipment blockage occurred at all.

Next, the mixed phenols extracted from the top line 11 of the flash column 10 were purified and distilled according to a conventional method to obtain products phenol, 0-cresol, and m/p-cresol. The obtained phenol, 0-cresol and l
For ll10-cresol, its purity and the content of impurities such as bases, thiophenols, and carboxylic acids were measured, and the coloring over time was determined using the Hazen color number (APHAN).
O, ). The results are shown in Table 1.

In addition, as a comparative example, crude phenols were purified in exactly the same manner as in the above example except that the alkali metal hydroxide treatment with caustic soda was omitted, and the obtained phenol, 0-cresol, and m/p-cresol were The purity and content of impurities such as bases, thiophenols and carboxylic acids were measured, and the coloration over time was determined as Hazen color number (APIIA No.). The results are shown in Table 1. Although purification was carried out continuously for about one month using the method of the comparative example, clogging of the distillation apparatus frequently occurred.

[Effects of the Invention] According to the method of the present invention, crude phenols obtained from, for example, tar oil, coal liquefied oil, coal gasified condensate oil, etc. are used as raw materials to produce products that are equivalent to synthetic products in terms of impurity content and coloration over time. In addition to being able to obtain high-quality fractionated phenols, clogging of the equipment does not occur during the purification process.

[Brief explanation of drawings]

FIG. 1 is a flow sheet of a purification method according to an example of the present invention. Patent applicant Nippon Steel Chemical Co., Ltd. Representative Patent attorney Katsuo Naruse
first name) pierce 1 leap

Claims (6)

[Claims] (1) In purifying crude phenols containing thiols, the crude phenols are treated with an oxidizing agent to make the thiols heavier, and brought into contact with an alkali metal hydroxide. A method for purifying phenols, which comprises performing alkali metal hydroxide treatment, then removing heavy substances by distillation, and then performing purification distillation. (2) The method for purifying phenols according to claim 1, wherein water content is removed by distillation prior to removing heavy substances. (3) The method for purifying phenols according to claim 2, wherein the temperature for removing contained water and heavy substances is 140° C. or lower. (4) The method for purifying phenols according to any one of claims 1 to 3, wherein the crude phenols are subjected to decarboxylic acid treatment, depitching treatment, and abasing treatment. (5) The method for purifying phenols according to any one of claims 1 to 4, wherein the pH of the crude phenols after contacting with an alkali metal hydroxide is 6 to 9. (6) The method for purifying phenols according to any one of claims 1 to 5, wherein the alkali metal hydroxide is caustic soda.