JPS5984832A - Preparation of high-purity 2,5-xylenol - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as a raw material for a pH indicator, etc. in high purity in high yield free from problems of a large amount of by-product and waste water, by subjecting m-cresol as a starting raw material to diorthomethylation with methanol, collecting a middle fraction of the prepared reaction mixture. CONSTITUTION:m-Cresol is reacted with methanol in a gaseous phase in a mixed catalyst preferably consisting of magnesium oxide and iron oxide at 400-470 deg.C, an unreacted methanol fraction and water fraction prepared as by-product as fractions of initial boiling point are collected from the prepared reaction mixture, a mixture of unreacted m-cresol and xylenols of intermediate reaction products is taken out as a middle fraction, and finally 2,3,6-trimethylphenol fraction is obtained. The middle fraction is cooled, crystallized, and precipitated to give the titled compound. The m-cresol content in the middle fraction is kept about 10-45wt%, and the cooling temperature is preferably 30-37 deg.C in case of about 10wt% content, 23-30 deg.C in case of about 20wt%, 18-25 deg.C in case of 30wt%, and 15-22 deg.C in case of 40wt%, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high-purity 2,5-xylenol, more specifically, from the middle distillate of a reaction mixture obtained by dimethylating the ortho position of m-cresol with methanol. The present invention relates to a method for separating and recovering high-purity 2,5-xylenol.

2.5-xylenol is used as a raw material for pIl indicator mulberry, or as a raw material for pharmaceuticals such as anti-lipid protein overload drugs.
It is known to be useful.

Conventionally, 2,5-xylenol was synthesized by sulfonating p-xylene with concentrated sulfuric acid or a fuming agent.

The obtained 2,5-''xylene sulfone i!!!2t was subjected to full califuration to produce 2,5-xylenol sodium salt.Then, this sodium salt was neutralized to give 2,5-xylenol sodium salt.
A method using 5-xylenol was adopted. However, this conventional method not only produces large amounts of gypsum and sodium sulfite as by-products, but also generates a large amount of waste water, which is problematic for commercial implementation.

The present invention proposes a method for producing highly pure 2,5-xylenol by orthomethylation reaction using 1m-cresol as a starting material, unlike the conventional method using p-xylene as a starting material. Both Yura and Abe, who are also the inventors of the present invention, published Japanese Patent Publication No. 51-36738 (Patent No. 862905)
A method for the orthoalkylation of phenols as taught in By using this method as previously proposed, m-cresol is diortmethylated with methanol.
．． A method for synthesizing 6-drimethylphenol was established. In this synthesis method, 2,5-xylenol and its isomer 2,3-xylenol are not produced as by-products! It was also acknowledged that it was generated unavoidably. However, as shown in Table 1, 2,5-xylenol and 2,3-xylenol have extremely similar boiling points and melting points. 2,3
-High purity 2,5-xylenol cannot be separated and recovered from a mixture of xylenol isomers.

Table 1 However, according to the research conducted by the present inventors, from the middle distillate of the reaction mixture produced by diortmethylation of 1m-cresol with methanol, although the distillate mainly contains the above-mentioned isomer mixture, Z, 2,5-xy L//-
It has been found that, unlike the case where 2,5-xylenol is separated and recovered from a mixture of 2,3-xylenol, highly pure 2,5-xylenol can be separated and recovered.

The method for producing high-purity 2,5-xylenol according to the present invention involves the orthomethylation reaction of 1m-cresol with methanol. a, 6-) A reaction mixture containing trimethylphenol is produced, and from this reaction mixture, an unreacted methanol fraction and a by-product water fraction are used as an initial distillate, and then unreacted m-cresol and an intermediate of the reaction are extracted. The product mixture with xylenols is separated as a middle distillate, and finally 2
．． 3.6-) The above-mentioned intermediate 'd fraction obtained when the trimethylphenol fraction is obtained as the main fraction is cooled to precipitate crystals, and the crystals are collected.

In the present invention, orthomethylation of m-cresol with methanol can be carried out under conditions that produce 2,3,6-)trimethylphenol, and in this sense, the orthomethylation reaction of the present invention is particularly suitable. As taught in Japanese Publication No. 51-36738, methanol and m-
It is preferable to adopt a method of reacting at a temperature of cresol t-400 to 470°C. According to this method, 2,
A reaction mixture containing 3,6-dolimethylphenol and further containing 2,5-xylenol and 2,3-xylenol as xylenol isomers can be obtained.

Its composition varies depending on the reaction conditions as shown in Table 2.

Table 2 However, from No. 644i of Table 1, it can be seen that the 2.5-xylenol content in the xylenol isomers contained in the reaction mixture is almost influenced by the reaction conditions.
, 80% in an extremely wide range of reaction rates for m-fresol
The previous and subsequent values are retained. Therefore, the reaction rate of 1m-cresol can be arbitrarily selected as long as the production of u,2,3.6-)trimethylphenol is guaranteed in the orthomethylation reaction of the present invention. however.

If the reaction rate is low, remove the middle distillate containing all xylenol isomers from the reaction mixture produced (this is not a good idea as the distillation load during sipping will be large).

The reaction rate of m-cresol in the present invention is 2°.3.
It is generally preferred to maintain the same level as for the purpose of producing 6-) trimethylphenol.

The reaction mixture produced by the orthomethylation reaction of the present invention contains 2,3,6-)methylphenol and xylenols (2,5-xylenol + 2,3-xylenol), and further contains unreacted m- Besides cresol and methanol.

It usually contains by-produced water. According to the present invention, this reaction mixture is subjected to a distillation operation to separate the unreacted methanol fraction, the by-produced water fraction, and the 2.3.6-) trimethylphenol fraction from the reaction mixture. A middle distillate containing xylenol isomers and unreacted m-cresol is obtained. According to the knowledge obtained by the present inventors, in order to separate and recover high-purity 2,5-xylenol from this middle distillate, m-cresol in the middle distillate:
It is possible to maintain it at about 1 liter to 45%.

The middle distillate is then cooled, thereby producing 2,5
-Xylenol crystals precipitate.

These crystals can be collected by filtration means such as Nutsche, centrifugation, etc. (To facilitate the operation, use benzene or toluene as necessary.

Aromatic solvents such as xylene, n-pentane, n-hexane, n-hebutane, cyclohexane.

Ligrolein 9 Aliphatic solvents such as petroleum ether.

Furthermore, methanol, ethanol, inzolopanol,
An alcoholic solvent such as t-citanol can be appropriately selected and used. In addition, if the crystals recovered from the middle distillate are washed with the above-mentioned organic solvent, even higher purity 2
, 5-xylenol can be obtained.

In order to obtain high-purity 2,5-xylenol according to the method of the present invention, it is essential to maintain the m-cresol content f in the middle distillate at about 10 to 45%, as described above. However, it is further desirable to appropriately select the temperature at which the middle distillate is cooled and filtered depending on the content of m-cresol in the middle distillate. That is, when the m-cresol content in the middle distillate is about 10%, the temperature is 30 to 37°C.

It is desirable to select a cooling filtration temperature of 23 to 30°C if the content is about 20%, 18 to 25°C if the content is 30%, and 15 to 22°C if the content is 40%. When the temperature is low, the purity of 62,5-xylenol decreases, and when the temperature is high, the amount of 2,5-xylenol recovered decreases.

As is clear from what has been detailed above.

The method for producing 2,5-xylenol according to the present invention is described in 2.3.
6-) It has the advantage that it can be carried out as part of the method for synthesizing 2,5-xylenol (as in the conventional method for producing 2,5-xylenol using p-xylene as a starting material, it does not produce a large amount of by-products). There is also no disadvantage of deriving water or wastewater.By the way.

In the method of the present invention, unreacted methanol and 2,5-xylenol crystals separated from the orthomethylation reaction mixture can be recycled to the orthomethylation reaction system.

Example 1 m-cresol was orthomethylated with methanol according to the method taught in Japanese Patent Publication No. 51-36738, and 2
, 3.6-) A reaction mixture containing methylphenol was obtained. From this reaction mixture, unreacted methanol and water were taken as the first distillate.

2.3.6-) 2-methylphenol was separated by rectification as the main distillate, and m-cresol 43.9% and '2.5-xylenol were separated as the middle distillate between the first distillate and the main distillate. 37.6
%, 2,3-xylenol 7.6%, 2,3.6-)trimethylphenol 4.7%, and other 6.2%.

The above middle distillate was cooled with stirring in a 100 g f 200 ml glass flask.

Acicular 2,5-xylenol crystals precipitated at 15°C.

Further cooling was continued until the temperature reached 10°C.

The precipitated crystals were filtered using a centrifuge. Then, centrifuge IJJI#tl'! using 23.6 g K' of cyclohexane. As a result of washing the crystals in a vacuum cleaner, 1ygt of 2,5-xylenol was obtained as a nearly white needle-like crystalline powder.

This product had a hanging point t/'J of 74-75°C and a purity of 99.5% as determined by gas chromatography.

Example 2 100 g of middle distillate obtained by distilling the orthomethylation reaction mixture obtained in the same manner as in Example 1 (m-cresol 30.7%, 2.5-xylenol 50.4%, 2,
3-xylenol 5.4%.

2.3.6-) methylphenol 1.4%, others”
When the mixture was cooled with stirring in a 20 ml glass flask, needle-shaped crystals were precipitated at 37°C.

After further cooling to 25°C, the crystals were filtered using a centrifuge, and the crystals were subsequently washed with 26 g of cyclohexane. As a result, 2°5-xylenol was obtained as a mostly white needle-like crystalline powder. I got 24 g'i. The melting point of this product was 1j74-75°C, and the purity by gas chromatography was 99.8%.

Example 3 100 g of middle distillate obtained by distilling the orthomethylation reaction mixture obtained in the same manner as in Example 1 (10% m-cresol, 72% 2,5-xylenol, 18% 2,3-xylenol) When cooled while stirring in a t2ooml glass flask, needle-shaped crystals precipitated at 40"C. After further cooling to 30°C, the crystals were filtered with a centrifugal separator and washed with 70g of cyclohexane. 2゜5-xylenol 39 as a white acicular crystalline powder
I got g'i. The melting point of this product was U73.8-75°C, and the purity by gas chromatography was 99.2%.

Example 4 20 g of cyclohexane was added to 100 g of a fraction having the same composition as the middle distillate used in Example 2, and when the mixture was cooled while stirring in a 200ml glass flask, needle-like crystals were precipitated at 27°C. After further cooling to 15°C, the crystals were filtered using a centrifuge and washed with 34 g of cyclohexane to obtain a white needle-shaped crystalline powder of 2,5-xylenol j1.
．． 6g was obtained. The melting point of this product is 3.8 to 75℃
The purity determined by gas chromatography was 99.2%.

Example 5 The same operation as in Example 2 was carried out except that the cyclohexane used for washing the crystals in Example 2 was replaced with n-pentane, and 25 g of 2,5-xylenol with a purity of 9.9.51% was used. 1
Star.

Comparative Example 2. 5-xylenol 80%, 2,3-xylenol 2
After heating and dissolving the 0% mixture in 30 g'i cyclohexane sog, the mixture was cooled while stirring in a 200 mJ glass flask.

Crystals precipitated at 30°C. More cooling? Continue to 15℃
After cooling down, filter the crystals using a centrifuge.

Washing with 30 g of cyclohexane gave 22.5 g of white needle-like crystalline powder. The purity of this product as measured by gas chromatography was 89.2%, and the presence of 2°3-xylenol was observed.

Patent applicant: Honshu Chemical Industry Co., Ltd.

Claims (1)

[Claims] 1. A reaction mixture containing 2.3.6-dolimethylphenol is produced by orthomethylation reaction of m-cresol with methanol. The unreacted methanol fraction and by-produced water fraction from this reaction mixture were subjected to rectification, and the unreacted methanol fraction and by-produced water fraction were used as the first distillate.
- A mixture of cresol and xylenol, which is an intermediate product of the reaction, is separated as a middle distillate, and finally 2,3.6
- A method for producing high-purity 2,5-xylenol, which comprises cooling the middle distillate obtained when obtaining dolimethylphenol as the main fraction to precipitate crystals, and collecting the crystals.