JPH0249745A - Method for purifying p-cresol - Google Patents

Abstract

PURPOSE:To obtain the subject high-purity p-cresol by reacting a cresol isomer mixture containing the p-cresol and m-cresol with an aldehyde in the presence of an aromatic sulfonic acid to form a cresol-aldehyde condensate, separating and removing the resultant condensate. CONSTITUTION:A cresol isomer mixture containing p-cresol and m-cresol is reacted with an aldehyde in the presence of an aromatic sulfonic acid (especially p-toluenesulfonic acid, etc.) to preferentially react the m-cresol and form a cresol-aldehyde condensate, which is then separated and removed to afford the purified p-cresol. The p-cresol is useful as a raw material for disinfectants, preservatives, surfactants, dyes, antioxidants, etc., and the cresol-aldehyde condensate is used as antioxidants, developers, etc.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for purifying para-cresol.

More specifically, para-cresol is produced by reacting a cresol isomer mixture containing para-cresol and metacresol with an aldehyde in the presence of an aromatic sulfonic acid, and separating and removing metacresol as a talesol-aldehyde condensate. Relating to a purification method.

Paracresol is a disinfectant, a preservative, a surfactant, a dye,
It is a compound useful as a raw material for antioxidants, etc., and is produced and used in large quantities.

On the other hand, cresol-aldehyde condensates are useful as antioxidants, color developers, and the like.

[Conventional technology]

Cresol has three isomers: ortho-cresol, meta-cresol, and para-cresol.

Examples of industrial methods for producing cresol include the alkali extraction method of tar fraction, the chlorination hydrolysis method of toluene, and the sulfonation alkali melting method of toluene. It is obtained as a mixture of three isomers: cresol, meta-cresol, and para-cresol.

By the way, the boiling point of orthocresol is 191°O"C, the boiling point of metacresol is 202.2°C, and the boiling point of para-cresol is 201.9°C. Therefore, orthocresol can be separated by distillation, but it is difficult to separate it from metacresol. Since para-cresol has very similar boiling points, it cannot be separated by simple distillation.

Various proposals have been made regarding methods for separating metacresol and valacresol.

For example, urea, 2,6-lutidine, sodium acetate,
A separation and purification method using the property that compounds such as phenol and metacresol form molecular compounds (Special Publication Publication No. 48
-10143, etc.), alkylated with isobutylene to obtain a di-tert-butylated product, separated by fractional distillation, and then separated and purified by dealkylation in the presence of an acid or a salt thereof (US Patent No. 2,297,588)
etc.), a method of separation by sulfonation and partial hydrolysis with heated steam (U.S. Pat. No. 378)
5776 etc.), molecular sieves, zeolites,
A method of separation by adhesion with an adsorbent such as (Japanese Patent Application Laid-Open No. 52-89624, etc.) has been proposed.

In addition, a method similar to the present invention, that is, a method in which cresol is reacted with formalin in the presence of hydrochloric acid and meta-cresol is separated as a cresol-aldehyde condensate (Industrial Chemistry Journal, 1663-1667 (1960)) has also been proposed. There is.

[Problem to be solved by the invention]

However, in the purification method that utilizes the property of forming molecular compounds, no compound has been found that satisfies both the purity and yield of purified valacresole, and the high cost of the conventional method described above has not been found. In methods that use raw materials, the loss of raw materials cannot be ignored.

Furthermore, the methods of alkylation and separation and sulfonation and separation require complicated operations and require expensive raw materials or large amounts of acids and bases.

Adsorption methods using molecular sieves and the like have not been found to be adsorbents that efficiently separate isomer mixtures, making it difficult to put them into practical use industrially.

Also, the above-mentioned document (Industrial Chemistry Magazine Competition, 1663-7 (1
960)), there is a specific description of using hydrochloric acid as a catalyst and reacting with formalin to obtain purified bala-cresol with a maximum purity of 97%, but the purity is still far from satisfactory and furthermore, the yield is extremely low. .

On the other hand, in the method of removing metacresol by selectively condensing only metacresol with formalin in the presence of an acid catalyst, after the condensation reaction, the reaction mass is heated and distilled in order to separate vala-cresol, so the condensation reaction The acid used must be removed.

One conceivable method for this method is to remove hydrochloric acid by washing with a large amount of water after the condensation reaction, but in that case, wastewater treatment also becomes a problem. Another possibility is to add an alkali such as soda to the reaction mass after the condensation reaction and remove the hydrochloric acid by neutralization, but in that case, the reaction mass containing alkali metals would be heated, so it is difficult to handle it for safety reasons. It becomes a problem.

It is extremely difficult to economically obtain such highly purified valacresol on an industrial scale, and this remains an unsolved problem.

[Means to solve the problem]

The present inventors have conducted intensive studies on a method for purifying high-purity vala-cresol that satisfies both purity and yield from a cresol isomer mixture containing vala-cresol and meta-cresol, and have conducted a method for purifying vala-cresol with aldehyde under certain specific conditions. The present invention was achieved by discovering that meta-cresol reacts preferentially with para-cresol and that a purified para-cresol product can be obtained with high purity and high yield.

That is, the present invention involves reacting a cresol isomer mixture containing bala-cresol and m-cresol with an aldehyde in the presence of an aromatic sulfonic acid, and separating m-cresol from bala-cresol as a cresol-aldehyde condensate.
This is a method for purifying balacresol, which is characterized by removing the balacresol.

In the method of the present invention, there is no particular restriction on the composition ratio of the cresol isomer mixture provided, but in particular the purity is 85-95.
It is highly effective in purifying % balacresol to a purity of 95% or higher.

The aldehyde compounds used in the condensation of the present invention include aliphatic low molecular aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde;
Examples include aromatic aldehydes such as benzaldehyde. Among these aldehydes, reactivity, selectivity,
When considering price, yield, use of the condensate, etc., formaldehyde and acetaldehyde are preferred. At this time, aldehyde can be used in aqueous solution, alcohol solution, dimer, polymer,
Alternatively, it may be used in any form of acecool. The amount of aldehyde used varies depending on the amount of metacresol to be removed, reaction conditions, etc., and the reaction conditions are selected to obtain highly pure para-cresol using a small amount of aldehyde. At this time, the aldehyde is usually used in an amount of 0.5 to 3 times the molar amount, preferably 0.5 to 1.5 times the molar amount of the metacresol contained.

In the present invention, aromatic sulfonic acids are used as catalysts. For example, benzenesulfonic acid, ortho, meta-
and para-toluenesulfonic acid, benzenedisulfonic acid and the like. In particular, para-toluenesulfonic acid is the most preferred M medium.

The amount used is usually 0.001 to 10 parts by weight, preferably 0.01 to 1 part by weight per 100 parts by weight of crude para-cresol. If the amount of catalyst used is large, the yield or purity of para-cresol will decrease, which is not preferable.

The reaction temperature of the present invention is usually in the range of -20 to 80°C, preferably 0 to 40°C. A high reaction temperature is undesirable because it lowers the purity of vala-cresol. Cresol isomer mixtures have various freezing points depending on their composition. Since we take
When the raw material cresol isomer mixture is solid in the temperature range in which the condensation reaction is carried out, a solvent that does not adversely affect the reaction may be used.

For example, aromatic hydrocarbons such as benzene, toluene, xylene, cumene, and mesitylene, aliphatic hydrocarbons such as hexane, heptane, and octane, and halogenated hydrocarbons such as chlorobenzene, orthodichlorobenzene, chloroform, carbon tetrachloride, and dichloroethane. , alcohols such as methanol, ethanol, isopropyl alcohol, and n-propyl alcohol, and nitriles such as acetonitrile and propionitrile. Purity of refined baracresol,
Toluene is one of the most preferred solvents when considering yield, solvent recovery, price, and operability. Further, when the raw material cresol isomer mixture is liquid at the reaction temperature, the above-mentioned solvents may be used, or the reaction may be carried out without a solvent.

If a solvent is used, the amount used is 100% crude cresol.
Usually 500 parts by weight or less, preferably 20 parts by weight
It is preferably 0 parts by weight or less.

The dehydration condensation reaction between cresol and aldehydes is an equilibrium reaction, so when the reaction mass is directly subjected to distillation, the metacresol-aldehyde condensate produced in the reaction process undergoes hydrolysis during distillation to become metacresol. Since it is mixed into the distillate, the purity of para-cresol decreases. Therefore, as described above, it is necessary to remove the acid used as a catalyst before distillation, and in the present invention, aromatic sulfonic acid is also removed before distillation.

The aromatic sulfonic acid can be removed by washing the reaction mass after the completion of the condensation reaction with water or by neutralizing it with a base. However, in the present invention, acid removal by neutralization does not affect the purity of the purified product in any way, so the preferred method for extracting valacresol in the present invention is to neutralize it with an excess amount of aqueous ammonia after the completion of the reaction, and then subject it to vacuum distillation. In the conventional purification method using hydrochloric acid as a catalyst, such as the one cited above, this method is not used because the ammonium chloride produced when neutralized with aqueous ammonia sublimes during distillation and mixes with baracresol. Therefore, the method of the present invention is extremely advantageous.

In the present invention, purified para-cresol can be obtained as a distillate by neutralizing with aqueous ammonia and then distilling it. After neutralization distillation, the cresol-aldehyde condensate and the ammonium salt of aromatic sulfonic acid remain in the pot, but if necessary, the ammonium salt of aromatic sulfonic acid can be washed with water, recrystallized, etc. to form cresol-aldehyde. It is also possible to purify and recover the condensate.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples.

Example-1 21.6.3 g (equivalent to 2.0 mol) of crude baracresol having the composition shown in Table 1 was placed in a 500D glass 4-tube flask.
, 8.5 g of 90% paraformaldehyde, and 0.2 g of P-toluenesulfonic acid were reacted by stirring at a reaction temperature of 20°C for 4 hours, followed by 0.1 g of 25% ammonia water.
After neutralization by adding d, distillation under reduced pressure brings the boiling point to 102°C/2.
160.2 g of a 0 nHg fraction (purified vala cresol) was obtained.

Its composition is shown in Table 1. The extraction yield of baracresol in terms of purity was 80.3%.

Example 2 159.7 g of purified para-cresol having the composition shown in Table 1 was obtained by carrying out the same process as in Example 1 except that the reaction temperature was changed to 80° C. and the reaction time was changed to 1 hour.

Example 3 The same procedure as in Example 1 was carried out except that the reaction temperature was changed to 0° C. and the reaction time was changed to 18 hours to obtain 162.0 g of purified para-cresol having the composition shown in Table 1.

Example-4 The same process as in Example-1 was performed except that 8.5 g of 90% paraformaldehyde was replaced with 21.8 g of a 35% formalin aqueous solution to produce 161.
7g was obtained.

Example-5 Separate para-cresol 1 having the composition shown in Table 1 was prepared in the same manner as in Example-1 except that 8.5 g of 90% paraformaldehyde was replaced with 11.9 g of 90% acetaldehyde aqueous solution.
60.9g was obtained.

Example-6 p-) 160.0 g of purified balacresol having the composition shown in Table 1 was obtained by the same process as in Example-1 except that 0.2 g of luenesulfonic acid was replaced with 0.2 g of benzenesulfonic acid. Ta.

Example 7 Using 100 d of toluene as a diluent, the same treatment as in Example 3 was carried out to obtain 162.4 g of purified para-cresol having the composition shown in Table 1.

(Left below) Table 1 Comparative example 5001! 216.3 g of crude para-cresol having the composition shown in Table 1 and 8.5 g of 90% 0% valamaldehyde were placed in a 4-tube glass flask and maintained at 100'C. Then, 36% hydrochloric acid 1- was charged and reacted at 100°C for 15 minutes.

Next, one paper of 25% ammonia water was added to neutralize the mixture, and the mixture was subjected to vacuum distillation. The fraction with a boiling point of 102°C/20mmHH contains 300ppm of ammonium chloride and is cloudy.
The purity of p-cresol was 94.2%, and the yield was 152.4 g.

In addition, a large amount of white crystals were observed to be attached to the distillation column.

〔Effect of the invention〕

The present invention is an industrial purification method that can separate vala-cresol from meta-cresol with a high yield as described above, and can also obtain highly pure vala-cresol.

Patent applicant Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1) Purification of para-cresol, which is characterized by reacting a cresol isomer mixture containing para-cresol and metacresol with an aldehyde in the presence of an aromatic sulfonic acid, and separating and removing metacresol as a cresol-aldehyde condensate. Method.