JPS63297334A - Purification of 2,4-xylenol - Google Patents

Abstract

PURPOSE:To obtain high-purity 2,4-xylenol in an industrial scale and on high yield, by preferentially reacting 2,5-xylenol in a crude mixture of 2,4-xylenol isomers with an aldehyde in the presence of an aromatic sulfonic acid, separating and removing. CONSTITUTION:A mixture of xylenol isomers containing 2,4-xylenol and 2,5- xylenol which can not be separated by mere distillation because of approximately the same boiling point is reacted with an aldehyde, preferably formaldehyde or acetaldehyde in the presence of an aromatic sulfonic acid, preferably p- toluenesulfonic acid and 2,5-xylenol is made into a xylenol-aldehyde condensate, separated from 2,4-xylenol and removed. 2,4-Xylenol useful as a raw material for synthetic resins, adhesives, antioxidants, herbicides and dyestuffs is obtained from the isomer mixture in high purity, industrially and advantageously.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for purifying 2,4-xylenol. For more information on Sara, see Crude 2.4- containing 2.5-xylenol.
The present invention relates to a method for obtaining high purity 2.4-xylenol by separating and removing 2.5-xylenol from a xylenol isomer mixture.

2.4-xylenol is used in synthetic resins, adhesives, insecticides,
It is a useful compound as a raw material for antioxidants, herbicides, pigments, etc., and is produced and used in large quantities, and high purity is required depending on the application.

(Prior art) There are six isomers of xylenol: 2,3-xylenol, 2.4-xylenol, 2.5-xylenol, 2.6-xylenol, 3.4-xylenol, and 3.5-xylenol. exists.

Because the boiling points of each of these isomers are close to each other, it is extremely difficult to efficiently separate a xylenol isomer mixture into each isomeric component by distillation, especially 2.4-xylenol and 2.5-xylenol. -Xylenol has almost the same boiling point and cannot be separated by simple rectification.

Various proposals have been made regarding methods for separating 2.4-xylenol and 2.5-xylenol. For example, a method of separating and purifying 2,4-xylenol using the property of forming molecular compounds with methylquinoline, aniline, toluidine, etc. (U.S. Pat. No. 2,526,807)
), a method of alkylating with isobutylene to obtain a tart,-butylated product, separating it by fractional distillation, and then separating and purifying it by dealkylating it in the presence of an acid (
British Patent No. 582.057, etc.), methods of separation by sulfonation and partial hydrolysis with superheated steam (US Pat. No. 2,327,312, etc.), and adsorbents such as molecular sieves, calcium oxide, and zeolites. A method using JP-A No. 56-68628, etc. has been proposed.

Furthermore, a method similar to the present invention, in which xylenol is reacted with formalin in the presence of a strong acid such as hydrochloric acid or a strong base such as caustic soda, and 2,5-xylenol is separated and removed as a xylenol-formalin resin has also been proposed. (U.S. Pat. No. 2,917,487).

(Problems 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 2,4-xylenol. First, in the method using expensive amines as in the conventional method described above, the loss of the amines 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.

Further, in the above-mentioned US Pat. No. 2,917,487, 2 to 8% by weight of hydrochloric acid is used as a catalyst based on xylenol,
- Maximum purity of xylenol 95.1%, purity conversion yield 6
Although there is a specific description that 7.3% was obtained, both purity and yield are not satisfactory.

Furthermore, in the method of removing 2.5-xylenol by selectively condensing only 2.5-xylenol with formalin in the presence of an acid catalyst, the reaction mass is Since it is heated and distilled, it is necessary to remove the acid used during the condensation reaction.

Specifically, in this method, hydrochloric acid is removed 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 obtain such highly purified 2,4-xylenol on an industrial scale, and this has been an unsolved problem.

(Means for Solving the Problem) The present inventors have developed highly pure 2.4-xylenol that can satisfy both purity and yield from a xylenol isomer mixture containing 2.4-xylenol and 2.5-xylenol. We conducted extensive research on the purification method for 2.5-xylenol and found that when it is reacted with aldehyde under certain conditions, 2.5-xylenol reacts preferentially, and purified 2.4-xylenol can be obtained with high purity and high yield. This discovery led to the present invention.

That is, in the present invention, a xylenol isomer mixture containing 2,4-xylenol and 2,5=xylenol is reacted with an aldehyde in the presence of an aromatic sulfonic acid, and 2,5-xylenol is converted into a xylenol-aldehyde condensate by reacting it with an aldehyde in the presence of an aromatic sulfonic acid.
．． This is a method for purifying 2,4-xylenol, which is characterized by separating and removing it from 4-xylenol.

Add 2.4-xylenol with a purity of 85 to 95% to
% or higher, and other xylenol isomers such as 2,3-xylenol can be separated by condensation reaction with aldehydes in the same way as 2,5-xylenol. Alkylphenols that are difficult to react with aldehydes, such as , 2,4°6-drimethylphenol, cannot be removed by the method of the present invention. Therefore, when a large amount of such alkylphenols is contained, other separation methods such as distillation or It is preferable to use the method of the present invention after removing it by recrystallization.

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 condensate, etc., formaldehyde and acetaldehyde are preferred. In this case, aldehyde can be used in aqueous solution, alcohol solution, dimer, polymer,
The amount of aldehyde used varies depending on the amount of 2.5-xylenol to be removed and the reaction conditions. The reaction conditions will be selected to obtain xylenol. At this time, it usually contains 2,
0.5 to 3 times the mole of 5-xylenol, preferably 0.
5 to 1.5 times the molar amount of aldehyde is used.

In the present invention, aromatic sulfonic acids are used as catalysts, such as benzenesulfonic acid, ortho-, meta-
and para-toluenesulfonic acid, benzenedisulfonic acid and the like. In particular, 'para-toluenesulfonic acid is the most preferred catalyst.

The amount used is usually 0.001 to 10 parts by weight, preferably 0.01 parts by weight, per 100 parts by weight of crude 2,4-xylenol.
~1 part by weight. 2.4 if the amount of catalyst used is large
-Unfavorable because the yield of xylenol decreases.

The reaction temperature in the present invention is usually in the range of -20 to 80°C, preferably 0 to 40°C. A high reaction temperature is not preferred because the yield of 2,4-xylenol will decrease.

Xylenol isomer mixtures have various freezing points depending on their composition, so if the raw material xylenol 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, benzene , aromatic hydrocarbons such as toluene, xylene, cumene, mesitylene, aliphatic hydrocarbons such as hexane, heptane, octane, halogenated hydrocarbons such as chlorobenzene, orthodichlorobenzene, chloroform, carbon tetrachloride, dichloroethane, methanol, Alcohols such as ethanol, isopropyl alcohol, and n-propyl alcohol, and nitriles such as acetonitrile and propionitrile can be used. Considering the purity, yield, solvent recovery rate, price, and operability of purified 2,4-xylenol, toluene is one of the most preferred solvents. Further, when the raw material xylenol 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.

When a solvent is used, the amount used is usually 500 parts by weight or less, preferably 200 parts by weight or less, per 100 parts by weight of crude 2,4-xylenol.

The dehydration condensation reaction between xylenol and aldehydes is an equilibrium reaction, so when the reaction mass is directly subjected to distillation, the 2,5-xylenol-aldehyde condensate produced in the reaction process undergoes hydrolysis during distillation, resulting in 2 Since it becomes .5-xylenol and is mixed into the distillate, the purity of 2.4-xylenol 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 recovering 2,4-xylenol in the present invention is to neutralize it with an excess amount of aqueous ammonia after the reaction, and then reduce the pressure. In the conventional purification method using hydrochloric acid as a catalyst, such as the one cited above, in which distillation is preferable, the ammonium chloride produced by neutralization with aqueous ammonia sublimes during distillation and mixes with 20.4-xylenol. Therefore, this method cannot be used, and the method of the present invention is therefore extremely advantageous.

In the present invention, purified 2°4-xylenol can be obtained as a distillate by neutralizing with aqueous ammonia and then distilling it. After neutralization distillation, xylenol-aldehyde condensate and ammonium p-)luenesulfonate remain in the pot, but be careful! Depending on the conditions, the condensate can be purified and recovered by conventional methods such as washing ammonium p-toluenesulfonate with water and recrystallizing it.

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

(Example-1) 244.4 g of crude 2.4-xylenol having the composition shown in Table 1, 6.6 g of 90% paraformaldehyde, and 0.2 g of p-toluenesulfonic acid were placed in a 500 m glass 4-tube flask. The reaction mixture was stirred for 4 hours at a reaction temperature of 20°C, neutralized by adding 0.1 t of 25% ammonia water, and then distilled under reduced pressure to a boiling point of 104°C/21 w.
Hg fraction (purified 2,4-xylenol) 196.1
I got g. Its composition is shown in Table 1. The extraction yield of 2.4-xylenol in terms of purity was 86.3%.

(Example-2) The same procedure as in Example-1 was carried out except that the reaction temperature was changed to 80°C and the reaction time was changed to 1 hour.
-195.0 g of xylenol was obtained.

(Example-3) The same process as in Example-1 was carried out except that the reaction temperature was changed to 0°C and the reaction time was changed to 20 hours, and then the preparations 2 and 4 having the compositions shown in Table 1 were prepared.
-195.3 g of xylenol was obtained.

(Example-4) The same procedure as in Example-1 was carried out except that 6.6 g of 90% paraformaldehyde was replaced with 17.2 g of 35% formalin aqueous solution to obtain purified 2,4-xylenol 1 having the composition shown in Table 1.
93.6g was obtained.

(Example-5) The same procedure as in Example-1 was carried out except that 6.6 g of 90% paraformaldehyde was replaced with 9.7 g of 90% acetaldehyde aqueous solution to obtain purified 2,4-xylenol 194 having the composition shown in Table 1. .9g was obtained.

(Example-6) P-) Precipitated 2,4-xylenol 195 having the composition shown in Table 1 was prepared in the same manner as in Example-1 except that 2 g of luenesulfone MO was replaced with 0.2 g of benzenesulfonic acid. .7g
I got it.

(Example-7) Crude 2.4-xylenol 244.4JI having the composition shown in Table 1, 6.6 g of 90% paraformaldehyde, 0.2 g of P-)luenesulfonic acid, and ) toluene were placed in a 500 m glass 4-tube flask. Prepare 200 d, 1 at 0℃
After the reaction was completed for 0 hours, 0.2 g of 25% ammonia water and 50 d of water were added while cooling, and after stirring for 1 hour, the liquid was separated. This was distilled under reduced pressure to obtain a boiling point of 104
"C/21ml 11g fraction (purified 2,4-xylenol)
1 g of 190° was obtained. The composition of purified 2,4-xylenol is shown in Table 1.

(Example-8) Crude 2.4-xylenol 244.4. of the composition shown in Table 1 was placed in a 500 m glass four-tube flask. , 17.2 g of 35% formalin aqueous solution, 0.1 g of p-)luenesulfonic acid were charged and reacted by stirring at 20°C for 4 hours.After the reaction was completed, 200 m of water was added, thoroughly stirred, and the liquid was separated. . Distill the oil layer under reduced pressure to a boiling point of 104℃/21wa
188.3 g of Hg fraction (purified 2,4-xylenol) was obtained. The composition of purified 2,4-xylenol is shown in Table 1.

(Hereinafter in the margin) (Comparative Example) A reaction was carried out according to US Pat. No. 2,917.487. That is, 244.4 g of crude 2,4-xylenol having the composition shown in Table 1 and 6.6 g of 90% bulk formaldehyde were placed in a 500 d glass four-tube flask and maintained at 100°C. Next, 1 d of 36% hydrochloric acid was charged and reacted at 100°C for 1 hour. Next, 1 m of 25% ammonia water was added to neutralize the mixture, and then distilled to obtain a fraction 194 with a boiling point of 104°C/21 sang.
．． 8. I got it. The fraction is cloudy and contains 40 Opp of ammonium chloride, and the purity of 2.4-xylenol is 94.
It was 9%. The main impurity was 2,5-xylenol.

(Effects of the Invention) The present invention is an industrial purification method that is capable of separating 2.4-xylenol from 2.5-xylenol in high yield and that also provides highly pure 2.4-xylenol. It is.

Patent applicant Mitsui Toatsu Kagaku Co., Ltd. Procedural amendment issued on September 9, 1948 Kunio Ogawa, Commissioner of the Patent Office 1. Indication of the case Patent application No. 131694 of 1988 2. Name of the invention 2. 4-Xylenol purification method 3, relationship with the case of the person making the amendment Patent applicant address 3-2-5 Kasumigaseki, Chiyoda-ku, Tokyo Name (31
2) Mitsui Toatsu Chemical Co., Ltd. 4. Number of inventions increased by amendment Zero (1) "Ammonium p-toluenesulfonate" on page 10 of the specification, line 5 from the bottom and lines 4 to 3 from the bottom. , r ammonium salt of aromatic sulfonic acid J.

(2) On page 11 of the specification, in lines 7 and 8, "after neutralization" is corrected to "after neutralization".

(3) Page 15 of the specification, line 6 “36% hydrochloric acid 1-”
Correct it to "36% hydrochloric acid 40-".

(4) Page 15 of the specification, line 7 “25% ammonia water l
111" is corrected to "25% ammonia water 30 dJ.

Claims (1)

[Claims] A xylenol isomer mixture containing 2,4-xylenol and 2,5-xylenol is reacted with an aldehyde in the presence of an aromatic sulfonic acid, and 2,5-xylenol is converted into a xylenol-aldehyde condensate to form 2,4-xylenol. 1. A method for purifying 2,4-xylenol, which comprises separating and removing 2,4-xylenol.