JPH0443893B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention provides m
- Concerning a new method for separating cresols.

Cresol has 3 o-, m-, and p-forms.
Although there are isomers of species, these isomers are commonly used, and there are applications where two or more isomers are used as a mixture, only one isomer is suitable for a specific application. In some cases it may be suitable. Common uses include disinfectants, preservatives, or raw materials for surfactants. In addition, suitable applications for o-cresol include analytical reagents and herbicides such as MCP agents (2-methyl-4-
chlorophenoxyacetic acid), etc., and a suitable use only for m-cresol is the insecticide sumithion [O,O-dimethyl-O-
(3-methyl-4-nitrophenyl) thiophosphate], and further, suitable uses for p-cresol only include raw materials for dyes and antioxidants.

[Description of prior art]

Industrial methods for producing cresol include alkali extraction of tar fraction, toluene chlorination hydrolysis, and toluene sulfonation alkali melting. In both of these methods, the cresol is o-, m-, and p-
It is obtained as a mixture of three isomers. Therefore, when applied to the above-mentioned common uses, it is not necessary to separate each isomer, but when each isomer is applied to a single use, each isomer must be separated.

By the way, the boiling point of o-cresol is 191.0℃,
The boiling point of m-cresol is 202.2°C, and the boiling point of p-cresol is 201.9°C. Therefore, o-
Cresol can be easily separated by distillation, but it is impossible to separate a mixture of m-cresol and p-cresol into each isomer component by a simple distillation operation.

Conventionally, a mixture containing three isomers of cresol is first separated by fractional distillation to separate o-cresol, which has a low boiling point, as the first distillate, and then sulfonates the remaining m- and p-cresol, followed by steam decomposition. It is separated into each isomer component by a complicated operation in which m-cresol is separated and obtained by decomposing the sulfonated product of m-cresol, which is easily decomposed, and finally p-cresol is obtained. Furthermore, in order to obtain each isomer with high purity, it is necessary to rectify the obtained m-cresol and recrystallize the o- and p-cresol.

[Requirements of the present invention]

In view of these circumstances, the inventors conducted extensive research with the aim of establishing a method that would allow a mixture of cresol isomers to be separated with simple operations. As a result, among the three isomers of cresol, only m-cresol is N, N, N', N'-
It was discovered that since it forms a complex with tetraisopropyl fumaric acid amide and precipitates, it can be separated from other isomers very easily, and this invention has been achieved.

That is, the present invention involves contacting a cresol isomer mixture with N,N,N',N'-tetraisopropyl fumaric acid amide in an organic solvent to produce a complex of m-cresol and the fumaric acid amide. The present invention provides an industrially advantageous method for separating m-cresol from a mixture of isomers of cresol by precipitating the compound, separating the complex, and then separating the complex.

[Detailed explanation of each requirement]

In this invention, the cresol isomer mixture can be a mixture of three isomers, o-, m-, and p-isomers, or a mixture of two isomers, m- and p-isomers. can also be targeted. That is, according to the present invention, m-cresol is first separated from a mixture of three isomers, and then o-cresol and p-cresol can be separated by distillation if necessary. Furthermore, by first separating o-cresol from a mixture of three isomers by distillation, and then applying the present invention to a mixture of m- and p-cresol, they can be easily separated. I can do it.

As mentioned above, according to the separation method of the present invention, m-cresol can be easily separated and recovered from "an isomer mixture containing at least m-cresol and p-cresol" which cannot be separated by a simple distillation operation. In addition, since a mixture containing p-cresol and o-cresol can be easily separated by a conventional method (distillation operation, etc.),
Ultimately, each isomer of cresol can be easily isolated and recovered.

N,N,N',N'-tetraisopropyl fumaric acid amide in this invention can be easily synthesized, for example, by reacting fumaric acid chloride and diisopropylamine, and is represented by the following structural formula.

In this invention, the amount of N,N,N',N'-tetraisopropyl fumaric acid amide used is determined by the amount of m-cresol contained in the isomer mixture of cresol.
The amount is 1 mol or more, preferably 2 to 10 mol.

The organic solvent used in this invention is such that it can sufficiently uniformly dissolve each isomer of cresol and N,N,N',N'-tetraisopropyl fumaric acid amide, and also dissolve the m-cresol produced in this invention and the A solvent in which the complex has a low solubility is desired so that the complex with fumaric acid amide precipitates.
Specifically, such organic solvents include petroleum ether, ethyl ether, chloroform, glycol, benzene, hexane, acetonitrile,
Ethyl acetate, mixtures thereof, and the like can be mentioned. These organic solvents include N, N,
N′,N′-tetraisopropyl fumaric acid amide 1
It is sufficient to use about 2 to 20 ml per g.

The contact (reaction) between the cresol isomer mixture and the fumaric acid amide is usually carried out at a temperature of 10 to 50° C. for about 1 to 20 hours. Through the contact operation, among the cresol isomers, in particular, only m-cresol forms a complex with the fumaric acid amide, and is precipitated from the solution in which each raw material component was initially dissolved. The complex precipitated in this way can be easily separated by operations such as filtration and decantation.
m-cresol can be separated and obtained by heating the complex to a temperature of about 50 to 300°C.

After the complex of m-cresol and the fumaric acid amide is precipitated, the remaining liquid from which the precipitate is separated can be subjected to a distillation operation to separate and obtain other isomers of cresol.

In the present invention, the N,N,N',N'-tetraisopropyl fumaric acid amide recovered during the separation and acquisition of m-cresol can be repeatedly used in the above-mentioned separation operation.

〔Example〕

Next, examples of this invention will be described.

Example 1 Cresol isomer mixture (composition: m-cresol; 54.11 mol%; p-cresol; 27.27 mol%; and 2,4 and 2,5-xylenol;
14.41 mol%) and 6.0 g of N,N,N',N'-tetraisopropyl fumaric acid amide were dissolved in 30 ml of petroleum ether and left at room temperature for 12 hours to form N,N,N', 3.0 g of crystals of a complex consisting of one molecule of N'-tetraisopropyl fumaric acid amide and one molecule of m-cresol were precipitated. N, N, N', N'-
Add 1.0g of tetraisopropyl fumaric acid amide,
After standing for an additional 12 hours, an additional 1.0 g of crystals of the same complex as above were obtained. The obtained crystals were combined and recrystallized once in 20 ml of petroleum ether.
When the crystals obtained by filtration were dried, 3.3 g of colorless needle crystals (melting point: 78-80°C) were obtained. When 3.3 g of crystals of this complex was heated to about 200° C. at about 30 mmHg, 0.91 g of m-cresol was distilled out.

Claims (1)

[Claims] 1. Contacting the isomer mixture of cresol with N,N,N',N'-tetraisopropyl fumaric acid amide in an organic solvent to generate and precipitate a complex of m-cresol and the fumaric acid amide, A method for separating m-cresol, which comprises separating the complex and then decomposing the complex.