JPH06116179A - Separation and concentration of 2,6-dimethylnaphthalene and reagent for separation and concentration - Google Patents

Abstract

PURPOSE:To provide a new method for separating the subject compound at low cost by bringing a specified mixture into contact with alpha-cyclodextrin and forming an alpha-cyclodextrin clathrate of 2,6-dimethylnaphthalene. CONSTITUTION:A mixture containing 2,6-dimethylnaphthalene is brought into contact with a substituted alpha-cyclodextrin synthesized by substituting H of OH in alpha-cyclodextrin with glucosyl, maltosyl, methyl, sulfonic acid, a carboxylalkyl, etc., preferably at 20 to 30 deg.C for several to several ten minutes so as to form an alpha-cyclodextrin clathrate of 2,6-dimethylnaphthalene. The resultant complex is heated at 60 to 70 deg.C so as to liberate 2,6-dimethylnaphthalene and these processes are repeated, thus producing the objective compound of high purity.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention separates and concentrates 2,6-dimethylnaphthalene which is a raw material of 2,6-naphthalenedicarboxylic acid useful as a monomer for high-functionality polyesters. Concerning the law. Specifically, α-cyclodextrin or substituted α-cyclodextrin is utilized by utilizing the function of forming an inclusion complex with high affinity to 2,6-dimethylnaphthalene, and α-cyclodextrin or substituted α-cyclodextrin. Was used as a drug for separation and concentration, and
Contacting a mixture containing 6-dimethylnaphthalene,
The present invention relates to a method of forming an inclusion complex and separating and concentrating it, a method of dissociating and collecting 2,6-dimethylnaphthalene from the formed inclusion complex, and a drug for separating and concentrating 2,6-dimethylnaphthalene. 2,6-Dimethylnaphthalene is present in gas light oils from coal tar and asphalt base crudes. Alternatively, it is synthesized by selective methylation of methylnaphthalene, dehydrogenation of dimethyltetralin, thermal polymerization of xylene, and the like. Dimethylnaphthalene has 1,3-, 1,4
-, 1,5-, 1,6-, 1,7-, 1,8-, 2,3
There are 10 types of isomers, i.e., 2,6- and 2,7-forms. These are used as a surfactant, a solvent, a heating medium and the like. Of these, the 2,6-body is particularly important as a raw material for chemical synthesis as described above. A purity of 99% or higher is required for use in the synthesis reaction. But,
The boiling point of the 2,6-body (262.0 ° C) is that of the 2,7-body (26
Since it is very close to 2.3 ℃), it cannot be separated by ordinary distillation method. Further, since both form a eutectic mixture, they cannot be separated by a usual crystallization method. Therefore, it has been strongly desired by the industry to develop an effective separation and purification method for obtaining highly pure 2,6-isomer. At present, many methods such as reaction crystallization (using complex formation), continuous crystallization, pressure crystallization, supercritical extraction, and adsorption have been submitted and are under study. SUMMARY OF THE INVENTION The present invention utilizes α-CD or substituted α-cyclodextrin to obtain 2,6-
It is an object of the present invention to provide a novel and economical method for effectively separating and concentrating dimethylnaphthalene and a separating and concentrating agent used therefor. According to the present invention, 2,6
-A mixture containing dimethylnaphthalene and hydrogen of at least one hydroxyl group of α-cyclodextrin or α-cyclodextrin, glucosyl group, maltosyl group, maltooligosaccharide residue, methyl group, hydroxyethyl group, hydroxypropyl group, sulfone A 2,6-dimethylnaphthalene inclusion complex of substituted α-cyclodextrin by contacting with the substituted α-cyclodextrin substituted with at least one of an acid group, an alkylene sulfonic acid group and a carboxyalkyl group. Method for separating and concentrating 2,6-dimethylnaphthalene, characterized in that 2,6-dimethylnaphthalene is dissociated and recovered from the formed inclusion complex. Method and α-cyclodextrin or α-cyclo The hydrogen of at least one hydroxyl group of kistrin is at least one of glucosyl group, maltosyl group, maltooligosaccharide residue, methyl group, hydroxyethyl group, hydroxypropyl group, sulfonic acid group, alkylenesulfonic acid group and carboxyalkyl group. There is provided a drug for separating and concentrating 2,6-dimethylnaphthalene, which comprises a substituted α-cyclodextrin substituted with. The present invention will be described in detail below. In the present invention, hydrogen of at least one hydroxyl group of α-cyclodextrin or α-cyclodextrin is used as an agent for separating and concentrating 2,6-dimethylnaphthalene, a glucosyl group, a maltosyl group, a maltooligosaccharide residue, a methyl group, a hydroxyethyl group. A substituted α-cyclodextrin substituted with at least one of a hydroxypropyl group, a sulfonic acid group, an alkylenesulfonic acid group and a carboxyalkyl group is used. In particular, these substituted α-cyclodextrins have various advantages because they and the dimethylnaphthalene inclusion complex have a large solubility in a solvent such as water as compared with the case of using other substituted compounds. is there. For example, it can be handled as a high-concentration solution without forming a slurry state. In addition, since the complex does not precipitate during the formation of the inclusion complex, the handling is convenient. The mixture containing 2,6-dimethylnaphthalene used in the present invention is a mixed oil comprising 2,6-dimethylnaphthalene and all or some components of 9 other dimethylnaphthalene isomers, or Examples of the mixed oil include 2,6-dimethylnaphthalene, 2,7-dimethylnaphthalene, and other organic solvents. In the present invention, α-cyclodextrin or the above-mentioned substituted α-cyclodextrin is dissolved in water, and a mixture containing 2,6-dimethylnaphthalene is brought into contact with this liquid for several seconds to several tens of minutes. Increasing the contact effect between the mixture containing 2,6-dimethylnaphthalene and α-cyclodextrin or substituted α-cyclodextrin by vigorous stirring or the like can promote the formation of inclusion complex. The temperature for forming the inclusion complex is 0 to 40 ° C, preferably 20 to 30 ° C. In order to dissociate and recover 2,6-dimethylnaphthalene from the formed inclusion complex, the inclusion complex is based on the known fact that the cyclodextrin inclusion complex is dissociated by heating at 60 to 70 ° C. or higher. By heating the complex, the clathrated 2,6-dimethylnaphthalene is dissociated. Alternatively, using a suitable solvent such as diethyl ether or n-hexane at room temperature or under heating,
-Dimethylnaphthalene can be extracted into the organic layer. If the purity of 2,6-dimethylnaphthalene is insufficient in one inclusion, the inclusion can be repeated to increase the purity of 2,6-dimethylnaphthalene. In all the above steps, α used in the present invention
-Cyclodextrin or substituted α-cyclodextrin does not decompose by itself, and can be repeatedly used for separation and concentration of 2,6-dimethylnaphthalene if 2,6-dimethylnaphthalene is eliminated. it can. The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Example 1 0.50 g of a commercially available dimethylnaphthalene mixture (composition as shown in Table 1) was added to 5 ml of an aqueous solution of α-cyclodextrin at a concentration of 0.10 mol / l, and the mixture was mixed at 25 ° C. for 3 hours.
Stir for 0 minutes. During this process, a white precipitate of cyclodextrin inclusion complex was formed. After the stirring was completed, the precipitate was filtered to a pore size of 0.
It was filtered with a 4 μm membrane filter, washed with water, washed with acetone, and dried. Suspend this inclusion complex in water,
The mixture was shaken with diethyl ether to extract the clathrate oil. The composition of this oil component is shown in Table 1. The analysis was performed with a gas chromatograph equipped with a capillary column having a liquid phase of 267DMN for analysis of 2,6-dimethylnaphthalene and 2,7-dimethylnaphthalene. Example 2 Concentration of monoglucosyl-α-cyclodextrin of 0.1
0.5 g of the same dimethylnaphthalene mixture used in Example 1 was added to 5 ml of a 0 mol / l aqueous solution, and the mixture was stirred at 25 ° C. for 30 minutes. In this case, no precipitation of the inclusion complex was generated, and 2,6-dimethylnaphthalene was converted into monoglucosyl-
It is concentrated in an α-cyclodextrin aqueous solution. The reaction product was centrifuged at 2,500 rpm for 5 minutes, the aqueous layer was taken out, and the mixture was shaken with diethyl ether to extract the encapsulated oil. The composition of this oil component is shown in Table 1. Example 3 Concentration of monomaltosyl-α-cyclodextrin 0.1
0.5 g of the same dimethylnaphthalene mixture used in Example 1 was added to 5 ml of a 0 mol / l aqueous solution, and the mixture was stirred at 25 ° C. for 30 minutes. Hereinafter, the same as the second embodiment. Example 4 0.5 g of the same dimethylnaphthalene mixture as used in Example 1 was added to 5 ml of an aqueous solution of 2,6-di-O-methyl-α-cyclodextrin having a concentration of 0.10 mol / l.
The mixture was stirred at 25 ° C for 30 minutes. Hereinafter, the same as the second embodiment. [Table 1] Example 5 Concentration of monoglucosyl-α-cyclodextrin of 0.1
To 5 ml of 0 mol / l aqueous solution, 0.3 g of a mixed oil in which 2,6-dimethylnaphthalene and 2,7-dimethylnaphthalene were dissolved in 1-methylnaphthalene (mass ratio is about 1: 1: 10) was added, and at 25 ° C. Stir for 30 minutes. Hereinafter, the same as the second embodiment. However, the composition of Table 2 is shown as a value excluding 1-methylnaphthalene. Example 6 0.3 g of the same mixed oil as used in Example 5 was added to 5 ml of an aqueous solution of 2,6-di-O-methyl-α-cyclodextrin having a concentration of 0.10 mol / l, and the mixture was added at 25 ° C. And stirred for 30 minutes. Hereinafter, the same as the second embodiment. However, the composition of Table 2 is shown as a value excluding 1-methylnaphthalene. [Table 2] According to the present invention, by bringing a mixture containing 2,6-dimethylnaphthalene into contact with α-cyclodextrin or substituted α-cyclodextrin, 2,6-dimethyl is effectively added. Naphthalene can be separated and concentrated. Further, the energy required to dissociate and recover the clathrated 2,6-dimethylnaphthalene can be small. Furthermore, since α-cyclodextrin or substituted α-cyclodextrin used as a drug for separation and concentration can be repeatedly used, it is possible to reduce the cost at a low cost.
6-Dimethylnaphthalene can be separated and concentrated.

Claims (1)

Claim: What is claimed is: 1. A mixture containing 2,6-dimethylnaphthalene and α-cyclodextrin are contacted with each other to form a 2,6-dimethylnaphthalene inclusion complex of α-cyclodextrin. 2, 6 characterized by
-A method for separating and concentrating dimethylnaphthalene. 2. A mixture containing 2,6-dimethylnaphthalene and hydrogen of at least one hydroxyl group of α-cyclodextrin are converted into glucosyl group, maltosyl group, maltooligosaccharide residue, methyl group, hydroxyethyl group, hydroxypropyl group. A group, a sulfonic acid group, an alkylene sulfonic acid group and a carboxyalkyl group, and a substituted α-cyclodextrin substituted with at least one of the substituted α-cyclodextrin
A method for separating and concentrating 2,6-dimethylnaphthalene, which comprises forming a 6-dimethylnaphthalene inclusion complex. 3. The dissociation of 2,6-dimethylnaphthalene from the inclusion complex formed in the above [1] to recover it.
A method for separating and concentrating 6-dimethylnaphthalene. 4. A method of dissociating and recovering 2,6-dimethylnaphthalene from the inclusion complex formed according to claim 2.
A method for separating and concentrating 6-dimethylnaphthalene. 5. The hydrogen atom of at least one hydroxyl group of α-cyclodextrin or α-cyclodextrin is glucosyl group, maltosyl group, maltooligosaccharide residue, methyl group, hydroxyethyl group, hydroxypropyl group, sulfonic acid group, alkylene. An agent for separating and concentrating 2,6-dimethylnaphthalene, which comprises a substituted α-cyclodextrin substituted with at least one of a sulfonic acid group and a carboxyalkyl group.