JPS6165837A - Method for separating 2-methyl-6-acetylnaphthalene - Google Patents

Abstract

PURPOSE:To separate advantageously the titled compd. useful for preparing 2,6-naphthalene dicarboxylic acid from isomers thereof, by separating the titled compd. as a complex compd. with-nitrobenzoic acid selectively from the isomers, followed by decomposing the complex. CONSTITUTION:After acetylating 2-methylnaphthalene, low-boiling materials such as unreacted raw materials and high-boiling material such as diacetyl compounds are preferably eliminated from the resulting reaction mixture to give a mixture containing the titled compound and isomers thereof. The mixture is preferably dissolved in a suitable solvent such as toluene, and reacted with m-nitrobenzoic acid to form a complex compd. comprising mainly the titled compd. and the acid. The complex compd. is then separated from the reaction mixture, and is decomposed to obtain selectively the titled compd. Acetylation product isomers other than the titled compd. also form the same complex compd. with the m-nitrobenzoic acid, but these are relatively unstable and can be eliminated easily by washing with a proper solvent or recrystallization, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for separating 2-methyl-6-acetylnaphthalene from a mixture containing 2-methyl-6-acetylnaphthalene.

2-Methyl-6-acetylnaphthalene can be converted into 2 by oxidation.
- Gives 6-naphthalene dicarboxylic acid.

2,6-Naphthalene dicarboxylic acid is a useful raw material for polymer synthesis. For example, polyesters derived from it are superior in various respects, such as mechanical strength, heat resistance, and dimensional stability, compared to polyesters made from terephthalic acid. It is known that it can give films and various molded products, and 2.6-
An inexpensive industrial method for producing naphthalene dicarboxylic acid has been strongly desired.

(Prior Art) Conventionally, 2,6-naphthalene dicarboxylic acid has been obtained by oxidizing 2,6-dialkylnaphthalene such as 2,6-dimethylnaphthalene. 2,6-dialkylnaphthalene can be obtained by alkylating naphthalene or 2-alkylnaphthalene, but it is difficult to obtain only 2,6 monomer, and it has the disadvantage that 2,7 monomer is produced in almost equal amounts as 2.6 monomer. have And since 2.6 and 2.7 are similar in physical and chemical properties such as boiling point and melting point,
It is difficult to selectively separate only the 2.6 unit.

On the other hand, apart from the above, 2-alkyl-6
- It is known that acylnaphthalenes are obtained.

According to U.S. Pat. No. 3,234,286, acylation of 2-methylnaphthalene was achieved with a selectivity of up to 89% using a metal halide such as aluminum chloride or ferric chloride as a catalyst and nitropropane as a solvent. It has been reported.

(Problems to be Solved by the Invention) According to the findings of the present inventors, in this reaction, 2-methyl-
In addition to 6-acetylnaphthalene, isomers such as 2-methyl-8-acetylnaphthalene and 2-methyl-1-acetylnaphthalene are produced. These isomers and 2-methyl-
Selective separation from 6-acetylnaphthalene is not easy using conventional methods such as distillation.

The present inventors have surprisingly discovered that m-nitrobenzoic acid selectively forms a stable complex with 2-6 monomers among the acetylated isomers of 2-methylnaphthalene. Furthermore, isomers other than 2.6 monomers also form complex compounds with m-nitrobenzoic acid, but these complex compounds are spectrally unstable and the resulting complex compounds can be washed with an appropriate solvent or recrystallized. It was discovered that the 2.6-unit complex compound can be easily purified and the present invention was achieved.

(Means for Solving the Problems) The present invention provides m-nitrobenzoic acid and 2-methyl- This is a method in which a complex compound mainly composed of 6-acetylnaphthalene is formed, and then the complex compound is separated and decomposed to recover 2-methyl-6-acetylnaphthalene.

Examples of mixtures containing 2-methyl-6-acetylnaphthalene and its isomers include reaction mixtures obtained by acetylating 2-methylnaphthalene, and preferably low-boiling substances such as 2-methylnaphthalene are extracted from this reaction mixture. It is a mixture after removing high-boiling substances such as and diacetylated substances.

Preferably, it is dissolved in a mixture containing 2-methyl-6-acetylnaphthalene using a suitable solvent such as benzene, toluene, alcohol, ether, ketone, or ester.

The amount of m-nitrobenzoic acid used relative to 2-methyl-6-acetylnaphthalene is at least equimolar, preferably 2 to 5 times the molar amount. A reaction is carried out by adding m-nitrobenzoic acid to a mixture containing 2-methyl-6-acetylnaphthalene, and the reaction is carried out with stirring at room temperature or higher, preferably from 60 to 150°C. The reaction time is usually 10 minutes to 3 hours. After the reaction is completed, the produced solid is separated by filtration or the like. In this case, isomers other than the 2.6 monomer may also form a complex and be accompanied, but in this case, they are washed or recrystallized using a solvent. Examples of this solvent include benzene, toluene,
Alcohols, ethers, ketones, esters, etc. are suitable. The separated solid, i.e., the complex, easily decomposes into 2-methyl-6-acetylnaphthalene when brought into contact with water and a solvent that decomposes 2-methyl-6-acetylnaphthalene, such as n-hebutane.
It is separated into a layer containing acetylnaphthalene and an aqueous layer containing m-nitrobenzoic acid. The temperature at this time is 50 to 100
It is preferable to set it as ℃.

2-Methyl-6-acetylnaphthalene is 2-methyl-6-acetylnaphthalene.
It can be easily recovered by cooling the layer containing 6-acetylnaphthalene or by distilling off the solvent.

(Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 42.6 g of 2-methylnaphthalene and 40.5 g of ferric chloride
Dissolve g in 200 g of 2-nitropropane, -2 to 0°
After cooling to C. acetyl chloride 27 with stirring.

6 g was added dropwise and reacted for 2 hours. After the reaction, ferric chloride was removed from the reaction mixture and distilled under reduced pressure to remove 2-nitroprobane, acetic acid, and 2-methylnaphthalene to obtain a residue. The bottom of the pot contains 91.5 wt% of monoacetylated 2-methylnaphthalene, and its composition is 2-methyl-6.
- Acetylnaphthalene 80.

6%, 2-methyl-8-acetylnaphthalene 8.1%,
The content was 3.6% for 2-methyl-1-acetylnaphthalene and 7.7% for others.

Remaining pot 20. 21.7 g of m-nitrobenzoic acid and 40 g of toluene were added to Og, and the mixture was heated and stirred at 110°C for 1 hour.

The solution was cooled to 15°C and the precipitated solid was centrifugally filtered.
To obtain 3.1 g of the complex, the filtrate at this time was referred to as filtrate-1). 130 Qml of water and 60 g of H-heptane were added to 23.1 g of this complex, and the mixture was heated and stirred at 98°C to decompose the complex. The n-hebutane layer was cooled to 15°C and 2-methyl-6
- 7.5 g of acetylnaphthalene was obtained. Purity is 98.
It was 0.3%.

Add 21.7 g of m-nitrobenzoic acid to filtrate-1, form a complex in the same manner as above, collect the complex by filtration (the filtrate at this time is referred to as filtrate-2), and decompose the complex to form 2-methyl-6-acetylnaphthalene3. 2g was obtained. Furthermore, the same operation was repeated for filtrate-2 to obtain 1.6% of 2-methyl-6-acetylnaphthalene.
I got g.

The combined recovery from these filtrates yields 2-methyl-6-
The recovery rate of acetylnaphthalene reaches more than 80%.
The purity of 2-methyl-6-acetylnaphthalene is 97%.
That was it.

Example 2 After washing the complex 23, Og obtained by the same reaction as in Example 1 with 20 ml of toluene, 6.1 g of 2-methyl-6-acetylnaphthalene was obtained using complex bone IW. The purity was 99.74%.

Claims (1)

[Claims] By reacting a mixture containing 2-methyl-6-acetylnaphthalene and its isomers with m-nitrobenzoic acid,
2-, which is characterized by forming a complex compound mainly consisting of nitrobenzoic acid and 2-methyl-6-acetylnaphthalene, and then separating and decomposing the complex compound to obtain 2-methyl-6-acetylnaphthalene. Method for separating methyl-6-acetylnaphthalene.