JPH0434979B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention relates to 1-methylnaphthalene and 2-methylnaphthalene containing impurities such as organic sulfur compounds and organic nitrogen compounds.
- A method for obtaining 2-methylnaphthalene with high purity and high yield from a mixture with methylnaphthalene. [Prior art] 2-Methylnaphthalene is a pharmaceutical vitamin K
It is also an important compound as a raw material for 2,6-naphthalene dicarboxylic acid, which is an intermediate raw material for polyester-based synthetic resins that have heat resistance and high tensile strength.
However, in order to be used for these purposes, it is important to have a high level of purity, and in particular, the presence of isomers of 1-methylnaphthalene, and organic sulfur and organic nitrogen compounds that act as catalyst poisons and reaction inhibitors must be avoided as much as possible. Must. Originally, 2-methylnaphthalene had a boiling point of 241.1
It is a white crystal with a melting point of 34.4°C and is contained in relatively large amounts in coal tar, petroleum cracked oil, etc.
For example, naphthalene oil obtained by distilling coal tar contains about 6 to 10%, and cleaning oil contains about 3 to 6%, so 2-methylnaphthalene is
Normally, these oils are used as raw materials and separated by distillation or other means.
or more distillate can be obtained. However, in addition to 1-methylnaphthalene, which has a boiling point close to that of 1-methylnaphthalene, it is inevitable that many other components are mixed in, and it cannot be used as a raw material for producing vitamin K and the like. When distillation separation is not applicable, it is a common method to adopt crystallization separation, but 1-
What are methylnaphthalene and 2-methylnaphthalene?
Since the latter produces a eutectic mixture at 17.5% composition,
Crystallization separation means cannot be applied. As a countermeasure against this, the 2-methylnaphthalene-containing oil is distilled so that the 2-methylnaphthalene content is 60% by weight or more and the naphthalene/2-methylnaphthalene weight ratio is 0.1 or less.
Continuously crystallize the methylnaphthalene fraction to obtain 2-
Method for separating and recovering methylnaphthalene (Unexamined Japanese Patent Publication No. 1983
-95923), a method in which a mixture of 1-methylnaphthalene and 2-methylnaphthalene is brought into contact with zeolite having an aperture diameter of 6 Å or more, and then chromatographically developed and separated using tetralin or anisole as a developing agent (Japanese Patent Laid-Open Publication No. 59/1989). -88432) etc. have been proposed. However, the method disclosed in JP-A-57-95923 prevents impurities such as methylbenzothiophenes, which have a melting point of 36 to 52°C, from contaminating 2-methylnaphthalene, which has a melting point of 34.4°C. Product purity 97
%, and the product yield is only about 50%. Furthermore, the method disclosed in JP-A-59-88432 not only cannot process a large amount at once due to its equipment, but also does not contain any information about the behavior of impurities other than methylnaphthalene, such as organic sulfur compounds and organic nitrogen compounds. This is questionable as an advanced purification separation method. In any case, there is a strong demand for the development of a method for separating and recovering highly pure 2-methylnaphthalene containing no organic sulfur compounds or organic nitrogen compounds from a 2-methylnaphthalene-containing fraction. [Problems to be Solved] Unlike the above-mentioned conventional techniques, the present invention can easily remove 1-methylnaphthalene and impurities such as organic sulfur compounds and organic nitrogen compounds that inhibit synthesis reactions and product quality. The present invention provides a method for purifying 2-methylnaphthalene with a high product yield. [Details of the invention] As a result of extensive testing and research on a method for purifying crude 2-methylnaphthalene, the present inventors added monoethanolamine, a polar solvent, to the crude 2-methylnaphthalene to dissolve the crude 2-methylnaphthalene. The inventors discovered that by cooling and separating the precipitated crystals, high-purity 2-methylnaphthalene containing almost no impurities such as organic sulfur compounds and organic nitrogen compounds could be recovered in high yield, leading to the present invention. did. That is, this invention adds a hydroxyalkylamine derivative to crude 2-methylnaphthalene,
2- characterized in that after dissolving 2-methylnaphthalene, it is cooled and the precipitated crystals are separated.
This is a method for purifying methylnaphthalene. Crude 2-methylnaphthalene in the present invention is
Refers to a mixture of 2-methylnaphthalene and 1-methylnaphthalene, or a mixture of an organic sulfur compound such as methylbenzothiophene or an organic nitrogen compound such as quinoline or indole, with 90% by weight or more of 2-methylnaphthalene, Preferably 95~
It contains 97% by weight. If the 2-methylnaphthalene content in the crude 2-methylnaphthalene is less than 90% by weight, the operability during recrystallization will be poor, the yield of purified 2-methylnaphthalene will be reduced,
It is also difficult to ensure purity of 99%. Hydroxyalkylamine derivatives such as monoethanolamine added to crude 2-methylnaphthalene have the property of extracting organic sulfur compounds and organic nitrogen compounds, which are contaminants other than 2-methylnaphthalene, more selectively than 2-methylnaphthalene. By cooling and crystallizing in this solution, 2-
Methylnaphthalene precipitates preferentially, and organic sulfur compounds and organic nitrogen compounds remain in the solution and are removed. If the precipitated crystals are separated by filtration, highly pure 2-methylnaphthalene containing almost no impurities such as organic sulfur compounds and organic nitrogen compounds can be obtained, but since hydroxyalkylamine derivatives are attached, it is difficult to remove them. It's a good idea. Various methods can be considered to remove it, but 2-methylnaphthalene is extracted using a solvent that does not dissolve the hydroxyalkylamine derivative, and then recrystallized in the solvent to separate and recover 2-methylnaphthalene. It is advantageous to do so. In particular, if a solvent with a boiling point of 100° C. or lower is used, highly pure 2-methylnaphthalene can be efficiently recovered by vacuum drying the recrystallized product after 2-methylnaphthalene extraction. As the hydroxyalkylamine derivative to be used, monoethanolamine, diethanolamine, triethanolamine, propanolamine, butanolamine, etc. can be used, but monoethanolamine is most suitable. The larger the amount of monoethanolamine added to the crude 2-methylnaphthalene, the better the result, but since the recovery rate of 2-methylnaphthalene will decrease, it should be added based on the amount of 2-methylnaphthalene in the crude 2-methylnaphthalene. The amount may be 2 to 6 times by weight, preferably 2 to 4 times by weight. If the amount added is less than 2 times by weight, the amount of monoethanolamine included in the 2-methylnaphthalene crystals precipitated during recrystallization will increase, making it difficult to separate the crystals. Recrystallization of 2-methylnaphthalene after addition of monoethanolamine is carried out in the usual manner, namely by dissolution-
This can be carried out by a method of cooling crystallization. The temperature at which the crude 2-methylnaphthalene is dissolved is suitably 30 to 40°C, which is higher than the freezing point of the raw material crude 2-methylnaphthalene. The temperature at which the homogeneous solution of dissolved crude 2-methylnaphthalene and monoethanolamine is cooled to precipitate crystals is preferably 10 to 20°C, which is higher than the freezing point of monoethanolamine. Solvents used to remove monoethanolamine attached to the separated 2-methylnaphthalene crystals include aliphatic hydrocarbons such as hexane and heptane,
Alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, or aromatic hydrocarbons such as benzene and toluene are suitable. The amount of these solvents added is 0.1 to 2-methylnaphthalene crystals.
It may be about 0.3 times the weight, and the temperature for extracting 2-methylnaphthalene may be 30 to 40°C. When the solvent used to extract this 2-methylnaphthalene is cooled and crystallized to recover purified 2-methylnaphthalene,
The temperature at which crystals are precipitated is 0 to 10°C, preferably around 5°C. Monoethanolamine for extracting and removing impurities in crude 2-methylnaphthalene and a solvent for removing monoethanolamine attached to 2-methylnaphthalene crystals are added continuously according to the conventional cooling crystallization method. It is also possible to perform crystallization at the same time. [Example] Example 1 400 g of monoethanolamine (2 times the weight) was added to 200 g of crude 2-methylnaphthalene having the composition shown in the raw materials in Table 1, and the mixture was heated to 40°C to dissolve the crude 2-methylnaphthalene. , let cool to room temperature, then 15℃
The mixture was cooled down to precipitate crystals, and 166.0 g of 2-methylnaphthalene crystals were obtained using a centrifugal filter. In order to remove monoethanolamine attached to this 2-methylnaphthalene crystal, heptane was added.
33.0g was added and heated to 40℃ to extract 2-methylnaphthalene, cooled to 5℃, centrifugally filtered, and vacuum dried to produce purified 2-methylnaphthalene 144.3 having the composition shown in Table 1 as a product. I got g. This purified 2-methylnaphthalene has a purity of 99.5
%, total sulfur 0.094%, basic nitrogen Trace,
Yield is 74.4% based on 2-methylnaphthalene
It was hot.

[Table] Example 2 200 g of monoethanolamine was added to 100 g of crude 2-methylnaphthalene having the composition shown in the raw materials in Table 2, heated to 40°C to dissolve the crude 2-methylnaphthalene, and allowed to cool to room temperature. Thereafter, the mixture was cooled to 15° C. to precipitate crystals, and 99.9 g of 2-methylnaphthalene crystals were obtained using a centrifugal filter. In order to remove monoethanolamine attached to this 2-methylnaphthalene crystal, 20 g of heptane was used.
was added and heated to 40°C to extract 2-methylnaphthalene, cooled to 5°C, centrifugally filtered, and vacuum dried to obtain 71.5g of purified 2-methylnaphthalene with the composition shown as a product in Table 2. Ta. This purified 2-methylnaphthalene had a purity of 99.3% and a yield of 78.6%.

[Table] Comparative Example 200g of crude 2-methylnaphthalene listed as the raw material in Table 1 used in Example 1 was placed in a beaker, 193g of methanol with a purity of 99.5% was added thereto, and dissolved at 40°C with stirring. The mixture was cooled to 5° C. and centrifugally filtered, thereby obtaining 106.9 g of recrystallized product. Its composition is shown in Table 3.

【table】

[Table] As shown in Table 3, the purity of 2-methylnaphthalene was 98.2%, total sulfur remained as much as 0.39%, and the yield was low at 54.4%. [Effects of the Invention] This invention provides the following advantages: After adding monoethanolamine to crude 2-methylnaphthalene and dissolving it by heating,
A simple operation of cooling, separating the precipitated crystals, extracting 2-methylnaphthalene with a solvent, and recrystallizing it almost completely eliminates organic sulfur compounds and organic nitrogen compounds, which are contaminants other than 2-methylnaphthalene. 2- with a purity of 99% or more
Methylnaphthalene can be easily obtained in high yield.

Claims (1)

[Claims] 1. A method for producing 2-methylnaphthalene, which is characterized by adding a hydroxyalkylamine derivative to crude 2-methylnaphthalene, dissolving the 2-methylnaphthalene, and then cooling to separate the precipitated crystals. Purification method. 2. The method for purifying 2-methylnaphthalene according to claim 1, characterized in that crude 2-methylnaphthalene containing 90% by weight or more of 2-methylnaphthalene is used. 3. The method for purifying 2-methylnaphthalene according to claims 1 and 2, characterized in that monoethanolamine, diethanolamine, triethanolamine, propanolamine, or butanolamine is used as the hydroxyalkylamine derivative. .