JPS6388141A - Separation of 2,6-diisopropylnaphthalene - Google Patents

Abstract

PURPOSE:To separate the titled compound in high yield and purity from a mixture containing 2,7- and 2,6-diisopropylnaphthalenes, by adding thiourea to the mixture, separating the produced adduct after maintaining the system at a definite temperature for a definite time and decomposing the separated adduct. CONSTITUTION:An isopropylnaphthalene mixture containing 2,7- diisopropylnaphthalene and 2,6-diisopropylnaphthalene is added with >=7mol, especially >=15mol of thiourea based on 1mol of 2,6-diisopropylnaphthalene to form an adduct. The adduct is separated from the solution after maintaining the solution at 3--30 deg.C for >=30min and 2,6-diisopropylnaphthalene is separated from the adduct. The total yield of 2,6-isomer can be improved by circulating the fraction which does not form the adduct to a transalkylation stage or isomerization stage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to 2,7-diisopropylnaphthalene and 2.6-diisopropylnaphthalene.
- A method for separating 2°6-diisopropylnaphthalene from an isopropylnaphthalene mixture containing diisopropylnaphthalene.

[Conventional technology]

2.6-diisopropylnaphthalene is synthesized from naphthalene or naphthalene MILL form and propylene by Frizol-Craft reaction or transalkylation reaction, but in this reaction, in addition to 2.6-diisopropylnaphthalene, monoisopropylnaphthalene, 2° Diisopropylnaphthalene other than 6-diisopropylnaphthalene and polyisopropylnaphthalene such as triisopropylnaphthalene are produced. Distillation and crystallization are methods for separating 2,6-diisopropylnaphthalene from such isopropylnaphthalene mixtures, but in W distillation, 2,6-diisopropylnaphthalene, which has a boiling point close to that of 2,6-diisopropylnaphthalene, is separated.
, 7-diisopropylnaphthalene is difficult to separate, and the yield is low in crystallization, and if the purity is attempted to be sufficiently increased, the yield will further decrease.

In Japanese Patent Publication No. 50-17986, 2.6-diisopropylnaphthalene is extracted from an isopropylnaphthalene mixture with an increased content of 2.6-diisopropylnaphthalene and 2.7-diisopropylnaphthalene.
．． A method for cooling and separating 6-diisopropylnaphthalene.

However, the purity of 2,6-diisopropylnaphthalene in the obtained solid portion is at most 78.3%.

RECUEIL 88 (1969), 1028 describes a method for synthesizing di-L-butylnaphthalene and diisopropylnaphthalene, and also describes a method for separating various isomers. Although an adduct-forming separation method using thiourea has been shown as a separation method, there is no quantitative description or anything that makes us aware of its industrial applicability. has not been found.

[Problem that the invention seeks to solve]

The present invention uses 2,6-diisopropylnaphthalene and 2,7-diisopropylnaphthalene.
The purpose of this method is to separate 2,6-diisopropylnaphthalene with high purity and high yield from an isopropylnaphthalene mixture containing diisopropylnaphthalene.

[Means for solving problems]

The present invention relates to 2.7-diisopropylnaphthalene and 2.7-diisopropylnaphthalene.
In separating 2゜6-diisopropylnaphthalene from an isopropylnaphthalene mixture containing 6-diisopropylnaphthalene, 7 moles or more of thiourea is added per mole of 2,6-')isopropylnaphthalene in the isopropylnaphthalene mixture. This is a method in which 2,6-diisopropylnaphthalene is separated by forming an adduct, holding the adduct-forming solution at 30 to -30°C for 30 minutes or more, separating it, and then decomposing the separated adduct.

The isopropylnaphthalene mixture has at least 2.7
- Diisopropylnaphthalene and 2,6-diisopropylnaphthalene, and other naphthalenes,
It may also contain polyisopropylnaphthalenes such as monoisopropylnaphthalene, diisopropylnaphthalene other than 2,6-diisopropylnaphthalene, and triisopropylnaphthalene, or isopropyltetralin. Preferably, the isopropylnaphthalene mixture is prepared by distilling a reaction product obtained by a free-sol fluorine reaction or a transalkylation reaction between naphthalene or a naphthalene derivative and propylene, and then distilling it into a low boiling point seafood and polyester such as naphthalene and monoisopronaphthalene. A distillate whose main component is diisopropylnaphthalene obtained by separating high-boiling seafood such as isopropylnaphthalene, and more preferably β
- It is a fraction in which isopropylnaphthalene is Q, 5 wt % or less, and monoisopropyl tetralin and diisopropyl tetralin are Q, 5 wt % or less. Such an isopropylnaphthalene mixture contains 3Qwt% or more of diisopropylnaphthalene, of which 2,6-diitupropylnaphthalene and 2,7-diisopropylnaphthalene account for 80% or more. The ratio of 2,6-diisopropylnaphthalene to 2,7-diisopropylnaphthalene is usually 1:1 or close to it due to equilibrium.

Thiourea is added to the isopropylnaphthalene mixture in an amount of 7 times or more, preferably 10 times or more, and more preferably 15 times or more by mole relative to 2,6-diisopropylnaphthalene in the isopropylnaphthalene mixture. If the amount of thiourea added is less than 7 times the mole, the yield of 2,6-diisopropylnaphthalene will decrease.

In some cases, thiourea can be added in solid form, but since the reaction rate is low, it is advantageous to dissolve it in a solvent and add it. As the solvent, alcohols such as methanol and ethanol, and ketones such as acetone can be used.

Water can be used as a solvent in the form of a saturated aqueous solution or mixed in a solvent as described above. It is most preferable to add thiourea to a solvent as a solution at or near saturation concentration, but thiourea may be moistened with a solvent.

2. In addition to the above-mentioned solvents, the adduct-forming reaction between 6-diitupropylnaphthalene and thiourea can be carried out using solvents that do not form adducts with thiourea and dissolve the isopropylnaphthalene mixture, such as paraffinic hydrocarbons, aromatic A hydrocarbon solvent or the like may also be present. In this reaction, if methanol solvent is used in order to proceed completely, 1.
At 20°C, 40 hours or more is often required, but in practice, the time required for most of the reaction to be completed, that is, in the above case, about 2 hours at 20°C is sufficient.

When separating the adduct, if a long time is required for cooling and standing, there is no need to take a particularly long reaction time, as the reaction also occurs during that time.
After uniformly melting for a short time of 1 hour or less at a temperature above normal temperature of about 0°C, it is slowly cooled to a temperature below normal temperature of 30 to -30°C, held for 30 minutes to several days, and then the formed adduct is melted. To separate. The lower the cooling temperature, the better the yield, but the lower the purity, so a temperature of about 20 to -15°C is suitable. The holding time is 30 minutes or more, preferably 1 hour or more, and about 2 to 24 hours is preferable from the viewpoint of yield.
It may be one hour or less. The formed adducts are separated by means such as filtration or centrifugation.The separated adducts are washed with ether etc. if necessary, and then decomposed.2.
6-Diitubropylnaphthalene is recovered. The adduct can be decomposed by contacting it under heating conditions with a solvent that dissolves 2.6 to diisopropylnaphthalene, although thiourea such as benzene and toluene does not dissolve, or by contacting the adduct with a solvent that dissolves thiourea such as water and benzene, toluene, etc. Known methods can be used, such as contacting the 2°6-diitubrobylnaphthalene with a solvent that is immiscible with water and dissolves the 2°6-ditubobylnaphthalene. Since the former decomposition method is an equilibrium reaction, it is preferable that the extracted 2,6-diituprobylnaphthalene is quickly separated from thiourea. For this purpose, a Soxhlet extractor or the like can be used. Furthermore, although the latter method can be carried out at room temperature, the reaction proceeds quickly when heated to 50° C. or higher.

After the decomposition is completed, 2,6-diitupropylnaphthalene is recovered by removing the solvent in which 2,6-diitubrobylnaphthalene is dissolved. 2 obtained in this way
, 6-diitupropylnafucrene can have a purity of 90% by weight or more, preferably 95% by weight or more. In addition, if the purity is insufficient, by repeating the method of the present invention using this as the raw material isopropylnaphthalene mixture, a purity of 99% by weight or higher can be easily obtained. Furthermore, it is easy to achieve a purity of 99% or higher by combining a recrystallization method or the like. The thiourea remaining after recovering the 2,6-diitupropylnaphthalene can be used repeatedly in adduct-forming reactions.

In the separation method of the present invention, components that do not form adducts can be recycled to the transalkylation or isomerization step, thereby increasing the total yield of 2,6-diituprobylnaphthalene. Here, since the transalkylation or isomerization step is an equilibrium reaction, it is desirable that the concentration of 2,6-diituprobylnaphthalene in the circulating components is as low as possible. The recovery rate of diisopropylnaphthalene is 2.6 to 80
% or more, preferably 90% or more.

〔Example〕

2,6-diisopropylnaphthalene was separated using the samples shown in the table. In each example, % represents weight %.

note.

IPTE: Isopropyltetralin DI PTE
Nidiisopropyltetralin IPN: Isobrobylnaphthalene DIPN: Diisopropylnaphthalene [Example 1] A mixture of thiourea, methanol, and isopropylnaphthalene in Sample Light 3 was uniformly dissolved at 50°C for 20 minutes, and then dissolved for 4 to 5 hours. The mixture was cooled slowly and kept at 0°C for 12 hours.

After filtering and washing the adduct with ethyl ether, the adduct was decomposed with distilled water and extracted with benzene or hebutane. The mixture of extract, filtrate and washing solution is
The yield and purity were determined by C analysis. The results are shown in Table 1.

[Example 2] After uniformly dissolving a mixture of thiourea, methanol and isopropylnaphthalene at 50°C for 20 minutes,
The mixture was slowly cooled over time and maintained at the temperature shown in Table 2 for 12 hours. Other conditions and results are shown in Table 2.

Table 2 [Example 3] A mixture of thiourea, methanol and isopropylnaphthalene of Sample 3 was reacted at 20° C. and kept at that temperature for the time shown in Table 3. Other conditions and results are shown in Table 3.

Table 3 [Example 4] A mixture of thiourea, methanol and isopropylnaphthalene was uniformly dissolved at 50'C for 20 minutes, and then heated to 0C.
It was held for 12 hours.

Other conditions and results are shown in Table 4.

Table 4 Table 4 (Continued) Adduct component composition [Effects of the invention] According to the method of the present invention, 2,6-dibutybrobylnaphthalene, which is difficult to separate, is separated from an isopropylnaphthalene mixture containing 2,6-ditubrobylnaphthalene. Itubrovirnaphthalene can be separated with high purity and high yield.

Claims (1)

[Claims] In separating 2,6-diisopropylnaphthalene from an isopropylnaphthalene mixture containing 2,7-diisopropylnaphthalene and 2,6-diisopropylnaphthalene, 2,6-diisopropylnaphthalene in the isopropylnaphthalene mixture is
- Adding 7 moles or more of thiourea per mole of diisopropylnaphthalene to form an adduct, holding the solution in which the adduct has formed for at least 30 minutes at 30 to -30°C, separating it, and then decomposing the separated adduct. A method for separating 2,6-diisopropylnaphthalene, characterized by