JPS6193165A - Method of separating and purifying quinaldine - Google Patents

Abstract

PURPOSE:In separating and purifying quinaldine from a mixture containing it, to purify quinaldine easily in high purity, by adding a diol to the mixture containing quinaldine to form an inclusion compound, separating, and decomposing it. CONSTITUTION:A mixture containing quinaldine and its isomer is reacted with >=0.5mol based on quinaldine, preferably 1-2mol of a diol shown by the formula (n is 0-2) (concretely, benzpinacol, 1,1,4,4-tetraphenyl-2-butyne-1,4-diol, etc.) at >= room temperature preferably at 40-100 deg.C for 1min-24hr in a reaction solvent such as a ketone, ether, etc., to form an inclusion compound of the diol and quinaldine. Then, the inclusion compound is separated, and decomposed to recover quinaldine.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for separating and purifying quinaldine from a mixture containing quinaldine (2-methylquinoline).

(Prior Art) Quinaldine is included in the bases separated from coal tar, and is useful as a raw material for dyes, pigments, medicines, etc. Quinaldine can be obtained by distilling quinoline residual oil, which is a tar fraction, but it has been difficult to obtain highly pure quinaldine by distillation alone due to the presence of components with similar boiling points. In particular, the boiling points of quinaldine and 8-methylquinoline are very close to each other at 247.6°C and 1247.8°C, so it was almost impossible to separate them by distillation.

For this reason, a method has been proposed in which urea is added to form a urea adduct, which is then purified and then decomposed to separate quinaldine (Japanese Patent Application Laid-Open No. 114574/1982).
. This method utilizes the phenomenon that quinaldine and urea selectively form adducts, but since other isomers also form adducts, albeit in relatively small amounts, impurities must be removed to achieve high purity. Depending on the type of adduct, it is necessary to refine the adduct to a high degree, which causes a problem in that the yield decreases to some extent.

(Problems to be Solved by the Invention) The present inventors have discovered the surprising fact that diols such as benzpinacol selectively form stable clathrates with quinaldine. Furthermore, compounds other than quinaldine also form clathrate compounds with diols such as benzpinacol, but these clathrate compounds are relatively unstable and can be easily processed by washing the resulting clathrate with an appropriate solvent or by recrystallization. The present invention was achieved by discovering that the quinaldine clathrate can be llnM.

(Means for Solving the Problems) The present invention involves adding a diol represented by the following general formula (1) to a mixture containing quinaldine and its isomers to form an inclusion compound of the diol and quinaldine, and then forming an inclusion compound of the diol and quinaldine. This is a method to recover quinaldine by separating the compound and decomposing it. The mixture containing quinaldine and its isomers is a mixture containing other methylquinoline in addition to quinaldine, such as quinoline residual oil, which is a tar fraction. Quinoline residual oil is the residual oil obtained after removing low-boiling substances such as quinoline from the basic fraction in the tar fraction, but it is preferably further rectified to remove low-boiling substances such as quinoline and dimethyl from the quinoline residual oil. This is a mixture after removing high boiling point substances such as quinoline.

Examples of diols include those represented by the general formula (1), (wherein n is an integer of O to 2), specifically benzpinacol,
11,4,4-tetraphenyl-2-butyno-4-diol, and l,1,6,6-tetraphenyl-2,
There is 4-hexadiyn-1,6-diol.

The amount of this diol to be used is 0.5 times or more, preferably 1 to 2 times in mole, relative to quinaldine in the mixture. A reaction is carried out by adding a diol to a mixture containing quinaldine, and the reaction is carried out by heating to a temperature above room temperature, preferably 40 to 100°C. The reaction time is usually 1 minute to 24 hours. Preferably, the reaction is carried out in a reaction solvent such as a hydrocarbon compound, ketone, ether, alcohol, or ester.

After the reaction is completed, the produced solid is separated by filtration or the like.
In this case, compounds other than quinaldine may also form clathrate compounds and be accompanied, but in this case, they are washed or recrystallized using a solvent. Suitable solvents include hydrocarbon compounds, alcohols, ethers, ketones, esters, etc., and mixed solvents thereof can also be used.

The separated solid, ie, the clathrate compound, is decomposed by heating, and the produced quinaldine is separated. Preferably, the clathrate is heated under reduced pressure to decompose the clathrate and quinaldine is distilled off at the same time, and the remaining diol can be reused. The pressure and temperature at this time are appropriately selected within the range in which quinaldine can be distilled off, but the temperature is preferably 150°C or less.

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

Example: 5.0 g of benzpinacol and quinoline residual oil (quinoline 4
．． 0%, isoquinoline 25.2%, quinaldine 20.4
%, 3.4% of 8-methylquinoline, 2.0% of 1-methylquinoline, 2.9% of 3-methylquinoline, 13.3% of 6-methylquinoline, and 28.8% of others). and a quinaldine mixture excluding high boilers (isoquinoline 1.5%, quinaldine 87.8%, 8-methylquinoline 7.8%, l-methylquinoline 0.8%, 3-
Methylquinoline 1.8%, 6-methylquinoline 0.2%
, other 0.2%) was added to 3 m I of acetone, kept at 50°C for about 5 minutes, and then left at room temperature for 12 hours to precipitate crystals of a 1:1 clathrate of benzpinacol and quinaldine. .

The precipitated crystals were collected by filtration and mixed with 1:1 of benzene and n-hexane.
After washing once with 20 ml of 1 mixed solvent and drying, 4.91 g of colorless prismatic crystals were obtained.

The obtained crystal 4., 91 g was placed under reduced pressure (5 mmHg),
When heated to 120° C., 1.31 g of quinaldine was distilled out.

The purity of the obtained quinaldine was approximately 100%.

Claims (1)

[Claims] A mixture containing quinaldine and an isomer represented by the following general formula (1)
Adding a diol represented by to form a clathrate compound of the diol and quinaldine, and then separating the clathrate compound,
A method for separating and purifying quinaldine, which comprises recovering quinaldine by decomposition. General formula (1), ▲Mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, n is an integer from 0 to 2.)