JPS6260386B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying cyclic ethers. More specifically, the present invention relates to a method for purifying a cyclic ether by removing water from the water-containing cyclic ether.

Conventionally, several methods have been known for removing water from a hydrous cyclic ether. That is, (1) a method using a solid alkali metal hydroxide. (2) A method using an aqueous solution of alkali metal hydroxide. (3)Azeotropic distillation method. (4) Extractive distillation methods, etc., each of which has major drawbacks. That is, the first method requires the handling of solids, so the operation is complicated, and the surface area of solid alkali metal hydroxides is generally small, so the dehydration rate is slow.
It takes a long time to remove water. Although the second method has the advantage of being easy to handle, it tends to form a fairly strong emulsion when the hydrous cyclic ether and the aqueous solution of alkali metal hydroxide are brought into contact. Separation takes a long time,
A major drawback is that in some cases large amounts of cyclic ether are lost into the aqueous phase. In addition, the third method involves distillation by adding an azeotropic dehydrating agent such as carbon disulfide or kerosene, and utilizes the fact that the azeotropic composition under reduced pressure or increased pressure is different from the azeotropic composition under normal pressure. This method is economically disadvantageous because it requires recovery of an azeotropic dehydrating agent and a plurality of distillation columns. The fourth method is a method of distillation using an extractant such as ethylene glycol or glycerin, and like the third method, it is economically disadvantageous.

An object of the present invention is to provide a simple and effective method for purifying cyclic ethers that overcomes the drawbacks of the conventional methods.

In order to achieve this objective, the present inventors have conducted various studies and found that water in the hydrous cyclic ether is extracted by bringing an aqueous solution containing an alkali metal hydroxide and an alkali metal halide into contact with the hydrous cyclic ether. The present inventors have discovered that this makes it possible to completely prevent the formation of emulsions and to remove water from the water-containing cyclic ether very easily, leading to the completion of the present invention.

Next, the present invention will be explained in detail.

The cyclic ether used in the present invention may be any compound that dissolves well in water and is chemically stable in an aqueous solution containing an alkali metal hydroxide and an alkali metal halide.
~7-membered cyclic ethers, or cyclic ether derivatives in which at least one hydrogen atom in these cyclic ethers is substituted with an arbitrary substituent. More specifically, typical examples include oxepane, dioxane, tetrahydropyran, tetrahydrofuran, and oxetane.

Although the content of water in the water-containing cyclic ether is not particularly limited, it is usually preferable to use a water-containing cyclic ether containing 20% by weight or less of water based on the cyclic ether. The above-mentioned cyclic ethers usually have the property of forming the lowest azeotropic compound with water, so in the case of a water-containing cyclic ether containing a large amount of water, by distilling it before carrying out the method of the present invention, It is easy to reduce the water content to 20% by weight or less.

As alkali metal hydroxides, lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, etc. are used.
Sodium hydroxide and potassium hydroxide are particularly advantageous in terms of performance, price, availability, and the like.

Further, as the alkali metal halide, any of alkali metal fluorides, alkali metal chlorides, alkali metal bromides, and alkali metal iodides can be used, but alkali metal chlorides are particularly preferable in terms of cost, etc. Specifically, sodium chloride and potassium chloride are preferable.

The concentration of the aqueous solution containing the alkali metal hydroxide and alkali metal halide is preferably such that the total amount of the alkali metal hydroxide and alkali metal halide is 20 to 70% by weight.

When the concentration is lower than 20% by weight, the ability to extract water from the hydrous cyclic ether decreases;
If the concentration is higher than that, there is a possibility that the aqueous solution itself will solidify, which is not preferable.

Further, the ratio of the alkali metal halide to the total amount of the alkali metal hydroxide and the alkali metal halide is preferably 0.3 to 50% by weight. When the proportion of alkali metal halide is less than 0.3% by weight, it tends to form an emulsion when extracting water from the hydrous cyclic ether, and when it is more than 50% by weight, the ability to extract water tends to decrease. Both are unfavorable.

When carrying out the present invention, an aqueous solution containing an alkali metal hydroxide and an alkali metal halide and a hydrous cyclic ether are mixed in a container equipped with a stirrer,
After fully contacting both liquids using a mixing device such as a static mixer or a line mixer and extracting the water in the water-containing cyclic ether, the mixed liquid is allowed to stand still and separated into an aqueous phase and a cyclic ether phase. A separation method is generally employed.

The amount of the aqueous solution containing an alkali metal hydroxide and alkali metal halide to be used for the hydrous cyclic ether depends on the content of water in the hydrous cyclic ether, the concentration of the aqueous solution containing the alkali metal hydroxide and alkali metal halide, etc. generally 10 to 300 for hydrous cyclic ethers, depending on
A range of weight percent is suitable. When it is less than 10% by weight, the water extraction effect tends to be insufficient, and
If it is used in an amount greater than 300% by weight, there will be no problem in terms of the water extraction effect, but it will become uneconomical, so either is not preferable.

In addition, the temperature during extraction, liquid separation, and separation is 0~
Performed at 100℃.

Since liquid separation and separation properties are extremely good, the standing time required for liquid separation and separation is 5 to 60 minutes.

Extraction, liquid separation, and separation can be carried out either batchwise or continuously.

In addition, it is possible to adopt either a single-stage or multi-stage extraction method, and a single-stage method is usually sufficient, but when using a hydrous cyclic ether with a high water content, a multi-stage method is generally used. It is more advantageous.

The water content in the cyclic ether phase after separation and separation is usually 0.5% by weight or less, and 0.3% by weight or less when carried out under the most preferred conditions of the present invention,
In addition, the content of impurities such as alkali metal hydroxides and alkali metal halides is less than 1 ppm, so
The cyclic ether can be used as it is for ordinary purposes, but when a nearly completely anhydrous cyclic ether is required, dehydration using a molecular sheep or the like or distillation may be performed.

On the other hand, the cyclic ether content in the aqueous phase after separation and separation varies depending on extraction conditions, etc., but is generally 0.3% by weight or less, and can be discarded.
It is also possible to recover the cyclic ether together with water by a method such as evaporation, and at the same time obtain a concentrated aqueous solution containing an alkali metal hydroxide and an alkali metal halide, each of which can be reused when extracting water from the hydrous cyclic ether. It is possible and economically more advantageous.

As detailed above, according to the present invention, water in the water-containing cyclic ether is easily extracted by bringing an aqueous solution containing an alkali metal hydroxide and an alkali metal halide into contact with the water-containing cyclic ether. It is extremely advantageous industrially because it is possible to obtain a cyclic ether with extremely low water content and to completely prevent the formation of an emulsion during extraction, thereby almost completely preventing loss of the cyclic ether. be.

The present invention will be specifically explained below using Examples and Comparative Examples.

Example 1 In a round bottom flask with an inner volume of 2 and equipped with a stirrer, 1000 g of hydrated dioxane consisting of 100 g of water and 900 g of dioxane and 500 g of an aqueous solution containing 45% by weight of sodium hydroxide and 1% by weight of sodium chloride were mixed at room temperature for 10 minutes. After stirring and mixing for a minute, the mixture was transferred to a separatory funnel, left to stand for 10 minutes to separate the two phases, and the aqueous phase was removed to obtain 901 g of purified dioxane. The water content in the purified dioxane was analyzed by the Karl Fischer method and was found to be 0.221% by weight. In addition, as a result of flame analysis, the Na content in purified dioxane was 0.2 ppm.
(NaOH equivalent).

Comparative Example 1 Hydrous dioxane and an aqueous sodium hydroxide solution were stirred and mixed in the same manner as in Example 1, except that 500 g of an aqueous solution containing only 45% by weight of sodium hydroxide and no sodium chloride was used.
The solution was transferred to a separatory funnel and left to stand. This mixture formed a fairly strong emulsion, and only a small amount of dioxane phase was formed in the upper layer even after it was allowed to stand for 10 minutes. Even after 5 hours had passed from the start of standing, the liquids were not separated sufficiently, so after standing for another 7 hours, the aqueous phase was removed and purified dioxane 870
I got g. As a result of the analysis, the moisture content was 0.340% by weight.
The Na content was 3.9 ppm (NaOH equivalent).

Example 2 After stirring and mixing 500 g of hydrous tetrahydrofuran consisting of 50 g of water and 450 g of tetrahydrofuran with 1000 g of an aqueous solution containing 35% by weight of sodium hydroxide and 5% by weight of sodium chloride at 40°C for 10 minutes, the mixture was transferred to a separatory funnel. After liquid separation by standing at 40°C for 10 minutes, the aqueous phase was removed to obtain 448 g of purified tetrahydrofuran. As a result of the analysis, the water content is 0.317% by weight, and the Na content is 0.317% by weight.
It was 0.4 ppm (NaOH equivalent).

Example 3 Water-containing tetrahydrofuran consisting of 150 g of water and 600 g of tetrahydrofuran and 750 g of an aqueous solution containing 49% by weight of sodium hydroxide and 1% by weight of sodium chloride were stirred and mixed at room temperature for 10 minutes, then transferred to a separatory funnel and stirred for 30 minutes. The mixture was allowed to stand still to separate two phases, and 601 g of purified tetrahydrofuran was obtained. As a result of the analysis, the moisture content was 0.310% by weight, and the Na content was 0.3ppm (NaOH conversion).
It was hot.

Comparative Example 2 Hydrous tetrahydrofuran and an aqueous sodium hydroxide solution were stirred and mixed in exactly the same manner as in Example 3, except that 750 g of an aqueous solution containing only 49% by weight of sodium hydroxide and no sodium chloride was used. The solution was transferred to a separatory funnel and left to stand. Since this liquid mixture had extremely poor liquid separation properties, after being allowed to stand for 15 hours, the aqueous phase was separated and removed to obtain 568 g of static tetrahydrofuran. As a result of analysis, the water content was 0.770% by weight and the Na content was 7.5 ppm (NaOH equivalent).

Example 4 Aqueous solution containing 50 g of hydrated tetrahydropyran, 35% by weight of potassium hydroxide and 5% by weight of potassium chloride, consisting of 5g of water and 45g of tetrahydropyran.
Using 100g of tetrahydropyran, stir mixing and static separation were performed in the same manner as in Example 2.
44.5g was obtained. As a result of analysis, the water content was 0.281% by weight and the K content (KOH equivalent) was 0.5 ppm.

Claims (1)

[Claims] 1. A method for removing water in a water-containing cyclic ether, which is characterized by bringing an aqueous solution containing an alkali metal hydroxide and an alkali metal halide into contact with the water-containing cyclic ether to extract water in the water-containing cyclic ether. Method for purifying cyclic ether.