JPH075492B2 - Method for purifying cis-2-butene-1,4-diol - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for purifying cis-2-butene-1,4-diol, which is a compound useful as a raw material for medicines, agricultural chemicals and the like.

[Prior Art and Problems to be Solved] Conventionally, 2-butene-1,4-diol has been obtained by alkynol synthesis from acetylene as a starting material, 2-butyne-1,4-diol.
Obtained by cis reduction of a diol using a specific catalyst.

Most of the 2-butene-1,4-diol obtained at this time was cis-
2-butene-1,4-diol (hereinafter abbreviated as cis form)
However, part of trans-2-butene-1,4-diol (hereinafter abbreviated as trans isomer) is mixed in it, and the boiling points of cis isomer and trans isomer are similar to each other. Etc., it is difficult to separate, and several wt% of the transformer body remains, and it is difficult to remove it.

And when the above product is used as a raw material for medical and agricultural chemicals,
Since a compound containing a trans form is produced, it is often difficult to remove the trans form at this point, and there is a problem that it is not economical.

[Means for Solving the Problems] The inventors of the present invention have made diligent studies to further reduce the content ratio of the trans-form that remains by several wt%, and as a result, acetone, methyl ethyl ketone or tetrahydrofuran (hereinafter abbreviated as THF). .), The solution was cooled, the solution was cooled to precipitate crystals, and the crystals were separated and washed. It has arrived.

That is, according to the present invention, cis-2-butene-1,4-diol containing trans-2-butene-1,4-diol (hereinafter abbreviated as butenediol) is dissolved in acetone, methyl ethyl ketone or tetrahydrofuran. A method for purifying cis-2-butene-1,4-diol, which comprises cooling, precipitating crystals, separating and washing.

The solvent used in the present invention is a solvent that dissolves butenediol and precipitates crystals when cooled, and is specifically acetone, methyl ethyl ketone or THF.

Usually, the dissolution step is carried out at room temperature, in which case the starting butenediol is completely dissolved in the solvent.

Further, the amount of acetone, methyl ethyl ketone, or THF with respect to the raw material for dissolving the raw material is preferably 300 to 1000 parts by weight with respect to 100 parts by weight of the raw material, and in washing after separation, 20 to 200 parts by weight with respect to 100 parts by weight of the raw material. Parts are preferred.

Then, the solution is cooled to crystallize butenediol in the solution. As a method for cooling the solution, there are a method of cooling from the outside of the liquid using a refrigerant and a method of directly pouring a refrigerant such as dry ice into the liquid.

Crystals gradually begin to precipitate from around -10 ° C, but in order to actually separate the precipitated crystals,
Precipitation is carried out at a temperature below -20 ° C and above the melting point of the solvent. However, it is not usually necessary to cool the temperature to a very low temperature, and it is preferable to use dry ice, which is easy to cool, to cool it to a temperature of about -40 to -60 ° C.

The precipitated crystals need to be separated from the solvent and can be separated by a method such as normal centrifugation or filtration.
At this time, what is important is to maintain the same temperature as much as possible so that the crystals do not melt. for that reason,
If necessary, it is necessary to perform processing such as cooling the separator. Also, the separation process itself needs to be performed quickly and in a short time.

The purity is greatly improved by precipitation and separation, but the purity can be increased by further washing the separated butenediol.

In the case of washing, it is usually necessary to use the same solvent as that used for the dissolution and perform the washing at the same temperature as during the precipitation so that the cooled crystals do not dissolve again.

Usually, industrially obtained cis-2-butene-1,4-diol contains about 1 to 3% of trans isomer, but the amount of cis-2-butene-1,4-diol is 1/3 or less by treatment by the method of the present invention. The same degree of purification can be achieved even if this operation is repeated twice, so that the purity can be reduced to 1/9 or less of the initial purity by repeating twice.

High purity cis-2-butene-1,4-obtained by the present invention
A diol is extremely useful as a raw material for medicines, agricultural chemicals, etc. when it is desired to reduce the amount of isomers produced as much as possible.

[Examples] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the examples.

Example 1 20 Kg of butenediol (purity of butenediol: 99.1 wt%, content of trans-2-butene-1,4-diol: 2.5 wt%) in a 250 l polytetrafluoroethylene lining container equipped with a stirrer Then, add 60 kg of acetone and stir well. On the other hand, commercially available dry ice is crushed, passed through a 10-mesh SUS sieve, and about 60 kg that has passed through is used and gradually poured into the solution over about 30 minutes while stirring. Crystals started to precipitate when the liquid temperature decreased to around -17 ° C, and the precipitation amount increased as the liquid temperature further decreased.
It is considered that the precipitation amount became almost saturated when the temperature reached around -40 to 45 ° C. Therefore, the centrifugal separator that had been cooled beforehand was used to separate it from acetone.

Then, 20 kg of acetone cooled to -40 ° C is added to the centrifuge to wash the precipitated crystals.

The obtained crystals were transferred to a container and left at room temperature to become liquid, so acetone was removed by simple vacuum distillation to obtain 19.2 kg of butenediol (yield: 96.0
%), And the purity of the cis-2-butene-1,4-diol present in the compound was 99.3 wt%.

For the analysis of the purity of butenediol and the purity of the cis isomer and the trans isomer, the obtained compound was subjected to trimethylsilylation and then measured by gas chromatography.

Example 2 The butenediol obtained in Example 1 was used as it was, and the amount of acetone for washing was changed to 10 kg. The same operation as in Example 1 was carried out. As a result, 16.8 kg of butenediol was obtained. (Yield: 87.5%) with a purity of 99.9wt%,
The purity of cis-2-butene-1,4-diol in the compound is
It was 99.8 wt%.

The yield of butenediol through Examples 1 and 2 was 84.0%.
Met.

Examples 3 to 8 The operation method was the same as in Example 1 except that the conditions such as the type and amount of the solvent were changed to the conditions shown in Table 1. The results are also shown in Table 1 at the same time.

Here, Examples 4, 6 and 8 were repurified using the compounds obtained in the previous numbered Examples.

As can be seen from the results of Examples 1 to 8, the cis-2-butene-1,4-diol in the butenediol had a purity of at least 99 wt% in the first purification, and 9% in the second purification.
It can be seen that the cis isomer has a very high purity of 9.8 wt% or more.

[Effect of the Invention] The purification method of the present invention comprises several wt% trans-2-butene-1,4-
Cis-2-butene-1,4-diol containing diol,
This is an extremely excellent purification method in which the amount of trans isomer can be reduced to 1/3 or less by a single purification by a simple method of dissolving acetone, methyl ethyl ketone or THF as a solvent and cooling.

Claims (1)

[Claims] 1. After dissolving cis-2-butene-1,4-diol containing trans-2-butene-1,4-diol in acetone, methyl ethyl ketone or tetrahydrofuran,
A method for purifying cis-2-butene-1,4-diol, which comprises cooling to precipitate crystals, separating and washing.