JPS6025970A - Purification of imidazole - Google Patents

Abstract

PURPOSE:To purify the titled compound useful as a raw material of fungicide and other agricultural chemicals or pharmaceuticals, by adding an amine compound such as alkylamine, diamine, polyamine, pyridine, etc. to a reaction liquid containing imidazole, and distilling the mixture. CONSTITUTION:For example, a mixture of an aqueous solution of glyoxal and an aqueous solution of formaldehyde is added dropwise, little by little to an aqueous solution of ammonia at 70-80 deg.C to obtain an imidazole-containing reaction liquid. The liquid is purified by adding an amine compound such as methylamine, ethylenediamine, diethylenetriamine, pyridine, hydrazine, etc. to the liquid in an amount of 0.5-20wt%, preferably 1.0-10wt%, based on the whole reaction liquid, and distilling the mixture. A product having extremely high purity can be produced compared with conventional purification process.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying imidazole for the purpose of removing impurities in a reaction solution containing imidazole.

Imidazole is useful as a fungicide, other agricultural chemicals, and a medical raw material, and the compound is glyoxal,
It has been widely known that it can be obtained by reacting formalin and ammonia. However, in this method, the reaction solution after the reaction contains, in addition to the target imidazole, byproducts accompanying the reaction (for example, formic acid and formic acid amide) and unreacted raw material water. Therefore, the impurities must be removed when producing a product. Distillation is the most practical purification method in industrial methods, but even if the reaction crude liquid is simply purified by vacuum distillation, impurities of several percent will still remain in the product, and purification is insufficient. be.

This is a big problem when it is carried out industrially, and even more efficient purification method U (one shot is a seven-shot method) is proposed.

However, in view of the problem described in item 1, the inventors of the tree conducted extensive research and found that by distilling the imidazole-containing reaction solution in the presence of an amine compound, the impurities would not be a problem in practice.11 They have discovered that it is possible to reduce the amount of heat to a certain extent, and have completed the present invention.

A known method is employed to prepare the imidazole-containing reaction product liquid that is the object of the present invention. That is, a reaction is carried out by dropping a mixture of a glyoxal aqueous solution and a formalin aqueous solution little by little into an ammonia aqueous solution at a temperature of 70 to 80°C. The optimum reaction molar ratio (in terms of solid content) for each is 1 mole of glyoxal to 0.00% formalin. 1.2 moles of ammonia, and 2.0 to 6.0 moles of ammonia. In general, each raw material is commercially available as an aqueous solution, so it is common to use it directly, but it may be diluted or concentrated if necessary. Suitable concentration ranges of the raw materials include glyoxal aqueous solution of 10 to 80% by weight, more preferably 55 to 50% by weight, and formalin aqueous solution of 10 to 80% by weight, more preferably 1%.
or 50 to 40% by weight, and an ammonia aqueous solution of 5 to 40% by weight.
% by weight, more preferably 10-50% by weight. After the reaction is completed, it is aged for 0.5 to 1 hour to obtain an imidazole-containing reaction solution.

The imidazole-containing reaction solution obtained in this way contains various impurities other than imidazole as mentioned above, so the most important feature is that it is distilled in the presence of an amine compound in order to remove these impurities. Such amine compounds have the general formula R'N 14 or Nl2-R'-Nl2, R
-NHN)L, (where R is an alkyl group and R1 is an alkylene group), and those represented by this formula include methylamine, ethylamine, propylamine,
Alkylamines such as isopropylamine, butylamine, hexylamine, diamines such as ethylenediamine, trimethylenediamine, putrescine, cagperine, hexamethylenediamine, polyamines such as diethylenetriamine, triethylenetetramine, tetraethylene pencune, pyridine, hydrazine and their derivatives. mentioned,
These can be used alone or in combination. However, the present invention is not limited to these. The above amine compound can be added at the Impo period before distillation.
It can be added directly to the imidazole-containing reaction solution and further concentrated and distilled;
You can also do step 1. The amount added is 0.0% based on the total amount of the reaction solution.
5-20 weight fj 1%, more preferable 1. υ〜10foldi
)%, and even if it is added above the 2nd limit of the range, the effect d will not change much compared to the amount added, and below the lower limit the effect of the present invention cannot be obtained.

Distillation can be carried out in the presence of the amine compound by a commonly known method and no special operation is required.

A typical method is to heat the imidazole-containing reaction concentrate to which the amine compound has been added at a reduced pressure of 190 to 21 torr or less, preferably 1 Otorr or less.
Vacuum distillation is carried out at 0°C to remove impurities and the residue is used to obtain the desired pure imidazole.

The imidazole thus obtained has a total impurity of 0.
It is less than 5% and has extremely high purity compared to conventional purification methods, so it has great industrial significance.

Hereinafter, the present invention will be explained in more detail with reference to Examples. However, unless otherwise specified, "96" in the examples is based on weight.

Example 1 2796 ammonia aqueous solution (11 mol) kept at 70°C
While stirring, add 5 mol of 40% glyoxal aqueous solution (!:3
A mixed solution of 5 mol of 796 formalin aqueous solution was added dropwise over a period of 2 minutes (17), and after the completion of the addition, the reaction was carried out by aging for 3D minutes. In this way, the imidazole-containing reaction solution is made into a liquid.

Next, the Al solution was condensed at 150° C. under normal pressure, and further concentrated under reduced pressure at 150° C. and 20 torr using an evaporator. Pour the test solution (131 solution).

(596% of ethylenediamine was added to the B solution and vacuum distilled at 210° C. and 5 torr in a bath EIL to obtain imidazole.

The composition of the obtained imidazole was analyzed using gas chromatography.

For reference, liquid (B) was also subjected to gas chromatography analysis.

The above results are shown in Table 1.

Comparative Example 1 In Example I, CBL without addition of diamine was added.
The liquid was directly distilled.

The results at this time are also shown in Table 1.

Table 1 0 Gas chromatography analysis conditions Column: Gas chromatography pack 54 (using 60-8o mesh) Column temperature: 225°C Inner rod substance: Equipment using 2-methylimidazole 2 m 1 Tsu GC-6A

Claims (1)

[Claims] A method for purifying imidazole, which comprises distilling an imidazole-containing reaction solution obtained from an aqueous solution of glyoxal, formalin, and ammonia in the presence of an amine compound.