JPH0560815B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention rectifies diethylaminoethanol synthesized from diethylamine and ethylene oxide,
Alternatively, diethylaminoethanol is characterized in that discoloration over time is prevented by reducing the dissolved oxygen concentration in the liquid to 1 ppm or less by efficiently contacting it with an inert gas such as nitrogen gas without rectification. The present invention relates to a manufacturing method.

<Prior Art> Diethylaminoethanol is synthesized by an addition reaction between diethylamine and ethylene oxide. Usually, diethylaminoethanol is produced by adding ethylene oxide in a liquid or gaseous state to diethylamine in a liquid state. It is also known that the reaction is greatly accelerated by using a lower aliphatic alcohol as a solvent. The reaction solution of diethylaminoethanol thus obtained contains various compounds in addition to diethylaminoethanol. Examples include diethylamine as a raw material, ethylene oxide, alcohol used as a solvent, and various compounds produced by side reactions. These substances are separated by distillation to obtain the target product, diethylaminoethanol, with high purity.

<Problems to be solved by the invention> However, the obtained diethylaminoethanol has a purity of 99.5% or more and is almost colorless with APHA5 or less, but this product becomes colored over time. . Even if the distillation conditions were made more precise, such as by increasing the number of stages in the distillation column or increasing the reflux ratio to achieve a purity of 99.9% or higher, it was difficult to avoid coloring over time.

Diethylaminoethanol has a wide range of uses in industry as a raw material for paints and medicines, and as an intermediate for various organic synthesis, and there has been a strong desire to improve its quality.

<Means for Solving the Problems> Therefore, as a result of extensive studies, the present inventor discovered that dissolved oxygen in diethylaminoethanol is deeply related to the cause of coloring over time.
The present invention has now been completed. The present invention will be explained in detail below.

The diethylaminoethanol used in the present invention is obtained by the reaction of diethylamine and ethylene oxide, and includes those using lower aliphatic alcohols as a solvent. Examples of lower aliphatic alcohols include methanol, ethanol, n-propanol, and the like. Here, the obtained reaction product is led to a distillation column to separate low-boiling point impurities and high-boiling point impurities, and high-purity diethylaminoethanol is obtained. The boiling point of diethylaminoethanol is 162℃, and the temperature of the liquid is high during atmospheric distillation.
Since a small amount of decomposition products are generated, which can also have a negative effect, distillation is generally carried out under reduced pressure.

If the target raw materials are reaction liquids and semi-finished products (re)
At the time of rectification or in the case of products, leave it as is,
It consists of bringing this into efficient contact with an inert gas such as nitrogen gas. These efficient contacts are
This is naturally determined by the point where the inert gas such as nitrogen is introduced and the amount of the inert gas added. In other words, the introduction point may be at the bottom of the distillation column or at the column section.
It is also possible to carry out the distillation by passing an inert gas such as nitrogen gas through the liquid during or after distillation.
The amount added is not particularly specified, but is appropriately determined through experiments.

What is necessary is to lower the dissolved oxygen concentration in the target liquid. Normally, when an inert gas such as nitrogen gas is not introduced, the dissolved oxygen concentration in the distillate from a distillation tower is 2 to 3 ppm, and in order to prevent discoloration over time, it is important to keep the dissolved oxygen concentration at 1 ppm, more preferably 0.5 ppm or less. be.

<Example> The following is a detailed explanation using examples and comparative examples.

Here, for convenience, as an accelerated test for coloration over time, the object was sealed in a glass container, kept in a constant temperature bath at 80°C for 10 hours, and then evaluated based on the degree of coloration (APHA).

Example 1 Diethylaminoethanol reaction solution (diethylaminoethanol 93.0% by weight, diethylamine 3.0% by weight)
(wt%) and other by-products (containing 4.0 wt%)
1000g of the distillate was charged into a can equipped with a batch distillation column (perforated plate, 30 stages). The distillation column was maintained at a pressure of 200 mmHg and rectification was performed at a reflux ratio of 3. At this time, nitrogen gas was supplied to the bottom of the tower at 5N/Hr using a capillary.
It was introduced in

First, 90 g of a fraction containing low-boiling substances was taken, and then 765 g of a product fraction (purity 99.9%, dissolved oxygen concentration 0.2 ppm) was obtained.

The APHA of this product was 5. 100ml of this
Seal it in a glass container and place it in a constant temperature bath kept at 80℃ for 10 minutes.
APHA was 8 after being left for an hour.

Comparative Example The same procedure as in Example 1 was carried out except that nitrogen gas was not introduced. The fraction containing low-boiling substances was 95 g, and an additional 725 g of product fraction (purity 99.9%, dissolved oxygen concentration 2.5 ppm) was obtained.

The APHA of this product was 5, and the APHA after the same aging test as in Example 1 was 70.

Example 2 The same procedure as in Example 1 was carried out except that 500 g of the product obtained in the comparative example was used as the charging solution. 42g was taken as the initial distillate, and 355g (purity) was taken as the product distillate.
99.9%, dissolved oxygen concentration 0.2 ppm) was obtained.

The APHA of this product was 5, and the APHA of this product after time testing was 8.

Example 3 Product obtained in comparative example (APHA5, amount of dissolved oxygen
2.5ppm) was placed in a 100ml glass container, and nitrogen gas was passed through it at 50N/H for 5 hours using an 8mmφ glass tube (normal pressure and room temperature).

The dissolved oxygen content of this product was 0.1 ppm, and the APHA of this product was 6 after the aging test.

Claims (1)

[Claims] 1 By rectifying diethylaminoethanol synthesized from diethylamine and ethylene oxide, or without rectifying it, by bringing it into efficient contact with an inert gas such as nitrogen gas, the dissolved oxygen concentration in the liquid can be reduced to 1 ppm or less. A method for producing diethylaminoethanol, which is characterized by preventing discoloration over time.