JPH0553783B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing dialkylaminoethanol (hereinafter abbreviated as DAAE) from dialkylamine and ethylene oxide. For more details, see the general formula (In the formula, R ¹ and R ² represent a C ₁ to _{C 4} lower alkyl group, and R ¹ and R ² may be the same or different.) (In the formula, R ¹ and R ² are the same as above) In producing dialkylaminoethanol, a liquid phase semi-batch method is adopted, and ethylene oxide is continuously charged into a solvent solution of dialkylamine for reaction. The present invention relates to a method for producing dialkylaminoethanol, characterized in that the reaction is terminated when a molar ratio of dialkylamine:ethylene oxide of 2 to 3:1 is reached. DAAE is currently used in many applications such as alkyd resin paints, polyurethane foaming catalysts, gas absorbents, solvents, and rust preventives, making it an industrially useful substance. It has been known that DAAE is produced by the reaction of dialkylamine and ethylene oxide.
(Later W, H, Horne and R, L, Shriner,
J.Amer.Chem.Soc., 2925 (1932)). In the same document (liquid phase semi-batch reaction), alcohols such as methanol are used as the reaction solvent, and it is stated that the best results (yield 75%) are given when dialkylamine/ethylene oxide = 1/1.3. ing. However, when a solvent having a hydroxyl group such as alcohol is used as a reaction solvent, for example, the solvent methanol itself reacts with ethylene oxide as a by-product, and ethylene glycol monoether such as ethylene glycol monomethyl ether (hereinafter abbreviated as MMG) is produced. formation, and the selectivity of the reaction decreases.
This will lead to a decrease in the yield of DAAE. Furthermore, when the dialkylamine is dimethylamine, the difference in boiling point between the main product dimethylaminoethanol and the by-product MMG is small, making it difficult to separate and purify the product by distillation. Also, on the other hand
DAAE itself has a hydroxyl group at the end of its molecule, and depending on conditions, it reacts sequentially with ethylene oxide to produce a high-boiling compound. Therefore, in this reaction, the reaction between the generated DAAE and ethylene oxide, and the reaction between the solvent and ethylene oxide, etc., should be suppressed as much as possible.
The most important issue is to ensure the selectivity of DAAE. The inventors of the present invention have conducted extensive research to achieve these goals, and have achieved their goals. According to the method of the present invention, the reaction between dialkylamine and ethylene oxide can be selectively carried out, and the reaction can be completed without causing a reaction between the product DAAE and the solvent and ethylene oxide. In other words, by continuously adding ethylene oxide to the dialkylamine solvent solution dropwise until the molar ratio of dialkylamine:ethylene oxide finally reaches 2 to 3:1, and then finishing the reaction, the system The molar ratio of dialkylamine:ethylene oxide within is very large, and the abundance of dialkylamine produced
By always ending the reaction at a time when the amount of DAAE is large, the formation of by-products is suppressed and DAAE is
An improvement in yield can be obtained. Next, the above phenomenon will be explained based on FIG. 1 (typical reaction between dialkylamine and ethylene oxide, operating conditions are based on Example 1). By sequentially dropping ethylene oxide to the dialkylamine charged in advance, dialkylamine (curve) decreases and DAAE (curve) increases. Ethylene oxide dialkylamine: ethylene oxide = 2
If the charging is stopped until the ratio reaches ~3:1 (shaded area in Figure 1), high boiling point compounds (curve) due to the sequential reaction of DAAE and reaction products between the solvent and ethylene oxide (curve) will be removed. ) formation is hardly observed, and as a result, the selectivity of DAAE is improved, and it is possible to improve the selectivity of DAAE by ordinary purification methods such as simple distillation.
It becomes possible to commercialize DAAE. As ethylene oxide is further charged beyond the range shown below and the conversion rate of dialkylamine is increased, the amount of side reaction products and products produced also increases.
DAAE selectivity decreases. Therefore, stopping the addition of ethylene oxide when dialkylamine:ethylene oxide ratio of 2 to 3:1 is reached increases the selectivity and yield of DAAE in this reaction, and
It is effective in improving the quality of the product DAAE. Incidentally, a continuous method for producing DAAE is already known, but for example, according to German Patent No. 2357076, a part of the reaction product is recycled at a high temperature of 140±5°C and under a pressure of 20 bar. This cannot be said to be an easy synthesis method in terms of equipment. In addition, compared to the semi-batch type, the continuous type actually
Only a small amount of dialkylamine/ethylene oxide can be selected (if it is large, it is economically disadvantageous), and the latter type of manual operation is not suitable. Furthermore, in Comparative Example 1 of reverse dripping of ethylene oxide from dialkylamine in a semi-batch method and Comparative Example 2 of simultaneous preparation of dialkylamine and ethylene oxide, large amounts of by-products were generated for the same reason as above.
Purification is difficult due to the quality of DAAE. In the present invention, the pressure used for the reaction may be arbitrary from normal pressure to elevated pressure, but from the viewpoint of equipment costs, it is preferable to carry out the reaction under atmospheric pressure. The reaction temperature can range from room temperature to the reflux temperature of the solvent used. As the solvent used in the reaction, alcohols such as methanol, ethanol, propanol, etc. and water can be used in the reaction, but methanol is preferably used. The amount of solvent can range from an equivalent weight to a large excess of ethylene oxide, but in consideration of the reaction between the solvent and ethylene oxide, an amount of 1 to 10 times is preferable. The DAAE thus obtained can be easily purified by conventional purification methods, such as distillation. The present invention will be described in further detail in the following examples. Example 1 45 parts by weight (1.0 mole parts) of dimethylamine and 100 parts by weight of methanol were placed in a 500 ml four-necked flask equipped with a Dimroth condenser, a stirrer dropping funnel, and a thermometer.
Add parts by weight of the solution and heat to 50°C on a water bath. A solution of 22 parts by weight (0.5 mole part) of ethylene oxide and 34 parts by weight of cold methanol is added dropwise over 1.0 hour. After the addition is completed, the mixture is further aged for 1.0 hour. As a result of gas chromatography analysis of this reaction crude liquid, the composition was as shown in Table 1. Dimethylaminoethanol yield based on ethylene oxide 90.0% Ethylene oxide conversion rate
It was 100%. Next, the Oldersho device (perforated plate tower, 40φ,
20N), apply the obtained reaction crude liquid to batch distillation. (Normal pressure, reflux ratio 1) The resulting yield was 17.8%,
A product fraction (134-135°C) was obtained. (Distillation yield 90.0
%) Note that this had sufficient commercial value. Comparative Example 1 Using the same reaction apparatus as in Example 1, a solution of 44 parts by weight (1.0 mol) of ethylene oxide and 44 parts by weight of methanol was charged and heated to 30°C on a hot water bath. A solution of 45 parts by weight (1.0 mole) of dimethylamine and 45 parts by weight of cold methanol is added dropwise over 1.0 hour. After further aging for 2.0 hours, gas chromatography analysis of this reaction crude liquid revealed that the composition was as shown in Table 1.
The yield of dimethylaminoethanol based on ethylene oxide was 68.0%, and the conversion rate of ethylene oxide was 74%. Comparative Example 2 Using a 500 ml autoclave, dimethylamine 45 parts by weight (1.0 mol part) ethylene oxide 22
Part by weight (0.5 mol part) and 134 parts by weight of methanol are charged simultaneously and heated to 50°C on a water bath. 30 more
After a few minutes had elapsed, gas chromatography analysis of the crude reaction solution revealed that the composition was as shown in Table 1. The yield of dimethylaminoethanol based on ethylene oxide was 78.5%, and the conversion rate of ethylene oxide was 95%.

[Table] Example 2 Using the same reaction apparatus as in Example 1, a reaction was carried out with 135 parts by weight (1.5 mol parts) of a 50% dimethylamine aqueous solution and 33 parts by weight (0.75 mol parts) of ethylene oxide. As a result of gas chromatography analysis of this reaction crude liquid, the yield of dimethylaminoethanol based on ethylene oxide was 95.2%, and the conversion rate of ethylene oxide was 92%. Example 3 Using the same reaction apparatus as in Example 1, a solution of 123 parts by weight (1.7 mol) of diethylamine and 51 parts by weight of methanol was charged and heated to 55°C on a water bath.
Add 30 parts by weight (0.68 moles) of ethylene oxide dropwise over 1.0 hour. After ripening, excess diethylamine was recovered by distillation. As a result of gas chromatography analysis of this reaction crude liquid, the yield was 83.7% based on diethylamine, and the conversion rate of ethylene oxide was 100%.

[Brief explanation of the drawing]

The accompanying drawings are diagrams showing a typical reaction between dialkylamine and ethylene oxide to explain the content of the present invention. A...Disappearance curve of dialkylamine, B...Production curve of dialkylaminoethanol, C...Production curve of high boiling point compound, D...Production curve of reaction product of solvent and ethylene oxide, E...Production curve of the present invention Area according to method.

Claims (1)

[Claims] 1. General formula (In the formula, R ¹ and R ² represent a C ₁ to _{C 4} lower alkyl group, and R ¹ and R ² may be the same or different.) (In the formula, R ¹ and R ² are the same as above) In producing dialkylaminoethanol, a liquid phase semi-batch method is adopted, and ethylene oxide is continuously charged into a solvent solution of dialkylamine for reaction. A method for producing dialkylaminoethanol, characterized in that the reaction is terminated when a molar ratio of dialkylamine:ethylene oxide of 2 to 3:1 is reached.