JPS6126983B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently producing fatty acid alkanolamide from an aliphatic lower alkyl ester and an alkanolamine while suppressing the production of by-products.

Fatty acid alkanolamide is a substance useful as various cleaning agent ingredients, cosmetic additives, etc.
Until now, there has been a method in which a fatty acid lower alkyl ester is reacted with a slightly excessive amount of alkanolamine in the presence of an alkali catalyst in a batch reaction tank (Japanese Patent Publication No.
13622), or a method in which a thin film is formed by flowing the reaction mixture down the wall of a thin film evaporator, and the reaction proceeds while instantaneously evaporating the lower alcohol produced by the reaction (US Pat. No. 2,863,888). ) was manufactured by.

However, the former method requires a high reaction temperature;
Since the reaction time has to be long, there are many by-products such as esteramide, and the latter method cannot maintain a residence time sufficient for the reaction to be completed, so the reaction temperature must be set at 150°C or higher. This has the disadvantage that there are many by-products such as esteramides. Moreover, in both cases, the reaction product requires a long aging time in order to improve the yield, which is extremely inconvenient for industrial implementation.

The present inventors have conducted extensive research in order to develop a method that can overcome the drawbacks of such conventional methods, suppress the production of by-products, and efficiently produce the target fatty acid alkanolamide. By using a plate distillation column as a reactor and conducting the reaction under specific conditions, the production of by-products was unexpectedly suppressed.
It was discovered that the desired product could be obtained in high yield, and the present invention was completed based on this finding.

That is, in the present invention, in the presence of an alkali catalyst,
In producing fatty acid alkanolamide by reacting a fatty acid lower alkyl ester with an alkanolamine, a tray-type vertical distillation column is used in which the internal pressure is maintained at 50 to 150 mmHg. Production of fatty acid alkanolamide characterized by supplying the raw material mixture from the upper part of the tower at a rate that gives a residence time of 5 to 60 minutes and reacting while introducing an inert gas at a passing rate of 0.1 m/sec or more. The present invention provides a method.

The fatty acid constituting the lower alkyl ester of fatty acid used in the present invention has 8 carbon atoms.
~22 saturated and unsaturated fatty acids are preferred, which may be linear or branched. Further, it may be a mixed fatty acid. As raw materials for the present invention, methyl esters, ethyl esters, propyl esters, isopropyl esters, and the like of these fatty acids are used.

On the other hand, the alkanolamines used in the present invention include monomethanolamine, monoethanolamine, monoisopropanolamine,
Mention may be made of monoalkanolamines such as monopropanolamine, and dialkanolamines such as dimethanolamine, diethanolamine, diisopropanolamine, dipropanolamine.

Further, in the present invention, the alkali catalyst used may be a normal alkali catalyst, but particularly preferred are sodium methylate, sodium ethylate, potassium methylate, and potassium ethylate, which dissolve uniformly in the reaction mixture.

In the present invention, the reaction between the lower alkyl ester of fatty acid and the alkanolamine is carried out in a tray distillation column. The tray structure of the tray distillation column is suitably a bubble bell, a perforated plate, or the like having a liquid depth of 30 to 100 mm, and the number of trays is 5 to 30, preferably 10 to 15. A suitable step spacing is 200 to 300 mm.

The plate distillation column is heated to 70-120°C. 70℃
At lower temperatures, the reaction does not proceed smoothly, and at higher temperatures than 120°C, the amount of by-products such as amide esters and amino esters increases, making it impossible to achieve the object of the present invention. The operating pressure is preferably in the range of 50 to 150 mmHg. If it is less than 50 mmHg, it will be difficult to condense the lower alcohol produced as the reaction progresses, and if it exceeds 150 mmHg, the evaporation of the lower alcohol will be slow, resulting in a decrease in the reaction rate, which is not preferable. The residence time of the reaction mixture in the column is 5~
A range of 60 minutes is preferred. If the reaction time is less than 5 minutes, unreacted raw materials remain, and if the reaction time exceeds 60 minutes, a large amount of by-products such as ester amide will be added.

According to the present invention, by introducing an inert gas from the middle or lower part of the tray distillation column and bringing it into contact with the reaction mixture present on the trays, lower alcohols produced as the reaction progresses are removed. Evaporation can be promoted and the reaction can proceed smoothly. As the inert gas introduced at this time, in addition to nitrogen gas, argon gas, etc., lower alcohol distilled out as the reaction progresses can also be used in the form of vapor. This method of circulating and using lower alcohols as vapor not only has economic advantages, but also because there is no drop in the partial pressure of lower alcohols.
It also has the advantage that the distilled lower alcohol is easily condensed, making it suitable for industrial implementation. The introduction speed of such an inert gas needs to be 0.1 m/sec or more as a column cross-sectional speed. If the introduction rate is slower than this, the reaction promotion effect will be insufficient.

Next, steps for implementing the present invention will be explained with reference to the accompanying drawings. The drawing is an explanatory diagram of an example of an apparatus used to implement the present invention.

A raw material mixture consisting of a fatty acid lower alkyl ester, an alkanolamine, and an alkali catalyst is fed into the tray distillation column from the raw material supply conduit 1 shown in the drawing, and is reacted with the trays 2, 2', 2''...
flow down one after another. Each tray has a tower heater 3,
3', 3'' to a predetermined temperature.At this time, the inert gas is introduced into the column from the inert gas introduction pipe 4 at a predetermined flow rate, and is mixed with the reaction mixture flowing sequentially down the trays. The lower alcohol produced as the reaction progresses is discharged from a discharge pipe 5 provided at the top of the column, condensed by a condenser 6, and stored in a distillate receiving tank 7.The distillate receiving tank 7 is It is connected to a vacuum line 8, thereby maintaining the pressure inside the column at a predetermined pressure.Fatty acid alkanolamide, which is the target product, is taken out from an extraction pipe 9 provided at the bottom of the column.

According to the present invention, in a reaction time of about 5 to 60 minutes, 90%
Fatty acid alkanolamide can be obtained in a high yield as described above, the reaction temperature is relatively low, and lower alcohol vapor generated as an inert gas can be used, so it is economical and suitable for industrial implementation. ing.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Inner diameter 60 with 10 glass perforated plates inside
A heating medium was passed along the outer periphery of a glass tray distillation column with a height of 400 mm and the column was heated to a temperature of 110° C. inside the column. A mixture consisting of 1.1 mole of diethanolamine, 1 mole of methyl coconut oil fatty acid, and 0.25% by weight of sodium methylate relative to the methyl coconut oil fatty acid ester was fed from the top of the column, and the trays were successively lowered to cause a reaction. . At this time, methanol vapor was introduced from the bottom of the column at a flow rate of 0.15 m/sec per cross-sectional area of the column. The pressure inside the tower is controlled to 100mmHg by a vacuum line connected to a methanol receiving tank with a condenser connected to the top of the tower.
was held at

The residence time was 18.8 minutes, and the yield of coconut oil fatty acid diethanolamide was 90.2% (in terms of coconut oil fatty acid ester).

Example 2 Coconut oil fatty acid diethanolamide was produced in the same manner as in Example 1, except that nitrogen gas was introduced as the introduced gas at a flow rate of 0.15 m/sec per column cross-sectional area.

The residence time was 20.0 minutes and the yield was 90.5%.

Comparative Example 1 The same raw material mixture as in Example 1 was heated to an internal pressure of 100 mm.
When the reaction was carried out in a Hg tank reactor at a reaction temperature of 130° C. for 2 hours, the yield of coconut oil fatty acid diethanolamide was 80.0%.

Comparative Example 2 The same raw material mixture as in Example 1 was heated to an internal pressure of 100 mm.
Hg was supplied to a thin film evaporator with an inner diameter of 50 mm and a length of 200 mm and an internal temperature of 150°C, and was caused to flow down the wall in a thin film form to cause a reaction. The residence time was 30 seconds. The yield of coconut oil fatty acid diethanolamide was 69.7%.

Example 3 Beef tallow fatty acid diethanolamide was produced in the same manner as in Example 1 except that methyl beef tallow fatty acid was used instead of methyl coconut oil fatty acid. Residence time is 20-25 minutes,
The yield was 89.8%.

Example 4 Coconut oil fatty acid diethanolamide was produced in the same manner as in Example 1 except that ethyl coconut oil fatty acid was used instead of methyl coconut oil fatty acid. Residence time is 20~
In 25 minutes, the yield was 88.3%.

Example 5 Coconut oil fatty acid monoethanolamide was produced in the same manner as in Example 1 except that monoethanolamine was used instead of diethanolamine. The residence time is
The yield was 90.8% in 20-25 minutes.

[Brief explanation of the drawing]

The drawing is an explanatory diagram of an apparatus used for carrying out the present invention, and the symbols in the drawing have the following meanings. 1... Raw material supply conduit, 2, 2', 2''... Shelf,
3, 3', 3''... Tower heater, 4... Inert gas introduction pipe, 5... Discharge pipe, 6... Condenser, 7...
... Distillate receiving tank, 8 ... Vacuum line, 9 ... Extraction pipe.

Claims (1)

[Scope of Claims] 1. A tray-type vertical distillation column that maintains the internal pressure at 50 to 150 mmHg in producing fatty acid alkanolamide by reacting a fatty acid lower alkyl ester with an alkanolamine in the presence of an alkali catalyst. The raw material mixture is introduced from the upper part of the tower for a residence time of 5 to 500 m/sec while introducing an inert gas from the center or lower part of the tower at a cross-sectional velocity of 0.1 m/sec or more.
A method for producing fatty acid alkanolamide, which comprises supplying and reacting at a rate of 60 minutes. 2. The method according to claim 1, wherein the fatty acid lower alkyl ester is a fatty acid methyl ester and the inert gas is gaseous methanol.