JPH01160947A - Method for purifying dialkylaminoethanol - Google Patents

Abstract

PURPOSE:To efficiently obtain the title compound useful as cationic polymer flocculants, etc., in high purity with hardly any coloring with time, by removing substances having a higher boiling point than that of a dialkylaminoethanol and treating the resultant dialkylaminoethanol in the presence of a hydrogenation catalyst, etc., under pressure of hydrogen. CONSTITUTION:A dialkylamine is reacted with ethylene oxide to provide a dialkylaminoethanol (e.g., dimethylaminoethanol). In the process, substances having a higher boiling point than that of the dialkylaminoethanol are initially removed therefrom and the resultant dialkylaminoethanol is then treated in the presence of a hydrogenation catalyst, or dehydrogenation catalyst under pressure of hydrogen and purified. The afore-mentioned catalyst is especially preferably an Ru based, Pd based, Pt based and Rh based noble metal catalysts, which are used as respective oxides or simple substances and, as necessary, supported on a carrier, such as alumina, silica or diatomaceous earth.

Description

DETAILED DESCRIPTION OF THE INVENTION [Graduation Field of Application] The present invention relates to a method for purifying dialkylaminoethanol. More specifically, the present invention is a method for efficiently obtaining dialkylaminoethanol, especially dimethylaminoethanol, with a high degree of purity and less coloring over time. This is a method of processing under hydrogen pressure in the presence of a dehydrogenation catalyst.

Dialkylaminoethanol, especially dimethylaminoethanol, is used as a raw material for cationic polymer flocculants, as well as for solvents, surfactants, paints, gas absorbents, urethane foaming catalysts, etc., and is an industrially useful substance. be.

[Prior art and its problems]

Dimethylaminoethanol will be explained below as an example of dialkylaminoethanol. Dimethylaminoethanol is synthesized by the reaction of dimethylamine and ethylene oxide. -For boat fishing, it is easily synthesized by introducing ethylene oxide in liquid or gaseous form into liquid anhydrous dimethylamine.

It is also known that the synthesis reaction is significantly accelerated when water or lower aliphatic alcohols (for example, methanol) are used as a reaction solvent.

Furthermore, a method for efficient synthesis without using a reaction solvent is also known. However, the products obtained by either method contain, for example, unreacted dimethylamine, ethylene oxide, side reaction products, and reaction solvents in addition to dimethylaminoethanol, which is the target substance.

Such a synthetic liquid is separated and purified into a product by ordinary operations such as distillation. However, although the purity itself can be increased by strictly carrying out such purification operations, it is unavoidable that the product will discolor over time. Several methods have been proposed to prevent this discoloration, especially discoloration over time.

For example, Japanese Patent Publication No. 49-10648 proposes a method in which nitric acid, its ammonium salt, or an amine nitrate is added to the reaction solution for ripening, and then dialkylaminoalkanol is separated. However, with this method, additives may remain in the product, and complicated distillation and purification operations are required to obtain a highly pure product. Furthermore, in JP-A No. 54-24807, the reaction solution was heated at 180 to 280°.
It has been proposed to treat at a high temperature of C for several hours to several tens of hours, but if the treatment is carried out at such a high temperature for a long time, there is a risk that dimethylaminoethanol will decompose and the yield of the target product will decrease. JP-A-50-146406 proposes a method of heat treatment in the presence of an aminoalcohol containing tertiary nitrogen, an inorganic acid, and a compound having an imidazole ring. However, in this case as well, there is a risk that the added compounds may remain in the product, and complicated distillation and purification operations are required to obtain a highly pure product. Furthermore, Japanese Patent Publication No. 52-28770 proposes decolorizing higher alkanolamines by heat treatment under hydrogen pressure using a Ni-based or CO-based hydrogenation catalyst or dehydrogenation catalyst. ing. When the desired product is heat-treated under hydrogen pressure using a direct hydrogenation catalyst or a dehydrogenation catalyst as in the method described in Japanese Patent Publication No. 52-28770, dimethylaminoethanol decomposes or colored components hydride remains in the product, and further complicated purification operations such as distillation are required after treatment. For example, when treated with a Ru-based catalyst as a hydrogenation catalyst or dehydrogenation catalyst, dimethylamine, ethanol, high-boiling substances, etc. are produced. On the other hand, according to the method described in Japanese Patent Publication No. 51-28770, it is also possible to directly treat the reaction mixture with a hydrogenation catalyst or a dehydrogenation catalyst and then perform a sufficient separation operation by ordinary distillation. However, a compound that cannot be separated from the target dimethylaminoethanol remains, making it impossible to improve the purity of the product.

In recent years, there has been a demand in the industry for highly pure products with little coloration, especially coloration over time, and the conventional purification methods described above cannot satisfy the above requirements, and further operations such as distillation must be carried out sufficiently. It won't happen.

The present invention does not require the above-mentioned complicated operations.
The objective is to efficiently obtain a product with high purity and little discoloration over time.

[Means for Solving the Problems] In order to solve the above problems, the present inventors have made extensive studies and found that compounds that are difficult to separate by ordinary separation operations such as distillation can be removed from the reaction synthesis solution. It has been found that certain compounds contained in substances with a boiling point higher than that of dimethylaminoethanol are produced during the hydrogenation reaction,
We have arrived at the present invention.

That is, in purifying dialkylaminoethanol synthesized from dialkylamine and ethylene oxide, the present invention first removes substances with a higher boiling point than dialkylaminoethanol, and then converts hydrogen into hydrogen in the presence of a hydrogenation catalyst or a dehydrogenation catalyst. The present invention relates to a method for purifying dialkylaminoethanol, which is characterized by treatment under pressure.

The method of the present invention is particularly effective in purifying dimethylamine ethanol, and enables the production of dimethylaminoethanol with higher purity and efficiency than ever before, and with less coloration over time.

The method of the present invention, as described above, first involves removing high-boiling substances from the reaction synthesis solution, and this removal can be carried out using general techniques such as ordinary image processing.

In the present invention, the removal rate of this high-boiling substance is difficult to determine unconditionally because it is related to the type of high-boiling substance in the reaction synthesis liquid, the selectivity of the synthesis reaction, the separation capacity, etc., but in general, it is It is sufficient to remove dimethylaminoethanol at a rate such that the amount of loss of dimethylaminoethanol in the liquid to be treated is within a range of 1 to 20% by weight.

Next, as the hydrogenation catalyst or dehydrogenation catalyst used to carry out the method of the present invention, a commonly used hydrogenation catalyst or dehydrogenation catalyst of a group 8 metal catalyst of the periodic table may be used. , especially Ru-based, Pd-based, Pt-based and R
H-based noble metal catalysts are preferred. These catalysts may be used as each oxide or as a single substance, and if desired, they may be supported on commonly used carriers such as alumina, silica, diatomaceous earth, and carbon. In this case, the amount supported is generally 10% by weight or less, preferably 0.3 to 7% by weight of the metal, based on the carrier. Further, the amount of catalyst is usually 0.3 to 10% by weight, preferably 0.5 to 3% by weight based on dimethylaminoethanol.

The contact time with the catalyst is 10 to 120 minutes in the case of a flow type;
In the case of batch type, 30 to 250 minutes is sufficient.

If the contact time is too short, the treatment will not be sufficient and a colored substance will remain, and if the contact time is too long, the target substance will decompose significantly, which is undesirable. Also, the hydrogen pressure is 3 to 50 kg/c+++”
G, but usually 5 to 15 kg/cn+”G
It is. The hydrogen used does not necessarily have to be of high purity, and hydrogen commonly used in industry is sufficient.

The reaction temperature during contact with the catalyst is determined by hydrogen pressure, catalyst amount,
Although it varies depending on the contact efficiency etc., -i is 50 to 180
It is advantageously carried out at a temperature of around 80-120°C. If this temperature is higher than 180°C, the target product dimethylaminoethanol is likely to decompose, which is not preferable.

The method of the present invention can be applied to either a batch method or a flow method (continuous method).

In the method of the present invention, after being treated under hydrogen pressure in the presence of a hydrogenation catalyst or a dehydrogenation catalyst, the liquid to be treated is purified by removing low-boiling components by ordinary image processing means, etc., and is purified over time. A product with very little coloring can be obtained.

In addition, the liquid to be treated after being treated under hydrogen pressure in the presence of a hydrogenation catalyst or dehydrogenation catalyst may be directly transferred to the next step when a fixed bed catalyst bed is used, or may be subjected to filtration, etc. when a bed other than a fixed bed is used. It is desirable to move on to the next step after removing the catalyst by a normal separation operation.

〔Effect of the invention〕

As described above, the present invention can efficiently obtain products with high purity and little discoloration over time without requiring complicated image manipulation, and is a meaningful method that can be exploited industrially. .

Examples of the present invention are described below.

Example 1 Using a batch reactor, dimethylamine and ethylene oxide were reacted using a water solvent, excess dimethylamine was recovered, and crude dimethylaminoethanol was obtained. The composition of this reaction synthesis liquid is 0.1% by weight of dimethylamine, 2.0% by weight of low boiling point, 17.9% by weight of water, 77.0% by weight of dimethylaminoethanol, and 3.0% by weight of high boiling point. % by weight.

500 g of the above reaction synthesis liquid was supplied to a cylindrical column with an inner diameter of 35.5 mm and a 1/4-inch McMahon backing packed irregularly to a height of 1 m, and the inside of the cylindrical column was filled with 11 g of 100 mm. The pressure was reduced to 450 g of low-boiling components containing dimethylaminoethanol. This recovered liquid contains 7
It contained 7.8% by weight of dimethylaminoethanol. 4.0 g of a 5% Ru carbon-supported catalyst was added to this recovered liquid, and the mixture was treated at a 100"C2 hydrogen partial pressure of 10 kg/cm"G for 3 hours while stirring. Treatment liquid 300 after cooling and filtering the catalyst
g was charged into the above-mentioned distillation column to make the inside of the column 100 m...I1 g, and at a reflux ratio of 20, 90.4 g of water and a low boiling point fraction were collected, and then 210 g of dimethylaminoethanol was recovered as a product fraction. The purity of this recovered liquid was 99.9%. The A P HA of this product at the time of distillation was 5 or less, and no coloration was observed over time after storage for one month.

Comparative Example 1 Add 5% to 400 g of the same reaction synthesis solution used in Example 1.
Add 3.5 g of Ru carbon supported catalyst and heat to 100°C with stirring.
The sample was treated at a hydrogen partial pressure of 10 kg/cm''G for 3 hours.

After cooling, 300 g of the treated liquid from which the catalyst had been filtered off was charged into a distillation tower similar to that in Example 1, and the inside of the tower was adjusted to 100 mm/g. First, 90 g of the low boiling point fraction was taken at a reflux ratio of 20, and then 210 g of dimethylamino as a product fraction was taken. Ethanol was collected. The purity of this recovered liquid was 98.5%.

Comparative Example 2 300 g of the same reaction synthesis liquid as used in Example 1 was charged into a distillation column similar to that in Example 1, and the inside of the column was heated to 110011II.
The temperature was maintained at IIH, and 90 g of water and a low boiling point fraction were collected at a reflux ratio of 20, and then 210 g of a product fraction was collected.

This product had an APHA of 5 at the time of distillation, but after one day of storage under a nitrogen seal at room temperature, the product became significantly colored and had an APHA of 50 or more.

Example 2 A reaction synthesis liquid having the following composition was used and a distillation tower similar to that in Example 1 was used for treatment.

DMA: 29.8 wt% EO: 1.2 wt% CH2OH: 19.5 wt% Low boiling point: 0.2 wt% DM OH: 48.3 ht% EGMME: 0.1 wt % High boiling content: 0.9 wt% ether 500 g of the synthetic solution having the above composition was charged into a distillation tower and treated at normal pressure to recover 145 g of dimethylamine.

Thereafter, the inside of the column was adjusted to 100 mmHg, and 33.5 g of low-boiling substances including dimethylaminoethanol were recovered. This recovered liquid contained 69% by weight of dimethylaminoethanol. 2.5 g of 5% Ru carbon-supported catalyst was added to this recovered liquid, and while stirring,
G for 3 hours. After cooling, 300 g of the treated liquid from which the catalyst was filtered was charged into the above-mentioned distillation tower, and 95 g of a low boiling point fraction containing methanol was collected at normal pressure, and then heated at 100 mmH.
195 g of product dimethylaminoethanol was recovered. The purity of this recovered liquid was 99.9%. Further, the APHA of this product at the time of distillation was 5 or less, and no coloration was observed over time after storage for one month.

Example 3 A similar synthesis liquid was purified using the same apparatus as in Example 1, except that 2.5 g of 5% Pd supported on carbon catalyst was used as a catalyst. The purity of the recovered liquid was 99.9%, and the A P HA at the time of distillation of the product was about 5th. No coloration over time was observed after storage for one month.

Example 4 A similar synthesis liquid was purified using the same apparatus as in Example 1, except that 2.5 g of 5% Pt carbon-supported catalyst was used as a catalyst. The purity of the recovered liquid was 99.9χ, and the A P HA at the time of distillation of the product was 5th. No coloration over time was observed after storage for one month.

Patent applicant: Mitsubishi Gas Chemical Co., Ltd. Agent Patent Attorney (9070) Paige Kobori Procedural amendment Mu month 1α day, 1986

Claims (6)

[Claims] (1) In purifying dialkylaminoethanol synthesized from dialkylamine and ethylene oxide, first remove substances with a higher boiling point than dialkylaminoethanol, then in the presence of a hydrogenation catalyst or a dehydrogenation catalyst,
A method for purifying dialkylaminoethanol, characterized by treatment under hydrogen pressure (2) The refining method according to claim 1, wherein the hydrogenation catalyst or dehydrogenation catalyst is at least one selected from group 8 metal catalysts of the periodic table. (3) The refining method according to claim 2, wherein the hydrogenation catalyst or dehydrogenation catalyst is at least one selected from Ru-based, Pd-based, and Rh-based noble metal catalysts. (4) The purification method according to claims 1 to 3, wherein the dialkylaminoethanol is dimethylamino alcohol. (5) The purification method according to claims 1 to 4, wherein the hydrogenation catalyst or dehydrogenation catalyst is a catalyst supported on alumina, silica, diatomaceous earth, or carbon. (6) The purification method according to claims 1 to 5, wherein the hydrogen pressure is 3 to 50 kg/cm^2G.