JP2526611B2 - Purification method of dialkylaminoethanol - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for purifying dialkylaminoethanol. More specifically, the present invention is a method for efficiently obtaining dialkylaminoethanol, which is less colored over time, and particularly dimethylaminoethanol, with high purity, in which a substance having a boiling point higher than that of dialkylaminoethanol is first removed, and then a hydrogenation catalyst or This is a method of treating under a pressure of hydrogen in the presence of a dehydrogenation catalyst.

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

[Prior art and its problems]

As the dialkylaminoethanol, dimethylaminoethanol will be described below as an example. Dimethylaminoethanol is synthesized by the reaction of dimethylamine and ethylene oxide. Generally, it is easily synthesized by introducing ethylene oxide in a liquid or gaseous form into liquid anhydrous dimethylamine. At this time, it is also known that the use of water or a lower aliphatic alcohol (for example, methanol) as a reaction solvent significantly accelerates the synthetic reaction. Further, a method for efficiently synthesizing without using a reaction solvent is also known. However, in addition to dimethylaminoethanol, which is the target substance, the product obtained by either method is, for example, unreacted dimethylamine or ethylene oxide,
Alternatively, it contains a side reaction product and further a reaction solvent and the like.

Such a synthetic solution is separated and purified by a normal operation such as a distillation operation to obtain a product. However, although the purity itself can be increased by rigorously performing such a refining operation, it is inevitable that the product is colored over time. Several methods have been proposed as methods for preventing this coloring, particularly over time coloring. For example, Japanese Patent Publication No. 10648/1974 proposes a method of adding nitric acid or its ammonium salt or a nitrate of amine to the reaction solution for aging, and then separating the dialkylaminoalkanol. However, in this method, additives may remain in the product, and complicated distillation and purification operations are required to obtain a highly pure product. Further, JP-A-54-24807 proposes to treat the reaction solution at a high temperature of 180 to 280 ° C. for several hours to several tens of hours, but dimethylaminoethanol is treated at such a high temperature for a long time. There is a risk that the product may decompose and the yield of the desired product may decrease. JP 50
JP-A-146406 proposes a method of heat-treating an amino alcohol containing tertiary nitrogen in the presence of an inorganic acid and a compound having an imidazole ring. However, in this case as well, the compound added in the product may remain, and complicated distillation and purification operations are required to obtain a highly pure product. Furthermore, Japanese Examined Patent Publication No. 52-28770 proposes to decolorize higher alkanolamines by heat treatment under hydrogen pressure using a Ni-based or Co-based hydrogenation catalyst or dehydrogenation catalyst. ing. When the product of interest as in the method described in JP-B-52-28770 is heat-treated under hydrogen pressure using a direct hydrogenation catalyst or a dehydrogenation catalyst, dimethylaminoethanol is decomposed or a coloring component is produced. The hydride of ## STR3 ## remains in the product, and a more complicated purification operation such as distillation is required after the treatment. For example, when treated with a Ru-based catalyst as a hydrogenation catalyst or a dehydrogenation catalyst, dimethylamine, ethanol, high boiling substances, etc. are produced. On the other hand, according to the method described in JP-B-52-28770, it is considered that the reaction synthesis liquid is directly treated with a hydrogenation catalyst or a dehydrogenation catalyst, and then a sufficient separation operation is performed by ordinary distillation or the like. The compound that cannot be separated from the target product, dimethylaminoethanol, remains and the purity of the product cannot be improved.

In recent years, there has been a demand for high-purity products with little coloring, particularly coloring with time, in the industry, and the above-mentioned requirements cannot be satisfied by the conventional refining methods as described above, and if operations such as distillation are not sufficiently performed. I won't.

An object of the present invention is to efficiently obtain a product having high purity and little coloring with time, without the need for complicated operations as described above.

[Means for solving problems]

As a result of intensive studies to solve the above problems, the present inventors have found that a compound that is difficult to separate by a normal separation operation such as distillation has a boiling point higher than that of dimethylaminoethanol in the reaction synthesis liquid. It has been found that a certain compound contained in the substance is produced along with the operation of the hydrogenation reaction, and the present invention has been completed.

That is, in the present invention, when purifying a dialkylaminoethanol synthesized from dialkylamine and ethylene oxide, first, a substance having a higher boiling point than dialkylaminoethanol is removed, and then a Ru-based, Pd-based or Ph-based precious metal catalyst is used. A method for purifying dialkylaminoethanol, which comprises treating under pressure of hydrogen in the presence of at least one selected hydrogenation catalyst or dehydrogenation catalyst.

The method of the present invention is particularly effective for the purification of dimethylaminoethanol, and can obtain a product of dimethylaminoethanol having a high purity and efficiency, which is unprecedented, and less coloring with time.

As described above, the method of the present invention is to remove the high-boiling substance in the reaction synthesis solution first, but for this removal, general techniques such as ordinary distillation are applied as they are. In the present invention, the removal rate of the high-boiling substance is generally difficult to determine in relation to the type of the high-boiling substance in the reaction synthesis solution, the selectivity of the synthetic reaction, the separation ability, etc. The loss of dimethylaminoethanol in the treatment liquid may be removed at a rate within the range of 1 to 20% by weight.

The hydrogenation or dehydrogenation catalysts used to carry out the process of the invention are then Ru-based, Pd-based and Rh-based noble metal catalysts. These catalysts are used as oxides or as a simple substance, and if desired, alumina, silica,
It is used by being carried on a commonly used carrier such as diatomaceous earth and carbon. In this case, the supported amount is generally 10% by weight or less, preferably 0.3 to 7% by weight, as a metal, with respect to the carrier. The catalyst amount 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 for the flow type, and 30 to 250 minutes for the batch type. If the contact time is too short, the treatment is not sufficient and the coloring substance remains, and if it is too long, the decomposition of the target substance becomes remarkable, which is not preferable. The hydrogen pressure is 3 to 50 kg / cm ² G, but usually 5 to 1
It is 5 kg / cm ² G. The hydrogen used does not necessarily have to be of high purity and may be industrially widely used.

The reaction temperature at the time of contact with the catalyst varies depending on the hydrogen pressure, the amount of the catalyst, the contact efficiency, etc., but is generally 50 to 180 ° C.
However, it is advantageous to carry out at a temperature of around 80 to 120 ° C. If the temperature is higher than 180 ° C., the desired product, dimethylaminoethanol, is easily decomposed, which is not preferable.

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

In the method of the present invention, after treatment under hydrogen pressure in the presence of a hydrogenation catalyst or a dehydrogenation catalyst, the liquid to be treated is highly pure by removing low boiling components and the like by ordinary distillation means, and colored with time. It is possible to obtain a product with very few

The liquid to be treated after being treated under pressure of hydrogen in the presence of a hydrogenation catalyst or a dehydrogenation catalyst is directly subjected to the next step when a fixed bed catalyst layer is used, and when it is other than a fixed bed, for example, such as filtration. After removing the catalyst by a normal separation operation, it is desirable to shift to the next step.

〔The invention's effect〕

As described above, the present invention is an industrially very significant method because it can efficiently obtain a product with high purity and little coloring with time without requiring a complicated distillation operation.

 Examples of the present invention will be described below.

Example 1 Using a batch reactor, dimethylamine and ethylene oxide were reacted with an aqueous solvent to recover excess dimethylamine to obtain crude dimethylaminoethanol. The composition of this reaction synthesis liquid contained 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.

500 g of the above reaction synthesis solution was supplied to a distillation column in which a 1/4 inch size McMahon packing was irregularly packed in a cylindrical column with an inner diameter of 35.5 mm to a height of 1 m, and the pressure in the distillation column was reduced to 100 mmHg. 450 g of a low boiling point component containing aminoethanol was recovered. This recovered liquid contained 77.8% 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 with stirring at 100 ° C. and a hydrogen partial pressure of 10 kg / cm ² G for 3 hours. After cooling, the treated liquid obtained by filtering off the catalyst 300 g was charged to the distillation column described above and the inside of the column was set to 100 mmHg, and 90.4 g was taken as water and a low boiling point fraction at a reflux ratio of 20 and then 210 g as a product fraction.
Of dimethylaminoethanol was recovered. The purity of this recovered liquid was 99.9%. The APHA of this product at the time of distilling was 5 or less, and no coloration over time after storage for 1 month was observed.

Comparative Example 1 5% Ru was added to 400 g of a reaction synthesis solution similar to that used in Example 1.
Add 3.5g of carbon-supported catalyst, stir at 100 ℃, hydrogen partial pressure of 10k
It was treated with g / cm ² G for 3 hours. After cooling, 300 g of the treatment liquid obtained by filtering off the catalyst was charged into the same distillation tower as in Example 1 and the inside of the tower was 100 mmH.
First, 90 g was taken as a low boiling point fraction with a reflux ratio of 20 as g, and then 210 g of dimethylaminoethanol was recovered as a product fraction. The purity of this recovered liquid was 98.5%.

Comparative Example 2 300 g of a reaction synthesis liquid similar to that used in Example 1 was charged into a distillation column similar to that of Example 1, the inside of the column was maintained at 100 mmHg, water and a low boiling point fraction of 90 g were taken at a reflux ratio of 20, and then 210 g of product fraction was collected. This product had an APHA of 5 at the time of distilling, but it was markedly colored after 1 day storage at room temperature under a nitrogen blanket, and APHA was 50%.
That's it.

Example 2 A reaction synthesis liquid having the following composition was used, and treatment was performed using the same distillation column as in Example 1.

Composition of reaction synthesis liquid DMA: 29.8 wt% EO: 1.2 wt% CH ₃ OH: 19.5 wt% Low boiling point: 0.2 wt% DMOH: 48.3 wt% EGMME: 0.1 wt% High boiling point: 0.9 wt% Note) DMA: Dimethyl Amine, EO: ethylene oxide, DMOH: dimethylaminoethanol, EGMME: ethylene glycol monomethyl ether 500 g of the synthetic solution having the above composition was charged into a distillation column and treated at atmospheric pressure to recover 145 g of dimethylamine. After that, 100 mmH in the tower
Low boiling point substance containing dimethylaminoethanol as g 33.5 g
Was recovered. The recovered liquid contained 69% by weight of dimethylaminoethanol. 2.5 g of 5% Ru carbon-supported catalyst was added to this recovered liquid, and the mixture was stirred at 100 ° C. and the hydrogen partial pressure was 10 kg / cm ² G.
Was treated for 3 hours. After cooling, the treatment liquid obtained by separating the catalyst by filtration 30
0 g was charged into the above-mentioned distillation column and 95 g of a low boiling point fraction containing methanol was taken at normal pressure and then distilled at 100 mmHg to recover 195 g of dimethylaminoethanol product. The purity of this recovered liquid was 99.9%. Further, the APHA of this product at the time of distilling was 5 or less, and no coloring with time after storage for 1 month was observed at all.

Example 3 A similar synthesis solution was purified by the same apparatus as in Example 1 except that 2.5 g of a 5% Pd-carbon-supported catalyst was used as the catalyst. The purity of the recovered liquid was 99.9%, and APHA at the time of distilling the product was 5 or less. No coloration with time after storage for one month was observed.

Example 4 A similar synthesis solution was purified by the same apparatus as in Example 1 except that 2.5 g of a 5% Pt carbon-supported catalyst was used as the catalyst. The purity of the recovered liquid was 99.9%, and APHA at the time of distilling the product was 5 or less. No coloration with time after storage for one month was observed.

Claims (4)

(57) [Claims] 1. When purifying a dialkylaminoethanol synthesized from a dialkylamine and ethylene oxide, first, a substance having a higher boiling point than that of the dialkylaminoethanol is removed, and then a noble metal catalyst of Ru type, Pd type and Ph type is used. A method for purifying dialkylaminoethanol, which comprises treating under pressure of hydrogen in the presence of at least one selected hydrogenation catalyst or dehydrogenation catalyst. 2. The method for purifying dialkylaminoethanol according to claim 1, wherein the dialkylaminoethanol is dimethylaminoethanol. 3. The method for purifying dialkylaminoethanol according to claim 1 or 2, wherein the hydrogenation catalyst or dehydrogenation catalyst is a catalyst supported on alumina, silica, diatomaceous earth, or carbon. 4. The method for purifying dialkylaminoethanol according to claim 1, wherein the hydrogen pressure is 3 to 50 kg / cm ² G.