JPH0456820B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently decarboxylating an aqueous solution of ethyleneamine carbonates. More specifically, the present invention relates to a method for decarboxylating an aqueous solution of ethyleneamine carbonate, which is characterized by adding alcohol and/or cyclic ether to the aqueous solution of ethyleneamine carbonate and decomposing it by heating.

In the present invention, ethyleneamines include chain-like ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, tris-(2-aminoethyl)-amine, piperazine, and N-aminoethylpiperazine. , a single amine or a mixture of amines including cyclic ethylene amines.

These ethyleneamines are used in a wide range of fields as main raw materials, auxiliary raw materials, or additives. For example, it is used for agricultural chemicals, paper strength enhancers, epoxy curing agents, lubricating oil additives, polyamides, etc.

Further, these ethyleneamines are mainly produced by the following two methods, but the ethyleneamines referred to in the present invention are not limited to those produced by these methods.

(a) EDC method: Ethylene dichloride (EDC) and ammonia are reacted under high temperature and pressure to produce hydrochloride of ethyleneamines, and the hydrochloride is metathesized with caustic soda to separate by-product sodium chloride.

(b) MEA method: Monoethanolamine (MEA) and ammonia are reacted under high temperature and pressure in the presence of a hydrogen catalyst to obtain ethyleneamines.

Ethylene amine carbonates are produced during the process of producing ethylene amines, or when ethylene amines are used in a reaction, when unreacted ethylene amines are treated with carbon dioxide and recovered as carbonates of ethylene amines. etc. to generate it.

For example, Japanese Patent Application No. 57-130482 (Tokukō 2-
No. 20622), ethylene amines are selectively extracted from an aqueous solution containing ethylene amines using an organic solvent, and ethylene amines are extracted from the organic phase using carbon dioxide gas or carbonated water. Produced when recovered as carbonate.

The ethyleneamine carbonate of the present invention is basically a reaction product of ethyleneamine and carbon dioxide, and is sometimes called a carbamate of ethyleneamine.

These ethyleneamine carbonates are rarely made into products as they are, and in many cases they are commercialized and sold as ethyleneamines. Therefore, the carbonate of ethyleneamines must be converted into ethyleneamines by removing the carbonate radical.

One possible method for this is to add a strong alkaline agent such as sodium hydroxide or calcium hydroxide to cause double decomposition and separate the by-products of sodium carbonate and calcium carbonate. however,
This method is not economical because it consumes a large amount of strong alkaline agent.

Therefore, the present inventors have conducted various studies on methods that completely convert ethyleneamine carbonates into ethyleneamines, which is economical and easy to operate. As a result, we learned that ethyleneamine carbonate decomposes into ethyleneamines when heated. However, it was found that heating alone could not completely decompose the substance, so further studies were conducted.

As a result, they discovered that complete decarboxylation can be achieved by the presence of alcohol and/or cyclic ether during thermal decomposition of an aqueous solution of ethyleneamine carbonate, and completed the present invention.

That is, the present invention resides in a method for decarboxylating ethyleneamine carbonates, which is characterized by adding alcohol and/or cyclic ether to an aqueous solution of ethyleneamine carbonates and decomposing them by heating.

The present invention will be explained in more detail below.

Ethyleneamine carbonate aqueous solution is decomposed by heating. The decomposition is easier as the concentration is lower, the temperature is higher, the ratio of secondary and tertiary amines to the total amino groups in the molecule is larger, and the higher the molecular weight of ethylene amines. However, complete decarboxylation is difficult. For example, the decomposition rate of 30 g of ethylenediamine carbonate as ethylenediamine under normal pressure is approximately 80%. If the concentration is lowered, decarboxylation will progress further, but a large amount of subsequent concentration energy will be required, and even in that case, complete decarboxylation will not be possible, resulting in poor quality.

However, during thermal decomposition, alcohol and/or
Alternatively, when a cyclic ether is present, almost complete decarboxylation can be achieved. It is understood that the action of alcohol is that the alcohol vapor lowers the partial pressure of carbon dioxide gas and promotes decarboxylation. As the alcohol, n-propanol and alcohol having 4 to 6 carbon atoms are preferable.
These alcohols do not completely dissolve in the ethyleneamine carbonate aqueous solution and form two liquid phases.

When the alcohol phase and the ethyleneamine carbonate aqueous solution phase were extracted during the thermal decomposition and both phases were analyzed, it was found that free ethyleneamines generated by the thermal decomposition were selectively extracted into the alcohol phase. This fact suggests that these alcohols were particularly effective. Alcohols lower than this dissolve. Further, alcohols having a carbon number larger than 6 have a small effect of selectively extracting free ethyleneamines.

As the cyclic ether, 1,4 dioxane, 1,
3-dioxane is preferred. Chained ether has no effect. The effect of cyclic ether is to lower the partial pressure of carbon dioxide gas, similar to that of alcohol.

However, an even more significant effect is the effect of lowering the pH of the ethyleneamine carbonate aqueous solution by adding it. It is inferred that decarboxylation progresses more as the pH decreases. Also in this case, two liquid phases are formed, and free ethyleneamines are extracted into the cyclic ether phase.

Further, it is preferable that the thermal decomposition temperature is set to the boiling point. If it is carried out at the boiling point, the alcohol and/or cyclic ether will be vaporized together with water and carbon dioxide gas, but it is sufficient to condense everything other than carbon dioxide gas in a reflux vessel.

That is, a total reflux method may be used. The pressure may be normal pressure, reduced pressure, or increased pressure. Alcohol and cyclic ether may be used in combination. The larger the amount of alcohol and/or cyclic ether used, the easier decarboxylation will be.

However, considering the equipment capacity and later separation from ethyleneamines, it is desirable that the capacity be 0.2 to 5 times that of the ethyleneamines carbonate aqueous solution.
In particular, 0.5 to 2 times the capacity is desirable.

Further, the aqueous solution of ethyleneamine carbonate is desirably 200 to 800 g of ethyleneamine.

In the above manner, ethyleneamines are almost completely decarboxylated.

If the aqueous solution of ethylene amines containing alcohol and/or cyclic ether obtained by decarboxylation forms two phases, the phases should be separated, and the dissolved alcohol and/or cyclic ether should be separated by distillation. good. At this time, since alcohol and/or cyclic ether and water usually undergo azeotropy, a concentrated aqueous solution of ethyleneamines is obtained. In the case of a homogeneous phase, only distillation is sufficient. The distilled alcohol and/or cyclic ether may be recycled as is to the thermal decomposition step, or may be recycled after being condensed and water is phase-separated.

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

Example 1 Ethylenediamine (EDA): 325g/,
_CO2 : 250ml of 238g/238g ethylenediamine carbonate aqueous solution and 250ml of 1,4 dioxane were placed in a round bottom flask equipped with a reflux device, and heated under total reflux for 5 hours at the boiling point (91.5°C) using a mantle heater as the heating source. When decomposed, 97% of CO ₂ could be removed.

Example 2 The same procedure as in Example 1 was repeated except that 250 ml of n-butanol was used instead of 1,4-dioxane. The boiling point was 104°C and CO ₂ was reduced to 95°C.
% could be removed.

Comparative Example 1 When the same procedure as in Example 1 was performed except that 1,4 dioxane was not added, the CO ₂ removal rate was
It was 77%. The boiling point was 108°C.

Example 3 EDA: 171g/, piperazine: 6g/, diethylenetriamine: 77g/, N-aminoethylpiperazine: 11g/, triethylenetetramine: 46g/, tetraethylenepentamine: 21
g/, pentaethylenehexamine: 16 g/,
250 ml of an aqueous solution of 217 g/CO ₂ and 125 ml of 1,4 dioxane were placed in a 500 ml round bottom flask and operated in the same manner as in Example 1. The boiling point was 92°C, and the CO ₂ removal rate was 99.6%.

Claims (1)

[Scope of Claims] 1. A method for decarboxylating an aqueous solution of ethyleneamine carbonate, which comprises adding alcohol and/or cyclic ether to the aqueous solution of ethyleneamine carbonate and decomposing it by heating. 2. The method according to claim 1, wherein the alcohol is one or more alcohols selected from n-propanol and alcohols having 4 to 6 carbon atoms.