JPH0220622B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for efficiently recovering ethyleneamines as a highly concentrated aqueous solution from an organic phase containing them. More specifically, for example, a reaction solution obtained by the reaction of ethane dichloride and aqueous ammonia, or a solution obtained by causticizing the reaction solution with an alkali such as sodium hydroxide or calcium hydroxide, is used in a solvent such as cyclohexanone. The present invention relates to a method for efficiently recovering ethyleneamines as a highly concentrated aqueous solution from an organic phase obtained by selectively extracting ethyleneamines. In the present invention, ethylene amines refer to amines including linear and cyclic amines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and piperazine, either singly or in mixtures. As mentioned above, ethyleneamines have at least two or more amino groups in their molecules, so they are extremely hydrophilic in nature, and solvents commonly used in extraction methods do not allow the aqueous phase to flow into the organic phase. It is substantially difficult to move. However, the present inventors have discovered that ethylene amines can be extracted selectively and efficiently into the solvent phase by using a specific organic solvent, and that specific organic solvents include, for example, carboxylic acids having 6 or more carbon atoms, cyclohexanone, etc. , aliphatic ketones such as cyclopentanone,
Furthermore, it was discovered that there are pendyl alcohols and the like. It is not clear why ethyleneamines are easily extracted when such a specific organic solvent is used, but it is possible that the organic solvent and the amino group of ethyleneamines form an adduct or interact with each other. It is presumed that this was achieved by softening the hydrophilic action of the amino groups and changing the ethyleneamines to be organophilic (hereinafter referred to as the property of being easily transferred to the organic solvent phase). Ethylene amines extracted into the solvent phase by such an extraction mechanism that involves a certain kind of chemical reaction are made organophilic, so when recovering ethylene amines from the solvent phase, ordinary back extraction is required. In the method, i.e., the method of contacting the solvent phase with water,
Ethyleneamines cannot be recovered. Therefore, in order to recover ethyleneamines from the solvent phase mentioned above, it is necessary to use an acid instead of water to form a salt of ethyleneamines and transfer it from the organic phase to the aqueous phase. . This method is very effective when the final target is a salt of ethylene amines, but when the target is free ethylene amines (which is usually the case), the recovered ethylene This is not preferable since it is necessary to causticize the amine salt with an alkali such as sodium hydroxide or calcium hydroxide and to separate the by-product sodium salt and calcium salt. Under these circumstances, the present inventors have repeatedly studied methods that do not require the supply of alkali necessary for causticization and the separation of by-product salts. The present invention was achieved by discovering that free ethyleneamines can be easily obtained by recovering ethyleneamines as carbonates and then thermally decomposing the carbonates. That is, the present invention involves selectively extracting ethyleneamines from an aqueous solution containing ethyleneamines using an organic solvent. After recovering the carbonate as a salt, the carbonate is thermally decomposed to obtain free ethyleneamines. The present invention will be explained in more detail below. As mentioned above, it is not possible to selectively extract ethyleneamine from a mixture of ethyleneamines and chlorides using ordinary organic solvents, but certain solvents, such as amino groups and adducts of ethyleneamines or have already proposed that ethyleneamines can be extracted very efficiently and selectively by using an organic solvent that has an ability to interact with adducts. For example, cyclohexanone is a solvent with a ketone group. It is thought that cyclopentanone, acetone, methyl ethyl ketone, etc. can be used as extraction solvents in this type of mechanism. As can be easily imagined from the fact that such adducts or intermediates are extremely easily extracted into the solvent phase, they are extremely stable in organic solvents;
Ethyleneamines have low solubility in water, and cannot be recovered by methods such as distillation of the organic phase or fusion of the organic phase with water. Therefore, in order to recover ethyleneamines, it is necessary to use a reagent, such as an acid, which binds more strongly to the amino group than the above-mentioned solvents and makes the product water-soluble. In the present invention, it is essential to use carbon dioxide gas or carbonated water as the acid for recovering ethyleneamines from the solvent phase. As is clear from the above explanation, ethyleneamines extracted into the solvent phase by an extraction mechanism using a chemical reaction are recovered as ethyleneamine salts from the organic phase, so it is difficult to obtain free ethyleneamines. In this case, it is necessary to add an alkali to the salt to make it caustic, and to remove the by-product salt at this time. However, in the method of the present invention, a preferable method that does not require causticization by addition of alkali and separation of by-product salts can be adopted. That is, the present inventors discovered that ethyleneamine carbonate is a thermally unstable compound,
As a result of studying the thermal decomposition of carbonates, it was found that, for example, in the case of ethylene amine, the carbonate decomposes as shown in the following formula, carbon dioxide gas evaporates, and free ethylene amines can be easily recovered. (CH ₂ NH ₂ ) ₂ H ₂ CO ₃ → (CH ₂ NH ₂ ) ₂ +CO ₂ ↑+H ₂ O Therefore, in the present invention, it is also an essential requirement to heat-treat the recovered carbonate of ethyleneamines. Become. The aqueous solution containing ethyleneamines in the present invention is not limited, but is usually a mixed solution of ethyleneamine hydrochloride, ammonium chloride, and free ammonia produced by the reaction of ethane dichloride and aqueous ammonia, or The main targets are solutions obtained by causticizing ethyleneamine hydrochloride by adding an alkali such as calcium hydroxide or sodium hydroxide to the mixed solution, as well as low-concentration amine aqueous solutions generated in various processes. In an aqueous solution containing such ethyleneamines,
Ethylene amines and a reactive organic solvent are mixed and allowed to settle to extract ethylene amines into an organic phase. Any organic solvent may be used as long as it interacts with ethyleneamines, such as benzyl alcohol, which has an unknown intermediate composition but is known to interact with ethyleneamines, in addition to solvents with ketone groups. , carboxylic acids that form organic salts with ethyleneamines, etc. Generally, carboxylic acids commonly used as extractants can be used, such as those having 6 or more carbon atoms, preferably 9 to 20 carbon atoms, such as naphthenic acid, pelargonic acid, etc.
Also, there is Versatic acid (trade name, manufactured by Ciel Chemical Co., Ltd.), which is a tertiary fatty acid. That is, the "organic solvent" referred to in the present invention is
It is an organic solvent that can extract ethyleneamines extremely efficiently and selectively, and in addition, it has the property that ethyleneamines cannot be separated from the organic phase by contact with water. This is a solvent whose mechanism can be inferred to be due to some kind of reactivity. Of course, the solvents used in the present invention can be used alone, but they can also be used in combination. In addition, solvents such as butyl alcohol and amyl alcohol, which cannot extract ethylene amines by themselves, are used.
The method of using a mixture of 30 to 90% by volume is also easy to handle,
This is a preferred method because it can improve phase separation properties and, in some cases, improve extractability. Extraction conditions vary depending on the type of solvent used, the ethyleneamine concentration, the mixing ratio of solvents, etc., and cannot be unconditionally defined, but usually under conditions of room temperature and normal pressure.
When the volume ratio of the solvent to the aqueous solution containing ethyleneamines is 1:1 to 10:1 and the number of extraction stages is 2 to 4, the ethyleneamines in the aqueous solution can be extracted substantially completely. The solvent phase thus obtained generally contains 50 to 300 g of ethylene amines. This solvent phase is transferred directly or after contacting with a small amount of water to remove a small amount of inorganic salt co-extracted into the solvent phase, to the ethyleneamine recovery step. In the recovery step, the organic phase containing ethyleneamines is brought into contact with carbon dioxide gas or carbonated water to form carbonates of ethyleneamines. This reaction progresses very quickly, so it does not pose any operational problems; however, if the solvent phase is brought into direct contact with carbon dioxide gas, extremely fine carbonate crystals of ethyleneamines will precipitate, increasing the viscosity. However, since contact with carbon dioxide gas tends to be poor, a more preferable method is to bring it into contact with carbon dioxide gas in the coexistence of water and recover it as an aqueous carbonate solution of ethyleneamines. There are no restrictions on the contact method, but the air lift method that simultaneously supplies a solvent phase containing ethylene amines, water, and carbon dioxide gas, or carbonated water in which carbon dioxide gas is dissolved in water under pressure in advance. A preferred form is a mixture of the solvent phase and the solvent phase. After the reaction, the mixed solution is stabilized and separated into an aqueous phase and a solvent phase. The carbonate of ethylene amines is not substantially dissolved in the solvent phase, and the entire amount is recovered as an aqueous solution, and the concentration of ethylene amines varies depending on the amount of water used, but is at least 200 g/min. The separated solvent phase is recycled as an extraction solvent for ethylene amines, and the aqueous phase is sent to the decarboxylation process. The carbon dioxide gas used in the recovery process can range from nearly 100% concentrated gas, which is a by-product of ammonia synthesis and petrochemistry, to 40% gas obtained from lime furnaces, but most of the carbon dioxide gas used in this process is The carbon dioxide gas supplied to the recovery process is
Even if the carbon dioxide gas supplied from outside the system is dilute, high concentration carbon dioxide gas can actually be used. Furthermore, since the amount of carbon dioxide consumed is small, the method of the present invention can be fully implemented even without a source of carbon dioxide such as a lime furnace. In the decarboxylation process, the purpose is achieved simply by heating the aqueous solution of ethylene amine carbonate at normal pressure, so no special equipment or operations are required.
Thermal decomposition temperature is usually 60~120℃, preferably 80~120℃
℃, the carbonate decomposes very efficiently and produces carbon dioxide gas. The decarboxylation rate varies somewhat depending on the ethylene amine concentration supplied, treatment temperature, and reaction time, but if the ethylene amine concentration is 200 g/1 at the boiling point and under decomposition conditions for 1 hour, the decarboxylation rate will be 90% of the supplied carbon dioxide. % or more, 80% or more can be removed at 300g/. Furthermore, when an organic solvent such as butyl alcohol is mixed, the decarboxylation rate is further improved and substantially all of the carbon dioxide gas can be removed. As mentioned above, in the present invention, a solvent reactive with ethylene amines and a solvent such as butyl alcohol can be used in combination, and butyl alcohol has the property of being soluble in water to some extent. Therefore, the aqueous solution of ethylene amine carbonates obtained in the recovery process generally contains a portion of a solvent such as butyl alcohol, which makes carbon dioxide removal effective in the decarboxylation process. . The free aqueous solution of ethyleneamines thus obtained usually contains 200 g/or more of ethyleneamines. If this aqueous solution of ethyleneamines contains a small amount of carbonate, it can be removed as sodium carbonate or calcium carbonate by adding a small amount of sodium hydroxide, calcium hydroxide, or the like. When sodium hydroxide is used, two phases, an aqueous sodium carbonate solution phase and an ethyleneamine phase are formed, so this is an industrially preferred method. The aqueous solution of ethylene amines obtained by the method of the present invention has a high concentration of 300 g/or more and contains almost no components other than ethylene amines and water, so various ethylene amines can be easily extracted by ordinary distillation operations. Obtainable. The advantages of the method of the present invention are listed below: (1) Ethylene amines can be concentrated in an extremely energy-saving operation. The concentration of ethyleneamines obtained by normal methods is about 100g/300g/
In order to heat and concentrate the ethylene amines, it is necessary to remove 6 times the weight of water based on the weight of ethyleneamines. (2) Since chloride ions can be separated by extraction method,
Does not require the use of expensive sodium hydroxide,
Calcium hydroxide, which is inexpensive, can be used. (3) It is extremely economical as it does not require acid in the recovery process or alkali to decompose the salts produced. (4) It is a simple process that does not require special equipment or operations unlike conventional methods such as crystallization and separation of sodium chloride. (5) A product of extremely high purity can be obtained. etc. Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. Examples 1 to 4 200 ml of an n-butanol mixture containing 67 ml of cyclohexanone was added to 200 ml of an aqueous solution containing 18.0 g of ethylene amines and 36.0 g of sodium chloride (NaCl), and after shaking for 10 minutes, static separation was performed. Next, 20 ml of pure water was added to 160 ml of the organic phase obtained by static separation, and 100 ml of water-saturated carbon dioxide was added to the organic phase.
The mixture was blown for 2 hours at a rate of 10 min, and the ethylene amines in the organic phase were back-extracted into the aqueous phase as carbonates, followed by static separation. Next, 20 ml of the aqueous phase obtained by static separation was put into a 50 ml three-necked round-bottomed flask equipped with a condenser, heated with a mantle heater, and carbonated with ethylene amines by total reflux method at the boiling point. Thermal decomposition of was carried out for 2 hours, and the results shown in Table 1 were obtained. Example 5 Aqueous solution of TETA: 106g/, Nacl: 225g/

[Table] Add 200ml of benzyl alcohol to 2.00ml, shake for 10 minutes, statically separate, and obtain TETA: 55.2g/
228ml of organic phase and TETA: 50.1g/, NaCl262
g/172 ml of aqueous phase were obtained. Next, add 15 ml of pure water to 150 ml of the organic phase,
Water-saturated carbon dioxide gas was blown into the solution at a rate of 100 ml/min for 2 hours for static separation, and the entire amount of TETA was converted into carbonate and back-extracted into the aqueous phase. Furthermore, when 15 ml of the aqueous phase was thermally decomposed in the same manner as in Example 1, TETA: 360 g/, CO ₂ :
18 g/aqueous solution was obtained. Example 6 Aqueous solution of EDA: 90g/, NaCl: 180g/
Add 300 ml of 1.5 mole/n-butanol solution of "Versatic acid-10" (manufactured by Ciel Kagaku Co., Ltd., trade name, carbon number 10) to 200 ml, shake for 10 minutes, statically separate, and EDA: 376 ml of 38.3 g/g organic phase were obtained. Next, 15 ml of pure water was added to 200 ml of the organic phase, and water-saturated carbon dioxide gas was blown in at a rate of 100 ml/min for 2 hours for static separation. EDA: 265 g/min.
:20.4 ml of aqueous phase containing 192 g/CO ₂ was obtained. Furthermore, 15 ml of the aqueous phase was thermally decomposed in the same manner as in Example 1 to obtain an aqueous solution containing 260 g/EDA and 29 g/CO ₂ . Examples 7 to 10 n-butanol mixture containing 67 ml of cyclopentanone in place of cyclohexanone in Examples 1 to 4
The same operations as in Examples 1 to 4 were performed except that 200 ml was used, and almost the same results as in Examples 1 to 4 were obtained. Example 11 A 50% calcium hydroxide cake was added to the reaction aqueous solution obtained by the reaction of ethane dichloride (EDC) and ammonia aqueous solution, and EDA: 65 g/,
DETA: 28g/, TETA: 16g/,
TEPA: 6.0g/, Pentaethylenehexamine (PEHA): 4.0g/, N-aminoethylpiprazine (N-AEP): 4.0g/, CaCl ₂ : 176g/
, NH ₃ :108 g/aqueous solution was obtained. The aqueous solution
Add 200ml of n-butanol mixture containing 67ml of cyclohexanone to 200ml, shake for 10 minutes, statically separate, EDA: 46g/, DETA: 17g/,
TETA: 9.2g/, TEPA: 3.0g/,
230 ml of organic phase containing 2.1 g/PEHA and 1.8 g/N-AEP was obtained. Next, 30 ml of pure water was added to 200 ml of the organic phase, water-saturated carbon dioxide gas was blown in at a rate of 100 ml/min for 2 hours, static separation was performed, and all ethyleneamines were back-extracted into the aqueous phase as carbonates. . Furthermore, 20 ml of the aqueous phase was thermally decomposed in the same manner as in Example 1 to give EDA: 204 g/, DETA: 75 g/
, TETA: 41g/, TEPA: 13g/,
PEHA: 9.3g/, N-AEP: 8.0g/,
An aqueous solution containing 50 g of CO ₂ was obtained. Example 12 Reaction solution obtained by reaction of EDC and ammonia aqueous solution, composition: EDA: 66g/, DETA: 29
g/, TETA: 16g/, TEPA: 6.4g/,
PEHA: 4.3g/, N-AEP: 4.3g/,
HCl: 117 g/, NH ₃ : 164 g/, and 200 ml of the aqueous solution contains n-
Add 200ml of butanol mixture and shake for 10 minutes.
Static separation, EDA: 38.0g/, DETA: 15.3
g/, TETA: 7.4g/, TEPA: 3.1g/
, PEHA: 2.1 g/, N-AEP: 1.4 g/230 ml of organic phase was obtained. Next, 30 ml of pure water was added to 200 ml of the organic phase, water-saturated carbon dioxide gas was blown in at a rate of 100 ml/min for 2 hours, static separation was performed, and all ethyleneamines were back-extracted into the aqueous phase as carbonates. . Furthermore, 20 ml of the aqueous phase was thermally decomposed in the same manner as in Example 1 to give EDA: 175 g/, DETA: 70 g/
, TETA: 34g/, TEPA: 14g/,
PEHA: 9.7g/, N-AEP: 6.4g/,
An aqueous solution containing 35 g of CO ₂ was obtained. Example 13 EDA obtained in Example 1: 335g/,
_CO2 : 240g/into 10ml of an aqueous solution of 56g/
After adding 4.7 ml of NaOH aqueous solution and shaking for 10 minutes,
When statically separated, it contains almost no CO ₂ .
10.8 ml of a 310 g/EDA aqueous solution and 3.9 ml of a 350 g/Na ₂ CO ₃ aqueous solution containing almost no EDA were obtained. Example 14 Reverse extract (EDA:
15 ml of n-butanol was added to 15 ml of 320 g/, _CO2 : 235 g/), and the mixture was thermally decomposed in the same manner as in Example 1.
An aqueous solution of EDA: 325 g/, CO ₂ : 10 g/ was obtained.

Claims (1)

[Claims] 1. Ethylene amines are extracted from an extracted phase obtained by selectively extracting ethylene amines from an aqueous solution containing ethylene amines using an organic solvent, using carbon dioxide gas or carbonated water. A method for recovering ethylene amines from an organic phase, which comprises recovering ethylene amines as carbonates, and then thermally decomposing the carbonates to obtain free ethylene amines. 2. The method according to claim 1, wherein the organic solvent is a mixed solvent. 3. The method according to claim 1 or 2, wherein part or all of the organic solvent is a solvent having a ketone group. 4. The method according to claim 1 or 2, wherein part or all of the organic solvent is benzyl alcohol. 5. The method according to claim 1 or 2, wherein a part of the organic solvent is a carboxylic acid.