JPH0313211B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for efficiently decarboxylating carbonates of ethylene amines by heating to obtain ethylene amines. For more details, see heat decarboxylation.
This invention relates to a method for decarboxylating ethyleneamine carbonates, which is carried out at a high temperature of 120°C or higher. In the present invention, ethyleneamines include chain-like ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, tris-(2-aminoethyl)-amine, piperazine, N-aminoethylpiperazine, etc. , means 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. Examples include agricultural chemicals, paper strength enhancers, epoxy curing agents, lubricating oil additives, and polyamides. 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, and by-product sodium chloride is separated and removed. (b) MEA method: Monoethanolamine (MEA) and ammonia are reacted under high temperature and pressure in the presence of a hydrogen catalyst to obtain ethyleneamines. Carbonates of ethyleneamines are recovered as carbonates of ethyleneamines during the process of producing ethyleneamines or when ethyleneamines are used in reactions, when carbon dioxide is applied to unreacted ethyleneamines and the carbonates of the ethyleneamines are recovered. etc. to generate it. For example, Japanese Patent Application No. 57-130482 (see Japanese Unexamined Patent Publication No. 59-20253)
Ethylene amines are selectively extracted from an aqueous solution containing ethylene amines using an organic solvent, and then ethylene amines are recovered as carbonates from the organic phase using carbon dioxide gas or carbonated water. Generate when. Incidentally, the carbonate of ethyleneamines of the present invention is basically a reaction product of ethyleneamines and carbon dioxide, and is sometimes called a carbamate of ethyleneamines. This carbonate of ethyleneamines may be used as a product as it is. However, since most products are commercialized and sold as ethylene amines, the carbonates of ethylene amines must be decarboxylated. A possible method for this decarboxylation is to add a strong alkaline agent such as sodium hydroxide or calcium hydroxide to double decompose and separate by-products sodium carbonate and calcium carbonate to obtain ethyleneamines. However, this method is not economical because it consumes a large amount of strong alkaline agent. Therefore, the present inventors have investigated various methods for decarboxylation without the use of chemicals such as sodium hydroxide and calcium hydroxide, and for efficient decarboxylation. As a result, we found that carbonates of ethyleneamines can be decarboxylated by heating. However, we learned that with simple heating, as decarboxylation progresses, the rate of decarboxylation slows down and eventually stops with a large amount of carbon dioxide (hereinafter referred to as CO ₂ ) remaining. In particular, this tendency became more pronounced as the concentration of ethyleneamines increased and as the content of ethylenediamine increased. However, the present inventors determined that the heating method could be an excellent method for decarboxylating carbonates of ethylene amines in terms of resource saving and simplification of operation, and conducted further studies. As a result, they discovered that the temperature during thermal decarboxylation is extremely important and that decarboxylation can be carried out efficiently above a certain temperature, and finally completed the present invention. That is, the present invention uses carbonates of ethyleneamines.
A method for decarboxylating carbonates of ethyleneamines, which is characterized by decarboxylating by heating at 120°C or higher. The present invention will be explained in more detail below. As mentioned above, the present inventors have attempted various methods of thermal decarboxylation of carbonates of ethyleneamines. As a result, regarding the carbonate aqueous solution of ethyleneamines,
The lower the concentration and the lower the proportion of primary amines in the amino groups of ethyleneamines, the better the decarboxylation. However, we have learned that decarboxylation becomes more difficult as the concentration increases and as the proportion of primary amines in the amino groups increases, and that decarboxylation is particularly difficult when the ethylene amine is ethylene diamine. The reason why decarboxylation becomes difficult as the concentration increases is estimated as follows. That is, the concentration of free ethylene amines produced by decarboxylation increases, and CO ₂ is retained more strongly, making decarboxylation less likely to proceed. Furthermore, the amino group of ethyleneamines consists of primary amine, secondary amine, and tertiary amine. Among these, primary amines are the most basic.
Therefore, the higher the proportion of primary amines in the amino groups, the more difficult decarboxylation becomes. For these reasons, it seemed impossible to thermally decompose carbonates of ethyleneamines containing ethylenediamine at high concentrations. However, after further investigation, we discovered an interesting fact. When 700g/concentrated aqueous solution of triethylenetetramine carbonate was heated and decarboxylated, almost complete decarboxylation was achieved within a short period of time. From the viewpoint of concentration, there is no way that decarboxylation will progress. This is an effect of temperature, and at this time
It was 122℃. Based on this knowledge, we investigated the effect of temperature on carbonates of various ethyleneamines.
They discovered that decarboxylation can be carried out efficiently if operated at temperatures above 120°C. If the temperature cannot be raised to 120°C or higher under normal pressure, apply pressure. Initially, pressurization would raise the temperature, but there was concern that the partial pressure of carbon dioxide would increase, making decarboxylation more difficult. However, the reality is different; decarboxylation progressed more because of the effect of the rise in temperature than the negative effect of pressurization. We infer the effect of this temperature as follows. Dissociation constant (Ka) of ethyleneamines
Generally, the PKa value decreases little by little as the temperature increases. This means that the basicity is weakened. This PKa value suddenly decreased around 120°C, and ethyleneamines began to act as a very weak base, which is probably why decarboxylation progressed. That is, the present invention uses carbonates of ethyleneamines.
It is an essential requirement to heat decarboxylation at 120℃ or higher. Ethyleneamines include ethylenediamine, diethylenetriamine, triethylenetetramine,
It means a single amine or a mixture of amines including tetraethylenepentamine, pentaethylenehexamine, and linear and cyclic ethyleneamines such as tris-(2-aminoethyl)-amine, piperazine, and N-aminoethylpiperazine. When the ethyleneamine is other than ethylenediamine (hereinafter referred to as polyamine), there is no particular need to pressurize it, and if it is a highly concentrated aqueous solution of 600g/or more, it can be heated to 120°C or higher at normal pressure. And the carbonate is 1
Almost complete decarboxylation can be achieved by heating in about an hour. If the concentration is low and the boiling point cannot be raised above 120°C, complete decarboxylation cannot be achieved. In this case, pressurize to 120℃
It is sufficient to do the above, and it can be almost completely decomposed within one hour. 120℃ or higher at gauge pressure 1Kg/ ^cm2 , 2Kg/cm2
Can be heated to 135℃ or higher in ^cm2 . From these, concentration 600
g/ or more, it can be seen that pressurized decarboxylation at normal pressure is advantageous in terms of simplifying the apparatus and reducing concentration costs. This is truly unique in light of the general knowledge that if the equipment can be simplified, the concentration cost will increase, and if the concentration cost is reduced, the equipment will become complicated. Ethylenediamine is the most basic among ethyleneamines, and it is difficult to thermally decarboxylate carbonates of ethyleneamines including ethylenediamine. However, decarboxylation can proceed by increasing the temperature to 120°C or higher. The decarboxylation rate varies depending on the concentration of ethylene amines and the ethylene diamine content, but in decarboxylation of an aqueous solution of 200 g of ethylene diamine carbonate, the boiling point at normal pressure is 103 °C, and the decarboxylation rate is 5 hours.
For a residual amount of CO ₂ of 100 kg/t-ethylenediamine, the boiling point was 138°C at a gauge pressure of 2 kg/cm ² for 5 hours.
Boiling point at 35Kg/t-ethylenediamine, 4Kg/ ^cm2
20 kg/t-ethylenediamine was obtained in 5 hours at 157°C, which clearly shows the effect of temperature. Moreover, ethylenediamine is azeotropic with water at normal pressure. Therefore, in order to remove water, dehydration is performed at a gauge pressure of 8 kg/cm ² or higher. Therefore, decarboxylation of an aqueous solution of carbonates of ethylene amines containing ethylene diamine was carried out at a gauge pressure of 8 Kg/cm ²
If the above treatment is carried out, dehydration can be carried out at the same time as decarboxylation, which makes it more reasonable. Thermal decarboxylation of carbonates of ethyleneamines is 130
It is preferable to operate at temperatures above 0.degree. C., and decarboxylation proceeds more rapidly. Further, it is preferable to carry out heating decarboxylation under boiling conditions because the partial pressure of carbon dioxide can be lowered, so that decarboxylation can be further progressed. In particular, this effect becomes even greater when water is present at 10 wt% or more. Furthermore, when there is substantially no water, some of the ethylene amines will be diffused, which will cause the ethylene amines to react with carbon dioxide gas in the condensation section and solidify, causing scale formation. However, the presence of water suppresses the vapor pressure of ethyleneamines, eliminating these problems. Also, regarding the upper limit of temperature,
The temperature may vary depending on the type of carbonate of ethyleneamines, pressure conditions, etc., but the point is that the temperature may be any temperature that does not cause deterioration of ethyleneamines, for example, about 250°C. Note that under the same conditions, (A) an aqueous carbonate solution of ethylenediamine, (B) an aqueous carbonate solution of ethylenediamine and polyamine, and (C) an aqueous carbonate solution of polyamine were decarboxylated and the decarboxylation rates were compared. Then, from the value calculated for case (B) from the experimental values of (A) and (C), (B)
The experimental value was found to be better. The higher the polyamine content, the better the effect, and it was effective when the ethylenediamine content was 80 wt% or less. In addition, in order to lower the partial pressure of carbon dioxide gas and further promote decarboxylation, it is also an effective means to introduce one or more types selected from water vapor, nitrogen, and air. Furthermore, if alcohol or ether is present during thermal decarboxylation, decarboxylation becomes even easier, and almost complete decarboxylation can be achieved in a short period of time. Butanol is good as an alcohol, and dioxane is good as an ether. Free ethyleneamines are thus obtained.
If this ethyleneamine contains a small amount of _CO2 , it can be removed as sodium carbonate or calcium carbonate by adding a small amount of sodium hydroxide, calcium hydroxide, etc. When sodium hydroxide is used, it is an industrially preferred method because two phases, an aqueous sodium carbonate phase and an ethyleneamine phase, are formed. Further, in this case, a small amount of sodium carbonate is dissolved in the ethyleneamine phase, but when ethylenediamine and/or water is distilled out, sodium carbonate precipitates out, so this can be separated and removed using a settler or the like. The advantages of the method of the invention are listed below. (1) Since carbonates of ethylene amines can be decarboxylated by heating, chemicals such as sodium hydroxide and calcium hydroxide are not required, resulting in a resource-saving process. (2) The number of steps is small, resulting in a simplified process. (3) In the case of decarboxylation of an aqueous solution of carbonates of ethyleneamines, decarboxylation and dehydration can be performed using the same operation and equipment. Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited only to these Examples. Examples 1 to 5 Aqueous carbonate solutions of ethyleneamines at various concentrations
100 ml was placed in a 200 ml four-necked round bottom flask equipped with a reflux condenser, heated at 210 W using a mantle heater, and decarboxylated by heating at the boiling point for 1 hour using a total reflux method to obtain the results shown in Table 1.

[Table] Example 6 Piperazine (P): 31g/, DETA: 374g/
, N-aminoethylpiperazine (N-AEP):
51g/, TETA: 221g/, TEPA: 102g/
, Pentaethylenehexamine (PEHA): 75
The same procedure as in Example 1 was carried out using 100 ml of an aqueous carbonate solution of mixed ethylene amines containing 410 g/g/, CO ₂ of 410 g/. As a result, the boiling point was 136 °C, and after 30 minutes P:
30g/, DETA: 380g/, N-AEP: 51g/
, TETA: 225g/, TEPA: 110g/,
An aqueous solution of mixed ethyleneamines containing 78 g/PEHA and 6.0 g/CO ₂ was obtained. Example 7 500 ml of an aqueous solution of triethylenetetramine carbonate with TETA: 500 g/, CO ₂ : 250 g/ was placed in a container equipped with a stainless steel reflux condenser and a magnetic stirrer.
Place it in a stainless steel cylindrical pressure-resistant container and heat it with a 300W mantle heater at a gauge pressure of 2Kg/ ^cm2 .
Decarboxylation was performed by heating at boiling point. Note that the pressure was adjusted using an automatic pressure regulator. As a result, after 1 hour the temperature reached 142℃ which is the boiling point.
After 1 hour TETA: 505g/, CO ₂ : 2
An aqueous solution of triethylenetetramine was obtained. Comparative Example 1 100 ml of an aqueous carbonate solution of ethyleneamines having the same composition as in Example 7 was operated in the same manner as in Example 1. As a result, the boiling point reached 108℃ after 3 hours.
A triethylenetetramine aqueous solution containing TETA: 510 g/, CO ₂ : 31 g/ was obtained. Examples 8-11 Aqueous solutions of ethylenediamine carbonate at various concentrations were operated in the same manner as in Example 7 at various gauge pressures. The results are shown in Table 2. Comparative Examples 2 to 4 Aqueous solutions of ethylenediamine carbonate at various concentrations were operated in the same manner as in Example 1 at normal pressure. The results are shown in Table 2.

【table】

[Table] Example 12 EDA: 168g/, P: 6.3g/, DETA: 77
g/, N-AEP: 11g/, TETA: 46g/,
TEPA: 21g/, PEHA: 15g/, _CO2 : 214
g/aqueous solution of carbonates of mixed ethylene amines 500
ml was heated and decarboxylated in the same manner as in Example 7 at a gauge pressure of 4 Kg/cm ² . As a result, _CO2 : 6.9 in 5 hours at a boiling point temperature of 155℃
g/g/ of an aqueous solution of ethyleneamines was obtained. Comparative Example 5 100 ml of the same mixed ethylene amine carbonate aqueous solution as in Example 12 was heated and decarboxylated in the same manner as in Example 1. As a result, the boiling point temperature was 105℃, and _CO2 : 28 in 5 hours.
An aqueous solution of mixed ethyleneamines containing g/g was obtained. Example 13 100 ml of an aqueous solution of triethylenetetramine carbonate having the same composition as in Example 3 was placed in a four-neck round bottom flask, the temperature was adjusted to the boiling point of 137°C, and water vapor was removed.
The mixture was introduced into an aqueous carbonate solution of triethylenetetramine at a rate of 100 ml/min for thermal decarboxylation. As a result, after 30 minutes TETA: 835g/, _CO2 :
3.3 g/aqueous solution of triethylenetetramine was obtained. Example 14 To aqueous solution 1 containing 90 g of EDA and 180 g of sodium chloride, n-butanol mixture 1 containing 330 ml of cyclohexanone was added, shaken for 10 minutes, and statically separated. Next, add 100 ml of pure water to 800 ml of the organic phase containing 60.5 g of EDA obtained by static separation, and add water-saturated carbon dioxide gas.
Blow at 300ml/min for 4 hours, EDA: 315g/
, CO ₂ :225 g/carbonate aqueous solution of ethylenediamine was obtained. Next, 100ml of the ethylenediamine carbonate aqueous solution
was placed in a 200ml stainless steel cylindrical pressure-resistant container equipped with a stainless steel reflux condenser, and the gauge pressure was 4Kg/ ^cm2.
was heated with a 210W mantle heater, and at the same time nitrogen gas was introduced into the ethylenediamine carbonate aqueous solution at 200N-ml/min. Note that the pressure was adjusted using an automatic pressure regulator. As a result, EDA: 320g/3 hours at a boiling point of 158℃
, CO ₂ :8.6 g/aqueous ethylenediamine solution was obtained.

Claims (1)

[Scope of Claims] 1. A method for decarboxylating ethyleneamine carbonates, which comprises decarboxylating ethyleneamine carbonates by heating at 120°C or higher. 2 Claim 1 in which one or more types selected from water vapor, nitrogen gas, and air are introduced during thermal decarboxylation.
The method described in section.