A PURIFICATION METHOD OF SODIUM CHLORIDE IN THE ETHYLENEAMINES MANUFACTURING PROCESS

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a process for lowering the content of organic compounds included in sodium chloride formed in the preparation of the ethyleneamines. More specifically, the present invention relates to a purification method of sodium chloride, using a centrifugal solid-liquid separator (centrifuge) for lowering the content of organic compounds included in sodium chloride formed after neutralizing ammonium chloride formed through the reaction of ethylene dichloride (EDC) and ammonia water by addition of sodium hydroxide.

(b) Description of the Related Art

Ethyleneamines were firstly synthesized by A.W. Hoffmann from ethylene dichloride and alcoholic ammonia, and industrially, these are prepared from ethylene dichloride and ammonia according to the technology of UCC Inc. (US).

Ethyleneamines can be prepared by ethylene dichloride (EDC) method or ethylene oxide (EO) method, and the basic reactions are as follows: [EDC Method]

C2H4CI2 + 4 H3 → C ₂ H ₈ 2 + 2NH ₄ C1

(EDC + Ammonia → EDA + Ammonium Chloride)

[EO Method]

C2H4O + 2NH ₃ → C ₂ H ₈ N ₂ + H2O

(EO + Ammonia → EDA + Water)

Among them, the EDC method needs the process for recovering ammonia from 2NH4CI formed because it uses excessive ammonia, and sodium hydroxide is used on this account.

[Ammonia Recovering Process]

NH4CI + NaOH→ NaCl + NH ₃ + H ₂ O

When ammonium chloride is reacted with the sodium hydroxide in order to recover ammonia, sodium chloride containing organic compounds is formed, and the organic compounds (ethyleneamines and the like) included therein must be eliminated in order to discard or reuse sodium chloride formed like above.

For this, there are various methods, such as an electrosorption method and a drying method (or processes) using high temperature carbon dioxide. However, these methods need many apparatuses and increase the investment cost for the apparatuses. Also, these methods may cause with some problems, for example, the low efficiency of ethyleneamine elimination and the recovery of carbon dioxide. Therefore, it has been needed to study the purification process of sodium chloride formed in the preparation of ethyleneamines which can eliminate numerous organic compounds formed in the preparation process of ethyleneamines and does not involve complex problems like the installation of dialysis facility or the recovery of carbon dioxide.

SUMMARY OF THE INVENTION

It is an aspect of the present invention to provide a purification method of sodium chloride which can effectively lower the content of organic compounds included in sodium chloride formed in the process for preparing ethyleneamines.

The present invention provides a purification method of sodium chloride, including the steps of: separating the solid-liquid phases of the solution or suspension containing sodium chloride formed after neutralizing ammonium chloride with sodium hydroxide through a centrifugal separation process; and recovering the solid phase formed by eliminating the liquid phase containing organic compounds after the solid- liquid separation, in the process for preparing ethyleneamines from ethylene dichloride and ammonia water.

In the present invention, water is used as a stripping agent for recovering the solid phase of sodium chloride.

The present invention may further include the step of adding water as the stripping agent to the solution or suspension containing sodium chloride before the centrifugal separation process.

Furthermore, the centrifugal separation process may be carried out with the solid:liquid weight ratio of 1:9 to 9:1.

The centrifugal separation process may be carried out under the temperature condition of 0 to 90 ^° C .

The centrifugal separation process may be repeatedly carried out 2 to 10 times repeatedly in addition.

Furthermore, the organic compound may be one or more compounds selected from the group consisting of ethylenediamine (EDA), diethylenetriamine (DETA), piperazine (PIP), aminoethylpiperazine (AEP), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), monoethanolamine (MEA), aminoethylethanolamine (AEEA), hexaethyleneheptamine (HEHA), and a mixture thereof, in the present invention.

In the present invention, the recovery rate of the solid formed after eliminating the liquid phase may be 65% or more.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a photo and a schematic drawing of the centrifugal separator according to one embodiment of the present invention. Fig. 2 is a process flow diagram showing the outline of the stripping process using the centrifugal separator according to one embodiment of the present invention.

Fig. 3 is a graph showing the result of the stripping test according to one embodiment of the present invention (solid:liquid=5:5).

Fig. 4 is a graph showing the result of stripping efficiency test in accordance with the solid:liquid ratio according to one embodiment of the present invention.

Fig. 5 is a graph showing the content variation of the organic compounds in accordance with the number of stripping process according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, the preparation method of ethyleneamines according to the concrete embodiment of the present invention is explained in more detail. However, the followings are only for the understanding of the present invention and the scope of the present invention is not limited to or by them, and it is obvious to a person skilled in the related art that the embodiments can be variously modified in the scope of the present invention.

In addition, "include" or "comprise" means to include any components (or ingredients) without particular limitation unless there is no particular mention about them in this description, and it cannot be interpreted as a meaning of excluding an addition of other components (or ingredients).

In the process of the repeated studies on the purification of sodium chloride formed in the preparation of ethyleneamines, the present inventors recognized that the organic compounds included in sodium chloride formed after neutralizing ammonium chloride formed through the reaction of ethylene dichloride (EDG) and ammonia water by addition of the sodium hydroxide (NaOH) could be effectively eliminated by using a centrifugal solid-liquid separator (centrifuge), and accomplished the present invention.

According to one embodiment of the present invention, a purification method of sodium chloride formed in the preparation of ethyleneamines by using ethylene dichloride and ammonia water is provided. The purification method of sodium chloride according to the present invention may include the steps of: carrying out the centrifugation of the solution or suspension containing sodium chloride formed after neutralizing ammonium chloride with sodium hydroxide; and recovering the solid phase of sodium chloride by eliminating the liquid phase containing organic compounds after the centrifugation, in the process for preparing ethyleneamines by using ethylene dichloride and ammonia water.

Particularly, in order to discard or reuse sodium chloride formed in the EDC method using ethylene dichloride and ammonia water, the present invention can remarkably lower the content of the organic compounds in sodium chloride below the requirements of recycling standards by adding fresh water, such as purified water and the like, as a stripping agent, and controlling the number of solid-liquid separation process by the centrifuge, such as the continuous process of solid-liquid separation.

The present invention provides a process for lowering the content of organic compounds included in sodium chloride by using water as the stripping agent for recovering the solid phase of sodium chloride.

The centrifugal separation process may be carried out after making the weight ratio of soliddiquid 1:9 to 9:1, preferably 5:5 to 9:1, more preferably 6:4 to 7:3, and still more preferably 8:2. At this time, the centrifugal separation process can be carried out with said solid-liquid weight ratio preferably, because higher solid recovery rate is better in the centrifugal separation process. The upper limit of the weight ratio may be controlled in terms of general maximum solid content operable in a commercial solid- liquid separator (centrifuge).

The solution or suspension containing sodium chloride used in the centrifugal separation process may include water. Furthermore, the centrifugal separation process may be carried out after adjusting the solid:liquid weight ratio as disclosed above by adding fresh water, such as purified water and the like, as the stripping agent to the solution or suspension. Particularly, the method may further include the step of adding water to the solution or suspension containing sodium chloride, before carrying out the centrifugal separation process.

The centrifugal separation process may be carried out under the temperature condition of 0 to 90 ^° C, and preferably 0 to 40 ^° C . At this time, it is preferable to carry out the process in low temperature condition, because it is advantageous in increasing the solid recovery rate to carry out the centrifugal separating process in the condition of low solubility of solid sodium chloride. In this respect, the process may be carried out at the temperature of 0 ^° C or more, and may be carried out at the temperature of 20 ^° C or less.

The centrifugal separation process may be carried out under the condition of 1,000 to 4,000 rpm, and preferably 1,500 to 3,500 rpm.

The centrifugal separation process may be carried out repeatedly 2 to 10 times, and preferably 3 to 7 times, in addition. In the present invention, the centrifugal separating process of sodium chloride formed in the preparation of ethyleneamines may be carried out repeatedly 2 times or more in terms of the minimum operating condition satisfying the content of recyclable organic compounds. And, the centrifugal separating process may be carried out repeatedly 10 times or less in terms of increasing the solid recovery rate.

In the present invention, also, the organic compounds which are included in sodium chloride and must be eliminated are basically the compounds formed in the preparation process of ethyleneamines by using ethylene dichloride and ammonia water. These can be separated in a liquid phase through the centrifugal separating process. Such organic compounds may include one or more compounds selected from the group consisting of ethylenediamine (EDA), diethylenetriamine (DETA), piperazine (PIP), aminoethylpiperazine (AEP), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), monoethanolamine (MEA), aminoethylethanolamine (AEEA), hexaethyleneheptamine (HEHA), heavyamines (or heavies) or polyamines, and a mixture thereof. Such mixture may be a mixture of pentaethylenehexamine (PEHA), hexaethyleneheptamine (HEHA), and tetraethylenepentamine (TEPA).

In one embodiment of the present invention, the solid obtained by the solid- liquid separator (centrifuge) using a centrifugal force may include salt compounds,such as sodium chloride and the likeabout 96% or more), and a small quantity of organic compounds (about 4% or less), but the solid composition may vary depending on the device used. The solid may include brine (about 4% or less), according to the performance of the centrifuge. Furthermore, the liquid phase obtained in company with the solid may include brine (about 70% or less), organic compounds (most, about 96% or more), and a small quantity of salts (about 1% or less).

Meanwhile, the purification method of sodium chloride of the present invention includes the steps of: carrying out the centrifugal separating process; and recovering the solid phase by eliminating the liquid phase containing organic compounds after the centrifugation.

The recovering process is a step of collecting the solid in the centrifugal separation process, and more specifically, a filtering apparatus may be used so as to separate the solid phase and the liquid phase. The recovering process may further include a washing process by using water or other aqueous solutions, and it may be carried out by using a vacuum filtration device as the case may be.

In the present invention, sodium chloride (NaCl) is the salt formed from the prcess for preparing ethyleneamines according to EDC method. Particularly, sodium chloride (NaCl), in the present invention, is formed in the process of neutralizing ammonium chloride, formed through the reaction of ethylene dichloride and ammonia water by adding sodium hydroxide.

According to one embodiment of the present invention, sodium chloride formed in the EDC method, is in the mixture of water and ethyleneamines and introduced into the 1 ^st centrifugal separator (centrifuge), and the mixture is separated into the solid phase and the liquid phase. Since the content of organic compounds included in sodium chloride separated as the solid phase by the 1 ^st centrifugal separator (centrifuge) does not satisfy the recycling standards, fresh water such as purified water is added to and mixed with the same, as a stripping agent, in order to lower the content of organic compounds. At this time, the quantity of fresh water added thereto may be determined according to the ratio of solid.liquid disclosed above. The content of organic compounds included in sodium chloride can be lowered below the standards by repeating the processes. Here, the term "ethyleneamines" means every compounds including one or more ethylene groups and one or more amine groups, i.e., amine compounds, and may include a plurality of polyamines (or heavy amines) and the like in company with ethylenediamine. Said ethyleneamines, namely, amine compounds may be one or more compounds selected from the group consisting of ethylenediamine (EDA), diethylenetriamine (DETA), piperazine (PIP), aminoethylpiperazine (AEP), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), monoethanolamine (MEA), aminoethylethanolamine (AEEA), and hexaethyleneheptamine (HEHA). Here, the collective name for diethylenetriamine (DETA), piperazine (PIP), aminoethylpiperazine (AEP), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), monoethanolamine (MEA), aminoethylethanolamine (AEEA), and hexaethyleneheptamine (HEHA), and the like, except ethylenediamine (EDA), is polyamines (or heavy amines).

The reaction for forming ethyleneamines by using ethylene dichloride and ammonia water may be carried out under the temperature condition of 50 to 180 ^° C, and preferably 100 to 150 ^° C . Furthermore, the reaction for forming said ethyleneamines may be carried out under the pressure condition of 80 to 180 bar, and preferably 100 to 150 bar. At this time, the reaction may be carried out after making the molar ratio of ethylenedichloride (EDC) and ammonia in ammonia water 1:5 to 1:15, preferably 1:5 to 1:12, and more preferably 1:6 to 1:10. Furthermore, the concentration of ammonia in said ammonia water may be 28 to 80 weight%(w/ v), preferably 30 to 70 weight%(w/ v), and more preferably 40 to 60 weight %(w/ v).

Furthermore, the reaction for forming said ethyleneamines may be carried out by a continuous process, and in this case, it may be carried out by using a tubular reactor.

In the present invention, the recovery rate of the solid obtained by eliminating the liquid phase after the centrifugal separation process may be 65% or more or 65% to 95%, preferably 70% or more, and more preferably 80% or more, because higher recovery rate is better. For example, the recovery rate of the solid may be 65% or more when the solid:liquid operating ratio is 5:5, and it may be 85% or less in the maximum operable condition.

Furthermore, the content of total organic compounds included in the final solid phase collected according to the present invention can be lowered academically to lppm or less, but it is possible to set up the optimal condition which can lower the content to 7 ppm or less by considering the operable condition of the centrifugal separator (centrifuge), the minimum use of the centrifugal separator (centrifuge), the recovery rate of the solid, the minimum use of fresh water, and so on. Particularly, the organic compounds included in the collected final solid substituents can be lowered to several ppm according to the quantity of water added in the purification process disclosed above. The present invention does not limit details other than the matters disclosed above because they are adjustable with necessity.

As explained above, in the process for preparing ethyleneamines by using ethylene dichloride and ammonia water, the present invention shows an excellent effect of raising the solid recovery rate and lowering the content of the organic compounds in sodium chloride by applying the optimized centrifugal separating process to sodium chloride formed after neutralizing ammonium chloride with sodium hydroxide.

Examples

Hereinafter, preferable examples and comparative examples are presented for understanding the present invention. However, the following examples are only for illustrating the present invention and the present invention is not limited to or by them.

Example 1

40% ammonia water and ethylenedichloride (EDC; C2H4CI2) were reacted under the pressure of 120 bar while maintaining the temperature of the latter part of the reactor to be 120 ^° C . After the reaction, 2NH4CI formed from the excess ammonia was neutralized with sodium hydroxide and fresh water was added to the solution/ suspension containing sodium chloride formed therefrom in order to make the weight ratio of solid:liquid 5:5, and then the process of separating the solid-liquid phases was carried out by using a centrifugal force, according to the following method.

At first, the inner tube and the outer tube of the centrifuge (Lab Scale Centrifuge of Ferrum Inc.) illustrated in Fig. 1 were combined, and then the solution/ suspension including said sodium chloride was injected into the inner tube equipped with a mesh as the mother solution to be separated. After then, the centrifugal separation process was carried out under the pressure condition of 700 atm for 10 minutes by using a centrifuge so as to separate solid and liquid, and a solid cake was obtained at the upper part of the centrifuge and liquid was obtained at the bottom part. The contents of the solid and the liquid were quantified by collecting and weighing the solid at the upper part of the centrifuge. And, fresh water was added to and mixed with the same. At this time, the quantity of fresh water was determined by considering the quantified content of the solid and the liquid. After then, the solid-liquid separation process was carried out 3 times repeatedly according to the stripping process illustrated in Fig. 2, and the separated liquid was collected. The content of total organic compounds (TOC) was checked by the TOC analyzer (SHIMADZU TOC-V MODEL), and the results are listed in the following Table 1.

[Table 1]

113,080 9,662 736 12

TOC, ppm - - ^■ - (112,295) (5,095) (234) (2) _

Theoretical value in ( )

At this time, the recovery rate of the solid was 65%, the content of total organic compounds (TOC) included in the final liquid phase collected was 12 ppm, and the content of total organic compounds (TOC) included in the final solid phase collected was 12 ppm (the contents of organic compounds in the separated solid and liquid were same before adding water thereto).

Example 2

The purification process of sodium chloride and the analysis of the result were carried out substantially according to the same method as in Example 1, except that the weight ratio of solid:liquid was 6:4. The experimental results are listed in the following Table 2. [Table 2]

At this time, the recovery rate of the solid was 70%, the content of total organic compounds (TOC) included in the final solid phase collected was 24 ppm, and the content of total organic compounds (TOC) included in the final liquid phase collected was 24 ppm.

Example 3

The purification process of sodium chloride and the analysis of the result were carried out substantially according to the same method as in Example 1, except that the weight ratio of solid:liquid was 7:3. The experimental results are listed in the following Table 3.

[Table 3]

At this time, the recovery rate of the solid was 75%, the content of total organic compounds (TOC) included in the final solid phase collected was 4 ppm, and the content of total organic compounds (T0C) included in the final liquid phase collected was 4 ppm.

Meanwhile, the stripping experimental results according to one embodiment of the present invention is shown in Fig. 3 (solid:liquid = 5:5). At this time, the content of fresh water was controlled so as to maintain the solid:liquid ratio of 5:5 and the solid- liquid separation process was carried out 3 times. Finally obtained sodium chloride was completely dissolved in water to make saturated salt water, and then, the content of total organic compounds (TOC) included therein was measured. Though there may have variations between thequantifiedvalues from the centrifuge being used in a commercial process and the lab-scale solid-liquid separator due to the difference of its efficiency, it was observed or confirmed that the TOC was lowered from 119,051 ppm to 93 ppm.

Furthermore, the experimental results of stripping efficiency to the solid:liquid ratio according to one embodiment of the present invention are illustrated in Fig. 4. At this time, the content variation of organic compounds was quantified while changing the soliddiquid ratio from 5:5 to 8:2 in order to confirm the stripping efficiency to the solid:liquid ratio.

In addition, the experimental results of the content variation of organic compounds to the number of stripping process according to one embodiment of the present invention are illustrated in Fig. 5. At this time, the case that the solid:liquid ratio was 6:4 and the case that the solid:liquid ratio was 8:2 were compared, in order to confirm the content variation of organic compounds to the the number of stripping process (number of solid-liquid separation). It was recognized that 3 times of the solid-liquid separation was required when the ratio was 6:4, and 4 times of the solid- liquid separation was required when the ratio was 8:2, in order to lower the final content of organic compounds below about 15 ppm. At this time, the solid collect rate was about 74% when the ratio was 6:4, and about 85% when the ratio was 8:2.