JP4217465B2 - Method for purifying 1,2-dichloroethane - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a novel purification method for extracting and removing iron components in crude 1,2-dichloroethane obtained by reacting ethylene and chlorine in the presence of an iron-based catalyst using water as an extractant. About. More specifically, the present invention provides a purification method in which the crude 1,2-dichloroethane and the extractant are brought into contact with each other, by preventing the adverse effects due to the solid content produced by the contact, and enabling continuous purification for a long period of time. .
[0002]
[Prior art]
As a method for producing 1,2-dichloroethane, a method of reacting chlorine and ethylene in the presence of an iron-based catalyst is performed. Since 1,2-dichloroethane obtained by such a reaction contains by-products such as 1,1,2-trichloroethane and ferric chloride as an iron-based catalyst, it is necessary to remove them by distillation.
[0003]
Conventionally, the purification employs a method in which an iron-based catalyst is extracted and removed from crude 1,2-dichloroethane using water as an extractant, and then by-products are separated by distillation.
[0004]
In the above purification method, when the iron-based catalyst is continuously removed using water as an extractant, a continuous countercurrent tower having a structure as shown in FIG. 3 is used. The continuous countercurrent tower is a perforated plate tower in which a plate made of a perforated plate is provided inside a liquid countercurrent portion 101 made of a cylindrical body extending in the vertical direction, and a plurality of stages are provided at intervals. A packed tower packed with a packing is generally used, and a heavy liquid having a specific gravity larger than that of the liquid supply port 107 provided at the upper part of the liquid counterflow part 101 is supplied, and a liquid supply provided at the lower part of the liquid counterflow part 1 Both liquids are brought into contact with each other by supplying a light liquid having a smaller specific gravity from the mouth 108 and bringing it into countercurrent contact at the liquid counterflow part. Then, the liquid after contact is taken out from the liquid outlets 102 and 103 through the liquid reservoirs 105 and 106, respectively.
[0005]
However, when the above-described continuous countercurrent tower is used to extract crude 1,2-dichloroethane, which is a heavy liquid, from the top and water, which is a light liquid, from the bottom, the iron-based catalyst is extracted. In the region where the pH in the vicinity of the water supply in the flow tower is 7 to 4, ferric chloride changes to iron hydroxide, and as a result, it adheres as a solid to a porous plate or packed bed provided in the tower as a scale. As a result, there is a problem in that the liquid passage in the tower is blocked and continuous purification for a long time becomes difficult.
[0006]
[Problems to be solved by the invention]
Therefore, the object of the present invention is to use the continuous counter-current tower having the liquid counter-current part, to convert the iron component such as iron-based catalyst contained in the crude 1,2-dichloroethane into the crude 1 An object of the present invention is to provide a purification method for extracting and removing from 2,2-dichloroethane, which prevents clogging due to scale generation in the tower and enables stable purification over a long period of time.
[0007]
[Means for Solving the Problems]
The inventors of the present invention have made extensive studies to achieve the above object. As a result, the concept of use of the continuous countercurrent tower was broken down, and the crude liquid 1,2-has been supplied as heavy liquid and light liquid to the respective supply ports without providing separate supply ports for the light liquid and heavy liquid of the tower. After premixing dichloroethane and water as the extractant, by supplying to the middle part of the liquid countercurrent part of the continuous countercurrent tower and separating it countercurrently, blockage due to scale generation in the tower is prevented, It has become possible to carry out stable purification over a long period of time and that the extraction rate of the iron component does not decrease, and the present invention has been completed.
[0008]
That is, the present invention extends in the vertical direction when purifying the iron component in crude 1,2-dichloroethane obtained by reacting ethylene and chlorine in the presence of an iron-based catalyst using water as an extractant. A liquid counterflow portion comprising a cylindrical body, having a liquid outlet at the upper and lower portions of the liquid countercurrent portion, and positioned between the upper and lower liquid outlets A continuous countercurrent tower having a liquid supply port is used, the crude 1,2-dichloroethane and the extractant are mixed in advance, and the resulting mixed liquid is supplied to the liquid supply port of the continuous countercurrent tower. 1,2-dichloroethane is recovered from the liquid outlet at the bottom thereof, and this is a method for purifying 1,2-dichloroethane.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, crude 1,2-dichloroethane to be purified is obtained by reacting ethylene and chlorine in the presence of an iron-based catalyst by a known method, and 1,2-dichloroethane is the main component. However, as a by-product, 1,1,2-trichloroethane is accompanied by an equivalent amount of hydrogen chloride. As described above, the iron component, which is another catalyst of the byproduct, is dissolved in this product, and it is necessary to remove the iron component before removing the byproduct by distillation.
[0010]
Moreover, in this invention, the water as an extractant for extracting an iron component from crude 1, 2- dichloroethane will not be restrict | limited especially if it is a state which can extract an iron component. For example, water such as industrial water, tap water, or pure water is generally used. Further, together with the pure water, water once used for extraction of iron components or a mixture obtained by mixing crude 1,2-dichloroethane described later and the pure water (hereinafter referred to as extractant-crude 1,2-dichloroethane mixed) A part of the liquid can also be recycled. The effect of this circulation is that when the flow load on the static mixer is reduced, the load can be adjusted to maintain the performance of the mixer.
[0011]
In the present invention, the amount of the extractant to be used for 1,2-dichloroethane is not particularly limited, but the extractant water is 0.05 to 1.5 per 1 part by weight of 1,2-dichloroethane. Part by weight, preferably 0.1 to 0.8 part by weight is suitable. Moreover, it is desirable to adjust the usage-amount of an extractant so that the pH of a liquid mixture may be 3 or less.
[0012]
Further, in the present invention, the continuous countercurrent tower has a liquid countercurrent portion composed of a vertically extending cylindrical body for separating the extractant water and 1,2-dichloroethane by a specific gravity difference. And if it has a liquid supply outlet in the location located in the intermediate part of each liquid extraction outlet in the upper part and the lower part of this liquid counterflow part, it will not restrict | limit in particular.
[0013]
FIG. 1 is a conceptual diagram showing a typical embodiment of a continuous countercurrent tower that can be suitably used in the present invention. As shown in FIG. 1, in the present invention, the continuous countercurrent tower has a liquid (water) outlet 2 at the top of the liquid counterflow section 1, a liquid (1,2-dichloroethane) outlet 3 at the bottom, The liquid supply port 4 is basically provided at an arbitrary position between the liquid discharge port 2 and the liquid discharge port 3.
[0014]
The liquid countercurrent section 1 of the continuous countercurrent tower is provided with a plate made of a perforated plate in the liquid countercurrent section or filled with a filler in order to effectively perform the countercurrent contact of the liquid here. This structure is preferably employed.
[0015]
Among such structures, a structure provided with a plate is particularly preferable because the extractant can be accurately separated from the extractant-crude 1,2-dichloroethane mixture described later. In this case, depending on the size of the tower, A structure in which a plurality of plates, specifically, 20 to 100 plates are arranged at intervals of 10 to 100 mm is preferable. Further, the opening ratio of the plate is generally about 30 to 70%. Furthermore, a structure having means for applying vibration to the liquid passing through the plate is preferably employed. For example, the structure which vibrates this plate to an up-down direction is mentioned. The stroke width of such vibration is preferably 5 to 50 mm, and the number of strokes is generally about 100 to 500 times / minute. As a method for applying vibration to the plate, known means are employed without particular limitation, but means for changing the rotation of the motor to vibration of the plate via the crankshaft is preferably employed.
[0016]
Moreover, it is preferable to provide the liquid storage parts 5 and 6 for storing the liquid after movement and performing phase separation more efficiently above and below the liquid counterflow part, respectively. In this case, the liquid outlet 2 is provided in the upper part of the liquid reservoir 5 serving as a water reservoir, and the liquid outlet 3 is provided in the lower part of the liquid reservoir 6 serving as a crude 1,2-dichloroethane reservoir. It is preferable.
[0017]
Moreover, the liquid supply port 4 provided in the liquid counterflow part 1 is a supply port which supplies the extractant-crude 1, 2- dichloroethane mixed liquid explained in full detail later to a continuous countercurrent tower. The mounting position is not particularly limited as long as it is between the liquid outlet 2 and the liquid outlet 3, but the preferable mounting position is the upper part of the liquid counterflow portion 1, particularly directly below the water reservoir 5, that is, In the vicinity of the upper end of the liquid counterflow portion.
[0018]
It goes without saying that the continuous countercurrent tower used in the present invention can be used by closing the liquid supply port (light liquid supply port) below the conventional countercurrent tower having two liquid supply ports.
[0019]
The greatest feature of the present invention is that a continuous countercurrent tower having the above-described structure is used, and a mixed liquid in which crude 1,2-dichloroethane and water as an extractant are mixed in advance is supplied from the liquid supply port of the continuous countercurrent tower. There is to do.
[0020]
By such mixing, the pH of the solvent-crude 1,2-dichloroethane mixture is uniformly lowered by the acid content contained in the crude 1,2-dichloroethane. The amount of solid content such as iron hydroxide that has been produced in large quantities due to the gradual change in pH due to countercurrent contact between 2-dichloroethane and water is suppressed, and the extractant with a low solid content—crude 1, A 2-dichloroethane mixture can be obtained. And this extractant-crude 1,2-dichloroethane mixed liquid shows acidity, and since solid content does not precipitate after mixing, when this mixed liquid is supplied to a continuous countercurrent tower, the solid in the tower Minute generation can be almost completely prevented.
[0021]
Also, by extracting the extractant and crude 1,2-dichloroethane with a static mixer, extraction of iron components contained in 1,2-dichloroethane into the extract simultaneously with mixing is started, and continuous countercurrent Extraction proceeds in an acidic state before being fed to the tower. The mixed solution is supplied to a continuous countercurrent tower, and exhibits the effect of separating the extractant containing iron finely dispersed in 1,2-dichloroethane as a separation tank, together with the conventional extraction effect, and with extremely high accuracy. The surprising effect that iron components can be removed from 1,2-dichloroethane is exhibited.
[0022]
A preferred embodiment of the purification method of the present invention is shown as a flow chart in FIG. According to FIG. 2, crude 1,2-dichloroethane 7 obtained by reacting ethylene and chlorine in the presence of an iron-based catalyst is supplied to the static mixer 9 immediately after contact with the industrial water 8 and instantly. The mixture is uniformly mixed and supplied to the continuous countercurrent tower 1 as an extractant-crude 1,2-dichloroethane mixed liquid to be phase-separated. In this case, the liquid mixed by the static mixer 9 can also be circulated through the line 10 and before the supply location of the industrial water 8. By this circulation, as described above, when the flow load on the static mixer is reduced, the load can be adjusted and the performance of the mixer can be maintained.
[0023]
The mixing method of the crude 1,2-dichloroethane and the extractant for obtaining the above-described extractant-crude 1,2-dichloroethane mixed solution is not particularly limited, but a method in which both are carried out within as short a time as possible after the contact is preferable. . For example, as shown in FIG. 4, to supply the extractant 8 to the crude 1,2-dichloroethane 7 in the same direction as the flow of the crude 1,2-dichloroethane and to the vicinity of the mixer 9 The method of mixing by carrying out with the insertion tube 11 is preferably employed. That is, when the mixing time becomes long or non-uniform mixing occurs, the above-described solid content tends to be generated, and the extractant-crude 1,2-dichloroethane mixed solution is removed in the continuous countercurrent tower. May accumulate. The instantaneous mixing is preferably performed within 10 seconds, particularly within 5 seconds. Moreover, as a means for performing such mixing, a known commercially available static mixer can be used without any limitation. Specifically, a plate-shaped or cup-shaped collision plate type static mixer, and Kenics type, Sulzer type, Etoflo type, Ray Hi-mixer type, Bran & Lube type, N-form type, Komax type, Lightnin type, Ross Examples thereof include ISG type and Prematenik PMR type static mixers. In particular, a collision plate type static mixer is preferable for instantaneous mixing of the crude 1,2-dichloroethane and the extractant, and is preferable because the coalescence of the extract dispersed in the crude 1,2-dichloroethane is small.
[0024]
The 1,2-dichloroethane obtained by the purification method of the present invention can be further purified by applying a known purification method such as distillation, if necessary.
[0025]
【The invention's effect】
As can be understood from the above description, according to the present invention, crude 1,2-dichloroethane and water as an extractant are mixed in advance, and then supplied to the continuous countercurrent tower to perform countercurrent separation. In addition, it is possible to prevent clogging due to generation of scale such as iron hydroxide in the tower, and to perform stable purification over a long period of time using the continuous countercurrent tower, and at a high extraction rate. By removing the iron component, purified 1,2-dichloroethane can be obtained.
[0026]
In particular, the effect of the present invention can be further improved by adopting an embodiment in which a static mixer is used to instantaneously mix the extractant and crude 1,2-dichloroethane.
[0027]
【Example】
EXAMPLES Hereinafter, examples will be shown to describe the present invention more specifically, but the present invention is not limited to these examples.
[0028]
Example 1
The continuous countercurrent tower was used with the following specifications having the structure shown in FIG.・ Liquid counterflow section Tower diameter 25mmφ, Height 3000mm
-Upper water storage part Tower diameter 51mmφ, height 300mm
・ Lower 1,2-dichloroethane reservoir, tower diameter 51mmφ, height 300mm
・ Plate open area 50%
・ Plate spacing 50mm, 56 plates installed for liquid counterflow part ・ Stroke length of plate vibration 25mm
・ Number of plate vibrations 300 strokes / min. 18.7 L / hr of 1,2-dichloroethane in which 30 ppm of iron is dissolved in the above continuous countercurrent tower and 3.3 L / hr of industrial water as extractant in a static mixer. The two solutions were brought into contact with each other so that the time from the contact between the two liquids to the outlet of the mixer was 2 seconds.
[0029]
The pH of the obtained liquid mixture was 1.5. This mixed solution was supplied from an intermediate portion of the liquid countercurrent portion of the continuous countercurrent tower.
[0030]
As a result, 1,2-dichloroethane containing 0.5 ppm of iron in the liquid was continuously taken out from the 1,2-dichloroethane outlet 3, and water containing 196 ppm of iron in the liquid was continuously taken out from the water outlet 2. It was.
[0031]
From the above results, the iron removal rate [%] was calculated by (iron concentration in inlet 1,2 dichloroethane−iron concentration in outlet 1,2 dichloroethane) / iron concentration in inlet 1,2 dichloroethane × 100. It was 98.3%.
[0032]
As a result of continuously operating the above operation for 50 days, no scale was observed inside the continuous countercurrent tower, and the iron removal rate was maintained at 98.3%.
[0033]
Comparative Example 1
Extraction was performed in the same manner as in Example 1 except that crude conventional 1,2-dichloroethane was supplied from the liquid supply port 107 and industrial water as an extractant was supplied from the liquid supply port 108 using the conventional continuous countercurrent tower shown in FIG. Purification of 1,2 dichloroethane by
[0034]
As a result, 1,2-dichloroethane containing 0.6 ppm of iron in the liquid was continuously taken out from the 1,2-dichloroethane outlet 3, and water containing 186 ppm of iron in the liquid was continuously taken out from the water outlet 2. It was. The iron removal rate in this case was 98.0%.
[0035]
As a result of continuous operation of the above operation for 50 days, scale adhered to the plate in the continuous countercurrent tower, 1,2-dichloroethane began to accumulate in the water reservoir, and the iron removal rate decreased to 93.3%.
[0036]
Example 2
It carried out similarly to Example 1 except having supplied the liquid mixture which mixed 1, 2- dichloroethane and industrial water with the static mixer to the liquid countercurrent part located just under the water storage part of a liquid countercurrent part. .
[0037]
As a result, 1,2-dichloroethane containing 0.3 ppm of iron in the liquid was continuously taken out from the 1,2-dichloroethane outlet 3, and water containing 198 ppm of iron in the liquid was continuously taken out from the water outlet 2. It was. In this case, the iron removal rate was 99.0%.
[0038]
As a result of continuous operation of the above operation for 50 days, no scale was observed inside the continuous countercurrent tower, and the iron removal rate was maintained at 99.0%.
[0039]
Example 3
As shown in FIG. 4, industrial water together with 1,2-dichloroethane is supplied to the static mixer through the insertion tube 11, and the time from the contact of both liquids to the outlet of the mixer is 0.5 seconds. The same procedure as in Example 1 was performed except that mixing was performed using a static mixer.
[0040]
As a result, 1,2-dichloroethane containing 0.5 ppm of iron in the liquid was continuously taken out from the 1,2-dichloroethane outlet 3, and water containing 196 ppm of iron in the liquid was continuously taken out from the water outlet 2. It was. The iron removal rate in this case was 98.3%.
[0041]
As a result of continuously operating the above operation for 100 days, no scale was observed inside the continuous countercurrent tower, and the iron removal rate was maintained at 98.3%.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing the structure of a typical continuous countercurrent tower used in the method of the present invention. FIG. 2 is a process diagram showing a preferred embodiment of the method of the present invention. FIG. 4 is a conceptual diagram showing the structure of a flow tower. FIG. 4 is a partial process diagram showing a preferred embodiment of the method of the present invention.
1: Liquid counter-flow part 2: Water outlet 3: 1,2-dichloroethane outlet 4: Liquid supply port 5: Water reservoir 6: 1,2-dichloroethane reservoir 7: Crude 1,2-dichloroethane 8: Water 9: Static mixer 11: Insertion tube

Claims (1)

When refining the iron component in crude 1,2-dichloroethane obtained by reacting ethylene and chlorine in the presence of an iron-based catalyst using water as an extractant, from a cylindrical body extending vertically A liquid counterflow portion, a liquid outlet is provided at each of the upper and lower portions of the liquid counterflow portion, and a liquid supply port is provided at the liquid countercurrent portion located between the upper and lower liquid outlets. Using the continuous countercurrent tower having the structure, the crude 1,2-dichloroethane and the extractant are mixed in advance, and the resulting mixed liquid is supplied to the liquid supply port of the continuous countercurrent tower, A process for purifying 1,2-dichloroethane, characterized in that dichloroethane is recovered from the liquid outlet at the bottom thereof.

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