JPH0769946A - Separation of m-/p-dichlorobenzene mixture from each other - Google Patents

Abstract

PURPOSE: To provide a process whereby p-dichlorobenzene can be separated from a mixture with m-dichlorobenzene at a very high selectivity at only one elution step.

CONSTITUTION: A mixture of m- and p-dichlorobenzene is separated by treating the mixture with zeolite in the presence of a solvent combination. The solvent combination comprises at least two different solvents selected from two groups, respectively, one group comprising compds. of formula I (wherein Hal is Cl or Br; R¹ is Hal or 1-4C alkyl; and R² is R¹ or H provided R¹ and R² may combine with each other to form an indan, tetralin, or naphthalene residue) excluding 4-chlorotoluene and dichlorobenzene and the other group comprising compds. of formula II (wherein R³ is 1-4C alkyl, 1-4C alkoxy, 1-4C alkylcarbonyl, or the like). The zeolite used is a pentasil zeolite contg. protons and cations of the first or second main group or of rare earth metals as exchangeable cations. A filtrate enriched with m-dichlorobenzene is taken off, and p- dichlorobenzene is recovered by the extraction from the zeolite.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

The present invention describes a method for separating a mixture of m- and p-dichlorobenzene, preferably separating p-dichlorobenzene from the mixture. The above separation is carried out on pentasil zeolites in the liquid phase using a solvent.

When chlorinating benzene or monochlorobenzene to give dichlorobenzene, a mixture of three isomeric dichlorobenzenes is generally produced. This dichlorobenzene fraction has a different boiling point and melting point than the other products present in the chlorination mixture, such as starting materials and higher chlorination products, so that its separation is It can be done easily. However, the separation of the individual dichlorobenzene isomers present in this fraction is difficult and very complicated. First, the dichlorobenzene fraction free of by-products is distilled, where m-
And p-dichlorobenzene and o-dichlorobenzene as bottom product. Since m-dichlorobenzene and p-dichlorobenzene have the same boiling point, further separation does not occur when distillation is used, and fractional crystallization is performed. Here, most of this p-dichlorobenzene is used. Are recovered in pure form to leave the m-dichlorobenzene concentrate, which concentrates 70 to 80% by weight m-dichlorobenzene and 30 to 20% p-dichlorobenzene, depending on the crystallization effort. % By weight (European patent 012 891). Adsorption methods are also known in principle, in which the separation of dichlorobenzene mixtures with molecular sieves or further separation is carried out. Therefore, European Patent No. 334 025 describes the separation of halogenoaromatics over any of the zeolites in the presence of aromatic hydrocarbons.
However, this description does not mention the separation of m- and p-dichlorobenzene over pentasil zeolite. European Patent No. 278 680
JP-A-62 / 175433 (1987) and U.S. Pat. No. 4,996,380 disclose m-dichlorobenzene from a mixture of m-dichlorobenzene and o- and p-dichlorobenzene without using an eluent. Separation is described. These methods consist of a mixture containing mainly o- and p-dichlorobenzene and containing a small amount of m.
Suitable for separating dichlorobenzene, but not suitable for separating p-dichlorobenzene. However, the treatment of the industrial dichlorobenzene product mixture by distillation and a simple crystallization step tends to produce m-dichlorobenzene concentrate from which the p-dichlorobenzene residue present there is distilled and crystallized. Even though it can be separated by m.p., it consumes time and energy, so a method that makes it possible to separate p-dichlorobenzene economically from m-dichlorobenzene concentrate is highly desirable. ing.

The separation of small amounts of p-dichlorobenzene from mixtures containing predominantly m-dichlorobenzene as described above with molecular sieves using the prior art has not been satisfactorily solved.

US Pat. No. 4,571,441 and JP-A-58 / 131924 (1983) disclose faujasite containing silver, copper, sodium or potassium as exchangeable cations or a large number thereof. X and Faujasite Y were used to obtain p- from a mixture of o- and m-dichlorobenzene and p-dichlorobenzene.
It is described to carry out the separation of dichlorobenzene.
Substituted aromatic hydrocarbons have been used as desorbents. The selectivity achieved with these methods is extremely low and does not guarantee an economical method.

Japanese Unexamined Patent Publication No. 4/330025 (JP 92 /
330025) describes that isomer dichlorobenzenes are separated on Pb-containing zeolites by using 3,4-dichlorotoluene as a desorbing agent. Pb
It is not advantageous to produce and use Pb-containing zeolites, since their compounds show toxicity. Since even trace amounts of Pb cannot be tolerated,
The isomers separated on the above lead-containing material cannot be used as intermediates of the active material.

Using zeolite in the presence of solvent, m- and p
-Finding a method for effecting the separation of said mixture by treating a mixture of dichlorobenzenes, which method comprises
Two mixtures of the mixture together with a solvent combination consisting of at least two different solvents from each of the two groups A and B.
Exchange cations at 0 to 250 ° C. for protons, cations of the first or second main group of the periodic table (Mendeleev), cations of rare earth metals, or many mixtures thereof. Included as Pentasil (pentas
il) treatment with zeolite to remove the enriched m-dichlorobenzene as filtrate and recover p-dichlorobenzene by extraction from the pentasil zeolite, the solvent combination being used in this extraction, where: A representative of the group A is the formula

[0007]

[Chemical 3]

Wherein Hal represents chlorine or bromine, preferably chlorine, R ¹ represents Hal or C ₁ -C ₄ -alkyl, and R ² represents hydrogen, Hal or C ₁ -C.
₄ -alkyl, wherein R ¹ and R ² together may represent an indane, tetralin or naphthalene-based residue]. -Excluding chlorotoluene and the dichlorobenzenes, and representatives of the group B have the formula

[0009]

[Chemical 4]

[Wherein Hal has the meaning given above and R ³ is hydrogen, C ₁ -C ₄ -alkyl, C ₁ -C
₄ - alkoxy, C ₁ -C ₄ - alkylcarbonyl, C ₁ -
Represents a C ₄ -alkoxy-carbonyl, phenyl, nitro or aldehyde group].

This provides a method which makes it possible to separate p-dichlorobenzene from a mixture with m-dichlorobenzene with only one elution step with very high selectivity. The method of the present invention is an intermittent (pulse)
d) It has the advantage that it can be operated both discontinuously in the process as well as continuous in the countercurrent process. The manner of carrying out these two variants is known to the person skilled in the art and is thus not the subject of the present invention.

In the process of the present invention, the pentachloro-type zeolite is contacted with the dichlorobenzene isomer mixture in the presence of a solvent under adsorption conditions as known in principle to a person skilled in the art, It separates p-dichlorobenzene from a mixture of p-dichlorobenzene and m-dichlorobenzene with very high selectivity.

[0013] Zeolites are generally in the empirical formula _{M 2 / n O · Al 2} O 3 · xSiO 2 · yH 2 O (I) [ wherein, M represents a exchangeable cation or multiple mixtures thereof, n represents the charge of the exchangeable cation, x
Represents an integer from 2 to 2000, and y represents the amount of sorbed water].

The sorbed water phase yH ₂ O can be reversibly removed without the zeolite skeleton losing its structure.

Of the numerous zeolites known to those skilled in the art, those having the pentasil structure are used according to the present invention.

Preferably the following pentasil structure type: ZSM
5, ZSM 11, ZSM 8, ZSM 5 / ZSM
11 Intermediates, Zeta 1, Zeta 3, ZBM
10, Ultrasil, Ultraset, TZ-0
1, NU-4, NU-5, AZ-1 are used. Pentacyl zeolites, in particular these individually indicated structural types,
Known to the person skilled in the art, for example EP 54 386, EP 65 401,
European Patent 34 727, European Patent 5
It has been described many times, such as in 7 016 and EP 113 116. Particularly preferred pentasil zeolites are ZSM 5, ZSM 8,
ZSM 11 and ZSM 5 / ZSM 11 intermediates. Very particularly preferably ZSM 5 and ZSM
Type 11 pentasil zeolites were used, where
This SiO ₂ / Al ₂ O ₃ ratio is not subject to any restrictions.

These pentasil zeolites may contain the above cations as the exchangeable cations M. Examples are the following elements: H, Li, Na, K, M
g, Ca, La, Ce, Pr, Nd, preferably H, L
It is a cation of i, Na, K and Mg. The introduction of these exchangeable cations M is known to those skilled in the art, and often uses an ion exchange method of contacting an aqueous solution of a metal salt with zeolite (DW Brec.
k "Zeolite Molecular Siev
es, Structure, Chemistry an
d Use ", J. Willer / Sons, New Y
ork, 1974).

Prior to using these pentasil zeolites in the process of the invention, the sorbed water phase yH ₂ O is removed by calcining at 100 to 500 ° C.

The process of the invention is carried out in such a way that a mixture of its isomeric dichlorobenzenes (DCB) is present as the liquid phase in the solvent combination described. For the economics of this process, it is important to be able to separate the solvent used from the DCB by simple distillation. Therefore,
So that it is not necessary to distill very large amounts of raffinate and extract, that is, it is necessary to distill DCB and some secondary amount of a second solvent, which has a boiling point lower than that of DCB. DCB so that
It is particularly advantageous to use a solvent having a boiling point higher than that of as the main component of the solvent combination.

The proportion of isomers to be separated can be varied within wide limits. Mixtures containing at least 50% by weight m-DCB are preferred, 70% by weight m-DCB.
Mixtures containing the above are particularly suitable.

The solvent combination used in the claimed method is at least two different solvents from groups A and B respectively represented by the above formulas (I) and (II),
Here, a typical group A has one or two additional substituents together with a halogen atom or at least two halogen atoms and optionally one additional substituent.
4-chlorotoluene and dichlorobenzenes are excluded, and the representatives of group B have only one halogen atom and optionally one additional substituent except the halogen atom. I have one. Typical representatives of group A are 1,2,3-trichlorobenzene,
1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, 2,4-dichlorotoluene, 2,6-dichlorotoluene, 3,4-dichlorotoluene, 2-chloro-p-xylene, 4-chloro -O-xylene, 2-chlorotoluene, 1-chloronaphthalene, chlorodiethylbenzenes and chlorocumene, and also corresponding brominated or mixed chlorinated / brominated representatives, chlorinated compounds being preferred. .

Typical representatives of group B are chlorobenzene, 4
-Chlorotoluene, 4-chloroacetophenone, 4-chloroanisole, 4-chlorobenzaldehyde, methyl 4-chlorobenzoate, 4-phenylchlorobenzene, 1
-Chloro-2-nitrobenzene and 1-chloro-3-
Nitrobenzene, and also the corresponding brominated or mixed chlorinated / brominated representatives, chlorinated compounds are preferred.

On the one hand, the representatives of group A contain trichlorobenzene and / or dichlorotoluene isomers and on the other hand the representatives of group B are chlorobenzene, 4-chlorotoluene, 4-chloro. Combinations containing anisole, methyl 4-chlorobenzoate and / or 4-chloroacetophenone are preferred. The isomeric trichlorobenzenes and / or the isomeric dichlorotoluenes in combination with chlorobenzene, p-chlorotoluene or p-chloroacetophenone are particularly preferred. Combinations containing 1,2,4-trichlorobenzene together with chlorobenzene or p-chlorotoluene, as well as chlorobenzene or p-
Very particular preference is given to combinations containing 3,4- or 2,6-dichlorotoluene together with chlorotoluene.

These combinations contain 50 parts of Group A solvent.
-98% by weight and 50-2% by weight of group B solvent, preferably 80-98% by weight of group A solvent and 20-2% by weight of group B solvent, particularly preferably these Contains 90-98% by weight of Group A solvent and 10-2% by weight Group B. All weight percentages are based on the total weight of the combination.

The amount of said solvent combination is 5-20 times, preferably 5-15 times, particularly preferably 5-10 times the amount of DCB mixture to be separated.

Based on the amount of the pentasil zeolite,
The amount of DCB mixture to be subjected to the separation is limited by the intended separation effect, which depends on the available DC.
It decreases with each separation step and stage as the amount of B mixture increases. In general, 0.05 to 2, preferably 0.1 to 1, particularly preferably 0.2 to 0.8 unit of DCB is used per unit of pentasil zeolite.

20 to 250 ° C., preferably 20 to 20
The method of the invention is carried out at a temperature of 0 ° C. The pressure is not critical in the process of the invention, and therefore is generally carried out at atmospheric pressure for the purpose of simplifying the reactor. However, if the solvent is used at an operating temperature above its boiling point, it is also possible to carry out the reaction under pressure.

The mixture of m- and p-DCB is dissolved in one of the solvent combinations specified above and contacted with the pentasil zeolite in powder or granular form. The preferentially adsorbed component p-DCB is removed from the mixture.
After this adsorption is complete, the liquid phase is separated from the zeolite. This is a greatly enriched form of m-DC
B is included. This liquid phase (solvent combination and residual DC
B isomer) is treated separately. The adsorbed p-DCB can be removed from the pentasil zeolite by desorption known per se, using the same solvent combination here. Therefore, no special extraction step for the adsorbed p-DCB, for example with additional auxiliaries, is necessary. Therefore, the zeolite also automatically regenerates as a result of this process operation.

This step can be carried out in conventional equipment known to those skilled in the art of separation using adsorption means. Suitable devices are those which allow the operation to be carried out continuously or batchwise. It is possible to optimize the shape and size of these adsorbers, which themselves are not the subject of the present invention. The method of the present invention is preferably carried out in a continuous countercurrent chromatography facility.

In the examples described below, the quality of adsorption characteristics is shown using the adsorption selectivity defined as follows.

[0031] Let A be the component p-dichlorobenzene that is selectively adsorbed among the dichlorobenzene isomers, and B be the component m-dichlorobenzene that is less adsorbed.
The α _{A / B} value increases as the separation becomes better.

Those skilled in the art will recognize that a separation system having an α value slightly higher than 1 or less than 1 is unsuitable for this type of separation process described. Separation factors that differ by a few orders of magnitude from the 1's place are also unsuitable for methods that eliminate additional desorption steps, such as the claimed method, because in such cases the elution of the solvent used will show. The force is insufficient for components that are adsorbed much more strongly. The advantage of the process according to the invention is that the adsorption and desorption of the two components is carried out in one step with a single eluent containing a combination of the two solvents.

[0033]

Examples 1 to 5 For the purpose of measuring the adsorption selectivity, in each case the m-dichlorobenzene (m-dichlorobenzene (m-
DCB) is 85% by weight and p-dichlorobenzene (p
5 g of a 10% strength solution of the mixture containing 15% by weight of DCB) was contacted with 2.5 g of powdered zeolite and the mixture was stirred at 25 ° C. for 1 hour. Then, this solution was separated from the zeolite, undecane was added as an internal standard, and then analyzed by gas chromatography. The results are shown in Table 1.

Comparative Examples 1-4 Experiments were conducted according to Examples 1-5. The results are shown in Table 1.
Shown in.

Table 1 Examples Adsorbents Desorbents α _{p / m} 1 Mg-ZSM 5 1,2,4-trichlorobenzene / 6.3 5 wt% p-chlorotoluene 2 Mg-ZSM 5 3,4- 3. Dichlorotoluene / 3.7 10% by weight chlorobenzene 3 Mg-ZSM5 3,4-dichlorotoluene / 8.3 5% by weight p-chloroacetophenone 4 SE-ZSM5 1,2,4-trichlorobenzene / 4. 25 wt% chlorobenzene 5 SE-ZSM 5 2,4-dichlorotoluene / 5.5 10 wt% chlorobenzene C1 Mg-ZSM 5 1,2,4-trichlorobenzene / 93.1 C2 Mg-ZSM 5 3, 4-Dichlorotoluene 133.5 C3 SE-ZSM 5 3,4-dichlorotoluene 407.0 C4 Mg-ZSM 5 Chlorobenzene 1 Comparative Example C1-using only Group A solvent as eluent.
C3 has a separation factor that is orders of magnitude higher than the separation factor achieved with the adsorbent / solvent combinations of the present invention. The affinity of the pure solvents of group A according to claim 1 for zeolites is too small for eluting the much more strongly adsorbed p-dichlorobenzene isomer to a sufficient degree. Comparative example C4 shows that the use of the individual solvents of group B as eluents led to the complete elimination of both isomers and thus the desired separation of these isomers was not obtained.

Comparative Examples 5 and 6 LiX-type zeolites prepared according to EP 0 334 025 were subjected to static experiments according to Examples 1-5 to determine their selectivity with respect to p-DCB. . However, in contrast to the examples of the present invention, the solvent used in the above patent specification, toluene, was used. This experiment was performed at 25 ° C (C5) and 80
It was carried out at C (C6). The results are shown in Table 2. As mentioned above, the experiments carried out in this way allow the technician in the field to determine whether an adsorbent / solvent system is suitable for the separation, and then It will be possible to determine whether it may be carried out in a continuous or batchwise process mode as described in the above European patent. If, in the above experiments, the adsorbent / solvent system of choice did not show a separating effect, one of ordinary skill in the art would consider this system unsuitable for continuous or batch processes.

Table 2 Examples Adsorbent T (° C) α _{p / m} C5 Li-X 25 -1 C6 Li-X 80 -1 The features and aspects of the present invention are as follows.

1. Using zeolite in the presence of solvent m
In a method for effecting the separation of the above mixture by treating a mixture of-and p-dichlorobenzene, two groups A
And 20 to 2 together with a solvent combination consisting of at least two different solvents from B and B respectively.
Treated at 50 ° C. with a pentasil zeolite containing protons, cations of the first or second main group of the periodic table (Mendelieve), cations of rare earth metals, or a mixture of many of them as exchange cations. And the enriched m-dichlorobenzene is removed as a filtrate and p-dichlorobenzene is recovered by extraction from the pentasil zeolite, the solvent combination being used in this extraction, where the representative of the group A. The expression is

[0039]

[Chemical 5]

Wherein Hal represents chlorine or bromine, preferably chlorine, R ¹ represents Hal or C ₁ -C ₄ -alkyl and R ² represents hydrogen, Hal or C ₁ -C.
₄ -alkyl, wherein R ¹ and R ² together may represent an indane, tetralin or naphthalene-based residue], but here 4-chlorotoluene And the dichlorobenzenes are excluded, and representatives of the group B are

[0041]

[Chemical 6]

Wherein Hal has the meaning given above and R ³ is hydrogen, C ₁ -C ₄ -alkyl, C ₁ -C
₄ - alkoxy, C ₁ -C ₄ - alkylcarbonyl, C ₁ -
C ₄ -alkoxy-carbonyl, phenyl, nitro or aldehyde group].

2. The following structural types: ZSM 5, ZSM
11, ZSM 8, ZSM 5 / ZSM 11 intermediate, Zeta 1, Zeta 3, ZBM 10, Ul
trasil, Ultraset, TZ-01, NU-
4, NU-5, AZ-1, preferably ZSM 5, ZSM
Process according to claim 1, characterized in that pentasil zeolites with 8, ZSM 11 and ZSM 5 / ZSM 11 intermediates, particularly preferably ZSM 5 and ZSM 11, are used.

3. Process according to claim 1, characterized in that a mixture containing at least 50% by weight of m-dichlorobenzene, preferably a mixture containing at least 70% by weight of m-dichlorobenzene is used.

4. The solvent combination used is a trichlorobenzene system and / or a typical one of the group A.
Or chlorobenzene, 4-chlorotoluene, 4-chloroanisole, methyl 4-chlorobenzoate and / or 4-chloroacetophenone as representatives of group B. The method according to claim 1, characterized in that

5. 5. The solvent combination used according to claim 4, characterized in that it contains the isomeric trichlorobenzenes and / or the isomeric dichlorotoluenes in combination with chlorobenzene, p-chlorotoluene and / or p-chloroacetophenone. Method.

6. The solvent combination used is 1,2, with chlorobenzene or p-chlorotoluene.
6. A combination containing 4-trichlorobenzene or a combination containing 3,4- or 2,6-dichlorotoluene together with chlorobenzene or p-chlorotoluene. the method of.

7. The solvent combination used is 50-98% by weight of the group A solvent and 50-98% by weight of the group B solvent.
2% by weight, preferably 80-98% by weight of group A and group B
20-2% by weight, particularly preferably 90-98% by weight of group A and 10-2% by weight of group B, all weight% being based on the total weight of the combination. The method according to claim 1, characterized in that

8. Process according to claim 1, characterized in that the amount of solvent combination is 5-20 times, preferably 5-15 times, the amount of dichlorobenzene mixture to be separated.

9. Item 1 characterized in that a mixture of 0.05 to 2, preferably 0.1 to 1, particularly preferably 0.2 to 0.8 unit of dichlorobenzene is used per unit of pentasil zeolite. The method described.

10. The method according to item 1, which is carried out at 20 to 200 ° C.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Roter Putupe Germany 51399 Brusshayt Ambayer 10 Ar (72) Inventor Michael Peas Germany 47249 Dowisburg Ambolhauser 23 (72) Inventor Hans-Ingolf Paul Germany 51375 Lef Erkusen Zuyul Darsheutrase 20 Ar

Claims (1)

[Claims] 1. A method for separating a mixture of m- and p-dichlorobenzene by treating the mixture of m- and p-dichlorobenzene with zeolite in the presence of a solvent, wherein at least two different groups from each of the two groups A and B are used. The mixture is mixed with a solvent combination consisting of solvents from 20 to 250
Treated with pentasil zeolite containing protons, cations of the first or second main group of the periodic table (Mendelieve), cations of rare earth metals, or a mixture of many of them as exchange cations at ℃ , The enriched m-dichlorobenzene was removed as filtrate and extracted from the pentasil zeolite to give p
-Recovering dichlorobenzene, but using the above solvent combination in this extraction, where representatives of the group A are:
Formula [1] [Wherein Hal represents chlorine or bromine, preferably chlorine, R ¹ represents Hal or C ₁ -C ₄ -alkyl,
And R ² represents hydrogen, Hal or C ₁ -C ₄ -alkyl, wherein R ¹ and R ² together may represent an indane, tetralin or naphthalene residue.] Correspondingly, but excluding 4-chlorotoluene and the dichlorobenzenes, and representatives of the group B are of the formula Where Hal has the meaning given above and R ³
Represents hydrogen, C ₁ -C ₄ -alkyl, C ₁ -C ₄ -alkoxy, C ₁ -C ₄ -alkylcarbonyl, C ₁ -C ₄ -alkoxy-carbonyl, phenyl, nitro or aldehyde groups] The method characterized by doing.