METHOD FOR SEPARATING HALOGENATED ETHYLBENZENE ISOMERS

Abstract: A method for isomerizing a halogenated ethylbenzene characterized by bringing the same into contact with an acidic zeolite containing at least one metal selected among metals of Groups 7 to 11; and a method of efficiently isolating a m-halogenated ethylbenzene from a mixture of halogenated ethylbenzene isomers by adsorption using a specific zeolite X or Y as the adsorbent. The isomerization method enables a halogenated ethylbenzene to be efficiently isomerized with the zeolite catalyst. The separation method enables m-chloroethylbenzene to be efficiently separated from a mixture of chloroethylbenzene isomers by using a specific zeolite as the adsorbent.

Description: The present invention relates to a method for separating halogenated ethylbenzene isomers. In more detail, the present invention relates to a method for separating and recovering a m-halogenated ethylbenzene from a mixture of halogenated ethylbenzene isomers. Background Arts Halogenated ethylbenzenes are known as important intermediate products of agricultural chemicals, etc. Especially m-chloroethylbenzene (hereinafter chloroethylbenzene is abbreviated as CEB) or m-bromoethylbenzene (hereinafter bromoethylbenzene is abbreviated as BEB) is expected as a raw material of agricultural chemicals with specific bioactivity as an isomer different from p- and o-isomers. CEB or BEB is mainly produced by aromatic ring chlorination or bromination reaction of ethylbenzene, but since the reaction is very strong in ortho-orientation and para-orientation, the m-isomer can be produced only in a small amount. Therefore, CEB and BEB isomerization methods have an important technical significance. Conventionally known isomerization reactions for these compounds include a method of using aluminum chloride, etc. as a catalyst disclosed in Olah. G. A. J. Org. CHEM. 27, 3464 (1962), a method of using HF-BF 3 as a catalyst disclosed in Japanese Patent Laid-Open (Kokai) 46-11809, etc. Furthermore, Idar A. Acta Chemica Scandinavica B39,437 (1985) describes a chloroethylbenzene isomerization reaction using a mordenite-type zeolite. Furthermore, methods for isomerizing a halogenated toluene using a zeolite as a catalyst are disclosed in Japanese Patent Laid-Open (Kokai) Nos. 57-40428, 85330, 163327 and 7-309792. However, in the isomerization reactions of halogenated ethylbenzenes, it has been difficult to efficiently isomerize using conventional catalysts such as aluminum chloride and HF-BF 3 since the disproportionation reaction accompanying the de-ethylation reaction or intermolecular migration of ethyl groups is likely to occur, unlike the isomerization reactions of halogenated toluenes. Furthermore, because of such problems as the enormous use of catalyst for isomerization, corrosion of reactor and environmental issue in the treatment of waste catalyst, the conventional methods are not efficient. The isomerization reaction using a mordenite catalyst is less in these problems, but has such a disadvantage that since the catalyst life is short, the zeolite must be regenerated after hundreds of hours. So, a method for more efficiently obtaining a desired halogenated ethylbenzene is strongly demanded. For separation of halogenated ethylbenzene isomers, since the halogenated ethylbenzene isomers are not so different in boiling point, a precision distillation column with a very large number of stages is necessary for separating them. So, it has been difficult to efficiently separate a m-halogenated ethylbenzene at high purity. As methods for separating the isomers of chlorotoluene structurally different from halogenated ethylbenzenes of the present invention, Japanese Patent Publication (Tokko) No. 37-5155 discloses an adsorption separation method using a zeolite X as the adsobent, and Japanese Patent Laid-Open (Kokai) Nos. 57-31627, 35528 and 91933 disclose adsorption separation methods using a K ion exchanged zeolite Y as the adsorbent. These methods can separate the m-isomer from the p-isomer by adsorption, but cannot separate the m-isomer from the o-isomer, and m-chlorotoluene cannot be singly separated as an extract component or raffinate component. Furthermore, Japanese Patent Laid-Open (Kokai) Nos. 58-131923 and 59-176223 disclose m-chlorotoluene separation methods using an Ag and K ion exchanged zeolite Y or a Na and Cu ion exchanged zeolite Y as the adsorbent, and these methods can separate m-chlorotoluene as a raffinate component. However, as far as the inventors examined, these adsorbents could little separate m-CEB. As described so far, no method for adsorbing and separating a halogenated ethylbenzene has been known at all, and there has been no idea of attempting it at all. Disclosure of the Invention The inventors studied intensively on the method for efficiently separating a halogenated ethylbenzene, and found that m-isomer can be efficiently separated from a mixture of halogenated ethylbenzene isomers, particularly of CEB or BEB, by adsorption separation, using an adsorbent containing a specific zeolite and a desorbent. Thus, the present invention as a method for separating halogenated ethylbenzene isomers has been completed. The present invention relates to a method for separating halogenated ethylbenzene isomers, comprising the step of separating a m-halogenated ethylbenzene from a mixture of halogenated ethylbenzene isomers using an adsorbent containing a zeolite X containing an alkali metal and/or alkaline earth metal, or an adsorbent containing a zeolite Y containing sodium, and a desorbent. In the present invention, the following two embodiments are preferable: a method for separating halogenated ethylbenzene isomers, comprising the step of separating a m-halogenated ethylbenzene as an extract component using an adsorbent containing a zeolite X containing alkali metal cations and not containing silver cations or containing silver cations by less than 10% of the ion exchange sites, or containing a zeolite Y containing sodium, and a method for separating halogenated ethylbenzene isomers, comprising the step of separating a m-halogenated ethylbenzene as a raffinate component using an adsorbent containing a zeolite X containing alkali metal and/or alkaline earth metal cations and containing silver cations by 10% or more of the ion exchange sites. The present invention is especially effective when the mixture of halogenated ethylbenzene isomers is a mixture of chloroethylbenzene isomers or a mixture of bromoethylbenzene isomers. Furthermore, in the present invention, it is preferable that the desorbent used is an alkyl substituted aromatic hydrocarbon, halogenated aromatic hydrocarbon or halogenated alkyl substituted aromatic hydrocarbon. Brief Description of the Drawing Fig. 1 is a diagram showing the amounts of the respective components eluted with the lapse of time in Example 16 of the present invention. The Best Embodiments of the Invention The method for separating halogenated ethylbenzene isomers of the present invention is described below in detail. The zeolite X or Y used in the method for separating halogenated ethylbenzene isomers of the present invention is a faujasite-type zeolite which is a crystalline aluminosilicate represented by the following formula: 0.970.2M 2 / n O:Al 2 O 3 :xSiO 2 :yH 2 O where M stands for cations, and n stands for their valence. In a faujasite-type zeolite, x is usually in a range of 2 to 6. The faujasite-type zeolite can be classified into a zeolite X with 2 to 3 as x, and a zeolite Y with 3 to 6 as x. y depends on the hydration degree. In the present invention, a specific zeolite X or a specific zeolite Y can be used. That is, a zeolite X containing an alkali metal and/or alkaline earth metal as cations M or a zeolite Y containing sodium as cations M is used. The faujasite-type zeolite is usually obtained as a zeolite containing sodium as cations M, and the cations can be replaced by various cations by ion exchange. The cation exchange is usually effected by bringing the zeolite into contact with an aqueous solution of a compound containing the intended cations such as a hydrochloride, nitrate, sulfate, carbonate or hydroxide, etc. The ion exchanged amount can be set as desired by the concentration of the aqueous solution, though depending on the kind of cations. After completion of ion exchange, the zeolite is sufficiently rinsed, to remove the sodium ions, chlorine ions, nitrate ions, etc. dissolved in the aqueous solution due to ion exchange. When a m-halogenated ethylbenzene is separated as an extract component in the present invention, a zeolite X containing alkali metal cations and not containing silver cations or containing silver cations by less than 10% of the ion exchange sites, and a zeolite Y containing sodium ions are preferable. The alkali metal cations of the zeolite X include Li, Na, K, Cs, etc., and sodium is especially preferable. When a m-halogenated ethylbenzene is separated as a raffinate component in the present invention, a zeolite X containing alkali metal and/or alkaline earth metal cations and containing silver cations by 10% or more of the ion exchange sites can be preferably used. The alkali metals include Li, Na, K, Cs, etc., and the alkaline earth metals include Mg, Ca, Sr, Ba, etc. Especially preferable combinations are Ag and Ba, Ag and K, etc. Such a zeolite can be obtained by ion-exchanging the sodium of a faujasite-type zeolite by an alkali metal or alkaline earth metal, and then ion-exchanging 10% to 70% of the sodium cation sites of the zeolite by silver. It is preferable to exchange 10% to 40%. When silver cations are not contained or contained by less than 10%, the m-halogenated ethylbenzene can be separated as an extract component. The adsorbent can be a solidified zeolite only or can be grains obtained by granulating a zeolite together with a binder such as alumina or clay. Before the adsobent is used, the crystal water in the zeolite is removed beforehand. Usually by heating at 200 to 600°C, most of crystal water can be removed. The adsorption separation technique for adsorbing and separating the CEB isomer mixture or BEB isomer mixture using the adsorbent of the present invention can be the so-called chromatographic fractionation method or an adsorption separation method using a simulated moving bed as a continuous version of said method. The continuous adsorption separation technique using a pseudo-moving bed is effected by continuously using the following adsorption operation, concentration operation and desorption operation in circulation. [1] Adsorption operation: The raw materials containing a halogenated ethylbenzene isomer mixture are brought into contact with the adsorbent of the present invention, and the most adsorbable component is selectively adsorbed. The most adsorbable component is recovered with the desorbent described later, as an extract component. [2] Concentration operation: The raffinate containing a less adsorbable component in a large amount is further brought into contact with the adsorbent, and the most adsorbable component is selectively adsorbed, while the less adsorbable component in the raffinate becomes highly purified. [3] Desorption operation: The highly purified less adsorbable component is recovered as a raffinate. On the other hand, the most adsorbable component is expelled from the adsorbent by a desorbent, and recovered as an extract component together with the desorbent. It is preferable that the desorbent used for the above adsorption separation method is an alkyl substituted aromatic hydrocarbon or a halogenated aromatic or halogenated alkyl substituted aromatic hydrocarbon. The alkyl substituted aromatic hydrocarbons which can be used here include, for example, toluene, ethylbenzene, xylene, propylbenzene, trimethylbenzene, diethylbenzene, tetramethylbenzene, etc. The halogenated aromatic hydrocarbons which can be used here include, for example, chlorobenzene, dichlorobenzene, trichlorobenzene, etc. The halogenated alkyl substituted aromatic hydrocarbons include, for example, chlorotoluene, dichlorotoluene, chloroxylene, etc. Especially for separation of m-CEB, preferable are p-xylene, 1,2,4-trimethylbenzene, m-chlorotoluene and 3,4-dichlorotoluene. For separation of m-BEB, preferable are p-xylene and 3,4-dichlorotoluene. Any or more as a mixture of these adsorbents can be used. As operation conditions of the adsorption separation method, the temperature is usually room temperature to 350°C, preferably 50 to 250°C, and the pressure is usually atmospheric pressure to 4 MPa, preferably atmospheric pressure to 3 MPa. The adsorption separation method of the present invention can be effected also in vapor phase, but to decrease the unpreferable side reactions of the raw materials and desorbent by lowering the operation temperature, it is preferable to execute the method in liquid phase. The adsorption separation may use as feed a m-halogenated ethylbenzene produced by isomerising the corresponding halogenated ethylbenzene by bringing it into contact with an acidic zeolite containing at last one Gp 7-11 metal, optionally in the presence of hydrogen. The halogen is typically chlorine or bromine, and the zeolite is advantageously a faujasite, mordenite, a pentasil or zeolite beta. Reaction is usually carried out at a temperature of 150 to 400°C, and a halogenated benzene, and/or benzene, may be present during reaction. Examples The present invention will be described below in more detail with reference to examples and comparative examples, which are not intended to restrict the scope of the invention. [Adsorption characteristics of adsorbents] In the examples, the adsorption characteristic of an adsorbent was expressed by the adsorption selectivity (α) of the following formula (1): where o, m or p stands for o-, m- or p-halogenated ethylbenzene respectively; A stands for adsorption phase; and U stands for liquid phase balanced with adsorption phase. If the α value in the above formula is larger than 1, the m-halogenated ethylbenzene is less likely to be adsorbed than the o- and p-halogenated ethylbenzenes, and if smaller than 1, the m-halogenated ethylbenzene is more likely to be adsorbed than the o- and p-halogenated ethylbenzenes. The adsorbent suitable for separating and recovering the m-halogenated ethylbenzene is preferably larger than 1 or smaller than 1, being close to 0 in both α (o/m) and α (p/m). [Preparation of adsorbents] The adsorbents 1 to 5 used in the examples were prepared according to the following methods: Adsorbent 1: Alumina sol (Nissan Chemical No. 200: Al 2 O 3 = 10 wt%) as a binder was added by 15 parts by weight as alumina to 100 parts by weight a sodium type zeolite X (hereinafter expressed as NaX) (Zeolam F-9 powder produced by Tosoh Corp.), and the mixture was granulated to 0.15 - 0.5 mm dia., to obtain a NaX type zeolite. It was dried at 120 °C and calcined at 500°C. Adsorbent 2: Alumina sol (Nissan Chemical No. 200: Al 2 O 3 = 10 wt%) as a binder was added by 15 parts by weight as alumina to 100 parts by weight of a sodium type zeolite Y (hereinafter expressed as NaY) (Zeolam Na-5.1Y powder produced by Tosoh Corp.), and the mixture was granulated to 0.15 - 0.5 mm dia., to obtain a NaY type zeolite. It was dried at 120 °C and calcined at 500°C. Adsorbent 3: Ag-BaX The adsorbent 1 was treated for ion exchange using 10 wt% barium nitrate aqueous solution (solid liquid ratio 3.0 l/kg) at 85°C for 1 hour six times and sufficiently washed with distilled water. Then, using a silver nitrate aqueous solution (solid liquid ratio 3.0 l/kg) as silver corresponding to 40% of the Na cation sites of NaX, it was allowed to stand at room temperature for 30 minutes and treated for ion exchange at 85°C for 1 hour, sufficiently washed with distilled water, dried at 120°C and calcined at 500°C. Adsorbent 4: Ag-NaX Using a silver nitrate aqueous solution (solid liquid ratio 3.0 l/kg) as silver corresponding to 5% of the Na cation sites of NaX, the adsorbent 1 was allowed to stand at room temperature for 30 minutes and treated for ion exchange at 85°C for 1 hour, sufficiently washed with distilled water, dried at 120°C and calcined at 500°C. Adsorbent 5: Ag-KY Using 10 wt% potassium nitrate aqueous solution (solid liquid ratio 3.0 l/kg), the adsorbent 2 was treated for ion exchange at 85°C for 1 hour ten times, and sufficiently washed with distilled water. Then, using a silver nitrate aqueous solution (solid liquid ratio 3.0 I/kg) as silver corresponding to 30% of the Na cation sites of NaY, it was allowed to stand at room temperature for 30 minutes and treated for ion exchange at 85°C for 1 hour, sufficiently washed with distilled water, dried at 120°C and calcined at 500°C. EXAMPLES 1-7 The adsorption selectivities between respective CEB isomers were measured using the adsorbent 1 and various desorbents. For measurement, a 5 ml autoclave was charged with 3 g of a liquid phase mixture and 1.5 g of the adsorbent calcined at 500°C, and the mixture was allowed to stand at 130°C for 1 hour with stirring sometimes. The composition of the supplied liquid phase mixture was n-nonane : desorbent : CEB (o : m : p =37% : 44% : 19%) 8% : 60% : 32%. The n-nonane was added as an internal standard substance for gas chromatography, which was substantially inactive in adsorption under the above experimental conditions. The composition of the liquid phase mixture after contact with the adsorbent was analyzed by gas chromatography, and adsorption selectivities between respective CEB isomers were obtained using the formula (1). The results are shown in Table1. Example Desorbent α(p/m) α(o/m) 1 p-xylene 0.21 0.46 2 iso-propylbenzene 0.41 0.71 3 1,2,4-trimethylbenzene 0.43 0.46 4 1,2,3,5-tetramethylbenzene 0.48 0.78 5 o-chlorotoluene 0.39 0.76 6 3,4-dichlorotoluene 0.48 0.78 7 1,2,4-trichlorobenzene 0.40 0.79 EXAMPLES 8-9 Experiments were performed as described in Example 1, except that the adsorbent 2 was used. In Example 8, o-xylene was used as the desorbent, and in Example 9, 1,2,4-trimethylbenzene was used as the desorbent. The results are shown in Table 2. Example Desorbent α(p/m) α(o/m) 8 o-xylene 0.20 0.54 9 1,2,4-trimethylbenzene 0.30 0.54 EXAMPLES 10-12 Experiments were performed as described in Example 1, except that the adsorbent 3 was used. In Example 10, o-xylene was used as the desorbent, and in Example 11, m-chlorotoluene was used as the desorbent. In Example 12, 3,4-dichlorotoluene was used as the desorbent. The results are shown in Table 3. Example Desorbent α(p/m) α(o/m) 10 o-xylene 1.38 1.28 11 m-chlorotoluene 2.54 1.71 12 3,4-dichlorotoluene 2.08 1.29 Example 13 An experiment was performed as described in Example 1, except that the adsorbent 4 was used and that 3,4-dichlorotoluene was used as the desorbent. The results are shown in Table 4. Example Desorbent α(p/m) α(o/m) 13 3,4-dichlorotoluene 0.45 0.88 Example 14 The adsorption selectivities between respective BEB isomers were measured using the adsorbent 1. The measuring method was as described in Example 1. The composition of the supplied liquid phase mixture was n-nonane : desorbent :.BEB (o : m : p = 34% : 40% : 26%) = 13% : 46% : 41%. The results are shown in Table 5. Example Adsorbent α(p/m) α(o/m) 14 p-xylene 0.24 0.44 Example 15 Adsorption selectivities between respective BEB isomers were measured using the adsorbent 3, as described in Example 1. As the desorbent, 3,4-dichlorotoluene was used. The composition of the supplied liquid phase mixture was n-nonane : desorbent : BEB (o : m : p = 34% : 40% : 26%) = 13% : 46% : 41%. The results are shown in Table 6. Example Desorbent α(p/m) α(o/m) 15 3,4-dichlorotoluene 2.23 1.13 Comparative Example 1 An experiment was performed as described in Example 1, except that the adsorbent 1 was used and that xylene was used as the desorbent. The adsorption characteristics of chlorotoluene and CEB were compared, and the results are shown in Table 7. Chlorotoluene CEB Adsorbent α(p/m) α(o/m) α(p/m) α(o/m) p-xylene 0.68 0.97 0.21 0.46 Comparative Example 2. An experiment was performed as described in Example 1, except that the adsorbent 5 was used and that 3,4-dichlorotoluene was used as the desorbent. The adsorption characteristics of chlorotoluene and CEB were compared, and the results are shown in Table 7 Chlorotoluene CEB Desorbent α(p/m) α(o/m) α(p/m) α(o/m) 3,4-dichlorotoluene 1.41 1.40 1.68 1.09 Example 16 A 1 m long 4.75 mm inner dia. stainless steel column was packed with the adsorbent 1, and p-xylene as a desorbent was fed at a flow rate of about 1.8 ml/min in a 130°C oil bath. While para-xylene was fed, about 1.6 ml of an isomer mixture consisting of CEB (o : m : p = 37% : 44% : 19%) : n-nonane = 4 : 1 (ratio by weight) was introduced into the inlet of the column, as a raw material to be separated. The n-nonane was used as a reference for elution time, and its adsorption is virtually negligible compared with other components. The eluate from the outlet of the column was analyzed by gas chromatography, and elution curves shown in Fig. 1 were obtained. Industrial Applicability According to the present invention, by an adsorption separation method using a specific zeolite X or Y as the adsorbent, a m-halogenated ethylbenzene can be efficiently obtained from a mixture of halogenated ethylbenzene isomers. Therefore, the present invention is suitable for industrial production of a desired halogenated ethylbenzene, above all, a m-halogenated ethylbenzene.

Claims: A method for separating a halogenated ethylbenzene isomer, comprising the step of separating m-halogenated ethylbenzene from a mixture of halogenated ethylbenzenes, using an adsorbent containing a zeolite X containing an alkali metal and/or alkaline earth metal, or an adsorbent containing a zeolite Y containing sodium, and a desorbent. A method for separating a halogenated ethylbenzene isomer, according to claim 1, wherein the halogen is chlorine and/or bromine. A method for separating a halogenated ethylbenzene isomer, according to claim 1 or 2, wherein an adsorbent containing a zeolite X containing alkali metal cations and not containing silver cations or containing silver cations by less than 10% of the ion exchange sites, or an adsorbent containing a zeolite Y containing sodium is used as the adsorbent, to separate the m-halogenated ethylbenzene as an extract component. A method for separating a halogenated ethylbenzene isomer, according to claim 1 or 2, wherein an adsorbent containing a zeolite X containing alkali metal and/or alkaline earth metal cations and containing silver cations by 10% or more of the ion exchange sites is used as the adsorbent, for separating the m-halogenated ethylbenzene as a raffinate component. A method for separating a halogenated ethylbenzene isomer, according to any one of claims 1 to 4, wherein the halogenated ethylbenzene isomer mixture is chloroethylbenzene isomer mixture. A method for separating a halogenated ethylbenzene isomer, according to any one of claims 1 to 4, wherein the desorbent is an alkyl substituted aromatic hydrocarbon, halogenated aromatic hydrocarbon or halogenated alkyl substituted aromatic hydrocarbon. A method according to any preceding claim wherein said isomer is a m-halogenated ethylbenzene produced by isomerising the corresponding halogenated ethylbenzene over an acidic zeolite catalyst containing at least one metal selected among the metals of Groups 7 to 11.

Inventors: MINOMIYA EIICHI, MIYATA SATORU, MINOMIYA, EIICHI, MIYATA, SATORU
Applicants: TORAY INDUSTRIES, TORAY INDUSTRIES, INC.
Application year: 1997
Main classification: C07C25
IPC codes: C07C17, B01J29