JP2001048815A - Method for adsorbing and separating alkyl group- substituted aromatic compound isomer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently obtain a specific isomer from the isomer mixture of an aromatic compound having one or more >=3C alkyl groups. SOLUTION: This method for adsorbing and separating an alkyl group- substituted aromatic compound isomer comprises adsorbing and separating the aromatic compound having one or more >=3C alkyl groups from the isomer mixture of the aromatic compound having one or more >=3C alkyl groups in the presence of a zeolite adsorbent containing at least one cation selected from alkali metal cations, alkaline earth metal cations, lead cation, thallium cation and silver cation as an exchanging cation. The aromatic compound having one or more >=3C alkyl groups can efficiently be obtained by the adsorption and separation method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an isomer mixture of an aromatic compound having an alkyl group having 3 or more carbon atoms.
The present invention relates to a method for adsorptive separation of an alkyl group-substituted aromatic compound isomer by separating and recovering an aromatic compound having an alkyl group having 3 or more carbon atoms.

[0002]

2. Description of the Related Art Aromatic compounds having an alkyl group having 3 or more carbon atoms are known as important intermediates for agricultural chemicals and the like. However, when the number of carbon atoms in the alkyl group increases, isomers are generated depending on the number of branches, and since the properties (boiling point, melting point, solubility, etc.) of the isomers are similar, it is difficult to separate them by distillation or crystallization. is there.

[0003] Considering the case of disubstituted benzene, in the case of disubstituted benzene substituted with an alkyl group having 1 or 2 carbon atoms, there are three types of isomers: o-, m- and p- isomers. There are only three types, but when it contains an alkyl group having 3 or more carbon atoms, two types of normal propyl group and isopropyl group are used for three carbon atoms, and normal butyl, isobutyl, and secondary butyl are used for four carbon atoms. Group, tertiary butyl group, and there are three types of isomers, i.e., o-, m-, and p-types. It is necessary to separate a specific isomer from a large number of isomers.

However, the difference in boiling point between these aromatic compound isomers is small and a precise distillation column having a very high number of stages is required, and the desired aromatic compound having an alkyl group having 3 or more carbon atoms can be purified. It has been difficult to separate well and efficiently.

As a method for separating a chlorotoluene isomer having a different structure from the aromatic compound according to the present invention, an adsorption separation method using X-type zeolite as an adsorbent is disclosed in JP-B-37-5155. Kaisho 57-3162
Nos. 7,35528 and 91933 each disclose an adsorption separation method using a K ion-exchanged Y-type zeolite as an adsorbent. There is no ability to adsorb and separate the o-isomer, and m-chlorotoluene cannot be separated alone as an extract component or a raffinate component. Further, JP-A-58-
JP-A-131923 and JP-A-59-176223 disclose methods for separating m-chlorotoluene using Ag and K ion-exchanged Y-type zeolites and Na and Cu ion-exchanged Y-type zeolites as adsorbents, respectively. ,
According to this method, m-chlorotoluene is separated as a raffinate component.

[0006]

In the known adsorbents, when an isomer exists in an alkyl group, the isomer could not be separated. Thus, there has been no known adsorption / separation method for an aromatic compound having an alkyl group having 3 or more carbon atoms.

Accordingly, an object of the present invention is to provide a method for adsorptive separation of an aromatic compound having an alkyl group having 3 or more carbon atoms.

[0008]

Means for Solving the Problems A method for adsorptive separation of an isomer of an alkyl group-substituted aromatic compound according to the present invention for solving the above problems mainly has the following constitution.

That is, when a specific isomer is adsorbed and separated from a mixture of isomers of an aromatic compound having an alkyl group having 3 or more carbon atoms, alkali metal, alkaline earth metal, lead, thallium and the like are used as exchangeable cations. And zeolite containing at least one kind of cation selected from silver and silver as an adsorbent.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The aromatic compound having an alkyl group having 3 or more carbon atoms in the present invention means essentially any aromatic compound having an alkyl group directly bonded to an aromatic ring having 3 or more carbon atoms. And an alkyl group containing a hetero atom in the alkyl group. As used herein, the term "hetero atom" includes nitrogen, oxygen, sulfur, and halogen.

The preferred alkyl group of the aromatic compound having an alkyl group having 3 or more carbon atoms to which the method of the present invention can be applied preferably has 3 to 8, particularly preferably 3 to 6 carbon atoms. The alkyl group may be linear or branched, or a mixture thereof. Further, it may have one or more different substituents other than the alkyl group. Examples of different types of substituents include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, phenyl, halogen, formyl, carboxyl, acyl, alkoxyl, nitro Groups, amino groups, amido groups, hydroxyl groups, cyano groups and the like. The propyl group, butyl group, pentyl group, hexyl group, heptyl group, and octyl group may be linear or branched. In particular, when the compound has a methyl group, an ethyl group, a propyl group, a phenyl group, a halogen group, etc., the industrial use is wide, and the economic effect is increased.

The aromatic ring of the aromatic compound having an alkyl group having 3 or more carbon atoms includes a benzene ring, a naphthalene ring, a phenanthrene ring, an anthracene ring, and the like, preferably a benzene ring. In particular,
Alkylbenzene, halogenated alkylbenzene, dialkylbenzene, alkylbenzaldehyde, alkylbenzoic acid, alkylacetophenone, alkylpropiophenone, alkoxyalkylbenzene, alkylnitrobenzene, alkylaniline, alkylbenzylamine, alkylbenzamide, alkylphenol, alkylbenzyl alcohol, alkylbenzonitrile, Alkyl naphthalene and the like can be mentioned.

Specific examples of the aromatic compound having an alkyl group having 3 or more carbon atoms include, as an alkylbenzene,
Propylbenzene, butylbenzene, pentylbenzene, hexylbenzene, heptylbenzene, octylbenzene, etc., and as halogenated alkylbenzene, fluoropropylbenzene, chloropropylbenzene, bromopropylbenzene, iodopropylbenzene, dichloropropylbenzene, dibromopropylbenzene , Fluorobutylbenzene, chlorobutylbenzene, bromobutylbenzene, iodobutylbenzene, dichlorobutylbenzene, dibromobutylbenzene, fluoropentylbenzene, chloropentylbenzene, bromopentylbenzene, iodopentylbenzene, dichloropentylbenzene, dibromopentylbenzene, fluoro Hexylbenzene, chlorohexylbenzene, bromohexylbenzene, Dehexylbenzene, dichlorohexylbenzene, dibromohexylbenzene, fluoroheptylbenzene, chloroheptylbenzene, bromoheptylbenzene, iodoheptylbenzene, dichloroheptylbenzene, dibromoheptylbenzene, fluorooctylbenzene, chlorooctylbenzene, bromooctylbenzene, iodo Octylbenzene, dichlorooctylbenzene, dibromooctylbenzene and the like can be mentioned. In addition, the alkyl group may be linear or branched.

Examples of the dialkylated benzene include propyltoluene, ethylpropylbenzene, dipropylbenzene, butylpropylbenzene, pentylpropylbenzene, hexylpropylbenzene, heptylpropylbenzene, octylpropylbenzene, propyldiphenyl, butyltoluene, butylethylbenzene, dibutyl Benzene, butylpentylbenzene, butylhexylbenzene, butylheptylbenzene, butyloctylbenzene, butyldiphenyl, pentyltoluene, ethylpentylbenzene, dipentylbenzene, hexylpentylbenzene, heptylpentylbenzene, octylpentylbenzene, pentyldiphenyl, hexyltoluene, ethylhexyl Benzene, dihexylbenzene, heptylhexylbenze , Hexyl octyl benzene,
Hexyl diphenyl, heptyl toluene, ethyl heptyl benzene, diheptyl benzene, heptyl octyl benzene, heptyl diphenyl, octyl toluene, ethyl octyl benzene, dioctyl benzene, octyl diphenyl, etc.Alkyl benzaldehyde, propyl benzaldehyde, butyl benzaldehyde, pentyl Benzaldehyde, hexyl benzaldehyde, heptyl benzaldehyde, octyl benzaldehyde and the like can be mentioned. In addition, the alkyl group may be linear or branched.

Examples of the alkyl benzoic acid include propyl benzoic acid, butyl benzoic acid, pentyl benzoic acid, hexyl benzoic acid, heptyl benzoic acid, octyl benzoic acid, and the like. , Hexyl acetophenone, heptyl acetophenone, octyl acetophenone, etc., and the alkyl propiophenones include propyl propiophenone, butyl propiophenone, pentyl propiophenone, hexyl propiophenone, heptyl propiophenone, octyl propiophenone And the like, and examples of the alkoxyalkylbenzene include propylanisole, butylanisole, pentylanisole, hexylanisole, and heptylanisole. Luanisole, octylanisole, propylphenetol, butylphenetol, pentylphenetol, hexylphenetol, heptylphenetol, octylphenetol, propylphenoxybenzene, butylphenoxybenzene, pentylphenoxybenzene, hexylphenoxybenzene, heptylphenoxybenzene, octyl Phenoxybenzene and the like. In addition, the alkyl group may be linear or branched.

Examples of the alkylnitrobenzene include propylnitrobenzene, butylnitrobenzene, pentylnitrobenzene, hexylnitrobenzene, heptylnitrobenzene and octylnitrobenzene.
Examples of the alkyl aniline include propyl aniline, butyl aniline, pentyl aniline, hexyl aniline, heptyl aniline, and octyl aniline.As the alkyl benzyl amine, propyl benzyl amine, butyl benzyl amine, pentyl benzyl amine,
Hexylbenzylamine, heptylbenzylamine, octylbenzylamine and the like can be mentioned, and as alkylbenzamide, propylbenzamide, butylbenzamide, pentylbenzamide, hexylbenzamide, heptylbenzamide, octylbenzamide and the like can be mentioned. In addition, the alkyl group may be linear or branched.

Alkyl phenols include propyl phenol, butyl phenol, pentyl phenol, hexyl phenol, heptyl phenol, octyl phenol and the like. Alkyl benzyl alcohols include propyl benzyl alcohol, butyl benzyl alcohol, pentyl benzyl alcohol, hexyl benzyl alcohol, heptyl Benzyl alcohol, octyl benzyl alcohol and the like can be mentioned, and as alkyl benzonitrile, propyl benzonitrile, butyl benzonitrile, pentyl benzonitrile, hexyl benzonitrile, heptyl benzonitrile, octyl benzonitrile and the like can be mentioned. In addition, the alkyl group may be linear or branched.

Examples of the alkylnaphthalene include propylnaphthalene, butylnaphthalene, pentylnaphthalene, hexylnaphthalene, heptylnaphthalene, octylnaphthalene and the like. In addition, chloropropylnaphthalene, chlorobutylnaphthalene, chloropentylnaphthalene, chlorohexylnaphthalene, chloroheptyl, chloroheptyl Naphthalene, chlorooctylnaphthalene, dichloropropylnaphthalene, dichlorobutylnaphthalene, dichloropentylnaphthalene, dichlorohexylnaphthalene, dichloroheptylnaphthalene, dichlorooctylnaphthalene, bromopropylnaphthalene, bromobutylnaphthalene, bromopentylnaphthalene, bromohexylnaphthalene,
Bromoheptylnaphthalene, bromooctylnaphthalene, dibromopropylnaphthalene, dibromobutylnaphthalene, dibromopentylnaphthalene, dibromohexylnaphthalene, dibromoheptylnaphthalene, dibromooctylnaphthalene, bromochloropropylnaphthalene, bromochlorobutylnaphthalene, bromochloropentylnaphthalene, bromochlorohexyl Naphthalene, bromochloroheptylnaphthalene, bromochlorooctylnaphthalene and the like can be mentioned. In addition, the alkyl group may be linear or branched.

As the alkyl group having 3 or more carbon atoms, normal propyl, isopropyl, normal butyl, isobutyl, secondary butyl, tertiary butyl, normal pentyl, isopentyl, neopentyl, secondary pentyl Group, tertiary pentyl group, normal hexyl group, isohexyl group, secondary hexyl group, tertiary hexyl group, etc., among which normal alkyl group, normal propyl group, normal butyl group, normal pentyl group, normal hexyl Groups, and isopropyl, secondary butyl, secondary pentyl, and secondary hexyl groups as secondary alkyl groups are important from the viewpoint of variety of uses.

Although the o, m, p-isomer can be separated by this technique, the o-, p-isomer is easily generated by direct alkylation to an aromatic ring and halogenation. This technique is particularly useful in obtaining

It is an object of the present invention to separate these exemplified compounds.
-Chloronormalpropylbenzene, m-chloronormalpropylbenzene, p-chloronormalpropylbenzene, o-chloroisopropylbenzene, m-chloroisopropylbenzene, p-chloroisopropylbenzene, o-bromonormalpropylbenzene, m-bromonormalpropyl Benzene, p-bromonormalpropylbenzene, o-bromoisopropylbenzene, m-bromoisopropylbenzene, p-bromoisopropylbenzene, o-iodonopropylpropylbenzene, m-iodonopropylpropylbenzene, p-iodonopropylpropylbenzene, o- Iodoisopropylbenzene, m
-Iodoisopropylbenzene, p-iodoisopropylbenzene, o-chloronormal butylbenzene, m-
Chloronormal butylbenzene, p-chloronormalbutylbenzene, o-chloroisobutylbenzene, m-chloroisobutylbenzene, p-chloroisobutylbenzene, o-chlorosecondary butylbenzene, m-chlorosecondary butylbenzene, p-chlorosecondary butylbenzene , O-chloro-tert-butylbenzene, m-chloro-tert-butylbenzene, p-chloro-tert-butylbenzene, o-bromo-n-butylbenzene, m-bromo-n-butylbenzene,
p-bromo normal butylbenzene, o-bromoisobutylbenzene, m-bromoisobutylbenzene, p-bromoisobutylbenzene, o-bromosecondary butylbenzene, m-bromosecondary butylbenzene,
p-bromo secondary butyl benzene, o-bromo tertiary butyl benzene, m-bromo tertiary butyl benzene, p-bromo tertiary butyl benzene, o-iodo normal butyl benzene, m-iodo normal butyl benzene, p-iodo normal butyl Benzene, o-iodoisobutylbenzene, m-iodoisobutylbenzene, p-iodoisobutylbenzene, o-
Iodosecondary butylbenzene, m-iodosecondary butylbenzene, p-iodosecondary butylbenzene, o-iodotertiary butylbenzene, m
-Iodotert-butylbenzene, p-iodotert-butylbenzene and the like, and more preferably, m-chloronormalpropylbenzene, m-chloroisopropylbenzene, m-bromonormalpropylbenzene, m-bromoisopropylbenzene, m-chloroisopropylbenzene, and m-chloroisopropylbenzene. -Chloro normal butyl benzene, m-chloro secondary butyl benzene, m-bromo normal butyl benzene, m
-Bromosecondary butylbenzene and the like are preferred.

In the present invention, a zeolite containing at least one selected from alkali metals, alkaline earth metals, lead, thallium and silver as cations is preferably used.

The zeolite used in the present invention is described in W. M. WM Meier, De. H. The book "Atlas Obzeolites Structure Types (ATLAS) by DH Olson et al.
OF ZEOLITE STRUCTURE TYPES) "(Zeolites 17,1 / 2,199
6; Elsevier), etc., may be any of the structures described in detail, but are preferably selected from faujasite type, pentasil type, mordenite type and beta type, more preferably Faujasite-type zeolites are preferred.

The zeolite used in the present invention is:
A so-called isomorphous zeolite in which part of silica (silicon), which is a component of zeolite, is replaced by germanium, or part of aluminum is replaced by gallium, chromium, iron, or the like, may be used.

The zeolite used in the present invention is:
A synthesized product may be used, or a commercially available product may be used. When a synthesized product is used, zeolite can be synthesized by a known method. For example, a method for synthesizing a faujasite-type zeolite is disclosed in US Pat.
No. 3,702,886, U.S. Pat. No. 4,5,5, U.S. Pat. No. 3,702,886, U.S. Pat. No. 4,130,007 and U.S. Pat.
No. 11,547.

The faujasite-type zeolites preferably used in the present invention are X-type zeolites and Y-type zeolites, which are crystalline aluminosilicates represented by the following formula.

0.9 ± 0.2M _{2 / n} O: Al ₂ O ₃ : xS
iO ₂ : yH ₂ O Here, M represents a cation, and n represents its valence.
In the faujasite type zeolite, x in the above formula is usually 2 to 2.
The range is 6. The faujasite-type zeolite has x
X-type zeolites having 2 to 3 and Y-type zeolites wherein x has 3 to 6 are distinguished. Further, y differs depending on the degree of hydration.

The alkali metals used in the present invention include lithium, sodium, potassium, cesium, rubidium and the like, and the alkaline earth metals include magnesium, calcium, strontium and barium.

The exchangeable cation in the zeolite can be replaced with various cations by ion exchange.
The cation exchange method is usually carried out by bringing zeolite into contact with an aqueous solution of a compound containing a desired cation, for example, a hydrochloride, nitrate, sulfate, carbonate, hydroxide or the like. The amount of ion exchange varies depending on the type of cation, but can be arbitrarily set depending on the concentration of the aqueous solution.
In particular, silver ions are preferably exchanged with an aqueous solution containing silver equivalent to 0 to 50% of the ion exchange sites, and more preferably exchanged with an aqueous solution containing silver equivalent to 2 to 20%. In the case of lead ions, it is preferable to exchange with an aqueous solution containing lead corresponding to 10 to 70% of the ion exchange sites, and more preferably 30 to 50%.
% Is preferably replaced with an aqueous solution containing lead.
Further, in the case of cesium ions, 0
It is preferable to exchange with an aqueous solution containing cesium corresponding to ５０50%, and more preferably with an aqueous solution containing cesium equivalent to 2 to 30%. After the ion exchange, the substrate is sufficiently washed with water to remove sodium ions, for example, chloride ions and nitrate ions, which have been exchanged and eluted in the aqueous solution.

Further, the adsorbent used in the present invention may be a solidified zeolite alone, or a granulated with a binder such as silica, alumina, silica-alumina, magnesia or clay mineral.

The zeolite used in the present invention may be used as a mixture of two or more zeolites, if necessary.

It is preferable that the adsorbent removes water of crystallization in the zeolite before use. Usually 200 to 60
By heating at 0 ° C., most of the crystallization water can be removed.

The adsorption separation technique for adsorbing and separating an isomer mixture of an alkyl group-substituted aromatic compound by using the adsorbent of the present invention may be a so-called chromatographic preparative method, or may be a continuous method. An adsorption separation method using a simulated moving bed may be used.

The continuous adsorption / separation technique using the simulated moving bed is performed by circulating the following adsorption operation, concentration operation and desorption operation continuously as basic operations. (1) Adsorption operation: A raw material feed containing an isomer mixture of an alkyl group-substituted aromatic compound is brought into contact with the adsorbent of the present invention, and the strongest adsorbed component is selectively adsorbed. The strongest adsorbed component is recovered as an extract component together with a desorbing agent described later. (2) Concentration operation: The raffinate containing a large amount of weakly adsorbed components is further contacted with an adsorbent, and the strongest adsorbed components are selectively adsorbed, so that the weakly adsorbed components in the raffinate are highly purified. (3) Desorption operation: The highly purified weakly adsorbed component is recovered as raffinate, while the strongest adsorbed component is expelled from the adsorbent by the desorbent and recovered as an extract component with the desorbent. .

As the desorbing agent used in the adsorption separation method, an alkyl-substituted aromatic hydrocarbon, a halogenated aromatic hydrocarbon, or a halogenated alkyl-substituted aromatic hydrocarbon is preferable. Specific examples of the alkyl-substituted aromatic hydrocarbon include toluene, ethylbenzene, xylene, propylbenzene, trimethylbenzene, diethylbenzene, and tetramethylbenzene.

Specific examples of the halogenated aromatic hydrocarbon include chlorobenzene, dichlorobenzene, and trichlorobenzene. Specific examples of the halogenated alkyl-substituted aromatic hydrocarbon include chlorotoluene, dichlorotoluene, and chloroxylene.

Among these desorbing agents, chlorotoluene, chlorobenzene and xylene are preferably used, and more preferably at least one selected from o-chlorotoluene, p-chlorotoluene, o-xylene and m-xylene. Preferably, a seed is used.

These desorbing agents may be used alone or as a mixture.

As the operating conditions of the adsorption separation method, the temperature is preferably from room temperature to 350 ° C., more preferably 50 to 350 ° C.
The temperature is 250 ° C., and the pressure is preferably from atmospheric pressure to 4 MPa, more preferably from atmospheric pressure to 3 MPa. Although the adsorption separation process of the present invention can be carried out in the gas phase, it is preferably carried out in the liquid phase to reduce the operating temperature and reduce undesired side reactions of the feedstock or desorbent.

In the present invention, when p-halogenated normal alkylbenzene is separated as an extract component, at least one selected from a pentasil-type zeolite containing an alkali metal cation and an alkali metal, an alkaline earth metal, lead, thallium and silver is used. X-type zeolites or Y-type zeolites containing at least one kind of cation are preferably used. Specific examples of the alkali metal include lithium, sodium, potassium, cesium, and rubidium, and specific examples of the alkaline earth metal include magnesium, calcium, strontium, and barium. Among them, pentasil-type zeolites containing lithium and / or sodium, and X-type zeolites or Y-type zeolites containing potassium and / or barium are preferable, and particularly preferable cations include sodium and barium. Further, specifically, chlorotoluene and chlorobenzene are preferably used as the desorbing agent, and more preferably, o-chlorotoluene is used.

In the present invention, when the m-halogenated normal alkylbenzene is separated as an extract component, X-type zeolite containing at least one or more cations selected from alkali metals, alkaline earth metals, lead, thallium and silver or Y-type zeolites are preferably used. Specific examples of the alkali metal include lithium, sodium, potassium, cesium, and rubidium, and specific examples of the alkaline earth metal include magnesium, calcium, strontium, and barium. Among them, X containing at least one or more cations selected from lithium, sodium, magnesium, calcium, strontium, lead, thallium and silver
Zeolite or Y zeolite is preferred, and particularly preferred cations include lithium, sodium, magnesium, calcium, strontium and silver. Also, specifically as a desorbent, chlorotoluene,
Preferably, chlorobenzene is used, and more preferably, o-chlorotoluene is used.

In the present invention, when the o-halogenated normal alkylbenzene is separated as an extract component, X-type zeolite containing at least one cation selected from alkali metals, alkaline earth metals, lead, thallium and silver, or Y-type zeolites are preferably used. Specific examples of the alkali metal include lithium, sodium, potassium, cesium, and rubidium, and specific examples of the alkaline earth metal include magnesium, calcium, strontium, and barium. Among them, at least one selected from sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, lead, thallium and silver
X-type zeolites or Y-type zeolites containing at least one kind of cation are preferred, and particularly preferred cations include sodium, potassium, rubidium, calcium, strontium and silver. Further, specifically, chlorotoluene and chlorobenzene are preferably used as the desorbing agent, and more preferably, p-chlorotoluene, m-chlorotoluene and chlorobenzene are used.

In the present invention, when p-halogenated secondary alkylbenzene is separated as an extract component, X-type zeolite containing at least one or more cations selected from alkali metals, alkaline earth metals, lead, thallium and silver or Y-type zeolites are preferably used. Specific examples of the secondary alkylbenzene include isopropylbenzene and isobutylbenzene. Further, specific examples of the alkali metal include lithium, sodium, potassium, cesium, and rubidium, and specific examples of the alkaline earth metal include magnesium, calcium, strontium, and barium. Among them, potassium, rubidium,
X-type zeolites or Y-type zeolites containing at least one cation selected from barium are preferred,
Particularly preferred cations include potassium and barium. Further, specifically, chlorotoluene and chlorobenzene are preferably used as the desorbing agent, and more preferably, o-chlorotoluene, m-chlorotoluene and chlorobenzene are used.

In the present invention, when the m-halogenated secondary alkylbenzene is separated as an extract component, X-type zeolite containing at least one cation selected from alkali metals, alkaline earth metals, lead, thallium and silver, or Y-type zeolites are preferably used. Specific examples of the secondary alkylbenzene include isopropylbenzene and isobutylbenzene. Further, specific examples of the alkali metal include lithium, sodium, potassium, cesium, and rubidium, and specific examples of the alkaline earth metal include magnesium, calcium, strontium, and barium. Among them, lithium, sodium,
X-type zeolites or Y-type zeolites containing at least one cation selected from rubidium, potassium, cesium, magnesium, barium and thallium are preferred, and particularly preferred cations are lithium, potassium, rubidium, cesium, magnesium, barium and thallium. Is mentioned. Further, specifically, chlorotoluene, chlorobenzene, and xylene are preferably used as the desorbing agent, and more preferably, p-chlorotoluene, m-chlorotoluene, o-chlorotoluene, and chlorobenzene are used.

In the present invention, when p-halogenated secondary alkylbenzene is separated as a raffinate component, X-type zeolite containing at least one cation selected from alkali metals, alkaline earth metals, lead, thallium and silver or Y-type zeolite containing at least one cation. Zeolite is preferably used. Specific examples of the secondary alkylbenzene include isopropylbenzene and isobutylbenzene. Further, specific examples of the alkali metal include lithium, sodium, potassium, cesium, and rubidium, and specific examples of the alkaline earth metal include magnesium, calcium, strontium, and barium. Among them, lithium, sodium, potassium, cesium, rubidium, magnesium, calcium, strontium, thallium and silver containing at least one kind of cation selected from the group consisting of zeolites and Y zeolites are preferred. Sodium, cesium, magnesium, calcium, strontium, thallium and silver. Further, specifically, chlorotoluene and chlorobenzene are preferably used as the desorbing agent, and more preferably p-chlorotoluene, m-chlorotoluene,
It is preferred to use chlorobenzene.

In the present invention, when an o-halogenated secondary alkylbenzene is separated as a raffinate component, a pentasil-type zeolite containing an alkali metal cation, an alkali metal, an alkaline earth metal, lead,
X-type zeolites or Y-type zeolites containing at least one or more cations selected from thallium and silver are preferably used. Specific examples of the secondary alkylbenzene include isopropylbenzene and isobutylbenzene. Specific examples of the alkali metal include lithium, sodium, potassium, cesium, and rubidium, and specific examples of the alkaline earth metal include magnesium, calcium, strontium, and barium. Among them, pentasil-type zeolites containing lithium and / or sodium, and X-type zeolites or Y containing at least one or more cations selected from lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, thallium and barium. Type zeolites are preferred, and particularly preferred cations include lithium, sodium, potassium, rubidium, cesium, magnesium, strontium, thallium and barium. Further, specifically, chlorotoluene and chlorobenzene are preferably used as the desorbing agent, and more preferably m-chlorotoluene and o-chlorotoluene are preferably used.

In the present invention, when the o-halogenated normal alkylbenzene is separated as a raffinate component, X-type zeolite or Y-type zeolite containing at least one cation selected from alkali metals, alkaline earth metals, lead, thallium and silver is used. Zeolite is preferably used. Specific examples of the alkali metal include lithium, sodium, potassium, cesium, and rubidium. Specific examples of the alkaline earth metal include magnesium,
Calcium, strontium, barium and the like can be mentioned. Among them, X-type zeolites or Y-type zeolites containing at least one kind of cation selected from lithium, cesium, magnesium, barium and thallium are preferable, and particularly preferable cations are lithium,
Cesium, magnesium and barium are mentioned. Further, specifically, chlorotoluene and chlorobenzene are preferably used as the desorbing agent, and more preferably, o-
Preferably, chlorotoluene is used.

In the present invention, when separating m-halogenated normal alkylbenzene as a raffinate component, a Y-type zeolite containing at least one cation selected from alkali metals, lead, thallium and silver is preferably used. Specific examples of the alkali metal include lithium, sodium, potassium, cesium, and rubidium. Among them, potassium, cesium, rubidium and lead are preferred, and particularly preferred cations include potassium, cesium and lead. Further, specifically, chlorotoluene, chlorobenzene, and xylene are preferably used as the desorbing agent, and more preferably, p-
It is preferable to use at least one selected from chlorotoluene, o-xylene and m-xylene.

In the present invention, when p-halogenated normal alkylbenzene is separated as a raffinate component, X-type zeolite containing at least one or more cations selected from alkali metals, alkaline earth metals, lead, thallium and silver, or Y-type zeolite Zeolite is preferably used. Specific examples of the alkali metal include lithium, sodium, potassium, cesium, and rubidium. Specific examples of the alkaline earth metal include magnesium,
Calcium, strontium, barium and the like can be mentioned. Among them, lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, barium, thallium, and silver zeolites containing at least one or more cations selected from the group consisting of silver and zeolites are preferable.
Potassium, cesium, magnesium, calcium, barium, thallium and silver. Further, specifically, chlorotoluene and chlorobenzene are preferably used as the desorbing agent, and more preferably m-chlorotoluene, o-chlorotoluene and chlorobenzene are preferably used.

In general, to express the adsorption characteristics of an adsorbent,
The adsorption selectivity (α) of the following equation (1) is used.

[0051]

(Equation 1)

Here, A and B represent any one of the isomers of the aromatic compound, S represents an adsorption phase, and L represents a liquid phase in equilibrium with the adsorption phase.

When the value of the above equation is larger than 1, the component A is selectively adsorbed, and when the value is smaller than 1, the component B is selectively adsorbed. Further, the adsorbent having an α value of greater than 1 in the above equation (or an adsorbent smaller than 1 and close to 0) facilitates the adsorption and separation of A and B.

[0054]

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

In the examples, the six isomers of chloropropylbenzene, o-chloroisopropylbenzene (oI),
Adsorbent for m-chloroisopropylbenzene (mI), p-chloroisopropylbenzene (pI), o-chloronormalpropylpropylbenzene (oN), m-chloronormalpropylbenzene (mN), p-chloronormalpropylbenzene (pN) Is represented by the adsorption selectivity (α) of the following equation (2).

[0056]

(Equation 2)

Here, A and B represent any one of chloropropylbenzene isomers, S represents an adsorption phase, and L represents a liquid phase in equilibrium with the adsorption phase. Also, o, m, p, N and I are used to represent chloropropylbenzene isomers.
o, m, and p represent o-, m-, and p-chloropropylbenzene, respectively, and I and N represent chloroisopropylbenzene and chloronormal propylbenzene, respectively. For example, mN indicates m-chloronormal propylbenzene, and pI indicates p-chloroisopropylbenzene. As A, mN (m-chloronormalpropylbenzene) is mainly used.

When the value of the above equation is larger than 1, the component A is selectively adsorbed, and when the value is smaller than 1, the component B is selectively adsorbed. Further, the adsorbent having an α value of greater than 1 in the above equation (or an adsorbent smaller than 1 and close to 0) facilitates the adsorption and separation of A and B. For example, when the A component is mN, the larger the α value in the above formula is, the more m-chloronormalpropylbenzene is converted to o-chloroisopropylbenzene, m-chloroisopropylbenzene, p-chloroisopropylbenzene, and o-chloroisopropylbenzene. It is more easily adsorbed than chloronormal propyl benzene and p-chloro normal propyl benzene, and if it is smaller than 1, m-chloro normal propyl benzene is o-chloroisopropyl benzene, m-chloro isopropyl benzene, p-chloro isopropyl benzene, o-chloro It is harder to adsorb than normal propyl benzene and p-chloro normal propyl benzene. That is, an adsorbent suitable for separating and recovering m-chloronormalpropylbenzene is α
_{It is preferable} that _{mN / oI} , _{αmN / mI} , _{αmN / pI} , _{αmN / oN} , and _{αmN / pN} are all greater than 1 or smaller than 1 and close to 0. An adsorbent suitable for separating and recovering other isomers, for example, m- _{chloroisopropylbenzene} as an extract component, has α _{mN / mI} smaller than 1, and the other four α, α _{mN / oI} , α _Preferably , _{mN / pI} , α _{mN / oN} and α _{mN / pN} are all larger than α _{mN / mI} . Further, an adsorbent suitable for separating and recovering other isomers such as p-chloroisopropylbenzene as a raffinate component has an α _{mN / pI} of more than 1, and the other four α, α _{mN / oI} ,
_Preferably , α _{mN / mI} , α _{mN / oN} , and α _{mN / pN} are all smaller than α _{mN / pI} . (Preparation of adsorbent) Table 1 shows a list of adsorbents used. The preparation method will be described later.

[0059]

[Table 1]

Adsorbent 1: 100 parts by weight of Na-Y sodium type Y zeolite (hereinafter referred to as NaY) (Zeolam Na-5.1Y powder manufactured by Tosoh Corporation) as an binder and alumina sol (Nissan) (Chemical No. 200; Al ₂ O ₃ = 10 wt%) was added in an amount of 15 parts by weight in terms of alumina, and the NaY-type zeolite granulated to 0.15 to 0.5 mmφ was dried at 120 ° C.
Fired at ℃. Adsorbents 2 to 8: MY The adsorbent 1 is prepared by using a 10 wt% aqueous solution of potassium, rubidium, cesium, magnesium, calcium, strontium and barium nitrate (solid-liquid ratio 4.0 L / kg).
Ion exchange treatment was performed 5 times at 80 ° C. for 30 minutes, washed sufficiently with distilled water, dried at 120 ° C., and fired at 500 ° C. Adsorbent 9: Pb-KY Adsorbent 1 was subjected to 10 times of 1 hour ion exchange treatment at 80 ° C. using a 10 wt% aqueous solution of potassium nitrate (solid-liquid ratio: 3.0 L / kg), and sufficiently washed with distilled water. After that, N of Na-Y
a Using an aqueous solution of lead nitrate converted to lead corresponding to 40% of the cation site (solid-liquid ratio: 3.0 L / kg) at room temperature
The mixture was left standing for 80 minutes, subjected to an ion exchange treatment at 80 ° C. for 2 hours, washed sufficiently with distilled water, dried at 120 ° C., and fired at 500 ° C. Adsorbent 10: Cs-Pb-KY Adsorbent 1 was ion-exchanged 10 times at 80 ° C for 1 hour using a 10 wt% aqueous solution of potassium nitrate (solid-liquid ratio: 3.0 L / kg) and distilled water. After sufficient washing, the Na-Y
a Using an aqueous solution of lead nitrate converted to lead corresponding to 40% of the cation site (solid-liquid ratio: 3.0 L / kg) at room temperature
For 2 hours at 80 ° C. and sufficiently washed with distilled water.
Using an aqueous solution of cesium nitrate in terms of cesium equivalent to 0% (solid-liquid ratio: 3.0 L / kg), leave it at room temperature for 30 minutes, perform ion exchange treatment at 80 ° C. for 2 hours, and sufficiently wash with distilled water. , Dried at 120 ° C and calcined at 500 ° C. Adsorbent 11: Na-X sodium type X zeolite (hereinafter referred to as NaX) (Zeolam F-9 powder product, manufactured by Tosoh Corporation) 10
20 parts by weight of bentonite gel (Bengel) was added as a binder to 0 parts by weight, and the NaX-type zeolite granulated to 0.15 to 0.3 mmφ was dried at 120 ° C.
Fired at ℃. Adsorbents 12 to 18: MX The adsorbent 11 was prepared using a 10 wt% aqueous solution of potassium, rubidium, cesium, magnesium, calcium, strontium and barium nitrate (solid-liquid ratio 4.0 L / k).
g) Ion exchange treatment was performed 5 times at 80 ° C. for 30 minutes, sufficiently washed with distilled water, dried at 120 ° C., and calcined at 500 ° C. Adsorbents 19 to 24: n% M-NaX The adsorbent 11 is a metal (M = silver, cesium, thallium, lithium) corresponding to n% of the Na cation site of Na-X.
Using an aqueous solution of metal nitrate converted to a (solid-liquid ratio of 3.0)
(L / kg) The mixture was allowed to stand at room temperature for 30 minutes, subjected to an ion exchange treatment at 85 ° C. for 1 hour, washed sufficiently with distilled water, dried at 120 ° C., and fired at 500 ° C. Adsorbent 25: Na-type pentasil (Na-MFI) solid sodium hydroxide (NaOH content 96.0 wt%, H ₂ O
7.3 g of tartaric acid powder (tartaric acid content: 99.7 wt%, H ₂ O content: 0.3 wt%, content: 4.0 wt%, Katayama Chemical)
(Katayama Chemical) 10.2 grams were dissolved in 583.8 grams of water. To this solution was added 35.4 g of a sodium aluminate solution (Al ₂ O ₃ content: 18.5 wt%, NaOH content: 26.1 wt%, H ₂ O content: 55.4 wt%, Sumitomo Chemical) to obtain a uniform solution. Silicic acid powder (SiO ₂ content: 91.6 wt%, Al ₂ O ₃ content: 0.33 wt%, Na
111.5 g of OH content 0.27 wt%, Nipsil VN-3, Nippon Silica) was gradually added with stirring.
A homogeneous slurry-like aqueous reaction mixture was prepared. The composition ratio (molar ratio) of this reaction mixture was as follows.

SiO ₂ / Al ₂ O ₃ 25 H ₂ O / SiO ₂ 20 OH − / SiO ₂ 0.164 A / Al ₂ O ₃ 1.0 A: Tartrate The reaction mixture is placed in a 1000 ml autoclave and sealed. Then, the mixture was reacted at 160 ° C. for 72 hours while stirring at 250 rpm to obtain a pentasil-type zeolite powder. This is washed 5 times with water, dried at 120 ° C. for about 12 hours, then heated from room temperature to 350 ° C., further raised to 550 ° C. every 50 ° C. every hour, and finally kept at 550 ° C. for 3 hours. It was fired by doing. This powder was tableted, crushed and sized to a particle size of 0.7 to 1.4 mm. (Adsorption experiment) Examples 1-8 Adsorption selectivity between chloropropylbenzene isomers was measured using adsorbents 1-8. The measuring method was as follows: 2.7 ml of the liquid phase mixture and 3.3 ml of the adsorbent calcined at 500 ° C. were charged into an autoclave having an internal volume of 5 ml, and the mixture was charged at 130 ° C. for 30 minutes.
It was left with occasional stirring. The composition of the charged liquid phase mixture was n-nonane: chloropropylbenzene (oI: mI: p
I: oN: mN: pN = 15: 28: 23: 1: 23: 10) = 5%: 95%.
n-Nonane was added as an internal standard substance in the gas chromatography method, and is a substance which is substantially inert to adsorption in the above experiment.

The composition of the liquid phase mixture after contact with the adsorbent was analyzed by gas chromatography, and the adsorption selectivity between chloropropylbenzene isomers was determined using the above formula (2). Table 2 shows the results and the strongly adsorbed and non-adsorbed components.

[0063]

[Table 2]

Examples 9 to 16 The same procedures as in Example 1 were carried out except that the adsorbents 11 to 18 were used. Table 3 shows the results and the strongly adsorbed and non-adsorbed components.

[0065]

[Table 3]

Example 17 Using the adsorbent 25, the composition of the liquid phase mixture charged was changed to 1,
3,5-triisopropylbenzene: chloropropylbenzene (oI: mI: pI: oN: mN: pN = 15: 28: 23: 1: 23: 10) = 5%: 95
% In the same manner as in Example 1. The results and the strongly adsorbed and non-adsorbed components are shown in Table 3. 1,3,
5-Triisopropylbenzene is added as an internal standard substance in the gas chromatography method, and is a substance which is substantially inert to adsorption in the above experiment.

Examples 18 to 24 Adsorption selectivities between chloropropylbenzene isomers were measured using adsorbents 1, 2, 4 to 8. The measuring method was as follows: 2.7 ml of the liquid phase mixture and 50 ml of autoclave were used.
Charge 3.3 ml of adsorbent calcined at 0 ° C,
Leave for 0 minutes with occasional stirring. The composition of the charged liquid phase mixture was o-chlorotoluene: n-nonane: chloropropylbenzene (oI: mI: pI: oN: mN: pN = 3: 4:
4: 2: 8: 2) = 70%: 6%: 24%. O-chlorotoluene was added as a desorbing agent, and n-nonane was added as an internal standard substance in gas chromatography, and was a substance which was substantially inert to adsorption in the above experiment.

The composition of the liquid phase mixture after contact with the adsorbent was analyzed by gas chromatography, and the adsorption selectivity between chloropropylbenzene isomers was determined using the above formula (2). Table 4 shows the results and the strongly adsorbed and non-adsorbed components.

[0069]

[Table 4]

Examples 25 to 32 The same procedures as in Example 18 were carried out except that the adsorbents 11, 12, 14 to 19 were used. Table 5 shows the results and the strongly adsorbed and non-adsorbed components.

[0071]

[Table 5]

Examples 33 to 39 Adsorption selectivities between chloropropylbenzene isomers were measured using adsorbents 1, 2, 4 to 8. The measuring method was as follows: 2.7 ml of the liquid phase mixture and 50 ml of autoclave were used.
Charge 3.3 ml of adsorbent calcined at 0 ° C,
Leave for 0 minutes with occasional stirring. The composition of the charged liquid phase mixture was p-chlorotoluene: n-nonane: chloropropylbenzene (oI: mI: pI: oN: mN: pN = 3: 5:
4: 2: 8: 2) = 70%: 5%: 25%. p-Chlorotoluene was added as a desorbing agent, and n-nonane was added as an internal standard substance in a gas chromatography method, and is a substance which is substantially inert to adsorption in the above experiment.

The composition of the liquid phase mixture after contact with the adsorbent was analyzed by gas chromatography, and the adsorption selectivity between chloropropylbenzene isomers was determined using the above formula (2). Table 6 shows the results and the strongly adsorbed and non-adsorbed components.

[0074]

[Table 6]

Examples 40 to 47 The same procedures as in Example 33 were carried out except that the adsorbents 11, 12, 14 to 19 were used. Table 7 shows the results and the strongly adsorbed and non-adsorbed components.

[0076]

[Table 7]

Examples 48 to 54 Adsorption selectivities between chloropropylbenzene isomers were measured using adsorbents 1, 2, 4 to 8. The measuring method was as follows: 2.7 ml of the liquid phase mixture and 50 ml of autoclave were used.
Charge 3.3 ml of adsorbent calcined at 0 ° C,
Leave for 0 minutes with occasional stirring. The composition of the charged liquid phase mixture was chlorobenzene: n-nonane: chloropropylbenzene (oI: mI: pI: oN: mN: pN = 3: 4: 4:
2: 9: 2) = 71%: 5%: 24%. Chlorobenzene was added as a desorbing agent, and n-nonane was added as an internal standard substance in a gas chromatography method, and was a substance substantially inactive in adsorption in the above experiment.

The composition of the liquid phase mixture after contact with the adsorbent was analyzed by gas chromatography, and the adsorption selectivity between chloropropylbenzene isomers was determined using the above formula (2). Table 8 shows the results and the strongly adsorbed and non-adsorbed components.

[0079]

[Table 8]

Examples 55 to 62 The same procedures as in Example 48 were carried out except that the adsorbents 11, 12, 14 to 19 were used. Table 9 shows the results and the strongly adsorbed and non-adsorbed components.

[0081]

[Table 9]

Examples 63 to 70 Adsorption selectivities between chloropropylbenzene isomers were measured using adsorbents 17, 14, 11, 20 to 24. The measuring method was as follows: 2.7 ml of the liquid phase mixture and 3.3 ml of the adsorbent calcined at 500 ° C. were charged into an autoclave having an internal volume of 5 ml, and the mixture was allowed to stand at 130 ° C. for 30 minutes with occasional stirring. The composition of the charged liquid phase mixture was o-chlorotoluene: n-nonane: chloropropylbenzene (oI: mI: pI: o
N: mN: pN = 16: 23: 8: 20: 21: 11) = 47%: 6%: 47%. O-chlorotoluene was added as a desorbing agent, and n-nonane was added as an internal standard substance in gas chromatography, and was a substance which was substantially inert to adsorption in the above experiment.

The composition of the liquid phase mixture after contact with the adsorbent was analyzed by gas chromatography, and the adsorption selectivity between chloropropylbenzene isomers was determined using the above formula (2). Table 10 shows the results and the strongly adsorbed and non-adsorbed components.

[0084]

[Table 10]

Example 71 The adsorption selectivity between chloropropylbenzene isomers was measured using the adsorbent 9. The measuring method is as follows.
2.7 ml of the liquid phase mixture and 3.3 ml of the adsorbent calcined at 500 ° C. were filled in a tocle and left at 130 ° C. for 30 minutes with occasional stirring. The composition of the charged liquid phase mixture was m-xylene: n-nonane: chloropropylbenzene (oI: mI: pI: oN: mN: pN = 12: 20: 17: 8: 27: 15) = 47.
%: 6%: 47%. m-xylene was added as a desorbing agent, and n-nonane was added as an internal standard substance in a gas chromatography method, and is a substance which is substantially inert to adsorption in the above experiment.

The composition of the liquid phase mixture after contact with the adsorbent was analyzed by gas chromatography, and the adsorption selectivity between chloropropylbenzene isomers was determined using the above formula (2). Table 11 shows the results and the strongly adsorbed and non-adsorbed components.

[0087]

[Table 11]

Examples 72 and 73 Adsorption selectivities between chloropropylbenzene isomers were measured using adsorbents 9 and 10. The measuring method is 5ml
The autoclave was filled with 2.7 ml of the liquid phase mixture and 3.3 ml of the adsorbent calcined at 500 ° C., and left at 130 ° C. for 30 minutes with occasional stirring. The composition of the charged liquid phase mixture was o-xylene: n-nonane: chloropropylbenzene (oI: mI: pI: oN: mN: pN = 12: 20: 17: 8: 27: 1)
5) = 47%: 6%: 47%. o-xylene is added as a desorbing agent, and n-nonane is added as an internal standard substance in a gas chromatography method, and is a substance which is substantially inert to adsorption in the above experiment.

The composition of the liquid phase mixture after contact with the adsorbent was analyzed by gas chromatography, and the adsorption selectivity between chloropropylbenzene isomers was determined using the above formula (2). Table 12 shows the results and the strongly adsorbed and non-adsorbed components.

[0090]

[Table 12]

[0091]

According to the present invention, as an exchangeable cation, an alkali metal, an alkaline earth metal, or an isomer mixture of an aromatic compound having an alkyl group having 3 or more carbon atoms is obtained.
By using a zeolite containing at least one cation selected from lead, thallium and silver as an adsorbent, an aromatic compound having an alkyl group having 3 or more carbon atoms can be efficiently obtained.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C07C 25/02 C07C 25/02 (72) Inventor Kazuyoshi Iwayama 9 Oecho, Minato-ku, Nagoya-shi, Aichi 1 Toray Industries, Inc. Nagoya Office F-term (reference) 4D017 AA03 AA04 BA04 BA05 CA17 DB02 4G066 AA61B AA62B CA33 CA51 DA09 GA11 4H006 AA02 AD17 BB11 BB12 DA15

Claims (9)

[Claims] The present invention relates to a method for adsorbing and isolating a specific isomer from an isomer mixture of an aromatic compound having an alkyl group having 3 or more carbon atoms, as an exchangeable cation, an alkali metal, an alkaline earth metal, lead, and thallium. And zeolite containing at least one kind of cation selected from silver and silver as an adsorbent. 2. The method for adsorptive separation of alkyl group-substituted aromatic compound isomers according to claim 1, wherein the aromatic compound having an alkyl group having 3 or more carbon atoms further has at least one halogen substituent. . 3. The alkyl group according to claim 1, wherein isomers having different numbers of branched alkyl groups are separated from a mixture of isomers of an aromatic compound having an alkyl group having 3 or more carbon atoms. A method for adsorptive separation of a substituted aromatic compound isomer. 4. The zeolite according to claim 1, wherein the zeolite is a faujasite type zeolite.
12. The method for adsorptive separation of an isomer of an alkyl group-substituted aromatic compound according to the above item. 5. The following formula: (Where R represents an alkyl group having 3 or more carbon atoms and X represents a halogen). M-halogenated normal alkylbenzene or m-halogenated secondary alkylbenzene is adsorbed and separated from an isomer mixture of halogenated alkylbenzene represented by the formula: The method for adsorptive separation of a halogenated alkyl group-substituted aromatic compound isomer according to any one of claims 1 to 4. 6. The method according to claim 1, wherein a zeolite containing at least one cation selected from lithium, calcium, magnesium, sodium, cesium, potassium, lead, thallium and silver as the exchangeable cation is used as the adsorbent. 6. The method for adsorptive separation of an isomer of an alkyl group-substituted aromatic compound according to any one of claims 5 to 5. 7. The alkyl group according to claim 1, wherein at least one member selected from the group consisting of xylene isomers, chlorotoluene isomers, and chlorobenzene is used as a desorbing agent. A method for adsorptive separation of a substituted aromatic compound isomer. 8. The method for adsorbing and separating an alkyl-substituted aromatic compound isomer according to claim 1, which has an alkyl group having 3 carbon atoms. 9. The method for adsorbing and separating an alkyl-substituted aromatic compound isomer according to claim 1, wherein the method has at least one chloro group.