JPS58150524A - Separation method of di-halogenated benzene isomer - Google Patents

Abstract

PURPOSE:To improve the performance, selectivity and economic efficiency in adsorbing and separating a mixture of isomers of dihalogenated benzene with a zeolite adsorbent, by using an adsorbent containing 3,4-dihalogenated toluene, etc. CONSTITUTION:In adsorbing and separating a mixture of isomers of dihalogenated benzene with a zeolite adsorbent, a desorbing agent containing 3,4-di- halogenated toluene and/or 4-halogenated o-xylene as an essential component is used as the desorbing agents. The desorbing agent may be used alone or as a mixture and further with a diluent, e.g. paraffin or cycloparaffin hydrocarbon, etc. The method is particularly effective for repeating the adsorptive and desorptive operations and separating and recovering the isomers continuously from any one of them without damaging the selective adsorptivity for the strongly adsorptive component in the isomers in the adsorbent by the presence of the above-mentioned desorbing agents.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for adsorption and separation of di-halogenated benzene isomers1), and more specifically, the present invention relates to a method for adsorption and separation of di-halogenated benzene isomers1). The present invention relates to an improvement in a desorbent in a method for adsorbing and separating di-halogenated benzene isomers.

It is known from Japanese Patent Publication No. 37-5155 that sigino-logenated benzene isomers are adsorbed and separated by a zeolite adsorbent, and chlorobenzene is known as a desorbent in this case.

However, conventionally known desorbents do not exhibit sufficient performance.

An object of the present invention is to provide a desorbent for adsorbing and separating di-halogenated benzene isomers using a zeolite-based adsorbent. The object of the present invention is to provide a novel desorbent that is highly effective in separating and recovering any di-halogenated benzene isomer from a benzene isomer mixture.

The di-halogenated benzene isomer mixture in the present invention is a di-halogen nucleus-substituted product of benzene), o 1
It is a mixture containing at least two isomers selected from mIp-di-halogenated benzene.

The continuous adsorption separation of the di-halogenated benzene isomers described above is basically constituted by combining the following adsorption operation and desorption operation. (1) In an adsorption operation, a feedstock containing a mixture of di-halogenated benzene isomers is (
It is brought into contact with the adsorbent that has completed the desorption operation described in 2),
The strongly adsorbed components in the raw material feed are selectively adsorbed while displacing a portion of the desorbent remaining in the adsorbent. At the same time, the less adsorbable components of the raw material feed are recovered together with the desorbent as a raffinate stream. (2) In a desorption operation, selectively adsorbed components are expelled from the adsorbent by a desorbent and recovered as an extract stream.

Furthermore, for high purification of strongly adsorbed components, a portion of the extract stream is brought into contact with an adsorbent during the adsorption and desorption operations.

The following points are important when selecting a desorbent to be used in the above adsorption separation method.

That is, in order to cycle and continuously perform the adsorption operation and desorption operation shown in (]) and (2), the desorbent must be able to expel the strongly adsorbed components adsorbed onto the adsorbent during the desorption operation. The desorbent produced and thus remaining on the adsorbent must be driven out by the strongly adsorbed components in the feedstock in the adsorption operation, allowing the adsorbent to be recycled and used continuously. In other words, in the desorption operation, it is preferable to use a desorbent that strongly adsorbs both strongly adsorbed components.
In adsorption operations, it is better to use a desorbent that weakly adsorbs both strongly adsorbed components. In order to satisfy these conflicting demands at the same time, it is necessary to select a desorbent whose adsorption power for strongly adsorbed components is similar to that of the adsorbent for the desorbent.

In addition, in this adsorption separation method, the adsorbent washed with a desorbent in order to drive out the strongly adsorbed components in the desorption operation (2) is transferred to the adsorption operation (1) while containing the desorbent, and the adsorbent is transferred to the adsorption operation (1) while containing the desorbent. Since selective adsorption of the strongly adsorbed components is carried out, competitive adsorption between the strongly adsorbed components and the desorbent remaining in the adsorbent occurs in the adsorption operation.

Therefore, another important factor required when selecting a desorbent is that since the selective adsorption of di-halogenated benzene is carried out in the presence of the desorbent, other than the strongly adsorbed components of the adsorbent The selective adsorption capacity for strongly adsorbed components as compared to the isomers of the desorbent must not be impaired by the presence of the desorbent.

The selective adsorption ability of the adsorbent for strongly adsorbed components when compared with isomers other than the strongly adsorbed components and the desorbent is expressed as the adsorption selectivity α (A/Ittake D) of the strongly adsorbed components expressed by the formula H. be done.

α (A/B or D) (weight fraction of A in non-adsorbed phase/B or D in non-adsorbed phase
(Weight fraction of components)...Here, A is a strongly adsorbed component, B is an isomer other than the strongly adsorbed component, and D is a desorbent, which is divided into an adsorbed phase and a non-adsorbed phase. is in equilibrium.

(In the formula, the larger the value of α(A/13') is compared to 1, the more strongly adsorbed components are adsorbed more selectively than other isomers.

α(A/B) close to 1 means that the adsorption selectivity of the strongly adsorbed component is small, and if a highly purified strongly adsorbed component is to be recovered, the concentration of the strongly adsorbed component in the raffinate stream will increase, The recovery rate of strongly adsorbed components decreases. If an attempt is made to improve the recovery rate of the strongly adsorbed components, isomers other than the strongly adsorbed components will increase in the extract stream, and a decrease in the purity of the recovered strongly adsorbed components will be unavoidable.

α(A/D') in the equation (Todoroki) indicates the adsorption selectivity of the strongly adsorbed component compared to the desorbent, but in order for the desorbent and the strongly adsorbed component to be adsorbed almost equally, α(A/D') is preferably in the vicinity of 1, particularly in the range of CL5 to 2.0. α
If (A/D) is much larger than 1, a large amount of desorbent is required to expel the strongly adsorbed components selectively adsorbed in the desorption operation from the adsorbent, or the strongly adsorbed components cannot be sufficiently expelled. This reduces the recovery rate of strongly adsorbed components and becomes uneconomical. On the other hand, if α(A//D) is too small by more than 1p, it will be difficult for the desorbent to be expelled by the strongly adsorbed components in the raw material feed during the adsorption operation, and as a result,
The adsorption of the strongly adsorbed components is hindered, resulting in a substantial decrease in the adsorption capacity of the strongly adsorbed components, the concentration of the strongly adsorbed components in the raffinate stream increases, and the recovery rate of the strongly adsorbed components decreases, which is also uneconomical.

Therefore, when selecting a desorbent to be used in a method for adsorptive separation of di-halogenated benzene isomer mixtures, it is important to consider that α(A/B) measured in the presence of the desorbent is higher and α(
Selecting a desorbent with A/D ) close to 1 is an extremely important requirement for improving the economic efficiency of the adsorption separation method of the present invention.

From the above points of view, the present inventors conducted extensive research to find a better desorbent, and as a result, compared to conventional ones, 6,4-dihalogenated toluene and/or 4-
The present invention was achieved by discovering that a desorbent containing northo-logenated ortho-xylene exhibits extremely high performance.

That is, the present invention provides a method for adsorbing and separating di-logenated benzene isomers using a zeolite adsorbent, in which 6,4-dino-logenated toluene and/or 4-logenated orne are used as the desorbent. The present invention provides a method for separating benzene isomers using a desorbent containing xylene as an essential component.

6,4-dino-logenated toluene and/or as desorbent
Alternatively, the usefulness of 4-no-logenated orun-xylene is that it maintains a high selective adsorption rate (α(A/B)) for the no-logenated toluene isomer, as is clear from the examples described below.
In addition, the selectivity α (A/D
) is close to 1.

Therefore, by using the desorbent of the present invention, it becomes possible to separate the sheet rogogenated benzene isomers more economically.

The desorbent used in the method of the present invention may be used alone or in combination, or may be used together with a diluent such as paraffin or cycloparaffinic hydrocarbon. Further, it is preferable to use the above-mentioned desorbent comprising the same type of dihalogenated benzene to be separated.

The zeolite-based adsorbent used in the method of the present invention is not limited to a specific one, but mainly faujasite containing one or more cations selected from Group 1A, Group 1A metals, and protons. Type zeolites and the like are preferred adsorbents.

In particular, Ay-type zeolites whose cations are sodium and/or potassium are preferred. Of course, it is also preferably used that additionally contains at least one other cation component such as silver, copper, strontium, barium, zirconium, yttrium, proton, and the like.

The operating conditions for the adsorption separation method of the present invention include a temperature of 0 to 5.
50° C., particularly preferably from room temperature to 250° C., and the pressure is selected from atmospheric pressure to 40 Kf/cr/L, particularly preferably from approximately atmospheric pressure to 30 Ky/cr/l.

Although the adsorption separation process of the present invention can be carried out in either the gas phase or the liquid phase, it is more preferred to carry out the process in the liquid phase in order to lower operating temperatures and reduce undesirable side reactions of the feedstock or desorbent.

Next, the method of the present invention will be explained by giving examples.

Example 1 The adsorbent was prepared by ion-exchanging sodium-type zeolite Y1 and sodium-type zeolite Y with potassium nitrate so that more than 90% of the sodium ions were ion-exchanged with potassium at 120°C.
After drying for 1 hour, 1.8 f of the adsorbent was prepared by baking at 500°C for 1 hour and placed in an autoclay
and dichlorobenzene (DCB) isomer mixture, 3,4
- Filled with 2.5f of a liquid phase mixture consisting of dichlorotoluene or 4-chloroorthoxylene and n-nonane,
The mixture was left at 0° C. for about 1 hour with occasional stirring.

The composition of the liquid phase mixture charged here is n-nonane:
o-DCB: m-DCB: p-DCB: 3
．． 4-dichlorotoluene 51Jt4-chloroorthoxylene = 1:2:2:1:s (weight ratio), n-nonane was added as a reference material in gas chromatography analysis, and under the above conditions It is a substance that is virtually inert to adsorbents.

The composition of the liquid phase mixture after contact with the adsorbent was analyzed by gas chromatography, and the adsorption selectivity was calculated from the amount of change in the composition of the liquid phase mixture. The results are shown in Table 1.

Table 1 Example 1. The adsorption power of the dichlorobenzene isomer to the -Y type adsorbent is in the following order: 0 body>9 body>m body. Therefore,
0 body and/or m from the o, m, p temperature mixture
It is possible to adsorb and separate and recover the body.

Furthermore, adsorption separation of a mixture of 0 and 9 bodies and a mixture of 9 and m bodies is possible. In any of the above cases, the desorbents of the present invention, 3,4-dichlorotoluene and 4-chloroornexylene, have αI)/D and α. /D is close to 1, indicating that it is an excellent desorbent.

-j, the adsorption power of the dichlorobenzene isomer to the Na-Y type adsorbent is in the following order: 9-isomer>0-isomer>m-isomer. Therefore,
It is effective in separating and recovering 9 bodies from the O + m + p body mixture. Furthermore, it can be used to separate mixtures of 9-isomer and m-isomer. Also in this case, αp/D of the desorbent of the present invention is 1.
It can be seen that it is an excellent desorbent with a value close to 0.

Comparative example 1゜Example 1. Table 2 shows the adsorption selectivity when toluene, chlorobenzene, and 2,4-dichlorotoluene were used as desorbents using the -Y type adsorbent.

Table 2 Comparative example 1. The toluene and chlorobenzene desorbent is αp
/m approaches 1, making it difficult to separate the 9-isomer and the m-isomer, and the αp/D value is also worse than that of the desorbent of the present invention.

Example 2゜Example 1. The -Y type zeolite was treated at 60°C with a silver nitrate aqueous solution containing silver ions equivalent to approximately 30 moles of the cations in the -Y type zeolite, and the -Y type adsorbent was prepared and desorbed to Af-. Using 3,4-dichlorotoluene as the agent, the adsorption selectivity of the adsorbent was measured in Example 1. It was measured in the same manner as.

The results are shown in Table 6.

Table 3 Example 2. The adsorption force of the dichlorobenzene isomer to the -Y type adsorbent is in the following order: o#>9 bodies>m bodies. Therefore, it is possible to adsorb and separate and recover the 0-form and/or the m-form from a Q, m, and p temperature mixture. Furthermore, adsorption separation of a mixture of 0 and 9 bodies and a mixture of 9 and m bodies is possible.

In any of the above cases, the desorbent of the present invention can be used at the venue ψ
・≠≠#ne is αp/D and α. /D is close to 1, indicating that it is an excellent desorbent.

Comparative Example 2゜Example 2. The adsorption selectivity was measured using chlorobenzene as a desorbent.

The results are shown in Table 4.

Table 4 Comparative example 2. It can be seen that chlorobenzene has a very strong adsorption power and is therefore an undesirable desorbent.

Patent applicant: Toshi Co., Ltd.

Claims (1)

[Claims] (1) In a method of adsorbing and separating a sheet rogenated benzene isomer mixture using a zeolite-based adsorbent,
A method for separating di-halogenated benzene isomers, which comprises using a desorbent containing 3,4-dihalogenated toluene and/or 4-halogenated orthoxylene as an essential component.