JPS6013727A - Separation of 3,5-dichlorotoluene - Google Patents

Abstract

PURPOSE:To separate and recover the objective compound as a raffinate component, in high efficiency, in the adsorptive separation and recovery of the titled compound useful as an intermediate of novel agricultural chemical from the mixture of its isomers, by using a faujasite-type zeolite adsorbent. CONSTITUTION:3,5-Dichlorotoluene (3,5-DCT) is separated and recovered by adsorption process, from the mixture of DCT isomers containing 3,5-DCT and obtained by the isomerization of a mixture of DCT isomers under isomerization reaction condition. In the above process, the objective compound can be separated and recovered from the DCT isomer mixture containing 2,4-, 2,5- and/or 2,6- DCT having nearly equal boiling point to that of the objective compound by using a faujasite-type zeolite adsorbent of formula [M is cation, especially the I A, I B,IIA group of the periodic table, T1, proton or ammonium; n is atomic valence of M; x is 2.5+ or -0.5 (X-type) or 3-6 (Y-type); y depends upon the degree of hydration].

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating 3,5-dichlorotoluene (hereinafter dichlorotoluene is abbreviated as OCT),
In particular, it is intended to separate and recover 3.5-[)CT from a DCT isomer mixture by adsorption.

3.5-DCT is expected to be used as an intermediate raw material for new agricultural chemicals, but an industrial production method has not yet been established. The reason for this is that in the nuclear chlorination reaction of polytoluene, it is difficult to produce 3.5-OCT with strong ortho and para orientations, and even if 3.5-DCT is produced by the isomerization reaction of OCT. Among other by-product OCT isomer mixtures, 2,4-12,5-12.6-DCT (bp: approx. 20
Since the boiling point is almost the same as that of 0°C, high purity 3.
One example is that it is virtually impossible to separate and recover 5-DCT.

For example, the present inventors have determined that 3,5-DCT can be separated by adsorption from a DCT isomer mixture containing 3,5-ocT-j obtained by isomerizing a DCT isomer or an OCT isomer mixture under isomerization reaction conditions. I've been researching ways to collect it. As such a method, a method for adsorption separation of DCT isomers using faujasite type zeolite is already known from US Pat. No. 4,254,062. However, in the above-mentioned known examples, there is no mention of adsorption separation of 3,5-DCT, and the article relates to a separation technique in a system that does not substantially contain 3,5-DCT, which is a nuclear chlorination product of toluene or chlorotoluene. . Therefore, it is unclear whether the adsorption power of 3.5-DCT of the faujasite-type zeolite adsorbent is strong or weak relative to other DCT isomers, or whether highly pure 3.5-DCT can be substantially extracted from a mixture of DCT isomers. Whether or not it will be possible to separate and recover them is a completely unknown problem.

Therefore, the present inventors conducted intensive research on a method for efficiently separating and recovering 3.5-DCT from a DCT isomer mixture containing 3.5-DCT by adsorption, and found that a faujasite-type zeolite adsorbent was found to be 3.5-DCT. The present invention has been achieved by discovering that it has specific adsorption performance for 5-DCT.

That is, in the present invention, when separating and recovering 3.5-DCT from a DCT isomer mixture containing 3.5-DCT by adsorption, 3.5-DCT is used as a raffinate component using a faujasite type zeolite adsorbent. This is a method for separating and recovering 3,5-DCT, which is characterized by separating and recovering.

According to the method of the invention, 3.5-DCT is used as a raffinate component, i.e. in a DCT isomer mixture.
DCT can be separated and recovered as the component with the weakest adsorption force.

The faujasite type zeolite used in the method of the present invention is a crystalline aluminosilicate represented by the following formula.

0,9±0.2M2/n O: Al 203:X
Si 02 :y H2O Here, M represents a cation, and n represents its valence.

Faujasite type zeolite is classified into X and 9 types, and the X type is represented by x=2.5±0.5, and the Y type is represented by x=3 to 6. Moreover, y varies depending on the degree of hydration.

The present invention is not limited to the cations of the faujasite type zeolite, but it is important that 3.5=DCT can be separated and recovered as a raffinate component.

However, particularly preferred cations are
At least one cation selected from Group 1B, Group mA, thallium, proton, and ammonium.

Methods of ion exchange of these cations are well known to those skilled in the art with knowledge of the production of crystalline aluminosilicates, and are usually carried out in an aqueous solution of a soluble salt of one or more cations to be added to the zeolite. It can be carried out by contacting the zeolite.

The adsorption separation technique used in the present invention may be a so-called chromatographic separation method or a continuous adsorption separation method using a simulated moving bed system.

Continuous adsorption separation technology using a simulated moving bed uses multiple adsorption chambers filled with adsorbent to continuously perform the following basic operations: adsorption, concentration, desorption, and desorbent recovery. It is carried out in cycles.

(1) Adsorption operation: The raw material mixture comes into contact with an adsorbent bed, and strongly adsorbed components are selectively adsorbed. The remaining weakly adsorbed components are extracted from the adsorbent bed along with the desorbent as a raffinate stream.

(2) mcondensation operation: The adsorbent that has selectively adsorbed strongly adsorbed components is brought into contact with a portion of the extract, which will be described later,
Weakly adsorbed components remaining on the adsorbent are expelled, and strongly adsorbed components are highly purified.

(3) Desorption operation: The adsorbent bed containing highly purified strongly adsorbed components is brought into contact with a desorbent, and the highly purified strongly adsorbed components are extracted from the adsorbent bed together with the desorbent as an extract stream.

(4) Recovery operation: The adsorbent bed containing the desorbent is contacted with a portion of the raffinate stream and the desorbent is extracted from the adsorbent bed.

Compounds that can be separated can be used, for example, alkyl-substituted aromatics, halogen-substituted aromatics.

Preferably, toluene, xylene, chloro1-toluene,
These include chlorobenzene, dichlorobenzene, diethylbenzene, etc.

The operating conditions for adsorption separation are as follows: temperature ranges from room temperature to 350°C, preferably 50 to 250°C, and pressure ranges from atmospheric pressure to 50 kg/cr! -G is preferably 40 to 8/dG from atmospheric pressure.

The adsorption separation according to the present invention may be carried out in the gas phase or in the liquid phase, but is preferably carried out in the liquid phase in order to lower the operating temperature and to suppress undesirable side reactions of the raw material feed or the desorbent.

Although the method of the present invention does not limit the composition of the DCT isomer mixture containing 3.5-DOT, in particular 3.5-D
2.4-12,5- and 2. whose boiling point is almost the same as CT.
This is a very effective method for separating and recovering 3.5-DCT when it contains at least one type of OCT among 6-DCT.

(7) The DCT isomer may contain components other than the DCT isomer, such as toluene, chlorotoluene, dichlorobenzene, trichlorotoluene, and the like.

DCT isomer mixtures containing 3.5-DCT may be
It is obtained by isomerizing a CT isomer or a mixture of DCT isomers under isomerization reaction conditions. The isomerization reaction can be carried out, for example, with a Friedel-Craft catalyst such as AI C13, optionally in combination with a protic acid such as HF-BF3. Alternatively, it can be carried out using a solid acid type zeolite catalyst consisting of pentasil type, mordenite type or faujasite type zeolite.

2.1-AI CI! DCT at 150℃! In the isomerization reaction experiment using Friedel-Krach reaction by , 3, 3
．． 5-DCT: 13.4%, 2,3-DCT: 3.
5%, 2.1-DCT: 30.3%, 2.5-DC
T: 38.0%, 2.6-DCT: 10.0%,
3.4-DCT: 4.8% was obtained.

These DCT isomer mixtures containing 3.5-DC-r may be directly adsorbed and separated to recover 3.5-DCT, or 2.3- and 3.4-DCT (bp:
208°C) and 2,4-12.5-12,6- and 3
．． After distilling and separating 5-OCT (bp: about 200°C), 3.5-OCT is extracted from the DCT isomer mixture containing 3.5-DCI-
, 5-DCT may be recovered by adsorption separation. Furthermore, the remaining liquid from which 3.5-DCT has been separated and recovered by adsorption may be subjected to isomerization reaction conditions to increase the content of 3.5-DOT, and then 3.5-DCT may be adsorbed and separated again.

Furthermore, DCT isomers other than 3.5-DCT may be recovered by adsorption separation before and/or after-treatment of 3.5-OCT.

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

In the examples, the adsorption characteristics of the adsorbent are expressed by the adsorption selectivity α of the following formula.

Here, X represents any one of DCT isomers other than 3',5-DCT, S represents an adsorption phase, and L represents a liquid phase in equilibrium with the adsorption phase. When the α value in the above formula is greater than 1, the X component is selectively adsorbed to 3.5-DCI-.

Therefore, when attempting to separate and recover 3.5-DCT as a raffinate component, other D
The α values of all CI-isomers must be 1.0 or more.

Example 1 Alumina sol was added as a binder to Na-X type (Si 02 / AI 203 = 2.5) zeolite powder as a binder.
24~ by adding 15wt% in terms of O3 and extrusion molding
A granulated product of 32 mesh was obtained.

This granulated product was dried at 100°C and then calcined at 500°C for 1 hour to prepare a Na-X type adsorbent.

Next, the adsorbent was subjected to ion exchange treatment with various nitrate aqueous solutions. The ion exchange conditions were a solid-liquid ratio of 5 and a temperature of about 90°C.

The drying and firing conditions for the adsorbent after ion exchange are the same as for the Na-X type.

In order to measure the adsorption selectivity between the DCT isomers of the above adsorbent, an autoclave with an internal volume of 5IIr1 was filled with 2 g of the adsorbent and 3'' of the DCT isomer mixture, and the mixture was heated at 130°C for 1 hour in the presence of various solvents. It was left to stand while stirring occasionally.

The composition of the charged DCT isomer mixture was 2.3-/2.
4-/2.5-/2.6-/3.4-/3.5-DCT
=3.5/30.3/38.0/10.0/4.8/1
The ratio is 3.4wt. Furthermore, 2
0 wt% n-nonane was charged at the same time. N-nonane is a material that is virtually inert with respect to the adsorption properties of the zeolite under the above adsorption conditions.

The composition of the liquid phase mixture after contact with the adsorbent was analyzed by gas chromatography to determine the adsorption selectivity α between OCT isomers.

The results are shown in Table 1.

In the table, an adsorbent showing only a single cation component indicates that the cation accounts for 90 equivalent % or more of the cations contained in the adsorbent. Also, for example, α2Ag-Na
-X indicates Na contained in the Na-X type adsorbent.
This shows that ion exchange was performed with a silver nitrate aqueous solution containing 20 equivalent % of cations.

Table 1 Example 2 Various adsorbents were prepared in the same manner as in Example 1 using Na-Y type (Si 02 /AI 203 = 5.2) zeolite powder.

Table 2 shows the measurement results of adsorption selectivity α between DCT isomers of type Y and adhesive.

Claims (1)

[Claims] (1) When separating and recovering 3,5-dichlorotoluene from a dichlorotoluene isomer mixture by adsorption, 3,5-dichlorotoluene is separated and recovered as a raffinate component using a faujasite-type zeolite adsorbent. A method for separating 3,5-dichlorotoluene, characterized by: