JPH02172931A - Separation of 2,7-diisopropylnaphthalene - Google Patents

Abstract

PURPOSE:To provide 2,7-diisopropylnaphthalene(DIPNP) isomer in a high purity by subjecting a mixture of DIPNP isomers to a combination of distillation and adsorptive separation. CONSTITUTION:A mixture of DIPNP isomers is distilled to separate 1,7- and 1,3-isomers. The remaining mixture not containing the isomers si subjected to an adsorptive separation treatment employing a zeolite adsorbent (e.g. potassium-substituted Y type zeolite) exhibiting a selectively 2,7-isomer-adsorbing property and a desorbing agent, e.g. an alkylbenzene derivative of the formula (R and R' are methyl, ethyl, n-propyl or isopropyl; n is 0 or 1) to provide an extract containing the 2,7-isomer and a raffinate containing other isomer. Or the mixture of the DIPNP isomers is subjected to an adsorptive separation treatment employing the adsorbent and the desorbing agent to separate an extract containing the 2,7- and 1,7-isomers, and the extract is distilled to separate the 2,7-isomer and 1,7-isomer from each other.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention provides for the production of diisopropylnaphthalene isomers from a
, 7-isomer is adsorbed and separated.

(Prior art and its problems) Polyester obtained from 2.7-naphthalene dicarboxylic acid is called a liquid crystal polymer and has a high five-liquid crystallinity, as described in JP-A-58-162630.

Since it is a polymer that exhibits strong overall mechanical properties, it is desired to establish an industrially advantageous method for producing 2,7-naphthalene dicarboxylic acid as a polyester JJx material.

2.7-naphthalene dicarboxylic acid is obtained by oxidizing 2,7-diisopropylnaphthalene obtained by converting naphthalene into an alkyl group with propylene.

can be manufactured.

However, the diisopropylnaphthalene fraction, which is an isopropylated product obtained by alkylating naphthalene with propylene, is an isomer mixture containing various isomers in addition to the 2,7-isomer.
- Naphthalenedicarbone m cannot be used as a raw material, and from its diisopropylnaphthalene isomer mixture,
Although it is necessary to separate the 2,7-isomer with high purity, no industrial technology has been established to separate the 2,7-isomer with high purity from such a mixture of diisopropylnaphthalene isomers. .

The present inventors previously proposed a technology for separating 2,6-lite propylnaphthalene by a two-stage adsorption separation method (
In this separation method, 2.6
-In addition to propylnaphthalene, a diisopropylnaphthalene mixture containing the 1.7 and 2.7 isomers is obtained. However, since this separation method is a technology for recovering 2,6-rightspropylnaphthalene with high purity, the adsorption strength is intermediate between the 2,7-isomer and the 2,6-isomer. 1,5-isomerism indicating 1,6-
Isomers, 1.4-isomers and 2.3-isomers etc. are 2.
These isomers are mixed in the 7-isomer and cannot be separated by distillation because their boiling points are close to the 2.7-isomer, resulting in highly pure 2,7-diisopropylnaphthalene. That is impossible.

(Problem of the Invention) An object of the present invention is to provide an industrially advantageous method capable of separating the 2,7-isomer with high purity from a diisopropylnaphthalene isomer mixture.

(Means for Solving the Problems) The present inventors have conducted extensive research to solve the above problems, and as a result, have completed the present invention.

That is, according to the first process of the present invention, when separating 2,7-rightspropylnaphthalene from a mixture of diisopropylnaphthalene isomers, the mixture is distilled to separate 1,7- and 1,3-isomers. a first step of separating 1, 7- and 1 obtained in the first step;

A diisopyrnaphthalene isomer mixture that does not contain the 3-isomer is adsorbed and separated using a zeolite adsorbent and desorbent that exhibits selective adsorption to the 2.7-isomer.
A process for the separation of 2,7-rightspronaphthalene is provided, characterized in that it consists of a second step of obtaining an extract containing the 7-isomer and a raffinate containing the other isomer.

According to the second process of the present invention, when separating 2,7-diisopropylnaphthalene from a mixture of diisopropylnaphthalene isomers, the mixture exhibits selective adsorption to 2,7- and 1,7-isomers. 2.7- and 1
．． A first step of obtaining an extract containing the 7-isomer and a raffinate containing other isomers, and distilling the extract obtained in the first step to obtain the 2,7-isomer and the 1,7-isomer. A process for the separation of 2,7-diisopropylnaphthalene is provided, characterized in that it comprises a second step of separating the isomers from each other to obtain the 2,7-isomer.

The diisopropylnaphthalene isomer mixture in the present invention is obtained by isopropylating naphthalene with propylene,
It can be obtained by separating a diisopropylnaphthalene fraction from the obtained product. Naphthalene, which is the raw material for isopropylation, may be of any type produced from petroleum oil, coal oil, etc. However,
If it contains components that poison the isopropylation catalyst, such as sulfur compounds and nitrogen compounds.

It is preferable to remove these compounds by a conventionally well-known purification technique, hydrorefining, activated clay treatment, etc. The isopropylation reaction is a conventionally well-known reaction, and is a conventionally known method. Accordingly, the reaction is carried out as a liquid or gas phase reaction.

Catalysts include solid acid catalysts such as silica/alumina, crystalline aluminosilicate, nickel oxide/silica, silver oxide/silica alumina, silica/magnesia, alumina/boria, solid phosphoric acid, aluminum chloride, hydrogen fluoride, and phosphorous. Friedel-Crafts catalysts such as those made by Co., Ltd. are used. In this isopropylation reaction, the isopropyl group attached to the naphthalene ring is easily rearranged to another naphthalene ring by a transalkylation reaction in the presence of the alkylation reaction catalyst as described above. Therefore, this isopropylation reaction is considered to be a reversible reaction through a transalkylation reaction, and an equilibrium composition exists between naphthalene and isopropylnaphthalenes. The amount of diisopropylnaphthalene produced depends on the ratio of naphthalene to propylene in the reaction, temperature, type and amount of catalyst, etc.

When carrying out the isopropylation reaction using a Friedelta raft catalyst, one reaction is carried out at room temperature -150°C, preferably between 50°C and 50°C.
A temperature of 100°C, a pressure of normal pressure to 10 atm, and a catalyst to raw material ratio of 0.05 to 1.0. Preferably 0.08-0
It is carried out under the conditions of ゜5. In order to increase the yield of diisopropylnaphthalene, the molar ratio of isopropyl groups to naphthalene nuclei in the total alkylated product should be adjusted to O,S~3.0.
．． Preferably it is 1.0-2.5.

When using a solid acid catalyst, the reaction temperature is 150 to 500°C.
, pressure 0-50 kg/a (G-contact time 0.02-6.
Ohr range, preferably temperature 200~350℃
, pressure 0~35kg/aJG, contact time 0.4~2,
It is in the 5hr range. If the temperature is high or the contact time is long, a decomposition reaction occurs and by-products are produced. Furthermore, when the temperature is low or the contact time is short, the yield of diisopropylnaphthalene decreases. In this isopropylation reaction step, an isopropylation product containing unreacted naphthalene, monoisopropylnaphthalene, diisopropylnaphthalene, triisopropylnaphthalene, and more polyisopropylnaphthalene is obtained, and the proportion of diisopropylnaphthalene therein is usually 10 ~50wt2.

Next, the isopropylated product obtained in the isopropylation reaction step is subjected to a distillation treatment to separate a diisopropylnaphthalene fraction. This distillation process generally produces a low-boiling fraction consisting of naphthalene and monoisopropylnaphthalene.

It is separated into a diisopropylnaphthalene fraction and a high boiling point fraction consisting of polyisopropylnaphthalene higher than triisopropylnaphthalene. Monoisopropylnaphthalene can be made into diisopropylnaphthalene by isopropylating it with propylene, and polyisopropylnaphthalene higher than triisopropylnaphthalene can be made into diisopropylnaphthalene by transalkylating it with naphthalene. It can be done.

The diisopropylnaphthalene fraction obtained above contains diisopropylnaphthalene 2,7-isomer, 1.3-isomer, 1.7-isomer, 1.4-isomer, 2,6-isomer, 1 , 6-isomer, t, S-isomer, 2,3-isomer, etc. According to the research conducted by the present inventors, among these isomers, the 2,7-isomer and the 1,7-isomer exhibit similar adsorption behavior on zeolite adsorbents, and are considered as strongly adsorbed components. Advantageously, the 2,7-isomer (boiling point 317°C) and the 1,7-isomer (boiling point 309°C) exhibit similar adsorption behavior. Since the 2,7-isomer can be separated by distillation, it has been found that the 2,7-isomer can be separated and recovered with high purity by combining distillation treatment before or after adsorption treatment.

The zeolite adsorbent used in the present invention selectively adsorbs 2,7-isomer and 1,7-isomer, and is a faujasite-type zeolite adsorbent.
Type zeolite is preferably used.

In this case, alkali metals and alkaline earth metals are used as the substitution metal, and potassium is particularly preferred.

The diisopropylnaphthalene isomer mixture is mixed with zeolite 1~
When adsorption treatment is performed with an adsorbent, the strength of the adsorption based on the 2,7-isomer of diisopropylnaphthalene isomer on the zeolite adsorbent is determined by the relative separation coefficient β (2,7/i
) and is expressed by the following formula.

β(2,7/1)=K(2,7)/K(i)
(1) Here, K(2,7) and K(i) represent the solid-liquid equilibrium constant of the 2,7-isomer and the solid-liquid IF equilibrium constant of isomer i, respectively, and are defined by the following formula. be done.

Isomers with a relative separation coefficient β (2,7/i) smaller than 1 indicate that they are more easily adsorbed than 2,7-isomers, and conversely, isomers larger than 1 are 2,7-isomers. It shows that it is less likely to be adsorbed than. 1 for zeolite adsorbent
, 7=The value of the relative separation coefficient β(2,7/1.7) of isomers is approximately 1, and the value of the relative separation coefficient β(2,7/1.7) of other isomers is approximately 1.
/i) indicates a value greater than 1. Therefore, by using a zeolite adsorbent, it is possible to selectively adsorb and separate the 2,7- and 1,7-isomers from the diisopropylnaphthalene isomer mixture.

In the present invention, it is preferable to use a zeolite adsorbent exhibiting a relative separation coefficient μ(2,7/i) of 2 or more for isomers other than 2,7- and 1,7-isomers.

The desorbent used in the present invention may be a substance that is quickly adsorbed to the zeolite adsorbent and has the ability to desorb the already adsorbed substance, and aromatic desorbents are preferably used in the present invention9. Particularly preferred are aromatic desorbents. The desorbent is an alkylbenzene represented by the following general formula.

In the above formula, R and R' represent a methyl group, an ethyl group, an n-propyl group, or an isopropyl group, and n is 0 or 1.

The desorbent used in the present invention has a relative separation coefficient β (2,7/D) of 0°5 to 3, preferably 0.5 to 3. It is preferable to use those in the range of 1 to 2. If the value of the relative separation coefficient β(2,7/D) of the desorbent is too large, a very large amount of desorbent will be required, while if it is too small, it will be necessary to use a large amount of zeolite adsorbent. So the economy' second unfavorable.

The adsorption separation according to the present invention is carried out by an adsorption separation technique using chromatography, and can be carried out using a fixed bed or a moving bed, but is preferably carried out by a self-flowing simulated moving bed system. Adsorption separation technology using a simulated moving bed method is
This is an already established technology and has been applied to the adsorption separation of xylene isomer mixtures.
It is described in Japanese Patent Publication No. 81, Japanese Patent Publication No. 50-10547, etc.

Next, the adsorption separation technology using this countercurrent type simulated moving bed method will be described in detail. In this adsorption separation technology, four basic operations, consisting of desorption operation, concentration operation, adsorption operation, and desorbent recovery operation, are performed simultaneously and continuously. Show the diagram. In this figure, 1 to 16 are adsorption chambers containing zeolite adsorbents, which are interconnected. 17 is a desorbent supply line, 18 is an extract extraction line, 19 is a raw material supply line, 20 is a raffinate extraction line, and 21 is a recycle line. Adsorption chambers 1 to 16 shown in the drawing
In the arrangement state of each line 17-21, desorption operation is performed in adsorption chambers 1-3.

Concentration operation in adsorption chamber 4-8, adsorption operation in adsorption chambers 9-13,
A desorbent recovery operation is performed in each of the adsorption chambers 13 to 16.

In such a simulated moving bed, each supply and withdrawal line is moved by one adsorption chamber in the liquid flow direction at regular time intervals by valve operation. Therefore, in the arrangement state of the primary adsorption chambers, the desorption operation is performed in adsorption chambers 2 to 4, and the desorption operation is performed in adsorption chamber 5.
Concentration operation is performed in ~9, adsorption operation is performed in adsorption chambers 10-14, and desorbent recovery operation is performed in adsorption chambers 15-1, respectively. By performing these operations one after another,
A simulated moving bed adsorptive separation process of a mixture of diisopropylnaphthalene isomers is achieved.

Next, the role of each operation will be explained.

(i) Desorption operation Enriched 2,7-isomer (or 2,7-isomer and 1
, 7-isomer, hereinafter simply referred to as 2.7=isomer), contacts the desorbent in this operating zone.

2.7 - The isomer is desorbed from the adsorbent by a desorbent.

Collected as extract. If the liquid flow rate in this zone is too small and the desorption of the 2,7-isomer is insufficient, the 2,7-isomer will be adsorbed onto the adsorbent, circulated, and mixed into the raffinate; 7-Recovery of isomer is reduced. Therefore, the ratio between the liquid flow rate and the adsorbent flow rate in this operating zone must be greater than a certain value, and preferably satisfies the following equation:

(5i) Concentration operation Components other than the 2,7-isomer adsorbed on the adsorbent are completely desorbed in this operation zone, and only the 2,7-isomer is concentrated and recovered as an extract. If the liquid flow rate in this zone is too low and desorption of components other than the 2,7-isomer is insufficient, these isomers will be mixed into the extract and reduce the purity of the 2,7-isomer. let Therefore, the ratio between the liquid flow rate and the adsorbent flow rate in this operation zone must be greater than a certain value, and preferably satisfies the following equation.

The 2,7-isomer contained in the raw material for (rapid) adsorption operation comes into contact with the adsorbent in this operation zone, is adsorbed, and is then transported to the concentration operation zone. Components other than the 2,7-isomer are recovered as a raffinate stream along with the desorbent. If the liquid flow rate in this zone is too high and the adsorption of the 2,7-isomer onto the adsorbent is insufficient, the 2,7-isomer will be mixed into the raffinate and the 2,7-isomer will be mixed into the raffinate.
- A decrease in isomer recovery occurs. Therefore, the ratio between the liquid flow rate and the adsorbent flow rate in this operation zone needs to be below a certain value, and preferably satisfies the following equation.

(iv) Desorbent recovery operation 2. Isomers other than the 7-isomer are completely adsorbed on the adsorbent, and these components are recovered from the raffinate.

From the bottom of this operating zone, desorbent free of any diisopropylnaphthalene isomer is recovered and recycled to the desorption operating zone. Therefore, if the liquid flow rate in this zone is too large, the components with weak adsorption power will not be adsorbed by the adsorbent, but will mix with the desorbent, circulate, and flow out during the extract.
- Decrease the purity of the isomer. In addition, if the liquid flow rate in this zone is too small, components with weak adsorption power existing in the liquid between adsorbent particles in the adsorption chamber will move as the adsorption chamber moves, and will be mixed into the extract. - Decrease the purity of the isomer. Therefore, the liquid flow rate in this zone needs to be set within a certain range, and preferably satisfies the following equation.

In the above formula, L (1), 1), l, (III) and L
(IV).

a desorption operation zone (i), a concentration operation zone (11), respectively;
adsorption operation zone (iii) and desorbent recovery operation zone (iv)
) shows the liquid flow ff1 (cc/hr) flowing through the flow. 5 (1
), S(II), 5(III) and 5(TV) are adsorption units moving through the desorption operation zone (i), concentration operation zone (ii), adsorption operation zone (ni) and desorbent recovery operation zone, respectively. The drug flow rate (cc/hr) is shown.

Next, a flow sheet of the first process of the present invention is shown in FIG. In FIG. 2, 31 is a distillation column, and 32 is an adsorption separation device.

Diisopropylnaphthalene isomer mixture is in line 33
is introduced into distillation column 3 through the isomer mixture, where the 1,7-isomer and 1,3-isomer are separated as column n1 products, and the remainder containing the 2,7-isomer is separated. The isomer mixture is introduced through line 35 into adsorptive separation device 32 .

In the adsorption separation device 32, the 2,7-isomer, which is an adsorbent component, and the other isomers, which are weakly adsorbable components, are separated, and the 2,7-isomer is extracted and passed through a line 36. The other isomers are withdrawn through line 37 as rifinate.

Next, flow sheets 1 to 3 of the second process of the present invention are
As shown in the figure.

Diisopropylnaphthalene isomer mixture is in line 33
is introduced into the adsorption separation device 32, where it is separated into 2,7-isomers and 1,7-isomers, which are strongly adsorbable components, and other isomers, which are weakly adsorbable components. Ru. 2
, 7-isomer and 1,7-isomer are withdrawn through line 36 as Ex-I lactate, and the other isomers are withdrawn through line 37 as Raffine-1. 2
The extract containing the ,7- and 1,7-isomers is introduced into a distillation column 31 where the 1,7-isomers are separated as overhead and the 2,7-isomers are separated as bottoms. Separated as

(Effects of the Invention) According to the present invention, 2,7-line propylnaphthalene can be separated and recovered with high purity from a diisopropylnaphthalene isomer mixture.

The 2,7-line propylnaphthalene obtained by the present invention is used as a starting material for 2,7-naphthalene dicarboxylic acid, which is a raw material for polyester, and is also used as various solvents.

(Example) Next, the present invention will be explained in more detail with reference to Examples.

Example 1 (1) Distillation treatment A diisopropylnaphthalene mixture 1.5Q having the composition shown in Table 1 obtained by isopropylating naphthalene with propylene was distilled using a batch distillation column packed with a McMahon backing having an inner diameter of 20 mo+ and a height of 1800 ml. Processed. The pressure during distillation was 50 mmHg and the reflux ratio was 20. As a result, from the diisopropylnaphthalene mixture,
About 0.85Q of isomer 64 compound having the composition shown in Table 2 from which the 1,3- and 1.7-isomers were removed was obtained.

Table 1 Table 2 (11> Adsorption Separation Treatment An adsorption separation experiment was conducted using a diisopropylnaphthalene isomer mixture having the composition shown in Table 2 as a raw material.The adsorbent used in the adsorption separation experiment was a Na-type wall type adsorbent. Zeolite Sx
O,/AQz 03 molar ratio = 4.6, particle size: 40-8
0 mesh) is ion-exchanged with a specified metal. Ion exchange was performed by the method shown below.

(Ion exchange) Approximately 10 g of Na-type Y-type zeolite is mixed with a metal chloride aqueous solution (0
, 5mo12IQ) was added, and the temperature was 9O-10.
It was left at 0°C for 2 hours. After repeating the above operation three times, it was dried and then baked at a temperature of 400° C. for 3 hours.

The adsorption separation experiment was carried out using the method shown below.

(Adsorption separation experiment) Adsorption spray 4#c in an autoclave with an internal volume of 30cc.

Approximately 6.5 g of raw oil, approximately 1 portion of diethylbenzene for desorption
．． 5 g was charged, the temperature was kept constant while stirring, and the temperature was maintained for 120 minutes. The adsorbent and the raw material residue were separated by filtration, and the adsorbent in the adsorbent was desorbed by Soxhlet extraction using a toluene solvent after washing the adsorbent with isooctane. The compositions of the residual liquid (liquid phase) and adsorbate (adsorption phase) were analyzed by gas chromatography, and the relative separation coefficients were calculated, and the results are shown in Table 3.

Example 2 The potassium-substituted Y-type zeolite shown in Example 1 was used as an adsorbent, and 80 parts by weight of the various desorption agents shown in Table 4 were applied to 20 parts by weight of the diisopropylnaphthalene isomer mixture shown in Table 2 as a raw material. Example using the weight part added! An adsorption separation experiment was conducted in the same manner as in the case of , and the β value was calculated. The results are shown in Table 4.

Example 3 Adsorption separation of 2,7-rightsbropylnaphthalene from the raw materials shown in Table 2 of Example 1 was carried out using the simulated moving bed type continuous adsorption unit #1 shown in FIG.

In the separation operation, the potassium-substituted Y shown in Example 1
Diethylbenzene was used as a zeolite adsorbent and desorbent. The adsorbent is column adsorption chamber 1 with an internal volume of 70 mtl.
16, the raw material was supplied from line 19, the desorbent was supplied from line 17, and the extract from line 8 and Rough Ine-1 from line 20 were extracted from Table 0.
As shown in Fig. 5, the flow rate in each operation zone was varied by changing the Jg material, the amount of desorbent supplied, the amount of extract, and the amount of raffinate drawn out.

In addition, each feed line for the raw material and desorbent, and each extraction line for extract and raffinate were simultaneously moved by one adsorption chamber in the liquid flow direction at regular intervals.

At this time, the adsorbent flow rate (S) in each zone was 818cc/hr.
Met.

Table 5 shows the purity and recovery rate of 2,7-line propylnaphthalene in the extract in each experiment.

In experiment h2, L(1)/S(1) is too small, so 2
゜7 - The isomer is circulated while being adsorbed on the adsorbent and mixed into the raffinate, reducing the recovery rate.

In experiment Nci3, since the value of 2)/S(II) was too small, isomers other than the 2°7-isomer were mixed into the extract, resulting in a decrease in purity.

In Experiment &4, L(III)/S(ill) was too large.

2. The 7-isomer is mixed into the raffinate, reducing the recovery rate.

In experiment &5''r, because L(IV)/S(fV) was too large, components other than the 2.7-isomer were mixed into the desorbent and circulated.

The purity of the 2,7-isomer decreases due to its contamination with the extract.

In experiment Nci6, since L(1■)/S(IV) was too small, components other than the 2,7-isomer were mixed into Ex1 to lacto, resulting in a decrease in the purity of the 2,7-isomer.

Example 4 (1) Adsorption separation treatment A diisopropylnaphthalene isomer mixture having the composition shown in Table 1 was used as a raw material, and potassium-substituted Y
Using zeolite type zeolite, an adsorption separation experiment was conducted in the same manner as in Example 1, and the relative separation coefficient was determined. As a result, β(
2,7/1.3): 21.0, β(2,7/1.7):
0.8, β(2,7/1.5): 2.3, β(2,7/
1.4): 9,4, β(2,7/1.6): 10.3.
β(2,7/2,3):5,4. β(2,7/2.6)
:Relative separation coefficients of 19 and 3 were obtained.

As can be seen from the above results, by adsorption separation treatment, ■,
It can be seen that the 7-isomer and the 2.7-isomer are separated from other isomers as strongly adsorbed components.

As shown in Table 1, there is a boiling point difference of 8°C between the 1,7-isomer and the 2,7-isomer.
It can be seen that the three components can be separated from each other by distillation.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of an adsorption separation apparatus using an m-like moving bed. FIG. 2 shows a flow sheet of the first process of the present invention in which distillation treatment and adsorption separation treatment are combined in that order. FIG. 3 shows a flow sheet of the second process of the present invention in which adsorption separation treatment and distillation treatment are combined in that order. 1 to 16...Adsorption chamber, I7...Desorbent supply line,
18... Extract withdrawal line, 19... Raw material mixture supply line, 20... Rough-in-1 extraction line, zl... Recycle line, 22... Recycle pump, 31... Distillation column , 32... adsorption separation device. Patent applicant: Chiyoda Corporation (1 idiot)

Claims (1)

[Scope of Claims] (1) From a diisopropylnaphthalene isomer mixture, 2,
In separating 7-diisopropylnaphthalene, the mixture is distilled to separate the 1,7- and 1,3-isomers, and the 1,7- and 1-isomers obtained in the first step are separated. , 3-isomer-free diisopropylnaphthalene isomer mixture is adsorbed and separated using a zeolite adsorbent and desorbent that selectively adsorbs the 2,7-isomer to contain the 2,7-isomer. 1. A method for separating 2,7-diisopropylnaphthalene, comprising a second step of obtaining an extract and a raffinate containing other isomers. (2) 2 from the diisopropylnaphthalene isomer mixture,
When separating 7-diisopropylnaphthalene, the mixture is adsorbed and separated using a zeolite adsorbent and desorbent that exhibits selective adsorption properties for 2,7- and 1,7-isomers. , 7-isomer and a raffinate containing other isomers; and the extract obtained in the first step is distilled to obtain the 2,7-isomer and the 1,7-isomer. -separate the isomers from each other,
A method for separating 2,7-diisopropylnaphthalene, characterized in that it comprises a second step to obtain the 2,7-isomer. (3) The adsorbent used in the adsorption separation process is potassium-substituted Y.
3. The method of claim 1 or 2, wherein the zeolite is a zeolite. (4) Claims 1 to 4, wherein the desorbent used in the adsorption separation process is an alkylbenzene derivative represented by the following general formula:
Either method 3. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R and R' are methyl group, ethyl group, n-propyl group, or isopropyl group, and n is 0 or 1.) (5) Adsorption separation treatment Four operations consisting of a desorption operation, a concentration operation, an adsorption operation, and a desorbent recovery operation are performed simultaneously and sequentially using a countercurrent type pseudo moving bed having multiple adsorption chambers filled with adsorbent. , and each operation band is performed under the following conditions. (i) Desorption operation zone L(I)/S(I)>0.2+L(IV)/S(I) (where L(I) is the liquid flow rate (c) flowing through the desorption operation zone
c/hr), S (I) is the adsorbent flow rate (cc/hr) moving through the desorption operation zone, and L (IV) is the liquid flow rate (cc/hr) flowing through the desorbent recovery zone) (ii) Concentration operation zone L (II) / S (II) > 0.1 + L (IV) / S (II) (wherein L (II) is the liquid flow rate (cc
(3) Adsorption operation Zone L(III)/S(III)<0.3+L(IV)/S(III) (where L(III) is the liquid flow rate (c
(c/hr), S (III) is the adsorbent flow rate (cc/hr) moving through the adsorption operation zone, and L (IV) is the liquid flow rate (cc/hr) flowing through the desorbent recovery zone) (iv) Desorbent recovery operation zone 0.8<L(IV)/S(IV)<1.0 (wherein, L(IV) is the liquid flow rate (cc/hr) flowing through the desorbent recovery operation zone, S(IV) (indicates the adsorbent flow rate (cc/hr) moving through the desorbent recovery operation zone)