JP2805051B2 - Method for separating 3,5-xylenol - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of separating 3,5-xylenol from a mixture of xylenol isomers by an adsorption separation treatment.

(Prior art and its problems) The xylenol fraction obtained by distilling the tar acid component of coal tar includes, in addition to 3,5-xylenol, 2,5-xylenol, 2,4-xylenol having a boiling point close to that of 3,5-xylenol Xylenol,
It contains isomers such as 2,3-xylenol and 3,4-xylenol. Among these isomers, 3,5-xylenol is an important substance as an agricultural chemical intermediate, and its separation and recovery from a xylenol fraction is desired. But 3,5
-Separation of xylenol from other isomers by distillation is very difficult because its boiling point is close to that of the other isomers.

JP-A-59-122433 discloses that in order to separate and recover 3,5-xylenol from a xylenol isomer mixture, the isomer mixture is adsorbed using a faujasite-type zeolite containing silver and / or copper as a cation component. Process, 3,5
A method for obtaining xylenol as a raffinate component is disclosed. According to this publication, for the zeolite adsorbent, the 3,5-isomer of the isomer mixture is another
Although it is recognized that it behaves as a weakly adsorbed component than the 3,4-3 isomer, the 2,6-isomer and the 2,4-isomer, there is a significant difference between these isomers in their adsorption power. Therefore, it is very difficult to obtain high-purity 3,5-xylenol even by the adsorption treatment using the zeolite adsorbent.

(Problems of the Invention) It is an object of the present invention to solve the problems found in the prior art and to provide a method capable of efficiently separating 3,5-xylenol from a xylenol isomer mixture with high purity. .

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

That is, according to the present invention, in a method for separating 3,5-xylenol from a xylenol isomer mixture, a faujasite-type zeolite adsorbed by replacing the mixture with at least one metal selected from potassium and barium. Adsorption separation treatment using the agent, mainly 2,5 and 3,4-
An extract consisting of xylenol and mainly 3,
A first step of obtaining a raffinate comprising 5-, 2,4- and 2,3-xylenol; and replacing the raffinate obtained in the first step with at least two metals selected from potassium, barium and lead. Using faujasite-type zeolite adsorbent, and mainly 2,4- and 2,3-
Extract consisting of xylenol and mainly 3,5
A second step of obtaining a raffinate consisting of xylenol.

The method of the present invention is a method in which a mixture of xylenol isomers is treated by two adsorption separation treatment steps. In the first step, an extract consisting mainly of 2,5- and 3,4 isomers and an extract consisting mainly of 3,5 -, 2,4- and 2,3-isomers are subjected to adsorption separation treatment to obtain a raffinate, and in the second step, the raffinate obtained in the first step is used as a raw material, from which, mainly, 2,4- and The adsorptive separation treatment is performed so as to obtain an extract comprising 2,3-xylenol and a raffinate mainly comprising 3,5-xylenol.

The adsorbent used in the present invention is a faujasite type zeolite, and is a crystalline aluminosilicate represented by the following composition formula.

0.9 ± M _{1 / n} O: Al ₂ O ₃ : xSiO ₂ : yH ₂ O In the above formula, M is a metal cation, and n is a valence of the metal cation. Faujasite type zeolites are classified into X type and Y type, and in the case of X type, X is 2.5 ± 0.5,
In the case of the Y type, x is 3 to 6. y varies depending on the degree of hydration, but generally ranges from 0 to 9.

In the first-stage adsorption separation treatment, a faujasite-type zeolite (M = K and / or Ba) substituted with at least one metal selected from potassium and barium is used as an adsorbent. For this zeolite adsorbent, the 2,5-isomer of the xylenol isomer mixture
It was confirmed that the 3,4-isomer behaved as a strongly adsorbed component, while the 3,5-isomer, 2,4-isomer and 2,3-isomer behaved as a weakly adsorbed component.

In the adsorptive separation treatment of the second stage, faujasite-type zeolite substituted with at least one metal selected from potassium, barium and lead as an adsorbent (M =
K, Ba and / or Pb) are used. When a mixture of 3,5-isomer, 2,4-isomer and 2,3-isomer is allowed to act on the zeolite adsorbent, the 2,4-isomer and 2,3
-Isomers are selectively adsorbed and separated as strongly adsorbed components,
It was confirmed that the 5-3 isomer migrated to raffinate as a weakly adsorbed component.

The conditions of the adsorption separation treatment are as follows: temperature: 30 to 200 ° C., preferably 60 to 100 ° C., pressure: normal pressure to 50 k for both the first and second stages
g / cm ² , preferably 3 to 30 kg / cm ² .

As the desorbing agent used in the adsorption separation process of the present invention, a substance capable of desorbing components adsorbed on the adsorbent may be used. In general, an aliphatic compound can be used as such a desorbing agent, and examples thereof include an aliphatic alcohol, an aliphatic ketone, and an aliphatic ester.
Further, when considering the separation from the desorbent by distillation after the adsorption separation treatment, the difference in boiling point between the desorbent and xylenol is desirably 10 ° C or more, preferably 20 ° C or more. Preferred examples of the desorbing agent used in the present invention include n-butanol, n-pentanol, n-hexanol, propyl acetate, butyl acetate, diethyl ketone, ethyl propyl ketone, and dipropyl ketone. it can.

The adsorption separation step used in the present invention is carried out by a chromatographic method, and employs a fixed bed, a fluidized bed, preferably a simulated moving bed. Adsorption separation by the simulated moving bed method is an established technique, and has been applied to the adsorption separation of xylene isomer mixtures.
No. 42-15681 and Japanese Patent Publication No. Sho 50-10547. In such an adsorption separation technique, an extract composed of a strongly adsorbed component and a desorbent is obtained, and a raffinate composed of a weakly adsorbed component and a desorbent is obtained. These extracts and raffinates are subjected to a distillation treatment and separated into respective components, and the separated desorbent is recycled again.

Next, the adsorption separation technique by the simulated moving bed method will be described in more detail. This adsorption separation technique continuously circulates the following adsorption operation, concentration operation, desorption operation and desorbent recovery operation as basic operations. Will be implemented.

(1) Adsorption operation: The xylenol isomer mixture comes into contact with the adsorbent, the strongly adsorbed component of the isomer mixture is selectively adsorbed, and the weakly adsorbed component is recovered together with the desorbent as a raffinate stream.

(2) Concentration operation: The adsorbent selectively adsorbing the strongly adsorbed component is brought into contact with a part of the extract described later, the weakly adsorbed component remaining on the adsorbent is expelled, and the strongly adsorbed component is concentrated. Is done.

(3) Desorption operation: The concentrated adsorbent containing the strongly adsorbed component is brought into contact with the desorbent, the strongly adsorbed component is expelled from the adsorbent, and is recovered as an extract stream with the desorbent.

(4) Desorbent recovery operation: The adsorbent having substantially adsorbed only the desorbent comes into contact with a part of the raffinate stream, and part of the desorbent contained in the adsorbent is recovered as a desorbent recovery stream.

The drawing shows a schematic diagram of an adsorption separation apparatus using a simulated moving bed. In this figure, reference numerals 1 to 16 denote adsorption chambers containing an adsorbent, which are interconnected. 17 is a desorbent supply line,
18 is an extract extraction line, 19 is a raw material supply line,
Reference numeral 20 denotes a raffinate extraction line, and reference numeral 21 denotes a recycling line. In the arrangement state of the adsorption chambers 1 to 16 and each line 17 to 20 shown in the drawing, a desorption operation is performed in the adsorption chambers 1 to 3, a concentration operation is performed in the adsorption chambers 4 to 8, an adsorption operation is performed in the adsorption chambers 9 to 13, and an adsorption chamber 14 is used. The desorbent recovery operation is performed at ~ 16.

In such a simulated moving bed, each supply and withdrawal line is moved in the direction of liquid flow by one adsorption chamber by a valve operation at regular time intervals. Therefore, in the next arrangement state of the adsorption chambers, the desorption operation is performed in the adsorption chambers 2 to 4, the concentration operation is performed in the adsorption chambers 5 to 9, the adsorption operation is performed in the adsorption chambers 10 to 14,
The desorbent recovery operation is performed in each of 〜1 and １1.
By sequentially performing such operations, the adsorption separation process using the simulated moving bed is achieved. Note that, in the drawings, the number of the suction chambers is specified as 16, but it should be noted that the number of the suction chambers is not limited.

As the xylenol isomer mixture used as a raw material in the present invention, a xylenol fraction obtained by distilling a tar acid component of coal tar is generally used. Of course, any mixture containing xylenol isomers may be used, and a mixture of xylenol isomers obtained by a synthesis method may be used.

(Effects of the Invention) According to the present invention, 3,5-xylenol, which has been difficult to separate by the prior art, can be separated and recovered with high purity and efficiency from a xylenol isomer mixture, and its industrial significance is significant. It is.

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

In the following, the relative separation coefficients β (3,5 / i) and β) 3,5 / D) based on 3,5-xylenol used as indices indicating the adsorption characteristics of the adsorbent are the components i and The values for the desorbing agent are shown by the following formula.

β (3,5 / i) = K (3,5) / K (i) (I) β (3,5 / D) = K (3,5) / K (D) (II) (3,5), K (i) and K (D) are the solid-liquid equilibrium constants of the i component and the desorbent of the 3,5-xylenol and xylenol isomer mixture, respectively, and Defined.

In addition, as the i component, specifically, 2,4-xylenol (2,4-X), 2,5-xylenol (2,5-
X), m-ethylphenol (mE), 2,3-xylenol (2,3-X), p-ethylphenol (P-
E), 3,5-xylenol (3,5-X) and 3,4-xylenol (3,4-X).

A mixed component i in which the relative separation coefficient β (3,5 / i) is smaller than 1 indicates that the adsorbent is more strongly adsorbed than 3,5-xylenol. The relative separation coefficient β (3,5 / i) is preferably 0.5 or less, and the component having such a relative separation coefficient can be easily adsorbed and separated from the 3,5-isomer. The value of the relative separation coefficient β (3,5 / D) of the desorbent is 0.1 to 2.
It is practically desirable to be in the range of 0.

Reference example (Preparation of various adsorbents) The adsorbent used in the adsorption separation experiment was Na-
Y-type zeolite _{(Si 2 / Al 2 O 3} = 5.5, particle size 40 to 80 mesh) is obtained by ion-exchanging a predetermined metal. Ion exchange was performed by the method shown below.

(Ion exchange) Metal chloride aqueous solution (0.5mo
l /) was added, and the mixture was left at a temperature of 90 to 100 ° C for 2 hours. After repeating the above operation three times, after drying, temperature 400
Calcination was performed at 3 ° C. for 3 hours.

Example 1 An autoclave having an internal volume of 30 cc was charged with 4 g of an adsorbent exchanged with various cations and about 6.5 g of a raw material oil having the composition shown in Table 1, and the temperature was kept constant while stirring and maintained for 120 minutes.
The adsorbent and the raw material residual liquid were separated by filtration, and the adsorbate in the adsorbent was washed with isooctane, and then desorbed with a Soxhlet extract using a toluene solvent. The composition of the raw material residual liquid (liquid phase) and the adsorbate (adsorbed phase) are analyzed by gas chromatography, and the relative separation coefficient is calculated,
Table 2 shows the results. From the results in Table 2, the potassium-type and barium-type Y-type zeolite adsorbents were 2,4-
And the relative separation coefficient β (3,5 / i) of the other components except for 2,3-xylenol is 0.5 or less, and is excellent as an adsorbent used in the first stage adsorption separation treatment of the present invention. I understand.

Example 2 Approximately 4 g of potassium-type Y zeolite adsorbent in an autoclave having an internal volume of 30 cc, and approximately 6.
5 g and about 1.5 g of a desorbing agent were charged, and the temperature was kept constant while stirring and maintained for 120 minutes. The adsorbent and the raw material residual liquid were separated by filtration, and the adsorbate in the adsorbent was washed with isooctane, and then desorbed by Soxhlet extraction using a toluene solvent. The composition of the raw material residual liquid (liquid phase) and adsorbate (adsorbed phase)
Analysis was performed by gas chromatography, and the relative separation coefficient was calculated. The results are shown in Table-3.

Example 3 The xylenol isomer mixture shown in Table 1 of Example 1 was used as a raw material, and the first-stage adsorption / separation treatment was carried out using the simulated moving bed continuous adsorption / separation apparatus shown in Table 1.

In the separation operation, n-hexanol was used as the potassium-substituted Y-type zeolite adsorbent and desorbent shown in Example 1. The adsorbent was a column adsorption chamber 1 with an internal volume of
The material was supplied to line 16, the raw material was supplied from line 19 at 80 ml / HR, and the desorbing agent was supplied from line 17 at 600 ml / HR. The extract was extracted from line 18 at 536 ml / HR, and the raffinate was extracted from line 20 at 144 ml / HR. During this period, the supply lines for the raw material and the desorbent and the extraction lines 9 for the extract and raffinate were simultaneously moved in the direction of the liquid flow by one adsorption chamber at an interval of 352 seconds. As a result, a raffinate containing the mixture of isomers containing 3,5-xylenol shown in Table 4 was obtained, and the recovery of 3,5-xylenol was 88 wt%.

Example 4 The desorbent was removed from the raffinate obtained in Example 3 by distillation to obtain a xylenol isomer mixture having the composition shown in Table-5. Using this isomer mixture as a raw material and n-hexanol as a desorbing agent, an adsorption separation experiment was carried out in the same manner as in Example 2. The relative separation coefficient of each isomer was calculated, and the results are shown in Table-6. From the results in Table-6,
It can be seen that the 3,5-isomer can be selectively separated from the 5-, 2,4- and 2,3-isomer mixture.

Example 5 Adsorption and separation of 3,5-xylenol from the mixture shown in Table 5 of the example were carried out using the simulated moving bed continuous adsorption and separation apparatus shown in FIG. In the separation operation, n-hexanol was used as the barium-substituted Y-type zeolite adsorbent and the desorbent shown in Example 4. Adsorbent is internal volume
Fill 70 ml column adsorption chambers 1 to 16 and feed line 19
The solution was supplied at 30 ml / HR, and the desorbing agent was supplied at 92 ml / HR from line 17. Extract was extracted from line 18 at 52 ml / HR, and raffinate was extracted from line 20 at 70 ml / HR. During this time, the supply lines for the raw material and the desorbent and the extraction lines for the extract and raffine were simultaneously moved in the liquid flow direction by one adsorption chamber at an interval of 350 seconds.
As a result, a raffinate containing 3,5-xylenol was obtained, and the purity of the 3,5-xylenol was 99% by weight on a desorbent-free basis.

[Brief description of the drawings]

FIG. 1 is a schematic view of an adsorption separation apparatus using a simulated moving bed. 1-16 Adsorption chamber 17 Desorbent supply line 18 Extract extraction line 19 Raw material mixture supply line 20 Raffinate extraction line 21 Recycle line 22 Pump

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-122433 (JP, A) JP-A-55-151522 (JP, A) JP-A-51-115292 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) C07C 39/06-39/07 C07C 37/82

Claims (2)

(57) [Claims] 1. A method for separating 3,5-xylenol from a xylenol isomer mixture, comprising using a faujasite-type zeolite adsorbent in which the mixture is substituted with at least one metal selected from potassium and barium. The extract is mainly composed of 2,5- and 3,4-xylenol, and the extract is mainly composed of 3,5- and 2,4-
And a first step of obtaining a raffinate comprising 2,3-xylenol, and adsorbing a faujasite-type zeolite in which the raffinate obtained in the first step is substituted with at least one metal selected from potassium, barium and lead Adsorbing and separating using an agent, and a second step of obtaining an extract consisting mainly of 2,4- and 2,3-xylenol and a raffinate consisting mainly of 3,5-xylenol 3,
Method for separating 5-xylenol. 2. The method according to claim 1, wherein the desorbing agent used in the adsorption separation step is at least one selected from aliphatic alcohols, aliphatic ketones and aliphatic esters.