JP2867830B2 - Method for separating p-toluidine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for separating and recovering p-toluidine from a mixture of toluidine isomers.

[0002] p-Toluidine is a substance useful as an intermediate for dyes and pigments and as an intermediate for pesticides.

[0003]

2. Description of the Related Art It has been known to adsorb and separate a mixture of isomers of toluidine using an X or Y type zeolite ion-exchanged with a cation in the group of Fe, Mo, Co, Ni or Zn as an adsorbent (Japanese Patent Application Laid-Open (JP-A) No. Sho-59-163). 60-922247
No.).

[0004]

However, Japanese Patent Application Laid-Open No.
In the known method described in JP-A-92-247, separation of p-toluidine and m-toluidine is insufficient, and is not industrially practical.

[0005]

Means for Solving the Problems The present inventors have intensively studied a method for efficiently separating p-toluidine from a mixture of isomers of toluidine, and have used zeolite as an adsorbent and alkylpyridine as a desorbent. It has been found that this object can be achieved by adsorption separation, and the present invention has been accomplished.

That is, the present invention is characterized in that when separating and recovering p-toluidine from a mixture of toluidine isomers by adsorption separation, zeolite is used as an adsorbent and alkylpyridine is used as a desorbent. And more preferably a method for separating p-toluidine, wherein a Y-type faujasite-type zeolite is used as an adsorbent.

The zeolite used in the method of the present invention is not particularly limited, but preferably a faujasite type zeolite is used. The faujasite-type zeolite is a crystalline aluminosilicate represented by the following formula.

[0008] 0.9 ± 0.2 M _{2 / n} O: Al ₂ O ₃ :
xSiO ₂ : yH ₂ O Here, M represents a cation, and n represents its valence.
The faujasite type zeolite of the above formula is classified into X type and Y type, X type is x = 2.5 ± 0.5, and Y type is x =
It is represented by 3-6. Further, y differs depending on the degree of hydration.

In the present invention, a Y-type faujasite-type zeolite is preferably used.

Further, the metal constituting the zeolite may be any metal. This metal can usually be exchanged as an ion. Further, a metal ion may be replaced with a hydrogen ion or an ammonium ion. Further, these metal ions may be substituted by two or more metal ions. Preferred specific examples of the metal constituting the faujasite-type zeolite include, for example, sodium, potassium, silver, calcium, strontium, barium, lead, cerium, magnesium, copper, aluminum, zirconium, vanadium, molybdenum, manganese, iron, cobalt, Nickel or platinum may be used.

Of these, periodic table Ia, IIa, II
Metals selected from the groups Ia and VIII can more preferably be used and include, for example, potassium, calcium, strontium, barium, cerium, magnesium, cobalt and the like. Among these, the most preferred zeolite is a K-substituted Y-type zeolite or a Y-type zeolite in which a part of the K is further substituted with at least one selected from Ca, Sr, Ba and Pb.

These cations are easily incorporated into the zeolite by the ion exchange method.

The method of ion exchange for cations is widely known to those skilled in the art having knowledge of the production of crystalline aluminosilicate, and any known techniques can be used for ion exchange, and the amount of ion exchange is arbitrary. It is. As a method of ion exchange, a water-soluble metal salt (for example, chloride, nitrate, sulfate, or the like is used) is dissolved in water. The concentration varies depending on the type of metal salt, but 1 to 10 wt%
About is preferred. This solution is brought into contact with zeolite for ion exchange. The method may be a batch type or a flow type. The contact may be repeated several times as necessary. The temperature at this time is used up to 20 to 100 ° C., but preferably 50 to 100 ° C. in order to reduce the exchange rate. The amount of ion exchange varies depending on the type of ions, but can be arbitrarily set depending on the concentration of the solution, the temperature at the time of ion exchange, and the like. The ion exchange treatment after e.g. chloride ion (C1 ^-) and nitrate ion (NO ₃ ^-) is washed thoroughly with water until no longer detected. In addition, it is necessary to remove the water of crystallization before using the zeolite as an adsorbent, that is, it is necessary to calcine the zeolite to a substantially anhydrous state. Usually, it is heated to 100 ° C. or more to reduce the water content of crystallization.
By heating at 00 to 600 ° C., most of the crystallization water can be removed.

In the present invention, it is important to use an alkylpyridine as a desorbing agent. As the alkyl group substituted by pyridine, a C1-4 lower alkyl group is particularly preferred, and two or more alkyl groups may be substituted.
Preferred specific examples of the alkylpyridine include methylpyridine, dimethylpyridine, ethylpyridine, diethylpyridine, propylpyridine, dipropylpyridine and the like, and among them, methylpyrazine or dimethylpyridine is most preferably used. Desorption agent is practical,
It is preferable to use them alone, but they can also be used as a mixture.

The technique for adsorptive separation of a mixture of toluidine isomers using the method of the present invention may be a so-called chromatographic preparative method, or may be an adsorptive separation method using a simulated moving bed in which this is continuous. .

The continuous adsorption / separation technique using a simulated moving bed is basically performed by continuously circulating the following adsorption operation, concentration operation and desorption operation.

(1) Adsorption operation: The toluidine isomer mixture is brought into contact with the faujasite-type zeolite adsorbent, and the strongly adsorbed component is adsorbed while leaving the weakly adsorbed component selectively. The strongly adsorbed component is recovered together with the desorbent as an extract component.

(2) Concentration operation: The raffinate containing a large amount of weakly adsorbed components is further brought into contact with an adsorbent to selectively adsorb the strongly adsorbed components, so that the weakly adsorbed components in the raffinate are highly purified.

(3) Desorption operation: The highly purified weakly adsorbed component is recovered together with the raffinate, while the adsorbed component is expelled from the adsorbent by the desorbent, and is recovered as an extract component together with the desorbent.

The operating conditions for the adsorption separation are as follows:
The temperature is from room temperature to 350 ° C., preferably 50 to 250 ° C., and the pressure is from atmospheric pressure to 50 kg / cm ² · G, preferably from atmospheric pressure to 40 kg / cm ² · G. The adsorption separation according to the invention may be in the gas phase or in the liquid phase, but is preferably carried out in the liquid phase in order to reduce the operating temperature and to suppress undesired side reactions of the raw material feed or the desorbent.

[0021]

Next, the method of the present invention will be described with reference to examples.

In Examples 1 to 7 and Comparative Examples 1 to 4, the adsorption characteristics are represented by the adsorption selectivity (α) of the following equation (1).

[0023]

(Equation 1) Here, A represents any one of the toluidine isomers, B
Represents any one of the toluidine isomers or a desorbing substance, S represents an adsorption phase, and L represents a liquid phase in equilibrium with the adsorption phase.

In the above equation, when the α value is 1.0, there is no selective adsorption between the two components A and B (adsorption to the same degree).
When the α value is larger than 1.0, the component A is selectively adsorbed, and when the α value is smaller than 1.0, the component B is selectively adsorbed. Therefore, regarding the separation of the two components A and B, the adsorbent having the α value of the above equation larger than 1.0 (or the adsorbent smaller than 1.0 and close to 0) is more easily adsorbed and separated from the component A and the component B. Become. On the other hand, for the desorbing agent, the α value is preferably close to 1.0 in order to replace the desorbed component in the next adsorption step after desorbing the adsorbed component.

Example 1 K-substituted Y-type faujasite-type zeolite (K
Y) 0.38 equivalents of the granulated product were ion-exchanged with Ba (0.
38Ba-KY), calcined at 500 ° C. for about 1 hour, and then cooled in a desiccator. About 1.5 g of this adsorbent and 2.8 g of the liquid phase mixture were charged into a 5 ml autoclave,
The composition ratio of the charged liquid phase mixture left at 30 ° C. for 1 hour was p-toluidine: o-toluidine: m-toluidine: 3-methylpyridine: n-nonane = 2: 2:
2: 2: 1 (weight ratio). The composition of the liquid phase mixture after contacting with the adsorbent was analyzed by gas chromatography, and the adsorption selectivity α was determined using the above formula (1) .N-nonane was the internal standard substance in gas chromatography analysis. As a substance which is substantially inert to the adsorbent under the above experimental conditions. Table 1 shows the results.

Example 2 An experiment was carried out in the same manner as in Example 1 except that 0.25 equivalents of K-substituted Y-type zeolite were ion-exchanged with Ca using zeolite (0.25Ca-KY) as an adsorbent. Table 1 shows the results.

Example 3 A zeolite obtained by ion-exchanging 0.5 equivalents of K-substituted Y-type zeolite with Ba (0.5Ba-KY) was used as an adsorbent, and the composition ratio was p-toluidine: o-toluidine: m-toluidine: 2-methylpyridine: n-nonane = 2: 2: 2:
An experiment was conducted in the same manner as in Example 1 using a liquid phase mixture of 2: 1 (weight ratio). Table 1 shows the results.

Example 4 A zeolite obtained by ion-exchanging 0.25 equivalents of K-substituted Y-type zeolite with Ba (0.25 Ba-KY) was used as an adsorbent and the composition ratio was p-toluidine: o-toluidine: m-toluidine: 3,4-dimethylpyridine: n-nonane =
Using a 2: 2: 2: 2: 1 (weight ratio) liquid phase mixture,
The experiment was similarly performed at 150 ° C. Table 1 shows the results.

Example 5 A zeolite obtained by ion-exchanging 0.38 equivalents of K-substituted Y-type zeolite with Sr (0.38 Sr-KY) was used as an adsorbent and the composition ratio was p-toluidine: o-toluidine: m-toluidine: 3-methylpyridine: n-nonane = 2: 2:
130 ° C. using a liquid phase mixture of 2: 2: 1 (weight ratio)
The same experiment was performed. Table 1 shows the results.

Example 6 A zeolite obtained by ion-exchanging 0.5 equivalents of K-substituted Y-type zeolite with Pb (0.5 Pb-KY) was used as an adsorbent.
The composition ratio is p-toluidine: o-toluidine: m-toluidine: 2,4-dimethylpyridine: n-nonane = 2:
Using a 2: 2: 2: 1 (weight ratio) liquid phase mixture, 15
The experiment was similarly performed at 0 ° C. Table 1 shows the results.

Example 7 A zeolite obtained by ion-exchanging 0.1 equivalents of K-substituted Y-type zeolite with Co (0.1Co-KY) was used as an adsorbent.
The composition ratio is p-toluidine: o-toluidine: m-toluidine: 3-ethylpyridine: n-nonane = 2: 2: 2:
The same experiment was performed at 150 ° C. using a liquid phase mixture of 2: 1 (weight ratio). Table 1 shows the results.

[0032]

[Table 1]

Comparative Example 1 The same 0.25 Ca-KY as in Example 2 was used as an adsorbent, and the composition ratio was p-toluidine: o-toluidine: m-toluidine: aniline: n-nonane = 2: 2: 2: 2: The same experiment was performed at 150 ° C. using a liquid phase mixture of 1 (weight ratio). Table 2 shows the results.

Comparative Example 2 The same experiment was conducted at 150 ° C. using the same 0.5 Pb-KY as in Example 6 as an adsorbent and a liquid phase mixture having the same composition ratio as in Comparative Example 1. Table 2 shows the results.

Comparative Example 3 K-substituted Y-type zeolite (KY) was used as an adsorbent, and the composition ratio was p-toluidine: o-toluidine: m-toluidine: aniline: n-nonane = 2: 2: 2: 2: 1 ( The experiment was performed using a liquid phase mixture (weight ratio). Table 2 shows the results.

Comparative Example 4 In Comparative Example 3, a liquid phase mixture having a composition ratio of p-toluidine: o-toluidine: m-toluidine: hexylamine: n-nonane = 2: 2: 2: 2: 1 (weight ratio) The experiment was performed using. Table 2 shows the results.

[0037]

[Table 2]

Example 8 0.38 Ba-KY adsorbent used in Example 1 was
m, packed in a 4.75 mm inner diameter stainless steel column,
The desorbent 3-methylpyridine was flowed at a flow rate of 1.8 ml / min in an oil bath at 0 ° C. Separation raw material p-toluidine: o
-Toluidine: m-Toluidine: n-nonane = 1: 1:
About 1.0 ml of a toluidine isomer mixture consisting of 1: 0.75 (weight ratio) was introduced into the column inlet. n-Nonane is used as a measure of the effluent time and its adsorption is virtually negligible compared to other components.

The effluent from the column outlet was periodically sampled and analyzed by gas chromatography to obtain the effluent curve shown in FIG.

EXAMPLE 9 A stainless steel column having a length of 1 m and an inner diameter of 4.75 mm was packed with KY as an adsorbent, and a desorbent 3,5-dimethylpyridine was supplied at a flow rate of 1.8 ml / min in an oil bath at 150 ° C. Shed. While flowing 3,5-dimethylpyridine, p-toluidine, o-toluidine, which is a separation raw material:
m-toluidine: n-nonane = 1: 1: 1: 0.75
Approx. 1.0 ml of toluidine isomer mixture consisting of (weight ratio)
Was introduced into the column inlet, and the liquid flowing out from the column outlet was periodically analyzed by gas chromatography in the same manner as in Example 7. The outflow curve is shown in FIG.

Comparative Example 5 An experiment was performed under the same conditions as in Example 8 except that 0.5Ni-KY was used as the adsorbent and aniline was used as the desorbing agent. The outflow curve is shown in FIG.

[0042]

According to the present invention, only p-toluidine can be separated and recovered from a toluidine isomer mixture more efficiently and with good yield. It is possible to sufficiently separate p-toluidine and m-toluidine, and to provide an industrially practical method for separating and recovering p-toluidine.

[Brief description of the drawings]

FIG. 1 is an outflow curve diagram showing a time change of an outflow amount of each component in Example 8 of the present invention.

FIG. 2 is an outflow curve diagram showing a time change of an outflow amount of each component in Example 9 of the present invention.

FIG. 3 is an outflow curve diagram showing a time change of an outflow amount of each component in Comparative Example 5 of the present invention.

Continuation of the front page (58) Fields investigated (Int.Cl. ⁶ , DB name) C07C 211/47 B01D 15/00 C07B 63/00 C07C 209/86 CA (STN) WPI / L (QUESTEL)

Claims (2)

(57) [Claims] 1. A method for separating p-toluidine, wherein z-lite is used as an adsorbent and alkylpyridine is used as a desorbing agent when p-toluidine is separated and recovered from the toluidine isomer mixture by adsorption separation. 2. The method for separating p-toluidine according to claim 1, wherein a Y-type faujasite-type zeolite is used as the adsorbent.