JPH05301830A - Production of 2, 6-dimethylnaphthalene - Google Patents

Abstract

PURPOSE:To obtain an industrial method capable of efficiently producing 2,6- dimethylnaphthalene in high purity. CONSTITUTION:The objection method for producing 2,6-dimethylnaphthalene consists of (i) a isomerization process for obtaining a dimethylnaphthalene isomer mixture containing 2,6-dimethylnaphthalene, 1,6-dimethylnaphthalene and 1,5-dimethylnaphthalene by isomerizing 1,5-dimethylnaphtalene, (ii) a process for separating compound having boiling point lower than dimethylnaphthalene and compound having boiling point higher than limethylnaphthalene and (iii) adsorption separation process for separating 2,6-dimethylnaphthalene as a raffinate and separating other dimethylnaphthalene as an extract by subjecting the resultant dimethylnaphthalene isomer mixture to absorption separation treatment using a Y type zeolite adsorbent in the presence of a desorbing agent expressed by the formula (R<1> and R<2> are lower alkyl; m is 0 or 1).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing 2,6-dimethylnaphthalene.

[0002]

2. Description of the Related Art Conventionally, 5- (O-tolyl) -pentene-produced by reacting O-xylene with butadiene for producing 2,6-dimethylnaphthalene.
A method is known in which 2 is cyclized to 1,5-dimethyltetralin, which is dehydrogenated to 1,5-dimethylnaphthalene and then isomerized (JP-A-48-61461).
No. 3-500052). This method is 2,6
-O-xylene and butadiene, which are petroleum products that can be stably supplied, are used as raw materials for the production of dimethylnaphthalene,
It can be said that it is an excellent industrial method,
There are some problems to be solved for its practical use. One of the major problems is the establishment of a high-purity separation method of 2,6-dimethylnaphthalene from a dimethylnaphthalene isomer mixture obtained by isomerization of 1,5-dimethylnaphthalene. In the above-mentioned JP-A-48-61461, for separating 2,6-dimethylnaphthalene from a dimethylnaphthalene isomer mixture, the dimethylnaphthalene mixture is cooled to about 15 ° C. to obtain crystals containing 2,6-dimethylnaphthalene. A method is disclosed in which, after precipitation, centrifugation is performed, and methanol is added to the obtained cake to recrystallize. However, the purity of 2,6-dimethylnaphthalene obtained by such a crystallization method is still low at about 96%, which is unsatisfactory as an industrial product.

[0003]

DISCLOSURE OF THE INVENTION The present inventors
-It is an object of the present invention to solve the above-mentioned problems found in the conventional method for producing dimethylnaphthalene and to provide an industrial method capable of efficiently producing 2,6-dimethylnaphthalene with high purity.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that isomerization products of 1,5-dimethylnaphthalene are subjected to a distillation treatment in advance to obtain naphthalene, methylnaphthalene and the like. After removing the low boiling point substances and high boiling point substances such as trimethylnaphthalene, the resulting dimethylnaphthalene isomer mixture is subjected to adsorption separation treatment using a Y-type zeolite adsorbent in the presence of a desorbing agent consisting of alkylbenzene, The inventors have found that 2,6-dimethylnaphthalene can be produced with high purity and efficiency, and have completed the present invention. That is, according to the present invention, 2,6
-In the production of dimethylnaphthalene, (i) 1,5-dimethylnaphthylene is isomerized to include 2,6-dimethylnaphthalene, 1,6-dimethylnaphthalene and 1,5-dimethylnaphthalene, and a dimethylnaphthalene isomer mixture. (Ii) a dimethylnaphthalene isomer mixture obtained in the isomerization step is subjected to a distillation treatment to obtain a low boiling point substance having a lower boiling point than dimethylnaphthalene and a high boiling point substance having a higher boiling point than methylnaphthalene contained therein. A distillation step of separating the boiling point substance, (iii) a dimethylnaphthalene isomer mixture obtained in the distillation step is represented by the general formula

[Chemical 1] (Wherein R ¹ and R ² represent a lower alkyl group, m represents 0 or 1, and R ¹ and R ² may be the same or different) in the presence of a desorption agent An adsorption separation step of performing an adsorption separation treatment using a zeolite adsorbent to separate 2,6-dimethylnaphthalene as a raffinate and another dimethylnaphthalene as an extract. A method of making dimethylnaphthalene is provided.

The 1,5-dimethylnaphthalene used as the isomerization raw material in the present invention can be obtained by a conventionally known method. For example, this product uses 0-xylene and butadiene as raw materials, and both are subjected to an alkylation reaction in the presence of a base catalyst to produce 5- (O-tolyl) -pentene-2, which is present in the presence of an acid catalyst. It can be obtained by carrying out a cyclization reaction under the following conditions to give 1,5-dimethyltetralin and then subjecting it to a dehydrogenation reaction.
See JP-A 8-61461 and JP-A 3-500052. Also, the isomerization reaction of 1,5-dimethylnaphthalene has been well known in the art, and the above-mentioned JP-A-48-6 is used.
It is described in detail in Japanese Patent Publication No. 1461 and Japanese Patent Publication No. 3-500052. That is, it can be carried out by contacting 1,5-dimethylnaphthalene with a solid acid catalyst. The reaction temperature is 200 to 450 ° C., preferably 270 to 350.
℃. Examples of the solid acid catalyst include silica alumina, silica magnesia, metal ion substitution type or non-substitution type zeolite, hydrogen type zeolite and the like.

In the present invention, the isomerization reaction product of 1,5-dimethylnaphthalene is subjected to a distillation treatment to obtain a low-boiling substance having a lower boiling point than 1,5-dimethylnaphthalene contained therein (for example, naphthalene or methyl). Naphthalene, etc.) and high-boiling substances having a higher boiling point than dimethylnaphthalene (for example, trimethylnaphthalene) are separated and removed, and the dimethylnaphthalene isomer mixture from which the low-boiling substances and high-boiling substances are separated and removed is adsorbed and separated, and adsorbed. Separate processing. According to the research conducted by the present inventors, the dimethylnaphthalene isomer mixture from which the low-boiling substance and the high-boiling substance are removed is subjected to Y-type zeolite in the presence of a desorbing agent composed of the aromatic compound represented by the above general formula. Surprisingly, the relative separation coefficient β value (hereinafter, also simply referred to as β value) of each dimethylnaphthalene isomer based on 2,6-dimethylnaphthalene was 2 when the adsorption separation treatment was performed using an adsorbent. It is larger than the β value of 6,6-dimethylnaphthalene, and therefore high-purity separation of 2,6-dimethylnaphthalene, which has been difficult to separate and recover from a dimethylnaphthalene isomer mixture with high purity, is possible. Was found.

In the adsorption separation step of the present invention, the dimethylnaphthalene isomer mixture is brought into contact with the Y-type zeolite adsorbent to selectively adsorb and separate dimethylnaphthalene other than 2,6-dimethylnaphthalene on the adsorbent. , An extract containing dimethylnaphthalene as a main component other than 2,6-dimethylnaphthalene and a raffinate containing 2,6-dimethylnaphthalene as a main component are obtained. In this adsorption separation step, 80% by weight or more, preferably 90 to 100% by weight, of 2,6-dimemethylnaphthalene contained in the dimethylnaphthalene isomer mixture is separated into raffinate. In this way, 2,6-dimethylnaphthalene can be separated from the dimethylnaphthalene isomer mixture with high purity and high recovery.

In the desorbent represented by the above general formula used in the present invention, the lower alkyl groups R ¹ and R ² are
Examples thereof include a methyl group, an ethyl group, a propyl group and a butyl group. Specific examples of the desorbent include, for example, isopropylbenzene, m-diethylbenzene, P-xylene, P-.
Examples include cymene and ethylbenzene. In the present invention, the boiling point is particularly 60 to 250 ° C., preferably 7
Preference is given to using desorbents in the range 0-200 ° C.

In the present invention, a conventionally known Y-type zeolite adsorbent is used as the adsorbent. In the present invention, a Y-type zeolite substituted with an alkali metal or an alkaline earth metal such as Li, Na, K and barium, preferably Y having a SiO ₂ / Al ₂ O ₃ molar ratio of 2 to 6 is used.
Type zeolite is used. These adsorbents can be used alone or in the form of a mixture. Further, these adsorbents preferably have a metal ion exchange rate of 80% or more, preferably 90% or more. The particle size of the adsorbent is about 3 to 300 mesh and may be appropriately selected according to the type of adsorbent bed. In addition, the adsorbent can be adjusted in its water content to improve its adsorption selectivity. The water present in the adsorbent is either partially contained at the cation or base exchange positions or contained within the voids of the adsorbent. The water content, measured by weight loss under burning at 1000 ° C, was 5% by weight of the adsorbent.
It is desirable to be in the range of ˜20 wt%. The water content can be adjusted by adding an appropriate amount of water to the raw material mixture. The temperature in the adsorption separation step in the present invention is 60 to 250 ° C, preferably 70 to 200 ° C, and the pressure may be a pressure sufficient to maintain the system in a liquid phase state.

The adsorption / separation step in the present invention is carried out by a chromatographic method and can be carried out by any system such as a fixed bed, a fluidized bed or a moving bed, but industrially it is carried out by a simulated moving bed system. Is preferred. Adsorption separation by a simulated moving bed system is an already established technique and is applied to adsorption separation of a xylene isomer mixture. For example, Japanese Patent Publication No. 42-15681 and Japanese Patent Publication No. 50-10.
No. 547, etc. In the adsorption separation step in the present invention, as described above, the target 2,6-dimethylnaphthalene can be separated and recovered with high purity from the dimethylnaphthalene isomer mixture which has a similar boiling point and is most difficult to separate from each other. it can. According to the adsorption separation technology by the above-mentioned simulated moving bed system, 2,6-dimethylnaphthalene is mixed with 9
It can be separated and collected with a high purity of 9% by weight or more.

The adsorption separation by the simulated moving bed system will be described in more detail. This adsorption separation technique is carried out by continuously circulating the following adsorption operation, concentration operation, desorption operation and desorbent recovery operation as basic operations. To be done. (1) Adsorption operation: The raw material to be treated comes into contact with the zeolite adsorbent, the target adsorption component as a strong adsorption component is selectively adsorbed, and the other weak adsorption component is recovered as a raffinate stream together with the desorbent. It (2) Concentration operation: The adsorbent that selectively adsorbs the adsorbed target component is brought into contact with a part of the extract described later, and the non-adsorbed component remaining on the adsorbent is expelled to concentrate the target component. It (3) Desorption operation: The adsorbent containing the concentrated adsorption target component is brought into contact with the desorption agent to expel the adsorption target component from the adsorbent, and is collected as an extract stream together with the desorption agent. (4) Desorbent recovery operation: The adsorbent that substantially adsorbs only the desorbent comes into contact with a part of the raffinate stream, and a part of the desorbent contained in the adsorbent is recovered as a desorbent recovery stream.

FIG. 1 shows a schematic diagram of an adsorption separation operation using a simulated moving bed. In this figure, 1 to 12 are adsorption chambers containing a zeolite adsorbent, which are mutually connected. 1
3 is a desorbent supply line, 14 is an extract extraction line, 15 is a raw material supply line, 16 is a raffinate extraction line, and 17 is a recycle line. In the arrangement state of the adsorption chambers 1 to 12 and the lines 13 to 16 shown in FIG. 1, desorption operation is performed in the adsorption chambers 1 to 3, concentration operation is performed in the adsorption chambers 4 to 6, adsorption operation is performed in the adsorption chambers 7 to 10, adsorption chambers The desorbent recovery operation is performed in each of 11 to 12. In such a simulated moving bed, the supply and withdrawal lines are moved by one valve in the liquid flow direction by one adsorption chamber at regular time intervals. Therefore, in the next arrangement state of the adsorption chamber, the desorption operation is performed in the adsorption chambers 2 to 4, the concentration operation is performed in the adsorption chambers 5 to 7, the adsorption operation is performed in the adsorption chambers 8 to 11, and the desorbent recovery operation is performed in the adsorption chambers 12 to 1, respectively. Will be done. By carrying out such an operation in sequence, the adsorption separation process by the simulated moving bed is achieved. It should be noted that although the number of adsorption chambers is specified to 12 in the drawings, the number of adsorption chambers is not limited.

FIG. 2 shows an example of a flow sheet for carrying out the adsorption separation step of the present invention. In FIG. 2, 20 is an adsorption separation column, and 21 and 22 are distillation columns. The raw material dimethylnaphthalene isomer mixture is fed from the line 25 to the adsorption separation column 2
0, and the circulating desorbent is introduced into the adsorption separation column 20 through the line 26. In the adsorption separation tower 20, components other than 2,6-dimethylnaphthalene are selectively adsorbed and separated. The extract mainly containing isomers other than 2,6-dimethylnaphthalene is extracted through a line 27, and the raffinate mainly containing 2,6-dimethinaphthalene is extracted through a line 28.
The raffinate withdrawn through the line 28 is introduced into the first distillation column 21, where it is subjected to a distillation treatment, and the desorbent contained in the raffinate is withdrawn through the line 29 to separate the desorbent. The raffinate (2,6-dimethylnaphthalene) after the recovery is recovered through line 30.
The extract withdrawn from the adsorption separation column 20 through the line 27 is introduced into the second distillation column 22, where it is subjected to a distillation treatment, and the desorbent contained in the extract is extracted through the line 31. .. From the bottom of the second distillation column 22, dimethylnaphthalene isomers other than 2,6-dimethylnaphthalene are separated and circulated in the above-mentioned isomerization step. The desorbent extracted from the second distillation top column 22 through the line 31 is circulated to the adsorption separation column 20 together with the desorbent extracted from the first distillation column 21 through the line 29. Line 33 shows a replenishment desorption agent line.

[0014]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. The relative separation coefficient β shown below
The value is the relative strength of the adsorptive power of the mixed components based on 2,6-dimethylnaphthalene when the dimethylnaphthalene isomer mixture containing 2,6-dimethylnaphthalene is subjected to adsorption treatment using a zeolite adsorbent. It gives an index and is expressed by the following formula. It is indicated that the larger the β value, the easier the adsorption and separation by the adsorbent. β [i] = K [i] / K [2,6] β [i]: Relative separation coefficient of mixed component i K [i]: Adsorption equilibrium constant of mixed component i K [2,6]: 2,6 -Adsorption equilibrium constant of dimethylnaphthalene K [i] = (% by weight of component i in the adsorption phase) / (component i in the liquid phase)
Wt%) K [2,6] = (wt% of 2,6-dimethylnaphthalene in the adsorption phase) / (wt% of 2,6-dimethylnaphthalene in the liquid phase)

Example (1) Alkylation step of O-xylene with butadiene (batch system) O was added to an autoclave having an internal volume of 250 cc.
-About 100 g of xylene and about 1.0 g of potassium metal were added, heated at 110 ° C. with stirring, and then butadiene was blown at a rate of about 8.5 g / HR and reacted for about 3 hours. As a result of composition analysis of the reaction product, about 35 g of 5- (O-tolyl) -pentene-2 was obtained. (2) Cyclization step of 5- (O-tolyl) -pentene-2 30 cc in a reactor having an inner diameter of 16.7 mm and a length of 300 mm.
After the solid phosphoric acid catalyst of No. 1 was charged and the reactor was heated to 240 ° C., 5- (O 2
-Tolyl) -Pentene-2 was sent. As a result of gas chromatographic analysis of the obtained reaction product, the product shown in Table 1 was obtained.

[0016]

[Table 1]

(3) Dehydrogenation step of 1,5-dimethyltetralin A stainless steel reactor having an inner diameter of 16.7 mm and a length of 300 mm was filled with 40 cc of a carbon catalyst supporting 10 wt% of palladium. Flow the reactor 25 while flowing nitrogen gas.
After the temperature was raised to 0 ° C., 2,5-dimethyltetralin was added to 2
Liquid was sent from the bottom of the reactor at 0 cc / HR. As a result of composition analysis of the reaction solution, the content of 1,5-dimethylnaphthalene in the reaction solution was 97.3 wt%.

(4) Isomerization step of 1,5-dimethylnaphthalene About 50 cc of H-mordenite catalyst was charged into a stainless steel reactor having an inner diameter of 16.7 mm and a length of 300 mm, and 1,5-dimethyl at a reaction temperature of 260 ° C. 15 cc / naphthalene
The liquid was sent at a flow rate of HR. The gas chromatographic analysis value of the obtained product is shown in Table 2.

[0019]

[Table 2]

(5) Adsorption / separation step of dimethylnaphthalene isomer mixture An adsorption separation experiment was carried out using a dimethylnaphthalene isomer mixture having the component composition shown in Table 3 as a raw material. In this case, the adsorbent used in the experiment is Na-Y type zeolite ion-exchanged with a predetermined metal. The ion exchange and adsorption separation experiments were carried out by the methods shown below.

[0022]

[Table 3]

(Ion exchange) Na type Y type zeolite About 1
About 10 g of metal chloride aqueous solution (0.5 mol / l) was added to 0 g.
0 g was added and the mixture was allowed to stand at a temperature of 90 to 100 ° C. for 2 hours. After repeating the above operation 3 times, after drying, the temperature is 400 ° C.
Burned for hours.

(Adsorption Separation Experiment) About 4 g of adsorbent, about 3.2 g of feed oil, and about 4.8 g of p-diethylbenzene as a desorbent were charged in an autoclave having an internal volume of 30 cc, and the temperature was raised to 110 ° C. with stirring. I kept it for a minute. The adsorbent and the raw material residual liquid are separated by filtration, and the adsorbent in the adsorbent is
After washing the adsorbent with isooctane, Soxhlet extraction was carried out for 2 hours using a toluene solvent for desorption. The composition of the raw material residual liquid (liquid phase) and the adsorbate (adsorption phase) was analyzed by gas chromatography, and the relative ratio of each dimethylnaphthalene isomer based on the 2,6-isomer (relative separation coefficient β value = 1) The separation factor β value was calculated. The results are shown in Table 4.

As can be seen from the results shown in Table 4, dimethylnaphthalene other than 2,6-dimethylnaphthalene has a large β value, and dimethylnaphthalene isomers other than 2,6-isomer are 2,6- It can be easily adsorbed and separated from isomers. In addition, Table 4 shows the weight of dimethylnaphthalene adsorbed per 1 g of the adsorbent as the adsorbate weight. From these results, it can be seen that the Y-type zeolite has excellent adsorption performance for dimethylnaphthalene.
The contents of the symbols shown in Table 4 are as follows. A: KY type zeolite B: Na-Y type zeolite C: Li-Y type zeolite

[0026]

[Table 4]

Comparative Example K-X type zeolite (adsorbent X) and K- as adsorbents
An adsorption separation experiment was carried out in the same manner as in Example except that L-type zeolite (adsorbent L) was used. The relative separation coefficient β value of each isomer based on the 2,6-isomer was calculated, and the results are shown in Table 5. As can be seen by comparing the results shown in Table 5 with the results shown in Table 4, in the case of these X-type zeolite and L-type zeolite, the isomers between Since the difference in relative separation coefficient β value is small, it is difficult to separate the 2,6-isomer from other isomers with high purity, and the weight of the adsorbate is small, so that the adsorption separation can be efficiently performed. Have difficulty.

[0028]

[Table 5]

[0029]

According to the present invention, as described above, 1,5-dimethylnaphthalene obtained from petroleum products o-xylene and butadiene as raw materials is used as the raw material for 2,6-
Dimethylnaphthalene can be produced with high purity and high yield. The 2,6-dimethylnaphthalene obtained in the present invention is suitable as a raw material for producing 2,6-naphthalenedicarboxylic acid used as a polyester raw material.

[0028]

[Brief description of drawings]

FIG. 1 is a schematic diagram of an adsorption separation operation using a simulated moving bed.

FIG. 2 is an example of a flow sheet for obtaining high-purity 2,6-dimethylnaphthalene from a dimethylnaphthalene isomer mixture.

[Explanation of symbols]

 1-12 Adsorption chamber 13 Desorbent supply line 14,29,31 Extract extraction line 15,19,27 Raw material supply line 16,26,28 Raffinate extraction line 17 Recycle line 18 Pump 20 Adsorption separation column 21,22 Distillation Tower

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location C07C 7/13 // C07B 61/00 300 (72) Inventor Kenji Shimokawa Tsurumi, Tsurumi-ku, Yokohama-shi, Kanagawa Chuo 2-12-1 Chiyoda Kakoh Construction Co., Ltd. (72) Inventor Mitsunori Shimura Tsurumi-ku Tsurumi-ku, Yokohama-shi, Kanagawa Chiyoda Kakoh Construction Co. Ltd. (72) Inventor Tomonori Kato Tokyo Chiyoda 1-1-2 Marunouchi, Nihon Steel Tube Co., Ltd. (72) Inventor Hiroaki Taniguchi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd. (72) Yasuyuki Takigawa Marunouchi, Chiyoda-ku, Tokyo 1-2 1-Nihon Steel Pipe Co., Ltd.

Claims (3)

[Claims] 1. In the production of 2,6-dimethylnaphthalene, (i) 1,5-dimethylnaphthalene is isomerized to give 2,6
An isomerization step of obtaining a dimethylnaphthalene isomer mixture containing dimethylnaphthalene, 1,6-dimethylnaphthalene and 1,5-dimethylnaphthalene, (ii) a distillation treatment of the dimethylnaphthalene isomer mixture obtained in the isomerization step Then, a distillation step of separating a low boiling point material having a lower boiling point than dimethylnaphthalene and a high boiling point material having a higher boiling point than methylnaphthalene contained therein, (iii) the dimethylnaphthalene isomer mixture obtained in the distillation step, General formula: (Wherein R ¹ and R ² represent a lower alkyl group, m represents 0 or 1, and R ¹ and R ² may be the same or different) in the presence of a desorption agent An adsorption separation step of performing an adsorption separation treatment using a zeolite adsorbent to separate 2,6-dimethylnaphthalene as a raffinate and another dimethylnaphthalene as an extract. Method for producing dimethylnaphthalene. 2. The method according to claim 1, wherein a dimethylnaphthalene isomer mixture other than 2,6-dimethylnaphthalene obtained in the adsorption separation step is recycled to the isomerization step. 3. The method according to claim 1, wherein the zeolite adsorbent is a Y-type zeolite ion-exchanged with at least one metal ion selected from alkali metals and alkaline earth metals.