JPH05310610A - Production of 2,6-diethylnaphthalene - Google Patents

Abstract

(57) [Summary] [Objective] To efficiently and inexpensively produce 2,6-diethylnaphthalene, which is useful as a raw material for 2,6-naphthalenedicarboxylic acid. [Summary] A reaction step of reacting naphthalene and / or ethylnaphthalene with polyethylbenzene in the presence of an acid catalyst, and distillation separation for separating 2,6-diethylnaphthalene from the reaction product produced in the reaction step. A separation step including adsorption separation and crystallization separation, wherein at least a part of the remaining naphthalene and ethylnaphthalene obtained by separating the 2,6-diethylnaphthalene obtained in the separation step is circulated to the reaction step. , 6-Diethylnaphthalene is produced. [Effect] According to the method of the present invention, 2,6-naphthalenedicarboxylic acid can be obtained more efficiently and cheaply than the conventional method, and the industrial significance is extremely high. In addition, if polyethylbenzene, which is a by-product of the ethylbenzene production process, is used as a raw material for the ethylating agent, not only can the treatment be omitted,
Since ethylbenzene is by-produced in the production method of the present invention,
Industrial significance is further enhanced in that it can be recovered as a useful product.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing 2,6-diethylnaphthalene, which is useful as a raw material for 2,6-naphthalenedicarboxylic acid.

[0002]

2. Description of the Related Art 2,6-Naphthalenedicarboxylic acid is a substance useful as a polymer material, a dye intermediate or the like. In particular, polyester containing 2,6-naphthalenedicarboxylic acid as a constituent component is superior to polyethylene terephthalate in heat resistance, breaking strength, gas barrier property, and the like, and is attracting attention as a material for films, food packaging materials, and the like. ing.

As a conventionally known method for producing 2,6-naphthalenedicarboxylic acid, naphthalene is methylated, and 2,6-dimethylnaphthalene is separated from the reaction product to obtain 2,6-naphthalenedicarboxylic acid. Liquid-phase oxidation of dimethylnaphthalene using cobalt, manganese, bromine, etc. as catalyst, naphthylation of naphthalenes, and separation of 2,6-diisopropylnaphthalene from the reaction product to obtain 2,6-diisopropylnaphthalene Liquid phase oxidation using cobalt, manganese, bromine or the like as a catalyst.

However, in the above method, although the liquid phase oxidation of 2,6-dimethylnaphthalene proceeds relatively easily, it is difficult to separate 2,6-dimethylnaphthalene from the methylation reaction product, and conversely. , Method 2,
Although the production of 6-diisopropylnaphthalene is relatively easy, there are problems that a large amount of catalyst is required in this liquid phase oxidation step, the weight yield is poor, and the like.

On the other hand, the method of ethylating naphthalene, separating 2,6-diethylnaphthalene from the reaction product, and subjecting this to liquid-phase oxidation using cobalt, manganese, bromine or the like as a catalyst has the method. It is possible to overcome the drawbacks, which is an advantageous method. In the method for producing 2,6-naphthalenedicarboxylic acid via 2,6-diethylnaphthalene, the liquid-phase oxidation reaction of 2,6-diethylnaphthalene proceeds easily in a high yield, and thus the key technology is efficient and inexpensive. This is a technique for producing 2,6-diethylnaphthalene. However, the conventional techniques have not been sufficient to efficiently and inexpensively produce 2,6-diethylnaphthalene. For example, JP-A-51-6953
Japanese Unexamined Patent Publication (KOKAI) No. 2003-242242 discloses a method of ethylating naphthalene and separating 2,6-diethylnaphthalene from the reaction product by cooling crystallization to obtain 2,6-diethylnaphthalene. In the method for separating 2,6-diethylnaphthalene from a naphthalene isomer mixture, 2,6
-It can be said that this is an inefficient production method because the temperature range in which only diethylnaphthalene is selectively precipitated is narrow. JP-A-3-258
746 describes a method for producing 2,6-diethylnaphthalene using an adsorption separation method. However, since ethylene is used as an ethylating agent, pitch is not produced when a homogeneous catalyst such as AlCl ₃ is used. There is a problem in that the catalyst is severely deactivated when a heterogeneous catalyst such as zeolite is used.

[0006]

SUMMARY OF THE INVENTION In view of such circumstances, an object of the present invention is to provide an industrially efficient and inexpensive method for producing 2,6-diethylnaphthalene.

[0007]

[Means for Solving the Problems] The present inventors have conducted research to establish the above-mentioned method, using polyethylbenzene as an ethylating agent in the ethylation reaction of naphthalene, and using 2,6-diethyl from the product. The present invention has been completed by finding that a more efficient and inexpensive method for producing 2,6-diethylnaphthalene can be obtained by separating the naphthalene by a separation method including adsorption separation.

That is, according to the present invention, a reaction step of reacting naphthalene and / or monoethylnaphthalene with polyethylbenzene in the presence of an acid catalyst, and separating 2,6-diethylnaphthalene from the product produced in the reaction step. A separation step including distillation separation, adsorption separation and crystallization separation for the purpose of separating the 2,6-diethylnaphthalene obtained in the separation step from the remaining naphthalene, ethylnaphthalene,
Including at least part of diethylnaphthalene, triethylnaphthalene, tetraethylnaphthalene, pentaethylnaphthalene in the reaction step 2,
It is a method for producing 6-diethylnaphthalene.

The present invention will be described below in detail for each step. "Reaction Step" The reaction raw materials in this step are naphthalene and polyethylbenzene, and the reaction product in this step
It consists of at least a part of a by-product excluding 6-diethylnaphthalene.

The naphthalene includes naphthalene and / or monoethylnaphthalene, and is normally selected from diethylnaphthalene, triethylnaphthalene, tetraethylnaphthalene, pentaethylnaphthalene, etc. which are recovered and circulated in a separation step described later. 1 or 2
Includes one or more polyethylnaphthalene. It is advantageous that naphthalene is the only naphthalene newly added to this reaction step. Ethylnaphthalenes are added in the form of circulating by-products. The newly added naphthalene is preferably in an amount commensurate with the taken out 2,6-diethylnaphthalene and a small amount of the reaction by-products discharged from this process and the naphthalene ring contained in the heavy product.

Polyethylbenzene used as an ethylating agent is ethylbenzene, 1,2-diethylbenzene,
1,3-diethylbenzene, 1,4-diethylbenzene, 1,2,3-triethylbenzene, 1,2,4-triethylbenzene, 1,3,5-triethylbenzene,
1,2,3,4-tetraethylbenzene, 1,2,3
One or a mixture of two or more selected from 5-tetraethylbenzene, 1,2,4,5-tetraethylbenzene, pentaethylbenzene and hexaethylbenzene, preferably ethyl group / benzene ring = 1.5 (mol / mol /
Mol) or more, more preferably ethyl group / benzene ring = 2
(Mole / mole) or more of the compound or mixture. If this ratio is small, the reaction proceeds slowly. Preferable examples include polyethylbenzene mainly containing diethylbenzene or triethylbenzene obtained as a by-product during the production of ethylbenzene. When the ethyl group / benzene ring (molar ratio) of polyethylbenzene is low and the ability as an ethylating agent is not sufficient, a small amount of ethylene, ethanol
, Ethyl halide can be used supplementarily as the ethylating agent.

The amount of polyethylbenzene added to this step is such that the molar ratio of the ethyl groups present in this reaction system to the naphthalene ring and the benzene ring {ethyl group / (naphthalene ring + benzene ring)} is 1.0 to 3.5, preferably 1.5
To 3.0, more preferably 1.5 to 2.8.

The remaining naphthalene, ethylnaphthalene, diethylnaphthalene, triethylnaphthalene obtained by separating 2,6-diethylnaphthalene obtained in the separation step,
Of tetraethylnaphthalene and pentaethylnaphthalene, diethylnaphthalene can be transethylated in another reactor (hereinafter referred to as reaction step II). In such a case, a reactor using polyethylbenzene, naphthalene, ethylnaphthalene, triethylnaphthalene, tetraethylnaphthalene, and pentaethylnaphthalene as main reaction raw materials (hereinafter, this reactor when reaction step II is provided is referred to as reaction step I If reaction step II is not provided, it is simply referred to as the reaction step.) Diethylnaphthalene is formed by transethylation reaction between molecules, so it is reacted to a thermodynamically equilibrium state. By selecting milder conditions than the reaction conditions, the yield of diethylnaphthalene is sufficiently high and 2,6-
The selectivity of diethylnaphthalene can be higher than the thermodynamic equilibrium value. In the reaction step II, isomerization, disproportionation, and disproportionation of diethylnaphthalene compounds, followed by transethylation reaction between the products, and a thermodynamically equilibrium composition is approached.

The acid catalyst used in this step may be any acid catalyst such as aluminum chloride, silica-alumina, zeolite, solid phosphoric acid, heteropolyacid, ion exchange resin, etc. in both reaction step I and reaction step II. Silica-alumina or zeolite is preferable in that a flow-through reaction format with a bed is possible and there are no by-products coming from the catalyst. The reaction step I and the reaction step II may use different catalysts.

The reaction temperature when the solid acid catalyst is used in this reaction step is 100 to 450 ° C. Reaction temperature is 100 ℃
If the reaction temperature is lower than 450 ° C., the reaction rate will be slow and not industrial, and if the reaction temperature is higher than 450 ° C., deethylation, decomposition of ethyl groups, polymerization of ethyl groups, coloration of products, etc. will occur. Reaction steps are Reaction Step I and Reaction Step II
In the case of performing the reaction with the same catalyst and the same SV in the case of dividing into 2,
Low reaction temperature. This is because the reaction step II is in a thermodynamically equilibrium state, and the reaction step I is in a state closer to the initial stage of the reaction than the thermodynamic equilibrium state.

The reaction pressure is normal pressure to 100 kg / cm ² ·
G, preferably 3 to 50 kg / cm ² · G. Considering the catalyst life, it is appropriate to select the reaction pressure so that naphthalene becomes liquid during the reaction.

The initial stage of the transethylation reaction is 2,6-
Both diethylnaphthalene / diethylnaphthalene and 2,6-diethylnaphthalene / 2,7-diethylnaphthalene are higher than the thermodynamic equilibrium value. In this reaction step, 2,6-diethylnaphthalene is produced by transethylation, but the selectivity of 2,6-diethylnaphthalene is increased by utilizing the property of transethylation at the initial stage of the reaction.

"Separation step" This step is a step of separating 2,6-diethylnaphthalene from the product of the previous reaction step mainly by distillation, adsorption separation and crystallization separation.

The purpose of distillation is to separate the diethylnaphthalene fraction containing 2,6-diethylnaphthalene from the fractions such as ethylnaphthalene fraction and triethylnaphthalene fraction. By this distillation, among the diethylnaphthalene isomers,
Although some of the diethylnaphthalene isomers having a boiling point relatively different from that of 2,6-diethylnaphthalene may be separated,
For this purpose, precision distillation is required, so it is advantageous to separate it as a diethylnaphthalene fraction containing an isomer of diethylnaphthalene. That is, it is advantageous to separate 1,3-diethylnaphthalene and 2,6-diethylnaphthalene as a diethylnaphthalene fraction containing other isomers. Note that 2,6-diethylnaphthalene and 1,3-diethylnaphthalene, which are difficult to be adsorbed and separated, may be separated by distillation, and in this case, the load of the crystallization separation step is reduced. Distillation also has the purpose of reducing the concentration of components that increase the adsorption load during adsorption separation and reducing the trace impurities that deactivate the adsorbent.

The purpose of adsorption separation is to separate an isomer mixture containing 2,6-diethylnaphthalene and 1,3-diethylnaphthalene from other isomers, or to isolate 2,6-diethylnaphthalene. ..

Therefore, in the separation step, 1,3-diethylnaphthalene and a diethylnaphthalene isomer mixture containing 2,6-diethylnaphthalene are separated by distillation, and then 2,6-diethylnaphthalene in the diethylnaphthalene isomer mixture is separated. A method of isolating naphthalene by an adsorption separation method and further purifying it by crystallization separation and a diethylnaphthalene fraction containing 1,3-diethylnaphthalene, 2,6-diethylnaphthalene and other isomers are separated by distillation, A method of separating a mixture of 2,6-diethylnaphthalene and 1,3-diethylnaphthalene in a diethylnaphthalene fraction by an adsorption separation method, and then separating this mixture by crystallization to isolate 2,6-diethylnaphthalene. There is. In either method, first, the reaction product is schematically separated by ordinary distillation to separate benzene fraction, ethylbenzene fraction, diethylbenzene fraction, naphthalene fraction, ethylnaphthalene fraction, diethylnaphthalene fraction, triethylnaphthalene fraction, etc. To separate. In this case, it is not necessary to use precision distillation to separate the isomers in each fraction. In the above method, only this ordinary distillation is necessary, and the distillation can be simplified. The above method requires precision distillation under the condition that at least 2,6-diethylnaphthalene and 1,3-diethylnaphthalene are separated from the diethylnaphthalene fraction. The ordinary distillation refers to distillation with a reflux ratio of about 10 in a distillation column having about 20 theoretical plates.

Precision distillation for separating 1,3-diethylnaphthalene and 2,6-diethylnaphthalene yields a recovery of 2,6-diethylnaphthalene of 90%,
When 3-diethylnaphthalene / 2,6-diethylnaphthalene = 0.005 (weight / weight), the distillation conditions are such that the theoretical number of distillation columns is about 70 and the reflux ratio is about 30.

The diethylnaphthalene fraction separated in the distillation step or the diethylnaphthalene fraction obtained by separating 1,3-diethylnaphthalene from this by precision distillation is separated in the adsorption separation step. The adsorbent used in the adsorption separation is zeolite showing the same powder X-ray diffraction image as faujasite, that is, H-type faujasite-type zeolite or metal-modified faujasite-type zeolite.
Such zeolites are, for example, X-type zeolite, Y
Commercially available as type zeolite.

Examples of the modifying metal include alkali metals such as lithium, sodium, potassium and rubidium, alkaline earth metals such as magnesium, calcium, strontium and barium, Group VIII transition metals such as iron, cobalt and nickel, and copper. Group Ib transition metals such as silver, Group IIb such as zinc
Group b transition metals are preferable, and two or more kinds may be modified.
Further, among the above metals, lithium, sodium, potassium, calcium, magnesium, barium, silver, nickel, copper and zinc are preferable, and sodium, potassium, barium, silver and copper are most preferable.

The method for modifying the metal of the faujasite-type zeolite includes a method of adding a metal component during hydrothermal synthesis of zeolite, a supporting method of impregnating zeolite with an aqueous solution of a metal salt to remove the solvent, and a method of adding zeolite to a solution of the metal salt. Although an ion exchange method or the like in which heat treatment is performed is possible, the ion exchange method is preferable because it is less likely to block the pore inlet as compared with the supporting method and does not affect the structure of the zeolite itself. The amount of modification of the metal with respect to the H-type faujasite-type zeolite is preferably 10 to 200%, more preferably the number of modifying metal x valence with respect to the number of Al atoms in the faujasite-type zeolite. Is 50 ~
It is 150%. When the metal is modified by the ion exchange method and the modification amount exceeds 100%, the metal exists as an ion and also exists as a zero-valent metal or a metal oxide, but a part of the modified metal is present. Such a form does not matter.

The silica-alumina ratio (molar ratio) of the faujasite type zeolite used for adsorption separation is 2 or more.
Usually, it is industrially easily available in the range of about 2 to 10, but it is possible to further increase the silica-alumina ratio by dealumination treatment or the like.

As the adsorbent used in the adsorption separation, a sufficiently dried one may be used, or one that has absorbed moisture to some extent may be used. An adsorbent that has absorbed moisture to some extent may have a higher adsorption capacity than a sufficiently dry adsorbent. To control the water content, use a sufficiently dry adsorbent, while
It is convenient to use a method in which a predetermined amount of water is mixed in the adsorbing liquid, and as a result, the adsorbent is absorbed. The amount of moisture to be absorbed is preferably 0.5 to 10% by weight with respect to the adsorbent.

In the adsorption separation, a diluent that does not interfere with the adsorption of the adsorbed substance is used in the adsorption operation, and thereafter, in the desorption operation, a desorption agent different from the diluent that rapidly desorbs the adsorbed substance is used. be able to. As the diluent used for such adsorption operation, paraffins having 5 to 12 carbon atoms such as n-heptane and isooctane, which can be easily separated from diethylnaphthalene and do not hinder the adsorption of diethylnaphthalene on zeolite, are preferable. .. Further, as the desorbing agent used in the desorption operation, toluene, o-xylene, m-xylene, p-xylene, which can be easily separated from diethylnaphthalene and have excellent desorption ability,
1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, ethylbenzene, p-ethylmethylbenzene, o-diethylbenzene, m-diethylbenzene,
7 to 1 carbon atoms such as p-diethylbenzene and cumene
One or a mixture of two or more selected from about 0 alkylbenzenes is preferable.

Further, in the adsorption separation, in the adsorption operation, a mixture containing the diethylnaphthalene isomer as a main component is brought into contact with the adsorbent while already containing the desorption agent, and thereafter, the same desorption as used in the adsorption operation is carried out. The agent can be used in the desorption operation. As the desorbing agent used for such desorption operation, toluene, o-xylene, m-xylene, p-xylene, 1,2,4, which can be easily separated from diethylnaphthalene and have excellent desorption ability, is used. 1 selected from alkylbenzenes having about 7 to 10 carbon atoms such as trimethylbenzene, 1,3,5-trimethylbenzene, ethylbenzene, p-ethylmethylbenzene, o-diethylbenzene, m-diethylbenzene, p-diethylbenzene and cumene. One kind or a mixture of two or more kinds is preferable.
In addition, in addition to such a releasing agent, n-
It is also possible to mix an appropriate amount of paraffins having 5 to 12 carbon atoms such as heptane and isooctane to adjust the desorption ability as a desorption agent.

The adsorption / separation operation may be a batch type so-called chromatographic type separation or a continuous type known as a simulated moving bed reverse flow type.

The adsorption temperature is preferably from room temperature to 350 ° C. If the adsorption temperature exceeds 350 ° C., the reaction such as isomerization cannot be ignored even with the metal-modified zeolite, which is not preferable. Adsorption pressure is from atmospheric pressure to 100 kg / cm ² ·
G, preferably from atmospheric pressure to 50 kg / cm ² · G.

In this adsorption separation step, 2,6-diethylnaphthalene and 1,3-diethylnaphthalene cannot be separated but other diethylnaphthalene isomers are separated. Therefore, 2,6-diethylnaphthalene is isolated by using the diethylnaphthalene fraction from which 1,3-diethylnaphthalene is removed in advance, and 2,6-diethylnaphthalene is isolated by removing the fraction which is not removed.
A mixture of diethylnaphthalene and 1,3-diethylnaphthalene is separated. However, even with the former method,
Since it is difficult to sufficiently raise the purity of 2,6-diethylnaphthalene, crystallization separation is performed.

The crystallization separation can be carried out by a method such as adding a solvent such as methanol, ethanol, propanol and the like, heating and dissolving, and then performing cooling crystallization. The solvent used in this case is preferably an alcohol having 1 to 4 carbon atoms and / or a paraffin having 6 to 8 carbon atoms,
More preferred are ethanol and isopropanol. When the purity of 2,6-diethylnaphthalene is insufficient, crystallization separation can be repeated.

Of the remaining naphthalene, ethylnaphthalene, diethylnaphthalene, triethylnaphthalene, tetraethylnaphthalene, and pentaethylnaphthalene obtained by separating 2,6-diethylnaphthalene from the reaction product obtained in the separation step of the present invention. At least a part of it can be circulated to the reaction step and used again as a raw material for 2,6-diethylnaphthalene. Further, at least a part of the remaining diethylnaphthalene obtained by separating 2,6-diethylnaphthalene from the reaction step product obtained in the separation step is subjected to the reaction step II in naphthalene, ethylnaphthalene, triethylnaphthalene, tetraethylnaphthalene. At least a part of the pentaethylnaphthalene can be circulated to the reaction step I to be used again as a raw material of 2,6-diethylnaphthalene. Regarding the amount to be circulated, it is preferable to circulate the whole amount except for a small amount of reaction by-products other than ethylation and a small amount of heavy substances that cannot be driven off by distillation.

Further, in this separation step, benzene, ethylbenzene, and polyethylbenzene higher than diethylbenzene which are by-produced from the polyethylbenzene used as the ethylating agent are also separated. Preferably, at least a part of polyethylbenzene, which is equal to or more than diethylbenzene, and more preferably all are recycled to the reaction step, and ethylbenzene is recovered as a product such as a styrene raw material. When the amount of polyethylbenzene added to the reaction step is within the preferred range, 50% by weight or more of the used polyethylbenzene is recovered as ethylbenzene. Therefore, the method of the present invention can be a method for producing ethylbenzene. (Margins below this page)

[0036]

EXAMPLES The present invention will be specifically described below based on examples. In addition, unless otherwise indicated, the part and% in an Example show a weight part and weight%, respectively. Each product,
Table 1 shows the composition of the compound having a naphthalene ring excluding the compound of the benzene ring from the analysis values of the fraction by gas chromatography, and Table 2 shows the composition of each isomer of the diethylnaphthalene mixture.

Example 1 "Reaction Step I" In an autoclave equipped with a stirrer, 51 parts of naphthalene, 100 parts of ethylnaphthalene, 140 parts of triethylnaphthalene, 10 parts of tetraethylnaphthalene containing a small amount of pentaethylnaphthalene, transethylation. 101 parts of polyethylbenzene as an agent and 80 parts of Y-type zeolite as a catalyst were charged, and an ethylation reaction was carried out at a reaction temperature of 230 ° C. After the reaction was completed, the catalyst was separated into solid and liquid. The catalyst after solid-liquid separation was thoroughly washed with isopropanol to remove the reaction product attached to the catalyst. Isopropanol was removed from the washing liquid, and the obtained reaction product was mixed with the reaction product previously solid-liquid separated to obtain a reaction product (A). The analytical values of the reaction product (A) are shown in the table. The polyethylbenzene used in the reaction contains diethylbenzene as a main component, and ethyl group / benzene ring = 2.2 (mol / mol).

"Reaction Step II" An autoclave equipped with a stirrer was charged with diethylnaphthalene 182 and 36 parts of Y-type zeolite as a catalyst, and an ethylation reaction was carried out at a reaction temperature of 250 ° C. After completion of the reaction, the catalyst was separated into solid and liquid. The catalyst after solid-liquid separation was thoroughly washed with isopropanol to remove the reaction product attached to the catalyst. Isopropanol was removed from the washing liquid, and the obtained reaction product and the reaction product previously solid-liquid separated were mixed to obtain a reaction product (B). The analytical values of the reaction product (B) are shown in Tables 1 and 2.

"Separation Step" 401 parts of the reaction product (A) in the reaction step I and 18 parts of the reaction product (B) in the reaction step II
1 part was mixed to give 582 parts of the reaction mixture (C). The whole amount of the reaction mixture (C) was distilled with a distillation apparatus having 20 theoretical plates, and 83 parts of an ethylbenzene fraction containing ethylbenzene and diethylbenzene, 110 parts of a low boiling fraction (D) containing monoethylnaphthalene as a main component, and diethyl It was separated into 238 parts of a naphthalene fraction (E), 146 parts of a high-boiling fraction (H) containing tri and tetraethylnaphthalene as a main component, and 5 parts of a residual oil. 238 parts of diethylnaphthalene fraction (E) was distilled with a distillation device having a theoretical plate number of 70 to obtain 74 parts of diethylnaphthalene fraction (F) containing 1,7-diethylnaphthalene and 1,3-diethylnaphthalene as main components. , 2,
It was separated into 164 parts of a diethylnaphthalene fraction (G) containing 6-diethylnaphthalene. The composition of each is shown in the table. 5 parts of the residual oil was further distilled by a small-sized distillation apparatus, and was divided into 3 parts of a fraction containing tetraethylnaphthalene as a main component and 2 parts of the residue.

K-modified Y-type zeolite 4 on a stainless steel cylinder
000 parts were filled and moistened with isooctane. After 164 parts of a diethylnaphthalene fraction (G) containing 2,6-diethylnaphthalene obtained by distillation was added in a pulse,
18,000 parts of isooctane were fed in 720 minutes. Then, isooctane was changed to p-xylene, and 18000 parts of p-xylene was supplied in 720 minutes. All operations were performed at room temperature. The fraction from the outlet of the cylinder was cut into 360 fractions and collected. The 100th fraction to the 180th fraction were mixed to obtain isooctane and p-xylene by evaporation.
The solid (I) was obtained in 50 parts. The analysis results are shown in the table. Ethanol was added to the solid (I) to once completely dissolve it. After cooling to 0 ° C., the precipitated solid was subjected to solid-liquid separation to obtain 45 parts of solid (J). This solid (J) was 2,6-diethylnaphthalene having a purity of 99.8% and had a melting point of 52.0 ° C to 52.5 ° C. The analysis results are shown in the table.

110 parts of a low-boiling fraction (D) containing monoethylnaphthalene as a main component obtained by the distillation operation in the separation step, 145 parts of a high-boiling fraction (H) containing tri- and tetraethylnaphthalene as a main component, and About 40 parts of naphthalene and about 100 parts of polyethylbenzene were added to a mixture of 3 parts of a fraction containing tetraethylnaphthalene as a main component, which was recovered from the distillation residual oil.
When parts are added, the composition and amount are almost the same as those of the reaction raw material in the reaction step I. Further, 74 parts of a diethylnaphthalene fraction (F) mainly composed of 1,7-diethylnaphthalene and 1,3-diethylnaphthalene separated by distillation and all the diethylnaphthalene fractions other than the solid (J) by adsorption. Together correspond to the reaction raw material of reaction step II. Therefore, it can be seen that the remaining substance obtained by separating 2,6-diethylnaphthalene from the reaction products of the reaction step I and the reaction step II by distillation and adsorption can be used as the reaction raw material of the reaction step I and the reaction step II again. In the separation step, benzene, ethylbenzene, and polyethylbenzene above diethylbenzene were recovered, polyethylbenzene was circulated to the reaction step I, and ethylbenzene was recovered as a product. (Margins below this page)

[0042]

[Table 1] (Margins below this page)

[0043]

[Table 2]

Example 2 The same procedure as in Example 1 was repeated until 238 parts of the diethylnaphthalene fraction (E) in the separation step was separated. A stainless steel cylinder was filled with 4000 parts of K-modified Y-type zeolite and moistened with isooctane. After 238 parts of a diethylnaphthalene fraction (E) containing 2,6-diethylnaphthalene obtained by distillation was pulsed, 26000 parts of isooctane was supplied in 720 minutes. After that, isooctane was changed to p-xylene, and p-xylene 26000 was used.
Parts were fed in 720 minutes. All operations were performed at room temperature. The fraction from the outlet of the cylinder was cut into 360 fractions and collected. Mix the 100th fraction to the 180th fraction,
Isooctane and p-xylene were removed by evaporation to obtain 107 parts of liquid (M). This liquid (M) 1
After adding 160 parts of ethanol to 07 parts and stirring,
It cooled to -10 degreeC and separated the depositing solid by filtration. The solid separated by filtration was washed with 30 parts of ethanol at −10 ° C., filtered, and dried to obtain a solid (N). This solid (N)
Was 2,6-diethylnaphthalene having a purity of 99.2% and a melting point of 51.0 to 52.0 ° C. The analysis results are shown in Tables 1 and 2.

110 parts of a low boiling fraction (D) containing monoethylnaphthalene as a main component and obtained by the distillation operation in the separation step, 145 parts of a high boiling fraction (H) containing tri and tetraethylnaphthalene as a main component, and About 40 parts of naphthalene and about 100 parts of polyethylbenzene were added to a mixture of 3 parts of a fraction containing tetraethylnaphthalene as a main component, which was recovered from the distillation residual oil.
When parts are added, the composition and amount are almost the same as those of the reaction raw material in the reaction step I. Further, if all the diethylnaphthalene components other than the obtained solid (N) are combined, they correspond to the reaction raw material of the reaction step II. Therefore, reaction step I and reaction step
It can be seen that the remaining substance obtained by separating 2,6-diethylnaphthalene from the reaction product of II by distillation and adsorption can be used again as the reaction raw material in reaction step I and reaction step II. In the separation step, benzene, ethylbenzene, and polyethylbenzene above diethylbenzene were recovered, polyethylbenzene was circulated to the reaction step I, and ethylbenzene was recovered as a product.

[0046]

Industrial Applicability According to the method of the present invention, 2,6-naphthalenedicarboxylic acid can be obtained more efficiently and cheaper than the conventional method, and its industrial significance is extremely high. Further, when polyethylbenzene by-produced in the ethylbenzene production process is used as a raw material for the ethylating agent, not only the treatment can be omitted but also ethylbenzene is by-produced in the production method of the present invention, so that it can be recovered as a useful product. Industrial significance is even higher in that it can be done.

Claims (5)

[Claims] 1. A reaction step of reacting naphthalene and / or monoethylnaphthalene with polyethylbenzene in the presence of an acid catalyst, and 2,6 from the product produced in the reaction step.
-Distillation separation for separating diethylnaphthalene, a separation step including adsorption separation and crystallization separation, and the remaining naphthalene, ethylnaphthalene, diethylnaphthalene obtained by separating 2,6-diethylnaphthalene obtained in the separation step A method for producing 2,6-diethylnaphthalene, characterized in that at least a part of the compounds, triethylnaphthalene, tetraethylnaphthalene, and pentaethylnaphthalene is circulated in the reaction step. 2. Reaction step I in which naphthalene and / or monoethylnaphthalene is reacted with polyethylbenzene in the presence of an acid catalyst, and 2,6 from the products produced in the reaction step.
-A separation step including distillation separation, adsorption separation and crystallization separation for separating diethylnaphthalene, and at least a part of the diethylnaphthalene remaining after separating 2,6-diethylnaphthalene obtained in the separation step is present in the presence of an acid catalyst. under,
A reaction step II in which a transethylation or an isomerization reaction is carried out, and the reaction step products of the reaction step I and the reaction step II are mixed as a raw material for the separation step, and 2,6-diethyl obtained in the separation step A method for producing 2,6-diethylnaphthalene, characterized in that at least a part of the remaining naphthalene after separation of naphthalene, ethylnaphthalene, triethylnaphthalene, tetraethylnaphthalene, pentaethylnaphthalene is circulated to the reaction step I. .. 3. Distillation separation into a diethylphthalene fraction containing 2,6-diethylnaphthalene, 1,3-diethylnaphthalene and other diethylnaphthalene isomers, an ethylnaphthalene fraction, a triethylnaphthalene fraction and the like. The method for producing 2,6-diethylnaphthalene according to claim 1 or 2, which is separated. 4. A separation step for obtaining a diethylphthalene fraction containing 1,3-diethylnaphthalene, 2,6-diethylnaphthalene and other diethylnaphthalene isomers, and adsorption of this diethylnaphthalene fraction. A step of separating a mixture of 1,3-diethylnaphthalene and 2,6-diethylnaphthalene by separation, and a crystallization separation of this mixture of 1,3-diethylnaphthalene and 2,6-diethylnaphthalene to give 2,6-diethylnaphthalene. The method for producing 2,6-diethylnaphthalene according to claim 1, 2 or 3, further comprising the step of isolating. 5. Among the ethylbenzene, polyethylbenzene and benzene above the diethylbenzene obtained in the separation step, at least a part of the polyethylbenzene is circulated in the reaction step, and ethylbenzene is recovered to produce ethylbenzene together with 2,6-diethylnaphthalene. The method for producing 2,6-diethylnaphthalene according to claim 1, 2, 3 or 4.