JPH06271486A - Isomerization of dialkylnaphthalene - Google Patents

Abstract

PURPOSE:To selectively isomerize the subject compound in an intra-group on an industrial scale at a low cost while minimizing the side reactions by heating a dialkylnaphthalene isomer in the presence of a zeolite catalyst exhibiting a specific X-ray diffraction peak. CONSTITUTION:Hexamethonium bromide is mixed into an aqueous solution containing sodium aluminate and sodium hydroxide, fine silica powder is added to the solution, the mixture is homogenized with a homogenizer and the product is crystallized by heating in an autoclave at 196 deg.C for 43hr to obtain a zeolite catalyst exhibiting an X-ray diffraction peak corresponding to the spacing (d) of 3.2-11.0Angstrom . At least one kind of dialkylnaphthalene isomer such as 1,5- dialkylnaphthalene, 1,6-dialkylnaphthalene and 2,6-dialkylnaphthalene is heated at 250 deg.C in the presence of the zeolite catalyst obtained by the above process to effect the selective and efficient intra-group isomerization of dialkylnaphthalene while minimizing the side reactions such as disproportionation and inter-group isomerization.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for isomerizing dialkylnaphthalene. For details, 2,6-
The present invention relates to a method for isomerizing dialkylnaphthalene, which is suitable for industrially producing dialkylnaphthalene, particularly 2,6-dimethylnaphthalene.

[0002]

BACKGROUND OF THE INVENTION There are many isomers of dialkylnaphthalene. For example, dimethylnaphthalene has 10 kinds of isomers, and these isomers can be classified into the following four groups (1), (2), (3) and (4), It is known that the intra-group isomerization reaction generally carried out in each group is relatively easy, while the inter-group isomerization reaction to other groups is difficult to occur. (For example, catalyst Vol.33 No.8 1991 559-565.
(Page) (1) 1,5-, 1,6- and 2,6-dimethylnaphthalene groups (hereinafter abbreviated as 2,6 groups) (2) 1,7-, 1,8- and 2,7-dimethyl Naphthalene group (hereinafter abbreviated as 2,7 group) (3) 1,3-, 1,4- and 2,3-dimethyl Naphthalene group (hereinafter abbreviated as 2,3 group) (4) 1,2-Dimethyl Naphthalene group (abbreviated as 1st and 2nd groups below)

By the way, one of the main uses of dimethylnaphthalene is the production of naphthalenedicarboxylic acid, and 2,6-dimethylnaphthalene is particularly preferably used as a raw material. In the case of obtaining 2,6-dimethylnaphthalene, generally, 2,6-dimethylnaphthalene is separated from a feed oil containing a mixture of dimethylnaphthalene isomers as a main component, but in order to utilize the raffinate after the separation of 2,6-dimethylnaphthalene. Required isomerization from other groups to groups 2,6.

For such an isomerization reaction, a method using various zeolite-based catalysts has been proposed (Japanese Patent Laid-Open No. Sho 5).
9-88433, etc.). However, in these methods, the thermodynamic equilibrium concentration in all isomers of the 2,6-isomer is only about 14%, and thus it is not always efficient as a method for obtaining the 2,6-isomer. . On the other hand, in recent years,
A method for producing dialkylnaphthalene, especially dimethylnaphthalene, from alkylbenzene has been proposed (Japanese Patent Publication No. 3-500052, etc.). That is, it is a method in which an alkylbenzene is reacted with butenes, butadiene, propylene, ethylene, etc. to form an alkyl chain having a straight chain portion with about 2 to 6 carbon atoms, and cyclization and dehydrogenation are performed to form a naphthalene ring. Depending on the method, a method of isomerizing only within the same group is used together. If this intra-group isomerization can be carried out, for example, the 2,6-dimethylnaphthalene concentration can be increased to the thermodynamic concentration within the 2,6-group.
Therefore, if this isomer mixture is used as a raw material and isomerization is carried out only within the 2,6 group, the thermodynamic concentration of 2,6-dimethylnaphthalene within the 2,6 group will be as high as about 50%. Therefore, it is extremely advantageous in industrial practice.

In an attempt to control isomerization only within the groups 2 and 6, a method of using a mixture of hydrogen type mordenite and acid clay as a catalyst (Japanese Patent Publication No. 55-47020).
Or using aluminoborosilicate (Table 1-
No. 503389 gazette), etc., and the intra-group isomerization reaction generally takes precedence, but it is very difficult to control side reactions such as inter-group isomerization, other disproportionation, and transalkylation. Met.

[0006]

DISCLOSURE OF THE INVENTION According to the present invention, isomerization of dialkylnaphthalene can be carried out by an easy operation, and
It is an object of the present invention to provide an isomerization reaction in which the isomerization reaction within the same group preferentially proceeds and the side reactions such as isomerization between groups and other disproportionation and transalkylation can be suppressed as much as possible. .

[0007]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies on the above problems, and have found that zeolite giving a specific X-ray diffraction peak is particularly excellent as a group isomerization catalyst. The present invention has been reached. That is,
The gist of the present invention is to treat at least one of dialkylnaphthalene isomers by heat treatment in the presence of a zeolite-based catalyst that gives an X-ray diffraction peak at an interplanar spacing d in Table 1 below. It exists in the isomerization method.

[0008]

[Table 2]

The present invention will be described in detail below. Dialkylnaphthalene as the isomerization raw material of the present invention is 1,5-
A group consisting of dialkylnaphthalene, 1,6-dialkylnaphthalene and 2,6-dialkylnaphthalene (2,6
One or more dialkylnaphthalenes selected from the group) or 1,8-dialkylnaphthalenes,
One or more dialkylnaphthalene selected from the group consisting of 1,7-dialkylnaphthalene and 2,7-dialkylnaphthalene (group 2,7), or 1,
Usually, 50% or more, preferably 80% or more, of one or more dialkylnaphthalene selected from the group consisting of 4-dialkylnaphthalene, 1,3-dialkylnaphthalene and 2,3-dialkylnaphthalene (Groups 2 and 3). %
It includes the above. The ratio of isomers within the family is 3
It is not particularly limited except that it is close to the ratio corresponding to the thermodynamic equilibrium value between the two isomers, but for example, in the groups 2 and 6, the demand for the 2,6-isomer is industrially large,
When it is desired to obtain the 2,6-isomer, it is preferable to use a raw material having a high concentration of the 1,5-isomer or the 1,6-isomer.

The inventors of the present invention have found that the temperature dependence of the distributions of 2,6-, 1,6- and 1,5-isomers in the 2,6-groups is minimum based on the measured values. It is found that it is expressed by the following estimation formulas (1), (2) and (3) obtained by the square method. In addition, 2,7 groups other than 2,6 groups, 2,3
We have also found that similar estimation formulas can be obtained for tribes.

[0011]

TABLE 3 2,6 _{isomer: C 2.6 = 56.9775-0.02835T ... (1} ) 1,6- _{isomer: C 1.6 = 39.1240 + 0.01781T ...} (2) 1,5- isomers : C _1.5 = 3.8085 + 0.01076T (3) (in the formulas (1), (2) and (3), C _2.6 , C
_1.6 and C _1.5 represent mol% in the group of each isomer, and T represents temperature (° C.). ) Examples of the alkyl group of dialkylnaphthalene include a methyl group, an ethyl group, an isopropyl group and the like, but a methyl group is preferable. Further, the origin of the raw material of the dialkylnaphthalene is not particularly limited, and it may be separated from an aromatic hydrocarbon feedstock or may be obtained by synthesis from naphthalene or the like.

Next, the present invention is characterized in that the solid acid catalyst used for isomerizing the above-mentioned dialkylnaphthalene raw material is zeolite having the powder X-ray diffraction peak shown in Table 1 above. This X-ray diffraction uses Cu-Kα rays as the X-ray source. Further, in Table-1, the relative strength means the surface spacing d = 4.3 ± 0.1.
60 to 10 when the intensity of the strongest peak is 100.
0 is "very strong", 40-60 is "strong", 20-4
0 is shown as "medium", and 2 to 20 is shown as "weak". Some peaks are usually recognized in addition to the peaks shown in Table-1, but as long as it has the peak pattern of Table-1, it can be used as the zeolite catalyst of the present invention.

Specific examples of the zeolite giving the X-ray diffraction peak are EU-1 type zeolite and NU-8.
Type 5 zeolite and the like are known (EP42226, E
P462745). An example of applying this type of zeolite as a catalyst is a method of obtaining an alkylated derivative of a polycyclic aromatic hydrocarbon such as naphthalene or biphenyl with an alkylating agent such as an olefin, an alkyl halide, or an alkyl aromatic hydrocarbon such as xylene. (JP-A-61-2675
30, GB8510196), SI (Spacialness Inde) proposed as an index of shape selectivity.
x) and the activity correlation were investigated by isomerization of 1-methylnaphthalene and alkylation of 2-methylnaphthalene with methanol (TOCAT 1990, Jens Wei.
tkamp et al., p291-301, Kodansha), etc., but specific application examples to the isomerization reaction of dialkylnaphthalene, especially the intra-group isomerization reaction of dialkylnaphthalene are not known. The catalytic activity of various kinds of so-called zeolites can be easily conceived by those skilled in the art, but the zeolite used in the present invention has only a particular reaction activity such as intra-group isomerization reaction of dialkylnaphthalene. Is a big feature.

The zeolite used in the present invention is synthesized by heating an aqueous medium containing a silica source, an alumina source, a metal source, an alkali source and an organic base in a closed container according to a known method. As the silica source, silica gel, silica sol, water glass, sodium silicate, precipitated silica, ironodils, clays, other silicic acid-containing minerals and the like can be used, but particularly preferably silica gel having a high specific surface area and high reactivity. And it is preferable that the particles are fine particles. As the alumina source, aluminum sulfate, aluminum chloride,
Various aluminum-containing compounds such as aluminum nitrate, sodium aluminate, and hydrated alumina are used.
As the metal source, compounds such as gallium, boron, iron, titanium, phosphorus, zinc, cobalt and nickel are used. As the alkali metal source, sodium hydroxide,
Alkali hydroxide such as potassium hydroxide, sodium carbonate,
Examples thereof include potassium carbonate and alkali carbonates. Furthermore, as the organic base, hexamethonium bromide (hereinafter abbreviated as HMB) [(CH ₃ ) ₃ N (CH ₂ ) ₆ N (CH ₃ ) ₃ ] Br ₂ or a hydroxide solution thereof is usually used as the organic base. Other organic bases, lower alcohols, etc. may be added to the organic base to the extent that it does not adversely affect crystallization.

Zeolite is obtained by reacting the above raw materials as a mixture by a conventional method. When a crystalline aluminosilicate is obtained as zeolite, it is usually reacted as a mixture having the following molar ratios.

[0016]

Table 4 _{SiO 2 / Al 2 O 3 =} 10~500 OH - / SiO 2 = 0.05~1 HMB / Al 2 O 3 = 0.5~20 H 2 O / SiO 2 = 10~100

The crystallization reaction temperature is usually 80 to 250 ° C.,
It is preferably 130 to 230 ° C. If the temperature is lower than the above temperature, it takes a long time to crystallize, and if the temperature is higher than the above temperature, decomposition of the organic base proceeds and brown foreign matter is formed in the system, which is not preferable. The produced crystals are filtered, washed, and then dried to be collected as powder. In order to use it in the reaction, it is usually used as a catalyst by previously performing ion exchange to H type (proton type) by a conventional method, and then performing drying, calcination and the like.

The zeolite catalyst may be in the form of powder, but a binder such as boehmite, alumina or kaolin silica is usually contained in an amount of 5 to 50% by weight, preferably 10% by weight, based on the amount of zeolite.
It is also possible to mix them in an amount of about 30 to 30% by weight and to use them by molding them into granules, pellets, spheres or the like having a particle diameter of about 0.1 to 5 mm. The catalyst whose activity has decreased due to long-term reaction can be regenerated by an oxidation treatment with an oxygen-containing gas or a hydrogenation treatment with a hydrogen-containing gas.

The isomerization reaction of dialkylnaphthalene compounds is carried out in a gas phase or a liquid phase, usually 80 to 500 ° C., preferably 15
Heat treatment is performed in the temperature range of 0 to 450 ° C. In the case of the gas phase reaction, the catalyst is processed into the above-mentioned molded body and filled in the reactor, and the reaction raw materials are preferably introduced under a hydrogen stream. The reaction temperature is preferably 300 to 450 ° C. On the other hand, when the isomerization is carried out by a liquid phase reaction, it is carried out in a liquid phase in which a reaction raw material and a zeolite catalyst are mixed, and the reaction temperature is preferably 150 to 350 ° C, particularly preferably 200 to 280 ° C.
When the isomerization is carried out in the liquid phase at a temperature equal to or higher than the boiling point of the reaction raw material, the system must be pressurized to keep the liquid phase. Further, in order to improve the suspended state of the catalyst, it is preferable to carry out the reaction under stirring. The product after the reaction is
Usually, separation is carried out by filtration, but this may be a batch operation or a continuous operation.

[0020]

EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. Zeolite production example Sodium aluminate (Al / NaOH molar ratio = 0.5
4) 1.99 g, sodium hydroxide 5.88 g 300
It was placed in a ml container, demineralized water 180.0 was added, and the mixture was dissolved with stirring to give an aqueous solution. Next, 15.01 g of hexamethonium bromide was added to the above aqueous solution and then dissolved by stirring (solution A). Solution A was added to 20.40 g of finely powdered silica (Tokusil U powder manufactured by Tokuyama Soda Co., Ltd.), and the mixture was homogenized at 7,000 rpm for 10 minutes.
Processed for a minute. The obtained contents were transferred to an autoclave equipped with a Teflon inner cylinder, and reacted under stirring at 196 ° C. for 43 hours for crystallization.

At this time, the charged molar ratio of the reaction raw materials is S
iO ₂ / Al ₂ O ₃ = 39.6, OH ⁻ / SiO ₂ =
0.45, H ₂ O / SiO ₂ = 73.6, Na / SiO
₂ = 0.50, which is N ⁺ / SiO ₂ = 0.122. After the reaction, the reaction solution was filtered, and the crystals were washed with water and dried.
7 g of dry powder was obtained. The results of X-ray diffraction are shown in Table-2. It is clear that the powder is a crystalline aluminosilicate having the diffraction peaks shown in Table 1. Next, this dry powder was calcined at 540 ° C. for 4 hours in an air stream to burn and decompose the organic base. The powder after firing was introduced into 600 ml of a 1.5 N ammonium nitrate aqueous solution, and heated under reflux with stirring. After refluxing for 2 hours, the mixture was filtered, washed with hot demineralized water, and then the above heating reflux operation was repeated twice more. After filtration and washing, it was dried at 120 ° C for one day. This dry powder was calcined under a nitrogen stream at 540 ° C. for 3 hours to obtain a catalyst powder. When the SiO ₂ / Al ₂ O ₃ molar ratio of the obtained proton-type catalyst powder was measured by fluorescent X-ray analysis, a value of 27 was obtained. The BET surface area measured by the nitrogen adsorption method was 363 m ² / g.

[0022]

[Table 5]

Example 1 2,6-dimethylnaphthalene (purity 99.9%) 9.0
g and 1.0 g of the catalyst prepared in the Zeolite Production Example were charged into a glass reactor having an internal volume of about 50 ml and under a nitrogen atmosphere.
The reaction was carried out with stirring at 50 ° C. for 5 hours. After the reaction
After returning to room temperature, a solvent (4-t-butyltoluene) was added to dissolve the reaction product, and the catalyst was filtered and analyzed by gas chromatography. As a result, the equilibrium arrival conversion rate of 2,6-DMN was 102.3%, the equilibrium arrival rate of 1,5-DMN was 105.4%, and the loss rate to the groups other than 2,6 was 0.4%.
The disproportionation rate was 0.3%.

The following items were defined and calculated as an index for evaluating the reaction results. Equilibrium reaching conversion rate (%) of 2,6-DMN = [1- (C
ap-Cae) / (Caf-Cae)] × 100 Equilibrium concentration arrival rate of 1,5-DMN (%) = (Cbp /
Cbe) × 100 “Loss ratio outside the 2,6 group” refers to the ratio of isomers other than 2,6 groups to the total dimethylnaphthalene in the reaction product. The "disproportionation ratio" refers to the ratio of the total amount of naphthalene, methylnaphthalene, and trimethylnaphthalene in the reaction product. The above Cap, Cae, Caf, Cbp, and Cbe mean the following.

[0025]

Table 6 Cap: Proportion (%) of 2,6-DMN in the reaction group in the 2,6 group Cae: Thermodynamic equilibrium of 2,6-DMN in the 2,6 group at 250 ° C Value (%) Caf: Ratio of 2,6-DMN in the reaction raw material (%) Cbp: Ratio of 1,5-DMN in the reaction product within the 2,6 group (%) Cbe: Within 2,6 group Thermodynamic equilibrium value (%) of 1,5-DMN at 250 ° C. Here, the value of the thermodynamic equilibrium composition at 250 ° C. of the 2,6-groups is 2,6-DMN: 1, 6-DMN:
Calculated as 1,5-DMN = 49.9: 43.5: 6.6.

Example 2 1,5-Dimethylnaphthalene (Purity 99.9%) 9.0
g and 1.0 g of the catalyst prepared in the Zeolite Production Example were charged into a glass reactor having an internal volume of about 50 ml, and the reaction was carried out under nitrogen atmosphere at 250 ° C. for 5 hours with stirring. After the reaction, the temperature was returned to room temperature, a solvent (4-t-butyltoluene) was added to dissolve the reaction product, and the catalyst was filtered and analyzed by gas chromatography. As a result, the equilibrium arrival conversion rate of 1,5-DMN was 98.1%, the equilibrium arrival rate of 2,6-DMN was 95.9%, and the loss rate to the groups other than 2,6 was 0.4.
%, And the disproportionation rate was 0.2%.

The following items were defined and calculated as an index for evaluating the reaction results. Equilibrium conversion rate (%) of 1,5-DMN = [1- (C
ap-Cae) / (Caf-Cae)] × 100 2,6-DMN equilibrium concentration arrival rate (%) = (Cbp /
Cbe) × 100 “Loss ratio outside the 2,6 group” refers to the ratio of isomers other than 2,6 groups to the total dimethylnaphthalene in the reaction product. The "disproportionation ratio" refers to the ratio of the total amount of naphthalene, methylnaphthalene, and trimethylnaphthalene in the reaction product. The above Cap, Cae, Caf, Cbp, and Cbe mean the following.

[0028]

Table 7 Cap: Proportion (%) of 1,5-DMN in the reaction group within the groups 2 and 6 Cae: Thermodynamic equilibrium of 1,5-DMN within the group 2 and 6 at 250 ° C. Value (%) Caf: Ratio of 1,5-DMN in the reaction raw material (%) Cbp: Ratio of 2,6-DMN in the reaction product in the 2,6 group (%) Cbe: In the 2,6 group Thermodynamic equilibrium value (%) of 2,6-DMN at 250 ° C. Here, the value of the thermodynamic equilibrium composition at 250 ° C. in the 2,6 group is 2,6-DMN: 1, 6-DMN:
It was calculated as 1,5-DMN = 49.9: 43.5: 6.6.

Example 3 2,7-Dimethylnaphthalene (Purity 99.9%) 9.0
g and 1.0 g of the catalyst prepared in the Zeolite Production Example were charged in a glass reactor having an internal volume of about 50 ml, and the reaction was carried out under nitrogen atmosphere at 250 ° C. for 1 hour with stirring. After the reaction, the temperature was returned to room temperature, a solvent (4-t-butyltoluene) was added to dissolve the reaction product, and the catalyst was filtered and analyzed by gas chromatography. As a result, the equilibrium arrival conversion rate of 2,7-DMN was 100.1%, the equilibrium arrival rate of 1,7-DMN was 100.1%, and the loss rate to the groups other than 2,7 was 0.
The disproportionation rate was 3% and 0.04%.

The following items were defined and calculated as an index for evaluating the reaction results. Equilibrium attainment conversion of 2,7-DMN (%) = [1- (C
ap-Cae) / (Caf-Cae)] × 100 1,7-DMN equilibrium concentration arrival rate (%) = (Cbp /
Cbe) × 100 “Loss ratio outside the 2,7 group” indicates the ratio of isomers other than the 2,7 group to the total dimethylnaphthalene in the reaction product. The "disproportionation ratio" refers to the ratio of the total amount of naphthalene, methylnaphthalene, and trimethylnaphthalene in the reaction product. The above Cap, Cae, Caf, Cbp, and Cbe mean the following.

[0031]

Table 8 Cap: Percentage (%) of 2,7-DMN in the reaction group within the 2,7 group Cae: Thermodynamic equilibrium of 2,7-DMN within the 2,7 group at 250 ° C Value (%) Caf: Ratio of 2,7-DMN in reaction raw material (%) Cbp: Ratio of 1,7-DMN in reaction product within 2,7 group (%) Cbe: Within 2,7 group Thermodynamic equilibrium value (%) of 1,7-DMN at 250 ° C. Here, the value of thermodynamic equilibrium composition at 250 ° C. in the 2,7 group is 2,7-DMN: 1,7. -DMN: 1,8
-Calculated as DMN = 56.5: 43.4: 0.1.

Example 4 2,3-Dimethylnaphthalene (Purity 99.0%) 9.0
g and 1.0 g of the catalyst prepared in the Zeolite Production Example were charged into a glass reactor having an internal volume of about 50 ml, and the reaction was carried out under nitrogen atmosphere at 250 ° C. for 5 hours with stirring. After the reaction, the temperature was returned to room temperature, a solvent (4-t-butyltoluene) was added to dissolve the reaction product, and the catalyst was filtered and analyzed by gas chromatography. As a result, the equilibrium arrival conversion rate of 2,3-DMN was 96.9%, the equilibrium arrival rate of 1,4-DMN was 93.3%, and the loss rate to the groups other than 2, 3 was 0.5.
%, And the disproportionation rate was 0.4%.

The following items were defined and calculated as an index for evaluating the reaction results. Equilibrium conversion rate of 2,3-DMN (%) = [1- (C
ap-Cae) / (Caf-Cae)] × 100 Equilibrium concentration arrival rate of 1,4-DMN (%) = (Cbp /
Cbe) × 100 “Loss ratio outside group 2,3” indicates the ratio of isomers other than groups 2,3 to the total dimethylnaphthalene in the reaction product. The "disproportionation ratio" refers to the ratio of the total amount of naphthalene, methylnaphthalene, and trimethylnaphthalene in the reaction product. The above Cap, Cae, Caf, Cbp, and Cbe mean the following.

[0034]

Table 9 Cap: Proportion (%) of 2,3-DMN in the reaction group within the groups 2 and 3 Cae: Thermodynamic equilibrium of 2,3-DMN within the group 2 and 3 at 250 ° C. Value (%) Caf: Proportion of 2,3-DMN in the reaction raw material (%) Cbp: Proportion of 1,4-DMN in the reaction product within groups 2 and 3 (%) Cbe: Within group 2 and 3 Thermodynamic equilibrium value (%) of 1,4-DMN at 250 ° C. Here, the value of the thermodynamic equilibrium composition at 250 ° C. in the groups 2 and 3 is 2,3-DMN: 1,4. -DMN: 1,8
Calculated as DMN = 26.3: 10.3.063.4.

Example 5 2,6-Dimethylnaphthalene (Purity 99.9%) 9.0
g and 3.9 g of the catalyst prepared in the Zeolite Production Example were charged into a glass reactor having an internal volume of about 50 ml, and the reaction was carried out under nitrogen atmosphere at 170 ° C. for 8 hours with stirring. After the reaction, the temperature was returned to room temperature, a solvent (4-t-butyltoluene) was added to dissolve the reaction product, and the catalyst was filtered and analyzed by gas chromatography. As a result, the equilibrium arrival conversion rate of 2,6-DMN was 68.3%, the equilibrium arrival rate of 1,5-DMN was 12.5%, and the loss rate to the groups other than 2,6 was 0.2.
%, The disproportionation rate was 0%.

The same index as in Example 1 was used as an index for evaluating the reaction results. Here, 2,
The value of the thermodynamic equilibrium composition at 170 ° C in Group 6 is
2,6-DMN: 1,6-DMN: 1,5-DMN = 5
Calculated as 2.2: 42.2: 5.6.

Example 6 A DMN isomer mixture containing 90.5% by weight of DMN, 7.1% by weight of ethylnaphthalene (abbreviated as EN) and 0.5% by weight of methylnaphthalene (abbreviated as MN), DM
2,6-DMN whose isomer composition in N is as shown in Table-3
The DMN isomer mixture liquid with a reduced concentration was 9.0 g, and 1 g of the catalyst prepared in the zeolite production example was used in an internal volume of about 50 ml.
In a glass reactor of No. 3, and under nitrogen atmosphere at 250 ℃ 3
The reaction was allowed to stir for hours. After the reaction, the temperature was returned to room temperature, a solvent (4-t-butyltoluene) was added to dissolve the reaction product, and the catalyst was filtered and analyzed by gas chromatography. As a result, the equilibrium arrival rate of the target 2,6-DMN was 95.7%, the loss rate of DMN was 1.0%, EN
The decomposition rate was 10.2%.

The same index as used in Example 1 was used as an index for evaluating the reaction results, and the decomposition rate of EN was determined as the ratio of the amount of EN decomposed by deethylation or the like in the raw material. Here, the value of the thermodynamic equilibrium composition at 250 ° C. in the 2,6 groups is 2,6-DMN: 1,6-DMN:
It was calculated as 1,5-DMN = 49.9: 43.5: 6.6.

[0039]

[Table 10]

Example 7 A DMN isomer mixture containing 90.6% by weight of DMN, 7.1% by weight of ethylnaphthalene (abbreviated as EN) and 0.5% by weight of methylnaphthalene (abbreviated as MN), DM
2,6-DMN whose isomer composition in N is as shown in Table 4
0.82 g / h of DMN isomer mixture liquid with reduced concentration
While entraining hydrogen gas of 0.7 Nl / hr at a speed of r,
It was poured into a glass reactor filled with 1.90 g of the catalyst prepared in the zeolite production example, and an isomerization reaction was carried out at 300 ° C. under normal pressure. The reaction liquid was collected at the outlet of the reactor and analyzed by gas chromatography. As a result, the equilibrium arrival rate of the target 2,6-DMN was 99.5%, the loss rate of DMN was 7.2%, and the decomposition rate of EN was 22.1%.

The same index as used in Example 1 was used as an index for evaluating the reaction results, and the decomposition rate of EN was determined as the ratio of the amount of EN decomposed by deethylation or the like. Here, the value of the thermodynamic equilibrium composition at 302 ° C. in the 2,6 groups is 2,6-DMN: 1,6-DMN:
It was calculated as 1,5-DMN = 48.5: 44.5: 7.0.

[0042]

[Table 11]

Comparative Example 1 2,6-DMN was isomerized in the same manner as in Example 1 except that a commercially available beta zeolite having a SiO ₂ / Al ₂ O ₃ molar ratio of 25 was used as a catalyst. . as a result,
The equilibrium conversion rate of 2,6-DMN is 102% and 1,5-
The equilibrium arrival rate of DMN was 104%, the loss rate to elements other than groups 2 and 6 was 3%, and the disproportionation rate was 17%.

Comparative Example 2 The same procedure as in Example 1 was carried out except that a commercially available zeolite omega (MAZ) having a SiO ₂ / Al ₂ O ₃ molar ratio of 6.4 was ion-exchanged into H type and used as a catalyst. 2,6-DMN
Was carried out. As a result, the equilibrium arrival conversion rate of 2,6-DMN was 103%, the equilibrium arrival rate of 1,5-DMN was 106%, the loss rate to other than 2 and 6 groups was 5%, and the disproportionation rate was 15%. Met.

COMPARATIVE EXAMPLE 3 A commercially available HY having a SiO ₂ / Al ₂ O ₃ molar ratio of 6.3.
Isomerization of 2,6-DMN was carried out in the same manner as in Example 1 except that type zeolite (FAU) was used as a catalyst. As a result, the equilibrium conversion rate of 2,6-DMN is 10
8%, equilibrium arrival rate of 1,5-DMN is 100%, 2,6
The loss rate to non-groups was 14% and the disproportionation rate was 46%.

[0046]

INDUSTRIAL APPLICABILITY According to the present invention, side reactions such as disproportionation and inter-group isomerization are suppressed to a minimum, and dialkylnaphthalene mainly undergoes isomerization within the group, whereby a desired isomer is obtained. It can be obtained efficiently.

Claims (3)

[Claims] 1. Isomerization of dialkylnaphthalene, characterized in that at least one of dialkylnaphthalene isomers is heat-treated in the presence of a zeolite-based catalyst that gives an X-ray diffraction peak at the interplanar spacing d in Table 1 below. Method. [Table 1] 2. The dialkylnaphthalene isomer is 1,5
The isomerization method according to claim 1, wherein the isomerization is at least one selected from dialkylnaphthalene, 1,6-dialkylnaphthalene and 2,6-dialkylnaphthalene. 3. The isomerization method according to claim 1, wherein the dialkylnaphthalene isomer is a dimethylnaphthalene isomer.