JPH0413637A - Preparation of 2,6-dimethylnaphthalene - Google Patents

Abstract

PURPOSE:To prepare the 2,6-isomer from dimethylnaphthalenes by subjecting naphthalene and the dimethylnaphthalenes to a transmethylation reaction and simultaneously subjecting the dimethylnaphthalenes to an isomerization reaction to prepare the dimethylnaphthalenes rich in the 2,6-isomer and further methylat ing the separated monomethyl isomer. CONSTITUTION:The transmethylation between naphthalene and dimethylnaphthalenes (DMNs) and the isomerization of the DMNs are performed in the presence of trimethylnaphthalenes(TMNs) and further monomethylnaphthalenes(MMNs) to the DMNs rich in the 2,6-isomer, followed by separating the unreacted naph thalene, MMNs, DMNs and TMNs from the reaction product. The 2,6-isomer is separated from the gathered DMNs. The TMNs are circulation-used. The above-mentioned method permits to reduce the loss of CH3 groups caused by the isomerization of only DMNs.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an industrially efficient method for producing 2,6-dimethylnaphthalene by methylating naphthalene and/or monomethylnaphthalene.

[Prior Art 1] Dimethylnaphthalenes (hereinafter sometimes abbreviated as DMN) obtained by methylating naphthaleneyamethylnaphthalene have 10 isomers. Among these isomers, 2.6-[)MN is particularly useful industrially.

2.6- D M N is oxidized to naphthalene-2,6
-Dicarboxylic acid is provided, and from the polyester obtained using the carboxylic acid as a raw material, excellent quality synthetic II materials, films, etc. can be obtained. Therefore, research on the production method of 2.6-DMN was conducted from an early stage, and coal dry-distilled oil and F
A method for producing 2,6-DMN from DMN contained in CC cycle oil by crystallization separation or complex extraction separation (Japanese Unexamined Patent Publication No. 7551/1983).

(Japanese Patent Publication No. 47-29893), and alkenylation using ortho-xylene and butadiene as raw materials as a synthesis method.
2.6-D by cyclization one theory hydrogen one reaction one crystallization separation
A method to obtain M N was also proposed (G, G.

Eberhardt, J. Orl: 1. Ch
ea, 30.82 (1965).

Special Publication No. 50-12430, Special Publication No. 56-3457
Publication No. 0.

Special Publication No. 47-47379, LISP 3,
244.7513>.

Furthermore, recently, methods for obtaining dimethylnaphthalene by methylating naphthalene and monomethylnaphthalene with methanol (JP-A-60-172937, JP-A-63-83) have been developed.
44, JP-A-63-14738, JP-A-6
3-14739), or a method of transmethylating with polymethylbenzene to obtain methylnaphthalene or dimethylnaphthalene (Japanese Patent Publication No. 53-5293, JP-A-61-267530, JP-A-63-14737)
Publication No.) etc. have been proposed.

These proposals are single-step; methylnaphthalene,
It is intended to obtain dimethylnaphthalene, and D obtained by methylating naphthalene or monomethylnaphthalene.
No proposal has been found regarding a suitable manufacturing process for producing 2,6-OM N from MN by crystallization separation. There is only one thing that the inventors
5532) proposed a method for efficiently producing 2,6-DMN from a dimethylnaphthalene mixture. Although the proposal was an innovative method at the time,
After partially hydrogenating the raw material DMN mixture and separating dimethyltetralin having two methyl groups on the same ring and dimethyltetralin having two methyl groups attached to separate rings from alkylbenzene that is not partially hydrogenated, by distillation, 2. by isomerization, then dehydrogenation, and crystallization separation.
This is a method for separating and producing 6-DMN, which requires steps of partial hydrogenation and dehydrogenation, and cannot be called an efficient production method.

[Objective of the Invention 1 The present invention solves the above-mentioned problems and provides a method for efficiently producing 2.6-DMN. More specifically, 2.6-D can be efficiently produced by a manufacturing process that mainly consists of a methylation step that methylates naphthalene or monomethylnaphthalene, and a transmethylation/isomerization step.
The object of the present invention is to provide a method for manufacturing MN.

[Structure of the Invention] The present invention provides the following steps: 1. Naphthalene is methylated in the presence of a catalyst and 2.6
- In producing dimethylnaphthalene, <I) transmethylation reaction of methylating naphthalene with dimethylnaphthalenes and isomerization reaction of dimethylnaphthalenes,
simultaneously in the presence of trimethylnaphthalenes; 2.
A first step of producing dimethylnaphthalenes enriched in 6-dimethylnaphthalene, (n) converting the transmethylation/isomerization reaction mixture of the above step I into unreacted naphthalene, monomethylnaphthalenes, dimethylnaphthalenes, and trimethylnaphthalenes. (III) step (III) of producing dimethylnaphthalenes by methylating the monomethylnaphthalenes separated in step (iii) with a methylating agent; (rV) the methyl obtained in the step (iv); The reaction mixture is converted into unreacted monomethylnaphthalenes.

Step (2) of separating dimethylnaphthalenes and trimethylnaphthalenes, and (V) separating 2,6-dimethylnaphthalene from the dimethylnaphthalenes obtained in step (1) and/or the dimethylnaphthalenes separated in step (2). This is a method for producing 2,6-dimethylnaphthalene, which comprises step V of separating.

It is preferable to circulate the trimethylnaphthalenes separated in the above-mentioned step (1) and/or step (2) to the step I.

The present invention is characterized in that dimethylnaphthalenes are isomerized in the presence of naphthalene, and dimethylnaphthalenes are isomerized while producing monomethylnaphthalenes and dimethylnaphthalenes by transmethylation of naphthalene with dimethylnaphthalenes. do. Furthermore, by making trimethylnaphthalenes present in this step,
Transmethylation of naphthalene and trimethylnaphthalenes produces monomethylnaphthalenes and dimethylnaphthalenes, and transmethylation of monomethylnaphthalenes and trimethylnaphthalenes produces dimethylnaphthalenes, resulting in 2.6-DMN. It becomes possible to increase the production activity of rich dimethylnaphthalenes, improve the yield of methyl groups, and at the same time improve the production of 2,6-D, which is the target product.
MN is efficiently manufactured.

In the present invention, for isomerization and transmethylation reactions,
It is also suitable to add monomethylnaphthalenes in addition to trimethylnaphthalenes.

The amount of monomethylnaphthalenes and trimethylnaphthalenes to be added is such that the molar ratio of all naphthalene rings to all methyl groups in naphthalene, monomethylnaphthalenes and trimethylnaphthalenes, that is, the methyl group/naphthalene ring molar ratio is 2 or less, preferably 0.17. It is as follows. Further, the amount of monomethylnaphthalene is 0.3 mol or less, preferably 0.2 mol or less based on naphthalene.

In the present invention, dimethylnaphthalenes refer to a mixture mainly consisting of isomers of dimethylnaphthalene. Monomethylnaphthalenes refer to mixtures consisting mainly of isomers of monomethylnaphthalene. Trimethylnaphthalenes refer to a mixture consisting mainly of isomers of trimethylnaphthalene.

These may contain impurities depending on the degree of separation and purification, and the degree of inclusion varies.

A major feature of the present invention is that the isomerization of dimethylnaphthalenes is carried out in the presence of naphthalene and trimethylnaphthalenes.

The present invention will be explained in detail below.

Step I〉 In this step, naphthalene is transmethylated with dimethylnaphthalenes and trimethylnaphthalenes, and at the same time,
This is a process for isomerizing dimethylnaphthalenes.

More specifically, dimethylnaphthalenes are isomerized in the presence of naphthalene and trimethylnaphthalenes, and at the same time as the isomerization, naphthalene is transmethylated with dimethylnaphthalenes and trimethylnaphthalenes to produce monomethylnaphthalenes, and at the same time, This is a process in which dimethylnaphthalenes are produced by transmethylation of monomethylnaphthalenes and trimethylnaphthalenes, and dimethylnaphthalenes enriched in 2,6-dimethylnaphthalene are simultaneously produced.

To this step, raw material naphthalene and dimethylnaphthalenes with a low content of 2,6-dimethylnaphthalene separated in the V step described below are fed.

In this step, it is also suitable to add monomethylnaphthalenes in addition to trimethylnaphthalenes. Monomethylnaphthalenes produce dimethylnaphthalenes through a transmethylation reaction with trimethylnaphthalenes.

In the present invention, as the monomethylnaphthalenes present during the reaction, it is preferable to use monomethylnaphthalenes separated in step rVI described below. Further, it is preferable to use trimethylnaphthalenes separated in the first step and/or the second step. Further, it is preferable to circulate the naphthalene separated in the first step to this step. Such naphthalenes contain monomethylnaphthalenes depending on the degree of separation.

A solid acid catalyst can be used in this step.

The preferred catalyst used in this step is a crystalline aluminosilicate zeolite used for the isomerization of dimethylnaphthalenes. A crystalline aluminosilicate zeolite having an Si/Au element ratio in the range of 5 to 100 is preferred. Crystalline aluminosilicate zeolite described in JP-A-60-38331 (published on February 21, 1985) is preferred. Such a catalyst is a crystalline aluminosilicate zeolite with a Si 02 /Au203 molar ratio in the range of 10 to 100 and a specific X-ray lattice spacing. A specific example of the method for preparing this catalyst is described in the same publication.

In this step, transmethylation and isomerization are performed simultaneously, and the reaction conditions are as follows.

The reaction temperature is in the range of 300 to 500°C, preferably 350°C.
-400°C. The pressure ranges from normal pressure to 20 atl, preferably from normal pressure to 10 atl. The reaction can be carried out in either liquid phase or gas phase. It is also possible to coexist hydrogen in the reaction. In this case, hydrogen/
The molar ratio of naphthalene ranges from O to 10, preferably from O to
The range is 5. Contact between naphthalene, dimethylnaphthalenes, and trimethylnaphthalenes occurs at weight hourly space velocity (
WH8V) in the range of 0.1 to 20, preferably 0.5 to
This can be done within the range of 3. Here, WH3V represents the total amount of contact 1 (g) of components involved in the reaction, such as naphthalene and dimethylnaphthalene, per unit time (hr) per catalyst (9).

In this step, it is preferable to feed dimethylnaphthalenes in which the composition of 2,6-dimethylnaphthalene is less than or equal to the thermodynamic equilibrium composition among all dimethylnaphthalenes. Further, it is preferable to feed dimethylnaphthalenes having a molar ratio of 2,6-dimethylnaphthalene/2,7-dimethylnaphthalene of 0.4210.58 or less.

Step (2) This step is a step in which the reaction mixture produced in Step I is separated into naphthalene, monomethylnaphthalenes, dimethylnaphthalenes, and trimethylnaphthalenes.

For separation, conventional means such as distillation and recrystallization can be used. Unreacted naphthalene separated in this step can be used as feed to stage 1I. The dimethylnaphthalenes rich in 2,6-dimethylnaphthalene are separated into 2,6-dimethylnaphthalene in Step V, which will be described later.

Monomethylnaphthalenes are methylated in the next step (1), but it is also preferable to partially circulate them to the first step. It is preferable that trimethylnaphthalenes be recycled to the first step.

<Step (ii)> This step is a step in which the monomethylnaphthalenes separated in step (ii) are methylated using a methylating agent. If necessary, unreacted monomethylnaphthalenes separated in the second step can also be fed.

The preferred catalyst used in this step is a catalyst containing crystalline aluminosilicate zeolite. Preferably S! 02/A! It is a crystalline aluminosilicate zeolite catalyst with a L20a molar ratio of 5 to 100. Most preferably, Japanese Patent Application Laid-Open No. 60172937 (Showa 6
(Published on September 6, 1988) or JP-A-63-112527 (Published on May 17, 1988).

In this step, the zeolite-containing catalyst is used to bring the monomethylnaphthalenes into contact with the methylating agent.

In this step, dimethylnaphthalenes are mainly produced from monomethylnaphthalenes. That is, one of the characteristics of using the zeolite-containing catalyst of the present invention is that the proportion of naphthalene compounds substituted with three or more methyl groups is extremely small, and dimethylnaphthalenes are mainly produced.

Methylation can be carried out in the gas phase or in the liquid phase; however, methods in which the methylation is carried out in the gas phase are preferred.

The methylating agent used in the methylation reaction may be one that is used for methylating the nuclear carbon of aromatic hydrocarbons on the membrane surface, such as methanol, methyl chloride,
Methyl bromide, dimethyl ether and the like are preferred, with methanol or dimethyl ether or mixtures thereof being most preferred. Such a methylating agent is advantageously used in a proportion of 0.01 to 2 moles, preferably 0.05 to 1 mole, relative to the monomethylnaphthalenes.
In particular, it is preferable to use monomethylnaphthalenes in excess of the methylating agent in order to suppress side reactions.

In the method of the present invention, the zeolite-containing catalyst is brought into contact with the monomethylnaphthalenes and the methylating agent in the gas phase or liquid phase at a weight hourly space velocity (WH3V) of 0.01 to 10.
This can be done within a range of 0.

Here, WH8V is defined as representing the total contact amount (9) of monomethylnaphthalenes and methylating agent per unit time (hr) per zeolite unit 1). Preferred W)-1sV values are in the range 0.1-10, especially in the range 0.5-5. If the WH8V value is less than 0.01, a product with a high content ratio of dimethylnaphthalenes as intended in the present invention cannot be obtained. On the other hand, the WH8V value is 1
If it exceeds 0.00, the contact time is too short and the conversion rate decreases, which is industrially disadvantageous.

It has already been mentioned that the methylation reaction of the present invention is preferably carried out in a gas phase rather than in a liquid phase, but when carried out in a gas phase,
It is desirable to carry out the reaction under a hydrogen stream, and by doing so, it may be possible to suppress deterioration of the activity of the catalyst. The amount of hydrogen supplied is preferably in the range of 0.1 to 20, preferably 0.5 to 10, expressed as hydrogen/(methylating agent and monomethylnaphthalenes) ratio (mol).

The reaction is also advantageously carried out at a temperature in the range from 250 to 600°C, preferably from 300 to 500°C, especially from 350 to 450°C. Further, the pressure may be reduced pressure, normal pressure, or increased pressure, but is usually normal pressure to increased pressure, for example, 1 to 30 KG,
Preferably it is carried out at a pressure of 1 to 10 kg.

The raw material to be methylated in the present invention is the monomethylnaphthalenes separated in step (1), but this does not need to be pure. As components other than naphthalenes in the raw material mixture, aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons other than naphthalenes can be used.

The reaction of the present invention can be carried out in either a fixed bed system or a fluidized bed system. Further, in the case of using a fixed bed system, the fixed bed may be one stage, or may be a multistage system of two or more stages.

<Step V> In this step, the dimethylnaphthalenes and unreacted monomethylnaphthalenes produced in the step (①) are removed.

This is a step in which trimethylnaphthalenes and unreacted methylating agent are separated.

Separation can be carried out by a method known per se; for example, the reaction mixture obtained in step (1) is sufficiently cooled in a cooler, and the concentrated product and gas are separated in a gas-liquid separator. The concentrated oil/water can then be separated and the oil fed to a distillation column to separate unreacted monomethylnaphthalenes, dimethylnaphthalenes and other side reaction products.

Unreacted monomethylnaphthalenes obtained by separation can be recycled to the first and/or second step. Dimethylnaphthalenes are fed to the next step V,
2. Separate 6-dimethylnaphthalene. It is preferable that the trimethylnaphthalenes be recycled to the second step.

<Step V> This step is a step of separating 2,6-dimethylnaphthalenes from dimethylnaphthalenes. The dimethylnaphthalenes separated in the above-mentioned step ① and step TVI are fed to this step.

Separation can be carried out by methods known per se, for example by distillation, crystallization separation, complex extraction separation. Regarding crystallization separation and complex extraction separation, see JP-A-48-7554 or JP-A-47-29893.
It can be carried out according to the method described in the publication.

In the present invention, the separation in step (1) and step V can also be performed in the same step.

Process diagram FIG. 1 shows an example of a specific process diagram of the present invention.

Further, FIG. 2 shows an example in which the step ① and the step VI are performed in the same step.

[Effects of the Invention] According to the present invention, dimethylnaphthalenes are isomerized in the presence of naphthalene and trimethylnaphthalenes, naphthalene is transmethylated with dimethylnaphthalenes simultaneously with the isomerization, and naphthalene and trimethylnaphthalenes are Transmethylation of monomethylnaphthalenes produces monomethylnaphthalenes and dimethylnaphthalenes, transmethylation of monomethylnaphthalenes and tri-methylnaphthalenes produces dimethylnaphthalenes, and loss of methyl groups occurs by isomerization of only dimethylnaphthalenes. It became possible to lower the It has also been achieved to provide an efficient combination of steps such as transmethylation, isomerization, and methylation.

[Example] Hereinafter, the present invention will be explained in detail by giving examples. It goes without saying that the present invention is not limited to these embodiments.

Preparation of catalyst Catalyst A 550 g of aluminum sulfate was gradually added to a solution of 425 g of sodium hydroxide dissolved in 8.5 ml of pure water while stirring.
A homogeneous solution was obtained. After adding I kg of common salt, 5 kg of silica vine (SiO2 30 wt%) was added with vigorous stirring to form a reaction mixture.

This mixture, 327 g of tetrabu-O-bylamine 3811 propyl bromide and 5009 methyl ethyl ketone were added to 2
It was placed in a 0 volume stainless steel autoclave and sealed.

While stirring by rotating the stirring blade at 150 revolutions per minute,
The reaction was carried out at 100°C for 1 day and at 160°C for 4 days.

After filtering the reaction product and thoroughly washing the cake with 200 ρ of pure water, it was dried at 100°C for a day and night, and then calcined at 500°C for 2 days in an air atmosphere to obtain base zeolite 1.3K.
I got g. The silica-alumina molar ratio of this product is 26.
It was 2.

The base zeolite 2009 obtained in this way,
The slurry was added to 800 d of water in which 409 sodium hydroxide was dissolved and stirred to obtain a uniform slurry, which was then charged into an 11-volume stainless steel autoclave, heated to 180° C. with stirring, and held for 8 hours.

After cooling, the contents were filtered, thoroughly washed with 5 g of pure water, and then dried at 100° C. overnight to obtain 135 g of cake. The silica-alumina ratio of this product was 16.8, and the X-ray diffraction pattern showed that it was substantially the crystalline aluminosilicate zeolite shown in Table 1.

This was brought into contact with a 10% aqueous ammonium chloride solution three times while heating to 10°C to exchange ions with NH4' ions, filtered, washed, dried, and then calcined at 500°C for 8 hours to form H-type zeolite. Converted.

Thoroughly mix i part of this H-type zeolite and 1 part by weight of alumina gel, mold into a size of 10 to 20 meshes,
Catalyst A was obtained by calcining at 50°C for 8 hours.

To a reaction mixture prepared from 1380 g of silica sol (S!02 30%), 153 g of aluminum sulfate, 176 g of sodium hydroxide, and 3 ml of water, 105 g of the base zeolite used in Catalyst A above was added, and the mixture was charged into a 5μ capacity stainless steel autoclave and stirred. At the same time, the temperature was raised to 180°C and held for 8 hours.

After cooling, the contents were filtered and thoroughly washed with pure water 5 times.
The mixture was dried at 00° C. overnight to obtain 405 g of cake.

The silica-alumina ratio of this product was 19.6, and the X-ray diffraction pattern was substantially that of the crystalline aluminosilicate zeolite shown in Table 1. This crystalline aluminosilicate zeolite 1509 was brought into contact with one volume of 10% ammonium chloride aqueous solution three times while heating to 70°C.
After ion exchange with H4+ ions, filtration, washing, and drying, the mixture was calcined at 500° C. for 8 hours to convert into H-type zeolite.

Thoroughly mix this H-type zeolite monolayer top part with 1 part by weight of alumina gel, form it into a size of 10 to 20 meshes, and
Catalyst B was obtained by calcining at 50° C. for 8 hours.

Catalyst C Crystalline aluminosilicate zeolite 25 same as catalyst B
0 g was placed in 2 fl of a 5% aqueous lithium nitrate solution, and the mixture was refluxed for 4 hours and brought into contact. This operation was repeated three times. After filtration, washing, and drying, it was calcined at 500°C for 8 hours to convert it into l-i type zeolite.

1 part by weight of this Li-type zeolite and 1 part by weight of alumina gel were thoroughly mixed and formed into a size of 10 to 20 meshes.
Catalyst C was obtained by calcining at 50°C for 8 hours.

1 part by weight of commercially available Y-type zeolite (H-type manufactured by Tosoh) and 1 part by weight of alumina gel were thoroughly mixed, formed into a size of 10 to 20 meshes, and fired at 450°C for 8 hours to remove the catalyst. Obtained.

Table 1 9.83 9.12 7.51 9.70 11.80 Weak Weak Weak 5.74 5.61 5.41 5.00 4.65 4.39 4.28 15.45 15.80 16.40 17.75 19.10 20.25 20.75 Weak Weak Weak Weak Weak Weak ~ Medium 3.75 3.74 3.66 23.70 23.80 24.30 Strong Strong Medium ~ Strong 3.33 3 .28 3.26 3.06 3.00 2.98 2.96 26.80 Weak to moderate 27.20 Weak 27.35 Weak 29.15 Weak to moderate 29.75 Weak to moderate 29.95 Weak ~ Medium (9), 20 Weak intensity (1/Io) is d (in) = 3.86 (2θ = 2
3.05) Relative intensity of each peak when the intensity (Io) of 40～
20 is expressed as M (medium), and 20 to 10 is expressed as W (weak).

Example ■ (Transmethylation/isomerization) In a stainless steel flow-through reaction tube filled with Catalyst A 2009, 29 parts by weight of naphthalene and 3 parts by weight of monomethylnaphthalene were added.
Parts by weight, 16% 2.6-dimethylnaphthalene and 2.7-
65 parts by weight of a dimethylnaphthalene mixture containing 22% dimethylnaphthalene and 3 parts by weight of a trimethylnaphthalene mixture
The mixed raw materials containing parts by weight were fed at a rate of 200 g/hr. The reaction pressure was 5Ks/CII under hydrogen pressure.
G, the reaction temperature was 375°C. This reaction was continued for 4 hours to obtain 800 g of a reaction mixture.

(Separation) This reaction mixture was distilled in a precision distillation device with 100 theoretical plates to produce 188 g of low-boiling distillate containing mainly naphthalene (from the initial stream to
225℃), 132g of monomethylnaphthalene (225℃)
5-250℃), dimethylnaphthalene distillate 4B7g (2
50 to 275°C) and 13 g of distillation residual oil mainly consisting of trimethylnaphthalene. Approximately 99% of the low boiling distillate was naphthalene.

The dimethylnaphthalene distillate contained 20% each of 2,6-dimethylnaphthalene and 2,7-dimethylnaphthalene. Let this be the full rice field.

(Methylation) On the other hand, 127 g of the above monomethylnaphthalene was added to another stainless steel flow-through reaction tube filled with 8200 g of catalyst.
485g of monomethylnaphthalene and 55g of methanol
9 mixture was delivered in 2.7 hours.

The reaction pressure was 5 K'j/t:i G under hydrogen pressure, and the reaction temperature was 400°C.

(all minutes) After separating the reaction mixture into water at 300C and 509 g of produced oil, the produced oil was distilled using the same precision distillation equipment as above to reduce the low boiling point fat content, mainly naphthalene and monomethylnaphthalene, to 42 g.
09 (initial flow ~ 250℃), dimethylnaphthalene distillation tank 8
It was separated into 5g (250-275℃) and 4g of distillation residue oil mainly consisting of trimethylnaphthalene.
% naphthalene.

The dimethylnaphthalene distillate contained 25% 2.6-dimethylnaphthalene and 26% 2.7-dimethylnaphthalene. Let this be the tank (b+).

(Separation) 551 g of a dimethylnaphthalene mixture obtained by heating the distillation tank and distillation tank <b) to 70°C and dissolving them was gradually cooled to 30°C. 2,6-dimethylnaphthalene 1 was added thereto as a seed crystal, and the mixture was kept at 30° C. for 20 hours. The resulting cake was filtered and further washed with 200-methanol. The resulting solid was dried in vacuum at room temperature for 4 hours to obtain 34 g of pure 1 [97% 2,6-dimethylnaphthalene].

In this series of experiments, the monomethylnaphthalene generated in the transmethylation step and the monomethylnaphthalene consumed in the methylation step were balanced;
The remaining dimethylnaphthalene discharged from the 6-dimethylnaphthalene separation process is recycled to the transmethylation process, so the actual amount of naphthalene consumed is 34 g after deducting the naphthalene generated in the methylation process. , the yield of 2,6-dimethylnaphthalene is 80% based on naphthalene.

Comparative Example (Transmethylation/Isomerization) A stainless steel flow-through reaction tube filled with Catalyst A 2009 contained 35 parts by weight of naphthalene, 16% of 2,6-dimethylnaphthalene, and 22% of 2,7-dimethylnaphthalene. A mixed raw material containing 65 parts by weight of a dimethylnaphthalene mixture was fed at a rate of 200 g/hr. The reaction pressure was 5 Ks/cMG under hydrogen pressure, and the reaction temperature was 375°C. This reaction was continued for 4 hours to obtain 800 g of a reaction mixture.

(Separation) This reaction mixture was distilled using a precision distillation device with 100 theoretical plates.
225℃), monomethylnaphthalene distillate 127g (225℃)
5-250℃), dimethylnaphthalene distillate 4359 (
250-275°C) and distillation residue oil 89. Approximately 98% of the low boiling point fat was naphthalene.

The dimethylnaphthalene distillate contained 20% each of 2,6-dimethylnaphthalene and 2,1-dimethylnaphthalene. This will be used as seedlings.

(Methylation) Meanwhile, 12 volumes of the above monomethylnaphthalene distillate were placed in another stainless steel flow-through reaction tube filled with catalyst B 2009.
A mixture of 630 g of monomethylnaphthalene containing 7 g and 70 fi of methanol was fed in over 3.5 hours.

The reaction pressure was 5K9/ciG under hydrogen pressure, and the reaction temperature was 400°C.

(Separation) After the reaction mixture was separated into 40 cc of water and 660 g of produced oil, the produced oil was distilled using the same precision distillation equipment as above, and a low-boiling fat content of 54%, mainly consisting of naphthalene and monomethylnaphthalene, was distilled.
59 (initial flow ~ 250℃), dimethylnaphthalene distillation tank 1
109 (250-275°C) and 5 g of distillation residue oil. The low boiling point fat contained 3% naphthalene.

The dimethylnaphthalene distillate contained 25% 2.6-dimethylnaphthalene and 26% 2.7-dimethylnaphthalene. Let this be the reservoir (b').

(Separation) The tank (seedling and tank b') was heated to 70°C, and 545 g of the dimethylnaphthalene mixture obtained by dissolving it was gradually cooled to 30°C. To this, 2.6~dimethylnaphthalene 19 was added as a seed crystal, kept at 30°C for 20 hours, the resulting cake was filtered, and an additional 200ad! of methanol. The obtained solid was dried in vacuum at v temperature for 4 hours to obtain 2,6-dimethylnaphthalene 339 with a purity of 97%.

In this series of comparative experiments, the naphthalene that was substantially consumed was 37 g after deducting the naphthalene generated in the methylation step, and the yield of 2,6-dimethylnaphthalene was 71% based on naphthalene.

Comparing Example 1 with an example in which motumethylnaphthalene and trimethylnaphthalene are not supplied to the transmethylation/isomerization step, the yield based on naphthalene is 80%, which is 9% higher, and the yield is 9% higher than that required in the methylation step. The amount of monomethylnaphthalene supplied was 485 g, compared to 630 g.
It has decreased by about 3/4. This is due to the reduction in loss due to the supply of monomethylnaphthalene and trimethylnaphthalene to the transmethylation step, and the contribution of dimethylnaphthalene newly generated by the transmethylation reaction.

Example ■ (Transmethylation/isomerization) 32 parts by weight of naphthalene and 6 parts by weight of monomethylnaphthalene were placed in a stainless steel flow-through reaction tube filled with catalyst [2009].
Parts by weight, 17% 2,6-dimethylnaphthalene and 2.7-
A mixed raw material containing 36 parts by weight of a dimethylnaphthalene mixture containing 24% dimethylnaphthalene and 26 parts by weight of a trimethylnaphthalene mixture was fed at 200 g/hr.
was supplied at a rate of The reaction pressure was 5K9/under hydrogen pressure.
The reaction temperature was 290°C.

This reaction was continued for 3.5 hours to obtain 700 g of a reaction mixture.

(Separation) This reaction mixture was distilled using a precision distillation device with 100 theoretical plates to produce 184 g of low-boiling distillate containing mainly naphthalene (first 8i
~225℃), monomethylnaphthalene distillate 2229 (
225-250℃), 201 g of dimethylnaphthalene distillate
<250-275°C) and 93 g of distillation residue oil mainly consisting of trimethylnaphthalenes.

97% of the low boiling distillate was naphthalene.

Further, the dimethylnaphthalene distillate contained 18% of 2,6-dimethylnaphthalene and 19% of 2,7-dimethylnaphthalene. Let this be the tank (C).

(Methylation) On the other hand, a mixture of monomethylnaphthalene 4509 containing 2229 monomethylnaphthalene distillates and 51 g of methanol was fed into a stainless steel flow-through reaction tube filled with catalyst 02009 over 2.5 hours. The reaction pressure was 51/2 under hydrogen pressure.
The reaction temperature was 400°C with dG.

(Separation) After separating the obtained reaction mixture into 29 cc of water and 471 g of produced oil, the produced oil was distilled using the same precision distillation equipment as above.
377 g of low-boiling components mainly consisting of naphthalene and monomethylnaphthalene (initial stream ~ 250°C), 899 volumes of dimethylnaphthalene (250-275°C), and 5 g of distillation residue oil
It was separated into

1% of the low boiling distillate was naphthalene.

The dimethylnaphthalene distillate contained 49% of 2.6-dimethylnaphthalene and 25% of 2.7-dimethylnaphthalene. Let's call this a small storage area.

(Separation) Gradually add 290 g of dimethylnaphthalene mixture obtained by heating distillate (C) and distiller (small) to 70°C to dissolve and mix them.
Cooled to ℃. here 2,6-dimethylnaphthalene 1
g was added as a seed crystal and kept at 30° C. for 5 hours, and the resulting cake was filtered and further washed with 200 m of methanol. The resulting solid was dried in vacuum at room temperature for 4 hours to a purity of 9.
7% of 2,6-dimethylnaphthalene 409 was obtained.

The naphthalene substantially consumed in this example was 41 g, and the yield of 2,6-dimethylnaphthalene based on naphthalene was 78%.

Example m (Transmethylation/isomerization) In a stainless steel flow-through reaction tube filled with catalyst A 2009, 31 parts by weight of naphthalene, 6 parts by weight of monomethylnaphthalene, 17% of 2.6-dimethylnaphthalene and 2.7-dimethyl were added. A mixture containing 48 parts by weight of a dimethylnaphthalene mixture containing 23% naphthalene and 151 parts by weight of a trimethylnaphthalene mixture was fed at a rate of 2009/hr. The reaction pressure was 5/ciG under hydrogen pressure, and the reaction temperature was 375°C. This reaction was continued for 2.5 hours to obtain a reaction mixture soog.

(Methylation) Meanwhile, in a stainless steel flow-through reaction tube filled with 200 g of catalyst C, 275 g of monomethylnaphthalene and 3 methanol
1 g was fed in 1.5 hours. The reaction pressure was 1 under hydrogen pressure.
The reaction temperature was 400''C at 0Kg/cIiG.

The reaction mixture was separated into 18 cc of water and 288 g of product oil.

(Separation) A total of 788 g of the two reaction mixtures obtained in the above transmethylation/isomerization step and methylation step was added to the theoretical plate 1.
Distilled in a 00-stage precision distillation device, containing 137g of low boiling point components mainly naphthalene (initial FIl ~ 225℃), monomethylnaphthalene fat content 342SF < 225~250℃)
, dimethylnaphthalene distillate (containing 26% and 21% of 2,6 and 2,7-dimethylnaphthalene, respectively) 269
g (250-275°C) and distillation residue oil 409 mainly containing trimethylnaphthalenes.

(Minute II) The dimethylnaphthalene distillate was heated to 70°C, mixed, and gradually cooled to 30°C. To this, 1 g of 2,6-dimethylnaphthalene was added as a seed crystal, and the resulting cake was filtered by keeping it at 30° C. for 10 hours, and the cake was further washed with 200 d of methanol. The obtained solid was dried at room temperature in vacuum for 4 hours to obtain 2.6-dimethylnaphthalene 329 with a purity of 97%.

In this example, 29 g of naphthalene was substantially consumed, and the yield of 2,6-dimethylnaphthalene based on naphthalene was 87%.

[Brief explanation of the drawing]

FIGS. 1 and 2 show process diagrams applicable to the manufacturing method of the present invention.

Claims (1)

[Claims] 1. Naphthalene is methylated in the presence of a catalyst to produce 2,6-
In producing dimethylnaphthalene, (I) A transmethylation reaction in which naphthalene is methylated with dimethylnaphthalenes and an isomerization reaction of dimethylnaphthalenes are simultaneously performed in the presence of trimethylnaphthalenes to produce 2,6-dimethylnaphthalene. (II) a second step of separating the transmethylation/isomerization reaction mixture of the first step into unreacted naphthalene, monomethylnaphthalenes, dimethylnaphthalenes, and trimethylnaphthalenes; (III) Step III in which the monomethylnaphthalenes separated in Step II are methylated with a methylating agent to produce dimethylnaphthalenes; (IV) The methylation reaction mixture obtained in Step III is untreated. A IV step of separating the reacted monomethylnaphthalenes, dimethylnaphthalenes and trimethylnaphthalenes, and (V) 2, A method for producing 2,6-dimethylnaphthalene, comprising a V step of separating 6-dimethylnaphthalene. 2. The production method according to claim 1, characterized in that the trimethylnaphthalenes separated in step II and/or step IV are recycled to step I.