JPH041142A - Production of 2,6-dimethylnaphthalene - Google Patents

Abstract

PURPOSE:To separate 2,6-DMN from DMNs by trans-methylating naphthalene in the presence of dimethylnaphthalenes and simultaneously isomerizing DMNs, separating into 3 components and methylating monomethylnaphthalenes. CONSTITUTION:DMNs rich in 2,6-isomer and monomethylnaphthalenes(MMN) are produced at the same time by isomerizing DMNs in the presence of naphthilene, thereby effecting trans-methylation simultaneous to the isomerization reaction. The reaction mixture is separated into naphthalene, MMNs and DMNs and the MMNs are methylated to DMNs. The produced DMNs are combined with the DMNs separated by the above process and 2,6-isomer is separated therefrom. A crystalline aluminosilicate zeolite having an Si/Al element ratio of 5-100 is preferably used as the catalyst in the first process and the process to methylate MMNs to DMNs. The process can reduce the loss of CH3 group formed by the isomerization of exclusively 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.

[Prior Art] There are ten isomers of dimethylnaphthalenes (hereinafter sometimes abbreviated as DMN) obtained by methylating naphthalene and methylnaphthalene. Among these isomers, 2.6-[)MN is particularly useful industrially.

2.6- D M N is oxidized to naphthalene-2,6
- Synthetic fibers, films, etc. of excellent quality can be obtained from polyester obtained by providing a dicarboxylic acid and using the carboxylic acid as a raw material. Therefore, research on the production method of 2.6-DMN was conducted from an early stage, and it was
A method for producing 2.6DMN from DMN contained in C-cycle oil by crystallization separation or complex extraction separation (Japanese Patent Application Laid-open No. 7551/1983).

(Japanese Patent Publication No. 47-29893@publication), 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.

E berhardt, J. Org.
Chegt, 30. 82 (1965).

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

Special Publication No. 47-47379, USP 3,2
44,758).

Furthermore, recently, methods for obtaining dimethylnaphthalene by methylating naphthalene and monomethylnaphthalene with methanol (JP-A-60-172937, JP-A-63-83) have been developed.
No. 44, JP-A-63-14738M, 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.1. This article aims to obtain methylnaphthalene and dimethylnaphthalene, and describes a suitable manufacturing process for producing 2.6-DMN by crystallization separation from DMN obtained by methylating naphthalene and monomethylnaphthalene. I don't see any suggestions at all. There is only one thing, the inventor of this work
proposed a method for efficiently producing 2,6-DMN from a dimethylnaphthalene mixture. The proposal was an innovative method at the time, but by partially hydrogenating the raw DMN mixture, dimethyltetralin, which has two methyl groups in the same ring, and alkylbenzene, which are not partially hydrogenated, can be converted into two methyl groups. is a method for separating and producing 2.6-D M N by crystallization separation after separating dimethyltetralin with each attached to a separate ring by distillation, isomerizing it, and then dehydrogenating it,
It requires steps of partial hydrogenation and dehydrogenation, and cannot be called an efficient production method.

[Object of the Invention] 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 methylation of naphthalene in the presence of a catalyst.
, 6-dimethylnaphthalene, (I> Transmethylation of naphthalene in the presence of dimethylnaphthalenes to produce monomethylnaphthalenes and dimethylnaphthalenes, and at the same time, isomerization of dimethylnaphthalenes, 2. a first step of producing dimethylnaphthalenes and monomethylnaphthalenes rich in 6-dimethylnaphthalene; (II) a second step of separating the transmethylation/isomerization reaction mixture of the first step into naphthalene, monomethylnaphthalenes and dimethylnaphthalenes; (TV) Methylation of the monomethylnaphthalenes separated in the step (I) using a methylating agent to produce dimethylnaphthalenes, (TV) 2. Step (2) of separating the reaction mixture into unreacted monomethylnaphthalenes and dimethylnaphthalenes, and (V) separating the dimethylnaphthalenes obtained in step (1) and/or the dimethylnaphthalenes separated in step (2). A method for producing 2,6-dimethylnaphthalene, comprising a step V of separating 6-dimethylnaphthalene.

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. 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 dimethylnaphthalenes are isomerized in the presence of naphthalene, and at the same time as the isomerization, naphthalene is transmethylated to produce monomethylnaphthalenes.

The present invention will be explained in detail below.

<First Step> This step is a step in which naphthalene is transmethylated in the presence of dimethylnaphthalenes and, at the same time, dimethylnaphthalenes are isomerized.

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

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.

Further, it is possible to feed the residue containing trimethylnaphthalene separated in the below-mentioned steps (1) and (2) and/or the unreacted naphthalene separated in the below-mentioned step (2).

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. Crystalline aluminosilicate zeolites having an elementalization of s;/Ai in the range of 5 to 100 are preferred. Crystalline aluminosilicate zeolite described in JP-A-60-38331 (published on February 27, 1985) is preferred. Such a catalyst has a molar ratio of 5iOz/A polishing 203 of 10
~100 and a specific xI! It is a crystalline aluminosilicate zeolite with 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 at, preferably from normal pressure to 10 at. 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. naphthalene, dimertine naphthalenes,
The contact of trimethylnaphthalenes is caused by the weight hourly space velocity (W
H8V) in the range of 0.1 to 20, preferably 0.5 to 3
This can be done within the range of Here, WH3V is a catalyst (
g) represents the total amount of contact (g) of components involved in the reaction such as naphthalene and dimethylnaphthalene per unit time (hr).

In this step, dimethylnaphthalenes in which the composition of 2,6-dimethylnaphthalene is less than or equal to the thermodynamic equilibrium composition among all dithylnaphthalenes can be fed. Also 2,
Dimethylnaphthalenes having a molar ratio of 6-dimethylnaphthalene/2,7-dimethylnaphthalene of 0.72 or less can be fed.

<Step (ii)> This step is a step in which the reaction mixture produced in step (ii) is separated into naphthalene, monomethylnaphthalenes, and dimethylnaphthalenes, respectively.

For separation, conventional means such as distillation and recrystallization can be used. The unreacted naphthalene separated in this step can be used as feed to the second step. 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 (2).

Step (2) This step is a step in which the monomethylnaphthalenes separated in the step (2) are methylated using a methylating agent.

The preferred catalyst used in this step is a catalyst containing crystalline aluminosilicate zeolite. Preferably, it is a crystalline aluminosilicate zeolite catalyst having a Si 02 /Al2O3 molar ratio of 5 to 100. More preferably, Japanese Patent Application Laid-open No. 60172937 (Showa 60
It is a catalyst described in Japanese Patent Application Laid-Open No. 112527/1983 (published on September 6, 1988) or Japanese Patent Application Laid-open No. 112527/1983 (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 in the membrane, such as methanol, methyl chloride,
Methyl bromide, dimethylneal, etc. are preferred, with methanol or dimethyl ether or mixtures thereof being most preferred. The methylating agent is used in an amount of 0.01 to 2 times, preferably 0.01 to 2 times the mole of monomethylnaphthalenes.
．． It is advantageous to use the monomethylnaphthalene in an amount of 0.5 to 1 mole, and it is particularly preferable to use monomethylnaphthalene in excess of the methylating agent in order to suppress side reactions.

In the method of the present invention, the zeolite-containing catalyst, monomethylnaphthalenes, and methylating agent are contacted in the gas phase or liquid phase at a weight hourly space velocity (WH8V) 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 t) of monomethylnaphthalenes and methylating agent per unit time (hr) per zeolite unit (SF). Preferred WH8V 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, when the WH8V value exceeds 100, 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 it is usually normal pressure to increased pressure, for example, 1 to 30 KG.
, preferably at a pressure of 1 to IOK G.

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 (2)> This step is a step in which the dimethylnaphthalenes produced in the step (1), unreacted monomethylnaphthalenes, 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.

The unreacted monomethylnaphthalenes and methylating agent obtained by the separation can be recycled to the second step. Dimethylnaphthalenes are fed to the next step V,
2. Separate 6-dimethylnaphthalene.

<Step V> This step is a step of separating 2,6-dimethylnaphthalenes from dimethylnaphthalenes. The dimethylnaphthalenes separated in the above-mentioned 1st step and 2nd step 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 of step (1) and step (2) can also be performed by the same step.

<Process chart> 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 (2) are performed in the same step.

[Effects of the Invention] According to the present invention, monomethylnaphthalenes are produced by isomerizing dimethylnaphthalenes in the presence of naphthalene, transmethylating the naphthalene simultaneously with the isomerization, and isomerizing only dimethylnaphthalenes. It became possible to reduce the loss of methyl groups caused by oxidation. 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 To a solution of 4259 sodium hydroxide dissolved in 8.51 g of pure water, ssog of aluminum sulfate was gradually added with stirring to form a homogeneous solution. After further adding 1 Kg of common salt, 5 Ks of silica sol (S i O 2 3 % by weight) was added with vigorous stirring to obtain a reaction mixture.

This mixture, 3819° tetrapropylamine, 327 g of propyl bromide and 500 g of methyl ethyl ketone were added.
The mixture was placed in a 201 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 fil of pure water, it was dried at 100° C. all day and night, and further dried at 50° C.

The base zeolite is calcined for 2 days in an air atmosphere at ℃.
1.3υ was obtained. The silica-alumina molar ratio of this product was 26.2.

200 liters of the base zeolite obtained in this way,
The slurry was added to 800 d of water in which sodium hydroxide of No. 409 was dissolved, stirred to make a uniform slurry, and charged into a stainless steel autoclave, heated to 180° C. and held for 8 hours while stirring.

After cooling, the contents were filtered, thoroughly washed with 5 scoops of pure water, and then dried at 100° C. overnight to obtain 135 gr of cake. The silica-alumina ratio of this product was 16.8, and the x1 diffraction pattern was substantially that of the crystalline aluminosilicate zeolite shown in Table 1.

This was brought into contact with 1N of 10% ammonium chloride aqueous solution three times while heating to 70°C to exchange ions with NH4'' ions, filtered, washed, dried, and then calcined at 500°C for 8 hours to convert it into H-type zeolite. did.

The H-type zeolite 1 layer and the alumina gel 1 layer were thoroughly mixed and formed into a size of 10 to 20 meshes.
Catalyst A was obtained by calcining at 50°C for 8 hours.

JLB silica sol (SiOz 30%> 13809, aluminum sulfate 1539, sodium hydroxide 1769.Water) Add the base zeolite 1059 used in Catalyst A above to the reaction mixture prepared from 3 times above, place it in a stainless steel autoclave, and stir. While doing so, the temperature was raised to 180° C. and maintained for 8 W#.

After cooling, the contents were filtered and thoroughly washed with pure water.
It was dried overnight at 00° C. to obtain 405 gr 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. 150 g of this crystalline aluminosilicate zeolite was brought into contact with 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.

1 part by weight of this H-type zeolite and 1 part by weight of alumino gel were thoroughly mixed and formed into a size of 10 to 20 meshes.
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 2:1 of a 5% aqueous lithium nitrate solution, 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 Li-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.

Catalyst 1 commercially available Y type zeolite (H type manufactured by Tosoh) 1 heavy chain part and 1 part by weight of alumina gel were thoroughly mixed, formed into a size of 10 to 20 meshes, and calcined at 450°C for 8 hours to prepare catalyst D@ Obtained.

XI! Lattice spacing d (in) 2, % Table 1 Diffraction angle 2θ 158°22.05 238°243° Relative intensity (1/Io) Medium weak ~ Medium weak Weak Weak Weak ~ Medium Weak Weak Weak Weak Weak Weak ~ Medium Weak ~ Medium Weak Very Strong Very Strong Strong Strong Medium ~ Strong Weak Weak ~ Medium Weak ~ Medium Weak Weak ~ Medium Weak Weak ~ Medium Weak ~ Medium Weak ~ Medium The weak intensity (1/Io) is d (in) = 3.86 (
The relative intensity of each peak [I/Io (%)] is 100 when the intensity (io) of 2θ=23.05) is 100.
~60 is VS (very strong), 60-40 is S (strong)
, 40-20 is represented by M (medium), and 20-10 is represented by W (weak).

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 56/dG under hydrogen pressure, and the reaction temperature was 375°C.
Met. This reaction was continued for 4 hours and the reaction mixture was
I got g.

(Separation) This reaction mixture was distilled in a precision distillation device with 100 theoretical plates, and 230 g of low-boiling distillate containing mainly naphthalene (from the initial stream to
225°C), monomethylnaphthalene fraction 127g (225°C), monomethylnaphthalene fraction 127g (225°C)
5-250℃), dimethylnaphthalene distillate 435g (2
50-275°C) and 8g of hot residual oil. Approximately 98% 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 tank (ω).

(Methylation) Meanwhile, in another stainless steel flow-through reaction tube filled with catalyst 82009, the monomethylnaphthalene reservoir 127
630g of monomethylnaphthalene containing 9 and methanol 7
0 g of mixture was delivered in 3.5 hours.

The reaction pressure was 5 knots/iG under hydrogen pressure and the reaction temperature was 400°C.
Met.

(Separation) After separating the reaction mixture into 40 cc of water and 660 g of produced oil, the produced oil was heated in the same precision distillation equipment as above and distilled into 54 volumes of low boiling point distillate mainly containing naphthalene and monomethylnaphthalene.
59 (initial flow ~ 250℃), dimethylnaphthalene distillation tank 1
Separated into 10 g (250-275° C.) and 5 g hot residual oil. The low boiling distillate contained 3% naphthalene.

The dimethylnaphthalene distillate contained 25% 2.6-dimethylnaphthalene and 26% 2.7-dimethylnaphthalene. Let this be Tamasu+b+.

(Separation) Distillation tank (a) and distillation tank +b+ were heated to 70°C, and 545 g of a dimethylnaphthalene mixture obtained by dissolving them was gradually cooled to 30°C. 2,6-dimethylnaphthalene 19 was added thereto as a seed crystal, and the resulting cake was filtered by keeping it at 30° C. for 20 hours, and the cake was further washed with 200 d of methanol. The resulting solid was dried in vacuo at room temperature for 4 hours,
2.6-dimethylnaphthalene 339 with a purity of 97% was obtained.

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 naphthalene actually consumed is 375F after deducting the naphthalene generated in the methylation process. , the yield of 2,6-dimethylnaphthalene is 71% based on naphthalene.

Comparative Example A dimethylnaphthalene mixture containing 16% of 2,6-dimethylnaphthalene and 22% of 2,7-dimethylnaphthalene was fed into a stainless steel flow-through reaction tube filled with 200 g of catalyst A at a rate of 2009/H.

The reaction pressure was 50/ciG under hydrogen pressure and the reaction temperature was 375
It was ℃. This reaction was continued for 2 hours and 35 minutes to obtain 520 g of a reaction mixture.

When this reaction mixture was heated in a precision distillation device with 100 theoretical plates, 369% of low-boiling components (mainly naphthalene) (
Initial flow ~225℃), monomethylnaphthalene distillate 7GSF
(225-250℃), dimethylnaphthalene distillation tank 39
09 (250-275°C) and 24 g of hot residual oil.

This is a significant increase compared to the 8g of hot-temperature leftover pickles obtained in Example (2), and it can be seen that the loss is large.

In addition, in the transmethylation process, the number of methyl groups in the product of Example ① was 6.61 mol compared to 6.67 mol in the raw material, whereas it was 5 in the comparative example. It was only .92 mol, indicating that about 10% of the methyl groups were lost.

Example ■ (Transmethylation/isomerization) A stainless steel flow-through reaction tube filled with catalyst [2009] contained 56 parts by weight of naphthalene, 18% of 2.6-dimethylnaphthalene, and 25% of 2.7-dimethylnaphthalene. A mixed raw material containing a dimethylnaphthalene mixture at a ratio of 44 parts was fed at a rate of 200 g/hr. The reaction pressure was 5Kg/sfG under hydrogen pressure and the reaction temperature was 290℃.
Met. This reaction was continued for 3.5 hours to form reaction mixture 1.
00g was obtained.

(Separation) This reaction mixture was heated in a precision distillation device with 100 theoretical plates, and 322 g of low-boiling distillate containing mainly naphthalene (from the initial stream to
225℃), monomethylnaphthalene distillate 1539 (2
25-250℃), dimethylnaphthalene fraction 2159
(250-275°C) and 10 g of hot residual oil.

97% of the low boiling distillate was naphthalene.

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 773 g of monomethylnaphthalene and 879 g of methanol, including 153 g of the above monomethylnaphthalene distillate, was fed into a stainless steel flow-through reaction tube filled with catalyst C2009 over 4.5 hours. The reaction pressure was 5 K under hydrogen pressure.
g/cm G and the reaction temperature was 400 °C.

(Separation) After separating the obtained reaction mixture into 50 cc of water and produced oil 8105F, the produced oil was soaked in the same precision distillation equipment as above, and the low boiling point components 6489 (initial stream) mainly consisting of naphthalene and monomethylnaphthalene were separated. ~250°C), dimethylnaphthalene distillate 1529 (250~275°C) and hot residual oil 109.

1% of the low boiling distillate was naphthalene.

The dimethylnaphthalene distillate contained 48% of 2.6-dimethylnaphthalene and 26% of 2.1-dimethylnaphthalene. This is called tamasho (small).

(Separation) 367 g of dimethylnaphthalene mixture obtained by heating distillate (C) and distiller (small) to 70°C, melting, and mixing were gradually added to 30
Cooled to ℃. here 2,6-dimethylnaphthalene 1
9 was added as a seed crystal and kept at 30° C. for 5 hours, 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.
56 g of 7% 2,6-dimethylnaphthalene were obtained.

The amount of naphthalene substantially consumed in this example was 729, and the yield of 2,6-dimethylnaphthalene based on naphthalene was 63%.

Example ■ (Transmethylation/isomerization) In a stainless steel flow-through reaction tube filled with Catalyst A 2009, dimethyl containing 45 parts by weight of naphthalene, 17% of 2,6-dimethylnaphthalene, and 24% of 2,7-dimethylnaphthalene. A mixture containing the naphthalene mixture in the proportion of parts by weight was fed at a rate of 2009/hr. The reaction pressure was 5 g/ajG under hydrogen pressure, and the reaction temperature was 375°C. This reaction was continued for 2.5 hours to obtain reaction mixture 5009.

(Methylation) Meanwhile, 420 g of monomethylnaphthalene and 4 ml of methanol were placed in a stainless steel flow-through reaction tube filled with 0.200 g of catalyst.
79 was fed in 2.5 hours. The reaction pressure was 1 under hydrogen pressure.
00/cdG and the reaction temperature was 400°C.

The reaction mixture was separated into 26 cc of water and 4409 ml of product oil.

(Separation) A total of 940 g of the two reaction mixtures obtained in the above transmethylation/isomerization step and methylation step was added to the theoretical plate 1.
00-stage precision distillation equipment, 1979 g of low-boiling components mainly consisting of naphthalene (initial year to 225°C), 41 Bg of monomethylnaphthalene distillate (225 to 250°C), and 41 Bg of dimethylnaphthalene distillate (2, 6, and 2 .7-dimethylnaphthalene 27% and 22% respectively) 3169 (
250-215°C) and 11 g of Kuroshio residual oil.

(Separation) The dimethylnaphthalene distillate was heated to 70°C, mixed, and gradually cooled to 30°C. 1 g of 2,6-dimethylnaphthalene was added thereto 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 399 with a purity of 97%.

In this example, the amount of naphthalene substantially consumed was 429, and the yield of 2,6-dimethylnaphthalene based on naphthalene was 74%.

[Brief explanation of the drawing]

1 and 2 show examples of process diagrams applicable to the manufacturing method of the present invention. "Parts by weight of the mixture" on page 29, line 2 of the Procedural Book Specification is corrected to read "Parts by weight of the mixture dated May 2, 1990."that's all

Claims (1)

[Claims] 1. Naphthalene is methylated in the presence of a catalyst to produce 2,6-
In producing dimethylnaphthalene, (I) transmethylating naphthalene in the presence of dimethylnaphthalenes to produce monomethylnaphthalenes and dimethylnaphthalenes, and at the same time isomerizing dimethylnaphthalenes to produce 2,6-dimethyl A plant that produces naphthalene-rich dimethylnaphthalenes and monomethylnaphthalenes.
Step I, (II) Step II of separating the transmethylation/isomerization reaction mixture of Step I above into naphthalene, monomethylnaphthalenes and dimethylnaphthalenes, (III) Step II of separating the monomethylnaphthalenes separated in Step II. a third step of producing dimethylnaphthalenes by methylation with a methylating agent; (IV) a fourth step of separating the methylation reaction mixture obtained in the third step into unreacted monomethylnaphthalenes and dimethylnaphthalenes; and (V) a V step of separating 2,6-dimethylnaphthalene from the dimethylnaphthalenes obtained in the IV step and/or the dimethylnaphthalenes separated in the II step. , 6-dimethylnaphthalene manufacturing method.