JP2613650B2 - Method for producing β, β'-dimethylnaphthalene - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to the production of β, β′-dimethylnaphthalene which is industrially useful, for example, as a raw material for synthesizing β, β′-dicarboxynaphthalene which is a monomer of polyethylene naphthalate. More particularly, the present invention relates to a method for producing β, β′-dimethylnaphthalene by transmethylation.

More specifically, β, β′-dimethylnaphthalene, that is, an isomer of dimethylnaphthalene, in which two methyl groups are both in the β-position and two methyl groups are located on different 6-membered rings, Specifically, the present invention relates to a method for producing 2,6-dimethylnaphthalene and 2,7-dimethylnaphthalene.

BACKGROUND OF THE INVENTION Dimethylnaphthalene, particularly β, β′-dimethylnaphthalene, has been an industrially useful compound as a raw material for synthesizing β, β′-dicarboxylnaphthalene which is a monomer of polyethylene naphthalate.

By the way, as a method of obtaining these methyl-substituted naphthalenes, a method of synthesizing naphthalene and dimethylnaphthalene by transmethylating monomethylnaphthalene is conventionally known.

However, this method has no selectivity in the substitution position of the methyl group, and it has not been possible to selectively synthesize industrially useful β, β′-dimethylnaphthalene.

Therefore, development of a production method for selectively synthesizing β, β′-dimethylnaphthalene from naphthalene or monomethylnaphthalene has been demanded.

As a method for alkylating an aromatic compound, French Patent 2,291,957 discloses a method for synthesizing P-xylene from toluene and polyalkylbenzene with high selectivity.

According to this method, P-xylene is produced by stereoselectively substituting a methyl group at the para-position from toluene using polyalkylbenzene as an alkylating agent.

However, the raw material used in this method is toluene, which is a mononuclear aromatic hydrocarbon compound. In this method, there is a technical problem that a dinuclear aromatic hydrocarbon compound such as naphthalene is used as a raw material. There is no suggestion about ideology.

JP-A-63-14737 discloses a method in which naphthalene or monomethylnaphthalene is used as a raw material and transmethylated at a temperature of 150 to 500 ° C. to synthesize β, β′-naphthalene.

Here, methylbenzene substituted with 1 to 4 methyl groups is used as an alkylating agent, and when the reactions described in the above publication are examined in detail, all of the above reactions are performed in the gas phase. It is being done.

By performing a reaction in the gas phase using such an alkylating agent, for example, when β-methylnaphthalene is used, a methyl group is selectively introduced into the 6-position or the 7-position of the compound to obtain a β-methylnaphthalene. , Β'-dimethylnaphthalene. That is, by using this alkylating agent, methyl groups are preferentially introduced into the 6- and 7-positions of β-methylnaphthalene, and methyl groups are introduced into the 1,3-, 4-, 5- and 8-positions. Is less likely to be introduced. Therefore, by using this method, it is difficult to generate a derivative in which a methyl group is substituted at a position adjacent to a previously introduced methyl group, and as a result, β, β′-dimethylnaphthalene has a certain probability. Generated by

However, in this method, since the activity of the alkylating agent is low, the reaction temperature must be increased. Not only the reaction becomes a gas phase reaction, but also the selectivity of the reaction decreases when the conversion of naphthalene increases. . In order to keep the selectivity high, a method of lowering the conversion can be adopted. However, the amount of β, β′-dimethylnaphthalene synthesized substantially is small relative to the raw material, and the yield ( So-called conversion) is not sufficiently high.

An object of the present invention is to solve the problems associated with the prior art as described above, in which β, β′-dimethylnaphthalene can be selectively produced, and β, β′-dimethylnaphthalene can be selectively produced.
It is an object of the present invention to provide a production method capable of producing disimethylnaphthalene at a high yield.

SUMMARY OF THE INVENTION In the production method according to the present invention, the transmethylation reaction is carried out in a liquid phase in producing β, β′-dimethylnaphthalene by transmethylating naphthalene and / or monomethylnaphthalene using an alkylating agent. Along with
As the alkylating agent, a monocyclic aromatic hydrocarbon compound in which five or more methyl groups are substituted on a benzene ring is used.

According to the process for producing β, β′-dimethylnaphthalene according to the present invention, pentamethylnaphthalene and / or hexamethylnaphthalene are used as alkylating agents, and this reaction is carried out in the liquid phase. The reaction yield increases, and β, β′-dimethylnaphthalene is selectively synthesized at a high yield.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, a method for producing β, β′-dimethylnaphthalene according to the present invention will be described.

The method for producing β, β′-dimethylnaphthalene according to the present invention is a method for producing naphthalene and / or monomethylnaphthalene into β, β′-dimethylnaphthalene by using pentamethylbenzene and / or hexamethylbenzene to form a liquid phase. The reaction is.

 First, the raw materials will be described.

The raw material used in the present invention is naphthalene or monomethylnaphthalene, and these may be used alone or in combination. In the present invention, β-monomethylnaphthalene is specifically used as monomethylnaphthalene.

Next, the alkylating agent used in the present invention will be described.

In the present invention, such naphthalene or β-
An alkylating agent is reacted with monomethylnaphthalene.

The alkylating agent used in this manner is a monocyclic aromatic compound in which five or more methyl groups are substituted on the benzene ring, and specifically, a substituted product in which five methyl groups are substituted and It is a substituted product in which 6 methyl groups are substituted.

Here, in the case of a 5-substituted methyl group, a substituent other than hydrogen may be introduced into the remaining one substitutable position. In this case, the substitutable substituent is specifically Represents a halogen atom, a phenyl group, a phenyloxy group and the like.

Here, the phenyl group and the phenyloxy group may be those in which one or more substituents or atoms such as an alkyl group, a halogen atom or an alkyloxy group are substituted.

Therefore, as the alkylating agent, specifically, pentamethylbenzene, 2,3,4,5,6-pentamethyldiphenyl, 1-chloro-2,3,4,5,6-pentamethylbenzene,
Examples thereof include 2,3,4,5,6-pentamethyldiphenyl ether and hexamethylbenzene.

Of these, pentamethylbenzene and hexamethylbenzene are preferred.

These alkylating agents may be used alone or in combination.

According to the study of the present inventors, it has been found that as the alkylating agent that can be used in the present invention, when the number of substituted methyl groups is 5 or more, the yield of the alkylation reaction is increased. That is, since this alkylating agent is a compound having a group having a large steric hindrance such as an aromatic ring, a methyl group can be selectively introduced into the β-position during the transmethylation reaction, It is difficult to introduce a methyl group, and it is also difficult to generate a compound having three or more methyl groups.

This alkylating agent is used in an amount of 1 to 1000 mol%, based on naphthalene and / or monomethylnaphthalene as raw materials.
It is preferably used in an amount of 5-200 mol%.

In the present invention, the transmethylation reaction is performed in a liquid phase.

Specifically, the above-mentioned alkylating agent and naphthalene or monomethylnaphthalene can be reacted in a liquid state by heating, but the reaction is preferably carried out using a reaction solvent as shown below.

As a solvent that can be used in the present invention, a compound that can dissolve an alkylating agent, naphthalene and monomethylnaphthalene as raw materials, and dimethylnaphthalene as a reaction product, and is stable under the reaction conditions is used.

As a solvent that can be used when using a solvent,
Specific examples include nitrobenzene, dichlorobenzene, trichlorobenzene, and chlorobenzene.

 Of these, o-dichlorobenzene is preferred.

In the present invention, a specific alkylating agent is used as described above, and the transmethylation reaction using such an alkylating agent is performed in a liquid phase, so that a high selectivity as described above is obtained. β, β′-dimethylnaphthalene can be produced and the conversion of these compounds
That is, the yield also becomes very high.

The reaction temperature under the above conditions can be appropriately set within a range in which a liquid phase reaction can be performed using the above-described alkylating agent, and is usually a temperature of 200 ° C. or lower, Preferably, the temperature is in the range of 30-130 ° C.

The reaction time at this time varies depending on the reaction conditions, but is usually 0.1 second to 50 hours, preferably 5 minutes to 10 hours.

The process of the present invention may use, for example, a catalyst as described below.

Specific examples of the catalyst that can be used in the method for producing β, β′-dimethylnaphthalene according to the present invention include protonic acids, Lewis acids, and solid acids.

Here, as the protonic acid, specifically, hydrogen fluoride, sulfuric acid, pentaphosphorus dioxide, phosphoric acid, polyphosphoric acid, borofluoric acid, hydrofluoric acid, methanesulfonic acid, p
-Toluenesulfonic acid, hydrochloric acid, hydrogen bromide, trifluoromethanesulfonic acid and fluorosulfonic acid.

Examples of the Lewis acid include aluminum chloride, ferric chloride, tellurium chloride, tin chloride, bismuth chloride, zinc chloride, titanium chloride, antimony chloride, aluminum bromide, and boron trifluoride. Can be.

Further, as solid acids, silica-alumina, silica-
Titania, alumina-boria, zeolite, mordenite, and the like, and those in which a Group VIII transition metal is supported thereon can be given. When zeolite is used as the catalyst here, ZSM-5, L-type, Y-type, H-type and HY-type can be used.

Among these catalysts, Lewis acids are preferred, and aluminum chloride and aluminum bromide are particularly preferred.

In the transmethylation reaction as described above, these catalysts are generally used in an amount of 0.01 to 100 parts by weight, preferably 0.1 to 50 parts by weight, based on 100 parts by weight of the raw material.

By setting suitable conditions and reacting in this way, the conversion of the reaction raw material can be increased to 10 mol% or more, and the selectivity of β, β′-dimethylnaphthalene can be increased to 40 mol%.
Mol% or more.

After removing, for example, a solvent and a catalyst from the reaction product generated by the transalkylation reaction as described above, by utilizing a known method such as concentration, extraction, and recrystallization, the desired β, β '-Dimethylnaphthalene can be obtained.

The β, β′-dimethylnaphthalene thus produced can be used as a raw material for producing, for example, β, β′-dicarboxynaphthalene.

Effects of the Invention According to the method for producing β, β′-dimethylnaphthalene according to the present invention, β, β′-dimethylnaphthalene having high industrial and industrial utility is selectively obtained from naphthalene and / or monomethylnaphthalene, and the conventional method is used. It can be obtained in higher yield compared to the method.

Further, since such a reaction is performed in a liquid phase, there is an advantage that a complicated apparatus or operation is not required as compared with the case of a gas phase reaction.

Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 In 100 ml of o-dichlorobenzene, 8.52 g of β-methylnaphthalene and 1.62 g of hexamethylbenzene were added and dissolved, and then 1.60 g of aluminum chloride was added to this solution.

 This solution was heated to 70 ° C. and reacted for 5 hours.

The obtained reaction product was analyzed using gas chromatography.

 Table 1 shows the results.

Example 2 A reaction was carried out in the same manner as in Example 1, except that pentamethylbenzene was used instead of hexamethylbenzene.

The obtained reaction product was analyzed in the same manner as in Example 1.

 Table 1 shows the results.

Example 3 A reaction was carried out in the same manner as in Example 1 except that aluminum bromide was used instead of aluminum chloride.

The obtained reaction product was analyzed in the same manner as in Example 1.

 Table 1 shows the results.

Example 4 A reaction was carried out in the same manner as in Example 1 except for using 1.07 g of naphthalene instead of 8.52 g of β-methylnaphthalene.

The obtained reaction product was analyzed in the same manner as in Example 1.

 Table 1 shows the results.

Example 5 A reaction was carried out in the same manner as in Example 2 except for using 1.07 g of naphthalene in place of 8.52 g of β-methylnaphthalene.

The obtained reaction product was analyzed in the same manner as in Example 1.

 Table 1 shows the results.

Comparative Example 1 In Example 1, instead of hexamethylbenzene, 1,
The reaction was carried out in the same manner as in Example 1 except that 1.34 g of 2,4,5-tetramethylbenzene was used.

The obtained reaction product was analyzed in the same manner as in Example 1.

 Table 1 shows the results.

Claims (2)

(57) [Claims] (1) transmethylating naphthalene and / or monomethylnaphthalene with an alkylating agent to obtain β,
In producing β'-dimethylnaphthalene, the transmethylation reaction is carried out in a liquid phase, and the alkylating agent is a monocyclic aromatic hydrocarbon compound having five or more methyl groups introduced into a benzene ring. A process for producing β, β'-dimethylnaphthalene, characterized by using 2. The reaction temperature in the transmethylation reaction is as follows:
2. The method according to claim 1, wherein the temperature is 200 [deg.] C. or lower.