JP2817382B2 - Method for modifying alkyl naphthalene mixture - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for reforming an alkylnaphthalene mixture, and more particularly to subjecting an alkylnaphthalene mixture to a conversion reaction in the presence of a solid acid catalyst and hydrogen. And modifying the alkylnaphthalene mixture by the method.

[Prior Art] Among alkylnaphthalenes, compounds having a specific structure are widely used industrially. For example, 2,6-dimethylnaphthalene is used as a raw material such as polyethylene naphthalate (PEN) having a high gas barrier property.

However, the alkylnaphthalene mixture contains various compounds having various isomers. Therefore,
The concentration of useful specific compounds themselves is often low, so that an effective separation method is desired, and it is important to effectively use other components remaining after the compounds are separated.
For example, the thermodynamic equilibrium concentration of 2,6-dimethylnaphthalene in all the dimethylnaphthalene isomers is about 14%, and in order to effectively use the raffinate remaining after separation, the concentration of 2,6-dimethylnaphthalene must be determined. Of the alkylnaphthalene by a conversion reaction to increase the content of the alkylnaphthalene is required.

In the exchange reaction for such reforming, reactions such as isomerization, disproportionation, alkylation or transalkylation occur in a complicated manner, and usually, various solid acid catalysts such as aluminosilicate and zeolite (for example, Kozo Tanabe et a
l., “New Solid Acids and Bases”, Kodansha-Elsevie
r, 1989) or a Lewis acid catalyst comprising a metal halide such as aluminum chloride in a gaseous or liquid phase under a hydrogen atmosphere. Particularly, industrially, a solid acid catalyst which is easily separated from a product is often used industrially, and hydrocarbon vapor is often reacted under a hydrogen stream for the purpose of suppressing coking due to by-products of high boiling components.

[Problems to be Solved by the Invention] However, when the conversion reaction is performed by the above method, trace amounts of methane and other ethane, paraffinic hydrocarbons such as propane, ethylene, It has been found that olefinic hydrocarbons such as propylene are contained.

For example, when a dimethylnaphthalene mixture is used as a reaction raw material as an alkylnaphthalene mixture, ethylnaphthalene is usually contained as an impurity in the raw material, and it has been confirmed that light-boiling hydrocarbons are also generated from such impurities. As the number of carbon atoms in the alkyl group increases, hydrocarbons are more easily generated.

And the solid acid catalyst used for such a reaction also contributes to the activation of lower olefins as in the case of activating alkylnaphthalene. Therefore, the olefin by-produced from the reaction system and the alkyl naphthalene cause a reaction such as alkylation, and the alkyl naphthalene having a higher degree of substitution is generated.As a result, there is an obstacle in obtaining a desired modified alkyl naphthalene. Problem.

For example, when a conversion reaction is performed using a dimethylnaphthalene isomer mixture as a raw material, if the hydrogen gas is circulated as it is, a compound having a higher boiling point than dimethylnaphthalene isomer such as trimethylnaphthalene or trialkylnaphthalene is generated. As a result, the yield of the target compound, 2,6-dimethylnaphthalene, in this case is reduced.

[Means for Solving the Problems] Accordingly, the present inventors have conducted intensive studies to solve the above problems, and as a result, by removing olefins produced as by-products when using an alkylnaphthalene mixture as a starting material, an excellent method was achieved. The present inventors have found that alkylnaphthalene can be modified, and have reached the present invention.

That is, an object of the present invention is to provide a method for modifying an alkylnaphthalene mixture to obtain a specific alkylnaphthalene efficiently and continuously.

The object of the present invention is to provide a method for reforming an alkylnaphthalene mixture by subjecting the alkylnaphthalene mixture to a conversion reaction in the presence of a solid acid catalyst and hydrogen, after separating the alkylnaphthalene mixture from the conversion reaction product. It is easily attained by a method for reforming an alkylnaphthalene mixture, which comprises removing an olefin by-produced in the reaction from the gas phase of the above, and recycling the gas phase as hydrogen in the reaction.

 Hereinafter, the present invention will be described in detail.

The alkylnaphthalene in the present invention has at least one alkyl group on a naphthalene ring,
Di-, tri- and tetra-forms. As the alkyl group, a lower alkyl group preferably having about 1 to 5 carbon atoms,
That is, it is a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group or the like.

The alkyl naphthalene mixture in the present invention is generally an oil obtained from coal tar or a petroleum heavy oil and containing 50% or more of an alkyl naphthalene component, and is preferably a specific product obtained by collecting components having the same boiling point region by distillation. Is an alkylnaphthalene mixture.

As a specific alkylnaphthalene mixture, for example, a dialkylnaphthalene mixture is a dialkylnaphthalene component including various isomers having different alkyl group substitution positions, usually containing 50% or more, preferably 90% or more, and as other components, Usually, a small amount of monoalkylnaphthalene, naphthalene, biphenyl, indene, indane and the like are contained.

The conversion reaction of the present invention is based on a complicated reaction such as isomerization, alkylation, and transalkylation. When an alkylnaphthalene mixture is subjected to the conversion reaction as a raw material, the arrangement state of the alkyl group is changed and reformed. When an alkylnaphthalene mixture having various numbers of substituents is used as a raw material, a dialkylnaphthalene having two substituents is particularly advantageously reformed and produced.

When a dialkylnaphthalene mixture is used as a raw material and subjected to a conversion reaction, a modified mixture having a composition close to the thermodynamic equilibrium concentration of each isomer of dialkylnaphthalene is obtained.

The solid acid catalyst used in the present invention is not particularly limited as long as it is used for a known isomerization reaction or transalkylation reaction, etc., but preferably a solid acid catalyst containing zeolite as a main active component. The catalyst is good, and specific examples thereof include H-mordenite type, H-faujasite type or H-pentasil type zeolite (H-ZSM-5 type, H-ZSM-11 type, etc.), and particularly H-mordenite. It is preferable to use a catalyst selected from the group consisting of zeolite, H-faujasite type or H-ZSM-5 type zeolite (for example, JP-A-58-210031, CSP4783569, USP4783570, etc.). Note that some of the protons of these H-type (proton) exchanged zeolites may be ion-exchanged with metal cations.

The conversion reaction in the present invention, in the presence of such a solid acid catalyst,
This is performed by introducing an alkylnaphthalene mixture into a hydrogen atmosphere. Conditions for such a reaction include a reaction temperature of 300 to 500 ° C.
The reaction pressure is preferably from normal pressure to 30 KG under a hydrogen stream, and the feed rate (LHSV) of the alkylnaphthalene mixture is usually 0.
01 to 10 h ^-1 , the supply amount of hydrogen is 0.1 to 10 in molar ratio to hydrocarbon
It is good to make it 0 mol.

Next, the modified alkylnaphthalene mixture is separated from the conversion reaction product and removed outside the reaction system. In this case, the separation can be easily performed by cooling the reaction product after the reaction.

On the other hand, the hydrogen supplied to the reaction contains a small amount of olefin by-produced in the reaction, and if the hydrogen is circulated to the reaction process as it is, the olefin gradually accumulates, and a part of the olefin reacts. And affect the conversion reaction.

Therefore, in the present invention, the olefinic compounds contained and accumulated in the circulating hydrogen are removed.

The method of removal is not particularly limited, such as hydrogenation, hydrogen decomposition, polymerization, adsorption, and extraction of the olefin. The removal is performed by reacting a lower olefin with a hydrogenation catalyst and / or a catalyst having a hydrogenation ability. The method is preferred.

Examples of such a catalyst include metal catalysts such as nickel, cobalt, palladium, ruthenium, platinum, iridium and rhodium, and supported catalysts in which these metals are supported on a carrier. Preferably, a catalyst such as supported nickel, supported ruthenium, and supported platinum is used. Alumina is generally used as the carrier, but is not particularly limited thereto.

When using a supported catalyst, the amount of supported metal is usually 0.1 to 50.
%, And the conditions for this reaction are that the reaction temperature is usually 10%.
0-500 ° C, preferably 250-400 ° C, and the reaction pressure is usually normal pressure to 100KG. The supply rate (GHSV) of the gaseous reaction product is usually 100 to 100,000 h ^-1 , preferably 2,000 to 20,000 h ^-1 .

As other methods, zeolite, activated carbon, alumina, adsorption separation method using an adsorbent such as silica gel,
A palladium alloy membrane method using the property of selectively permeating hydrogen molecules can be used.

In the present invention, the olefin contained in the gaseous reaction product is converted to lower paraffin by the treatment, thereby removing the olefinic compound. The hydrogen containing the lower olefins from which the olefin has been removed is recycled to the above-mentioned conversion reaction zone and reused.

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to the following Examples as long as the gist is not exceeded.

The raw materials and reactants were analyzed by gas chromatography and gas chromatography mass spectrometer.

Reference Example 1 A dimethylnaphthalene mixture having a reduced concentration of 2,6-dimethylnaphthalene (0.9% of 2,6-dimethylnaphthalene, 89.6% of other dimethylnaphthalene isomers, and a small amount of other monoalkylnaphthalene, biphenyl, etc.) was separated by chromatography. Was used for the conversion reaction.

ZSM-5 type zeolite as a catalyst _{(SiO 2 / Al 2 O 3} = 32.
5) was calcined, then ion-exchanged to NH ₄ ⁺ type, and further calcined to be converted to H ⁺ type, and the obtained zeolite obtained by tableting was used.

The above catalyst (particle size) was placed in a hard glass reactor with an inner diameter of 20 mm.
10-20 mesh) 3.1 g (5.2 ml) is filled, a glass bead layer is filled on top of the catalyst layer, and the above dimethylnaphthalene mixture (DMN) is supplied by being vaporized and entrained in pure hydrogen gas. Then, the conversion reaction was carried out by flowing at a temperature of 390 ° C., a pressure of 10 kg / cm ² , H2 / DMN (molar ratio) = 25, and LHSV = 0.6.

The concentration of 2,6-dimethylnaphthalene in the total dimethylnaphthalene in the reaction product solution was improved to 13.2%. Ethylmethylnaphthalene was not detected.

On the other hand, the generated gas in the gas phase after the reaction product liquid separation is 0.4%
(99.6% hydrogen), and the organization is as follows:

Reference Example 2 The reaction was performed in the same manner as in Reference Example 1 except that hydrogen gas containing 2.5% of ethylene was used instead of pure hydrogen. went. As a result, the concentration of 2,6-dimethylnaphthalene in the dimethylnaphthalene isomer mixture was 13.0%. Generation of high boiling components such as naphthalene was confirmed.

Reference Example 3 A reaction was carried out in the same manner as in Reference Example 1 except that hydrogen gas containing 2.5% of methane was used instead of pure hydrogen.
No effect on the reaction was observed.

Example 1 Hydrogen gas containing the gas generated in Reference Example 1 was led to a hydrocracking catalyst and made harmless. The reaction was carried out at 360 ° C, 10 kg / cm ² and a hydrogen supply rate of 10,000 h ^-1 using a ruthenium catalyst supported on alumina (support rate: 0.5%). The proportion of methane in it reached 45%, revealing that at least some of the lower hydrocarbons were methanated. When a conversion reaction was performed in the same manner as in Reference Example 1 using such a hydrogen gas containing a lower hydrocarbon, no influence on the reaction was observed.

Comparative Example A reaction was conducted in the same manner as in Example 1 except that hydrogen containing the reaction product gas of Reference Example 1 was directly used instead of pure hydrogen, and the reaction of 2,6-dimethylnaphthalene in the reaction product solution was performed. Concentration in all dimethylnaphthale isomers is 13.0
%, And a little ethylmethylnaphthalene was detected. On the other hand, the composition of the reaction product gas was almost the same as in Example 1, but the amount of the product gas was 0.7% of the total hydrogen.
Increased.

[Effects of the Invention] According to the present invention, a desired dialkylnaphthalene can be efficiently obtained without accumulating an olefinic compound in a reaction system, which greatly contributes to the industrial production of the present invention.

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Claims (4)

(57) [Claims] 1. A method for modifying an alkylnaphthalene mixture by subjecting the alkylnaphthalene mixture to a conversion reaction in the presence of a solid acid catalyst and hydrogen, wherein the modified alkylnaphthalene mixture is separated from a conversion reaction product. A method for reforming an alkylnaphthalene mixture, comprising removing an olefin by-produced in the reaction from a gas phase and circulating the gas phase as hydrogen in the reaction. 2. The process according to claim 1, wherein the olefin is removed by contacting the gas phase with a hydrogenation catalyst and / or a catalyst having a hydrogenation capability. 3. The method according to claim 1, wherein the alkylnaphthalene mixture contains at least 50% of dialkylnaphthalene. 4. The method according to claim 1, wherein the conversion reaction is carried out in the gas phase.