JP2767993B2 - Process for producing dimethylnaphthalene isomer mixture with increased 2,6-dimethylnaphthalene concentration - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a dimethylnaphthalene isomer mixture, and more particularly, to a dimethylnaphthalene isomer mixture in which the concentration of 2,6-dimethylnaphthalene is increased. The method relates to a method for producing the same.

[Background Art] Dimethylnaphthalene, for example, 2,6-dimethylnaphthalene, is used as a raw material such as polyethylene naphthalate (PEN) having high heat resistance and gas barrier properties, and is a raw material containing a dimethylnaphthalene isomer mixture as a main component. Separated from oil.

Dimethylnaphthalene is a compound in which two methyl groups are bonded to a naphthalene skeleton, and has various isomers.
Therefore, the concentration of individual isomers was low, and the effective use of the isomer mixture after separation of the required isomers was necessary. For example, the thermodynamic equilibrium concentration of 2,6-dimethylnaphthalene in the total dimethyl form is about 14%, and in order to effectively utilize the raffinate after separation, the concentration of the 2,6-dimethyl form is increased. A conversion reaction, such as isomerization or transalkylation, was required.

Such isomerization or transalkylation reaction is carried out by 1
It relates to the transfer of a substituted alkyl group within one molecule or the transfer of a substituted alkyl group between two types of molecules, and is usually performed using various solid acid catalysts such as aluminosilicate and zeolite (for example, Kozo Tanabe et al., “New Solid Acids and Base
s "Kodansha-Elsevier, 1989, etc.) or a gaseous or liquid phase under a hydrogen atmosphere using a Lewis acid catalyst comprising a metal halide such as aluminum chloride. As a method for obtaining 2,6-dimethylnaphthalene, for example, JP-A-63-147
37, JP-A-63-14738, JP-A-63-8344, etc., and faujasite-type zeolites are known to exhibit high activity in the reaction for producing a dimethylnaphthalene isomer mixture from the structure thereof. .

[Problems to be Solved by the Invention] However, such a faujasite-type zeolite has a supercage, that is, a structure having large voids inside the pores, so that clogging occurs due to coke precipitation inside the pores. There is a problem that the reaction activity is rapidly lowered. Also, iron-containing faujasite-type zeolites are known as faujasite-type zeolites (for example, JP-A-58-2214, JP-A-59-121115, 59-196745, JP-A-62-207713, JP-A-63-64914, etc.) are effective in using monocyclic aromatic compounds such as alkylbenzenes as disclosed in JP-A-1-135728. Although,
The effectiveness with polycyclic aromatic compounds such as alkylnaphthalene compounds has not been known.

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the dimethylnaphthalene isomer in which the concentration of 2,6-dimethylnaphthalene is smaller than the thermodynamic equilibrium concentration. By reacting the mixture in the presence of a specific catalyst, 2,6
-It has been found that a dimethylnaphthalene isomer mixture having an increased concentration of dimethylnaphthalene can be obtained stably over a long period of time, and has reached the present invention.

That is, an object of the present invention is to provide a method for efficiently obtaining a dimethylnaphthalene isomer mixture in which the concentration of 2,6-dimethylnaphthalene is increased.

The purpose is to increase the concentration of 2,6-dimethylnaphthalene by reacting a mixture of dimethylnaphthalene isomers whose concentration of 2,6-dimethylnaphthalene is smaller than the thermodynamic equilibrium concentration in the presence of a solid acid catalyst. A method for producing a dimethylnaphthalene isomer mixture, wherein the iron-containing faujasite-type zeolite is used as a solid acid catalyst. Is achieved.

 Hereinafter, the present invention will be described in detail.

In the present invention, the dimethylnaphthalene isomer mixture in which the concentration of 2,6-dimethylnaphthalene is smaller than the thermodynamic equilibrium concentration is 2,6-dimethylnaphthalene and its positional isomer, that is, 2,7-dimethylnaphthalene, 2 1,3-dimethylnaphthalene, 1,3-dimethylnaphthalene, 1,8-dimethylnaphthalene, 1,7-dimethylnaphthalene, 1,6-dimethylnaphthalene, 1,5-dimethylnaphthalene, 1,4-dimethylnaphthalene, and 1 A mixture of isomers containing at least one of the 9,9,2-dimethylnaphthalenes, wherein the concentration of 2,6-dimethylnaphthalene in all isomers is lower than the thermodynamic equilibrium concentration of the isomers.

The isomer mixture can be obtained from an aromatic hydrocarbon feedstock containing a dimethylnaphthalene isomer mixture by a known method, for example, column chromatography using a specific adsorbent and a desorbing agent, and further separation and crystallization. It can be easily obtained by a method of separating 2,6-dimethylnaphthalene (Japanese Patent Laid-Open No. 1-168628), which is combined with precipitation and separation. More specifically, it is preferable that the concentration of 2,6-dimethylnaphthalene in all isomers of dimethylnaphthalene is about 0.1 to 10%, preferably about 0.2 to 5%.

Further, in this isomer mixture, naphthalene, methylnaphthalene, ethylnaphthalene, methylethylnaphthalene, trimethyltephthalene, tetramethylnaphthalene,
It may contain other aromatic hydrocarbons such as biphenyl, methyl biphenyl, etc., but these are usually 50% or less, preferably 10% or less of the whole.

In the present invention, starting from such a mixture of isomers, 2,6-
This is to obtain a dimethylnaphthalene isomer mixture in which the concentration of dimethylnaphthalene is increased. Here, increasing the concentration of 2,6-dimethylnaphthalene means that the concentration of 2,6-dimethylnaphthalene in the isomer mixture as a starting material is higher than, for example, near or above the thermodynamic equilibrium concentration. Specifically, it means that the concentration of 2,6-dimethylnaphthalene in all the isomers of dimethylnaphthalene is about 10 to 20%.

In the present invention, an iron-containing faujasite-type zeolite is used as a solid acid catalyst used to obtain a dimethylnaphthalene isomer mixture having an increased concentration of 2,6-dimethylnaphthalene. Here, the iron-containing faujasite-type zeolite contains iron, and at least a part of the iron is incorporated in a skeleton or an ion-exchange site of a crystal or is covalently bonded. And the faujasite-type zeolite X and / or Y
It is preferable to use a type zeolite, and particularly to use a super-stabilized Y type zeolite (USY zeolite) which has been subjected to a dealumination treatment and has a low aluminum content.

Such iron-containing faujasite-type zeolites include, for example, those disclosed in JP-A-58-2214. That is, the ratio of silica to alumina (SiO ₂ / AI ₂ O ₃ )
Is an iron-containing faujasite-type zeolite obtained by contacting a crystalline aluminosilicate having a pH of 4.6 or more and an Na ₂ O content of 2.4% by weight or less with an aqueous iron salt solution having a pH of 2 or less.

As iron salts to be brought into contact with zeolite, ferrous chloride,
Examples include ferric chloride, ferrous nitrate, ferric nitrate, ferrous sulfate, ferric sulfate, and ammonium ferric sulfate.

The catalyst used in the present invention can be obtained by the above-mentioned method, and particularly preferably a catalyst in which a part of the contained iron is incorporated in the skeleton or is covalently bonded.

Then, the iron content in such catalysts as the Fe ₂ O _3, generally 1 to 10 wt%, and it is preferably a 4-8% by weight. Further, if necessary, an element such as molybdenum, tungsten, nickel or cobalt may be added to the catalyst of the present invention in the form of sulfide or oxide. The addition amount of such a compound may be about 0.5 to 20% by weight.

Iron in the iron-containing faujasite-type zeolite thus obtained usually exists in various forms such as sulfides, oxides or silicates, but is preferably present in the form of sulfides from the viewpoint of activity. . Therefore, in the present invention, before the iron-containing faujasite-type zeolite is subjected to the reaction, the iron-containing faujasite-type zeolite is preliminarily treated with a sulfur-containing gas, for example, an H ₂ -H ₂ S mixed gas to convert at least a part of the iron into a sulfide state. It is suitable for use in the reaction of the invention.

Although the iron-containing faujasite-type zeolite catalyst maintains high activity for a long time, it can be regenerated after the reaction by oxidation treatment with an oxygen-containing gas or hydrogenation treatment with a hydrogen-containing gas.

In the present invention, such an iron-containing faujasite-type zeolite is used as a catalyst, and from the above-mentioned dimethylnaphthalene isomer mixture in which the concentration of 2,6-dimernaphthalene is a value smaller than the thermodynamic equilibrium concentration value, 2 A dimethylnaphthalene isomer mixture having an increased concentration of 6,6-dimethylnaphthalene is obtained.In such a reaction zone, isomerization reaction, disproportionation reaction, conversion reaction such as alkylation reaction or transalkylation reaction occurs complicatedly, At the end of the reaction, a dimethylnaphthalene isomer mixture with an increased concentration of 2,6-dimethylnaphthalene is obtained as a result.

Regarding the conditions for such a reaction, the reaction temperature is not particularly limited, and may be generally selected from the range of 200 to 500 ° C, preferably 250 to 450 ° C. The reaction pressure is
It can be carried out under normal pressure or under pressure, and it can be carried out in either liquid phase or gas phase. The reaction method may be any of a batch method and a continuous method. In the reaction atmosphere, the catalytic activity is easily degraded in the absence of hydrogen. Therefore, it is preferable to carry out the reaction in the presence of hydrogen gas, particularly in the presence of a mixed gas of hydrogen gas and hydrogen sulfide gas, from the viewpoint of maintaining catalytic activity. . The concentration of hydrogen sulfide gas in such a mixed gas is usually 10% by volume or less, and preferably in the range of 0.01 to 5% by volume.

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.

 Parts and% indicate parts by weight and% by weight, respectively.

Example 1 Preparation of Catalyst Ultra-stable Y-type zeolite (USY zeolite, manufactured by Tosoh Corporation, composition [SiO ₂ 79.0%, Al ₂ O ₃ 21.1%, Na ₂ O
26%], SiO ₂ / Al ₂ O ₃ molar ratio 6.4, the alumina binder 15
Parts to 100 parts of anhydrous zeolite, 250-400μm particle size spherical)
8.0 g was added to 330 ml of 2 mol / 1 aqueous ammonium nitrate solution.
An ion exchange treatment was performed at 00 ° C. for 2 hours with stirring, followed by filtration and washing with warm water. Hereinafter, similarly, ion exchange treatment,
Filtration and washing were repeated twice. Next, after drying all day and night at a temperature of 120 ° C., the obtained NH ₄ type USY zeolite 32.4 g was obtained.
Was stirred in 260 ml of a 0.25 mol / 1 aqueous ferric nitrate solution at pH = 1.1 and at a temperature of 50 ° C. for 2 hours. The pH of the liquid after the treatment was 1.9. Next, the mixture is washed with warm water of 50 ° C., dried at a temperature of 50 ° C., and calcined at 500 ° C. for 3 hours in an air stream to obtain iron-containing USY zeolite (hereinafter, “Fe-USY”). Obtained.

Table 1 shows the X-ray diffraction pattern of this Fe-USY. Dimethylnaphthalene conversion reaction 2.9 g of the Fe-USY obtained above was charged into a glass reaction tube having an inner diameter of 20 mm, and a mixed gas of H ₂ -H ₂ S (0.2% by volume) 3.6 l / hr at 350 ° C. under normal pressure. For 30 minutes. Next, a dimethylnaphthalene isomer mixture in which the concentration of 2,6 dimethylnaphthalene in all dimethylnaphthalene was reduced to 2.8% by chromatographic separation at a flow rate of 6.0 g / hr was passed under this condition, and the reaction was carried out. The dimethylnaphthalene isomer mixture was analyzed by gas chromatography, and the amount of coke deposited on the catalyst was analyzed by combustion. The results are shown in Table 2.

Comparative Example 1 Y-type zeolite (manufactured by Tosoh Corporation, composition: SiO ₂ 67.0)
%, Al ₂ O ₃ 20.5%, Na ₂ O 12.4%), 13 parts of alumina binder to 100 parts of anhydrous zeolite, particle size of 250-400 μm spherical product) 37.3 g at 100 ° C. in 330 ml of 2 mol / 1 ammonium nitrate aqueous solution, The mixture was subjected to an ion exchange treatment under stirring for 2 hours, followed by filtration and washing with warm water. Hereinafter, the ion exchange treatment, filtration, and washing were similarly repeated twice. Next, at a temperature of 120 ° C
After drying all day and night with NH ₄ type zeolite obtained
Calcination was performed in an air stream at 5 ° C. for 5 hours to obtain H-type Y zeolite (hereinafter, referred to as “HY”). The thus obtained H-Y 2.9 g was filled in a glass reaction tube having an inner diameter of 20 mm,
The reaction was carried out by passing the same mixture of dimethylnaphthalene isomers as in Example 1 at 6.0 g / hr at 350 ° C. and a hydrogen flow rate of 3.6 l / hr under normal pressure.

 The results are shown in Table 2.

[Effects of the Invention] According to the present invention, a dimethylnaphthalene isomer mixture in which the concentration of 2,6-dimethylnaphthalene is increased can be stably obtained over a long period of time, and the industrial utility value is high.

Claims (3)

(57) [Claims] A dimethylnaphthalene isomer mixture in which the concentration of 2,6-dimethylnaphthalene is smaller than the thermodynamic equilibrium concentration is reacted in the presence of a solid acid catalyst to obtain 2,6-dimethylnaphthalene.
A process for producing a dimethylnaphthalene isomer mixture having an increased concentration of dimethylnaphthalene, comprising using an iron-containing faujasite-type zeolite as a solid acid catalyst, wherein the dimethylnaphthalene isomer having an increased concentration of 2,6-dimethylnaphthalene is used. Method for producing the mixture. 2. The method according to claim 1, wherein the iron-containing faujasite-type zeolite is an X-type and / or a Y-type zeolite. 3. The method according to claim 1, wherein the iron-containing faujasite-type zeolite is one in which the exchangeable cation site of the faujasite-type zeolite is ion-exchanged with iron.