JP2649412B2 - Method for producing 2,6-dimethylnaphthalene - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to the production of 2,6-dimethylnaphthalene useful as a raw material for polyethylene naphthalate. (Hereinafter, dimethylnaphthalene is abbreviated as DMN.) (Prior art and problems to be solved by the invention) Polyethylene naphthalate is an engineering plastic that has features such as high heat resistance and high breaking strength, and is a new material. At present, development is stagnant because it is difficult to obtain high-purity 2,6-DMN, which is one of the raw materials.

2,6-DMN is a hydrocarbon having a boiling point of 262 ° C and a melting point of 112 ° C,
Included in various petroleum or coal tar fractions as a mixture with other DMN isomers. Various studies have been made on the concentration, separation, purification, etc. For example, while fractions obtained by fractionation of coal tar contain DMN, coal-based fractions generally contain a large amount of heteroatoms such as sulfur. 2307
As described in JP-A No. 35, JP-A-62-230736 and JP-A-62-230737, desulfurization or denitrification is an important issue when a hydrocarbon compound is used. DMN is also contained in the catalytic cracking oil of petroleum, and this fraction usually contains several hundred ppm of sulfur. In addition, the sulfur and nitrogen components contained in these coal-tar or catalytic cracking oil-based DMN fractions are mainly contained as compounds having a heterocyclic structure, and coexist. -A raw material for synthetic polymers without affecting DMN
It is not easy to perform desulfurization and denitrification to satisfy the quality of 2,6-DMN.

However, in the production of polyethylene naphthalate from 2,6-DMN as a starting material, sulfur and nitrogen contained as impurities have adverse effects such as coloring of the product or physical properties of the product and generation of by-products. It is required to be a highly purified high-purity 2,6-DMN. On the other hand, in the petroleum industry, the catalytic reforming reaction of naphtha is widely used in the production of gasoline for automobiles having a high octane number and the production of aromatics used as petrochemical raw materials. However, this reaction is composed of various complicated reactions, and the main reaction is to produce aromatic compounds by performing cyclization dehydrogenation, isomerization, and hydrocracking using hydrocarbons having 6 to 10 carbon atoms as raw materials. The purpose is to manufacture.

In general, the heavier aromatics are liable to cause a coke formation reaction that causes a decrease in the activity of the catalyst as a side reaction, and if the number of carbon atoms is 11 or more, the activity of the catalyst is likely to be sharply reduced. Hydrocarbons of number 11 or more are not used.

Generally, as a catalytic reforming of naphtha, a fraction having a boiling point of 70 to 170 ° C. is used, and is used as a gasoline material source or for the production of petrochemical aromatics such as benzene and xylene. However, when naphtha in this normal boiling point range is used as a raw material,
The resulting DMN fraction is extremely small and is unsuitable as a raw material for producing DMN. However, it is known that the activity of the catalyst is difficult to maintain due to the carbonaceous by-produced during the reforming reaction of the fraction having a high boiling point as described above.

As described above, it has conventionally been impossible to industrially produce DMN from a petroleum fraction as a raw material.

In view of the above facts, as a result of intensive studies, it has been found that the addition of a certain boiling point fraction can significantly increase the production of DMN without affecting the catalyst by the catalytic reforming method.

On the other hand, DMN has ten types of isomers, but these are all mixed in petroleum-based feedstocks and coal-tar-based feedstocks, and their physical and chemical properties are close to each other.
Separation is extremely difficult.

Conventionally, a precision distillation method has been used as a separation method, and recently, a separation method based on complex formation (for example, Japanese Patent Publication No. 47-29894).
Pressure crystallization method (JP-A-63-275528). However, the precision distillation method has insufficient separation, the complex formation method has a complicated operation, and the pressure crystallization method has a performance problem.
It could not be applied unless it had a 2,6-DMN concentration above a certain level. As a result of various studies to cope with such a fact, it has been found that 2,6-DMN can be selectively extracted and concentrated by using an alcohol having a specific mixing ratio. By utilizing the present invention, it is possible to easily produce high-purity 2,6-DMN by combining it with the subsequent steps.

(Means for Solving the Problems) The present invention is characterized by using a DMN fraction produced by catalytic reforming of heavy naphtha containing a certain fraction of a heavy fraction, from which 2,6-DMN Of high purity 2,6-D with almost no impurities such as sulfur and nitrogen
An object of the present invention is to provide a method for manufacturing MN.

That is, in a method of obtaining a fraction containing DMN by catalytically reforming naphtha containing a heavy fraction and separating 2,6-DMN therefrom, in a method of separating raw material DMN-containing oil, a sulfur content of 1 ppm or less and a nitrogen content of A method for producing 2,6-DMN, characterized by using a petroleum catalytic reforming oil of 1 ppm or less. That is, the petroleum heavy naphtha fraction contains a fraction having a boiling point of 170 to 210 ° C. in an amount of 30% by volume or less, preferably 5 to 20% by volume, and a sulfur content of 1 ppm or less, a nitrogen content of 1 ppm or less, and more preferably, Is 0.
It is preferable to use heavy naphtha containing 5 ppm or less as a raw material and subject it to catalytic reforming by an ordinary method.

At this time, for the catalytic reforming reaction, for example, a commercially available platinum catalyst supported on alumina or a platinum rhenium catalyst is used,
The reaction is performed at 450 to 550 ° C., at a pressure of 5 to 40 kg / cm ² , a hydrogen / hydrocarbon molar ratio of 2 to 7, and a liquid hourly space velocity of 0.5 to 4 hr ⁻¹ . By this reaction, the DMN content is increased 10 times or more as compared with the normal case.

The method of separating 2,6-DMN is not particularly limited, but can be arbitrarily selected within a range that can achieve the object of the present invention.

For example, the reaction product may have a boiling point of less than 200
The former is used as a normal gasoline material source or as a raw material for producing aromatics. The fraction at 200 ° C or higher is used as a DMN raw material.

The fraction obtained at 200 ° C. or higher obtained in this manner was subjected to a reflux ratio of 10/1.
Precise distillation under normal pressure from / 150 / 1,10 mmHg to obtain a fraction of DMN 75% by weight or more, preferably 85% by weight or more. Usually, this contains 5 to 30% by weight of 2,6-DMN. In addition, DMN75
When the amount is less than the weight%, the next separation operation becomes complicated.

The fraction obtained by concentrating DMN is 10 ° C. or less, preferably -5 to 5
After cooling to 2, the crystals mainly composed of 2,6-DMN are separated. Considering the recovery of DMN as a crystal, the higher the temperature is cooled, the higher the recovery rate is, but the more DMN that becomes a crystal, the worse the selectivity of 2,6-DMN is.

However, according to the present invention, by using a certain solvent, the recovery and selectivity of 2,6-DMN can be increased.

According to this method, not only the catalytic reforming oil but also a liquid hydrocarbon containing 5-70% by weight of 2,6-DMN, for example, a cracking oil or a coal tar oil can be used.

As the solvent to be used, alcohols are preferable. For example, methanol, ethanol, propanol, butanol or ethylene glycol can be used alone or in combination. However, DMN generally dissolves in alcohol to some extent, and the longer the alkyl group of the alcohol, the higher the solubility.

Therefore, regarding the recovery, it is better to use a small amount of methanol. However, by using a mixed alcohol of methanol and other alcohols, it is expected that both the recovery and selectivity of 2,6-DMN can be improved. I found it.

Among them, when a mixed solution of methanol and 1-butanol is used as a solvent, there is a specific effect. The mixing ratio of methanol and 1-butanol is 1-butanol 1
1 to 10 parts by volume of methanol is used per part by volume, and a mixing ratio of 3 to 6 parts by volume is particularly preferable. This mixed alcohol is used in an amount of 1 to 10 parts by volume, particularly 1 part by volume of the DMN solution,
By adding 3 to 6 parts by volume, the recovery of 2,6-DMN and the concentration of 2,6-DMN can be increased.

Alternatively, 2,6 by adsorption separation using zeolite
-DMN can also be highly concentrated. The zeolite may be replaced with a metal ion.

In this way, high-purity 2,6-DMN can be separated by various methods from the fraction in which the concentration of 2,6-DMN is concentrated to 70 to 90% by weight.

For example, it is possible to highly purify 2,6-DMN by performing crystallization again using the solvent used in the concentration step,
Alternatively, compression crystallization is performed, for example, at a temperature of 80 to 120 ° C. and a pressure of 500.
High purity 2,6-DMN can be obtained by performing the reaction at 20002000 kg / cm ² . Alternatively, by forming a complex,
6-DMN may be separated and purified. For example, metanitrobenzoic acid, 2,4,7-trinitro-9-fluorenone (hereinafter abbreviated as TNF), bisthiadiazolotetracyanoquinodimethane, trimellitic anhydride, pyromellitic anhydride, etc. Concentration of 2,6-DMN from a dilute solution or 2,6-DN utilizing the selective complex formation of 2,6-DMN
Separation or purification of high-purity 2,6-DMN from a high concentration solution of MN is performed.

Thus, high-purity 2,6-DMN having a sulfur content and a nitrogen content of 1 ppm or less and a purity of 98.5% by weight or more can be obtained.

(Example) Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto.

Reference Example A method for producing heavy naphtha used in the present invention is described below.

Straight run naphtha boiling point 70-220 ° C (sulfur content 380ppm, nitrogen content 1.5p
pm) using a commercially available alumina-supported cobalt molybdenum catalyst, at a temperature of 320 ° C., a pressure of 20 kg / m ² , and a hydrogen / hydrocarbon molar ratio of 300.
Hydrorefining was performed under the conditions of scf / Bbl and a liquid hourly space velocity of 3.0 hr ^-1 .
The produced oil had a sulfur content of 0.3 ppm and a nitrogen content of 0.4 ppm. The purified naphtha was distilled to prepare three kinds of samples having different boiling points. The properties of samples A, B and C are shown in Table 1.

Example 1 Sample A shown in Reference Example was contacted with a commercially available alumina-supported platinum catalyst under the conditions of a temperature of 495 ° C., a pressure of 10.5 kg / cm ² , a hydrogen / hydrocarbon molar ratio of 4.0, and a liquid hourly space velocity of 0.8 hr ^−1. A reforming reaction was performed.

 The yield of the catalytic reforming oil is shown in Table 2.

Precision distillation was performed using the contact reforming oil as a raw material. Using a distillation column having 30 theoretical plates, distillation was carried out at a normal pressure and a reflux ratio of 10/1 up to a boiling point of 210 ° C. Then, the remaining oil in the kettle is
Set in a 100-stage distillation column, top pressure 100 mmHg, reflux ratio 30/1
Thus, a fraction at a normal pressure of 254 to 266 ° C. (fraction A in Table 4) was obtained. This corresponds to 14% by weight of the bottom oil. The DMN content in this fraction was 85.0% by weight, and the 2,6-DMN content was 12.
At 0% by weight, the ratio of 2,6-DMN / 2,7-DMN was 1.1. A mixed alcohol of 500 g of methanol (JIS K8891) and 100 g of 1-butanol (JIS K8810) was added to 100 g of the distillate, and the mixture was cooled to ° C. The resulting crystals were separated by suction filtration. The recovery of 2,6-DMN was 70% by weight, and the crystal composition was 71.2% by weight of 2,6-DMN, 9.5% by weight of 2,7-DMN, and 19.3% by weight. Take 5 g of these crystals, dissolve in dichloromethane, and add TNF3
00 mg was added and mixed and stirred at room temperature for 5 hours. The generated precipitate was separated by filtration, washed with n-hexane, and dried under reduced pressure.
The solid containing this complex was thermally decomposed at 15 to 120 ° C. under a reduced pressure of 15 mmHg, and the generated gas was cooled to recover the separated substance.

As a result of analyzing the separated oil by gas chromatography,
The content was 68.8% by weight of 6-DMN, 0.6% by weight of 2,7-DMN, and 0.6% by weight.

Example 2 The same catalytic reforming as in Example 1 was carried out using Sample B shown in Reference Example. The properties of the formed oil are shown in Table 2.

Further, the same operation as in Example 1 was performed based on this reformed oil to obtain 2,6-DMN having a purity of 98.9% by weight.

Comparative Example 1 Using the sample C shown in the reference example, catalytic reforming was performed under the same conditions as in Example 1. The properties of the produced oil are as shown in Table 2.
The DMN content was 1/10 or less of the examples of the present invention.

Comparative Examples 2 and 3 A fraction having a boiling point of 250 to 275 ° C. of petroleum catalytic cracking oil was hydrorefined using a commercially available alumina-supported cobalt molybdenum catalyst. The results are shown in Table 3.

As is clear from the results, the sulfur content and the nitrogen content are decreasing, but the DMN is also decreasing.

Comparative Examples 4 and 5 The catalytic reforming oil produced in Example 1 was subjected to precision distillation in the same manner as in Example 1 to obtain a fraction containing DMN as a main component (fraction A). Using this as a raw material, crystallization separation was performed at 0 ° C. while changing the solvent usage ratio. The results are shown in Table 4.

(Effects) According to the present invention, 2,6-DMN, which is useful as a raw material for high-performance engineering plastics using petroleum-based raw materials, can be produced with high purity, containing almost no impurities such as sulfur and nitrogen, and economically. Can be manufactured. Also, 2,6-D
By using a mixed alcohol of methanol and 1-butanol in the MN separation step, 2,6-DMN can be easily concentrated at a high recovery rate.

Claims (3)

(57) [Claims] 1. A catalytic reforming reaction of heavy naphtha containing 5 to 20% by weight of a fraction having a boiling point of 170 to 210 ° C. as a heavy oil fraction and having a sulfur content of 1 ppm or less and a nitrogen content of 1 ppm or less. A method for producing 2,6-dimethylnaphthalene, comprising obtaining a contact reforming oil having a content of 1 ppm or less and a nitrogen content of 1 ppm or less, and separating 2,6-dimethylnaphthalene from the contact reforming oil. 2. A solid produced by adding 1 to 10 parts by volume of a mixed alcohol of methanol and 1-butanol to 1 part by volume of an oil containing 2,6-dimethylnaphthalene and cooling to -5 to 5 ° C. A method for concentrating 2,6-dimethylnaphthalene. 3. A method for concentrating 2,6-dimethylnaphthalene from the catalytic reforming oil, wherein 2,6-dimethylnaphthalene 5 is concentrated.
1 to 10 parts by volume of a mixed alcohol of methanol and 1-butanol is added to 1 part by volume of an oil containing
2. The method for producing 2,6-dimethylnaphthalene according to claim 1, wherein a solid produced by cooling to 2 ° C. is separated.