JPH02264733A - Preparation of 2,6-dimethylnaphthalene - Google Patents

Abstract

PURPOSE:To readily and profitably prepare the subject highly pure compound substantially not containing impurities such as sulfur and useful as a raw material for polyethylene naphthalate by subjecting a heavy naphtha having a specific amount of sulfur content, etc., as a raw material to a catalytic reformation reaction. CONSTITUTION:A heavy naphtha containing 5-20wt.% of a distillate having boiling points of 170-210 deg.C as a heavy oil distillate, a sulfur content of <=1ppm and a nitrogen content of <=1ppm is subjected to a catalytic reformation reaction to prepare a catalytically reformed oil having a sulfur content of <=1ppm and a nitrogen content of <=1ppm, which is mixed with 10 volume parts of a mixture of methanol and 1-butanol per volume part of the prepared 2,6- dimethylnaphthalene-containing oil and cooled at -5 to 5 deg.C to separate the solid 2,6-dimethylnaphthalene useful as a raw material for high quality engineering plastics.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to the production of 2,6-dimethylnaphthalene, which is useful as a raw material for polyethylene naphthalate. (Hereinafter, dimethylnaphthalene will be abbreviated as DMN.

) (Prior art and problems to be solved by the invention) As an engineering plastic, polyethylene naphthalate has the characteristics of high heat resistance and high breaking strength.
It is attracting attention as a new material, and currently one of its raw materials, high purity 2. [Due to difficulty in obtaining 1-DMN, development has stalled.

2.6-DMN is a hydrocarbon with a boiling point of 262°C and a melting point of 112°C, and is contained in various petroleum or coal tar-based fractions as a mixture with other DMN isomers. Various methods such as concentration 2 separation and purification 1 have already been studied. For example, the fraction obtained by fractional distillation of coal tar contains DMN, but coal-based fractions generally contain large amounts of heteroatoms such as sulfur. No.-230735, JP-A-62-2H73
No. 6, JP-A No. 62-2: 10737, desulfurization or denitrification becomes an important issue when using hydrocarbon compounds. Further, catalytic cracking oil of petroleum also contains DMN, but this fraction also usually contains several hundred ppm of sulfur. Moreover, the sulfur and nitrogen content contained in these coal tar-based or catalytic cracked oil-based DMN fractions are mainly contained as compounds with a heterocyclic structure, and two coexisting two
, 6-DM N It is not easy to perform desulfurization and denitrification that satisfies the quality of 2,6-DM N, which is a raw material for synthetic polymers, without affecting 2,6-DM N.

However, when producing polyethylene naphthalate using 2,6-DMN as a starting material, the sulfur and nitrogen content contained as impurities can have an adverse effect on the coloring of the product, the physical properties of the product, and the formation of by-products. It is required that highly purified 2.6-D M N be sufficiently purified in order to give a 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 with a high octane number and in the production of aromatics used as raw materials for petrochemicals. However, this reaction consists of various complex reactions, but the main reaction is to perform cyclodehydrogenation reaction, isomerization reaction, and hydrogenolysis reaction using hydrocarbons with 8 to 10 carbon atoms as raw materials to produce aromatic compounds. The purpose is to manufacture.

Normally, heavy aromatics tend to cause a coke formation reaction as a side reaction, which causes a decrease in catalyst activity.If the number of carbon atoms is 11 or more, it tends to cause a sudden decrease in catalyst activity, so they can be used as raw materials for DMN. Hydrocarbons having a carbon number of more than it are not used.

Generally, for catalytic reforming of naphtha, the boiling point is 70 to 170℃.
The fraction is used as a source of gasoline or in the production of aromatics for petrochemicals such as benzene and xylene.

However, when naphtha with a normal boiling point range is used as a raw material, the DMN fraction produced is extremely small;
It is not suitable as a manufacturing raw material. However, as mentioned above, it is known that it is difficult to maintain the activity of the catalyst in a high-boiling-point fraction due to carbonaceous substances produced as by-products during the reforming reaction.

Thus, conventionally it has been impossible to industrially produce DMN using petroleum fractions as raw materials.

In view of the above-mentioned facts, as a result of intensive studies, it was discovered that by adding the following boiling point fractions, the production of DMN can be significantly increased by the catalytic reforming method without affecting the catalyst.

On the other hand, there are 10 types of isomers of DMH, but all of these are mixed in petroleum-based feedstock oil and coal tar-based feedstock oil, and their physical and chemical properties are similar. Separation is extremely difficult.

Traditionally, precision distillation has been used as a separation method, and recently,
Separation method by complex formation (for example, Japanese Patent Publication No. 47-29894)
(No.) and pressure crystallization method (Japanese Unexamined Patent Publication No. 63-275528) have been studied. However, the precision distillation method does not provide sufficient separation, the complex formation method is complicated to operate, and the pressure crystallization method is not suitable for performance unless the concentration of 2,6-D MN exceeds a certain level. could not. As a result of various studies to deal with this fact, it was discovered that 2,6-DMN can be selectively extracted and concentrated by using alcohol at a specific mixing ratio. By utilizing the present invention, and further by combining it with subsequent steps, it becomes possible to easily produce highly purified 2.6-DMN.

(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 proportion of heavy fraction, and from which 2.6-D The present invention provides a method for producing high-purity 2.6-D MN that contains almost no impurities such as sulfur and nitrogen by separating MN.

That is, a DMN-containing fraction is obtained by catalytically reforming naphtha containing a heavy fraction, and 2.6-D M
A method for separating N, characterized in that a petroleum-based catalytically reformed oil having a sulfur content of 1 ppff1 or less and a nitrogen content of 1 ppm or less is used as the raw material DMN-containing oil.
This is a manufacturing method. That is, the petroleum-based heavy naphtha content contains a fraction with a boiling point of 170 to 210°C at 30% by volume or less, preferably 5 to 20% by volume, and has a sulfur content of 1. ppm or less,
It is preferable to use heavy naphtha as a raw material containing 1 ppm or less of nitrogen, more preferably 0.5 ppm or less, and catalytically reform this using a conventional method.

At this time, the catalytic reforming reaction is carried out using, for example, a commercially available platinum catalyst supported on alumina or a platinum rhenium catalyst at a temperature of 4.
50-550°C, pressure 5-40 kg/cd.

Hydrogen/hydrocarbon molar ratio 2-7. Liquid space velocity 0.5~4h
This reaction increases the DMN content by more than 10 times compared to the usual case.

The method for separating 2.6-D M N is not particularly limited, but can be arbitrarily selected within the range that can achieve the object of the present invention.

For example, the reaction product can be distilled to a boiling point of less than 200°C and 200°C.
Divided into fractions above 00°C, the former is used as a regular gasoline source,
Alternatively, it is used as a raw material for producing aromatics. 200
It is used as a raw material for DMN distilled at temperatures above ℃.

The thus obtained fraction at a temperature of 200°C or higher is heated at a reflux ratio of 10
Precise distillation is performed under normal pressure from No. 1 to 50/1.10 ma+Hg to obtain a fraction having a D M N of 75% by weight or more, preferably 85% by weight or more. Usually this includes 2,6-DM
It contains 5 to 30% by weight of N. Furthermore, D M N 7
If it is less than 5% by weight, the subsequent separation operation will be complicated.

The DMN-concentrated fraction is heated to 10°C or lower, preferably from -5 to
It is cooled to 5° C. and crystals mainly composed of 2,6-DM N are separated. Considering the recovery of D M N as a crystal,
The lower the temperature, the higher the recovery rate.
As the amount of DMN crystallized increases, the selectivity of 2,6-DMN deteriorates.

However, by using specific solvents according to the present invention, the recovery and selectivity of 2,6-DM N can be increased.

According to this method, not only catalytic reformed oil but also 2,6-DM
As long as it is a liquid hydrocarbon containing 5 to 70% by weight of N, for example, cracked oil, coal tar oil, etc. can be used.

The solvent to be used is preferably alcohol, such as methanol, ethanol, propatool, butanol or ethylene glycol, which may be used alone or in combination. However, shotically, DMN is soluble in alcohol to some extent, and the longer the alkyl group of the alcohol, the higher the solubility.

Therefore, in terms of recovery rate, it is better to use a small amount of methanol, but by using a mixed alcohol of methanol and other alcohols, 2,6-DM
It has been found that both the N recovery rate and the selectivity are improved.

Among these, a mixture of methanol and 1-butanol is particularly effective when used as a solvent. The mixing ratio of methanol and 1-butanol is 1 to 10 parts by volume of methanol to 1 part by volume of 1-butanol, and a mixing ratio of 3 to 6 parts by volume is particularly preferred. 2.1 to 10 parts by volume of this mixed alcohol per 1 part by volume of DMN solution,
In particular, by adding 3 to B capacitance parts, 2.6-D
The recovery rate of M N and the concentration of 2°8-D M N can be increased.

Alternatively, 2,6
- DMN can also be highly concentrated. Zeolite substituted with metal ions may also be used.

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

For example, it is possible to highly purify 2.6-D M NO by performing crystallization again using the solvent used in the concentration step, or by performing pressure crystallization at a temperature of 80 to 12
High purity 2,6-DMN can be obtained by carrying out the reaction at 0°C and a pressure of 500 to 2000 kg/c-.

Alternatively, by forming a complex, 2.6-D M
N may be separated and purified. For example, metanitrobenzoic acid, 2.4.7-dolinitro-9-fluorenone (hereinafter abbreviated as TNF), bisthiadiazolotetracyanoquinodimethane, trimellitic anhydride, pyromellitic anhydride, etc. Utilizing the fact that 6-DMN selectively forms complexes, it is possible to concentrate 2.6-DMN from a dilute solution or to obtain highly purified 2,6-DMN from a highly concentrated 2.6-DMN solution. Separation or purification of D M N.

Let's do it.

In this way, high purity 2,6-DMN with both sulfur content and nitrogen content of 1 ppm or less and a purity of 98.5% by weight or more is produced.
can be obtained.

(Example) The present invention will be described below with reference to Examples, but the present invention is not limited thereto.

(Reference example) The method for producing heavy naphtha used in the present invention is shown below.

Straight-run naphtha boiling point 70-220℃ (sulfur content 3801) pl
l = nitrogen content 1.5 ppm) using a commercially available alumina-supported cobalt molybdenum catalyst at a temperature of 320°C and a pressure of 20°C.
Kg/d.

Hydrorefining was carried out under the conditions of a hydrogen/hydrocarbon molar ratio of 300 scf/BM and a liquid hourly space velocity of 3.0 hr-1. The sulfur content of the produced oil was 0.3 ppm, and the nitrogen content was 0.4 ppm. The purified naphtha was distilled to prepare three types of samples with different boiling point ranges. The properties of samples A, B, and C are shown in Table 1.

Table 1 Example 1 For sample A shown in the reference example, a commercially available platinum catalyst supported on alumina was used at a temperature of 495°C and a pressure of 10.5 kg/cd.
.

Hydrogen/hydrocarbon molar ratio 4.0. Liquid space velocity 0.6hr-
A catalytic reforming reaction was carried out under the following conditions.

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

Precision distillation was performed using the catalytically reformed oil as a raw material. Using a distillation column with 30 theoretical plates, normal pressure up to the boiling point of 210°C,
Distillation was carried out at a reflux ratio of 1O/1. After that, this pot residual oil was charged into a distillation column with 100 theoretical plates, and the column top pressure was 10hmH.
A fraction (fraction A in Table 4) having a temperature of 254 to 266°C in terms of normal pressure was obtained at a reflux ratio of 30/1. This corresponds to 14% by weight of the pot residue. The DMN content in this fraction is 85.0
% by weight, and the 2,6-DMN content is 12.0% by weight, and the 2,6-DMN/2.7-DMN content is 12.0% by weight.
The ratio was 1.1. Methanol (
A mixed alcohol of 500 g of JIS K8891) and 100 g of 1-butanol (JIS K8810) was added, and the mixture was cooled to 0°C. The resulting crystals were separated by suction filtration.

The recovery rate of 2,6-DM N was 70% by weight, and the composition of the crystals was 2,6-DM N 71.2% by weight, 2.7
-DMN was 9.5% by weight, and others were 19.3% by weight. 5 g of this crystal was taken and dissolved in dichloromethane, 80 hg of TN F was added thereto, and the mixture was mixed and stirred at room temperature for 5 hours. The generated precipitate was filtered, washed with n-hexane, and then dried under reduced pressure. The solid containing this complex was
The mixture was thermally decomposed at 115 to 120° C. under a reduced pressure of 1.5 g, and the generated gas was cooled to recover separated oil.

As a result of analyzing the separated oil by gas chromatography, 2.
6-DMN 98.6% by weight, 2.7-DMN
0.6% by weight, and 0.6% by weight of others.

Example 2 Catalytic modification was carried out in the same manner as in Example 1 using Sample B shown in Reference Example. The properties of the produced oil are shown in Table 2.

Furthermore, the same operation as in Example 1 was performed using this reformed oil to obtain 2,6-DMN with a purity of 98.9% by weight.

Comparative Example 1 Catalytic modification was carried out under the same conditions as in Example 1 using Sample C shown in Reference Example. The properties of the produced oil are D as shown in Table 2.
The MN content was 1/10 or less of the example of the present invention.

Part 2 table Ru.

Table 3 Comparative Example 2.3 A fraction of petroleum-based catalytic cracking oil with a boiling point of 250 to 275°C 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 combined amounts of sulfur and nitrogen decreased, but at the same time, D M N also decreased.
5 The catalytically reformed oil produced in Example 1 was precision distilled in the same manner as in Example 1 to obtain a fraction containing DMN as the main component (Fraction A). Using this as a raw material, crystallization separation was performed at 0° C. by changing the ratio of solvent used.

The results are shown in Table 4.

Table 4 can be done.

Claims (1)

[Claims] 1. 5 fractions with a boiling point of 170 to 210°C as heavy oil fractions.
Contains ~20% by weight, sulfur content 1 ppm or less, nitrogen content 1
ppm or less heavy naphtha is subjected to a catalytic reforming reaction to obtain a catalytically reformed oil with a sulfur content of 1 ppm or less and a nitrogen content of 1 ppm or less, and 2,6-dimethylnaphthalene is separated from the catalytically reformed oil. A method for producing 2,6-dimethylnaphthalene. 2 1 to 1 volume part of 2,6-dimethylnaphthalene-containing oil mixed alcohol of methanol and 1-butanol
A method for concentrating 2,6-dimethylnaphthalene, which comprises adding 10 parts by volume, cooling to -5 to 5°C, and separating the produced solid. 3 As a method for concentrating 2,6-dimethylnaphthalene from the catalytic reformed oil, 2,6-dimethylnaphthalene 5-2
1 to 10 times the volume part of mixed alcohol of methanol and 1-butanol is added to 1 volume part of oil containing 0% by weight, and -5 to 5% by volume is added.
2. A method for producing 2,6-dimethylnaphthalene according to claim 1, characterized in that the solid produced is separated by cooling to .degree.