JPH06184009A - Method for producing purified naphthalene - Google Patents

Abstract

(57) [Summary] [Objective] Purified naphthalene is obtained by efficiently removing these impurities from crude naphthalene containing an organic sulfur compound or an organic nitrogen compound. [Structure] Organic sulfur compounds and crude naphthalene containing organic sulfur compounds as impurities have a tetralin production rate of 3 or less.
%, The desulfurization rate (S conversion) is 99% or more, and the denitrification rate (N conversion) is 90% or less, and is slightly hydrorefined, and then charged into a continuous crystallizer. High-purity purified naphthalene is produced by purification. [Effect] According to the method of the present invention, a purified naphthalene having a high purity, a low sulfur content, and a low nitrogen content can be produced from a crude naphthalene containing benzothiophene and other impurities which are difficult to separate by a usual distillation or fractional crystallization method. You can In the production method of the present invention, the refining naphthalene yield can be made extremely high by circulating the by-product and mother liquor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing purified naphthalene by removing organic sulfur compounds such as benzothiophene and organic nitrogen compounds from crude naphthalene.

[0002]

BACKGROUND OF THE INVENTION Naphthalene is a drug, dye, surfactant,
It is an important substance as a raw material for phthalic anhydride, anthraquinone, alkylnaphthalenes and the like. Further, naphthalene oil and middle oil fraction obtained by distilling coal tar and coal liquefied oil,
The crude naphthalene separated and recovered by distillation, fractional crystallization or the like usually has a purity of about 95%, and is generally called 95% naphthalene. The crude naphthalene contains neutral components such as methylnaphthalene, basic components such as quinoline, acidic components such as methylphenol, and impurities such as sulfur compounds such as benzothiophene. As a method for producing purified naphthalene by removing these impurities, a hydrogenation method (JP-A-53-119856 and JP-A-54-1443) is used.
49), a recrystallization method using methanol (Japanese Patent Publication No. 47-4).
7020), an anhydrous aluminum chloride addition method (Japanese Patent Publication No. 4)
No. 7-47021, Japanese Examined Patent Publication No. 204212), combined use of fractional crystallization and clay treatment (Japanese Patent Publication No. 47-47023), oxalic acid addition method (Japanese Patent Publication No. 53-144557), acetic anhydride addition method (Japanese Patent Publication No. 6047). No. 3051), metal or metal oxide catalyst addition method (JP-A-54-81247, JP-A-53)
No. 147048) is known.

Of the above-mentioned conventional methods, the fractional crystallization method is insufficient in the removal of sulfur compounds. Therefore, when low sulfur naphthalene is required, it is necessary to add a desulfurization step separately. The anhydrous aluminum chloride addition method is a method of removing impurities by polymerizing or decomposing them, but the desulfurization effect is not always sufficient, and equipment corrosion by aluminum chloride or acidic substances by-produced in the reaction, or treatment of waste, etc. Therefore, there is a problem in economy. The purification by hydrogenation, that is, the hydrorefining method can be said to be excellent in that it has a high desulfurization rate, but if an attempt is made to increase the desulfurization rate, a large amount of by-products such as tetralin are produced.

[0004]

The present invention provides a technique for efficiently and economically producing naphthalene of high purity and low sulfur content.

[0005]

According to the present invention, crude naphthalene containing an organic sulfur compound and an organic nitrogen compound as impurities is used, and the production rate of tetralin is 3% or less and the desulfurization rate (S
(Converted) is 99% or more and the denitrification rate (N converted) is 90% or less, and hydrorefining is performed, and then this is charged into a continuous crystallizer for purification, and purified naphthalene is produced. Is the way.

The crude naphthalene used in the present invention is not limited as long as it contains an organic sulfur compound such as benzothiophene or an organic nitrogen compound such as quinoline as an impurity, but is preferably coal tar or coal liquefaction. It is a crude naphthalene separated from oil or the like and has a purity of about 90 to 99% by weight. A crude naphthalene called 95% naphthalene or the like is preferable.

Crude naphthalene is first subjected to hydrorefining under the conditions that the production rate of tetralin is 3% or less, preferably 2% or less, the desulfurization rate (S conversion) is 99% or more, and the denitrification rate (N conversion). ) Is 90% or less, preferably 80% or less (% is mol%). That is, this condition is a relatively mild condition, and de-chisso remains unsatisfactory. If the denitrification rate is higher than this, decomposition and polymerization of naphthalene and by-products such as tetralin and decalin increase.

Suppression of the by-product of tetralin can be achieved to some extent by making the hydrorefining reaction a mild condition, but tetralin is added to the reaction system to adjust the tetralin concentration at or near the equilibrium concentration under that condition. By setting the concentration, it can be effectively performed. The equilibrium concentration varies depending on the reaction conditions, but is greatly affected by the reaction temperature, and is, for example, 360 ° C., 15 kg / cm ² ·
G and hydrogen / naphthalene molar ratio = 2, tetralin / naphthalene (weight ratio) was 0.67, and 400
° C, 20 kg / cm ² · G, hydrogen / naphthalene molar ratio =
Under the condition of 2, the tetralin / naphthalene (weight ratio) is 0.28. Theoretically, if the raw material is mixed in such an amount, the proportion of tetralin will not increase. The equilibrium concentration can be calculated by a known method. Therefore, the production rate of tetralin can also be kept below a certain level by mixing the raw material crude naphthalene charged into the hydrorefining reaction step with tetralin in such an amount.

The hydrorefining reaction is carried out in the presence of a hydrogenation catalyst,
It can be performed under hydrogen pressure. As a catalyst,
6B group metals such as tungsten and molybdenum, cobalt,
It is possible to use a known hydrogenation catalyst containing one or two or more compounds of Group 8 metals such as nickel, palladium and platinum, or compounds such as oxides thereof. Preferably, Co-Mo
/ Alumina catalyst, Ni-Mo / Alumina catalyst, Ni-W
/ Alumina catalyst, Ni-Co-Mo / alumina catalyst. Moreover, you may use 2 or more types of these catalysts.
For example, two types of catalysts may be used by filling them in two layers. The reaction temperature varies depending on the type of catalyst, etc., but 330 to 440 ° C., preferably 360 to 400 ° C. is suitable, and the reaction pressure is 10 to 50 kg / cm ² ·.
G, preferably about 15 to 30 kg / cm ² · G is suitable. Further, hydrogen / naphthalene (molar ratio) is 1 to 5,
About 1.5 to 3.5 is preferable, and LHSV is suitable.
Alternatively, the residence time is expressed by LHSV and is 0.1 to 2.0 / h.
r, preferably about 0.5 to 1.5 / hr is suitable. When the reaction is carried out under such conditions, when tetralin is mixed with the reaction raw material, the mixing ratio of tetralin is 0.1 to 2.0, preferably 0.17 to 1.60 in terms of tetralin / naphthalene (weight ratio). It becomes a range of degree. And
From such a range, conditions are selected so that the tetralin production rate, the desulfurization rate, and the denitrification rate fall within the above ranges.

The hydrorefining reaction product is taken out of the reactor and charged into a continuous crystallizer. When a large amount of tetralin is contained in the product, it is distilled to obtain a tetralin concentration of 20% by weight. After the following, it is preferable to charge the continuous crystallizer. This is because the continuous crystallizer can effectively remove organic nitrogen compounds and the like, but the higher the concentration of tetralin, the lower the purification efficiency of the continuous crystallizer. In particular, when a large amount of tetralin is added to the reaction raw material, since the tetralin concentration is high, a fraction mainly containing tetralin is taken out and at least a part of this may be circulated as tetralin to be added to the reaction raw material. It is advantageous. When the concentration of tetralin in the hydrogenation reaction product is 20% by weight or less, it is advantageous to omit this distillation step.

The continuous crystallizer is capable of continuously or intermittently taking out the crystals precipitated by cooling it or the molten liquid obtained by melting the crystals, and has the same refining function as that of multi-stage crystallization. It has the function of That is,
It has a mechanism in which crystals once precipitated are melted and become crystals again, and the melt becomes a cleaning liquid for other crystals. Preferable examples of such a continuous crystallizer include JP-B-55-18521 and JP-B-54-
There are devices such as those described in Japanese Patent No. 34705. For example, the device described in the former has a cooling means at the top of the tower,
An apparatus having a heating means in the lower part, a mother liquor extraction port in the upper part and a target product extraction port in the bottom part, and a raw material supply port in the middle or upper part, a cooling crystallization part from the upper part of the column to the lower part, crystal refining Part and a crystal melting part are formed, crystals are precipitated in the cooling crystallization part, and when the precipitated crystals flow down through the crystal refining part, by countercurrent contact with a part of the melt generated in the melting part It is a device for continuous refining, reaching the lower melting portion, melting there, part of which is withdrawn as a product, and part of the product being refluxed as the molten liquid for refining. This device has a melting part at the bottom, and due to high temperature and low specific gravity, an unstable state occurs in the system, but this is well prevented by the action of the stirring blade. Of course, the continuous crystallizer that can be used in the present invention is not limited to such one. The operating conditions of such a device can be appropriately selected by those skilled in the art. In this case, the solvent may or may not be added, but it is advantageous to carry out without adding, since the mother liquor can be directly returned to the hydrogenation reaction step.

The purified naphthalene extracted from the continuous crystallizer is a highly pure naphthalene by effectively removing the organic nitrogen compounds and the like that could not be removed by hydrorefining. Further, the mother liquor is naphthalene in which impurities are concentrated, and it is advantageous to return this as a hydrorefining reaction raw material. When the impurities are concentrated by returning the total amount, a part of them is purged or the heavy components are separated by distillation and returned. However, impurities such as organic nitrogen compounds are decomposed in the hydrorefining reaction, so there is little concern about accumulation.

Therefore, the mother liquor extracted from the continuous crystallizer and the tetralin recovered from distillation and the like, if necessary, can be recycled almost entirely, and as a result, the product discharged out of the system is purified naphthalene. Other than the above, it is possible to use only a part of heavy substances and low-boiling substances, and the yield can be extremely increased. Similarly, the gas mainly containing hydrogen discharged from the hydrorefining step can be returned to the hydrorefining reaction step after removing hydrogen sulfide and the like.

[0014]

[Function] By first lightly hydrogenating and purifying,
Most of the highly reactive organic sulfur compounds are removed, but the removal of the less reactive organic nitrogen compounds can be limited to a part to prevent decomposition of naphthalene and side reactions. Then, by charging this into a continuous crystallizer and purifying it, the organic nitrogen compounds can be effectively removed, and a highly purified purified naphthalene can be obtained overall.

[0015]

EXAMPLES In the examples, "part" means "part by weight" and "%" means "% by weight". Example 1 Crude naphthalene (naphthalene purity 98.5%, nitrogen content (N conversion) 400 ppm, sulfur content (S conversion) 5500)
(ppm) 60 parts by weight and 40 parts by weight of tetralin, and Co-M
o / in the presence of alumina catalyst, 360 ° C., 15 kg / cm
^The hydrogenation reaction was performed under the conditions of 2.G and hydrogen / naphthalene (molar ratio) of 2.0. After the reaction product was separated into gas and liquid, the liquid was sent to a distillation column and distilled to extract about 41 parts of a fraction mainly containing tetralin and a small amount of a low boiling point such as ethylbenzene from the top of the column. Naphthalene distillate (sulfur content 40
ppm, nitrogen content 180 ppm), about 56 parts were taken out. As described in JP-B-55-18521, this has a cooling means at the top of the tower, a heating means at the bottom, a mother liquor outlet at the top and a product outlet at the bottom, and a raw material supply inlet at the middle stage. A device having a cooling crystallization part, a crystal refining part and a crystal melting part are formed from the upper part of the tower toward the bottom, and crystals are precipitated in the cooling crystallization part, and the precipitated crystals pass through the crystal refining part. When flowing down, it is continuously purified by countercurrent contact with a part of the melt generated in the melting part, reaches the lower melting part, where it is melted and part is extracted as a product, and partly Is an apparatus for refining by refluxing as the above-mentioned melt, and was charged into an apparatus having a stirring blade to continuously perform crystallization refining. in this case,
The product is extracted at 80 ℃, the mother liquor is extracted at 75 ℃, and the raw material is 100
Supplied at ° C. The extracted mother liquor was about 13 parts (87% naphthalene, 9% tetralin, 3% neutral oil, 1% basic Chisso compound). Purified naphthalene was about 43 parts, which contained 8 ppm sulfur, 2 ppm nitrogen, and 100 ppm tetralin.

Example 2 Crude naphthalene (naphthalene purity 98.5%, nitrogen content (N conversion) 400 ppm, sulfur content (S conversion) 5500)
(ppm) 65 parts with tetralin 35 parts mixed, Co-M
In the presence of o / alumina catalyst, 380 ° C., 20 kg / cm
^The hydrogenation reaction was performed under the conditions of 2.G and hydrogen / naphthalene (molar ratio) of 2.0. After the reaction product was separated into gas and liquid, the liquid was sent to a distillation column and distilled to extract about 38 parts of a fraction mainly containing tetralin and a small amount of a low boiling fraction such as ethylbenzene from the top of the column. Naphthalene fraction (sulfur content 1
About 59 parts were taken out. This was subjected to continuous crystallization purification in the same manner as in Example 1.
Mother liquor extracted (87% naphthalene, 9 tetralin
%, Neutral oil 3%, basic Chisso compound 1%) was 14 parts. Purified naphthalene was about 46 parts, which contained 3 ppm sulfur and 1 ppm nitrogen.

Example 3 To a mixture of 70 parts of crude naphthalene of Example 2 and 30 parts of tetralin, 25% of the crude naphthalene obtained by removing the heavy components in the mother liquor of Example 2 was added. This mixture had a sulfur concentration of 5520 ppm and a nitrogen concentration of 510 ppm. This was subjected to hydrogenation reaction under the same conditions as in Example 2. The sulfur content in the naphthalene fraction was 15 ppm, and the nitrogen content was 150 ppm. Then, this was subjected to continuous crystallization purification in the same manner as in Example 2. The purified naphthalene contained 3 ppm of sulfur and 2 ppm of nitrogen.

[0018]

According to the method of the present invention, purified naphthalene of high purity, low sulfur content and low nitrogen content is produced from crude naphthalene containing benzothiophene and other impurities which are difficult to separate by ordinary distillation or fractional crystallization methods. can do. The production method of the present invention, by circulating the by-product and mother liquor,
The refined naphthalene yield can be made extremely high.

Claims (6)

[Claims] 1. A crude naphthalene containing an organic sulfur compound and an organic nitrogen compound as impurities, the production rate of tetralin is 3% or less, the desulfurization rate (S conversion) is 99% or more, and the denitrification rate (N conversion) is 90%. A process for producing purified naphthalene, which comprises hydrorefining under the following conditions and then charging the same into a continuous crystallizer for purification. 2. The method for producing purified naphthalene according to claim 1, wherein the crude naphthalene is crude naphthalene having a purity of 90 to 98% by weight obtained from coal-based oil. 3. A continuous crystallizer comprises a mother liquor outlet in the upper part, a purified naphthalene melted in the lower part, and a part of the melted naphthalene used as a reflux liquid for purifying crystals falling from the upper part. The method for producing purified naphthalene according to claim 1, further comprising a heating device and a purified naphthalene outlet for taking out a part of the melted naphthalene as purified naphthalene. 4. The reaction liquid flowing out from the hydrorefining reaction step is distilled to separate a fraction mainly containing tetralin to a tetralin concentration of 20% by weight or less and then charged into a continuous crystallizer. The method for producing the purified naphthalene according to claim 1. 5. The purification according to claim 4, wherein at least a part of the tetralin-containing fraction and / or the mother liquor extracted from the continuous crystallizer is mixed with crude naphthalene charged to the hydrorefining reaction step. Method for producing naphthalene. 6. The method for producing purified naphthalene according to claim 1 or 5, wherein the production rate of tetralin is 3% by weight or less by controlling the ratio of crude naphthalene and tetralin charged to the hydrorefining reaction step.