JP2000128809A - Recovery of high-purity tetra-nuclearly substituted alkylbenzene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an industrially advantageous method for efficiently recovering a high-purity tetra-nuclearly substituted alkylbenzene useful as a raw material, etc., for pyromellitic acid or pyromellitic anhydride from an aromatic hydrocarbon process fluid containing the tetra-nuclearly substituted alkylbenzene. SOLUTION: An aromatic hydrocarbon process fluid containing a tetra- nuclearly substituted alkylbenzene is subjected to a crystallization treatment to separate a solid matter by solid-liquid separation. The resultant solid matter is then washed with a wash liquid comprising the same component as at least one kind of the aromatic hydrocarbon component constituting the above process fluid to provide the high-purity tetra-nuclearlr substituted alkylbenzene. The washing waste liquor thereof is further recycled to any step before the crystallization step.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering high purity tetranuclear substituted alkylbenzene. More specifically, the present invention provides a high-purity tetranuclear-substituted alkylbenzene useful as an intermediate material of a polyimide resin or a heat-resistant plasticizer, a material of pyromellitic acid or pyromellitic anhydride used as an epoxy resin curing agent, and the like. The present invention relates to an industrially advantageous method for efficiently recovering from a hydrocarbon process fluid containing a tetranuclear substituted alkylbenzene.

[0002]

2. Description of the Related Art Tetranuclear-substituted alkylbenzenes are used as intermediate raw materials for polyimide resins and heat-resistant plasticizers, which have been increasing in demand in recent years, or as raw materials for pyromellitic acid and pyromellitic anhydride used as epoxy resin curing agents. It is known to be an important compound. The tetranuclear substituted alkylbenzene is generally produced by a method of separating, by concentrating, crystallizing or adsorbing the tetranuclear substituted alkylbenzene contained in a catalytic reforming oil or the like, or a method of methylating pseudocumene. Such tetranuclear-substituted alkylbenzene is obtained by an intermolecular transfer reaction of an alkyl group, and the tetranuclear-substituted alkylbenzene obtained by an intermolecular transfer reaction of the alkyl group contains various isomers. It is known that Table 1 shows the total carbon number of 1
Among the various isomers of 0-alkyl-substituted benzene, the boiling point and the freezing point of those having an alkyl group of a methyl group and an ethyl group are shown.

[0003]

[Table 1]

[0004] Among the alkyl-substituted benzenes having 10 carbon atoms, tetranuclear-substituted alkylbenzene A is an industrially extremely important compound. As can be seen from Table 1, the boiling point of each isomer is in the range of about 183 to 205 ° C. From this isomer mixture, a highly pure tetranuclear substituted alkylbenzene A (boiling point of 196. (8 ° C.) requires a very large number of distillation columns, which is expensive. However, the freezing point of the tetranuclear substituted alkylbenzene A is as high as 79.2 ° C, while the freezing points of the other isomers are about -6 to -84 ° C. It can be seen that separation is possible. In order to isolate the tetranuclear alkylbenzene A by the crystallization treatment, it is advantageous to increase the concentration of the tetranuclear alkylbenzene A in the liquid to be crystallized as much as possible.

[0005] When the target compound is recovered from a mixed solution containing various compounds by a crystallization method, generally, the mixed solution is first subjected to a distillation treatment or the like to increase the concentration of the target compound, and then to a crystallization treatment. Then, after taking out the crystals by solid-liquid separation means such as centrifugation, washing treatment with a low boiling point washing solution, after replacing the mother liquor attached to the crystal surface with the washing solution,
A method has been used in which the target compound is recovered by drying the crystals. In such a crystallization method, a solvent which is a poor solvent for the target compound is usually used as a washing solution in order to minimize washing loss. Then, a separate distillation step is provided for the purpose of recovering the target compound from the washing wastewater and reusing the washing liquid, and the washing wastewater is subjected to a distillation treatment. in this case,
Since the distillation step is added, there is a problem that the production cost of the target compound cannot be avoided.

[0006]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides an intermediate material for a polyimide resin or a heat-resistant plasticizer.
Industrially efficiently recovering high-purity tetranuclear substituted alkylbenzenes useful as raw materials for pyromellitic acid and pyromellitic anhydride used as epoxy resin curing agents from hydrocarbon process fluids containing tetranuclear substituted alkylbenzenes It is intended to provide an advantageous method.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that a hydrocarbon process fluid containing a tetranuclear alkylbenzene is subjected to crystallization treatment, followed by solid-liquid separation. The obtained crystals are washed with a washing solution comprising the same component as at least one of the hydrocarbon components constituting the process fluid, and the washing wastewater is recycled to any of the tetranuclear substituted alkylbenzene recovery steps. No additional distillation step is required,
In addition, they have found that the desired high-purity tetranuclear-substituted alkylbenzene can be efficiently and industrially advantageously recovered. The present invention has been completed based on such findings. That is, in the present invention, in the step of recovering the tetranuclear-substituted alkylbenzene from the hydrocarbon process fluid containing the tetranuclear-substituted alkylbenzene, after the crystallization treatment of the hydrocarbon process fluid, the obtained slurry is subjected to solid-liquid separation. The obtained solid component is washed with a washing solution comprising the same component as at least one of the hydrocarbon components constituting the hydrocarbon process fluid to obtain a high purity tetranuclear substituted alkylbenzene, and the washing wastewater after washing is washed An object of the present invention is to provide a method for recovering high-purity tetranuclear-substituted alkylbenzene, characterized in that it is recycled in the recovery step and reused while containing a cleaning solution.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The method of recovering a high-purity tetranuclear-substituted alkylbenzene according to the present invention is particularly applicable to a tetranuclear-substituted alkylbenzene having an alkyl group as a methyl group and a nucleus at the 1,2,4,5-position (hereinafter referred to as a "nuclear"). This may be referred to as a tetranuclear substituted alkylbenzene A.), wherein the hydrocarbon process fluid containing the tetranuclear substituted alkylbenzene A is used as a raw material. There is no particular limitation on the origin of the hydrocarbon process fluid containing the tetranuclear alkylbenzene A. For example, (1) the distillation residue of reformed gasoline, and (2) xylene in the xylene production process by the intermolecular transfer reaction of the alkyl group. Distillation residue, (3) a combination thereof, and the like.

The composition of the above-mentioned hydrocarbon process fluid is not particularly limited, and examples thereof include those mainly containing an aromatic hydrocarbon such as benzene, toluene, xylene and alkyl-substituted benzene having 9 or more carbon atoms. And especially those containing 98% by weight or more of an aromatic hydrocarbon component. In particular, benzene, toluene, an alkyl-substituted benzene having a total of 10 carbon atoms, or a mixture containing an alkyl-substituted benzene having a total of 10 carbon atoms and toluene is preferably used.

In the present invention, the above-mentioned hydrocarbon process fluid is subjected to crystallization. When the content of the tetranuclear alkylbenzene A is low, the crystallization efficiency is poor. To enhance
Advantageously, the process fluid is subjected to a distillation treatment by the method described below. First, in the first distillation column, an aromatic hydrocarbon fraction having a total carbon number of 9 or less is distilled from the top of the column, and a distillation residue containing an alkyl-substituted benzene having a total carbon number of 10 or more is obtained from the column bottom. This distillation residue may be subjected to a crystallization treatment as it is, or further led to a second distillation column in order to increase the concentration of the tetranuclear alkylbenzene A,
A distillate containing an alkyl-substituted benzene having a total of 10 carbon atoms is distilled off from the top of the column, and an aromatic hydrocarbon having a total of 11 or more carbon atoms is discharged as a distillation residue from the bottom of the column. The distillate may be crystallized.

By such a distillation operation, a concentrated oil containing the tetranuclear substituted alkylbenzene A is preferably at least 15% by weight, more preferably at least 20% by weight, particularly preferably at least 25% by weight. Can be performed efficiently. The distillation operation in the distillation column may be either normal pressure distillation or reduced pressure distillation. The aromatic hydrocarbon fraction having a total carbon number of 9 or less distilled from the top of the first distillation column may be supplied as it is to an alkyl group intermolecular transfer reaction step or the like, or may be subjected to a distillation treatment if necessary. Then, it can be separated into benzene, toluene, xylene, ethylenebenzene, and a fraction mainly composed of aromatic hydrocarbons having 9 total carbon atoms, and can be used for respective applications.

Next, the crystallization process will be described. In the crystallization treatment, first, the hydrocarbon process fluid or the tetranuclear substituted alkylbenzene concentrated oil obtained by distilling the process fluid as described above is cooled to precipitate crystals of the tetranuclear substituted alkylbenzene A. Let it. The crystallization temperature is not particularly limited as long as it is a temperature at which the tetranuclear-substituted alkylbenzene A is crystallized.
A range of 0 ° C. is preferred. If the temperature is lower than −25 ° C., the recovery of the tetranuclear alkylbenzene A is high, but the purity is low, and a desired high-purity product may not be obtained. If the temperature exceeds 30 ° C., a high-purity product may be obtained. However, the recovery rate of the tetranuclear alkylbenzene A is low, which is not practical. Tetranuclear substituted alkylbenzene A
From the viewpoint of the balance between the recovery rate and the purity, the more preferable range of the crystallization temperature is −20 to 25 ° C.,
A range from 10 to 20C is preferred.

At this time, if necessary, a seed crystal of tetranuclear substituted alkylbenzene A having a high purity of 99% or more may be added to grow the crystal of the tetranuclear substituted alkylbenzene A. As the crystallization method, any of the commonly used crystallization methods such as normal pressure crystallization and pressure crystallization can be employed. Next, the crystallized tetranuclear-substituted alkylbenzene is subjected to solid-liquid separation using a conventionally known solid-liquid separator, for example, a centrifuge, and the obtained solid component is washed.

[0014] In the present invention, a cleaning liquid comprising the same component as at least one of the hydrocarbon components constituting the hydrocarbon process fluid is used for the cleaning treatment. The type of the cleaning liquid may be the same as at least one of the hydrocarbon components constituting the process fluid, and is not particularly limited. However, a low-boiling aromatic compound is preferred because it is easily dried after the cleaning treatment. Benzene or toluene which is a group compound is preferably used. In the present invention, the above-mentioned hydrocarbon component may be used alone or as a mixture of two or more thereof as the cleaning liquid. The washing method is not particularly limited, and a method conventionally used for washing solids can be used.

The solid component after the washing treatment is dried by various conventionally known methods to obtain a tetranuclear substituted alkylbenzene A having a purity of 98% or more. On the other hand, since the cleaning solution used in the present invention is a good solvent for tetranuclear alkylbenzene A, the cleaning effluent contains a considerable amount of tetranuclear alkylbenzene A. In the present invention, for the purpose of recovering the tetranuclear-substituted alkylbenzene A and reusing the cleaning liquid, the cleaning waste liquid is recycled to the tetranuclear-substituted alkylbenzene recovery step while containing the cleaning liquid. This recycling may be carried out in any step of the recovery step, that is, in any stage of the process fluid before crystallization. In particular, recycling to the upstream of the first distillation column is an industrial step. It is economically advantageous. At this time, it is also optional to add various operations such as heating, cooling, and further dilution to the washing waste liquid as needed.

By employing such a washing method, there is no need to separate the washing solution in the washing waste liquid, and there is no need to separately provide a separation step such as a distillation step for separation. Can be efficiently collected. Next, regarding a preferred embodiment of the present invention,
This will be described with reference to the accompanying drawings. FIG. 1 is a process chart of an example for carrying out the method of the present invention. According to FIG. 1, first, a hydrocarbon process fluid U is supplied to a first distillation column 1, and an aromatic hydrocarbon fraction (total carbon number 9 or less) distilled from the top of the first distillation column ( C9L) may be supplied as it is to an alkyl group intermolecular transfer reaction step or the like, or if necessary, may be distilled to obtain a residue mainly composed of benzene, toluene, xylene, ethylbenzene and an aromatic hydrocarbon having 9 carbon atoms. It may be separated into minutes.

On the other hand, the distillation residue (C10H) containing alkyl-substituted benzene having a total carbon number of 10 or more discharged from the bottom of the distillation column 1 is supplied to the second distillation column 2. In this second distillation column 2, the total number of carbon
The fraction (C10) V containing the alkyl-substituted benzene is supplied to the crystallization step 3, while the distillation residue (C11) containing aromatic hydrocarbons having a total carbon number of 11 or more discharged from the bottom of the column (C11)
H) is taken out of the system. In the crystallization step 3, the fraction containing alkyl-substituted benzene having a total carbon number of 10 and subjected to crystallization treatment (C1
0) is led to a centrifugation step 4 to be separated into a solid and a liquid, and the solid component is washed in a washing step 5 with a washing liquid (preferably benzene or toluene) W. A part of the filtrate X discharged from the centrifugal separation step 4 goes out of the system, and the remainder is recycled together with the cleaning waste liquid Y discharged from the cleaning step 5 to the recovery step, particularly to the hydrocarbon process fluid U. One distillation column 1 is supplied. The solid component subjected to the washing treatment in the washing step 5 is led to the drying step 6, where it is subjected to a drying treatment to be a product (high-purity tetranuclear-substituted alkylbenzene A) Z.

[0018]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Example 1 (1) A process corresponding to distillation by the distillation columns 1 and 2 shown in FIG. 1 was performed on 205 g of the hydrocarbon process liquid U to obtain 100 g of a concentrated oil (V) containing 30% by weight of a tetranuclear alkylbenzene A. This concentrated oil (V) is temporarily cooled to 70 ° C.
After heating to 1.5 hours, stirring slowly for 1.5 hours.
After cooling to 5 ° C., the mixture was left at 25 ° C. for 2 hours to precipitate crystals. Next, this was centrifuged by a centrifugal filter at 1 centrifugal force.
After centrifugal filtration under the conditions of 000 G, shaking time 30 seconds,
The cake was washed under the same conditions using 2.5 g of toluene. At this time, 4.6 g of washing waste liquid was obtained. Next, this wet cake was placed under a nitrogen atmosphere at a degree of vacuum of 250 torr.
r, dried at 50 ° C. for 1 hour to give a purity of 99.78.
% Of dry tetranuclear substituted alkylbenzene A 2.79 g were obtained. The recovery of tetranuclear alkylbenzene A is
9.3% by weight. (2) The entire amount of the obtained washing waste liquid is used as the hydrocarbon process liquid U
After mixing to 205 g, a series of treatments including the distillation operation shown in the above (1) was performed in the same manner. Further, when this operation was repeated four times, the cooling liquid contained 31.1% by weight of the tetranuclear substituted alkylbenzene A, and the amount was 103.1 g. This is centrifugally filtered, washed and dried to obtain a dried tetranuclear-substituted alkylbenzene A having a purity of 9.59%.
3.98 g were obtained. This corresponds to a recovery rate of the tetranuclear alkylbenzene A of 13.3% by weight based on the raw material excluding the recycle wastewater.

Example 2 The procedure of Example 1 was repeated, except that benzene was used instead of toluene, and the purity was 99.4.
2.94 g of 0% dry tetranuclear substituted alkylbenzene A was obtained. The recovery of tetranuclear alkylbenzene A is 9.8.
% By weight. When the above operation was repeated 5 more times in the same manner as in Example 1, the cooling liquid was centrifugally filtered,
After washing and drying, 3.99 g of dry tetranuclear-substituted alkylbenzene A having a purity of 9.9.4% was obtained. This corresponds to a recovery rate of the tetranuclear alkylbenzene A of 13.3% by weight based on the raw material excluding the recycle wastewater.

Example 3 100 g of a concentrated oil containing 30% by weight of a tetranuclear substituted alkylbenzene A was once heated to 70.degree. C., cooled to 5.degree.
The crystals were left to stand for a period of time to precipitate. Next, this was centrifugally filtered by a centrifugal filter under the conditions of a centrifugal force of 1000 G and a shake-off time of 30 seconds, and the cake was washed with 10 g of toluene. Next, this wet cake was subjected to a nitrogen atmosphere at a degree of vacuum of 250 torr and a temperature of 50 ° C. for 2 hours.
After drying for 0 minutes, 12.52 g of dry tetranuclear-substituted alkylbenzene A having a purity of 9.9.76% was obtained.
The recovery of tetranuclear alkylbenzene A was 41.7% by weight. When the above operation was further repeated 5 times in the same manner as in Example 1, the cooling liquid was centrifugally filtered, washed, and dried to obtain 18.01 g of a dried tetranuclear-substituted alkylbenzene A having a purity of 9.9.76%. Obtained. This corresponds to a recovery rate of the tetranuclear-substituted alkylbenzene A of 60.0% by weight based on the raw material excluding the recycle wastewater.

Example 4 In Example 3, 10 g of benzene was used instead of toluene.
The same procedure as in Example 3 was followed, except that the dried tetranuclear-substituted alkylbenzene A 1 having a purity of 9.32% was used.
3.41 g were obtained. The recovery of tetranuclear alkylbenzene A was 44.7% by weight. When the above operation was repeated 5 more times in the same manner as in Example 1, the cooling liquid was subjected to centrifugal filtration, washing, and drying to obtain a purity of 99.32.
% Of dry tetranuclear-substituted alkylbenzene A 18.02 g
was gotten. This indicates that the recovery rate of tetranuclear alkylbenzene A was 60.
This corresponds to 1% by weight.

Comparative Example 1 In the same manner as in Example 1, except that the washing was not performed, 4.90 g of dry tetranuclear-substituted alkylbenzene A having a purity of 85.43% was obtained. The recovery of tetranuclear alkylbenzene A was 16.3% by weight. Comparative Example 2 In the same manner as in Example 3 except that the washing was not performed, 22.35 g of a dry tetranuclear-substituted alkylbenzene A having a purity of 82.95% was obtained. The recovery of tetranuclear alkylbenzene A was 74.5% by weight. Comparative Example 3 In Example 3, 20.12 g of dry tetranuclear alkylbenzene having a purity of 87.14% was prepared in the same manner as in Example 3 except that washing was performed using 10 g of pure water as a poor solvent instead of toluene. Obtained. Tetranuclear substituted alkylbenzene A
Was 67.1% by weight.

[0023]

According to the method of the present invention, a hydrocarbon process fluid containing a tetranuclear substituted alkylbenzene is
Highly purified tetranuclear substituted alkylbenzene can be produced efficiently and industrially advantageously. The high-purity tetranuclear-substituted alkylbenzene obtained by the method of the present invention is suitably used as an intermediate material of a polyimide resin or a heat-resistant plasticizer, or a material of pyromellitic acid or pyromellitic anhydride used as an epoxy resin curing agent. Can be used.

[Brief description of the drawings]

FIG. 1 is a process chart of an example for carrying out the method of the present invention.

[Explanation of symbols]

 1. 1. first distillation column 2. Second distillation column Crystallization step 4. Centrifugation step Cleaning process 6. Drying process U.S. Hydrocarbon process fluid Distillate containing C10 fraction Cleaning solution X. Filtrate Y. Wash drainage Z. Product

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsunori Takeda 4th Towada, Kamisu-cho, Kashima-gun, Ibaraki Pref. F-term (reference) 4H006 AA02 AD15 AD17 BC51 BD35 BD42 BD53 BD84

Claims (6)

[Claims] In the step of recovering a tetranuclear substituted alkylbenzene from a hydrocarbon process fluid containing the tetranuclear substituted alkylbenzene, the hydrocarbon process fluid is crystallized, and then the obtained slurry is subjected to solid-liquid separation. The obtained solid component is washed with a washing liquid comprising the same component as at least one of the hydrocarbon components constituting the hydrocarbon process fluid to obtain a high-purity tetranuclear alkylbenzene, and the washing waste liquid after washing is washed with the washing liquid. And recovering the high-purity tetranuclear-substituted alkylbenzene while recycling the same in the recovery step. 2. The method according to claim 1, wherein the washing liquid is toluene or benzene. 3. The method of claim 1, wherein the hydrocarbon process fluid has a total carbon number of 10
2. An alkyl-substituted benzene according to claim 1.
Or the collection method according to 2. 4. The method according to claim 1, wherein the hydrocarbon process fluid is distilled to obtain a distillation residue containing an alkyl-substituted benzene having a total carbon number of 10 or more, and the distillation residue is subjected to crystallization treatment. The collection method described. 5. A hydrocarbon process fluid is distilled to obtain a distillation residue containing an alkyl-substituted benzene having a total carbon number of 10 or more, and the distillation residue is further distilled to produce an alkyl-substituted benzene having a total carbon number of 10. The method according to any one of claims 1 to 3, wherein a distillate containing the distillate is obtained, and then the distillate is subjected to crystallization treatment. 6. The recovery method according to claim 1, wherein the cleaning effluent after cleaning is recycled and reused as a hydrocarbon process fluid before crystallization while containing the cleaning liquid.