JPH11292801A - Production of high-purity tetra-nuclearly substituted alkylbenzene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an industrially advantageous method for efficiently producing a high-purity tetra-nuclearly substituted alkylbenzene useful as a raw material, etc., for pyromellitic acid or pyromellitic anhydride by using a raw material oil containing an alkyl-substituted benzene having >=9 total number of carbon atoms. SOLUTION: An alkyl-substituted benzene having >=9 total number of carbon atoms is treated to provide a product oil containing an alkyl-substituted benzene having 10 total number of carbon atoms and at least 2.5 average value of nuclearly substituted methyl groups in one molecule. The resultant product oil is then concentrated by distillation and a tetra-nuclearly substituted alkylbenzene is subsequently crystallized and separated to thereby produce the high-purity tetra-nuclearly substituted alkylbenzene.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a high-purity tetranuclear-substituted alkylbenzene, and more particularly to a method for producing the same.
High-purity tetranuclear substituted alkylbenzene useful as a raw material for pyromellitic acid or pyromellitic anhydride used as an intermediate material for polyimide resins and heat-resistant plasticizers and as a curing agent for epoxy resins, etc. TECHNICAL FIELD The present invention relates to an industrially advantageous method for efficiently producing a raw material oil containing the same.

[0002]

2. Description of the Related Art Tetranuclear alkylbenzene is used as an intermediate material for polyimide resins and heat-resistant plasticizers, for which demand is increasing in recent years, or as a raw material for pyromellitic acid or pyromellitic anhydride used as an epoxy resin curing agent. It is known to be an important compound. Conventionally, as a method for producing this tetranuclear-substituted alkylbenzene,
A method of separating, by concentrating, crystallizing or adsorbing tetranuclear alkylbenzenes contained in a catalytic reforming oil or the like, a method of methylating pseudocumene, and the like have been carried out. However, in the former method, since the concentration of the tetranuclear substituted alkylbenzene contained in the raw material of the catalytic reforming oil is low, there is a problem that the separation and purification thereof is enormous and the production amount is limited. . On the other hand, in the pseudocumene methylation method,
Using an acid catalyst such as Friedel Crafts catalyst or HF,
In order to perform the methylation, a corrosion-resistant reactor and a step of separating a catalyst and a reaction product are required, and there is a problem that the cost of the resulting tetranuclear alkylbenzene is inevitable. Incidentally, alkyl-substituted benzenes having a total of 10 carbon atoms obtained by intermolecular rearrangement of alkyl groups and the like contain various isomers. Table 1 shows the boiling points and freezing points of the various isomers in which the alkyl group is a methyl group or an ethyl group.

[0003]

[Table 1]

[0004] 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 alkylbenzene A (98% or more) can be obtained by distillation. In order to isolate (boiling point: 196.8 ° C.), a very large number of distillation columns are required, resulting in high cost. However, the freezing point of the tetranuclear substituted alkylbenzene A is as high as 79.2 ° C., whereas the freezing points of the other isomers are about −6 to −84 ° C.
It can be seen that the separation of the tetranuclear substituted alkylbenzene A is possible. In order to isolate the tetranuclear alkylbenzene A by the crystallization, it is important to increase the concentration of the tetranuclear alkylbenzene A in the liquid to be crystallized as much as possible.

[0005]

SUMMARY OF THE INVENTION The present invention provides a highly purified tetranuclear-substituted alkylbenzene useful as a raw material for pyromellitic acid or pyromellitic anhydride in such a situation. It is an object of the present invention to provide an industrially advantageous method for efficiently producing a raw material oil containing benzene.

[0006]

Means for Solving the Problems The present inventors have repeatedly studied the recovery of high-purity tetranuclear-substituted alkylbenzene by distillation-crystallization treatment, and found that the recovery rate of tetranuclear-substituted alkylbenzene is the same as that of tetranuclear in the liquid to be crystallized. The higher the concentration of the substituted alkylbenzene, the higher the concentration. The lower the content of the isomer having an alkyl group other than a methyl group among the alkyl-substituted benzene isomers having 10 carbon atoms, the lower the concentration of the tetranuclear alkylbenzene by distillation. We focused on the fact that it can be easily raised. The present inventors have, in order to achieve the above object,
As a result of further intensive research based on this attention, the alkyl-substituted benzenes having 9 or more carbon atoms undergo intermolecular rearrangement of alkyl groups, and the average value of the number of nucleus-substituted methyl groups in one molecule is a certain value or more. After obtaining a product oil containing an alkyl-substituted benzene having a total of 10 carbon atoms, concentrated by distillation,
Next, it has been found that the object can be achieved by crystallizing and separating the tetranuclear alkylbenzene. The present invention has been completed based on such findings. That is, according to the present invention, (A) a feedstock containing an alkyl-substituted benzene having a total carbon number of 9 or more is reacted in the presence of hydrogen, and the average number of nucleus-substituted methyl groups in one molecule is at least 2 (B) a step of obtaining a product oil containing an alkyl-substituted benzene having a total carbon number of 10; and (B) distilling the product oil obtained in the step (A) to reduce the concentration of the alkyl-substituted benzene having a total carbon number of 10. (C) cooling the concentrated oil obtained in the step (B), crystallizing and separating the tetranuclear alkylbenzene, and producing a high-purity tetranuclear alkylbenzene. It provides a method.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The process for producing a high-purity tetranuclear-substituted alkylbenzene according to the present invention uses a raw oil containing an alkyl-substituted benzene having 9 or more carbon atoms as a raw material, (A) a reaction step, and (B) It comprises a distillation step and a (C) crystallization step. As the feedstock oil containing an alkyl-substituted benzene having 9 or more carbon atoms used as a feedstock in the method of the present invention, as long as the object of the present invention is not impaired,
It may contain other components such as at least one selected from benzene, toluene, xylene and ethylbenzene, and also indane compounds and naphthalene compounds as appropriate. Those containing 30% by weight or more are preferable, and those containing 50% by weight or more are particularly preferable. The origin of the feedstock containing the alkyl-substituted benzene having a total carbon number of 9 or more is not particularly limited as long as it has the composition described above, and may be of any origin. Examples of such a substance include (1) a distillation residue of reformed gasoline, (2) a xylene distillation residue in a xylene production process by an intermolecular rearrangement reaction of an alkyl group, and (3) a combination thereof.

Next, each step will be described. (A) Step In this step, the feedstock oil containing the alkyl-substituted benzene having a total carbon number of 9 or more is contacted with a catalyst in the presence of hydrogen,
This is a step of performing an intermolecular rearrangement reaction of the alkyl group to obtain a product oil containing an alkyl-substituted benzene having 10 carbon atoms in which the average value of the number of nucleus-substituted methyl groups in one molecule is at least 2.5. The total number of carbon atoms in the product oil obtained by this reaction is 1
When the average value of the number of nucleus-substituted methyl groups in one molecule of the alkyl-substituted benzene of 0 is less than 2.5, the concentration of the tetra-nucleus-substituted alkylbenzene is increased to a desired concentration in the concentration by distillation in the next step (B). Difficult,
The recovery of the tetranuclear substituted alkylbenzene by crystallization is reduced. From the viewpoint of the recovery rate of tetranuclear alkylbenzene, the average value of the number of nuclear substituted methyl groups in one molecule is
3.0 or more is preferable.

Therefore, in this step, the average value of the number of nucleus-substituted methyl groups in one molecule of the alkyl-substituted benzene having 10 carbon atoms in the produced oil is 2.5 or more, preferably 3.0 or more. As described above, it is important to appropriately select the type of catalyst and the reaction conditions. The catalyst can be appropriately selected and used from known catalysts conventionally used for intermolecular rearrangement of alkyl groups of alkyl-substituted benzene. As such a catalyst, for example, at least one metal selected from metals belonging to Groups 6, 7, and 10 of the periodic table is added to zeolite at 0.00.
Those supported at a ratio of 1 to 5% by weight, preferably 0.02 to 1% by weight are exemplified. As the above zeolite, H
Mordenite zeolite, or a dealkalized Y-type zeolite is preferable.
The metals of Group 10 include chromium, molybdenum, tungsten and the like, the metals of Group 7 include manganese and rhenium, and the metals of Group 10 include nickel, palladium and platinum.

The reaction is carried out in the presence of hydrogen. The reaction temperature depends on the type of the catalyst used, but is generally 150 ° C.
To 550 ° C, preferably 200 to 450 ° C. The reaction pressure is usually about 0.5 to 6 MPa, and the weight hourly space velocity (WHSV) is preferably in the range of 0.5 to 10 / hr. Thus, a part of the alkyl-substituted benzene having 9 or more carbon atoms is converted into an alkyl-substituted benzene having 10 carbon atoms in total by the intermolecular rearrangement reaction of the alkyl group. That is, the alkyl-substituted benzene having a total of 10 carbon atoms obtained by such treatment has a small number of alkyl groups having 2 or more carbon atoms, and most of the alkyl groups are methyl groups. Is about 5 to 25% by weight, and about 95 to 75% by weight of tetranuclear substituted alkylbenzenes, particularly those in which the alkyl group is a methyl group.

(B) Step In this step, the product oil obtained in the step (A) is distilled to cut an aromatic hydrocarbon having 9 or less carbon atoms and an aromatic hydrocarbon having 11 or more carbon atoms, This is a step of increasing the concentration of the alkyl-substituted benzene having 10 carbon atoms. To carry out this step industrially, for example, two distillation columns are arranged in series, and in the first distillation column, an aromatic hydrocarbon fraction having 9 or less carbon atoms is distilled from the top of the column, and from the bottom of the column, To the second distillation column to distill an alkyl-substituted benzene fraction having a total of 10 carbon atoms from the top of the column, and to discharge aromatic hydrocarbons having 11 or more carbon atoms as a distillation residue from the bottom of the column. Just do it. In this way, a concentrated oil containing the tetranuclear substituted alkylbenzene, preferably at least 15% by weight, more preferably at least 20% by weight, particularly preferably at least 25% by weight is obtained. The distillation operation in the distillation column may be either normal pressure distillation or reduced pressure distillation. The aromatic hydrocarbon fraction having a carbon number of 9 or less distilled from the top of the first distillation column is separated, if necessary, by distillation of benzene, toluene, xylene, ethylbenzene, etc., and then the carbon fraction having a carbon number of 9 is removed. The fraction mainly composed of aromatic hydrocarbons can be recycled to the step (A).

Further, of the distillation residue discharged from the bottom of the second distillation column, the alkyl-substituted benzene can be recycled to the step (A). (C) Crystallization Step This step is a step of cooling the alkyl-substituted benzene concentrated oil obtained in the above step (B), crystallizing the tetranuclear -substituted alkylbenzene, and separating the same. The crystallization temperature is not particularly limited as long as the tetranuclear-substituted alkylbenzene is crystallized, but is preferably in the range of −25 to 30 ° C. If this temperature is lower than −25 ° C., the recovery rate of the tetranuclear alkylbenzene is high, but the purity is low, and a desired high-purity product may not be obtained.
If it exceeds, a high-purity product can be obtained, but the recovery of the tetranuclear alkylbenzene is low, which is not practical.
The crystallization temperature is more preferably in the range of −20 to 25 ° C., and particularly preferably in the range of −10 to 20 ° C., in view of the balance between the recovery rate and the purity of the tetranuclear alkylbenzene.

At this time, if necessary, a seed crystal of tetranuclear-substituted alkylbenzene having a high purity of 99% or more may be added to grow a crystal of tetranuclear-substituted alkylbenzene. As the crystallization method, a commonly used crystallization method such as normal pressure crystallization or pressure crystallization can be employed. The crystallized tetranuclear-substituted alkylbenzene is subjected to solid-liquid separation using a conventionally known solid-liquid separator, for example, a centrifugal separator, and if necessary, washed with naphtha or the like to obtain a tetra-purity of 98% or more. A nucleus-substituted alkylbenzene is obtained. In the tetranuclear-substituted alkylbenzene obtained by the production method of the present invention, all of the alkyl groups are methyl groups, and these nucleus substitution positions are in the 1-, 2-, 4- and -5-positions.

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) Preparation of catalyst Zeolite was synthesized by the method disclosed in US Pat. No. 3,965,207. The composite was identified as ZSM-5 from the X-ray diffraction pattern. The resulting compound was
After calcining at 50 ° C. for 16 hours in an electric muffle furnace in an air atmosphere, 20 g of a 5 wt% NH ₄ Cl aqueous solution 200 was added.
C. and ion exchange at 80.degree. C. for 24 hours. Then, wash thoroughly with water, dry at 100 ° C, and further at 450 ° C for 1 hour.
Calcination was performed in an air atmosphere in an electric muffle furnace for 6 hours. Next, 0.052 g of Pt (NH ₄ ) ₄ Cl ₂ was dissolved in 30 cc of water, and the H-form ZSM-5 obtained by the above method was added thereto.
Was immersed. After performing an ion exchange treatment at 50 ° C. for 8 hours, the powder was filtered, sufficiently washed with water, and then dried in an electric dryer at 100 ° C. for 8 hours and then at 200 ° C. for 16 hours. The resulting catalyst contained 0.27% platinum, based on total weight.

(2) Reaction Using a feedstock oil having the composition shown in Table 2 and a fixed bed flow reactor filled with the catalyst prepared in (1) above, the reaction was carried out under the following conditions. As a result, a product oil having the composition shown in Table 3 was obtained. <Reaction conditions> Temperature: 400 ° C. Pressure: 3.5 MPa WHSV: 50 hr ⁻¹ hydrogen / feed oil (molar ratio): 4.0

[0016]

[Table 2]

[0017]

[Table 3]

From the results in Table 3, the total number of carbon atoms in the product oil was 1
The average value of the number of nucleus-substituted methyl groups in the alkyl-substituted benzene of 0 was 3.6. (3) Concentration by distillation The product oil obtained in the above (1) was rectified at a reflux ratio of 1 using a 15-stage rectification column, and the degree of vacuum at the top of the column was 10 mmH
g, a fraction at 60 to 80 ° C was collected to obtain a concentrated oil. Its composition is as follows. C9 component: 1.95% by weight C10 component: 86.98% by weight (tetranuclear alkylbenzene A): (24.82
(% By weight) C11 or more component: 11.07% by weight (4) Crystallization / separation 100 parts by weight of the concentrated oil obtained in the above (3) was once mixed with 70 parts by weight.
After heating to 5 ° C., the mixture was cooled to 5 ° C. at a rate of 1 ° C./min with slow stirring, and then left at 5 ° C. for 2 hours to precipitate crystals of tetranuclear alkylbenzene. Then, the crystals were collected by filtration to obtain 10.6 parts by weight of tetranuclear substituted alkylbenzene A having a purity of 99.3%. The recovery of the tetranuclear alkylbenzene was 42.8%.

Example 2 The procedure of Example 1 (4) was repeated, except that the crystallization temperature was changed to -20 ° C., and a tetranuclear substituted alkylbenzene A having a purity of 99.0% was obtained. A recovery rate of 72.5% was obtained.

[0020]

According to the present invention, a high purity tetranuclear substituted alkylbenzene can be produced extremely efficiently and industrially advantageously using a feedstock oil containing an alkyl substituted benzene having a total carbon number of 9 or more. . 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.

Claims (3)

[Claims] 1. A reaction is performed in the presence of hydrogen on a feedstock oil containing (A) an alkyl-substituted benzene having a total carbon number of 9 or more, and the average number of nucleus-substituted methyl groups in one molecule is at least 2. (B) a step of obtaining a product oil containing an alkyl-substituted benzene having 10 carbon atoms, and (B) increasing the concentration of the alkyl-substituted benzene having 10 carbon atoms by distilling the product oil obtained in the step (A). And (C) cooling the concentrated oil obtained in the step (B), crystallizing and separating the tetranuclear substituted alkylbenzene, and sequentially separating the same. . 2. The high-purity tetranuclear alkylbenzene according to claim 1, wherein the feedstock oil contains at least one selected from benzene, toluene, xylene and ethylbenzene together with an alkyl-substituted benzene having a total carbon number of 9 or more. Production method. 3. The process for producing a high-purity tetranuclear alkylbenzene according to claim 1, wherein the concentrated oil contains at least 15% by weight of the tetranuclear substituted alkylbenzene.