JP2909571B2 - Method for producing high-purity benzene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing high-purity benzene. The purified high-purity benzene obtained by the present invention is useful as a raw material for producing fine chemicals, such as pharmaceuticals, which require high purity.

[0002]

2. Description of the Related Art There have been many studies on the purification of benzene at the petrochemical level, and many reports have been made in literatures and patents. However, many of these require special equipment and, in terms of purity, have not been satisfactory for fine chemical applications. Conventionally, commercially available industrial benzene contains, for example, 0.0846% of toluene (benzene / benzene gas chromatography area ratio) as an alkyl-substituted benzene. When such industrial benzene is used as a raw material, in an electrophilic substitution reaction such as the Friedel-Crafts reaction, an alkyl-substituted benzene contained as an impurity, for example, toluene, xylene, ethylbenzene, cumene, etc. is more reactive. Therefore, even if the content is very small, the content of the alkyl-substituted benzene derivative as an impurity in the obtained product tends to be high.

[0003] In chemical synthesis, it is desirable to use a raw material having few impurities in the initial stage. Therefore, it is preferable to use benzene after purifying it in the raw material stage. However, benzene and alkyl-substituted benzene have a large difference in physical properties. In fact, removal is difficult with simple purification methods such as recrystallization and distillation. Therefore, an object of the present invention is to provide a method for easily producing high-purity benzene.

[0004]

Means for Solving the Problems The inventors of the present invention have found that
Impurities have higher reactivity in the electrophilic substitution reaction.
The reverse is used to add an acylating agent to commercially available benzene.
Selectively increases alkyl-substituted benzene as an impurity
Surprisingly requires rectification column by converting to boiling point substance
Benzene of sufficient purity can be obtained
And found that the present invention was completed. Immediately
That is, the gist of the present invention is to disclose the alkyl group contained in benzene.
Exchange benzeneAcylateConvert to high-boiling substances and distill
Benzene production method characterized by the fact thatabout
You.

As a method for converting the alkyl-substituted benzene in a high boiling point substances in the present invention is conveniently is A acylation derivatives synthesized, moreover acylation is needed use since it is easily available acylating agent. The type of the acylating agent is not particularly limited as long as it can be derived to a high-boiling substance, and examples thereof include acetyl chloride, propionyl chloride, benzoyl chloride, and acetic anhydride. Among them, for example, acetyl chloride, benzoyl chloride and the like are preferably used from the viewpoint of availability. The amount of the acylating agent to be used is usually 1 to 150 equivalents to the mixed alkyl-substituted benzene. For example, in commercial industrial benzene, the content of alkyl-substituted benzene is about 0.0846%.
Usually, 1 to 10% equivalent of the total benzene amount is appropriate, and preferably 2 to 5% equivalent. This makes it possible to sufficiently acylate the alkyl-substituted benzene.

[0006] These reactions may be carried out in the presence of a catalyst. For example, a Lewis acid catalyst is exemplified. As the Lewis acid catalyst, aluminum chloride, zinc chloride, and boron trifluoride are generally used. When a catalyst, for example, a Lewis acid catalyst is used, it may be used in an equimolar amount with the acylating agent, but it goes without saying that it is appropriately changed depending on the catalyst. The reaction temperature is usually 20 to 30 ° C., which enables selective acylation of the alkyl-substituted benzene. The reaction time is usually 1-2 hours.

[0007] The high boiling substance derived from the alkyl-substituted benzene may be any substance having a boiling point as high as possible than the boiling point of benzene (80 ° C).
It is preferably a substance having a high boiling point of not less than ° C. For example, when acetyl chloride is reacted with commercially available benzene containing a trace amount of toluene (boiling point: 110 ° C.), toluene is converted into p-methylacetophenone (boiling point: 224 ° C.), and the boiling point difference from benzene (boiling point: 80 ° C.) 30 ° C to 122 ° C to 144
° C and fractionation becomes very easy.

Then, after the above-mentioned reaction, distillation was carried out at a distillation temperature of 81.
High-purity benzene can be obtained by obtaining a fraction at or below ° C.

[0009]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Example 1 527.4 industrial benzene was added to a reactor equipped with a stirrer and a thermometer.
g (6.8 mol) to 18.0 g of aluminum chloride (0.
14 mol), 10.6 g (0.14 mol) of acetyl chloride was added dropwise over 10 minutes while maintaining the temperature at 20 to 30 ° C., and the mixture was further reacted for 1 hour. Separated. After azeotropic dehydration of the upper layer, distillation was performed to obtain a toluene content of 0.0005 from a fraction of 81 ° C. or less.
% Benzene was obtained (yield: 454.9 g,
Yield: 86%).

Example 2 In a reactor equipped with a stirrer and a thermometer, 527.4 industrial benzene was added.
g (6.8 moles) to 9.0 g (0.0
68 mol), 5.3 g (0.068 mol) of acetyl chloride was added dropwise over 10 minutes while maintaining the temperature at 20 to 30 ° C., and the mixture was further reacted for 1 hour. Then, 300 ml of water was added, the mixture was stirred for 30 minutes, and allowed to stand. Separated. After the upper layer was azeotropically dehydrated and distilled, the toluene content (toluene /
Gasoline area ratio of benzene, the same applies hereinafter) 0.0010%
Was obtained (yield: 450.9 g, yield: 86%).

Example 3 In a reactor equipped with a stirrer and a thermometer, 527.4 industrial benzene was added.
g (6.8 mol) to 90.0 g of aluminum chloride (0.
68 mol) was added, 95.0 g (0.68 mol) of benzoyl chloride was added dropwise over 10 minutes while maintaining the temperature at 20 to 30 ° C., and the mixture was further reacted for 1 hour. Separated. After azeotropic dehydration of the upper layer, distillation yields a fraction of 81 ° C. or less with a toluene content of 0.00
<01%, and high-purity benzene was obtained (yield:
265.9 g, yield: 50%).

[0012]

The method of the present invention exhibits, only simple reaction to convert a higher boiling material selectively acylating the alkylated benzene which is an impurity in the benzene, simple distillation is not particularly required rectification column This is an industrially advantageous method that enables high-purity benzene to be obtained. Benzene obtained by the method of the present invention is useful as a raw material for the production of fine chemicals requiring high purity, among others,
It is particularly useful for the synthesis of pharmaceuticals that have strict regulations on the mixture of related substances.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C07C 15/04 C07C 7/04 C07C 7/148 C07C 7/17

Claims (1)

(57) [Claims] 1. A alkyl-substituted benzene contained in the benzene is acylated into a high boiling point substances, by distillation
A method for producing high-purity benzene, characterized in that :