JPS58174336A - Separation of dichlorobenzene isomer - Google Patents

Abstract

PURPOSE:To separate 1,3-dichlorobenzene and 1,4-dichlorobenzene from a mixture containing the same, in high purity and efficiency, by the extractive distillation using a specific solvent such as 1,2-propanediol, etc. CONSTITUTION:A mixture containing both 1,3-dichlorobenzene and 1,4-dichlorobenzene is mixed with one or more extraction solvents selected from 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol, 2-nitroanisole, 1,3-dimethyl-2-imidazolidinone, 1,8-diazabicyclo(5,4,0)undecene-7, N-phenylmorpholine and isophorone, and subjected to the extractive distillation under reduced pressure to obtain the 1,3- isomer having a purity of as high as >=99%. The solvent is then distilled to obtain the 1,4-isomer having a purity of >=99%. The molar ratio of the extraction solvent to the isomer mixture is preferably (1-4):1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for extracting one dichlorobenzene isomer which is extremely difficult to separate in a mixture of dichlorobenzene isomers by an extractive distillation method using a specific solvent.
．． The present invention relates to a method for efficiently separating t4-isomer and t4-isomer with high purity.

As is well known, dichlorobenzene is produced by chlorination of benzene, in which t2-1t5- and t4
The production of three types of isomers cannot be avoided.

When isolating each isomer from this dichlorobenzene, it is clear from the respective physical properties that 5IC1,2-dichlorobenzene can be easily distilled using normal distillation because it has a large boiling point difference compared to t5- and t4-dichlorobenzene. can be separated by different methods. However, since the boiling point difference between 1.3 and 1.4 is only tO°C, it would be industrially impossible to separate them by ordinary distillation, which would require a huge rectification column.

Extractive distillation is known as a recent separation method, and an example thereof is JP-A-50-19722. In this method, a neutral polar organic solvent having a dielectric constant of more than 20 and a dipole efficiency of more than 50 Debye is used as an additive solvent, but some of these solvents have drawbacks in terms of toxicity. Further, JP-A-54-160522 discloses a method of carrying out extractive distillation using sulfolane, decyl alcohol, ortho-cresol, meta-cresol or para-cresol. However, these solvents have disadvantages in relative evaporation coefficients or specific volatility, odor, and handling difficulties.

As a result of intensive studies to overcome these acid sites, the present inventors have completed the present invention, which is an additive solvent for extractive distillation that is effective for separating 1,3-dichlorobenzene and t4-dichlorobenzene. did.

That is, the present invention provides t3-dichlorobenzene and t4
-As an extraction solvent from a mixture containing dichlorobenzene-
(Separate 1,2-propanediol, 1.5-bentanediol, 2-nitroanisole, 1,5-dimethyl-2-imidasilidinone, t8-diazabisipho(翫4IO) undecene-7, N-phene form, This is a method for separating dichlorobenzene isomers, which is characterized in that the 1,4 monomer is then separated by distillation from the above-mentioned solvent.

By using the extraction solvent in the method of the present invention, it is possible to increase the relative volatility of both t3 and L4, making it extremely easy to separate them. Therefore, it was possible to isolate both isomers with high purity exceeding 99%. This is clear from the following specific volatility values of both isomers when the extraction solvent is added in the method of the present invention.

1.3 Mixture K containing equal amounts of both monomer and t4-dichlorobenzene isomers is added to the extraction solvent (the molar ratio of solvent/dichlorobenzene is set to 4).

The results of measuring the specific volatility under reduced pressure of 95 wHF are shown below.

The amount of extraction solvent used in the present invention is 1.3 and t4-
Any ratio can be selected for the dichlorobenzene mixture, but is determined by the nature of the solvent and the efficiency of the extractive distillation apparatus, and is preferably between 1 and 4 molar ratios in order to economically carry out the process of the invention. .

The degree of vacuum during extractive distillation is not particularly limited, but it is preferable to carry out the distillation under reduced pressure because if it is carried out under atmospheric pressure, it will have negative effects on the specific volatility, stability of the solvent, and economic efficiency.

The method of the present invention consists of a conventional extractive distillation step to first separate 1,3-dichlorobenzene, and then a conventional distillation step to separate the 1,4-dichlorobenzene from the extraction solvent. An example of this embodiment is illustrated by the accompanying drawings at the end.

A mixture containing both isomers of 1,3-dichlorobenzene and 1,4-dichlorobenzene was supplied from route (2) to an extractive distillation column (1) with a diameter of 150 mm and a height of 5 m packed with a ball ring as a packing material, and the mixture containing both isomers of 1,3-dichlorobenzene and 1,4-dichlorobenzene was fed at the top of the column. The extraction solvent is supplied from route (2). The extracted and separated 1,3-dichlorobenzene vapor passes through path (1) and is condensed in condenser (2), and a portion of it is refluxed at a reflux ratio of 25 through path (2) to the top of the column. The remaining part is taken out from route (1) as a highly purified product, 1,3-benzene.

The composition of the bottom liquid consists mostly of the extraction solvent and 1,4-dichlorobenzene. And the distillation column - mailer
■It is heated with.

The bottom liquid passes through route ① and is packed into a ball ring ti.
It is supplied to a distillation column 0 with a diameter of 75-1 and a height of 3 m.

The 1,4-dichlorobenzene vapor with a purity of 98% or more is condensed in condenser 〇 along path Ot, and a part of it is refluxed to the top of the column at a reflux ratio of 5. The remaining part is taken out via route O as a highly purified product, 1,4-dichlorobenzene. The heat required for this distillation is supplied by the boiler OK.

The bottom liquid consists mostly of the extraction solvent.

Through route 01, it is used for circulation, and a portion of it is supplied to the extractive distillation column (2) along with a portion of the fresh extraction solvent (2).

Examples will be described below.

EXAMPLE Using the configuration as described above (figures shown at the end), 15 kg/h of dichlorobenzene consisting of an equal mixture of 1.3 and 1.4 units was added as extraction solvent L5-dimethyl-2-
55kL of Iidazolidinone (hereinafter abbreviated as DMI)
/w# to the extractive distillation column.

Extractive distillation was carried out at a reduced pressure of 95 w)lr' and a reflux ratio of 25 to obtain 1,3-dichlorobenzene with a purity of 99.5%.

The bottom liquid is supplied to the next distillation column, and the pressure reduction degree is 95mHP, Mf
Distillation was performed at a ratio of 5 to obtain t4-dichlorobenzene with a purity of 99.2%. This distillation column bottom liquid was pure DMI and was recycled for extractive distillation.

[Brief explanation of drawings]

The accompanying drawings are flow sheets for carrying out the method of the present invention. In the figure, ■ indicates an extractive distillation column, and O indicates a distillation column. Hodogaya Chemical Industry Co., Ltd.ゝ□. Procedural amendment (1 shame) June 7, 1981 Director General of the Patent Office Tori January Indication of Donkanden 1 case 1988 Patent application No. Tough 3o5 No. 2 Name of invention dichlorobenzene trade l)'4m , Difficulties in the body A5 Relationship with the person making the amendment Patent applicant postal code 105 Address 4-2-5 Toranomon-chome, Minato-ku, Tokyo Number of inventions increased by the amendment None. 6. Claims column of the specification subject to amendment Column 7: Detailed description of the invention in the specification 7. Contents of the amendment (1) Claims column of the specification As attached (2) Description of the specification Detailed description of the invention column (a) Page 3, line 11, next to "1,2-propanediol", add "l,4-butanediol". (b) Page 7, line 7 [Part of it says J, then C
Add the route (string street). (C) In the 8th line of page 7, [Mei 1aoJ] is corrected to ``route@.'' Hodogaya Chemical Industry Co., Ltd.'□: 1 Scope of Claim 1 . From a mixture containing 3-dichlorobenzene and 1,4-dichlorobenzene, 1.2-propanediol, 1.4-butanediol, 1.5-bentanediol, 2-nitroanisole, 1.3- Dimethyl-2-imidazolidinone, 1,8-diazabicyclo(5
,4,0) undecene-7, N-phenylmorpholine,
Using one or more selected from the group of quinoline or isophorone, 1.3 is separated by extractive distillation, and then 1.
1. A method for separating dichlorobenzene isomers, which comprises separating dichlorobenzene isomers by distillation from the above-mentioned solvent.

Claims (1)

[Claims] 1, s-dichlorobenzene (1) L 4-')
lo. From a mixture containing benzene, 1.2-furopanediol, 1.5-bentanediol, 2-nitroanisole, t,5-dimethyl-2-imidasilidinone% 1.8-diazabiditalo(5,4,0 ) using one or more selected from the group of undecene-7, N-phenylmorpholine, quinoline or isophorone, separating the t5 unit by extractive distillation, and then separating the 1.4 unit by distillation from the above solvent. A method for separating dichlorobenzene isomers.