JP2518095B2 - Method for producing dichlorobenzene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Purpose of the invention [Industrial field of application] The present invention is directed to chlorinating benzene (hereinafter abbreviated as BZ) and / or monochlorobenzene (hereinafter abbreviated as CB), and dichlorobenzene (hereinafter referred to as CB). (Hereinafter abbreviated as DCB)).

DCB is an industrially important compound and is used as a raw material intermediate in many products.

DCB includes paradichlorobenzene (hereinafter abbreviated as PDCB), orthodichlorobenzene (hereinafter abbreviated as ODCB).
There are three isomers of metadichlorobenzene (abbreviated as MDCB hereinafter). Among them, PDCB is in the highest demand and attracts attention as a raw material for polyphenylene sulfide, which is an engineering plastic, in addition to insect repellents.

[Conventional technology]

Conventionally, DCB is produced by chlorinating BZ or CB using a Friedel-Crafts type catalyst such as ferric chloride. However, this method has a low PDCB selectivity of about 60%, and many ODCBs with low utility value are by-produced.

In order to improve this, a method of using a sulfur or selenium-based inorganic or organic compound in combination with ferric chloride has been proposed. Although this method improves the selectivity of PDCB to 70-80%, it still has the problem that there are many by-products of highly chlorinated benzene such as trichlorobenzene, which is generally found in reactions using ferric chloride as a catalyst. Has been done. Further, it is extremely difficult to reuse the catalyst because a step such as washing with water is required to remove the catalyst from the reaction product contaminated with these catalysts.

Moreover, in recent years, BZ and / or using zeolite as a catalyst
Several proposals have been made for selective chlorination of CB. For example, JP-A-57-77631 discloses a gas phase chlorination reaction using a zeolite having an average pore size of 5 to 13Å as a catalyst, and JP-A-59-163329 discloses an L-type zeolite as a catalyst. Liquid phase chlorination reactions are disclosed. But,
Although these methods have a high PDCB selectivity of 80 to 90%, they have the drawback that the catalytic activity decreases in a short time.

The present inventors previously used active alumina as a catalyst to have a high PDCB selectivity, suppress high-boiling highly chlorinated benzene by-products, and maintain the chlorine conversion rate at a high rate for a long time. Invented to obtain, and has already applied (Japanese Patent Laid-Open No.
-93550). However, there has been a demand for a method for producing PDCB capable of maintaining a high chlorine conversion rate for surface time.

[Problems to be Solved by the Invention]

When producing DCB by reacting BZ and / or CB under a chlorine using a catalyst, the present inventors have a high PDCB selectivity and a high chlorine conversion rate for a long time, which is industrially very advantageous. The present invention has been completed as a result of earnest research on a method for manufacturing such a PDCB.

B) Structure of the Invention [Means for Solving the Problems] In the present invention, in producing DCB by chlorinating BZ and / or CB, activated alumina is used as a catalyst, and BZ and / or water content of 50 wtppm or less is used. Alternatively, it is a method for producing DCB, which is characterized by chlorinating CB.

In the present invention, BZ and / or CB has a water content of 50.
It is wtppm, preferably 10 wtppm or less, and when it exceeds 50 wtppm, the chlorine conversion rate decreases. The method for adjusting the water content is not particularly limited, and a known dehydration treatment method, for example, a method using a dehydrating agent such as molecular sieve, a method of dehydrating by distillation, etc. can be mentioned.

In the present invention, both liquid phase reaction and gas phase reaction can be carried out, but liquid phase reaction is particularly preferable. Further, either a batch method or a continuous method is possible. An example of the reaction method is as follows. The batch reaction can be carried out by blowing a chlorinating agent, particularly preferably chlorine gas, into a suspension of the catalyst in BZ or CB. The continuous reaction can be carried out by circulating BZ or CB and chlorine in a reaction column filled with a catalyst. Chlorine may be diluted with an inert gas in a nitrogen tower before use.

The optimum supply ratio of chlorine to the reaction system is determined by the reaction temperature, the raw material / catalyst ratio, etc. For example, in the case of a fixed bed continuous reaction, 1 to 1500 mol / kg-cat · h
r is preferable, and more preferably 5 to 500 mol / kg-cat · hr.
Is. If the amount of chlorine is too small, chlorination will not be carried out sufficiently, and if it is too large, unreacted chlorine will increase, which is not economical.

It is desirable that the amount of chlorine supplied to BZ and / or CB be slightly in excess of the theoretical amount.

Taking the batch type as an example, the use ratio of the catalyst is preferably 0.1 g of activated alumina, and more preferably 1.0 g to 20 g per mol of BZ or CB. If it is less than 0.1 g, the load of the catalyst becomes large, and there is a possibility that a sufficient chlorine conversion rate cannot be obtained.

In addition, the contact time of BZ or CB when carrying out the continuous reaction is preferably 1 to 100 g-cat · hr / mol, more preferably 10 to 100 g-cat · hr / mol. If the amount is too small, it cannot be said that a sufficient chlorine conversion rate can be obtained as in the batch system. If the amount is too large, the effect commensurate with the amount of the catalyst used cannot be expected.

The activated alumina used as a catalyst in the present invention refers to metastable alumina excluding α-alumina, and generally corresponds to κ, θ, δ, γ, η, χ, ρ alumina.
It may be a mixture of these.

The shape of the catalyst can be arbitrarily selected according to the reaction method, and includes powder, granules, spheres, cylinders, and rings. The shape and size of activated alumina have no essential influence on the reaction result.

If the reaction is continuously carried out for a long time, the water content in the activated alumina increases, which greatly affects the reactivity and the life of the catalyst, and the chlorination rate may decrease. 5.0 wt% or less, more preferably 0.1 wt
% Or less. The water content of the activated alumina may be adjusted by a drying treatment. The drying temperature is preferably 100 ° C to 500 ° C. If the drying temperature is too high, the structure of activated alumina may be transformed into α-alumina.

The present invention can be carried out at room temperature to the boiling point of the reaction mixture, but industrially preferably 30 ° C to 130 ° C.

In carrying out the present invention, the type of apparatus used is not particularly limited, and an ordinary fixed bed may be used, but a fluidized bed or a moving bed may also be used.

Separation and purification of the product after the reaction do not require means such as washing with water, and general separation and purification means such as fractional distillation and crystallization may be used.

[Examples and Comparative Examples]

Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples.

Example Reaction tube equipped with reflux condenser, thermometer, stirrer, gas blowing tube and reaction product distillation outlet (Pyrex: 36 m
mφ × 330mmL), 60g of ring-shaped molded active alumina
At a reaction temperature of 70 ° C, BZ: chlorine = 0.46: 0.6m
The reaction was carried out by supplying at ol / hr for 150 hours.

As the BZ, the water content was previously measured by molecular sieve.
Moisture content is obtained by dehydration up to 10wtppm, and activated alumina is dried at 400 ℃ for 3 hours in advance.
The thing adjusted to 0.1 wt% or less was used.

The reaction product distilled out and the amount of unreacted chlorine flowing out were analyzed at regular intervals. As a result, the PDCB selectivity remained unchanged at 75%, and the chlorine conversion rate at the start of the reaction was 99.8%.
There was no change in the chlorine conversion rate even after the lapse of time.

PDCB selectivity and chlorine conversion are values calculated by the following formula.

Comparative Example A reaction was carried out in the same manner as in Example except that the raw material BZ having a water content of about 100 wtPPm was used as it was without pretreatment, and only activated alumina was pretreated in the same manner as in Example.

As a result, the PDCB selectivity was 74.2%, which was a little low and remained unchanged, but the chlorine conversion at the start of the reaction was 99.2%, but after 150 hours, the chlorine conversion had dropped to 90.0%.

C) Effect of the Invention According to the present invention, the selectivity of PDCB is high, the catalyst life is long, the chlorine conversion rate can be maintained at a high rate for a long time, and DCB can be produced industrially extremely advantageously. .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-93550 (JP, A) JP-A-62-87536 (JP, A)

Claims (1)

(57) [Claims] 1. When producing dichlorobenzene by chlorinating benzene and / or monochlorobenzene, activated alumina is used as a catalyst and the water content is 50.
A method for producing dichlorobenzene, which comprises chlorinating wtppm or less of benzene and / or monochlorobenzene.