JPH0699333B2 - 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 gas phase direct chlorination of benzene (hereinafter abbreviated as BZ) and / or monochlorobenzene (hereinafter abbreviated as CB), The present invention relates to a method for producing dichlorobenzene (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 (hereinafter abbreviated as MDCB). Among them, PDCB is the most in demand, and is attracting attention as a raw material for polyphenylene sulfide, which is an engineering plastic, in the field of insect repellent.

[Conventional technology]

Conventionally, DCB is produced by directly 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%,
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.

In recent years, BZ and / or CB using zeolite as a catalyst
Several proposals have been made for the selective direct chlorination of. For example, JP-A-59-163329 discloses a liquid phase direct chlorination reaction using L-type zeolite as a catalyst. Although the selectivity of PDCB in this reaction is as high as 80 to 90%, it has a drawback that the catalytic activity decreases in a short time. Further, Japanese Patent Application Laid-Open No. 61-17144 discloses a gas-phase direct chlorine reaction using an offretite-erionite zeolite as a catalyst. The selectivity of PDCB in this reaction is as high as 85 to 90%, and chlorine and BZ and / or CB can be supplied to the zeolite catalyst layer separately without being premixed to improve the catalyst life. However, the improvement of the catalyst life cannot be said to be sufficient.

[Problems to be Solved by the Invention]

The present inventors industrially have a high PDCB selectivity and can provide a long catalyst life in producing DCB by subjecting BZ and / or CB to a gas phase direct chlorination reaction using zeolite as a catalyst. The present invention has been completed as a result of intensive research on an advantageous method for producing DCB.

B) Structure of the Invention [Means for Solving the Problems] The present invention uses a zeolite as a catalyst, and uses BZ and / or CB as a simple substance chlorine (hereinafter simply referred to as chlorine) to carry out a gas phase direct chlorination reaction. This is a method for producing DCB, which is characterized by reacting in the presence of molecular oxygen in producing DCB.

Zeolite used as a catalyst in the present invention is usually called crystalline aluminosilicate,
In the present invention, although not particularly limited, mordenite zeolite is preferably used. Some of the zeolites are naturally present, but it is also possible to synthesize them. In the present invention, either natural zeolite or synthetic zeolite may be used, but there are few impurities and the crystallinity is high. Synthetic zeolites are more preferred.

Zeolites usually contain metal cations such as Na ions and K ions, but in the present invention, zeolites containing such alkali metal ions or alkaline earth metal ions are preferred.

The shape of the catalyst is not particularly limited and can be arbitrarily selected depending on the reaction type, and includes powder, granules, spheres, cylinders, and rings. Zeolite can be used as a mixture with an inert filler such as glass beads.

In the present invention, the zeolite is not used as a carrier for the catalyst as it is in the so-called oxychlorination reaction, but is itself used as a catalyst.

The molar ratio of chlorine supplied to BZ or CB in the present invention is preferably 0.1 to 3.0, more preferably 0.5 to 2.0, based on BZ. If the supply molar ratio of chlorine to BZ or CB is too low, the yield of PDCB may be low, and if it is too high, the amount of higher chlorinated by-products may increase. Further, in the present invention, chlorine alone is used as the chlorine source.

In the present invention, the proportion of molecular oxygen present in the reaction system is 0.02 to 20 in terms of molar ratio based on BZ or / and CB.
Is preferred. If it is less than 0.02, the effect of improving the catalyst life cannot be expected so much, and if it exceeds 20, further improvement in the effect may not be expected.

Molecular oxygen may be present alone, but it is desirable to coexist with other gases, and as coexistent gases, nitrogen, helium, an inert gas such as argon, carbon dioxide,
Examples thereof include hydrogen chloride, and air is particularly preferable in terms of safety, economy, and the like.

When other gas is allowed to coexist, the ratio of molecular oxygen is preferably 5 to 50% by volume of molecular oxygen with respect to the total amount of other gas and molecular oxygen. If it is less than 5% by volume, it may be necessary to increase the volume of the catalyst layer in order to allow the necessary and sufficient amount of molecular oxygen to exist, and if it exceeds 50% by volume.
It may lead to combustion of organic substances such as BZ.

In the present invention, BZ and / or CB, chlorine and molecular oxygen may be brought into contact with the catalyst layer by mixing the respective components in advance and then bringing them into contact with each other, or by supplying each of the components separately. It does not matter if you do.

The contact time = W / F (se is the ratio of the contact of zeolite with BZ and / or CB, chlorine or molecular oxygen.
c) [W (cc): Zeolite, F (cc / sec): BZ and / or CB, when chlorine and molecular oxygen and other gases are used in combination, the total supply amount of these gases] Therefore, the range is preferably 0.5 to 500 seconds, more preferably 1 to 100 seconds. If it is less than 0.5 sec, it cannot be said that a sufficient chlorine conversion rate can be obtained, and if it exceeds 500 sec, the effect of increasing the catalyst amount may not be expected.

The present invention is a gas phase reaction, and the reaction temperature is preferably 100 ° C to 400 ° C, more preferably 150 ° C to 300 ° C. If the reaction temperature is less than 100 ° C, it cannot be said that a sufficient chlorine conversion rate can be obtained. If the reaction temperature exceeds 400 ° C, the PDCB selectivity may decrease.

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.

Examples and Comparative Examples The reaction was carried out using an ordinary fixed bed reactor, and a reaction tube (Pyrex; 30 mmφ × 500 mmL) was filled with a mixture of 10 cc of mordenite zeolite (Nippon Kagaku Kogyo's product name Zeostar NM100P) and 90 cc of glass beads. However, at a reaction temperature of 200 ° C., BZ: chlorine: air (Example) or BZ: chlorine: nitrogen (Comparative Example) = 1: 1: 1 (molar ratio) and W / F (connection time) = 5 sec. Was supplied to carry out the reaction.

The amount of reaction product and unreacted chlorine flowing out were analyzed at regular intervals. The results are shown in Table 1. Figure 1 shows the changes over time in PDCB selectivity and chlorine conversion.

PDCB selectivity was defined by the following formula.

The chlorine conversion rate was defined by the following formula.

Note) The mordenite-type zeolite used for the reaction was 300% after compression molding Zeostar NM100P into 10-14 mesh.
It was dried at ℃ for 3 hours.

C) Effect of the Invention According to the present invention, by-product of ODCB can be suppressed, PDCB can be produced with a high selectivity, the catalyst life can be long, and the chlorine conversion can be maintained at a high rate for a long time. Therefore, DCB can be manufactured industrially extremely advantageously.

[Brief description of drawings]

FIG. 1 is a graph showing changes over time in chlorine conversion rate and PDCB selectivity of BZ according to Examples and Comparative Examples of the present invention.

Claims (1)

[Claims] 1. When dichlorobenzene is produced by subjecting benzene and / or monochlorobenzene to a gas phase direct chlorination reaction using a single chlorine as a catalyst, the reaction is carried out in the presence of molecular oxygen. A method for producing dichlorobenzene, which comprises: