JPS60239452A - Preparation of pentachlorobenzonitrile - Google Patents

Abstract

PURPOSE:To obtain the titled high-purity compound useful as an intermediate for synthesizing agricultural chemicals, drugs, etc. without requiring complicated after-treatment operation, by reacting benzonitrile with chloride in a gaseous phase by the use of active carbon and an iron compound as catalysts. CONSTITUTION:Benzonitrile is reacted with chlorine by the use of active carbon and an iron compound (e.g., metallic iron, or iron oxide) as catalysts in a gaseous phase, to give pentachlorobenzonitrile. The aimed compound having >=97% purity is obtained by the use of the catalyst, further the catalytic life is prolonged, for example, the aimed compound having 99% purity is obtained even 80hr after the beginning of the reaction. An amount of the catalyst used is 1- 100pts.wt., preferably 5-50pts.wt. when the reaction is carried out in a fluidized bed which is advantageous for mass production by long-time continuous operation and 100pts.wt. raw material (BN) is fed per hour, and an amount of the iron compound supported is 2-20pts.wt. calculated as iron based on 100pts.wt. active carbon.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses activated carbon and an iron compound as a catalyst to react benzonitrile and chlorine in the gas phase, thereby producing various pesticides and
The present invention relates to a method for producing pentachlorobenzonitrile, which is useful as an intermediate raw material for medicines, dyes, and the like.

Conventionally, benzonitrile (hereinafter abbreviated as BN) was used as a raw material,
As a method for producing pentachlorobenzonitrile (hereinafter abbreviated as PCBN) in the gas phase in the presence of a catalyst, for example, the method described in Japanese Patent No. 618767 is known.

However, in the patented method, 4 to 7% of hexachlorobenzene and other by-products are present due to the chlorination decomposition reaction of nitrile groups. Because such by-products exist in large quantities, PCBN is used industrially and in large quantities.
When producing and subjecting this product to the next reaction step, complicated classification, purification means, and other post-treatments are required. In addition, when we conducted an experiment on the method described in the above patent, we found that when only activated carbon was used as a catalyst, the reaction started from 1 to 1.
After 2 hours, the purity was 96% as stated in the specification.
It was confirmed that the front and rear PCBNs could be obtained. However, as the experiment progressed further, the purity of PCBH decreased to around 90% 5 hours after the start of the reaction, and around 70% after 10 hours, making it necessary to activate or replace the catalyst, and the reaction was temporarily stopped. The situation had to be interrupted. In addition, when using a catalyst in which chlorides of alkali metals and alkaline earth metals, such as potassium chloride and barium chloride, are attached to activated carbon, no catalytic activity is observed, as in the case where activated carbon alone is used as the catalyst. However, no improvement in catalyst life was observed.

Under these circumstances, the method of the above patent provides highly pure,
We had no choice but to conclude that it would be difficult to continuously mass-produce PCBN over a long period of time without requiring complicated post-processing operations.

The present inventors have developed a method for producing high-purity PCB by gas-phase chlorination of BN.
In order to find a way to mass produce N continuously over a long period of time,
As a result of various studies, we have found that when activated carbon and iron compounds are used as catalysts, PCBN with a purity of 97% or more can be obtained, and the catalyst life is also extended. It was discovered that PCBN could be obtained, and the present invention was completed.

That is, the present invention provides a method for producing pentachlorobenzonitrile by reacting benzonitrile and chlorine in the gas phase in the presence of a catalyst, characterized in that activated carbon and an iron compound are used as the catalyst. This is a method for producing nitrile.

Examples of iron compounds that are one of the catalyst components used in the present invention include metallic iron, iron oxides, hydroxides, inorganic acid salts, organic acid salts, and carbonyl compounds. During the reaction, these iron compounds exist as iron chlorides and are thought to act as catalysts.

The method of the present invention is carried out by filling the reaction section of the reactor with a catalyst and supplying the raw materials BN and chlorine therein either separately or in a mixture. The catalyst component used here is such that at least one of metallic iron, iron oxide, hydroxide, inorganic acid salt, organic acid salt, or carbonyl compound is supported on activated carbon that also acts as a carrier. The supporting method is not particularly limited, but for example, a method of mixing an iron compound aqueous solution and activated carbon, a method of introducing chlorine in the presence of activated carbon and adding an iron compound thereto, or a method of introducing chlorine in the presence of activated carbon and an iron compound. There are ways to introduce it.

The catalyst is filled into a catalyst bed prior to the chlorination reaction of the present invention, and then chlorine is added to the catalyst bed at a concentration of, for example, 200 to 50%.
It is also possible to activate the catalyst components for 0.5 to 2 hours at a temperature of 0°C. Of course, the catalyst is a fixed bed,
It may be formed in advance into granules or pellets of an appropriate size so as to be filled into a reactor in the form of a fluidized bed or the like. Industrially, activated carbon is made of metallic iron, iron oxides, hydroxides,
Those carrying at least one of inorganic acid salts, organic acid salts, or carbonyl compounds are preferred, and among them, iron chloride, metallic iron, iron hydroxide, iron sulfate, iron nitrate, iron carbonate, iron carbonyl, organic acid iron, etc. are preferable. Preferably, activated carbon supports iron chloride, metallic iron, iron oxide, or iron hydroxide. The amount of catalyst to be used is not specified, but when the reaction is carried out in a fluidized bed, which is advantageous for long-term continuous mass production, raw material B is generally used.
When adding 100 parts by weight of N per hour, the catalyst
100 parts by weight, preferably 5 to 50 parts by weight, and the supporting ratio of the iron compound is generally 2 to 20 parts by weight, preferably 5 to 15 parts by weight of iron per 100 parts by weight of activated carbon.
Particularly preferably, the amount is 7 to 13 parts by weight.

The supporting ratio of iron compounds is particularly important; for example, if it is too low, sufficient catalyst activity and catalyst life cannot be obtained, and if it is too high, a state of overchlorination is likely to occur, and by-products may be generated. This is undesirable because the purity of the target product decreases.

It should be noted that the catalyst may further support other metal compounds such as nickel, chromium, etc. In this case, more desirable effects such as lowering the supported ratio of the iron compound may be obtained.

When carrying out the chlorination reaction of the method of the present invention, an inert diluent such as nitrogen, helium, or argon may be used, and this diluent may be introduced into the reaction tube together with other raw materials or separately. good. The amount of inert diluent to be used cannot be specified as one type, but it is usually 0 to 30 mol per 1 mol of BN,
The amount is preferably 3 to 10 moles. In the chlorination reaction of the present invention, the raw material is usually introduced into the reaction tube in a gaseous state,
For example, this can be done by vaporizing BN and introducing it as it is. The amount of chlorine used is usually 5 to 10 per mole of BN.
mol, preferably 5 to 6.5 mol. The reaction temperature of the chlorination reaction of the present invention is generally 300 to 600°C, preferably 400 to 500°C.

The gaseous substances discharged from the reactor include chlorinated products mainly composed of PCBN, unreacted raw materials, by-product hydrochloric acid gas, and in some cases, inert diluent. The target product, PCBN, can be isolated as a highly purified product by simple methods such as cooling, filtration, and washing with water.

In the method of the present invention, by appropriately selecting the catalyst conditions and each reaction condition, purity of 97% can be maintained for 10 hours or more.
Furthermore, by selecting various conditions, it is possible to obtain the target product with a purity of 99% or higher over a long period of time.

Example 1 As a reactor, the reaction part has an inner diameter of 1.00 mm and a height of 1.20 mm.
This is an Inconel vertical reaction tube with a catalyst fluidized bed of 0m+n, to which an Inconel preheating tube with an inner diameter of 40mm and a length of 550mm is connected, and these are covered with an electric heater and heat insulating material so that the temperature can be controlled. It was used.

Under a nitrogen stream, 2,900 g of activated carbon (GL-60 manufactured by Tsurumicol) adjusted to a particle size of 32 to 100 mesh was placed in the catalyst-packed section of the reaction tube, heated to 350°C, and then chlorine gas was added at 12.2ρ/min. , nitrogen gas was introduced at a rate of 14.60/min, and 20 minutes after the start of introduction, 320 g of iron powder was introduced from the top of the reactor to activate the catalyst for about 1 hour.

Benzonitrile 10.6+n(!/min) was passed through a vaporizer, nitrogen gas was introduced into the reaction tube along with 12.3ρ/min through a preheating tube, and chlorine gas 12.2θ/min was introduced into the reaction tube through another preheating tube. The reaction was carried out for about 10 hours at a temperature of °C.

The gas discharged from the reactor is absorbed into a slurry using a water scrubber, separated by filtration using a filter, washed, and dried to a purity of 99%.
．． 1% of target material (white crystals) 16.15 to 8 (yield 93
．． 1%).

Examples 2 to 13 In the same manner as in Example 1, catalyst activation and the following first
Table 1 shows the results of the reaction according to the conditions shown in the table.

In addition, PCBN content (%) at each reaction time in Table 1
) is the result of sampling from the sampling port provided at the top of the reactor and analyzing it by gas chromatography.

In addition, the yield of the target product in each example was 92 to 96%.
Met.

Note) The abbreviations in the table are as follows.

A, C,: Activated carbon Fe; iron powder is introduced from the top of the reactor Ni; nickel powder; Cr; chromium powder; CrCθ3
・6H20; Chromium chloride Q -Fe00tl;
Dacite is KCρ; Potassium chloride is BaCρ2・2H20: Barium chloride is t ++ 1
+ 1 +++ Bedding 1 1, ;l l + = : C:! , = Hm-purple"

Claims (1)

[Claims] A method for producing pentachlorobenzonitrile by reacting benzonitrile and chlorine in the gas phase in the presence of a catalyst, the method comprising using activated carbon and an iron compound as the catalyst.