DE2225695B2 - Process for the preparation of chlorinated benzonitriles - Google Patents

Description

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In Japanese Patent No. 22,591, the production is of pentachlorobenzonitrile by reacting tolunitrile in vapor form with chlorine gas Described temperatures from 200 to 400 ° C in the presence of a catalyst. The patent specification states that pentachlorobenzonitrile as a chemical for agricultural purposes as well as a raw material is suitable for the production of heat-resistant resins. as

In the article "Thermal Stability of Some Organic Compounds" in the Journal of Chemical and Engineering Data. 7, 277 (1962) it is stated that benzonitrile decomposes in the gas phase at 570 to 600 ° C.

You first carried out your own laboratory research showed that benzonitrile reacts to chlorine under the most varied of reaction conditions is quite stable even in the presence of chlorination catalysts when attempting the chlorination perform in the liquid phase. The invention, at high temperature in the gas phase The procedures carried out represent an improvement over the state of the art in this respect. than no catalyst is required. This eliminates the need for costly cleaning processes and more In addition, both extremely high yields and sales are achieved.

The invention relates to a process for the preparation of chlorinated bezonitriles by reaction of chlorine with benzonitrile or a partially chlorinated benzonitrile in the gas phase, which thereby is characterized in that chlorine is mixed with the benzonitrile in an open reaction tube (a Throughput pipe; see below) at a temperature of 650 to 850 ° C in the presence of an inert Diluent gas and sets.

Benzonitrile or partially halogenated benzonitrile can thus by the action of chlorine at high Temperature in the gas phase can be halogenated smoothly in the absence of a catalyst. The non-catalytic one Gas-phase chlorination of benzonitrile can be conducted so that pentachlorochlorobenzonitrile is higher Purity is formed. Since the decomposition temperature of benzonitrile given in the literature is 5 70 to 600 ° C, it had to be assumed that in the high-temperature process according to the invention a decomposition of the starting material take place and as a result of the expected cleavage of the benzonitrile Hexachlorobenzene would be obtained.

The following examples show the conditions that exist in various gas phase reactions between Chlorine and benzonitrile can be used in the presence of nitrogen as diluents. The implementers, are carried out in a 533 x 25 mm tube made of chemical-resistant, heat-resistant glass, which is heated in its entire length from the outside by an electric furnace. The m The maximum temperature given in the examples is that which occurs approximately in the middle of the reaction tube In all examples, the chlorine is injected into the reactor and measured by a rotameter. That Benzonitrile is pumped into an evaporation vessel with the aid of a metering pump (i »Ruska«). That gaseous benzonitrile is mixed with nitrogen, which is also introduced into the evaporation vessel The gaseous mixture of benzonitrile and nitrogen is then passed to the reactor inlet, where it comes into contact with the chlorine. Chlorine, benzonitrile and nitrogen then flow through that Reaction tube, and the halogenated product formed is collected in a water scrubber. The purity of the product obtained is determined by gas-liquid chromatography. Included w * d found that the proportion of the product that does not consist of pentachlorobenzonitrile, a mixture of less strongly chlorinated benzonitrile products represents.

The invention is illustrated by the following examples explained in more detail. Under the conditions used, the yield (conversion of benzonitrile in a chlorinated benzonil (ril) at or near 100%.

example 1

A mixture of 91.2 liters per hour of chlorine, 173.11 nitrogen per hour and benzonitrile per hour 12 ml per hour in a tubular reactor system made of Vycor glass (533 x 25 mm) initiated with an electric oven about 4.8 hours to a maximum Reactor temperature of 721 ° C is heated. The material emerging from the reactor is collected through a collecting system which leads to a sodium hydroxide scrubber. There are 159.0 g (yield 99.4%) obtained colorless pentachlorobenzonitrile which melts at 212 to 214 ° C.

Analysis for C ₇ Cl, N:

ber .: Cl 64.34%

gof .: Cl 64.3%

After recrystallizing twice from chlorobenzene, the melting point of the substance is 214 up to 214.5 ° C.

Analysis for C ₇ CUN:

found: C 30.53%; Cl 64.34%; N 5.09%;

Found: C 30.71%; Cl 63.88%; N 5.03%.

The purity of the pentachlorobenzonitrile is accordingly over 96%. It also shows the gas chromatographic Analysis of the crude reaction product that benzonitrile conversion is complete; d. H. IOD "/, is.

Example 2

The reactor and collection system described in Example 1 are also used in the im the following halogenation is applied:

Benzonitrile (32.0 ml per hour), chlorine and nitrogen in a molar ratio of 1: 19.2: 20.3 are 4 Introduced into the reaction tube at a maximum reactor temperature of 741 ° C. for hours. It will 341 g (yield 99.7%) of pentachlorobenzonitrile isolated with a purity of 95%. The benzonitrile

conversion is 100%. 98.0% increased.

Together with the gaseous chlorine and the at the same temperature and the same ratio

Gaseous Benzonitrü being a diluent the reactant can reduce the contact time with introduced into the reaction zone. The diluting effects comparable to those of increasing the medium must be changed from short to long during the reaction between chlorine 5, and the benzonitrile behave inertly and called the Re- The same applies to the ratio of chlorine to the action temperature be gaseous. Gold-treated zonitrile.

Diluents are, for example, nitrogen and through appropriate adjustment of the chlorine and

Hydrogen chloride. The nitrogen content of the feed gas can do that

The degree of chlorination and the percentage ratio of chlorine to benzonitrile changed who conversion of the benzonitrile to the chlorinated den, the approximate contact time would be three Benzonitrile is held by the seconds in the implementation. In a number of verses Temperature, the ratio of the small reactions became the ratio of chlorine to benzonitrile participant and the speed of the sentence varies within the range of 10: 1 to 34.6: 1. Since the process according to the invention 15 changes, while the reaction temperature is about 720 several different reactants were kept below ± 6 ° C. In all experiments of this kind and several different products were obtained, the benzonitrile conversion was quantitative. Under can be maintained, no generally these reaction conditions resulted in an increase specify valid parameters. The molar ratio of chlorine to benzonitrile of Applying reaction conditions can, however, increase the purity of the pentaeinem in ao 10: 1 to 1S: 1 simple preliminary test determined chlorobenzonitrile from 62.6 to 73.5% by increasing it will. the ratio of chlorine to benzonitrile to 93.6%

Increased at a minimum temperature above the boiling point, and by increasing the ratio of point of benzonitrile and chlorine, about 400 ° C, chlorine to benzonitrile to 35: 1 was the purity the reactants begin in the gas 23 of the pentachlorobenzonitrile increased to 96.1%. To the first phase to react with each other, so that a partial generation of pentachlorobenzonitrile with high pure halogenated Benzonitrile should therefore be obtained in low yield, the chlorination in the presence of a will. As the temperature rises, the yield of a relatively large excess of chlorine increases and degree of halogenation. Another temperature should be carried out, preferably at an increase leads to a practically 100 percent ratio of chlorine to benzonitrile of over 15: 1 Yield of chlorinated benzonitrile. If the tem- use of ratios above 25: 1 is jeperature increased even further, the halogen level also reached for the formation of high-purity pentachlorobennination a value of about 100%. As already zonitrile is not required. When pentachlorbene mentions itself, is the temperature at which an auszonitrile with a purity of less than 100% yield of about 100% and a halogenation of 35 can be achieved by increasing the reaction rate by about 100% takes place, namely from 650 to 850 ° C, temperature, the contact time and the ratio of The purity of the pentachlorine decomposition temperature is considerably higher than the chlorine to benzonitrile reported in the literature the aromatic compound so- zonitrile can be increased.

such as the halogenated aromatic compound, and the purity of the pentachlorobenzonitrile formed

nevertheless, in the method according to the invention, it also fluctuates with the duration of contact. At a no decomposition. The maximum temperature, in a series of experiments, was the contact time at konweicher an approximately 100 percent yield of the constant molar ratio of chlorine to benzonitrile of about 100% chlorinated benzonitrile is obtained, 34.5: 1 and a temperature of 710 ± 6 ° C variliegt at about 850 ° C. With comparable proportions. An increase in contact time from 1.4 to Sen of chlorine to benzonitrile and comparable Kon- 45 2.6 seconds resulted in an increase in the purity of the cycle times is increased by increasing the maximum temperature of pentachlorobenzonitrile from 75.7 to 94.9%. The Bentur In the reactor from 702 to 719 "C the purity of de * zonitrile conversion was quantified in these experiments Pentachlorobenzonitrile from 84.3% to titative.

Claims (1)

Claim: Process for the production of chlorinated benzonitriles by reacting chlorine with Benzonitrile or a partially chlorinated Βεη-zonitrile in the gas phase, characterized in that chlorine is mixed with the benzonitrile in an open reaction tube at a temperature from 650 to 850 ° C in the presence of an inert diluent gas.