DE1286001B - Process for the preparation of aromatic carboxylic acid nitriles - Google Patents

Description

ί 286 001

1 2

It is from the German patent 482 943 be or anilines, which by an alkyl group and a knows that carboxylic acid nitriles are obtained when halogen atoms are substituted. For example, let the vapors of formic acid primary amines in the case of the formyl compounds of 2,3-dimethylaniline, elevated temperature over highly porous catalysts, 2,4-dimethylaniline, 2,5-dimethylaniline, 3,5-dimewie Silica gel, activated carbon or alumina conducts. 5 thylaniline, 3,5 - dichloroaniline, 2,6 - dichloroaniline, The reaction takes place via the N-formyl compound 2 - methyl - 3 - chloroaniline, 2 - methyl - 4 - chloroaniline, as an intermediate. However, the 2-chloro-4-methylaniline or the 3-chloro-4-methyl expected 3-chloro-4-methylaniline is not formed Use isonitrile, but rather aniline as a result of a rearrangement.

a nitrile which contains one more carbon atom than C _a -C ₄ fatty acid nitriles can be used as a solvent

the amine used. In this process, however, io or C ^ Cg-Benzolcarbonsäurenitrile, z. B. acetonitrile, the yields and in particular the sales unbe- propionitrile, butyric acid nitrile, benzonitrile, tolunitrile satisfactory. Another disadvantage of the method of working or using the nitriles to be produced themselves. The fact is that the catalysts are not suitable for the furthermore that the formyl compounds of C ₁ -C ₃ continuous operation are not suitable. Alkylamines and primary aromatic C ₆ -C _8, namely, are completely lost after just a few hours. 15 monoamines, e.g. B. methylamine, ethylamine, from the German patent 1117 121 is known / 3-methoxyethylamine, aniline, o-, m- and p-toluidine that when using a relatively wide-pored solvent use. The solvents used as catalysts are the desired carboxonitriles, generally in amounts of 10 to 40 percent by weight, in higher yields and higher percentages, based on the starting material. Sentences are obtained. In addition, the catalyst described there has a long service life as the catalyst preferably used as a solid. In the case of silica gels or silicates, the starting materials which may have higher melting points, e.g. B. in addition an oxide of a metal of III. to VI. Group N-formyl compounds of the xylidines or halogen of the Periodic Table and those of the supersubstituted anilines, however, difficulties occur predominantly, preferably more than 75%> pores with regard to a precisely metered product supply and 25 with a radius of 10 to 200 Å, preferably a radius 12 resinification in the catalyst zone. Even more difficult to 100 Å, a mean pore radius of 20 to ker, the difficulties are significant if the 100 Å, preferably 20 to 60 Å, and a specific nitrile is to be produced on a larger scale and surface area of at most 550 m ² / g , preferably from the formyl compound to be pumped into the furnace, have a maximum of 500m ² / g. One must invent that. Crystallization leads to blockages in the method according to the invention, for example in such a way that the supply line or pump malfunctions. Finally, the solvent from the German Auslegeschrift 1 068 241 is added to the N-formyl compound in a certain ratio and the gelation of aromatic nitriles by catalytic molten mixture via a preheater, steam-dehydration of aromatic derivatives of the between 460 and ^{formamide heated to 560 °} C. at an elevated temperature, with catalyst conducting. The formyl compounds are expediently brought together either in the presence of the starting compound, an inert gas, such as nitrogen, an inert carrier gas, or vaporized by the application of material, carbon monoxide, ammonia or any desired negative pressure. This process is for mixing these gases in about 0.5 to 20 times the maximum position of the nitriles described below from laren amount, based on the N-formylamine. N-formyl compounds with a higher melting point are unsuitable. The dwell time of the mixture on the catalyst is net because the measures described in German Auslegeschrift 1,068,241 are generally from 0.5 to 10 seconds, advantageously 1.5 to 1.5 seconds, and the 3 seconds The space velocity is about 25 to prevent resin build-up in the catalyst zone. 35 kg of N-formylamine per liter of catalyst and day.

It has now been found that aromatic The reaction is advantageously carried out under atmospheric carbonitriles through implementation of N-formy pressure, however, are also decreased or increased primary aromatic monoamines with one pressure possible. One can be continuous or dis-melting work continuously at a temperature above 80 ° C. The procedure can be both from 460 to 560 ° C with the help of solid silica in a fixed bed as well as in a fluidized bed, gels or silicates, which may also be substances that can be produced by the process

Oxide of a metal of the III. to VIII. Group of 50 valuable intermediates, e.g. B. contain for the production of the periodic table and the predominant part of dyes or pesticides. Part, preferably more than 75%> pores from. -I ₁

Radius 10 to 200 Å with a mean pore radius Example 1

from 20 to 100 Å and a specific surface area of 200 cm long and 5 cm wide perpendicular

have a maximum of 550 m ² / g, as catalysts, standing pipe made of stainless steel is optionally obtained in the presence of an inert gas, in very lower and upper thirds with clay rings, in medium-good yields and in a very simple manner, leren third with filled with the catalyst. To prepare the reaction with a solution of the Nf or- ment of the catalyst, 200 g of a silica gel, mylated primary aromatic monoamines a) containing 90% pores with a radius of 10 to 200 Å, a C ₂ -C ₄ fatty acid nitrile, b) in a C ₇ -C ₉ benzene 60 has an average pore radius of 48.9 Å and a carboxylic acid nitrile, c) in an N-formylated primary specific surface area of 314 m ² / g, with a C ₁ -C ₃ -Alkylamine or d) in an N-formylated solution of 5 g of titanium tetrachloride in 100 g of absolute primary aromatic C ₆ -C ₈ monoamine, which is offset by the alcohol. The mixture of N-formyl compound to be reacted for V4 hours is left to stand in the air and then 40 g of water are carried out. 65 to. The catalyst is in one before use

The starting materials used are a stream of high-melting ammonia heated to 300 ° C. for 10 hours. on Formyl compounds of primary aromatic the vertical tube is as product pre-monoamines, like dialkylanilines, dihaloanilines another 100 cm long and 5 cm wide warmer

Stainless steel tube, filled with clay rings, attached. Both pipes are heated from the outside so that the temperature in the Produktvorwärmer 450 to 500 ⁰ C and in the catalyst zone 450 is up to 520 ⁰ C. 75 liters of nitrogen per hour are now passed into the furnace from above and, at the same time, 2 kg of a liquid mixture of 4 kg of N-formyl-2,4-dimethyl-aniline and 1 kg of benzonitrile are also pumped into the upper part of the furnace. From 75 kg of the formyl compound, with a conversion of 93%, 61.5 kg of 2,4-dimethylbenzonitrile with a boiling point of ₂₀ = 114 ° C. is obtained. This corresponds, taking into account the 2,4-dimethylaniline recovered, to a yield of 98% of the Theory. The added solvent is recovered almost quantitatively by distillation.

Example 2

A 100 cm long and 5 cm wide vertical quartz tube is used as the reaction tube, the lower and upper third of which is filled with glass rings and the middle third with the catalyst described in Example 1 and is heated from the outside. Every hour, 200 ml of a solution of 1.6 kg of N-formylamino-4-chloroaniline in 0.4 kg of benzonitrile and 25 liters of nitrogen are continuously fed into the furnace. The temperature in the catalyst zone is, the furnace discharge is heated with 800 g of 89% aqueous formic acid at normal pressure to 100 ⁰ C and distilling off the excess formic acid 480-500 ⁰ C.. The benzonitrile is then recovered under reduced pressure. The fraction between 100 and 125 ^° C. at a pressure of 12 mm Hg is recrystallized from ethanol after solidification. 1065 g of 4-chlorobenzonitrile with a melting point of 92 ° C. are obtained. The conversion is 75%. 240 g of unreacted N-formylamino-4-chloroaniline are recovered. The yield is 90% of theory.

Example 3

In the same device as in Example 2, a mixture of 1400 g of N-formyl-S-chloroM-methylaniline and 600 g of formanilide is reacted. The furnace throughput is 100 g / hr., The temperature of the catalyst zone is from 480 to 51O ⁰ C and the amount of nitrogen 201 / hr. The reaction mixture is treated as described in Example 2 for formylation

of regressed 3-chloro-4-methylanilm with formic acid. 939 g of 3-chloro-4-methylbenzonitrile with a boiling point of ₂ == 90 ^° C. are obtained. With a conversion of 75%, the yield of converted starting material is 82%.

Example 4

A 100 cm long and 5 cm wide vertical quartz tube is used as the reaction tube, the lower and upper third of which is filled with glass rings and the middle third with the catalyst described in Example 1 and is heated from the outside. Every hour, ml of a solution of 0.6 kg of N-formylamino-2,6-dichloroaniline in 0.4 kg of benzonitrile and 25 liters of nitrogen are continuously fed into the furnace. The temperature in the catalyst zone is from 480 to 520 ⁰ C. The furnace discharge is worked up in the usual manner. 790 g of 2,6-dichlorobenzonitrile are obtained, corresponding to 87% of theory, based on converted 2,6-dichloroformanilide.

Claims (1)

Claim: A process for the production of aromatic carboxylic acid nitriles by the reaction of N-formylated aromatic primary monoamines having a melting point higher than 8O ⁰ C at a temperature of 460-560 ⁰ C with the aid of solid silica gels or silicates, which may additionally contain an oxide of a metal of III. to VIII. Group of the Periodic Table and which for the most part, preferably more than 75%, have pores with a radius of 10 to 200 Å with an average pore radius of 20 to 100 Å and a specific surface area of at most 550 m ² / g, as Catalysts, optionally in the presence of an inert gas, characterized in that the reaction is carried out with a solution of the N-formylated primary aromatic monoamines a) in a C ₂ -C ₄ fatty acid nitrile, b) in a C ₇ -C ₉ benzenecarboxylic acid nitrile, c ) in an N-formylated primary Ci-Cs-alkylamine or d) in an N-formylated primary aromatic C _e -C _a monoamine which is different from the N-formyl compound to be converted.