DE2141595C3 - Process for the preparation of 11-cyanoundecanoic acid - Google Patents

Description

The invention relates to a process for the preparation of 11-cyanoundecanoic acid, wherein cyclohexanone converted into!, i'-Peroxydicyclohexylamine and the 3,1'-peroxydicyclohexylamine is pyrolyzed to produce 11-cyanoundecanoic acid.

From the Belgian patent 7 01327 it is already known, l.r-Peroxydicyclohexylamin by Implementation of cyclohexanone, hydrogen peroxide and ammonia in the presence of a catalyst and Manufacture stabilizer. Various catalysts are known for this process, in particular the ammonium salts of inorganic or organic carboxylic acids. With these you will get best results achieved by using ammonium nitrate. It is also known to use various salts and / or complexes of ethylenediaminetetraacetic acid as a stabilizer to use for this reaction!. These stabilizers include the di- and tetrasodium salts of ethylenediaminetetraacetic acid and the aluminum, Zinc, barium, nickel, lanthanum and similar complexes of the disodium salt.

From the Belgian patent 7 54 599 it is already known that the l, l'-peroxydicyclohexylamine thus obtained to 11 -cyanoundecanoic acid by pyrolysis of the peroxydicyclohexyiamine at higher temperatures üiiü at atmospheric or higher Pressure can be transferred.

So far, the cyclohexanone, which is used to obtain the starting material for this? proceedings used, supplied from an independent source. Own attempts to use the cyclohexanone by-product from the pyrolysis stage immediately appeared to be uneconomical because this would reduce the yield of lJ'-peroxydicyclohexylamine significantly decreased. This was mainly due to the impurities present in the cyclohexanone attributed and therefore had to cumbersome methods for the separation and purification of the cyclohexanone must be accepted before it is used again as food for the production of!,! '- peroxydicyclohexylamine could be used.

Surprisingly, it has now been found that improved yields of 1.l'-peroxydicyclohexylamine by partial separation of the nitriles and other impurities contained in the cyclohexanone by-product are present using any conventional technique be able. It was completely surprising that the presence of nitriles reduced the yield of 1,1'-peroxydicyclohexylamine decreased as these are viewed as inert impurities or diluents willu. Furthermore, it was completely surprising that by reducing their concentration the yield of the peroxyamine no longer falls below a certain limit value in recycled hexanone

ίο is worsened.

The inventive method is characterized in that the existing after pyrolysis Cyclohexanone purified to a nitrile content of less than 0.5 percent by weight and used as a food in the Procedure is returned.

Cyclohexanone can be converted into 1,1'-peroxydicyclohexylamine by reacting the cyclohexanone with hydrogen peroxide with the formation of 1. J'-dihydroxycyclohexyl peroxide, whereupon an all the more bvt-jng des l.r-DihydroxydicycIohexyiperoxyds with Ammonia follows. Instead, the cyclohexanone can become!, I'-peroxydicyclohexylamine in a single Stage can be converted by simultaneous reaction with hydrogen peroxide and ammonia.

11-cyanoundecanoic acid can be obtained by feeding U'-peroxydicyclohexylamine in the form of liquid droplets into a gas. which is inert under the reaction conditions, and maintained the elevated temperature in an essentially adiabatic reactor with no fill a pressure in the range of 300 mm Hg to 3 atmospheres absolute.

The gas into which the liquid droplets of l.r-PeroxydicycIohexyiamine are fed for the purpose of pyrolysis can be any gas which is inert under the reaction conditions. Examples suitable gases are nitrogen, water vapor and combustion exhaust gases.

1, Γ-Peroxydicyclohexylamine can be in the form liquid droplets can be obtained by any suitable method. These droplets can They only emerge from peroxydicyclohexyiamine exist, but they can also contain other substances. The peroxydicyclohexylamine can are obtained in the form of liquid droplets by spraying them into the reactor as a liquid phase into it. For example, Ι.Γ-Pero..ydicyclohexylamir are converted into droplets by atomizing a stream of the peroxydicyclohexylamine in the liquid phase by the action of a gas flow maintained at higher temperatures. Atomize is accomplished in the same way as the well-known fragrance spraying and suitable atomizers are well known. Instead, the liquid droplets can be obtained by injecting of the peroxydicyclohexylamine in the liquid phase by a suitable spray device without the Exposure to a gas flow is required for atomization. Other types of atomizers, e.g. B. rotating Cup atomizers can also be used.

Temperatures at which the gas is maintained in the reactor can vary over a fairly wide range. Temperatures in the range from 250 to 1000 ° C can be used. The lower temperature ^{limit is preferably 300.degree.} C., while the upper limit is preferably 600.degree. These temperatures relate to

understandable on the reaction zone and not on the temperatures of a gas stream before it enters the zone entry. The residence time of the peroxydicyclohexylamine in the reactor can be over a fairly wide range vary. Examples of suitable times are those in the range 0.05 to 5 seconds.

The inert gas under the reaction conditions is preferably in the reaction zone with a such a rate that the molar ratio of inert gas to the peroxydicyclohexylamine ranges from 5: 1 to 500: 1.

The reaction products of this pyrolysis stage include 11-cyanoundecanoic acid, cyclohexanone, some nitriles and other minor by-products. The cyclohexanone can be separated from the 11-cyanoundecanoic acid, which is the major product of the pyrolysis reaction, and from some of the less volatile impurities by any conventional technique and recovered for recycling. For example, it can be separated off by distillation in the presence of water, namely the water used as a dilution in the pyrolysis reaction. The azeotrope exiting the top of the column can be cooled and allowed to separate into two layers. The lower aqueous layer can be continuously returned to the top of the column as reflux and the upper cyclohexanone layer can be continuously removed. This C) -lohexanene layer is contaminated by the nitriles and other minor impurities, the exact amount of which depends on the effectiveness of the distillation. If further purification of this cyclohexanone is desired, it can be continuously used in an efficient column (e.g. Oldershaw column, with a 10-plate rectification compartment, 25-plate stripping compartment, reflux ratio about 3 to 4: 1) can be fractionated. The amount of nitriles and other impurities in the recovered cyclohexanone can thereby be reduced to about 0.5 percent by weight.

The one responsible for the reduction in the yield of 1,1'-peroxydicyclohexylamine responsible impurity if impure cyclohexanone is recycled has not yet been identified. The effect of the impurities in the edible cyclohexanone however, appears to be proportional to the amount of cyclohexanone present in the fed Nitriles. For example, if the amount of nitriles present in the edible cyclohexanone below 0.5 percent by weight, based on the total weight of the cyclohexanone food can, can 90% yield of Ι, Γ-peroxydicyclohexylamine can be achieved with nominal concentration (0.08 percent by weight) of the sodium salt of Ethylenediaminetetraacetic acid as a stabilizer. This yield can also be maintained, though greater than 0.5 weight percent nitriles are present in the cyclohexanone, provided that the stabilizer concentration is increased in a corresponding manner. Thus, although the exact nature of the adverse If the constituent is not known, it appears possible to determine the effectiveness of the procedure by means of rules to regulate the nitrile content in the cyclohexanone food.

The recovered cyclohexanone can be mixed with about 3 volumes of fresh Cyclohexanone and the mixture can then be used in the first stage for the production of Ι, Γ-peroxydicyclohexylamine be fed in. Instead, the impure cyclohexanone layer, which has a larger Contains proportion of nitriles and other impurities, mixed with fresh cyclohexanone before the distillation is carried out to partially remove the nitriles and impurities.

It has been observed that when the cyclohexanone food is used in the first stage of the preparation of 1,1'-pejoxydicyclohexylamine, less than 0.5 percent by weight of nitriles, preferably between 0.05 and 0.2 percent by weight, based on the total weight of the Cy _1. ' hexanone food contains, the best yields of peroxydicvciohexylamine can be obtained. The Reini-

Of course, the cyclohexanone produced in the pyrolysis of peroxydicyclohexylamine can be used be effected in a number of ways, of which the one mentioned above is only one preferred example is.

ao Further embodiments of the invention are provided explained in the following examples. In these examples, all references to the scheme the nitrile concentration in the cyclohexanone food also regulates the concentration of the disruptive Cover the ingredient in the cyclohexanone dish.

example 1

Recovery of Cyclohexanone
from the pyrolysis product

3935 g of crude Ι, Γ-peroxydicyclohexylamine containing 3463 g of the peroxide and 354 g of cyclohexanone were added for 50 minutes together with 5500 l / h Steam passed through a tubular reactor kept at 500 ° C. The residence time was 0.19 seconds. The products separate into an organic phase containing 1896 g of 11-cyanoundecanoic acid. 382 g caprolactam, 58 y, -a mixture of hexane and hexenoic acid and 738 g of cyclohexanone, and in an aqueous phase containing 14Gg of caprolactam and approximately 100 g cyclohexanone. Both phases were fed at the top of a 25-plate Oldershaw column. What came out at the top of the column separated into two phases and the organic phase became he removed and delivered 996 g of a product containing 836 g of cyclohexanone and 54 g of a mixture from nitriles.

Purification of Cyclohexanone ^

Recovered cyclohexanone containing 5.4% of a mixture of nitriles was on the 25th plate of a 35-plate Oldershaw column fed. The product obtained on Κυμί contained 0.62% nitrile and was mixed with fresh cyclohexanone to produce Ι, Γ-peroxydicyclohexylamine used.

Production of Ι, Γ-peroxydicyclohexylamine
using purified

circulated cyclohexanone

Cyclohexanone (2.13 moles / h; containing 0.05% nitriles from the addition of the steam-distilled product from crude nitrilic acid to fresh cyclohexanone), ammonia solution (spec. wt. 0.880; 2.8 Moles / h NHa) and hydrogen peroxide solution (39 percent by weight; 1.13 moles / h) were continuously pumped to a two-stage cascade system. the Ammonia solution contained ammonium nitrate as ca-

analyzer (6.1 percent by weight of the total reaction mixture) and the aluminum complex of diethylenediaminetetraacetic acid as a stabilizer (0.08 percent by weight of the total reaction mixture). Both reactors were heated to 30 ° C and the liquid levels therein adjusted to give a total residence time of 9 hours. the The yield of peroxyamine was 90 percent by weight based on the cyclohexanone.

For the purpose of comparison with the above example, a reaction was carried out under the same conditions as above, but with 5% nitriles in the cyclohexanone dish, carried out, the yield falling to 81%.

Example 2

Another attempt was made; - * .: Conditions of Example 1 above ... Inrt with the modification that disodium ethylenediaminetetraacetic acid was fed in as a stabilizer in place of the aluminum complex in ammonia (0.08 percent by weight of the total reaction mixture) and the cyclohexanone food contained 1.4% nitriles. The yield of peroxyamine was 90%.

Pyrolysis of 1,1'peroxydicyclohexylamine,
made from circulating cyclohexanone

3757 g of crude peroxyamine containing 3006 g of the peroxide and 49 g of nitriles were over 80 min together with 4400 l / h of steam through a tubular reactor kept at 500 ° C directed as food. The residence time was 0.24 sec. The products contained 1568 g of 11-cyanoundecanoic acid, 459 g of caprolactam and 70 g of a mixture of hexanoic and hexenoic acid.

Claims (2)

Patent claims: 1. A process for the preparation of 11-cyanoundecanoic acid, wherein cyclohexanone is converted into Ι, Γ-peroxydicyclohexylamine and the 1,1'- peroxydicyclohexylamine is pyrolyzed to produce ll-cyanoundecanoic acid, characterized in that the cyclohexanone present after the pyrolysis to a nitrile content of less than 0.5 percent by weight is purified and fed back into the process as food. 2. The method according to claim 1, characterized in that the cyclohexanone to one Nitrile content of 0.05 to 0.2 percent by weight is purified.