DE1037464B - Process for the preparation of unsymmetrical dialkyl hydrazines by catalytic reduction of dialkyl nitrosamines - Google Patents

Description

Process for the preparation of asymmetrical dialkylhydrazines by catalytic Reduction of Dialkylnitrosamines The invention relates to a process for the preparation unsymmetrical dialkylhydrazines.

Dialkylhydrazines are important as fuels, as intermediates for chemical syntheses, etc. It is known to produce them by reducing dialkylnitrosamines to manufacture. These dialkvlnitrosamines can be made according to a more recent proposal produced by treating secondary amines with mixtures of nitrogen dioxide and nitric oxide. The previously known method for reducing unsymmetrical dialkylnitrosamines to unsymmetrical dialkylhydrazines work using costly chemical Reducing agents such as metallic zinc in acetic acid. After a Another proposal is to use lithium-aluminum hydride to reduce dialkylnitrosamines be used.

So far it has not been possible to obtain asymmetrically disubstituted hydrazines by catalytic hydrogenation of corresponding nitrosamines with satisfactory yields to manufacture. Paal and Yao (Chem. Ber., 63 B [1930], p.65) used one on calcium carbonate deposited palladium contact for the hydrogenation of di-npropylnitrosamine however, even after 154 hours of treatment, only a yield of 3.7% Di @ ropylhydrazine. As described in Grillot (J. Am. Chem. Soc., 66 i '1944], p. 2124), was used in the hydrogenation of diphenylnitrosamine in the presence of Raney nickel or Platinum oxide received only diphenylamine and ammonia. So what was missing was a simple direct process for the preparation of dialkyl hydrazines by hydrogenation of dialkyl nitrosamines.

The invention solves this problem by showing a way to simple manner with good yields unsymmetrical dialkylhydrazines by hydrogenation of dialkylnitrosamines.

It has been found that unsymmetrical dialkylhydrazines are easier Manner and can be produced with good yields. when dialkylnitrosamines having 1 to 6 carbon atoms in each alkyl group, preferably dimethylnitrosamine or diethylnitrosamine, in the presence of one of platinum on carbon, palladium Catalyst based on carbon or rhodium on carbon as a carrier be hydrogenated.

This process is of particular importance for the reduction of dimethylnitrosamine and diethylnitrosamine. Hydrogenation is preferably carried out at temperatures between 20 and 75 ° C. An overpressure of at least 3 kg / cm2 is expediently applied.

In one embodiment of the method of the invention, the nitrosamine initially in water or a low molecular weight alkanol or in an alkane oil ; Dissolved water mixture, mixed with catalyst and then by pressing hydrogenated by hydrogen.

The following examples illustrate the process of the invention. The specified parts are parts by weight. The one for the sales The percentages shown are calculated from the quantities actually received of hydrazines, based on the achievable from the dialkylnitrosamines used theoretical yield.

Example 1 2 parts of a 10% palladium on carbon as a carrier containing catalyst were placed in a heated shaking autoclave to 10 parts of diethylnitrosamine dissolved in 122 parts of 95% ethanol. The shaking autoclave was evacuated and then hydrogen at a pressure of 4 kg / cm2 pressed on. After the equilibrium was established, the Shaking started and continued until it reached a certain temperature Maintained at 35 ° C mixture did not take up any more hydrogen.

The catalyst was now removed by filtration, the filtrate acidified with hydrochloric acid and the ethanol stripped off under vacuum. Of the Hydrochloric acid residue became basic by adding an aqueous sodium hydroxide solution made and the aqueous layer extracted with ether. The ethereal solution was dried, the ether is distilled off and the residue is dried again. By fractional distillation of the residue was 4.4 parts of N, N-diethylhvdrazine obtained corresponding to a conversion of 50 0j0. Example 2 was diethvlnitrosamine hydrogenated according to the method described in Example 1, the following amounts being used were: 5 parts of diethylnitrosamine, 122 parts of ethanol, 1 part of a 10 ° 0 palladium-on-carbon catalyst.

The hydrogenation was carried out in a high pressure shaking autoclave equipped with a heater. 7. At the beginning, hydrogen was released at a pressure of Example 4 15 parts of dimethylnitrosamine, dissolved in 200 parts of 950/0 ethanol, and 4 parts of a 10070 palladium-on-carbon catalyst were placed in the low-pressure shaking autoclave according to Example 1. After evacuation, hydrogen was injected with a pressure of about 3.5 kg cm2. After equilibrium had been established in the system, the mixture was shaken until there was no further uptake of hydrogen. During the shaking, the temperature of the mixture rose from 28 to 46 ° C. After the uptake of hydrogen had ceased, the catalyst was removed by filtration.

In the ethanol filtrate were on konduktometrisclicni Wi-ge 2.6 parts N, N-dimethylhydrazine found. Example 5 Analogously to Example 1, a solution was used Diethvlnitrosamin and catalyst composition containing mixture prepared, wherein the The following amounts were used: 20 parts of dietivitrosamine and 137 parts of 500/0 1lethanol, 2 parts of a 1000 palladium-on-carbon catalyst.

The `mixture was appropriately placed in a low-pressure autoclave Example 1 given, de: autoclave evacuated, hydrogen at a pressure of 3.5 kg @ lcm2 pressed on and after setting the equilibrium; started shaking. A temperature of 60 ° C. was maintained during the hydrogenation. After 2 hours the hydrogen uptake was over.

After the catalyst had been removed by filtration, 10.9 parts of N, N-diethyllydrazip were determined analytically, corresponding to a conversion of 62.10 / 0. A test distillation showed that 99, 40.0 of the analytically determined amount of N, N-diethylhydrazine was present. The distilled 69 kg / cm2 pressed on and then shaken at a temperature of about 50 ° C. After the uptake of hydrogen had ceased, the catalyst was removed. 3.2 parts of N, N-diethylhydrazine, corresponding to a conversion of 720/0, were detected in the mixture by titration. Example 3 The following series of tests were carried out using the methods given in Examples 1 and 2. The amount of N, N-diethylhydrazine present in the mixture was determined using the titrimetric method given in Example 2. N, N-diethylhydrazine was identified via the oxalic acid salt. Melting point 136-137 ° C. EXAMPLE 6 150 parts of an aqueous solution containing 15 parts of dimethylnitrosamine and 1 part of a 100% palladium-on-carbon catalyst were placed in a low-pressure shaking autoclave and hydrogenated as described in Example s, except that one during the hydrogenation Temperature of 45 ° C was maintained. The uptake of hydrogen had ceased after 4 hours. 8.8 parts of N, N-diniethylhydrazine, corresponding to a conversion of 59.70 / " , of the analytically detected N, N-dimethylhydrazine could be obtained by distillation of an aliquot of the mixture, such as in Example S. The oleic acid salt of N, N-dimethylhydrazine had a melting point of 146 ° to 147 ° (', -Carbon catalyst, 150 parts of water.

The procedure was as described in Example 5, but one temperature of 45 ° C is maintained. The uptake of hydrogen had ceased after 2.75 hours. To Filtering off the catalyst, 12.1 parts of N.N-dimethylhydrazine were correspondingly a conversion of 81.7 °! 0 obtained.

Example 8 In a high-pressure shaking autoclave of the type used in Example 2, which, however, had no heating device, 7.5 parts of dimethyl nitrosamine and 0.1 part of a; 50/0 strength rhodium-on-carbon catalyst in 40 parts of water. Hydrogen was injected with an initial pressure of about 66 kg / cml and a temperature of 27 to 30 ° C. was maintained during the hydrogenation. The uptake of hydrogen ceased after 2 hours. 4.6 parts of N, N-dimethylhydrazine were determined analytically in the filtrate, corresponding to a conversion of 62 ° 10. 780 "'of the analytically detected N, N-dimethylhyd @ azine could be obtained by distilling an aluot fraction. EXAMPLE 9 Table II below shows the results obtained with catalysts derived from the platinum used according to the invention -, palladium or rhodium-on-carbon catalysts are different.In all cases, the procedures described in the preceding examples were followed.The analytical method according to Example 2 was used to determine the amount of N, N-diethylhydrazine formed. Comparison of the results obtained in Table II and Example 9 using known catalysts with the data obtained in the process of the invention clearly shows the superiority of the new process. The use of the catalysts according to the invention is the decisive measure of the new process.

As can be seen from Experiments E and F in Table I, decreases with hydrogenation temperatures above 75 ° C. the yield of asymmetrically disubstituted hydrazine decreases. As a solvent Lower Dialkvläther have also proven themselves.

The uptake of hydrogen was generally over after 2 to 10 hours, when the catalysts of the invention were used. The duration of the hydrogenation depended on general conditions. For example, was the hydrogen uptake in the embodiment according to the examples ended after 3.5 hours, while in the experiment A of Example 3 still took up hydrogen after hydrogenation for 10 hours became. In each case, the yield of N, N-diethylhydrazine was greater than 70 ° 7, reached.

The process according to the invention can also be used with other dialkylnitrosamines, for example di-n-propylnitrosamine or diisobutylnitrosamine. Under the term alkyl in the context of the invention is not only the saturated, aliphatic hydrocarbons of the general formula Cn H2n "corresponding To understand alkyl radicals. Also the cyclic, aliphatic hydrocarbons radicals corresponding to the formula CnH, n belong here. First and foremost it will Process for the hydrogenation of such dialkylnitrosamines used in which the Alkyl radicals saturated, aliphatic hydrocarbons of the two described Species correspond and n means numbers from 1 to 6.

Claims (4)

PATENT CLAIMS: 1. Process for the preparation of asymmetrical dialkylhydrazines by catalytic reduction of dialkylnitrosamines, characterized in that dialkylnitrosamines with 1 to 6 carbon atoms in each alkyl group, preferably dimethylnitrosamine or diethylnitrosamine, in the presence of one made of platinum on carbon, palladium on carbon or rhodium on carbon hydrogenated as a carrier existing catalyst. 2. The method according to claim 1, characterized in that at temperatures hydrogenated between 20 and 75 ° C. 3. The method according to claim 1 and 2, characterized in that that one hydrogenates at an overpressure of at least 3 kg / cmz. 4. Procedure according to Claim 1 to 3, characterized in that the nitrosamine in water or dissolves in a low molecular weight alkanol or in an alkanol-water mixture Added catalyst mass and then hydrogenated.