DE2727832C3 - Process for the preparation of N'-methylacethydrazide - Google Patents

Description

The invention relates to a process for the preparation of N'-methylacethydrazide. N'-Methylacethydrazid is an important intermediate in the Manufacture of methylhydrazine.

From CH-PS 3 07 629 a process for the production of isopropylhydrazine is known in the an acylhydrazide is first condensed with acetone, the resulting acetone-N'-acylhydrazone is formed with formation hydrogenated by isopropyl-N'-acylhydrazine and so Hydrogenated product formed hydrolyzed Although, according to the CH-PS mentioned, other carbonyl compounds besides acetone can also be used, but is it is essential that the carbonyl group with the

ίο hydrazine with formation of the desired N'-acylated Hydrazones can condense. Formaldehyde is also used as an example of such a carbonyl compound mentioned, however, there is no indication of the use of paraformaldehyde, as is the case for the rest has no free carbonyl groups Even if one considers the process of the said CH-PS as a one-step If the process were to be carried out, the use of conventional formaldehyde would still be more aqueous Formaldehyde solution, only an unsatisfactory yield obtain.

From »Houben - Weyl«, methods of organic Chemie, Volume Χ / 2 (1967), pages 43 to 48, is known that aliphatic hydrazines can be prepared by reducing acylhydrazones.

The object of the invention is a process for the preparation of N'-methylacethydrazide with a economical reaction rate and good yields, which can be carried out in one step can.

This object is achieved in that one acethydrazide, paraformaldehyde and hydrogen in a solvent selected from the group consisting of water, lower aliphatic alcohols and their mixtures in Presence of a palladium catalyst at a

Temperature of 20 to 150 ⁰ C converts with a Acethydrazide to paraformaldehyde molar ratio

from 0.1 / 1 to 10/1 and a hydrogen partial pressure of 0.07 to 703 kg / cm ^{2 is} adhered to.

The implementation takes place according to the following

40 equation:

CH ₃ CONHNH ₂ + paraformaldehyde + H ₂ CH3CONHNHCH3 + H ₂ O

Acethydrazide can be prepared by known methods.

Palladium or palladium oxide or any other salts or complexes can be used as the catalyst use of palladium, which are converted in situ with the formation of palladium and whose non-palladium components in no way hinder the conversion. The catalyst can be either unsupported or supported, for example carbon. Alumina. Silica, silica-alumina, alkaline earth carbonates. Kieselguhr, zeolites. Pumice. Volume. Cellulose and asbestos. The catalyst can be used in powdered form for sludge reactions or in the form of extrudates, pellets, beads or Granules can be used for fixed bed reactions. The catalyst concentration for batch reactions is 0.001 to 50 parts, preferably 0.05 to 10 Parts and especially from 0.10 to 5 parts of catalyst per 100 parts of acethydrazide, all parts are based on weight.

The lower aliphatic alcohols are to be understood as meaning alcohols having 1 to 6 carbon atoms. The solvents used for the process according to the invention are preferably methanol and ethanol. Isopropanol or their mixtures with water are used. Most preferred is water. Methanol and their Mixtures. The ratio of solvent to total non-gaseous reactants (Acethydrazide plus Paraformaldehyde) is 0.2 / 1 to

so 50/1. usually at OJ / 1 to 5/1> 'nd in particular at 03/1 to 2/1, in units of ml / g.

The molar ratio of acethydrazide to paraformaldehyde is preferably between 3/1 and 0.33 / 1 especially at 1.2 / 1 to 0.8 / 1.

The gas phase feed to the reaction vessel can be pure hydrogen or a mixture containing hydrogen. The hydrogen partial pressure. which is adhered to when carrying out this method is preferably 0.7 to 352 kg / cm ² , in particular around

μ 7.0 to 176 kg / cm ² .

The reaction is preferably carried out in the temperature range from 50 to 120.degree.

The reaction can be carried out batchwise, semi-continuously or continuously.

When using a batch process, a liquid containing acethydrazide, paraformaldehyde, the palladium catalyst and the solvent is used Phase used in the reaction vessel, and then

is the reaction vessel with an inert gas, for example Nitrogen or helium, and then cleaned with hydrogen. After that, the reaction vessel if necessary, while stirring the reaction mixture with hydrogen to the desired pressure and the Stirring started or continued. If necessary, the reaction vessel is heated or cooled around the to achieve the desired reaction temperature. During the reaction time, which is between 10 min and 24 h for batch reaction vessels, additional hydrogen is added to the through the Implementation to compensate for hydrogen consumption. (The dwell or contact time may vary depending on the the desired conversion and the reaction system used vary widely; for example, the Residence time in a continuous fixed bed process in the range from 1 s to 30 min.)

At the end of the conversion period, the excess hydrogen is removed. The content of the «: The reaction vessel is then filtered to remove the catalyst, and standard procedures such as for example distillation or crystallization, can be used to extract the crude product from the to obtain a catalyst-free mixture. A pure product can be made from the crude product by known Recrystallization process can be obtained. If necessary, the contents of the reaction vessel can be adjusted Release of the excess hydrogen and without further purification immediately for the production of Methylhydrazine can be used.

The various reaction parameters (solvent, concentrations, the reactants and the catalyst, temperature, hydrogen partial pressure, residence or contact time, flow system and conversions of the paraformaldehyde and the A '. "Ethydrazide per pass) are related to one another and can be within those listed above Areas can be selected so that the entire manufacturing system is optimized.

The following examples serve to explain the invention in more detail.

Example IA

A mixture of 29.6 g (0.40 mol) of acethydrazide, 12.4 g (0.40 equivalents) of 97% paraformaldehyde, 83 ml of water and 0.20 g of 5% palladium on carbon was placed in a stainless steel Magne Drive Steel autoclave (600 ml) used. The autoclave was sealed, cleaned first with nitrogen and then with hydrogen and placed under a hydrogen pressure of 35.2 kg / cm ³ (manometer pressure). The autoclave was stirred at 70 to 75 ° C. for 2.7 hours and 28.1 to 42 ^ kg / cm ² (gauge pressure) is heated with little or no gas absorption in the last 0.2 hours the

ίο Autoclave was cooled and vented The reaction mixture was filtered through diatomaceous earth to separate the catalyst Rotary evaporator removed on a steam bath at reduced pressure in a nitrogen atmosphere codistillation with benzene was used at the end of the water removal process. Of the liquid residue was determined by quantitative gas-liquid chromatography analyzed The product contained approx. 0.2 g (<1% recovery) unreacted Acethydrazide, 29.4 g. (83% yield) N'-methylacethydrazide and 4.2 g (10% yield) Ν ', Ν'-dimethylacethydrazide.

Example IB

Example IA was made with methanol as the solvent 2.7 Hours at 70 to 75 ° C and 28.1 to 42.2 kg / cm2 (Manometer pressure) repeated approx. 0.3 g (< 1% recovery) unreacted acethydrazide, 26.1 g (74% yield) N'-methylacethydrazide and 33 g (8% yield) of N'-N'-dimethylacethydrazide were obtained.

Example 2

The procedure of Examples IA and IB was followed at different temperatures, times and catalyst concentrations each experiment was repeated in a 600 ml stainless steel Magne Drive autoclave containing 44.4 g (0.60 moles) of acethydrazide, 20.4 g (0.66 equivalents) 97 °, oigem paraformaldehyde, bC ml solvent and the specified catalysis tons of 5% palladium on carbon carried out Reaction products were treated and analyzed as in Example 1. The results are shown in FIG summarized in the table below.

Tabel Temp. manometer
pressure Weight of
Kataly Solution
middle Time (h) ^h ) Retreat
acquisition yield
N'- N'.N'- Example 2 (U (kg / cm ² ) sators
(G) ^a ) 4.3 ^C ) Acet
hydrazide Methyl-
acet-
hydrazide Dimethyl
acet-
hydrazide Ver
search 70 28.1 -42.2 0.10 water 5.0 5.8 3 67 20th 70 28.1 -42.2 0.10 Methanol 6.4 5.6 <1 68 19th A. 100 7.03-14.1 0.15 water 5.6 5.0 3 5 18th B. 100 7.03-14.1 0.15 Methanol 5.6 5.0 18th 38 36 C. 100 28.1-42.2 0.05 water 5.0 4.0 15th 19th 33 D. 100 28.1-42.2 0.05 Methanol 5.0 4.2 9 42 29 E. 100 28.1-42.2 0.125 water 4.7 0.7 17th 35 34 F. 100 28.1-42.2 0.125 Methanol 1.5 5 64 23 O M.

Temp. 5 Weight of
Kataly 27 27 832 ^b ) 6th yield
N'- N'.N'- (Ο sators
(E) 3.3 Methyl-
acet-
hydrazide Dimethyl
acet-
hydrazide continuation 100 manometer
pressure 0.025 Solution
middle Time (h) 2.7 Retreat
acquisition 28 31 Ver
search 100 (kg / cm ² ) 0.025 ·> 8.7 Acet
hydrazide 46 28 130-5 63.3-84.4 0.05 water 3.3 0.8 17th 19th 19th I. 130-5 63.3-84.4 0.05 Methanol 3.3 8th 37 19th J 28.1 -42.2 water 8.7 18th K 28.1 -42.2 Methanol 1.5 16 L.

^a ) Time at the specified temperature.

^b ) Time at the specified temperature during hydrogen absorption.

^c ) Absorption of 1.05 moles H ₂ / mole acethydrazide.

Example 3

Example! 2F was repeated with isopropanol as solvent Sa hours at 100 ⁰ C and 28.1 to 42 ^ kg / cm ² (manometer pressure) and resulted in 6.5 g (16% recovery) of unreacted acethydrazide, 18.8 g (36% Yield) N'-methylacethydrazide and 18.6 g (30% yield) N'.N'-dimethylacethydrazide.

Comparative example 1

A mixture of 44.4 g (0.60 mol) of acethydrazide, 2.1 g (0.66 equivalents) of a 38% strength aqueous formaldehyde solution (stabilized with 10 to 15% methanol), 0.10 g of 5% palladium on carbon and water enough to make the solvent volume approximately 60 ml was placed in a Magne Drive stainless steel • utoclave (600 ml). The autoclave was closed, cleaned first with nitrogen and then with hydrogen and placed under a hydrogen pressure of 35.2 kg / cm ² (manometer pressure). The autoclave was stirred under a manometer for 15 minutes; jck heated from 36.8 kg / cm ² to 70 ° C; During this time there was no absorption of the necessary reactant, hydrogen, and consequently no reaction either. In contrast to this, the hydrogen absorption in the process according to the invention was indicated practically immediately after the start of the reaction. In the procedure of Comparative Example 1, essentially no N'-methylacethydrazide was formed.

Comparative example 2 _M

A mixture of 44.4 g (0.60 mol) of acethydrazide, 2.1 g (0.66 equivalents) of a 38% strength aqueous formaldehyde solution with a content of 10 to 15% ethanol, 33 ml of water and 2.5 g 5% palladium on carbon was placed in a stainless Magne Drive-steel autoclave (600 ml) ~. <ix autoclave was sealed, initially with Stickstof and then purged with hydrogen, and under a hydrogen pressure of 35.2 kg / cm ² (gauge pressure ) The autoclave was heated for 3 hours with stirring at 45 to 50 ° C. and 28.1 to 42.2 kg / cm ² (manometer pressure) (absorption of 0.83 mol H 2 / MOI acethydrazide). The autoclave was cooled and vented. The reaction mixture was filtered through diatomaceous earth to separate the catalyst. The solvent was removed on a rotary evaporator on a steam bath under reduced pressure in a nitrogen atmosphere, and at the end of the process, codistillation with benzene was used to remove water. The liquid residue was analyzed by quantitative gas-liquid chromatography. The product contained 2.4 g (53% recovery) of unreacted acethydrazide, 11.9 g (23% yield) of N'-methylacethydrazide and 14.6 g (4% yield ) N'.N'-dimethylacethydrazide. Lower temperatures and higher catalyst loadings than in Comparative Example 1 accordingly favor the formation of the desired product, but the molar yield of N'-methylacethydrazide was only 23% even under the very favorable conditions of Comparative Example 2. During the last of the 3 hour reaction time only about 8% of the total absorbed hydrogen was absorbed, indicating that only an insignificant additional amount of product is formed as the time progresses.

The results show that with the aid of the method according to the invention using Paraformaldehyde achieved a superior yield of N'-methylacethydrazide in comparison with formaldehyde will.

Claims (1)

Patent claims: J. Process for the preparation of N'-methylacethydrazide, characterized in that acethydrazide, paraformaldehyde and hydrogen are reacted in a solvent from the group consisting of water, lower aliphatic alcohols and their mixtures in the presence of a palladium catalyst at a temperature of 20 to 150 "C, a molar ratio of acethydrazide to paraformaldehyde of 0.1 / 1 to 10/1 and a hydrogen ^{partial pressure of 0.07 to 703 kg / cm 2} being maintained. Z Process according to Claim 1, characterized in that the solvent used is methanol, Ethanol, isopropanol or their mixtures with water are used 3. The method according to any one of the preceding claims, characterized in that one carries out the reaction at a temperature of 50 to 120 ⁰ C. 4. The method according to any one of the preceding claims, characterized in that one Palladium or palladium oxide is used as a catalyst 5. The method according to any one of the preceding claims, characterized in that a hydrogen partial pressure of 0.7 to 352 kg / cm ^{2 is maintained} b. Method according to one of the preceding claims, characterized in that one Molar ratio of acethydrazide to paraformaldehyde of 0.33 / 1 to 3/1