CH405246A - Process for the preparation of cyclohexylhydroxylamine - Google Patents

Description

  

  
 



  Process for the preparation of cyclohexylhydroxylamine
The present invention relates to a process for the preparation of cyclohexylhydroxylamine by hydrogenating nitrocyclohexene.



   Nitrocyclohexane, an important intermediate in the manufacture of caprolactam, is obtained from the nitration of cyclohexane at elevated temperature and under pressure. In doing so, considerable amounts of nitrocyclohexane are often produced. However, if you want to make the multi-stage process for caprolactam production economical, you have to ensure that the starting material is optimally used.



   It has been proposed to convert cyclohexylhydroxylamine into cyclohexanone oxime. The latter then delivers caprolactam through the well-known Beckmann rearrangement. Cyclohexylhydroxylamine is usually converted to the oxime by air oxidation.



   A process has now been found in which the undesired nitrocyclohexene is returned to the caprolactam process by converting it into cyclohexylhydroxylamine. This method works economically and effectively.



   It consists in reacting 1 mole of nitrocyclohexene with 3 to 31A moles of hydrogen and working in the presence of a palladium or platinum catalyst and at 0-65 and 7-140 atm.



   An inert organic solvent can be used in the process according to the invention.



  Methanol, ethanol, isopropanol, ether etc. are suitable for this purpose. Methanol is preferably used.



   The preferred reaction conditions are about 20-300 and 35-85 atm.



   Finely divided palladium or platinum is used as a reduction catalyst with priority on activated carbon.



   The above-mentioned molar ratio of nitrocyclohexene to hydrogen, such as 1: 3 to 3.5, is critical.



   example 1
A one-liter shaking autoclave made of stainless steel is charged with 31.8 g of nitrocyclohexene, 135 g of methanol and 1 g of 5% palladium-carbon.



   The reaction mixture is heated to about 300 under a hydrogen pressure of 35 atm and the hydrogen pressure is increased to 70 atm until 3/4 mol of hydrogen has been absorbed. Then you stop the reaction. The reduction product contains 52.6% cyclohexylhydroxylamine.



   Example II
The procedure is analogous to Example I, but using a platinum catalyst. The test results were similar.



   PATENT CLAIM
Process for the preparation of cyclohexylhydroxylamine, characterized in that nitrocyclohexene is hydrogenated with hydrogen in the presence of palladium or platinum as the hydrogenation catalyst at 0-65 and 7-140 atm, using 3-3 t / 2 moles of hydrogen per mole of nitrocyclohexene.



   SUBCLAIMS
1. The method according to claim, characterized in that one works at a pressure of 35-85 atm and at a temperature of 20-300.



   2. The method according to claim, characterized in that palladium is used as a catalyst.



   3. The method according to claim, characterized in that platinum is used as a catalyst.

** WARNING ** End of DESC field could overlap beginning of CLMS **.



   

 

Claims (1)

** WARNING ** Beginning of CLMS field could overlap end of DESC **. Process for the preparation of cyclohexylhydroxylamine The present invention relates to a process for the preparation of cyclohexylhydroxylamine by hydrogenating nitrocyclohexene. Nitrocyclohexane, an important intermediate in the manufacture of caprolactam, is obtained from the nitration of cyclohexane at elevated temperature and under pressure. In doing so, considerable amounts of nitrocyclohexane are often produced. However, if you want to make the multi-stage process for caprolactam production economical, you have to ensure that the starting material is optimally used. It has been proposed to convert cyclohexylhydroxylamine into cyclohexanone oxime. The latter then delivers caprolactam through the well-known Beckmann rearrangement. Cyclohexylhydroxylamine is usually converted to the oxime by air oxidation. A process has now been found in which the undesired nitrocyclohexene is returned to the caprolactam process by converting it into cyclohexylhydroxylamine. This method works economically and effectively. It consists in reacting 1 mole of nitrocyclohexene with 3 to 31A moles of hydrogen and working in the presence of a palladium or platinum catalyst and at 0-65 and 7-140 atm. An inert organic solvent can be used in the process according to the invention. Methanol, ethanol, isopropanol, ether etc. are suitable for this purpose. Methanol is preferably used. The preferred reaction conditions are about 20-300 and 35-85 atm. Finely divided palladium or platinum is used as a reduction catalyst with priority on activated carbon. The above-mentioned molar ratio of nitrocyclohexene to hydrogen, such as 1: 3 to 3.5, is critical. example 1 A one-liter shaking autoclave made of stainless steel is charged with 31.8 g of nitrocyclohexene, 135 g of methanol and 1 g of 5% palladium-carbon. The reaction mixture is heated to about 300 under a hydrogen pressure of 35 atm and the hydrogen pressure is increased to 70 atm until 3/4 mol of hydrogen has been absorbed. Then you stop the reaction. The reduction product contains 52.6% cyclohexylhydroxylamine. Example II The procedure is analogous to Example I, but using a platinum catalyst. The test results were similar. PATENT CLAIM Process for the preparation of cyclohexylhydroxylamine, characterized in that nitrocyclohexene is hydrogenated with hydrogen in the presence of palladium or platinum as the hydrogenation catalyst at 0-65 and 7-140 atm, using 3-3 t / 2 moles of hydrogen per mole of nitrocyclohexene. SUBCLAIMS 1. The method according to claim, characterized in that one works at a pressure of 35-85 atm and at a temperature of 20-300. 2. The method according to claim, characterized in that palladium is used as a catalyst. 3. The method according to claim, characterized in that platinum is used as a catalyst.