Preparation of secondary amines

Abstract

Disclosed herein is a process for the reductive alkylation of primary amines to form secondary amines, by high pressure reaction of the primary amine with an alkylating agent and hydrogen in the presence of a catalyst which comprises metallic palladium. A process of the present invention is characterized in having high conversion rates and high selectivities, both greater than 95% on a first pass through the reactor. According to a preferred embodiment, the secondary amine produced comprises at least one 2-alkyl group bonded to the nitrogen atom of the primary amine product.

What is claimed is:  
     
         1 ) A process for producing a secondary amine from a primary amine according to the reaction:  
       
         
           
           
               
               
           
         
       
       in which R may be any alkyl or alkylaryl group, straight-chain, branched or cyclic, R′ and R″ are each independently selected from the group consisting of: hydrogen; C 1 -C 20  alkyl, whether straight-chain, branched, or cyclic, subject to the proviso that both R′ and R″ are not simultaneously hydrogen, whereby tertiary amine by-product is minimized, which process comprises: 
 reacting a mixture comprising: 
 hydrogen;  
 said primary amine; and  
 said carbonyl compound,  
 
 under any degree of pressure in the range of 100.0 psig to 3000.0 psig, including every tenth psig therebetween, and at any temperature in the range of 80° C. to 200° C., including every degree therebetween, in the presence of an effective catalytic amount of a catalyst comprising metallic palladium and having a surface area of at least 50 m 2  per gram,  
 wherein the amount of tertiary amine impurity produced during said process is less than 3.00% by weight of the total amount of secondary amine produced.  
 
     
     
         2 ) A process according to  claim 1  in which said catalyst has a surface area of at least 100 m 2  per gram.  
     
     
         3 ) A process according to  claim 1  in which said primary amine is a diamine.  
     
     
         4 ) A process according to  claim 1  in which the product secondary amine is produced in a yield of at least 97.00% by weight based on all amine products produced.  
     
     
         5 ) A process according to  claim 1  in which the amount of tertiary amine impurity produced is less than 2.0% by weight based on all amine products produced.  
     
     
         6 ) A process according to  claim 1  wherein said catalyst comprises palladium on carbon.  
     
     
         7 ) A process according to  claim 6  wherein said carbon comprises charcoal.  
     
     
         8 ) A process according to  claim 1  wherein said carbonyl compound comprises a ketone selected from the group consisting of: acetone, methylethyl ketone, methylisobutyl ketone, methylisoamyl ketone, 2-butanone, 2-pentanone, 2-hexanone, and 2-ethylhexanone.  
     
     
         9 ) A process according to  claim 3  in which said primary amine is isophorone diamine, said carbonyl compound is acetone, and in which the product N,N′-Diisopropylisophorone Diamine is produced in a yield of at least 97.00% by weight based on all amine products produced.  
     
     
         10 ) A process according to  claim 3  in which said primary amine is isophorone diamine, said carbonyl compound is acetone, and in which amount of tertiary amine impurity produced is less than 2.0% by weight based on all amine products produced.