Preparation of secondary amines
View Patent ↗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.
1. A process for producing a secondary amine product which comprises heating a mixture comprising: a) hydrogen; b) a carbonyl compound represented by:
and c) a primary amine reactant represented by the structure R—NH 2 to any temperature in the range of about 80° C. to about 230° C. and under any pressure in the range of about 100 psig to about 3000 psig in the presence of an effective catalytic amount of a catalyst comprising metallic palladium, wherein said secondary amine product has the formula:
in which R is any alkyl, aminoalkyl, alkylaryl, or aminoalkylaryl group, whether 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, wherein the amount of tertiary amine produced during said process is less than 3.00% by weight of the total amount of secondary amine produced, and further wherein the secondary amine product is produced in a yield of at least 97.00% by weight based on all amine products 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 reactant is a diamine.
4. A process according to claim 3 wherein said diamine contains two —NH 2 groups.
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.
11. A process for producing a secondary amine product from a primary amine reactant, which process comprises heating a mixture that comprises the components:
a) hydrogen;
b) a carbonyl compound represented by the structure:
in which 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, and
c) an amine reactant comprising one or more alkoxylated amines having a primary amine function and described by the formula:
in which R 1 and R 2 are each independently selected from the group consisting of: hydrogen; an alkyl group having 1, 2, 3, 4, 5, or 6 carbon atoms, whether straight-chain or branched; or a radical of the formula:
in which R 3 may be an alkyl group having any number of carbon atoms selected from 1, 2, 3, 4, 5, or 6, straight-chain or branched; R 4 is a straight-chain or branched alkyl bridging group having 1, 2, 3, 4, 5, or 6 carbon atoms; Z is a hydroxy group or alkyl group containing 1, 2, 3, 4, 5, or 6 carbon atoms, straight-chain or branched; q is any integer between 0 and 400; and wherein X is any of:
i) a hydroxy group or an alkyl group having any number of carbon atoms selected from 1, 2, 3, 4, 5, or 6; or
ii) a group in which R 5 and R 6 are each independently selected from the group consisting of: hydrogen; an alkyl group having 1, 2, 3, 4, 5, or 6 carbon atoms, whether straight-chain or branched; or
as defined above in which Z is a hydroxy group or an alkoxy group having 1, 2, 3, 4, 5, or 6 carbon atoms, and in which R 7 is a straight-chain or branched alkylene bridging group having 1, 2, 3, 4, 5, or 6 carbon atoms; or
iii) a moiety of the formula:
in which R 10 , R 11 , R 14 , and R 15 are each independently selected from the group of: hydrogen; an alkyl group having 1, 2, 3, 4, 5, or 6 carbon atoms, straight-chain or branched; the moiety
as defined above in which Z is a hydroxy or alkoxy group having 1, 2, 3, 4, 5, or 6 carbon atoms; R 8 and R 12 are each independently alkyl groups having 1, 2, 3, 4, 5, or 6 carbon atoms, straight-chain or branched; R 9 , R 13 , and R 21 are each independently selected from a straight-chain or branched alkyl bridging linkage having 1, 2, 3, 4, 5, or 6 carbon atoms; R 16 , R 17 , R 18 , R 19 , R 20 are each independently selected from hydrogen or an alkyl group having 1, 2, 3, 4, 5, or 6 carbon atoms; d is 0 or 1; and a is any integer between 0 and 100, with the proviso that when X is a moiety of the formula given in iii) above, the sum of a+b+c is any number between 2 and 400, to any temperature in the range of about 80° C. to about 200° C. and under any pressure in the range of about 100 psig to about 3000 psig in the presence of an effective catalytic amount of a catalyst comprising metallic palladium, wherein the total amount of tertiary amine produced during said process is less than 3.00% by weight of the total amount of secondary amine produced, and further wherein the secondary amine product is produced in a yield of at least 97.00% by weight based on all amine products produced.
12. A process according to claim 11 in which said catalyst has a surface area of at least 100 m 2 per gram.
13. A process according to claim 11 in which said amine reactant is a diamine.
14. A process according to claim 13 wherein said diamine contains two —NH 2 groups.
15. A process according to claim 11 in which the amount of tertiary amine impurity produced is less than 2.0% by weight based on all amine products produced.
16. A process according to claim 11 wherein said catalyst comprises palladium on carbon.
17. A process according to claim 16 wherein said carbon comprises charcoal.
18. A process according to claim 11 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-ethyihexanone.