Hydrogenation of methylenedianiline
The invention is directed to an improvement in a catalytic process for the ring hydrogenation of a methylenedianiline feedstock, including crude methylenedianiline. One component of the improvement is a pretreatment process which resides in passing the crude methylenedianiline feedstock over a ruthenium catalyst carried on a fixed bed support, cooling without venting, and then hydrogenation of the pretreated crude methylenedianiline feedstock over a rhodium catalyst or a mixed Rh/Ru catalyst carried on a monolith support and carrying out the ring hydrogenation in a batch reaction. Another component in the improvement is the employment of a catalyst comprised of rhodium and ruthenium carried on a monolith support.
1. In a process for the ring hydrogenation of crude methylenedianiline, wherein said methylenedianiline is contacted with hydrogen in the presence of a catalyst, the improvement which comprises:
pretreating the crude methylenedianiline feedstock by partially hydrogenating said feedstock in the presence of a catalyst comprised of ruthenium carried on a fixed bed support to produce a pretreated feedstock; and then,
hydrogenating the pretreated feedstock in the presence of a catalyst comprised of rhodium carried on a monolith support incorporating a wash coat.
2. The process of claim 1 wherein the catalyst comprised of rhodium carried on a monolith support also includes ruthenium in an amount from 1 to 40 weight parts rhodium per weight part ruthenium.
3. The process of claim 2 wherein the combination of rhodium and ruthenium is carried on said monolith support in an amount of from 0.5 to 5% by weight of the wash coat and the weight parts rhodium per weight part ruthenium is from 10 to 25.
4. The process of claim 3 wherein the wash coat is comprised of a support material selected from the group consisting of alumina, silica, mixed metal oxides, spinel LiAl 5 O 8 , lithium aluminate, and titanium oxide.
5. The process of claim 4 wherein the ruthenium is carried on a monolith support.
6. The process of claim 5 where the pretreatment of said crude methylenedianiline feedstock is carried out at a temperature of 140 to 225° C.
7. The process of claim 6 wherein the pretreated feedstock from the pretreatment is cooled to a temperature of from 100 to 130° C. without venting of hydrogen gas and solvent vapor prior to conducting hydrogenation of said pretreated feedstock.
8. The process of claim 7 wherein the temperature for hydrogenation of the pretreated feedstock is increased incrementally from 100 to 130° C. to a final temperature of from 170 to 225° C.
9. The process of claim 8 wherein the pretreatment pressure is from 300 to 2500 psig.
10. The process of claim 9 wherein the Rh/Ru catalyst is treated with base modifier to limit secondary amine formation, the base modifier selected from the group consisting of ammonia, lithium hydroxide, sodium hydroxide, potassium hydroxide, and lithium carbonate.
11. In a process for the ring hydrogenation of crude methylenedianiline wherein said methylenedianiline is contacted with hydrogen in the presence of a catalyst, the improvement which comprises:
employing a catalyst comprised of rhodium and ruthenium carried on a monolith support.
12. The process of claim 11 wherein the monolith support incorporates a wash coat for the monolith support and said wash coat is comprised of a support material selected from the group consisting of alumina, silica, mixed metal oxides, spinel LiAl 5 O 8 , lithium aluminate, and titanium oxide.
13. The process of claim 12 wherein the rhodium is provided in an amount, based upon its weight as metal, sufficient to provide from 0.1 to 25 weight parts rhodium per 100 weight parts wash coat (dry weight).
14. The process of claim 13 wherein a catalyst system is formed such that rhodium and ruthenium are present and the rhodium to ruthenium weight ratio is from about 4 to 15 weight parts rhodium per weight part of ruthenium.
15. The process of claim 14 wherein the catalyst is treated with a base modifier selected from the group consisting of ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide, and lithium carbonate.
16. The process of claim 15 wherein the monolith support has from 100 to 800 cells per square inch.
17. The process of claim 16 wherein the reaction is carried out at a temperature of from 130 to 225° C.
18. The process of claim 17 wherein the reaction pressure is from 700 to 2500 psig.
19. The process of claim 18 wherein the crude methylenedianiline feedstock is MDA-85.