Lithium aluminate as a catalyst support for hydrogenation of...

Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing

Reexamination Certificate

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C564S451000

Reexamination Certificate

active

06184416

ABSTRACT:

BACKGROUND OF THE INVENTION
Ring hydrogenation of aromatic amines using Group 6 and Group 8 metals carried on a support is well known. Two aspects in the hydrogenation process are problematic. First, contaminants in the aromatic amine substrate can poison the catalyst thus impacting catalyst activity and catalyst life. Second, catalyst attrition can occur thereby resulting in catalyst loss and plugging of catalyst filtration equipment.
Representative patents which illustrate various processes for the hydrogenation of aromatic amines are as follows:
U.S. Pat. Nos. 2,606,925 and 2,606,927 disclose the hydrogenation of nitroaromatics and aromatic amines. The ′925 patent shows the use of ruthenium oxide as a catalyst whereas the ′927 discloses the use of cobalt on alumina.
U.S. Pat. Nos. 3,636,108 and 3,697,449 disclose the hydrogenation of aromatic compounds and, particularly, 4,4-methylenedianiline to produce a product referred to as PACM, using an alkali metal-moderated ruthenium catalyst. Alkali moderation is accomplished by depositing a ruthenium compound on a support from an aqueous solution of sodium or potassium bicarbonate, hydroxide, or the like. A wide variety of carriers such as calcium carbonate, rare earth oxides, alumina, barium sulfate, kieselguhr and the like are shown as candidate supports. The ′449 patent discloses the in situ alkali moderation of the catalyst.
U.S. Pat. No. 4,754,070 discloses an improved process for the hydrogenation of methylenedianiline contaminated with catalyst poisoning impurities. A catalyst comprised of rhodium and ruthenium was found to be effective in the hydrogenation of a crude methylenedianiline, i.e., one containing oligomers. Alkali moderation via addition of lithium hydroxide activation was shown to be effective for the combined catalyst. Carriers suited for the rhodium/ruthenium catalyst included alumina, carbonates, etc.
U.S. Pat. No. 5,545,756 discloses a process for the hydrogenation of aromatic amines, whether mononuclear or polynuclear, using a catalyst of rhodium carried on a titania support. Examples of titania supports include TiA1
2
O
5
, TiSiO
4
and TiSrO
3
. The titania support permitted the use of rhodium alone as the active metal in the hydrogenation of crude methylenedianiline. Rhodium carried on titania in combination with ruthenium on alumina was also suited as a catalyst. Lithium hydroxide activation results in enhanced activity.
BRIEF SUMMARY OF THE INVENTION
This invention relates to an improvement in a process for the catalytic hydrogenation of aromatic amines and to the resultant catalyst. The basic process for hydrogenating both mononuclear and polynuclear aromatic amines comprises contacting an aromatic amine with hydrogen in the presence of a rhodium containing catalyst under conditions for effecting ring hydrogenation. The improvement in the ring hydrogenation process resides in the use of a catalyst comprised of rhodium carried on a lithium aluminate support.
The following represents some of the advantages that can be obtained by the use of the catalysts under specified conditions, they are:
an ability to achieve effective selectivity control to primary amine formation;
an ability to reuse the catalyst over an extended period of time;
an ability to be used in combination with alkali metal reaction promoters without adverse effects;
an ability to tolerate some water through its low solubility in water;
an ability to minimize catalyst loss and product contamination by virtue of excellent attrition resistance; and,
an ability to achieve enhanced production through excellent reaction rates.


REFERENCES:
patent: 2606925 (1952-08-01), Whitman
patent: 2606927 (1952-08-01), Barkdoll et al.
patent: 3636108 (1972-01-01), Brake
patent: 3697449 (1972-10-01), Brake
patent: 4754070 (1988-06-01), Casey et al.
patent: 5545756 (1996-08-01), Vedage et al.

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