Modification of a hydrogenation catalyst

Details Modification of a hydrogenation catalyst Modification of a hydrogenation catalyst

2000-11-30

2003-02-18

Davis, Brian (Department: 1764)

Catalyst, solid sorbent, or support therefor: product or process

Catalyst or precursor therefor

Metal, metal oxide or metal hydroxide

C502S020000, C502S033000, C502S034000, C502S172000, C502S501000, C502S514000, C502S523000, C564S413000, C564S415000, C564S487000, C564S448000, C564S490000

Reexamination Certificate

active

06521564

ABSTRACT:

FIELD OF THE INVENTION
The present invention is a process for the modification of a hydrogenation catalyst of the Raney nickel, Raney cobalt, nickel-on-carrier, or cobalt-on-carrier type.
SUMMARY OF THE INVENTION
As a consequence of the process, in which such a catalyst is treated with carbon monoxide, carbon dioxide, formaldehyde, a lower aliphatic aldehyde, an aromatic aldehyde, an aliphatic ketone, an aromatic ketone, a mixed aliphatic/aromatic ketone, glyoxal, pyruvaldehyde or glyoxylic acid, when the thus-modified catalyst is used in the hydrogenation of a nitrile to the corresponding amine the selectivity is increased. The increased selectivity favors significantly the amount of the primary amine vis-à-vis the undesired secondary amine in the hydrogenation product compared with the case when the corresponding unmodified catalyst is employed. The mode of the modification and the increased selectivity resulting therefrom are surprising. Accordingly, the present invention concerns, in a second aspect, a process for the hydrogenation of a nitrile to the corresponding primary amine using a thus-modified catalyst.
One embodiment of the invention is a process for modifying a hydrogenation catalyst of a Raney nickel, Raney cobalt, nickel-on-carrier or cobalt-on-carrier type. This process includes providing a hydrogenation catalyst of the Raney nickel, Raney cobalt, nickel-on-carrier, or cobalt-on-carrier type; and treating the hydrogenation catalyst at temperatures of about 0° C. to about 120° C. with a modification agent selected from the group consisting of carbon monoxide, carbon dioxide, formaldehyde, a lower aliphatic aldehyde, an aromatic aldehyde, an aliphatic ketone, an aromatic ketone, a mixed aliphatic/aromatic ketone, glyoxal, pyruvaldehyde, and glyoxylic acid in a liquid dispersion medium consisting of water or an organic solvent for about 15 minutes to about 24 hours.
Another embodiment of the invention is a process for the catalytic hydrogenation of a nitrile to its corresponding primary amine. This process includes providing a modified hydrogenation catalyst formed by treating a hydrogenation catalyst selected from the group consisting of a Raney nickel, Raney cobalt, nickel-on-carrier, and cobalt-on-carrier type catalyst at temperatures of about 0° C. to about 120° C. with a modification agent selected from the group consisting of carbon monoxide, carbon dioxide, formaldehyde, a lower aliphatic aldehyde, an aromatic aldehyde, an aliphatic ketone, an aromatic ketone, a mixed aliphatic/aromatic ketone, glyoxal, pyruvaldehyde, and glyoxylic acid in a liquid dispersion medium consisting of water or an organic solvent for a duration of about 15 minutes to about 24 hours; and contacting a nitrile with the modified hydrogenation catalyst to catalyze the reaction of the nitrile to its corresponding primary amine.
DETAILED DESCRIPTION OF THE INVENTION
The process in accordance with the invention for the modification of a hydrogenation catalyst of the Raney nickel, Raney cobalt, nickel-on-carrier or cobalt-on-carrier type includes treating the hydrogenation catalyst at temperatures of about 0° C. to about 120° C. with carbon monoxide, carbon dioxide, formaldehyde, a lower aliphatic aldehyde, an aromatic aldehyde, an aliphatic ketone, an aromatic ketone, a mixed aliphatic/aromatic ketone, glyoxal, pyruvaldehyde, or glyoxylic acid as the modification agent in a liquid dispersion medium consisting of water or an organic solvent for about 15 minutes to about 24 hours.
When the modification agent is formaldehyde, it can also be used in the form of metaldehyde or paraformaldehyde. Preferably, formaldehyde is used in the form of its aqueous solution, i.e. as formalin, in which case water then forms at least part of the liquid dispersion medium.
The “lower aliphatic aldehyde” which can be used as the modification agent in the present invention is preferably an aldehyde of the formula R
1
CHO in which R
1
is an alkyl group with 1 to 5 carbon atoms optionally substituted with hydroxy. The alkyl group can be straight-chained or branched depending on the number of carbon atoms. In the case where the alkyl group is substituted with hydroxy, one or more hydroxy substituents can be present. Preferably, acetaldehyde is used as such a modification agent.
The “aromatic aldehyde” which can be used as the modification agent in the present invention is especially an aldehyde of the formula R
2
CHO in which R
2
is an aryl or heteroaryl group. The term “aryl” as used herein embraces not only the usual unsubstituted aryl groups, i.e. phenyl and naphthyl, but also the corresponding substituted phenyl and naphthyl groups. The substituents may be, for example, halogen atoms and C
1-4
-alkyl, hydroxy, C
1-4
-alkoxy, amino, carbamoyl, and phenyl groups; in each case one or more substituents can be present. Fluorine, chlorine, bromine, or iodine is to be understood under the term “halogen.” An alkyl or alkoxy group can be straight-chain or branched depending on the number of carbon atoms. In the case of multiple substituents the substituents may be the same or different. Normally, not more than 5 (for phenyl) or 7 (for naphthyl) halogen atoms, 3 alkyl groups, 2 hydroxy groups, 3 alkoxy groups, 2 amino groups, 2 carbamoyl groups, or one phenyl group may be present as a substituent. The term “heteroaryl” as used herein embraces heteroaryl groups which have one or more hetero atoms in the ring, such as nitrogen, oxygen, and/or sulphur atoms; pyridyl and pyrimidinyl are examples of such heteroaryl groups. Preferably, benzaldehyde or anisaldehyde is used as the aromatic aldehyde in the role of the modification agent.
The “aliphatic, aromatic or mixed aliphatic/aromatic ketone” which can be used as the modification agent in the present invention is preferably a ketone of the formula R
3
COR
4
in which R
3
and R
4
each independently signify an alkyl, aryl, or heteroaryl group. The term “alkyl,” “aryl,” or “heteroaryl” as used herein are to be understood as above in connection with the definitions of R
1
and R
2
. Preferably, acetone is used as such a modification agent.
In one embodiment of the invention carbon monoxide, formaldehyde or a lower aliphatic aldehyde is used as the modification agent.
The hydrogenation catalysts of the Raney nickel and Raney cobalt type which can be modified in the modification process in accordance with the invention are well known to a person skilled in the art and are readily obtainable commercially. The same applies to the catalysts of the nickel-on-carrier and cobalt-on-carrier type which likewise can be modified in the process. The carrier in these two cases may be, for example, silica, titanium oxide, aluminum oxide, kieselguhr, or active carbon.
Suitable organic solvents in which, in addition to water, the modification may be carried out include aliphatic hydrocarbons (e.g. pentane and hexane), aromatic hydrocarbons (e.g. benzene and toluene), alkanols (e.g. methanol, ethanol, and propanol), aliphatic and cyclic ethers (e.g. diethyl ether and, respectively, tetrahydrofuran, and dioxan), as well as heteroaromatics (e.g. pyridine). The dispersion medium can consist of water alone or of a single organic solvent or of two or more of such liquids. For example, an aqueous alkanol, e.g. aqueous ethanol, can be used as the liquid dispersion medium. In general, the process is carried out by dispersing the hydrogenation catalyst in water and/or such an organic solvent, because a dissolution of the catalyst does not take place due to its nature. On the other hand, the modification agent must at least partially dissolve in the dispersion medium, as will be explained in more detail below.
Based on the amount of hydrogenation catalyst to be modified, the amount of modification agent which is employed is as follows in the different cases:
Modification Agent
Conveniently
Preferably
Carbon monoxide
0.5-5
weight
1-2
wt. %
percent (wt. %)
Carbon dioxide
1-30
wt. %
5-15
wt. %
Formaldehyde, glyoxal,
0.25-50
wt. %
1-15
wt. %
pyruvaldehyde, glyoxylic acid
Lower aliphatic aldehyde
0.25-50

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