Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Patent
1996-09-24
1998-11-24
Dees, Jose G.
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
564491, 564492, 564375, 502301, B01J 2502, C07C20900
Patent
active
058409890
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/FR94/01476 filed Dec. 16, 1994.
The field of the invention is that of the catalytic reduction of nitriles to amines.
More precisely, it is in this instance a question of the catalytic hydrogenation of nitriles using catalysts of Raney nickel type, that is to say obtained by alkaline attack on a precursor Ni/Al alloy.
The present invention particularly relates to a catalyst for the hydrogenation of nitriles, especially of dinitriles to diamines, the said catalyst being of Raney nickel type doped with at least one element chosen from groups IIb and IVb to VIIb of the periodic classification.
Another subject of the present invention is a process for the preparation of a catalyst for the hydrogenation of nitriles to amines of doped Raney Ni type such as that targeted above.
The present invention additionally relates to a process for the hydrogenation of nitriles to amines which makes use of the catalysts considered above.
Within the meaning of the invention, nitriles denotes all aromatic and/or aliphatic mono- and dinitriles and, in particular but non-limitingly, the dinitriles resulting from dicarboxylic acids, preferably C3 to C6 dicarboxylic acids, such as adiponitrile, glutaronitrile, succinonitrile or malononitrile, optionally substituted by lower alkyl groups having from 1 to 6 carbon atoms, such as especially methyl or ethyl.
Raney nickels are catalysts which are widely used in industry and in the laboratory for hydrogenation reactions. They are prepared by alkaline attack on aluminium-rich Al/Ni alloys. The catalyst consists of agglomerates of nickel crystallites with a high specific surface and with a variable residual aluminium content.
In the field of catalysis in general and of hydrogenation catalysis in particular, the objectives ceaselessly targeted are, on the one hand, the optimization of the activity and selectivity of the catalyst with respect to the substrate to be hydrogenated and, on the other hand, the stability.
It is obvious that these three key parameters are indissolubly linked to the other constraints which are the ease of manufacture of the catalyst, its low cost price and the flexibility and convenience of its use in hydrogenation.
Thus, it has already been proposed to dope Raney nickel catalysts using promoters such as titanium, chromium, iron, cobalt, copper, molybdenum, tantalum, zirconium or other metals, with a view to improving their activity and/or their selectivity.
These promoters have the function of modifying the electronic and structural factors of Raney nickel. They are conventionally added to the Ni/Al alloy in the molten state, in accordance with a so-called "metallurgic" doping technique.
Patent FR 913 997 describes in particular the use of a Raney Ni, prepared from an Al/Ni alloy containing from 0.5% to 3.5% by weight of chromium with respect to the nickel, for the hydrogenation of adiponitrile to hexamethylenediamine.
The document B. N. Tyutyunnikov et al.--The Soviet Chemical Industry, No. 6, June 1991, as well as the article L. Kh. Freidlin et al.--Russian Chemical Reviews--Vol. 33, No. 6--Jun. 1964, among others, relate to the catalytic reduction of aliphatic nitriles (dinitriles) using Raney hydrogenation catalysts which have been promoted using metal doping agents.
Such catalysts are relatively difficult to obtain because they require the use of means for bringing the precursor alloy into the molten state and for maintaining it there. In addition, the known processes for obtaining these catalysts are relatively inflexible, especially as regards adjusting the amount of doping agents introduced into the alloy. In fact, mixing of the precursor alloy with the doping agent may sometimes not be homogeneous and may thus generate significant compositional variations or significant variations in the content of doping agent in the body of the catalyst. It should also be pointed out that phenomena which take place in the melt are not controlled. It is thus possible, in certain cases, to witness the formation of complex crystallographic s
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Russian Chemical Reviews, Uspekhi Khimii, vol. 33, 1964.
Cordier Georges
Fouilloux Pierre
Laurain Nathalie
Badio Barbara
Dees Jos,e G.
Rhone-Poulenc Chimie
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