Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Patent
1997-09-15
1999-11-09
Richter, Johann
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
C07C25504
Patent
active
059817909
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the hemihydrogenation of dinitriles to corresponding aminonitriles.
The hydrogenation of dinitriles is generally carried out in order to prepare the corresponding diamines; thus, particularly, the hydrogenation of adiponitrile produces hexamethylenediamine, itself one of the two base compounds for the preparation of polyamide 6,6.
However, it may sometimes be found necessary to prepare not the diamine but the intermediate aminonitrile. This, for example, is the case--although no limitation is implied thereby--of the hemihydrogenation of adiponitrile to aminocapronitrile, a compound capable of being subsequently converted into caprolactam, a base compound for polyamide 6, or directly into polyamide 6.
Thus, U.S. Pat. No. 4,389,348 describes a process for hydrogenation of dinitrile to omega-aminonitrile, using hydrogen in an aprotic solvent medium and ammonia in the presence of rhodium deposited on a basic support.
U.S. Pat. No. 5,151,543 describes a process for partial hydrogenation of dinitriles to aminonitriles in a solvent in a molar excess of at least 2/1 in relation to the dinitrile, including liquid ammonia or an alkanol containing an inorganic base which is soluble in the said alkanol, in the presence of a catalyst of the Raney nickel or cobalt type.
WO-A-93/16034 describes a process for the preparation of 6-aminocapronitrile by the hydrogenation of adiponitrile, under pressure and at a temperature of 50 to 90.degree. C., in the presence of an alkaline metal hydroxide or ammonium hydroxide, of a low valent transition metal complex and a Raney nickel catalyst. This process is carried out according to the examples in solvent such as a lower alkanol or a hydrocarbon.
The present invention deals with the preferential hydrogenation of a single nitrile functional group of a dinitrile (called hemihydrogenation in this text), so as to prepare the corresponding aminonitrile as a major product and the diamine only as a minor product.
More precisely, the invention relates to a process for the hemihydrogenation of aliphatic dinitriles to the corresponding aminonitriles, with the aid of hydrogen and in the presence of a catalyst chosen from Raney nickel, Raney cobalt, Raney nickel comprising a doping element chosen from the elements of groups IVb, VIb, VIIb and VIII of the Periodic Classification of the elements, as published in the Handbook of Chemistry and Physics (Weast, 5th edition of 1970-1971) and zinc and Raney cobalt comprising a doping element chosen from the elements of groups IVb, VIb, VIIb and VIII of the Periodic Classification of the elements and zinc, and of a strong inorganic base derived from an alkali or alkaline-earth metal, characterized in that: least 0.5% by weight relative to the totality of the liquid compounds of the said mixture, the diamine and/or the aminonitrile which are liable to be formed from the dinitrile to be hydrogenated and the unconverted dinitrile in a proportion of 80% to 99.5% for the combined total of these three compounds relative to the totality of the liquid compounds of the said mixture, the aminonitriles being aimed at of at least 60%.
The degree of conversion of the dinitrile is preferably at least 70%.
The aliphatic dinitriles which may be used in the process of the invention are more particularly the dinitriles of general formula (I): containing from 1 to 12 carbon atoms.
Dinitriles of formula (I) in which R denotes a linear or branched alkylene radical containing from 1 to 6 carbon atoms are preferably used in the process of the invention.
Examples of such dinitriles which may be mentioned are especially adiponitrile, methylglutaronitrile, ethylsuccinonitrile malononitrile, succinonitrile and glutaronitrile and mixtures thereof, especially the mixtures of adiponitrile and/or methylglutaronitrile and/or ethylsuccinonitrile that are liable to originate from the same process for the synthesis of adiponitrile.
In practice, the case where R=(CH.sub.2).sub.4 will be the most frequent one, because this corresponds to the use of adiponit
REFERENCES:
patent: 4248799 (1981-02-01), Drake
patent: 4362671 (1982-12-01), Diamond et al.
patent: 5151543 (1992-09-01), Ziemecki
Cotting Marie-Christine
Gilbert Laurent
Leconte Philippe
Rhone-Poulenc Fiber and Resin Intermediates
Richter Johann
Sackey Ebenezer
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