Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Utility Patent
2000-02-01
2001-01-02
McKane, Joseph K. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
Utility Patent
active
06169198
ABSTRACT:
This Appln. is a 371 of PCT/EP 98/04851 filed Aug. 4, 1998.
The present invention relates to a process for preparing mixtures of monoolefinic C
5
mononitriles with nonconjugated C═C and C≡N bonds by catalytic hydrocyanation of a 1,3-butadiene-containing hydrocarbon mixture.
There is a great demand throughout the world for &agr;,&ohgr;-alkylenediamines which are important starting materials in the industrial preparation of polyamides (nylons). The &agr;,&ohgr;-alkylenediamines such as hexamethylenediamine are obtained almost exclusively by hydrogenation of the corresponding dinitriles. Virtually all industrial routes for preparing hexamethylenediamine are therefore essentially variants of the preparation of adiponitrile, about 1.0 million tons of which are produced around the world each year.
Four routes, which differ in principle, for preparing adiponitrile are described in K. Weissermel, H.-J. Arpe, Industrielle Organische Chemie, 4th edition, VCH Weinheim, pages 266 et seq.:
1. dehydrating amination of adipic acid with ammonia in the liquid or gas phase with intermediate formation of the diamide;
2. indirect hydrocyanation of 1,3-butadiene via intermediate 1,4-dichlorobutenes;
3. hydrodimerization of acrylonitrile in an electrochemical process, and
4. direct hydrocyanation of 1,3-butadiene with hydrogen cyanide.
In the last-mentioned process, monoaddition in a first stage results in a mixture of isomeric pentenonitriles, which is isomerized in a second stage mainly to 3- and 4-pentenonitriles. In a subsequent third stage, anti-Markownikoff addition of hydrogen cyanide onto 4-pentenonitrile results in adiponitrile. This reaction takes place in the liquid phase in a solvent such as tetrahydrofuran at a temperature in the range 30-150° C. under atmospheric pressure. The catalysts used for this are nickel complexes with phosphine or phosphite ligands and metal salt promoters. Complex phosphine ligands bound to metallocenes for stabilizing the nickel are not described in the abovementioned review.
There is a general description of the addition, with heterogeneous and homogeneous catalysis, of hydrogen cyanide onto olefins in Applied Homogeneous Catalysis with Organometalic Compounds, Vol. 1, VCH Weinheim, pages 465 et seq. The catalysts used for this are, in particular, based on phosphine and phosphite complexes, not bound to metallocenes, of nickel and palladium, which make high product selectivity, improved conversions and reduced reaction times possible. Adiponitrile is prepared by hydrocyanation of butadiene mainly using nickel(0) phosphite catalysts, in the presence or absence of a Lewis acid as promoter. The reaction can generally be divided into three steps:
1. synthesis of mononitriles by hydrocyanation of 1,3-butadiene;
2. isomerization; 3. synthesis of dinitriles. Formation of the monoadduct results in an isomer mixture composed of 3-pentenonitrile and 2-methyl-3-butenonitrile, and the selectivity for the linear 3-pentenonitrile is about 70% or less, depending on the catalyst used. If this first reaction step is carried out in the absence of Lewis acids, generally there is no second addition of hydrogen cyanide and the resulting product mixture can be subjected to an isomerization using the same catalyst systems as in the first reaction step, but this time in the presence or absence of a Lewis acid such as ZnCl
2
as promoter.
In this there is, on the one hand, isomerization of 2-methyl-3-butenonitrile to 3-pentenonitrile and, on the other hand, isomerization of 3-pentenonitrile to the various n-pentenonitriles. This publication mentions that the most thermodynamically stable isomer, 2-pentenonitrile in which the C,N triple bond is conjugated with the C,C double bond, inhibits the reaction because it acts as catalyst poison. The required isomerization to 4-pentenonitrile is made possible only because 3-pentenonitrile is isomerized considerably faster to 4-pentenonitrile than to 2-pentenonitrile.
The usual catalysts for the hydrocyanation of 1,3-butadiene are, in particular, the abovementioned nickel(0) phosphite catalysts with phosphite ligands without complex modification.
EP-A-0 274 401 describes a process for the hydrocyanation of pure butadiene using a nickel catalyst having a mixture of phenyl and m,p-tolyl phosphite ligands.
C. A. Tolman et al. describe, in Organometallics 3 (1984) 33 et seq., a catalytic hydrocyanation of olefins by nickel(0) phosphite complexes specifically taking account of the effects of Lewis acids on the addition of hydrogen cyanide.
In Advances in Catalysis, Volume 33, 1985, Academic Press, Inc., page 1 et seq. there is a review-like description of the homogeneous nickel-catalyzed hydrocyanation of olefins. This deals in particular with mechanistic aspects of the monohydrocyanation of butadiene to isomeric pentenonitriles, of the isomerization of 2-methyl-3-butenonitrile to 3-pentenonitrile and of the second addition of hydrogen cyanide to prepare adiponitrile. The catalysts employed are nickel (0) complexes, preferably with phosphite ligands.
Usual phosphines such as triphenylphosphine or 1,2-bis(diphenylphosphino)ethane have only low catalytic activity, if any, in the hydrocyanation of olefins.
WO 95/30680 describes bidentate phosphine chelate ligands in which the phosphine groups are bonded to aryl radicals which are fused by two bridges in ortho positions. In these, the first bridge comprises an O or S atom and the second bridge comprises an O, S or substituted N, Si or C atom. The two phosphine ligands are each located on a different aryl radical in the position ortho to the first bridge. These bidentate phosphine ligands are suitable, in the form of their transition metal complexes, as catalysts for hydroformylation, hydrogenation, polymerization, isomerization, carboxylation, crosscoupling, metathesis and hydrocyanation.
J. Chem. Soc., Chem. Commun. (1995) 2177 et seq. describes the effect of the bonding angle of the abovementioned bidentate phosphine ligands on the activity and selectivity in the nickel-catalyzed hydrocyanation of styrene.
None of the abovementioned publications describes a process for catalytic hydrocyanation using monodentate or polydentate nickel(0)-phosphorus(III) complexes in which the phosphorus(III) ligands in turn are covalently bonded to one or both of the cyclopentadienyl ligands of a metallocene.
EP-A 564 406 and EP-A 612 758 describe ferrocenyldiphosphines as ligands for homogeneous catalysts and the use of these catalysts for enantioselective hydrogenation. In these ligands, two phosphine groups are bonded in the ortho position to the same cyclopentadienyl ligand of the ferrocene, one of them directly to the C
5
ring and the other via a substituted C
1
-alkylene group. The rhodium and iridium complexes with these ligands are suitable as homogeneous enantioselective catalysts for hydrogenation of prochiral compounds with carbon or carbon/heteroatom double bonds. The use of these catalysts for hydrocyanation is not described.
Catalysts for asymmetric addition of hydrogen cyanide onto alkenes based on transition metal(0) complexes have been disclosed. Thus, Aust. J. Chem. 35 (1982) 2041 et seq. describes the use of [(+)-(diop)]
2
Pd and [(+)-(diop)]
2
Ni ((+)-(diop)=(+)-(2S,3S)-(2,3-isopropylidenedioxy-1,4-butanediyl)bis(diphenyl-phosphine)) as catalysts in enantioselective hydrocyanation.
J. Am. Chem. Soc. 118 (1996) 6325 et seq. describes the relationship of the electronic asymmetry of the ligands to the observed enantioselectivity in asymmetric hydrocyanation using electronically nonsymmetrical bis-3,4-diarylphosphonite ligands based on &agr;-D-fructofuranosides.
It is an object of the present invention to provide a process for hydrocyanation in which the catalysts employed are to show high selectivity and good catalytic activity especially in the hydrocyanation of 1,3-butadiene-containing hydrocarbon mixtures to prepare mixtures of monoolefinic C
5
-mononitriles with nonconjugated C═C and C≡N bonds and in the first and second addit
Fischer Jakob
Siegel Wolfgang
BASF Aktiengesellshaft
Keil & Weinkauf
McKane Joseph K.
Sackey Ebenezer
LandOfFree
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