Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Reexamination Certificate
1999-06-16
2001-05-08
Nazario-Gonzalez, Porfirio (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
C556S138000, C564S408000
Reexamination Certificate
active
06229035
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods for the production phenyl-p-phenylenediamine (PPDA) and higher amines of structural formula (I) below from the starting material of structural formula(II) below. More particularly it relates to a method for preparing PPDA wherein aniline is oxidized in the presence of alkali metal pentacyano ferrate(II)complexes containing various water soluble ligands, such as ammonia, mono alkyl amine, dialkyl amines, and trialkyl amines, and utilizing oxygen or hydrogen peroxide as the oxidizing agents. The complex is then reduced by hydrogenation using suitable heterogeneous metal catalysts.
wherein n equals 2 to 5, and R
1
and R
2
are as set forth below
R
1
and R
2
may be the same or different, must be ortho or meta to the amino group, and may be hydrogen, C
1
-C
4
alkyl, C
1
-C
4
alkoxy, halogen, cyano, carboxylate salts and amides of carboxylic acids or mixtures thereof.
The invention relates to the production of PPDA with the ability to recycle the transition-metal complex, high selectivity and yield. The conversion of aniline to N-phenyl-p-phenylenediamine is in the range of 40-85%. The yield of PPDA ranges from 91 to 97%. The method of this invention is also cost effective and produces no environmentally undesirable byproducts.
2. Background of the Related Art
The production of p-phenylenediamine and its derivatives is widespread and its uses are widely known. In U.S. Pat. Nos. 5,858,321 and 5,728,882 a complex made using ferrous chloride was used to prepare p-phenylenediamine. In U.S. Pat. No. 5,117,063, Stern et al., disclose various methods of preparing N-phenyl-p-phenylenediamine wherein aniline and nitrobenzene are reacted under specific conditions.
In other publications, the oxidative dimerization of aniline to produce N-phenyl-p-phenylenediamine is disclosed. British patent No. 1,400,767 and European patent 0-261096 utilize an alkali metal ferricyanide whereas European patent 0-272-238 utilizes a hypohalite oxidizing agent. None of these processes are very selective, nor do they give good conversions.
J. Bacon and R. N. Adams in J. Am. Chem. Soc., 90 p 6596 (1968) report the anodic oxidation of aniline to N-phenyl-p-quinonediimine but no conversions or yields are given. E. Herrington, in J. Chem. Soc. p 4683 (1958) reports the oxidative dimerization of aniline with disodium pentacyanoamminoferrate (III) to form a complex containing N-phenyl-p-phenylenediamine which is then reduced chemically with reducing agents such as hydrazine hydrate, sodium dithionate, sodium hydrogen sulfite and hydrogen sulfide. The use of the trisodium pentacyanoamminoferrate (II) complex and catalytic reduction with hydrogen of this invention distinguish over this publication and the differences result in a significantly improved process. The stoichiometry of the instant invention is much improved over Herrington since higher ratios of aniline to complex can be used in the process disclosed herein.
It is therefore an object of this invention to provide a method for the production of N-phenyl-p-phenylenediamine and related compounds. It is a further object of this invention to disclose a method for the production of such compounds via an aqueous process that allows the easy removal of unreacted aniline and subsequent separation of the reconstituted starting complex from the desired end product [formula (I)] after reduction giving a process which is commercially viable, involving both low cost and recyclability.
It is still a further object of this invention to provide a process that favors the p-phenylenediamine product, with both high yield and good selectivity. It is yet a further object of this invention to furnish a process with produces less waste and effluent streams. A still further objective is the production of phenylenediamine derivatives which may be used industrially as antidegradants made from the high purity products of the process of this invention.
SUMMARY OF THE INVENTION
The present invention is directed to an improved method for preparation of substituted aromatic amines of formula (I) comprising the steps of: a) oxidizing an aromatic amine of formula (II) in the presence of a specially prepared metal pentacyano ferrate (II) complex to form an arylenediaminopentacyanoferrate complex, said metal being selected from the group consisting of potassium and sodium; and b) catalytically reducing said arylenediaminopentacyanoferrate complex with hydrogen using a heterogeneous metal catalyst, producing the corresponding substituted aromatic amine of formula (I).
wherein n equals 2 to 5, and R
1
and R
2
are as set forth below
R
1
and R
2
may be the same or different, must be ortho or meta to the amino group, and may be hydrogen, C
1
-C
4
alkyl, C
1
-C
4
alkoxy, halogen, cyano, carboxylate salts and amides of carboxylic acids or mixtures thereof.
The most preferred embodiment is directed to a process which oxidizes aniline in the presence of trisodium pentacyano ferrate (II) complexes containing various water soluble ligands, such as ammonia, mono alkyl amine, dialkyl amines, trialkyl amines and the like. Oxidizing agents may be oxygen or hydrogen peroxide. The N-phenyl-p-phenylenediamino pentacyano ferrate complex is then reduced with hydrogen using a heterogeneous metal catalyst, which may be supported or not supported. Suitable supports could include those known to the art such as, for example, carbon or alumina. The mixture of aniline and N-phenyl-p-phenylenediamine is then extracted with a suitable solvent after filtration of the heterogenous catalyst. Preferred solvents are environmentally friendly, water-immiscible, and easily recyclable. The aqueous layer containing the pentacyano ferrate (II) complex is then recycled.
DETAILED DESCRIPTION OF THE INVENTION
A preferred method of the present invention for producing N-phenyl-p-phenylenediamine (PPDA) involves the steps of a) the oxidation of aniline in the presence of trisodium pentacyano ferrate (II) complexes with the optional use of a heterogeneous metal catalyst; followed by b) reduction of the N-phenyl-p-phenylenediamino-pentacyano ferrate complex with hydrogen using a heterogeneous metal catalyst.
In most cases, both steps (a) and (b) will use the same heterogeneous catalyst. In the first step, any suitable oxidant including either oxygen or hydrogen peroxide may be used as the oxidizing agent. Oxygen is the preferred oxidizing agent. Still more preferred is the use of oxygen under pressure and at elevated temperatures which will increase the rate of oxidation and facilitate the completion of step a.
The metal pentacyano ferrate (II) complexes useful in this invention must be of a water soluble type having water soluble ligands as a part of the complex. Preferred metals are the alkali metals such as sodium or potassium. The most preferred, trisodium pentacyano ferrate (II) complex containing various water soluble ligands, is illustrative of the class of complexes useful. These ligands may be ammonia, monoalkyl amines, dialkyl amines, or trialkyl amines. A preferred structure for this preferred complex is Na
3
[Fe(CN)
5
NH
3
.xH
2
O], or its dimer.
In the second step of the preferred reaction, the N-phenyl-p-phenylenediamino-pentacyano ferrate complex is reduced with hydrogen using a heterogeneous metal catalyst. This catalyst is selected from the heterogeneous metals of Group VIII such as palladium, platinum, ruthenium, rhodium, or nickel. The catalyst may or may not be supported. If supported, the supports may be carbon, alumina, and the like, many of which are known to those familiar with the art.
The mixture of aniline and PPDA that is the product of the reaction is extracted with a suitable solvent. Then the heterogeneous catalyst is filtered off. Suitable solvents include those that are water-immiscible and easily recyclable. The aqueous layer containing the pentacyano ferrate (II) complex is then recycled.
The compounds of this invention can be synthesized advantageously by the following general me
Simon Mark W.
Wheeler Edward L.
Nazario-Gonzalez Porfirio
Thompson Raymond D.
Uniroyal Chemical Company, Inc.
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