Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Reexamination Certificate
2001-06-22
2002-10-22
Solola, T. A. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
Reexamination Certificate
active
06469194
ABSTRACT:
CROSS-REFERENCE TO COMPANION APPLICATION
Our copending application Ser. No. 09/886,289, filed concurrently herewith, assigned to the assignee hereof and also expressly incorporated by reference.
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to the hydrocyanation of ethylenically unsaturated organic compounds for the preparation of nitriles and, more particularly, to the hydrocyanation of diolefins or of substituted olefins for the production of dinitriles and/or to the isomerization of nitriles obtained via hydrocyanation.
The present invention relates more especially to hydrocyanation reactions catalyzed by nickel-based compounds.
2. Description of the Prior Art
French Patent No. 1,599,761 describes a process for the preparation of nitriles by addition of hydrocyanic acid to organic compounds containing at least one ethylenic double bond in the presence of a nickel catalyst and of a triaryl phosphite. This reaction can be carried out in the presence or in the absence of a solvent.
When a solvent is used in this process of the prior art, it is preferably a hydrocarbon, such as benzene or xylenes, or a nitrile, such as acetonitrile.
The catalyst employed is an organic nickel complex comprising ligands such as phosphines, arsines, stilbines, phosphites, arsenites or antimonites.
The presence of a promoter to activate the catalyst, such as a boron compound or a metal salt, generally a Lewis acid, is also recommended.
The hydrocyanation of compounds having at least one site of ethylenic unsaturation in the presence of an aqueous solution of a compound of a transition metal, in particular nickel, palladium or iron, and of a sulfonated phosphine, is described in FR-2,338,253.
The sulfonated phosphines described in this '253 patent are sulfonated triarylphosphines and more particularly sulfonated triphenylphosphines.
This process permits satisfactory hydrocyanation, in particular of butadiene and pentenenitriles, and an easy separation of the catalytic solution by a simple separation by settling and, consequently, avoids as far as possible the discharge of effluents or of waste comprising metals serving as catalysts.
However, in these processes, the overall lifetime of the catalyst is adversely affected by a loss of nickel during each sequence of the catalyst in the reactor. This loss is due, in particular, to a nickel hydroxide precipitate. This precipitate is also disadvantageous in the operation of the process as it contaminates the manufacturing plants, requiring either periodic cleaning of the latter or a stage of separation and removal of the precipitate. In the latter embodiment, an environmentally harmful effluent is produced.
SUMMARY OF THE INVENTION
Accordingly, a major object of the present invention is the provision of an improved hydrocyanation process which permits treating the precipitate indicated above, on the one hand to eliminate the risks of contamination of the production facility or of the environment and, on the other, to decrease the losses of catalyst.
Briefly, the present invention features a process for the hydrocyanation of ethylenically unsaturated organic compounds via reaction with hydrogen cyanide in the presence of an aqueous solution of a catalyst comprising at least one nickel compound and at least one water-soluble phosphine and, after reaction, separation of the organic and aqueous phases.
The process of the invention entails treating the recovered aqueous phase, which comprises a solid phase (colloids, gel or solid in suspension, or precipitated) formed during the hydrocyanation reaction, with hydrogen cyanide in order to dissolve said solid phase.
Thus, the aqueous phase can be recycled at least partially in the reactor without contaminating the production facility.
In another embodiment of the invention, the recovered aqueous phase A comprising the solid phase formed is subjected to a separation stage in order to extract the solid phase, the purified or clarified aqueous phase A
1
subsequently being at least partially recycled in the hydrocyanation reactor, the solid phase being dissolved by treatment with hydrogen cyanide.
DETAILED DESCRIPTION OF BEST MODE AND SPECIFIC/PREFERRED EMBODIMENTS OF THE INVENTION
More particularly according to the present invention, in a preferred embodiment thereof, the treatment of the separated solid phase with hydrogen cyanide is carried out in the presence of an aqueous solution comprising a water-soluble phosphine. The solution B thus recovered is, in another preferred embodiment, conveyed to a stage of regeneration of the catalyst which includes, in sum, a reduction of nickel in the (II) oxidation state to nickel in the (O) oxidation state. This reduction is carried out advantageously after addition of nickel in the (O) oxidation state to the solution obtained by dissolution of the solid phase.
In another preferred embodiment of the invention, the solution B is mixed with at least a portion of the clarified aqueous solution A
1
before the reduction regeneration treatment. Thus, as this solution A
1
comprises nickel in the (O) oxidation state, regeneration of all of the catalyst is possible.
According to another embodiment of the invention, the treatment with hydrogen cyanide of the solid phase formed, either after clarification of the recovered liquid phase A or directly in this liquid phase, is carried out by addition of hydrogen cyanide to the aqueous solution advantageously comprising a water-soluble phosphine or hydrocyanation catalyst and stirring the reaction mixture for the time necessary for the, preferably complete, dissolution of the precipitate.
The temperature of the reaction mixture is advantageously less than 100° C., and preferably ranges from 20° C. to 80° C. The hydrogen cyanide is added in liquid form or in solution in water, or in a solution of water-soluble phosphine.
The amount of hydrogen cyanide added is at least equal to the stoichiometric amount required for converting the precipitated or insoluble nickel into soluble nickel cyanide. This minimum amount can be determined as a function of the weight of precipitate to be dissolved and by considering that this precipitated or insoluble Ni is nickel hydroxide.
The amount of hydrogen cyanide added will advantageously be from 30% to 400% greater than the stoichiometric amount.
The stage of regeneration of the catalyst, or, stated differently, the reduction of the nickel to the 0 oxidation state, can be carried out by several processes, such as a reduction by gaseous hydrogen, an electrochemical reduction, or addition of an organic or inorganic reducing agent. The reduction processes are known and are described, in particular, in WO 97/24184, EP 0,715,890 and FR 1,599,761.
Suitable water-soluble phosphine compounds include those compounds described in FR-2,338,253 or in WO 97/12857 and EP 0,650,959. These are exemplary only and not limiting.
Thus, suitable phosphines according to this invention have the following structural formula (I):
in which Ar
1
, Ar
2
and Ar
3
, which may be identical or different, are each an aryl radical; Y
1
, Y
2
and Y
3
, which may be identical or different, are each an alkyl radical having from 1 to 4 carbon atoms, an alkoxy radical having from 1 to 4 carbon atoms, a halogen atom, a CN group, an NO
2
group, an OH group, an NR
1
R
2
radical, wherein R
1
and R
2
, which may be identical or different, are each an alkyl radical having from 1 to 4 carbon atoms; M is an inorganic or organic cationic residue selected, such that the compound of formula (I) is soluble in water, from the group consisting of H
+
, cations derived from alkali metals or alkaline earth metals, N(R
3
R
4
R
5
R
6
)
+
, wherein R
3
, R
4
, R
5
and R
6
, which may be identical or different, are each an alkyl radical having from 1 to 4 carbon atoms or a hydrogen atom, and other metal cations, the benzenesulfonic acid salts of which are soluble in water; m
1
, m
2
and m
3
which may be identical or different, are each an integer ranging from 0 to 5; and n
1
, n
2
and n
3
, w
Burattin Paolo
Coqueret Pierre
Huser Marc
Burns Doane Swecker & Mathis L.L.P.
Murray Joseph
Rhodia Fiber & Resin Intermediates
Solola T. A.
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