Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-02-08
2002-09-24
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S451000, C556S018000, C502S168000, C502S166000, C502S161000, C502S162000, C502S167000
Reexamination Certificate
active
06455740
ABSTRACT:
The invention relates to a process to separate a group 8-10 metal/phosphite ligand complex from an organic liquid mixture.
A process to recover rhodium from an organic liquid derived from a hydroformylation process is described in EP-A-355837. In this known process, the rhodium containing liquid is firstly contacted with an ion-exchange resin having bonded ionically thereto an organophosphorous ligand (adsorption of rhodium). Subsequently rhodium is desorped from the thus obtained support by treating the support with a liquid in which the different or preferably the corresponding organophosphorous ligand is dissolved. According to this disclosure the rhodium concentration in the liquid is preferably low, i.e. less than 20 ppm rhodium.
It has been found that, when a phosphite ligand is present in the organic mixture, the phosphite ligand is not recovered by the process according to EP-A-355837. Furthermore the efficiency of the process is low, resulting in that under practical conditions only mixtures can be treated having a low concentration of the group 8-10 metal. According to a preferred embodiment of the process as described in EP-A-355837 the desorption is performed starting with organic mixtures containing dissolved organophosphorus ligands having an ionic moiety. Thus a group 8-10 metal/organophosphorus ligand complex, in which the ligand has an ionic moiety, is at the end obtained. It is however advantageous to directly use the resulting complex in a hydroformylation reaction. Because ligands having ionic moieties are normally used for water soluble catalyst systems and because phosphite ligands are unstable in the presence of water one skilled in the art would not be motivated to use the teachings of EP-A-355837 for the separation of a group 8-10 metal/phosphite ligand complex from an organic liquid mixture.
The object of the invention is a process to separate a group 8-10 metal/phosphite ligand complex from an organic liquid and in which the complex can be recovered and simply reused as a catalyst.
The object is achieved in that the following steps are performed
(1) contacting the organic liquid with a support having bonded thereto an organophosphine ligand and separating the organic mixture which is poor in group 8-10 metal/phosphite ligand complex,
(2) contacting the thus obtained loaded support with an organic solvent and carbon monoxide and separating the thus obtained organic solvent rich in group 8-10 metal/phosphite ligand complex, and
(3) reusing the support obtained in step (2) in step (1).
It has been found that with the process according to the invention group 8-10 metal/phosphite ligand complex can be separated from the organic liquid with a high yield in step (1) and recovered for further use in step (2) in its original, catalytically active form. A further advantage of the process according to the invention is that the group 8-10 metal may be present in the liquid in high concentrations. Another advantage is that the process of the invention regenerates the support for direct reuse.
The use of a group 8-10 metal of the Periodic System of the Elements (New IUPAC notation; Handbook of Chemistry and Physics, 70th edition, CRC Press, 1989-1990) such as rhodium or iridium as part of a homogeneous catalyst system is well known in the art. Typical examples of such processes include the hydroformylation of an unsaturated compound with carbon monoxide and hydrogen to give an aldehyde, the hydrocyanation of unsaturated compounds, the hydrogenation of olefinic compounds and the polymerisation of olefins. In such a process, the group 8-10 metal catalyst generally is stabilized with a ligand.
The organic liquid to be treated in the process according to the invention is for example obtained in a hydroformylation process in which a homogeneous catalyst system is used comprising the group 8-10 metal/phosphite ligand complex. It has been found that the group 8-10 metal/phosphite ligand complex can advantageously be separated from the product stream of such process.
A problem in such hydroformylation processes is the possible accumulation of high boiling compounds in the recirculating catalyst stream. It is therefor necessary to separate the high boiling compounds by means of a purge. For a commercially interesting process it is necessary to recover the catalyst system comprising the group 8-10 metal/phosphite ligand complex from such a purge stream. This is especially advantageous when using valuable group 8-10 metal/phosphite ligand complexes such as for example described in WO-A-9518089.
The group 8-10 metal complex to be recovered by the process according to the invention is present as a soluble group 8-10 metal complex. Without wishing to be bound to any particular theory, it is believed that in step (1) of the process according to the invention the group 8-10 metal complex forms a coordination complex with the organophosphine ligand which is bonded on the support, whereby at least one ligand of the complex is displaced for the organophosphine ligand. Accordingly, it is preferred that at least one exchangeable ligand (L) is present in the complex to be recovered.
Examples of suitable group 8-10 metals are nickel, cobalt, ruthenium, rhodium, palladium, platinum, osmium and iridium. The invention is especially directed to recover rhodium because of its high price.
The mechanism of the first step can, for example for rhodium, be represented as follows:
in which P
1
is the immobilized organophosphine ligand and P
2
is the phosphite ligand and L is the exchangeable ligand.
L is for example CO, a phosphine, phosphite, phosphinite, phosphonite, olefin, nitrile, &bgr;-diketone or a &bgr;-ketoester. L is preferably CO.
The temperature applied during the adsorption of the rhodium complex is generally between 0° C. and 150° C., preferably between 15 and 80° C. and most preferably between 20 and 30° C. The temperature is preferably relatively low to minimize degradation of the support and the immobilized complex.
The pressure applied during the adsorption is generally not critical and will in practice be between atmospheric pressure and pressures high enough to overcome any pressure drop in the process equipment.
The adsorption of the group 8-10 metal complex on the support having bonded thereto organo-phosphine ligands can simply be performed by contacting the liquid containing the rhodium complex and the support batchwise, semi-continuously or continuously. When performing the contacting batchwise, an appropriate amount of the support is stirred with the liquid to be treated until a sufficient degree of adsorption is achieved, for example during for about 0,5 to 6 hours. Subsequently, the loaded support is separated from the treated organic liquid with any known solid-liquid separation method. Examples of suitable separation methods are filtration and centrifugation. Preferably, the contacting is performed continuously by passing the liquid to be treated continuously over one or more beds of the support, whereby the separation of the rhodium loaded support from the liquid is inherently facilitated. The bed may be a fixed bed or a liquid fluidized bed. Preferably a fixed bed is used.
The group 8-10 metal complex can subsequently be removed from the loaded support by contacting the loaded support with a suitable organic solvent and carbon monoxide to desorb at least a part of the adsorbed group 8-10 metal phosphite complex from the support (step (2)). Preferably also some hydrogen is present. The desorption of the group 8-10 metal complex is performed in the presence of an organic solvent in which the desorbed group 8-10 metal phosphite complex is soluble. Without wishing to be bound to any particular theory, it is believed that at least the organophosphine ligand of the support is displaced for the carbon monoxid used in step (2), when the group 8-10 metal phosphite complex dissolves in the organic solvent. The temperature applied during the desorption is generally between 0° C. and 150° C., more preferably between 60° C. and 120° C.
Suitable solvents are aromatic solvents
Broeders Nicolaas L. H. L.
Gelling Onko J.
Martens Hendrik F.
Meinema Harmen A.
Timmer Klaas
DSM N.V.
Padmanabhan Sreeni
Pillsbury & Winthrop LLP
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