Separation off of a homogeneous catalyst from a reaction mixture with the help of organophilic nanofiltration
The invention deals with the separation of homogeneous catalysts from reaction mixtures with the help of organophilic nanofiltration. It is based on the object of indicating an option as to how organophilic nanofiltration can be used economically for separating off homogeneous catalysts from reaction mixtures if the separation-active material of the membrane satisfying the separation aim is not available in sufficiently large amounts or only at high cost. This object is achieved by taking into consideration a particular membrane performance indicator during the design and/or the execution of the corresponding membrane separation process.
1. A method for separating a homogeneous catalyst or degradation products thereof from a reaction mixture with organophilic nanofiltration, the method comprising the steps of:
A) hydroformylating an alkene in the presence of the homogeneous catalyst comprising an organometallic complex compound comprising a central metal atom selected from the group consisting of cobalt, rhodium, iridium, ruthenium, and palladium in a reactor, generating a reaction mixture comprising a liquid hydroformylation discharge comprising aldehyde, unreacted alkene synthesis gas being dissolved in the liquid:
B) drawing the reaction mixture off the reactor:
C) partially decompressing the reaction mixture in a degasser:
D) placing the degassed reaction mixture into a nanofiltration membrane separation unit comprising the membrane, which is carried out under carbon monoxide partial vapor pressure in order to prevent the catalyst from losing its activity, wherein the reaction mixture further comprises a liquid organic solvent and the homogeneous catalyst or constituents or degradation products of the homogeneous catalyst, wherein the membrane comprises a separation-active layer made of silicone acrylate;
E) separating the reaction mixture on the membrane into a retentate and a permeate, wherein the homogeneous catalyst or its constituents or degradation products is enriched in the retentate, wherein the concentration of the homogeneous catalyst or of its constituents or degradation products in the retentate is greater than in the permeate; and
F) removing the dissolved synthesis gas from the permeate.
2. The method of claim 1 , wherein the central atom is selected from the group consisting of cobalt and rhodium.
3. A hydroformylation system for reacting a mixture by a a hydroformylation reaction of an alkene utilizing an homogenous catalyst comprising an organometallic complex compound comprising a central metal atom selected from the group consisting of cobalt rhodium, iridium, ruthenium, and palladium in the presence of a liquid solvent, and the system comprising:
a hydroformylation reactor generating a reaction mixture which forms a liquid hydroformylation discharge comprising aldehyde, unreacted alkene, and synthesis gas dissolved in the liquid solvent;
a first degasser device configured to partially decompress the reaction mixture;
a separator for separating off homogeneous catalyst or degradation products thereof from the partially decompressed reaction mixture by way of organophilic nanofiltration, wherein the separator comprises a membrane which has an inlet for a feed, an outlet for a retentate and an outlet for a permeate,
wherein the membrane comprises a separation-active layer made of silicone acrylate; and
a second degasser device to remove the dissolved synthesis gas from the permeate.
4. The device of claim 3 , wherein the central atom is selected from the group consisting of cobalt and rhodium.
5. The device of claim 3 , where the the central atom is rhodium.