Method for enriching a homogenous catalyst from a process flow

[0001] The invention relates to a method for enriching a homogeneous catalyst from a process stream which comprises this homogeneous catalyst as a component. For enrichment, the process stream is passed through at least one membrane.

[0002] The catalyst systems used in homogeneous catalysis must, as a rule, be partly or completely removed from the respective reaction mixture. The reasons for this may be the product's purity requirements or the recovery of the catalyst system as a valuable substance that can even be brought back directly or indirectly into the reaction.

[0003] Especially when using transition metal complexes, such as rhodium as a catalyst or using more expensive ligands, the separation of the catalyst system represents an important process step because of the costs of the catalyst. Technical methods that are carried out using transition metal complexes in the homogeneous phase are, for example, telomerization, metathesis, hydrogenation or hydroformylation. Technically common and associated with relatively high catalyst costs are reactions with rhodium complexes.

[0004] Rhodium complexes are used as a catalyst, e.g. in the industrial hydroformylation of olefins to one C atom richer aldehydes and / or alcohols. In particular, rhodium complexes with phosphine, phosphite, phosphonine or phosphinine ligands are used as a catalyst.

[0005] The type of separation can have a significant impact on the profitability of the whole method. The easiest way to separate the catalyst from the reaction mixture is through a thermal separation process, for example by separating the reaction product and optionally educate from the catalyst-containing reaction mixture by evaporation. A disadvantage with this method is that the catalyst and / or ligand may decompose during distillation. The products derived from a catalyst in the distillation residue often cannot be converted into an active catalyst system in the process. Thus, they must be discharged and subjected to costly processing before being reintroduced into the process. This is especially true for the treatment of hydroformylation mixtures, which contain rhodium complexes with ligands as catalysts, which enter into complexes with rhodium less than phosphines. During distillation, these ligand complexes may degrade by carbon monoxide due to lack of stabilization, which can lead to rhodium clustering. Rhodium clusters cannot be converted to active catalyst under hydroformylation conditions. Thus, during distillation, partial ligand degradation may occur.

[0006] Potentially sparing separation of homogeneous catalyst systems offers the concentration of homogeneous catalyst process membranes with streams in one or multi-stage connection with each other.

[0007] EP 0 781 166 describes the separation of dissolved rhodium-organophosphite complex catalyst and free ligand in a non-aqueous hydroformylation reaction mixture on the membrane of at least 90% by mass of catalyst and free ligand. As the membrane polymer, teflon, polydimethylsiloxane (PDMS), polyethylene, polyisobutadiene, polystyrene, polymethyl methacrylate, polyvinyl chloride, cellulose diacetate, polyvinylidene chloride and polyacrylonitrile are mentioned. Separation of high boilers from the catalyst system is not described.

[0008] EP 1 232 008 describes the separation of high boilers from the catalyst feed stream again using a membrane (PDMS). The re-feed stream is formed during the distillation treatment of the discharge of an organometallic catalysed reaction. The educates and primary products are distilled off and the bottom product remains in the high boiling mixture in which the catalyst system is dissolved. This is fed back to the reactor. Because small amounts of high boilers are formed here, some of them must be separated to maintain a constant concentration of high boilers. In EP 1 232 008, high boilers are separated from the bottom product by the addition of a diluent. So much diluent is added that the proportion of high boilers in the solution that is fed into the membrane is less than 50% by mass. Separation of high boilers takes place in the temperature range from 10 to 50 ° C and in the pressure range from 0.1 to 10 MPa. The addition of a diluent is disadvantageous because the amount of substance through the membranes increases. In addition, some of the added solvent is separated from the high boilers, whereby costs are borne by the solvent or recovery.

[0009] DE 10 2005 046250 describes a method for separating an organometallic catalyst system. In the first stage, the organic discharge of the reaction to the retentate is separated with a major part of the catalyst system and permeate, which consists of educts, primary products, high boilers and the catalyst system. The retentate is directly fed back to the reactor. The permeate is separated by distillation into an overhead product, which primarily contains educates and primary reaction products, and a bottom product with a catalyst system dissolved in high boilers. In this document, as an optional treatment variant, separation of a portion of high boilers from the bottom product by means of a membrane is presented before it is fed back into the reactor. Membrane materials generally used are polydimethylsiloxane (PDMS), polyimide (PI), polyamideimide (PAI), acrylonitrile / glycidyl methacrylate (PANGMA), polyamide (PA), polyether ether ketone (PEEK), polymers with internal microporosity (PIM) and hydrophobed ceramic membranes. However, no details are given for the discharge of high boilers with membranes, such as the types of membranes that can be used.

[0010] DE 10 2005 060784A1 describes a method for recovering a catalyst-enriched metal (> 200 dalton) stream. The reactor discharge is separated by distillation into a low boiling stream and a higher boiling stream containing the catalyst

- 3 bottom stream. The bottom stream is separated by means of a membrane into a permeate stream and a catalyst-enriched retentate stream, which is fed again completely or partially to the reaction. Only ceramic membranes with a separation limit (MWCO) of more than 500 Daltons and polymer membranes with a separation limit of more than 10,000 Daltons are given. There is no statement about activity as a significant measure for the quality of the catalyst system being retained.

[0011] The catalyst exemplified has a molecular weight of approximately 12,000 Daltons and is thus one order of magnitude higher than the conventionally used technical catalysts. By means of the explanation of DE 10 2005 060784A1, it is not possible to transfer to technically important and lower molecular weight catalyst systems.

[0012] Furthermore, it is not indicated which stop is the separation limit and in which system the separation limit has been determined. Depending on the manufacturer, the data is usually based on 90 or 95% retention. The separation boundary does not serve as an absolute limit, but as a qualitative aid for choosing a membrane for a particular separation problem (see Melin, Rautenbach: Membranverfahren. 2. Auflage 2004 Springer-Verlag Berlin, Heidelberg.). It is therefore doubtful whether the given separation limits apply to a metal complex catalyst. The necessity of retaining the ligand is not mentioned.

[0013] Said membranes are only porous membranes whose separation limits, as is further shown below, are not suitable for the catalyst system according to the method. In addition to the various membranes mentioned, in addition to various ceramic membranes, only polytetrafluoroethylene, polyvinylidene fluoride (PVDF), polysulfone, polyethersulfone, polydimethylsiloxane (PDMS), polyetherketone, polyamide and polyimide are mentioned as possible membrane materials.

[0014] In US 2006 / 0246273A1, a novel polymer with internal microporosity (PIM) is laid. Due to the rigid spiro bond, this polymer or polymer mixtures based on it have a large free volume within the polymer matrix. The polymer is potentially applicable for the separation or enrichment of gas, steam or liquid mixtures. The use of a polymer as a membrane material is suitable due to the high free volume especially for gas separation. Fritsch et al. (J.Mem.Sci. 251, 263-269 (2005)) achieve proportionally high transmittances.

[0015] In addition to gas separation, PIM-based membranes can also potentially be used to separate chiral molecules such as amino acids, to separate organic substances, e.g., alcohol from aqueous systems, to separate isomers, in pharmacy and biotechnology to separate proteins or other thermally unstable components , in fermentation vats and bioreactors for fumigation and separation of biomass as well as for the removal of microorganisms from air and water.

[0016] Further potential applications are water purification, detection or removal of trace components or metal salts from air or water,

- 4 separation of liquid mixtures by means of evaporation (e.g. in the production of ethanol) as well as gas / steam separation (e.g. separation of steam or organic gas) and liquid-liquid separation of organic components or also improvement of yield in equilibrium reactions by selective discharge of the product. The separation of dissolved solids such as homogeneous catalysts is not described. Membrane thicknesses from 10 to 500 μm are also too thick for the desired separation task.

[0017] WO 2005/113121 A1 describes the production of composite membranes with a thin layer of microporous material with high internal microporosity. In addition to membrane production, possible applications of membranes, such as fluid separation and separation of low molecular weight solids from fluids are also mentioned. Also mentioned is the separation of hydrogen and hydrocarbons, N2 or CO, separation of CO2, H2O and H2S from natural gas, separation of nitrogen and oxygen, separation of VOC (Volatile Organic Compounds) and other lower hydrocarbons from air and other gases, separation of traces of organic components from aqueous streams as well as separation of low-molecular components and oligomers from fluids and especially from solvents.

[0018] A disadvantage of the prior art methods is that the methods either cannot separate the catalyst system sparingly enough and thus, while maintaining its activity and / or active catalyst systems cannot be sufficiently retained. Especially when retaining an active catalyst system having less than 1500 g / mol, which has a clearly lower molar mass than the clustered catalyst species, it is difficult to separate components with a membrane with a molar mass difference of less than 100 g / mol. At the same time, the membrane must be sufficiently permeable to organic components to allow for profitability.

[0019] Since there is no known satisfactory solution for a sparing enrichment of the catalyst system from hydroformylation streams of higher olefins (C4 and higher), consisting of a metal complex catalyst and its cluster as well as a free ligand, the task remained to develop a process that separates the stream process containing a catalyst system (e.g. discharge of the reactor or bottom product) into the stream enriched by the catalyst system and the stream impaired in the catalyst system and has a high degree of retention of the catalyst system, especially for metal components.

[0020] The technical task of the invention is therefore to provide a method for the enrichment of a homogeneous catalyst, in which the catalyst system, while maintaining its activity, can be enriched or separated, whereby the method must have a high degree of retention for the catalyst system, for recovery no diluents and no clustering of the catalyst metal proportion or disintegration of the catalyst complex is also observed.

[0021] This technical task is solved by a method of enriching a homogeneous catalyst from a process stream that contains this homogeneous catalyst as a component, wherein the process stream is passed through at least one membrane and wherein the membranes consist entirely or partly of a polymer which It has

- 5 flat polymer units that are attached to each other by a rigid connector, the connector being twisted in such a way that at least one flat polymer unit is bonded through the connector in a non-planar arrangement with at least one other flat polymer unit.

[0022] These polymers are referred to below as internal microporosity (PIM) polymers.

[0023] It has been surprisingly found that both the metal-catalyzed and organic discharges produced from the discharges of the reaction, enriched with high boilers, bottom distillate that contains high-boilers, metal complexes, its clusters and free ligands can be separated by one or more membrane (s) high boilers, product and educt from the catalyst system, wherein the retention of the metal component is greater than 70% depending on the membrane and for the free ligand greater than 60% when separation occurs on membranes that contain polymers with internal microporosity (PIM). Preferably, the process is carried out with a separation limit of 400 to 2000 g / mol in a temperature range of 40 to 150 ° C and in a range of transmembrane pressure (pressure difference between the membrane) of 5 to 60 bar.

[0024] Also, at high boiling concentrations above 50% by mass, no diluent is needed, because also at high high boiling concentrations, permeate flow and separation selectivity is high enough for technical implementation. It is surprising that with membranes based on the PIM catalyst complex, whose molar masses are in the same order of value as these high boilers, they are better retained than high boilers.

[0025] High boilers in the sense of the invention are substances that grow at a temperature higher than primary hydroformylation products (aldehydes and / or alcohols with one C atom more than the olefin used) and have higher molar masses and are formed during hydroformylation. These include aldolization products and acetalization products as well as esters that are formed by the reaction of alcohols and acids, with alcohols and acids being formed by the disproportion of aldehydes. High boilers that are present in hydroformylation process streams generally have boiling points above 55 ° C at 0.1 MPa.

[0026] In a preferred embodiment, the polymers have spirobisindane bonds inside the polymer structures that serve as linkers.

[0027] In a particularly preferred embodiment, the polymers have substituted or unsubstituted spirobis [indane] substrates inside the polymer structures that serve as linkers.

[0028] Spirobisindane bonds in the sense of the invention are 1, 1'-spirobis [indan], 1, 2'-spirobis [indan] and 2,2'-spirobis [indan]; whose structures can be represented as follows:

<img file="PL2401078T3_D0001.tif" />

<img file="PL2401078T3_D0002.tif" />

[0029] The spirobisindane bond is not a chemical bond in the strict sense but rather a structured bond between the polymers.

[0030] A particularly preferred spirobisindane bond is the substructure with the 3, 3, 3 ', 3'-tetramethyl-1,1'-spirobis [indan] compound:

<img file="PL2401078T3_D0003.tif" />

[0031] Polymers that have repeating units of one or more of the following formulas are particularly preferred as the membrane-active membrane material.

7 wherein n represents the number of units and is preferably between 10 and 100,000.

<img file="PL2401078T3_D0004.tif" />

[0032] The polymers mentioned earlier are referred to below as PIM (polymers with internal microporosity).

[0033] Enrichment in the sense of the invention is not only meant to enrich the homogeneous catalyst, but also to completely separate the homogeneous catalyst from the process stream.

[0034] It is preferred that the PIM-based membranes have a particularly high retention of organic solids dissolved in solvents such as homogeneous catalysts and their ligands compared to existing membranes, and at the same time have a high permeate flow.

[0035] In addition, a particularly delicate separation can be achieved for the catalyst system when the catalyst system is possibly processed in the presence of carbon monoxide and hydrogen, since this can further avoid clustering. It is also possible to cover with carbon monoxide or hydrogen, especially when separated through the membrane.

[0036] The amount of synthesis gas during separation should be exceeded at least in the stoichiometric amount required to form active catalyst species to be able to prevent the formation of inactive or even irreversibly precipitated catalyst species.

Interconnection of the membrane [0037] The method according to the invention can be carried out using one,

- 8 two or more membranes or using one, two or more membrane separation steps. Depending on the membrane separation efficiency and the desired retention, the desired retention can be achieved by interconnecting the many separation steps on the membrane with each other. In particular, two or more membrane separation steps may be carried out in the method of the invention. The separation steps on the membrane can be carried out directly in succession. The interconnection may occur such that either the retentate or permeate, preferably the permeate of the first separation step on the membrane is fed to the further separation steps on the membrane as an inflow stream. Optionally following a first separation step on the membrane according to the invention, the separation steps on the membrane can be carried out in the same manner as the first. One or more membranes may be used on the membrane in the separation step. Preferably, two or more membranes are used on the membrane separation step.

[0038] With a multi-stage membrane separation process it may be advantageous to use different membranes in the membrane separation steps. Thus, in the previously incorporated membrane separation step, in one membrane separation step, it is preferable to use a more permeable membrane. The resulting classification leads to better permeability in the subsequently switched membrane separation step.

[0039] In the process according to the invention, an upper temperature limit is previously given for the separation steps on the membrane by the stability of the membrane used and the stability of the catalyst system. The lower temperature limit depends on the viscosity of the solution to be separated and on the temperature of the solubility of the catalyst system therein. Preferably, in the method of the invention, the membrane separation step, especially the first membrane separation step is carried out at a temperature of 40 to 150 ° C, particularly preferably at a temperature of 60 to 90 ° C. If in the process according to the invention for the separation of the catalyst from hydroformylation reaction mixtures are used those obtained during hydroformylation of C12 olefins, the separation step on the membrane, especially the first separation step on the membrane is preferably carried out at a temperature of 60 to 90 ° C. If in the process according to the invention for the separation of the catalyst from hydroformylation reaction mixtures are used those obtained during hydroformylation of C8 olefins, the separation step on the membrane, especially the first separation step on the membrane is preferably carried out at a temperature of 40 to 80 ° C. Carrying out the process according to the invention at favorable temperatures can, on the one hand, result in a higher flow through the membrane. On the other hand, by maintaining said preferred temperature ranges, catalyst degradation is avoided, which otherwise may lead to active catalyst losses and deposition of catalyst degradation products on the membrane. As a result of deposition, the flow rate through the membrane can be reduced. In extreme cases, the quantitative flow can be completely stopped by blocking.

[0040] The transmembrane pressure (pressure on the membrane between the retentate and permeate side) at which the process according to the invention is preferably carried out is preferably 5 to 60 bar, particularly preferably 10 to 30 bar.

[0041] In the process according to the invention, PIM membranes may be used which, due to their chemical or physical properties, are suitable, metal complex catalysts, especially organophosphorus metal complex catalysts, are retained to a degree of at least 60%, especially above 80%, and have a separation limit of 400 to 2000 g / mol. Another requirement for the applicability of the membrane is that the membrane must be stable to all compounds present in the reaction mixture, especially to solvents.

PIM [0042] The term microporous also includes materials that could be referred to as nanoporous. To date, there are two classes of internally microporous materials. Zeolites and amorphous activated carbon. Due to the lack of solubility in organic solvents, films and therefore also membranes cannot be produced from these materials. This is different with polymers.

[0043] By PIM (polymer with internal microporosity), the recently developed polymer class is defined, which is preferably characterized by a rigid, spirally twisting polymer structure, spirobisindane bond. The random arrangement of the spiro bond prevents the polymer from thickening. Stiff twisting (flat polymer chains) on a spirobisindane bond leads to a higher proportion of free, related volumes. Microporosity is referred to as internal because it occurs independently of the thermal pre-treatment and polymer treatment.

The representative for a polymer with internal microporosity is the so-called PIM-1. By PIM-1 is meant one of the first polymers in this class of polymer. The name CA Index is 1,4 benzenedicarbonitrile, 2, 3, 5, 6-tetrafluoro polymer with 2, 2 ', 3, 3'-tetrahydro- 3, 3, 3', 3'-tetramethyl-1, 1'- spirobi [1H-indeno] - 5, 5 ', 6, 6'-tetrol with the number CA 67645048-9. PIM-1 is obtained from the reaction of 5, 5 ', 6, 6'-tetrahydroxy-3, 3, 3', 3'-tetramethyl-1, 1-spirobisindane with 2, 3, 5, 6-tetrafluorophthalonitrile:

<img file="PL2401078T3_D0005.tif" />

[0044] Further representatives of polymers with internal microporosity are disclosed in US2006 / 0246273A1 and in WO2005 / 113121.

[0045] Further representatives of the comonomers that are suitable for PIM-1 modification are:

<img file="PL2401078T3_D0006.tif" />

<img file="PL2401078T3_D0007.tif" />

<img file="PL2401078T3_D0008.tif" />

<img file="PL2401078T3_D0009.tif" />

Comonomer 6 [0046] Comonomer 3 is produced by bromination of spirobisindane.

[0047] Further representatives of the starting materials are 9, 9'-spirobifluorenes, modified as 2, 2'-dicarboxy-9, 9'-spiroflourenes or 2,2'-diamino-9, 9'-spirobifluorenes, which are suitable for internal production microporous polyamides and p olimides.

[0048] In addition to the above-mentioned polymers with internal microporosity, the membranes may have further materials. Membranes may in particular have support or support materials onto which PIM is applied as a thin, release active layer. In addition to the actual membrane, support material is also present with these connected membranes. The choice of support materials is described in EP 0 781 166, to which reference is expressly made. In addition, reinforcing materials, such as inorganic oxide particles or inorganic fibers, such as ceramic or glass fibers, which can increase membrane stability, especially in the presence of pressure fluctuations or high pressure differences, may be present in the usable membrane of the invention.

The thickness of the membrane separation layer for the method according to the invention is preferably

- 1000 nm, particularly preferably 100 - 700 nm.

Technical modules [0049] Membranes are preferably used in the method of the invention in the form of membrane modules. In these modules, the membranes are arranged in such a way that the retentate side of the membrane can be such that the polarization of the concentration of the separated components, here the catalyst-ligand system, counteracts and otherwise can be influenced by the necessary driving force (pressure). The permeate is led together to the permeate collection space on the permeate side of the membrane and discharged from the module. The membrane modules used have membranes in the form of membrane slices, membrane pads or membrane pockets. Preferably, the method of the invention uses membrane modules in the form of membranes, which have membrane modules with open-channel cushion module systems wherein the membranes are thermally welded or glued to membrane pockets or cushions, or open-ended coil modules (Wide-spacer type) channels at which the membranes are glued or welded to the pockets of membranes or membrane cushions and with power walks wrapped around the permeate collection tube.

Flow, separation step [0050] To avoid deposition on the membrane, some flow ratios must be maintained within the membrane separation step. It turned out that the risk of postponing the flow depends on turbulence, and therefore on its Reynolds number. Therefore, regardless of the type of membrane module construction, care must be taken that the Reynolds number is between 55 and 13500, preferably between 100 and 3500 and particularly preferably between 170 and 900. The kinematic viscosity should be less than 10 mPas and preferably 1 mPas. Sedimentation is avoided with these flow ratios.

[0051] To transform these flow ratios using coil membranes with a tube length of 1 m and a pressure loss of 1.5 bar and a kinematic viscosity of 1 mPas to avoid membrane deposition, the process is preferably carried out so that the separation step on the membrane in particular the first separation step on the membrane occurs at a flow rate on the membrane of 0.1 to 15 m / s, preferably 0.2 to 4 m / s, preferably 0.3 to 1 m / s.

[0052] Preferably, the method of the invention is driven such that the separated solution is led to the membrane as an inflow stream and the retentate stream is partly re-fed to the membrane. In this case, the partial stream, which is again fed to the membrane, is previously combined with the separated solution. The part of the retentate stream that is not fed back to the membrane is either used as an inflow stream for one or more subsequent separation steps, or is fed back to the reaction.

[0053] If an inlet stream is fed to the membrane separation step with a low proportion of high boilers and a high proportion of primary products, as is the case with the discharge of the reactor without prior concentration

- 12 high boilers, the volume flow has a ratio of permeate stream to reactor feed stream (no retentate fed) 1 to 1.1 to 1 to 5, preferably 1 to 1.4 to 1 and 3 and particularly preferably from 1 to 1 , 6 to 1 to 2.

[0054] If, in the reverse case, a stream significantly enriched in high boilers for reactor discharge is fed to the membrane separation step after the reactor, e.g. through a thermal separation step, then the ratio of permeate stream volume to reactor inflow stream (without retentate feed) it is preferably 1 to 5 to 1 to 20, preferably 1 to 7.5 to 1 to 12.5 and particularly preferably from 1 to 9 to 1 to 11.

[0055] It can be advantageous if the volume flow through the membrane is clearly higher than the volume flow of the permeate stream, because a high flow rate on the membrane can be set by this straight path. Preferably, the ratio of the volume stream flow to the membrane, especially to the first membrane of the first membrane separation step (feed from the reactor including the retentate fed back) to the permeate stream is from 10 to 10,000 to 1, preferably from 50 to 5,000 to 1 and particularly preferably from 200 to 2000 to 1. Preferably, a relatively high volume flow is also circulated through the membrane. The size of the portion of the retentate stream that is fed back to the reaction or fed back to the next separation is obtained from the difference of the inflow stream (without the retentate fed back) and the permeate stream.

[0056] At higher permeabilities, it may also be beneficial to interconnect the membranes in a Christmas tree structure.

[0057] As a stream for separation on the membrane, a direct discharge of the reaction catalyzed by organic metal complexes or a concentrate made thereof can be used. The reaction discharges contain educates, primary products, by-products, such as high boilers, a catalyst system and possibly a solvent. When this mixture is treated according to the invention, the catalyst system, especially the metal complex, remains predominantly in the retentate. The permeate, which is treated in the next separation stage, jointly educates, products and high boilers. In this case, the permeate stream is significantly larger than the retentate stream that is not fed back to the membrane. This conditions a large membrane surface and suboptimal stopping of the catalyst system.

[0058] Thus, preferably, most of the educts and products are separated by a thermal separation step. Such a thermal separation step may e.g. be carried out by one or more thermal separation devices, e.g. a thin film evaporator, a film precipitation evaporator, a flash evaporator or distillation columns. Education and primary products are generally separated as the peak product. As a bottom product, a mixture with high boilers and a catalyst system is produced. If the reaction mixture is a hydroformylation mixture, then the product

- the peak usually contains hydroformylation products, e.g. aldehyde and / or alcohol as well as optionally unreacted hydrocarbons, e.g. olefins or aliphates, and a solvent used for hydroformylation, which has a boiling point in the hydroformylation range or lower, which may be back brought to further processing. The bottom product of the thermal separation step is a mixture that contains the complex catalyst and / or free ligands, optionally boiling at a higher temperature than the hydroformylation solvent, as well as high boilers formed during the hydroformylation.

[0059] The proportion of high boilers in the bottom product depends on the reaction conditions and the product used between 50 and 98% by mass, in particular between 60 and 90% by mass. These solutions can be fed back for separation on the membrane without the addition of a diluent.

[0060] Optionally, before the thermal separation step, the reaction mixture can be separated by means of a membrane into a stream with a higher catalyst concentration and into a stream with a lower catalyst concentration. The stream with the higher catalyst concentration is fed back to the reactor. The stream with low catalyst concentration is fed to the thermal separation step. Such a method is described, for example, in DE 10 2005 046250.2.

[0061] By means of the invention, mixtures which are formed by reactions using uniformly dissolved metal catalysts can be separated.

[0062] Representatives of such reactions include hydrogenation, hydroformylation, metathesis, hydrocyanation and hydrocarboxyalkylation of olefins. Preferably, hydroformylation mixtures that contain rhodium complex catalysts are treated.

[0063] The hydroformylation reaction mixtures may be derived from a process for hydroformylation of olefins, preferably with 2 to 25 carbon atoms, particularly preferably 4 to 16, particularly very preferably from 6 to 12 and especially from 8, 9, 10, 11 or 12 carbon atoms to corresponding aldehydes. Particularly very preferably, the hydroformylation reaction mixture has as the hydroformylation product an aldehyde which is selected from aldehydes with 5 to 17 hydrocarbon atoms, preferably 9 or 13 hydrocarbon atoms, especially isononanal and isotridecanal.

[0064] The complex catalysts and / or free organophosphorus ligands present in the hydroformylation reaction mixture can be compounds and complexes known in the art. Preferably the complex catalysts or free ligands have such ligands that are selected from phosphines, phosphites, phosphinites, phosphonites. The ligands may have one or more phosphine, phosphite, phosphonite or phosphinite groups. Likewise, it is possible that the ligands have two or more different groups selected from phosphine, phosphite, phosphonite or phosphinite groups. The ligands may in particular be bisphosphite, bisphosphine, bisphosphonite, bisphosphite, phosphine phosphite, phosphine phosphite, phosphine phosphite, phosphite phosphite, phosphite phosphite, or phosphonite phosphite. Complex catalyst ligands and free ligands may be the same

- 14 or different. Preferably the organophosphorus complex catalyst ligands and free ligands are identical.

[0065] Representatives for possible catalysts for complexes or ligands and their preparation in hydroformylation can be e.g. taken from EP 0 213 639, EP 0 214 622, EP 0 155 508, EP 0 781 166, EP 1209164, EP 1201675, DE 10114868, DE 10140083, DE 10140086, DE 10210918 or WO 2003/078444, to which explicit reference is made.

[0066] Representatives of preferred ligands are:

Phosphines: triphenylphosphine, tris (p-tolyl) phosphine, tris (m-tolyl) phosphine, tris (o-tolyl) phosphine, tris (p-methoxyphenyl) phosphine, tris (p-dimethylamino-phenyl) phosphine, tricyclohexylphosphine, tricyclohexylphosphine tri- (1-naphthyl) phosphine, tribenzylphosphine, tri-butylphosphine, tri-t-butylphosphine.

[0067] Phosphites: trimethyl phosphite, triethyl phosphite, tri-n-propyl phosphite, tri-i-propyl phosphite, tri-n-butyl phosphite, tri-i-butyl phosphite, tri-t-butyl phosphite, tris (2-methylphosphoryl) di-t-butylphenyl) phosphite, tris (2-t-butyl-4-methoxyphenyl) phosphite, tris (2-t-butyl-4-methylphenyl) phosphite, tris (p-cresyl) phosphite.

[0068] Phosphonites: methyldiethoxyphosphine, phenyldimethoxyphosphine, phenyldiphenoxyphosphine, 2-phenoxy-2h-dibenz [c, e] [1, 2] oxaphosphite and its derivatives in which hydrogen atoms are completely or partly replaced by alkyl residues and / or aryl residues halogen.

[0069] Available phosphinite ligands are diphenyl (phenoxy) phosphine and its diphenyl (methoxy) phosphine and diphenyl (ethoxy) phosphine derivatives.

[0070] Furthermore, the hydroformylation mixtures may have an acyl or heteroacyl phosphite or a ligand having an acyl or heteroacyl phosphite group as an organophosphorus ligand. Acyl phosphite or ligands having acyl phosphite groups whose production and use in hydroformylation are even described in DE 100 53 272 Heteroacyl phosphite or ligands having heteroacyl phosphite groups whose production and use in hydroformylation are even described in DE 10 2004 013 514.

[0071] In the following, the invention is described, for example, without limiting the protective scope of the invention, the protective scope of which is claimed, but not limited to the claims and description.

[0072] The process of the invention for separating components with higher temperature boiling from homogeneous catalysts or homogeneous catalyst systems, by separation with membranes based on an internal microporosity polymer (PIM) will be described below, for example, for a rhodium complex hydroformylation of C4 to C16 olefins catalysed.

[0073] According to Fig. 1 hydroformylation educta (1), olefin and synthesis gas are fed to the reactor (R). In the presence of a catalyst system placed in the reactor

Hydroformylation of olefin to aldehyde takes place. The reacted educt as aldehyde and by-products and subsequent products, among them high boilers such as aldol condensation products and unreacted educt as well as the catalyst system are discharged as a reaction mixture (2) from the reactor and fed to a selective separation step on the membrane (M). At the same time, the retentate (3) enriches and the permeate (4) depletes the catalyst or catalyst system.

[0074] Fig. 2 shows the extension of the method of Fig. 1, by feeding the permeate (4) of the separation step on the membrane to the thermal separation step (D). In the thermal separation stage, the permeate stream (4) is separated into components boiling at a higher temperature, such as by-products of the reaction part, and stream (6) enriched in catalyst components not kept in the membrane separation step, and into the boiling stream, predominantly aldehyde-containing product stream (5) ). To avoid enrichment by-products boiling at a higher temperature, the stream (6) or the partial stream (8) can be excluded from the stream (6) according to the method. Unless required, the total stream (6) is turned off, it may be advantageous to feed back the remaining reaction stream (7), especially when the stream (7) still contains parts of the catalyst system.

[0075] Depending on the maintenance of the value of stream (6) with respect to the catalyst components, it may be advantageous to separate stream 6 by a second separation step on the membrane into a stream (7) enriched with catalyst relative to stream (6) and suitably leaned with catalyst stream (8) to disable high-boiling components (see Fig. 3). Depending on the activity of the catalyst enriched in stream (7), it may be advantageous to feed this reaction stream directly or indirectly.

[0076] The interconnection according to Fig. 3 can also be advantageous without a separation step on the membrane after discharge of the reaction. Figure 4 illustrates this interconnection.

[0077] A further object of the invention is a method for producing tridecanal, which comprises the following steps:

a. Hydroformylation of tributene to tridecanol using a homogeneous catalyst system consisting of rhodium and an organophosphorus compound.

b. Distillation separation of the discharge of the reaction into a distillate that contains unreacted olefins and aldehydes and a bottom product that contains high boilers and a catalyst system,

c. carrying out the process according to the invention for enriching the homogeneous catalyst, the high boilers being separated from each other as permeate and the catalyst system as retentate,

d. returning the retentate with the enriched catalyst system to the hydroformylation reactor.

[0078] In a preferred embodiment, tributene is used to prepare tridecanal, which is produced by oligomerization of linear butenes on nickel-containing solid catalysts.

[0079] In a particularly preferred embodiment, the organophosphorus compound is tris (2,4-dimertiarobutylphenyl) phosphite.

[0080] Even without further embodiments, it is assumed that one skilled in the art can use the above description to the fullest extent. Preferred embodiments and examples should therefore only be understood as discussing, but in no way limiting, disclosures. The invention is explained in more detail below using examples. Alternative embodiments of the invention are obtained analogously.

Examples

Example according to the invention [0081] As an example, the most demanding separation task according to Fig. 4 due to the high proportion of high boilers was selected from previous interconnections for the membrane separation step. The reaction is rhodium / phosphite catalyzed hydrofomylation of the dodecene mixture butene). The rhodium precursor used is rhodium acetylacetonate and the ligand used is tris (2,4-di-tert-butyl-phenyl) phosphite. The rhodium concentration was 10 mg / kg. The ratio of rhodium to ligand was 20. The reacted educt as aldehyde (isotridecanal) and by-products, among them high boilers such as aldol condensation products and unreacted educt as well as the catalyst system are fed to the thermal separation stage, which enriched in high boilers and catalyst product bottom is fed through a separation step on the membrane. The share of high boilers is above 50%. The molar mass difference between the active catalyst species and high boilers is less than 500 g / mol.

[0082] It could even be shown that the rhodium retention by means of a PIM membrane in the high boilers stream is above 95% (Figure 5).

The membrane filtration was carried out at least at a diaphragm pressure of 25 bar and a temperature of 60 ° C. The flow from the supply side was 1.7 m / s, the pressure loss in the pipe was below 1 bar, the Reynolds number was about 1200. This high feedback retention could be proved by an experiment duration of over 20 days. The permeate flows achieved were between 0.63 and 1.41 kg / (m²h). The rhodium concentration in the feed of the membrane separation step was 50 to 133 mg / kg.

Comparative Example [0083] Experiments have shown that the method instruction of DE 10 2005 060784A1 cannot be used for the separation task according to the method. An important reason is the insufficient sharpness of separation of the membranes and membrane materials listed there. [0084] Table 1 shows the corresponding results for the selection from those mentioned in DE 10 2005

- 17 060784A1 membrane types. When feeding the separation step on the membrane, as in the example of the method, it is enriched with high boilers by the thermal separation step, the discharge stream of the rhodium / phosphite catalyzed dodecene hydroformylation reactor. Accordingly, this stream includes the reacted educt like aldehyde (isotridecanal) and by-products and subsequent products, among them high boilers such as aldol condensation products and unreacted educt as well as the catalyst system. Ceramic membranes from Inopor® and Velterop® have a good permeate flow, but they cannot retard sufficiently the catalyst system for longer. Polymer membranes have elevated to ceramic membranes, however, insufficient catalyst retention. The Starmem 240® polyimide membrane additionally has an inadequately low permeability.

Tab. 1 TMP = transmembrane pressure

<td>Production/ Membrane</td><td>Material</td><td>Power rh</td><td>permeate rh</td><td>Stopping feedback</td><td>Flow</td><td>Pressure membrane spanning</td><td>temp.</td>

<td></td><td></td><td>^[mg^{/ k}g^]</td><td>^[mg^{/ k}g^]</td><td> [%]</td><td>[Kg / (h * m2)]</td><td>[bar]</td><td>[° C]</td>

<td>Inopor nano 0.9 nm</td><td>TI02</td><td> 20</td><td> 11</td><td> 45,0</td><td> 3,08</td><td> 20</td><td> 121</td>

<td>Velterop 0.1 nm</td><td>Al2O3</td><td> 77</td><td> 62</td><td> 19,5</td><td> 11,42</td><td> 15</td><td> 150</td>

<td>UNDERWORLD Starmem240</td><td>PI</td><td> 120</td><td> 62,5</td><td> 47,9</td><td> 0,29</td><td> 30</td><td> 90</td>

<td>GMT oNF2</td><td>PDMS</td><td> 120</td><td> 27,5</td><td> 77,1</td><td> 1,74</td><td> 25</td><td> 60</td>

[0085] The examples show that the method according to the invention is clearly better than the prior art methods to enrich the catalyst system. Thus, the process can be carried out clearly more profitably due to the higher degree of back-stop for the catalyst system. This is especially true for catalyst systems that contain valuable metals, such as rhodium.

Mirosława Ważyńska

Patent Attorney