Variable self-regulating permeate recirculation in organic hydrophilic nanofiltration

Abstract

To provide improved control of processing and a processing technology which continuously separate one component from liquid mixture containing catalysts by using a membrane unit.SOLUTION: At least a part of obtained total penetrated liquid F-4 flow is recirculated via a supply container B-1 and / or a conveying device via the supply container. It is possible to use especially catalysts homogeneously dissolved for separation from liquid reaction mixture. The supply container supplies a deposition stage F-1 with mixture liquid. The mixture liquid is led to a membrane module M-1 by a supply pump P-1 from the supply container, and membrane separation is performed. Then, holding liquid F-3 is extracted from the membrane module via a discharge valve V1 and the total penetrated liquid. The total penetrated liquid is then divided from the deposition stage and the membrane unit by discharging (F-5) the total penetrated liquid part via a discharge valve V2, and the rest of the penetrated liquid F-6 is recirculated in the supply container via the recirculation valve V3.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to improvements in the control and process technology of a process for continuously separating one component from one liquid mixture using a membrane unit. The improvement is that at least part of the obtained total permeate flow is recirculated upstream of the conveying device via the supply container and / or the supply container. The process of the present disclosure can be used particularly for separating a homogeneously dissolved catalyst from a liquid reaction mixture.

Background Art

[0002] For example, the principle of the membrane separation method for separating a homogeneously dissolved catalyst from a reaction mixture is known in the prior art. Here, as an example, Patent Document 1 is exemplified.

[0003] Improvements in the control technology of this type of membrane separation method have already been reported. For example, Patent Document 2 discloses a membrane separation process for separating a homogeneously dissolved catalyst from a reaction mixture, and by maintaining two control parameters, namely the retention liquid flow rate of the membrane separation unit and the retention liquid flow rate of the membrane separation unit, constant technically, fluctuations in operating conditions, particularly fluctuations in the volume flow rate of the reaction mixture generated from the reaction zone, are compensated.

[0004] In order to keep the above control parameters constant, Patent Document 2 proposes the control of temperature and / or pressure in an overflow circuit for adjusting the flow rate of the retention liquid or maintaining it constant, and for adjusting the amount of the retention liquid or maintaining the retention constant.

[0005] One of the problems with the proposed process is that maintaining a constant hold on the membrane separation unit is not advantageous for all processes. Rather, considering the processing capacity of the factory and the membrane area of ​​the already installed membrane separation unit, optimization, and often maximization, of the hold on the membrane separation unit during the process is necessary. With flow resistor control as described in Patent Document 2, the already installed membrane surface may not be operated at the optimal membrane permeation pressure, but at a lower pressure. Furthermore, in the process described in Patent Document 2, the total permeation flow and the resulting recirculated permeation flow (the portion of the total permeation flow that is recirculated into the membrane separation unit) based on a simple mass balance considering the discharged permeation flow may be smaller than possible and / or desirable, given the predetermined total processing capacity of the system and the resulting discharged permeate flow (the portion of the permeate flow that is led out of the membrane separation unit on the permeate side).

[0006] A further drawback of the process described in Patent Document 2 is the provision of both a container and a pump for the permeate in order to obtain a constant control system on the permeate side. However, providing a pump to send the permeate from the permeate container to an overflow circulation or feed tank is associated with increased plant inventory and costs, for example, for procurement or operation, maintenance and repair, and may also lead to plant failures and, consequently, production losses.

[0007] Furthermore, when a container is installed, the permeate side of the membrane separation stage is usually not filled with hydraulic pressure, which can increase safety risks, especially when using toxic liquids. In addition, if there is a container on the permeate side in addition to the supply container, the control of the levels of the two containers may cause fluctuations in the container on the opposite side. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2014 / 131623 [Patent Document 2] International Publication No. 2014 / 183952 [Overview of the project] [Problems that the invention aims to solve]

[0009] Therefore, the problem that the present invention aims to solve is to provide a more cost-effective process for continuously separating components from a mixture, preferably for continuously separating a homogeneous catalyst from a reaction mixture. Furthermore, a further problem that the present invention aims to solve is to provide a self-controlled permeate recirculation in a process for continuously separating components from a mixture, preferably for continuously separating a homogeneous catalyst from a reaction mixture, in which the installed membrane region is optimally utilized even under different load conditions, for example, to maximize the retained liquid volume or yield. [Means for solving the problem]

[0010] The fundamental problem can be solved by the process described in claim 1. Preferred embodiments and models are described in the dependent claims.

[0011] The process according to the present invention is a process for continuously separating one component from one liquid mixture using a membrane unit, comprising at least one membrane stage and supplying the mixture as a feed: A membrane stage comprises at least a transport device, one or more membrane modules, and a supply container connected upstream of the transport device, wherein the mixture from the supply container is supplied to the one or more membrane modules by the transport device, so that the separated components are depleted in the resulting permeate flow and concentrated in the resulting retaining flow, or vice versa, compared to the mixture supplied to each of the membrane modules. The total permeate flow obtained in the final membrane stage is divided, and one portion of the total permeate flow, the recirculated permeate, is recirculated to the supply container and / or downstream of the supply container and upstream of the conveying device, while the other portion of the total permeate flow, the discharged permeate, is discharged from the final membrane stage to the permeate side membrane unit, where the recirculation of the recirculated permeate to the supply container and / or downstream of the supply container and upstream of the conveying device is recirculated hydraulically, not by the conveying device, i.e., by the pressure difference existing between the permeate side of the membrane unit and the conveying device or the suction side of the supply container, to the supply container and / or upstream of the conveying device.

[0012] In the context of this invention, the term "separated components" means components that are intended to permeate the membrane less depending on their ratio and / or permeability, i.e., components that are retained by the membrane. Thus, the separated components have a positive retention force for each specific membrane module. Furthermore, the separated components may be a single specific chemical substance or a group of chemical substances that can be considered in a common context from a process technology perspective.

[0013] In the context of this invention, "membrane unit" refers to the entire membrane separation unit to which a liquid mixture containing the components to be separated is supplied. The membrane unit consists of at least one membrane stage. Downstream processing or purification steps, and storage of permeate discharged from the container are, by definition, not part of the membrane unit.

[0014] The term "membrane stage" refers to at least one part of a membrane unit, including at least one transport device, such as a pump, and one or more membrane modules. In the case of a single membrane stage, the terms "membrane unit" and "membrane stage" are understood to be synonymous. The membrane stage has a feed container upstream of the transport device into which a liquid mixture, such as effluent from a homogeneous catalytic reaction, is introduced and supplied from there to one or more membrane elements. Alternatively, recirculated permeate may be supplied to the feed container. Furthermore, or alternatively, the recirculated permeate may not be supplied to the feed container but to a point downstream of the feed container and upstream of the transport device, i.e., in the conduit between the feed container and the transport device.

[0015] The term "membrane module" used to describe this invention refers to a technical subunit of a membrane stage. Therefore, a membrane module is an interconnection of one or more membrane elements. Membrane modules can be designed as membrane loops or membrane racks. A membrane loop refers to a subunit having at least one membrane element and at least one transporter, thereby forming a moving overflow circulation. On the other hand, the term "membrane rack" refers to a subunit having at least one membrane element but lacking a transporter, and consequently, no moving overflow circulation occurs.

[0016] In the context of this invention, the term "membrane element" means a membrane or a structure or apparatus comprising a membrane in which a desired separation of substances is actually carried out, i.e., components are separated from a mixture or a homogeneous catalyst is separated from a reaction solution. For example, it may be a so-called spiral-wound element, which is used in many applications of industrial membrane separation.

[0017] The present invention is based on splitting only the total permeate flow obtained in the last membrane stage into recirculated permeate and discharged permeate. If there is only one membrane stage, this single membrane stage is also the last membrane stage. If there are two or more membrane stages, no splitting occurs in the first membrane stage, and the total permeate flow is completely supplied to the next membrane stage. Then, the above splitting occurs only in the membrane stage of the last membrane. In the context of the present invention, the term “splitting” refers only to the volume or mass flow rate of the total permeate and does not explicitly mean any additional separation steps to remove further components from the total permeate, i.e., no distillation, extraction, crystallization, or further membrane separation steps.

[0018] One advantage of the process according to the present invention is that one portion of the total permeate flow from the final membrane stage, i.e., the recirculated permeate, does not leave the membrane stage and / or membrane unit, but remains within at least one membrane stage and / or membrane unit, and is then returned, for example, via a permeate container, and from there is either returned to the supply container and / or recirculated downstream of the supply container but upstream of the transport device. Because the recirculation of the permeate is controlled according to the load, there is no need for an overflow circulation or a downstream pump to return the permeate to the supply container. The recirculation of the permeate to the supply container and / or downstream of the supply container and upstream of the supply device is therefore not carried out by the supply device, but hydraulically, i.e., by the pressure difference existing between the permeate side of the membrane unit and the suction side of the supply device or supply container. In other words, there is no further transport device, especially a pump, between the permeate side and the supply container.

[0019] To control the outflow of the permeate, at least one adjustable flow resistor is present on the permeate side, through which the mass flow rate of the permeate can be controlled. In this invention, a “flow resistor” refers to an actuator that can control the mass flow rate of the flow, such as a valve. In a more preferred embodiment, at least two adjustable flow resistors, preferably exactly two, are present on the permeate side, and these resistors can be used to adjust the mass flow rate of the discharged permeate, as well as the permeate pressure, particularly the busbar pressure. The flow resistor is in particular a valve.

[0020] Of the total permeate flow from the final membrane stage, the portion discharged outside the membrane stage and membrane unit on the permeate side, i.e., the discharged permeate, can be supplied to a subsequent process step. In the context of the present invention, the term "process step" can be understood to mean any subsequent process, such as further processing or purification process steps or a combination thereof. This includes purification by known processes, in particular, of (further) reaction, distillation, evaporation, etc. of the separated components. It may also be a subsequent filling or transport step. Prior to the subsequent processing steps, the permeate may be pre-stored in a suitable container, such as a permeate container. If a permeate container is present, the division of the total permeate according to the present invention is performed upstream of the permeate container, and only the discharged permeate reaches the permeate container. In some cases, it is understood that several process steps, such as purification, then reaction of the purified components, and further purification of the reaction products, can be carried out sequentially via pre-storage.

[0021] According to the membrane separation process of the present invention, the mass flow rate of the feed to the membrane unit provides a stable external mass balance corresponding to the mass flow rates of the permeate flow and / or retaining fluid flow derived from the membrane unit. This situation can be utilized. In a preferred embodiment of the present invention, the mass flow rate of one of three flows selected from the feed to the membrane unit, the permeate removal, and the retaining fluid from the membrane unit is predetermined by an upstream or downstream process step, and the other of the three flows is controlled toward a target value, for example, a constant retaining fluid flow rate, a constant ratio of the feed amount to the retaining fluid, etc. As a result, the external mass balance becomes the third of the three flows. Depending on the size and number of membrane modules, the scale, i.e., the absolute mass flow rate, can be adjusted over a wide range in some cases. In a preferred embodiment, the ratio of the retaining fluid mass flow rate to the feed mass flow rate is 1 to 99%, preferably 10 to 90%, and particularly preferably 15 to 80%. In a more preferred embodiment, the ratio of the mass flow rate of discharged permeate to the mass flow rate of total permeate is 1 to 99%, preferably 30 to 98%, and particularly preferably 60 to 97%. In the context of the present invention, “process steps” means a plant or process unit, e.g., upstream or downstream chemical reactions in which the permeate / holding liquid is used, further separation steps, e.g., thermal separation such as thin-film evaporation or distillation, or logistics, i.e., particularly upstream or downstream tank storage or filling. The upstream steps are carried out in particular continuously, through which the liquid mixture is continuously supplied to the membrane separation process. Preferably, these are continuous chemical reactions, e.g., hydroformylation or alkoxycarbonylation, which are described in detail below.

[0022] Furthermore, in particular, there is also a balanced internal mass balance (the mass flow rate of the total permeate is equal to the sum of the mass flow rates of the recycled permeate and the discharged permeate). According to the present invention, the internal mass balance is preferably substantially independent of the external mass balance, that is, the external mass balance basically only represents a lower limit for the internal mass balance. Therefore, according to the present invention, since the mass flow rate of the recycled permeate can vary, it is preferably set as a function of the mass flow rate of the discharged permeate, preferably as a direct function, that is, in a state without an intermediate permeate container. This also means that when the mass flow rate of the total permeate is greater than the mass flow rate of the discharged permeate, the mass flow rate of the total permeate can be controlled independently of the above external mass balance regardless of technical constraints (due to pumps, flow resistors, membrane surfaces, etc.).

[0023] Therefore, the mass flow rate of the total permeate depends on various parameters such as, for example, the temperature (of the membrane module) and the concentration of components in the mixture. Thus, in a preferred embodiment of the present invention, the total permeate flow rate is optimized or a desired amount of the total permeate flow rate is obtained by controlling the pressure on the retentate side and / or the pressure on the permeate side, or the resulting transmembrane pressure (TMP = pressure difference between the permeate side and the retentate side), and optionally, the membrane module temperature.

[0024] From the perspective of control technology, the membrane separation process according to the present invention can be controlled in different processes according to the variables to be controlled, the actuators that can be used to affect the controlled variables, and the control priorities. In this process, there are various control variables, such as the filling level of the supply container, the pressures on the retentate side and the permeate side, the transmembrane pressure (TMP) resulting from the difference, and the mass flow rates of the retentate and the permeate, and these can be affected by various actuators such as, for example, conveying devices and one or more adjustable flow resistors.

[0025] In a preferred embodiment, the membrane separation process according to the present invention is controlled in terms of control techniques such that the mass flow rates of the retaining liquid and TMP remain constant. The precise order of control priorities for these two parameters can be set as desired, resulting in the highest control priority. That is, the mass flow rate of the retaining liquid has the highest control priority, and TMP has the second highest control priority.

[0026] The mass flow rate of the (first) membrane module in the process of the present invention can be controlled by a process known to those skilled in the art, for example, via a conveying device used in the (first) membrane stage. The exact embodiment for controlling the supply mass flow rate to the (first) membrane stage is variable and usually depends on technical constraints, such as the type of pump selected, the supply speed, the supply pressure, etc. For example, the supply mass flow rate can be controlled using a pump that is directly controlled by speed, such as a gear pump, piston pump, piston dialysis pump, or possibly a multistage centrifugal pump. Another option for controlling the supply mass flow rate is to use a centrifugal pump with an adjustable flow resistor such as a (control) valve. A further option would be to use the pump, such as a gear pump, piston pump, piston dialysis pump, or centrifugal pump, in combination with an adjustable recirculation flow line, for example, from the discharge side to the suction side of the pump.

[0027] The pressure on the retaining fluid side (retaining fluid pressure) can be controlled by the transport device and / or optionally by other actuators, such as a supply pressure regulator. The retaining fluid pressure in the process of the present invention may be 1 to 100 bar, preferably 10 to 80 bar, more preferably 30 to 60 bar. The retaining fluid pressure here is greater than the pressure on the permeate side (permeation pressure). Here, the osmotic pressure may be 0 to 50 bar, preferably 0 to 10 bar, more preferably 1 to 5 bar. In a preferred embodiment, the osmotic pressures in all present membrane modules are approximate (mutual dispersion of 10% or less) or identical.

[0028] The membrane permeation pressure formed by the difference between the retaining fluid pressure and osmotic pressure in the process of the present invention may be 1 to 90 bar, preferably 10 to 80 bar, and more preferably 30 to 60 bar. The membrane unit or individual membrane stage preferably includes pressure control on the retaining fluid side, including at least a conveying device and a pressure gauge, and the retaining fluid pressure can be adjusted according to the pressure gauge. Here, the retaining fluid pressure can be controlled (by the pressure gauge) according to the measured retaining fluid pressure, for example by adjusting the conveying amount of the conveying device, and optionally using other actuators, such as a supply pressure regulator, and based on a preset target value for the retaining fluid pressure, the conveying amount of the conveying device decreases when the retaining fluid pressure increases and / or rises, and the conveying amount of the conveying device increases when the retaining fluid pressure decreases and / or falls.

[0029] Alternatively, the retaining fluid pressure may be controlled via a pressure gauge and an adjustable flow resistor, particularly in combination with a valve on the retaining fluid side. The retaining fluid pressure can be controlled, for example, by valve position according to the measured retaining fluid pressure (by pressure gauge), where the valve is opened when the retaining fluid pressure increases and / or rises, and further closed when the retaining fluid pressure decreases and / or falls, based on a preset target value for the retaining fluid pressure.

[0030] In the process according to the present invention, the mass flow rate of the retaining fluid (retaining fluid mass flow rate) is preferably controlled by a retaining fluid-side mass flow regulator comprising at least one mass flow meter and an adjustable flow resistor, preferably a valve. The retaining fluid mass flow rate can here be controlled by adjusting the mass flow controller as a function of the measured retaining fluid mass flow rate, and with reference to a preset target value for the retaining fluid mass flow rate, the retaining fluid mass flow rate is further closed by the valve of the retaining fluid mass flow regulator when the retaining fluid mass flow rate increases and / or rises, and further opened by the valve of the retaining fluid mass regulator when the retaining fluid mass flow rate decreases and / or falls. Thus, the retaining fluid pressure can be freely selected within the range of the minimum required load and the maximum possible load on the membrane stage.

[0031] In other embodiments, however, the retaining fluid mass flow rate may be controlled by a combination of a mass flow meter and a conveying device. This allows the retaining fluid mass flow rate to be controlled, for example, by adjusting the conveying volume of the conveying device according to a measured value of the retaining fluid mass flow rate. Based on a predetermined target value of the retaining fluid mass flow rate, the conveying volume of the conveying device decreases when the retaining fluid mass flow rate increases and / or rises, and increases when the retaining fluid mass flow rate decreases and / or falls.

[0032] A sensor and actuator for controlling the mass flow rate on the retaining fluid side, comprising at least a transport device, or an adjustable flow resistor and mass flow meter, and a sensor and actuator for controlling the pressure on the retaining fluid side, comprising at least a transport device, or an adjustable flow resistor and pressure gauge, can be connected to each other in any desired manner from the viewpoint of control technology to control two controlled variables, the retaining fluid mass flow rate and the retaining fluid pressure. The relative priority of the two controlled variables, the retaining fluid mass flow rate and the retaining fluid pressure, can be any desired selection in the process of the present invention. Preferably, the priority of the two controlled variables, the retaining fluid mass flow rate and the retaining fluid pressure (and therefore TMP), is higher than the priority of all other controlled variables in the membrane separation stage, i.e., exhibits the fastest response behavior.

[0033] The mass flow rate of the permeate discharged (from the final membrane stage) depends directly or indirectly on the filling level of the supply container and can preferably be continuously controlled, which is preferably 20% to 80%, more preferably 30% to 70%, of the maximum possible filling level, based on a preset target value for the filling level of the supply container. The mass flow rate of the discharged permeate increases with increasing filling level of the supply container and decreases with decreasing filling level of the supply container. This type of control is necessary because the supply container is not completely filled, otherwise the filling level would become unknown by being at or above the upper end of the measurement range, and as a result, control over the target value would become impossible. The mass flow rate of the discharged permeate is specifically controlled via at least one adjustable flow resistor. In the case of continuous control, the filling level of the supply container is preferably kept constant therein. The control principle based on the filling level of the supply container will have the effect that, for example, when the level inside the supply container becomes low, the mass flow rate of the discharged permeate will further decrease, and in some cases, no more permeate will be discharged.

[0034] The temperatures of the three flows—feed, retaining fluid, and permeate—can be varied over a wide range. The temperatures of each of the three flows—feed, retaining fluid, and permeate—are preferably -30 to 150°C, more preferably 0 to 100°C, and most preferably 20 to 80°C—independently of each other.

[0035] The structure of the membrane unit, which will be described in more detail below, also contributes to the realization of the above-described control engineering embodiment of the process according to the present invention.

[0036] The membrane unit used in the process of the present invention for separating components from a mixture includes at least one membrane stage. Alternatively, the membrane unit may include multiple membrane stages connected in series with each other. In this case, the entire permeate flow is separated only at the last membrane stage.

[0037] The membrane stage of the membrane unit in the process of the present invention comprises a conveying device according to the above definition. The conveying device, which supplies the mixture as feed to one or more membrane modules, is preferably adjustable with respect to the amount supplied. The pressure of supply to one or more membrane modules may be 1 to 100 bar, preferably 10 to 80 bar, and more preferably 30 to 60 bar. A suitable conveying device is a pump known to those skilled in the art, such as a centrifugal pump, piston pump, piston dialysis pump, rotary piston pump, or gear pump.

[0038] The membrane stage of the membrane unit according to the present invention further comprises one or more membrane modules. Theoretically, there is no upper limit to the number of membrane modules, but it depends on general process parameters and the desired membrane area. In a preferred embodiment, the membrane stage consists of a plurality of membrane modules, which are more preferably connected in series. The mixture that has reached the membrane unit is supplied to the (first) membrane stage, where it is supplied to one or more membrane modules using a conveying device. In the membrane stage, it is separated into permeate and retaining liquid, and the permeate is taken out from each membrane module.

[0039] If there are multiple membrane modules, a number of permeate flows is generated corresponding to the number of membrane modules. The membrane modules are preferably connected to each other on the permeate side, for example, via busbars. However, especially in the case of series connections, only one permeate flow is obtained because the retaining fluid from the first membrane module is supplied to the next membrane module, the permeate is further separated from the retaining fluid, and then the retaining fluid from the second membrane module is supplied to the next membrane module, or, if there are only two membrane modules, is discharged outside the membrane stage and / or membrane unit.

[0040] The membrane stage according to the process of the present invention is equipped with a supply container upstream of a conveying device, from which the supply is supplied to at least two membrane modules by the conveying device. When there is one membrane stage, both the supply to the membrane stage and the recirculated permeate from the membrane stage may be introduced into the supply container and recovered there before being supplied by the conveying device as the supply to at least two membrane modules. When there are multiple membrane stages, the supply to the membrane stages and the retaining liquid of one of the next stages can be recovered into the supply container of the first stage, while the permeate from the previous membrane stage can be recovered into the retaining liquid of the next stage, or in the case of the last membrane stage, the recirculated permeate can be recovered into the supply container of the next stage. The structure and specifications of such supply containers are known to those skilled in the art. The supply container preferably includes a filling level measuring unit. In both modifications, the recirculated flow may not be supplied into the supply container, but rather beyond the supply container and supplied upstream of the conveying device.

[0041] The membrane stage may further include sensors and / or actuators to satisfy the preferred control specifications described above. These include, in particular, measuring and / or control units for parameters such as temperature, pressure, and mass flow rate. Corresponding measuring and control units are known to those skilled in the art.

[0042] The membrane modules according to the present invention may have one or more present in a membrane stage and may contain one or more membrane elements. In principle, the membrane modules can be designed as either membrane loops or membrane racks. Preferably, the membrane modules present in one or more membrane stages according to the present invention are membrane loops.

[0043] A membrane loop comprises one or more membrane elements and at least one transport device. Preferably, a membrane loop comprises only one transport device. This transport device is not identical to the transport device of the corresponding membrane stage, and there are at least two transport devices in the system as a whole. The transport device of the membrane loop is usually involved in the circulation of the membrane loop, and the transport device of the membrane stage is usually involved in pressurizing the membrane module or membrane loop. The transport device used may be any suitable pump. Such pumps are known to those skilled in the art. The pump used as a transport device in the membrane loop is preferably a centrifugal pump. The transport device generates a moving overflow circulation. The overflow circulation ideally improves mass transfer and therefore the separation performance of the membrane. The overflow circulation can be set independently of the overall control concept and external and internal mass balance.

[0044] The membrane loop may also include a unit for measuring and / or controlling parameters such as temperature, pressure difference (axial pressure loss), and circulation speed, for example, a heating or cooling system for regulating temperature. Such measuring and control units are known to those skilled in the art. In a preferred embodiment, the pressures of all membrane groups present in the membrane stage are approximate (variance < 10%) or identical. This pressure, at least similar, can be set without the presence of a specific control unit, but can also be set by a pressure regulator. The pressure regulator for the permeate pressure is preferably the slowest to respond compared to the other actuators, namely, the control of the mass flow on the permeate side, the control of the mass flow on the retaining fluid side, and the control of the pressure on the retaining fluid side.

[0045] In contrast to the membrane loop described above, a membrane module designed as a membrane rack lacks a transport device and may contain one or more membrane elements and, optionally, additional measurement and control units.

[0046] One or more membrane elements present in a membrane module, preferably a membrane loop, are prefabricated elements for industrial use, and can be considered as basic units of the membrane separation method according to the present invention, comprising a membrane and indivisible. The membrane elements may be used as they are within the membrane module, or they may be placed in a pressure housing, for example, a pressure tube. A pressure tube considered individually may contain one or more membrane elements, preferably up to five. When the membrane elements are placed in a pressure housing, preferably a pressure tube, the membrane module may include a plurality of pressure tubes. Preferably, the flow passes continuously through the membrane elements placed in the pressure tubes on the feed side or the retaining fluid side, and they are preferably connected on the permeate side. Basic units that can be used as membrane elements may be spiral-wound elements known to those skilled in the art. One or more spiral-wound elements can then be present in a pressure housing, preferably a pressure tube.

[0047] The membranes used are preferably cellulose acetate, cellulose triacetate, cellulose nitrate, regenerated cellulose, polyimide, polyamide, polyether ether ketone, sulfonated polyether ether ketone, aromatic polyamide, polyamide imide, polybenzimidazole, polybenzimidazolone, polyacrylonitrile, polyaryl ether sulfone, polyester, polycarbonate, polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, organically modified siloxanes with modified ends or sides, polydimethylsiloxane, silicon, silicon acrylate, polyphosphazene, polyphenyl sulfide, polybenzimidazole, nylon 6,6 (registered trademark), polysulfone, polyaniline, polypropylene, polyurethane, acrylonitrile / glycidyl methacrylate (PANGMA), polytrimethylsilylpropyne, polymethylpentene, polyvinyltrimethylsilane, polyphenylene oxide, α-aluminum oxide, γ-aluminum oxide, titanium dioxide, silicon dioxide, zirconium oxide, European Patent No. 1 603 Examples include having a separation active layer containing a substance selected from the group consisting of a silane-hydrophobized ceramic film as described in 663, a polymer having intrinsic micropores (PIMs) such as PIM-1 as described in European Patent No. 0781166, or a mixture thereof. The substance may be in the form of a crosslinked form in the separation active layer by the addition of an auxiliary agent, or in the form of a mixed matrix film with a filler, such as carbon nanotubes, metal-organic frameworks or hollow spheres, and particles of inorganic oxides or inorganic fibers, such as ceramic fibers or glass fibers.

[0048] Particularly preferred as the separation active layer is a membrane having a polymer layer of siloxane, polydimethylsiloxane, silicon acrylate, or polyimide with organically modified ends or sides, formed from a polymer with intrinsic micropores (PIM) such as PIM-1, or a separation active layer formed from a hydrophobic ceramic membrane. It is even more preferable to use a membrane formed from siloxane or polydimethylsiloxane with organically modified ends or sides. Such membranes are commercially available.

[0049] Similar to the materials described above, the membrane may contain further materials. More specifically, the membrane may include a support or carrier material to which the separation active layer is applied. The selection of support materials is described in European Patent No. 0781166, which is explicitly mentioned therein.

[0050] In a particularly preferred embodiment, the described process is used for membrane separation of a homogeneous catalyst. The separated component is the homogeneous catalyst, and the liquid mixture is the reaction mixture obtained from the reaction step.

[0051] Therefore, a particularly preferred process according to the present invention is a process for continuously separating a homogeneous catalyst from a liquid reaction mixture using a membrane unit, the process comprising at least one membrane stage, and wherein the reaction mixture containing the homogeneous catalyst derived from the reaction zone is supplied as a feed. Here, A membrane stage comprises at least a transport device, one or more membrane modules, and a supply container connected upstream of the transport device, wherein the reaction mixture from the supply container is supplied to the one or more membrane modules by the transport device, thereby the homogeneous catalyst is depleted in the resulting permeate flow of each membrane module and concentrated in the resulting retaining flow of each membrane module compared to the mixture supplied to each membrane module. The resulting total permeate flow is divided, and one portion of the total permeate flow, the recirculated permeate, is recirculated to the supply container and / or downstream of the supply container and upstream of the conveying device, while the other portion of the total permeate flow, the discharged permeate, is discharged from at least one of the membrane stages to the outside of the permeate-side membrane unit.

[0052] The reaction mixture originates from a reaction zone suitable for each process, preferably one or more suitable reaction vessels. The retaining liquid stream containing at least the majority of the homogeneous catalyst is preferably recycled back into the reaction zone, particularly the reaction vessel, after pre-purification and / or post-treatment of the catalyst. Since the mass flow rate from the reaction zone can vary due to manufacturing-related circumstances, the above-described control and plant-related functions can also be used for the separation of the homogeneous catalyst.

[0053] Therefore, a homogeneous catalytic reaction is carried out in a reaction zone, preferably one or more reaction vessels. The reaction is as follows: Examples of oxidation, epoxidation, hydroformylation, hydroamination, hydroaminomethylation, hydrocyanation, hydrocarboxylation, hydroxycarbonylation, hydrocarboxyalkylation, alkoxycarbonylation, alkoxycarbonylation, amination, ammonoxylation, oxidation, hydrosilylation, ethoxylation, propoxylation, carbonylation, telomerization, metaceth, Suzuki coupling, and hydrogenation.

[0054] Preferably, the reaction is hydroformylation. Hydroformylation is preferred. Hydroformylation is particularly the hydroformylation of olefins having 3 to 15 carbon atoms, preferably 8 to 12 carbon atoms. Hydroformylation is preferably homogeneous catalytic hydroformylation in which the catalyst system is (completely) dissolved in the liquid phase of the reaction mixture. The catalyst system for hydroformylation preferably comprises a transition metal from group 8 or 9 of the periodic table and at least one organophosphorus-containing ligand. It has a group from the periodic table of elements (PSE) and at least one organophosphorus-containing ligand. Preferably, the phosphorus-containing ligand is a monodentate phosphorus-containing ligand, such as tris(2,4-di-tert-butylphenyl) phosphite, although the phosphorus-containing ligand is known to those skilled in the art.

[0055] In particular, iron, ruthenium, iridium, cobalt, or rhodium may be used as the transition metal, preferably cobalt or rhodium, and especially preferably rhodium. As the catalytically active species, (ligand)-carbonyl complexes of metal atoms are usually discussed, which are formed in the liquid reaction mixture under high temperature and high pressure.

[0056] Hydroformylation can be carried out in the presence of a solvent, in which case the solvent should be compatible with the hydroformylation method. Suitable solvents known to those skilled in the art can be used for hydroformylation, such as alkanes, aromatic hydrocarbons, water, ethers, esters, ketones, alcohols, and hydroformylation reactions or by-products of aldehydes and aldehyde condensates.

[0057] Furthermore, hydroformylation can be carried out at a pressure of 10 to 400 bar, preferably 15 to 270 bar. The temperature during hydroformylation may be 70 to 250°C, preferably 100 to 200°C, and more preferably 120 to 160°C.

[0058] The present invention is illustrated by the following figures, which illustrate specific embodiments. These figures are for illustrative purposes only and should not be considered limiting. [Brief explanation of the drawing]

[0059] [Figure 1]This figure shows an exemplary structure of a membrane unit including one membrane stage. The membrane stage here consists of a supply container (B-1), a pump (P-1), and a membrane module (M-1). The supply container (B-1) supplies a mixture as a supply to the membrane stage (F-1). From the supply container (B-1), the liquid mixture is guided by the supply pump (P-1) (F-2) to the membrane module (M-1) (e.g., a membrane loop), where the actual membrane separation takes place. Subsequently, the retaining liquid (F-3) is removed from the membrane module (M-1) via a discharge valve (V-1) and the total permeate (F-4). The total permeate (F-4) is then separated by discharging a portion of the entire permeate (F-5) from the membrane stage and membrane unit via the discharge valve (V-2), and the remaining portion of the permeate (F-6) is recirculated to the supply container (B-1) via the recirculation valve (V-3). [Figure 2] This figure shows an exemplary structure of a membrane unit comprising one membrane stage and multiple membrane modules. The membrane stage consists of a supply container (B-1), a pump (P-1), and two membrane modules (M-1 / M-2). The supply container (B-1) supplies a mixed liquid as a supply to the membrane stage (F-1). From the supply container (B-1), the liquid mixture is supplied by the supply pumps (P-1) (F-2) to the first membrane module (M-1) (e.g., a membrane loop). Here, in this case, the first membrane separation occurs. From the membrane module (M-1), the retaining liquid (F-3) and the permeate (F-4) of the first membrane module are extracted. The retaining liquid (F-3) is supplied to the second membrane module (M-2), where further membrane separation occurs, producing permeate (F-8) and retaining liquid (F-7) from the second membrane module (M-2). The residue (F-7) is discharged through the discharge valve (V-1). The two permeates (F-4 / F-8) from the two membrane modules (M-1 / M-2) are combined to obtain the total permeate (F-14), which is then divided. As a result, the portion of the total permeate (F-5) can be removed through the discharge valve (V-2), and the other portion of the permeate (F-6) can be recirculated to the supply container (B-1) through the recirculation valve (V-3). [Figure 3]This figure shows an exemplary structure of a membrane unit including two membrane stages. Each membrane stage consists of a supply container (B-1 / B-2), a pump (P-1 / P-2), and a membrane module (M-1 / M-2). The supply container (B-1) supplies a mixed liquid as a supply to the membrane stage (F-1). From the supply container (B-1), the liquid mixture (F-2) is supplied by the supply pump (P-1) to the membrane module (M-1) (e.g., a membrane loop), where membrane separation takes place. From the membrane module (M-1), the total permeate (F-4) and retained liquid (F-3) from the first membrane stage are then removed via a discharge valve (V-1). The permeate (F-4) from the first membrane module (M-1) is supplied to a supply container (B-2) for the second membrane stage, and then pumped (P-2) to the membrane module (M-2) of the second membrane stage (M-2) (F-9), where further membrane separation takes place. From the membrane module (M-2) of the second membrane stage, the total permeate (F-11) and retaining liquid (F-10) are removed. The retaining liquid (F-10) is then supplied to the supply container (B-1) of the first membrane stage via a discharge valve (V-4). The entire permeate (F-11) is divided after leaving the membrane module (M-2). As a result, a portion of the permeate (F-12) is removed via the discharge valve (V-5), and the remaining portion of the permeate (F-13) is recirculated to the supply container (B-2) of the second membrane stage (M-2) via the recirculation valve (V-6). [Figure 4]This figure essentially corresponds to Figure 1, that is, it includes only one membrane stage, but also includes additional markings to illustrate the mass balance in question. The term “mass balance” as used herein is based on two fundamental assumptions. The first relevant assumption is that the system is a steady-state system. This means that, in this case, no accumulation of the mixture of substances occurs within the membrane unit over time, although transient fluctuations may occur at most. Thus, the total mass in the system remains the same regardless of time. Simultaneously, the second assumption is that no reactions occur in the mass balance circuit according to the present invention. This means that not only the total mass but also the masses of the individual components remain the same. The external overall mass balance is shown by the dotted line in Figure 4. The mass flow rate of raw material F-1 is equal to the sum of the mass flow rates of residue F-3 and permeate F-5, i.e., F-1 = F-3 + F-5.

[0060] The internal total mass balance based on the box with two dotted lines around the membrane stage M-1 in Figure 4 is defined accordingly: the mass flow of the supply F-2 is equal to the sum of the mass flow of the residue F-3 and the mass flow of the entire permeate F-4, i.e., F-2 = F-3 + F-4.

[0061] Therefore, if two flows are specified for external mass balance, the third flow is what brings about the external mass balance. Thus, only two of the three flows can be independently determined or controlled externally. It should be noted here that external mass balance always specifies at least one flow for internal mass balance, and the situation is the same for internal mass balance. Therefore, overall, two flows can be fixed for external mass balance and only one more flow for internal mass balance. All other flows are simply the result.

Claims

1. A process for continuously separating one component from a liquid mixture using a membrane unit, comprising at least one membrane stage and supplying the liquid mixture as a feed, wherein: A membrane stage comprises at least a transport device, one or more membrane modules, and a supply container connected upstream of the transport device, wherein the liquid mixture is supplied from the supply container to the one or more membrane modules by the transport device, thereby separating components that are reduced in the resulting permeate flow of each membrane module and concentrated in the resulting retained flow of each membrane module compared to the liquid mixture supplied to each membrane module. The total permeate flow obtained in the final membrane stage is divided, and one portion of the total permeate flow, the recirculated permeate, is recirculated to the supply container and / or downstream of the supply container and upstream of the conveying device, and the other portion of the total permeate flow, the discharged permeate, is discharged from the final membrane stage to the membrane unit on the permeating side, where the recirculation of the recirculated permeate to the supply container and / or downstream of the supply container and upstream of the conveying device is not done by the conveying device but hydraulically, i.e., by the pressure difference existing between the permeate side of the membrane unit and the conveying device or the suction side of the supply container, and The aforementioned one component is a homogeneous catalyst separated from the liquid mixture. process.

2. The process according to claim 1, wherein the mass flow rate of one of three flows selected from the supply to the membrane unit, the discharged permeate, and the retaining liquid from the membrane unit is predetermined by an upstream or downstream process step, and the other of the three flows is controlled to a target value.

3. The process according to claim 1 or 2, wherein the mass flow rate of the recirculated permeate is variable and regulated as a function of the mass flow rate of the discharged permeate.

4. The process according to any one of claims 1 to 3, wherein a predetermined amount of total permeate flow rate is obtained by controlling the pressure on the retaining liquid side and / or the pressure on the permeate liquid side, or the resulting membrane permeation pressure, or the temperature of the membrane module.

5. The process according to any one of claims 1 to 4, wherein the mass flow rate and permeate pressure of the discharged permeate are both controlled by adjustable flow resistors, respectively.

6. The process according to any one of claims 1 to 5, wherein the mass flow rate of the discharged permeate depends directly or indirectly on the filling level of the supply container, or is subject to continuous control, wherein the control is such that, with respect to a predetermined set value for the filling level of the supply container, the mass flow rate of the discharged permeate increases as the filling level of the supply container increases, and the mass flow rate of the discharged permeate decreases as the filling level of the supply container decreases.

7. The process according to any one of claims 1 to 6, wherein the pressure on the retaining fluid side is controlled by the supply container from which the feed is supplied to one or more of the membrane modules.

8. The process according to claim 7, further controlled by a further actuator, wherein the further actuator is a supply pressure regulator, or a combination of a pressure gauge and an adjustable flow resistor, or a retaining fluid side valve.

9. The process according to any one of claims 1 to 7, wherein the mass flow rate on the holding fluid side is controlled by an auxiliary mass flow control device comprising at least a mass flow meter and an adjustable flow resistor or valve, or by a combination of a mass flow meter and the conveying device.

10. The process according to any one of claims 1 to 9, wherein the conveying device is a pump.

11. A process for continuously separating a homogeneous catalyst from a liquid mixture using a membrane unit, comprising at least one membrane stage, wherein the liquid mixture containing the homogeneous catalyst derived from the reaction zone is supplied as a feed, and here, A membrane stage includes at least a transport device, one or more membrane modules, and a supply container connected upstream of the transport device, wherein the liquid mixture is supplied from the supply container to the one or more membrane modules by the transport device, thereby reducing the homogeneous catalyst in the resulting permeate flow of each membrane module and concentrating it in the resulting retained flow of each membrane module compared to the liquid mixture supplied to each membrane module. The obtained total permeate flow is divided, and one portion of the total permeate flow, the recirculated permeate, is recirculated to the supply container and / or downstream of the supply container and upstream of the conveying device, while the other portion of the total permeate flow, the discharged permeate, is discharged from at least one of the membrane stages to the outside of the permeate-side membrane unit. process.

12. The process according to claim 11, wherein the liquid mixture is taken from a reaction zone in which a homogeneous catalytic reaction takes place.

13. The process according to claim 12, wherein the homogeneous catalytic reaction is selected from the group of reactions: oxidation, epoxidation, hydroformylation, hydroamination, hydroaminomethylation, hydrocyanation, hydrocarboxylation, hydroxycarbonylation, hydrocarboxyalkylation, alkoxycarbonylation, alkoxycarbonylation, amination, ammonoxylation, oxidation, hydrosilylation, ethoxylation, propoxylation, carbonylation, telomerization, metaceth, Suzuki coupling, and hydrogenation.

14. The process according to claim 13, wherein the homogeneous catalytic reaction is hydroformylation.

Images