Improved variable self-control type penetrated liquid recirculation in organic hydrophilic NANO filtration

Abstract

To provide cost-effective processing for continuously separating components from mixture, or preferably continuously separating homogeneous catalysts from reaction mixture.SOLUTION: Improvement in control and a processing technology for processing to continuously remove components from liquid mixture by using a membrane unit including at least one deposition stage is provided. According to the improvement, a part of the total penetrated liquid flow is recirculated upstream of a supply container and / or a conveying device through the supply container, the rest of the total penetrated liquid flow is discharged, and the penetrated liquid recirculated has components to be separated of high concentration. The disclosed processing is especially applicable to separation of catalysts homogenously dissolved from liquid reaction mixture.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to improvements in control and process technology for a process of continuously removing components from a liquid mixture using a membrane unit comprising at least one membrane stage. The improvement is that a part of the total permeate flow is recirculated upstream of the supply vessel and / or the conveying device through the supply vessel, the remaining part of the total permeate flow is discharged, and the recirculated permeate has a higher concentration of the component to be separated than the discharged permeate. 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] Regarding improvements in the control technology of this type of membrane separation method, there have already been reports. 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 retentate flow rate of the membrane separation unit and the retentate flow rate of the membrane separation unit, technically constant, 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 control of the temperature and / or pressure in the overflow circuit for adjusting or maintaining the flow rate of the retentate, and for adjusting or maintaining the retentate flow rate constantly.

[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 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 (a portion of the permeate flow supplied to the membrane stage or 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 Initiative] [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 present invention relates to 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 the membrane stage comprises at least one transport device, at least two membrane modules connected in series, and a supply container connected upstream of the transport device, and the following: The liquid mixture from the supply container is supplied by the conveying device to the first membrane module of the at least two membrane modules, thereby the separated components are depleted in the permeate flow resulting from the first membrane module and concentrated in the retaining flow resulting from the first membrane module, relative to the mixture supplied to the first membrane module; The permeate flow from the first membrane module is supplied to the second membrane module, and the components to be separated are reduced in the permeate flow of the second membrane module and concentrated in the permeate flow of the second membrane module relative to the permeate flow of the first membrane module; A step in which at least two membrane modules are connected to each other on the permeate side such that at least two permeate flows are each supplied to a common pipeline, thereby generating a total permeate flow in the pipeline; The process includes the steps of: at least two membrane modules being connected in opposite directions to the common pipeline on the permeate side, so that the circulating permeate flow, which is part of the total permeate flow, is circulated at least partially through the supply container and / or the supply container upstream of the conveying device, while the remaining part of the total permeate flow, which is the discharged permeate, is supplied at least partially from the membrane stage, and the concentration of the separated components in the recirculated permeate is higher than the concentration of the separated components in the discharged permeate;

[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] The process of the present invention may include two or more membrane modules. If there are three or more membrane modules, it is preferable that the retaining liquid of the previous membrane module is supplied to the subsequent membrane module (not applicable to the last membrane module), thereby the components to be separated are depleted in the permeate stream obtained in the subsequent membrane module based on the retaining liquid of the previous membrane module, and concentrated in the retaining liquid stream obtained in the subsequent membrane module.

[0014] 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.

[0015] 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 supply 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, the recirculated permeate may not be supplied to the supply container, but rather to a point downstream of the supply container and upstream of the transport device, i.e., in the conduit between the supply container and the transport device.

[0016] 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 in which at least one membrane element and at least one transporter are present, thereby forming a moving overflow circulation. On the other hand, the term "membrane rack" refers to a subunit in which at least one membrane element is present but there is no transporter, and as a result no moving overflow circulation occurs.

[0017] 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.

[0018] 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, adsorption, or further membrane separation steps.

[0019] 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.

[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 this 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 step, it 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 in sequence via pre-storage.

[0021] According to the present invention, at least two membrane modules are connected in reverse to a common pipeline on the permeate side, and at least a large portion of the total permeate originates from the last membrane module on the backflow side (backflow; recirculated permeate), which is at least partially returned (circulated) to the supply container and / or downstream of the supply container and upstream of the conveying device, while at least a large portion of the total permeate originates from the first membrane module on the backflow side (discharge; removed permeate), which is at least partially discharged from the membrane stage. Therefore, the permeate from all membrane modules present in such a membrane stage is supplied to the common pipeline, where it is separated. In the common pipeline, it is preferable that there are no control actuators, such as valves or separation units, between the connections of the first membrane module and the last membrane module to the piping. However, this does not rule out the presence of uncontrolled actuators, i.e., actuators that are present but do not intervene in the process, such as valves that are permanently and continuously open. The concept according to the present invention makes it easy from a plant technology standpoint to ensure that the recirculated permeate has a higher concentration of components to be separated than the discharged permeate. These system and control requirements mean that, in the case of a disadvantage where there is no supply from the upstream process to the supply container, all module permeates are completely recirculated to the supply container or membrane unit.

[0022] In the process of the present invention, it means that the permeates of the two membrane modules do not mix completely, that is, a mixture in which the separated components have the same concentration is not formed in a common pipeline. What should be finally achieved is that the concentration of the separated components of the recycled permeate is higher than the concentration of the separated components of the discharged permeate, which would not be achieved if they were completely mixed. This can also be illustrated by Figure 1. For example, in the process of the present invention, in the process according to the present invention, the concentration of the separated components must be higher in the recycled permeate than in the discharged permeate. Therefore, based on the concentration of the separated components, F-11 > F-12 always applies. Preferably, the concentration of the separated components in the recycled permeate is higher than the concentration in the common pipeline between the connection of the first and the last membrane modules, and the result is that the concentration of the separated components is higher than the concentration in the discharged permeate. Therefore, based on the concentration of the separated components, F-11 > F-10 > F-12. The prevention of complete mixing can be achieved by various methods of plant technology. A preferred option according to the present invention is the characteristics (such as length, diameter, etc.) of the common pipeline, which are adjusted so as to avoid complete mixing of the overall permeate.

[0023] In order to control the flow rate of the recycled and discharged 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. The "flow resistor" as referred to in the present invention is an actuator that can control the mass flow rate of the flow, for example, a valve corresponds to this. In a more preferred embodiment, at least two adjustable flow resistors, preferably exactly two adjustable flow resistors, are present on the permeate side, and by means of these resistors, the mass flow rate of the discharged permeate, as well as the permeate pressure, especially the pressure of the busbar, can be adjusted. The flow resistor is especially a valve. The valve preferably does not exist between the connection of the first and the last membrane modules to the pipeline, but exists in the flow direction of the recycled or discharged permeate through the said connection to the pipeline.

[0024] According to the membrane separation process of the present invention, a stable external mass balance can be obtained in which the mass flow rate of the feed to the membrane unit corresponds to the mass flow rate of the permeate stream and / or the retentate stream 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 the three streams selected from the feed to the membrane unit, the removal of the permeate, and the retentate from the membrane unit is predetermined by an upstream or downstream process step, and the other of the three streams is controlled towards a target value such as, for example, a constant retentate flow rate, a ratio of the feed amount to the constant retentate, etc. Also, as a result, by the external mass balance, it becomes the third flow of the above three flows. Depending on the size and number of membrane modules, the scale, that is, the absolute mass flow rate, can be adjusted widely in some cases. In a preferred embodiment, the ratio of the retentate mass flow rate to the feed mass flow rate is 1 to 99%, preferably 10 to 90%, particularly preferably 15 to 80%. In a further preferred embodiment, the ratio of the mass flow rate of the discharged permeate to the mass flow rate of the total permeate is 1 to 99%, preferably 30 to 98%, particularly preferably 60 to 97%. "Process step" in the context of the present invention means a plant or process unit, for example an upstream or downstream chemical reaction in which the permeate / retentate is used, a further separation step, for example a thermal separation such as thin-film evaporation or distillation, or a material flow, that is, particularly upstream or downstream tank storage or filling. The upstream process is particularly carried out continuously, and through this process, a liquid mixture is continuously provided to the present membrane separation process. Preferably, these are continuous chemical reactions, such as hydroformylation or alkoxycarbonylation, which are described in detail below.

[0025] Furthermore, a well-balanced internal mass balance exists in particular (the total mass flow rate of the permeate, i.e., the sum of the total permeate flows in the membrane module, is equal to the sum of the mass flow rates of the recirculated and discharged permeate). According to the present invention, the internal mass balance is preferably substantially independent of the external mass balance, i.e., the external mass balance basically represents only a lower limit for the internal mass balance. Therefore, according to the present invention, since the mass flow rate of the recirculated permeate can fluctuate, it is preferable to set it as a function of the mass flow rate of the discharged permeate, preferably as a direct function, i.e., without an intermediate permeate container. This also means that if the total mass flow rate of the permeate is greater than the mass flow rate of the discharged permeate, the total mass flow rate of the permeate can be controlled independently of the external mass balance, regardless of technical constraints (caused by pumps, flow resistors, membrane surfaces, etc.).

[0026] Therefore, the total permeate mass flow rate depends on various parameters, such as the temperature (of the membrane module) and the concentration of components in the mixture. Accordingly, in a preferred embodiment of the present invention, the total permeate flow rate is optimized or a desired amount of total permeate flow rate is obtained by controlling the pressure on the retaining liquid side and / or the permeate side, or the resulting membrane permeation pressure (TMP = pressure difference between the permeate side and the retaining liquid side), and optionally the membrane module temperature.

[0027] From the viewpoint of control technology, the membrane separation process according to the present invention can be controlled by different processes depending on each variable being controlled, the actuators that can be used to influence the variables being controlled, and the control priority. In this process, various control variables exist, such as the filling level of the supply container, the pressure on the retaining fluid side and the permeate side, the resulting membrane permeation pressure (TMP), and the mass flow rates of the retaining fluid and permeate. These can be affected by various actuators, such as conveying devices and one or more adjustable flow resistors.

[0028] 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.

[0029] 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.

[0030] The pressure on the retaining fluid side (retaining fluid pressure) can be controlled by a conveying 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 fluid side (permeation pressure). The membrane permeation pressure formed by the difference between the retaining fluid pressure and the osmotic pressure may be 1 to 90 bar, preferably 10 to 80 bar, and even more preferably 30 to 60 bar.

[0031] 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. This can preferably be established via a supply pressure regulator on the permeation side, because the pressure in individual membrane modules is preferably not controlled independently of the total pressure on the permeation side, for example, a common pipeline.

[0032] The membrane unit or individual membrane stages preferably include 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 volume 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 volume of the conveying device decreases when the retaining fluid pressure increases and / or rises, and increases when the retaining fluid pressure decreases and / or falls.

[0033] 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.

[0034] 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 flow 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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 leads the mixture as feed to at least two series-connected membrane modules, is preferably adjustable with respect to its conveying volume. The pressure of the feed to the at least two membrane modules may be 1 to 100 bar, preferably 10 to 80 bar, more preferably 30 to 60 bar. Suitable conveying devices are pumps known to those skilled in the art, such as centrifugal pumps, piston pumps, piston dialysis pumps, rotary piston pumps, or gear pumps.

[0042] The membrane stage of the membrane unit according to the present invention further includes at least two series-connected 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 includes two or more membrane modules connected in series with each other. 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 removed from each membrane module.

[0043] Therefore, in the presence of at least two membrane modules, a number of permeate flows is generated corresponding to the number of membrane modules. The membrane modules are connected in opposite directions to a common pipeline on the permeate side, as described above. Meanwhile, the permeate from the first membrane module is supplied to the next membrane module, where further permeate is separated from it, and the permeate 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, resulting in only one permeate flow.

[0044] 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. If 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. If there are two or more membrane stages, the supply to the first membrane stage and the retaining liquid from one subsequent stage 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 upstream of the conveying device.

[0045] 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.

[0046] The membrane modules according to the present invention may have at least two present in a membrane stage and may include 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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 contains explicit references.

[0054] 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.

[0055] Therefore, a particularly preferred process according to the present invention is a process for continuously separating one homogeneous catalyst from one liquid reaction mixture using a membrane unit, comprising at least one membrane stage and supplying the reaction mixture containing the homogeneous catalyst as a feed, wherein the membrane stage comprises at least one transport device, at least two membrane modules connected in series, and a supply container connected upstream of the transport device, as follows: The reaction mixture from the supply container is supplied by the conveying device to a first membrane module of the at least two membrane modules, thereby the homogeneous catalyst is depleted in the resulting permeate flow from the first membrane module and concentrated in the resulting retaining flow from the first membrane module, relative to the reaction mixture supplied to the first membrane module; The permeate from the first membrane module is supplied to the second membrane module, and the homogeneous catalyst is reduced in the permeate flow of the second membrane module relative to the permeate from the first membrane module, and concentrated in the permeate flow of the second membrane module; A step in which at least two membrane modules are continuously coupled to each other on the permeate side such that at least two permeate flows form a total permeate flow in which the individual permeate flows are not completely mixed; The recirculated permeate, which is a portion of the total permeate, is recirculated to the supply container and / or downstream of the supply container and upstream of the conveying device, while the remaining portion of the total permeate, which is the discharged permeate, is discharged from the membrane stage, and the recirculated permeate has a higher concentration of homogeneous catalyst than the discharged permeate. Includes.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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]

[0063] [Figure 1] This figure shows an exemplary configuration of a membrane unit having a membrane stage with two membrane modules. The membrane stage consists of a supply container (B-1), a pump (P-1), and two membrane modules (M-2 / M-3). The supply container (B-1) supplies a mixed liquid to the membrane stage (F-1). From the supply container (B-1), the liquid mixture is supplied by the supply pump (P-1) (F-5) to the first membrane module (M-2) (e.g., a membrane loop), in which case the first membrane separation takes place. From the membrane module (M-2), the retaining liquid (F-6) and the permeate (F-8) of the first membrane module are extracted. The retaining liquid (F-6) is supplied to the second membrane module (M-3), where further membrane separation takes place to obtain the permeate (F-9) and retaining liquid (F-7) of the second membrane module (M-3) or the last membrane module (F-9), respectively. The retaining fluid (F-7) is removed via the discharge valve (V-2). The two permeates (F-8 / F-9) from the two membrane modules (M-2 / M-3) are supplied to a common pipeline (F-10). In the context of this invention, the two permeates (F-8 / F-9) constitute the total permeate flow (dotted rectangle), which exists at least as a computational variable, even without complete mixing. Two permeate flows, the recirculated permeate flow (F-11) and the discharged permeate flow (F-12), are removed from the common pipeline (F-10). The discharged permeate (F-12) is discharged via the discharge valve (V-4), and the recirculated permeate (F-11) is sent to the supply container (B-1) via the recirculation valve (V-3). Alternatively, the recirculated permeate (F-11) may not be supplied to the supply container (B-1), but rather between the supply container (B-1) and the pump (P-2) (not shown). [Figure 2]This figure shows an exemplary construction of a membrane unit with two membrane stages. Each membrane stage consists of a supply container (B-1 / B-2), its respective pump (P-1 / P-2), and one or two membrane modules (M-1 / M-2 / M-3). The supply container (B-1) supplies a mixture as a supply to the membrane stage (F-1). The liquid mixture from the supply container (B-1) is supplied by the supply pumps (P-1) (F-2) to the membrane module (M-1) (e.g., a membrane loop), where membrane separation takes place. From the membrane module (M-1), the permeate (F-4) and retained liquid (F-3) from the first membrane stage are drawn out 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 supplied to the first membrane module (M-2) of the second membrane stage by a supply pump (P-2) (F-5). For example, membrane separation occurs in the membrane loop. From the membrane module (M-2), the retaining liquid (F-6) and the permeate (F-8) from the first membrane module are removed. The retaining liquid (F-6) is led to the second or last membrane module (M-3) of the second membrane stage, where further membrane separation occurs, and permeate (F-9) and retaining liquid (F-7) can be obtained from the second membrane module (M-3). The retaining liquid (F-7) is then supplied to the supply container (B-1) of the first membrane stage via a discharge valve (V-2). Two permeate streams (F-8 / F-9) from two membrane modules (M-2 / M-3) are supplied to a common pipeline (F-10). Two permeate streams, recirculated permeate (F-11) and discharged permeate (F-12), are taken out of the common pipeline. The discharged permeate (F-12) is discharged through a discharge valve (V-4), and the recirculated permeate (F-11) is sent to a supply container (B-1) through a recirculation valve (V-3). Alternatively, the recirculated permeate (F-11) may be supplied between the supply container (B-1) and the pump (P-2) instead of being supplied to the supply container (B-1) (not shown).

Claims

1. 1. A process for continuously separating a component from a liquid mixture using a membrane unit, comprising at least one membrane stage and supplying the liquid mixture as a feed, the membrane stage being composed of at least one conveying device, at least two membrane modules connected in series, and a feed vessel connected upstream of the conveying device, the process comprising: feeding the liquid mixture from the feed vessel by the conveying device to a first membrane module of the at least two membrane modules, whereby a component to be separated is depleted in a resulting permeate stream of the first membrane module and enriched in a resulting retentate stream of the first membrane module relative to the mixture fed to the first membrane module; a permeate stream of the first membrane module is fed to a second membrane module, and the components to be separated are depleted in the permeate stream of the second membrane module relative to the permeate stream of the first membrane module and concentrated in the permeate stream of the second membrane module; at least two membrane modules are connected to each other on the permeate side such that at least two permeate streams are each fed into a common pipeline, thereby generating a total permeate stream in said pipeline; at least two membrane modules are connected in opposite directions to the common pipeline on the permeate side, so that a circulating permeate flow, which is a part of the total permeate flow, is circulated at least partially through the feed vessel and / or the feed vessel upstream of the conveying device, while a remaining part of the total permeate flow, which is a discharged permeate, is at least partially fed from the membrane stage, so that the concentration of the separated components in the recycled permeate is higher than the concentration of the separated components in the discharged permeate; The process includes:

2. 2. The process of claim 1, wherein the concentration of the components to be separated is higher in the recirculated permeate than in the common pipeline between the junction of the first and last membrane modules and is higher in the common pipeline than in the discharged permeate.

3. A process as described in claim 1 or 2, wherein there is no control actuator in the common pipeline between the connection of the first membrane module and the last membrane module to the pipeline.

4. 4. The process of claim 1, wherein the recirculation of recycled permeate to the feed vessel and / or downstream of the feed vessel and upstream of the conveying device is performed hydraulically rather than by the conveying device.

5. 5. The process of claim 1, wherein the mass flow rate of one of three streams selected from the feed to the membrane unit, the permeate discharge, and the retentate from the membrane unit is predetermined by an upstream or downstream process step, and the other one of the three streams is controlled to a target value.

6. The process according to any one of claims 1 to 5, wherein the mass flow rate of the recycled permeate can be varied and adjusted depending on the mass flow rate of the discharged permeate.

7. The process of claim 1, wherein the mass flow rate of the discharged permeate and the pressure of the permeate are both each regulated by an adjustable flow resistor.

8. A process as described in any one of claims 1 to 7, wherein the mass flow rate of the discharged permeate is directly or indirectly dependent on the fill level of the supply vessel or is subject to continuous control, the continuous control being based on a predetermined set point for the fill level of the supply vessel, such that an increase in the fill level of the supply vessel increases the mass flow rate of the discharged permeate and a decrease in the fill level of the supply vessel decreases the mass flow rate of the discharged permeate.

9. 9. The process according to any one of claims 1 to 8, wherein the pressure on the retentate side (retentate pressure) is controlled by the conveying device through which the feed is supplied to the one or more membrane modules and, optionally, by a further actuator, or a feed pressure regulator, or a combination of a pressure gauge and an adjustable flow resistor, or a valve on the retentate side.

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

11. The process of any one of claims 1 to 10, wherein the component is a homogeneous catalyst separated from the reaction mixture.

12. The process of any one of claims 1 to 11, wherein the conveying device is a pump.

13. 1. 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 supplying a reaction mixture containing said homogeneous catalyst as a feed, the membrane stage being composed of at least one conveying device, at least two membrane modules connected in series, and a feed vessel connected upstream of the conveying device, the process comprising: feeding the reaction mixture from the feed vessel by the conveying device to a first membrane module of the at least two membrane modules, whereby the homogeneous catalyst is depleted in a resulting permeate stream of the first membrane module and enriched in a resulting retentate stream of the first membrane module relative to the reaction mixture fed to the first membrane module; a permeate of the first membrane module is fed to a second membrane module, and the homogeneous catalyst is depleted in the permeate stream of the second membrane module relative to the permeate of the first membrane module and concentrated in the permeate stream of the second membrane module; at least two membrane modules are serially coupled to each other on the permeate side such that at least two permeate streams form a total permeate stream in which the individual permeate streams are not completely mixed; a portion of the total permeate, a recycled permeate, is recycled to the feed vessel and / or downstream of the feed vessel and upstream of the conveying device, while a remaining portion of the total permeate, a discharged permeate, is discharged from the membrane stage, the recycled permeate being enriched in the homogeneous catalyst relative to the discharged permeate; The process includes:

14. The process of claim 13, wherein the reaction mixture is removed from a reaction zone in which a homogeneous catalytic reaction takes place.

15. 15. The process of claim 14, wherein the homogeneous catalytic reaction is selected from the group of reactions: oxidation, epoxidation, hydroformylation, hydroamination, hydroaminomethylation, hydrocyanation, hydrocarboxylation, hydroxycarbonylation, hydrocarboxyalkylation, alkoxycarbonylation, alkoxycarbonylation, amination, ammonoxidation, oximation, hydrosilylation, ethoxylation, propoxylation, carbonylation, telomerization, metathesis, Suzuki coupling and hydrogenation.

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