Method for separating insoluble salt from metal organic precursor raw material liquid and separation device used in the method

Abstract

The application belongs to the technical field of solid-liquid separation, and particularly provides a separation method for insoluble salt in metal organic precursor raw material liquid and a separation device used in the method. The separation method comprises the following steps: feeding the precursor raw material liquid into a pretreatment tank for stirring and preheating to obtain preheated raw material liquid; feeding the preheated raw material liquid into a pipeline type microwave processor for microwave irradiation to induce agglomeration of insoluble salt particles in the raw material liquid, and obtaining agglomerated raw material liquid; monitoring the particle size of the agglomerated raw material liquid by using an online particle size monitor, and feeding the agglomerated raw material liquid into a countercurrent filtration device for countercurrent filtration to filter out insoluble salt particles when the particle size of the agglomerated raw material liquid is μ≥d. The separation method of the application not only reduces the separation difficulty, but also improves the purity of the target product (metal organic precursor) and reduces the residue of insoluble salt.

Description

Technical Field

[0001] This invention belongs to the field of solid-liquid separation technology, specifically providing a method for separating insoluble salts from a metal-organic precursor feedstock liquid, as well as the separation device used in this method. Background Technology

[0002] In the field of advanced materials synthesis, a "precursor" refers to an intermediate compound that can be transformed into a target functional material through thermal decomposition, chemical reaction, or deposition process. Organometallic precursors, due to their unique coordination structure and tunable chemical activity, have become key raw materials for preparing high-performance inorganic materials (such as metal oxides, nitrides, and carbides) or functional organometallic compounds. Specific applications of organometallic precursors include: (1) Chemical vapor deposition (CVD) and atomic layer deposition (ALD): the precursor decomposes under high temperature or plasma conditions to deposit a high-purity thin film on the substrate surface; (2) Solution synthesis of nanomaterials; (3) Homogeneous catalysis and organic synthesis. In these applications, the purity of the precursor and the stability of the ligands directly determine the performance of the end material (such as film density, nanocrystal morphology, and catalytic efficiency). The synthesis of organometallic precursors usually involves ligand exchange reactions or metallization reactions, during which insoluble salts (such as lithium halides) and other byproducts are inevitably generated. Insoluble salts remaining in the precursor solution can lead to increased impurity concentrations in the film during subsequent applications (such as CVD deposition), affecting device performance. Therefore, it is necessary to separate insoluble salts from the precursor.

[0003] Separating residual insoluble salts from precursors is currently quite challenging. On one hand, it's difficult to balance the separation efficiency of insoluble salts with the stability of the product. Insoluble salts, such as LiCl, are typically dispersed in the precursor solution as particles, making conventional solid-liquid separation methods, such as filtration and centrifugation, inefficient. To improve purity, existing techniques often employ multiple solvent washes or introduce adsorbents; however, these operations can easily lead to physical entrainment losses of the precursor or chemical decomposition due to contact with trace amounts of water and oxygen, or localized high temperatures. On the other hand, precursors generally suffer from thermal instability; when the temperature exceeds their thermal decomposition temperature, they are prone to breakage, generating impurities such as lithium hydroxide. In recent years, although microwave-assisted purification and membrane separation techniques have been explored to accelerate the separation and removal of insoluble salts, the significant difference between the dielectric properties of organic solvents and the strong microwave absorption capabilities of metal halides can easily lead to localized overheating of the system, causing rapid decomposition of the precursor.

[0004] Given the stability requirements of precursors, traditional preparation processes are typically carried out entirely under an inert atmosphere and at low temperatures, combined with filtration technologies (such as filter cloths and metal screens) to filter insoluble salts. However, traditional filtration technologies suffer from a series of problems due to insufficient pore size matching. Taking lithium chloride (LiCl) as an example, its crystal particle size distribution as a byproduct is in the nanometer range, significantly smaller than the effective retention range (micrometer range) of conventional filter media. Existing separation processes using filter cloths and metal screens suffer from problems such as high filter cake liquid content (>40%), high LiCl particle penetration, high energy consumption, high fine particle escape rate (escape rate ≥25%), and increased operating costs due to insufficient pore size matching, resulting in issues such as high filter cake liquid content (>40%), high LiCl particle penetration, high energy consumption, high fine particle escape rate (escape rate ≥25%), and frequent filter cloth replacement. If the filter cake liquid content is too high, a large amount of mother liquor will remain in the filter cake pores, which not only increases the energy consumption for subsequent drying but also easily causes LiCl deliquescence and agglomeration; while a large number of fine particles penetrate the filter media and enter the filtrate, requiring multiple filtration cycles, thus prolonging the process time. Furthermore, while centrifugation (≥6000 rpm) can improve the retention rate to some extent, the high-speed shear force can destroy the LiCl crystal structure, generating metastable microcrystals and reducing product stability. Escaping fine LiCl particles can also easily adsorb onto the surface of the target product, hindering subsequent reactivity and affecting the downstream application performance of the product. Filter cloths become rapidly clogged due to nanoparticles embedding into the pores, requiring multiple filter media replacements per batch, increasing consumable costs. Frequent shutdowns for cleaning the filtration system also reduce effective working hours and significantly lower capacity utilization.

[0005] The aforementioned separation challenges are common in the production of organometallic precursors and have become a bottleneck hindering the high-purity, large-scale production of such products. Therefore, the development of new separation methods is extremely urgent. Summary of the Invention

[0006] The purpose of this invention is to provide a method and apparatus for separating insoluble salts from organometallic precursor feedstock solutions. This separation method not only reduces the difficulty of separation but also improves the purity of the target product (organometallic precursor) and reduces the residue of insoluble salts.

[0007] In a first aspect, the present invention provides a method for separating insoluble salts from a metal-organic precursor feed solution, comprising:

[0008] The organometallic precursor feed solution is fed into a pretreatment tank for stirring and preheating to obtain a preheated feed solution.

[0009] The preheated raw material liquid is sent to a pipeline microwave processor for microwave irradiation to induce the aggregation of insoluble salt particles in the raw material liquid, resulting in aggregated raw material liquid.

[0010] The particle size of the aggregated feed liquid was monitored using an online particle size analyzer. When the particle size μ of the aggregated feed liquid was ≥ d, the aggregated feed liquid was sent to a countercurrent filtration device for countercurrent filtration to remove insoluble salt particles, where d = 40–60 μm;

[0011] The pipeline-type microwave processor includes N pipelines, which are numbered from the first pipeline to the Nth pipeline according to the flow direction of the raw material liquid, where N > 2 and is an even number. Each pipeline is independently equipped with a microwave source to alternately control the operating frequency of the N pipelines. The operating frequencies of two adjacent pipelines are a and b, respectively, and the microwave frequency of the first pipeline is a. a and b satisfy the relationship: 2 < b / a < 3.

[0012] In the separation method of the present invention, the preheated metal-organic precursor raw material liquid is fed into a microwave processor with a multi-segment pipeline, and the insoluble salt is induced to coagulate by alternating microwave irradiation treatment, thereby increasing the particle size of the insoluble salt. This not only reduces the separation difficulty but also improves the purity of the target product. Combined with multi-stage gradient countercurrent filtration, high-efficiency and low-energy-consumption processing can be achieved, thereby improving economic benefits.

[0013] In a second aspect, the present invention provides a separation apparatus used in the method for separating insoluble salts from the organometallic precursor feed solution of the first aspect of the present invention, comprising:

[0014] A pretreatment tank is used to stir and preheat the metal-organic precursor raw material liquid to obtain a preheated raw material liquid;

[0015] A pipeline microwave processor is used to irradiate preheated raw material liquid with microwaves to induce the aggregation of insoluble salt particles in the raw material liquid, thereby obtaining aggregated raw material liquid.

[0016] An online particle size analyzer is used to detect the particle size of the aggregated raw material liquid;

[0017] A countercurrent filtration device is used to filter agglomerated raw material liquid in a countercurrent manner to remove insoluble salt particles.

[0018] In the separation device of the present invention, microwave-induced agglomeration by a pipeline microwave processor is used to increase the size of insoluble salt particles. Combined with a countercurrent filtration device, it can improve the retention efficiency of insoluble salts in the feed liquid and reduce the risk of filter material clogging. Furthermore, the integrated online particle size monitoring can adapt to fluctuations in the composition of the feed liquid and ensure the stability of continuous separation of the feed liquid.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0021] Figure 1 This is a schematic diagram of a separation device according to one embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of a pipeline structure according to one embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the structure of a filter according to one embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of material flow in a countercurrent filtration process according to one embodiment of the present invention.

[0025] Explanation of reference numerals in the attached figures

[0026] 1: Pretreatment tank; 2: Centrifugal pump; 3: In-line microwave processor

[0027] 3-1: Spiral guide channel; 4: Online particle size analyzer; 5: Countercurrent filtration device.

[0028] 5a: Intake pipe; 5b: Exhaust pipe; 5c: Liquid inlet pipe

[0029] 5d: Flushing outlet pipe; 5-1: Filter membrane assembly; 5-2: Viewing window.

[0030] 5-3: Discharge port; 6: Receiving tank Detailed Implementation

[0031] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0032] The "scope" disclosed in this invention is defined in the form of a lower limit and / or an upper limit, whereby a given scope is defined by selecting a lower limit and / or an upper limit. This scope may or may not include endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form an undefined scope, and any lower limit can be combined with other lower limits to form an undefined scope, similarly, any upper limit can be combined with any other upper limit to form an undefined scope. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and can be combined with any other point or single value, or with other lower or upper limits, to form an undefined scope.

[0033] Unless otherwise specified, all embodiments and optional embodiments of the present invention may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present invention.

[0034] The "scope" disclosed in this invention is defined in the form of a lower limit and / or an upper limit, whereby a given scope is defined by selecting a lower limit and / or an upper limit. This scope may or may not include endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form an undefined scope, and any lower limit can be combined with other lower limits to form an undefined scope, similarly, any upper limit can be combined with any other upper limit to form an undefined scope. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and can be combined with any other point or single value, or with other lower or upper limits, to form an undefined scope.

[0035] It should be noted that the terms "first", "second", "I", and "II" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0036] This invention provides a method for separating insoluble salts from a metal-organic precursor feed solution, comprising the following steps:

[0037] The organometallic precursor feed solution is fed into a pretreatment tank for stirring and preheating to obtain a preheated feed solution.

[0038] The preheated raw material liquid is sent to a pipeline microwave processor for microwave irradiation to induce the aggregation of insoluble salt particles in the raw material liquid, resulting in aggregated raw material liquid.

[0039] The particle size of the aggregated raw material liquid is monitored by an online particle size analyzer. When the particle size μ of the aggregated raw material liquid is ≥ d, the aggregated raw material liquid is sent to a countercurrent filtration device for countercurrent filtration to remove insoluble salt particles, where d = 40-60 μm.

[0040] In this invention, the organometallic precursor feed solution is a solid-liquid mixture containing insoluble salt particles, typically a suspension. Specifically, the organometallic precursor feed solution includes an organic solvent and an organometallic precursor and insoluble salt distributed therein. According to some embodiments, the general chemical formula of the organometallic precursor is RM[N(CH3)2]n, where R represents a ligand, specifically cyclopentadienyl (Cp) or a cyclopentadienyl derivative (such as indenyl, fluorenyl, methylcyclopentadienyl), M represents a metal, specifically selected from transition metals (e.g., Fe, Co, Ti, Zr, Hf, or Ta) or rare earth metals (e.g., La, Y), n = m-1, m represents the valence of metal M, and m ≥ 2, for example, 4. As some specific examples, the organometallic precursor is tris(dimethylamino)cyclopentadienyl hafnium or tris(dimethylamino)cyclopentadienyl zirconium. The insoluble salt in the organometallic precursor feed solution can be lithium halide, such as lithium chloride (LiCl), and the mass content of the insoluble salt in the feed solution can be 8% to 15%, for example, 8%, 8.5%, 9%, 9.2%, 10%, 11%, 12%, 14%, 15%, etc. Typically, the lithium halide particle size is <1 μm, and further, the lithium halide particle size distribution is 20–200 nm. The mass content of the organometallic precursor in the feed solution can be, for example, 30% to 70%, for example, 32%, 45%, 48%, 50%, 55%, 60%, 70%, etc. This invention aims to illustrate a method for separating insoluble salts from organometallic precursor feed solutions; therefore, there are no restrictions on the source of the organometallic precursor feed solution, and it can be obtained according to methods well known in the art. For example, the organometallic precursor feed solution can be obtained using a three-step method, specifically by following the reaction pathways shown in S1 to S3 below, in the presence of an organic solvent and under the protection of an inert gas (such as nitrogen or argon):

[0041] S1, n-BuLi+HN(CH3)2→LiN(CH3)2+n-BuH

[0042] The n-butyllithium (n-BuLi) and dimethylamine (HN(CH3)2) are reacted at a molar ratio of 1:(1.2-1.5) at a low temperature (20℃ to 10℃) for 3-5 hours to form a mixture containing dimethylaminolithium (LiN(CH3)2) and n-butane (n-BuH). The mixture is then heated to 30-40℃ and purged with nitrogen for 1-2 hours to remove as much unreacted dimethylamine and n-butane as possible.

[0043] S2,mLiN(CH3)2+MX m →M[N(CH3)2]m+mLiX

[0044] Add metal halide (MX) to the system obtained in S1 m MX mThe molar ratio of N-butyllithium to N-butyllithium can be (0.95–1):1. The reaction system temperature is maintained at 20°C to 10°C, and the reaction is stirred for 8–12 hours to form M[N(CH3)2]. m The mixture of LiX and LiX was allowed to stand and separate into layers to remove some of the LiX, thus obtaining a liquid product.

[0045] S3: M[N(CH3)2]m+RH→RM[N(CH3)2]n+HN(CH3)2

[0046] Add cyclopentadiene or cyclopentadiene derivatives (RH, RH and MX) to the liquid product obtained from S2. m The molar ratio is 1:(1.1~1.2), the reaction system temperature is maintained at 20℃ to 10℃ and the reaction is stirred for 8~12h to obtain the organometallic precursor raw material solution.

[0047] Understandably, depending on the reaction method, in addition to the organometallic precursor and insoluble salt, the feed solution may contain other organic impurities, such as excess unreacted feedstock and other byproducts obtained during the reaction. As some embodiments, the mass content of other organic impurities in the organometallic precursor feed solution is ≤8%, for example, 3% to 8%. The organic solvent can be selected from aprotic solvents such as hydrocarbons and ethers. As some examples, the organic solvent is n-hexane or toluene.

[0048] In this invention, by stirring and preheating the metal-organic precursor liquid, the viscosity of the system can be reduced, and the initial dispersion and mixing of the solid and liquid phases can be promoted. Preferably, the preheating temperature is 40-45°C, such as 40°C, 42°C, 43°C, 45°C, etc. Controlling the temperature within this range can avoid thermal decomposition of the metal-organic precursor and improve the mass transfer efficiency in the subsequent microwave field. When the stirring makes the liquid homogenized (without visible agglomerates), the preheated liquid can be sent to a tubular microwave processor for induced agglomeration.

[0049] In this invention, the preheated raw material liquid can be transported to the pipeline microwave processor via a centrifugal pump. According to some embodiments, the flow rate of the preheated raw material liquid entering the pipeline microwave processor is 0.8–1.2 m / s, for example, 0.8 m / s, 1 m / s, 1.1 m / s, etc. Under these conditions, crystal deposition due to excessively low flow rates can be suppressed, while excessively high flow rates can be avoided from affecting the stable swirling flow of the raw material liquid in the microwave pipeline.

[0050] In this invention, the tubular microwave processor comprises N tubular segments, where N > 2 and is an even number, preferably an even number between 4 and 8, specifically 4, 6, or 8. Too few tubular segments may result in incomplete crystallization: insufficient microwave energy density reduces solution supersaturation, leading to a decrease in the nucleation rate of insoluble salt crystals, resulting in a low final crystallization rate and uneven particle size distribution. Too many tubular segments increase energy consumption and may cause secondary breakage of agglomerated crystals: excessive microwave disturbance can damage the formed crystal structure, leading to an increase in the proportion of micropowder in the product. Furthermore, multiple tubular segments require more microwave shielding and cooling systems, increasing maintenance costs. More preferably, N = 6; the six-segment design reduces the power of a single microwave source segment, avoiding electromagnetic compatibility issues caused by concentrated use of high-voltage power supplies.

[0051] Specifically, according to the flow direction of the raw material liquid, the pipeline microwave treatment includes a first pipeline, a second pipeline, ..., an Nth pipeline connected in sequence. Each pipeline segment is independently equipped with a microwave source to alternately control the operating frequency of the N pipeline segments. The operating frequencies of two adjacent pipeline segments are a and b, respectively, and the microwave frequency of the first pipeline is a. The relationship between a and b is: 2 < b / a < 3. Low-frequency microwaves (operating frequency a) and high-frequency microwaves (operating frequency b) in the N pipeline segments are arranged in a staggered manner. Low-frequency microwaves can promote the directional growth of insoluble salt crystals, while high-frequency microwaves can quickly establish a saturated environment. This not only promotes the formation of chain-like or layered ordered aggregates of crystals, but also improves the separation efficiency of insoluble salts and saves energy. It should be understood that N in "Nth pipeline" represents an ordinal number, which corresponds to the number of "Nth pipeline segments". For example, when N in "Nth pipeline segment" is 4, "Nth pipeline" refers to the fourth pipeline. According to some implementation methods, a is 910 to 928 MHz, such as 915 MHz or 920 MHz; b is 2.40 to 2.50 GHz, such as 2.42 GHz or 2.45 GHz.

[0052] In this invention, each section of the pipeline is matched with an independent microwave source to achieve segmented control of the microwave field intensity. By optimizing the energy utilization rate through segmented design, local overheating or insufficient energy can be avoided, and the supersaturation of the solution can be precisely adjusted to affect the crystallization rate and crystal form.

[0053] In this invention, all N pipe segments can be quartz pipes. According to some embodiments, the inner diameter (Φ) of each individual pipe segment can independently be 10–15 mm, for example, 10 mm, 11 mm, 12 mm, 14 mm, 15 mm, etc., and the length of each pipe segment can be 1–3 m, for example, 1 m, 1.2 m, 1.5 m, 1.7 m, 2 m, 2.4 m, 2.5 m, 2.8 m, 3 m, etc. The frequency range of the microwave source can be 600 MHz to 3 GHz.

[0054] In some embodiments, spiral guide grooves are provided on the inner wall of each section of the pipe. These spiral guide grooves can guide the raw material liquid to form a rotating flow, improving heat or mass transfer efficiency, reducing particulate matter deposition, and shortening the cleaning cycle. Furthermore, the pitch of the spiral guide grooves can be 20–50 mm, for example, 20 mm, 30 mm, 35 mm, 40 mm, 50 mm, etc., and the depth of the spiral guide grooves can be 2–5 mm, for example, 2 mm, 2.5 mm, 3 mm, 4 mm, 5 mm, etc.

[0055] In some embodiments, the surface of the spiral guide channel is coated with an anti-corrosion layer with a thickness of 0.1 to 0.3 mm. The material of the anti-corrosion layer can be polytetrafluoroethylene (PTFE). It is understood that when the surface of the spiral guide channel is coated with an anti-corrosion layer, the depth of the guide channel refers to the distance from the top of the guide channel to the anti-corrosion layer.

[0056] In this invention, the particle size of the aggregated feed liquid from the Nth pipeline is monitored online using an online particle size analyzer. When the particle size μ ≥ d, the aggregated feed liquid is sent to a countercurrent filtration device for countercurrent filtration. The online particle size analyzer can be the OMEC At-line online particle size detection system, which performs particle size analysis based on laser diffraction. It is understood that when observing particle size using an online particle size analyzer, if the detected particle size μ satisfies ≥ d (not infinitely large), the feed liquid meeting the particle size requirement needs to be continuously sent to the countercurrent filtration device for filtration and separation. Furthermore, d is 40–60 μm, for example, 40 μm, 45 μm, 50 μm, 55 μm, etc. Selecting d that satisfies the above values ​​as the critical particle size ensures efficient separation of the aggregates during gravity settling or countercurrent filtration, avoiding secondary suspension problems caused by excessively small particles; it also prevents particles that are too large from breaking apart due to inertial collisions during separation, thus reducing separation efficiency. In some implementations, the monitored particle size μ is D50.

[0057] In this invention, when the particle size of the aggregated raw material liquid detected by the online particle size monitor is <d, the separation method further includes: returning the aggregated raw material liquid to the pretreatment tank for preheating, and then continuing to induce agglomeration.

[0058] In this invention, the aggregated raw material liquid (μ≥d) is sent to a countercurrent filtration device for countercurrent filtration, which can remove the insoluble salt and complete the separation of the organometallic precursor and solvent from the insoluble salt, that is, to obtain the organometallic precursor solution and the insoluble salt respectively.

[0059] In some embodiments, the countercurrent filtration device includes a multi-stage gradient filter, each stage containing a filter membrane assembly, such as a ceramic membrane assembly, with the filtration accuracy increasing progressively in the direction of the feed liquid flow. Preferably, the countercurrent filtration device includes a primary filter, a secondary filter, and a tertiary filter connected in sequence, wherein the filtration accuracy P1 of the primary filter, the filtration accuracy P2 of the secondary filter, and the filtration accuracy P3 of the tertiary filter satisfy the following relationship:

[0060] P2 = 0.2 × P1, P3 = 0.2 × P2; where,

[0061] P1 is 3–8 μm, for example, 3 μm, 5 μm, 6 μm, etc.

[0062] In some embodiments, the countercurrent filtration is performed under closed conditions and includes an initial stage and a steady-state stage. The transmembrane pressure difference is controlled to be 0.2–0.3 MPa, for example, 0.3 MPa, during the initial stage; and 0.4–0.6 MPa, for example, 0.5 MPa, during the steady-state stage. It is understood that the transmembrane pressure difference refers to the pressure difference between membranes within the same filter. The initial stage refers to the transition period from system startup until membrane fouling or flux stabilization, during which a stable fouling layer has not yet formed on the membrane surface, and the flux decay rate is rapid. The steady-state stage refers to the period when membrane fouling reaches dynamic equilibrium, and the permeate flux tends to stabilize.

[0063] In this invention, the countercurrent filtration is carried out under anhydrous and oxygen-free closed conditions, preferably under the protection of an inert gas (such as nitrogen).

[0064] In some embodiments, the contact angle between the aggregated feed liquid and the filter membrane module is 160-170°, for example, 165°.

[0065] In this invention, to maintain the efficient and stable operation of the filtration device, the method further includes: backwashing the countercurrent filtration device with an organic solvent. The organic solvent may be, for example, hexane, pentane, or toluene, preferably the same type as the solvent in the feed liquid.

[0066] In some embodiments, the filtration device of the present invention may employ an integrated pulse backwash structure. The integrated pulse backwash structure typically includes a pulse-type backwash module, a countercurrent solvent channel, a membrane module self-cleaning unit, etc. The specific structure and connection methods are well known in the art and will not be described in detail here.

[0067] Preferably, the backwashing operating conditions include: a pressure of 0.8 to 1.2 MPa, a pulse frequency of 0.5 to 2 s / time, an interval of 3 to 8 s, for example 5 s, and a flushing time of 5 to 10 min.

[0068] The present invention also provides a separation device used in the separation method. The pretreatment tank, pipeline microwave processor, online particle size analyzer and countercurrent filter device in the device have been described in at least part above. The parts that have been described will not be repeated below.

[0069] According to some implementation methods, see reference Figures 1 to 3 The separation device of the present invention includes: a pretreatment tank 1, a pipeline microwave processor 3, an online particle size analyzer 4, and a countercurrent filter 5, wherein,

[0070] Pretreatment tank 1 is used to stir and preheat the organometallic precursor raw material liquid;

[0071] The pipeline microwave processor 3 is used to irradiate insoluble salts in the preheated raw material liquid with microwaves to induce the aggregation of insoluble salt particles.

[0072] The online particle size analyzer 4 is used to detect the particle size of the aggregated raw material liquid;

[0073] The countercurrent filtration device 5 is used to perform countercurrent filtration on the agglomerated raw material liquid to remove agglomerated insoluble salt particles.

[0074] In some embodiments, the separation device further includes a receiving tank 6. The receiving tank 6 is used to collect the metal-organic precursor solution produced by the countercurrent filtration device 5.

[0075] In some embodiments, the separation device includes a centrifugal pump 2, and a pretreatment tank 1 is connected to a pipeline microwave processor 3 via the centrifugal pump 2 to pump the preheated raw material liquid into the pipeline microwave processor 3.

[0076] In some embodiments, the pipeline microwave processor 3 includes N pipelines connected in series, which are designated as the first pipeline, ..., the Nth pipeline according to the flow direction of the raw material liquid. The outlet of the centrifugal pump 2 is connected to the inlet of the first pipeline, and an online particle size monitor 4 is installed on the outlet pipe of the Nth pipeline to monitor the particle size of the aggregated raw material liquid in real time.

[0077] Furthermore, the pipeline-type microwave processor 3 includes six pipelines connected in series, namely, the first pipeline, the second pipeline, the third pipeline, the fourth pipeline, the fifth pipeline, and the sixth pipeline. During microwave irradiation, the first pipeline, the third pipeline, and the sixth pipeline each use a low-frequency microwave source, while the second pipeline, the fourth pipeline, and the sixth pipeline each use a high-frequency microwave source.

[0078] In some implementations, such as Figure 2 As shown, in the pipeline microwave processor 3, each pipeline section has a spiral guide groove 3-1 on its inner wall.

[0079] In some embodiments, one end of the outlet pipe of the Nth pipe (e.g., the sixth pipe) is connected to two branch pipes, which are respectively connected to the countercurrent filter device 5 and the pretreatment tank 1. Each branch pipe is equipped with valve I and valve II. When the online particle size analyzer 4 detects that the particle size μ of the raw material liquid is ≥ d, valve I is opened to allow the raw material liquid to enter the countercurrent filter device 5. When the online particle size analyzer 4 detects that the particle size μ of the raw material liquid is < d, valve II is opened to allow the raw material liquid to return to the pretreatment tank 1. In addition, the particle size signal from the online particle size analyzer 4 can be received by a PLC to control the opening and closing of valves I and II.

[0080] In some embodiments, the countercurrent filtration device 5 includes a multi-stage gradient filter, where "gradient" means that the filtration accuracy of multiple filters increases progressively with the direction of flow of the raw material liquid.

[0081] In some implementations, such as Figure 3 As shown, each filter includes a filter membrane module 5-1 and multiple pipes connected to it. Specifically, the top of the filter is connected to an air inlet pipe 5a, a feed liquid inlet pipe, an exhaust pipe 5b, a liquid inlet pipe 5c, a product liquid outlet pipe, a flushing liquid outlet pipe 5d, and a discharge port 5-3. Each pipe is independently equipped with a valve to control the entry or discharge of the corresponding material. The air inlet pipe 5a is used to introduce an inert gas, such as nitrogen. Nitrogen provides protection, preventing oxidation of the filter module and feed liquid, and also provides the pressure required for flushing liquid discharge. During the unloading process, nitrogen can also be used to purge the membrane module to remove filter residue and keep the membrane clean. For filters that require backwashing, the valves of the liquid inlet pipe 5c and the flushing liquid outlet pipe 5d can be opened, and a countercurrent solvent (backwashing solvent, such as n-hexane) can be introduced through the liquid inlet pipe 5c to backwash the filter. The flushing liquid obtained from backwashing is returned to the pretreatment tank 1 through the flushing liquid outlet pipe 5d. After rinsing, close the valve of the liquid inlet pipe 5c, open the valve of the air inlet pipe 5a, and introduce nitrogen gas to force the remaining rinsing liquid into the pretreatment tank 1 through the rinsing outlet pipe 5d. When unloading is required, close the valve of the air inlet pipe 5a, open the valve of the exhaust pipe 5b to reduce the pressure to below 0.02 MPa, open the discharge port 5-3, and begin unloading. Optionally, each filter also includes a viewing window 5-2 to observe the accumulation of solid material, determining whether backwashing and unloading operations are necessary.

[0082] In some embodiments, the countercurrent filtration device 5 includes a three-stage gradient filter, specifically comprising a primary filter, a secondary filter, and a tertiary filter connected in sequence. The outlet of the Nth pipe (e.g., the sixth pipe) is connected to the feed liquid inlet of the primary filter. The filtration accuracy of the primary, secondary, and tertiary filters increases progressively. The primary filter removes large particulate impurities from the feed liquid, ensuring that subsequent filters are not clogged. The secondary filter further removes medium-sized particles from the filtrate from the primary filter. The tertiary filter retains particles smaller than micrometers from the filtrate from the secondary filter, further improving product purity. Gradient filtration reduces the load on the membrane modules, lowers the likelihood of clogging, and improves the operational stability of the device. The filtrate from the tertiary filter enters the receiving tank 6 for further filtration, while the insoluble salt residue from each stage of the filter is collected through the discharge port 5-3. Figure 4 This is a schematic diagram of material flow in an exemplary countercurrent filtration process. As shown in the figure, the contact angle (i.e., the countercurrent angle) between the aggregated feed liquid and the membrane surface is an obtuse angle. The flow direction of the aggregated feed liquid as the feed liquid is opposite to that of the filtered product liquid (i.e., the precursor solution) as the permeate liquid.

[0083] In some embodiments, the flushing outlet pipes 5d of the primary filter, secondary filter and tertiary filter are connected in parallel to the pretreatment tank 1 to return the flushing liquid to the pretreatment tank 1.

[0084] In some embodiments, the top of the pretreatment tank 1 is also provided with a return interface, which is connected to the outlet of the centrifugal pump 2. This interface can return part of the raw material liquid to the pretreatment tank to promote the flow of materials in the tank, eliminate dead zones, prevent the materials from stratifying or precipitating due to long-term stasis or uneven stirring, and can also play a role in adjusting and stabilizing the outlet flow rate.

[0085] The following describes embodiments of the present invention. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0086] The following examples are combined Figures 1 to 4This invention describes a method for separating insoluble salts from a metal-organic precursor feed solution and the separation apparatus used therein. Unless otherwise stated, the tubular microwave processor 2 comprises six sections of quartz tubing, each Φ12mm × 2.5m in size, with spiral guide channels (30mm pitch, 3mm depth) inside to induce swirling flow. The countercurrent filtration device 5 comprises a three-stage gradient filter, with the first, second, and third stages all using ceramic membrane modules, achieving filtration accuracies of 5μm, 1μm, and 0.2μm, respectively. The processed precursor feed solution is a tris(dimethylamino)cyclopentadienyl hafnium feed solution prepared in three steps using n-hexane as solvent and n-butyllithium, dimethylamine, hafnium chloride, and cyclopentadiene as raw materials. The feed solution contains 15% lithium chloride by mass, 54% tris(dimethylamino)cyclopentadienyl hafnium by mass, 6% other organic impurities, and the remainder is solvent.

[0087] Example 1

[0088] The precursor raw material liquid is added to the pretreatment tank, heated to 45°C, and continuously stirred until homogenized. Then, it is pumped to the pipeline microwave processor using a centrifugal pump, with the flow rate controlled at 1.0 m / s. The preheated raw material liquid enters six pipelines sequentially. The operating frequencies of the six pipelines are alternately arranged at 915 MHz and 2.45 GHz. Microwave irradiation induces the directional aggregation of lithium chloride particles. After aggregation, the raw material liquid flows out from the sixth pipeline. After online particle size monitoring, the target particle size (d) D50 is set to 50 μm by PLC. When the feedback shows that the aggregated particle size μ < 50 μm, the return pipeline to the pretreatment tank is automatically opened. The raw material liquid returned to the pretreatment tank is stirred and preheated before re-entering the pipeline microwave processor. When the feedback shows that μ ≥ 50 μm, the countercurrent gradient filter is automatically opened. The raw liquid entering the countercurrent gradient filtration device undergoes three-stage gradient filtration to obtain solid salt and n-hexane solutions of the precursor, respectively. The solid salt is discharged from the bottom discharge port, while the n-hexane solution of the precursor is discharged from the three-stage filter and collected in the receiving tank. The pressure difference of the membrane module is controlled at 0.3 MPa in the initial stage and 0.5 MPa in the steady stage.

[0089] Backwashing and unloading of the countercurrent gradient filter: Backwashing and unloading operations are performed when the filter pressure exceeds 0.5 MPa or when excessive solid material accumulation is observed through the sight glass. For filters requiring backwashing, hexane is introduced through the inlet pipe for backwashing. During backwashing, the backwash liquid is returned to the pretreatment tank through the outlet pipe. Backwashing pressure: 1.2 MPa (pulse type, duration 0.5 s / cycle), 10 min. After backwashing, nitrogen is introduced through the inlet pipe, and the remaining backwash liquid is forced back into the pretreatment tank through the outlet pipe. During unloading, the inlet pipe is closed, the exhaust pipe is opened to reduce the pressure to below 0.02 MPa, the bottom discharge port is opened, and unloading begins.

[0090] After backwashing and unloading, install the bottom discharge port, maintain pressure at 0.5 MPa, and if the pressure does not decrease for 2 hours, continue the filtration operation.

[0091] Comparative Example 1

[0092] Lithium chloride was separated according to the method in Example 1, except that the operating frequency of all six pipelines was controlled at 915MHz.

[0093] Comparative Example 2

[0094] Lithium chloride was separated according to the method of Example 1, except that the operating frequency of all six pipelines was controlled at 2.45 GHz.

[0095] Comparative Example 3

[0096] Lithium chloride was separated according to the method of Example 1, except that the operating frequency of the first, second and third pipes was controlled at 915MHz, and the operating frequency of the fourth, fifth and sixth pipes was controlled at 2.45GHz.

[0097] Comparative Example 4

[0098] Lithium chloride was separated according to the method of Example 1, except that the operating frequency of the first, second and third pipes was controlled at 2.45 GHz, and the operating frequency of the fourth, fifth and sixth pipes was controlled at 915 MHz.

[0099] Comparative Example 5

[0100] Lithium chloride was separated according to the method of Example 1, except that only a single-section pipe (Φ12mm×2.5m) was used, and the operating frequency of the single-section pipe was controlled at 915MHz.

[0101] Comparative Example 6

[0102] Lithium chloride was separated according to the method of Example 1, except that only a single-section pipe (Φ12mm×2.5m) was used, and the operating frequency of the single-section pipe was controlled at 2.45GHz.

[0103] Comparative Example 7

[0104] This comparative example uses PTFE filter cloth to separate lithium chloride. The specific operation is as follows: the precursor raw material solution is added to the pretreatment tank, heated to 45°C, and continuously stirred until homogenized. Then, it is pumped to a closed autoclave filter bag filter using a centrifugal pump, with the flow rate controlled at 1.0 m / s. Filtration is performed using PTFE filter cloth, and the filtration pressure is controlled at 0.1-0.5 MPa. The precursor solution is then collected.

[0105] Comparative Example 8

[0106] This comparative example uses a metal screen (316L stainless steel) to separate lithium chloride. The specific operation is as follows: the precursor raw material solution is added to a pretreatment tank, heated to 45°C, and continuously stirred until homogenized. Then, it is pumped to a closed autoclave screen filter using a centrifugal pump, with the flow rate controlled at 1.0 m / s and the filtration pressure controlled at 0.1 to 0.5 MPa. The precursor solution is then collected.

[0107] Example 2

[0108] Lithium chloride was separated according to the method of Example 1, except that the preheated raw material liquid was transported to the pipeline microwave processor by a centrifugal pump, and the flow rate was controlled at 0.8 m / s. The preheated raw material liquid entered six pipelines in sequence, and the operating frequencies of the six pipelines were arranged alternately at 920 MHz and 2.42 GHz.

[0109] In Examples 1 and 2 and Comparative Examples 1-6, the microwave processing was stable for 120 hours (15 batches). In Comparative Examples 7 and 8, the following performance tests were performed after the filter was stable for 120 hours.

[0110] LiCl residual concentration: The lithium chloride content in the precursor solution was analyzed using ICP-MS and a chloride ion detector.

[0111] Particle Retention Limit: The Pro-Tech PMT-2 liquid particle counter is used to test the particle retention of the raw material liquid after passing through the filtration device. The minimum particle size corresponding to a retention efficiency of ≥99% is used as the retention rate lower limit. The performance of the entire separation device is verified by the particle retention limit. The smaller the measured minimum particle size, the better the filtration effect. Product Thermal Damage Risk: The reaction start temperature of the organometallic precursor is determined by differential scanning calorimetry (DSC) at 87℃. Based on this, the potential thermal decomposition risk of the precursor raw material liquid during microwave treatment is identified to evaluate the microwave source control method. Specifically, when the microwave treatment process temperature T < 50℃, the thermal damage risk is recorded as "low"; when the microwave treatment process temperature T meets the condition of 50℃ ≤ T ≤ 70℃, the thermal damage risk is recorded as "medium"; and when the microwave treatment process temperature T > 70℃, the thermal damage risk is recorded as "high".

[0112] The test results are shown in Table 1.

[0113] Table 1

[0114]

[0115] Note: In Examples 1-2 and Comparative Examples 1-6, the particle retention limit is the test result of the three-stage filtration device.

[0116] Based on the data in Table 1, comparing Examples 1-2, Comparative Examples 1-6, and Comparative Examples 7-8, it can be seen that although filter cloth filtration and metal screen filtration are simple to operate, both PTFE filter cloth filtration and metal screen filtration lead to excessive residual concentrations and cannot remove particles <1μm. Furthermore, although PTFE filter cloth has high filtration accuracy, it needs to be replaced every 1-3 batches. In contrast, the filtration device in Examples 1-2 maintained a particle retention limit of <1μm after multiple batches of raw material liquid treatment, eliminating the need to replace the filter membrane assembly and resulting in lower processing costs.

[0117] Comparing Examples 1-2 with Comparative Examples 1-2, it can be seen that when low-frequency microwave treatment is used alone (a), the particle size is small and the residual concentration is high. When high-frequency microwave treatment is used alone (b), although it can accelerate the directional aggregation, the local temperature is high and the solvent is easily volatile, resulting in system instability. The alternating microwave treatment in Examples 1-2 results in the lowest LiCl residual concentration, and the temperature of the precursor raw material liquid during microwave treatment can be controlled below 50°C, with a low risk of thermal damage. In addition, the overall effect of Examples 1-2 is also better than the treatment methods of Comparative Examples 3-4, which use low-frequency followed by high-frequency and vice versa.

[0118] In summary, the alternating low-to-high microwave method not only improves the purity of the target product, but also reduces the residue of insoluble salts, simplifies separation, and increases economic efficiency.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for separating insoluble salts from a metal-organic precursor feed solution, characterized in that, include: The organometallic precursor feed solution is fed into a pretreatment tank for stirring and preheating to obtain a preheated feed solution. The preheated raw material liquid is sent to a pipeline microwave processor for microwave irradiation to induce the aggregation of insoluble salt particles in the raw material liquid, resulting in aggregated raw material liquid. The particle size of the aggregated feed liquid was monitored using an online particle size analyzer. When the particle size μ of the aggregated feed liquid was ≥ d, the aggregated feed liquid was sent to a countercurrent filtration device for countercurrent filtration to remove insoluble salt particles, where d = 40–60 μm; The pipeline microwave processor includes N pipelines, which are arranged in order from the first pipeline to the Nth pipeline according to the flow direction of the raw liquid, where N>2 and is an even number. Each pipeline is independently equipped with a microwave source to alternately control the working frequency of the N pipelines. The working frequencies of two adjacent pipelines are a and b, respectively, and the microwave frequency of the first pipeline is a. a and b satisfy the relationship: 2<b / a<3. In the organometallic precursor feed solution, the general chemical formula of the organometallic precursor is RM[N(CH3)2]n, where R represents cyclopentadienyl or cyclopentadiene derivative, M represents metal, n = m-1, m represents the valence of the metal, and m≥2; the insoluble salt is lithium halide.

2. The separation method according to claim 1, characterized in that, The lithium halide is lithium chloride; the mass content of lithium halide in the organometallic precursor feed solution is 8%~15%.

3. The separation method according to claim 1, characterized in that, The preheating temperature is 40–45°C.

4. The separation method according to any one of claims 1-3, characterized in that, The flow rate of the preheated raw material liquid entering the pipeline microwave processor is 0.8 to 1.2 m / s.

5. The separation method according to any one of claims 1-3, characterized in that, All N sections of the pipeline are quartz pipelines.

6. The separation method according to any one of claims 1-3, characterized in that, N=6, the inner diameter of a single pipe section is 10-15mm, and the length is 1-3m.

7. The separation method according to any one of claims 1-3, characterized in that, a is 910–928 ​​MHz, and b is 2.40–2.50 GHz.

8. The separation method according to any one of claims 1-3, characterized in that, The frequency range of the microwave source is 600MHz to 3GHz.

9. The separation method according to any one of claims 1-3, characterized in that, In the aforementioned pipeline microwave processor, each section of the pipeline has a spiral guide groove on its inner wall. The spiral guide groove has a pitch of 20–50 mm and a depth of 2–5 mm.

10. The separation method according to claim 9, characterized in that, The surface of the spiral guide groove is also coated with a PTFE anti-corrosion layer with a thickness of 0.1 to 0.3 mm.

11. The separation method according to any one of claims 1-3, characterized in that, When the particle size μ of the aggregated raw material liquid is less than d, the separation method further includes: returning the aggregated raw material liquid to the pretreatment tank.

12. The separation method according to any one of claims 1-3, characterized in that, According to the flow direction of the raw liquid, the countercurrent filtration device includes a primary filter, a secondary filter and a tertiary filter connected in sequence, with the filtration accuracy of each filter increasing progressively.

13. The separation method according to claim 12, characterized in that, The filtration accuracy P1 of the primary filter, the filtration accuracy P2 of the secondary filter, and the filtration accuracy P3 of the tertiary filter satisfy the following relationship: P2 = 0.2 × P1, P3 = 0.2 × P2, Among them, P1 is 3-8 μm.

14. The separation method according to any one of claims 1-3, characterized in that, The countercurrent filtration is carried out under closed conditions, wherein the transmembrane pressure difference is controlled to be 0.2-0.3 MPa in the initial stage and 0.4-0.6 MPa in the steady-state stage.

15. The separation method according to any one of claims 1-3, characterized in that, In the countercurrent filtration, the contact angle between the aggregated feed liquid and the filter membrane module is 160-170°.

16. The separation method according to any one of claims 1-3, characterized in that, The method further includes: after the countercurrent filtration is completed, backwashing the countercurrent filtration device with an organic solvent.

17. The separation apparatus used in the method for separating insoluble salts from the organometallic precursor feed solution according to any one of claims 1-16, characterized in that, The separation device includes: A pretreatment tank is used to stir and preheat the metal-organic precursor raw material liquid to obtain a preheated raw material liquid; A pipeline microwave processor is used to irradiate preheated raw material liquid with microwaves to induce the aggregation of insoluble salt particles in the raw material liquid, thereby obtaining aggregated raw material liquid. An online particle size analyzer is used to detect the particle size of the aggregated raw material liquid; A countercurrent filtration device is used to filter agglomerated raw material liquid in a countercurrent manner to remove insoluble salt particles.

Images