Process for purifying organoaluminum compounds

Abstract

This invention relates to a method for purifying organoaluminum compounds, comprising the steps of precipitating the organoaluminum compounds to separate a clarified stream and a stream with an increased slurry content; and the step of filtering the clarified stream on an inorganic membrane to obtain a purified product. This invention enables the production of highly purified and efficient organoaluminum compounds with a slurry content of less than 0.1% by weight. The invention is also simple and energy-efficient because it eliminates the need for energy-intensive centrifugation and / or vacuum distillation steps that generate waste requiring subsequent recovery. This invention also allows for a reduction in the consumption rates of aluminum and olefins during the production of organoaluminum compounds.

Description

Technical Field

[0001] This invention relates to a method for purifying organoaluminum compounds (OACs) by inorganic membrane filtration, such as triethylaluminum (TEA), triisobutylaluminum (TIBA), diisobutylaluminum hydride (DIBAH), other alkylaluminum compounds and their derivatives. Background Technology

[0002] Organoaluminum compounds have wide applications in various processes. For example, as shown in [EP 0130607] (UnionCarbide, published July 2, 1984), ethylene polymerization in the presence of a chromium catalyst can be significantly improved by adding a suitable OAC, which helps to both increase the reaction rate and reduce catalyst consumption rates. It is also known that OAC, together with metallocene catalysts, can be used as a neutralizing agent for poisons that reduce catalyst activity [US5614457, Fina Technology, published March 25, 1997].

[0003] The quality of semiconductor materials depends to a large extent on the impurities directly contained in OAC, and alkyl aluminum compounds, such as trimethylaluminum (TMA), are also used in their synthesis.

[0004] Therefore, the effectiveness of using OAC in all of the above fields depends on the impurities it contains; thus, methods for obtaining high-purity or high-concentration OAC, especially purification methods, are the most important steps in OAC production.

[0005] The method of purifying alkylaluminum by sedimentation is known [NI Korneev, Khimiya i tekhnologiyaalyuminiyorganicheskich soedineniy. - Moscow: Khimiya, 1979, pp. 187-189]. This method is effective for removing large particles, but cannot remove finely dispersed particles smaller than 50 μm that exist in suspension in OAC. Another disadvantage of this method is that it requires a significant amount of time to prepare a single batch of product.

[0006] Centrifugation is a more efficient method for separating most impurities. To remove finely dispersed solid particles, improved, but increasingly complex, OAC centrifugation techniques are being developed. However, even modernized equipment has failed to achieve the required OAC purity.

[0007] European Patent EP 1259516 [Akzo Nobel, published September 24, 2003] discloses a method for purifying organometallic compounds such as TMA by recrystallization from a solvent by cooling. The organometallic compound is first mixed with a solvent to form a solution, and then recrystallized from the solvent by cooling.

[0008] The main drawbacks of this method include the need to cool the solvent to below 0°C and the requirement to regenerate and recycle it for recrystallization of organometallic compounds. Using these methods leads to increased energy consumption. Furthermore, the above-described technical solutions are only applicable to organometallic compounds containing 1 to 4 carbon atoms.

[0009] A method for producing OAC is known from patent RU 2460733 [Otkrytoe aktsionernoe obshchestvo 'EKTOS-Volga', published on September 10, 2012], which includes reacting aluminum, hydrogen, olefins, and recycled OAC in an organic solvent at elevated temperature and pressure, followed by purifying the OAC solution by filtration to remove finely dispersed solid impurities. Prior to filtration, the OAC solution is further settled at 10-30°C for 4-15 hours, with an initial OAC content of 40-70% by weight.

[0010] This method is limited to applications with products containing between 40% and 70% OAC in the feed stream. Furthermore, the method involves a lengthy two-step sedimentation process, involving both sedimentation of the feed material before filtration and sedimentation of the purified product itself in a separate tank, as well as distillation of the solvent from the product under vacuum, which significantly reduces the method's energy efficiency. It is also noteworthy that solvent is used to clean the filter, which contains slurry and trace amounts of OAC, and this cleaning process must subsequently be completed.

[0011] The closest prior art is the invention described in document EP 0024462 [Conoco, Inc., published February 17, 1981], which describes filtering triethylaluminum (TEA) from a solution containing TEA itself, solvent, and aluminum impurities in the form of solid particles. To obtain a product suitable for fatty alcohol synthesis, a continuous extraction of high-quality alkyl aluminum is achieved by using an alternating tubular filter system to remove solid impurities.

[0012] The main drawbacks of this technical solution are as follows: (a) Solvents are required to empty the filter feed tank and therefore recycle it; (b) High-pressure purified inert gas is required for the filter cleaning process, which may cause cavitation in the pump of the filter unit circulation loop. (c) The slurry content in the filter feed tank needs to be monitored (not exceeding 20% ​​by weight), and periodically discharged and subsequently cleaned; (d) To achieve continuous filtration, at least two filter feed tanks are required; (e) Limitations on OAC filtration – Permissible solvent content ranges from 15% to 55% by weight; (f) A filter with a pore size of 2-5 μm is required, which results in a large proportion of fine slurry particles remaining in the product; (g) The content of solid impurities (slurry) in the feed stream entering the filter is limited to a maximum of 15% by weight.

[0013] All of the above-mentioned inventions have many drawbacks that hinder the achievement of maximum efficiency in OAC purification methods. Therefore, it is meaningful to seek an efficient purification method. Summary of the Invention

[0014] The purpose of this invention is to develop an efficient method for purifying OAC from slurry by filtration on an inorganic membrane, wherein the OAC is, for example, TEA, TIBA, DIBAH, tri-n-hexyl aluminum (TNHAL), ethylaluminium sesquichloride (EASC), diethylaluminium chloride (DEAC), etc.

[0015] The technical advantage lies in obtaining high-purity and high-efficiency OAC with a slurry content of less than 0.1% by weight.

[0016] Another additional technological benefit is the simplicity and energy efficiency of the solution, as it eliminates the need for energy-intensive steps such as centrifugation and / or vacuum distillation, which generate waste requiring further disposal.

[0017] Another additional technological benefit is the reduction in aluminum and olefin consumption during OAC production.

[0018] The technical problem is solved by a method for purifying OAC, and the desired technical effect is achieved, the method comprising: (a) The step of settling organoaluminum compounds, separating a clarified stream / layer and a stream with a higher slurry content, the stream with the higher slurry content optionally being sent as a seed to the initial stage of OAC synthesis and / or for disposal; and (b) The step of filtering the clarified stream onto an inorganic membrane, the pore size of which may vary between 10 and 1000 nm, to produce purified OAC.

[0019] In the filtration step, the clarified stream is separated into purified OAC, permeate, and residue. The residue is preferably fed into circulation within the filtration unit to maintain the operation of the unit, and / or is fed as a recycle material to the OAC synthesis step as seed crystals. The residual organoaluminum product in the slurry stream acts as an activator for fresh aluminum during the synthesis process, while unreacted aluminum from the slurry is returned to the synthesis process, thereby reducing the consumption rate of raw material components such as aluminum and olefins, and / or can be wholly or partially sent to the recycling of OAC-containing waste. Attached Figure Description

[0020] supply Figure 1-2 This invention discloses the essential technical solution of the present invention, but does not limit the invention.

[0021] Figure 1 A schematic diagram of an apparatus for purification by filtration on an inorganic membrane is shown.

[0022] Figure 2 A schematic diagram showing the arrangement of short and long siphons in the filter feed tank is shown. Invention Details In the following text, the term "organoaluminum compound" or "OAC" refers to an organometallic compound containing an Al-C bond, preferably an alkylaluminum compound.

[0024] The term "slurry" refers to solid compounds, including unreacted aluminum powder and aluminum compounds, particularly aluminum oxides and hydroxides, salts, oligomers and other low-molecular-weight compounds.

[0025] The term "residue" refers to the OAC stream with increased slurry content that leaves the filtration unit, which is either recycled back to the filtration unit or used as seed crystals in the OAC synthesis step.

[0026] The term "seed crystal" refers to a circulating OAC stream with an increased slurry content, which is obtained after settling or consists of residues and is required to activate fresh aluminum at the start of the OAC production process.

[0027] The term "permeate" refers to the desired product, which is OAC with the slurry removed.

[0028] The terms “transmembrane pressure” and “TMP” refer to the pressure difference between the permeate side and the exudate side of the membrane.

[0029] The term "coarse particles" refers to solid particles larger than 200 µm.

[0030] In various embodiments, the present invention relates to a method for purifying organoaluminum compounds, preferably alkylaluminum compounds such as TEA, TIBA, DIBAH, TNHAL, EASC, DEAC, etc., from a slurry by filtration over an inorganic membrane to obtain a highly purified and efficient product.

[0031] In various embodiments of the present invention, the OAC may be in concentrated form or in solution form.

[0032] Prior to purification, the organoaluminum compound contains up to 30% by weight, preferably up to 20% by weight, of slurry.

[0033] The purification method is in Figure 1 The process is carried out in the apparatus shown, the apparatus comprising: - A filtration unit, which consists of one or more filters F1...Fn containing inorganic membranes; - One or more filter feed tanks E1...E1 / n, from which OAC material streams free of large slurry particles are continuously fed to the filter unit, wherein one or two of the tanks are settling tanks; - Pump P1 is used to pump the feed stream 2 and the permeate circulation feed stream 6 to the membrane filter; - Optional heat exchanger T1 for cooling the circulating flow of residual material; - Optional intermediate permeate storage tank E2 located before the product is sent to the loading / unloading ramp or to other synthesis processes; - Optional intermediate permeate storage tank E3 for backwashing and device for generating countercurrent pulsation, such as piston pump P2; - Optional intermediate residue storage tank E4 for use as seed crystals.

[0034] exist Figure 1 In this process, stream 1 consists of unpurified OAC with a high slurry content, and exits the OAC synthesis step from the reactor and / or storage tank, being fed to one or more filter feed tanks E1...E1 / n, where a settling step takes place in at least one tank E1; wherein a portion of the slurry settles to the bottom of the lower layer by gravity and / or with the aid of a stirrer, while the purified portion (constituting stream 2) has a slurry content of 0.2-30% by weight, which is pumped through a first siphon (which is a short siphon) to a filtration unit, which may contain one or more filters F1...Fn, in which purification is carried out on an inorganic membrane by circulation using a centrifugal pump P1. The lower layer is fed through a second long siphon from tank E1 as stream 8 with an increased slurry content, and then it is mixed with the residue in tank E4, or separately as seed crystals, to the OAC synthesis step, with the aim of activating fresh aluminum and reducing the loss of unreacted aluminum.

[0035] The main portion of the material flow 3 leaving the filtration unit, which contains 70-95% by weight, preferably 80-90% by weight, of the total material flow 2 and from which slurry has been removed, constitutes a permeate flow that goes to other processes for further use, and / or to the loading / unloading ramp, and / or to the intermediate tank E2.

[0036] In various embodiments of the invention, to ensure uninterrupted membrane operation, when the pressure differential exceeds 0.5 MPa, the remaining permeate is sent to tank E3. The feed stream 4 from tank E3 is fed to the membrane backwash via piston pump P2 or any other device capable of generating flow pulsation and / or high pressure. The backwashing can also be performed using high-pressure gas, preferably nitrogen.

[0037] The residue is preferably discharged in whole or in part through flow 6, which constitutes a residue recirculation within the filtration unit to maintain the operation of the unit, and / or is used through flow 5 for recovery by neutralization, heat treatment or other means.

[0038] The residual material recirculation flow 6 preferably passes through a heat exchanger T1, which ensures the safe and stable operation of the filtration unit, prevents uncontrolled heating and deformation of the equipment, and reduces the loss of temperature-sensitive organic aluminum products when the temperature of the flow 6 rises due to friction within the membrane and heat transfer from the pump P1.

[0039] A portion of the residue from the filtration step—10-20% by weight, with a slurry concentration of up to 30% by weight—is fed via stream 7 as a seed crystal to the OAC synthesis step, thereby reducing the consumption rate of aluminum and olefins to 15% by weight during the production of the OAC compound, and / or being fed into intermediate tank E4 before being used as a seed crystal.

[0040] The inorganic membrane is a ceramic membrane. Specifically, the inorganic membrane is a porous, thin ceramic filter produced by sintering metal oxides, such as alumina (Al₂O₃), titanium dioxide (TiO₂), zirconium oxide (ZrO₂), or mixtures thereof, at ultra-high temperatures. The ceramic membrane can have a symmetrical or asymmetrical structure, comprising a macroporous support layer and an active membrane layer. The macroporous substrate provides mechanical stability, while the active layer performs separation functions in the range of 10 nm to 10,000 nm, i.e., in the range of microfiltration, ultrafiltration, and even nanofiltration.

[0041] The inorganic membrane always operates in a continuous tangential flow filtration mode. The unpurified OAC-containing stream or clarified stream is filtered at a rate of 5-25 l / (h·mm). 2The purified product passes through one or more filters in the filtration unit at a high linear velocity within the range of [value missing]. With multiple filters installed, the purification rate and thus the yield of the purified product will be even higher. Under the action of the TMD, the purified product passes through the membrane perpendicular to the circulating feed stream, while solid particles such as slurry and polymers are retained in the residue.

[0042] In various embodiments, the pore size of the inorganic membrane is between 10 nm and 1000 nm, preferably between 20 nm and 500 nm, and more preferably between 50 nm and 200 nm.

[0043] In various embodiments, the inorganic membrane is purified by backwashing with a liquid, preferably a permeate, or by backwashing with a high-pressure gas, preferably nitrogen.

[0044] In various implementations, the inorganic membrane is regenerated by backwashing using a device that generates pulsations.

[0045] In various embodiments of the invention, at least one filter feed tank has a short siphon and a long siphon. The first siphon is as follows: Figure 2 The short siphon i, as shown, is through which the clarified OAC stream is pumped to the filtration unit. The second siphon is a long siphon ii, through which a layer with an increased slurry content (similar to the residue obtained during filtration) is discharged. In a preferred embodiment of the invention, the layer with the increased slurry content is discharged through the long siphon and through stream 8, which is recycled as seed crystals in the OAC synthesis step to activate aluminum and / or for recovery. A significant advantage of operating siphons i and ii is that there is no need to flush the settling tank, as there will be no slurry concentration therein, and therefore no need for its subsequent flushing, which involves slurry dilution and its discharge for recovery. According to the invention, siphon i ensures the required flow quality before filtration due to the absence of large slurry particles and / or a high concentration of such particles, while siphon ii ensures the continuous removal of the lower layer with an increased slurry content, preferably for seed crystals, without the need to dilute accumulated slurry with solvents and periodically pump it out for recovery, and without interrupting the pumping of the clarified layer to the filtration step, thus making the filtration method continuous.

[0046] The inventors of this invention unexpectedly discovered that the above-mentioned technical effect is achieved because OAC, preferably alkyl aluminum, such as Lewis acid, has a chemical affinity for the membrane material, which is preferably produced by sintering various forms of alumina—α-, β-, and other forms—Al2O3, in which case it exhibits its alkaline properties; separating OAC, preferably alkyl aluminum, from the slurry in such a ceramic membrane is more efficient than in polymer membranes or other membranes or filters.

[0047] In various embodiments of the present invention, the purified OAC can be effectively used in the polymerization of rubber and olefins as an additive to the catalytic system to improve its efficiency. Detailed Implementation

[0048] Description of the test method 1. The determination of free slurry is as follows: Liquid OAC samples (1–3 g) were filtered through a 0.45 µm syringe filter in a nitrogen chamber. The filter was rinsed with cyclohexane and passed through nitrogen until a constant mass was reached. The increase in the mass of the filter was measured, and its ratio to the initial mass of the feed stream passing through the filter was calculated.

[0049] 2. The total aluminum was determined as follows.

[0050] The OAC sample (1–2 g) was diluted with diethyl ether (50 ml) and dissolved in a 10% (w / w) aqueous hydrochloric acid solution with stirring. Inorganic aluminum was determined by complexometric titration of the aqueous solution.

[0051] 3. The particle size distribution of the aluminum paste was determined as follows.

[0052] The composition was determined using a Horiba LA-950V2 laser particle size analyzer by dispersing 20–50 mg of concentrated samples in cyclohexane (15 ml) and comparing them with pure, dry cyclohexane samples.

[0053] The present invention is described in more detail in the embodiments given below, which are provided for illustrative purposes only and do not limit the invention.

[0054] Example 1 (Comparative) 300 kg of concentrated TIBA containing 90 wt% of the main component, 9.67 wt% of the slurry, and an average particle size distribution of 0.81 μm was placed in a tank and allowed to settle for 12 hours. Afterward, 150 kg of the upper clarified layer was removed; the slurry content was 0.95 wt%. The remaining layer, totaling 150 kg, was used as seed crystals for the TIBA synthesis step.

[0055] Example 2 (Comparative) A solution of DIBAH in a petroleum solvent (76 wt% major component, 5.93 wt% slurry, 1,044 kg weight, average particle size 1.9 μm) was placed in a tank and allowed to settle for 12 hours. The upper clarified layer, weighing 626 kg, containing 1.12 wt% slurry, was then removed. This clarified layer was centrifuged to obtain 519 kg of a DIBAH solution with a slurry content of 0.48 wt%. 107 kg of the DIBAH solution with a slurry concentration of 4.21 wt%, along with 418 kg of the bottom layer obtained during settling, was used as seed crystals in the DIBAH synthesis step in the petroleum solvent.

[0056] Example 3 (according to the present invention) 300 kg of concentrated TIBA containing 90 wt% of the main component and 9.67 wt% of slurry was fed to tank E1 for sedimentation for 4 hours. After sedimentation, 200 kg of a clarified layer containing 7 wt% slurry and an average particle size of 0.81 μm was removed via a first siphon and passed through a single filter tank containing a membrane with an average pore size of 200 nm, composed of 99% α-Al₂O₃ and 1% ZrO₂. 100 kg of TIBA (slurry content 21 wt%) from the lower layer of tank E1 was used as seed crystals for the TIBA synthesis step.

[0057] During filtration, permeate backwashing is performed whenever the permeate flow rate decreases and / or the TMD increases to prevent membrane pore blockage and reduced productivity.

[0058] The purified TIBA permeate was a clear liquid with no visible signs of slurry. The slurry content in the purified TIBA was 0.073% by weight.

[0059] TIBA residue contains 34% by weight aluminum slurry and is completely recycled within the filter unit.

[0060] The filtration method yielded 185 kg (92.5% by weight of the clarified layer) of purified TIBA.

[0061] Example 4 (according to the present invention) A solution of DIBAH in a petroleum solvent, containing 76 wt% of the main component in a quantity of 1,044 kg and a slurry content of 5.93 wt%, was sent to a settling tank (E1) for 6 hours. After settling, 875 kg of the clarified layer, containing 3.4 wt% slurry with an average particle size of 1.9 μm, was collected and passed through a single filter tank containing a membrane with an average pore size of 200 nm, composed of 95% α-Al₂O₃ and 5% TiO₂. A total of 169 kg of DIBAH (slurry content of 19 wt%) from the lower layer of tank E1 was sent as seed crystals to the DIBAH synthesis step.

[0062] During filtration, permeate backwashing is performed periodically whenever permeate productivity decreases and / or TMD increases to prevent membrane pore blockage and reduced productivity.

[0063] The purified DIBAH permeate was a clear liquid with no visible signs of slurry. The slurry content in the purified DIBAH was 0.045% by weight.

[0064] A DIBAH residue with an aluminum paste content of 7.3% by weight is sent as seed crystals to the DIBAH synthesis step at a rate of 10% of its flow rate; the remainder continues to circulate in the filter unit.

[0065] The filtration yielded 748 kg (85.5% by weight of the clarified layer) of purified DIBAH.

[0066] Example 5 (according to the present invention) 300 kg of concentrated DEAC, with a main component content of 87.2 wt% and a slurry content of 12.76 wt%, was sent to tank E1 for sedimentation for 6 hours. After sedimentation, 240 kg of clarified layer containing 8.9 wt% slurry and an average particle size of 0.1 μm was extracted through a first siphon and passed through a single filter tank containing a membrane with an average pore size of 50 nm, composed of 98% α-Al₂O₃, 1% TiO₂, and 1% ZrO₂. 60 kg of DEAC (slurry content of 28 wt%) from the lower layer of tank E1 was sent as seed crystals to the DEAC synthesis step.

[0067] During filtration, permeate backwashing is performed periodically whenever permeate productivity decreases and / or TMD increases to prevent membrane pore blockage and reduced productivity.

[0068] The purified DEAC permeate was a clear liquid with no visible signs of slurry. The slurry content in the clear DEAC was 0.018% by weight.

[0069] The DEAC residue contains 44.6% by weight of aluminum paste and is sent to the DEAC synthesis step as a seed crystal.

[0070] Filtration yielded 192 kg (80% by weight of the initial mass) of purified DEAC.

[0071] Example 6: Polymerization using TIBA The purified TIBA, as described in Example 1, was added as a solution to the reactor, followed by the addition of a catalytic system for the synthesis of linear low-density polyethylene (PE). PE synthesis was carried out in a device equipped with a stirrer and jacket at a temperature of 70–100 °C; the product was then separated and dried at a temperature of 50–80 °C.

[0072] In the presence of TIBA co-catalyst, the catalyst activity is 5 kg PE / g cat. The content of fine particle fraction (less than 375 µm) was 2.7% by weight.

[0073] Example 7: Polymerization using purified TIBA The purified TIBA, as described in Example 3, was added as a solution to the reactor, followed by the catalytic system for PE synthesis. PE synthesis was carried out in a device equipped with a stirrer and jacket at a temperature of 70-100 °C; the product was then separated and dried at a temperature of 50-80 °C.

[0074] In the presence of purified TIBA co-catalyst, the catalyst activity was 5.9 kg PE / g cat. The content of fine particle fraction (less than 375 µm) was 1.4 wt%.

[0075] Example 8: Polymerization using DIBAH The purified DIBAH, as described in Example 2, was added in solution to the catalytic system used for the synthesis of SKD-ND butadiene rubber. Rubber synthesis was carried out in a device equipped with a stirrer and jacket at a temperature of 60-90 °C; the product was then separated and dried at 80-90 °C.

[0076] Complete conversion of butadiene was achieved within 1 hour of the polymerization process.

[0077] Example 9: Polymerization using purified DIBAH The purified DIBAH, as described in Example 4, was added in solution to the catalytic system used for the synthesis of SKD-ND butadiene rubber. Rubber synthesis was carried out in a device equipped with a stirrer and jacket at a temperature of 60-90 °C; the product was then separated and dried at 80-90 °C.

[0078] Complete conversion of butadiene was achieved within 0.5 hours of the polymerization process.

[0079] As can be seen from Examples 3, 4, and 5, the technical solution according to the present invention allows for the purification of organoaluminum compounds in solution and concentrated forms from slurry to a content of less than 0.1% by weight, i.e., from 0.018% by weight to 0.073% by weight. Such OACs constitute ready-to-use commercially available products. Furthermore, streams with increased slurry content and residues can be fed into the initial stage of OAC synthesis without any recovery loss, and this eliminates the need for additional solvent flushing of equipment during purification, nor the need to add solvent to the material during the purification process. Moreover, the recycling of streams with high slurry content, where residual organoaluminum products act as activators for fresh aluminum during synthesis, and unreacted aluminum from the slurry is returned to the synthesis process, enables a reduction in the consumption rate of initial feedstock components such as aluminum and olefins.

[0080] Examples 7 and 9 also demonstrate the effectiveness of the OAC obtained according to the invention in processes such as polymerization. For PE production processes, increased catalytic activity and reduced amounts of byproduct fractions were observed; for rubber production processes, reduced reaction times were achieved. These were subsequently applied to empirical industrial tests in the synthesis of linear low-density polyethylene and SKD-N butadiene rubber, which were successfully completed—the products met technical specifications (TS) without any decrease in the activity of the catalytic complex or an increase in consumption rate.

Claims

1. A method for purifying organoaluminum compounds, comprising: (a) The step of settling organoaluminum compounds to separate the clarified stream and the stream with increased slurry content; and (b) The step of filtering the clarified stream on an inorganic membrane to obtain a purified organoaluminum compound.

2. The method according to claim 1, wherein the slurry stream with increased slurry content is fed as a seed crystal to the synthesis step of the organoaluminum compound and / or used for recycling.

3. The method according to claim 1, wherein in the filtration step, the clarified stream is separated into purified permeate and residual material.

4. The method of claim 3, wherein the residue is sent to the filtration unit for recycling and / or sent as seed crystals to the synthesis step of the organoaluminum compound via recycling, and / or may be sent to recovery in whole or in part.

5. The method according to claim 1, wherein the organoaluminum compound is triethylaluminum, triisobutylaluminum, diisobutylaluminum hydride, tri-n-hexylaluminum, sesquiethylaluminum chloride, diethylaluminum chloride, and other alkylaluminum compounds.

6. The method according to claim 5, wherein the organoaluminum compound is triisobutylaluminum or diisobutylaluminum hydride.

7. The method according to claim 1, 5 or 6, wherein the organoaluminum compound may be in concentrated form or in solution form.

8. The method according to any one of claims 1, 5-7, wherein the organoaluminum compound contains at most 30% by weight, preferably at most 20% by weight, of a slurry before purification.

9. The method according to claim 1, wherein the inorganic membrane is a ceramic membrane.

10. The method according to any one of claims 1-9, wherein the inorganic membrane is selected from alumina, titanium dioxide, zirconium oxide, or mixtures thereof.

11. The method of claim 1, wherein the filtering is performed in a continuous tangential flow filtering mode.

12. The method of claim 1, wherein the filtering step is performed in a filtering unit that may contain one or more filters.

13. The method according to claim 1, wherein the pore size of the inorganic membrane is from 10 nm to 1000 nm, preferably from 20 nm to 500 nm, and more preferably from 50 nm to 200 nm.

14. The method of claim 1, wherein the settling step is performed in at least one filter feed tank.

15. The method according to any one of claims 1-14, wherein during the settling step, a portion of the slurry is retained at the bottom of the filter feed tank by gravity and / or due to the action of the agitator.

16. The method of claim 14, wherein at least one filter feed tank has a short siphon and a long siphon, wherein the clarified stream of the organoaluminum compound is pumped through the short siphon and the layer having an increased slurry content is discharged through the long siphon.

17. The method of claim 16, wherein the clarified stream of the organoaluminum compound is pumped to the filtration unit via the short siphon.

18. The method of claim 16, wherein the layer having an increased slurry content is discharged through the long siphon and fed as a recycled material as a seed crystal to the synthesis step of the organoaluminum compound.

19. The method according to any one of claims 1-17, wherein the clarified material stream having a slurry content of 0.2-30% by weight is pumped through the short siphon.

20. The method of claim 1, wherein the inorganic membrane is cleaned by backwashing with a liquid, preferably a permeate, or by backflushing with a high-pressure gas, preferably nitrogen.

21. The method of claim 1, wherein the inorganic membrane is regenerated by backwashing with liquid using a device that generates pulsations.

22. The method of claim 1, wherein the clarified material stream and the recirculated leachate stream in the filtration unit are pumped by a single pump, preferably a centrifugal pump.

23. The method of claim 1, wherein the recirculated permeate stream is passed through a heat exchanger to stabilize the temperature of the stream.

24. The method according to any one of claims 1-3, wherein the permeate stream constitutes 70-95% by weight, preferably 80-90% by weight, of the clarified stream, and is sent to other processes for further use and / or to an unloading / loading ramp and / or to an intermediate tank.

25. The method of claim 1, wherein the clarifying flow rate is 5-25 l / (h·mm) 2 High linear velocity within the range passes through one or more filters in the filter unit.

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