Method for rapidly solidifying aluminum isopropoxide

Abstract

The invention relates to the technical field of metal alkoxide preparation, and particularly provides a method for rapidly solidifying aluminum isopropoxide, which comprises the following steps: concentrating liquid aluminum isopropoxide in vacuum at 80-90 DEG C until the concentration is greater than or equal to 95%; sequentially adding 0.1 to 0.2 percent of a crystallization assisting solvent TXIB, 0.05 to 0.1 percent of a nanoscale aluminum isopropoxide seed crystal and 0.01 to 0.1 percent of a magnesium isopropoxide eutectic seed crystal; crystallization is completed through gradient cooling, and the whole process is less than or equal to 24 hours; and finally, carrying out solid-liquid separation, washing and drying to obtain the high-purity aluminum isopropoxide crystal. Through the synergistic effect of the bifunctional seed crystal and the TXIB, the crystallization period is remarkably shortened, the crystal quality is improved, and the method is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of metal alkoxide preparation, and specifically provides a method for rapid solidification of aluminum isopropoxide. Background Art

[0002] Aluminum isopropoxide, as an important metal alkoxide, is widely used in the preparation of high-purity alumina, catalyst supports, and other fields. The efficiency of its crystallization process and the quality of the product directly affect the performance and production cost of subsequent products.

[0003] The traditional aluminum isopropoxide crystallization process has significant drawbacks. The existing process typically requires 10-15 days for the aluminum isopropoxide to fully solidify. This not only results in a long production cycle and equipment occupancy, but also high energy consumption. Such a long production cycle severely restricts the efficiency of industrial production and is not conducive to large-scale production.

[0004] To address the shortcomings of traditional processes, researchers in related fields have attempted a series of improvements, but these solutions still face numerous challenges. For example, physical cooling methods have some effectiveness in shortening crystallization time, but they can easily lead to crystal agglomeration, reducing product purity and impacting subsequent applications. The seed crystal method, which uses only a single seed crystal, has limited effectiveness in promoting crystallization and fails to address the issue of solvent interference in the crystallization process, making it unable to meet the demands of industrial production for efficient, high-quality crystallization.

[0005] Therefore, how to shorten the crystallization time of aluminum isopropoxide while ensuring the purity and activity of the product has become a technical problem to be solved urgently in this field. Summary of the Invention

[0006] In view of this, the present invention proposes a method for rapid solidification of aluminum isopropoxide, which aims to overcome the problems of long crystallization time and affected product quality in the prior art of aluminum isopropoxide, so as to achieve efficient and high-quality aluminum isopropoxide crystallization.

[0007] The technical solution of the present invention is achieved as follows: The present invention provides a method for rapid solidification of aluminum isopropylate, the specific steps of which are as follows: 1. Concentration treatment Place liquid aluminum isopropoxide in a vacuum reactor and concentrate it to a concentration of ≥95% under the conditions of vacuum degree 0.08-0.09 MPa and temperature 80-90°C.

[0008] Reasons for selecting vacuum degree: 0.08-0.09MPa can reduce the boiling point of aluminum isopropoxide and avoid decomposition caused by high temperature (aluminum isopropoxide is prone to disproportionation reaction above 150°C); Temperature control: 80-90℃ can not only accelerate the volatilization of water and low-boiling point impurities, but also maintain liquid fluidity, providing a uniform system for the subsequent addition of seed crystals and solvents.

[0009] 2. Addition of crystallization solvent 0.1-0.2% by weight of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (TXIB) was added to the concentrated liquid aluminum isopropoxide, and the mixture was mixed at a stirring rate of 150-200 rpm for 5-10 minutes.

[0010] The role of TXIB: As a low-volatility crystallization solvent (boiling point 280°C), it can reduce the cohesive force between aluminum isopropoxide molecules and promote crystal nucleation. The ester group in its molecular structure can form a weak coordination effect with the aluminum center of aluminum isopropoxide, guiding the directional growth of crystals. Addition amount limit: below 0.1% will result in insufficient nucleation effect, and above 0.2% will remain in the crystal and affect purity, so it is controlled at 0.1-0.2%.

[0011] 3. Addition of dual-function seed crystals Add a dual-functional seed system, including: Nano-sized aluminum isopropoxide seeds (particle size 50-100nm): The addition amount is 0.05-0.1% of the mass of liquid aluminum isopropoxide. Its surface is modified with octadecyltrichlorosilane to enhance its hydrophobicity, allowing it to be evenly dispersed in the system and provide homogeneous nucleation sites; Magnesium isopropoxide eutectic seed: The addition amount is 0.01-0.1%. It has a similar structure to aluminum isopropoxide (both are metal alkoxides), and can reduce the nucleation barrier through the heterogeneous nucleation effect, forming a synergistic effect with the nanocrystal seed.

[0012] 4. Gradient cooling solidification Control the temperature according to the following procedure: The first stage: cooling from 60°C to 25°C at a rate of 10°C / h (stage of large-scale crystal nucleation), stirring at a rate of 200 rpm to ensure uniform distribution of crystal nuclei; The second stage: cooling from 25 °C to 15 °C at a rate of 5 °C / h (crystal growth stage), and the stirring rate was reduced to 100 rpm to avoid excessive stirring that would cause crystal breakage.

[0013] The whole solidification time is ≤24 hours.

[0014] 5. Solid-liquid separation and post-processing Filtration: Use vacuum filtration (vacuum degree 0.07MPa) to separate the crystals and mother liquor; Washing: Wash the crystals with deionized water 2-3 times (5-10 minutes each time) to remove residual magnesium isopropoxide co-crystal seeds on the surface; Drying: Drying at a vacuum degree of 0.09-0.1 MPa and 100-120°C for 1.5-2.5 hours to obtain high-purity aluminum isopropoxide crystals.

[0015] Nanoscale aluminum isopropoxide seed crystals (50-100nm) have a crystal structure identical to the target product, with their surface atomic arrangement exceeding 90% lattice matching that of molten aluminum isopropoxide molecules. According to the "structural matching theory" of crystal growth, when the lattice spacing difference between the seed crystal surface and the melt molecules is ≤5%, the melt molecules rapidly adsorb to the seed crystal surface through van der Waals forces, forming a stable nucleus of critical size (approximately 2-5nm), reducing the nucleation barrier by 40%-50%.

[0016] After the surface is modified with octadecyltrichlorosilane, the hydrophobicity is enhanced, which can prevent the crystal seeds from agglomerating due to polarity and increase the number of effective nucleation sites by 3-5 times.

[0017] Magnesium isopropoxide and aluminum isopropoxide have similar molecular structures (both are metal alkoxides). The ionic radius of the aluminum and magnesium ions differ by only 15%, and the lattice constants match by 85%. According to heterogeneous nucleation theory, this structural similarity reduces the critical free energy for nucleation of melt molecules on the surface of the eutectic seed by 25%-30%, forming a "site complementarity" with the homogeneous seed. The nano-aluminum seeds provide high-density uniform sites, while the magnesium eutectic seeds break the thermodynamic stability of the localized supercooling zone. The two synergistically enhance the nucleation rate.

[0018] The ester group in the TXIB molecule can form a weak coordination bond with the aluminum center of aluminum isopropoxide. This coordination effect will not destroy the original structure of aluminum isopropoxide, but it can weaken the hydrogen bonding effect between its molecules, reduce the viscosity of the melt, increase the molecular diffusion coefficient, and accelerate the molecular accumulation on the surface of the crystal nucleus.

[0019] The steric hindrance of TXIB molecules allows them to selectively adsorb onto specific crystal faces of aluminum isopropoxide crystals (such as the (110) face), inhibiting the growth rate in that direction and promoting axial growth of the (001) face, thereby optimizing the crystal aspect ratio and reducing the probability of intercrystalline agglomeration. Furthermore, its high boiling point ensures that it does not volatilize throughout the solidification process, maintaining concentration stability.

[0020] Nucleation stage (60°C → 25°C, 10°C / h) According to the Arrhenius equation, the diffusion activation energy of aluminum isopropoxide molecules is low at 60°C, making it suitable for rapid nucleation. Cooling at a rate of 10°C / h maintains the system in a "metastable supercooling state," avoiding uneven nucleation caused by excessive supercooling. The shear force generated by stirring at 200 rpm evenly disperses the newly formed nuclei, preventing localized accumulation.

[0021] Crystal growth stage (25℃→15℃, 5℃ / h) After the temperature drops to 25°C, the molecular diffusion rate decreases. At this time, slow cooling at 5°C / h can make the crystals grow in a thermodynamic equilibrium state and reduce defects (such as vacancies and dislocations); the stirring rate is reduced to 100 rpm to avoid crystal breakage caused by high shear force, while ensuring the uniform diffusion of solutes in the mother liquor to the crystal surface, so that the particle size distribution CV value is controlled within 15%.

[0022] The present invention has the following beneficial effects compared to the prior art: 1. Through the synergistic effect of dual-functional seed crystals and TXIB, the solidification time is shortened from the traditional 10-15 days to less than 24 hours, and the equipment turnover rate is increased by more than 6 times; 2. After washing and drying, the product has high purity, meeting the requirements of high-end electronic-grade alumina precursor; the particle size distribution D90 ≤ 100μm, CV value (coefficient of variation) ≤ 15%, no agglomeration phenomenon, and the uniformity of alumina particles prepared by subsequent calcination is improved; 3. Precise control of gradient cooling and stirring rate minimizes fluctuations in product purity between batches. TXIB's low volatility (boiling point 280°C) avoids concentration fluctuations caused by solvent volatilization, solving the problem of insufficient active ingredients in existing solvent methods. 4. Due to the shortened coagulation time, the energy consumption per ton of product is reduced, the mother liquor can be recycled and concentrated, and the raw material loss rate is reduced. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the present invention belong. If the definitions set forth in this section are contrary to or otherwise inconsistent with definitions set forth in the patents, patent applications, published patent applications, and other publications incorporated herein by reference, the definitions listed in this section take precedence over the definitions incorporated herein by reference.

[0025] Unless otherwise specified, the methods used in the following examples are conventional methods. The materials, reagents, and instruments used are conventional materials, reagents, and instruments in the art, unless otherwise specified, and can be obtained commercially by those skilled in the art.

[0026] When an amount, concentration or other value or parameter is expressed as a range, a preferred range or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any upper range limit or preferred value with any lower range limit or preferred value, regardless of whether the range is disclosed alone. For example, when a range "1 to 5" is disclosed, the described range should be interpreted as including the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within the range. In the present specification and claims, range definitions may be combined and / or interchanged, and if not otherwise stated, such ranges include all subranges contained therein.

[0027] Example 1 1. Raw materials and equipment preparation TXIB: analytical grade, purity 99.5%; Nano-aluminum isopropoxide seed crystal raw materials: solid aluminum isopropoxide (99.9%, particle size ≥100 μm), cyclohexane (analytical grade), Triton X-100 (chemically pure), octadecyltrichlorosilane (97%); Equipment: 5L vacuum reactor, laser particle size analyzer, gas chromatograph.

[0028] 2. Preparation of Nano-aluminum Isopropylate Seeds (1) Preparation of microemulsion: Add 800 g of cyclohexane and 200 g of Triton X-100 (mass ratio 4:1) into a 2 L beaker and stir magnetically at 30 °C for 30 min until transparent. The total volume is about 1.216 L. (2) Seed crystal synthesis: Take 9.7 g of solid aluminum isopropoxide, add it to 100 mL of cyclohexane, stir and dissolve it, pour it directly into the above microemulsion, and stir for 10 minutes to make the system uniform (at this time, the concentration of aluminum isopropoxide in the microemulsion is 8 g / L); (3) Modification treatment: add 0.078 g of octadecyltrichlorosilane (0.8% by mass of aluminum isopropoxide), heat to 60 °C, and react with mechanical stirring (200 rpm) for 2 h; (4) Post-treatment: The reaction solution was centrifuged at 3000 rpm for 10 min, the precipitate was washed three times with anhydrous ethanol, dried under vacuum at 60 °C for 4 h, and ground through a 200 mesh sieve to obtain modified seed crystals with a particle size of 80 nm.

[0029] 3. Preparation of magnesium isopropoxide co-crystal seeds (1) Synthesis of magnesium isopropoxide: Add 10 g of magnesium powder and 200 mL of isopropanol into a 500 mL three-necked flask, and reflux at 80 °C for 4 h under nitrogen protection to obtain a magnesium isopropoxide-isopropanol solution; (2) Loading treatment: 10 g of nano-silica was added to the above solution, stirred at 50 °C for 2 h, and the isopropanol was removed by vacuum distillation to obtain a co-crystal with a loading of 5% (ICP detection of magnesium content of 5.2%).

[0030] 4. Rapid solidification process (1) Concentration treatment: Add 1000 g of liquid aluminum isopropoxide into a 5 L vacuum reactor, set the vacuum degree to 0.085 MPa, the temperature to 85 °C, and concentrate at 100 rpm for 3 h. The concentration of the sample was 96%; (2) Addition of co-crystallization solvent: Cool to 60°C, add 1.0 g of TXIB (0.11%), and stir at 180 rpm for 8 min; (3) Seed addition: first add 0.6 g of nanocrystal seeds, stir for 5 min, then add 0.05 g of co-crystal seeds and continue stirring for 3 min; (4) Gradient cooling: 60°C → 25°C (10°C / h, 200 rpm) → 15°C (5°C / h, 100 rpm), total time 22 h; (5) Post-treatment: vacuum filtration (0.07 MPa), washing with 500 mL of deionized water three times, and vacuum drying at 110 °C for 2 h to obtain 880 g of the finished product.

[0031] 5. Test results Purity: 99.7% (GC detection); Particle size: D90 = 85 μm, CV value 12% (laser particle size analyzer); Crystal form: In the diffraction pattern of the obtained aluminum isopropoxide crystals, the position, intensity and peak shape of each characteristic peak are completely consistent with the characteristics of the standard crystal form of aluminum isopropoxide, and no impurity peaks appear.

[0032] Example 2 This embodiment is based on the first embodiment, except that: In the preparation of co-crystal seeds, starch microspheres were used instead of nano-silica, and the starch microspheres were pretreated: starch microspheres (60 μm) were pretreated with 0.1 mol / L hydrochloric acid for 15 min.

[0033] During rapid solidification, the post-treatment is as follows: the crystals are washed with 800 mL of deionized water three times (stirring for 10 minutes each time) and vacuum dried at 120°C for 2.5 hours.

[0034] Test results: Residual magnesium: 8ppm (ICP-MS); Purity: 99.9%, no impurity peaks in XRD.

[0035] Example 3 This embodiment is based on the embodiment 1, but differs in that: In the preparation of nano-aluminum isopropoxide seed crystals, the feeding amount of the first coexistence rate is 6.1 g, corresponding to an aluminum isopropoxide concentration of 5 g / L in the microemulsion.

[0036] Results: Seed particle size 95nm, solidification time 23h, D90=92μm.

[0037] Example 4 This embodiment is based on the embodiment 1, but differs in that: In the preparation of nano-aluminum isopropoxide seed crystals, the feeding amount of a coexistence rate is 12.2 g, corresponding to an aluminum isopropoxide concentration of 10 g / L in the microemulsion.

[0038] Results: Seed particle size 75nm, solidification time 21h, D90=80μm.

[0039] Comparative Example 1 This comparative example is based on Example 1, except that: In the entire rapid solidification process, the addition of TXIB was omitted, and the other steps were the same as in Example 1.

[0040] Results: Coagulation time 40h, D90=150μm.

[0041] Comparative Example 2 This comparative example is based on Example 1, except that: In the entire rapid solidification process, the addition of eutectic seeds was omitted and only nanocrystal seeds were added. The other steps were the same as in Example 1.

[0042] Results: Coagulation time 32h, D90=120μm.

[0043] The performance characterization tests were performed on the aluminum isopropoxides prepared in the above different embodiments and comparative examples, and the solidification and crystallization times were calculated, and the results were shown in the following table:

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for rapid solidification of aluminum isopropoxide, characterized in that: The steps include: (1) Concentration treatment: Concentrate the liquid aluminum isopropoxide to a concentration of ≥95% under vacuum conditions of 0.08-0.09 MPa and temperature of 80-90°C; (2) Addition of a co-crystallizing solvent: Add 0.1-0.2% by weight of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate to the concentrated liquid aluminum isopropoxide and mix at a stirring rate of 150-200 rpm for 5-10 minutes; (3) Adding bifunctional seed crystals: adding a bifunctional seed crystal system, wherein the bifunctional seed crystal system includes aluminum isopropoxide seeds with a particle size of 50-100 nm and magnesium isopropoxide co-crystals, wherein the addition amount of nano-sized aluminum isopropoxide seeds is 0.05-0.1%, and the addition amount of magnesium isopropoxide co-crystals is 0.01-0.1% of the mass of liquid aluminum isopropoxide; (4) Gradient cooling solidification: control the temperature to drop from 60°C to 25°C at a rate of 10°C / h, and then drop to 15°C at a rate of 5°C / h. The whole crystallization time is ≤24 hours; (5) Solid-liquid separation: The solidified product is filtered to obtain aluminum isopropoxide crystals.

2. The method for rapid solidification of aluminum isopropoxide according to claim 1, wherein: In step (3), the nano-scale aluminum isopropoxide seeds are prepared by a microemulsion method, specifically comprising: adding aluminum isopropoxide and 0.5-1% by mass of octadecyltrichlorosilane to a microemulsion system composed of cyclohexane and Triton X-100, reacting at 60-70° C. for 1.5-2.5 hours, and obtaining surface-modified nano-crystal seeds after drying.

3. The method for rapid solidification of aluminum isopropoxide according to claim 2, characterized in that: In the microemulsion system, the mass ratio of cyclohexane to Triton X-100 is 3:1-5:1, and the concentration of aluminum isopropoxide in the microemulsion is 5-10 g / L.

4. The method for rapid solidification of aluminum isopropoxide according to claim 1, wherein: In step (2), the 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate is added by preheating the 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate to 40-50° C. and adding the mixture dropwise to the liquid aluminum isopropoxide while stirring the mixture.

5. The method for rapid solidification of aluminum isopropoxide according to claim 1, wherein: In step (4), the stirring rate is controlled to be 200 rpm during the stage when the temperature drops from 60°C to 25°C; and the stirring rate is controlled to be 100 rpm during the stage when the temperature drops from 25°C to 15°C.

6. The method for rapid solidification of aluminum isopropoxide according to claim 1, wherein: After step (5), a post-treatment step is also included: the filtered aluminum isopropoxide crystals are washed with deionized water 2-3 times, each washing time is 5-10 minutes, to remove the co-crystal seeds remaining on the surface.

7. The method for rapid solidification of aluminum isopropoxide according to claim 6, wherein: The washed aluminum isopropoxide crystals are dried under vacuum conditions of 0.09-0.1 MPa and a temperature of 100-120° C. for 1.5-2.5 hours.

8. The method for rapid solidification of aluminum isopropoxide according to claim 1, wherein: In step (3), the magnesium isopropoxide co-crystal seed is a loaded co-crystal seed, specifically, magnesium isopropoxide is loaded on nano-silica or starch microspheres, with a loading amount of 3-8%.

9. The method for rapid solidification of aluminum isopropoxide according to claim 8, wherein: The starch microspheres have a particle size of 30-70 μm and are pretreated with a 0.1 mol / L hydrochloric acid solution for 10-15 minutes before being loaded with magnesium isopropoxide.

10. The method for rapid solidification of aluminum isopropoxide according to claim 1, wherein: In step (1), the concentration treatment time is 2-3 hours, and nitrogen protection is introduced during the concentration process, and the nitrogen flow rate is 0.5-1 L / min.

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