A method for preparing butyl hafnate from hafnium chloride

Abstract

The application provides a method for preparing butyl hafnate from hafnium tetrachloride. The method comprises the following steps: (1) adding n-butanol and an organic solvent into a reaction kettle under the protection of inert gas, and then adding hafnium tetrachloride to obtain an initial reaction system; (2) adding a hafnium-based organometallic framework catalyst into the initial reaction system, heating to 40-65 DEG C, controlling the reaction pressure to be 0.1-0.3 MPa, and stirring for 3-8 h to obtain an esterification reaction liquid; (3) cooling the esterification reaction liquid to 20-30 DEG C, separating the solid components in the system by pressure filtration to obtain a filtrate; and (4) sequentially performing normal pressure distillation, vacuum rectification and precision filtration on the filtrate to obtain butyl hafnate. By using the hafnium-based catalyst, the reaction efficiency and product purity of butyl hafnate prepared from hafnium tetrachloride are improved, and the side reaction and equipment corrosion are effectively inhibited. The method has mild process conditions and is suitable for industrial large-scale production of butyl hafnate.

Description

Technical Field

[0001] This invention relates to the field of organometallic compound preparation technology, and specifically to a method for preparing hafnium butyl ester from hafnium tetrachloride. Background Technology

[0002] Hafnium butyl ester, chemically known as tetra(butoxy)hafnium, has the molecular formula C2. 16 H 36 HfO4, with a relative molecular mass of 470.94, is an important organohafnium compound. As a precursor for ultra-high temperature ceramics, electronic thin film materials, and fine chemical intermediates, butyl hafnium oxide is widely used in high-end fields such as the preparation of ultra-high temperature ceramic matrix composites for aerospace, high-K dielectric thin film deposition for integrated circuits, modification of solid electrolytes for lithium-ion batteries, and synthesis of nano-hafnium oxide powder. With the rapid development of the electronics and information industry and the new energy industry, the market demand for high-purity, high-yield butyl hafnium oxide continues to rise, especially with increasingly stringent requirements for controlling the content of chlorine and metal impurities in the product.

[0003] Currently, the mainstream industrial process for preparing butyl hafnium chloride is the direct esterification reaction of hafnium tetrachloride (HfCl4) with n-butanol (C4H9OH). This process has the advantages of readily available raw materials and a simple reaction route, but it also suffers from numerous technical bottlenecks, severely restricting the improvement of product quality and production efficiency. The main shortcomings of the existing technology are as follows:

[0004] First, the reaction efficiency is low and side reactions are severe. The reaction of hafnium tetrachloride with n-butanol generates a large amount of hydrogen chloride (HCl) as a byproduct. HCl not only undergoes substitution reactions with n-butanol to produce byproducts such as chlorobutane, reducing the selectivity of the target product, but also increases the acidity of the reaction system, causing partial hydrolysis of butyl hafnium acid ester to generate impurities such as butyl hydroxyhafnium acid ester and hafnium oxide, further reducing product purity and yield. To suppress side reactions, traditional processes typically use vacuum removal to remove HCl. However, the vacuum process can trap some n-butanol feedstock, increasing feedstock loss. Furthermore, the strong corrosiveness of HCl can severely damage reaction equipment, shortening its lifespan and increasing production costs.

[0005] Secondly, the reaction suffers from poor mass and heat transfer, and a long reaction cycle. Existing processes often employ batch-type batch reactors, resulting in uneven mixing of the reaction system and high mass transfer resistance. This leads to incomplete reaction between hafnium tetrachloride and n-butanol, typically requiring a long reaction time (8-12 hours) to achieve a certain conversion rate, resulting in low production efficiency. Furthermore, the limited heat transfer in batch reactors easily leads to excessively high local temperatures, exacerbating side reactions and further affecting product quality stability.

[0006] Third, the separation and purification of the product is difficult, and the purity is hard to meet. In traditional processes, the separation of reaction products from solvents, byproducts, and unreacted raw materials mainly relies on distillation and centrifugation. However, because the boiling points of byproducts and target products are similar, the separation efficiency is low, resulting in product purity that cannot meet the requirements of high-end fields. In particular, the chlorine impurity content is difficult to control below 0.10% by weight, and the content of metal impurities (such as iron, aluminum, silicon, etc.) is also prone to exceeding the index requirements, limiting the application of hafnium butyl ester in fields such as integrated circuits and high-end ceramics.

[0007] Fourth, the catalyst performance is insufficient, failing to balance efficiency and selectivity. In existing processes, some researchers have attempted to optimize the reaction using Lewis acid catalysts (such as aluminum trichloride and zinc chloride) or basic catalysts (such as pyridine and triethylamine). However, Lewis acid catalysts further exacerbate the corrosive effect of HCl, while basic catalysts readily react with HCl to generate salt impurities, increasing the difficulty of separation. Furthermore, these traditional catalysts have single active sites and small specific surface areas, failing to effectively activate the reaction sites of hafnium tetrachloride and n-butanol, making it difficult to simultaneously improve reaction efficiency, selectivity, and yield. Moreover, the catalysts are difficult to recover and reuse, resulting in resource waste and environmental pollution.

[0008] To address the problems of low reaction efficiency, numerous side reactions, insufficient product purity, and poor catalyst performance in existing processes, a highly efficient and selective method for preparing hafnium butyl ester is developed. This method aims to achieve a synergistic improvement in reaction efficiency, product quality, and production economics, and has significant industrial value and application prospects. Summary of the Invention

[0009] Based on the technical problems described above, the purpose of this invention is to overcome the defects of the prior art in the preparation of butyl hafnium ester from hafnium tetrachloride and n-butanol, such as low reaction efficiency, many side reactions, insufficient product purity and poor catalyst performance. By adopting a new hafnium-based organometallic framework catalyst, the invention achieves efficient catalysis, side reaction suppression and high-purity product preparation, improves yield and selectivity, reduces equipment corrosion and raw material loss, thereby improving production economy and environmental friendliness.

[0010] Specifically, according to one aspect of the present invention, a method for preparing butyl hafnium chloride from hafnium tetrachloride is provided, the method comprising the following steps:

[0011] (1) Under the protection of an inert gas, n-butanol and an organic solvent are added to a reaction vessel and stirred until homogeneous. Then, hafnium tetrachloride is added to obtain an initial reaction system, wherein: the organic solvent is one or more of n-heptane, petroleum ether and xylene; the weight ratio of hafnium tetrachloride to n-butanol is 1:2.5-1:4.5; and the weight ratio of the organic solvent to n-butanol is 0.8:1-1.5:1;

[0012] (2) Add hafnium-based organometallic framework catalyst to the initial reaction system obtained in step (1), heat to 40-65℃, control the reaction pressure to 0.1-0.3 MPa, stir the reaction for 3-8 h to obtain esterification reaction solution. The hafnium-based organometallic framework catalyst is hafnium tetrachloride-2,6-naphthalenedicarboxylic acid-coordinated organometallic framework catalyst, and the weight ratio of the added hafnium-based organometallic framework catalyst to the hafnium tetrachloride added in step (1) is 0.8:1-2:1.

[0013] (3) Cool the esterification reaction solution obtained in step (2) to 20-30℃, and separate the solid components in the system by pressure filtration to obtain the filtrate;

[0014] (4) The filtrate obtained in step (3) is subjected to atmospheric distillation, vacuum distillation and precision filtration in sequence to obtain hafnium butyl ester.

[0015] According to certain preferred embodiments of the present invention, the method further includes a raw material pretreatment step before step (1), wherein hafnium tetrachloride is dried to control the moisture content ≤0.5% by weight, and n-butanol is purified by distillation to control the purity of the purified n-butanol ≥99.8% by weight and the moisture content ≤0.1% by weight.

[0016] According to certain preferred embodiments of the present invention, the drying conditions for hafnium tetrachloride are as follows: drying at a vacuum of 0.08-0.1 MPa and a temperature of 80-120°C for 2-4 h; the distillation purification of n-butanol is carried out using a packed distillation column with 20-30 theoretical plates, a reflux ratio of 3:1-5:1, and a distillation temperature of 117-118°C.

[0017] According to certain preferred embodiments of the present invention, in step (1), hafnium tetrachloride is added slowly during the addition process, the system temperature is maintained at 15-25°C during the addition process, and stirring is continued for 10-30 min after the addition is completed to obtain the initial reaction system.

[0018] According to certain preferred embodiments of the present invention, in step (3), the filtration pressure of the pressurized filtration is 0.3-0.6 MPa, the filter medium is a ceramic membrane, and the pore size of the ceramic membrane is 0.1-0.5 μm.

[0019] According to certain preferred embodiments of the present invention, in step (1), the inert gas is nitrogen or argon, and the inert gas protection is implemented by: evacuating the reactor to 0.05-0.12 MPa, introducing the inert gas, repeating the evacuation-introduction operation 3-6 times, and then continuously introducing the inert gas to maintain the inert atmosphere inside the reactor.

[0020] According to certain preferred embodiments of the present invention, the hafnium-based organometallic framework catalyst is prepared by a method comprising the following steps:

[0021] (a) Hafnium tetrachloride was added to N,N-dimethylformamide and ultrasonically dispersed at 25-40°C for 10-30 minutes to obtain a hafnium source solution;

[0022] (b) Add 2,6-naphthalenedicarboxylic acid to the hafnium source solution and continue stirring for 20-60 minutes until dissolved to obtain a mixed precursor solution;

[0023] (c) Add acetic acid to the mixed precursor solution while stirring, and adjust the pH to 3.5-5.5 to obtain the final precursor solution;

[0024] (d) The final precursor solution is placed in a closed reaction vessel and reacted at 100-150°C for 12-36 hours. After the reaction is completed, the mixture is cooled to obtain a precipitate mixture.

[0025] (e) The precipitate mixture is filtered, the solid precipitate is collected, and the solid precipitate is washed and then dried under vacuum at 80-120°C for 8-16 hours to obtain the hafnium-based organometallic framework catalyst, wherein:

[0026] Based on the total weight of hafnium tetrachloride and 2,6-naphthalenedicarboxylic acid as 100%, hafnium tetrachloride accounts for 55-65% and 2,6-naphthalenedicarboxylic acid accounts for 35-45%; and the ratio of the total weight of hafnium tetrachloride and 2,6-naphthalenedicarboxylic acid to the weight of N,N-dimethylformamide is in the range of 1:10 to 3:10.

[0027] According to certain preferred embodiments of the present invention, in step (d), the final precursor solution is placed in a closed reaction vessel and reacted at 120-140°C for 12-36 hours. After the reaction is completed, the mixture is cooled to obtain the precipitate mixture.

[0028] According to certain preferred embodiments of the present invention, in step (e), the solid precipitate is washed 3-5 times with N,N-dimethylformamide and anhydrous ethanol, and then dried at 80-120°C and under vacuum of -0.08 to -0.1 MPa for 8-16 hours to obtain the hafnium-based organometallic framework catalyst.

[0029] According to certain preferred embodiments of the present invention, in step (e), the drying is carried out for 10-14 hours at 100-110°C and a vacuum of -0.09 to -0.1 MPa.

[0030] According to certain preferred embodiments of the present invention, the sealed reaction vessel is a reaction vessel with a polytetrafluoroethylene liner.

[0031] According to certain preferred embodiments of the present invention, the hafnium-based organometallic framework catalyst has a specific surface area of ​​1000-2500 m². 2 / g.

[0032] According to certain preferred embodiments of the present invention, the average particle size of the hafnium-based organometallic framework catalyst is in the range of 50 nm to 2 μm.

[0033] According to certain preferred embodiments of the present invention, the weight ratio of the hafnium-based organometallic framework catalyst added in step (2) to the hafnium tetrachloride added in step (1) is 1.2:1-1.5:1.

[0034] According to certain preferred embodiments of the present invention, in step (3), after the pressure filtration, the solid components obtained by filtration are washed 2-3 times with the treated n-butanol, and the washing liquid is incorporated into the filtrate.

[0035] According to certain preferred embodiments of the present invention, in step (4), the conditions for atmospheric distillation are: distillation temperature 90-120℃, distillation time 2-3 h, theoretical plate number of the distillation column 15-20, and reflux ratio 2:1-3:1.

[0036] According to certain preferred embodiments of the present invention, in step (4), the conditions for vacuum distillation are: vacuum degree 0.09-0.095 MPa, distillation temperature 140-160℃, distillation time 4-6 h, theoretical plate number of vacuum distillation column is 30-40, and reflux ratio is 4:1-6:1.

[0037] According to certain preferred embodiments of the present invention, in step (4), the precision filtration is performed using an ultrafiltration membrane, wherein the ultrafiltration membrane has a molecular weight cutoff of 500-1000 Da and a filtration pressure of 0.2-0.4 MPa.

[0038] Compared with existing technologies, the beneficial effects of this invention are as follows: First, the hafnium-based organometallic framework catalyst used exhibits excellent catalytic activity and selectivity, significantly shortening reaction time, improving reaction conversion rate and product selectivity, while suppressing side reactions. Second, the catalyst possesses a porous structure, enhancing the mass transfer efficiency of the reaction system and facilitating the adsorption of hydrogen chloride generated during the reaction, significantly reducing equipment corrosion and the risk of product hydrolysis. Furthermore, the optimized overall process conditions are mild, highly adaptable to raw material purity, and produce high-purity products with low impurity content, meeting the needs of high-end applications and facilitating large-scale, environmentally friendly industrial production. Attached Figure Description

[0039] The accompanying drawings are provided in this specification to more clearly explain the technical solutions of the present invention; however, the art is not limited thereto.

[0040] Figure 1 A process flow diagram for preparing butyl hafnium chloride from hafnium tetrachloride according to the present invention is shown;

[0041] Figure 2 A scanning electron microscope (SEM) image of the hafnium tetrachloride-2,6-naphthalenedicarboxylic acid-coordinated organometallic framework catalyst prepared in Preparation Example 1 is shown.

[0042] Figure 3 The X-ray diffraction (XRD) pattern of the hafnium tetrachloride-2,6-naphthalenedicarboxylic acid-coordinated organometallic framework catalyst prepared in Preparation Example 1 is shown. Detailed Implementation

[0043] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It will be understood that other embodiments may be implemented without departing from the scope or spirit of the invention. Therefore, the following detailed description is non-limiting.

[0044] Unless otherwise specified, all figures used in this specification to represent characteristic dimensions, quantities, and physical properties should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters listed in the foregoing specification are approximations, and those skilled in the art can appropriately modify these approximations to obtain the desired properties using the teachings disclosed herein.

[0045] As mentioned above, the existing process for preparing butyl hafnium chloride by esterification of hafnium tetrachloride and n-butanol has the following problems: low reaction efficiency, severe side reactions leading to poor product selectivity; the generated hydrogen chloride byproduct causing severe equipment corrosion and initiating product hydrolysis; poor mass and heat transfer in traditional batch reactors, resulting in long production cycles; insufficient activity and selectivity of traditional catalysts (such as Lewis acids or bases), and the inability to recover them, easily causing pollution; and difficulty in separating and purifying the final product, with high chlorine impurity content, making it difficult to meet the requirements for high-purity applications. This invention aims to solve these problems.

[0046] Metal-organic frameworks (MOFs), as a novel class of porous crystalline materials, are formed by the self-assembly of inorganic metal ions or metal clusters and organic ligands through coordination bonds. They possess excellent properties such as highly ordered pore structures, tunable pore sizes, large specific surface areas, and good chemical stability. Among them, hafnium-based MOFs show great potential in the field of catalysis due to the high coordination number, strong coordination ability, and good chemical stability of hafnium ions. The porous structure of hafnium-based MOFs provides sufficient active sites, enabling the enrichment of reactant molecules and efficient mass transfer; the hafnium ion active centers in their framework can activate reactant molecules through coordination interactions, lowering the activation energy of the reaction; simultaneously, organic ligands can regulate catalytic activity and selectivity through electronic effects and steric hindrance effects, achieving the control of target reactions. Currently, there are no reports on the application of hafnium-based organometallic framework catalysts in the reaction of hafnium tetrachloride and n-butanol to prepare butyl hafnium acid ester. This invention is the first to develop hafnium-based organometallic framework materials as dedicated catalysts for the synthesis of butyl hafnium acid ester. This catalyst, through its unique pore structure, the synergistic effect of hafnium active centers and organic ligands, achieves efficient activation of reactants, enhanced mass transfer, and effective suppression of side reactions. This improves reaction efficiency and product purity while solving problems such as catalyst recovery and equipment corrosion.

[0047] Specifically, this invention provides a highly efficient and selective method for preparing high-purity butyl hafnium chloride from hafnium tetrachloride. The core of this method lies in the first-time development of a specific hafnium-based organometallic framework (Hf-MOF) material as a dedicated catalyst, applied to the esterification reaction of hafnium tetrachloride and n-butanol. Combined with optimized raw material pretreatment, reaction engineering, and product separation and purification processes, this method synergistically solves the technical bottlenecks in existing technologies, such as low reaction efficiency, numerous byproducts, severe equipment corrosion, and insufficient product purity.

[0048] Figure 1 A process flow diagram for preparing butyl hafnium chloride from hafnium tetrachloride according to the present invention is shown, including:

[0049] (1) Under the protection of an inert gas, n-butanol and an organic solvent were added to the reactor, followed by the addition of hafnium tetrachloride to obtain the initial reaction system;

[0050] (2) Add hafnium-based organometallic framework catalyst to the initial reaction system, heat to 40-65℃, control the reaction pressure at 0.1-0.3 MPa, stir the reaction for 3-8 h to obtain esterification reaction solution;

[0051] (3) Cool the esterification reaction solution to 20-30℃, and separate the solid components in the system by pressure filtration to obtain the filtrate;

[0052] (4) The filtrate was subjected to atmospheric distillation, vacuum distillation and precision filtration in sequence to obtain hafnium butyl ester.

[0053] Specifically, the method of the present invention mainly includes the following steps: (1) establishing a protected initial reaction system; (2) catalyzing esterification reaction; (3) solid-liquid separation; and (4) product purification. Optionally, a raw material pretreatment step may be included before step (1).

[0054] Specifically, according to one aspect of the present invention, a method for preparing butyl hafnium chloride from hafnium tetrachloride is provided, the method comprising the following steps:

[0055] (1) Under the protection of an inert gas, n-butanol and an organic solvent are added to a reaction vessel and stirred until homogeneous. Then, hafnium tetrachloride is added to obtain an initial reaction system, wherein: the organic solvent is one or more of n-heptane, petroleum ether and xylene; the weight ratio of hafnium tetrachloride to n-butanol is 1:2.5-1:4.5; and the weight ratio of the organic solvent to n-butanol is 0.8:1-1.5:1;

[0056] (2) Add hafnium-based organometallic framework catalyst to the initial reaction system obtained in step (1), heat to 40-65℃, control the reaction pressure to 0.1-0.3 MPa, stir the reaction for 3-8 h to obtain esterification reaction solution. The hafnium-based organometallic framework catalyst is hafnium tetrachloride-2,6-naphthalenedicarboxylic acid-coordinated organometallic framework catalyst, and the weight ratio of the added hafnium-based organometallic framework catalyst to the hafnium tetrachloride added in step (1) is 0.8:1-2:1.

[0057] (3) Cool the esterification reaction solution obtained in step (2) to 20-30℃, and separate the solid components in the system by pressure filtration to obtain the filtrate;

[0058] (4) The filtrate obtained in step (3) is subjected to atmospheric distillation, vacuum distillation and precision filtration in sequence to obtain hafnium butyl ester.

[0059] According to the technical solution of the present invention, the method further includes a raw material pretreatment step before step (1). Hafnium tetrachloride (HfCl4) is hygroscopic, and moisture may trigger its hydrolysis, generating impurities such as hafnium oxychloride. This not only consumes the raw material but also increases the acidity of the system, exacerbates equipment corrosion, and promotes the hydrolysis side reaction of the product butyl hafnium ester. Therefore, it is preferable to dry the hafnium tetrachloride (HfCl4) raw material. It is preferable to dry it for 2-4 hours under vacuum conditions of 0.08-0.1 MPa and temperature of 80-120°C. This mild vacuum thermal drying condition can effectively remove physically adsorbed water and some crystal water, controlling the moisture content to no more than 0.05% by weight (more preferably ≤0.03% by weight).

[0060] In addition, n-butanol may contain water, other alcohols, and trace amounts of aldehydes, ketones, and other impurities. Water may participate in side reactions, and other organic impurities may enter the final product. Packed distillation columns are preferred for purifying n-butanol. By controlling the number of theoretical plates (20-30), the reflux ratio (3:1-5:1), and the distillation temperature (117-118℃), impurities can be efficiently separated, yielding high-purity butanol with a purity ≥99.8% by weight and a water content ≤0.1% by weight.

[0061] In step (1), preferably, the reactor is first evacuated to 0.05-0.12 MPa, and then inert gas is introduced to atmospheric pressure or a slightly positive pressure. This process is repeated 3-6 times. This "vacuum-induction" cycle can efficiently replace the air inside the reactor, reducing the oxygen and moisture content to extremely low levels (typically <10 ppm). Subsequently, a small amount of inert gas is continuously introduced to maintain a slightly positive pressure and prevent air backflow.

[0062] The organic solvent is one or more of n-heptane, petroleum ether (60-90℃ fraction), and xylene. These solvents share the following characteristics: (a) they have good solubility or dispersibility for both hafnium tetrachloride and n-butanol, but do not participate in the reaction; (b) they have moderate boiling points, facilitating subsequent distillation separation; and (c) they are chemically stable and do not react with reactants, products, or catalysts under reaction conditions. Their main functions are to dilute reactants, adjust the viscosity of the reaction system, improve mass and heat transfer, and act as azeotropic agents to assist in the removal of some of the HCl generated in the reaction. The weight ratio of organic solvent to n-butanol is 0.8:1 to 1.5:1. Within this ratio range, the system exhibits good fluidity and dispersibility. If the solvent is too small (e.g., 0.5:1), the system viscosity increases, mass transfer deteriorates, potentially leading to excessively high local concentrations, increased side reactions, and decreased yield and purity; if the solvent is too large, equipment utilization decreases, and subsequent separation energy consumption increases.

[0063] In step (1), the weight ratio of hafnium tetrachloride to n-butanol is 1:2.5 to 1:4.5. This ratio is based on the theoretical stoichiometry (approximately 1:2.9) of the reaction equation HfCl4 + 4C4H9OH → Hf(OC4H9)4 + 4HCl, with an appropriate margin. Excess n-butanol helps to shift the reaction equilibrium to the right, increasing the conversion rate of hafnium tetrachloride and neutralizing some of the generated HCl, thus reducing corrosion. However, excessive excess (e.g., >1:4.5) reduces economic efficiency and increases the recovery load. If the ratio is too low (e.g., 1:2.0), insufficient n-butanol leads to incomplete reaction, significantly reduced yield, and unreacted HfCl4 may form other hafnium oxychloride species, increasing impurities. When adding hafnium tetrachloride, it is preferable to add it slowly and control the system temperature at 25-35°C to avoid local overheating and side reactions caused by rapid feeding and exothermic reactions. After adding the material, continue stirring for 10-30 minutes to ensure a uniform suspension or solution system is formed.

[0064] In step (2), a highly efficient and selective conversion was achieved by introducing a specific Hf-MOF catalyst and reacting under optimized conditions.

[0065] The catalyst used in this invention is a hafnium tetrachloride-2,6-naphthalenedicarboxylic acid-coordinated organometallic framework catalyst. This catalyst is a crystalline porous material formed by self-assembly of hafnium tetrachloride as the metal source and 2,6-naphthalenedicarboxylic acid as the organic linker via a hydrothermal / solvothermal method.

[0066] The characteristics of hafnium tetrachloride-2,6-naphthalenedicarboxylic acid-coordinated organometallic framework catalysts are:

[0067] 1. The BET specific surface area of ​​the catalyst can reach 1000-2500 m². 2 / g. The large specific surface area provides abundant adsorption sites and diffusion channels for reactant molecules (HfCl4, C4H9OH), improving mass transfer efficiency and solving the problem of uneven mixing in traditional batch reactors.

[0068] 2. Hafnium ions (Hf) in the framework 4+ As the Lewis acid active center, it can effectively activate the hydroxyl oxygen atom of n-butanol and / or the hafnium center in hafnium tetrachloride, reducing the activation energy of the esterification reaction and thus accelerating the reaction.

[0069] 3. The 2,6-naphthalenedicarboxylic acid ligand has a large conjugated system and a rigid structure. Its steric hindrance and electronic effects can modulate the electron density and pore microenvironment of the hafnium center, stabilize the reaction transition state, and to a certain extent inhibit the formation of large byproducts such as chlorobutane through steric confinement, thereby improving the selectivity of the target product.

[0070] 4. The porous structure of MOF materials can physically adsorb the reaction byproduct HCl. This "in-situ capture" effect can effectively reduce the concentration of free HCl in the reaction solution, thereby: inhibiting the further reaction of HCl with n-butanol to form chlorobutane; reducing the acidity of the reaction system and lowering the risk of hydrolysis of butyl hafnium ester under acidic conditions (forming butyl hydroxyhafnium ester, etc.); mitigating the corrosion of the reaction vessel (especially the metal parts) by HCl and extending the equipment life.

[0071] The specific preparation method of hafnium tetrachloride-2,6-naphthalenedicarboxylic acid-coordination organometallic framework catalyst can refer to the methods described in existing technical literature (e.g., New Data on the Reactions of Zirconium and Hafnium Tetrachlorides with Aliphatic Acids, Victor D. Makhaev et al., Compounds, 2024, 4, 338–350).

[0072] For example, hafnium tetrachloride-2,6-naphthalenedicarboxylic acid-coordinated organometallic framework catalysts can be prepared by the following steps:

[0073] Steps (a)-(b) involve the preparation of the precursor solution, wherein hafnium tetrachloride is ultrasonically dispersed in N,N-dimethylformamide (DMF) at 25-40°C to form a homogeneous hafnium source solution. Subsequently, 2,6-naphthalenedicarboxylic acid is added and stirred to dissolve. The ratio of metal source to ligand (by total weight, HfCl4 accounts for 55-65%, and ligand accounts for 35-45%) is a crucial factor determining the MOF framework composition and structural stability. The ratio of the total weight of hafnium tetrachloride and 2,6-naphthalenedicarboxylic acid to the weight of N,N-dimethylformamide is between 1:10 and 3:10; this concentration range is conducive to ordered crystal growth and obtaining a highly crystalline product.

[0074] Step (c) involves pH adjustment, wherein acetic acid is added to adjust the pH to a weakly acidic range of 3.5–5.5. This acidic environment helps suppress the vigorous hydrolysis of hafnium ions, promoting their controlled coordination with ligands to form crystals rather than amorphous precipitates.

[0075] Step (d) involves a solvothermal reaction, wherein the final precursor solution is placed in a closed reaction vessel lined with polytetrafluoroethylene and reacted at 100-150°C (preferably 120-140°C) for 12-36 hours. These mild hydrothermal / solvothermal conditions provide the necessary energy and time for the self-assembly of the MOF crystals. Temperature and time together affect the crystal size, crystallinity, and specific surface area.

[0076] Step (e) involves post-treatment, wherein: after cooling of the reaction, the solid precipitate is obtained by filtration. Preferably, the precipitate is washed sequentially with DMF and anhydrous ethanol to remove residual unreacted substances, ligands, and solvent molecules from the pores. Subsequently, the precipitate is dried at 80-120°C (preferably 100-110°C) and a vacuum of -0.08 to -0.1 MPa for 8-16 hours to remove the solvent from the pores, yielding an activated porous catalyst.

[0077] In step (2) of the method for preparing butyl hafnium chloride from hafnium tetrachloride described above, the weight ratio of catalyst to hafnium tetrachloride is 0.8:1 to 2:1, preferably 1.2:1 to 1.5:1. Sufficient catalyst ensures adequate active sites and HCl adsorption capacity. Too little catalyst results in poor catalytic and adsorption effects; too much catalyst, while potentially improving the effect, reduces economic efficiency and increases the load on subsequent solid-liquid separation.

[0078] In the esterification reaction of step (2) of the method for preparing butyl hafnium chloride from hafnium tetrachloride described above, the reaction temperature is preferably 40-65°C. This mild temperature range is sufficient to activate the reaction while avoiding excessively high temperatures that could lead to aggravated side reactions (such as dehydration of alcohol, thermal decomposition of the product, or deep transesterification). The reaction pressure is 0.1-0.3 MPa (gauge pressure). Maintaining a certain slight positive pressure has several advantages: first, it prevents low-boiling-point components (such as solvents and generated HCl) from vaporizing prematurely, keeping the reaction system homogeneous; second, the pressure promotes the diffusion and adsorption of the gaseous product HCl into the catalyst pores; third, compared with conventional atmospheric or negative pressure operation, slight positive pressure can reduce the loss of n-butanol with the extraction of HCl and improve the utilization rate of raw materials. In addition, the reaction time is 3-8 hours. Under the action of the catalyst, the reaction rate of the method for preparing butyl hafnium chloride from hafnium tetrachloride according to the present invention is greatly improved, and a high conversion rate can be achieved in 3 hours, which is much less than the 8-12 hours of the conventional process.

[0079] Step (3) of the method according to the invention involves a solid-liquid separation step, wherein after the esterification reaction is completed, the system is cooled to 20-30°C to allow the catalyst and any small amounts of solid byproducts that may be generated (such as trace amounts of hydrolysis products) to settle more effectively. Preferably, pressure filtration (0.3-0.6 MPa) using a ceramic membrane (pore size 0.1-0.5 μm) as the filter medium can efficiently and thoroughly separate the solid catalyst. After filtration, the solid filter cake can be washed 2-3 times with a small amount of purified n-butanol to wash out the products trapped in the catalyst channels and between particles, and this product can be added to the filtrate, which can improve the product yield.

[0080] Step (4) of the method according to the invention relates to product purification. Specifically, the filtrate contains the target product butyl hafnium acid, excess n-butanol, organic solvent, trace amounts of unreacted HfCl4, dissolved HCl, and possible high-boiling byproducts. A high-purity product can be obtained through the following three purification steps.

[0081] Atmospheric distillation: Distill at 90-120℃ for 2-3 hours using a distillation column with 15-20 theoretical plates and a reflux ratio of 2:1-3:1. This step mainly removes most of the low-boiling-point organic solvents (n-heptane, petroleum ether) and some excess n-butanol, while also carrying away a small amount of low-boiling-point impurities (such as chlorobutane).

[0082] Vacuum distillation: Distillation is carried out under high vacuum (0.09-0.095 MPa) and 140-160℃, using a high theoretical plate number (30-40 plates) and a high reflux ratio (4:1-6:1). Under these conditions, butyl hafnium oxide (with a high boiling point) is efficiently separated from residual n-butanol and high-boiling-point impurities (such as butyl hydroxyhafnium oxide, dimers, etc.).

[0083] Precision filtration: Finally, the product is filtered through an ultrafiltration membrane with a molecular weight cutoff of 500-1000 Da at a pressure of 0.2-0.4 MPa. This step removes trace amounts of colloidal particles, polymers, or fine solid impurities that may remain in the distillation product, meeting the requirements of high-end applications for mechanical impurities and solution stability.

[0084] This invention develops a novel method for the efficient, selective, high-purity, and environmentally friendly preparation of butyl hafnium ester by using a specific hafnium-based organometallic framework catalyst and combining it with an optimized reaction and separation purification process, which has potential industrial application value.

[0085] The present invention will now be described in more detail with reference to embodiments. It should be noted that these descriptions and embodiments are intended to facilitate understanding of the present invention and are not intended to limit the invention.

[0086] Example

[0087] In this invention, unless otherwise specified, all reagents used are commercially available products and are used directly without further purification. Furthermore, "%" refers to "weight %" and "parts" refers to "parts by weight".

[0088] Table 1 below lists specific information about the raw materials used in the embodiments and comparative examples of the present invention.

[0089] Table 1 List of Experimental Materials

[0090]

[0091] Table 2 below lists specific information about the experimental equipment used in the embodiments and comparative examples of the present invention.

[0092] Table 2 List of Experimental Equipment

[0093]

[0094] Test methods

[0095] (a) Yield

[0096] The yields of the products prepared in the following examples and comparative examples were determined according to the methods described below.

[0097] Specifically, calculations were performed based on hafnium tetrachloride (HfCl4). First, the theoretical weight of the target product, butyl hafnium acid ester (Hf(OC4H9)4), was calculated according to the reaction equation HfCl4 + 4C4H9OH → Hf(OC4H9)4 + 4 HCl.

[0098] Theoretical product weight (g) = Mass of HfC4 input (g) × [Molar mass of Hf(OC4H9)4 (470.94 g / mol) / Molar mass of HfC4 (320.30 g / mol)].

[0099] After reaction, separation, and purification, the actual weight (g) of the final hafnium butyl ester product was accurately weighed. Yield (%) = (actual product weight / theoretical product weight) × 100%.

[0100] In this invention, the catalyst is completely separated by pressure filtration, and subsequent distillation and rectification processes further remove trace impurities. There is no residual hafnium catalyst in the product, which does not affect the yield calculation.

[0101] (ii) Purity

[0102] The purity of the products prepared in the following examples and comparative examples was determined according to the methods described below.

[0103] Accurately weigh 0.1 g of the hafnium butyl ester product prepared in each example and comparative example in a nitrogen-protected glove box (moisture content ≤10 ppm), dilute to 10 mL with anhydrous n-heptane dried with molecular sieves, and shake well to prepare a homogeneous sample solution. An Agilent 7890B-5977A gas chromatograph-mass spectrometer was used, equipped with an HP-5MS column (30 m × 0.25 mm × 0.25 μm); the injection port temperature was 280℃, the split ratio was 10:1, and the injection volume was 1 μL; the carrier gas was high-purity helium (purity ≥99.999%), the column flow rate was 1.0 mL / min; the column temperature program was: initial 80℃, hold for 2 min, increase to 300℃ at 10℃ / min, hold for 10 min; the mass spectrometer ion source temperature was 230℃, the electron impact energy was 70 eV, and the scan range was 50-600 m / z. Prepare a standard solution of butyl hafnium acid (purity ≥99.9%) and a mixed standard solution of major impurities (butane, n-butanol, and butyl hydroxyhafnium acid). Inject these solutions under the chromatographic conditions described above. Plot a calibration curve with concentration on the x-axis and peak area on the y-axis, and calculate the response factors for each component. Inject the sample solution into a GC-MS for analysis, record the total ion chromatogram, and qualitatively confirm the main peak of butyl hafnium acid and impurity peaks using a mass spectrometry library search. Calculate the percentage of the corrected peak area of ​​butyl hafnium acid to the total corrected area using the correction area normalization method, based on the response factors of each component. This percentage represents the product purity (%).

[0104] (III) Cl impurity content (%)

[0105] Referring to the national standard "Determination of chloride ions in industrial circulating cooling water and boiler water" (GB / T 15453-2018), the Cl impurity content (%) in the products prepared in each example and comparative example was determined by potentiometric titration.

[0106] Specifically, silver nitrate standard solution (concentration 0.01 mol / L), glacial acetic acid-sodium acetate buffer solution (pH=3.5), and anhydrous ethanol (purity ≥99.7%) were selected. A Metrohm 902 Titrando automatic potentiometric titrator equipped with a silver ion selective electrode and a dual salt bridge reference electrode was used. In a nitrogen-protected glove box (moisture content ≤10 ppm), 5.0 g of hafnium butyl ester sample was weighed into a 100 mL titration cup, and 50 mL of anhydrous ethanol was added. The mixture was magnetically stirred for 15 min until completely dissolved, and 10 mL of buffer solution was added to adjust the pH of the system. The electrode was immersed in the silver ion standard solution for calibration. The titration endpoint determination mode was set to "potential jump method," and the titration rate was 0.05 mL / min. Measurement was performed after the electrode response stabilized. Silver nitrate standard solution was slowly added to the sample solution, and the potential change was recorded. Titration was stopped at the potential jump, and the volume consumed was recorded. A blank experiment was performed simultaneously, using 50 mL of anhydrous ethanol and 10 mL of glacial acetic acid-sodium acetate buffer solution. mL of buffer solution was titrated using the same procedure, subtracting the volume consumed in the blank titration.

[0107] Cl impurity content (weight %) = (C × (V - V0) × 35.45) / (m × 1000) × 100%

[0108] Where: C is the concentration of silver nitrate (mol / L), V is the volume of sample consumed (mL), V0 is the volume of blank consumed (mL), 35.45 is the molar mass of Cl (g / mol), and m is the mass of sample taken (g).

[0109] Preparation Example 1

[0110] In Preparation Example 1, a hafnium-based organometallic framework catalyst 1 was prepared according to the formulation shown in Table 3 below. The preparation method specifically includes the following steps:

[0111] (1) Preparation of hafnium source solution: Add 55 g hafnium tetrachloride (HfCl4) to a beaker containing 1000 g N,N-dimethylformamide (DMF) and sonicate at 30°C for 15 minutes to obtain hafnium source solution.

[0112] (2) Preparation of mixed precursor solution: Add 45 g of 2,6-naphthalenedicarboxylic acid to the hafnium source solution and stir at 300 rpm for 40 minutes until the solid dissolves to obtain mixed precursor solution.

[0113] (3) While stirring the mixed precursor solution, add acetic acid to the mixed precursor solution to adjust the pH to 5.5, and continue stirring for 30 minutes to obtain the final precursor solution.

[0114] (4) The final precursor solution was transferred to a stainless steel reactor lined with polytetrafluoroethylene, sealed and placed in an oven, and reacted at 120°C for 24 hours.

[0115] (5) After the reaction is complete, allow the mixture to cool naturally to room temperature. Filter the precipitate mixture in the vessel and collect the solid precipitate. Wash the solid precipitate three times each with DMF and anhydrous ethanol.

[0116] (6) Drying: The washed solid was placed in a vacuum drying oven and dried at 100℃ and -0.09 MPa for 12 hours to obtain a white powdery hafnium-based organometallic framework catalyst 1.

[0117] The specific surface area of ​​this catalyst, as measured by a BET surface area analyzer, is approximately 1850 m². 2 / g. The average particle size was determined to be approximately 120 nm using a laser particle size analyzer. Figure 2 A scanning electron microscope (SEM) image of the hafnium tetrachloride-2,6-naphthalenedicarboxylic acid-coordinated organometallic framework catalyst prepared in Preparation Example 1 is shown, which shows that the catalyst has a particulate structure. Figure 3 The X-ray diffraction (XRD) pattern of the hafnium tetrachloride-2,6-naphthalenedicarboxylic acid-coordinated organometallic framework catalyst prepared in Preparation Example 1 is shown. The XRD pattern shows that it has typical crystal diffraction peaks.

[0118] Preparation Examples 2-4

[0119] Preparation Examples 2-4 were prepared in a manner similar to that of Preparation Example 1 to prepare hafnium-based organometallic framework catalysts 2-4, except that the formulation and / or preparation conditions were changed as shown in Table 3 below.

[0120] Furthermore, the specific surface area, particle size, SEM, and XRD of the obtained hafnium-based organometallic framework catalyst 2-4 were tested in the same manner as those tested for the hafnium-based organometallic framework catalyst 1 prepared in Preparation Example 1. The results of specific surface area and particle size are shown in Table 3 below. The SEM and XRD test results of the hafnium-based organometallic framework catalyst 2-4 are similar to those of the hafnium-based organometallic framework catalyst 1, showing that the hafnium-based organometallic framework catalyst 2-4 has a particulate structure and the X-ray diffraction pattern has typical crystal diffraction peaks.

[0121] Table 3 Formulations and process conditions for preparation examples 1-4

[0122]

[0123] Example 1

[0124] Example 1 is performed according to the following steps.

[0125] 1. Raw material pretreatment

[0126] (1) Hafnium tetrachloride drying: Hafnium tetrachloride (HfCl4) was placed in a vacuum drying oven. It was dried for 3 hours at a temperature of 100℃ and a vacuum of -0.09 MPa. After drying, a sample was taken, and the moisture content was determined to be approximately 0.03 wt% using a Karl Fischer moisture analyzer.

[0127] (2) Purification of n-Butanol: n-Butanol was added to a packed distillation column (25 theoretical plates). The reflux ratio was controlled at 4:1, and atmospheric distillation was carried out at 117.5℃. The distillate was collected. Gas chromatography analysis showed that the purity of the purified butanol was 99.85% by weight, and the water content was 0.08% by weight (Karl Fischer method).

[0128] 2. Reaction process

[0129] (1) Establishing an inert atmosphere: In a 316L stainless steel reactor with a jacket and mechanical stirrer, first evacuate to -0.08 MPa, then purge with high-purity nitrogen (99.999%) until a slightly positive pressure is reached. Repeat this "evacuation-nitrogen purging" operation 4 times. Finally, keep nitrogen continuously flowing in to maintain a slightly positive pressure inert atmosphere inside the reactor.

[0130] (2) Preparation of the initial reaction system: Add 500 g of the purified n-butanol and 400 g of n-heptane (n-butanol:n-heptane weight ratio = 1:0.8) sequentially to the reactor. Start stirring at 200 rpm, and control the system temperature at 30℃ using the jacketed circulating water. Add 200 g of dried hafnium tetrachloride in 5 slow batches to the reactor under stirring, with a 5-minute interval between each batch, ensuring the system temperature remains at 30±2℃ throughout the addition process. After all materials have been added, continue stirring for 20 minutes to obtain a homogeneous initial reaction system.

[0131] (3) Catalytic esterification reaction: 160 g of hafnium-based organometallic framework catalyst 1 (prepared from Preparation Example 1) was added to the above system, at which point the weight ratio of catalyst to hafnium tetrachloride was 0.8:1. The reactor was sealed, and the stirring speed was adjusted to 350 rpm. The reaction temperature was controlled at 40±1℃ by heating with a jacketed oil bath. The system pressure was stabilized at 0.1 MPa using a back pressure valve at the top of the reactor. The reaction was carried out under these conditions for 3 hours.

[0132] 3. Post-processing and purification

[0133] (1) Filtration and separation: After the reaction is completed, the esterification reaction solution is cooled to 25°C by circulating cooling water. A pressure filtration device is used with a ceramic membrane (0.2 μm pore size) as the filter medium to filter at a pressure of 0.4 MPa to separate the solid catalyst and other components, and obtain a clear filtrate.

[0134] (2) Atmospheric distillation: Transfer the filtrate into a glass distillation apparatus (18 theoretical plates). Control the reflux ratio at 2.5:1 and distill at 110°C for 2.5 hours to remove most of the n-heptane and a small amount of low-boiling impurities.

[0135] (3) Vacuum distillation: The residue from atmospheric distillation is transferred to a vacuum distillation column (theoretical plates 35). Distillation is carried out at 150°C under a vacuum of 0.092 MPa and a reflux ratio of 5:1 for 5 hours, and the hafnium butyl ester main fraction is collected.

[0136] (4) Precision filtration: The collected fraction is passed through an ultrafiltration membrane module (molecular weight cutoff 800 Da) and subjected to terminal precision filtration at a pressure of 0.3 MPa to further remove any trace solid particles or colloids that may remain, and finally obtain colorless and transparent hafnium butyl ester product.

[0137] The yield, purity, and chlorine impurity content (%) of Example 1 were analyzed according to the test methods described in detail above, and the results are shown in Table 4 below.

[0138] Examples 2-12 and Comparative Examples 1-5

[0139] Examples 2-12 and Comparative Examples 1-5 were prepared in a manner similar to that of Example 1, except that the formulations and preparation conditions were changed as shown in Tables 4 and 5 below.

[0140] The yield, purity, and chlorine impurity content (%) of Examples 2-12 and Comparative Examples 1-5 were analyzed according to the test methods described in detail above, and the results are shown in Tables 4 and 5 below, respectively.

[0141] Table 4. Formulations and test results of Examples 1-12

[0142]

[0143] Table 5. Formulations and test results of Comparative Examples 1-5

[0144]

[0145] The test results above show that the method for preparing butyl hafnium chloride from hafnium tetrachloride provided by this invention has significant advantages in terms of reaction efficiency, product purity, and impurity control.

[0146] In the preparation example, by adjusting parameters such as the ratio of hafnium tetrachloride to 2,6-naphthalenedicarboxylic acid, the reaction pH, the amount of solvent, and the reaction temperature and time, different specific surface areas (1550-2400 m²) were prepared. 2Hafnium-based organometallic framework catalysts (Preparation Examples 1-4) with average particle size (approximately 120 nm-1.5 μm) and average particle size (approximately 120 nm-1.5 μm). All catalysts exhibited typical crystal diffraction peaks (XRD) and particulate morphology (SEM), indicating that the prepared materials possess a regular porous structure and high crystallinity, making them suitable as highly efficient catalysts. Among them, the catalyst prepared in Preparation Example 1 (with a specific surface area of ​​approximately 1850 m² / g) showed the following characteristics. 2 The particles (approximately 120 nm in size) exhibited excellent catalytic activity and mass transfer performance in subsequent examples.

[0147] In terms of the embodiments, using the method described in this invention (Examples 1-12), under optimized process conditions, the yield of hafnium butyl ester reached over 90%, with a maximum of 97.2% (Example 12), the product purity was over 99.4%, with a maximum of 99.9%, and the chlorine impurity content was less than 0.10% by weight, with a minimum of only 0.02% by weight (Examples 11-12). Specifically, when the weight ratio of hafnium tetrachloride to n-butanol is 1:2.5-1:4.5, the weight ratio of organic solvent to n-butanol is 0.8:1-1.5:1, the weight ratio of catalyst to hafnium tetrachloride is 0.8:1-2:1, the reaction temperature is 40-65℃, the reaction pressure is 0.1-0.3 MPa, and the reaction time is 3-8 h (as in Examples 1-9), the system can achieve high conversion and high selectivity under relatively mild conditions, demonstrating the synergistic effect of hafnium-based organometallic framework catalysts in activating reactants, promoting mass transfer, and suppressing side reactions. Furthermore, when the weight ratio of catalyst to hafnium tetrachloride is increased to 1.2:1-1.5:1 (Examples 10-12), the reaction efficiency and product purity are further improved, while the chlorine impurity content is significantly reduced. This indicates that appropriately increasing the catalyst dosage can more fully adsorb the HCl generated in the reaction, reduce equipment corrosion, and reduce the residual chlorine impurities in the product.

[0148] In comparative examples, without a catalyst (Comparative Example 1), the reaction yield was only 68.5%, the product purity was 95.2%, and the chlorine impurity content was as high as 0.35% by weight, indicating low reaction efficiency and severe side reactions under catalyst-free conditions. Using the conventional Lewis acid catalyst AlCl3 (Comparative Example 2), although there was some improvement compared to the non-catalyst-free method, the yield (72.3%) and purity (96.8%) were still far lower than those of the embodiments of the present invention, and the chlorine impurity content (0.28% by weight) was still relatively high, reflecting the shortcomings of conventional catalysts in terms of activity, selectivity, and byproduct control. Furthermore, when the ratio of hafnium tetrachloride to n-butanol was reduced to 1:2.0 (Comparative Example 3), or the amount of organic solvent was reduced (Comparative Example 4), or the reaction temperature was increased to 80°C (Comparative Example 5), the yield and purity decreased, and the chlorine impurity content increased, indicating that the reactant ratio, solvent amount, and temperature control have a significant impact on reaction equilibrium, side reaction suppression, and product purity.

[0149] Obviously, those skilled in the art can make various modifications and variations to this disclosure without departing from the spirit and scope of this disclosure. Therefore, if such modifications and variations fall within the scope of this invention, this disclosure is also intended to include such modifications and variations.

Claims

1. A method for preparing butyl hafnium chloride from hafnium tetrachloride, characterized in that, Includes the following steps: (1) Under the protection of an inert gas, n-butanol and an organic solvent are added to a reaction vessel and stirred until homogeneous. Then, hafnium tetrachloride is added to obtain an initial reaction system, wherein: the organic solvent is one or more of n-heptane, petroleum ether and xylene; the weight ratio of hafnium tetrachloride to n-butanol is 1:2.5-1:4.5; and the weight ratio of the organic solvent to n-butanol is 0.8:1-1.5:1; (2) Add hafnium-based organometallic framework catalyst to the initial reaction system obtained in step (1), heat to 40-65℃, control the reaction pressure to 0.1-0.3 MPa, stir the reaction for 3-8 h to obtain esterification reaction solution. The hafnium-based organometallic framework catalyst is hafnium tetrachloride-2,6-naphthalenedicarboxylic acid-coordinated organometallic framework catalyst, and the weight ratio of the added hafnium-based organometallic framework catalyst to the hafnium tetrachloride added in step (1) is 0.8:1-2:

1. (3) Cool the esterification reaction solution obtained in step (2) to 20-30℃, and separate the solid components in the system by pressure filtration to obtain the filtrate; (4) The filtrate obtained in step (3) is subjected to atmospheric distillation, vacuum distillation and precision filtration in sequence to obtain hafnium butyl ester.

2. The method for preparing butyl hafnium chloride from hafnium tetrachloride according to claim 1, characterized in that, The method further includes a raw material pretreatment step before step (1), wherein hafnium tetrachloride is dried to control the moisture content ≤0.05% by weight, and n-butanol is purified by distillation to control the purity of the purified n-butanol ≥99.8% by weight and the moisture content ≤0.1% by weight.

3. The method for preparing butyl hafnium chloride from hafnium tetrachloride according to claim 1, characterized in that, In step (3), the filtration pressure of the pressurized filtration is 0.3-0.6 MPa, the filter medium is a ceramic membrane, and the pore size of the ceramic membrane is 0.1-0.5 μm.

4. The method for preparing butyl hafnium chloride from hafnium tetrachloride according to claim 1, characterized in that, The hafnium-based organometallic framework catalyst is prepared by a method comprising the following steps: (a) Hafnium tetrachloride was added to N,N-dimethylformamide and ultrasonically dispersed at 25-40°C for 10-30 minutes to obtain a hafnium source solution; (b) Add 2,6-naphthalenedicarboxylic acid to the hafnium source solution and stir for 20-60 minutes until dissolved to obtain a mixed precursor solution; (c) Add acetic acid to the mixed precursor solution while stirring, and adjust the pH to 3.5-5.5 to obtain the final precursor solution; (d) The final precursor solution is placed in a closed reaction vessel and reacted at 100-150°C for 12-36 hours. After the reaction is completed, the mixture is cooled to obtain a precipitate mixture. (e) The precipitate mixture is filtered, the solid precipitate is collected, and the solid precipitate is washed and then dried under vacuum at 80-120°C for 8-16 hours to obtain the hafnium-based organometallic framework catalyst, wherein: Based on the total weight of hafnium tetrachloride and 2,6-naphthalenedicarboxylic acid as 100%, hafnium tetrachloride accounts for 55-65% and 2,6-naphthalenedicarboxylic acid accounts for 35-45%; and the ratio of the total weight of hafnium tetrachloride and 2,6-naphthalenedicarboxylic acid to the weight of N,N-dimethylformamide is in the range of 1:10 to 3:

10.

5. The method for preparing butyl hafnium chloride from hafnium tetrachloride according to claim 4, characterized in that, The hafnium-based organometallic framework catalyst has a specific surface area of ​​1000-2500 m². 2 / g.

6. The method for preparing butyl hafnium chloride from hafnium tetrachloride according to claim 4, characterized in that, The average particle size of the hafnium-based organometallic framework catalyst is in the range of 50 nm to 2 μm.

7. The method for preparing butyl hafnium chloride from hafnium tetrachloride according to claim 1, characterized in that, The weight ratio of the hafnium-based organometallic framework catalyst added in step (2) to the hafnium tetrachloride added in step (1) is 1.2:1-1.5:

1.

8. The method for preparing butyl hafnium chloride from hafnium tetrachloride according to claim 1, characterized in that, In step (4), the conditions for atmospheric distillation are: distillation temperature 90-120℃, distillation time 2-3 h, theoretical plate number of the distillation column 15-20, and reflux ratio 2:1-3:

1.

9. The method for preparing butyl hafnium chloride from hafnium tetrachloride according to claim 1, characterized in that, In step (4), the conditions for vacuum distillation are: vacuum degree 0.09-0.095 MPa, distillation temperature 140-160℃, distillation time 4-6 h, theoretical plate number of vacuum distillation column is 30-40, and reflux ratio is 4:1-6:

1.

10. The method for preparing butyl hafnium chloride from hafnium tetrachloride according to claim 1, characterized in that, In step (4), the precision filtration is performed using an ultrafiltration membrane, wherein the ultrafiltration membrane has a molecular weight cutoff of 500-1000 Da and a filtration pressure of 0.2-0.4 MPa.

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