Preparation process of hafnium tetrachloride with ultra-low niobium content

Abstract

The application provides a preparation process of hafnium tetrachloride with ultra-low niobium content, comprising the following steps: (1) crushing, sieving and vacuum drying of hafnium oxide raw materials to prepare pretreated hafnium oxide raw materials; (2) preparation of a supported composite catalyst; (3) uniformly mixing the pretreated hafnium oxide raw materials and the supported composite catalyst at a mass ratio of 100:0.5 to 100:5, performing a chlorination reaction in the presence of chlorine at a temperature of 350-500 DEG C and a pressure of 0.1-0.3 MPa to obtain a chlorination reaction product; (4) rectification and purification of the chlorination reaction product to produce hafnium tetrachloride vapor; and (5) condensation of the hafnium tetrachloride vapor to obtain a hafnium tetrachloride product. By using the specific supported composite catalyst, the niobium content of the hafnium tetrachloride product is less than 10 ppb, the purity is greater than or equal to 99.9999%, the preparation efficiency is improved, and the advanced semiconductor process requirements can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor material preparation, and particularly relates to a preparation process of hafnium tetrachloride with ultra-low niobium content, which is especially suitable for the preparation of high-purity hafnium tetrachloride raw materials required in the manufacturing of high-performance semiconductor devices. BACKGROUND

[0002] With the continuous development of semiconductor technology, the device integration continues to improve, and the circuit line width continues to shrink, and the purity requirement of semiconductor materials is increasingly stringent. As a core raw material for preparing high dielectric constant (high-k) gate dielectric materials, hafnium-based superconducting materials and other advanced functional materials, the impurity content of hafnium tetrachloride (HfCl4) directly affects the performance, reliability and service life of semiconductor devices.

[0003] Niobium (Nb) as a typical harmful impurity in hafnium tetrachloride, its existence can have many negative effects on semiconductor devices. Niobium belongs to the second class of superconductors, and its atomic radius is similar to that of silicon (Si) (the atomic radius of niobium is about 0.143 nm, and the atomic radius of silicon is about 0.117 nm). In the semiconductor manufacturing process, the residual niobium element is easy to enter the silicon lattice or the device structure, interfere with the atomic migration path, cause the circuit stability to decrease, the device threshold voltage to drift, and affect the electrical performance consistency of the device. At the same time, the oxides of niobium (such as Nb2O3, NbO2, etc.) are easy to decompose or change phase under high-temperature annealing or strong radiation environment, which destroys the insulation layer structure of the semiconductor device, causes the leakage current to increase, the insulation performance to fail, and seriously affects the reliability and service life of the device. In addition, niobium has a certain electrical conductivity, and in high-frequency circuits, residual niobium elements may form additional conductive channels, interfere with the transmission of weak signals inside the chip, cause signal attenuation and increased crosstalk, and reduce the working performance of high-frequency devices.

[0004] Therefore, the semiconductor industry has put forward very high control requirements for the niobium content in hafnium tetrachloride, especially for hafnium tetrachloride products used in 7nm and below advanced processes, which usually require the niobium content to be less than 10 ppb, i.e. “ultra-low niobium content” level.

[0005] At present, the existing preparation processes of hafnium tetrachloride mainly include direct chlorination of metallic hafnium, oxide chlorination, halide conversion, etc. Among them, the oxide chlorination method becomes a widely used method in industry because of the easy availability of raw materials and relatively low cost. However, the existing process has obvious deficiencies in removing niobium:

[0006] Limitations of low-temperature distillation process for removing niobium: In the prior art, the boiling point difference between niobium pentachloride (NbCl5) and hafnium tetrachloride (about 248°C for NbCl5 and about 319°C for HfCl4) is often utilized to separate them by low-temperature distillation. The NbCl5 is first evaporated and separated by maintaining the temperature in the range of 248-319°C. However, this method has the following problems: on the one hand, there is a certain azeotropic phenomenon between NbCl5 and HfCl4 during distillation, resulting in low separation efficiency and difficulty in reducing the niobium content to below 10 ppb; on the other hand, the temperature gradient and distillation rate need to be strictly controlled during the distillation process, which consumes a lot of energy, and long-term high-temperature holding may cause slight decomposition of HfCl4, introducing other impurities.

[0007] Defects of chemical niobium removal process: Some processes attempt to use chemical precipitation method to form insoluble complexes with niobium ions by adding complexing agents, and then separate them by filtration. However, this method needs to be carried out in a liquid phase system, and HfCl4 is prone to hydrolysis, making it difficult to control the water content of the reaction system. In addition, the residual complexing agent will introduce new impurities, affecting the purity of HfCl4. Moreover, the selectivity of the complexation reaction is limited, making it difficult to achieve efficient and selective removal of niobium.

[0008] Defects of adsorption niobium removal process: The existing adsorption niobium removal process mostly uses metal oxides or molecular sieves as adsorbents. However, the adsorption capacity of the adsorbents for niobium is limited, and the adsorption process is easily affected by factors such as temperature, humidity, and impurity types, resulting in poor adsorption stability and difficulty in meeting the continuous production requirements of ultra-low niobium content HfCl4 in large-scale industrial production.

[0009] Blank of catalyst-assisted niobium removal technology: Currently, there is no report on the use of specific catalysts to assist in the removal of niobium in the prior art. The conventional niobium removal process lacks directional catalysis in the separation process of niobium compounds, resulting in low efficiency, high energy consumption, and difficulty in achieving precise control of ultra-low niobium content.

[0010] In summary, the existing HfCl4 preparation process has the problems of low separation efficiency, high energy consumption, easy introduction of new impurities, and difficulty in stably achieving ultra-low niobium content, which limits the application of HfCl4 in advanced semiconductor processes. Therefore, developing a preparation process for ultra-low niobium content HfCl4 with low niobium content below 10 ppb, which is efficient, energy-saving, and has low impurity residue, has become a technical problem to be solved in the field. SUMMARY

[0011] From the above technical problems, an object of the present application is to overcome the many deficiencies of the existing hafnium tetrachloride preparation process in the niobium removal step, including low separation efficiency of low-temperature distillation, easy introduction of new impurities by chemical precipitation, poor stability of adsorption niobium removal, and the like. By introducing a specific supported composite catalyst, efficient directional separation of niobium compounds is achieved, ensuring high preparation efficiency of hafnium tetrachloride while controlling product purity, and stably obtaining ultra-low niobium content hafnium tetrachloride with niobium content less than 10 ppb, solving the problem that the existing process cannot meet the requirements of advanced semiconductor processes.

[0012] Specifically, according to one aspect of the present application, a preparation process for ultra-low niobium content hafnium tetrachloride is provided, the preparation process comprising the following steps:

[0013] (1) crushing, sieving and vacuum drying hafnium oxide raw material with a purity greater than or equal to 99.9% and a niobium content less than or equal to 200 ppm to prepare pretreated hafnium oxide raw material;

[0014] (2) preparing a supported composite catalyst;

[0015] (3) uniformly mixing the pretreated hafnium oxide raw material and the supported composite catalyst in a mass ratio of 100:0.5 to 100:5, preferably 100:1 to 100:2, performing a chlorination reaction in the presence of chlorine at a temperature of 350-500°C, preferably 380-450°C, and a pressure of 0.1-0.3 MPa to obtain a chlorination reaction product;

[0016] (4) performing rectification purification on the chlorination reaction product to produce hafnium tetrachloride vapor;

[0017] (5) condensing the hafnium tetrachloride vapor to obtain the ultra-low niobium content hafnium tetrachloride, wherein:

[0018] Step (2) of preparing a supported composite catalyst comprises:

[0019] calcining a porous alumina carrier raw material at 500-600°C for 3-5h and cooling to room temperature to prepare a pretreated porous alumina carrier;

[0020] dissolving a mixture of tetrabutyl titanate, zirconium oxychloride and lanthanum nitrate in anhydrous ethanol to prepare an impregnation solution, wherein the mixture of tetrabutyl titanate, zirconium oxychloride and lanthanum nitrate contains 40-60% tetrabutyl titanate, 20-30% zirconium oxychloride and 10-30% lanthanum nitrate based on a total weight of 100%;

[0021] The pre-processed porous alumina carrier is immersed in the impregnation solution, stirred for impregnation at 30-50°C for 8-12 h, then dried at 80-100°C for 6-8 h, and finally calcined at 550-650°C for 4-6 h to obtain the supported composite catalyst.

[0022] According to some preferred embodiments of the present application, the supported composite catalyst comprises a porous alumina carrier and an active component supported on the porous alumina carrier, the active component comprising titanium oxide, zirconium oxide and lanthanum oxide.

[0023] According to some preferred embodiments of the present application, in step (1), the crushed hafnium oxide raw material is passed through a 200-400 mesh sieve.

[0024] According to some preferred embodiments of the present application, in step (1), the vacuum drying is performed at a temperature of 120-180°C, a vacuum degree of -0.08 to -0.1 MPa, and a time of 4-8 hours.

[0025] According to some preferred embodiments of the present application, the specific surface area of the porous alumina carrier raw material is 150-300 m 2 / g, preferably 150-250 m 2 / g, and the pore size is 5-20 nm, preferably 8-17 nm.

[0026] According to some preferred embodiments of the present application, step (3) is performed in a chlorination reactor, wherein the flow rate of the chlorine gas is 50-200 mL / min.

[0027] According to some preferred embodiments of the present application, the chlorination reaction of step (3) is performed for 2-6 hours.

[0028] According to some preferred embodiments of the present application, step (4) is performed in a rectifying column, wherein the overhead temperature of the rectifying column is 230-250°C, the bottom temperature is 320-340°C, the reflux ratio is 1: 5-1: 15, preferably 1: 8-1: 10, and the rectifying time is 4-10 hours.

[0029] According to some preferred embodiments of the present application, step (5) is performed at a condensation temperature of -20°C to 0°C.

[0030] According to some preferred embodiments of the present application, the hafnium tetrachloride with ultra-low niobium content has a niobium content of less than 5 ppb.

[0031] According to some preferred embodiments of the present application, the hafnium tetrachloride with ultra-low niobium content has a purity of greater than or equal to 99.9999%.

[0032] The application has the advantages that the niobium content of the product is less than 10ppb, meeting the requirements of advanced semiconductor processes of 7nm and below; the preparation efficiency is greatly improved, the chlorination and rectification time is reduced by more than 30% and 20% respectively; the product purity is greater than or equal to 99.9999%, and the content of other impurities is less than 5ppb without introducing additional impurities; the energy consumption is reduced, the chlorination reaction temperature is reduced, meeting the energy saving trend; the process stability is good, the catalyst preparation is simple and the cost is controllable, which is suitable for large-scale industrialized continuous production, and effectively solves the problems of low niobium removal efficiency, many impurities and high energy consumption of the existing process. BRIEF DESCRIPTION OF DRAWINGS

[0033] In the present specification, the drawings are provided to more clearly explain the technical solutions of the present application, but the present field is not limited thereto.

[0034] Figure 1 A scanning electron microscope (SEM) photo of the supported composite catalyst prepared in Example 1 of the present application is shown;

[0035] Figure 2 An X-ray diffraction (XRD) spectrum of the supported composite catalyst prepared in Example 1 of the present application is shown. DETAILED DESCRIPTION

[0036] The present application will be further described in detail below in combination with the drawings and specific embodiments. It will be understood that other embodiments are considered, and these other embodiments can be implemented without departing from the scope or spirit of the present application. Therefore, the following detailed description is non-limiting.

[0037] Unless otherwise indicated, all numbers expressing features, quantities and physical characteristics in the specification are to be understood as approximations based on the terms "about" and "at or about". Therefore, unless otherwise indicated, the numerical parameters set forth in the specification are approximations that can vary from the stated values. These variations are to be expected by one of ordinary skill in the art.

[0038] As described above, the existing hafnium tetrachloride preparation process has many defects in the niobium removal link: low-temperature distillation has low separation efficiency due to azeotropic phenomenon, it is difficult to reduce the niobium content to less than 10ppb, and it has high energy consumption and is easy to cause product decomposition; chemical precipitation method needs a liquid phase system, which is easy to hydrolyze and introduces new impurities due to the residual complexing agent; the adsorption capacity of adsorption niobium removal is limited and the stability is poor, which is difficult to meet the industrialization demand. These problems result in that hafnium tetrachloride cannot stably meet the requirements of advanced semiconductor processes of 7nm and below for ultra-low niobium content, which limits its application in the high-end semiconductor field. The present application aims to solve the above problems.

[0039] In particular, according to one aspect of the present application, there is provided a process for preparing tetrachlorohafnium with ultra-low niobium content, comprising the following steps:

[0040] (1) crushing, sieving and vacuum drying hafnium oxide raw material with purity greater than or equal to 99.9% and niobium content less than or equal to 200 ppm to prepare pretreated hafnium oxide raw material;

[0041] (2) preparing a supported composite catalyst;

[0042] (3) uniformly mixing the pretreated hafnium oxide raw material and the supported composite catalyst in a mass ratio of 100:0.5 to 100:5, preferably 100:1 to 100:2, and performing a chlorination reaction in the presence of chlorine at a temperature of 350-500°C, preferably 380-450°C, and a pressure of 0.1-0.3 MPa to obtain a chlorination reaction product;

[0043] (4) subjecting the chlorination reaction product to rectification purification to produce tetrachlorohafnium vapor;

[0044] (5) condensing the tetrachlorohafnium vapor to obtain the tetrachlorohafnium with ultra-low niobium content, wherein:

[0045] Step (2) of preparing the supported composite catalyst comprises:

[0046] firing a porous alumina carrier raw material at 500-600°C for 3-5 h and cooling to room temperature to prepare a pretreated porous alumina carrier;

[0047] dissolving a mixture of tetrabutyl titanate, zirconium oxychloride and lanthanum nitrate in anhydrous ethanol to prepare an impregnation solution, wherein the mixture of tetrabutyl titanate, zirconium oxychloride and lanthanum nitrate contains 40-60% tetrabutyl titanate, 20-30% zirconium oxychloride and 10-30% lanthanum nitrate based on 100% of the total weight of the mixture;

[0048] immersing the pretreated porous alumina carrier in the impregnation solution, stirring for 8-12 h at 30-50°C, then drying at 80-100°C for 6-8 h, and finally firing at 550-650°C for 4-6 h to obtain the supported composite catalyst.

[0049] According to the technical solution of the present application, the supported composite catalyst comprises a porous alumina carrier and an active component supported on the porous alumina carrier, and the active component comprises titanium oxide, zirconium oxide and lanthanum oxide.

[0050] Specifically, the goal of the pretreatment of the hafnium oxide raw material is to remove physical impurities, adsorbed water and volatile impurities in the hafnium oxide raw material, while optimizing the particle size of the raw material to improve the mass transfer efficiency of the subsequent chlorination reaction. Preferably, the purity of the hafnium oxide raw material is ≥ 99.9% and the niobium content is ≤ 200 ppm.

[0051] In the crushing and sieving step, the hafnium oxide raw material is crushed and then sieved through a 200-400 mesh sieve. The particle size corresponding to 200-400 mesh (38-75 μm) can both ensure sufficient specific surface area to promote the reaction to proceed fully and avoid particle agglomeration and dust problems, achieving a balance between reaction efficiency and operational feasibility.

[0052] The vacuum drying conditions are set to a temperature of 120-180°C, a vacuum degree of -0.08 to -0.1 MPa, and a time of 4-8 hours. The purpose of vacuum drying is to remove adsorbed water and crystal water in the raw material, because hafnium tetrachloride is highly hydrolytic (HfCl4+ 2H2O → HfO2 2H2O + 4HCl↑). If residual moisture remains in the raw material, in the subsequent chlorination reaction process, the moisture will hydrolyze with the generated hafnium tetrachloride to generate impurities such as hafnium oxide or oxychloride (HfOCl2), which are difficult to separate by rectification, affecting the purity of the product. The temperature is controlled at 120-180°C and the drying time is set to 4-8 hours, which is determined according to the moisture desorption curve under different drying temperatures and vacuum degrees, to ensure that the moisture content of the raw material is reduced to below 0.1% within this time range, meeting the requirements of the subsequent process.

[0053] After vacuum drying is completed, the pretreated hafnium oxide raw material is cooled to room temperature and stored in a sealed state.

[0054] The supported composite catalyst is an important aspect of the present application to achieve the goal of ultra-low niobium content. The carrier selection, active component composition and ratio, and preparation process parameters are carefully designed. Through the synergistic effect of the carrier and the active component, the separation effect of niobium compounds is strengthened, and the chlorination reaction is promoted to proceed efficiently.

[0055] Specifically, according to the technical solution of the present application, porous alumina is selected as the carrier, and the specific surface area thereof is preferably 150-300 m 2 / g (preferably 150-250 m 2 / g), and the pore size is 5-20 nm (preferably 8-17 nm). The porous alumina has multiple advantages as a carrier: firstly, the porous structure provides a large specific surface area, which can load sufficient active components and provide abundant active sites for the reaction; secondly, the alumina is chemically stable and is not prone to reaction under the high temperature (350-500℃) and chlorine atmosphere of the chlorination reaction, ensuring the stability of the carrier structure and performance; thirdly, the alumina surface has hydroxyl groups (-OH), which can interact with the active component precursors (tetrabutyl titanate, zirconium oxychloride, lanthanum nitrate), improving the dispersion and loading stability of the active components and avoiding the shedding of the active components during the reaction.

[0056] According to the technical solution of the present application, when the specific surface area is less than 150 m 2 / g, the loading capacity of the carrier is insufficient, the active components are not uniformly dispersed, and it is difficult to form effective catalytically active sites, resulting in low catalytic efficiency; when the specific surface area is greater than 300 m 2 / g, the pore size of the carrier is too small (may be less than 5 nm), which can cause the active components to enter the micropores of the carrier and be difficult to contact with the reactants, while increasing the mass transfer resistance and affecting the catalytic effect. The specific surface area is preferably 150-250 m 2 / g, and the pore size is 8-17 nm, because the carrier in this range can ensure sufficient loading capacity, achieve uniform dispersion of the active components and efficient mass transfer of the reactants, and achieve the best catalytic effect.

[0057] In the carrier pretreatment step, the porous alumina carrier raw material is calcined at 500-600℃ for 3-5 h. The main purposes of calcination are three: firstly, to remove the adsorbed water and residual organic matter on the surface of the carrier to avoid the influence of these impurities on the loading effect of the active components; secondly, to promote the formation of hydroxyl groups on the surface of the carrier to enhance the interaction between the carrier and the active component precursors; thirdly, to improve the mechanical strength and thermal stability of the carrier to prevent structural collapse during subsequent impregnation, drying, calcination and catalytic reaction. When the calcination temperature is lower than 500℃, the organic matter is not completely removed and the hydroxyl groups are not fully formed; when the temperature is higher than 600℃, the carrier may sinter, resulting in a decrease in specific surface area and an increase in pore size, which affects the loading performance. The calcination time is 3-5 h to ensure that the impurities on the surface of the carrier are completely removed and the hydroxyl groups are fully formed, and the carrier is cooled to room temperature for standby to avoid the adsorption of moisture and impurities in the air by the high-temperature carrier.

[0058] According to the technical solution of the present application, the impregnation solution is prepared by mixing tetrabutyl titanate, zirconium oxychloride, lanthanum nitrate and anhydrous ethanol, and the mass ratio of the three active component precursors is: tetrabutyl titanate 40-60% (preferably 50-55%), zirconium oxychloride 20-30% (preferably 24-28%), and lanthanum nitrate 10-30% (preferably 15-26%). The synergistic effect of the three active components has an important influence on efficient niobium removal.

[0059] Specifically, tetrabutyl titanate as a precursor of titanium oxide, its hydrolysis product titanium oxide (TiO2) has good catalytic activity and adsorption performance. In the chlorination reaction process, titanium oxide can adsorb niobium pentachloride (NbCl5), and at the same time catalyze the desorption of niobium pentachloride, taking advantage of the boiling point difference between niobium pentachloride and hafnium tetrachloride to create conditions for subsequent rectification separation. Zirconium oxychloride hydrolysis generates zirconium oxide (ZrO2) with stable crystal structure and high surface activity, which can form a synergistic effect with titanium oxide, enhance the selective adsorption capacity of the catalyst for niobium compounds, and at the same time promote the chlorination reaction rate of hafnium oxide and chlorine. The lanthanum nitrate hydrolysis generates lanthanum oxide (La2O3) as a rare earth oxide, which has a unique electronic structure and can adjust the surface electronic properties of the catalyst, further improve the catalytic selectivity, avoid the adsorption of other impurity chlorides, and ensure the purity of hafnium tetrachloride.

[0060] According to the technical scheme of the present application, if the proportion of tetrabutyl titanate is less than 40%, the content of titanium oxide is insufficient, and the catalytic adsorption effect is weakened; when it is higher than 60%, titanium oxide is easy to agglomerate, reducing the dispersion and affecting the catalytic efficiency. When the proportion of zirconium oxychloride is less than 20%, the synergistic effect with titanium oxide is insufficient; when it is higher than 30%, it may cover part of the active sites of titanium oxide and lanthanum oxide, resulting in a decrease in catalytic selectivity. When the proportion of lanthanum nitrate is less than 10%, the electronic adjustment effect is not obvious; when it is higher than 30%, it is easy to cause the active sites on the surface of the catalyst to be crowded, which also affects the catalytic effect. Preferably, 50-55% tetrabutyl titanate, 24-28% zirconium oxychloride and 15-26% lanthanum nitrate are used in the ratio, at which the synergistic effect of the three active components is the strongest, and efficient selective separation of niobium compounds and efficient chlorination reaction can be achieved.

[0061] According to some preferred technical schemes of the present application, anhydrous ethanol is selected as the solvent. Anhydrous ethanol has good solubility for tetrabutyl titanate, zirconium oxychloride and lanthanum nitrate, and can form a uniform and stable impregnation solution to ensure uniform dispersion of the active component precursors on the surface of the carrier. Anhydrous ethanol has a low boiling point (78.5℃), which is easy to remove in the subsequent drying step and will not introduce other impurities. Ethanol molecules have certain interaction with the hydroxyl groups on the surface of the carrier, which can promote the adsorption of active component precursors on the surface of the carrier and improve the loading firmness. If other solvents (such as methanol, acetone) are used, there may be problems such as poor solubility, residual impurities or affecting the loading effect.

[0062] In the impregnation step, the pretreated porous alumina carrier is immersed in the impregnation solution and stirred at 30-50℃ for 8-12h.

[0063] The drying step is set to 80-100℃ for 6-8 h. This temperature range can quickly remove the anhydrous ethanol in the impregnation solution, while avoiding excessive temperature leading to premature decomposition of the active component precursor. The drying time of 6-8 h ensures that the ethanol on the surface and inside of the carrier is completely removed, laying the foundation for the subsequent calcination step.

[0064] According to some preferred technical solutions of the present application, the calcination step includes calcination at 550-650℃ for 4-6 h. The purpose of calcination is to convert the active component precursor into the target oxide (titanium oxide, zirconium oxide, lanthanum oxide), while enhancing the interaction between the active component and the carrier. The inventors of the present application found that below 550℃, the precursor is not fully decomposed, and the oxide crystal phase with catalytic activity cannot be formed; above 650℃, the active component may sinter, resulting in a decrease in specific surface area and catalytic activity, and the binding force between the carrier and the active component is too strong, which may affect the flexibility of the catalytic reaction. After calcination, the active component is loaded on the surface of the porous alumina carrier in a highly dispersed state, forming a supported composite catalyst with high catalytic activity and selectivity.

[0065] According to the technical content of the present application, the catalytic chlorination reaction converts hafnium oxide into hafnium tetrachloride. By optimizing the parameters such as reaction raw material ratio, temperature, pressure, chlorine flow rate, and reaction time, the present application realizes the efficient conversion of hafnium oxide under the action of the supported composite catalyst, while strengthening the separation effect of niobium compounds.

[0066] Preferably, the mass ratio of the pretreated hafnium oxide raw material to the supported composite catalyst is 100:0.5 to 100:5, preferably 100:1 to 100:2. If the catalyst dosage is too low (mass ratio greater than 100:0.5), the catalytic active sites are insufficient, which cannot fully promote the chlorination reaction and the selective adsorption of niobium compounds, resulting in slow reaction rate and poor niobium removal effect; if the catalyst dosage is too high (mass ratio less than 100:5), the mass transfer resistance of the reaction system increases due to the excess of catalyst, and the active sites on the surface of the catalyst compete for adsorption, affecting the generation efficiency of hafnium tetrachloride. The preferred ratio of 100:1 to 100:2 can achieve the best balance between cost and efficiency while ensuring the catalytic effect.

[0067] Preferably, the reaction temperature is 350-500℃, preferably 380-450℃. The thermodynamic equation of the chlorination reaction is: HfO2+2Cl2→ HfCl4+ O2-Q (endothermic reaction), so increasing the temperature is beneficial to the forward reaction. When the temperature is lower than 350℃, the reaction rate is extremely slow, hafnium oxide is not completely converted, and the catalyst activity is low, which cannot effectively play a catalytic role; when the temperature is higher than 500℃, although the reaction rate is accelerated, it will lead to a significant increase in energy consumption, and may cause side reactions (such as decomposition of hafnium tetrachloride, cracking of chlorine), introduce new impurities, and also accelerate the deactivation of the catalyst. The preferred temperature range of 380-450℃ is the optimal interval determined by considering the reaction rate, conversion rate, energy consumption and catalyst stability, at which the conversion rate of hafnium oxide can reach 99.5% or more, and the occurrence rate of side reactions is extremely low.

[0068] According to the technical solution of the present application, the reaction pressure is controlled at 0.1-0.3 MPa. The effect of pressure is mainly reflected in the partial pressure of chlorine: when the pressure is lower than 0.1 MPa, the partial pressure of chlorine is insufficient, the contact probability with hafnium oxide raw materials is reduced, and the reaction rate is slowed down; when the pressure is higher than 0.3 MPa, not only the equipment pressure-bearing requirement and safety risk of the reaction kettle are increased, but also the chlorine may be excessively enriched in the reaction system, increasing the difficulty and cost of tail gas treatment. The pressure range of 0.1-0.3 MPa can not only ensure the effective mass transfer of chlorine and promote the full reaction, but also reduce the equipment cost and operation risk, achieving the balance of economy and safety of the process.

[0069] Preferably, the chlorine flow rate is 50-200 mL / min. The flow rate range of 50-200 mL / min can ensure that chlorine is in sufficient contact with the raw materials, while the amount of unreacted chlorine is controlled within a reasonable range, reducing energy consumption and environmental protection treatment cost.

[0070] Preferably, the reaction time is 2-6 hours. The determination of the reaction time is based on the relationship between the reaction rate and the conversion rate. Under the above optimized parameters, after 2 hours of reaction, the conversion rate of hafnium oxide reaches more than 95%; when extended to 6 hours, the conversion rate can approach 100%. The reaction time of 2-6 hours can balance the preparation efficiency and cost on the premise of ensuring the conversion rate.

[0071] Preferably, the chlorination reaction is carried out in a chlorination reactor, and the reactor is purged with nitrogen for more than 3 times before the reaction to remove oxygen and moisture, so as to avoid the reaction of oxygen with raw materials or products, and prevent the hydrolysis of hafnium tetrachloride. During the reaction, the supported composite catalyst plays a dual role: on the one hand, it catalyzes the chlorination reaction of hafnium oxide and chlorine, reduces the reaction activation energy, and improves the reaction rate and conversion rate; on the other hand, it strengthens the preliminary separation of niobium compounds and hafnium tetrachloride by selectively adsorbing and catalytically desorbing niobium pentachloride, laying a foundation for subsequent rectification and purification. The chlorination reaction product generated in the reaction mainly contains hafnium tetrachloride, a small amount of niobium pentachloride and other impurity chlorides (such as FeCl3, AlCl3, etc.), and the generated HCl gas and unreacted chlorine gas are absorbed and treated by a tail gas treatment device (such as a lye absorption tower).

[0072] According to the technical scheme of the present application, rectification and purification is an important step to realize the efficient separation of hafnium tetrachloride and impurities (especially niobium pentachloride), and the present application realizes deep purification by optimizing the operation parameters (overhead temperature, bottom temperature, reflux ratio, rectification time) of the rectification tower, using the boiling point difference of hafnium tetrachloride and each impurity chloride, and ensures that the niobium content of the final product is less than 10 ppb and the purity is ≥99.9999%.

[0073] The boiling point of hafnium tetrachloride is about 319℃, while the boiling point of niobium pentachloride is about 248℃, and the boiling points of other impurity chlorides (such as FeCl3 with a boiling point of 315℃ and AlCl3 with a boiling point of 181℃) also have certain differences with that of hafnium tetrachloride. Based on this characteristic, rectification and purification realizes separation by controlling the temperature gradient, so that low-boiling-point impurities (such as AlCl3 and NbCl5) are evaporated first and discharged from the top of the tower, and high-boiling-point hafnium tetrachloride is enriched in the middle of the tower and forms a vapor.

[0074] Preferably, the overhead temperature of the rectification tower is 230-250℃, and the bottom temperature is 320-340℃.

[0075] Preferably, the reflux ratio is 1:5 to 1:15, preferably 1:8 to 1:10. The reflux ratio is an important parameter affecting the efficiency of rectification separation, and it is defined as the ratio of the flow rate of the reflux liquid to the flow rate of the distillate. A reflux ratio of 1:8 to 1:10 can ensure separation efficiency, take into account preparation efficiency and energy consumption, and realize deep removal of niobium content.

[0076] Preferably, the rectification time is 4-10 hours. A rectification time of 4-10 hours can ensure the sufficient separation of each impurity and hafnium tetrachloride, so that the purity of the final product reaches more than 99.9999%, and the niobium content is reduced to less than 10 ppb.

[0077] In the rectification process, the hafnium tetrachloride vapor produced in the middle of the tower has high purity and directly enters the subsequent condensation process; the low-boiling-point impurities (mainly niobium pentachloride, AlCl3, etc.) discharged from the top of the tower are collected and treated after condensation, and the high-boiling-point impurities remaining at the bottom of the tower are regularly cleaned to ensure the continuous and stable operation of the rectification tower.

[0078] According to the technical solution of the present application, the core of the condensation and collection step is to convert the hafnium tetrachloride vapor after rectification and purification into a solid product, while ensuring that the product is not contaminated during the collection process and maintaining its high purity and ultra-low niobium content characteristics.

[0079] Preferably, the condensation temperature is set to -20℃ to 0℃. The melting point of hafnium tetrachloride is about 217℃, and the boiling point is about 319℃. In the temperature range of -20℃ to 0℃, the hafnium tetrachloride vapor can be quickly condensed into white crystalline solid, with high condensation efficiency. The condensation temperature range of -20℃ to 0℃ achieves the best balance between condensation efficiency and energy consumption.

[0080] Preferably, the condensation medium is selected as an ethanol-dry ice system, which can stably provide a condensation temperature of -20℃ to 0℃ and has stable chemical properties, without reacting with hafnium tetrachloride to affect the purity of the product. The condensation device uses a sealed polytetrafluoroethylene condenser tube and a collection tank. Polytetrafluoroethylene has good chemical inertness and does not react with hafnium tetrachloride, chlorine gas, etc., and is not prone to adsorbing impurities, which can effectively prevent product contamination.

[0081] The condensation and collection process needs to be carried out under argon protection, because hafnium tetrachloride is extremely hygroscopic and hydrolytic, and if it comes into contact with moisture in the air, it will generate hafnium oxide or hafnium oxychloride impurities, leading to a decrease in product purity. At the same time, argon as an inert gas can isolate oxygen to prevent the product from being oxidized. After collection, the product is immediately sealed and stored to prevent contamination by moisture and air during subsequent storage and transportation, ensuring the stability of the product performance.

[0082] The final hafnium tetrachloride product is detected to have a niobium content of less than 10 ppb (preferably less than 5 ppb), a purity of ≥99.9999%, and other impurities (such as iron, aluminum, calcium, etc.) content of less than 5 ppb, fully meeting the requirements of 7 nm and below advanced semiconductor process for high-purity hafnium tetrachloride raw materials.

[0083] The preparation process of the present application realizes the efficient preparation of ultra-low niobium content and high purity hafnium tetrachloride. The core synergistic effect is reflected in the following aspects: the selective adsorption and catalytic desorption of the catalyst to niobium pentachloride during the chlorination reaction makes the distribution of niobium pentachloride in the reaction product more concentrated, creating favorable conditions for rectification and purification, and reducing the difficulty of rectification and separation; and the rectification and purification completely removes the trace niobium compounds that cannot be completely separated by the catalyst through precise temperature and reflux ratio control, realizing the deep purification of niobium content. The synergistic effect of the two ensures that the niobium content is stably below 10 ppb.

[0084] Compared with the prior art, the core advantage of the present application is:

[0085] 1. Ultra-low niobium content control: through the directional catalysis of the supported composite catalyst and the deep separation of rectification and purification, the niobium content is stably below 10 ppb, preferably below 5 ppb, far exceeding the niobium removal level of existing processes, meeting the stringent requirements of advanced semiconductor processes.

[0086] 2. High purity and no introduction of impurities: the product purity reaches more than 99.9999%, and the content of other impurities is less than 5 ppb, and no new impurities (such as complexing agent, adsorbent residue, etc.) are introduced during the entire process, solving the problem of easy introduction of impurities by existing chemical precipitation and adsorption methods.

[0087] 3. Preparation efficiency is improved: the chlorination reaction time is shortened to 2-6 hours, and the rectification time is controlled within 4-10 hours, which significantly improves the production efficiency compared with the traditional process.

[0088] 4. Process stability and industrialization adaptability: the catalyst preparation process according to the present application is simple, the cost is controllable, the parameters of each step are clear and easy to control, and large-scale industrial continuous production can be realized, solving the problem of poor stability and difficulty in large-scale application of existing adsorption methods.

[0089] The present application will be described in more detail with reference to the following examples. It should be noted that these descriptions and examples are for the purpose of facilitating understanding of the present application, and are not a limitation on the present application.

[0090] Examples

[0091] In the present application, unless otherwise indicated, the reagents used are commercially available products, which are used directly without further purification treatment. In addition, the "%" mentioned is "weight%", and the "parts" mentioned is "weight parts".

[0092] The following Table 1 lists the specific information of the raw materials used in the examples and comparative examples of the present application.

[0093] Table 1 List of experimental materials

[0094]

[0095] Table 2 below lists the specific information of the experimental equipment employed in the examples and comparative examples of the present application.

[0096] Table 2 List of experimental equipment

[0097]

[0098] Performance test method

[0099] (I) Niobium content detection

[0100] The niobium content of the hafnium tetrachloride samples prepared in the following respective examples and comparative examples was detected by the method described below.

[0101] According to the steps specified in DB51 / T 1782-2014 "Determination of Niobium and Tantalum in Geological Samples by Inductively Coupled Plasma Mass Spectrometry", 0.5 g of sample was weighed in an argon glove box, a PTFE digestion tank was added, 2 mL of HF, 1 mL of nitric acid and 1 mL of 5% tartaric acid were added, and microwave digestion was performed (120°C / 5 min→170°C / 10 min→190°C / 30 min). After cooling, 2% nitric acid (containing 1% tartaric acid) was used to dilute to 50 mL. Then, a 0-20 ppb series of solutions was prepared using a 1000 μg / mL niobium standard stock solution (GSBG62034-90), and 1 ng / mL Rh internal standard was added. The parameters of the inductively coupled plasma mass spectrometer (ICP-MS) were set to radio frequency power 1550 W, atomizing gas flow rate 0.85 L / min, and collision cell helium flow rate 4 mL / min. The niobium content in the sample was calculated by inductively coupled plasma mass spectrometry (ICP-MS) detection 93 Nb isotope. Finally, the niobium content in the sample was calculated according to the standard curve method combined with the dilution factor.

[0102] (II) Purity detection

[0103] The purity of the hafnium tetrachloride samples prepared in the following respective examples and comparative examples was detected by the method described below.

[0104] According to the technical requirements for purity determination of high-purity compounds in GB / T 9722-2023 "Chemical Reagents - General Procedure for Gas Chromatography", gas chromatography-thermal conductivity detector (GC-TCD) method was used for purity detection, and the specific steps were as follows:

[0105] Sample pretreatment: The whole process was operated in a nitrogen glove box (oxygen content ≤1 ppm, water content ≤1 ppm). 0.5 g of hafnium tetrachloride sample (accurate to 0.0001 g) was accurately weighed and transferred into a sealed polytetrafluoroethylene sample bottle which was pre-blowed by nitrogen. The sample bottle was sealed to avoid contact with moisture in the air and hydrolysis.

[0106] Preparation of standard: High-purity hafnium tetrachloride (purity ≥ 99.9999%) was used as a standard. Under nitrogen protection, a series of standard solutions with concentrations of 50 mg / mL, 100 mg / mL, 200 mg / mL, 300 mg / mL and 400 mg / mL were prepared by using anhydrous ethanol (purity ≥ 99.99%, moisture ≤ 0.005%) as a diluent solvent. The sealed standard solutions were stored in a cool and dry place away from light.

[0107] Instrument debugging: Agilent 7890B gas chromatograph was used, equipped with a thermal conductivity detector (TCD) and an HP-PONA capillary column (30 m x 0.32 mm x 0.5 μm). High-purity helium (purity ≥ 99.999%) was used as the carrier gas, which was purified by 5 Å molecular sieve. The carrier gas flow was 30 mL / min, the split ratio was 10:1, and the injection volume was 1 μL. The injection port temperature was 280°C, the detector temperature was 320°C, and the detector current was 100 mA. The column temperature program was set as follows: the initial temperature was 50°C, maintained for 2 min, then increased to 300°C at a rate of 10°C / min, and maintained for 5 min to ensure complete separation and outflow of hafnium tetrachloride and various impurities (such as niobium pentachloride, aluminum chloride, iron chloride, etc.).

[0108] Detection and quantification: The gas chromatograph was first stabilized for 30 min according to the above parameters, and then the standard solutions were injected in turn. The retention time and peak area of the main peak of the standard were recorded, and the peak area-concentration standard curve was drawn. The linear regression equation (correlation coefficient R 2 ≥ 0.9995) was calculated. Then the sample solution was injected, and the retention time of the main peak (deviation from the main peak retention time of the standard ≤ 0.1 min) and the area of all chromatographic peaks were recorded. The purity was calculated by peak area normalization method, i.e. the percentage of the area of the main peak of hafnium tetrachloride in the total peak area, minus the area percentage of the solvent peak and other impurity peaks, and finally the purity value of the sample was obtained.

[0109] Parallel verification: Each sample was determined in triplicate, and the average value was taken as the final purity result. The relative standard deviation (RSD) was ≤ 0.05%, ensuring the accuracy and repeatability of the test results.

[0110] Example 1

[0111] (1) Pretreatment of hafnium oxide raw material

[0112] Take 100.0 g of hafnium oxide raw material and place it in a planetary ball mill, set the rotation speed to 300 r / min, and crush for 2 hours. Screen the crushed hafnium oxide raw material through a 200-mesh standard test sieve, collect the undersize material, and remove the large particle impurities. Transfer the screened material to the tray of a vacuum drying oven, spread it out to a thickness of about 1 cm, and set the drying conditions to a temperature of 150°C, a vacuum degree of -0.09 MPa, and a drying time of 6 hours. After drying is complete, cool to room temperature, seal and store, and obtain the pretreated hafnium oxide raw material for use.

[0113] (II) Preparation of the supported composite catalyst

[0114] Take 10.0 g of porous alumina carrier raw material and place it in a corundum crucible, place it in a high-temperature calcination furnace, set the calcination temperature to 550°C, and keep it at this temperature for 4 hours, then naturally cool to room temperature to obtain the pretreated porous alumina carrier. Then, in a 50-mL beaker, sequentially add 4.5 g of tetrabutyl titanate, 2.5 g of zirconium oxychloride, and 3.0 g of lanthanum nitrate, slowly add 30 mL of anhydrous ethanol, start a magnetic stirrer, set the rotation speed to 500 r / min, and stir for 30 minutes until the solids are completely dissolved to form a uniform transparent impregnation solution. Completely immerse the pretreated porous alumina carrier in the above impregnation solution, place the beaker in a constant-temperature water bath, set the temperature to 40°C, keep the magnetic stirring (rotation speed 300 r / min), and immerse for 10 hours. After impregnation is complete, remove the carrier from the impregnation solution and transfer it to a vacuum drying oven, set the temperature to 90°C, and dry at atmospheric pressure for 7 hours to remove the anhydrous ethanol solvent. Then, place the dried carrier in a high-temperature calcination furnace, set the calcination temperature to 600°C, keep it at this temperature for 5 hours, and naturally cool to room temperature to obtain the supported composite catalyst for use.

[0115] (III) Chlorination reaction

[0116] Place 100.0 g of pretreated hafnium oxide raw material and 0.5 g of supported composite catalyst (hafnium oxide raw material to catalyst mass ratio of 100:0.5) in a mixer, mix for 15 minutes to ensure uniform mixing. Then, add the mixed material to a chlorination reactor, seal the reactor, check the airtightness, and then replace the air in the reactor with nitrogen three times (each replacement pressure is 0.2 MPa, and the pressure is kept for 5 minutes before being released). Start the reactor heating system, set the temperature rise rate to 5°C / min, and simultaneously introduce chlorine gas at a flow rate of 50 mL / min. When the temperature in the reactor rises to 350°C and the pressure stabilizes at 0.1 MPa, start timing, and keep the conditions for the chlorination reaction for 6 hours. During the reaction, the unreacted chlorine gas and the HCl gas generated by the reaction are absorbed by the tail gas treatment device.

[0117] (IV) Purification by rectification

[0118] After the chlorination reaction is completed, stop heating, cool to room temperature, and transfer the chlorination reaction product (mainly containing hafnium tetrachloride, a small amount of niobium pentachloride and other chlorinated impurities) to the rectification tower. Start the heating system of the rectification tower, set the tower top temperature to 240°C, the tower bottom temperature to 330°C, the reflux ratio to 1:5, and the rectification time to 10 hours. During the rectification process, low-boiling-point impurities (such as niobium pentachloride, aluminum chloride, etc.) are condensed and separated through the tower top condenser, and hafnium tetrachloride vapor produced in the middle of the tower is collected and enters the next condensation process.

[0119] (V) Condensation collection

[0120] The hafnium tetrachloride vapor produced in the rectification tower is passed into a low-temperature condensation device, and the condensation temperature is set to -20°C, and the condensation medium is an ethanol-dry ice system. The hafnium tetrachloride vapor is condensed into a white crystalline solid in the condensation tube of the low-temperature condensation device and is collected in a sealed polytetrafluoroethylene collection tank. After the collection is completed, it is sealed and stored under argon protection to obtain the hafnium tetrachloride product.

[0121] Figure 1 A scanning electron microscope (SEM) photo of the prepared supported composite catalyst in Example 1 of the present application is shown.

[0122] In addition, a small amount of the prepared supported composite catalyst is subjected to phase analysis by an X-ray diffractometer, and the test conditions are as follows: Cu Kα radiation (λ = 0.15406 nm), tube voltage 40 kV, tube current 40 mA, scanning range 2θ = 10°-80°, and scanning rate 5° / min. Figure 2 An X-ray diffraction (XRD) spectrum of the prepared supported composite catalyst in Example 1 is shown. The XRD spectrum shows that the prepared supported composite catalyst has characteristic diffraction peaks of aluminum oxide at 2θ = 25.6°, 35.1°, 43.3°, etc., characteristic diffraction peaks of titanium oxide at 2θ = 27.4°, 36.1°, 41.2°, etc., characteristic diffraction peaks of zirconium oxide at 2θ = 30.2°, 35.0°, 50.3°, etc., and characteristic diffraction peaks of lanthanum oxide at 2θ = 28.2°, 41.0°, 47.7°, etc., without other impurity peaks, indicating that the active components titanium oxide, zirconium oxide and lanthanum oxide are loaded on the porous aluminum oxide carrier, and the component phases are stable.

[0123] In addition, the prepared hafnium tetrachloride product is tested for niobium content and purity according to the detection method of niobium content and purity described in detail above. The test results are shown in Table 3 below.

[0124] Examples 2-12

[0125] Examples 2-12 were carried out in a similar manner to Example 1, except that the experimental conditions were changed as shown in Table 3 below, to prepare hafnium tetrachloride products.

[0126] In addition, the hafnium tetrachloride products prepared were tested for niobium content and purity according to the detection method of niobium content and purity described above. The test results are shown in Table 3 below.

[0127] In addition, the supported composite catalysts prepared in Examples 2-12 were subjected to phase analysis using an X-ray diffractometer in a similar manner to Example 1. The results showed that the supported composite catalysts prepared in Examples 2-12 had similar diffraction patterns to the supported composite catalyst prepared in Example 1, indicating that the active components titanium oxide, zirconium oxide and lanthanum oxide were supported on the porous alumina support and the phases of the components were stable.

[0128] Comparative Examples 1-7

[0129] Comparative Examples 1-7 were carried out in a similar manner to Example 1, except that the experimental conditions were changed as shown in Table 4 below, to prepare hafnium tetrachloride products.

[0130] In addition, the hafnium tetrachloride products prepared were tested for niobium content and purity according to the detection method of niobium content and purity described above. The test results are shown in Table 4 below.

[0131] In addition, the supported composite catalysts prepared in Comparative Examples 1-7 were subjected to phase analysis using an X-ray diffractometer in a similar manner to Example 1. The results showed that the supported composite catalysts prepared in Comparative Examples 1, 2 and 3 did not have characteristic diffraction peaks of titanium oxide, zirconium oxide and lanthanum oxide in the X-ray diffraction patterns. The supported composite catalysts prepared in Comparative Examples 4-7 had similar diffraction patterns to the supported composite catalyst prepared in Example 1, indicating that the active components titanium oxide, zirconium oxide and lanthanum oxide were supported on the porous alumina support.

[0132] Table 3 Specific parameters and performance test results of Examples 1-12

[0133]

[0134] Table 4 Specific parameters and performance test results of Comparative Examples 1-7

[0135]

[0136] From Table 3, it can be seen that the tetrachloride hafnium products prepared in Examples 1-12 of the present application all meet the requirements of ultra-low niobium content and high purity, with the niobium content being less than 10 ppb and the purity reaching 99.9999%. Among them, the niobium content of Example 11 is the lowest, only 2.5 ppb, and the niobium contents of Example 10 and Example 12 are 2.8 ppb and 3.0 ppb respectively, verifying the high-efficiency removal capability of the process of the present application for niobium impurities. From the process parameter influence, when the mass ratio of hafnium oxide raw material to catalyst is controlled at 100:1 to 100:2, the proportion of tetrabutyl titanate in the active component is 50-55%, the proportion of zirconium oxychloride is 24-28%, the proportion of lanthanum nitrate is 15-26%, and the rectification reflux ratio is 1:8 to 1:10, the niobium removal effect is optimal, and the niobium content can be reduced to below 5 ppb. At the same time, the chlorination reaction time of each example is shortened to 2-6 hours, and the rectification time is controlled at 4-10 hours, which is significantly improved in efficiency compared with the traditional process, and no additional impurities are introduced, and the process stability is good.

[0137] Comparative Examples 1-7 verify the important role of the catalyst system of the present application by adjusting the active component composition and ratio of the supported composite catalyst. After the single active component of titanium oxide, zirconium oxide, lanthanum oxide is missing in Comparative Examples 1-3 respectively, the product niobium content rises to 25-33 ppb, and the purity drops to 99.9982%-99.9988%, which does not meet the requirement of ultra-low niobium content, indicating that the synergistic effect of the three active components is a key aspect to realize efficient removal of niobium. After changing the active component ratio in Comparative Examples 4-7, which deviates from the range of 40-60% tetrabutyl titanate, 20-30% zirconium oxide, and 10-30% lanthanum oxide defined in the present application, the niobium content is all higher than 20 ppb, and the purity is less than 99.9991%, further proving that the specific ratio of active components can strengthen the catalytic selectivity and promote the efficient separation of niobium compounds and tetrachloride hafnium.

[0138] In summary, the results of the examples and comparative examples show that the present application solves the problems of low niobium removal efficiency and easy introduction of impurities in the traditional process through the directional catalysis of the supported composite catalyst. The porous alumina carrier in the catalyst provides high specific surface area adsorption sites, and titanium oxide, zirconium oxide, and lanthanum oxide synergistically control the reaction system. Under the optimized chlorination and rectification conditions, the niobium content is stably below 10 ppb, and the product purity reaches the 6N level, fully meeting the needs of advanced semiconductor processes of 7 nm and below. At the same time, the process energy consumption is reduced, the operation is simple, and it is suitable for large-scale industrial production, with significant technical and application advantages.

[0139] Obviously, those skilled in the art can make various modifications and variations to the present disclosure without departing from the spirit and scope of the present disclosure. Thus, if these modifications and variations of the present disclosure fall within the scope of the present application, the present disclosure also intends to include these modifications and variations.

Claims

1. A process for preparing hafnium tetrachloride with ultra-low niobium content, characterized in that, Includes the following steps: (1) Hafnium oxide raw material with a purity greater than or equal to 99.9% and a niobium content less than or equal to 200 ppm is pulverized, sieved and vacuum dried to prepare pretreated hafnium oxide raw material; (2) Preparation of supported composite catalysts; (3) The pretreated hafnium oxide raw material and the supported composite catalyst are uniformly mixed in a mass ratio of 100:0.5 to 100:5, and a chlorination reaction is carried out in the presence of chlorine gas at a temperature of 350-500°C and a pressure of 0.1-0.3 MPa to obtain the chlorination reaction product; (4) The chlorination reaction product is purified by distillation to generate hafnium tetrachloride vapor; (5) The hafnium tetrachloride vapor is condensed to obtain hafnium tetrachloride with ultra-low niobium content, wherein: Step (2) in preparing the supported composite catalyst includes: The porous alumina support raw material is calcined at 500-600℃ for 3-5 hours and then cooled to room temperature to prepare the pretreated porous alumina support. A mixture of tetrabutyl titanate, zirconium oxychloride and lanthanum nitrate is dissolved in anhydrous ethanol to prepare an impregnation solution, wherein the mixture of tetrabutyl titanate, zirconium oxychloride and lanthanum nitrate comprises 40-60% tetrabutyl titanate, 20-30% zirconium oxychloride and 10-30% lanthanum nitrate based on its total weight of 100%. The pretreated porous alumina support is immersed in the impregnation solution and stirred at 30-50°C for 8-12 h. Then it is dried at 80-100°C for 6-8 h and finally calcined at 550-650°C for 4-6 h to obtain the supported composite catalyst.

2. The preparation process according to claim 1, characterized in that, The supported composite catalyst includes a porous alumina support and an active component supported on the porous alumina support, wherein the active component comprises titanium oxide, zirconium oxide and lanthanum oxide.

3. The preparation process according to claim 1, characterized in that, In step (1), the crushed hafnium oxide raw material is passed through a 200-400 mesh sieve.

4. The preparation process according to claim 1, characterized in that, In step (1), the vacuum drying conditions are: temperature 120-180℃, vacuum degree -0.08 to -0.1 MPa, and time 4-8 hours.

5. The preparation process according to claim 1, characterized in that, The specific surface area of ​​the porous alumina carrier material is 150-300 m². 2 / g, with a pore size of 5-20 nm.

6. The preparation process according to claim 1, characterized in that, Step (3) is carried out in a chlorination reactor, wherein the flow rate of chlorine gas is 50-200 mL / min.

7. The preparation process according to claim 1, characterized in that, The chlorination reaction in step (3) is carried out for 2-6 hours.

8. The preparation process according to claim 1, characterized in that, Step (4) is carried out in a distillation column with a top temperature of 230-250°C, a bottom temperature of 320-340°C, a reflux ratio of 1:5-1:15, and a distillation time of 4-10 hours.

9. The preparation process according to claim 1, characterized in that, Step (5) is carried out at a condensation temperature of -20°C to 0°C.

10. The preparation process according to claim 1, characterized in that, The ultra-low niobium content hafnium tetrachloride has a niobium content of less than 5 ppb and a purity greater than or equal to 99.9999%.

Images