A method for purifying electronic grade metal chlorides

Abstract

The application provides a purification method of electronic-grade metal chloride, and the purification method comprises the following steps: mixing a crude metal chloride with a reducing powder, and performing a reduction reaction under the conditions of high temperature, inert atmosphere and continuous mixing; after the reduction reaction, cooling the reaction product, performing vacuum sublimation purification, and then condensing and collecting the product. According to the purification method, electronic-grade high-purity metal chloride with a purity of 6N is directly prepared through the steps of high-temperature ball milling reduction and vacuum sublimation process, no high-pressure operation is performed in the whole process, and the process is simple and complete impurity removal.

Description

Technical Field

[0001] This invention relates to the field of metal chloride preparation, and more specifically, to a method for purifying electronic-grade metal chlorides. Background Technology

[0002] Zirconium tetrachloride and hafnium tetrachloride can be used as important intermediate raw materials for the preparation of metallic zirconium, metallic hafnium, zirconium-hafnium compounds, and organozirconium and organohafnium precursors. With the increasing application of zirconium tetrachloride and hafnium tetrachloride in electronic materials, semiconductor precursors, and the preparation of high-purity metal compounds, the requirements for controlling non-zirconium-hafnium metal impurities such as iron, aluminum, chromium, niobium, and tantalum are constantly increasing. Electronic-grade high-purity hafnium tetrachloride requires a purity of 6N (99.9999%), and the impurities of metals such as niobium, iron, aluminum, and titanium need to be controlled to the ppb level.

[0003] Industrial crude hafnium tetrachloride raw materials often contain metal chloride impurities such as niobium pentachloride (NbCl5), ferric chloride (FeCl3), and aluminum trichloride (AlCl3). Among them, niobium pentachloride and hafnium tetrachloride, as well as ferric chloride and hafnium tetrachloride, have very similar boiling points and vapor pressures, and conventional single-stage sublimation purification methods cannot achieve deep separation.

[0004] Existing technologies have reported the use of hydrogenation to reduce the metallic valence state of impurity compounds, such as converting FeCl3 to FeCl2, to increase the boiling point of the impurities, followed by sublimation separation (see patent CN117509727A). However, hydrogenation reactors are high-risk and have poor operational safety; additionally, there is the problem of uneven gas-solid reaction, requiring multiple reaction-sublimation steps to reduce Fe to the ppm level. Furthermore, conventional hydrogenation methods are not easily effective in removing Nb.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The primary objective of this invention is to provide a method for purifying electronic-grade metal chlorides. This method directly prepares electronic-grade high-purity metal chlorides with a purity of 6N through a high-temperature ball milling reduction + vacuum sublimation process. The entire process involves no high-pressure operation, is simple, and thoroughly removes impurities.

[0007] The second objective of this invention is to provide an electronic-grade metal chloride product obtained by the above purification method. The product has a purity of up to 6N electronic level, is safe and environmentally friendly, and has a wide range of applications.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0009] This invention provides a method for purifying electronic-grade metal chlorides, comprising the following steps:

[0010] The crude metal chloride product was mixed with a reducing powder, and after heating, a reduction reaction was carried out under an inert atmosphere, normal pressure, and continuous mixing conditions.

[0011] After cooling the reaction product, it was purified by sublimation under reduced pressure, and then collected by condensation.

[0012] The purification method for electronic-grade metal chlorides of the present invention employs an integrated purification method of high-temperature ball milling selective reduction and vacuum sublimation. Preferably, the reducing powder is a metal powder, a carbonyl metal powder, or a combination of both.

[0013] Preferably, as a further feasible option, when the reducing powder comprises carbonyl metal powder, the temperature of the reduction reaction is higher than the temperature at which the carbonyl metal decomposes into the corresponding metal, but lower than the temperature at which the metal chloride is in a molten state.

[0014] Specifically, taking hafnium tetrachloride as an example, crude hafnium tetrachloride (metal purity > 3N) is used as raw material. Under high-temperature sealed ball milling conditions, the grinding, mixing and reduction integrated reaction is completed. Highly active nano-metal elements are generated through in-situ decomposition of carbonyl metals. Combined with ball milling shear enhancement mass transfer and reduction process coupling, difficult-to-separate impurities are converted into high-boiling-point components under mild conditions, and then the purpose of sublimation preparation of 6N grade high-purity hafnium tetrachloride is achieved.

[0015] Preferably, as a further feasible option, for crude metal chloride with a metal purity of about 3N, the molar amount of reducing powder to be added can be calculated based on the molar amount of metal chloride. Specifically, the molar ratio of crude metal chloride to reducing powder is 100:(3-20).

[0016] Preferably, as a further feasible option, the carbonyl metal powder is at least one of carbonyl manganese, carbonyl chromium, and carbonyl iron, with a purity ≥3N and a particle size of 100-300 mesh.

[0017] Preferably, as a further feasible option, the metal powder is at least one selected from manganese, chromium, iron, zinc, and magnesium.

[0018] Preferably, as a further feasible option, the manganese, chromium, and iron powders are produced by high-temperature decomposition of carbonyl metal compounds.

[0019] Based on long-term research and understanding of carbonyl metal compounds, the inventors proposed using reducing metals generated from the in-situ decomposition of carbonyl metals to reduce impurity components during the purification process of metal chlorides. The metal powder produced by the decomposition of carbonyl metals possesses unique properties compared to metal powders prepared by conventional methods, such as higher chemical reactivity and smaller particle size. Generally, in the 200... oAbove a certain temperature (C), carbonyl metal compounds begin to decompose gradually, reaching complete decomposition above 300 °C, generating highly active elemental metals with particle sizes of 1-10 nm and trace amounts of carbon monoxide gas. The inventors proposed applying these advantages to the purification process of hafnium tetrachloride. Carbonyl metal powder is used as a reducing agent, directly added to crude hafnium tetrachloride. The carbonyl metal generates highly active nano-metal elements in situ at high temperatures. Through ball milling, these elements continuously react with impurity chlorides in hafnium tetrachloride, significantly increasing the reaction contact area. Simultaneously, the ball milling process effectively prevents low-valent chlorides from occupying the active sites of the reducing metal for extended periods, thus reducing the reactivity of the elemental metal. Experiments have shown that this method can rapidly reduce high-valent impurities such as NbCl5, FeCl3, and AlCl3 to high-boiling-point, non-sublimable low-valent metal chlorides (NbCl3, FeCl2, AlCl2). The trace amounts of carbon monoxide generated during decomposition further enhance the reducing atmosphere of the system, inhibiting secondary oxidation of low-valent impurities without introducing solid impurity residues.

[0020] Preferably, as a further feasible option, the reduction reaction process involves ball milling to premix crude metal chloride and reducing powder.

[0021] Preferably, as a further feasible option, the reduction reaction is carried out in a ball mill reactor, with agate balls as the grinding media, having a particle size of 5-10 mm and a material-to-ball mass ratio of 1:3.

[0022] In addition, the present invention also provides an electronic-grade high-purity metal chloride product obtained by purification method, which has high purity and wide applicability.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1) This invention uses reducing metals to reduce and transform impurities such as Nb and Fe in crude hafnium tetrachloride to change the boiling point of the impurities, and then uses vacuum sublimation to separate the target product from the impurities.

[0025] 2) The present invention employs high-temperature dynamic ball milling during the reduction reaction process. Compared with static heating after grinding and mixing only before the reaction, this method can enhance mixing and significantly improve the removal effect of Nb and Fe impurities.

[0026] 3) Using carbonyl metal compounds such as carbonyl manganese and carbonyl chromium as reducing metal powders can achieve lower Nb and Fe residues with less loss of target products compared to directly adding the corresponding manganese or chromium powders.

[0027] 4) This invention directly uses carbonyl metal powder for the reduction reaction, utilizing its properties at 300°C. oThe system utilizes the characteristic of complete in-situ decomposition above C, generating highly active nano-metallic elements with particle sizes of 1-10 nm in situ, while simultaneously releasing trace amounts of carbon monoxide to enhance the reducing atmosphere. Combined with ball milling shearing action, it improves the contact between nano-metals and metal chlorides, achieving the reduction of trace impurities such as NbCl5 and FeCl3. Compared to directly using reducing metal powders, this method can improve reduction activity, enhance mixing, and reduce the introduction of impurities. This approach can stably reduce the residual niobium impurities in crude hafnium tetrachloride to below 20 ppb. Detailed Implementation

[0028] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0029] Example 1

[0030] 1) Raw material loading:

[0031] In an anhydrous and oxygen-free glove box, take 120g of 3N grade crude hafnium tetrachloride and add 14.6g of high-purity carbonyl manganese (purity ≥5N, 100 mesh), and put them into a high-temperature sealed planetary ball mill reactor (customized equipment: ball mill jar volume 1.2 L, 10 MPa, material HC 276). Add agate balls (5~10 mm) into the jar, with a material-to-ball mass ratio of 1:3.

[0032] 2) High-temperature reduction reaction:

[0033] The reactor was sealed and purged three times with high-purity nitrogen (≥99.999%), each time evacuated to -0.1 MPa and then purged with nitrogen to 0.1 MPa. The ball mill and heating system were turned on, maintaining a constant temperature of 350℃ and a ball milling speed of 300 r / min, alternating between forward and reverse rotation (30 min / cycle) for 6 hours. During the reaction, hafnium tetrachloride sublimated into a gaseous state, and manganese carbonyl decomposed in situ to release highly reactive metallic manganese. The gaseous hafnium tetrachloride and metallic manganese continuously reacted in contact during the ball milling process.

[0034] 3) Decompression sublimation purification:

[0035] After the reaction was complete, the mixture was allowed to cool naturally to room temperature. Under an anhydrous and oxygen-free atmosphere, the product was transferred to a 1L vacuum sublimation apparatus; the vacuum was then evacuated to 50 Pa, and the product was sublimated at 5... o Heating to 220°C at a rate of C / min and holding for 5 hours; then condensing to 30°C. o C, collect the products.

[0036] 4) Product testing:

[0037] According to ICP-MS testing, the product purity reached 6N (99.9999%), and the material yield was 95.2%.

[0038] Examples 2-7

[0039] The implementation methods of Examples 2-7 are the same as those of Example 1, except that the reducing powders added to the reactor are iron powder, carbonyl chromium, carbonyl iron (solid complex), manganese powder, chromium powder, and magnesium powder, respectively.

[0040] The specific examples using metallic iron powder as a reducing agent are as follows:

[0041] 1) Raw material loading:

[0042] In an anhydrous and oxygen-free glove box, weigh 120 g of crude hafnium tetrachloride with a metal purity of 3N and add 2.1 g of high-purity iron powder (purity not less than 5N, particle size 100 mesh). Load the crude hafnium tetrachloride and high-purity iron powder together into a high-temperature sealed planetary ball mill reactor (pressure resistant 10 MPa, 0-500... o C, at a rotation speed of 0-3000 rpm. Agate balls with a particle size of 5-10 mm are added to the ball mill jar, with a material-to-agate ball mass ratio of 1:3, and then the ball mill reactor is sealed.

[0043] 2) High-temperature reduction reaction:

[0044] The sealed reactor was purged with high-purity nitrogen gas with a purity of not less than 99.999% for a total of 3 times; each time, the pressure was first evacuated to about -0.1 MPa, and then nitrogen gas was introduced to the pressure of 0.1 MPa.

[0045] After nitrogen purging, the ball mill and heating system were turned on, the reaction temperature was raised to 350 ℃ and kept constant, the ball mill speed was controlled at 300 r / min, and the ball milling was carried out by alternating forward and reverse rotation. The rotation direction was switched every 30 min, and the reaction was continued for 6 h.

[0046] 3) Decompression sublimation purification:

[0047] After the reaction is complete, allow the ball mill reactor to cool naturally to room temperature. Under anhydrous and oxygen-free conditions, transfer the reaction product to a 1 L vacuum sublimation apparatus.

[0048] The sublimation apparatus was evacuated to 50 Pa, and then 5... o Heating rate increased to 220 °C / min o C, and kept at this temperature for 5 h to sublimate hafnium tetrachloride; the sublimation product is then processed at 30 °C. o The hafnium tetrachloride product was obtained by condensing and collecting the hafnium tetrachloride under C conditions.

[0049] 4) Product testing:

[0050] The metal impurity content in the obtained product was detected by ICP-MS. The test results showed that the metal purity of the obtained hafnium tetrachloride product reached 6N grade, i.e., 99.9999%, and the product yield was 96.3%.

[0051] The results of the remaining examples are shown in Table 1. As can be seen from the results of Examples 2-7, under the same reaction temperature and reducing agent dosage, different types of reducing agents showed significant differences in the removal effect of impurities from crude hafnium tetrachloride and the product yield. Using carbonyl metals as reducing agents, compared to directly using the corresponding metal powders, can achieve more thorough impurity removal while maintaining a higher product yield. On the other hand, excessively strong reducing power may lead to increased loss of the target product. In summary, the actual effect of the reducing agent is difficult to predict due to the influence of multiple factors such as impurity removal ability, reaction selectivity, and the residual elements of the reducing agent itself. Among them, carbonyl manganese and carbonyl chromium showed better overall purification effects.

[0052] Examples 8-9

[0053] The implementation methods of Examples 8-9 are the same as those of Example 1, except that after the ball mill and heating system are turned on in the reactor, the constant temperature is changed to 360°C. o C, 370 o C.

[0054] Examples 10-13

[0055] The implementation methods of Examples 10-13 are the same as those of Example 1, except that the amount of carbonyl manganese added is changed.

[0056] Example 10 is a process blank example, in which no reducing powder was added, but it still underwent the same high-temperature dynamic ball milling and vacuum sublimation treatment as Example 1. Testing showed that the content of equipment-related metal impurities such as Ni, Cr, and Mo in the product did not increase significantly before and after the high-temperature ball milling treatment. Some impurities with significantly different volatility from hafnium tetrachloride could be directly separated during vacuum sublimation, thus increasing the purity of the obtained product to 4N, but niobium and iron impurities were not effectively removed.

[0057] Comparative Example 1

[0058] The steps in this comparative example are basically the same as those in the embodiment, except that the impurity reduction process in this comparative example does not use ball milling for mixing. Instead, the coarse HfCl4 and metallic manganese powder are thoroughly ground in a mortar in a glove box, and then directly reduced using a conventional high-pressure autoclave. The temperature during the reduction process is set to 350°C. o C, the reaction time was 6 h. After the reaction, the system was cooled and purified by sublimation under reduced pressure using the same method as in Example 1 to obtain the product.

[0059] Analysis revealed that the product purity was 4N, with a niobium content >10 ppm. This demonstrates that directly reacting a metal powder with impurity chloride using a suitable reducing agent can replace hydrogen in reducing impurity metal ions. However, the niobium content remains relatively high, and there are significant batch-to-batch variations. This suggests that conventional static solid-solid reactions suffer from limited contact area, uneven reaction, and passivation of the reducing agent.

[0060] Comparative Example 2

[0061] This comparative example uses the traditional sublimation purification method, directly sublimating crude hafnium tetrachloride under reduced pressure, repeated 3 times.

[0062] The conditions, product purity, and key impurity content of each embodiment are summarized in Table 1 (Example 2 is not repeated).

[0063] Table 1. Conditions and product purity of each embodiment and comparative example.

[0064]

[0065] Although the invention has been illustrated and described with reference to specific embodiments, it should be understood that many other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, it is intended that all such changes and modifications falling within the scope of the invention be included in the appended claims.

Claims

1. A method for purifying electronic-grade metal chlorides, characterized in that, Includes the following steps: The crude metal chloride product is mixed with a reducing powder and a reduction reaction is carried out under high temperature, inert atmosphere and continuous mixing conditions. After the reduction reaction, the reaction product was cooled, purified by sublimation under reduced pressure, and then collected by condensation.

2. The purification method according to claim 1, wherein the reducing powder is a metal powder, a carbonyl metal powder, or a combination of both.

3. In the purification method according to claim 2, when the reducing powder includes carbonyl metal powder, the temperature of the reduction reaction is higher than the temperature at which the carbonyl metal decomposes into the corresponding metal, but lower than the temperature at which the metal chloride is in a molten state.

4. In the purification method according to claim 1, the molar ratio of the crude metal chloride to the reducing powder is 100:(3-20).

5. The purification method according to claim 2, characterized in that, The metal powder is at least one of manganese powder, chromium powder, iron powder, zinc powder, and magnesium powder.

6. The purification method according to claim 2, characterized in that, The metal powder is obtained by high-temperature in-situ decomposition of the corresponding carbonyl metal compound.

7. The purification method according to claim 2, characterized in that, The carbonyl metal powder is at least one of carbonyl manganese, carbonyl chromium, and carbonyl iron, with a purity ≥3N and a particle size of 100-300 mesh.

8. The purification method according to claim 1, characterized in that, In the reduction reaction process, ball milling is used to promote the reaction between crude metal chloride and reducing powder.

9. The purification method according to claim 8, characterized in that, The reduction reaction is carried out in a ball mill reactor, with agate balls as the grinding medium. The agate balls have a particle size of 5-10 mm and a material-to-ball mass ratio of 1:

3.

10. The electronic-grade metal chloride obtained by the purification method according to any one of claims 1-9.

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