A method for preparing tetra(dimethylamino)hafnium

Abstract

The application discloses a preparation method of tetra (dimethylamine) hafnium and belongs to the technical field of group IVB metal organic compound preparation. The preparation method comprises the following steps: S1, once rectification of tetra (dimethylamine) hafnium crude product, and collection of the first main distillate; S2, dissolution of the first main distillate, and recrystallization to obtain crystals; S3, dissolution of the crystals for secondary rectification, and collection of the second main distillate. The tetra (dimethylamine) hafnium crude product is derived from waste liquid in a production process of cyclopentadienyl tris (dimethylamine) hafnium, and the crude product contains ≤8.0 ppm of Fe and ≤1.0 ppm of Ti; the application realizes 6N level (more than 99.9999%) ultra-high purity recovery of TDMAHf product in CpHf synthesis waste liquid by optimizing key parameters such as rectification and recrystallization parameters, the recovered product fully meets the strict requirements of high-end fields such as semiconductor thin film deposition on metal precursors, the preparation method has the advantages of short process cycle, high processing efficiency and no introduction of other impurities, and can realize industrial application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of Group IVB metal organic compound preparation, and particularly relates to a preparation method of tetra (dimethylamino) hafnium. BACKGROUND

[0002] As a high-purity hafnium-based precursor, tetra (dimethylamino) hafnium (TDMAHf for short) has important applications in semiconductor manufacturing processes, especially in atomic layer deposition technology. In industry, TDMAHf is often synthesized by ligand exchange reaction of cyclopentadiene monomer or metal compounds containing cyclopentadienyl with TDMAHf to synthesize another important ALD precursor, i.e. cyclopentadienyl tris (dimethylamino) hafnium (CpHf for short).

[0003] In the synthesis process of CpHf, part of TDMAHf fails to coordinate with cyclopentadiene monomer, resulting in unreacted TDMAHf in the reaction waste liquid after the reaction is completed. In industry, vacuum distillation process is generally used to separate and recover the TDMAHf crude product from the reaction waste liquid. However, since each reaction raw material itself contains trace amounts of metal impurities (such as Fe and Ti), and additional impurities may be introduced due to equipment corrosion during high-temperature reaction and distillation, the Fe and Ti impurity content of the obtained TDMAHf crude product is significantly over-standard, which is difficult to meet the strict requirements of semiconductor-grade precursors on purity, which brings great obstacles to the recycling and reuse of precursors in waste liquid.

[0004] The existing purification technologies (such as conventional rectification and molecular sieve adsorption) have limited effect on the removal of metal impurities, mainly because the boiling points of Fe and Ti impurities are close to that of TDMAHf, and conventional distillation cannot effectively separate them; in addition, metal impurities may exist in the form of complex state or colloidal particles, and traditional adsorption method has poor selectivity and insufficient capacity.

[0005] Therefore, it is of great significance to develop a refining method that can efficiently and deeply remove impurity elements, especially Fe and Ti impurities, in TDMAHf crude product, to realize the high-value recycling of TDMAHf, improve the utilization rate of raw materials, and ensure the safety of semiconductor precursor supply chain. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of tetra (dimethylamino) hafnium to solve the problem of high impurity content and difficult removal of tetra (dimethylamino) hafnium recovered from CpHf synthesis waste liquid. By sequentially performing rectification, recrystallization, and rectification treatment on the tetra (dimethylamino) hafnium separated from the waste liquid, and further optimizing process parameters and other process conditions, the purity of the recovered tetra (dimethylamino) hafnium can reach 6N or more, and the preparation method is time-saving and efficient, which can be applied on a large scale in industry.

[0007] In order to achieve the above technical effects, the present application is achieved by the following technical means:

[0008] Firstly, the present application provides a preparation method of tetra (dimethylamine) hafnium, comprising the following steps:

[0009] S1, once rectification of tetra (dimethylamine) hafnium crude product, the rectification temperature is 80-100℃, the pressure is 0.3-1.0mbar, and the first main fraction is collected;

[0010] S2, using solvent to dissolve the first main fraction, recrystallization at-20~15℃ to obtain crystals;

[0011] S3, dissolving the crystals of S2 for secondary rectification, the rectification temperature is 80-100℃, the pressure is 0.4-1.2mbar, and the secondary main fraction is collected.

[0012] Further, the tetra (dimethylamine) hafnium crude product is derived from the waste liquid of cyclopentadienyl tris (dimethylamine) hafnium (i.e. CpHf) production process; in an embodiment, the preparation steps of the cyclopentadienyl tris (dimethylamine) hafnium include: (1) tetra (dimethylamine) hafnium and cyclopentadiene monomer reaction to generate CpHf; (2) distillation to separate out CpHf. Further, the preparation of the cyclopentadienyl tris (dimethylamine) hafnium can be one-pot method or step-by-step method, which is not particularly specified in the present application; further, the tetra (dimethylamine) hafnium crude product is derived from the waste liquid after step (3) distillation.

[0013] Further, the tetra (dimethylamine) hafnium crude product contains ≤8.0ppm of Fe and ≤1.0ppm of Ti; in an embodiment, the tetra (dimethylamine) hafnium crude product contains 2.5-8.0ppm of Fe and 0.1-1.0ppm of Ti. In an embodiment, the tetra (dimethylamine) hafnium crude product contains 2.5-5.0ppm of Fe and 0.1-0.5ppm of Ti. In an embodiment, the tetra (dimethylamine) hafnium crude product contains 2.5-4.0ppm of Fe and 0.1-0.3ppm of Ti.

[0014] Further, the rectification temperature in S1 is 85-95℃, for example but not limited to any one of 85℃, 86℃, 87℃, 88℃, 89℃, 90℃, 91℃, 92℃, 93℃, 94℃, 95℃.

[0015] Further, the distillation pressure in S1 is 0.6-1.0 mbar, for example but not limited to any one of 0.6 mbar, 0.65 mbar, 0.7 mbar, 0.75 mbar, 0.8 mbar, 0.85 mbar, 0.9 mbar, 0.95 mbar, 1.0 mbar.

[0016] Further, the pre-distillate in S1 accounts for 5-15% of the mass of the crude product, and the primary main distillate accounts for 60-90% of the mass of the crude product; the balance is the post-distillate and the pot residue; preferably, the pre-distillate accounts for 7-12% of the mass of the crude product, and the primary main distillate accounts for 70-85% of the mass of the crude product.

[0017] Further, the collection rate of the pre-distillate in S1 is 10-50 d / min, preferably 20-40 d / min, for example but not limited to any one of 10 d / min, 12 d / min, 15 d / min, 20 d / min, 23 d / min, 25 d / min, 28 d / min, 30 d / min, 32 d / min, 35 d / min, 37 d / min, 39 d / min, 40 d / min.

[0018] Further, the collection rate of the primary main distillate in S1 is 35-60 d / min, preferably 40-50 d / min, for example but not limited to any one of 35 d / min, 38 d / min, 40 d / min, 42 d / min, 44 d / min, 45 d / min, 46 d / min, 50 d / min, 52 d / min, 55 d / min, 57 d / min, 59 d / min, 60 d / min. The unit "d / min" in the present application means "drops per minute", and the weight of every 20 drops is about 1 g.

[0019] Further, the solvent is selected from alkanes, including but not limited to at least one of n-butane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-dodecane. In a preferred embodiment, the solvent comprises n-hexane.

[0020] Further, the amount of solvent is 1-3 times the mass of the primary main distillate.

[0021] Further, the recrystallization temperature is -15-10℃, preferably -10-8℃; for example but not limited to any one of -15℃, -14℃, -13℃, -12℃, -11℃, -10℃, -9℃, -8℃, -7℃, -6℃, -5℃, -4℃, -3℃, -2℃, -1℃, 0℃, 1℃, 2℃, 3℃, 4℃, 5℃, 6℃, 7℃, 8℃.

[0022] Further, the recrystallization time is ≥24h, preferably 24-60h.

[0023] Further, the Fe content in the tetrakis(dimethylamino)hafnium crystals obtained from S2 is <0.5ppm, and the Ti content is ≤0.1ppm.

[0024] Further, the distillation pressure in S3 is 0.4-0.8mbar.

[0025] Further, in S3, the front fraction accounts for 5-15% of the feed mass, the second main fraction accounts for 70-90% of the feed mass, and the rest is the rear fraction and the pot residue.

[0026] Further, in S3, the front fraction is collected at a speed of 20-40d / min, and the second main fraction is collected at a speed of 40-50d / min.

[0027] Further, the same distillation device is used in S1 and S3, and the column height of the distillation column is ≥1m, for example but not limited to any one of 1m, 1.5m, 2m, 2.5m, 3m, 3.5m, 4m, etc.

[0028] Further, the distillation column is loaded with packing, and the packing includes glass spring packing; in an embodiment, the glass spring packing is filled to the top end of the distillation column, and the filling length accounts for 1 / 20-1 / 5 of the column height of the distillation column.

[0029] Further, the packing further includes at least one of stainless steel structured packing, stainless steel triangular spiral packing, and metal Pall ring. In an embodiment, the packing includes glass spring packing filled to the top end of the distillation column and stainless steel triangular spiral packing filled to the rest of the distillation column.

[0030] Further, the second main fraction collected in S3 is used as electronic-grade tetrakis(dimethylamino)hafnium, and the Fe content in the second main fraction is ≤0.1ppm, and the Ti content is ≤0.01ppm.

[0031] Compared with the prior art, the present application has at least the following beneficial effects:

[0032] (1) The present application realizes the recovery of 6N (99.9999% or more) ultra-high purity TDMAHf product from the CpHf synthesis waste liquid through the optimized three-stage purification process of “primary distillation-recrystallization-secondary distillation”, and the recovered product fully meets the stringent requirements of high-end fields such as semiconductor thin film deposition on metal precursors. The above treatment processes work together to solve the problem of difficult removal of Fe, Ti and other impurities in TDMAHf, and the Fe impurity content in the recovered product is less than 0.1ppm, and the Ti impurity content is less than 0.01ppm.

[0033] (2) The application can further improve the product yield on the basis of improving the purity of TDMAHf product by optimizing the key parameters such as rectification and recrystallization parameters, and has significant economic benefits.

[0034] (3) The application does not require special reaction devices, has a short process cycle, high processing efficiency and does not introduce other impurities, and can realize industrial application. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0036] In the following examples and comparative examples, the tetra (dimethylamine) hafnium crude product is derived from the front-end distillation waste liquid in the CpHf production process, wherein the Fe element content is 2.825 ppm, and the Ti element content is 0.217 ppm; the collection speed unit d / min means drop / minute, and the weight of every 20 drops is about 1 g.

[0037] Example 1

[0038] The embodiment provides a preparation method of tetra (dimethylamine) hafnium, comprising the following steps:

[0039] S1, set up the rectification device and check for leaks, and then pump 2.353 kg of tetra (dimethylamine) hafnium crude product into the rectification kettle under negative pressure, vacuumize the kettle to 0.8 mbar, start the -10℃ condensate water and heat the kettle, heat to about 90℃ in the kettle, and the overhead temperature rises to about 40℃, collect the front-end fraction at a rate of 30 d / min, and the collection amount is 10% of the mass of the crude product, then switch to the main fraction, and control the collection speed of the main fraction to be 45 d / min under nitrogen protection, and the collection amount is 80% (about 1.882 kg) of the mass of the crude product, and stop the rectification when there is basically no reflux in the kettle, turn off the heating, replace the product receiving bottle under nitrogen protection, and the kettle temperature basically drops to room temperature to obtain the rear-end fraction.

[0040] S2, completely dissolve the main fraction by using n-hexane, the amount of n-hexane is 2 times the total mass of the main fraction, and the n-hexane is sealed and stored at 2℃ for 48 h for recrystallization, then the crystals are taken out and the crystal surface is washed with n-hexane, the residual mother liquor is washed clean, and then the n-hexane on the surface of the crystals is pumped away under vacuum to obtain tetra (dimethylamine) hafnium crystals (about 1.712 kg).

[0041] S3, set up the rectification device and leak detection, the crystal obtained in S2 was completely melted and then was drawn into the rectification kettle under negative pressure, the kettle was vacuumized to 0.8 mbar, -10 ℃ condensing water was opened and the kettle was heated, the temperature in the rectification kettle was heated to about 95 ℃, the temperature at the top of the column was increased to about 40 ℃, the secondary pre-distillate was collected at a rate of 30 d / min, the collection amount was 10% of the mass of the feed, after the end, the main distillate was switched, the collection speed of the secondary main distillate was controlled to be 40 d / min under nitrogen protection, the collection amount was 85% of the mass of the feed (about 1.456 kg), when there was basically no reflux in the kettle, the rectification was stopped, the heating was turned off, the product receiving bottle was replaced under nitrogen protection, and when the temperature in the kettle was basically reduced to room temperature, the after-distillate was obtained.

[0042] The same rectification device was used in S1 and S3, the height of the rectification column was 1.5 m, and the rectification column filler included glass spring filler and stainless steel triangular spiral filler, wherein the glass spring filler was located at the top end of the rectification column, and the filling amount at the top end was 1 / 10 of the column height of the rectification column.

[0043] The tetra (dimethylamino) hafnium crystal of S2 and the secondary main distillate of S3 were used for ICP-MS purity detection, the results showed that the content of Fe in the crystal was 0.412 ppm, the content of Ti was 0.005 ppm, the content of Fe in the secondary main distillate was 0.065 ppm, and the content of Ti was 0.002 ppm, and the 6N grade tetra (dimethylamino) hafnium obtained by the above preparation method had a qualified product yield of 61.88%.

[0044] No Zr and Nb elements were detected in the qualified product, and the content of other element impurities was also within the industry control range, meeting the requirements of electronic grade chemicals.

[0045] Example 2

[0046] The embodiment provides a preparation method of tetra (dimethylamino) hafnium, comprising the following steps:

[0047] S1, set up the rectification device and leak detection, 2.550 kg of tetra (dimethylamino) hafnium crude was drawn into the rectification kettle under negative pressure, the kettle was vacuumized to 0.9 mbar, -10 ℃ condensing water was opened and the kettle was heated, the temperature in the rectification kettle was heated to about 100 ℃, the temperature at the top of the column was increased to about 40 ℃, the pre-distillate was collected at a rate of 40 d / min, the collection amount was 7% of the mass of the crude, after the end, the first main distillate was switched, the collection speed of the first main distillate was controlled to be 50 d / min under nitrogen protection, the collection amount was 75% of the mass of the crude (about 1.913 kg), when there was basically no reflux in the kettle, the rectification was stopped, the heating was turned off, the product receiving bottle was replaced under nitrogen protection, and when the temperature in the kettle was basically reduced to room temperature, the after-distillate was obtained.

[0048] S2, completely dissolve the first main fraction with n-hexane, the amount of n-hexane is 1.5 times of the mass of the first main fraction, store the mixture at 5℃ for 24 hours to recrystallize, then take out the crystals and rinse the surface of the crystals with n-hexane, rinse the residual mother liquor, and then remove the n-hexane on the surface of the crystals under vacuum to obtain the tetra (dimethylamine) hafnium crystals (1.588 kg).

[0049] S3, set up the rectification device and check for leaks, melt the crystals obtained in S2 and then pump them into the rectification kettle under negative pressure, vacuumize the kettle to 0.6 mbar, open the -10℃ condenser and heat the kettle, heat until the temperature in the rectification kettle is about 90℃, the temperature at the top of the column is about 42℃, collect the second pre-distillate at a rate of 40 d / min, the amount of the second pre-distillate is 5% of the mass of the feed, then switch to the second main fraction, control the collection rate of the second main fraction to be 45 d / min under nitrogen protection, the amount of the second main fraction is 90% of the mass of the feed (about 1.429 kg), stop the rectification when there is basically no reflux in the kettle, turn off the heating, replace the product receiving bottle under nitrogen protection, and then the temperature in the kettle basically decreases to room temperature.

[0050] The same rectification device is used in S1 and S3, the height of the rectification column is 2 m, the rectification column is filled with glass spring filler and stainless steel triangular spiral filler, and the glass spring filler is located at the top of the rectification column, and the filling amount at the top is 1 / 8 of the column height.

[0051] The ICP-MS purity detection result shows that the content of Fe in the crystals is 0.615 ppm, and the content of Ti is 0.042 ppm; in the second main fraction, the content of Fe is 0.095 ppm, and the content of Ti is 0.013 ppm. The above preparation method obtains 6N grade tetra (dimethylamine) hafnium, and the yield of qualified products is 56.04%.

[0052] Example 3

[0053] The embodiment provides a preparation method of tetra (dimethylamine) hafnium, which comprises the following steps:

[0054] S1, set up the rectification device and check for leaks, pump 1.860 kg of tetra (dimethylamine) hafnium crude into the rectification kettle under negative pressure, vacuumize the kettle to 0.6 mbar, open the -10℃ condenser and heat the kettle, heat until the temperature in the rectification kettle is about 85℃, the temperature at the top of the column is about 40℃, collect the pre-distillate at a rate of 20 d / min, the amount of the pre-distillate is 5% of the mass of the crude, then switch to the first main fraction, control the collection rate of the first main fraction to be 40 d / min under nitrogen protection, the amount of the first main fraction is 85% of the mass of the crude (about 1.581 kg), stop the rectification when there is basically no reflux in the kettle, turn off the heating, replace the product receiving bottle under nitrogen protection, and then the temperature in the kettle basically decreases to room temperature to obtain the post-distillate.

[0055] S2, completely dissolve the first main fraction with n-hexane, the amount of n-hexane is 1 times of the mass of the first main fraction, store it at -4℃ for 60h to recrystallize, then take out the crystal and rinse the surface of the crystal with n-hexane, rinse the residual mother liquor clean, and then remove the n-hexane on the surface of the crystal with vacuum to obtain the tetra (dimethylamine) hafnium crystal (1.455kg).

[0056] S3, set up the rectification device and check for leaks, melt the crystal obtained in S2 and then pump it into the rectification kettle under negative pressure, vacuumize the kettle to 0.7mbar, open the -10℃ condensate water and heat the kettle, heat it to about 95℃ in the rectification kettle, the overhead temperature rises to about 40℃, collect the second pre-distillate at a rate of 20d / min, the amount is 15% of the mass of the feed, then switch to the second main fraction, control the collection rate of the second main fraction to be 50d / min under nitrogen protection, the amount is 80% of the mass of the feed (about 1.164kg), stop the rectification when there is basically no reflux in the kettle, turn off the heating, replace the product receiving bottle under nitrogen protection, and then the temperature in the kettle basically drops to room temperature.

[0057] The same rectification device is used in S1 and S3, the height of the rectification column is 1.5m, the rectification column is filled with glass spring filler and stainless steel triangular spiral filler, and the glass spring filler is located at the top of the rectification column, and the filling amount at the top is 1 / 10 of the column height.

[0058] The ICP-MS purity test results show that the Fe content in the crystal is 0.485ppm, and the Ti content is 0.022ppm; the Fe content in the second main fraction is 0.088ppm, and the Ti content is 0.019ppm. The above preparation method can obtain 6N grade tetra (dimethylamine) hafnium, and the yield of qualified products is 62.58%.

[0059] Comparative Example 1

[0060] This comparative example provides a preparation method of tetra (dimethylamine) hafnium, which is basically the same as Example 1, except that the stainless steel spiral filler in the rectification column is replaced by metal theta ring filler.

[0061] The ICP-MS purity test results show that the Fe content in the crystal is 0.825ppm, and the Ti content is 0.127ppm; the Fe content in the second main fraction is 0.213ppm, and the Ti content is 0.109ppm, and no 6N grade tetra (dimethylamine) hafnium qualified product is obtained.

[0062] Comparative Example 2

[0063] The comparative example 1 provides a preparation method of tetra (dimethylamine) hafnium, which is basically the same as that of the example 1, except that the full load triangular spiral fillers are used in the rectification columns S1 and S3.

[0064] The ICP-MS purity detection result shows that the Fe content in the crystal is 0.735 ppm, and the Ti content is 0.011 ppm; in the secondary main fraction, the Fe content is 0.153 ppm, and the Ti content is 0.007 ppm. No qualified product of 6N tetra (dimethylamine) hafnium is obtained.

[0065] Comparative example 3

[0066] The comparative example 1 provides a preparation method of tetra (dimethylamine) hafnium, which is basically the same as that of the example 1, except that the full load triangular spiral fillers are used in the rectification columns S1 and S3.

[0067] The ICP-MS purity detection result shows that the Fe content in the crystal is 0.335 ppm, and the Ti content is 0.012 ppm; in the secondary main fraction, the Fe content is 0.095 ppm, and the Ti content is 0.007 ppm. The above preparation method can obtain 0.303 kg of 6N tetra (dimethylamine) hafnium, and the yield of qualified product is 13.76%. Although qualified product is produced, the yield is too low.

[0068] Comparative example 4

[0069] The comparative example 1 provides a preparation method of tetra (dimethylamine) hafnium, which is basically the same as that of the example 1, except that the full load triangular spiral fillers are used in the rectification columns S1 and S3.

[0070] The ICP-MS purity detection result shows that the Fe content in the crystal is 1.446 ppm, and the Ti content is 0.153 ppm; in the secondary main fraction, the Fe content is 0.912 ppm, and the Ti content is 0.125 ppm. No qualified product of 6N tetra (dimethylamine) hafnium is obtained by the above preparation method.

[0071] Comparative example 5

[0072] The comparative example 1 provides a preparation method of tetra (dimethylamine) hafnium, which is basically the same as that of the example 1, except that the full load triangular spiral fillers are used in the rectification columns S1 and S3.

[0073] The ICP-MS purity detection result shows that the Fe content in the crystal is 0.405 ppm, and the Ti content is 0.009 ppm; in the secondary main fraction, the Fe content is 0.208 ppm, and the Ti content is 0.004 ppm. No qualified product of 6N tetra (dimethylamine) hafnium is obtained.

[0074] Comparative Example 6

[0075] This comparative example provides a preparation method of tetra (dimethylamino) hafnium, which is basically the same as Example 1, except that diethyl ether is used to dissolve the first main fraction for recrystallization in S2.

[0076] The ICP-MS purity test results show that the Fe content in the crystal is 1.253 ppm, and the Ti content is 0.115 ppm; in the second main fraction, the Fe content is 0.807 ppm, and the Ti content is 0.094 ppm, and no 6N grade tetra (dimethylamino) hafnium qualified product is obtained.

[0077] The ICP-MS test results of the above examples and comparative examples are summarized in Table 1.

[0078] Table 1

[0079]

[0080] From the above results, it can be seen that the protection scheme of the present application can obtain the optimal product purity and product yield, and can be used for industrialized treatment of CpHf synthesis waste liquid to recover TDMAHf, and has high economic benefits.

[0081] It should be noted that in this text, relational terms such as first and second are used merely to distinguish one entity or action from another, without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus including a series of elements includes not only those elements, but also other elements not explicitly listed or inherent to such a process, method, article or apparatus.

[0082] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for the preparation of tetra (dimethylamino) hafnium, characterized in that, The method comprises the following steps: S1, primary distillation of the tetra (dimethylamine) hafnium crude product, the distillation temperature is 80-100℃, the pressure is 0.3-1.0mbar, and the primary main distillate is collected; wherein, the front distillate accounts for 5-15% of the mass of the crude product, the primary main distillate accounts for 60-90% of the mass of the crude product, and the collection speed of the primary main distillate is 35-60d / min; S2, the primary main distillate is dissolved using a solvent, and recrystallized at-20~15℃ to obtain crystals; the solvent is selected from an alkane solvent; S3, the crystals of S2 are dissolved and subjected to secondary distillation, the distillation temperature is 80-100℃, the pressure is 0.4-1.2mbar, and the secondary main distillate is collected; The tetra (dimethylamine) hafnium crude product contains ≤8.0ppm of Fe and ≤1.0ppm of Ti; The distillation column is loaded with packing, and the packing comprises glass spring packing and stainless steel triangular spiral packing; the glass spring packing is filled to the top end of the distillation column, and the filling length accounts for 1 / 20-1 / 5 of the column height of the distillation column.

2. The production method according to claim 1, characterized by, The tetra (dimethylamine) hafnium crude product is derived from waste liquid in the production process of cyclopentadienyl tris (dimethylamine) hafnium; and / or, the tetra (dimethylamine) hafnium crude product contains 2.5-8.0ppm of Fe and 0.1-1.0ppm of Ti.

3. The preparation method according to claim 1, characterized in that The distillation temperature in S1 is 85-95℃; and / or, the distillation pressure in S1 is 0.6-1.0mbar; and / or, the collection speed of the front distillate in S1 is 10-50d / min.

4. The method of claim 1, wherein, The front distillate accounts for 7-12% of the mass of the crude product, and the primary main distillate accounts for 70-85% of the mass of the crude product; and / or, the collection speed of the front distillate is 20-40d / min; and / or, the collection speed of the primary main distillate is 40-50d / min.

5. The preparation method according to claim 1, characterized in that The alkane solvent comprises at least one of n-butane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, and n-dodecane; and / or, the amount of the solvent is 1-3 times the mass of the primary main distillate; and / or, the recrystallization temperature is-15~10℃; and / or, the recrystallization time is ≥24h.

6. The preparation method according to claim 1, characterized in that The recrystallization temperature is-10~8℃; and / or, the recrystallization time is 24-60h; and / or, the Fe content in the tetra (dimethylamine) hafnium crystals obtained in S2 is <0.5ppm, and the Ti content is ≤0.1ppm.

7. The preparation method according to claim 1, characterized in that The distillation pressure in S3 is 0.4-0.8mbar; and / or, the front distillate accounts for 5-15% of the mass of the feed, and the secondary main distillate accounts for 70-90% of the mass of the feed; and / or, the collection speed of the front distillate in S3 is 20-40d / min; and / or, the collection speed of the secondary main distillate is 40-50d / min.

8. The method of claim 1, wherein, The Fe content in the secondary main distillate is ≤0.1ppm, and the Ti content is ≤0.01ppm.

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