Preparation method of high-purity tetraalkyl ammonium hydroxide solid

Abstract

The invention relates to a preparation method of a high-purity tetraalkyl ammonium hydroxide solid, which is characterized in that a raw material solution is a 20-40% tetraalkyl ammonium hydroxide aqueous solution, a seed crystal is obtained by explosion nucleation of a supercooled solution, 0.1-10% of the seed crystal is added, the temperature is kept constant for a certain time to eliminate the degree of supersaturation in the solution, and then stage cooling is performed to obtain the high-purity tetraalkyl ammonium hydroxide solid. And after crystallization, the purity of the final product is improved through crystal curing, mother liquor separation, crystal washing and the like, and the electronic-grade tetraalkyl ammonium hydroxide crystal with the all-metal content of less than or equal to 5ppb is obtained. By accurately controlling the crystallization process, the content of metal impurities is effectively reduced, the high-purity electronic-grade tetraalkyl ammonium hydroxide crystal is prepared, the problems that in the prior art, the purification technology of electronic-grade tetraalkyl ammonium hydroxide is high in barrier and difficult to meet the high-purity requirement can be effectively solved, and the requirement of the high-end electronic manufacturing industry is met.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical engineering, and particularly relates to a method for preparing high-purity tetraalkylammonium hydroxide solid. Background Art

[0002] With the rapid development of the electronic industry, the manufacturing technology of very large scale integrated circuits (VLSI) has put forward higher requirements for the purity and cleanliness of chemical materials. As a key basic chemical material, tetraalkylammonium hydroxide plays an important role in the wet cleaning and wet etching processes. The purity and cleanliness of tetraalkylammonium hydroxide directly affect the yield, electrical properties and reliability of integrated circuits. However, various impurities, especially metal impurities, are often introduced in the existing production process of tetraalkylammonium hydroxide, and the presence of these impurities seriously affects the application performance of tetraalkylammonium hydroxide. At present, the market demand for high-purity tetraalkylammonium hydroxide is increasing day by day, but the existing purification process has high technical barriers and it is difficult to meet this demand. Summary of the Invention

[0003] In view of the above problems, the present invention provides a method for preparing tetraalkylammonium hydroxide solid. By adjusting the concentration of the initial solution and exploring the cooling crystallization process, tetraalkylammonium hydroxide crystals with single metal impurities less than 5 ppb are prepared, including the following steps: S1: Prepare the crystallization initial solution: Dilute the tetraalkylammonium hydroxide stock solution with ultrapure water to adjust the concentration, and then heat it to 30 - 40 °C and stir evenly. S2: Cooling crystallization: After adding the seed crystal, keep the temperature constant for 0.5 - 2 h, and then gradually cool down to the final crystallization temperature. S3: Crystal aging: Keep the temperature constant at 15 - 20 °C for 1 - 2 h for crystal cultivation at the end of crystallization. S4: Separation and washing: Separate and wash the crystal slurry to obtain high-purity tetraalkylammonium hydroxide solid.

[0004] In step S1, the tetraalkylammonium hydroxide includes any one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide or tetrabutylammonium hydroxide, and the tetraalkylammonium hydroxide stock solution is diluted with ultrapure water to a concentration of 20 - 40%.

[0005] For those skilled in the art, it is known without any significance that in the preparation process of tetramethylammonium hydroxide solid, the tetramethylammonium hydroxide stock solution and the crystals of tetramethylammonium hydroxide are used. Similarly, for other tetraalkylammonium hydroxides, the corresponding stock solutions and crystals are used.

[0006] In step S2, the seed crystal is small-sized crystals generated by stimulating nucleation after the tetraalkylammonium hydroxide aqueous solution is supercooled, and the obtained seed crystal after cooling crystallization until the liquid has no fluidity. The supercooling temperature is 3 - 10 °C.

[0007] In step S2, the addition amount of the seed crystal is 0.1-10% of the total mass of the initial solution.

[0008] In step S2, the addition amount of the seed crystal is 1-8% of the total mass of the initial solution.

[0009] In step S2, after adding the seed crystal, keep it at a constant temperature of 25-35°C for 1.5-2 h.

[0010] The initial constant temperature time should be long enough to ensure that the crystals have sufficient growth time, eliminate the supersaturation of the solution, and then perform stepwise cooling after the crystal particle size grows to reduce the wall sticking phenomenon.

[0011] In step S2, stepwise cooling means cooling at different cooling rates in each stage, the temperature difference in each stage is 2-5°C, and the end temperature of cooling is 15-20°C.

[0012] In step S3, after the cooling is completed, keep it at a constant temperature of 15-20°C for crystal cultivation for 1-2 h. During this process, since the solubility of small particles is greater than that of large particles, this step can effectively eliminate fine crystals, increase the driving force in the solution, and at the same time promote the recrystallization of large particle crystals.

[0013] In step S4, the washing liquid is ultrapure water during the washing process. To completely separate the residual mother liquor on the crystal surface, the washing liquid is selected as ultrapure water, and the dosage is 3-20% of the crystal mass.

[0014] In another solution of the present invention, the mother liquor separated in step S3 and the washing liquid obtained by washing are passed through an ion exchange resin to obtain a purified liquid, and the purified liquid is returned to step S1 for the preparation of the initial solution.

[0015] The ion exchange resin is obtained by transforming an ion exchange resin with an electronic grade dilute sulfuric acid solution. The ion exchange resin is a chelating resin with a macroporous structure of styrene-divinylbenzene copolymer with a weak acidic functional group, preferably any one of D840, D850, D851, D852, and D860.

[0016] The related resin pretreatment for obtaining the ion exchange resin by transforming with an electronic grade dilute sulfuric acid solution is as follows: Pack the Na-type ion exchange resin in a resin column, the aspect ratio of the resin column is 5-8. After flushing with ultrapure water for 5-10 Bv at the liquid inlet end of the resin column, pass through an electronic grade dilute sulfuric acid solution for transformation. The mass concentration of the electronic grade dilute sulfuric acid solution is 5-10%. Monitor the content of Na and other metal ions in the solution at the liquid outlet end. When the metal ion level in the solution at the liquid outlet end is similar to that at the liquid inlet section, it means that the resin transformation is complete. Flush the resin with ultrapure water from the liquid inlet end and monitor the conductivity of the liquid outlet end until the conductivity of the eluate ≤ the conductivity of ultrapure water.

[0017] The separated mother liquor and washing liquor are passed through an ion exchange resin column using a peristaltic pump at a certain flow rate to obtain a purified solution. After measuring the content, it is returned to step S2 for standby. The column passing rate is 2-10 Bv / h.

[0018] The present invention provides a method for preparing high-purity tetraalkylammonium hydroxide solid, which has the following beneficial effects: 1. High purity: By precisely controlling the crystallization process, the present invention effectively reduces the content of metal impurities. Among them, Na, Al, Ca, K, Mg, Mn, Co, Zn, Mo, Ag, Pt, Ni, Cu, Cr, Fe, Au, Pb, and B are less than 5 ppb, further preferably less than 3 ppb, and further preferably less than 1 ppb. The yield is more than 30%, further preferably more than 35%, and further preferably more than 40%.

[0019] The preparation of high-purity tetraalkylammonium hydroxide crystals can effectively solve the problems of high purification technical barriers and difficulty in meeting high-purity requirements in the prior art, and meet the needs of the high-end electronic manufacturing industry.

[0020] 2. Simple process: Compared with the traditional complex purification process, the preparation method of the present invention is simple to operate and easy to industrialize.

[0021] 3. Cost-effective: The present invention reduces the high-cost materials and energy consumption required in the purification process and reduces the production cost.

[0022] 4. Environmentally friendly: This method produces less waste during the production process and has little impact on the environment, meeting the requirements of green and sustainable development. Brief description of the drawings

[0023] Figure 1 It is the process flow chart of Example 1 of the present invention.

[0024] Figure 2 It is the physical diagram of tetraalkylammonium hydroxide crystals.

[0025] Figure 3 It is the process flow chart of Examples 11, 12, and 13 of the present invention. Detailed description of the invention

[0026] Example 1 S1: Preparation of crystal seeds: Place the bottle containing 25% by mass of tetraalkylammonium hydroxide aqueous solution in an environment of 5°C. When the solution temperature drops to 5°C, stimulate the solution to generate crystals with fine and uniform particles by nucleation until the liquid in the bottle has no fluidity.

[0027] S2: Prepare the initial crystallization solution: Dilute the stock solution of tetraalkylammonium hydroxide with a relatively high concentration to 35% using ultrapure water, heat it to 35 °C and start stirring to evenly distribute the solute in the solution.

[0028] S3: Introduce seed crystals: When the solution cools to 32 °C, add seed crystals accounting for 2% of the total mass of the solute.

[0029] S4: Cooling crystallization: After adding the seed crystals, keep the jacket water at a constant temperature for 1.5 h, and then set the stepwise cooling program as: 32 °C → 30 °C → 28 °C → 25 °C → 22 °C → 20 °C, with a cooling time of 1 h for each stage.

[0030] S5: Crystal aging: Set the jacket water temperature at 20 °C and keep it at a constant temperature for 1.5 h.

[0031] S6. Separation and washing: Pump the crystal slurry into a centrifuge for mother liquor separation, and then add 5% ultrapure water for washing after the mother liquor separation.

[0032] Example 2 The method steps are the same as those in Example 1, where the cooling program in step S4 is adjusted to: 32 °C → 30 °C → 28 °C → 25 °C → 22 °C → 20 °C → 15 °C, and the cooling time for each stage is 1 h.

[0033] In step S5, set the jacket water temperature at 15 °C and keep it at a constant temperature for 1.5 h.

[0034] Example 3 The method steps are the same as those in Example 1, where after adding the seed crystals in step S4, keep the jacket water at a constant temperature for 0.5 h, and then set the stepwise cooling program as: 32 °C → 30 °C → 28 °C → 25 °C → 22 °C → 20 °C, with a cooling time of 0.5 h for each stage.

[0035] Example 4 The method steps are the same as those in Example 1, where the amount of seed crystals added in step S3 is adjusted to 10%.

[0036] Example 5 The method steps are the same as those in Example 1, where the concentration of the initial solution in step S2 is adjusted to 30%.

[0037] Add the seed crystals when the solution temperature in step S3 drops to 27 °C.

[0038] In step S4, after adding the seed crystals, keep the jacket water at a constant temperature for 1 h, and then set the stepwise cooling program as: 27 °C → 25 °C → 22 °C → 18 °C → 15 °C, with a cooling time of 0.5 h for each stage.

[0039] In step S5, set the jacket water temperature at 15 °C and keep it at a constant temperature for 1 h.

[0040] Example 6: The method steps are the same as those in Example 5, where the constant temperature time in step S5 is adjusted to 2 h.

[0041] Example 7: The method steps are the same as those in Example 5, where the medium temperature reduction program in step S2 is adjusted to: 27°C → 25°C → 20°C → 15°C.

[0042] Example 8: The method steps are the same as those in Example 5, where the amount of seed crystal added in step S3 is adjusted to 8%.

[0043] Example 9: The method steps are the same as those in Example 1, where the initial solution concentration in step S2 is adjusted to 25%.

[0044] When the solution temperature in step S3 drops to 24°C, add the seed crystal.

[0045] After adding the seed crystal in step S4, keep the jacket water at a constant temperature for 0.5 h, and then set the stage temperature reduction program as: 24°C → 22°C → 20°C → 15°C → 10°C, and the temperature reduction time for each stage is 0.5 h.

[0046] In step S5, set the jacket water temperature to 10°C and keep it at a constant temperature for 0.5 h.

[0047] Example 10: The method steps are the same as those in Example 9, where the medium temperature reduction program in step S2 is adjusted to: 24°C → 20°C → 15°C → 10°C.

[0048] Table 1 shows the metal ion concentrations of the tetraalkylammonium hydroxide crystals in Examples 1 - 10 (the values in the table are uniformly converted to 100%). Table 1

[0049] Example 11: S1: Prepare the seed crystal: Place the bottle containing a 25% aqueous solution of tetraalkylammonium hydroxide in an environment of 5°C. When the solution temperature drops to 5°C, stimulate the solution to generate nuclei and produce crystals with fine and uniform particles until the liquid in the bottle has no fluidity.

[0050] S2: Prepare the initial crystallization solution: Dilute the higher-concentration tetraalkylammonium hydroxide stock solution with ultrapure water or a low-concentration aqueous solution of tetraalkylammonium hydroxide to 35%, heat it to 35°C and start stirring to make the solute evenly distributed in the solution.

[0051] S3: Introduce the seed crystal: When the solution drops to 32°C, add the seed crystal accounting for 2% of the total mass of the solute.

[0052] S4: Cooling crystallization: After adding crystal seeds and keeping the jacket water at a constant temperature for 1.5 h, set the stepwise cooling program as: 32°C → 30°C → 28°C → 25°C → 22°C → 20°C, with a cooling time of 1 h for each stage.

[0053] S5: Crystal aging: Set the jacket water temperature at 20°C and keep it constant for 1.5 h.

[0054] S6: Separation and washing: Pump the crystal slurry into a centrifuge for mother liquor separation, and then add 5% ultrapure water for washing after the mother liquor separation.

[0055] S7: Product formulation: Dissolve the crystals separated in step S6 and ultrapure water in a certain proportion to finally obtain a 10% high-purity tetraalkylammonium hydroxide aqueous solution.

[0056] S8: Resin pretreatment: Pack the D840 ion exchange resin in a resin column. Flush the resin column with ultrapure water at the liquid inlet end for 5 - 10 bed volumes (Bv), then pass a 5% electronic grade dilute sulfuric acid solution for transformation. Monitor the content of Na and other metal ions in the solution at the liquid outlet end. When the metal ion level in the solution at the liquid outlet end is similar to that at the liquid inlet section, it means the resin transformation is complete. Flush the resin with ultrapure water from the liquid inlet end and monitor the conductivity of the liquid at the liquid outlet end until the conductivity of the eluate ≤ the conductivity of ultrapure water.

[0057] S9: Waste liquid purification: Use a peristaltic pump to pass the mother liquor and washing liquid separated in step S6 through the ion exchange resin column at a column passing rate of 5 Bv / h to obtain a purified liquid. After measuring the content, return it to step S2 for standby.

[0058] Table 1 shows the measurement results of the concentrations of various metal ions in Example 1. The concentration of the tetraalkylammonium hydroxide solution is uniformly converted to 10%.

[0059] Table 1

[0060] Example 12: S1: Preparation of crystal seeds: Place the bottle containing a 25% mass fraction tetraalkylammonium hydroxide aqueous solution in an environment of 5°C. When the solution temperature drops to 5°C, stimulate the solution to generate fine and uniform crystals by nucleation until the liquid in the bottle has no fluidity.

[0061] S2: Preparation of the initial crystallization solution: Dilute the higher concentration tetraalkylammonium hydroxide stock solution with ultrapure water or a low-concentration tetraalkylammonium hydroxide aqueous solution to 30%, heat it to 32°C and start stirring to make the solute evenly distributed in the solution.

[0062] S3: Introduction of crystal seeds: When the solution drops to 27°C, add crystal seeds accounting for 5% of the total mass of the solute.

[0063] S4: Cooling crystallization: After adding the seed crystals and keeping the jacket water at a constant temperature for 1 h, set the stepwise cooling program as: 27°C → 25°C → 22°C → 18°C → 15°C, with a cooling time of 0.5 h for each stage.

[0064] S5: Crystal aging: Set the jacket water temperature at 15°C and keep it constant for 1 h.

[0065] S6: Separation and washing: Pump the crystal slurry into a centrifuge for mother liquor separation, and then add 10% ultrapure water for washing after the mother liquor separation.

[0066] S7: Product formulation: Dissolve the crystals separated in step S6 and ultrapure water in a certain proportion to finally obtain a 10% high-purity tetraalkylammonium hydroxide aqueous solution.

[0067] S8: Resin pretreatment: Pack the D851 ion exchange resin in a resin column. Flush the inlet end of the resin column with ultrapure water for 5 - 10 Bv, then pass a 5% electronic-grade dilute sulfuric acid solution for transformation. Monitor the content of Na and other metal ions in the solution at the outlet end. When the metal ion level in the solution at the outlet end is similar to that in the inlet section, it means the resin transformation is complete. Flush the resin with ultrapure water from the inlet end and monitor the conductivity of the solution at the outlet end until the conductivity of the eluate ≤ the conductivity of ultrapure water.

[0068] S9: Waste liquid purification: Use a peristaltic pump to pass the mother liquor and washing liquid separated in step S6 through the ion exchange resin column at a column passing rate of 4 Bv / h to obtain a purified liquid. After measuring the content, return it to step S2 for standby.

[0069] Table 2 shows the measurement results of the concentrations of various metal ions in Example 2. The concentration of the tetraalkylammonium hydroxide solution is uniformly converted to 10%.

[0070] Table 2

[0071] Example 13: S1: Preparation of seed crystals: Place the bottle containing a 25% tetraalkylammonium hydroxide aqueous solution in an environment of 5°C. When the solution temperature drops to 5°C, stimulate the solution to generate fine and uniform crystals by nucleation until the liquid in the bottle has no fluidity.

[0072] S2: Preparation of the initial crystallization solution: Dilute the higher-concentration tetraalkylammonium hydroxide stock solution with ultrapure water or a low-concentration tetraalkylammonium hydroxide aqueous solution to 25%, heat it to 30°C and start stirring to make the solute evenly distributed in the solution.

[0073] S3: Introduction of seed crystals: When the solution drops to 24°C, add seed crystals accounting for 5% of the total mass of the solute.

[0074] S4: Cooling crystallization: After adding crystal seeds and keeping the jacket water at a constant temperature for 0.5 h, set the stepwise temperature reduction program as: 24°C → 22°C → 20°C → 15°C → 10°C, and the temperature reduction time for each stage is 0.5 h.

[0075] S5: Crystal aging: Set the jacket water temperature at 10°C and keep it constant for 0.5 h.

[0076] S6. Separation and washing: Pump the crystal slurry into a centrifuge for mother liquor separation, and then add 8% ultrapure water for washing after the mother liquor separation.

[0077] S7: Product formulation: Dissolve the crystals separated in step S6 and ultrapure water in a certain proportion to finally obtain a 10% high-purity tetraalkylammonium hydroxide aqueous solution.

[0078] S8: Resin pretreatment: Pack the D860 ion exchange resin in a resin column. Flush the inlet end of the resin column with ultrapure water for 5 - 10 Bv, and then pass a 5% electronic-grade dilute sulfuric acid solution for transformation. Monitor the content of Na and other metal ions in the solution at the outlet end. When the metal ion level in the solution at the outlet end is similar to that at the inlet section, it means the resin transformation is complete. Flush the resin with ultrapure water from the inlet end and monitor the conductivity of the solution at the outlet end until the conductivity of the eluate ≤ the conductivity of ultrapure water.

[0079] S9: Waste liquid purification: Use a peristaltic pump to pass the mother liquor and washing liquid separated in step S6 through the ion exchange resin column at a column passing rate of 2 Bv / h to obtain a purified liquid. After measuring the content, return it to step S2 for standby.

[0080] Table 3 shows the measurement results of the concentrations of various metal ions in Example 3, and the concentration of the tetraalkylammonium hydroxide solution is uniformly converted to 10%.

[0081] Table 3

[0082] The above embodiments are only the preferred technical solutions of the present invention, rather than limitations on the present invention. The embodiments and the features in the embodiments in this application can be arbitrarily combined with each other without conflict. The protection scope of the present invention should be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, the equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A method for preparing a high-purity tetraalkylammonium hydroxide solid, characterized in that, It includes the following steps: S1: Prepare the initial crystallization solution: Dilute the tetraalkylammonium hydroxide stock solution with ultrapure water to adjust the concentration, and then heat it to 30 - 40°C and stir evenly; S2: Cooling crystallization: After adding the seed crystal, keep the temperature constant for 0.5 - 2 h, and then carry out stepwise cooling to the final crystallization temperature; S3: Crystal aging: Keep the temperature constant at 15 - 20°C for 1 - 2 h for crystal cultivation; S4: Separation and washing: Separate and wash the crystal slurry to obtain high-purity tetraalkylammonium hydroxide solid.

2. The preparation method of the high-purity tetraalkylammonium hydroxide solid according to claim 1, characterized in that, In step S1, the tetraalkylammonium hydroxide includes any one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, and the tetraalkylammonium hydroxide stock solution is diluted with ultrapure water to a concentration of 20 - 40%.

3. The preparation method of the high-purity tetraalkylammonium hydroxide solid according to claim 1, characterized in that, In step S2, the seed crystal is small-sized crystals generated by stimulated nucleation after the tetraalkylammonium hydroxide aqueous solution is supercooled. The seed crystal is obtained after cooling crystallization until the liquid has no fluidity, and the supercooling temperature is 3 - 10°C.

4. The method for preparing a high-purity tetraalkylammonium hydroxide solid according to claim 3, characterized in that, In step S2, the addition amount of the seed crystal is 0.1 - 10% of the total mass of the initial solution.

5. The preparation method of the high-purity tetraalkylammonium hydroxide solid according to claim 3, characterized in that, In step S2, after adding the seed crystal, first keep the temperature constant at 25 - 35°C for 1.5 - 2 h, and then carry out stepwise cooling crystallization.

6. The method for preparing a high-purity tetraalkylammonium hydroxide solid according to claim 5, characterized in that, In step S2, stepwise cooling means cooling at different cooling rates in each stage, the temperature difference in each stage is 2 - 5°C, and the cooling end temperature is 15 - 20°C.

7. The preparation method of the high-purity tetraalkylammonium hydroxide solid according to claim 1, characterized in that, The mother liquor separated in step S3 and the washing liquid obtained by washing are passed through an ion exchange resin to obtain a purified liquid, and the purified liquid is returned to step S1 for the preparation of the initial solution.

8. The method for preparing a high-purity tetraalkylammonium hydroxide solid according to claim 7, wherein The ion exchange resin is obtained by transforming the ion exchange resin with an electronic-grade dilute sulfuric acid solution. The ion exchange resin is a chelating resin with a macroporous structure of styrene - divinylbenzene copolymer with a weak acidic functional group, preferably any one of D840, D850, D851, D852, D860.

9. The method for preparing a high-purity tetraalkylammonium hydroxide solid according to claim 1, wherein In step S3, during the washing process, the washing liquid is ultrapure water, and the dosage is 3 - 20% of the crystal mass.

10. The high-purity tetraalkylammonium hydroxide solid prepared by the preparation method according to any one of claims 1 - 9, wherein the content of Na, Al, Ca, K, Mg, Mn, Co, Zn, Mo, Ag, Pt, Ni, Cu, Cr, Fe, Au, Pb, B in the prepared high-purity tetraalkylammonium hydroxide solid is less than 5 ppb, more preferably less than 3 ppb, and even more preferably less than 2 ppb.

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