Preparation method of electronic-grade ammonium acetate

Abstract

The invention provides a preparation method of electronic-grade ammonium acetate. The obtained electronic-grade ammonium acetate is suitable for the electronic industry. The method comprises the following steps: S1, dissolving industrial-grade ammonium acetate at room temperature, and preliminarily removing impurities such as metals and anions in an ammonium acetate aqueous solution by using anion-cation exchange resin to obtain a resin purified solution; and S2, concentrating the resin purified liquid under reduced pressure until the concentration of ammonium acetate is 75-80% wt, cooling and crystallizing, centrifuging, washing, dissolving and filtering to obtain a 60-65% wt electronic grade ammonium acetate solution with the metal ion content of less than 1 ppb, the anion content of less than 10 ppb and the particle size of 0.3 mu m of less than 10 pcs / ml. The whole preparation process can be cyclically produced, the production process is mild and pollution-free, and the method is simple in process and suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the field of chemical synthesis, and in particular to a method for preparing electronic-grade ammonium acetate. Background Art

[0002] Ammonium acetate is a white crystal with an acetic acid smell. As an organic salt, it can be used in preservatives, pharmaceuticals, analytical reagents, and can also be used as a corrosion inhibitor and additive in the electronics industry such as silicon wafer etching solutions, electroplating solutions, and cleaning agents.

[0003] Industrially, ammonium acetate is mainly obtained by the reaction of acetic acid and ammonia. During its production, transportation and storage, due to reasons such as raw materials and equipment, some dust particles, metal ions, unreacted raw materials and other impurities are inevitably introduced into the product. The presence of these impurities, especially metal ions and trace particles, can easily lead to the generation of staggered layers, thereby increasing the risk of leakage current, breakdown and reducing the life of carriers. Therefore, for integrated circuits with smaller line widths, a few metal ions or dust particles are enough to scrap the entire circuit. With the rapid development of the integrated circuit (IC) industry, the requirements for the impurity content of various electronic-grade reagents are becoming higher and higher. From the perspective of technological trends, meeting the processing needs of nano-scale integrated circuits is the development direction of electronic-grade reagents.

[0004] At present, the ammonium acetate on the market mainly focuses on high content and low water content, and pays less attention to metal trace impurities, anionic impurities, and particulate impurities. Therefore, it is of great significance to develop a preparation method for electronic grade ammonium acetate solution with low metal and low particulate impurities suitable for the IC industry. Summary of the invention

[0005] In order to solve the technical problem of high impurity content of metals, anions and particles in ammonium acetate in the prior art, the present invention aims to provide a method for preparing electronic-grade ammonium acetate to obtain an electronic-grade ammonium acetate product suitable for the chip industry. The method has a simple process and is suitable for large-scale production.

[0006] The method firstly removes metal, anion and other impurities in industrial-grade ammonium acetate through ion exchange resin, concentrates the resin purified liquid and then cools it for crystallization, and after centrifugation, washing, dissolving and filtering, an ultra-clean and high-purity electronic-grade ammonium acetate product with metal impurities less than 1 ppb, anion content less than 10 ppb, and 0.3 μm particles less than 10 pcs / ml can be obtained.

[0007] Specifically, the present invention provides a method for preparing electronic grade ammonium acetate, the preparation method comprising the following steps: Step 1: After dissolving industrial-grade ammonium acetate, an anion and cation exchange resin is used to preliminarily remove impurities such as metals and anions in the ammonium acetate aqueous solution to obtain a resin-purified ammonium acetate solution; Step 2: The ammonium acetate solution purified by the resin in step 1 is concentrated under reduced pressure and then crystallized, the crystallization temperature in the system is controlled, and ammonium acetate slurry is obtained after cooling and crystallization; Step 3: Centrifuge and wash the ammonium acetate slurry in step 2 to obtain a filtrate and ammonium acetate crystals; Step 4: dissolving and filtering the ammonium acetate crystals in step 3 to obtain an electronic grade ammonium acetate product.

[0008] The above provides a method for preparing electronic grade ammonium acetate. In the step 1, preferably, the ammonium acetate used is industrial grade ammonium acetate with a content greater than 99%.

[0009] In the step 1, preferably, the concentration of industrial-grade ammonium acetate after being dissolved at room temperature is 60-70%wt.

[0010] More preferably, the ammonium acetate mass concentration is 65%wt.

[0011] In the step 1, preferably, the anion exchange resin is a gel-type strong base anion exchange resin; and the cation exchange resin is a gel-type strong acid cation exchange resin.

[0012] More preferably, the anion exchange resin is an OH type resin, which is any one of SA680N, SA550U or D315 resin; the cation exchange resin is an H type resin, which is any one of SC650U, SC980N or NRW160. Both the anion and cation resins need to be rinsed with pure water before use until the conductivity of the effluent is consistent with that of pure water.

[0013] In the step 1, preferably, the flow rate in the anion resin column is 1-8 Bv / h, and the flow rate in the cation resin column is 1-8 Bv / h.

[0014] More preferably, the flow rates of the cation resin columns are 2-6 Bv / h, respectively. In the cation resin column, when the effluent is 2.5 times the volume of the resin, the ammonium acetate solution purified by the resin is collected.

[0015] In the step 2, preferably, after concentration under reduced pressure, the concentration of ammonium acetate is controlled at 75-80%wt.

[0016] In the step 3, preferably, the initial crystallization temperature of ammonium acetate is 60-70° C., and the final crystallization temperature is 10-20° C. At this temperature, ammonium acetate crystals are well precipitated.

[0017] In the step 3, preferably, the cooling rate during the crystallization of ammonium acetate is 2-10° C. / h.

[0018] More preferably, the cooling rate is 4-8°C / h, and the temperature is slowly lowered to allow the crystals to precipitate slowly, so that the metal is not easily included in the crystals.

[0019] In the step 3, preferably, the stirring speed during the crystallization of ammonium acetate is 50-200 r / min.

[0020] The above provides a method for preparing electronic grade ammonium acetate. In the step 4, preferably, the washing is centrifugal spray washing.

[0021] In the step 4, preferably, a 60-65%wt high-purity ammonium acetate solution is prepared after the crystals are washed.

[0022] In the step 4, preferably, 60-65%wt of the high-purity ammonium acetate solution is finely filtered using a 0.1-0.3 μm PP, PES or PTFE filter element to remove particles.

[0023] More preferably, a 0.1 μm PTFE filter element is used to filter out particles.

[0024] The invention obtains an ultra-clean and high-purity electronic-grade ammonium acetate product by coupling cooling crystallization with ion exchange resin to meet the processing requirements of nano-scale integrated circuits.

[0025] Compared with the prior art, the advantages of the present invention are: 1. The present invention provides a method for preparing electronic-grade ammonium acetate, which is simple to operate and easy to industrialize, and can obtain an electronic-grade ammonium acetate product with a metal ion content of less than 1 ppb, an anion content of less than 10 ppb, and 0.3 μm particles of less than 10 pcs / ml, meeting the requirements of electronic-grade ammonium acetate.

[0026] 2. The entire production process can be recycled. The ion exchange resin can initially remove metal and anion impurities, and subsequent crystallization can further remove trace impurities. The obtained ammonium acetate crystals can be configured as electronic grade ammonium acetate products, and the centrifugal washing filtrate can be returned to the resin tower for purification. 3. In the centrifugal washing process of the present invention, high-speed centrifugation and spray washing are used to quickly separate the filtrate attached to the surface of the ammonium acetate crystals, so that a purer ammonium acetate product can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 The present invention is a production process flow chart of electronic grade ammonium acetate. DETAILED DESCRIPTION

[0028] In the following examples and comparative examples, the content of ammonium acetate was determined by potentiometric titration or near infrared, the content of metal ion impurities was detected by ICP-MS, the content of anionic impurities was detected by IC, and the particulate impurities were detected by LPC.

[0029] Example 1 A method for preparing electronic grade ammonium acetate comprises the following steps: Step 1: Weigh 6.5 kg of 98% industrial grade ammonium acetate raw material, add 3.5 kg of pure water to dissolve, and obtain ~65%wt ammonium acetate solution; Step 2: Take 200mL SA550U anion exchange resin and 200mL SC650U cation exchange resin in a beaker, rinse with pure water, and then load them into two PFA resin columns. Use pure water to rinse the two resins until the conductivity of the effluent is close to that of pure water. After the resin pretreatment is completed, a 65%wt ammonium acetate solution is first flowed from the top of the anion resin column at a flow rate of 3 Bv / h, and the effluent is then flowed from the top of the cation resin column at a flow rate of 3 Bv / h. When the purified solution is 2.5 times the volume of the resin (i.e. after 500mL), start collecting the ammonium acetate aqueous solution purified by the resin.

[0030] Step 3: Place the ammonium acetate solution purified by the resin in a jacketed reactor, increase the circulating water temperature to 65°C, and concentrate under reduced pressure until the concentration of ammonium acetate is 78-80%wt; Step 4: After the concentration is complete, turn off the vacuum pump, raise the reaction system to normal pressure, and adjust the stirring speed to 100r / min; at this time, the initial crystallization temperature of the solution is 65°C, adjust the program temperature control device, adjust the cooling rate of the circulating water to 4°C / h, and when the temperature drops to 55°C, add ammonium acetate seeds to induce crystallization. When the solution temperature drops to 10°C, the crystallization process is terminated to obtain ammonium acetate slurry; Step 5: After the crystallization is completed, the crystal slurry is placed in a centrifuge to centrifuge and separate the filtrate to obtain ammonium acetate crystals. The crystals are dissolved into a 60%wt ammonium acetate solution, and then filtered through a 0.1μm PTFE filter element to obtain an electronic grade ammonium acetate solution.

[0031] Example 2 A method for preparing electronic grade ammonium acetate comprises the following steps: Step 1: Weigh 6.5 kg of 98% industrial grade ammonium acetate raw material, add 3.5 kg of pure water to dissolve, and obtain ~65%wt ammonium acetate solution; Step 2: Take 200mL SA680N anion exchange resin and 200mL NRW160 cation exchange resin in a beaker, rinse with pure water, and then load them into two PFA resin columns. Use pure water to rinse the two resins until the conductivity of the effluent is close to that of pure water. After the resin pretreatment is completed, a 65%wt ammonium acetate solution is first flowed from the top of the anion resin column at a flow rate of 6 Bv / h, and the effluent is then flowed from the top of the cation resin column at a flow rate of 6 Bv / h. When the purified solution is 2.5 times the volume of the resin (i.e. after 500mL), start collecting the ammonium acetate aqueous solution purified by the resin.

[0032] Step 3: Place the ammonium acetate solution purified by the resin in a jacketed reactor, increase the circulating water temperature to 65°C, and concentrate under reduced pressure until the concentration of ammonium acetate is 75-77wt%; Step 4: After the concentration is complete, turn off the vacuum pump, raise the reaction system to normal pressure, and adjust the stirring speed to 100r / min; at this time, the initial crystallization temperature of the solution is 65°C, adjust the program temperature control device, adjust the cooling rate of the circulating water to 8°C / h, and when the temperature drops to 60°C, add ammonium acetate seeds to induce crystallization. When the solution temperature drops to 10°C, the crystallization process is terminated to obtain ammonium acetate slurry; Step 5: After the crystallization is completed, the crystal slurry is placed in a centrifuge to centrifuge and separate the filtrate to obtain ammonium acetate crystals. The crystals are dissolved into a 60%wt ammonium acetate solution, and then filtered through a 0.1μm PTFE filter element to obtain an electronic grade ammonium acetate solution.

[0033] Comparative Example 1 Compared with Example 1, no crystallization was performed after the resin purification.

[0034] Comparative Example 2 Compared with Example 1, industrial-grade ammonium acetate raw material is used for direct primary crystallization without resin purification.

[0035] Table 1: Content of prepared ammonium acetate solution and its impurity content

[0036] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A method for preparing electronic grade ammonium acetate, characterized in that: The preparation process includes the following steps: resin adsorption, concentration crystallization, centrifugal washing, dissolution and filtration: Step 1: After dissolving industrial-grade ammonium acetate, use anion and cation exchange resin to remove metal and anion impurities in the ammonium acetate aqueous solution; Step 2: The purified resin solution of step 1 is concentrated under reduced pressure and then crystallized, the crystallization temperature in the system is controlled, and ammonium acetate slurry is obtained after cooling and crystallization; Step 3: Centrifuge and wash the crystal slurry obtained in step 2 to obtain a filtrate and ammonium acetate crystals; Step 4: dissolving and filtering the ammonium acetate crystals after centrifugal washing in step 3 to obtain an electronic grade ammonium acetate product.

2. The preparation process according to claim 1, characterized in that: In step 1, the ammonium acetate used is industrial grade ammonium acetate, and the content is greater than 98%wt. The concentration of the industrial grade ammonium acetate after dissolution is 60%-70%wt.

3. The preparation process according to claim 1, characterized in that: In step 1, the ammonium acetate aqueous solution first passes through an anion resin column and then passes through a cation exchange resin column. The anion exchange resin is a gel-type strong base anion exchange resin; and the cation exchange resin is a gel-type strong acid cation exchange resin.

4. The preparation method according to claim 1, characterized in that: The anion exchange resin is any one of SA680N, SA550U or D315 resin; the cation exchange resin is any one of SC650U, SC980N or NRW160.

5. The preparation method according to claim 1, characterized in that: The flow rate of the ammonium acetate aqueous solution over the anion resin is 1~8 Bv / h, and the flow rate over the cationic resin is 1~8 Bv / h.

6. The preparation method according to claim 1, characterized in that: In step 2, the concentration of ammonium acetate after concentration is 75-80%wt, the starting crystallization temperature of ammonium acetate is 60-70°C, the ending crystallization temperature is 10-20°C, the temperature for adding seed crystals is 45-60°C, and the amount of seed crystals added is 0.5-1% of the mass of the crystallization solution.

7. The preparation method according to claim 1, characterized in that: In step 2, the cooling rate during crystallization of ammonium acetate is 2-10°C / h, and the stirring speed during crystallization is 50-200 r / min.

8. The preparation process according to claim 1, characterized in that: In step three, the washing is centrifugal spray washing.

9. The preparation process according to claim 1, characterized in that: In step 4, the ammonium acetate crystals are dissolved to obtain a 60% to 65% wt ammonium acetate solution, and the filtration is performed using one or more of 0.1 to 0.5 μm PP, PES or PTFE filter elements.

10. The preparation process according to any one of claims 1 to 9, characterized in that: The concentration of the electronic grade ammonium acetate is 60-65%wt, the metal ion content is less than 1ppb, the anion content is less than 10ppb, and the 0.3μm particles are less than 10 pcs / ml.

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