A method for preparing electronic grade tartaric acid by combining fractional recrystallization

Abstract

This invention belongs to the field of electronic-grade tartaric acid preparation technology, specifically relating to a method for preparing electronic-grade tartaric acid using stepwise recrystallization. The method includes the following steps: preparing a tartaric acid solution from raw material and filtering it through a membrane to obtain preliminarily purified tartaric acid solid; preparing the preliminarily purified tartaric acid solid into a solution and cooling it to a first temperature to crystallize, followed by solid-liquid separation to obtain a first filtrate; cooling the first filtrate to a second temperature to crystallize, followed by solid-liquid separation and drying to obtain recrystallized tartaric acid solid; preparing the recrystallized tartaric acid solid into a solution and passing it through a resin column packed with a strongly acidic cation exchange resin for ion exchange to obtain an electronic-grade tartaric acid solution. This invention utilizes stepwise recrystallization combined with ion exchange resin to remove metal ions from tartaric acid and improve its purity. This method is not only highly efficient and low-cost, but also achieves a metal ion removal rate of up to 81% after a single recrystallization, providing a more efficient method for removing metal impurities from tartaric acid.

Description

Technical Field

[0001] This invention belongs to the field of electronic-grade tartaric acid preparation technology, specifically relating to a method for preparing electronic-grade tartaric acid by stepwise recrystallization. Background Technology

[0002] L(+)-Tartaric acid is a naturally occurring dicarboxylic acid widely found in various fruits such as grapes, bananas, and tamarind, and is its most common dextrorotatory optical isomer. Electronic-grade tartaric acid is an ultra-high purity chemical used in semiconductor manufacturing. Its core function is as a key complexing agent in chemical mechanical polishing (CMP) slurries, strongly chelating and removing metal ions from the wafer surface to achieve nanoscale planarization. It can also be used as an electroplating additive to ensure uniform and dense metal coatings. Its value lies in its extreme purity—the content of metal impurities is controlled at the ppb or even ppt level. Any trace contamination can lead to chip failure, making it an indispensable core material for ensuring chip yield and performance.

[0003] Currently, solid electronic products similar to tartaric acid are mainly purified using single or coupled techniques such as recrystallization, ion exchange, membrane separation, chemical precipitation, chromatographic separation, extraction crystallization, and sublimation distillation to deeply remove metal ions, organic impurities, particles, and insoluble substances. These are followed by concentration, crystallization, centrifugation, and washing to ultimately obtain high-purity / ultra-pure products that meet the requirements of semiconductor, new energy, and other fields. However, research on electronic-grade tartaric acid is scarce. This invention provides a method for improving the purity and removing metal ions of tartaric acid through stepwise recrystallization combined with ion exchange resin, resulting in metal ion levels in tartaric acid below 1 ppb. Summary of the Invention

[0004] In view of the problems and shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing electronic-grade tartaric acid by combining stepwise recrystallization.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention provides a method for preparing electronic-grade tartaric acid by stepwise recrystallization, comprising the following steps: S1. Membrane filtration: Dissolve the raw material tartaric acid in ultrapure water to obtain a tartaric acid solution. Perform membrane filtration on the tartaric acid solution, collect the filtrate, concentrate and dry the filtrate to obtain preliminarily purified tartaric acid solid. S2, Stepwise recrystallization: 1) First step crystallization: Under heating conditions, the tartaric acid solid obtained in step S1 is dissolved in ultrapure water to obtain solution A. Solution A is cooled to the first temperature to crystallize and precipitate. Solid-liquid separation is performed to obtain the first filtrate. 2) Second step crystallization: The first filtrate is cooled to a second temperature to crystallize and precipitate. The solid and liquid are separated and dried to obtain recrystallized tartaric acid solid. S3, Ion exchange: Dissolve the recrystallized tartaric acid solid obtained in step S2 in ultrapure water to obtain solution B. Pass solution B through a resin column packed with a strong acid cation exchange resin for ion exchange, collect the effluent, and obtain an electronic grade tartaric acid solution.

[0006] Preferably, in step S2, the first temperature is 70-90°C; the second temperature is 10-20°C.

[0007] Preferably, in step S2, the heating temperature is 95–100°C.

[0008] Preferably, in step S1, the raw material tartaric acid is L(+)-tartaric acid with a purity ≥99.7%.

[0009] Preferably, in step S1, the membrane used in the membrane filtration device is a PTFE membrane.

[0010] Preferably, in step S3, the strongly acidic cation exchange resin is an electronic-grade strongly acidic cation exchange resin. Preferably, in step S3, the resin columns are two-stage series.

[0011] Preferably, in step S3, before performing ion exchange, a pretreatment step is included: backwashing the resin column with electronic-grade sulfuric acid solution, and then rinsing with ultrapure water until neutral.

[0012] More preferably, the electronic-grade sulfuric acid solution is prepared by electronic-grade sulfuric acid and ultrapure water, and has a mass percentage concentration of 1.5%.

[0013] Preferably, in step S3, the flow rate of solution B through the resin column is 3-5 Bv / h.

[0014] Preferably, in step S1, the tartaric acid solution has a mass percentage concentration of 40% to 60%.

[0015] Preferably, in step S2, the mass percentage concentration of solution A is 75%.

[0016] Preferably, in step S3, the mass percentage concentration of solution B is 30% to 50%.

[0017] Preferably, the ultrapure water used in the method is ultrapure water with metal ion concentrations of <1ppt.

[0018] The second aspect of the present invention provides electronic-grade tartaric acid prepared by the method described in the first aspect above.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention provides a method for removing metal ions from tartaric acid using stepwise recrystallization. In an electronic-grade Class 1000 cleanroom environment (≥0.3µm particles less than 1000), 99.7% pure food additive L(+)-tartaric acid is prepared into a tartaric acid solution using ultrapure water with <1ppt of metal ions. After dissolution, it is filtered through a membrane filter, concentrated by a rotary evaporator, and dried to obtain solid tartaric acid. At 100°C, a tartaric acid solution is prepared using ultrapure water with <1ppt of metal ions. After complete dissolution, the solution is slowly cooled to temperatures 1 (90°C, 80°C, and 70°C) to crystallize. After filtration, the solution is further cooled to 20°C to crystallize again. The purity can be increased to a maximum of 99.93%, and the metal ion content can be reduced by up to 81%. After recrystallization, a tartaric acid solution is prepared at 20°C using ultrapure water with <1ppt of metal ions. Metal ions are removed using a secondary electronic-grade strong acid cation exchange resin, achieving a metal ion removal rate of up to 99.98%.

[0020] (2) This invention utilizes stepwise recrystallization combined with ion exchange resin to remove metal ions from tartaric acid and improve its purity. This method is not only highly efficient and low-cost, but also achieves a high removal rate of metal ions of up to 81% after one recrystallization, providing a more efficient method for removing metal impurities from tartaric acid.

[0021] (3) The present invention significantly increases the removal rate of tartaric acid metal ions through stepwise recrystallization, and its purity is also significantly improved. During stepwise recrystallization, the crystal growth is slower and more regular in the second recrystallization process, which can further reduce the formation of lattice defects, intergranular inclusions and surface adsorption, and the residual trace metal ions continue to remain in the mother liquor. Compared with one-step direct cooling crystallization, the stepwise process avoids the problem of impurity inclusion caused by rapid nucleation, and can achieve a higher metal ion removal rate. Attached Figure Description

[0022] Figure 1 The flowcharts for the method of preparing electronic-grade tartaric acid by stepwise recrystallization in Examples 1-3 of this invention are shown. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Before proceeding with the embodiments of this invention, the following preparatory work is required: 1) Conduct experiments in an electronic-grade Class 1000 cleanroom environment (≥0.3µm particles less than 1000) to ensure that the cleanroom air does not interfere with the experimental metal ions; 2) Ensure that the chromatography column soaked in ultrapure water does not interfere with the experimental metal ions; 3) Ensure that the use of a membrane filtration device does not interfere with the experimental metal ions; 4) Ensure that the use of electronic-grade sulfuric acid does not interfere with the experimental metal ions; 5) Ensure that the use of PFA and PTFE materials on equipment does not interfere with the experimental metal ions; 6) Detect the status of the instruments and prepare the required standard curves.

[0024] Example 1: A method for preparing electronic-grade tartaric acid using stepwise recrystallization, comprising the following steps: S1, Membrane filtration: After purging dissolving tank 1 with 99.999% nitrogen, 600g of 99.7% pure food additive L(+)-tartaric acid and 400g of ultrapure water with metal ions <1ppt were weighed and placed into dissolving tank 1. The solution was dissolved at room temperature to prepare a 60% tartaric acid solution. The tartaric acid solution was then filtered using a membrane filtration device, and the filtrate was collected. The filtrate was concentrated using a rotary evaporator and dried under 99.999% nitrogen to obtain preliminarily purified tartaric acid solid. A PTFE membrane (item number CHVR0020SW44EMD, pore size 0.2µm) was used in the membrane filtration device.

[0025] S2, Stepwise recrystallization: Weigh 600g of the preliminarily purified tartaric acid solid obtained in step S1 and 200g of ultrapure water with metal ions <1ppt and place them in dissolving tank 2. Dissolve the solid at 100℃ to prepare a 75% tartaric acid solution. Cool the solution to 90℃ to crystallize and precipitate the solid. Filter the solution under 99.999% nitrogen to obtain the first filtrate. Transfer the first filtrate to dissolving tank 3 and cool the solution to 20℃ to crystallize and precipitate the solid. Filter the solution under 99.999% nitrogen and dry it to obtain recrystallized tartaric acid solid.

[0026] S3, Ion exchange: Weigh 500g of recrystallized tartaric acid solid obtained in step S2 and 500g of ultrapure water with metal ions <1ppt and place them in storage tank 1. Dissolve them at 20℃ to prepare a 50% tartaric acid aqueous solution. Then, pass the solution into a secondary resin system for ion exchange at a flow rate of 5 Bv / h. Collect the effluent in storage tank 2 to obtain an electronic grade tartaric acid solution.

[0027] The secondary resin system consists of two series of resin columns with a height-to-diameter ratio of 16:1 and a diameter of 25 mm. The resin loading in the column is 200 g, and the resin is an electronic-grade strong acidic cation exchange resin (product number ZG C UP 60, capacity 4.8 mmol / g) (rinsed with an equal volume of <1 ppt of ultrapure water, with metal ions less than 50 ppt). Before the solution is introduced into the secondary resin system, the secondary resin system needs to be pretreated. The specific operation steps are as follows: (1) Purge the resin column with 99.999% nitrogen to remove air and prevent oxidation and contamination; (2) Prepare a 1.5% electronic-grade sulfuric acid solution with ultrapure water containing <1 ppt of metal ions, and then backwash the resin column with an electronic-grade sulfuric acid solution of 3 times the resin volume; (3) Rinse the resin column with ultrapure water containing <1 ppt of metal ions until neutral.

[0028] Example 2: A method for preparing electronic-grade tartaric acid by combining stepwise recrystallization is basically the same as that in Example 1, except that in step S2, the first temperature is 80°C.

[0029] Example 3: A method for preparing electronic-grade tartaric acid by combining stepwise recrystallization is basically the same as that in Example 1, except that in step S2, the first temperature is 70°C.

[0030] Performance testing: To verify the effectiveness of the method of the present invention, the metal ion removal rate and tartaric acid solution purity of Examples 1-3 were tested, and the test methods are as follows: 1. Purity test Take appropriate amounts of raw tartaric acid, preliminarily purified tartaric acid solid, and recrystallized tartaric acid solid, dissolve them in ultrapure water with metal ions <1ppt, and prepare raw tartaric acid solution, preliminarily purified tartaric acid solution, and recrystallized tartaric acid solution, respectively. Use HPLC to determine the purity of raw tartaric acid solution, preliminarily purified tartaric acid solution, and recrystallized tartaric acid solution.

[0031] 2. Metal ion removal rate test Take appropriate amounts of raw tartaric acid, preliminarily purified tartaric acid solid, and recrystallized tartaric acid solid, and dissolve them respectively in ultrapure water with metal ion concentrations <1 ppt to prepare raw tartaric acid solution, preliminarily purified tartaric acid solution, and recrystallized tartaric acid solution. According to the SJ / T11637-2016 electronic industry standard, use ICP-MS to determine the metal ion content of the raw tartaric acid solution, preliminarily purified tartaric acid solution, recrystallized tartaric acid solution, and the final electronic-grade tartaric acid solution. Calculate the metal ion removal rate using the formula shown below: Metal ion removal rate = (Metal ion content in raw tartaric acid - Metal ion content in treated tartaric acid) / Metal ion content in raw tartaric acid.

[0032] The purity and metal ion removal rate of Examples 1-3 of the present invention were tested, and the results are shown in Tables 1-3.

[0033] Table 1 Metal ion removal rate in Example 1 Table 2 Metal ion removal rate in Example 2 Table 3 Metal ion removal rate in Example 3 As shown in Tables 1-3, comparing Examples 1-3, it was found that by combining membrane filtration with stepwise recrystallization at different temperatures, the removal rate of tartaric acid metal ions reached a maximum of 81.03%, and the purity could be increased to 99.93%. Among these, the highest metal ion removal rate and purity were achieved after stepwise recrystallization at 70°C following membrane filtration. After a cyclic resin test, the removal rate of tartaric acid metal ions further reached 99.98%. This is because the metal ions in tartaric acid react with the H+ in the electron-grade strong acidic cation exchange resin. + Ion exchange occurs, further reducing its metal ion content.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Those skilled in the art can modify or make equivalent substitutions to the technical solutions of the present invention based on the concept of the present invention, without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing electronic-grade tartaric acid by combining stepwise recrystallization, characterized in that, Includes the following steps: S1. Membrane filtration: Dissolve the raw material tartaric acid in ultrapure water to obtain a tartaric acid solution. Perform membrane filtration on the tartaric acid solution, collect the filtrate, concentrate and dry the filtrate to obtain preliminarily purified tartaric acid solid. S2, Stepwise recrystallization: 1) First step crystallization: Under heating conditions, the tartaric acid solid obtained in step S1 is dissolved in ultrapure water to obtain solution A. Solution A is cooled to the first temperature to crystallize and precipitate. Solid-liquid separation is performed to obtain the first filtrate. 2) Second step crystallization: The first filtrate is cooled to a second temperature to crystallize and precipitate. The solid and liquid are separated and dried to obtain recrystallized tartaric acid solid. S3, Ion exchange: Dissolve the recrystallized tartaric acid solid obtained in step S2 in ultrapure water to obtain solution B. Pass solution B through a resin column packed with a strong acid cation exchange resin for ion exchange, collect the effluent, and obtain an electronic grade tartaric acid solution.

2. The method for preparing electronic-grade tartaric acid by stepwise recrystallization according to claim 1, characterized in that, In step S2, the first temperature is 70-90°C; the second temperature is 10-20°C.

3. The method for preparing electronic-grade tartaric acid by stepwise recrystallization according to claim 1, characterized in that, In step S2, the heating temperature is 95-100°C.

4. The method for preparing electronic-grade tartaric acid by stepwise recrystallization according to claim 1, characterized in that, In step S1, the raw material tartaric acid is L(+)-tartaric acid with a purity ≥99.7%.

5. The method for preparing electronic-grade tartaric acid by stepwise recrystallization according to claim 1, characterized in that, In step S1, the membrane used for membrane filtration is a PTFE membrane.

6. The method for preparing electronic-grade tartaric acid by stepwise recrystallization according to claim 1, characterized in that, In step S3, the strong acid cation exchange resin is an electronic-grade strong acid cation exchange resin.

7. The method for preparing electronic-grade tartaric acid by stepwise recrystallization according to claim 1 or 6, characterized in that, In step S3, before ion exchange, a pretreatment step is also included: backwashing the resin column with electronic grade sulfuric acid solution and then rinsing it with ultrapure water until neutral.

8. The method for preparing electronic-grade tartaric acid by stepwise recrystallization according to claim 1, characterized in that, In step S1, the mass percentage concentration of the tartaric acid solution is 40%–60%; in step S2, the mass percentage concentration of solution A is 75%; and in step S3, the mass percentage concentration of solution B is 30%–50%.

9. The method for preparing electronic-grade tartaric acid by stepwise recrystallization according to any one of claims 1-8, characterized in that, The ultrapure water used in the method is ultrapure water with metal ion concentrations of <1ppt.

10. Electronic-grade tartaric acid prepared by the method according to any one of claims 1-9.

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