A preparation process of high-purity tetraethylammonium hydroxide and high-purity quaternary ammonium base prepared therefrom

Abstract

This application discloses a process for preparing high-purity tetraethylammonium hydroxide and the high-purity quaternary ammonium base produced therefrom, relating to the technical field of high-purity quaternary ammonium base production. The process for preparing high-purity tetraethylammonium hydroxide comprises the following steps: S1: preparing tetraethylammonium chloride, adding water to prepare an aqueous solution, and adding an adsorbent; preparing a pretreatment solution; the adsorbent containing acetate ions; S2: adding the pretreatment solution to the feed chamber of an electrolytic cell. Through electrolysis, tetraethylammonium cations pass through a cationic membrane into the cathode chamber, where they combine with hydroxide ions generated at the cathode to form tetraethylammonium hydroxide, thereby producing the quaternary ammonium base. This process for preparing high-purity tetraethylammonium hydroxide has the advantage of helping to improve the quality of quaternary ammonium base products.

Description

Technical Field

[0001] The present application relates to the technical field of high-purity organic quaternary ammonium base production, and in particular to a preparation process of high-purity tetraethylammonium hydroxide and the high-purity quaternary ammonium base prepared therefrom. Background Art

[0002] Tetraethylammonium hydroxide is commonly used in the synthesis of SAPO-34 molecular sieves. SAPO-34 molecular sieves synthesized with tetraethylammonium hydroxide exhibit advantages such as high diene selectivity and long catalyst life when used in MTO (methanol to olefins) catalysts. With the development of the methanol to olefins industry, the use of SAPO-34 molecular sieves and tetraethylammonium hydroxide has increased significantly, leading to increasing research in the industry into the production process of tetraethylammonium hydroxide.

[0003] Tetramethylammonium hydroxide (TMAH) is a wet electronic chemical widely used in cleaning chips, semiconductors, photovoltaics, and other fields. However, TMAH easily decomposes to form trimethylamine, a highly odorous substance. This odor is a problem for TMAH chip cleaning. With the development of high-end chips, TMAH is increasingly unable to meet the needs of chip manufacturing.

[0004] Tetraethylammonium hydroxide (TEAH) has begun replacing tetramethylammonium hydroxide (TMAH) for cleaning chips and other applications. Currently, TEAH is primarily used in molecular sieve synthesis and is typically an industrial-grade product with metal ion concentrations typically in the ppm range (typically 1-5 ppm). However, wet electronic chemicals used for chip cleaning generally require metal ion concentrations of less than 100 ppb (G1 grade). Existing TEAH production processes do not produce the high-purity TEAH required by these high-purity wet electronic chemicals. Summary of the Invention

[0005] In order to improve the quality of tetraethylammonium hydroxide, the present application provides a preparation process of high-purity tetraethylammonium hydroxide and the high-purity quaternary ammonium base prepared therefrom.

[0006] In a first aspect, the present application provides a process for preparing high-purity tetraethylammonium hydroxide, which adopts the following technical solution:

[0007] A preparation process for high-purity tetraethylammonium hydroxide comprises the following steps:

[0008] S1 ingredients: take tetraethylammonium chloride, add water to prepare an aqueous solution, add an adsorbent to prepare a pretreatment solution; the adsorbent contains acetate ions;

[0009] S2 electrolysis: The pretreatment liquid is added to the raw material chamber of the electrolytic cell. Through electrolysis, tetraethylammonium cations pass through the cationic membrane into the cathode chamber and combine with the hydroxide ions produced at the cathode to form tetraethylammonium hydroxide to produce quaternary ammonium base.

[0010] By adopting the above technical solution, with tetraethylammonium chloride as the raw material, during the electrolysis process, tetraethylammonium cations enter the cathode chamber through the cationic membrane and combine with hydroxide ions generated in the cathode chamber to form tetraethylammonium hydroxide; by adding an acetate-containing adsorbent to the pretreatment liquid, the metal ions in the tetraethylammonium chloride raw material are stabilized in the raw material chamber, reducing the probability of the metal ions entering the product chamber through the cationic membrane, helping to reduce the metal ion content in the product and improving the product quality.

[0011] Preferably, the acetate ion concentration in the raw material chamber is 10ppm-300ppm. More preferably, the acetate ion concentration in the raw material chamber is 80ppm-150ppm

[0012] By adopting the above technical solution, in the present application, the inventors found that too little acetate ion cannot reduce the metal ion content; too much acetate ion has a poor effect; and acetate ion needs to be within an appropriate range.

[0013] Preferably, the adsorbent is one or more of acetic acid, ammonium acetate, and tetraethylammonium acetate. Preferably, the adsorbent is acetic acid.

[0014] By adopting the above technical solution and using acetic acid, ammonium acetate, and tetraethylammonium acetate as the components of the adsorbent of the present application, the introduction of other components can be avoided, which is beneficial to improving product quality. In the actual quaternary ammonium hydroxide production process, the product obtained by electrolysis generally needs to be vacuum concentrated to the desired concentration. During the concentration process, ammonium ions introduced by the ammonium acetate adsorbent are removed during the vacuum concentration. Therefore, using ammonium acetate as an adsorbent does not introduce new impurities.

[0015] Preferably, the electrolytic cell includes an anode chamber, a raw material chamber and a cathode chamber adjacent to each other in sequence; an anode plate is installed in the anode chamber, a cathode plate is installed in the cathode chamber, and the anode plate and the cathode plate are connected through a power supply; the anode chamber and the raw material chamber are connected through an anion membrane, and the raw material chamber and the cathode chamber are connected through a cation membrane.

[0016] By adopting the above technical solution and using a three-chamber two-membrane electrolysis method, tetraethylammonium chloride is added to the raw material chamber during the electrolysis process, and the tetraethylammonium cations enter the cathode chamber (product chamber) through the cationic membrane; the acetate ions are anions and are not easy to pass through the cationic membrane; a part of the acetate ions fix the metal ions in the raw material chamber in the raw material chamber; a part of the acetate ions enter the anode chamber through the anionic membrane, which helps to reduce the probability of cations in the anode chamber entering the raw material chamber and helps to improve product quality.

[0017] Preferably, the raw material chamber in step S2 contains ethanol.

[0018] By adopting the above technical solution, ethanol is added to the raw material chamber. The inventors of the present application found in actual research that the ethanol and acetate ions in the raw material chamber have a synergistic effect. The combination of the two can significantly reduce the metal ion content in the product, which helps to better improve the product quality.

[0019] Preferably, the weight concentration ratio of ethanol to acetate ions in the raw material chamber in step S2 is 5-15.

[0020] By adopting the above technical solution, the inventors found in actual research that the ratio of ethanol to acetic acid has a great influence on the metal ion content in the product. Both too low and too high a ratio of the two are not ideal, and the best effect is achieved when the ratio is within an appropriate range.

[0021] Preferably, the mass concentration of tetraethylammonium chloride in the raw material chamber in step S2 is 10.5-13.5%.

[0022] By adopting the above technical solution, the concentration of tetraethylammonium chloride in the raw material chamber needs to be moderate. If it is too high or too low, the effect will be affected. By controlling the concentration of tetraethylammonium chloride in the raw material chamber, it is helpful to improve product quality.

[0023] In a second aspect, the present application provides a high-purity quaternary ammonium base, which adopts the following technical solution: a high-purity quaternary ammonium base is prepared by the above-mentioned preparation process of high-purity tetraethylammonium hydroxide.

[0024] By adopting the above technical solution and using the method disclosed in the present application to produce tetraethylammonium hydroxide, it is helpful to reduce the metal ion content in the product and help improve the product quality.

[0025] In summary, this application includes at least one of the following beneficial technical effects:

[0026] 1. This application uses electrolysis to produce tetraethylammonium hydroxide. Adding an acetate-containing adsorbent to the pretreatment solution helps reduce the probability of metal ions passing through the cathodic membrane into the cathode chamber (product chamber), thereby helping to improve product quality.

[0027] 2. In the electrolysis process, ethanol and acetate ions are added to the raw material chamber. Ethanol and acetate ions have a synergistic effect, which helps to reduce the metal ion content in the product and improve the product quality.

[0028] 3. In this application, the ratio of ethanol to acetic acid has a certain influence on the metal ions in the product. By controlling the ratio of ethanol to acetic acid, it helps to improve the product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the electrolytic cell structure used in this application.

[0030] Figure numerals: 1, anode chamber; 2, raw material chamber; 3, cathode chamber; 4, anode plate; 5, cathode plate; 6, anion membrane; 7, cation membrane. DETAILED DESCRIPTION

[0031] In the process of preparing tetraethylammonium hydroxide by electrolysis, tetraethylammonium chloride is generally used as a raw material to prepare tetraethylammonium hydroxide by electrolysis. The inventors have found in practice that chloride ions have certain corrosiveness and the produced tetraethylammonium hydroxide contains a high content of metal ions.

[0032] Based on the above technical background, the present application proposes a technical solution that adds a small amount of acetic acid and ethanol to the raw material chamber of the electrolyzer. The combined effect of the two can significantly reduce the metal ion content in the product, helping to improve product quality. The synergistic effect of ethanol and acetic acid helps to reduce the metal ion content. Due to production process reasons, a small amount of ethanol is generally retained in the tetraethylammonium chloride raw material. The residual ethanol content in the tetraethylammonium chloride raw material is generally less than 10ppm. The small amount of ethanol remaining in the tetraethylammonium chloride raw material also plays a certain role.

[0033] During electrolysis, acetate ions pass through the anionic membrane into the cathode chamber, while ethanol does not pass through either the anionic or cationic membranes. Therefore, acetate ions are added to a tetraethylammonium chloride aqueous solution. As electrolysis proceeds, tetraethylammonium cations enter the cathode chamber, reducing the tetraethylammonium cation concentration in the feed chamber. By adding pretreatment solution to the feed chamber, the tetraethylammonium chloride concentration in the feed chamber is maintained within the desired range, while also maintaining the acetate ion concentration within an appropriate range. Instead of adding ethanol to the pretreatment solution, ethanol is added directly to the feed chamber, maintaining a reasonable ethanol-to-acetic acid ratio. During actual operation, ethanol loss is minimal; a certain amount of ethanol is added upon startup, with subsequent additions requiring minimal amounts. In actual production, as electrolysis progresses, a small amount of solid matter, such as precipitate or flocs, adheres to the inner walls of the feed chamber. Therefore, regular cleaning of the electrolysis chamber, such as once a month, is necessary to maintain consistent product quality.

[0034] The details are described in the following specific implementation manner.

[0035] The water used in the following examples is deionized water with a conductivity of no more than 20 μs / cm. The power supply for the electrolysis process is a direct current power supply. The mass concentration of tetraethylammonium chloride in the raw material chamber during the electrolysis process is no more than 15%, preferably 10.5-13.5%. During the electrolysis process, the chloride ion concentration in the raw material chamber is titrated with silver nitrate, and the tetraethylammonium chloride concentration is measured by conversion to track the concentration of tetraethylammonium chloride in the raw material chamber during the electrolysis process; based on the concentration change of tetraethylammonium chloride in the raw material chamber, pretreatment liquid is added to the raw material chamber during the electrolysis process to maintain the mass concentration of tetraethylammonium chloride in the raw material chamber at 10.5-13.5%. The concentration of tetraethylammonium chloride in the pretreatment liquid can be prepared as needed. In the embodiment, the concentration of tetraethylammonium chloride in the pretreatment liquid is 36%. When the machine is turned on, water is added to the raw material chamber to maintain the concentration of tetraethylammonium chloride in the raw material chamber at 10.5-13.5%. In this embodiment, the acetate ion concentration in the pretreatment solution is 30 ppm to 900 ppm. The water in the feed chamber controls the acetate ion concentration in the feed chamber within the desired range. The acetate ion concentration in the feed chamber is adjusted to the desired value by changing the acetate concentration in the pretreatment solution. The acetate ion concentration is determined by ion chromatography, the ethanol concentration is determined by headspace chromatography, and the metal ions are determined by ICP-MS.

[0036] The following examples use the same electrolysis equipment. Before starting the power supply to begin electrolysis, water is filled in the electrolyzer.

[0037] The present application is further described in detail below with reference to the accompanying drawings.

[0038] Example

[0039] Example 1: A method for preparing high-purity tetraethylammonium hydroxide, comprising the following steps:

[0040] S1 ingredients: Take 5 kg of tetraethylammonium chloride, add pure water to prepare a tetraethylammonium chloride aqueous solution with a mass concentration of 36%, stir, add 0.42 g of acetic acid to prepare a pretreatment solution with an acetate concentration of 30 ppm.

[0041] Electrolysis S2: Tetraethylammonium chloride prepared in step S1 is added to the feed chamber 2 of the electrolytic cell and diluted with water until the mass concentration of tetraethylammonium chloride in the feed chamber 2 is 12% and the acetate ion concentration is approximately 10 ppm. The electrolytic cell comprises an anode chamber 1, a feed chamber 2, and a cathode chamber 3, which are adjacent to each other in sequence. An anode plate 4 is installed in the anode chamber 1, and a cathode plate 5 is installed in the cathode chamber 3. The anode plate 4 and the cathode plate 5 are connected by a power supply. The anode chamber 1 and the feed chamber 2 are connected by an anion membrane 6, and the feed chamber 2 and the cathode chamber 3 are connected by a cation membrane 7. Water is added to the anode chamber 1 and the cathode chamber 3 in step S2. In step S2, an aqueous solution of tetraethylammonium chloride is first added to the feed chamber 2. Through electrolysis, tetraethylammonium cations enter the cathode chamber 3 through the cation membrane 7 and combine with hydroxide ions generated at the cathode to form tetraethylammonium hydroxide.

[0042] During the electrolysis process, the materials in the anode chamber 1, the feed chamber 2, and the cathode chamber 3 were circulated using circulating pumps. The circulation rate of the materials in the anode chamber 1 and the cathode chamber 3 was 80 ml / min, and the circulation rate of the materials in the feed chamber 2 was 150 ml / min. Based on the concentration of tetraethylammonium chloride in the feed chamber 2, the tetraethylammonium chloride aqueous solution was added to the feed chamber 2 during the electrolysis process to maintain the tetraethylammonium chloride concentration in the feed chamber 2 at 10.5-13.5%, and the acetate ion concentration was approximately 10 ppm. After 24 hours of electrolysis, the concentration of the tetraethylammonium hydroxide product in the cathode chamber 3 increased to approximately 25%. Water was added to the cathode chamber 3 to maintain the concentration at approximately 25%. 1 kg of product was discharged from the cathode chamber 3 every 8 hours. The electrolysis lasted for 48 hours, and the metal ion content of the product generated at the 48th hour was measured.

[0043] Example 2

[0044] The difference between Example 2 and Example 1 is that 200 ppm of ethanol is added to the raw material chamber in step S2 of Example 2, and samples are taken every 4 hours during the electrolysis process to detect the ethanol content in the raw material chamber by headspace chromatography. Based on the test results, ethanol is added to maintain the ethanol content in the raw material chamber at about 200 ppm. The rest remains the same as Example 1.

[0045] Example 3

[0046] The difference between Example 3 and Example 2 is that the acetic acid content in the raw material chamber of Example 3 is 80 ppm and the ethanol content is 200 ppm, and the other contents are consistent with Example 2.

[0047] Example 4

[0048] The difference between Example 4 and Example 3 is that the acetic acid content in the raw material chamber of Example 4 is 80 ppm and the ethanol content is 1200 ppm, and the other contents are consistent with Example 3.

[0049] Example 5

[0050] The difference between Example 5 and Example 4 is that the acetic acid content in the raw material chamber of Example 5 is 150 ppm and the ethanol content is 750 ppm. Other contents are consistent with Example 3.

[0051] Examples 6-10

[0052] The difference between Example 6-10 and Example 5 is that the concentrations of acetate and ethanol in the raw material chamber of Example 6-10 are different, and the rest are consistent with Example 5. The concentrations of the components in the raw material chamber of step S2 of Example 6-10 are shown in Table 1.

[0053] Table 1 Molar ratio of each raw material in Examples 6-10

[0054]

[0055] Comparative Example

[0056] Comparative Example 1

[0057] The difference between Comparative Example 1 and Example 1 is that no acetic acid is added in Comparative Example 1, and the other steps are the same as those in Example 1.

[0058] Table 2 Comparison of metal ion content in products after 48h electrolysis

[0059] Experiment number <![CDATA[Na + (ppb)]]> <![CDATA[K + (ppb)]]> <![CDATA[Ca 2+ (ppb)]]> <![CDATA[Cl - (ppm)]]> Example 1 105.1 74.8 23.4 19 Example 2 71.8 65.3 18.2 17 Example 3 59.7 48.5 15.6 17 Example 4 12.9 16.3 2.4 8 Example 5 10.6 12.7 3.5 7 Example 6 37.2 36.1 13.8 12 Example 7 39.4 41.5 11.2 14 Example 8 8.3 9.6 2.7 5 Example 9 6.1 10.8 1.6 6 Example 10 7.2 5.8 1.9 4 Comparative Example 1 154.3 87.5 48.6 35

[0060] Comparative Example 1: Tetraethylammonium hydroxide was prepared using a conventional electrolytic method. The resulting product had a sodium ion content exceeding 100 ppb, a potassium ion content approaching 100 ppb, a relatively high impurity content, and poor product quality. Comparison of the experimental results of Example 1 with those of Comparative Example 1 reveals that the addition of an acetate-containing adsorbent during the preparation of tetraethylammonium hydroxide has a certain adsorption effect on metal ions, tending to immobilize the metal ions in the raw material cavity, thereby reducing the probability of metal ions entering the product cavity through the cationic membrane, thereby reducing the impurity content in the product and improving product quality.

[0061] Comparing the experimental results of Example 1 and Example 2, the addition of ethanol and acetic acid to the feed chamber in Example 2 further reduced the metal ion content. In Example 3, the amount of acetic acid added was appropriate, and the ratio of ethanol to acetic acid was not within the optimal range, resulting in a slight reduction in metal ions.

[0062] Comparing the experimental results of Examples 4-5 with those of Example 3, the added acetic acid content in Examples 4-5 was appropriate, and the ratio of ethanol to acetic acid was within an optimal range, resulting in a product with low metal ion content and high product quality. In Examples 6-7, although the amount of acetic acid was appropriate, the ratio of ethanol to acetic acid was inappropriate, resulting in a high metal ion content. In Examples 8-10, the amount of acetic acid was appropriate, and the ratio of ethanol to acetic acid was appropriate, resulting in a product with low metal ion content, low chloride ion content, and high product quality.

[0063] The embodiments of this specific implementation method are all preferred embodiments of the present application and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A process for preparing high-purity tetraethylammonium hydroxide, characterized in that: The following steps are involved: S1 ingredients: take tetraethylammonium chloride, add water to prepare an aqueous solution, add an adsorbent to prepare a pretreatment solution; the adsorbent contains acetate ions; S2 electrolysis: The pretreatment solution is added to the raw material chamber of the electrolytic cell. Through electrolysis, tetraethylammonium cations pass through the cationic membrane into the cathode chamber and combine with the hydroxide ions generated at the cathode to produce tetraethylammonium hydroxide; The electrolytic cell comprises an anode chamber (1), a raw material chamber (2) and a cathode chamber (3) which are adjacent to each other in sequence; the acetate ion concentration in the raw material chamber in step S2 is 10 ppm-300 ppm; and the mass concentration of tetraethylammonium chloride in the raw material chamber in step S2 is 10.5-13.5%.

2. A process for preparing high-purity tetraethylammonium hydroxide according to claim 1, wherein: The adsorbent is one or more of acetic acid, ammonium acetate, and tetraethylammonium acetate.

3. A process for preparing high-purity tetraethylammonium hydroxide according to claim 2, wherein: The adsorbent is acetic acid.

4. A process for preparing high-purity tetraethylammonium hydroxide according to claim 1, wherein: An anode plate (4) is installed in the anode chamber (1), and a cathode plate (5) is installed in the cathode chamber (3). The anode plate (4) and the cathode plate (5) are connected via a power supply. The anode chamber (1) and the raw material chamber (2) are connected via an anion membrane (6), and the raw material chamber (2) and the cathode chamber (3) are connected via a cation membrane (7).

5. A process for preparing high-purity tetraethylammonium hydroxide according to claim 1, wherein: The raw material chamber in step S2 contains ethanol.

6. A process for preparing high-purity tetraethylammonium hydroxide according to claim 5, characterized in that: In step S2, the weight concentration ratio of ethanol to acetate ions in the raw material chamber is 5-15.

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