Preparation process of high-purity tetraethylammonium hydroxide and prepared high-purity quaternary ammonium base

Abstract

The invention discloses a preparation process of high-purity tetraethylammonium hydroxide and high-purity quaternary ammonium base prepared by the preparation process, and relates to the technical field of high-purity quaternary ammonium base production. The preparation process of the high-purity tetraethylammonium hydroxide comprises the following steps: S1, material preparation: taking tetraethylammonium chloride, adding water to prepare an aqueous solution, and adding an adsorbent; pre-treatment liquid is prepared; the adsorbent contains acetate ions; and S2, electrolysis is conducted, specifically, the pretreatment liquid is added into a raw material chamber of an electrolytic bath, through electrolysis, tetraethylammonium cations enter a cathode chamber through a cation membrane and are combined with hydroxyl ions generated by a cathode, tetraethylammonium hydroxide is formed, and quaternary ammonium base is prepared. The preparation process of the high-purity tetraethylammonium hydroxide has the advantage of being beneficial to improving the quality of a quaternary ammonium base product.

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 often used to synthesize SAPO-34 molecular sieves. The SAPO-34 molecular sieve synthesized with tetraethylammonium hydroxide has the advantages of high diene selectivity and long catalyst life when used as MTO (methanol to olefins) catalyst. With the development of the methanol to olefins industry, the usage of SAPO-34 molecular sieves and tetraethylammonium hydroxide is increasing. The industry is also conducting more and more research on the production process of tetraethylammonium hydroxide.

[0003] As a wet electronic chemical, tetramethylammonium hydroxide is widely used in cleaning agents for chips, semiconductors, photovoltaics, etc. However, tetramethylammonium hydroxide is easily decomposed to form trimethylamine with a strong odor, and there is a problem of strong odor when tetramethylammonium hydroxide is used as a chip cleaning agent. With the development of high-end chips, it is increasingly difficult for tetramethylammonium hydroxide to meet the needs of chip manufacturing.

[0004] People began to use tetraethylammonium hydroxide instead of tetramethylammonium hydroxide for cleaning fields such as chips. Currently, tetraethylammonium hydroxide is generally used in the field of molecular sieve synthesis and is generally an industrial-grade product. The metal ion content in the product is generally ppm level (usually 1-5ppm). However, wet electronic chemicals used for chip cleaning generally require metal ions to be less than 100ppb (G1 level). The product quality of tetraethylammonium hydroxide produced by the existing tetraethylammonium hydroxide production process is difficult to meet the needs of 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 prepared high-purity quaternary ammonium base.

[0006] In the first aspect, the present application provides a preparation process of high-purity tetraethylammonium hydroxide, using the following technical solution:

[0007] A preparation process of 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 solution is added into the raw material chamber of the electrolytic cell. Through electrolysis, tetraethylammonium cations pass through the cation membrane into the cathode chamber and combine with the hydroxide ions produced at the cathode to form tetraethylammonium hydroxide to produce quaternary ammonium hydroxide.

[0010] By adopting the above technical scheme, with tetraethylammonium chloride as 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 metal ions entering the product cavity through the cationic membrane, which helps to reduce the metal ion content in the product and helps to improve 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; acetate ions need to be within a suitable 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, 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 the product quality. In the actual production process of quaternary ammonium alkali, the product obtained by electrolysis usually needs to be vacuum concentrated to the required concentration. During the concentration process, the ammonium ions introduced by the ammonium acetate adsorbent will be removed along with the vacuum concentration. Therefore, using ammonium acetate as an adsorbent will not introduce new impurities.

[0015] Preferably, the electrolytic cell comprises an anode chamber, a raw material chamber and a cathode chamber which are 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 scheme, using the three-chamber two-membrane electrolysis method, during the electrolysis process, tetraethylammonium chloride is added to the raw material chamber, and the tetraethylammonium cation enters the cathode chamber (product chamber) through the cation membrane; the acetate ion is an anion and is not easy to pass through the cation 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 enters the anode chamber through the anion 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. Too low or too high a ratio of the two is not ideal, and the effect is best when it 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, and the effect will be affected if it is too high or too low; by controlling the concentration of tetraethylammonium chloride in the raw material chamber, it is helpful to improve the product quality.

[0023] In a second aspect, the present application provides a high-purity quaternary ammonium base, which adopts the following technical scheme: 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 scheme 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 to improve the product quality.

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

[0026] 1. The present 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 of the present application, 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 the present 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 This is a 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, in which a small amount of acetic acid and ethanol are added to the raw material chamber of the electrolyzer, and the two can work together to significantly reduce the metal ion content in the product, which helps to improve the product quality. The synergistic effect of ethanol and acetic acid helps to reduce the metal ion content. Due to the production process, a small amount of ethanol generally remains in the tetraethylammonium chloride raw material, and the ethanol residue in the tetraethylammonium chloride raw material is generally less than 10ppm. The small amount of ethanol remaining in the tetraethylammonium chloride raw material will also play a certain role.

[0033] During the operation of the electrolyzer, acetate ions will enter the cathode chamber through the anion membrane, and ethanol will not pass through the anion membrane and the cation membrane; therefore, acetate ions are added to the tetraethylammonium chloride aqueous solution. As the electrolysis proceeds, tetraethylammonium cations enter the cathode chamber, and the concentration of tetraethylammonium cations in the raw material chamber decreases. By adding pretreatment liquid to the raw material chamber, the concentration of tetraethylammonium chloride in the raw material chamber is kept within the required range, and the acetate ion concentration is kept within the appropriate range. Instead of adding ethanol to the pretreatment liquid, ethanol is directly added to the raw material chamber to keep the ratio of ethanol to acetic acid within a reasonable range; in the actual operation process, ethanol loss is small, a certain amount of ethanol will be added when the electrolyzer is turned on, and the amount of ethanol added later is small. In the actual production process, as the electrolysis time increases, a small amount of solid substances such as precipitation or flocs will adhere to the inner wall of the raw material chamber; therefore, it is necessary to clean the electrolyzer regularly, such as once a month, which will help maintain the stability of product quality.

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

[0035] The water used in the following embodiments is deionized water, and the conductivity is not more than 20μs / 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 not 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 concentration of tetraethylammonium chloride is measured by conversion, and the concentration of tetraethylammonium chloride in the raw material chamber during the electrolysis process is tracked; according to the concentration change of tetraethylammonium chloride in the raw material chamber, the pretreatment liquid is added to the raw material chamber during the electrolysis process so that the mass concentration of tetraethylammonium chloride in the raw material chamber is maintained at 10.5-13.5%. The concentration of tetraethylammonium chloride in the pretreatment liquid can be prepared as needed. The concentration of tetraethylammonium chloride in the pretreatment liquid in the embodiment is 36%. When the machine is turned on, water is added to the raw material chamber so that the concentration of tetraethylammonium chloride in the raw material chamber is maintained at 10.5-13.5%. In the embodiment, the acetate ion concentration in the pretreatment liquid is 30ppm-900ppm, and the water in the raw material chamber controls the acetate ion concentration in the raw material chamber within a desired range. The acetate ion concentration in the raw material chamber is adjusted to a desired value by changing the acetate concentration in the pretreatment liquid. The acetate ion concentration is detected by ion chromatography, the ethanol is detected by headspace chromatography, and the metal ions are detected by ICP-MS.

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

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

[0038] Example

[0039] Embodiment 1: The preparation method of high-purity tetraethylammonium hydroxide comprises 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] S2 electrolysis: take the tetraethylammonium chloride prepared in step S1, add it to the raw material chamber 2 of the electrolytic cell, and add water to dilute it until the mass concentration of tetraethylammonium chloride in the raw material chamber 2 is 12%, and the acetate ion concentration is about 10ppm. The electrolytic cell comprises an anode chamber 1, a raw material chamber 2 and a cathode chamber 3 adjacent to each other in sequence; an anode plate 4 is installed in the anode chamber 1, a cathode plate 5 is installed in the cathode chamber 3, and the anode plate 4 and the cathode plate 5 are connected by a power supply; the anode chamber 1 and the raw material chamber 2 are connected by an anion membrane 6, and the raw material 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 of step S2; step S2 first adds a tetraethylammonium chloride aqueous solution to the raw material chamber 2, and through electrolysis, the tetraethylammonium cations enter the cathode chamber 3 through the cation membrane 7, and combine with the hydroxide ions generated by the cathode to form tetraethylammonium hydroxide.

[0042] During the electrolysis process, the materials in the anode chamber 1, the raw material chamber 2 and the cathode chamber 3 are circulated by a circulation pump respectively. The circulation flow rate of the materials in the anode chamber 1 and the cathode chamber 3 is 80 ml / min, and the circulation flow rate of the materials in the raw material chamber 2 is 150 ml / min. According to the concentration change of tetraethylammonium chloride in the raw material chamber 2, the tetraethylammonium chloride aqueous solution is added to the raw material chamber 2 during the electrolysis process to keep the concentration of tetraethylammonium chloride in the raw material chamber 2 at 10.5-13.5%, and the acetate ion is about 10 ppm. After 24 hours of electrolysis, the concentration of tetraethylammonium hydroxide product in the cathode chamber 3 increases to about 25%, and water is added to the cathode chamber 3 to keep the concentration at about 25%. 1 kg of product is released from the cathode chamber 3 every 8 hours, and the electrolysis is performed for 48 hours. The metal ion content in the product generated after 48 hours of electrolysis is detected.

[0043] Example 2

[0044] The difference between Example 2 and Example 1 is that 200 ppm 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 is consistent with 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 others 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 rest is 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, and the rest is consistent with Example 3.

[0051] Embodiment 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 is prepared by conventional electrolysis method, and the sodium ion content of the obtained product exceeds 100 ppb, the potassium ion content is close to 100 ppb, there are many impurities, and the product quality is poor. By comparing the experimental results of Example 1 with those of Comparative Example 1, it can be seen that in the preparation process of tetraethylammonium hydroxide, the addition of an adsorbent containing acetate has a certain adsorption effect on metal ions, so that the metal ions tend to be fixed in the raw material cavity, reducing the probability of metal ions entering the product cavity through the cationic membrane, which is conducive to reducing the impurity content in the product and improving the product quality.

[0061] Comparing the experimental results of Example 1 with that of Example 2, the metal ion content was further reduced by adding ethanol and acetic acid simultaneously into the raw material chamber of Example 2. The acetic acid content added in Example 3 was appropriate, the ratio of ethanol to acetic acid was not in the optimal range, and the metal ion content was slightly reduced.

[0062] Comparing the experimental results of Examples 4-5 with those of Example 3, the content of acetic acid added in Examples 4-5 is appropriate, and the ratio of ethanol to acetic acid is within a preferred range, the metal ion content of the obtained product is low, and the product quality is high. In Examples 6-7, although the amount of acetic acid is appropriate, the ratio of ethanol to acetic acid is not appropriate, and the metal ion content is high. In Examples 8-10, the amount of acetic acid is appropriate, the ratio of ethanol to acetic acid is appropriate, the metal ion content of the obtained product is low, the chloride ion content is low, and the product quality is high.

[0063] The embodiments of this specific implementation method are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Therefore, all equivalent changes made based on the structure, shape, and principle of the present application should be included in the protection scope 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 into the raw material chamber of the electrolytic cell. Through electrolysis, tetraethylammonium cations pass through the cation membrane into the cathode chamber and combine with the hydroxide ions produced at the cathode to form tetraethylammonium hydroxide to produce quaternary ammonium hydroxide.

2. A process for preparing high-purity tetraethylammonium hydroxide according to claim 1, characterized in that: The acetate ion concentration in the raw material chamber is 10ppm-300ppm.

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

4. A process for preparing high-purity tetraethylammonium hydroxide according to claim 3, characterized in that: The adsorbent is acetic acid.

5. A process for preparing high-purity tetraethylammonium hydroxide according to claim 1, characterized in that: 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; an anode plate (4) is installed in the anode chamber (1), a cathode plate (5) is installed in the cathode chamber (3), and 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).

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

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

8. A process for preparing high-purity tetraethylammonium hydroxide according to claim 1, characterized in that: The mass concentration of tetraethylammonium chloride in the raw material chamber of step S2 is 10.5-13.5%.

9. A high-purity quaternary ammonium hydroxide, characterized in that: The high-purity tetraethylammonium hydroxide is prepared by the preparation process of any one of claims 1 to 8.

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