Preparation method of colorless low-water-content glacial acetic acid
By performing two activation and drying processes on the molecular sieve, combined with solid-liquid separation and distillation steps, the problems of deep dehydration of glacial acetic acid and preparation of colorless and transparent products were solved, realizing the preparation of colorless glacial acetic acid with low water content, meeting the needs of high-end chemical synthesis.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-04-07
AI Technical Summary
Existing technologies cannot achieve deep dehydration of glacial acetic acid without introducing impurities, and existing methods cannot meet the requirements for colorless and transparent high-quality glacial acetic acid.
A molecular sieve was used for two activation and drying processes, combined with solid-liquid separation and distillation steps. The molecular sieve was then soaked in glacial acetic acid for a second activation and drying process to obtain colorless glacial acetic acid with low water content.
The preparation of colorless, low-water-content glacial acetic acid has been achieved, meeting the requirements of certain high-end chemical synthesis processes such as esterification and acylation reactions.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of chemical reagent technology, and in particular to a method for preparing colorless glacial acetic acid with low water content. Background Technology
[0002] Glacial acetic acid, also known as anhydrous acetic acid or glacial acetic acid, is a colorless, transparent crystalline solid at room temperature (below 16.6℃) when pure (≥99.5%), hence the name "glacial" acetic acid. It has a boiling point of 117.9℃, a melting point of 16.6℃, and a density of 1.049 g / cm³. 3 Glacial acetic acid is miscible with water, alcohols, and ethers, and has a strong, pungent acidic odor. It is a weak acid (pKa = 4.76), but its corrosiveness is high, and contact with skin can cause severe burns. Glacial acetic acid is one of the most important basic organic acids and platform compounds in modern chemical industry. It is an indirect raw material for producing lithium battery electrolyte additives (such as ethyl acetate and carbonates), and a starting material or intermediate for the synthesis of many drugs such as aspirin, penicillin, and chloramphenicol. It is also widely used as a solvent in the coatings, inks, and adhesives industries.
[0003] In the dehydration process of polar solvents such as glacial acetic acid, the commonly used drying methods mainly include azeotropic distillation, molecular sieve drying, chemical desiccants, and high-vacuum distillation. However, these methods often have their limitations. While azeotropic distillation can remove water using the azeotropic system, the glacial acetic acid-water azeotropic system still contains some water at its ppm level, making it difficult to achieve extremely low water content requirements. Chemical desiccants (such as phosphorus pentoxide and acetic anhydride) can absorb water to some extent, but they often introduce new chemical substances, potentially leading to side reactions or residue problems, and thus cannot consistently achieve ultra-high dehydration standards. High-vacuum distillation, while lowering the boiling point and reducing the risk of thermal decomposition, has extremely high requirements for equipment sealing and operating conditions, and its efficiency in removing trace amounts of water is still limited, making it difficult to meet the needs of applications with extremely strict moisture content control. Molecular sieve drying, with its regular pore structure and strong adsorption properties, can effectively reduce moisture to extremely low levels, theoretically meeting or even exceeding moisture control targets. However, a significant drawback has been discovered in practical applications of this method: certain silicate components in the molecular sieve material gradually dissolve under prolonged contact or specific conditions and enter the glacial acetic acid system. These dissolved impurities can cause a color change in glacial acetic acid, typically manifesting as a noticeable yellow hue, thus affecting the product's appearance and purity, making it impossible to obtain the desired colorless and transparent high-quality glacial acetic acid.
[0004] Therefore, finding a drying method that can achieve deep dehydration while avoiding the introduction of impurities and maintaining the stability of the solvent's physicochemical properties remains a challenging task. Summary of the Invention
[0005] In view of the problems existing in the prior art, the present invention provides a method for preparing colorless glacial acetic acid with low water content, which can obtain colorless glacial acetic acid with low water content, thus meeting the requirements of certain high-end chemical synthesis (such as water-sensitive esterification and acylation reactions).
[0006] To achieve this objective, the present invention adopts the following technical solution:
[0007] This invention provides a method for preparing colorless, low-water-content glacial acetic acid, the method comprising the following steps:
[0008] The molecular sieve is activated once to obtain a primary activated molecular sieve.
[0009] The primary activated molecular sieve is mixed with glacial acetic acid and then subjected to a primary drying process.
[0010] The mixture after the first drying process is subjected to solid-liquid separation to obtain a solid molecular sieve and purified glacial acetic acid. The purified glacial acetic acid is then subjected to distillation to obtain colorless glacial acetic acid.
[0011] The solid molecular sieve is pretreated and then activated twice to obtain a secondary activated molecular sieve.
[0012] The secondary activated molecular sieve was mixed with colorless glacial acetic acid and then dried twice to obtain the colorless glacial acetic acid with low water content.
[0013] This invention utilizes molecular sieves soaked in glacial acetic acid for secondary activation and drying to obtain colorless glacial acetic acid with low water content, which meets the requirements of certain high-end chemical synthesis (such as water-sensitive esterification and acylation reactions).
[0014] The molecular sieve was activated in a muffle furnace, cooled down, and then transferred to a glass desiccator for further cooling. The cooled molecular sieve was then placed in a brown glass bottle, the cap was tightened, and the bottle was cooled overnight for later use.
[0015] After drying for several days, the moisture content of glacial acetic acid was within acceptable limits, but the solution turned yellow.
[0016] As a preferred embodiment of the present invention, the molecular sieve includes 3A molecular sieve.
[0017] As a preferred technical solution of the present invention, the temperature of the first activation is 390-410℃, for example, it can be 390℃, 395℃, 400℃, 405℃ or 410℃, etc., but is not limited to the listed values. Other unlisted values within the range are also applicable.
[0018] Preferably, the activation time is 3-5 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but not limited to the listed values. Other unlisted values within the range are also applicable.
[0019] As a preferred technical solution of the present invention, the drying time is 12-16 days, for example, it can be 12 days, 13 days, 14 days, 15 days or 16 days, but is not limited to the listed values. Other unlisted values within the range are also applicable.
[0020] As a preferred technical solution of the present invention, the solid-liquid separation is performed by vacuum filtration.
[0021] As a preferred technical solution of the present invention, the distillation includes atmospheric distillation.
[0022] As a preferred embodiment of the present invention, the pretreatment includes cleaning and forced-air drying.
[0023] As a preferred technical solution of the present invention, the temperature of the secondary activation is 390-410℃, for example, it can be 390℃, 395℃, 400℃, 405℃ or 410℃, etc., but is not limited to the listed values. Other unlisted values within the range are also applicable.
[0024] As a preferred technical solution of the present invention, the secondary activation time is 3-5 hours, for example, it can be 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but is not limited to the listed values. Other unlisted values within the range are also applicable.
[0025] As a preferred technical solution of the present invention, the secondary drying time is 12-16 days, for example, it can be 12 days, 13 days, 14 days, 15 days or 16 days, but it is not limited to the listed values. Other unlisted values within the range are also applicable.
[0026] Compared with existing technical solutions, the present invention has at least the following beneficial effects:
[0027] This invention utilizes molecular sieves soaked in glacial acetic acid for secondary activation and drying to obtain colorless glacial acetic acid with low water content, which meets the requirements of certain high-end chemical synthesis processes, such as water-sensitive esterification and acylation reactions. Detailed Implementation
[0028] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.
[0029] In one specific embodiment, the present invention provides a method for preparing colorless glacial acetic acid with low water content, the preparation method comprising the following steps:
[0030] 3A molecular sieves are activated once at 390-410℃ for 3-5 hours to obtain a primary activated molecular sieve. The primary activated molecular sieve is mixed with glacial acetic acid and dried once for 12-16 days. The mixture after primary drying is separated into solid and liquid by vacuum filtration to obtain a solid molecular sieve and purified glacial acetic acid. The purified glacial acetic acid is then subjected to atmospheric pressure distillation to obtain colorless glacial acetic acid. The solid molecular sieve is washed, dried by forced air, and reactivated a second time at 390-410℃ for 3-5 hours to obtain a secondary activated molecular sieve. The secondary activated molecular sieve is mixed with colorless glacial acetic acid and dried a second time for 12-16 days to obtain colorless glacial acetic acid with low water content.
[0031] It should be clarified that any use of the process provided in the embodiments of the present invention or any substitution or change of conventional data falls within the protection and disclosure scope of the present invention.
[0032] Example 1
[0033] This embodiment provides a method for preparing colorless glacial acetic acid with low water content, the preparation method comprising the following steps:
[0034] 3A molecular sieves were activated once at 400℃ for 4 hours to obtain a primary activated molecular sieve. After cooling to 280℃, the sieves were transferred to a glass desiccator for further cooling for half an hour. The cooled molecular sieves were then placed in a 2.5L brown glass bottle, the cap was tightened, and the bottle was left to cool overnight for later use. The primary activated molecular sieves were mixed with glacial acetic acid and dried once for 14 days. The mixture after the primary drying was separated into solid and liquid phases by vacuum filtration to obtain a solid molecular sieve and purified glacial acetic acid. The purified glacial acetic acid was then distilled under normal pressure to obtain colorless glacial acetic acid. The solid molecular sieves were washed, dried by forced air, and reactivated at 400℃ for 4 hours to obtain a secondary activated molecular sieve. The secondary activated molecular sieves were mixed with the colorless glacial acetic acid and dried again for 14 days to obtain the colorless glacial acetic acid with low water content.
[0035] Example 2
[0036] This embodiment provides a method for preparing colorless glacial acetic acid with low water content, the preparation method comprising the following steps:
[0037] 3A molecular sieves were activated once at 390℃ for 5 hours to obtain a primary activated molecular sieve. After cooling to 280℃, the sieves were transferred to a glass desiccator for further cooling for half an hour. The cooled molecular sieves were then placed in a 2.5L brown glass bottle, the cap was tightened, and the bottle was left to cool overnight for later use. The primary activated molecular sieves were mixed with glacial acetic acid and dried once for 12 days. The mixture after the primary drying was separated into solid and liquid phases by vacuum filtration to obtain a solid molecular sieve and purified glacial acetic acid. The purified glacial acetic acid was then distilled at atmospheric pressure to obtain colorless glacial acetic acid. The solid molecular sieves were washed, dried by forced air, and reactivated at 410℃ for 3 hours to obtain a secondary activated molecular sieve. The secondary activated molecular sieves were mixed with the colorless glacial acetic acid and dried again for 16 days to obtain the colorless glacial acetic acid with low water content.
[0038] Example 3
[0039] This embodiment provides a method for preparing colorless glacial acetic acid with low water content, the preparation method comprising the following steps:
[0040] 3A molecular sieves were activated once at 410℃ for 3 hours to obtain a primary activated molecular sieve. After cooling to 280℃, the sieves were transferred to a glass desiccator for further cooling for half an hour. The cooled molecular sieves were then placed in a 2.5L brown glass bottle, the cap was tightened, and the bottle was left to cool overnight for later use. The primary activated molecular sieves were mixed with glacial acetic acid and dried once for 16 days. The mixture after the primary drying was separated into solid and liquid phases by vacuum filtration to obtain a solid molecular sieve and purified glacial acetic acid. The purified glacial acetic acid was then distilled at atmospheric pressure to obtain colorless glacial acetic acid. The solid molecular sieves were washed, dried by forced air, and reactivated at 390℃ for 5 hours to obtain a secondary activated molecular sieve. The secondary activated molecular sieves were mixed with the colorless glacial acetic acid and dried again for 12 days to obtain the colorless glacial acetic acid with low water content.
[0041] Example 4
[0042] This embodiment provides a method for preparing colorless glacial acetic acid with low water content. The only difference between this method and Example 1 is that the initial activation temperature is 380°C, while the rest is the same as in Example 1.
[0043] Example 5
[0044] This embodiment provides a method for preparing colorless glacial acetic acid with low water content. The only difference between this method and Example 1 is that the initial activation temperature is 420°C, while the rest is the same as in Example 1.
[0045] Example 6
[0046] This embodiment provides a method for preparing colorless glacial acetic acid with low water content. The only difference between this method and Example 1 is that the secondary activation temperature is 380°C, while the rest is the same as in Example 1.
[0047] Example 7
[0048] This embodiment provides a method for preparing colorless glacial acetic acid with low water content. The only difference between this method and Example 1 is that the secondary activation temperature is 420°C, while the rest is the same as in Example 1.
[0049] Comparative Example 1
[0050] This comparative example provides a method for preparing colorless glacial acetic acid with low water content. The only difference between this method and Example 1 is that the molecular sieve is not activated once, while the rest is the same as in Example 1.
[0051] Comparative Example 2
[0052] This comparative example provides a method for preparing colorless glacial acetic acid with low water content. The only difference between this method and Example 1 is that the molecular sieve is not reactivated. All other aspects are the same as in Example 1.
[0053] Comparative Example 3
[0054] This comparative example provides a method for preparing colorless glacial acetic acid with low water content. The only difference between this method and Example 1 is that secondary drying is not performed; all other aspects are the same as in Example 1.
[0055] Comparative Example 4
[0056] This comparative example provides a method for preparing colorless glacial acetic acid with low water content. The only difference between this method and Example 1 is that the molecular sieve used in the second drying is a new molecular sieve, instead of a molecular sieve that has been reactivated using the molecular sieve used in the first drying. All other aspects are the same as in Example 1.
[0057] The glacial acetic acid provided in Examples 1-7 and Comparative Examples 1-4 was tested, and the results are shown in Table 1.
[0058] Table 1
[0059]
[0060] As can be seen from Table 1, the present invention utilizes molecular sieves soaked in glacial acetic acid for secondary activation and drying to obtain colorless glacial acetic acid with a low water content of less than 50 ppm.
[0061] A comprehensive comparison of Examples 1 and Examples 4-7 shows that both increasing and decreasing the activation temperature of the molecular sieve weakens its drying ability, and Example 1 represents the optimal conditions.
[0062] A comprehensive comparison of Example 1 and Comparative Examples 1-2 shows that reducing the number of activations of the molecular sieve will reduce the drying effect.
[0063] A comprehensive comparison of Example 1 and Comparative Example 3 shows that reducing the pre-drying process of the molecular sieve reduces the activation effect of the molecular sieve, thereby weakening its drying capacity.
[0064] A comprehensive comparison of Example 1 and Comparative Example 4 shows that the molecular sieve used in the second drying was a new molecular sieve. Although the moisture content could be reduced to below 50 ppm, colorless glacial acetic acid could not be obtained.
[0065] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.
Claims
1. A method for preparing colorless, low-water-content glacial acetic acid, characterized in that, The preparation method includes the following steps: The molecular sieve is activated once to obtain a primary activated molecular sieve. The primary activated molecular sieve is mixed with glacial acetic acid and then subjected to a primary drying process. The mixture after the first drying process is subjected to solid-liquid separation to obtain a solid molecular sieve and purified glacial acetic acid. The purified glacial acetic acid is then subjected to distillation to obtain colorless glacial acetic acid. The solid molecular sieve is pretreated and then activated twice to obtain a secondary activated molecular sieve. The secondary activated molecular sieve was mixed with colorless glacial acetic acid and then dried twice to obtain the colorless glacial acetic acid with low water content.
2. The preparation method according to claim 1, characterized in that, The molecular sieve includes 3A molecular sieve.
3. The preparation method according to claim 1 or 2, characterized in that, The temperature for the first activation is 390-410℃; Preferably, the activation time is 3-5 hours.
4. The preparation method according to any one of claims 1 to 3, characterized in that, The drying time for one cycle is 12-16 days.
5. The preparation method according to any one of claims 1 to 4, characterized in that, The solid-liquid separation is performed by vacuum filtration.
6. The preparation method according to any one of claims 1 to 5, characterized in that, The distillation includes atmospheric distillation.
7. The preparation method according to any one of claims 1 to 6, characterized in that, The pretreatment includes washing and blower drying.
8. The preparation method according to any one of claims 1 to 7, characterized in that, The temperature for the secondary activation is 390-410℃.
9. The preparation method according to any one of claims 1 to 8, characterized in that, The secondary activation time is 3-5 hours.
10. The preparation method according to any one of claims 1 to 9, characterized in that, The secondary drying time is 12-16 days.