Sodium bicarbonate crystal as well as preparation method and application thereof

Abstract

The invention provides a sodium bicarbonate crystal as well as a preparation method and application thereof. The method comprises the following steps: putting sodium carbonate, sodium bicarbonate and purified water in a mass ratio of 1: (0.4-1.4): (4-8) into a reaction crystallizer, heating to 75-85 DEG C under a stirring condition, adding a sodium bicarbonate seed crystal into the reaction crystallizer, introducing carbon dioxide gas, reacting at 75-85 DEG C for 0.5-4 hours, cooling to 40-75 DEG C at a cooling rate of 0.05-0.2 DEG C / min, and carrying out cooling crystallization, sodium bicarbonate crystals are obtained. The crystallization process is simple, the reaction and crystallization processes can be completed in one set of device, and a fine grain eliminating device is not needed. The prepared sodium bicarbonate is highly uniform in particle size, and the average particle size is 250-400 microns; the product is in the form of monodisperse blocky particles, which is beneficial to the post-treatment process; the product has high fluidity and high compressive strength, and is convenient for transportation and long-term storage.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical engineering industrial crystallization, and in particular relates to a sodium bicarbonate crystal and a preparation method and application thereof. Technical Background Sodium bicarbonate, commonly known as baking soda, is an important basic chemical raw material and commonly used medicine. Its application fields span the chemical, pharmaceutical, food, light industry and textile industries. In the medical field, sodium bicarbonate is one of the earliest easily absorbed antacids. Due to its precise efficacy and low price, it is still a "veteran" drug widely used around the world. As countries have higher and higher requirements for raw materials, the market demand for high-quality sodium bicarbonate continues to increase.

[0002] In the field of hemodialysis, sodium bicarbonate is one of the main raw materials for dialysis powder. At present, the dialysis products used by most hemodialysis centers in my country are imported dialysis products, and the main imported products are large-particle sodium bicarbonate. However, the cost of imported dialysis products is high, which increases the economic burden on patients. Therefore, the development of large-particle-size, high-purity sodium bicarbonate products is an urgent problem to be solved in my country's sodium bicarbonate industry.

[0003] CN206428008U adopts a recrystallization method, prepares a certain composition of raw material liquid at 90°C, and cools and crystallizes at 30-40°C. The particle size range of the large particle product is within 180-425 μm, but no information on the product morphology is given.

[0004] CN105819471B adopts the soda ash carbonization method and innovatively designs the reaction crystallizer structure. It obtains a large-particle product by eliminating fine crystals and adding crystal seeds, of which the particle size is greater than 180 μm and accounts for more than 75%. However, the product morphology is long rod-shaped, which may cause problems such as poor fluidity, affecting product post-processing and practical application in hemodialysis.

[0005] Therefore, it is very necessary to develop a new preparation method of sodium bicarbonate crystals. Summary of the invention

[0006] In order to overcome the defects of small crystal size and poor morphology of existing sodium bicarbonate products, the present invention provides a preparation method for preparing pharmaceutical-grade sodium bicarbonate products, wherein the obtained sodium bicarbonate crystals have good morphology and are monodispersed blocks; the particle size is highly uniform, and the average particle size is 250 to 400 microns; the product has high fluidity and the angle of repose is between 25° and 35°; the product purity is higher than 99.5%, and there are few impurities, which meets the quality standards of the Chinese Pharmacopoeia. At the same time, the crystallization process has streamlined equipment and simple process, which is convenient for large-scale production and application.

[0007] The object of the present invention is to provide a method for preparing sodium bicarbonate crystals. The method first provides supersaturation for the growth of sodium bicarbonate seed crystals by gas-liquid reaction between sodium carbonate solution and carbon dioxide gas, and then cools and crystallizes to further increase the product particle size. The preparation method comprises the following steps: Sodium carbonate, sodium bicarbonate and purified water in a mass ratio of 1:(0.4-1.4):(4-8) are placed in a reaction crystallizer, and the temperature is raised to 75-85°C (e.g., 75°C, 78°C, 80°C, 82°C, 85°C, etc.) under stirring, and the temperature is maintained until all the solids are dissolved. Then, sodium bicarbonate seeds are added to the reaction crystallizer, and carbon dioxide gas is introduced at 75-85°C (e.g., 75°C, 78°C, 80°C, 82°C, 85°C, etc.) for reaction for 0.5-4 h (e.g., 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h, 24 h, 25 h, 26 h, 27 h, 28 h, 29 h, 30 h, 31 h, 32 h, 33 h, 34 h, 35 h, 36 h, 37 h, 38 h, 39 h, 40 h, 41 h, 42 h, 43 h, 44 h, 45 h, 46 h, 47 h, 48 h h, etc.), and then cooled to 40-75°C (e.g., 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, etc.) at a cooling rate of 0.05-0.2°C / min (e.g., 0.05°C / min, 0.08°C / min, 0.1°C / min, 0.12°C / min, 0.15°C / min, 0.18°C / min, 0.2°C / min, etc.) for cooling crystallization to obtain sodium bicarbonate crystals.

[0008] Preferably, the amount of sodium bicarbonate seed crystals added is 5-20% (e.g., 5%, 8%, 10%, 12%, 15%, 18%, 20%, etc.) of the total mass of sodium bicarbonate solute under the condition that sodium carbonate is theoretically completely converted into sodium bicarbonate; Preferably, after adding the sodium bicarbonate seed crystals, the solid-liquid mass ratio in the solution is 2-8% (e.g., 2%, 3%, 4%, 5%, 6%, 7%, 8%, etc.).

[0009] Preferably, based on the volume of the solution in the reaction crystallizer as 1 L, the flow rate of the carbon dioxide gas is 0.02-1.5 L / min (e.g., 0.02 L / min, 0.05 L / min, 0.08 L / min, 0.1 L / min, 0.3 L / min, 0.5 L / min, 0.8 L / min, 1 L / min, 1.3 L / min, 1.5 L / min, etc.).

[0010] Preferably, the stirring rate is 200-400 rpm (eg, 200 rpm, 220 rpm, 250 rpm, 280 rpm, 300 rpm, 320 rpm, 350 rpm, 380 rpm, 400 rpm, etc.).

[0011] Preferably, the method further comprises sequentially performing solid-liquid separation, washing and drying on the mixture obtained after the cooling crystallization.

[0012] A second object of the present invention is to prepare sodium bicarbonate crystals according to the preparation method described in one of the objects.

[0013] Preferably, the sodium bicarbonate crystals are in a monodisperse blocky morphology; Preferably, the average particle size of the sodium bicarbonate crystals is 250-400 μm (eg, 250 μm, 280 μm, 300 μm, 320 μm, 350 μm, 380 μm, 400 μm, etc.).

[0014] Preferably, the angle of repose of the sodium bicarbonate crystals is 25-35° (e.g., 25°, 28°, 30°, 32°, 33°, 34°, 35°, etc.); Preferably, the purity of the sodium bicarbonate crystals is above 99.5%.

[0015] The third object of the present invention is to use the sodium bicarbonate crystals according to the second object in the preparation of dialysis powder.

[0016] Technical features and beneficial effects of the present invention: (1) The present invention combines the soda carbonization reaction crystallization process with the cooling crystallization process to increase the product particle size and realize the preparation of large-particle products. By first adding a certain amount of seed crystals into the system, a certain initial solid-liquid ratio is provided, the supersaturation in the crystallization process is consumed, and the occurrence of secondary nucleation is inhibited, so that the product particle size distribution is more uniform; (2) The sodium bicarbonate product prepared by the present invention has an average particle size of 250-400 μm, a uniform particle size distribution, a good morphology, a monodisperse, blocky shape, high purity, and meets the purity requirements of the Chinese Pharmacopoeia for dialysis-grade sodium bicarbonate products; and has good flow properties, providing excellent conditions for post-processing of the sodium bicarbonate product. (3) The process equipment of the present invention is simple, and the preparation of large-particle sodium bicarbonate is effective and reliable, and can be further scaled up for production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 : Scanning electron microscope image of domestic commercially available medicinal sodium bicarbonate products; Figure 2 : Optical microscope image of bulk monodisperse sodium bicarbonate product; Figure 3 : Scanning electron microscope image of bulk monodisperse sodium bicarbonate product; Figure 4 : The particle size distribution of the sodium bicarbonate product of embodiment 1; DETAILED DESCRIPTION

[0018] Embodiment 1: (1) In a 1 L reactor at 80°C, a mixed solution of sodium carbonate and sodium bicarbonate was prepared according to the mass ratio of sodium carbonate, sodium bicarbonate and purified water of 1:0.78:5.56. After stirring and dissolving, 7% seed crystals were added to the reactor; (2) At a reaction temperature of 80°C, a stirring rate of 250 rpm, and a gas rate of 0.3 L / min, carbon dioxide gas was introduced for reaction for 90 min; (3) cooling the mixture to 70°C at a cooling rate of 0.05°C / min. After the temperature reaches the end point of the cooling, the slurry is filtered, washed, and dried to obtain a large-particle monodisperse sodium bicarbonate product. Optical microscope images of large-sized monodisperse bulk sodium bicarbonate crystals are shown in Figure 2 , SEM images are shown in Figure 3 , compared with domestically available pharmaceutical grade products ( Figure 1 ) compared with the above, its crystal morphology has been greatly improved. The purity of the sodium bicarbonate crystals in Example 1 is 99.8%. The particle size distribution of the sodium bicarbonate crystals in Example 1 is as follows Figure 4 As shown, the average particle size is 313 μm and the angle of repose is 32°.

[0019] Embodiment 2: (1) In a 1 L reactor at 85°C, a mixed solution of sodium carbonate and sodium bicarbonate was prepared according to the mass ratio of sodium carbonate, sodium bicarbonate and purified water of 1:1.1:6.7. After stirring and dissolving, 8% of seed crystals were added to the reactor; (2) At a reaction temperature of 85°C, a stirring rate of 350 rpm, and a gas rate of 0.2 L / min, carbon dioxide gas was introduced for reaction for 180 min; (3) cooling the mixture to 40°C at a cooling rate of 0.17°C / min. After the temperature reaches the end point of the cooling process, the slurry is filtered, washed, and dried to obtain a large-particle monodisperse sodium bicarbonate product. The sodium bicarbonate product obtained in this example has a monodisperse block morphology, an average particle size of 325 μm, a purity of 99.6%, and an angle of repose of 26°.

[0020] Embodiment 3: (1) In a 1 L reactor at 75°C, a mixed solution of sodium carbonate and sodium bicarbonate was prepared according to the mass ratio of sodium carbonate, sodium bicarbonate and purified water of 1:0.45:5. After stirring and dissolving, 17% of seed crystals were added to the reactor; (2) At a reaction temperature of 85°C, a stirring rate of 300 rpm, and a gas flow rate of 1 L / min, carbon dioxide gas was introduced for reaction for 240 min; (3) cooling the mixture to 55°C at a cooling rate of 0.1°C / min. After the temperature reaches the end point of the cooling process, the slurry is filtered, washed, and dried to obtain a large-particle monodisperse sodium bicarbonate product. The sodium bicarbonate product obtained in this example has a monodisperse block morphology, an average particle size of 320 μm, a purity of 99.7%, and a repose angle of 31°.

[0021] Embodiment 4: (1) In a 1 L reactor at 79°C, a mixed solution of sodium carbonate and sodium bicarbonate was prepared in a mass ratio of 1:0.65:5.1 of sodium carbonate, sodium bicarbonate, and purified water. After stirring and dissolving, 14% of seed crystals were added to the reactor; (2) At a reaction temperature of 79°C, a stirring rate of 280 rpm, and a gas rate of 0.8 L / min, carbon dioxide gas was introduced for reaction for 200 min; (3) cooling the mixture to 65°C at a cooling rate of 0.08°C / min. After the temperature reaches the end point of the cooling, the slurry is filtered, washed, and dried to obtain a large-particle monodisperse sodium bicarbonate product. The sodium bicarbonate product obtained in this example has a monodisperse block morphology, an average particle size of 322 μm, a purity of 99.8%, and an angle of repose of 32°.

[0022] Comparative Example 1: The only difference from Example 1 is that sodium bicarbonate seed crystals are not added, and the rest of the preparation method is the same as that of Example 1.

[0023] This comparative example did not obtain a bulk sodium bicarbonate product, and the crystal morphology was long needle-like, with an aspect ratio greater than 4, an average particle size of only 105 μm, and a repose angle of 47°.

[0024] By comparing Example 1 and Comparative Example 1, it can be seen that when no sodium bicarbonate seed crystals are added, the system is prone to explosive nucleation, the crystal morphology is long needles with a relatively large aspect ratio, the product particle size is small, and the fluidity is poor.

[0025] Comparative Example 2: The only difference from Example 1 is that the seed amount is changed to 2%, and the rest of the preparation method is the same as Example 1.

[0026] This comparative example did not obtain blocky sodium bicarbonate crystals, the crystal morphology was mainly long needle-shaped, the product particle size was small, the average particle size was only 182 μm, and the repose angle was 45°.

[0027] By comparing Example 1 and Comparative Example 2, it can be seen that when the amount of seed crystal added is lower than the specified range of the present invention, nucleation will explode, the crystal morphology is long needle-shaped, and the product fluidity is poor.

[0028] Comparative Example 3: The only difference from Example 1 is that the flow rate of carbon dioxide gas is 2 L / min, and the rest of the preparation method is the same as Example 1.

[0029] This comparative example did not obtain blocky sodium bicarbonate crystals with good morphology. The crystal morphology was mainly long needle-shaped and a small part was block-shaped, and the particle size was small. The average particle size of the product was 210 μm, the angle of repose was 43°, and the compacted density was 1.30 g / mL.

[0030] By comparing Example 1 and Comparative Example 3, it can be seen that when the carbon dioxide gas velocity is higher than the specified range of the present invention, secondary nucleation will occur, resulting in more fine crystals, the crystal morphology is long needle-shaped, and the product fluidity is poor.

[0031] Comparative Example 4: The only difference from Example 3 is that the mass ratio of sodium carbonate, sodium bicarbonate and purified water is 1:0.45:5, and the reaction temperature is 65°C.

[0032] This comparative example did not obtain blocky sodium bicarbonate crystals with good morphology, and the crystal morphology was rod-shaped, the aspect ratio of the product was greater than 2.5, the average particle size of the product was 250 μm, and the angle of repose was 38°.

[0033] By comparing Example 3 and Comparative Example 4, it can be seen that when the temperature is lower than the specified range of the present invention, the product morphology will be relatively long in aspect ratio and poor in morphology, which will affect the fluidity of the product.

[0034] Comparative Example 5: The difference from Example 1 is that the sum of the masses of sodium carbonate and sodium bicarbonate in Example 1 is replaced by an equal mass of sodium carbonate.

[0035] This comparative example did not obtain blocky sodium bicarbonate crystals with good morphology, and the crystal morphology was long needle-like, the average particle size of the product was 150 μm, and the angle of repose was 46°.

[0036] By comparing Example 1 and Comparative Example 5, it can be seen that when the sodium carbonate and sodium bicarbonate in the raw materials are replaced with sodium carbonate of equal mass, explosive nucleation is likely to occur during the crystallization process, and the product is in the shape of long needles with poor fluidity.

[0037] The present invention discloses and proposes a method for preparing a pharmaceutical-grade large-particle monodisperse sodium bicarbonate product. Those skilled in the art can achieve this by appropriately changing the mixing reaction temperature, sodium carbonate concentration, reaction time, carbon dioxide gas velocity, seed amount, cooling interval and other links by referring to the content of this article. The method of the present invention has been described through preferred embodiments, and relevant technical personnel can obviously modify or appropriately change and combine the methods and products described herein without departing from the content, spirit and scope of the present invention to realize the technology of the present invention. It is particularly important to point out that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the spirit, scope and content of the present invention.

Claims

1. A method for preparing sodium bicarbonate crystals, characterized in that, The preparation method comprises the following steps: Sodium carbonate, sodium bicarbonate and purified water in a mass ratio of 1:(0.4-1.4):(4-8) are placed in a reaction crystallizer, and the temperature is raised to 75-85°C under stirring conditions. Then, sodium bicarbonate seeds are added to the reaction crystallizer, and carbon dioxide gas is introduced to react at 75-85°C for 0.5-4 h, and then the temperature is reduced to 40-75°C at a cooling rate of 0.05-0.2°C / min for cooling crystallization to obtain sodium bicarbonate crystals.

2. The preparation method according to claim 1, characterized in that: The amount of sodium bicarbonate seed crystals added is 5-20% of the total mass of sodium bicarbonate solute under the condition that sodium carbonate is completely converted into sodium bicarbonate in theory.

3. The preparation method according to claim 1, characterized in that: After the sodium bicarbonate seed crystals are added, the solid-liquid mass ratio in the solution is 2-8%.

4. The preparation method according to claim 1, characterized in that: Based on the volume of the solution in the reaction crystallizer being 1 L, the flow rate of the carbon dioxide gas is 0.02-1.5 L / min.

5. The method according to claim 1, characterized in that The method further comprises sequentially performing solid-liquid separation, washing and drying on the mixture obtained after the cooling crystallization.

6. prepare sodium bicarbonate crystals according to the preparation method described in any one of claims 1-5.

7. The sodium bicarbonate crystals according to claim 6, characterized in that The sodium bicarbonate crystals are monodisperse block crystals; The average particle size of the sodium bicarbonate crystals is 250-400 μm.

8. The sodium bicarbonate crystals according to claim 6, characterized in that The angle of repose of the sodium bicarbonate crystals is 25-35°C; The purity of the sodium bicarbonate crystals is above 99.5%.

9. Use of sodium bicarbonate crystals according to any one of claims 6 to 8 in preparing dialysis powder.

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