Preparation method of sodium metaaluminate solution with low caustic ratio

Abstract

The invention belongs to the technical field of chemical products, and provides a preparation method of a sodium metaaluminate solution with a low caustic ratio. The method comprises the following steps: S1, adding aluminum hydroxide powder and sodium hydroxide powder into a sodium hydroxide solution with a set temperature, and carrying out a microwave reaction; s2, after the aluminum hydroxide powder in a reaction system of the microwave reaction is completely dissolved, adding a stabilizer to continue the microwave reaction to obtain a mixed solution; and S3, carrying out solid-liquid separation on the mixed solution to obtain a sodium metaaluminate solution. Part of sodium hydroxide powder is added into the high-concentration caustic soda liquid, so that hydroxyl ions with relatively high concentration can be ensured to exist in a reaction solution system. The method is beneficial to more sufficient reaction of aluminum hydroxide and sodium hydroxide, and the conversion rate is improved, so that the caustic ratio of the sodium metaaluminate solution is reduced, and meanwhile, the stability of the sodium metaaluminate solution is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical products, and more particularly, relates to a method for preparing sodium aluminate solution with a low caustic ratio. Background Art

[0002] Sodium aluminate (NaAlO) is an important inorganic compound with good surface activity and emulsifying properties. It can form stable emulsions and disperse oil-water mixtures to a certain extent. Its molecular structure contains carboxyl and hydrocarbon groups, which endows it with unique properties in many chemical reactions and industrial processes.

[0003] In the production of aluminosilicate molecular sieves, sodium aluminate is one of the important raw materials for preparing molecular sieves. Molecular sieves are solid materials with specific pore structures and surface properties, which can be used in fields such as separation, purification, and catalysis. Sodium aluminate reacts with raw materials such as silicon sources (e.g., silica gel) under certain conditions to form aluminosilicate molecular sieves with specific structures and properties. Among them, the caustic ratio (i.e., the molar ratio of sodium oxide to aluminum oxide) is one of the key factors controlling the structure and properties of molecular sieves. However, in the production process of aluminosilicate molecular sieves, the caustic ratio and concentration of sodium aluminate solution have important effects on the stability and quality of the product. When the caustic ratio is low or the solution concentration is low, the sodium aluminate solution is prone to hydrolysis to produce aluminum hydroxide gel, thus affecting the quality and performance of the molecular sieve. Therefore, in the production process, it is necessary to strictly control the caustic ratio and concentration of the sodium aluminate solution to ensure the stability and quality of the product. For the sodium aluminate solution with a caustic ratio of 2.1 required in the production of aluminosilicate shape-selective molecular sieves, the current production method needs to control the reaction feeding caustic ratio to be 1.9 - 2.0. However, due to the too low reaction caustic ratio, there are problems such as insufficient reaction between liquid caustic and aluminum hydroxide powder, poor reaction effect, slow speed, and low conversion rate. To solve these problems, researchers are constantly exploring and improving the production method to increase the caustic ratio and stability of the sodium aluminate solution, so as to meet the requirements of aluminosilicate molecular sieve production. Chinese Patent CN 109382085 A discloses a high-efficiency production method for sodium aluminate solution with a low caustic ratio. By adding partial caustic flakes to high-concentration liquid caustic, it can ensure a high concentration of hydroxide ions in the reaction solution system, enabling aluminum hydroxide to react more fully with it, increasing the conversion rate, ensuring the reaction effect, and improving the product quality. However, the prepared sodium aluminate solution has poor stability and is prone to hydrolysis to produce aluminum hydroxide gel. Therefore, based on the above description, how to increase the stability of the sodium aluminate solution while reducing its caustic ratio is a technical problem that urgently needs to be solved at present. Summary of the Invention

[0004] Aiming at the above deficiencies in the prior art, the purpose of the present invention is to improve the stability of sodium aluminate solution while reducing the caustic ratio of sodium aluminate solution.

[0005] The present invention is achieved through the following technical solutions:

[0006] A preparation method of sodium aluminate solution with a low caustic ratio, the preparation method of the sodium aluminate solution with a low caustic ratio includes the following steps:

[0007] S1. Add aluminum hydroxide powder and sodium hydroxide powder into a sodium hydroxide solution with a set temperature for microwave reaction;

[0008] S2. Wait until the aluminum hydroxide powder in the reaction system of the microwave reaction is completely dissolved, add a stabilizer, and continue the microwave reaction to obtain a mixed solution;

[0009] S3. Perform solid-liquid separation on the mixed solution to obtain sodium aluminate solution.

[0010] In the preparation process of the present invention, by adding part of sodium hydroxide powder into high-concentration liquid caustic, it can ensure a high concentration of hydroxide ions in the reaction solution system. This helps the reaction between aluminum hydroxide and sodium hydroxide to be more complete, improves the conversion rate, and thus obtains a higher-quality sodium aluminate solution.

[0011] The present invention adds a stabilizer to ensure the stability of the solution during and after the reaction. Thus, by adjusting the ionic strength, osmotic pressure of the solution, preventing particle aggregation and precipitation, etc., the stabilizer helps to obtain a high-quality sodium aluminate solution with a low caustic ratio. The microwave reaction promotes the reaction between aluminum hydroxide and sodium hydroxide, making it proceed more quickly and completely, thereby improving the conversion rate and obtaining a higher-quality sodium aluminate solution.

[0012] Further, by mass, the stabilizer includes the following chemical components: 10-20 parts of sodium sulfate, 20-40 parts of polyvinyl alcohol, 5-15 parts of mannitol, 10-20 parts of maleic anhydride styrene copolymer, 2-5 parts of sodium dodecyl sulfate, and 100 parts of deionized water.

[0013] In the preparation process of sodium aluminate solution with a low caustic ratio, the addition of stabilizers is crucial for improving the stability and performance of the solution. Each component in the stabilizer constructs a stable and efficient system through intermolecular interactions. Sodium sulfate: Sodium sulfate ionizes into sodium ions and sulfate ions in aqueous solution. These ions can undergo weak ion exchange or charge shielding with other components (such as aluminate ions in sodium aluminate), reducing the electrostatic repulsion between ions in the solution and contributing to the stability of the solution. Polyvinyl alcohol (PVA): Polyvinyl alcohol is a polymer, and its molecular chain contains a large number of hydroxyl groups. These hydroxyl groups can form hydrogen bonds with other components (such as hydroxyl groups remaining on the surface of aluminum hydroxide powder, carboxylic acid groups in maleic anhydride-styrene copolymer), increasing the intermolecular interaction force. The long-chain structure of PVA can also play a role in physical cross-linking, connecting different components in the solution together to form a more compact network structure, improving the stability and viscosity of the solution. Mannitol: Mannitol is a polyol, and its molecular structure contains multiple hydroxyl groups. These hydroxyl groups can also form hydrogen bonds with other components, further increasing the stability of the solution. At the same time, mannitol can also act as an osmotic pressure regulator, preventing the separation or precipitation of components in the solution due to osmotic pressure differences by regulating the osmotic pressure in the solution. Maleic anhydride-styrene copolymer (SMA): SMA is a copolymer, and its molecular chain contains structural units of maleic anhydride (MAH) and styrene (St) at the same time. The carboxylic acid groups in the MAH units can form ester bonds with the hydroxyl groups on the molecular chains of polymers such as PVA, further enhancing the intermolecular interaction. The St units endow the copolymer with certain rigidity and hydrophobicity, contributing to improving the mechanical properties and water resistance of the solution. The addition of SMA can also improve the dispersibility and fluidity of the solution, making the solution more uniform and stable. Sodium dodecyl sulfate (SDS): SDS is an anionic surfactant, and its molecular structure contains a long-chain alkyl group and a sulfate ion. At the same time, the long-chain alkyl group of SDS can insert between the molecular chains of polymers, playing a role in lubrication and dispersion to prevent the agglomeration and precipitation of polymer molecules. The sulfate ion is hydrophilic, enabling the SDS molecules to be better dispersed in the solution, improving the wettability and fluidity of the solution. Synergistic effect: In the preparation process of sodium aluminate solution with a low caustic ratio, each component in the stabilizer constructs a stable and efficient system through intermolecular interactions (such as ion exchange, charge shielding, hydrogen bonds, ester bonds, physical cross-linking, etc.). These interactions not only improve the stability and viscosity of the solution but also enhance the dispersibility, fluidity, and mechanical properties of the solution. At the same time, there is a complementary and synergistic effect between the components, making the entire stabilizer system more perfect and efficient. Thus, the stability of sodium aluminate solution is improved.

[0014] Further, the added mass of the stabilizer is 0.5-5% of the total mass of the mixed solution.

[0015] Further, the power of the microwave reaction is 25w - 100w, and the total time of the microwave reaction is 10 - 30min.

[0016] Further, the sodium hydroxide in the sodium hydroxide solution accounts for 50 - 60% of the total reaction feed of sodium hydroxide.

[0017] Further, the mass ratio of the aluminum hydroxide powder to the sodium hydroxide powder is (0.95 - 1.05):1.

[0018] Further, the set temperature is 80 - 100°C.

[0019] Further, the volume concentration of the sodium hydroxide solution is 600 - 800g / L.

[0020] Further, the caustic ratio of the sodium aluminate solution is 2.0 - 2.2.

[0021] Further, the temperature of the solid-liquid separation is 40 - 50°C.

[0022] The beneficial effects of the present invention are as follows:

[0023] (1) During the preparation process of the present invention, precisely controlling the ratio of aluminum hydroxide powder to sodium hydroxide powder, as well as their ratio to the sodium hydroxide solution, is the key to ensuring complete reaction and product stability. At the same time, by adjusting the raw material ratio, the caustic ratio can be adjusted to a certain extent while ensuring the stability of the reaction product.

[0024] (2) The selection of the microwave reaction power has an important influence on the reaction rate and product selectivity. In the preparation of sodium aluminate, using microwave heating can significantly increase the reaction rate because microwaves can directly act on the reactant molecules, generating heat inside them and thus accelerating the reaction process. The power and time of the microwave reaction of the present invention have an important influence on the product stability. Selecting appropriate microwave power and time can, while ensuring the reaction rate, reduce the occurrence of side reactions and improve the product stability. At the same time, during the microwave reaction process, the temperature of the reaction system should be kept stable to avoid instability caused by too high or too low temperature.

[0025] (3) By adding part of the sodium hydroxide powder to the high-concentration liquid caustic, the present invention ensures a high concentration of hydroxide ions in the reaction solution system. This helps the aluminum hydroxide react more fully with the sodium hydroxide, thereby improving the reaction efficiency and conversion rate. This can not only reduce the unreacted solid impurities but also improve the purity of the product.

[0026] (4) In the process of the microwave reaction of the present invention, a stabilizer is added, which can further promote the reaction and help obtain a more stable sodium aluminate solution. The addition of the stabilizer can inhibit the hydrolysis reaction in the solution and prevent the precipitation of aluminum hydroxide gel, thereby improving the stability of the product. Detailed implementation mode

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are followed. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0028] Example 1

[0029] This example provides a method for preparing a sodium aluminate solution with a low caustic ratio, including the following steps:

[0030] S11. Add aluminum hydroxide powder and sodium hydroxide powder to a sodium hydroxide solution with a set temperature for microwave reaction; wherein, the sodium hydroxide in the sodium hydroxide solution accounts for 60% of the total reaction feed of sodium hydroxide, the volume concentration of the sodium hydroxide solution is 600 g / L, the mass ratio of the aluminum hydroxide powder to the sodium hydroxide powder is 1:1, and the temperature of the sodium hydroxide solution is 80 °C;

[0031] S21. After the aluminum hydroxide powder in the reaction system of the microwave reaction is completely dissolved, add a stabilizer to continue the microwave reaction to obtain a mixed solution; the power of the microwave reaction is 50 w, and the total time of the microwave reaction is 20 min. The stabilizer consists of the following chemical components: 15 parts of sodium sulfate, 30 parts of polyvinyl alcohol, 10 parts of mannitol, 15 parts of maleic anhydride styrene copolymer, 5 parts of sodium dodecyl sulfate, and 100 parts of deionized water. The added mass of the stabilizer is 2% of the total mass of the mixed solution;

[0032] S31. Perform solid-liquid separation on the mixed solution to obtain a sodium aluminate solution. The temperature of the solid-liquid separation is 40 °C.

[0033] Example 2

[0034] The difference between this example and Example 1 is that the power of the microwave reaction is 25 w, and the total time of the microwave reaction is 30 min.

[0035] Example 3

[0036] The difference between this example and Example 1 is that the power of the microwave reaction is 100 w, and the total time of the microwave reaction is 10 min.

[0037] Example 4

[0038] The difference between this embodiment and Embodiment 1 lies in that the stabilizer consists of the following chemical components: 20 parts of sodium sulfate, 40 parts of polyvinyl alcohol, 15 parts of mannitol, 20 parts of maleic anhydride-styrene copolymer, 5 parts of sodium dodecyl sulfate, and 100 parts of deionized water.

[0039] Embodiment 5

[0040] The difference between this embodiment and Embodiment 1 lies in that the stabilizer consists of the following chemical components: 10 parts of sodium sulfate, 20 parts of polyvinyl alcohol, 5 parts of mannitol, 10 parts of maleic anhydride-styrene copolymer, 2 parts of sodium dodecyl sulfate, and 100 parts of deionized water.

[0041] Embodiment 6

[0042] The difference between this embodiment and Embodiment 1 lies in that the added mass of the stabilizer is 0.5% of the total mass of the mixed solution.

[0043] Embodiment 7

[0044] The difference between this embodiment and Embodiment 1 lies in that the added mass of the stabilizer is 5% of the total mass of the mixed solution.

[0045] Comparative Example 1

[0046] The difference between this comparative example and Embodiment 1 lies in that the microwave reaction is changed to a hydrothermal reaction.

[0047] Specifically, this comparative example provides a method for preparing a sodium aluminate solution with a low caustic ratio, including the following steps:

[0048] S11. Add aluminum hydroxide powder and sodium hydroxide powder to a sodium hydroxide solution with a set temperature to carry out a hydrothermal reaction; wherein, the sodium hydroxide in the sodium hydroxide solution accounts for 60% of the total reaction feed of sodium hydroxide, the volume concentration of the sodium hydroxide solution is 600 g / L, the mass ratio of the aluminum hydroxide powder to the sodium hydroxide powder is 1:1, and the temperature of the sodium hydroxide solution is 80°C;

[0049] S21. After the aluminum hydroxide powder in the reaction system of the hydrothermal reaction is completely dissolved, add a stabilizer to continue the microwave reaction to obtain a mixed solution; the temperature of the hydrothermal reaction is 100°C, and the total time of the hydrothermal reaction is 360 min. The stabilizer consists of the following chemical components: 15 parts of sodium sulfate, 30 parts of polyvinyl alcohol, 10 parts of mannitol, 15 parts of maleic anhydride-styrene copolymer, 5 parts of sodium dodecyl sulfate, and 100 parts of deionized water. The added mass of the stabilizer is 2% of the total mass of the mixed solution;

[0050] S31. Carry out solid-liquid separation on the mixed solution to obtain a sodium aluminate solution. The temperature of the solid-liquid separation is 40°C.

[0051] Comparative Example 2

[0052] The difference between this comparative example and Example 1 is that no stabilizer is added during the microwave reaction.

[0053] Comparative Example 3

[0054] The difference between this comparative example and Example 1 is that the added mass of the stabilizer is 0.1% of the total mass of the mixed solution.

[0055] Comparative Example 4

[0056] The difference between this comparative example and Example 1 is that the added mass of the stabilizer is 10% of the total mass of the mixed solution.

[0057] Comparative Example 5

[0058] The stabilizer consists of the following chemical components: 15 parts of sodium sulfate, 10 parts of mannitol, 15 parts of maleic anhydride-styrene copolymer, 5 parts of sodium dodecyl sulfate, and 100 parts of deionized water.

[0059] Comparative Example 6

[0060] The difference between this comparative example and Example 1 is that the stabilizer consists of the following chemical components: 15 parts of sodium sulfate, 30 parts of polyvinyl alcohol, 10 parts of mannitol, 5 parts of sodium dodecyl sulfate, and 100 parts of deionized water.

[0061] Comparative Example 7

[0062] The difference between this comparative example and Example 1 is that the stabilizer consists of the following chemical components: 30 parts of polyvinyl alcohol, 10 parts of mannitol, 15 parts of maleic anhydride-styrene copolymer, 5 parts of sodium dodecyl sulfate, and 100 parts of deionized water.

[0063] Comparative Example 8

[0064] The difference between this comparative example and Example 1 is that the stabilizer consists of the following chemical components: 15 parts of sodium sulfate, 30 parts of polyvinyl alcohol, 10 parts of mannitol, 5 parts of sodium dodecyl sulfate, and 100 parts of deionized water.

[0065] The sodium aluminate solutions obtained in the examples and comparative examples were subjected to caustic ratio and stability tests, and the results are shown in Table 1.

[0066] Table 1 Caustic ratio and stability of sodium aluminate solution

[0067]

[0068]

[0069] As can be seen from Table 1, in the examples, the sodium aluminate solution obtained by the preparation method of the present invention has a low caustic ratio and high stability, and can be stored for a long time without flocculation precipitation. In Comparative Example 1, the hydrothermal heating method was used, and the obtained sodium aluminate solution had a low caustic ratio and high stability, but the preparation time was long, which was not conducive to industrial production; in Comparative Example 2, no stabilizer was added, and the stability of the obtained sodium aluminate solution was very poor, which was not conducive to storage and transportation; in Comparative Example 3, too little stabilizer was added, and in Comparative Example 4, too much stabilizer was added, which was not conducive to long-term preservation; in Comparative Examples 5 to 8, the stabilizer lacked important components, which was not conducive to long-term preservation.

[0070] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a sodium aluminate solution with a low caustic ratio, characterized in that: The following steps are involved: S1, adding aluminum hydroxide powder and sodium hydroxide powder into a sodium hydroxide solution with a set temperature to perform a microwave reaction; S2, after the aluminum hydroxide powder in the microwave reaction system is completely dissolved, a stabilizer is added to continue the microwave reaction to obtain a mixed solution; S3, separating the mixed solution into solid and liquid to obtain a sodium aluminate solution.

2. The method for preparing a sodium aluminate solution with a low caustic ratio according to claim 1, characterized in that: The stabilizer comprises the following chemical components in parts by mass: 10-20 parts of sodium sulfate, 20-40 parts of polyvinyl alcohol, 5-15 parts of mannitol, 10-20 parts of maleic anhydride styrene copolymer, 2-5 parts of sodium dodecyl sulfate and 100 parts of deionized water.

3. The method for preparing a sodium aluminate solution with a low caustic ratio according to claim 1, characterized in that: The added mass of the stabilizer is 0.5-5% of the total mass of the mixed solution.

4. The method for preparing a sodium aluminate solution with a low caustic ratio according to claim 1, characterized in that: The power of the microwave reaction is 25W-100W, and the total time of the microwave reaction is 10-30min.

5. The method for preparing a sodium aluminate solution with a low caustic ratio according to claim 1, characterized in that: The sodium hydroxide in the sodium hydroxide solution accounts for 50-60wt% of the total sodium hydroxide reaction feed.

6. The method for preparing a sodium aluminate solution with a low caustic ratio according to claim 1, characterized in that: The mass ratio of the aluminum hydroxide powder to the sodium hydroxide powder is (0.95-1.05):

1.

7. The method for preparing a sodium aluminate solution with a low caustic ratio according to claim 1, characterized in that: The set temperature is 80-100°C.

8. The method for preparing a sodium aluminate solution with a low caustic ratio according to claim 1, characterized in that: The volume concentration of the sodium hydroxide solution is 600-800 g / L.

9. The method for preparing a sodium aluminate solution with a low caustic ratio according to claim 1, characterized in that: The caustic ratio of the sodium aluminate solution is 2.0 to 2.

2.

10. The method for preparing a sodium aluminate solution with a low caustic ratio according to claim 1, characterized in that: The temperature of the solid-liquid separation is 40-50°C.

Images