A solid-liquid two-phase convertible directing agent, 4A molecular sieve and preparation method

Abstract

The present invention discloses a solid-liquid two-phase convertible guiding agent, 4A molecular sieve and preparation method, wherein the molar ratio of Si to Al in the guiding agent is 20.5-50, and the molar ratio of Na to Al is 25.5-60; the guiding agent can realize solid-liquid phase conversion at 30-60°C, and the guiding agent is solid at less than 30-60°C and liquid at more than 30-60°C. The guiding agent disclosed in the present invention can be stored in a solid form at low temperature when not in use, and the internal components can be ensured to be uniform and stable. When in use, it is heated to 30-60°C in a water bath or other manner, and can be taken after it is liquefied, which overcomes the disadvantage that the existing liquid guiding agent is difficult to store stably. The particle size of the 4A molecular sieve prepared by the guiding agent disclosed in the present invention is uniform, and the particle size of 1-4 microns can reach more than 95-99%.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of 4A molecular sieves, and in particular relates to a solid-liquid two-phase convertible directing agent, a 4A molecular sieve and a preparation method. Background Art

[0002] In the production of 4A molecular sieves prepared by hydrothermal synthesis, the role of the directing agent is crucial. It not only shortens the aging reaction time, improves equipment production capacity, and reduces energy consumption, but also directly affects the grain size and particle size distribution of the product. The directing agent is a kind of aluminum silicate sol (or gel) specially prepared according to the type of synthetic molecular sieve, and the size of the sol particles is about tens of nanometers. This colloidal particle is an anion of polymerized silicate, and the negative charge mainly comes from the OH on the surface of the particle. - After aging for a certain period of time at a certain temperature, the sol is gradually transformed into crystal nuclei with extremely small particles (generally around 0.04μm). As the aging temperature increases and the aging time prolongs, the microcrystalline nuclei enter the growth period of the crystals. At this time, a large number of silicate ions and aluminate ions polymerize and enter the skeleton, causing the crystals to grow continuously. During this crystallization process, the crystals grow rapidly but the number does not increase.

[0003] At present, the directing agent used in production is in an unstable liquid state. During storage, liquid and solid stratification is easy to occur, so it needs to be stirred evenly before use. Moreover, in actual use, it is usually necessary to store it at a specific temperature, otherwise the composition will be uneven, resulting in uneven particle size of the final prepared 4A molecular sieve. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a solid-liquid two-phase convertible directing agent, a 4A molecular sieve and a preparation method, which specifically include the following contents:

[0005] A solid-liquid two-phase convertible guiding agent, the guiding agent contains sodium aluminosilicate, the molar ratio of Si to Al in the guiding agent is 20.5-50 (for example, the silicon-aluminum ratio can be 20.5, 22.0, 25.5, 26.5, 27.8, 29.0, 30.5, 31.5, 32.5, 33.5, 35, 38, 40, 42, 43, 45, 48, 50, etc.); the molar ratio of Na to Al in the guiding agent is 25.5-60 (for example, the sodium-aluminum ratio can be 25.5, 26.5, 27.8, 29.0, 30.5, 31.5, 32.5, 33.5, 35, 38, 40, 42, 43, 45, 48, 50, 55, 60, etc.); the guiding agent can realize solid-liquid phase conversion at a temperature of 30-60°C. The guiding agent is made of sodium aluminate, sodium hydroxide and water glass as raw materials, and the ingredients of the guiding agent include sodium aluminosilicate. The Si and Al molar ratios can be 22:1, 26:1, 30:1, 34:1, 38:1, 42:1, 46:1, 50:1, etc. Depending on the molar ratio of silicon to aluminum, the ingredients of the guiding agent may also include sodium aluminate or sodium silicate, and may also include sodium hydroxide. The guiding agent is solid when it is lower than 30-60°C and liquid when it is higher than 30-60°C. Depending on the difference in specific ingredients, the specific phase transition temperature can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, etc. Therefore, the guiding agent disclosed in the present invention can be stored in a solid form at low temperature when not in use, which can ensure that the internal ingredients are uniform and stable. When in use, it is heated to 30-60°C in a water bath or other manner, and it can be taken out after it is liquefied.

[0006] A method for preparing a solid-liquid two-phase convertible directing agent comprises the following steps:

[0007] (1) preparing a sodium aluminate solution having an Al2O3 concentration of 20 to 70 g / L; the specific concentration may be 20 g / L, 22 g / L, 25 g / L, 35 g / L, 40 g / L, 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, etc.;

[0008] (2) adding sodium aluminate solution to a reaction device, adding caustic soda flakes or liquid caustic soda to the sodium aluminate solution, so that the concentration of Na2O in the solution is 300-750 g / L (e.g., 300 g / L, 350 g / L, 400 g / L, 450 g / L, 500 g / L, 550 g / L, 650 g / L, 700 g / L, etc.), and controlling the solution temperature to 20-60° C. (e.g., 20° C., 22° C., 25° C., 30° C., 35° C., 40° C., 45° C., 50° C., 55° C., 60° C., etc.);

[0009] (3) Start stirring, and then add water glass with a SiO2 concentration of 50-260 g / L (e.g., 50 g / L, 55 g / L, 60 g / L, 65 g / L, 80 g / L, 90 g / L, 100 g / L, 150 g / L, 180 g / L, 200 g / L, 250 g / L, 260 g / L, etc.) into the reaction device while stirring, and control the volume ratio of the sodium aluminate solution to the water glass to be 1: (1-20), specifically 1:1, 1:2, 1:3 , 1:5, 1:8, 1:10, 1:12, 1:15, 1:18, 1:20, etc.; control the reaction temperature to 20-60°C (for example, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, etc.), and the addition time to 10-60min (for example, 10min, 12min, 15min, 18min, 20min, 25min, 30min, 35min, 50min, 60min, etc.);

[0010] (4) Continue stirring for 10 to 30 minutes (for example, 10 minutes, 12 minutes, 15 minutes, 18 minutes, 20 minutes, 24 minutes, 26 minutes, 28 minutes, 30 minutes, etc.), then stop stirring and age for 24 to 48 hours (24 hours, 26 hours, 28 hours, 30 hours, 35 hours, 40 hours, 45 hours, 48 ​​hours, etc.) to obtain a solid-liquid two-phase convertible directing agent finished product.

[0011] Preferably, the preparation method of the sodium aluminate solution in step (1) is: mixing the sodium aluminate solution produced in the production of alumina and unqualified evaporation return water in proportion, and then performing liquid-solid separation to obtain a sodium aluminate solution with an Al2O3 concentration of 20 to 70 g / L.

[0012] Preferably, the Al2O3 concentration in the sodium aluminate solution produced in the alumina production is 20-180 g / L (for example, 20 g / L, 40 g / L, 80 g / L, 100 g / L, 150 g / L, 180 g / L, etc.), and the Na2O concentration is 50-300 g / L (for example, 50 g / L, 80 g / L, 100 g / L, 150 g / L, 200 g / L, 250 g / L, 300 g / L, etc.).

[0013] Preferably, the purity of the caustic soda flakes in step (2) is 90-95% (e.g., 92%, 93%, 94%, etc.); the liquid caustic soda is heavy liquid caustic soda, and the mass concentration is 30-50% (e.g., 30%, 35%, 40%, 45%, etc.).

[0014] Preferably, the reaction device in step (2) is a mixing gelling tank with a water-cooling interlayer, and the method for controlling the temperature of the solution is to turn on the cooling water to cool it down.

[0015] A 4A molecular sieve prepared by using a solid-liquid two-phase convertible directing agent.

[0016] A method for preparing 4A molecular sieve, characterized in that it comprises the following steps:

[0017] (1) adding water glass to the sodium aluminate solution while stirring to obtain a uniformly mixed slurry;

[0018] (2) transporting the slurry to a crystallization tank, starting stirring, and then adding 3‰ to 3% (e.g., 3‰, 5‰, 8‰, 9‰, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, etc.) of a solid-liquid two-phase convertible directing agent to the slurry, heating the crystallization tank to 85-95° C. (e.g., 85° C., 88° C., 90° C., 92° C., 93° C., 95° C., etc.), and keeping the temperature for 1 to 3 h (e.g., 1 h, 1.5 h, 1.8 h, 2 h, 2.2 h, 2.5 h, 2.8 h, 3 h, etc.) to obtain a crystallized slurry;

[0019] (3) filtering the crystallized slurry, and then washing it at least once to obtain a filter cake, and then drying the filter cake to obtain a 4A molecular sieve.

[0020] Preferably, the pH of the last washing water in step (3) is ≤11; and the water content of the obtained filter cake is not higher than 50%.

[0021] Preferably, the drying method in step (3) is: sending the filter cake into a hot air furnace for drying, so that the mass of the filter cake is reduced by 18-20%.

[0022] Beneficial effects of the present invention:

[0023] (1) The guiding agent disclosed in the present invention is solid when the temperature is below 30-60°C and liquid when the temperature is above 30-60°C. The specific phase transition temperature is slightly different depending on the specific components. When not in use, the guiding agent disclosed in the present invention can be stored in a solid form at low temperature to ensure that the internal components are uniform and stable. When in use, it can be heated to 30-60°C in a water bath or other manner, and can be used after it is liquefied, thereby overcoming the disadvantage that the existing liquid guiding agent is difficult to store stably.

[0024] (2) The preparation method of the directing agent disclosed in the present invention controls the addition ratio of sodium aluminate, sodium hydroxide and sodium silicate, the reaction temperature, reaction time, aging time, etc., so that the final directed agent prepared can easily achieve liquid-solid phase transformation at a temperature not lower than 30-60°C under certain conditions.

[0025] (3) The particle size of the 4A molecular sieve prepared by using the directing agent disclosed in the present invention is uniform, and the proportion of particles with a particle size of 1 to 4 microns can reach more than 95 to 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention discloses a flow chart of the preparation method of 4A molecular sieve. DETAILED DESCRIPTION

[0027] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments shown below do not limit the invention content described in the claims. In addition, the entire contents of the structures represented by the following embodiments are not limited to those necessary as solutions to the invention described in the claims.

[0028] Example 1

[0029] A method for preparing a solid-liquid two-phase convertible directing agent comprises the following steps:

[0030] (1) The sodium aluminate solution produced in the production of alumina and unqualified evaporation return water are mixed in proportion, and then the liquid and solid are separated to obtain a sodium aluminate solution with an Al2O3 concentration of 45 g / L. The sodium aluminate solution produced in the production of alumina has an Al2O3 concentration of 70 g / L and a Na2O concentration of 100 g / L.

[0031] (2) Add the sodium aluminate solution into a mixed gelling tank with a water-cooled interlayer, add caustic soda flakes with a purity of 93% into the sodium aluminate solution, and make the Na2O concentration in the solution 690 g / L; turn on the cooling water to cool down and control the solution temperature to 35°C.

[0032] (3) Start stirring, then add water glass with a SiO2 concentration of 80 g / L into the mixed gel tank while stirring, control the volume ratio of sodium aluminate solution to water glass to be 1:15, use cooling water to cool down, control the reaction temperature to be 35°C, and add time to be 25 min;

[0033] (4) Continue stirring for 20 minutes, then stop stirring and age for 48 hours to obtain a solid-liquid two-phase convertible guiding agent product. The main components of the obtained guiding agent include sodium aluminosilicate, sodium hydroxide, sodium silicate, etc. The molar ratio of Si to Al in the guiding agent is 22.7, and the molar ratio of Na to Al is 25.23. The guiding agent is solid when it is below 40°C and liquid when it is above 40°C. At 40°C, solid-liquid phase conversion can be achieved.

[0034] Example 2

[0035] A method for preparing a solid-liquid two-phase convertible directing agent comprises the following steps:

[0036] (1) The sodium aluminate solution produced in the production of alumina and unqualified evaporation return water are mixed in proportion, and then the liquid and solid are separated to obtain a sodium aluminate solution with an Al2O3 concentration of 25 g / L. The sodium aluminate solution produced in the production of alumina has an Al2O3 concentration of 120 g / L and a Na2O concentration of 150 g / L.

[0037] (2) adding the sodium aluminate solution into a mixed gelling tank with a water-cooled interlayer, adding liquid caustic soda into the sodium aluminate solution to make the Na2O concentration in the solution 400 g / L; turning on the cooling water to cool the solution and controlling the solution temperature to 55°C; the liquid caustic soda is heavy liquid caustic soda with a mass concentration of 45%.

[0038] (3) Start stirring, then add water glass with a SiO2 concentration of 150 g / L into the mixing gel tank while stirring, control the volume ratio of sodium aluminate solution to water glass to be 1:9, use cooling water to cool down, control the reaction temperature to be 55°C, and add time to be 55 min;

[0039] (4) Continue stirring for 12 minutes, then stop stirring and age for 30 hours to obtain a solid-liquid two-phase convertible guiding agent product. The main components of the obtained guiding agent include sodium aluminosilicate, sodium hydroxide, and sodium silicate. The molar ratio of Si to Al in the guiding agent is 46.2, and the molar ratio of Na to Al is 26.32. The guiding agent is solid when it is below 50°C and liquid when it is above 50°C. At 50°C, solid-liquid phase conversion can be achieved.

[0040] Example 3

[0041] A method for preparing a solid-liquid two-phase convertible directing agent comprises the following steps:

[0042] (1) The sodium aluminate solution produced in the production of alumina and unqualified evaporation return water are mixed in proportion, and then the liquid and solid are separated to obtain a sodium aluminate solution with an Al2O3 concentration of 46 g / L. The sodium aluminate solution produced in the production of alumina has an Al2O3 concentration of 180 g / L and a Na2O concentration of 300 g / L.

[0043] (2) adding the sodium aluminate solution into a mixed gelling tank with a water-cooled interlayer, adding liquid caustic soda into the sodium aluminate solution to make the Na2O concentration in the solution 750 g / L; turning on the cooling water to cool the solution and controlling the solution temperature to 60°C; the liquid caustic soda is heavy liquid caustic soda with a mass concentration of 50%.

[0044] (3) Start stirring, then add water glass with a SiO2 concentration of 100 g / L into the mixing gel tank while stirring, control the volume ratio of sodium aluminate solution to water glass to be 1:20, use cooling water to cool down, control the reaction temperature to be 60°C, and add time to be 60 min;

[0045] (4) Continue stirring for 30 minutes, then stop stirring and age for 45 hours to obtain a solid-liquid two-phase convertible guiding agent product. The main components of the obtained guiding agent include sodium aluminosilicate, sodium hydroxide, and sodium aluminate. The molar ratio of Si to Al in the guiding agent is 37, and the molar ratio of Na to Al is 26.82. The guiding agent is solid when it is below 60°C and liquid when it is above 60°C. At 60°C, solid-liquid phase conversion can be achieved.

[0046] Example 4

[0047] A method for preparing 4A molecular sieve comprises the following steps:

[0048] (1) adding water glass to the sodium aluminate solution while stirring to obtain a uniformly mixed slurry;

[0049] (2) The slurry was transferred to a crystallization tank, stirring was started, and then 3‰ of the solid-liquid two-phase convertible directing agent prepared in Example 1 was added to the slurry, and the crystallization tank was heated to 88° C. and kept warm for 1.3 h to obtain a crystallized slurry;

[0050] (3) Filter the crystallized slurry, and then wash it at least once, the pH of the last washing water is ≤11, to obtain a filter cake with a water content of no more than 50%, and then send the filter cake to a hot air furnace for drying, so that the mass of the filter cake is reduced by 19-20%. Finally, 4A molecular sieve is obtained. After testing, the content of particles with a particle size of 1-4 microns is not less than 95%.

[0051] Example 5

[0052] A method for preparing 4A molecular sieve comprises the following steps:

[0053] (1) adding water glass to the sodium aluminate solution while stirring to obtain a uniformly mixed slurry;

[0054] (2) The slurry was transferred to a crystallization tank, stirring was started, and then 1% of the solid-liquid two-phase convertible directing agent prepared in Example 2 was added to the slurry, and the crystallization tank was heated to 92° C. and kept warm for 2 h to obtain a crystallized slurry;

[0055] (3) Filter the crystallized slurry and then wash it at least once, with the pH of the last washing water being ≤11, to obtain a filter cake with a water content of no more than 50%, and then send the filter cake to a hot air furnace for drying to reduce the mass of the filter cake by 18-19%. Finally, a 4A molecular sieve is obtained. After testing, the content of particles with a particle size of 1-4 microns is not less than 97.5%.

[0056] Example 6

[0057] A method for preparing 4A molecular sieve comprises the following steps:

[0058] (1) adding water glass to the sodium aluminate solution while stirring to obtain a uniformly mixed slurry;

[0059] (2) The slurry was transferred to a crystallization tank, stirring was started, and then 2.5% of the solid-liquid two-phase convertible directing agent prepared in Example 3 was added to the slurry, and the crystallization tank was heated to 95° C. and kept warm for 3 h to obtain a crystallized slurry;

[0060] (3) Filter the crystallized slurry, and then wash it at least once, the pH of the last washing water is ≤11, to obtain a filter cake with a water content of no more than 50%, and then send the filter cake to a hot air furnace for drying, so that the mass of the filter cake is reduced by 18-20%. Finally, 4A molecular sieve is obtained. After testing, the content of particles with a particle size of 1-4 microns obtained by the obtained 4A molecular sieve is not less than 99%.

[0061] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A solid-liquid two-phase convertible directing agent, characterized in that: The molar ratio of Si to Al in the directing agent is 20.5-50; the molar ratio of Na to Al in the directing agent is 25.5-60; the directing agent can realize solid-liquid phase transformation at 30-60°C, the directing agent is solid at below 30-60°C, and is liquid at above 30-60°C; the directing agent is prepared by the following method: (1) preparing a sodium aluminate solution having an Al2O3 concentration of 20 to 70 g / L; (2) adding sodium aluminate solution to a reaction device, adding caustic soda flakes or liquid caustic soda to the sodium aluminate solution to make the Na2O concentration in the solution 300-750 g / L, and controlling the solution temperature to 20-60° C.; (3) Start stirring, then add water glass with a SiO2 concentration of 50-260 g / L into the reaction device while stirring, control the volume ratio of sodium aluminate solution to water glass to be 1: (1-20), control the reaction temperature to be 20-60° C., and the addition time to be 10-60 min; (4) Continue stirring for 10 to 30 minutes, then stop stirring and age for 24 to 48 hours to obtain a solid-liquid two-phase convertible directing agent product.

2. A solid-liquid two-phase convertible directing agent according to claim 1, characterized in that: The preparation method of the sodium aluminate solution in step (1) is: the sodium aluminate solution produced in the production of alumina and unqualified evaporation return water are mixed in proportion, and then liquid-solid separation is performed to obtain a sodium aluminate solution with an Al2O3 concentration of 20 to 70 g / L.

3. A solid-liquid two-phase convertible directing agent according to claim 2, characterized in that: The sodium aluminate solution produced during the alumina production has an Al2O3 concentration of 20 to 180 g / L and a Na2O concentration of 50 to 300 g / L.

4. A solid-liquid two-phase convertible directing agent according to claim 1, characterized in that: The purity of the caustic soda flakes in step (2) is 90-95%; the liquid caustic soda is heavy liquid caustic soda with a mass concentration of 30-50%.

5. The solid-liquid two-phase convertible directing agent according to claim 1, characterized in that: In the step (2), the reaction device is a mixing gelling tank with a water-cooling interlayer, and the method for controlling the solution temperature is to turn on the cooling water to cool down.

6. A 4A molecular sieve prepared using a solid-liquid two-phase convertible directing agent as described in any one of claims 1 to 5.

7. A method for preparing the 4A molecular sieve according to claim 6, characterized in that: The following steps are involved: (1) adding water glass to the sodium aluminate solution while stirring to obtain a uniformly mixed slurry; (2) transporting the slurry to a crystallization tank, starting stirring, and then adding 3‰ to 3% of a solid-liquid two-phase convertible directing agent to the slurry, heating the crystallization tank to 85-95° C., and keeping the temperature for 1 to 3 hours to obtain a crystallized slurry; (3) filtering the crystallized slurry, and then washing it at least once to obtain a filter cake, and then drying the filter cake to obtain a 4A molecular sieve.

8. The method for preparing a 4A molecular sieve according to claim 7, characterized in that: The pH of the last washing water in step (3) is ≤11; the water content of the obtained filter cake is not higher than 50%; the drying method is: sending the filter cake into a hot air furnace for drying, so that the mass of the filter cake is reduced by 18-20%.

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