Acid-resistant 3a molecular sieve and preparation method thereof

Abstract

This invention discloses an acid-resistant 3A molecular sieve and its preparation method. The preparation method includes: (1) preparing an additional solution; (2) using sodium silicate as a silicon source and sodium aluminate as an aluminum source; adding the sodium silicate and sodium aluminate to the additional solution to prepare a crude molecular sieve; (3) preparing a modified molecular sieve; and (4) preparing an acid-resistant 3A molecular sieve. The 3A molecular sieve prepared by the method of this invention has good adsorption and acid resistance, and can still maintain high performance after acid corrosion testing, which improves the durability of the 3A molecular sieve and broadens its application scenarios.

Description

Technical Field

[0001] This invention relates to the field of 3A molecular sieve technology, and in particular to an acid-resistant 3A molecular sieve and its preparation method. Background Technology

[0002] 3A molecular sieves are a type of 3A zeolite molecular sieve, whose main chemical composition is alkali metal aluminosilicate. Due to their regular microporous structure, excellent water selective adsorption performance, high thermal stability and mechanical strength, they are widely used in petrochemical, natural gas, refrigerant, insulating glass, fine chemical and other fields. They are mainly used for the deep drying and dehydration of ethylene, propylene, cracked gas, oilfield gas, ethanol and various organic solvents, effectively avoiding pipeline ice blockage, side reactions and equipment corrosion. They are an indispensable adsorbent material in industrial drying and gas purification processes.

[0003] Conventional 3A molecular sieves maintain structural stability under neutral and weakly alkaline conditions, but are prone to significant structural degradation and performance decline in acidic environments. Acidic media attack the aluminum-oxygen bonds in the framework, causing framework dealuminization, increased lattice defects, and decreased crystallinity, which in turn leads to pore collapse, reduced adsorption capacity, decreased mechanical strength, and even pulverization and increased bed resistance. In scenarios such as raw material drying containing trace amounts of acidic gases (e.g., CO2, H2S, organic acids), acidic solvent dehydration, and acidic tail gas treatment, conventional 3A molecular sieves are prone to rapid deactivation, significantly shortening their service life and resulting in a marked decrease in the stability and economy of the equipment operation. Summary of the Invention

[0004] Therefore, the present invention provides an acid-resistant 3A molecular sieve and a method for preparing the same, the preparation method comprising: (1) Imidazole and potassium carbonate are added to acetonitrile and stirred to form a mixture. The mixture is heated in a water bath and kept warm, and refluxed during the warming process. Then p-bromobenzoic acid is added to the mixture. After the addition is completed, the mixture is kept warm in a water bath and stirred. After the reaction is completed, the solid and liquid are separated, the solid phase is washed and dried. The dried material is added to sodium hydroxide solution in the reaction vessel, the reaction vessel is sealed, heated and stirred magnetically, and then cooled to room temperature to obtain an additional solution. (2) Sodium silicate is used as the silicon source and sodium aluminate is used as the aluminum source; the sodium silicate and sodium aluminate are added to the additional solution, heated in a water bath, and stirred at a constant temperature to obtain a gel; then heated to crystallize to form molecular sieve crystals, solid-liquid separation is performed, the solid phase is washed until the washing liquid is neutral, dried, and then soaked in a potassium chloride solution kept warm in a water bath. After soaking, solid-liquid separation is performed, the solid phase is washed, dried, and crude molecular sieve is obtained. (3) Prepare chitosan oligosaccharide solution, add the crude molecular sieve to the chitosan oligosaccharide solution, stir evenly under ultrasonic environment, then place in vacuum box, vacuum pressure and stand, after standing, take out, solid-liquid separation, solid phase drying, after drying, add to sodium polystyrene sulfonate solution, stir evenly under ultrasonic environment, then add glutaraldehyde, stir evenly after adding, place in vacuum box again, vacuum pressure and stand for treatment, after treatment, solid-liquid separation, solid phase washing, drying, to obtain modified molecular sieve; (4) The modified molecular sieve is added to deionized water and ultrasonically stirred to form a dispersion. Then, β-mercaptoethylamine and 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone are added. After the addition is completed, the mixture is stirred evenly and placed in a vacuum chamber for vacuum pressure treatment. Then, it is taken out and treated with ultraviolet light. After the treatment, the solid and liquid are separated, the solid phase is washed, and dried to obtain the acid-resistant 3A molecular sieve.

[0005] Further, in step (1), the ratio of imidazole, potassium carbonate, p-bromobenzoic acid, and acetonitrile used is imidazole:potassium carbonate:p-bromobenzoic acid:acetonitrile = 1.1-1.4g:4-5g:6-8g:500mL; the ratio of dried material added to sodium hydroxide solution is dried material:sodium hydroxide solution = 1-2g:100mL, wherein the concentration of sodium hydroxide in the sodium hydroxide solution is 3-4g / 100mL, and the solvent is water.

[0006] Further, in step (1), the mixture is kept at a constant temperature of 50±5℃ in a water bath; after sealing the reaction vessel, it is heated to 120~125℃ and magnetically stirred for 3~5h.

[0007] Further, in step (2), sodium silicate and sodium aluminate are added to the additional solution in a silicon-aluminum molar ratio of n(SiO2):n(Al2O3):n(H2O)=2:1:200~240; the solution is heated to 60±5℃ in a water bath and stirred for more than 3 hours; the solution is then heated to 90±3℃ in a sealed reaction vessel and held for 1~2 hours, and then heated to 102±2℃ and held for 4~5 hours to complete crystallization.

[0008] Further, in step (2), the concentration of potassium chloride in the potassium chloride solution is 10-15 g / 100 mL, and the solvent is water; the water bath temperature of the potassium chloride solution is 85±5℃, and the soaking time is 2-3 h.

[0009] Further, in step (3), the concentration of chitosan oligosaccharide in the chitosan oligosaccharide solution is 50-60 g / L, and the solvent is water; the concentration of sodium polystyrene sulfonate in the sodium polystyrene sulfonate solution is 36-40 g / L, and the solvent is water; the ratio of crude molecular sieve to chitosan oligosaccharide solution is crude molecular sieve: chitosan oligosaccharide solution = 1 g: 50-100 mL; the ratio of dried solid phase and glutaraldehyde to sodium polystyrene sulfonate solution is dried solid phase: glutaraldehyde: sodium polystyrene sulfonate solution = 1 g: 3-4 g: 80-100 mL.

[0010] Further, in step (4), the ratio of the added modified molecular sieve, β-mercaptoethylamine, 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone and deionized water is modified molecular sieve: β-mercaptoethylamine: 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone: deionized water = 1g: 2~3g: 0.5~0.6g: 50mL.

[0011] The beneficial effects of this invention are as follows: the 3A molecular sieve prepared by the method described in this invention has good adsorption and acid resistance, and can maintain high performance even after acid corrosion testing, thus improving the durability of the 3A molecular sieve and broadening its application scenarios. Comparative examples 3 and other comparative examples show that this invention, by optimizing the molecular sieve preparation process, can further improve the adsorption and acid resistance of the molecular sieve. The main reason for this may be that this invention first introduces a lattice directing agent by preparing an alkaline additional solution instead of the traditional simple sodium hydroxide solution, inhibiting the formation of aluminum-rich phases in the molecular sieve lattice, and simultaneously lowering the nucleation energy barrier of the high-silicon structure, increasing the silicon-to-aluminum ratio in the molecular sieve, thereby improving the acid resistance of the molecular sieve. Subsequently, a protective layer is coated on the surface of the molecular sieve, which can passivate the surface of the molecular sieve in an acidic environment, further improving the acid resistance of the molecular sieve. Detailed Implementation

[0012] The present invention will be further described below with reference to the embodiments.

[0013] Example 1

[0014] An acid-resistant 3A molecular sieve and its preparation method, the preparation method comprising: (1) Imidazole and potassium carbonate were added to acetonitrile and stirred for 20 min to form a mixture. The mixture was heated to 50°C in a water bath and kept at that temperature. During the heat preservation process, the mixture was refluxed. Then, p-bromobenzoic acid was added to the mixture. The ratio of imidazole, potassium carbonate, p-bromobenzoic acid and acetonitrile was imidazole:potassium carbonate:p-bromobenzoic acid:acetonitrile = 1.1g:4g:6g:500mL. After the addition was completed, the mixture was kept at 50°C in a water bath and stirred for 50 h. After stirring, the solid and liquid phases were separated. The solid phase was washed three times with deionized water and dried at 80°C for 2 h. The dried material was added to sodium hydroxide solution in a reaction vessel. The ratio of dried material to sodium hydroxide solution was dried material:sodium hydroxide solution = 1g:100mL. The concentration of sodium hydroxide in the sodium hydroxide solution was 3g / 100mL and the solvent was water. The reaction vessel was sealed and heated to 120°C and stirred magnetically for 4 h. Then it was cooled to room temperature to obtain an additional solution. (2) Sodium silicate is used as the silicon source, and sodium aluminate is used as the aluminum source. Sodium silicate and sodium aluminate are added to the additional solution in a silicon-to-aluminum molar ratio of n(SiO2):n(Al2O3):n(H2O)=2:1:200. The mixture is heated to 60°C in a water bath and kept at that temperature for 3 hours to obtain a gel. Then, the mixture is heated to 90°C in a sealed reactor and kept at that temperature for 1 hour, and then heated to 102°C and kept at that temperature for 4 hours to complete crystallization and form molecular sieve crystals. Solid-liquid separation is performed, and the solid phase is washed with deionized water until the washing liquid is neutral. The solid phase is dried at 100°C for 5 hours and then soaked in a potassium chloride solution kept at a water bath temperature of 10 g / 100 mL. The potassium chloride solution is kept at a water bath temperature of 85°C for 2 hours. After soaking, solid-liquid separation is performed, and the solid phase is washed with deionized water three times and dried at 100°C for 5 hours to obtain crude molecular sieve. (3) Prepare a chitosan oligosaccharide solution, wherein the concentration of chitosan oligosaccharide in the solution is 50 g / L, and the solvent is water; add the crude molecular sieve product to the chitosan oligosaccharide solution, wherein the ratio of crude molecular sieve product to chitosan oligosaccharide solution is 1 g: 50 mL; stir evenly under ultrasonic conditions for 30 min, then place in a vacuum chamber, evacuate to 0.01 standard atmospheres, maintain pressure and stand for 30 min to ensure full contact between the solution and the surface of the molecular sieve; after standing, remove, separate the solid and liquid phases, dry the solid phase at 80℃ for 3 h, and then add it to a sodium polystyrene sulfonate solution. The mixture was stirred for 30 minutes under ultrasonic conditions until homogeneous, and then glutaraldehyde was added. The concentration of sodium polystyrene sulfonate in the sodium polystyrene sulfonate solution was 36 g / L, and the solvent was water. The ratio of the dried solid phase to the sodium polystyrene sulfonate solution was 1 g: 3 g: 80 mL. After adding the materials, the mixture was stirred for 1 hour until homogeneous. The mixture was then placed in a vacuum chamber and evacuated to 0.01 atmospheres. The pressure was maintained and the mixture was allowed to stand for 30 minutes. After the treatment, the solid and liquid phases were separated. The solid phase was washed three times with deionized water and dried at 80°C for 6 hours to obtain the modified molecular sieve. (4) The modified molecular sieve was added to deionized water and ultrasonically stirred for 30 min to disperse it into a dispersion. Then, β-mercaptoethylamine and 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone were added. The ratio of the modified molecular sieve, β-mercaptoethylamine, 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone and deionized water was 1 g: 2 g: 0.5 g: 50 mL. After the addition was completed, the mixture was stirred for 1 h to homogenize it. The mixture was placed in a vacuum chamber and evacuated to 0.01 atmospheres. It was then allowed to stand for 30 min for treatment. After that, it was taken out and treated with ultraviolet light for 1 h. After treatment, the solid and liquid phases were separated. The solid phase was washed twice with ethanol and then three times with deionized water. The solid phase was dried at 80°C for 6 h to obtain the acid-resistant 3A molecular sieve.

[0015] Example 2

[0016] An acid-resistant 3A molecular sieve and its preparation method, the preparation method comprising: (1) Imidazole and potassium carbonate were added to acetonitrile and stirred for 20 min to form a mixture. The mixture was heated to 50°C in a water bath and kept at that temperature. During the heat preservation process, the mixture was refluxed. Then, p-bromobenzoic acid was added to the mixture. The ratio of imidazole, potassium carbonate, p-bromobenzoic acid and acetonitrile was imidazole:potassium carbonate:p-bromobenzoic acid:acetonitrile = 1.2g:4g:7g:500mL. After the addition was completed, the mixture was kept at 50°C in a water bath and stirred for 50 h. After stirring, the solid and liquid phases were separated. The solid phase was washed three times with deionized water and dried at 80°C for 2 h. The dried material was added to sodium hydroxide solution in a reaction vessel. The ratio of dried material to sodium hydroxide solution was dried material:sodium hydroxide solution = 1g:100mL. The concentration of sodium hydroxide in the sodium hydroxide solution was 3g / 100mL and the solvent was water. The reaction vessel was sealed and heated to 120°C and stirred magnetically for 4 h. Then it was cooled to room temperature to obtain an additional solution. (2) Sodium silicate is used as the silicon source, and sodium aluminate is used as the aluminum source. Sodium silicate and sodium aluminate are added to the additional solution in a silicon-to-aluminum molar ratio of n(SiO2):n(Al2O3):n(H2O)=2:1:200. The mixture is heated to 60°C in a water bath and kept at that temperature for 3 hours to obtain a gel. Then, the mixture is heated to 90°C in a sealed reactor and kept at that temperature for 1 hour, and then heated to 102°C and kept at that temperature for 4 hours to complete crystallization and form molecular sieve crystals. Solid-liquid separation is performed, and the solid phase is washed with deionized water until the washing liquid is neutral. The solid phase is dried at 100°C for 5 hours and then soaked in a potassium chloride solution kept at a water bath temperature of 10 g / 100 mL. The potassium chloride solution is kept at a water bath temperature of 85°C for 2 hours. After soaking, solid-liquid separation is performed, and the solid phase is washed with deionized water three times and dried at 100°C for 5 hours to obtain crude molecular sieve. (3) Prepare a chitosan oligosaccharide solution, wherein the concentration of chitosan oligosaccharide in the solution is 55 g / L, and the solvent is water; add the crude molecular sieve product to the chitosan oligosaccharide solution, wherein the ratio of crude molecular sieve product to chitosan oligosaccharide solution is 1 g: 50 mL; stir evenly under ultrasonic conditions for 30 min, then place in a vacuum chamber, evacuate to 0.01 standard atmospheres, maintain pressure and stand for 30 min to ensure full contact between the solution and the surface of the molecular sieve; after standing, remove, separate the solid and liquid phases, dry the solid phase at 80℃ for 3 h, and then add it to a sodium polystyrene sulfonate solution. The mixture was stirred for 30 minutes under ultrasonic conditions until homogeneous, and then glutaraldehyde was added. The concentration of sodium polystyrene sulfonate in the sodium polystyrene sulfonate solution was 38 g / L, and the solvent was water. The ratio of the dried solid phase to the sodium polystyrene sulfonate solution was 1 g: 3 g: 80 mL. After adding the materials, the mixture was stirred for 1 hour until homogeneous. The mixture was then placed in a vacuum chamber and evacuated to 0.01 atmospheres. The pressure was maintained and the mixture was allowed to stand for 30 minutes. After the treatment, the solid and liquid phases were separated. The solid phase was washed three times with deionized water and dried at 80°C for 6 hours to obtain the modified molecular sieve. (4) The modified molecular sieve was added to deionized water and ultrasonically stirred for 30 min to disperse it into a dispersion. Then, β-mercaptoethylamine and 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone were added. The ratio of the modified molecular sieve, β-mercaptoethylamine, 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone and deionized water was 1 g: 2 g: 0.5 g: 50 mL. After the addition was completed, the mixture was stirred for 1 h to homogenize it. The mixture was placed in a vacuum chamber and evacuated to 0.01 atmospheres. It was then allowed to stand for 30 min for treatment. After that, it was taken out and treated with ultraviolet light for 1 h. After treatment, the solid and liquid phases were separated. The solid phase was washed twice with ethanol and then three times with deionized water. The solid phase was dried at 80°C for 6 h to obtain the acid-resistant 3A molecular sieve.

[0017] Example 3

[0018] An acid-resistant 3A molecular sieve and its preparation method, the preparation method comprising: (1) Imidazole and potassium carbonate were added to acetonitrile and stirred for 20 min to form a mixture. The mixture was heated to 50°C in a water bath and kept at that temperature. During the heat preservation process, the mixture was refluxed. Then, p-bromobenzoic acid was added to the mixture. The ratio of imidazole, potassium carbonate, p-bromobenzoic acid and acetonitrile was imidazole:potassium carbonate:p-bromobenzoic acid:acetonitrile = 1.3g:5g:7g:500mL. After the addition was completed, the mixture was kept at 50°C in a water bath and stirred for 50 h. After stirring, the solid and liquid phases were separated. The solid phase was washed three times with deionized water and dried at 80°C for 2 h. The dried material was added to sodium hydroxide solution in a reaction vessel. The ratio of dried material to sodium hydroxide solution was dried material:sodium hydroxide solution = 2g:100mL. The concentration of sodium hydroxide in the sodium hydroxide solution was 4g / 100mL and the solvent was water. The reaction vessel was sealed and heated to 120°C and stirred magnetically for 4 h. Then it was cooled to room temperature to obtain an additional solution. (2) Sodium silicate is used as the silicon source, and sodium aluminate is used as the aluminum source. Sodium silicate and sodium aluminate are added to the additional solution in a silicon-to-aluminum molar ratio of n(SiO2):n(Al2O3):n(H2O)=2:1:200. The solution is heated to 60°C in a water bath and stirred for 3 hours to obtain a gel. The solution is then heated to 90°C in a sealed reactor and held for 1 hour, and then heated to 102°C and held for 4 hours to complete crystallization and form molecular sieve crystals. Solid-liquid separation is performed, and the solid phase is washed with deionized water until the washing liquid is neutral. The solution is dried at 100°C for 5 hours. After drying, the solution is soaked in a potassium chloride solution kept in a water bath. The concentration of potassium chloride in the potassium chloride solution is 15 g / 100 mL, and the solvent is water. The water bath temperature of the potassium chloride solution is 85°C, and the soaking time is 2 hours. After soaking, solid-liquid separation is performed, and the solid phase is washed three times with deionized water and dried at 100°C for 5 hours to obtain crude molecular sieve. (3) Prepare a chitosan oligosaccharide solution, wherein the concentration of chitosan oligosaccharide in the solution is 55 g / L, and the solvent is water; add the crude molecular sieve product to the chitosan oligosaccharide solution, wherein the ratio of crude molecular sieve product to chitosan oligosaccharide solution is 1 g: 50 mL; stir evenly under ultrasonic conditions for 30 min, then place in a vacuum chamber, evacuate to 0.01 standard atmospheres, maintain pressure and stand for 30 min to ensure full contact between the solution and the surface of the molecular sieve; after standing, remove, separate the solid and liquid phases, dry the solid phase at 80℃ for 3 h, and then add it to a sodium polystyrene sulfonate solution. The mixture was stirred for 30 minutes under ultrasonic conditions until homogeneous, and then glutaraldehyde was added. The concentration of sodium polystyrene sulfonate in the sodium polystyrene sulfonate solution was 38 g / L, and the solvent was water. The ratio of the dried solid phase to the sodium polystyrene sulfonate solution was 1 g: 4 g: 80 mL. After adding the materials, the mixture was stirred for 1 hour until homogeneous. The mixture was then placed in a vacuum chamber and evacuated to 0.01 atmospheres. The pressure was maintained and the mixture was allowed to stand for 30 minutes. After the treatment, the solid and liquid phases were separated. The solid phase was washed three times with deionized water and dried at 80°C for 6 hours to obtain the modified molecular sieve. (4) The modified molecular sieve was added to deionized water and ultrasonically stirred for 30 min to disperse it into a dispersion. Then, β-mercaptoethylamine and 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone were added. The ratio of the modified molecular sieve, β-mercaptoethylamine, 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone and deionized water was 1 g: 3 g: 0.6 g: 50 mL. After the addition was completed, the mixture was stirred for 1 h to homogenize it. The mixture was then placed in a vacuum chamber and evacuated to 0.01 atmospheres. The pressure was maintained and the mixture was left to stand for 30 min. The mixture was then removed and irradiated with ultraviolet light for 1 h. After the treatment, the solid and liquid phases were separated. The solid phase was washed twice with ethanol and then three times with deionized water. The solid phase was dried at 80 °C for 6 h to obtain the acid-resistant 3A molecular sieve.

[0019] Example 4

[0020] An acid-resistant 3A molecular sieve and its preparation method, the preparation method comprising: (1) Imidazole and potassium carbonate were added to acetonitrile and stirred for 20 min to form a mixture. The mixture was heated to 50°C in a water bath and kept at that temperature. During the heat preservation process, the mixture was refluxed. Then, p-bromobenzoic acid was added to the mixture. The ratio of imidazole, potassium carbonate, p-bromobenzoic acid and acetonitrile was imidazole:potassium carbonate:p-bromobenzoic acid:acetonitrile = 1.4g:5g:8g:500mL. After the addition was completed, the mixture was kept at 50°C in a water bath and stirred for 50 h. After stirring, the solid and liquid phases were separated. The solid phase was washed three times with deionized water and dried at 80°C for 2 h. The dried material was added to sodium hydroxide solution in a reaction vessel. The ratio of dried material to sodium hydroxide solution was dried material:sodium hydroxide solution = 2g:100mL. The concentration of sodium hydroxide in the sodium hydroxide solution was 4g / 100mL and the solvent was water. The reaction vessel was sealed and heated to 120°C and stirred magnetically for 4 h. Then it was cooled to room temperature to obtain an additional solution. (2) Sodium silicate is used as the silicon source, and sodium aluminate is used as the aluminum source. Sodium silicate and sodium aluminate are added to the additional solution in a silicon-to-aluminum molar ratio of n(SiO2):n(Al2O3):n(H2O)=2:1:200. The solution is heated to 60°C in a water bath and stirred for 3 hours to obtain a gel. The solution is then heated to 90°C in a sealed reactor and held for 1 hour, and then heated to 102°C and held for 4 hours to complete crystallization and form molecular sieve crystals. Solid-liquid separation is performed, and the solid phase is washed with deionized water until the washing liquid is neutral. The solution is dried at 100°C for 5 hours. After drying, the solution is soaked in a potassium chloride solution kept in a water bath. The concentration of potassium chloride in the potassium chloride solution is 15 g / 100 mL, and the solvent is water. The water bath temperature of the potassium chloride solution is 85°C, and the soaking time is 2 hours. After soaking, solid-liquid separation is performed, and the solid phase is washed three times with deionized water and dried at 100°C for 5 hours to obtain crude molecular sieve. (3) Prepare a chitosan oligosaccharide solution, wherein the concentration of chitosan oligosaccharide in the solution is 60 g / L, and the solvent is water; add the crude molecular sieve product to the chitosan oligosaccharide solution, wherein the ratio of crude molecular sieve product to chitosan oligosaccharide solution is 1 g: 50 mL; stir evenly under ultrasonic conditions for 30 min, then place in a vacuum chamber, evacuate to 0.01 standard atmospheres, maintain pressure and stand for 30 min to ensure full contact between the solution and the surface of the molecular sieve; after standing, remove, separate the solid and liquid phases, dry the solid phase at 80℃ for 3 h, and then add it to a sodium polystyrene sulfonate solution. The mixture was stirred for 30 minutes under ultrasonic conditions until homogeneous, and then glutaraldehyde was added. The concentration of sodium polystyrene sulfonate in the sodium polystyrene sulfonate solution was 40 g / L, and the solvent was water. The ratio of the dried solid phase to the sodium polystyrene sulfonate solution was 1 g: 4 g: 80 mL. After adding the materials, the mixture was stirred for 1 hour until homogeneous. The mixture was then placed in a vacuum chamber and evacuated to 0.01 atmospheres. The pressure was maintained and the mixture was allowed to stand for 30 minutes. After the treatment, the solid and liquid phases were separated. The solid phase was washed three times with deionized water and dried at 80°C for 6 hours to obtain the modified molecular sieve. (4) The modified molecular sieve was added to deionized water and ultrasonically stirred for 30 min to disperse it into a dispersion. Then, β-mercaptoethylamine and 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone were added. The ratio of the modified molecular sieve, β-mercaptoethylamine, 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone and deionized water was 1 g: 3 g: 0.6 g: 50 mL. After the addition was completed, the mixture was stirred for 1 h to homogenize it. The mixture was then placed in a vacuum chamber and evacuated to 0.01 atmospheres. The pressure was maintained and the mixture was left to stand for 30 min. The mixture was then removed and irradiated with ultraviolet light for 1 h. After the treatment, the solid and liquid phases were separated. The solid phase was washed twice with ethanol and then three times with deionized water. The solid phase was dried at 80 °C for 6 h to obtain the acid-resistant 3A molecular sieve.

[0021] Comparative Example 1 A comparative 3A molecular sieve and its preparation method thereof, the preparation method comprising: (1) Prepare a sodium hydroxide solution as an additional solution for this comparative example, wherein the concentration of sodium hydroxide in the sodium hydroxide solution is 4 g / 100 mL and the solvent is water; (2) Sodium silicate is used as the silicon source, and sodium aluminate is used as the aluminum source. Sodium silicate and sodium aluminate are added to the additional solution in a silicon-to-aluminum molar ratio of n(SiO2):n(Al2O3):n(H2O)=2:1:200. The solution is heated to 60°C in a water bath and stirred for 3 hours to obtain a gel. The solution is then heated to 90°C in a sealed reactor and held for 1 hour, and then heated to 102°C and held for 4 hours to complete crystallization and form molecular sieve crystals. Solid-liquid separation is performed, and the solid phase is washed with deionized water until the washing liquid is neutral. The solution is dried at 100°C for 5 hours. After drying, the solution is soaked in a potassium chloride solution kept in a water bath. The concentration of potassium chloride in the potassium chloride solution is 15 g / 100 mL, and the solvent is water. The water bath temperature of the potassium chloride solution is 85°C, and the soaking time is 2 hours. After soaking, solid-liquid separation is performed, and the solid phase is washed three times with deionized water and dried at 100°C for 5 hours to obtain crude molecular sieve. (3) Prepare a chitosan oligosaccharide solution, wherein the concentration of chitosan oligosaccharide in the solution is 55 g / L, and the solvent is water; add the crude molecular sieve product to the chitosan oligosaccharide solution, wherein the ratio of crude molecular sieve product to chitosan oligosaccharide solution is 1 g: 50 mL; stir evenly under ultrasonic conditions for 30 min, then place in a vacuum chamber, evacuate to 0.01 standard atmospheres, maintain pressure and stand for 30 min to ensure full contact between the solution and the surface of the molecular sieve; after standing, remove, separate the solid and liquid phases, dry the solid phase at 80℃ for 3 h, and then add it to a sodium polystyrene sulfonate solution. The mixture was stirred for 30 minutes under ultrasonic conditions until homogeneous, and then glutaraldehyde was added. The concentration of sodium polystyrene sulfonate in the sodium polystyrene sulfonate solution was 38 g / L, and the solvent was water. The ratio of the dried solid phase to the sodium polystyrene sulfonate solution was 1 g: 4 g: 80 mL. After adding the materials, the mixture was stirred for 1 hour until homogeneous. The mixture was then placed in a vacuum chamber and evacuated to 0.01 atmospheres. The pressure was maintained and the mixture was allowed to stand for 30 minutes. After the treatment, the solid and liquid phases were separated. The solid phase was washed three times with deionized water and dried at 80°C for 6 hours to obtain the modified molecular sieve. (4) The modified molecular sieve was added to deionized water and ultrasonically stirred for 30 min to disperse it into a dispersion. Then, β-mercaptoethylamine and 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone were added. The ratio of the modified molecular sieve, β-mercaptoethylamine, 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone and deionized water was 1 g: 3 g: 0.6 g: 50 mL. After the addition was completed, the mixture was stirred for 1 h to homogenize it. The mixture was then placed in a vacuum chamber and evacuated to 0.01 atmospheres. The pressure was maintained and the mixture was allowed to stand for 30 min. The mixture was then removed and irradiated with ultraviolet light for 1 h. After the treatment, the solid and liquid phases were separated. The solid phase was washed twice with ethanol and then three times with deionized water. The solid phase was dried at 80 °C for 6 h to obtain the 3A molecular sieve described in this comparative example.

[0022] Comparative Example 2 A comparative 3A molecular sieve and its preparation method thereof, the preparation method comprising: (1) Imidazole and potassium carbonate were added to acetonitrile and stirred for 20 min to form a mixture. The mixture was heated to 50°C in a water bath and kept at that temperature. During the heat preservation process, the mixture was refluxed. Then, p-bromobenzoic acid was added to the mixture. The ratio of imidazole, potassium carbonate, p-bromobenzoic acid and acetonitrile was imidazole:potassium carbonate:p-bromobenzoic acid:acetonitrile = 1.3g:5g:7g:500mL. After the addition was completed, the mixture was kept at 50°C in a water bath and stirred for 50 h. After stirring, the solid and liquid phases were separated. The solid phase was washed three times with deionized water and dried at 80°C for 2 h. The dried material was added to sodium hydroxide solution in a reaction vessel. The ratio of dried material to sodium hydroxide solution was dried material:sodium hydroxide solution = 2g:100mL. The concentration of sodium hydroxide in the sodium hydroxide solution was 4g / 100mL and the solvent was water. The reaction vessel was sealed and heated to 120°C and stirred magnetically for 4 h. Then it was cooled to room temperature to obtain an additional solution. (2) Sodium silicate is used as the silicon source, and sodium aluminate is used as the aluminum source. Sodium silicate and sodium aluminate are added to the additional solution in a silicon-to-aluminum molar ratio of n(SiO2):n(Al2O3):n(H2O)=2:1:200. The solution is heated to 60°C in a water bath and stirred for 3 hours to obtain a gel. The solution is then heated to 90°C in a sealed reactor and held for 1 hour, and then heated to 102°C and held for 4 hours to complete crystallization and form molecular sieve crystals. Solid-liquid separation is performed, and the solid phase is washed with deionized water until the washing liquid is neutral. The solution is dried at 100°C for 5 hours. After drying, the solution is soaked in a potassium chloride solution kept in a water bath. The concentration of potassium chloride in the potassium chloride solution is 15 g / 100 mL, and the solvent is water. The water bath temperature of the potassium chloride solution is 85°C, and the soaking time is 2 hours. After soaking, solid-liquid separation is performed, and the solid phase is washed three times with deionized water and dried at 100°C for 5 hours to obtain crude molecular sieve. (3) Prepare a chitosan oligosaccharide solution, wherein the concentration of chitosan oligosaccharide in the chitosan oligosaccharide solution is 55 g / L and the solvent is water; add the crude molecular sieve to the chitosan oligosaccharide solution, wherein the ratio of crude molecular sieve to chitosan oligosaccharide solution is 1 g: 50 mL; stir evenly under ultrasonic conditions for 30 min, then place in a vacuum chamber, evacuate to 0.01 standard atmospheres and hold for 30 min to allow the solution and molecular sieve surface to fully contact; after standing, remove, separate solid and liquid, and dry the solid phase at 80 °C for 3 h to obtain the modified molecular sieve of this comparative example; (4) The modified molecular sieve was added to deionized water and ultrasonically stirred for 30 min to disperse it into a dispersion. Then, β-mercaptoethylamine and 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone were added. The ratio of the modified molecular sieve, β-mercaptoethylamine, 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone and deionized water was 1 g: 3 g: 0.6 g: 50 mL. After the addition was completed, the mixture was stirred for 1 h to homogenize it. The mixture was then placed in a vacuum chamber and evacuated to 0.01 atmospheres. The pressure was maintained and the mixture was allowed to stand for 30 min. The mixture was then removed and irradiated with ultraviolet light for 1 h. After the treatment, the solid and liquid phases were separated. The solid phase was washed twice with ethanol and then three times with deionized water. The solid phase was dried at 80 °C for 6 h to obtain the 3A molecular sieve described in this comparative example.

[0023] Comparative Example 3 A comparative 3A molecular sieve and its preparation method thereof, the preparation method comprising: (1) Imidazole and potassium carbonate were added to acetonitrile and stirred for 20 min to form a mixture. The mixture was heated to 50°C in a water bath and kept at that temperature. During the heat preservation process, the mixture was refluxed. Then, p-bromobenzoic acid was added to the mixture. The ratio of imidazole, potassium carbonate, p-bromobenzoic acid and acetonitrile was imidazole:potassium carbonate:p-bromobenzoic acid:acetonitrile = 1.3g:5g:7g:500mL. After the addition was completed, the mixture was kept at 50°C in a water bath and stirred for 50 h. After stirring, the solid and liquid phases were separated. The solid phase was washed three times with deionized water and dried at 80°C for 2 h. The dried material was added to sodium hydroxide solution in a reaction vessel. The ratio of dried material to sodium hydroxide solution was dried material:sodium hydroxide solution = 2g:100mL. The concentration of sodium hydroxide in the sodium hydroxide solution was 4g / 100mL and the solvent was water. The reaction vessel was sealed and heated to 120°C and stirred magnetically for 4 h. Then it was cooled to room temperature to obtain an additional solution. (2) Sodium silicate is used as the silicon source, and sodium aluminate is used as the aluminum source. Sodium silicate and sodium aluminate are added to the additional solution in a silicon-to-aluminum molar ratio of n(SiO2):n(Al2O3):n(H2O)=2:1:200. The solution is heated to 60°C in a water bath and stirred for 3 hours to obtain a gel. The solution is then heated to 90°C in a sealed reactor and held for 1 hour, and then heated to 102°C and held for 4 hours to complete crystallization and form molecular sieve crystals. Solid-liquid separation is performed, and the solid phase is washed with deionized water until the washing liquid is neutral. The solution is dried at 100°C for 5 hours. After drying, the solution is soaked in a potassium chloride solution kept in a water bath. The concentration of potassium chloride in the potassium chloride solution is 15 g / 100 mL, and the solvent is water. The water bath temperature of the potassium chloride solution is 85°C, and the soaking time is 2 hours. After soaking, solid-liquid separation is performed, and the solid phase is washed three times with deionized water and dried at 100°C for 5 hours to obtain crude molecular sieve. (3) Prepare a chitosan oligosaccharide solution, wherein the concentration of chitosan oligosaccharide in the solution is 55 g / L and the solvent is water; add the crude molecular sieve to the chitosan oligosaccharide solution, wherein the ratio of crude molecular sieve to chitosan oligosaccharide solution is 1 g: 50 mL; stir evenly under ultrasonic conditions for 30 min, then place in a vacuum chamber, evacuate to 0.01 standard atmospheres and hold for 30 min to ensure full contact between the solution and the surface of the molecular sieve; after standing, remove the solution, separate the solid and liquid phases, dry the solid phase at 80℃ for 3 h, and then add it to a sodium polystyrene sulfonate solution, and so on under ultrasonic conditions. The mixture was stirred for 30 minutes under ambient conditions until homogeneous, and then glutaraldehyde was added. The concentration of sodium polystyrene sulfonate in the sodium polystyrene sulfonate solution was 38 g / L, and the solvent was water. The ratio of the dried solid phase to the sodium polystyrene sulfonate solution was 1 g: 4 g: 80 mL. After adding the materials, the mixture was stirred for 1 hour until homogeneous. The mixture was then placed in a vacuum chamber and evacuated to 0.01 atmospheres. The pressure was maintained and the mixture was allowed to stand for 30 minutes. After the treatment, the solid and liquid phases were separated. The solid phase was washed three times with deionized water and dried at 80°C for 6 hours to obtain the 3A molecular sieve described in this comparative example.

[0024] Example 5

[0025] The static water adsorption performance of the molecular sieves prepared by the methods described in the above embodiments and comparative examples was tested according to the requirements of standard GB / T6287-2021. Then, the molecular sieves were immersed in 0.5 mol / L hydrochloric acid for 1 h. After immersion, the static water adsorption performance of the molecular sieves was tested again. The results are shown in Table 1.

[0026] Table 1 As shown in Table 1, the 3A molecular sieve prepared using the method described in this invention exhibits excellent adsorption and acid resistance. Even after acid corrosion testing, it maintains high performance, improving the durability of the 3A molecular sieve and broadening its application scenarios. Comparing Example 3 and the comparative examples, it can be seen that this invention, by optimizing the molecular sieve preparation process, can further improve the adsorption and acid resistance of the molecular sieve. The main reason for this may be that this invention first replaces the traditional simple sodium hydroxide solution with an alkaline auxiliary solution, introducing a lattice directing agent to inhibit the formation of aluminum-rich phases in the molecular sieve lattice, while simultaneously lowering the nucleation energy barrier of the high-silicon structure, increasing the silicon-to-aluminum ratio in the molecular sieve, and thus improving the acid resistance of the molecular sieve. Subsequently, a protective layer is coated onto the surface of the molecular sieve. This protective layer can passivate the surface of the molecular sieve in an acidic environment, further improving the acid resistance of the molecular sieve.

[0027] The technical solutions provided by the present invention have been described in detail above. For those skilled in the art, there will be changes in specific implementation methods and application scope based on the ideas of the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An acid-resistant 3A molecular sieve and its preparation method, characterized in that, Preparation methods include: (1) Imidazole and potassium carbonate are added to acetonitrile and stirred to form a mixture. The mixture is heated in a water bath and kept warm, and refluxed during the warming process. Then p-bromobenzoic acid is added to the mixture. After the addition is completed, the mixture is kept warm in a water bath and stirred. After the reaction is completed, the solid and liquid are separated, the solid phase is washed and dried. The dried material is added to sodium hydroxide solution in the reaction vessel, the reaction vessel is sealed, heated and stirred magnetically, and then cooled to room temperature to obtain an additional solution. (2) Sodium silicate is used as the silicon source and sodium aluminate is used as the aluminum source; the sodium silicate and sodium aluminate are added to the additional solution, heated in a water bath, and stirred at a constant temperature to obtain a gel; then heated to crystallize to form molecular sieve crystals, solid-liquid separation is performed, the solid phase is washed until the washing liquid is neutral, dried, and then soaked in a potassium chloride solution kept warm in a water bath. After soaking, solid-liquid separation is performed, the solid phase is washed, dried, and crude molecular sieve is obtained. (3) Prepare chitosan oligosaccharide solution, add the crude molecular sieve to the chitosan oligosaccharide solution, stir evenly under ultrasonic environment, then place in vacuum box, vacuum pressure and stand, after standing, take out, solid-liquid separation, solid phase drying, after drying, add to sodium polystyrene sulfonate solution, stir evenly under ultrasonic environment, then add glutaraldehyde, stir evenly after adding, place in vacuum box again, vacuum pressure and stand for treatment, after treatment, solid-liquid separation, solid phase washing, drying, to obtain modified molecular sieve; (4) The modified molecular sieve is added to deionized water and ultrasonically stirred to form a dispersion. Then, β-mercaptoethylamine and 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone are added. After the addition is completed, the mixture is stirred evenly and placed in a vacuum chamber for vacuum pressure treatment. Then, it is taken out and treated with ultraviolet light. After the treatment, the solid and liquid are separated, the solid phase is washed, and dried to obtain the acid-resistant 3A molecular sieve.

2. The acid-resistant 3A molecular sieve and its preparation method according to claim 1, characterized in that, In step (1), the ratio of imidazole, potassium carbonate, p-bromobenzoic acid, and acetonitrile used is imidazole:potassium carbonate:p-bromobenzoic acid:acetonitrile = 1.1-1.4g:4-5g:6-8g:500mL; the ratio of dried material added to sodium hydroxide solution is dried material:sodium hydroxide solution = 1-2g:100mL, wherein the concentration of sodium hydroxide in the sodium hydroxide solution is 3-4g / 100mL, and the solvent is water.

3. The acid-resistant 3A molecular sieve and its preparation method according to claim 1, characterized in that, In step (1), the mixture is kept at a constant temperature of 50±5℃ in a water bath; after sealing the reaction vessel, it is heated to 120~125℃ and magnetically stirred for 3~5h.

4. The acid-resistant 3A molecular sieve and its preparation method according to claim 1, characterized in that, In step (2), sodium silicate and sodium aluminate are added to the additional solution in a silicon-aluminum molar ratio of n(SiO2):n(Al2O3):n(H2O)=2:1:200-240; the solution is heated to 60±5℃ in a water bath and stirred for more than 3 hours; the solution is then heated to 90±3℃ in a sealed reaction vessel and held for 1-2 hours, and then heated to 102±2℃ and held for 4-5 hours to complete crystallization.

5. The acid-resistant 3A molecular sieve and its preparation method according to claim 1, characterized in that, In step (2), the concentration of potassium chloride in the potassium chloride solution is 10-15 g / 100 mL, and the solvent is water; the water bath temperature of the potassium chloride solution is 85±5℃, and the soaking time is 2-3 h.

6. The acid-resistant 3A molecular sieve and its preparation method according to claim 1, characterized in that, In step (3), the concentration of chitosan oligosaccharide in the chitosan oligosaccharide solution is 50-60 g / L, and the solvent is water; the concentration of sodium polystyrene sulfonate in the sodium polystyrene sulfonate solution is 36-40 g / L, and the solvent is water; the ratio of crude molecular sieve to chitosan oligosaccharide solution is crude molecular sieve: chitosan oligosaccharide solution = 1 g: 50-100 mL; the ratio of dried solid phase and glutaraldehyde to sodium polystyrene sulfonate solution is dried solid phase: glutaraldehyde: sodium polystyrene sulfonate solution = 1 g: 3-4 g: 80-100 mL.

7. The acid-resistant 3A molecular sieve and its preparation method according to claim 1, characterized in that, In step (4), the ratio of the added modified molecular sieve, β-mercaptoethylamine, 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone and deionized water is modified molecular sieve: β-mercaptoethylamine: 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone: deionized water = 1g: 2-3g: 0.5-0.6g: 50mL.

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