Fau structure molecular sieve and method for making same

Abstract

The application relates to the field of molecular sieve preparation, and discloses a FAU structure molecular sieve and a preparation method thereof. The preparation method comprises the following steps: performing first ion exchange on Na-FAU molecular sieve and an ammonium salt, and then performing filtration, washing and first calcination to obtain a first calcined molecular sieve; performing second ion exchange on the first calcined molecular sieve and the ammonium salt, and then performing filtration, washing and second calcination to obtain a second calcined molecular sieve; performing acid treatment on the second calcined molecular sieve by using fluosilicic acid and an organic acid, and then performing filtration and washing; performing sodium hydroxide solution treatment on the obtained molecular sieve, and then performing filtration and washing; performing ammonium salt solution treatment on the obtained molecular sieve, and then performing filtration and washing to obtain a FAU structure molecular sieve product. The preparation method can obtain the FAU structure molecular sieve which simultaneously has a high silicon-aluminum ratio, high crystallinity, a high specific surface area and a high mesopore volume.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve preparation, specifically to a method for preparing FAU structured molecular sieves and the FAU structured molecular sieves obtained by this method. Background Technology

[0002] VOCs are one of the most critical factors in air pollution, and have become the second most significant contributor after SO2. x NO x VOCs, the third largest gaseous pollutant emitted annually, have complex compositions, diverse treatment technologies, and varying applicability, requiring high standards for technology selection and system matching. Various methods exist for VOCs removal, with adsorption being the most effective due to its high efficiency, low energy consumption, simple operation, and recyclability. Rotary adsorption concentration technology is a feasible technology developed for treating large volumes of low-concentration VOCs. The adsorption effect of adsorption depends primarily on the properties of the adsorbent, the types of gaseous pollutants, and the process conditions of the adsorption system (such as operating temperature and humidity). Therefore, the key issue in adsorption lies in the selection of the adsorbent. While most solids possess some adsorption capacity, only solids with high selectivity and large adsorption capacity can be used as industrial adsorbents. Adsorbents should have a dense microporous structure, large internal surface area, good adsorption performance, stable chemical properties, resistance to acids and alkalis, water, high temperature and pressure, and be resistant to breakage and low air resistance. Commonly used adsorbents include molecular sieves, activated carbon (granular) and activated carbon fibers, activated alumina, and silica gel. High silica-to-alumina ratio molecular sieves are characterized by high inertness and non-flammability, good hydrophobicity, and strong VOCs adsorption capacity at low concentrations. They exhibit excellent selectivity for VOCs in environments with high relative humidity, enabling efficient VOCs adsorption.

[0003] High silica-to-alumina ratio Y molecular sieves can be obtained through direct synthesis and post-treatment modification.

[0004] For the direct synthesis of high-silica Y molecular sieves, organic structure-directing agents are usually required. US4,714,601 discloses a polymorph of FAU called ECR 4 with a silica-to-alumina ratio greater than 6, which is obtained by hydrothermal crystallization at 70–120 °C in the presence of seed crystals using alkyl or hydroxyalkyl quaternary ammonium salts as template agents. US4,931,267 discloses a polymorph of FAU called ECR 32 with a silica-to-alumina ratio greater than 6, which is obtained by hydrothermal crystallization at 90–120 °C using tetrapropyl and / or tetrabutylammonium hydroxide as structure-directing agents, and has high thermal stability. Delprato et al. (Zeolites, 1990, 10(6):546552) first synthesized a cubic FAU molecular sieve with a framework silica-to-alumina ratio close to 9.0 using crown ethers as template agents, but the high cost and high toxicity of crown ethers limit their industrial application. Subsequently, US5,385,717 synthesized Y-type molecular sieves with a silica-to-alumina ratio greater than 6 using polyethylene oxide as a template agent. Although the silica-to-alumina ratio of Y-type molecular sieves prepared by the template agent method can reach above 6.0, the template agent used is expensive, increasing production costs. In addition, the removal of the template agent affects the relative crystallinity of the molecular sieve and causes environmental pollution.

[0005] In post-processing modification methods, high silica-to-alumina ratio (S / A) Y-type molecular sieves can be obtained through acid treatment, hydrothermal calcination, and gas-solid phase modification. While acid treatment or hydrothermal calcination can yield high S / A ratio Y-type molecular sieves, the sieve's framework structure is easily damaged, resulting in a significant decrease in relative crystallinity and a substantial impact on the stability and acidity of the Y-type molecular sieve. Shen Baojian et al. disclosed a method for preparing high S / A ratio Y-type zeolite with abundant secondary pores in CN103539151B. This method first synthesizes FeY molecular sieves, then performs two ammonium exchange processes and hydrothermal calcination, resulting in Y-type zeolite with a higher S / A ratio and more abundant secondary pores. A representative method for obtaining high S / A ratio Y-type molecular sieves through gas-solid phase modification is CN102553630B, which uses in-situ crystallization to prepare NaY / matrix, followed by gas-phase ultrastabilization treatment to prepare a high S / A ratio small-crystal Y-type zeolite catalytic cracking catalyst with high activity, hydrothermal stability, and good selectivity for the target product. In existing methods, when preparing molecular sieves with high silicon-to-aluminum ratios using post-processing modification, the dealumination process can cause some damage to the molecular sieve structure, resulting in significant losses in crystallinity and specific surface area. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem of reduced crystallinity and specific surface area when preparing FAU structured molecular sieves with a high silicon-to-aluminum ratio in the prior art, and to provide a method for preparing FAU structured molecular sieves that can simultaneously obtain FAU structured molecular sieves with a high silicon-to-aluminum ratio, high crystallinity and specific surface area, and high mesopore volume.

[0007] After conducting in-depth research on the preparation method of FAU structured molecular sieves with high silicon-to-aluminum ratio, the inventors of this invention unexpectedly discovered that by using a combination of fluorosilicic acid and organic acid as a dealuminating agent, the silicon-to-aluminum ratio can be increased without affecting the framework structure of the molecular sieve. Subsequently, pore-expanding treatment with alkali can be performed to obtain FAU structured molecular sieves with high silicon-to-aluminum ratio, high crystallinity and specific surface area, and high mesopore volume.

[0008] To achieve the above objectives, the present invention provides a method for preparing FAU-structured molecular sieves, the method comprising the following steps:

[0009] (1) Na-FAU molecular sieve is subjected to a first ion exchange with ammonium salt; in the first ion exchange, the weight ratio of Na-FAU molecular sieve to ammonium salt and water on a dry basis is 1:0.4 to 1:5 to 10, and the value of the first ion exchange solution is 3 to 4.5.

[0010] (2) The product obtained in step (1) is filtered, washed, and first calcined to obtain a calcined molecular sieve;

[0011] (3) The bismuth molecular sieve obtained in step (2) is subjected to a second ion exchange with ammonium salt; in the second ion exchange, the weight ratio of bismuth molecular sieve to ammonium salt and water on a dry basis is 1:0.1-0.4:5-10, and the pH value of the second ion exchange solution is 2.5-3.5.

[0012] (4) The product obtained in step (3) is filtered, washed, and calcined a second time to obtain a double-calcined molecular sieve.

[0013] (5) The bis(4) molecular sieve obtained in step (4) is treated with fluorosilicic acid and organic acid, then filtered and washed; in the acid treatment, the weight ratio of the bis(4) molecular sieve to fluorosilicic acid, organic acid and water on a dry basis is 1:0.01~0.1:0.05~0.25:5~10, and the pH value of the acid treatment solution is 1.6~2.6;

[0014] (6) The molecular sieve obtained in step (5) is treated with sodium hydroxide solution, then filtered and washed;

[0015] (7) After treating the molecular sieve obtained in step (6) with an ammonium salt solution, filter and wash to obtain the FAU structure molecular sieve product.

[0016] Preferably, the FAU structured molecular sieve is a Y-type molecular sieve.

[0017] Preferably, in steps (1), (3) and / or (7), the ammonium salt is selected from one or more of ammonium sulfate, ammonium chloride, ammonium oxalate, ammonium fluoride, ammonium fluorosilicate, and ammonium fluoroborate.

[0018] Preferably, in steps (1), (3), and / or (5), the pH values ​​of the first ion exchange solution, the second ion exchange solution, and the acid treatment solution are adjusted using an inorganic acid. More preferably, the inorganic acid is selected from one or more of hydrochloric acid, sulfuric acid, and nitric acid.

[0019] Preferably, in step (1), the temperature of the first ion exchange is 70-95°C and the time is 0.5h or more.

[0020] Preferably, in step (2), the conditions for the first calcination include: a temperature of 350 to 650°C, a steam atmosphere of 1 to 100%, and a time of 0.5 hours or more.

[0021] Preferably, in step (3), the temperature of the second ion exchange is 50-90°C and the time is 0.5h or more.

[0022] Preferably, in step (4), the conditions for the second calcination include: a temperature of 350-650°C, a steam atmosphere of 1-100%, and a time of 0.5 hours or more.

[0023] Preferably, in step (5), the acid treatment temperature is 50-90°C and the time is 0.5h or more.

[0024] Preferably, in step (5), the organic acid is selected from one or more of ethylenediaminetetraacetic acid, oxalic acid, citric acid, and sulfosalicylic acid.

[0025] Preferably, in step (6), the weight ratio of molecular sieve to sodium hydroxide and water on a dry basis is 1:0.02-0.3:5-10; more preferably, the sodium hydroxide solution treatment temperature is 50-90°C and the time is 0.5h or more.

[0026] Preferably, in step (7), the weight ratio of molecular sieve to ammonium salt and water on a dry basis is 1:0.1-0.4:5-10; more preferably, the temperature of the ammonium salt solution treatment is 50-90°C and the time is 0.5h or more.

[0027] A second aspect of the present invention provides an FAU-structured molecular sieve prepared using the preparation method of the present invention described above.

[0028] Through the above technical solution, this invention employs a combination of fluorosilicic acid and organic acids to perform dealumination modification on molecular sieves. Simultaneously, an inorganic acid is used to adjust the pH of the system, which better preserves the integrity of the framework during dealumination and constructs a partial mesoporous structure. This facilitates further adjustment of the mesopore volume through subsequent alkaline treatment under mild conditions. Compared with molecular sieves provided by existing technologies, this invention achieves higher crystallinity, higher specific surface area, and larger mesopore volume while maintaining the same silicon-to-aluminum ratio. The preparation method of this invention is simple to operate and can yield FAU-structured molecular sieves with high silicon-to-aluminum ratio, high crystallinity, and high specific surface area. Detailed Implementation

[0029] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0030] The present invention provides a method for preparing FAU-structured molecular sieves, which includes the following steps:

[0031] (1) Na-FAU molecular sieve is subjected to a first ion exchange with ammonium salt; in the first ion exchange, the weight ratio of Na-FAU molecular sieve to ammonium salt and water on a dry basis is 1:0.4 to 1:5 to 10, and the value of the first ion exchange solution is 3 to 4.5.

[0032] (2) The product obtained in step (1) is filtered, washed, and first calcined to obtain a calcined molecular sieve;

[0033] (3) The bismuth molecular sieve obtained in step (2) is subjected to a second ion exchange with ammonium salt; in the second ion exchange, the weight ratio of bismuth molecular sieve to ammonium salt and water on a dry basis is 1:0.1-0.4:5-10, and the pH value of the second ion exchange solution is 2.5-3.5.

[0034] (4) The product obtained in step (3) is filtered, washed, and calcined a second time to obtain a double-calcined molecular sieve.

[0035] (5) The bis(4) molecular sieve obtained in step (4) is treated with fluorosilicic acid and organic acid, then filtered and washed; in the acid treatment, the weight ratio of the bis(4) molecular sieve to fluorosilicic acid, organic acid and water on a dry basis is 1:0.01~0.1:0.05~0.25:5~10, and the pH value of the acid treatment solution is 1.6~2.6;

[0036] (6) The molecular sieve obtained in step (5) is treated with sodium hydroxide solution, then filtered and washed;

[0037] (7) After treating the molecular sieve obtained in step (6) with an ammonium salt solution, filter and wash to obtain the FAU structure molecular sieve product.

[0038] In this invention, the FAU-structured molecular sieve is a Y-type molecular sieve. Na-FAU molecular sieves are not particularly limited and can be prepared using conventional methods or commercially available.

[0039] According to the present invention, in step (1), the ammonium salt may be one or more selected from ammonium sulfate, ammonium chloride, ammonium oxalate, ammonium fluoride, ammonium fluorosilicate, and ammonium fluoroborate. Preferably, in the first ion exchange, the weight ratio of Na-FAU molecular sieve to ammonium salt and water on a dry basis is 1:0.6-0.8:7-9. Preferably, the pH value of the first ion exchange solution is 3.2-3.7. The pH value of the first ion exchange solution is adjusted by an inorganic acid, which may be one or more selected from hydrochloric acid, sulfuric acid, and nitric acid, preferably sulfuric acid. As conditions for the first ion exchange, the temperature may be 70-95°C, preferably 80-85°C, and the time may be 0.5h or more, preferably 0.5-2h.

[0040] According to the present invention, in step (2), the conditions for the first calcination include: a temperature of 350-650°C, a water vapor atmosphere of 1-100%, and a time of 0.5h or more; preferably, a temperature of 500-600°C, a water vapor atmosphere of 90-100%, and a time of 1-5h.

[0041] According to the present invention, in step (3), the ammonium salt may be one or more selected from ammonium sulfate, ammonium chloride, ammonium oxalate, ammonium fluoride, ammonium fluorosilicate, and ammonium fluoroborate. Preferably, the weight ratio of the methoxymethylene molecular sieve to the ammonium salt and water on a dry basis is 1:0.25-0.4:7-9. Preferably, the pH value of the second ion exchange solution is 2.8-3.2. The pH value of the second ion exchange solution is obtained by adjusting with an inorganic acid, which may be one or more selected from hydrochloric acid, sulfuric acid, and nitric acid, preferably sulfuric acid. As conditions for the second ion exchange, the temperature may be 50-90°C, preferably 80-85°C, and the time may be 0.5 h or more, preferably 0.5-2 h.

[0042] According to the present invention, in step (4), the conditions for the second calcination include: a temperature of 350-650°C, a steam atmosphere of 1-100% and a time of 0.5h or more; preferably, a temperature of 500-600°C, a steam atmosphere of 90-100% and a time of 1-5h.

[0043] According to the present invention, in step (5), the organic acid is selected from one or more of ethylenediaminetetraacetic acid, oxalic acid, citric acid, and sulfosalicylic acid. Preferably, the weight ratio of the dimethicone molecular sieve to fluorosilicic acid, organic acid, and water on a dry basis is 1:0.04-0.08:0.15-0.25:7-9. Preferably, the pH value of the acid treatment solution is 1.9-2.1. The pH value of the acid treatment solution is adjusted by an inorganic acid, which can be one or more selected from hydrochloric acid, sulfuric acid, and nitric acid, preferably sulfuric acid. As for the acid treatment conditions, the temperature can be 50-90°C, preferably 75-85°C, and the time can be 0.5h or more, preferably 0.5-2h.

[0044] According to the present invention, in step (6), during the sodium hydroxide solution treatment, the weight ratio of molecular sieve to sodium hydroxide and water (on a dry basis) can be 1:0.02-0.3:5-10, preferably 1:0.04-0.1:7-9. The conditions for the sodium hydroxide solution treatment are a temperature of 50-90°C, preferably 75-85°C, and a time of 0.5 h or more, preferably 0.5-2 h.

[0045] According to the present invention, in step (7), the ammonium salt may be one or more selected from ammonium sulfate, ammonium chloride, ammonium oxalate, ammonium fluoride, ammonium fluorosilicate, and ammonium fluoroborate. In the ammonium salt treatment, the weight ratio of molecular sieve to ammonium salt and water (dry basis) may be 1:0.1–0.4:5–10, preferably 1:0.2–0.3:7–9. As for the conditions for ammonium salt solution treatment, the temperature is 50–90°C, preferably 75–85°C, and the time is 0.5 h or more, preferably 0.5–2 h.

[0046] In this invention, the method of filtering and washing the molecular sieve is not particularly limited, and any conditions commonly used for the treatment of FAU structure molecular sieves can be adopted. The washing temperature is preferably above 50°C, for example, 50 to 70°C.

[0047] In addition, in order to improve the effectiveness of the first ion exchange, the second ion exchange, acid treatment, sodium hydroxide solution treatment, and ammonium salt solution treatment, the molecular sieve and the corresponding treatment solution are brought into contact under stirring conditions during the above treatment processes.

[0048] A second aspect of the present invention provides an FAU-structured molecular sieve prepared using the preparation method of the present invention described above.

[0049] By employing the method of the present invention described above, FAU-structured molecular sieves possessing high silica-to-alumina ratio, high crystallinity, and high specific surface area can be obtained. Specifically, the FAU-structured molecular sieve of the present invention can achieve a silica-to-alumina ratio of 13.0 or higher, a crystallinity of 69% or higher, and a specific surface area of ​​698 m². 2 / g or higher, the mesoporous specific surface area can reach 118m² 2 / g or more.

[0050] The present invention will be described in detail below through examples. In the present invention, crystallinity is determined using the standard method of RIPP145-90; n(SiO2) / n(Al2O3), i.e., the silicon-aluminum ratio, is calculated from the content of silicon oxide and aluminum oxide, and the content of silicon oxide and aluminum oxide is determined using the standard method of GB / T 30905-2014; specific surface area is determined using the standard method of GB5816; pore volume is determined using the standard method of GB5816.

[0051] Example 1

[0052] 100g of NaY molecular sieve (produced by Qilu Branch of Catalyst Company, on a dry basis) was mixed with ammonium sulfate and water at a weight ratio of NaY molecular sieve:ammonium sulfate:water = 1:0.7:8. The mixture was stirred until homogeneous, and the pH of the slurry was adjusted to 3.7 with a 20% sulfuric acid solution. The mixture was heated to 80℃ and stirred at this temperature for 0.5h, then filtered and washed with water. The resulting product was calcined at 560℃ under a 100% steam atmosphere for 1h to obtain a mono-calcined molecular sieve. This mono-calcined molecular sieve was then mixed with ammonium sulfate at a weight ratio of 1:0.3:8, and the pH was adjusted to 3.0 with sulfuric acid. The mixture was heated to 80℃ and stirred at this temperature for 0.5h, then filtered and washed with 50℃ washing water. The resulting product was calcined at 560℃ under a 100% steam atmosphere for 1h to obtain a di-calcined molecular sieve. The obtained dibaked molecular sieve was mixed with fluorosilicic acid and oxalic acid in a weight ratio of dibaked molecular sieve:fluorosilicic acid:oxalic acid:water = 1:0.05:0.15:8. The pH was adjusted to 2.0 with sulfuric acid, and the mixture was heated to 80℃ and stirred at a constant temperature for 0.5 h. The mixture was then filtered and washed with 50℃ washing water. The resulting molecular sieve was then slurried with water, and sodium hydroxide was added in a ratio of molecular sieve:sodium hydroxide:water = 1:0.10:8. The mixture was heated to 80℃ and stirred at a constant temperature for 0.5 h. The mixture was then filtered and washed. Finally, the resulting molecular sieve was mixed with ammonium sulfate in a weight ratio of molecular sieve:ammonium sulfate:water = 1:0.3:8. The mixture was heated to 80℃ and stirred at a constant temperature for 0.5 h. The mixture was then filtered and washed to obtain the modified molecular sieve HMY-1. The physicochemical properties of the molecular sieve are listed in Table 1.

[0053] Example 2

[0054] 100g of NaY molecular sieve (produced by Qilu Branch of Catalyst Company, on a dry basis) was mixed with ammonium sulfate and water at a weight ratio of NaY molecular sieve:ammonium sulfate:water = 1:0.6:9. The mixture was stirred until homogeneous, and the pH of the slurry was adjusted to 3.5 with a 20% sulfuric acid solution. The mixture was heated to 85℃ and stirred at this temperature for 0.5h, then filtered and washed with water. The resulting product was calcined at 500℃ under a 100% steam atmosphere for 2h to obtain a bis-calcined molecular sieve. This bis-calcined molecular sieve was then mixed with ammonium sulfate at a weight ratio of 1:0.4:8, and the pH was adjusted to 3.2 with sulfuric acid. The mixture was heated to 85℃ and stirred at this temperature for 0.5h, then filtered and washed with 50℃ washing water. The resulting product was calcined at 500℃ under a 100% steam atmosphere for 2h to obtain a di-calcined molecular sieve. The obtained dibaked molecular sieve was mixed with fluorosilicic acid and citric acid in a weight ratio of dibaked molecular sieve:fluorosilicic acid:citric acid:water = 1:0.04:0.18:8. The pH was adjusted to 2.1 with sulfuric acid, and the mixture was heated to 85℃ and stirred at a constant temperature for 0.5 h. The mixture was then filtered and washed with 50℃ washing water. The resulting molecular sieve was then slurried with water, and sodium hydroxide was added in a ratio of molecular sieve:sodium hydroxide:water = 1:0.07:8. The mixture was heated to 80℃ and stirred at a constant temperature for 0.5 h. The mixture was then filtered and washed. Finally, the resulting molecular sieve was mixed with ammonium sulfate in a weight ratio of molecular sieve:ammonium sulfate:water = 1:0.25:8. The mixture was heated to 85℃ and stirred at a constant temperature for 0.5 h. The mixture was then filtered and washed to obtain the modified molecular sieve HMY-2. The physicochemical properties of the molecular sieve are listed in Table 1.

[0055] Example 3

[0056] 100g of NaY molecular sieve (produced by Qilu Branch of Catalyst Company, on a dry basis) was mixed with ammonium sulfate and water at a weight ratio of NaY molecular sieve:ammonium sulfate:water = 1:0.8:8. The mixture was stirred until homogeneous. The pH of the slurry was adjusted to 3.2 with a 20% sulfuric acid solution. The mixture was heated to 80℃ and stirred at this temperature for 0.5h. The mixture was then filtered and washed with water. The resulting product was calcined at 560℃ under a 100% steam atmosphere for 1h to obtain a mono-calcined molecular sieve. This mono-calcined molecular sieve was then mixed with ammonium sulfate at a weight ratio of 1:0.25:8. The pH was adjusted to 2.8 with an inorganic acid. The mixture was heated to 80℃ and stirred at this temperature for 0.5h. The mixture was then filtered and washed with 50℃ washing water. The resulting product was calcined at 600℃ under a 100% steam atmosphere for 2h to obtain a di-calcined molecular sieve. The obtained dibaked molecular sieve was mixed with fluorosilicic acid and ethylenediaminetetraacetic acid (EDTA) at a weight ratio of 1:0.08:0.25:8. The pH was adjusted to 1.9 with sulfuric acid, and the mixture was heated to 75°C and stirred for 0.5 h. The mixture was then filtered and washed with 50°C washing water. The resulting molecular sieve was then slurried with water, and sodium hydroxide was added at a ratio of 1:0.04:8. The mixture was heated to 80°C and stirred for 0.5 h. The mixture was then filtered and washed. Finally, the resulting molecular sieve was mixed with ammonium sulfate at a weight ratio of 1:0.2:8. The mixture was heated to 75°C and stirred for 0.5 h. The mixture was then filtered and washed to obtain the modified molecular sieve HMY-3. The physicochemical properties of the molecular sieve are listed in Table 1.

[0057] Example 4

[0058] The modified molecular sieve was prepared according to the method of Example 1, except that the obtained dibaked molecular sieve was mixed with fluorosilicic acid and oxalic acid in a weight ratio of dibaked molecular sieve: fluorosilicic acid: oxalic acid: water = 1:0.03:0.17:8 to obtain the modified molecular sieve HMY-4. The physicochemical properties of the molecular sieve are listed in Table 1.

[0059] Example 5

[0060] The modified molecular sieve was prepared according to the method in Example 3, except that the obtained dibaked molecular sieve was mixed with fluorosilicic acid and ethylenediaminetetraacetic acid in a weight ratio of dibaked molecular sieve: fluorosilicic acid: ethylenediaminetetraacetic acid: water = 1:0.08:0.15:8 to obtain the modified molecular sieve HMY-5. The physicochemical properties of the molecular sieve are listed in Table 1.

[0061] Example 6

[0062] The modified molecular sieve was prepared according to the method of Example 1, except that the obtained dibaked molecular sieve was mixed with fluorosilicic acid and oxalic acid in a weight ratio of dibaked molecular sieve: fluorosilicic acid: oxalic acid: water = 1:0.02:0.15:8 to obtain the modified molecular sieve HMY-6. The physicochemical properties of the molecular sieve are listed in Table 1.

[0063] Comparative Example 1

[0064] 100g of NaY molecular sieve (produced by Qilu Branch of Catalyst Company, on a dry basis) was mixed with ammonium sulfate and water at a weight ratio of NaY molecular sieve:ammonium sulfate:water = 1:0.7:8. The mixture was stirred until homogeneous, heated to 80℃ and stirred at a constant temperature for 0.5h, then filtered and washed with water. The resulting product was calcined at 560℃ under a 100% steam atmosphere for 1h to obtain a bis-calcined molecular sieve. Then, it was mixed with ammonium sulfate at a weight ratio of bis-calcined molecular sieve:ammonium sulfate:water = 1:0.3:8. The pH was adjusted to 3.0 with sulfuric acid, heated to 80℃ and stirred at a constant temperature for 0.5h, then filtered and washed with washing water at a temperature ≥50℃. The resulting product was calcined at 560℃ under a 100% steam atmosphere for 1h to obtain a di-calcined molecular sieve. The obtained dibaked molecular sieve was mixed with fluorosilicic acid at a weight ratio of dibaked molecular sieve:fluorosilicic acid:water = 1:0.15:8. The pH was adjusted to 2.0 with sulfuric acid, and the mixture was heated to 80℃ and stirred at a constant temperature for 0.5 h. The mixture was then filtered and washed with 50℃ washing water. The resulting molecular sieve was then slurried with water, and sodium hydroxide was added at a ratio of molecular sieve:sodium hydroxide:water = 1:0.10:8. The mixture was heated to 80℃ and stirred at a constant temperature for 0.5 h. The mixture was then filtered and washed. Finally, the resulting molecular sieve was mixed with ammonium sulfate at a weight ratio of molecular sieve:ammonium sulfate:water = 1:0.3:8. The mixture was heated to 80℃ and stirred at a constant temperature for 0.5 h. The mixture was then filtered and washed to obtain modified molecular sieve DY-1. The physicochemical properties of the molecular sieve are listed in Table 1.

[0065] Comparative Example 2

[0066] 100g of NaY molecular sieve (produced by Qilu Branch of Catalyst Company, on a dry basis) was mixed with ammonium sulfate and water at a weight ratio of NaY molecular sieve:ammonium sulfate:water = 1:0.6:9. The mixture was stirred until homogeneous, heated to 85℃ and stirred at a constant temperature for 0.5h, then filtered and washed with water. The resulting product was calcined at 500℃ under a 100% steam atmosphere for 2h to obtain a bis-calcined molecular sieve. This bis-calcined molecular sieve was then mixed with ammonium sulfate at a weight ratio of bis-calcined molecular sieve:ammonium sulfate:water = 1:0.4:8. The pH was adjusted to 3.2 with sulfuric acid, and the mixture was heated to 85℃ and stirred at a constant temperature for 0.5h. The mixture was then filtered and washed with washing water at 50℃. The resulting product was calcined at 500℃ under a 100% steam atmosphere for 2h to obtain a di-calcined molecular sieve. The obtained dibaked molecular sieve was mixed with citric acid and water at a weight ratio of 1:0.24:8. The pH was adjusted to 2.3 with sulfuric acid, and the mixture was heated to 85℃ and stirred at a constant temperature for 0.5 h. The mixture was then filtered and washed with 50℃ water. The resulting molecular sieve was then slurried with water and sodium hydroxide was added at a ratio of 1:0.07:8. The mixture was heated to 80℃ and stirred at a constant temperature for 0.5 h. The mixture was then filtered and washed. Finally, the resulting molecular sieve was mixed with ammonium sulfate at a weight ratio of 1:0.25:8. The mixture was heated to 85℃ and stirred at a constant temperature for 0.5 h. The mixture was then filtered and washed to obtain the modified molecular sieve DY-2. The physicochemical properties of the molecular sieve are listed in Table 1.

[0067] Comparative Example 3

[0068] Modified molecular sieves were prepared according to the method in Example 1, except that only fluorosilicic acid was used in the acid treatment. Specifically, the resulting bis(calcined) molecular sieve was mixed with fluorosilicic acid at a weight ratio of bis(calcined) molecular sieve: fluorosilicic acid: water = 1:0.05:8 to obtain modified molecular sieve DY-3. The physicochemical properties of the molecular sieves are characterized in Table 1.

[0069] Comparative Example 4

[0070] Modified molecular sieves were prepared according to the method in Example 1, except that only oxalic acid was used in the acid treatment. Specifically, the resulting dibaked molecular sieve was mixed with oxalic acid at a weight ratio of dibaked molecular sieve: oxalic acid: water = 1:0.15:8 to obtain modified molecular sieve DY-4. The physicochemical properties of the molecular sieve are listed in Table 1.

[0071] Table 1

[0072]

[0073] Table 1 (continued)

[0074]

[0075] As can be seen from the results in Table 1, compared with the comparative example, the embodiments of the present invention can maintain high crystallinity and obtain more abundant mesopores under conditions of higher silicon-to-aluminum ratio.

[0076] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A process for the preparation of a FAU structure molecular sieve, characterized by, The preparation method comprises the following steps: (1) performing first ion exchange on the Na-FAU molecular sieve and an ammonium salt; in the first ion exchange, the weight ratio of the Na-FAU molecular sieve to the ammonium salt and water is 1:0.4-1:5-10 on a dry basis, and the pH value of the first ion exchange solution is 3-4.5; (2) filtering, washing and performing first calcination on the product obtained in step (1) to obtain a calcined molecular sieve; (3) performing second ion exchange on the calcined molecular sieve obtained in step (2) and an ammonium salt; in the second ion exchange, the weight ratio of the calcined molecular sieve to the ammonium salt and water is 1:0.1-0.4:5-10 on a dry basis, and the pH value of the second ion exchange solution is 2.5-3.5; (4) filtering, washing and performing second calcination on the product obtained in step (3) to obtain a second calcined molecular sieve; (5) after the second calcined molecular sieve obtained in step (4) is subjected to acid treatment with fluosilicic acid and an organic acid, filtering and washing; in the acid treatment, the weight ratio of the second calcined molecular sieve to the fluosilicic acid, the organic acid and water is 1:0.01-0.1:0.05-0.25:5-10 on a dry basis, and the pH value of the acid treatment solution is 1.6-2.6; (6) after the molecular sieve obtained in step (5) is treated with a sodium hydroxide solution, filtering and washing; (7) after the molecular sieve obtained in step (6) is treated with an ammonium salt solution, filtering and washing to obtain a FAU structure molecular sieve product.

2. The production method according to claim 1, wherein, The FAU structure molecular sieve is a Y-type molecular sieve.

3. The production method according to claim 1, wherein The ammonium salt is selected from one or more of ammonium chloride, ammonium sulfate, ammonium oxalate, ammonium fluoride, ammonium fluosilicate and ammonium fluoroborate.

4. The production method according to any one of claims 1 to 3, wherein In step (5), the organic acid is selected from one or more of ethylenediaminetetraacetic acid, oxalic acid, citric acid and sulfosalicylic acid.

5. The production method according to any one of claims 1 to 3, wherein An inorganic acid is used to adjust the pH values of the first ion exchange solution, the second ion exchange solution and the acid treatment solution.

6. The production method according to claim 5, wherein The inorganic acid is selected from one or more of hydrochloric acid, sulfuric acid and nitric acid.

7. The production method according to any one of claims 1 to 3, wherein In step (2), the first calcination is performed under the following conditions: a temperature of 350-650 ℃, a 1-100% water vapor atmosphere and a time of 0.5 h or more.

8. The production method according to any one of claims 1 to 3, wherein In step (4), the second calcination is performed under the following conditions: a temperature of 350-650 ℃, a 1-100% water vapor atmosphere and a time of 0.5 h or more.

9. The production process according to any one of claims 1 to 3, wherein In step (1), the first ion exchange is performed at a temperature of 70-95 ℃ for 0.5 h or more.

10. The method of making according to any one of claims 1-3, wherein, In step (3), the second ion exchange is performed at a temperature of 50-90 ℃ for 0.5 h or more.

11. The method of making according to any one of claims 1-3, wherein, In step (5), the acid treatment is performed at a temperature of 50-90 ℃ for 0.5 h or more.

12. The method of making according to any one of claims 1-3, wherein, In step (6), the weight ratio of the molecular sieve to the sodium hydroxide and water is 1:0.02-0.3:5-10 on a dry basis.

13. The method of making according to claim 12, wherein, The sodium hydroxide solution treatment is performed at a temperature of 50-90 ℃ for 0.5 h or more.

14. The method of making according to any one of claims 1-3, wherein, In step (7), the weight ratio of the molecular sieve to the ammonium salt and water is 1:0.1-0.4:5-10 on a dry basis.

15. The method of manufacturing according to claim 14, wherein, The ammonium salt solution treatment is performed at a temperature of 50-90 ℃ for 0.5 h or more.

16. A FAU structure molecular sieve prepared by the preparation method in any one of claims 1-15.

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