Method for recycling fluorine resource and synthesizing A-type molecular sieve by using fluorine-containing silicon powder
By reacting fluorinated silica powder with sodium hydroxide and sodium aluminate to generate clear solutions and gel solutions, type A molecular sieves are synthesized. This solves the problems of low fluorine separation efficiency and impurities affecting the quality of fluorinated silica powder, and realizes the synthesis of high-purity, low-defect molecular sieves and resource recovery.
Patent Information
- Application Number
- CN202511024670.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-24
- Publication Date
- 2025-10-31
AI Technical Summary
Fluorine separation efficiency in fluorinated silicon powder is low, and impurities affect the quality of molecular sieves, leading to environmental pollution and resource waste.
Fluorinated silica powder was mixed with sodium hydroxide solution and heated to produce a clear solution and sodium fluoride precipitate. The solution was then mixed with sodium aluminate alkaline solution to form a gel solution, which was then heated to crystallize, resulting in low-modulus sodium silicate gel. After filtration and drying, type A molecular sieves were synthesized.
It significantly improves the efficiency of fluorine-silicon separation, removes organic impurities, and produces high-purity A-type molecular sieves with fewer crystal defects, thus enabling effective resource utilization and reducing environmental pollution.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of fluorine-containing chemical technology, and in particular relates to a method for recovering fluorine resources and synthesizing type A molecular sieves using fluorine-containing silicon powder. Background Technology
[0002] my country's fluorite (calcium fluoride) is the source of fluorochemicals, but its resources are nearly depleted due to years of mining. Phosphate rock contains nearly 90% of the world's fluorine reserves, making fluorine recovery from phosphate rock extremely valuable. Recovering fluorine from phosphoric acid is the primary method for fluorine recovery from phosphate rock. Statistics show that the world currently produces approximately 40 million tons of phosphate fertilizer, consuming over 100 million tons of phosphate rock raw materials and generating about 1.3 million tons of fluorine-containing byproducts. The fluorine in these byproducts is mainly recovered as fluorosilicic acid. Further processing of fluorosilicic acid into fluorochemical products, such as anhydrous hydrogen fluoride, produces a large amount of fluorinated silicon powder. Fluorinated silicon powder is a new type of solid waste, containing approximately 55% water, 35% silicon dioxide, and 10% fluorine. Fluorinated silicon powder is corrosive; direct discharge or large-scale stockpiling will cause serious environmental pollution. Furthermore, the abundant fluorine and silicon resources it contains are not effectively utilized, representing a significant waste.
[0003] Type A (NaA) molecular sieve (Na 12 [(AlO2) 12 (SiO2) 12 The pore size of ]·27H2O is Type A molecular sieves adsorb water, formaldehyde, ethanol, hydrogen sulfide, and carbon dioxide. Their selective adsorption of water is higher than any other molecule, and they can also absorb smaller molecules. They are one of the most widely used molecular sieve varieties in industry, possessing high economic value and demand. Industrial Type A molecular sieves are produced from silicon sources, aluminum sources, and sodium hydroxide through aging, crystallization, filtration, washing, and drying. Fluorinated silicon powder has a high silicon content and theoretically can be used as a raw material for synthesizing Type A molecular sieves. However, the conveyor belts used in the production of fluorinated silicon powder operate for extended periods, generating significant friction and wear. The resulting debris easily accumulates on the conveyor belt surface, forming black particles. These black particles mix with the fluorinated silicon powder as impurities, affecting its quality. Furthermore, the low fluorine separation efficiency in fluorinated silicon powder negatively impacts the quality of the molecular sieve. Summary of the Invention
[0004] The purpose of this invention is to provide a method for recovering fluorine resources and synthesizing type A molecular sieves using fluorinated silica powder. The method of this invention utilizes fluorinated silica powder to recover fluorine resources and simultaneously synthesizes type A molecular sieves with low impurity content and pure phase.
[0005] This invention provides a method for recovering fluorine resources and synthesizing type A molecular sieves using fluorine-containing silica powder, comprising the following steps:
[0006] A) Fluorine-containing silicon powder is mixed with sodium hydroxide solution and heated to react, resulting in a clear solution and sodium fluoride precipitate.
[0007] The silicon and sodium in the clarified solution are calculated as SiO2 and Na2O, with a molar ratio of SiO2 to Na2O of 1.9 to 2.4.
[0008] B) Mix sodium aluminate with sodium hydroxide solution to obtain an alkaline solution of sodium aluminate. Mix the clarified solution from step A) with the alkaline solution of sodium aluminate and stir to obtain a gel solution.
[0009] C) The gel solution is heated and crystallized to obtain type A molecular sieve.
[0010] Preferably, the fluorinated silicon powder is a byproduct of the production of anhydrous hydrogen fluoride using the fluorosilicic acid sulfuric acid process.
[0011] Preferably, the mass concentration of the sodium hydroxide solution in step A) is 35-38%;
[0012] In step A), the mass ratio of fluorinated silicon powder to sodium hydroxide solution is 1:(1.13-1.18).
[0013] Preferably, the heating reaction temperature in step A) is 90–100°C, and the heating reaction time is 4–8 hours.
[0014] Preferably, the molar ratio of SiO2 to Al2O3 in the gel solution is 2.00 to 2.44.
[0015] Preferably, the Na2O / SiO2 molar ratio in the gel solution is 1.00 to 1.74.
[0016] Preferably, the molar ratio of H2O to Na2O in the gel solution is 32 to 60.
[0017] Preferably, the temperature for heating and crystallization in step C) is 80–100°C, and the heating and crystallization time is 3–4 hours.
[0018] Preferably, in step A), after the heating reaction is completed, the mixture is filtered to obtain a clear solution and a precipitate. The precipitate is dried at 95–105°C to obtain sodium fluoride.
[0019] Preferably, in step C), after the heating and crystallization is completed, the solid product is filtered, washed until the pH is 9-11, and then dried at 100-105°C for 1-3 hours to obtain type A molecular sieve.
[0020] This invention provides a method for recovering fluorine resources and synthesizing type A molecular sieves using fluorinated silica powder, comprising the following steps: A) mixing fluorinated silica powder with sodium hydroxide solution and heating to react, obtaining a clear solution and a precipitate of sodium fluoride; the silicon and sodium in the clear solution are calculated as SiO2 and Na2O, and the molar ratio of SiO2 to Na2O is 1.9 to 2.4; B) mixing sodium aluminate with sodium hydroxide solution to obtain an alkaline solution of sodium aluminate, mixing the clear solution from step A) with the alkaline solution of sodium aluminate, and stirring to obtain a gel solution; C) heating the gel solution to crystallize, obtaining type A molecular sieves. This invention utilizes fluorinated silicate powder to prepare a low-modulus sodium silicate gel solution, resulting in a significantly reduced residual fluorine content (<0.68 wt%), thus significantly improving the fluorine-silicon separation efficiency. Organic impurities introduced into the fluorinated silicate powder by the conveyor belt will enter the sodium fluoride precipitate phase during the solid-liquid separation of the sodium silicate solution and the sodium fluoride precipitate (which can be removed by calcination later), without affecting the quality of the synthesized 4A molecular sieve powder. The small amount of residual fluorine in the sodium silicate gel solution can act as a structure-directing agent and electron balancer, which is beneficial for obtaining 4A molecular sieves with fewer crystal defects. This invention, through the preparation of low-modulus sodium silicate, filtration separation, and the removal of residual fluorine in the sodium silicate gel, achieves the removal of organic impurities from fluorinated silicate powder, efficient separation of fluorine and silicon, and the synthesis of high-purity, low-crystal-defect 4A molecular sieves. Attached Figure Description
[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0022] Figure 1 This is a process flow diagram of the present invention for recovering fluorine resources and synthesizing type A molecular sieves using fluorine-containing silicon powder;
[0023] Figure 2 Photograph (a) and XRD phase diagram of fluorinated silicon powder;
[0024] Figure 3 The XRD patterns of type A molecular sieves synthesized in Examples 1-6 of this invention are shown below.
[0025] Figure 4 This is a SEM image of the type A molecular sieve of Example 1 of the present invention;
[0026] Figure 5 This is a SEM image of the type A molecular sieve in Example 2 of the present invention;
[0027] Figure 6 This is a SEM image of the type A molecular sieve in Example 3 of the present invention;
[0028] Figure 7 This is a SEM image of the type A molecular sieve in Example 4 of the present invention;
[0029] Figure 8 This is a SEM image of the type A molecular sieve in Example 5 of the present invention;
[0030] Figure 9 This is a SEM image of the type A molecular sieve in Example 6 of the present invention. Detailed Implementation
[0031] This invention provides a method for recovering fluorine resources and synthesizing type A molecular sieves using fluorine-containing silica powder, comprising the following steps:
[0032] A) Fluorine-containing silicon powder is mixed with sodium hydroxide solution and heated to react, resulting in a clear solution and sodium fluoride precipitate.
[0033] The silicon and sodium in the clarified solution are calculated as SiO2 and Na2O, with a molar ratio of SiO2 to Na2O of 1.6 to 2.4.
[0034] B) Mix sodium aluminate with sodium hydroxide solution to obtain an alkaline solution of sodium aluminate. Mix the clarified solution from step A) with the alkaline solution of sodium aluminate and stir to obtain a gel solution.
[0035] C) The gel solution is heated and crystallized to obtain type A molecular sieve.
[0036] In this invention, the fluorinated silicon powder is preferably a byproduct of the production of anhydrous hydrogen fluoride by the fluorosilicic acid sulfuric acid process. The content of fluorine and silicon in the fluorinated silicon powder is not particularly limited. In one embodiment of this invention, the mass fraction of silicon dioxide in the fluorinated silicon powder is preferably 30-40%, more preferably 35-38%, and the mass fraction of F is preferably 8-10%, more preferably 9-10%.
[0037] In this invention, the mass concentration of the sodium hydroxide solution is preferably 35-38%, more preferably 36-37%, such as 35%, 36%, 37%, 38%, preferably within the range of any of the above values as the upper or lower limit. The mass ratio of the fluorinated silicon powder to the sodium hydroxide solution is preferably 1:(1.13-1.18), more preferably 1:(1.15-1.16), such as 1:1.13, 1:1.14, 1:1.15, 1:1.16, 1:1.17, 1:1.18, preferably within the range of any of the above values as the upper or lower limit. In the range of sodium hydroxide solution provided by this invention, sodium hydroxide is in excess, which can ensure complete fluorine precipitation and reaction with amorphous silicon dioxide.
[0038] In this invention, the temperature of the heating reaction is preferably 90-100°C, more preferably 92-98°C, such as 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, preferably within a range where any of the above values is the upper or lower limit; the heating reaction time is preferably 4-8 hours, more preferably 5-6 hours, and the heating reaction is preferably carried out under stirring conditions.
[0039] In this invention, after the heating reaction is completed, the reaction product is allowed to stand and filtered to obtain a clear solution and a precipitate. The precipitate is dried to obtain sodium fluoride, thus achieving efficient recovery of fluorine resources. The fluorine recovery rate in this invention is 98.6% to 99.8%.
[0040] In this invention, the drying temperature is preferably 95-105°C, more preferably 100-102°C.
[0041] In this invention, the clarified solution is a sodium silicate solution, and the modulus of sodium silicate is 1.9 to 2.4, more preferably 1.9 to 2.3.
[0042] In this invention, sodium aluminate and sodium hydroxide solution are mixed to obtain an aluminum source solution, and then the clarified solution is added to the aluminum source solution and stirred continuously to obtain a gel solution.
[0043] In this invention, sodium hydroxide is first dissolved in water to prepare a sodium hydroxide solution. The mass concentration of the sodium hydroxide solution is preferably 35-38%, more preferably 36-37%, such as 35%, 36%, 37%, or 38%, and preferably within a range where any of the above values is the upper or lower limit. In this invention, the molar ratio of SiO2 to Al2O3 in the gel solution is preferably 2.00-2.44, more preferably 2.1-2.4, such as 2.00 or 2.0. The values are preferably within the range of 5, 2.10, 2.15, 2.20, 2.25, 2.30, 2.35, 2.40, and 2.44, with any of the above values as the upper or lower limit. The molar ratio of Na₂O to SiO₂ is preferably 1.00–1.74, and the molar ratio of H₂O to Na₂O is preferably 32–60, more preferably 40–55, such as 32, 35, 40, 45, 50, 55, and 60, with any of the above values as the upper or lower limit. The amounts of sodium hydroxide, sodium aluminate, water, and the clarified solution are calculated and weighed according to the gel composition.
[0044] After obtaining sodium silicate gel, the present invention places the gel solution in a polytetrafluoroethylene reactor, and directly heats it for crystallization without aging. After the crystallization reaction is completed, it is filtered, washed until the pH value is 9-11, and then dried at 100-105℃ for 1-3 hours to obtain type A molecular sieve.
[0045] In this invention, the temperature for heating and crystallization is preferably 80-100°C, more preferably 85-95°C, such as 80°C, 85°C, 90°C, 95°C, 100°C, preferably within the range of any of the above values as the upper or lower limit, and the heating and crystallization time is preferably 3-4 hours.
[0046] This invention provides a method for recovering fluorine resources and synthesizing type A molecular sieves using fluorinated silica powder, comprising the following steps: A) mixing fluorinated silica powder with sodium hydroxide solution and heating to react, obtaining a clear solution and a precipitate of sodium fluoride. The silicon and sodium in the clear solution are calculated as SiO2 and Na2O, with a molar ratio of SiO2 to Na2O of 1.9 to 2.4; B) mixing sodium aluminate with sodium hydroxide solution to obtain an alkaline solution of sodium aluminate, mixing the clear solution from step A) with the alkaline solution of sodium aluminate, and stirring to obtain a gel solution; C) heating the gel solution to crystallize, obtaining type A molecular sieves. This invention utilizes fluorinated silicate powder to prepare a low-modulus sodium silicate gel solution, resulting in a significantly reduced residual fluorine content (<0.68 wt%), thus significantly improving the fluorine-silicon separation efficiency. Organic impurities introduced into the fluorinated silicate powder by the conveyor belt will enter the sodium fluoride precipitate phase during the solid-liquid separation of the sodium silicate solution and the sodium fluoride precipitate (which can be removed by calcination later), without affecting the quality of the synthesized 4A molecular sieve powder. The small amount of residual fluorine in the sodium silicate gel solution can act as a structure-directing agent and electron balancer, which is beneficial for obtaining 4A molecular sieves with fewer crystal defects. This invention, through the preparation of low-modulus sodium silicate, filtration separation, and the removal of residual fluorine in the sodium silicate gel, achieves the removal of organic impurities from fluorinated silicate powder, efficient separation of fluorine and silicon, and the synthesis of high-purity, low-crystal-defect 4A molecular sieves.
[0047] To further illustrate the present invention, the following describes in detail, with reference to embodiments, a method for recovering fluorine resources and synthesizing type A molecular sieves provided by the present invention, but it should not be construed as a limitation on the scope of protection of the present invention.
[0048] Example 1
[0049] (1) Recovery of fluorine resources: 197.5g of sodium hydroxide was dissolved in 367.5g of deionized water to prepare a 30% alkaline solution. Then, 500g of fluorine-containing silicon powder was mixed with 565.0g of alkaline solution and heated to 90℃. The mixture was stirred and reacted for 8h. After standing and filtration, clear solution A was obtained. The theoretical modulus of sodium silicate in clear solution A was 2.34 and the measured modulus was 2.20. Precipitate B was dried at 105℃ for 2h to obtain sodium fluoride. The fluorine recovery rate was calculated to be 99.7%.
[0050] (2) Preparation of type A molecular sieve gel solution: The gel composition is SiO2 / Al2O3 molar ratio 2.32, Na2O / SiO2 molar ratio 1.14, and H2O / Na2O molar ratio 43. Prepare a sodium hydroxide solution (1.218g NaOH + 44.59g H2O), and dissolve sodium aluminate (5.317g) in the prepared sodium hydroxide solution to obtain solution C. Add solution C to the clarified solution A (14.811g), and stir continuously to obtain type A molecular sieve gel solution.
[0051] (3) Synthesis of type A molecular sieve: The type A molecular sieve gel solution was placed in a polytetrafluoroethylene reactor and directly heated to 80°C for crystallization without aging. After crystallization for 4 hours, the solution was filtered, washed to pH 11, and dried at 105°C for 2 hours to obtain type A molecular sieve powder with a relative crystallinity of 80%.
[0052] Example 2
[0053] (1) Recovery of fluorine resources: 197.5g of sodium hydroxide was dissolved in 367.5g of deionized water to prepare a 30% alkaline solution. Then, 500g of fluorine-containing silicon powder was mixed with 565.0g of alkaline solution and heated to 95℃. The mixture was stirred continuously for 6h and then filtered to obtain a clear solution A. The theoretical modulus of sodium silicate in the clear solution A was 2.34 and the measured modulus was 2.20. Precipitate B was dried at 105℃ for 2h to obtain sodium fluoride. The fluorine recovery rate was calculated to be 99.8%.
[0054] (2) Preparation of type A molecular sieve gel solution: The gel composition is SiO2 / Al2O3 molar ratio 2.44, Na2O / SiO2 molar ratio 1.53, and H2O / Na2O molar ratio 43. Prepare a sodium hydroxide solution (3.233g NaOH + 61.44H2O), and dissolve sodium aluminate (5.044g) in the prepared sodium hydroxide solution to obtain solution C. Add solution C to the clarified solution A (14.811g), and stir continuously to obtain type A molecular sieve gel solution.
[0055] (3) Synthesis of type A molecular sieve: The type A molecular sieve gel solution was placed in a polytetrafluoroethylene reactor and directly heated to 90°C for crystallization without aging. After crystallization for 4 hours, the solution was filtered, washed to pH 10, and dried at 105°C for 2 hours to obtain type A molecular sieve powder with a relative crystallinity of 95%.
[0056] Example 3
[0057] (1) Recovery of fluorine resources: 197.5g of sodium hydroxide was dissolved in 367.5g of deionized water to prepare a 30% alkaline solution. Then, 500g of fluorine-containing silicon powder was mixed with 565.0g of alkaline solution and heated to 100℃. The mixture was stirred and reacted for 4h. After standing and filtration, clear solution A was obtained. The theoretical modulus of sodium silicate in clear solution A was 2.34 and the measured modulus was 2.20. Precipitate B was dried at 105℃ for 2h to obtain sodium fluoride. The fluorine recovery rate was calculated to be 99.6%.
[0058] (2) Preparation of type A molecular sieve gel solution: The gel composition is SiO2 / Al2O3 molar ratio 2.32, Na2O / SiO2 molar ratio 1.65, and H2O / Na2O molar ratio 43. Prepare a sodium hydroxide solution (3.138g NaOH + 61.87H2O), and dissolve sodium aluminate (5.317g) in the prepared sodium hydroxide solution to obtain solution C. Add solution C to the clarified solution A (14.811g), and continue stirring to obtain the type A molecular sieve gel solution.
[0059] (3) Synthesis of type A molecular sieve: The type A molecular sieve gel solution was placed in a polytetrafluoroethylene reactor and directly heated to 100°C for crystallization without aging. After crystallization for 3 hours, the solution was filtered, washed to pH 9, and dried at 105°C for 2 hours to obtain type A molecular sieve powder with a relative crystallinity of 102%.
[0060] Example 4
[0061] (1) Recovery of fluorine resources: 197.5g of sodium hydroxide was dissolved in 367.5g of deionized water to prepare a 30% alkaline solution. Then, 500g of fluorine-containing silicon powder was mixed with 565.0g of alkaline solution and heated to 100℃. The mixture was stirred and reacted for 4h. After standing and filtration, clear solution A was obtained. The theoretical modulus of sodium silicate in clear solution A was 2.34 and the measured modulus was 2.20. Precipitate B was dried at 105℃ for 2h to obtain sodium fluoride. The fluorine recovery rate was calculated to be 99.6%.
[0062] (2) Preparation of type A molecular sieve gel solution: The gel composition is SiO2 / Al2O3 molar ratio 2.32, Na2O / SiO2 molar ratio 1.45, and H2O / Na2O molar ratio 32. Prepare a sodium hydroxide solution (2.178g NaOH + 46.98H2O), and dissolve sodium aluminate (5.317g) in the prepared sodium hydroxide solution to obtain solution C. Add solution C to the clarified solution A (14.811g), and stir continuously to obtain type A molecular sieve gel solution.
[0063] (3) Synthesis of type A molecular sieve: The type A molecular sieve gel solution was placed in a polytetrafluoroethylene reactor and directly heated to 100°C for crystallization without aging for 3.5 h. After filtration and washing to pH 11, the raw powder of type A molecular sieve was obtained by drying at 105°C for 2 h with a relative crystallinity of 105%.
[0064] Example 5
[0065] (1) Recovery of fluorine resources: 197.5g of sodium hydroxide was dissolved in 367.5g of deionized water to prepare a 30% alkaline solution. Then, 500g of fluorine-containing silicon powder was mixed with 565.0g of alkaline solution and heated to 95℃. The mixture was stirred continuously for 6h and then filtered to obtain a clear solution A. The theoretical modulus of sodium silicate in the clear solution A was 2.34 and the measured modulus was 2.20. Precipitate B was dried at 105℃ for 2h to obtain sodium fluoride. The fluorine recovery rate was calculated to be 99.2%.
[0066] (2) Preparation of type A molecular sieve gel solution: The gel composition is SiO2 / Al2O3 molar ratio 2.32, Na2O / SiO2 molar ratio 1.74, and H2O / Na2O molar ratio 42. Prepare a sodium hydroxide solution (4.098g NaOH + 79.92H2O), and dissolve sodium aluminate (5.317g) in the prepared sodium hydroxide solution to obtain solution C. Add solution C to the clarified solution A (14.811g), and stir continuously to obtain type A molecular sieve gel solution.
[0067] (3) Synthesis of type A molecular sieve: The type A molecular sieve gel solution was placed in a polytetrafluoroethylene reactor and directly heated to 100°C for 3.0 h without aging. After filtration and washing to pH 10, the raw powder of type A molecular sieve was obtained by drying at 105°C for 2 h with a relative crystallinity of 103%.
[0068] Example 6
[0069] (1) Recovery of fluorine resources: 220g of sodium hydroxide was dissolved in 367.5g of deionized water to prepare a 30% alkaline solution. Then, 500g of fluorine-containing silicon powder was mixed with 587.5g of alkaline solution and heated to 100℃. The mixture was stirred and reacted for 4h. After standing and filtration, clear solution A was obtained. The theoretical modulus of sodium silicate in clear solution A was 1.916 and the measured modulus was 1.90. Precipitate B was dried at 105℃ for 2h to obtain sodium fluoride. The fluorine recovery rate was calculated to be 99.9%.
[0070] (2) Preparation of type A molecular sieve gel solution: The gel composition is SiO2 / Al2O3 molar ratio 2.00, Na2O / SiO2 molar ratio 1.00, and H2O / Na2O molar ratio 60. Prepare a sodium hydroxide solution (1.00g NaOH + 64.80H2O), and dissolve sodium aluminate (5.02g) in the prepared sodium hydroxide solution to obtain solution C. Add solution C to the clarified solution A (12.45g), and stir continuously to obtain type A molecular sieve gel solution.
[0071] (3) Synthesis of type A molecular sieve: The type A molecular sieve gel solution was placed in a polytetrafluoroethylene reactor and directly heated to 90°C for crystallization for 3.5 h without aging. After filtration and washing to pH 10, the raw powder of type A molecular sieve was obtained at 105°C for 2 h with a relative crystallinity of 100%.
[0072] Comparative Example
[0073] (1) Recovery of fluorine resources: 157.5g of sodium hydroxide was dissolved in 367.5g of deionized water to prepare a 30% alkaline solution. Then, 500g of fluorine-containing silicon powder was mixed with 525g of alkaline solution and heated to 100℃. The mixture was stirred continuously for 4h and then filtered to obtain a clear solution A with a theoretical modulus of 3.869 and a measured modulus of 3.51. The residual F content in the solution was 6.8%, and precipitate B was obtained. Precipitate B was dried at 105℃ for 2h to obtain sodium fluoride. The fluorine recovery rate was calculated to be only 86%.
[0074] (2) Preparation of type A molecular sieve gel solution: The gel composition is SiO2 / Al2O3 molar ratio 2.00, Na2O / SiO2 molar ratio 1.00, and H2O / Na2O molar ratio 60. Prepare a sodium hydroxide solution (4.482g NaOH + 129.60H2O), and dissolve sodium aluminate (5.317g) in the prepared sodium hydroxide solution to obtain solution C. Add solution C to the clarified solution A (14.811g), and stir continuously to obtain type A molecular sieve gel solution.
[0075] (3) Synthesis of type A molecular sieve: The type A molecular sieve gel solution was placed in a polytetrafluoroethylene reactor and directly heated to 100°C for crystallization without aging. After crystallization for 4 hours, the solution was filtered, washed to pH 11, and dried at 105°C for 2 hours to obtain type A molecular sieve powder with a relative crystallinity of 91%.
[0076] Table 1. Composition of fluorinated silicon powder in Examples 1-6 (wt%)
[0077]
[0078] Table 2 Chemical composition of type A molecular sieves synthesized in Examples 1-6 / wt%
[0079]
[0080] In Table 2, "-" indicates not detected. As shown in Table 2, the 4A molecular sieve products prepared in Examples 1-6 do not contain fluorine. The fluorine remaining in solution A did not have a harmful effect on the molecular sieve. In fact, a small amount of fluorine... - It can also be used as a mineralizing agent, electronic balancer, and structure directing agent, which is beneficial to the synthesis of type A molecular sieves.
[0081] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for recovering fluorine resources and synthesizing type A molecular sieves using fluorine-containing silica powder, comprising the following steps: A) Fluorine-containing silicon powder is mixed with sodium hydroxide solution and heated to react, resulting in a clear solution and sodium fluoride precipitate. The silicon and sodium in the clarified solution are calculated as SiO2 and Na2O, with a molar ratio of SiO2 to Na2O of 1.9 to 2.
4. B) Mix sodium aluminate with sodium hydroxide solution to obtain an alkaline solution of sodium aluminate. Mix the clarified solution from step A) with the alkaline solution of sodium aluminate and stir to obtain a gel solution. C) The gel solution is heated and crystallized to obtain type A molecular sieve.
2. The method for recovering fluorine resources and synthesizing type A molecular sieves using fluorine-containing silicon powder according to claim 1, characterized in that, The fluorinated silicon powder is a byproduct of the production of anhydrous hydrogen fluoride using the fluorosilicic acid sulfuric acid process.
3. The method for recovering fluorine resources and synthesizing type A molecular sieves using fluorine-containing silicon powder according to claim 1, characterized in that, The mass concentration of the sodium hydroxide solution in step A) is 35-38%. In step A), the mass ratio of fluorinated silicon powder to sodium hydroxide solution is 1:(1.13-1.18).
4. The method for recovering fluorine resources and synthesizing type A molecular sieves using fluorine-containing silicon powder according to claim 1, characterized in that, In step A), the heating reaction temperature is 90–100°C, and the heating reaction time is 4–8 hours.
5. The method for recovering fluorine resources and synthesizing type A molecular sieves using fluorine-containing silicon powder according to claim 1, characterized in that, In the gel solution, the molar ratio of SiO2 to Al2O3 is 2.00 to 2.
44.
6. The method for recovering fluorine resources and synthesizing type A molecular sieves using fluorine-containing silicon powder according to claim 1, characterized in that, The Na2O / SiO2 molar ratio in the gel solution is 1.00 to 1.
74.
7. The method for recovering fluorine resources and synthesizing type A molecular sieves using fluorine-containing silicon powder according to claim 1, characterized in that, In the gel solution, the molar ratio of H2O to Na2O is 32–60.
8. The method for recovering fluorine resources and synthesizing type A molecular sieves using fluorine-containing silicon powder according to claim 1, characterized in that, In step C), the temperature for heating and crystallization is 80–100°C, and the time for heating and crystallization is 3–4 hours.
9. The method for recovering fluorine resources and synthesizing type A molecular sieves using fluorine-containing silicon powder according to claim 1, characterized in that, In step A), after the heating reaction is completed, the mixture is filtered to obtain a clear solution and a precipitate. The precipitate is dried at 95–105°C to obtain sodium fluoride.
10. The method for recovering fluorine resources and synthesizing type A molecular sieves using fluorine-containing silicon powder according to claim 1, characterized in that, In step C), after the heating and crystallization is completed, the solid product is filtered, washed until the pH is 9-11, and then dried at 100-105℃ for 1-3 hours to obtain type A molecular sieve.