A strongly acidic fau-type molecular sieve and a method for preparing the same
By doping Zr atoms into the FAU-type molecular sieve framework and conducting isomorphic substitution reaction with gaseous SiCl4, a FAU-type molecular sieve with high acidity, high silicon-to-aluminum ratio and high crystallinity was prepared. This solved the problem of increasing the acidity content in the existing technology, simplified the production process and reduced the cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2023-09-18
- Publication Date
- 2026-05-15
AI Technical Summary
Existing technologies cannot effectively increase the strong acidity content of FAU-type molecular sieves while ensuring high crystallinity and a high silicon-to-aluminum ratio, resulting in insufficient catalytic performance.
Strongly acidic FAU-type molecular sieves were prepared by doping Zr atoms into the framework of FAU-type molecular sieves and reacting them with gaseous SiCl4 via isomorphic substitution reaction, followed by calcination.
It has achieved a significant increase in the strong acidity content of FAU-type molecular sieves, a significant increase in the silicon-aluminum ratio, and a high degree of crystallinity. In addition, the production process has been simplified, reducing costs and ammonia nitrogen wastewater discharge.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of molecular sieve preparation technology, specifically relating to a strongly acidic FAU type molecular sieve and its preparation method. Background Technology
[0002] FAU-type molecular sieves possess a three-dimensional, unobstructed framework structure, relatively high specific surface area, adjustable pore size and acidity, and excellent thermal and hydrothermal stability, making them widely used in petroleum refining and chemical industries, particularly in fluidized bed catalytic cracking and catalytic pyrolysis reactions, where they play an irreplaceable role. Simultaneously, FAU-type molecular sieves also exhibit excellent adsorption performance for volatile organic compounds. However, their application in the direct catalytic cracking of crude oil to produce low-carbon olefins presents several substantial problems, such as severe catalyst coking, low selectivity for low-carbon olefin products, short catalyst lifetime, the need for adjustment of acidity levels, and low catalyst activity. To further improve the catalytic performance of FAU-type molecular sieves and their application value in actual production processes, researchers generally modify the molecular sieves to meet the required performance. Among them, the modification of acidity of FAU-type molecular sieves, especially the increase of strong acid content, is of great significance to improving the catalytic performance of FAU-type molecular sieves. However, existing modification methods for FAU-type molecular sieves are difficult to effectively increase the strong acid content, especially while taking into account both high silica-alumina ratio and high crystallinity.
[0003] Therefore, there is still a need to study simple and easy-to-implement technical solutions that can significantly increase the strong acidity content of FAU-type molecular sieves while ensuring high crystallinity and high silicon-to-aluminum ratio. Summary of the Invention
[0004] The purpose of this invention is to provide a technical solution that can significantly increase the strong acid content of FAU-type molecular sieves; the FAU-type molecular sieves prepared by this technical solution have high strong acid content, high crystallinity and high framework silicon-aluminum ratio.
[0005] To achieve the above objectives, the present invention provides the following two technical solutions.
[0006] In a first aspect, the present invention provides a method for preparing a strongly acidic FAU-type molecular sieve, wherein the method comprises:
[0007] FAU-type molecular sieves containing Zr in the framework were subjected to isomorphic substitution reaction with gaseous SiCl4 at a mass ratio of 0.1-20:1, and then calcined to obtain FAU-type molecular sieves with a high silicon-to-aluminum ratio.
[0008] The reaction temperature for isomorphic substitution reaction is 200-600℃;
[0009] Among them, the molar ratio of ZrO2 to Al2O3 in FAU-type molecular sieves containing the metal element Zr in the framework is 0.01-10.0.
[0010] The technical solution provided by this invention involves first doping Zr into the framework of a FAU-type molecular sieve, and then conducting an isomorphic substitution reaction with gas-phase SiCl4. This achieves a significant increase in the strong acidity content of the FAU-type molecular sieve while simultaneously increasing the silicon-to-aluminum ratio and maintaining high crystallinity. The strong acid FAU-type molecular sieve obtained by the technical solution provided by this invention is a strong acid FAU-type molecular sieve with a framework containing heteroatoms Zr. In the technical solution provided by this invention, Zr atoms are first doped into the FAU-type molecular sieve framework to replace a small portion of the Al atoms in the framework. Then, an isomorphic substitution reaction is carried out with gas-phase SiCl4. The gas-phase SiCl4 and the heteroatoms Zr in the FAU-type molecular sieve framework further interact synergistically to isomorphically replace Al atoms, resulting in a significant increase in the strong acidity content and the silicon-to-aluminum ratio, while the prepared FAU-type molecular sieve exhibits relatively high crystallinity.
[0011] According to a preferred embodiment of the first aspect, the method further includes the step of preparing an FAU-type molecular sieve containing the metal element Zr in its framework, specifically including:
[0012] Sodium hydroxide, aluminum source, silicon source and water were mixed according to the molar ratio of (10-30)Na2O:Al2O3:(10-30)SiO2:(180-400)H2O and aged at 0-80℃ to obtain the directing agent;
[0013] The directing agent, sodium hydroxide, silicon source, aluminum source, zirconium source, and water were mixed according to the molar ratio of (1-10)Na2O:Al2O3:(0.01-10.0)ZrO2:(5-20)SiO2:(120-360)H2O to obtain the crystallization reaction system. The crystallization reaction system was crystallized at 60-120℃ to obtain FAU type molecular sieves containing the metal element Zr in the framework. Among them, based on the mass of Al2O3 in the crystallization reaction system as 100%, the mass of Al2O3 provided by the directing agent accounts for 3-25% of the mass of Al2O3 in the crystallization reaction system.
[0014] This preferred technical solution introduces Zr heteroatoms into the framework of a molecular sieve through direct synthesis. The resulting Zr-containing FAU-type molecular sieve is then subjected to an isomorphic substitution reaction with gaseous SiCl4 at a specific temperature, followed by calcination to obtain a strongly acidic FAU-type molecular sieve with a Zr heteroatomation framework. The FAU-type molecular sieve prepared in this way not only possesses high strong acidity but also high crystallinity and a high silica-to-alumina ratio. Furthermore, it eliminates the need for multiple ammonium ion exchange and hydrothermal treatment processes, allowing the sodium oxide content of the molecular sieve to be reduced to below 1.0 wt%. Compared to traditional metal impregnation and hydrothermal ultra-stable technologies, this preferred technical solution produces FAU-type molecular sieves with higher strong acidity, a higher silica-to-alumina ratio, and higher crystallinity. Moreover, the preparation process eliminates the need for ammonium ion exchange and hydrothermal treatment, shortening the production process, reducing production costs, and decreasing ammonia nitrogen wastewater discharge.
[0015] This preferred technical solution introduces Zr heteroatoms into the molecular sieve framework through direct synthesis (by directly adding a metal Zr source to the synthetic gel during molecular sieve synthesis and then crystallizing it). This method offers significant advantages over traditional impregnation or ion exchange methods. Impregnation or ion exchange methods can easily clog the molecular sieve structure and pores, resulting in a weak bond between the Zr component and the molecular sieve. In practical applications, frequent impacts and thermal vibrations from high-velocity airflow can cause Zr components to detach, leading to the loss of effective components and shortening the catalyst's lifespan. Direct synthesis, on the other hand, effectively reduces Zr loss during use and facilitates the modification of the molecular sieve's acidity and pore structure, enhancing its applications in shape-selective and acid catalysis.
[0016] Furthermore, in FAU-type molecular sieves containing the metal element Zr in the framework, the molar ratio of ZrO2 to Al2O3 is 0.05-3.0.
[0017] Furthermore, in the preparation of the directing agent, sodium hydroxide, aluminum source, silicon source and water are mixed according to the molar ratio of (10-20)Na2O:Al2O3:(10-20)SiO2:(240-360)H2O;
[0018] Furthermore, in the preparation of the reaction system to be crystallized, the directing agent, sodium hydroxide, silicon source, aluminum source, zirconium source and water are mixed according to the molar ratio of (1-5)Na2O:Al2O3:(0.01-5.0)ZrO2:(5-15)SiO2:(150-300)H2O to obtain the reaction system to be crystallized (gel mixture). The reaction system to be crystallized is then carried out at 60-120℃.
[0019] Furthermore, during the preparation of the directing agent, the directing agent is obtained by aging at 10-60℃;
[0020] Furthermore, the aging time is 1-60 hours; even further, the aging time is 2-50 hours.
[0021] Furthermore, crystallization is carried out at 70-110°C;
[0022] Furthermore, the crystallization time is 0.5-72 hours; even further, the crystallization time is 12-48 hours.
[0023] Furthermore, the crystallized sample is filtered, washed, and dried; even further, the drying is carried out at 120°C for 24 hours.
[0024] Furthermore, the silicon source includes, but is not limited to, at least one of ethyl silicate, water glass, and silica sol.
[0025] Furthermore, the aluminum source includes, but is not limited to, at least one of sodium aluminate, aluminum sulfate, aluminum isopropoxide, tert-butylaluminum, and alumina;
[0026] Furthermore, the zirconium source includes, but is not limited to, at least one of zirconium chloride, zirconium sulfate, and zirconium oxychloride.
[0027] According to a preferred embodiment of the first aspect, when carrying out the isomorphic substitution reaction, the mass ratio of the FAU-type molecular sieve containing the metal element Zr in the framework to the gaseous SiCl4 is 0.5-10:1.
[0028] According to a preferred embodiment of the first aspect, the reaction temperature of the isomorphic substitution reaction is 280-580°C.
[0029] According to a preferred embodiment of the first aspect, the reaction time for the isomorphic substitution reaction is 10 minutes to 5 hours.
[0030] According to a preferred embodiment of the first aspect, the method further includes cooling, washing, filtering, and drying the isomorphic substitution reaction product before calcination after the isomorphic substitution reaction.
[0031] Furthermore, cooling is carried out under N2 purging.
[0032] According to a preferred embodiment of the first aspect, the calcination temperature is 500-600°C.
[0033] According to a preferred embodiment of the first aspect, the roasting time is 2-6 hours.
[0034] In a second aspect, the present invention provides a strongly acidic FAU-type molecular sieve prepared by the preparation method of the strongly acidic FAU-type molecular sieve provided in the first aspect;
[0035] The strong acid FAU type molecular sieve framework contains heteroatoms Zr, the proportion of strong acid in the total acid content is more than 40%, the framework silicon-aluminum molar ratio n(SiO2) / n(Al2O3) is more than 6, and the relative crystallinity is more than 80%.
[0036] Metal heteroatoms differ from Si and Al atoms in the molecular sieve framework in terms of ionic radius, electronegativity, and complexing ability. Therefore, the introduction of metal heteroatoms can regulate the acidity and surface properties of molecular sieve catalysts. However, due to the diversity of heteroatom types and molecular sieve pore structures, the effects of different heteroatoms on the performance of different molecular sieves vary. Thus, determining the appropriate heteroatom type for each molecular sieve and its corresponding performance impact has always been a research challenge in the field of molecular sieves. This invention achieves a significant improvement in the performance of FAU-type molecular sieves by introducing Zr atoms into the framework and then performing an isomorphic substitution reaction with SiCl4. Compared with existing technologies, it has the following beneficial effects:
[0037] 1. The technical solution provided by the present invention achieves a significant increase in the strong acid content of FAU-type molecular sieve by isomorphically substituting FAU-type molecular sieve containing metal element Zr in the skeleton with gaseous SiCl4 and then calcining it. The strong acid content of the obtained FAU-type molecular sieve is more than 40%.
[0038] 2. The technical solution provided by the present invention achieves a significant increase in the silicon-to-aluminum ratio of the framework of FAU-type molecular sieve by isomorphically substituting FAU-type molecular sieve containing metal element Zr in the framework with gaseous SiCl4 and then calcining it. The prepared FAU-type molecular sieve has a framework silicon-to-aluminum molar ratio n(SiO2) / n(Al2O3) of more than 6.
[0039] The technical solution provided by this invention can obtain FAU-type molecular sieves with different silicon-to-aluminum ratios by adjusting the reaction conditions of FAU-type molecular sieves containing the metal element Zr in the framework with gas-phase SiCl4. In the preferred technical solution, the silicon-to-aluminum molar ratio n(SiO2) / n(Al2O3) of the FAU-type molecular sieve framework can reach more than 17 or even more than 20.
[0040] 3. The FAU-type molecular sieve prepared by the technical solution provided by the present invention has strong acidity and high framework silicon-aluminum ratio while also having high crystallinity, with a crystallinity of over 80%.
[0041] 4. The technical solution provided by this invention obtains a highly acidic, high silicon-to-aluminum ratio, and highly crystallinity FAU-type molecular sieve by isomorphically substituting a FAU-type molecular sieve containing the metal element Zr in its framework with gaseous SiCl4 and then calcining it. It can reduce the sodium oxide content of the FAU-type molecular sieve to below 1.0 wt% without the need for multiple ammonium ion exchanges and harsh hydrothermal treatment (600℃-700℃). The production process is simple, the production cost is low, and the discharge of ammonia nitrogen wastewater is reduced. Attached Figure Description
[0042] Figure 1 The XRD patterns of the molecular sieves provided in Examples 1-5.
[0043] Figure 2 XRD patterns of the molecular sieves provided for Comparative Examples 1-3. Detailed Implementation
[0044] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.
[0045] In this invention, the relative crystallinity, cell parameters, and framework silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the molecular sieve were determined by X-ray diffraction (XRD), and spectra with 2θ angles ranging from 5 to 40° were recorded. The metal element content and Na2O content of the molecular sieve were determined by X-ray fluorescence spectrometry, the specific surface area and pore structure parameters were obtained by low-temperature nitrogen adsorption-desorption measurement, and the proportion of strong acid to total acid content was determined by NH3-TPD using a chemisorption analyzer.
[0046] Sodium hydroxide: Produced by Beijing Chemical Plant, with a purity of 99%;
[0047] Sodium aluminate: Produced by Tianjin Jinke Fine Chemical Research Institute, with Al2O3 content of 45wt%, Na2O content of 41wt%, and the balance being water;
[0048] Water glass: Produced by Beijing Hongxing Sodium Silicate Factory, with SiO2 content of 28.83wt%, Na2O content of 8.84wt%, and the balance being water;
[0049] Silica sol: Produced by Tianjin Jinke Fine Chemical Research Institute, with SiO2 content of 28.88 wt% and the remainder being water;
[0050] Aluminum sulfate: Produced by Nanzhao Huaxin Chemical Co., Ltd., with a purity of 99%;
[0051] Zirconium nitrate (ZrNO3·5H2O): Produced by Beijing Chemical Plant, purity 99%.
[0052] Zirconium chloride (ZrCl4): Produced by Tianjin Jinke Fine Chemical Research Institute, purity 99%.
[0053] Zirconium oxychloride (ZrOCl2·8H2O): Produced by Tianjin Jinke Fine Chemical Research Institute, with a purity of 99%.
[0054] Ammonium chloride: Produced by Beijing Chemical Plant, with a purity of 99%.
[0055] Aluminum isopropoxide: Shanghai Maclean Biochemical Technology Co., Ltd., purity 99.8%;
[0056] Alumina: Shanghai Maclean Biochemical Technology Co., Ltd., purity 99.99%;
[0057] Ethyl silicate: Shanghai Maclean Biochemical Technology Co., Ltd., with a SiO2 content of 28.83 wt% and the balance being water.
[0058] Example 1
[0059] This embodiment provides a strongly acidic FAU-type molecular sieve, which is prepared by the following method:
[0060] 37.09g silica sol, 15.48g sodium hydroxide, 3.06g sodium aluminate and 44.38g distilled water were mixed at 50℃ and stirred for 30min to achieve uniform mixing. The mixture was then aged at 40℃ for 4h to obtain the directing agent.
[0061] Add 20.27g NaOH and 79.7g distilled water to 132.47g silica sol, stir for 30min to mix evenly, then add 80g of directing agent, stir for 1h, then add 1.58g sodium aluminate and 81.54g distilled water, stir for 1h, then add 98.72g aluminum sulfate solution (Al2O3 mass concentration of 7.6wt%), stir for 1h, then add 10.8g zirconium nitrate (ZrNO3·5H2O), continue stirring for 1h to obtain the crystallization reaction system; place the crystallization reaction system into a stainless steel container. After being sealed in a steel crystallization autoclave, the product was dynamically crystallized in a rotary oven at 95°C for 32 hours. Then, it was filtered, washed, and the filter cake was dried in an oven at 120°C for 24 hours. The dried product was then transferred to a quartz tube reactor in a rotary tube furnace, purged with high-purity nitrogen, and the temperature was programmed to rise (4°C / min) to 550°C. The product was then calcined at 550°C for 4 hours to obtain an FAU-type molecular sieve with Zr in its framework (the molar ratio of ZrO2 to Al2O3 was 0.26).
[0062] Then, 8.61 g of gaseous SiCl4 was introduced into a quartz tube reactor in a rotary tube furnace containing 50 g of FAU-type molecular sieve with Zr in its framework, and an isomorphic substitution reaction was carried out at 380 °C for 1 hour. The product of the isomorphic substitution reaction was then repeatedly washed with deionized water, filtered, dried, and calcined at 550 °C under a nitrogen atmosphere for 4 hours to obtain the FAU-type molecular sieve containing Zr, named Zr-FAU-1-isomorphic substitution. The physicochemical properties of the sample are shown in Table 1, and the XRD pattern is shown in [reference needed]. Figure 1 .
[0063] Example 2
[0064] This embodiment provides a strongly acidic FAU-type molecular sieve, which is prepared by the following method:
[0065] 38.58g of ethyl silicate, 15.48g of sodium hydroxide, 70g of distilled water and 3.06g of sodium aluminate were mixed and stirred at 30°C for 1 hour, and then aged at 30°C for 6 hours to obtain the directing agent.
[0066] Add 23.27g NaOH and 182.43g distilled water to 137.79g tetraethyl orthosilicate and stir for 1 hour to mix thoroughly. Then add 100g of a directing agent and stir for 1 hour. Dissolve 1.58g sodium aluminate in 101.54g distilled water and add it to the above solution, stirring for 1 hour. Dissolve 1.11g aluminum isopropoxide in 92g water and add it to the mixed solution, stirring for 1 hour. Then add 12.8g zirconium nitrate (ZrNO3·5H2O) and continue stirring for 1 hour to obtain the crystallization reaction system. The crystallization reaction system was placed in a stainless steel crystallization kettle, sealed, and then dynamically crystallized in a rotary oven at 100°C for 28 hours. After filtration and washing, the filter cake was dried in an oven at 120°C for 24 hours. The dried product was then transferred to a quartz tube reactor in a rotary tube furnace, purged with high-purity nitrogen, and the temperature was programmed to rise (4°C / min) to 550°C. The product was then calcined at 550°C under a nitrogen atmosphere for 4 hours to obtain FAU-type molecular sieves containing the metal element Zr (the molar ratio of ZrO2 to Al2O3 is 1.11).
[0067] Then, 7.78 g of gaseous SiCl4 was introduced into a quartz tube reactor in a rotary tube furnace containing 25 g of FAU-type molecular sieve with Zr in its framework, and an isomorphic substitution reaction was carried out at 410 °C for 1 hour. The product of the isomorphic substitution reaction was then repeatedly washed with deionized water, filtered, dried, and calcined at 550 °C for 4 hours to obtain a strongly acidic FAU-type molecular sieve, named Zr-FAU-2-isomorphic substitution. The physicochemical properties of the sample are shown in Table 1, and the XRD pattern is shown in [reference needed]. Figure 1 .
[0068] Comparative Example 1
[0069] This comparative example provides a Y-type molecular sieve, which is prepared by a conventional hydrothermal USY-type molecular sieve preparation method, specifically:
[0070] 38.58g of ethyl silicate, 15.48g of sodium hydroxide, 70g of distilled water and 3.06g of sodium aluminate were mixed and stirred at 30°C for 1 hour, and then aged at 30°C for 6 hours to obtain the directing agent.
[0071] Add 23.27g NaOH and 182.43g distilled water to 137.79g ethyl silicate and stir for 1 hour to mix evenly. Then add 100g directing agent and stir for 1 hour. Dissolve 1.58g sodium aluminate in 101.54g distilled water and add it to the above solution, stirring for 1 hour. Dissolve 1.11g aluminum isopropoxide in 92g water and add it to the mixed solution, stirring for 1 hour. Continue stirring for 1 hour to obtain the reaction system to be crystallized. Place the reaction system to be crystallized in a stainless steel crystallization kettle, seal it, and perform dynamic crystallization in a rotary oven at 100℃ for 28 hours. After filtration and washing, dry the filter cake in an oven at 120℃ for 24 hours. Transfer the dried product to a quartz tube reactor in a rotary tube furnace, purge with high-purity nitrogen, and program the temperature to rise (4° / min) to 550℃. Calcinate at 550℃ under a nitrogen atmosphere for 4 hours to obtain NaY type molecular sieve.
[0072] NaY-type molecular sieves were mixed with a 1 mol / L ammonium chloride solution at a mass ratio of 1:10 and subjected to ion exchange at 90℃ for 1 hour. The mixture was then filtered, repeatedly washed, and the filter cake was dried in a 120℃ oven for 24 hours. Finally, it was treated with 100% steam at 600℃ for 2 hours. This process was repeated once more for ion exchange and steam treatment to obtain hydrothermal USY molecular sieves, named USY-1. The physicochemical properties of the sample are shown in Table 1, and the XRD pattern is shown in [reference needed]. Figure 2 .
[0073] Comparative Example 2
[0074] This comparative example provides a Y-type molecular sieve, which is prepared by the following method:
[0075] 38.58g of ethyl silicate, 15.48g of sodium hydroxide, 70g of distilled water and 3.06g of sodium aluminate were mixed and stirred at 30°C for 1 hour, and then aged at 30°C for 6 hours to obtain the directing agent.
[0076] Add 23.27g NaOH and 182.43g distilled water to 137.79g of tetraethyl orthosilicate and stir for 1 hour to mix thoroughly. Then add 100g of a directing agent and stir for 1 hour. Dissolve 1.58g of sodium aluminate in 101.54g of distilled water and add it to the above solution, stirring for 1 hour. Dissolve 1.11g of aluminum isopropoxide in 92g of water and add it to the mixed solution, stirring for 1 hour to form a gel mixture. Continue stirring for 1 hour to obtain the crystallization reaction system. The crystallization reaction... The system was placed in a stainless steel crystallization kettle, sealed, and dynamically crystallized in a rotary oven at 100℃ for 28 hours. After filtration and washing, the filter cake was dried in an oven at 120℃ for 24 hours. The dried product was transferred to a quartz tube reactor in a rotary tube furnace, purged with high-purity nitrogen, and the temperature was programmed to rise (4° / min) to 550℃. The product was then calcined at 550℃ in a nitrogen atmosphere for 4 hours to obtain NaY-type molecular sieve, named NaY-1. The physicochemical properties of the sample are shown in Table 1.
[0077] NaY type molecular sieve was mixed with 1 mol / L ammonium chloride solution at a mass ratio of 1:10 and ion exchanged at 90℃ for 1 hour. The mixture was then filtered, repeatedly washed, and the filter cake was dried in an oven at 120℃ for 24 hours. The above steps were repeated to perform another ion exchange to obtain HY type molecular sieve, named HY-1. The physicochemical properties of the sample are shown in Table 1.
[0078] Comparative Example 3
[0079] This comparative example provides an FAU-type molecular sieve, which is prepared by the following method:
[0080] 38.58g of ethyl silicate, 15.48g of sodium hydroxide, 70g of distilled water and 3.06g of sodium aluminate were mixed and stirred at 30°C for 1 hour, and then aged at 30°C for 6 hours to obtain the directing agent.
[0081] Add 23.27g NaOH and 182.43g distilled water to 137.79g tetraethyl orthosilicate and stir for 1 hour to mix thoroughly. Then add 100g of a directing agent and stir for 1 hour. Dissolve 1.58g sodium aluminate in 101.54g distilled water and add it to the above solution, stirring for 1 hour. Dissolve 1.11g aluminum isopropoxide in 92g water and add it to the mixed solution, stirring for 1 hour. Then add 12.8g zirconium nitrate (ZrNO3·5H2O) and continue stirring for 1 hour to obtain the crystallization reaction system. The crystallization reaction system was placed in a stainless steel crystallization kettle, sealed, and then dynamically crystallized in a rotary oven at 100°C for 28 hours. After filtration and washing, the filter cake was dried in an oven at 120°C for 24 hours. The dried product was then transferred to a quartz tube reactor in a rotary tube furnace, purged with high-purity nitrogen, and the temperature was programmed to rise (4°C / min) to 550°C. The product was then calcined at 550°C under a nitrogen atmosphere for 4 hours to obtain FAU-type molecular sieves containing the metal element Zr (the molar ratio of ZrO2 to Al2O3 is 1.11).
[0082] FAU-type molecular sieves containing Zr in the framework were mixed with a 1 mol / L ammonium chloride solution at a mass ratio of 1:10 and subjected to ion exchange at 90℃ for 1 hour. The mixture was then filtered, repeatedly washed, and the filter cake was dried in a 120℃ oven for 24 hours. Finally, it was treated with 100% steam at 600℃ for 2 hours. This process was repeated once more with ion exchange and steam treatment to obtain a hydrothermal FAU molecular sieve containing Zr heteroatoms, named Zr-FAU-hydrothermal. The physicochemical properties of the sample are shown in Table 1, and the XRD pattern is shown in [reference needed]. Figure 2 .
[0083] Comparative Example 4
[0084] This comparative example provides an FAU-type molecular sieve, which is prepared by the following method:
[0085] 38.58g of ethyl silicate, 15.48g of sodium hydroxide, 70g of distilled water and 3.06g of sodium aluminate were mixed and stirred at 30°C for 1 hour, and then aged at 30°C for 6 hours to obtain the directing agent.
[0086] Add 23.27g NaOH and 182.43g distilled water to 137.79g ethyl silicate and stir for 1 hour to mix thoroughly. Then add 100g of directing agent and stir for 1 hour. Dissolve 1.58g sodium aluminate in 101.54g distilled water and add it to the above solution, stirring for 1 hour. Dissolve 1.11g aluminum isopropoxide in 92g water and add it to the mixed solution, stirring for 1 hour. Then add 12.8g zirconium nitrate (ZrNO3·5H2O) and continue stirring for 1 hour to obtain the crystallization reaction system. Place the crystallization reaction system into a stainless steel crystallization kettle. After being sealed, the sample was dynamically crystallized in a rotary oven at 100℃ for 28 hours. Then, it was filtered, washed, and the filter cake was dried in an oven at 120℃ for 24 hours. The dried product was then transferred to a quartz tube reactor in a rotary tube furnace, purged with high-purity nitrogen, and the temperature was programmed to rise (4° / min) to 550℃. The sample was then calcined at 550℃ under a nitrogen atmosphere for 4 hours. The FAU-type molecular sieve containing the metal element Zr (the molar ratio of ZrO2 to Al2O3 is 1.11) was named Zr-Na-FAU-non-isomorphic substitution. The physicochemical properties of the sample are shown in Table 1.
[0087] The molecular sieve Zr-Na-FAU-unisomorphically substituted was mixed with a 1 mol / L ammonium chloride solution at a mass ratio of 1:10 and subjected to ion exchange at 90℃ for 1 hour. After filtration, repeated washing, and drying of the filter cake in an oven at 120℃ for 24 hours, the above steps were repeated to perform another ion exchange to obtain the H-type molecular sieve, named Zr-H-FAU-unisomorphically substituted. The physicochemical properties of the sample are shown in Table 1.
[0088] Comparative Example 5
[0089] This comparative example provides a Y-type molecular sieve, which is prepared by the following method:
[0090] 38.58g of ethyl silicate, 15.48g of sodium hydroxide, 70g of distilled water and 3.06g of sodium aluminate were mixed and stirred at 30°C for 1 hour, and then aged at 30°C for 6 hours to obtain the directing agent.
[0091] Add 23.27g NaOH and 182.43g distilled water to 137.79g of ethyl silicate and stir for 1 hour to mix thoroughly. Then add 100g of directing agent and stir for 1 hour. Dissolve 1.58g of sodium aluminate in 101.54g of distilled water and add it to the above solution, stirring for 1 hour. Dissolve 1.11g of aluminum isopropoxide in 92g of water and add it to the mixed solution, stirring for 1 hour. Continue stirring for another hour to obtain the crystallization reaction system (the molar ratio of each component in the gel mixture is Na2O:Al2O3:S). The reaction system to be crystallized was placed in a stainless steel crystallization vessel, sealed, and dynamically crystallized in a rotary oven at 100°C for 28 hours. After filtration and washing, the filter cake was dried in an oven at 120°C for 24 hours. The dried product was then transferred to a quartz tube reactor in a rotary tube furnace, purged with high-purity nitrogen, and heated to 550°C (4° / min). The product was then calcined at 550°C in a nitrogen atmosphere for 4 hours to obtain NaY-type molecular sieves without heteroatoms Zr.
[0092] Then, 7.78 g of gaseous SiCl4 was introduced into a quartz tube reactor of a rotary tube furnace containing NaY-type molecular sieves free of heteroatoms Zr, and an isomorphic substitution reaction was carried out at 350 °C for 1 hour. The product of the isomorphic substitution reaction was then repeatedly washed with deionized water, filtered, dried, and calcined at 550 °C for 4 hours to obtain FAU-type molecular sieves free of heteroatoms Zr, named FAU-2-Zr-free. The physicochemical properties of the sample are shown in Table 1, and the XRD pattern is shown in [reference needed]. Figure 2 .
[0093] Comparative Example 6
[0094] This comparative example provides an FAU-type molecular sieve, which is prepared by the following method:
[0095] 2.22g sodium aluminate, 8.21g sodium hydroxide, 35.62g distilled water, and 30.61g water glass were mixed in sequence and stirred evenly. The mixture was then aged at 25°C for 24 hours to obtain the directing agent.
[0096] 188.7g of water glass, 46.3g of 30wt% sodium aluminate solution, 42.8g of 50wt% aluminum sulfate solution, 3.99g of zirconium nitrate, and 40.3g of directing agent were mixed and stirred vigorously until homogeneous to obtain the crystallization reaction system (gel mixture). The crystallization reaction system was placed in a stainless steel crystallization kettle, sealed, and dynamically crystallized in a rotary oven at 100℃ for 28h. After filtration and washing, the filter cake was dried in an oven at 120℃ for 24h to obtain an FAU-type molecular sieve containing the metal element Zr in the framework, named Zr-D1-FAU. The physicochemical properties of the sample are shown in Table 1.
[0097] Comparative Example 7
[0098] This comparative example provides an FAU-type molecular sieve, which is prepared by the following method:
[0099] The FAU-type molecular sieve provided in Comparative Example 6 was rinsed three times with a 1.5 mol / L ammonium sulfate solution at 85°C, and then calcined at 540°C for 2 hours. The calcined molecular sieve was then rinsed three times with a 0.5 mol / L ammonium sulfate solution. A 0.5 mol / L manganese sulfate solution was added to the wet filter cake, stirred evenly, and then transferred to a hydrothermal device. It was calcined at 600°C with steam for 4 hours to obtain an ultrastable FAU-type molecular sieve. The sample was named Zr-D1-FAU hydrothermal, and the physicochemical properties of the sample are listed in Table 1.
[0100] Example 3
[0101] This embodiment provides a strongly acidic FAU-type molecular sieve, which is prepared by the following method:
[0102] Add 9.02g of sodium hydroxide to 40.52g of distilled water and stir for 30 minutes. Then add 2.46g of sodium aluminate and 45g of water glass, stir evenly, and then age at 30℃ for 6 hours to obtain the directing agent.
[0103] Add 90g of the guiding agent to 210g of water glass and stir for 1h. Then add 12.70g of sodium hydroxide, 3.46g of sodium aluminate and 140.09g of distilled water and stir for 1h. Then add 136.20g of aluminum sulfate solution (Al2O3 mass concentration of 7.6wt%) and stir for 1h. Then add 8.1g of zirconium chloride (ZrCl4) and continue stirring for 1h to obtain the reaction system to be crystallized (gel mixture). The reaction system to be crystallized was placed in a stainless steel crystallization kettle, sealed, and crystallized in a rotary oven at 105°C for 24 hours. After filtration and washing, the filter cake was dried in an oven at 120°C for 24 hours. The dried product was then transferred to a quartz tube reactor in a rotary tube furnace, purged with high-purity nitrogen, and the temperature was programmed to rise (4°C / min) to 550°C. The product was then calcined at 550°C under a nitrogen atmosphere for 4 hours to obtain an FAU-type molecular sieve with Zr in its framework (the molar ratio of ZrO2 to Al2O3 is 0.29).
[0104] Then, 8.61 g of gaseous SiCl4 was introduced into a quartz tube reactor in a rotary tube furnace containing 30 g of FAU-type molecular sieve with Zr in its framework, and an isomorphic substitution reaction was carried out at 450 °C for 1 hour. The product of the isomorphic substitution reaction was then repeatedly washed with deionized water, filtered, dried, and calcined at 550 °C under a nitrogen atmosphere for 4 hours to obtain a strongly acidic FAU-type molecular sieve, named Zr-FAU-3-isomorphic substitution. The physicochemical properties of the sample are shown in Table 1, and the XRD pattern is shown in [reference needed]. Figure 1.
[0105] Example 4
[0106] This embodiment provides a strongly acidic FAU-type molecular sieve, which is prepared by the following method:
[0107] Add 8.51g of sodium hydroxide to 38.62g of distilled water, stir for 30 minutes, then add 2.25g of sodium aluminate and 37.09g of silica sol, stir evenly, and then age at 60℃ for 2 hours to obtain the directing agent.
[0108] 45.3g of the guiding agent was added to 140.47g of silica sol and stirred for 1 hour. Then, 23.27g of NaOH, 160g of distilled water, and 1.58g of sodium aluminate were added and stirred for 1 hour. Then, 98.72g of aluminum sulfate solution (Al2O3 mass concentration of 7.6wt%) was added and stirred for 1 hour. Finally, 2.3g of zirconium oxychloride (ZrOCl2·8H2O) was added and stirred for another 1 hour to obtain the crystallization reaction system (gel mixture). The crystallization reaction system was then placed in a stainless steel container. After being sealed in a crystallization vessel, the product was dynamically crystallized in a rotary oven at 94°C for 28 hours. Then, it was filtered, washed, and the filter cake was dried in an oven at 120°C for 24 hours. The dried product was then transferred to a quartz tube reactor in a rotary tube furnace, purged with high-purity nitrogen, and the temperature was programmed to rise (4°C / min) to 550°C. The product was then calcined at 550°C under a nitrogen atmosphere for 4 hours to obtain an FAU-type molecular sieve with Zr in its framework (the molar ratio of ZrO2 to Al2O3 was 0.083).
[0109] Then, 8.05 g of gaseous SiCl4 was introduced into a quartz tube reactor in a rotary tube furnace containing 20 g of FAU-type molecular sieve with Zr in its framework, and an isomorphic substitution reaction was carried out at 450 °C for 1 hour. The product of the isomorphic substitution reaction was then repeatedly washed with deionized water, filtered, dried, and calcined at 550 °C under a nitrogen atmosphere for 4 hours to obtain a strongly acidic FAU-type molecular sieve, named Zr-FAU-4-isomorphic substitution. The physicochemical properties of the sample are shown in Table 1, and the XRD pattern is shown in [reference needed]. Figure 1 .
[0110] Example 5
[0111] This embodiment provides a strongly acidic FAU-type molecular sieve, which is prepared by the following method:
[0112] Add 24.02g of sodium hydroxide to 40.52g of distilled water, stir for 30 minutes, then add 2.46g of sodium aluminate and 25g of water glass, stir evenly, and then age at 40℃ for 4 hours to obtain the directing agent.
[0113] Add 50g of the guiding agent to 100g of water glass and stir for 1 hour. Then add 25.70g of sodium hydroxide, 3.46g of sodium aluminate and 200g of distilled water and stir for 1 hour. Next, add 136.20g of aluminum sulfate solution (Al2O3 mass concentration of 7.6wt%) and stir for 1 hour. Then add 20g of zirconium chloride (ZrCl4) and continue stirring for 1 hour to obtain the reaction system to be crystallized (gel mixture). The reaction system to be crystallized was placed in a stainless steel crystallization kettle, sealed, and crystallized in a rotary oven at 105°C for 24 hours. After filtration and washing, the filter cake was dried in an oven at 120°C for 24 hours. The dried product was transferred to a quartz tube reactor in a rotary tube furnace, purged with high-purity nitrogen, and the temperature was programmed to rise (4° / min) to 550°C. The product was then calcined at 550°C under a nitrogen atmosphere for 4 hours to obtain an FAU-type molecular sieve with Zr in its framework (the molar ratio of ZrO2 to Al2O3 is 0.72).
[0114] Then, 8.61 g of gaseous SiCl4 was introduced into a quartz tube reactor in a rotary tube furnace containing 20 g of FAU-type molecular sieve with Zr in its framework, and an isomorphic substitution reaction was carried out at 480 °C for 1 hour. The product of the isomorphic substitution reaction was then repeatedly washed with deionized water, filtered, dried, and calcined at 550 °C under a nitrogen atmosphere for 4 hours to obtain a strongly acidic FAU-type molecular sieve, named Zr-FAU-5-isomorphic substitution. The physicochemical properties of the sample are shown in Table 1, and the XRD pattern is shown in [reference needed]. Figure 1 .
[0115] Table 1
[0116]
[0117]
[0118] As shown in Table 1, there is a synergistic effect between framework Zr doping and gas-phase SiCl4 isomorphic substitution reaction during the process of increasing the proportion of strong acid in FAU molecular sieves. With the combination of framework Zr doping and gas-phase SiCl4 isomorphic substitution reaction, a significant increase in the silicon-to-aluminum ratio of the FAU molecular sieve framework can be achieved. This effect cannot be obtained by only framework Zr doping, only SiCl4 isomorphic substitution reaction, only hydrothermal ultrastability, or both framework Zr doping and SiCl4 isomorphic substitution reaction.
Claims
1. A method for preparing a strongly acidic FAU-type molecular sieve, wherein, The method includes: FAU-type molecular sieves containing Zr in the framework were subjected to isomorphic substitution reaction with gaseous SiCl4 at a mass ratio of 0.1-20:1, and then calcined to obtain FAU-type molecular sieves with a high silicon-to-aluminum ratio. The reaction temperature for isomorphic substitution reaction is 200-600℃; Among them, the molar ratio of ZrO2 to Al2O3 in FAU-type molecular sieves containing the metal element Zr in the framework is 0.01-10.0; The steps for preparing FAU-type molecular sieves with Zr in the framework include: Sodium hydroxide, aluminum source, silicon source and water were mixed according to the molar ratio of (10-30)Na2O:Al2O3:(10-30)SiO2:(180-400)H2O and aged at 0-80℃ to obtain the directing agent; The directing agent, sodium hydroxide, silicon source, aluminum source, zirconium source, and water were mixed according to the molar ratio of (1-10)Na2O:Al2O3:(0.01-10.0)ZrO2:(5-20)SiO2:(120-360)H2O to obtain the crystallization reaction system. The crystallization reaction system was crystallized at 60-120℃ and then calcined to obtain FAU type molecular sieves containing the metal element Zr in the framework. The Al2O3 provided by the directing agent accounted for 3-25% of the mass of Al2O3 in the crystallization reaction system. The process of mixing the directing agent, sodium hydroxide, silicon source, aluminum source, zirconium source, and water to obtain the crystallization reaction system is achieved through the following method: Sodium hydroxide and some water were added to the silicon source, followed by a directing agent, then an aluminum source and the remaining water, and finally a zirconium source to obtain the reaction system to be crystallized.
2. The method according to claim 1, wherein, In the preparation of the directing agent, sodium hydroxide, aluminum source, silicon source and water are mixed according to the molar ratio of (10-20)Na2O : Al2O3 : (10-20)SiO2 : (240-360)H2O.
3. The method according to claim 1, wherein, In the process of preparing the reaction system to be crystallized, the molar ratio of (1-5)Na2O:Al2O3:(0.01-5.0)ZrO2:(5-15)SiO2:(150-300)H2O is used to mix the directing agent, sodium hydroxide, silicon source, aluminum source, zirconium source and water.
4. The method according to claim 1 or 2, wherein, The aging process is carried out at 10-60℃.
5. The method according to claim 1 or 3, wherein, Crystallization is carried out at 70-110℃.
6. The method according to any one of claims 1, 2, and 3, wherein, The silicon source includes at least one of ethyl silicate, water glass, and silica sol; The aluminum source includes at least one of sodium aluminate, aluminum sulfate, aluminum isopropoxide, tert-butylaluminum, and alumina; Zirconium sources include at least one of zirconium chloride, zirconium sulfate, and zirconium oxychloride.
7. The method according to claim 1, wherein, When carrying out isomorphic substitution reactions, the mass ratio of FAU-type molecular sieves containing the metal element Zr in the framework to gaseous SiCl4 is 0.5-15:
1.
8. The method according to claim 1, wherein, The reaction temperature for isomorphic substitution is 280-580℃.
9. The method according to claim 1, wherein, The molar ratio of ZrO2 to Al2O3 in FAU-type molecular sieves containing the metal element Zr in the framework is 0.05-3.
0.
10. The strongly acidic FAU-type molecular sieve prepared by the method according to any one of claims 1-9; in, The strong acid content of the strongly acidic FAU-type molecular sieve accounts for more than 40% of the total acid content.