ZSM-23 Molecular Sieve and Method for Preparing It
By using alkali-treated amorphous silica and surfactants, a ZSM-23 molecular sieve with a rich mesoporous structure and high thermal stability is produced, addressing stability and cost issues in existing methods, improving its performance in petrochemical applications.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2022-01-07
- Publication Date
- 2026-05-12
AI Technical Summary
Existing methods for introducing mesoporous structures into ZSM-23 molecular sieves often result in insufficient stability, complex processes, or high costs, while maintaining the microporous structure is challenging, limiting their applicability to larger molecules.
A method involving alkali-treated amorphous silica as a silicon source, combined with a surfactant and controlled alkaline treatment, followed by crystallization and calcination, to create a ZSM-23 molecular sieve with a rich mesoporous structure, high crystallinity, and thermal stability.
The resulting ZSM-23 molecular sieve has a high mesopore volume, large pore size, and excellent thermal stability, enhancing its performance as an adsorbent and catalyst in petrochemical reactions.
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Abstract
Description
Detailed description of the invention
[0001] [Technical Field] The present invention relates to ZSM-23 molecular sieves, as well as methods for preparing and using them, and more particularly to ZSM-23 molecular sieves rich in mesopores, as well as methods for preparing and using them.
[0002] [Background technology] ZSM-23 molecular sieves are molecular sieve materials with a high SiO2 / Al2O3 ratio and an MTT topology structure, and their one-dimensional teardrop-shaped porous channels are composed of 10-membered rings. Due to their unique porous channel structure and tunable acid properties, ZSM-23 molecular sieves are widely used in the fields of separation, adsorption, and catalysis, playing an irreplaceable role. In the petrochemical industry in particular, they demonstrate excellent performance in the hydrocracking of long-chain alkanes and olefins, and the isomerization of alkanes and aromatic hydrocarbons. However, since ZSM-23 is a microporous molecular sieve, its ability to handle larger molecules is limited due to the limited porous channel size. Therefore, to further expand its range of applications, it is crucial to prepare high-performance ZSM-23 molecular sieves with abundant mesopores.
[0003] Currently, there are very few published patents for introducing a mesoporous structure into a microporous ZSM-23 molecular sieve.
[0004] CN106513035 discloses a method for preparing a composite molecular sieve using a ZSM-23 molecular sieve as the core and MCM-41 or SBA-15 as the shell. According to this method, the mesopores are provided by the mesoporous molecular sieve MCM-41 or SBA-15. Due to its inherent stability and limited silica-alumina ratio range, the prepared composite molecular sieve also has drawbacks such as insufficient stability and a narrow range of adjustable silica-alumina ratios.
[0005] CN105540607 discloses a method for preparing multi-stage pore channel composite molecular sieves ZSM-22 / ZSM-23. However, since both ZSM-22 and ZSM-23 molecular sieves have a microporous structure, the mesoporous structure involved is mainly stacked pores, resulting in low regularity and stability.
[0006] According to CN107235497, starch is added to modify the synthesis pathway of ZSM-23 molecular sieves and removed by calcination in a later stage, resulting in ZSM-23 molecular sieves with a mesoporous-microporous hierarchical composite structure. This method is simple and low-cost, but the removal of the pore-expanding agent results in a mesoporous structure, which affects thermal and hydrothermal stability.
[0007] Common methods for preparing micropore-mesopore composite molecular sieves include post-treatment with alkalis or acids, hard template methods, and surfactant methods, and detailed processing methods have been reported multiple times in papers or patents. However, these methods can lead to the destruction of the microporous structure of the molecular sieves, resulting in insufficient stability of the resulting products, or the processes may be too complex and costly, raising concerns about their applicability.
[0008] Therefore, developing a ZSM-23 molecular sieve rich in mesoporous structures that is simple to process, low-cost, and possesses excellent product performance is a technical challenge that needs to be solved by those skilled in the art.
[0009] [Summary of the Invention] To overcome the shortcomings of existing technologies, the present invention provides a ZSM-23 molecular sieve and a method for preparing the same, the molecular sieve having a rich mesoporous structure and good hydrothermal stability.
[0010] The present invention provides a ZSM-23 molecular sieve in which the pore size of the molecular sieve is 3 to 8 nm, preferably 3 to 6 nm, and the pore volume of the mesopores is 45 to 90%, preferably 50 to 85%, and more preferably 55 to 81%, of the total pore volume of the molecular sieve; the relative crystallinity of the molecular sieve is 95 to 120%, and the relative crystallinity retention rate of the molecular sieve after hydrothermal treatment with steam at 600°C for 2 hours is 95 to 100%.
[0011] According to the molecular sieve described above, the molecular sieve has a specific surface area of 300-430 m². 2 The value is / g, and the pore volume is 0.31-0.5 cm³. 2 The value is / g, and the specific surface area of the micropores is 50-170m². 2 The value is / g, and the specific surface area of the mesopores is 150-310m². 2 The specific surface area is 320-405 m² / g, preferably 320-405 m². 2 The density is / g, and the pore volume is 0.34-0.45 cm³. 3 The value is / g, and the specific surface area of the micropores is 80-140m². 2 The density is / g, and the specific surface area of the mesopores is 261-295 m². 3 It is / g.
[0012] The present invention also provides a method for preparing a ZSM-23 molecular sieve, comprising the following steps: (1) A step of preparing or selecting a silicon source, such as amorphous silica, for preparing a ZSM-23 molecular sieve; (2) A step of performing an alkali treatment on the silicon source for preparing the ZSM-23 molecular sieve described in step (1); (3) A step of preparing a ZSM-23 molecular sieve using alkali-treated amorphous silica as a silicon source.
[0013] In step (1) of the method described above, the silicon source used to prepare the ZSM-23 molecular sieve may be amorphous silica, as well as one or more other silicon sources known in the art, such as fumed silica, silica sol, and water glass.
[0014] In step (1) of the above method, the amorphous silica has a specific surface area of 600 to 1300 m 2 / g, preferably 700 to 1200 m 2 / g; the pore volume is 0.6 to 1.3 cm 3 / g, preferably 0.7 to 1.2 cm 3 / g; and the pore diameter is 1 to 15 nm, preferably 2 to 10 nm.
[0015] In step (1) of the above-described method, the method for preparing amorphous silica is a step of adding a silicon source to deionized water and uniformly dispersing it, and then adding a surfactant and stirring; a step of adjusting the pH of the obtained solution to 1 to 5, preferably 1.5 to 4, and then heating it in a water bath for a certain period of time; a step of preparing amorphous silica by filtration, washing, drying, and firing.
[0016] According to the above-described method, in the preparation of the amorphous silica, the silicon source is an inorganic silicon source, preferably one or more of water glass, silica sol, or white carbon black.
[0017] According to the above-described method, in the preparation of the amorphous silica, the surfactant is one or more of hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and octadecyltrimethylammonium bromide.
[0018] According to the above-described method, in the preparation of the amorphous silica, the molar ratio of the silicon source as SiO2 to the surfactant is 1:(0.02 to 0.3), preferably 1:(0.05 to 0.2).
[0019] According to the above-described method, in the preparation of the amorphous silica, the molar ratio of the silicon source as SiO2 to deionized water is 1:(30 to 300), preferably 1:(50 to 220).
[0020] According to the method described above, in preparing amorphous silica, the heating temperature is 30 to 80°C, preferably 40 to 70°C, and the heating time is 0.5 to 8 hours, preferably 3 to 6 hours.
[0021] In step (2) of the method described above, the alkali treatment includes adding the amorphous silica prepared in step (1) to the alkaline solution, heating, and stirring.
[0022] According to the method described above, the alkaline treatment is carried out using an inorganic alkali, which is one or more of sodium hydroxide, potassium hydroxide, or aqueous ammonia.
[0023] According to the method described above, in the alkali treatment, the heating and stirring time is 0.5 to 12 hours, preferably 2 to 8 hours; and the heating temperature is 25 to 60°C, preferably 30 to 50°C.
[0024] According to the method described above, OH - The molar ratio of the inorganic alkali is 0.05 to 0.24, preferably 0.06 to 0.22. - The number of moles of inorganic alkali can be obtained using conventional analytical chemistry methods, and the details will not be repeated here.
[0025] In step (3) of the method described above, in preparing the ZSM-23 molecular sieve by using alkali-treated amorphous silica as a silicon source, any known method for preparing a ZSM-23 molecular sieve in the existing art can be used, or a method for preparing a ZSM-23 molecular sieve that is not yet known in the existing art but may become known in the future can be used. For example, known methods are disclosed, for example, in Rohrman Jr, AC, et al. "The framework topology of ZSM-23: A high silica zeolite." Zeolites 5.6 (1985): 352-354, US4076842, US5405596, US5707601 and US7157075.
[0026] In step (3) of the method described above, preferably, alkali-treated amorphous silica is used as a silicon source, and the silicon source is mixed with an aluminum source, an alkali source (MOH), a template agent (R), and water to form a gel, which is then crystallized, filtered, washed, dried, and calcined to prepare a ZSM-23 molecular sieve; More preferably, in the gel, the molar ratio of silicon source (as SiO2):aluminum source (as Al2O3):alkali source (as hydroxide):template agent:H2O is 1:(0.003~0.03):(0.03~0.3):(0.05~2):(10~90); even more preferably, in the gel, the molar ratio of silicon source (as SiO2):aluminum source (as Al2O3):alkali source (as hydroxide):template agent:H2O is 1:(0.005~0.02):(0.03~0.16):(0.08~1.6):(20~70); and / or, More preferably, the gel is crystallized at 150-200°C, preferably 170-180°C, for 24-96 hours, preferably 36-72 hours, then filtered, washed, dried, and calcined to prepare a ZSM-23 molecular sieve; and / or More preferably, the drying temperature is 80-120°C, the drying time is 4-12 hours, the firing temperature is 500-600°C, and the firing time is 2-6 hours.
[0027] Specifically, the present invention discloses the following technical solutions: 1. A ZSM-23 molecular sieve characterized in that the pore volume of mesopores, where the pore size of the molecular sieve is 3 to 8 nm, preferably 3 to 6 nm, is 45 to 90%, preferably 50 to 85%, and more preferably 55 to 81% of the total pore volume of the molecular sieve.
[0028] 2. The ZSM-23 molecular sieve according to Solution 1, characterized in that the relative crystallinity of the molecular sieve is 95-120%, and the relative crystallinity retention rate of the molecular sieve after hydrothermal treatment with steam at 600°C for 2 hours is 95-100%.
[0029] 3. The specific surface area of the molecular sieve is 300-430 m². 2 The value is / g, and the pore volume is 0.31-0.5 cm³. 3 The value is / g, and the specific surface area of the micropores is 50-170m². 2 The value is / g, and the specific surface area of the mesopores is 150-310m². 2 The value is / g, and for example, the specific surface area of the molecular sieve is 320-405 m². 2 The density is / g, and the pore volume is 0.34-0.45 cm³. 3 The value is / g, and the specific surface area of the micropores is 80-140m². 2 The density is / g, and the specific surface area of the mesopores is 261-295 m². 2 A ZSM-23 molecular sieve according to solution 1 or 2, characterized by being / g.
[0030] 4. The ZSM-23 molecular sieve according to any one of Solutions 1 to 3, characterized in that the XRD pattern of the ZSM-23 molecular sieve includes a characteristic peak shown at 2θ degrees: approximately 11.3° ± 0.3° (e.g., + / - 0.2° or + / - 0.1°).
[0031] 5. The ZSM-23 molecular sieve according to any one of Solutions 1 to 4, characterized in that the XRD pattern of the ZSM-23 molecular sieve includes characteristic peaks shown at 2θ degrees: 11.2~11.5°, 19.5~19.9°, 20.7~21.0°, and 22.8~23.1°.
[0032] 6. A method for preparing a ZSM-23 molecular sieve as described in any one of Solutions 1 to 3, including the following steps: (1) A step of preparing or selecting a silicon source, such as amorphous silica, for preparing a ZSM-23 molecular sieve; (2) A step of performing an alkali treatment on the silicon source for preparing the ZSM-23 molecular sieve described in step (1); (3) A step of preparing a ZSM-23 molecular sieve using alkali-treated amorphous silica as a silicon source.
[0033] 7. Use of alkali-treated amorphous silica obtained in step (2) of the method described in Solution 4 as a silicon source in the preparation of ZSM-23 molecular sieves.
[0034] 8. In step (1), the amorphous silica has a specific surface area of 600 to 1300 m². 2 / g, preferably 700-1200m 2 It is / g; the pore volume is 0.6~1.3cm³ 3 / g, preferably 0.7-1.2cm 3 The method or use of any of Solutions 1 to 7, characterized by being / g and having a pore diameter of 1 to 13 nm, preferably 2 to 10 nm.
[0035] 9. The method for preparing amorphous silica in step (1) is characterized by the steps of: adding a silicon source to deionized water and dispersing it uniformly, then adding a surfactant and stirring; adjusting the pH of the resulting solution to 1 to 5, preferably 1.5 to 4, then heating it in a water bath for a certain period of time; and filtration, washing, drying, and calcining to prepare amorphous silica, as described or used in any of Solutions 1 to 8.
[0036] 10. The method or use of any of Solutions 1 to 9, characterized in that in step (1), the silicon source is an inorganic silicon source, preferably one or more of water glass, silica sol, or white carbon black.
[0037] 11. The method or use of any of Solutions 1 to 10, characterized in that in step (1), the surfactant is one or more of hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octodecyltrimethylammonium chloride, and octodecyltrimethylammonium bromide.
[0038] 12. The method or use of any of Solutions 1 to 11, characterized in that in step (1), the molar ratio of the silicon source as SiO2 to the surfactant is 1:(0.02~0.3), preferably 1:(0.05~0.2).
[0039] 13. The method or use of any of Solutions 1 to 12, characterized in that in step (1), the molar ratio of the silicon source as SiO2 to deionized water is 1:(30 to 300), preferably 1:(50 to 220).
[0040] 14. The method or use of any of Solutions 1 to 13, characterized in that in step (1), the heating temperature is 30 to 80°C, preferably 40 to 70°C, and the heating time is 0.5 to 8 hours, preferably 3 to 6 hours.
[0041] 15. The method or use of any of Solutions 1 to 14, characterized in that in step (1), the drying temperature is 80 to 120°C, the drying time is 4 to 12 hours, the firing temperature is 500 to 600°C, and the firing time is 2 to 6 hours.
[0042] 16. The method or use of any of Solutions 1 to 15, characterized in that step (2) comprises adding amorphous silica prepared in step (1) to an alkaline solution, heating, and stirring.
[0043] 17. The method or use according to any one of Solutions 1 to 16, characterized in that, in step (2), the alkali treatment is carried out using an inorganic alkali, and the inorganic alkali is one or more of sodium hydroxide, potassium hydroxide, or aqueous ammonia.
[0044] 18. The method or use of any of Solutions 1 to 17, characterized in that, in step (2), the heating and stirring time in the alkali treatment is 0.5 to 12 hours, preferably 2 to 8 hours; and the heating temperature is 25 to 60°C, preferably 30 to 50°C.
[0045] 19. In step (2), the OH group is formed from amorphous silica as SiO2. - The method or use of any of Solutions 1 to 18, characterized in that the molar ratio of the inorganic base is 0.05 to 0.24, preferably 0.06 to 0.22.
[0046] 20. The method or use of any of Solutions 1 to 19, characterized in that in step (3), alkali-treated amorphous silica is used as a silicon source, the silicon source is mixed with an aluminum source, an alkali source (MOH), a template agent (R), and water to form a gel, which is then crystallized, filtered, washed, dried, and calcined to prepare a ZSM-23 molecular sieve.
[0047] 21. The method or use of any of Solutions 1 to 20, characterized in that, in the gel, the molar ratio of silicon source (as SiO2):aluminum source (as Al2O3):alkali source (as hydroxide):template agent:H2O is 1:(0.003~0.03):(0.03~0.3):(0.05~2):(10~90); more preferably, in the gel, the molar ratio of silicon source (as SiO2):aluminum source (as Al2O3):alkali source (as hydroxide):template agent:H2O is 1:(0.005~0.02):(0.03~0.16):(0.08~1.6):(20~70).
[0048] 22. The method or use of any of Solutions 1 to 21, characterized by crystallizing the gel at 150 to 200°C, preferably 170 to 180°C, for 24 to 96 hours, preferably 36 to 72 hours, followed by filtration, washing, drying, and calcination to prepare a ZSM-23 molecular sieve.
[0049] 23. The method or use of any of Solutions 1 to 22, characterized in that in step (3), the drying temperature is 80 to 120°C, the drying time is 4 to 12 hours, the firing temperature is 500 to 600°C, and the firing time is 2 to 6 hours.
[0050] 24. Specific surface area of 600-1300 m² 2 / g, preferably 700-1200m 2 It is / g; the pore volume is 0.6~1.3cm³ 3 / g, preferably 0.7-1.2cm 3 Alkali-treated amorphous silica characterized by having a density of / g and a pore size of 1 to 13 nm, preferably 2 to 10 nm.
[0051] 25. Specific surface area of 600-1300 m² 2 / g, preferably 700-1200m 2 It is / g; the pore volume is 0.6~1.3cm³ 3 / g, preferably 0.7-1.2cm 3 The pore size is 1 to 13 nm, preferably 2 to 10 nm; Alkali-treated amorphous silica, characterized in that the alkali treatment is carried out according to step (2) of the method described in any of solutions 6 and 8 to 19.
[0052] Compared to prior art, the present invention offers the following advantages with respect to the ZSM-23 molecular sieve, as well as its preparation method and use: According to the method of the present invention, mesoporous amorphous silica is first prepared with the help of a surfactant and used as a silicon source for the subsequent synthesis of ZSM-23 molecular sieves. The amorphous silica produced during this process has a mesoporous structure and is not highly crystallized to a stable crystalline form. After further treatment in a low-concentration alkaline solution for a certain period of time, some of the -Si-O- bonds are opened, thereby promoting the formation of -Si-O-Al bonds in the molecular sieve structure; however, the majority of the mesoporous structure is retained, and in a later stage, under the action of a microporous template agent, a microporous structure is generated in a suitable ZSM-23 molecular sieve synthesis system. At the same time, the mesoporous structure is further crystallized and stabilized, resulting in the production of a microporous-mesoporous composite ZSM-23 molecular sieve. This method is a viable industrial production route due to its easy operation, relatively low usage of surfactants and micropore template agents, relatively low cost, and the excellent product performance of the resulting molecular sieves.
[0053] The ZSM-23 molecular sieve synthesized by the method of the present invention not only possesses adjustable acidity properties that contribute to a microporous structure, but also large pore properties, high specific surface area and pore volume that contribute to a mesoporous structure, as well as high crystallinity, high thermal stability, and high hydrothermal stability. It can be used as an excellent adsorbent or catalytic material and has broader applicability in the field of shape-selective catalysis, further improving its applicability in petrochemical reactions such as the decomposition and isomerization of long-chain alkanes and olefins, and the isomerization of aromatics.
[0054] [Brief explanation of the drawing] Figure 1 shows the XRD spectrum of the synthesis product of Example 1 of the present invention.
[0055] Figure 2 shows the nitrogen gas physicoadsorption diagram of the synthesis product of Example 1 of the present invention.
[0056] [Detailed explanation] Analytical method according to the present invention: The specific surface area and pore volume of the molecular sieve were measured using an ASAP 2405 physicoadscopy device manufactured by Micromeritics, Inc. (USA), where the specific surface area refers to the sum of the specific surface areas of micropores and mesopores.
[0057] The XRD spectrum of the sample is obtained using a Dmax2500 X-ray diffractometer manufactured by Rigaku Corporation (Japan), and the relative crystallinity of the sample is obtained by calculation. The relative crystallinity of the molecular sieve is determined by taking the sum of the diffraction peak heights at approximately 11.3° and approximately 19.5-23° (2θ degrees) in the XRD spectrum of a typical ZSM-23 molecular sieve as the 100% crystallinity, and comparing it with other samples to obtain the relative crystallinity.
[0058] According to the present invention, the ZSM-23 molecular sieve has an XRD pattern that includes a characteristic peak shown at 2θ degrees: approximately 11.3° ± 0.3° (e.g., ± 0.2° or ± 0.1°).
[0059] According to the present invention, the ZSM-23 molecular sieve has an XRD pattern that includes characteristic peaks shown at 2θ degrees: 11.2~11.5°, 19.5~19.9°, 20.7~21.0°, and 22.8~23.1°.
[0060] To better illustrate the present invention, it will be further described below in conjunction with examples and comparative examples. However, the scope of the present invention is not limited to the scope of these examples.
[0061] Example 1 (1) Preparation of a mesoporous silicon source 50 g of water glass (containing 27% SiO2 by mass fraction) was added to 250 g of deionized water. The mixture was stirred to uniformly disperse it. Then, octodecyltrimethylammonium chloride (C) was added. 18 Add TMACl, stir the resulting mixture for 0.5 hours, and C 18The molar ratio of SiO2 to TMACl was 1:0.08. The pH of the solution was adjusted to 2 with hydrochloric acid and heated in a 50°C water bath for 4 hours. The reaction system was then filtered, washed, dried at 80°C for 8 hours, and calcined at 550°C for 3 hours to obtain amorphous silica.
[0062] (2) Preparation of microporous-mesoporous ZSM-23 molecular sieve a) Dissolve 0.35 g of NaOH in 35 mL of deionized water and prepare the mesoporous silicon source (OH) prepared in step (1). - (SiO2 molar ratio = 0.14) 3.7g was added, and the mixture was stirred in a 45°C water bath for 3 hours.
[0063] b) Aluminum sulfate and isopropylamine (IPA) are sequentially dissolved in the remaining water, and the silicon source dispersion obtained in step a) is added to the resulting mixture, so that the total molar ratio is SiO2 in the silicon source: Al2O3 in the aluminum source:OH - A gel with the ratio :IPA:H2O = 1:0.01:0.08:1.0:50 was prepared. The obtained gel was crystallized at 180°C for 48 hours, filtered, washed, dried, and calcined. The relative crystallinity, specific surface area, pore volume, and pore size distribution of the obtained product were measured; and after hydrothermal treatment with steam at 600°C for 2 hours, the hydrothermal stability was measured. The XRD spectrum is shown in Figure 1 (confirming that the obtained product is a ZSM-23 molecular sieve), and the nitrogen gas physicoadsorption curve is shown in Figure 2. The specific properties are shown in Table 1.
[0064] Example 2 (1) Preparation of a mesoporous silicon source 50 g of water glass (containing 27% SiO2 by mass fraction) was added to 250 g of deionized water. The mixture was stirred to uniformly disperse it. Then, octodecyltrimethylammonium chloride (C) was added. 18 Add TMACl, stir the resulting mixture for 0.5 hours, and C 18The molar ratio of SiO2 to TMACl was 1:0.08. The pH of the solution was adjusted to 2 with hydrochloric acid and heated in a 50°C water bath for 4 hours. The reaction system was then filtered, washed, dried at 100°C for 4 hours, and calcined at 550°C for 3 hours to obtain amorphous silica.
[0065] (2) Preparation of microporous-mesoporous ZSM-23 molecular sieve a) Dissolve 0.42 g of NaOH in 40 mL of deionized water, and prepare the mesoporous silicon source (OH) prepared in step (1). - (SiO2 molar ratio = 0.17) Add 3.7g and stir the mixture in a 35°C water bath for 6 hours; b) Aluminum sulfate and isopropylamine (IPA) are sequentially dissolved in the remaining water, and the silicon source dispersion obtained in step a) is added to the resulting mixture, so that the total molar ratio is SiO2 in the silicon source: Al2O3 in the aluminum source:OH - A gel with the ratio :IPA:H2O = 1:0.005:0.10:1.0:50 was prepared. The obtained gel was crystallized at 180°C for 48 hours, filtered, washed, dried, and calcined. The relative crystallinity, specific surface area, pore volume, and pore size distribution of the obtained product were measured; and after hydrothermal treatment with steam at 600°C for 2 hours, the hydrothermal stability was measured. The XRD spectrum was similar to that in Figure 1, and the nitrogen gas physicoadsorption curve was similar to that in Figure 2. The specific properties are shown in Table 1.
[0066] Example 3 (1) Preparation of a mesoporous silicon source 50 g of water glass (containing 27% SiO2 by mass fraction) was added to 1200 g of deionized water. The mixture was stirred and uniformly dispersed. Then, octodecyltrimethylammonium chloride (C) was added. 18 Add TMACl) and stir the resulting mixture for 2 hours. 18 The molar ratio of SiO2 to TMACl was 1:0.2. The pH of the solution was adjusted to 3 with hydrochloric acid and heated in a 50°C water bath for 4 hours. The reaction system was then filtered, washed, dried at 80°C for 4 hours, and calcined at 500°C for 3 hours to obtain amorphous silica.
[0067] (2) Preparation of microporous-mesoporous ZSM-23 molecular sieve a) Dissolve 0.15 g of NaOH in 35 mL of deionized water and prepare the mesoporous silicon source (OH) prepared in step (1). - (SiO2 molar ratio = 0.06) Add 3.7g and stir the mixture in a 45°C water bath for 3 hours; b) Aluminum sulfate, isopropylamine (IPA), and NaOH are sequentially dissolved in the remaining water, and the silicon source dispersion obtained in step a) is added to the resulting mixture, so that the total molar ratio is SiO2 in the silicon source: Al2O3 in the aluminum source:OH - A gel with the ratio :IPA:H2O = 1:0.01:0.08:1.0:50 was prepared. The obtained gel was crystallized at 180°C for 48 hours, filtered, washed, dried, and calcined. The relative crystallinity, specific surface area, pore volume, and pore size distribution of the obtained product were measured; and after hydrothermal treatment with steam at 600°C for 2 hours, the hydrothermal stability was measured. The XRD spectrum was similar to that in Figure 1, and the nitrogen gas physicoadsorption curve was similar to that in Figure 2. The specific properties are shown in Table 1.
[0068] Example 4 (1) Preparation of a mesoporous silicon source 50 g of water glass (containing 27% SiO2 by mass fraction) was added to 800 g of deionized water. The mixture was stirred and uniformly dispersed. Then, octodecyltrimethylammonium chloride (C) was added. 18 Add TMACl) and stir the resulting mixture for 2 hours. 18 The molar ratio of SiO2 to TMACl was 1:0.15. The pH of the solution was adjusted to 4 with hydrochloric acid and heated in a 50°C water bath for 4 hours. The reaction system was then filtered, washed, dried at 90°C for 4 hours, and calcined at 550°C for 3 hours to obtain amorphous silica.
[0069] (2) Preparation of microporous-mesoporous ZSM-23 molecular sieve a) Dissolve 0.42 g of NaOH in 40 mL of deionized water, and prepare the mesoporous silicon source (OH) prepared in step (1).- (SiO2 molar ratio = 0.17) Add 3.7g and stir the mixture in a 40°C water bath for 3 hours; b) Aluminum sulfate and isopropylamine (IPA) are sequentially dissolved in the remaining water, and the silicon source dispersion obtained in step a) is added to the resulting mixture, so that the total molar ratio is SiO2 in the silicon source: Al2O3 in the aluminum source:OH - A gel with the ratio :IPA:H2O = 1:0.005:0.10:1.0:50 was prepared. The obtained gel was crystallized at 180°C for 48 hours, filtered, washed, dried, and calcined. The relative crystallinity, specific surface area, pore volume, and pore size distribution of the obtained product were measured; and after hydrothermal treatment with steam at 600°C for 2 hours, the hydrothermal stability was measured. The XRD spectrum was similar to that in Figure 1, and the nitrogen gas physicoadsorption curve was similar to that in Figure 2. The specific properties are shown in Table 1.
[0070] Example 5 (1) Preparation of a mesoporous silicon source 50 g of water glass (containing 27% SiO2 by mass fraction) was added to 210 g of deionized water. The mixture was stirred and uniformly dispersed. Then, octodecyltrimethylammonium chloride (C) was added. 18 Add TMACl and stir the resulting mixture for 1 hour. 18 The molar ratio of SiO2 to TMACl was 1:0.05. The pH of the solution was adjusted to 2 with hydrochloric acid and heated in a 60°C water bath for 4 hours. The reaction system was then filtered, washed, dried at 80°C for 8 hours, and calcined at 550°C for 3 hours to obtain amorphous silica.
[0071] (2) Preparation of microporous-mesoporous ZSM-23 molecular sieve a) Dissolve 0.35 g of NaOH in 35 mL of deionized water and prepare the mesoporous silicon source (OH) prepared in step (1). - (SiO2 molar ratio = 0.14) Add 3.7g and stir the mixture in a 50°C water bath for 2 hours; b) Aluminum sulfate and isopropylamine (IPA) are sequentially dissolved in the remaining water, and the silicon source dispersion obtained in step a) is added to the resulting mixture, so that the total molar ratio is SiO2 in the silicon source:Al2O3 in the aluminum source:OH - A gel with the ratio :IPA:H2O = 1:0.01:0.08:1.0:50 was prepared. The obtained gel was crystallized at 180°C for 48 hours, filtered, washed, dried, and calcined. The relative crystallinity, specific surface area, pore volume, and pore size distribution of the obtained product were measured; and after hydrothermal treatment with steam at 600°C for 2 hours, the hydrothermal stability was measured. The XRD spectrum was similar to that in Figure 1, and the nitrogen gas physicoadsorption curve was similar to that in Figure 2. The specific properties are shown in Table 1.
[0072] Example 6 (1) Preparation of a mesoporous silicon source 50 g of water glass (containing 27% SiO2 by mass fraction) was added to 210 g of deionized water. The mixture was stirred and uniformly dispersed. Then, octodecyltrimethylammonium chloride (C) was added. 18 Add TMACl) and stir the resulting mixture for 1 hour. 18 The molar ratio of SiO2 to TMACl was 1:0.06. The pH of the solution was adjusted to 2 with hydrochloric acid and heated in a 60°C water bath for 4 hours. The reaction system was then filtered, washed, dried at 80°C for 8 hours, and calcined at 550°C for 3 hours to obtain amorphous silica.
[0073] (2) Preparation of microporous-mesoporous ZSM-23 molecular sieve a) Dissolve 0.10 g of NaOH and 1.36 g of concentrated ammonia water (with a mass fraction of approximately 27%) in 35 mL of deionized water, and prepare the mesoporous silicon source (OH) prepared in step (1). - (SiO2 molar ratio = 0.22) Add 3.7g and stir in a 40°C water bath for 6 hours; b) Aluminum sulfate and isopropylamine (IPA) are sequentially dissolved in the remaining water, and the silicon source dispersion obtained in step a) is added to the resulting mixture, so that the total molar ratio is SiO2 in the silicon source: Al2O3 in the aluminum source:OH- A gel with the ratio :IPA:H2O = 1:0.01:0.15:1.0:50 was prepared. The obtained gel was crystallized at 180°C for 48 hours, filtered, washed, dried, and calcined. The relative crystallinity, specific surface area, pore volume, and pore size distribution of the obtained product were measured; and after hydrothermal treatment with steam at 600°C for 2 hours, the hydrothermal stability was measured. The XRD spectrum was similar to that in Figure 1, and the nitrogen gas physicoadsorption curve was similar to that in Figure 2. The specific properties are shown in Table 1.
[0074] Comparative Example 1 (See CN105540607A) While stirring at 35°C, 0.51 g of pseudoboehmite and 0.3 g of sodium hydroxide were added to 26 mL of deionized water. The resulting solution was homogenized, then 0.3 g of isopropylamine was added, followed by 21 g of white carbon black, and the resulting mixture was further homogenized and mixed for 1 hour. 24.5 g of cereal starch was added, and the resulting mixture was heated to 90°C, stirred, and aged for 6 hours. Finally, the resulting mixture was transferred to a hydrothermal reaction vessel lined with PTFE, statically crystallized at 160°C for 144 hours, removed, cooled, filtered, and dried at 80°C to obtain the raw material powder for molecular sieves. The raw material powder was calcined at 500°C for 12 hours in an air atmosphere to produce a microporous-mesoporous composite ZSM-23 molecular sieve. Its relative crystallinity, specific surface area, pore volume, and pore size distribution were measured, and after hydrothermal treatment with steam at 600°C for 2 hours, its hydrothermal stability was measured. The specific characteristics are shown in Table 1.
[0075] Comparative Example 2 (1) Preparation of a mesoporous silicon source 50 g of water glass (containing 27% SiO2 by mass fraction) was added to 250 g of deionized water. The mixture was stirred to uniformly disperse it. Then, octodecyltrimethylammonium chloride (C) was added. 18 Add TMACl and stir the resulting mixture for 0.5 hours. 18The molar ratio of SiO2 to TMACl was 1:0.08. The pH of the solution was adjusted to 2 with hydrochloric acid and heated in a 50°C water bath for 4 hours. The reaction system was then filtered, washed, dried, and calcined at 550°C to produce amorphous silica.
[0076] (2)a) Disperse 3.7 g of the mesoporous silicon source prepared in step (1) in 35 mL of deionized water, and stir the mixture in a 50°C water bath for 2 hours; b) Aluminum sulfate, isopropylamine (IPA), and NaOH were sequentially dissolved in the remaining water. To the resulting mixture, the silicon source dispersion obtained in step a) was added to prepare a gel with a total molar ratio of SiO2 in the silicon source:Al2O3 in the aluminum source:NaOH:IPA:H2O = 1:0.01:0.08:1.0:50. The obtained gel was crystallized at 180°C for 48 hours, filtered, washed, dried, and calcined. The relative crystallinity, specific surface area, pore volume, and pore size distribution of the obtained product were measured; and after hydrothermal treatment with steam at 600°C for 2 hours, the hydrothermal stability was measured. The specific properties are shown in Table 1.
[0077] Comparative Example 3 (1) Preparation of a mesoporous silicon source 50 g of water glass (containing 27% SiO2 by mass fraction) was added to 1200 g of deionized water. The mixture was stirred and uniformly dispersed. Then, octodecyltrimethylammonium chloride (C) was added. 18 Add TMACl) and stir the resulting compound for 2 hours. 18 The molar ratio of SiO2 to TMACl was 1:0.2. The pH of the solution was adjusted to 3 with hydrochloric acid and heated in a 50°C water bath for 4 hours. The reaction system was then filtered, washed, dried, and calcined at 550°C to produce amorphous silica.
[0078] (2) a) Dissolve 0.70 g of NaOH in 40 mL of deionized water and prepare the mesoporous silicon source (OH) prepared in step (1). - (SiO2 molar ratio = 0.28) Add 3.7g and stir the resulting mixture in a 45°C water bath for 3 hours; b) Aluminum sulfate and isopropylamine (IPA) were sequentially dissolved in the remaining water, and the silicon source dispersion obtained in step a) was added to the resulting mixture to prepare a gel with a total molar ratio of SiO2 in the silicon source:Al2O3 in the aluminum source:NaOH:IPA:H2O = 1:0.01:0.16:1.0:50. The resulting gel was crystallized at 180°C for 48 hours, filtered, washed, dried, and calcined. The relative crystallinity, specific surface area, pore volume, and pore size distribution of the obtained product were measured; and after hydrothermal treatment with steam at 600°C for 2 hours, the hydrothermal stability was measured.
[0079] Comparative Example 4 (1) Preparation of a mesoporous silicon source 50 g of water glass (containing 27% SiO2 by mass fraction) was added to 1200 g of deionized water. The mixture was stirred and uniformly dispersed. Then, octodecyltrimethylammonium chloride (C) was added. 18 Add TMACl) and stir the resulting mixture for 2 hours. 18 The molar ratio of SiO2 to TMACl was 1:0.2. The pH of the solution was adjusted to 3 with hydrochloric acid and heated in a 50°C water bath for 4 hours. The reaction system was then filtered, washed, dried, and calcined at 550°C to produce amorphous silica.
[0080] (2) a) Dissolve 0.10 g of NaOH in 40 mL of deionized water and prepare the mesoporous silicon source (OH) prepared in step (1). - (SiO2 molar ratio = 0.04) 3.7g is added, and the resulting mixture is stirred in a 45°C water bath for 3 hours; b) Aluminum sulfate, isopropylamine (IPA), and sodium hydroxide were sequentially dissolved in the remaining water, and the silicon source dispersion obtained in step a) was added to the resulting mixture to prepare a gel with a total molar ratio of SiO2 in the silicon source:Al2O3 in the aluminum source:NaOH:IPA:H2O = 1:0.01:0.08:1.0:50. The resulting gel was crystallized at 180°C for 48 hours, filtered, washed, dried, and calcined. The relative crystallinity, specific surface area, pore volume, and pore size distribution of the obtained product were measured; and after hydrothermal treatment with steam at 600°C for 2 hours, the hydrothermal stability was measured.
[0081] Comparative Example 5 (Preparation of conventional ZSM-23 molecular sieve) A gel was prepared by mixing water glass, aluminum sulfate, isopropylamine (IPA), sodium hydroxide, and water, with a total molar ratio of SiO2 in the silicon source:Al2O3 in the aluminum source:NaOH:IPA:H2O = 1:0.01:0.08:1.0:50. The resulting gel was heated at 180°C for 72 hours, filtered, washed, dried, and calcined. The relative crystallinity of the resulting product was measured, and its hydrothermal stability was measured after hydrothermal treatment with steam at 600°C for 2 hours. The specific properties are shown in Table 1.
[0082] [Table 1]
[0083] From the data in Table 1, it can be seen that the preparation method in the examples of the present invention allows for the preparation of ZSM-23 molecular sieves having a micropore-mesopore composite structure through a simple synthesis process using relatively low cost and relatively small amounts of surfactant. The resulting product, the micropore-mesopore composite ZSM-23 molecular sieve, has high crystallinity, large specific surface area and pore volume, high mesopore content, a relatively concentrated size distribution, good thermal and hydrothermal stability, and broad applicability.
[0084] The performance of the ZSM-23 molecular sieve sample was evaluated using a fixed-bed microreactor. For the hydroisomerization reaction of linear C 20 ~C 30 The reaction conditions and catalyst results for Comparative Example 1, Comparative Example 5, Example 4, and Example 6 were as follows: Reaction feedstock: 90 wt% decahydronaphthalene, 10 wt% C 20 ~C 30 linear alkane; Reaction conditions: reaction temperature 280 °C; liquid hourly space velocity 1.0 h -1 , hydrogen-to-oil ratio 600; reaction hydrogen pressure 4.0 MPa; Comparative Example 1: Liquid yield (C5 + ): 93%; C 20 ~C 30 Isomerization degree: 100%; C 20 ~C 30 Isomerization product yield: 46%; C 20 ~C 30 Ratio of multi-branched chain components to single-branched chain components in the isomerization product: 0.6.
[0085] Comparative Example 5: Liquid yield (C5 + ): 94%; C 20 ~C 30 Isomerization degree: 100%; C 20 ~C 30 Isomerization product yield: 44%; C 20 ~C 30 Ratio of multi-branched chain components to single-branched chain components in the isomerization product: 0.5.
[0086] <00,00419>Example 4: Liquid yield (C5 + ): 95%; C 20 ~C 30 Isomerization degree: 100%; C 20 ~C 30 Isomerization product yield: 53%; C 20 ~C 30 Ratio of multi-branched chain components to single-branched chain components in the isomerization product: 2.1.
[0087] Example 6: Liquid yield (C5+ ): 96%; C 20 ~C 30 Degree of isomerization: 100%; C 20 ~C 30 Yield of isomerization product: 54%; C 20 ~C 30 Ratio of the multi-branched chain component to the single-branched chain component in the isomerization product: 2.3.
Brief Description of Drawings
[0088] [Figure 1] Figure 1 shows the XRD spectrum of the synthetic product of Example 1 of the present invention. [Figure 2] Figure 2 shows the nitrogen gas physical adsorption diagram of the synthetic product of Example 1 of the present invention.
Claims
1. The ZSM-23 molecular sieve is characterized in that the pore volume of mesopores, where the pore size of the molecular sieve is 3 to 8 nm, is 45 to 90% of the total pore volume of the molecular sieve.
2. The ZSM-23 molecular sieve according to Claim 1, characterized in that the pore volume of mesopores with a pore size of 3 to 8 nm is 50 to 85% of the total pore volume of the molecular sieve.
3. The ZSM-23 molecular sieve according to Claim 1, characterized in that the pore volume of mesopores with a pore size of 3 to 6 nm is 55 to 81% of the total pore volume of the molecular sieve.
4. The ZSM-23 molecular sieve according to any one of claims 1 to 3, characterized in that the relative crystallinity of the molecular sieve is 95 to 120%, and the relative crystallinity retention rate of the molecular sieve after hydrothermal treatment with steam at 600°C for 2 hours is 95 to 100%.
5. The specific surface area of the molecular sieve is 300 to 430 m². ２ The concentration is / g, and the pore volume is 0.31 to 0.5 cm³. ３ The density is / g, and the specific surface area of the micropores is 50-170 m². ２ The ratio is / g, and the specific surface area of the mesopores is 150-310 m². ２ A ZSM-23 molecular sieve according to any one of claims 1 to 4, characterized in that it is / g.
6. The ZSM-23 molecular sieve according to claim 5, characterized in that the specific surface area of the molecular sieve is 320 to 405 m² / g, the pore volume is 0.34 to 0.45 cm³ / g, the specific surface area of the micropores is 80 to 140 m² / g, and the specific surface area of the mesopores is 261 to 295 m² / g.
7. A method for preparing a ZSM-23 molecular sieve according to any one of claims 1 to 6, comprising the following steps: (1) A step of preparing or selecting a silicon source for preparing a ZSM-23 molecular sieve; (2) A step of performing an alkali treatment on the silicon source for preparing the ZSM-23 molecular sieve described in step (1); (3) A step of preparing a ZSM-23 molecular sieve using alkali-treated amorphous silica as a silicon source.
8. In step (1), the silicon source is amorphous silica, and the amorphous silica has a specific surface area of 600 to 1300 m². ２ It is / g; the pore volume is 0.6 to 1.3 cm³. ３ The method according to claim 7, characterized in that the amount is / g and the pore size is 1 to 13 nm.
9. The method according to claim 8, characterized in that in step (1), the method for preparing amorphous silica is a step of adding a silicon source to deionized water and dispersing it uniformly, then adding a surfactant and stirring; adjusting the pH of the obtained solution to 1 to 5, then heating it in a water bath for a certain period of time; and filtration, washing, drying, and calcination to prepare amorphous silica.
10. The method according to claim 9, characterized in that the silicon source in step (1) is an inorganic silicon source.
11. The method according to any one of claims 9 to 10, characterized in that in step (1), the surfactant is one or more of hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octodecyltrimethylammonium chloride, and octodecyltrimethylammonium bromide.
12. In step (1), SiO ２ The method according to any one of claims 9 to 11, characterized in that the molar ratio of the silicon source as and the surfactant is 1:(0.02 to 0.3).
13. In step (1), SiO ２ The method according to any one of claims 9 to 12, characterized in that the molar ratio of the silicon source as described above to deionized water is 1:(30 to 300).
14. The method according to any one of claims 9 to 13, characterized in that in step (1), the heating temperature is 30 to 80°C and the heating time is 0.5 to 8 hours.
15. The method according to any one of claims 9 to 14, characterized in that in step (1), the drying temperature is 80 to 120°C, the drying time is 4 to 12 hours, the firing temperature is 500 to 600°C, and the firing time is 2 to 6 hours.
16. The method according to any one of claims 8 to 15, characterized in that in step (2), the alkali treatment includes adding amorphous silica prepared in step (1) to an alkaline solution, heating, and stirring.
17. The method according to claim 16, characterized in that in step (2), the alkali treatment is carried out using an inorganic alkali, and the inorganic alkali is one or more of sodium hydroxide, potassium hydroxide, or ammonia water.
18. The method according to any one of claims 16 to 17, characterized in that, in step (2), the heating and stirring time in the alkali treatment is 0.5 to 12 hours; and the heating temperature is 25 to 60°C.
19. In step (2), the molar ratio of OH as ２ to amorphous silica as SiO － to inorganic alkali as is 0.05 to 0.24, and the method according to any one of claims 8 to 18, characterized in that.
20. The method according to any one of claims 7 to 19, characterized in that in step (3), alkali-treated amorphous silica is used as a silicon source, the silicon source is mixed with an aluminum source, an alkali source (MOH), a template agent (R), and water to form a gel, and the gel is crystallized, filtered, washed, dried and calcined to prepare a ZSM-23 molecular sieve.
21. In the aforementioned gel, the silicon source (SiO ２ As): Aluminum source (Al ２ O ３ As): Alkali source (as hydroxide): Template agent: H ２ The method according to claim 20, characterized in that the molar ratio of O is 1:(0.003-0.03):(0.03-0.3):(0.05-2):(10-90).
22. The method according to claim 21, characterized in that, in the gel, the molar ratio of silicon source (as SiO₂): aluminum source (as Al₂O₃): alkali source (as hydroxide): template agent: H₂O is 1:(0.005-0.02):(0.03-0.16):(0.08-1.6):(20-70).
23. The method according to any one of claims 20 to 22, characterized in that the gel is crystallized at 150 to 200°C for 24 to 96 hours, filtered, washed, dried, and calcined to prepare a ZSM-23 molecular sieve.
24. The method according to any one of claims 20 to 23, characterized in that in step (3), the drying temperature is 80 to 120°C, the drying time is 4 to 12 hours, the firing temperature is 500 to 600°C, and the firing time is 2 to 6 hours.