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JP-7857299-B2 - ZSM-23 molecular sieve and method for preparing the same

JP7857299B2JP 7857299 B2JP7857299 B2JP 7857299B2JP-7857299-B2

Inventors

  • 陳玉晶
  • 樊宏飛
  • 于政敏
  • 孫暁艶

Assignees

  • 中国石油化工股▲ふん▼有限公司
  • 中石化（大連）石油化工研究院有限公司

Dates

Publication Date
20260512
Application Date
20220107
Priority Date
20210107

Claims (20)

  1. The ZSM-23 molecular sieve is characterized in that the pore volume of mesopores with a pore size of 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 ZSM-23 molecular sieve according to any one of claims 1 to 4, characterized in that the specific surface area of the molecular sieve is 300 to 430 m² /g, the pore volume is 0.31 to 0.5 cm³ /g, the specific surface area of the micropores is 50 to 170 m²/g, and the specific surface area of the mesopores is 150 to 310 m² /g.
  6. The specific surface area of the molecular sieve is 320 to 405 m². 2 The concentration is /g, and the pore volume is 0.34–0.45 cm³. 3 The density is /g, and the specific surface area of the micropores is 80-140 m². 2 The density is /g, and the specific surface area of the mesopores is 261-295 m². 2 The ZSM-23 molecular sieve according to claim 5, characterized in that it is /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 Z SM-23 molecular sieves; (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. The method according to claim 7, wherein in step (1), the silicon source is amorphous silica, and the amorphous silica has a specific surface area of 600 to 1300 m² / g ; a pore volume of 0.6 to 1.3 cm³ / g ; and a pore diameter of 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 preparing amorphous silica by filtration, washing, drying, and calcination .
  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. The method according to any one of claims 9 to 11 , characterized in that in step (1), the molar ratio of the silicon source as SiO₂ to the surfactant is 1:(0.02 to 0.3 ) .
  13. The method according to any one of claims 9 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 ) .
  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 aqueous ammonia .
  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. The method according to any one of claims 8 to 18 , characterized in that in step (2), the molar ratio of inorganic alkali as OH- to amorphous silica as SiO2 is 0.05 to 0.24 .
  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.

Description

Detailed description of the invention [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. [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, because 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. Currently, there are very few published patents for introducing a mesoporous structure into microporous ZSM-23 molecular sieves. 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 suffers from drawbacks such as insufficient stability and a narrow range of adjustable silica-alumina ratios. 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. According to CN107235497, starch is added to modify the synthesis pathway of the ZSM-23 molecular sieve and removed by calcination in a later stage, resulting in a ZSM-23 molecular sieve with a mesoporous-microporous hierarchical composite structure. While this method is simple and low-cost, the removal of the pore-expanding agent results in a mesoporous structure, which affects thermal and hydrothermal stability. 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 and 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. Therefore, developing a ZSM-23 molecular sieve rich in mesoporous structures that is simple, low-cost, and possesses excellent product performance is a technical challenge that needs to be solved by those skilled in the art. [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. 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%. According to the molecular sieve described above, the molecular sieve has a specific surface area of 300 to 430 m² /g, a pore volume of 0.31 to 0.5 cm² /g, a specific surface area of micropores of 50 to 170 m² /g, and a specific surface area of mesopores of 150 to 310 m² /g; preferably, a specific surface area of 320 to 405 m² /g, a pore volume of 0.34 to 0.45 cm³ /g, a specific surface area of micropores of 80 to 140 m² /g, and a specific surface area of mesopores of 261 to 295 m³ /g. 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