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JP-7855593-B2 - ZSM-23 molecular sieve and method for preparing the same

JP7855593B2JP 7855593 B2JP7855593 B2JP 7855593B2JP-7855593-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
20260508
Application Date
20220107
Priority Date
20210107

Claims (20)

  1. A ZSM-23 molecular sieve, characterized in that the total acid content of the ZSM-23 molecular sieve is 0.05 to 0.25 mmol/g; the strong acid content of the ZSM-23 molecular sieve is 5 to 33% of the total acid content; and the strong acid refers to an acid whose desorption temperature in NH3 thermal desorption ( NH3 -TPD) is 350°C or higher.
  2. The ZSM-23 molecular sieve according to claim 1, characterized in that the total acid content of the ZSM-23 molecular sieve is 0.06 to 0.22 mmol/g; and the strong acid content of the ZSM-23 molecular sieve is 9 to 33% of the total acid content.
  3. The ZSM-23 molecular sieve according to claim 1, characterized in that the total acid content of the ZSM-23 molecular sieve is 0.06 to 0.20 mmol/g; and the strong acid content of the ZSM-23 molecular sieve is 10 to 28% of the total acid content.
  4. The molecular sieve according to any one of claims 1 to 3, characterized in that the particle size of the ZSM-23 molecular sieve is 100 to 700 nm.
  5. The ZSM-23 molecular sieve is characterized in that it has a molar ratio of SiO₂ / Al₂O₃ of 35 to 300 , a specific surface area of 200 to 400 m² /g, and a pore volume of 0.25 to 0.50 cm³ /g, as described in any one of claims 1 to 4.
  6. The ZSM-23 molecular sieve is characterized in that it has a molar ratio of SiO₂ / Al₂O₃ of 38 to 200 , a specific surface area of 280 to 370 m² /g, and a pore volume of 0.28 to 0.40 cm³ /g, as described in any one of claims 1 to 5.
  7. The ZSM-23 molecular sieve is characterized by having a relative crystallinity of 95-130% after firing, and a relative crystallinity of 93-120% after hydrothermal treatment with steam at 600°C for 2 hours, as described in any one of claims 1 to 6.
  8. The ZSM-23 molecular sieve is characterized by having a relative crystallinity of 98-120% after firing, and a relative crystallinity of 95-115% after hydrothermal treatment with steam at 600°C for 2 hours, as described in any one of claims 1 to 7.
  9. A method for preparing a ZSM-23 molecular sieve according to any one of claims 1 to 8, characterized by comprising the following steps: (1) A step of preparing a mixed solution comprising a template agent and amorphous silica-alumina and/or amorphous silica-alumina precursor, wherein the amorphous silica-alumina and/or amorphous silica-alumina precursor is derived from an alkaline aluminum source (e.g., aluminates or metaaluminates such as sodium aluminate, potassium aluminate, sodium metaaluminate, and potassium metaaluminate); (2) A step of adding an alkali source and a silicon source to the mixed solution of step (1); (3) A step of crystallizing the substance obtained in step (2), filtering , washing, drying, and calcining to produce a ZSM-23 molecular sieve.
  10. The method according to claim 9, characterized in that, in step (1), the template agent is one or more of isopropylamine, pyrrolidine, N,N-dimethylformamide, and dimethylamine.
  11. The method according to any one of claims 9 to 10, characterized in that, in step (1), the molar ratio of silicon (as silica):aluminum (as alumina) in the mixed solution is 1:(0.10 to 0.85); and the molar ratio of aluminum (as alumina):the template agent is 1:(10 to 100).
  12. The method according to claim 11, characterized in that, in step (1), the molar ratio of silicon (as silica):aluminum (as alumina) in the mixed solution is 1:(0.24 to 0.78); and the molar ratio of aluminum (as alumina):the template agent is 1:(20 to 65).
  13. In step (1), an amorphous silica-alumina precursor is prepared by carbonization, and then a template agent is added to the amorphous silica-alumina precursor to produce a mixed solution. The method for preparing the amorphous silica-alumina precursor in step (1) above is: A step of preparing a solution of an aluminum source and a solution of a silicon-containing compound, respectively; The method according to any one of claims 9 to 12, characterized by the steps of mixing the aluminum source solution with a portion of the silicon-containing compound solution, introducing CO2 gas to cause gelation, adding the remaining portion of the silicon-containing compound solution when the volume of introduced CO2 gas reaches 50 to 100% of the total volume of introduced CO2 gas, and aging to produce an amorphous silica-alumina precursor.
  14. The method according to claim 13, characterized in that the remaining portion of the solution of the silicon-containing compound as silica contains 5 to 85% by weight of the total amount of the solution of the silicon-containing compound as silica added.
  15. The method according to any one of claims 13 to 14, characterized in that the gelation reaction temperature is 10 to 40°C and the pH after gelation is controlled to 9 to 12.
  16. The method according to any one of claims 13 to 15, characterized in that the solution of the silicon-containing compound is a solution of water glass and/or sodium silicate.
  17. The method according to any one of claims 13 to 16 , characterized in that the concentration of the aluminum source solution, based on the mass of Al₂O₃ , is 15 to 60 g Al₂O₃ /L, the concentration of the silicon-containing compound solution, based on the mass of SiO₂ , is 40 to 260 g SiO₂ /L, and the concentration of CO₂ gas is 30 to 60 volume%.
  18. The method according to any one of claims 13 to 17, characterized in that the maturation time is 5 to 60 minutes; and the maturation temperature is 10 to 40°C.
  19. The method according to any one of claims 9 to 18, characterized in that, in step (1), the mixed solution is stirred at 10 to 35°C for 0.2 to 1.5 hours.
  20. In step (2), The method according to any one of claims 9 to 19, characterized in that, based on the aluminum (as alumina) in the mixed solution of step (1), the total molar ratio of SiO₂ : Al₂O₃ : R₂O (an alkali source, where R is an alkali metal such as sodium and potassium): H₂O = 1 : (0.0025 to 0.025) : (0.015 to 0.08) : (30 to 80), and the total molar ratio of template agent (SDA)/SiO₂ = 0.10 to 1.8.

Description

Detailed description of the invention [Technical Field] This invention relates to a ZSM-23 molecular sieve, as well as a method for producing and using the same, and more particularly to a ZSM-23 molecular sieve with a low strong acid content, as well as a method for producing and using the same. [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 particular, in the petrochemical industry, they exhibit excellent performance in the hydrocracking of long-chain alkanes and olefins, and in the isomerization of alkanes and aromatic hydrocarbons. Therefore, preparing ZSM-23 molecular sieves with superior performance is extremely important. Currently, there are numerous methods for preparing ZSM-23 molecular sieves. US4076842 was the first to disclose a method for synthesizing ZSM-23 molecular sieves using pyrrolidine as a template agent. Subsequently, US4490342 and US5707601 successively disclosed conditions for synthesizing ZSM-23 molecular sieves in systems using bis-quaternary ammonium salts (diquat-7) or small molecule amines and neutral amines as template agents. CN101214971 discloses a method for synthesizing nano-ZSM-23 molecular sieves. A reaction mixture consisting of an aluminum source, a silicon source, sodium hydroxide, and isopropylamine was hydrothermally crystallized to produce ZSM-23 molecular sieves with an average grain diameter of 100 nm or less. CN101613114 discloses a method for synthesizing ZSM-23 molecular sieves using ZSM-22 or ZSM-23 molecular sieves as crystalline species and a small number of template agents, such as ethylamine and n-butylamine. CN102897785 describes a stepwise process in which an organic template agent or an aqueous solution thereof and an aluminum source are mixed in a sealed reaction vessel at 50-190°C for a certain period of time; then a silicon source, an organic template agent, water, and crystalline species are added; and the reaction system is hydrothermally crystallized at high temperature to prepare HZSM-23 molecular sieves. Furthermore, CN102992346 discloses a method for synthesizing ZSM-23 molecular sieves without template agents, in which water and an aluminum source are mixed, a sodium source and a silicon source are added; the resulting mixture is uniformly stirred, crystalline species are added; and the reaction system is hydrothermally crystallized to produce the raw material powder for ZSM-23 molecular sieves. Among the publicly available techniques for ZSM-23 molecular sieves, the focus has mainly been on exploring the synthesis of new template agents, improving the structure of their porous channels, or reducing preparation costs by improving the synthesis process. There are few methods available to adjust its acidity. A paper (Journal of Catalysis, 1990, 121, 89-98) reported a method to increase the weak acid content of ZSM-23 by isomorphic substitution of Fe atoms with Al atoms. A paper (Ind. Eng. Chem. Res. 2013, 52, 15359-15365) disclosed a method to adjust the acidity distribution of ZSM-23 and thereby adjust its reaction performance by adding auxiliary MgO at a later stage. However, these techniques have limited ability to adjust the acidity of the molecular sieves, and the prepared ZSM-23 molecular sieves still have relatively high acid content, limiting their use in the field of shape-selective catalysis. [Summary of the Invention] To overcome the shortcomings of existing technologies, the present invention provides a ZSM-23 molecular sieve, as well as a method for preparing and using the same. The ZSM-23 molecular sieve has a low strong acid content, and the method for preparing the ZSM-23 molecular sieve is simple. The present invention relates to a ZSM-23 molecular sieve, wherein the total acid content of the ZSM-23 molecular sieve is 0.05 to 0.25 mmol/g, preferably 0.06 to 0.22 mmol/g, more preferably 0.06 to 0.20 mmol/g; the strong acid content of the ZSM-23 molecule is 5 to 33% of the total acid content, preferably 7 to 33%, more preferably 9 to 33%, or even more preferably 7 to 31%, and even more preferably 10 to 28%; where the strong acid refers to an acid whose desorption temperature in NH3 temperature-induced desorption ( NH3- TPD) is 350°C or higher, and optionally the ZSM-23 molecular sieve is calcined or uncalcined. In the present invention, ZSM-23 molecular sieve refers to the product obtained by drying after crystallization in molecular sieve preparation (i.e., uncalcined), or the product obtained by drying and calcining after crystallization in molecular sieve preparation (i.e., calcined). According to the ZSM-23 molecular sieve described above, the