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CN-121990586-A - Micropore-mesopore modified ZSM-5 molecular sieve and preparation method and application thereof

CN121990586ACN 121990586 ACN121990586 ACN 121990586ACN-121990586-A

Abstract

The invention discloses a micropore-mesopore modified ZSM-5 molecular sieve and a preparation method and application thereof, wherein the nanometer ZSM-5 molecular sieve after hydrothermal treatment is taken as a parent body, potassium hydroxide or sodium hydroxide is taken as an alkali source for alkali treatment, then a mesoporous template agent is added, the pH value is regulated to a certain range by utilizing an alkaline reagent, and then a zinc compound and a thio compound are introduced in situ. Meanwhile, in order to promote the action of zinc and skeleton aluminum, a stable complex is formed by introducing a proper complexing agent and a zinc compound to change the coordination environment of zinc ions, and then the complex reacts with a thio compound to promote the action of zinc and skeleton aluminum to generate medium-strength L acid (ZnOH +), so that the low-temperature aromatization activity and shape selectivity of the catalyst are effectively improved, the product distribution is improved, and the anti-carbon performance of the catalyst is enhanced.

Inventors

  • JU YANA
  • FENG QI
  • ZHANG RAN
  • LV ZHONGWU
  • LIU KUNHONG
  • LI RONGGUAN
  • ZHANG YALIN
  • SONG SHAOTONG
  • CHEN YANFEI
  • ZHANG ZHANQUAN

Assignees

  • 中国石油天然气股份有限公司

Dates

Publication Date
20260508
Application Date
20241101

Claims (19)

  1. 1. The preparation method of the microporous-mesoporous modified ZSM-5 molecular sieve is characterized by comprising the following steps of: The nanometer HZSM-5 molecular sieve is subjected to hydrothermal aging treatment to obtain a dealuminated nanometer HZSM-5 molecular sieve; Adding the dealuminated nano HZSM-5 molecular sieve into inorganic alkali solution, adding a mesoporous template agent, controlling the pH of the system to be 13-14, adding a zinc compound, a complexing agent and a thio compound, and performing hydrothermal crystallization, filtering, drying and roasting to obtain the micropore-mesoporous modified ZSM-5 molecular sieve.
  2. 2. The method of claim 1, wherein the molar ratio of the complexing agent to the zinc-containing compound is 0.6 to 2.5; the molar ratio of the zinc-containing compound to the thio compound is 0.6-1.
  3. 3. The preparation method of claim 1, wherein the molar ratio of the inorganic base in the inorganic base solution to the mesoporous template agent is 0.3-1; The mass ratio of the dealuminated nano HZSM-5 molecular sieve, the zinc-containing compound and the mesoporous template agent is 1 (0.18-0.40) to 0.7-1.1.
  4. 4. The method of claim 1, wherein after adding the medium Kong Moban, the pH of the system is controlled with an alkaline agent selected from urea and/or aqueous ammonia.
  5. 5. The method according to claim 1, wherein the hydrothermal aging treatment is carried out at a temperature of 400-600 ℃, a mass space velocity of 0.5-3 h -1 , and a time of 1-5 h.
  6. 6. The method according to claim 1, wherein the hydrothermal crystallization is performed by a process comprising a step of hydrothermal crystallization at 100 to 120 ℃ for 12 to 24 hours and a step of hydrothermal crystallization at 160 to 200 ℃ for 12 to 24 hours.
  7. 7. The preparation method of claim 1, wherein the drying temperature is 120-180 ℃ and the drying time is 60-180 min; the roasting temperature is 450-550 ℃ and the roasting time is 240-360 min.
  8. 8. The method of claim 1, wherein the thio compound is selected from thioacetamide and/or amine thiosulfate; The complexing agent is at least one selected from monoammonium phosphate, ethylenediamine and EDTA; the mesoporous template agent is selected from cetyl trimethyl ammonium bromide or cetyl trimethyl ammonium chloride; The inorganic alkali solution is selected from inorganic sodium salt solution or inorganic potassium salt solution, the inorganic potassium salt solution is at least one of potassium carbonate solution, potassium hydroxide solution and potassium bicarbonate solution, the inorganic sodium salt solution is at least one of sodium carbonate, sodium hydroxide and sodium bicarbonate, and the concentration of the inorganic alkali solution is preferably 0.1-0.3 mol/L; the zinc-containing compound is at least one selected from zinc acetate dihydrate, zinc nitrate and zinc sulfate.
  9. 9. The method of claim 8, further comprising the steps of ammonium exchanging the modified ZSM-5 molecular sieve, washing to neutrality, secondary drying, and secondary calcination when the inorganic alkaline solution is selected from inorganic sodium salt solutions.
  10. 10. The process according to claim 9, wherein the ammonium exchange step employs an ammonium solution selected from the group consisting of ammonium chloride and/or ammonium nitrate, preferably, The temperature of the secondary drying is 120-180 ℃ and the time is 60-180 min; The temperature of the secondary roasting is 450-550 ℃ and the time is 240-360 min.
  11. 11. The method according to claim 8, further comprising the step of separating the product of the hydrothermal crystallization and washing with an ammonium chloride solution or an ammonium nitrate solution to a pH of 8 to 9 before the drying when the inorganic alkali solution is selected from an inorganic potassium salt solution.
  12. 12. A microporous-mesoporous modified ZSM-5 molecular sieve prepared by the method for preparing a microporous-mesoporous modified ZSM-5 molecular sieve according to any one of claims 1 to 11.
  13. 13. The use of the micropore-mesopore modified ZSM-5 molecular sieve prepared by the preparation method of the micropore-mesopore modified ZSM-5 molecular sieve as defined in any one of claims 1-11 in the preparation of a catalyst.
  14. 14. The preparation method of the low-carbon hydrocarbon aromatization catalyst carrier is characterized by comprising the following steps of mixing and molding a microporous-mesoporous modified ZSM-5 molecular sieve, a binder and an extrusion aid, drying and roasting to obtain the low-carbon hydrocarbon aromatization catalyst carrier; Wherein the micropore-mesopore modified ZSM-5 molecular sieve is selected from the micropore-mesopore modified ZSM-5 molecular sieves prepared by the preparation method of the modified ZSM-5 molecular sieve according to any one of claims 1-11.
  15. 15. A method for preparing a low-carbon hydrocarbon aromatization catalyst, which is characterized by comprising the following steps: Impregnating a catalyst carrier with a supported metal auxiliary agent, and drying and roasting to obtain the low-carbon hydrocarbon aromatization catalyst; The catalyst carrier is selected from the group consisting of the low-carbon hydrocarbon aromatization catalyst carrier produced by the process for producing a low-carbon hydrocarbon aromatization catalyst carrier according to claim 14; The metal auxiliary agent is at least one selected from VIII group metal salt, IIIA group metal salt and IIIB group metal salt.
  16. 16. A process for preparing a low carbon hydrocarbon aromatization catalyst as claimed in claim 15, which comprises a support comprising nano ZSM-5 molecular sieve and alumina, and an active component comprising zinc, a group IIIA metal, a group VIII metal and a group IIIB metal.
  17. 17. The low carbon hydrocarbon aromatization catalyst of claim 16 further comprising potassium oxide and/or phosphorus oxide therein.
  18. 18. The low-carbon hydrocarbon aromatization catalyst of claim 16 or 17, wherein the low-carbon hydrocarbon aromatization catalyst has a micropore-mesopore structure, the total acid content of the low-carbon hydrocarbon aromatization catalyst is 0.10 to 0.30mmol/g, the strong B acid content is 0.01 to 0.08mmol/g, the medium strong acid ratio is not less than 30%, and the L/B is 2 to 8.
  19. 19. An aromatization reaction of distillate oil, characterized by using the low-carbon hydrocarbon aromatization catalyst produced by the process for producing a low-carbon hydrocarbon aromatization catalyst according to claim 16, or the low-carbon hydrocarbon aromatization catalyst according to claim 17 or claim 18.

Description

Micropore-mesopore modified ZSM-5 molecular sieve and preparation method and application thereof Technical Field The invention relates to the field of catalyst materials, in particular to a microporous-mesoporous modified ZSM-5 molecular sieve, and a preparation method and application thereof. Background The nano ZSM-5 molecular sieve has excellent aromatization performance due to the characteristics of short pore canal, multiple pore mouths, small in intra-crystal diffusion resistance, good thermal stability and the like, and is particularly applied to the industry in the process of aromatizing low-carbon hydrocarbon. However, due to the small aperture (< 0.6 nm), high acid content on the outer surface and the like of the ZSM-5 molecular sieve, the diffusion of reactants and products in the pore canal is limited, the occurrence of side reactions such as cracking, polycyclic aromatic hydrocarbon generation and the like is facilitated, and particularly in the aromatization process of gasoline, the aromatization selectivity is poor, coking and inactivation are easy to occur due to the factors such as low mesoporous ratio of the catalyst, high strong acid content on the surface and the like, and the long-period service life of the catalyst and the product distribution are influenced. The acid center is used as the catalytic active center of the aromatization reaction and is the key of the moderate aromatization reaction. The improvement of the reaction temperature is favorable for aromatization reaction, but also promotes side reactions such as cracking, cyclizing coking and the like, and accelerates the deactivation of the catalyst. Therefore, by regulating and controlling the synergistic effect of the metal active center and the acid center of the catalyst, the pore channel structure of the molecular sieve is optimized, and the development of the aromatization catalyst suitable for low temperature is a key for solving the problems that the aromatization selectivity of the existing catalyst is poor, the catalyst is easy to coke and deactivate and is unfavorable for long-period stable operation. At present, a post-treatment method and a template agent method are mainly adopted to perform reaming treatment on the ZSM-5 molecular sieve, but the crystallinity and acid quantity of the molecular sieve are easy to be reduced, and removed non-framework aluminum or silicon remains in the pore canal of the molecular sieve to influence the acid distribution of the molecular sieve, so that the low-temperature aromatization activity is not favorably exerted. The metal active center and the acid center of the catalyst are regulated and controlled to cooperate by adopting an impregnation method, an ion exchange method and the like, so that the problems that a metal auxiliary agent is accumulated on the surface of a carrier, a catalyst pore channel is blocked, the accessibility of the acid center and the metal active center in the pore channel is influenced and the like are easily caused. For example, chinese patent document CN106215973a discloses a preparation method of a modified ZSM-5 molecular sieve catalyst, specifically, a precursor aqueous solution is prepared by mixing and stirring a ZSM-5 molecular sieve, an aluminum source, a template agent, a structure auxiliary agent, an additive, alkali and water, then the precursor aqueous solution is crystallized, solid-liquid separated and roasted to obtain a modified molecular sieve raw powder, then the modified molecular sieve raw powder is mixed and stirred with an ammonium salt solution, filtered and stirred with the ammonium salt solution for a plurality of times, filtered and roasted to obtain a hydrogen-type ZSM-5 molecular sieve, and then the hydrogen-type ZSM-5 molecular sieve raw powder is mixed with a metal precursor solution, dried and roasted to obtain an aromatization catalyst. Although the catalyst has the characteristic of high aromatic selectivity, the catalyst is easy to coke and deactivate and is not suitable for low-temperature aromatization reaction. Chinese patent document CN107876082A discloses a method for treating ZSM-5 molecular sieve by post-treatment, which uses organic alkali solution to treat ZSM-5 molecular sieve by alkali, then crystallize, reamed the molecular sieve, realize the repair of skeleton structure, improve the crystallinity of molecular sieve, and prepare microporous-mesoporous-macroporous hierarchical molecular sieve. However, the catalyst prepared by the molecular sieve has poor aromatization selectivity and is not suitable for low-temperature aromatization reaction. Disclosure of Invention In view of the above, the invention provides a microporous-mesoporous modified ZSM-5 molecular sieve, a preparation method and application thereof, wherein the microporous-mesoporous modified ZSM-5 molecular sieve is firstly subjected to alkali treatment by taking nano ZSM-5 molecular sieve after hydrothermal treatment as a matrix and potassium