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CN-121990585-A - Modified ZSM-5 molecular sieve and preparation method and application thereof

CN121990585ACN 121990585 ACN121990585 ACN 121990585ACN-121990585-A

Abstract

The invention discloses a preparation method of a modified ZSM-5 molecular sieve, which comprises the following steps of carrying out hydrothermal aging treatment on a nano HZSM-5 molecular sieve to obtain a dealuminated nano HZSM-5 molecular sieve, adding an inorganic alkali solution, a zinc-containing compound, a thio compound and a mesoporous template agent into the dealuminated nano HZSM-5 molecular sieve to carry out hydrothermal crystallization, and drying and roasting to obtain the modified ZSM-5 molecular sieve. The catalyst prepared by the modified ZSM-5 molecular sieve has high aromatization activity, and can ensure the gasoline yield and reduce the dry point backward shift of the product.

Inventors

  • JU YANA
  • XU HUA
  • ZHANG RAN
  • ZHANG YALIN
  • SONG SHAOTONG
  • LI YANG
  • LIU KUNHONG
  • LV ZHONGWU
  • CHEN YANFEI
  • JIANG ZENGKUN

Assignees

  • 中国石油天然气股份有限公司

Dates

Publication Date
20260508
Application Date
20241101

Claims (17)

  1. 1. The preparation method of the modified ZSM-5 molecular sieve is characterized by comprising the following steps: The nanometer HZSM-5 molecular sieve is subjected to hydrothermal aging treatment to obtain a dealuminated nanometer HZSM-5 molecular sieve; adding inorganic alkali solution, zinc-containing compound, thio compound and mesoporous template agent into the dealuminated nanometer HZSM-5 molecular sieve for hydrothermal crystallization, drying and roasting to obtain the modified ZSM-5 molecular sieve.
  2. 2. The method according to claim 1, wherein the molar ratio of the zinc-containing compound to the thio compound is 0.6 to 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 is 0.3-1.
  4. 4. The preparation method of claim 1, wherein the mass ratio of the dealuminated nano HZSM-5 molecular sieve to the thio compound to the mesoporous template is 1 (0.06-0.36) (0.36-1.1).
  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 or amine thiosulfate; 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 solution used in the ammonium exchange step is selected from the group consisting of ammonium chloride solution and/or ammonium nitrate solution, 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, wherein when the inorganic alkaline solution is selected from inorganic potassium salt solutions, the method further comprises 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.
  12. 12. A modified ZSM-5 molecular sieve prepared by the method of preparing the modified ZSM-5 molecular sieve as claimed in any one of claims 1 to 11.
  13. 13. Use of a modified ZSM-5 molecular sieve prepared by the method for preparing a 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 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 modified ZSM-5 molecular sieve is prepared from the modified ZSM-5 molecular sieve prepared by the preparation method of the modified ZSM-5 molecular sieve according to any one of claims 1 to 11.
  15. 15. A method for preparing a low-carbon hydrocarbon aromatization catalyst, which is characterized by comprising the following steps: Loading a metal auxiliary agent on a catalyst carrier by adopting an impregnation method, 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 low carbon hydrocarbon aromatization catalyst prepared by the process for preparing a low carbon hydrocarbon aromatization catalyst as claimed in claim 15, comprising a support and an active component, wherein the support comprises nano ZSM-5 molecular sieve and alumina, the active component comprises zinc, a group IIIA metal, a group VIII metal and a group IIIB metal, and preferably, the low carbon hydrocarbon aromatization catalyst further comprises potassium oxide.
  17. 17. The low carbon hydrocarbon aromatization catalyst of claim 16 having a micropore-mesopore structure with a total acid content of 0.10 to 0.25mmol/g, a strong B acid content of 0.02 to 0.1mmol/g, and an L/B of 2 to 6.

Description

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 modified ZSM-5 molecular sieve, a preparation method and application thereof. Background Aromatic hydrocarbons are widely used in synthetic fibers, resins and rubber and various fine chemicals, are indispensable basic organic chemical raw materials, and are also important blending components for producing high-octane gasoline. In recent years, as downstream aromatic products develop rapidly, the market demand for aromatic hydrocarbons continues to grow. Lower hydrocarbons and lower hydrocarbon-containing mixed hydrocarbons are byproducts of the petrochemical and refinery industries, produced from ethylene engineering, refineries, and natural gas purification processes. The low-carbon hydrocarbons are converted into aromatic hydrocarbons through an aromatization process, so that a new raw material source can be opened up for aromatic hydrocarbon production, light hydrocarbon resources can be optimally utilized, and the economic benefit of petrochemical enterprises is improved. Current research on aromatization of low carbon hydrocarbons has focused mainly on molecular sieve catalysts, particularly on ZSM-5 molecular sieves. 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. 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 pore channels is limited, side reactions such as cracking and polycyclic aromatic hydrocarbon generation are facilitated, the reduction of olefin in the products is insufficient, condensate oil is increased, the dry point of the products is moved backwards, the aromatization activity of the olefin of the catalyst and the yield of the gasoline are affected, and multiple requirements of greatly reducing olefin, maintaining octane number, controlling the distillation range and the like in the quality upgrading process of national VIB standard gasoline are difficult to meet. Therefore, how to regulate the ZSM-5 molecular sieve pore structure and acid distribution, increase molecular diffusion, inhibit side reactions such as polycyclic aromatic hydrocarbon generation and the like, and exert the synergistic effect of the metal active center and the acid center of the catalyst, thus becoming a key technical problem to be solved by the catalyst for the hydrogenation aromatization of the catalytic cracking gasoline. Aiming at the problems, a post-treatment method and a template agent method are mainly adopted to carry out reaming treatment on the ZSM-5 molecular sieve at present. The post-treatment method mainly comprises a hydrothermal treatment method, an acid treatment method and an alkali treatment method, which are all capable of destroying the framework structure of the molecular sieve, and meanwhile, the obtained mesoporous is irregular and easy to cause the reduction of crystallinity, and the template agent method is expensive, has complex steps and is difficult to industrialize. In the aspect of regulating and controlling the acid distribution of the catalyst to exert the synergistic effect of the metal active center and the acid center, the metal auxiliary agent is often modified by adopting an impregnation method, an ion exchange method, mechanical mixing and the like, so that the problems that the metal auxiliary agent is easily 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, CN112973772a discloses a gasoline aromatization isomerization catalyst, and the carrier in the catalyst adopts nano ZSM-5 particles obtained by growth along 051 crystal face direction, alumina and extrusion aid, and then the composite carrier is obtained by drying and roasting. When the catalyst prepared by impregnating the active metal component with the composite carrier is used for the olefin reduction reaction of the gasoline with high olefin content, the isomerization reaction and the aromatization reaction can be carried out while the olefin of the gasoline is greatly reduced, the octane number of the product is improved by 1.7-7 units, the desulfurization rate is more than 45%, the yield of the gasoline product is more than 98%, and the service life is more than 3000 hours. However, the composite carrier mainly focuses on regulating and controlling the aromatization performance through the growth orientation of the crystal face direction of the molecular sieve, the pore expansion treatment is not carried out, the diffusion limit of a catalyst micropore duct is difficult to change, t