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CN-118047393-B - Method for synthesizing SSZ-39 molecular sieve and application thereof

CN118047393BCN 118047393 BCN118047393 BCN 118047393BCN-118047393-B

Abstract

The invention belongs to the technical field of zeolite molecular sieve synthesis, and particularly relates to a method for synthesizing an SSZ-39 molecular sieve and application thereof. The synthesis method comprises the steps of uniformly stirring a template agent, water, an alkali source, an amorphous silicon source and an amorphous aluminum source, adding a pH regulator, uniformly stirring, adding SSZ-39 molecular sieve seed crystals, uniformly stirring to obtain initial gel, and sequentially carrying out crystallization treatment, filtration, washing, drying and roasting to obtain the Na-type molecular sieve. The invention adopts a conventional silicon source and an aluminum source, and is assisted by a small amount of seed crystals from an amorphous raw material, thereby avoiding the use of an expensive FAU type molecular sieve in the traditional method for synthesizing the SSZ-39 molecular sieve, realizing the low-cost synthesis of the SSZ-39 molecular sieve and obtaining higher yield, and realizing the direct synthesis of the SSZ-39 molecular sieve from the amorphous raw material for the first time, wherein the yield breaks through 72 percent. The obtained molecular sieve sample shows excellent catalytic performance and high hydrothermal stability in NH 3 -SCR reaction after Cu modification.

Inventors

  • LIU JIAXU
  • WANG HUI

Assignees

  • 大连理工大学

Dates

Publication Date
20260508
Application Date
20240112

Claims (9)

  1. 1. A method for synthesizing SSZ-39 molecular sieves, comprising at least the steps of: S1, mixing a template agent, an alkali source, an amorphous aluminum source, an amorphous silicon source and water, uniformly stirring, adding a pH regulator, uniformly stirring, and then adding SSZ-39 molecular sieve seed crystals, uniformly stirring to obtain initial gel, wherein the pH regulator is at least one of malic acid, lactic acid, oxalic acid, tartaric acid, citric acid, sulfuric acid, nitric acid and hydrochloric acid; S2, placing the initial gel into a reaction kettle, performing crystallization treatment, filtering, washing with water, drying and roasting to obtain a Na-type SSZ-39 molecular sieve; In the step S1, the molar ratio of the active ingredients SiO 2 、Al 2 O 3 , the alkali source, the template agent, the pH regulator and H 2 O in the initial gel is 1 (0.002-0.10), 0.20-0.40, 0.09-0.42, 0.02-0.10 and 12-35.
  2. 2. The method for synthesizing SSZ-39 molecular sieve according to claim 1, further comprising the steps of subjecting the Na-type SSZ-39 molecular sieve obtained in the step S2 to ammonium exchange by using an ammonium salt aqueous solution, and then filtering, washing, drying and roasting to obtain the H-type SSZ-39 molecular sieve.
  3. 3. The method of synthesizing SSZ-39 molecular sieves according to claim 1 or 2, wherein the aluminum source is selected from at least one of sodium aluminate, aluminum sulfate, boehmite, metallic aluminum, aluminum nitrate, aluminum isopropoxide, and aluminum hydroxide, and the silicon source is selected from at least one of silica sol, solid silica gel, water glass, sodium silicate, ethyl orthosilicate, and white carbon black.
  4. 4. The method of synthesizing SSZ-39 molecular sieves according to claim 1 or 2, wherein the source of alkalinity is sodium hydroxide and/or potassium hydroxide.
  5. 5. The method for synthesizing SSZ-39 molecular sieve according to claim 1 or 2, wherein the template agent is selected from the group consisting of N, N-dimethyl-2, 6-dimethylpiperidinium hydroxide, N-dimethyl-3, 5-dimethylpiperidinium hydroxide, N, at least one of N-diethyl-2-ethylpiperidinium, N-ethyl-N-methyl-2, 6-dimethylpiperidinium hydroxide, N-dimethyl-9-azocationic bicyclononane compound, N-diethyl-2, 2-dimethyl-2, 5-dihydropyrrole cationic compound and 2,4, 6-pentamethylene-2-azocationic bicyclooctane compound.
  6. 6. The method for synthesizing an SSZ-39 molecular sieve according to claim 1 or 2, wherein the SSZ-39 molecular sieve seed crystal is added in an amount of 2 to 10% of the sum of the mass of solid silica in the silicon source and the mass of alumina in the aluminum source.
  7. 7. The method for synthesizing an SSZ-39 molecular sieve according to claim 1 or 2, wherein the crystallization treatment is carried out at a temperature of 130-190 ℃ for 8-108 h.
  8. 8. The method for synthesizing SSZ-39 molecular sieve according to claim 2, wherein the concentration of the ammonium salt aqueous solution is 0.4-1M and the ammonium exchange temperature is 50-80 ℃.
  9. 9. A preparation method of the Cu-SSZ-39 catalyst is characterized by comprising the step of carrying out ion exchange modification on the H-type SSZ-39 molecular sieve obtained by the method of claim 2 in copper salt solution to obtain the Cu-SSZ-39 catalyst.

Description

Method for synthesizing SSZ-39 molecular sieve and application thereof Technical Field The application belongs to the technical field of zeolite molecular sieve synthesis, and particularly relates to a method for synthesizing an SSZ-39 molecular sieve and application thereof. Background The diesel engine discharges NO X diesel vehicle tail gas after combusting diesel. Exhaust gas components include hundreds of compounds, and the exhaust gas discharged to the environment is inhaled in a large amount to damage the health of people. Ammonia selective catalytic reduction (NH 3 -SCR) is currently the most effective NOx pollutant emission control technology. The catalyst used in the NH 3 -SCR technology mainly comprises noble metal catalyst, metal oxide catalyst, perovskite catalyst, metal supported molecular sieve catalyst, carbon-based catalyst and the like. In recent years, cu exchange small pore molecular sieves having 8 membered ring pores have played an important role in basic research and industrial fields due to their excellent catalytic and separation properties. Cu-exchanged small pore molecular sieves with 8 membered rings are considered to be the most suitable catalysts in NH 3 -SCR reactions. In particular, cu-SSZ-13 molecular sieves with CHA topology have been commercially used as SCR catalysts in diesel engines in 2010. The SSZ-39 molecular sieve structurally comprises a three-dimensional small pore system formed by crossed arrangement of double six rings (D6 Rs), and in 2012, moliner et al report that Cu-SSZ-39 shows excellent catalytic activity and high stability in NH 3 -SCR reaction for the first time, and Cu-SSZ-39 has the advantages of wider activity temperature window, higher denitration efficiency, better hydrothermal stability and the like compared with Cu-SSZ-13, and is expected to become a new generation diesel vehicle tail gas treatment catalyst for replacing Cu-SSZ-13. Extensive research has been conducted into the synthesis of SSZ-39 molecular sieves. Generally, SSZ-39 molecular sieves having an AEI topology are synthesized by intergranular transport of molecular sieves under basic conditions, guided by an organic templating agent. In the existing method for synthesizing the SSZ-39 molecular sieve, an ultrastable Y molecular sieve (USY) or a high-silicon Y molecular sieve (HSY) with a FAU topological structure is always used as a silicon source and an aluminum source and plays a role in structure guiding. In 2014, tsuneji Sano et Al reported for the first time that SSZ-39 molecular sieves were synthesized in alkaline medium using tetraethylphosphine hydroxide TEPOH as an organic template, and the Si/Al ratio of the obtained product was as high as 15, however, the starting material high-silicon Y molecular sieves were obtained by dealuminizing with high-temperature steam at 700 ℃ and dealuminizing with H 2SO4 acid washing after treatment, the treatment means were complicated and the cost was high. And TEPOH belongs to a phosphorus-containing template agent, phosphorus species in the obtained product crystal cages are difficult to completely remove after high-temperature roasting, and a large amount of TEPOH is used to pollute the environment (chem. Lett.2014,43, 302-304). Patent CN115893445A discloses a method for preparing SSZ-39 molecular sieve using cheap template agent, which adopts double template agent method, uses mixed solution of low-cost amine and conventional template agent as template agent, and uses USY molecular sieve to provide aluminium source. Patent CN116040646a discloses a method for preparing SSZ-39 molecular sieve by using X molecular sieve as raw material, through simple and easy operation method, using relatively easily available and low-cost X molecular sieve and a small amount of template agent, the pure-phase SSZ-39 molecular sieve is synthesized by means of crystal transformation, and the use of FAU type molecular sieve is still not avoided. Because the HSY is obtained by the complex dealumination post-treatment of a low-silicon Y molecular sieve (LSY), the crystal transformation synthesis method is high in cost, and factors such as silicon-aluminum ratio, crystallinity, non-framework aluminum content and heteroatom doping of the used HSY have great influence on the quality of the product SSZ-39 molecular sieve. If the synthesis conditions without adding the Y molecular sieve can be found, the industrial production cost can be obviously reduced. The university of Zhejiang, xiao et al, proposes to use conventional silica sol and conventional aluminum sodium aluminate instead of FAU type molecular sieve for the first time, so as to realize the synthesis of SSZ-39 molecular sieve, but the synthesis is limited by the chemical condition of gel, the interval of the pure phase SSZ-39 molecular sieve synthesized by the method is narrow, and the product is always accompanied with the heterogeneous molecular sieve with MOR, ANA and other structures. And the silicon-alu