Search

CN-118005030-B - MWW structure molecular sieve and preparation method and application thereof

CN118005030BCN 118005030 BCN118005030 BCN 118005030BCN-118005030-B

Abstract

The invention provides an MWW structure molecular sieve, and a preparation method and application thereof. The preparation method comprises the steps of mixing an aluminum source, water, an alkali source, a first template agent, a second template agent, a silicon source and seed crystals to form gel, and crystallizing the gel to obtain the MWW structure molecular sieve, wherein the first template agent comprises cyclohexylamine, and the second template agent comprises at least one of diisopropylamine, di-N-butylamine, diisobutylamine, 1, 4-diazabicyclo [2.2.2] octane, 1, 6-hexamethylenediamine, N, N-tetramethyl-1, 6-hexamethylenediamine. The invention also provides the MWW structure molecular sieve prepared by the preparation method and application of the MWW structure molecular sieve. The MWW structure molecular sieve can be directly synthesized under the condition of not using hexamethyleneimine, piperidine and homopiperazine by using the method of the seed crystal and the two templates to assist crystallization in a synergic manner.

Inventors

  • CUI YAN
  • Zhang shang
  • XING SHIYONG
  • HAN MINGHAN
  • WANG XIAOHUA
  • GUO CHENGYU
  • XIE YIN
  • YU HONGYUE
  • QIAO LIANG
  • CHI KEBIN

Assignees

  • 中国石油天然气股份有限公司

Dates

Publication Date
20260512
Application Date
20221108

Claims (14)

  1. 1. A method for preparing a molecular sieve of MWW structure, wherein the method comprises: mixing an aluminum source, water, an alkali source, a first template agent, a second template agent, a silicon source and a seed crystal to form gel, and crystallizing the gel to obtain the MWW structure molecular sieve; Wherein the first template agent comprises cyclohexylamine, and the second template agent comprises one or more than two of diisopropylamine, di-N-butylamine, diisobutylamine, 1, 4-diazabicyclo [2.2.2] octane, 1, 6-hexamethylenediamine, N, N-tetramethyl-1, 6-hexamethylenediamine; The molar ratio of the first template agent to the second template agent is 0.5-20:1; The seed crystal is a molecular sieve with an MWW topological structure; Wherein, the alkali source is marked as MOH, the silicon source is calculated by SiO 2 , the aluminum source is calculated by Al 2 O 3 , the alkali source is calculated by M 2 O, the sum of the first template agent and the second template agent is marked as T, and the chemical composition of the gel meets the following mole ratio range: Al 2 O 3 /SiO 2 =0.005-0.05,M 2 O/SiO 2 =0.03-0.50,T/SiO 2 =0.10-0.75,H 2 O/SiO 2 =8-120; The mass ratio of the seed crystal to the silicon source is as follows, based on the dry matrix: seed/SiO 2 = 0.01-0.25; the crystallization temperature is 120-170 ℃, and the crystallization time is 12-120h.
  2. 2. The preparation method according to claim 1, wherein the chemical composition of the gel satisfies the following molar ratio range of H 2 O/SiO 2 = 15-120.
  3. 3. The method of claim 1, wherein the silicon source comprises one or a combination of two or more of silica, silicate ester.
  4. 4. The method of claim 1, wherein the silicon source comprises one or a combination of more than two of silica sol, solid silica gel, white carbon black, water glass, and ethyl orthosilicate.
  5. 5. The method of claim 1, wherein the aluminum source comprises one or a combination of two or more of meta-aluminates, aluminum sulfate, aluminum oxide, pseudo-boehmite.
  6. 6. The method of claim 1, wherein the seed crystals comprise MCM-22 molecular sieves and/or MCM-49 molecular sieves.
  7. 7. The method of claim 1, wherein the alkali source comprises sodium hydroxide and/or potassium hydroxide.
  8. 8. The production method according to any one of claims 1 to 7, wherein the production method comprises: Mixing an aluminum source, water, an alkali source, a first template agent and a second template agent to obtain an intermediate solution, adding a silicon source and a seed crystal into the intermediate solution, mixing to form gel, and crystallizing the gel to obtain the MWW structure molecular sieve.
  9. 9. A MWW structured molecular sieve obtained by the production process according to any one of claims 1 to 8.
  10. 10. The MWW structured molecular sieve according to claim 9, wherein the specific surface area of the MWW structured molecular sieve is 500m 2 g or more.
  11. 11. The MWW structured molecular sieve according to claim 9, wherein the MWW structured molecular sieve has a micropore specific surface area of 350m 2 g or more and the MWW structured molecular sieve has a mesopore specific surface area of 140m 2 g or more.
  12. 12. The MWW structured molecular sieve of claim 9, wherein the MWW structured molecular sieve has a pore volume of 0.60cm 3 g or more.
  13. 13. The MWW structured molecular sieve according to claim 9, wherein the MWW structured molecular sieve has a micropore volume of 0.16cm 3 g or more.
  14. 14. Use of a MWW structure molecular sieve according to any of claims 9-13 in the catalysis of alkylation, isomerization or cracking reactions.

Description

MWW structure molecular sieve and preparation method and application thereof Technical Field The invention relates to the technical field of molecular sieve material synthesis, in particular to an MWW structure molecular sieve, a preparation method and application thereof. Background The MWW structure molecular sieve has a very typical two-dimensional flaky shape, and the flaky structure is formed by stacking a plurality of basic monolayers, also forms a unique pore channel structure and mainly comprises a two-dimensional sine ten-membered ring pore channel of an ab axis plane, a twelve-membered ring super-cage structure and a half super-cage structure along the direction of a c axis. The size of the opening of the ten-membered ring channel is 0.41nm multiplied by 0.51nm, the ten-membered ring channel is distributed outside the super-cage structure, the size of the twelve-membered ring super-cage is 0.71nm multiplied by 1.82nm, the ten-membered ring super-cage is communicated with six identical super-cages on the ab-axis plane around the ten-membered ring channel, the size of the semi-super-cage distributed on the surface of the sheet layer is 0.71nm multiplied by 0.8nm, and the open twelve-membered opening of the semi-membered ring channel is very favorable for the diffusion of reactants, has excellent catalytic reaction performance for macromolecular reaction and is widely applied to the reaction processes such as alkylation. The MWW structure molecular sieve can be subdivided into a plurality of varieties according to different stacking modes of basic monolayers, wherein the MWW structure molecular sieve mainly comprises an MCM-22 molecular sieve, an MCM-49 molecular sieve with oxygen bridging between single layers, an MCM-36 molecular sieve with a column structure formed between layers, an MCM-56 molecular sieve with disordered stacking between layers, an ITQ-2 molecular sieve with a monolayer structure and the like. The MCM-22 molecular sieve is obtained by dehydrating the silicon hydroxyl groups between the roasting layers to form oxygen bridge bonds, and the crystal structure of the roasted MCM-22 molecular sieve is the same as that of the MCM-49 molecular sieve. Templates for direct induction synthesis of MWW structure molecular sieves typically include hexamethyleneimine, piperidine, homopiperazine. Among them, hexamethyleneimine is most used, but has disadvantages of easy volatility, flammability and high toxicity. Piperidine is difficult to obtain commercially. High piperazine is expensive and difficult to use. It is therefore important to develop an inexpensive, green method of synthesizing MWW structure molecular sieves. The synthesis of the existing MWW structure molecular sieve is generally realized by adopting hexamethyleneimine and another organic amine to be matched. It has been found from the prior art that direct seeding is not feasible to synthesize due to the specificity of molecular sieves of MWW structure, and that complete MCM-49 molecular sieves can be constructed by adding an organic amine based on seeding. The prior art for synthesizing MCM-22 molecular sieves without using hexamethyleneimine, piperidine and homopiperazine has not existed, so that development of a preparation method of MWW molecular sieves such as green and low-cost MCM-22 molecular sieves with strong operability is needed. Disclosure of Invention In order to solve the problems, the invention aims to provide an MWW structure molecular sieve, and a preparation method and application thereof. The MWW structure molecular sieve can be directly synthesized under the condition of not using hexamethyleneimine, piperidine and homopiperazine by using the method of the seed crystal and the two templates to assist crystallization in a synergic manner. In order to achieve the aim, the invention provides a preparation method of an MWW structure molecular sieve, which comprises the steps of mixing an aluminum source, water, an alkali source, a first template agent, a second template agent, a silicon source and seed crystals to form gel, and crystallizing the gel to obtain the MWW structure molecular sieve, wherein the first template agent comprises cyclohexylamine, and the second template agent can comprise one or more of diisopropylamine (with a molecular formula of C 6H15 N), di-N-butylamine (with a molecular formula of C 8H19 N), diisobutylamine (with a molecular formula of C 8H19 N), 1, 4-diazabicyclo [2.2.2] octane (with a molecular formula of C 6H12N2), 1, 6-hexamethylenediamine (with a molecular formula of C 6H16N2), N, N-tetramethyl-1, 6-hexamethylenediamine (with a molecular formula of C 10H24N2). In the preparation method, the first template agent and the second template agent both adopt low-toxicity and low-cost organic amine. The first template agent is used as a main template agent and can be matched with the seed crystal to realize the construction of a molecular sieve foundation layer structure. The second templ