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CN-121974372-A - Crystal form E enriched silicon-aluminum-germanium Beta molecular sieve and preparation method and application thereof

CN121974372ACN 121974372 ACN121974372 ACN 121974372ACN-121974372-A

Abstract

The invention provides a crystal E-enriched silicon-aluminum-germanium Beta molecular sieve and a preparation method and application thereof, belonging to the technical field of molecular sieve material synthesis and catalysis application thereof. The molecular sieve framework contains silicon, germanium and aluminum elements, and the powder X-ray diffraction pattern of the molecular sieve framework shows strongest diffraction peaks at 2 theta = 9.78 degrees +/-0.3 degrees and 22.14 degrees +/-0.3 degrees, and the proportion of the crystal form E is not less than 80 percent. The preparation method uses tetraethylammonium hydroxide as a template agent, optimizes the Ge/Si/Al molar ratio, and optionally adds ITQ-1 seed crystal, and prepares the material after hydrothermal crystallization and roasting. The molecular sieve of the invention has a unique single-crystal hierarchical pore structure, effectively improves mass transfer limitation, and has far higher catalytic activity, low-carbon olefin selectivity and stability than the traditional ZSM-5 molecular sieve in hydrocarbon catalytic cracking, methanol-to-olefin and furfural/furfuryl alcohol etherification reactions, and has wide industrial application prospect.

Inventors

  • LU KUN
  • CHEN LIYU
  • LIU QIAN

Assignees

  • 上海理工大学

Dates

Publication Date
20260505
Application Date
20251202

Claims (10)

  1. 1. A crystal E enriched silicon-aluminum-germanium Beta molecular sieve is characterized in that germanium oxide, aluminum oxide and silicon oxide are connected with each other in a tetrahedral form to form an ordered hierarchical pore nanoparticle aggregate with a complete crystalline structure; the X-ray diffraction pattern of the molecular sieve at least comprises the following diffraction peaks when Cu-K alpha radiation is used: 2θ=9.78° ±0.3°, relative intensity VS; 2θ=22.14° ±0.3°, relative intensity VS; 2θ=6.87° ±0.3°, relative intensity S; 2θ=21.85 ° ± 0.3 °, relative intensity S; The proportion of the crystal form E in the molecular sieve is not less than 80 percent, and the framework of the molecular sieve contains silicon, germanium and aluminum elements.
  2. 2. Form E enriched silicoaluminogermanium Beta molecular sieve according to claim 1, characterized in that, The molecular sieve is expressed as xGeO 2 ·yAl 2 O 3 ·zSiO 2 in terms of the molar ratio of oxide, wherein the molar ratio of Ge/Si represented by x/z is 0.2-1.25, the molar ratio of Al/Si represented by y/z is 0-0.1, and the molecular sieve has a multi-stage pore structure composed of micropores and intra-crystalline/inter-crystalline mesopores.
  3. 3. The crystalline form E enriched Si-Al-Ge Beta molecular sieve according to claim 1, wherein the molecular sieve has a chemical composition of Ge a H + b Al c SiO d , wherein a is the molar ratio of Ge to Si and the variation range is 1/5-5/4, b is the molar ratio of H + to Si and the variation range is 1/100-1/5;c is the molar ratio of Al to Si and the variation range is 0-1/10, d is the molar ratio of O to Si, and d= (4) a +b+3 c+4)/2。
  4. 4. A preparation method of a crystal E-enriched silicon-aluminum-germanium Beta molecular sieve, preparing a crystalline form E enriched silicoaluminogermanium Beta molecular sieve according to any of claims 1 to 3, comprising: S1, mixing a germanium source, an aluminum source, an organic template agent and water to obtain a mixed solution; S2, adding a silicon source into the mixed solution, and stirring and reacting for 0.5-24 hours at 25-100 ℃ to prepare mixed gel, wherein the molar ratio of the germanium source calculated by GeO 2 to the aluminum source calculated by Al 2 O 3 to TEAOH to the silicon source calculated by SiO 2 to H 2 O in the mixed gel is 1.0:0-0.1:0.1-0.5:1-10:10-400; And S3, carrying out hydrothermal crystallization reaction on the mixed gel for 2-5 days at the temperature of 130-200 ℃, and then carrying out filtration separation, washing, drying and roasting on the obtained crystallized product to obtain the molecular sieve.
  5. 5. The method for preparing the crystal form E enriched silicon-aluminum-germanium Beta molecular sieve according to claim 4, wherein in the step S2, the ITQ-1 molecular sieve is taken as a seed crystal to be added together with the silicon source, and the adding amount of the seed crystal is 1 to 20 percent of the total mass of SiO 2 in the mixed gel; The stirring reaction temperature of the mixed gel is 70-90 ℃, and the stirring time is 2-5 hours; In the step S3, the hydrothermal crystallization reaction temperature is preferably 150-180 ℃.
  6. 6. The method for preparing a crystal form E enriched silicon-aluminum-germanium Beta molecular sieve according to claim 4, wherein the preferred molar ratio of germanium source calculated as GeO 2 to aluminum source calculated as Al 2 O 3 to TEAOH to silicon source calculated as SiO 2 to H 2 O in the mixed gel is 1.0:0-0.1:0.2-0.5:1-3:20-50.
  7. 7. The preparation method of the crystal form E enriched silicon-aluminum-germanium Beta molecular sieve according to claim 4, wherein the silicon source is one or more than two of silica sol, silicic acid, fuming silica gel, tetraalkyl silicate and ITQ-1, the germanium source is germanium oxide, the aluminum source is one or more than two of sodium metaaluminate, aluminum sulfate, aluminum isopropoxide, aluminum nitrate and aluminum hydroxide, and the organic template agent is tetraethylammonium hydroxide.
  8. 8. A method for preparing low-carbon olefin by catalytic cracking of hydrocarbon, which is characterized in that the crystal form E enriched silicon-aluminum-germanium Beta molecular sieve as the catalyst is used, and the hydrocarbon raw material is contacted and reacted with the silicon-aluminum-germanium Beta molecular sieve catalyst under the catalytic cracking reaction condition to generate a product containing C 2 -C 4 olefin.
  9. 9. A method for preparing low-carbon olefin from methanol, which is characterized in that the crystal form E enriched silicon-aluminum-germanium Beta molecular sieve as the catalyst is used for carrying out contact reaction on methanol or dimethyl ether raw material and the silicon-aluminum-germanium Beta molecular sieve catalyst under the reaction condition of preparing olefin from methanol to generate a product containing C 2 -C 4 olefin.
  10. 10. A method for preparing an oxygen-containing compound by converting furfural or furfuryl alcohol, which is characterized in that the crystal form E-enriched silicon-aluminum-germanium Beta molecular sieve is used as a catalyst, and the furfural or furfuryl alcohol and the silicon-aluminum-germanium Beta molecular sieve catalyst are contacted and reacted in the presence of a polar solvent under the reaction condition to generate furan derivatives, dienes or oxygen-containing compounds.

Description

Crystal form E enriched silicon-aluminum-germanium Beta molecular sieve and preparation method and application thereof Technical Field The invention relates to the technical field of molecular sieve material synthesis and catalytic application thereof, in particular to a crystal E-enriched silicon-aluminum-germanium Beta molecular sieve, and a preparation method and application thereof. Background The molecular sieve is a crystalline porous material with a regular microporous structure, and is widely applied to the fields of petrochemical industry, coal chemical industry, biomass conversion and the like due to the unique molecular sieving effect and adjustable acidity. Beta molecular sieve is taken as a typical macroporous molecular sieve, and the three-dimensional crossed twelve-membered ring pore canal structure of the Beta molecular sieve endows the Beta molecular sieve with excellent diffusion performance and catalytic activity. However, conventional Beta zeolites are intergrowth structures of A, B isopycnic amorphous stacks, which limits to some extent their performance optimisation. In recent years, researchers have successfully synthesized Beta family members with novel topologies, such as type C (BEC) and D/E intergeneration structures (e.g., SU-78, HPM-8), by introducing germanium (Ge) to stabilize the double four-ring (D4R) unit. However, the prior art suffers from the following prominent drawbacks: form E is difficult to enrich, so far, no successful synthesis of pure phase or enriched phase Beta molecular sieves with a proportion of form E exceeding 50% has been reported. In the known D/E intergrowth structure, D phase is usually dominant. The structure stability is poor, the existing silicon germanium D/E intergrowth structure molecular sieve (such as SU-78) is unstable in skeleton structure and easy to collapse after the template agent is removed by roasting, and the practical application of the molecular sieve is severely restricted. The difficulty in acid regulation is that the Bronsted acid is not enough or stable in acidity due to the difficulty in introducing aluminum (Al) into a stable D/E structure, so that the application of the Bronsted acid in various acid catalytic reactions is limited. The synthesis cost is high, complex and expensive organic template agents (such as imidazolium long-chain di-cations) are often needed to realize the guidance of the D/E structure, the economy is poor, and the industrialization is difficult to realize. In addition, the single microporous structure of the traditional zeolite can cause low mass transfer efficiency of macromolecular reactants and products, and carbon deposition deactivation is easy to cause. Therefore, developing a Beta molecular sieve with stable structure, adjustable acidity, controllable cost and rich crystal form E is a technical problem to be solved in the field. Disclosure of Invention The invention aims to overcome the defects of the prior art and provide the silicon-aluminum-germanium Beta molecular sieve with high crystal form E proportion, stable structure, multistage pore canal and adjustable acid position and the preparation method thereof. It is still another object of the present invention to provide the use of the molecular sieve in catalytic cracking, methanol to olefins and furfural/furfuryl alcohol conversion reactions, which exhibits excellent catalytic activity, selectivity and stability in the above reactions. In order to achieve the aim, the invention provides a crystal E-enriched silicon-aluminum-germanium Beta molecular sieve, which is characterized in that germanium oxide, aluminum oxide and silicon oxide are connected with each other in a tetrahedral form to form an ordered hierarchical pore nanoparticle aggregate with a complete crystal structure; the X-ray diffraction pattern of the molecular sieve at least comprises the following diffraction peaks when Cu-K alpha radiation is used: 2θ=9.78° ±0.3°, relative intensity VS; 2θ=22.14° ±0.3°, relative intensity VS; 2θ=6.87° ±0.3°, relative intensity S; 2θ=21.85 ° ± 0.3 °, relative intensity S; The powder X-ray diffraction pattern of the molecular sieve has characteristic diffraction peaks and relative intensities shown in the following table 1 when Cu-kα radiation (λ=1.5406 a) is used, and the proportion of the crystal form E is not less than 80%, and the framework of the molecular sieve contains silicon (Si), germanium (Ge) and aluminum (Al) elements. Table 1:E X-ray diffraction structure data sheet of enriched Si-Al-Ge Beta molecular sieve In the table, (a) is the relative intensity grade of diffraction peak in a powder X-ray diffraction spectrogram, W is a weak diffraction peak, M is a medium diffraction peak, S is a strong diffraction peak, VS is a strongest diffraction peak, the maximum value of diffraction peak intensity is 100, the strongest diffraction peak is 60-100, the strong diffraction peak is 45-60, the medium diffraction peak is 18-45, and the weak