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CN-122006786-A - Self-synthesis all-silicon Beta molecular sieve catalyst for preparing butadiene from ethanol, and preparation method and application thereof

CN122006786ACN 122006786 ACN122006786 ACN 122006786ACN-122006786-A

Abstract

The invention discloses a self-synthesis all-silicon Beta molecular sieve catalyst for preparing butadiene from ethanol, and a preparation method and application thereof. The catalyst takes an all-silicon Beta molecular sieve which is directly synthesized by a hydrothermal method and does not contain framework aluminum as a carrier, cu and Pr are loaded on the carrier as bimetallic active components, cu provides excellent alcohol dehydrogenation activity, pr and a silicon hydroxyl nest interact to form Lewis acid sites, an active center for aldol condensation and MPV hydrogen transfer is provided for the catalyst, and the synergistic effect of Cu and Pr promotes the efficient directional progress of a reaction path to butadiene. The catalyst has the advantages of no strong acid pollution in the preparation process, low cost of active components, adjustable structure, excellent catalytic performance and the like, and has good prospect in industrial application of preparing butadiene from bioethanol.

Inventors

  • WANG CHAN
  • LIU XINGYU
  • BAO XIAOJUN
  • YUE YUANYUAN
  • LI TIESEN
  • CUI QINGYAN

Assignees

  • 福州大学

Dates

Publication Date
20260512
Application Date
20260311

Claims (10)

  1. 1. The preparation method of the self-synthesis all-silicon Beta molecular sieve catalyst for preparing butadiene from ethanol is characterized by comprising the following steps of: 1) Mixing and stirring a template agent, an alkali source and water to obtain a solution, and then adding a silicon source to form an initial gel mixture; 2) Aging the initial gel mixture at room temperature for 10-20 h, adding a commercial dealuminated Beta molecular sieve as a seed crystal, continuously aging at room temperature for 10-20 h, transferring the gel mixture to a polytetrafluoroethylene lining, placing the polytetrafluoroethylene lining in a stainless steel hydrothermal synthesis kettle, crystallizing at 120-160 ℃ for 24-42 h, filtering and washing the crystallized product to be neutral, and drying to obtain a dried sample; 3) Grinding a dried sample, mixing with NH 4 Cl solution, then carrying out ion exchange in a water bath kettle at 50-100 ℃ for 2-8 h, centrifuging to recover solid, repeating for 1 time, and calcining the centrifugally dried sample to obtain a catalyst carrier, namely the Si-Beta molecular sieve; 4) Dissolving a Cu metal precursor and a Pr metal precursor into water to form a precursor solution, adding the precursor solution into a Si-Beta molecular sieve, uniformly stirring, standing at room temperature, drying, and calcining in a muffle furnace to obtain the Cu-Pr/Beta catalyst.
  2. 2. The preparation method of the self-synthesis all-silicon Beta molecular sieve catalyst for preparing butadiene from ethanol according to claim 1 is characterized in that the template agent is one of tetraethyl ammonium hydroxide, tetrabutyl ammonium hydroxide and tetrapropyl ammonium hydroxide, the silicon source is one of white carbon black, tetraethyl orthosilicate, silica sol and solid silica gel, and the alkali source is one or two of sodium hydroxide, tetraethyl ammonium chloride, sodium chloride and ammonia water.
  3. 3. The method for preparing a self-synthesized all-silicon Beta molecular sieve catalyst for preparing butadiene from ethanol according to claim 1, wherein the molar ratio of the template agent to the silicon source is 0.15-0.35, and the molar ratio of water to the silicon source is 3-8.
  4. 4. The method for preparing the self-synthesis all-silicon Beta molecular sieve catalyst for preparing butadiene from ethanol according to claim 1, wherein the alkali source is a mixture of tetraethyl ammonium chloride and sodium chloride, the molar ratio of the tetraethyl ammonium chloride to the silicon source is 0.05-0.15, and the molar ratio of the sodium chloride to the silicon source is 0.06-0.13.
  5. 5. The method for preparing a self-synthesized all-silicon Beta molecular sieve catalyst for preparing butadiene from ethanol according to claim 1, wherein in the step 2), the crystallization time is 30-36 h, in the step 3), the concentration of the NH 4 Cl solution is 1 mol/L, the solid-to-liquid ratio of a dried sample to the NH 4 Cl solution is 1:3-12, and the calcination is performed at 300-600 ℃ for 3-8 h.
  6. 6. The method for preparing the self-synthesis all-silicon Beta molecular sieve catalyst for preparing butadiene by ethanol according to claim 1, wherein in the step 4), the Cu metal precursor is one of copper nitrate, copper chloride and copper acetate, and the Pr metal precursor is one of praseodymium nitrate, praseodymium chloride and praseodymium acetate.
  7. 7. The method for preparing a self-synthesized all-silicon Beta molecular sieve catalyst for butadiene production from ethanol according to claim 1, wherein in the step 4), the standing time is 3-6 h, the drying condition is 90-110 ℃ and 6-12 h, and the calcining condition is 300-600 ℃ and 3-8 h.
  8. 8. The preparation method of the self-synthesis all-silicon Beta molecular sieve catalyst for preparing butadiene from ethanol according to claim 1, wherein the loading of Cu element in the Cu-Pr/Beta catalyst is 0.1-0.5 wt%, and the loading of Pr element in the Cu-Pr/Beta catalyst is 4-6 wt%.
  9. 9. A Cu-Pr/Beta catalyst obtainable by the process according to any of claims 1-8.
  10. 10. Use of the Cu-Pr/Beta catalyst according to claim 9 for the direct conversion of ethanol to 1, 3-butadiene.

Description

Self-synthesis all-silicon Beta molecular sieve catalyst for preparing butadiene from ethanol, and preparation method and application thereof Technical Field The invention relates to the technical field of catalysts, in particular to a self-synthesis all-silicon Beta molecular sieve catalyst for preparing butadiene from ethanol, and a preparation method and application thereof. Background Butadiene is the third largest olefin chemical feedstock following ethylene and propylene, and is widely used in the manufacture of synthetic rubber, synthetic resins, and nylon products. The synthetic rubber prepared by using the rubber as a raw material mainly comprises polybutadiene rubber, nitrile rubber, chloroprene rubber and styrene-butadiene rubber. And the former global butadiene production mostly uses a C4 fraction extraction method, and the raw material source is highly dependent on petroleum resources. Along with the gradual maturation of coal-based ethanol and bioethanol production technologies, the production cost is continuously reduced. Under the background, in order to promote the development of coal chemical industry and reduce the dependence on petroleum routes, the synthesis of butadiene by using renewable ethanol as a raw material is a technical route which accords with the 'two carbon' strategy and is green and feasible. In the reaction mechanism of preparing butadiene from ethanol, aldol condensation route is widely accepted by academia, and the core is that butadiene is generated by condensation and dehydration of acetaldehyde. The method comprises the steps of 1, generating acetaldehyde by ethanol dehydrogenation, 2, generating 3-hydroxy butyraldehyde by aldol condensation of two molecules of acetaldehyde, 3, generating crotyl alcohol by the process of Meerwein-Pondorf-Verley by crotonaldehyde and ethanol, and 4, generating butadiene by dehydration of crotyl alcohol. The process of preparing butadiene from ethanol is a very complex series reaction process, so that the catalyst is required to have dehydrogenation active sites and Lewis acid sites at the same time, and the synergistic effect of the active sites is a key for improving the reaction performance of the catalyst. Beta molecular sieves are considered to be ideal catalyst supports or active components because of their regular microporous structure, tunable acidity and good hydrothermal stability. Ivanova et al [Sushkevich V L, Ivanova, II, Ordomsky V V, et al. Design of a Metal-Promoted oxide catalyst for the selective synthesis of butadiene from ethanol[J]. Chemsuschem, 2014, 7(9): 2527-2536.] have proposed the concept of coexistence of "closed" and "open" sites in Zr-BEA, and have also found that Zr "open" sites are more active for aldol condensation of acetaldehyde. However, the preparation method has inherent defects that authors use concentrated nitric acid to carry out severe dealumination treatment on commercial Beta zeolite to create silicon hydroxyl nest defect sites to anchor metal active centers. Not only does this process produce large amounts of strong acid waste liquid, it is environmentally unfriendly, but the intense acid treatment can compromise the structural integrity of the molecular sieve. In addition, the catalyst performance is not ideal, the ethanol conversion rate is only 48%, and the butadiene selectivity is 56%, which indicates that the catalyst system has a huge improvement space in both the ethanol conversion rate and the butadiene selectivity. Patent application CN118454730a discloses a Nb-second metal (m=zn, cu, etc.) dual-function catalyst supported on a dealuminated Beta molecular sieve. Although the technology is designed to integrate the isolated Nb (V) Lewis acid center of the framework with dehydrogenation metal (such as Zn) and realize higher ethanol conversion rate of 94.8%, the reported optimal catalyst has butadiene selectivity of only 64.9% under optimal conditions, which shows that the combination of Nb and conventional transition metals (Zn, cu, co and the like) has inherent limitations in regulating complex reaction paths and inhibiting the generation of byproducts. At the same time, the process produces a large amount of strong acid waste liquid containing aluminum, which pollutes the environment, and severe acid treatment may irreversibly destroy the integrity of the molecular sieve framework, affecting the long-term stability of the catalyst. The Davis et al [K. Mamedov, R.J. Davis, Cascade Reaction of Ethanol to Butadiene over Ag-Promoted, Silica- or Zeolite-Supported Ta, Y, Pr, or La Oxide Catalysts, ACS Catalysis, 13 (2023) 3333-3344.] system investigated the effect of different Lewis acid cations (Ta, Y, pr, la) on the reaction of ethanol to butadiene on dealuminated Beta zeolite and amorphous SiO 2 support. The research proves that the Beta zeolite can obviously promote the C-C coupling rate as a carrier, which highlights the advantages of the micropore limit effect. However, in the aspec