阅读说明：本技术 一种无氟条件下Sn-Beta沸石分子筛的合成方法 (Synthesis method of Sn-Beta zeolite molecular sieve under fluorine-free condition ) 是由 姜久兴 纪红兵 严丹萍 王永庆 马飞 于 2019-11-20 设计创作，主要内容包括：本发明公开了一种无氟条件下Sn-Beta沸石分子筛的合成方法。该方法通过浓溶胶制备、加Beta分子筛晶种、恒温加热晶化等制备工艺得到Sn-Beta沸石分子筛。本发明避免了高毒性氟物种的使用,所合成出的Sn-Beta分子筛具有高锡量和高结晶度。本发明具有环境友好、价格低廉、工艺简单等优点。(The invention discloses a synthesis method of a Sn-Beta zeolite molecular sieve under a fluorine-free condition. The method obtains the Sn-Beta zeolite molecular sieve by the preparation processes of thick sol preparation, Beta molecular sieve seed crystal addition, constant-temperature heating crystallization and the like. The invention avoids the use of highly toxic fluorine species, and the synthesized Sn-Beta molecular sieve has high tin content and high crystallinity. The invention has the advantages of environmental protection, low price, simple process and the like.)

1. A method for synthesizing Sn-Beta zeolite molecular sieve under fluorine-free condition is characterized by comprising the following steps:

dissolving a template agent, an alkali source and a tin source together, adding a silicon source, stirring and mixing at room temperature to form concentrated sol, adding Beta molecular sieve seed crystals into the concentrated sol, controlling the water content within the molar ratio of the silicon source to water =5 ~ 12, transferring to a reaction kettle, heating in an oven at constant temperature for crystallization reaction, cooling at room temperature after the reaction is finished, and then carrying out suction filtration and drying on the obtained product to obtain the Sn-Beta zeolite molecular sieve.

2. The synthesis method according to claim 1, wherein the raw materials are added in a molar ratio of silicon source, alkali source, template agent and tin source =1:0.1 ~ 5:0.3 ~ 6:0.002 ~ 0.032.032.

3. The synthesis method according to claim 1, wherein the silicon source is silica white, the alkali source is sodium hydroxide, the template agent is tetraethylammonium hydroxide, and the tin source is tin tert-butoxide or tin pentahydrate tetrachloride.

4. The synthesis method according to claim 1, wherein the Beta molecular sieve seed crystal is added in an amount of 1 ~ 15% by mass based on the silicon source.

5. The synthesis method of claim 1, wherein the crystallization reaction temperature is 120 ~ 200 ℃ and the crystallization reaction time is 1 ~ 6 days.

Technical Field

The invention belongs to the field of molecular sieve preparation, and particularly relates to a method for quickly synthesizing a Sn-Beta zeolite molecular sieve by concentrated sol under a fluorine-free condition.

Background

Since the Beta zeolite is first synthesized by a hydrothermal method in Wadlinger R L of Mobil corporation in 1967, the Beta zeolite shows excellent catalytic performance in chemical fields such as hydrocracking reaction, isomerization reaction, alkylation reaction and the like due to high thermal stability and hydrothermal stability and good carbon deposit resistance. Sn is an element of the IV main group, the atomic radius is 0.14nm,¹¹⁹the Sn MAS-NMR spectrum proves that Sn and O can form tetrahedron to replace Al or Si in the framework of the Beta zeolite to form heteroatom Sn-Beta zeolite. After 20 years of research, Sn-Beta zeolite becomes an important solid Lewis acid catalyst and is used for glucose isomerization, Baeyer-Villiger oxidation and other reactions. The main synthesis methods of Sn-Beta zeolite include a hydrothermal method, an isomorphous substitution method and a dry glue method. The physical and chemical properties and morphology of the zeolite prepared by the 3 methods are different. The challenge of the current Sn-Beta zeolite synthesis is to find a preparation method for preparing Sn-Beta zeolite with high crystallinity and high Sn content, simplify the synthesis process, shorten the crystallization time and reduce the synthesis cost.

1997, open literatureChem. Commun,1997,5425-426 reported a method for the hydrothermal synthesis of Sn-Beta zeolite. The method is technically characterized in that in the process of preparing the silicon-aluminum gel, crystalline stannic chloride is added into raw materials, the Sn-Al-Beta zeolite is synthesized by a hydrothermal method, dealumination treatment is carried out on the Sn-Al-Beta zeolite by concentrated nitric acid, the dealuminated zeolite is used as seed crystal, and the Sn-Beta zeolite is prepared by the hydrothermal synthesis again. The Sn-Beta zeolite synthesized by the method has low content of framework Sn, and a plurality of Al atoms still exist in the framework.

2001, open literatureNature,2001,412423-425 improves the hydrothermal synthesis method, tetraethyl silicate is used as a silicon source, crystallized stannic chloride is used as an Sn source, HF solution is used as a mineralizer, and the Sn-Beta zeolite with high crystallinity is synthesized after 413K crystallization for 11 days. As the Si-Sn gel is difficult to spontaneously crystallize and nucleate under the hydrothermal condition, the crystallization time generally needs more than 10 days, and meanwhile, a fluorine-containing mineralizer with strong corrosivity, such as HF, is needed in the synthesis process. In the context of the subsequent reports,Proc. Natl. Acad. Sci. U. S. A., 2010, 107, 6164–6168，Angew. Chem. Int. Ed.,2012,51, 11736 –11739，Green Chem., 2013,15, 2101–2109，J. Mol. Catal. Chem., 2013, 379, 294- 302，Chem. Engin. J., 2013, 218, 425-432，Micropor. Mesopor. Mater.,2019,287,85-92，RSCAdv.2012,2，10475-10477，ChemNanoMat,2015,1,155-158，J. Catal.2017,352,1-12，Micropor. Mesopor. Mater.2018,266242, 251, etcDifferent Sn source medicines are used for synthesizing Sn-Beta zeolite, but due to the same problems, the crystallization time is too long, and the use of a fluorine-containing system causes serious energy waste, environmental pollution and the like, so that the application of the methods is limited.

Open literatureInorg. Chem. Front.2018,52763-2771A method using N-cyclohexyl-N, N-dimethylcycloheximide hydroxide as structure directing agent in the absence of F^-And performing hydrothermal synthesis on the Sn-Beta zeolite with different Sn contents in the system. Albeit in the absence of F^-The method is synthesized in a system, but the used structure directing agent is complex and high in price, and the crystallization time is too long, namely up to 14 days, so that the practicability of the work is influenced.

The preparation of Sn-Beta zeolite by isomorphous substitution method mainly has gaseous ion exchange methodChin. J.Catal,2015,36,820-828，J. Phys Chem. C,2011,115, 3663-3670，J.Catal.2015,330545-557 liquid ion exchange methodGreen Chemistry, 2013,152777-ACS Catalysis,2015,5928-ACSCatal.2014,4, 2801-2810,ACS Catal,2016,6, 4047- 4063,Angew. Chem. Int. Ed.2012,51, 11736-11739,Chin. J. Catal，2017,38, 426-433，App. Catal. A,Gen,2018,55652-63 and the Chinese patent of invention (CN108727180A) to prepare Sn-Beta zeolite.

Compared with hydrothermal synthesis, the isomorphous substitution method shortens the preparation time and can obtain the Sn-Beta zeolite with higher Sn content. However, the zeolite prepared by this method has a lower crystallinity, a large number of surface defect sites, and a high hydrophilicity, as compared with the sample prepared by hydrothermal synthesis in a fluorine-containing system.

Open literatureChem. Engin. J,2013,218425-432 reported a dry gel process for the rapid synthesis of Sn-Beta zeolite. The method is technically characterized in that fumed silica is used as a silicon source, and tin tetrachloride pentahydrate (SnCl) is used₄·5H₂O) as a tin source, tetraethylammonium hydroxide as a template agent, NH₄F is mineralizer, and the crystallization temperature is 180 ℃. The method can synthesize Sn-Beta zeolite in 3-6 hours, but NH is still required to be added into gel₄And F, a mineralizer. PublicOpen literatureGreen Chem, 2015,172943-2951 reports the synthesis of Sn-Beta zeolite by a dry gel method. The method is technically characterized in that gas-phase silicon dioxide is used as a silicon source, tin tert-butoxide is used as a tin source, tetraethylammonium hydroxide is used as a template agent, and the crystallization temperature is 180 ℃ to synthesize the Sn-Beta zeolite. Although no fluorine-containing compound is added, the synthesized Sn-Beta zeolite has low crystallinity and more defect sites.

In addition, the synthesis of zeolite molecular sieve by dry glue method requires the use of a special reaction kettle, and the reaction device is difficult to be industrially scaled up.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for quickly synthesizing the Sn-Beta zeolite molecular sieve under the fluorine-free condition without adding a fluorine-containing mineralizer in an aging stage.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for synthesizing a Sn-Beta zeolite molecular sieve under a fluorine-free condition comprises the following steps:

dissolving a template agent, an alkali source and a tin source together, adding a silicon source, and stirring and mixing at room temperature to form concentrated sol; adding Beta molecular sieve crystal seeds into the concentrated sol, controlling the water content, transferring the sol to a reaction kettle, and heating the sol in a drying oven at constant temperature to perform crystallization reaction; and after the reaction is finished, cooling at room temperature, and then carrying out suction filtration and drying on the obtained product to obtain the Sn-Beta zeolite molecular sieve.

In the above synthesis method, the raw materials are preferably added in a molar ratio of silicon source, alkali source, templating agent and tin source =1:0.1 ~ 5:0.3 ~ 6:0.002 ~ 0.032.032.

Preferably, in the above synthesis method, the silicon source is white carbon black, the alkali source is sodium hydroxide, the template agent is tetraethylammonium hydroxide, and the tin source is tin tert-butoxide or tin pentahydrate tetrachloride.

Preferably, in the above synthesis method, the Beta molecular sieve seed crystal is added in an amount such that the mass ratio of the silicon source is 1 ~ 15%.

Preferably, in the above synthesis method, the crystallization reaction temperature is 120 ~ 200 ℃, and the crystallization reaction time is 1 ~ 6 days.

Compared with the prior art, the invention has the beneficial effects that:

1. the method for synthesizing the Sn-Beta zeolite molecular sieve by using the concentrated sol under the fluorine-free condition avoids the use of high-toxicity fluorine species and greatly reduces the synthesis risk.

2. The invention can synthesize the Sn-Beta zeolite molecular sieve with high crystallinity and silicon-tin ratio (Si/Sn) of 50 ~ 200 within 48 hours, and promote the wide application of the Sn-Beta molecular sieve.

3. The inorganic raw materials adopted by the invention are environment-friendly, the price is low, the operation steps are simple and feasible, and the method has important significance in the field of actual chemical production.

Drawings

FIG. 1 is the XRD spectrum of the product of example 1.

FIG. 2 is an SEM image of the product of example 1.

FIG. 3 is a nitrogen sorption and desorption isotherm curve of the product of example 1.

Detailed Description

The invention is described in further detail below with reference to the following detailed description and accompanying drawings: