CN113998707B - Super-macroporous IRR structure silicate molecular sieve material and preparation method thereof - Google Patents

Abstract

The invention discloses a super-macroporous silicate molecular sieve with an IRR (iron-reducing) framework crystal structure, which has a chemical composition form of p (M) _1/n XO ₂ )·qYO ₂ ·SiO ₂ Wherein M represents a proton or an inorganic cation of + n valency; x represents one or more trivalent elements; y represents one or more tetravalent elements other than Si and Ge; p =0-0.03, q =0-0.03. The molecular sieve has oversized 18-membered pore channels in the c-axis direction of a unit cell, 12-membered pore channels in the a-axis and b-axis directions, and 18 multiplied by 12 crossed three-dimensional pore channels. The invention further discloses a preparation method of the molecular sieve, which is obtained by using an organic template and a certain amount of seed crystals to promote crystallization through a hydrothermal synthesis method, and the molecular sieve has a stable skeleton structure after the organic template is removed, and has potential application value in the field of catalysis.

Description

A kind of ultra-large pore IRR structure silicate molecular sieve material and preparation method thereof

technical field

The invention belongs to the technical field of preparation of zeolite molecular sieves, and in particular relates to a preparation method of a super-large-pore IRR structure silicate molecular sieve material.

Background technique

Molecular sieves are a class of porous materials composed of TO ₄ (T=Si, Al, Ge, etc.) tetrahedrons through shared vertices, with excellent chemical and hydrothermal stability, variable chemical composition, specific pore diameters and pore channels Shape, so as to show properties such as solid acidity, gas selective adsorption and separation, ion exchange, and guest molecule transport. Has an empirical chemical formula: x(M _{1/ n} XO ₂ )·yYO ₂ ·zR·qH ₂ O, wherein M represents one or more +n-valent organic or inorganic cations; X represents one or more trivalent elements; Y represents one or more tetravalent elements, usually Si; R represents one or more organic molecules.

According to the number of TO ₄ tetrahedrons surrounding the channels, molecular sieve materials can be divided into small-pore, medium-pore, large-pore and ultra-large-pore molecular sieves, which correspond to 8-membered rings (that is, composed of 8 TO ₄ tetrahedra), 10 The number of window rings below the 12-membered ring, below the 12-membered ring, and above the 12-membered ring. The pore size of molecular sieve materials successfully applied in industry is usually below 1nm, which limits the molecular size and shape of reaction substrates in the adsorption, separation, and catalysis processes, and becomes a constraint in the practical application of molecular sieve materials. Ultra-large pore molecular sieves have great application prospects in cracking processes, fine chemical production, selective catalysis, and separation of macromolecules due to their large pores, and have long attracted the attention of chemists and industries. Although the synthesis of ultra-large pore molecular sieves has made great progress in the past few decades, the preparation of stable ultra-large pore molecular sieves is still a challenge.

Crystallization of ultra-large pore silicate molecular sieves is very difficult, and the number of synthesized silicate molecular sieve materials with ultra-large pore structure is very limited. In recent years, the successful synthesis of ultra-large pore molecular sieves is mainly attributed to the use of special organic structure-directing agents and heteroatoms in the synthesis process. Among them, the presence of germanium has lower geometric constraints on the formation of primary structural units, making it prone to form double four-membered rings or double three-membered rings, which makes it easier to form ultra-large pore molecular sieves, leading to the synthesis of a series of silicon germanate molecular sieves . However, germanium is a relatively rare and expensive element, and the hydrothermal stability of germanosilicate molecular sieves is poor, which limits its industrial application.

J.Yu,A.Corma,Angew.Chem.Int.Ed.2010,49:4986)。所述三维孔道在晶胞c方向具有一个十八元环孔道，而a，b方向各具有一个十二元环孔道，形成与十八元环孔道交叉的孔道结构。令人遗憾的是，ITQ-44骨架中大量锗的存在，不仅成本高，而且使这种材料的水热稳定性有限，很大程度上限制了其工业应用，而该结构仍然没有合成出纯硅酸盐(二氧化硅)和硅铝酸盐的形式。纯硅酸盐和硅铝酸盐分子筛水热稳定性好，且铝原子引入酸性位点，可直接用于酸催化。因此，合成开发超大孔IRR结构的纯硅酸盐和硅铝酸盐沸石分子筛具有非常重要的应用价值。The IRR structure (IRR is the structure code confirmed by the International Molecular Sieve Association) ultra-large pore germanosilicate molecular sieve ITQ-44 has 18 × 12 × 12 intersecting three-dimensional channels and a secondary structural unit composed of double three-membered ring cages (J. Jiang, JL, Jorda, MJ

J. Yu, A. Corma, Angew. Chem. Int. Ed. 2010, 49:4986). The three-dimensional channel has an 18-membered ring channel in the c direction of the unit cell, and a 12-membered ring channel in each of the a and b directions, forming a channel structure intersecting with the 18-membered ring channel. Regrettably, the existence of a large amount of germanium in the framework of ITQ-44 not only has high cost, but also makes this material have limited hydrothermal stability, which greatly limits its industrial application, and this structure still has not been synthesized into pure Silicate (silicon dioxide) and aluminosilicate forms. Pure silicate and aluminosilicate molecular sieves have good hydrothermal stability, and aluminum atoms introduce acidic sites, which can be directly used for acid catalysis. Therefore, the synthesis and development of pure silicate and aluminosilicate zeolite molecular sieves with ultra-large pore IRR structure has very important application value.

Contents of the invention

The object of the present invention is to provide a silicate molecular sieve with ultra-macroporous IRR structure, which can be obtained by hydrothermal synthesis method, using an organic template and a certain amount of IRR seed crystals (containing or not containing germanium) to promote crystallization. The ultra-large-pore IRR silicate molecular sieve has an IRR framework crystal structure, does not contain germanium in the framework, and has good hydrothermal stability. The molecular sieve provides a new choice for the application of molecular sieve materials in industrial catalysis.

Technical scheme of the present invention is as follows:

A silicate molecular sieve with an ultra-large pore IRR structure, which has an IRR skeleton crystal structure, and has a chemical composition in the form of p(M _{1/ n} XO ₂ )·qYO ₂ ·SiO ₂ , wherein M represents a proton or an inorganic cation with a valence of +n; X represents one or more trivalent elements; Y represents one or more tetravalent elements other than silicon and germanium; p=0-0.03, q=0-0.03.

Preferably M represents proton or sodium; X is Al or B, X is Ti, p=0-0.02; q=0-0.02.

The ultra-macroporous IRR structure silicate molecular sieve of the present invention can be prepared by the following method, including the following steps: (1) proportioning silicon source material, boron group element compound, tetravalent element compound except silicon and germanium, organic Template agent, fluorine source material, IRR seed crystal Seed and water are mixed evenly under stirring, and the reaction can be performed under static or dynamic stirring conditions to obtain a reaction gel. The chemical composition of the reaction gel is: rROH:aHF:xX ₂ O ₃ :yYO ₂ :SiO ₂ :bSeed:wH ₂ O, wherein R represents the positively charged group of the organic template; X represents one or more trivalent elements, preferably X is Al or B; Y represents the addition of silicon and germanium One or more tetravalent elements other than Y, preferably Y is Ti; r=0.1-1.0, a=0-1.0, b=0.001-0.05, x=0-0.03, y=0-0.03, w=1-50 , preferably r=0.5-0.75, a=0.5-0.75, b=0.01-0.05, x=0-0.02, y=0-0.02, w=1-10; R is Ar-(im) ⁺ organic cation, wherein Ar represents the tert-butylbenzyl group substituted in the meta-position, and im represents N-substituted imidazole;

(2) Remove the excess solvent from the reaction gel (such as under an infrared lamp or in an oven at 80°C) to the theoretical weight, then transfer the reaction gel to a stainless steel reaction kettle, and react for 7-30 days at 140-170°C under sealed conditions , preferably 14-20 days;

(3) washing and drying the crystallized product in step (2), and roasting in an air atmosphere at 400-650° C. for 2-5 hours to obtain a super-macroporous silicate molecular sieve without template.

Preferably, the silicon source material is one or more of water glass, silica sol, ethyl orthosilicate or butyl orthosilicate. The boron compound is preferably one or more of sodium metaaluminate, aluminum isopropoxide, aluminum sulfate hexadecahydrate, aluminum hydroxide or boric acid. Preferably, the fluorine source substance is hydrofluoric acid and/or ammonium fluoride. Preferred tetravalent element compounds other than silicon and germanium are tetra-n-butyl titanate and tin dioxide.

In the preparation method of the above ultra-large pore molecular sieve, the organic template is tert-butyl benzyl imidazolium salt, and the positively charged group R is preferably listed in Table 1.

Table 1

J.Yu,A.Corma,Angew.Chem.Int.Ed.2010,49:4986；R.Bai,Q.Sun,N.Wang,Y.Zou,G.Guo,S.Iborra,A.Corma,J.Yu,Chem.Mater.2016,28:6455)制备而成ITQ-44硅锗酸盐。可以进一步将本发明所述的纯硅酸盐、硅铝酸盐或硅钛酸盐分子筛作为晶种用于大规模生产。The IRR seed crystal seed described in the above preparation method is a molecular sieve with an IRR structure of germanosilicate, pure silicate, aluminosilicate or titanosilicate. The IRR germanosilicate ITQ-44 can be prepared by using a germanium-containing compound, such as germanium dioxide, in step (1) on the basis of the preparation method of the present invention. Or use the methods in the literature (such as J.Jiang, JLJorda, MJ

J. Yu, A. Corma, Angew. Chem. Int. Ed. 2010, 49:4986; R. Bai, Q. Sun, N. Wang, Y. Zou, G. Guo, S. Iborra, A. Corma, J.Yu, Chem.Mater.2016,28:6455) prepared from ITQ-44 silicon germanate. The pure silicate, aluminosilicate or titanosilicate molecular sieve described in the present invention can be further used as a seed crystal for large-scale production.

In the above method, before the preparation of the reaction gel, the organic template is exchanged into the form of hydroxide alkali (ROH) through the ion exchange resin, and its concentration is calibrated by 0.1M hydrochloric acid solution before use.

To prepare titanosilicate or germanosilicate molecular sieves, first add the compound containing titanium or germanium into the obtained basic template solution, stir and dissolve, then add silicon source and continue stirring, and finally add the corresponding boron group elements compound, stir evenly, add fluorine source material, heat under infrared lamp or oven to remove excess solvent in the system, and obtain the target gel.

Advantage of the present invention:

The present invention utilizes specific templating agent, by adding certain IRR structure seed crystal (containing germanium or not containing germanium), hydrothermal synthesis prepares the silicate molecular sieve containing trace germanium or germanium-free ultra-macroporous IRR structure, avoids the previous synthesis of this Structural molecular sieves first use germanium to synthesize germanium silicate ITQ-44 with IRR structure, and then remove germanium and supplement silicon or supplement aluminum to obtain the shortcomings of pure silicate and aluminosilicate molecular sieves with IRR structure. The IRR structure silicate molecular sieve prepared by the present invention has 18-membered channels in the direction of the crystallization axis c, and 12-membered channels in the directions a and b, has good thermal stability, can be mixed with heteroatoms, and has potential in the field of catalysis. application value.

Description of drawings

Figure 1 is the X-ray powder diffraction pattern (Cu target) of the synthesized product.

Fig. 2 is a scanning electron micrograph of the synthesized all-silicon molecular sieve product.

detailed description

The specific steps of the present invention are illustrated below through the examples, but not limited by the examples.

The terms used in the present invention, unless otherwise specified, generally have the meanings commonly understood by those skilled in the art.

The present invention will be described in further detail below in conjunction with specific examples and with reference to data. It should be understood that these examples are only for illustration of the present invention, but not to limit the scope of the present invention in any way.

In the following examples, various procedures and methods not described in detail are conventional methods well known in the art.

Embodiment 1: Taking the template agent 1 in Table 1 as an example, the synthesis process of the template agent is illustrated.

Dissolve 15mL of 4-tert-butylbenzyl chloride in 150mL of tetrahydrofuran, then add 6.2mL of 1-methylimidazole, and reflux for 2 days. After cooling down to room temperature, the white solid product was obtained by suction filtration, washed with diethyl ether (3×10 mL), and dried in vacuo overnight, with a yield of 95%. The product was characterized by liquid NMR (D ₂ O) and electrospray mass spectrometry, and it was confirmed to be the target compound.

The resulting product was dissolved in 100 mL of deionized water, and ion-exchanged by 717 strong basic anion-exchange resin to obtain an aqueous alkali solution of the template agent in the form of hydroxide. Weigh an appropriate amount of this solution, calibrate it with 0.1mol/L hydrochloric acid solution, and use phenolphthalein as an indicator. The calibration results confirmed that the exchange efficiency of template agent 1 chloride salt to hydroxide base reached 94%.

Template agents 2-4 in Table 1 can be prepared by referring to the above method.

此分子筛在结构上与ITQ-44同构，在结晶轴c方向具有一个18元环孔道，在a，b轴方向上存在12元孔道，是具有IRR结构的硅锗酸盐分子筛ITQ-44。根据单晶X射线结果对分子筛的粉末衍射进行理论分析拟合，结果与实际粉末X射线衍射分析结果一致。上述硅锗酸盐分子筛可用作合成硅(铝)酸盐分子筛的晶种。Example 2: Prepare the gel synthesized by molecular sieves according to the molar ratio of 1SiO ₂ : 0.2GeO ₂ : 0.5ROH: 0.5HF: 3H ₂ O, the steps are as follows: Weigh the metered template agent 1 alkali solution, add 0.2mmol ( 0.0209g) of germanium dioxide and 1mmol (0.2084g) of tetraethyl orthosilicate, stirred at room temperature for about two hours to dissolve them completely, then added a designed amount of hydrofluoric acid solution, stirred evenly, and placed the mixed gel in an infrared Under a lamp or in an oven at 80°C, remove excess solvent to theoretical weight. The final reaction gel was transferred to a 15mL stainless steel reaction kettle with a polytetrafluoroethylene liner, and reacted at 160°C for 15 days under sealed conditions. The product was washed twice with water and twice with ethanol, and dried for use. The single crystal X-ray diffraction test was carried out at -180°C, and the results showed that the crystallized in the space group P6/mmm,

This molecular sieve is structurally isomorphic to ITQ-44, has an 18-membered ring channel in the direction of the crystal axis c, and has 12-membered channels in the directions of the a and b axes. It is a germanosilicate molecular sieve ITQ-44 with an IRR structure. According to the single crystal X-ray results, the powder diffraction of molecular sieves was theoretically analyzed and fitted, and the results were consistent with the actual powder X-ray diffraction analysis results. The above-mentioned germanosilicate molecular sieves can be used as crystal seeds for synthesizing silicon (aluminum) salt molecular sieves.

Example 3: Prepare the gel synthesized by molecular sieves according to the molar ratio of 1SiO ₂ : 0.75ROH: 0.03Seed: 0.75HF: 3H ₂ O, the steps are as follows: Weigh the measured template agent 1 alkali solution, add 1mmol (0.2084g) orthosilicate, stirred at room temperature for about two hours to completely dissolve the orthosilicate, then added a designed amount of hydrofluoric acid solution, stirred evenly, and finally added 0.03mmol (0.0120g) of the product of Example 2 to obtain a crystal First, place the mixed gel under an infrared lamp or in an oven at 80°C to remove excess solvent to a theoretical weight. The final reaction gel was transferred to a 15mL stainless steel reaction kettle with a polytetrafluoroethylene liner, and reacted at 160°C for 15 days under sealed conditions. The product was washed twice with water and twice with ethanol, and dried for use. X-ray powder diffraction phase identified it as a silicate molecular sieve with an IRR structure (named NUD-16). The above-mentioned molecular sieve was calcined at 550°C for 4 hours in an air atmosphere to remove template molecules, and its structure remained stable, as shown in the figure. 1. Scanning electron micrographs show that the product is spherical (as shown in Figure 2).

Example 4: According to the molar ratio of 1SiO ₂ : 0.5ROH: 0.01Al ₂ O ₃ : 0.03Seed: 0.5NH ₄ F: 3H ₂ O, the gel synthesized by molecular sieves is prepared, and the steps are as follows: Weigh the metered template agent 1 base solution, first add 0.01mmol (0.0021g) of aluminum isopropoxide to it, stir for about half an hour, then add 1mmol (0.2084g) of tetraethyl orthosilicate, and stir at room temperature for about two hours to make orthosilicate The ester is completely dissolved, then add a designed amount of ammonium fluoride solution, stir evenly, and finally add 0.03mmol (0.0120g) of the product of Example 3 as a seed crystal, place the mixed gel under an infrared lamp or in an oven at 80°C, and remove Excess solvent to theoretical weight. Transfer the final reaction gel to a 15mL stainless steel reaction kettle with a polytetrafluoroethylene liner, and react at 160°C for 20 days under sealed conditions. The product is washed twice with water and twice with ethanol, and identified by X-ray powder diffraction. It is an aluminosilicate molecular sieve Al-NUD-16 with an IRR structure. The above-mentioned molecular sieve is calcined in an air atmosphere at 550°C for 2 hours to remove template agent molecules, and its structure remains stable. The X-ray powder diffraction results of molecular sieves are shown in Fig. 1 .

Example 5: According to the molar ratio of 1SiO ₂ : 0.75ROH: 0.01TiO ₂ : 0.05Seed: 0.75HF: 3H ₂ O, the gel synthesized by molecular sieves was prepared. Add 0.01mmol (0.0035g) of tetrabutyl titanate, stir for about half an hour, then add 1mmol (0.2084g) of tetrabutyl orthosilicate, and stir for about two hours at room temperature to completely dissolve the orthosilicate , then add a designed amount of hydrofluoric acid solution, stir evenly, and finally add 0.05mmol (0.0200g) of the product of Example 3 as a seed crystal, place the mixed gel under an infrared lamp or in an oven at 80°C, and remove excess solvent to theoretical weight. The final reaction gel was transferred to a 15mL stainless steel reaction kettle with polytetrafluoroethylene lining, and reacted at 170°C for 15 days under sealed conditions. The product was washed twice with water and twice with ethanol, and identified by X-ray powder diffraction. It is titanosilicate molecular sieve Ti-NUD-16 with IRR structure. The above-mentioned molecular sieve is calcined in an air atmosphere at 550°C for 2 hours to remove template agent molecules, and its structure remains stable. The X-ray powder diffraction results of molecular sieves are basically consistent with those shown in Figure 1.

Example 6: Prepare molecular sieve synthesis gel and carry out synthesis according to the material ratio and steps of Example 3, except that the template agent used is an alkaline solution of para-substituted methyl benzyl imidazolium cation. The obtained product was identified as amorphous by X-ray powder diffraction (as shown in FIG. 1 ).

Claims (9)

1. The super-macroporous silicate molecular sieve with IRR structure is characterized by having IRR framework crystal structure and having chemical composition form ofp(M _1/n XO ₂ )·qYO ₂ ·SiO ₂ Wherein M represents a proton or an inorganic cation of + n valency; x represents one or more trivalent elements; y represents one or more tetravalent elements other than silicon and germanium;p = 0–0.03，q=0-0.03, the ultra-large pore IRR structure silicate molecular sieve adopts the following componentsThe preparation method comprises the following steps:

(1) Uniformly mixing a silicon source substance, a boron family element compound, a tetravalent element compound except silicon and germanium, an organic template agent, a fluorine source substance, an IRR Seed crystal Seed and water in proportion under stirring to obtain a reaction gel, wherein the reaction gel comprises the following chemical components:rROH:aHF:xX ₂ O ₃ : yYO ₂ :SiO ₂ :b Seed: wH ₂ o, wherein R represents a positively charged group of the organic templating agent; x represents one or more trivalent boron group elements; y represents one or more tetravalent elements other than silicon and germanium,r=0.1-1，a=0-1，b=0.001-0.05，x=0-0.03，y=0-0.03，w1-50; r is Ar- (im) ⁺ An organic cation wherein Ar represents para-or meta-substituted tert-butylbenzyl, im represents N-substituted imidazole;

(2) Removing excessive solvent from the reaction gel, transferring the reaction gel into a stainless steel reaction kettle, and reacting for 7-30 days at 140-170 ℃ under a sealed condition;

(3) And (3) washing and drying the product crystallized in the step (2), and roasting for 2-5 hours at 400-650 ℃ in the air atmosphere to obtain the super-macroporous silicate molecular sieve without the template agent.

2. Molecular sieve according to claim 1, characterized in that M represents a proton or sodium, X is Al or B, Y is Ti,p =0-0.02；q =0-0.02。

3. the method for preparing the ultra-large pore IRR structure silicate molecular sieve according to claim 1 or 2, characterized by comprising the following steps:

(1) Uniformly mixing a silicon source substance, a boron family element compound, a tetravalent element compound except silicon and germanium, an organic template agent, a fluorine source substance, an IRR Seed crystal Seed and water in proportion under stirring to obtain a reaction gel, wherein the reaction gel comprises the following chemical components:rROH:aHF:xX ₂ O ₃ : yYO ₂ :SiO ₂ :b Seed: wH ₂ o, wherein R represents the positive charge of the organic templating agentA group; x represents one or more trivalent boron group elements; y represents one or more tetravalent elements other than silicon and germanium,r=0.1-1，a=0-1，b=0.001-0.05，x=0-0.03，y=0-0.03，w1-50; r is Ar- (im) ⁺ An organic cation wherein Ar represents para-or meta-substituted tert-butylbenzyl, im represents N-substituted imidazole;

(2) Removing excessive solvent from the reaction gel, transferring the reaction gel into a stainless steel reaction kettle, and reacting for 7-30 days at 140-170 ℃ under a sealed condition;

(3) And (3) washing and drying the product crystallized in the step (2), and roasting for 2-5 hours at 400-650 ℃ in the air atmosphere to obtain the super-macroporous silicate molecular sieve without the template agent.

4. The method according to claim 3, wherein step (1) X is Al and/or B.

5. The preparation method according to claim 3, wherein the silicon source substance is selected from one or more of white carbon black, water glass, silica sol, ethyl orthosilicate and butyl orthosilicate; the boron group element compound is selected from one or more of sodium metaaluminate, aluminum isopropoxide, aluminum sulfate hexadecahydrate, aluminum hydroxide or boric acid; the fluorine source substance is hydrofluoric acid and/or ammonium fluoride; the tetravalent element compound except silicon and germanium is tetrabutyl titanate and/or tin dioxide.

6. The production method according to claim 3 or 4, characterized in that step (1)r、a、x、yAndwrespectively as follows:r=0.5-0.75，a=0.5-0.75，b=0.01-0.05，x=0-0.02，y=0-0.02，w=1-10。

7. the method according to claim 3, wherein R is selected from one or more of the following structures:

。

8. the method of claim 3, wherein the IRR Seed is an IRR structure molecular sieve selected from the group consisting of a silicon germanosilicate, a pure silicate, an aluminosilicate, and a titanosilicate.

9. The use of the extra-large pore IRR structure silicate molecular sieve of claim 1 or 2 as an adsorption material, a separation material, a catalyst in the chemical and chemical field.

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