Synthesis of SFE framework type molecular sieve
阅读说明：本技术 Sfe骨架型分子筛的合成 (Synthesis of SFE framework type molecular sieve ) 是由 谢丹 于 2018-06-04 设计创作，主要内容包括：提供了一种使用选自1,2,3,5-四甲基-1H-吡唑-2-鎓阳离子和1,2,3,4-四甲基-1H-咪唑-3-鎓阳离子中的一种或多种作为结构导向剂合成SFE骨架型的分子筛的方法。(A method for synthesizing an SFE framework type molecular sieve using one or more selected from the group consisting of 1,2,3, 5-tetramethyl-1H-pyrazol-2-ium cation and 1,2,3, 4-tetramethyl-1H-imidazol-3-ium cation as a structure directing agent is provided.)
1. A method of synthesizing an SFE framework-type molecular sieve, the method comprising:
(a) preparing a reaction mixture comprising:
(1) a silicon oxide source;
(2) a source of an oxide of a trivalent element (X);
(3) optionally, a source of a group 1 or 2 metal (M);
(4) a structure directing agent (Q) comprising one or more of a 1,2,3, 5-tetramethyl-1H-pyrazol-2-ium cation and a 1,2,3, 4-tetramethyl-1H-imidazol-3-ium cation;
(5) hydroxyl ions; and
(6) water; and
(b) subjecting the reaction mixture to crystallization conditions sufficient to form crystals of the molecular sieve.
2. The method of claim 1, wherein the reaction mixture has a composition, in terms of mole ratios, of:
。
3. The method of claim 1, wherein the reaction mixture has a composition, in terms of mole ratios, of:
4. the method of claim 1, wherein the trivalent element X is selected from one or more of boron, aluminum, gallium, and iron.
5. The method of claim 1, wherein the trivalent element X comprises boron.
6. The method of claim 1, wherein the reaction mixture further comprises seed crystals.
7. The process of claim 6, wherein the reaction mixture comprises 0.01 to 10,000ppm by weight of seed crystals.
8. The method of claim 6, wherein the seed comprises a crystalline material of the SFE framework type.
9. The method of claim 1, wherein the crystallization conditions comprise a temperature from 125 ℃ to 200 ℃.
10. A molecular sieve of the SFE framework type and comprising, in its as-synthesized form, within its pores one or more of a 1,2,3, 5-tetramethyl-1H-pyrazol-2-ium cation and a 1,2,3, 4-tetramethyl-1H-imidazol-3-ium cation.
11. The molecular sieve of claim 10 and having a SiO of 20 to 3002/X2O3Wherein X is selected from one or more of boron, aluminum, gallium and iron.
12. The molecular sieve of claim 11, wherein X comprises boron.
Technical Field
The present invention relates to the synthesis of crystalline molecular sieves of the SFE framework type, such as SSZ-48.
Background
SSZ-48 is a crystalline molecular sieve material having a unique one-dimensional 12-membered ring pore system. The structure committee of the international zeolite association has specified the framework structure of SSZ-48 as the three-letter code SFE.
U.S. patent No.6,080,382, which discloses the composition and characteristic X-ray diffraction pattern of SSZ-48, also describes the use of decahydroquinolinium cations as structure directing agents to prepare the molecular sieves.
The high cost of the decahydroquinolinium cation structure directing agent required for its synthesis in U.S. patent No.6,080,382 has hindered the commercial development of SSZ-48, and thus there is great interest in finding alternative, less expensive structure directing agents for the synthesis of SSZ-48.
In accordance with the present disclosure, it has now been found that the cations described herein are effective as structure directing agents in the synthesis of SSZ-48.
Summary of the invention
In one aspect, there is provided a method of synthesizing an SFE framework-type molecular sieve, the method comprising: (a) preparing a reaction mixture comprising: (1) a silicon oxide source; (2) a source of an oxide of a trivalent element (X); (3) optionally, a source of a group 1 or 2 metal (M); (4) a structure directing agent (Q) comprising one or more of a 1,2,3, 5-tetramethyl-1H-pyrazol-2-ium cation and a 1,2,3, 4-tetramethyl-1H-imidazol-3-ium cation; (5) hydroxyl ions; and (6) water; and (b) subjecting the reaction mixture to crystallization conditions sufficient to form crystals of the molecular sieve.
In another aspect, a molecular sieve of the SFE framework type is provided and comprises, in its as-synthesized form, one or more of a 1,2,3, 5-tetramethyl-1H-pyrazol-2-ium cation and a 1,2,3, 4-tetramethyl-1H-imidazol-3-ium cation within its pores.
The molecular sieve has a chemical composition, as-synthesized and in anhydrous form, that includes the following molar relationship:
range of
Typical value
SiO2/X2O3
20 to 300
100 to 200
Q/SiO2
>0 to 0.1
>0 to 0.1
M/SiO2
0 to 0.1
>0 to 0.1
Wherein X is a trivalent element (e.g., one or more of boron, aluminum, gallium, and iron); q comprises one or more of a 1,2,3, 5-tetramethyl-1H-pyrazol-2-ium cation and a 1,2,3, 4-tetramethyl-1H-imidazol-3-ium cation; and M is a group 1 or 2 metal.
Brief description of the drawings
Figure 1 is a powder X-ray diffraction (XRD) pattern of the as-synthesized molecular sieve prepared in example 1.
Figure 2 is a Scanning Electron Microscope (SEM) image of the as-synthesized molecular sieve prepared in example 1.
Detailed Description
Introduction to
The term "skeleton type" is used in the sense described in the "Atlas of Zeolite Framework Types," Sixth RevisedEdition, Elsevier (2007).
The term "as-synthesized" as used herein refers to the molecular sieve in its form after crystallization and prior to removal of the structure directing agent.
The term "anhydrous" as used herein refers to zeolites substantially free of physisorbed and chemisorbed water.
As used herein, the numbering scheme for groups of the periodic table is as described in chem.eng.news1985,63(5), 26-27.
Reaction mixture
Generally, the molecular sieves herein can be synthesized by: (a) preparing a reaction mixture comprising: (1) a silicon oxide source; (2) a source of an oxide of a trivalent element (X); (3) optionally, a source of a group 1 or 2 metal (M); (4) a structure directing agent (Q) comprising one or more of a 1,2,3, 5-tetramethyl-1H-pyrazol-2-ium cation and a 1,2,3, 4-tetramethyl-1H-imidazol-3-ium cation; (5) hydroxyl ions; and (6) water; and (b) subjecting the reaction mixture to crystallization conditions sufficient to form crystals of the molecular sieve.
The composition of the reaction mixture forming the molecular sieve, in terms of mole ratios, is set forth in table 1 below:
TABLE 1
Reactants
Useful in
Exemplary of
SiO2/X2O3
5 to 400
150 to 250
M/SiO2
0 to 0.50
0.10 to 0.30
Q/SiO2
0.05 to 0.50
0.10 to 0.30
OH/SiO2
0.10 to 0.50
0.15 to 0.40
H2O/SiO2
10 to 60
15 to 40
Wherein the constituent variables X, M and Q are as described above.
Suitable silica sources include fumed silica, colloidal silica, precipitated silica, alkali metal silicates, and tetraalkyl orthosilicates.
Suitable sources of trivalent element X depend on the selected element X (e.g., boron, aluminum, gallium, and iron). In embodiments where X is boron, suitable sources of boron include boric acid, sodium tetraborate, and potassium tetraborate.
Examples of suitable group 1 or 2 metals (M) include sodium, potassium and calcium, with sodium being preferred. The metal is usually present in the reaction mixture in the form of a hydroxide.
The structure directing agent (Q) comprises one or more of a 1,2,3, 5-tetramethyl-1H-pyrazol-2-ium cation and a 1,2,3, 4-tetramethyl-1H-imidazol-3-ium cation, represented by the following structures (1) and (2), respectively:
suitable sources of Q are the hydroxides and/or salts of the relevant quaternary ammonium compounds.
The reaction mixture may also contain seed crystals of crystalline material, such as SSZ-48 from a previous synthesis, desirably in an amount of 0.01 to 10,000ppm by weight (e.g., 100 to 5000ppm by weight) of the reaction mixture. Seeding may be advantageous to reduce the time required for complete crystallization to occur. In addition, seeding may allow for an increase in purity of the product obtained by promoting nucleation and/or formation of SSZ-48 on any undesirable phase.
For each of the embodiments described herein, the molecular sieve reaction mixture may be provided from more than one source. Also, one source may provide two or more reaction components.
The reaction mixture may be prepared batchwise or continuously. The crystal size, morphology and crystallization time of the molecular sieves described herein may vary with the nature of the reaction mixture and the crystallization conditions.
Crystallization and post-synthesis treatment
Crystallization of the molecular sieve from the above reaction mixture may be carried out under static, tumbling or stirring conditions in a suitable reactor vessel, such as a polypropylene tank or teflon liner or stainless steel autoclave, at a temperature of from 125 ° to 200 ℃ for a time sufficient for crystallization to occur at the temperature used, for example, 2 to 50 days. Crystallization is usually carried out in a closed system under autogenous pressure.
Once the molecular sieve crystals are formed, the reaction mixture is separated from the solid product by standard mechanical separation techniques such as centrifugation or filtration. The crystals were washed with water and then dried to obtain as-synthesized molecular sieve crystals. The drying step is typically carried out at a temperature below 200 ℃.
As a result of the crystallization process, the recovered crystalline molecular sieve product contains within its pore structure at least a portion of the structure directing agent used in the synthesis.
The molecular sieves described herein may be subsequently treated to remove some or all of the structure directing agent (Q) used in their synthesis. This is conveniently done by heat treatment (calcination) which heats the as-synthesized material at a temperature of at least about 370 ℃ for at least 1 minute and typically no longer than 20 hours. The heat treatment may be carried out at a temperature of up to 925 c. Although the heat treatment may be carried out using a pressure lower than atmospheric pressure, atmospheric pressure is desirably used for convenience. Additionally or alternatively, the structure directing agent can be removed by treatment with ozone (see, e.g., a.n. parikh et al, micropor.mesopor.mater.2004,76, 17-22).
Depending on the desired extent, the group 1 or 2 metal cation (e.g., Na) in the as-synthesized molecular sieve+) May be replaced by ion exchange with other cations according to techniques well known in the art. Preferred replacing cations include metal ions (e.g., rare earth metals and metals from groups 2-15 of the periodic table), hydrogen ions, hydrogen precursor ions (e.g., ammonium ions), and combinations thereof.
SSZ-48 containing framework aluminum can be prepared indirectly from borosilicate SSZ-48 by post-synthesis displacement of boron in the borosilicate SSZ-48 framework with aluminum. Replacement of boron in borosilicate SSZ-48 with aluminum can be accomplished by appropriate treatment of the borosilicate SSZ-48 with an aluminum salt, such as aluminum nitrate, as described in U.S. patent nos. 6,468,501 and 6,790,433. The proportion of boron in the borosilicate SSZ-48 that may be replaced with aluminum may be in the range of greater than 0 to about 100% (at least 50%, at least 75%, or about 85% to 100%).
SSZ-48 may be formulated into a catalyst composition by combining with other materials, such as a binder and/or matrix material (which provides additional hardness or catalytic activity to the finished catalyst). When mixed with these components, the relative proportions of SSZ-48 and matrix can vary widely from 1 to 90 wt% SSZ-48 of the total catalyst. (e.g., 2 to 80 wt%).
Characterization of the molecular sieves
In its as-synthesized and anhydrous form, the molecular sieve herein has a chemical composition comprising the following molar relationship:
range of
Typical value
SiO2/X2O3
20 to 300
100 to 200
Q/SiO2
>0 to 0.1
>0 to 0.1
M/SiO2
0 to 0.1
>0 to 0.1
Wherein X is a trivalent element (e.g., one or more of boron, aluminum, gallium, and iron); q comprises one or more of a 1,2,3, 5-tetramethyl-1H-pyrazol-2-ium cation and a 1,2,3, 4-tetramethyl-1H-imidazol-3-ium cation; and M is a group 1 or 2 metal.
It should be noted that the as-synthesized forms of the molecular sieves herein can have a different molar ratio than the molar ratio of the reactants used to prepare the as-synthesized form of the reaction mixture. This result may occur due to incomplete introduction of 100% of the reactants into the crystals formed (from the reaction mixture).
As taught in U.S. patent No.6,080,382, molecular sieve SSZ-48 has an X-ray diffraction pattern comprising at least the peaks listed in table 2 below in its as-synthesized form and at least the peaks listed in table 3 below in its calcined form.
TABLE 2
Characteristic peaks of as-synthesized SSZ-48
2-θ(a)
d-spacing, nm
Relative strength(b)
6.55
1.35
S
8.0
1.10
VS
9.4
0.940
M
11.3
0.782
M-W
20.05
0.442
VS
22.7
0.391
VS
24.1
0.369
VS
26.5
0.336
S
27.9
0.320
S
35.85
0.250
M
(a)±0.3
(b)The powder XRD patterns provided are based on relative intensity scale, with the strongest line in the XRD pattern being assigned a value of 100: weak (W) ((weak))>0 to 20); m ═ medium (>20 to less than or equal to 40); (strong: (S)>40 to less than or equal to 60); VS very strong (>60 to 100).
TABLE 3
Characteristic peaks of SSZ-48 after calcination
2-θ(a)
d-spacing, nm
Relative strength(b)
6.55
1.35
VS
8.0
1.10
VS
9.4
0.940
S
11.3
0.782
M
20.05
0.442
M
22.7
0.391
M
24.1
0.369
M
26.5
0.336
M
27.9
0.320
W
35.85
0.250
W
(a)±0.3
(b)The powder XRD patterns provided are based on relative intensity scale, with the strongest line in the XRD pattern being assigned a value of 100: weak (W) ((weak))>0 to 20); m ═ medium (>20 to less than or equal to 40); (strong: (S)>40 to less than or equal to 60); VS very strong (>60 to 100).
The powder X-ray diffraction patterns shown herein were collected by standard techniques. The radiation is CuK α radiation. The peak height and position as a function of 2 θ (where θ is the bragg angle) is read from the relative intensity of the peak (adjusted according to the background) and the facet spacing d corresponding to the trace can be calculated.
Small variations in the X-ray diffraction pattern are due to changes in the lattice constant, possibly caused by variations in the molar ratio of the framework species of a particular sample. In addition, sufficiently small crystals will affect the shape and intensity of the peak, resulting in significant peak broadening. Small changes in the diffraction pattern can be caused by changes in the organic compounds used in the preparation process. Calcination can also result in a slight shift in the XRD pattern. Despite these minor disturbances, the basic lattice structure remains unchanged.
Examples
The following illustrative examples are intended to be non-limiting.