JP4781567B2 - Method for producing zeolite single crystal having straight intermediate pores - Google Patents

Description

脱アルミニウムおよび空隙容積実験の結果は、ストレート孔を持つ中間細孔多孔質ゼオライトの形態および結晶度がゼオライトの炭素製ナノチューブ−マトリックス除去、脱アルミニウムおよびイオン交換を含めた後合成変性にもかかわらず維持されることを示している。
【図面の簡単な説明】
【図１】図１は例１の中間細孔ゼオライトの透過電子顕微鏡写真である。
【図２】図２は例２の中間細孔ゼオライトの透過電子顕微鏡写真である。
【図３】図３はか焼後の中間細孔多孔質シリカライト−１をテンプレート加工した炭素製ナノチューブの例４の透過電子顕微鏡写真である。[0001]
[Technical field to which the invention belongs]
The present invention relates to a method for producing zeolite crystals having a straight intermediate pore system.
[0002]
[Prior art]
Zeolites are widely used as heterogeneous catalysts. For many applications, the problem is that the zeolite has only micropores. This is because the micropores have a diffusion limit and thus limit the reaction rate. In the past, several attempts have been made to provide zeolite crystals having a mesoporous system. One possible method is to reduce the size of the zeolite crystals [Madsen C. Jacobsen, CJH, Chem. Comm. (1999) (673)] and the other possible methods are intermediate Porous porous MCM-41 type materials are used [eg Beck, JS et al., J. Am. Chem. Soc. 114 (1992) 10832]. Both of these methods shall be entered here. However, MCM-41 type materials only exhibit a strict two-dimensional state and therefore do not have the same acidity as a three-dimensional state zeolite.
[0003]
[Structure of the invention]
The present invention is a method for producing a zeolite single crystal having a tunable pore system of straight intermediate pores with individual zeolite crystals.
[0004]
The invention also relates to zeolite single crystals and catalyst materials having straight intermediate pores produced by the process of the invention.
[0005]
The invention further relates to an activated catalyst material containing zeolite single crystals with straight intermediate pores that have been subjected to dealumination and / or ion exchange treatment.
[0006]
The method of the present invention requires that the zeolite be crystallized inside and on the surface of a matrix composed mostly of particles in the size range of 10 to 500 nm. This method allows the zeolite to grow into a large single crystal that envelops some of the matrix particles. Zeolite is applied both on the inside and on the surface of the matrix when the amount of impregnation solution (zeolite gel) applied is greater than the pore volume (characteristic) of the matrix (the amount of excess gel compared to the initial wetting). Impregnated with.
[0007]
When carbon is used as the matrix, the zeolite crystals can be isolated by removing the carbon by controlled combustion or by hydrogenation. Other types of matrix can be used and removed, for example, by selective dissolution or by hydrolysis. In heterogeneous catalysts, such pores are essential to allow the reaction components and reaction products to be transported to and from the active catalyst site without interference.
[0008]
The resulting intermediate porous zeolite single crystal has footprints from the carbon matrix. The carbon matrix affects the mesopore system and the size of the pores can be adjusted by appropriate selection of carbon. Causing crystal intracrystalline mesopores are generally serpentine significantly applying carbon black as pore template.
[0009]
The intermediate porosity of the zeolite crystals can be controlled by adjusting the amount of zeolite gel relative to the amount of carbon matrix. During crystallization, it is important that the zeolite gel precursor is located both around and inside the pore system of the matrix. Otherwise, large single crystals do not occur and instead small isolated crystals can be obtained as described in Chem. Comm. (1999), (673).
[0010]
The matrix is preferably inert and stable under zeolite synthesis conditions and provides a suitable pore morphology. By removing the matrix from the large single crystal, intermediate pores are formed within each large single crystal (ie, crystal internal type intermediate pores).
[0011]
Large zeolite crystals with internal crystal pores are easily separated from the synthesis medium by filtration, while microzeolitic crystals (from which internal crystal internal pores can be formed) are ultracentrifuged to separate from the synthesis medium Requires separation. Another advantage of large zeolite single crystals is that the hydrothermal stability of the zeolite is improved.
[0012]
It is advantageous to remove the matrix to such an extent that the transport of the reaction components and products in the intermediate pores is not delayed. However, it is not necessary to completely remove the matrix. It is advantageous that the residual amount of matrix material inside the zeolite crystal is as small as possible.
[0013]
The method of the present invention can generally be used in the production of mesoporous zeolite single crystals and in the production of crystalline materials that are crystallized in and around the pore system of the matrix from which the material can be removed. The matrix can be removed from the zeolite crystals by combustion, hydrogenation, selective decomposition (or dissolution) and / or evaporation.
[0014]
Intermediate pore porous zeolites have great potential in a diffusion-limited manner. Furthermore, by adjusting the tortoise of the pores, the diffusion limitation is not so noticeable. The winding factor [J. Kaerger, DM Ruthven, Diffusion in zeolites and other microporous solids, John Wiley & Sons, New York, (1992), p. 342] is as follows: Expressed:
D = ε _p D _p / τ
D = diffusivity ε _p = porosity D _p = diffusivity of straight channels of the same diameter τ = torsion factor The general torsion factor for pores caused by agglomeration of primary particles is 3-5, which is the same This means that the diffusion for an ideal straight channel of diameter is 3 to 5 times faster. This demonstrates the advantages of straight crystal internal mesopores compared to serpentine mesopores of the same diameter. The active sites available for catalytic reactions can be used more easily in intermediate pore porous crystals with straight pores than in crystals with tortuous pores.
[0015]
Carbon fibers can be used to produce straight channel pore systems and, for example, by applying carbon nanotubes as intermediate pore templates, i.e., crystallizing zeolite around the intermediate pores, straight channels or An internal crystal intermediate pore system with pores can be obtained.
[0016]
Improves the control of the intermediate pore properties of zeolites that can be obtained with a high degree of control over the diameter of the carbon nanotubes. Carbon nanotubes are an inexpensive template material that can be used with low impurity concentrations. An intermediate pore template that yields straight intermediate pores can be obtained using the following template:
-Carbon nanotubes surrounded by a single wall-carbon nanotubes surrounded by multiple walls-carbon whisker-a mixture of these materials.
[0017]
Other tubular materials with diameters between 2 nm and 50 nm and length: diameter-ratio greater than 5 can also be used as templates for straight intermediate pores.
[0018]
In the following examples, zeolite single crystals and catalyst materials with straight intermediate pores are synthesized using various template processing materials. An example of post-synthetic modification of a mesoporous zeolite that results in an activated catalyst material is also provided. This modification is exemplified by dealumination and cation exchange treatments.
[0019]
The illustrated mesoporous zeolite is produced by subsequent impregnation of carbon nanotubes or whiskers. Carbon nanotubes have an average diameter of 12 nm, and nanotubes surrounded by multiple walls consist of 6-8 graphene layers. In general, a nanotube has a length of several μm. It is important that the nucleation of the zeolite occurs exclusively between the carbon nanotubes while the zeolite single crystal grows around the carbon nanotubes. Nucleation between the nanotubes does not occur when the nanotubes are simply dip coated with a zeolite synthesis gel. Zeolite is therefore synthesized in the gaps between the nanotubes by subsequent impregnation of the individual synthetic gel components.
[0020]
Zeolite dealumination is generally obtained by selectively removing M ³⁺ from the framework and crystal structure of the zeolite and is typically obtained by removing Al ³⁺ ions. The ratio of Si to Al in the zeolite is important for its catalytic activity, absorbency and ion exchange capacity, and thus control of this ratio is important for the properties of the zeolitic catalyst. Dealumination agents include mineral acids and polyvalent acids and chelating agents.
[0021]
Cation exchange of the zeolite is generally obtained by contacting the zeolite with an aqueous solution of a cation exchange agent, generally an ammonium containing agent, under conditions sufficient to exchange the cations in the zeolite.
[0022]
Both dealumination and cation exchange can be performed simultaneously by using an aqueous solution of the above agent under mild conditions.
[0023]
The post-synthesis modification process is specifically described using the following method:
Dealumination method:
- chelating route using an oxalate compound - HCl or acid dealumination using HNO _3.
[0024]
Cation exchange method:
-Ammonium oxalate solution-Ammonium chloride solution.
[0025]
Combined method:
-Abbreviations of some compounds used in oxalic acid-oxalic acid / ammonium oxalate solution are as follows:
Tetrapropylammonium hydroxide ... TPAOH
Tetraethylorthosilicate ・ ・ ・ TEOS
Tetrapropylammonium oxide TPA ₂ O
Ethanol ... EtOH
Tetraethylammonium hydroxide ... TEAOH
Characterization method:
The mesopore and macropore features before and after dealumination were obtained using the Hg-penetration porosity measurement method. Crystallinity and crystal morphology were obtained using X-ray powder diffraction (XRPD) and transmission electron microscope (TEM), respectively.
[0026]
Carbon nanotubes (CNT's) were provided by Hyperion Catalysis International and carbon black pearls 2000 was provided by Carbot Corp.
[0027]
【Example】
Example 1 (comparative example):
Production of mesoporous zeolite with tortuous pores:
In a special embodiment of the invention, 15 g of carbon black pearls 2000 is used with a clear solution consisting of TPAOH, sodium hydroxide, sodium aluminate (corresponding to about 50% zeolite), water and ethanol, Impregnation is performed in an excess amount of about 30% compared to the initial wetting. After evaporating the ethanol, the carbon particles are impregnated with 18.3 g of TEOS (this corresponds to a 30% excess of the volume of ethanol to be evaporated). The composition of the synthesis gel is on a molar basis: 1 Al ₂ O ₃ : 20 TPA ₂ O: 1 Na ₂ O: 100 SiO ₂ : 200 H ₂ O: 200 EtOH
It is.
[0028]
Carbon black impregnated after aging for 3 hours at room temperature is introduced into a stainless steel autoclave containing a sufficient amount of water to produce saturated water vapor and heated to 180 ° C. for 72 hours. After the autoclave has cooled to room temperature, the product is suspended in water, suction filtered, suspended again in water and filtered again. This operation is repeated four times. Finally, the product is dried at 110 ° C. for 10 hours. The carbon black-matrix is removed by burning in a muffle furnace at 550 ° C. for 8 hours. A transmission electron micrograph of the obtained zeolite is shown in FIG.
[0029]
Example 2:
Synthesis of mesoporous porous silicalite-1 with straight pores 2g carbon nanotubes (pre-dried overnight at 130C) in a beaker are impregnated with 4g TEOS added dropwise. The sample is then left on a 25 wt% aqueous ammonia solution for 10 hours in a desiccator to hydrolyze the TEOS. Then 1.35 g H ₂ O was added and after 3 hours digestion, premixed with 4.0 g 40 wt% TPAOH, 0.5 g H ₂ O and 1.0 g EtOH. The clear solution is added dropwise in an amount not exceeding the pore volume. The resulting gel has the following molar composition:
20 TPA ₂ O: 100 SiO ₂ : 1230 H ₂ O
Samples are aged at room temperature for 10 hours. The sample is then transferred to a porcelain cup in an autoclave charged with a sufficient amount of water to produce a saturated steam atmosphere at hydrothermal crystallization conditions. The autoclave is heated to 175 ° C. and maintained at this temperature for 24 hours. The cooled sample is washed with distilled water, filtered through a Buchner filter and dried at 110 ° C. The matrix is then removed by heating (calcining) the sample at 2 ° C./min to 600 ° C. and this temperature is maintained for 11 hours.
[0030]
The characteristics of XRPD demonstrate the presence of crystalline MFI-type material and the TEM of the resulting zeolite crystals is shown in FIG. In this figure, the zeolite crystals can be recognized as dark elements along with the bright spots and channels. These straight channels produced by the removal of the matrix reflect the size of the carbon nanotubes.
[0031]
Electron diffraction demonstrates that the mesoporous material does not produce small crystal agglomeration, but rather that each mesocrystalline pore, i.e., each micron-sized region, is individually crystallized. The individual crystals produced in Example 2 are generally 0.5 × 0.5 × 0.7 μm ³ in size.
[0032]
Example 3:
Synthesis of mesoporous ZSM5 with straight pores 2g of carbon nanotubes (pre-dried overnight at 130C) in a beaker is impregnated by dropwise addition of 4g of TEOS. The sample is then left on a 25 wt% aqueous ammonia solution in a desiccator for 10 hours to hydrolyze the TEOS. Then 1.35 g H ₂ O was added and heat treated for 3 hours followed by 4.0 g of 40 wt% TPAOH, 0.036 g sodium aluminate (ie 54 wt% Al ₂ O ₃ and 41 wt%). % Na ₂ O ₂ ), 0.5 g H ₂ O and 1.0 g EtOH premixed clear solution is added dropwise in an amount not exceeding the pore volume. The resulting gel has the following molar composition:
1 Al ₂ O ₃ : 20 TPA ₂ O: 1.25 Na ₂ O: 100 SiO ₂ : 1230 H ₂ O
The sample is aged at room temperature for 10 hours, after which the sample is transferred to a porcelain cup in an autoclave charged with a sufficient amount of water to produce saturated water vapor under hydrothermal crystallization conditions. The autoclave is heated to 175 ° C. and maintained at this temperature for 72 hours. The cooled sample is washed with distilled water, filtered through a Buchner filter and dried at 110 ° C. The matrix is then removed by heating the sample to 600 ° C. at 2 ° C./min and this temperature is maintained for 11 hours.
[0033]
This material is characterized by the mesoporous porous silicalite obtained in Example 2 with the exception of the aluminum content incorporated into the framework, known to introduce ion exchange capacity and potential acidity. Similar to -1.
[0034]
Example 4:
Synthesis of mesoporous β-zeolite with straight pore channels 2 g of carbon nanotubes pre-dried at 130 ° C. for 2 hours were prepared in Example 2 with a transparent mixture of 2.6 g TEOS and 0.5 g ethanol. Impregnation as described. The sample is aged overnight in a desiccator over 25% by weight aqueous ammonia to hydrolyze TEOS. Next, a clear premixed solution consisting of 3.2 g of 30 wt% TEAOH and 0.088 g of NaAlO ₂ is added to the sample by impregnation. The final gel composition has the following molar composition:
1.6 Al ₂ O ₃ : 15.7 TEA ₂ O: 2.3 Na ₂ O: 50 SiO ₂ : 510 H ₂ O
After aging the sample for 3 hours at room temperature, the impregnated carbon nanotubes are transferred to a stainless steel autoclave containing a sufficient amount of water to produce saturated water vapor and heated at 140 ° C. for 5 days. After quenching, the product is resuspended in water and filtered with suction. Repeat this four times. Finally, the carbon nanotube-matrix is removed by calcination at 600 ° C. for 11 hours.
[0035]
FIG. 3 shows a TEM of carbon nanotubes templated with calcined mesoporous porous silicalite-1. The observed crystalline zeolite lattices extend throughout the crystal, demonstrating that high crystallinity has been achieved, and that the carbon nanotube intermediate pores are a bright spot in the zeolite crystal. Observed.
[0036]
Example 5:
Synthesis of mesoporous ZSM5 with straight pores Whisker made of carbon (generally about 20 nm and solid filamentary carbon having a diameter greater than 5 μm) 2.5 g (pre-dried overnight at 130 ° C.) in a beaker Impregnation is carried out by dropwise addition of 4 g of TEOS. The sample is then placed in a desiccator over 25% strength by weight aqueous ammonia for 10 hours to hydrolyze the TEOS. Then 1.35 g of H ₂ O was added and heat treated for 3 hours before 4.0 g of 40 wt% TPAOH, 0.036 g sodium aluminate (ie 54 wt% Al ₂ O ₃ and 41 A premixed clear solution consisting of NaAlO ₂ ) consisting of wt% Na ₂ O), 0.5 g H ₂ O and 1.0 g ethanol (EtOH) is added dropwise in an amount not exceeding the pore volume.
[0037]
The resulting gel has the following molar composition:
1 Al ₂ O ₃ : 20 TPA ₂ O: 1.25 Na ₂ O: 100 SiO ₂ : 1230 H ₂ O
The sample is aged at room temperature for 10 hours, after which the sample is transferred to a porcelain cup in an autoclave charged with a sufficient amount of water to produce saturated water vapor under hydrothermal crystallization conditions. The autoclave is heated to 175 ° C. and this temperature is maintained for 72 hours. The cooled sample is washed with distilled water, filtered through a Buchner filter and dried at 110 ° C. The matrix is then removed by heating the sample to 600 ° C. at 2 ° C./min and this temperature is maintained for 11 hours.
[0038]
The characteristics of this material are similar to the mesoporous ZSM5 obtained in Example 3 except for the different average internal crystal pore morphology, ie diameter and connectivity, consistent with the differences in the fibrous template material. .
[0039]
Example 6:
2 molar oxalic acid solution (50.4 g of oxalic acid ZSM5 zeolite 200mL of 5g of dealumination <br/> Example 3 of mesoporous porous ZSM5 by oxalic acid solution, the amount necessary to the 200mL total H ₂ O)
1. The stirred suspension is refluxed at 65 ° C. for 1 hour.
2. The suspension is then filtered and washed 3 times with distilled water.
3. Dry at 120-150 ° C. for 4 hours.
4). Calcinate at 600 ° C. for 4 hours in air.
[0040]
Example 7:
Dealumination of mesoporous ZSM5 with nitric acid solution 200 g of 5 g of ZSM5 zeolite from Example 3 2 molar nitric acid solution The stirred suspension is refluxed at 65 ° C. for 5 hours.
2. The suspension is then filtered and washed 3 times with distilled water.
3. Dry at 120-150 ° C. for 4 hours.
4). Calcinate at 600 ° C. for 4 hours in air.
[0041]
Example 8:
A. Oxalic acid 2 molar oxalic acid solution (50.4 g of β- zeolite 200mL of dealumination <br/> Example 4 5g of intermediate pore porous β- zeolite according oxalic acid solution, required for the 200mL total Amount of H ₂ O)
1. The stirred suspension is refluxed at 65 ° C. for 1 hour.
2. The suspension is then filtered and washed 3 times with distilled water.
3. Dry at 120-150 ° C. for 4 hours.
4). Calcinate at 600 ° C. for 4 hours in air.
[0042]
B. Simultaneous dealumination and cation exchange of mesoporous porous β-zeolite with oxalic acid solution 200 mL of 2 g oxalic acid solution of 5 g β-zeolite from Example 4 (50.4 g oxalic acid, totaling 200 mL) Amount of H ₂ O required for
1. The stirred suspension is refluxed at 65 ° C. for 1 hour.
2. The suspension is then filtered.
3. The filtered product is then resuspended in a 1 molar oxalic acid / 0.5 molar ammonium oxalate buffer solution.
4). The stirred suspension is refluxed at 65 ° C. for 1 hour.
5. The suspension is filtered and washed 3 times with distilled water.
6. Dry at 120-150 ° C. for 4 hours.
7). Calcinate at 600 ° C. for 4 hours in air.
[0043]
Example 9:
A. Dealumination of mesoporous β-zeolite with nitric acid solution 200 g of 2 g nitric acid solution of 5 g β-zeolite from Example 4 The stirred suspension is refluxed at 50 ° C. for 5 hours.
2. The suspension is then filtered and washed 3 times with distilled water.
3. Dry at 120-150 ° C. for 4 hours.
4). Calcinate at 600 ° C. for 4 hours in air.
[0044]
B. Cation exchange treatment of mesoporous β-zeolite with ammonium oxalate 200 mL of 5 g β-zeolite of Example 4 in 1 molar NH ₄ CH ₃ COO solution.
5. The stirred suspension is refluxed at 50 ° C. for 5 hours.
6). The suspension is then filtered and washed 3 times with distilled water.
7. Dry at 120-150 ° C. for 4 hours.
8). Calcinate at 600 ° C. for 4 hours in air.
[0045]
The Si / Al ratio and aluminum percentage obtained by chemical analysis with the mesoporous ZSM-5 and mesoporous β-zeolite before and after the dealumination test are shown in Table 1 below:

The results of dealumination and void volume experiments show that the morphology and crystallinity of a mesoporous zeolite with straight pores is despite post-synthesis modification including zeolite carbon nanotube-matrix removal, dealumination and ion exchange It is maintained.
[Brief description of the drawings]
1 is a transmission electron micrograph of the intermediate pore zeolite of Example 1. FIG.
FIG. 2 is a transmission electron micrograph of the intermediate pore zeolite of Example 2.
FIG. 3 is a transmission electron micrograph of Example 4 of carbon nanotubes obtained by tempering mesoporous porous silicalite-1 after calcination.

Claims (7)

Zeolite single crystal having straight intermediate pores by applying a synthetic gel containing a zeolite precursor composition in the pore system and on the surface of the template made of the particulate matrix carbon material, characterized in that it comprises the following steps: How to manufacture:
Providing a template material having a diameter of 2-50 nm and a length: diameter-ratio of at least 5;
Applying a zeolite precursor to the surface of the template material using a sequential impregnation treatment;
-Subjecting the precursor composition to crystallization conditions; and-isolating zeolite porous single crystals with straight intermediate pores by removing the matrix-template material. The method of claim 1, wherein the template material comprises carbon nanotubes. The method of claim 1 wherein the template matrix material is removed from the zeolite crystals by combustion, hydrogenation, selective dissolution and / or evaporation. A zeolite single crystal having straight intermediate pores produced by the method according to claim 1. The catalyst material which consists of a zeolite single crystal which has the straight intermediate | middle pore manufactured by the method as described in any one of Claims 1-3. 3. An activated catalyst material comprising a zeolite single crystal having straight intermediate pores produced according to the method of claim 1 or 2, characterized in that the zeolite single crystal is subjected to dealumination treatment. . 3. An activated catalyst material comprising a zeolite single crystal having straight intermediate pores produced according to the method of claim 1 or 2, wherein the zeolite single crystal is subjected to an ion exchange treatment. .

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