JP2012218998A - Microcrystalline zeolite having emt structure, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microcrystalline zeolite having a hexagonal plate-like shape and EMT structure which is expected to be used as a catalyst, an absorbent or the like, and also to provide a method for producing zeolite having such an EMT structure.SOLUTION: The hexagonal plate-like zeolite includes an EMT structure, has an average thickness of ≥0.03 and ≤0.3 μm and preferably has an average bottom diameter of ≥0.1 μm and ≤1.0 μm. Such zeolite is manufactured by crystallizing a reaction mixture having a following composition while stirring. In the reaction mixture, the molar ratio of Si/Alis 9-11, the molar ratio of HO/Si is 12-16, the molar ratio of (18-crown-6)/Si is 0.06-0.10, the molar ratio of Na/Si is 0.43-0.50, and the molar ratio of OH/Si is 0.43-0.50.

Description

  The present invention relates to a microcrystalline zeolite having a hexagonal plate shape and an EMT structure, and a method for producing the same.

  The zeolite having the EMT structure is a zeolite represented by the structure code EMT defined by the International Zeolite Association, and is known as, for example, the substance name “EMC-2” (Non-patent Document 1).

  Zeolite having an EMT structure reported so far is a zeolite having 3 μm hexagonal plate crystals (Non-patent Document 2), hexagonal plate crystals having an average diameter of 4 to 5 μm and a thickness of 0.5 to 1.0 μm. (Non-patent Document 3) and the like, both of which have a relatively large EMT structure.

ATLAS OF ZEOLITE FRAMEWORK TYPES, 6th revised edition, p. 122-123, Elsevier (2007) Zeolites, 10, p. 546 (1990) VERIFEDED SYNTHESIS OF ZEOLITIC MATERIALS, 2nd revised edition, p. 145-146, Elsevier (2001)

  Zeolites are widely used as catalysts, adsorbents or ion exchangers. In these applications, zeolite with a small crystal diameter is required. However, the zeolite having the EMT structure reported so far has a large crystal size and is not suitable for these applications.

  The present invention provides a microcrystalline zeolite having a hexagonal plate shape and an EMT structure, which can be expected to be used in a catalyst, an adsorbent and the like. Moreover, the manufacturing method of the zeolite which has the said EMT structure is provided.

  As a result of intensive studies on the microcrystalline zeolite having the EMT structure, the present inventors have completed the present invention.

  That is, the present invention is a hexagonal plate-like zeolite having an average thickness of 0.03 μm or more and 0.3 μm or less and having an EMT structure.

  Hereinafter, the hexagonal plate zeolite having the EMT structure of the present invention (hereinafter referred to as “the zeolite of the present invention”) will be described.

  The zeolite of the present invention has an EMT structure in crystal structure. The EMT structure is described in COLLECTION OF SIMULATED XRD POWDER PATTERNS FOR ZEOLITES, 5th revised edition, p. 146-147, Elsevier (2007) (hereinafter referred to as Reference Document 1), showing a powder X-ray diffraction pattern. Therefore, whether or not the zeolite has the EMT structure can be confirmed by comparing the powder X-ray diffraction pattern shown in Reference 1 and the zeolite powder X-ray diffraction pattern.

  The zeolite of the present invention preferably has a crystal structure composed of a pure phase having an EMT structure. Note that the pure phase of the EMT structure means that only X-ray diffraction peaks derived from the EMT structure exist in the powder X-ray diffraction pattern.

  The shape of the zeolite of the present invention, that is, the shape of the primary particles of the zeolite of the present invention is a hexagonal plate shape. The shape of the hexagonal plate and the crystal plane being clear indicate that the hexagonal EMT structure is highly crystalline.

  The zeolite of the present invention has an average thickness of 0.03 μm or more and 0.3 μm or less. When the average thickness is larger than 0.3 μm, not only the activity, selectivity and coking resistance are inferior when used as a catalyst, but also a sufficient adsorption rate when used as an adsorbent or ion exchanger. And the ion exchange rate cannot be obtained. Therefore, the average thickness of the zeolite of the present invention is 0.3 μm or less, preferably 0.2 μm or less, and more preferably 0.15 μm or less. On the other hand, when the average thickness is less than 0.03 μm, the heat resistance and hot water resistance are low. Therefore, the average thickness of the zeolite of the present invention is 0.03 μm or more, and preferably 0.05 μm or more.

  The zeolite of the present invention preferably has an average bottom diameter of 0.1 μm or more and 1.0 μm or less. When the average bottom diameter is 1.0 μm or less, preferably 0.9 μm or less, when used as a catalyst, activity, selectivity, and coking resistance are likely to increase. Furthermore, when the zeolite of the present invention is used as an adsorbent or ion exchanger, the adsorption rate and ion exchange rate tend to increase. Further, when the average bottom diameter is 0.1 μm or more, preferably 0.2 μm or more, more preferably 0.4 μm or more, heat resistance and hot water resistance are likely to be increased.

  Thus, the zeolite of the present invention is not only a hexagonal plate shape, but also has an average thickness and further an average bottom diameter in the above range, so that the catalyst, adsorbent or ion exchanger Suitable as

  The average thickness and the average bottom diameter of the zeolite of the present invention can be measured by the methods shown in the following examples.

Zeolites of the present invention, the _SiO 2 / _Al 2 _{O 3} is not particularly limited, examples thereof _include the SiO 2 / _Al 2 _{O 3} is 7-9 molar ratio.

  Next, the manufacturing method of the zeolite of this invention is demonstrated.

  The hexagonal plate-like zeolite having the EMT structure of the present invention can be produced by crystallizing a reaction mixture having the following composition while stirring.

Si / Al ₂ molar ratio = 9-11
H ₂ O / Si molar ratio = 12-16
(18-crown-6) / Si molar ratio = 0.06-0.10
Na / Si molar ratio = 0.43 to 0.50
OH / Si molar ratio = 0.43 to 0.50

  In the production method of the present invention, it is preferable to use a silica source, an alumina source, a sodium source, an organic structure directing agent, and water as raw materials. In order to promote crystallization of the reaction mixture, seed crystals may be added to the raw material.

  Examples of the silica source include sodium silicate, silica sol, fumed silica, precipitated silica, silica alumina gel, and tetraethoxylane.

  Examples of the alumina source include sodium aluminate, aluminum hydroxide, pseudoboehmite, alumina sol, silica alumina gel, and aluminum isopropoxide.

  Examples of the sodium source include sodium hydroxide, sodium silicate, and sodium aluminate.

  It is preferable to use 18-crown-6 (also known as 18-crown-6-ether or 1,4,7,10,13,16-hexaoxacyclooctadecane) as the organic structure directing agent.

  In the production method of the present invention, the reaction mixture has the following composition. When the composition of the reaction mixture is outside the following range, the zeolite of the present invention cannot be obtained.

Si / Al ₂ molar ratio = 9-11
H ₂ O / Si molar ratio = 12-16
(18-crown-6) / Si molar ratio = 0.06-0.10
Na / Si molar ratio = 0.43 to 0.50
OH / Si molar ratio = 0.43 to 0.50

  In the production method of the present invention, the reaction mixture is crystallized with stirring. Thereby, not only the reaction mixture is uniformly mixed, but also the reaction is accelerated. Furthermore, since the formation of crystal nuclei is promoted during crystallization, the resulting zeolite crystals having an EMT structure become fine.

  The reaction mixture can be stirred with a stirring blade or a stirrer. Further, examples of the rotation speed at that time include 10 rotations / minute to 600 rotations / minute.

  Furthermore, it is preferable to stir the reaction mixture by putting the reaction mixture into a reaction vessel and rotating the reaction vessel. When rotating the reaction vessel, the rotation method is not particularly limited. The rotation method of the reaction vessel may be either rotation that rotates around a point or axis inside the reaction vessel, or revolution that rotates around a point or axis outside the reaction vessel.

  In the case of rotating the reaction vessel, the number of rotations may be 10 to 120 rotations / minute.

  The crystallization is preferably performed at a crystallization temperature of 105 ° C. or higher and 115 ° C. or lower. By performing the crystallization temperature within this range, the zeolite of the present invention is easily formed.

  The reaction mixture after crystallization is sufficiently cooled, solid-liquid separated, washed with a sufficient amount of pure water, and dried at an arbitrary temperature of 40 ° C to 300 ° C. Thereby, the zeolite which has an EMT structure containing an organic structure directing agent is obtained.

  In the production method of the present invention, it is preferable to remove the organic structure directing agent. Examples of the method for removing the organic structure directing agent include removal by baking or decomposition.

  When the organic structure directing agent is removed by firing, examples of firing conditions include 400 ° C. to 800 ° C., 0.5 hours to 12 hours, and a gas flow including oxygen. When the organic structure directing agent is removed by decomposition, examples of the conditions for decomposition include a condition in which a 10% or more aqueous hydrogen peroxide solution and zeolite are brought into contact with each other at room temperature or more and 1 hour or more and 24 hours or less.

  The zeolite of the present invention can be subjected to ion exchange and metal loading in order to enhance the functions as a catalyst, an adsorbent and an ion exchanger. Ion exchange is performed to replace some or all of the exchange ions. It can be obtained by contacting an aqueous solution containing ions to be introduced, etc., solid-liquid separation, and washing with pure water as necessary.

  The zeolite having the EMT structure of the present invention can be expected to have high activity, high selectivity, and high coking resistance when used as a catalyst. Furthermore, when it is used as an adsorbent or an ion exchanger, a high adsorption rate / ion exchange rate can be expected.

The figure which shows a hexagonal plate-shaped model (thickness and bottom face diameter). The figure which shows the powder X-ray-diffraction pattern of the hexagonal plate-shaped zeolite which has the EMT structure manufactured in Example 1. FIG. The scanning electron micrograph which shows the crystal structure of the hexagonal plate-shaped zeolite which has the EMT structure manufactured in Example 1 (magnification = 50,000 times, scale = 0.5 micrometer in a figure). The scanning electron micrograph which shows the crystal structure of the hexagonal plate-shaped zeolite which has the EMT structure manufactured in Example 1 (magnification = 10,000 times, scale = 1 micrometer in a figure). The figure which shows the powder X-ray pattern of the hexagonal plate-shaped zeolite which has the EMT structure manufactured by the comparative example 1. FIG. The scanning electron micrograph which shows the crystal structure of the hexagonal plate-shaped zeolite which has the EMT structure manufactured in the comparative example 1 (magnification = 10,000 times, scale = 1 micrometer in a figure). The scanning electron micrograph which shows the crystal structure of the hexagonal plate-shaped zeolite which has the EMT structure manufactured by the comparative example 1 (magnification = 2,000 times, scale = 10 micrometers in the figure).

The present invention will be specifically described by the following examples, but the present invention is not limited to these examples. In addition, each measuring method in an Example and a comparative example is as follows.
(Powder X-ray diffraction)
Using the MXP3 system made by Mac Science, X-ray source CuKα, acceleration voltage 40 kV, tube current 30 mA, operation speed 2θ = 0.02 ° / sec, sampling interval 0.02 sec, divergence slit 1 deg, scattering slit 1 deg, light receiving slit 0 .3 mm, using a monochromator, evaluated with a gonio radius of 185 mm.
(Measurement of average thickness and average bottom diameter)
The average thickness and the average bottom diameter were evaluated from observation with a scanning electron microscope (manufactured by JEOL, JSM-6390LV). A schematic diagram of evaluation of thickness and bottom diameter is shown in FIG. The thickness and bottom diameter of 10 or more primary particles were measured, and the weighted average was used to obtain the average thickness and average bottom diameter.

Example 1
30 wt% silica sol (Nissan Chemical, Snowtex N-30), liquid sodium aluminate (Sumitomo Chemical), 18-crown-6 (Tokyo Kasei), 48 wt% sodium hydroxide (Tosoh), Pure water was used as a raw material. These raw materials were mixed so as to have the following composition and stirred for 1 hour to obtain a reaction mixture.

Si / Al ₂ = 10
H ₂ O / Si = 14
(18-crown-6) /Si=0.087
Na / Si = 0.44
OH / Si = 0.44

  Next, the obtained reaction mixture was transferred to a reaction vessel made of SUS having a volume of about 200 ml and allowed to stand at room temperature (about 25 ° C.) for 24 hours.

  Thereafter, the reaction vessel was installed in a revolution type reactor, and the temperature was raised to 110 ° C. over about 30 minutes while revolving the reaction vessel at 50 rpm. After the temperature increase, the reaction vessel was held for 12 days while revolving. The slurry after crystallization dissipated heat, washed with pure water, and then dried at 110 ° C. to obtain a powder.

  The powder X-ray diffraction pattern of the obtained powder is shown in FIG. 2, and scanning electron micrographs are shown in FIGS. The obtained powder was a powder composed of zeolite having an EMT structure pure phase.

  Moreover, the obtained zeolite was hexagonal plate shape, the average thickness was 0.16 micrometer, and the average bottom face diameter was 0.89 micrometer. Thus, it was found that the zeolite of the present invention was a fine crystal.

Further, the composition of the obtained zeolite was measured by ICP analysis. As a result, the zeolite had a SiO ₂ / Al ₂ O ₃ molar ratio of 7.8.

Comparative Example 1
A powder was obtained in the same manner as in Example 1 except that the crystallization was performed in a stationary state.

  A powder X-ray diffraction pattern of the obtained powder is shown in FIG. 5, and scanning electron micrographs are shown in FIGS. From the powder X-ray diffraction pattern, it was found that the obtained powder was a powder made of zeolite having an EMT structure pure phase.

  Moreover, although the obtained zeolite was hexagonal plate shape, the average thickness was 0.52 micrometer and the average bottom face diameter was 4.2 micrometers, and it was a large crystal zeolite.

Further, the composition of the obtained zeolite was measured by ICP analysis. As a result, the zeolite had a SiO ₂ / Al ₂ O ₃ molar ratio of 7.8.

  The zeolite of the present invention can be used as a catalyst, an adsorbent, and an ion exchanger. For example, as a catalyst for fluid catalytic cracking, hydrocracking, hydrodewaxing, alkane isomerization, etc. in petroleum refining or refining using coal, natural gas, bio-raw materials, high activity, high selectivity, high resistance Caulking properties can be expected. High activity, high selectivity, and high coking resistance can be expected as a catalyst for aromatization, alkylation, hydration reaction, dehydration reaction, transfer reaction, etc. using petrochemical or coal, natural gas, bio raw materials. .

Claims (5)

  A hexagonal plate-like zeolite having an average thickness of 0.03 μm or more and 0.3 μm or less and having an EMT structure.   2. The hexagonal plate-like zeolite having an EMT structure according to claim 1, wherein an average bottom diameter is 0.1 μm or more and 1.0 μm or less. The method for producing a hexagonal plate-like zeolite having an EMT structure according to claim 1 or 2, wherein a reaction mixture having the following composition is crystallized while stirring.
Si / Al ₂ molar ratio = 9-11
H ₂ O / Si molar ratio = 12-16
(18-crown-6) / Si molar ratio = 0.06-0.10
Na / Si molar ratio = 0.43 to 0.50
OH / Si molar ratio = 0.43 to 0.50   4. The production method according to claim 3, wherein the reaction mixture is put into a reaction vessel and the reaction mixture is stirred by rotating the reaction vessel.   The method according to claim 3 or 4, wherein the crystallization is performed at 105 ° C or higher and 115 ° C or lower.

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