JPS6346006B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel zeolite and a method for synthesizing the same, and particularly provides a novel zeolite based on an offretite crystal structure but which is essentially different from known zeolites in its fine structure and adsorption properties, and its synthesis method. It is something. Zeolite is a crystalline aluminosilicate containing zeolite water, which comes from the Greek word for "boiling stone." Its composition is generally expressed by the following formula based on Al ₂ O ₃ . xM ² /nO・Al ₂ O ₃・(2~∞)SiO ₂・yH ₂ O (Here, M is a cation with a valence of n, and x and y are coefficients.) Also, its basic structure is based on silicon. A SiO ₄ tetrahedron with four oxygen atoms arranged at its vertices as a center and an AlO ₄ tetrahedron with aluminum as the center instead of silicon are arranged so that the atomic ratio of O/(Al+Si) is 2. They are shared and regularly arranged in three dimensions. As a result, a network structure having pores of different sizes and shapes is formed due to the difference in the arrangement of the tetrahedrons. Also, the negative charge of the AlO ₄ tetrahedron is balanced by bonding with cations such as alkali metals or alkaline earth metals. The pores formed in this way have sizes ranging from 3 angstroms to over 10 angstroms, and are made smaller by exchanging the metal cations bonded to the AlO ₄ tetrahedrons with other metal cations. It is also possible to change the size of the holes. Zeolite is widely used industrially as a gaseous or liquid dehydrating agent or as a molecular sieve for adsorbing and separating components of interest by utilizing its property that specific molecules are trapped in its pores. In addition, metal cations exchanged with hydrogen ions act as solid acids, so
It is used as a catalyst in many industries. Offretite, a type of zeolite, exists naturally, and its crystals have a hexagonal crystal system (lattice constant a:
13.29 Å, c = 7.58 Å), and has a 6.4 Å diameter pore consisting of a 12-membered ring that can adsorb cyclohexane. Since offretite can be synthesized in the presence of tetramethylammonium ions (hereinafter abbreviated as TMA ions), synthetic offretite is called TMA-offretite. TMA-offretite is found in its crystals.
TMA− ions are incorporated, and the chemical composition is x {(TMA) ₂ , K ₂ , Na ₂ }O・Al ₂ O ₃・ (5–10) SiO ₃・yH ₂ O (where x and y are coefficients) It is expressed as When this zeolite is calcined in air at a temperature of 500 to 600°C, TMA ions are decomposed and released, becoming H ions and remaining in the offretite structure. Eryonite is a zeolite whose structure is very similar to offretite. In offretite crystals, ε cages (canclinite cages) are stacked in the same direction along the C axis, sandwiching double six-membered rings, and have a diameter of 6.4 Å.
It forms a pore consisting of a 12-membered ring. On the other hand, in erionite, the ε cages sandwich the double six-membered ring and are rotated 60 degrees alternately and stacked in the C-axis direction.
In addition to the 12-membered ring, an 8-membered ring of 3.6 x 5.2 Å is formed coaxially. (Lattice constant a: 13.26Å, c=15.12Å)
Differences due to slight differences in these crystal structures appear as “odd line” in the X-ray powder diffraction diagram.
The so-called peaks at 2θ = 9.6°, 16.6°, 21.4°, and 31.9° (measured by CuKα doublet) do not exist at all in the case of offretite, but in the case of erionite, these sharp peaks are present. It appears in the observation, and offretite and erionite are
They can be clearly distinguished by line powder diffraction. Also, offretite adsorbs cyclohexane, but erionite does not adsorb cyclohexane, so there is a large difference in their adsorption characteristics. By the way, it is known that in certain types of zeolites, these two crystal phases are simultaneously contained in one crystal particle. A zeolite called Zeolite T is one such zeolite, and it is reported that these two crystal phases are irregularly grown internally. (JMBennett and JAGard
2θ =
There are only two, 9.6° and 21.4°, and their adsorption properties are characterized by the fact that they do not adsorb cyclohexane at all. (by DWBreck “Zeolite Molecular
In addition, the zeolite called ZSM-34 disclosed in Japanese Patent Application Laid-Open No. 53-58499 filed by Mobil,
In its X-ray powder diffraction diagram, broad peaks at 2θ = 9.6°, 16.6°, 21.4°, and 31.9°, which are “odd line”, are observed, indicating that this zeolite contains very small erionite in the offretite structure. It is said that the area has grown internally. or,
It has the ability to adsorb n-hexane and cyclohexane, and is said to be effective in various catalytic reactions. However, for its synthesis, it is essential to use choline, which is an organic nitrogen-containing compound, or a derivative thereof. This organic nitrogen-containing cation is produced
It is incorporated into the crystal structure of ZSM-34 as part of the cation. For this reason, ZSM-34 is 500~
Unless organic nitrogen-containing cations are decomposed and removed by calcining at 600°C, adsorption and catalytic activity will not occur. As a result of wide-ranging studies on these offretite-type zeolites, the present inventors have found that, while based on the offretite-type crystal structure, they do not use any expensive organic nitrogen-containing compounds such as TMA ions or choline. We succeeded in synthesizing a new zeolite whose structure and adsorption properties are different from conventional offretite-type zeolites. The new zeolite of the present invention (hereinafter referred to as zeolite OE)
) has the following composition: xM ² /nO・Al ₂ O ₃・(5-10)SiO ₂・yH ₂ O (where M represents a cation of valence n,
x, y are coefficients) M is in the combined state,
K ⁺ and Na ⁺ . Part or all of K ⁺ or Na ⁺ can be exchanged with other cations by known methods. x varies depending on the degree of cleanliness of the crystal, but is 0.8~
It is 2. y varies depending on the degree of dryness of the crystal, but is 0
~10. Additionally, zeolite OE has significant characteristics in its X-ray powder diffraction pattern. The diffraction angle 2θ (degrees) and the resulting lattice spacing (d-Å) measured using a copper Kα doublet are shown in Table 1.

[Table] Offretite, TMA-offretite is 9.6°,
There is no peak at 16.4°, and erionite has a strong peak at that angle, whereas zeolite
OE is weak and a broad peak is observed. Zeolite T has no peak at 14.0°, whereas zeolite OE has a peak at that angle.
The strongest peaks of offretite, TMA-offretite, erionite, ZSM-34, and theolite T are
Zeolite OE has its strongest peak at 23.6°, while it is 7.7°. Structural analysis of zeolite OE by electron beam diffraction revealed that it is not simply a mixture of known zeolites, but that it has an offretite structure as its basis, with a small amount of erionite phase regularly growing inside. The zeolite OE of the present invention has adsorption properties not found in known zeolites such as Zeolite T. Eryonite and Zeolite T are 500-600℃
It hardly adsorbs cyclohexane even if it is activated by heating and baking. On the other hand, ZSM−34,
After synthesis, TMA-offretite does not adsorb cyclohexane at all when heated at 100 to 350°C.
Cyclohexane can only be adsorbed after activation treatment at ~600°C. However, zeolite OE can adsorb cyclohexane by simply washing it with water after synthesis and dehydrating it at a relatively low temperature of room temperature to 350°C. Next, a method for producing the novel zeolite OE of the present invention will be described. The raw materials for synthesizing zeolite OE are silica source, alumina source, alkali source, sodium source,
A source of potassium and water. Silica sources include sodium silicate and amorphous silicic acid, but zeolite
In order to synthesize OE with high purity, the apparent specific gravity is 0.3.
Synthetic amorphous silicic acid, so-called white carbon, with a concentration of less than g/ml is most preferred. The zeolite OE of the present invention cannot be obtained if the silica source is colloidal silica, so-called silica sol. As the alumina source, sodium aluminate, aluminum hydroxide, aluminum sulfate, and aluminum nitrate can be suitably used. Sodium hydroxide and potassium hydroxide are preferable as the alkali source. The coexisting alkali of sodium silicate and sodium aluminate can also be an alkali source. Potassium ions are essential for carrying out the present invention. Therefore, if potassium is not supplied as an alkali, potassium ions must be supplied in the form of a salt such as potassium chloride or potassium sulfate. When using aluminum sulfate or aluminum nitrate as an alumina source, it is necessary to add alkali for neutralization according to the following formula. Al ₂ (SO ₄ ) ₃ +6NaOH = 3Na ₂ SO ₄ +Al ₂ O ₃ +3H ₂ O 2Al(NO ₃ ) ₃ +6NaOH = 6NaNO ₃ +Al ₂ O ₃ +3H ₂ O These silica sources, alumina sources, alkali sources, sodium sources, By reacting and mixing the potassium source and water with thorough stirring, a reaction mixture having the composition expressed in the following molar ratio is obtained. SiO ₂ /Al ₂ O ₃ = 6-40 OH/SiO ₂ = 0.3-1 K/K+Na = 0.1-0.9 H ₂ O/SiO ₂ = 10-70 Zeolite OE cannot be obtained outside this composition. The desirable composition of the reaction mixture is: SiO ₂ /Al ₂ O ₃ = 10-30 OH/SiO ₂ = 0.4-0.85 K/K+Na = 0.2-0.8 H ₂ O/SiO ₂ = 12-60; crystallinity zeolite
OE can be obtained without coexistence of impurities. And furthermore, within the range of the desired reaction mixture composition, i.e. in the region, the SiO ₂ /Al ₂ O ₃
When the molar ratio of SiO 2 /Al 2 O 3 is high (and tends to be high), the OH/SiO ₂ molar ratio should be set in the highest possible range, and conversely when the molar ratio of SiO ₂ /Al ₂ O ₃ is low (and OH/
A more desirable composition is to maintain the molar ratio of SiO ₂ in the lowest possible range. In addition, when calculating OH, sodium aluminate is
2NaAlO ₂ + H ₂ O = 2NaOH + Al ₂ O ₃ , and sodium silicate is Na ₂ SiO ₃ + H ₂ O = 2NaOH + SiO ₂
be considered as Also, consider and add aluminum sulfate as Al ₂ (SO ₄ ) ₃ + 3H ₂ O = Al ₂ O ₃ + 3H ₂ SO ₄ and aluminum nitrate as 2Al (NO ₃ ) ₃ + 3H ₂ O = Al ₂ O ₃ + 6HNO ₃ . Subtract the neutralization equivalent from the alkali obtained. However, the OH of Al(OH) ₃ is removed from the calculation. When calculating K/K+Na, use KOH or NaOH.
In addition, K and Na supplied in the form of salt are also considered. When calculating H ₂ O/SiO ₂ , in addition to water supplied as pure water, water supplied as an aqueous solution, as well as H ₂ O according to the following formula and water generated by neutralization, should be considered. Consider. 2Al(OH) ₃ = Al ₂ O ₃ + 3H ₂ O 2NaOH = Na ₂ O + H ₂ O 2KOH = K ₂ O + H ₂ O The reaction mixture prepared to the above composition was stirred,
Crystallize by heating at 120-200℃. During crystallization,
By performing stirring, not only the crystallization time is shortened, but also a zeolite with high crystallinity can be obtained without coexisting impurities. A desirable crystallization temperature is 130-180°C, and a crystallization time is 5-40 hours. If the crystallization temperature is less than 120°C, it will not crystallize. Moreover, above 200°C, zeolite P-based impurities coexist. After crystallization is completed, solid-liquid separation is carried out using a conventional method, followed by washing with water.
Dry at °C to obtain zeolite OE. The zeolite OE of the present invention exhibits sufficient activity when dried at 100 to 200°C, and exhibits sufficient activity when dried at 100 to 200°C.
- Adsorbs pentane, cyclohexane, etc.
It can be used as an adsorbent for these. or,
Because it has extremely high dehydration ability, it can also be effectively used as a desiccant for gases and liquids. Note that there is no problem in using the product after heat treatment at 500 to 600°C. Furthermore, since it exhibits strong solid acidity when exchanged with other cations such as H ⁺ by a conventional method, it can be used as a catalyst for various reactions. In addition, the zeolite OE of the present invention is
Not only as a powder, but also shaped into spheres or columns,
It can be used for various purposes. Examples will be described below. <Method for measuring apparent specific gravity> Place 1g of sample into the cylinder of the apparent specific gravity measuring device, insert the piston, hold it lightly with your fingers and drop it gently, leave it for 30 minutes, then measure the difference in height between the piston and the cylinder in Hcm. It is calculated using the following formula. Apparent specific gravity = 1/(H-1.2 ^* ) x 3.8 ^** (Note) The apparent specific gravity measuring device consists of a metal cylinder and a matching piston. The cylinder has an inner diameter of 2.2 cm and a depth of 11.5 cm. length
It is 12.7cm and weighs 190g. The apparent specific gravity measured with this measuring device is the weight of 1 ml of sample when compressed with a pressure of 50 g per 1 cm ² expressed in grams. * 1.2 = 12.7 - 11.5 * 3.8 = Cylinder area = 1.1 x 1.1 x 3.14 <Measurement of cyclohexane adsorption amount> Measure with a Matsukubein-Baker type adsorption device. After activating approximately 1 g of the sample under vacuum at 350°C for 2 hours, the sample temperature is maintained at 25°C, cyclohexane vapor at a pressure of 48 mmHg is introduced, and the amount of adsorption after 3 hours is determined. <X-ray powder diffraction> After drying the sample, hydrate it at a relative humidity of 80%, and
The Kα doublet is used as a radiation source, Ni filter, tube voltage,
Measure at 35KV and tube current 25mA. Example 1 701.2 g of pure water contains 23.6 g of solid sodium hydroxide (NaOH: 93 wt%), 26.8% of solid potassium hydroxide (KOH: 85 wt%), aqueous sodium aluminate solution (Na ₂ O: 19.2 wt%, Al _{2O3 :} 20.66wt%)51.4
g to make a homogeneous solution, and then add white carbon (SiO ₂ : 87.7wt%,
Al ₂ O ₃ : 0.5wt%, apparent specific gravity 0.14g/ml) 142.9
A reaction mixture having the following composition with the oxide molar ratio was obtained. 3.9Na ₂ O・1.83K ₂ O・Al ₂ O ₃・18.8SiO ₂・
382H ₂ O The reaction mixture is: SiO ₂ /Al ₂ O ₃ = 18.8 OH/SiO ₂ = 0.61 K/K+Na = 0.32 H ₂ O/SiO ₂ = 20.3. Put this in an autoclave,
It was heated at 150° C. for 40 hours while stirring at 250 rpm.
The resulting slurry was separated into solid and liquid, washed thoroughly with water,
It was dried at 150°C for 5 hours to obtain the following powder. 0.22Na ₂ O・0.96K ₂ O・Al ₂ O ₃・8.5SiO ₂・5.8H ₂ O As shown in FIG. 1, the result of X-ray powder diffraction of this powder was that it was zeolite OE. Also, the amount of cyclohexane adsorbed was 1.9 wt% (25°C, 48 mmHg). Examples 2 to 4 and Comparative Examples 1 to 3 Table 2 shows the results of experiments conducted in the same manner as in Example 1 by varying the silica source, composition, and crystallization conditions of the reaction mixture. The silica source used in Comparative Example 2 was
It is a silica sol containing 30wt% _SiO2 .

【table】 [Brief explanation of the drawing]

Figure 1 shows the zeolite obtained in Example 1.
It is an X-ray powder diffraction diagram of OE.

Claims (1)

[Claims] 1 The following composition expressed in molar ratio of oxides: xM ² /nO・Al ₂ O ₃・(5-10)SiO ₂・yH ₂ O (M represents a cation with a valence n, x, y are coefficients) and have the X-ray powder diffraction pattern shown in Table 1, and 1wt% or more of cyclohexane (measurement conditions: 25°C, 48mmHg) without baking at a temperature higher than 350°C. ) Zeolite that can be adsorbed. 2 Consists of a silica source, an alumina source, an alkali source, a sodium source, a potassium source, and water, expressed in molar ratio under the following conditions: SiO ₂ /Al ₂ O ₃ = 6 to 40 OH/SiO ₂ = 0.3 to 1 K/K+Na = 0.1 to 0.9 H ₂ O / SiO ₂ = 10 to 70, and the reaction mixture was stirred for 120 to 200
A method for producing a zeolite having an X-ray powder diffraction pattern shown in Table 1, which is characterized by crystallizing at ℃. 3. The method according to claim 2, wherein the silica source is synthetic amorphous silicic acid with an apparent specific gravity of 0.3 (g/ml) or less.