JPH0547484B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a new zeolite and a method for producing the same, and more specifically to ZSM-5.
The present invention relates to a new zeolite whose basic structure is a type zeolite, but whose fine structure and adsorption properties are significantly different from those of known zeolites, and a method for producing the same. [Prior art] Zeolite has the general formula xM _2/o O・Al ₂ O ₃・ySiO ₂・zH ₂ O (where M is a cation, n is the valence of M, and x is the valence of M).
A number in the range of 0.8 to 2, y is a number of 2 or more, and z is a number of 0 or more. ) is a crystalline aluminosilicate represented by There are many types of zeolite, each with its own unique crystal structure.
Its chemical composition, especially the SiO ₂ /Al ₂ O ₃ molar ratio and adsorption pore diameter, greatly depends on its crystal structure, so even if you change the synthesis conditions or exchange ion species, these characteristics can be changed within a range. is a very narrow range. In addition, ZSM-5 type zeolite, which has become widely used as a solid acid catalyst in recent years, can be made into crystals by changing the synthesis conditions.
It is a type of zeolite that can greatly change the SiO ₂ /Al ₂ O ₃ molar ratio, and the SiO ₂ /Al ₂ O ₃ molar ratio can be made as high as possible, but by changing the synthesis conditions, the SiO ₂ /Al About 20 is the limit in reducing _{the 2} O ₃ molar ratio. Catalytic properties when using zeolite as a solid acid catalyst depend on the type of zeolite, its structure, and
It depends on the solid acid properties caused by the SiO ₂ /Al ₂ O ₃ molar ratio, etc. Among solid acid properties, acid strength is the property of crystals.
The higher the SiO ₂ /Al ₂ O ₃ molar ratio, the stronger the acid content.
It is known that the SiO/Al ₂ O ₃ molar ratio is often lower. However, as mentioned above, there is a limit to changing the SiO ₂ /Al ₂ O ₃ molar ratio depending on the synthesis conditions, so solid acid properties cannot be freely adjusted. Therefore, the modification of solid acid properties caused by the SiO ₂ /Al ₂ O ₃ molar ratio has conventionally been achieved by removing Al in the crystal skeleton (dealumination) or replacing Al with Si by various methods. It was done by [Problems to be Solved by the Invention] The present inventors have discovered that although the SiO ₂ /Al ₂ O ₃ molar ratio is 10 to 30 and basically has a ZSM-5 type skeleton structure, The object of the present invention is to provide a new zeolite whose structure, adsorption properties, and physical and chemical properties are significantly different from the conventionally known ZSM-5 type zeolite, and a method for producing the same. That is, as mentioned above, the SiO ₂ /Al ₂ O ₃ molar ratio of ZSM-5 type zeolite cannot be adjusted to 20 by simply changing the synthesis conditions using any known method.
You cannot get the following: The physical and chemical properties, catalytic properties, adsorption properties, etc. of zeolite greatly depend on the SiO ₂ /Al ₂ O ₃ molar ratio.
Zeolite with a low SiO ₂ /Al ₂ O ₃ molar ratio that maintains the unique pore structure and pore diameter of ZSM-5 type zeolite should have different characteristics from the conventional ZSM-5 type zeolite. be. In addition, ZSM-5 type zeolite generally has strong solid acidity and at the same time has an intermediate pore diameter that conventional zeolites do not have, which is why it has unique molecular shape selectivity. However, the performance cannot be fully exhibited only by satisfying these conditions. That is, in order to fully utilize these characteristics, it is necessary that the size of each crystal, that is, the crystallite diameter, be sufficiently small. Therefore, an object of the present invention is to provide a novel ZSM-5 type zeolite having a low SiO ₂ /Al ₂ O ₃ molar ratio and a small crystallite diameter, and a method for producing the same. [Means for solving the problem] The present inventors have been involved in the synthesis of zeolite for many years,
As a result of intensive research into the crystal structure and adsorption properties, we simultaneously solved the above problems by heat-treating the synthesized ZSM-5 type zeolite in an alkaline aqueous solution with a specific composition. We have discovered that a new zeolite can be obtained and have arrived at the present invention. ZSM used for producing the zeolite of the present invention
Type-5 zeolite can be used regardless of the manufacturing method as long as it has the X-ray lattice spacing shown in Table 1. The most important feature of ZSM-5 type zeolite with the X-ray lattice spacing shown in Table 1 is that the diffraction line corresponding to the strongest peak, d = 3.83 Å, is a single peak depending on the width. be. ZSM-5 type zeolite with such characteristics is disclosed in Japanese Patent Publication No. 10064/1983 and Japanese Patent Application Laid-open No. 39716/1983.
It can be produced by the methods disclosed in Japanese Patent Application Publication No. 59-54620 and the like. obtained
If the ZSM-5 type zeolite contains tetrapropylene ammonium ions, etc. that cannot be easily ion-exchanged, they are decomposed and removed by calcination before use, but it is necessary to convert them into H-type by further ion exchange. There isn't. These ZSM-5 type zeolites are then placed in an alkaline aqueous solution and heat treated. Alkaline aqueous solutions generally include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; alkaline earth metal hydroxides such as barium hydroxide; and aqueous solutions such as sodium silicate, potassium silicate, and amines. is used. Its concentration ranges from 0.5 to 15 wt%, preferably from 3 to 8 wt%. 0.5wt%
If the amount is less than 15 wt%, it is difficult to effectively lower the SiO ₂ /Al ₂ O ₃ molar ratio, and even if the amount exceeds 15 wt%, the crystal structure is likely to be destroyed. In addition, the processing temperature is 80°C above room temperature.
℃, preferably in the range of 30 to 80℃. If it is too low, it will be difficult to reduce the SiO ₂ /Al ₂ O ₃ molar ratio. The higher the treatment temperature, the more likely it is that the SiO ₂ /Al ₂ O ₃ molar ratio will decrease, but the crystal structure is also more likely to be destroyed at high temperatures, so it must be kept below 80°C. In addition, the amount of alkaline aqueous solution used can be processed at any concentration of 5 to 50% in terms of slurry concentration (zeolite weight percentage relative to the weight of alkaline aqueous solution), but if the slurry concentration is low, the efficiency will be poor, and if the concentration is high, In this case, the slurry viscosity becomes high and becomes difficult to handle, so it is preferable to treat the slurry at a concentration of about 20%. The SiO ₂ /Al ₂ O ₃ molar ratio of the resulting zeolite is determined by the combination of the concentration of the alkaline aqueous solution, the slurry concentration, and the treatment temperature and time. Therefore, by optimally combining these conditions, a novel ZSM-5 type zeolite with any SiO ₂ /Al ₂ O ₃ molar ratio in the range of 10 to 30 can be obtained. Further, during the treatment, it is preferable to stir the slurry so that the treatment temperature is uniform and there is no difference in the SiO ₂ /Al ₂ O ₃ molar ratio between the zeolite crystal particles. After heat treatment in an alkaline aqueous solution, solid-liquid separation is performed, the solid content is thoroughly washed, and this is further dried.
A new ZSM-5 type zeolite with a low SiO ₂ /Al ₂ O ₃ molar ratio can be obtained. [Operations and Effects] That is, according to the production method of the present invention, (1) Expressed in molar ratio of oxides, 0.8 to 2M _2/o O.Al ₂ O _3.10 to 30SiO _{2.wH 2} O (where M is a cation, n is the valence of M, w is 0
or represents a positive number. ), and (2) the X-ray lattice spacing has the characteristics shown in Table 1, and (3) in the sodium form, at 25°C and 47 mm.
The adsorption capacity of cyclohexane under Hg pressure is 8 wt% or more, and (4) the crystallite diameter is 1000 Å or less. A novel zeolite is obtained which is particularly characterized. As mentioned above, the SiO ₂ /Al ₂ O ₃ molar ratio of the new ZSM-5 type zeolite obtained by heat treatment in an alkaline aqueous solution with a specific composition is higher than the SiO ₂ /Al ₂ O ₃ molar ratio of the raw material zeolite. It will definitely decrease.
However, since the crystallinity determined from the X-ray diffraction diagram of the obtained zeolite is sufficiently maintained, the crystal structure is not significantly destroyed. Also, the M _{2 /o} Al ₂ O ₃ molar ratio does not decrease, typically the ratio is 1, and varies from 0.8 to 2 depending on the degree of washing after treatment. In addition, some or all of the cations contained in the zeolite after treatment are occupied by the cations in the alkaline aqueous solution used. Therefore, for example, after a sodium-type zeolite is treated in an aqueous lithium hydroxide solution, the cations in the zeolite become only lithium ions or mixed ions of sodium ions and lithium ions. The number of adsorbed water molecules, represented by w, depends on the type of cation, the SiO ₂ /Al ₂ O ₃ molar ratio, and the degree of drying after washing. Novel ZSM obtained by the method of the present invention
One of the major characteristics of type 5 zeolite is that it has the X-ray lattice spacing shown in Table 1. That is, the diffraction line corresponding to the strongest peak, d=3.83 Å, is one broad peak, and is never split into two. In recent years, the basic feature in the X-ray diffraction diagram is that even though it is similar to the ZSM-5 type zeolite described in Japanese Patent Publication No. 46-10064, there are two diffraction lines corresponding to the strongest peak at d = 3.83 Å. Zeolites that have been split into It is clearly different from ZSM-5. The reason for this is not clear, but it is thought to be due to differences in fine crystal structure. Therefore, the above d=3.83Å
It must be considered that zeolites whose diffraction lines correspond to a single broad peak are different from zeolites whose diffraction lines correspond to two peaks. First table lattice spacing (d, Å) Relative strength 11.1±0.3 Strong 9.9±0.3 Strong 7.4±0.2 Weak 6.7±0.2 Weak 6.3±0.2 Weak 6.0±0.2 Weak 5.7±0.1 Weak 5.6±0.1 Weak 5.0±0.1 Weak 4.37 ± 0.08 weak 4.27 ± 0.08 Weak 4.00 ± 0.08 Weak 3.83 ± 0.07 Very strong 3.73 ± 0.05 strong 3.66 ± 0.05 Weak 3.45 0.05 Weak 3.36 ± 0.05 Weak 3.36 ± 0.05 Weak 3.31 ± 0.05 weak 3.05 ± 0.03 Weak 2.98 ± 0.03 .02 Weak method of the present invention New results obtained by
One of the major features of ZSM-5 type zeolite is that it exhibits specific adsorption properties. For example, SiO ₂ /ZSM-5 type zeolite obtained by heat treatment in an alkaline aqueous solution according to the method of the present invention
Although the Al ₂ O ₃ molar ratio decreases, the adsorption capacity for organic compounds and the like increases compared to before treatment. This adsorption capacity increases as the SiO ₂ /Al ₂ O ₃ ratio decreases. That is, when the same zeolite is used as a raw material, the lower the SiO ₂ /Al ₂ O ₃ molar ratio, the higher the adsorption capacity. Furthermore, when comparing zeolites with the same SiO ₂ /Al ₂ O ₃ molar ratio, the higher the SiO ₂ /Al ₂ O ₃ molar ratio of the raw material zeolite, the larger the adsorption capacity. Therefore,
More preferable zeolite obtained is SiO ₂ /Al ₂ O ₃
The molar ratio ranges from 10 to 20. like this
The increase in adsorption capacity with the reduction of the SiO ₂ /Al ₂ O ₃ molar ratio is due to the increase in the adsorption capacity due to the hydrophobization of ZSM-5 type zeolite with a high SiO ₂ /Al ₂ O ₃ molar ratio obtained by synthesis. This is a major feature of the zeolite of the present invention. By the way, since the adsorption capacity value changes depending on the type of cation contained in the zeolite, it is necessary to standardize the types of cation contained when making a comparison. The ZSM-5 type zeolite according to the present invention is characterized in that, in the sodium form, the cyclohexane adsorption capacity at 25° C. and a pressure of 47 mmHg is 8 wt% or more. On the other hand, Na type with a SiO ₂ /Al ₂ O ₃ molar ratio of 20 to 30 obtained by conventional synthesis
The cyclohexane adsorption capacity of ZSM-5 type zeolite under the same conditions is 6 to 7 wt%, and
Unless the SiO ₂ /Al ₂ O ₃ molar ratio is 50 or more, the cyclohexane adsorption capacity will not exceed 8 wt%.
Furthermore, the increase in adsorption capacity of the novel zeolite of the present invention is not limited to cyclohexane, but also applies to organic compounds such as n-hexane and benzene. Although the cause of this increase in adsorption capacity is not clear, it is presumed that the treatment under relatively mild conditions generates new adsorption active sites without destroying the crystal structure. The adsorption capacity of the above organic compounds is
Measured with a Baker-type adsorption device. The method involves activating approximately 1 g of sample under vacuum at 350°C for 2 hours, then
Maintain the sample temperature at 25°C, introduce organic compound vapor at a predetermined pressure, and determine the adsorption capacity after 16 hours. It is already well known that when zeolite is used as a catalyst and adsorbent, its performance is greatly influenced by the ease of diffusion of molecules within the zeolite pores and the external surface area of the crystals. If the size of each crystal, that is, the crystallite diameter, is small enough, the outer surface area per unit weight will be large and the intracrystal diffusion distance will be short, so the characteristics of the zeolite used in catalytic reactions and adsorption can be used as is. However, as the crystallite size increases, the opposite is true, and many disadvantageous phenomena such as coking in the catalytic reaction and shortened lifespan occur. The novel ZSM-5 type zeolite obtained by the method of the present invention is characterized by a crystallite diameter of 1000 Å or less. Preferably it is 500 Å or less. The crystallite diameter is
It can be determined from the spread of the half-width of the diffraction line in the line diffraction diagram using the following Sherrer equation. β=Cλ/d cosθ+b where, β: Half width of diffraction line of measurement sample (radian) c: Constant (0.9) λ: Measured X-ray wavelength (CuKα λ=1.5418Å) d: Crystallite diameter (Å) θ : Bragg angle of the diffraction line (degrees) b: Half-width of the diffraction line of the standard sample (radians) It can be effectively applied when distinguishing between those with a diameter of 1000 Å or less and those with a diameter of 1000 Å or less.
For the following example, the surface index hkl = (642) (20≒
29.2°) diffraction lines were measured. Moreover, α-quartz was used as a standard sample. The new zeolite according to the method of the invention can be made into various cationic forms by ion exchange. The proton-exchanged zeolite can be used as a solid acid catalyst, and the metal ion-exchanged zeolite can be used as an adsorbent for separation and purification in the form of a molded body, if necessary. The present invention will be explained in further detail in Examples. Example 1 Zeolite as a raw material was synthesized according to the method described in JP-A-59-39716. That is, amorphous solid silicic acid with an apparent specific gravity of 0.4 g/ml or less is used as a silica source, and the reaction mixture obtained by mixing this with sodium aluminate, caustic soda, and water is crystallized by heating at 160°C for 72 hours with stirring. ,
Zeolites A and B were obtained by washing and drying. Further, according to the method described in JP-A No. 59-54620, a granular amorphous sodium aluminosilicate homogeneous compound was crystallized by heating in an aqueous sodium hydroxide solution at 158° C. for 72 hours with stirring, washing,
Zeolite C was obtained by drying. Zeolites A, B, and C all had the X-ray lattice spacing shown in Table 1, and the diffraction line corresponding to d=3.83 Å was a single broad peak. Table 2 shows the chemical compositions of zeolites A, B, and C on an anhydrous basis and their adsorption capacities for cyclohexane, n-hexane, and benzene.

[Table] 200g of dry powder of zeolite A obtained above
was placed in a 5 wt% aqueous sodium hydroxide solution maintained at 30°C and stirred. After 6 hours, 25 hours and 48 hours, one-third of the mixed slurry was taken out and separated into solid and liquid, and the solids were thoroughly washed with warm water. All of the obtained zeolites had the X-ray lattice spacings shown in Table 1. Figure 1 shows the X-ray diffraction patterns of zeolite treated for 6 hours and 25 hours, respectively.
Shown in Figure 2. In addition, the chemical composition of each zeolite on an anhydrous basis and cyclohexane, n
- Adsorption capacity and crystallite diameter for hexane and benzene are shown in Table 3.

[Table] Example 2 Dry powder of zeolite B obtained in Example 1
220g was placed in a 5wt% aqueous sodium hydroxide solution maintained at 50°C and stirred. Heat after 7 hours,
Stirring was stopped, solid and liquid were separated, and the solids were thoroughly washed with warm water. The obtained zeolite has X shown in Table 1.
The diffraction line having a line lattice spacing and corresponding to d=3.83 Å was a single broad peak. Moreover, the chemical composition on an anhydrous basis was 1.02Na ₂ O・Al ₂ O ₃・15.8SiO ₂ . The cyclohexane adsorption capacity at 25°C and 47 mmHg was 13.3 w%, and the crystallite diameter was 490 Å. Example 3 Dry powder of zeolite C obtained in Example 1
220g was placed in a 5wt% lithium hydroxide aqueous solution kept at 30°C and stirred. After 7 hours and 25 hours, half of the mixed slurry was taken out and separated into solid and liquid, and the solids were thoroughly washed with warm water. The obtained zeolites all have the lattice spacings shown in Table 1, and d
The diffraction line corresponding to =3.83 Å was a single broad peak. The chemical composition, cyclohexane adsorption capacity and crystallite diameter of the obtained zeolite on an anhydrous basis were
Shown in the table. Example 4 Dry powder of zeolite C obtained in Example 1
220g was placed in a 5wt% potassium hydroxide absorption solution maintained at 30°C, and treated in exactly the same manner as in Example 3. All of the obtained zeolites had the lattice spacings shown in Table 1, and the diffraction line corresponding to d=3.83 Å was a single broad peak. Table 4 shows the chemical composition and crystallite diameter of the obtained zeolite on an anhydrous basis. Furthermore, the zeolite treated for 25 hours was further ion-exchanged in an aqueous sodium nitrate solution, and the cyclohexane adsorption capacity of the zeolite, which was made into a sodium form, was 8.1 wt%.

[Table] Comparative Example 1 According to the method described in JP-A No. 59-54620, a granular amorphous sodium aluminosilicate homogeneous compound was heated and crystallized in an aqueous sodium hydroxide solution at 163°C under stirring for 72 hours. After washing and drying, a zeolite having a chemical composition of 1.2Na ₂ O・Al ₂ O ₃・37.9SiO ₂ on an anhydrous basis was obtained. The X-ray lattice spacing of this zeolite is similar to that shown in Table 1, except that the diffraction line corresponding to the strongest peak is split into two lines, d = 3.85 Å and d = 3.82 Å. This was different from that of the present invention. 110g of this zeolite dry powder
It was placed in a 4wt% aqueous sodium hydroxide solution heated to 90°C and stirred for 24 hours. After washing and drying, a zeolite having a chemical composition of 1.3Na ₂ O・Al ₂ O ₃・22.3SiO ₂ on an anhydrous basis was obtained. The X-ray lattice spacing of this zeolite is similar to that shown in Table 1, but it is different from that of the present invention in that the diffraction line corresponding to the strongest peak is split into two lines like the raw material zeolite. It was different. The X-ray diffraction diagram of this zeolite is shown in FIG.
Moreover, the cyclohexane adsorption capacity at 25°C and 47 mmHg was 6.8 wt%, and the crystallite diameter was 2300 Å.

[Brief explanation of the drawing]

1 and 2 show X-ray diffraction patterns of the zeolite obtained in Example 1. Figure 3 shows comparative example 1.
The X-ray diffraction pattern of the zeolite obtained in is shown.

Claims (1)

[Claims] 1 (a) Expressed in molar ratio of oxides: 0.8 to 2M _2/o O.Al ₂ O _3.10 to 30SiO _{2.wH 2} O (where M is a cation and n is M valence, w represents 0 or a positive number), and (b) the X-ray lattice spacing has the characteristics shown in Table 1, and (c) the crystallite diameter is 1000 Å. (d) In the sodium form, 25℃, 47mm
A zeolite characterized by a cyclohexane adsorption capacity of 8wt% or more under Hg pressure. 2 A zeolite having an X-ray lattice spacing as shown in Table 1 is heated in an alkaline aqueous solution at a temperature of less than 80°C _{. /o} O・Al ₂ O ₃・10~30SiO ₂・wH ₂ O (where M is a cation, n is the valence of M, and w is 0 or a positive number), and (b) The X-ray lattice spacing has the characteristics shown in Table 1, (c) The crystallite diameter is 1000 Å or less, and (d) In the sodium form, at 25°C and 47 mm.
A method for producing a zeolite characterized by a cyclohexane adsorption capacity of 8 wt% or more under Hg pressure.