JPH0339971B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new method for producing crystalline aluminosilicate zeolite having a five-membered oxygen ring, and more specifically, it is highly pure without using any organic mineralizing agent, and is SiO ₂ /Al ₂ O ₃ . The object of the present invention is to provide a method for easily producing zeolite having a high molar ratio with excellent reproducibility. Zeolite is a crystalline aluminosilicate containing zeolite water, and its composition is generally expressed by the following formula. M _2/o O・Al ₂ O ₃・xSiO ₂・yH ₂ O (Here, n is the valence of the cation M, x is a number of 2 or more, and y is a number of 0 or more.) Also, its basics The structure consists of a SiO ₄ tetrahedron with silicon as the center and four oxygen atoms coordinated at its vertices, and an AlO ₄ tetrahedron with aluminum as the center instead of silicon, so that the atomic ratio of O (Al + Si) is 2. They are regularly bonded three-dimensionally by sharing oxygen with each other. As a result, a three-dimensional network structure having pores of different sizes and shapes is formed due to the difference in the bonding method of the tetrahedrons. Further, the negative charges of the AlO ₄ tetrahedron are electrically neutralized by bonding with cations such as alkali metals or alkaline earth metals. Generally, the pores formed in this way have a size of 2 to 3 angstroms to more than 10 angstroms, but the metal cations bonded to the AlO ₄ tetrahedron are exchanged with other metal cations of different sizes. By doing so, the size of the pores can be changed. Zeolite uses these pores to act as an industrial gas or liquid dehydrating agent or as a molecular sieve that adsorbs and separates only specific molecules, and when metal cations are exchanged with hydrogen ions, it acts as a solid acid. Taking advantage of this property, it is also used in many industrial catalysts. There are many types of zeolite, and each type has a different name depending on its crystal structure. Each zeolite exhibits adsorption properties, catalytic properties, ion exchange properties, etc. unique to the zeolite due to its crystal structure, chemical composition, etc. The present invention relates to a novel method for producing synthetic ferrierite-type zeolite, which belongs to zeolites having five-membered oxygen rings. Ferrierite is a type of naturally occurring zeolite with a lattice constant a=
It is a crystalline aluminosilicate belonging to the orthorhombic system with dimensions of 19.16 Å, b = 14.13 Å, and c = 7.49 Å, and has the lattice spacing (d value) shown in Table 1. Further, its typical composition is represented by (Na ₂ , Mg)O.Al ₂ O ₃ .11.1SiO ₂ .6.5H ₂ O. Its crystal structure consists of a skeletal unit of 5-membered oxygen rings, and is characterized by having a 4.3 x 5.5 Å pore consisting of a 10-membered oxygen ring and a 3.4 x 4.8 Å pore consisting of an 8-membered oxygen ring. Can be attached. On the other hand, the zeolite obtained by the present invention is
By substantially having the lattice spacing (d value) shown in Table 2,

【table】

[Table] Table 2 Lattice spacing (d value) (Å) Relative strength 9.50±0.2 Very strong 7.1±0.1 Weak 7.0±0.1 Weak 7.0±0.1 Weak 6.6±0.1 Weak 3.99±0.08 Strong 3.86 ±0.08 weak 3.78±0.08 strong 3.67±0.07 weak 3.53±0.07 very strong 3.47±0.05 strong 3.32±0.05 weak 3.14±0.05 weak 3.05±0.05 weak As characterized in Table 1 It has some differences from the natural ferrierite shown. However, since the d values shown in Table 2 closely resemble the characteristics of the theoretically conceivable ferrierite crystal structure, the zeolite obtained by the method of the present invention will be referred to as a synthetic ferrierite zeolite. Various methods for synthesizing ferrierite-type zeolite have been proposed so far as described below. However, these methods have advantages and disadvantages, and the reality is that no method that is industrially satisfactory has been developed yet. For example, (1) Mr. CLKibby proposed a method to obtain ferrierite by crystallizing a mixture of SiO ₂ /Al ₂ O ₃ = 8 to 12 prepared using colloidal silica sol under static conditions [Journal of Catalysis Vol 35, 256 ~272
Page (1974)]. This method leads to crystallization of approximately
Since it requires a high temperature of 300°C or higher, it not only necessitates the use of a high-temperature, high-pressure reaction vessel, but also makes it difficult to produce high-purity ferrierite. (2) Furthermore, JP-A-51-106700 discloses that ferrierite is produced by crystallizing silica-alumina cogel obtained by a special formulation such as co-precipitation of aluminum hydroxide on a precipitate of silica hydrogel. A method for obtaining the information is disclosed. Although this method can carry out crystallization at a relatively low temperature, not only is the preparation of silica alumina, which is a raw material, complicated, but it is also essential to add potassium ions to the reaction system. It is also an essential condition to add mineralizing agents such as sodium and/or potassium salts of organic or inorganic polybasic acids. As described above, this method requires complicated selection of raw materials, setting of reaction conditions, etc., and cannot be used as an industrial production method. (3) The method disclosed in JP-A-50-127898 uses N-methylpyridine hydroxide, and the method disclosed in JP-A-55-85415 uses piperidine and/or alkyl-substituted piperidine as an organic It is essential to use it as a mineralizing agent. These organic nitrogen-containing compounds are not only expensive, but also organic amines are incorporated into the zeolite produced. The zeolite must be calcined in the presence of oxygen at a high temperature of 500°C or higher to remove these organic substances before use. In order to use the material for specific purposes in this way, it is necessary to perform pretreatment. (4) The method disclosed in JP-A-53-144500 is a method for synthesizing a ferrierite-type zeolite called ZSM-35 using butanediamine or an organic nitrogen-containing compound derived therefrom. Similar to method (3) above, this method also has the disadvantage that the synthesized zeolite must be pretreated before use. Until now, zeolites such as ferrierite, molydenite, and ZSM-5, whose zeolite skeleton constituent units are composed of 5-membered oxygen rings, have been relatively
Although it is known that products with a high SiO ₂ /Al ₂ O ₃ molar ratio are produced, the synthesis method requires the addition of organic nitrogen-containing compounds or other organic compounds to the reaction system, as described above. It was common to use the following method. The present inventors investigated the conditions for producing crystalline aluminosilicate zeolite from the M2 _/o O- _Al2O3 - _SiO2 - _H2O system (n is the valence of the cation M), especially _the mixture. As a result of many years of intensive research into the mixing ratio of each component during preparation, crystallization temperature, crystallization mechanism of zeolite, etc., we developed a method that is completely different from the known methods described above and completed the present invention. did. The present invention produces synthetic ferrierite-type zeolite with a relatively high SiO ₂ /Al ₂ O ₃ molar ratio by crystallizing a mixture consisting of a silica source, an alumina source, and water without using any expensive organic mineralizing agents. The main idea is to easily manufacture. The method for preparing the mixture of the present invention is to dissolve the alumina source and the alkali source in water and then add the silica source while stirring.As long as an appropriate amount of water is present in the mixture, the viscosity will not increase. This makes stirring easy and is one of the effective preparation methods. By heating the mixture thus prepared while stirring, a highly pure synthetic ferrierite zeolite can be obtained. However, if this mixture is heated in a static state, it is difficult to obtain a highly pure mixture. An unexpected fact is that the mixture obtained by the preparation method in which the order of addition of the silica source and the alumina source is reversed, that is, the silica source and the alkali source are dissolved in water, and then the alumina source is added under stirring. The viscosity of the mixture becomes abnormally high, making it difficult to stir the mixture to even out the reaction temperature, and even if the mixture is forcibly stirred, it will not be effective. This difference is explained by the mechanism of crystallization from aluminosilicate gel to zeolite. Based on these findings, by repeatedly devising and optimally combining the composition of raw materials, their preparation conditions, stirring conditions, crystallization temperature, etc., we were able to synthesize products with high purity and a relatively high SiO ₂ /Al ₂ O ₃ molar ratio. This led to the completion of a method for producing ferrierite-type zeolite. The industrial significance of the present invention is extremely great considering that although known methods are possible in the laboratory, they have many difficulties in terms of economy, quality, operation, etc. in industrial applications. The present invention will be explained in more detail. The present invention does not use any organic mineralizer,
It consists of a silica source, an alumina source, an alkali source, and water, and has the following composition range expressed in molar ratio of oxides: SiO ₂ /Al ₂ O ₃ = 10 to 50 Na ₂ O/SiO ₂ = 0.01 to 0.11 H ₂ O/ _SiO2 = _8-100 Preferably _SiO2 / _Al2O3 = _{13-35 Na2O} /SiO2 = 0.025-0.10 _H2O / _SiO2 = 10-40 _Na2O / _Al2O3 = _0.8- 2. By crystallizing a mixture prepared to
To provide a method for easily producing a synthetic ferrierite type zeolite having a relatively high SiO ₂ /Al ₂ O ₃ molar ratio and having substantially the lattice spacing (d value) shown in Table 2 in the sodium form. It is something. The silica source used in the present invention may be any of amorphous solid silica, colloidal silica sol, sodium silicate, silica gel, and silica sand, but amorphous solid silica is preferably used. Alumina sources include sodium aluminate, aluminum hydroxide,
These include aluminum sulfate, aluminum nitrate, and aluminum oxide. Preferably, an aqueous sodium aluminate solution is used, the alkaline component of which becomes part of the alkali source. It is preferable to use sodium hydroxide as the alkali source. However, when using sodium aluminate, if the amount of alkali contained in it exceeds the amount of alkali necessary to prepare a mixture within the above composition range, mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, etc. Prepare the amount of alkali using still,
When calculating the amount of Na ₂ O, the neutralization equivalent of the added acid should be subtracted from the total amount of Na ₂ O. One of the preferred methods for preparing the mixture is, as described above, by dissolving the alumina source and the alkali source in water and then adding the silica source while stirring. The mixture is charged into an autoclave and crystallized. The effect of stirring during crystallization is as described above,
Although not essential in carrying out the present invention, stirring is preferred in order to obtain a highly pure product. The stirring intensity is determined by the circumferential speed (m/sec) defined as (π)(d)(v)/60 when the maximum diameter of the stirring blade during rotation is d (m) and the stirring speed is v (rpm). The speed is preferably 0.1 m/sec or more, more preferably 0.5 m/sec or more. The crystallization temperature is 140-300°C and the time is about 4 hours to 20 days. Almost no crystallization occurs at temperatures below 140°C, and synthesis at temperatures above 300°C not only requires high-temperature, high-pressure reactors on an industrial scale, but is also economically unsatisfactory. But it's not a good idea. A preferred embodiment, which is effective even when carrying out the present invention under conditions where it takes a long time to complete crystallization, is to mix synthetic ferrierite-type zeolite produced by the method of the present invention. By adding it as a seed crystal, the time required for crystallization can be significantly shortened. In this case, the addition ratio of the seed crystals is preferably in the range of 0.1 to 20 wt% based on the solid weight of the mixture. Below 0.1wt%, the effect of adding seed crystals is small, and above 20wt%, it becomes ineffective. After crystallization is completed, the formed crystals are separated from the mother liquor, washed with water, and dried to obtain crystal powder. The synthetic ferrierite type zeolite thus obtained is characterized as having substantially the lattice spacing (d value) shown in Table 2 in the sodium form. The d value is determined from a powder X-ray diffraction diagram, but in powder X-ray diffraction, the d value and relative intensity change depending on the type of exchangeable cations in the zeolite, processing conditions, measurement conditions, etc. Therefore, even forms other than the sodium form or those subjected to special treatment are essentially included in the present invention. The chemical composition of _the sodium _- type synthetic ferrierite-type zeolite obtained by the method of the present _{invention is} as follows _: Although it varies depending on the degree of water washing, it is usually around 1.Also, the value of y varies depending on the degree of drying and dehydration, but it is a number of 0 or more. This synthetic ferrierite-type zeolite is used for various purposes, such as as an adsorbent and a catalyst, in the form of a powder or a molded body, after being exchanged with appropriate cations as necessary. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 1.1 g of solid sodium hydroxide and aqueous sodium aluminate solution (Al ₂ O ₃ 20.1 wt%,
56.4 g of Na ₂ O (19.4 wt%) was dissolved, and then amorphous solid silica (Nipsil VN manufactured by Nippon Silica Kogyo Co., Ltd.) was dissolved.
−3, SiO ₂ 87.7wt%, Al ₂ O ₃ 0.5wt%,
A mixture having the following composition was prepared by adding 151 g of H ₂ O (11.8 wt%) with stirring. Na ₂ O / SiO ₂ = 0.086 SiO ₂ / Al ₂ O ₃ = 18.6 H ₂ O / SiO ₂ = 20.1 This mixture was placed in an autoclave and heated to 170°C.
and its autogenous pressure for 72 hours under stirring. The solid product was separated from the mother liquor and washed with water at 110℃.
It was dried. As a result of powder X-ray diffraction, the obtained crystals contained all the d values shown in Table 2, and were confirmed to be synthetic ferrierite type zeolite. The powder X-ray diffraction pattern is shown in FIG. In the figure, the vertical axis indicates the diffraction intensity, and the horizontal scale indicates 2θ. The composition of the crystal obtained as a result of chemical analysis was Na ₂ O.Al ₂ O 3.16.8SiO _{2.4.5H 2} O expressed in _molar ratio of oxides. After activating a part of this crystal in a Matsukubain Baker type adsorption device at 350°C under vacuum for 2 hours, the adsorption amount measured was as follows:
It was 6.8wt% at 25°C and 95mmHg, and in the case of cyclohexane, it was 1.0wt% at 25°C and 46mmHg. Example 2 Using the same raw materials as used in Example 1, a mixture with the following composition was prepared. Na ₂ O / SiO ₂ = 0.083 SiO ₂ / Al ₂ O ₃ = 18.6 H ₂ O / SiO ₂ = 20.1 This mixture was placed in an autoclave and heated to 180°C.
and heating under its autogenous pressure for 48 hours with stirring. The powder X-ray diffraction pattern of the obtained crystals contained all the d values shown in Table 2. As a result of chemical analysis, the composition of the obtained crystal was 1.1Na ₂ O.Al ₂ O ₃ .17.0SiO ₂ .5.0H ₂ O expressed in molar ratio of oxides. Example 3 Using the same raw materials as used in Example 1, a mixture with the following composition was prepared. Na ₂ O / SiO ₂ = 0.076 SiO ₂ / Al ₂ O ₃ = 20 H ₂ O / SiO ₂ = 20 This mixture was placed in an autoclave and heated to 190°C.
and heated under autogenous pressure for 80 hours with stirring. The powder X-ray diffraction pattern of the obtained crystals contained all the d values shown in Table 2. As a result of chemical analysis, the composition of the obtained crystal was Na ₂ O.Al ₂ O _3.18.2SiO 2.4.8H ₂ O expressed in molar ratio _of oxides. Example 4 A mixture having the following composition was prepared using the same raw materials as used in Example 1, except that sulfuric acid was used instead of solid sodium hydroxide. Na ₂ O/SiO ₂ = 0.053 SiO ₂ /Al ₂ O ₃ = 25 H ₂ O/SiO ₂ = 20 To 770 g of this mixture was added 11.5 g of the crystals produced in Example 1 as seed crystals. This was placed in an autoclave and heated at 200° C. and its autogenous pressure for 95 hours with stirring. The powder X-ray diffraction pattern of the obtained crystals contained all the d values shown in Table 2. As a result of chemical analysis, the composition of the obtained crystal, expressed in molar ratio of oxides _, was Na ₂ O.Al ₂ O 3.23.1SiO _{2.5.1H 2} O. Example 5 A mixture with the following composition was prepared using the same raw materials as used in Example 1, except that sulfuric acid was used instead of solid sodium hydroxide. Na ₂ O/SiO ₂ = 0.07 SiO ₂ /Al ₂ O ₃ = 14 H ₂ O/SiO ₂ = 20 11.5 g of the crystals produced in Example 1 were added as seed crystals to 766 g of this mixture. This was placed in an autoclave and heated at 190° C. and its autogenous pressure for 116 hours with stirring. The powder X-ray diffraction pattern of the obtained crystals contained all the d values shown in Table 2. As a result of chemical analysis, the composition of the obtained crystal, expressed in molar ratio of oxides, was Na ₂ O.Al ₂ O _{3.12.3SiO 2.4.0H 2} O. Comparative Example 1 Using the same raw materials as those used in Example 1, a mixture with the following composition was prepared. Na ₂ O / SiO ₂ = 0.12 SiO ₂ / Al ₂ O ₃ = 20 H ₂ O / SiO ₂ = 20 This mixture was placed in an autoclave and heated to 170°C.
and heated under autogenous pressure for 72 hours with stirring. The obtained crystals were confirmed by powder X-ray diffraction to be mordenite type zeolite. Comparative Example 2 A mixture having the following composition was prepared using the same raw materials as those used in Example 1, except that sulfuric acid was used instead of solid sodium hydroxide. Na ₂ O/SiO ₂ = 0.1 SiO ₂ /Al ₂ O ₃ = 8 H ₂ O/SiO ₂ = 20 This mixture was charged into an autoclave and heated under stirring at 170° C. and its autogenous pressure for 72 hours. The obtained solid was confirmed to be an amorphous solid by powder X-ray diffraction.

[Brief explanation of the drawing]

Figure 1 The product obtained in Example 1
Powder X-ray diffraction diagram measured using a double line.

Claims (1)

[Claims] 1. A mixture having the following composition (oxide molar ratio): SiO ₂ /Al ₂ O ₃ = 10-50 Na ₂ O/SiO ₂ = 0.01-0.11 H ₂ O/SiO ₂ = 8-100 1. A method for synthesizing zeolite, which comprises crystallizing the zeolite to obtain a crystalline aluminosilicate zeolite having substantially the lattice spacing (d value) shown in Table 2 in the sodium form. 2. The method according to claim 1, wherein the mixture is a mixture obtained by dissolving an alumina source and an alkali source in water and then adding a silica source under stirring. 3. The method according to claim 1 or 2, characterized in that the mixture is heated at a temperature of 140 to 300° C. while stirring.