JPH0343208B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to mordenite, which is a type of zeolite, and relates to a method for producing high-silica mordenite in the form of a fine powder with uniform crystal grain sizes. Crystalline aluminosilicate zeolite has a certain crystal structure and has many voids and tunnels within the structure, which has the function of adsorbing molecules of a certain size but excluding molecules larger than that, and is a molecular sieve. Also called. Pores due to voids and tunnels are determined by the form in which SiO ₄ and AlO ₄ bond by sharing oxygen in the crystal structure. The structure of mordenite, a type of crystalline aluminosilicate zeolite, was analyzed by WMMeier, but SiO ₄
It is characterized by a tunnel structure of two-dimensionally connected 12-membered rings in a structure in which AlO 4 and AlO ₄ are bonded by sharing oxygen, and its basic structure is Na ₈ (AlO ₂ ) ₈
(SiO ₂ ) ₄₀・24H ₂ O (WMMeier; Z.
Kristallogr., 115, 439-450 (1961)). Mordenite is used industrially as an adsorbent due to its adsorption properties, and is also widely used as an industrial catalyst in petrochemistry due to its solid acidity. Mordenite has a high SiO ₂ /Al ₂ O ₃ ratio among naturally occurring zeolites and has excellent heat resistance and acid resistance, but in recent years the demand for this has become even stronger, and compared to naturally occurring zeolites, mordenite has a high SiO ₂ /Al ₂ O ₃ ratio. There has been interest in the synthesis method of mordenite with a high ratio, and the following reports have been made. (1) Report of OJ Whittemore Jr. (American
Mineralogist, 57, 1146-1151 (1972)) (2) JP-A-56-160316 (Toa Fuel Industry Co., Ltd.) (3) JP-A-58-88118 (Toyo Soda Kogyo Co., Ltd.) The synthesis methods listed above all use SiO ₂ source, Al ₂ O ₃
High silica mordenite is synthesized by mixing sources, alkali, water, etc. and subjecting it to hydrothermal treatment, but all of these preparation methods seem to be difficult. That is, regarding (1), the viscosity of the aqueous mixture is high during the preparation of the raw materials, making it difficult to obtain a uniform aqueous mixture. Furthermore, there are technical difficulties in synthesizing uniform mordenite, such as poor heat conduction during hydrothermal treatment. Regarding (2), in Japanese Patent Application Laid-open No. 58-88119 filed by the same applicant,
The formation of a crystalline material that appears to be a mixture of ZSM-5 and mordenite under almost the same hydrothermal conditions has been reported, indicating that the synthesis of high-silica mordenite using this method is not very reproducible. Furthermore, even in Comparative Example 2, which was carried out to reproduce the method described as Example 1 of this reference, it was not possible to synthesize high-silica mordenite with high purity. Regarding (3), it is not preferable in that an expensive quaternary ammonium salt must be used as raw materials in addition to a SiO ₂ source, an Al ₂ O ₃ source, an alkali, and water. As a result of repeated research to overcome the above drawbacks, the inventors of the present invention have found that when mixing raw materials, the amount of water is increased.
By adjusting the SiO ₂ source, Al ₂ O ₃ source, Na source, water, etc. to specific composition ratios, the mixture becomes a homogeneous and transparent solution, making it easy to handle. Unlike the case of aqueous mixtures, there is no need for an aging operation to make the mixture homogeneous. What is more important is that the mordenite crystals obtained by hydrothermal treatment are uniform in size, and are finely dispersed in the reaction solution. The present inventors have discovered that mordenite can be obtained in a form that is easy to clean, and that the SiO ₂ /Al ₂ O ₃ ratio of the mordenite obtained is higher than that of natural mordenite, leading to the present invention. That is, the present invention uses SiO ₂ source, Al ₂ O ₃ source, Na ⁺ source and the following composition ratio in terms of molar ratio: SiO ₂ /Al ₂ O ₃ = 50 to 120 OH ^- /SiO ₂ = 0.5 to 0.8 Na ⁺ / A mixture of SiO ₂ = 0.5 to 1.8 H ₂ O/SiO ₂ = 50 to 150 was heated at 160 to 200°C for 10 to 10 minutes.
This invention relates to a method for producing high-silica mordenite fine powder with uniform crystal size, which is characterized by hydrothermal treatment under autogenous pressure for 50 hours. Next, the method for producing high silica mordenite of the present invention will be specifically described. In this method, SiO ₂ source,
Mix _{Al2O3 source} , Na ⁺ source and water in a predetermined ratio,
By treating this mixture under hydrothermal conditions that yield zeolite, washing the resulting solid product with water, and drying it, it is possible to produce high-silica mordenite in the form of a fine powder with uniform crystal grain size. I can do it. Water glass, silica sol, silica gel, and silica can be used as the SiO ₂ source, and water glass and silica sol are preferably used. As the Al ₂ O ₃ source, aluminum sulfate, aluminum nitrate, aluminum chloride, sodium aluminate, alumina sol, alumina, metallic aluminum, etc. can be used, but aluminum sulfate and sodium aluminate are preferable. As the sodium source, in addition to sodium hydroxide, it is also possible to use SiO ₂ sources and Al ₂ O ₃ sources, such as sodium oxide and sodium aluminate contained in water glass. Furthermore, in order to adjust the proportion of OH ^- , that is, hydroxyl groups in the mixture, a mineral acid such as sulfuric acid or hydrochloric acid or an inorganic base such as sodium hydroxide may be added as appropriate. When mixing the above-mentioned SiO ₂ source, Al ₂ O ₃ source, etc. in a predetermined ratio, the mixing order and mixing method are not particularly limited. The mixture thus obtained becomes a homogeneous and transparent solution, which is convenient to handle, and has the advantage of omitting the ripening operation to make it uniform, which is required when the mixture is viscous. This mixture is then hydrothermally treated under conditions such that zeolite is produced. i.e. 10 at 160-200℃
Hydrothermally treat in a closed container for ~50 hours under autogenous pressure with stirring. After hydrothermal treatment, the solid components of the reaction product are separated by filtration or centrifugation, excess ionic substances are removed by washing with water, and high silica mordenite with uniform crystal size is obtained by drying at 100°C. . The mordenite of the present invention has a higher SiO ₂ /Al ₂ O ₃ ratio than natural mordenite, and because it is obtained as a fine powder with uniform crystal size, it is easy to perform cleaning operations after the reaction is completed. have Table 1 shows the X-ray diffraction pattern of one example of high silica mordenite obtained according to the present invention. Note that this is similar to Example 1 (SiO ₂ /
Al ₂ O ₃ = 98, H ₂ O/SiO ₂ = 130).
The diffraction data was obtained by standard X-ray techniques with K-alpha irradiation of the copper, and the peak height I is recorded on a recorder as a function of twice the Bragg angle θ, 2θ. I/I. is the relative intensity, and is a relative value when 2θ = 25.74°, which indicates the strongest peak, is set as 100.

[Table] The high silica mordenite obtained by the present invention can be used as an adsorbent or a catalyst in the same way as ordinary mordenite. One of the uses as a catalyst is as a catalyst for the decomposition reaction of methanol and/or dimethyl ether. When used as a catalyst, it is preferably a hydrogen type in which Na ions as cations after synthesis are completely or partially exchanged with protons by an ion exchange method. This exchange can be carried out using known ion exchange techniques by treating with an aqueous ammonium solution, such as an aqueous ammonium chloride solution, to convert the Na ions into ammonium ions, which can then be post-calcined to drive off the ammonia and convert it into the proton form.
It is also possible to convert it into protons by direct treatment with an aqueous chloride solution. After being treated with an ammonia aqueous solution or a hydrogen chloride aqueous solution, it is thoroughly washed with water, dried, and then calcined to serve as a catalyst for methanol and/or dimethyl ether conversion reaction. The reaction can be carried out under a wide range of conditions using a method that allows sufficient contact between the raw materials and the catalyst. Next, examples of the present invention will be described in detail, but the present invention is not limited thereto unless it exceeds the gist thereof. Example 1 4.23 g of aluminum sulfate 16-18 hydrate and 27.3 g of sodium hydroxide (purity 95%) were dissolved in 600 g of water to make solution A, and No. 4 water glass (SiO ₂ 24%, Na ₂ O 6.5
%) was dissolved in 600 g of water and this was used as Solution B. Solution B was added to solution A while stirring, and then 212 ml of a 2.5N sulfuric acid aqueous solution was added thereto to obtain a mixture.
The molar ratio of this mixture is SiO ₂ /Al ₂ O ₃ = 98, OH ^- /
SiO ₂ = 0.65, Na ⁺ /SiO ₂ = 1.54, 2SO ^2- ₄ /SiO ₂ =
0.89, H ₂ O/SiO ₂ =130. The mixture was charged into an autoclave with an internal volume of 2, and hydrothermal treatment was performed at 180°C under autogenous pressure for 16 hours with stirring (500 rpm). The reaction mixture is separated into solid and liquid components using a centrifuge.
The solid components were thoroughly washed and dried at 100°C. When the obtained white powder product was analyzed by X-ray diffraction, it showed the pattern shown in Table 1 and FIG. 1, and it was confirmed that there was no other zeolite or gel. When the product was examined using a scanning electron microscope, it was observed that the crystals were cigar-shaped with a major axis of 3 μm and a minor axis of 1 μm, and that the individual crystal sizes were uniform. After this product was calcined in air at 530°C for 8 hours, water was saturated and adsorbed. As a result of chemical analysis, the composition was 1.10Na ₂ O, 16.0SiO ₂ , and 9.4H ₂ O. The moisture content was determined from the weight loss during firing at 500°C for 1 hour. Comparative Example 1 1.64 g of aluminum sulfate 16-18 hydrate and 11.1 g of sodium hydroxide were dissolved in 51 g of water to make solution A.
62 g of No. 1 water glass was dissolved in 30 g of water, and this was used as liquid B. Solution B was added to solution A while stirring, and then 82 ml of 2.5N sulfuric acid aqueous solution was added thereto to obtain a mixture.
The molar ratio of this mixture is SiO ₂ /Al ₂ O ₃ = 98, OH ^- /
SiO ₂ = 0.65, Na ⁺ /SiO ₂ = 1.54, 2SO ^2- ₄ /SiO ₂ =
0.89, H ₂ O/SiO ₂ =44. Pour the mixture into an autoclave with an internal volume of 300 ml and place it under autoclave pressure.
Hydrothermal treatment was carried out at 180° C. with stirring (500 rpm) for 16 hours. A large solid was obtained in the reaction solution. This was crushed, thoroughly washed, and dried at 100°C. When the obtained product was analyzed by X-ray diffraction, it showed a pattern with the same characteristics as in Table 1, and was confirmed to be mordenite. Furthermore, observation using a scanning electron microscope revealed that irregularly sized crystals of about 0.5 to 5 μm were accumulated to form large crystals. As a result of chemical analysis of the product in the same manner as in Example 1, the composition was 1.2Na ₂ O・Al ₂ O ₃・
It was 11.2SiO ₂ .7.0H ₂ O. Examples 2 to 4 The same operations as in Example 1 were performed except that the raw material composition was changed as shown in Table 2. Examples 2 to 4,
In each case, the crystal size and product composition determined by chemical analysis are listed in Table 2. Comparative Example 2 Example 1 described in JP-A-56-160316
I conducted a follow-up test. Aluminum sulfate 16-18 hydrate 9.1% in 150g of water
Dissolve g, 1.1 g of concentrated sulfuric acid, and 14 g of sodium chloride,
To this, No. 3 water glass (SiO ₂ 29%, Na ₂ O 9.5%) 49
g was added to obtain an aqueous mixture. The molar composition of this mixture is SiO ₂ /Al ₂ O ₃ = 17, OH ^- /SiO ₂ = 019,
Na ⁺ /SiO ₂ =1.64, (2SO ^2- ₄ +Cl ^- )/SiO ₂ = 38. After stirring and aging this mixture at room temperature for 1 hour,
The mixture was placed in an autoclave and subjected to hydrothermal treatment at 180°C for 20 hours under self-pressure. The obtained solid component was thoroughly washed with water and then dried at 100°C. When this was analyzed by X-ray diffraction, it was found to be a mixture of mordenite and ZSM-5 type crystals.

[Table] Example 5 1 g of calcined mordenite obtained in Example 1 was mixed with 50 ml of a 5% ammonium chloride aqueous solution, and the operation of stirring at room temperature for 1 hour was repeated three times to remove sodium ions. was ammonium ion exchanged. After that, wash thoroughly and
It was dried at ℃ and then calcined in air at 500 ℃ for 16 hours to convert it into a hydrogen form. Pressure 400
Compressed into tablets at Kg/cm ² and then crushed into 10 x 20
2 ml of the mesh was filled into a reaction tube with an inner diameter of 10 mm. Liquid methanol was sent to the vaporizer at a rate of 4 ml/hr, where it was mixed with argon gas sent at 45 ml/min, led to the reaction tube, heated to 300°C for 4 hours, then heated to 320°C for 2 hours. The reaction was carried out at 340°C for 2 hours. Analysis of the product was performed using a gas chromatograph. The results are shown in Table 3.

【table】

[Table] Yield

[Brief explanation of drawings]

FIG. 1 is an X-ray diffraction chart of mordenite synthesized in Example 1.

Claims (1)

[Claims] 1. The following compositional ratio of SiO ₂ source, Al ₂ O ₃ source, Na ⁺ source, and water: SiO ₂ /Al ₂ O ₃ = 50 to 120 OH ^- /SiO ₂ = 0.5 to 0.8 Na ⁺ /SiO ₂ = 0.5 to 1.8 H ₂ O / SiO ₂ = 50 to 150 (Here, OH ^- is a free hydroxyl group in the mixture.) The mixture was heated to 160 to 200°C. in 10
A method for producing high-silica mordenite fine powder with uniform crystal size, characterized by hydrothermal treatment under autogenous pressure for ~50 hours.