JPH06100314A - Production of a type zeolite - Google Patents

Abstract

(57) [Summary] [Structure] In the production of A-type zeolite mainly composed of coal ash, the coal ash is heated in an alkaline solution at a temperature of 60 to 90.
After stirring at 30 ° C. for 5 minutes to 5 hours, an aluminum source, a sodium source and water are added, and the mixture is heated and stirred for reaction. [Effect] It is possible to recycle the coal ash, which was conventionally a waste, and to produce the A-type zeolite in a high yield by a simple operation and procedure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention recycles coal ash, which was conventionally regarded as industrial waste, and uses it as a main raw material to produce an A-type zeolite useful as an adsorbent for gas molecules and low-molecular organic compounds. The present invention relates to a method that can be efficiently manufactured.

[0002]

2. Description of the Related Art Type A zeolite is produced by hydrothermally crystallizing aluminosilicate gel. That is, the aluminosilicate gel can be obtained, for example, by adding a silica gel aqueous solution to a highly basic sodium aluminate aqueous solution, or by adding aluminum hydroxide powder to a highly basic sodium silicate aqueous solution, and mixing the resulting aluminosilicate gel. When is heated, the crystal nucleation and crystal growth of the A-type zeolite gradually progress in the gel, and all or most of it is changed to crystalline A-type zeolite.

By the way, since A-type zeolite is a metastable phase crystal in terms of thermodynamics, the temperature at the time of hydrothermal crystallization, the composition of raw materials, etc. are limited. That is, if the heating temperature is too high, stable phase crystals of P-type zeolite are likely to be produced, and if sodium is excessive, stable phase crystals of hydroxysodalite are also likely to be produced. However, since P-type zeolite and hydroxysodalite have a smaller specific surface area than A-type zeolite and have low catalytic ability, adsorption ability, and ion exchange ability, the performance is greatly inferior.
It is only used as a soil conditioner and is not suitable as a high-performance adsorbent. Therefore, in the production of A-type zeolite, research has been conducted with a focus on how to suppress the change to a stable phase crystal and stop it in a metastable phase crystal state (Japanese Patent Publication No. 56-37166). No.

However, even in the method using an aluminosilicate gel as a raw material as described above, when excessive thermal energy is applied in the crystallization step (when the temperature is too high or the reaction time is too long), the movement of each ion is active. Then, rearrangement to the stable phase occurs, and hydroxysodalite is generated. Further, if the gel network structure is too strong and the movement of each ion in the gel is excessively limited, the crystallization reaction itself becomes difficult to occur and the production rate of metastable phase crystals cannot be increased.

On the other hand, in order to recycle the coal ash which has been conventionally regarded as industrial waste, an attempt has been made to produce zeolite by using the coal ash as a main raw material (Japanese Patent Laid-Open No. 56-14).
9313, JP-A-59-35019, JP-A-61-
178416, JP-A 64-24014, etc.).
In these, a silica source, an aluminum source, and a sodium source are added to coal ash, and the mixture is heated and stirred to synthesize zeolite.

However, coal ash has poor reactivity as compared with conventional chemical raw materials, and due to various problems such as complicated behavior during reaction due to non-uniform system, conditions for forming A-type zeolite are maintained. Difficult to do. That is, in order to accelerate the elution of the coal ash component and increase the reaction rate, high temperature and high alkali concentration are desirable, but in this case, by-products such as P-type zeolite and hydroxysodalite are easily generated, and A-type zeolite Yield decreases. In addition, the elution amount changes with time, and the elution of ash components is inhibited when the surface of the coal ash is covered with the reaction product, so that the reaction system becomes longer than the A-type zeolite when the reaction time becomes long. It becomes more difficult to adjust to the production condition range.

For these reasons, in the conventional coal ash zeolite formation method, the yield of A-type zeolite is low, or in order to increase the yield, the raw material must be limited to highly soluble coal ash. There's a problem.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art as described above, and its purpose is to utilize coal ash, which was conventionally regarded as industrial waste, as a recycle resource. Then, it is intended to provide a method for efficiently producing an A-type zeolite, which is excellent in adsorption performance and the like as compared with P-type zeolite or hydroxysodalite, by using it as a main raw material.

[0009]

[Means for Solving the Problems] The structure of the manufacturing method according to the present invention, which has been able to solve the above-mentioned problems, is the manufacturing of A-type zeolite using coal ash as a main raw material. The gist is to add the aluminum source, the sodium source, and water, and then heat and stir to react after stirring at ˜90 ° C. for 30 minutes to 5 hours. That is, the coal ash is heated and stirred in an alkaline solution at a temperature and concentration range where a reaction does not occur, and silica, alumina, and other coal ash components are eluted, and then an aluminum source, a sodium source, etc. are added to form a composition. It is prepared and reacted to efficiently produce A-type zeolite. As the alkaline solution, it is preferable to use a 1 to 5 normal aluminum hydroxide solution.

Although sodium hydroxide is used as the alkali source when the present invention is carried out, potassium hydroxide, sodium carbonate or the like can be used in addition to the sodium hydroxide. As the aluminum source, sodium aluminate, aluminum hydroxide, aluminum chloride or the like is used. As the sodium source, sodium hydroxide, sodium aluminate, sodium carbonate, etc. are used.

[0011]

As a result of various investigations, the present inventors have found that even if coal ash is heated in an alkaline solution, the method disclosed in JP-A-61-1784 is used.
It was found that there is a region (temperature, alkali concentration, etc.) in which a reaction such as 16 does not occur and a product such as P-type zeolite does not occur, but only elution of components such as silica and alumina occurs. By carrying out the hydrothermal synthesis reaction at low temperature and for a short time after carrying out this alkali treatment, by-products can be suppressed, and the synthesis rate of the A-type zeolite can be significantly improved. Further, since the coal ash becomes porous due to the elution, it was found that the alkali treatment also contributes to the increase in surface area, and the present invention has been completed.

In alkali treatment, temperature and alkali concentration are important factors. The higher the temperature and the alkali concentration, the more the elution of coal ash is promoted, but if a certain limit is exceeded, a reaction will occur. Further, these must be within a range that can be adjusted to an appropriate composition when performing the hydrothermal synthesis reaction. That is, when sodium hydroxide is used as the alkali source, a high coal ash elution rate can be obtained by selecting an appropriate combination within a temperature range of 60 to 90 ° C. and a concentration range of 1 to 5 N. Elution occurs even when the treatment temperature is 60 ° C. or lower or the concentration is 1 N or lower, but the treatment effect is small because the elution amount is low. When the concentration is 4 to 5 N, only elution occurs up to 80 ° C, but hydroxysodalite occurs at 85 ° C or higher. Above 6 normals, these products become noticeable,
Si and Al that contribute to hydrothermal synthesis decrease, and the synthesis rate of A-type zeolite decreases. Further, when the sodium concentration becomes high, it becomes difficult to dilute it into an appropriate concentration range when carrying out the hydrothermal synthesis reaction, which is not preferable. Processing time is 3
It is 0 minutes or more, preferably 1 hour or more. Even if the mixture is stirred for 3 hours or longer, the increase in the elution rate is small. As the alkali source, potassium hydroxide, sodium carbonate or the like may be used.

After this alkali treatment, water synthesis is carried out by further adding an aluminum source and, if necessary, a sodium source and water. The molar ratio at this time is SiO ₂
/ Al ₂ O ₃ = 0.3 to 3.0, H ₂ O / Na ₂ O = 1
It is preferable to adjust it in the range of 0 to 150. At this time, if the amount of aluminum is too small, P-type zeolite is likely to be produced, and as the concentration of sodium is high, hydroxysodalite is likely to be produced. As the aluminum source, sodium aluminate is generally used, but when the amount of sodium is too large, aluminum hydroxide or aluminum chloride may be used.

The synthesis temperature is 60 to 90 ° C. and the synthesis time is 10
It is within an hour, preferably within a range of 1 to 5 hours. The higher the temperature, the shorter the reaction time, while the lower the temperature, the less likely by-products are to form. If the synthesis time is short, a sufficient reaction does not occur, but if it is too long, the production of P-type zeolite and hydroxysodalite becomes remarkable, and the yield of A-type zeolite decreases.

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and any modification or implementation is within the scope of the present invention without departing from the gist thereof. It is included in the technical scope of.

[0016]

EXAMPLES Evaluation method For the samples obtained in the following examples and comparative examples, powder X-ray diffraction (hereinafter referred to as XRD) method was used for crystal identification, specific surface area measurement, and thermal desorption (hereinafter referred to as TPD) method. The amount of adsorbed ammonia was measured and evaluated by observing crystals with a scanning electron microscope (hereinafter referred to as SEM). In addition, raw material coal ash, an example of synthetic zeolite obtained by the production method of the present invention, and XRD measurement results of A-type zeolite as a chemical raw material are shown in FIG.
2 to 4 are SEM photographs substituting for drawings showing the crystal structure thereof.
Shown in. It was confirmed that the higher the peak intensity of the A-type zeolite in XRD and the higher the number of A-type zeolite crystals observed in the SEM, the higher the specific surface area. Further, a positive proportional relationship was obtained between the specific surface area and the desorption peak area of TPD, that is, the ammonia adsorption amount, as shown in FIG. Thus, it was confirmed that the larger the amount of type A zeolite produced, the larger the surface area and the better the adsorption capacity.

Example 1 Coal ash heat-treated in air at 850 ° C. was stirred in an aqueous 1.8, 3.6N sodium hydroxide solution at a temperature of 60 to 90 ° C. for 0.5 to 5 hours and then washed. , Dried. FIG. 6 shows changes over time in the amounts of Si and Al eluted at this time.
Shown in. The amounts of Si and Al are based on the total amounts of Si and Al in the raw material coal ash containing hardly soluble components such as mullite. The change in surface area is shown in FIG.

Example 2 Coal ash heat-treated in air at 850 ° C. was heated and stirred in a 1 to 5 N aqueous sodium hydroxide solution at a temperature of 60 to 90 ° C. for 3 hours, and then washed and dried. FIG. 8 shows changes in the amounts of Si and Al eluted at this time.

Example 3 Coal ash heat-treated in air at 850 ° C. was stirred in a 3N aqueous sodium hydroxide solution at a temperature of 85 ° C. for 0.5 to 3 hours. Sodium aluminate, sodium hydroxide and water were added to this slurry to obtain SiO ₂ / Al ₂ O ₃ = 1.
5, H ₂ O / Na ₂ O = 57 was adjusted. This slurry was heated and stirred at 85 ° C. for 3 hours to cause a reaction, and then washed,
Drying was performed to obtain zeolite. Specific surface area at this time,
Table 1 shows the intensity ratio of the XRD peaks of A-type zeolite and SiO ₂ .

[0020]

[Table 1]

Comparative Example 1 Coal ash heat-treated in air at 850 ° C. was heated and stirred at 4 ° C. for 3 hours at 85 ° C. in a 4-8 normal sodium hydroxide aqueous solution. The elution rates of Si and Al at this time are shown in Table 2.
It was confirmed that the elution amount of i or Al was significantly reduced. Further, FIG. 9 shows the XRD measurement results when the concentration was 5 N, and the peak of hydroxysodalite clearly appeared.

[0022]

[Table 2]

Comparative Example 2 Coal ash, sodium aluminate, sodium hydroxide, water
SiO₂ / Al₂ O ₃ = 1.5, H₂ O / Na₂ O =
Mixed at a ratio of 57. Then react at 85 ° C for 4-6 hours
After that, cooling, washing and drying were performed. At this time
Specific surface area, type A zeolite and SiO₂ And XRD peak
The strength ratio is shown in Table 3.

[0024]

[Table 3]

[0025]

The present invention is configured as described above,
Alkali treatment is performed before hydrothermal synthesis to sufficiently elute Si and Al components, and then the components are adjusted and reacted to react with coal ash and by-products (such as P-type zeolite and hydroxysodalite). ) Can be controlled,
It has become possible to produce the A-type zeolite in good yield.

[Brief description of drawings]

FIG. 1 is a diagram showing an X-ray diffraction result of coal ash, synthetic zeolite obtained by the production method of the present invention, and A-type zeolite as a reagent raw material.

FIG. 2 is a drawing-substitute scanning electron micrograph showing the crystal structure of coal ash.

FIG. 3 is a drawing-substitute scanning electron micrograph showing the crystal structure of synthetic zeolite obtained by the production method of the present invention.

FIG. 4 is a drawing-substitute scanning electron micrograph showing the crystal structure of A-type zeolite as a chemical raw material.

FIG. 5 is a diagram showing the relationship between the specific surface area of zeolite and the ammonia adsorption amount measurement result by the temperature programmed desorption method.

FIG. 6 is a diagram showing changes over time in the elution rates of Si and Al under each alkaline treatment condition of Example 1.

FIG. 7 is a view showing a change with time of a specific surface area according to Example 1.

FIG. 8 is a diagram showing a relationship between each alkaline treatment condition and an elution rate according to Example 2.

9 is a diagram showing an X-ray diffraction result of coal ash according to Comparative Example 1. FIG.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaru Horii 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Prefecture Kobe Steel Works, Ltd. Kobe Research Institute

Claims (2)

[Claims] 1. In the production of A-type zeolite using coal ash as a main raw material, the coal ash is heated in an alkaline solution at a temperature of 60 to 60.
After stirring at 90 ° C for 30 minutes to 5 hours, an aluminum source, a sodium source, and water are added, and the mixture is heated and stirred for reaction to produce an A-type zeolite. 2. The method for producing an A-type zeolite according to claim 1, wherein a 1-5 normal sodium hydroxide aqueous solution is used as the alkaline solution.