JPH07196315A - Zeolite synthesis method - Google Patents

Abstract

PURPOSE:To improve reactivity in hydrothermal reaction during synthesis of a zeolite even in the existence of impurities in a raw material and to obtain efficiently synthesize the zeolite having a high specific surface area. CONSTITUTION:This method for synthesizing zeolite comprises carrying out the processes shown below using raw material powder such as industrial waste. First, the raw material powder is mixed with Na2CO3 and baked at 750-900 deg.C. Next, the baked material is treated with an acid (except sulfuric acid) at pH<=4 and washed with water. Finally, the washed material is subjected to hydrothermal reaction of zeolite in an alkali solution at 80-85 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently producing an adsorbent for gas molecules or low molecular weight organic compounds and a zeolite having a large specific surface area, which is useful as an ion exchange material, from industrial waste.

[0002]

_2. Description of the Related Art M _{2 / n} O ・ Al ₂ O ₃・ xSiO ₂・ y
Zeolite having a chemical composition represented by H ₂ O (M is a metal, x is 2 or more, y is a number of 0 or more) and has pores suitable for adsorption / separation in crystals is produced as a natural mineral. Besides, it is artificially synthesized. Since these pore-containing zeolites must be crystallized as a metastable phase in a non-equilibrium state, complicated factors are entangled in the reaction, and the crystallization mechanism is still completely understood at this time. Absent.

As a concrete synthesis method, there is a method using sodium silicate and sodium aluminate as chemical reagents, but the cost is inevitable. So, natural clay
A resource-saving method is to obtain zeolite by adding silica source, aluminum source and sodium source to coal ash, which is an industrial waste, in addition to using minerals as raw materials, and performing hydrothermal reaction at 85 ° C for 3 hours. -Many studies have been conducted from the viewpoint of recycling (JP-A-59-35019, JP-A-64-24014, JP-A-2-
No. 229709).

However, coal ash contains a large amount of impurities and has a low synthesis rate, and there is a fatal problem in industrial production that the synthesis rate varies depending on the place of production of the coal ash. Further, since many of the obtained zeolites have a small specific surface area and a low value, a method for efficiently synthesizing a zeolite having a large pore size from industrial waste is required.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its purpose is to achieve a hydrothermal reaction during zeolite synthesis even if impurities are present in the raw material. And a method for efficiently synthesizing a zeolite having a large specific surface area by improving the reactivity of the zeolite.

[0006]

Means for Solving the Problems The method for synthesizing zeolite of the present invention which has been able to solve the above-mentioned problems is as follows: First step: 750 to 9 by adding Na ₂ CO ₃ to the raw material powder.
Bake at 00 ° C. Second step: acid (excluding sulfuric acid) treatment and water washing are performed under pH 4 or less. Third step: hydrothermal reaction of zeolite in an alkaline solution at 80 to 85 ° C. It has the gist of including as an essential step. After the second step, before the third step, a pre-stage heat treatment is carried out in an alkaline solution under a temperature / time condition such that zeolite synthesis is not performed, before the third step or before the pre-stage heat treatment. Prior to the addition of a sodium source and / or an aluminum source is a preferred embodiment of the method of the invention.
The method of the present invention is a zeolite synthesis method suitable for a raw material powder selected from the group consisting of coal ash, sewage sludge incinerator, papermaking sludge incinerator, FRP combustion residue, and ironmaking slag.
The method of the present invention also includes a method of synthesizing a calcium-type zeolite by ion exchange using calcium ions when the acidic effluent discharged in the second step contains calcium ions.

[0007]

The present inventors have been conducting researches for synthesizing useful zeolite by utilizing industrial waste, and have made some results. For example, Japanese Patent Application No. 4-247756
In the publication, in synthesizing A-type zeolite using coal ash as a main raw material, heating and stirring are performed before the hydrothermal reaction, whereby the synthesis of zeolite having a specific surface area of about 180 m ² / g is successful. In addition, in Japanese Patent Application No. 5-254513,
It was disclosed that the A-type zeolite synthesis rate could be increased by removing the calcium compound. In this case, the maximum specific surface area is 3
Although it was improved to about 80 m ² / g, even if the same treatment method was adopted, the specific surface area was 150 to 380 depending on the type of coal ash.
It was found that there was a variation with m ² / g. The present invention has been made as a result of an examination on how to efficiently synthesize a zeolite having a higher specific surface area based on these findings. Hereinafter, the present invention will be described in detail.

The raw materials used in the present invention are:
In addition to clay minerals and natural minerals, volcanic ash such as Shirasu, volcanic glass, sediments such as diatomaceous earth, natural products such as sedimentary rocks such as tuff,
Alternatively, artificial materials such as iron-making slag can be used, but since the method of the present invention can efficiently synthesize high-quality zeolite even with a raw material containing a large amount of impurities, particularly coal ash, sewage sludge, which is an industrial waste. Incineration, paper sludge incineration,
FRP combustion residue and ironmaking slag generated in the ironmaking / steelmaking process can be used as raw materials. The raw material is preferably a powder in order to enhance the reactivity, and when it is not available as a powder, the raw material may be pulverized in advance. A preferable raw material powder particle diameter is 50 μm at maximum and about 10 μm on average.

The essential first step of the method of the present invention is a step of mixing the raw material powder and Na ₂ CO ₃ and firing at 750 to 900 ° C. In this step, SiO ₂ and Al ₂ O in the raw material are
₃ has an effect of making the Si source and the alumina source easily contribute to the zeolite synthesis reaction in the third step, and an effect of making the impurity calcium easy to be amorphized. A calcium compound is a component that is inevitably included in coal ash because an excessive amount of calcium is added for desulfurization of flue gas, and is a component that is almost always included in other industrial waste raw materials. Is.
This calcium becomes an amorphous calcium silicate (CaSiO ₃ ) in an alkaline solution to deprive the Si component thereof, and is an impurity that inhibits the zeolite synthesis reaction.
This calcium compound also includes a compound that is stable against acid, which is disclosed in Japanese Patent Application No. 5-254513.
This is considered to be one of the reasons why the zeolite synthesis rate varies depending on the coal ash production area. That is, the presence of a calcium compound that cannot be completely removed by simple acid treatment or other treatment methods adversely affected the subsequent zeolite synthesis step.

This calcium compound was stable even at high temperatures, and it was difficult to dissolve in an acid only through a simple firing step. As a result of various studies, it was found that the calcium component can be made amorphous by elution into the acid solution by adding Na ₂ CO ₃ to the raw material and firing it. Therefore, the first step is essential in the method of the present invention. The process. Since the calcium component can be removed as much as possible by the first step and the second step, a good zeolite synthesis result was obtained even if the raw material contained a large amount of calcium component.

Preferred Na ₂ CO in the first step
The addition amount of ₃ is 0.5 to 2.0 by weight ratio to the raw material 1. Na ₂ CO ₃ is less than 0.5 (vs. raw material 1),
Alternatively, if the firing temperature is lower than 750 ° C., the calcium compound is not completely amorphized. Na ₂ CO
_{When 3} is more than 2.0 or the firing temperature is more than 900 ° C, silica and alumina in the raw material and Na ₂ CO ₃
React with each other, and many crystal phases that are difficult to dissolve in acid or alkali are generated, so that the zeolite synthesis rate decreases. The firing is preferably performed in the air atmosphere for about 2 hours.

After the first step, the second step including the acid (excluding sulfuric acid) treatment and the washing with water is performed under the condition of pH 4 or less. The second step is performed to dissolve the above-mentioned calcium compound in the acidic solution and remove it from the raw material. The acid used is an inorganic or organic acid other than sulfuric acid. Sulfuric acid reacts with calcium and is sparingly water-soluble
It becomes SO ₄ and remains in the raw material, which hinders the subsequent zeolite synthesis reaction in the alkaline solution, which is not preferable. Acid treatment is performed by adding an aqueous solution of acid to the raw material slurry and adjusting the pH to 4
It may be carried out by a method such as stirring until it becomes below, and the concentration of the acid aqueous solution is 0.0005 to 5 depending on the concentration of the raw material slurry.
It may be changed appropriately within the 0.2 rule. After the acid treatment, filtration and washing with water are performed according to a conventional method. The steps of acid treatment and water washing may be repeated appropriately. In this acid treatment step, hydration of the reactive component in the raw material which has been amorphized by firing proceeds to promote gelation, which is more advantageous for zeolite synthesis in the next step.

In the subsequent third step, a hydrothermal synthesis reaction of zeolite is carried out.
Zeolite is synthesized by reacting at 85 ° C. for 1 to 4 hours. As the alkaline solution, a 1-5N NaOH solution, more preferably a 3N NaOH solution is used. At this time, when the aluminum source and the sodium source are small in the raw material, sodium aluminate (also useful as a sodium source), aluminum hydroxide is added before the third step or before the “preliminary heat treatment step” described later. An aluminum source such as aluminum chloride or a sodium source such as sodium carbonate may be added.

In the method of the present invention, after the second step, a pre-stage heat treatment of heating and stirring under a temperature condition where zeolite is not synthesized may be carried out. The first-stage heat treatment is performed not for the synthesis reaction of zeolite, but for the purpose of sufficiently eluting the Si source and the aluminum source in the raw material into the alkaline solution or promoting the gelation of these reactive components in the raw material. Therefore, it is necessary to perform the temperature and time conditions at which zeolite does not precipitate. FIG. 1 shows the relationship between the heating temperature in a 3N alkaline solution and the time until zeolite is deposited. The pre-stage heat treatment is preferably performed under the conditions in the zeolite non-precipitation region in the figure, and most preferably under the conditions on the dotted line. The dotted line in FIG. 1 can be represented by y = ax ² −bx + c (y is time, x is absolute temperature), but the coefficients a, b, and c vary depending on the concentration of the alkaline solution, and a
= 140 to 150 × 10 ⁻⁴ , b = 100 to 110 × 10
^-3 , c = 180 to 200.

As a concrete practical first stage heat treatment condition, the alkali solution slurry prepared at room temperature is heated to 60 ° C. and mixed for about 10 hours, or at 80 ° C. for 2 to 2 hours.
It suffices to adjust the time and temperature to meet all the formulas such as mixing for about 3 hours. As an alkaline solution, the third
It is recommended to use a 1-5N NaOH solution, more preferably a 3N NaOH solution so that it can be used as it is in the process. If the former heating step is performed, the production of hydroxysodalite can be suppressed, and the synthesis rate of zeolite with large pores can be increased.

In the method of the present invention described above, sodium-type zeolite is mainly synthesized. In addition to A-type zeolite,
It is possible to synthesize X, Y-type zeolite and other zeolites having large pores, and the produced zeolite has a large specific surface area of 600 m ² / g or more. In the method of the present invention, when calcium type zeolite is obtained from sodium type zeolite by a known ion exchange method, effective use of calcium ions can be achieved by using the waste liquid discharged in the acid treatment in the second step.

[0017]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited by the following examples. Experimental Example 1 (Study of effects of calcination and acid treatment in a system without addition of Na ₂ CO ₃ ) In order to find an optimum zeolite synthesis process, 6 types of coal ash (Sample Nos. 1 to 6: average particle size 10 μm)
In contrast to m), as a first-stage heat treatment, 80 ° C in 3N NaOH aqueous solution
In for 2 hours heating and stirring, then fired 85 ° C. for 3 hours zeolite synthesis reaction for 2 hours at 800 ° C. without the addition of (front heating + Step 3) Na ₂ CO _3, water alone without the addition of acid After washing with, (1st process variation type + 2nd process variation type + pre-stage heating + 3rd process) Na ₂ CO ₃ is not added and baking is performed at 800 ° C. for 2 hours,
After performing acid treatment with 0.1N hydrochloric acid at pH 4 and washing with water to remove Ca, the following three treatments are performed (variation of the first step + second step + pre-heating + third step). The formation state of A-type zeolite and hydroxysodalite (having no pores) was grasped by comparing with the peak intensity of SiO ₂ by the powder X-ray diffraction method (XRD relative intensity), and the specific surface area was also evaluated. .

FIG. 2a shows the XRD relative intensity of the reaction product obtained under the conditions, FIG. 2b shows the specific surface area, and FIG. 3 shows the XRD relative intensity of the reaction product obtained under the conditions. 4a shows the XRD relative intensities of the reaction products obtained under the conditions of, and FIG. 4b also shows the specific surface areas of and. In addition, of the above coal ash, No.
1 and No. The results of composition analysis of No. 5 are shown in Table 1.

[0019]

[Table 1]

2a and 2b, coal ash N
o. It can be seen that a synthesis result satisfying only 1 can be obtained. No. In No. 5, neither type A zeolite nor hydroxysodalite was formed. The specific surface area corresponds to the average value of all reaction products, and the higher the specific surface area, the higher the production rate of A-type zeolite (or other zeolite having large pores). In FIG. 3 showing the result of the synthesis condition, coal ash No. In 3, 4, and 6, the synthesis rate of the A-type zeolite was slightly improved from the synthesis conditions, but it was not remarkable. On the other hand, in FIG. 4a showing the result of the synthesis condition, the A-type zeolite can be synthesized from all the coal ash. Considering the comparison result of the specific surface area with the synthesis condition of FIG. 4b and the amount of CaO in Table 1, it is understood that the calcium removal effect by the acid treatment is exhibited.

Experimental Example 2 (Study of Effect of Na ₂ CO ₃ ) Next, 6 kinds of coal ash (Sample Nos. 2 to 7: No.
2 to 6 are the same coal ash as used in the above experimental example), Na ₂ CO ₃ is added in the same weight as the raw material, and the mixture is calcined at 800 ° C. for 2 hours and treated with 0.1N hydrochloric acid at pH 4 After washing with water to remove Ca, the following is performed (first step + second step + pre-stage heating + third step, method of the present invention). Compared things. The peak intensity of the XRD of the reaction product obtained under the condition (1) is shown in Fig. 5a, and the specific surface area result is shown together with the result under the condition (2) in Fig. 5b.

From FIGS. 5a and 5b, it can be seen that hydroxysodalite having no pores is scarcely synthesized in the synthetic experimental example corresponding to the best mode of the method of the present invention, which shows an excellent synthesis rate of A-type zeolite. It can be seen that the specific surface area of the product is significantly increased by adding and baking Na ₂ CO ₃ as compared with the case of not adding.

A synthetic experiment under the conditions of Experimental Example 3 (examination of influence of pre-heating treatment) and under the same conditions as above except that pre-heating was not carried out () was conducted using coal ash No. It went about 3. Table 2 shows the proportion (%) of the A-type zeolite in the obtained product and the specific surface area of the reaction product.

[0024]

[Table 2]

From Table 2, it can be seen that good A is obtained even when the former stage heating is not performed.
Type zeolite synthesis rate was shown, and it was revealed that when the former stage heating was performed, higher type A zeolite synthesis rate and higher specific surface area were exhibited. From the above experimental results, it was found that the condition (1) or (2) is the condition under which the zeolite with large pores can be synthesized in the best condition. So coal ash N
o. 1 was used to examine the effect of acid treatment again under the conditions of. The results are shown in Table 3.

[0026]

[Table 3]

By the acid treatment, the production rate of hydroxysodalite is greatly reduced, and the synthesis rate of A-type zeolite and the specific surface area are higher. Example 1 (Specific Example under Conditions) Six types of coal ash (No. 8 to 13: average particle size of about 10 μm)
And high-purity kaolin (SiO ₂ is contained as quartz and cristobalite: average particle size 5 μm) was mixed with the same weight of Na ₂ CO ₃ and calcined at 800 ° C. for 2 hours. A 0.1 mol / liter hydrochloric acid aqueous solution was added to this fired product until the pH of the slurry became about 4, and the mixture was stirred. After filtration and washing with water, 1.2 kg of the obtained cake was slurried with 20 liters of water, and 2.4 kg of sodium hydroxide was further added. After stirring at 80 ° C. for 2 hours to perform the first heat treatment, crystallization reaction was performed at 85 ° C. for 2 hours. After the product was filtered and washed with water, the zeolite production rate was measured by the X-ray diffraction method, and the results are shown in Table 4.

Comparative Example The six kinds of coal ash and kaolin used in Example 1 were calcined as they were at 800 ° C. for 2 hours, 1.2 kg was slurried with 20 liters of water, and 2.4 kg of sodium hydroxide was added. . The crystallization reaction was performed at 80 to 85 ° C. for 2 hours without performing the first-stage heat treatment. Table 4 shows the measurement results of the production rate of zeolite.
Also described in.

[0029]

[Table 4]

As is clear from Table 4, all the Examples of the present invention method exhibited a higher zeolite synthesis rate than the Comparative Examples. Further, in the example using kaolin, a SiO ₂ peak was observed in the reaction product in the comparative example from the result of X-ray diffraction,
It was found that the impurity SiO ₂ was not converted into a reactive component, and no SiO ₂ peak was observed in the examples. Therefore, even if a raw material containing quartz or cristobalite is used as a reactive component, It became clear.

Example 2 Using an FRP incineration residue and a papermaking sludge incineration product having the compositions shown in Table 5 as raw materials and pulverizing until the average particle size was 20 μm or less, 1/2 weight of Na ₂ CO ₃ was added to the raw materials. Was added and mixed, and the mixture was baked at 800 ° C. for 2 hours. A 0.1 mol / l hydrochloric acid aqueous solution was added to the calcined product as a slurry liquid.
Addition and stirring were performed until H became about 4. After filtering and washing with water, 3N NaOH aqueous solution was added to the obtained cake, and the mixture was stirred at 80 ° C. for 2 hours and subjected to the first-stage heat treatment,
The synthesis reaction was performed at 85 ° C. for 2 hours. At this time NaAlO
₂ was added before the synthesis reaction so that the molar ratio of SiO ₂ : Al ₂ O ₃ was 1, and that which was not added and the synthesis reaction was performed only with the raw material was compared. As a result, when NaAlO ₂ was not added, the A-type zeolite synthesis rate was low and the specific surface area was about 200 m ² / g. However, in the system to which NaAlO ₂ as the Al source was added, the FRP incineration residue and papermaking A type synthesis rate is 40 for any raw material of sludge incineration
60%, a specific surface area was significantly improved with 300~500m ² / g.

[0032]

[Table 5]

Example 3 60 g of the sodium A-type zeolite (samples 1 and 2) obtained in Example 1 was added to 1 liter of the effluent (prepared to have a calcium ion concentration of 40 g / l) discharged by the acid treatment. After suspending and holding at 30 ° C. for 2 hours, Na → Ca ion exchange was performed. The reaction product was washed with water and dried, and then the specific surface area was measured. 6a and 6b,
The X-ray diffraction charts of Samples 1 and 2 before and after ion exchange are shown.

[0034]

[Table 6]

From Table 6, it can be seen that the specific surface area of each sample is improved by about 10% by ion exchange. In addition, the X-ray diffraction results show that Na → Ca ion exchange was performed and the A-type structure was retained.

[0036]

The method of the present invention is constituted as described above,
Since the calcium component, which is an impurity, can be removed almost completely, it is possible to use a zeolite that has not been suitable as a raw material in the past as a raw material for zeolite and to greatly increase the synthesis rate of zeolite having large pores. The resulting zeolite has a large specific surface area of 600 m ² / g or more. Further, since the reaction efficiency was improved, the synthesis time, which was required for one day or more when the conventional aging was also included in the coal ash raw material, could be greatly reduced. Further, when the calcium-type zeolite is obtained from the sodium-type zeolite by a known ion exchange method, the calcium ions can be effectively used by using the waste liquid discharged in the acid treatment in the second step.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between heating temperature and zeolite precipitation time.

FIG. 2 (a) is a graph showing the XRD relative intensity of the reaction product obtained under the synthesis conditions of Experimental Example 1, and FIG. 2 (b) is a graph showing the specific surface area of the reaction product.

FIG. 3 is a graph showing XRD relative intensities of reaction products obtained under the synthesis conditions in Experimental Example 1.

FIG. 4 (a) shows the XRD relative intensities of the reaction products obtained under the synthetic conditions of Experimental Example 1, and (b) shows the reaction products obtained under the synthetic conditions of Experimental Example 1. It is a graph which shows the specific surface area of both things.

5 (a) shows the XRD relative intensities of the reaction products obtained under the synthetic conditions of Experimental Example 2, and (b) shows the reaction products obtained under the synthetic conditions of Experimental Example 2. It is a graph which shows the specific surface area of both things.

6A is an X-ray diffraction chart showing the ion exchange before and after the ion exchange in Sample 1 of Example 3, and FIG.
Is a chart in.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masaru Horii 1-3-18 Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo Kobe Steel Works, Ltd. Kobe Head Office

Claims (5)

[Claims] 1. A method for synthesizing zeolite, characterized in that the method for synthesizing zeolite from the raw material powder includes the following steps. First step: 750-9 by adding Na ₂ CO ₃ to the raw material powder
Bake at 00 ° C. Second step: acid (excluding sulfuric acid) treatment and water washing are performed under pH 4 or less. Third step: hydrothermal reaction of zeolite in an alkaline solution at 80 to 85 ° C. 2. The pre-stage heat treatment in an alkaline solution under the temperature and time conditions such that zeolite synthesis is not performed after the second step and before the third step. A method for synthesizing the described zeolite. 3. The method for synthesizing zeolite according to claim 1, wherein a sodium source and / or an aluminum source is added before the third step or before the first-stage heat treatment. 4. The raw material powder is coal ash, sewage sludge incinerator,
The zeolite synthesis method according to any one of claims 1 to 3, which is selected from the group consisting of papermaking sludge incineration products, FRP combustion residues, and ironmaking slag. 5. When the acidic drainage discharged in the second step contains calcium ions, the calcium ions are utilized to convert the zeolite according to any one of claims 1 to 4 into calcium-type zeolite. A method for synthesizing zeolite, comprising: