JP2848227B2 - Synthetic method of zeolite - Google Patents

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 zeolite having a large specific surface area useful as an adsorbent for gas molecules and low molecular weight organic compounds and an ion exchange material from industrial waste.

[0002]

BACKGROUND OF THE INVENTION _{M 2 / n O · Al 2} O 3 · xSiO 2 · y
A zeolite having a chemical composition represented by H ₂ O (M is a metal, x is 2 or more, y is 0 or more), and has pores suitable for adsorption and separation in a crystal is produced as a natural mineral. In addition, it is artificially synthesized. Since these pore-containing zeolites must be crystallized in a non-equilibrium state as a metastable phase, the reaction is proceeding with complicated factors involved, and although the crystallization mechanism has been completely understood at this time, Absent.

[0003] As a specific synthesis method, there is a method using sodium silicate and sodium aluminate as chemical reagents, but the cost is unavoidable. So, natural clay
In addition to using minerals as raw materials, a method of obtaining zeolite by adding a silica source, an aluminum source and a sodium source to coal ash, which is industrial waste, and performing a hydrothermal reaction at about 85 ° C. for 3 hours to obtain resources. -Many studies have been made in terms of recycling (JP-A-59-35019, JP-A-64-24014, JP-A-2-
No. 229709).

[0004] However, coal ash contains many impurities, has a low synthesis rate, and has a fatal problem in industrial production in which the synthesis rate varies depending on the production area of the coal ash. In addition, since the obtained zeolite has a small specific surface area and is often of low value, a method for efficiently synthesizing a zeolite having a large pore diameter from industrial waste is required.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to solve the problem of hydrothermal reaction during the synthesis of zeolite 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]

The method for synthesizing the zeolite of the present invention which can 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: An acid (excluding sulfuric acid) treatment and water washing are performed under the condition of pH 4 or less. Third step: The zeolite is hydrothermally reacted at 80 to 85 ° C. in an alkaline solution. Is included as an essential step. After the second step and before the third step, performing a first-stage heat treatment in an alkaline solution at a temperature and time condition such that zeolite synthesis is not performed, before the third step or the first-stage heat treatment Prior to the addition of a source of sodium and / or aluminum is a preferred embodiment of the process of the invention.
The method of the present invention is a zeolite synthesis method particularly suitable for a raw material powder selected from the group consisting of coal ash, sewage sludge incineration, paper sludge incineration, FRP combustion residue, and steelmaking slag.
In addition, a method of synthesizing a calcium zeolite by ion exchange using calcium ions when the acidic effluent discharged in the second step contains calcium ions is also included in the method of the present invention.

[0007]

The present inventors have been conducting research on synthesizing useful zeolites using industrial waste, and have achieved some results. For example, Japanese Patent Application No. 4-247756
In No. 1, when synthesizing A-type zeolite using coal ash as a main raw material, a zeolite having a specific surface area of about 180 m ² / g was successfully synthesized by performing heating and stirring before a hydrothermal reaction. Also, in Japanese Patent Application No. 5-254513,
It has been disclosed that the A-type zeolite synthesis rate can be increased by removing the calcium compound. In this case, the specific surface area is up to 3
Although it was improved to about 80 m ² / g, the specific surface area was 150 to 380 depending on the type of coal ash even if the same treatment method was adopted.
was found that variations in the m ² / g. The present invention was made as a result of studying 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 include:
In addition to clay minerals and natural minerals, natural products such as volcanic ash such as shirasu, volcanic glass, sediments such as diatomaceous earth, sedimentary rocks such as tuff,
Alternatively, artificial materials such as iron-made slag can be used, but the method of the present invention can efficiently synthesize high-quality zeolite even with a raw material containing a large amount of impurities, and particularly, coal ash and sewage sludge, which are industrial wastes. Incineration, paper sludge incineration,
FRP combustion residues and steelmaking slag generated in the steelmaking and steelmaking processes can be used as raw materials. The raw material is preferably a powder in order to enhance the reactivity. If the raw material is not available, the raw material may be ground in advance. The preferred particle size of the raw material powder is a maximum of 50 μm in diameter 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 or Al ₂ O
₃ has an effect of making these Si and alumina sources easily contribute to the zeolite synthesis reaction in the third step, and an effect of making amorphous which easily removes calcium as an impurity. Calcium compounds are, for example, components that are inevitably contained in coal ash because an excessive amount of calcium is added for desulfurization of flue gas, and components that are almost always contained in other industrial waste raw materials. It is.
This calcium becomes amorphous calcium silicate (CaSiO ₃ ) in an alkaline solution and deprives the Si component, so that it is an impurity that inhibits the zeolite synthesis reaction.
Among these calcium compounds, compounds stable to acids are also included, which is disclosed in Japanese Patent Application No. 5-254513.
This is considered to be one of the causes of the variation in the rate of zeolite synthesis depending on the coal ash production area. That is, the presence of calcium compounds that could not be completely removed by simple acid treatment or other treatment methods had an adverse effect on the subsequent zeolite synthesis step.

The calcium compound is stable even at a high temperature, and is hardly soluble in an acid only after a calcination step. As a result of various studies, it has been found that by adding Na ₂ CO ₃ to the raw material and calcining it, the calcium component can be made amorphous and can be eluted into an acid solution. Process. By the first step and the subsequent second step, the calcium component can be removed as much as possible, so that a good zeolite synthesis result was obtained even with a raw material containing a large amount of the calcium component.

The preferred Na ₂ CO in the first step
The amount of ₃ added is 0.5 to 2.0 in terms of weight ratio with respect to the raw material 1. Na ₂ CO ₃ is less than 0.5 (based on raw material 1),
Alternatively, when the firing temperature is lower than 750 ° C., the calcium compound is not completely converted to an amorphous state. Na ₂ CO
₃ is more than 2.0 or the sintering temperature is higher than 900 ° C., silica and alumina in the raw material and Na ₂ CO ₃
Reacts with each other to generate a large number of crystal phases that are hardly soluble in acids and alkalis, so that the zeolite synthesis rate decreases. The firing is preferably performed in an air atmosphere for about 2 hours.

After the first step, a second step including acid (excluding sulfuric acid) treatment and water washing is performed under the condition of pH 4 or less. This second step is performed to dissolve the above-mentioned calcium compound in the acidic solution and remove it from the raw material. The acids used are inorganic or organic acids other than sulfuric acid. Sulfuric acid reacts with calcium to make water sparingly soluble Ca
It is not preferable because it becomes SO ₄ and remains in the raw material and hinders the subsequent zeolite synthesis reaction in an alkaline solution. The acid treatment is carried out at pH 4 while adding an aqueous solution of an acid to the raw material slurry.
It may be carried out by a method such as stirring until the concentration becomes below, and the concentration of the acid aqueous solution is 0.0005 to 5 depending on the concentration of the raw material slurry.
What is necessary is just to change suitably between 0.2 specifications. After the acid treatment, filtration and washing with water are performed according to a conventional method. The process of acid treatment and washing with water may be repeated an appropriate number of times. In this acid treatment step, hydration of the reactive component in the raw material that has been made amorphous by firing proceeds to promote gelation, which is more advantageous for the next step of zeolite synthesis.

The third step is to carry out a hydrothermal synthesis reaction of the zeolite.
By reacting at 85 ° C. for 1 to 4 hours, zeolite is synthesized. As the alkaline solution, a 1-5N NaOH solution, more preferably a 3N NaOH solution is used. At this time, if the raw material contains a small amount of an aluminum source or a sodium source, sodium aluminate (also useful as a sodium source), aluminum hydroxide before the third step or before the “pre-heating treatment step” described later. And an aluminum source such as aluminum chloride and a sodium source such as sodium carbonate.

In the method of the present invention, after the second step, a pre-stage heat treatment may be performed in which the mixture is heated and stirred under such a temperature condition that zeolite is not synthesized. The pre-heating treatment is performed not for the synthesis reaction of the zeolite but for sufficiently elute the Si source and the aluminum source in the raw material into the alkaline solution, or to promote the gelation of these reactive components in the raw material. Therefore, it is necessary to perform the reaction under 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 the zeolite precipitates. The pre-stage heat treatment is preferably performed under the condition of the zeolite non-precipitation region in the figure, and most preferably under the condition 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 coefficients a, b, and c vary depending on the concentration of the alkaline solution.
= 140-150 × 10 ^-4 , b = 100-110 × 10
^-3 , c = 180-200.

As a specific practical pre-heating condition, the alkali solution slurry prepared at room temperature is heated to 60 ° C. and mixed for about 10 hours,
It is only necessary to adjust the time and temperature so as to match all the formulas, such as mixing for about 3 hours. As the 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 directly used in the process. By performing the first heating step, it is possible to suppress the generation of hydroxysodalite and increase the synthesis rate of zeolite having large pores.

In the method of the present invention described above, sodium-type zeolite is mainly synthesized. In addition to A-type zeolite,
X and Y type zeolites and other zeolites having large pores can be synthesized, and the specific surface area of the formed zeolite is as large as 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, the effective use of calcium ions can be achieved by using the drainage discharged in the acid treatment in the second step.

[0017]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to the following Examples. Experimental Example 1 (Examination of the effects of calcination and acid treatment in a system to which Na ₂ CO ₃ was not added) In order to find the optimum zeolite synthesis process, six types of coal ash (sample Nos. 1 to 6: average particle size of 10 μm) were used.
m) in a 3N NaOH aqueous solution at 80 ° C
For 2 hours, and then perform a zeolite synthesis reaction at 85 ° C. for 3 hours (first stage heating + third step) Calcining at 800 ° C. for 2 hours without adding Na ₂ CO _3, and adding only water without adding acid (Variable type of first step + variant type of second step + preliminary heating + third step) and calcined at 800 ° C. for 2 hours without adding Na ₂ CO ₃ ,
After performing acid treatment at pH 4 with 0.1N hydrochloric acid, washing with water and removing Ca, the treatment is carried out (variable type of first step + second step + pre-heating + third step). The state of formation of A-type zeolite and hydroxysodalite (having no pores) was determined by comparing with the peak intensity of SiO ₂ by X-ray powder diffraction (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 shown in FIG. 2, FIG. 2b shows the specific surface area, and FIG. 3 shows the XRD relative intensity of the reaction product obtained under the conditions shown in FIG. 4a shows the XRD relative intensity of the reaction product obtained under the above conditions, and FIG. 4b also shows the specific surface area. In the above coal ash, No.
1 and No. Table 1 shows the results of the composition analysis of Sample No. 5.

[0019]

[Table 1]

2A and 2B, the coal ash N
o. It can be seen that a synthesis result satisfying only 1 is not obtained. No. In No. 5, neither A-type 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 generation rate of A-type zeolite (or other zeolite having large pores). In FIG. 3 showing the results of the synthesis conditions, coal ash No. In 3, 4, and 6, the synthesis rate of A-type zeolite was slightly improved from the synthesis conditions, but was not remarkable. On the other hand, in FIG. 4a showing the results of the synthesis conditions, A-type zeolite was synthesized from all the coal ash. Considering the result of comparison of the specific surface area with the synthesis conditions in FIG. 4b and the amount of CaO in Table 1, it can be seen that the decalcification effect by the acid treatment is exhibited.

Experimental Example 2 (Investigation of the Influence of Na ₂ CO ₃ ) Next, six types of coal ash (samples Nos. 2 to 7;
2 to 6 are the same coal ash as used in the above experimental example), added with the same weight of Na ₂ CO ₃ as the raw material, calcined at 800 ° C. for 2 hours, and acid-treated with 0.1 N hydrochloric acid at pH 4 (1st step + 2nd step + pre-heating + 3rd step, the method of the present invention), and a treatment under the following conditions: Things were compared. The XRD peak intensity of the reaction product obtained under the conditions described in FIG. 5a is shown in FIG. 5a, and the specific surface area results are shown in FIG.

From FIGS. 5a and 5b, it can be seen that hydroxysodalite having no pores is hardly synthesized in the synthetic experimental example corresponding to the best mode of the method of the present invention, and shows an excellent synthesis rate of type A zeolite. It can be seen that the specific surface area of the product is greatly increased by calcining with addition of Na ₂ CO ₃ as compared with the case without addition.

The synthesis experiment under the same conditions () as in Experimental Example 3 (investigation of the effect of the pre-stage heat treatment) and under the same conditions () except that the pre-stage heating was not performed was performed on coal ash No. 3 was performed. Table 2 shows the ratio (%) of 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 even when the pre-stage heating is not performed, good A
It shows that the zeolite synthesis rate is higher, and when the pre-heating is performed, a higher zeolite A synthesis rate and a higher specific surface area are exhibited. From the above experimental results, it was found that the above condition or the condition was the condition under which the zeolite having large pores could be synthesized most preferably. So coal ash N
o. Using No. 1, the effect of the acid treatment was again examined under the following conditions. Table 3 shows the results.

[0026]

[Table 3]

The acid treatment significantly reduces the production rate of hydroxysodalite and shows a higher synthesis rate of type A zeolite and a higher specific surface area. Example 1 (Specific example according to conditions) Six types of coal ash (No. 8 to 13: average particle size of about 10 μm)
And high-purity kaolin (containing SiO ₂ as quartz and cristobalite: average particle size 5 μm), mixed with the same weight of Na ₂ CO _3, and calcined at 800 ° C. for 2 hours. An aqueous 0.1 mol / liter hydrochloric acid solution was added to the calcined product until the pH of the slurry became about 4, followed by stirring. 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 and performing a pre-heating treatment, a crystallization reaction was performed at 85 ° C. for 2 hours. After the product was filtered and washed with water, the production rate of zeolite was measured by X-ray diffraction method, and the results are shown in Table 4.

COMPARATIVE EXAMPLE After the six types of coal ash and kaolin used in Example 1 were directly calcined 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 zeolite formation rate.
It was also described in.

[0029]

[Table 4]

As is evident from Table 4, all of the working examples of the present invention exhibited a higher zeolite synthesis rate than the comparative examples. In the case of using kaolin, the peak of SiO ₂ 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. Since no peak of SiO ₂ was observed in the examples, even if the raw material contained quartz or cristobalite, these were effectively used as the reactive component. It became clear that there was.

[0031] The FRP incineration residues and paper sludge incineration the composition shown in Example 2 in Table 5 as a raw material, was ground to average particle size below 20 [mu] m, relative to the starting material, 1/2 of the weight of the Na ₂ CO ₃ And baked at 800 ° C. for 2 hours. A 0.1 mol / liter hydrochloric acid aqueous solution is added to this calcined product by p
The addition and stirring were performed until H became about 4. After filtration and washing with water, a 3N aqueous solution of NaOH was added to the obtained cake, and the mixture was stirred at 80 ° C. for 2 hours to perform a 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 became 1, and the case where the synthesis reaction was performed using only the raw materials without the addition was compared. As a result, when NaAlO ₂ was not added, the synthesis rate of A-type zeolite 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, FRP incineration residue, papermaking, etc. The type A synthesis rate is 40 for any of the sludge incineration raw materials.
６０60%, and the specific surface area was greatly improved to 300 to 500 m ² / g.

[0032]

[Table 5]

Example 3 60 g of the sodium-type A zeolite obtained in Example 1 (samples 1 and 2) were placed in 1 liter of a drainage liquid (prepared to a calcium ion concentration of 40 g / l) discharged by acid treatment. The suspension was maintained at 30 ° C. for 2 hours to perform Na → Ca ion exchange. After washing and drying the reaction product, the results of measuring the specific surface area are shown in Table 6. 6a and 6b,
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 was improved by about 10% by ion exchange. In addition, the results of X-ray diffraction show that Na → Ca ion exchange was performed and that the A-type structure was maintained.

[0036]

The method of the present invention is constituted as described above.
Since the removal of the calcium component, which is an impurity, can be performed almost completely, a material which was not conventionally suitable as a raw material can be used as a zeolite raw material, and the synthesis rate of zeolite having large pores can be greatly increased. The specific surface area of the obtained zeolite is as large as 600 m ² / g or more. In addition, since the reaction efficiency was improved, the synthesis time required for one day or more was also significantly reduced when coal ash raw materials were conventionally included in aging. Further, when calcium-type zeolite is obtained from sodium-type zeolite by a known ion exchange method, calcium ions can be effectively used by using the drainage discharged in the acid treatment in the second step.

[Brief description of the drawings]

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

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

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

4 (a) shows the XRD relative intensity of the reaction product obtained under the synthesis conditions of Experimental Example 1, and FIG. 4 (B) shows the reaction product obtained under the synthesis conditions of Experimental Example 1. It is a graph which shows the specific surface area of both of a thing.

5 (a) shows the XRD relative intensity of the reaction product obtained under the synthesis conditions of Experimental Example 2, and FIG. 5 (B) shows the reaction product obtained under the synthesis conditions of Experimental Example 2. It is a graph which shows the specific surface area of both of a thing.

6 (a) is an X-ray diffraction chart showing before and after ion exchange in sample 1 of Example 3, and FIG. 6 (b) is sample 2
It is a chart in.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shunichi Toyama 1-3-18 Wakihama-cho, Chuo-ku, Kobe City, Hyogo Prefecture Kobe Steel, Ltd. Kobe Main Office (72) Inventor Masaru Horii Wakihama, Chuo-ku, Kobe City, Hyogo Prefecture 1-3-18, Kobe Kobe Steel, Ltd. Kobe Head Office (58) Field surveyed (Int. Cl. ⁶ , DB name) C01B 39/00-39/54

Claims (5)

(57) [Claims] 1. A method for synthesizing zeolite, wherein the method for synthesizing zeolite from raw material powders includes the following steps. First step: 750 to 9 by adding Na ₂ CO ₃ to the raw material powder
Bake at 00 ° C. Second step: An acid (excluding sulfuric acid) treatment and water washing are performed under the condition of pH 4 or less. Third step: The zeolite is hydrothermally reacted at 80 to 85 ° C. in an alkaline solution. 2. The method according to claim 1, wherein after the second step and before reaching the third step, a first-stage heat treatment is performed in an alkaline solution at a temperature and a time condition such that zeolite synthesis is not performed. A method for synthesizing the described zeolite. 3. The method for synthesizing a 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 incineration,
The method for synthesizing zeolite according to any one of claims 1 to 3, wherein the method is selected from the group consisting of incinerated papermaking sludge, FRP combustion residue, and ironmaking slag. 5. When the acidic effluent discharged in the second step contains calcium ions, the zeolite according to any one of claims 1 to 4 is converted into a calcium-type zeolite using the calcium ions. A method for synthesizing a zeolite.