JPS63182214A - Production of zeolite - Google Patents

Abstract

PURPOSE:To obtain a inexpensive zeolite and to produce a zeolite contg. A-type and X-type zeolite as well as P-type zeolite also by allowing the finely pulverized coal ash to cause thermal-reaction in an aq. soln. of caustic alkali and repeatedly using the reaction filtrate. CONSTITUTION:The coal ash is finely pulverized and allowed to crystallize by heating in the aq. soln. of caustic alkali. Then the solid matter is filtered and obtained from the reaction mixture and dried after washing with water. On the other hand, the filtrate is added to the pulverized new coal ash and is repeatedly used while adjusting the molar ratio of silica/alumina. The A-type zeolite is easily obtained by adjusting the molar ratio of silica/alumina to about 0.1-2 and the X-type zeolite is easily obtained by adjusting the above-mentioned ratio to about 2-5.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for producing zeolite.

[Prior art and its problems]

According to the government's interim report on Japan's provisional outlook for energy supply and demand, the future expansion of coal use will increase from 7.8QO million tons of coal supply in FY 1980 to 1 in FY 1986.
It is expected to increase at an annual rate of 5%, reaching 63.5 million tons and 198 million tons in 1985.

As a problem associated with the expansion of coal use, the issue of disposing of coal ash, which is a controlled industrial waste, is considered to be as important as air pollution. The 15-20% ash content in coal is
It is a source of large amounts of industrial waste, as coal ash burned in boilers, as blast furnace sludge in the steel industry, and as sludge in coal liquefaction, gasification processes, and coal cleaning. The utilization rate of coal ash generated from coal-fired power plants in Japan is one-fourth of the amount generated.

Most of the effective use of coal ash is as a raw material for cement;
More than 1.5 million tons of coal ash that was not used effectively is disposed of in landfills on land, inland water, and at sea.

It is estimated that the amount of coal ash that will be generated due to the expanded use of thermal coal will reach 8 million tons in 1965, and even 12 million tons in 1970, just from the electric power industry alone. Therefore, it is necessary to proactively and boldly proceed with research and development aimed at expanding the effective use of coal ash and its usage.

Taking into consideration the various situations mentioned above, and from the standpoint of expanding the effective use of coal ash and promoting the smooth expansion of coal use, we focused on the silica and alumina components in coal ash, and turned it into zeolite through a hydrothermal reaction. We planned the application of synthetic zeolite to wastewater treatment and industrial waste treatment.

Conventional synthetic zeolite production methods rely on silica sources (e.g.
water glass, silica gel, silica sol, etc.) and an alumina source (aluminum oxide, sodium aluminate, etc.)
It is synthesized by adding caustic soda and water and causing a heating reaction. S
Various types of zeolites (e.g. Y type, A type, P type, etc.) can be made with a mixing ratio of iOz + A''z O31Na20. However, the raw materials, silica gel and alumina, are both expensive, so conventional synthetic zeolites are extremely expensive. It was something.

The present inventors have previously discovered a method using coal ash as a raw material as an inexpensive method for producing P-type zeolite. (Unexamined Japanese Patent Publication No. 6
0-14565).

P-type zeolite selectively adsorbs lead, cadmium, and strontium ions, and is not significantly interfered with by other metal ions. When utilizing these characteristics of P-type zeolite and applying it to the treatment of industrial wastewater and waste, it competes with naturally produced zeolite, and in that case, not only performance but also price issues determine the superiority or inferiority of the two. Therefore, in order to further reduce the unit manufacturing cost, we considered reducing the amount of caustic alkali, which is the most expensive manufacturing raw material, and thoroughly utilizing coal ash components. There was a need to produce zeolites of higher value than P-type zeolites in a similar manner.

The purpose of the present invention is to produce a very inexpensive zeolite using coal ash, and to provide a method for producing zeolite including not only the P type but also the A type and the X type by recycling the reaction filtrate. do.

[Means for solving problems]

The present invention involves finely pulverizing coal ash, heating and crystallizing it in an aqueous caustic solution, filtering the solid matter from the reaction mixture, washing with water and drying it, and using the filtered filtrate as freshly pulverized coal ash. In addition to this, it is a method for producing zeolite in which the molar ratio of silica/alumina is adjusted and recycled to 2 to 5.

The method of producing from coal ash according to the present invention will be briefly described.

The raw material coal ash is fly ash, clinker ash (bottom ash), single coal combustion ash, etc., which are pulverized and stirred in a caustic alkali aqueous solution of a predetermined concentration, for example, about 1 to 4 N, and subjected to a heating reaction. The obtained reaction mixture was filtered into a solid substance and a filtrate, and a predetermined amount of coal ash was added to the filtrate.
For example, add a 1/10 (weight/volume) amount, add a sodium source such as sodium hydroxide or sodium aluminate, and stir again while heating to react.

This operation is repeated and the filtrate is recycled. The solid material obtained by filtration after the heating reaction is washed with water and then dried to obtain the desired zeolite.

The raw material coal ash is preferably pulverized to about 200 mesh particles rather than being a solid material. This is because powder reacts more easily.

The reaction is carried out in an alkaline aqueous solution, and the higher the alkalinity of the aqueous solution, the easier the reaction is. However, if it exceeds 4N, side reactions are likely to occur, which is not preferable. As the alkali, caustic soda can be used for the purpose of obtaining a sodium source.

If the heating temperature is too low, the reaction will be difficult to proceed, and if it is too high, it will be thermally uneconomical, so it is not preferable. The heating time varies depending on the heating temperature, but it is usually 60℃~
The temperature is 200°C for 1 hour or more. However, even if the heating time is too long, it does not have much effect on the amount produced.

In the present invention, the filtered filtrate is added to freshly pulverized coal ash, and the filtrate is recycled and used. At that time, the molar ratio of silica/alumina in the reaction solution is adjusted.

The reaction solution is prepared by using a caustic alkali such as sodium hydroxide, potassium hydroxide, sodium aluminate, water glass, etc., and optionally adding an alkali source and an aluminum source. In this case, when the silica/alumina molar ratio is adjusted to 0.1 to 2, type A zeolite is easily obtained, and when adjusted to 2 to 5, type X zeolite is easily obtained.

The zeolite produced in this way can be confirmed, for example, by scanning electron microscopy, and its purity can be determined by
For example, it can be verified by powder X-ray diffractogram.

According to the present invention, sodium and silica in the reaction mother liquor can be effectively utilized.

The present invention will be explained below using examples.

〔Example〕

Preparation example 1゜Fly ash 50g, 3N NaOH aqueous solution 500c
c. and heated at 90 to 100°C for about 18 hours. After the reaction is complete, solid substances are filtered out and washed with water until the pH of the solution reaches 10.
Wash thoroughly until it reaches 5. And 24 at 110℃
Dry for an hour. P-type zeolite with a crystallinity of about 45% is 4
7.2g was obtained. The production of P-type zeolite was confirmed by scanning electron micrographs in comparison with conventional P-type zeolite synthesized from water glass, sodium aluminate, and sodium hydroxide. In addition, its purity is A in the powder X-ray diffraction diagram.
Using a 37M card, the peak area (cd
) was tested.

Next, the filtrate of the reaction solution after filtering off solid substances was collected.

Preparation Example 2 50g of tarinka ash, 500g of 3N NaOH aqueous solution
cc was mixed and heated at 90 to 100°C for about 18 hours. After the reaction, the solid content was filtered out and the pH of the washing solution was adjusted to 101 with water.
Wash thoroughly until it reaches 5. And 24 at 110℃
Dry for an hour. P-type zeolite with a crystallinity of about 45% is 4
8.5g was obtained. The production and purity of the obtained P-type zeolite were confirmed in the same manner as in Preparation Example 1.

Next, the filtrate of the reaction solution after filtering off solid substances was collected.

Preparation Example 3゜Ikeshima charcoal combustion ash 50g, 2N NaOH aqueous solution 500c
c and heated at 90 to 100°C for about 20 hours. After the reaction, the solid content was filtered out and washed with water until the pH of the solution was 10.5.
Wash thoroughly until dry and dry at 110°C for 24 hours. 43.3 g of P-type zeolite with a crystallinity of about 35% was obtained. The production and purity of the obtained P-type zeolite were confirmed in the same manner as in Preparation Example 1.

01'n'f Example 1 1.51 of each of the collected filtrates obtained by the method described in each of the preparation examples above was placed in a 21-sized Kolben, and 45 g of water glass was added and stirred to dissolve the filtrate. Component concentrations were quantitatively analyzed.

Representative examples of the results are shown in Table 1.

”” Representative example 5ift A 1 , O, Na, 0
1 31.250.614 56.4
82 35.76 0.417
61.88 (g/j?> (NazO/5iOz molar ratio = 4) Next, put 150 ml of each into a 300 ml ton corben and add sodium aluminate and alkaline solution in the proportions shown in Table 2. For Example 1, the silica/alumina molar ratio was adjusted to 0.1-2, and for Representative Example 2, the silica/alumina molar ratio was adjusted to 2.5-5.

0.5 4 40 25.45 1.67 8
8.101 4 40 10.67 7.7
0 81.691.5 4 40 8.39
7.98 B1.222 4 40
4.78 11.74 80.822.5 4
40 5.76 13.83 114.013
4 40 4.79 14.30
113.833.5 4 40 4.
09 14.64 113.834 4
40 3.56 14.90 113.7?
4.5 4 40 3.16 15.
10 113.735 4 40
3.83 15.26 113.70 Each solution was stirred for 30 minutes and reacted by heating in a 100° C. oil bath for 3.5 hours.

The resulting reaction solution was suction filtered, and the solid material was washed with distilled water and dried at 80° C. or higher for 20 hours or more. It was determined by powder >1 diffraction using an internal standard method using aluminum oxide as a standard substance.

The results are shown in FIG.

As can be seen from the figure, the silica/alumina molar ratio is 0.1.
When the molar ratio of silica/alumina is 2 to 5, the amount of type A zeolite produced is large.

Example 2 The recovered filtrate obtained by the method described in each of the preparation examples above was quantitatively analyzed for component concentration in the filtrate.

Other representative examples of the results are shown in Table 3.

Jyu1 Representative example 5ift A l z03 N
azO318,790,60249,66 419,840,65249,48 (g/j (NazO/5tOz molar ratio = 7) Next, put 150 ml of each into 300 ml of colchen, and in the proportions shown in Table 4, Sodium aluminate and an alkaline solution were added to adjust the silica/alumina molar ratio to 0.1-2 for Representative Example 3 and 2.5-5 for Representative Example 4.

0.5 7 40 15.26 7.62 9
6.961 7 40 7.56 13.
38 76.121.5 7 40 4.9
9 14.62 95.832 7 40
3.70 15.26 95.692.5
7 40 3.10 1? , 12 1
09.493 7 40 2.56
17.38 109.433.5 7 4
0 2.1? 17.57 109.394
7 40 1.88 17. n
109.364.5 7 40 1.
65 1? ,82 109.335 7
40 1.47 17.90 109.30 For each solution, stir for 30 minutes and store in an oil bath at 100°C for 30 minutes.
．． The mixture was heated and reacted for 5 hours.

The resulting reaction solution was suction filtered, and the solid material was washed with distilled water and dried at 80° C. or higher for 20 hours or more. It was determined by powder X-ray diffraction using an internal standard method using aluminum oxide as a standard substance.

Also in this example, results were obtained in which a large amount of type A zeolite was produced when the silica/alumina molar ratio was O01 to 2, and a large amount of X type zeolite was produced when the silica/alumina molar ratio was 2 to 5.

〔Effect of the invention〕

As explained above, according to the present invention, waste coal ash is used and the reaction filtrate is recycled, so olide can be obtained at a much more economical cost than conventional synthetic zeolites. Further, by adjusting the silica/alumina molar ratio, any type of zeolite with high purity can be produced.

[Brief explanation of the drawing]

FIG. 1 shows SiO□/A1 obtained according to an example of the present invention.
．． 2 is a graph showing the relationship between the molar ratio of 03, the weight ratio of A-type, P-type, and X-type zeolites, and the yield ffi/Al□03.

Claims (3)

[Claims] (1) Finely pulverize coal ash, heat and crystallize it in an aqueous caustic solution, filter the solid matter from the reaction mixture, wash with water and dry it, and add the filtered filtrate to freshly pulverized coal ash. In addition, a method for producing zeolite characterized by recycling and using the silica/alumina while adjusting the molar ratio. (2) The molar ratio of silica/alumina in the reaction solution was set to 0.1.
2. The manufacturing method according to claim 1. (3) The molar ratio of silica/alumina in the reaction solution is 2 to 5.
The manufacturing method according to claim 1.