JPH08268709A - Production of layerlike alkali metal silicate - Google Patents

Abstract

PURPOSE: To produce a layerlike alkali metal silicate in an industrially advantageous condition in much shorter time compared to a conventional method. CONSTITUTION: At least one kind salt (B) selected from organic salts and inorganic salts is added to a water-containing amorphous product A of an alkali metal silicate having SiO2 /M2 O molar ratio of 1-10 (whereby M is an alkali metal) or its aqueous solution at 0.1-300wt.% ratio based on solids of the alkali metal silicate, and then the reaction product is heat-treated at 80-250 deg.C, thus the layerlike alkali metal silicate represented by a composition formula; M2 Six O2x+1 .yH2 O (whereby M is the alkali metal, (x) is a number in the range of 3.0-9.0 and (y) is a number of >=1), is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for producing a layered alkali metal silicate. More specifically, the present invention relates to a method for producing a crystalline alkali metal silicate having a layered structure efficiently in a short time and industrially advantageously.

[0002]

2. Description of the Related Art Crystalline alkali metal having a layered structure
Examples of silicates include disilicate (Na₂Si₂O
_Five), Macatite (Na₂Si_FourO₉・ 5H₂O), Islay
-Ait (Na₂Si₈O₁₇・ 10H₂O), Magadia
Ito (Na₂Si₁₄O₂₉・ 10H ₂O), Kenyaite
(Na₂Si₂₀O₄₁・ 10H₂O) etc. are generally known
There is. All of these are layered structures consisting of silicates only
And contains alkali metal ions between its layers,
From structural characteristics to ion exchangers, adsorbents, catalysts, etc.
Is expected to be applied. In addition, the above-mentioned layered alkaline gold
In the genus silicate, some or all of Na is other alkali gold.
Those that have been replaced by genus are also commonly called with the same substance name
There is.

In the field of application of such layered alkali metal silicates, the more exchangeable cations (Na ⁺ in the above-exemplified substances) existing between layers, the more (ie N).
The higher the a ₂ O / SiO ₂ molar ratio), the higher the function can be expected to be expressed. However, since these are often used in an aqueous solution, those having water solubility such as disilicate are more likely to be used. Layered alkali metal silicates such as macatite and ilaite, which are substantially unsuitable and therefore contain a relatively large amount of exchangeable Na ⁺ and are insoluble or sparingly soluble, are considered to be beneficial.

Macatite is a natural product of Kenya ["Am.
Mineral. 55, 358 (197)
0)] and Russia ["Dokl Akad Nauk
SSSR ", Volume 255, Page 971 (1980
Year)]. However, in order to use this macatite for the above-mentioned purpose, it is desirable that it has few impurities, but natural products have many impurities and are unsuitable.

Highly pure macatite can be obtained by synthesizing it. However, examples of actually synthesizing macatite have hitherto been synthesized by the hydrothermal reaction of SiO ₂ —Na ₂ O—H ₂ O system. "Z. Kristallogr."
Vol. 197, page 1 (1991)] and synthesized by adding diethanolamine [“Z. Krist”
allgr. 159, pp. 203 (198
Only 2 years)], and the synthesis conditions are unclear in the latter report. On the other hand, Aylerite is a substance that was first discovered by synthesis ["J. Col.
loid Sci. Volume 19, pp. 648 (19
64)], the synthesis conditions are also described in this report,
It is reproducible.

[0006] However, in the case of producing the macatite or the ironerite according to the above-mentioned synthesis example, there is a problem that the synthesis takes a very long time. For example, Eilerite takes at least a week and mcatite takes about a month. Thus, if the synthesis time is extremely long,
This causes an increase in the manufacturing cost of makatites and aylerites, making them difficult to use in the expected application fields.

By the way, S of the layered alkali metal silicate
In the iO ₂ —Na ₂ O—H ₂ O system hydrothermal reaction, it is the easiest and most effective to raise the temperature during crystallization in order to shorten the synthesis time. However, each layered alkali metal silicate has a specific “limit temperature” that can be synthesized, with Kenyaite at 240 ° C and Magadiite at 2 ° C.
Although it is possible to synthesize up to 00 ° C, it is believed that Iylerite is up to 120 ° C [Chem. Tech.] No. 39.
Vol., P. 459 (1987)]. Further, by analogy with this, it is possible to estimate that the limit temperature of macatite is 120 ° C. or lower.

Kenyaite and Magadiite are 100 ° C
Although a synthesis time of at least 1 month or more is required in the vicinity, crystallization can be performed within about tens of hours by synthesizing at 170 ° C. [“J. Ceram. So.
c. Japan "Vol. 100, p. 326 (198
2 years)].

On the other hand, a compositional formula M ₂ Si _x O _{2x +} 1.yH ₂ O (M in the formula is an alkali metal, x is a number of 3.0 to 9.0) centered on ironerite and macatite.
The production of the layered alkali metal silicate represented by (y is a number of 1 or more) has the above-mentioned limit temperature, so that it is not possible to shorten the synthesis time by increasing the crystallization temperature. It was impossible to inexpensively produce the layered alkali metal silicate represented by the above composition formula.

Various methods have been proposed as a method for producing a layered alkali metal silicate (Japanese Patent Laid-Open Publication No. Sho 6-96).
1-286215 gazette, Japanese Patent Publication No. 5-53729 gazette), and actually Na such as macatite and aylerite.
_No production examples for those having a high ₂ O content are disclosed. Incidentally, Japanese Patent Publication No. 5-53729 and Japanese Patent Laid-Open No. 61-
No. 286215 discloses a crystalline layered alkali in which an acidic compound is mixed with a water-soluble or amorphous alkali metal silicate and the temperature is kept at 70 to 250 ° C. until the layered alkali metal silicate is crystallized. Although a method for producing a metal silicate has been disclosed, in fact, even if such a method is used, it is not possible to produce a layered alkali metal silicate having a high Na ⁺ content such as macatite and ilaite in a short time. It was impossible.

[0011]

Under the circumstances described above, the present invention is intended to provide a method for producing a layered alkali metal silicate efficiently in a short time and industrially advantageously. It is a thing.

[0012]

The inventors of the present invention have conducted various studies on a method for producing a layered alkali metal silicate in a short time, and as a result, have found that the alkali metal silicate is hydrated amorphous or aqueous solution. By adding salt and treating it at a given temperature, it can be produced within 100 hours,
It has been found that the object can be achieved, and the present invention has been completed based on this finding.

That is, according to the present invention, (A) molar ratio SiO
₂ / M ₂ O (where M is an alkali metal) is a water-containing amorphous amorphous silicate of alkali metal silicate of 1 to 10 or at least 1 selected from (B) organic salt and inorganic salt. The composition is characterized in that the seed salt is added in a proportion of 0.1 to 300% by weight with respect to the solid content of the alkali metal silicate, and then the reaction mixture is heat-treated at a temperature of 80 to 250 ° C. formula _{M 2 Si x O 2x + 1} · yH 2 O (M in the formula is an alkali metal, x is the number of 3.0 to 9.0,
y is a number greater than or equal to 1) The present invention provides a method for producing a layered alkali metal silicate.

In the method of the present invention, as raw materials,
(A) A water-containing amorphous substance or aqueous solution of an alkali metal silicate is used. SiO ₂ contained in (A) of this raw material
And the ratio of M ₂ O (M is an alkali metal) is SiO ₂ / M
It is necessary that the ₂ O molar ratio be in the range of 1-10.
The upper limit of this molar ratio is set depending on the type of the desired layered alkali metal silicate, and for example, the proportion for producing macatite is 6 or less, preferably 4 or less, and 10 or less for producing Ilarite, It is preferably 8 or less. Further, if the molar ratio is less than 1, the crystallization time becomes long, and therefore, from the viewpoint of the crystallization time, the molar ratio is preferably 1.5 or more.

Examples of the alkali metal in the water-containing amorphous or aqueous solution of the alkali metal silicate include lithium, sodium, potassium, rubidium, and cesium. Among these, versatility and price of the product are mentioned. From the aspect, sodium and potassium are preferable.
In addition, one kind of these alkali metals may be contained, or two or more kinds thereof may be contained.

The water-containing amorphous or aqueous solution of the alkali metal silicate has a starting material of SiO ₂ / M ₂
The O molar ratio is not particularly limited as long as it has a desired value, but generally available water glass or a combination of an alkali metal hydroxide or carbonate aqueous solution and powder silica is used. It is advantageous from the point of view of production cost to prepare it by using such as.

If the water content of the water-containing amorphous or aqueous solution of this alkali metal silicate (value obtained by firing at a temperature of 800 ° C. for 1 hour) is too high, the water content after adjustment will be adjusted. Therefore, a large amount of energy is required, so that the range of 20 to 99.5% by weight is desirable.

In the method of the present invention, an organic salt or an inorganic salt is added to the water-containing amorphous or aqueous solution of the alkali metal silicate. As the organic salt and the inorganic salt, various ones can be used, but particularly alkali metals such as citric acid, tartaric acid, acetic acid, sulfuric acid, hydrochloric acid, hydrogen bromide, hydrogen iodide, thiocyanic acid, nitric acid, and chloric acid. Salt is preferable in terms of effect. These organic salts and inorganic salts may be used alone or in combination of two or more.

In the present invention, these organic salts and inorganic salts may be added in a proportion of 0.1 to 300% by weight with respect to the solid content of the water-containing amorphous or alkali metal silicate. is necessary. If the amount added is less than 0.1% by weight, the effect of adding salt will not be sufficiently exerted, and
If it exceeds 0% by weight, the effect is not improved for the amount, and it is substantially meaningless. From the viewpoint of the effect, the preferable addition amount of the salt is in the range of 0.1 to 100% by weight based on the solid content.

The method of adding the organic salt or the inorganic salt is not particularly limited, and may be added as a powder, or in the form of an aqueous solution in order to enhance the homogeneity of the reaction system. It may be added at room temperature or under heating. It is necessary to stir at the time of addition. When adding salt under heating, it is advantageous to add an effective device for condensing evaporated water vapor and returning it to the mixture, if necessary, so that abnormal thickening and solidification of the mixture do not occur. Is. When salt is added in a closed system, a self-generated pressure is generated in the container, so it is desirable to use a pump that can deliver liquid even under such conditions.

The water content of the hydrous amorphous substance or aqueous solution of the alkali metal silicate thus prepared and the organic salt or inorganic salt is adjusted as necessary. This adjustment of water content is carried out by adjusting H ₂ O / M ₂ O [M is (A) in the reaction mixture.
Alkali metal contained in component] molar ratio is 0.5 to 1
It is desirable to carry out so as to be in the range of 00. This molar ratio is appropriately selected according to the kind of the desired layered alkali metal silicate, and for example, in the case of producing macatite, 0.5 to
The range of 10 is preferable, while the range of 10 to 40 is preferable when manufacturing eyerite. This water content adjustment may be performed by any method and conditions, for example, simply heating, or a method utilizing spray drying or reduced pressure drying may be used. Further, by heating at the time of adjusting the water content, crystallization of the target substance may occur at the same time. In this case, the water content needs to be adjusted at a temperature of 250 ° C. or lower. If it exceeds 250 ° C, it is difficult to obtain the desired layered silicate.

The reaction mixture thus prepared is
By the heat treatment, the layered alkali metal silicate is obtained. This heat treatment needs to be performed at a temperature in the range of 80 to 250 ° C. If the heat treatment temperature is lower than 80 ° C, the treatment takes a long time, which is not practical.
If the temperature exceeds ° C, the desired layered silicate is difficult to be produced. To obtain the desired layered silicate efficiently in a short processing time,
The heat treatment temperature is preferably in the range of 90 to 200 ° C. This heat treatment may be maintained at a certain constant temperature, or the temperature may be gradually raised or lowered in some cases. Further, the material that has been heated during the above-mentioned water content adjustment can be directly transferred to this heat treatment. In this case, the water content adjusting step and the heat treatment step are inseparable, but the amount of water finally remaining in the mixture is H ₂ O / M ₂ O [M is contained in the component (A)] molar ratio Should be in the range of 0.5 to 100. This heat treatment can also be carried out with the reaction mixture under the flow of steam.

The time required for this heat treatment is determined by the degree of crystallization, but it can be completed within 100 hours at the longest, and usually within several tens of hours.

In order to promote crystallization, it is also effective to add a seed crystal of the desired layered alkali silicate to the above reaction mixture. This seed crystal is preferably added in an amount of 0.1 to 50% by weight, preferably 0.5 to 15% by weight, based on SiO ₂ contained in the alkali metal silicate. If the added amount is less than 0.1% by weight, the effect of addition is not sufficiently exhibited, and if the added amount exceeds 50% by weight, the effect is not improved for the amount, and it is rather economically disadvantageous. The seed crystals are preferably added after the salt is added to the reaction mixture. This is because if added before that, a part of the seed crystal will be dissolved and the effect as the seed crystal will not be exhibited. The addition of this seed crystal shortens the time required for crystallization.

The desired layered alkali metal silicate can be obtained by washing the reaction mixture thus heat-treated in water, separating it by solid-liquid separation and drying it. The solid-liquid separation method is not particularly limited, and any method may be used. Further, the drying treatment is preferably performed at a temperature of 120 ° C. or lower, because if the temperature is too high, the crystal structure changes and it is difficult to obtain the desired layered alkali metal silicate.

The layered alkali metal silicate thus produced can be converted into a layered silicic acid by acid treatment. This layered silicic acid is represented by the following composition formula (H ₂ O is omitted), for example, corresponding to the layered alkali metal silicate as the base. Layered alkali metal silicate → (acid treatment) → layered silicate Na ₂ Si ₄ O ₉ (macatite) → H ₂ Si ₄ O ₉ (acid type macatite) Na ₂ Si ₈ O ₁₇ (Ilarite) → H ₂ Si ₈ O ₁₇ (acid type eyelerite)

[0027]

According to the present invention, the layered alkali metal silicate can be industrially produced in a much shorter time than the conventional method. The layered alkali metal silicate obtained by the method of the present invention is, for example, an ion exchanger, an adsorbent,
It can be used as a catalyst. Further, by acid-treating this layered alkali metal silicon salt, it can be converted into a corresponding layered silicic acid, which can also be suitably used for various applications.

[0028]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. Note that powder X-ray diffraction was used to identify the crystal structure, and “Z. Krista” was used for macatite.
llgr. 197, pp. 1 (1991)
It was carried out in comparison with the measurement result described in “J. Colloid Sci.” Vol. 19, page 648 (1964). In addition, the composition analysis shows that the water content is 80
SiO ₂ / M ₂ O determined by ignition loss at 0 ° C for 1 hour
The molar ratio was determined by the fluorescent X-ray method.

Example 1 The SiO ₂ / Na ₂ O molar ratio was 3.07 and the solid content was 37.6.
10% by weight aqueous solution of sodium silicate (No. 3 water glass)
Add 0 parts by weight of sodium chloride to this while stirring.
77.5 parts by weight of an aqueous solution obtained by dissolving 7.5 parts by weight (47% by weight based on the solid content of the sodium silicate aqueous solution) was added. Next, the water content of this mixture was adjusted at 120 ° C. so that the total amount became 77.5 parts by weight. At this time H ₂ O
The molar ratio of / Na ₂ O (Na is derived from an aqueous sodium silicate solution) was 7. This mixture was placed in a stainless steel closed container and crystallized at a temperature of 120 ° C. for 48 hours, then discharged from the container, washed with water to separate solid and liquid, and dried at 50 ° C. The obtained powder has a composition of Na ₂ Si _3.9 O _8.8
It was 4.7 H ₂ O, and it was confirmed that it was mcatite together with the result of powder X-ray diffraction.

Example 2 SiO prepared from precipitated silica, KOH and NaOH
₂ / M ₂ O molar ratio is 2.5, M is a mixture of K and Na,
K ₂ O / Na ₂ O molar ratio 0.15, solid content 41% by weight
While stirring 100 parts by weight of the aqueous solution of alkali metal silicate, 100 parts by weight of an aqueous solution in which 15 parts by weight of sodium sulfate (47% by weight based on the solid content of the aqueous solution of alkali metal silicate) was dissolved was added. . Then, the mixture was adjusted to a water content at 120 ° C. and the H ₂ O / M ₂ O molar ratio was adjusted to 7.
It was set to 5. This mixture was put in a closed stainless steel container and crystallized at a temperature of 120 ° C. for 48 hours, then discharged from the container, washed with water and dried at 50 ° C. The obtained powder has a composition of Na _1.95 K _0.05 Si _4.0 O _9.0 / 5.
It was 0H ₂ O, and it was confirmed that it was macatite together with the result of powder X-ray diffraction.

Example 3 The procedure up to the point where the sodium chloride aqueous solution of Example 1 was added was the same, but the water content was not adjusted, and the solution was spread on a Teflon coated plate whose temperature could be adjusted. The temperature of the plate was raised from room temperature to 200 ° C in 40 minutes. Then, it was allowed to cool, cooled to room temperature, and the solidified product on the plate was recovered.
The amount of water in the solidified product is N derived from the alkali metal silicate.
Based on a ₂ O, the H ₂ O / Na ₂ O molar ratio was 6.5. Next, this solidified product was once dispersed in water, washed, filtered, and then dried at 80 ° C. The resulting powder composition is _{Na 2 Si 4.1 O 9.2 · 4.9H} 2 O, it is makatite was observed together with the results of powder X-ray diffraction.

Example 4 In Example 1, the water content was adjusted until the molar ratio of H ₂ O / Na ₂ O (Na is derived from an aqueous solution of sodium silicate) was 6. The obtained mixture was placed in a stainless steel container in which steam can flow, the steam temperature and the container temperature were set to 120 ° C., and crystallization was performed for 24 hours while circulating steam.
Thereafter, in the same manner as in Example 1, washing with water, solid-liquid separation, and drying were performed. The obtained powder has a composition of Na ₂ Si _3.9 O _8.8
It was 4.9H ₂ O, and it was confirmed that it was mcatite together with the result of powder X-ray diffraction.

Example 5 In Example 2, the mixture obtained after adjusting the water content contained 5% by weight of Example 1 based on SiO ₂ contained in the mixture.
The macatite obtained by the manufacturing method of 1. was added. Hereinafter, the same treatment as in Example 2 was performed except that the time required for crystallization was 10 hours. The obtained powder has a composition of Na _1.94 K.
_0.06 Si _4.1 O _9.2 · 5.0H was ₂ O, it is makatite was observed together with the results of powder X-ray diffraction.

Example 6 Using silica gel, NaOH and water, 100 parts by weight of a sodium silicate hydrate amorphous substance having a SiO ₂ / Na ₂ O molar ratio of 4.6 and a solid content of 58.5% by weight was prepared. 5.9 parts by weight of sodium sulfate (10% by weight based on the solid content of the sodium hydrate-containing amorphous substance) was mixed with this using a biaxial kneader. At this time, the molar ratio of H ₂ O / Na ₂ O (Na is derived from a sodium silicate hydrous amorphous substance) was 13.3. Place the mixture in a stainless steel closed container and press 120
Crystallization was carried out at a temperature of ℃ for 10 hours, then discharged from the container, washed with water and dried at 50 ℃. The obtained powder had a composition of Na ₂ Si _8.2 O _17.4 · 10.2H ₂ O and powder X
It was confirmed together with the results of the line diffraction that it was Ilarite.

Comparative Example 1 In Example 1, the aqueous solution of sodium chloride was not added, and the water content was adjusted in the same manner as in Example 1 until the H ₂ O / Na ₂ O molar ratio reached 7. This was placed in a stainless steel closed container, and crystallization was tried at 120 ° C. A part was taken out in the same 48 hours as in Example 1, washed with water, separated into solid and liquid, dried at 50 ° C., and the crystal structure was examined by X-ray diffraction. The rest was continued to crystallize at 120 ° C., and the progress of crystallization was examined in the same manner over time.
Although crystallization of the macatites was slightly observed in 20 days, 30 days were required to have the same crystallinity as in Example 1 (judged by the intensity of X-ray diffraction).

Comparative Example 2 To 100 parts by weight of the aqueous sodium silicate solution of Example 1, 109 parts by weight of silica gel was added in terms of dry weight to obtain SiO ₂ /
Sodium silicate water-containing amorphous substance having a molar ratio of Na ₂ O of 15 (solid content 70% by weight), sodium chloride 73 parts by weight (sodium silicate water-containing amorphous substance solid content 5
250 parts by weight of an aqueous solution containing 0% by weight) was added. Thereafter, the same treatment as in Example 1 was performed. The obtained product was magadiite by X-ray diffraction.

Comparative Example 3 Precipitated silica, NaOH and purified water were used for SiO ₂ / N.
300 parts by weight of an aqueous sodium silicate solution having a molar ratio of a ₂ O of 4 and a solid content of 29% by weight was prepared. Apart from this, 0.1
434 parts by weight of N-sulfuric acid was prepared and added to the above sodium silicate aqueous solution with stirring. Then, it was transferred to a stainless steel closed container and crystallized at 120 ° C. When observed after 1 week, no particle formation was observed.

Comparative Example 4 To 300 parts by weight of the same sodium silicate aqueous solution as in Comparative Example 3, 140 parts by weight of 1N sulfuric acid was stirred at 100 ° C. in a container equipped with a device for condensing evaporated steam and returning it to the reaction system. When added while adding, it turned cloudy and gelled. This gel was washed, solid-liquid separated, and then dried at 50 ° C. to obtain amorphous silica.

Claims (5)

[Claims] 1. A molar ratio of (A) SiO ₂ / M ₂ O (however,
(M is an alkali metal) 1 to 10 water-containing amorphous metal silicate of an alkali metal silicate or an aqueous solution thereof is added with at least one salt selected from (B) organic salt and inorganic salt. After adding 0.1 to 300% by weight to the solid content of acid salt, the reaction mixture was added to 80 to 25% by weight.
A compositional formula M ₂ Si _x O _{2x + 1} · yH ₂ O, wherein M is a heat treatment at a temperature of 0 ° C. (M in the formula is an alkali metal, x is a number in the range of 3.0 to 9.0, y is a number of 1 or more), the method for producing a layered alkali metal silicate. 2. The method according to claim 1, wherein the alkali metal M is sodium and / or potassium. 3. The molar ratio of H ₂ O / M ₂ O [M is an alkali metal contained in the component (A)] in the reaction mixture is 0.
The method according to claim 1 or 2, which is 5 to 100. 4. A seed crystal in the reaction mixture is 0.1 to 50% by weight based on SiO ₂ contained in the alkali metal silicate.
The method according to claim 1, 2 or 3, wherein the heat treatment is carried out by adding at a ratio of. 5. The method according to claim 1, wherein the organic salt and the inorganic salt are alkali metal salts.