JPH04254409A - Production of hydroxysodalite - Google Patents

Abstract

PURPOSE:To efficiently produce hydroxysodalite by a simple operation in a short time without transforming zeolite having a metastable phase into hydroxysodalite having a stable phase by phase transition requiring a large quantity of heat energy and a long time. CONSTITUTION:An aq. sodium hydroxide soln. contg. aluminate ions is mixed with an aq. sodium hydroxide soln. contg. silicate ions at 40-100 deg.C to preferentially form hydroxysodalite.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for obtaining hydroxysodalite in a simple manner and in good yield.

0002

[Prior Art] As is well known, sodalite is a crystal having pores with an effective diameter of more than 2 Å, consisting of a six-membered oxygen ring, and can be used for the inclusion of various gases (for example, hydrogen and radioactive krypton). .

In other words, if various gases are forcibly adsorbed into hydroxysodalite molecules under high temperature and high pressure conditions, even if the temperature is lowered and the pressure lowered, the gases clathrated within the molecules will not be desorbed, so hydrogen gas will not be absorbed. It can be effectively used for storing radioactive gases such as krypton or isolating radioactive gases such as krypton.

[0004] Hydroxysodalite is a type of aluminosilicate, and is usually produced by heating and aging aluminosilica gel in an aqueous sodium hydroxide solution, and this method is similar to the method for producing synthetic zeolite.

[0005] By the way, the production technology for type A zeolite is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-275016, in which hydroxysodalite is recognized as a by-product, and the main focus is to suppress the by-product. It becomes.

The difference between various synthetic zeolites including type A and hydroxysodalite is that their phase form is thermodynamically metastable or stable. Efforts have been focused on how to efficiently generate metastable phase crystals.

On the other hand, regarding the production of hydroxysodalite, for example, "Zeolite and Its Utilization" (edited by Zeolite and Its Utilization Editorial Committee, published by Gihodo in December 1968)
As described in page 13 of 1999 (Published on May 1st), a common method for producing aluminosilica gel is to treat it in a highly concentrated aqueous sodium hydroxide solution.

More specific production conditions include adding colloidal silica to an aqueous sodium hydroxide solution in which aluminum is dissolved, and forming Na2O:Al2O3:SiO2:H2
With a composition ratio of O = 10:0.2:1:200 (molar ratio), it takes 120 to 180 hours at 80℃, 3 to 96 hours at 90℃, and 2.5 to 8 hours at 100℃. It has been reported that hydroxysodalite can be obtained as the main component by heating and ripening each (Pang Weign).
et al. :New Developments
in Zeolite Science and Te
Chnology、Proceeding of th
e 7th International Zeoli
te Conference, Tokyo, August
t 17-22, 1986), or pre-synthesized A
It is reported that when A-type zeolite is heated at 85°C for 1 hour in an 80 mol/liter aqueous sodium hydroxide solution in the presence of a small amount of hydroxysodalite seed crystals, about 90% of A-type zeolite is converted to hydroxysodalite. (E. Grujic et al., Zeolite:
Fact Figures Future P. 261
, 1981, Elsevier Science Pu.
blishers B. V. Amsterdam) etc.

[0009]

[Problems to be Solved by the Invention] As mentioned above, in the conventional hydroxysodalite production technology, metastable phase zeolite is created during the production process, and then a stable phase of hydroxysodalite is produced by high temperature and long-term treatment. It performs a transformation (phase transition).

Although the conversion rate increases in proportion to the processing time, the conversion speed gradually slows down as the conversion rate increases, and it takes a very long time to achieve 100% conversion.

[0011] A possible reason for this is that this transformation is a solid phase-solid phase transition, and microscopically the formation of the crystal constituent atoms must be rearranged. Furthermore, when attempting to supply the energy necessary to promote this type of conversion reaction with thermal energy, it is unavoidable that a considerable amount of energy loss will occur.

Furthermore, in the conventional zeolite synthesis method, it is customary to mix an aluminate solution and a silicate solution to once form a gel, and then heat and age it to obtain zeolite crystals. Visually, the solid-phase product precursors formed in solution at the initial stage of the reaction lose their fluidity and become gel-like, forming a state in which their positions are restrained, and then gradually over a long period of time. The desired zeolite crystals are grown.

This method is effective as a method for obtaining zeolite, which is a metastable phase, as the final product, but when attempting to obtain hydroxysodalite as the final target, the process is as follows: mixed solution → gel formation → zeolite crystals It is not an efficient method because heat energy must be continuously applied for a long time during the entire process of step-by-step conversion from growth to hydroxysodalite.

The present invention was made in view of the above-mentioned circumstances, and its object is to produce a mixture of an aluminate aqueous solution and a silicate aqueous solution without passing through a gel or metastable phase zeolite. The present invention aims to provide a method by which hydroxysodalite crystals can be obtained directly in high yield.

[0015]

[Means for Solving the Problems] The structure of the production method of the present invention that can solve the above problems is that a sodium hydroxide aqueous solution containing aluminate ions and a sodium hydroxide aqueous solution containing silicate ions are mixed in a liquid solution. The gist is that the mixture is mixed to a temperature of 40 to 100°C, and heated within this temperature range for 5 minutes to 10 hours.

The aluminate ion-containing sodium hydroxide used here has an aluminate ion concentration of 0.
The silicate ion-containing sodium hydroxide aqueous solution preferably has a silicate ion concentration of 0.005 to 2 mol/liter. Further, it is preferable to adjust the sodium concentration of each of these aqueous sodium hydroxide solutions so that when both solutions are mixed, the sodium ion concentration in the mixed solution is 0.1 to 8 mol/liter.

[0017]

[Operation] The present inventors have been able to directly produce hydroxysodalite using an aluminate aqueous solution and a silicate aqueous solution as raw materials without going through a gel or metastable phase zeolite using the prior art as described above. We wondered whether this would be possible, and conducted various experiments focusing on the concentration of the raw material aqueous solution, the reaction temperature, the type of salt, etc.

As a result, a sodium hydroxide aqueous solution containing aluminate ions and a sodium hydroxide aqueous solution containing silicate ions were used as raw materials, and the temperature at the time of mixing was 40 to 10.
If the temperature of each aqueous solution is adjusted to 0℃ before mixing, hydroxysodalite will be preferentially generated immediately after mixing without generating metastable phase zeolite, and it will last for 5 minutes to 10 hours in this temperature range. It was confirmed that hydroxysodalite can be produced in good yield simply by holding the sample.

That is, when the temperature at the time of mixing the above two types of aqueous solutions is set to room temperature (around 25° C.), aluminosilica gel is formed in the initial stage, and from the aluminosilica gel, the phase progresses to metastable phase zeolite and then to hydroxysodalite. Although long-term heating is required to achieve the transition, simply by setting the temperature during mixing between 40 and 100°C, hydroxysodalite is produced preferentially from the early stage of the reaction, and alumino-silica gel and metastable phase zeolite are produced as secondary components. Hydroxysodalite can be obtained in high yield without any oxidation.

[0020] In the present invention, it is sufficient that the liquid temperature when both aqueous solutions are mixed falls within the above range, and it is not necessary to set the temperatures of each aqueous solution to the same temperature in advance. It is also possible to bring the liquid temperature during mixing into the above range by heating the solution, but it is better to heat both aqueous solutions to a predetermined temperature and then mix them, since the hydroxysodalite production reaction will occur throughout the entire process. This is advantageous because it progresses quickly.

At this time, if the temperature at the time of mixing is less than 40°C, aluminosilica gel is preferentially produced as described above, so the intended purpose of the present invention cannot be achieved, and even if the mixing temperature exceeds 100°C, hydroxyl The preferential production reaction of sodalite is not accelerated any further, and it is rather impractical from the viewpoint of operability, thermal energy economy, etc.

The holding time in the above temperature range is preferably 5 minutes to 10 hours; if it is less than 5 minutes, the production rate of hydroxysodalite will not increase sufficiently; on the other hand, if the holding time exceeds 10 hours, it will be too short. Even if it is extended, the production rate will not increase any further, so it is useless.

As mentioned above, the preferential production reaction of hydroxysodalite is most influenced by the temperature during mixing, but in order to proceed with this reaction more efficiently, aluminate ion-containing sodium hydroxide aqueous solution The concentration of ions is 0.005 to 0.5 mol/liter, more preferably 0.01 to 0.4 mol/liter, and the concentration of silicate ions in the silicate ion-containing sodium hydroxide aqueous solution is 0.005 to 2. mol/liter, more preferably 0.05 to 1 mol/liter, and
Sodium ion concentration in the solution after mixing is 0.1 to 8
mol/liter, more preferably 0.5 to 5 mol/liter
It is desirable to adjust the sodium ion concentration of each aqueous sodium hydroxide solution so that the concentration is within the range of liters.

If the concentration of the aluminate ions and silicate ions is too low, the reaction rate for producing hydroxysodalite is slow, and even if heated for a long time at a considerably high temperature, it is difficult to obtain only a small amount of hydroxysodalite, and conversely, the concentration is too low. If is too high, gelation may occur immediately after mixing the two liquids, fluidity may be lost, and phase transition may become difficult, and the amount of hydroxysodalite produced tends to decrease.

Furthermore, if the sodium ion concentration in the mixed solution is too low, gelation tends to occur, making it difficult for the hydroxysodalite production reaction to proceed sufficiently, while if it is too high, the solubility of aluminic acid and silicic acid increases. Therefore, the solution itself becomes stable and precipitation of aluminosilicate compounds no longer occurs even when heated.

The method of mixing both aqueous solutions is not limited at all, but the most common method is to heat each aqueous solution to a predetermined temperature and then combine them all at once and stir and mix. After mixing, the temperature is maintained at the above temperature range for a predetermined period of time, and the precipitates formed are collected by filtration.
After washing and drying, high purity hydroxysodalite is obtained.

[0027]

[Example] Example 1 Sodium silicate (Lot.SAQ373 manufactured by Wako Pure Chemical Industries, Ltd.)
9) [Na2O: 19.4%, SiO2: 58.2%
] and 2.2 g of sodium hydroxide manufactured by the same company were added to 39.6 g of water and heated at 70° C. for 10 minutes to prepare a transparent aqueous sodium hydroxide solution containing silicate ions.

On the other hand, sodium aluminate (Lot. 308D1442) manufactured by Kanto Kagaku Co., Ltd. [Na2O: 33.2
%, Al2O3: 36.3%] and 4.4 g of sodium hydroxide manufactured by Wako Pure Chemical Industries, Ltd. were added to 59.6 g of water and heated at 70°C for 10 minutes to form a transparent hydroxide containing aluminate ions. A sodium aqueous solution was made.

Both aqueous solutions obtained above were combined while still hot and mixed (total volume of the mixed solution was approximately 100 ml, silicate ion concentration =
0.12 mol/liter, aluminate ion concentration = 0
．． 12 mol/liter, sodium ion concentration=1.
9 mol/liter, liquid temperature 70°C), the temperature was immediately raised to 90°C, and stirring was continued at the same temperature for 2 hours. During this time, a white precipitate was formed and the liquid volume decreased to about 60 ml due to evaporation of water.

[0030] The formed precipitate was collected by filtration, washed with water and dried.
Identification by line diffraction revealed that it was hydroxysodalite. This X-ray diffraction chart is shown in FIG. 1, and a scanning electron micrograph showing the crystal structure is shown in FIG.

Example 2 2.53 g of sodium silicate (same as before) manufactured by Wako Pure Chemical Industries, Ltd. and 7.02 g of sodium hydroxide manufactured by Wako Pure Chemical Industries, Ltd.
g of water and heated at 70°C for 20 minutes to prepare a transparent aqueous sodium hydroxide solution containing silicate ions.

On the other hand, 0.66 g of sodium aluminate (same as above) manufactured by Kanto Kagaku Co., Ltd. and 7.08 g of sodium hydroxide manufactured by Wako Pure Chemical Industries, Ltd. were added to 34.4 g of water, and the mixture was heated at 70°C for 2 hours.
The mixture was heated for 0 minutes to produce a transparent aqueous sodium hydroxide solution containing aluminate ions.

Both solutions obtained above were combined while still hot and mixed (the total volume of the mixed solution was approximately 100 ml, silicate ion concentration = 0).
．． 24 mol/liter, aluminate ion concentration=0.
047 mol/liter, sodium ion concentration=3
．． 8 mol/liter, liquid temperature 70℃), 90 at the same temperature
Heated for a minute.

The produced white precipitate was collected by filtration, washed with water and dried, and then identified by X-ray diffraction, and was confirmed to be hydroxysodalite. An X-ray diffraction chart of this product is shown in FIG.

Comparative Example 1 1 containing 0.12 mol/liter of aluminate ion
．． 44 mol/liter sodium hydroxide aqueous solution 5m
1 (room temperature) and 5 ml (room temperature) of a 0.60 mol/liter aqueous sodium hydroxide solution containing 0.56 mol/liter silicate ions and heated to the same temperature (room temperature, approximately 25°C).
) (aluminate ion concentration=0.06 mol/liter, silicate ion concentration=0.28 mol/liter, sodium ion concentration=1.02 mol/liter), a white precipitate was immediately formed. 2 at room temperature
After standing for a day, the precipitate was collected by filtration, washed with water, dried, and then identified by X-ray diffraction. As a result, it was found to be amorphous with almost no formation of hydroxysodalite. A scanning electron micrograph showing the structure of this precipitate is shown in FIG.

Comparative Example 2 1 containing 0.06 mol/liter aluminate ion
．． 17 mol/liter sodium hydroxide aqueous solution 5m
1 (room temperature) and 5 ml (room temperature) of a 2.16 mol/liter aqueous sodium hydroxide solution containing 0.38 mol/liter silicate ions and heated to the same temperature (room temperature, approximately 25°C).
) When mixed with (aluminate ion concentration = 0.023
mol/liter, silicate ion concentration=0.19 mol/
liter, sodium ion concentration=1.67 mol/liter), a gel-like precipitate was immediately formed. When this precipitate was heated at 65° C. for 4 hours, it remained amorphous and no formation of hydroxysodalite was observed.

[0037]

Effects of the Invention The present invention is constructed as described above, and the aqueous sodium hydroxide solution containing aluminate ions and the aqueous sodium hydroxide solution containing silicate ions are mixed not at room temperature but at a temperature range of 40 to 100°C. By mixing, hydroxysodalite can be preferentially produced without producing gel-like substances or metastable phase zeolite, and hydroxysodalite can be efficiently produced with extremely simple and short processing time. became.

[Brief explanation of the drawing]

FIG. 1 is an X-ray diffraction chart of hydroxysodalite obtained in Example 1.

FIG. 2 is a scanning electron micrograph used as a drawing showing the crystal structure of hydroxysodalite obtained in Example 1.

FIG. 3 is an X-ray diffraction chart of hydroxysodalite obtained in Example 2.

FIG. 4 is a scanning electron micrograph used as a drawing showing the crystal structure of the precipitate obtained in Comparative Example 1.

Claims (2)

[Claims] Claim 1: A sodium hydroxide aqueous solution containing aluminate ions and a sodium hydroxide aqueous solution containing silicate ions are mixed so that the liquid temperature at the time of mixing is 40 to 100°C, and the mixture is heated in this temperature range for 5 minutes. A method for producing hydroxysodalite characterized by heating for ~10 hours. Claim 2: The concentration of aluminate ions is 0.005.
A sodium hydroxide aqueous solution containing aluminate ions with a concentration of ~0.5 mol/liter and a silicate ion concentration of 0.0
Using an aqueous silicate ion-containing sodium hydroxide solution having a concentration of 0.05 to 2 mol/liter, and mixing the above-mentioned aqueous sodium hydroxide solutions, the sodium ion concentration in the mixture becomes 0.1 to 8 mol/liter. 2. The method for producing hydroxysodalite according to claim 1, wherein the sodium ion concentration of each aqueous sodium hydroxide solution is adjusted accordingly.