KR860001488B1 - Method of preparation for microcrystalline zeolites - Google Patents

Abstract

Microcrystalline zeolite of less than 1 . is prepd. of a gel soln. by controlling the aging time and temp. The gel soln. of sodium silicate, sodium aluminate and caustic soda is aged below 30≰C for at least 10 hrs. and heated for crystallization at 90-110≰C for 0.5-5 hrs. The final compn. of the gel soln. is 2.5± (1.0) Na2O; 1.0 Al2O3; 1.8±(0.6) SiO2; 80±(20) H2O.

Description

Method for producing particulate zeolite

1 is a correlation curve showing the effect of aging time on the crystal size.

FIG. 2 (a) is a photograph (magnification 2000x) which taken the crystal | crystallization by the sample number 15-1 with the scanning electron microscope.

2 (b) is a photograph (magnification 4000 ×) of the crystal | crystallization by the sample number 15-1 taken with the scanning electron microscope.

3 (a) is a photograph (magnification 4000 ×) of the crystal | crystallization by the sample number 15-2 taken with the scanning electron microscope.

3 (b) is a photograph (magnification 6000 ×) of the crystal obtained by the sample number 15-2 taken with a scanning electron microscope.

4 (a) is a photograph (magnification 10,000 ×) which took the crystal | crystallization by the sample number 15-3 with the scanning electron microscope.

4 (b) is a photograph (magnification: 15,000 ×) which taken the crystal | crystallization by the sample number 15-3 with the scanning electron microscope.

5 (a) is a photograph (magnification 10,000x) which taken the crystal | crystallization by the sample number 16-4 with the scanning electron microscope.

5 (b) is a photograph (magnification 10,000 ×) of the crystal | crystallization by the sample number 15-4 rephotographing with the scanning electron microscope.

6 is a comparative diagram of the adsorption capacities of nitrogen and oxygen in Sample Nos. 15-1 and 15-4.

The present invention relates to a novel method for preparing particulate zeolite A having a particle size of 1 μm or less, which is most suitable as a detergent builder or adsorbent and catalyst for detergents, excluding low yield and high energy consumption in the conventional manufacturing method. The present invention has been completed by developing a simple yet economical synthesis method.

General methods for synthesizing zeolite A have been known for a long time. There are two examples.

(1) A method of obtaining zeolite A crystals by heating a predetermined amount of an alda acid soda solution, a silicate soda solution, and a caustic soda solution for a predetermined time.

(2) Activated using kaolin clay and heated in caustic soda solution to obtain zeolite A crystals.

In the above two methods, the method of (1) has a merit of synthesizing a zeolite with higher purity but higher purity of the raw material, and the method of (2) can use natural mineral as a raw material to produce at low cost. There is an advantage that it can be, but there is a disadvantage that the purity of the crystal, such as impurities contained in zeolite, such as iron contained in natural minerals. The conventional synthesis method only pays attention to the crystallinity or yield of the zeolite and little attention to the particle size of the bottom. Recently, however, as the application of zeolite A as a synthetic detergent builder attracts attention, it has been found that the zeolite A has various advantages, and thus, the synthesis of zeolite A having a fine particle size, in particular a particle size of 1 μm or less is required.

It has been known that the zeolite of particulates is advantageous because of its fast adsorption rate even in the application field of the adsorbent and catalyst, which has been used in the past, but the zeolite A synthesis of 1 μ or less is notable because of the 3-10 μ inlet. I did not receive it. In this situation, as the application of detergent builders began to grow, many overseas companies began to work on synthesizing particulate zeolite A of 1μ or less, and many invention patents have already been published. However, they may be crystallized by heating the silicate soda solution and the soda aluminate solution at the mixing ratio of low yield of zeolite A without instant mixing and then heating (Japanese Patent No. 56-56918 KK) Non-economical methods are known, such as using high slurry concentrations and excess caustic soda and requiring vigorous stirring (Japanese Patent No. 56-92113 CENTRAL SUPER KK).

In the present invention, a simple and economical synthesis method has been developed that eliminates such low yield and high energy consumption. That is, according to the present invention, it was found that the particle size of the crystal produced in the second step can be controlled by adjusting the temperature and reaction time of the first step by dividing the synthesis step of the zeolite A into two steps according to the conventional method of synthesizing zeolite A. It is. As a preliminary step, the synthesis of zeolite is carried out by mixing a solution of soda, sodium silicate and caustic soda in a mixture suitable for the desired zeolite type to make a uniform gel (GEL) solution first. When the gelling agent is reacted at a suitable temperature for a predetermined time, desired zeolite crystals are produced. However, in the present invention, before a crystal of zeolite is produced, a kind of atypical seed (species) or nucleus, which can be called as a parent, must be formed, and a crystal of zeolite is formed and grows around this nucleus to increase its particle size. I found out. Therefore, if the gel-like solution is treated in the first step under conditions that promote the formation of the nucleus but inhibit the formation of crystals, a larger number of nuclei can be formed. In this first step, not all reactants in the gelled solution form nuclei, but after a certain time, a specific equilibrium relationship is established between the nuclei and the reactant material. The gelled solvent, which has undergone the first step, is gradually heated in the second step and maintained at a temperature suitable for zeolite crystal formation, i.e., around 100 ° C. The nuclei begin to crystallize first, and the rest of the reactants in the gel solution begin to crystallize around the nucleus, and the crystals gradually grow in size, indicating the growth of crystals. The reaction is complete when all the reactants in the gel solution are determined. At this time, if the number of nuclei formed in the first step is large, a larger number of crystals are formed, and if the number is relatively small, a small number of crystals are formed. However, since the amount of the reactants in the gel solution is fixed, if the number of nuclei is too large, all the reactants are exhausted before the grain size of the crystal grows largely, and the growth of the crystal ends in the middle, thereby obtaining a small particle zeolite. On the other hand, if the number of nuclei is relatively small, crystals can grow, resulting in zeolite crystals of larger particle size. In other words, if the first stage is longer, more nuclei are generated, and the grain size of the crystal is smaller, and if the first stage is shorter, the number of nuclei formed is smaller, resulting in larger crystals. This has been demonstrated through experiments and the results are reported in the Examples.

In the present invention, it was found that the optimum condition of the first step is to leave the gel-like solution at room temperature, i.e., 25 ° C or lower. If this settling time is long, the number of nuclei formed increases and reaches parallel in 24 to 36 hours. The titration temperature of the second stage is around 100 ° C and the determination time is 30 minutes-5 hours.

These zeolite synthesis steps according to the present invention are shown below.

Example 1

318.4 g caustic soda (NaOH) was dissolved in 318 ml of water, a clear solution was obtained, heated to 100 ° C., and 312 g of aluminum hydroxide (Al (OH) ₃ ) was added slowly while stirring to dissolve. It became a clear solution and then cooled to room temperature to obtain a soda solution of alminate.

Next, 1700 ml of water was first charged into a 5 l container, and the above-mentioned soda solution was added thereto and diluted well.

While continuously stirring the above dilution solution, 960 g of the following industrial sodium silicate solution was slowly added thereto.

* Properties of Sodium Silicate Solution:

Specific gravity: 1.26

Silicate Concentration: 28.99%

(Si-10.5%)

SiO ₂ / Na ₂ O = 3.53

The addition of the sodium silicate solution took about 30 minutes. The gel solution thus obtained was well stirred and homogenized, and then divided into four containers and sealed. Their chemical composition was Na ₂ O: Al ₂ O ₃ : SiO ₂ : H ₂ O = 2.5: 1.0: 1.8: 80.0. These four gelled solutions were aged at room temperature for different periods as follows (first step: nucleation step).

During the ripening period they were stopped indoors and without stirring. At the end of each maturation, the mixture was transferred into a reactor equipped with a reflux condenser, a thermometer, and a stirrer and entered a second stage reaction (crystallization). The reactor was heated with slow stirring to stop stirring when it reached 100 ° ± 1 ° C. and maintained at this temperature for 3 hours. At the end of this crystallization step, the contents of the reactor were mixed with cold water, cooled, filtered to separate the mother liquor and crystals, and the crystals were washed with water and dried at 100 ° C. The decision thus obtained was tested and evaluated in the following manner.

X-ray diffraction curve analysis

Scanning electron microscopy

Adsorption capacity measurement

Ca ⁺⁺ ion exchange capacity measurement

These results are as follows.

(1) X-ray diffraction curve analysis

This test is to compare the purity and crystallinity of the synthetic crystals and took the x-ray diffraction curve from 2 ° angle to 5 ° to 35 °. As a result of examining the position of each peak (ie 2θ angle) in the X-ray diffraction curve, all four samples showed only the peaks of the A-type zeolite, and the presence of impurities was not found.

A comparison of the crystallinity of zeolites can be obtained by comparing the heights (ie, strengths) of the main peaks in the x-ray diffraction curve.

In other words, the higher the height, the larger the crystallinity is. However, since zeolite has strong hygroscopicity, moisture is absorbed in the air and its moisture content is likely to change. In addition, several of the major peaks vary in height depending on the moisture content of the zeolite, so that accurate comparison is difficult unless the moisture content of the test is the same. However, the following four peaks are known to be not affected by the moisture content of the A-type zeolite, and the crystallinity can be compared as the sum of these peak heights.

The sum of these peak heights of the four samples above is as follows.

From this result, Sample No. 15-4 seems to have the highest crystallinity, but it can be seen as approximately the same crystallinity as a whole.

(2) scanning electron micrograph

Photographs taken with a scanning electron microscope show the crystals of the zeolite and are ideal for measuring the particle size. Depending on the size of the particle size, the magnification was changed to 2000-x, 4000-x, 6000-x, 10,000-x or 15,000-x. Some of these are shown in FIGS. The crystal of A-type zeolite is a regular cubic tongue, and its particle diameter is conventionally expressed as the length of one side of a cube. The particle diameters of the various crystals in the picture were measured and averaged to determine the particle size of the sample. These results are shown in the following table and FIG.

As a result, the particle size of the zeolite crystal is directly related to its ripening time (first stage). That is, the shorter the aging time, the larger the grain size, and the longer the aging time, the smaller the particle size. When the aging time is about 22 hours or more, the particle diameter no longer becomes about 1 μm.

(3) adsorption capacity measurement

The crystallinity of zeolite can be compared also by measuring the adsorption capacity. As a result of measuring and comparing the adsorption amount of nitrogen and oxygen in numbers 15-1 and 15-4 of the above samples, it was found that they have similar adsorption capacity. This adsorption capacity was measured by the BET adsorption test method (volume welding).

(4) Ca ⁺⁺ ion exchange capacity measurement

This test is a measure of Ca ⁺⁺ ion removal power that causes water hardness as directly related to its application as a type A zeolite synthetic detergent builder.

The measurement of Ca ⁺⁺ ion exchange capacity was followed as follows. (Ca ⁺⁺ ion exchange capacity measurement method)

First, a CaCl ₂ solution of 300 mg / 1 was converted to CaO, and 0.500 g of purified and dried zeolite crystals were added to 500 ml of the solution, followed by stirring at 30 ° C. for 20 minutes. The zeolite was then separated by filtration to determine the concentration of Ca ⁺⁺ ions remaining during filtration.

Initial concentration and ion exchange of Ca ⁺⁺ were measured.

The Ca ⁺⁺ ion exchange capacity measurement results are as follows.

The Ca ⁺⁺ ion exchange capacity measurement results of the samples according to the present invention are compared with the Ca ⁺⁺ ion exchange capacity of the zeolite according to the prior art.

Comparison

It can be seen from the Ca ⁺⁺ ion exchange capacity that the samples according to the present invention have excellent crystallinity. Therefore, Ca ⁺⁺ ion exchange capacity as a builder for synthetic detergents is sufficient.

Claims (2)

In preparing the particulate zeolite, the sodium silicate, sodium phosphate and caustic soda solutions were prepared using 2.5 ± (1.0) Na ₂ O.1.0Al ₂ O _3. 1.8 ± (0.6) SiO ₂ . Mix to obtain a composition of 80 ± (20) H ₂ O to obtain a uniform gel solution, and then aged at 30 ° C or lower for 10 hours or more and heated to 90-110 ° C for 30 minutes to 5 hours at this temperature. A method of producing A-type zeolite crystals having fine particles of 1 μm or less. The method of claim 1, wherein the aging conditions, the fine crystalline zeolite of less than 1μ characterized in that aged for at least 16 hours at 307 or less.

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