JPS6049130B2 - Manufacturing method of A-type zeolite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing type A zeolite comprising crystal grains with uniformity and rounded particle surfaces.

It has been known for a long time that zeolite (crystalline sodium aluminosilicate) has ion exchange ability, and recently progress has been made to develop applications using this as a builder for detergents. General formula [(1,O±0.2)Na20
-A120s・(20±0.5)SiO2・F(0~
5) Type A zeolite represented by H20] is also a type of zeolite, but it is generally produced by mixing solutions of each component to form an amorphous aluminosilicate gel (hereinafter simply referred to as "gel"). It is based on a method of precipitating and crystallizing this. 5. The production of zeolite depends on many factors such as the raw material solution concentration, molar ratio (Siq/A1.O.), gel production method, aging temperature, aging time, etc.
Many manufacturing methods have been proposed in which various combinations of these factors are used depending on the intended use. Type A zeolite is a crystal that originally belongs to an equiaxed crystal system, so its particle shape tends to be a typical cube, and those produced using conventional methods are mostly composed of square, dice-shaped crystal particles. It's on.

However, type A zeolite, which is made up of angular crystal grains, is generally inferior in purity and various properties compared to type A zeolite, which is made up of spherical or rounded crystal particles. It is desired to establish a method for producing type A zeolite consisting of: In particular, when used as a detergent builder, A-type zeolite, which has angular crystal particles, has the disadvantage that it tends to form aggregate particles due to secondary aggregation, and deposits on clothes are noticeable during washing, and fundamental improvements are needed. is desired. In addition, uniform primary particles are desired in various fields of use due to their favorable particle characteristics. The present inventors conducted various experiments on a method for producing A-type zeolite by reacting a sodium silicate aqueous solution and a sodium aluminate aqueous solution to produce an aluminosilicate gel, and then aging and crystallizing the gel.・As a result of repeated research, it has been found that type A zeolite, which consists of uniform crystal particles with rounded particle surfaces, can be efficiently obtained by carrying out the reaction between an aqueous solution of sodium silicate and an aqueous sodium aluminate solution under specific conditions. They discovered this and completed the present invention.

That is, the present invention is a method for producing A-type zeolite by reacting a sodium silicate aqueous solution and a sodium aluminate aqueous solution to produce an aluminosilicate gel, and then aging and crystallizing the gel. The method for producing A-type zeolite is characterized in that a gel is obtained by a continuous reaction in the absence of a zeolite, and then the obtained gel is aged and crystallized in a forced diffusion state.

The raw materials used in the production method according to the present invention are an aqueous sodium silicate solution and an aqueous sodium aluminate solution, and their concentrations are preferably in the following ranges. Sodium silicate aqueous solution: Na
2O5~20% SiO25~20
% Sodium aluminate aqueous solution: Na2O25-15%
Al2O35-15% One of the important requirements in the production method of the present invention is the gel preparation method in the reaction of mixing a sodium aluminate solution and a sodium silicate solution to obtain an amorphous aluminosilicate gel.

That is, the first feature is that a uniform gel is prepared by continuously and completely combining a sodium aluminate aqueous solution and a sodium silicate aqueous solution without back-mixing.

For this purpose, the present invention uses a tubular static mixing device, a centrifugal pump, etc., into which a sodium aluminate aqueous solution and a sodium silicate aqueous solution are simultaneously injected to continuously prepare a uniform gel. A reaction without back mixing means that when a reaction is carried out by mixing liquids A and B, the reaction is always carried out by direct contact and mixing of liquids A and B in the reaction system. means the state of being

In general, such conditions can be achieved by rapidly introducing both reaction solutions into a small volume reaction system with a strong stirring effect and by quickly discharging the reaction products from the system (i.e., extremely (by complete mixing of both reaction solutions within a short residence time), but in the case of the present invention, the average residence time in the reaction system or mixing device as defined below is less than or equal to about 108 It is desirable that this is the case, and it is necessary that complete mixing be carried out during this period.

Reactions under such conditions can be carried out by introducing liquids A and B into a reaction system in which a significant amount of reaction products have already accumulated, or by introducing liquids B or A into liquid A or B. This is essentially different from a reaction that involves gradual addition and mixing (reaction that involves no backmixing).

In the latter reaction (reaction involving back mixing), both liquids A and B are mixed with the reaction products and have some influence on the concentration of the liquid, the particle state of the products, etc. This is because they come into contact with each other and react.

Note that JP-A-50-7028 describes a method for preparing a gel by simultaneously adding a sodium silicate solution and a sodium aluminate solution, but this method is a batch method in which mixing is performed by applying shearing force for a long time. Therefore, this method involves back mixing and is essentially different from the manufacturing method of the present invention.

In the method of the present invention, a small-volume mixing device that exhibits a strong stirring effect is used as a reactor in order to carry out the reaction continuously without back-mixing. Preferably, a device, centrifugal pump or the like is used.

The reaction is carried out by simultaneously injecting a sodium silicate aqueous solution and a sodium aluminate aqueous solution into these reactors and passing them through the reaction system.The average residence time θ (seconds) in the reaction system at that time is expressed by the following relationship It can be calculated based on the formula.

θ=Maki 7 a+b where v is the volume of the reactor ('), and a and b are the injection rates ('/sec) of the sodium silicate aqueous solution and the sodium aluminate aqueous solution, respectively.

In the method of the present invention, the quantitative ratio of the sodium aluminate aqueous solution and the sodium silicate aqueous solution to be injected into the reactor is 2.2.
5 or less, preferably 1.0 to 2.0. In this case, the lower the value of the molar ratio (SiO2/AI2O3), the easier it is to obtain rounded crystal particles that are close to spherical.
Molar ratio (SlO2/Al.

If O3) is less than 0.5, the slurry concentration of the reaction product will be low, and the efficiency of production will decrease accordingly, which is not preferable. The reaction temperature when preparing the gel, that is, the temperature of the sodium silicate aqueous solution and the sodium aluminate aqueous solution, does not need to be particularly limited and may be appropriately selected depending on the desired particle size of the A-type zeolite.

Generally, the higher the reaction temperature, the higher the activity of the gel produced.
Crystallization due to subsequent aging also tends to be completed in a shorter time, and the particle size of the resulting zeolite tends to be larger. The gel thus obtained is aged as it is for immediate crystallization. The second feature of the present invention is that the ripening for crystallization is performed in a forced diffusion state. The forced diffusion state refers to dispersing particles violently or forcibly by a method other than normal stirring and mixing, for example, at a rotation speed of 1000 R. P. Examples of operations include high-speed stirring of M or higher, ultrasonic vibration, shearing force, and wet grinding.
Of course, such a forced diffusion state may be maintained throughout the entire time required for crystallization by aging of the gel, and may also be maintained for a period of time.

Further, the operation to support this forced diffusion may be incorporated into normal stirring and mixing. The aging conditions during this time vary depending on the operation and reaction conditions to be used, but generally a range of 1 to 10 hours at 50 to 150°C is appropriate. In this case, when the temperature is low, the crystallization time becomes longer and the particles tend to become smaller. After crystallization, the mother liquor is separated and removed from the zeolite slurry by filtration, washed by a conventional method, and then dried and pulverized as necessary to obtain a product. On the other hand, the mother liquor separated in this step is an aqueous solution whose main component is caustic soda, and in the present invention,
This mother liquor can be reused cyclically in the raw material system, if necessary concentrated. That is, it can be used as a liquid for preparing a sodium aluminate aqueous solution and/or a sodium silicate aqueous solution.

The A-type zeolite produced by the method according to the present invention has crystal grains with rounded and smooth surfaces and has an average particle size of 0.
5 to 5μ, and the width of the particle size distribution is narrow and substantial.

The above can be confirmed by observing individual crystal grains using electron micrographs, which show that they are spherical or extremely rounded without sharp apexes or ridges, and at the same time, the particle size distribution is extremely uniform. It will be done.

The A-type zeolite made of rounded crystal particles according to the present invention generally has high purity and excellent ion exchange ability, and also has dispersibility and suspension stability in aqueous solutions such as silicate sorg and surfactants. Because of its excellent properties, it is most suitable as a builder for detergents, and can be particularly effectively used as type A zeolite for the preparation of zeolite slurry for detergents (Japanese Patent Application Laid-Open No. 54-64504, etc.).

As described above, the A-type zeolite according to the present invention is composed of crystal grains with rounded surfaces, has a uniform particle size distribution, and has various excellent properties. In addition, the manufacturing process is based on a continuous reaction, and the mother liquor can be circulated and used.The equipment is compact and consumes little energy, and products of constant quality can be efficiently obtained with short reaction time and aging time. It is of high value. below,
This will be explained in detail using examples. Example 1 Sodium silicate aqueous solution (Na2O8.1%, S) 026.6
%) and aqueous aluminate sorg solution (Na, O9.3%, A
The molar ratio of the reaction system (SlO, /Al, O3) is 1.8 and 2.0, respectively, through a pump.
Aluminosilicate gel was generated by instantaneous complete mixing without back mixing by simultaneously and continuously injecting the gel into a static mixer (a type of tubular static mixing device manufactured by Nippon Toki Co., Ltd.) in a quantitative ratio such that Ta.

However, the average residence time of the contents in the static mixer during the reaction was 1. The temperature of each raw material aqueous solution was 80°C. The reaction product continuously flowing out from the static mixer was collected in fixed amounts into a receiver. The gel-like reaction product thus obtained by the reaction at each molar ratio was placed in a container equipped with a stirrer and an ultrasonic oscillator, and heated at 80°C under moderate stirring and ultrasonic vibration (25 KHz). After heating for 2 hours, a highly fluid slurry consisting of fine particles of crystallized type A zeolite and an alkaline solution was obtained. The zeolite in this slurry is separated from the mother liquor by filtration and washing, then dried and pulverized.
The substance content, particle shape, particle size distribution, Ca ion exchange capacity, etc. were measured using a line diffraction, an electron microscope, a sedimentation method particle size distribution analyzer, etc., and the results shown in Table 1 were obtained. When looking at the obtained zeolite with an electron microscope, for example, the raw material molar ratio (Si
When O2/Al2O3) is 1.4, the zeolite is
Zeolite, which is a spherical particle and has a size of 2.0, is composed of cubic crystals with rounded corners and a particle size of 2 to 3p, and is made up of uniform particles with an extremely sharp particle size distribution. Furthermore, each particle exists separately from other particles, and no secondary aggregation is observed, indicating good dispersibility.Example 2 Mol of SlO2/Al,O3 obtained in Example 1 Ratio 2.0
The gel was aged under the same conditions as in Example 1 except that a homogenizer (Kokusan Seiko Co., Ltd. No. 1 machine) was incorporated and the gel was passed through the homogenizer with a shearing force of 350 kg/Clt. A slurry was obtained. Next, the mother liquor was separated and the physical properties of the obtained fine particles were examined. As a result, the particles had a uniform roundness with a very narrow particle size distribution similar to that of Example 1. They were zeolite type particles.

Example 3 The same sodium silicate aqueous solution and sodium aluminate aqueous solution used in Example 1 were each added at 340 mL/Mi.
Centrifugal pump (Iwaki Magnet Pump MD-
By simultaneously and continuously injecting into the suction port of 15),
An aluminosilicate gel was produced by instantaneous complete mixing without back mixing.

Claims (1)

[Claims] 1. A method for producing A-type zeolite by reacting an aqueous sodium silicate solution and an aqueous sodium aluminate solution, according to the following formula θ=V/(a+b) [where θ is the average residence time (seconds), a and b represent the injection rate (l/sec) of the aqueous sodium silicate solution and the aqueous sodium aluminate solution, respectively, and V represents the volume (l) of the reactor] for back mixing with an average residence time of about 10 seconds or less. Production of A-type zeolite, which is characterized by producing a gel by continuously reacting a sodium silicate aqueous solution and sodium aluminate in a free state, and then aging and crystallizing the obtained gel in a forced diffusion state. Law. 2. A method for producing A-type zeolite according to claim 1, characterized in that a sodium silicate aqueous solution and a sodium aluminate aqueous solution are gelled at a molar ratio SiO_2/Al_2O_3 in the range of 0.5 to 2.5. . 3. The method for producing type A zeolite according to claim 1 or 2, wherein the continuous reaction without back mixing is carried out using a tubular static mixing device. 4. A according to claim 1, wherein the forced diffusion state is achieved by applying at least one of high-speed stirring, ultrasonic vibration, shearing force, or wet grinding.
Method for producing type zeolite. 5. The method for producing type A zeolite according to claim 1 or 4, wherein the forced diffusion state is the entire time during which the gel matures and crystallizes. 6. Claim 1 or 4, characterized in that the forced diffusion state is a part of the time during which the gel matures and crystallizes.
Method for producing type A zeolite as described in Section 1. 7. A-type zeolite according to claim 1, 4, 5, or 6, characterized in that crystallization by aging of the gel is performed by stirring and mixing and forced diffusion. manufacturing method.