KR20030091263A - A process for manufacturing NaX zeolite by continuous crystallization method - Google Patents

Abstract

PURPOSE: A preparation method of NaX zeolite by continuous crystallization is provided to prepare a well developed single phased NaX zeolite crystal by continuously growing crystal of zeolite through hydrothermal reaction. CONSTITUTION: The preparation method of NaX zeolite by continuous crystallization comprises the steps of preparing sodium aluminate, colloidal silicate and sodium hydroxide aqueous solutions respectively; preparing a mixed solution of silica and sodium hydroxide by adding sodium hydroxide solution to the silica solution as heating the silica solution in the aqueous solutions; synthesizing mother solution by proceeding agitation of the mixed solution as adding aluminum aqueous solution to the mixed solution of silica and sodium hydroxide; and continuously crystallizing the mother solution through hydrothermal reaction, washing the continuously crystallized mother solution and drying the washed mother solution so that a final product is prepared, wherein the hydrothermal reaction is performed at a temperature of 80 to 100 deg.C, and wherein the final product prepared by continuously supplying the mother solution, thereby crystallizing the mother solution before hydrothermal reaction of the mother solution is finished.

Description

A process for manufacturing NaX zeolite by continuous crystallization method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the preparation of synthetic zeolites, and more particularly, to a method for preparing single-phase NaX zeolites with well-developed crystals by continuously growing crystals of zeolites through hydrothermal reaction.

Zeolite is an alumino silicate synthetic inorganic material, and is used as an adsorbent for removing high performance than conventional silica gel. Generally, the synthesized zeolite has a crystal size of 0.1-10 μm, which is sufficient to be used as a catalyst, ion exchange, etc. in addition to the adsorbent. However, at least 50-100 μm crystal size is required for molecular or ion separation membranes or for electrochemical and zeolite single crystal structure analysis. In particular, zeolites with more advanced crystals have been developed based on accurate crystal analysis as well as next-generation host-guest materials capable of improving the quality and process of all petrochemical processes, chemical sensors, semiconducting clusters and hydrogen ions Many applications are also expected in the field of basic science.

However, in general, the synthesized zeolite NaA zeolite, when the crystallization reaction is prolonged phase transition to sodalite, NaX and NaY zeolite phase transition to NaP zeolite. Due to the phase transition of the synthetic zeolite, it has not been possible to grow zeolite crystal growth to 20 μm or more by hydrothermal synthesis. In 1992, NASA, the US aerospace center, grew NaX zeolites in zero gravity, outside the atmosphere, to obtain NaX zeolites with a crystal size of 80 µm. This, of course, has invested enormous research costs.

Accordingly, an object of the present invention is to provide a crystal of a well-developed single-phase NaX zeolite by continuously undergoing a crystallization reaction of the NaX zeolite single phase through a hydrothermal reaction.

NaX zeolite production method of the present invention for achieving the above object, preparing a sodium aluminate (sodium aluminate, NaAlO ₂ ), colloidal silicate (colloidal silicate) and sodium hydroxide aqueous solution;

Preparing a mixed solution of silica and sodium hydroxide by adding a sodium hydroxide solution while heating the silica solution in the aqueous solution;

Synthesizing a reaction mother solution by dropwise adding an aluminum aqueous solution to the silica and sodium hydroxide mixed solution; And

The reaction mother liquor is continuously crystallized through hydrothermal reaction, washed and dried to form a final product.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The preparation of the synthetic zeolite according to the present invention is accomplished by preparing a reaction mother liquor and continuously growing single phase zeolite crystals through hydrothermal reaction.

The reaction mother solution was prepared by preparing sodium aluminate, colloidal silicate and aqueous sodium hydroxide solution respectively, adding sodium hydroxide solution to the silica solution to prepare a mixture of silica and sodium hydroxide, and then adding aluminum to the silica and sodium hydroxide mixed solution. It is obtained by adding dropwise an aqueous solution. At this time, since the gelation of the mixed solution occurs in the process of mixing the sodium hydroxide solution into the silica solution, it is necessary to stir while heating the mixed solution.

In the present invention, the target composition of the zeolite is mole%, Na ₂ O: Al ₂ O ₃ : SiO ₂ : H ₂ O is adjusted to be in the range of 3.00 ~ 4.12%: 1%: 2.0 ~ 3.5%: 500 ~ 2000% It is desirable to.

The reaction mother liquor thus obtained is continuously crystallized through hydrothermal reaction. In the synthesis of zeolite by hydrothermal reaction, an S-shaped crystallization curve is drawn according to the reaction time. That is, in the early 'nucleation induction period', nucleation proceeds from the reaction gel for crystallization. During this period, when the nucleation reaches a certain concentration and reaches the crystallization phase, the crystallization curve becomes steep as the crystal grows. Increase and nucleation decreases drastically. Finally, at the stabilization stage, crystallization is complete and all the gel phase already present is consumed.

The synthesis of zeolite by hydrothermal reaction is carried out in a Teflon container containing the reaction mother liquor and crystallization is carried out in an autoclave. The use of seeds in zeolite synthesis can increase crystal growth. In the present invention, it is preferable to use NaX seeds having a size of 10 to 20 µm.

In addition, the hydrothermal reaction temperature is preferably in the range of 80 to 100 ° C. When the hydrothermal reaction temperature is low, the crystal size of the final product may be large because a small number of crystals grow at the same reaction amount. As the hydrothermal reaction temperature increases, the nucleation time and crystal growth rate increase, so that the crystallization end time of the same reaction amount is shortened.

On the other hand, the zeolite synthesized by the conventional hydrothermal reaction method is produced under non-equilibrium conditions and is known as a metastable phase in terms of thermodynamics. In other words, the crystallization process can be regarded as a dynamic equilibrium state whose state is continuously changed with temperature and reaction time, and in the situation where the true equilibrium is predominant, crystallization and crystal growth of zeolite cannot be continuously progressed. none. Therefore, the present invention is characterized by growing the crystals of NaX zeolite by extending the crystallization reaction by continuously supplying the reaction mother liquor before the reaction is terminated in the conventional hydrothermal synthesis method. For example, the hydrolysis reaction may be continuously supplied at about 80 ° C. to prolong the crystallization reaction to about 50 days.

The hydrothermal reaction proceeds through the continuous supply of the reaction mother solution, and the products obtained sequentially are washed with distilled water. The washing is required to be less than pH 9 of the washing solution. The product obtained through washing and filtration is dried to obtain the final product.

As such, the NaX zeolite crystals obtained according to the invention are well developed and have a size of at least 20-60 μm. Such crystals can be used as a highly functional dehumidifying agent of ceramic rotors for semiconductor clean rooms, surface coatings of catalysts, adsorbents, and gas separation materials, as well as next-generation zeolites having structural stability and various fine pore structures. It is the most ideal crystal as a host-guest material of a nanocluster as a zeolite-based nanostructure.

Hereinafter, the present invention will be described in detail through examples.

EXAMPLE

Inventive Example 1

As starting materials, each of the starting materials was dissolved in a predetermined amount of distilled water using sodium aluminate, colloidal silicate and sodium hydroxide for 30 minutes, and each aqueous solution was prepared.

Then, the sodium hydroxide solution was mixed with the silica solution so that the target composition of the zeolite was mole%, and Na ₂ O: Al ₂ O ₃ : SiO ₂ : H ₂ O was 3.5: 1: 2.1: 1000. A sodium mixed solution was obtained. At this time, since the gelation of the mixed solution occurs, it was heated to about 80 ℃ range to make an aqueous solution. Thereafter, the silica and sodium hydroxide mixed solution and the aluminum aqueous solution were filtered using a glass filter (glass filter, 5 to 10㎛), and the reaction mixture was synthesized by slowly adding dropwise addition of the aluminum aqueous solution to the silica mixed solution. .

Then, the reaction solution was placed in a Teflon container containing NaX seeds having a size of 10-20 μm, and crystallization was performed in an autoclave adjusted to about 80 ° C. At this time, while supplying the reaction mother liquor during the hydrothermal reaction proceeds by extending the crystallization reaction up to about 50 days.

Then, the products obtained sequentially according to the reaction time were washed with distilled water to the pH of the washing solution or less. The product obtained after such washing and filtration was dried in a vacuum drier at about 100 ° C. for about 24 hours to obtain a final product.

The final product thus prepared was a single phase NaX zeolite having a octahedron crystal shape with lattice constant a ^o = 24.99, with a crystal size of 50-60 μm.

Inventive Example 2

The crystals of NaX zeolite were grown in the same manner as in Inventive Example 1 except that the crystallization reaction proceeded up to 30 days at the hydrothermal reaction temperature of 90 ° C. As a result, NaX zeolite crystals had a size of 30 to 35 µm.

Inventive Example 3

The crystals of NaX zeolite were grown in the same manner as in Inventive Example 1 except that the crystallization reaction was carried out at 100 ° C. for 15 days. As a result, NaX zeolite crystals showed a size of 20 to 25 µm.

Comparative Example 1

NaX zeolite was grown in the same manner as in Inventive Example 1 except that the hydrothermal reaction was performed at 80 ° C. without supplying any further reaction mother liquor during the crystallization reaction in the autoclave. The time of nucleation was about 7 days at the reaction temperature of 80 ° C., and it was confirmed that some amorphous phases still coexist in the 20 days of the reaction. As a result of the hydrothermal reaction in Comparative Example 1, a single-phase NaX zeolite having a size of about 22 μm was obtained.

Comparative Example 2

NaX zeolite was grown in the same manner as in Comparative Example 1 except that the hydrothermal reaction was performed at 90 ° C. The time of nucleation was about 5 days at the reaction temperature of 90 ° C., and a single phase NaX zeolite having a size of about 18 μm was obtained.

Comparative Example 3

NaX zeolite was grown in the same manner as in Comparative Example 1 except that the hydrothermal reaction was performed at 100 ° C. The nucleation period was about 2 days at the reaction temperature of 100 ° C., and only 9 days of the reaction showed a perfect crystal phase without an amorphous phase. As a result, a single phase NaX zeolite having a size of about 15 μm was obtained.

As described above, according to the present invention, a single-phase NaX zeolite with well-developed crystals can be obtained through a hydrothermal reaction for continuously supplying the reaction mother liquor, and the NaX zeolite is a dehumidifying agent of a ceramic rotor, which is a core part of a clean room of a semiconductor factory. It can be used as a dehumidifying agent for water management in precision manufacturing and electronic control manufacturing processes, packaging factories, pharmaceutical companies, food companies and laboratories, and in particular, it is expected to be used as a host-guest material.

Claims (3)

In the manufacturing method of the zeolite, Preparing sodium aluminate, colloidal silicate and aqueous sodium hydroxide solution; Preparing a mixed solution of silica and sodium hydroxide by adding a sodium hydroxide solution while heating the silica solution in the aqueous solution; Synthesizing the reaction mother liquor by stirring while dropwise adding an aluminum aqueous solution to the silica and sodium hydroxide mixed solution; And The method of producing a NaX zeolite by the continuous crystallization method comprising the step of continuously crystallizing the reaction mother liquor through hydrothermal reaction, washing and drying to produce the final product. The method of claim 1, The hydrothermal reaction is carried out at a temperature of 80 ~ 100 ℃ method for producing NaX zeolite by the continuous crystallization method. The method of claim 1, The final product is a method for producing NaX zeolite by the continuous crystallization method, characterized in that the reaction solution is prepared by continuously supplying the reaction solution before the end of the hydrothermal reaction of the reaction solution.