JPS5939716A - Method for synthesizing zeolite - Google Patents

Abstract

PURPOSE:To obtain inexpensively high purity zeolite similar to ZMS-5 by reacting synthetic amorphous silicic acid having low apparent specific gravity with an alumina source, an alkali adjusting agent and water in a specified ratio and by crystallizing the mixed reaction product by stirring and heating. CONSTITUTION:Synthetic amorphous silicic acid having <=0.4g/ml apparent specific gravity is reacted with an alumina source such as Al2O3 in the presence of an alkali adjusting agent such as NaOH and water to prepare a mixed reaction product having SiO2/Al2O3=20-200, Na2O/SiO2=0.05-0.3 and H2O/SiO2= 12-70 when expressed by molar ratios between oxides. The reaction product is crystallized by heating at 120-220 deg.C under stirring to obtain the desired zeolite. The zeolite is similar to ZSM-5 in crystal structure and has practically alpha-values shown in the table by X-ray powder diffraction pattern. The zeolite is economically obtd. without using an org. mineralizer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for hydrothermal synthesis of zeolite, and in particular to a method for synthesizing zeolite.
Oy'A403 molar ratio (hereinafter single K S io, /A4o
The present invention provides an improved method for synthesizing zeolites with relatively high zeolites (denoted as , ).

Zeolite is a crystalline aluminosilicate containing zeolite water, from the Greek word for boiling stone.

Its basic structure consists of a Sin4 tetrahedron formed around silicon with four oxygen atoms placed at the vertices, and an Ate4 tetrahedron in which silicon is substituted with aluminum.
They are regularly arranged three-dimensionally while sharing oxygen so that the atomic ratio of (At-4-sl) is 2.

The negative charge of the AjO, tetrahedron is balanced by the inclusion of alkali metal or alkaline earth metal cations. In addition, pores of various sizes are formed depending on the arrangement of the tetrahedrons, and water molecules and exchangeable cations usually exist in the pores. Zeolites in which the cations are exchanged with other appropriate cations can be used as so-called molecular sieves that have the function of capturing specific molecules in their pores, or as catalysts that allow reactions to occur only within the pores, or as catalysts that can react only within the pores. exchange body,
Furthermore, it is used in various fields such as as a catalyst carrier.

Zeolites are known to have various crystal structures and chemical compositions, and these differences have different adsorption properties, catalytic properties,
They have different physical properties such as ion exchange characteristics, and are attached with different zeolite salts.

Among these, mordenite, offretite, erionite, clinoptilolite, and chabasite exist naturally, and can also be synthesized by hydrothermal synthesis.

Zeolite) A, X, and Y do not exist in nature and are synthesized by hydrothermal synthesis.

A zeolite very similar to the zeolite according to the present invention is ZSM-5. ZSM-51d organic mineralizer,
For example, it is hydrothermally synthesized using tetrapropylammonium ions as an essential raw material, and is a crystalline aluminosilicate with a constant orthorhombic lattice system, and has the lattice spacing (α-value) shown in the X-ray powder diffraction diagram shown in Table 1. In addition, tetrapropylammonium ions are present in the crystals as part of the cations constituting the zeolite crystals.

Various methods have been disclosed as improved synthesis methods for 78M-5 or for synthesis of zeolites similar to ZSM-5. For example, a method using an organic sulfur compound as an organic mineralizing agent is disclosed in JP-A-54-157,500, and a method using a cyclic ether is disclosed in JP-A-56-140,025.
The method using alcohol amine is described in Japanese Patent Application Laid-open No. 1983.
-17.920 and JP-A-57-7.817 disclose a method using amino acids.

These all involve synthetic methods that require organic mineralizing agents. However, recently an attempt was made to synthesize a zeolite similar to ZSM-5 using an organic mineralizing agent, and
7.819 discloses a method of synthesis by adding crystals synthesized in the coexistence of tetrapropylammonium bromide as seed crystals.

1st table Lattice spacing (α-value) Relative intensity 11.1±α
3 Strong 1 [LD±13 Strong 7.4±0.2 Weak 7.1±0.2 Weak 6.3±α2 Weak &04±02 Weak 5.56±0.1 Weak 5.01 Shi01 Weak 4. 60 ten 0.08 weak 4.25± [108 weak! L85±α07 Very strong A71±0.05 Strong 504±[103 Weak 2.99±a02 Weak 2.94 Sat0.02 Weak Furthermore, in Japanese Patent Publication No. 1985-49,851, as a silica source A method for synthesizing ZSM-5-like zeolite without coexisting an organic mineralizing agent by using silica sol is disclosed.

As a result of extensive research on the above zeolite synthesis method, the present inventors discovered the important facts detailed below and succeeded in synthesizing highly pure ZSM-5-like zeolite extremely economically and stably. I have now perfected a method to do this. That is, it is extremely difficult to synthesize a zeolite similar to zsM-s without using an organic mineralizing agent, and even if the disclosed synthesis method is faithfully followed and implemented, it is not always possible to synthesize it efficiently.

It has been discovered that synthesis can only be achieved by complex combinations of silica raw materials, mixing order of raw materials, f#, presence or absence of stirring, etc. When colloidal silica (silica sol), which is conventionally used as a silica source, is stirred during crystallization, ZSM-5 will not work even if the raw material composition and crystallization temperature are varied.
It did not become a similar zeolite. In addition, when heating was performed without stirring at t, 1 other than when preparing raw materials, in the case of Nitonto in numerous experiments, the product was amorphous or mainly composed of mordenite. Well, exceptionally 28M=
Although zeolites similar to 5 were observed, impurities such as mordenite were always present.

When a sodium silicate aqueous solution was used as a silica source, a zeolite similar to ZSM-5 was obtained only when fine ZSM-5 was added as a seed crystal and crystallized by heating while stirring. However, mordenite and kenyite coexisted as impurities. Various attempts were made using an aqueous solution of sodium silicate as a silica source without using seed crystals, but all were unsuccessful.

However, when synthetic amorphous silicic acid, commonly called white carbon, is used as a silica source, the desired ZSM-5-like zeolite can only be obtained by heating and crystallizing the raw material reaction mixture while stirring. I was able to do that. Furthermore, when the same reaction mixture as described above was heated under the same conditions without stirring, the product did not crystallize. Also, surprisingly, when preparing the reaction mixture of raw materials, A
No, 0. A zeolite similar to ZSM-5, which is obtained by adding synthetic amorphous silicic acid to an aqueous alkaline solution containing a source with stirring and crystallizing the reaction mixture under stirring, contains no impurities and has extremely high crystallinity. It was a high-quality zeolite. That is, according to the present invention, a zeolite similar to ZSM-5 of high purity can be produced using relatively inexpensive white carbon as a raw material, without using an organic mineralizer, or without using a crystallization aid such as a seed crystal. It has become possible to synthesize extremely easily with good reproducibility. Although conventional methods are possible in the laboratory, they have many disadvantages in terms of economics, quality, and management, and the present invention has great industrial significance.

The present invention will be explained in more detail.

The present invention is characterized by the use of a specific silica source.

That is, the silica source used in the present invention is limited to so-called white carbon, which is synthetic amorphous silicic acid and has an apparent specific gravity of 0.49 or less as measured by the method described below. Desirably it is 0.259/me or less. The method of synthesizing white carbon is not particularly limited, and a conventional method produced from water glass and sulfuric acid may be used.

The method of the present invention cannot be carried out when the silica source is sodium silicate, silica sol, silica second coat lattice spacing (α-value) relative strength 2.94 7 gel, or a siliceous natural product.

As the alumina source, aluminum oxide, aluminum hydroxide, sodium aluminate, aluminum sulfate, aluminum nitrate, etc. can be used, although there is no particular limitation.

Most preferred is an aqueous solution of sodium aluminate.

Sodium hydroxide is preferred as the Burqa IJ 14 conditioner.

In the present invention, it is essential to prepare a reaction mixture for the following molarization from a silica source, an alumina source, an alkaline modifier, and water, and to subject it to crystallization.

EliO〆A40. -20~20O Na, O/SiO, -0,05~03 nto/s1o, -12~70 A method for preparing a reaction mixture having the above composition from these raw materials is preferably such that the alumina source and sodium hydroxide are mixed with water. After dissolving, add the silica source without stirring. The reaction mixture was charged into an autoclave and heated to 120~
Heat at 220°C to crystallize. The time required for crystallization is 10 to 200 hours, depending on the heating temperature.

In the present invention, stirring during crystallization is essential. When the maximum diameter of the stirring blade during rotation is d (m) and the stirring speed is V (rpm), the circumferential speed defined as ('') (= 1) (v) is 0 ''/e e c ) 75f O,1tys is required to be 8° or more, preferably 0.51n/8oo or more.The amount of water is important for effective stirring.

If H,O/S i O, is lower than 12, the effect of stirring will not appear. Moreover, when H,O/SiO, is 7D or more, the yield per unit volume decreases, which is not only undesirable from an industrial standpoint, but also impurities are likely to be generated.

After crystallization is completed, solid-liquid separation is performed according to a known method, thoroughly washed with water,
Dry to make a product.

Table 2 shows the lattice spacings (α-values) determined from the X-ray powder diffraction pattern (copper α doublet) of representative products synthesized by the method of the present invention. This material is found to be a zeolite similar to Z SM-5. The zeolite obtained in the present invention is 1
0. OA and 9.8A, 3.85A and Yu OIA, Yu/D
A and 5. It is characteristic that /ZA, Z, SoγA and 2.98 are each doublets. Also, 1 i
It is also one of the characteristics of the zeolite produced by the method of the present invention that the peak intensity of IA is 10, and the peak intensity of OA is almost the same.

The composition of the product synthesized by the method of the present invention can be expressed by the following formula.

xNa20IIAt, 0.・(15N100)S102
-11H20 However, X varies depending on the degree of water washing of the product, but is usually around 1. Also, y is 0 or a positive number and is also dry.

It varies depending on the degree of dehydration. Product S i O2/A403
There are following ways to adjust. High 5io2/Az,
o3 raw reaction mixture or Na2o/e1
If one with low o2 is used, the product S i O2/'
A40su will be more expensive.

In addition, if the 5ioy"A403 of the raw material reaction mixture is lowered or the Na, O/EIiO2 is increased, the Si of the product
02A40s will be lower. On the other hand, the ratio of Sin recovered as crystals to 5in2 used as a raw material, that is, S10. In order to increase the yield, it is desirable to lower the Na2o/s:t02 of the raw material reaction mixture.

However, if it deviates from the range defined in the present invention, impurities will be produced, amorphous substances will increase, the degree of crystallinity will decrease, and eventually crystallization will not proceed at all.

The ZSM-5-like zeolite obtained by the method of the present invention can be ion-exchanged with suitable cations by a known method after powdering or molding, and can be used for various purposes, such as dehydrating agents, adsorption/separation agents, and catalysts.

This will be explained below using examples.

<Appearance is the method of measuring specific gravity> Appearance is the difference in height between the piston and the cylinder when 1 g of sample is placed in the cylinder of the specific gravity meter, the piston is inserted into the cylinder of the specific gravity measuring device, the piston is gently held with fingers, it is gently dropped, and the difference in height between the piston and the cylinder is left for 30 minutes. H
em, and is calculated by the following formula.

(Note) The apparent specific gravity measuring device consists of a metal cylinder and a matching piston, and the cylinder has an inner diameter of 2.2 mm.
Depth: 11.5 tyn, piston length: 12.7 α
9 It weighs 190g.

The apparent specific gravity measured with this measuring device is 50 per 1 d.
The weight of sample 1- when compressed at a pressure of 9 is expressed in q number.

*1.2-12.7-11.5 **3L8-area of cylinder-1, IXl, IX3.
14 Example 1 Put pure water & 7t in a container and do solid hydroxide) IJum 1
179. Sodium aluminate aqueous solution (Na2019,
2 wt Chi, At20s 20.7 wt Chi, H2
Add 127 g of O60, I wt) to make a homogeneous aqueous solution, and then add white carbon (manufactured by Nippon Sirikani Gyo Co., Ltd., trade name Tsubu Seal, apparent specific gravity [11497 m1!, 5
in2B 7. Owt%.

A40, 0.48 wt%) 1.06 kg was added with stirring to prepare a reaction mixture having the following composition.

6Na20-A/1.203@50S102-1250
In addition, 5in27'A403-s.

Na2O//5102-α12 H20/5iO2-25 It is.

This reaction mixture was placed in a 10 t autoclave at a circumferential speed of 1 m/Bo. While stirring, the mixture was heated at 165°C for 172 hours to crystallize. The product obtained by separating solid and liquid, thoroughly washing with water, and drying at 110°C had the following composition.

1.4 Na20-At, 03-! 18 El i
The X-ray powder diffraction pattern of the O,-8,8H,0 product is shown in Figure 1. All peaks shown in Table 1 are included.

Example 2 The experiment was carried out using the same raw materials as in Example 1.

Put 1.45t of pure water in a container and add 3 t of solid sodium hydroxide.
2 g of sodium aluminate aqueous solution was added to make a homogeneous aqueous solution, and then 113 g of white carbon was added with stirring to prepare a reaction mixture having the following composition.

25 Na2O・At203-10O5in2-500
0 H, 0, 5to2/Az, o3-10 ONa
, O/SiO, -0,25 n, o/5to2-50.

This reaction mixture was placed in an autoclave with a peripheral speed of 1
The mixture was crystallized by heating at 198°C for 118 hours while stirring at 1n/8oo. The result of X-ray powder diffraction of the product obtained by solid-liquid separation, thorough washing with water, and drying at 110°C was substantially the same as that shown in Figure 1, with almost no impurities observed.

[Brief explanation of drawings]

Figure 1 is an X-ray powder diffraction pattern of the product obtained in Example 1. It was measured using an alpha doublet on copper. Patent Applicant: Toyo Soda Kogyo Co., Ltd. Procedural Amendment September 24, 1980 1F, 5 Director General Kazuo Wakasugi 1 Matter V [Display of Patent Application No. 146911 of 1981 2 Name of Invention Method for Synthesizing Zeolite Relationship with the case of the person making the amendment Patent applicant address 4560 Oaza Tomita, Shinnanyo City, Yamaro Prefecture 746 Name (330) Toyo Soda Kogyo Co., Ltd. Representative Higashi Morishima Telephone number (585) 3311 4 Amendment order Japanese Imma 1 5. Specification to be amended 6. Type of amended statement 7. Attachment type (printed specification)

Claims (3)

[Claims] (1) Contains no organic mineralizer and is substantially Sin. A403. A method of crystallizing a reaction mixture consisting of Na, 0.11.0 and synthesizing a crystalline aluminosilicate having an α-value substantially as shown in the X-ray powder diffractogram shown in Table 5 of the present specification. As a source, the apparent specific gravity is 0
．． Using synthetic amorphous silicic acid of 49/ne or less, expressed in molar ratio of oxides, 5iOv/A403-20~20O Na, O/5iO2-0,05~0.3H20/SiO
, -12 to 70, and heating the reaction mixture at a temperature of 120 to 220''C with stirring to crystallize. (2) The method according to claim 1, characterized in that, in preparing the reaction mixture, the 5i02 source is added to the alkaline solution containing substantially the majority of the A403 source with stirring. (3) S i O, source has apparent specific gravity α259/n
Claim 1 or 2 which is synthetic amorphous silicic acid below
The method described in section.