JPH07247115A - Film-shaped zeolite and its production - Google Patents

Abstract

PURPOSE:To enable production without using a base such as a Teflon base and produce film-shaped ZSM-5 synthetic zeolite having a specified crystalline structure. CONSTITUTION:A tetraalkoxysilane is hydrolyzed in the presence of an acid catalyst,to obtain an aqueous hydrolyzed solution having about >=5mPa.s viscosity (room temperature) and an aqueous solution of an alkali metal source, tetrapropylammonium as a crystallization agent (and an alumina source) is added thereto. The resultant aqueous mixture is put in a pressure vessel in a tightly sealed state and subjected to hydrothermal synthesis, thus producing the objective film-shaped ZSM-5 type synthetic zeolite composed of prism polycrystal.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a membranous synthetic zeolite and a method for producing the same. More specifically, the synthesized zeolite relates to a membranous ZSM-5 type synthetic zeolite and a method for producing the same.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 4-227,826 discloses colloidal silica, sodium aluminate, sodium hydroxide,
An aqueous mixture consisting of tetrapropylammonium bromide and water (synthetic mother liquor) was enclosed in an autoclave equipped with a Teflon strip, and immediately heated to 180 ° C, whereby the synthesized zeolite was membranous ZSM-5. A method for producing synthetic zeolite on a Teflon surface is described. However, the formation of the membranous synthetic zeolite on such a Teflon substrate has a problem that the range of use as a separation membrane is limited such that it cannot be spread on other substrates, and the weight of the separation membrane increases. I have.

[0003]

The object of the present invention is to produce a film-shaped ZSM-containing zeolite having a specific crystal which can be produced without using a substrate such as a Teflon substrate.
It is to provide a type 5 synthetic zeolite and a method for producing the same.

[0004]

According to the present invention, there is provided a film-like ZSM-5 made of a polycrystal of prismatic crystals. The film-like ZSM-5 made of a polycrystal of prismatic crystals is obtained by hydrolyzing tetraalkoxysilane in the presence of an acid catalyst, and has a viscosity (room temperature) of about 5 mPas or more in a hydrolyzed aqueous solution. ,
It is manufactured by enclosing an aqueous mixture containing an aqueous solution of an alkali metal source and a tetrapropylammonium salt (and an alumina source) as a crystallization agent in a pressure resistant vessel and performing hydrothermal synthesis.

Aqueous mixtures which form synthetic mother liquors are generally
It consists of an aqueous solution of a silica source, an alumina source, an alkali metal source and a crystallization agent. As the silica source, a tetraalkoxysilane such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, or tetra-n-butoxysilane is used, and tetraethoxysilane is preferably used from the viewpoint of economy and safety to the environment. To be These tetraalkoxysilanes, generally tetra-lower alkoxysilanes, are added to an aqueous solution in the presence of an acid catalyst typified by an inorganic salt such as hydrochloric acid, nitric acid or sulfuric acid, and hydrolyzed. At this time, water is used in an amount of about 8 to 20 times mol, preferably about 10 to 15 times mol, with respect to the tetraalkoxysilane, and by adjusting the stirring time during hydrolysis, the solution does not cause phase separation and Viscosity of hydrolyzed aqueous solution (room temperature)
Is about 5 mPa · s or more, preferably about 7 mPa · s or more to form SiO ₂ . When the viscosity of the hydrolyzed aqueous solution is below this range, only powdery or small pieces of membranous synthetic zeolite can be obtained, and the range of the composition ratio of the synthetic mother liquor from which the membranous synthetic zeolite can be obtained is narrowed.

As the alumina source used as needed, sodium aluminate, aluminum nitrate, aluminum sulfate, powdered alumina and the like are used, but sodium aluminate NaAlO ₂ can also function as an alkali metal source, and is therefore preferable. Used in Further, sodium hydroxide and potassium hydroxide are generally used as the alkali metal source. As the crystallization agent (structure control agent), a tetrapropylammonium salt having a molecular size and a structure suitable for forming a ZSM-5 type synthetic zeolite, generally tetrapropylammonium bromide is used, and other tetra-lower Alkylammonium salts do not form ZSM-5 type synthetic zeolites.

A synthetic mother liquor comprising each of these components and water is generally used as an aqueous mixture having the following composition ratio (molar ratio). SiO ₂ / Al ₂ O ₃ = about 20 or more (preferably about 30 to 200) crystallizing agent / SiO ₂ = about 0.05 to 0.5 (preferably about 0.05 to 0.3) alkali metal oxides / SiO ₂ = about 0.2 to 0.5 (Preferably about 0.
_{2 to} 0.35) H ₂ O / SiO ₂ = about 60 to 400 (preferably about 100 to 200)

The synthetic mother liquor can be prepared, for example, by the following method. (1) Tetraalkoxysilane was added to an aqueous solution containing an acid catalyst so that the solution did not undergo phase separation and the solution viscosity was about
Hydrolysis is performed by stirring until it becomes 5 mPa · s or more to form SiO ₂ . (2) In the hydrolyzed aqueous solution of this tetraalkoxysilane,
Add an aqueous solution of an alkali metal source compound and stir. (3) When an alumina source compound is used, its aqueous solution,
Add the crystallization agent aqueous solution and stir. (4) To the aqueous solution prepared in (2) above, the crystallization agent aqueous solution or the aqueous solution prepared in (3) above is added and stirred at room temperature for about 12 to 48 hours.

The aqueous mixture, which is the synthetic mother liquor thus prepared, is enclosed in a pressure-resistant container such as an autoclave having a Teflon inner cylinder, and the whole is heated uniformly, for example, in an oven, and at that time water is removed from room temperature. The temperature distribution of the synthetic mother liquor is narrowed by increasing the heating rate up to the thermal synthesis temperature from 0.1 to 5 ° C / min, and the hydrothermal synthesis temperature from 160 to 200 ° C is maintained for about 24 to 60 hours to obtain a membranous synthetic zeolite. Can be formed. If this heating rate is higher than this, the ZSM-5 type synthetic zeolite is produced but is in the form of powder and not in the form of a film. The membranous synthetic zeolite is produced on the upper part of the powdery zeolite deposited on the bottom of the pressure vessel or on the wall surface of the Teflon inner cylinder of the autoclave without the need for a substrate or the like.

[0010]

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to obtain a membranous synthetic zeolite in which the synthesized zeolite is membranous and is ZSM-5 without using a Teflon substrate or the like. The obtained membranous ZSM-5 type synthetic zeolite is a prismatic crystal having a large apparent surface area per unit volume or per unit mass, and a usual membranous synthetic zeolite composed of a plate-shaped or spherical crystalline polycrystal. By comparison, the apparent surface area is estimated to be about 2 to 20 times larger, and therefore, when it is used as a catalyst or an adsorbent, an increase in reaction rate and adsorption rate is achieved.

[0011]

EXAMPLES The present invention will now be described with reference to examples.

Examples 1 to 5, Comparative Examples 1 to 4 (1) Tetraethoxysilane was added to ion-exchanged water containing a small amount of nitric acid so that the molar ratio of tetraethoxysilane / H ₂ O was about 12. Stir to hydrolyze. (2) A sodium hydroxide aqueous solution is added to the tetraethoxysilane hydrolysis aqueous solution of the above (1), and the mixture is stirred. (3) Tetrapropylammonium bromide (TPABr) aqueous solution is added to the sodium aluminate aqueous solution and stirred. (4) The aqueous solution of (3) above is added to the aqueous solution of (2) above, and the mixture is stirred at room temperature. However, in Example 5 and Comparative Example 4,
No sodium aluminate was used.

The synthetic mother liquor having various composition ratios prepared by the above procedure was enclosed in an autoclave, and stored in an oven at 2 ° C. /
The temperature was raised at a temperature rising rate of 10 minutes (however, 10 ° C./minute in Comparative Example 3), and the hydrothermal synthesis condition was 180 ° C. for 36 hours (however, in Example 1).
At 160 ° C. for 60 hours, and in Example 4 at 200 ° C. for 24 hours)
Hydrothermal synthesis was performed. Table SiO ₂ / TPABr Na ₂ O / H ₂ O / Hydrolysis Room temperature stirring Al ₂ O ₃ / SiO ₂ SiO ₂ SiO ₂ Viscosity of liquid Stirring time Example Molar ratio Molar ratio Molar ratio Molar ratio (mPa ・ s) (hrs) Example 1 102 0.158 0.225 200 18 24 〃 2 30.0 0.101 0.240 80.0 10 12 〃 3 39.8 0.099 0.216 100 150 36 〃 4 50.4 0.103 0.240 102 420 48 〃 5-0.100 0.205 200 1000 24 Comparative Example 1 19.6 〃 0.252 150 12 〃 〃 2 83.3 0.101 0.204 100 2 36 〃 3 32.5 0.100 0.218 88.8 〃 48 〃 4-0.101 0.225 200 〃 24

In each of the examples, a membranous product was obtained, and it was confirmed from the results of X-ray diffraction measurement (FIG. 1) that all of them consisted of ZSM-5 type synthetic zeolite. Also, SE
According to the morphological observation with M (FIG. 2), it was a polycrystal of prismatic crystals. On the other hand, in each of the comparative examples, only powdery ZSM-5 type synthetic zeolite was obtained.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction pattern of a membranous synthetic zeolite obtained by the present invention after pulverization.

FIG. 2 SE of the membranous synthetic zeolite obtained by the present invention
It is an M photo image.

Claims (3)

[Claims] 1. A film-shaped ZSM- comprising a polycrystal of prismatic crystals.
Type 5 synthetic zeolite. 2. A hydrolyzed aqueous solution having a viscosity (room temperature) of about 5 mPa · s or more obtained by hydrolyzing tetraalkoxysilane in the presence of an acid catalyst, and tetrapropyl as an alkali metal source and a crystallization agent. An aqueous mixture containing an aqueous solution of an ammonium salt is enclosed in a pressure-resistant container for hydrothermal synthesis, and the synthesized zeolite is a membranous ZSM-5 type synthetic zeolite composed of a polycrystalline body of prismatic crystals. Manufacturing method. 3. A hydrolyzed aqueous solution having a viscosity (room temperature) of about 5 mPa · s or more obtained by hydrolyzing tetraalkoxysilane in the presence of an acid catalyst is used as an alumina source, an alkali metal source and a crystallization agent. Membrane ZSM-5 type, in which the synthesized zeolite is composed of polyhedral prismatic crystals, characterized in that an aqueous mixture containing an aqueous solution of tetrapropylammonium salt is encapsulated in a pressure-resistant container for hydrothermal synthesis. Method for producing synthetic zeolite.