JP5080107B2 - Modification of beta zeolite - Google Patents

Description

  The present invention relates to a modification of beta zeolite, and more particularly to a beta zeolite characterized in that the outer surface of aluminum-containing beta zeolite is made of silica and a method for producing the same.

  Zeolite, which is a crystalline aluminosilicate, has micropores and acid sites, and is therefore used as a catalyst for various solid acid reactions. Examples of the reaction include para-xylene synthesis from ortho-xylene or meta-xylene and skeletal isomerization reaction of normal paraffin. In these reactions, since the zeolite has micropores, the selectivity of the target product is higher than that of amorphous aluminosilicate represented by silica alumina. However, shape selectivity due to micropores cannot be expected on the outer surface of the zeolite particles, and as a result, an undesirable reaction occurs.

Inhibiting the reaction that takes place on the outer surface of the zeolite is important for improving the yield of the desired product. In order to suppress the reaction on the outer surface of the zeolite, it is considered effective to deactivate the acid sites on the outer surface. Examples of the method include an adsorption method of a nitrogen compound that does not enter the micropores and a silylation method of the outer surface. Examples thereof are described in Non-Patent Document 1 and Non-Patent Document 2, for example.
“Journal of Catalysis”, 1996, 161, p. 687 “Journal of Catalysis”, 1991, 128, p. 551

However, in the acid point inactivation method by adsorption of nitrogen compounds, nitrogen compounds are desorbed from the zeolite during the reaction, and as a result, the selectivity of the target product may be reduced. Further, inactivation by silylation changes the micropore diameter of the outer surface of the zeolite, and as a result, the reactivity may be lowered or the selectivity of the target product may be lowered. These are disadvantages of the prior art, and a method for further improving the selectivity of the target product is required. That is, there is a demand for a method for producing zeolite that maintains the original micropore structure without having acid sites on the outer surface.
The present invention provides a beta zeolite comprising an outer surface of an aluminum-containing beta zeolite made of inert silica and a method for producing the same.

  As a result of intensive studies, the present inventors have found that beta zeolite containing aluminum as a core during hydrothermal synthesis can be produced only under special synthesis conditions, and that a beta zeolite composed of silica can be produced. The invention has been completed.

  That is, the present invention relates to a beta zeolite characterized in that the outer surface of aluminum-containing beta zeolite is made of silica.

  In addition, the present invention provides Step 1 for producing beta zeolite containing aluminum, and after preparing a gel solution using hydrogen fluoride, the beta zeolite containing aluminum produced in Step 1 is added to the gel solution. The present invention relates to a process for producing a beta zeolite having an outer surface made of silica, characterized in that it comprises a step 2 in which hydrothermal synthesis is carried out under a stirring condition at ˜200 ° C. for 10 hours to 30 hours.

  The present invention also relates to a method for producing beta zeolite having an outer surface made of silica according to claim 2, wherein step 1 involves a calcination process.

  In the present invention, the composition of the gel solution is such that the weight ratio of nitrogen to silicon 1 is 0.4 to 0.8, the weight ratio of fluorine is 0.3 to 0.8, and the weight ratio of water is 5 to 10. The method according to claim 2, wherein the outer surface is made of silica.

  Further, in the present invention, the mass ratio of the aluminum-containing beta zeolite to the gel solution is 0.3 to 10% by mass, The method for producing a beta zeolite having an outer surface made of silica according to claim 2 About.

  By the method of the present invention, beta zeolite whose outer surface is made of silica can be produced.

The present invention is described in detail below.
The method of the present invention for producing a beta zeolite having an outer surface made of silica comprises step 1 of producing an aluminum-containing beta zeolite, and crystal growth from the nucleus by hydrothermal synthesis using the produced beta zeolite as a nucleus. Comprises step 2 of producing a beta zeolite comprising silica.

First, the process 1 which manufactures the beta zeolite containing aluminum is demonstrated.
The aluminum-containing beta zeolite used as the nucleus can be synthesized by known conventional methods. An example of the synthesis procedure is shown below.
As the mold agent (template), for example, tetraethylammonium hydroxide or tetraethylammonium fluoride can be used.
The aluminum source is not particularly limited, and generally inexpensive aluminum nitrate can be used.
Tetraethoxysilane is usually used as the silica source.

First, the mold, the aluminum source, and the silica source are mixed and stirred well at room temperature, usually for 1 to 3 hours.
Next, ethanol produced from the gel solution obtained is removed under vacuum. If the removal of ethanol is insufficient, beta zeolite may be difficult to produce.
After removing ethanol, an aqueous hydrogen fluoride solution can be added as necessary to adjust the crystal particle size of the produced beta zeolite.
The gel solution thus obtained is put into an autoclave, and hydrothermal synthesis is performed for 5 to 8 days with stirring at 120 to 200 ° C, preferably 140 to 160 ° C. After hydrothermal synthesis, the solid (beta zeolite) is separated by filtration and washed thoroughly with ion-exchanged water.

  Finally, calcination is performed in air at 400 to 600 ° C., preferably 450 to 550 ° C. for 5 to 20 hours, and the mold is removed to obtain an aluminum-containing beta zeolite. If it is used in the next step 2 while containing the mold without performing this calcination, it tends to be difficult to form a beta zeolite having an outer surface made of silica as the final target product, which is not preferable.

Next, the process 2 which manufactures the beta zeolite which an outer surface consists of silica is demonstrated.
In Step 2, the necessary gel preparation is first performed. As the mold, the tetraethylammonium hydroxide or tetraethylammonium fluoride used in Step 1 can be used. The mold may be used as it is, but usually it is preferably used as a 20 to 50% by mass aqueous solution. For example, tetraethoxysilane as a silica source is added to the aqueous solution of the mold, and the mixture is stirred at room temperature for 30 minutes or more, preferably for 1 hour or more. When the stirring time is less than 30 minutes, it tends to be difficult to produce beta zeolite whose outer surface is made of silica, which is not preferable.

Next, ethanol and water generated from the above mixed solution under degassing (for example, using an evaporator) are removed, and finally, water and an aqueous hydrogen fluoride solution are added to prepare a gel solution having the composition shown below.
As the composition of the gel solution, the weight ratio of nitrogen to silicon 1 is 0.4 to 0.8, the weight ratio of fluorine is 0.3 to 0.8, and the weight ratio of water is 5 to 10. If these weight ranges are not satisfied, it is not preferable because it is not possible to synthesize beta zeolite whose outer surface, which is the target product, is composed of silica.

  The aluminum containing beta zeolite synthesize | combined at the process 1 is put into the obtained gel solution. The mass ratio of the aluminum-containing beta zeolite to the gel solution is preferably 0.3 to 10 mass%, more preferably 1.0 to 6.0 mass%. If this ratio is less than 0.3% by mass, amorphous silica tends to be by-produced, and if it exceeds 10% by mass, aluminum tends to be partially exposed on the outer surface, which is not preferable.

  Further, it is necessary to add the aluminum-containing beta zeolite after the gel solution is prepared, and if it is added during the preparation of the gel solution, it tends to be difficult to produce a beta zeolite composed of silica whose outer surface is the target product.

The gel solution and the core aluminum-containing beta zeolite are put into an autoclave and hydrothermal synthesis is performed. The temperature is 110-200 ° C, preferably 140-170 ° C. If the synthesis temperature is less than 110 ° C. or exceeds 200 ° C., the desired product cannot be obtained.
In addition, the stirring speed and stirring time during hydrothermal synthesis are also important factors. The stirring speed is preferably 3 to 20 revolutions / minute. The stirring time is preferably 10 hours or more and 30 hours or less, and more preferably 15 to 20 hours. If the stirring time is less than 10 hours, amorphous silica tends to be formed as a by-product, and if it exceeds 30 hours, aluminum tends to exist on the outer surface of the product, which is not preferable.

After completion of the stirring for a predetermined time, the hydrothermal synthesis is terminated by allowing the mixture to stand for 50 hours or more, more preferably 70 hours or more while maintaining the synthesis temperature.
After the hydrothermal synthesis is complete, the solid (target beta zeolite) and liquid are separated by filtration and washed with ion-exchanged water. Finally, calcination is performed in air at 400 to 600 ° C., preferably 450 to 550 ° C., preferably for 3 to 20 hours, and the mold is removed to obtain beta zeolite whose outer surface is made of silica.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these.

(Synthesis of aluminum-containing beta zeolite)
Aluminum-containing beta zeolite was synthesized as follows.
In a 200 ml polytetrafluoroethylene beaker, 25.1 g of tetraethylammonium hydroxide (35% aqueous solution) and 1.52 g of aluminum nitrate nonahydrate were mixed with stirring, and then 20.7 g of tetraethoxysilane was mixed. The stirring was continued for 1.5 hours.
This mixed solution was transferred to an evaporator and heated to 40 ° C. under vacuum to remove generated ethanol and water. Water and 2.59 g of a hydrogen fluoride aqueous solution (46% aqueous solution) were added to the residue so as to have the gel ratio shown below to prepare a gel solution. The gel composition at this time is Si: Al: N: F: H ₂ O = 1: 0.04: 0.6: 0.6: 7.5 by weight ratio.
The obtained gel solution was evenly placed in two 45 ml autoclaves and hydrothermal synthesis was performed at 150 ° C. During hydrothermal synthesis, stirring was performed at a rate of 20 revolutions / minute for 60 hours and then allowed to stand for 115 hours. The produced solid and liquid were separated by filtration, and the solid was sufficiently washed with ion-exchanged water.
Finally, the solid was calcined in the air at 550 ° C. for 4 hours to obtain the target aluminum-containing beta zeolite.
It was confirmed by X-ray diffraction measurement that the solid substance was beta zeolite, and the crystal particle size was found to be 6 to 9 μm by scanning electron microscope measurement.
The aluminum-containing beta zeolite obtained here is commonly used in the following examples and comparative examples.

Example 1
In a 200 ml polytetrafluoroethylene beaker, 25.1 g of tetraethylammonium hydroxide (35% aqueous solution) as a mold and 20.7 g of tetraethoxysilane were added and stirring was continued for 1.5 hours.
This mixed solution was transferred to an evaporator and heated to 40 ° C. under vacuum to remove generated ethanol and water. Water and 2.59 g of a hydrogen fluoride aqueous solution (46% aqueous solution) were added to the residue so as to have the gel ratio shown below to prepare a gel solution. The gel composition at this time is Si: N: F: H ₂ O = 1: 0.6: 0.6: 7.5 by weight.
The obtained gel solution and 0.50 g of aluminum-containing beta zeolite as a core were evenly placed in two 45 ml autoclaves, and hydrothermal synthesis was performed at 140 ° C. During hydrothermal synthesis, stirring was performed at a rate of 20 revolutions / minute for 20 hours, and then allowed to stand for 90 hours. The produced solid and liquid were separated by filtration, and the solid was sufficiently washed with ion-exchanged water.
Finally, the solid was calcined in air at 550 ° C. for 4 hours. In order to judge the particle size of the obtained solid and whether or not the solid is a single crystal, a measurement with a scanning electron microscope was performed. Further, in order to confirm that the outer surface is made of silica, a fluorescent X-ray analysis was performed. The measurement results are shown in Table 1.

(Comparative Example 1)
When 25.1 g of tetraethylammonium hydroxide (35% aqueous solution) and 20.7 g of tetraethoxysilane were mixed in a 200 ml polytetrafluoroethylene beaker, 0.50 g of aluminum-containing beta zeolite was also mixed at the same time. Except for this, the same synthesis as in Example 1 was performed. In order to judge the particle size of the obtained solid and whether or not the solid is a single crystal, a measurement with a scanning electron microscope was performed. Further, in order to confirm that the outer surface is made of silica, a fluorescent X-ray analysis was performed. The measurement results are shown in Table 1.

(Comparative Example 2)
Synthesis was performed in the same manner as in Example 1 except that the aqueous hydrogen fluoride solution was not added to the prepared gel solution. In order to judge the particle size of the obtained solid and whether or not the solid is a single crystal, a measurement with a scanning electron microscope was performed. Further, in order to confirm that the outer surface is made of silica, a fluorescent X-ray analysis was performed. The measurement results are shown in Table 1.

(Comparative Example 3)
The same synthesis as in Example 1 was performed except that the stirring time during hydrothermal synthesis was 50 hours. In order to judge the particle size of the obtained solid and whether or not the solid is a single crystal, a measurement with a scanning electron microscope was performed. Further, in order to confirm that the outer surface is made of silica, a fluorescent X-ray analysis was performed. The measurement results are shown in Table 1.

  From the above, it can be seen that beta zeolite whose outer surface is composed of silica can be synthesized only under special conditions.

Claims (5)

A beta zeolite characterized in that the outer surface of an aluminum-containing beta zeolite is made of silica having a beta zeolite structure . Step 1 for producing beta zeolite containing aluminum, and after preparing a gel solution using a mold, a silica source, water and hydrogen fluoride for producing beta zeolite , the gel solution was produced in Step 1 The outer surface is composed of silica having a beta zeolite structure, characterized in that it comprises a step 2 in which beta zeolite containing aluminum is placed and hydrothermal synthesis is carried out at 110 to 200 ° C. for 10 to 30 hours under stirring conditions. A method for producing beta zeolite. The method for producing beta zeolite comprising silica having an outer surface of beta zeolite structure according to claim 2, wherein step 1 involves a calcination process. The composition of the gel solution is characterized in that the weight ratio of nitrogen to silicon 1 is 0.4 to 0.8, the weight ratio of fluorine is 0.3 to 0.8, and the weight ratio of water is 5 to 10. A method for producing a beta zeolite comprising silica having an outer surface according to claim 2 having a beta zeolite structure . The method for producing a beta zeolite comprising silica whose outer surface has a beta zeolite structure according to claim 2, wherein the mass ratio of the aluminum-containing beta zeolite to the gel solution is 0.3 to 10% by mass.