JP2013112546A - Method for producing beta-zeolite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for easily producing beta-zeolite with a high Si/Al ratio without destroying a crystal structure of zeolite.SOLUTION: In the method for producing beta-zeolite, the beta-zeolite with a heightened Si/Al ratio is obtained by transforming a raw material beta-zeolite into an ammonium-type beta-zeolite via ion exchange, subsequently exposing the resultant beta-zeolite to water vapor, and then subjecting the beta-zeolite after exposure to a treatment with an acid. The raw material beta-zeolite to be subjected to the ion exchange is preferably one synthesized without using any structure-directing agent.

Description

  The present invention relates to a method for producing a beta zeolite with an increased Si / Al ratio from a beta zeolite as a raw material.

  Beta-type zeolites are useful as solid acid catalysts and adsorbents, and are currently used in large quantities around the world as catalysts in the petrochemical industry and as hydrocarbon traps for exhaust gas purification of internal combustion engines. Various methods for synthesizing beta zeolite have been proposed. A general method is a method in which a compound containing tetraethylammonium ions is used as a structure directing agent (hereinafter abbreviated as “organic SDA”). Such a method is described in Patent Document 1 below, for example. However, since compounds containing tetraethylammonium ions are expensive and most of the excess is decomposed after the crystallization of the beta-type zeolite is completed, the amount taken into the crystals cannot be removed by any method other than decomposition. It cannot be recovered and reused. Therefore, the beta zeolite produced by this method is expensive. Furthermore, since tetraethylammonium ions are taken into the crystal, it must be removed by calcination when used as an adsorbent or a catalyst. The exhaust gas at that time causes environmental pollution and also requires many chemicals for the detoxification treatment of the synthetic mother liquor. Thus, since the synthesis method of beta-type zeolite using tetraethylammonium ions is not only expensive, but also a production method with a large environmental load, it has been desired to realize a production method that does not use organic SDA.

Under such circumstances, Patent Document 2 recently proposed a method for synthesizing beta-type zeolite that does not use organic SDA. In this document, a silica source, an alumina source, an alkali source, and water are mixed so as to be a reaction mixture having a specific composition; the SiO ₂ / Al ₂ O ₃ ratio is 8 to 30 and the average particle size is Beta-type zeolite containing no organic compound having a diameter of 150 nm or more is used as a seed crystal, and this is added to the reaction mixture in a proportion of 0.1 to 20% by mass with respect to the silica component in the reaction mixture; The reaction mixture to which the seed crystals have been added is hermetically heated at 100 to 200 ° C. to synthesize beta-type zeolite without using organic SDA.

  By the way, when using beta-type zeolite as a catalyst in the petrochemical industry or when using it as a hydrocarbon trap for exhaust gas purification of an internal combustion engine, it is advantageous from the viewpoint of performance improvement to increase its Si / Al ratio. is there. As a technique for increasing the Si / Al ratio in beta-type zeolite, for example, as described in Patent Document 3, a method of performing steam treatment and acid treatment in this order is known.

US Pat. No. 3,308,069 International publication 2011/013560 pamphlet JP 2010-215434 A

  However, depending on the type of beta zeolite used as a raw material, when the above-described treatment is performed as a technique for increasing the Si / Al ratio, the crystal structure of the zeolite may be destroyed.

  The subject of this invention is providing the manufacturing method of the beta type zeolite which can eliminate the various fault which the prior art mentioned above has.

  In the present invention, the raw beta-type zeolite is made into an ammonium type by ion exchange, then the beta-type zeolite is exposed to water vapor, and the exposed beta-type zeolite is subjected to an acid treatment to increase the Si / Al ratio. The above-mentioned problems are solved by providing a method for producing a beta zeolite, which is characterized in that a beta zeolite is obtained.

  According to the present invention, a beta zeolite having a high Si / Al ratio can be easily produced without destroying the crystal structure of the zeolite.

FIG. 1 is a schematic view showing an apparatus used for water vapor exposure of a beta zeolite. FIG. 2 is an X-ray diffraction pattern of the beta zeolite obtained in Examples 1 to 5 using a beta zeolite synthesized without using an organic structure-directing agent as a raw material. FIG. 3 is an X-ray diffraction pattern of the beta zeolite obtained in Examples 6 to 10 using a beta zeolite synthesized using an organic structure-directing agent as a raw material. FIG. 4 is an X-ray diffraction pattern of the beta zeolite obtained in Comparative Examples 1 and 2. FIG. 5 is a schematic view of an apparatus for evaluating the catalytic activity of the beta zeolite obtained in Examples 2 and 7.

  The production method of the present invention includes (1) an ion-exchange treatment step of a raw material beta zeolite, (2) a step of exposing the ion-exchanged raw material beta zeolite to water vapor, and (3) a raw material beta type exposed to water vapor. It includes 3 steps of acid treatment of zeolite. Hereinafter, each of these steps will be described.

(1) Ion exchange treatment process of raw material beta-type zeolite The raw material beta-type zeolite generally contains an alkali metal such as sodium. Beta-type zeolite containing alkali metals is removed by ion exchange because it does not exhibit the desired characteristics when used as a catalyst in the petrochemical industry or as a hydrocarbon trap for exhaust gas purification of internal combustion engines. Thus, an ammonium type beta zeolite is obtained.

  As the raw material beta-type zeolite to be subjected to the ion exchange treatment, for example, a low Si / Al ratio having a Si / Al ratio of 4 to 100, preferably 4 to 8, and more preferably 5 to 7 is used. By using the raw material beta zeolite having a low Si / Al ratio, the effect of the production method of the present invention becomes remarkable.

  As the raw material beta-type zeolite, (i) those synthesized without using organic SDA (hereinafter also referred to as “OSDA free beta-type zeolite”) and (b) those synthesized using organic SDA (hereinafter “ Both of them are also referred to as “OSDA beta type zeolite”). Of these (a) and (b), the beta zeolite of (a) is likely to break the crystal structure of the zeolite when the Si / Al content is increased by the conventional method. found. However, when the beta-type zeolite (a) is treated by the method of the present invention, Si / Al can be increased while suppressing the destruction of the crystal structure as much as possible. Therefore, among (A) and (B), when the beta zeolite of (A) is used as a raw material, the characteristics of the present invention become more prominent. In addition, the use of the beta zeolite of (A) is advantageous from the viewpoint of economic efficiency and environmental load because it does not use organic SDA.

  In the case of using the beta zeolite of (A), as a synthesis method of the beta zeolite, for example, a method described in International Publication 2011/013560 pamphlet can be employed. Moreover, the method described in Chinese Patent Application Publication No. 10129968A can also be employed. Furthermore, the method described in Chemistry of Materials, Vol. 20, No. 14, p.4533-4535 (2008) can also be employed.

An example of the synthesis method of (a) beta zeolite is as follows.
(I) A silica source, an alumina source, an alkali source, and water are mixed so as to be a reaction mixture having a composition represented by a molar ratio shown below.
SiO ₂ / Al ₂ O ₃ = 40 to 200, especially 44 to 200
Na ₂ O / SiO ₂ = 0.22 to 0.4, especially 0.24 to 0.35
H ₂ O / SiO ₂ = 10-50, especially 15-25
(Ii) Beta-type zeolite not containing an organic compound having a SiO ₂ / Al ₂ O ₃ ratio of 8 to 30 and an average particle diameter of 150 nm or more, particularly 150 to 1000 nm, particularly 200 to 600 nm, as a seed crystal Used, and added to the reaction mixture at a ratio of 0.1 to 20% by mass with respect to the silica component in the reaction mixture,
(Iii) The reaction mixture to which the seed crystal has been added is hermetically heated at 100 to 200 ° C, particularly 120 to 180 ° C.

  The beta zeolite of (b) may be obtained by synthesis or a commercially available product may be used. To synthesize (b) beta-type zeolite, for example, an aqueous solution containing tetraethylammonium hydroxide (organic structure-directing agent) and sodium hydroxide is added to and mixed with an aqueous solution of colloidal silica and aluminum sulfate. It can be obtained by carrying out the reaction for 1 to 10 days under heating at 100 to 200 ° C. Since the beta-type zeolite thus obtained has tetraethylammonium hydroxide remaining in the pores, it is removed by calcination. Firing can be performed in an air atmosphere under heating at 500 to 600 ° C. for 1 to 10 hours.

  An ammonium compound is used for ion exchange of the raw material beta zeolite, and ammonium nitrate, ammonium chloride, ammonium acetate, and ammonium sulfate are particularly preferably used. When ion exchange is performed with an ammonium compound such as ammonium nitrate or ammonium chloride, 100 to 1000 mL, particularly 400 to 600 mL, of an aqueous solution having an ammonium ion concentration of 0.1 to 10 mol / L is added to 10 g of the raw material beta zeolite. It is preferable to do. Ion exchange can be performed under a heated state of an aqueous solution containing ammonium ions or under a non-heated state. When heating the aqueous solution containing ammonium ions, the heating temperature is preferably 40 to 100 ° C, particularly 70 to 90 ° C. The raw beta zeolite is dispersed in an aqueous solution containing ammonium ions to form a dispersion, and this state is maintained for a predetermined time to perform ion exchange. The holding time is preferably 1 to 48 hours, particularly preferably 12 to 24 hours. The dispersion may be in a stationary state or in a stirred state.

  After holding the dispersion for a predetermined time, the dispersion is filtered to separate the raw beta zeolite and washed with water. If necessary, the combination of the ion exchange treatment and the water washing may be performed a plurality of times. After performing the ion exchange treatment in this way, the raw material beta zeolite is dried to obtain an ammonium beta zeolite. This ammonium-type beta-type zeolite thus has an extremely reduced content of alkali metal ions.

(2) Step of exposing ion-exchanged raw material beta-type zeolite to water vapor To expose the ammonium-type raw material beta-type zeolite to water vapor, for example, the raw material beta-type zeolite is allowed to stand in a water vapor atmosphere, What is necessary is just to arrange | position raw material beta-type zeolite in it. Specifically, the raw material beta zeolite can be exposed to water vapor using the apparatus shown in FIG. The apparatus 10 shown in the figure has a holding tube 11 in which a raw material beta zeolite is held. Both ends of the holding tube 11 are open. The lower end 11a is open to the atmosphere. An upper end portion 11 b of the holding tube 11 serves as a water vapor inlet, and is connected to a water vapor supply source 12 and an inert gas supply source 13. The water vapor supply source 12 includes a bottomed cylindrical body 12a having an upper end opened. One end of an inert gas bubbling tube 12b is inserted into the cylindrical body 12a. The other end of the bubbling tube 12b is connected to an inert gas supply source (not shown). Further, water 14 is placed in the cylinder 12a. The height of the water surface is higher than the position of the end of the bubbling tube 12b inserted into the bottomed cylindrical body 12a. A heating means 15 is installed around the holding tube 11. The heating means 15 can heat the raw material beta-type zeolite held in the holding tube 11 and water vapor flowing through the holding tube 11. A predetermined amount of water vapor is supplied into the holding tube 11 by bubbling the inert gas through the bubbling tube 12b in the water vapor supply source 12 while supplying an inert gas such as argon from the inert gas supply source 13. The The supply amount of water vapor is determined by the balance of the supply amounts of inert gas in the inert gas supply source 13 and the water vapor supply source 12. The water vapor supplied into the holding tube 11 is heated by the heating means 15 together with the raw material beta zeolite. The raw beta zeolite is exposed to water vapor heated to a predetermined temperature. By this exposure, it is considered that aluminum atoms constituting the raw material beta-type zeolite are desorbed from predetermined sites in the crystal lattice, and silicon atoms migrate to the desorbed sites. However, when exposed to water vapor, there is no change in the Si / Al ratio in the raw material beta zeolite. Moreover, when the raw material beta-type zeolite is exposed to water vapor, the zeolite is converted from an ammonium type to a proton type.

  The temperature of the water vapor used for the exposure of the raw material beta zeolite is 150 to 1000 ° C., particularly 600 to 900 ° C., because it can promote the desorption of aluminum while suppressing the destruction of the crystal structure of the zeolite. preferable. For the same reason, the exposure time of water vapor is preferably 1 to 48 hours, more preferably 1 to 24 hours, particularly 12 to 24 hours when the temperature of the water vapor is within the above-mentioned range. The pressure (partial pressure) of water vapor at the time when the raw material beta zeolite contacts with water vapor is atmospheric pressure or lower because the lower end in the holding tube 11 is open. A preferable partial pressure of water vapor is 1 to 101.3 kPa.

(3) Acid treatment step of raw material beta zeolite exposed to water vapor The raw material beta zeolite exposed to water vapor is subjected to acid treatment, thereby causing dealumination from the beta zeolite. As the acid used for the acid treatment, various mineral acids are preferably used. For example, nitric acid, sulfuric acid and hydrochloric acid can be used. The higher the acid concentration during the acid treatment, the more dealumination takes place and the higher the Si / Al ratio of the beta zeolite. Accordingly, in order to obtain a beta zeolite having a desired Si / Al ratio, it is easy to adjust the acid concentration. From this viewpoint, the concentration of the acid varies depending on the type of acid used, but in many cases, it is preferably 0.1 to 100% by mass, particularly preferably 0.1 to 60% by mass. For example, when nitric acid is used as the mineral acid, the nitric acid concentration is preferably 0.1 to 70% by mass, particularly 0.5 to 5% by mass. As described above, the dealumination proceeds when the acid concentration is high. As a result, the crystal structure of the zeolite is easily destroyed. In particular, when OSDA free beta zeolite is used as a raw material, the crystal structure is easily broken. However, in the present invention, even when the treatment with the high-concentration acid is performed using OSDA free beta zeolite as a raw material due to the above-mentioned water vapor exposure treatment prior to the acid treatment. The crystal structure of zeolite is less likely to break.

  The amount of acid in the acid treatment is preferably 10 to 500 mL, particularly 100 to 200 mL of the acid having the above-mentioned concentration per 1 g of the raw beta-type zeolite because efficient dealumination occurs. The acid treatment may be performed under heating or may be performed under non-heating. When the acid treatment is carried out under heating, the acid temperature is preferably set to 40 to 100 ° C, particularly 70 to 90 ° C, from the viewpoint of efficient dealumination. In addition, when the acid treatment is performed under heating, the acid may be refluxed. When the acid treatment time and the acid concentration are in the above-mentioned ranges, the acid treatment time is 1 to 24 hours, particularly 2 to 12 hours. It is preferable from the point of carrying out.

  When the acid treatment is completed, solid-liquid separation is performed, and the filtered beta zeolite is washed with water one or more times and then dried. In this way, a beta zeolite having a higher Si / Al ratio than the raw beta zeolite is obtained. This beta zeolite has been converted to a proton type as described above.

  In this way, a beta zeolite with an increased Si / Al ratio is obtained. The Si / Al ratio in the beta zeolite is a high value of 5 or more, preferably 15 or more, more preferably 15 to 200, and even more preferably 40 to 100. In spite of such a high Si / Al ratio, the beta zeolite obtained by this production method maintains the crystal structure of the zeolite.

  The beta-type zeolite obtained by this production method is promising as a solid acid catalyst or an adsorbent. For example, a long-chain hydrocarbon (for example, hexane) cracking catalyst in the petrochemical industry, various internal combustion engines such as a gasoline engine and a diesel engine. It is especially promising as a hydrocarbon trap for exhaust gas purification.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” means “mass%”.

[Example 1]
(1) Synthesis of Seed Crystal Using tetraethylammonium hydroxide as organic SDA, sodium aluminate as an alumina source, and finely powdered silica (Mizukasil P707) as a silica source by a conventionally known method, stirring and heating at 165 ° C. for 96 hours Thus, a beta zeolite having a SiO ₂ / Al ₂ O ₃ ratio of 24.0 was synthesized. This was baked at 550 ° C. for 10 hours while circulating air in an electric furnace to produce a crystal containing no organic matter. As a result of observing this crystal with a scanning electron microscope, the average particle size was 280 nm. The crystals of beta zeolite that do not contain organic substances were used as seed crystals.

(2) Synthesis of OSDA-free beta zeolite 0.235 g of sodium aluminate and 1.828 g of 36% sodium hydroxide were dissolved in 13.9 g of pure water. A mixture of 2.024 g of finely divided silica (Cab-O-sil, M-5) and 0.202 g of the seed crystal was added to the aqueous solution little by little and mixed by stirring to obtain a reaction mixture. . In this reaction mixture, the SiO ₂ / Al ₂ O ₃ ratio was 70, the Na ₂ O / SiO ₂ ratio was 0.3, and the H ₂ O / SiO ₂ ratio was 20. This reaction mixture was placed in a 60 mL stainless steel airtight container and left to stand at 140 ° C. for 34 hours under autogenous pressure without aging and stirring. After cooling the sealed container, the product was filtered and washed with warm water to obtain a white powder. When this product was subjected to X-ray diffraction measurement, it was confirmed to be a beta zeolite containing no impurities. As a result of the compositional analysis, the Si / Al was 6.4.

(3) Ion exchange treatment The obtained OSDA-free beta zeolite was used as a raw material and dispersed in an aqueous ammonium nitrate solution. The mass ratio of OSDA free beta zeolite, ammonium nitrate, and water was 1: 2: 50. The dispersion was allowed to stand for 24 hours under heating at 80 ° C. for ion exchange. Thereafter, filtration was performed to separate the beta zeolite. The ion exchange and filtration operations were repeated once more, then washed with water and dried at 80 ° C. to obtain an ammonium type beta zeolite.

(4) Exposure to Water Vapor Ammonium type beta zeolite was filled in the apparatus shown in FIG. The filling amount was 1 g. A mixed gas of argon-water vapor was continuously circulated for 24 hours under the state of being heated to 700 ° C. by the heating means 15 shown in FIG. The partial pressure of water vapor was 12.2 kPa. Upon exposure to water vapor, the beta zeolite was converted from ammonium to proton form.

(5) Acid treatment Beta-type zeolite after exposure to water vapor was acid-treated with a 0.1 mol / L nitric acid aqueous solution. The temperature of the aqueous nitric acid solution was 80 ° C. 10 mL of nitric acid aqueous solution was added to 1 g of beta zeolite. The treatment was carried out for 2 hours while stirring the liquid with a magnetic stirrer. In this way, the intended beta zeolite was obtained. The X-ray diffraction pattern of the obtained beta zeolite is shown in FIG. Moreover, Si / Al ratio calculated | required from the elemental analysis was described in the figure.

[Examples 2 to 5]
In Example 1, the concentration of the aqueous nitric acid solution used for the acid treatment was 0.5 mol / L (Example 2), 1.0 mol / L (Example 3), 2.0 mol / L (Example 4), and 8. It was set to 0 mol / L (Example 5). Except this, it carried out similarly to Example 1, and obtained the beta type zeolite by which Si / Al ratio was raised. The X-ray diffraction pattern of the obtained beta zeolite is shown in FIG. Moreover, Si / Al ratio calculated | required from the elemental analysis was described in the figure.

Example 6
(1) Synthesis of OSDA beta-type zeolite An aqueous solution containing tetraethylammonium hydroxide (OSDA) and sodium hydroxide was stirred at room temperature, and colloidal silica was added thereto. As colloidal silica, Ludox HS-40 (silica content 40%) was used. After adding colloidal silica, stirring was performed for 30 minutes, and then an aqueous aluminum sulfate solution was added, and stirring was further performed for 30 minutes to obtain a gel. The composition of this gel was 0.033 mol of Al ₂ O ₃ , 0.24 mol of sodium hydroxide, 0.50 mol of tetraethylammonium hydroxide, and 20 mol of water with respect to 1 mol of SiO ₂ . . This gel was placed in an autoclave and reacted for 7 days under the condition of being heated to 150 ° C. In this way, a beta zeolite was obtained. This zeolite was heated at 550 ° C. for 6 hours in an air atmosphere to decompose and remove OSDA, tetraethylammonium hydroxide. When this product was subjected to X-ray diffraction measurement, it was confirmed to be a beta zeolite containing no impurities. As a result of the compositional analysis, the Si / Al was 13.1.

(2) Ion exchange, water vapor exposure, and acid treatment Under the same conditions as in Example 1, ion exchange, water vapor exposure, and acid treatment were performed. In this way, the intended beta zeolite was obtained. The X-ray diffraction pattern of the obtained beta zeolite is shown in FIG. Moreover, Si / Al ratio calculated | required from the elemental analysis was described in the figure.

[Examples 7 to 10]
In Example 6, the concentration of the aqueous nitric acid solution used for the acid treatment was 0.5 mol / L (Example 7), 1.0 mol / L (Example 8), 2.0 mol / L (Example 9) and 8. It was set to 0 mol / L (Example 10). Except this, it carried out similarly to Example 6, and obtained the beta type zeolite by which Si / Al ratio was raised. The X-ray diffraction pattern of the obtained beta zeolite is shown in FIG. Moreover, Si / Al ratio calculated | required from the elemental analysis was described in the figure.

[Comparative Example 1]
In Example 1, beta-type zeolite was obtained without ion treatment and ion exchange and water vapor exposure. The X-ray diffraction pattern of the obtained beta zeolite is shown in FIG. Moreover, Si / Al ratio calculated | required from the elemental analysis was described in the figure.

[Comparative Example 2]
In Example 1, ion exchange and water vapor exposure were not performed, and only acid treatment was performed to obtain a beta zeolite. The X-ray diffraction pattern of the obtained beta zeolite is shown in FIG. Moreover, Si / Al ratio calculated | required from the elemental analysis was described in the figure.

  As is apparent from the results shown in FIGS. 2 and 3, it can be seen that the beta zeolite obtained by the method of the present invention has an increased Si / Al ratio while maintaining the crystal structure of the zeolite. . On the other hand, the beta zeolite of Comparative Example 1 obtained using OSDA-free beta zeolite as a raw material and not subjected to acid treatment maintains the crystal structure of the zeolite, but has a Si / Al ratio. There was no improvement. In addition, the beta zeolite of Comparative Example 2 obtained by using only OSD, using OSDA-free beta zeolite as a raw material, without performing ion exchange and water vapor exposure, has an increased Si / Al ratio. It can be seen that the crystal structure of the zeolite is destroyed.

Examples 11 and 12
For the beta zeolite obtained in Examples 2 and 7, the catalytic activity in the hexane cracking reaction was evaluated by the following procedure.
Prior to the evaluation of the catalytic activity, powdered beta zeolite was molded and sized. Specifically, 1 to 2 g of beta-type zeolite powder was packed in a tablet molding machine having an inner diameter of 20 mm, and then press-molded at 0.4 MPa with a hydraulic press to obtain pellets having a diameter of 20 mm. The pellets were appropriately pulverized on a sieve and sized to 500 to 600 μm and used as a catalyst.

The catalytic reaction in this example was performed using a fixed bed normal pressure flow reactor. A schematic diagram of the apparatus is shown in FIG. Hexane as a reactant was supplied from a syringe using a syringe pump and introduced into a nitrogen (1%)-argon mixed gas as a carrier gas. Hexane supplied from the syringe pump was evaporated into gas because it was introduced into the preheated vaporization chamber, and this gas was accompanied by the carrier gas. A stainless steel pipe with an inner diameter of 2 mm was used for the gas line of the reactor, and the condensation of vaporized hexane was prevented by heating from the outside to an appropriate temperature with a heater. As the reaction tube, a quartz tube having an inner diameter of 8 mm was used, and 100 mg of the previously sized beta-type zeolitic catalyst was packed therein, and the catalyst layer was held at the center of the reaction tube with quartz wool. As a pretreatment for the reaction, the temperature was raised to 650 ° C. at a rate of temperature rise of about 7 ° C./min under air flow, and kept in this atmosphere for 1 hour. Then, after switching to helium circulation, the reaction tube temperature was lowered to 450 ° C. at 5 ° C./min. After confirming that it was stable at 450 ° C., a methane-helium mixed gas accompanied by hexane was supplied to the catalyst layer to initiate a catalytic reaction. The partial pressure of hexane was 5.0 kPa. After 5 minutes from the start of the reaction, the hexagonal valve is switched to introduce the reaction product accumulated in the sampling loop into the gas chromatograph, and after separation with a capillary column, each product and unreacted with a flame detector (FID). Qualitative and quantitative analysis of the product was performed. After a predetermined time (70 minutes), the supply of hexane to the catalyst layer was stopped and the helium flow was switched to. Thereafter, when the temperature was stabilized by heating to 500 ° C. at 1 to 2 ° C./min, hexane was supplied again to carry out the catalytic reaction. The same operation was continued at 550 and 600 ° C. The W / F during the catalytic reaction was 19.8 g-catalyst h (mol-hexane) ⁻¹ at any reaction temperature. After stopping the catalytic reaction at 600 ° C., it was allowed to cool naturally under helium flow. The results are shown in Table 1 below. The selectivity for each product was determined on a carbon basis (in terms of carbon atoms). The yield of propylene (C ₃ =) was determined from “conversion rate × selectivity to propylene (C ₃ =)”. In addition, reaction temperature is measured between the heater installed so that the quartz reaction tube of a fixed bed normal pressure flow reaction apparatus may be heated from the outside, and the reaction tube.

As is apparent from the results shown in Table 1, when the beta zeolite obtained in Examples 2 and 7 was used as a catalyst and hexane cracking was performed, C ₃ = (propylene), a substance useful as a chemical raw material, was obtained. It can be seen that it is produced in high yield. It can also be seen that no deactivation of the beta zeolite is observed.

DESCRIPTION OF SYMBOLS 10 Water vapor exposure apparatus 11 Holding pipe 12 Water vapor supply source 13 Inert gas supply source 14 Water 15 Heating means

Claims (6)

  Beta-type zeolite whose Si / Al ratio is increased by converting the raw beta-type zeolite into an ammonium type by ion exchange, then exposing the beta-type zeolite to water vapor, and subjecting the beta-type zeolite after the exposure to acid treatment A process for producing a beta zeolite, characterized in that   The production method according to claim 1, wherein the raw material beta-type zeolite subjected to ion exchange is synthesized without using a structure-directing agent.   The production method according to claim 1, wherein the raw material beta-type zeolite subjected to ion exchange is synthesized using a structure-directing agent.   The manufacturing method as described in any one of Claim 1 thru | or 3 which exposes the raw material beta-type zeolite after ion exchange to 150-1000 degreeC water vapor for 1-48 hours.   The manufacturing method as described in any one of Claims 1 thru | or 4 which attaches | subjects the raw material beta-type zeolite after exposure to water vapor | steam to mineral acid at 40-100 degreeC over 1 to 24 hours.   The production method according to any one of claims 1 to 5, wherein a beta-type zeolite having a Si / Al ratio of 5 or more is obtained.