MFI / MEL zeolite composite

Abstract

To provide a zeolite with a structure that is less prone to caulking than conventional zeolites.SOLUTION: A composite of a ZSM-5(MFI) type zeolite and a ZSM-11 (MEL) type zeolite is provided. The MFI type / MEL type zeolite composite is characterized by an aspect ratio of primary particles (average major axis diameter of particles / average minor axis diameter of particles) of 1.5 or more and 10 or less, and a ratio of an intensity I1 of a diffraction peak assigned to crystal lattice (101) plane and / or (011) plane to an intensity I2 of a diffraction peak assigned to crystal lattice (200) plane and / or (020) plane observed by X-ray diffraction (I2 / I1) of 1 or more and 3 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an MFI / MEL zeolite composite, and more particularly to an MFI / MEL zeolite composite useful as a catalyst for use in a methanol conversion reaction or the like. [Background technology]

[0002] Zeolite is a general term for crystalline aluminosilicates, and its composition formula is M 2 / n It is represented by O·Al2O3·xSiO2·yH2O (M is a cation, n is the valence of the cation, and x≧2, y≧0), and is used as an adsorbent, a catalyst for various reactions, etc. Zeolites are classified according to their crystal structure, and examples include ABW-type zeolites (see, for example, Patent Document 1) which have a three-dimensional pore structure composed of 3.8 × 3.4 angstrom eight-membered oxygen rings, CHA-type zeolites (see, for example, Patent Document 2) which have a three-dimensional pore structure composed of 3.8 × 3.4 angstrom eight-membered oxygen rings, and pentasil-type zeolites which have a structure in which five-membered oxygen rings are linked.

[0003] The above-mentioned pentasil-type zeolite has been variously studied as a catalyst in petroleum refining processes such as lower hydrocarbon synthesis reactions and fluid catalytic cracking (see, for example, Patent Document 3). Among the pentasil zeolites, ZSM-5 zeolites have a crystal structure composed of 10-membered oxygen rings, with linear through-pores along the b-axis and zigzag through-pores along the a-axis. Due to their unique pore structure and solid acidity, ZSM-5 zeolites have been extensively studied as acid catalysts for hydrocarbon isomerization and alkylation reactions.

[0004] Regarding ZSM-5 type zeolite, for example, Patent Document 4 discloses ZSM-5 type zeolite having a predetermined structure. Patent Document 5 discloses a silicate-coated MFI zeolite obtained by coating MFI zeolite with silicate, characterized in that in the X-ray diffraction spectrum of the silicate-coated MFI zeolite, the peak area ratio b / a of peak a at 2θ=7.0 to 8.4° and peak b at 2θ=8.4 to 9.7° is 1 or more, and the pKa value measured with a Hammett indicator is +3.3 or more. Furthermore, Patent Document 6 discloses a method for coating zeolite crystals in which the a-axis length of the MFI zeolite crystals to be coated is 350 nm or more and less than 8 μm, the b-axis length is 200 nm or more and less than 3 μm, and the c-axis length is 500 nm or more and less than 20 μm, and the ratios of the a-axis length, the b-axis length, and the c-axis length satisfy a predetermined relationship.

[0005] ZSM-11 zeolite, a type of pentasil zeolite, has cavities formed by the same intersecting pores as ZSM-5 zeolite, but also cavities with a volume that is approximately 30% larger than that of ZSM-5 zeolite. Therefore, it is known that in, for example, a methanol conversion reaction, reaction selectivity in which there are fewer C1-C3 hydrocarbons and more C6 or higher hydrocarbons can be easily obtained, and Non-Patent Document 1 reports on the catalytic performance of ZSM-11 zeolite. ZSM-11 zeolites have a larger pore volume than ZSM-5 zeolites, so when used as catalysts for hydrocarbon synthesis reactions, the deposition of carbonaceous materials is suppressed, and as a result, it is expected that the catalyst will have a longer life. However, ZSM-11 zeolites are more unstable than ZSM-5 zeolites, and it is difficult to synthesize them as simple substances.

[0006] Since ZSM-5 zeolite and ZSM-11 zeolite have the same secondary building blocks that make up their crystals, ZSM-5 and ZSM-11 zeolites may coexist (intergrowth) in a single crystal particle depending on the synthesis conditions. Non-Patent Document 2 reports on the synthesis of ZSM-5 / ZSM-11 cocrystals and their catalytic activity for the conversion of methanol to propylene. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-237585 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-007912 [Patent Document 3] Japanese Patent Application Laid-Open No. 2019-178049 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-178745 [Patent Document 5] International Publication No. 2013 / 147261 [Patent Document 6] Japanese Patent Application Laid-Open No. 2004-002160 [Non-patent literature]

[0008] [Non-Patent Document 1] Yoshinari Kawamura and 4 others, Journal of the Petroleum Society (Japan), 1991, Vol. 34, No. 3, pp. 273-279 [Non-patent document 2] J. Tao (Jiayi Tao) and 5 others, "Crystal Research and Technology" (Germany), 2020, Vol. 55, No. 7, 200027 Summary of the Invention [Problem to be solved by the invention]

[0009] As described above, various zeolites and methods for producing zeolites have been disclosed in the past. However, the conventional zeolites do not have a structure that can sufficiently suppress catalyst deterioration due to the generation of polymeric hydrocarbons (coking), and there is room for development of zeolites with a structure that is less susceptible to coking.

[0010] The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide a zeolite having a structure that is less susceptible to coking than conventional zeolites. [Means for solving the problem]

[0011] The present inventors have conducted extensive research into zeolites and have come to the conclusion that when a composite of ZSM-5 (MFI) type zeolite and ZSM-11 (MEL) type zeolite is synthesized using predetermined materials under predetermined conditions, particles having an aspect ratio within a predetermined range and pores that have grown large in the b-axis direction (long straight channels) are obtained. These characteristics are thought to make coking less likely to occur, and this leads to an excellent solution to the above-mentioned problems, leading to the completion of the present invention.

[0012] That is, the present invention relates to a composite of ZSM-5 (MFI) zeolite and ZSM-11 (MEL) zeolite, and the MFI / MEL zeolite composite has a primary particle aspect ratio (average major axis diameter of particles / average minor axis diameter of particles) of 1.5 or more and 10 or less, and an X-ray diffraction measurement result in which the ratio (I2 / I1) of the intensity I1 of the diffraction peak assigned to the crystal lattice (101) plane and / or the (011) plane to the intensity I2 of the diffraction peak assigned to the crystal lattice (200) plane and / or the (020) plane is 1 or more and 3 or less.

[0013] The MFI / MEL zeolite composite preferably has a primary particle major axis diameter of 9 μm or more and 20 μm or less, and a primary particle minor axis diameter of 2 μm or more and 6 μm or less.

[0014] The MFI / MEL zeolite composite preferably has a ZSM-11 ratio of 0.6 or more and 1 or less.

[0015] The present invention is also a method for producing the above-mentioned MFI / MEL zeolite composite, which includes a step (I) of mixing a silicon atom-containing compound, a quaternary alkylammonium compound, and a base and aging the mixture, and a step (II) of hydrothermally reacting the product obtained in the aging step (I).

[0016] The method for producing the MFI / MEL zeolite composite preferably includes a step (III) of calcining the product obtained in the hydrothermal step (II). [Effects of the Invention]

[0017] The MFI / MEL zeolite composite of the present invention has the above-described configuration and has pores that have grown large in the b-axis direction. Therefore, the composite has a structure that is less susceptible to coking than conventional zeolites, and therefore catalyst deterioration can be suppressed, and a longer life can be expected. [Brief explanation of the drawings]

[0018] [Figure 1] 1 shows a schematic diagram of a rod-shaped particle for calculating the rod-shaped degree. [Figure 2] 1 is an SEM photograph (magnification: 1000 times) of the MFI type / MEL type zeolite composite obtained in Example 1. [Figure 3] 1 is an SEM photograph (magnification: 1000 times) of the MFI type / MEL type zeolite composite obtained in Comparative Example 1. [Figure 4] 1 is an SEM photograph (magnification: 1000 times) of the MFI type / MEL type zeolite composite obtained in Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0019] Preferred embodiments of the present invention will be specifically described below, but the present invention is not limited to the following description and can be appropriately modified and applied within the scope of the present invention. Note that combinations of two or more of the individual preferred embodiments of the present invention described below also fall within the scope of preferred embodiments of the present invention.

[0020] The MFI / MEL zeolite composite of the present invention is characterized in that the aspect ratio of the primary particles is 1.5 or more and 10 or less, and the ratio (I2 / I1) of the intensity I1 of the diffraction peak attributable to the crystal lattice (101) plane and / or (011) plane to the intensity I2 of the diffraction peak attributable to the crystal lattice (200) plane and / or (020) plane, observed by X-ray diffraction, is 1 or more and 3 or less. In this specification, the MFI / MEL zeolite composite means a zeolite having the skeletal structure of MFI zeolite and the skeletal structure of MEL zeolite in one crystal particle. The MFI / MEL zeolite composite of the present invention has a rod-like shape because the aspect ratio of the primary particles is within the above range, and has pores (long straight channels) that have grown large in the b-axis direction because the diffraction peak intensity ratio I2 / I1 is within the above range. This structure makes coking less likely to occur, and therefore catalyst deterioration can be suppressed, and a longer life can be expected. Furthermore, since the MFI / MEL zeolite composite particles are rod-shaped with a high aspect ratio, they are easy to orient when used as a catalyst. The aspect ratio of the primary particles can be calculated by the method described in the Examples.

[0021] The aspect ratio of the primary particles of the MFI / MEL zeolite composite is preferably 1.7 to 7.6, and more preferably 2 to 6.

[0022] The MFI / MEL zeolite composite has a rod-like shape with an aspect ratio of the primary particles in the above range, and the average rod-likeness L2' / L1' calculated by the following method is preferably 0.25 or more, more preferably 0.3 or more, and even more preferably 0.35 or more. The rod-likeness is an index relating to the shape of zeolite, and refers to the degree of rod-likeness when the zeolite is observed two-dimensionally in an SEM image. The closer the zeolite is to a polygonal columnar shape, the higher the rod-likeness, and the closer the zeolite is to an oblong spheroid shape, the lower the rod-likeness. <Calculation method for rod-likeness L2 / L1> As shown in the schematic diagram in Figure 1, assuming that the particle is rod-shaped with a flattened portion parallel to the major axis diameter, the length of the flattened portion parallel to the major axis diameter of the particle is L2, and the remaining part of the major axis diameter is 2L1, the major axis diameter is expressed as (2L1 + L2), and the minor axis diameter of the particle is expressed as 2W. Using the major axis diameter (2L1+L2) and minor axis diameter (2W) of the above particle, the particle area S0 and the area S1 of the rectangle circumscribing the particle can be expressed by the following formulas (1) and (2), respectively. S0 and S1 of actual particles can be measured by image processing based on SEM images. S1=4L1W+2L2W (1) S0=πL1W+2L2W (2) From the above formulas (1) and (2), S0 / S1 can be expressed as (πL1+2L2) / (4L1+2L2)=1-(4-π) / (4+2L2 / L1), so the rod-likeness L2 / L1 can be calculated by substituting the measured values ​​of S0 and S1 into the following formula (3). L2 / L1=(2(S0 / S1)-π / 2) / (1-S0 / S1) (3) Image processing based on the above SEM image is performed on 20 particles on a line drawn randomly on the electron microscope photograph, and the average value of L2 / L1 is taken as the average rodlikeness (average value of the rodlikeness of 20 particles) L2' / L1'. If the rodlikeness is difficult to measure, measure it using a photograph taken at an appropriately increased magnification.

[0023] The diffraction peak intensity ratio (I2 / I1) is preferably 1 to 2.5, and more preferably 1 to 2.

[0024] In the MFI / MEL zeolite composite, the intensity ratio (I2 / I1) of the diffraction peaks as an index of growth in the b-axis direction may be 1 or more and 3 or less, but the ratio (I2' / I1') of the peak intensity I1' appearing at 2θ=7.0 to 8.4° and the peak intensity I2' appearing at 2θ=8.4 to 9.7° observed by X-ray diffraction is preferably 1 or more and 3 or less. The peak intensity ratio (I2' / I1') is preferably 1 to 2.5, and more preferably 1 to 2.

[0025] The ratio of ZSM-11 calculated by the following method in the above MFI-type / MEL-type zeolite composite is preferably 0.6 or more and 1 or less. Since ZSM-11 has a larger pore volume than ZSM-5, if the ratio of ZSM-11 is 0.6 or more, coking can be more sufficiently suppressed, and thus the catalyst life can be extended. In addition, ZSM-11 has cavities about 30% larger in volume than those formed by the same intersecting pores as ZSM-5. Therefore, in, for example, the methanol conversion reaction, it is easy to obtain a reaction selectivity with less C1-C3 hydrocarbons and more C6+ hydrocarbons. Therefore, when the ratio of ZSM-11 is within the above range, the proportion of C6+ hydrocarbons in the methanol conversion reaction can be increased more. More preferably, the ratio of ZSM-11 is 0.65 or more, and still more preferably 0.7 or more. <Measurement method of ZSM-11 ratio> The ratio of ZSM-11 is calculated by the reference intensity ratio (RIR) method using the intensity ratio of the diffraction lines of ZSM-11 and the diffraction lines of ZSM-5 obtained from the X-ray diffraction pattern by powder X-ray diffraction measurement.

[0026] In the above MFI-type / MEL-type zeolite composite, the long axis diameter of the primary particles is preferably 9 μm or more and 20 μm or less, and the short axis diameter of the primary particles is preferably 2 μm or more and 6 μm or less. Thereby, the orientation control of the crystals in the catalytic reaction becomes easy, and thus higher catalytic activity can be exhibited. More preferably, the long axis diameter of the primary particles is 10-18 μm. More preferably, the short axis diameter of the primary particles is 3-5 μm.

[0027] The molar ratio of SiO2 to Al2O3 (SiO2 / Al2O3) in the above MFI-type / MEL-type zeolite composite is not particularly limited, but is preferably 20 or more. More preferably, it is 30-3000, and still more preferably 50-2000. The molar ratio of SiO2 to Al2O3 in the above MFI-type / MEL-type zeolite composite can be measured by EZ scan, which is the elemental scanning function of a fluorescent X-ray analyzer (manufactured by Rigaku Corporation: model number ZSX PrimusII).

[0028] <Method for Producing MFI-Type / MEL-Type Zeolite Composite> The method for producing the MFI-type / MEL-type zeolite composite of the present invention is not particularly limited, but it is preferable to carry out a step (I) of mixing and aging a silicon atom-containing compound, a quaternary alkylammonium compound, and a base, and a step (II) of subjecting the product obtained in the aging step (I) to a hydrothermal reaction. By such a method, an MFI-type / MEL-type zeolite composite having an aspect ratio of primary particles of 1.5 or more and 10 or less and an above-mentioned diffraction peak intensity ratio I2 / I1 of 1 or more and 3 or less can be sufficiently obtained. A method for producing an MFI-type / MEL-type zeolite composite including the above aging step (I) and the above hydrothermal step (II) is also one of the present inventions.

[0029] The silicon atom-containing compound used in the above aging step (I) is not particularly limited as long as it contains a silicon atom, but it is preferably one containing silica. Examples of the silicon atom-containing compound containing silica include industrial silica, silicon alkoxide, rice husk ash, etc. However, effective utilization of biomass resources such as rice husk ash is more preferable because it also leads to solving problems for a sustainable society.

[0030] The quaternary alkylammonium compound used in the above aging step (I) is not particularly limited as long as it is a quaternary alkylammonium compound having four alkyl groups, but the following formula (4); [NR 1 4] + X - (4) [[ID=2\6]](In the formula, R 1 represents an alkyl group having 1 to 10 carbon atoms, which may be the same or different. X represents a halogen atom.) The compound represented by this is preferable. The above R 1The alkyl group in the formula (I) has more preferably 1 to 9 carbon atoms, and further preferably 2 to 8 carbon atoms. The quaternary alkylammonium compound is more preferably tetrabutylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, or tetraoctylammonium bromide, and more preferably tetrabutylammonium bromide.

[0031] The base used in the aging step (I) is not particularly limited, and examples thereof include alkali metal or alkaline earth metal hydroxides such as sodium hydroxide, potassium hydroxide, calcium hydroxide, etc.; alkali metal carbonates and bicarbonates such as sodium carbonate and sodium bicarbonate; ammonia; organic amines, etc. Among these, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide are preferred, and sodium hydroxide is more preferred.

[0032] The amounts of the silicon atom-containing compound and quaternary alkylammonium compound used in the aging step (I) may be determined in consideration of the molar ratio of SiO2 to Al2O3 in the resulting MFI / MEL zeolite composite, and the amount of the quaternary alkylammonium compound used is preferably 1 to 25 mol%, more preferably 4 to 20 mol%, and even more preferably 8 to 15 mol%, relative to 100 mol% of the silicon atom-containing compound.

[0033] The amount of base used in the aging step (I) is not particularly limited as long as it can hydrolyze the silicon atom-containing compound, but is preferably 5 to 40 mol % relative to 100 mol % of the silicon atom-containing compound, more preferably 10 to 35 mol %, and even more preferably 15 to 30 mol %.

[0034] In the aging step (I), the order in which the silicon atom-containing compound, the quaternary alkylammonium compound, and the base are mixed is not particularly limited, but it is preferable to mix the silicon atom-containing compound and the base first and then mix the quaternary alkylammonium compound.

[0035] In the aging step (I), when the silicon atom-containing compound and the base are mixed in advance, it is preferable to mix them and then stir them for 1 to 300 minutes. The temperature during the above mixing and stirring is preferably 10 to 50°C.

[0036] In the aging step (I), the aging temperature for the mixture of the silicon atom-containing compound, the quaternary alkylammonium compound, and the base is preferably 60 to 100°C. This makes it possible to increase the diffraction peak intensity ratio I2 / I1 and the proportion of ZSM-11 in the resulting MFI / MEL zeolite composite. The aging temperature is more preferably 65 to 95°C, and even more preferably 70 to 90°C. The aging time of the mixture is preferably 1 to 200 hours. By aging the mixture at the above-mentioned preferred temperature for 1 to 200 hours before the hydrothermal reaction, the proportion of ZSM-11 can be further increased, and when rice husk ash or the like is used as the raw material for the silicon atom-containing compound, the technical significance of carrying out the aging step (I) in such a preferred form is more pronounced. The aging time is more preferably 20 to 100 hours.

[0037] In the hydrothermal step (II), it is preferable to hydroheat the product obtained in the aging step (I). This can increase the diffraction peak intensity ratio I2 / I1 and the proportion of ZSM-11 in the resulting MFI / MEL zeolite composite. The hydrothermal temperature is preferably 105 to 220°C, more preferably 110 to 200°C.

[0038] The time for the hydrothermal reaction in the hydrothermal step (II) is not particularly limited, but is preferably 1 to 200 hours, more preferably 2 to 100 hours.

[0039] The amount of water in the above hydrothermal step (II) is preferably 200 to 1000% by mass based on 100% by mass in total of the above silicon atom-containing compound, the quaternary alkylammonium compound, and the base. More preferably, it is 400 to 900% by mass.

[0040] The method for producing the above MFI-type / MEL-type zeolite composite preferably includes a step (III) of firing the product obtained in the above hydrothermal step (II). Thereby, the growth of the MFI-type / MEL-type zeolite composite in the b-axis direction can be further promoted.

[0041] The firing temperature in the above firing step (III) is not particularly limited, but is preferably 150 to 800 °C. More preferably, it is 200 to 750 °C, and still more preferably, it is 250 to 700 °C.

[0042] The firing time in the above firing step (III) is not particularly limited, but is preferably 0.1 to 72 hours. More preferably, it is 0.5 to 48 hours, and still more preferably, it is 1 to 24 hours.

[0043] The method for producing the above MFI-type / MEL-type zeolite composite preferably includes a step of washing the product obtained in the hydrothermal step (II) before the above firing step (III). Thereby, the growth of the MFI-type / MEL-type zeolite composite in the b-axis direction can be further promoted. The washing method in the above washing step is not particularly limited, but is preferably performed by filtration or the like. In the method for producing the above MFI-type / MEL-type zeolite composite, it is also preferable to perform drying after the above washing step.

[0044] <Use of MFI-type / MEL-type zeolite composite> The MFI-type / MEL-type zeolite composite of the present invention can be suitably used as a catalyst or the like in a petroleum refining process. Preferably, it is a catalyst used in a methanol conversion reaction or the like.

Examples

[0045] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0046] <Physical property evaluation> The physical properties of the obtained MFI / MEL zeolite composite were evaluated by the following procedure. (1) Aspect ratio measurement Using a field-emission scanning electron microscope (JEOL, JSM-7000F), electron micrographs were taken so that approximately 50 to 10,000 particles were captured. The average value of the major axes of 20 particles on a line drawn randomly on this electron micrograph was taken as the average major axis diameter of the composite. When the major axis diameter was difficult to measure, measurements were taken using photographs taken at an appropriately increased magnification. The average minor axis diameter (average value of the minor axis diameters of 20 particles) was calculated in the same manner, and the aspect ratio was calculated by dividing the average major axis diameter by the average minor axis diameter.

[0047] (2)XRD measurement Powder X-ray diffraction patterns (also simply referred to as X-ray diffraction (XRD) patterns) were measured under the following conditions. -Analysis conditions- Machine used: Rigaku RINT-TTRIII Source: CuKα Voltage: 50kV Current: 300mA Sample rotation speed: 60 rpm Divergence slit: 1.00 mm Divergence vertical limit slit: 10 mm Scattering slit: open Receiving slit: open Scanning mode: Continuous Scan Speed: 1 Counting unit: Counts Step width: 0.0100° Operation axis: 2θ / θ Scanning range: 10.0000~70.0000° ZSM-5 and ZSM-11 were identified using JCPDS cards, which are a compilation of peak profiles obtained by X-ray diffraction for various substances. ZSM-5: JCPDS Card 01-089-142 ZSM-11: JCPDS Card 01-088-178 The ZSM-11 ratio was measured using the RIR method for 2θ = 22.5 to 25°, with the RIR value of ZSM-11 being 4.09 (JCPDS card 01-088-178) and the RIR value of ZSM-5 being 1.79 (JCPDS card 01-089-142).

[0048] (3) SEM observation The surface of each powder was observed using a field emission scanning electron microscope (JEOL, JSM-7000F). From the SEM photographs, the actual particle area S0 and the area of ​​the rectangle circumscribing the particle S1 were calculated using the software WinROOF2015 (Mitani Shoji Co., Ltd.). 、 The rod-likeness was calculated.

[0049] Example 1 <Aging process (I)> 1.5 g of rice husk ash (amorphous SiO2 content: 91 wt%) was added to 18.0 g of 0.3 mol / L aqueous solution of sodium hydroxide (Fujifilm Wako Pure Chemical Industries, Ltd., product code 198-13765 (special grade reagent)). After stirring for 30 minutes at 25°C, 0.82 g of tetrabutylammonium bromide (Tokyo Chemical Industry Co., Ltd.) was added as an organic structure-directing agent and mixed. The resulting mixture was aged at 80°C for 68 hours to prepare a mixed gel. <Hydrothermal process (II) and firing process (III)> The mixed gel obtained in the aging step (I) was placed in a 100 mL stainless steel autoclave equipped with a fluororesin inner cylinder and subjected to hydrothermal synthesis at 170°C for 48 hours. The resulting product was filtered and dried at 120°C. The resulting dried powder was calcined at 550°C for 2 hours to obtain powdered zeolite. XRD spectrum confirmed that the obtained zeolite was a composite of MFI and MEL zeolites. Furthermore, no peaks derived from other zeolites or amorphous silica-alumina were observed. The obtained particles had a ZSM-11:ZSM-5 ratio of 0.74:0.26, S0 / S1 = 0.82, and L2' / L1' = 0.58.

[0050] (Comparative Example 1) An MFI / MEL zeolite composite was produced in the same manner as in Example 1, except that in the aging step (I), the aging temperature was changed to 25° C. and the aging time was changed to 30 minutes.

[0051] (Comparative Example 2) An MFI / MEL zeolite composite was produced in the same manner as in Example 1, except that in the aging step (I), the aging time at 80°C was changed from 68 hours to 30 minutes.

[0052] The physical properties of the products (MFI / MEL zeolite composites) obtained in Example 1 and Comparative Examples 1 and 2 are shown in Table 1, and SEM photographs thereof are shown in FIGS. In Comparative Example 1, the ZSM-11 ratio, minor axis diameter, major axis diameter, aspect ratio, and average rodlikeness could not be measured because no zeolite particles were obtained.In Comparative Example 2, the minor axis diameter, major axis diameter, aspect ratio, and average rodlikeness could not be measured because the remains of rice husk-derived particles remained.

[0053] [Table 1]

[0054] In Example 1, by carrying out the reaction under predetermined conditions, an MFI / MEL zeolite composite was obtained in which the ratio (I2 / I1) of the intensity I1 of the diffraction peak attributable to the crystal lattice (101) plane and / or (011) plane to the intensity I2 of the diffraction peak attributable to the crystal lattice (200) plane and / or (020) plane was 1 or more and 3 or less. A composite with such characteristics has pores (long straight channels) that have grown large in the b-axis direction, and therefore is thought to be less susceptible to coking.

Claims

1. A composite of ZSM-5 (MFI) type zeolite and ZSM-11 (MEL) type zeolite, The MFI / MEL zeolite composite has a primary particle aspect ratio (average major axis diameter of the particle / average minor axis diameter of the particle) of 1.5 or more and 10 or less, Intensity I of the diffraction peaks attributed to the (101) and / or (011) crystal lattice planes observed by X-ray diffraction １ and the intensity I of the diffraction peaks attributed to the crystal lattice (200) plane and / or (020) plane. ２ The ratio of (I ２ / I １ ) is 1 or more and 3 or less, An MFI / MEL zeolite composite characterized in that the ratio of ZSM-11 calculated by the following method is 0.6 or more and 1 or less. <Method for measuring ZSM-11 ratio> The ratio of ZSM-11 is calculated by the Reference Intensity Ratio (RIR) method using the intensity ratio between the diffraction line of ZSM-11 and the diffraction line of ZSM-5 obtained from the X-ray diffraction pattern by powder X-ray diffraction measurement.

2. The MFI / MEL zeolite composite according to claim 1, characterized in that the major axis diameter of the primary particles of the MFI / MEL zeolite composite is 9 μm or more and 20 μm or less, and the minor axis diameter of the primary particles is 2 μm or more and 6 μm or less.

3. A method for producing the MFI / MEL zeolite composite according to claim 1 or 2, comprising: The production method includes a step (I) of mixing a silicon atom-containing compound, a quaternary alkylammonium compound, and a base and aging the mixture; and a step (II) of hydrothermally reacting the product obtained in the aging step (I).

4. 4. The method for producing an MFI / MEL zeolite composite according to claim 3, further comprising a step (III) of calcining the product obtained in the hydrothermal step (II).

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