Method for producing zeolite

Abstract

To provide a method for producing zeolite without requiring a step of reacting rice husks with an alkali solution, the method achieving superior soot collection performance and long-term pressure loss performance.SOLUTION: A method for producing zeolite includes a step of preparing a mixture comprising a rice husk-derived silica source containing 0.3 to 3.0 wt.% of potassium and a structure-directing agent, a step of heating the mixture to obtain a zeolite precursor, and a step of calcining the zeolite precursor.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a zeolite. [Background technology]

[0002] Zeolites are used in a variety of applications, including as catalysts for organic synthesis, filters for removing PM particles from automobile exhaust, and exhaust gas purification catalysts for reducing NOx in automobiles. Zeolites are found in large numbers in selective reduction process catalysts (SCR catalysts), particularly those in which ammonia or an ammonia precursor is used as the reducing agent.

[0003] In recent years, in order to promote a sustainable society, the automotive industry has added new regulations requiring the proportion of recycled plastics used in automobiles, and regulations regarding greenhouse gas emissions (LCA) from manufacturing to disposal are increasing. As a result, there is an increasing demand for zeolites derived from materials with low LCA and low environmental impact. In particular, research is being actively conducted on zeolites that use rice husk ash, a non-edible biomass with a high silica content, as a silica source.

[0004] For example, Patent Document 1 discloses a method for synthesizing zeolite by carrying out a hydrothermal synthesis reaction using, as a silica source, a silicon-containing alkaline solution obtained by reacting rice husks with an alkaline aqueous solution.

[0005] Furthermore, Patent Document 2 discloses that the addition of prismatic MFI-type zeolite to exhaust gas purification filters for gasoline automobiles improves pressure loss. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 01-037412 [Patent Document 2] JP 2022-66003 A Summary of the Invention [Problem to be solved by the invention]

[0007] The method for synthesizing zeolite proposed in Patent Document 1 includes a step of reacting rice husks with an alkaline solution, and an additional ion exchange step is required in the subsequent step to convert the zeolite to H-type zeolite, which may be disadvantageous in terms of productivity.In addition, the zeolite disclosed in Patent Document 2 has some degree of effect in soot collection performance and long-term pressure drop performance, but is not satisfactory.

[0008] In view of the above problems, one object of the present disclosure is to provide a method for producing zeolite that has excellent soot collection performance and long-term pressure drop performance without requiring a step of reacting rice husks with an alkaline solution. [Means for solving the problem]

[0009] As a result of extensive research, the present inventors have found that by adjusting the potassium content in a rice husk-derived silica source to a predetermined range, it is possible to produce a zeolite that is excellent in soot collection performance and long-term pressure drop performance, and is also highly productive, and have completed the present invention.

[0010] According to one embodiment of the present disclosure, there is provided a method for producing a zeolite, comprising the steps of: preparing a mixture containing a silica source derived from rice husks containing 0.3 to 3.0 wt. % potassium and a structure-directing agent; heating the mixture to obtain a zeolite precursor; and calcining the zeolite precursor. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a method for producing zeolite that has excellent soot trapping performance and long-term pressure drop performance, without requiring a step of reacting rice husks with an alkaline solution. [Brief explanation of the drawings]

[0012] [Figure 1] The results of powder X-ray diffraction analysis (XRD) performed on the zeolites of Example 1 and Comparative Examples 1 and 2 are shown below. [Figure 2] The results of observing the zeolites of Example 1 and Comparative Examples 1 and 2 with a scanning electron microscope (SEM) are shown. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present disclosure provides a method for producing a zeolite, comprising: A step of preparing a mixture containing a silica source derived from rice husks containing 0.3 to 3.0 wt% potassium and a structure-directing agent; heating the mixture to obtain a zeolite precursor; and Calcining the zeolite precursor The manufacturing method of the present disclosure will be described in detail below.

[0014] [Preparation of a mixture containing a silica source derived from rice husks containing potassium and a structure-directing agent] According to one embodiment of the present disclosure, a step of preparing a mixture containing a rice husk-derived silica source containing 0.3 to 3.0 wt % of potassium and a structure-directing agent (hereinafter also referred to as a "preparation step") is carried out.

[0015] The mixture may be a mixture of the rice husk-derived silica source and the structure-directing agent mixed in advance (for example, a commercially available product), or may be a mixture of the rice husk-derived silica source and the structure-directing agent mixed under desired conditions. The conditions for mixing the rice husk-derived silica source and the structure-directing agent can be appropriately adjusted by a person skilled in the art. The temperature for mixing the rice husk-derived silica source and the structure-directing agent may be, for example, 0 to 100°C, preferably 0 to 60°C, and more preferably 0 to 40°C. The time for mixing the rice husk-derived silica source and the structure-directing agent may be, for example, 0.5 to 72 hours, preferably 4 to 48 hours, and more preferably 6 to 24 hours.

[0016] [Silica source derived from rice husks] According to one embodiment of the present disclosure, the silica source derived from rice husks contains 0.3 to 3.0% by weight of potassium. In this disclosure, "rice husks" refers to the outermost husk of unhulled rice or unhulled rice. The rice husks may be derived from seed rice. The silica source is not particularly limited as long as it contains 0.3 to 3.0% by weight of potassium. Untreated rice husks may be used, or rice husks that have been treated by heat treatment, acid treatment, or the like. The amount of potassium in the silica source may be measured by known methods (e.g., XRD, ICP).

[0017] The amount of SiO2 contained in the rice husk-derived silica source may be, for example, 50 to 99% by weight, preferably 70 to 98.5% by weight, more preferably 90 to 98% by weight, even more preferably 92 to 97.5% by weight, and even more preferably 95 to 97% by weight, based on the total weight of the rice husk.

[0018] According to a preferred embodiment of the present disclosure, the preparation step includes a step of calcining rice husks (hereinafter also referred to as a "rice husk calcining step"). Including the rice husk calcining step is advantageous in that it can remove carbon that causes OSDA inactivation and makes it easier to form the zeolite of the present invention. The rice husk calcining step is preferably carried out until at least a portion of the rice husks (preferably, substantially all of the rice husks) is reduced to ash. Therefore, according to a more preferred embodiment of the present disclosure, the preparation step includes a step of ashing the rice husks.

[0019] The conditions (temperature, time, pressure, etc.) for the rice husk burning step are not particularly limited as long as the object of the present disclosure can be achieved, and those skilled in the art can adjust them as appropriate. The burning temperature may be, for example, 200 to 1000°C, preferably 300 to 600°C, and more preferably 350 to 500°C. The burning time may be, for example, 0.1 to 48 hours, preferably 0.5 to 12 hours, and more preferably 1 to 6 hours. The burning pressure may be, for example, 0.01 MPa to 10 MPa, preferably 0.05 to 1 MPa, and more preferably normal pressure.

[0020] According to a preferred embodiment of the present disclosure, the preparation step includes a step of adjusting the potassium content of the silica source to 0.3 to 3.0 wt % by acid treatment (hereinafter also referred to as the "acid treatment step"). The inclusion of the acid treatment step is advantageous in that phosphorus oxide (e.g., P2O5), sodium oxide, chloride, etc. in the rice husks can be removed.

[0021] Examples of the acid include, but are not limited to, inorganic acids such as hydrochloric acid, nitric acid, nitrous acid, and sulfuric acid; and organic acids such as acetic acid, citric acid, malic acid, lactic acid, succinic acid, and ascorbic acid. These may be used alone or in combination of two or more. From the viewpoints of corrosiveness and safety in the production process, the acid is preferably an organic acid, and more preferably citric acid.

[0022] The amount of the acid used is not particularly limited as long as it is an amount that allows the potassium content of the silica source to be 0.3 to 3.0 wt %, and can be adjusted appropriately by a person skilled in the art. Furthermore, the conditions for the acid treatment (temperature, time, etc.) can be adjusted appropriately by a person skilled in the art. The temperature for the acid treatment may be, for example, 0 to 100°C, preferably 0 to 60°C, and more preferably 0 to 40°C. The time for the acid treatment may be, for example, 5 seconds to 24 hours, preferably 0.5 minutes to 12 hours, and more preferably 1 minute to 1 hour.

[0023] According to a more preferred embodiment of the present disclosure, the preparation step includes a step of obtaining the silica source derived from the rice husks by a step including a step of burning the rice husks and a step of treating the rice husks with an acid.

[0024] [Structure directing agent] In the present disclosure, the term "structure-directing agent" (SDA) refers to a material that contributes to determining the structure of the zeolite obtained by the method of the present disclosure. The structure-directing agent may function as a template for the zeolite.

[0025] The structure-directing agent is not particularly limited as long as the desired zeolite can be obtained, but examples thereof include organic bases such as quaternary ammonium compounds. More specifically, examples of the structure-directing agent include tetrapropylammonium compounds such as tetrapropylammonium hydroxide, dimethylpropylammonium compounds such as dimethyldipropylammonium hydroxide, tetraethylammonium compounds such as tetraethylammonium hydroxide, or their phosphates, fluorides, chlorides, bromides, or acetates; dipropylamine (DPA); triethylamine; cyclohexylamine; 1-methylamidazole; morpholine; pyridine; piperidine; diethylethanolamine (DEA); and the like. These may be used alone or in combination of two or more. The structure-directing agent preferably contains at least a quaternary ammonium compound, more preferably at least one selected from the group consisting of tetrapropylammonium compounds and dimethyldipropylammonium compounds, and even more preferably at least one selected from the group consisting of tetrapropylammonium hydroxide and dimethyldipropylammonium hydroxide.

[0026] [Mixture containing a silica source derived from rice husks and a structure-directing agent] The amount of the rice husk-derived silica source in the mixture containing the rice husk-derived silica source and the structure-directing agent is not particularly limited as long as the object of the present disclosure can be achieved. The amount of the rice husk-derived silica source in the mixture may be, for example, 10 to 90 wt %, preferably 30 to 85 wt %, more preferably 50 to 80 wt %, and even more preferably 55 to 75 wt %, based on the total weight of the mixture.

[0027] The amount of the structure-directing agent in the mixture is not particularly limited as long as the object of the present disclosure can be achieved. The amount of the structure-directing agent in the mixture may be, for example, 0.1 to 30 wt %, preferably 1 to 25 wt %, more preferably 5 to 20 wt %, and even more preferably 8 to 18 wt %, based on the total weight of the mixture.

[0028] The ratio of the rice husk-derived silica source to the structure-directing agent in the mixture is not particularly limited as long as the object of the present disclosure can be achieved. The ratio of the rice husk-derived silica source to the structure-directing agent in the mixture (rice husk-derived silica source / structure-directing agent) may be, for example, 0.3 to 100, preferably 1 to 50, more preferably 1.5 to 30, and even more preferably 2 to 10, based on the weight of the silica source and the structure-directing agent in the mixture.

[0029] The mixture containing the rice husk-derived silica source and the structure-directing agent may contain other components in addition to the rice husk-derived silica source and the structure-directing agent, as long as the object of the present disclosure is not impaired. Examples of other components include, but are not limited to, halides, sulfates, nitrates, organic acid salts, solvents, etc., which may be used alone or in combination of two or more.

[0030] Examples of halides include, but are not limited to, fluorides (e.g., ammonium fluoride), ammonium hydrogen fluoride, and dimethyl propyl ammonium fluoride, which may be used alone or in combination of two or more. According to one embodiment of the present disclosure, the mixture contains a fluoride (preferably ammonium fluoride). The inclusion of a fluoride in the mixture is advantageous in that it facilitates the formation of the zeolite shape of the present invention.

[0031] Examples of sulfates include, but are not limited to, ammonium sulfate, and these may be used alone or in combination of two or more.

[0032] The nitrate is not limited to these, but examples thereof include ammonium nitrate, and these may be used alone or in combination of two or more kinds. Examples of organic acid salts include, but are not limited to, ammonium acetate, and these may be used alone or in combination of two or more.

[0033] Examples of solvents include, but are not limited to, water; alcohols such as methanol and ethanol, polar solvents such as ethyl acetate and tetrahydrofuran; and non-polar solvents such as hexane, cyclohexane, carbon tetrachloride and isopropyl ether. These may be used alone or in combination of two or more.

[0034] Furthermore, it is preferable that the mixture does not contain any alkaline solution other than that of the rice husk-derived silica source, which is advantageous in that the ion exchange step can be omitted when obtaining H-type zeolite.

[0035] The mixture may be, but is not limited to, SiO2, Al2O3, TPA, etc. + , DMDPA + , H2O, OH - , F - , NH4 + It may also contain ingredients such as:

[0036] According to one embodiment of the present disclosure, the molar ratio of aluminum oxide (Al2O3) to SiO2 (Al2O3 / SiO2) contained in the mixture is 0.001 or less, preferably 0.0005 or less, and more preferably 0.0003 or less.

[0037] According to one embodiment of the present disclosure, the TPA contained in the mixture + and SiO2 molar ratio (TPA + / SiO2) is 0.0002 to 0.02, preferably 0.0004 to 0.01, and more preferably 0.0006 to 0.002.

[0038] According to one embodiment of the present disclosure, DMDPA contained in the mixture + and SiO2 molar ratio (DMDPA+ / SiO2) is 0.02 to 0.2, preferably 0.03 to 0.16, and more preferably 0.04 to 0.12.

[0039] According to one embodiment of the present disclosure, the molar ratio of H2O to SiO2 (H2O / SiO2) contained in the mixture is 0.5-5, preferably 0.7-3, and more preferably 0.9-2.

[0040] According to one embodiment of the present disclosure, the OH contained in the mixture - and SiO2 molar ratio (OH - / SiO2) is 0.01 to 0.5, preferably 0.03 to 0.3, and more preferably 0.06 to 0.15.

[0041] According to one embodiment of the present disclosure, F contained in the mixture ― and SiO2 molar ratio (F ― / SiO2) is 0.01 to 0.2, preferably 0.016 to 0.16, and more preferably 0.02 to 0.12.

[0042] According to one embodiment of the present disclosure, the NH4 + and SiO2 molar ratio (NH4 + / SiO2) is 0.01 to 0.2, preferably 0.016 to 0.16, and more preferably 0.02 to 0.12.

[0043] According to a preferred embodiment of the present disclosure, the mixture satisfies the following requirements in molar ratio: Al2O3 / SiO2 less than 0.001 TPA of 0.0002 to 0.02 + / SiO2 0.02~0.2 DMDPA + / SiO2 0.5~5 H2O / SiO2 0.01~0.5 OH - / SiO2, and F of 0.01 to 0.4 - / SiO2 Meet the following.

[0044] According to a more preferred embodiment of the present disclosure, the mixture satisfies the following requirements in molar ratio: Al2O3 / SiO2 less than 0.001 TPA of 0.0002 to 0.02 + / SiO2 0.02~0.2 DMDPA + / SiO2 0.5~5 H2O / SiO2 0.01~0.5 OH - / SiO2 F of 0.01 to 0.4 - / SiO2, and 0.01-0.2 NH4 + / SiO2 Meet the following.

[0045] According to a further preferred embodiment of the present disclosure, the mixture meets the following requirements in molar ratio: Al2O3 / SiO2 less than 0.0003 TPA of 0.0006 to 0.002 + / SiO2 0.04~0.12 DMDPA + / SiO2 0.9~2 H2O / SiO2 0.06~0.15 OH - / SiO2 F of 0.02 to 0.12 - / SiO2, and 0.02~0.12 NH4 + / SiO2 Meet the following.

[0046] [Step of heating the mixture to obtain a zeolite precursor] According to one embodiment of the present disclosure, a step of heating a mixture containing the rice husk-derived silica source and the structure-directing agent to obtain a zeolite precursor (hereinafter also referred to as a "mixture heating step") is carried out. In the mixture heating step, a zeolite precursor is obtained from the mixture by a hydrothermal reaction. In the present disclosure, a "zeolite precursor" refers to a substance that is the source of zeolite. The zeolite precursor generally has a structure in which a molecule of the structure-directing agent is at the center and is surrounded by silica fine particles. By further calcining the zeolite precursor, at least a portion of the structure-directing agent is removed, and a zeolite can be obtained.

[0047] The conditions (temperature, time, etc.) for the mixture heating step are not particularly limited as long as the object of the present disclosure can be achieved, and those skilled in the art can adjust them as appropriate. The heating temperature may be, for example, 80 to 500°C, preferably 100 to 300°C, and more preferably 120 to 250°C. The heating time may be, for example, 1 to 240 hours, preferably 12 to 120 hours, and more preferably 24 to 100 hours.

[0048] [Step of calcining zeolite precursor] According to one embodiment of the present disclosure, a step of calcining the zeolite precursor (hereinafter also referred to as a "precursor calcination step") is carried out. The precursor calcination step may be carried out until at least a portion of the structure-directing agent in the zeolite precursor is removed (preferably until substantially all of the structure-directing agent is removed).

[0049] The conditions (temperature, time, pressure, etc.) for the precursor calcination step are not particularly limited as long as the objectives of the present disclosure can be achieved, and those skilled in the art can adjust them as appropriate. The calcination temperature may be, for example, 100 to 1000°C, preferably 200 to 900°C, and more preferably 400 to 800°C. The calcination time may be, for example, 0.5 to 48 hours, preferably 1 to 24 hours, and more preferably 2 to 12 hours. The calcination pressure may be, for example, 0.01 MPa to 10 MPa, preferably 0.05 to 1 MPa, and more preferably atmospheric pressure. Whether the calcination has been carried out to the desired extent may be confirmed by measuring the structure-directing agent remaining in the calcined material (e.g., zeolite) using a known method (e.g., XRD, ICP, etc.).

[0050] In addition to the above-described steps, other steps (e.g., a drying step, a washing step, etc.) may be performed as needed, as long as the object of the present disclosure can be achieved. Such other steps may be performed at any timing before or after the above-described steps.

[0051] [Zeolite] According to the manufacturing method of the present disclosure, a desired zeolite can be manufactured.

[0052] [Zeolite ingredients] The zeolite may contain any component as long as it can constitute the desired zeolite. Examples of components contained in the zeolite include, but are not limited to, silica, alumina, titania, zirconia, and composite oxides thereof.

[0053] According to one embodiment of the present disclosure, the zeolite has an SAR (silica / alumina ratio) of 100 or more, preferably 100 to 10,000, and more preferably 400 to 5,000. Setting the SAR at such a value is advantageous in that it can reduce the effects of dealumination, which is one of the causes of zeolite deterioration. In the present disclosure, SAR refers to the composition ratio of SiO2 to Al2O3 (based on the molar ratio of oxides, SiO2 / Al2O3).

[0054] The zeolite may have any framework structure identified by a three-letter alphabetic code by the International Zeolite Association (IZA). Examples of the zeolite structure include, but are not limited to, MFI type, BEA type, ACO type, AEI type, AEN type, AFN type, AFT type, AFX type, ANA type, APC type, APD type, ATT type, CDO type, CHA type, DDR type, DFT type, EAB type, EDI type, EPI type, ERI type, GIS type, GOO type, IHW type, ITE type, ITW type, LEV type, KFI type, MER type, Examples of zeolites include MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, and ZON types. Orthorhombic zeolites such as MFI, AEI, AEN, APC, APD, ATT, CDO, GOO, IHW, ITE, PHI, UEI, and ZON types are preferred. These may be used alone or in combination. According to one embodiment of the present disclosure, the zeolite contains at least an MFI structure. According to a preferred embodiment of the present disclosure, the zeolite has an MFI structure. The framework structure of the zeolite may be confirmed, for example, by matching the X-ray diffraction pattern published by the International Zeolite Association (IZA).

[0055] According to one embodiment of the present disclosure, the zeolite is a silicalite containing 1 mol % or less (preferably 0.3 mol % or less, more preferably 0.1 mol % or less) of aluminum element.

[0056] [Zeolite shape] According to one embodiment of the present disclosure, the zeolite includes at least substantially spherical aggregates in which columnar shapes are arranged radially from a center. The zeolite of the present disclosure preferably does not substantially contain amorphous portions. In the present disclosure, "substantially does not contain amorphous portions" means that the amorphous portions contained in the zeolite account for 5% or less of the amorphous portions based on 100 random zeolites selected from a scanning electron microscope (SEM) image.

[0057] The zeolite pillar-shaped object may be an approximately prismatic pillar (e.g., an approximately triangular pillar, an approximately square pillar, or an approximately circular pillar), preferably an approximately square pillar. The zeolite pillar-shaped object may have a cross section of a long side that is approximately square, preferably an approximately rectangular shape.

[0058] The lengths of the major axis, minor axis, and thickness of the zeolite pillar-shaped object are not particularly limited as long as the object of the present disclosure can be achieved. In the present disclosure, the major axis of the pillar-shaped object refers to the longer side of the planar (approximately rectangular) shape of the pillar-shaped object, the minor axis of the pillar-shaped object refers to the shorter side of the planar (approximately rectangular) shape of the pillar-shaped object, and the thickness of the pillar-shaped object refers to the depth of the planar (approximately rectangular) shape of the pillar-shaped object. The lengths of the major axis, minor axis, and thickness of the zeolite pillar-shaped object may be measured, for example, based on images taken with a scanning electron microscope, or may be average values ​​obtained by measuring multiple points in this manner. For example, the average major axis of the zeolite pillar-shaped object may be 5 to 15 μm, preferably 5.5 to 13 μm, and more preferably 6 to 10 μm. For example, the average minor axis of the zeolite pillar-shaped object may be 0.1 to 10 μm, preferably 0.5 to 6 μm, and more preferably 1 to 3 μm. For example, the average thickness of the columnar shaped zeolite may be 0.1 to 2.0 μm, preferably 0.1 to 1.5 μm, and more preferably 0.2 to 1.0 μm. The aspect ratio (major axis / minor axis) of the zeolite may be, for example, 2 to 8, preferably 3 to 7, and more preferably 4 to 6. The zeolite having the above shape is advantageous in that it becomes easier to ensure space for trapping particles (PM) inside the spherical particles, and soot trapping performance is easily improved.

[0059] According to one embodiment of the present disclosure, the zeolite has a columnar shape with an average major axis length of 5-15 μm and an aspect ratio (major axis / minor axis) of 2-8.

[0060] The diameter (particle size) of the approximately spherical shape of the zeolite is not particularly limited as long as the object of the present disclosure can be achieved. The diameter of the approximately spherical shape of the zeolite may be measured, for example, based on an image taken with a scanning electron microscope, or may be an average value of multiple points measured in this manner. According to one embodiment of the present disclosure, the diameter of the approximately spherical shape of the zeolite is 7 to 20 μm, preferably 8 to 18 μm, and more preferably 9 to 16 μm.

[0061] The specific surface area of ​​the zeolite is not particularly limited as long as the object of the present disclosure can be achieved. The specific surface area of ​​the zeolite may be calculated, for example, by t-plot analysis in specific surface area measurement by nitrogen adsorption. According to one embodiment of the present disclosure, the specific surface area of ​​the zeolite measured by t-plot analysis is 200 to 600 m 2 / g, preferably 250 to 500 m 2 / g, more preferably 300 to 450m 2 / g.

[0062] The porosity of the zeolite is not particularly limited as long as the object of the present disclosure can be achieved. The porosity of the zeolite may be calculated, for example, from bulk specific gravity. The bulk specific gravity can be expressed as (true specific gravity) × (1 - porosity). According to one embodiment of the present disclosure, the porosity of the zeolite calculated from the bulk specific gravity is 60 to 80%, preferably 65 to 75%.

[0063] According to another embodiment of the present disclosure, there is provided a zeolite produced by the production method of the present disclosure.

[0064] [Uses of zeolite] The zeolite can be used for various purposes. Since the zeolite can be used to collect soot, it may be used, for example, as an exhaust gas purification catalyst, a selective adsorption material utilizing the micropores inherent to zeolite, etc.

[0065] The present disclosure encompasses the following. [1] A step of preparing a mixture containing a silica source derived from rice husks containing 0.3 to 3.0 wt% potassium and a structure-directing agent; heating the mixture to obtain a zeolite precursor; and calcining the zeolite precursor; Zeolite manufacturing method. [2] The above preparation step is Burning the rice husks; and a step of adjusting the potassium content of the silica source to 0.3 to 3.0% by weight by acid treatment; The manufacturing method according to [1], further comprising a step of obtaining the silica source derived from rice husks by a step comprising: [3] The manufacturing method according to claim 2, wherein the acid includes at least citric acid. [4] The method according to any one of [1] to [3], wherein the structure-directing agent contains at least a quaternary ammonium compound. [5] The method according to any one of [1] to [4], wherein the structure-directing agent comprises at least one selected from the group consisting of tetrapropylammonium compounds and dimethyldipropylammonium compounds. [6] The method according to any one of [1] to [5], wherein the mixture further contains a fluoride. [7] The method according to any one of [1] to [6], wherein the mixture does not contain any alkaline solution other than the rice husk-derived silica source. [8] The above mixture satisfies the following requirements in molar ratio: Al2O3 / SiO2 less than 0.001 TPA of 0.0002 to 0.02 + / SiO2 0.02~0.2 DMDPA + / SiO2 0.5~5 H2O / SiO2 0.01~0.5 OH - / SiO2, and F of 0.01 to 0.4 - / SiO2 The manufacturing method according to any one of [1] to [7], wherein the above-mentioned conditions are satisfied. [9] The method according to any one of [1] to [8], wherein the zeolite has an SAR of 100 or more.

[10] The method according to any one of [1] to [9], wherein the zeolite has an MFI structure.

[11] The method according to any one of [1] to

[10] , wherein the zeolite is silicalite containing 1 mol % or less of aluminum element.

[12] The method according to any one of [1] to

[11] , wherein the zeolite comprises a substantially spherical shape in which columnar shapes are radially arranged from a center.

[13] The manufacturing method according to

[12] , wherein the columnar objects have an average major axis length of 5 to 15 μm and an aspect ratio (major axis / minor axis) of 2 to 8.

[14] The method according to

[12] or

[13] , wherein the diameter of the approximately spherical particles is 7 to 20 μm. [Example]

[0066] The hydrocracking catalyst of the present disclosure will be described in more detail below using examples. However, the following examples are not intended to limit the hydrocracking catalyst of the present disclosure in any way. Unless otherwise specified, percentages and ratios described herein are by mass. Furthermore, unless otherwise specified, units and measurement methods described herein are in accordance with the provisions of the Japanese Industrial Standards (JIS).

[0067] [Example 1: Synthesis of zeolite using rice husk silica]

[0068] Smoked rice husk charcoal (manufactured by Cainz Corporation, product name: Smoked Charcoal 3L) was heated at 400°C for 2 hours to obtain ash derived from the rice seeds. The obtained ash was contacted with a 20% citric acid solution, stirred at room temperature for 15 minutes, and dried to obtain citric acid-treated ash. This was used as the silica source in Example 1. The composition of the silica source before and after citric acid treatment is shown in Table 1 below. Therefore, the silica source before citric acid treatment contained approximately 3.2 wt% potassium, and the silica source after citric acid treatment contained approximately 1.6 wt% potassium. Furthermore, while the impurities CaO, PO, MgO, MnO, and NaO are preferably present in smaller amounts, the citric acid treatment reduced their contents to an acceptable level to prevent adverse effects on the subsequent synthesis system.

[0069] [Table 1]

[0070] 9.20 g (dry basis) of the silica source obtained above, 0.1 g of a 40% aqueous solution of tetrapropylammonium hydroxide, 4.2 g of 40% dimethyldipropylammonium hydroxide, and 0.3 g of ammonium fluoride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were mixed and stirred overnight. The composition of the resulting mixture (raw material composition) was as shown in Table 2 below. Note that the numerical values ​​in the table below represent the molar ratios of the amounts of substances when the amount of substance of SiO2 is taken as 1.

[0071] [Table 2]

[0072] Next, the mixture (raw material composition) obtained above was placed in a stainless steel autoclave, and the temperature was raised from room temperature to 170°C over 3 hours while stirring, and then the temperature was maintained at 170°C and kept with stirring for 69 hours. The products after this hydrothermal treatment were all dried at 105°C and pulverized, and then calcined at 600°C for 5 hours to obtain the zeolite of Example 1.

[0073] Powder X-ray diffraction analysis (XRD, apparatus: Spectris Inc., XPert Pro Cu-Ka beam 45 kV 40 mA) showed that the zeolite of Example 1 was a single-phase MFI zeolite ( FIG. 1 ). Furthermore, composition analysis using X-ray fluorescence (XRF: X-ray Fluorescence, apparatus: Spectris Inc., Axios analysis software UniQuant5) showed that the zeolite of Example 1 had an SAR of 4100. Evaluation using a scanning electron microscope (SEM, device: ProX PREMIUM II, manufactured by Phenom-World) revealed that the zeolite of Example 1 was a roughly spherical aggregate with columnar shapes arranged radially from the center (Fig. 2). Furthermore, measurement of the lengths of the columnar shapes at 10 random points on the image revealed that the average major axis was 7.5 µm and the average minor axis was 1.5 µm (aspect ratio (major axis / minor axis): 5), and the diameter of the spheres was 11 µm (Table 3).

[0074] [Table 3]

[0075] [Comparative Example 1: Synthesis of zeolite using fumed silica] The same procedure was repeated to obtain the zeolite of Comparative Example 1, except that fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) was added to the silica source in place of the citric acid-treated rice husk ash so that the amount of SiO was the same. The fumed silica used had a composition of 95.00% SiO and 5.00% HO, and did not contain potassium or AlO. The composition of the raw material composition in Comparative Example 1 was as shown in Table 2.

[0076] Powder X-ray diffraction analysis (XRD) revealed that the zeolite of Comparative Example 1 was an MFI-type zeolite (FIG. 1). Evaluation by scanning electron microscope (SEM) showed that the zeolite of Comparative Example 1 was an aggregate of pillars, but had an irregular shape (Fig. 2). Cotton-like amorphous portions were also observed (Fig. 2). Measurement of the lengths of the pillars at 10 random points in the SEM image revealed that the average major axis was 37.5 μm and the average minor axis was 10 μm (aspect ratio (major axis / minor axis): 3.75) (Table 3).

[0077] Comparative Example 2: Synthesis of zeolite using precipitated silica The same procedure as in Example 1 was repeated, except that precipitated silica (Nipsil ER, manufactured by Tosoh Corporation) was added as the silica source instead of the citric acid-treated rice husk ash so that the amount of SiO was the same, to obtain the zeolite of Comparative Example 2. The precipitated silica used had a composition of 91.67% SiO, 0.16% AlO, and 8.17% HO, and did not contain potassium. The composition of the raw material composition in Comparative Example 2 was as shown in Table 2.

[0078] Powder X-ray diffraction analysis (XRD) revealed that the zeolite of Comparative Example 2 was an MFI-type zeolite (FIG. 1). Composition analysis by X-ray fluorescence (XRF) revealed that the zeolite of Comparative Example 2 had an SAR of 950. As a result of evaluation using a scanning electron microscope (SEM), the zeolite of Comparative Example 2 was found to have a columnar shape (FIG. 2). In addition, cotton-like amorphous portions were observed (FIG. 2). The lengths of the columnar particles were measured at 10 random points in the SEM image, and the average major axis was 28 μm, and the average minor axis was 5 μm (aspect ratio (major axis / minor axis): 5.6) (Table 3).

[0079] In Example 1, since the potassium content of the silica source was within the predetermined range, spherical zeolite with radially arranged pillars was obtained. On the other hand, when a silica source with a potassium content exceeding the predetermined range (for example, a potassium content of 3.2 wt%) was used, spherical zeolite with radially arranged pillars was not obtained.

[0080] For example, in automotive GPFs, a coating layer is obtained by applying catalyst particles to a filter substrate (carrier). In this case, exhaust gas passes through the gaps between the catalyst particles. When fine particles (soot) are contained in the exhaust gas, they get caught in the narrow parts of the flow path and are captured, but in doing so, they block part of the flow path, increasing pressure loss. For example, the pillared zeolite of Comparative Example 1 is thought to partially block the main flow path due to particle capture, preventing the long-term effect of suppressing pressure drop. Also, the zeolite of Comparative Example 2 is thought to have insufficient fine particle capture performance due to the large particle size and irregular shape of the pillared particles. On the other hand, the zeolite of the present disclosure is a spherical body with pillars arranged radially from the center. Therefore, it is believed that soot is mainly captured by the radial pillar crystals. Even if fine particles are captured between these pillars, the main flow path itself, which is made up of the gaps between the spheres, is not partially blocked, which is advantageous in that an increase in pressure loss can be expected to be suppressed.

Claims

1. preparing a mixture containing a rice husk-derived silica source containing 0.3 to 3.0 wt. % potassium and a structure-directing agent; heating the mixture to obtain a zeolite precursor; and Calcining the zeolite precursor A method for producing zeolite, comprising:

2. The preparation step includes: Burning the rice husks; and a step of adjusting the potassium content of the silica source to 0.3 to 3.0% by weight by acid treatment; The method according to claim 1 , further comprising the step of obtaining the silica source derived from rice husks by a process comprising the steps of:

3. The method according to claim 2 , wherein the acid comprises at least citric acid.

4. The method according to claim 1 , wherein the structure-directing agent comprises at least a quaternary ammonium compound.

5. The method according to claim 1 , wherein the structure-directing agent comprises at least one selected from the group consisting of a tetrapropylammonium compound and a dimethyldipropylammonium compound.

6. The method of claim 1 , wherein the mixture further comprises a fluoride.

7. The method according to claim 1 , wherein the mixture does not contain any alkaline solution other than the rice husk-derived silica source.

8. The mixture comprises, in molar ratios, the following requirements: Al of 0.001 or less ２ O ３ / SiO ２ ・TPA of 0.0002 to 0.02 ＋ / SiO ２ 0.02 to 0.2 DMDPA ＋ / SiO ２ ・H of 0.5 to 5 ２ O / SiO ２ 0.01 to 0.5 OH － / SiO ２ , and ・F of 0.01 to 0.4 － / SiO ２ The method according to claim 1 , wherein the above formula (I) is satisfied.

9. The method according to claim 1, wherein the zeolite has an SAR of 100 or more.

10. 2. The process according to claim 1, wherein the zeolite has an MFI structure.

11. 2. The method according to claim 1, wherein the zeolite is a silicalite containing 1 mol % or less of aluminum element.

12. The method according to claim 1 , wherein the zeolite comprises a substantially spherical shape in which columnar shapes are radially arranged from a center.

13. The method according to claim 12, wherein the columnar objects have an average major axis length of 5 to 15 μm and an aspect ratio (major axis / minor axis) of 2 to 8.

14. The method according to claim 12, wherein the diameter of the approximately spherical shape is 7 to 20 μm.

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