JP2017007914A - Manufacturing method of zeolite, the zeolite therewith, and manufacturing method of honeycomb catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a zeolite which can get CHA type zeolite having high crystallinity and being small particle size at low cost.SOLUTION: A manufacturing method of a zeolite having CHA structure includes: a synthesis step synthesizing zeolite particles having CHA structure by using a raw material composition containing Si source, Al source, alkali source and structure directing agent; a miniaturization step miniaturizing the zeolite having CHA structure provided in the synthesis step; and a recrystallization step mixing the zeolite having CHA structure miniaturized in the miniaturization step and solution for recrystallization, and hydrating them. The solution for recrystallization contains 0.01-0.5 mol/L of Si and 0.08-0.5 mol/L of Na.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing zeolite, a zeolite obtained by the method, and a method for producing a honeycomb catalyst.

  Conventionally, an SCR (Selective Catalytic Reduction) system that uses ammonia to reduce NOx to nitrogen and water has been known as one of systems for purifying exhaust gas from automobiles. Zeolite having a site (Chabazite: CHA) structure has attracted attention as a zeolite having an SCR catalytic action.

  In an SCR system using a zeolite having a CHA structure on which Cu is supported, a honeycomb unit having a large number of longitudinally extending through holes through which exhaust gas passes is used as an SCR catalyst carrier (for example, Patent Documents). 1).

Patent Document 2 discloses that the composition ratio SiO ₂ / Al ₂ O ₃ is less than 15 and the particle diameter is 1. for the purpose of improving heat resistance and durability when used as an SCR catalyst carrier. A zeolite having a CHA structure of 0 to 8.0 μm (hereinafter referred to as CHA-type zeolite) is disclosed.

  On the other hand, Patent Document 3 discloses a technique for synthesizing and crushing a faujasite (FAU) type zeolite, and subsequently increasing the crystallinity by 1.2 to 5 times by hydrothermal treatment.

JP 2007-296521 A JP 2012-211066 A JP 2014-139124 A

  In order to increase the crack resistance of the honeycomb unit as in prior art 1, it is necessary to reduce the average particle diameter of the zeolite having the CHA structure (hereinafter referred to as CHA-type zeolite) to be used. In order to make the performance constant, it is desired that the variation in particle diameter is small. However, it has been difficult to synthesize CHA-type zeolite stably each time, having high crystallinity, a small average particle diameter, and a small variation. Moreover, it has been difficult to synthesize such CHA-type zeolite at low cost.

When CHA-type zeolite having a large average particle size is used as a honeycomb catalyst, the amount of water absorption displacement is large, and cracks are likely to occur during production and use as a catalyst. However, the CHA-type zeolite described in Patent Document 2 has an average particle size of 1.0 μm or more, and cannot solve the problem of cracking when it is used as a honeycomb catalyst.
Patent Document 3 discloses nothing about the recrystallization of CHA-type zeolite, including the concentrations of Si and Na contained in the solution used during the recrystallization, and has a fine and high crystallinity. It was difficult to obtain a CHA-type zeolite.

The present invention has been made to solve the above-described problems, and provides a method for producing a zeolite capable of obtaining a low-cost CHA-type zeolite having high crystallinity and a small average particle diameter. Objective.
Another object of the present invention is to provide a method for producing a honeycomb catalyst having excellent crack resistance and NOx purification performance using the zeolite produced by the production method.

  As a result of intensive studies, the present inventor synthesized CHA-type zeolite, then refined it, and then mixed and refined the refined CHA-type zeolite and a specific recrystallization solution, It has been found that a CHA-type zeolite having high crystallinity and a small average particle diameter can be produced.

  The method for producing a zeolite of the present invention is a method for producing a zeolite having a CHA structure, and synthesizes a zeolite having a CHA structure using a raw material composition containing a Si source, an Al source, an alkali source and a structure directing agent. A synthesis step, a refinement step for refining the zeolite having a CHA structure obtained in the synthesis step, a zeolite having a CHA structure refined by the refinement step and a recrystallization solution, A recrystallization step for summing treatment, wherein the recrystallization solution contains Si at a concentration of 0.01 to 0.5 mol / L and Na at a concentration of 0.08 to 0.5 mol / L.

The average particle size can be easily reduced by refining the CHA-type zeolite obtained in the synthesis step in the refining step, and the crystallinity is reduced in the refining step in the subsequent recrystallization step. By hydrating the CHA-type zeolite with a solution containing Si and Na in a prescribed concentration range, the crystallinity can be increased. If the concentration of Si in the recrystallization solution is less than 0.01 mol / L, the skeleton of the zeolite cannot be repaired. If it is greater than 0.5 mol / L, Si does not enter the skeleton of the zeolite and precipitates as SiO _2. . Further, by setting the concentration of Na to 0.08 to 0.5 mol / L, Na ions having a small ionic radius enter even inside the zeolite particles, so that recrystallization easily proceeds. Therefore, it becomes possible to easily obtain a CHA-type zeolite having a small average particle diameter and high crystallinity.

  In the method for producing a zeolite of the present invention, it is desirable that the recrystallization solution further contains K at a concentration of 0.008 to 0.1 mol / L. Since K is a stronger base than Na, the reactivity is high, and by setting the concentration of K to 0.08 to 0.1 mol / L, recrystallization of the surface of the zeolite is facilitated. Therefore, it becomes possible to easily obtain a CHA-type zeolite having higher crystallinity.

In the method for producing a zeolite of the present invention, the SiO ₂ / Al ₂ O ₃ composition ratio (SAR) in the zeolite having a CHA structure after the recrystallization step is less than 15 and the average particle size is 0.5 μm or less. Is desirable. By setting the SAR to less than 15, the amount of a metal such as Cu that functions as a catalyst can be increased, and high NOx purification performance can be obtained even with a small amount of zeolite. Further, when the average particle diameter is 0.5 μm or less, cracks do not occur when a honeycomb catalyst is formed.

  The method for producing a zeolite of the present invention comprises the integrated intensities of the (211) plane, (104) plane and (220) plane of the X-ray diffraction spectrum of the zeolite having the CHA structure after the recrystallization step by X-ray powder analysis. The sum is desirably 50,000 or more. A higher integrated intensity indicates better crystallinity, and a high integrated NOx purification performance can be obtained when the sum of integrated intensity is 50,000 or more.

  The method for producing zeolite of the present invention further includes a step of performing Cu ion exchange on the zeolite having the CHA structure after the recrystallization step, and the Cu / Al (molar ratio) of the obtained zeolite on which Cu is supported. Is preferably 0.2 to 0.5. By setting Cu / Al to 0.2 to 0.5, it is possible to manufacture an SCR catalyst that exhibits high NOx purification performance even with a small amount of zeolite.

  The zeolite of the present invention can be obtained by the above-described method for producing a zeolite of the present invention. The zeolite thus obtained exhibits high NOx purification performance when used as a material for honeycomb catalysts for SCR applications.

  The manufacturing method of the honeycomb catalyst of the present invention includes a step of mixing the zeolite obtained by the above-described manufacturing method of the zeolite of the present invention and an inorganic binder. Since it is a honeycomb catalyst using a zeolite manufactured by a manufacturing method capable of obtaining a CHA-type zeolite having a small average particle diameter, the amount of water absorption displacement is small. Therefore, the crack resistance is high. Moreover, since the crystallinity of the CHA-type zeolite is high, high NOx purification performance is exhibited.

As described above, according to the present invention, it is possible to provide a method for producing zeolite that can easily obtain a CHA-type zeolite having high crystallinity and a small particle diameter.
Further, according to the present invention, it is possible to provide a method for manufacturing a honeycomb catalyst having excellent crack resistance and NOx purification performance using the zeolite manufactured by the manufacturing method.

It is a perspective view which shows typically an example of the honeycomb catalyst of this invention. It is sectional drawing which shows typically an example of the exhaust gas purification apparatus of this invention. It is a perspective view which shows typically another example of the honeycomb catalyst of this invention. Fig. 4 is a perspective view schematically showing an example of a honeycomb unit constituting the honeycomb catalyst shown in Fig. 3. 3 is a chart showing an XRD pattern of CHA-type zeolite obtained in the synthesis step of Example 1. FIG. 2 is a chart showing an XRD pattern of CHA-type zeolite obtained in the refinement process of Example 1. FIG. 2 is a chart showing an XRD pattern of CHA-type zeolite obtained in the recrystallization process of Example 1. FIG.

(Detailed description of the invention)
Hereinafter, the present invention will be specifically described. However, the present invention is not limited to the following description, and can be appropriately modified and applied without departing from the scope of the present invention.

  The method for producing a zeolite of the present invention includes a synthesis step of synthesizing a zeolite having a CHA structure using a raw material composition containing a Si source, an Al source, an alkali source and a structure directing agent, and the CHA structure obtained in the synthesis step. A refining step of refining the zeolite having a refining process, and a recrystallization step of mixing a zeolite having a CHA structure refined by the refining step and a recrystallization solution and hydrating the mixture. The preparation solution contains Si at a concentration of 0.01 to 0.5 mol / L and Na at a concentration of 0.08 to 0.5 mol / L.

  The zeolite produced according to the present invention is named and classified by the structure code of CHA at the International Zeolite Association (IZA), and has a crystal structure equivalent to that of naturally occurring chabazite. Zeolite.

<Synthesis process>
In the synthesis process of the present invention, first, a raw material composition comprising a Si source, an Al source, an alkali source, water and a structure directing agent is prepared.

The Si source refers to a compound, a salt, and a composition that are raw materials for the silicon component of zeolite.
As the Si source, for example, fumed silica, colloidal silica, amorphous silica, sodium silicate, tetraethylorthosilicate, aluminosilicate gel, and the like can be used, and two or more of these may be used in combination. Of these, colloidal silica is desirable.

  Examples of the Al source include aluminum sulfate, sodium aluminate, aluminum hydroxide, aluminum chloride, alumino-silicate gel, and dry aluminum hydroxide gel. Of these, dry aluminum hydroxide gel is preferred.

In the method for producing a zeolite of the present invention, in order to produce the target CHA-type zeolite, a Si source and an Al source having a molar ratio (SiO ₂ / Al ₂ O ₃ ) substantially equal to the molar ratio of the zeolite to be produced. It is desirable to use a molar ratio (SiO ₂ / Al ₂ O ₃ ) in the raw material composition of 10 to 15.

  Examples of the alkali source include sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, lithium hydroxide, alkali components in aluminate and silicate, alkali components in aluminosilicate gel, and the like. Two or more of these may be used in combination. Of these, potassium hydroxide, sodium hydroxide, and lithium hydroxide are desirable. In order to obtain a single phase of zeolite, it is particularly preferable to use potassium hydroxide and sodium hydroxide in combination.

The amount of water is not particularly limited, but the ratio of the number of moles of water to the total number of moles of Si of the Si source and Al of the Al source (H ₂ O moles / total moles of Si and Al) is The ratio of the number of moles of water to the total number of moles of Si of the Si source and Al of the Al source (the number of moles of H ₂ O / the total number of moles of Si and Al) is preferably 15 to 25. It is more desirable.

A structure directing agent (hereinafter also referred to as SDA) refers to an organic molecule that defines the pore diameter and crystal structure of zeolite. The structure of the obtained zeolite can be controlled by the type of the structure-directing agent.
Structure directing agents include hydroxides, halides, carbonates, methyl carbonates, sulfates and nitrates with N, N, N-trialkyladamantanammonium as a cation; and N, N, N-trimethylbenzylammonium ions , N-alkyl-3-quinuclidinol ions, or hydroxides, halides, carbonates, methyl carbonate salts, sulfates and nitrates having N, N, N-trialkylexoaminonorbornane as a cation. At least one selected from can be used. Among these, N, N, N-trimethyladamantanammonium hydroxide (hereinafter also referred to as TMAAOH), N, N, N-trimethyladamantanammonium halide, N, N, N-trimethyladamantanammonium carbonate, It is desirable to use at least one selected from the group consisting of N, N, N-trimethyladamantanammonium methyl carbonate salt and N, N, N-trimethyladamantanammonium sulfate, and it is more desirable to use TMAAOH.

  In the synthesis step of the present invention, zeolite seed crystals may be further added to the raw material composition. By using the seed crystal, the crystallization speed of the zeolite is increased, the time for producing the zeolite can be shortened, and the yield is improved.

  As a zeolite seed crystal, it is desirable to use CHA-type zeolite.

  The amount of zeolite seed crystals added is preferably small, but considering the reaction rate, the effect of suppressing impurities, etc., it should be 0.1 to 20% by mass with respect to the silica component contained in the raw material composition. Desirably, it is more desirable that it is 0.5-15 mass%. If it is less than 0.1% by mass, the contribution to improving the crystallization rate of the zeolite is small, and if it exceeds 20% by mass, impurities are likely to enter the zeolite obtained by synthesis.

  In the synthesis step of the present invention, zeolite is synthesized by reacting the prepared raw material composition. Specifically, it is desirable to synthesize zeolite by hydrothermal synthesis of the raw material composition.

  The reaction vessel used for hydrothermal synthesis is not particularly limited as long as it is used for known hydrothermal synthesis, and may be a heat and pressure resistant vessel such as an autoclave. The zeolite can be crystallized by putting the raw material composition into the reaction vessel, sealing and heating.

  When synthesizing the zeolite, the raw material mixture may be in a stationary state, but is preferably in a state of being stirred and mixed.

  The heating temperature when synthesizing the zeolite is preferably 100 to 200 ° C, and more preferably 120 to 180 ° C. When the heating temperature is less than 100 ° C., the crystallization rate becomes slow, and the yield tends to decrease. On the other hand, when the heating temperature exceeds 200 ° C., impurities are likely to be generated.

  The heating time in the synthesis step is desirably 10 to 200 hours. If the heating time is less than 10 hours, unreacted raw materials remain and the yield tends to decrease. On the other hand, even when the heating time exceeds 200 hours, the yield and crystallinity are hardly improved.

  The pressure in the synthesis process is not particularly limited, and the pressure generated when the raw material composition placed in a closed container is heated to the above temperature range is sufficient, but if necessary, an inert gas such as nitrogen gas is added. May be boosted.

  It is desirable that the zeolite obtained by the synthesis step be sufficiently cooled, separated into solid and liquid, and washed with a sufficient amount of water.

  Since the zeolite obtained by the synthesis process contains SDA in the pores, it may be removed as necessary. For example, SDA can be removed by a liquid phase treatment using an acidic solution or a chemical solution containing an SDA decomposition component, an exchange treatment using a resin, a thermal decomposition treatment, or the like.

The average particle diameter of the CHA-type zeolite obtained by the above synthesis process is, for example, 0.2 to 5 μm.
In addition, the average particle diameter of zeolite measured the length of all the diagonal lines of ten particles by taking a SEM photograph using a scanning electron microscope (SEM, Hitachi High-Tech, S-4800). Calculate from the average value. Measurement conditions are as follows: acceleration voltage: 1 kV, emission: 10 μA, WD: 2.2 mm or less. In general, the CHA-type zeolite particles are cubic, and become a square when two-dimensionally imaged by an SEM photograph. Therefore, there are two diagonal lines of particles.

<Refining process>
In the refinement | miniaturization process of this invention, it is the process which refines | miniaturizes CHA type zeolite obtained at the synthesis | combination process to desired particle diameter, for example, 0.5 micrometer or less, Preferably it is 0.1-0.5 micrometer. As a refinement means employed in the refinement process, an apparatus capable of pulverizing the CHA-type zeolite obtained in the synthesis process to a desired particle size may be used as appropriate, and is not particularly limited. Alternatively, a ball mill, a bead mill, a jet mill or the like can be used. In the present invention, wet grinding using a wet bead mill is preferably employed. By using a wet bead mill, a CHA-type zeolite having a small average particle diameter can be easily obtained while suppressing a decrease in crystallinity due to pulverization. In addition, the wet bead mill is configured by inserting the coarse powder of the material to be crushed and the beads as a medium together with a dispersion medium made of a liquid such as water into a pulverization chamber, and rotating a rotating blade that can rotate in the pulverization chamber at a high speed. The object to be pulverized is refined by stirring the beads and applying frictional force or shearing force generated by the beads to the object to be pulverized.

  When the micronization process of the present invention is performed using a wet bead mill, the beads used are preferably at least one selected from the group consisting of zirconia and alumina, and zirconia is particularly preferable.

  The particle diameter of the beads is preferably 30 to 1000 μm, more preferably 50 to 500 mm, in order to make the average particle diameter of the CHA zeolite 0.5 μm or less.

  The beads are preferably used 0.5 to 5 times, preferably 2 to 4 times the volume of the zeolite having the CHA structure. It is preferable for the amount of beads used to be in the above-mentioned range because the target average particle diameter can be miniaturized in a short time.

  As operating conditions of the wet bead mill, the rotational speed of the wet bead mill is preferably 1000 to 4200 rpm, and more preferably 1500 to 3500 rpm. The pulverization time is preferably 5 to 60 minutes, more preferably 10 to 45 minutes. When the rotation speed and pulverization time are in the above ranges, zeolite having a desired average particle diameter can be produced, and good productivity can be ensured.

  Moreover, water is mentioned as a dispersion medium, The quantity of the dispersion medium introduce | transduced into a wet bead mill is 2-10 times in volume conversion with respect to the quantity of a CHA type zeolite.

<Recrystallization process>
The recrystallization process of the present invention comprises CHA-type zeolite refined by the above-described refinement process, Si having a concentration of 0.01 to 0.5 mol / L, and Na having a concentration of 0.08 to 0.5 mol / L. It is a step of mixing and hydrating a solution containing the solution (hereinafter sometimes referred to as a recrystallization solution). The recrystallization solution may further contain K having a concentration of 0.008 to 0.1 mol / L. Furthermore, the recrystallization solution may contain Al.
In the recrystallization solution, Si can be derived from a Si source that can be used in the synthesis process. Na and K can also be derived from an alkali source that can be used in the synthesis step. The solvent is exemplified by water.

In the recrystallization solution, if the Si concentration is less than 0.01 mol / L, the zeolite skeleton cannot be repaired, and if it exceeds 0.5 mol / L, Si does not enter the zeolite skeleton and precipitates as SiO _2. End up.
Further, by setting the concentration of Na to 0.08 to 0.5 mol / L, Na ions having a small ionic radius enter even inside the zeolite particles, so that recrystallization easily proceeds.
Moreover, it becomes easy to advance recrystallization of the surface of a zeolite by containing K by the density | concentration of 0.008-0.1 mol / L.
In the recrystallization step of the present invention, the concentration of Si is more preferably 0.01 to 0.3 mol / L from the viewpoint of preventing SiO ₂ precipitation and increasing crystallinity in the recrystallization solution, The concentration of is more preferably 0.08 to 0.4 mol / L. The concentration of K is more preferably 0.008 to 0.05 mol / L.

  The recrystallization process of the present invention can be prepared by mixing fumed silica as a Si source and sodium hydroxide as a Na source in a recrystallization solution, for example, using water as a solvent, and allowing to stand for 3 to 24 hours.

  In the recrystallization step of the present invention, the mixing ratio of the refined CHA-type zeolite and the recrystallization solution is, for example, 1 to 12 when the mass of the CHA-type zeolite is 1, Preferably it is 1-8. By setting the mass ratio of the CHA-type zeolite and the recrystallization solution to 1 to 12, the crystal structure can be restored in a relatively short time.

  For the hydration treatment in the recrystallization step, for example, the same conditions as in the hydrothermal synthesis of the raw material composition in the synthesis step can be adopted.

  By the recrystallization process as described above, the crystal structure of the CHA-type zeolite damaged in the refinement process is restored, and the crystallinity can be sufficiently enhanced.

  Analysis of the crystal structure of the CHA-type zeolite can be performed using an X-ray diffraction (XRD) apparatus. The CHA-type zeolite is an X-ray diffraction spectrum by a powder X-ray analysis method, and the (211) plane of the CHA-type zeolite crystals at 2θ = 20.7 °, 25.1 °, and 26.1 °, respectively ( The peaks corresponding to the (104) plane and the (220) plane appear.

XRD measurement is performed using an X-ray diffractometer (Uriga IV manufactured by Rigaku Corporation). The measurement conditions are as follows.
Radiation source: CuKα (λ = 0.154 nm), measurement method: FT method, diffraction angle: 2θ = 5-48 °, step width: 0.02 °, integration time: 1 second, divergence slit, scattering slit: 2 / 3 °, divergence length limiting slit: 10 mm, acceleration voltage: 40 kV, acceleration current: 40 mA.
The sample weight should not be changed by 0.1% or more before and after the XRD measurement. The obtained XRD data is subjected to peak search using the powder X-ray diffraction pattern comprehensive analysis software JADE 6.0, and the half width and integrated intensity of each peak are calculated. The peak search conditions are as follows.
Filter type: parabolic filter, Kα2 peak elimination: yes, peak position definition: peak top, threshold σ: 3, peak intensity% cutoff: 0.1, BG determination range: 1, BG averaging points: 7 .
From the obtained data, the (211) plane (near 2θ = 20.7 °), (104) plane (near 2θ = 25.1 °), (220) plane (near 2θ = 26.1 °) of the zeolite. it can be the sum X ₀ of the integrated intensity. The reason why the integrated intensity of the peaks of the (211) plane, (104) plane, and (220) plane of zeolite is used is that the influence of water absorption of the sample is small.

According to the present invention, the sum of the integrated intensities of the CHA zeolite after the refinement process is 20000 to 45000, whereas the CHA zeolite obtained by the recrystallization process has its crystal structure restored, The sum of strengths can be 50000 or more, preferably 52000 or more. That is, the sum of the integrated strengths of the CHA-type zeolite obtained by the recrystallization step can be 1.15 to 3 times the sum of the integrated strengths of the CHA-type zeolite after the refinement step.
Note that the average particle size of the CHA-type zeolite after the recrystallization step is substantially the same as the average particle size of the CHA-type zeolite obtained after the refining step.

In the zeolite produced according to the present invention, the SiO ₂ / Al ₂ O ₃ composition ratio (SAR) is preferably less than 15. The composition ratio of SiO ₂ / Al ₂ O ₃ means the molar ratio (SAR) of SiO ₂ to Al ₂ O ₃ in the zeolite. When the composition ratio SiO ₂ / Al ₂ O ₃ is less than 15, the acid sites of the zeolite can be made a sufficient number, and the acid sites can be used for ion exchange with metal ions. As a result, it is possible to carry a large amount of catalytic metal such as the above, and therefore it is excellent in NOx purification performance.
A more preferable SiO ₂ / Al ₂ O ₃ composition ratio is 10 to 14.9.
The molar ratio of zeolite (SiO ₂ / Al ₂ O ₃ ) can be measured using fluorescent X-ray analysis (XRF).

  As described above, the average particle diameter of the zeolite was measured using a scanning electron microscope (SEM, manufactured by Hitachi High-Tech, S-4800) to measure the length of all diagonal lines of 10 particles. And the average value is obtained. Measurement conditions are as follows: acceleration voltage: 1 kV, emission: 10 μA, WD: 2.2 mm or less.

  As described above, the average particle size of the CHA-type zeolite obtained by the production method of the present invention is preferably 0.5 μm or less, and more preferably 0.1 to 0.4 μm. When the average particle diameter is 0.5 μm or less, the amount of water absorption displacement when the honeycomb catalyst is used is small, cracks are hardly generated during production and use as the catalyst, and the durability is excellent.

The production method of the present invention preferably further includes a step of performing Cu ion exchange on the CHA-type zeolite after the recrystallization step.
The Cu ion exchange method can be carried out by immersing CHA-type zeolite in a kind of aqueous solution selected from an aqueous copper acetate solution, an aqueous copper nitrate solution, an aqueous copper sulfate solution, and an aqueous copper chloride solution. Of these, it is preferable to use an aqueous copper acetate solution. This is because a large amount of Cu can be supported at one time. For example, Cu can be supported on the CHA-type zeolite by ion exchange of an aqueous solution of copper (II) acetate having a copper concentration of 0.1 to 2.5% by mass at a solution temperature of room temperature to 50 ° C. and atmospheric pressure.

  The Cu content of the zeolite carrying Cu obtained in the production method of the present invention is preferably such that Cu / Al (molar ratio) is 0.2 to 0.5, preferably 0.25 to 0.48. More preferably. When the Cu / Al (molar ratio) is 0.2 or more, high NOx purification performance can be obtained with a small amount of zeolite. Further, when the molar ratio is 0.5 or less, it is possible to prevent NOx purification performance from being deteriorated due to ammonia oxidation at a high temperature. The amount of Cu supported can be measured by ICP emission spectroscopic analysis (ICP-AES). The amount of Al can be measured using the X-ray fluorescence analyzer described above, and the Cu / Al molar ratio can be calculated.

ICP-AES can be measured using an ICP emission spectroscopic analyzer (manufactured by Shimadzu Corporation: ICPE-9000). The measurement conditions are as follows.
As a pretreatment of the sample, 0.1 g of zeolite after Cu ion exchange dried at 400 ° C. for 4 hours is placed in a platinum dish, 5 ml of nitric acid, 20 ml of hydrofluoric acid, and 5 ml of sulfuric acid are added until sulfuric acid white smoke is generated. Heat. This is adjusted to be a 50 ml aqueous solution and used as a measurement sample.
A measurement sample is put into the apparatus, and Cu element is designated to perform measurement.

Next, a method for manufacturing the honeycomb catalyst of the present invention will be described. The method for manufacturing a honeycomb catalyst of the present invention includes a step of mixing the CHA-type zeolite obtained by the above manufacturing method and an inorganic binder.
A honeycomb catalyst manufactured according to the present invention (hereinafter referred to as the honeycomb catalyst of the present invention) is a honeycomb catalyst including a honeycomb unit in which a plurality of through holes are arranged in parallel in the longitudinal direction with partition walls therebetween.

  FIG. 1 shows an example of the honeycomb catalyst of the present invention. A honeycomb catalyst 10 shown in FIG. 1 includes a single honeycomb unit 11 in which a plurality of longitudinally extending through-holes 11a are arranged in parallel with a partition wall 11b therebetween, and an outer peripheral coating layer is formed on the outer peripheral surface of the honeycomb unit 11. 12 is formed. The honeycomb unit 11 contains zeolite and an inorganic binder.

  In the honeycomb catalyst of the present invention, the maximum peak pore diameter of the partition walls of the honeycomb unit (hereinafter sometimes referred to as the maximum peak pore diameter of the honeycomb unit) is preferably 0.03 to 0.15 μm. It is more desirable that it is 05-0.10 micrometer. If the maximum peak pore size of the honeycomb unit is less than 0.03 μm, the exhaust gas cannot be sufficiently diffused into the partition walls, and the NOx purification performance may be deteriorated. If it exceeds 0.15 μm, the number of pores is reduced. Therefore, the zeolite may not be effectively used for NOx purification.

  The pore diameter of the honeycomb unit can be measured using a mercury intrusion method. The mercury contact angle is 130 °, the surface tension is 485 mN / m, and the pore diameter is in the range of 0.01 to 100 μm. The value of the pore diameter at the maximum peak in this range is called the maximum peak pore diameter.

  In the honeycomb catalyst of the present invention, the porosity of the honeycomb unit is preferably 40 to 70%. When the porosity of the honeycomb unit is less than 40%, the exhaust gas hardly enters the partition walls of the honeycomb unit, and the zeolite is not effectively used for the purification of NOx. On the other hand, when the porosity of the honeycomb unit exceeds 70%, the strength of the honeycomb unit becomes insufficient.

The porosity of the honeycomb unit can be measured by a gravimetric method.
The method for measuring the porosity by the gravimetric method is as follows.
The honeycomb unit is cut into a size of 7 cells × 7 cells × 10 mm to obtain a measurement sample. This sample is ultrasonically cleaned with ion-exchanged water and acetone, and then dried at 100 ° C. in an oven. Next, using a measurement microscope (Nikon, Measuring Microscope MM-40, magnification 100 times), the dimensions of the cross-sectional shape of the sample are measured, and the volume is obtained from geometric calculation. When the volume cannot be obtained from geometric calculation, the volume is calculated by image processing of a cross-sectional photograph.
Thereafter, the weight when the sample is assumed to be a complete dense body is calculated from the calculated volume and the true density of the sample measured with a pycnometer.
The measurement procedure with a pycnometer is as follows. The honeycomb unit is pulverized to prepare 23.6 cc of powder, and the obtained powder is dried at 200 ° C. for 8 hours. Then, true density is measured based on JIS-R-1620 (1995) using Auto Pycnometer 1320 (made by Micromeritics). The exhaust time at this time is 40 minutes.
Next, the actual weight of the sample is measured with an electronic balance (HR202i manufactured by Shimadzu Corporation), and the porosity is calculated by the following calculation formula.
Porosity (%) = 100− (actual weight / weight as dense body) × 100

  In the honeycomb catalyst of the present invention, the zeolite contained in the honeycomb unit is a zeolite having a CHA structure manufactured according to the present invention. Since the zeolite has been described in detail in the description of the zeolite of the present invention, detailed description thereof will be omitted here.

  The zeolite content in the honeycomb unit is preferably 40 to 90% by volume, and more preferably 50 to 80% by volume. If the zeolite content is less than 40% by volume, the NOx purification performance is lowered. On the other hand, when the content of zeolite exceeds 90% by volume, the amount of other materials contained is too small and the strength tends to decrease.

  In the honeycomb catalyst of the present invention, the honeycomb unit may contain zeolite other than CHA-type zeolite and silicoaluminophosphate (SAPO) within a range not impairing the effects of the present invention.

  In the honeycomb catalyst of the present invention, the honeycomb unit preferably contains 100 to 320 g / L of the zeolite of the present invention per apparent volume of the honeycomb unit, and more preferably 120 to 300 g / L. If it is less than 100 g / L, the NOx purification performance is lowered, and if it exceeds 320 g / L, the strength of the honeycomb unit may be lowered.

  In the honeycomb catalyst of the present invention, the inorganic binder contained in the honeycomb unit is not particularly limited, but is contained in alumina sol, silica sol, titania sol, water glass, sepiolite, attapulgite, boehmite, etc. from the viewpoint of maintaining strength as a honeycomb catalyst. The solid content is suitable, and two or more kinds may be used in combination.

The content of the inorganic binder in the honeycomb unit is desirably 3 to 20% by volume, and more desirably 5 to 15% by volume. When the content of the inorganic binder is less than 3% by volume, the strength of the honeycomb unit is lowered.
On the other hand, when the content of the inorganic binder exceeds 20% by volume, the content of zeolite in the honeycomb unit decreases, and the NOx purification performance decreases.

  In the honeycomb catalyst of the present invention, the honeycomb unit may further contain inorganic particles in order to adjust the pore diameter of the honeycomb unit.

  The inorganic particles contained in the honeycomb unit are not particularly limited, and examples thereof include particles such as alumina, titania, zirconia, silica, ceria, and magnesia. Two or more of these may be used in combination. The inorganic particles are preferably one or more particles selected from the group consisting of alumina, titania and zirconia, and more preferably any one of alumina, titania and zirconia.

The average particle size of the inorganic particles is desirably 0.01 to 1.0 μm, and more desirably 0.03 to 0.5 μm. When the average particle size of the inorganic particles is 0.01 to 1.0 μm, the pore size of the honeycomb unit can be adjusted.
The average particle size of the inorganic particles is the particle size (Dv50) at an integrated value of 50% in the particle size distribution (volume basis) obtained by the laser diffraction / scattering method.

  The content of inorganic particles in the honeycomb unit is preferably 10 to 40% by volume, and more preferably 15 to 35% by volume. When the content of the inorganic particles is less than 10% by volume, the effect of lowering the absolute value of the linear expansion coefficient of the honeycomb unit due to the addition of the inorganic particles is small, and the honeycomb unit is easily damaged by thermal stress. On the other hand, when the content of the inorganic particles exceeds 40% by volume, the content of the zeolite of the present invention is lowered and the NOx purification performance is lowered.

  The volume ratio of the zeolite and inorganic particles of the present invention (CHA type zeolite: inorganic particles) is desirably 50:50 to 90:10, and more desirably 60:40 to 80:20. When the volume ratio of the zeolite of the present invention and the inorganic particles is in the above range, the pore diameter of the honeycomb unit can be adjusted while maintaining the NOx purification performance.

  In the honeycomb catalyst of the present invention, the honeycomb unit may further include one or more selected from the group consisting of inorganic fibers and scale-like substances in order to improve strength.

  The inorganic fiber contained in the honeycomb unit is desirably composed of one or more selected from the group consisting of alumina, silica, silicon carbide, silica alumina, glass, potassium titanate, and aluminum borate. The scaly substance contained in the honeycomb unit is preferably made of one or more selected from the group consisting of glass, muscovite, alumina, and silica. This is because all of them have high heat resistance, and even when used as a catalyst carrier in an SCR system, there is no melting damage and the effect as a reinforcing material can be maintained.

  The content of inorganic fibers and scale-like substances in the honeycomb unit is preferably 3 to 30% by volume, and more preferably 5 to 20% by volume. When the content is less than 3% by volume, the effect of improving the strength of the honeycomb unit is reduced. On the other hand, when the content exceeds 30% by volume, the content of zeolite in the honeycomb unit decreases, and the NOx purification performance decreases.

  In the honeycomb catalyst of the present invention, the opening ratio of the cross section perpendicular to the longitudinal direction of the honeycomb unit is preferably 50 to 75%. If the opening ratio of the cross section perpendicular to the longitudinal direction of the honeycomb unit is less than 50%, zeolite is not effectively used for NOx purification. On the other hand, when the opening ratio of the cross section perpendicular to the longitudinal direction of the honeycomb unit exceeds 75%, the strength of the honeycomb unit becomes insufficient.

In the honeycomb catalyst of the present invention, it is desirable that the density of through-holes in a cross section perpendicular to the longitudinal direction of the honeycomb unit is 31 to 155 holes / cm ² . If the density of the through-holes having a cross section perpendicular to the longitudinal direction of the honeycomb unit is less than 31 / cm ² , it becomes difficult for the zeolite and the exhaust gas to come into contact with each other, and the NOx purification performance decreases. On the other hand, when the density of the through holes in the cross section perpendicular to the longitudinal direction of the honeycomb unit exceeds 155 holes / cm ² , the pressure loss of the honeycomb catalyst increases.

  In the honeycomb catalyst of the present invention, the thickness of the partition walls of the honeycomb unit is desirably 0.1 to 0.4 mm, and more desirably 0.1 to 0.3 mm. When the thickness of the partition walls of the honeycomb unit is less than 0.1 mm, the strength of the honeycomb unit decreases. On the other hand, when the thickness of the partition wall of the honeycomb unit exceeds 0.4 mm, the exhaust gas hardly enters the inside of the partition wall of the honeycomb unit, and the zeolite is not effectively used for purification of NOx.

  In the honeycomb catalyst of the present invention, when the outer peripheral coat layer is formed on the honeycomb unit, the thickness of the outer peripheral coat layer is preferably 0.1 to 2.0 mm. When the thickness of the outer peripheral coat layer is less than 0.1 mm, the effect of improving the strength of the honeycomb catalyst becomes insufficient. On the other hand, when the thickness of the outer peripheral coat layer exceeds 2.0 mm, the content of zeolite per unit volume of the honeycomb catalyst decreases, and the NOx purification performance decreases.

  The shape of the honeycomb catalyst of the present invention is not limited to a cylindrical shape, and examples thereof include a prismatic shape, an elliptical cylindrical shape, a long cylindrical shape, and a rounded chamfered prismatic shape (for example, a rounded chamfered triangular prism shape).

  In the honeycomb catalyst of the present invention, the shape of the through hole is not limited to a quadrangular prism shape, and examples thereof include a triangular prism shape and a hexagonal prism shape.

Next, an example of a method for manufacturing the honeycomb catalyst 10 shown in FIG. 1 will be described.
First, including a zeolite and an inorganic binder, and if necessary, extruding using a raw material paste further containing one or more inorganic particles and inorganic fibers and scale-like substances, and in a plurality of longitudinal directions A cylindrical honeycomb formed body in which extending through-holes are arranged in parallel with a partition wall therebetween is produced.

  The inorganic binder contained in the raw material paste is not particularly limited, but is added as alumina sol, silica sol, titania sol, water glass, sepiolite, attapulgite, boehmite, etc., and two or more kinds may be used in combination.

  Moreover, you may add an organic binder, a dispersion medium, a shaping | molding adjuvant, etc. to a raw material paste suitably as needed.

  Although it does not specifically limit as an organic binder, Methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, polyethyleneglycol, a phenol resin, an epoxy resin etc. are mentioned, You may use 2 or more types together. In addition, as for the addition amount of an organic binder, it is desirable that it is 1-10% with respect to the total mass of a zeolite, an inorganic particle, an inorganic binder, an inorganic fiber, and a scaly substance.

  Although it does not specifically limit as a dispersion medium, Alcohol, such as water, organic solvents, such as benzene, methanol, etc. are mentioned, You may use 2 or more types together.

  Although it does not specifically limit as a shaping | molding adjuvant, Ethylene glycol, dextrin, a fatty acid, fatty acid soap, a polyalcohol etc. are mentioned, You may use together 2 or more types.

Furthermore, a pore former may be added to the raw material paste as necessary.
Although it does not specifically limit as a pore making material, A polystyrene particle, an acrylic particle, starch, etc. are mentioned, You may use 2 or more types together. Of these, polystyrene particles are desirable.

  By controlling the particle diameters of the zeolite and the pore former, the pore diameter distribution of the partition walls can be controlled within a predetermined range.

  Even when no pore former is added, the pore size distribution of the partition walls can be controlled within a predetermined range by controlling the particle sizes of zeolite and inorganic particles.

  When preparing the raw material paste, it is desirable to mix and knead, and it may be mixed using a mixer, an attritor or the like, or may be kneaded using a kneader or the like.

  Next, the honeycomb formed body is dried by using a dryer such as a microwave dryer, a hot air dryer, a dielectric dryer, a vacuum dryer, a vacuum dryer, or a freeze dryer to produce a honeycomb dried body.

  Further, the honeycomb dried body is degreased to produce a honeycomb degreased body. The degreasing conditions can be appropriately selected depending on the type and amount of organic matter contained in the dried honeycomb body, but it is desirable that the degreasing conditions be 200 to 500 ° C. for 2 to 6 hours.

  Next, the honeycomb degreased body is fired to produce a columnar honeycomb unit 11. The firing temperature is desirably 600 to 1000 ° C, and more desirably 600 to 800 ° C. When the firing temperature is less than 600 ° C., the sintering does not proceed and the strength of the honeycomb unit 11 is lowered. On the other hand, if the calcination temperature exceeds 1000 ° C., the sintering proceeds too much and the reaction sites of the zeolite decrease.

  Next, the outer peripheral coat layer paste is applied to the outer peripheral surface excluding both end surfaces of the columnar honeycomb unit 11.

  Although it does not specifically limit as a paste for outer periphery coating layers, The mixture of an inorganic binder and an inorganic particle, the mixture of an inorganic binder and an inorganic fiber, the mixture of an inorganic binder, an inorganic particle, and an inorganic fiber etc. are mentioned.

  Although the inorganic binder contained in the outer periphery coating layer paste is not particularly limited, it is added as silica sol, alumina sol or the like, and two or more kinds may be used in combination. Among these, it is desirable to add as silica sol.

  The inorganic particles contained in the outer coat layer paste are not particularly limited, but oxide particles such as zeolite, eucryptite, alumina and silica, carbide particles such as silicon carbide, and nitride particles such as silicon nitride and boron nitride. Etc., and two or more of them may be used in combination. Among them, eucryptite particles having a thermal expansion coefficient close to that of the honeycomb unit are desirable.

  Although it does not specifically limit as an inorganic fiber contained in the paste for outer periphery coating layers, A silica alumina fiber, a mullite fiber, an alumina fiber, a silica fiber, etc. are mentioned, You may use 2 or more types together. Among these, alumina fibers are preferable.

The outer periphery coating layer paste may further contain an organic binder.
Although it does not specifically limit as an organic binder contained in the paste for outer periphery coating layers, Polyvinyl alcohol, methylcellulose, ethylcellulose, carboxymethylcellulose, etc. are mentioned, You may use 2 or more types together.

  The outer periphery coating layer paste may further include balloons, pore formers, and the like, which are fine hollow spheres of oxide ceramics.

  The balloon contained in the outer peripheral coat layer paste is not particularly limited, and examples thereof include alumina balloons, glass micro balloons, shirasu balloons, fly ash balloons, mullite balloons and the like, and two or more kinds may be used in combination. Among these, an alumina balloon is preferable.

  The pore former contained in the outer periphery coat layer paste is not particularly limited, and examples thereof include spherical acrylic particles and graphite, and two or more kinds may be used in combination.

  Next, the honeycomb unit 11 to which the outer peripheral coat layer paste is applied is dried and solidified to produce a columnar honeycomb catalyst 10. At this time, when the outer peripheral coat layer paste contains an organic binder, it is desirable to degrease. The degreasing conditions can be appropriately selected depending on the kind and amount of the organic substance, but it is desirable that the degreasing conditions be 500 ° C. for 1 hour.

As a specific application example of the honeycomb catalyst of the present invention, there is an exhaust gas purification device.
FIG. 2 shows an example of the exhaust gas purifying apparatus. The exhaust gas purification apparatus 100 shown in FIG. 2 can be manufactured by canning the metal container (shell) 30 in a state where the holding sealing material 20 is disposed on the outer peripheral portion of the honeycomb catalyst 10. Further, in the exhaust gas purifying apparatus 100, in the pipe (not shown) on the upstream side of the honeycomb catalyst 10 with respect to the flow direction of the exhaust gas (in FIG. 2, the exhaust gas is indicated by G and the flow of the exhaust gas is indicated by an arrow). Further, an injection means (not shown) such as an injection nozzle that injects ammonia or a compound that decomposes to generate ammonia is provided. As a result, ammonia is added to the exhaust gas flowing through the pipe, so that NOx contained in the exhaust gas is reduced by the zeolite contained in the honeycomb unit 11.

  The compound that decomposes to generate ammonia is not particularly limited as long as it can be hydrolyzed in the pipe to generate ammonia, but urea water is preferable because of excellent storage stability.

  FIG. 3 shows another example of the honeycomb catalyst of the present invention. In the honeycomb catalyst 10 ′ shown in FIG. 3, a plurality of honeycomb units 11 ′ (see FIG. 4) in which a plurality of longitudinally extending through holes 11 a are arranged with a partition wall 11 b therebetween are bonded via an adhesive layer 13. Except for this, the configuration is the same as that of the honeycomb catalyst 10.

The cross-sectional area of the cross section perpendicular to the longitudinal direction of the honeycomb unit 11 ′ is desirably 10 to ²⁰⁰ cm ² . When the cross-sectional area is less than 10 cm ² , the pressure loss of the honeycomb catalyst 10 ′ increases. On the other hand, when the cross-sectional area exceeds 200 cm ² , it is difficult to bond the honeycomb units 11 ′.

  The honeycomb unit 11 ′ has the same configuration as the honeycomb unit 11 except for the cross-sectional area of the cross section perpendicular to the longitudinal direction.

  The thickness of the adhesive layer 13 is desirably 0.1 to 3.0 mm. When the thickness of the adhesive layer 13 is less than 0.1 mm, the adhesive strength of the honeycomb unit 11 ′ becomes insufficient. On the other hand, when the thickness of the adhesive layer 13 exceeds 3.0 mm, the pressure loss of the honeycomb catalyst 10 ′ increases or cracks occur in the adhesive layer.

Next, an example of a method for manufacturing the honeycomb catalyst 10 ′ shown in FIG. 3 will be described.
First, in the same manner as the honeycomb unit 11 constituting the honeycomb catalyst 10, a fan-shaped honeycomb unit 11 ′ is manufactured. Next, an adhesive layer paste is applied to the outer peripheral surface excluding the arc side of the honeycomb unit 11 ′, the honeycomb unit 11 ′ is adhered, and dried and solidified to produce an aggregate of the honeycomb units 11 ′.

  Although it does not specifically limit as a paste for contact bonding layers, The mixture of an inorganic binder and an inorganic particle, the mixture of an inorganic binder and an inorganic fiber, the mixture of an inorganic binder, an inorganic particle, and an inorganic fiber etc. are mentioned.

  The inorganic binder contained in the adhesive layer paste is not particularly limited, but is added as silica sol, alumina sol or the like, and two or more kinds may be used in combination. Among these, it is desirable to add as silica sol.

  The inorganic particles contained in the adhesive layer paste are not particularly limited, but oxide particles such as zeolite, eucryptite, alumina and silica, carbide particles such as silicon carbide, nitride particles such as silicon nitride and boron nitride, etc. And two or more of them may be used in combination. Among them, eucryptite particles having a thermal expansion coefficient close to that of the honeycomb unit are desirable.

  Although it does not specifically limit as an inorganic fiber contained in the paste for contact bonding layers, A silica alumina fiber, a mullite fiber, an alumina fiber, a silica fiber etc. are mentioned, You may use 2 or more types together. Among these, alumina fibers are preferable.

The adhesive layer paste may contain an organic binder.
Although it does not specifically limit as an organic binder contained in the paste for contact bonding layers, Polyvinyl alcohol, methylcellulose, ethylcellulose, carboxymethylcellulose etc. are mentioned, You may use 2 or more types together.

  The adhesive layer paste may further include balloons, pore formers, and the like, which are fine hollow spheres of oxide ceramics.

  Although it does not specifically limit as a balloon contained in the paste for contact bonding layers, An alumina balloon, a glass micro balloon, a shirasu balloon, a fly ash balloon, a mullite balloon etc. are mentioned, You may use 2 or more types together. Among these, an alumina balloon is preferable.

  The pore former contained in the adhesive layer paste is not particularly limited, and examples thereof include spherical acrylic particles and graphite, and two or more kinds may be used in combination.

  Next, in order to increase the roundness, the aggregate of the honeycomb units 11 ′ is cut and polished as necessary to produce the aggregate of the cylindrical honeycomb units 11 ′.

  Next, the outer peripheral coat layer paste is applied to the outer peripheral surface excluding both end surfaces of the aggregate of the cylindrical honeycomb units 11 ′.

  The outer periphery coating layer paste may be the same as or different from the adhesive layer paste.

  Next, a columnar honeycomb catalyst 10 ′ is manufactured by drying and solidifying the aggregate of columnar honeycomb units 11 ′ to which the outer periphery coating layer paste has been applied. At this time, when the adhesive for the adhesive layer and / or the paste for the outer peripheral coat layer contains an organic binder, it is desirable to degrease. The degreasing conditions can be appropriately selected depending on the kind and amount of the organic substance, but it is desirable that the degreasing conditions be 500 ° C. for 1 hour.

  The honeycomb catalyst 10 ′ is configured by bonding four honeycomb units 11 ′ via the adhesive layer 13, but the number of honeycomb units constituting the honeycomb catalyst is not particularly limited. For example, a columnar honeycomb catalyst may be configured by adhering 16 square columnar honeycomb units via an adhesive layer.

  The honeycomb catalyst 10 or 10 ′ may not have the outer peripheral coat layer 12 formed thereon.

  As described above, in the honeycomb catalyst of the present invention, NOx purification performance can be improved by forming a honeycomb unit using the zeolite of the present invention as the zeolite.

  Examples in which the present invention is disclosed more specifically are shown below. In addition, this invention is not limited only to this Example.

<Analysis of crystal structure>
In each of the following examples, the crystal structure of zeolite was analyzed as follows.
XRD measurement was performed on CHA-type zeolite using an X-ray diffractometer (manufactured by Rigaku Corporation, Ultimate IV), and the sum of integrated intensities of the (211), (104) and (220) planes of the X-ray diffraction spectrum ( X ₀ ) was calculated.
Measurement conditions are: radiation source: CuKα (λ = 0.154 nm), measurement method: FT method, diffraction angle: 2θ = 5-48 °, step width: 0.02 °, integration time: 1 second, diverging slit, scattering Slit: 2/3 °, divergence length limiting slit: 10 mm, acceleration voltage: 40 kV, acceleration current: 40 mA.
Analysis of the obtained XRD data was performed using powder X-ray diffraction pattern comprehensive analysis software JADE 6.0. The analysis conditions are: filter type: parabolic filter, elimination of Kα2 peak: yes, peak position definition: peak top, threshold σ: 3, peak intensity% cutoff: 0.1, BG determination range: 1, BG average The number of conversion points was set to 7.

<Measurement of average particle diameter>
In each of the following examples, the average particle size of zeolite was measured as follows.
Using a scanning electron microscope (SEM, Hitachi High-Tech, S-4800), SEM photographs of CHA-type zeolite were taken and their particle sizes were measured. The measurement conditions were acceleration voltage: 1 kV, emission: 10 μA, WD: 2.2 mm or less. The measurement magnification was 20000 times. The particle diameter was measured from two diagonal lines of 10 particles, and the average value was obtained.

<Measurement of molar ratio of zeolite (SiO ₂ / Al ₂ O ₃ )>
In each Example, the measurement of the molar ratio of zeolite (SAR: SiO ₂ / Al ₂ O ₃ ) was performed as follows.
The molar ratio (SAR: SiO ₂ / Al ₂ O ₃ ) of CHA-type zeolite was measured using an X-ray fluorescence analyzer (XRF, ZSX Primus 2 manufactured by Rigaku Corporation). The measurement conditions were: X-ray tube: Rh, rated maximum output: 4 kW, detection element range: F to U, quantitative method: SQX method, analysis region: 10 mmφ.

<Measurement of Cu loading>
In each of the following examples, the measurement of the amount of Cu supported on zeolite was performed as follows.
The amount of Cu supported on the CHA-type zeolite was measured using an ICP emission spectroscopic analyzer (manufactured by Shimadzu Corporation: ICPE-9000).
As a pretreatment of the sample, 0.1 g of zeolite after Cu ion exchange dried at 400 ° C. for 4 hours is placed in a platinum dish, 5 ml of nitric acid, 20 ml of hydrofluoric acid, and 5 ml of sulfuric acid are added until sulfuric acid white smoke is generated. Heat. This is adjusted to be a 50 ml aqueous solution and used as a measurement sample.
The measurement sample was put in the apparatus, and Cu element was designated and measured. The Cu / Al molar ratio was calculated from the measured value of the Cu loading.

Example 1
<Synthesis process>
Colloidal silica (manufactured by Nissan Chemical Industries, Snowtex) as the Si source, dry aluminum hydroxide gel (manufactured by Tomita Pharmaceutical) as the Al source, sodium hydroxide (manufactured by Tokuyama) and potassium hydroxide (Toagosei Co., Ltd.) as the alkali source Manufactured), N, N, N-trimethyladamantanammonium hydroxide (TMAAOH) 25% aqueous solution (manufactured by Sachem) as a structure directing agent (SDA), SSZ-13 as a seed crystal, and deionized water A composition was prepared. The molar ratios of the raw material compositions were SiO ₂ : 15 mol, Al ₂ O ₃ : 1 mol, NaOH: 1.6 mol, KOH: 0.53 mol, TMAAOH: 1.62 mol, and H ₂ O: 300 mol. Further, 5.0% by mass of seed crystals was added to SiO ₂ and Al ₂ O ₃ in the raw material composition. The raw material composition was charged into a 500 L autoclave, and hydrothermal synthesis was performed at a heating temperature of 160 ° C. and a heating time of 24 hours to synthesize CHA-type zeolite.
The average particle diameter of the obtained CHA-type zeolite was 0.74 μm, and the sum of integrated intensities (X ₀ ) was 54357.

<Refining process>
Using a wet bead mill (Labstar Mini, manufactured by Ashizawa Finetech Co., Ltd.), the micronization process was performed under the following conditions.
Bead type: ZrO ₂ beads Bead particle size: 300 μm
Number of rotations of rotor blade: 2900 rpm
Milling time: 60 minutes Then, for evaluation, 550 ° C., 10 hours, and heated in an air atmosphere, was calculated sum of the average particle diameter of the integrated intensity of the (X _0). As a result, the average particle size was 0.12 μm, and the sum of integrated intensities (X ₀ ) was 33991.

<Recrystallization process>
The CHA-type zeolite and the recrystallization solution after the refining process were recrystallized while being stirred in an autoclave at 200 ° C. for 24 hours.
In the recrystallization solution, fumed silica is used as the Si source, NaOH is used as the Na source, KOH is used as the K source, and these various raw materials are mixed with water as a solvent so as to have the concentrations shown in Table 1. The solution for recrystallization was prepared by allowing to stand for 12 hours.
The ratio of the CHA-type zeolite after the refining process and the recrystallization solution was 1: 8 as the former: the latter (mass ratio).
The sum (X ₀ ) of the average particle diameter and integrated intensity of the CHA-type zeolite obtained after the recrystallization step, and the molar ratio (SAR) of the CHA-type zeolite were determined. As a result, the average particle size was 0.12 μm, the sum of integrated intensities (X ₀ ) was 53379, and the SAR was 12.2. The results are shown in Table 1.
From the above, it was found that the crystal structure of the CHA-type zeolite damaged in the refinement process was almost restored to the crystal structure immediately after the synthesis process by performing the recrystallization process.

  Subsequently, the CHA-type zeolite obtained after the recrystallization step was used for the first ion exchange with an aqueous copper (II) acetate solution having a copper concentration of 2.34% by mass, and for the second ion exchange, the copper concentration was 0.59. Using a mass% aqueous solution of copper (II) acetate, ion exchange was performed for 1 hour at a solution temperature of 50 ° C. and atmospheric pressure.

FIG. 5 shows the XRD pattern of the CHA-type zeolite obtained in the synthesis step of Example 1, FIG. 6 shows the XRD pattern of the CHA-type zeolite obtained in the refinement step of Example 1, and FIG. 1 shows an XRD pattern of a CHA-type zeolite obtained in one recrystallization step.
FIG. 5 shows that the zeolite obtained in the synthesis process is a CHA-type zeolite, FIG. 6 shows that the crystal structure of the CHA-type zeolite was damaged by the refinement process, and FIG. It was found that the crystal structure damaged by the process was repaired by the recrystallization process.

(Examples 2 to 5 and Comparative Example 1)
The CHA obtained after the recrystallization step was carried out in the same manner as in Example 1 except that the conditions for the recrystallization step, the Si concentration, the Na concentration and the K concentration in the recrystallization solution were changed to those shown in Table 1. The sum (X ₀ ) of the average particle size and integrated intensity of the type zeolite and the molar ratio (SAR) of the CHA type zeolite were determined. The results are shown in Table 1.

(Comparative Example 2)
A CHA-type zeolite carrying Cu was obtained in the same manner as in Example 1 except that the refinement process and the recrystallization process were not performed.

(Preparation of honeycomb catalyst)
Glass having 25% by mass of CHA-type zeolite obtained in Examples 1 to 5 and Comparative Examples 1 to 2, 19% by mass of 0.2 μm titania, 11% by mass of pseudoboehmite as an inorganic binder, and an average fiber length of 100 μm 4% by mass of fibers, 6% by mass of methylcellulose, 3% by mass of surfactant, 5% by mass of polystyrene particles as a pore former, and 27% by mass of ion-exchanged water were mixed and kneaded to prepare a raw material paste. The CHA-type zeolite used was after copper ion exchange.

Next, the raw material paste was extruded using an extrusion molding machine to produce a honeycomb formed body. Then, using a vacuum microwave dryer, the honeycomb formed body was dried at an output of 4.5 kW and a reduced pressure of 6.7 kPa for 7 minutes, and then degreased and fired at an oxygen concentration of 1% and 700 ° C. for 5 hours. Unit). The honeycomb unit had a regular quadrangular prism shape with a side of 35 mm and a length of 150 mm, a through hole density of 124 holes / cm ² , and a partition wall thickness of 0.20 mm.

<Measurement of NOx purification rate>
A cylindrical test piece having a diameter of 25.4 mm and a length of 38.1 mm was cut out from the honeycomb unit using a diamond cutter. NOx flowing out from the test piece using a catalyst evaluation apparatus (SIGU-2000 / MEXA-6000FT, manufactured by Horiba, Ltd.) while flowing a simulated gas at 200 ° C. at a space velocity (SV) of 40000 hr ^−1. The outflow amount was measured, and the NOx purification rate (%) represented by the following formula (1) was calculated. The components of the simulated gas were nitrogen monoxide 262.5 ppm, nitrogen dioxide 87.5 ppm, ammonia 350 ppm, oxygen 10%, carbon dioxide 5%, water 5%, and nitrogen (balance).
Purification rate (%) = (NOx inflow amount−NOx outflow amount) / (NOx inflow amount) × 100 (1)
Similarly, the NOx purification rate (%) was calculated while flowing a simulated gas at 525 ° C. at SV: 100000 hr ⁻¹ . The constituent components of the simulated gas at this time were 315 ppm nitric oxide, 35 ppm nitrogen dioxide, 385 ppm ammonia, 10% oxygen, 5% carbon dioxide, 5% water, and nitrogen. Table 2 shows the NOx purification rates of the honeycomb catalysts using the CHA-type zeolites obtained in Examples 1 to 5 and Comparative Examples 1 and 2.

<Measurement of water absorption displacement>
Using a diamond cutter from the honeycomb unit, a square columnar test piece having a side of 35 mm and a length of 10 mm was cut out. This test piece was dried with a dryer at 200 ° C. for 2 hours. Thereafter, using a measuring microscope (Mekoning Microscope MM-40 manufactured by Nikon at a magnification of 100 times), the distance between the outermost walls at the time of drying (distance between the outermost wall on the opposite side from the honeycomb outermost wall of the test piece) was measured. The measurement position was the center of the outer periphery of the test piece, and only one side. Subsequently, after immersing a test piece in water for 1 hour and removing the water on the surface of a test piece with air blow, the distance between the outermost walls at the time of water absorption was measured with the same measuring method. The water absorption displacement was calculated by equation (2).
Water absorption variation (%) = (distance between outermost walls when absolutely dry-distance between outermost walls when absorbing water) / (distance between outermost walls when absolutely dry) × 100 (2)
Table 2 shows the water absorption displacement of the honeycomb catalyst using the CHA-type zeolite obtained in Examples 1 to 5 and Comparative Examples 1 and 2.

From the results in Tables 1 and 2, the CHA-type zeolites obtained in Examples 1 to 5 were manufactured through the synthesis process, the refinement process, and the recrystallization process in the present invention. Was 50000 or more, and the crystal structure was repaired and had high crystallinity. Moreover, a CHA-type zeolite having an average particle size of 0.5 μm or less could be easily obtained. Furthermore, it was found that the honeycomb catalyst using the CHA-type zeolite obtained in Examples 1 to 5 was excellent in crack resistance and NOx purification performance.
On the other hand, in Comparative Example 1, since the recrystallization solution does not contain Na, it was confirmed that the crystallinity of the CHA-type zeolite damaged in the refining process is not sufficiently repaired in the recrystallization process. It was found that the honeycomb catalyst using the CHA-type zeolite obtained in Example 1 was inferior in NOx purification performance to less than 90%.
In addition, the honeycomb catalyst using the CHA-type zeolite obtained in Comparative Example 2 was not subjected to the fine pulverization step and the recrystallization step, and the average particle size was as large as 0.74 μm, so the water absorption displacement was 0.2. %, And cracks due to water absorption were likely to occur.

10, 10 'Honeycomb catalyst 11, 11' Honeycomb unit 11a Through-hole 11b Partition 12 Outer peripheral coat layer 13 Adhesive layer 20 Holding sealing material 30 Metal container 100 Exhaust gas purification device G Exhaust gas

Claims (7)

A method for producing a zeolite having a CHA structure, comprising:
A synthesis step of synthesizing a zeolite having a CHA structure using a raw material composition containing a Si source, an Al source, an alkali source and a structure-directing agent;
A refining step of refining the zeolite having the CHA structure obtained in the synthesis step;
A recrystallization step of mixing a zeolite having a CHA structure refined by the refinement step and a recrystallization solution, and hydrating.
The method for producing a zeolite, wherein the recrystallization solution contains Si having a concentration of 0.01 to 0.5 mol / L and Na having a concentration of 0.08 to 0.5 mol / L.   The method for producing a zeolite according to claim 1, wherein the recrystallization solution further contains K having a concentration of 0.008 to 0.1 mol / L. The SiO ₂ / Al ₂ O ₃ composition ratio (SAR) in the zeolite having a CHA structure after the recrystallization step is less than 15, and the average particle size is 0.5 μm or less. A method for producing zeolite.   The sum of integrated intensities of the (211) plane, (104) plane and (220) plane of the X-ray diffraction spectrum by the powder X-ray analysis method for the zeolite having the CHA structure after the recrystallization step is 50000 or more. Item 4. The method for producing a zeolite according to any one of Items 1 to 3.   The zeolite having the CHA structure after the recrystallization step further includes a step of performing Cu ion exchange, and the obtained Cu-supported zeolite has a Cu / Al (molar ratio) of 0.2 to 0.5. The manufacturing method of the zeolite of any one of Claims 1-4 which is.   The zeolite obtained by the manufacturing method of any one of Claims 1-5.   The manufacturing method of a honeycomb catalyst including the process of mixing the zeolite obtained by the manufacturing method of any one of Claims 1-5, and an inorganic binder.

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