Metal ion-exchanged zeolite

Abstract

This zeolite is a BEA-type zeolite ion-exchanged with Ag and Cs, wherein in FT-IR measured by adsorbing CO to the zeolite, the ratio (I2192 / I2184) of the peak intensity I2192 of a peak having a wavelength of 2,192 cm-1 to the peak intensity I2184 of a peak having a wavelength of 2,184 cm-1 is 0.40 or less.

Description

Metal ion exchange zeolite

[0001] This invention relates to metal ion exchange zeolites. More specifically, it relates to metal ion exchange zeolites that have been ion-exchanged with Ag ions and Cs ions.

[0002] Exhaust gases emitted from internal combustion engines of automobiles and other vehicles contain HC (hydrocarbons), CO (carbon monoxide), NOx (nitrogen oxides), and other components. These components are purified by exhaust gas purification catalysts located in the engine's exhaust system before being released into the atmosphere. As exhaust gas purification catalysts, three-way catalysts are known that promote the oxidation purification of HC and CO, as well as the reduction purification of NOx.

[0003] In conventional technology, it is known that such a three-way catalyst is used in combination with an HC adsorption material. When a three-way catalyst and an HC adsorption material are used together, when the catalyst is at a low temperature, such as when the engine is started, HC is adsorbed onto the HC adsorption material, and after the catalyst has warmed up, the HC adsorbed onto the HC adsorption material is desorbed, and oxidation and purification can be performed by the three-way catalyst.

[0004] For example, Patent Document 1 describes an exhaust gas purification catalyst that combines a three-way catalyst layer and an HC adsorption layer, wherein the HC adsorption layer contains zeolite. Furthermore, Patent Documents 2 and 3 describe that the HC adsorption capacity of zeolite can be improved by ion exchange with Ag.

[0005] Furthermore, Patent Documents 4 and 5 propose using Ag in combination with other elements as ion exchange elements for zeolites. Patent Document 4 explains that when Ag is used in combination with Ti, Ni, B, Pd, Si, Al, Cu, Cr, or Zr as ion exchange elements, aggregation and evaporation of Ag are prevented, and the deterioration of the HC adsorbent material can be suppressed. Patent Document 5 explains that when Ag is used in combination with alkali metals as ion exchange elements, when ion exchange is performed with Ag in zeolites, the ion exchange proceeds uniformly and Ag is highly dispersed.

[0006] Japanese Patent Application Laid-Open No. 2008-110303, Japanese Patent Application Laid-Open No. 2005-144253, Japanese Patent Application Laid-Open No. 2007-160168, Japanese Patent Application Laid-Open No. 2006-021153, Japanese Patent Application Laid-Open No. 2017-154965

[0007] In the prior art, it is known that even when Ag ion-exchanged zeolite uses Ag and other elements in combination as ion-exchange elements, its durability resistance is insufficient, and the HC adsorption ability decreases due to durability, and improvement is required.

[0008] The present invention has been made in view of the above, and its object is to provide an HC adsorption material that exhibits a high HC adsorption amount even after durability.

[0009] The present invention is as follows.

[0010] <<Aspect 1>> A BEA-type zeolite ion-exchanged with Ag and Cs, in the FT-IR measured by adsorbing CO to the zeolite, at a wavelength of 2,192 cm －１ the peak intensity I of the peak ２１９２ and the peak intensity I of the peak at a wavelength of 2,184 cm [[ID=Heading ID=17]] －１ of the ratio (I ２１８４ and (I ２１９２ / I ２１８４ ) is 0.40 or less. Zeolite. <<Aspect 2>> SiO of the zeolite ２ / Al ２ O ３A zeolite according to Embodiment 1, wherein the molar ratio is 20 or more and 100 or less. Embodiment 3 A zeolite according to Embodiment 1 or 2, wherein the molar amount of Ag relative to the molar amount of Al in the zeolite is 0.10 or more and 0.40 or less. Embodiment 4 A zeolite according to any one of Embodiments 1 to 3, wherein the molar amount of Cs relative to the molar amount of Al in the zeolite is 0.20 or more and 0.60 or less. Embodiment 5 A zeolite according to any one of Embodiments 1 to 4, wherein the molar amount of Cs relative to the molar amount of Ag in the zeolite is 0.5 or more and 5.0 or less. Embodiment 6 A hydrocarbon adsorbent comprising the zeolite according to any one of Embodiments 1 to 5. Embodiment 7 An exhaust gas purification catalyst apparatus having a substrate and a catalyst layer on the substrate, wherein the catalyst layer contains the zeolite according to any one of Embodiments 1 to 5. <Aspect 8> An exhaust gas purification method comprising arranging the exhaust gas purification catalyst device described in Aspect 7 in the exhaust system of an internal combustion engine to purify the exhaust gas discharged from the internal combustion engine. <Aspect 9> A method for producing zeolite according to any one of Aspects 1 to 5, comprising ion-exchanging BEA type zeolite with Ag and then ion-exchanging it with Cs. <Aspect 10> A method for producing zeolite according to any one of Aspects 1 to 5, comprising ion-exchanging BEA type zeolite with Cs and then ion-exchanging it with Ag.

[0011] According to the present invention, an HC adsorption material is provided that exhibits a high HC adsorption amount even after durability has been maintained.

[0012] Figure 1 shows the FT-IR chart of adsorbed CO before and after hydrothermal endurance testing for the metal ion exchange zeolite of Example 2. Figure 2 shows the FT-IR chart of adsorbed CO before and after hydrothermal endurance testing for the metal ion exchange zeolite of Comparative Example 1. Figure 3 shows the FT-IR chart of adsorbed CO before hydrothermal endurance testing for the metal ion exchange zeolite of Comparative Example 7.

[0013] 《Metal Ion Exchange Zeolite》 The metal ion exchange zeolite of the present invention is a BEA-type zeolite that has been ion-exchanged with Ag and Cs, and in FT-IR measurements taken after adsorbing CO onto the zeolite, the wavelength was 2,192 cm.－１ Peak intensity I ２１９２ And, wavelength 2,184 cm －１ Peak intensity I ２１８４ Ratio to (I ２１９２ / I ２１８４ It is a zeolite whose ) is 0.40 or less.

[0014] The inventors first investigated the relationship between the crystal structure of zeolite and the amount of HC adsorbed in zeolite that had been ion-exchanged with Ag. As a result, they found that BEA-type zeolite was suitable.

[0015] The inventors then conducted a detailed investigation using various analytical methods to determine the reason for the insufficient durability of the Ag ion-exchange zeolite. As a result, they found that the BEA-type zeolite, which has been ion-exchanged with Ag, contains at least two types of Ag ions with different durability levels. Furthermore, the inventors found that in the FT-IR chart of adsorbed CO measured by adsorbing carbon monoxide (CO) onto the Ag-type zeolite, which has been ion-exchanged with Ag, the CO adsorbed onto the Ag ions with low durability levels was at a wavelength of 2,192 cm⁻¹. －１ CO, which shows a peak at a wavelength of 2,184 cm², is adsorbed onto highly durable Ag ions. －１ We found that it shows a peak at [a certain point].

[0016] The inventors have also found that when Ag and Cs are used together as ion exchange elements, Cs preferentially exchanges ions with sites that have low durability resistance, resulting in a higher proportion of Ag ions with high durability resistance. Interestingly, Cs displaces Ag ions with low durability resistance that are already supported on the zeolite and occupies those sites.

[0017] Furthermore, it was found that when BEA-type zeolite that has been ion-exchanged with Ag is ion-exchanged with Cs, the Cs ions replace Ag ions at sites with low durability resistance, thereby reducing the proportion of Ag ions with low durability resistance. Conversely, when BEA-type zeolite that has been ion-exchanged with Cs is ion-exchanged with Ag, the Ag ions replace Cs at sites with high durability resistance, thereby increasing or decreasing the proportion of Ag ions with high durability resistance.

[0018] As a result of these factors, when BEA-type zeolite is used as the raw material zeolite, and Ag and Cs are used in combination as ion exchange elements, the proportion of Ag ions, which have high durability and resistance, increases regardless of the order of ion exchange with the zeolite.

[0019] Furthermore, the inventors have measured the FT-IR chart of adsorbed CO by adsorbing CO onto BEA-type zeolite that has been ion-exchanged with Ag and Cs, and found that at a wavelength of 2,192 cm², －１ Peak intensity I ２１９２ And, wavelength 2,184 cm －１ Peak intensity I ２１８４ Ratio to (I ２１９２ / I ２１８４ We discovered that when the value of the zeolite is smaller than a certain value, the zeolite exhibits sufficiently high durability for practical use, which led to the present invention.

[0020] Furthermore, the present invention is not bound by any particular theory.

[0021] The metal ion exchange zeolite of the present invention will be described below.

[0022] The skeletal structure of the metal ion exchange zeolite of the present invention is of the BEA type. The advantageous effects of the present invention are thought to be effects that specifically appear when the zeolite skeletal structure is of the BEA type. The reason why at least two types of Ag ions with different durability resistances are generated when BEA-type zeolite is ion-exchanged with Ag is not clear. However, it is presumed that the stability of the Ag ions is derived from the stability of Al, which is the ion exchange site. That is, it is presumed that the stability of Al ions changes depending on the positional relationship (e.g., angle, etc.) with adjacent atoms, and that the stability of these Al ions affects the stability of the supported Ag ions. It should be noted that the present invention is not bound by any particular theory.

[0023] Zeolite SiO ２ / Al ２ O ３From the viewpoint of increasing durability, the molar ratio may be 20 or more, 22 or more, 24 or more, or 26 or more, and from the viewpoint of ensuring the amount of Ag supported and improving the amount of HC adsorption, it may be 100 or less, 80 or less, 60 or less, 50 or less, 40 or less, or 30 or less.

[0024] The metal ion exchange zeolite of the present invention is ion-exchanged by Ag and Cs. The amount of Ag supported, expressed as the ratio of the molar amount of Ag to the molar amount of Al in the zeolite (Ag / Al), may be 0.10 or more, 0.15 or more, 0.20 or more, 0.25 or more, or 0.30 or more from the viewpoint of sufficiently increasing the amount of HC adsorption, and may be 0.40 or less, 0.35 or less, 0.30 or less, 0.25 or less, or 0.20 or less from the viewpoint of securing Cs support sites and suppressing the generation of Ag ions with low durability.

[0025] The mass-based amount of Ag supported, defined as the ratio of the mass of Ag to the total mass of the metal ion exchange zeolite, may be 1.0% by mass or more, 1.5% by mass or more, 2.0% by mass or more, 2.5% by mass or more, or 3.0% by mass or more from the viewpoint of ensuring a sufficiently high amount of HC adsorption, and may be 5.0% by mass or less, 4.5% by mass or less, 4.0% by mass or less, 3.5% by mass or less, 3.0% by mass or less, or 2.5% by mass or less from the viewpoint of suppressing the generation of Ag ions with low durability.

[0026] On the other hand, the amount of Cs supported, expressed as the ratio of the molar amount of Cs to the molar amount of Al in the zeolite (Cs / Al), may be 0.20 or more, 0.25 or more, 0.30 or more, 0.35 or more, or 0.40 or more from the viewpoint of suppressing the generation of Ag ions with low durability, and may be 0.60 or less, 0.55 or less, 0.50 or less, 0.45 or less, 0.40 or less, 0.35 or less, or 0.30 or less from the viewpoint of increasing the amount of Ag supported at sites with high durability.

[0027] The mass-based amount of Cs supported, defined as the ratio of the mass of Cs to the total mass of the metal ion exchange zeolite, may be 3.0% by mass or more, 3.5% by mass or more, 4.0% by mass or more, 4.5% by mass or more, or 5.0% by mass or more from the viewpoint of suppressing the generation of Ag ions with low durability, and may be 8.0% by mass or less, 7.5% by mass or less, 7.0% by mass or less, 6.5% by mass or less, 6.0% by mass or less, 5.5% by mass or less, or 5.0% by mass or less from the viewpoint of increasing the amount of Ag supported at sites with high durability.

[0028] The ratio of the molar amount of Cs to the molar amount of Ag in the metal ion exchange zeolite (Cs / Al) may be 0.5 or more, 0.6 or more, 0.8 or more, 1.0 or more, 1.5 or more, 2.0 or more, or 2.5 or less, and may be 5.0 or less, 4.0 or less, 3.0 or less, 2.0 or less, or 1.5 or less.

[0029] The metal ion exchange zeolite of the present invention, when measured by FT-IR after adsorbing CO, showed a wavelength of 2,192 cm⁻¹. －１ Peak intensity I ２１９２ And, wavelength 2,184 cm －１ Peak intensity I ２１８４ Ratio to (I ２１９２ / I ２１８４ ) is 0.40 or less.

[0030] By satisfying this requirement, the proportion of Ag with low durability among the ion-exchanged Ag in the metal ion-exchange zeolite is small, and therefore, it is ensured that a high HC adsorption amount is maintained even after durability. From the objective of the present invention, which is to provide an HC adsorption material that exhibits a high HC adsorption amount even after durability, the ratio (I ２１９２ / I ２１８４ The requirement that the ratio (I) is 0.40 or less is a value that the metal ion exchange zeolite should satisfy before durability (typically after preparation and before use). However, as verified by the examples described below, the metal ion exchange zeolite of the present invention maintains a ratio (I) even after durability. ２１９２ / I ２１８４ The requirement that ) is 0.40 or less is met.

[0031] In contrast, conventional Ag-BEA type zeolite, which is ion-exchanged using only Ag without using Cs, has a ratio (I) before durability. ２１９２ / I ２１８４ The proportion of Ag, which has low durability resistance, is large. Therefore, in conventional Ag-BEA type zeolite, the amount of HC adsorbed is reduced after durability. In conventional Ag-BEA type zeolite, after durability, the wavelength 2,192 cm, which has low durability resistance, is large. －１ Because the Ag site corresponding to the peak collapses, the apparent ratio (I ２１９２ / I ２１８４ In some cases, the ratio (I) may become smaller. However, in this case, the absolute amount of Ag sites contributing to HC adsorption is insufficient. Therefore, conventional Ag-BEA type zeolites, after durability, have a ratio (I ２１９２ / I ２１８４ Even if the size is small, the amount of HC adsorption will be insufficient.

[0032] The ratio of the metal ion exchange zeolite of the present invention (I ２１９２ / I ２１８４ The ratio (I) is 0.40 or less, and may be 0.35 or less, 0.30 or less, 0.25 or less, or 0.20 or less. ２１９２ / I ２１８４ The lower limit of ) is ideally 0, but in practice it may be 0.05 or higher, or 0.10 or higher.

[0033] The metal ion exchange zeolite of the present invention is ion-exchanged with Ag and Cs. The metal ion exchange zeolite of the present invention may also be ion-exchanged with elements other than Ag and Cs. The elements other than Ag and Cs may be, for example, hydrogen, alkali metals other than Cs, alkaline earth metals, rare earth metals, transition metals, etc.

[0034] In order to maximize the effects of the present invention, the metal ion exchange zeolite of the present invention may have a small amount of elements other than Ag and Cs supported on it. The mass ratio of elements other than Ag and Cs to the total mass of the metal ion exchange zeolite may be 1.0% by mass or less, 0.5% by mass or less, 0.3% by mass or less, 0.1% by mass or less, 0.05% by mass or less, or 0.01% by mass or less, or it may be 0% by mass.

[0035] The metal ion exchange zeolite of the present invention may be classified to an appropriate size or molded into an appropriate shape for use, depending on the purpose. For example, when the metal ion exchange zeolite of the present invention is used as a hydrocarbon adsorbent contained in the catalyst layer of an exhaust gas purification catalyst, the metal ion exchange zeolite may be in particulate form with a particle size of 0.1 μm or more and 10 μm or less.

[0036] 《Method for producing metal ion exchange zeolite》 In another aspect of the present invention, the method for producing the metal ion exchange zeolite of the present invention described above is provided.

[0037] The present invention's method for producing metal ion exchange zeolite may include preparing a BEA-type zeolite and performing ion exchange with Ag and Cs on the BEA-type zeolite.

[0038] The raw material BEA-type zeolite may be selected according to the zeolite in the desired metal ion exchange zeolite, and therefore the SiO of the raw material BEA-type zeolite ２ / Al ２ O ３ The molar ratio may be, for example, 20 or greater.

[0039] Ion exchange may be carried out by known methods or by methods thereon with appropriate modifications by those skilled in the art. For example, ion exchange may be carried out by immersing the raw material BEA-type zeolite in a solution in which a precursor of the exchange metal is dissolved in a suitable solvent, recovering it, then washing it as necessary, removing the solvent as necessary, and then calcining it.

[0040] The solvent used for ion exchange may be, for example, water, or a mixture of water and a water-soluble organic solvent, typically water. The precursor of the exchange metal may be a solvent-soluble salt of the desired metal, for example, a nitrate, hydrochloride, sulfate, or halide of the desired metal. Calcination may be carried out, for example, at a temperature of 400°C to 800°C for a time of, for example, 10 minutes to 24 hours. The ambient atmosphere during calcination may be an oxidizing atmosphere, a reducing atmosphere, or an inert atmosphere, and air is sufficient.

[0041] The order of ion exchange between Ag and Cs is arbitrary. Ion exchange may be performed in a single step using a solution containing predetermined amounts of Ag precursor and Cs precursor, or it may be performed in several steps using a predetermined amount of solution containing Ag precursor and a predetermined amount of solution containing Cs precursor in any order.

[0042] Here, as can be seen from the results of the examples described later, when ion exchange is performed in the order of Ag and Cs, the wavelength is 2,192 cm. －１ It is thought that Ag ions introduced into sites with low durability are replaced by Cs ions. Furthermore, if ion exchange occurs in the order of Cs and then Ag, the wavelength will temporarily change to 2,184 cm. －１ It is thought that Cs ions introduced into highly durable sites are replaced by Ag ions.

[0043] Therefore, according to the present invention's method for producing metal ion exchange zeolite, the ratio (I) is independent of the order of ion exchange between Ag and Cs. ２１９２ / I ２１８４ A metal ion exchange zeolite with a small value of ) can be obtained.

[0044] Therefore, the method for producing metal ion exchange zeolite according to the present invention may include ion exchange of BEA-type zeolite with Ag and then ion exchange with Cs, or ion exchange of BEA-type zeolite with Cs and then ion exchange with Ag. In this case, ion exchange with Ag and ion exchange with Cs may be performed once each, or one or both of these may be performed in two or more separate steps.

[0045] Alternatively, performing ion exchange with Ag, ion exchange with Cs, and ion exchange with Ag in this order, as well as performing ion exchange with Cs, ion exchange with Ag, and ion exchange with Cs in this order, are also included in preferred embodiments of the method for producing metal ion exchange zeolite according to the present invention.

[0046] 《Hydrogen Adsorbent》 The metal ion exchange zeolite of the present invention is suitable as a hydrocarbon adsorbent. Therefore, in yet another aspect of the present invention, a hydrocarbon adsorbent comprising the metal ion exchange zeolite of the present invention is provided.

[0047] 《Exhaust Gas Purification Catalyst Device》 In yet another aspect of the present invention, an exhaust gas purification catalyst device using the metal ion exchange zeolite of the present invention is provided.

[0048] The exhaust gas purification catalyst device of the present invention is an exhaust gas purification catalyst device having a substrate and a catalyst layer on the substrate, wherein the catalyst layer contains the zeolite of the present invention.

[0049] The exhaust gas purification catalyst device of the present invention may have the same configuration as known exhaust gas purification catalyst devices, except that the catalyst layer contains the metal ion exchange zeolite of the present invention. For example, the catalyst layer may have a laminated configuration consisting of two layers, with the lower layer being an HC adsorption layer containing the metal ion exchange zeolite of the present invention and the upper layer being a three-way catalyst layer. Such an exhaust gas purification catalyst device is suitable, for example, as an underfloor catalyst device installed in the exhaust system of an automobile.

[0050] 《Exhaust Gas Purification Method》 In yet another aspect of the present invention, an exhaust gas purification method using the exhaust gas purification catalyst device of the present invention is provided.

[0051] The exhaust gas purification method of the present invention is an exhaust gas purification method that includes purifying the exhaust gas discharged from an internal combustion engine by arranging the exhaust gas purification catalyst device of the present invention in the exhaust system of the internal combustion engine.

[0052] Examples 1-3 and Comparative Examples 1-8: In Examples 1-3 and Comparative Examples 1-8, SiO ２ / Al ２ O ３ Using BEA-type zeolite with a molar ratio of 28 as a raw material, metal ion exchange zeolites were prepared and evaluated according to the following method.

[0053] 1. Ion exchange method: 80 g of pure water was mixed with 20 g of raw material zeolite and a predetermined amount of nitrate of the exchange metal, and the mixture was stirred at room temperature for 2 hours. Zeolite was filtered off from the mixture after stirring. Subsequently, 200 g of pure water was added to the zeolite on the filter paper in two batches to wash the zeolite. The zeolite on the filter paper was collected and dried at 120°C for 2 hours and then at 250°C for 8 hours in that order, and then calcined at 500°C for 2 hours to obtain zeolite that had been exchanged with metal ions.

[0054] Furthermore, the filtrate obtained by filtering the zeolite from the mixed solution after stirring, and the washings obtained by washing the zeolite, were subjected to ICP analysis to measure the amount of metal supported.

[0055] The prescribed amount of nitrate for the exchange metal was as shown in Table 1 for each type of metal.

[0056] Metal ion exchange zeolites were prepared by performing the above ion exchange procedure three times in the order shown in Table 2, with or without changing the metal species.

[0057] 2. Measurement of Metal Loading (1) In the "1. Ion Exchange Method" described above, the filtrate and washings obtained from each ion exchange were diluted with pure water and used as samples for radiofrequency inductively coupled plasma (ICP) analysis. The amount of metal loaded onto the zeolite was calculated by converting the obtained measurement values ​​to values ​​per total volume of filtrate and washings and subtracting them from the amount of metal nitrate used.

[0058] ICP analysis was performed using an Agilent Technologies Inc. multi-type ICP emission (ICP-OES) spectrometer, model "Agilent 5100 / 5110ICP-OES". After making up the sample to 1 L, it was further diluted to a ratio of 20 to 200 times so that the metal concentration in the sample fell within the concentration range suitable for ICP analysis, and then subjected to analysis.

[0059] 3. Measurement of Metal Loading Amount (2) The loading amounts of Ag and Cs were measured by X-ray fluorescence (XRF) analysis of the metal ion exchange zeolite (final product) obtained in Example 2. This will be described later.

[0060] 4. FT-IR Measurement of Adsorbed CO The FT-IR measurement of adsorbed CO was performed using the transmission method with a Fourier transform infrared spectrophotometer, model "FT / IR-6000", manufactured by JASCO Corporation (resolution 4 cm). －１ Measurement range: 1,000 cm －１ Among 4,000 －１ Detector: MCT (Mercury Cadmium Telluride) detector).

[0061] As the sample, 20 mg of metal ion exchange zeolite powder, immediately after preparation, was molded into a 10 mm diameter disc using a laboratory press mold. The sample was subjected to a flow rate of 200 mL / min at 20 volume% O₂ ２ (N ２ (Balanced) Under airflow, pre-treatment is performed for 30 minutes at a catalyst bed temperature of 500°C, followed by treatment at a catalyst bed temperature of 50°C with a flow rate of 200 cm³. ３ 1 / 1 volume % CO(N) ２ (Balanced) Airflow is circulated for 15 minutes, and then N2 is conditioned at a catalyst bed temperature of 50°C for 5 minutes. ２ The samples were subjected to measurement while purged.

[0062] CO adsorbs only to Ag ions in the metal ion exchange zeolite. In FT-IR of adsorbed CO, the concentration is 2,192 cm⁻¹, corresponding to the state of the Ag ions to which the CO has adsorbed. －１ and 2,184 cm －１ Peaks appear at two wavelengths. Here, at a wavelength of 2,192 cm², －１ Peak intensity I ２１９２ And, wavelength 2,184 cm －１ Peak intensity I ２１８４ The ratio (intensity ratio I) ２１９２ / I ２１８４ The proportion of each Ag ion was investigated by calculating the ratio of each ion.

[0063] Furthermore, the metal ion exchange zeolites obtained in Example 2 and Comparative Example 1 were subjected to hydrothermal endurance testing under the conditions described in the next section, and then FT-IR measurements of adsorbed CO were performed using the procedure described above. This will be explained later.

[0064] 5. For measuring the amount of HC adsorbed after durability testing, a sample was used which was obtained by compacting and then crushing metal ion exchange zeolite and forming it into pellets. Propylene was used as the HC species.

[0065] The sample underwent hydrothermal endurance testing under the following conditions, followed by pretreatment under the conditions below. Then, a model gas containing HC (propylene) was passed through it until breakthrough, and the cumulative difference between the inlet and outlet gases was defined as the amount of HC adsorbed.

[0066] <Hydrothermal endurance conditions> Rich gas containing 10% water by volume (CO: 5% by volume, N) ２ : Balance) and lean gas (O) containing 10% by volume of water ２ : 2.5% by volume, N ２ The two settings (balance) are switched alternately every 10 minutes, with each setting having a flow rate of 1 L / min (space velocity 1,800 h). －１ The test was conducted for 10 hours while the gas was being circulated. The gas temperature was set to 800°C.

[0067] <Pretreatment conditions> Flow rate 11,781 mL / min (space velocity 40,000 h) －１ ) O ２ : 1 volume% (N ２ (Balanced) The sample was heated at 500°C for 5 minutes under a flowing airflow.

[0068] <HC Distribution Conditions> Model gas containing HC (Propylene: 600 ppm C, Water: 3 volume%, and N ２ (Balance) with a spatial velocity of 127,400 h －１ The model gas was distributed via [method / service name]. The model gas temperature was set to 100°C.

[0069] The results are shown in Tables 2 and 3.

[0070] Regarding the amount of metal supported, Table 2 shows only the amount of metal supported (amount of metal supported in the final product) calculated from ICP analysis after three ion exchanges, while Table 3 shows the amount of metal supported for Examples 1 to 3 and Comparative Examples 1 and 2, calculated from ICP analysis after each ion exchange.

[0071]

[0072]

[0073] According to Table 2, the metal ion-exchanged zeolites of Examples 1 to 3, and Comparative Examples 1 and 3 to 6, in which the zeolite framework is of the BEA type and ion-exchanged with a significant amount of Ag, all showed a certain HC adsorption ability. In contrast, the metal ion-exchanged zeolite of Comparative Example 2 ion-exchanged only with Cs had a significantly lower HC adsorption ability. From these facts, it is considered that HC selectively adsorbs to the Ag ions of the metal ion-exchanged zeolite.

[0074] However, the metal ion-exchanged zeolite of Comparative Example 1 ion-exchanged only with Ag had a large intensity ratio I ２１９２ / I ２１８４ in the FT-IR measurement of adsorbed CO, and the HC adsorption amount after durability was insufficient. In contrast, the metal ion-exchanged zeolites of Examples 1 to 3 ion-exchanged with Ag and Cs had a small intensity ratio I ２１９２ / I ２１８４ and a sufficiently large HC adsorption amount after durability.

[0075] From these facts, the Ag ions corresponding to CO-Ag showing a peak at a wavelength of 2,192 cm －１ in the FT-IR of adsorbed CO have their HC adsorption ability impaired after durability, while the Ag ions corresponding to CO-Ag showing a peak at a wavelength of 2,184 cm －１ are considered to maintain their HC adsorption ability even after durability.

[0076] Also, since the intensity ratio I ２１９２ / I ２１８４ of the metal ion-exchanged zeolites of Examples 1 to 3 ion-exchanged with Ag and Cs was small, it is considered that Cs ions were selectively introduced into the sites at a wavelength of 2,192 cm －１ .

[0077] Further, according to Table 3, in Example 1 ion-exchanged in the order of Ag, Ag, and Cs, the Ag loading amount after the second ion-exchange was 0.46 as the molar ratio to Al, whereas the Ag loading amount after the third ion-exchange with Cs decreased to 0.13 as the molar ratio to Al.

[0078] Here, the metal ion-exchanged zeolite of Example 1 had a smaller amount of Ag supported and a smaller intensity ratio I ２１９２ / I ２１８４ than those of Comparative Example 1. From this, it is considered that once the Ag ions introduced into the site at a wavelength of 2,192 cm －１ were replaced by Cs ions and desorbed.

[0079] On the other hand, in Example 2 where ion exchange was carried out in the order of Cs, Cs, and Ag, the amount of Cs supported after the second ion exchange was 0.50 as a molar ratio to Al, whereas the amount of Cs supported after the ion exchange with Ag in the third time decreased to 0.28 as a molar ratio to Al. Further, in Example 3 where ion exchange was carried out in the order of Cs, Ag, and Ag, the amount of Cs supported after the first ion exchange was 0.50 as a molar ratio to Al, whereas the amount of Cs supported after the ion exchange with Ag in the second time decreased to 0.35 as a molar ratio to Al, and the amount of Cs supported after the ion exchange with Ag in the third time further decreased to 0.29 as a molar ratio to Al.

[0080] Similar to the case of Example 1, the intensity ratio I ２１９２ / I ２１８４ of the metal ion-exchanged zeolites of Examples 2 and 3 was small. From this, it is considered that once the Cs ions introduced into the site at a wavelength of 2,184 cm －１ were replaced by Ag ions.

[0081] The metal ion-exchanged zeolites of Comparative Examples 7 and 8 in which the zeolite framework was of the MFI type had a lower HC adsorption ability than the metal ion-exchanged zeolites of Examples 1 to 3 using the BEA type zeolite.

[0082] 《Comparative Example 9》 In Comparative Example 9, for the sample obtained by physically mixing the metal (Ag) ion-exchanged zeolite obtained in Comparative Example 1 and 1 mass% Cs-supported Al ２ O ３ , FT-IR measurement of adsorbed CO was carried out in the same manner as in Example 1 and the intensity ratio I ２１９２ / I ２１８４ was calculated.

[0083] 1 mass% Cs-supported Al ２ O ３It was prepared by the following method.

[0084] Al ２ O ３ 30g was added and stirred for 30 minutes. The solid was collected and dried in a dryer heated to 120°C for 12 hours, and then calcined at 500°C for 2 hours to obtain a powdered 1% by mass Cs-supported Al ２ O ３ I obtained it.

[0085] The 1 mass% Cs-supported Al obtained above ２ O ３ The Ag ion exchange zeolite obtained in Comparative Example 1 was ground and mixed with the Ag ion exchange zeolite obtained in Comparative Example 1 in a mass ratio of 1:1 using an agate mortar to obtain a sample for FT-IR measurement. When the FT-IR of adsorbed CO was measured for this sample, the intensity ratio was 1 ２１９２ / I ２１８４ The intensity ratio of the sample in Comparative Example 1 is 0.51. ２１９２ / I ２１８４ It decreased slightly from 1.43.

[0086] From this, we can see that Ag ion exchange zeolite and Cs-supported Al ２ O ３ Through physical mixing with, a wavelength of 2,192 cm² is also produced. －１ It is thought that some of the Ag ions corresponding to the peak observed in CO-Ag are substituted by Cs ions. However, in the case of physical mixing, the degree to which Ag ions are substituted by Cs ions is insufficient, and the amount of HC adsorbed after endurance is considered to be low.

[0087] 《Comparison of Metal Loading Measurement Methods》 0.7 g of the metal ion exchange zeolite (final product) obtained in Example 2 was placed in a powder sample holder, and Ag and Cs were quantified by X-ray fluorescence (XRF) analysis under the following conditions. The loading amounts of each were determined by the fundamental parameter method (FP method). X-ray fluorescence spectrometer: Bruker energy-dispersive X-ray fluorescence analyzer (EDXRF), model "S2-PUMA" X-ray tube: Pd tube Detector: SDD Measurement rays: Ag-K rays, Cs-K rays Measurement method: Measurement was performed under the conditions shown in Table 4 below.

[0088] The results obtained above, as well as the load amount calculated from ICP analysis, are shown in Table 5.

[0089]

[0090] As shown in Table 5, the amount of metal ion-exchange zeolite loaded, calculated from ICP analysis during production, and the amount of metal ion-exchange zeolite loaded, calculated from XRF analysis of the final product, showed good agreement within the range of experimental error.

[0091] 《Comparison of FT-IR of Adsorbed CO Before and After Durability Testing》 For the metal ion exchange zeolites of Example 2 and Comparative Example 1, obtained using BEA-type zeolite as the raw material, FT-IR measurements of adsorbed CO were performed before and after hydrothermal durability testing under the above conditions, and the measurement results were compared. Figure 1 shows the FT-IR chart of adsorbed CO before and after hydrothermal durability testing for the metal ion exchange zeolite of Example 2, and Figure 2 shows the FT-IR chart of adsorbed CO before and after hydrothermal durability testing for the metal ion exchange zeolite of Comparative Example 1.

[0092] Furthermore, Figure 3 shows the FT-IR chart of adsorbed CO before hydrothermal endurance measured for the metal ion exchange zeolite of Comparative Example 7, which was obtained using MFI-type zeolite as the raw material zeolite.

[0093] In the FT-IR charts of the adsorbed CO obtained using BEA-type zeolite as the raw material zeolite in Example 2 and Comparative Example 1, the wavelength was 2,192 cm⁻¹. －１ and wavelength 2,184 cm －１ Two types of CO peaks were observed.

[0094] As shown in Table 2, the metal ion exchange zeolite of Example 2 had a sufficiently large amount of HC (propylene) adsorption after hydrothermal endurance. As shown in Figure 1, the FT-IR chart of adsorbed CO of the metal ion exchange zeolite of Example 2 shows that at a wavelength of 2,184 cm², both before and after hydrothermal endurance, the adsorption was high. －１ The CO peak was the main peak. Here, the wavelength was 2,192 cm. －１ Peak intensity I ２１９２ And, wavelength 2,184 cm －１ Peak intensity I ２１８４Ratio to (I ２１９２ / I ２１８４ The value was 0.19 before hydrothermal endurance testing (immediately after preparation) (see Table 2), and 0.14 after hydrothermal endurance testing, both showing small values.

[0095] In contrast, the metal ion exchange zeolite of Comparative Example 1 showed insufficient HC adsorption after hydrothermal endurance. As shown in Figure 2, the FT-IR chart of adsorbed CO of the metal ion exchange zeolite of Comparative Example 1 shows that before hydrothermal endurance, the adsorption rate was 2,192 cm². －１ The CO peak was the primary peak, but it was confirmed that the intensity of this peak decreased significantly after hydrothermal endurance testing.

[0096] Based on the above, the wavelength is 2,192 cm. －１ The Ag ion site corresponding to the CO peak is easily decayed by hydrothermal endurance, whereas at a wavelength of 2,184 cm², －１ The Ag ion site corresponding to the CO peak is presumed to have high resistance to hydrothermal stress and be resistant to decay. Note that the wavelength in Figure 2 is 2,172 cm. －１ The shoulder peaks observed in the vicinity are thought to be attributed to CO adsorbed onto the Ag clusters.

[0097] On the other hand, in Comparative Example 7, the metal ion exchange zeolite obtained using an MFI-type zeolite showed only one CO peak, and the amount of HC adsorbed after hydrothermal endurance was insufficient.

[0098] From the above results, it can be seen that BEA-type zeolite ion-exchanged with Ag and Cs, in a fresh state, has a wavelength of 2,184 cm in the FT-IR chart of adsorbed CO. －１ The CO peak intensity at a wavelength of 2,192 cm² －１ It was verified that metal ion exchange zeolites with a small ratio of CO peak intensities exhibited high HC adsorption even after hydrothermal endurance.

Claims

1. A BEA-type zeolite that has been ion-exchanged with Ag and Cs, wherein CO is adsorbed onto the zeolite and measured in FT-IR at a wavelength of 2,192 cm⁻¹. －１ Peak intensity I ２１９２ And, wavelength 2,184 cm －１ Peak intensity I ２１８４ Ratio to (I ２１９２ / I ２１８４ Zeolite with a value of 0.40 or less.

2. The SiO ２ / Al ２ O ３ molar ratio of the zeolite is 20 or more and 100 or less, and the zeolite according to claim 1.

3. The zeolite according to claim 1, wherein the molar amount of Ag relative to the molar amount of Al in the zeolite is 0.10 or more and 0.40 or less.

4. The zeolite according to claim 1, wherein the molar amount of Cs relative to the molar amount of Al in the zeolite is 0.20 or more and 0.60 or less.

5. The zeolite according to claim 1, wherein the molar amount of Cs relative to the molar amount of Ag in the zeolite is 0.5 or more and 5.0 or less.

6. A hydrocarbon adsorbent comprising the zeolite described in any one of claims 1 to 5.

7. An exhaust gas purification catalyst apparatus having a substrate and a catalyst layer on the substrate, wherein the catalyst layer contains the zeolite described in any one of claims 1 to 5.

8. An exhaust gas purification method comprising purifying exhaust gas discharged from an internal combustion engine by arranging the exhaust gas purification catalyst device described in claim 7 in the exhaust system of the internal combustion engine.

9. A method for producing a zeolite according to claim 1, comprising ion-exchanging a BEA-type zeolite with Ag and then ion-exchanging it with Cs.

10. A method for producing a zeolite according to claim 1, comprising ion-exchanging a BEA-type zeolite with Cs and then ion-exchanging it with Ag.

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