Metal ion exchange zeolite

Abstract

To provide an HC adsorption material that exhibits a high HC adsorption capacity even after durability has been maintained. [Solution] 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, the wavelength is 2,192 cm. -1 Peak intensity I 2192 And, wavelength 2,184 cm -1 Peak intensity I 2184 The ratio (I 2192 / I 2184 Zeolite with a value of 0.40 or less.

Description

[Technical Field]

[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. [Background technology]

[0002] Exhaust gases emitted from internal combustion engines in 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 an exhaust gas purification catalyst, a three-way catalyst is known that promotes 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 is used in combination with an HC adsorption material, 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 HC adsorbent materials 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. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2008-110303 [Patent Document 2] Japanese Patent Publication No. 2005-144253 [Patent Document 3] Japanese Patent Publication No. 2007-160168 [Patent Document 4] Japanese Patent Publication No. 2006-021153 [Patent Document 5] Japanese Patent Publication No. 2017-154965 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] This invention addresses the fact that conventional Ag ion-exchange zeolites, even when Ag is used in combination with other elements as ion-exchange elements, have insufficient durability, and it is known that their HC adsorption capacity decreases with durability, thus requiring improvement.

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

[0009] The present invention is as follows:

[0010] <Aspect 1> A BEA-type zeolite that has been ion-exchanged with Ag and Cs, In FT-IR measurements taken after adsorbing CO onto the aforementioned zeolite, at a wavelength of 2,192 cm², -1 Peak intensity I 2192 And, wavelength 2,184 cm -1 Peak intensity I 2184 The ratio (I 2192 / I 2184 ) is 0.40 or less. Zeolite. <Aspect 2> The zeolite according to aspect 1, wherein the SiO2 / Al2O3 molar ratio of the zeolite is 20 or more and 100 or less. <Aspect 3> The zeolite according to aspect 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. <Aspect 4> The zeolite according to aspect 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. <Aspect 5> The zeolite according to aspect 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. Appearance 6: A hydrocarbon adsorbent comprising the zeolite described in any one of Appearances 1 to 5. Appearance 7: An exhaust gas purification catalyst device having a substrate and a catalyst layer on the substrate, The catalyst layer includes the zeolite described in any one of embodiments 1 to 5. Exhaust gas purification catalyst device. <Aspect 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 Aspect 7 in the exhaust system of the internal combustion engine. [Aspect 9] A method for producing a zeolite according to aspect 1, comprising ion-exchanging a BEA-type zeolite with Ag and then ion-exchanging it with Cs. [Aspect 10] A method for producing a zeolite according to aspect 1, comprising ion-exchanging a BEA-type zeolite with Cs and then ion-exchanging it with Ag.

Advantages of the Invention

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

Brief Description of the Drawings

[0012] [Figure 1] FIG. 1 is an FT-IR chart of adsorbed CO before and after hydrothermal durability measured for the metal ion-exchanged zeolite of Example 2. [Figure 2] FIG. 2 is an FT-IR chart of adsorbed CO before and after hydrothermal durability measured for the metal ion-exchanged zeolite of Comparative Example 1. [Figure 3] FIG. 3 is an FT-IR chart of adsorbed CO before hydrothermal durability measured for the metal ion-exchanged zeolite of Comparative Example 7.

Modes for Carrying Out the Invention

[0013] 《Metal Ion-Exchanged Zeolite》 The metal ion-exchanged zeolite of the present invention is a BEA-type zeolite ion-exchanged with Ag and Cs, in the FT-IR measured by adsorbing CO to the zeolite, the peak intensity I of the peak at a wavelength of 2,192 cm -1 and the peak intensity I of the peak at a wavelength of 2,184 cm 2192 The ratio (I -1 / I 2184 ) is 0.40 or less, 2192 / I 2184 ) is a zeolite. is a zeolite.

[0014] The inventors first examined the relationship between the crystal structure of the zeolite and the HC adsorption amount for the zeolite ion-exchanged with Ag. As a result, it was found that the BEA-type zeolite is suitable.

[0015] The inventors then investigated in detail, using various analytical methods, the reasons why the Ag ion-exchange zeolite exhibited insufficient durability. As a result, they found that the BEA-type zeolite, which had been ion-exchanged with Ag, contained 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-ion-exchanged BEA-type zeolite, the CO adsorbed onto the Ag ions with low durability levels was found to be at a wavelength of 2,192 cm⁻¹. -1 A peak is observed, and CO adsorbed onto highly durable Ag ions is detected at a wavelength of 2,184 cm⁻¹. -1 We found that it shows a peak at [a certain point].

[0016] The inventors 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 cm⁻¹, -1 Peak intensity I2192 And, wavelength 2,184 cm -1 Peak intensity I 2184 The ratio (I 2192 / I 2184 We discovered that when the value of ) 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. It is not clear why at least two types of Ag ions with different durability are generated when BEA-type zeolite is ion-exchanged with Ag. 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) 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] The SiO2 / Al2O3 molar ratio of the zeolite may be 20 or more, 22 or more, 24 or more, or 26 or more from the viewpoint of increasing durability, and may be 100 or less, 80 or less, 60 or less, 50 or less, 40 or less, or 30 or less from the viewpoint of ensuring sufficient Ag loading and improving HC adsorption.

[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 Cs loading amount, defined as the ratio of Cs mass 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 loaded on 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 The ratio (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 zeolites, which are ion-exchanged using only Ag without Cs, have 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 adsorption 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 ) 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 to 10 μm.

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

[0037] The present invention provides a method for producing metal ion exchange zeolite. Prepare BEA-type zeolite, and The aforementioned BEA-type zeolite is subjected to ion exchange with Ag and Cs. The method may include the following:

[0038] The raw material BEA-type zeolite may be selected according to the zeolite in the desired metal ion exchange zeolite; therefore, the SiO2 / Al2O3 molar ratio of the raw material BEA-type zeolite may be, for example, 20 or more.

[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 the less durable sites are replaced by Cs ions. Also, 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 the 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 ) is obtained.

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

[0045] Or, The ion exchange with Ag, the ion exchange with Cs, and the ion exchange with Ag should be carried out in this order, and Perform ion exchange with Cs, ion exchange with Ag, and then ion exchange with Cs in this order. This is also included in preferred embodiments of the method for producing metal ion exchange zeolite according to the present invention.

[0046] Hydrocarbon 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 system 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, The catalyst layer contains the zeolite of the present invention. This is an exhaust gas purification catalyst device.

[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 methods In yet another aspect of the present invention, a method for purifying exhaust gas using the exhaust gas purification catalyst device of the present invention is provided.

[0051] The exhaust gas purification method of the present invention is This 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. [Examples]

[0052] Examples 1-3 and Comparative Examples 1-8 In Examples 1-3 and Comparative Examples 1-8, metal ion exchange zeolites were prepared and evaluated using BEA-type zeolite with an SiO2 / Al2O3 ratio (molar ratio) of 28 as a raw material, according to the method described below.

[0053] 1. Ion exchange method 80g of pure water was mixed with 20g of raw zeolite and a predetermined amount of nitrate, the metal used for exchange, and stirred at room temperature for 2 hours. The zeolite was filtered off from the mixture after stirring. Subsequently, 200g of pure water was added to the zeolite on the filter paper in two batches to wash it. 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. [Table 1]

[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 load (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 inductively coupled plasma (ICP) analysis. The amount of metal supported on the zeolite was calculated by converting the obtained measurements to values ​​per total volume of filtrate and washings and subtracting this from the amount of metal nitrate used.

[0058] ICP analysis was performed using an Agilent Technologies Inc. multi-type ICP emission (ICP-OES) instrument, model "Agilent 5100 / 5110ICP-OES". After making up the sample volume to 1 L, it was further diluted by a factor of 20 to 200 to ensure that the metal concentration in the sample fell within the concentration range suitable for ICP analysis before being subjected to analysis.

[0059] 3. Measurement of metal load (2) The amount of Ag and Cs loaded onto the metal ion exchange zeolite (final product) obtained in Example 2 was measured by X-ray fluorescence (XRF) analysis. This will be described later.

[0060] 4. FT-IR measurement of adsorbed CO FT-IR measurements of adsorbed CO were 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 ~4,000cm -1 Detector: MCT (Mercury Cadmium Telluride) detector.

[0061] The sample used was 20 mg of freshly prepared metal ion exchange zeolite powder, molded into a 10 mm diameter disc using a laboratory press mold. The sample was pretreated for 30 minutes at a catalyst bed temperature of 500°C under a flow rate of 200 mL / min of 20 volume% O2 (N2 balanced) airflow, and then subjected to a flow rate of 200 cm³ at a catalyst bed temperature of 50°C. 3The system was subjected to measurements after a 1 / min volume %CO (N2 balanced) airflow was circulated for 15 minutes, followed by N2 purging at a catalyst bed temperature of 50°C for 5 minutes.

[0062] CO adsorbs only onto Ag ions in metal ion exchange zeolites. In FT-IR of adsorbed CO, the state of the adsorbed Ag ions corresponds to 2,192 cm⁻¹. -1 and 2,184cm -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 Ratio to (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. Measurement of HC adsorption amount after durability test The sample used was a pelletized metal ion exchange zeolite that had been compressed, crushed, and then processed. 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. A model gas containing HC (propylene) was then passed through the sample until breakthrough, and the cumulative difference between the inlet and outlet gases was defined as the amount of HC adsorbed.

[0066] <Hydrothermal durability conditions> A rich gas containing 10% water by volume (CO: 5% by volume, N2: balance) and a lean gas containing 10% water by volume (O2: 2.5% by volume, N2: balance) are alternately switched every 10 minutes, with a flow rate of 1 L / min (space velocity 1,800 h) for each. -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 11,781mL / min (space velocity 40,000h -1 The sample was heated at 500°C for 5 minutes under an airflow of 1% O2 (balanced N2).

[0068] <HC distribution conditions> A model gas containing HC (propylene: 600 ppmC, water: 3 volume%, and N2: balance) was tested at a space velocity of 127,400 h⁻¹. -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 loading amount calculated from ICP analysis after three ion exchange cycles (loading amount in the final product). Table 3 shows the loading amounts calculated from ICP analysis after each ion exchange for Examples 1-3 and Comparative Examples 1 and 2.

[0071] [Table 2]

[0072] [Table 3]

[0073] According to Table 2, the metal ion exchange zeolites of Examples 1-3 and Comparative Examples 1 and 3-6, which had a BEA-type zeolite skeleton and were ion-exchanged with a significant amount of Ag, all showed a certain level of HC adsorption capacity. In contrast, the metal ion exchange zeolite of Comparative Example 2, which was ion-exchanged with Cs alone, showed significantly lower HC adsorption capacity. From these findings, it is considered that HC is selectively adsorbed onto Ag ions in metal ion exchange zeolites.

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

[0075] Based on these findings, the FT-IR of adsorbed CO shows a wavelength of 2,192 cm⁻¹. -1 While the Ag ions corresponding to CO-Ag, which show a peak at 2,184 cm², lose their HC adsorption capacity after endurance, the Ag ions at 2,184 cm² exhibit a loss of HC adsorption capacity. -1 The Ag ions corresponding to the CO-Ag peak, which are observed in the spectroscopy reaction, are thought to maintain their HC adsorption capacity even after the spectroscopy period.

[0076] Furthermore, the metal ion exchange zeolites of Examples 1-3, which were ion-exchanged with Ag and Cs, had an intensity ratio of I 2192 / I 2184 Because the size was small, the Cs ion had a wavelength of 2,192 cm. -1 It is believed to have been selectively implemented on the site.

[0077] Furthermore, according to Table 3, in Example 1, where ion exchange was performed in the order of Ag, Ag, and Cs, the amount of Ag loaded after the second ion exchange was 0.46 in terms of Al molar ratio, whereas the amount of Ag loaded after the third ion exchange with Cs decreased to 0.13 in terms of Al molar ratio.

[0078] Here, the metal ion exchange zeolite of Example 1 has a lower amount of Ag supported and a higher intensity ratio compared to Comparative Example 1. 2192 / I 2184 It was small. From this, the wavelength was 2,192 cm. -1 It is thought that the Ag ion introduced into the site was replaced by a Cs ion and subsequently removed.

[0079] On the other hand, in Example 2, where ion exchange was performed in the order of Cs, Cs, and Ag, the amount of Cs loaded after the second ion exchange was 0.50 in terms of Al molar ratio, while the amount of Cs loaded after the third ion exchange with Ag decreased to 0.28 in terms of Al molar ratio. Furthermore, in Example 3, where ion exchange was performed in the order of Cs, Ag, and Ag, the amount of Cs loaded after the first ion exchange was 0.50 in terms of Al molar ratio, while the amount of Cs loaded after the second ion exchange with Ag decreased to 0.35 in terms of Al molar ratio, and the amount of Cs loaded after the third ion exchange with Ag decreased further to 0.29 in terms of Al molar ratio.

[0080] The metal ion exchange zeolites in Examples 2 and 3 had the same intensity ratio as in Example 1. 2192 / I 2184 It was small. From this, the wavelength was 2,184 cm. -1 It is thought that the Cs ions introduced into the site were replaced by Ag ions.

[0081] The metal ion exchange zeolites of Comparative Examples 7 and 8, whose zeolite skeleton was of the MFI type, had lower HC adsorption capacity compared to the metal ion exchange zeolites of Examples 1 to 3, which used BEA type zeolites.

[0082] Comparative Example 9 In Comparative Example 9, a sample obtained by physically mixing the metal (Ag) ion-exchange zeolite obtained in Comparative Example 1 with 1 mass% Cs-supported Al2O3 was subjected to FT-IR measurement of adsorbed CO in the same manner as in Example 1, and the intensity ratio I 2192 / I 2184 The result was calculated.

[0083] 1 mass% Cs-supported Al2O3 was prepared by the following method.

[0084] 30g of Al2O3 was added to an aqueous solution obtained by dissolving 1.80g of cesium nitrate in 70g of pure water, and the mixture was stirred for 30 minutes. The solid was recovered, dried in a dryer heated to 120°C for 12 hours, and then calcined at 500°C for 2 hours to obtain powdered 1 mass% Cs-supported Al2O3.

[0085] The 1% Cs-supported Al2O3 obtained above and the Ag ion-exchange zeolite obtained in Comparative Example 1 were ground and mixed 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 on 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, it can be seen that even by physical mixing of Ag ion exchange zeolite and Cs-supported Al2O3, wavelength 2,192 cm² is produced. -1 It is thought that some of the Ag ions corresponding to the CO-Ag peak 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 thought to be low.

[0087] Comparison of Metal Load 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 amount of each substance loaded was then 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 line: Ag-Κ line, Cs-Κ line Measurement method: Measurements were performed under the conditions shown in Table 4 below. [Table 4]

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

[0089] [Table 5]

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

[0091] 《Comparison of FT-IR measurements 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 endurance under the above conditions, and the measurement results were compared. Figure 1 shows the FT-IR chart of adsorbed CO before and after hydrothermal endurance measured for the metal ion exchange zeolite of Example 2, and Figure 2 shows the FT-IR chart of adsorbed CO before and after hydrothermal endurance measured 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 adsorbed CO obtained using BEA-type zeolite as the raw material zeolite for 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 rate 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 I2184 The ratio (I 2192 / I 2184 ) was 0.19 before hydrothermal durability (immediately after preparation) (see Table 2), and 0.14 after hydrothermal durability, both showing small values.

[0095] In contrast, the metal ion-exchanged zeolite of Comparative Example 1 had insufficient HC adsorption amount after hydrothermal durability. Looking at Fig. 2, in the FT-IR chart of adsorbed CO of the metal ion-exchanged zeolite of Comparative Example 1, the CO peak at a wavelength of 2,192 cm -1 was the main peak before hydrothermal durability, but it was confirmed that the intensity of this peak decreased significantly after hydrothermal durability.

[0096] From the above, the Ag ion sites corresponding to the CO peak at a wavelength of 2,192 cm -1 are likely to collapse due to hydrothermal durability, while the Ag ion sites corresponding to the CO peak at a wavelength of 2,184 cm -1 are highly durable against hydrothermal durability and are推测 to be difficult to collapse. The shoulder peak seen around a wavelength of 2,172 cm in Fig. 2 is considered to be attributed to CO adsorbed on the Ag clusters. -1 On the other hand, in the metal ion-exchanged zeolite of Comparative Example 7 obtained using an MFI-type zeolite, there was only one type of CO peak, and the HC adsorption amount after hydrothermal durability was insufficient.

[0097] From the above results, it was verified that a metal ion-exchanged zeolite which is a BEA-type zeolite ion-exchanged with Ag and Cs and has a small ratio of the CO peak intensity at a wavelength of 2,192 cm to the CO peak intensity at a wavelength of 2,184 cm in the FT-IR chart of adsorbed CO in the fresh state also has a large HC adsorption amount after hydrothermal durability.

[0098] -1 The ratio of the CO peak intensity at a wavelength of 2,192 cm to the CO peak intensity at a wavelength of 2,184 cm in the FT-IR chart of adsorbed CO in the fresh state also has a large HC adsorption amount after hydrothermal durability. -1 ​​

Claims

1. A BEA-type zeolite that has been ion-exchanged with Ag and Cs, In the FT-IR measurement, which was performed by adsorbing CO onto the zeolite, 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 ) is 0.40 or less. Zeolite.

2. The SiO of the zeolite ２ / Al ２ O ３ The molar ratio is 20 or more and 100 or less. 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 device having a substrate and a catalyst layer on the substrate, The catalyst layer comprises the zeolite described in any one of claims 1 to 5. Exhaust gas purification catalyst device.

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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