KR102416759B1 - Method for synthesizing CHA zeolite and CHA zeolite with large particle size therefrom - Google Patents

Abstract

The present invention relates to a method for producing a chabazite (CHA) zeolite and a high-purity zeolite in the form of large particles prepared therefrom, and more particularly, by using two types of specific structure directing agents (SDA). , a method for producing a CHA zeolite that has a controllable particle size from 0.5 to 4 microns and suppresses the generation of impurities to synthesize pure CHA zeolite, and a CHA zeolite prepared therefrom and grown in particle size to be applicable to an SDPF filter.

Description

CHA zeolite manufacturing method and CHA zeolite of large particles prepared therefrom {Method for synthesizing CHA zeolite and CHA zeolite with large particle size therefrom}

The present invention relates to a method for producing a chabazite (CHA) zeolite and a high-purity zeolite in the form of large particles prepared therefrom, and more particularly, by using two types of specific structure directing agents (SDA). , a method for producing a CHA zeolite that has a controllable particle size from 0.5 to 4 microns and suppresses the generation of impurities to synthesize pure CHA zeolite, and a CHA zeolite prepared therefrom and grown in particle size to be applicable to an SDPF filter.

Zeolite is an aluminosilicate crystalline material having a rather uniform pore size in the range of about 3 to 10 Angstroms in diameter, depending on the type and the type and content of cations included in the lattice. The double chabazite form is a zeolite having a three-dimensional pore structure consisting of an oxygen 8-member ring of 3.8 × 3.8 Å, and an example of a synthetic CHA zeolite is SiO ₂ /Al ₂ O ₃ Molar ratio of 3.45 to 4.9 Zeolite R, or SiO ₂ /Al ₂ O ₃ molar ratio of 5 to 50, so-called high silica chabazite type zeolite SSZ-13 (Standard Oil Synthetic Zeolite-13) and the like are known.

As a catalyst for the selective catalytic reduction (SCR) of nitrogen oxides in automobile exhaust gas, chabazite-type zeolite on which copper is supported is attracting attention. However, these chabazite-type zeolite catalysts are insufficient in durability under a high-temperature steam atmosphere, that is, durability in water heat. On the other hand, when the CHA zeolite that can be coated on SDPF (SCR ON DIESEL PARTICULAR FILTER) has a small particle size, the zeolite slurry is introduced into the filter pores, making it difficult to flow the gas in the filter. There is a problem that arises. In addition, in manufacturing zeolite, USY zeolite is used as a starting material as a silicon raw material and aluminum raw material. At this time, the purity of the CHA zeolite finally produced by the Si/Al ratio of USY and single silicon and aluminum existing outside the skeleton And there were limitations in the manufacturing method, such as the degree of crystallinity is affected.

As described above, in order to improve the problems of the prior art, a high-purity CHA zeolite having excellent hydrothermal durability and a large particle size is desired, and an improvement in a CHA zeolite synthesis method capable of synthesizing it is required.

The present invention provides a method for producing CHA zeolite using two types of specific structure-inducing substances.

The method for producing CHA zeolite includes preparing a synthetic mother liquid including a raw material containing aluminum oxide and silica and two types of complex structure-inducing materials, and hydrothermal synthesis of the synthetic mother liquid to form a solid product, The two types of composite structure-inducing material are composed of a first structure-inducing material containing an adamantyl group and a second structure-inducing material containing a benzyl group. The first structure-inducing material is selected from the group consisting of hydroxides, halides, carbonates and sulfates having TMAda (Trimethyladamantylammonium) as a cation, and the second structure-inducing material is benzyltrimethylammonium, benzyltriethylammonium, benzyltripropylammonium And it may be selected from the group consisting of hydroxides, halides, carbonates and sulfates having benzyltributylammonium as a cation.

Without limitation, in the present invention, the molar ratio of the first structure-inducing material containing an adamantyl group/the second structure-inducing material containing a benzyl group is characterized in that it is 0.03-0.33, and includes the aluminum oxide and silica. The raw material used may be de-aluminized Y zeolite, preferably USY zeolite. In addition, in the manufacturing method of the present invention, the silica / alumina (SiO ₂ /Al ₂ O ₃ ) molar ratio of the USY zeolite is 35 to 44 in which only CHA can be purely produced without the resultant zeolite of another phase being made at the end of the synthesis step. and a copper ion exchange step may be further added after the step of forming the solid product to contain copper in the zeolite. The copper ion exchange step is copper nitrate (copper nitrate), copper chloride (copper chloride), copper acetate (copper acetate) and amine (amine) precursor tetraamine copper nitrate (tetraammine copper Nitrate), tetraamine copper chloride (Tetraammine copper chloride), characterized in that a copper solution that can be selected from the group consisting of tetraamine copper sulfate (Tetraammine copper sulfate) is added, and accordingly, the crystal structure is maintained even after hydrothermal treatment at 900 ° C. and selective catalytic reduction ( It is possible to produce Cu-containing CHA zeolite used as a catalyst for SCR) reaction.

Compared with the zeolite of 0.5 to 1.0 microns produced by the conventional zeolite manufacturing method, the particle size of the zeolite according to the present invention can be adjusted to 0.5 to 4.0 microns, so that CHA zeolite with a particle size applicable to SDPF can be produced. And, in the synthesis method according to the present invention, the generation of impurities is suppressed, and finally, pure CHA zeolite with a very uniform particle shape is synthesized. The Cu-containing CHA zeolite according to the present invention showed high hydrothermal durability in the high temperature region as a result of the SCR activity evaluation.

1 is a flowchart showing a method for manufacturing a zeolite using two types of structure-inducing materials, a TMAda (trimethyladamantylammonium) ion and a BTMA (benzyltrimethylammonium) ion, according to an embodiment of the present invention.
2 is an SEM photograph of the zeolite prepared in Examples and Comparative Examples.
3 is a photograph of the zeolite of Example 1 and the copper-supported zeolite in which copper is supported.
4 shows XRD patterns of zeolites prepared in Examples and Comparative Examples.
5 is a graph comparing the SCR activity of zeolites prepared in Examples and Comparative Examples.

1 is a method for preparing a CHA zeolite using a structure-inducing material of TMAda (trimethyladamantylammonium) ions and BTMA (benzyltrimethylammonium) ions according to a preferred embodiment, and copper-supported CHA zeolite by supporting copper on the produced CHA zeolite. is a flowchart showing First, a method for producing CHA zeolite will be described, and then a method for producing a copper-supported CHA zeolite for this will be described in detail.

Referring to Figure 1, the CHA zeolite manufacturing method is largely composed of a synthetic mother liquor preparation step and a hydrothermal synthesis step.

The synthetic mother liquor is a Y zeolite as a starting material containing aluminum oxide and silica, an adamantyl group as a first structure-inducing material, for example, a TMAda (trimethyladamantylammonium) ion-containing material, a second structure-inducing material Examples include a substance containing a benzyl group as the BTMA (benzyltrimethylammonium) ion-containing substance, a basic substance, and distilled water.

The Y zeolite may be preferably ultra-stable zeolite Y (Ultra Stable Zeolite Y, zeolite USY), and in the present invention, a zeolite having a SiO ₂ /Al ₂ O ₃ molar ratio of 35 (hereinafter referred to as de-Al-Y) is used. was used.

The basic material is a material for making a basic aqueous solution by mixing with the distilled water, and may be used regardless of any basic material having no problem in compatibility with the synthetic mother liquid, for example, NaOH may be used.

Subsequently, the hydrothermal synthesis step of the synthetic mother liquor may be performed in an atmosphere of 130-150 ° C. Preferably, the hydrothermal synthesis was performed at a temperature of 135 to 145 ° C. while rotating at 20 to 60 rpm for 3 to 7 days.

According to another embodiment of the present invention, copper-supported CHA zeolite can be prepared through the process of supporting copper on the prepared CHA zeolite. Before loading copper, the CHA zeolite powder is first treated with an aqueous ammonium solution and ion exchanged in the form of NH ₄ -CHA, filtered/washed/dried, and then NH ₄ -CHA zeolite powder ion-exchanged with ammonium is treated with copper. A copper-supported CHA zeolite catalyst is prepared by adding to the solution, stirring, and then filtering/washing/drying/calcining. Also provided is a method for preparing a copper-containing zeolite having a CHA structure in which copper is exchanged for the Na+ form of chabazite using a liquid copper solution. Copper solution is copper nitrate (copper nitrate), copper chloride (copper chloride), copper acetate (copper acetate) and amine (amine) precursor tetraamine copper nitrate (tetraammine copper Nitrate), tetraamine copper chloride (Tetraammine copper) chloride), tetraamine copper sulfate, and copper oxide (CuO). Copper-supported CHA zeolites are used in selective reduction catalysts of nitrogen oxides, particularly selective reduction catalysts (SCR) using ammonia as a reducing agent.

According to another embodiment of the present invention, there is provided a CHA zeolite or a copper-supported CHA zeolite prepared by the above-described manufacturing methods.

The CHA zeolite according to this embodiment has a silica/alumina (SiO ₂ /Al ₂ O ₃ ) molar ratio of 22 to 66, and among them, when only pure CHA zeolite containing no raw material is produced, the silica/alumina molar ratio is 22 to 25 and has a particle size of 0.5 to 3.0 μm, low aluminum content, excellent hydrothermal stability, and can be applied to SDPF because the particle size is large enough not to enter the filter pores.

Hereinafter, specific examples of the present invention will be presented, but prior to this, a method for manufacturing Y zeolite used as a silicon raw material and an aluminum raw material in the examples will be described.

<Preparation of Y zeolite as a starting material>

Y zeolite is prepared by the following method and is also referred to as de-Al-Y.

First, Y zeolite having a SiO ₂ /Al ₂ O ₃ molar ratio of 5.0 was introduced into the tubular reactor, and then a temperature atmosphere of 600° C. was created inside the reactor. Thereafter, distilled water was mixed with air in the mixing tank, and then injected into the tube-type reactor at a flow rate of 200 ml/min. After the steam activation process for about 4 hours, the Y zeolite was discharged from the reactor, and then added to 1 mole of sulfuric acid solution to remove aluminum desorbed from the Y zeolite framework. After the sulfuric acid treatment was completed, de-Al-Y of SiO ₂ /Al ₂ O ₃ molar ratio = 35 was prepared by drying at 100° C. for about 12 hours and calcining at 500° C. for about 2 hours. The change of the SiO ₂ /Al ₂ O ₃ molar ratio could be achieved by adjusting the flow rate of the mixed gas of distilled water and air.

<Example 1>

Manufacture of CHA zeolite using TMadaOH and BTMACl as structural inducing materials

1. Synthetic mother liquor preparation step

As the first structural derivative (referred to as SDA-1), 8.45 g of TMadaOH (Trimethyladamantylammonium Hydroxide, SACHEM) was put into a 1L Teflon container, and 432 g of distilled water (DIWater) was added thereto and stirred for about 1 hour to be completely dispersed. After adding 12.37 g of sodium hydroxide (NaOH, Aldrich) to the solution and stirring for about 1 hour, 56.27 g of BTMACl (Benzyltrimethylammonium Chloride, Aldrich) was added as a second structural derivative (referred to as SDA-2) to about 1 Time stirring was performed. After that, 57 g of de-aluminized de-Al-Y zeolite (SiO ₂ /Al ₂ O ₃ molar ratio = 35, specific surface area 884 m ² /g) prepared in advance was added and stirred for about 3 hours to prepare a final synthetic mother solution.

2. Hydrothermal Synthesis Step

The prepared synthetic mother liquid was placed in a container made of Teflon inside and sufficiently stirred, put into a stirrable stainless steel reactor, sealed, heated to 135° C., and hydrothermal reaction was performed for 96 hours. After completion of the reaction, the product was separated from the reactor, filtered/washed, and dried at 100° C. for 12 hours in an air circulation dryer. After drying, CHA zeolite was obtained by performing a heat treatment process for 12 hours in an atmosphere of 580 ° C. using a furnace to remove organic matter.

<Example 2-6>

It was carried out in the same manner as in Example 1, except that the content of TMadaOH, which is SDA-1, was changed.

<Example 7-9>

CHA zeolite was prepared in the same manner as in Example 3, except that the SiO ₂ /Al ₂ O ₃ molar ratio of de-Al-Y in the composition of the synthetic mother liquor was changed to 26, 44, and 80, respectively.

<Comparative Example 1-2>

CHA zeolite was prepared in the same manner as in Example 2, except that TMadaOH and BTMACl alone were used as the structure-inducing substances used in the synthetic mother liquor, respectively.

The composition of the synthetic mother liquor of Examples 1 to 6 is as follows, and Table 1 shows the composition of the synthetic mother liquor according to Examples and Comparative Examples in detail.

1 SiO ₂ : 0.028 Al ₂ O ₃ : 0.3 NaOH: 0.3 BTMACl: (0.01-0.30) TMadaOH: 28 H ₂ O

<Production of copper-supported CHA zeolite>

A process of supporting copper was performed on the CHA powders prepared in Examples and Comparative Examples. Before loading copper, the CHA zeolite powder was first treated with 0.5 mol of ammonium nitrate aqueous solution at 60° C. for 6 hours, ion exchanged in the form of NH ₄ -CHA zeolite, and dried at 60° C. for 12 hours after filtration/washing. did After that, the NH ₄ -CHA zeolite powder ion-exchanged with ammonium was put in an aqueous solution of copper acetate (copper acetate, Aldrich) calculated to have a copper/aluminum molar ratio of 0.3-0.4, stirred at 60° C. for 6 hours, and filtered. / After washing process, it was maintained at 60℃ in a dryer for 12 hours. Thereafter, it was calcined at 550° C. for 4 hours to finally prepare a copper-supported CHA zeolite catalyst.

As another copper loading method, the prepared CHA powder is mixed with copper oxide (CuO) as a copper precursor and acetic acid (CH ₃ COOH) as a binder in distilled water and dispersed, and then milled/dried/fired at room temperature for at least 10 minutes. A copper-supported CHA zeolite catalyst can also be prepared.

The following equipment was used for characterization of CHA zeolite. First, the structure/crystallinity analysis was analyzed using an X-ray diffraction device (XRD, X-ray diffraction), the particle shape of the zeolite was analyzed using a scanning electron microscope (SEM), and the constituent elements and content were X Line spectroscopy (XRF, X-ray fluorescence), zeolite pores and specific surface area were measured using a nitrogen adsorption characteristic analyzer (BET N ₂ physisorption).

Table 2 shows the physical properties of the zeolite synthesized in Examples and Comparative Examples and the results of copper ion exchange for CHA zeolite (Example 1-4, Comparative Example 1-2) showing a crystallinity of 95% or more. arranged. In addition, a scanning electron microscope photograph of the CHA zeolite prepared in Examples and Comparative Examples is shown in FIG. 2 , and a photo of the copper-supported CHA zeolite in Example 1 is shown in FIG. 3 .

<Evaluation>

According to the results in Table 2, as in Example 1-9 and Comparative Example 1-2, when synthesizing by varying the SDA type, SDA ratio, and raw material SiO ₂ /Al ₂ O ₃ molar ratio, the crystallinity of the produced zeolite product , particle size, specific surface area, etc. were found to be different.

Example 1-6 was synthesized using two types of composite SDA with different ratios of de-Al-Y having a SiO ₂ /Al ₂ O ₃ molar ratio of 35 and SDA-1(TMadaOH)/SDA-2(BTMACl). , as a result, it was confirmed that the crystallinity and particle size of the produced CHA zeolite were different according to the ratio of SDA-1(TMadaOH)/SDA-2(BTMACl). In particular, up to the ratio of SDA-1(TMadaOH)/SDA-2(BTMACl) to 0.33, the particle size is gradually increased from 0.5 microns to a maximum of 3.0 microns. It was found that the two types of composite SDA were an important factor influencing the particle size.

On the other hand, when the ratio of SDA-1(TMadaOH)/SDA-2(BTMACl) exceeds 0.33, in addition to CHA zeolite, beta zeolite and quartz phase are generated together as impurities, resulting in crystallinity and purity of the final product was found to have an effect on This is a result that shows that the optimal point of the complex ratio of the two types of SDA exists, and when the amount of TMadaOH is increased, the composition of the synthetic mother liquor is expected to change to an atmosphere in which Beta and Quartz can be produced in addition to CHA zeolite.

In Examples 3 and 7-9, the ratio of SDA-1(TMadaOH)/SDA-2(BTMACl) is the same as 0.16, but the SiO ₂ /Al ₂ O ₃ molar ratio of the raw material de-Al-Y is different. As a result, in Examples 7 and 9 with SiO ₂ /Al ₂ O ₃ molar ratios of 26 and 80, in addition to CHA, mordenite and beta zeolite were produced together as impurities, and SiO ₂ /Al ₂ In the case of Example 8 in which the O ₃ molar ratio was 44, de-Al-Y, a raw material, was present, but it was found that the product was pure CHA. In the case of de-Al-Y raw materials remaining in the product, it was confirmed that pure CHA zeolite can be synthesized between SiO ₂ /Al ₂ O ₃ molar ratio =35-44 because it can be converted to CHA when the synthesis atmosphere is adjusted. .

In addition, comparing Example 4 and Comparative Example 1-2 in order to confirm the effect of the two types of composite SDA, in the case of particle size, compared with the case of using a single SDA, it has an effect of increasing the particle size by about 3 times In addition, CHA having high purity and crystallinity was synthesized when using complex SDA compared to when single SDA-2 (BTMACl) of Comparative Example 2 was used.

<Experimental Example 1: Evaluation of hydrothermal stability of copper-supported CHA zeolite>

For evaluation of zeolite structural stability after high-temperature hydrothermal treatment of CHA zeolite synthesized with a crystallinity of 95% or more through Examples 1-9 and Comparative Example 1-2, samples were prepared as follows, and the results are shown in Table 3. .

The copper-supported CHA zeolite powder prepared in the above Examples and Comparative Examples was placed in a heat treatment apparatus with an air flow, and gas space velocity (GHSV) of 20,000 h ^{- 1} at a ratio of 10% water vapor/90% air at room temperature After raising the temperature to 900°C, it was maintained for 1 hour to prepare a hydrothermal-treated catalyst. 4 shows the crystallinity of CHA zeolite synthesized with a crystallinity of 95% or more before and after high-temperature hydrothermal treatment as a result of X-ray diffraction analysis.

<Evaluation>

According to the results in Table 3, in the case of the zeolite of Examples 1-4 using two types of composite SDA, a relatively similar degree of crystallinity was maintained even after hydrothermal treatment at 900 ° C. When compared with the zeolite of Comparative Example 1 using a single SDA-1 After hydrothermal treatment, the crystallinity was about 10% higher. In particular, in the case of the zeolite of Comparative Example 2 using a single SDA-1, the crystallinity fell to less than 10% after hydrothermal treatment, which is why mordenite impurities affect the stability of the CHA zeolite. It appears to have collapsed and changed to an amorphous form.

Accordingly, it can be seen that the degree of densification and stabilization of the zeolite skeleton is high when two types of composite SDA are used, and the main skeleton of the zeolite can still be maintained even after high-temperature hydrothermal treatment.

<Experimental Example 2: Evaluation of differential pressure after coating on DPF>

After coating on a filter (DPF) for Cu-supported CHA zeolite powder synthesized with a crystallinity of 95% or more through Examples 1-9 and Comparative Examples 1-2, the differential pressure of the coated specimen was evaluated, and the results are shown in Table 4 shown in First, the copper-supported zeolite was coated in a filter after making a slurry of 35% concentration using a surfactant and water. Thereafter, a copper-supported zeolite filter was prepared by drying at 100° C. for 8 hours and heat treatment at 500° C. for 6 hours in a calcination furnace. The back pressure measurement was calculated as the pressure change after injection into the filter with a flow of 600 m ³ /hr, and the unit was expressed in mbar. The differential pressure was expressed as the difference after measuring the back pressure of the filter before and after the initial slurry coating.

<Evaluation>

In order to be applied to the actual automobile exhaust filter catalyst, smooth discharge of the gas passing through the filter catalyst is an important factor. do. According to the results in Table 4, in the case of the zeolite of Examples 1-4 using two types of composite SDA, as the particle size increased from 0.5 microns to 3.0 microns, the back pressure in the filter did not increase significantly, and the differential pressure was also lowered accordingly. Could know. As a result of Comparative Example 1-2, it can be seen that the differential pressure increases. In particular, in Comparative Example 2, the particle size of the zeolite powder is widely distributed as 0.2-1.0 microns, so it is densely located in the filter pores, and the differential pressure rises higher. seems to have gone As a result, it was found that the size and uniformity of the zeolite catalyst particles had a very high effect on the actual filter differential pressure, and it was confirmed that the larger the particle size, the easier it was to be applied as a filter catalyst.

<Experimental Example 3: Evaluation of SCR activity of Cu-supported CHA zeolite>

With respect to the zeolite synthesized with a crystallinity of 95% or more through Examples 1-9 and Comparative Example 1-2, the nitrogen oxide (NOx) conversion performance was evaluated as follows after high-temperature hydrothermal treatment of the sample coated on the filter, as a result is shown in Table 5 and FIG. 5 .

The composition of the reaction gas in the reactor is nitrogen oxide (NO) 500 ppm, ammonia (NH ₃ ) 500 ppm, carbon monoxide (CO) 200 ppm, carbon dioxide (CO ₂ ) 5%, oxygen 9.5%, moisture 5% in a nitrogen gas atmosphere. The gas space velocity (GHSV) of 80,000 h ^{- 1} was injected into the reactor and the conversion rate of nitrogen oxide was measured while changing the reaction temperature from 150°C to 600°C.

<Evaluation>

According to the results in Table 5 and FIG. 5, the NOx conversion rate before hydrothermal treatment was the case of the copper-supported zeolite of Example 1-4 using two types of composite SDA and the copper-supported zeolite of Comparative Example 1-2 using single SDA-1. About 85-88%, it appears almost the same. On the other hand, when comparing the NOx conversion performance after 900 °C hydrothermal treatment, the catalysts of Examples and Comparative Examples show the same performance in the low temperature region around 300 °C, but compared to Comparative Example 1-2 in the high temperature region above 400 °C The NOx conversion performance of 1-4 was evaluated to be excellent by about 30%, and compared to the catalyst before hydrothermal treatment, the reduction in the conversion rate was also low, resulting in improved catalyst performance stability.

This is a result consistent with the comparison of the crystallinity of Examples 1-4 and Comparative Examples 1-2 after hydrothermal treatment, and in Example 1-4, which has a strong zeolite skeleton, high NOx treatment ability was shown even under more severe treatment conditions. . In the case of Comparative Example 2, overall, after hydrothermal treatment, the NOx conversion performance in the low-temperature and high-temperature regions was very low, and the reduction in the conversion rate was also about 3 times higher than in Example 4, so the skeleton of the CHA zeolite was mostly collapsed. lose Therefore, the zeolite according to the present invention can suppress the generation of differential pressure during catalyst production compared to the conventional zeolite, has excellent hydrothermal durability, and thus has excellent nitrogen oxide conversion efficiency.

Claims (8)

A method for manufacturing high-purity CHA zeolite having high-temperature hydrothermal durability and particle size control, comprising:
Preparing a synthetic mother liquid containing a raw material containing aluminum oxide and silica and two types of complex structure-inducing materials; and
forming a solid product by hydrothermal synthesis of the synthetic mother liquor; including,
The two types of complex structure-inducing material are composed of a first structure-inducing material including an adamantyl group and a second structure-inducing material including a benzyl group, and the first structure-inducing material including an adamantyl group The molar ratio of the substance/the second structure-inducing material containing the benzyl group is 0.03-0.33,
The raw material containing the aluminum oxide and silica is a silica / alumina (SiO ₂ /Al ₂ O ₃ ) molar ratio of 35 to 44 A method for producing CHA zeolite, characterized in that it is de-aluminized Y zeolite. The method of claim 1, wherein the first structure-inducing material is selected from the group consisting of hydroxides, halides, carbonates and sulfates having TMAda (Trimethyladamantylammonium) as a cation, and the second structure-inducing material is benzyltrimethylammonium, benzyltriethylammonium, A method for producing CHA zeolite, characterized in that it is selected from the group consisting of hydroxides, halides, carbonates and sulfates having benzyltripropylammonium and benzyltributylammonium as cations. delete delete delete The method of claim 1 , wherein a copper ion exchange step is added following the step of forming the solid product so that the product zeolite contains copper. According to claim 6, wherein the copper ion exchange step is copper nitrate (copper nitrate), copper chloride (copper chloride), copper acetate (copper acetate) and amine (amine) as a precursor tetraamine copper nitrate (tetraammine copper Nitrate) , tetraamine copper chloride (Tetraammine copper chloride), tetraamine copper sulfate (Tetraammine copper sulfate), characterized in that by adding a copper precursor that can be selected from the group consisting of copper oxide (CuO), CHA zeolite manufacturing method. delete

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