KR20230074361A - DeNOx CATALYST LOADED WITH POROUS FLAKE MgO AND METHOD FOR PREPARATION OF THE SAME - Google Patents

Abstract

The present invention relates to a denitrification catalyst for removing nitrogen oxides by an ammonia selective reduction method and a method for producing the same, and more particularly, to a magnesium oxide dispersion slurry in the form of a porous plate, which is prepared by supporting a titania-based catalyst. It relates to a titania-based denitrification catalyst supported with platelet magnesium oxide and a method for preparing the same. The denitrification catalyst of the present invention can solve the problem of alkali metal poisoning by improving alkali resistance to denitrification.

Description

Denitrification catalyst supported with porous plate-like magnesium oxide and method for producing the same

The present invention relates to a denitrification catalyst for removing nitrogen oxides by an ammonia selective reduction method and a method for producing the same, and more particularly, to a magnesium oxide dispersion slurry in the form of a porous plate, which is prepared by supporting a titania-based catalyst. It relates to a titania-based denitrification catalyst supported with platelet magnesium oxide and a method for preparing the same. The denitrification catalyst of the present invention can solve the problem of alkali metal poisoning by improving alkali resistance.

As energy consumption increases, the use of fossil fuels increases through thermal power plants, industrial boilers, waste incineration facilities, petrochemical plants, etc. As a result, various harmful exhaust gases are generated by burning fossil fuels, resulting in air pollution. This is becoming a problem. Nitrogen oxide (NOx), a typical pollutant among these combustion exhaust gases, is not only harmful to the human body, but also a major cause of environmental pollution such as photochemical smog and acid rain.

As a prior art for removing these nitrogen oxides, Selective Catalytic Reduction (SCR) is the most widely used. The selective catalytic reduction method is a denitration method using ammonia as a reducing agent, mixing it with NOx and passing it through a catalyst layer to remove nitrogen and water vapor in the form of nitrogen and water vapor. Here, a vanadium/titania catalyst is mainly used as a catalyst.

However, in the case of the denitrification catalyst used in the selective catalytic reduction method, there is a problem in that the catalyst is poisoned by potassium nanoparticles generated by decomposition and condensation of potassium compounds at high temperatures during the combustion of biomass.

In order to solve the above problems, various techniques for improving the catalyst used in the selective catalytic reduction method have been developed. Among them, as technologies for coating an active metal on a catalyst, for example, international patent application PCT/EP10/70087 describes a technology for improving catalyst performance by wash-coating the catalyst surface to a thickness of 1 to 100 μm. U.S. Patent No. 4,152,296 discloses a technique for improving the formation of ruthenium oxide at a high temperature by coating Al-O and MgO on a catalyst.

However, the above patents only disclose changing the catalyst manufacturing process by including wash coating or additional coating metal material on the catalyst, adjusting the content of magnesium oxide supported on the catalyst, and especially denitrifying by supporting porous plate-shaped MgO material. There is no hint at all about the technological idea that efficiency can be improved.

[Patent Document 1] International Patent Application PCT/EP10/70087 [Patent Document 2] US Patent No. 3,990,998 [Patent Document 3] Domestic Patent Publication No. 10-2010-0084463 [Patent Document 4] Domestic Patent Publication No. 10-2013-0125377 [Patent Document 5] Domestic Patent Publication No. 10-2014-0035323

An object of the present invention is to provide a denitration catalyst that can be suitably applied to an NH ₃ -SCR denitration process operated in a large combustion engine. In particular, an object of the present invention is to provide an alkali-resistant NOx removal catalyst that exhibits high NOx removal efficiency even when the catalyst is poisoned by including magnesium oxide in the form of a porous plate.

In addition, an object of the present invention is to provide a method for preparing the alkali-resistant denitrification catalyst.

The denitration catalyst according to the present invention is characterized by comprising a titania-based support, porous plate-like magnesium oxide supported on the titania-based support, and an active metal compound.

In the denitration catalyst of the present invention, the porous plate-like magnesium oxide may be included in an amount of 0.1 to 2.0% by weight based on the total weight of the denitration catalyst.

The particle size of the porous plate-like magnesium oxide may be 20 to 5000 nm.

In the denitration catalyst of the present invention, the titania-based support may be an anatase-phase titania (TiO ₂ ) support.

In the denitration catalyst of the present invention, the active metal compound may be included in an amount of 0.1 to 10.0% by weight based on the total weight of the denitration catalyst.

The active metal oxide may be at least one selected from tungsten oxide, manganese oxide, cerium oxide, molybdenum oxide, and vanadium oxide.

The method for preparing a denitration catalyst according to the present invention is characterized by comprising the following steps:

1) preparing an anatase-phase titania-based carrier;

2) preparing porous plate-like magnesium oxide;

3) supporting at least one of magnesium hydroxide and porous plate-like magnesium oxide in step 2) and an active metal compound on the titania-based carrier in step 1);

4) Calcining the product of step 3) to prepare a denitration catalyst supported with porous plate-like magnesium oxide.

In the method for preparing the denitration catalyst of the present invention, step 1) may include mixing the titanium precursor compound and distilled water, followed by hydrolysis, followed by solid-liquid separation, washing with water, and neutralization.

The titanium precursor compound may be at least one selected from TiOSO ₄ , TiOCl ₂ , TiCl ₄ , and Ti{OCH(CH ₃ ) ₂ } ₄ .

The hydrolysis may be performed at 70 to 100 ° C for 5 to 48 hours.

The neutralization may be performed by adjusting the pH to 7-8.

Step 1) may further include supporting at least one active metal compound selected from tungsten oxide, manganese oxide, cerium oxide, molybdenum oxide, and vanadium oxide on the titania-based carrier obtained after the neutralization.

In the production method of the denitration catalyst of the present invention, in step 2), the porous plate-like magnesium oxide may be prepared in powder form by calcining magnesium hydroxide. The firing may be performed at 400 to 700 ° C for 1 to 10 hours.

In the method for preparing the denitration catalyst of the present invention, in step 3), a slurry of at least one of magnesium hydroxide and porous plate-like magnesium oxide of step 2) and a liquid precursor for carrying an active metal compound are mixed with the slurry of the titania-based carrier It can be added to and impregnated.

The impregnation treatment may be performed under conditions of 150 to 200 mmbar and 80 to 100° C. in a rotary vacuum distillation machine.

In the method for preparing the denitration catalyst of the present invention, step 3) may further include supporting silicon oxide (SiO ₂ ) on the titania-based carrier.

In the manufacturing method of the denitration catalyst of the present invention, the firing in step 4) may be performed at 400 to 600 ° C. for 1 to 10 hours.

The denitrification catalyst for NH ₃ -SCR (Selective Catalytic Reduction) according to the present invention uses wood pellets by improving catalyst poisoning caused by alkali metals, fly ash, and foreign substances while changing from an existing thermal power plant to a biomass thermal power plant. It has the advantage of showing high denitrification performance in thermal power plants.

In addition, according to the method for preparing a denitration catalyst according to the present invention, a denitration catalyst with improved catalyst poisoning performance due to improved alkali resistance by supporting porous plate-like magnesium oxide on the catalyst and controlling the loading amount of porous plate-like magnesium oxide can be manufactured

1 is a flowchart of a manufacturing process of a denitration catalyst according to an embodiment of the present invention.
2 is a TEM photograph of porous plate-like magnesium oxide prepared by calcining magnesium hydroxide at 600° C. according to an embodiment of the present invention.
3 is a TEM photograph of plate-like magnesium hydroxide without pores before firing.
4 is a graph showing a comparison between the denitrification efficiency of the denitration catalyst according to Example 1 of the present invention and the denitration efficiency after potassium poisoning.
5 is a graph showing the comparison between the denitrification efficiency of the denitration catalyst according to Comparative Example 1 and the denitrification efficiency after potassium poisoning.

The advantages and features of the present invention, and how to achieve them, will become clear with reference to the detailed description of the embodiments below. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only the present embodiments allow the disclosure of the present invention to be complete, and the common knowledge in the art to which the present invention belongs. It is provided to fully inform the holder of the scope of the invention, and the present invention is only defined by the scope of the claims.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used in a meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in commonly used dictionaries are not interpreted ideally or excessively unless specifically defined explicitly.

Hereinafter, a denitrification catalyst and a manufacturing method thereof according to the present invention will be described in detail.

The denitration catalyst according to the present invention is characterized by comprising a titania-based support, porous plate-like magnesium oxide and an active metal compound supported on the titania-based support.

The denitrification catalyst according to the present invention can be mainly used in the NH ₃ -SCR process for removing NOx generated from large combustion engines such as biomass-fired power plants.

Wood pellets used in biomass thermal power plants poison catalysts due to alkali metals, fly ash, foreign substances, etc., and the denitration catalyst according to the present invention is supported by porous plate-shaped magnesium oxide, thereby reducing V ₂ O when poisoned. ₅ WO ₃ /TiO ₂ It exhibits higher denitrification activity than the catalyst, so it has the effect of solving the above-mentioned problems of the conventional catalyst.

In the denitration catalyst of the present invention, the porous plate-shaped magnesium oxide may be included in an amount of 0.1 to 2.0% by weight, preferably 0.5 to 1.5% by weight, based on the total weight of the denitration catalyst. The effect of supporting the upper magnesium oxide is insufficient, and if the content exceeds the above range, the active area of the catalyst surface may decrease due to the content of magnesium oxide higher than necessary, which may cause deterioration in denitrification performance, which is not preferable.

The particle size of the porous plate-like magnesium oxide may be 20 to 5000 nm, preferably 20 to 500 nm. If it is out of the above range, it cannot be sufficiently supported in the active space of the carrier or cannot sufficiently form an active area, and denitration at high temperature During operation, the ammonia oxidation reaction of the catalyst is accelerated, which is undesirable. The above particle size means the average value of the width and length of the plate-like body observed with a TEM electron microscope. When the particles in which the porous plate-like bodies are agglomerated are observed with a particle size analyzer after mild milling and dispersion, a particle size of 100 to 6000 nm is observed. The thickness of the porous plate-like body may be about 1 to 10 nm.

In the denitrification catalyst of the present invention, the titania-based support preferably has an anatase phase. Titania (TiO ₂ ) generally has three crystal structures: brookite, rutile, and anatase. , which has better catalytic activity compared to other phases.

In the denitration catalyst of the present invention, the active metal compound is preferably supported in an amount of 0.1 to 10.0% by weight, particularly 1 to 3% by weight, based on the total weight of the denitration catalyst. The effect of the support of the metal compound is insufficient, and if it exceeds 10.0% by weight, the cost for commercialization of the catalyst increases, which is undesirable because economical efficiency decreases.

The active metal oxide may be at least one selected from tungsten oxide, manganese oxide, cerium oxide, molybdenum oxide and vanadium oxide, but is not limited thereto, and tungsten oxide and vanadium oxide are particularly preferred.

The method for preparing a denitration catalyst according to the present invention may include the following steps.

1) preparing an anatase-phase titania support;

2) preparing porous plate-like magnesium oxide;

3) supporting at least one of magnesium hydroxide and porous plate-like magnesium oxide in step 2) and an active metal compound on the titania-based carrier in step 1);

4) Calcining the product of step 3) to prepare a denitration catalyst supported with porous plate-like magnesium oxide.

In the method for preparing the denitration catalyst of the present invention, step 1) may include mixing the titanium precursor compound and distilled water, followed by hydrolysis, followed by solid-liquid separation, washing with water, and neutralization.

The titanium precursor compound is obtained from titanyl sulfate (TiOSO ₄ ), titanium oxychloride (TiOCl ₂ ), titanium tetrachloride (TiCl ₄ ), titanium isopropoxide (Ti{OCH(CH ₃ ) ₂ } ₄ ; TTIP), and the like. It may be one or more selected, but is not limited thereto, and TiOSO ₄ is particularly preferred.

The hydrolysis may be carried out at 70 to 100 ° C for 10 to 20 hours, preferably at 90 to 100 ° C for 15 to 18 hours for effective hydrolysis.

The neutralization may be performed by adjusting the pH to 7-8 by adding a basic compound such as ammonia water, and such neutralization treatment is also for effective support of the active metal compound thereafter.

In the production method of the denitration catalyst of the present invention, the production of porous plate-like magnesium oxide in step 2) may be performed by calcining magnesium hydroxide. At this time, the firing may be performed at 400 to 700 ° C, preferably 500 to 600 ° C for 1 to 10 hours, preferably 2 to 5 hours.

In the method for preparing the denitration catalyst of the present invention, in step 3), a slurry of at least one of magnesium hydroxide and porous plate-like magnesium oxide of step 2) and a liquid precursor of an active metal compound are added to the slurry of the titania-based carrier. It can be performed by adding and impregnating.

The impregnation treatment may be carried out at 150 to 200 mmbar, preferably 150 to 180 mmbar, most preferably 170 mmbar, and 80 to 100 ° C., preferably 90 ° C., in a rotary vacuum distillation chamber for effective impregnation.

The active metal compound supported in the step 3) serves to expand the active temperature of the catalyst and acid sites, and inhibit sintering and phase transition.

In the step 3), the order in which at least one of the magnesium hydroxide and the porous plate-like magnesium oxide and the active metal compound are loaded is not particularly limited.

In the method for preparing the denitration catalyst of the present invention, the firing in step 4) may be performed at 400 to 600 ° C, preferably 500 to 580 ° C for 1 to 10 hours, preferably 3 to 4 hours.

Hereinafter, the present invention will be described in more detail through examples for preparing a denitration catalyst carrying porous plate-shaped magnesium oxide and comparative examples for preparing an amorphous denitration catalyst according to the present invention. are not limited by

Example 1

According to the manufacturing process of the denitration catalyst shown in FIG. 1, a denitration catalyst supported with porous plate-shaped MgO was prepared as follows.

Titanyl sulfate (TiOSO ₄ ) The powder was mixed with distilled water and hydrolyzed at 100° C. for 16 hours to prepare 100-150 g/L of anatase titania (TiO ₂ ) slurry (TiO ₂ sol). The TiO ₂ slurry and the solvent were separated using a high-speed centrifuge, distilled water was added to remove the sulfuric acid component in the slurry, mixed with a shaker, solid-liquid separation was performed again by high-speed centrifugation, and the mixture was washed twice in total. Distilled water was added to the washed slurry, and ammonia water was added to neutralize the slurry to pH 7-8 to prepare a TiO ₂ sol.

A tungsten precursor ((NH ₄ ) ₆ W ₁₂ O _{39 X} H ₂ O (Ammonium meta tungstate)) and NH ₄ VO ₃ were added to 200 ml of distilled water so that tungsten _oxide (WO ₃ ) was 2% by weight relative to the TiO 2 sol. After dissolving, the solution to which C ₂ H _{2 O 4} was added and magnesium hydroxide (Mg(OH) ₂ ) were calcined at 600 ° C for 4 hours. It was mixed with TiO ₂ sol to a weight % and stirred for 2 hours to prepare a MgO-V ₂ O ₅ WO ₃ /TiO ₂ material. The stirred MgO-V ₂ O ₅ WO ₃ /TiO ₂ slurry was distilled under reduced pressure to evaporate the solvent to prepare a powder, calcined at 500 ° C for 4 hours, and porous plate MgO supported MgO-V ₂ O ₅ A WO ₃ /TiO ₂ denitrification catalyst was prepared.

A TEM photograph of the porous plate-like magnesium oxide used in this example is shown in FIG. 2, and a TEM photograph of the magnesium hydroxide used in the preparation of the porous plate-like magnesium oxide before firing is shown in FIG.

In addition, FIG. 4 shows a graph comparing the denitrification efficiency of the denitration catalyst before and after potassium poisoning of the denitration catalyst supported on the porous plate-like magnesium oxide prepared in this example.

Example 2

In the catalyst preparation step of Example 1, instead of the porous plate-like MgO having an average particle size of 200 nm obtained by calcining magnesium hydroxide at 600 ° C. for 4 hours, magnesium hydroxide with an average particle size of 200 nm obtained by calcining magnesium hydroxide at 500 ° C. for 4 hours A MgO-V ₂ O ₅ WO ₃ /TiO ₂ denitration catalyst supported with porous plate-like MgO was prepared in the same manner as in Example 1, except that plate-like MgO was used.

Example 3

In the catalyst preparation step of Example 1, instead of porous plate-like MgO having an average particle size of 200 nm obtained by calcining magnesium hydroxide at 600 ° C. for 4 hours, magnesium hydroxide with an average particle size of 200 nm obtained by calcining magnesium hydroxide at 700 ° C. for 4 hours A MgO-V ₂ O ₅ WO ₃ /TiO ₂ denitration catalyst supported with porous plate-like MgO was prepared in the same manner as in Example 1, except that plate-like MgO was used.

Example 4

In the catalyst preparation step of Example 1, porous plate MgO was prepared in the same manner as in Example 1, except that the slurry of porous plate MgO was mixed with TiO ₂ sol so that the slurry was 1.5% by weight relative to the weight of TiO ₂ and supported. A supported MgO-V ₂ O ₅ WO ₃ /TiO ₂ denitrification catalyst was prepared.

Example 5

In the catalyst preparation step of Example 1, porous plate-like MgO having an average particle size of 50 nm or less obtained by calcining a slurry of plate-like Mg(OH ₂ ) at 600 °C for 4 hours was used, and MgO-V ₂ O ₅ WO ₃ /TiO ₂ MgO-V ₂ O ₅ WO ₃ /TiO ₂ Denitration catalyst carrying porous plate-like MgO in the same manner as in Example 1, except that the powder prepared from the slurry was calcined at 600 ° C for 4 hours. was manufactured.

Comparative Example 1

In Example 1, a powdered V ₂ O ₅ WO ₃ /TiO ₂ denitration catalyst was prepared in the same manner as in Example 1, except that the porous plate-like MgO was not supported.

FIG. 5 shows a graph comparing the denitrification efficiency of the denitration catalyst prepared in this comparative example before and after potassium poisoning.

Comparative Example 2

In Example 1, porous plate MgO slurry having an average particle size of 200 nm was carried out in the same manner as in Example 1, except that the TiO ₂ sol was mixed and supported so as to be 2.5% by weight relative to the weight of TiO ₂ . A supported MgO-V ₂ O ₅ WO ₃ /TiO ₂ denitrification catalyst was prepared.

Comparative Example 3

In Example 1, except that the porous plate-like MgO slurry having an average particle size of 200 nm was mixed with the TiO ₂ sol to be 4.0% by weight relative to the weight of TiO ₂ and supported, the porous plate was obtained in the same manner as in Example 1. A MgO-V ₂ O ₅ WO ₃ /TiO ₂ denitration catalyst loaded with MgO was prepared.

Comparative Example 4

In Example 1, zirconium-supported Zr-V was carried out in the same manner as in Example 1, except that 1% by weight of zirconium oxide (ZrO ₂ ) was mixed and supported in TiO ₂ sol instead of porous plate-like MgO. ₂ O ₅ WO ₃ /TiO ₂ A denitrification catalyst was prepared.

Comparative Example 5

In Comparative Example 1, aluminum was obtained in the same manner as in Example 1, except that 1 wt% of gamma-alumina (γ-Al ₂ O ₃ ) was mixed and supported in the TiO ₂ sol instead of porous plate-like MgO. A supported Al-V ₂ O ₅ WO ₃ /TiO ₂ denitrification catalyst was prepared.

[Characteristic evaluation]

1. Characteristic evaluation of porous plate-like magnesium oxide

2 shows a TEM photograph of porous plate-like magnesium oxide prepared by calcining magnesium hydroxide at 600° C. for 4 hours, and FIG.

2. Characteristic evaluation of denitrification catalyst

The denitration properties of the denitration catalysts prepared in Examples 1 to 5 and Comparative Examples 1 to 5 It was evaluated as follows.

N ₂ gas was used as a balance gas, the concentrations of NOx and NH ₃ gas were fixed at 300 ppm, and the reaction ratio between NOx and NH ₃ was set to 1:1. The oxygen concentration in the reaction gas was injected at 5 vol%, and the gas flow rate in the reactor was maintained at 300 cc/min. The catalyst fixing layer for removing NOx was maintained at a space velocity of 60,000 (hr ^-1 ), and a powder fixing layer was formed using ceramic wool by adjusting the catalyst amount according to the space velocity. The evaluation method is to stabilize the catalyst until the expected concentration is constant by flowing N ₂ , O ₂ , NO, NH ₃ gas after installing the catalyst on the reactor. As for the NOx removal efficiency, the NOx concentration change was observed at a heating rate of 5°C/min from 25°C to 500°C.

The evaluation results of the NOx removal characteristics of the NOx removal catalysts according to Examples and Comparative Examples are shown in Table 1 below.

Note): 1) Denitration conversion rate: Means the denitrification efficiency at 380℃.

K2%, K3%: As a result of poisoning the catalyst with 2% by weight and 3% by weight of potassium (K), and measuring the denitrification efficiency from 25 to 500 ° C, it means the denitrification efficiency at 380 ° C.

2) Mg(OH) ₂ used in Example 5 has a particle size of 50 nm or less compared to the average particle size of 200 nm in Examples 1 to 4.

As shown in Table 1, the V ₂ O ₅ WO ₃ /TiO ₂ denitrification catalysts supported with magnesium oxide in the form of porous plates prepared in Examples according to the present invention are superior to the denitration catalysts prepared in Comparative Examples. , it can be seen that the denitrification conversion rate is high. In addition, it can be confirmed that the V ₂ O ₅ WO ₃ /TiO ₂ denitrification catalysts supported with porous plate-like magnesium oxide prepared in Examples according to the present invention have significantly higher denitrification conversion rates than those of Comparative Examples when potassium is poisoned. can

As confirmed by the above results, the denitrification catalyst according to the present invention is an alkali-resistant denitrification catalyst, and has excellent resistance to poisoning by alkali metals in the NH ₃ -SCR denitrification process operated in a biomass thermal power plant, thereby reducing the catalytically active point. It can be maintained for a longer time, which can improve economic efficiency.

Claims (15)

A denitration catalyst comprising a titania-based support, porous plate-like magnesium oxide and an active metal compound supported on the titania-based support. The denitration catalyst according to claim 1, wherein the porous plate-shaped magnesium oxide is included in an amount of 0.1 to 2.0% by weight based on the total weight of the denitration catalyst. The denitration catalyst according to claim 1, wherein the magnesium oxide is magnesium oxide (MgO) obtained by calcining magnesium hydroxide. The denitration catalyst according to claim 1, wherein the porous plate-like magnesium oxide has an average particle size of 20 to 5000 nm. The denitration catalyst according to claim 1, wherein the titania-based support is an anatase-phase titania (TiO ₂ ) support. The denitration catalyst according to claim 1, wherein the active metal compound is included in an amount of 0.1 to 10.0% by weight based on the total weight of the denitration catalyst. The denitration catalyst according to claim 1, wherein the active metal oxide is at least one selected from tungsten oxide, manganese oxide, cerium oxide, molybdenum oxide and vanadium oxide. A method for preparing the NOx removal catalyst according to any one of claims 1 to 7, comprising the following steps:
1) preparing an anatase-phase titania-based carrier;
2) preparing porous plate-like magnesium oxide;
3) supporting at least one of magnesium hydroxide and porous plate-like magnesium oxide in step 2) and an active metal compound on the titania-based carrier in step 1);
4) Calcining the product of step 3) to prepare a denitration catalyst supported with porous plate-like magnesium oxide. The method of claim 8, wherein the step 1) comprises mixing the titanium precursor compound with distilled water, hydrolyzing it, followed by solid-liquid separation, washing with water, and neutralization. The method of claim 9, wherein the titanium precursor compound is at least one selected from TiOSO ₄ , TiOCl ₂ , TiCl ₄ , and Ti{OCH(CH ₃ ) ₂ } ₄ . The method of claim 9, wherein the hydrolysis is performed at 70 to 100° C. for 5 to 48 hours, and the neutralization is performed by adjusting the pH to 7 to 8. [Claim 9] The method according to claim 8, wherein in step 2), the porous plate-like magnesium oxide is prepared by calcining magnesium hydroxide at 400 to 700 °C for 1 to 10 hours. The method of claim 8, wherein step 3) adds a slurry of at least one of magnesium hydroxide and porous plate-like magnesium oxide of step 2) and a liquid precursor for supporting an active metal compound to the slurry of the titania-based carrier, followed by impregnation. A method for producing a denitration catalyst performed by treatment. The method of claim 13, wherein the impregnation treatment is performed in a rotary vacuum distillation machine at 150 to 200 mmbar and 80 to 100 ° C. The method of claim 8, wherein the firing in step 4) is performed at 400 to 600° C. for 1 to 10 hours.

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