KR20230073794A - DeNOx CATALYST LOADED WITH CRYSTALLINE ZEOLITES AND METHOD FOR PREPARATION OF THE SAME - Google Patents

Abstract

The present invention relates to a deNOx catalyst for removing nitrogen oxides by selective ammonia reduction and a method for preparing the same, and more specifically, to a titania-based deNOx catalyst supported with crystalline zeolites, the catalyst which is prepared by supporting crystalline zeolites prepared without a template on a titania-based catalyst, and a method for preparing the same. The deNOx catalyst of the present invention has improved alkali-resistant deNOx properties, thereby solving the problem of alkali metal poisoning.

Description

DeNOx catalyst supported with crystalline zeolite and method for producing the same

The present invention relates to a denitration catalyst for removing nitrogen oxides by an ammonia selective reduction method and a method for producing the same, and more particularly, to a catalyst supported on a crystalline zeolite prepared by supporting a crystalline zeolite prepared without a template material on a titania-based catalyst. It relates to a titania-based denitrification catalyst 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 uses ammonia as a reducing agent, mixes it with NOx and passes it through a catalyst layer to remove nitrogen and vapor in the form of nitrogen and water vapor. Zeolite is used as a catalyst for SCR of NOx.

However, the NH ₃ -SCR catalyst has problems in that catalytic activity is reduced and catalyst poisoning occurs due to alkali metals.

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, Korean Patent Publication No. 10-2019-0003863 discloses a technique for preparing a catalyst by exchanging NH4 ⁺ ion with zeolite, and Korean Patent Publication No. 10-2003-0046881 discloses natural zeolite for heating and acid treatment. A technology for preparing a catalyst support sample is disclosed, and in Korean Patent Publication No. 10-2018-7025353, Fe-AEI zeolite, which does not require a complexing agent, is directly synthesized and has high activity at a temperature of 300 ^° C or higher. A catalyst manufacturing technology is disclosed.

However, the above patents only disclose a catalyst manufacturing process using zeolite obtained by heat treatment, acid treatment, or ion exchange of natural zeolite, and by carrying crystalline zeolite prepared without a template material on the catalyst, the denitration efficiency is improved and It does not suggest at all about the technical idea that the catalyst poisoning problem can be solved.

[Patent Document 1] Domestic Patent Publication No. 10-2019-0003863 [Patent Document 2] Korean Patent Publication No. 10-2003-0046881 [Patent Document 3] Domestic Patent Publication No. 10-2018-7025353 [Patent Document 4] Korean Patent Registration No. 10-0996794

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 a crystalline zeolite prepared without a template material.

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, a crystalline zeolite and an active metal compound supported on the titania-based support.

In the denitration catalyst of the present invention, the crystalline zeolite may be included in an amount of 1.0 to 10.0% by weight based on the total weight of the denitration catalyst.

The crystalline zeolite is a zeolite prepared without a template material, and ZSM-5, beta zeolite, L zeolite, natural zeolite, mordenite, and zeolite ion-exchanged with metal ions or metal oxides It may be at least one selected from the supported zeolites.

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 a crystalline zeolite without a template material;

3) supporting the crystalline zeolite and the active metal compound prepared without the template material in step 2) on the titania-based carrier in step 1);

4) Calcining the product of step 3) to prepare a denitration catalyst supported with crystalline zeolite.

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.

In the method for preparing the denitration catalyst of the present invention, in step 2), the crystalline zeolite is prepared by mixing a hydroxyl ion source with a mixed solution containing a silica precursor and an alumina precursor without an organic template material, followed by milling and hydrothermal synthesis. It can be.

In the preparation method of the denitration catalyst of the present invention, step 3) may be performed by adding the crystalline zeolite and the active metal compound to the slurry of the titania-based carrier and performing an impregnation treatment.

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 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 improves catalyst poisoning caused by alkali metals, fly ash, foreign substances, etc. in thermal power plants, resulting in high denitrification performance in thermal power plants using wood pellets. has the advantage of showing

In addition, according to the method for preparing a denitration catalyst according to the present invention, by using crystalline zeolite prepared without pretreatment of zeolite and without a template material, it is advantageous in terms of economy of catalyst production, and by supporting the crystalline zeolite on the catalyst , it is possible to prepare a denitration catalyst with improved catalyst poisoning performance due to improved alkali resistance.

1 is a flowchart of a manufacturing process of a denitration catalyst according to an embodiment of the present invention.
2 shows XRD (X-ray Diffractometer) patterns of a denitration catalyst supported with mordenite and mordenite according to an embodiment of the present invention.
3 shows a FE-SEM image of mordenite according to an embodiment of the present invention.
4 is a graph showing the comparison of denitrification efficiency according to an embodiment of the present invention, before and after potassium poisoning of a denitration catalyst carrying ZSM-5 (25).
5 is a graph showing the comparison of denitrification efficiencies before and after potassium poisoning of a denitration catalyst prepared without supporting crystalline zeolite according to Comparative Example 1.

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, a crystalline zeolite and an active metal compound supported on the titania-based support.

In the denitration catalyst of the present invention, the crystalline zeolite may be included in an amount of 1.0 to 10.0% by weight, preferably 2 to 8% by weight, based on the total weight of the denitration catalyst. If the effect is insufficient, and if the content exceeds the above range, the active area of the catalyst surface may decrease due to the higher than necessary content of zeolite, resulting in a decrease in denitrification performance. In addition, despite the low-cost zeolite manufacturing technology, It is not preferable because it has the disadvantage of relatively increasing cost compared to the above method.

The crystalline zeolite is It may be at least one selected from ZSM-5, beta zeolite, L zeolite, natural zeolite, mordenite, and zeolite ion-exchanged with metal ions, such as Fe-mordenite, or zeolite supported with metal oxide.

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-based carrier;

2) preparing a crystalline zeolite without a template material;

3) supporting the crystalline zeolite and the active metal compound prepared without the template material in step 2) on the titania-based carrier in step 1);

4) Calcining the product of step 3) to prepare a denitration catalyst supported with crystalline zeolite.

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.

The active metal compound may include at least one selected from among tungsten oxide, manganese oxide, cerium oxide, molybdenum oxide, and vanadium oxide, but is not limited thereto.

In the method for preparing the denitration catalyst of the present invention, in step 2), the crystalline zeolite is prepared by mixing a hydroxyl ion source with a mixed solution containing a silica precursor and an alumina precursor without an organic template material, followed by milling and hydrothermal synthesis may include doing According to this manufacturing method, crystalline zeolite can be obtained at a low manufacturing cost. In addition, when preparing the crystalline zeolite, adding or ion-exchanging a metal oxide or metal ion may be further included. According to a preferred embodiment of the present invention, the crystalline zeolite may be prepared according to the method described in Korean Patent Registration No. 10-0996794, and the Korean Patent Registration is incorporated herein by reference in its entirety.

In the preparation method of the denitration catalyst of the present invention, step 3) may be performed by adding a slurry containing the crystalline zeolite and an active metal compound to the slurry of the titania-based carrier, and subjecting the slurry to impregnation.

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 the crystalline zeolite 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 450 to 550 ° 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 prepared without a template material and supported with crystalline zeolite and a comparative example for preparing an amorphous denitration catalyst according to the present invention. It is not limited by the examples.

Example 1

According to the manufacturing process of the denitration catalyst shown in FIG. 1, a denitration catalyst supported with ZSM-5 (25) as a crystalline zeolite prepared without a template material was prepared.

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). A tungsten precursor ((NH ₄ ) ₆ W ₁₂ O _39·X H ₂ so that 10% by weight of crystalline zeolite (ZSM-5 (25)) and tungsten oxide (WO ₃ ) are 3% by weight relative to the TiO ₂ sol After dissolving NH ₄ VO ₃ in 200 ml of distilled water so that O (Ammonium meta tungstate) and vanadium oxide are 1% by weight, the solution to which C ₂ H ₂ O ₄ was added was stirred for 2 hours to obtain Zeolite/V ₂ O ₅ WO ₃ /TiO ₂ material was prepared. The stirred Zeolite/V ₂ O ₅ WO ₃ /TiO ₂ slurry was distilled under reduced pressure to evaporate the solvent to prepare a powder, and calcined at 500° C. for 4 hours to obtain Zeolite/V ₂ O ₅ WO loaded with crystalline zeolite. A ₃ /TiO ₂ denitrification catalyst was prepared.

FIG. 4 shows a graph comparing the denitrification efficiency of the denitrification catalyst prepared in this example, the ZSM-5-supported denitrification catalyst before and after potassium poisoning.

Example 2

In the catalyst preparation step of Example 1, it was carried out in the same manner as in Example 1, except that ZSM-5 (1000) was used instead of ZSM-5 (25) as a crystalline zeolite prepared without a template material. A Zeolite/V ₂ O ₅ WO ₃ /TiO ₂ denitrification catalyst was prepared.

Example 3

In the catalyst preparation step of Example 1, except that 3 wt% of mordenite (20) was used instead of 10 wt% of ZSM-5 (25) as a crystalline zeolite prepared without a template material, A Zeolite/V ₂ O ₅ WO ₃ /TiO ₂ denitration catalyst was prepared in the same manner as in Example 1.

Example 4

In the catalyst preparation step of Example 1, Zeolite was carried out in the same manner as in Example 1, except that mordenite (20) was used instead of ZSM-5 (25) as a crystalline zeolite prepared without a template material. /V ₂ O ₅ WO ₃ /TiO ₂ A denitrification catalyst was prepared.

The XRD patterns of the mordenite 20 used in this example and the denitration catalyst supported by the mordenite 20 are shown in FIG. 2, and the FE-SEM image of the mordenite 20 is shown in FIG. 3 .

Example 5

After adding the mordenite powder to an aqueous solution of FeCl ₂ .4H ₂ O, ion exchange was performed by stirring at 60° C. for 24 hours, and the ion exchange solution was washed with distilled water. The above process was performed twice to prepare ion-exchanged Fe-mordenite (20).

In the catalyst preparation step of Example 1, Example 1, except that the Fe-mordenite (20) prepared above was used instead of ZSM-5 (25) as a crystalline zeolite prepared without a template material. Zeolite/V ₂ O ₅ WO ₃ /TiO ₂ denitrification catalyst was prepared in the same manner as in

Example 6

In the catalyst preparation step of Example 1, Zeolite was carried out in the same manner as in Example 1, except that beta zeolite (13) was used instead of ZSM-5 (25) as a crystalline zeolite prepared without a template material. /V ₂ O ₅ WO ₃ /TiO ₂ A denitrification catalyst was prepared.

Example 7

In the catalyst preparation step of Example 1, Zeolite was carried out in the same manner as in Example 1, except that natural zeolite (2.5) was used instead of ZSM-5 (25) as a crystalline zeolite prepared without a template material. /V ₂ O ₅ WO ₃ /TiO ₂ A denitrification catalyst was prepared.

Comparative Example 1

In Example 1, V ₂ O ₅ WO ₃ /TiO ₂ denitrification in powder state was carried out in the same manner as in Example 1, except that ZSM-5 (25), which is a crystalline zeolite manufactured without a template material, was not supported. A catalyst was prepared.

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

Comparative Example 2

In Example 1, except that 3% by weight of ZrO 2 was supported instead of 10% by weight of ZSM-5 (25), ZrO _{2 /} V supported with porous plate-shaped MgO was carried out in the same manner as in Example 1. ₂ O ₅ WO ₃ /TiO ₂ A denitrification catalyst was prepared.

Comparative Example 3

In Example 1, Al ₂ O _{3 /} V 2 O 5 was carried out in the same manner as in Example 1, except that 3% by weight of Al ₂ O ₃ was supported instead of 10% by weight of ZSM- ₅ (25). A WO ₃ /TiO ₂ denitrification catalyst was prepared.

[Characteristic evaluation]

1. Characteristic evaluation of denitrification catalyst

The denitration properties of the denitration catalysts prepared in Examples 1 to 7 and Comparative Examples 1 to 3 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℃.

2) K1%, K2%: As a result of poisoning the catalyst with 1% by weight and 2% by weight of potassium (K), and measuring the denitrification efficiency from 25 to 500 ° C, it means the denitrification efficiency at 380 ° C.

As shown in Table 1, the Zeolite/V ₂ O ₅ WO ₃ /TiO ₂ denitrification catalysts supported with crystalline zeolite prepared without a template material prepared in Examples according to the present invention are denitrification catalysts prepared in Comparative Examples. It can be seen that the denitration conversion rate is higher than that of the catalyst. In addition, the Zeolite/V ₂ O ₅ WO ₃ /TiO ₂ denitrification catalysts supported with crystalline zeolite prepared without a template material prepared in Examples according to the present invention have a higher denitration conversion rate than comparative examples when potassium is poisoned. It can be seen that this is remarkably high.

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 (14)

A denitration catalyst comprising a titania-based support, a crystalline zeolite and an active metal compound supported on the titania-based support. The denitration catalyst according to claim 1, wherein the crystalline zeolite is included in an amount of 1.0 to 10.0% by weight based on the total weight of the denitration catalyst. The crystalline zeolite according to claim 1, wherein the crystalline zeolite is a zeolite prepared without a template material, and includes ZSM-5, beta zeolite, L zeolite, natural zeolite, mordenite, and zeolite ion-exchanged with metal ions or metal oxides. At least one denitrification catalyst selected from supported zeolites. 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 producing the NOx removal catalyst according to any one of claims 1 to 6, comprising the following steps:
1) preparing an anatase-phase titania-based carrier;
2) preparing a crystalline zeolite without a template material;
3) supporting the crystalline zeolite and the active metal compound prepared without the template material in step 2) on the titania-based carrier in step 1);
4) Calcining the product of step 3) to prepare a denitration catalyst supported with crystalline zeolite. The method of claim 7, 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 8, 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 8, 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. The denitration catalyst according to claim 7, wherein the production of the crystalline zeolite in step 2) is performed by mixing a hydroxyl ion source with a mixed solution containing a silica precursor and an alumina precursor without an organic template material, followed by milling and hydrothermal synthesis. manufacturing method. The method of claim 7, wherein the step 3) is performed by adding the crystalline zeolite and the active metal compound to the slurry of the titania-based carrier and performing an impregnation treatment. The method of claim 12, wherein the impregnation treatment is performed in a rotary vacuum distillation machine at 150 to 200 mm bar and 80 to 100 ° C. The method of claim 7, wherein the firing in step 4) is performed at 400 to 600° C. for 1 to 10 hours.

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