KR102758432B1 - DeNOx CATALYST LOADED WITH CRYSTALLINE ZEOLITES AND METHOD FOR PREPARATION OF THE SAME - Google Patents

Abstract

The present invention relates to a denitrification catalyst for removing nitrogen oxides by a selective reduction of ammonia and a method for producing the same, and more particularly, to a titania-based denitrification catalyst supported on a crystalline zeolite, which is produced by supporting a crystalline zeolite produced without a template material on a titania-based catalyst, and a method for producing the same. The denitrification catalyst of the present invention can solve the problem of alkali metal poisoning by improving the alkaline resistance denitrification characteristics.

Description

DeNOx CATALYST LOADED WITH CRYSTALLINE ZEOLITES AND METHOD FOR PREPARATION OF THE SAME

The present invention relates to a denitrification catalyst for removing nitrogen oxides by a selective reduction of ammonia and a method for producing the same, and more particularly, to a titania-based denitrification catalyst supported on a crystalline zeolite, which is produced by supporting a crystalline zeolite produced without a template material on a titania-based catalyst, and a method for producing 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 incinerators, petrochemical plants, etc., and as a result, various harmful exhaust gases are generated by the combustion of fossil fuels, which has become a problem of air pollution. Nitrogen oxides (NOx), a representative pollutant among these combustion exhaust gases, are not only harmful to the human body, but also a major cause of environmental pollution such as photochemical smog and acid rain.

The most widely used conventional technology for removing these nitrogen oxides is the Selective Catalytic Reduction (SCR) method. The Selective Catalytic Reduction method is a denitrification method that uses ammonia as a reducing agent, mixes it with NOx, and passes it through a catalyst layer to remove it in the form of nitrogen and water vapor. Zeolite is used as a catalyst for the SCR of NOx.

However, NH3 _- SCR catalysts have problems with decreased catalytic activity and catalyst poisoning caused by alkali metals.

To solve the problems described above, various technologies have been developed for improving catalysts used in selective catalytic reduction methods. Among them, Korean Patent Publication No. 10-2019-0003863 discloses a technology for producing a catalyst by exchanging zeolite with NH4 ⁺ ions, Korean Patent Publication No. 10-2003-0046881 discloses a technology for producing a catalyst support sample by heating and acid treating natural zeolite, and Korean Patent Publication No. 10-2018-7025353 discloses a technology for producing a catalyst having high activity at a temperature of 300 ^o C or higher by directly synthesizing Fe-AEI zeolite that does not require a complexing agent.

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 do not suggest at all the technical idea that by supporting a crystalline zeolite manufactured without a template material on a catalyst, denitrification efficiency can be improved and the catalyst poisoning problem can be solved.

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

The present invention aims to provide a denitrification catalyst, particularly a denitrification catalyst that can be suitably applied to an NH ₃ -SCR denitrification process operated in a large combustion engine. In particular, the present invention aims to provide an alkali-resistant denitrification catalyst that exhibits high denitrification efficiency even when the catalyst is poisoned by including a crystalline zeolite manufactured without a template material.

In addition, the present invention aims to provide a method for producing the alkaline denitrification catalyst.

The denitrification catalyst according to the present invention is characterized by including a titania-based carrier, a crystalline zeolite supported on the titania-based carrier, and an active metal compound.

In the denitrification catalyst of the present invention, the crystalline zeolite may be included in an amount of 1.0 to 10.0 wt% relative to the total weight of the denitrification catalyst.

The above crystalline zeolite is a zeolite manufactured without a template material, and may be at least one selected from ZSM-5, beta zeolite, L zeolite, natural zeolite, mordenite, and a zeolite ion-exchanged with a metal ion or a zeolite supported with a metal oxide.

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

In the denitrification catalyst of the present invention, the active metal compound may be included in an amount of 0.1 to 10.0 wt% relative to the total weight of the denitrification catalyst.

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

The method for manufacturing a denitrification catalyst according to the present invention is characterized by including the following steps:

1) Step of preparing an anatase-phase titania carrier;

2) A step for producing crystalline zeolite without a template material;

3) a step of supporting the crystalline zeolite and active metal compound produced without the template material of step 2) on the titania-based support of step 1);

4) A step of producing a denitrification catalyst loaded with crystalline zeolite by calcining the result of step 3).

In the method for manufacturing a denitrification catalyst of the present invention, step 1) may include mixing a titanium precursor compound and distilled water, hydrolyzing the mixture, and then performing solid-liquid separation, washing, and neutralization.

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

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

The above neutralization can be performed by adjusting the pH to 7 to 8.

In the method for producing a denitrification catalyst of the present invention, in step 2), a crystalline zeolite can be produced by mixing a hydroxyl ion source into a mixed solution containing a silica precursor and an alumina precursor without an organic template material, and then performing milling and hydrothermal synthesis.

In the method for manufacturing a denitrification catalyst of the present invention, step 3) can be performed by adding the crystalline zeolite and the active metal compound to the slurry of the titania-based carrier and performing impregnation treatment.

The above impregnation treatment can be performed in a rotary vacuum distiller under conditions of 150 to 200 mmbar and 80 to 100°C.

In the method for manufacturing a denitrification catalyst of the present invention, the calcination in step 4) can be performed at 400 to 600°C for 1 to 10 hours.

The NH ₃ -SCR (Selective Catalytic Reduction) denitrification catalyst according to the present invention has the advantage of exhibiting high denitrification performance in a thermal power plant using wood pellets by improving catalyst poisoning caused by alkali metals, fly ash, foreign substances, etc. in a thermal power plant.

In addition, according to the method for manufacturing a denitrification catalyst according to the present invention, since crystalline zeolite manufactured without a template material and without pretreatment of zeolite is used, not only is it advantageous in terms of the economic aspect of catalyst manufacturing, but also, by supporting the crystalline zeolite on the catalyst, a denitrification catalyst with improved alkaline resistance and improved catalyst poisoning performance can be manufactured.

Figure 1 is a flow chart showing a manufacturing process of a denitrification catalyst according to one embodiment of the present invention.
FIG. 2 shows an XRD (X-ray Diffractometer) pattern of a denitrification catalyst and mordenite supported on mordenite according to one embodiment of the present invention.
FIG. 3 shows an FE-SEM image of mordenite according to one embodiment of the present invention.
Figure 4 is a graph comparing the denitrification efficiency of a denitrification catalyst loaded with ZSM-5 (25) before and after potassium poisoning according to one embodiment of the present invention.
Figure 5 is a graph comparing the denitrification efficiency of a denitrification catalyst manufactured without supporting a crystalline zeolite according to Comparative Example 1 before and after potassium poisoning.

The advantages and features of the present invention, and the method for achieving them, will become clear with reference to the embodiments described in detail below. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, and the present embodiments are provided only to make the disclosure of the present invention complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims.

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

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

The denitrification catalyst according to the present invention is characterized by including a titania-based carrier, a crystalline zeolite supported on the titania-based carrier, and an active metal compound.

In the denitrification catalyst of the present invention, the crystalline zeolite may be included in an amount of 1.0 to 10.0 wt%, preferably 2 to 8 wt%, based on the total weight of the denitrification catalyst. If the amount is less than the above range, the effect of supporting the zeolite is insufficient, and if the amount is more than the above range, the active area of the catalyst surface may decrease due to the unnecessary high zeolite content, which may result in a decrease in the denitrification performance. In addition, although it is a manufacturing technology for low-cost zeolite, there is a disadvantage in that the cost is relatively high compared to titania-based supports, and therefore, it is not preferable.

The above 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, it is preferable that the titania-based support has an anatase phase. Titania (TiO ₂ ) generally has three crystal structures: brookite, rutile, and anatase. Titania having an anatase crystal structure has chemical stability that does not easily react with sulfur compounds, and has superior catalytic activity compared to other phases.

In the denitrification catalyst of the present invention, it is preferable that the active metal compound is supported in an amount of 0.1 to 10.0 wt%, particularly 1 to 3 wt%, based on the total weight of the denitrification catalyst. However, if the supported amount is less than 0.1 wt%, the effect of supporting the active metal compound is insufficient, and if it exceeds 10.0 wt%, the cost for commercializing the catalyst increases, which lowers economic feasibility, and is therefore not preferable.

The above 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.

A method for manufacturing a denitrification catalyst according to the present invention may include the following steps.

1) Step of preparing an anatase-phase titania carrier;

2) A step for producing crystalline zeolite without a template material;

3) a step of supporting the crystalline zeolite and active metal compound produced without the template material of step 2) on the titania-based support of step 1);

4) A step of producing a denitrification catalyst loaded with crystalline zeolite by calcining the result of step 3).

In the method for manufacturing a denitrification catalyst of the present invention, step 1) may include mixing a titanium precursor compound and distilled water, hydrolyzing the mixture, and then performing solid-liquid separation, washing, and neutralization.

The above titanium precursor compound may be at least one selected from titanyl sulfate (TiOSO ₄ ), titanium oxychloride (TiOCl ₂ ), titanium tetrachloride (TiCl ₄ ), titanium isopropoxide (Ti{OCH(CH ₃ ) ₂ } ₄ ; TTIP), etc., but is not limited thereto, and TiOSO ₄ is particularly preferred.

The above hydrolysis can be performed 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 above neutralization can be performed by adjusting the pH to 7 to 8 by adding a basic compound such as ammonia water, and this neutralization treatment is also for the effective loading of the active metal compound thereafter.

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

In the method for producing a denitrification catalyst of the present invention, the production of crystalline zeolite in step 2) may include mixing a hydroxyl ion source into a mixed solution including a silica precursor and an alumina precursor without an organic template material, followed by milling and hydrothermal synthesis. According to this production method, crystalline zeolite can be obtained at a low production cost. In addition, the production of the crystalline zeolite may further include adding or ion-exchanging a metal oxide or a metal ion. According to a preferred specific example of the present invention, the crystalline zeolite can be produced according to the method described in Korean Patent No. 10-0996794, which is incorporated herein by reference in its entirety.

In the method for manufacturing a denitrification catalyst of the present invention, step 3) can be performed by adding a slurry containing the crystalline zeolite and an active metal compound to a slurry of the titania-based carrier and performing an impregnation treatment.

The above impregnation treatment can be performed in a rotary vacuum distiller at 150 to 200 mmbar, preferably 150 to 180 mmbar, most preferably 170 mmbar, and at 80 to 100°C, preferably 90°C, for effective impregnation.

The active metal compound loaded in step 3 above plays a role in increasing the activation temperature of the catalyst, expanding the acid site, and suppressing sintering and phase transition.

In the above step 3), there is no particular limitation on the order of supporting the crystalline zeolite and the active metal compound.

In the method for manufacturing a denitrification catalyst of the present invention, the calcination in step 4) can 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 producing a denitrification catalyst supported on a crystalline zeolite produced without a template material according to the present invention and comparative examples for producing an amorphous denitrification catalyst. However, the present invention is not limited to the following examples.

Example 1

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

Titanium sulfate (TiOSO ₄ ) After the powder was mixed with distilled water, it was hydrolyzed at 100℃ for 16 hours to prepare an anatase titania (TiO ₂ ) slurry (TiO ₂ sol) having a density of 100 to 150 g/L. For the TiO ₂ sol, 10 wt% of crystalline zeolite (ZSM-5(25)), 3 wt% of tungsten oxide (WO ₃ ) as a tungsten precursor ((NH ₄ ) ₆ W ₁₂ O _39·X H ₂ O (Ammonium meta tungstate)) and 1 wt% of vanadium _oxide were dissolved in 200 ml of distilled water, and then C ₂ H ₂ O ₄ was _added . The solution was stirred for 2 hours to prepare a Zeolite/V ₂ O ₅ WO ₃ /TiO ₂ material. The Zeolite/V ₂ O ₅ WO ₃ /TiO ₂ slurry, after stirring, was distilled under reduced pressure to evaporate the solvent to produce a powder, which was then calcined at 500°C for 4 hours to produce a Zeolite/V ₂ O ₅ WO ₃ /TiO ₂ denitrification catalyst loaded with crystalline zeolite.

A graph comparing the denitrification efficiency of the ZSM-5-loaded denitrification catalyst manufactured in this example before and after potassium poisoning is shown in Figure 4.

Example 2

In the catalyst preparation step of Example 1, a Zeolite/V 2 O 5 WO 3 /TiO 2 denitrification catalyst was prepared in the same manner as in Example 1, except that ZSM-5 (1000) was used instead of ZSM-5 ( _{25 )} , which was a crystalline zeolite prepared without a _template material, as a _support .

Example 3

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

Example 4

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

The XRD pattern of the mordenite (20) used in this example and the denitrification catalyst loaded with the mordenite (20) is shown in Fig. 2, and the FE-SEM image of the mordenite (20) is shown in Fig. 3.

Example 5

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

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

Example 6

In the catalyst preparation step of Example 1, a Zeolite/V 2 O 5 WO 3 /TiO 2 denitrification catalyst was prepared in the same manner as in Example 1, except that beta zeolite (13) was used as a support instead of _ZSM - ₅ ( _{25 )} , which is a crystalline zeolite prepared without a template material.

Example 7

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

Comparative Example 1

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

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

Comparative Example 2

In Example 1, a ZrO ₂ /V 2 O 5 WO 3 /TiO 2 denitration catalyst loaded with porous plate-like MgO was manufactured in the same manner as in Example 1, except that ₃ wt% of ZrO ₂ was loaded instead of ₁₀ wt _% of ZSM- ₅ (25).

Comparative Example 3

In Example 1, an Al ₂ O ₃ /V ₂ O ₅ WO 3 /TiO 2 denitration catalyst was manufactured in the same manner as in Example 1, except that ₃ wt% of Al ₂ O ₃ was supported instead of ₁₀ wt% of ZSM-5 (25).

[Characteristic evaluation]

1. Evaluation of the characteristics of the denitrification catalyst

The denitrification characteristics of the denitrification catalysts manufactured in Examples 1 to 7 and Comparative Examples 1 to 3 It was evaluated as follows.

_N2 gas was used as a balance gas, the concentrations of NOx and _NH3 gases were fixed at 300 ppm, and the reaction ratio of NOx and _NH3 was 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 fixed layer for removing NOx was maintained at a space velocity of 60,000 (hr ^-1 ), and a powder fixed layer was formed using ceramic wool by adjusting the catalyst amount according to the space velocity. The evaluation method was to install the catalyst on the reactor, and then flow _N2 , _O2 , NO, and _NH3 gases to stabilize until the expected concentration became constant. The NOx removal efficiency was observed by observing the change in NOx concentration at a heating rate of 5°C/min from 25°C to 500°C.

The results of evaluating the denitrification characteristics of denitrification catalysts according to examples and comparative examples are shown in Table 1 below.

Note): 1) Denitrification conversion rate: Refers to the denitrification efficiency at 380℃.

2) K1%, K2%: The catalyst was poisoned with 1 wt% and 2 wt% of potassium (K), respectively, and the denitrification efficiency was measured from 25 to 500°C. This refers to the denitrification efficiency at 380°C.

As shown in Table 1 above, it can be seen that the Zeolite/V ₂ O ₅ WO ₃ /TiO ₂ denitrification catalysts supported on a crystalline zeolite manufactured without a template material in the examples according to the present invention have a higher denitrification conversion rate than the denitrification catalysts manufactured in the comparative examples. In addition, it can be seen that the Zeolite/V ₂ O ₅ WO ₃ /TiO ₂ denitrification catalysts supported on a crystalline zeolite manufactured without a template material in the examples according to the present invention have a significantly higher denitrification conversion rate than the comparative examples when potassium is poisoned.

As confirmed by the above results, the denitrification catalyst according to the present invention is an alkaline-resistant denitrification catalyst, and thus has excellent resistance to poisoning by alkali metals in the NH ₃ -SCR denitrification process operated in a biomass thermal power plant, thereby enabling the catalytic activity site to be maintained for a longer period of time, thereby improving economic efficiency.

Claims (14)

A denitrification catalyst comprising a titania-based support, a crystalline zeolite supported on the titania-based support, and an active metal compound, wherein the crystalline zeolite is selected from mordenite, beta zeolite, and natural zeolite, and the active metal compound is tungsten oxide and vanadium oxide. In the first paragraph, the denitrification catalyst is comprised of the crystalline zeolite in an amount of 1.0 to 10.0 wt% relative to the total weight of the denitrification catalyst. delete In the first paragraph, the titania-based support is a denitrification catalyst which is an anatase-phase titania (TiO ₂ ) support. In the first paragraph, a denitrification catalyst, wherein the active metal compound is contained in an amount of 0.1 to 10.0 wt% relative to the total weight of the denitrification catalyst. delete A method for producing a denitrification catalyst according to claim 1 or claim 2 or claim 4 or claim 5, comprising the following steps:
1) Step of preparing an anatase-phase titania carrier;
2) A step of producing a crystalline zeolite selected from mordenite, beta zeolite and natural zeolite without a template material;
3) A step of supporting the crystalline zeolite produced without the template material of step 2) and tungsten oxide and vanadium oxide as active metal compounds on the titania-based support of step 1);
4) A step of producing a denitrification catalyst loaded with crystalline zeolite by calcining the result of step 3). In claim 7, step 1) is a method for producing a denitrification catalyst including mixing a titanium precursor compound and distilled water, hydrolyzing the mixture, and then performing solid-liquid separation, washing, and neutralization. A method for producing a denitrification catalyst in 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 . A method for producing a denitrification catalyst in 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. In the 7th paragraph, the production of the crystalline zeolite in the step 2) is a method for producing a denitrification catalyst, which is performed by mixing a hydroxyl ion source into a mixed solution containing a silica precursor and an alumina precursor without an organic template material, and then milling and hydrothermal synthesis. In the 7th paragraph, the step 3) is a method for producing a denitrification catalyst, which 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. A method for producing a denitrification catalyst in claim 12, wherein the impregnation treatment is performed under conditions of 150 to 200 mmbar and 80 to 100°C in a rotary vacuum distiller. A method for producing a denitrification catalyst in claim 7, wherein the calcination in step 4) is performed at 400 to 600°C for 1 to 10 hours.