KR101022247B1 - Catalyst for simultaneous reduction of N2O and NOX and its preparation method - Google Patents

Abstract

The present invention is a catalyst for the simultaneous reduction of nitrous oxide (N ₂ O) and nitrogen oxides (NO _x ), characterized in that it comprises a zeolite loaded with iron (Fe) and potassium (K), a method for preparing the catalyst and the catalyst It relates to a method for simultaneously removing nitrous oxide (N ₂ O) and nitrogen oxides (NO _x ) using.

Catalyst for simultaneous reduction of zeolite support, iron (Fe), potassium (K), nitrous oxide (N2O) and nitrogen oxides (NOx)

Description

Catalyst for simultaneous reduction of N2O and NOX and its manufacturing method {CATALYST FOR REDUCING N2O AND NOx AND METHOD FOR PREPARING THE SAME}

The present invention relates to a catalyst for the simultaneous reduction of N ₂ O and NO _x , a method for preparing the same and a method for removing N ₂ O and NO _x using the same.

Many processes, for example combustion processes or industrial production processes of nitric acid, produce exhaust gases carrying nitrogen monoxide (NO), nitrogen dioxide (NO ₂ ) and nitrous oxide (N ₂ O). NO and NO ₂ have long been recognized as compounds with ecologically detrimental effects (acid ratio, smog formation), their maximum allowable emission limits are set worldwide, and nitrous oxide is the decomposition and stratification effect of stratospheric ozone. Environmental protection has been increasingly focused on nitrous oxide in recent years as it has a significant impact on the environment. Thus, for environmental protection reasons many possible methods for the separate removal of N ₂ O and NO _x with NO _x emissions are already known.

The NO _x concentration is reduced mainly by the method involving catalytic reduction of NO _x using various reducing agents, zeolite catalysts have often been used. Apart from Cu-containing zeolites, Fe-containing zeolites have particular advantages in practical applications. The reducing agent used is mainly ammonia [see US Pat. No. 5,451,387] or hydrocarbons [see Feng, K and WK Hall in Journal of catalysis 166, pp. 368-376 (1997)].

Japanese Laid-Open Patent Publication No. 7-060126 also describes a catalyst for reducing N ₂ O to NH ₃ in the presence of a Fe containing zeolite of pentasil type (MFI). However, thermal stability of the catalyst is particularly required since industrially usable decomposition rates are only achieved at temperatures above 450 ° C.

US-A-4571329 discloses a priority to promote the reaction of NH ₃ with NO _x by forming the H ₂ O N _2, and also promoting the reaction of NH ₃ to N ₂ O in the following to form the H ₂ O and N ₂ A method of reducing NO _x and N ₂ O with ammonia in the presence of a Fe substituted zeolite catalyst is disclosed. Catalysts mentioned as suitable are zeolites which are iron substituted from the group consisting of mordenite (MOR), clinoptilolite (NZ), faujasite and zeolite Y.

The decomposition of N ₂ O using a catalyst is classified into high temperature, medium temperature, and low temperature according to the temperature. Among them, the high temperature treatment method decomposes N ₂ O in a temperature range of about 550 ° C. or higher without introducing a reducing agent. In addition, the selective catalytic reduction (SCR) method that is effectively decomposed at around 450 ℃ when the reducing agent is injected is mainly used in the existing chemical manufacturing process.

In the case of NO _x , a method of injecting and removing a reducing agent by the SCR method has been widely used. The reaction temperature is about 300 to 400 ° C., and as the temperature is increased, the removal efficiency of NO _x is known to decrease. Recently, researches to increase the activity of the low temperature part for the removal of N ₂ O and NO _x are in progress in each country, in particular efforts to increase the activity of the low temperature part is underway.

The N ₂ O decomposition catalyst, which has been invented at home and abroad, has been used as an SCR method of injecting a reducing agent. NO _x The SCR method has already been proven in commercial processes. There is no case where the technology of simultaneously reducing N ₂ O and NO _x is applied in one reactor, and it is only a basic test step at home and abroad. Among them, the SCR technique is known to be effective for the simultaneous reduction of N ₂ O and NO _x , but this is usually when ammonia is used as a reducing agent, and when ammonia is used as a reducing agent, the reaction temperature ranges of NO _x and N ₂ O are different. There are many difficulties in the reduction. Therefore, it was determined that the development of a reducing agent capable of replacing ammonia as well as the development of a new catalyst is necessary.

The prior art has a problem in that the catalytic reaction conditions (reaction temperature and injection conditions of the reducing agent, etc.) of each of NO _x and N ₂ O are different, so that the catalyst reactor must be removed in two stages. In particular, Patent Application No. 2002-7009062 discloses a method for removing NO _x by decomposing N ₂ O in the first stage and injecting ammonia in the second stage by providing the catalyst layer in two stages. Patent application 2003-7011939 No. discloses a method for removing N ₂ O and NO _x using ammonia as a reducing agent using an iron-supported zeolite catalyst below 450 ° C., and patent application 2004-7020303 describes two catalyst beds made of zeolite. A method of decomposing N ₂ O and NO _x by decomposing N ₂ O in the first stage and injecting a reducing agent in the second stage is disclosed. This is because the optimum decomposition temperature of N ₂ O and NO _x is different, it appears that there is a need to develop a condition or catalyst to meet the optimum temperature.

In particular, when ammonia is used as the reducing agent, not only the handling of the reducing agent is easy, but also the need for another reducing agent is additionally required because the reaction temperature range of N ₂ O and NO _x is different.

An object of the present invention is a catalyst capable of simultaneously reducing N ₂ O and NO _x in one selective catalytic reduction (SCR) reaction tower, a method for preparing such a catalyst, and a method for simultaneously removing N ₂ O and NO _x using the same. To provide.

In accordance with the above object, the present invention provides a catalyst for the simultaneous reduction of nitrous oxide (N ₂ O) and nitrogen oxides (NO _x ) comprising a zeolite bearing iron (Fe) and potassium (K).

According to a preferred embodiment of the present invention, the zeolite is preferably selected from the group consisting of pentasil (MFI) zeolite, mordenite (MOR) zeolite, clinoptilolite natural (NZ) zeolite and mixtures thereof.

It is also preferred that Fe is 0.1 to 10.0% by weight based on the total weight of the catalyst, and K is 0.1 to 10.0% by weight based on the total weight of the catalyst.

In addition, the present invention comprises the steps of preparing a zeolite; Supporting Fe in the zeolite; Supporting K on the Fe-supported zeolite; And it provides a method for producing a catalyst for the simultaneous reduction of nitrous oxide (N ₂ O) and nitrogen oxides (NO _x ) comprising the step of drying and calcining the Fe and K-supported zeolite.

According to a preferred embodiment of the present invention, the zeolite is preferably selected from the group consisting of pentasil (MFI) zeolite, mordenite (MOR) zeolite, clinoptilolite natural (NZ) zeolite and mixtures thereof.

In addition, the zeolite can be supported by ion exchange by a method of supporting Fe, and the impregnation method can be used as a method of supporting K on a Fe-supported zeolite.

According to a preferred embodiment of the present invention, it is preferable that Fe is 0.1 to 10.0% by weight based on the total weight of the catalyst, and K is 0.1 to 10.0% by weight based on the total weight of the catalyst.

In addition, the present invention comprises reacting the catalyst prepared by the production method with a gas containing nitrous oxide (N ₂ O) and nitrogen oxides (NO _x ), nitrous oxide (N ₂ O) and nitrogen oxides (NO _x ) provides a method of simultaneous removal.

According to a preferred embodiment of the present invention, the reaction is preferably carried out in the presence of a reducing agent selected from the group consisting of CH ₄ , C ₃ H ₆ , C ₃ H ₈ , NH ₃ and mixtures thereof.

In addition, it is preferable that the said reaction is performed at 400 degrees C or less.

Since the catalyst according to the present invention can reduce N ₂ O and NO _x simultaneously in one SCR reaction tower, it can be usefully used not only in N ₂ O and NO _x generation sites but also in simultaneous generation sites. It is expected to be applicable to combustion facilities and chemical manufacturing facilities.

Hereinafter, the present invention will be described in more detail.

The catalyst of the present invention includes a zeolite carrying iron and potassium.

The zeolite that can be used as the zeolite support of the present invention is preferably selected from the group consisting of pentasil (MFI) zeolite, mordenite (MOR) zeolite, clinoptilolite natural (NZ) zeolite and mixtures thereof, Most preferably, it is a MOR zeolite. At this time, the ratio of SiO ₂ / Al ₂ O ₃ of the zeolite carrier is preferably 13 to 90.

Iron (Fe) is preferably supported on the zeolite by ion exchange, the iron is preferably 0.1 to 10.0% by weight based on the total weight of the catalyst.

Potassium (K) is preferably supported on the iron-supported zeolite by the impregnation method, the potassium is preferably 0.1 to 10.0% by weight based on the total weight of the catalyst.

The catalyst bed using the catalyst of the invention can be constructed in any way. For example, it may be in the form of a tube reactor or a radial basket reactor. The manner in which the gas reducing agent is introduced into the gas stream to be treated can also be freely chosen as long as it is done upstream of the reaction zone.

In the method for preparing a catalyst according to the present invention, an industrially available zeolite support is prepared, preferably washed and dried three times or more, and an ion exchange step for supporting iron in the zeolite support and after drying, iron is supported. It may be composed of an impregnation step and a drying / baking step for supporting potassium in the zeolite carrier. First, the zeolite carrier is preferably prepared by washing the first distilled distilled water with tertiary distilled water passed through an ion exchange filter or a hollow fiber membrane filter at least three times and then drying. Then, iron is supported on the zeolite for at least 6 hours, preferably 4 hours at a temperature of 60 to 90 ° C, preferably 70 to 80 ° C for ion exchange of iron, which is a transition metal. Thereafter, the zeolite carrier is dried at a temperature of about 100 to 120 ° C, preferably about 105 to 115 ° C for at least 24 hours, preferably at least 12 hours. Next, after impregnating potassium on the iron-supported zeolite carrier by using a rotary evaporator, at a temperature of 100 to 120 ° C., preferably 105 to 115 ° C., at least 24 hours, preferably at least 12 hours. It is dried and calcined at 450 to 550 ° C. or higher, preferably at 500 ° C. or higher for 3 to 5 hours or more, preferably 4 hours or more to prepare a Fe—K-zeolite carrier catalyst. In this case, iron and potassium as precursors of the active material may include anion composed of NO ₃ ⁻ , Cl ⁻ , CO ₃ ^−, and SO ₄ ⁻ .

The method of removing nitrous oxide (N ₂ O) and nitrogen oxides (NO _x ) by the selective catalytic reduction method using the catalyst according to the present invention is a catalyst according to the present invention 200 to 500 ℃, preferably with nitrous oxide and nitrogen oxides, preferably Preferably it is carried out by contacting at a reaction temperature of 300 to 400 ℃ and a space velocity of 10,000 to 20,000 h ^-1 . In addition, nitrogen dioxide and nitrogen oxides may be removed by further using a reducing agent commonly used in the reaction. In this case, the reducing agent to be injected may be selected from the group consisting of CH ₄ , C ₃ H ₆ , C ₃ H ₈ , NH ₃ and mixtures thereof, and the concentration of the reducing agent may be 300 to 3,000 ppm.

Hereinafter, the present invention will be described in detail by way of examples. However, the following examples are illustrative of the present invention, and the present invention is not limited to the following examples.

Comparative Example 1

The zeolite carrier was prepared by first washing distilled water obtained by distilling the first industrially available NZ zeolite (Kwangpyo Chemical) with tertiary distilled water through an ion exchange filter or a hollow fiber membrane filter and drying at least three times. Thereafter, 0.1 N of iron was supported on NZ zeolite for 4 hours at a temperature of 70 to 80 ° C. for iron ion exchange. The NZ zeolite was dried at 105 ° C. and calcined at 500 ° C. for at least 4 hours to produce a Fe-NZ catalyst.

Comparative Example 2

A Fe-MOR catalyst was prepared in the same manner as in Preparation Example 1, except that MOR zeolite (Zeolyst, Sud-chemi) was used instead of NZ zeolite.

Comparative Example 3

A Fe-MFI catalyst was prepared in the same manner as in Preparation Example 1, except that MFI zeolite (Zeolyst, Sud-chemi) was used instead of NZ zeolite.

Example

A zeolite carrier was prepared by first washing distilled water obtained by distilling MOR zeolite (Zeolyst, Sud-chemi) first with distilled water passed through an ion exchange filter or a hollow fiber membrane filter at least three times. Thereafter, 0.1 N of iron was supported on MOR zeolite for 4 hours at a temperature of 70 to 80 ° C. for iron ion exchange. Thereafter, MOR zeolite was dried at 105 DEG C for at least 12 hours, and potassium was impregnated using a rotary evaporator, followed by further drying at 105 DEG C for at least 12 hours, and calcining at 500 DEG C for at least 4 hours to form Fe-. K-MOR catalyst was prepared.

Experimental Example 1

Removal rates of nitrous oxide and nitrogen oxides were tested using the catalysts prepared according to Comparative Examples 1 to 3 and Examples. 1,000 ppm of N ₂ O, NO _x and 2,000 ppm of reducing agent (CH ₄ , C ₃ H ₆ , C ₃ H ₈ or NH ₃ ) were injected into the reaction tower together with the catalysts prepared according to Comparative Examples 1 to 3 and Examples. And a reaction temperature of 350 ° C. and a space velocity of 10,000 to 20,000 h ⁻¹ .

Table 1 shows the conversion of N ₂ O and NO _x . Table 1 (a) is the conversion of NO _x and (b) means the conversion of N ₂ O.

Experimental Example  2

Except that the reaction temperature was 400 ℃ was carried out in the same manner as in Experiment 1 to test the removal rate of nitrous oxide and nitrogen oxides.

Table 2 shows the conversion of N ₂ O and NO _x . (A) of Table 2 is the conversion rate of NO _x and (b) means the conversion rate of N ₂ O.

As shown in Experimental Examples 1 and 2, it can be seen that the Fe-K-MOR catalyst according to the embodiment of the present invention has a high conversion rate for N ₂ O as well as for NO _x , unlike the catalysts according to Comparative Examples 1 to 3. . In addition, the conversion rate is higher than other catalysts even at a low temperature of 350 ℃, especially in the presence of C ₃ H ₆ and C ₃ H ₈ reducing agent, both NO _x and N ₂ O can be seen that more than 70% removal rate. In addition, in the case of 400 ℃, both NO _x and N ₂ O exhibits a removal rate of 95% or more, showing that the catalyst of the present invention is more effective in simultaneous removal of NO _x and N ₂ O than other catalysts.

1 is a view showing the conversion of N ₂ O and NO _x according to the temperature change when using C ₃ H ₆ as a reducing agent.

2 is a view showing the conversion of N ₂ O and NO _{x with} temperature change when using C ₃ H ₈ as a reducing agent.

Claims (13)

Nitrous oxide (N ₂ O) and nitrogen oxides (NO _x ) comprising zeolite loaded with iron (Fe) and potassium (K), and containing potassium (K) in an amount of 0.1 to 10.0 wt% based on the total weight of the catalyst. ) Co-reduction catalyst. The method of claim 1, Nitrous oxide (N ₂ O) and nitrogen characterized in that the zeolite is selected from the group consisting of pentasil (MFI) zeolite, mordenite (MOR) zeolite, clinoptilolite natural (NZ) zeolite and mixtures thereof Oxide (NO _x ) co-reduction catalyst. The method of claim 1, A catalyst for the simultaneous reduction of nitrous oxide (N ₂ O) and nitrogen oxides (NO _x ), characterized in that iron (Fe) is 0.1 to 10.0% by weight based on the total weight of the catalyst. delete Preparing a zeolite; Supporting iron (Fe) on the zeolite; Supporting potassium (K) in the iron (Fe) -supported zeolite at 0.1 to 10.0 wt% based on the total weight of the catalyst; And Method for producing a catalyst for the simultaneous reduction of nitrous oxide (N ₂ O) and nitrogen oxides (NO _x ) comprising the step of drying and calcining the iron (Fe) and potassium (K) -supported zeolite. The method of claim 5, Nitrous oxide (N ₂ O) and nitrogen, characterized in that the zeolite is selected from the group consisting of pentasil (MFI) zeolite, mordenite (MOR) zeolite, clinoptilolite natural (NZ) zeolite and mixtures thereof Oxide (NO _x ) co-reduction catalyst production method. The method of claim 5, A method for the simultaneous reduction of nitrous oxide (N ₂ O) and nitrogen oxides (NO _x ), wherein iron (Fe) is supported on zeolite by ion exchange. The method of claim 5, A method for preparing a catalyst for simultaneously reducing nitrous oxide (N ₂ O) and nitrogen oxides (NO _x ), characterized by impregnating potassium (K) on an iron (Fe) -supported zeolite. The method of claim 5, Iron (Fe) is 0.1 to 10.0% by weight based on the total weight of the catalyst nitrous oxide (N ₂ O) and nitrogen oxides (NO _x ) simultaneous reduction catalyst production method. delete Any one of claims 1 to, nitrous oxide (N ₂ O) and nitrogen oxides (NO, which comprises a gas and the reaction containing the nitrous oxide (N ₂ O) and nitrogen oxides (NO _x) to any one of the catalyst of 3 _x ) Simultaneous removal method. The method of claim 11, wherein The reaction is carried out in the presence of a reducing agent selected from the group consisting of CH ₄ , C ₃ H ₆ , C ₃ H ₈ , NH ₃ and mixtures thereof Nitrous oxide (N ₂ O) and nitrogen oxides (NO _x ) Simultaneous removal method. The method of claim 11, wherein Simultaneous removal of nitrous oxide (N ₂ O) and nitrogen oxides (NO _x ), characterized in that the reaction is carried out at 400 ℃ or less.

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