KR20140095512A - Catalyst composition and method for use in selective catalytic reduction of nitrogen oxides - Google Patents

Abstract

A catalyst composition for selective reduction and soot oxidation of nitrogen oxides comprising at least one acidic zeolite or a physical mixture of at least one redox active metal compound and a selective reduction and soot oxidation of nitrogen oxides by use of the catalyst composition .

Description

TECHNICAL FIELD The present invention relates to a catalyst composition for use in selective catalytic reduction of nitrogen oxides, and more particularly to a catalyst composition and method for use in selective catalytic reduction of nitrogen oxides.

The present invention relates to a catalyst composition for use in the selective reduction of nitrogen oxides in off-gas by reaction with ammonia or its precursors.

Catalysts for the selective reduction of nitrogen oxides (NOx) by NH ₃ -SCR, i. E. The use of ammonia as reducing agent, are well known in the art. These catalysts include zeolitic materials optionally catalyzed by copper or iron.

The problem to be solved by the present invention is to provide a catalyst composition and method for the reduction of nitrogen oxides having DeNOx activity at reaction temperatures of 150-550 ° C.

The off-gas from the lean-burn engine contains hydrocarbons, CO and soot particles in addition to NOx, which can be reduced or eliminated by catalytic oxidation. As a result, the catalyst compositions and methods of the present invention should further include soot and hydrocarbon oxidation activity simultaneously with DeNOx activity.

Our recent work has revealed some examples of synergistic effects in composite catalysts prepared by mechanical mixing of acidic zeolite or zeotype powder with redox active metal compounds.

We have found that a catalyst composition comprising at least one acidic zeolite or zeotype component physically mixed with at least one redox active metal compound is obtained by selective reduction of nitrogen oxides contained in the off-gas and oxidation of hydrocarbons, CO and soot ≪ / RTI > activity.

As used herein, the term " redox active metal compound "refers to a metal compound that can be reversibly oxidized and reduced in terms of changes in the oxidation state, or the oxidation number of metal atoms or compounds.

In accordance with the above discovery, the present invention provides a method of forming a thin film of at least one redox selected from the group consisting of Cu / Al ₂ O ₃ , Mn / Al ₂ O ₃ , CeO ₂ -ZrO ₂ , Ce-Mn / Al ₂ O _3, For selective reduction and soot oxidation of nitrogen oxides comprising at least one acidic zeolite or zeotext component selected from the group consisting of BEA, MFI, FAU, FER, CHA, MOR, or mixtures thereof physically mixed with an active metal compound Lt; / RTI >

Catalyst compositions prepared by mechanical mixing of the redox metal components with the above-mentioned zeolite or zeotype materials admixed in accordance with the present invention exhibit pronounced synergistic effects. The DeNOx activity of these complex catalysts significantly exceeds the activity of their individual components.

The acidic zeolite or zeotype component can be used in the form of protons, or can be promoted with Fe.

Preferably, the weight ratio between the zeolite component and the redox component is from 1: 1 to 1:50.

In one embodiment of the invention, the redox components are _{Al 2 O 3, TiO 2,} SiO 2, Ce0 2, Zr0 2 or is dispersed on a support selected from the group consisting of a mixture thereof.

According to the present invention, it is generally preferred that the average molar ratio Si / Al of the zeolite component is 5 to 100.

The catalyst compositions described above according to the present invention can be used as coatings or as coatings on structures of metals, ceramics, metal oxides, SiC or silica materials or fibers.

Accordingly, the present invention also provides a monolith structure coated with a catalyst composition according to any of the above disclosed embodiments of the present invention.

The monolith structure is preferably made of a metal, ceramic, metal oxide, SiC or silica fiber material.

The monolith structure may be in the form of a particle filter, for example a honeycomb structured filter or a wallflow filter.

In a further embodiment, the catalyst composition is coated on the structure in parallel with two or several separate catalyst layers in series or as two or several catalyst layers, wherein the layers have different composition and layer thicknesses.

Specific advantages obtained from the present invention are as follows:

1) Addition of CeO ₂ -ZrO ₂ , Cu / Al ₂ O ₃ , Mn / Al ₂ O ₃ or Ce-Mn / Al ₂ O _{3 to} the protonic or iron-promoted acidic zeolite or zeotype, to thereby significantly improve the DeNOx activity in the _reaction without increasing T <250 ℃. In this case, the total volume of the catalyst is increased by the volume of the redox component added.

2) Alternatively or in addition, the amount of the expensive zeolite / zeotype component in the composite catalyst can be significantly reduced by substituting the equivalent volume of the redox component. In this case, the total volume of the catalyst is kept constant, but the amount of zeolite component can be reduced by 2-5 times without noticeable sacrifice of DeNOx performance. Ce-Mn / Al ₂ 0 _3, when the component is used in the catalyst preparation in spite of a reduced amount of zeolite component and a remarkable improvement of the NOx conversion noted in _reaction T <250 ℃ is observed.

3) In addition to advantageous DeNOx activity, [Ce0 ₂ -Zr0 ₂ + zeolite / fifth type] or _{[Ce-Mn / Al 2 0} 3 + zeolite / fifth type] The composition shows a significant soot oxidation activity, which these one-piece DeNOx Making it a promising candidate for the development of the DeSoot catalyst system.

4) In addition to advantageous DeNOx activity, [Ce0 ₂ -Zr0 ₂ + zeolite / fifth type] or _{[Ce-Mn / Al 2 0} 3 + zeolite / fifth type; composition at high temperatures is significantly more due to selective oxidation of excess ammonia Low ammonium slip.

The present invention further relates to a method for producing a composite oxide comprising at least one redox active metal compound selected from the group consisting of Cu / Al ₂ O ₃ , Mn / Al ₂ O ₃ , CeO ₂ -ZrO ₂ , Ce-Mn / Al ₂ O _3, Contacting the catalyst composition comprising at least one acidic zeolite or zeotext component selected from the group consisting of BEA, MFI, FAU, FER, CHA, MOR or mixtures thereof physically mixed with off-gas in the presence of ammonia A method for selective reduction of nitrogen oxides contained in the off-gas and oxidation of the soot.

The acidic zeolite or zeotype component can be used in the form of protons, or can be promoted with Fe.

In one embodiment of the method according to the invention, the at least one redox active metal compound is dispersed on a support selected from the group consisting of Al ₂ O ₃ , TiO ₂ , SiO ₂ , CeO ₂ , ZrO ₂ or mixtures thereof .

In another embodiment of the process according to the invention, the catalyst composition is contacted with the off-gas at a temperature of 250 DEG C or less.

In a further embodiment of the process according to the invention, the excess of ammonia is selectively oxidized to nitrogen by contact with the catalyst composition.

Example

Example  One

Ce0 ₂ -Zr0 ₂ + H- beta zeolite synergistic effect in the NH ₃ -DeNOx on the catalyst composition.

74 wt% CeO ₂ - 26 wt% ZrO ₂ powder was thoroughly mixed with H-beta zeolite at a weight ratio of 10 to prepare a [CeO ₂ -ZrO ₂ + H-beta zeolite] composite catalyst. The weight ratio of components results in a volume ratio of _{Ce0 2 -Zr0 2 / H-Beta} = 3/1 due to the density difference between these materials. The powder was completely ground in an agate mortar bowl for 10-15 minutes and then pelleted. The pellets were broken and sieved to collect 0.2-0.4 mm fractions for catalyst testing. 74 wt% CeO ₂ - 26 wt% ZrO ₂ , H-beta, and Fe-beta zeolite similarly made of pellets were used as reference samples.

The catalyst was tested in NH ₃ -DeNOx at a temperature range of 150-550 ° C. The test was carried out under the following conditions: 2 ℃ / min speed to reduce the reaction temperature, the feed gas composition: to the _{500ppm NO, 540ppm NH 3, 10} vol% O 2, 6 vol% H 2 O, the rest to the N ₂ A total flow rate of 300 mL / min was obtained.

Catalyst loading and GHSV obtained:

0.197 g 74 wt% CeO ₂ -ZrO ₂ + 0.02 g H-beta zeolite, catalyst volume 0.134 ml, GHSV = 135 000 h ^-1 .

In these conditions Ce0 ₂ -Zr0 ₂ + H- beta zeolite composite catalyst showed the DeNOx activity, which substantially separately _{74wt% Ce0 2 -Zr0 2 (0.131g} Ce0 2 -Zr0 2, catalyst volume 0.067 ml, GHSV = 270,000 h ^-1 ) and H-beta zeolite (0.04 g, catalyst volume 0.067 ml, GHSV = 270 000 h ^-1 ), which is clearly synergistic between the components of the composite catalyst as shown in Figure 1 Effect.

NOx conversion on composite catalysts is similar to NOx conversion on commercial Fe-Beta zeolite (Fe-Beta) at 230-550 ° C and exceeds NOx conversion on Fe-Beta at 150-200 ° C.

Example  2

T _reaction <at _{250 ℃ [Ce0 2 -Zr0 2 +} Fe- beta] DeNOx increase the performance of the composite catalyst.

Was prepared by thoroughly grinding 26wt% Zr0 ₂ and Fe- beta zeolite powder - [Ce0 ₂ -Zr0 ₂ + Fe- zeolite beta] two samples of 74wt% Ce0 ₂ of the composite catalyst.

The first sample was prepared by mixing 74 wt% CeO ₂ - 26 wt% ZrO ₂ and Fe-beta zeolite powder in a weight ratio of 3.3. At this weight ratio, the volume ratio of 74 wt% CeO ₂ -26 wt% ZrO ₂ / Fe-beta component in the composite catalyst is 1/1. The second sample was prepared by mixing 74 wt% CeO ₂ - 26 wt% ZrO ₂ and Fe-beta powder in a weight ratio of 10. In the case of the second sample, the volume ratio of 74 wt% CeO ₂ -26 wt% ZrO ₂ / Fe-beta component is equal to 3/1.

The mixture was ground for 10-15 minutes in an agate mortar and pelletized. The pellets were broken and sieved to collect 0.2-0.4 mm fractions for catalyst testing. Similarly, Fe-beta zeolite made from pellets was used as a reference.

The activity of the prepared sample was tested using the following catalyst loading, the amount of Fe-beta zeolite component in the reactor being kept constant:

A first sample of a 1/1 volume ratio _{composition: [0.065g 74% Ce0 2 -Zr0} 2 + 0.02g Fe- beta zeolite;

Second sample of 3/1 volume component ratio: [0.197 g 74% CeO ₂ -ZrO ₂ + 0.02 g Fe-beta zeolite];

Reference sample: 0.02 g Fe-beta zeolite.

The catalyst was tested in NH ₃ -DeNOx at a temperature range of 150-550 ° C. The test was carried out under the following conditions: 2 ℃ / min speed to reduce the reaction temperature, the feed gas composition: to the _{500ppm NO, 540ppm NH 3, 10} vol% O 2, 6 vol% H 2 O, the rest to the N ₂ A total flow rate of 300 mL / min was obtained.

Catalyst loading and GHSV obtained:

0.197 g 74 wt% CeO ₂ -ZrO ₂ + 0.02 g Fe-beta zeolite, catalyst volume 0.134 ml,

GHSV = 135 000 h ^-1 ;

[0.065 g 74 wt% CeO ₂ -ZrO ₂ + 0.02 g Fe-beta zeolite], catalyst volume 0.067 ml, GHSV = 270 000 h ^-1 ;

0.02 Fe-beta zeolite, catalyst volume = 0.034 ml, GHSV = 540 000 h ^-1 .

In these test conditions [Ce0 ₂ -Zr0 ₂ + Fe- zeolite beta] complex catalyst showed the DeNOx activity increase in the low temperature range (150-300 ℃), which, as shown in Fig. 2 individually Fe- beta zeolite Activity significantly exceeded. Ce0 ₂ -Zr0 It is important to note that when the amount of the _second component increases the activity of the _[2 + Ce0 ₂ -Zr0 Fe- zeolite beta] improved.

Example  3

Wherein the amount of zeolite component is reduced.

It was prepared by thoroughly grinding 26wt% Zr0 ₂ powder and a zeolite powder Fe- beta - [Ce0 ₂ -Zr0 ₂ + Fe- zeolite beta] Three samples of a composite catalyst 74wt% Ce0 _2.

The first sample was prepared by mixing 74 wt% CeO ₂ - 26 wt% ZrO ₂ and Fe-beta powder in a weight ratio of 3.3. In this weight ratio, the volume ratio of 74 wt% CeO ₂ -26 wt% ZrO ₂ / Fe-beta zeolite is equal to 1/1.

The second sample was prepared by mixing 74 wt% CeO ₂ - 26 wt% ZrO ₂ and Fe-beta zeolite powder at a weight ratio of 15.5. In the second sample, the volume ratio of 74 wt% CeO ₂ -26 wt% ZrO ₂ and Fe-beta zeolite components is equal to 5/1.

The third sample was prepared by mixing 74 wt% CeO ₂ - 26 wt% ZrO ₂ and Fe-beta zeolite powder at a weight ratio of 30. In the third sample, the volume ratio of 74 wt% CeO ₂ -26 wt% ZrO ₂ and Fe-beta zeolite components is equal to 10/1.

The mixture was ground for 10-15 minutes in an agate mortar and pelletized. The pellets were broken and sieved to collect 0.2-0.4 mm fractions for catalyst testing. Similarly, Fe-beta zeolite made from pellets was used as a reference.

The activity of the prepared sample was tested using the following catalyst loading, wherein the amount of Fe-beta zeolite component in the reactor remained constant. The total volume of the catalyst loaded in all the experiments described below was 0.067 ml, this GHSW ~ 270 000 h ^- resulting in a ^1:

The first sample (1/1 volume ratio _{component): [0.065g 74wt% Ce0 2} -Zr0 2 + 0.02g Fe- beta zeolite;

The second sample (5/1 volume ratio _{component): [0.109g 74wt% Ce0 2} -Zr0 2 + 0.007g Fe- beta zeolite;

The third sample (10/1 by volume component _{ratio): [0.119g 74wt% Ce0 2} -Zr0 2 + 0.0035g Fe- beta zeolite;

Reference sample: 0.02 g Fe-beta zeolite;

Feed gas composition: 540 ppm NH ₃ , 500 ppm NO, 10% O ₂ , 6% H ₂ O, balance N ₂ .

In these conditions [Ce0 ₂ -Zr0 ₂ + Fe- zeolite beta] complex catalyst naetneunde that the DeNOx performance, this complex [Ce0 ₂ -Zr0 ₂ + Fe- zeolite beta] a zeolite catalyst loaded into the reactor as part of the (Fe- Beta zeolite) was essentially the same as that of the standard Fe-beta zeolite sample.

Figure 3 data indicate that the amount of zeolite can be reduced at least 10 times without Ce0 ₂ being substituted with a corresponding volume of _{-Zr0 2 [Ce0 2 -Zr0 2 +} Fe- zeolite beta] sacrifice of performance of the DeNOx.

Example  4

T _reaction <at 250 ℃ [Ce-Mn / Al 2 O 3 + Fe- zeolite beta] DeNOx increase the performance of the composite catalyst.

The total volume of the catalyst was maintained at the same constant of 0,8: 1; Ce-Mn / Al ₂ O ₃ + Fe-beta] powders were prepared by thoroughly mixing 15 wt% of Ce - 15 wt% Mn / Al ₂ O ₃ powder and Fe-beta powder at a weight ratio of 1,7: 1 and 3,4: To prepare a composite catalyst. These weight ratios are due to the difference in density of these materials, the volume ratio of the components Ce-Mn / Al ₂ O ₃ / Fe-Beta = 2/1; 1/1 and 1/2. The powder was completely ground in an agate mortar bowl for 10-15 minutes and then pelleted. The pellets were broken and sieved to collect 0.2-0.4 mm fractions for catalyst testing. Similarly, Fe-Beta made from pellets was used as a reference.

The catalyst was tested in NH ₃ -DeNOx at a temperature range of 150-550 ° C. The test was carried out under the following conditions: 2 ℃ / min speed to reduce the reaction temperature, the feed gas composition: to the _{500ppm NO, 540ppm NH 3, 10} vol% O 2, 6 vol% H 2 O, the rest to the N ₂ A total flow rate of 300 mL / min was obtained.

Catalyst load: 0.04g Fe- and beta _{[0.045g Ce-Mn / Al 2} 0 3 + 0.013g Fe-Beta] (2/1 ratio), [0.034g Ce-Mn / Al 2 0 3 + 0.02g Fe- Beta] (1/1 ratio), [0.022 g Ce-Mn / Al ₂ O ₃ + 0.027 g Fe-beta] (1/2 ratio).

In these conditions [Ce-Mn / Al ₂ O ₃ + Fe- beta] complex catalyst showed the DeNOx activity, which was significantly greater than the individual Ce-Mn / Al ₂ O ₃ of the active at a temperature below 350 ℃, which Suggesting a pronounced synergistic effect between the components of the composite catalyst (FIG. 4). In addition, the ammonia slip in the composite catalyst was significantly lower than the standard Fe-Beta catalyst suggesting that these complex systems could be used as an integrated DeNOx-ASC.

Example  5

Enhanced DeNOx performance of [10 wt% Cu / Al ₂ O ₃ + H-zeolite] composite catalysts.

Three samples of the [10 wt% Cu / Al ₂ O ₃ + H-zeolite] composite catalyst were thoroughly pulverized with 10 wt% Cu / Al ₂ O ₃ and H-Beta, H-ZSM- .

The first sample was prepared by mixing 10 wt% Cu / Al ₂ O ₃ and H-beta (Si / Al = 20) powders at a weight ratio of 1/1.

The second sample was prepared by mixing 10 wt% Cu / Al ₂ O ₃ and H-ZSM-5 powder (Si / Al = 20) at a weight ratio of 1/1.

The third sample was prepared by mixing 10 wt% Cu / Al ₂ O ₃ and H-ferrierite powder (Si / Al = 32) at a weight ratio of 1/1.

The mixture was ground for 10-15 minutes in an agate mortar and pelletized. The pellets were broken and sieved to collect 0.2-0.4 mm fractions for catalyst testing.

Similarly, zeolites made of the corresponding pellets (H-beta, H-ZSM-5 and H-ferrierite) were used as standards.

The activity of the prepared sample was tested using the following catalyst loading, the amount of zeolite component in the reactor being kept constant:

First sample of 1/1 weight component ratio: [0.040 g 10 wt% Cu / Al ₂ O ₃ + 0.040 g H-Beta];

Second sample of 1/1 weight component ratio: [0.040 g 10 wt% Cu / Al ₂ O ₃ + 0.040 g H-ZSM-5];

Third sample of 1/1 weight component ratio: [0.040 g 10 wt% Cu / Al ₂ O ₃ + 0.040 g H-ferrierite];

Reference sample: 0.040 g H-beta; 0.040 g H-ZSM-5, or H-ferrierite, or 0.040 g 10 wt% Cu / Al ₂ O ₃ .

The catalyst was tested in NH ₃ -DeNOx at a temperature range of 150-550 ° C. The test was carried out under the following conditions: 2 ℃ / min speed to reduce the reaction temperature, the feed gas composition: to the _{500ppm NO, 540ppm NH 3, 10} vol% O 2, 6 vol% H 2 O, the rest to the N ₂ A total flow rate of 300 mL / min was obtained.

Catalyst loading and GHSV obtained:

[0.040 g 10 wt% Cu / Al ₂ O ₃ + 0.040 g H-beta], catalyst volume = 0.134 ml,

GHSV = 135 000 h ^-1 ;

[0.040 g 10 wt% Cu / Al ₂ O ₃ + 0.040 g H-ZSM-5], catalyst volume = 0.134 ml,

GHSV = 135 000 h ^-1 ;

[0.040 g 10 wt% Cu / Al ₂ O ₃ + 0.040 g H-ferrierite], catalyst volume = 0.134 ml,

GHSV = 135 000 h ^-1 ;

Reference catalyst

0.040 g H-beta, catalyst volume = 0.067 ml,

GHSV = 270,000 h ^-1 ;

0.040 g H-ZSM-5, catalyst volume = 0.067 ml,

GHSV = 270,000 h ^-1 ;

0.040 g H-ferrierite, catalyst volume = 0.067 ml,

GHSV = 270,000 h ^-1 ;

0.040 g Cu / Al ₂ O ₃ , catalyst volume = 0.067 ml,

GHSV = 270,000 h ^-1 .

Under these test conditions, the [10 wt% Cu / Al ₂ O ₃ + H-zeolite] composite catalyst exhibited enhanced DeNOx within the entire temperature range (150-550 ° C) Significantly exceeding the activity of the individual components.

Example  6

Catalyst with increased soot oxidation activity.

A _[2 + Ce0 ₂ -Zr0 Fe- beta] ratio of 3/1 by volume component was prepared as described in Example 2. To examine the soot oxidation activity of [CeO ₂ -ZrO ₂ + Fe-beta], a part of the sample made of pellets was crushed and the catalyst powder was soaked with soot ("Printex U", Degussa) . The soot and the catalyst were mixed by shaking in a glass bottle for 5 minutes to establish loose contact between the soot and the catalyst. The reference sample was prepared in a similar manner using Fe-beta powder.

Soot oxidation was carried out at a temperature gradient of 10 캜 / min in a dry air flow. [Ce0 ₂ -Zr0 ₂ + Fe- beta] and the soot oxidation profile is depicted in Figure 7 on the Fe- beta. From ~ 660 ℃ for a (beta + Fe- _{soot) ([Ce0 2 -Zr0 2 +} Fe- beta] + soot), as evidenced by the movement of the soot oxidation maximum value to ~ 420 ℃ about, [Ce0 ₂ - Zr0 showed a ₂ + Fe- beta] is significantly higher activity in the soot oxidation more individually Fe- beta.

Claims (16)

At least one redox active metal compound selected from the group consisting of Cu / Al ₂ O ₃ , Mn / Al ₂ O ₃ , CeO ₂ -ZrO ₂ , Ce-Mn / Al ₂ O ₃ , A catalyst composition for the selective reduction and soot oxidation of nitrogen oxides comprising at least one acidic zeolite or zeotext component selected from the group consisting of BEA, MFI, FAU, FER, CHA, MOR or mixtures thereof. The catalyst composition of claim 1, wherein the weight ratio between the zeolite component and the redox component is from 1: 1 to 1:50. According to claim 1 or 2, wherein the at least one redox active metal compound is Al ₂ 0 _3, Ti0 _2, Si0 _2, Zr0 _2, and characterized in that distributed on the selected substrate from the group consisting of a mixture thereof Catalyst composition. 4. Catalyst composition according to any one of claims 1 to 3, wherein the at least one acidic zeolite or zeotype component is in the form of a proton or is promoted with Fe. 5. Catalyst composition according to any one of claims 1 to 4, characterized in that the average molar ratio of Si / Al of the at least one acidic zeolite or zeotype component is from 5 to 100. 6. Catalyst composition according to any one of claims 1 to 5, wherein the at least one acidic zeolite or zeotype component is selected from the group consisting of beta-zeolite, ZSM-5 and ferrierite. A monolith structure coated with a catalyst composition according to any one of claims 1 to 6. 8. The monolith structure according to claim 7, wherein the monolith structure is in the form of a particle filter. 9. A catalyst composition according to claim 7 or 8, wherein the catalyst composition is coated on the structure in a line with two or several separate catalyst beds, or parallel to the structure as two or several catalyst beds, Wherein the monolith structure has a different composition or layer thickness. At least one redox active metal compound selected from the group consisting of Cu / Al ₂ O ₃ , Mn / Al ₂ O ₃ , CeO ₂ -ZrO ₂ , Ce-Mn / Al ₂ O ₃ , Contacting a catalyst composition comprising at least one acidic zeolite or zeotext component selected from the group consisting of BEA, MFI, FAU, FER, CHA, MOR or mixtures thereof with an off-gas in the presence of ammonia. Method for selective reduction of nitrogen oxides contained in off-gas and oxidation of soot. 11. The method of claim 10, wherein the at least one redox active metal component dispersed on the surface of the at least one zeolite component comprises Ce, Mn, Zr, Cr, or mixtures thereof. 12. A process according to claim 10 or 11, characterized in that the catalyst composition is contacted with the off-gas at a temperature of 250 DEG C or less. 13. A process according to any one of claims 10 to 12, characterized in that an excess of ammonia is selectively reduced to nitrogen by contact with the catalyst composition. 14. A process according to any one of claims 10 to 13, characterized in that the at least one acidic zeolite or zeotype component is in the form of a proton or is promoted to Fe. 15. Process according to any one of claims 10 to 14, characterized in that the average molar ratio of Si / Al of the at least one acidic zeolite or zeotype component is from 5 to 100. 16. The process according to any one of claims 10 to 15, wherein the at least one acidic zeolite or zeotype component is selected from the group consisting of beta-zeolite, ZSM-5 and ferrierite.

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