KR100654885B1 - Method for decomposing nitrogen oxides with carbon monoxide - Google Patents

Abstract

A method for simply and economically decomposing industrially generated NOx, or NOx and N2O at the same time using a CO reducing agent in the presence of a mixed metal oxide catalyst prepared from a hydrotalcite-like precursor is provided. A method for decomposing NOx using carbon monoxide comprises decomposing NOx, or NOx and N2O at the same time by reacting a waste gas containing NOx, or NOx and N2O with a gas mixture comprising a CO reducing agent in the presence of a mixed metal oxide catalyst prepared from a hydrotalcite-like precursor, or a catalyst prepared by depositing or interlayer-coupling a precious metal onto the mixed metal oxide catalyst. The hydrotalcite-like precursor is represented by a formula, [M^2+ 1-xN^3+ x(OH)2][A^n- x/nÀbH2O], wherein M^2+ is selected from the group consisting of Mg^2+, Ca^2+, Ni^2+, Zn^2+, Sr^2+, Ba^2+, Fe^2+, Cu^2+, Co^2+, Pa^2+ and Mn^2+, N^3+ is selected from the group consisting of Al^3+, Mn^3+, Fe^3+, Co^3+, Ni^3+, Cr^3+, Ga^3+, B^3+, La^3+, Ce^3+ and Rh^3+, A^n- is selected from the group consisting of CO3^2-, NO3^-, SO4^2-, Cl^-, OH^-, SiO3^2-, MnO4^2-, HPO3^2-, MnO4^2-, HGaO3^2-, HVO4^2-, ClO4^- and BO3^2-, x is ranged from 0.01 to 0.5, and b is an integer from 0 to 20.

Description

Method for decomposing nitrogen oxides with carbon monoxide

The present invention relates to a method for decomposing nitrogen oxides using carbon monoxide (CO), and more particularly, to a method for decomposing nitrogen oxides using a CO reducing agent in the presence of a mixed metal oxide catalyst prepared from hydrotalcite.

Nitrous oxide (N ₂ O) has a greenhouse effect of 310 times that of CO ₂ , and it is estimated to remain in the atmosphere for about 20 to 100 years since it is inertly stable under atmospheric pressure and destroys the ozone layer in the stratosphere. It is known that ozone is reduced by 10% when the concentration is doubled.

Nitrogen oxides are inevitably generated in the process of incineration of fuel devices and various wastes using fossil fuels, and by-produce photochemical smog and various secondary pollutants (O ₃ , PAN, etc.) harmful to the human body through photochemical reactions in the atmosphere. It is important in terms of air pollution. In order to cope with the crisis caused by climate change, research and development are needed to efficiently remove nitrogen oxides such as nitrous oxide (N ₂ O) and NOx.

Existing techniques for the decomposition of N ₂ O and NO x have been proposed such as temperature control of the furnace, recirculation of exhaust gas, and installation of special burners, but the performance is low. Thereafter, the selective catalytic reduction denitrification (SCR) has been put into practice, but there is a problem in that the equipment cost is high and the performance is deteriorated due to catalyst aging.

Alini et al. Proposed a method of decomposing N ₂ O gas using a hydrotalcite-type catalyst in European Patent Publication No. 1262224. Using a Rh catalyst, a very low concentration of N ₂ O of 200 ppm or less can be obtained. There is a disadvantage that the target to be reacted at a high temperature of 400 ℃ or more.

Korean Patent No. 0359675 describes a method for catalytically reducing nitrogen oxides contained in exhaust gas produced by combustion by contacting combustion exhaust gas with beta zeolite exchanged with an appropriate amount of cobalt salt in the presence of light hydrocarbon as a reducing agent. The amount of the reducing agent is more than twice the amount, the reaction temperature is high as 500 ℃ and has a low conversion rate.

Looking at the International Publication No. PCT / US02 / 06463 by Javier Perez-Ramirez et al., There is a nitrogen oxide removal technology using zeolite, but most of them do not show 100% conversion even at 400 ℃ or more to apply in actual process it's difficult.

Xavier Perez-Ramirez et al. Reduction of N ₂ O with CO Over FeMFI zeolites., Catal. 223 (2004)] confirmed that the Fe 2 zeolite catalyst was used to reduce N ₂ O in the presence of a CO reducing agent, thereby improving the decomposition performance of the N ₂ O single component.

In addition, there is also a direct catalytic reduction method for reducing nitrogen oxides without using a separate reducing agent in a metal-supported catalyst using a solid powder mixture as a carrier as a technique mentioned in Korean Patent No. 0408880, but also at 400 ° C. It has the disadvantage of showing low resolution of less than 50%.

Accordingly, the present inventors have studied to solve the problems of the existing technology, and found a method of improving the decomposition performance of N ₂ O and NO x using CO as a reducing agent in the presence of a mixed metal oxide catalyst prepared from a hydrotalcite precursor. The present invention has been completed based on this.

Accordingly, an object of the present invention is to decompose a nitrogen oxide using a CO reducing agent capable of simultaneously decomposing N ₂ O and NO x at a temperature of 300 ° C. or less in the presence of a CO reducing agent using a hydrotalcite containing a small amount of precious metal components as a catalyst. To provide.

Decomposition method of nitrogen oxide using a CO reducing agent to achieve the above object is a mixed metal oxide catalyst prepared from a hydrotalcite-type precursor, or in the presence of a catalyst in which a noble metal is attached or interlayer bonded to the mixed metal oxide catalyst, NOx, Or by reacting a waste gas containing NOx and N ₂ O and a gas mixture containing a CO reducing agent to simultaneously decompose NOx or NOx and N ₂ O.

Looking at the present invention in more detail as follows.

As described above, the present invention is a simple and simultaneous use of industrially generated N ₂ O, or NO x and N ₂ O using CO as a reducing agent in the presence of a mixed metal oxide catalyst prepared from a hydrotalcite type precursor. It relates to a method of economical decomposition.

Hydrotalcite compounds are generally anionic clays and are composed of hydrates such as magnesium and aluminum which are abundantly present on earth, and can be synthesized at room temperature and atmospheric pressure. To date, hydrotalcite is mainly used as a precursor of an oxide catalyst, and the application of a compound carrying, adding, or intercalating a hydrotalcite compound has not been put to practical use.

The hydrotalcite precursor used in the present invention may be represented by the following Chemical Formula 1.

[M ²⁺ _1-x N ³⁺ _x (OH) ₂ ] [A ^n- _{x /} nbH ₂ O]

In the hydrotalcite-type precursor, M ²⁺ and N ³⁺ are metal cations, respectively, and M ²⁺ is Mg ²⁺ , Ca ²⁺ , Ni ²⁺ , Zn ²⁺ , Sr ²⁺ , Ba ²⁺ , Fe ^A divalent metal cation selected from ²⁺ , Cu ²⁺ , Co ²⁺ , Pd ²⁺ and Mn ²⁺ is used, and N ³⁺ is Rh ³⁺ , Al ³⁺ , Mn ³⁺ , Fe ³⁺ , Co ^Trivalent metal cations selected from ³⁺ , Ni ³⁺ , Cr ³⁺ , Ga ³⁺ , B ³⁺ , La ³⁺ , Ce ^3+, and the like are used. The molar ratio of M ²⁺ and N ³⁺ is 1: 1 to 100: 1, more preferably 1: 1 to 5: 1. Further, in the hydrotalcite-type precursors, A ^n- is -1, -2 or -3 charge having a CO ₃ ^2- in the NO _{3 ^{- SO 4 2-, Cl -,}} OH -, SiO 3 2-, MnO ₄ ^2- , HPO ₃ ^2- , MnO ₄ ^2- , _{^{HGaO 3 2-, HVO 4 2-,}} ClO 4 - and a compound composed of an anion such as BO ₃ ^2-, used alone or in combination of two or more, and x is from 0.01 to 0.5, b is an integer from 0 to 20 .

The hydrotalcite precursor is prepared in the form of a mixed metal oxide after firing in a range of 100 to 1000 ° C., and selectively increases Mo, Ti, Pt, Au, Ag, Rh, in order to increase the catalytic activity of the mixed metal oxide catalyst. At least one precious metal selected from Pd, La, Ir, V, Kr, Nd, Nb, Se, Sc, Ru, In, Y, Zr and the like is attached or interlayer bonded to the mixed metal oxide.

According to the present invention, in the simultaneous decomposition of NOx or NOx and N ₂ O using a mixed metal oxide catalyst prepared from a hydrotalcite-type precursor, the gas mixture passing through the catalyst layer is 0.001 to 30% by weight of N ₂ O 0 to 1% by weight of NO, 0.001 to 40% by weight of CO reducing agent, And the rest include other contaminants and inert gases such as N ₂ .

The amount of the reducing agent in the gas mixture is preferably 0.001 to 40% by weight. If the amount of the reducing agent is less than 0.001% by weight, the reduction ability is insufficient, so that NO and N ₂ O cannot be sufficiently reduced to N ₂ and O ₂ , and 40% by weight. If it exceeds, there is a problem in that a lot of unreacted reducing agent and reaction by-products are generated to add a process for removing them.

In the present invention, the CO reducing agent, such as methane, ethane, propane, butane, pentane, hexane, isopropane, isobutane, 2-butane, isopentane, 2-pentane, tertiary pentane, isohexane and 2-hexane Hydrocarbons having 1 to 6 carbon atoms and alcohols having 1 to 6 carbon atoms such as methanol, ethanol, propanol, butanol and hexanol may be selectively included as another reducing agent.

In addition, oxygen (O ₂ ) can be used together with the reducing agent, the amount of O ₂ in the gas mixture is preferably 0.001 to 21% by weight. When the amount is less than 0.001% by weight, the hydrocarbon-based reducing agent (or non-CO reducing agent) fails to oxidize to reduce nitrogen oxides. When the amount is more than 21% by weight, O ₂ occupies the active point of the catalyst and NO and N ₂ O does not react, so the rate of decomposition decreases significantly.

In addition, although the amount of CO reducing agent used in the decomposition reaction of the present invention improves the decomposition performance of nitrogen oxide even by a small amount, in order to maximize the decomposition performance, it is preferable to inject the ratio of nitrogen oxide and CO in a ratio of 1: 1 to 1.5. Preferably, when using a CO reducing agent more than that the improvement of the degradation performance is minimal.

In the decomposition reaction of the present invention, the gas hour space velocity (GHSV) of gas passing through the catalyst layer is between 1,000 h ⁻¹ and 100,000 h ⁻¹ , preferably 30,000 to 60,000 h ⁻¹ . If the GHSV is less than 1,000 h ^{−1, the} throughput is low and economical. If the GHSV is more than 100,000 h ⁻¹ , the contact time with the catalyst is short, which leads to a reduction in the decomposition efficiency of NOx or N ₂ O.

Meanwhile, the pressure of the gas passing through the catalyst bed is preferably at least 1 atm, and the decomposition rate increases as the pressure increases.

According to the present invention, in the simultaneous decomposition of NO x or NO x and N ₂ O using the mixed metal oxide catalyst prepared from the hydrotalcite-type precursor, the temperature of the gas passing through the catalyst layer is 100 to 1,000 ℃, more Preferably it is 200-500 degreeC. If the temperature of the gas passing through the catalyst bed is less than 100 ° C., sufficient activation energy cannot be obtained and NOx and N ₂ O cannot be decomposed. If it exceeds 1000 ° C., too much energy is used, which is expensive for NOx and N ₂ O decomposition. There is a problem that is consumed.

Hereinafter, the present invention will be described in more detail with reference to the following Examples, but the scope of the present invention is not limited to the following Examples.

Comparative Example 1

By using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Ce-Al (2 / 0.01 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm and the amount of the remaining gas were nitrogen. N ₂ O was decomposed 97% at 500 ° C and 89% at 450 ° C or higher at a flow rate of 200 ml / min (SV 42,000hr-1).

Example 1

Using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Ce-Al (2 / 0.01 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, CO 2,500 ppm and the amount of remaining gas were nitrogen N ₂ O was decomposed 97% at 450 ° C. and 100% at 500 ° C. or higher under a flow rate of 200 ml / min (SV 42,000hr ⁻¹ ) of the total gas.

Example 2

Using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Ce-Al (2 / 0.01 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, CO 12,500 ppm and the amount of remaining gas were nitrogen N ₂ O was decomposed 96% at 200 ° C. and 100% at 250 ° C. or higher under a flow rate of 200 ml / min (SV 42,000 hr ⁻¹ ) of the total gas.

Example 3

Using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Ce-Al (2 / 0.01 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, CO 50,000 50,000 ppm and the remaining gas amount were nitrogen N ₂ O was decomposed 98% at 200 ° C and 100% at 250 ° C or higher under a flow rate of 200 ml / min (SV 42,000hr ^-1 ) of the total gas.

Example 4

N ₂ O 12,500 ppm, CO 17,500 ppm, 100 ppm NO and the remaining gases using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Ce-Al (2 / 0.01 / 0.01 / 1) prepared from hydrotalcite precursors the amount of nitrogen to a total gas 200ml / min at a flow rate condition of (SV 42,000hr ^-1) N ₂ O at 200 ℃ 96% NO 98%, at least 250 ℃ N ₂ O and NO is decomposed 100% .

Example 5

N ₂ O 12,500 ppm, CO 125,000 ppm, NO 100 ppm and the remaining gas using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Ce-Al (2 / 0.01 / 0.01 / 1) prepared from hydrotalcite precursors the amount of nitrogen to a total gas 200ml / min at a flow rate condition of (SV 42,000hr ^-1) N ₂ O at 200 ℃ 99%, 100% NO, N ₂ O and NO than 250 ℃ was decomposed 100% .

Comparative Example 2

Using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Al (2 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm and the amount of the remaining gas were nitrogen, 200 ml / min. At a flow rate of (SV 30,000hr ⁻¹ ), N ₂ O decomposed 85% at 500 ° C., 75.5% at 450 ° C., and 61% at 400 ° C.

Example 6

Using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Al (2 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, CO 17,500 ppm and the amount of the remaining gases were nitrogen At a flow rate of 200 ml / min (SV 30,000 hr ⁻¹ ), N ₂ O decomposed 95% at 500 ° C., 94% at 450 ° C., and 91% at 400 ° C.

Example 7

Using 0.4 g of a metal oxide catalyst having a molar ratio of Co-Pd-Al (2 / 0.01 / 1) prepared from hydrotalcite precursors, N ₂ O 12,500 ppm, CO 17,500 ppm and the amount of the remaining gas were nitrogen At a flow rate of 200 ml / min (SV 15,000 hr ⁻¹ ), N ₂ O was decomposed 100% at 450 ° C. or higher and 95% at 400 ° C.

Comparative Example 3

Using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Al (2 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, NO 100 ppm and the amount of the remaining gas are nitrogen, 200 ml of total gas. N ₂ O at 80 ° C, 83% NO at 80 ° C, 80% N ₂ O at 80 ° C, 79% NO at 79 ° C, and N ₂ O at 400 ° C at flow conditions of / min (SV 30,000hr ^-1 ). %, NO decomposed 76%.

Example 8

Using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Al (2 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, CO 12,500 ppm, NO 100 ppm and the amount of the remaining gas to nitrogen 93% N ₂ O at 500 ° C, 91% NO at 90 ° C, 90% N ₂ O at 87 ° C, 87% NO at 400 ° C under a flow rate of 200 ml / min (SV 30,000hr ^-1 ) N ₂ O decomposed 88% and NO decomposed 85%.

Example 9

Using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Al (2 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, CO 17,500 ppm, NO 100 ppm and the amount of the remaining gas were nitrogen 94% N ₂ O at 90 ° C, 90% NO at 92 ° C, 92% N ₂ O at 89 ° C, 89% NO at 400 ° C, at a flow rate of 200 ml / min (SV 30,000hr- ¹ ) N ₂ O decomposed 89% and NO decomposed 86%.

[Comparative Example 4]

Using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Ce-Al (2 / 0.01 / 0.02 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm and the amount of the remaining gas were nitrogen and the total gas was At a flow rate of 200 ml / min (SV 38,000 hr ⁻¹ ), N ₂ O decomposed 89% at 500 ° C., 74% at 450 ° C., and 56% at 400 ° C.

Example 10

Using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Ce-Al (2 / 0.01 / 0.02 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, CO 17,500 ppm and the amount of remaining gas were nitrogen As a result, N ₂ O was decomposed 98% at 250 ° C. and N ₂ O was decomposed 100% at 300 ° C. or more under a flow rate of 200 ml / min (SV 38,000 hr ⁻¹ ) of the total gas.

Example 11

Using 0.1 g of a metal oxide catalyst having a molar ratio of Co-Pd-Ce-Al (2 / 0.01 / 0.02 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, CO 1,500 ppm and the amount of the remaining gas were nitrogen in the total gas 100ml / min N ₂ O at a flow rate condition of (SV 38,000hr ^-1) is 87% at 450 ℃, N ₂ O at more than 500 ℃ decomposition was 100%.

[Comparative Example 5]

By using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Ce-Al (2 / 0.01 / 0.05 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm and the amount of the remaining gas were nitrogen. At a flow rate of 200 ml / min (SV 48,000 hr ⁻¹ ), N ₂ O was decomposed 87% at 500 ° C., 70% at 450 ° C. and 40% at 400 ° C.

Example 12

Using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Ce-Al (2 / 0.01 / 0.05 / 1) prepared from a hydrotalcite precursor, 10,000 ppm of N ₂ O, 10,000 ppm of CO and the remaining amount of nitrogen were N ₂ O was decomposed at 300 ° C. 90% and 100% at 350 ° C. or higher under a flow rate of 200 ml / min (SV 48,000hr ⁻¹ ) of the total gas.

Example 13

Using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Ce-Al (2 / 0.01 / 0.05 / 1) prepared from a hydrotalcite precursor, 10,000 ppm of N ₂ O, 20,000 ppm of CO, and the remaining gas amount were nitrogen N ₂ O was decomposed 100% at 300 ° C. and 93% at a flow rate of 200 ml / min (SV 48,000 hr ⁻¹ ).

Example 14

N ₂ O 12,500 ppm, CO 17,500 ppm, NO 100 ppm and the remaining gas using 0.2 g of a metal oxide catalyst having a molar ratio of Co-Pd-Ce-Al (2 / 0.01 / 0.05 / 1) prepared from a hydrotalcite precursor the amount of the nitrogen in the total gas flow rate condition of ^{200ml / min (SV 48,000hr -1)} N 2 O is 91% 300 ℃, NO is N ₂ O and NO at 94%, at least 350 ℃ decomposition was 100%.

Comparative Example 6

Using 0.162 g of a metal oxide catalyst having a molar ratio of Co-La-Ce-Al (4/1 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm and the amount of the remaining gas were nitrogen. At a flow rate of 200 ml / min (SV 30,000 hr ⁻¹ ), N ₂ O decomposed 84% at 500 ° C., 39% at 450 ° C., and 17% at 400 ° C.

Example 15

Using 0.162 g of a metal oxide catalyst having a molar ratio of Co-La-Ce-Al (4/1 / 0.01 / 1) prepared from hydrotalcite precursors, N ₂ O 12,500 ppm, CO 17,500 ppm and the amount of remaining gas were nitrogen N ₂ O was decomposed 80% at 350 ° C. and 100% at 400 ° C. or higher at a flow rate of 200 ml / min (SV 30,000hr ⁻¹ ) of the total gas.

Example 16

The amount of N ₂ O 12,500 ppm, CO 17,500 ppm and the amount of the remaining gas were reduced using 0.081 g of a metal oxide catalyst having a molar ratio of Co-La-Ce-Al (4/1 / 0.01 / 1) prepared from a hydrotalcite precursor. N ₂ O was decomposed 100% at 350 ° C. and 76% at 400 ° C. or higher at a flow rate of 200 ml / min (SV 60,000hr ⁻¹ ) of the total gas.

Comparative Example 7

By using 0.17 g of a metal oxide catalyst having a molar ratio of Co-Pd-Rh-Al (1 / 0.01 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm and the amount of the remaining gas were nitrogen. At a flow rate of 200 ml / min (SV 30,000 hr ⁻¹ ), N ₂ O was decomposed at 500 ° C., 100%, 450 ° C. 99%, 400 ° C. 93%, and 350 ° C. 77.5%.

Example 17

Using 0.17 g of a metal oxide catalyst having a molar ratio of Co-Pd-Rh-Al (1 / 0.01 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, 500 ppm CO and the amount of remaining gas were nitrogen. N ₂ O was decomposed 100% at 350 ° C 79%, 400 ° C 97%, and 450 ° C or higher at a flow rate of 200 ml / min (SV 30,000hr- ¹ ).

Example 18

Using 0.17 g of a metal oxide catalyst having a molar ratio of Co-Pd-Rh-Al (1 / 0.01 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, CO 17,500 ppm and the amount of remaining gas were nitrogen N ₂ O was decomposed to 79% at 300 ° C. and 100% at 350 ° C. or higher under a flow rate of 200 ml / min (SV 30,000hr ⁻¹ ) of the total gas.

Example 19

Using 0.17 g of a metal oxide catalyst having a molar ratio of Co-Pd-Rh-Al (1 / 0.01 / 0.01 / 1) prepared from a hydrotalcite precursor, the amount of N ₂ O 12,500 ppm, 100,000 ppm CO and the remaining gas was With nitrogen, N ₂ O was decomposed at 82 ° C at 300 ° C and 100% at 350 ° C or higher under a flow rate of 200 ml / min (SV 30,000hr ⁻¹ ) of total gas.

Comparative Example 8

Using 0.322 g of a metal oxide catalyst having a molar ratio of Co-Ce-Al (2 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm and the amount of the remaining gas were nitrogen and a total gas of 200 ml / min ( N ₂ O was decomposed at 95 ° C., 450 ° C. 83%, 400 ° C. 58%, and 350 ° C. 33% at 500 ° C. at a flow rate of 30,000 hr ⁻¹ .

Example 20

Using 0.322 g of a metal oxide catalyst having a molar ratio of Co-Ce-Al (2 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, CO 17,500 ppm and the amount of the remaining gases were nitrogen At a flow rate of 200 ml / min (SV 30,000 hr ⁻¹ ), N ₂ O decomposed 80.5% at 350 ° C. and 100% at 400 ° C. or higher.

Comparative Example 9

200 ml of total gas using N ₂ O 12,500 ppm, NO 100 ppm and the remaining gas as nitrogen using 0.322 g of a metal oxide catalyst having a molar ratio of Co-Ce-Al (2 / 0.01 / 1) prepared from a hydrotalcite precursor. At flow rates of / min (SV 30,000hr ^-1 ), N ₂ O decomposed 56% at 450 ° C, 24% at 450 ° C and 14% at 400 ° C.

Example 21

Using 0.322 g of a metal oxide catalyst having a molar ratio of Co-Ce-Al (2 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, CO 17,500 ppm, NO 100 ppm and the amount of the remaining gas were nitrogen. N ₂ O was 350 ° C. 82%, NO was 85%, and N ₂ O and NO were 100% decomposed at a flow rate of 200 ml / min (SV 30,000hr ⁻¹ ).

Comparative Example 10

Using 0.4 g of a metal oxide catalyst having a molar ratio of Co-Rh-Ce-Al (1 / 0.2 / 0.01 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm and the amount of the remaining gas were nitrogen. At a flow rate of 200 ml / min (SV 30,000 hr ⁻¹ ), N ₂ O decomposed 92% at 350 ° C. and 100% at 400 ° C. or higher.

Example 22

Using 0.4 g of a metal oxide catalyst having a molar ratio of Co-Rh-Ce-Al (1 / 0.2 / 0.01 / 1) prepared from hydrotalcite precursors, N ₂ O 12,500 ppm, CO 12,500 ppm and the amount of remaining gas were nitrogen N ₂ O was decomposed 100% at 200 ° C. and 98% at 250 ° C. or higher under the flow rate of 200 ml / min (SV 30,000hr ⁻¹ ) of the total gas.

Example 23

N ₂ O 12,500 ppm, CO 12,500 ppm, 100 ppm NO and the remaining gas using 0.4 g of a metal oxide catalyst having a molar ratio of Co-Rh-Ce-Al (1 / 0.2 / 0.01 / 1) prepared from hydrotalcite precursors the amount of the nitrogen N ₂ O in the total gas flow rate condition of 200ml / min (SV 30,000hr ^-1) is 200 ℃ 99%, NO is 100%, N ₂ O and NO at least 250 ℃ decomposition was 100%.

Comparative Example 11

Using 0.3 g of a metal oxide catalyst having a molar ratio of Co-Rh-Al (1 / 0.2 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm and the amount of the remaining gas were nitrogen, and the total gas was 200 ml / min ( SV 20,000 hr ^-1 ) N ₂ O was decomposed 94% at 300 ℃, 100% above 350 ℃.

Example 24

Using 0.3 g of a metal oxide catalyst having a molar ratio of Co-Rh-Al (1 / 0.2 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, CO 17,500 ppm and the amount of the remaining gas were nitrogen. Under a flow rate of 200 ml / min (SV 30000 hr ⁻¹ ), N ₂ O decomposed 98% at 200 ° C. and 100% at 250 ° C. or higher.

Comparative Example 12

Using 0.285 g of a metal oxide catalyst having a molar ratio of Co-Pd-Al (1 / 0.1 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm and the amount of the remaining gas were nitrogen, 200 ml / min Under flow rate conditions of (SV 30,000hr ^-1 ), N ₂ O decomposed 87% at 400 ° C and 100% above 450 ° C.

Example 25

Using 0.285 g of a metal oxide catalyst having a molar ratio of Co-Pd-Al (1 / 0.1 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, CO 12,500 ppm and the amount of the remaining gas were nitrogen. At a flow rate of 200 ml / min (SV 30,000 hr ⁻¹ ), N ₂ O decomposed 100% at 200 ° C. or higher.

Comparative Example 13

Using 0.285 g of a metal oxide catalyst having a molar ratio of Co-Pd-Al (1 / 0.1 / 1) prepared from a hydrotalcite precursor, 100 ppm of NO, 12,500 ppm of N ₂ O and the remaining amount of nitrogen were 200 ml of total gas. N ₂ O decomposed at 36 ° C. at 400 ° C., 77% at 450 ° C., and 96.4% at 500 ° C. at a flow rate of / min (SV 30,000hr ⁻¹ ).

Example 26

Using 0.285 g of a metal oxide catalyst having a molar ratio of Co-Pd-Al (1 / 0.1 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, CO 12,500 ppm, NO 100 ppm and the remaining gas amount were nitrogen N ₂ O and NO were decomposed 100% above 200 ° C. at a flow rate of 200 ml / min (SV 30,000 hr ⁻¹ ) of total gas.

Comparative Example 14

Using 0.228 g of a metal oxide catalyst having a molar ratio of Co-Rh-Pd-Al (2 / 0.1 / 0.1 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm and the amount of the remaining gas were nitrogen. At a flow rate of 200 ml / min (SV 30,000 hr ⁻¹ ), N ₂ O decomposed 76% at 350 ° C., 94.4% at 400 ° C., and 100% at 450 ° C. or higher.

Example 27

Using 0.228 g of a metal oxide catalyst having a molar ratio of Co-Rh-Pd-Al (2 / 0.1 / 0.1 / 1) prepared from a hydrotalcite precursor, N ₂ O 12,500 ppm, CO 17,500 ppm and the amount of remaining gas were nitrogen N ₂ O was decomposed at 250 ° C. 57% and 100% at 300 ° C. or higher at a flow rate of 200 ml / min (SV 30,000hr ⁻¹ ) of the total gas.

Example 28

N ₂ O 12,500 ppm, CO 17,500 ppm, CH ₄ 500 ppm, O using 0.228 g of a metal oxide catalyst having a molar ratio of Co-Rh-Pd-Al (2 / 0.1 / 0.1 / 1) prepared from hydrotalcite precursors ₂ 1,000 ppm and the amount of the remaining gas were nitrogen, and N ₂ O was decomposed 100% at 200 ° C. and 49%, 250 ° C. and 89%, and 300 ° C. and higher at a flow rate of 200 ml / min (SV 30,000hr ⁻¹ ).

Example 29

N ₂ O 12,500 ppm, CO 17,500 ppm, CH ₄ 3,500 ppm, using 0.228 g of a metal oxide catalyst having a molar ratio of Co-Rh-Pd-Al (2 / 0.1 / 0.1 / 1) prepared from a hydrotalcite precursor 7,000 ppm of O ₂ and the amount of remaining gas were nitrogen, and N ₂ O was decomposed at 200 ° C. 57%, 250 ° C. 93%, and 100% above 300 ° C. at a flow rate of 200 ml / min (SV 30,000hr ⁻¹ ) of the total gas. .

According to the method of the present invention, the use of a CO reducing agent in the decomposition of NOx and N ₂ O results in the same molar ratio as Rh instead of expensive noble metal catalysts such as Rh of mixed metal oxide catalysts prepared from hydrotalcite-type precursors. Using Pd of 20 or using Pd and Ce in a 1/10 to 1/20 molar ratio of the Rh molar ratio can achieve the same performance as a catalyst containing a large amount of Rh. In addition, it simultaneously decomposes NOx and N ₂ O, and shows 100% decomposition performance even at 200 to 250 ° C.

Claims (8)

Waste gas containing NOx or NOx and N ₂ O in the presence of a mixed metal oxide catalyst prepared from a hydrotalcite type precursor, or a catalyst in which a noble metal is impregnated or interlinked with the mixed metal oxide catalyst, and A method for decomposing nitrogen oxides using carbon monoxide, comprising: reacting a gas mixture containing a CO reducing agent to simultaneously decompose NOx or NOx and N ₂ O. The method of claim 1, wherein the hydrotalcite-type precursor is represented by Formula 1 below. Formula 1 [M ²⁺ _1-x N ³⁺ _x (OH) ₂ ] [A ^n- _{x /} nbH ₂ O] Wherein M ²⁺ is Mg ²⁺ , Ca ²⁺ , Ni ²⁺ , Zn ²⁺ , Sr ²⁺ , Ba ²⁺ , Fe ²⁺ , Cu ²⁺ , Co ²⁺ , Pa ²⁺ and Mn ²⁺ N ³⁺ is selected from the group consisting of Al ³⁺ , Mn ³⁺ , Fe ³⁺ , Co ³⁺ , Ni ³⁺ , Cr ³⁺ , Ga ³⁺ , B ³⁺ , La ³⁺ , Ce ³⁺ and is selected from the group consisting of Rh ^3+, a ^n- is ^{_{CO 3 2-, NO 3 -,}} SO 4 2-, Cl -, OH -, SiO 3 2-, MnO 4 2-, HPO 3 2-, ^{_{MnO 4 2-, HGaO 3 2-,}} HVO 4 2-, ClO 4 - and is selected from the group consisting of BO ₃ ^2-, x is from 0.01 to 0.5, b is an integer from 0 to 20. The method of claim 1, wherein the precious metal is Mo, Ti, Pt, Au, Ag, Rh, Pa, La, Ir, V, Kr, Nd, Nb, Se, Sc, Ru, In, Y, Z and mixtures thereof It is selected from the group consisting of, Decomposition method of nitrogen oxides using carbon monoxide, characterized in that the content of the noble metal in the interlayer bonded catalyst is 0.01 to 50% by weight. The method of claim 1, wherein the reducing agent further comprises a component selected from the group consisting of hydrocarbons having 1 to 6 carbon atoms, alcohols having 1 to 6 carbon atoms, and mixtures thereof. The method for decomposing nitrogen oxides using carbon monoxide according to claim 1, wherein the space hourly velocity of the gas passing through the catalyst is 1,000 h ⁻¹ to 100,000 h ⁻¹ . The method for decomposing nitrogen oxides using carbon monoxide according to claim 1, wherein the reaction temperature is 100 to 1,000 ° C. The method of claim 1, wherein the gas mixture is 0.001 to 30% by weight of N ₂ O, 0 to 1% by weight of NO, 0.001 to 40% by weight of reducing agent, And the rest of the nitrogen oxides using carbon monoxide, characterized in that it comprises other pollutants and inert carrier gas. The method of claim 7, wherein the gas mixture further comprises 0.001 to 21% by weight of O ₂ .