KR20130123311A - Mixed oxide catalyst materials for treating an exhaust gas, preparing methods thereof and methods for treating the exhaust gas using the same - Google Patents

Abstract

The present invention relates to a mixed metal oxide catalyst for treating exhaust gas, a manufacturing method thereof, and a method for treating exhaust gas using the same. The mixed metal oxide catalyst according to the present invention oxidizes NO, CO, and HC included in combustible exhaust gas with high efficiency, effectively adsorbs and separates nitrogen oxide, allows dissolution of CO and NOx without oxygen, and allows dissolution of NOx through reduction at a low temperature of less than 500 using CO or HC when treating NOx and N2O under oxygen which is difficult to be dissolved without additional use of a reducing agent. [Reference numerals] (AA) Example 1-4;(BB) NO conversion rate (%);(CC) Temperature ()

Description

Mixed oxide catalyst materials for treating an exhaust gas, preparing methods etc. and methods for treating the exhaust gas using the same}

The present invention relates to a mixed metal oxide catalyst for treating exhaust gas, a method for preparing the same, a method for treating exhaust gas using the same, and a method for activating the mixed metal oxide catalyst.

As the damage caused by climate change increases worldwide, interest in air pollution has recently increased. The use of fossil energy and emissions from their combustion (also abbreviated as “gas”) lead to large emissions of greenhouse gases and emissions of carbon monoxide (CO) and hydrocarbons (HC) and NOx, which are major contributors to environmental pollution. Among them, CO and HC are oxidized and discharged by Diesel Oxidation Catalyst (DOC), which uses expensive precious metals such as platinum (Pt), but nitrogen oxides are used under exhaust gas conditions containing excessive oxygen. Since the process of reducing NOx to nitrogen (N ₂ ) and oxygen (O ₂ ) is not easy, many studies have been conducted to develop this NOx reduction technology.

While it is necessary to increase the combustion efficiency of fuels in order to suppress greenhouse gas emissions, in order to meet the tightening regulations on emission of NOx, it has been directed to low-temperature combustion to reduce the generation of NOx, but this acts as a factor to lower the combustion efficiency. This tendency is due to the lack of post-treatment technology for NOx treatment of exhaust gas in any part, such as technology convenience, economical efficiency and treatment efficiency.

Currently, SCR (Selective catalytic reduction) method, which is widely used in the treatment of exhaust gases such as boilers and incinerators, uses ammonia (NH ₃ ) as a representative reducing agent. Due to oxidation of NH ₃ and incomplete reduction of NOx, the greenhouse effect causes N ₂ O production, which is known to be 310 times higher than CO ₂ .

In addition to the regulation of air emissions in the general industry, the automotive industry is also trying to lower the NOx emission limit to the level of gasoline engines, especially for diesel engines with high fuel efficiency but high air-fuel ratio. The NOx treatment technology for the exhaust gas of lean burn engines containing excessive oxygen is expected to be the SCR technology using ammonia (NH ₃ ) reducing agent, but it is necessary to carry a separate urea tank for ammonia supply. Low NOx conversion should be combined with exhaust gas recirculation (EGR).

In the case of HC-SCR using hydrocarbon (HC) as a reducing agent, fuel may be used as a reducing agent, so it may not be necessary to install a separate storage tank, but at least 300 or more may be inconvenient to use and fuel economy. The effect is to reduce the efficiency. CO, and H ₂ as a reducing agent, the non-selective oxidation reaction between these reducing agents and oxygen proceeds in addition to the reaction with NOx, and thus the LNT (Lean NOx Trap ) System, in which case the complexity of the apparatus as well as the reduction agent are obtained from the fuel and lead to a reduction in the fuel efficiency.

Due to these problems, the potent NOx reducing agents (CO, H ₂ and HC) presently contained in a large amount of exhaust gas are oxidized and discharged through a diesel oxidation catalyst rather than being used for NOx reduction.

On the other hand, a lot of research has been conducted on the direct decomposition method that decomposes lean NOx more easily without using a reducing agent. Kustova et al. (Applied Catalysis B: Environmental 67 (2006) 6067) show that traditional Cu-ZSM-5 catalysts, which many people are interested in, are only active at around 1000 ° C, and Wang et al. (Catalysis Today 96, 1120, 2004) is the result of the direct decomposition of NO and N ₂ O using Pt catalysts, or Iwakuni et al. (Applied Catalysis B: Environmental 74, 299306, 2007) used the Perovskite catalyst to As shown in the results of attempts, it was usually only a certain level of activity only above 800 ℃.

The researchers attempted to directly decompose NO by the high temperature firing of metal oxides, minimization of lattice oxygen, adsorption of NO into oxygen vacancies (Oxygen vacancy) and decomposition into N ₂ . Only in the presence of oxygen, especially in the presence of oxygen exhibits a characteristic that the activity is significantly lowered due to the strong adsorption of oxygen, the situation is showing a large distance from the technology that can be put to practical use.

In addition, Korean Patent No. 0408880 has devised a method of directly reducing nitrogen oxides by catalytic reduction using a catalyst having a metal supported on a solid powder mixture carrier in a direct decomposition method to remove lean NOx. As shown in the examples, the carbon monoxide (CO), which is known to be the strongest reducing agent at a relatively low oxygen concentration of about 4%, contains an amount equivalent to that of the NOx concentration, and since the actual NOx removal performance is suspected, it is recognized as a direct decomposition effect. Have a bunch.

As described above, in the conventional method in which reducing agents such as NH ₃ , CO and / or HC are used in the decomposition treatment of lean NOx, N ₂ , which is a greenhouse gas in the incomplete NOx reduction region, except for problems of process complexity and economic efficiency, is used. It has several problems, including the occurrence of O. In addition, the direct decomposition, which is considered the most ideal, has not been shown to be practical.

Accordingly, the present inventors have conducted extensive research to solve the above-mentioned problems of the prior art, and as a result of the catalytic decomposition reaction of NOx, the most effective NOx in an environment where the affinity between the catalyst and oxygen is weakened among the gases in which oxygen coexists. It was determined that a reduction decomposition reaction could be expected. Based on this, the metal oxide that minimizes the excess oxygen adsorption by combining oxygen to the catalyst layer as a base material, and has a pore structure that can effectively adsorb the hydrocarbons and NOx having an affinity with oxygen, platinum It oxidizes CO, hydrocarbons (HC) and NO with comparable or higher performance without using expensive precious metals such as (Pt), and further reduces CO or HC contained in exhaust gas or direct decomposition of NOx in the adsorbed catalyst bed. The present invention envisions a mixed metal oxide catalyst incorporating an active catalyst component capable of promoting a reduction reaction of NOx, and the present invention has been completed based on this.

Accordingly, one aspect of the present invention is a mixed metal oxide having a large specific surface area in which a pore structure is developed, in which excess oxygen, which is larger than the conventional stoichiometric oxygen amount, forms weak bonds with transition metals and oxidizing or decomposition performance thereof. The present invention provides a catalyst for treating exhaust gas whose activity is increased by the addition of a metal having a high viscosity.

Another aspect of the present invention is to provide various methods for efficiently preparing the mixed metal oxide catalyst for treating the exhaust gas.

Another aspect of the present invention is to provide a method for treating the exhaust gas using the mixed metal oxide catalyst for treating the exhaust gas.

Another aspect of the present invention is to provide a method for activating a mixed metal oxide catalyst for treating the exhaust gas.

The mixed metal oxide catalyst for treating the exhaust gas of the present invention for achieving the above aspect is represented by the following formula (1), and is composed of a mixed metal oxide or a mixture of metal oxides of at least two kinds of metals.

[Formula 1]

M (II) uM (III) vM (IV) wM (V) xM (VI) yOz

Where

M (II) is selected from the group consisting of valence Mg, Ca, Ni, Zn, Sr, Ba, Be, Fe, Cu, Co, Pd and Mn,

M (III) is at least one selected from the group consisting of trivalent Al, Mn, Fe, Co, Ni, Cr, Bi, Ga, B, La, Ce, Sc and Rh,

M (IV) is at least one selected from the group consisting of tetravalent Ti, Mn, Nb, Rh, Sn, Pd, Ce, La, Mo, W, Ge, Re, Ru, and Os,

M (V) is at least one selected from the group consisting of pentavalent V, Re, Ir, Os, Bi, and Ru,

M (VI) is one or more selected from the group consisting of hexavalent Mo, W, Ir, Ru, Re, Cr,

u, v, w, x, and y are real numbers between 0 and 18 equal to or different from each other,

z is a (u + 3v / 2 + 2w + 5x / 2 + 3y) and a is a real number greater than 1 and less than or equal to 5;

In the catalyst of the present invention, the catalyst is K, Li, Na, Fr, Ag, Au, Pt, Pd, Rh, Ir, Ru, Mg, Sr, Nb, Sc, Ge, La, Mn, Fe, and Cu Further comprising at least one component selected from the group consisting of ion exchange, impregnation or interlayer bonding, the content of the component is characterized in that 0.01 to 30% by weight based on the total catalyst.

In the catalyst of the present invention, the catalyst is characterized by having a specific surface area in the range of 5 to 500 m 2 / g.

Method for producing a mixed metal oxide catalyst for the treatment of exhaust gas to achieve another aspect of the present invention is represented by the following formula (2), a mixed metal oxide catalyst precursor composed of at least two or more mixed metal oxides or metal oxide mixture Providing; And lyophilizing the precursor or drying at 70 to 150 ° C. and then calcining at 100 to 950 ° C. to form a mixed metal oxide represented by the following Formula 1.

[Formula 1]

M (II) uM (III) vM (IV) wM (V) xM (VI) yOz

(2)

[M (II) uM (III) vM (IV) wM (V) xM (VI) y (OH) o] ^{p +} A ^{n -} p / nmH ₂ O

Where

M (II) is at least one selected from the group consisting of divalent Mg, Ca, Ni, Zn, Sr, Ba, Be, Fe, Cu, Co, Pd and Mn,

M (III) is at least one selected from the group consisting of trivalent Al, Mn, Fe, Co, Ni, Cr, Bi, Ga, B, La, Ce, Sc and Rh,

M (IV) is at least one selected from the group consisting of tetravalent Ti, Mn, Nb, Rh, Sn, Pd, Ce, La, Mo, W, Ge, Re, Ru, and Os,

M (V) is at least one selected from the group consisting of pentavalent V, Re, Ir, Os, Bi, and Ru,

M (VI) is one or more selected from the group consisting of hexavalent Mo, W, Ir, Ru, Re, Cr,

u, v, w, x, and y are real numbers between 0 and 18 equal to or different from each other,

z is a (u + 3v / 2 + 2w + 5x / 2 + 3y) and a is a real number greater than 1 and less than or equal to 5;

p and o are o = (2u + 3v + 4w + 5x + 6y-p) is determined according to the relationship, A ^{n -} is an anion _{^{CO 3 2-, NO 3 -,}} SO 4 2 -, Cl -, OH _{^{-, SiO 3 2 -, MnO}} 4 2 -, WO 4 2 -, HGaO 3 2 -, HPO 4 2 -, HVO 4 2 -, ClO 4 - is selected from the acid, adipic acid, and oxalic acid, ^- and BO ₃ ² If p + a, 0 is (valence) a ^{n -} is a hydroxide of mixed metal-free anions represented by.

In the preparation method of the catalyst of the present invention, the precursor for the mixed metal oxide catalyst is a precipitation, deposition-precipitation, co-precipitation or sol-gel method of the mixed metal oxide (Sol-) Gel process), or a peroxide treatment.

In the method for preparing the catalyst of the present invention, the method is K, Li, Na, Fr, Ag, Au, Pt, Pd, Rh, Ir, Ru, Mg, Sr, Nb, Sc, Ge, La, Mn, Fe And at least one component selected from the group consisting of Cu, and impregnating, coating or ion-bonding the precursor or the mixed metal oxide by a method of ion exchange.

The first processing method of an exhaust gas using a mixed metal oxide for the treatment of exhaust gases to achieve another aspect of the invention catalyst are NO _x, N, using the support of the person or the catalyst for the above mixed metal oxide catalytic coating _{2 O, O 2, HC,} CO, CO 2, H 2 O, SO 2, or NO in the condition that at least 0.1% by volume or more of oxygen (O ₂₎ from the exhaust gas containing a mixture thereof present, CO and HC Simultaneously oxidize with high efficiency.

In order to achieve another aspect of the present invention, a second method for treating exhaust gas using a mixed metal oxide catalyst for treating exhaust gas may be performed by using a mixed metal oxide catalyst represented by Chemical Formula 1 or a catalyst coated support. NO _x , N ₂ O, O ₂ , HC, CO, CO ₂ , H ₂ O, SO ₂ , or a mixture thereof and NO _x , N from an exhaust gas containing at least 0.1% by volume of oxygen (O ₂ ) to ₂ O, or the NOx and the CO or HC as a reducing agent that at the same time to decompose the nitrogen oxides directly to N ₂ and O _2, or the co-adsorption of mixtures from oxygen, N ₂ and CO ₂ and H ₂ O, etc. Reduction decomposition.

In the second processing method, the support is characterized in that the pellet or honeycomb structure.

In the second treatment method, the method comprises an hourly space velocity of the exhaust gas passing through the catalyst in the range of 1,000 h ⁻¹ to 300,000 h ⁻¹ , and a gas pressure of atmospheric pressure (1 atm) or higher, and between 550 ° C. at room temperature. Characterized in that carried out in the temperature range.

A third method of treating the exhaust gas using the mixed metal oxide catalyst for treating the exhaust gas to achieve another aspect of the present invention is to use the mixed metal oxide catalyst represented by Formula 1 directly or on the support coated with the catalyst. From the exhaust gas comprising NO _x , N ₂ O, O ₂ , HC, CO, CO ₂ , H ₂ O, SO ₂ , or mixtures thereof, to HC, CO, NO, NO ₂ , N ₂ O, or these The mixture of is selectively adsorbed from oxygen and CO ₂ and then reacted with reducing agent CO or H ₂ to reduce desorption to N ₂ , CO ₂ , and H ₂ O.

In the third treatment method, the adsorption is carried out in a temperature range of 500 ℃ from room temperature, the reduction reaction is characterized in that carried out in the temperature range of 150 ~ 500 ℃.

A fourth method of treating the exhaust gas using the mixed metal oxide catalyst for treating the exhaust gas to achieve another aspect of the present invention uses the mixed metal oxide catalyst represented by Formula 1 directly or on the support coated with the catalyst. Exhaust gas containing NO _x , N ₂ O, CO ₂ , H ₂ O, SO ₂ , CO or mixtures thereof produced during combustion using only limited amounts of air or oxygen below the theoretical air-fuel ratio. Or by reacting with a gas comprising CO, which is a reducing agent, to decompose the NO _x , N ₂ O, or mixtures thereof into N ₂ and CO ₂ .

In the fourth treatment method, the reaction is characterized in that carried out at 150 to 550 ℃.

In order to achieve another aspect of the present invention, a fifth method for treating exhaust gas using a mixed metal oxide catalyst for treating exhaust gas may be performed by using the mixed metal oxide catalyst represented by Formula 1 directly or on a support coated with the catalyst. the _{NO x, N 2 O, O} 2, CO 2, H 2 O, SO 2, or by reaction with the gas mixture to the exhaust gas containing a mixture thereof comprising the reducing agent of NH ₃ of nitrogen oxides wherein the NO _x mixture Is subjected to Selective Catalytic Reduction with N ₂ and H ₂ O.

In the fifth treatment method, the reaction is characterized in that carried out at a temperature of 100 ~ 350 ℃.

A method of activating a mixed metal oxide catalyst for treating exhaust gas to achieve another aspect of the present invention includes NO _x , N ₂ O, HC, CO, CO ₂ , H ₂ O, oxygen, or a mixture thereof. Before treating the exhaust gas, at least one selected from the group consisting of infrared (IR) treatment, ultraviolet (UV) treatment, supersonic treatment, microwave treatment, and plasma treatment to the mixed metal oxide catalyst represented by Chemical Formula 1 Apply treatment.

The mixed metal oxide catalyst according to the present invention effectively adsorbs and separates HC, CO, and nitrogen oxides contained in combustion exhaust gas, and when oxygen does not coexist, enables perfect NOx reduction with CO, and is known to be very difficult to reduce decomposition. Nitrogen oxide treatment in the presence of oxygen also exists in the exhaust gas, unlike in the case of directly decomposing NOx and N ₂ O in the state adsorbed on the catalyst bed or receiving a reducing agent from outside, such as SCR method by NH ₃ and urea. Reduction of NOx at a lower temperature by reacting with CO or HC has the advantage of being able to decompose very superior in the efficiency and economic efficiency of the process compared to the SCR method or the LNT method that is being developed.

In addition, the catalyst of the present invention can be used as a lean NOx trap (Lean NOx Trap) material for separation adsorption and decomposition desorption of NOx to have a superior NOx adsorption performance compared to oxygen. In addition, the catalyst has a high selective adsorption performance and decomposition activity, and thus the decomposition reaction of NOx in the combustion exhaust gas containing nitrogen oxide at about 110 ° C., which is much lower than the NH ₃ -SCR reaction using a conventional reducing agent. In the case of using H ₂ and CO, it is possible to perform effective NOx decomposition even in the case of an efficient lean operation cycle and a temperature lower than 250 ° C. in comparison with the conventional LNT operation.

1 is a graph showing the conversion rate of NO according to the change of temperature according to Examples 1 to 4 of the present invention, Ex 1, Ex 2, Ex 3, and Ex 4 are each of Example 1, Example 2, Example 3, and Example 4.
2 to 5 are graphs showing the oxidation performance of CO and HC and the conversion rate of NO x according to the temperature change according to Examples 5 to 8 of the present invention.

The objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and the preferred embodiments associated with the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description of the present invention, detailed description of related arts which may unnecessarily obscure the gist of the present invention will be omitted.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In order to decompose lean nitrogen oxides containing N ₂ O, the present invention provides a catalyst composition capable of adsorbing HC, CO, and NOx separated from oxygen, and a catalyst composition capable of effectively reducing and decomposing adsorbed NOx. Therefore, NOx can be effectively decomposed and removed by the direct reaction or co-existence with CO and HC, which coexists with or without oxygen in the general exhaust gas temperature range, without using other reducing agents such as NH ₃ . Provided are a mixed metal oxide catalyst, a method for preparing the catalyst, a method for treating exhaust gas by oxidation, reduction or selective catalytic reduction using the catalyst, and new uses of the catalyst.

According to an embodiment of the present invention, the alkali metal, alkaline earth metal, rare earth metals, transition metals and other metals of aluminum at least in a certain molar ratio by selecting two or more metals having high adsorption performance and decomposition properties for NOx. A mixed nitrate is prepared by co-precipitation of the supersaturated solution while reacting by slowly adding a nitrate solution to a homogeneous mixed solution of alkali metal hydroxide (M (I) OH) and carbonate (M (I) ₂ CO ₃ ). A precursor of the catalyst can be obtained. Synthesis of the precursor is carried out in an alkaline state of at least pH = 10 or more, and allows time for the precipitate to be sufficiently aged while adding the appropriate amount of hydrogen peroxide (H ₂ O ₂ ) after synthesis as necessary.

The precursor thus prepared is washed with distilled water, dried and pulverized to maintain a oxidizing atmosphere of the precursor while passing a sufficient amount of air in a furnace, and then fired in a temperature atmosphere rising to 500 ° C. to prepare a mixed metal oxide catalyst. do. The mixed metal oxides prepared as described above are composed of a single metal oxide [M (x) ₂ Ox], spinel [M (II) M (III) ₂ O ₄ ], perovskite ( Perovskite) [M (II) M (IV) O ₃ ], Ferrite [M (Fe _x O _y )] based oxides and other oxides and a complex of these oxides.

As such, the oxide catalyst may basically have a spinel, perovskite, ferrite, and other crystal structures, and may include an active metal attached or interlayer bonded to the mixed metal oxide. The mixed metal oxide catalyst can totally decompose various combustion exhaust gases. For example, the present invention possesses high selectivity adsorption properties for CO, HC and NOx, has excellent oxidation performance of HC, CO and NO and high efficiency without the use of precious metals such as Pt in the presence of oxygen It has direct decomposition effect to enable NOx decomposition and selective catalytic reduction reaction (HC-SCR and NH ₃ -SCR) by CO, HC and NH ₃ , and reducing agent such as CO and H ₂ after adsorbing and storing NOx Almost all NOx treatment methods for NOx decomposition, such as LNT (Lean NOx Trap) method for reducing the temperature, and NOx reduction reaction (TWC) in the case where there is no oxygen and there is no oxygen because the oxygen concentration is tightly tuned.

When alkali metals such as Na are added to the mixed metal oxide by impregnation or ion exchange, the lean NOx treatment is made by directly decomposing the adsorbed NOx or reacting with CO or HC even in the presence of oxygen to allow the decomposition of the NOx. Performance. In the case of lean NOx treatment using a mixed metal oxide catalyst, a high NOx removal efficiency can be achieved by a passive method without injecting a reducing agent from the outside, thereby minimizing the fuel penalty due to the additional reducing agent, and the NH. _When the SCR process using a reducing agent is employed, redox activity can be increased to reductively decompose NOx in a lower temperature range than the conventional reaction temperature range. In the case of the LNT process of selectively adsorbing lean NOx and reducing or desorption with a reducing agent such as HC, CO or H ₂ , all NO, NO ₂ and N ₂ O are reduced compared to the conventional process leading to the adsorption of NO ₂ after oxidation of NO. It is possible to provide an energy-saving process of adsorption and reduction desorption at lower temperatures with higher selectivity relative to oxygen.

Oxygen bonding method of the catalyst according to the present invention is the oxygen bonding method in which oxygen forms an oxide in the high valency state of the transition metal or by the transition metals and Peroxo (O ₂ ) ^2- ligand (Ligand) There is a method of forming a peroxide, such that the excess oxygen is weakly bound to the metal, this excess bound oxygen is considered to facilitate the oxidation of the reactants by preventing further oxygen attack on the catalytic active site. do. The adsorption and oxidation reaction mechanism of such a reactant is particularly advantageous in the process of decomposition and reduction of NOx to facilitate the NOx reduction reaction by CO or HC. The bound oxygen, which participated in the reaction, can continuously maintain the oxidation activity of the catalyst by reversibly taking the oxidation process of the catalyst metal to maintain the peroxide form.

In the present invention, in order to obtain a mixed metal oxide catalyst having a large specific surface area with advanced pore structure, a precursor in the form of fine particles is synthesized by coprecipitation reaction in a liquid homogeneous system, and the pore and peroxide Forming process.

Synthesis of the precursor may use sol-gel method, solution combustion (Solution Combustion) method in addition to the co-precipitation method is first recommended, and does not exclude the heterogeneous solid-phase reaction as a method for producing nanoparticles.

Incidentally, the present invention increases the activity of the catalyst by ion exchange, impregnation, or interlayer bonding of other active or active auxiliary metals to the catalyst, thereby enhancing the selective adsorption performance of CO, HC and nitrogen oxides even when oxygen is present in excess. This resulted in high activity in the reduction decomposition reaction of NOx, and when using a reducing agent such as NH ₃ and CO provides a low energy consumption type NOx treatment process showing the activity at a lower temperature.

The catalytically active material exhibits high NOx decomposition activity and high CO and HC oxidation characteristics without the use of any other type of reducing agent in the coexistence state of CO, HC and oxygen, except for the use of expensive precious metals except for special purposes. It has the characteristic of processing gas efficiently.

The catalyst according to the present invention has a sufficient adsorption space, but forms an oxide in which a transition metal component and more than one oxygen ligand are combined to prevent excess oxygen adsorption. However, the catalyst improves the adsorption performance for NOx components such as HC, CO and NO which have affinity with oxygen, and conversely, the selective adsorption performance for components such as N ₂ , O ₂ , CO ₂ , and / or H ₂ O is low. If the components are a product or if the components are excessively included in the reactants to interfere with the formation of the product, they block or prevent their involvement in various reactions in the catalyst bed. In addition, when the components are produced, the adsorption performance of the components is lowered and the desorption is facilitated, thereby greatly improving the reaction activity.

The mixed metal oxide catalyst for treating the exhaust gas according to the present invention is represented by the following Chemical Formula 1, and is composed of a mixed metal oxide or a mixture of metal oxides of at least two or more kinds of metals.

[Formula 1]

M (II) uM (III) vM (IV) wM (V) xM (VI) yOz

Where

M (II) is at least one selected from the group consisting of divalent Mg, Ca, Ni, Zn, Sr, Ba, Be, Fe, Cu, Co, Pd and Mn,

M (III) is at least one selected from the group consisting of trivalent Al, Mn, Fe, Co, Ni, Cr, Bi, Ga, B, La, Ce, Sc and Rh,

M (IV) is at least one selected from the group consisting of tetravalent Ti, Mn, Nb, Rh, Sn, Pd, Ce, La, Mo, W, Ge, Re, Ru, and Os,

M (V) is at least one selected from the group consisting of pentavalent V, Re, Ir, Os, Bi, and Ru,

M (VI) is one or more selected from the group consisting of hexavalent Mo, W, Ir, Ru, Re, Cr,

u, v, w, x, and y are real numbers between 0 and 18 equal to or different from each other.

z is a (u + 3v / 2 + 2w + 5x / 2 + 3y) and a is a real number greater than 1 and less than or equal to 5;

As such, the catalyst according to the present invention consists of a mixed metal oxide or a mixture of metal oxides of at least two or more metals, the transition metals having an excess of oxygen bonds, or peroxox, weakly bound in at least high oxidation states. ₂ ) It has oxygen bond by peroxide by ^2- ligand, so it is formed to minimize other oxygen adsorption and maximize the adsorption of nitrogen oxides such as NO as Lewis base. In the above formula, z = a (u + 3v / 2 + 2w + 5x / 2 + 3y), which means the amount of oxygen, a is the excess of oxygen by oxo (Oxo) or peroxo (O ₂ ) ^2- ligand of oxygen and the like. It is a measure of the degree of bonding and has a real number greater than 1 and less than 5. The oxygen amount can minimize other oxygen adsorption by maintaining a stable peroxidation state in the above-described range, and can maximize the adsorption of nitrogen oxides such as NO as a Lewis salt.

In addition, the catalyst according to the present invention is a K, Li, Na, Fr, Mg, Sr, Nb, Sc, Ge, La, Mn, Fe, Cu, Ag in addition to the synthesis and bonding method through the homogeneous reaction of the mixed metal oxide One or more active ingredients or auxiliary metals selected from the group consisting of Au, Pt, Pd, Rh, Ir, and Ru can be ion exchanged, impregnated or intercalated to enhance their properties. The content of the active ingredient is preferably 0.01 to 30% by weight with respect to the total catalyst, less than 0.01% by weight is insignificant, and more than 30% by weight is meaningless because it is beyond the nature of the auxiliary metal.

In addition, the present invention comprises the steps of preparing a precursor represented by the formula (2) for the production of the mixed metal oxide catalyst through a homogeneous liquid phase reaction; And freeze-drying or drying the precursor at 70 to 150 ° C. and then calcining at 100 to 950 ° C. to form a mixed metal oxide. Optionally, the method may further include impregnating the mixed metal oxide with an active or auxiliary metal.

The mixed metal oxide preferably has a specific surface area and pore structure in the range of 5 to 500 m 2 / g sufficient for the catalytic reaction. The catalyst of the present invention having such a structure can be prepared synthetically from a mixed metal oxide precursor of Formula 2 consisting of a hydroxide salt of a metal through a homogeneous liquid phase reaction.

(2)

[M (II) uM (III) vM (IV) wM (V) xM (VI) y (OH) o] ^{p +} A ^{n -} p / nmH ₂ O

Where

M (II), M (III), M (IV), M (V), and M (VI) are as described above,

u, v, w, x, and y are also as described above,

p and o are o = (2u + 3v + 4w + 5x + 6y-p) is represented by the relational expression, A ^{n -} is an anion _{^{CO 3 2-, NO 3 -,}} SO 4 2 -, Cl -, OH - , SiO ₃ ^{2 -} and BO ₃ ^2-, etc., such as an inorganic anion and adipic acid, oxalic acid of a _{^{-, MnO 4 2 -, WO}} 4 2 -, HGaO 3 2 -, HPO 4 2 -, HVO 4 2 -, ClO 4 If the organic acid is selected from such as, p + ⁿ is 0 Cain a ^- it is a hydroxide of mixed metal-free anions represented by.

Precursor for the mixed metal oxide catalyst of the present invention is a homogeneous reaction of the precipitation, deposition-precipitation, co-precipitation or sol-gel process of the mixed metal oxide It can be formed through. It should be noted that the reactants that are put in a certain molar ratio in the process of synthesizing the precursor through a homogeneous liquid phase reaction may be produced in the same ratio because the composition of the mixed metal may vary depending on the crystal structure of the precipitate during the reaction to the precipitate. In principle, metal residues that do not participate in the reaction should be removed during cleaning.

The precursor solution thus obtained is preferably aged for a predetermined time or more, and at this time, a small amount of hydrogen peroxide (H ₂ O ₂ ) may be added to the solution to promote peroxide formation of the transition metal. After the precipitate is aged, it is washed, dried, and pulverized and calcined to obtain a mixed metal oxide catalyst. At least one metal selected from components consisting of K, Li, Na, Mg, Sr, Nb, Sc, Ge and La, Mn, Fe, Cu, Ag, Au, Pt, Pd, and Rh before entering the firing process The step of attaching or depositing the layers may be optionally performed by methods such as deposition, coating and ion exchange. At this time, the drying temperature is suitable to 70 ~ 150 ℃ but may be vacuum or freeze drying, and the firing temperature is in the range of 400 ~ 950 ℃ but when the temperature is low around the center 500 ℃ may be incomplete firing temperature If higher, the specific surface area of the catalyst may decrease or oxygen vacancies may occur, thereby inhibiting catalytic activity.

The precursor may abbreviate the precursor manufacturing and firing process by the liquid phase method, and may select a method of preparing a mixed metal oxide by a solution combustion method in which a solution of a mixed ratio of mixed metal salts is directly combusted at 100 to 950 ° C. However, the performance of the catalyst may be degraded due to the difference in the degree of formation of oxygen ligand and the characteristic of the pore structure, etc., compared to a method of preparing a precursor by a homogeneous co-precipitation method or a sol-gel method.

Precursor compound by homogeneous reaction is combined with anion group such as CO ₃ ^{2 -} in the layer structure of OH and forms regular and developed pores due to bubbles generated when heat is applied to the precursor during the firing process. It forms a very small powdery mixed metal oxide with a large specific surface area and thermal stability.

The mixed metal oxide catalyst of the present invention exhibits high adsorption characteristics for HC, CO, NOx and N ₂ O relative to oxygen according to the composition of the catalyst metal component, and is included in all kinds of combustion exhaust gases regardless of the presence or absence of oxygen. In HC, CO, NOx, and N ₂ O treatment, the reaction mode such as the active reaction temperature varies depending on the treatment method, but shows high activity overall.

The mixed metal oxide catalyst of the present invention has a high affinity for HC, CO, and NOx based on the excess oxygen bonds, so that the adsorption performance is increased, and the direct decomposition without the oxidation and reducing agent of HC, CO, and NO is required. It was confirmed that it effectively acts in the reduction process of NOx by CO, HC, etc., and that oxygen in gas is required to maintain continuous activity. It is a kind of Mars-van Krevelen reaction, in which the reduction and oxidation of the catalyst by the weakly bound oxygen of the oxo or perox ligand to the reactant and the metal oxide alternately, as found in the oxidation reaction of HC by the mixed metal oxide. A similar process to the apparatus is assumed, but N _{2 of} NO x reacts with CO or HC. And the reduction desorption process to CO ₂ or H ₂ O requires more clarification.

In the case of using a reducing agent such as CO and NH ₃ to decompose NOx by mixed metal oxides, desorption proceeds easily since it is decomposed into N ₂ , CO ₂ and H ₂ O and the adsorption performance of these decomposition products is reduced. Interpreted

According to the present invention, NOx, N ₂ O, O ₂ , of the exhaust gas generated during the combustion of fossil fuels using a mixed metal oxide catalyst prepared by the above methods or a support such as pellets or honeycomb coated with the catalyst are used. In an exhaust gas comprising HC, CO, CO ₂ , H ₂ O, SO ₂ , or a mixture thereof, NOx, such as HC, CO, NO, NO ₂ , N ₂ O, or a mixture thereof is removed from oxygen and CO _2, etc. It can be selectively adsorbed and stored separately. The adsorption temperature can be carried out at room temperature (typically about 20 ℃) at a temperature of 500 ℃, which increases the catalyst adsorption capacity as the temperature is lower, while considering the characteristics that the adsorption rate is slow, the appropriate temperature range is required It is preferable at the point of view. In the case of the NOx absorption is performed in the lean combustion exhaust gas, can be stored primarily at the same time to NO than other lean NOx storage catalyst of Pt / BaO system to adsorb the NO _2, the oxidation to NO ₂ does not require the use of noble metal catalysts such as Pt It is economical because it can be made, and HC and CO generated in the combustion process are beneficial to the reduction reaction of NOx.

According to the present invention, by using the mixed metal oxide catalyst or a support such as pellets or honeycomb coated with the catalyst, NO _x , N ₂ O, O ₂ , HC, CO CO and HC and NO can be oxidized simultaneously in the presence of at least 0.1% by volume or more of oxygen (O ₂ ) from exhaust gases comprising CO ₂ , H ₂ O, SO ₂ , or mixtures thereof. This means that unreacted HC and CO generated in low temperature combustion such as engine start or insufficient oxygen can be oxidized to excess oxygen to remove harmful components of exhaust gas.

In addition, using the mixed metal oxide catalyst according to the present invention or a support such as pellets or honeycomb coated with the catalyst, NOx, N ₂ O, O ₂ , HC, CO, HC, CO, NOx, N ₂ O or a mixture thereof is separated and adsorbed from oxygen in an exhaust gas comprising CO ₂ , H ₂ O, SO ₂ , or a mixture thereof, and at the same time, 0.1 vol% or more of oxygen is present. It is possible to directly decompose NOx into N ₂ , CO ₂ and H ₂ O using CO or HC as a reducing agent, without the aid of any reducing agent to be introduced from the outside. The nitrogen oxide concentration to be treated is preferable in that the range of 0.00001 to 30 vol% is the maximum expected range, and the oxygen concentration should be at least 0.1 vol% or more since it should be more than the amount necessary for the oxidation and NOx reduction process of HC. In the case of NOx reduction, the reaction temperature is in the range of 550 ° C at room temperature, and when higher conversion is required, it is possible to operate in the range of 150 to 550 ° C. If the temperature is higher than this range, the oxidation equilibrium is lowered, so the NO state is more stable, which makes oxidation and decomposition difficult, and at lower temperatures, the progress of the reaction slows down and the conversion rate drops.

The hourly space velocity of the gas passing through the catalyst is from 1,000 h ^-1 to 300,000 h ^-1 , the pressure of the gas is at least atmospheric pressure (1 atm), especially in the process of reducing NOx by residual HC or CO, such as CO or NH ₃ . Unlike the case where N ₂ O is generated by incomplete reduction when using a reducing agent, N ₂ O is hardly generated. The reduction method of NOx and N ₂ O by the mixed metal oxide catalyst of the present invention can not only completely replace the SCR method by NH ₃ reducing agent which is currently used in boiler and diesel engine exhaust gas treatment, If applied, a high increase in removal efficiency is expected.

On the other hand, the present invention is LNT or NSR (reduction and desorption of N ₂ and CO ₂ , H ₂ O and the like by reacting the exhaust gas selectively separated and adsorbed from oxygen and CO ₂ and the like as described above with CO, H _2, etc.) NOx Storage and Reduction In the LNT process, a separate process of oxidizing NO and N ₂ O to NO ₂ is not required, thereby making the process simple, efficient, and economical. In particular, the direct decomposition of NOx can be expected from the fuel lean or rich operation exhaust gas, and in the presence of CO and HC, a higher effect can be expected. The reduction reaction temperature may typically be carried out at a temperature of about 150 ℃ to 500 ℃, which is preferable in terms of the appropriate temperature range for the adsorption and reaction of the reducing agent.

In addition, the mixed metal oxide catalyst of the present invention is NO _x , N ₂ O, HC, CO, CO ₂ , H ₂ O, SO in the exhaust gas exhausted by using a limited amount of air or oxygen in the theoretical air-fuel ratio in the combustion process ₂ , or a mixture thereof, may be reacted with a gas containing CO or a reducing agent thereof to decompose the NOx, N ₂ O, or a mixture thereof into N ₂ and CO ₂ with high efficiency. When using the mixed metal oxide catalyst of the present invention, the reaction of the decomposition process proceeds in the range of 150 to 550 ° C., preferably at about 200 ° C. or more, almost complete NOx decomposition is achieved. The oxygen concentration is at most 0.1 vol% or at most 1/2 the CO concentration, the hourly space velocity of the gas passing through the catalyst is from 1,000 h ⁻¹ to 300,000 h ⁻¹ , and the pressure of the gas is at least atmospheric pressure (1 atm).

The mixed metal oxide catalyst of the present invention comprises an exhaust gas comprising NO x, N ₂ O, O ₂ , CO ₂ , H ₂ O, SO ₂ , or a mixture thereof and a gas mixture comprising NH ₃ , a reducing agent of nitrogen oxides. By reacting, the NO _x mixture also exhibits high activity in selective catalytic reduction of N ₂ , H ₂ O and the like. In the SCR decomposition process, since the driving cost increase due to the use of an excessive reducing agent is large, the nitrogen oxide is suitably within 1 vol%, and the oxygen concentration is 25 vol% or less. Although the reaction temperature varies depending on the catalyst composition, it is generally 100 to 350 ° C. for NOx, and the higher the temperature, the higher the NOx conversion rate, but since the generation of N ₂ O tends to increase, it is necessary to select an appropriate reaction temperature.

In general, when a suitable amount of catalyst is used, the gas passing through the catalyst can maintain an hourly space velocity of more than atmospheric pressure (1 atm) and within 1,000 h ⁻¹ to 300,000 h ⁻¹ , but preferably 3,000 h ⁻¹ to 100,000 h ^{− If the} space velocity is less than 1,000 h ^−1, economic losses due to the use of excess catalyst are concerned, and if the space velocity exceeds 300,000 h ⁻¹ , the pressure loss due to the fluid flow may increase and mechanically exacerbate the apparatus.

On the other hand, the method of decomposing NOx by attaching Na or Li to the present mixed metal oxide can be used by attaching to the existing metal oxide catalyst when the NOx adsorption performance is good, and mixing based on the non-noble metal according to the present invention. Applying at least one treatment method selected from the group consisting of infrared (IR) treatment, ultraviolet (UV) treatment, supersonic treatment, microwave treatment, and plasma treatment to the metal oxide catalyst increases the activity of the catalyst to increase NOx. Nitrogen oxides can be more easily decomposed from exhaust gases including N ₂ O, O ₂ , CO ₂ , H ₂ O, SO ₂ , or mixtures thereof. Such treatments are well known in the art, and the present invention is applicable to such known treatments.

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.

Production Example 1

Preparation of Precursors and Mixed Metal Oxides

Generally, alkali metal hydroxides [M (I) OH] and carbonates [M (I) ₂ CO ₃ ] of Na or K are dissolved in distilled water at a ratio of about 4: 1, added to the reactor, and then stirred at a constant rate. A precipitate was obtained by gradually adding an aqueous solution of nitrate of a selected metal at a constant molar ratio as described in the Examples for 4 hours, and the resulting precipitate was heated to 50-65 ° C. under slow stirring again and aged for up to 16 hours to mix the mixed metal. The hydroxide carbonate can be produced uniformly. At this time, in order to form the peroxide of the mixed metal, hydrogen peroxide in a concentration range of 0-10% may be gradually added. Thereafter, the residual alkali solution is separated, washed with excess distilled water and dried in an oven at 110 ° C. to obtain a precursor of the mixed metal oxide. The precursor thus obtained is slowly heated in an atmosphere passing through the air and calcined at about 500 ° C. for about 4 hours to volatilize components such as H ₂ O and CO ₂ to obtain a final mixed metal oxide catalyst.

In the co-precipitation method, a precursor is made of an nitrate aqueous solution having M (I) as Na and Al and Co in a ratio of 1: 2, and the mixed metal oxide prepared by calcining at 500 ° C. is composed of spinel crystals of AlCo ₂ O ₄ . It was analyzed to have a similar structure, but strictly the ratio of Al / Co / O has a distribution from 1 / 1.7 / 8.5 to 1 / 2.4 / 12.7, which has a crystal structure mainly composed of the spinel, but in which multiple phases are combined. It is a multi-phase oxide, and it can be seen that oxygen is bonded in excess.

A mixed metal oxide having a similar crystal structure was also prepared from an aqueous solution of nitrate containing a small amount of precious metal such as Pd and Rh in a 1: 2 ratio of Al and Co. In addition, the mixed metal oxide through the precursor was prepared by changing the ratio of Al and Co and adding or substituting metals such as La, Fe, Ni, Mn, and NOx and O ₂ , depending on the composition of the catalyst. The adsorption and desorption performance and decomposition characteristics of CO ₂ and the like were respectively shown.

Energy Dispersive X-Ray Spectroscopy (EDS) analysis showed that XRD (X) for mixed metal oxides with Al / Co / Mn / O ratios in the molar ratios of 0.7 / 1.8 / 1 / 8.5 to 0.8 / 2.0 / 1 / 10.4 -ray diffraction results show spinel crystal peaks such as AlCoMnO ₄ , MnCo ₂ O ₄ , (Co, Mn) (Co, Mn) ₂ O ₄ , etc. It can be seen that it is mixed with oxide in the oxidized state of trivalent and trivalent, and the composition of oxygen is sufficiently combined.

For the binding of the active metals, ion exchange, impregnation, or intercalation may be employed. A nitrate solution may be prepared according to the amount of the metal component to be impregnated, and the mixed metal oxide or precursor may be impregnated and slowly stirred overnight. After evaporation, it was tested by heating and drying trace amounts of Sr, Cu, Fe, Ag, Pd, Pt, Rh and the like, and is particularly effective as an efficient method of using expensive precious metals.

Decomposition Performance of Nitric Oxide

[Comparative Example 1]

NO Decomposition Activity at the Reaction Temperature of 650-900 ° C in the Decomposition of NO to N ₂ and O ₂ by LaNiO ₃ Perovskite Catalyst and La (1x) CexSrNiO ₄ (0≤x≤0.3) Mixed Metal Oxide Catalyst with Ce It confirmed that it represents.

[Comparative Example 2]

The precursor was prepared in a 300 ° C. high-pressure reactor by the glycothermal method with a Mn / Ce ratio of 1/3, and calcined at 400 ° C., followed by the addition of BaNO ₃ and baking at 800 ° C. A Ba-CeMn mixed oxide catalyst was used to obtain a NO conversion of up to 67% with SV = 5,000 / h at 800 ° C.

[Comparative Example 3]

Conventional to use the solid-phase reaction method using _{La 0 .7 Ba 0 .3 Mn 0} .8 In 0 .2 O 3 catalyst in a LaMnO ₃ perovskite prepared by baking the coated Ba and In at 1000 ℃ max The conversion to N ₂ of 63.7% was obtained, but the activity of the catalyst gradually decreased due to the strong adsorption of oxygen.

[Comparative Example 4]

Preparing a precursor with citric acid combustion (combustion Citrate), and obtained by firing at _{900 ℃ La 1 .6 Ba 0 .8} NiO 4 mixed metal oxide catalyst 2% in a state in which oxygen is present in an about SV = 3000 / h 850 ℃ 75% conversion of NO to N ₂ was obtained.

[Comparative Example 5]

After freeze-drying the precursor composition mixed with the catalyst component ratio, followed by firing at 650 ℃ obtained perovskite-type mixed metal oxide is _{La 0 .8 Sr 0 .2 Cu 0} .15 Fe 0 .85 O 3 -δ catalyst In the absence of oxygen, SV was set to about 3000 / h to obtain an N ₂ conversion of 45% at 650 ° C., but the conversion fell below 20% at 6% oxygen.

[Comparative Example 6]

Nitrogen mixed with 1000 ppm C ₃ H ₆ , 500 ppm NO, 5% CO ₂ , 600 ppm CO, 12% O ₂ , 5% H ₂ O using a catalyst coated with 2% -Ag on γ-alumina Passing the gas at SV = 40,000 / h showed activity above 350 ° C. and a conversion peak of NOx near 500 ° C. showing 72%.

[Comparative Example 7]

In addition, when a gas of 5% -Cu impregnated with ZSM-5 was passed through the gas under the same conditions as in [Comparative Example 5], the activity was exhibited from 250 ° C or higher, and the NOx conversion peak was 45% around 400 ° C. .

[Example 1]

In Preparation Example 1, 412 ppm of NO, 9.6% of O ₂ , and the remainder in a powder catalyst layer having 4.7% Ag added to a mixed metal oxide prepared in a molar ratio of Al / Co / O (1/2 / 8.9) through a co-precipitation method. When the gas filled with nitrogen was passed through the space velocity SV 30,000h ^-1, the oxidation conversion rate from NO to NO ₂ was 54.4% at 200 ° C, 94.2% at 250 ° C, 93.7% at 300 ° C, and 85.9% at 350 ° C. It showed high activity over a wide temperature range.

[Example 2]

In Preparation Example 1, NO 215ppm, O ₂ to the powder catalyst layer impregnated with 3.0% Ag in the mixed metal oxide prepared in a molar ratio of Al / Co / Mn / O (0.8 / 1.9 / 1/10) through the co-precipitation method 13.06%, CO ₂ 11.54% and the remainder, when the gas filled with nitrogen was passed through the space velocity SV 30,000h ^-1 flow rate, the conversion rate of NO gas to NO ₂ was 32.1% at 200 ° C, 81.9% at 250 ° C, and 300 ° C. At 89.3%, 79.1% at 350 ° C and 63.3% at 400 ° C.

[Example 3]

In Preparation Example 1, NO 402ppm, O in a powder catalyst layer impregnated with 4.7% Ag on a mixed metal oxide prepared in a molar ratio of Al / Ni / Mn / O (1 / 1.9 / 1.1 / 9.3) through a coprecipitation method. ₂ 9.8%, CO ₂ 8.8%, H ₂ O 5% and the remainder, when the gas filled with nitrogen was passed through the space velocity SV 30,000 h ^-1 flow rate, the conversion rate of NO gas to NO ₂ was 56.5% at 150 ° C, 200 It showed high activity over a wide temperature range of 67.4% at 250 ° C, 80.1% at 250 ° C, 90.8% at 300 ° C, 86.8% at 350 ° C, 74.9% at 400 ° C, and 44.5% at 500 ° C.

[Example 4]

In Preparation Example 1, NO 405 ppm, O ₂ to a powder catalyst layer impregnated with 2.3% Ag on a mixed metal oxide prepared in a molar ratio of Al / Co / Pd / O (1 / 2.2 / 0.03 / 5.6) through a coprecipitation method. 11.11%, CO ₂ 11.54% and the remainder, when the gas filled with nitrogen was passed through the space velocity SV 30,000h ^-1 flow rate, the conversion of NO gas to NO ₂ was 20.5% at 200 ° C, 81.2% at 250 ° C, and 300 ° C. At 87.7%, 73.6% at 350 ° C and 53.3% at 400 ° C.

[Example 5]

In Preparation Example 1, a powder catalyst layer having 3% silver (Ag) attached to a mixed metal oxide prepared at a molar ratio of Al / Co / Mn / O (0.8 / 2/1/10) through a coprecipitation method was used. 311ppm CO, 817ppm CO, 847ppm C ₃ H _6, 847ppm O ₂ 10.3%, and the rest is nitrogen-filled gas at room velocity SV 100,000h ^-1 As a result of measuring the oxidation efficiency of these, C ₃ H ₆ showed a conversion of 50% at 150 ℃, 100% of 200 ℃, CO showed a conversion of 50% at 120 ℃, 98% at 250 ℃, NO The conversion to NO2 was about 42% at 300 ° C.

[Example 6]

In Preparation Example 1, 50% of a powder catalyst layer impregnated with 3% Ag was coated on a powder catalyst of a mixed metal oxide prepared at a molar ratio of Al / Co / Mn / O (1.5 / 3.5 / 1/18) through a coprecipitation method. 300 ppm NO, CO 851 ppm, O ₂ 11%, C ₃ H ₆ 983 ppm and the rest are nitrogen-filled gases with a temperature of SV 132,000 h ^-1 As a result of measuring the oxidation efficiency of these, C ₃ H ₆ showed a conversion of 50% at 160 ℃, 99% at 200 ℃, CO 50% at 110 ℃, 85% at 200 ℃, NO Conversion to NO2 was 60% at around 300 ° C.

[Example 7]

50 ° C of a powder catalyst layer in which 10% sodium (Na) was added to a mixed metal oxide prepared at a molar ratio of Al / Co / Mn / O (1.5 / 3.5 / 1/18) through a coprecipitation method in Preparation Example 1 Out of temperature increase at a rate of 20 per minute up to ℃ 450 ℃ NOx 293ppm, CO 1017ppm, one of the C ₃ H ₆ HC 1352ppm, O ₂ 10.5%, and the rest of the space velocity in the gas filling with nitrogen SV 123,000h ^- The oxidation conversion of CO and C ₃ H ₆ was decreased by the addition of Na at ¹ flow, but NOx was removed in all temperature ranges, especially between 80% and 95% in 250 ° C and 420 ° C. It was.

[Example 8]

50 ° C of a powder catalyst layer in which 20% sodium (Na) was added to a mixed metal oxide prepared in a molar ratio of Al / Co / Mn / O (1.5 / 3.5 / 1/18) through the coprecipitation method in Preparation Example 1 Out of temperature increase at a rate of 20 per minute up to ℃ 450 ℃ NOx 319ppm, CO 1056ppm, one of the C ₃ H ₆ 852ppm HC, O ₂ 11.9%, and the rest of the space velocity in the gas filling with nitrogen SV 165,000h ^- The oxidation conversion of CO and C ₃ H ₆ was decreased due to the increase of Na addition when passed at ¹ flow rate, but NOx was removed more stably in all temperature ranges, especially about 80% to 97% at 250 ° C and 420 ° C. Conversion between.

[Example 9]

In order to add an oxidation effect in addition to 10% sodium (Na) to the mixed metal oxide prepared in the molar ratio of Al / Co / Mn / O (1.5 / 3.5 / 1/18) through the coprecipitation method in Preparation Example 1 712 ppm, 9.4% of O ₂ 306ppm, CO 1035ppm, C ₃ H _{6, which} is one of NOx, while heating the powder catalyst layer impregnated with silver (Ag) at a rate of 20 ° C. per minute from 50 ° C. to 450 ° C. Is a gas filled with nitrogen, and CO and C ₃ H ₆ were 50% at 230 ° C and 380 ° C, respectively, and passed at 400 ° C and 90% and 55% at the rate of space velocity SV 129,000h ^-1 , respectively. NOx showed a conversion in the range of 60% to 70% in the 300 to 420 ° C range, so that the increase in oxidation performance did not lead to an increase in the NOx conversion.

[Example 10]

In addition to the mixed metal oxide prepared in the molar ratio of Al / Co / Mn / O (1.5 / 3.5 / 1/18) through the coprecipitation method in Preparation Example 1 and in addition to 20% sodium (Na), The powder catalyst layer impregnated with% silver (Ag) was heated at a rate of 20 ° C. per minute from 50 ° C. to 450 ° C., while NOx 285 ppm, CO 1035 ppm, and C ₃ H _{6, which} is one of HC, 481 ppm, O ₂ 8.8%, and The remainder was nitrogen-filled gas and CO and C ₃ H ₆ were 50% at 200 ° C and 320 ° C and 80% at 370 ° C, respectively, when passed through the space velocity SV 142,800h ^-1. Shows a conversion of 80% to 90% in the 230 ℃ 400 ℃ section.

[Example 11]

3% silver (Ag) and 10% sodium (Na) in the mixed metal oxide prepared in the molar ratio of Al / Co / Mn / O (1.5 / 3.5 / 1/18) through the coprecipitation method in Preparation Example 1 The catalyst layer having the impregnated powder was heated at a rate of 20 ° C. per minute from 50 ° C. to 450 ° C., while NOx 286 ppm, CO 0 ppm, and HC ₃ , C ₃ H _6, were 718 ppm, O ₂ 9.6%, and the rest were filled with nitrogen. C ₃ H ₆ was 50% at 280 ° C and more than 90% oxidation at 400 ° C, while NOx was 70% to 82% at 200 ° C and 400 ° C when passed through the gas at a space velocity SV 110,000h ^-1 The conversion rate of is shown.

[Example 12]

3% silver (Ag) and 10% sodium (Na) in the mixed metal oxide prepared in the molar ratio of Al / Co / Mn / O (1.5 / 3.5 / 1/18) through the coprecipitation method in Preparation Example 1 The powder catalyst layer impregnated with nitrogen was heated at a rate of 20 ° C. per minute from 50 ° C. to 450 ° C., while NOx 312 ppm, CO 1045 ppm, C ₃ H ₆ 0 ppm, O ₂ 10.1%, and the rest were filled with nitrogen to obtain a space velocity SV. CO was 50% at 220 ° C. and 80% oxidation at 400 ° C., while NOx showed a conversion of 60% to 70% at 400 ° C. at 250 ° C. when passed at a flow rate of 116,000 h ⁻¹ .

[Example 13]

50 ° C of a powder catalyst layer in which 20% sodium (Na) was added to a mixed metal oxide prepared in a molar ratio of Al / Co / Mn / O (1.5 / 3.5 / 1/18) through the coprecipitation method in Preparation Example 1 NOx 319ppm, CO 0ppm, C ₃ H ₆ 0ppm, O ₂ 10.4%, and the remainder were passed through a nitrogen-filled gas at a space velocity SV 153,000h ^-1 NOx showed a conversion of 90% to 95% in the 250 ℃ to 450 ℃ interval.

[Example 14]

A powder catalyst layer having 3.0% Li attached to a mixed metal oxide prepared at a molar ratio of Al / Co / Mn / O (0.8 / 2.0 / 1/10) through the coprecipitation method in Preparation Example 1 from 50 ° C. to 450 ° C. While heating up at a rate of 20 ° C. per minute, NOx 301ppm, CO 1003ppm, C ₃ H ₆ 435ppm, O ₂ 11.3%, and the rest is nitrogen-filled gas, passing CO at a space velocity SV 46,000h ^-1 The oxidation rate was higher than 90%, and C ₃ H ₆ was completely oxidized at 170 ℃ or higher by participating in NOx reduction, and the NOx showed more than 60% conversion in the temperature range of 230 ℃ to 320 ℃. Compared to the performance was not.

Example 15

In the Preparation Example 1, a powder catalyst having 3.0% Na attached to a mixed metal oxide prepared at a molar ratio of Al / Co / Mn / O (0.8 / 2.0 / 1/10) through a coprecipitation method was used as an LNT catalyst. When the conditions of the lean combustion exhaust gas were alternately passed at SV 40000 / h at NO 335 ppm, C ₃ H ₆ 502 ppm, O ₂ 11.7%, and the conditions of the rich combustion exhaust gas were CO 9237 ppm and C ₃ H ₆ 1209 ppm. A lean / rich run cycle of 12 minutes / 3 minutes and 4 minutes / 1 minute showed NOx removal efficiencies of at least 80% and at least 90%, despite the long occlusion time, respectively.

Example 16

In Preparation Example 1, NO 288ppm, O ₂ 11.2% and the rest of the nitrogen in the powder catalyst layer of the mixed metal oxide prepared in a molar ratio of Al / Ni / Mn / O (1 / 1.9 / 1.1 / 9.3) through the co-precipitation method 2,000 ppm of NH ₃ was injected into the gas filled with nitrogen, and the reduction decomposition efficiency of NOx was measured at a space velocity of SV 30,000 h ^-1 , which showed 95.0% at 110 ° C and 100% at 120 ° C or higher. , N ₂ O was generated from 130 ° C., and the N ₂ O concentration was increased with increasing temperature.

Example 17

In Preparation Example 1, CO 2145ppm, O ₂ 7.04% in the powder catalyst layer of the mixed metal oxide prepared in a molar ratio of Al / Ni / Mn / O (1 / 1.9 / 1.1 / 9.3) through the co-precipitation method, the rest is nitrogen The oxidation efficiency of CO was measured at a rate of space velocity SV of 30,000 h ^-1 and the conversion rate of 97% at 150 ° C, 100% at 200 ° C and higher.

Table 1 shows the more specific NO and NOx conversion ratios of Examples 1 to 8, particularly Examples 1 to 4 related to oxidation of NO, Examples 5 to 6 related to CO and HC oxidation, and Examples 7 to 8 related to NOx treatment. 1 and 2 and in FIGS. 1-5.

Reaction Conditions and Results of Examples 1-4 Temperature (℃) NO conversion rate (%) Example 1 Example 2 Example 3 Example 4 100 8.9 35 0 150 21.6 10.2 56.5 2.1 200 54.4 32.1 67.4 20.5 250 94.2 81.9 80.1 81.2 300 93.7 89.3 90.8 87.7 350 85.9 79.1 86.8 73.6 400 73.3 63.3 74.9 53.3 500 39.6 24.7 44.5 16.7 catalyst
(Catalyst) 4.7% Ag /
AlCo (1/2) 3.0% Ag /
AlCoMn (0.8 / 1.9 / 1) 4.7% Ag /
AlNiMn (1 / 1.9 / 1.1) 2.3% Ag /
AlCoPd (1 / 2.2 / 0.03)
Reaction conditions
(Input
Condition)
NO 412ppm
O ₂ 9.6%
SV 30,000 / h
NO 215ppm
O ₂ 13.06%
CO ₂ 11.54%
SV 30,000 / h NO 402ppm
O ₂ 9.8%
CO ₂ 8.8%
H ₂ O 5%
SV 30,000 / h
NO 405ppm
CO ₂ 11.54%
O ₂ 11.11%
SV 30,000 / h

Reaction Conditions and Results of Examples 5-8 Temperature (℃) CO / HC conversion rate (%) Lean NOx Conversion Rate (%) Example 5 Example 6 Example 7 Example 8 100 29/10 33/30 60 52 200 90/100 85/99 30 35 250 98/100 96/100 80 78 300 100/100 98/100 93 93 350 100/100 100/100 95 96 400 100/100 100/100 90 95 catalyst
(Catalyst) 3% Ag /
AlCoMn (0.8 / 2/1) 3% Ag /
AlCoMn (1.5 / 3.5 / 1) 10% Na /
AlCoMn (1.5 / 3.5 / 1) 20% Na /
AlCoMn (1.5 / 3.5 / 1)
Reaction conditions
(Input
Condition)

20 ℃ / min elevated temperature NO 311ppm
CO 817ppm
C ₃ H ₆ 847 ppm
O ₂ 10.3%
SV 100,000h ^-1 NO 300ppm
CO 851ppm
C ₃ H ₆ 983 ppm
O ₂ 11%
SV 132,000h ^-1 NOx 293ppm
CO 1017ppm
C ₃ H ₆ 1352ppm
O ₂ 10.5%
SV 123,000h ^-1 NOx 319 ppm
CO 1056ppm
C ₃ H ₆ 852ppm
O ₂ 11.9%
SV 165,000h ^-1

The scope of the present invention for various methods of decomposing nitrogen oxides is not limited to the above comparative examples and examples. In the mixed metal oxide catalyst of the present invention, the affinity for oxygen adsorption is weakened and the adsorption and oxidation performance of NOx, such as CO, HC, and NO, are relatively increased, and the selective oxidation of NOx is caused by oxidation of CO or HC coexisting in the exhaust gas. By facilitating a reduction reaction (SCR), the reduction decomposition activity of NOx was greatly increased, and the composition of a catalyst capable of producing more than the exhaust gas conditions and performances shown in Comparative Examples and Examples can be sufficiently predicted. .

The specific parts of the present invention have been described in detail above, and it is apparent to those skilled in the art that such specific descriptions are merely preferred embodiments, and thus the scope of the present invention is not limited thereto. something to do. It is therefore intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims (17)

A mixed metal oxide catalyst for treating exhaust gas, which is represented by the following Chemical Formula 1 and composed of a mixture of at least two kinds of mixed metal oxides or metal oxides.
[Chemical Formula 1]
M (II) uM (III) vM (IV) wM (V) xM (VI) yOz
In this formula,
M (II) is selected from the group consisting of valence Mg, Ca, Ni, Zn, Sr, Ba, Be, Fe, Cu, Co, Pd and Mn,
M (III) is at least one selected from the group consisting of trivalent Al, Mn, Fe, Co, Ni, Cr, Bi, Ga, B, La, Ce, Sc and Rh,
M (IV) is at least one selected from the group consisting of tetravalent Ti, Mn, Nb, Rh, Sn, Pd, Ce, La, Mo, W, Ge, Re, Ru, and Os,
M (V) is at least one selected from the group consisting of pentavalent V, Re, Ir, Os, Bi, and Ru,
M (VI) is one or more selected from the group consisting of hexavalent Mo, W, Ir, Ru, Re, Cr,
u, v, w, x, and y are the same or different real numbers between 0 and 18, at least two of which are not zero,
z is a (u + 3v / 2 + 2w + 5x / 2 + 3y) and a is a real number greater than 1 and less than or equal to 5;
The method according to claim 1,
The catalyst is at least one selected from the group consisting of K, Li, Na, Fr, Ag, Au, Pt, Pd, Rh, Ir, Ru, Mg, Sr, Nb, Sc, Ge, La, Mn, Fe, and Cu Further comprising a component by ion exchange, impregnation or interlayer bonding method, the content of the component is a mixed metal oxide catalyst for the treatment of exhaust gas, characterized in that 0.01 to 30% by weight relative to the total catalyst.
The method according to claim 1,
The catalyst is a mixed metal oxide catalyst for the treatment of exhaust gas, characterized in that it has a specific surface area in the range of 5 to 500 m 2 / g.
Providing a precursor for a mixed metal oxide catalyst represented by Formula 2, consisting of at least two or more mixed metal oxides or a mixture of metal oxides; And
The precursor is freeze-dried or dried at 70 to 150 ℃, or calcined at 100 to 950 ℃ to form a mixed metal oxide represented by the formula (1) comprising the step of producing a mixed metal oxide catalyst for the treatment of exhaust gas.
[Chemical Formula 1]
M (II) uM (III) vM (IV) wM (V) xM (VI) yOz
(2)
[M (II) uM (III) vM (IV) wM (V) xM (VI) y (OH) o] ^{p +} A ^{n -} p / nmH ₂ O
In this formula,
M (II) is at least one selected from the group consisting of divalent Mg, Ca, Ni, Zn, Sr, Ba, Be, Fe, Cu, Co, Pd and Mn,
M (III) is at least one selected from the group consisting of trivalent Al, Mn, Fe, Co, Ni, Cr, Bi, Ga, B, La, Ce, Sc and Rh,
M (IV) is at least one selected from the group consisting of tetravalent Ti, Mn, Nb, Rh, Sn, Pd, Ce, La, Mo, W, Ge, Re, Ru, and Os,
M (V) is at least one selected from the group consisting of pentavalent V, Re, Ir, Os, Bi, and Ru,
M (VI) is one or more selected from the group consisting of hexavalent Mo, W, Ir, Ru, Re, Cr,
u, v, w, x, and y are real numbers between 0 and 18 equal to or different from each other,
z is a (u + 3v / 2 + 2w + 5x / 2 + 3y) and a is a real number greater than 1 and less than or equal to 5;
p and o are o = (2u + 3v + 4w + 5x + 6y-p) is represented by the relational expression, A ^{n -} is an anion _{^{CO 3 2-, NO 3 -,}} SO 4 2 -, Cl -, OH - _{^{, SiO 3 2 -, MnO 4}} 2 -, WO 4 2 -, HGaO 3 2 -, HPO 4 2 -, HVO 4 2 -, ClO 4 - and BO ₃ ^2-, is selected from adipic acid, and oxalic acid.
The method of claim 4,
The precursor for the mixed metal oxide catalyst is a method of producing a mixed metal oxide catalyst for the treatment of exhaust gas, characterized in that formed through the homogeneous reaction of precipitation, deposition-precipitation, co-precipitation or sol-gel method, or peroxide treatment.
The method of claim 4,
The method comprises K, Li, Na, Fr, Ag, Au, Pt, Pd, Rh, Ir, Ru, Mg, Sr, Nb, Sc, Ge, La, Mn, Fe, and Cu to the precursor or mixed metal oxide. Method for producing a mixed metal oxide catalyst for the treatment of exhaust gas further comprising the step of ion exchange, impregnation or interlayer bonding of at least one component selected from the group consisting of.
The mixed metal oxide catalyst according to any one of claims 1 to 3, directly or in a catalyst-coated support, is used to support NO _x , N ₂ O, O ₂ , HC, CO, CO ₂ , H ₂ O, SO ₂ Or oxidizes CO, HC and NO in the presence of at least 0.1 volume percent of oxygen (O ₂ ) from the exhaust gas comprising a mixture thereof, or at the same time NO, NO ₂ , N ₂ O, or mixtures thereof A method for treating exhaust gas using a mixed metal oxide catalyst for treating exhaust gas, which is separated and adsorbed from oxygen and decomposed directly, or reduced and decomposed into N ₂ , CO ₂ and H ₂ O by co-existing CO or HC.
The method of claim 7,
The method is characterized in that it is carried out in the hourly space velocity of the exhaust gas passing through the catalyst in the range of 1,000 h ⁻¹ to 300,000 h ⁻¹ , and the gas pressure above atmospheric pressure (1 atm), and a temperature range between 550 ° C. at room temperature. An exhaust gas treatment method using a mixed metal oxide catalyst for treating exhaust gas.
The mixed metal oxide catalyst according to any one of claims 1 to 3, directly or in a catalyst-coated support, is used to support NO _x , N ₂ O, O ₂ , HC, CO, CO ₂ , H ₂ O, SO ₂ And exhaust gas oxidizing and releasing residual CO and HC which are present as unreacted substances under the conditions in which at least 0.1 vol% or more of oxygen (O ₂ ) is present from the exhaust gas including a mixture thereof, and simultaneously oxidizing NO to NO ₂ . Method for treating exhaust gas using a mixed metal oxide catalyst for treatment of sewage.
NO _x , N ₂ O, O ₂ , CO ₂ , H ₂ O, SO ₂ , or their mixed metal oxide catalysts according to claim 1, directly or in a catalyst-coated support From the exhaust gas comprising the mixture, NO, NO ₂ , N ₂ O, or a mixture thereof is selectively adsorbed from oxygen and CO ₂ and then reacted with a reducing agent CO or H ₂ to react N ₂ , CO ₂ , and H _2. A method for treating exhaust gas using a mixed metal oxide catalyst for treating exhaust gas with reduction and desorption with O.
The method of claim 10,
A method for treating exhaust gas using a mixed metal oxide catalyst for treating exhaust gas, wherein the support is a pellet or honeycomb structure.
The method of claim 10,
The adsorption is carried out in a temperature range of room temperature to 500 ℃, the reduction reaction is a method of treating the exhaust gas using a mixed metal oxide catalyst for the treatment of exhaust gas, characterized in that carried out at a temperature range of 150 ~ 500 ℃.
Combustion with an oxygen concentration of 0.1% or less in a combustion exhaust gas using only a limited amount of air or oxygen in a theoretical air-fuel ratio by using the mixed metal oxide catalyst according to any one of claims 1 to 3 directly or in a support coated with the catalyst. The exhaust gas containing NO _x , N ₂ O, CO ₂ , H ₂ O, SO ₂ , CO or a mixture thereof generated in the process is reacted with its own CO to produce the NO _x , N ₂ O, or a mixture thereof. A method of treating exhaust gases using a mixed metal oxide catalyst for treating exhaust gases, which decomposes them into N ₂ and CO ₂ .
The method according to claim 13,
The reaction method of the exhaust gas using the mixed metal oxide catalyst for the treatment of exhaust gas, characterized in that carried out at 150 to 550 ℃.
NO _x , N ₂ O, O ₂ , CO ₂ , H ₂ O, SO ₂ , or their mixed metal oxide catalysts according to claim 1, directly or in a catalyst-coated support Exhaust gas using a mixed metal oxide catalyst for treating exhaust gas, which reacts the exhaust gas containing the mixture with a gas mixture including NH ₃ , a reducing agent of nitrogen oxides, to selectively catalytically reduce the NO _x mixture to N ₂ and H ₂ O. Method of treating gas.
16. The method of claim 15,
The reaction method of the exhaust gas using the mixed metal oxide catalyst for the treatment of exhaust gas, characterized in that the reaction is carried out at a temperature of 100 ~ 350 ℃.
The mixed metal according to any one of claims 1 to 3 for decomposing nitrogen oxides from exhaust gases comprising NO _x , N ₂ O, CO ₂ , H ₂ O, CO, HC, oxygen, or mixtures thereof. A method of activating a mixed metal oxide catalyst by applying a treatment method selected from the group consisting of infrared (IR) treatment, ultraviolet (UV) treatment, ultrasonic treatment, microwave treatment, and plasma treatment to the oxide catalyst.

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