KR20150113643A - Manufacturing method of mixed metal oxides catalyst - Google Patents

Abstract

The present invention relates to a method for manufacturing a mixed metal oxide catalyst. More specifically, the method comprises: a synthesis step for synthesizing a precursor solution by stirring a mixed metal solution, which is prepared by dissolving two or more metals among Al, Mn, Fe, Co, Ni, Cr, Bi, Ga, B, La, Ce, Sc, and Rh in distilled water, and a reaction solution, which is prepared by dissolving NaOH and Na_2CO_3 in distilled water, at 300-500 rpm at a temperature of 60-70°C; a maturing step for uniformizing the precursor solution by stirring the precursor solution synthesized in the synthesis step at a temperature of 60-70°C for 15-17 hours; a washing step for removing residues to have a pH between 6.5 and 7.5 by washing the precursor solution matured in the maturing step; a pulverization step for drying the precursor solution washed in the washing step at a temperature of 70-110°C for 12-13 hours and pulverizing the same; a first plasticizing step for plasticizing the precursor powder pulverized in the pulverization step by raising the temperature, 2 degrees per minute, up to 500°C and keeping the temperature at 500°C for 3.5-4.5 hours; and an immersion step for immersing the precursor powder sintered in the plasticizing step in a metal solution, in which 3 parts by weight of metallic Ag, with respect to 100 parts by weight of the precursor powder, is dissolved, for 1-12 hours. The method for manufacturing the mixed metal oxide catalyst in accordance with the present invention synthesizes and matures the mixed metal solution and the reaction solution at the best temperature, thereby reducing the temperature for reaching a conversion rate of 50%.

Description

Technical Field [0001] The present invention relates to a mixed metal oxide catalyst,

The present invention relates to a mixed metal oxide catalyst preparation method, and more particularly, to a mixed metal oxide catalyst preparation method capable of lowering a temperature at which a conversion rate reaches 50% by synthesizing and aging a mixed metal solution and a reaction solution at the most appropriate temperature .

As the damage caused by climate change is increasing worldwide, interest in the atmospheric environment has been increasing recently. The use of fossil fuels and exhaust gases (hereinafter also abbreviated as "fuels") resulting from the combustion of these fuels contribute to the emission of large quantities of greenhouse gases and CO (carbon monoxide), HC (hydrocarbons) and NOx (nitrogen oxides) . Of these, CO and HC are oxidized and discharged by a diesel oxidation catalyst (DOC) using expensive noble metals such as Pt (platinum). However, in the case of exhaust gas containing excess oxygen, (Nitrogen) and O2 (oxygen), it has not been easy to reduce the amount of NOx. Therefore, many studies have been made to develop a technique for reducing NOx.

In order to suppress the emission of greenhouse gases, it is necessary to increase the combustion efficiency of the fuel. On the other hand, in order to meet the regulation of the emission of NOx, the combustion is intended to lower the NOx generation. This tendency is caused by the lack of post-treatment technology for NOx treatment of exhaust gas in any part of the convenience of technology, economical efficiency and treatment efficiency.

Currently, selective catalytic reduction (SCR), which is widely used in the treatment of various exhaust gases such as boilers and incinerators, uses NH3 (ammonia) as a typical reducing agent. In addition to the economic burden and inconvenience of use, And the incomplete reduction of NOx, N ₂ O production, which is known to have a greenhouse effect of 310 times CO ₂ .

In addition to air emissions regulations in the general industry, fuel efficiency is high in the automotive industry, but for diesel engines that require high air-to-air ratios, especially for NOx emissions, they are seeking to reduce emissions to almost the level of gasoline engines. The NOx treatment technology of exhaust gas of lean burn engine which contains excessive oxygen is expected to be effective in the SCR technology by NH ₃ reducing agent but it is necessary to carry a separate element tank for ammonia supply or low NOx conversion (Exhaust gas recirculation) method.

In the case of HC-SCR using HC (hydrocarbon, hydrocarbon) as a reducing agent, the fuel can be used as a reducing agent, so there is no need to install a separate storage tank. However, It appears to reduce the efficiency. In the case of using CO and H2 as a reducing agent, a non-selective oxidation reaction between the reducing agent and oxygen proceeds in addition to the reaction with NOx, and thus an LNT (Lean NOx Trap) separating and adsorbing NOx separately in a state where oxygen coexists, , In which case the complexity of the apparatus, as well as the reduction of the fuel are obtained from the fuel, leading to a reduction in fuel efficiency.

Due to these problems, the potential NOx reducing agents (CO, H2 and HC), which are presently contained in the exhaust gas, are not used for NOx reduction but are oxidized and discharged through the diesel oxidation catalyst.

On the other hand, direct decomposition methods for decomposing NOx more easily without using a reducing agent have been studied. Kustova et al. (Applied Catalysis B: Environmental 67 (2006) 6067) Conventional Cu-ZSM-5 catalysts, which many researchers are interested in, show activity only at around 1000 ° C., and Wang et al. (Catalysis Today 96, 1120, 2004 ) And the result of direct decomposition of NO and N2O using Pt catalyst or Iwakuni et al. (Applied Catalysis B: Environmental 74, 299306, 2007) attempted direct decomposition of NO by using perovskite catalyst As can be seen, it was only at a certain level of activity at 800 ° C or higher.

These researchers attempted to decompose N2 into NO by adsorbing NO to oxygen vacancies at a high temperature, mainly by calcining the metal oxide at a high temperature, In particular, when oxygen is present, the activity is markedly lowered due to the strong adsorption of oxygen. Thus, the present invention shows a great distance from the technology that can be put to practical use.

Korean Patent Laid-Open No. 10-2013-0123311 (published on November 12, 2013) for solving such problems relates to a mixed metal oxide catalyst for treating exhaust gas, a method for producing the same, and a method for treating exhaust gas using the same, Registered Patent No. 10-1029646 (Registered Apr. 4, 2011) relates to a method for decompositionally treating lean NOx through a parallel arrangement of a high-absorbance mixed metal oxide catalyst.

Recently, the performance improvement according to precursor synthesis conditions such as the mixed metal oxide catalyst for treating the exhaust gas of the above-mentioned prior art 1, the method for producing the same, the method for treating the exhaust gas using the same, and the catalyst for treating nitrogen oxides in the prior art 2 .

Korean Patent Laid-Open No. 10-2013-0123311 (Dec. 12, 2013) Korean Registered Patent No. 10-1029646 (registered on April 4, 2011)

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a mixed metal oxide catalyst capable of lowering the temperature at which a mixed metal solution and a reaction solution are synthesized and aged at a most suitable temperature, And a method of manufacturing the same.

According to another aspect of the present invention, there is provided a method for preparing a mixed metal oxide catalyst, the method comprising the steps of: preparing a mixed metal oxide catalyst comprising a mixture of at least two of Al, Mn, Fe, Co, Ni, Cr, Bi, Ga, B, La, A mixed metal solution dissolved in distilled water, and a reaction solution in which NaOH and Na ₂ CO ₃ are dissolved in distilled water, at a temperature of 60 ° C to 70 ° C at 300 to 500rpm; Aging the precursor solution synthesized in the synthesis step at a temperature of 60 ° C to 70 ° C for 15 to 17 hours to homogenize the precursor solution; A washing step of washing the aged precursor solution in the aging step to remove the residual components so as to have a pH of 6.5 to 7.5; A pulverizing step of drying and pulverizing the precursor washed in the washing step at a temperature of 70 ° C to 110 ° C for 12 to 13 hours; A first firing step of increasing the powder of the precursor pulverized in the pulverization step to 500 ° C at a rate of 1 to 3 ° C per minute and holding the powder at 500 ° C for 3 hours and 30 minutes to 4 hours and 30 minutes; An impregnation step of immersing the precursor powder calcined in the first calcination step in a metal solution dissolving 3 parts by weight of metal Ag for 1 to 12 hours with respect to 100 parts by weight of the precursor powder; A second calcination step in which the precursor powder immersed in the immersion step is dried and baked for 1 to 2 hours at a rate of 4 to 6 ° C per minute; And the precursor powder calcined in the second calcination step is heated to 400 ° C. for 1 hour, heated from 400 ° C. to 500 ° C. for 2 hours, heated at 500 ° C. for 1 hour 30 minutes to 2 hours And a second firing step of firing the first firing step.

At this time, in the synthesis step, the mixed metal solution and the reaction solution may be synthesized at a temperature of 65 ° C.

In addition, the washing step may remove the residual components so that the pH of the aged precursor solution is 7.

In the method for preparing a mixed metal oxide catalyst according to the present invention, the mixed metal solution and the reaction solution can be synthesized and aged at the most suitable temperature to lower the temperature at which the conversion rate reaches 50%.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart showing a method for producing a mixed metal oxide catalyst according to an embodiment of the present invention,
FIG. 2 is a graph showing a conversion rate according to a temperature change when a catalyst of a precursor synthesized at room temperature is used,
FIG. 3 is a graph showing a conversion rate according to a temperature change when a catalyst of a precursor synthesized at 55 ° C. is used,
FIG. 4 is a graph showing a conversion rate according to a temperature change when a catalyst of a precursor synthesized at 65 ° C. is used,
5 is a graph showing a conversion rate according to a temperature change when a catalyst of a precursor synthesized at 75 ° C is used,
6 is a graph showing a conversion rate according to a temperature change when a catalyst of a precursor synthesized at 80 ° C is used,
7 is a graph comparing the difference in the synthesis temperature of the precursor and the change in CO conversion according to the change,
FIG. 8 is a graph comparing the change of the precursor synthesis temperature and the change of the conversion rate of C ₃ H ₆ according to the change. FIG.

Hereinafter, a method for preparing a mixed metal oxide catalyst according to the present invention will be described in detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart illustrating a method for preparing a mixed metal oxide catalyst according to one embodiment of the present invention. FIG.

In order to decompose nitrogen oxides in a lean state including N ₂ O, the present invention is characterized by a catalytic characteristic capable of adsorbing HC, CO and NO x by separating them from oxygen, and a catalyst composition capable of effectively decomposing NO x adsorbed thereon It is possible to effectively decompose and remove NOx by a reaction characteristic directly correlated with CO or HC which is directly decomposed or coexisted with or without coexistence of oxygen in a general exhaust gas temperature range without using any other reducing agent which should be separately supplied from the outside such as NH ₃ The present invention provides a method for producing a mixed metal oxide catalyst.

The method for producing a mixed metal oxide catalyst according to the present invention comprises eight steps of: synthesizing step (S10), aging step (S20), washing step (S30), pulverizing step (S40), first firing step (S50) An immersion step S60, a second firing step S70, and a third firing step S80.

The synthesis step S10 is a step of synthesizing at least two or more metals having high adsorption performance and decomposition characteristics for NOx among Al, Mn, Fe, Co, Ni, Cr, Bi, Ga, B, La, And a solution of NaOH and Na2CO3 dissolved in distilled water is slowly added to the reaction solution to co-precipitate the supersaturated solution to obtain a mixed metal oxide catalyst precursor solution. At this time, the synthesis of the precursor solution should be carried out at a speed of 300 to 500 rpm and a temperature of 60 ° C to 70 ° C, and it is most preferable to synthesize the precursor solution while maintaining the synthesis temperature of the precursor solution at 65 ° C.

Thereafter, in the aging step (S20), the precursor solution synthesized in the synthesis step (S10) is stirred at a temperature of 60 ° C to 70 ° C for 15 to 17 hours for homogenization. Next, in the cleaning step (S30), the aged precursor solution is aged in the aging step (S20) to remove the residual components so that the pH is 6.5 to 7.5.

At this time, it is preferable that the precursor solution has pH = 7.

The precursor in which the residual components have been removed in the washing step S30 is dried and pulverized at a temperature of 70 to 110 DEG C for 12 to 13 hours in the pulverization step S40, Lt; RTI ID = 0.0 > ° C. ≪ / RTI >

Thereafter, the precursor powder fired in the first firing step (S50) is immersed in a metal solution having 3 parts by weight of metal Ag dissolved therein for 1 to 12 hours with respect to 100 parts by weight of the precursor powder (S60) In the sintering step (S70), it is increased by 4 to 6 ° C per minute for 1 to 2 hours, and then dried and fired.

The precursor powder thus fired in the second firing step (S70) was heated to 400 deg. C for 1 hour, heated from 400 deg. C to 500 deg. C for 2 hours and then cooled to 500 deg. For 30 minutes to 2 hours and 30 minutes to prepare a mixed metal oxide catalyst.

The mixed metal oxides thus prepared are classified into a single metal oxide [M (x) 2Ox], spinel [M (II) M (III) 2O4], perovskite [ M (II) M (IV) O3], and ferrite [M (FexOy)] based oxides and other oxides and complexes of these oxides.

Thus, the oxide catalyst may have spinel, perovskite, ferrite, and other crystal structures basically and may include an active metal impregnated 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 has high selectivity adsorption properties for CO, HC, and NOx, and has excellent oxidation performance of HC, CO, and NO without using noble metals such as Pt in a state where oxygen coexists, (HC-SCR and NH3-SCR) by CO, HC, and NH3, adsorbs and stores NOx, and reduces it to a reducing agent such as CO and H2. A Lean NOx Trap (LNT) method, and almost all of NOx treatment methods for NOx decomposition such as NOx reduction reaction (TWC) when oxygen concentration is tightly regulated and there is no oxygen and excess CO exists.

When alkali metal such as Na is added to the mixed metal oxide by impregnation or ion exchange, even in the presence of oxygen, it is possible to directly decompose the adsorbed NOx or react with CO or HC to enable decomposition of NOx, Performance. In the case of the lean NOx treatment using the mixed metal oxide catalyst, the fuel penalty due to the additional reducing agent can be minimized by exhibiting a high NOx removal efficiency even by a passive method in which there is no reductant injection from the outside, When the SCR process using a reducing agent is employed, the reduction activity of NOx can be reduced at a lower temperature range than the conventional reaction temperature range by increasing the Redox activity. In the LNT process, which selectively adsorbs lean NOx and then desorbs it with a reducing agent such as HC, CO or H2, all of the NO, NO2 and N2O are oxidized to NO 2 It is possible to provide an energy reduction type process of adsorbing and reducing and desorbing at a lower temperature.

The catalyst prepared by the mixed metal oxide catalyst preparation method of the present invention has a sufficient adsorption space, but forms an oxide in which a transition metal component and a sufficient amount of oxygen ligand are combined to prevent excessive oxygen adsorption. However, the catalyst improves the adsorption performance for NOx components such as HC, CO and NO having affinity for oxygen, and conversely, the selective adsorption performance for components such as N2, O2, CO2, and / or H2O is low, Or intercepts or inhibits their intervention in various reactions at the catalyst bed, if the components are contained in excess in the reactants and interfere with the formation of the product. 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 the treatment of exhaust gas according to the present invention is represented by the following general formula (1), and is composed of a mixture of at least two kinds of metal mixed metal oxides or metal oxides.

[Chemical Formula 1]

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

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, 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, (V) is at least one selected from the group consisting of pentavalent V, Re, Ir, Os, Bi, and Ru, at least one selected from the group consisting of Pd, Ce, La, Mo, W, Ge, Re, One or more selected from the group consisting of Mo, W, Ir, Ru, Re and Cr, and u, v, w, x and y are the same or different from 0 to 18 It is a mistake between. 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.

Thus, the catalyst according to the present invention is composed of a mixture of at least two or more metals with a mixed metal oxide or metal oxide, the transition metals having an excessively weak oxygen bond, at least in a high oxidation state, ) ^2- ligand, thereby minimizing other oxygen adsorption and maximizing the adsorption of nitrogen oxides such as NO as a Lewis base. And z = a (u + 3v / 2 + 2w + 5x / 2 + 3y) in which the expression, means that the amount of oxygen, is a combination of excess oxygen due oxo (Oxo) or Fe rokso (O2) ^2- ligand of oxygen , And has a real number of more than 1 and less than 5. The oxygen amount maintains a stable peroxidation state within the above-mentioned range, thereby minimizing other oxygen adsorption and maximizing the adsorption of nitrogen oxides such as NO as Lewis salts.

In addition, the catalyst according to the present invention can be synthesized and combined by a uniform reaction of the mixed metal oxide, and can be used in combination with K, Li, Na, Fr, Mg, Sr, Nb, Sc, Ge, La, Mn, , Au, Pt, Pd, Rh, Ir, and Ru may be ion-exchanged, impregnated or intercalated to increase the properties of the active component or the auxiliary metal. The content of the active ingredient is preferably 0.01 to 30% by weight based on the total catalyst, and if it is less than 0.01% by weight, the effect of addition is insignificant. If it exceeds 30% by weight,

According to another aspect of the present invention, there is provided a method for preparing a mixed metal oxide catalyst, comprising: preparing a precursor represented by the following general formula (2) And drying the precursor at 70 to 150 ° C. and calcining the precursor at 100 to 950 ° C. to form a mixed metal oxide. Optionally, the method may further comprise impregnating the mixed metal oxide with an active or auxiliary metal.

Preferably, the mixed metal oxide has a pore structure and a specific surface area in the range of 5 to 500 m 2 / g, which is advantageous for the catalytic reaction. The catalyst of the present invention having such a structure can be synthesized from a mixed metal oxide precursor of the following formula (2) comprising a hydroxide salt of a metal through a homogeneous liquid phase reaction.

(2)

(OH) o] ^{p +} A ^{n -} p / n.mH ₂ O (III) vM (IV)

In the above formula, M (II), M (III), M (IV), M (V), and M (VI) are as described above and u, v, w, x, and y are also as described above , p and o are represented by the relationship o = (2u + 3v + 4w + 5x + 6y-p), where A ^{n -} is an anion such as 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 -} inorganic anion, such as adipic acid, oxalic acid, etc. And an hydroxide of a mixed metal selected from the group consisting of an anion-free metal represented by A ^{n -} when p + is zero.

The precursor for the mixed metal oxide catalyst of the present invention can be prepared by a method such as Precipitation, Deposition-Precipitation, Co-precipitation or Sol-Gel process of the mixed metal oxide As shown in FIG. It is important to note that the reactants incorporated at a certain molar ratio in the process of synthesizing the precursor through the homogeneous liquid phase reaction are necessarily produced in the same ratio because the composition of the mixed metal can be changed according to the crystal structure of the precipitate during the reaction with the precipitate , And the remnants of the metal not participating in the reaction should be cleanly removed during the cleaning.

The precursor solution thus obtained is preferably aged for a certain period of time. At this time, it is possible to promote the peroxide formation of the transition metal by adding a small amount of hydrogen peroxide (H2O2) to the solution. After aging the precipitate, it is washed, dried and pulverized and then calcined to obtain a mixed metal oxide catalyst. A metal selected from the group consisting of K, Li, Na, Mg, Sr, Nb, Sc, Ge and La, Mn, Fe, Cu, Ag, Au, Pt, Pd and Rh, The step of interlayer bonding or impregnation may be selectively conducted by a method such as impregnation, coating and ion exchange. The drying temperature may be in the range of 70 to 150 ° C, but it may be vacuum or freeze-dried. The calcination temperature may be in the range of 400 to 950 ° C, but if the temperature is low around 500 ° C, the calcination may be incomplete. If it is increased, the specific surface area of the catalyst may decrease or oxygen vacancies may be generated, which may hinder the catalytic activity.

The precursor may be prepared by a solution combustion method in which a solution of a mixed metal salt is directly burned at a temperature ranging from 100 to 950 ° C by reducing the precursor preparation and firing process by a liquid phase method, However, the performance of the catalyst may be deteriorated due to the degree of oxygen ligand formation and the characteristics of the pore structure, compared to a method of uniformly co-precipitating or through a sol-gel method.

The precursor compounds due to the homogeneous reaction are formed by the formation of regular and developed pores due to the bubbles generated when heat is applied to the precursor in the firing process due to the bonding of the anion groups such as CO 3 ^{2 -} Resulting in a very small size powdery mixed metal oxide with specific surface area and thermal stability.

The mixed metal oxide catalyst of the present invention exhibits high adsorption characteristics to HC, CO, NOx and N2O with respect to oxygen according to the composition of the catalytic metal component and exhibits high adsorption characteristics with respect to HC, In the treatment of CO, NOx and N2O, there are aspects such as the reaction reaction temperature which vary depending on the treatment method, but they show high activity as a whole.

It is considered that the mixed metal oxide catalyst of the present invention has a high affinity for HC, CO, and NOx based on excessive oxygen bonding, and thus the adsorption performance is enhanced. The oxidation of HC, CO and NO, , Reduction process of NOx by CO or HC, and it was confirmed that oxygen in the gas is necessary for the maintenance of the continuous activity. This is due to the fact that the reduction and oxidation of the catalyst due to the weak bonding oxygen of the oxo (oxo) or peroxo ligand alternately occurs in the reactants and the metal oxide, as found in the oxidation reaction of HC by the mixed metal oxide, It is assumed that the mechanism is similar to the process, but the process of reduction desorption of NOx reacting with CO or HC into N ₂ and CO ₂ or H ₂ O requires more definite identification.

In the case of using a reducing agent such as CO and NH ₃ for the decomposition of NOx by the mixed metal oxide, decomposition into N ₂ , CO ₂ and H ₂ O and the like deteriorate the adsorption performance of these decomposition products, Is interpreted.

According to the invention, NOx, N ₂ O, O ₂ in the exhaust gas generated by the combustion of fossil fuel to a mixed metal oxide catalyst or the catalyst made of the above methods using a support such as a coated pellet or a honeycomb, from _{HC, CO, CO 2, H} 2 O, SO 2, or _{HC, CO, NO, NO 2} , N 2 O , such as NOx, or an oxygen and CO _2, such as a mixture thereof in the exhaust gas containing a mixture thereof Selectively adsorbed and separated and stored. The adsorption temperature can be carried out at a temperature of 55 ° C to 500 ° C, which is preferable in that the lower the temperature is, the more the catalyst adsorption performance is increased, while the appropriate temperature range is required in consideration of the slow adsorption rate. 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 And HC and CO generated in the combustion process are beneficial to the reduction reaction of NOx.

According to the invention, the mixing by using the metal oxide catalyst or a pellet or a support such as a honeycomb of the catalyst is coated, of the exhaust gas generated by the combustion of fossil fuels, NOx, N ₂ O, O _2, HC, CO, It is possible to simultaneously oxidize CO, HC and NO under the condition that at least 0.1 volume% or more of oxygen (O ₂ ) exists from the exhaust gas containing CO ₂ , H ₂ O, SO ₂ , or a mixture thereof. This means that it is possible to remove harmful components of the exhaust gas by oxidizing unreacted HC and CO generated with low temperature combustion such as engine starting or oxygen inadequate, with extra oxygen.

Further, by using the mixed metal oxide catalyst or a pellet or a support such as a honeycomb of the catalyst is coated in accordance with the present invention, the exhaust gas generated by the combustion of fossil fuels, NOx, N ₂ O, O _2, HC, CO, CO, NOx, N ₂ O, or a mixture thereof in an exhaust gas containing CO ₂ , H ₂ O, SO ₂ , or a mixture thereof, and at the same time, at least 0.1 vol% The NOx can be decomposed directly without the aid of any reducing agent to be introduced from the outside, or the NOx can be reduced and decomposed into N ₂ , CO ₂ and H ₂ O by using CO or HC as a reducing agent. The nitrogen oxide concentration to be treated is preferably in the range of 0.00001 to 30% by volume, which is the maximum generation range that can be usually predicted, and the oxygen concentration should be at least 0.1% by volume or more because it must be more than the amount required for the oxidation of HC and the NOx reduction process , The reaction temperature ranges from room temperature to 550 ° C in the case of NOx reduction, and it is possible to operate in the range of 150 to 550 ° C if higher conversion is required. When the temperature is higher than this range, the oxidation state is lowered because the oxidation equilibrium is lowered, and oxidation and decomposition are more difficult. At lower temperatures, the reaction rate is lowered and the conversion rate is lowered.

Hourly space velocity of the gas passing through the catalyst is a 1,000h ^-1 to 300,000h ^-1, the pressure of the gas is not less than the atmospheric pressure (1atm), the specific residual reduction process of the NOx by HC or CO, such as CO or NH ₃ Unlike the case where N ₂ O is produced by incomplete reduction when using a reducing agent, there is little occurrence of N ₂ O. The reduction method of NOx and N ₂ O by the mixed metal oxide catalyst of the present invention can completely replace the SCR system by the NH ₃ reducing agent currently used in the boiler and diesel engine exhaust gas treatment, Higher removal efficiencies are expected when applied.

On the other hand, the present invention provides for the reduction of desorption with the selective separation of the exhaust gas adsorbed from nitrogen, oxygen and CO ₂ such as described above, CO, H _2, etc. with a reducing agent by reacting N ₂ and CO _2, H ₂ O, such as LNT or NSR ( NOx Storage and Reduction). In the LNT process, a separate process of oxidizing NO and N ₂ O to NO ₂ is not necessary, and the process is simple, efficient, and economical. Especially, direct decomposition of NOx in the exhaust gas of fuel lean or rich operation can be expected, and in the presence of CO and HC, a higher effect can be expected for NOx removal. The reduction reaction temperature can be generally carried out at a temperature of about 150 ° C to 500 ° C, which is preferable in view of a suitable temperature range for adsorption and reaction of the reducing agent.

In addition, the mixed metal oxide catalyst of the present invention can be used in a combustion process in which NOx, N ₂ O, HC, CO, CO ₂ , H ₂ O, SO ₂ , Or a mixture thereof, can be decomposed with high efficiency into N ₂ and CO ₂ by reacting the NO x, N ₂ O, or a mixture thereof with a gas containing CO or a reducing agent CO itself. When the mixed metal oxide catalyst of the present invention is used, the reaction of the decomposition step proceeds in the range of 150 to 550 ° C, and preferably at about 200 ° C or more, almost complete NO x decomposition is achieved. The oxygen concentration is 0.1 vol% or less or 1/2 of the CO concentration, the space velocity of the gas passing through the catalyst is 1,000 h ^-1 to 300,000 h ^-1 , and the gas pressure is atmospheric pressure (1 atm) or more.

The mixed metal oxide catalyst of the present invention can be produced by mixing an exhaust gas containing NO x, N ₂ O, O ₂ , CO ₂ , H ₂ O, SO ₂ , or a mixture thereof with a gas mixture comprising NH ₃ , And exhibits high activity in selective catalytic reduction of the NOx mixture with N ₂ and H ₂ O or the like. In the SCR decomposition process, the increase in operating cost due to the use of an excess amount of reducing agent is large. Therefore, the nitrogen oxide content is preferably within 1 vol% and the oxygen content is less than 25 vol%. The reaction temperature depends on the catalyst composition is generally 100 to 350 ℃ case of NOx, the higher the temperature the higher NOx conversion rate, but it is necessary because it represents the tendency of N ₂ O generated is increased to select the proper reaction temperature.

Overall, the gas passing through the catalyst when used for a suitable amount of catalyst at atmospheric pressure (1atm), but to keep more than the hourly space velocity within the 1,000h ^-1 to 300,000h ^-1, preferably 3,000h ^-1 to 100,000h ^{- 1. If the} space velocity is less than 1,000 h ^-1, economical loss due to the use of an excessive catalyst is feared. If the space velocity is more than 300,000 h ^-1 , the pressure loss due to the fluid flow becomes large, which may cause mechanical impossibility.

On the other hand, the method of impregnating Na or Li to the present mixed metal oxide to perform the decomposition of NOx can be used to adhere to existing metal oxide catalysts when the NOx adsorption performance is good, and the use of the non- Application of at least one selected method 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, , N ₂ O, O ₂ , CO ₂ , H ₂ O, SO ₂ , or mixtures thereof. These treatment methods are well known in the art, and the known treatment methods known in the art can be applied in the present invention.

The precursor synthesis conditions for describing the examples of the mixed metal oxide catalyst production method are shown in Table 1 below.

Precursor
Synthesis temperature Room temperature (about 25 ℃) 55 ° C 65 ℃ 75 ℃ 80 ℃ Total flow 2.7 L / min 2.65 L / min 2.7 L / min 2.7 L / min 2.7 L / min NOX 338 ppm 328 ppm 309 ppm 352 ppm 304ppm CO 845ppm 851 ppm 828ppm 860ppm 871 ppm C ₃ H ₆ 640ppm 636 ppm 631 ppm 630 ppm 647ppm O ₂ 9.38% 9.66% 9.14% 9.7% 9.19% Catalyst volume 1ml 1ml 1ml 1ml 1ml Temperature 20 ° C / min rise
(max 470) C 20 ° C / min rise
(max 470) C 20 ° C / min rise
(max 470) C 20 ° C / min rise
(max 470) C 20 ° C / min rise
(max 470) C

At this time, Wcat was 0.60 g / 1 ml and P was 0.014 MPa under the conditions for synthesizing the precursor.

FIG. 2 is a graph showing a conversion rate according to a temperature change when a catalyst of a precursor synthesized at room temperature is used. FIG. 3 is a graph showing a conversion rate according to a temperature change when a catalyst of a precursor synthesized at a temperature of 55 ° C. is used And FIG. 4 is a graph showing the conversion rate according to the temperature change when the catalyst of the precursor synthesized at 65 ° C was used. FIG. 5 is a graph showing the conversion rate according to the temperature change when the catalyst of the precursor synthesized at 75 ° C was used. And FIG. 6 is a graph showing a conversion rate according to a temperature change when a precursor catalyst synthesized at 80 ° C. is used.

Referring to FIG. 2 to FIG. 6, which is a graph of the conversion rate when the catalyst of the precursor synthesized according to the synthesis conditions of Table 1 is used, when the catalyst of the precursor synthesized at normal temperature conditions is used, when the conversion rate reaches 50% The conversion rate reached 50% at the CO: 153.5 ° C and C ₃ H ₆ : 176 ° C and at 55 ° C using the catalyst of the precursor, the temperatures of CO: 128.5 ° C and C ₃ H ₆ : 173.9 ° C , And 65 ° C, the conversion rate reached 50% when the catalyst was 142.5 ° C and C ₃ H ₆ : 153.03 ° C, and when the precursor catalyst synthesized at 75 ° C was used At the time when the conversion rate reached 50%, CO: 165.6 ° C and C ₃ H ₆ : 171.3 ° C. When the catalyst of the precursor synthesized at 80 ° C was used, the conversion rate reached 50% C ₃ H ₆ : 153.12 ° C.

FIG. 7 is a graph comparing the difference in the precursor synthesis temperature and the change in CO conversion according to the change, and FIG. 8 is a graph comparing the change in the conversion rate of C ₃ H ₆ with the difference in the precursor synthesis temperature and the change.

7 and FIG. 8, the conversion temperature and the conversion temperature of 50% in the graph comparing the conversion rates of CO and C ₃ H ₆ according to the change are shown in Table 2 below.

Synthesis temperature At room temperature (25 ° C) 55 ° C 65 ℃ 75 ℃ 80 ℃ CO 153 ℃ 128.5 DEG C 142.5 DEG C 165.6 ° C 160 ° C C ₃ H ₆ 176 ° C 173.9 DEG C 153.03 C 171.3 DEG C 153.12 캜

As can be seen from Table 2, when the conversion rate of CO reached 50%, the catalyst synthesized precursor at 55 ° C was most effective at 128.5 ° C. However, when a catalyst synthesized at a temperature of 65 ° C was used CO and C ₃ H ₆ reached 142.5 ° C and 153.03 ° C, respectively, and the temperature at which the conversion rate reached 50% was lower than that of the catalyst synthesized on the average under different conditions was effective.

In the method for preparing a mixed metal oxide catalyst according to the present invention, the mixed metal solution and the reaction solution can be synthesized and aged at the most suitable temperature to lower the temperature at which the conversion rate reaches 50%.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined by the appended claims. It is obvious that you can do it.

Claims (3)

The reaction solution of the Al, Mn, Fe, Co, Ni, Cr, Bi, Ga, B, La, Ce, mixed metal solution and, NaOH and Na ₂ CO ₃ or more at least two of Sc and Rh is dissolved in distilled water in the distilled water At a temperature of 60 ° C to 70 ° C at 300 to 500 rpm;
Aging (S20) stirring the precursor solution synthesized in the synthesis step (S10) at a temperature of 60 ° C to 70 ° C for 15 to 17 hours to homogenize the precursor solution;
A cleaning step (S30) of washing the aged precursor solution in the aging step (S20) to remove residual components so as to have a pH of 6.5 to 7.5;
A pulverizing step (S40) of drying and pulverizing the precursor washed in the cleaning step (S30) at a temperature of 70 ° C to 110 ° C for 12 to 13 hours;
A first firing step (S50) in which the precursor powder pulverized in the pulverization step (S40) is heated to 500 deg. C at a rate of 1 to 3 deg. C per minute and maintained at 500 deg. C for 3 hours and 30 minutes to 4 hours and 30 minutes;
An impregnation step (S60) of immersing the precursor powder calcined in the first calcination step (S50) in a metal solution in which 3 weight parts of metal Ag is dissolved with respect to 100 weight parts of the precursor powder for 1 to 12 hours;
A second firing step (S70) in which the precursor powder immersed in the immersion step (S60) is dried and baked at a rate of 4 to 6 DEG C per minute for 1 to 2 hours; And
The precursor powders calcined in the second calcination step (S70) were heated to 400 DEG C for 1 hour, increased from 400 DEG C to 500 DEG C for 2 hours, and then calcined at 500 DEG C for 1 hour and 30 minutes to 2 A third firing step (S80) for firing for 30 minutes;
≪ / RTI > wherein the mixed metal oxide catalyst is prepared by a process comprising the steps of:
2. The method of claim 1, wherein the combining step (S10)
Wherein the mixed metal solution and the reaction solution are synthesized at a temperature of 65 ° C.
The method of claim 1, wherein the cleaning step (S30)
Wherein the residual component is removed so that the pH of the aged precursor solution is < RTI ID = 0.0 > 7. ≪ / RTI >

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