KR20190084512A - NOx Adsorbent in Which Copper Oxide And Barium Oxide Are Co-Impregnated And Method of Removing NOx Using the Same - Google Patents

Abstract

The present invention relates to a nitrogen oxide adsorbent in which a copper oxide and a barium oxide are co-impregnated, and a method for removing a nitrogen oxide using the same. A nitrogen oxide adsorbent in which a copper oxide and a barium oxide, as adsorption active materials, are co-impregnated to a carrier is manufactured so the desorption temperature of the adsorbed nitrogen oxide is reduced and desorption performance to the adsorbed nitrogen oxide is excellent.

Description

TECHNICAL FIELD The present invention relates to a nitrogen oxide adsorbent having copper oxides and barium oxides co-impregnated therein, and a method for removing nitrogen oxides using the same.

The present invention relates to a nitrogen oxide adsorbent co-impregnated with copper oxide and barium oxide, and a method for removing nitrogen oxides using the same. More specifically, the present invention relates to a nitrogen oxide adsorbent comprising copper oxide and barium oxide, The present invention relates to a nitrogen oxide adsorbent having copper oxide and barium oxide co-impregnated with an adsorbed nitrogen oxide having a desorbing temperature lower than that of adsorbed nitrogen oxide, and a method for removing nitrogen oxide using the same.

Regulations for automobile emissions are being strengthened to solve environmental problems around the world, and technologies for reducing harmful gas emissions from gasoline and diesel vehicles are being developed.

However, due to the application of the high fuel consumption technology for reducing the fuel consumption, the efficiency of the conventional three-way catalyst used for removing nitrogen oxides has been reduced. This is because the amount of air introduced during combustion increases and the amount of nitrogen oxides is increased, and the exhaust gas temperature is lowered, which is not suitable for the activation temperature of the conventional catalyst. Further, according to the investigation, it was confirmed that the amount of nitrogen oxides discharged during running was measured. As a result, it was confirmed that the amount of nitrogen oxide discharged from the so-called cold-start section was larger when the engine was running without being heated sufficiently. Accordingly, if an adsorbent capable of efficiently adsorbing and desorbing nitrogen oxides at low temperature is developed, it will be useful not only as a nitrogen oxide adsorbent applicable to a fuel-efficient technology, but also in lowering energy consumption in a desorption process, thereby realizing a low- .

Techniques for removing nitrogen oxides are divided into two categories: selective catalytic reaction (SCR) and NOx storage and reduction (NSR) or lean-NO _x trap (LNT). SCR is a method in which nitrogen oxide is directly reacted with NH ₃ through a catalytic reaction to reduce it to nitrogen and oxygen. This technique uses a urea water which is used as a precursor of NH ₃ , so that there is a problem that an additional storage tank is required and the urea water is continuously charged. In comparison, NSR uses adsorbents and catalysts with reducibility, adsorbing nitrogen oxides under lean-burn conditions and desorbing nitrogen oxides under rich-burn conditions . This technique is relatively inexpensive because it requires no separate equipment, but has a disadvantage in that the removal efficiency of nitrogen oxide is lower than that of SCR.

Japanese Patent Laid-Open No. 2007-319768A discloses a barium oxide-type adsorbent in which aluminum is impregnated with barium acetate using a support, and Korean Patent No. 10-1018576 discloses an adsorbent comprising barium, cerium, strontium or a combination thereof ≪ / RTI >

Examples of adsorbents using copper oxide include a number of patents including copper oxide based on zeolite as an example of application to SCR. Examples thereof include Cu-CHA type adsorbents (U.S. Patent No. US 20110305614 A1) and Cu -ZSM34 adsorbent (US patent publication US 201200148767 A1) is disclosed.

The developed alumina-based barium oxide adsorbent has a relatively high adsorption / desorption temperature (optimum adsorption temperature: 300 to 400 ° C., desorption temperature: 500 to 600 ° C.). Therefore, there is a problem that it is difficult to apply the material to a fuel-efficient technology with relatively low gas temperature after combustion. In order to efficiently use the adsorbent, it is desired to develop an adsorbent having a relatively low desorption temperature in order to reduce not only the absolute adsorption amount but also the regenerated energy.

The adsorbent using the developed copper oxide exhibits excellent performance for promoting the reduction reaction to nitrogen oxides, but has a problem that it exhibits relatively low adsorptivity in terms of simple adsorption.

As a result of intensive efforts to solve the above problems, the inventors of the present invention focused on the fact that the desorption temperature for the nitrogen oxide is low in the copper oxide, and the copper oxide and the barium oxide are simultaneously impregnated with the adsorbing active material , The desorption temperature of the adsorbed nitrogen oxide is decreased, and the desorbing performance of the already adsorbed nitrogen oxide is remarkably increased. Thus, the present invention has been completed.

An object of the present invention is to provide a nitrogen oxide adsorbent having a desorbing temperature which is low and which is excellent in desorbing ability to nitrogen oxide already adsorbed, and a method for producing the same.

It is another object of the present invention to provide a method for removing nitrogen oxide at low temperature using the nitrogen oxide adsorbent.

In order to attain the above object, the present invention provides a nitrogen oxide adsorbent, wherein copper oxide and barium oxide are co-impregnated with a carrier as an adsorbent active material.

(A) co-impregnating and drying an aqueous solution containing a copper oxide precursor and an aqueous solution containing a barium oxide precursor to a support; (b) repeating the step (a) from one time to several times; (c) drying; And (d) firing the mixture while flowing air. The present invention also provides a method for producing the nitrogen oxide adsorbent.

The present invention also provides a method for removing nitrogen oxides, which comprises adsorbing and desorbing a nitrogen oxide-containing gas of nitrogen monoxide (NO) or nitrogen dioxide (NO ₂ ) using the nitrogen oxide adsorbent.

According to the present invention, unlike a conventional alumina-based nitrogen oxide adsorbent, copper oxide and barium oxide are simultaneously impregnated with an adsorbing active material, whereby not only nitrogen oxide of nitrogen gas and nitrogen dioxide which are adsorption gases but also nitrogen monoxide And oxygen can adsorb and desorb nitrogen oxides at a low temperature and can be desorbed at a lower temperature than existing adsorbents.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an XRD spectrum of a material with different adsorbent active materials according to an embodiment of the present invention (barium oxide alone impregnated, barium oxide and copper oxide impregnated, copper oxide sole impregnated material from below).
2 is a nitrogen adsorption / desorption curve of a material according to an adsorbent active material according to an embodiment of the present invention.
Figure 3 is a TPD Analysis of the material results in accordance with the nitrogen oxide composition in accordance with one embodiment of the present invention ((a) NO 10% / He (b) NO 10% / O 2 10% / He (c) NO 2 10 % / He).

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is well known and commonly used in the art.

In an embodiment of the present invention, when nitrogen oxides are adsorbed at a low temperature (150 ° C) by co-impregnating copper oxide with barium oxide to lower the adsorption / desorption temperature of the adsorbent, copper oxides And barium oxide impregnated material decreased to 400 ℃ or lower when compared with the conventional adsorbent.

Accordingly, the present invention relates to a nitrogen oxide adsorbent characterized in that copper oxide and barium oxide are co-impregnated with a carrier as an adsorbent active material in one aspect.

The present invention is to analyze the coprecipitation effect and the optimum mass ratio of copper oxide and barium oxide in a method for preparing a carrier-based adsorbent such as alumina by coprecipitation for capturing nitrogen compounds at low temperatures.

In the present invention, the content of the adsorptive active material may be 1 to 30% by weight, preferably 3 to 20% by weight. When the content of the adsorptive active material is 1 to 30% by weight, the adsorptive active material can be distributed evenly on the support. When the amount of the adsorbing active material is less than 1% by weight, it is difficult to observe a difference in adsorption amount of the adsorbing active material. When the amount of the adsorbing active material is more than 30% by weight, the adsorbing active material can not reach the support.

In the present invention, the mass ratio of the copper oxide to the barium oxide may be 1: 0.25 to 4, preferably 1: 0.5 to 2. When the mass ratio of the copper oxide to the barium oxide is 1: 0.25 to 4, copper oxide and barium oxide coexist so that the copper oxide can lower the desorption temperature of the barium oxide. When the ratio is less than 1: 0.25, there is a problem that the adsorption amount and desorption amount are greatly reduced. When the ratio is more than 1: 4, the effect of reducing the desorption temperature due to copper oxide is reduced.

In the present invention, the mass ratio of the adsorptive active material to the carrier may be 1: 2 to 99, preferably 1: 4 to 33. When the mass ratio of the adsorptive active material to the support is in the range of 1: 2 to 99, the adsorptive active material can be distributed evenly on the support. When the ratio is less than 1: 2, there is a problem that the adsorbing active material can not reach the support and can not be equally divided. When the ratio exceeds 1:99, it is difficult to observe the difference in the adsorbed amount of the adsorbing active material.

In the present invention, the nitrogen oxide adsorbent may have a surface area of 110 to 130 m ² / g, a pore volume of 0.6 to 0.7 cm ³ / g and a pore size of 17 to 19 nm.

In the present invention, the support may be formed of alumina, polypropylene, polyethylene, polytetrafluoroethylene, polysulfone, polyimide, silica, glass gamma-alumina, mullite, zirconia, titania, Yttria, ceria, vanadia, silicon, stainless steel and carbon, and preferably at least one selected from the group consisting of alpha-alumina, beta-alumina or gamma-alumina Or the like may be used, but the present invention is not limited thereto.

Another aspect of the present invention is a process for preparing a metal oxide nanoparticle comprising: (a) co-impregnating and drying an aqueous solution containing a copper oxide precursor and a barium oxide precursor to a carrier; (b) repeating the step (a) from one time to several times; And (c) firing the mixture while flowing air. The present invention also relates to a method for producing the nitrogen oxide adsorbent.

Another aspect of the present invention is a method for producing a porous oxide precursor, comprising: (a) co-impregnating and drying an aqueous solution containing a copper oxide precursor and an aqueous solution containing a barium oxide precursor to a carrier; (b) repeating the step (a) from one time to several times; (c) after the step (b) is completed, drying for a long time; And (d) firing the mixture while flowing air.

In the present invention, the copper oxide precursor may be at least one selected from the group consisting of copper acetate and copper nitrate, preferably copper acetate, but not limited thereto. The barium oxide precursor may be selected from the group consisting of barium acetate and barium nitrate, and preferably barium acetate is used, but it is not limited thereto.

In the present invention, the drying may be performed at 100 to 120 ° C for 0.5 to 2 hours in the step (a).

In the present invention, drying may be performed at 100 to 120 ° C for 12 to 24 hours in the step (c).

In the present invention, the calcination may be performed at 500 to 800 ° C for 1 to 8 hours in the step (d).

In another embodiment of the present invention, the adsorbent co-impregnated with copper oxide and barium oxide simultaneously with the adsorbing active material according to the present invention can be used to remove either nitrogen monoxide or nitrogen oxide of nitrogen dioxide alone or nitrogen monoxide As a result of adsorption and desorption in a gas mixed with oxygen, it was confirmed that desorption temperature was decreased when nitrogen oxide was adsorbed at a low temperature, and thus the adsorbability to nitrogen oxides at a low temperature was excellent.

Therefore, the present invention relates to a method for removing nitrogen oxides, which adsorbs and desorbs nitrogen monoxide-containing gas of nitrogen monoxide or nitrogen dioxide using the nitrogen oxide adsorbent from another viewpoint.

According to the present invention, a NOx storage and reduction (NSR) method is applied to remove nitrogen oxide. NSR is a method of adsorbing nitrogen oxides under lean-burn conditions and desorbing nitrogen oxides under rich-burn conditions using adsorbents and catalysts with reducing ability. This technique is relatively inexpensive because it requires no separate equipment, but has a disadvantage in that the removal efficiency of nitrogen oxide is lower than that of SCR.

In the method for removing nitrogen oxides according to the present invention, at least one catalytically active substance selected from the group consisting of sodium, potassium, lithium, magnesium, zinc and copper may be further included.

The nitrogen oxide removal method of the present invention can be carried out at a low temperature of 150 to 400 ° C. In particular, desorption can be carried out at a low temperature.

In the present invention, the nitrogen oxide-containing gas is _{He, CH 4, N 2,} O 2, C 2 H 4, C 2 H 6, C 3 H 6 And it may further comprise a gas selected from the group consisting of C ₃ H _8.

As such, it is also applicable to the reduction of NOx of automobile exhaust gas, and it is expected to show a very high possibility for the atmospheric purification technology.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are for illustrative purposes only and that the scope of the present invention is not limited by these embodiments.

[Example]

Example  1: copper oxide and barium oxide Impregnated  Synthesis of adsorbent

Copper acetate and barium acetate were used as precursors of copper oxide and barium oxide to be adsorbed active materials, respectively. The alumina used as the support was gamma-phase alumina and impregnated using incipient wetness impregnation.

The masses of copper acetate and barium acetate used were 1.14 g and 0.83 g, respectively, and the mass of gamma-phase alumina used as the support was 4 g.

The synthesis ratio is 1: 4, and the mass ratio of copper oxide to barium oxide is 1: 1. The aqueous solution of copper acetate or barium acetate was impregnated in the same volume over 6 times, dried in an oven maintained at 110 ° C after impregnation once. The compound having been impregnated six times was dried in an oven at 110 DEG C for 24 hours and then fired while flowing air at 600 DEG C for 8 hours.

Figure 1 shows the XRD analysis results of the synthesized adsorbent. The alumina structure used as the support was found in all the materials, and the materials using only barium oxide or copper oxide could confirm the structure of the active material, respectively. However, in the case of a material in which copper oxide and barium oxide are co-impregnated, the characteristic peak for copper oxide is slightly reduced in size and the characteristic peak for barium oxide is small. Considering that the atomic size of copper is small and the pyrolysis temperature of copper acetate is low in the process of calcination of copper acetate and barium acetate in oxide form, it can be concluded that copper oxide is predominantly crystalline form . The synthesized material is represented by the numerical mass percentage with the element symbol of the impregnated active material, Ac indicates that acetic acid type precursor is used, and Al indicates that alumina is used as the support. Followed by firing conditions (temperature, atmosphere).

Table 1 and Fig. 2 show the adsorption and desorption curves of the synthesized materials at a temperature of 77K under nitrogen adsorption. The result is calculated by BET equation and BJH removable equation.

Table 1 shows that the impregnated materials did not impregnate all but impaired surface properties compared to aluminum that had undergone only the same firing conditions. In addition, it can be seen that the surface characteristics of each of them are not largely changed when the impregnation is carried out by different adsorbing active materials. However, it can be seen that the use of barium having a large atom size is slightly smaller than when copper is used.

The BET surface area, pore volume, pore size Sample Textural property BET Surface area
(m ² / g) Pore volume (cm ³ / g) Pore size
(nm) γ-Al ₂ O ₃ _600C (air) 155.5 1.04 19.3 Ba20AcAl_600C (air) 118.7 0.63 18.3 Cu10Ba10AcAl_600C (air) 124.4 0.67 18.6 Cu20AcAl_600C (air) 127.1 0.65 17.8

It can be seen that the adsorption / desorption curve of FIG. 2 shows that the total adsorption amount of nitrogen is higher than the curves of other materials impregnated with curves for pure aluminum, and hysteresis through adsorption / desorption has a similar tendency as a whole.

Example  2: Nitrogen oxide Absorption / desorption  Performance

FIG. 3 shows the result of TPD (Temperature programmed desorption) analysis when the compositions of nitrogen oxides are different for each material. The pretreatment was carried out at 600 ° C for 1 hour, followed by adsorption of nitrogen oxides at 150 ° C, followed by heating at 3 ° C / min. Thus, the amount of adsorbed nitrogen oxide can be indirectly compared with the adsorption amount through the area of the peak along with the desorption amount depending on the temperature. NO, NO + O ₂ , and NO ₂ gases were adsorbed in order from the top.

In all the graphs, it can be seen that nitrogen oxides are desorbed at high temperatures in the case of a material impregnated with barium oxide. Compared with the desorption temperature up to 400 ° C, the amount of desorption of copper oxide and barium oxide impregnated material was higher than that of the material used singly, and the desorption peaks at 400 ° C It was confirmed that it was formed at a lower temperature. When the NO ₂ gas was flowed, the desorption amount of the material impregnated with the copper oxide was found to be larger than that when the NO or NO + O ₂ was supplied. However, the desorption amount was still higher in the material in which the copper oxide and the barium oxide were co- Can be confirmed.

The amount of nitrogen oxide desorbed at 400 ° C or less for each material derived from TPD results Sample Desorbed quantity until 400 ° C NO 10% / He
(mmol / g _cat ) NO 10% / O ₂ 10% / He
(mmol / g _cat ) NO ₂ 10% / He
(mmol / g _cat ) Ba20AcAl_600C (air) 0.437 0.536 0.449 Cu10Ba10AcAl_600C (air) 0.855 0.817 0.833 Cu20AcAl_600C (air) 0.175 0.298 0.524

As shown in Table 2, the amount of nitrogen oxide desorbed at 400 ° C or less was calculated through 'ChemMaster' software (software) linked to the TPD analyzer and analyzed for each material.

As shown in Table 2 and Fig. 3, it can be seen that when the copper oxide and the barium oxide are co-impregnated, the amount desorbed at 400 캜 or less is much larger. Thus, it was confirmed that when copper oxide and barium oxide are co-impregnated with alumina, the amount of adsorption at low temperature can be increased and the energy for regeneration can be reduced.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereto will be. Accordingly, the actual scope of the invention will be defined by the claims and their equivalents.

Claims (15)

Wherein the carrier is impregnated with copper oxide and barium oxide as an adsorbing active material.
The adsorbent according to claim 1, wherein the content of the adsorptive active material is 1 to 30% by weight.
2. The nitrogen oxide adsorbent according to claim 1, wherein the mass ratio of the copper oxide to the barium oxide is 1: 0.25-4.
The adsorbent according to claim 1, wherein the mass ratio of the adsorptive active material to the support is 1: 2 to 99.
The nitrogen oxide adsorbent according to claim 1, having a surface area of 110 to 130 m ² / g, a pore volume of 0.6 to 0.7 cm ³ / g and a pore size of 17 to 19 nm.
The method according to claim 1, wherein the carrier is selected from the group consisting of alumina, polypropylene, polyethylene, polytetrafluoroethylene, polysulfone, polyimide, silica, glass gamma-alumina, mullite, zirconia, titania Wherein the nitrogen oxide adsorbent is at least one selected from the group consisting of yttria, ceria, vanadia, silicon, stainless steel, and carbon.
A method for producing a nitrogen oxide adsorbent comprising the steps of:
(a) co-impregnating and drying an aqueous solution containing a copper oxide precursor and an aqueous solution containing a barium oxide precursor in a carrier;
(b) repeating the step (a) from one time to several times;
(c) drying; And
(d) firing while flowing air.
The method of claim 7, wherein the copper oxide precursor is at least one selected from the group consisting of copper acetate and copper nitrate, and the barium oxide precursor is at least one selected from the group consisting of barium acetate and barium nitrate. (2).
The method of claim 7, wherein the drying is performed at 100 to 120 ° C for 0.5 to 2 hours in the step (a).
The method of claim 7, wherein the drying is performed at 100 to 120 ° C for 12 to 24 hours in the step (c).
The method of claim 7, wherein the calcination is performed at 500 to 800 ° C for 1 to 8 hours in the step (d).
A method for removing nitrogen oxides, comprising adsorbing and desorbing a nitrogen oxide-containing gas of nitrogen monoxide or nitrogen dioxide using the nitrogen oxide adsorbent of any one of claims 1 to 6.
13. The method of claim 12, further comprising at least one catalytically active material selected from the group consisting of sodium, potassium, lithium, magnesium, zinc, and copper.
The method for removing nitrogen oxides according to claim 12, wherein the removal is performed at a temperature of 150 to 400 ° C.
Of claim 12, wherein the gas containing the nitrogen oxides are _{He, CH 4, N 2,} O 2, C 2 H 4, C 2 H 6, C 3 H 6 and C ₃ to H ₈ gas is selected from the group consisting of Further comprising the step of removing nitrogen oxides.

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