WO2011040787A2 - Lean nitrogen oxide breakdown method employing a high-adsorption mixed metal oxide catalyst - Google Patents

Abstract

The present invention relates to a breakdown method for nitrogen oxides using a mixed metal oxide catalyst, and more specifically provides a method for breaking down lean nitrogen oxides in exhaust gas during engine combustion by using a mixed metal oxide catalyst produced from a hydrotalcite form of precursor having an outstanding adsorption performance, thereby providing the advantageous effect of efficient nitrogen oxides removal from the exhaust gas by isolating and adsorbing lean NOx and N2O and then using the CO and HC in the exhaust gas as the only reducing agents with no other reducing agents being used, when the engine is running rich, such that the occluded nitrogen oxides are broken down and desorbed.

Description

Decomposition of Dilute Nitrogen Oxides by Highly Adsorbable Mixed Metal Oxide Catalysts

The present invention relates to a method for decomposing nitrogen oxides using a mixed metal oxide catalyst, and more particularly, using a mixed metal oxide catalyst prepared from a hydrotalcite-type precursor to decompose lean nitrogen oxide from exhaust gas during engine combustion. It is about a method of processing.

Nitrogen oxides (NOx) produce photochemical smog and various secondary pollutants (O ₂ , PAN, etc.) that are harmful to the human body through photochemical reactions of various smogs, acid rain and air, and cause eutrophication of aquatic ecosystems. It is a pollutant.

In addition, nitrogen oxide is an exhaust gas regulation substance that is inevitably generated during the combustion of most fossil fuels.It is a method of decomposing and removing the three-way catalyst of gasoline engine, selective catalyst reduction using NH ₃ and hydrocarbons as reducing agents (SCR). ) Technology is used in various ways.

These methods rapidly degrade the decomposition efficiency when other components such as oxygen are present. In addition, the selective catalytic reduction method, which has been put to practical use, has a problem in that the reaction temperature range is narrow, performance decreases due to aging of the catalyst, and facilities and operation costs are high.

In engine lean combustion, excess oxygen is present in the exhaust gas. In this case, the remaining oxygen greatly consumes the NOx reducing agent or greatly reduces the reduction performance. Therefore, there is a need for a method of adsorbing and storing NOx separately and desorption reduction to prevent deterioration of NOx reduction performance due to the presence of oxygen and to efficiently decompose NOx. According to these demands, research and development on NOx storage materials has been made.

The NOx storage materials are BaO, which is an alkaline earth metal oxide, and these oxides require a catalyst to oxidize and adsorb NO, since the adsorption performance for NO is lower than that of NO _2. It is added and used. However, these sorbents usually have a maximum occupancy capacity of only 10-20 mg-NOx / g-cat at 350 ° C., and their capacity drops significantly when the temperature is increased or decreased. In addition, since the occlusion component is mainly composed of NO ₂ rather than NO, there is a problem in that the rate of decomposing NOx in the desorption process is lowered to serve as an effective occlusion material.

Patent Document 1 discloses nitrogen oxide reduction decomposition. However, the patent relates to the reduction decomposition of nitrogen oxides in the absence of oxygen, which is difficult to apply to the case of containing oxygen as described above.

Patent Document 2 discloses a method for decomposing nitrogen oxides using carbon monoxide. However, the patent has a disadvantage in that additional oxygen is required as much as the equivalent ratio of oxygen in addition to the nitrogen oxide when there is oxygen.

In addition, Patent Document 3 discloses a method of supplying CO by partially oxidizing CH ₄ and decomposing N ₂ O and NO x using an MMO catalyst. However, for the decomposition of lean NOx and N ₂ O, a separate measure from the above patent is required.

When oxygen is present in excess, CO requirements to remove it can be very large, since it can generally be present in% much higher than NOx concentrations of up to several thousand ppm. In this case, the cost of NOx treatment increases due to the consumption of reducing agent, it is difficult to find a suitable CO supply method, and the amount of CO ₂ emitted may also be a problem.

Patent Document 1: Korean Registered Patent No. 563903

Patent Document 2: Korean Registered Patent No. 654885

Patent Document 3: Korean Patent No. 638835

The present invention, in order to solve the problems of the prior art described above, when using a mixed metal oxide catalyst prepared from a hydrotalcite-type precursor, from the exhaust gas during the engine lean operation containing nitrogen oxides such as NOx and N ₂ O It was found that the ability to occlude the nitrogen oxides can be improved and completed based on this.

Accordingly, an object of the present invention is to store NOx and N ₂ O in the excess oxygen state in the engine lean operation for a relatively longer time than the prior art, and then operate the engine in a rich state again for a predetermined time to exhaust the exhaust gas The present invention provides a method for removing NOx and N ₂ O from a gas discharged by performing a cycle of decomposition and desorption of the occluded NOx and N ₂ O using CO and HC in the reducing agent.

The method of the present invention for achieving the above object, in the method for occluding and desorption of nitrogen oxide during lean combustion of the engine,

In the method for occluding and desorption of nitrogen oxides in lean combustion of the engine,

i) a mixed metal oxide catalyst prepared from a hydrotalcite or brucite compound precursor, a catalyst in which a noble metal is impregnated or bonded to the mixed metal oxide catalyst, or a cocatalyst to the mixed metal oxide catalyst Providing a catalyst layer having at least one of a catalyst to which is added and a non-noble metal is impregnated or interlayer bonded;

ii) passing the exhaust gas during the lean operation of the engine to the catalyst layer to occlude nitrogen oxides of the exhaust gas;

iii) after the step, passing the exhaust gas generated by operating the engine to a rich state through the catalyst bed; And

iv) decomposing and desorbing the nitrogen oxide stored in the catalyst layer by CO and HC in the exhaust gas;

Characterized in that it comprises a.

In one embodiment of the present invention, the method is characterized by repeating the steps ii) and iv).

In one embodiment of the present invention, the hydrotalcite type or brucite type compound precursor in step i) is represented by the following formula (1):

[Formula 1]

As _{^{[M 2+ 1-x N 3+}} x (OH) 2] x + [A n- x / n · bH 2 O], wherein M ²⁺ and N ³⁺ are each a metal cation, Mg ²⁺ M roneun ^{2 A} divalent metal cation selected from ⁺ , Ca ²⁺ , Ni ²⁺ , Zn ²⁺ , Sr ²⁺ , Ba ²⁺ , Fe ²⁺ , Cu ²⁺ , Co ²⁺ , Pd ²⁺ and Mn ²⁺ is used. N ^{3+ may be represented} by Rh ³⁺ , Al ³⁺ , Mn ³⁺ , Fe ³⁺ , Co ³⁺ , Ni ³⁺ , Cr ³⁺ , Ga ³⁺ , B ³⁺ , La ³⁺ and Ce ^3+. and trivalent metal cations selected, a ^n- is CO ₃ ^2- has a charge of -1, -2 or _{^{-3, NO 3 -, SO 4}} 2-, Cl -, OH -, SiO 3 2-, MnO _{^{4 2-, HPO 3 2-, MnO}} 4 2-, HGaO 3 2-, HVO 4 2-, ClO 4 - and a compound composed of an anion BO ₃ ^2-, used alone or in combination of two or more, x is 0.0 to 0.5, b is an integer from 0 to 20.

In one embodiment of the invention, the precious metal is Mo, Ti, Pt, Au, Ag, Rh, Pa, La, Ir, V, Kr, Nd, Nb, Se, Sc, Ru, In, Y, Z and It is characterized in that it is selected from the group consisting of a mixture thereof.

In one embodiment of the invention, the promoter is selected from the group consisting of K, Rb, and Cs, the non-noble metal is Ni, Co, Fe, Mn, Al, Ce, Zr, Cu, Zn, Ba, At least one selected from the group consisting of Mg, Ca, Sr, and mixtures thereof, characterized in that the content of the noble metal in the interlayer bonded catalyst is 0.01 to 20% by weight.

In one embodiment of the present invention, the step ii) is characterized in that it is made for 20 seconds to 30 minutes.

In one embodiment of the present invention, the step iii) and iv) is characterized in that made for 2 seconds to 10 minutes.

In one embodiment, the method is characterized in that the hourly space velocity of the exhaust gas GHSV (Gas Hourly Space Velocity), which has passed through the catalyst layer of 10,000~200,000h ^-1.

In one embodiment of the invention, the method is characterized in that the temperature of the gas passing through the catalyst bed is 200 to 500 ℃.

In one embodiment of the invention, the step ii) is characterized in that 20 seconds to 30 minutes.

In one embodiment of the present invention, the step ii) and iv) is characterized in that it is repeatedly carried out with a cycle period of 5 seconds to 10 minutes.

According to the method of the present invention, it is possible to occlude NOx and N2O in the exhaust gas during the lean operation of the engine for a longer time.

In addition, since the stored nitrogen oxides are decomposed and desorbed using CO and HC in the exhaust gas as a reducing agent, it does not require a separate reducing agent.

1A and 1B are graphs of examples of cycle operation according to the method of the present invention.

2A and 2B are graphs of examples of another cycle operation according to the present invention.

Automotive engines, especially diesel engines, are characterized by lean combustion, making it difficult to remove NOx from the exhaust gases. Efforts have been made to use ammonia or urea as reducing agents in existing SCR catalysts, but it is not desirable and most expected is the method of desorption and reduction of NOx with HC, CO, H _2, etc. Therefore, there has been a study on a catalyst having excellent NOx selectivity and easy desorption reduction. When the adsorption property is good and the desorption is good, the breakthrough curve concentration increases later or slower than the adsorption time, so the lean operation time can be increased and the rich operation time can be reduced, resulting in a longer cycle period. System operation becomes convenient and flexible. On the contrary, when the adsorption performance decreases, the breakthrough curve concentration increases rapidly, so that a high concentration of NO is discharged compared to the same time, which means that the time must be shortened. To date, lean / rich operation for diesel engines considers 50/10 sec operation as the best condition to remove 80-90% NOx, and increasing the occlusion time leads to a sharp decrease in NOx treatment efficiency (for example, a two minute occlusion time). NOx treatment efficiency of 40-50%). Currently, the exhaust gas treatment method of diesel engines is adopted to reduce the NOx generation, the EGR system that lowers the operating temperature of the engine, which reduces the NOx but decreases the engine efficiency and increases the smoke so that the NOx removal technology is applied The elimination of the EGR system increases engine efficiency and reduces smoke emissions.

The present invention has been devised based on this aspect.

Looking at the present invention in more detail as follows.

As described above, the present invention allows the mixed metal oxide catalyst layer prepared from a hydrotalcite type or brucite type compound precursor to pass the exhaust gas during the lean operation of the engine for a predetermined time. N2O, or storing NOx and N ₂ O, and to re-schedule the operation of the engine in a rich state for a time repeating the exhaust gases CO and recalled storing the decomposed desorb the NOx and N ₂ O by using the HC as a reducing agent A method of simultaneously removing NOx and N ₂ O from exhaust gas discharged by performing a cycle operation.

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

Hydrotalcite type or brucite type compound precursors used in the present invention may be represented by Chemical Formula 1. In other words,

Same as [M ²⁺ _1-x N ³⁺ _x (OH) ₂ ] ^{x +} [A ^n- _{x /} nbH ₂ O], in the hydrotalcite-type precursor, M ²⁺ and N ³⁺ are each a metal As cations, M ²⁺ includes Mg ²⁺ , Ca ²⁺ , Ni ²⁺ , Zn ²⁺ , Sr ²⁺ , Ba ²⁺ , Fe ²⁺ , Cu ²⁺ , Co ²⁺ , Pd ²⁺ and Mn ²⁺ A divalent metal cation selected from among others is used. As N ³⁺ , Rh ³⁺ , Al ³⁺ , Mn ³⁺ , Fe ³⁺ , Co ³⁺ , Ni ³⁺ , Cr ³⁺ , Ga ³⁺ , B ³⁺ A trivalent metal cation selected from, La ³⁺ and Ce ³⁺ and the like is used. The molar ratio of M ²⁺ and N ³⁺ is 1: 1 to 100: 1, more preferably 1: 1 to 5: 1. Further, in the hydrotalcite-type precursors, A ^n- is -1, -2 or -3 charge the C _O3 ^2- NO ₃ having a _{^{- SO 4 2-, Cl -,}} OH -, SiO 3 2-, MnO _{^{4 2-, HPO 3 2-, MnO}} 4 2-, HGaO 3 2-, HVO 4 2-, ClO 4 - and a compound composed of an anion such as BO ₃ ^2-, used alone or in combination of two or more, x Is 0.01 to 0.5, b is an integer of 0 to 20.

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

According to one embodiment of the present invention, the MMO catalyst used in the method may be a mixed metal oxide catalyst is a non-noble metal is impregnated or interlayer bonded. In general, noble metals have problems such as high cost, and it is desirable to reduce their contents. However, in addition to the combination of non-noble metals such as Ni, Co, Al, and Ba, a catalyst such as K can be used to increase the catalytic activity. It can also replace precious metals.

The promoter used herein may be an alkali metal. Preferably from Na, K, Rb, and Cs. The non-noble metal may be at least one selected from the group consisting of Ni, Co, Fe, Mn, Al, Ce, Zr, Cu, Zn, Ba, Mg, Ca, Sr, and mixtures thereof. The content of the non-noble metal in the interlayered catalyst is preferably 0.01 to 20% by weight.

The present invention utilizes the adsorption performance of the MMO catalyst, and the adsorption strength adsorbed on the MMO catalyst is usually (NO, N ₂ O, NO ₂ , SO ₂ )>CO> O ₂ . That is, NO, N ₂ O, NO ₂ , and SO ₂ have higher adsorption strength than CO and O ₂ , but the adsorption strength between NO, N ₂ O, NO ₂ , and SO ₂ may vary depending on the composition of the catalyst. have.

Therefore, since the genie the characteristics such as NO and N ₂ O better absorption compared to the oxygen, because if the exhaust gas containing excess oxygen passing through the adsorption catalyst NO and N ₂ O is more occurs are adsorbed as compared to oxygen Most of the oxygen passes through as it is, and NO and N ₂ O are adsorbed in the catalyst layer, which is separated from the oxygen. Thus separated NO and N ₂ O is easily reduced by a reducing agent such as CO and can exclude the reaction with oxygen, characterized in that the consumption of CO is small and the desorption rate is faster.

MMO catalysts generally exhibit higher occlusion performance with respect to NO alone components, and SO ₂ , commonly known as a catalyst poison, is relatively strongly adsorbed compared to CO, O _2, etc., but exhibits similar adsorption strengths to NO, NO _2, and the like. However, the adsorbed SO ₂ is desorbed by CO, NO, NO ₂ , O ₂ , N _2, etc., so that NOx storage efficiency decrease or catalyst activity decrease due to SO ₂ accumulation rarely occurs.

According to one embodiment of the invention, the time to occlude NOx and / or N ₂ O in the method may be 20 seconds to 30 minutes. If the occlusion time is less than 20 seconds, it will not be able to occlude enough NOx and / or N ₂ O to reduce the treatment efficiency and engine efficiency of the nitrogen oxide, and if the occlusion time exceeds 30 minutes, it will be out of the occlusion capacity of the catalyst. There is a problem that the nitrogen oxides can not be occluded and discharged. Although conventional occlusion techniques generally use an occlusion time of about 50 seconds, the catalyst used in the method of the present invention has an excellent occlusion performance, and thus an advantage of occluding nitrogen oxides for a longer time. Has

According to one embodiment of the present invention, the desorption decomposition of the occluded nitrogen oxides into CO and HC contained in the exhaust gas during the engine rich operation may be performed for about 5 seconds to 10 minutes. In this case, when the desorption decomposition time is less than 5 seconds, the occluded nitrogen oxides do not sufficiently react with CO and HC. In the case of 10 minutes or more, after the occluded nitrogen oxides are all reacted, the engine may be operated in a rich state excessively, leading to excessive CO and HC emissions as well as a problem in that fuel efficiency (fuel efficiency) may be lowered.

According to one embodiment of the invention, the period of the cycle of the method can be adjusted in the range of 20 seconds to 30 minutes. This is because a heavy duty engine with high NOx generation and a light duty engine with relatively low NOx generation can have a shorter or longer occlusion cycle, respectively. ) And lower than necessary, the NOx storage and removal efficiency of the catalyst may be reduced.

In one embodiment of the invention, the gas hour space velocity (GHSV) of the exhaust gas passing through the catalyst bed is preferably 10,000 to 200,000 h ⁻¹ . If the GHSV is less than 10,000 h ^{-1, the} amount of catalyst is relatively low compared to the throughput, and if the GHSV is more than 200,000 h ^-1 , the contact time with the catalyst is short, so the adsorption efficiency of NOx or N ₂ O is short. In addition to the possibility of this decrease, the negative pressure caused by the exhaust gas is increased, and the engine is heavily loaded.

Meanwhile, although the applied pressure may vary depending on the engine used, the pressure of the gas passing through the catalyst bed is preferably at least 1 atm, and the adsorption rate increases as the pressure increases, but the engine load increases. Be careful not to.

According to the invention, the temperature of the gas passing through the catalyst bed is preferably between 200 and 500 ° C. If the temperature of the gas passing through the catalyst bed is less than 200 ℃ the same as the initial start of the engine, the adsorption rate and reduction desorption reaction is slow, if the temperature exceeds 500 ℃ there is a problem that causes thermal damage to the catalyst and the support.

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.

Example 1.

2.746 g of a metal oxide catalyst having a molar ratio of Al: Pd: Co = 1: 0.05: 1 prepared from a hydrotalcite precursor was used for 500 ml / min of nitrogen gas containing 547 ppm of NO and 1.54% of O ₂ at a temperature of 300 ° C. SV 21,000hr ^-1 ) was passed for 30 minutes and the nitrogen gas containing 4,590ppm CO was passed for 30 minutes at 500ml / min (SV 21,000hr ^-1 ) flow rate. Decomposition and removal.

Example 2.

700 ml / min of nitrogen gas containing 270 ppm of NO and 1.27% of O ₂ at a temperature of 300 ° C. using 1.285 g of a metal oxide catalyst having a molar ratio of Al: Pd: Co = 1: 0.02: 1 prepared from a hydrotalcite precursor. SV 55,000hr ^-1 ) 10 minutes at a flow rate, and nitrogen gas containing 4,400ppm CO 10 minutes at 700ml / min (SV 55,000hr ^-1 ) flow rate is repeated, after a total of 92.2% of NO is adsorbed It was almost decomposed.

Example 3.

Nitrogen gas containing 461 ppm of NO and 1.5% of O ₂ at a temperature of 300 ° C using 3.71 g (V = 3 mL) of a metal oxide catalyst having a molar ratio of Ni: Al: Pd = 1: 1: 0.1 prepared from a hydrotalcite precursor. 2 minutes at 500 ml / min (SV 30,000 hr ^-1 ) flow rate and nitrogen gas containing 4,000 ppm CO at 2 minutes at 500 ml / min (SV 30,000 hr ^-1 ) flow rate. After NO was adsorbed, it was almost decomposed.

Example 4.

700 ml / min of nitrogen gas containing 252 ppm of NO and 1.26% of O ₂ at 250 ° C using 1.294 g of a metal oxide catalyst having a molar ratio of Al: Pd: Co = 1: 0.05: 1 prepared from a hydrotalcite precursor. SV 52,500hr ^-1 ) was passed for 10 minutes and nitrogen gas containing 4,600ppm CO was passed for 10 minutes at 700ml / min (SV 52,000hr ^-1 ) flow rate. Almost completely decomposed and desorbed.

Example 5.

1.95 g of a metal oxide catalyst having a molar ratio of Al: Pd: Co = 1: 0.05: 1 prepared from a hydrotalcite precursor was used for 3 minutes by weight of NOx 395 ppm, O ₂ 1.45%, and remaining gas at 300 ° C. for 10 minutes. by the adsorbed gas with a total ^{500ml / min (SV 30,000hr -1)} , CO 4,000ppm and the rest of the amount of gas in the decomposition of nitrogen desorption from the catalyst total gas 500ml / min (SV 30,000hr ^-1) flow conditions 10 As a result of repeating every minute, 96% of NOx was adsorbed and almost desorbed.

Example 6.

2.200 g of a metal oxide catalyst having a molar ratio of Al: Ni: Co = 1: 1: 1 prepared from a hydrotalcite precursor was used for 500 ml / min of nitrogen gas containing 400 ppm of NOx and 1.52% of O ₂ at a temperature of 300 ° C. SV 30,000hr ^-1 ) was passed through for 5 minutes and nitrogen gas containing 4500ppm of CO was passed through 500ml / min (SV 30,000hr ^-1 ) for 5 minutes. Decomposition and removal.

Example 7.

2.200 g of a metal oxide catalyst having a molar ratio of Al: Ni: Co = 1: 1: 1 prepared from a hydrotalcite precursor was used for 500 ml / min of nitrogen gas containing 400 ppm of NOx and 1.52% of O ₂ at a temperature of 300 ° C. When 2 minutes were passed through the flow rate of SV 30,000hr ^-1 ), and nitrogen gas containing 4500ppm of CO was passed through the flow rate at 500ml / min (SV 30,000hr ^-1 ) for 2 minutes, almost 97.65% of NOx was adsorbed. Decomposition and removal.

As can be seen from the above examples, when the method of the present invention was used, almost all of the nitrogen oxides could be adsorbed and desorbed. This shows up to 90% DeNOx efficiency for Lean / Rich (50 / 10sec) for the existing Pt-BaO / Al ₂ O ₃ catalyst, and is significantly superior to 50% DeNOx efficiency for 2 minutes of Lean Operation time. It can be seen that.

In addition, it can be seen that the improved efficiency compared to the NOx removal efficiency decreases as the cycle time increases in the storage capacity of the conventional representative Pt / BaO catalyst.

1A and 1B show an example of cycle operation according to the present invention. The cycle conditions were Lean / Rich 20min / 20min cyclic with AlCoPd (1/1 / 0.05) cat., GHSV 30000 / h, O ₂ : 1.38%, T = 250 ° C Input NOx: 231ppm, NOx removal efficiency was 94 Was%.

2A and 2B show an example of another cycle operation according to the present invention. The cycle conditions were Lean / Rich 30min / 30min cyclic with AlCoPd (1/1 / 0.05) cat., Flow rate: 500ml / min GHSV: 21000 / hr, O ₂ : 1.54%, T = 300 ° C.-250 ° C., Input NOx was 547 ppm and DeNOx efficiency was 90%.

1 to 2 it can be seen that the method according to the present invention does not have a large decrease in DeNOx efficiency over time.

On the other hand, the present invention is not limited to the described embodiments, it is apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, such modifications or variations should also be seen as belonging to the claims of the present invention.

Claims (11)

1. In the method for occluding and desorption of nitrogen oxides in lean combustion of the engine,

   i) a mixed metal oxide catalyst prepared from a hydrotalcite type or brucite type compound precursor, a catalyst in which a noble metal is impregnated or interlayer bonded to the mixed metal oxide catalyst, or a cocatalyst to the mixed metal oxide catalyst Providing a catalyst layer having at least one of a catalyst to which is added and a non-noble metal is impregnated or interlayer bonded;

   ii) passing the exhaust gas during the lean operation of the engine to the catalyst layer to occlude nitrogen oxides of the exhaust gas;

   iii) after the step, passing the exhaust gas generated by operating the engine to a rich state through the catalyst bed; And

   iv) decomposing and desorbing the nitrogen oxide stored in the catalyst layer by CO and HC in the exhaust gas;

   Method for removing nitrogen oxides from the exhaust gas of the engine comprising a.
2. The method of claim 1, wherein the method is performed by repeating steps ii) to iv).
3. The method of claim 1 or 2, wherein the hydrotalcite or brucite compound precursor in step i) is represented by the following formula (1) to remove nitrogen oxides from the exhaust gas of the engine: Way:

   <Formula 1>

   [M ²⁺ _1-x N ³⁺ _x (OH) ₂ ] ^{x +} [A ^n- _{x /} nbH ₂ O], where M ²⁺ and N ³⁺ are each metal cations and M ²⁺ is Mg ^{2 Is a} divalent metal cation selected from ⁺ , Ca ²⁺ , Ni ²⁺ , Zn ²⁺ , Sr ²⁺ , Ba ²⁺ , Fe ²⁺ , Cu ²⁺ , Co ²⁺ , Pd ²⁺ and Mn ²⁺ , N ³⁺ is selected from Rh ³⁺ , Al ³⁺ , Mn ³⁺ , Fe ³⁺ , Co ³⁺ , Ni ³⁺ , Cr ³⁺ , Ga ³⁺ , B ³⁺ , La ³⁺ and Ce ³⁺ and trivalent metal cation, a ^n- is CO ₃ ^2- has a charge of -1, -2 or _{^{-3, NO 3 -, SO 4}} 2-, Cl -, OH -, SiO 3 2-, MnO 4 2 _{^{-, HPO 3 2-, MnO 4}} 2-, HGaO 3 2-, HVO 4 2-, ClO 4 - and a is one or two or more in combination selected from anionic compounds consisting of BO ₃ ^2-, x is 0.0 to 0.5 And b is an integer from 0 to 20.
4. The method of claim 1 or 2, wherein the precious metal is Mo, Ti, Pt, Au, Ag, Rh, Pa, La, Ir, V, Kr, Nd, Nb, Se, Sc, Ru, In, Y, Z and their A method for removing nitrogen oxides during lean combustion of an engine, characterized in that it is selected from the group consisting of mixtures.
5. The method according to claim 1 or 2, wherein the promoter is selected from the group consisting of Na, K, Rb, and Cs, the non-noble metal is Ni, Co, Fe, Mn, Al, Ce, Zr, Cu, Zn, Ba, At least one selected from the group consisting of Mg, Ca, Sr, and mixtures thereof, wherein the content of the noble metal in the interlayered catalyst is 0.01 to 20% by weight. .
6. The method of claim 1 or 2, wherein the step ii) is performed for 20 seconds to 30 minutes.
7. The method of claim 1 or 2, wherein steps iii) and iv) are performed for 5 seconds to 10 minutes.
8. The method according to claim 1 or 2, wherein the method removes nitrogen oxides from the exhaust gas of an engine, wherein the gas hour space velocity (GHSV) of the exhaust gas passing through the catalyst bed is 10,000 to 200,000 h ⁻¹ . How to.
9. The method according to claim 1 or 2, wherein the temperature of the gas passing through the catalyst bed is 200 to 500 ° C.
10. The method of claim 6, wherein the step ii) has a cycle time of 20 seconds to 30 minutes.
11. The method of claim 1 or 2, wherein steps ii) to iv) are repeatedly performed with a cycle period of 25 seconds to 40 minutes.

Images