JP2018023945A - Catalyst for exhaust purification - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst for exhaust purification that satisfactorily purifies exhaust, particularly NOx-containing exhaust.SOLUTION: A catalyst for exhaust purification has at least one cluster selected from the group consisting of a cluster composed of two gold atoms and one copper atom, a cluster composed of one gold atom and one copper atom, and a cluster composed of one gold atom and two copper atoms.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an exhaust gas purification catalyst.

  In exhaust gas discharged from internal combustion engines for automobiles, for example, gasoline engines or diesel engines, carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), etc. Contains ingredients.

  For this reason, in general, an exhaust gas purification device for purifying these components is provided in the internal combustion engine, and these components are substantially decomposed by the exhaust gas purification catalyst attached in the exhaust gas purification device. Has been. An example of such an exhaust gas purification catalyst is a copper (Cu) -based exhaust gas purification catalyst.

  This Cu-based exhaust gas purification catalyst is known to have a relatively high performance for catalyzing a reduction reaction of NOx. However, the efficiency of the reduction reaction is not sufficient. Therefore, techniques for efficiently reducing and decomposing NOx have been studied.

  The exhaust gas purifying catalyst of Patent Document 1 is a bimetallic cluster that includes a support made of a metal oxide and metal particles supported on the support, and the metal particles include Au and Cu. Patent Document 1 discloses that the bimetallic cluster is composed of tens to tens of thousands of Cu atoms and Au atoms.

JP 2012-217970 A

  It is an object of the present invention to provide an exhaust gas purification catalyst that is excellent in purifying exhaust gas, particularly exhaust gas containing NOx.

  The present inventors have found that the above problems can be solved by the following means.

  <1> A cluster composed of two gold atoms and one copper atom, a cluster composed of one gold atom and one copper atom, and a cluster composed of one gold atom and two copper atoms An exhaust gas purification catalyst comprising at least one cluster selected from the group.

  ADVANTAGE OF THE INVENTION According to this invention, the exhaust gas purification catalyst excellent in purifying exhaust gas, especially the exhaust gas containing NOx can be provided.

FIG. 1 is a diagram showing an apparatus for manufacturing and measuring an exhaust gas purification catalyst. FIG. 2 is a diagram showing a part of an apparatus for manufacturing and measuring an exhaust gas purification catalyst. FIG. 3 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the cluster Au ₁ Cu ₁ and oxygen. FIG. 4 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the clusters Au ₁ Cu ₂ and oxygen. FIG. 5 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the cluster Au ₂ Cu ₁ and oxygen. FIG. 6 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the cluster Au ₀ Cu ₁ and oxygen. FIG. 7 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the cluster Au ₀ Cu ₂ and oxygen. FIG. 8 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the cluster Au ₀ Cu ₃ and oxygen. FIG. 9 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the cluster Au ₀ Cu ₄ and oxygen. FIG. 10 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the clusters Au ₀ Cu ₅ and oxygen. FIG. 11 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the clusters Au ₁ Cu ₃ and oxygen. FIG. 12 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the clusters Au ₁ Cu ₄ and oxygen. FIG. 13 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the clusters Au ₁ Cu ₅ and oxygen. FIG. 14 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the cluster Au ₂ Cu ₂ and oxygen. FIG. 15 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the cluster Au ₂ Cu ₃ and oxygen. FIG. 16 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the cluster Au ₂ Cu ₄ and oxygen. FIG. 17 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the cluster Au ₃ Cu ₁ and oxygen. FIG. 18 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the clusters Au ₃ Cu ₂ and oxygen. FIG. 19 is a diagram showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the cluster Au ₃ Cu ₃ and oxygen. FIG. 20 shows the mass-to-charge ratio (m / z) and intensity (arbitrary units) when the concentration of NO gas is 0%, 1%, and 7% for the reaction between the cluster Au ₁ Cu ₁ and NO gas. FIG. FIG. 21 shows the mass-to-charge ratio (m / z) and strength (arbitrary unit) when the NO gas concentration is 1% and 7% for the NOx reduction reaction cycle between the cluster Au ₁ Cu ₁ and NO gas. It is a figure which shows the relationship. FIG. 22 is a diagram showing the relationship between the temperature (K) and the intensity ratio when the concentration of NO gas is 7% with respect to the NOx reduction reaction cycle between the cluster Au ₁ Cu ₁ and NO gas. FIG. 23 shows the mass-to-charge ratio (m / z) and intensity (arbitrary units) when the concentration of NO gas is 0%, 1%, and 7% for the reaction between the cluster Au ₁ Cu ₂ and NO gas. FIG. FIG. 24 is a diagram showing the relationship between the temperature (K) and the intensity ratio when the concentration of NO gas is 7% with respect to the NOx reduction reaction cycle between the cluster Au ₁ Cu ₂ and NO gas. FIG. 25 is a diagram showing the relationship between the mass-to-charge ratio (m / z) and the intensity (arbitrary unit) when the concentration of NO gas is 7% with respect to the reaction between the cluster Au ₂ Cu ₁ and NO gas. It is. FIG. 26 is a diagram showing the relationship between the temperature (K) and the intensity ratio when the concentration of NO gas is 7% with respect to the NOx reduction reaction cycle between the cluster Au ₂ Cu ₁ and NO gas.

  Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be implemented with various modifications within the scope of the gist of the present invention.

《Conventional exhaust gas purification catalyst》
In the conventional Cu-based exhaust gas purification catalyst, NOx reduction reaction hardly occurs. This is not limited by any theory, but the oxygen atom-copper atom bond generated in the middle of the reduction reaction is relatively strong and stable, so that the reaction to be reduced to metallic copper as the catalyst metal is suppressed. It is thought to be for this purpose.

  In this regard, there is conventionally known a technique in which a reducing agent such as CO is further used to cut the oxygen atom-copper atom bond and reduce it to metallic copper, thereby efficiently proceeding the above reduction reaction. However, in this technique, since a reducing agent is an essential configuration, there are limitations on the NOx reduction conditions.

  Conventionally, as in Patent Document 1, an exhaust gas purifying catalyst containing a bimetallic cluster containing Au and Cu can relatively reduce the NOx reduction reaction without requiring a reducing agent as an essential component. Is possible. This is not bound by any theory, but the oxygen atom-copper atom bond is destabilized because the hard-to-oxidize gold atom is close to the oxidizable copper atom at the atomic level. This is considered to be because the reaction reduced to metallic copper is promoted. Such bimetallic clusters containing Au and Cu are generally composed of tens to tens of thousands of atoms on average.

  On the other hand, the present inventors adopt a bimetallic cluster in which the number of gold atoms and the number of copper atoms are specified, thereby destabilizing the oxygen atom-copper atom bond, and thereby the catalyst. It has been found that the reaction reduced to metallic copper as a metal is significantly promoted. The invention is shown below.

<< Exhaust gas purification catalyst of the present invention >>
The exhaust gas purification catalyst of the present invention comprises a cluster composed of two gold atoms and one copper atom, a cluster composed of one gold atom and one copper atom, and one gold atom and two copper atoms. Including at least one cluster selected from the group consisting of:

<Method for producing exhaust gas purification catalyst>
The exhaust gas purification catalyst can be produced, for example, by a method including the following steps.
Irradiating a target material containing gold and copper with a laser to generate a plurality of bimetallic clusters containing gold and copper (cluster generation process), and a plurality containing gold and copper The bimetallic cluster is sorted into bimetallic clusters in which the number of gold atoms and the number of copper atoms are specified (cluster sorting step).

<Cluster generation process>
In the cluster generation step, a laser ablation method such as a laser evaporation method can be employed. In general, the laser evaporation method is a method in which a target material is irradiated with a laser, and atoms, molecules, and / or clusters, etc. are evaporated and ionized from the irradiated portion to generate plasma vapor composed of these components. It is.

  The cluster generation step may further include a step of cooling the plasma vapor from the viewpoint of efficiently generating the bimetallic cluster from the plasma vapor.

(atmosphere)
The atmosphere in the cluster generation step may be substantially a carrier gas atmosphere that moves the generated clusters and the like. The atmosphere in the cluster generation step is not particularly limited, but may be, for example, an inert gas atmosphere from the viewpoint of stabilizing the plasma vapor. The inert gas atmosphere may contain other trace components, for example, trace element components. The temperature of the atmosphere in the cluster generation step is not particularly limited, but may be affected by the temperature of the plasma vapor. The pressure of the atmosphere in the cluster generation step is not particularly limited. For example, the pressure is more than 0 Pa, 1.0 × 10 ⁻⁵ Pa or more, 1.0 × 10 ⁻⁴ Pa or more, or 1.0 × 10 ⁻³ Pa or more. And / or 1 × 10 ⁶ Pa or less, 0.7 × 10 ⁶ Pa or less, 1.0 × 10 ² Pa or less, or 1.0 × 10 ¹ Pa or less, particularly stabilizing plasma vapor, and It is preferable that the pressure is low such that the energy loss of the laser is small, for example 1.0 × 10 ⁻⁵ Pa or more and 1.0 × 10 ² Pa or less.

(laser)
Examples of lasers include, but are not limited to, solid lasers such as Nd: YAG lasers; gas lasers; liquid lasers; and semiconductor lasers.

  Examples of laser oscillation include continuous oscillation and pulse oscillation. Among them, the energy of a pulsed laser is instantaneously higher than that of a continuous wave laser and the pulse width of the pulsed oscillation is shorter (for example, in femtosecond units). Steam can be easily generated.

  The wavelength of the laser is not particularly limited. The wavelength of the laser can be appropriately determined in consideration of the properties of the target to be irradiated with the laser, for example, properties such as the laser absorptance, reflectance, and transmittance.

An example of the continuous wave laser power density is not particularly limited, but may be 1 W / cm ² or more. An example of the fluence of pulse oscillation is not particularly limited, but may be 0.5 mJ / cm ² or more. Note that the output of these lasers can be adjusted as appropriate according to the mass, size, thickness, properties, etc. of the target to be irradiated with the laser.

  Needless to say, examples of the laser include an nth harmonic laser (n is a natural number) generated by applying means such as a nonlinear optical crystal to the above laser.

(Target material)
Examples of the target material containing gold and copper are not particularly limited. For example, two target materials (multiple target material) including gold and copper are alternately used. An arrayed target material (alternate array type target material), a micro mixed target material (micro mixed type target material) obtained by mixing and molding gold powder and copper powder, and the like can be used.

  In addition, the easiness of metal repelling by sputtering differs depending on each metal element. Therefore, the composition ratio of these metal elements in the target material may be determined in consideration of the ease of repelling gold and copper. Furthermore, the composition ratio when the gold powder and the copper powder are mixed may be correlated or proportional to the composition ratio of gold and copper in the bimetallic cluster generated by laser ablation.

  When two target materials are used, one containing gold and one containing copper, each target material may be irradiated with a laser, and each plasma vapor generated thereby may be mixed to generate a bimetallic cluster. .

  As an example of the target material in which gold and copper are alternately arranged, for example, a disk-like material in which gold and copper are alternately arranged in a radial manner can be used. According to such a disk-shaped target material, the area or area ratio of gold and copper may be changed to generate a bimetallic cluster having a desired composition ratio of gold and copper.

  When the micro mixed target material is adopted, the composition ratio of gold and copper in the target material may be changed to generate a bimetallic cluster having a desired composition ratio of gold and copper.

<Cluster selection process>
In the cluster selection process, a mass spectrometer such as a time-of-flight time-of-flight, a magnetic deflector, a quadrupole, an ion trap, or a combination of these is used. A tandem mass spectrometer may be used. By using these devices, clusters can be selected based on the difference in mass-to-charge ratio (m / z) between the plurality of clusters.

(atmosphere)
Regarding the atmosphere in the cluster selection process, the description of the atmosphere in the cluster generation process can be referred to.

  The exhaust gas purifying catalyst of the present invention and the method for producing the above exhaust gas purifying catalyst can be referred to in relation to each other. For example, with respect to the configuration and characteristics of the exhaust gas purification catalyst, the above-described method for producing an exhaust gas purification catalyst can be referred to.

  The present invention will be described in more detail with reference to the following examples, but it goes without saying that the scope of the present invention is not limited by these examples.

"apparatus"
An apparatus for manufacturing and measuring an exhaust gas purification catalyst is shown in FIG. 1, and a part of the apparatus is shown in FIG. The apparatus 1 shown in FIG. 1 includes a cluster generation reaction unit 100 and a cluster selection measurement unit 200.

  FIG. 2 is a diagram illustrating the cluster generation reaction unit 100. The cluster generation reaction unit 100 of FIG. 2 includes a cluster generation unit 110, a cluster reaction unit 120, and a heating unit 130.

  In the cluster generation unit 110, the gold-containing target material 101 and the copper-containing target material 102 are irradiated with lasers 111 and 112, respectively, thereby generating plasma vapor and generating various bimetallic clusters. The plasma vapor and / or the bimetallic cluster is carried to the cluster reaction unit 120 by the carrier gas 103.

  In the cluster reaction unit 120, the reaction gas 123 is added to the carrier gas 103 as necessary, and the reaction gas 123 reacts with the bimetallic cluster or the like in the plasma vapor. Furthermore, the carrier gas 103 containing the plasma vapor is cooled by the cooling unit 122, which makes it easy to generate a bimetallic cluster. The carrier gas 103 circulated through the cooling unit 122 passes through the heat insulating unit 121 and reaches the heating unit 130.

  The heating unit 130 includes a heating coil 131 and a tube 132 around which the heating coil 131 is wound. The carrier gas 103 that has passed through the tube 132 of the heating unit 130 then reaches the cluster selection measurement unit 200 (FIG. 1).

  In the cluster selection measurement unit 200 of FIG. 1, the carrier gas 103 including a bimetallic cluster or the like reaches the interface unit 210. The interface unit 210 is configured by a skimmer cone for differential exhaust, and the carrier gas 103 passes through this to reach the ion lens unit 220. Charged clusters or the like contained in the carrier gas 103 are converged by the electric field of the ion lens unit 220, and as a result, a cluster beam 230 is formed.

  The cluster beam 230 reaches the accelerating electrode unit 240, and the charged clusters and the like are accelerated by being changed in direction by the electric field generated by the electrode unit 240. The charged clusters are changed in direction, and the accelerated charged clusters and the like are deflected according to the charge and mass by passing through the voltage changeover switch 250 and the deflector 260, and go to the two-stage reflectron 270. And so on. In the two-stage reflectron 270, the clusters and the like are subjected to correction of errors resulting from their initial velocities. The clusters 281 and 282 and the like that have come out of the two-stage reflectron 270 reach the detection unit 290.

The present invention will be described in more detail with reference to the apparatus of FIGS. 1 and 2 and the above procedure. In the present specification, “Au _n Cu _m ” is also referred to as a cluster composed of n gold atoms and m copper atoms. Here, n and m are integers of 0 or more.

Various clusters of gold and copper were obtained using the apparatus of FIGS. 1 and 2 above. The cluster generation conditions, particularly the conditions in the cluster generation unit 110 are shown below.
-Gold-containing target material 101:
Gold rod, manufactured by Furuya Metal Co., Ltd., diameter 5 mm, height 30 mm, purity 99.95%
Copper-containing target material 102:
Copper rod, manufactured by Niraco Co., Ltd., diameter 5 mm, height 30 mm, purity 99.9%
Carrier gas 103:
Helium gas, flow rate 100 ml / min (pressure 0.7 MPa, jetted at 10 Hz from a pulse valve, average pressure 1.3 × 10 ⁻³ Pa in the chamber of the cluster generator)

  The relationship between the number of gold atoms and copper atoms in the obtained cluster is shown in Table 1 below. In a time-of-flight mass spectrometer (Time-of-Flight Mass Spectrometer) that uses the principle that light ions arrive at the detector earlier than heavy ions when a plurality of ions receive the same acceleration voltage at the same time. By measuring the time that each ion flies over the same distance, ions having different mass-to-charge ratios (charged particle mass-to-charge ratio) can be detected separately on the time axis.

<Evaluation>
With respect to the clusters shown in Table 1 above, evaluation of oxygen affinity and evaluation of NOx reduction reaction cycle were performed.

<Example 1: Evaluation of oxygen affinity>
When producing a cluster, the oxygen is further added to the carrier gas 103 and the heating coil 131 of the heating unit 130 is continuously heated to evaluate the affinity between the cluster and oxygen. It was. Conditions in the cluster generation unit 110 are shown below, and the evaluation results are shown in FIG. 3 and FIGS. Note that only the components of the carrier gas 103 described below are substantially present in the chamber of the cluster generation unit, and the other components are extremely small, and therefore are not described.
Carrier gas 103 (pressure about 0.7 MPa, jetted from a pulse valve at 10 Hz):
Helium gas, flow rate 100 ml / min (partial pressure 2.5 × 10 ⁻³ Pa in the chamber of the cluster generator)
Oxygen gas, flow rate 1 ml / min (partial pressure 2.9 × 10 ⁻⁴ Pa in the chamber of the cluster generator)

Specific evaluation results for each cluster are shown in FIGS. The “intensity ratio” in each figure can be expressed by the following formula (I). In addition, the intensity | strength of a cluster etc. can be measured with a mass spectrometer, for example, the detection part 290 of said FIG.
Intensity ratio = I _CLUSTER / I _SUM (I)
[Where:
I _CLUSTER : The intensity value of the target cluster, or the intensity value of oxygen adsorbed or bound to this cluster,
I _SUM : A value obtained by adding together the values of the intensity of the target cluster and the intensity of oxygen bonded to the cluster. ]

3-5, with respect to the affinity between the _{Au 1 Cu 1, Au 1 Cu} 2 respectively, and _Au 2 Cu ₁ and oxygen is a diagram showing the relationship between the temperature (K) and the intensity ratio. 3-5 to show _{Au 1 Cu 1 O x, Au} 1 Cu 2 O x, and _Au 2 _Cu 1 _{O x} of x represents the number of oxygen atoms. From these figures, it can be seen that, regarding these clusters, the proportion of those not bonded to oxygen is high, that is, the proportion of those having x of 0 is high. This result is observed in the measured temperature range of 300K to 1000K.

Moreover, 6 to 19, with respect to the affinity between the clusters and oxygen, such as Au ₀ Cu ₁ are diagrams showing the relationship between the temperature (K) and the intensity ratio. From these figures, it can be seen that regarding these clusters, the proportion of those not bonded to oxygen is low, that is, the proportion of those having x of 0 is low. From FIG. 17, it can be seen that for the cluster Au ₃ Cu ₁ , the proportion of those not bonded to oxygen is relatively high, and the proportion of those bonded to oxygen is also relatively high.

<Example 2: Evaluation of NOx reduction reaction cycle>
The NOx reduction reaction cycle was evaluated by adding the reaction gas 123 to the carrier gas 103 and continuously heating the heating coil 131 of the heating unit 130. Conditions (1) to (3) in the cluster generation unit 110 and the cluster reaction unit 120 are shown below, and the evaluation results are shown in FIGS. In the chamber of the cluster generation unit, only the following carrier gas 103 component or only the following carrier gas 103 component and reaction gas 123 component are substantially present, and the other components are: Since it is extremely small, the description is omitted.
(1) When the concentration of NO gas as the reaction gas 123 is 0% Carrier gas 103 (injected at 10 Hz from a pulse valve):
Helium gas, flow rate 10 ml / min (partial pressure 2.5 × 10 ⁻³ Pa in the chamber of the cluster generator)
(2) When the concentration of NO gas as the reaction gas 123 is 1% Carrier gas 103 (injected at 10 Hz from the pulse valve):
Helium gas, flow rate 10 ml / min (partial pressure 1.5 × 10 ⁻³ Pa in the chamber of the cluster generator)
・ Reaction gas 123
NO gas, flow rate 0.1 ml / min (partial pressure 9.6 × 10 ⁻⁵ Pa in the chamber of the cluster generator)
(3) When the concentration of NO gas as the reaction gas 123 is 7% Carrier gas 103 (injected at 10 Hz from the pulse valve):
Helium gas, flow rate 10 ml / min (partial pressure 1.5 × 10 ⁻³ Pa in the chamber of the cluster generator)
・ Reaction gas 123
NO gas, flow rate 0.7 ml / min (partial pressure 1.3 × 10 ⁻⁴ Pa in the chamber of the cluster generator)

(Evaluation of NOx reduction reaction cycle of cluster Au ₁ Cu ₁ )
FIG. 20 shows the mass-to-charge ratio (m / z) and intensity (arbitrary units) when the concentration of NO gas is 0%, 1%, and 7% for the reaction between the cluster Au ₁ Cu ₁ and NO gas. FIG. In FIG. 20, n, m, and l of Au _n Cu _m (NO) _l are integers of 0 or more, and the numerical values in parentheses attached to a predetermined peak are the n, m, and l, respectively. It corresponds to. For example, ( ₁ , _{1, 0} ) means Au ₁ Cu ₁ (NO) ₀ .

From FIG. 20, only the peak of Au ₁ Cu ₁ is observed at a NO concentration of 0%; furthermore, Au ₁ Cu ₁ (NO) ₁ , Au ₁ Cu ₁ (NO) ₂ , and Au ₁ Cu at a NO concentration of 1%. It can be seen that the peak of ₁ (NO) ₃ was observed; and the peaks of Au ₁ Cu ₁ (NO) ₂ and Au ₁ Cu ₁ (NO) ₃ were mainly observed at the NO concentration of 7%. That is, it is understood that NO is adsorbed or bonded to the Au ₁ Cu ₁ cluster.

FIG. 21 shows the mass-to-charge ratio (m / z) and strength (arbitrary unit) when the NO gas concentration is 1% and 7% for the NOx reduction reaction cycle between the cluster Au ₁ Cu ₁ and NO gas. It is a figure which shows the relationship. In FIG. 21, n, m, l, and k of A _n Cu _m N _l O _k are integers of 0 or more, and the numerical values in parentheses attached to a predetermined peak are the n, m, Corresponding to l and k. For example, ( _{1, 1, 0, 2} ) means Au ₁ Cu ₁ N ₀ O ₂ .

FIG. 21 shows that the peak of Au ₁ Cu ₁ N ₁ O ₁ is observed under the conditions of NO concentration of 1% and 300K, and thus it can be seen that NO is adsorbed or bonded to Au ₁ Cu ₁ .

In addition, FIG. 21 shows that Au ₁ Cu ₁ N ₀ O ₂ (also referred to as Au ₁ Cu ₁ O ₂ ) increased under the conditions of NO concentration of 7% and 300K.

This, NO 2 molecules adsorbed or bonded to the _Au 1 Cu _1, resulting _Au 1 _Cu 1 _{(NO) 2} from the nitrogen _{(N 2)} is considered _{to be} because _Au 1 _Cu 1 _{O 2} desorbed is increased. This means that the peak intensity of Au ₁ Cu ₁ N ₁ O ₁ under the conditions of NO concentration of 7% and 300K is smaller than that of the conditions of NO concentration of 1% and 300K; and the conditions of NO concentration of 7% and 300K It can be understood from the fact that the peak of Au ₁ Cu ₁ O ₂ is observed.

Further, FIG. 21 shows that the Au ₁ Cu ₁ O ₂ peak is almost invisible and the Au ₁ Cu ₁ N ₁ O ₁ is increased under the conditions of NO concentration of 7% and 400K.

This is because oxygen (O ₂ ) is desorbed from Au ₁ Cu ₁ O ₂ and returns to the Au ₁ Cu ₁ cluster as the catalyst metal ( _one cycle of the NOx reduction reaction cycle is completed), and again NO is adsorbed or bound thereto. This is probably because Au ₁ Cu ₁ N ₁ O ₁ was generated. This means that the peak intensity of Au ₁ Cu ₁ N ₁ O ₁ under the conditions of NO concentration of 7% and 400K is larger than that of the conditions of NO concentration of 7% and 300K; and the conditions of NO concentration of 7% and 400K It can be understood from the fact that almost no Au ₁ Cu ₁ O ₂ peak is visible.

From these facts, the Au ₁ Cu ₁ cluster significantly destabilizes the oxygen atom-copper atom bond generated in the middle stage of the NOx reduction reaction cycle, thereby promoting the reaction to be reduced to metallic copper as the catalyst metal. As a result, it is understood that the NOx reduction reaction is efficiently catalyzed.

FIG. 22 is a diagram showing the relationship between the temperature (K) and the intensity ratio when the concentration of NO gas is 7% with respect to the NOx reduction reaction cycle between the cluster Au ₁ Cu ₁ and NO gas. Regarding the “intensity ratio” in FIG. 22, please refer to the description in the above formula (I), noting that what is adsorbed or bonded to the cluster is not oxygen but NOx. Further, x and y of Au ₁ Cu ₁ N _x O _y in FIG. 22 are integers of 0 or more, and the numerical values in parentheses attached to a predetermined line correspond to the x and y. . For example, (3,4) means Au ₁ Cu ₁ N ₃ O ₄ .

From Figure _{22, Au 1 Cu 1 N 3} O 4 is relatively large between the _{300K~500K; Au 1 Cu 1 N 3} O 4 between 500K~600K is being reduced _Au 1 _Cu 1 _N 2 _{O 3} There increased; it can be seen that and _Au 1 _Cu 1 _N 2 _{O 3} between 600K~750K there is _Au 1 _Cu 1 _N 1 _{O 2} being reduced increases.

That is, in FIG. 22, it is understood that the NOx reduction reaction cycle of NO adsorption, N ₂ desorption, and O ₂ desorption proceeds in each temperature region. From this, it is understood that the cluster Au ₁ Cu ₁ efficiently catalyzes the NOx reduction reaction in a wide temperature range.

(Evaluation of NOx reduction reaction cycle of cluster Au ₁ Cu ₂ )
FIG. 23 shows the mass-to-charge ratio (m / z) and intensity (arbitrary units) when the concentration of NO gas is 0%, 1%, and 7% for the reaction between the cluster Au ₁ Cu ₂ and NO gas. FIG. The description regarding n, m, and l of Au _n Cu _m (NO) ₁ in FIG. 23 is the same as the description in FIG.

From FIG. 23, only the peak of Au ₁ Cu ₂ is observed at a NO concentration of 0%; furthermore, the peak of Au ₁ Cu ₂ (NO) ₂ is observed at a NO concentration of 1%; It can be seen that a peak of Au ₁ Cu ₂ (NO) ₂ was observed. That is, it is understood that NO is adsorbed or bonded to the Au ₁ Cu ₂ cluster.

FIG. 24 is a diagram showing the relationship between the temperature (K) and the intensity ratio when the concentration of NO gas is 7% with respect to the NOx reduction reaction cycle between the cluster Au ₁ Cu ₂ and NO gas. Regarding the “intensity ratio” in FIG. 24, refer to the description in the above formula (I), noting that what is adsorbed or bonded to the cluster is not oxygen but NOx. For the x and y of Au ₁ Cu ₂ N _x O _y in FIG. 24, refer to the description in FIG.

FIG from _{24, Au 1 Cu 2 N 2} O 2 is declining among _{300K~400K, Au 1 Cu 2 N 0} O 2 increases; _Au 1 between 400K~500K _{Cu 2 N} 0 _O 2 There reduced _Au 1 _Cu 2 _{N 0 O} 0 increases while; it can be seen _{that Au} 1 _Cu 2 _{N 0 O} 0 is significantly increased between and 500K～800K.

That is, in FIG. 24, N ₂ desorption occurs between 300K and 400K; O ₂ desorption occurs between 400K and 500K to regenerate cluster Au ₁ Cu ₂ ; and cluster Au between 400K and 800K. It is understood that the regeneration of ₁ Cu ₂ is proceeding remarkably. From this, it is understood that the cluster Au ₁ Cu ₂ efficiently catalyzes the NOx reduction reaction in a wide temperature range.

(Evaluation of NOx reduction reaction cycle of cluster Au ₂ Cu ₁ )
FIG. 25 is a diagram showing the relationship between the mass-to-charge ratio (m / z) and the intensity (arbitrary unit) when the concentration of NO gas is 7% with respect to the reaction between the cluster Au ₂ Cu ₁ and NO gas. It is. The description regarding n, m, and l of Au _n Cu _m (NO) ₁ in FIG. 25 is the same as the description in FIG.

FIG. 25 shows that peaks of Au ₂ Cu ₁ (NO) ₂ and Au ₂ Cu ₁ (NO) ₃ were observed at an NO concentration of 7%. That is, it is understood that NO is adsorbed or bonded to the Au ₂ Cu ₁ cluster.

FIG. 26 is a diagram showing the relationship between the temperature (K) and the intensity ratio when the concentration of NO gas is 7% with respect to the NOx reduction reaction cycle between the cluster Au ₂ Cu ₁ and NO gas. Regarding the “intensity ratio” in FIG. 26, refer to the explanation in the above formula (I), noting that what is adsorbed or bonded to the cluster is not oxygen but NOx. Further, _{x in} Au ₂ Cu ₁ (NO) _x in FIG. 26 represents the number of nitric oxide molecules.

From FIG. 26, it can be seen that Au ₂ Cu ₁ (NO) ₀ significantly increases between 300K and 600K. That is, in FIG. 26, it is understood that the regeneration of the cluster Au ₂ Cu ₁ is proceeding significantly between 300K and 600K. From this, it is understood that the cluster Au ₂ Cu ₁ may efficiently catalyze the NOx reduction reaction in a wide temperature range.

  Although preferred embodiments of the present invention have been described in detail, those skilled in the art will recognize that modifications can be made without departing from the scope of the claims.

DESCRIPTION OF SYMBOLS 1 Apparatus for manufacturing and measuring exhaust gas purification catalyst 100 Cluster generation reaction part 101 Gold-containing target material 102 Copper-containing target material 103 Carrier gas 110 Cluster generation part 111,112 Laser 120 Cluster reaction part 121 Heat insulation part 122 Cooling part 123 Reaction gas 130 Heating unit 131 Heating coil 132 Tube 200 Cluster selection measurement unit 210 Interface unit 220 Ion lens unit 230 Cluster beam 240 Accelerating electrode unit 250 Voltage changeover switch 260 Deflector 270 Two-stage reflectron 281 and 282 Bimetallic cluster 290 Detection unit

Claims (1)

  Selected from the group consisting of a cluster consisting of two gold atoms and one copper atom, a cluster consisting of one gold atom and one copper atom, and a cluster consisting of one gold atom and two copper atoms An exhaust gas purification catalyst comprising at least one type of cluster.

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