JP6683571B2 - Exhaust gas purification catalyst - Google Patents

Description

  The present invention relates to an exhaust gas purification catalyst.

  In the exhaust gas discharged from an internal combustion engine for automobiles such as a gasoline engine or a diesel engine, carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), etc. Contains ingredients.

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

  It is known that this Cu-based exhaust gas purification catalyst has a relatively high performance of catalyzing the NOx reduction reaction. However, the efficiency of the reduction reaction is not sufficient. Therefore, techniques for efficiently reducing and decomposing NOx are being studied.

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

JP 2012-217970 A

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

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

  <1> 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 containing at least one cluster selected from the group.

  According to the present invention, it is possible to provide an exhaust gas purifying catalyst which is excellent in purifying exhaust gas, particularly exhaust gas containing NOx.

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

  Hereinafter, embodiments of the present invention will be described in detail. It should be noted that the present invention is not limited to the following embodiments and can be variously modified and implemented within the scope of the gist of the present invention.

<Conventional exhaust gas purification catalyst>
The conventional Cu-based exhaust gas purifying catalyst is unlikely to cause a NOx reduction reaction. This is not bound by any theory, but since the oxygen atom-copper atom bond generated in the middle stage of the reduction reaction is relatively strong and stable, the reaction of reduction to metallic copper as the catalyst metal is suppressed. It is thought to be for.

  In this regard, conventionally, a technique is known in which a reducing agent such as CO is further used to cleave the oxygen atom-copper atom bond to reduce it to metallic copper, whereby the above reduction reaction is efficiently advanced. However, in this technique, since the reducing agent is an essential component, there are restrictions on the NOx reduction conditions.

  Further, conventionally, as in Patent Document 1, an exhaust gas purification catalyst containing a bimetallic cluster containing Au and Cu does not require a reducing agent as an indispensable component and relatively reduces the NOx reduction reaction. It is possible to Although not bound by any theory, this is because the gold atom, which is difficult to be oxidized, is close to the copper atom, which is easily oxidized, at the atomic level, so that the oxygen atom-copper atom bond is destabilized. This is probably because the reaction of reduction to metallic copper is promoted. The bimetallic cluster containing such Au and Cu is generally composed of tens to tens of thousands of atoms on average.

  On the other hand, the present inventors have adopted a bimetallic cluster in which the number of gold atoms and the number of copper atoms are specified, whereby the oxygen atom-copper atom bond becomes more unstable, which results in a catalyst. It was found that the reaction of reduction to metallic copper as a metal is remarkably promoted. The invention is shown below.

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

<Method for manufacturing exhaust gas purifying catalyst>
The exhaust gas purifying 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 formation step), and a plurality of containing gold and copper The above-mentioned 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>
A laser ablation method, for example, a laser evaporation method can be used in the cluster generation step. The laser evaporation method is generally a method of irradiating a target material with a laser to evaporate and ionize atoms, molecules, and / or clusters, etc. from the irradiated portion to generate plasma vapor composed of these components. Is.

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

(atmosphere)
The atmosphere in the cluster generation step may be substantially a carrier gas atmosphere for moving the generated clusters and the like. The atmosphere in the cluster generation step is not particularly limited, but from the viewpoint of stabilizing plasma vapor, for example, an inert gas atmosphere may be used. The inert gas atmosphere may contain other trace components such as trace elemental components. The temperature of the atmosphere in the cluster generation step is not particularly limited, but may be influenced by the temperature of plasma vapor. The pressure of the atmosphere in the cluster generation step is not particularly limited, but is, for example, 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, and in particular stabilizes plasma vapor, and It is preferable that the pressure is such that the laser energy loss 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-state lasers such as Nd: YAG lasers; gas lasers; liquid lasers; and semiconductor lasers.

  Examples of laser oscillation include continuous oscillation and pulsed oscillation. Among these, the energy of the pulsed laser is momentarily higher than the energy of the continuous wave laser, and the shorter the pulse width of the pulsed oscillation (for example, in femtoseconds), the larger the peak power becomes. 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 properties of the object to be irradiated with the laser, for example, properties of the laser such as absorptance, reflectance and transmittance.

An example of continuous wave laser power density is not particularly limited, but may be 1 W / cm ² or more. An example of the pulse oscillation fluence is not particularly limited, but may be 0.5 mJ / cm ² or more. The output of these lasers can be appropriately adjusted according to the mass, size, thickness, properties, etc. of the object 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 a 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, but, for example, two target materials containing gold and copper (plural target material), gold and copper are alternated. It is possible to use an arrayed target material (alternate array type target material), a micro mixed target material (micro mixed target material) in which gold powder and copper powder are mixed, molded, and sintered.

  Note that the easiness of repulsion of metal by sputtering differs depending on each metal element. Therefore, the composition ratio of the metal elements in the target material may be determined in consideration of the repellency of gold and copper. Further, 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, one containing gold and the other containing copper, are employed, each target material may be irradiated with a laser and the plasma vapors generated thereby may be mixed to generate bimetallic clusters. .

  As an example of the target material in which gold and copper are alternately arranged, for example, a disc-shaped material in which gold and copper are radially alternately arranged 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 a 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 step, a mass spectrometer, for example, time-of-flight Time-of-Flight, magnetic field deflection type (Magnetic Sector), quadrupole type (Quadrupole), ion trap type (Ion Trap), or a combination thereof. 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) among a plurality of clusters.

(atmosphere)
For the atmosphere in the cluster selection step, the description of the atmosphere in the cluster generation step 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 association with each other. For example, with respect to the structure and characteristics of the exhaust gas purifying catalyst, the above-mentioned method for manufacturing the exhaust gas purifying 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 producing and measuring an exhaust gas purifying 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 showing the cluster formation reaction part 100. The cluster generation reaction part 100 of FIG. 2 is composed of a cluster generation part 110, a cluster reaction part 120, and a heating part 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, whereby plasma vapor is generated and various bimetallic clusters are generated. The plasma vapor and / or the bimetallic clusters are carried to the cluster reaction section 120 by the carrier gas 103.

  In the cluster reaction unit 120, the reaction gas 123 is added to the carrier gas 103 as needed, and the reaction gas 123 reacts with the bimetallic cluster in the plasma vapor. Further, the carrier gas 103 containing plasma vapor is cooled by the cooling unit 122, which facilitates the formation of bimetallic clusters. The carrier gas 103 flowing 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 measuring unit 200 (FIG. 1).

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

  The cluster beam 230 reaches the accelerating electrode section 240, where charged clusters and the like are accelerated by changing their directions by the electric field created by the electrode section 240. The charged clusters are changed in direction, and the accelerated charged clusters are deflected according to the charge and the mass by passing through the voltage changeover switch 250 and the deflector 260 to the two-stage reflectron 270. And so on. In the two-stage reflectron 270, the clusters etc. are subject to error correction due to their initial velocity. The clusters 281 and 282 and the like emitted from 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 Figures 1 and 2 above. The generation conditions of the cluster, 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 about 0.7 MPa, injection at 10 Hz from pulse valve, average pressure in chamber of cluster generation part 1.3 × 10 ⁻³ Pa)

  The relationship between the numbers of gold atoms and copper atoms in the obtained cluster is shown in Table 1 below. In addition, in a time-of-flight mass spectrometer, which uses the principle that light ions arrive at a detector before heavier ions when a plurality of ions are simultaneously subjected to the same acceleration voltage, a time-of-flight mass spectrometer is used. , By measuring the time taken for each ion to fly over the same distance, ions having different mass-to-charge ratios (ratio of mass to charge of charged particles) can be detected separately on the time axis.

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

<Example 1: Evaluation of oxygen affinity>
At the time of forming the cluster, 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 The conditions in the cluster generation unit 110 are shown below, and the evaluation results are shown in FIG. 3 and FIGS. It should be noted that only the following components of the carrier gas 103 are substantially present in the chamber of the cluster generation unit, and the other components are extremely small in amount, and therefore the description thereof is omitted.
-Carrier gas 103 (pressure about 0.7 MPa, injection at 10 Hz from pulse valve):
Helium gas, flow rate 100 ml / min (partial pressure 2.5 × 10 ⁻³ Pa in the chamber of the cluster generation part)
Oxygen gas, flow rate 1 ml / min (partial pressure 2.9 × 10 ⁻⁴ Pa in the chamber of the cluster generation unit)

The specific evaluation results for each cluster are shown in FIGS. The “strength ratio” in each figure can be expressed by the following formula (I). The intensity of clusters and the like can be measured by a mass spectrometer, for example, the detection unit 290 in FIG. 1 described above.
Intensity ratio = I _CLUSTER / I _SUM (I)
[In the formula,
I _CLUSTER : intensity value of a target cluster, or intensity value of oxygen adsorbed or bound to this cluster,
I _SUM : The sum of the intensity value of the target cluster and the intensity value of oxygen bound to this cluster. ]

3 to 5 are diagrams showing the relationship between the temperature (K) and the intensity ratio regarding the affinity between Au ₁ Cu ₁ , Au ₁ Cu ₂ , and Au ₂ Cu ₁ and oxygen, respectively. _{X of} Au ₁ Cu ₁ O _x , Au ₁ Cu ₂ O _x , and Au ₂ Cu ₁ O _x shown in FIGS. 3 to 5 represents the number of oxygen atoms. From these figures, it can be seen that for these clusters, the proportion of those not bound to oxygen is high, that is, the proportion of those in which x is 0 is high. This result is observed in the measured temperature range of 300K to 1000K.

Further, FIGS. 6 to 19 are diagrams showing the relationship between the temperature (K) and the intensity ratio with respect to the affinity between the clusters such as Au ₀ Cu ₁ and oxygen. From these figures, it can be seen that for these clusters, the proportion of those not bound to oxygen is low, that is, the proportion of those in which x is 0 is low. From FIG. 17, it can be seen that in the cluster Au ₃ Cu ₁ , the proportion of those not bound to oxygen is relatively high, and the proportion of those bound 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, substantially only the following components of the carrier gas 103, or only the components of the following carrier gas 103 and the reactive gas 123 are substantially present, and the other components are The description is omitted because the amount is extremely small.
(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 in the chamber of the cluster generation part 2.5 × 10 ⁻³ Pa)
(2) When the concentration of NO gas as the reaction gas 123 is 1%: Carrier gas 103 (injected at 10 Hz from a pulse valve):
Helium gas, flow rate 10 ml / min (partial pressure in the chamber of the cluster generation part 1.5 × 10 ⁻³ Pa)
・ Reaction gas 123
NO gas, flow rate 0.1 ml / min (partial pressure in chamber of cluster generation part 9.6 × 10 ⁻⁵ Pa)
(3) When the concentration of NO gas as the reaction gas 123 is 7%: Carrier gas 103 (injected at 10 Hz from a pulse valve):
Helium gas, flow rate 10 ml / min (partial pressure in the chamber of the cluster generation part 1.5 × 10 ⁻³ Pa)
・ Reaction gas 123
NO gas, flow rate 0.7 ml / min (partial pressure in chamber of cluster generation part 1.3 × 10 ⁻⁴ Pa)

(Evaluation of NOx reduction reaction cycle of cluster Au ₁ Cu ₁ )
FIG. 20 shows the mass-to-charge ratio (m / z) and the intensity (arbitrary unit) when the concentration of NO gas is 0%, 1%, and 7% for the reaction between cluster Au ₁ Cu ₁ and NO gas. ) Is a diagram showing a relationship with FIG. The n, m, and l of Au _n Cu _m (NO) _l in FIG. 20 are integers of 0 or more, and the numbers in parentheses attached to the predetermined peaks are the n, m, and l. 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 the NO concentration of 0%; further, Au ₁ Cu ₁ (NO) ₁ , Au ₁ Cu ₁ (NO) ₂ , and Au ₁ Cu are observed at the NO concentration of 1%. It can be seen that the peak of ₁ (NO) ₃ was observed; and that 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 bound to the Au ₁ Cu ₁ cluster.

FIG. 21 shows the mass-to-charge ratio (m / z) and the intensity (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 the NO gas. It is a figure which shows the relationship with. The n, m, l, and k of Au _n Cu _m N _l O _k in FIG. 21 are integers of 0 or more, and the numerical value in parentheses attached to a predetermined peak is the n, m, or It corresponds to l and k. For example, (1,1,0,2) means Au ₁ Cu ₁ N ₀ O ₂ .

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

Further, it can be seen from FIG. 21 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 NO concentration of 7% and 300K is smaller than that of NO concentration of 1% and 300K; and NO concentration of 7% and 300K. It is understood that the peak of Au ₁ Cu ₁ O ₂ is observed in.

Further, it can be seen from FIG. 21 that under the conditions of NO concentration of 7% and 400K, the peak of Au ₁ Cu ₁ O ₂ was almost invisible and Au ₁ Cu ₁ N ₁ O ₁ increased.

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 a catalyst metal ( _one cycle of NOx reduction reaction cycle is completed), and NO is adsorbed or bound to the cluster again. It is considered that 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 that the peak of Au ₁ Cu ₁ O ₂ is almost invisible.

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 a catalyst metal. As a result, it is understood that it efficiently catalyzes the NOx reduction reaction.

FIG. 22 is a diagram showing the relationship between the temperature (K) and the intensity ratio when the NO gas concentration is 7% with respect to the NOx reduction reaction cycle between the cluster Au ₁ Cu ₁ and the NO gas. Regarding the “intensity ratio” in FIG. 22, refer to the explanation in the above formula (I), while paying attention to the fact that what is adsorbed or bound to the cluster is NOx instead of oxygen. 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 value in parentheses attached to a predetermined line corresponds to the x and y. . For example, (3,4) means Au ₁ Cu ₁ N ₃ O ₄ .

From FIG. 22, it can be seen that Au ₁ Cu ₁ N ₃ O ₄ is relatively large between 300K and 500K; Au ₁ Cu ₁ N ₃ O ₄ is decreasing between 500K and 600K, and Au ₁ Cu ₁ N ₂ O ₃ is reduced. 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-charge ratio (m / z) and the intensity (arbitrary unit) when the concentration of NO gas is 0%, 1%, and 7% with respect to the reaction between the cluster Au ₁ Cu ₂ and NO gas. ) Is a diagram showing a relationship with FIG. The description about n, m, and l of Au _n Cu _m (NO) _l in FIG. 23 is the same as the description in FIG. 20 above.

From FIG. 23, only the peak of Au ₁ Cu ₂ is observed at the NO concentration of 0%; further, the peak of Au ₁ Cu ₂ (NO) ₂ is observed at the NO concentration of 1%; and also at the NO concentration of 7%, 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 bound 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 NO gas concentration is 7% in the NOx reduction reaction cycle between the cluster Au ₁ Cu ₂ and the NO gas. Regarding the “strength ratio” in FIG. 24, please refer to the explanation in the above formula (I), while paying attention to the fact that what is adsorbed or bound to the cluster is NOx instead of oxygen. Further, regarding x and y of Au ₁ Cu ₂ N _x O _y in FIG. 24, refer to the description in FIG. 22 above.

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 It can be seen that Au ₁ Cu ₂ N ₀ O ₀ increases while the value decreases, and that Au ₁ Cu ₂ N ₀ O ₀ significantly increases between 500K and 800K.

That is, in FIG. 24, N ₂ desorption occurs between 300 K and 400 K; O ₂ desorption occurs between 400 K and 500 K to regenerate the cluster Au ₁ Cu ₂ ; and between 400 K and 800 K, the cluster Au. It is understood that the regeneration of ₁ Cu ₂ is significantly progressing. 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 NO gas concentration is 7% regarding the reaction between the cluster Au ₂ Cu ₁ and the NO gas. Is. The description about n, m, and 1 of Au _n Cu _m (NO) _l in FIG. 25 is the same as the description in FIG. 20 above.

From FIG. 25, it can be seen 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 bound 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 NO gas concentration is 7% with respect to the NOx reduction reaction cycle between the cluster Au ₂ Cu ₁ and the NO gas. Regarding the “intensity ratio” in FIG. 26, please refer to the explanation in the above formula (I), paying attention to the fact that what is adsorbed or bound to the cluster is NOx instead of oxygen. Further, _x of 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 remarkably progressing 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.

  While the preferred embodiment of the invention has been described in detail, those skilled in the art will appreciate that changes can be made without departing from the scope of the claims.

1 Device for Manufacturing and Measuring Exhaust Gas Purification Catalyst 100 Cluster Generation Reaction Section 101 Gold-Containing Target Material 102 Copper-Containing Target Material 103 Carrier Gas 110 Cluster Generation Section 111, 112 Laser 120 Cluster Reaction Section 121 Thermal Insulation Section 122 Cooling Section 123 Reaction gas 130 Heating part 131 Heating coil 132 Tube 200 Cluster selection measuring part 210 Interface part 220 Ion lens part 230 Cluster beam 240 Accelerating electrode part 250 Voltage changeover switch 260 Deflector 270 Two-stage reflectron 281,282 Bimetallic cluster 290 Detection part

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 purifying catalyst consisting of at least one type of cluster.

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