JPH07136512A - Catalyst for purifying exhaust gas from engine and production thereof - Google Patents

Abstract

PURPOSE:To suppress contamination of Pd with S and provide such a catalyst for purifying exhaust gas from an engine that contains Pd as the catalyst component and has excellent low temp. HC activity. CONSTITUTION:An alloy mixture is prepared by adding a Pd powder to powders of Cu, Ni, Ti, Mn, Mo, etc., and pulverized to obtain an alloy mixture powder. This alloy mixture is added by a specified proportion of <=10wt.% to a slurry (wash coating liquid) prepared by carrying Pd on Al2O3. The obtd. wash coating liquid is used to form a catalyst layer on a carrier. Otherwise, a mixture of Pd nitrate, Ca(OH)2 and Mg(OH) is prepared and an aq. soln. of the mixture is made to impregnate a coating layer carrying Pd. Otherwise, nitrate of Ni and nitrate of Ca are carried on the coating layer. Or, a multiple oxide of Pd and Ca is deposited and then impregnated with Ni nitrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust gas purifying catalyst.

[0002]

2. Description of the Related Art Pt (platinum), Rh (rhodium) is used as an exhaust gas purifying catalyst for automobile engines.
It is general that a noble metal such as the above is supported on a carrier as a catalyst component.

However, the conventional catalyst using such Pt does not have a sufficient purification rate of HC (hydrocarbon) at low temperature. Therefore, Pd (palladium) has attracted attention as a catalyst component capable of improving the purification performance of HC at low temperatures, and a catalyst using this Pd as a catalyst component has been developed. JP 62
An example of a catalyst using this Pd is described in JP-A-57651.

[0004]

Pd is originally excellent in the oxidizing ability of HC, and it is considered that the use of this as a catalyst can improve the HC purification rate at low temperatures. However, Pd is vulnerable to poisoning components such as S (sulfur), and if Pd is poisoned, the exhaust gas purification performance deteriorates, and particularly the HC activity in a low temperature range decreases. Therefore, it is an indispensable technical subject to suppress S poisoning of Pd.

By the way, the problem of S poisoning of Pd is
This is remarkable when the amount of S in gasoline is large. Pd is P
The catalytic reaction is carried out by passing oxygen (O ₂ ) such that dO (palladium oxide) becomes Pd and conversely Pd becomes PdO, but when PdO releases O ₂ and becomes Pd, in gasoline If a large amount of SO _{2 and the} like produced by S is present, Pd and SO ₂ easily form a compound when the air-fuel ratio is relatively rich, such as PdS or PdS.
It has now been found that the cause of S poisoning is that it is easily converted to O ₄ and thus the compound of Pd and S is easily formed.

The present invention has been made in view of the above problems, and provides a catalyst for purifying exhaust gas of an engine, which suppresses poisoning of Pd by S, and which uses Pd as a catalyst component and has excellent low temperature HC activity. The purpose is to be able to.

[0007]

The engine exhaust gas purifying catalyst of the present invention is an engine exhaust gas purifying catalyst having a coating layer carrying Pd as a catalyst component on the surface of a carrier, and carrying Pd. It is characterized in that the coating layer carries a mixture of Pd and a material that easily reacts with sulfur oxides to form sulfides.

In this method for producing an exhaust gas purifying catalyst, a mixture of Pd and a material that easily reacts with sulfur oxides to form a sulfide is prepared, and the mixture is added to a washcoat liquid carrying Pd. Thus, it is characterized in that it is supported on the coat layer on the surface of the catalyst carrier, or on the coat layer supporting Pd after formation.

In this manufacturing method, for example, the mixture is C
It is an alloy mixture in which an alloy powder or complex containing at least one of transition metals such as u, Ni, Ti, Mn, and Mo is mixed with Pd powder, and the alloy mixture is crushed to obtain an alloy mixture powder. In addition to a washcoat solution supporting Pd, the washcoat solution is used to form a catalyst layer, or the mixture is an aqueous solution in which Pd is mixed with at least one of calcium hydroxide and magnesium hydroxide. And impregnating the coating layer supporting Pd with the aqueous solution to support the mixture on the coating layer.

The engine exhaust gas purifying catalyst of the present invention also carries a material having a strong property of reacting with sulfur oxide more easily than Pd and forming a sulfide by reacting with sulfur oxide. can do. What is that material?
For example, Ni compounds and Ca compounds, especially Ni compounds
A mixture of Nitrate of Ca and Nitrate of Ca is preferred. The mixing ratio of the Ni nitrate and Ca nitrate is 1 by weight.
It is preferably 0/1 to 1/10.

In this case, in the production of the exhaust gas purifying catalyst, the weight ratio of Ni nitrate and Ca nitrate of 5 to 10 g / liter is added to the wash coat solution or the impregnating solution to form a coat layer. It is preferable to support it, or it is preferable to support it by supporting a composite oxide of Pd and Ca on the coating layer and then impregnating it with a Ni compound.

The engine exhaust gas purifying catalyst of the present invention may be provided with a coat layer for supporting Pd on zeolite.

[0013]

The Pd-supported wash was carried out by pulverizing an alloy mixture obtained by mixing an alloy powder or complex containing at least one transition metal such as Cu, Ni, Ti, Mn, and Mo with Pd powder to obtain an alloy mixture powder. By being added to the coating solution and immersing the carrier in this wash coating solution,
A catalyst layer is formed in which the transition metal and Pd alloy mixture powder is dispersed and contained. The alloy mixture thus pulverized and dispersed and contained in the catalyst layer easily absorbs the sulfur oxide at the interface that appears when pulverized, and easily reacts with the S component to generate a sulfide.

Further, an aqueous solution is prepared by mixing Pd with at least one of calcium hydroxide and magnesium hydroxide, and the coating layer carrying Pd is impregnated with this aqueous solution, whereby Pd, Ca (calcium) and M are added.
A catalyst layer is formed in which a mixture with at least one of g (magnesium) is dispersed and contained. In the mixture thus dispersedly contained in the catalyst layer, Ca and Mg easily react with the S component to form sulfide.

In the catalyst produced as described above, in which the Pd-supported coating layer contains a mixture of Pd and a material that easily reacts with sulfur oxides to form a sulfide, the S component is a mixture. By reacting with S to form a sulfide, S poisoning of Pd carried as a catalyst component on the coat layer is suppressed.

As a material having a strong property of reacting with sulfur oxide more easily than Pd and forming a sulfide by reacting with sulfur oxide, for example, Ni nitrate, C
By supporting the nitrate of a and the like, and particularly by supporting the mixture of the nitrate of Ni and the nitrate of Ca, the reaction in which Ni and Ca react with sulfur oxide to produce NiS or Ca (SO ₄ ) ₂ proceeds. As a result, S poisoning of Pd is suppressed. The S poisoning suppression of Pd by the synergistic effect of Ni and Ca is great when the mixing ratio of the carried Ni nitrate and Ca nitrate is 10/1 to 1/10 by weight. , Ni nitrate and Ca nitrate 5 to 5
The effect is large when the mixture of Ni nitrate and Ca nitrate is carried on the Pd-carrying coating layer on the surface of the catalyst carrier by using the slurry added at a rate of 10 g / liter.

Further, in the case of suppressing the S poisoning of Pd by the synergistic effect of Ni and Ca, if the composite oxide of Pd and Ca is supported on the coating layer in advance and then impregnated with the Ni compound,
It is possible to prevent the catalytic activity from decreasing due to the direct reaction of Ni with Pd.

In addition, when a mixture of a Ni compound and a Ca compound is supported on a catalyst in which Pd is supported on zeolite to form a coat layer on the surface of a catalyst carrier, excellent adsorption of HC at low temperature by the zeolite is achieved. It is possible to suppress the deterioration of the ability and prevent Sd poisoning of Pd.

[0019]

EXAMPLES Examples of the present invention will be described below.

Example 1. FIG. 1 is a schematic structural diagram of a catalyst of Example 1 of the present invention. The catalyst of this example has Pd on Al ₂ O ₃ as a first catalyst layer on the surface of the honeycomb-shaped carrier 1.
Is formed and a base coat layer 2 is formed by dispersing and containing an alloy mixture powder formed by mixing Cu, Ni and Ti with Pd, and Pd is deposited on CeO ₂ as a second catalyst layer on the base coat layer 2. Cu and Ni
And an overcoat layer 3 in which an alloy mixture powder formed by mixing Ti and Pd is dispersed and contained.

The method for producing this catalyst is as follows.

(1) First catalyst layer Pd powder in an amount equal to the mixed powder of Cu, Ni and Ti is added to an equal amount of mixed powder of Cu, Ni and Ti to form an alloy mixture by mechanical alloying. Then, this is pulverized into an alloy mixture powder. On the other hand, to 480 g of γ-Al ₂ O ₃ powder produced by the alkoxide method or the like, 120 g of boehmite (hydrated alumina), 1 liter of water, and 10 cc of HNO ₃ (nitric acid) were added and stirred, and the slurry was mixed with zinc. An aqueous solution of trodiamine Pd (adjusted to have an arbitrary amount of Pd supported) is added. Then, the above alloy mixture powder is added thereto at a predetermined ratio of 10% by weight or less, and the carrier 1 is immersed in this slurry (washcoat liquid), pulled up, air blown, and dried at 250 ° C. for 2 hours.
Bake at 600 ° C for 2 hours. Thus, the base coat layer (first catalyst layer) 2 is formed on the surface of the carrier 1. The base coat layer 2 has Al ₂ O ₃ loaded with Pd as a catalyst component and dispersedly containing Cu, Ni and an alloy mixture powder formed by mixing Ti and Pd. The alloy mixture contains Mn, Cu, Ni, and Ti, in addition to Cu, Ni, and Ti.
Mo and the like may be included. Further, it may contain at least one of those transition metals.

(2) Second catalyst layer 1 liter of water was added to 540 g of CeO ₂ and stirred, and an aqueous solution of gintrodiamine Pd (adjusted to have an arbitrary amount of Pd supported) was added to the slurry and stirred. After drying, firing and crushing with a ball mill, 60 g of boehmite and 10 cc of HNO ₃ are added to the powder and the mixture is stirred. Then, an alloy mixture powder prepared in the same manner as in the above (1) is added to the slurry (washcoat solution) at a predetermined ratio of 10% by weight or less, and the carrier 1 having the basecoat layer 2 formed thereon is immersed in the slurry (washcoat solution). It is pulled up and dried at 200 ° C. for 2 hours, and then baked at 600 ° C. for 2 hours. Thus, the overcoat layer (second catalyst layer) 3 is formed on the base coat layer 2. This overcoat layer is obtained by supporting Pd as a catalyst component on CeO ₂ and dispersing and containing Cu, Ni, and an alloy mixture powder formed by mixing Ti and Pd. Also in this case, the alloy mixture may contain Mn, Mo, etc. in addition to Cu, Ni, Ti, or may contain at least one of these transition metals.

Next, the test results of the exhaust gas purification performance of the catalyst of Example 1 will be described.

FIG. 2 is a time chart showing the test method, in which the horizontal axis represents time and the vertical axis represents the catalyst inlet temperature. This test was carried out in the mode of ~ as shown in the figure.

First, in the mode, the air-fuel ratio is 13.5 (a relatively rich state in which PdO easily becomes Pd).
Then, the SO ₂ concentration was adjusted to 50 ppm, and the catalyst inlet temperature was raised to 500 ° C at 30 ° C / min. Then, in the mode, the air-fuel ratio of 13.5, the SO ₂ concentration of 50 ppm, and the catalyst inlet temperature of 500 ° C. are kept stable for 10 minutes, and are naturally cooled to room temperature in the mode. Then, in the mode, the test was started with the air-fuel ratio close to the theoretical air-fuel ratio of 14.5, and it was observed how the purification performance of the catalyst changed as the catalyst inlet temperature increased.

FIG. 3 shows the test results of the exhaust gas purification performance of the catalyst manufactured by the above method, in which (a) is a change in the HC purification rate with respect to the catalyst inlet temperature, and (b) is a change in the CO purification rate. (C) shows the change in the NOx purification rate. Further, in the figure, the data of the catalyst produced by the method of this example is plotted by circles, and the data of the comparative example is shown by x.
It is shown in the plot of the mark. This comparative example does not contain the alloy mixture powder dispersed therein. As can be seen from the test results, the catalyst of this example contains the alloy mixture powder, so that the effect of Pd SO ₂ poisoning is reduced, and the state of high purification rate is maintained.

FIG. 4 shows the change in the HC purification rate of the catalyst with the amount of alloy mixture (catalyst inlet temperature 300 ° C.). The HC purification rate is particularly high when the ratio of the alloy mixture powder is 10% by weight or less.

Further, the catalyst of this embodiment has a structure in which Pd is added to CeO ₂ on the base coat layer (first catalyst layer) 2 in which Pd is supported on Al ₂ O ₃ in the form of a complex oxide as described above. An overcoat layer 3 (second catalyst layer) supporting the above is provided, and by separating the catalyst layer into two phases in this way, the following effects occur.

(1) Pd supported on CeO ₂ can be secured, and the dissociation reaction of PdO to form Pd and O ₂ can be suppressed by the action of CeO ₂ to shift it to a higher temperature side. It is possible to prevent sintering and melting on the low temperature side due to the above.

(2) The catalyst layer of Pd supported on CeO ₂ is on the catalyst layer of Pd supported on Al ₂ O ₃ , and Ce
O ₂ and Pd are separated from Al ₂ O ₃ and coexist with each other, so that oxygen can be smoothly transferred such that Pd becomes PdO and PdO becomes Pd, and the low temperature activity of the catalyst is improved.

Example 2. Next, Example 2 in which a mixture of Pd and at least one of Ca and Mg is dispersed and contained in the coating layer supporting Pd will be described.

The catalyst of this Example 2 is such that the first catalyst layer and the second catalyst layer are formed on the surface of the honeycomb-shaped carrier as in the case of the above Example 1, and the catalyst manufacturing method in this case is as follows. It is as follows.

(1) First catalyst layer Boehmite 12 was added to 480 g of γ-Al ₂ O ₃ powder.
0 g, 1 liter of water and 10 cc of HNO ₃ are added and stirred to form a slurry. Then, the honeycomb-shaped carrier is dipped in the slurry, pulled up and air blown,
After drying at 0 ° C for 2 hours, baking is performed at 600 ° C for 2 hours. Then, the carrier is impregnated with an aqueous solution of gintrodiamine Pd adjusted to have an arbitrary amount of Pd supported, and 250
After drying at ° C for 2 hours, it is baked at 600 ° C for 2 hours. Thus, the base coat layer (first catalyst layer) is formed on the surface of the carrier. This base coat layer carries Pd as a catalyst component on Al ₂ O ₃ .

(2) Second catalyst layer 1 liter of water was added to 540 g of CeO ₂ and stirred, and an aqueous solution of gintrodiamine Pd (adjusted to have an arbitrary amount of Pd supported) was added to the slurry and stirred. After drying, firing and crushing with a ball mill, 60 g of boehmite and 10 cc of HNO ₃ are added to the powder and the mixture is stirred. Then, the carrier having the base coat layer formed thereon is dipped in this slurry (wash coat liquid),
It is pulled up and dried at 200 ° C. for 2 hours, and then baked at 600 ° C. for 2 hours. Thus, the overcoat layer (second catalyst layer) is formed on the base coat layer.

Next, nitric acid compounds Pd and Ca (OH)
Make a mixture of ₂ (calcium hydroxide) and Mg (OH) (magnesium hydroxide). And Ca (OH) ₂
And the content of Mg (OH) is 5 for each coat.
The above-mentioned overcoat layer is impregnated with an aqueous solution adjusted to be about wt%, dried and baked. Thereby,
The overcoat layer is composed of CeO ₂ carrying Pd as a catalyst component and Ca and Mg dispersed therein. Note that either Ca or Mg may be dispersed and contained.

FIG. 5 shows the test results of the exhaust gas purification performance of the catalyst manufactured by the above method. (A) shows the change of the HC purification rate with respect to the catalyst inlet temperature, (b) shows the change of the CO purification rate, (C) shows the change in the NOx purification rate. Further, in the figure, the data of the catalyst produced by the method of this example is plotted by circles, and the data of the comparative example is shown by x.
It is shown in the plot of the mark. In this comparative example, Ca and Mg are not dispersedly contained in the coat layer. Also in this case, the test was performed in the mode shown in FIG. As can be seen from the results of this test, the catalyst of this example shows that S ₂ of Pd was absorbed by SO ₂ adsorbed on Ca and Mg.
The effect of poisoning by O ₂ is reduced, and a high purification rate is maintained.

FIG. 6 shows the change in the HC purification rate of the above catalyst depending on the impregnation amount of the mixture (catalyst inlet temperature 300 ° C.). The HC purification rate is high when the mixing ratio of Ca (OH) ₂ and Mg (OH) is 5% by weight.

Also, in the catalyst of the second embodiment, since the catalyst layer is separated into two phases, sintering and melting can be prevented as in the case of the first embodiment, and the catalyst of the catalyst can be prevented. The low temperature activity can be improved.

In the second embodiment, only the overcoat layer contains Ca and Mg as described above, but the base coat layer may contain Ca and Mg in the same manner.

Example 3. In Example 3, Ni nitrate and C
The mixture of the nitrate of a is supported on the coat layer on the surface of the catalyst carrier, and in this case also, the catalyst forms the first catalyst layer and the second catalyst layer on the surface of the honeycomb carrier. And
The manufacturing method is as follows.

(1) First catalyst layer γ-Al ₂ O ₃ powder 4 produced by the alkoxide method or the like
For 80 g, 120 g of boehmite, 1 liter of water and H
NO ₃ 10 cc was added, and a mixture of Ni nitrate and Ca nitrate in a weight ratio of 10/1 to 1/10 was added to a total ratio of 5 to 10 g / liter and stirred to prepare a slurry. To make. Then, the honeycomb-shaped carrier is immersed in the slurry, pulled up, blown with air, dried at 250 ° C. for 2 hours, and then baked at 600 ° C. for 2 hours. Then, a gintrodiamine Pd aqueous solution (Pd amount of 10
Gram / liter), dried at 250 ° C. for 2 hours, and then calcined at 600 ° C. for 2 hours. Thus, the base coat layer (first catalyst layer) is formed on the surface of the carrier.

The Ni nitrate and the Ca nitrate may be impregnated after Pd is loaded on alumina (γ-Al ₂ O ₃ ). In that case, the Ni nitrate and Ca are impregnated.
The carrier is immersed in a slurry containing a mixture of the nitrates of 10 / 1-1 / 10 in a weight ratio of 10/1 to 1/10 and added at a rate of 5 to 10 g / liter, and then calcined.

(2) Second catalyst layer An aqueous solution of gintrodiamine Pd is added to CeO ₂ , stirred, dried, baked, and then pulverized with a ball mill. Then, 60 g of boehmite, 1 liter of water, and 10 cc of HNO ₃ are added to 540 g of the powder and stirred to form a slurry, and the carrier having the base coat layer formed thereon is immersed in the slurry, dried, and fired. Thus, the overcoat layer (second catalyst layer) is formed.

It should be noted that this overcoat layer may also carry Ni nitrate and Ca nitrate. In that case, the nitrates are added to the slurry in the above weight ratio and the above proportion, and the above is added therein. The carrier on which the base coat layer is formed is dipped, dried and fired.

The nitrate of Ni and the nitrate of Ca may be impregnated after Pd is loaded on ceria (CeO ₂ ), and in this case, the nitrate of Ni and the nitrate of Ca are still in the above weight ratio. And the above proportions are added, and the carrier is dipped in it and fired.

FIG. 7 shows the test results of the exhaust purification performance of the catalyst manufactured by the method of Example 3, where (a) is the change in the HC purification rate with respect to the catalyst inlet temperature, and (b) is the same CO.
Change in purification rate, (c) shows change in the same NOx purification rate. In the figure, the catalyst prepared by the method of this example (Ni
/ Ca ratio 1/1, Ni / Ca amount 5 g / liter, P
The data of the d amount of 10 grams / liter) is plotted by circles, and the data of the comparative example is plotted by Xs. This comparative example is an example of a catalyst in which the nitrates of Ni and Ca are not supported on the coat layer. The test was also performed in the mode shown in FIG. As can be seen from the results of this test, the catalyst of this example is less affected by the poisoning of Pd by SO _{2 and} maintains a high purification rate.

FIG. 8 shows Ni / C of the HC purification rate of the above catalyst.
The change with a ratio (Ni / Ca amount 5 g / liter fixed) is shown. The HC purification rate is the Ni / Ca ratio (Ni
Weight ratio of nitrate of Ca to nitrate of Ca) is 10/1 to 1/1
It is high in the range of 0 and peaks when the Ni / Ca ratio is 1.

Further, FIG. 9 shows N of the HC purification rate of the above catalyst.
The change due to the i / Ca amount (Ni / Ca ratio fixed at 1/1) is shown. As for the HC purification rate, the Ni / Ca amount (total amount of nitrates of Ni and Ca in 1 liter of slurry) is 5 to 1
High in the range of 0 grams / liter.

Example 4. In Example 4, a composite oxide of Pd and Ca (CaPd ₃ O ₄ ) was previously supported on the coat layer on the surface of the catalyst carrier and then impregnated with Ni nitrate. Also in this case, the catalyst forms the first catalyst layer and the second catalyst layer on the surface of the honeycomb-shaped carrier, and the manufacturing method thereof is as follows.

(1) First catalyst layer γ-Al ₂ O ₃ powder 4 produced by the alkoxide method or the like
120 g of boehmite, 1 liter of water and HN for 80 g
O ₃ 10 cc is added, and further a complex compound of Pd and Ca (CaPd ₃ O ₄ ) is added and stirred to form a slurry.
Then, the honeycomb-shaped carrier is immersed in the slurry, pulled up, air-blown, and dried at 250 ° C. for 2 hours,
Then, it is baked at 600 ° C. for 2 hours. Next, this carrier is dipped in an aqueous solution of Ni nitrate to impregnate it with Ni nitrate, dried at 250 ° C. for 2 hours, and then calcined at 600 ° C. for 2 hours. Here, C supported in the form of the above-mentioned composite compound
a and the amount of Ni supported in the form of nitrate are Ni / Ca
The ratio is 1/1, the amount of Ni / Ca corresponds to 5 g / liter, and Pd is contained in the slurry at 10 g / liter.

(2) Second catalyst layer An aqueous solution of gintrodiamine Pd is added to CeO ₂ , stirred, dried, baked, and then pulverized with a ball mill. Then, 60 g of boehmite, 1 liter of water, and 10 cc of HNO ₃ are added to 540 g of the powder, and the mixture is stirred to make a slurry. The carrier having the base coat layer formed thereon is dipped in the slurry, dried, and baked.

The overcoat layer may also be loaded with a composite oxide of Pd and Ca and then impregnated with a nitrate of Ni. In that case, the above slurry contains a composite of Pd and Ca. An oxide is added, and the carrier after being dipped in the slurry and fired is dipped in a Ni nitrate aqueous solution and fired.

FIG. 10 shows the test results of the exhaust purification performance of the catalyst manufactured by the method of Example 4, where (a) shows the change in the HC purification rate with respect to the catalyst inlet temperature, and (b) shows the same C.
Change in O purification rate, (c) shows change in NOx purification rate. The circled plots in the figure are the data of the catalyst (Ni / Ca ratio 1/1, Ni / Ca amount 5 g / liter, Pd amount 10 g / liter) produced by the method of this example, and are indicated by X symbols. The plot is data of a comparative example (catalyst not supporting Ni and Ca). The test mode is still as shown in FIG. Also in the case of the catalyst of this example, P
It can be seen that the poisoning of d is small and a high purification rate is maintained. Further, in the case of this embodiment, it is possible to prevent the catalytic activity from being lowered due to the direct reaction between Pd and Ni.

Example 5 In Example 5, a mixture of Ni nitrate and Ca nitrate is supported on the surface of the catalyst carrier on which Pd is supported by ZSM5 type zeolite.

In this example, ZSM type zeolite 48
To 0 g, 120 g of boehmite and 1 liter of water are added and stirred to make a slurry. Then, the honeycomb-shaped carrier is immersed in this slurry, pulled up, blown with air, dried at 250 ° C. for 2 hours, and fired at 600 ° C. for 2 hours. Then, the carrier is replaced with Ca, Ni, Ce, Pd.
Is immersed in an aqueous solution of nitrate or gintrodiamine salt adjusted to have an arbitrary supported amount, dried at 250 ° C. for 2 hours, and then baked at 600 ° C. for 2 hours.

FIG. 11 shows the test results of the exhaust gas purification performance of the catalyst in the case of Example 5, where (a) shows the change in the HC purification rate with respect to the catalyst inlet temperature, and (b) shows the change in the CO purification rate. , (C) show changes in the NOx purification rate. The circled plots in the figure indicate the catalyst of this example (Ni / Ca ratio 1/1, Ni / Ca amount 5 g / liter, Pd amount 10 g /
Liters), and the plots marked with x are the data of comparative examples (those not loaded with Ni or Ca). The test mode is still as shown in FIG. From this test result, it was confirmed that P
It can be seen that S poisoning of d is reduced and a high purification rate is maintained.

Further, in the case of this embodiment, since Ni and Ca are supported, it is possible to suppress the deterioration of the HC adsorption capacity of the zeolite.

FIG. 12 and FIG. 13 show tests comparing the differences in the HC adsorption capacities of the catalyst of this example in which Ni and Ca were supported and the comparative example in which Ni and Ca were not supported.

In this test, exhaust gas at the time of operating at an air-fuel ratio of 14.5 was flown into the catalyst to determine the amount of HC adsorbed with the passage of time. Changes in the catalyst inlet temperature up to the lapse of seconds are shown, and FIG. 13 shows the HC adsorption amount relative ratio (%).
In FIG. 13, the plot marked with ◯ indicates the case of this embodiment,
Plots marked with x are the case of the comparative example. From this test result, it can be seen that the adsorption of Ni and Ca increases the HC adsorption capacity of the zeolite.

[0061]

EFFECTS OF THE INVENTION Since the present invention is constituted as described above, sulfur oxide is adsorbed by an alloy mixed powder of Pd and a transition metal such as Cu and Ni dispersedly contained in the coating layer,
Alternatively, by adsorbing sulfur oxides by Ca and Mg dispersedly contained in the catalyst layer, Ni and C
By supporting a in the form of a compound such as a nitrate, it is possible to suppress S poisoning of Pd supported on the coat layer, and thus to obtain a catalyst having Pd as a catalyst component and excellent in low-temperature HC activity. You can

[Brief description of drawings]

FIG. 1 is a schematic structural diagram of a catalyst of Example 1 of the present invention.

FIG. 2 is a time chart explaining a test method of the catalyst of Example 1 of the present invention.

FIG. 3 is a graph showing the results of an exhaust gas purification rate test for the catalyst of Example 1 of the present invention.

FIG. 4 is a graph showing the test results of the alloy mixture amount dependency of the HC purification rate of the catalyst of Example 1 of the present invention.

FIG. 5 is a graph showing the results of an exhaust gas purification rate test for the catalyst of Example 2 of the present invention.

FIG. 6 is a graph showing the test results of the mixture amount dependency of the HC purification rate of the catalyst of Example 2 of the present invention.

FIG. 7 is a graph showing the results of an exhaust purification rate test of a catalyst of Example 3 of the present invention.

FIG. 8 shows the HC purification rate of the catalyst of Example 3 of the present invention as Ni /
Graph showing test results of Ca ratio dependence

FIG. 9 shows the HC purification rate of the catalyst of Example 3 of the present invention, which is Ni /
Graph showing the test results of Ca content dependency

FIG. 10 is a graph showing the results of exhaust gas purification rate tests for the catalyst of Example 4 of the present invention.

FIG. 11 is a graph showing the results of an exhaust gas purification rate test for the catalyst of Example 5 of the present invention.

FIG. 12 is a graph showing the relationship between time and catalyst inlet temperature in the HC adsorption test of the catalyst of Example 5 of the present invention.

FIG. 13 is a graph showing the results of an HC adsorption test for the catalyst of Example 5 of the present invention.

[Explanation of symbols]

 1 carrier 2 base coat layer (first catalyst layer) 3 overcoat layer (second catalyst layer)

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B01J 23/89 ZAB A 8017-4G // B01J 35/04 ZAB 8017-4G 301 L 8017-4G 37/02 ZAB 8017-4G 301 L 8017-4G (72) Inventor Yasuhito Watanabe 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Motor Corporation

Claims (11)

[Claims] 1. A catalyst for purifying exhaust gas of an engine, comprising a coat layer carrying Pd as a catalyst component on the surface of a carrier, wherein the coat layer carrying Pd reacts with sulfur oxide to produce a sulfide. A catalyst for purifying exhaust gas of an engine, which carries a mixture of an easy material and Pd. 2. A mixture of Pd with a material that easily reacts with sulfur oxides to form sulfides, and the mixture is mixed with Pd.
Is added to the wash coat solution supporting P to support it on the coat layer on the surface of the catalyst carrier, or P after formation.
A method for producing an exhaust gas purifying catalyst for an engine, comprising depositing d on a coat layer. 3. The alloy mixture is a mixture of an alloy powder or complex containing at least one kind of transition metal and Pd powder. The alloy mixture is crushed to form an alloy mixture powder, and the alloy mixture powder is loaded with Pd. The method for producing a catalyst for purifying exhaust gas of an engine according to claim 2, wherein a coat layer is formed on the surface of the catalyst carrier by using the washcoat liquid in addition to the washcoat liquid. 4. The mixture is an aqueous solution in which Pd is mixed with at least one of calcium hydroxide and magnesium hydroxide, and the coat layer supporting Pd on the surface of the catalyst carrier is impregnated with the aqueous solution to form the coat layer. The method for producing an exhaust gas purifying catalyst for an engine according to claim 2, wherein the mixture is supported. 5. An exhaust gas purifying catalyst for an engine having a coat layer carrying Pd as a catalyst component on the surface of a carrier, wherein the coat layer carrying Pd reacts more easily with sulfur oxides than Pd, A catalyst for purifying exhaust gas from engine, which is loaded with a material having a strong property of reacting with sulfur oxide to generate sulfide. 6. The exhaust gas purifying catalyst according to claim 5, wherein the material is a mixture of a Ni compound and a Ca compound. 7. The engine exhaust gas purifying catalyst according to claim 6, wherein the material is a mixture of Ni nitrate and Ca nitrate. 8. The engine exhaust gas purifying catalyst according to claim 7, wherein the material has a mixing ratio of Ni nitrate and Ca nitrate in a weight ratio of 10/1 to 1/10. 9. A Ni nitrate and a Ca nitrate in an amount of 5 to 10
A method for producing an exhaust gas purifying catalyst for engine, wherein a mixture of these nitrates is carried on a coat layer on the surface of a catalyst carrier by using a slurry added at a rate of gram / liter. 10. A method for producing an exhaust gas purifying catalyst, comprising supporting a composite oxide of Pd and Ca on a coat layer on the surface of a catalyst carrier, and then impregnating the coat layer with a Ni compound. 11. The engine exhaust gas purifying catalyst as claimed in claim 5, wherein the coat layer is for supporting Pd on zeolite.