JPS6014615B2 - Catalyst for reducing nitrogen oxides in internal combustion engine exhaust gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalyst for reducing nitrogen oxides in exhaust gas from an internal combustion engine, and particularly provides a metal carbide catalyst with excellent performance and durability.

Conventionally, various proposals have been made regarding this type of catalyst, but all of them have some drawbacks, and there is a demand for the development of a catalyst with further improved performance and durability.

The present invention provides TIC, VC, Cr3C2, Z, N ratio, M
o2C, HIC, TaC, WC, or a component to which one or more of copper, nickel, cobalt, and iron is added in an amount of 5% by volume or less; In addition to the theoretical carbon content of the metal carbide, 0.4 to 20% by weight
The content is a carbide-based catalyst for reducing nitrogen oxides in internal combustion engine exhaust gas containing excess carbon.

Hereinafter, one embodiment of the catalyst for reducing nitrogen oxides in internal combustion engine exhaust gas according to the present invention will be described.

The catalyst of the present invention is a carbide-based catalyst, including TIC, VC
, Cr3C2, ZrC, NbC, Mo2C, FKC, T
It is based on a mixture, compound, or Oka solution of one or two of aC and WC.

Alternatively, one or more of copper, nickel, cobalt, and iron may be added to the carbide component in an amount of 5% by solubility or less. Since these are generally manufactured by powder metallurgy, these metal components serve as a binding material for the silk body and when used as a catalyst for reducing nitrogen oxides in internal combustion engine exhaust gas. This is to suppress the production of ammonia. In this case, the reason why the metal component is set to 5% by volume or less is because if the metal component exceeds this value, the catalyst performance will deteriorate. The carbide catalyst of the present invention is
In addition to the theoretical carbon content of the metal carbide in this component, 0.4~
It is characterized by containing 20% by weight of surplus carbon, which is expected to improve durability.

Furthermore, in order to enhance the catalytic ability of the catalyst thus obtained, 0.0005% by weight or more of ruthenium and rhodium may be added. It is carried out in the form of an organic compound by methods such as powder mixing and immersion vapor deposition.

As is clear from the experimental examples described below, the catalyst according to the present invention is characterized by good initial performance and good durability, which is due to the fact that it contains excess carbon. .

In this case, if a porous material is obtained using a powder metallurgy method, the contact rate with exhaust gas can be increased and even better performance can be obtained.

Next, the content of the present invention will be explained more specifically and in detail by showing experimental examples. Experimental Example 1 The catalyst consisted of 90% chromium carbide (Cr3C2), 10% nickel and different amounts of carbon powder, and after mixing them, 3.5×3.
Press molded into a cylindrical shape on the side and heated to 1400 oo in a hydrogen atmosphere.
Samples A to J were prepared by drying.

In this case, each sample was made into a porous body by adding an additive material that transpires, such as sodium chloride.
In order to change the amount of surplus carbon in the components, the amount of carbon powder is varied.

Therefore, the amount of carbon in each sample A to J is A=0, B=
0.2, C; 0.4, D=0.9, E=2.4 F:5
．． 9 G; 10-1, H=15.2, 1=19. G.J.
=25.8. Next, each of these samples A
~J, oxygen spike durability test using CFR engine (Japan Automobile Research Institute Research Report No. 32, 1976 1)
(Based on the January edition ``Automotive N0x Reduction Catalyst Evaluation Test Method''). In this case, commercially available unleaded gasoline was used as the fuel, and the gas temperature at the catalyst inlet was set at 600'0. Also, the engine operating conditions are air fuel ratio 13.
8, after 3 minutes of steady operation, 5% secondary air was injected between the three exhaust gases. This operation was repeated until the total exposure time reached 10 periods. These results are shown in Figure 1 as oxygen spike time versus NO conversion for each catalyst.

According to Figure 1, for A and B, the NO variation depth rate has decreased by about 25%, while for C it is less than 10%, and for D
The change was approximately 5% in B to J, and almost no change was observed in B to J. However, the result of measuring the crushing strength (pressure strength k9) using the Kiya hardness tester based on the same report was A~○>10.
．． 0, E=10.0, F=8. Fu G=67, H=3Q
I=2.2 and J=0.2, and from this point of view J was not preferable. Therefore, the effects of the present invention were clearly demonstrated in the oxygen spike durability test, and the object of the present invention was also sufficiently achieved in terms of pressure resistance.

In addition, almost the same tendency was observed even when the weight ratio of chromium carbide to nickel was changed for each sample in this experiment.

In addition, TIC, VC, ZrC, N “MQC, HfC,
A single component selected from TaC, WC, and this,
Experiments were also conducted with components containing copper, nickel, and cobalt, either singly or in combination, and almost the same tendency was observed. In this case, if the metal component exceeded 5% by volume based on the metal carbide, the catalyst performance deteriorated and favorable results were not obtained. Furthermore, when each sample was made into a non-porous composite, the contact rate with exhaust gas decreased, resulting in a decrease in catalytic performance. I could see the direction.

Experimental Example 2 The catalyst was composed of 70% titanium carbide (TiC), 20% molybdenum carbide (MQC), 10% nickel and different carbon powders, and under the same conditions as Experimental Example 1, K ~ Samples up to R were manufactured.

At this time, the amount of surplus carbon in each sample K~R is K=0.2
, L=0.0 M=1.9 N=4.0 0=7.5
P=13. & Q was set to be 19.7 and R = 24.4. Experimental Example 3 Regarding the catalyst, as shown in Table 1, No. 1~No
．． Eleven samples were produced.

For each of these ingredients, as in Experimental Example 1, each mixed powder was
It was press-formed into a cylindrical shape with 3.5 sides and 3.5 ribs at a pressure of 100 mm/mm, and was brazed at 140 mm in a hydrogen atmosphere. In this case, each sample was made into a porous sintered body by adding sodium chloride in the same way, and the amount of excess carbon (C) was as follows:
The total amount was 9% by weight. Furthermore, for each of these materials, the NO conversion rate (%) was measured at the initial stage and at each time point after 10 vowels.

The measurement results are shown in Table 2.
Both values are 92% or more, which indicates that the effects of the present invention are significant. Next, 0.01% by weight of ruthenium was added to these samples by the impregnation method, and the oxygen spike durability test described in Experimental Example 1 was conducted using the samples.

As shown in Figure 2, this result is approximately 20
%, but in the case of L it was about 8%, and in the cases of M to R there was almost no change, and the effect of the present invention was remarkable.

However, as in Experimental Example 1, the pressure resistance (k9) was measured and the results showed that K~M>10. Stop N=9.9, 0=8.0
, P=4.8, Q=3.2, and R=0.5, and from this point it was found that R was not preferable. In addition, VC, ZrC
Various experiments were conducted on composite components of metal carbides such as , WC, etc., and all of them showed the trend as shown in FIG. We also conducted experiments with rhodium added instead of ruthenium, and with both ruthenium and rhodium added, and both were found to be effective.If the amount added is 0.0005% by weight or more, the catalyst performance could be improved. It was found that this contributes to improvement. Furthermore, even in the case of non-porous catalysts, catalyst performance deteriorated, but durability was similarly compromised.

Table 1 Unit: Weight *Second
Table Unit: Son As explained above, the present invention provides a metal carbide-based catalyst for reducing nitrogen oxides in internal combustion engine exhaust gas, a specified nitrogen carbide-metallic catalyst, or a catalyst containing ruthenium and/or Durability can be particularly enhanced by selecting catalysts containing rhodium and adding at least 0.4% by weight of excess carbon to these catalysts.

[Brief explanation of drawings]

Figure 1 is a diagram showing the initial performance and durability results of one example of the catalyst for reducing nitrogen oxides in internal combustion engine exhaust gas of the present invention, and Figure 2 is a diagram showing the initial performance and durability results of another example. It is a figure showing a result. O′ diagram O Z diagram

Claims (1)

[Claims] 1 TiC, VC, Cr_3C_2, ZrC, NbC,
One or more components of Mo_2C, HfC, TaC, WC, or 50% by volume or less (not including 0%)
A component to which one or more of copper, nickel, cobalt, and iron is added, in addition to the theoretical carbon amount of the metal carbide in the component, an excess carbon of 0.4 to 20% by weight based on the total component. A catalyst for reducing nitrogen oxides in internal combustion engine exhaust gas, characterized by containing the following. 2. Claim 1, wherein the nitrogen oxide reduction catalyst is formed as a porous sintered catalyst.
A catalyst for reducing nitrogen oxides in internal combustion engine exhaust gas as described in . 3 TiC, VC, Cr_3C_2, ZrC, NbC,
One or more of Mo_2C, HfC, TaC, WC, or one or more of copper, nickel, cobalt, iron added to these in an amount of 50% by volume or less (excluding 0%), Consists of a component containing 0.0005% by weight or more of one or both of ruthenium and rhodium, and in addition to the theoretical carbon content of the metal carbide in these components, it is 0.4 to 20% by weight based on the total component. A catalyst for reducing nitrogen oxides in exhaust gas from an internal combustion engine, characterized in that the catalyst contains surplus carbon. 4 The nitrogen oxide reduction catalyst is:
The catalyst for reducing nitrogen oxides in internal combustion engine exhaust gas according to claim 3, characterized in that it is formed as a porous sintered catalyst.