Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Nitrogen compound containing
Reexamination Certificate
2002-01-03
2004-08-17
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Nitrogen compound containing
C502S180000, C502S181000, C502S182000, C502S185000, C502S240000, C502S242000, C502S250000, C502S300000, C502S350000, C502S355000
Reexamination Certificate
active
06777368
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a molten-salt type catalyst which can efficiently purify particulate materials (hereinafter abbreviated to as “PM”), contained in an exhaust gas emitted from an internal combustion engine, such as a diesel engine, etc., in a range of exhaust gas temperature.
2. Description of the Related Art
“PM” are contained in an exhaust gas which is emitted from an internal combustion engine. The “PM” are composed of carbon, “SOF” (i.e., soluble organic fractions), polymerized organic compounds, sulfuric acid mists, and so on. In view of air pollution and adverse effects to human bodies, there arises a growing tendency toward the suppression of “PM” emission. In order to control the “PM” emission, there are two ways. One of them is to catch “PM” with a filter. The other one of them is to burn and remove “PM.” The engineering developments have been carried out in which the two ways are applied independently or in which the both of them are combined.
In order to burn “PM,” it is possible to think of using an oxidizing catalyst on which a noble metal, for example, Pt, and the like, is loaded. In this case, however, since the solid phase of “PM” and the solid phase of the oxidizing catalyst contact with each other, “PM” and the oxidizing catalyst contact with each other with a low probability. Accordingly, it is difficult to efficiently burn and purify “PM.” In particular, the noble metal, such as Pt, hardly effects to appreciably burn and purify carbonaceous components, which are contained in “PM.”
Hence, it was thought of turning a catalyst into a liquid phase and then contacting it with “PM.” For instance, in Appl. Cat. B21 (1999) pp. 35-49, there is a report on molten-salt type catalysts, such as Cs
2
MoO
4
—V
2
O
5
, CsVO
3
—MoO
3
and CS
2
SO
4
—V
2
O
5
. Such molten-salt type catalysts are used under the favorable conditions that they exhibit a high oxidizing capability, they evaporate less and the combustion temperature is low. In this literature, there is a description that Cs
2
MoO
4
—V
2
O
5
and CsVO
3
—MoO
3
were preferable catalysts because they exhibited high activities at 620 K (i.e., 347° C.) or more and were stable up to 1,025 K (i.e., 752° C.) in air.
Moreover, in Japanese Unexamined Patent Publication (KOKAI) No. 9-144,528, there is set forth a catalytic apparatus. In the catalytic apparatus, a eutectic composition, such as Cs
2
O·V
2
O
5
and K
2
O
5
·V
2
O
5
, is loaded on a carrier, such as a monolithic substance. The eutectic composition has a melting point of from 300 to 500° C., and exhibits a catalytic activity in the combustion of soot.
In addition, in a Patent Cooperation Treaty International Publication No. W000/43,109 (PCT/JP00/00194), there is set forth that “PM” can be burned and purified by putting magnesium nitrate and magnesium carbonate in a liquid reservoir and contacting them with an exhaust gas at a temperature of from about 185 to 270° C.
A temperature of an exhaust gas, which is emitted from a diesel engine, is usually less than 300° C. Moreover, when a diesel engine is started, the temperature is much lower. Accordingly, when a molten-salt type catalyst has a melting point of 300° C. or more, it is not turned into a liquid phase in an exhaust gas which is emitted from a diesel engine. Consequently, it is difficult for such a molten-salt type catalyst to efficiently burn and remove “PM.”
It is required that a molten-salt type catalyst be turned into a liquid phase. However, since it is turned into a liquid phase, there is a fear in that it is flowed to and is concentrated on a downstream side when it contacts with an exhaust gas flow. Hence, in the technology disclosed in Patent Cooperation Treaty International Publication No. W000/43,109, such a primitive technique as the liquid reservoir is employed. However, from the viewpoint of boarding the liquid reservoir onto an automobile, it is not practical because the liquid level is made unstable by increments of exhaust gas pressure, vibrations during driving, and so on.
SUMMARY OF THE INVENTION
The present invention has been developed in view of the aforementioned circumstances. It is therefore an object of the present invention to make a practical molten-salt type catalyst which can burn and remove “PM” even in a low temperature range, and which can be stably disposed in an exhaust system of an automobile.
A molten-salt type catalyst according to the present invention can achieve the aforementioned object. The present molten-salt type catalyst is adapted for purifying particulate materials, which are contained in an exhaust gas emitted from an internal combustion engine and containing carbon, and comprises: a solid support; and a catalytic ingredient loaded on the solid support including at least one member selected from the group consisting of silver nitrate, alkali metal nitrate, alkaline-earth metal nitrate and rare-earth nitrate.
The solid support can preferably be a basic support. Moreover, the catalytic ingredient can preferably include alkali metal nitrate. In addition, the catalytic ingredient can more preferably further include an oxidation facilitating ingredient.
Thus, in accordance with the present invention, not only it is possible to burn and remove “PM” even in a low temperature range, but also it is possible to stably dispose the present molten-salt type catalyst in an exhaust system of an automobile. Hence, the present molten-salt type catalyst is an extremely practical one.
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patent: 3754074 (1973-08-01), Grantham
patent: 4415757 (1983-11-01), Pyke et al.
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patent: 4943643 (1990-07-01), Pennington et al.
patent: 4959486 (1990-09-01), Pennington
patent: 5053372 (1991-10-01), Brownscombe
patent: 5884474 (1999-03-01), Topsøe
patent: 5942099 (1999-08-01), Nitschke et al.
patent: 6565820 (2003-05-01), Weimer et al.
patent: 0 761 938 (1997-03-01), None
patent: 9-144528 (1997-06-01), None
patent: WO00/43109 (2000-07-01), None
S. J. Jelles, et al., “Molten Salts as Promising Catalysts for Oxidation of Diesel Soot: Importance of Experimental Conditions in Testing Procedures”, Applied Catalysis B: Environmental 21, 1999, pp. 35-49. Jan. 1999.
Kayama Tomoyuki
Sakakibara Yuji
Shinjoh Hirofumi
Bell Mark L.
Hailey Patricia L.
Kabushiki Kaisha Toyota Chuo Kenkyusho
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