Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Waste gas purifier
Reexamination Certificate
1998-03-20
2001-01-09
Tran, Hien (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Waste gas purifier
C422S171000, C422S180000, C060S297000
Reexamination Certificate
active
06171557
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a system for exhaust gas purification, capable of effectively purifying the harmful substances present in the exhaust gas emitted from an internal combustion engine, particularly the hydrocarbons discharged from the engine in a large amount during the cold start.
(2) Description of Related Art
Active researches and developments have heretofore been made on systems for exhaust gas purification, used for purifying the harmful substances present in exhaust gas from automobile engines, such as nitrogen oxides (NO
x
), carbon monoxide (CO), hydrocarbons (HC) and the like. In recent years, as the regulation on exhaust gas has become stricter, the purification of HC during engine start (cold start) has become an important technical task.
The reason is as follows. During the cold start of engine when the temperature of exhaust gas from engine is low, the catalyst disposed in exhaust pipe of engine does not reach its light-off temperature and has a low purification ability. Moreover, during this period, as compared with the period of continuous operation of engine, a large amount of HC is discharged from the engine. As a result, the HC discharged during the cold start occupies a large proportion of the total harmful substances discharged from the engine and needs to be removed.
As one means for achieving the above-mentioned technical task, there has been proposed a system for exhaust gas purification disposed in the exhaust pipe of an internal combustion engine, comprising not only a catalyst but also zeolite (as adsorbent) having an adsorbability for HC. In this system, zeolite is used to adsorb a large amount of the unburnt HC discharged from the engine during the cold start, temporarily for the period from the start of catalyst heating to the activation of catalyst.
In the above system for exhaust gas purification using zeolite, its performance varies greatly depending upon the HC adsorption capacity of the zeolite used. Also, the HC amount discharged from an internal combustion engine during the cold start varies greatly depending upon the engine used. Consequently, the performance of an exhaust gas purification system using a zeolite having a certain HC adsorption capacity varies greatly depending upon the engine in which the system is used. Therefore, in order to effectively adsorb and purify a large amount of the HC discharged from an engine during its cold start, it is necessary to allow the exhaust gas purification system disposed in the engine, to contain a zeolite having an adsorption capacity allowing for effective adsorption of the HC discharged from the engine during a certain period of cold start.
However, there is hardly known a system for exhaust gas purification in which sufficient consideration is made of the relation between the amount of HC discharged during cold start and the HC adsorption capacity of zeolite.
SUMMARY OF THE INVENTION
In view of the above situation, the present invention has an object of providing a system for exhaust gas purification, wherein the adsorption capacity of the zeolite used as a HC adsorbent component is optimized against the amount of the HC discharged from an engine during a certain period of the cold start and thereby the HC is effectively adsorbed and purified.
According to the present invention, there is provided a system for exhaust gas purification (the first system for exhaust gas purification) disposed in the exhaust pipe of an internal combustion engine, comprising a zeolite as adsorbent component capable of adsorbing the hydrocarbons present in the exhaust gas emitted from the engine and a catalyst capable of reducing the harmful substances present in the exhaust gas, which system satisfies the following condition:
a/c=
3 to 50 cc/g
wherein a is the total volume of the pores of diameters of 10 Å or smaller possessed by the zeolite as measured using N
2
, and c is the total amount of the hydrocarbons emitted from the engine during the period of 140 seconds from the start of the engine when the engine is operated in accordance with the LA-4 mode of FTP.
According to the present invention, there is also provided a system for exhaust gas purification (the second system for exhaust gas purification) disposed in the exhaust pipe of an internal combustion engine, comprising a zeolite as adsorbent component capable of adsorbing the hydrocarbons present in the exhaust gas emitted from the engine and a catalyst capable of reducing the harmful substances present in the exhaust gas, which system satisfies the following condition:
b/c=
2 to 30 cc/g
wherein b is the total volume of the pores of diameters of 10 Å or smaller possessed by the zeolite as measured using toluene, and c is the total amount of the hydrocarbons emitted from the engine during the period of 140 seconds from the start of the engine when the engine is operated in accordance with the LA-4 mode of FTP.
According to the present invention, there is also provided a system for exhaust gas purification (the third system for exhaust gas purification) disposed in the exhaust pipe of an internal combustion engine, comprising a zeolite as adsorbent component capable of adsorbing the hydrocarbons present in the exhaust gas emitted from the engine and a catalyst capable of reducing the harmful substances present in the exhaust gas, which system satisfies the following conditions:
a/c=
3 to 50 cc/g
b/c=
2 to 30 cc/g
wherein a is the total volume of the pores of diameters of 10 Å or smaller possessed by the zeolite as measured using N
2
, b is the total volume of the pores of diameters of 10 Å or smaller possessed by the zeolite as measured using toluene, and c is the total amount of the hydrocarbons emitted from the engine during the period of 140 seconds from the start of the engine when the engine is operated in accordance with the LA-4 mode of FTP.
REFERENCES:
patent: 5538697 (1996-07-01), Abe et al.
patent: 0 639 699 A2 (1995-02-01), None
patent: 0 661 098 A2 (1995-07-01), None
patent: 7-124467 (1995-05-01), None
patent: 7-155613 (1995-06-01), None
Hiramatsu Takuya
Noda Naomi
Shibagaki Yukinari
Takahashi Akira
NGK Insulators Ltd.
Parkhurst & Wendel L.L.P.
Tran Hien
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