Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Sulfur or sulfur containing component
Reexamination Certificate
1997-12-26
2001-07-31
Dunn, Tom (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Sulfur or sulfur containing component
C423S244010, C423S244020, C423S244090, C423S213200, C423S213500, C502S312000, C502S313000, C502S314000, C502S315000, C502S316000, C502S318000, C502S319000, C502S324000, C502S326000, C502S331000, C502S337000, C502S338000, C502S339000, C502S345000, C502S353000
Reexamination Certificate
active
06267941
ABSTRACT:
BACKGROUND OF THE INVENTION
1
. FIELD OF THE INVENTION
The present invention relates to a catalyst for deodorization and a deodorizing apparatus using the catalyst and in particular, relates to a catalyst for deodorization which provides an excellent deodorization effect to a mixture of sulfur compounds and compounds such as aldehydes, alcohols or hydrocarbon compounds, and an apparatus for deodorization using the same.
2
. PRIOR ART
Hitherto, noble metal catalysts in which platinum, palladium, or both platinum and palladium are supported on a suitable support have been used as a catalyst for deodorization. These catalysts promote a reaction wherein a gas to be deodorized is oxidized and decomposed by oxygen in air so as to provide a deodorization effect, which are, in particular, effective on aldehydes, alcohols and hydrocarbon compounds.
However, These catalyst are deactivated by materials to be deodorized which contain sulfur compounds of low oxidation state such as dimethyl sulfide or methanethiol. Therefore, when such materials to be deodorized are present, it is difficult to use these catalysts as the deodorization catalyst.
In case of materials to be deodorized which contain sulfur compounds, catalysts having an oxide of cobalt, manganese, etc. as an active component, which have relatively strong resistance against such materials are used. For example, Japanese Patent KOKAI(Laid-Open) No.31128/94 discloses a deodorant which comprises an oxide of cobalt and/or manganese, and zeolite. Furthermore, in Japanese Patent KOKAI Nos.47645/96 and 284670/95, a catalyst containing an activated manganese dioxide, a copper-supporting zeolite and copper oxide as an effective component is used so as to attempt a deodorization thereby. However, all of such catalysts provide some effects on the sulfur compounds, while insufficient or no effects on aldehydes, alcohols and the like.
On the other hand, gases, which are emitted from crude waste disposal machines, contain aldehydes, amines, alcohols and the like as well as we sulfur compounds, and therefore, it was impossible to treat such gases, with the conventional cataysts mentioned above.
SUMMARY OF THE INVENTION
It is, because a sulfur atom of dimethylsulfide or the like strongly adsorbs on active sites of the noble metal catalysts mentioned above, that these catalysts are deactivated by dimethylsulfide or the like. It has been found that the effect that the catalyst is deactivated by such an adsorption is remarkable in compounds which have a sulfur atom of low oxidation state, while such effect is little observed in a sulfur compound of high oxidation state. The present inventor has been found that prolongation of life of a noble metal catalyst and a high-efficient oxidative decomposition are achieved by using a combination of a noble metal catalyst and a catalyst which oxidizes compounds having a sulfur atom of low oxidation state such as dimethylsulfide to a high oxidation state such as sulfons.
It is an object of the present invention to provide a catalyst system which has an effective deodorization effect on materials to be deordorized which contain compounds such as aldehydes, alcohols, amines or hydrocarbon compounds, as well as sulfur compounds of low oxidation state.
It is another object of the present invention to provide an apparatus in which a catalyst system is arranged so that the catalyst system has an effective deodorization effect on materials to be deodorized which contain compounds such as aldehydes, alcohols, amines or hydrocarbon compounds, as well as sulfur compounds of low oxidation state.
According to one aspect of the present there is provided a catalyst system for deodorization which comprises a pretreating catalyst and a noble metal catalyst, the pretreating catalyst being a catalyst for converting a sulfur compound of low oxidation state which is included in materials to be deodorized into a sulfur compound of high oxidation state, wherein the materials to be deodorized are brought into contact with the pretreating catalyst prior to being brought into contact with the noble metal catalyst.
According to another aspect of the present invention, there is provided an apparatus for deodorization which is provided with a catalyst tower inside which the pretreating catalyst is positioned upstream of channels for a gas to be deodorized, and the noble metal catalyst is positioned downstream of the channels, wherein the pretreating catalyst is the one for converting the sulfur compound of low oxidation state which is included in the gas to be deodorized into a sulfur compound of high oxidation state.
Furthermore, the catalyst system for deodorization of the present invention is characterized by comprising a pretreating catalyst and a noble metal catalyst, the pretreating catalyst comprising at least one selected from the group consisting of vanadium, chromium, manganese, iron, cobalt, nickel, copper and oxides thereof, and the noble metal catalyst comprising at least one selected from the group consisting of ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum and gold.
In particular, the catalyst system for deodorization of the present invention preferably comprises a pretreating catalyst which contains manganese oxide(IV) and/or vanadium oxide(V), and a noble metal catalyst which contains palladium and/or platinum.
Further another aspect of the present invention relates to a use of a catalyst system which comprises a noble metal catalyst and a pretreating catalyst for deodorizing a malodorous gas containing materials which provides a deactivation effect on the noble metal catalyst, wherein the use comprises the steps of: bringing the gas to be deodorized which contains materials which provides the deactivation effect on the noble metal catalyst into contact with the pretreating catalyst prior to bringing the gas into contact with the noble metal catalyst so as to convert the gas into other materials having less deactivation effect; and then, bringing the gas into contact with the noble metal catalyst.
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Dunn Tom
Hayes Soloway Hennessey Grossman & Hage PC
NEC Corporation
Nguyen Cam N.
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