Hazardous or toxic waste destruction or containment – Containment – Solidification – vitrification – or cementation
Patent
1992-12-29
1995-07-04
Straub, Gary P.
Hazardous or toxic waste destruction or containment
Containment
Solidification, vitrification, or cementation
423240S, 4232453, 423247, A62D 300
Patent
active
054302307
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for disposing by oxidative decomposition of organohalogen compounds contained in waste gas coming from incinerators, cleaning, and many other processes. More particularly, the present invention relates to a method for disposing by oxidative decomposition of organohalogen compounds while preventing the formation of carbon monoxide by oxidative decomposition and removing organohalogen compounds together with nitrogen oxides and carbon monoxide contained in waste gas.
BACKGROUND ART
There are several known methods for disposing of harmful organohalogen compounds contained in waste gas. One method is by direct heating of waste gas at temperatures above 800.degree. C. Another method is by adsorption on an adsorbent such as activated carbon. The former method requires a large amount of fuel and evolves toxic halogens and carbon monoxide during decomposition under certain operating conditions. The latter method suffers the disadvantage that the adsorption efficiency fluctuates depending on the concentration of substances for disposal and the adsorption is inhibited by coexistent substances.
There has been proposed a method for oxidative decomposition by the aid of a transition metal oxide as a catalyst. (Japanese Patent Laid-open Nos. 22699/1976 and 47516/1991.) This method permits oxidative decomposition at comparatively low temperatures; however, it still suffers the disadvantage that oxidation is not complete and toxic carbon monoxide remains in the treated gas.
The present invention was completed to address the above-mentioned problems. It is an object of the present invention to provide a method for efficiently disposing of organohalogen compounds together with nitrogen oxides and carbon monoxide contained in waste gas by oxidative decomposition at low temperatures without the formation of toxic chlorine gas.
DISCLOSURE OF THE INVENTION
The gist of the present invention resides in a method for disposing of organohalogen compounds by oxidative decomposition, said method comprising catalytically reacting waste gas at a temperature between 150.degree.-600.degree. C. with a catalyst containing as catalyst component A a composite oxide of two or more metals selected from the group consisting of Si, Ti, and Zr, and as catalyst component B an oxide of one or more metals selected from the group consisting of V, Mo, Sn, Ce, and W.
According to the present invention, the catalyst may additionally contain as catalyst component C, in the form of simple substance or oxide, one or more metals selected from the group consisting of Cr, Mn, Fe, Cu, Ru, Rh, Pd, Pt, and Au. The additional catalyst component C prevents the formation of carbon monoxide. Moreover, if ammonia is added to waste gas, it is possible to remove nitrogen oxides simultaneously with oxidative decomposition of organohalogen compounds and carbon monoxide contained in waste gas.
BEST MODE FOR CARRYING OUT THE INVENTION
The present inventors found that it is possible to perform efficient oxidative decomposition on organohalogen compounds at low temperatures (150.degree.-600.degree. C.) by the use of catalyst component A, which is a composite oxide of two or more metals selected from the group consisting of Si, Ti, and Zr, and catalyst component B, which is an oxide of one or more metals selected from the group consisting of V, Mo, Sn, Ce, and W. The present inventors also found that it is possible to minimize the formation of carbon monoxide by the combined use of one or more metals, in the form of simple substance or oxide, selected from the group consisting of Cr, Mn, Fe, Cu, Ru, Rh, Pd, Pt, and Au. These findings led to the present invention.
In addition, the method of the present invention permits the oxidative decomposition of organohalogen compounds and carbon monoxide as well as the removal of nitrogen oxides if ammonia gas is added to waste gas.
The present invention will be described in more detail in the following.
The organohalogen compounds referred to in the present invention are
REFERENCES:
patent: 4957717 (1990-09-01), Imamura et al.
Ishii Toru
Mitsui Kiichiro
Nishikawa Kazuyoshi
Nippon Shokubai Co. , Ltd.
Straub Gary P.
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