Method for treating organohalogen compounds with catalyst

• US 6,077,482 A
• Filed: 01/09/1998
• Issued: 06/20/2000
• Est. Priority Date: 12/28/1994
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kawagoshi, Hiroshi, Kato, Akira, Arato, Toshiaki, Tamata, Shin, Kanno, Shuichi, Yamashita, Hisao, Azuhata, Shigeru
• Primary Examiner(s): TRAN, HIEN THI
• Application Number:
  US09/004,981
• Time in Patent Office: 893 Days
• Field of Search: 422/199, 422/211, 422/171, 422/177, 422/189, 422/174, 422/173, 588/209, 588/226, 588/248, 423/659, 423/481, 570/227, 570/229, 502/309
• US Class Current: 422/173
• CPC Class Codes: A62D 2101/22 containing halogen
• CPC Class Codes: A62D 3/20 by hydropyrolysis or destructive steam gasification, e.g. using water and heat or supercritical water, to effect chemical change
• CPC Class Codes: B01D 53/8662 Organic halogen compounds
• CPC Class Codes: B01J 21/063 Titanium; Oxides or hydroxides thereof
• CPC Class Codes: B01J 23/30 Tungsten
• CPC Class Codes: B01J 37/0201 Impregnation

Abstract

A treating apparatus for decomposing organohalogen compounds such as chlorofluorocarbons (CFC'"'"'s), trichloroethylene, methylbromide, halon, and the like, effectively, with a high activity of catalyst, is provided. The apparatus includes a reactor in which organohalogen compounds are decomposed by contact at a temperature in a range of 200°˜500° C. with a catalyst which comprises titania and tungsten oxide by an atomic ratio of Ti and W in a range from 20 mol % to 95 mol % Ti and from 5 mol % to 80 mol % W, with at least the surface of the titania being covered with a porous layer of the tungsten oxide. In accordance with the present invention, organic compounds containing any of fluorine, chlorine and bromine will be decomposed with a high efficiency, and the activity of the catalyst can be maintained for a long time.

Claims

1. A treating apparatus for decomposing organohalogen compounds used for performing a decomposing method of the organohalogen compounds with catalyst comprising:

a reactor filled with a catalyst,

means for adding air to gas flow containing organohalogen compounds,

means for conducting the gas flow containing said organohalogen compounds and air into said reactor,

means for heating said reactor so that the gas flow contacts with the catalyst at a temperature in a range of 200˜

500°

C.,

means for adding an effective amount of water vapor to the gas flow for decomposing said organohalogen compounds, and

alkaline absorbers for washing organohalogen decomposition products, which are generated by contacting said gas flow with the catalyst filled into said reactors, with an alkaline aqueous solution in order to neutralize a part of carbon dioxide and halogenated hydrogen in said organohalogen decomposition products, wherein

said catalyst comprises titania and tungsten oxide, the titania having a surface,

said catalyst has an atomic ratio of Ti and W in a range from 20 mol % to 95 mol % Ti and from 5 mol % to 80 mol % W, and

at least the surface of said titania is covered with a porous layer of tungsten oxide.

2. A treating apparatus for decomposing organohalogen compounds as claimed in claim 1, wherein a means for adsorbing carbon monoxide in said decomposition products which are not neutralized at the alkaline absorbers is provided downstream of said alkaline absorbers.

3. A treating apparatus for decomposing organohalogen compounds as claimed in claim 1, wherein the porous layer of tungsten oxide covers the surface of the titania so as to prevent poisoning of the titania by fluorine.

4. A treating apparatus for decomposing organohalogen compounds as claimed in claim 1, wherein said catalyst consists essentially of titania and tungsten oxide.

5. A treating apparatus for decomposing organohalogen compounds as claimed in claim 1, wherein said porous layer has a thickness of 1 Å

to 5 mm.

6. A treating apparatus for decomposing organohalogen compounds as claimed in claim 1, wherein said catalyst has an atomic ratio of Ti and W in a range 40 mol % to 90 mol % Ti and from 10 mol % to 60 mol % W.

7. A treating apparatus for decomposing organohalogen compounds as claimed in claim 1, wherein said catalyst has an atomic ratio of Ti and W in a range 20 mol % to 85 mol % Ti and from 15 mol % to 80 mol % W.

8. A treating apparatus for decomposing organohalogen compounds as claimed in claim 1, wherein said reactor is selected from the group consisting of a fixed bed reactor, a fluidized bed reactor and a mobile bed reactor.

9. A treating apparatus for decomposing organohalogen compounds as claimed in claim 1, further comprising a preheater upstream of the reactor.

10. A treating apparatus for decomposing organohalogen compounds as claimed in claim 1, wherein said catalyst is a catalyst prepared by a method including impregnating TiO₂ with a solution containing W, and wherein said catalyst has an atomic ratio of Ti and W in a range from 20 mol % to 90 mol % Ti and 10 mol % to 80 mol % W.

11. A treating apparatus for decomposing organohalogen compounds as claimed in claim 10, wherein said catalyst is a catalyst prepared by a method including the further step of calcining the TiO₂ impregnated with said solution, to convert the W to WO₃.