Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Halogenous component
Reexamination Certificate
2000-08-07
2004-01-06
Silverman, Stanley S. (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Halogenous component
C423S245100, C588S253000, C588S249000
Reexamination Certificate
active
06673326
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to catalysts and catalytic processes for the degradation of perfluorinated compounds and hydrofluorocarbons.
Perfluorinated compounds (PFCs) are used extensively in the manufacture of semiconductor materials, such as dry chemical etching and chamber cleaning processes. PFCs are defined as fully fluorinated compounds made of carbon, nitrogen, or sulfur, or mixtures thereof. Examples of PFCs include nitrogen trifluoride (NF
3
), tetrafluoromethane (CF
4
), hexafluoroethane (C
2
F
6
), sulfur hexafluoride (SF
6
), octafluoropropane (C
3
F
8
), decafluorobutane (C
4
F
10
), and octafluorocyclobutane (c-C
4
F
8
).
Hydrofluorocarbons (HFCs) are also used in the manufacture of semiconductor material and are generated as by-products during semiconductor manufacture. HFCs are compounds made of hydrogen, fluorine and carbon. Examples of HFCs include trifluoromethane (CHF
3
) and 1,1,1,2-tetrafluoroethane (CF
3
CFH
2
). The global warming potential of PFC and HFC compounds are estimated to be many times greater than that of carbon dioxide (Langan et al., 1996), resulting in a need for economical technologies for achieving emissions control requirements. Other applications for PFCs and HFCs include uses as polymer blowing agents and as refrigerants.
Catalytic technologies have been and continue to be widely used as an “end-of-the-pipe” means of controlling industrial emissions. This technology involves passing a contaminated stream over a catalyst in the presence of oxygen and/or water at an elevated temperature to convert the pollutants in the emissions stream to carbon dioxide, water, and mineral acids, should the parent compounds contain halogens. This technology offers many advantages over thermal incineration as a means of controlling emissions. The advantages are connected to the use of the catalyst, which reduces the temperature required to decompose the pollutants by several hundreds of degrees Celsius. These advantages include energy savings (which translates into lower operating costs), lower capital costs, small foot print of resulting abatement unit, a more controllable process, and no generation of thermal NO
x
.
An important factor in any catalytic abatement strategy is the catalyst itself. The catalytic destruction of PFCs and HFCs results in the formation of highly corrosive fluorine-containing products, such as F
2
, HF and/or COF
2
. In order for a catalyst to effectively decompose PFCs and HFCs, the catalyst must be able to maintain its integrity in the resulting highly corrosive environment. Many typical catalytic materials will not maintain their integrity in this reaction environment due to fluorine attack.
Campbell and Rossin (“Catalytic Oxidation of Perfluorocyclobutene over a Pt/TiO
2
Catalyst,” 14th N. Am. Catal. Soc. Meeting, 1995) suggested the use of a Pt/TiO
2
catalyst to destroy perfluorocyclobutene (c-C
4
F
6
) at reaction temperatures between 320° C. and 410° C. The authors reported some loss of reactivity over the duration of the near 100 hour reaction exposure. The authors also note the beneficial effects of water on improving the stability of the catalyst. The authors stated that even at a reaction temperature of 550° C., the catalyst did not decompose perfluorocyclobutane (c-C
4
F
8
), a PFC used in the manufacture of semiconductor materials. Results presented in this study suggested that perfluoroalkanes are significantly more difficult to destroy than the corresponding perfluoroalkene.
Aluminum oxide, particularly of the high surface area gamma phase, is widely used as a support for catalytically active metals. Aluminum oxide offers a combination of high surface area and excellent thermal stability, being able to maintain its integrity at temperatures of approximately 800° C. for short periods of time. Aluminum oxides however, do not fare well as catalyst supports for the destruction of fluorine-containing compounds. For example, Farris et al. (“Deactivation of a Pt/Al
2
O
3
Catalyst During the Oxidation of Hexafluoropropylene,”
Catal., Today
, 501, 1992) report the destruction of hexafluoropropylene over platinum supported on a high surface area aluminum oxide catalyst. It was not reported whether the platinum or the aluminum oxide is responsible for the destruction of hexafluoropropylene. The catalyst could readily destroy hexafluoropropylene at reaction temperatures between 300° C. and 400° C.; however, severe deactivation of the catalyst was noted. Over the course of the experiment (less than 100 hours), the aluminum oxide was converted to aluminum trifluoride, which resulted in a severe loss of catalytic activity. This transformation of the aluminum oxide to aluminum trifluoride suggests that aluminum oxide will not be able to maintain its integrity in a fluorine environment for an extended period of operation.
Thus, there exists a need for novel and improved catalysts and catalytic processes for the degradation of perfluorinated compounds and hydrofluorocarbon compounds.
SUMMARY OF THE INVENTION
Catalyst compositions containing Al
2
O
3
and/or ZrO
2
along with one or more enhancers are described. The enhancers may be nickel, cobalt, or sulfate. The catalyst compositions may further contain an oxidation catalyst such as platinum, palladium, rhodium, iridium, silver, nickel, copper, iron, vanadium, or cerium.
The catalyst compositions are particularly useful in catalytic processes for the destruction of perfluorinated compounds and/or hydrofluorocarbons.
REFERENCES:
patent: 3760565 (1973-09-01), Fish
patent: 3899444 (1975-08-01), Stephens
patent: 3980584 (1976-09-01), Dronov et al.
patent: 3983072 (1976-09-01), Stephens
patent: 4053557 (1977-10-01), Kageyama
patent: 4059683 (1977-11-01), Lindberg et al.
patent: 4092403 (1978-05-01), Rectenwald et al.
patent: 4390456 (1983-06-01), Sanchez et al.
patent: 4435379 (1984-03-01), Olson et al.
patent: 4459372 (1984-07-01), Arenn
patent: 4587116 (1986-05-01), Livingston et al.
patent: 4810685 (1989-03-01), Twigg et al.
patent: 4868150 (1989-09-01), Spooner et al.
patent: 4902664 (1990-02-01), Wan
patent: 5151263 (1992-09-01), Okazaki et al.
patent: 5176897 (1993-01-01), Lester
patent: 5276240 (1994-01-01), Timmons et al.
patent: 5276249 (1994-01-01), Greene et al.
patent: 5283041 (1994-02-01), Nguyen et al.
patent: 5290429 (1994-03-01), Delaney et al.
patent: 5396022 (1995-03-01), Wu et al.
patent: 5416247 (1995-05-01), Webster
patent: 5430230 (1995-07-01), Mitsui
patent: 5457268 (1995-10-01), Greene et al.
patent: 5593654 (1997-01-01), Decker, Jr. et al.
patent: 5622682 (1997-04-01), Tom
patent: 5653949 (1997-08-01), Chen et al.
patent: 5817284 (1998-10-01), Nakano et al.
patent: 5863515 (1999-01-01), Davis et al.
patent: 6022489 (2000-02-01), Izumikawa et al.
patent: 6023007 (2000-02-01), Nakajo et al.
patent: 6069291 (2000-05-01), Rossin et al.
patent: 6110436 (2000-08-01), Scholz et al.
patent: 6162957 (2000-12-01), Nakajo et al.
patent: 0 475 442 (1998-12-01), None
patent: 0 885 648 (1998-12-01), None
patent: 2 066 690 (1981-07-01), None
patent: 57-7254 (1982-01-01), None
patent: 57-7255 (1982-01-01), None
patent: 07080303 (1995-03-01), None
patent: 9-57103 (1997-03-01), None
patent: 9-253453 (1997-09-01), None
patent: 10-66867 (1998-03-01), None
patent: 10192653 (1998-07-01), None
Bickle et al, Catalytic Destruction of Chlorofluorocarbons and Toxic Chlorinated Hydrocarbons, Appl. Catal. B:Env., 1994, pp. 141-153, Elservier, Amsterdam Sep.
Bond & Sadeghi, Catalysed Destruction of Chlorinated Hydrocarbons J. Appl. Chem. Biotechnol. 1975, pp. 241-248, Society of Chemical Industry, London No month.
Burdenuic & Crabtree, Mineralization of Chlorofluorocarbons and Aromatization of Saturated Fluorocarbons by a Convenient Thermal Process, Science, 1996, pp. 340-341, Amer. Assoc. for the Advancement of Science, D.C. Jan.
Fan & Yates, Infared Study of the Oxidation of Hexafluoropropene On TiO2, J. Phys. Chem. 1994, pp. 10621-10627, Americal Chemical Society, Easton, PA No month.
Karmakar & Green, An Investigation of CFC12 (CCL2F2) Decomposition on TiO2Cata
Feaver William B.
Rossin Joseph A.
Baker & Botts L.L.P.
Guild Associates, Inc.
Johnson Edward M.
Silverman Stanley S.
LandOfFree
Catalytic processes for the reduction of perfluorinated... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Catalytic processes for the reduction of perfluorinated..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Catalytic processes for the reduction of perfluorinated... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3211711