Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – Clay
Reexamination Certificate
2000-09-18
2002-07-30
Griffin, Steven P. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
Clay
C502S080000, C502S350000, C502S340000, C502S343000, C502S305000, C502S352000, C502S215000, C502S216000
Reexamination Certificate
active
06426312
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the purification of air-borne particulates and gasses, in particular volatile organic compounds.
BACKGROUND OF THE PRESENT INVENTION
It has been known for some time that titanium dioxide can achieve photodechlorination of PCB'S, as described by J. H. Carey et al in “Photodechlorination of PCB's in the Presence of Titanium Dioxide in Aqueous Suspensions,” “Bulletin of Environmental Contamination & Toxicology,” Vol. 16, No. 6, pp. 697-701, 1976 Springer-Verlag New York Inc. Carey et al describe irradiation by ultra violet light with a wavelength of 365 nm of a 25 ppb aqueous solution of Aroclor 1254 in the presence of suspended particulate titanium dioxide. After 30 minutes no unreacted Aroclor could be detected in solution or adsorbed on the surface of the TiO
2
. Similar experiments were conducted with other PCB's and resulted in an observed disappearance of the chlorinated biphenyls and the production of chloride ions. It has been reported the conversion (often called “mineralization”) of a number of organic compounds to carbon dioxide by exposure to near ultra violet light in aqueous suspensions of anatase, a form of crystalline titanium dioxide. The solutes studied were benzene, benzoic acid, benzoate ion, salicylate ion, phenol, chlorobenzene, aniline, anilinium ion, nitrobenzene, chloroform and formic acid. Also it had been earlier reported that similar results with benzoic acid or sodium benzoate (“Hydroxylation Reactions Induced by Near-Ultraviolet Photolysis of Aqueous Titanium Dioxide Suspensions,” J. Chem. Soc. Faraday Trans. 1, 1984, 80, pp 457-471).
Chen-Yung Hsiao et al. have also reported the mineralization of chloromethanes to CO
2
and HCl by the heterogeneous photocatalyst TiO
2
(“Heterogeneous Photocatalysis: Degradation of Dilute Solutions of Dichloromethane (CH
2
Cl
2
), Chloroform (CHCl
3
), and Carbon Tetrachloride (CCl
4
) with Illuminated TiO
2
Photocatalyst,” Journal of Catalysis 82, 1983, pp 418-423). Similar reactions have not been limited to TiO
2
. Other metal semiconductors, such as ZnO, CdS, WO
3
and SnO
2
, have been utilized in photocatalytic processes for the degradation of environmental contaminants (“Photocatalysis Over TiO
2
Supported On A Glass Substrate,” by N. Serpone et al, Solar Energy Materials 14(1986) pp 121-127, Elsevier Science Publishers B.V.-North-Holland Physics Publishing Divisions, Amsterdam).
Robertson et al. in U.S. Pat. No. 4,966,759 disclose and claim a matrix for use in a method of removing, reducing or detoxifying organic pollutants from a fluid. The matrix is a substrate in the form of a plurality of layers of a filamentous, fibrous or stranded base material, and a photoreactive metal semiconductor material bonded with, to or into surfaces of the layers. And at least one of the layers being at least partially transparent to light at a wavelength to which the semiconductor material photoreacts. The filamentous, fibrous or stranded base material disclosed by Robertson et al. are fiberglass, glass wool, and steel.
The filamentous, fibrous or stranded base materials of glass wool and fiberglass, as found by the present applicant, were unable to withstand extended periods in ultraviolet light without altering the adherence of the anatase to the base material. Similarly, steel is unable to withstand extended periods of exposure to hydroxyl compounds without rusting. Also, these base materials are not water absorbent because an object of Robertson et al.'s invention was to use a base material for the water to flow through or on it, not be trapped within. (First paragraph of the Detailed Description of the Invention.) Hence, water is not trapped in the material, which is an embodiment of the present invention in order to upon reaction with UV light and anatase form hydroxyl radicals, which create undesirable effect on the steel substrate which is discussed above.
SUMMARY OF THE INVENTION
The present invention solves these problems of the prior art. This invention is an air purifying matrix to remove, reduce or detoxify organic pollutants. The matrix has an inert substrate, a photoreactive semiconductor material, and aqueous particles. The inert substrate is water absorbent, transparent to ultraviolet light, able to withstand extended periods of exposure to all wavelengths of ultraviolet light side of the spectrum without decomposing or altering the structure thereof, able to withstand high concentrations of hydroxyl radicals without decomposing or altering the structure thereof, and in the form of an expanded granular type with spaces therein. The photoreactive semiconductor material is crystallized within the spaces. And the aqueous particles are within the spaces to form photoreactive metal semiconductor material nano-reactors within the matrix. These nano-reactors generate high concentrations of hydroxyl radicals which surround and diffuse through the matrix, and remove, reduce or detoxify organic pollutants within and surrounding the matrix. Moreover, the ultraviolet light is at a wavelength which the semiconductor material photoreacts.
REFERENCES:
patent: 4892712 (1990-01-01), Robertson et al.
patent: 4966759 (1990-10-01), Robertson et al.
patent: 5264404 (1993-11-01), Takahama et al.
patent: 5468699 (1995-11-01), Zhang et al.
patent: 5516492 (1996-05-01), Dong et al.
patent: 5616532 (1997-04-01), Heller et al.
patent: 5736055 (1998-04-01), Cooper
patent: 5778664 (1998-07-01), Janata et al.
patent: 5779912 (1998-07-01), Gonsalez-Martin et al.
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Griffin Steven P.
Hodgson & Russ LLP
Ildebrando Christina
LandOfFree
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