Chemistry: electrical and wave energy – Processes and products – Processes of treating materials by wave energy
Reexamination Certificate
2000-01-06
2002-01-08
Wong, Edna (Department: 1741)
Chemistry: electrical and wave energy
Processes and products
Processes of treating materials by wave energy
C204S158200
Reexamination Certificate
active
06336998
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for fabricating a UV lamp for treating waste gas and to a UV lamp for treating waste gases fabricated therefrom, which is designed and fabricated based on solgel coating techniques by coating a sol of photocatalytic materials on a glass-fiber-cloth, and/or then impreganate this cloth with oxidation catalysts and finally, wrap and fix this cloth on a UV lamp. The invention relates also to a process for treating waste gases by using said UV lamp for treating waste gas through irradiating UV light therefrom on the surface of such photocatalytic materials to generate free electron and electron hole pairs which can decompose waste gases such as organic or inorganic pollutants in the air into unharmful gases.
2. Description of the Prior Art
Solgel techniques have been emphasized today by technically advanced countries for several main reasons. Developments of traditional chemical and physical technologies have met bottle-necks, and in particular, inorganic materials produced through traditional techniques can no longer satisfy requirements, especially, for thin film coating. Materials having multiple components and special structures that cannot be coated by conventional physical and/or chemical methods, as well as when coating those materials on irregularly curved surfaces, such cannot be achieved by conventional evaporative disposition techniques. The solgel technique, on the other hand, can easily generate a metal oxide film, and at the same time, it is the characteristic feature of the solgel technique that a photocatalytic film obtained thereby has a porous crystallite structure required for photocatalytic action. Therefore, solgel coating techniques have become one of the most interesting techniques for research and development in the latter part of the twentieth century.
Recently, preparation of catalysts by solgel techniques also received emphasis by chemical industries, and in particular, photocatalytic techniques is the most important one, including the early developed photocatalytic powders for treating waste water, such as. For example, Robat A. Clyde, U.S. Pat. No. 4,446,236; Robat E. Hetrick Ford Motor Company, U.S. Pat. No. 4,544,470; Yashiaki Harada et al., Osaka Gas Company, U.S. Pat. No. 4,699,720; Tomoji Kawai, et al., Nomura Micro Science Co., U.S. Pat. No. 4,863,608; David G. Ritchie, U.S. Pat. No. 5,069,885; Gerald Cooper, et al., Photo Catalytics Inc., U.S. Pat. Nos. 5,116,582; 5,118,422; 5,174,877; and 5,294,315; Adam Heller, et al., Board of Regents, The University of Texas System, U.S. Pat. No. 5,256,616; Ali Safarzedeh-Amiri, Cryptonics Corporation, U.S. Pat. No. 5,266,214; Fausto Miano & Borgarello, Eniricerche S.p.a., U.S. Pat. No. 5,275,741; Nancy S. Foster et al., Regents of the University of Colorado, U.S. Pat. No. 5,332,508; Ivan Wlassics et al., Ausimont S.p.a., U.S. Pat. No. 5,382,337; Paul C. Melanson & James A. Valdez, Anatol Corporation, U.S. Pat. No. 5,395,522; Henry G. Peebles III et al., American Energy Technology, Inc., U.S. Pat. No. 5,449,466; Brain E. Butters & Anthony L. Powell, Purific Environmental Technologies, Inc., U.S. Pat. Nos. 5,462,674; 5,554,300; and 5,589,078; Yin Zhang, et al., Board of Control of Michigan Technology University, U.S. Pat. No. 5,501,801; Clovis A. Linkous, University of Central Florida, U.S. Pat. No. 5,518,992; and Eiji Normura & Tokuo Suita, Ishihara Sanyo Kaisha Ltd,. U.S. Pat. No. 5,541,096.
The above-mentioned U.S. patents relate chiefly to water treatments, which in the case of granular catalysts, a filtration recovering apparatus is invariably used, and it is of the most importance that such photocatalysis needs sufficient dissolved oxygen in water, otherwise, an aerating operation must carry out for supplying oxygen required by the photocatalytic degradation.
Since then, photocatalysts were used also for treating waste gases, such as those described in, for example, Gregory B. Roupp & Lynette A. Dibble, Arizona State University, U.S. Pat. No. 5,045,288; Jeffrey g. Sczechowski et al., The University of Colorado, U.S. Pat. No. 5,439,652; William A. Jacoby & Danial M. Blake, U.S. Pat. No. 5,449,443; Zhenyyu Zhang & James R. Fehlner, Inrad, U.S. Pat. No. 5,468,699; and Franz D. Oeste, Olga Dietrich Neeleye, U.S. Pat. No. 5,480,524.
The above-mentioned patents relate originally to treatment of waste gases, and basically, were carried out in a closed reactor, and therefore, utilization or operation of granular catalysts or catalysts coating granules usually needed, in general, complicate equipments.
The above-described disadvantages made the prior art photocatalysts difficult to apply for treating polluted air in our living environment. Among them, the only waste water and/or waste gas disposal photocatalytic reactor comprises a UV lamp wrapped with a photocatalyst coated film having fibers as supports therefor was the one described in U.S. Pat. No. 4,982,712 to Michael K. Robertson & Robert B. Henderson, Nutech Energy Systems Inc. As above mentioned, such reactor was a closed type such that counterflowing must be forced by a blower which made such reaction system inconvenient to practice in our living environment.
As for the use of a UV lamp for treating waste gases, it is generally based on the sustained oxidative degradation of organic and/or inorganic hazardous materials in the air by a photocatalytic reaction, to render them into non-harmful substances such as water or carbon dioxide. Since the photocatalytic reaction takes place on the catalyst through UV irradiating of hazardous waste gases and oxygen, it is inactive in cases where the UV light can not reach the catalyst. Accordingly, only the catalyst in the extremely thin top layer (less than one micron) that received UV light becomes active under such conditions. Therefore, in practice, a film coating of photocatalysts on carry substrate materials which are transmittable to UV light are used to prepare a photocatalyst film.
Photocatalytic action can be effected only in the case of direct UV irradiation on coating, while it is inactive in the case of backside irradiation. The reason therefor relates to the fact that electron hole pairs generated during UV irradiation on the surface of photocatalyst will combine in an extremely short time period (microseconds) and releases thermal energy before reacting with oxygen and/or materials to be reacted.
Nevertheless, a photoelectric-chemical catalyst having an electroconductive layer incorporated in the coating film structure can transfer electron generated during UV irradiating via the conductor therein to the positive electrode, such that the electron hole can be retained and the persisting time period of reactive positions can be postponed and thereby improves the efficiency of UV irradiation. However, such coating film is not easy to fabricate and practice. Consequently, it is essential for photocatalytical reaction to take place in simultaneous presence of oxygen, moisture, reactants and catalysts as well as in combination with UV irradiation to give rise the oxidative degradation.
Since the effective thickness of photocatalysts is extremely small, it is sufficient for a layer of photcatalytic material having a thickness of less than 1 micron to be deposited on a UV transmittable substrate by a solgel coating technique. Because photocatalytic materials are in general metal oxides, it is conventional to use vacuum deposition, redox plating, and aqueous precipitation/adsorption coating techniques to form a thin film. Among them, the vacuum deposition technique is usually employed for depositing on the surface of a flat structure, which cannot meet the practical requirement in this field. Furthermore, since vacuum deposition is not capable of obtaining a porous structure of catalysts and a crystalline structure having photcatalytic action, it becomes useless therefor. The aqueous precipitation/adsorption coating technique consists of precipitating a photocatalytic metal oxide on the surface of a substrate. However, beca
Chung Shan Institute of Science and Technology
Rosenberg , Klein & Lee
Wong Edna
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