Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Nitrogen or nitrogenous component
Patent
1997-08-21
2000-06-20
Griffin, Steven P.
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Nitrogen or nitrogenous component
2041573, 427523, 427529, 427530, 502 5, 502349, 502350, 585377, B01J 800, B01J 3734, B01J 2300, B01D 5300, C23C 1400, C23C 1408, C23C 1406, C07C 523
Patent
active
060774924
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention pertains to photocatalysts which can exhibit catalytic activity even upon irradiation with visible light, a process for producing the photocatalysts, and photocatalytic reactions methods, e.g., the decomposition reaction of nitrogen oxides and the isomerization reaction of butenes under light in the wavelength regions of not only ultraviolet but also visible. Specifically, the photocatalysts comprise titanium oxide catalysts into which specific metal ions are incorporated by an ion implantation method, i.e., the implantation of the titanium oxide catalysts with metal ions accelerated by high voltage.
BACKGROUND ART
Photocatalytic reactions using the titanium oxide catalyst have been the focus of our research as an environmentally-friendly and safe means of converting light energy into useful chemical energy at ordinary temperatures without generating any pollutants. Investigations into the application of such photocatalysts for reactions that can decontaminate and detoxify the environment have been one of the most significant objectives. In particular, investigations into particle size reduction to form ultrafine particles as well as the addition of metals such as Pt, Ag, or Ni into the titanium oxide catalyst have enhanced the efficiency of the reactions. Furthermore, parallel investigations on the adsorption of a dye onto titanium oxide catalysts have been carried out to explore the possibility of the use of visible light (about 400 nm-800 nm).
However, until now, photocatalytic reactions in prior art photocatalysts could proceed only when the reaction systems were irradiated with ultraviolet-light in wavelength regions shorter than about 380 nm, but could not proceed constantly in the visible region having long wavelengths. Examples of photocatalytic reactions using prior art titanium oxide photocatalysts include a decomposition reaction of nitrogen oxides and an isomerization reaction of butenes. However, these photocatalytic reactions proceed efficiently only when the reaction systems are irradiated with ultraviolet light.
Titanium oxide catalysts do not allow for the use of visible light and make use of only about 5% of solar beams that reach the earth, necessitating the use of an ultraviolet light source such as a mercury lamp.
DISCLOSURE OF THE INVENTION
An objective of the present invention is to provide titanium oxide photocatalysts that have been modified, to thereby shift their photoabsorption bands from ultraviolet to visible light regions, hence enabling them to operate efficiently as photocatalysts even under visible light irradiation. Furthermore, another objective of the present invention is to provide various photocatalytic reactions such as a decomposition reaction of nitrogen oxides and an isomerization reaction of butenes by irradiating the photocatalysts with ultraviolet to visible light in the presence of nitrogen oxides, butenes and the like.
These objectives of the present invention have been accomplished by a titanium oxide photocatalyst having metal ions of one or more metals incorporated therein selected from the group consisting of Cr, V, Cu, Fe, Mg, Ag, Pd, Ni, Mn and Pt, wherein the metal ions are implanted from the surface to deep inside of the bulk of the photocatalyst in an amount of at least 1.times.10.sup.15 ions per g of the titanium oxide.
Furthermore, these objectives of the present invention have been accomplished by a process for producing a photocatalyst, which comprises accelerating metal ions of one or more metals selected from the group consisting of Cr., V, Cu, Fe, Mg, Ag, Pd, Ni, Mn and Pt to an energy level of at least 30 keV and implanting the accelerated metal ions into a titanium oxide.
Moreover, these objectives of the present invention have been a photocatalytic reaction method, which comprises irradiating light in the wavelength regions from ultraviolet to visible on the titanium oxide photocatalyst.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows absorption spectra in the ultraviolet and visible light regi
REFERENCES:
patent: 4391901 (1983-07-01), Land et al.
patent: 5759948 (1998-06-01), Takaoka et al.
International Search Report from the Japanese Patent Office dated Apr. 2, 1997.
Anpo et al.: "Photocatalysis on Ti-Al Binary Metal Oxides", J. Phys. Chem., vol. 92, 1988, pp. 438-440, XP002098080.
Kodama; Yagi: "Reaction Mechanisms for the Photocatalytic Isomerization and Hydrogenation of cis-2-butene over Ti02", J. Phys. Chem., vol. 93, No. 11, Jun. 1, 1989, pp. 4556-4561, XP002098081.
Anpo Masakazu
Fujimoto Takanori
Kanai Sakunobu
Sato Kazuhito
Yamashita Hiromi
Griffin Steven P.
Medina Maribel
Petroleum Energy Center
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