Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2000-08-09
2002-06-04
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S309000, C502S312000, C502S315000, C502S349000, C501S084000, C501S095100, C428S364000, C428S401000, C428S436000, C428S439000, C428S440000, C428S442000, C423S598000, C423S610000
Reexamination Certificate
active
06399540
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a porous titania, a catalyst comprising the porous titania, a method for producing the porous titania and a method for the catalyst comprising the porous titania. Specifically, the present invention relates to a porous titania which can be used as a catalyst, and a catalyst comprising the porous titania, which can be used for removal of nitrogen oxides, oxidation of organic substances, decomposition of dioxine compounds, or decomposition and removal of organic solvents, surfactant and the like.
2. Description of the Related Art
Titania catalysts are known as catalysts for removal of nitrogen oxides in order to remove nitrogen oxides contained in waste gases from incinerators. Various improvements have previously been proposed for titania catalysts in order to attain long term retaining of catalyst activity. For example, JP-A-5-184923 discloses that a titania catalyst can be obtained by heat-treating amorphous fibers to deposit a crystal of an anatase-form titanium oxide and a vanadium oxide, in which amorphous fibers is produced by the sol-gel method of hydrolyzing a alkoxide in a mixed solution of a titanium alkoxide, a vanadium compound and other alkoxide, successively gelling.
The titania catalyst described in JP-A-5-184923, however, has problems in that the activity is low and the performance of removal of nitrogen oxides is low.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a porous titania which can be used as a catalyst for removal of nitrogen oxides, oxidation of organic substances, decomposition of dioxine compounds, or decomposition and removal of organic solvents, surfactant and the like.
An other object of the present invention is to provide a catalyst comprising the porous titania, which can be used for removal of nitrogen oxides, oxidation of organic substances, decomposition of dioxine compounds, or decomposition and removal of organic solvents, surfactant and the like.
An other object of the present invention is to provide a method for producing the porous titania.
An other object of the present invention is to provide a method for producing the catalyst comprising the porous titania.
The present inventors have devoted intensive efforts to improving catalytic activity of titania. As a result, the present inventors have discovered a porous titania having a high degree of anatase crystallinity, a large specific surface area and a large pore volume, which is obtainable by adding a mixed solution containing water and a solvent to the titanium alkoxide solution to perform hydrolysis and simultaneous polymerization to give a polymer solution, adding a fatty acid to the titanium alkoxide solution or the polymer solution, separating a polymer containing the fatty acid from the polymer solution, and calcining the polymer containing the fatty acid, which exhibits an excellent catalytic activity for removal of nitrogen oxides and the like.
Therefore, the present invention provides a porous titania, which has an anatase-form crystalline structure, an average crystallite diameter of 3 nm to 10 nm, a degree of anatase crystallinity of 60% or more, a BET specific surface area of 10 m
2
/g or more, a total pore volume of 0.05 cm
3
/g or more, and a volume of pores having a pore radius of 1 nm or more of 0.02 cm
3
/g or more.
The present invention also provides a catalyst formed by molding the porous titania described above.
The present invention also provides a catalyst comprising the porous titania described above and at least one catalyst component selected from the group consisting of V, W, Al, As, Ni, Zr, Mo, Ru, Mg, Ca, Fe, Cr and Pt.
The present invention also provides a method for producing the porous titania described above, which comprises the steps of:
dissolving a titanium alkoxide in a solvent to give a titanium alkoxide solution;
adding a mixed solution containing water and a solvent to the titanium alkoxide solution to perform hydrolysis and simultaneous polymerization to give a polymer solution;
adding a fatty acid to the titanium alkoxide solution or the polymer solution;
separating a polymer containing the fatty acid from the polymer solution; and
calcining the polymer containing the fatty acid.
The present invention also provides a method for producing the catalyst described above, which comprises the steps of:
dissolving a titanium alkoxide in a solvent to give a titanium alkoxide solution;
adding a mixed solution containing water and a solvent to the titanium alkoxide solution to perform hydrolysis and simultaneous polymerization to give a polymer solution;
adding a fatty acid to the titanium alkoxide solution or the polymer solution;
adding at least one catalyst component selected from the group consisting of V, W, Al, As, Ni, Zr, Mo, Ru, Mg, Ca, Fe, Cr and Pt to the titanium alkoxide solution or the polymer solution;
separating a polymer containing the fatty acid and the catalyst component from the polymer solution; and
calcining the polymer containing the fatty acid and the catalyst component.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
DETAILED DESCRIPTION OF THE INVENTION
Titania has a chemical formula: TiO
2
and is known to have a crystalline structure of anatase-form, rutile-form or amorphous structure. The porous titania of the present invention has an anatase-form crystalline structure and has here a requirement that its crystallite diameter is about 3 nm or more and about 10 nm or less as calculated by the Scherrer's equation based on a half width of peak and a peak position in (101) plane of anatase obtained by X-ray diffraction method. It is preferred that the crystallite diameter is about 5 nm or more and about 9 nm or less.
The second requirement for identifying the porous titania of the invention is a degree of anatase crystallinity. The degree of anatase crystallinity can be calculated by measuring a peak area of (101) plane of anatase by X-ray diffraction method. In the present invention, it is required that the degree of anatase crystallinity is about 60% or more. It is preferred that the degree of anatase crystallinity is about 65% or more, further about 70% or more, and about 95% or less, further about 90% or less. It is difficult to obtain a sufficient activity as a catalyst when the porous titania has the degree of anatase crystallinity of less than about 60%, even if the anatase crystallite diameter as described above falls within a range of about 3 nm to about 10 nm.
Other requirements for identifying the porous titania of the invention is a BET specific surface area, a total pore volume and a volume for pores having a pore radius of about 1 nm or more. In the present invention, it is required that the BET specific surface area is about 10 m
2
/g or more, the total pore volume is about 0.05 cm
3
/g or more, and the volume for pores having a pore radius of about 1 nm or more is about 0.02 cm
3
/g or more. It is preferred that the BET specific surface area is about 180 m
2
/g or more, further about 200 cm
2
/g or more, the total pore volume is about 0.2 cm
3
/g or more, and the volume for pores having a pore radius of about 1 nm or more is about 0.2 cm
3
/g or more. It is difficult to obtain a porous titania having an excellent catalytic activity when the BET specific surface area is less than about 10 m
2
/g, the total pore volume is less than about 0.05 cm
3
/g, or the volume for pores having a pore radius of about 1 nm or more is less than about 0.02 cm
3
/g. The BET specific surface area, the total pore volume, and the volume for pores having a pore radius of about 1 nm or more ca
Koike Hironobu
Oki Yasuyuki
Takeuchi Yoshiaki
Fitch Even Tabin & Flannery
Hailey Patricia L
Sumitomo Chemical Co,. Ltd.
Wood Elizabeth D.
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