Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2002-04-04
2002-11-19
Silverman, Stanely S. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S327000, C502S328000, C502S329000, C502S330000, C502S332000
Reexamination Certificate
active
06482767
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a novel photo-catalyst. Especially, the present invention relates to a photo-catalyst comprising RuO
2
-loaded A
2
X
n
O
m
or RuO
2
-loaded BX
n
O
m
(wherein A is an alkali metal atom, B is an alkali earth metal atom or Zn, X is a metallic ion with d
10
configuration, n=m/2 or n=m/3 and n is 2), more especially relates to a photo-catalyst used for complete decomposition of water.
BACKGROUND OF THE INVENTION
The photo decomposition reaction of water is broadly interested from the view point of photo energy transformation. While, a photo-catalyst which shows activity to the photo decomposition reaction of water can be considered to be a high quality photo functional material possessing functions such as photo absorption, electric charge separation or surface oxidation-reduction reaction.
Kudo, Kato et al are explaining that alkali tantalate or alkali earth elements are the photo-catalyst showing high activity to the complete photo decomposition reaction of water by quoting various prior arts [Catal. Lett., 58(1999). 153-155, Chem. Lett., (1999), 1207, Surface Vol.36, No.12(1998), 625-645 (shortened to document A)].
In above mentioned document A, there is an explanation about an useful photo-catalyst materials for proceeding the decomposition reaction of water to hydrogen and oxygen using a photo-catalyst, and many indications about photo-catalyst used for complete photo decomposition reaction of water are mentioned.
In the document, it is reported that the authors has first at all found, that tantalate acts as a photo-catalyst which generates oxygen and hydrogen from pure water according to stoichiometric ratio without a promoter, and then has found that the catalyst activity is remarkably improved by carrying NiO promoter (right column of 635
th
page).
Further, there is an explanation reporting that also K
4
Nb
6
O
17
can generate oxygen and hydrogen from pure water without a promoter, and the fine crystalline of it obtained by pulverizing it indicates remarkably high activity. Furthermore, there is an illustration that a compound having perovskite structure such as K
2
La
2
Ti
3
O
10
has excellent photo-catalyst activity, because the hydration reaction can easily occur between layers.
In FIG. 6 of 629
th
page, there is an explanation about main elements composing of un-uniform type photo-catalyst materials, and in which there is a description explaining that the oxide composed of a transition metal ion possessing d
0
and d
10
electron arrangement or a metal ion of p-block. And, in 640
th
page, following explanations are described. Namely, the band gap of In
2
O
3
(ZnO)
m
composed of laminated structure of In
2
O and ZnO
3
is smaller than that of In
2
O
3
or ZnO alone, and generates hydrogen by photo decomposition of methanol aqueous solution under the visible radiation or generates oxygen by photo decomposition of AgNO
3
aqueous solution under the visible radiation. Further, regarding to &bgr;-Ga
2
O
3
, there is also following explanation. Namely, by forming a solid solution with In
2
O
3
, the band gap of it becomes smaller maintaining the structure of &bgr;-Ga
2
O
3
, and can generate hydrogen and oxygen by photo decomposition of water under the presence of methanol or AgNO
3
which are a sacrificial reagent, but not extends to the responsibility for visible radiation. However, there is no explanation teaching activity in regard to water decomposition reaction or Sb.
Concerning above mentioned circumstances, the inventors of the present invention have carried out intensive study to make the photo-catalyst which uses a transition metal ion possessing d
10
electron arrangement generate high activity, especially have repeatedly continued various experiments in regard to various compounds aiming to provide a catalyst which make enable the photo decomposition of water.
From the results conduced by these experiments, the inventors of the present invention have found the following fact and have accomplished the present invention. That is, the salt of alkali metal or alkali earth metal and transition metal ion possessing d
10
electron arrangement can act as a catalyst which make enable the complete photo decomposition of water by loading RuO
2
, without the presence of methanol or AgNO
3
which are a sacrificial reagent used in above mentioned prior arts.
DISCLOSURE OF THE INVENTION
The present invention is the photo-catalyst comprising RuO
2
-loaded A
2
X
n
O
m
or RuO
2
-loaded BX
n
O
m
(wherein A is an alkali metal atom, B is an alkali earth metal atom or Zn, X is a metal ion with d
10
configuration, n=m/2 or n=m/3 and n is 2). Desirably, A
2
X
n
O
m
or BX
n
O
m
(wherein A is an alkali metal atom, B is an alkali earth metal atom or Zn, X is a metal ion with d
10
configuration, n=m/2 or n=m/3 and n is 2) is the photo-catalyst obtained by a coprecipitation powder calcination method calcined at the temperature of 1150 to 1200° C., more desirably, X is In, Ga or Sb, an alkali metal atom is Na, K or Rb and an alkali earth metal atom is Ca, Sr or Ba.
The second important point of the present invention is the photo-catalyst for photo decomposition reaction of water comprising RuO
2
-loaded A
2
X
n
O
m
or RuO
2
-loaded BX
n
O
m
(wherein A is an alkali metal atom, B is an alkali earth metal atom or Zn, X is a metal ion with d
10
configuration, n=m/2 or n=m/3 and n is 2).
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patent: 7-88370 (1995-04-01), None
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J. Sato, “New Photocatalyst Group for Water Decomposition of RuO2-Loaded p-Block Metal (In, Sn, and Sb) Oxides With d-10 Configuration”, Journal of Physical Chemistry B, Jul., 2001, vol. 105, No. 26, pp. 6061-6063.
Japan Science & Technology Corporation
Nguyen Cam N.
Sherman & Shalloway
Silverman Stanely S.
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