Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
1999-10-22
2001-06-26
Dunn, Tom (Department: 1754)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C502S344000
Reexamination Certificate
active
06252095
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a catalyst for partial oxidation of unsaturated hydrocarbon and a process for preparing an epoxide using said catalyst.
BACKGROUND ART
Methods industrially carried out for epoxidation generally employ chlorohydrin, organic peroxide, hydrogen peroxide or like oxidizing agents. However, these methods inevitably pose problems of requiring multi-stage reaction and generating by-products.
It is more convenient to convert unsaturated hydrocarbon to the corresponding epoxide using molecular oxygen as an oxidizing agent. However, this technique has been employed on an industrial scale only for the production of ethylene oxide from ethylene. The production of an epoxide from other unsaturated hydrocarbon, for example, propylene oxide directly from propylene by oxidation with oxygen, is very difficult to accomplish. Some methods for oxidation of propylene directly to propylene oxide with oxygen were proposed in publications (Japanese Examined Patent Publication No.39404/1978, Japanese Unexamined Patent Publication No.97378/1995, etc.). However, all of the proposed methods raise problems of low selectivity, low activity and other defects from the viewpoint of efficiency.
Proposed methods of producing an epoxide from unsaturated hydrocarbon with a high selectivity include methods comprising partially oxidizing unsaturated hydrocarbon in the presence of molecular hydrogen using a catalyst comprising gold and titanium oxide (Japanese Unexamined Patent Publications No. 127550/1996 and No.5590/1998). Yet, the proposed methods are problematic in that although active in some degree in the initial stage of reaction, the catalyst lowers its activity with time and shows an insufficient activity in a stationary state.
DISCLOSURE OF THE INVENTION
The present invention was accomplished to overcome the foregoing prior art problems. It is a principal object of the invention to provide a catalyst for partial oxidation of unsaturated hydrocarbon, the catalyst being useful in efficiently producing an epoxide from unsaturated hydrocarbon with a high selectivity and the catalyst being rarely deactivated with time and having a prolonged service life.
The inventors of the present invention carried out extensive research in view of the foregoing prior art problems, and found the following. When a catalyst comprises finely divided gold particles immobilized on a titanium-containing oxide and is subjected to a silylating treatment or a hydrophobilizing treatment, the catalyst can effectively exhibit its inherent properties depending on reaction conditions such as a reaction temperature and a reaction pressure in a reaction for preparing an epoxide from unsaturated hydrocarbon. Further, such catalyst hardly diminishes its activity with time and can stably retain a high selectivity, a high activity and like excellent catalytic capability for a long term. This invention was accomplished based on this novel finding.
According to the present invention, there are provided the following catalysts for partial oxidation of unsaturated hydrocarbon and a process for preparing an epoxide using the catalysts:
1. a catalyst for partial oxidation of unsaturated hydrocarbon, characterized in that the catalyst comprises finely divided gold particles immobilized on a titanium-containing oxide and is one subjected to a silylating treatment;
2. a catalyst for partial oxidation of unsaturated hydrocarbon, characterized in that the catalyst comprises finely divided gold particles immobilized on a titanium-containing oxide and is one subjected to a hydrophobilizing treatment;
3. the catalyst as defined in item 2, wherein the hydrophobilizing treatment is conducted using at least one hydrophobilizing agent selected from the group consisting of organic fluorinating agents and silylating agents;
4. the catalyst as defined in item 1 or 2, wherein the finely divided gold particles are ultra-fine particles having a particle size of 10 nm or less;
5. the catalyst as defined in item 1 or 2, wherein the titanium-containing oxide is at least one member selected from the group consisting of titanium oxides, titanates, oxide mixtures of titanium oxide and silicon-containing oxide physically mixed together, and composite oxides prepared by chemically bonding titanium and silicon via oxygen;
6. the catalyst as defined in item 1 or 2, wherein the titanium-containing oxide contains at least one element selected from the group consisting of alkali metals, alkaline earth metals, lanthanoids and thallium;
7. the catalyst as defined in item 1, wherein the silylating treatment is carried out by bringing the titanium-containing oxide into contact with a silylating agent at a temperature of 450° C. or lower before or after immobilizing the finely divided gold on the titanium-containing oxide;
8. the catalyst as defined in item 2, wherein the hydrophobilizing treatment is carried out by bringing the titanium-containing oxide into contact with a hydrophobilizing agent at a temperature of 450° C. or lower before or after immobilizing the finely divided gold on the titanium-containing oxide; and
9. a process for preparing an epoxide, characterized in that unsaturated hydrocarbon is partially oxidized with oxygen in the presence of the catalyst as defined in any of items 1-8 and molecular hydrogen.
The catalyst of the present invention comprises finely divided gold particles immobilized on a titanium-containing oxide, the catalyst being one subjected to a silylating treatment or a hydrophobilizing treatment.
Said catalysts are described below in more detail.
Titanium-containing Oxide
The titanium-containing oxide for use herein includes, for example, titanium oxides, titanates, oxide mixtures of titanium oxide and silicon-containing oxide physically mixed together (hereinafter referred to as “titanium-containing mixed oxide”) and composite oxides prepared by chemically bonding titanium and silicon via oxygen (hereinafter referred to as “titanium-containing composite oxide”). These titanium-containing oxides can be used either alone or in combination. It is preferred to use a titanium-containing oxide having a large specific surface area. The shapes of the oxides are not limited, and include powders and other shapes of moldings.
Among the titanium-containing oxides, useful titanium oxides are not limited in respect of the crystalline structure, shape, size and the like, and include, for example, those having anatase-type structure, rutile-type structure or like crystal structure or having an amorphous structure. Preferred titanium oxides include those of anatase-type structure or amorphous structure and those having a relatively small primary particle size of about 10 to about 200 nm and a relatively large specific surface area of about 5 m
2
/g or larger.
Examples of useful titanates are metal titanates such as MgTiO
3
, CaTiO
3
, BaTiO
3
, PbTiO
3
, FeTiO
3
and the like.
Among the titanium-containing mixed oxides and titanium-containing composite oxides, it is suitable to use those which are porous and which have a large specific surface area, preferably 1 m
2
/g or larger, more preferably 50 to 1200 m
2
/g.
Silicon-containing oxides to be used in the titanium-containing mixed oxide include, for example, amorphous silica; silicalite having crystal structure; silicon-containing oxide such as a metal silicate which comprises as a main component a silicon oxide; composite oxides comprising silicon and other metal, typical examples of the composite oxides being amorphous silica-alumina and zeolite which is crystal form of silica-alumina.
Useful titanium-containing composite oxides include (1) those having titanium oxide supported only on the surface of a silicon-containing oxide and (2) those having titanium existing inside the silicon-containing oxide as well as on the surface thereof. The titanium-containing composite oxides having titanium oxide supported only on the surface of a silicon-containing oxide as described above in item (1) are those with titanium supported in the form of titanium oxide having
Haruta Masatake
Hayashi Toshio
Tsubota Susumu
Wada Masahiro
Armstrong Westerman Hattori McLeland & Naughton LLP
Director--General of Agency of Industrial Science and Technology
Dunn Tom
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