Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
1999-06-16
2002-05-21
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S303000, C502S328000, C502S329000, C502S333000, C502S335000, C502S336000, C502S337000, C502S338000, C502S339000, C502S330000, C502S353000
Reexamination Certificate
active
06391821
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an oxidation catalyst suitable for use in producing a benzyl ester such as p-methylbenzyl acetate or p-xylylene diacetate by reacting a benzyl compound such as p-xylene with a carboxylic acid such as acetic acid, and relates to a method of preparing such an oxidation catalyst and a method of producing such a benzyl ester.
BACKGROUND OF THE INVENTION
Aromatic esters (benzyl esters) such as p-methylbenzyl acetate and p-xylylene diacetate are generally used as starting materials for synthetic resins such as polyester resin, as chemical substances such as aromatics and solvents, and as starting materials for producing such chemical substances. With regard to methods of producing such aromatic esters, Japanese Unexamined Patent Publication No. 63-174950/1988 (Tokukaisho 63-174950, published on Jul. 19, 1988), for example, discloses a method of producing p-methylbenzyl acetate and p-xylylene diacetate by reacting p-xylene and acetic acid in the presence of oxygen, using a palladium-bismuth compound and/or a palladium-lead compound as a catalyst. Again, Japanese Unexamined Patent Publication No. 62-273927/1987 (Tokukaisho 62-273927, published on Nov. 28, 1987), for example, discloses a method of producing p-xylylene diacetate by reacting p-xylene and acetic acid in the presence of oxygen, using a catalyst containing palladium and bismuth.
Further, Japanese Unexamined Patent Publication No. 8-231466/1996 (Tokukaihei 8-231466, published on September 10, 1996), for example, discloses a method of producing p-xylylene diacetate by reacting p-xylene and acetic acid in the presence of oxygen, using a catalyst made of palladium and gold on a support.
However, the activity of catalysts disclosed in the foregoing Japanese Unexamined Patent Publication Nos. 63-174950/1988 and 62-273927/1987 is low (the turnover factor per unit of palladium per unit time being around 15), and thus, in order to improve production efficiency, it is necessary to use a large amount of catalyst in comparison to the reaction substrate p-xylene. In other words, a large amount of palladium, which is a precious metal, must be used. Further, the palladium may elute into the reaction solution during the reaction, and in this case, activity of the catalyst is further decreased, and it becomes necessary to separate and recover the eluted palladium. For these reasons, the foregoing catalyst cannot be said to be suited to industrial production methods.
Further, the catalyst disclosed in Japanese Unexamined Patent Publication No. 8-231466/1996 also has low activity, and thus in order to improve production efficiency, it is necessary to use a large amount of catalyst in comparison to the reaction substrate p-xylene. Accordingly, neither can the foregoing catalyst be said to be suited to industrial production methods.
In other words, because of their low catalytic activity, the foregoing conventional catalysts are unsuitable for industrial production methods, and thus have the drawback that benzyl ester cannot be produced efficiently and at low cost.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an oxidation catalyst suitable for use in producing a benzyl ester such as p-methylbenzyl acetate or p-xylylene diacetate by reacting a benzyl compound such as p-xylene with a carboxylic acid such as acetic acid in the presence of oxygen, and to provide a method of preparing such an oxidation catalyst and a method of producing such a benzyl ester efficiently and at low cost.
The inventors of the present invention conducted assiduous investigation in connection with oxidation catalysts for oxidizing benzyl compounds, methods of preparing such oxidation catalysts, and methods of producing benzyl esters. As a result, the inventors found that an oxidation catalyst containing palladium, ultrafine gold particles, and at least one element selected from the group consisting of alkaline metals and the elements of Groups IIA, IIIA, VIA, IIB, VB, and VIII of the Periodic Table had high catalytic activity in a reaction for producing a benzyl ester from a benzyl compound and a carboxylic acid in the presence of oxygen, i.e., that such an oxidation catalyst was suitable for industrial production of a benzyl ester. The inventors then confirmed that by using the foregoing oxidation catalyst it was possible to industrially produce a benzyl ester efficiently and at low cost, thus completing the present invention.
In order to attain the foregoing object, an oxidation catalyst according to the present invention is a catalyst for oxidation of a benzyl compound, and contains palladium, ultrafine gold particles, and at least one element selected from the group consisting of alkaline metals and the elements of Groups IIA, IIIA, VIA, IIB, VB, and VIII of the Periodic Table. Further, an oxidation catalyst according to the present invention may be characterized in that the element selected from the foregoing group is at least one element selected from the group consisting of bismuth, molybdenum, iron, nickel, zinc, lanthanum, an alkaline earth metal, and an alkaline metal. Further, an oxidation catalyst according to the present invention may be characterized in that the ultrafine gold particles are supported on a support.
Each of the foregoing oxidation catalysts has higher catalytic activity than conventional catalysts, and is suitable for use in an industrial production method. Consequently, with any of the foregoing structures, an oxidation catalyst can be provided which is suitable for use in producing a benzyl ester such as p-methylbenzyl acetate or p-xylylene diacetate by reacting a benzyl compound such as p-xylene with a carboxylic acid such as acetic acid.
Further, in order to attain the foregoing object, a method of preparing an oxidation catalyst according to the present invention includes the steps of: (a) heat processing a gold compound at 150° C. to 800° C. to obtain ultrafine gold particles; and (b) mixing the ultrafine gold particles obtained in step (a) with a palladium compound and a compound containing at least one element selected from the group consisting of alkaline metals and the elements of Groups IIA, IIIA, VIA, IIB, VB, and VIII of the Periodic Table. Further, in order to attain the foregoing objects, another method of preparing an oxidation catalyst according to the present invention includes the steps of: (a) heat processing a gold compound and a palladium compound at 150° C. to 800° C. to obtain a mixture containing ultrafine gold particles and palladium; and (b) mixing the mixture obtained in step (a) with a compound containing at least one element selected from the group consisting of alkaline metals and the elements of Groups IIA, IIIA, VIA, IIB, VB, and VIII of the Periodic Table.
Using either of the foregoing methods, it is possible to prepare an oxidation catalyst having higher catalytic activity than conventional catalysts. Consequently, with any of the foregoing structures, an oxidation catalyst can be provided which is suitable for use in producing a benzyl ester such as p-methylbenzyl acetate or p-xylylene diacetate by reacting a benzyl compound such as p-xylene with a carboxylic acid such as acetic acid.
Further, in order to attain the foregoing object, a method of producing benzyl ester according to the present invention is a method of producing benzyl ester by an oxidation reaction between a benzyl compound and a carboxylic acid in the presence of oxygen and an oxidation catalyst containing palladium, ultrafine gold particles, and at least one element selected from the group consisting of alkaline metals and the elements of Groups IIA, IIIA, VIA, IIB, VB, and VIII of the Periodic Table. Another method of producing benzyl ester according to the present invention is characterized in that the foregoing oxidation reaction is carried out in a liquid phase.
With the foregoing production method, it is possible to industrially produce benzyl ester efficiently and at low cost. For example, a benzyl ester such as p-methylbenzyl acetate or p-xylylen
Hayashi Toshio
Iida Toshiya
Satoh Yuuichi
Tatsumi Jun
Bell Mark L.
Colin David G.
Dike Bronstein Roberts & Cushman IP Group
Hailey Patricia L.
Nippon Shokubai Co. , Ltd.
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