Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
1999-11-16
2001-11-06
Griffin, Steven P. (Department: 1754)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
active
06313325
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a carrier to be used in the preparation of a catalyst for use in the production of ethylene oxide, a catalyst obtained by depositing a silver-containing catalytic component on the carrier and used for the production of ethylene oxide, and a method for the production of ethylene oxide by the use of the catalyst.
2. Description of the Related Art
Concerning the catalyst for use in the production of ethylene oxide by gas phase oxidation of ethylene and the carrier therefor, numerous reports have been heretofore introduced to literature.
JP-A-57-171,435, for example, has a description to the effect that a carrier obtained by adding mullite, colloidal silica, etc. to &agr;-alumina having a deliberately lowered sodium content has a high specific surface area, a uniform pore distribution, and moreover high wear-resistant properties. EP-B-0,207,550 has a description to the effect that a carrier having a small impurity is obtained by mixing an aluminum compound with the salt of a Group IA metal in the Periodic Table of the Elements and calcining the resultant mixture and a catalyst using this carrier excels in stability. JP-A-04-363,139 discloses a carrier containing &agr;-alumina the elements of the fourth, fifth, and sixth periods (such as, for example, titanium, tin, and hafnium) of the IIIa—VIIa and IIIb—Vb groups in the Periodic Table of the Elements and contains a description to the effect that a catalyst using this carrier has high selectivity and a long life. Further, U.S. Pat. No. 5,100,859 discloses a carrier comprising high-purity &agr;-alumina, the oxide of an alkaline earth metal, a silicon oxide, and zirconium oxide and contains a description to the effect that a catalyst using this carrier has high initial selectivity and a long life.
We have also proposed a catalyst obtained by depositing silver and cesium as catalytic components on a carrier having a coating layer of amorphous silica disposed on the surface of &agr;-alumina and used for the production of ethylene oxide (U.S. Pat. No. 5,077,256) and a catalyst obtained by disposing a coating layer of amorphous silic-alumina on the surface of &agr;-alumina and depositing silver and cesium as catalytic components on the resultant carrier and used for the production of ethylene oxide (U.S. Pat. No. 5,395,812).
The catalysts which are disclosed in U.S. Pat. No. 5,077,256 and U.S. Pat. No. 5,395,812 are excellent in catalytic performance and are fully satisfactory from the commercial point of view. Ethylene oxide, however, is produced on a large scale. Even such a small addition to selectivity as 1%, therefore, results in a notable saving in ethylene as a raw material. In the light of the prominence of the economic effect of such an improvement in the selectivity, the desirability of developing a catalyst of more improved performance for the production of ethylene oxide has been finding growing recognition.
An object of this invention, therefore, is to provide a carrier to be used in the preparation of a catalyst for the production of ethylene oxide, a catalyst obtained by depositing silver-containing catalytic component on the carrier and used for the production of ethylene oxide, and a method for the production of ethylene oxide by the use of the catalyst.
Another object of this invention is to provide a carrier which permits preparation of a catalyst possessed of excellent catalytic performance in terms of activity, selectivity, a and used for the production of ethylene oxide, a catalyst obtained by using the carrier just described, endowed with excellent catalytic performance, and used for the production of ethylene oxide, and a method for the production of ethylene oxide by the use of the catalyst just described.
SUMMARY OF THE INVENTION
The objects mentioned above are accomplished by the following items (1)-(8).
(1) A carrier for the catalyst to be used in the production of ethylene oxide, obtained by adding an aluminum compound, a silicon compound, and an alkali metal compound to a low-alkali content &agr;-alumina powder having an alkali metal content in the range of 1-70 m.mols/kg of powder and calcining the resultant mixture, the aluminum compound content as reduced to aluminum being in the range of 0-3 mols/kg of carrier, the silicon compound content as reduced to silicon in the range of 0.01-2 mols/kg of carrier, and the alkali metal content as reduced to alkali metal in the range of 0.01-2 mols/kg of carrier respectively in the carrier.
(2) A carrier according to the item (1) mentioned above, wherein the atomic ratio of the alkali metal content in the powder/the alkali metal content in the carrier is in the range of 0.0001-0.8.
(3) A method for the production of a carrier to be used in the production of ethylene oxide, which comprises mixing a low-alkali content &agr;-alumina powder having an alkali metal content in the range of 1-70 m.mols/kg of powder with an aluminum compound, a silicon compound, and an alkali metal compound at ratios such that in the produced carrier, the aluminum compound content as reduced to aluminum is in the range of 0-3 mols/kg of carrier, the silicon compound content as reduced to silicon in the range of 0.01-2 mols/kg of carrier, and the alkali metal compound content as reduced to alkali metal in the range of 0.01-2 mols/kg of carrier, forming the resultant mixture in a prescribed shape, and then calcining the formed mixture.
(4) A method according to the item (3) mentioned above, wherein the atomic ratio of the alkali metal content in the powder/the alkali metal content in the carrier is in the range of 0.0001-0.8.
(5) A catalyst to be used in the production of ethylene oxide, obtained by depositing a silver-containing catalytic component on a carrier set forth in the item (1) or the item (2) mentioned above.
(6) A method for the production of a catalyst to be used for the production of ethylene oxide, which comprises depositing a silver-containing catalytic component on a carrier set forth in the item (1) or the item (2) mentioned above and then calcining the resultant composite.
(7) A method according to the item (6) mentioned above, wherein the calcination is effected in the current of an inert gas at a temperature in the range of 400°-700° C.
(8) A method for the production of ethylene oxide, which comprises subjecting ethylene to catalytic gas phase oxidation with a molecular oxygen-containing gas in the presence of a catalyst set forth in the item (5) mentioned above.
The catalyst to be used in the production of ethylene oxide which is obtained by using the carrier of this invention excels in catalytic properties, particularly in selectivity.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The &agr;-alumina to be used in this invention must have an alkali metal content in the range of 1-70 m.mols per kg thereof (indicated as “1-70 m.mols/kg of powder” in the present invention). The &agr;-alumina itself does not need to be limited particularly but may be selected from among all the species of &agr;-alumina which are in popular use. The &agr;-alumina which is obtained by the Bayer calcining method, for example, necessarily contains an alkali metal, especially sodium, by reason of the process of manufacture thereof. This invention must use a low-alkali &agr;-alumina which has an alkali metal content thereof controlled in the range of 1-70 m.mols/kg of powder.
If the alkali metal content is less than 1 m.mol/kg of powder or in excess of 70 m.mols/kg of powder, the produced catalyst will manifest too low selectivity for ethylene oxide to accomplish the objects of this invention. The &agr;-alumina which has an alkali metal content in the range of 3-30 m.mols/kg of powder, especially in the range of 5-20 m.mols/kg of powder, is advantageously used.
To be used advantageously in this invention, the &agr;-alumina has an alumina crystal diameter (primary particle diameter) in the range of 0.1-5 &mgr;m, an average particle diameter (secondary particle diameter) in the range of 50-100 &mgr;m, a BET specific surface are
Shima Masahide
Takada Hitoshi
Fish & Richardon P.C.
Griffin Steven P.
Nguyen Cam N.
Nippon Shokubai Co. , Ltd.
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