Claims
- 1. A method for activating a chromium-containing catalyst supported on a silica-containing base which comprises the successive steps of:
- (a) heating the catalyst in an oxidizing atmosphere at an oxidizing activation temperature from 600.degree. to 850.degree. C. until at least a part of the chromium present in the catalyst is converted to the hexavalent state;
- (b) cooling the catalyst in an oxidizing atmosphere until it reaches a temperature below the oxidizing activation temperature and from 550.degree. to 750.degree. C. at the end of said cooling;
- (c) replacing the said oxidizing atmosphere by a non-oxidizing atmosphere at the temperature reached at the end of step (b) and maintaining the catalyst at the said temperature for a time from 15 minutes to 20 hours to achieve at least partial self-reduction of at least a portion of the chromium present in the catalyst to a lower valence state; and
- (d) cooling the catalyst in the said non-oxidizing atmosphere from the temperature of step (c) to ambient temperature.
- 2. A method according to claim 1 wherein the oxidizing atmosphere is anhydrous air.
- 3. A method according to claim 1 wherein the oxidizing activation temperature of step (a) is within the range of 800.degree.-850.degree. C. and the temperature reached at the end of cooling step (b) is within the range of 600.degree.-650.degree. C.
- 4. A method according to claim 1 wherein the non-oxidizing atmosphere is an inert atmosphere.
- 5. A method according to claim 4 wherein the inert atmosphere is nitrogen.
- 6. A method according to claim 4 wherein the inert atmosphere is argon.
- 7. A method according to claim 1 wherein the silica-containing base is in the form of a silica gel.
- 8. An activated chromium-containing catalyst produced by the method of claim 1.
Parent Case Info
This application is a continuation of application Ser. No. 652,147, filed Sept. 18, 1984, which is a continuation of Ser. No. 481,877, filed Apr. 4, 1983, both now abandoned.
US Referenced Citations (15)
Foreign Referenced Citations (1)
Number |
Date |
Country |
1083178 |
Sep 1967 |
GBX |
Continuations (2)
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Number |
Date |
Country |
Parent |
652147 |
Sep 1984 |
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Parent |
481877 |
Apr 1983 |
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