Systems and methods for chromium catalyst activation

A process comprising:

• (1) exposing a pre-catalyst in a fluidized bed vessel to feed cycles of a second oxidizing gas and a second inert gas at a temperature T2 in a range from 250° F. to 700° F. (121° C. to 371° C.) to a temperature T3 in a range from 700° F. to 950° F. (371° C. to 510° C.), wherein:
• a duration of each second oxidizing gas feed cycle independently is from 10 sec to 15 min;
• a duration of each second inert gas feed cycle independently is from 10 sec to 15 min;
• an average duration of the second oxidizing gas feed cycles is less than an average duration of the second inert gas feed cycles;
• and
• an average temperature rate increase in step (1) is from 0.5 to 10° F./min (0.3 to 6° C./min);
• and
• (2) heating the pre-catalyst, while introducing a third inert gas or a third oxidizing gas into the fluidized bed vessel, to a temperature T4 in a range from 1000° F. to 1600° F. (538° C. to 871° C.) and holding the pre-catalyst at T4 in the third inert gas or the third oxidizing gas for a hold time t1 in a range from 1 hr to 15 hr.

A process comprising:

• (1) exposing a pre-catalyst in a fluidized bed vessel to a feed of a first dilute oxidizing gas at a temperature T2 in a range from 250° F. to 700° F. (121° C. to 371° C.) and up to and including a temperature T3 in a range from 700° F. to 950° F. (371° C. to 510° C.),
• wherein the first dilute oxidizing gas comprises from 1 to 10 vol % oxygen;
• and
• wherein an average temperature rate increase in step (1) is from 0.5 to 10° F./min (0.3 to 6° C./min);
• and
• (2) heating the pre-catalyst, while introducing a third inert gas or a third oxidizing gas into the fluidized bed vessel, to a temperature T4 in a range from 1000° F. to 1600° F. (538° C. to 871° C.) and holding the pre-catalyst at T4 in the third inert gas or the third oxidizing gas for a hold time t1 in a range from 1 hr to 15 hr.